SAASTAMOINEN SIRPA (FI)
| WO2013062783A1 | 2013-05-02 | |||
| WO2013109441A1 | 2013-07-25 | |||
| WO2009109705A1 | 2009-09-11 | |||
| WO2015007954A1 | 2015-01-22 |
| US20160264786A1 | 2016-09-15 | |||
| US3510335A | 1970-05-05 | |||
| US3945965A | 1976-03-23 |
| Claims 1. A composite pigment composition comprising titanium dioxide and at least one precipitated porous pigment, which is selected from aluminium silicates, calcium sil icates, magnesium silicates, aluminium magnesium silicates, aluminium calcium sil- icates, aluminium calcium magnesium silicates, zinc silicates, aluminium zinc sili- cates, calcium zinc silicates, calcium magnesium silicates, aluminium calcium zinc silicates, aluminium calcium magnesium zinc silicates, aluminium magnesium zinc silicates, a combination/mixture of any other aluminium, magnesium, calcium and/or zinc silicate, silicas or any mixture thereof, wherein the average particle size of the composite pigment composition is at most 10 pm, determined by a laser diffraction technique. 2. The composite pigment composition of claim 1 , which comprises at least one precipitated porous pigment, which is selected from aluminium silicates, magnesium silicates, aluminium magnesium silicates and/or silicas. 3. The composite pigment composition of claim 1 , which comprises at least one precipitated porous pigment, which is selected from silicas. 4. The composite pigment composition of any one of claims 1 to 3, which comprises Na-, K-, L-, S04-, SO3-, P04-, BO3-, B-, PO3-, NO2-, NO3-, F-, carbonic acid-, car- boxylic acid-, zinc-, manganese-, iron-, zirkonium-, nickel-, cobolt-, chrome-, barium-, sulphur-, strontium-, carbon- and/or Cl- residues. 5. The composite pigment composition of any one of claims 1 to 4, which contains about 5-50% by weight, about 10-50% by weight, about 15-50% by weight or about 15-30% by weight of titanium dioxide based on the total weight of the final composite pigment composition. 6. The composite pigment composition of claim 5, which contains about 50% by weight, about 30% by weight, about 15% by weight, about 10% by weight or about 5% by weight of titanium dioxide based on the total weight of the final composite pigment composition. 7. The composite pigment composition of any one of claims 1 to 6, wherein the average particle size of the composite pigment composition is below 10 pm, below 5 pm, below 2 pm or below 1 pm, determined by a laser diffraction technique. 8. The composite pigment composition of any one of claims 1 to 7, wherein the average particle size of the composite pigment composition is at most 5 pm, at most 2 pm or at most 1 pm, determined by a laser diffraction technique. 9. The composite pigment composition of any one of claims 1 to 7, which has an average particle size in the range of 0.1-10 pm, in the range of 0.1-5 pm, in the range of 0.1-2 pm, in the range of 0.1-1 pm or in the range of 0.1-0.6 pm, deter- mined by a laser diffraction technique. 10. The composite pigment composition of any one of claims 1 to 9, wherein the pores inside the composition contain air. 1 1 . Use of the composite pigment composition of any one of claims 1 to 10 as a pigment in fillers of paper, carton, plastic, rubber, laminate or printing ink, or as a filler in any material wherein high light scattering is needed. 12. Use of the composite pigment composition of any one of claims 1 to 10 as a pigment in coating composition which is used for coating paper, carton, plastic, rub- ber, concrete, metal , composite or wood or as a filler for a material where high light scattering is needed. 13. Use of the composite pigment composition of any one of claims 1 to 10 as a pigment in decor- paper or a paint. 14. Use of the composite pigment composition of any one of claims 1 to 10 as a substitute for titanium dioxide as a pigment in a filler of paper, carton, plastic, rub- ber, laminate or printing ink, in a coating composition which is used as a coating in paper, carton, plastic, rubber, concrete, metal, composite or wood or in any other material wherein high light scattering is needed, in a paint or decor-paper. 15. The use of claim 14, wherein the composite pigment composition replaces 25- 100% by weight, 50-100% by weight, 75-100% by weight, about 100% by weight of titanium dioxide. 16. Use of the composite pigment composition of any one of claims 1 to 10 in re- ducing the basis weight of paper and/or carton or in thinning the coating layers, or paint or laminate without imparing the optical properties of the material. 