CN118541234A - Plastic material and method for processing plastic material - Google Patents

Abstract

The invention relates to a method for processing plastic materials, wherein the plastic material is processed with a laser and is thus modified or de-crosslinked. The plastic material is then irradiated to at least partially re-crosslink the plastic material. The invention also relates to a plastic material, in particular an ocular implant or an intraocular lens, having at least one region in which the plastic material has been vaporized with a laser and which has been reprocessed in order to re-crosslink the plastic material.

Description

Plastic material and method for processing plastic material

The invention relates to a method for processing plastic materials, wherein the plastic materials are processed by laser.

Depending on the type of plastic material and the processing parameters, in particular in the case of thermoset materials, de-crosslinking (de-crosslinking) or depolymerization of the plastic material may occur when ablating material above or during modification of the material below the vaporization threshold, which has a negative effect on the properties of the plastic material. This affects mechanical and chemical properties such as strength, elasticity, fatigue strength under cyclic bending stress, inertness and solubility. The invention further relates to a plastic material, in particular an ocular implant or an intraocular lens, having at least one region in which the plastic material has been vaporized or modified by means of a laser.

It is known to treat plastic materials with a laser to remove the material and/or polish the surface. An example of such a treatment of plastic materials is shown in DE 102017002986B 4. In this patent, an artificial crystal is used by way of example to show how the material is ablated with a laser and, in addition, how the surface finish is performed with a laser.

US2017/0371180A1 describes a method of manufacturing a contact lens, wherein the lumen in the contact lens is filled with a water soluble polymer. For this purpose, the cavity is drilled with a laser from the outside of the contact lens and then the water-soluble material in the cavity is dissolved with ultraviolet light. Finally, the hole is closed again.

However, the present invention is not only concerned with the treatment of intraocular lenses, ocular implants, methacrylate plastic materials or thermoplastics, but also relates generally to the treatment of plastic materials in which the plastic material is processed with a laser.

Laser processing methods for vaporizing plastic materials or even for merely improving or melting plastic materials improve the cross-linking of molecules in the plastic material. This also improves the properties of the plastic material at least in the areas where the plastic material has been processed. This is particularly relevant for the geometry in the case of ablation and melting. However, during the melting and modification process, the mechanical and chemical properties are also modified, in particular the refractive index in the surface or volume of the plastic material.

In the context of the present invention, the term "plastic material" is understood to mean a solid body whose basic constituent is formed from a synthetically or semisynthetically produced polymer having organic groups. Synthetic plastic materials are produced from monomers by polymerization (polyaddition, polycondensation, etc.).

The degree of crosslinking is reduced during the heat treatment of the plastic material, in particular, for example, during melting and vaporization, or indeed for the purpose of improving the refractive index of the material. This reduces hardness, toughness and melting point and increases solubility. This facilitates the processing of the plastic material and this enables, for example, blanks or blanks that have been pretreated with laser light to be further processed with polishing laser light.

However, after polishing the blank with the polishing laser, the plastic material still has a lower degree of cross-linking than the untreated blank. This results in the plastic material no longer being as hard and tough as the untreated blank.

It is therefore the object of the present invention to process or post-process plastic materials in such a way that the disadvantages associated with de-crosslinking of the plastic material are compensated or at least minimized.

Fortunately, it has been shown that this problem can be solved by a method having the features of patent claim 1, and that the problem of the invention can also be solved by a plastic material as described in claim 15.

The basic concept of the present invention is that even with USP lasers with pulse durations of less than 1ns and pulse energies of 0.1 muj to 10 muj, even changing the method of ablation, melting or modification of the plastic material, the processed plastic material is adversely affected. The basic idea of the invention is to be able to irradiate the plastic material after laser processing to at least partially re-crosslink the plastic material, instead of more and more optimizing the processing method.

The particle beam is suitable for irradiation. An electron beam, gamma radiation or a photon beam, in particular an Ultraviolet (UV) photon beam, may be used as the particle beam. The radiation activates the de-crosslinked polymer chain moieties in an electronically excited or ionized form, which then results in increased crosslinking with other polymer chain moieties. The effect is confirmed by a test of the variation of the particle energy and the particle beam power with respect to the incident power per unit area.

In contrast to the previous methods, according to the present invention, a new method for reducing the decrosslinking of plastic material during laser processing is not proposed, but rather the decrosslinking of plastic material during laser processing is accepted, followed by irradiation of the plastic material to at least partially re-crosslink the plastic material. In this way, the de-crosslinking of the processed blank can be reduced, the plastic material can recover the properties of the blank after treatment, and even an increased degree of crosslinking compared to the degree of crosslinking of the blank can be obtained, to increase the hardness, toughness and melting point, and to reduce the solubility.

