Polymer compositions for laser marking

Abstract

The present invention relates to a polymer composition comprising a polyamide or polyester carrier polymer matrix having embedded therein special polymer particles, a process for making the polymer composition, its use as a laser marking or laser welding additive in organic polymer compositions, and laser-markable or laser-weldable organic polymer compositions comprising the polymer composition.

Description

[Technical Field]

[0001] Technical Field The present invention relates to a polymer composition comprising a polyamide or polyester carrier polymer matrix having embedded therein special polymer particles, a process for making the polymer composition, its use as a laser marking or laser welding additive in organic polymer compositions, and laser-markable or laser-weldable organic polymer compositions comprising the polymer composition. [Background technology]

[0002] prior art Labeling of plastic products has been a hot topic for a long time and its importance is constantly increasing. Traditional labeling processes such as printing, applying adhesive labels, and embossing on intermediate or final products continue to be used, but they have become more complex and often have disadvantages in terms of label durability.

[0003] Laser marking of plastic products has also been used for some time. This can be done without contact during the ongoing production process, resulting in a durable mark without the use of consumable materials for the actual marking, reducing waste and system downtime. In this respect, laser marking offers clear advantages over traditional labeling methods, both in terms of materials and technology. Laser marking is extremely durable. Because laser marking occurs within the material, there are no adhesion issues, as occurs with adhesive labels or direct printing processes.

[0004] Light or dark laser markings on plastics can be produced by various reactions within the plastic. Either the organic matrix of the plastic itself or added laser additives can absorb the laser radiation, thereby releasing energy into the plastic and resulting in foaming or carbonization of the plastic. In addition, laser additives present in plastics can also react intrinsically to laser radiation and produce color, for example by darkening, under the influence of the emitted laser energy.

[0005] Few plastics react very well to laser radiation without additional additives, but most types of plastics often show only weak marking, no marking at all, or only a slight reaction to laser radiation of certain wavelengths.

[0006] For example, polyamide grades without the corresponding laser additives are virtually impossible to mark with good contrast using conventional laser equipment, as their chemical properties often result in only a faint mark. Polyamides usually tend to foam when laser marked. Technical applications primarily use Nd:YAG or fiber lasers emitting at wavelengths of 1064 nm or 1062-1070 nm. Marking with these lasers does not meet market requirements.

[0007] There is also a market demand for better dark markings on polyesters, primarily due to the use of flame retardants in compounds, for example in electrical and electronic applications, which also cause strong foaming and therefore prevent dark markings.

[0008] US 3,839,064 describes a polymer microcapsule system consisting of discrete spherical particles, each having a polymer core with dispersed inorganic particles and a solid polymer shell surrounding the polymer core. These particles have high opacity and tunable gloss, and are particularly useful as colorants for fiber-containing products. The microcapsule core preferably consists of polystyrene, within which inorganic particles such as titanium dioxide, barium sulfate, calcium carbonate, or carbon black may be dispersed. The solid shell preferably consists of a hydroxylated polymer such as methyl cellulose, polyvinyl alcohol, or gelatin. Polyamides can also be used as shell materials. It has not been reported whether and to what extent fiber systems containing these particles respond to laser radiation.

[0009] WO9530716A1 describes a molding composition based on a thermoplastic or thermosetting plastic A), which comprises 0.05 to 10% by weight, based on A), of a micropowder with spherical particles having a substantially smooth surface structure, and which comprises as an essential component at least one polymer B) different from A), which is selected from the group consisting of polyphenylene ethers, polyarylene ether sulfones, polyarylene ether ketones, or polyimides. Additives, such as bone ash or carbon black, may optionally be present.

[0010] WO 9858805 describes laser-markable plastics characterized in that the difficult-to-laser-treat plastic contains an inherently laser-markable polymer as an absorber in the form of microground particles with a particle size of 0.1 to 100 μm. Example 3 describes a composition of 99 parts polyamide 6 and 1 unit of polyimide sulfone. Example 4 describes a composition of 99.6 parts polyamide 6 and 0.4 parts polyphenylene sulfide. Example 6 describes a composition of 99 parts unsaturated polyester resin and 1 part polyphenylene sulfide, with co-octate and cyclohexanone peroxide present as additives. Example 8 describes a mixture of 96 parts polyphenylene sulfide and 4 parts basic copper phosphate, which can be incorporated into plastics such as polyamides in an amount of 0.4%.

[0011] WO2004050766A1 discloses laser-light-absorbing particles. The laser-light-absorbing particles have a first polymer core containing an absorber and a second polymer attached to the core surface via functional groups, with the first and second polymers having different functional groups. Preferably, three, or optionally four, polymers are used. Antimony trioxide, tin dioxide, barium titanate, titanium dioxide, aluminum oxide, copper phosphate, and anthraquinone or azo dyes are listed as preferred absorbers. Polyamides and polyesters are listed as preferred for the core. A preferred second polymer is a polyolefin polymer with specific unsaturated functional groups.

[0012] WO09090057 proposes a process for preparing laser-markable polymeric materials. A difficult-to-laser-mark base polymer is mixed with an inherently laser-markable sensitive polymer, and optionally with other polymeric materials, none of which have functional groups. The mixture is melted to form a masterbatch material, which is then converted into a dilute mixture with a dilute polymer, which then forms a laser-markable polymeric material by melting the base polymer and the dilute polymer. For example, polyamide 6 can be mixed with polyphenylene sulfide, and antimony-doped tin oxide can be incorporated.

[0013] WO2014206523A1 describes microspheres consisting of core-shell particles dispersed in a polyolefin matrix as a carrier polymer, the core containing a mixture of elemental carbon and at least one metal oxide and / or metal titanate as an absorber, and at least one non-olefin polymer compound as a color former, and the shell containing at least one compatibilizer.

[0014] WO2017016645A1 describes special composite pigments as laser additives, which can be introduced into the plastics to be marked in the same way as standard industrial processes, as dry pigment mixtures, liquid preparations or pastes, or via plastic- or wax-based concentrates, so-called masterbatches.

[0015] US20210388206A1 describes a polymer / ceramic composite in which ceramic fillers are dispersed within a polymer matrix.

