RECYCLABLE PLASTIC PARTS WITH METALLIC APPEARANCE AND BEING AUTOMATICALLY RECOGNIZABLE BY NIR SPECTROSCOPY AND SORTABLE

Abstract

Plastic part having a mean thickness t.sub.pl containing a mixture of effect pigments comprising flaky aluminum pigments obtained by milling of aluminum or aluminum-based alloy powder in a concentration c.sub.Al and silvery, absorbing pearlescent pigments in a concentration c.sub.P, wherein i) for flaky aluminium pigments having a D.sub.107.0 m: c.sub.Al*t.sub.pl is in a range of 0.0 to 0.20 wt. % cm, or ii) for flaky aluminium pigments having a D10<7.0 m: c.sub.Al*t.sub.pl is in a range of 0.0 to 0.036 wt. % cm, wherein each concentration refers in wt. % to the total plastic part.

Claims

1. plastic part having a mean thickness t.sub.pl containing a mixture of effect pigments comprising flaky aluminum pigments obtained by milling of aluminum or aluminum-based alloy powder in a concentration c.sub.Al and silvery, absorbing pearlescent pigments in a concentration c.sub.P, wherein i) for flaky aluminum pigments having a D.sub.107.0 m: c.sub.Al*t.sub.pl is in a range of 0.0 to 0.20 wt. % cm, or il) for flaky aluminum pigments having a D.sub.10<7.0 m: c.sub.Al*t.sub.pl is in a range of 0.0 to 0.036 wt. % cm, wherein each concentration refers in wt. % to the total weight of the plastic part.

2. The plastic part of claim 1, wherein the silvery, absorbing pearlescent pigments are selected from the group consisting of: a) pearlescent pigments comprising a transparent substrate which is coated with a high-refractive index layer with n>1.8, which comprises an iron-oxide with Fe(II)-ions, b) pearlescent pigments comprising a transparent substrate which is coated with a high-refractive index layer with n>1.8, which comprises titanium suboxide or a pearlescent pigment comprising a substrate with a high-refractive index with n>1.8 layer, which comprises titanium suboxide that is optionally coated with a high-refractive index layer with n>1.8, c) pearlescent pigments comprising a transparent substrate which is coated with a high-refractive index layer with n>1.8, which comprises titanium oxynitride, d) pearlescent pigments comprising a transparent substrate which is coated with a layer comprising carbon, wherein the carbon is enclosed in a particulate form in another metal oxide layer or is formed as a separate, individual layer, e) a transparent substrate coated with a first layer comprising a mixture of the oxides of titanium, iron and at least one of cobalt and chromium and a second layer on the first layer, wherein the second layer comprises an oxide of titanium, and mixtures or combinations of the pearlescent pigments a) to e) or pearlescent pigments with mixtures or combinations of the various coating layers mentioned in the pearlescent pigments a) to e).

3. The plastic part of claim 1, wherein the flaky aluminum effect pigment has a d.sub.50 in a range of 7.0 to 95.0 m, preferably in a range of 8.0 to 40.0 m.

4. The plastic part of claim 1, wherein the flaky aluminum effect pigments of type i) have a mean thickness h.sub.Al in a range of 100 to 350 nm or/and wherein the flaky aluminum effect pigments of type ii) have a mean thickness h.sub.Al in a range of 80 to 170 nm.

5. The plastic part of claim 1, wherein for flaky aluminum effect pigments of type i) c.sub.Al*t.sub.pl is in a range of 0.02 to 0.2 wt. % cm or for flaky aluminum effect pigments of type ii) c.sub.Al*t.sub.pl is in a range of 0.0020 to 0.030 wt % cm.

