USE OF COLORED EFFECT PIGMENTS FOR ENHANCING THE INFRARED ABSORPTION CAPACITY OF COLORED POLYMERS

Abstract

The present invention is related to the use of colored effect pigments for enhancing the infrared absorption capacity of colored polymers and to a method for enhancing the infrared absorption capacity of colored polymers.

Claims

1. Use of colored effect pigments for enhancing the infrared absorption capacity of colored polymers, characterized in that the colored effect pigments comprise at least one layer which is composed of carbon.

2. Use according to claim 1, characterized in that the colored polymers absorb infrared light in the wavelength range of from 750 to 3000 nm of the solar spectrum.

3. Use according to claim 1, characterized in that the colored effect pigments are based on flaky substrate particles which are coated with at least one interference layer and with at least one layer being composed of carbon.

4. Use according to claim 1, characterized in that the layer composed of carbon is the outermost layer of the colored effect pigment and consists of a mixture of nanocrystalline carbon and amorphous carbon in a ratio of from 5:95 to 95:5.

5. Use according to claim 1, characterized in that the layer composed of carbon has a geometrical thickness in the range of from 1 to 10 nm.

6. Use according to claim 1, characterized in that the colored effect pigments have a particle size in the range of from 1 to 400 μm.

7. Use according to claim 1, characterized in that the colored polymers are colored by the colored effect pigments.

8. Use according to claim 1, characterized in that the colored polymers are colored thermoplastics or colored thermoset materials.

9. Use according to claim 1, characterized in that the colored polymers are supposed to be heated or re-heated by the action of infrared radiation.

10. Use according to claim 9, characterized in that the heating or re-heating by the action of infrared light is a thermoforming process, an injection molding process, an injection blow molding process, an injection stretch blow molding process, a polymer welding process, a polymer drying process or a process for polymerizing and/or curing polymer materials.

11. Use according to claim 1, characterized in that the colored polymers are selected from the group consisting of polyethylene (PE, HDPE, LDPE), polypropylene (PP), polyamides, polyesters, polyester-esters, polyether-esters, polyphenylene ether, polyacetals, polyalkylene terephthalates, polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), polyvinylacetals, polyvinyl chloride (PVC), polyphenylene oxide (PPO), polyoxymethylene (POM), polystyrene (PS), acrylonitrile styrene (AS), acrylonitrile-styrene-acrylate (ASA), acrylonitrile-butadiene-styrene (ABS), styrene butadiene copolymer (SBC), polycarbonates (PC), polyether sulfones (polyurethanes (TPU), polyether ether ketones (PEEK), or copolymers or mixtures thereof.

12. Use according to claim 1, characterized in that the colored effect pigments are present in the colored polymer in an amount in the range of from 0.1 to 10% by weight, based on the weight of the colored polymer.

13. Method for enhancing the infrared absorption capacity of colored polymers, characterized in that a polymer composition is mixed with a colored effect pigment which comprises at least one layer which is composed of carbon, in an amount of from 0.1 to 10% by weight, based on the weight of the total of effect pigment and polymer composition, whereby the polymer composition is provided with color and enhanced infrared absorption capability.

14. Method according to claim 13, characterized in that the polymer composition absorbs infrared light in the wavelength range of from 750 to 3000 nm of the solar spectrum.

15. Method for thermoforming, injection blow molding, injection stretch blow molding, welding, drying or curing of a colored plastic part, comprising irradiating said plastic part with infrared radiation in the wavelength range of from 750 to 3000 nm of the solar spectrum, wherein the plastic part is composed of a colored thermoplastic or thermosetting polymer composition comprising colored effect pigments which comprise at least one layer which is composed of carbon, in an amount of from 0.1 to 10% by weight, based on the weight of the total of effect pigment and polymer composition, whereby the thermal conductivity of the colored plastic part is increased compared to an otherwise identical colored plastic part that does not contain said colored effect pigment having said at least one layer of carbon.

Description

[0065] FIG. 1a: shows the distribution of carbon black in a polymer matrix containing common colored effect pigments and carbon black particles.

[0066] FIG. 1b: shows the distribution of carbon black in a polymer matrix containing the colored effect pigments according to the present invention.

[0067] FIG. 2a: shows the difference in temperature between the surfaces inside and outside the preform in an ISBM process performed for 800 bottles per hour, 100% IR lamp energy, and the composition of comparative example 2.

