LASER-MARKABLE AND LASER-WELDABLE POLYMERIC MATERIALS

Abstract

The present invention relates to laser-markable and laser-weldable polymeric materials which are distinguished by the fact that they comprise, as laser absorber, at least one copper-doped zinc sulfide.

Claims

1. Laser-markable and/or laser-weldable polymers, characterised in that they comprise, as absorber, at least one copper-doped zinc sulfide.

2. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the copper content in the zinc sulfide is 0.5-15 mol %, based on the sum of copper sulfide and zinc sulfide.

3. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the copper-doped zinc sulfide has a particle size of 20-1000 nm.

4. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the copper-doped zinc sulfide is applied to an inorganic support.

5. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the copper-doped zinc sulfide is additionally provided on the surface with a zinc sulfide layer.

6. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the copper-doped zinc sulfide additionally has an organic post-coating.

7. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the laser additive is employed in concentrations of 0.01 to 1% by weight, based on the polymer.

8. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the polymer is a thermoplastic, thermoset or elastomer.

9. Laser-markable and/or laser-weldable polymers according claim 1, characterised in that the polymer additionally comprises one or more coloured pigments and/or dyes.

10. Process for the preparation of laser-markable and/or laser-weldable polymers according to characterised in that the addition of the copper-doped zinc sulfide is carried out simultaneously or successively by compounding, via a masterbatch or via pastes or by direct addition to the polymer, and one or more additives are optionally added and the polymer is then shaped under the action of heat.

11. A method for the production of moulding compositions, semi-finished products or finished parts and for imaging which comprises incorporating the laser-markable and/or laser-weldable polymers according to claim 1 into the compositions, products or parts.

12. Moulding compositions, semi-finished products and finished parts consisting of the laser-markable and laser-weldable polymer according to claim 1.

13. Copper-doped zinc sulfide, characterised in that it comprises 0.5-15 mol % of copper, based on the sum of copper sulfide and zinc sulfide, and has a particle size of 20-1000 nm.

Description

EXAMPLES

Example 1

[0051] 50 g of zinc sulfide having a particle size of 0.3 μm (D.sub.50) are suspended in 200 ml of water. 100 ml of a copper(II) sulfate solution which contains 6.4 g of CuSO.sub.4*5 H.sub.2O and has been adjusted to pH 4 using acetic acid are added dropwise at room temperature with stirring. When the addition is complete, the suspension is warmed to 60° C. and stirred for a further 1 hour. The product is subsequently filtered off, washed with water and dried at 110° C. The grey-green product comprises 5 mol % of copper sulfide, based on the sum of zinc sulfide and copper sulfide.

[0052] 1 kg of PP granules (Metocene 648T, Basell) is wetted with 2 g of dispersion aid (Process-Aid 24, Colormatrix) in a drum mixer. 5 g of the pigment from Example 1 and 1 g of organic green coloured pigment (PV Fast Green GG01, Clariant) are added and incorporated for 2 min in the drum mixer. The resulting mixture is compounded in a co-rotating twin-screw extruder with high shear at a jacket temperature of 250-260° C., extruded through a pelletising die, cooled in a water bath and granulated by means of a rotating blade. The compound obtained is dried at 100° C. for 1 h and converted into plates measuring 60 mm×90 mm×1.5 mm (W×H×D) in an injection moulding machine. The plastic plates are then laser-marked using a pulsed YVO4 laser having a wavelength of 1064 nm and a maximum output power of 10.5 W. The test grid varies the speed between 500 and 5000 mm/s and the frequency between 20 and 100 kHz. Filled areas with a line spacing of 50 μm and also line text are lasered. Stable pale laser markings are obtained up to a speed of 3000 mm/s. The line marking is very defined with accurate detail and confirms the homogeneous distribution of the additive in the plastic.

Example 2

[0053] 12.8 g of CuSO.sub.4×5 H.sub.2O are dissolved in 500 ml of H.sub.2O, and the pH is adjusted to 4 using acetic acid. 50 g of talc Plustalc H05AW, Mondo Minerals, are stirred into the solution at room temperature with vigorous stirring, and 50 g of zinc sulfide powder (particle size: D.sub.50=0.3 μm) are subsequently introduced with stirring. The suspension is stirred at room temperature for 30 minutes and at 60° C. for a further 60 minutes. After filtration and washing, the product is dried at 110° C. and finally very finely powdered (D.sub.50≦1000 nm) in a planetary grinder. The proportion of copper sulfide is 10 mol %, based on the sum of copper sulfide and zinc sulfide. The colour of the powder is a pale olive green.

[0054] The pigment powder obtained is incorporated into polypropylene analogously to Example 1. The same starting weights and likewise the green coloured pigment are used. The laser treatment under the same conditions likewise gives stable pale laser markings up to a speed of 3000 mm/s. The line marking is very defined and accurately detailed and also confirms the homogeneous distribution of the laser additive in the plastic in Example 2.

Example 3

[0055] 5.4 g of CuSO.sub.4*5 H.sub.2O are dissolved in 500 ml of H.sub.2O. 100 g of zinc sulfide powder (particle size: D.sub.50=0.3 μm) are subsequently introduced at room temperature with stirring. A pH of 4.5 is set. The suspension is stirred at room temperature for 30 minutes and subsequently at 60° C. for a further 60 minutes. The solid is then filtered off, washed and dried at 110° C., giving a pale grey-green powder. The copper sulfide content is 2 mol %, based on the sum of zinc sulfide and copper sulfide.

[0056] The mixture is processed further analogously to Example 1 firstly to give a compound and subsequently to give small plates. The plates are subsequently laser-marked with the test grid corresponding to Example 1.

[0057] The pigment powder obtained is incorporated into polypropylene analogously to Example 1. The same starting weights and likewise the green coloured pigment are used. The laser treatment under the same conditions likewise gives stable pale laser markings up to a speed of 2000 mm/s. The line marking is very defined and accurately detailed and also confirms the homogeneous distribution of the laser additive in the plastic in Example 3.

Example 4

Laser Welding

[0058] In order to test the laser welding, plastic plates from Example 1 are used. The plates form, as laser-absorbent material, the underside of the element to be welded. The upper side consists of a laser-transparent plate of pure polypropylene (Metocene 648T, Basell). The laser-transparent plate like-wise has the dimensions 60 mm×90 mm×1.5 mm (W×H×T) and is produced on an injection-moulding machine under the same conditions as in Example 1. In order to test the weldability, the 1064 nm laser (Trumpf Vectormark 5, 10.5 W maximum output power) is again used, only this time in continuous (cw) mode, i.e. unpulsed. The laser beam here is set so that the focus is 4 mm below the surface of the lower laser-absorbent plate. The laser-transparent plate, which is additionally fixed at the edges by magnets, lies on the laser-absorbent plate which comprises the copper-doped ZnS. The maximum laser power (100%) is set. The speed of the laser beam is 200 mm/s. 1000 parallel lines having a length of 1 mm and a separation of 50 μm are lasered successively. With an advance of 10 mm/s, a weld seam with a width of 1 mm thus forms. The weld seam is produced cleanly and both parts are firmly connected.