Coated pigments for dyeing PVC

Abstract

The present invention relates to pigments comprising at least one inorganic compound selected from the group of iron oxides, iron oxide hydroxides, zinc ferrites, zinc oxides, magnesium ferrites and manganese ferrites, wherein the at least one inorganic compound is equipped with a coating comprising at least one hydroxide or oxide of magnesium or calcium and at least one fatty acid salt, to processes for production thereof, to the use thereof for coloring polyvinyl chloride (PVC) and to processes for coloring PVC and to PVC colored with such pigments, and also to plastics products comprising such pigments.

Claims

1. A pigment comprising at least one inorganic compound selected from the group consisting of iron oxides, iron oxide hydroxides, zinc ferrites, zinc oxides, magnesium ferrites, and manganese ferrites, wherein the at least one inorganic compound comprises a coating, and the coating consists of: at least one hydroxide and/or oxide of magnesium and/or calcium; and at least one calcium salt and/or magnesium salt of a fatty acid of the general formulae C.sub.nH.sub.2n+1COOH(I), C.sub.nH.sub.2n1COOH(II), C.sub.nH.sub.2n3COOH(III) and/or C.sub.nH.sub.2n5COOH(IV), where n is from 10 to 20, wherein the coating of the at least one inorganic compound consists of an outer layer and an inner layer, wherein A) one of the two layers is said at least one hydroxide or oxide of magnesium or calcium and B) the other of the two layers is said at least one calcium salt or magnesium salt of a fatty acid of the general formulae C.sub.nH.sub.2n1COOH (I), C.sub.nH.sub.2n1COOH (II), C.sub.nH.sub.2n3COOH (III) and/or C.sub.nH.sub.25COOH (IV), where n is from 10 to 20, wherein the layer according to A) is the inner layer.

2. The pigment as claimed in claim 1, wherein the coating is bonded directly to the at least one inorganic compound.

3. The pigment as claimed in claim 1, wherein the pigment comprises 0.3% to 30% by weight of magnesium and/or calcium, calculated as the sum total of the contents of the elements magnesium and calcium, where the sum total of the contents of the elements magnesium and calcium is based on the total weight of the pigment.

4. A method of coloring polyvinyl chloride, the method comprising mixing the pigment as claimed in claim 1 with polyvinyl chloride.

5. The pigment as claimed in claim 1, wherein: the coating is bonded directly to the at least one inorganic compound; the coating of the at least one inorganic compound consists of an outer layer and an inner layer, wherein A) one of the two layers is said at least one hydroxide or oxide of magnesium or calcium and B) the other of the two layers is said at least one calcium salt or magnesium salt of a fatty acid of the general formulae C.sub.nH.sub.2n+1COOH (I), C.sub.2n1COOH (II), C.sub.nH.sub.2n3COOH (III) and/or C.sub.nH.sub.2n5COOH (IV), where n is from 15 to 19, the pigment comprises 0.5 to 25% by weight of magnesium and calcium, calculated as the sum total of the contents of the elements magnesium and calcium, where the sum total of the contents of the elements magnesium and calcium is based on the total weight of the pigment; and the pigment comprises 0.2% to 15% by weight of the at least one calcium salt and/or magnesium salt of a fatty acid.

Description

EXAMPLES AND METHODS

(1) I. Description of the Measurement and Test Methods Used

(2) The results of the measurements for the examples are summarized in table 1.

(3) I.1 Mg and Ca Determination

(4) The magnesium and calcium content of the pigments was measured via optical emission spectrometry after excitation in an inductively coupled plasma (ICP-OES: inductively coupled plasma-optical emission spectrometry) as the content of the elements.

(5) I.2 Oil Value

(6) The oil value was determined according to standard DIN ISO 787/5 in g of oil/100 g of sample. Sample means either the uncoated pigment or the pigment of the invention.

(7) I.3 Testing of PVC Stability by Means of Thermo Haake Rheomix 600p Kneader (Kneader Stability)

(8) A pulverulent PVC mixture consisting of 50% by weight of Vestolit B 7021 Ultra+50% by weight of SorVyl DB 6668 Natur 3/03 is mixed homogeneously with the pulverulent pigment sample to be tested (4% by weight based on 100% PVC composition).

(9) A pulverulent PVC mixture consisting of 50% by weight of Vestolit B 7021 Ultra+50% by weight of SorVyl DB 6668 Natur 3/03 is mixed homogeneously with the pulverulent pigment sample to be tested (4% by weight based on 100% PVC composition) or the mixture to be tested.

(10) The pigmented PVC mixture is introduced manually into the recording kneader (Thermo Haake Rheomix 600p with R6 roil rotors) which has been preheated to 190 C. and is equipped with a rotary rheometer. The recording program (PolyLab Monitor) is started and records the torque on the roll rotors and the temperature of the sample against time. The pigmented PVC mixture is kneaded at 190 C. and 50 rpm. In order to determine the suitability of the coated pigment with regard to the stabilization of PVC, the maximum torque on the time axis in minutes at which the highest product temperature was measured is reported. After this maximum torque, the torque declines significantly, since the PVC breaks down to an increasing degree after this time and the viscosity of the kneaded product decreases as a result. These values are compared with the corresponding value for the same, albeit uncoated, pigment powder. The longer the period of time until said maximum, the higher the stability of the PVC colored with the coated pigment.

