WO1999054106A2

WO1999054106A2 - Method for producing a matrix which is filled with cavities and device with a matrix of this type

Info

Publication number: WO1999054106A2
Application number: PCT/EP1999/002532
Authority: WO
Inventors: Werner Wagner
Original assignee: Hcd Hygienic Composites Development Gmbh
Priority date: 1998-04-18
Filing date: 1999-04-15
Publication date: 1999-10-28
Also published as: DE19817237C2; WO1999054106A3; DE19817237A1; AU3816999A; WO1999054106A8

Abstract

The invention relates to a method for producing a matrix (25) which is densely packed with capillary-type cavities (20). A metal jacket is produced simply by galvanoplasty, in the form of a metal deposit on a core (33). The jacket is then removed from the core and provided with cavities (20) using electromagnetic beams with a high power density, especially laser beams.

Description

Process for producing a matrix with cavities and device with such a matrix

The invention relates to a method for producing a matrix filled with capillary-like cavities in high density on a surface for forming thermoplastic semi-finished products, in which cavities are produced in a solid substrate with the aid of electromagnetic beams of high power density, in particular laser beams. wherein the substrate is made in the form of an open or closed jacket made of a metal which is then to be brought into contact with a deformable thermoplastic composition.

DE 195 24 076 Cl describes a method for producing a surface-structured, sheet-like semi-finished product from a thermoplastic. A roll surface with a negative structure (matrix) is used, which has an outer layer made of a plastic. The cladding layer is suitable for producing semi-finished products provided with a velor-like surface and comprises hair-fine pores which are introduced into the cladding layer with the aid of an energy beam, preferably a laser beam.

The plastic mentioned in the prior art as a solid substrate is preferably polytetrafluoroethylene (TEFLON or VITON, trademarks of DuPont, USA). It has shows that the production of matrices with such plastics is indeed possible, but has the particular disadvantage that the exhaust gases produced during laser drilling contain highly corrosive HF (hydrogen fluoride gas or hydrofluoric acid), which entail considerable technological effort, especially the need for exhausters and the like.

In addition, it was found that the surface of these plastic rollers is too soft and therefore wears out quickly. The relatively soft matrix surface also makes it difficult to separate the plastic applied in the process; the resulting plastic film can only be removed relatively slowly and carefully. The film take-off thus determines the speed for the entire process and thus significantly influences the production costs. It was also observed that if the speed is too high, the webs between the roller perforations can also break.

Furthermore, from WO 94/29070 a method is known for introducing a geometric structure into different substances, such as aluminum, lead, wood, ceramic, glass, copper or steel, using laser radiation. The cited document shows various patterns and the possibility of applying the method to flat substrates, but does not describe how a cavity structure can be introduced into the surface in a simple manner in the case of a metal-coated or metal roller.

It is therefore the task of specifying a method for producing a matrix with capillary-like cavities, in which these can be produced with laser beams without undesired plastic evaporation occurring on the one hand, but when using a substrate from metal this should be easy to manufacture in a cylindrical shape.

This object is achieved by a method in which, in order to produce a matrix filled with cavities, a metal jacket is produced by electroplating as a metal deposit on a core, is removed from the core and with the cavities with the aid of electromagnetic rays of high power density, in particular laser beams is provided, which are formed in the form of blind holes or continuous perforations, and is then placed on a new roller core.

If, in addition to the velor or hair configuration, a graining, that is to say a structure of lesser depth, is to be provided, it is proposed that the coat be provided with a grained structure before perforation.

A CO? High-power laser or another high-power laser is preferably used in the process.

A device for carrying out the method can work with a matrix which is formed by a jacket which is placed around the core cylinder and which is to be brought into contact with a deformable thermoplastic composition. The core cylinder is seamlessly shaped using the aforementioned galvanoplastic process.

In order to achieve a faster and better penetration of the capillaries with thermoplastic molten mass, the core cylinder or the band is underlaid with a vacuum-producing device in the case of continuous bores. As is known, the core cylinder can also have a central cavity which is formed by a jacket made of sintered, air-permeable material, on which the perforated metal jacket is placed.

The device equipped with the matrix can also be connected directly to the outlet nozzle of an extruder from which a thermoplastic can be brought out in the molten state. Here, in particular, a device is considered, such as that mentioned and described in the above-mentioned patent specification 195 24 076 C1.