6. The plastic part of claim 1, wherein the product of t.sub.pl with the concentration of silvery, absorbing pearlescent pigment c.sub.P is: I. for the case that c.sub.Al*t.sub.pl=0.000 cm wt %, 0.40 cm wt. %c.sub.P*t.sub.pl<about 2.0 cm wt. %, or II. for the aluminum effect pigments being of type i): $\begin{array}{cc}0.02\mathrm{cm}\mathrm{wt}.\%c_{\mathrm{Al}}*t_{\mathrm{pl}}0.05\mathrm{cm}\mathrm{wt}.\%,0.1\mathrm{cm}\mathrm{wt}.\%c_P*t_{\mathrm{pl}}\mathrm{about}1.\mathrm{cm}\mathrm{wt}.\%,& )\end{array}$ $\begin{array}{cc}0.05\mathrm{cm}\mathrm{wt}.\%<c_{\mathrm{Al}}*t_{\mathrm{pl}}0.1\mathrm{cm}\mathrm{wt}.\%,0.05\mathrm{cm}\mathrm{wt}{c}_P*t_{\mathrm{pl}}\mathrm{about}1.\mathrm{cm}\mathrm{wt}.\%,& )\end{array}$ $\begin{array}{cc}0.1\mathrm{cm}\mathrm{wt}.\%<c_{\mathrm{Al}}*t_{\mathrm{pl}}0.2\mathrm{cm}\mathrm{wt}.\%,0.02\mathrm{cm}\mathrm{wt}.\%<c_P*t_{\mathrm{pl}}\mathrm{about}0.8\mathrm{cm}\mathrm{wt}.\%,& )\end{array}$ or III. for the aluminum effect pigments being of type ii): $\begin{array}{cc}0.002\mathrm{cm}\mathrm{wt}.\%c_{\mathrm{Al}}*t_{\mathrm{pl}}0.02\mathrm{cm}\mathrm{wt}.\%,0.1\mathrm{cm}\mathrm{wt}.\%c_P*t_{\mathrm{pl}}\mathrm{about}0.8\mathrm{cm}\mathrm{wt}.\%,& )\end{array}$ $\begin{array}{cc}0.02\mathrm{cm}\mathrm{wt}.\%<c_{\mathrm{Al}}*t_{\mathrm{pl}}0.03\mathrm{cm}\mathrm{wt}.\%,0.02\mathrm{cm}\mathrm{wt}{c}_P*t_{\mathrm{pl}}\mathrm{about}0.3\mathrm{cm}\mathrm{wt}.\%.& )\end{array}$

7. The plastic part of claim 1, wherein the product of t.sub.pl with the concentration of silvery, absorbing pearlescent pigment c.sub.P is: I. for the case that c.sub.Al*t.sub.pl=0.00 cm wt. %, 0.40 cm*wt. %c.sub.P*t.sub.pl<about 2.0 cm wt. %, or II. for the aluminum effect pigments being of type i): $\begin{array}{cc}0.04\mathrm{cm}\mathrm{wt}.\%c_{\mathrm{Al}}*t_{\mathrm{pl}}0.05\mathrm{cm}\mathrm{wt}.\%,0.3\mathrm{cm}\mathrm{wt}.\%c_P*t_{\mathrm{pl}}\mathrm{about}1.\mathrm{cm}\mathrm{wt}.\%,& )\end{array}$ $\begin{array}{cc}0.06\mathrm{cm}\mathrm{wt}.\%<c_{\mathrm{Al}}*t_{\mathrm{pl}}0.1\mathrm{cm}\mathrm{wt}.\%,0.05\mathrm{cm}\mathrm{wt}{c}_P*t_{\mathrm{pl}}\mathrm{about}0.8\mathrm{cm}\mathrm{wt}.\%,& )\end{array}$ $\begin{array}{cc}0.1\mathrm{cm}\mathrm{wt}.\%<c_{\mathrm{Al}}*t_{\mathrm{pl}}0.2\mathrm{cm}\mathrm{wt}.\%,0.02\mathrm{cm}\mathrm{wt}.\%<c_P*t_{\mathrm{pl}}\mathrm{about}0.7\mathrm{cm}\mathrm{wt}.\%,& )\end{array}$ or III. for the aluminum effect pigments being of type ii): $\begin{array}{cc}0.04\mathrm{cm}\mathrm{wt}.\%c_{\mathrm{Al}}*t_{\mathrm{pl}}0.02\mathrm{cm}\mathrm{wt}.\%,0.12\mathrm{cm}\mathrm{wt}.\%c_P*t_{\mathrm{pl}}\mathrm{about}0.8\mathrm{cm}\mathrm{wt}.\%,& )\end{array}$ $\begin{array}{cc}0.02\mathrm{cm}\mathrm{wt}.\%<c_{\mathrm{Al}}*t_{\mathrm{pl}}0.03\mathrm{cm}\mathrm{wt}.\%,0.08\mathrm{cm}\mathrm{wt}{c}_P*t_{\mathrm{pl}}\mathrm{about}0.26\mathrm{cm}\mathrm{wt}.\%.& )\end{array}$

