METHOD FOR THE MANUFACTURE OF A COLORED POLYMER COMPOSITION

Abstract

Method for the manufacture of a colored polymer composition comprising a polymer, a release agent and a colorant, the method comprising the steps of feeding a solid form of a release agent composition comprising said release agent and said colorant to a feed section of a melt mixing device, feeding said polymer to said melt mixing device and mixing said release agent composition and said polymer in said melt mixing device at a temperature above the melting temperature of said polymer, whereinsaid colorant is a pigment, or a dye which is soluble in said release agent, said polymer comprises or consists of polycarbonate, the release agent is selected from the group consisting of penta-erythritol tetra stearate, glycerol monostearate, glycerol tristearate and mixtures thereof.

Claims

1. A method for the manufacture of a colored polymer composition comprising a polymer, a release agent and a colorant, the method comprising the steps of feeding a solid form of a release agent composition comprising said release agent and said colorant to a feed section of a melt mixing device, and feeding said polymer to said melt mixing device and mixing said release agent composition and said polymer in said melt mixing device at a temperature above the melting temperature of said polymer, wherein said colorant is a pigment, or a dye which is soluble in said release agent, said polymer composition comprises polycarbonate, and the release agent consists of penta-erythritol tetra stearate, glycerol monostearate, glycerol tristearate or a mixture thereof.

2. The method of claim 1 wherein said colorant comprises a dye.

3. The method of claim 1 wherein the solid form of the release agent consists of one or more of pellets, powder, flakes or beads.

4. The method of claim 1 wherein the release agent composition further comprises one or more functional additives, wherein the one or more functional additives comprises anti-oxidants, UV stabilisers, hydrolytical stabilisers, flame retardants, catalyst quenchers, anti-static agents or a mixture thereof.

5. The method of claim 1 wherein the release agent composition comprises at least 40.00 wt. % of the release agent, based on the weight of the release agent composition.

6. The method of claim 1 wherein said polymer comprises at least 60 wt. % of the polycarbonate based on the weight of the polymer.

7. The method of claim 1 wherein the polymer consists of an aromatic polycarbonate or a mixture of at least two aromatic polycarbonates.

8. The method of claim 1 wherein the melt mixing device is an extruder.

9. The method of claim 1 further comprising a step of preparing said release agent composition by mixing said release agent and said colorant and optionally one or more functional additives, wherein the one or more functional additives comprises anti-oxidants, UV stabilisers, hydrolytical stabilisers, flame retardants, catalyst quenchers or anti-static agents at a temperature above the melting temperature of said release agent.

10. A method for the manufacture of a batch of semi-finished or finished article comprising converting the colored polymer composition obtained by the method of claim 1 into said article by means of injection moulding, blow moulding, rotation moulding, compression moulding, sheet extrusion or profile extrusion.

11. A release agent composition comprising a release agent and a colorant for the manufacture of a colored polymer composition by melt mixing of a polymer and said release agent composition at a temperature above the melting temperature of the polymer wherein said colorant is a pigment, or a dye which is soluble in said release agent, said polymer comprises or consists of polycarbonate, the release agent consists of penta-erythritol tetra stearate, glycerol monostearate, glycerol tristearate or a mixture thereof; wherein the release agent composition is in particulate form.

12. The release agent composition of claim 11 for improving the color consistency of articles prepared from the colored polymer composition; wherein the colored polymer composition has an average dE* of at most 0.050 measured in accordance with ASTM E308-15 (Standard Practice for Computing the Colors of Objects by Using the CIE System) using spectral transmission data for D65 illumination and 100 observer.

13. A release agent composition comprising at least 40 wt. % of a release agent and at least 0.0001 wt. % of a colorant, wherein said release agent is in a particulate form, wherein said colorant is a pigment, or a dye which is soluble in said release agent, and wherein said release agent consists of penta-erythritol tetra stearate, glycerol monostearate, glycerol tristearate or a mixture thereof.

14. The release agent composition of claim 13 wherein said colorant consists of Solvent Green 3, Solvent Green 28, Solvent Green 38, Pigment Green 50, Pigment Green 36, Solvent Red 52, Solvent Red 101, Solvent Red 111, Solvent Red 135, Solvent Red 169, Solvent Red 179, Solvent Red 207, Pigment Red 101, Disperse Red 22, Vat Red 41, Solvent Orange 60, Solvent Orange 63, Disperse Orange 47, Solvent Violet 13, Solvent Violet 14, Solvent Violet 36, Solvent Violet 50, Disperse violet 26/31, Pigment Blue 29, Pigment Blue 60, Copper Phthalocyanine Pigment Blue 15.4, Phthalocyanine Blue BN, Pigment Blue PB 15, Disperse Blue 73, Solvent Blue 97, Solvent Blue 101, Solvent Blue 104, Solvent Blue 122, Solvent Blue 138, Pigment Yellow 53, Pigment Yellow 138, Pigment Yellow 139, Disperse Yellow 201, Solvent Yellow 33, Solvent Yellow 114, Solvent Yellow 93, Solvent Yellow 98, Solvent Yellow 163, Solvent Yellow 160:1, Solvent Yellow 188, Pigment Brown 24, Amino Ketone Black, chrome oxides, or a mixture of at least two of the foregoing colorants; and wherein the release agent composition is free of a carbon based pigment.

15. The release agent composition of claim 13 comprising 60 to 99 wt. % of the release agent based on the weight of the release agent composition; 0.001 to 0.1 wt. % of the colorant based on the weight of the release agent composition; and 0.9 to 40 wt. % of an additive based on the weight of the release agent composition.