Thus, the plastic material is subjected to a subsequent process by which the viscosity reduction due to the previous polishing due to the shortening of the polymer chains is turned to the other direction and is increased by crosslinking, and thus, preferably, the original values of the material in terms of hardness, solubility and toughness are largely restored. This may occur outside the lens surface but may also occur inside the lens material. Because of the polishing process and the restoration of the initial properties, generally on the surface, in particular on the outer surface, additional crosslinking is appropriate and this can be achieved in a particularly advantageous manner with a particle beam.

In order to increase the crosslinking, a possible treatment of the plastic material is with a crosslinking agent. Crosslinking agents of this type feature at least two reactive groups. Crosslinking agents having two identical reactive groups are described as homobifunctional (homobifunctional) crosslinking agents; on the other hand, a crosslinker having two different groups is described as a heterobifunctional (heterobifunctional) crosslinker.

The crosslinking of the existing polymer chains, known as curing, can be achieved by appropriate choice of reaction conditions, via functional groups already present in the polymer, or by using multifunctional, low molecular weight substances.

Depending on the degree of crosslinking, as crosslinking increases, crosslinking of the polymer initially produces an elastomer, which also produces a thermoset.

However, according to the invention, the usual crosslinking agents are not used, but the plastics material is irradiated after the decrosslinking. The irradiation enables the plastic material that has been treated with the laser beam to be subsequently treated with a specific irradiation suitable for increasing the crosslinking.

While irradiation with laser light may result in de-crosslinking of the plastic material in the case of ablation, melting, polishing or modification, irradiation with other light beams or parameters may result in crosslinking of the plastic material.

The method of the invention thus means that the plastic material can be processed by vaporization or polishing by irradiation alone, and thus in a contactless manner, and then in a contactless manner regain its hardness or improve the properties of the material.

These steps of the method may be performed directly one after the other. They may also be carried out simultaneously, wherein the decrosslinking takes place during the processing of the blank, the laser being focused on the interior region of the blank and/or its surface, the irradiation with the particle beam counteracting the decrosslinking. In order to be able to process plastic parts in a continuous process, these parts can be transported on a transport device through treatment stations (e.g. blank placement, ablation, polishing, crosslinking, final cleaning, final inspection, packaging). However, a stationary blank may be machined and irradiated with a beam of laser light. This makes it particularly easy to change the chronological order of the method steps.

During processing, the plastic part may be heated by radiation to facilitate processing. However, they can also be heated by separately introduced infrared heating, for example, in particular in order to accelerate polishing and/or crosslinking.

In particular, thermosets and thermoplastics are suitable for use in the methods of the present invention, and thermosets and thermoplastics may be crosslinked by some form of irradiation to form an elastomer or thermoset.

Acrylic or methacrylic esters are particularly preferred as plastics materials which are processed with laser light and then crosslinked with irradiation.

The method is also particularly suitable for manufacturing implants. Laser processing refers to a special implant, preferably also for special surgical treatments, which can be manufactured from a blank, which implant can then be hardened again by cross-linking the plastic material. By a contactless treatment of the plastic material is meant that the plastic material suitable for use as an implant can actually be de-crosslinked and then re-crosslinked, but eventually has a similar or identical crosslinking as the crosslinking of the starting material. This avoids problems that may occur when the plastic material authorized for use in the manufacture of the implant is modified by laser treatment and associated de-crosslinking so as to no longer be suitable for use as an implant.

Good results have been obtained with this method for ocular implants, in particular for intraocular lenses.

Processing of plastic materials with ultrashort pulse lasers (USP lasers) is particularly suitable for the inventive processing of plastic materials, since particularly precise improvements to plastic materials can be obtained here, from partial improvements in the properties of the material by vaporization of the material region to subsequent polishing by melting of the material on the surface of the plastic material.

In order to be able to manufacture specific plastic articles for use as mechanical components or as implants, for example, it is advantageous to use a laser to vaporize a portion of the plastic material during processing or to modify the refractive index inside the blank. Furthermore, during processing, the plastic material may be polished with a laser, during which certain areas of the material are ablated or liquefied, thus obtaining an improved surface tension effect, with the aim of smoothing the surface to prevent microstructures on the surface.

When machining plastic material with laser light on the surface of the plastic material, a simple machining of the plastic material is obtained. However, even if the surface of the plastic material is machined, a machined area of the plastic material must be created inside the plastic material, below the surface.

In addition to this type of machining near the surface, the laser beam may also be used to perform specific machining of the plastic material inside the plastic material. This relates in particular to a region of plastics material at least 0.2mm from the surface of the plastics material.

By coordinating the decrosslinking of the laser and the crosslinking of the irradiation, specific predetermined material properties can be set in the surface region or volume region of the blank.