17. A method for producing the composite pigment composition of any one of claims 1 to 10, wherein the method comprises: a) optionally providing and/or adding at least one compound containing mag- nesium and/or compound containing calcium and/or compound containing zinc in a liquid form, or optionally bringing at least one compound containing magnesium and/or compound containing calcium and/or compound containing zinc into a liquid form, b) optionally providing and/or adding at least one compound containing alu- minium, acid such as sulphur acid or carbon dioxide, a base or any mixture thereof, c) providing and/or adding titanium dioxide, d) providing and/or adding at least one compound containing silicon, e) mixing with a peripheral speed of at least 1 m/s, preferably 1-500 m/s, more preferably 1-250 m/s., f) filtrating the obtained composition, g) optionally dispersing the filter cake, h) optionally grinding the dispersion, i) optionally drying the dispersion. 18. The method of claim 17, wherein, the steps a), b), c), d) and/or e) can be per- formed in any order. 19. The method of claim 17 or claim 18, wherein the compounds used in the method steps a), b), c) and/or d) can be provided and/or added at once or in several portions during the precipitation. 20. The method of any one of claims 17-19, wherein the mixing is performed with rotor-rotor-mixing and/or rotor-stator-mixing. 21. The method of claim any one of claims 17 - 20, wherein there is no grinding step h). |
FIELD OF THE INVENTION
The present invention relates to a composite pigment composition which comprises titanium dioxide and at least one precipitated porous pigment. The in- vention also relates to the use of such a composite pigment composition as a pig ment providing opacity and/or brightness. Further, the invention relates to the use of the composite pigment composition according to the invention as a titanium di- oxide substitute without impairment of the optical properties. The invention also re- lates to a method for preparing the composite pigment composition of the inven- tion.
BACKGROUND OF THE INVENTION
Titanium dioxide (T1O2) is commonly used as a white pigment in paints, fillers of paper, carton, plastic, rubber, laminate and printing inks as well as in different kinds of coatings. The most important properties achived by the use of titanium di- oxide are opacity, coverage, brightness, tintability and L-value. T1O2 is the most ef- fective and very expensive pigment providing optical properties. White titanium di- oxide is commercially available as anatase crystals and rutile crystals. Both anatase and rutile crystals are non-amorphous and widely commercially available. There are also amorphous forms of T1O2 but these are not commercially widely available.
Because T1O2 is expensive and hard to recycle, so-called extenders are typi- cally added to titanium dioxide to substitute part of the required amount of titanium dioxide. Extenders are pigments or fillers, which are substantially cheaper than tita nium dioxide and which can be used to separate physically the crystals of titanium dioxide from each other and have the distances of the crystals more fitted for light scattering.
The amount of extenders should, however, be kept low, since the high refrac- tive index of T1O2 (about 2.49 - 2.61 ) gives finally the highest light scattering effi ciency and bigger amounts of extenders diminish the light scattering efficiency. Typ- ically, at most 25% by weight of titanium dioxide can be replaced in different appli- cations without losing the optical properties achvieved with titanium dioxide, es- pcially opacity. In addition, the producers of titanium dioxide commonly coat titanium dioxide with different organic and/or inorganic precipitation or polymer products of chemicals in an amount of 1 -20% based on the weight of the pigment.
Patent publication WO 2009/109705 (FP-Pigments Oy) discloses replacing ti- tanium dioxide partly with calsium carbonate. Patent publication WO 2015/007954 (FP-Pigments Oy) discloses compositions comprising titanium dioxide and addi- tives, which can be used for substitution of at least part of the titanium dioxide in said composition. The first additive comprises a composite pigment comprising a shell-forming component and an optical pigment, and a second additive comprises a reactive polymer. The shell-forming component is preferably an inorganic corn- pound having a low water solubility, such as precipitated calcium carbonate, calcium sulphate, barium sulphate, magnesium carbonate, magnesium silicate, aluminium hydroxide or aluminium silicate.