[0068] FIG. 2b: shows the difference in temperature between the surfaces inside and outside the preform in an ISBM process performed for 800 bottles per hour, 96% IR lamp energy, and the composition of example 2.

[0069] FIG. 3: shows a comparison of the color changes of plates produced according to examples 3, 4 and 5 and comparative examples 3, 4 and 5 after 1000 h artificial weathering.

[0070] FIG. 4: shows the IR absorption capability of an uncoated colored effect pigment (1) (Iriodin® 6103 Icy White), of a carbon coated effect pigment used according to the present invention (3) (Iriodin® 6301 Icy White coated with about 1 wt. % carbon) and of a blend of uncoated colored effect pigment and carbon (2) (Iriodin® 6301 Icy White blended with about 0.01 wt. % carbon, based on 100 percent by weight of the blend).

[0071] The present invention is described in more detail in the following examples, but should not be limited to these.

Example 1 and Comparative Example 1

[0072] Thermoforming

[0073] A wide variety of plastic articles are made by a thermoforming method. Typically, a thermoforming system includes a source of a thermoplastic sheet material such as a roll unwinding station, a heating station to heat the thermoplastic sheet material and a thermoforming form press station, wherein the heated thermoplastic sheet material is formed by a vacuum-pressure system employing upper and lower platens to thermoform molded articles in the sheet material. A heating station for heating the thermoplastic sheet material is used to heat the top and/or bottom of the sheet material to a preselected temperature, usually ranging from 80° to 150° C. The preheat station, for example, may employ typical IR-heaters (quartz heaters for example).

[0074] For comparison of thermoforming characteristics of colored plastic parts according to the invention (example 1) and according to the prior art (comparative example 1) films having a thickness of 600 μm are produced from ABS (Terluran® GP22 from BASF SE) which are pigmented as follows:

[0075] Example 1: 1% by weight of a colored effect pigment used according to the present invention (Iriodin® 111 Rutil Fine Satin from Merck KGaA, Darmstadt, coated with 6 wt. % carbon, based on the weight of the resulting pigment). The pigment and the film made therewith exhibit a metallic grey color.

[0076] Comparative Example 1: 1% by weight of Iriodin® 111 Rutil Fine Satin and 0.05% Carbon Black (Printex® P60). The concentration of 0.05% Carbon Black is chosen to match the color of example 1. The resulting film exhibits a metallic grey color.

[0077] The films have a similar color. Parts are shaped from these films using a thermoforming machine from Formech (model 450DT) with 70% of the maximum emitter power. The heat-up time required for an optimum result which is comparable between the individual films is measured in each case (see Table 1). Film pieces measuring 10 cm×15 cm are used for the thermoforming tests and irradiated using a quartz emitter.

TABLE-US-00001 TABLE 1 Polymer Formulation Heat-up time Terluran ® 1 wt. % pigment according to example 1 20 sec GP22 (i.e. 0.06 wt. % C in final polymer formulation) Terluran ® 1 wt. % pigment according to comp. ex. 30 sec GP22 1 + 0.05% Printex ® P60 (carbon black)

[0078] As the measurement values show, the concentration of 1 wt. % of the colored effect pigment used in the present invention already has a small measurable influence in this plastic system. The final carbon concentration in the polymer corresponds to 0.06% C, however, a significant shortening of the heat-up time by 10 sec, i.e. about 30%, can be achieved.

[0079] In addition, the temperature of the film is measured after the heat-up time of 20 seconds. The results in Table 2 show a higher temperature for the plastic part according to example 1 in comparison to comparative example 1.

TABLE-US-00002 TABLE 2 temperature after 20 sec Polymer Formulation Heat-up time Terluran ® Example 1 136° C. GP22 Terluran ® Comparative 131° C. GP22 example 1

[0080] Heating of a pearlescent pigment containing polymer matrix by using IR will probably not be homogenous due to the different IR absorption nature of the polymer and the pearlescent pigment. The carbon black particles are non-homogeneously distributed in the polymer matrix and enhance the IR absorption correspondingly in a non-homogeneous manner. In contrast, the homogenous C layer deposited on top of the pearlescent pigment improves the heating-conductivity of the polymer formulation pigmented with the special pearlescent pigments according to the present invention.

[0081] The differences in distribution of carbon black in a polymer matrix according to the present invention and in a polymer matrix containing a common colored effect pigment and carbon black particles according to the prior art (ex. 1 and comp. ex.1) are shown in FIG. 1a (comp. ex. 1) and 1 b (ex.1).

