MATTING ADDITIVES

Abstract: TiO2 pigments are used as matting additives for incorporation in polyester. To improve the processability of the TiO2 pigments, the same are embedded in an organic substance in a fine dispersion.

Description: Matting Additives Description This invention relates to matting additives for the further processing in polyesters, in particular for the production of synthetic fibers, films and bottles, consisting of Ti0 pigments with an average grain size d 50 of 0.2 to 0.7 μm. It is known that during the production of synthetic fibers Ti0 2 pigments are added in an amount of 0.03 to 3 wt-% , in order to achieve a matting, i.e. a reduction of the greasy lustre or the transparency of the synthetic fibers and to produce a surface structure which provides for an improvement of the running properties of the synthetic fibers during the further manufacturing process. In the production of polyester fibers, the matting additive is added to the mass flow in the form of a suspension between the esterification or transesterification stage and the pre- polycondensation stage. In the journal Chemiefaser/Textilindustrie 40/92, 1990, Deut- scher Fachverlag GmbH, Frankfurt/Main, pp. 1063 to 1066 the melt matting process is described, where after the polycon- densation stage the polyester melt is divided into two partial streams. From the partial stream to be modified another partial stream is branched off, and the matting additives are dispersed in the same in a double-shaft extruder. One aspect of the melt matting process consists in the use of correspondingly composed master batches. In the production of polyesters it is important that the grain size of the Ti0 2 pigments used as matting additives is not much larger than 1/10 of the diameter of the polyester fibers of 3 to 30 μm. This means that optimally dispersed Ti0 2 pigments may have a grain size of 0.2 to 0.3 μm. Larger Ti0 2 pigments can act as "predetermined breaking points" in the synthetic fibers. It is therefore necessary that Ti0 2 pigments used for the production of polyester fibers have a rather small content of oversize particles of > 1 μm. Moreover, the filter packs disposed before the spinning nozzles are clogged by oversize particles and thus have a reduced service life. Therefore, a manufacturer of fibers must control the quality of the employed Ti0 2 pigments before using the same, must safely handle the dosage of the Ti0 2 pigments and ensure their optimum dispersion. However, this involves a considerable technical effort and manpower. It is the object of the present invention to create matting additives for the further processing, in particular in polyester fibers, films and bottles, on the basis of Ti0 2 pigments which can be processed by the user with comparatively distinctly reduced effort, can easily be dispersed in the mass flow, do not tend to reflocculate and contain no oversize particles. This object is solved in that 0.2 to 50 wt-% of the Ti0 2 pigments are embedded in at least one of the organic substances polyols, polyglycols and polethers in a fine dispersion. Preferred embodiments of the inventive matting additives are represented in claims 2 to 4. For producing the matting additives, 20 to 60 wt-% Ti0 2 pigments are dispersed in an aqueous solution containing 0.2 to 50 w " t-% (based on the Ti0 2 content) dissolved organic substance, the dispersion is ground wet to an average grain size d 50 of 0.2 to 0.5 μm, the content of oversize particles of > 1 μm is separated, and then the suspension is dried. Claims 6 to 8 include preferred aspects of the manufacturing process. The matting additives composed in accordance with the invention are flowable, easy to meter, easily dispersible and system-compatible. In addition, the Ti0 2 contained in the matting additives is free from oversize particles and shows no tendency to reflocculate. This provides in particular for the use of low shear forces when incorporating the same in the polyester mass flow for the production of staple fibers, films and bottles, and leads to a homogeneous distribution in the mass flow. It was surprisingly found out that the matting additives composed in accordance with the invention can be used as catalysts which clearly accelerate the polycondensation during the production of polyesters. Up to now, it has been assumed that the addition of matting additives has no positive or negative influence on the polycondensation rate. In conventional processes for the production of polyesters by esterification of terephthalic acid or transesterification of dimethyl terephthalate and subsequent prepolycondensation and polycondensation, special catalysts, in particular compounds containing antimony, such as antimony trioxide or antimony acetate, are generally added to the mass flow prior to the prepolycondensation stage. By incorporating the inventive matting additives in the mass flow, the duration of the polycondensation is reduced by up to 20 % with the same amount of catalyst. This effect leads to an increase of the throughput in the polycondensation stage and thus to an increase in capacity in the production of polyesters. It is also advantageous that the amount of catalyst consisting of antimony- containing compounds can be reduced. The invention will subsequently be explained in detail and by way of example. In an open stirred tank, 8515 g fully deionized water and 585 g polyethylene glycol type 2000 (corresponds to 15 % based on the solids content) are provided, and 3900 g (corresponds to 30 % based on the dispersing preparation) finely divided Ti0 pigments are added in portions by stirring. Upon predispers- ing this mixture by means of a dissolver, bead grinding is effected by means of a continuously operating 1.4 1 bead mill with a throughput of about 8 1/h. For separating the oversize particles of > 1 μm, the outlet of the bead mill is charged into a sedimentation plant, whose outlet is spray-dried by means of an electric spray tower. Of this matting additive, 250 g are introduced by means of a dissolver disk at a low speed of 2000 rpm into 175 g of the ethylene glycol provided in a dispersion vessel. Subsequently, the suspension thus obtained is dispersed for 15 min at a speed of 7000 rpm. By adding additional ethylene glycol, the suspension is then diluted to a Ti0 2 content of 20 wt-% (matting suspension in accordance with the invention) . As compared to this, Ti0 2 pigments of the anatase modification are dispersed in accordance with the prior art in the same way as described above, and then the suspension is subjected to bead grinding for 30 min at a temperature of 30 °C and a speed of 1000 rpm, where as grinding beads glass beads with a diameter of 1160 to 1400 μm are used. Upon separating the glass beads, the suspension is diluted to a Ti0 2 content of 20 wt-% by adding ethylene glycol (reference suspension in accordance with the prior art). For the use of the matting suspension in accordance with the invention and the reference suspension in accordance with the prior art as matting additives for polyethylene terephthalate (PET), dimethyl terephthalate (DMT) is each transesterified with ethylene glycol in a molar ratio of 1:2.5 in an autoclave at a temperature of 150 to 200 °C by adding 0.05 wt-% manganese-acetate catalyst. For matting purposes, matting suspension in accordance with the invention is added to the molten transesterification product in one case, and in the other case reference suspension in accordance with the prior art is added, so that there is each achieved a concentration of 0.3 wt-% Ti0 based on the polyester to be formed. Upon transesterification, the excess ethylene gylcol is removed from the suspension by increasing the temperature to 250 °C. Then, further condensation up to an intrinsic viscosity of 0.65 dl/g is effected in the polycondensation stage at a temperature up to 285°C under a vacuum of about 0.1 bar and by adding antimony trioxide as polycondensation catalyst. By employing the inventive matting additives in the form of the matting suspension, the polycondensation time is reduced by 15 % as compared to the use of the reference suspension.