BRIEF DESCRIPTION OF THE INVENTION
An object of the present invention is to provide a composite pigment compo- sition, which comprises titanium dioxide and at least one precipitated porous pig ment. The composite pigment composition according to the invention is suited to be used in fillers of paper, carton, plastic, rubber, laminate and printing inks, in coating compositions for coating paper, carton, plastic, rubber, concrete, metal, composites and wood as well as in decor papers and paints. An object of the pre- sent invention is to provide a composite pigment composition, which comprises ti- tanium dioxide and at least one precipitated porous pigment for use as a pigment providing opacity and/or brightness. Further, an object of the present invention is the use of a composite pigment composition comprising titanium dioxide and at least one precipitated porous pigment as a titanium dioxide substitute without im- pairment of the optical properties. An object of the present invention is also to pro- vide a method for preparing the composite pigment composition.
The objects of the invention are achieved by the product, the use and the method characterized by what is stated in the independent claims. The preferred embodiments of the invention are disclosed in the dependent claims.
DETAILED DESCRIPTION OF THE INVENTION
The invention is directed to a composite pigment composition comprising tita- nium dioxide and at least one precipitated porous pigment, which composition is suitable to be used in fillers of paper, carton, plastic, rubber, laminate and printing inks, in coatings of paper, carton, plastic, rubber, concrete, metal, composites and wood, as well as in paints. The invention is directed to a use of the composite pig ment compostion as a pigment providing opacity and brightness. Further, the pre- sent invention is directed to the use of the composite pigment composition of the invention as a titanium dioxide substitute without impairment of the optical proper- ties. The invention is also directed to a method for producing the composite pig ment composition of the invention. The following facts affect the optical efficiency or the light scattering in a mate- rial when light attempts to traverse the material in coated or uncoated materials:
- air-solid -interfaces (the refractive index of air is about 1 , whereas usually the refractive indexes of other substances, such as plastics, fibers, rubbers and the most of pigments and fillers, are in the range of 1.4 -1.8),
- the distance between the pigments,
- the empty air pores of the pigments
- the refractive indexes of substances,
- the small average particle size of the pigments - optimum half of the wave- lenght of the light (visible light is in the range of 400-780 nm).
Critical Pigment Volume Concentration (CPVC) is, especially in coatings, an important measure describing the ratio of the binder and the pigment in the coat- ing, wherein the pigments are totally coated with the binder and the pores of the pigment are filled with the binder. With values smaller that CPVC, the portion of the binder is higher than the one of pigments in the coating, and the other way around, when the value is higher than CPVC. In the coatings of papers and in pri- mers, there is usually considerably more pigment than binder. In gloss paints, on the other hand, there is considerably more binder than pigment.
It was suprisingly found that titanium dioxide can be replaced partly (about 1 % by weight, 1-5% by weight, 5-15% by weight, 10-25% by weight ,at least 25% by weight, 25-50% by weight, 50-75% by weight, 75-100% by weight) or totally (100% by weight) with the composite pigment composition of the invention as a pigment providing optical properties (opacity and brightness) without imparing the optical properties provided to the produced material.
It was suprisingly found that pigments and fillers cheaper than titanium diox- ide can be replaced with the composite pigment composition of the invention hav- ing a better cost/light-scattering ability which offers a possibility to modify the ratios of the materials in order to have overall savings.
Thus, the raw material expenses of coated and uncoated materials can be reduced because of the excellent light-scattering ability and low cost of the compo- site pigment composition of the invention, or the materials can be thinned down without imparing the optical properties.
The invention works best when the average particle size of the composite pigment composition is about half of the wavelenght of light. It is advantageous to the invention that the pores of the pigment are full of air after the drying.