Example 2 and Comparative Example 2

[0082] Injection Stretch Blow Molding (ISBM)

[0083] As known to a skilled person, the ISBM process starts with a first step where a thermoplastic material, typically a thermoplastic resin, is melted and then injected into a preform mold, so to form a preform. When the preform is then released from the preform mold it can be immediately processed, but more typically it is cooled and stored and processed at a stretch blow molding station at a subsequent time and/or location. In a second step the preform is introduced into a stretch blow molding equipment where the preform is blow molded to its final shape via heating (for example, IR-heating) and stretching, typically using a core rod. In the ISBM process, different to other blow molding processes, the preform is reheated to a temperature warm enough to allow the preform to be inflated so that a biaxial molecular alignment in the sidewall of the resulting blow-molded container is achieved. With the preform held at the neck, air pressure, and usually a stretch rod, are used to stretch the preform in the axial direction, and optionally also in the radial direction. In the case of bottles the neck portion of the article can contain threads or flanges suitable for a closure and are typically unchanged with respect to the preform as the neck part is often not stretched. The articles obtained by injection stretch blow-molding can be significantly longer than the preform.

[0084] An injection stretch blow molded (ISBM) bottle is prepared by way of injection molding a tubular preform followed by reheating and concurrently stretching and blow-molding the IR-heated preform into a container. The polymer composition pigmented in accordance with the invention can be used in all areas where thermoplastics are re-heated.

[0085] For making the preforms used in ISBM, a 20 wt. % masterbatch containing a pearlescent pigment (prior art, comparative example 2) or a modified pearlescent pigment (according to the invention, example 2) is produced. The carbon black content in the comparative example is chosen to match the color of the polymer composition according to example 2.

[0086] An Indorama Ventures resin product brand, Polyclear® PET 1101, as used in example 2 and comparative example 2 is a commercial grade copolymer packaging resin. It is typically used in carbonated soft drink bottles, packaging and other injection/stretch-blow molded applications. The pellets are dried at about 85° C. under vacuum for about 8 hours to remove residual moisture before use.

[0087] The polymer compositions having the ingredients as disclosed hereunder are injection-molded into preforms and further stretch-blow molded into 450 ml, 33 g bottles.

[0088] Preforms are made using a 150-ton injection molding machine which produces two preforms per shot. Each cylindrical preform weighing approximately 33 g is about 120 mm in length with a screw top base.

[0089] Polyester injection molding takes place at about 270° C. The preforms are blown into 450 ml bottles. Linear stretch is 2:1 maximum. Circumferential stretch is from 2.5:1 (flat face) to 4.5:1 at sides.

[0090] The preforms of example 2 and comparative example 2 are designed to exhibit a similar color. The final concentration of pigments in the formulation is as follows:

Example 2

[0091] 1 wt. % colored effect pigment used according to the invention per 100 wt. % colored polymer composition (based on Iriodin® 6103 Icy White with 1 wt. % C deposited on pigment, i.e. 0.01 wt. % C in final polymer formulation). The pigment and the preform made therewith exhibit a metallic grey color.

Comparative Example 2

[0092] 1 wt. % Iriodin® 6103 Icy White+0,005% Carbon Black (Printex® P60) per 100 wt. % colored polymer composition. The resulting preform exhibits a metallic grey color.

[0093] Set up was set at 800 bottles per hour, 100% IR lamp energy at the beginning for Comparative Example 2.

[0094] FIG. 2a shows a significant difference in temperature between the surfaces inside the preform and outside the preform when the process is performed in this way using the polymer composition according to comparative example 2 (“height” is the length of the resulting bottle from neck to bottom).

[0095] For example 2, it became immediately clear in pre-tests that there will occur a significant difference in inner and outer surface temperature of the preforms in case the production conditions as in comparative example 2 would be used. For this reason, the heater power reduction is possible and necessary. Thus, the energy of the IR lamp is reduced to 96%.

[0096] FIG. 2b shows the relation of inner and outer surface temperature for the production of 800 bottles per hour, 96% IR lamp energy, using the colored polymer composition of example 2.

[0097] Afterwards, the production speed is increased to 1000 bottles per hour at the IR lamp energy of 96%.

[0098] For example 2, no significant difference in inner/outer preform temperature is observed.

[0099] For comparative example 2, the production of good quality bottles at this high speed and with only 96% IR lamp energy failed. Instead, stretch marks, variable wall thicknesses of the bottles and malformed bottles are observed due to insufficient preform heating.