[0016] As noted above, the use of known laser additives produces usable markings. However, they still do not meet market requirements, particularly when marking colored polyamide or polyester plastics, especially when they also contain flame retardants. Therefore, there remains a need for improved laser marking or laser welding additives for polyamide or polyester plastics that, when irradiated with a laser of the type typically used in the industry, will produce an improved, durable, high-contrast marking with a dark, sharp edge on products made therefrom. The laser additive should enable this high-contrast marking with laser light at both slow and fast laser marking speeds. A further objective of product development is to minimize odors generated during and after laser treatment, especially when using sulfur-containing polymers.

[0017] It has now been found that the polymer compositions described or preferably described below achieve these objectives and overcome the disadvantages of the prior art.

[0018] Thus, it has been shown that such desirable laser behavior of polyamide or polyester plastics, or products made therefrom with durable, dark, high-contrast markings with sharp edges, can be achieved when a polymer composition having a polyamide or polyester carrier matrix and comprising polymer particles containing a sulfur-containing polymer that changes color upon laser radiation in addition to laser radiation-absorbing particles, is added to the polyamide or polyester material to be marked or welded. Due to the synergistic effect between the two absorbers and the intrinsically active sulfur-containing polymer, the light-colored polymer composition can function as a laser additive with improved laser marking performance compared to the above-mentioned known laser additives in terms of contrast, edge sharpness, and speed of the dark marking compared to the color of the base material of the plastic being marked. Summary of the Invention

[0019] Summary of the Invention Accordingly, the present invention first relates to a polymer composition comprising a carrier polymer matrix of polyamide or polyester in which polymer particles are embedded, wherein the polymer particles consist of particulate titanium oxide or particulate titanate, respectively, which may be doped, and a sulfur-containing polymer matrix in which a composite pigment is uniformly embedded, wherein at least 80% by weight of the composite pigment consists of titanium dioxide (TiO2) and antimony-doped tin dioxide [(Sb,Sn)O2], based on the total weight of the composite pigment.

[0020] The invention furthermore encompasses a process for preparing the polymer composition, the use of the polymer composition as a laser engraving or laser welding additive, and a laser-engravable or laser-weldable organic polymer composition comprising a polymer composition according to the invention.

[0021] In particular, polyamide as a carrier matrix polymer for polymer particles can significantly reduce the formation of odors generated during laser marking. DETAILED DESCRIPTION OF THE INVENTION

[0022] Description of the Invention For the purposes of the present invention, laser marking is understood to mean any kind of labeling of plastics, which can be produced by the action of a laser beam on plastics in the form of an inscription, code, label, decoration or similar visible optical change, and coatings containing these plastics on articles. The abbreviation for polyamide is PA. The term "laser-absorbing particles" is used synonymously with "absorber" and "absorbing particles."

[0023] The preferred delivery form of the polymer composition according to the invention is as described, or preferably as described above and below, as a granule. It is a bulk material that is easy to transport and further process due to its free-flowing nature. Alternatively, the delivery form of the polymer composition according to the invention may be a powder, a flowable mass, or a paste.

[0024] The polymer composition according to the present invention comprises a carrier polymer matrix of polyamide or polyester, the type of polyamide or polyester being not limited. The carrier polymer matrix can be linear or branched and can be selected from homopolymers, copolymers, or polymer blends of polyamide(s) or polyester(s). Those skilled in the art are not limited to the chemical nature of the polyamide or polyester and can select from a large number of commercially available products. Ideally, the type of polyamide or polyester of the carrier polymer matrix is selected to be compatible with the plastic to be laser marked.

[0025] In a preferred embodiment of the carrier polymer matrix, the polyamide or polyester has a melting point in the range of 160-250°C.

[0026] In a particularly preferred embodiment of the carrier polymer matrix, the polyamide is selected from PA6 or PA12, in particular PA 12. A particularly preferred PA12 is the product Vestamid® L1600, available from Evonik Operations GmbH.

[0027] In particularly preferred embodiments of the carrier polymer matrix, the polyester is selected from polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), or polybutylene terephthalate (PBT).

[0028] In addition to the polyamide or polyester carrier polymer matrix in which the polymer particles are uniformly embedded, the polymer composition according to the present invention may contain further additives such as adhesion promoters, stabilizers, fillers, or colorants, as described above, or preferably as described below.

[0029] Suitable adhesion promoters are, for example, thermoplastic polymers with functional groups, including both end groups and additionally introduced functional groups. These are generally graft or block copolymers. Suitable adhesion promoters are maleic anhydride graft polymers, such as Fusabond™ from Dow.

[0030] Suitable stabilizers are, for example, phenolic antioxidants such as Irganox® 1010 and 1098 from BASF, and phosphites such as Irgafos® 168.

[0031] Suitable fillers are, for example, various silicates, SiO2, talc, kaolin, mica, wollastonite, glass fibers, glass beads, carbon fibers, and the like.

[0032] Considered colorants are both organic dyes and inorganic or organic color pigments. Because the polymer compositions according to the present invention are very light in color and therefore easily colorable, virtually any soluble dye or insoluble color pigment suitable for polyamide or polyester can be used. Examples that may be mentioned here are the particularly frequently used white pigments TiO2, ZnO, BaSO4, and CaCO3. The amount and type of filler and / or colorant added are well known to those skilled in the art and are limited only by the specific material properties of the respective laser-engravable or laser-weldable organic polymer compositions into which the polymer compositions according to the present invention are incorporated for their intended use.

[0033] In a preferred embodiment of the polymer composition according to the invention, it consists of a carrier polymer matrix, as described or preferably as described above, in which polymer particles are embedded, where polymer particles has the meaning as described above or preferably as described below.

[0034] In a preferred embodiment of the polymer particles embedded in a carrier polymer matrix, as described above, the sulfur-containing polymer of the polymer matrix is selected from polysulfones or from polyphenylene sulfides.

[0035] The polymer matrix can be selected from homopolymers, copolymers, or polymer blends of polysulfone or polyphenylene sulfide, which can be linear or branched. Those skilled in the art are not limited to the chemistry of the polysulfone or polyphenylene sulfide and can choose from a large number of commercially available products. The term "polysulfone" is used to describe a class of polymers, but is also used in combination with the abbreviation PSU to refer to a specific polymer.