The composite pigment composition according to the invention comprises ti- tanium dioxide and at least one precipitated porous pigment selected from alumin- ium silicates, calcium silicates, magnesium silicates, aluminium magnesium sili- cates, aluminium calcium silicates, aluminium calcium magnesium silicates, zinc silicates, aluminium zinc silicates, calcium zinc silicates, calcium magnesium sili cates, aluminium calcium zinc silicates, aluminium calcium magnesium zinc sili- cates, aluminium magnesium zinc silicates, a combination/mixture of any other al- uminium, magnesium, calcium and/or zinc silicate, silicas or any mixture thereof.
In one embodiment, the composite pigment composition according to the in- vention comprises titanium dioxide and at least one precipitated porous pigment selected from the group consisiting of aluminium silicates, calcium silicates, mag- nesium silicates, aluminium magnesium silicates, aluminium calcium silicates, alu- minium calcium magnesium silicates, zinc silicates, aluminium zinc silicates, cal- cium zinc silicates, calcium magnesium silicates, aluminium calcium zinc silicates, aluminium calcium magnesium zinc silicates, aluminium magnesium zinc silicates, a combination/mixture of any other aluminium, magnesium, calcium and/or zinc sil icate, silicas or any mixture thereof.
In one embodiment of the invention, the composite pigment composition con- sists of titanium dioxide and at least one precipitated porous pigment selected from aluminium silicates, calcium silicates, magnesium silicates, aluminium mag- nesium silicates, aluminium calcium silicates, aluminium calcium magnesium sili- cates, zinc silicates, aluminium zinc silicates, calcium zinc silicates, calcium mag- nesium silicates, aluminium calcium zinc silicates, aluminium calcium magnesium zinc silicates, aluminium magnesium zinc silicates, a combination/mixture of any other aluminium, magnesium, calcium and/or zinc silicate, silicas or any mixture thereof, optionally Na-, K-, L-, S0 4 -, SO3-, P0 4 -, BO3-, B-, PO3-, NO2-, NO3-, F-, carbonic acid-, carboxylic acid-, zinc-, manganese-, iron-, zirkonium-, nickel-, cobolt-, chrome-, barium-, sulphur-, strontium-, carbon-, Cl- residues and/or resi- dues of other elements as well as optionally stabilizing agents, dispersing agents, surfactants and/or other conventional additives.
In one embodiment of the invention, the composite pigment composition comprises titanium dioxide and at least one precipitated porous pigment selected from aluminium silicates, calcium silicates, magnesium silicates, zinc silicates, alu- minium magnesium silicates, aluminium calcium silicates, aluminium zinc silicates, silicas, or any mixture thereof. In one embodiment of the invention, the composite pigment composition comprises titanium dioxide and at least one precipitated po- rous pigment selected from aluminium silicates, calcium silicates, magnesium sili cates, aluminium magnesium silicates, aluminium calcium silicates, aluminium cal- cium magnesium silicates, silicas, or any mixture thereof. In one embodiment of the invention, the composite pigment composition comprises titanium dioxide and at least one precipitated porous pigment selected from aluminium silicates, mag- nesium silicates and/or aluminium magnesium silicates. In one embodiment of the invention, the composite pigment composition comprises titanium dioxide and at least one precipitated porous pigment selected from calcium silicates, aluminium silicates and/or aluminium calcium silicates. In one embodiment of the invention, the composite pigment composition comprises titanium dioxide and at least one precipitated porous pigment selected from aluminium silicates, zinc silicates and/or aluminium zinc silicates.
In addition, the precipitated porous pigments of the invention may contain Na-, K-, L-, S0 4 -, SO3-, P0 4 -, BO3-, B-, PO3-, NO2-, NO3-, F-, carbon acid-, car- boxylic acid-, zinc-, manganese-, iron-, zirkonium-, nicel-, cobolt-, chrome-, barium-, sulphur-, strontium-, carbon-, Cl-residues and/or residues of other ele- ments. The type of these residues and/or elements depends on the starting mate- rials and/or other compounds used in the manufacture of the pigment composition.
The composite pigment composition of the invention does not contain poly- mers as additives. The composite pigment composition of the invention does not contain any shell structures.