Examples 3, 4, 5 and Comparative Examples 3, 4, 5

[0100] UV Ageing:

[0101] The colored polymer composition system pigmented in accordance with the invention can be used in all areas where thermoplastics have been employed to date. For outdoor applications, UV-resistance is of importance and is tested accordingly. Surprisingly, having C deposited on the basic colored effect pigment improves the UV-resistance of a colored polymer composition when compared with colored polymer compositions where carbon black particles are added to the polymer matrix colored with basic effect pigments.

[0102] Plastic granules (PMMA Plexiglas® 7N from Evonik Industries) are mixed with 0.2% wetting agent Process Aid 24 (product of ColorMatrix Group, Inc.) in a laboratory drum hoop mixer for 5 minutes. 1 wt % pearlescent pigment per 100% by weight polymer composition is added to the wetted granules and tumbled for additional 5 minutes.

[0103] The granules produced as described are then processed in an injection molding machine (Kraus-Maffei CX 130280) at 270° C. and molded into 1.5 mm thick plates.

[0104] The polymer plates are subjected to artificial weathering according to ISO 4892-2 (Xenotest® Beta+). Optically visible changes are assessed using the gray scale according to DIN EN 20105-A02 after 1000 h.

[0105] The polymer compositions include the following pigmentation (the polymer compositions of the comparative examples are chosen to match the color of the polymer compositions of the respective examples in each case):

Example 3

[0106] 1% by weight colored effect pigment per 100% by weight colored polymer composition used according to the present invention (colored effect pigment based on Iriodin® 111 Rutile Fine Satin coated with 1.5 wt. % carbon). The pigment and the plates made therewith exhibit a metallic grey color.

Comparative Example 3

[0107] 1% by weight of Iriodin® 111 Rutile Fine Satin+0.01% by weight Carbon Black (Printex® P60) per 100% by weight colored polymer composition. The resulting plates exhibit a metallic grey color.

Example 4

[0108] 1% by weight colored effect pigment per 100% by weight colored polymer composition used according to the present invention (colored effect pigment based on Iriodin® 7205 Ultra Rutile Platinum Gold coated with 1.6 wt. % carbon). The pigment and the plates made therewith exhibit a dark golden color.

Comparative Example 4

[0109] 1% by weight of Iriodin® 7205 Ultra Rutile Platinum Gold+0,015% Carbon Black (Printex® P60) per 100% by weight colored polymer composition. The resulting plates exhibit a dark golden color.

Example 5

[0110] 1% by weight colored effect pigment per 100% by weight colored polymer composition used according to the present invention (colored effect pigment based on Xirallic® NXT T250-23 Galaxy Blue coated with 2 wt. % carbon). The pigment and the plates made therewith exhibit a metallic blue color.

COMPARATIVE EXAMPLE 5

[0111] 1% by weight of Xirallic® NXT T250-23 Galaxy Blue+0.01% Carbon Black (Printex® P60). The resulting plates exhibit a metallic blue color.

[0112] In Table 3, the visual evaluation at 90° and 45° viewing angle of the polymer plates (color change according to grey scale) is demonstrated.

TABLE-US-00003 TABLE 3 Comp. Comp. Comp. Formulation Ex. 3 Ex. 3 Ex. 4 Ex. 4 Ex. 5 Ex. 5 Visual +4 +1 +5 +2 +5 +1 evaluation at 90° Visual +2 +1 +5 +1 +5 +1 evaluation at 45°

[0113] A comparison of the plates after 1000 h artificial weathering shows clearly less color changes using the pigments according to the present invention (examples 3, 4 and 5). A respective visualization is shown in FIG. 3.

[0114] Grey scales are used for assessing color change and staining during color fastness testing (here artificial weathering). It is used for visual assessment using a rating from 1 to 5, where 5 means “poor” and 1 means “good”. The illuminant/observer conditions are D65 with a visual evaluation angle of 90° and 45°.

[0115] In FIG. 4, the IR absorption capability of an uncoated colored effect pigment (1) (Iriodin® 6301 Icy White), of a carbon coated effect pigment used according to the present invention (3) (Iriodin® 6301 Icy White coated with about 1 wt. % carbon) and of a blend of uncoated colored effect pigment and carbon (2) (Iriodin® 6301 Icy White blended with about 1 wt. % carbon, based on 100 percent by weight of the blend) is shown.