(11) II: Examples

(12) II.1 Properties of the Inorganic Pigments and Plastics Used

(13) Bayferrox 110 pigment powder from LANXESS Deutschland GmbH: hematite (red iron oxide, -Fe2O3) having a BET surface area to DIN ISO 9277 of 13-16 m.sup.2/g.

(14) Bayferrox 920: goethite, -FeOOH paste from LANXESS Deutschland GmbH, from which Bayferroxe 920 powder is produced by drying and grinding. The pulverulent pigment has a BET surface area to DIN ISO 9277 of 11-15 m.sup.2/g. Alternatively, it is also possible to mix the pulverulent Bayferrox 920 pigment with water to give a slurry having the appropriate pigment concentration (see examples).

(15) Calcium stearate: Powder from VWR BCH PROLABOV with Ca content between 9% and 11% by weight (calculated as CaO),

(16) SorVyl DB 6668 Natur 3/03: Rigid PVC compound from Polymerchemie (powder form, stabilized with Ca/Zn, where the content of bis(pentane-2,4-dionato)calcium is less than 1% by weight, with softening point>120 C., flashpoint>190 C., ignition temperature>303 C., density to DIN EN ISO 1183-1, method A of 1.39 g/cm.sup.3, bulk density to DIN EN ISO 60 of 0.54 g/ml, thermal stability to DIN EN 60811-3-2 of greater than/equal to 25 min.).

(17) VESTOLIT B 7021 Ultra: Mikro-S-PVC homopolymer from Vestolit (powder form, K value to DIN EN ISO 1628-2 of 70, viscosity number to DIN EN ISO 1628-2 of 125 cm.sup.3/g, bulk density to DIN EN ISO 60 of 0.3 of g/cm.sup.3, sieve analysisresidue on 0.063 mm sieve to DIN EN ISO 1624 of <1%, water content according to K. Fischer DIN 53 715 of 0.3%, pH of the aqueous extract to DIN EN ISO 1264 of 8, 1.5/s paste viscosity of 1.8 Pa s, 45/s paste viscosity of 2.2 Pa s).

(18) II.2 Inventive Examples and Comparative Examples

Example 1 (Comparative Example)

(19) 145.5 g of Bayferrox 110 pigment and 4.5 g of calcium stearate were added to the Henschel FM4 mixer. The two substances were mixed together at 161 C. and 1000 rpm for 20 min. The pulverulent product is used for the testing without further treatment.

Example 2 (Comparative Example)

(20) 141 g of Bayferrox 110 pigment and 9 g of calcium stearate were added to the Henschel FM4 mixer. The two substances were mixed together at 164 C. and 1000 rpm for 20 min. The pulverulent product is used for the testing without further treatment.

(21) Starting Material 1 for Examples 3 and 4

(22) To 3.3 dm.sup.3 of aqueous suspension of Bayferrox 110 (6.26 mol of Fe.sub.2O.sub.3) having a pH of 4.9 were added, at 60 C. while stirring, 1923 mL of an MgSO.sub.4 solution (2.58 mol/dm.sup.3 as MgO). Subsequently, 5.12 mol of NaOH per mole of Fe.sub.2O.sub.3 were added dropwise as a solution while stirring within 30 min. (2850 g with concentration 16.6 mol/dm.sup.3). The suspension was stirred for a further 60 min. The pH of the suspension was >11. After the reaction had ended, the pigment was filtered through a suction filter, washed until the conductivity of the filtrate was below 300 S/cm, dried to constant weight in a drying cabinet at 120 C. and ground in a Bauemieister mill (cross-beater mill with a sieve insert, mesh size 1 mm).

Example 3 (Inventive)

(23) 145.5 g of pigment (starting material 1) and 4.5 g of calcium stearate were added to the Henschel FM4 mixer. The two substances were mixed together at 162 C. and 1000 rpm for 20 min. The pulverulent product is used for the testing without further treatment.

Example 4 (Inventive)

(24) 141 g of pigment (starting material 2) and 9 g of calcium stearate were added to the Henschel FM4 mixer. The two substances were mixed together at 165 C. and 1000 rpm for 20 min. The pulverulent product is used for the testing without further treatment.

(25) The properties of the products are summarized in Table 1.

(26) TABLE-US-00001 TABLE 1 Calcium Oil value stearate (g of oil/ Kneader Mg content content 100 g of stability Example (% by wt.) (% by wt.) sample) (min.) Bayferrox 110 .sup.a) 0.01 0 24.8 14 1 0.01 3 24.8 14 2 0.01 6 23.6 14 3 10.5 3 33.1 19 4 10.2 6 29.4 20 .sup.a) uncoated pigment as direct comparison with examples 1 to 4