The composite pigment composition of the invention contains at most 50% titanium dioxide by weight based on the weight of the final composite pigment composition. In one embodiment of the invention, the composite pigment composi- tion contains titanium dioxide about 50% by weight based on the weight of the final composite pigment composition. In one embodiment of the invention, the compo- site pigment composition contains titanium dioxide about 30% by weight based on the weight of the final composite pigment composition. In one embodiment of the invention, the composite pigment composition contains titanium dioxide about 15% by weight based on the weight of the final composite pigment composition. In one embodiment of the invention, the composite pigment composition contains titanium dioxide about 10% by weight based on the weight of the final composite pigment composition. In one embodiment of the invention, the composite pigment composi- tion contains titanium dioxide about 5% by weight based on the weight of the final composite pigment composition. In one embodiment of the invention, the compo- site pigment composition contains titanium dioxide about 5-50% by weight based on the weight of the final composite pigment composition. In one embodiment of the invention, the composite pigment composition contains titanium dioxide about 10-50% by weight based on the weight of the final composite pigment composi- tion. In one embodiment of the invention, the composite pigment composition con- tains titanium dioxide about 15-50% by weight based on the weight of the final composite pigment composition. In one embodiment of the invention, the compo- site pigment composition contains titanium dioxide about 15-30% by weight based on the weight of the final composite pigment composition.
The composite pigment composition of the invention can be used for provid- ing opacity and/or brightness in applications where organic binders are used in such amounts that they create a uniform film with the pigments. In these cases, CPVC-value is not attained. Applications of this kind include decor-paper, gloss paints, semi-gloss paints and outdoor paints.
The composite pigment composition of the invention may also contain addi- tives, such as stabilizing agents, dispersing agents, biocides and/or surfactants. The type of the additive depends on the purpose of use of the composite pigment composition.
The particles of the composite pigment composition of the invention are ag- gregates, which have a cluster-type formation made up of primary/ultimate parti- cles. Aggregates have a definite pattern of molecules formed of primary (ele- mental) particles by an irreversible process and they cannot be broken by me- chanical forces. As a result of the process, the specific surface area of an aggre- gate is smaller than the sum of its primary particles. Agglomerates consist of pri mary particles and/or aggregates which are joined loosely together e.g. at the cor- ners or edges and can be broken by mechanical forces.Thus agglomerates can change their size and shape.
The average particle size of the composite pigment composition of the inven- tion is at most 10 pm (0-10 pm), determined by laser measurement. In one em- bodiment, the average particle size of the pigment composition of the invention is below 10 pm, determined by laser measurement. In one embodiment of the inven- tion, the average particle size of the composite pigment composition is in the range of 0.1-10 pm or in the range of 0.2-10 pm, determined by laser measure- ment. In one embodiment of the invention, the average particle size of the compo- site pigment composition is in the range of 1-10 pm, determined by laser meas- urement. In one embodiment, the average particle size of the composite pigment composition of the invention is at most 5 pm (0-5 pm), determined by laser meas- urement. In one embodiment, the average particle size of the composite pigment composition of the invention is below 5 pm, determined by laser measurement. In one embodiment of the invention, the average particle size of the composite pig ment composition is in the range of 0.1-5 pm or in the range of 0.2-5 pm, deter- mined by laser measurement. In one embodiment of the invention, the average particle size of the composite pigment composition is in the range of 1-5 pm, de- termined by laser measurement. In one embodiment, the average particle size of the pigment composition of the invention is at most 2 pm (0-2 pm), determined by laser measurement. In one embodiment, the average particle size of the compo- site pigment composition of the invention is below 2 pm, determined by laser measurement. In one embodiment of the invention, the average particle size of the composite pigment composition is in the range of 0.1- 2 pm or in the range of 0.2- 2 pm. In one embodiment of the invention, the average particle size of the compo- site pigment composition is 1-2 pm, determined by laser measurement. In one embodiment, the average particle size of the composite pigment composition of the invention is at most 1 pm (0-1 pm), determined by laser measurement. In one embodiment, the average particle size of the composite pigment composition of the invention is below 1 pm, determined by laser measurement. In one embodi- ment of the invention, the average particle size of the composite pigment composi- tion is in the range of 0.1-1 pm or in the range of 0.2-1 pm determined by laser measurement. In one embodiment of the invention, the average particle size of the composite pigment composition is 0.1-0.6 pm or 0.2-0.6 pm, determined by laser measurement.