8. The plastic part of claim 1, wherein the optical density OD of the plastic part is 1.5.

9. The plastic part of claim 1, wherein the aluminum effect pigment is coated with a metal oxide which is selected from the group consisting of SiO.sub.2, Ce-oxide, Mo-oxide, V-oxide, Cr-oxide and mixtures or combinations thereof.

10. The plastic part of claim 1, wherein the silvery pearlescent pigments are selected from the group consisting of: a) pearlescent pigments of type a), wherein the pearlescent pigment has a coating comprising a metal oxide layer comprising Ti- and Fe-ions, wherein the Fe-ions are mainly Fe(II) ions, which is preferably an ilmenite (FeTiO.sub.3) layer, magnetite (Fe.sub.3O.sub.4) or mixtures thereof, b) pearlescent pigments of type b), wherein the titanium suboxide can be represented by the formula
Ti.sub.nO.sub.2n-1(III) wherein n in an integer of 1 to 10, c) pearlescent pigments of type c), wherein the titanium oxynitride can be represented by the formula
Ti.sub.xN.sub.yO.sub.z(IV) wherein x is 0.2 to 0.6, y is 0.05 to 0.6 and z is 0.1 to 0.9, which comprises a solid solution of nitrogen in titanium monoxide, and mixtures or combinations of the pearlescent pigments a) to c) or pearlescent pigments with mixtures or combinations of the various coating layers mentioned in the pearlescent pigments a) to c).

11. The plastic part of claim 1, wherein the silvery pearlescent pigment is of type a) and comprises the following structure: (a) a transparent platelet-shaped synthetic substrate, (b) a titanium oxide layer, followed by (c) a metal oxide layer comprising Ti- and Fe-ions, wherein the Fe-ions are mainly Fe(II)-ions.

12. The plastic part of claim 1, wherein the plastic material is selected from the group consisting of polypropylene (PP high density polyethylene (HDPE), low density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polyethylene terephthalate (PET), polystyrene (PS), polyurethane (PUR), polyacrylate, polyamide (PA) or nylons, polyvinylchloride (PVC), polycarbonate (PC) and ABS/MABS

13. The plastic part of claim 1 further comprising at least one of additives, fillers, conventional color pigments, and additional pearlescent pigments, which are not silvery absorbing pearlescent pigments.

14. The plastic part of claim 1, wherein the total amount of the effect pigments of the effect pigment mixture, optional additional pearlescent pigments and optional additional conventional pigments is equal to or less than 10.0 wt. %, based on the plastic part based on the total amount of the plastic part.

15. The plastic part of claim 1, wherein the mean thickness t.sub.pl is in a range of 50 m to 5 mm.

16. The plastic part of claim 1, wherein the flaky aluminum pigments of type i) have a D.sub.10 value in the range of 7.0 m to 12.0 m.

17. (canceled)

18. A method of separation of waste plastic parts comprising the steps of: a) automatically identifying the nature of plastic parts in a waste mixture of plastics by NIR spectroscopy wherein the waste mixture of plastics comprises the plastic part of claim 1 and b) separating the plastic part of claim 1, which had been identified in step a) from the waste.