Claims: Claims 1. Matting additives for incorporation in polyester, in particular for the production of staple fibers, films and bottles, consisting of Ti0 2 pigments with an average grain size d 50 of 0.2 to 0.7 μm, characterized in that 0.2 to 50 wt-% of the Ti0 2 pigments are embedded in at least one of the organic substances polyols, polyglycols and polyethers in a fine dispersion. 2. The matting additives as claimed in claim 1, characterized in that 0.2 to 35 wt-%, preferably 10 to 30 wt-% of the Ti0 2 pigments are embedded in at least one of the organic substances in a fine dispersion. 3. The matting additives as claimed in any of claims 1 and 2, characterized in that the Ti0 2 pigments are embedded in polyethylene glycol in a fine dispersion, preferably with molar masses of 1000 to 3000. 4. The matting additives as claimed in any of claims 1 to 3 , characterized in that the organic substance into which the Ti0 2 pigments are embedded in a fine dispersion contains up to 5 wt-%, preferably up to 2 wt-% of an anti- oxidant . 5. A process of producing the matting additives for incorporation in polyester, in particular for the production of staple fibers, films and bottles, consisting of Ti0 2 pigments with an average grain size d 50 of 0.2 to 0.7 μm, which in an amount of 0.2 to 50 wt-% are embedded in at least one of the organic substances polyols, polyglycols and polyethers in a fine dispersion, characterized in that in an aqueous solution containing 0.2 to 50 wt-% (based on the Ti0 2 content) dissolved organic substance 20 to 60 wt-% Ti0 2 pigments are dispersed, the dispersion is ground wet to an average grain size d 50 of 0.2 to 0.5 μm, ' the content of oversize particles of > 1 μm is removed from the suspension, and the suspension is dried. 6. Use of the matting additives as claimed in any of claims 1 to 4 as catalyst for the production of polyesters.

Inventors: KASTNER JUERGEN, MEYERS FRANZ, WEDLER MICHAEL, WEISER PETER, KASTNER, JUERGEN, MEYERS, FRANZ, WEDLER, MICHAEL, WEISER, PETER
Applicants: KASTNER JUERGEN, METALLGESELLSCHAFT AG, MEYERS FRANZ, WEDLER MICHAEL, WEISER PETER, KASTNER, JUERGEN, MEYERS, FRANZ, WEDLER, MICHAEL, WEISER, PETER
Application year: 1999
Main classification: C08K9
IPC codes: C08K9, C08L67, D01F1