The cavity density should be between 3600 and 16000 cavities per cm ² and should have a diameter between 10 and 100 µm. The depth of the cavities depends on the thickness of the core shell, with thicknesses of 150 to 500 μm having been found to be possible and advantageous. To the

To get the mass out of the cavity more quickly, it is proposed that the bores within the metal shell diverge in diameter towards the outside.

Further properties and advantages are explained on the basis of exemplary embodiments.

The figures in the drawing show:

FIG. 1 shows an application example of a matrix in a first embodiment,

FIG. 2 in a second exemplary embodiment,

FIG. 3 in a third exemplary embodiment,

Figure 4 is an enlarged view of the matrix, and

Figure 5 shows the manufacture of a matrix cylinder. In FIG. 4, a jacket section 30 which has been laid flat for the sake of the drawing and which is provided with cavities 20 is shown enlarged. The section shown in FIG. 4 consists of electrodeposited iron with a thickness of 200 μm and is provided with numerous frustoconical cavities 20, which have a diameter of approximately 40 to 60 μm on the upper side and 10 to 20 μm in diameter on the underside. The cavities 20 are generated with the aid of pulse lasers through a focused laser beam with a hollow power density. The metal struck by the laser beam evaporates. It is immediately sucked off by a suction nozzle, which is arranged directly above the exit of the laser, and then condenses.

The configuration shown in FIG. 4 is based on a cavity density of 5000 cavities per cm ² . Wide variations are possible here, depending on the diameter of the individual cavity and the desired pile density. Up to 1600 cavities per cm ² can preferably be introduced. Section 30 is part of a core cylinder. The result is a roller jacket 5, as shown in Figure 1. The starting point is a hollow roller 4 which has a porous, sintered roller cylinder 24. The roller jacket 5 is applied to the roller cylinder 24, so that there is a matrix on the outside which comprises the numerous fine cavities. The cavities 20 are continuous and end above the air-permeable sintered material of the roll shell.

An LLDP polymer of average molecular weight with a melt index of -15 (2.16 kg / 190 ° C.) and a density of 0.94 is used to produce a polyethylene velor material. In a single-screw extruder, schematically indicated by the reference number 1, which has a screw length greater than 20 times the diameter with a screw diameter of 90 mm, the material is melted and homogenized. The plastic melt 3 passes through a corresponding channel to the extruder mouth 2. During the homogenization and extrusion, a compression ratio of 1: 2.5 and a screw temperature of 250 ° C. are maintained. The polyethylene melt 3 is fed to the discharge nozzle with the mouth 2 under constant pressure.

A vacuum chamber 6 with the opening 16 is provided in front of the discharge nozzle 2 in the direction of rotation of the roller 4. The vacuum in the vacuum chamber spreads to the roller surface. Although part of the vacuum can be equalized by the air flowing in through the roller cylinder 24, it must first be noted that the cavities have a negative pressure with respect to the outside air pressure.

The matrix roller is kept at a temperature of 130 ° C. in the area of the matrix surface. For this purpose, heating elements, not shown, are provided. The negative pressure directly at the extruder mouth 2 is to be measured at 0.2 to 0.5 bar. When the exit front 17 of the thermoplastic melt is reached by the cavities, they immediately fill through the roll shell with thermoplastic and at the same time form a back layer on the roll shell 5. When the roll 5 is turned further, this layer comes into a cooling zone with numerous air nozzles 11. which are connected to a cooling fan. After passing through the first air cooling section, another will appear

Downstream water bath 23 that cools the film sustainably. After passing through the water bath 23, the plastic material lying on the surface is solidified by cooling, wherein it assumes the surface structure corresponding to the matrix 25 on the side brought into contact with the roller. Shortly before the vacuum chamber 6, a take-off roller 14 is arranged, which picks up the film or the semi-finished product and pulls it off the roller 4 or the roller shell. The removed semi-finished product 9 is then, for example, pulled through a pair of cooling or embossing rollers 15 and then wound on a supply roll with low tension.

The production method of a roll shell made of nickel, reference number 31, is shown schematically in FIG. Here, a metal deposit made of nickel with a thickness of 150 μm is produced on a core 33 in a manner known per se. After the galvanoplastic deposition has ended, the core is provided with a jacket 31 with the aid of a pulse laser 32 with fine continuous cavities 20 with a diameter of 60 μm ± 10 μm with a density of 10,000 cavities per cm ² . The core 33 is then removed, the jacket 31 is pulled off and fitted onto a new roller core 23 or roller cylinder 24. The resulting roller 4 is shown in Figure 2.

