LASER-MARKABLE AND LASER-WELDABLE POLYMERIC MATERIALS

Abstract

The present invention relates to coloured laser-markable and laser-weldable polymeric materials which are distinguished by the fact that they comprise, as absorber, at least one doped tin oxide or indium oxide having a large specific surface area.

Claims

1. Laser-markable and/or laser-weldable polymers, characterised in that the polymer comprises at least one colorant and, as absorber (laser additive), a doped tin oxide or indium oxide having a specific surface area (BET, N.sub.2 absorption) of at least 15 m.sup.2/g.

2. Laser-markable and/or laser-weldable polymers according to

1. , characterised in that they comprise, as absorber, at least one fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO) or indium tin oxide (ITO).

3. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the content of one or more dopants in the tin oxide is 1-15 mol %, based on the tin oxide.

4. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the absorber has a number average particle size of <5 m, measured at the D.sub.90 by means of laser diffraction (determined using a Malvern Mastersizer 2000).

5. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the absorber consists of aggregates of primary particles having a diameter of less than 100 nm.

6. Laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the laser additive is employed in concentrations of 0.005 to 1% by weight, based on the polymer.

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

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

9. Process for the preparation of laser-markable and/or laser-weldable polymers according to claim 1, characterised in that the addition of the laser additive 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.

10. A method for imaging, comprising marking the laser-markable and/or laser-weldable polymers according to claim 1.

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

Description

EXAMPLES

Example 1: Antimony-Doped Tin Oxide Having a Large Specific Surface Area

[0044] A mixture of 446 g of a 50% by weight aqueous SnCl.sub.4 solution, 135 ml of HCl (37% by weight), 96.5 g of a 35% by weight aqueous SbCl.sub.3 solution is metered continuously to the suspension over the course of 90 min into 1.5 litres of initially introduced dilute hydrochloric acid in a stirred reactor at 60 C. with vigorous stirring. The pH is kept constant at pH 2 by simultaneous metered addition of sodium hydroxide solution. After addition of the entire amount of the solution, the mixture is stirred at 60 C. for a further 30 min, subsequently cooled to room temperature with stirring, and the pigment obtained is filtered off via a suction filter, washed with water, dried at 140 C. and calcined at 700 C. under air for 30 min. A grey pigment powder is obtained. The Sn:Sb ratio in the coating is about 92:8. The X-ray diffraction pattern of the pigment shows only cassiterite. The pigment powder is ground in a planetary ball mill with zirconium balls and sieved. The particle size distribution is measured by means of laser diffraction in a Malvern Mastersizer 2000. The product has a volume average D.sub.90 of 9.1 m and a D.sub.10 of 1.8 m. The BET surface area of the pigment is determined by nitrogen adsorption using a Micrometrics ASAP 2420 instrument. The specific surface area (BET) is 52 m.sup.2/g.

Example 2: Antimony-Doped Tin Oxide Having a Moderate Specific Surface Area

[0045] A pigment is prepared by modifying the procedure from Example 1 in the parameters temperature and metering rate of the starting materials. At a temperature of 80 C. and with metering of the starting materials over 6 hours, a pigment having a specific surface area of 17 m.sup.2/g is obtained.

Example 3: Antimony-Doped Tin Oxide Having a Large Specific Surface Area

[0046] A mixture of 465 g of a 50% by weight aqueous SnCl.sub.4 solution, 135 ml of HCl (37% by weight), 48.2 g of a 35% by weight aqueous SbCl.sub.3 solution is metered to the suspension over the course of 90 min at pH 1.6 into 1.5 litres of initially introduced dilute hydrochloric acid in a stirred reactor at 40 C. with vigorous stirring. After addition of the entire amount of the solution, the mixture is stirred at 40 C. for a further 30 min, subsequently cooled with stirring, and the pigment obtained is filtered off via a suction filter, washed with water, dried at 140 C. and calcined at 700 C. under air for 30 min. A blue-grey pigment powder is obtained. The Sn:Sb ratio in the coating is about 96:4. The pigment powder is ground in a ball mill and then sieved. The particle size distribution is measured by means of laser diffraction (Malvern Mastersizer 2000). The product has a volume average D.sub.90 of 7.4 m and a D.sub.10 of 0.9 m, the specific surface area (BET) is 38 m.sup.2/g. Under a scanning electron microscope, strongly aggregated particles having primary particles with a size of 30-40 nm are evident.