Description

EXAMPLES

A Manufacture of Samples:

[0097] Several samples were prepared by extruding masterbatches of metal effect pigments (comparative examples) or absorbing, silvery pearlescent pigments or mixtures thereof in varying concentrations with polypropylene. As aluminum effect pigments a commercially available silver dollar pigment (originally Metalux (abbrev. MEX) 2156, Eckart GmbH) and a commercially available cornflake type (STAPA WM Chromal V/80, Eckart GmbH) were used. The silver dollar pigment paste was first pelletized with a polyolefin to a pellet with 80 wt. % metal pigment and 20 wt. % of the binder (commercially available as MASTERSAFE MP 16-20B, Eckart GmbH). In all references to the pure aluminum pigments these types are abbreviated 2156 and Chromal V hereinafter. As silvery, absorbing pearlescent pigments the commercially available products Symic C604, Symic B604 and Symic A 604 (all from Eckart GmbH) were used. These pearlescent pigments were based on synthetic mica and had a coating of TiO.sub.2 and Fe.sub.2O.sub.3 which were calcined under reducing conditions forming a mixed oxide of TiO.sub.2 and Fe-oxide which includes Fe(II) ions.

[0098] The effect pigments were mixed with polypropylene and extruded to form a masterbatch of 10 wt. % effect pigment concentration. To produce the respective masterbatches of these effect pigments, the process was as follows: [0099] a) Pigments in powder form (pearlescent pigments):
870 g of polypropylene (PP; polypropylene R7051-10N BR, from Braskem, Brazil) in granular form and 100 g of the respective powdered pearlescent pigment, were mixed in a tumbling mixer and then processed to form a granular material in a twin-screw extruder (from Labtech, Bangkok; diameter 20 mm, 28 L/D) at a processing temperature of approx. 230 C. [0100] b) Pigment in paste form (STAPA WM Chromal V/80):
845 g of the polypropylene in granular form, 125 g of STAPA WM Chromal V/80 (a medical white oil paste with a pigment content of 80 wt. %, relative to the total weight of the paste) were mixed in a tumbling mixer and then processed to form a granular material in a twin-screw extruder (from Labtech, Bangkok; diameter 20 mm, 28 L/D) at a processing temperature of approx. 230 C. [0101] c) Pigment in pellet form (MASTERSAFE MP 16-20B):
845 g of polypropylene in granular form and 125 g of MASTERSAFE MP 16-20B (with a pigment content of 80 wt. %, relative to the total weight of the pellet) were mixed in a tumbling mixer and then processed to form a granular material in a twin-screw extruder (from Labtech, Bangkok; diameter 20 mm, 28 L/D) at a processing temperature of approx. 230 C.

[0102] The thus obtained masterbatch granular materials were further diluted with the polypropylene to the desired final pigment contents relative to the proportion by weight of the plate. The final concentrations of the effect pigments are depicted in tables 2 (pure effect pigments) and table 3 (effect pigment mixtures). These masterbatch granular materials were then processed to form plates with a surface area of 100 mm70 mm and a thickness of 2 mm by means of the injection-molding machine (Arburg 221 K-75-250) at a processing temperature of 250 C.

A1 Evaluation of Pure Effect Pigments:

[0103] Comparative Example series 1: Various concentrations of Metalux 2156 (processed as Mastersafe mp 16-20b) without pearlescent pigments. This aluminium effect pigment is of silver dollar type. Its particle size parameters as measured with a Helios/BR are: D.sub.10:9.6 m, D.sub.50=18.0 m and D.sub.90=28.8 m.

[0104] Comparative Example series 2: Various concentrations of STAPA WM Chromal V/80 without pearlescent pigments. This aluminium effect pigment is of cornflake type. Its particle size parameters as measured with a Helios/BR are: D.sub.10:4.3 m, D.sub.50=14.8 m and D.sub.90=33.0 m.

[0105] Example series 3: Various concentrations of Symic C604. This is a silvery absorbing pearlescent pigment comprising a high-refractive index layer comprising Fe(II)-ions. The median particle size d.sub.50,p is 22 m.

[0106] Example series 4: Various concentrations of Symic B604. This is a silvery absorbing pearlescent pigment comprising a high-refractive index layer comprising Fe(II)-ions. The median particle size d.sub.50,p is 14 m.