[0036] In a particularly preferred embodiment of the polymer matrix, the polysulfone is selected from polysulfone (PSU), polyarylene sulfone (PAS), polybisphenylsulfone (PSF), polyethersulfone (PES), or polyphenylene sulfone (PPSU). Polysulfone is commercially available from BASF under the name Ultrason®.

[0037] In a particularly preferred embodiment of the polymer matrix for the polymer particles, polyphenylene sulfide (PPS) is selected. The PPS preferably has a viscosity of 200-600 Pa*s measured in a capillary rheometer according to ISO 11443 at 310° C. and a shear rate of 1200 1 / s as described, or preferably as described above. The PPS particularly preferably has a viscosity of 300 to 500 Pa*s measured in a capillary rheometer at 310° C. and a shear rate of 1200 1 / s according to ISO 11443 as described or preferably as described above. Particularly preferred commercially available products are Celanese's Fortron® 0320C0 and Fortron® 1200L1.

[0038] According to the present invention, two types of particles that absorb laser light are incorporated into a polymer matrix as described, or preferably as described above, and then together with the polymer matrix form polymer particles: the first type of particles that absorb laser light are particulate oxides of titanium, or particulate titanates, each of which may be doped, and the second type are composite pigments, at least 80% by weight of which, based on the total weight of the composite pigment, consists of titanium dioxide (TiO2) and antimony-doped tin dioxide ((Sb,Sn)O2).

[0039] In general, the skilled artisan is not limited in the choice of particulate oxides and titanates of titanium. The particle size of the laser light-absorbing particles selected from particulate oxides of titanium or particulate titanates is determined by the requirement that the particles be miscible with the polymer matrix as described, or preferably as described above. Those skilled in the art will recognize that this miscibility is determined by the total surface area of a given weight of laser light-absorbing particles, and that those skilled in the art can easily determine the lower particle size limit given the desired size of the polymer particles and the desired amount of laser light-absorbing particles to be mixed.

[0040] In a particularly preferred embodiment of the polymer particles, particulate titanium dioxide, which may be doped, is incorporated into the polymer matrix as described, or preferably as described above.

[0041] The particulate titanium dioxide may be in rutile, anatase, or amorphous form, but is preferably in rutile form. The preferred average particle size is in the range of 0.1 to 4 μm, with a range of 0.15 to 2 μm being particularly preferred. The particulate titanium dioxide can have any conceivable shape. Preferably, the particulate titanium dioxide has an isotropic shape. These are shapes that are ideally more or less the same in all directions around the core when viewed from an imaginary center point, i.e., they have no preferred direction. These include not only spherical and cubic cores, but also irregular, compact, granular cores, as well as regular or semiregular polyhedral shapes with n faces (Platonic and Archimedean solids), where n ranges from 4 to 92. Of course, the terms spherical, cubic, or regular apply herein to core shapes that are not ideally spherical, ideally cubic, or ideally regular in the geometric sense. Because particulate titanium dioxide is produced by an industrial process, deviations from the ideal geometric shape due to technology, such as rounded edges in polyhedrons, or surfaces that vary slightly in size or shape, are also included herein.

[0042] Titanium dioxide may also be doped. In the present invention, doping is understood to mean the presence of small amounts of the corresponding ions as defects in the crystal lattice of titanium dioxide. Preferred doping is with iron or cerium ions. Very particular preference is given to doping titanium dioxide with iron ions. Particulate titanium dioxide suitable for incorporation into a polymer matrix according to the present invention can be obtained by a variety of methods well known to those skilled in the art, for example, by pyrolysis (e.g., flame pyrolysis), sol-gel, plasma, hydrothermal, or a combination of various processes.

[0043] In a further variant of the invention, however, it is preferred that the particulate titanium dioxide is undoped. Suitable particulate titanium dioxide of the stated size is available on the market, for example, under the trade names KRONOS® (KRONOS Worldwide, Inc.), HOMBITEC® (Venator), or TiPAque® (Ishihara Corp.). A particularly preferred particulate titanium dioxide is the product KRONOS® 2220, available from KRONOS Worldwide Inc.

[0044] Salts or esters of titanic acid are called titanates. Alternatively, they can be considered mixed oxides. The particulate titanates that can be used in accordance with the present invention may be naturally occurring or synthetic. Natural titanium minerals that can be used as particulate titanates in accordance with the present invention include perovskite, baryoperovskite, macedonite, ilmenite, geikierite, pyrophanite, and tausonite, which can be used after being appropriately refined and ground.

[0045] In a particularly preferred embodiment of the polymer particles, a particulate titanate selected from aluminum titanate, bismuth titanate, copper titanate, iron titanate, magnesium titanate, potassium titanate, sodium titanate, zinc titanate, cerium titanate, calcium titanate, barium titanate, or strontium titanate is incorporated into the polymer matrix as described, or preferably as described above. Preferred particulate titanates are aluminum titanate (Al2TiO5), sodium titanate (Na2TiO3), potassium titanate (K2TiO3), zinc titanate (ZnTiO3), calcium titanate (CaTiO3), cerium titanate (CeTiO4), barium titanate (BaTiO3), or magnesium titanate (MgTiO3). Particularly preferred particulate titanates are sodium titanate, potassium titanate, zinc titanate, and magnesium titanate.

[0046] As described above, the average particle size of the particulate titanate is preferably in the range of 0.1 to 20 μm, particularly 0.2 to 15 μm, and most preferably 0.5 to 10 μm. Suitable metal titanates are, for example, 99% calcium titanate (d50 max. 3.5 μm), potassium titanate, magnesium titanate from ABCR GmbH & Co. KG, 99+% calcium titanate from Alfa Aesar, 99.9% nano barium titanate (approx. 400 nm, BET 2.3-2.7 μm) from ABCR GmbH & Co. KG. 2 / g).

[0047] In a preferred embodiment of the polymer particles, a composite pigment comprising a titanium dioxide core and at least one antimony-doped tin dioxide coating is incorporated into a polymer matrix, further comprising, in addition to the first type of particles that absorb laser light, optionally an outer protective layer and / or one or more intermediate layer(s) between the titanium dioxide core and the [(Sb,Sn)O] coating as described, or preferably as described above.

[0048] When a single composite pigment particle consists only of a single core and a coating disposed thereon, the composite pigment used in accordance with the present invention consists only of primary particles and is therefore monodisperse. However, a more frequent and therefore preferred embodiment is when the composite pigment used is an aggregate of two or more primary particles, each of which has a core and a coating disposed thereon.