[0116] In the following, the production of the carbon coated colored effect pigments used in the present invention is explained. The basic colored effect pigments used are all commercially available products of

[0117] MerckKGaA, Darmstadt, Germany. [0118] A) Production of carbon coated Iriodin® 111 Rutil Fine Satin used in example 1

[0119] 1 kg of Iriodin® 111 Rutil Fine Satin pigment particles are heated up to 750° C. in a fluidized bed reactor (DI: 100 mm) under a constant inert gas atmosphere (N.sub.2). Volumetric flow is adjusted to reach the minimal fluidization velocity of 2 mm/s, thus excellent mixing and heat and mass transfer properties are guaranteed. As soon as the reaction temperature of 750° C. is reached the C precursor toluene, pre-heated up to 90° C., is dosed to the fluidization flow. Due to the elevated reaction temperature the C precursor will decompose in a way that the growth of the C layer on the particles' surfaces is initiated. The CVD process is run for 90 min in order to achieve a C layer thickness of 6 nm. After a cooling phase under inert gas atmosphere (N.sub.2) the final pigments are removed from the reactor and sieved. [0120] B) Production of carbon coated Iriodin® 6103 Icy White used in example 2

[0121] 1 kg of Iriodin® 6103 Icy White pigment particles are heated up to 650° C. in a fluidized bed reactor (DI: 100 mm) under a constant inert gas atmosphere (N2). Volumetric flow is adjusted to reach the minimal fluidization velocity of 2 mm/s, thus excellent mixing and heat and mass transfer properties are guaranteed. As soon as the reaction temperature of 650° C. is reached the C precursor acetone is dosed to the fluidization flow. Due to the elevated reaction temperature the C precursor will decompose in a way that the growth of the C layer on the particles' surfaces is initiated. The CVD process is run for 90 min in order to achieve a C layer thickness of about 1 nm. After a cooling phase under inert gas atmosphere (N2) the final pigments are removed from the reactor and sieved. [0122] C) Production of carbon coated Iriodin® 111 Rutil Fine Satin used in example 3

[0123] 1 kg of Iriodin® 111 Rutil Fine Satin pigment particles are heated up to 600° C. in a fluidized bed reactor (DI: 100 mm) under a constant inert gas atmosphere (N2). Volumetric flow is adjusted to reach the minimal fluidization velocity of 2 mm/s, thus excellent mixing and heat and mass transfer properties are guaranteed. As soon as the reaction temperature of 600° C. is reached the C precursor acetone is dosed to the fluidization flow. Due to the elevated reaction temperature the C precursor will decompose in a way that the growth of the C layer on the particles' surfaces is initiated. The CVD process is run for 120 min in order to achieve a C layer thickness of around 2 nm. After a cooling phase under inert gas atmosphere (N2) the final pigments are removed from the reactor and sieved. [0124] D) Production of carbon coated Iriodin® 7205 Ultra Rutile Platinum Gold used in example 4

[0125] 1 kg of Iriodin® 7205 Ultra Rutile Platinum Gold pigment particles are heated up to 658° C. in a fluidized bed reactor (DI: 100 mm) under a constant inert gas atmosphere (N2). Volumetric flow is adjusted to reach the minimal fluidization velocity of 2 mm/s, thus excellent mixing and heat and mass transfer properties are guaranteed. As soon as the reaction temperature of 658° C. is reached the C precursor acetone is dosed to the fluidization flow. Due to the elevated reaction temperature the C precursor will decompose in a way that the growth of the C layers on the particles' surfaces is initiated. The CVD process is run for 120 min in order to achieve a C layer thickness of around 2 nm. After a cooling phase under inert gas atmosphere (N2) the final pigments are removed from the reactor and sieved. [0126] E) Production of carbon coated Xirallic® NXT T250-23 Galaxy Blue used in example 5

[0127] 1 kg of Xirallic® NXT T250-23 Galaxy Blue pigments particles are heated up to 660° C. in a fluidized bed reactor (DI: 100 mm) under a constant inert gas atmosphere (N2). Volumetric flow is adjusted to reach the minimal fluidization velocity of 2 mm/s, thus excellent mixing and heat and mass transfer properties are guaranteed. As soon as the reaction temperature of 660° C. is reached the C precursor acetone is dosed to the fluidization flow. Due to the elevated reaction temperature the C precursor will decompose in a way that the growth of the C layer on the particles' surfaces is initiated. The CVD process is run for 75 min in order to achieve a C layer thickness of around 2 nm. After a cooling phase under inert gas atmosphere (N2) the final pigments are removed from the reactor and sieved.