A vacuum can be set within the roller 4, which is, for example, - 0.5 bar. Two extruder nozzles are mounted above the roller 4, so that a two-layer film can be produced by applying it to the matrix 25. From one of the two extruder heads 1, 1 ^λ , a melt 3 ^X lying on the top, which consists of a tough, mechanically loadable polymer and has a melt index of 18 to 30 and a layer thickness of 20 to 60 μm, is produced. The surface is kept at 130 ° C so that there is a slight flow.

Due to the slightly conical inwardly converging cavities 20, a velor layer with knobs or hairs that can be easily pulled out of the jacket 31 is created. The two-layer film, one side of which can be very easily deformed on the surface and which is provided with the properties required for further processing by the tough backing layer, is pressed firmly onto the jacket 31 with the aid of a pressure roller 41. A further cooling takes place in a water bath 23. The semi-finished product 9 is drawn off via the take-off roller 14 and the pair of rollers 15.

According to FIG. 3, a matrix roller 4 with a matrix 25 of the type described above is used, but here we also have a film 39 from an extruder on the cylinder

Pressed on by a pressure roller 44. The film material is heated to about 125 ° C. by means of a heater 40, so that it becomes practically flowable. With further rollers 42, which are kept at a temperature of 110 ° C., the material is pressed firmly into the cavities, with the material additionally being sucked through suction channels 34 inside the roller 4 through the cavities of the matrix. After penetration of the cavities, cooling takes place through the cooling units 43. The thermoplastic material cools and hardens and is then removed as a semi-finished product via the take-off roller.

With a multilayer film in particular, semi-finished products are easy to deform, which are characterized by a tough backing layer, but on the other hand develop a deep velor pile due to the good flow behavior of the soft layer.

Steel or nickel is preferred as the metal for the matrix 25, since the technology of laser drilling has meanwhile been developed far enough for these materials. Cylindrical, but preferably cone-like bores can be achieved, so that the film comes with the easily deformable side this tool roller is sucked in and caused to completely fill the fine cavities. The back of the film remains completely unchanged.

The film can be preheated by infrared emitters or by hot air. After cooling and pulling off the tool surface, a fibrous or studded semi-finished film is created.

Claims

Claims:

1. A method for producing a matrix (25) with capillary-like cavities (20) with a high density on a surface for forming thermoplastic semi-finished products (9), in which cavities are formed with the aid of electromagnetic rays having a high power density, in particular laser beams a solid substrate can be produced, the substrate being produced in the form of an open or closed jacket made of a metal, which is then to be brought into contact with a deformable thermoplastic composition, characterized in that a metal jacket (5; 31) is electrolytically deposited as a metal deposit a core (33) is produced, from which the core (33) is removed and is provided with the cavities (20), which are formed in the form of blind holes or continuous perforations, with the aid of electromagnetic beams of high power density, in particular laser beams, and then placed on a new roll core.

2. The method according to claim 1, characterized in that the metal jacket is provided with a grained structure before perforating.

3. The method according to claim 1, characterized in that the laser beam is generated by a high-power laser, preferably a high-power C0 ₂ laser.

4. Apparatus for forming thermoplastic semi-finished products (9) with a velor-like surface, comprising an according Manufactured covered core cylinder (24) or roller cylinder with a heatable outer surface, the outside of which has a matrix (25) which is filled with capillary-like cavities (20) which are formed in the form of blind holes or continuous perforations, characterized in that Core cylinder has a central cavity (4) which is formed by a jacket made of sintered, air-permeable material, on which the perforated metal jacket (5; 31) is placed.

Apparatus according to claim 4, characterized in that in the case of continuous bores the core cylinder is underlaid with a vacuum-producing device.

6. The device according to claim 4 or 5, characterized in that the core cylinder is seamlessly shaped.

7. The device according to at least one of the preceding claims, characterized in that the matrix has a cavity density of 3600 to 16000 cavities per cm ² .

8. The device according to at least one of the preceding claims, characterized in that the diameter of the cavities is between 10 and 100 microns.

9. The device according to at least one of the preceding claims, characterized in that the bores within the metal shell diverge in diameter towards the outside.

0. Device according to at least one of the preceding claims, characterized in that the metal shell is between 150 and 500 microns thick.