[0049] According to the present invention, composite pigments can be used in which the primary particles have any of the following layer structures: core / functional layer, core / intermediate layer(s) / functional layer, core / functional layer / protective layer(s), or core / intermediate layer(s) / functional layer / protective layer(s). The functional layer is a coating of antimony-doped tin dioxide.

[0050] The total weight proportion of the core layer and the functional layer, i.e., the total weight proportion of TiO2 and antimony-doped tin dioxide, is at least 80% by weight, preferably at least 90% by weight, and particularly 95 to 100% by weight, based on the total weight of the composite pigment.

[0051] When an intermediate layer and / or a protective layer is present, the intermediate layer is primarily made of an inorganic material. Highly suitable intermediate layers are metal oxides, in particular SiO2, SnO2, Al2O3, ZnO, CaO, ZrO2, Sb2O3, or mixtures thereof.

[0052] In contrast, the protective layer that may be present on the surface of the composite pigment used can be either inorganic or organic. These are generally applied when the use of the composite pigment in the application medium, i.e., in this case, the sulfur-containing polymer matrix, can be further simplified by a corresponding surface coating. In the case of inorganic protective layers, they are preferably ZrO2, Ce2O3, Cr2O3, CaO, SiO2, Al2O3, ZnO, TiO2, SnO2, Sb2O3, or the corresponding oxide hydrates, as well as mixtures of two or more thereof.

[0053] The organic protective layer generally consists of a suitable organosilanes, organotitanates, or organozirconates. Suitable substances are known to those skilled in the art as surface coatings and post-surface coatings for effect pigments.

[0054] The total weight proportion of the intermediate layer and / or protective layer is at most 20% by weight, preferably at most 10% by weight, particularly preferably 0 to 5% by weight, based on the total weight of the composite pigment.

[0055] In a particularly preferred embodiment of the composite pigment, the composite pigment used consists solely of TiO2 and (Sb, Sn)O2. Due to the nature of the titanium dioxide or antimony-doped tin dioxide used, there is a slight possibility that other components may be present in extremely small amounts (0.001 to 0.1 wt % of foreign ions).

[0056] In a preferred embodiment of the composite pigment, the antimony-doped tin dioxide coating consists of a material in which the weight percentage ratio of antimony to tin is 2 to 35% by weight, preferably 8 to 30% by weight, in particular 10 to 20% by weight, based on the total weight of antimony and tin.

[0057] In a preferred embodiment of the present invention, the composite pigment used in accordance with the present invention consists solely of one or more primary particles, each of which consists of a core and a functional coating located on the core, i.e., a TiO2 core, and a (Sb,Sn)O2 coating. However, in the most preferred embodiment, the composite pigment consists of each primary particle(s) consisting of a TiO2 core and a (Sb,Sn)O2 coating.

[0058] The core of the composite pigment used according to the present invention may have any conceivable shape. Preferably, the core of the composite pigment has an isotropic shape. These are shapes that, when viewed from an imaginary center point, are ideally more or less the same in all directions of the core, i.e., they have no preferred direction, as explained above for particulate titanium dioxide. Similar statements about shape apply equally. Because the cores of composite pigments are produced by industrial processes, deviations from the ideal geometric shape due to technology, such as rounded edges in polyhedrons or surfaces that vary slightly in size or shape, are also included herein.

[0059] The core of the composite pigment used according to the invention has a particle size in the range of 0.001 to 10 μm, preferably 0.001 to 5 μm, in particular 0.01 to 3 μm. These consist of commercially available TiO2 in the stated size ranges, for example, TiO2 particles available under the trade names KRONOS® (KRONOS Worldwide, Inc.), HOMBITEC® (Venator), or TiPAque® (Ishihara Corp.).

[0060] The primary particles of the composite pigment used according to the present invention have a coating on the surface of a core having the above-mentioned size and material composition, with a layer thickness in the range of 1 to 500 nm, preferably in the range of 1 to 200 nm.

[0061] As already explained above, the coating comprises at least one functional layer. If intermediate layer(s) or protective layer(s) are present, they are also counted as part of the coating. The above-mentioned rules regarding the coating thickness apply both to coatings consisting of only functional layers as described above and to coatings which, in addition to the functional layer, also have one or more intermediate and / or protective layers. In the case of coatings consisting of only [(Sb,Sn)O2] functional layers, as described or preferably as described above, a layer thickness range of 1 to 100 nm is particularly preferred.

[0062] The proportion of the coating is 5 to 70% by weight, based on the total weight of the primary particles, and 5 to 70% by weight, based on the total weight of the composite pigment. These data refer both to coatings consisting only of the functional layer as described above, and to coatings which, in addition to the functional layer, also contain one or more intermediate and / or protective layers.

[0063] In a preferred embodiment of the composite pigment having a TiO2 core and an antimony-doped tin dioxide ((Sb,Sn)O2) coating, the proportion of this coating is preferably in the range of 35 to 55% by weight, in particular in the range of 40 to 50% by weight, based on the total weight of the primary particles or based on the total weight of the composite pigment.

[0064] The particle size of the composite pigment used according to the present invention is in the range of 0.1 to 10 μm, preferably 0.2 to 5 μm. 90 It is particularly preferred to use composite pigments with a value in the range of 0.70 to 0.90 μm.

[0065] All particle sizes shown above or below can be determined using conventional methods of particle size determination. Particularly preferred is a particle size measurement method using laser diffraction, which can advantageously determine both the nominal particle size of individual particles and their percentage particle size distribution. All particle size determinations performed in the present invention are performed by laser diffraction using a Malvern 2000 instrument from Malvern Instruments Ltd., UK, in accordance with the standard conditions of ISO / DIS 13320.