In the same way, the increase in decrosslinking can be compensated for by an increase in crosslinking, or by a combination of defined decrosslinking and defined crosslinking to establish the desired material properties.

However, the defined combination of material properties may also be used to provide different degrees of de-crosslinking and cross-linking at different points, surface areas or volume areas. This means that the blank obtains different material properties depending on the blank area under consideration.

For example, the blank may have an outer surface region that is particularly hardened by irradiation and an inner region that is less strongly hardened by irradiation.

In this way, for example in the case of a lens, the refractive index in one region may be increased while the refractive index in another region may be decreased or increased in the beam path through the lens to balance the variations caused by processing the blank or to obtain a particular refractive index.

As in the case of lasers, the total duration, pulse duration and intensity may all be varied, and so these parameters may also be used to alter the effect of irradiation on the properties of the material in the irradiated region.

In order to irradiate the plastic material after de-crosslinking to obtain at least a partial re-crosslinking of the plastic material, it is proposed to irradiate with photons.

However, it has also proven advantageous to irradiate the plastic material with electrons, beta radiation or gamma radiation.

The treatment of the plastic material with high energy electron beam, beta radiation or gamma radiation imparts the plastic material with the thermal, mechanical and chemical properties of the high performance plastic material. This means that inexpensive commodity plastics can also be used in the process. The radiation crosslinking may be performed after the shaping as a final processing step in the processing chain. The specific processing, in particular the surface hardness thus obtained, means that the plastic material parts can also be loosely packed in a pallet box or cardboard box. Because a precise dose of radiation is applied, crosslinking can be precisely controlled. The material properties can be precisely defined in advance and achieved by means of a precisely positioned-precise (pinpoint-accurate) irradiation. The shielding can even change the degree of crosslinking inside the molded part. In this way, the plastic material parts can have different durometers.

In contrast to chemical crosslinking methods, radiation crosslinking is performed at low temperatures; this facilitates processing.

Particularly good results are obtained with the crosslinking of Polyethylene (PE), polyamide (PA), polybutylene terephthalate (PBT) and polyvinyl chloride (PVC). Furthermore, the method of the present invention is applicable to thermoplastic elastomers (TPE) and polypropylene (PP), but is also applicable to thermosets (e.g., methacrylates and polymethacrylates).

The invention therefore also relates to a plastic material, in particular an ocular implant or an intraocular lens, having at least one region in which the plastic material has been processed with a laser, in which connection the decrosslinking of the plastic material is carried out with a laser and the plastic material is post-treated in at least one region to re-crosslink the plastic material. One example of this type of laser machining is vaporizing a portion of the plastic material or actually polishing the plastic material by modifying its surface.

It is particularly preferred that the plastic material is polished after vaporizing a portion of the plastic material and that they are post-treated to crosslink the plastic material again.

The term "plastic material" as used in the context of the present invention is understood to mean any plastic material as a raw material, any plastic material as a formed part or any plastic material part (e.g. a mechanical element or an implant), or indeed also a plastic surface or a plastic material area inside another part.

Exemplary embodiments of the present invention describe the manufacture of intraocular lenses. The lens is made from a blank that is initially material ablated using an ablative laser. In this regard, the region of the blank irradiated with the laser light onto the blank is vaporized. This material ablation of 0.01 μm/pulse to 10 μm/pulse is achieved with a laser with a pulse energy of 0.1 μm J to 10. Mu.J. In this regard, the pulse duration of the USP laser is less than 1ns, and the laser wavelength is preferably between 193nm and 370 nm. Advantageously, the focal diameter is between 5 and 5 μm.

The blank composed of acrylate is then initially shaped by vaporization of the surface area so that it almost reaches the prescribed final shape. Next, the blank is further processed with a polishing laser.

As this results in a de-crosslinking in the processing areas, and then the blank is treated with electron beams, with beta radiation or with gamma radiation in at least these areas. The duration of the treatment is such that the processed surface at least resumes the degree of crosslinking of the blank, or may even have a higher degree of crosslinking at least in the component.

This makes it possible to manufacture plastic material parts, in particular medical implants having a particularly hard and solvent-resistant surface, and thus bio-resistance.

The combination of a de-crosslinking method using a laser and a crosslinking method by radiation treatment means that plastic material parts can also be produced with different densities. Thus, for example, for protection purposes, an intraocular lens manufactured by this method may have a layer of plastic material on the surface that is harder (i.e. more cross-linked) than the interior (interor). A cross-linking gradient can be obtained in a cross-section through the plastic material part and, due to the prescribed cross-linking, the refractive index inside the lens or even inside (inside) can be specifically changed.