16. The release agent composition of claim 13 comprising 60 to 99 wt. % of penta-erythritol tetra stearate based on the weight of the release agent composition; 0.001 to 0.1 wt. % of a dye based on the weight of the release agent composition; and 0.9 to 40 wt. % of the UV stabilizer based on the weight of the release agent composition; wherein the release agent composition is free of a carbon based pigment.

17. The method of claim 1, wherein the release agent composition comprises 60 to 99 wt. % of the release agent based on the weight of the release agent composition; 0.001 to 0.1 wt. % of the colorant based on the weight of the release agent composition; wherein the release agent composition is free of a carbon based pigment; and 0 to 40 wt. % of a UV stabilizer based on the weight of the release agent composition; and wherein the polymer comprises 90 to 100 wt. % of a polycarbonate or a mixture of at least two aromatic polycarbonates based on the weight of the polymer.

Description

EXAMPLES

[0066] The present invention will now be further elaborated based on the following non-limiting examples.

[0067] The following release agent compositions, referred to as A and B were prepared by mixing the respective ingredients at a temperature of about 70 C. followed by forming more or less circular pellets from said molten composition by allowing droplets of the molten release agent composition to cool on a flat surface. The pellets had a diameter of about 3 mm and a maximum thickness of between about 1 and 2 mm.

[0068] The amounts are in parts by weight. The compositions A and B did not contain any further materials. The sum of the weight of the components in table 1 adds up to 100 parts by weight for each of the compositions A and B.

TABLE-US-00001 TABLE 1 CAS # Material A B 115-83-3 Release agent penta-erythritol tetrastearate ~99.98 ~66.66 31570-04-4 Antioxidant tris(2,4-di-t-butylphenyl)phosphite 8.33 3147-75-9 UV stabiliser 2-(2-hydroxy-5-t-octylphenyl)benzotriazole 25.00 82-16-6 colorant Solvent Violet 36 0.0132 0.00882 147-14-8 colorant Pigment Blue PB 15 0.00330 0.00221

[0069] Based on the raw materials and the release agent compositions A and B the following colored polymer compositions were manufactured. All example polymer compositions were manufactured with identical settings using a co-rotating twin screw extruder. The extruder had a length of 2880 mm (8 barrels), a screw diameter of 92 mm and operated at a screw speed of 600 rpm delivering an output of about 2500 kg/hr. The barrel temperature in the wetted length and the temperature of the die head was set to 300 C. The extruder was equipped with a bulk feeder for feeding the polymer in the form of powder, a blender feeder for feeding a blend of individual components in comparative examples 1 and 2 and a pellet feeder for feeding the pellets of compositions A and B. The bulk feeder, blender feeder and pellet feeder all fed the respective materials to the same feed section in the extruder located at the first barrel. The colored polymer compositions were extruded to a strand which was cooled and cut into pellets.

[0070] Samples of the obtained pellets were taken at regular intervals during the manufacture of the compositions. These samples were dried and injection moulded into sets of 5 plaques of about 6 cm by 6 cm and having a thickness of 4 mm.

[0071] The color of the plaques was measured using a color spectrophotometer applying the CieLAB system resulting in L*, a*, b* values for each plaque. For the purpose of the examples in the present application the L*, a* and b* value for each sample was the average value of the 5 plaques per sample.

[0072] For the calculation of dE* the reference consisted of the average value for L*, a* and b* which was based on all plaques measured within an example composition.

[0073] The reported average dE* in Table 3 below is the average of all individual dE* measurements within the example composition.

[0074] The reported max dE* represents the value of dE* for the sample having the highest determined color difference.

[0075] Thus, in Comparative Example 1 (CE1) 16 samples were taken at regular intervals during the manufacture of the colored polymer composition. From each of these 16 samples five plaques of 4 mm thickness were prepared via injection moulding. Each plaque was subjected to color measurement using the CIElab system resulting in a dataset of 16 times 5 individual color measurements. The average color values for L*, a* and b* formed the reference values for calculation of the dE* following the formula above.

TABLE-US-00002 TABLE 2 CAS # Material CE1 CE2 E1 E2 Bulk feeder Polycarbonate 90.0 90.0 90.0 99.4 Blender feeder 115-83-3 penta-erythritol tetrastearate 0.4 0.4 31570-04-4 tris(2,4-di-t-butylphenyl)phosphite 0.05 0.05 0.05 Polycarbonate 9.40 9.40 9.4 3147-75-9 2-(2-hydroxy-5-t-octylphenyl) 0.15 0.15 0.15 benzotriazole 82-16-6 Solvent violet SV36 0.000048 0.000048 147-14-8 Pigment Blue PB 15 0.000012 0.000012 Pellet feeder Mix A 0.4 Mix B 0.6

[0076] The polycarbonate fed via the bulk feeder and via the blender feeder was identical and consisted of a linear bisphenol A polycarbonate having a Mw of about 30500 g/mol (PC standard) and a melt volume rate of about 6.0 cm.sup.3/10 min (ISO 1133, 300 C., 1.2 kg). The polycarbonate was prepared using the interfacial process wherein bisphenol A reacts with phosgene and the resulting polymer powder was fed to bulk and blender feeder of the extruder.

[0077] Table 3 shows the color variation as measurements on plaques prepared from the examples.

TABLE-US-00003 TABLE 3 CE1 CE2 E1 E2 # of samples in lot 16 24 25 19 Average dE* 0.088 0.072 0.032 0.047 Max dE* 0.2 0.166 0.076 0.122

[0078] The results in Table 3 show that upon the use of release agent composition containing the colorant the color variation in moulded plaques, i.e. articles, can be significantly reduced. The present inventors believe that this observed improved color consistency means that the concentration of the colorant in articles prepared from the polymer composition shows less variation.