In one embodiment, the average particle size of the composite pigment corn- position of the invention after the precipitation step and before any grinding step is at most 10 pm (0-10 pm). In one embodiment, the average particle size of the composite pigment composition of the invention after the precipitation step and be- fore any grinding step is below 10 pm, determined by laser measurement. In one embodiment of the invention, the average particle size of the composite pigment composition after the precipitation and before grinding is in the range of in the range of 0.1-10 pm, 0.2-10 pm or 1-10 pm, determined by laser measurement. In one embodiment, the average particle size of the composite pigment composition of the invention after the precipitation and before grinding is at most 5 pm (0-5 pm), determined by laser measurement. In one embodiment, the average particle size of the composite pigment composition of the invention after the precipitation and before grinding is below 5 pm, determined by laser measurement. In one em- bodiment of the invention, the average particle size of the composite pigment corn- position after the precipitation and before grinding is in the range of in the range of 0.1-5 pm, 0.2-5 pm or 1-5 pm, determined by laser measurement. In one embod- iment, the average particle size of the composite pigment composition after the precipitation and before grinding is at most 2 pm (0-2 pm), determined by laser measurement. In one embodiment, the average particle size of the pigment corn- position after the precipitation and before grinding is below 2 pm, determined by laser measurement. In one embodiment of the invention, the average particle size of the composite pigment composition after the precipitation and before grinding is in the range of 0.1-2 miti, 0.2-2 miti or 1-2 miti, determined by laser measurement. In one embodiment, the average particle size of the composite pigment composi- tion after the precipitation and before grinding is at most 1 pm (0-1 pm), deter- mined by laser measurement. In one embodiment, the average particle size of the composite pigment composition after the precipitation and before grinding is below 1 pm, determined by laser measurement. In one embodiment of the invention, the average particle size of the composite pigment composition after the precipitation and before grinding is in the range of 0.1-1 pm or 0.2-1 pm determined by laser measurement. In one embodiment of the invention, the average particle size of the composite pigment composition after the precipitation and before grinding is in the range of 0.1-0.6 pm or 0.2-0.6 pm, determined by laser measurement.
In one embodiment of the invention, the average particle size and/or the par- ticle size distribution of the composite pigment composition is determined by laser diffraction technique. In one embodiment of the invention, the average particle size and/or the particle size distribution of the composite pigment composition is deter- mined by laser diffraction technique using equipment which is able to determine particle sizes in the range of 0.02-2000 pm. In one embodiment of the invention, the average particle size and/or the particle size distribution of the composite pig ment composition is determined with Malvern 2000-analyzer. The pore volume of the composite pigment composition of the invention is typically in the range of 0.15- 0.20 cm 3 /g.
In one embodiment, the composite pigment composition of the invention is not subjected to a grinding step after the precipitation. Grinding the precipitated composite pigment composition after the precipitation may break the structure of the pigment and thus affect harmfully to the light scattering ability of the pigment.
In addition, energy is saved when the grinding step can be omitted in the prepara- tion of the composite pigment composition.
In one embodiment, the composite pigment composition of the invention is prepared using a wet method of production.
In one embodiment of the invention, the air pores of the precipitated pig ments are kept empty after the drying, wherein the difference between the refrac- tive index of the air in the pores (about 1 ) and the refractive index of the pigment (1 .4-1 .8) can be utilized as light scattering, which is shown as better opacity and brightness.
The composite pigment composition of the invention is suited to be used as a pigment in fillers of paper, carton, plastic, rubber and printing inks. In addition to the pigment, filler compositions of this kind also contain conventional manufactur- ing agents and additives of fillers. In addition, the composite pigment composition of the invention is suited to be used as a pigment in coating composition which are used for coating paper, carton, plastic, rubber, laminate, concrete, metal, composites and wood. In addi- tion to the pigment, coating compositions of this kind also contain also conven- tional manufacturing agents and additives of coating compositions.