[0066] The layer thickness of each coating is determined numerically using SEM and / or TEM images, as is commonly known to those skilled in the art. The composite pigments used according to the present invention are produced by known methods. Titanium dioxide particles used as cores are provided with a coating, as described, or preferably as described above. Since these are inorganic starting materials, coating the cores with functional layers is preferably carried out in aqueous suspension by precipitating the respective metal oxides or metal oxide hydrates and then converting them to metal oxides. The precursor materials for the resulting metal oxides, typically metal salts, are added in dissolved form to an aqueous suspension of the respective core material, and at an appropriately set pH, they are precipitated on the cores, usually in the form of metal oxide hydrates. The metal oxide hydrates are then converted to the corresponding oxides by treatment at high temperatures. Coating the cores with any applied intermediate and / or protective layers can be carried out in a similar manner, provided they are inorganic. Organic post-coating processes are also carried out by methods customary in the prior art, in particular by directly contacting the surface of the composite particles with the corresponding organic material in a suitable medium.

[0067] The preparation of a preferred embodiment of the composite pigment, consisting of a TiO2 core provided with a functional coating of antimony-doped tin dioxide, is described in detail in the Examples section (Synthesis Example 1). A particularly preferred composite pigment for use according to the present invention is commercially available under the name Iriotec® 8850 from Merck KGaA, Darmstad.

[0068] In a preferred embodiment of the polymer particles as described or preferably as described above as constituents of the polymer composition according to the invention, the weight percentage of the particulate titanium oxide or particulate titanate as described or preferably as described above relative to the composite pigment is 50 to 99% by weight, based on the total weight of the particulate titanium oxide or particulate titanate as described or preferably as described above and the composite pigment.

[0069] In this embodiment of the polymer particles as constituents of the polymer composition according to the invention, the weight percentage of the particulate titanium oxide or particulate titanate as described or preferably as described above relative to the composite pigment is preferably 60 to 97.5% by weight, particularly preferably 70 to 95% by weight, based on the total weight of the particulate titanium oxide or particulate titanate and the composite pigment as described or preferably as described above.

[0070] The described laser-light-absorbing particles, the composition of which and their weight percentage proportions relative to one another are as described or preferably as described above, are present in the sulfur-containing polymer matrix in an amount of 5 to 90% by weight, preferably 10 to 80% by weight, in particular 30 to 70% by weight, based on the total weight of the sulfur-containing polymer matrix and the laser-light-absorbing particles forming the polymer particles, respectively.

[0071] The particle size of the polymer particles formed during the preparation of the polymer composition according to the present invention as a constituent of the polymer composition according to the present invention is in the range of 0.5 to 50 μm, preferably 1 to 20 μm, particularly 2 to 10 μm. The size of the polymer particles can be determined by SEM / TEM studies.

[0072] It is advantageous if the particles are significantly smaller than 50 μm as this allows for good resolution during laser marking.

[0073] The production of the polymer particles is carried out in situ during the preparation of the polymer composition according to the invention. Suitable precursors for the in situ production of polymer particles are described in the following process. In a preferred process, particulate titanium oxide or particulate titanate is first thoroughly mixed with the composite pigment as described, or preferably as described above, while maintaining the stated weight ratios, to obtain a solid mixture. Any mixer, such as a tumble mixer, can be used for this purpose. Next, the powder mixture is uniformly mixed with the sulfur-containing polymer in the stated weight ratios, as described, or preferably as described above, and extruded to solidify, obtaining a precursor. The term "extrusion" is widely known in the art and refers to the extrusion of a solidifiable mass through an opening. In this process, an extruder is used for this purpose. Extruders are also known in the art and commercially available. The term extruder refers to a conveyor device for carrying out the extrusion. For example, a single-screw or twin-screw extruder can be used. The selection and combination of suitable extruder screws, particularly their shapes, based on the corresponding process engineering tasks, such as feeding, conveying, homogenizing, softening, and compressing, are part of the general knowledge of those skilled in the art.

[0074] A powder mixture of laser-absorbing particles and sulfur-containing polymer in the form of powder, flowable mass, and / or granules is preferably mixed in a co-rotating twin-screw extruder. The mixture is melted and subjected to intense shear within the extruder to ensure uniform distribution, and then extruded and solidified. The powder mixture of laser-absorbing particles and sulfur-containing polymer may be added simultaneously from two different sources, alternately in succession, or sequentially or simultaneously from a single source. The precursor is preferably produced at a temperature above the melting point of the sulfur-containing polymer, preferably between 280°C and 320°C. The extrudate is typically granulated using a strand pelletization method. The solidified mixture exits the extruder, for example, through a perforated plate. The molten strand is then cooled in a water bath and converted into granules by a rotating blade. A typical perforated plate has a nozzle diameter of 1-2 mm.

[0075] In the next step, the precursor is mixed with a carrier polymer, i.e., polyamide or polyester. The mixture is then mixed again in an extruder; in a preferred embodiment, a co-rotating twin-screw extruder is again used. The processing temperature should be above the melting point of the sulfur-containing polymer, preferably between 280°C and 320°C. The high shear in the extruder leads to the formation of polymer particles consisting of the sulfur-containing polymer containing the two types of absorbing particles, as described above. The melt is then discharged through a perforated plate and formed into strands. These are then converted into granules by a rotating blade in a strand pelletization process. The resulting product is suitable for laser marking and has the optimal properties already mentioned.

[0076] The in situ generated polymer particles are present in a polyamide or polyester carrier polymer matrix as described, or preferably as described above, in an amount of 10 to 90% by weight, preferably 20 to 80% by weight, in particular 30 to 70% by weight, in each case based on the total weight of the polymer composition, as described, or preferably as described above.

[0077] In the in situ preparation of polymer particles, the corresponding precursors, as described or preferably as described above, can also be used in a mixture with other additives known from the prior art in the polymer composition according to the invention, which comprises a carrier polymer matrix. In the latter case, the proportion of the precursor is reduced by the proportion of the other additive(s). Overall, the proportion of other additives in the polymer composition according to the invention is 0 to 40% by weight, particularly preferably 0.1 to 25% by weight, and very particularly preferably 0 to 10% by weight. Suitable additives have already been described above.

[0078] In a preferred embodiment of the present invention, the polymer composition according to the present invention is a polymer composition in which each component corresponds to a preferred embodiment.

[0079] In a particularly preferred embodiment of the present invention, the polymer composition comprises a polyamide carrier polymer matrix having embedded polymer particles, wherein the polymer particles consist of undoped particulate titanium dioxide and a polyphenylene sulfide polymer matrix having uniformly embedded therein a composite pigment, the composite pigment consisting of a TiO2 core having a functional coating of antimony-doped tin dioxide.

