Laser-markable and laser-weldable polymeric materials

Abstract

The present invention relates to colored 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. A laser-markable and/or laser-weldable polymer composition, said polymer composition comprising: a polymer, at least one colorant and, as an absorber, a doped tin oxide or indium oxide having a specific surface area of at least 15 m.sup.2/g, wherein said absorber is in the form of porous aggregates of primary particles, and said at least one colorant is selected from organic pigments and dyes.

2. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein said absorber is at least one fluorine-doped tin oxide, antimony-doped tin oxide, or indium tin oxide.

3. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein said absorber is a doped tin oxide in which the content of dopants is 1-15 mol %, based on the tin oxide.

4. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein the porous aggregates of absorber have a number average particle size of <5 m, measured at the D.sub.90 by means of laser diffraction.

5. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein the primary particles have a diameter of less than 100 nm.

6. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein said absorber is employed in a concentration of 0.005 to 1% by weight, based on the polymer.

7. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein the polymer is a thermoplastic, thermoset or elastomer.

8. A process for preparation of laser-markable and/or laser-weldable polymer compositions according to claim 1, said process comprising adding the absorber simultaneously or successively by compounding, via a masterbatch or via pastes or by direct addition to the polymer, optionally adding one or more additives, and shaping the polymer under the action of heat.

9. A method for imaging, comprising marking a laser-markable and/or laser-weldable polymer compositions according to claim 1.

10. A molding composition, semi-finished product, or finished part comprising a laser-markable and laser-weldable polymer composition according to claim 1.

11. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein the absorber has a specific surface area of at least 20 m.sup.2/g.

12. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein the absorber has a specific surface area of at least 25 m.sup.2/g.

13. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein the absorber has a weight average particle size of 10 m, measured at the D.sub.90 by means of laser diffraction.

14. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein the absorber has a weight average particle size of 2 m, measured at the D.sub.90 by means of laser diffraction.

15. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein the primary particles have a diameter of less than 50 nm.

16. The laser-markable and/or laser-weldable polymer composition according to claim 6, wherein said absorber is employed in a concentration of 0.05-0.5% by weight, based on the polymer.

17. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein said absorber is a support-free antimony-doped tin oxide or a fluoride-doped tin oxide, wherein the content of dopants in the tin oxide is 1-15 mol %.

18. The laser-markable and/or laser-weldable polymer composition according to claim 1, wherein said absorber is a support-free antimony-doped tin oxide or a fluoride-doped tin oxide, wherein the content of dopants in the tin oxide is 3-10 mol %.

Description

EXAMPLES

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

(1) 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 liters 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

(2) 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

(3) 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 liters 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

(4) 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

(5) 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 liters 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

(6) 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 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

(7) 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

(8) 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

(9) 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

(10) 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.

(11) 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.