[0107] Example series 5: Various concentrations of Symic A604. This is a silvery absorbing pearlescent pigment comprising a high-refractive index layer comprising Fe(II)-ions. The median particle size d.sub.50,p is 9.5 m.

A2Evaluation of Effect Pigment Mixtures:

[0108] Examples series 6: Mixtures of MASTERSAFE MP 16-20B with aluminum pigment content of 1.00% and various amounts of Symic B604.

[0109] Examples series 7: Mixtures of MASTERSAFE MP 16-20B with aluminum pigment content of 0.25% and various amounts of Symic B604.

[0110] Examples series 8: Mixtures of MASTERSAFE MP 16-20B with aluminum pigment content of 0.50% and various amounts of Symic B604.

[0111] Examples series 9: Mixtures of STAPA WM Chromal V/80 with 0.1% aluminum pigment content various amounts of Symic A604.

[0112] Examples series 10: Mixtures of STAPA WM Chromal V/80 with 0.15% aluminum pigment content and various amounts of Symic A604.

B Pigment Characterization and Testing Methods:

[0113] B1 Determination of average thickness of aluminum effect pigments by SEM:

[0114] The aluminum pigments were originally present in the form of a paste and were each first washed with acetone and then dried.

[0115] The aluminum powder than was poured onto a conductive adhesive label (Spectro tabs from Plano GmbH, Germany). By this procedure, a certain amount of the flaky aluminium pigments become fixed into an upright position. Under the SEM these particles can be well identified and their thickness at the pigments edge was determined. For each sample 100 particles were counted and the average thickness tai was determined. [0116] B2: The specific surface was measured with the BET method using a three-point method. [0117] B3: Particles size distribution measurements:

[0118] These measurements are conducted e.g. by means of laser granulometry using a particle size analyzer manufactured by Sympatec GmbH (model: Helos/BR). The measurements are conducted according to data from the manufacturer. With this apparatus powdered samples as well as pastes can be measured.

[0119] Table 2 summarises the different samples with respect to the effect pigments used and the respective concentrations.

[0120] Rectangular test sheets having a length of 100 mm, a width of 70 mm and a thickness of 2.0 mm were obtained. [0121] B4: The optical densities of these test sheets were determined using a SW-densitometer (Heiland electronic GmbH TRD 2, Wetzlar, Germany) using a blend with diameter of 3 mm. This apparatus can measure the optical density until a maximum value of 5.5 log*D in transmission mode. After this value, a saturation region is reached (overload). [0122] B5: L*-values were measured at different angles of observation (15, 15, 25, 45, 75 and 110) using a Byk-Mac in the CILAB system. The conditions used were D65 (light source) and 10 for the standard photometric observer; the angle of incidence was 45. L*.sub.15 was used as measure of the brightness and the flop was calculated to the well-known formula (V):

[00007]$\begin{array}{cc}\mathrm{Flop}=2.69\frac{{\left(L_{15}^{*}-L_{110}^{*}\right)}^{1.11}}{L_{45}^{*0.86}}& \left(V\right)\end{array}$

[0123] Underearth of the sample plates black and white papers were deposited and the L*-values were measured. For the ratio L*.sub.10,black/L*.sub.110,white it was found that the OD was at 1.5 if this ratio was less than 1%. [0124] B6: Furthermore the NIR separating behavior of the samples was evaluated by the following tests developed and conducted by cyclos-HTP for the NIR detection and sorting performance of packaging samples.

[0125] The test equipment was a setup by Steinert UniSort (Germany) and included a high-resolution operational NIR camera with a full-spectral analysis. The samples were placed on an accelerator belt with 1 m width and a speed of 2.5 m/s. This accelerator belt passed a valve block with 13 mm nozzle distance and 7 bar air pressure and included nineteen operational classifiers. The measured data were read out by a software and visualized for the NIR image. Each kind of detectable plastic was highlighted by a predetermined color.