[0080] In a particularly preferred embodiment of the present invention, the polymer composition comprises a polyester carrier polymer matrix having embedded therein polymer particles, wherein the polymer particles comprise a polyphenylene sulfide polymer matrix uniformly embedded with undoped particulate titanium dioxide and a composite pigment, the composite pigment comprising a TiO2 core having a functional coating of antimony-doped tin dioxide.

[0081] Particularly preferred embodiments of the present invention apply mutatis mutandis to the statements regarding preferred polymers and components that absorb laser light and their weight proportions with respect to one another.

[0082] According to the above description, the present invention further relates to a process for preparing a polymer composition as described or preferably as described above, characterized in that: (i) in a first process step, the particulate titanium oxide or particulate titanate is intimately mixed with the composite pigment as described or preferably as described above, maintaining the stated weight proportions; (ii) in a second process step, this solid mixture from (i) is intimately and uniformly mixed with a sulfur-containing polymer to form a powder mixture; (iii) in a third process step, the powder mixture is plasticized and homogenized to form precursors of the in situ produced polymer particles; and (iv) in a fourth process step, the precursors of the in situ produced polymer particles from step (iii) are homogeneously extruded and consolidated with a polyamide or polyester carrier polymer matrix.

[0083] Process steps (i) to (iii) can be carried out in one apparatus and process step (iv) can be carried out in a second apparatus or at different times in the same apparatus, although all process steps can also be carried out continuously in one extruder.

[0084] Process steps (i), (ii) and (iii), and (iv) can be carried out at different times, and the intermediate products from these process steps can be appropriately stored until further use. Suitable storage conditions are known to those skilled in the art.

[0085] In a preferred embodiment of the process for preparing the polymer composition according to the present invention, the third and / or fourth process step is melt extrusion.

[0086] The present invention further relates to an alternative process for producing a polymer composition as described or preferably as described above, characterized in that (i) the particulate titanium oxide or particulate titanate is metered together with the composite pigment and the sulfur-containing polymer as described or preferably as described above, maintaining the stated weight proportions, directly into an extruder to form precursors of the in situ produced polymer particles, and (ii) in a second process step, the precursors of the in situ produced polymer particles from step (i) are homogeneously extruded together with a polyamide or polyester carrier polymer matrix and solidified.

[0087] In a preferred embodiment of the alternative process for the preparation of the polymer composition according to the present invention, both process steps are melt extrusions.

[0088] The granules of the polymer composition according to the invention obtained according to a preferred embodiment preferably have a diameter in the range of 0.1 to 5 mm, preferably 2 to 3 mm, measured as a numerical average by optical methods. The preferably obtained granules preferably have a diameter in the range of 0.1 mm to 5 mm, preferably 2 to 3 mm, measured by sieving methods, whereby at least 90% of the granule particles, particularly preferably at least 99% of the granule particles, have a diameter in the range of 0.1 to 5 mm, preferably 2 to 3 mm, whereby the stated percentages refer to the number of particles.

[0089] In the case of non-spherical granules, the diameters mentioned above refer to the smallest dimension of the granule particle.

[0090] The present invention further relates to the use of a polymer composition as described, or preferably as described above, as a laser engraving or laser welding additive in an organic polymer composition.

[0091] For purposes of this invention, the term "plastic to be marked" is intended to be synonymous with "organic polymer composition to be marked."

[0092] The present invention further relates to a laser-engravable or laser-weldable organic polymer composition comprising a polymer composition comprising a polyamide or polyester carrier polymer matrix in which polymer particles are embedded, wherein the polymer particles consist of particulate titanium oxide or particulate titanate, each of which may be doped, and a sulfur-containing polymer matrix in which a composite pigment is uniformly embedded, and wherein at least 80 wt. % of the composite pigment, based on the total weight of the composite pigment, consists of titanium dioxide (TiO) and antimony-doped tin dioxide ((Sb,Sn)O), as described, or preferably as described above.

[0093] The polymer compositions according to the invention, which comprise a polyamide carrier polymer matrix, are particularly suitable for incorporation into plastics to be marked that are compatible with polyamide.

[0094] Polymer compositions according to the present invention containing a polyester carrier polymer matrix are particularly suitable for incorporation into polyester-compatible plastics to be marked.

[0095] The incorporation of the polymer composition according to the invention into the plastics to be marked as described, or preferably as described above, as a laser engraving or laser welding additive is carried out by conventional methods known to those skilled in the art, for example by mixing and molding, optionally under the influence of heat. For example, the preparation of the organic polymer composition to be marked is carried out by mixing the organic polymer, for example as polymer granules, with the polymer composition according to the invention as a laser marking or laser welding additive, and optionally further additives such as adhesion promoters, stabilizers, flame retardants, fillers or colorants, in a suitable mixer.

[0096] The pigmentation of plastics is usually carried out by means of color concentrates (masterbatches) or compounds. The mixture obtained in this way can be processed directly in an extruder or injection molding machine. The molded parts obtained in this type of processing exhibit a very uniform distribution of the laser-engraved or laser-welded additive. The resulting extrudates can be further converted into any plastic molded part and can also be marked with laser light. Molded parts produced by the injection molding process, or films or coatings on the articles, can then be conventionally marked using a suitable laser. The addition of the laser marking or laser welding additive to the plastic material can be performed simultaneously or sequentially. Adhesives and stabilizers can optionally be added to the plastic material (preferably plastic granules) when incorporating the laser additive.

[0097] The laser marking or laser welding additive according to the invention is added to the organic polymer or plastic intended for laser marking in a proportion of 0.1 to 30% by weight, preferably 0.5 to 20% by weight, particularly preferably 1 to 10% by weight, based on the weight of the plastic to be marked.

[0098] Therefore, the present invention further relates to a laser-markable or laser-weldable organic polymer composition, characterized in that the proportion of the laser-marking or laser-welding additive according to the invention is 0.1 to 30% by weight, based on the weight of the organic polymer composition.

[0099] Solid-state or fiber lasers with wavelengths of 355 nm (UV), 534 nm (green laser), 1064 nm or 1062 nm (NIR laser, NIR = near infrared) are generally very suitable for laser marking of plastics or plastic-containing coatings on articles.