The composite pigment composition of the invention is suited to be used as a raw material in any material wherein high light scattering is needed.
The composite pigment composition of the invention is suited to be used as a pigment in decor-papers. Decor-papers of this kind also contain, in addition to the pigment, manufacturing agents and additives known to a person skilled in the art. Further, the pigment composition of the invention is suited to be used as a pigment in paints. In addition to the pigment, paints of this kind also contain conventional manufacturing agents and additives of paints. Titanium dioxide, other pigments, binders, rheological modifiers, adhesives and other necessary additives depending on the application can be used with the composite pigment composition of the in- vention.
In one embodiment of the invention, the composite pigment composition is suited to be used as a pigment providing opacity and/or brightness.
In one embodiment of the invention, the composite pigment composition is suited to be used to replace titanium dioxide without impairing the optical charac- teristics. The composite pigment composition of the invention is suited to be used as a substitute for titanium dioxide in fillers of paper, carton, plastic, rubber, lami- nate and printing inks. In addition, the composite pigment composition of the in- vention is suited to be used as a substitute for titanium dioxide in coating composi- tions which are used as coatings in paper, carton, plastic, rubber, concrete, metal, composites and wood, and as a pigment in paints and decor-papers.
About 1 -100 by weight of titanium dioxide can be replaced with the composite pigment composition of the invention without any detectable impairment in the op- tical characteristics. In one embodiment of the invention, 5 -100% by weight, 10- 100% by weight, 15-100% by weight of titanium dioxide can be replaced with the composite pigment composition of the invention without any detectable impairment in the optical characteristics. In one embodiment of the invention, 25 -100% by weight of titanium dioxide can be replaced with the composite pigment composi- tion of the invention without any detectable impairment in the optical characteris- tics. In one embodiment of the invention, 50 -100% by weight of titanium dioxide can be replaced with the composite pigment composition of the invention without any detectable impairment in the optical characteristics. In one embodiment of the invention, 75-100 % by weight of titanium dioxide can be replaced with the compo- site pigment composition of the invention without any detectable impairment in the optical characteristics. In one embodiment of the invention, about 25% by weight, about 50% by weight, about 75% by weight, about 85% by weight, about 95% by weight or about 100% by weight of titanium dioxide can be replaced with the com- posite pigment composition of the invention without any detectable impairment in the optical characteristics. In one embodiment of the invention, about 100% by weight of titanium dioxide can be replaced with the composite pigment composi- tion of the invention without any detectable impairment in the optical characteris- tics.
Since titanium dioxide can be replaced partially or totally with the composite pigment composition of the invention, remarkable savings in raw material costs can be achieved. With the composite pigment composition of the invention an equivalent light-scattering ability is achieved more advantageously than with tita- nium dioxide. With the composite pigment composition of the invention the materi- als to be produced can be thinned and/or lightened without weakening the attaina- ble light-scattering ability (brightness and opacity) compared to the use of titanium dioxide. Thus, lowering the basis weight of paper or carton is enabled, the number of coating layers can be reduced, coating layers from multilayer structures can be removed as unnecessary, or the coating layers, paint or laminate can be thinned without weakening the spreading capacity and/or brightness and opacity. Each of these actions leads to the reduction of material costs, increase in productivity and environmental sustainability.
The present invention also relates to a method for producing the described composite pigment composition, which method comprises the following steps: a) optionally providing and/or adding at least one compound containing mag- nesium and/or at least one compound containing calcium and/or at least one corn- pound containing zinc in a liquid form, or optionally bringing at least one corn- pound containing magnesium and/or at least one compound containing calcium and/or at least one compound containing zinc into a liquid form,
b) optionally providing and/or adding at least one compound containing alu- minium, acid such as sulphur acid or carbon dioxide, a base or any mixture thereof,
c) providing and/or adding titanium dioxide,
d) providing and/or adding at least one compound containing silicon, e) mixing with a peripheral speed of at least 1 m/s,
f) filtrating the obtained composition,
g) optionally dispersing the filter cake, h) optionally grinding the dispersion,
i) optionally drying the dispersion.