1.2 Sample Preparation:

[0126] For a statistical evaluation of measurable surfaces the probability of different positions) of the samples were evaluated.

[0127] Also all relevant components of the test samples were evaluated.

[0128] As specimen size 10 pieces per article were used.

1.3 NIR-Spectrometric Measurement Details and Assessment:

Test 1: Identification of the Structure

[0129] 1. A sample scan was conducted including the NIR-spectrometric detail imaging and a visual evaluation of the detected materials at 0.5 m/s in reflection. [0130] 2. Recording of results (intensity image, classification image, result image) [0131] 3. Evaluation/plausibility check of images (repeat, if necessary) [0132] 4. Expert evaluation of the test result

[0133] This first test was passed when at least 90% of the pixels generated from the sample were attributable to a certain kind of plastic.

Test 2: Practical Transfer and Testing of the Discharge Behavior:

[0134] 1. Verification test with operational classifier [0135] 2. Determination of the discharge behavior with a minimum of 10 trials of each sample at 2.5 m/s were evaluated. [0136] 3. Evaluation of NIR results:

[0137] The sorting test was passed when the discharge behavior is 80%.

[0138] A limited sorting behavior is attributed to a discharge behavior of >30% to <80% (test failed) and the sorting test is definitely failed when the discharge behavior is 30%.

Results:

[0139] In table 1 the results characterizing the metal effect pigments are summarized:

TABLE-US-00001 Span Average D.sub.10 D.sub.50 D.sub.90 D thickness BET Aspect Sample [m] [m] [m] [m] [nm] [m.sup.2/g] ratio 2156 9.5 19.3 33.9 1.3 254 2.8 76 Chromal 4.3 14.8 33.0 1.9 100 7.3 148 V

[0140] 2156 clearly belongs to type i) of aluminum pigments while Chromal V belongs to type ii).

TABLE-US-00002 TABLE 2 Results for the Experiments of pure effect pigment samples Concen- Fraction Automatic tration of Sorting Pearl- Effect pixels discharge Metal escent pigm. PP in % behavior Sample pigment pigment [wt. %] (test 1) (test 2) OD Comp. 2156 0.25% 99% 80% 1.6 Ex. 1a Comp. 0.5% 97% 80% 3.2 Ex. 1b Comp. 0.75% 97% 80% 4.5 Ex. 1c Comp. 1.0% 96% 80% 5.3 Ex. 1d Comp. 1.25% 84% >30% to <80% 5.5 Ex. 1e Comp. 1.50% 70% <30% 5.5 Ex. 1f Comp. Chromal 0.10% 98% 80% 2.6 Ex. 2a V Comp. 0.15% 94% 80% 4.0 Ex. 2b Comp. 0.20% 95% <30% 4.9 Ex. 2c Comp. 0.25% 47% <30% 5.5 Ex. 2d Comp. 0.30% 51% <30% 5.5 Ex. 2e Comp. 0.40% 0% <30% 5.5 Ex. 2f Comp. 0.50% 0% <30% 5.5 Ex. 2g Comp. Symic 0.25 100% 80% 0.4 Ex. 3a C604 Comp. 0.50 100% 80% 0.7 Ex. 3b Comp. 0.75 100% 80% 1 Ex. 3c Comp. 1.00 100% 80% 1.4 Ex. 3d Ex. 3e 1.25 100% 80% 1.6 Ex. 3f 1.50 100% 80% 1.9 Ex. 3g 1.75 100% 80% 2.2 Ex. 3h 2.00 100% 80% 2.4 Ex. 3i 3.00 98% 80% 3.3 Ex. 3j 5.00 98% 80% 4.8 Ex. 3k 10.00 96% 80% 5.2 Comp. Symic 0.25 100% 80% 0.5 Ex. 4a B604 Comp. 0.5 100% 80% 0.9 Ex. 4b Comp. 0.75 100% 80% 1.3 Ex. 4c Ex. 4d 1.00 100% 80% 1.7 Ex. 4e 1.25 100% 80% 2 Ex. 4f 1.50 100% 80% 2.3 Ex. 4g 1.75 100% 80% 2.6 Ex. 4h 2.00 100% 80% 2.9 Ex. 4i 3.00 99% 80% 4 Ex. 4j 4.00 98% 80% 4.8 Ex. 4k 5.00 97% 80% 5.1 Ex. 4l 7.5 91% 80% 5.2 Ex. 4m 10.0 94% 80% 5.5 Comp. Symic 0.25 100% 80% 0.6 Ex. 5a A604 Comp. Symic 0.50 100% 80% 1.3 Ex. 5b A604 Ex. 5c 0.75 100% 80% 1.7 Ex. 5d 1.00 100% 80% 2 Ex. 5e 1.25 100% 80% 2.7 Ex. 5f 1.50 100% 80% 3.3 Ex. 5g 1.75 99% 80% 3.4 Ex. 5h 2.00 100% 80% 4 Ex. 5i 3.00 98% 80% 5 Ex. 5j 5.00 98% 80% 5.5 Ex. 5k 10.00 99% 80% 5.5