[0100] Pulsed solid-state or fiber lasers with a wavelength of 1064 nm or 1062 nm have proven particularly suitable, for example solid-state lasers with an emission wavelength of 1064 nm or fiber lasers with an emission wavelength of 1064 / 1062 nm made of Nd:YAG or Nd:yttrium vanadate single crystals.

[0101] The laser markings produced are abrasion resistant and can be used on light-colored or colored plastics wherever very dark markings with sharp edges need to be produced.Example applications, although not exhaustive, include: control panels and accessories in the automotive and aerospace industries, electrical engineering / electronics and machinery manufacturing; engraving and marking on appliances, appliances and consumer goods such as washing machines, coffee makers, smartphones and televisions; logos, type designations and individual markings on all kinds of equipment, containers, toys and tools, as well as decorative labels in the advertising field.

[0102] The present invention will be described below with reference to examples, but the present invention is not limited to these. [Example]

[0103] example Preparation of composite pigments: 100 g of roughly spherical TiO2 particles (Kronos 2900, KRONOS Inc.) with an average particle size ranging from 100 to 300 nm (measured under standard conditions by laser diffraction using a Malvern 2000 measuring instrument, Malvern Ltd., UK) were heated to 75 °C while stirring in 2 L of demineralized water. The pH of the suspension was adjusted to 2.0 using 10% hydrochloric acid. Next, a tin antimony chloride solution in hydrochloric acid consisting of 264.5 g of 50% SnCl4 solution, 60.4 g of 35% SbCl3 solution, and 440 g of 10% hydrochloric acid was slowly added while the pH of the suspension was kept constant by simultaneously slowly adding 32% sodium hydroxide solution. After the addition was complete, the mixture was stirred for another 15 minutes. Next, the pH was adjusted to 3.0 by adding 32% sodium hydroxide solution, and the mixture was stirred for another 30 minutes. The product is filtered, washed, dried, calcined at a temperature of 500-900°C for 30 minutes, and sieved through a 50µm sieve.

[0104] Particle size range of 0.1 to 1.7 μm, D of 0.18 μm 50 A composite pigment containing TiO2 and (Sb,Sn)O2 is obtained having a D90 value of 0.74 μm. The composite pigment has a pale greenish-gray masstone. The Sn:Sb ratio in the coating is 85:15.

[0105] Preparation of laser additives: The following starting materials are used for the preparation of the polymer compositions according to the invention and for the comparative examples:

[0106] As absorbing particles: A-1: Kronos® 2220 - Kronos titanium dioxide A-2: Iriotec® 8850 - Merck KGaA - composite pigment corresponding to the above example A-3: Iriotec® 8815 - Antimony tin oxide from Merck KGaA A-4: Iriotec® 8820 - Antimony tin oxide from Merck KGaA, titanium dioxide on mica A-5: Iriotec® 8841 - Merck KgaA copper hydroxyphosphate (90%) + antimony tin oxide (10%)

[0107] In Table 1, the absorbent particles used in each case are referred to as absorber 1 and / or absorber 2. As matrix polymer: M-1: Celanese's Fortron® 1200L1-PPS As carrier polymer: T-1: Vestamid® L1600-PA12 from Evonik Test polymers: P-1: BASF Ultramid® B3K-PA6 Test pigments: PP-1: KRONOS® 2220 - KRONOS titanium dioxide

[0108] Precursor preparation: The various precursors were prepared using a twin-screw extruder (Leistritz Mikro 27, screw diameter 27 mm, length 36 D). The precursor compositions are listed in Table 1. When using two types of absorbents, a premix of the two powder absorbent particles and pre-ground matrix polymer was first prepared in a tumble mixer. The material was then fed into the main hopper of the extruder and extruded. The screw rotation speed was 250 rpm. The throughput for all compounds was 12 kg / h. The temperature in zones 1 to 10 was 290 °C, as was the temperature at the extrusion head. The material was extruded through a perforated plate with two 2 mm diameter nozzles, forming strands, which were cooled in a water bath and then cut into cylindrical granules by a rotating blade.

[0109] [Table 1]

[0110] Preparation of laser marking concentrates, i.e., compositions comprising polyamide as carrier polymer and polymer particles produced in situ according to the precursors of Table 1 The series of laser marking concentrates K-1 to K-6 were prepared using the same extruder (Leistritz Mikro 27, screw diameter 27 mm, length 36D). The compositions are shown in Table 2. For this purpose, the precursor and carrier polymer were mixed in a tumble mixer and added through the main hopper of the extruder. The screw rotation speed was 250 rpm, and the throughput was 15 kg / h. The temperatures were 320°C in zone 1, 300°C in zone 10, and 300°C at the extrusion head. The discharged melt was converted into granules by strand pelletization as described above. The laser marking concentrates are referred to as "concentrates" in Table 2 and in the other examples.

[0111] [Table 2]

[0112] Preparation of laser-markable plastics Laser-markable polyamides were prepared by extrusion in a twin-screw extruder (LabTech, screw diameter 16 mm, length 40 D). The composition of the laser-markable polyamides is shown in Tables 3a and 3b. The laser-markable concentrates in Table 2 were mixed with the test polymer and, optionally, the test pigment in a tumble mixer, and the mixture was added to the main hopper of the extruder. The screw rotation speed was 400 rpm, and the throughput was 4 kg / h. The temperature was 260 °C in zone 1 and 250 °C in zone 10 and the extruder head. Strands were produced through a perforated plate with a 2 mm diameter nozzle. They were cooled in a water bath and granulated with a rotating blade.

[0113] For the laser-markable plastics in Table 3a, each laser-marking concentrate is tested with a test polymer. The laser-markable plastics in Table 3b represent blends of a carrier polymer and titanium dioxide as the test pigment. The performance of the materials in opaque formulations is evaluated through the plastics in Table 3. This is important because the laser additives according to the present invention are frequently used in opaque, highly filled systems. The laser-markable plastics are referred to as "compounds" in Tables 3a and 3b.

[0114] [Table 3a]

[0115] [Table 3b]

[0116] The laser-markable plastics C-1 to C-8 are then converted into tiles using an injection molding process in an Arburg Allrounder 320D. The tiles have dimensions of 60 x 90 x 1.5 mm and a smooth surface. The injection molding temperature corresponds to the specifications of the test polymer P-1. The heating zone is correspondingly set at 260°C. The tiles are used to verify the laser marking.