Example 4: ITO Pigment

[0047] 20 g of yellow ITO nanopowder from Nanoni Materials&Technology is calcined at 450 C. under forming gas (5% of H.sub.2) in a tubular oven for 45 min, subsequently ground and sieved. A blue-grey powder having a BET surface area of 25 m.sup.2/g and a particle size of the aggregates of 8 m (D.sub.90) is obtained. The primary particles are <50 nm (SEM).

Example 5: Comparative Example

[0048] A mixture of 110 ml of hydrochloric acid (37% of HCl), 357.7 g of SnCl.sub.2 solution (49% by weight of SnCl.sub.2) and 52.1 g of SbCl.sub.3 solution (35% by weight) and 130 g of a 30% hydrogen peroxide solution is metered over the course of 8 hours into 1.5 litres of initially introduced dilute hydrochloric acid in a stirred reactor at 80 C. with vigorous stirring. After addition of the entire amount of the solution, the mixture is stirred for a further 30 min, subsequently cooled to room temperature with stirring, and the reaction mixture is adjusted to pH 3. The pigment obtained is filtered off via a suction filter, washed with water, dried at 140 C. and calcined at 800 C. under air for 30 min. A grey pigment powder is obtained. The Sn:Sb ratio in the coating is about 92:8. The X-ray diffraction pattern of the pigment shows only cassiterite. The pigment powder is ground in a planetary ball mill with zirconium balls and sieved. The product has a volume average D.sub.90 of 8.3 m, the specific surface area (BET) is 11.8 m.sup.2/g.

Example 6

[0049] 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

[0050] 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 mm90 mm1.5 mm (whd) in an injection moulding machine. The plastic plates are then laser-marked using a pulsed YVO.sub.4 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 m 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.

Example 7

[0051] Small plastic plates which comprise the laser pigment from Example 2 are produced using the process from Example 3. The plates are laser-treated analogously to Example 6. Stable and accurately detailed pale markings are also obtained here.

Example 8: Pale Marking with ITO

[0052] 990 g of PE granules are wetted with 2 g of dispersion aid (process aid 24) in a drum mixer. 1 g of the pigment from Example 4 and 10 g of dark-brown masterbatch (Polyone 2001-BN-50 PE) are subsequently added and incorporated in the drum mixer for 2 min. The mixture obtained is compounded in a co-rotating twin-screw extruder under 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 mm90 mm1.5 mm (BHT) in an injection-moulding machine. The red-brown plastic plates are laser-marked described analogously to Example 6. Perfect pale laser marks are also obtained here up to a speed of 3000 mm/s. The line marking is very defined with accurate detail.

Example 9: Comparative Example Without Colorant

[0053] Small plastic plates are produced by the process described in Example 6, but without addition of the green coloured pigment PV Fast Green GG01. In this way, pale opaque plastic plates are obtained. These are laser-treated as described in Example 6. When the surface is examined closely, a marking with a pale appearance can also be discerned here, but without significant contrast to the background. The marking is only discernible with difficulty and is unusable for practical use. The experiment shows that the pigment in the plastic only gives rise to a usable pale marking in combination with a colorant.

Example 10: Comparative ExamplePigment Having a Small Specific Surface Area

[0054] 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 5 and 1 g of organic green coloured pigment (PV Fast Green GG01) are subsequently added and incorporated in the drum mixer for 2 min. The mixture obtained is converted into plates measuring 60 mm90 mm1.5 mm (BHT) analogously to Example 6 and laser-marked.

[0055] Pale-grey to dark-grey markings are obtained up to a speed of 3000 mm/s. The dark inscriptions are difficult to see on the dark background. The result shows that ATO pigments having a specific surface area of less than 15 m.sup.2/g do not produce perfect pale markings.