[0141] The hiding behavior of the two different aluminum effect pigments is strikingly different: for Chromal V the sorting tests ale fulfilled only at extremely low concentrations (0.15%), whereas for the 2156 samples the concentration can be up to 1.0 wt. % to pass the sorting tests. The Chromal samples are much smaller and thinner yielding a larger number of particles per gram metal pigment. Also, they exhibit a broad particle size distribution (span) yielding a better hiding power compared to the other sample.

[0142] The three pearlescent effect pigments have no effect on the discharge behavior irrespective of their concentrations. The hiding power is largest for Symic A604 (Example 5 series), followed by the Symic B604 series (Example 4 series) and the Symic C604 (Example 3 series). This behavior can be attributed to the smaller particle sizes (the D.sub.50-values increases within this series).

[0143] As smaller synthetic mica is obtained by milling also fractions of smaller particle sizes yield thinner particles. As the layer thickness of TiO.sub.2 is the same (about 40 nm) for all samples the smallest and thinnest particles (A-series) will exhibit the highest TiO.sub.2 content. As this high-refractive index layer is mainly responsible for the hiding power the smallest fractions have a high hiding power.

[0144] From these tests the possible highest concentrations for each aluminum pigment can be estimated. To work with these high concentrations, however, may lower the process stability as the plastic bodies may behave different in different shapes and also the sorting behavior may in reality differ from device to device. Therefore mixtures of the metal pigments with the pearlescent pigments are more favourable.