[0117] Laser marking rating: Laser marking is verified using a Trumpf VMc5 12-watt vanadate IR laser system. First, a so-called test grid is marked. The marking speed (v [mm / s]) and frequency (f [kHz]) are varied with a predefined power (p [%]). The focus is precisely set on the material surface, with a constant line spacing of 50 μm. The power is set constant at 100%. The speed is between 500 and 5000 mm / s, and the frequency is between 20 and 100 kHz. Such a test grid is primarily used for the initial evaluation of the marking contrast achievable under optimal laser conditions. In a second step, a solid rectangle measuring 5 cm x 3 cm is printed on another tile with the laser. Here, the laser power is set to 100%. The marking speed is 3000 mm / s, and the frequency is 80 kHz. The line spacing is 50 μm.

[0118] The area of the laser-marked rectangle and the color of the tile are then measured using a Minolta CR-400 color spectrometer according to CIE Lab. The contrast of the marking results from the difference between the L value of the tile color and the L value of the marking. A particularly high value indicates good contrast of the marking.

[0119] [Table 4a]

[0120] Table 4a clearly shows that only the laser-markable plastic C-1 according to the invention with the polymer composition K-1 according to the invention, which comprises M-1, A-1, A-2 and T-1, has the desired properties, in particular high marking contrast.

[0121] The two laser-markable plastics, each consisting of individual components (C-2 only A-1, C-3 only A-2), fall significantly short of the blend's properties. Other comparative examples (C-4 containing pure antimony tin oxide A-3, C-5 containing a composite pigment without the titanium dioxide core A-4, and C-6 containing copper hydroxyphosphate A-5) also fall significantly short in performance.

[0122] [Table 4b]

[0123] Table 4b clearly shows that the colored laser-markable plastic C-7 containing the laser concentrate K-1 according to the invention offers advantages with respect to the neutral color of the test tiles in combination with a very dark laser marking, which results in the desired high marking contrast.

[0124] Thus, the laser marking additive K-1 according to the present invention is easier to color than the comparative additive K-5, which represents an important market requirement.

[0125] When a carrier polymer comprising BASF's Ultramid® B3K-PA6 is used instead of T-1, the laser marking results show the same advantages as the concentrate according to the invention (replacement of K-1* with PA6) compared to the comparative concentrates (replacements of K-2 to K-6 with PA6).

Claims

1. A polymer composition comprising a carrier polymer matrix of polyamide or polyester in which polymer particles are embedded, wherein the polymer particles consist of particulate titanium oxide or particulate titanate, respectively, which may be doped, and a sulfur-containing polymer matrix in which a composite pigment is uniformly embedded, wherein at least 80% by weight of the composite pigment, based on the total weight of the composite pigment, is titanium dioxide (TiO 2 ) and antimony-doped tin dioxide [(Sb, Sn)O 2 The polymer composition comprising:

2. 2. The polymer composition according to claim 1, wherein the polyamide or polyester has a melting point in the range of 160 to 250°C.

3. 2. The polymer composition according to claim 1, characterized in that the polyamide is PA6 or PA12.

4. 2. The polymer composition according to claim 1, characterized in that the polyester is polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), or polybutylene terephthalate (PBT).

5. 2. The polymer composition according to claim 1, wherein the sulfur-containing polymer is polysulfone or polyphenylene sulfide.

6. 6. The polymer composition according to claim 5, characterized in that the polysulfone is selected from polysulfone (PSU), polyarylene sulfone (PAS), polybisphenylsulfone (PSF), polyethersulfone (PES) or polyphenylene sulfone (PPSU).

7. 2. The polymer composition according to claim 1, wherein the particulate titanium oxide is particulate titanium dioxide which may be doped.

8. 2. The polymer composition according to claim 1, wherein the particulate titanate is aluminum titanate, bismuth titanate, copper titanate, iron titanate, magnesium titanate, potassium titanate, sodium titanate, zinc titanate, calcium titanate, cerium titanate, barium titanate, or strontium titanate.

9. The composite pigment comprises a titanium dioxide core and at least one antimony-doped tin dioxide coating, and optionally a titanium dioxide core and (Sb, Sn)O 2 2. The polymer composition according to claim 1, characterized in that it has an outer protective layer and / or one or more intermediate layer(s) between the coatings.

10. 10. The polymer composition of claim 9, wherein the antimony-doped tin dioxide coating is made of a material having a weight percentage ratio of antimony to tin of 2 to 35 wt. %, based on the total weight of antimony and tin.

11. 2. The polymer composition according to claim 1, wherein the weight percentage of the particulate titanium oxide or particulate titanate relative to the composite pigment is 50 to 99% by weight, based on the total weight of the particulate titanium oxide or particulate titanate and the composite pigment.

12. A process for preparing the polymer composition according to any one of claims 1 to 11, comprising: (i) in a first process step, intimately mixing particulate titanium oxide or particulate titanate with a composite pigment; (ii) in a second process step, intimately and uniformly mixing this solid mixture from (i) with a sulfur-containing polymer to form a powder mixture; (iii) the powder mixture is plasticized and homogenized in a third process step to form in situ precursors of the polymer particles to be produced; (iv) in a fourth process step, homogeneously extruding and solidifying the in situ produced polymer particle precursors from step (iii) together with a polyamide or polyester carrier polymer matrix; The process, characterized by:

13. A process for preparing the polymer composition according to any one of claims 1 to 11, comprising: (i) particulate titanium oxide or particulate titanate is metered directly into an extruder together with a composite pigment and a sulfur-containing polymer to form a precursor of polymer particles produced in situ; (ii) in a second process step, homogeneously extruding and solidifying the in situ produced polymer particle precursors from step (i) together with a polyamide or polyester carrier polymer matrix; The process, characterized by:

14. Use of the polymer composition according to any one of claims 1 to 11 as a laser engraving or laser welding additive in an organic polymer composition.

15. A laser-markable or laser-weldable organic polymer composition comprising the polymer composition of any one of claims 1 to 11.

16. 16. The laser-markable or laser-weldable organic polymer composition according to claim 15, characterized in that the proportion of the polymer composition according to any one of claims 1 to 11 is 0.1 to 30 wt.-%, based on the weight of the organic polymer composition.