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AssigneeDr. Hans Heubach GmbH & Co. KG
InventorsIngrid Ressler, Gerhard Adrian, Walter Horn, Donald Gray
Estimating the term…
Plastics are described which contain, in intimate contact with the pigments, boric acid in a quantity of 1 to 20% by weight, preferably 2 to 15% by weight, of the dry pigment. Also described is the process for producing said plastics, in which the usual plastic granules or powders are mixed with the above-mentioned quantities of boric acid before, during or after addition of the pigment, and the boric acid is brought into intimate contact with the pigment before further processing, of the particulate plastic is mixed with the pigment containing the above mentioned quantities of boric acid before being subjected to further processing under thermal stress.
An improved temperature-stable pigment-colored plastic composition which comprises a thermoplastic synthetic resin, a pigment and a temperature-stabilizing additive capable of retarding the discoloration of the composition upon extended exposure to elevated temperatures, wherein said pigment is not an iron oxide pigment and wherein said additive consists of 1-15% by weight boric acid, based on starting pigment weight, in intimate contact with said pigment.
An injection moldable composition comprising a thermoplastic resin and an intimate dispersion of a sufficient amount of a pigment to impart noticeable color to the resin and a temperature-stabilizing additive capable of retarding the discoloration of the composition upon extended exposure to elevated temperatures, wherein said pigment is not an iron oxide pigment and wherein said additive consists of 1-15% by weight of boric acid based on starting pigment weight.
Dependencies are inferred from the claim text.
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Compounding polymers with additives, e.g. colouring: solid polymers with solid and/or liquid additives
Use of inorganic substances as compounding ingredients: boron-containing compounds
Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties: treatment with…
Particle morphology: particles consisting of a mixture of two or more inorganic phases
Term ended 4 May 2010 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
In hot processing of pigment-colored plastic compositions, as Polyethylene (HDPE , LDPE), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyphenylene oxide (PPO), polycarbonate (PC) and polypropylene (PP), the pigments are subjected, e.g. upon injection molding or extrusion, to a temperature strain that may lead to changes in color of the pigments.
Various methods are known in order to improve the temperature stability in the case of inorganic pigments. Methods which deal with the application of a homogeneous amorphous silicate layer, also in combination with other metal oxides, have been described specifically for chromate pigments in the U.S. Pat. Nos. 3,370,971, 3,798,045, 3,929,500, 3,942,998, 4,017,328 and 4,059,549. Precipitation of these components takes place through the addition of dissolved metal salts and subsequent precipitation of the corresponding insoluble metal oxides by way of control of the pH. In that regard, a treatment with water-soluble boron compounds takes place beforehand according to the U.S. Pat. Nos. 3,929,500 and 3,942,998.
The improvement in thermal stability that is obtained in this way is to be termed good to very good for many purposes of use.
19 g of a lead chromate, corresponding to C.I. Pigment Yellow 34, CONST. NO. 77600, which is stabilized lightly in known manner with minor amounts of silicic acid and/or metal oxides, were homogeneously blended with 1 g of boric acid.
A lead chromate-pigment preparation (pigment 2) was obtained, which exhibited a distinctly better temperature stability upon processing by injection molding, for instance in high-pressure polyethylene, as opposed to the one with the same lead chromate pigment without boric acid (pigment 1). So as to check on the temperature stability, 20 g of the pigment preparation or, resp., of the pigment were mixed with 1000 g of high-pressure polyethylene granulate and injected on the injection molding machine at 250.degree. C. (30 sec. residence time) and 300.degree. C. (5 min. residence time) to form 50.times.70.times.2 mm large chips. Subsequently thereto, the color difference DE was measured by means of the Zeiss-color measuring apparatus RFC 3, standard type of light D 65, the chip injected at 250.degree. C. (30 sec. residence time) respectively having served as 0-sample. The color differences DE are set forth in Table 1.
1000 g of high pressure polyethylene granulate were mixed with 2 g of boric acid and subsequently thereto there were added 18 g of a commercial lead sulfochromate (pigment 4) of the type C. I. Pigment Yellow 34, CONST. NO. 77603, medium-stabilized with SiO.sub.2 and metal oxides. Processing and temperature loading on the injection molding machine occurred in the manner as described in Example 1. Thereafter, the color differences DE were measured by comparison with the corresponding sample without addition of boric acid (pigment 3), respectively over against the corresponding 0-sample (see Example 1). The color differences DE are set forth in Table 1.