TABLE-US-00003 TABLE 3 Results for Mixtures of metal effect pigments and pearlescent pigments Concentration C.sub.P and c.sub.p + t.sub.pl Automatic Pearlescent Fraction sorting: Metal pigm. of pixels discharge Pigment Pearlescent [wt. %]/ PP in % behaviour Sample and C.sub.M pigment [cm*wt. %] (test 1) (test 2) OD Flop L*.sub.15 Comp. 2156 Symic 0.00% 93% 80% 5.1 14.9 121.4 Ex. 6 1.0% B604 Ex. 6a 0.25%/ 98% 80% 5.5 15.0 121.4 0.05 Ex. 6b 0.50/ 92% 80% 5.5 15.2 121.6 0.10 Ex. 6c 1.00/ 91% 80% 5.5 15.4 120.7 0.20 Ex. 6d 2.00/ 99% 80% 5.5 15.5 121.5 0.40 Ex. 6e 3.00/ 80% 80% 5.5 15.6 122.3 0.60 Comp. 5.00/ 30% <30% 5.5 15.5 124.6 Ex. 6f 1.00 Comp. 2156 Symic 0.00% 98% 80% 1.6 13.9 119.3 Ex. 7a 0.25% B604 Ex. 7b 0.25/ 98% 80% 2.2 14.4 118.3 0.05 Ex.7c 0.50/ 97% 80% 2.5 14.3 117.2 0.10 Ex. 7d 1.00/ 97% 80% 3.4 14.6 116.7 0.20 Ex. 7e 2.00%/ 97% 80% 4.7 15.3 118.4 0.40 Ex. 7f 3.00/ 97% 80% 5.5 15.7 120.0 0.60 Ex. 7g 5.00/ 96% 80% 5.5 16.0 122.6 1.00 Comp. 2156 Symic 0.00% 98% 80% 3.2 14.6 120.8 Ex. 8a 0.50% B604 Ex. 8b 0.25/ 96% 80% 3.5 14.8 120.1 0.050 Ex. 8c 0.50/ 97% 80% 4.0 14.9 119.6 0.10 Ex. 8d 1.00/ 97% 80% 4.8 15.1 119.4 0.20 Ex. 8e 2.00/ 96% 80% 5.5 15.4 119.9 0.40 Ex. 8f 3.00/ 97% 80% 5.5 15.8 121.0 0.60 Ex. 8g 5.00/ 96% 80% 5.5 15.7 122.9 1.00 Comp. Chromal V Symic 0.00% 98% 80% 2.6 11.5 104.9 Ex. 9a 0.10% A604 Ex. 9b 0.25/ 99% 80% 3.3 12.1 106.0 0.050 Comp. 0.50/ 98% 80% 3.9 12.6 107.1 Ex. 9c 0.10 Ex. 9d 1.00/ 98% 80% 4.3 12.9 107.4 0.20 Ex. 9e 2.00/ 98% 80% 4.8 13.4 108.2 0.40 Ex. 9f 3.00/ 98% 80% 5.5 13.8 109.6 0.60 Ex. 9g 5.00/ 99% 80% 5.5 14.4 111.6 1.00 Ex. 9h 0.25/ 99% 80% 5.5 15.0 114.1 0.050 Comp. 5.00/ Not <30% 5.5 15.3 117.3 Ex. 9i 1.00 measurable Comp. Chromal V Symic 0.00% 98% 80% 4.0 11.5 104.9 Ex. 10a 0.15% A604 Ex. 10b Chromal V Symic 0.25/ 99% 80% 4.5 12.1 106.0 0.15% A604 0.05 Ex. 10c 0.50/ 98% 80% 5.1 12.63 107.1 0.10 Ex. 10d 0.75/ 99% 80% 5.1 12.9 107.4 0.15 Ex. 10e 1.0/ 95% 80% 5.3 13.6 108.2 0.20 Comp. 1.50/ 97% <30% to <80% 5.5 13.8 109.6 Ex. 10f 0.30 Comp. 2.00/ Not 30% 5.5 14.4 111.6 Ex. 10g 0.40 measurable Comp. 3.00/ Not <30% 5.5 15.0 114.1 Ex. 10h 0.60 measurable

Discussion

[0145] For the silver dollar aluminum pigment 2156 the example series for lower metal pigment concentrations (0.25% for Examples series 7 and 0.50% for Examples series 8) show that the upper limit of adding pearlescent pigments at least of up to 5.0 wt. % do not hinder the sorting behavior and the identification of the polypropylene plastic by NIR spectroscopy. For the series with the upper limit of aluminum pigment (1.0 wt. %; Examples series 6) the discharge behavior was not passed at a pearlescent concentration of 5.0 wt. %, while it was passed for all lower concentrations. In all three series a slight increase of the flop compared to the samples without pearlescent pigments (Comp. Examples 6a, 7a and 8a) can be observed. Apparently, the addition of pearlescent pigments improves the flop behavior. The brightness L*.sub.15 is not affected generally by the addition of pearlescent pigments. At higher concentrations of 3.0 wt. % or 5.0 wt. % an increase compared to the pure metal pigment can be seen whilst for lower concentrations the results are irregular. For the Examples series with the Chromal V pigment (Examples series 9 and 10) the critical concentrations of the metal pigment are much lower. The addition of pearlescent pigments leads to earlier fail of the sorting behavior. For both series, a range of pearlescent pigment concentrations can be identified wherein the sorting behavior is fine. In all cases the flop as well as the lightness were improved significantly by the addition of pearlescent pigments.