This allows the light beam passing through the plastic material object to be influenced not only by the material properties and shape of the surface of the plastic material object, in particular the lens, but also by the preset material density in the plastic material, in particular also by the internal density gradient of the plastic material.

In a preferred exemplary embodiment, the plastic material blank is modified during the laser processing and then irradiated in such a way that after irradiation the plastic material again has the material properties of the plastic material blank.

The method described in DE 102017002986A1 is particularly advantageous in view of the processing of plastic materials with lasers.

An exemplary embodiment is shown in the drawings, which will be described below.

The figure shows diagrammatically a side view of the processing unit.

The conveyor belt shown in fig. 1 conveys lenses 2 (generally numbered only) through a plurality of processing stations. By way of example only, the IR emitter 3 (heated lens 2) is shown as a first processing station. The next processing station is a laser 4 specifically modifying the lens shape. Next, there is a processing station 5 with a laser, which polishes the surface of the lens. The fourth station is an emitter 6 for a high-energy electron beam, beta radiation or gamma radiation. The last station is a packaging station 7 where the lenses 3 are packaged in a sterile manner.

As an alternative, the lens may also be in a rest position and various processing stations are directed past the lens. Furthermore, a combination of these two modes of operation may be implemented.

Irradiation for crosslinking can be performed with an electron beam. In this respect, electron energies of e=150 keV to 300keV can be used, which can also be up to 1.5MeV in the limit. For example, the average power of the electron beam is p=1 to 5kW.

A suitable dose may be pd=50-500 kGy (kGy). The dose may also be provided in several doses administered in succession. For this purpose, the emitter may be passed through the workpiece a plurality of times, thereby eventually applying the required total dose for obtaining the desired cross-linking.

In practice, the irradiated surface A is 2X 20cm. This results in an intensity I of 0.5kW/cm2 to 3kW/cm2. A suitable advancement speed of the surface is v=3-10 cm/s.

In order to obtain an appropriate intensity per unit area, the data may be enlarged or reduced.

In the case of stationary irradiation, the appropriate intensities, irradiation durations and dose levels are calculated.

The method described in DE 102017002986A1 is the normal processing of plastic material blanks with a laser. In this respect, the decrosslinking takes place, which should then be compensated for. On the other hand, the material properties of the plastic material blank are specifically improved on its surface and optionally on its internal volume by a combination of pre-specified de-crosslinking and crosslinking.

The special processing described in DE 10201002986 B4 also describes the decrosslinking method steps of the exemplary embodiment, followed by the crosslinking method steps described in the present application.

Claims (16)

1. A method for processing a plastic material of an object of plastic material, wherein the plastic material is processed with a laser and is at least partly modified, wherein the plastic material is de-crosslinked and then irradiated to at least partly resume the crosslinking of the plastic material, characterized in that during the processing of the plastic material with the laser, the plastic material is ablated in a processing area, while or subsequently the processing area is polished with the laser or another laser, and the plastic material is irradiated in the polished processing area.

2. The method of claim 1, wherein the processing region is located on an outer surface of the plastic material object.

3. Method according to one of the preceding claims, characterized in that the plastic material is a thermoplastic or a thermosetting plastic.

4. Method according to one of the preceding claims, characterized in that the plastic material is an acrylate, preferably a methacrylate.

5. The method according to one of the preceding claims, characterized in that the plastic material is an ocular implant.

6. Method according to one of the preceding claims, characterized in that the plastic material contributes to vision, such as, in particular, an intraocular lens or a contact lens.

7. The method according to any of the preceding claims, wherein the laser is a USP laser.

8. Method according to one of the preceding claims, characterized in that during the processing a part of the plastic material is vaporized with the laser.

9. Method according to one of the preceding claims, characterized in that the plastic material is polished with the laser during or after the processing.

10. Method according to one of the preceding claims, characterized in that the plastic material is processed with the laser on its surface.

11. Method according to one of the preceding claims, characterized in that the plastic material is also processed with the laser at least inside the plastic material.

12. Method according to one of the preceding claims, characterized in that the plastic material is irradiated with a particle beam, in particular an electron beam.

13. Method according to one of the preceding claims, characterized in that the plastic material is irradiated with photons.

14. Method according to one of the preceding claims, characterized in that the plastic material is irradiated with beta radiation or gamma radiation.

15. Method according to one of the preceding claims, characterized in that a plastic material blank is modified during laser machining and then irradiated in such a way that after irradiation the plastic material again has the material properties of the plastic material blank.

16. A plastic material, in particular an ocular implant or an intraocular lens, having at least one region in which the plastic material has been laser-machined and thus at least partially improved, characterized in that the region has been post-treated to re-crosslink the plastic material, wherein in the region, after vaporization of a portion of the plastic material, the plastic material has been polished.