In the method of the invention, the method steps a), b), c), d) and/or e) can be performed in any order. Selection of the order of performing the method steps belongs to the knowledge of a skilled person and depends, among other things, on the compounds and reaction conditions to be used. In one embodiment of the in- vention, the method for producing the composite pigment composition does not contain a step of grinding the precipitated pigment (step h).
The compounds used in the method steps a), b), c) and/or d) can be pro- vided and/or added at once or in several portions during the precipitation. The compounds used in the method of the invention can be added simultaneously or separately. In the method of the invention, several compounds can be used. Typi- cally, the reactions of the method take place in a solution. The“at least one corn- pound containing magnesium” can be any compound that is suitable for the method, such as magnesium hydroxide, magnesium carbonate, magnesium sul- phate and/or magnesium chloride. The“at least one compound containing cal- cium” can be any compound that is suitable for the method, such as calcium hy- droxide, calcium carbonate, calcium sulphate and/or calcium chloride. The“at least one compound containing zinc” can be any compound that is suitable for the method, such as zinc sulphate, zinc chlorate, zinc chloride, zinc nitrate and/or zinc oxide. The“at least one compound containing aluminium” can be any compound that is suitable for the method, such as aluminium sulphate, polyaluminium chlo- ride and/or sodiumaluminate. The“at least one compound containing silicon" can be any compound that is suitable for the method, such as Na-, K- and/or L-silicate.
The composite pigment composition of the invention can be produced with an industrially applicable method, wherein mixing having peripheral speed of at least 1 m/s is utilized at least once in at least one method step. In a method according to one embodiment of the invention, the peripheral speed is 1 - 500 m/s. In a method according to one embodiment of the invention, the peripheral speed is 1 - 250 m/s. The mixing is performed preferably with mixers operating with rotor-rotor and/or rotor-stator techniques. In the mixing, a shock mixer, rotors rotating into op- posite directions, rotors rotating into the same direction with big relative speed dif- ference, dropping, a pin mill, strikes and/or counter strikes can be exploited. In ro- tors and stators the mixing elements are pins, wings, plates with holes, furrows or other corresponding bodies of different forms. The speed difference between the circles of rotors rotating to opposite directions or to the same direction or the cir cles of the adjacent rotors and stators is typically in the range of 5-400 m/s, pref- erably in the range of 5-200 m/s. Consequently, the material is subjected to very strong turbulence, shear and impact forces during processing (disintegration and atomization).
The following examples are given to illustrate the invention without, however, restricting the invention thereto.
Example 1
The preparation of the pigment sample was started with adding T1O2 solutions of magnesium hydroxide and aluminium sulphate into the medium of the reactor. A temperature above the freezing point of water and uniform mixing were used in the preparation. Dilute aluminium sulphate and sodium silicate were added into this so- lution so that the target pH was kept constant. Sodium silicate was used at least in an amount which is required for the stoichiometric reaction of magnesium and alu- minium. Rotor-rotor-mixing with peripheral speed of at least 1 m/s is was utilized along during the preparation. Finally before dispersing the filter cake into an aque- ous slurry, the pigment sample was filtrated and washed with water. The pigment sample thus obtained is called OPA2. OPA2 comprised 30.1 % Ti0 2 by weight and 69.9% precipitated aluminium magnesium silicate by weight. The average particle size of OPA2 was 0.44 pm.
In addition, a pigment sample OPA1 , which did not contain T1O2 , was prepared in a similar way than OPA2 expect for the addition of T1O2.
Example 2
The preparation of the pigment sample was started with adding T1O2 to a dilute solution of sodium silicate. A temperature above the freezing point of water and uniform mixing were used in the preparation. Dilute sulphuric acid was added into this solution so that the target pH was kept constant and sodium silicate was stoi- chiometrically reacted into silica (S1O2). Rotor-rotor-mixing with peripheral speed of at least 1 m/s was utilized along during the preparation. Finally before dispersing the filter cake into an aqueous slurry, the pigment sample was filtrated and washed with wa- ter. This composite pigment contained 15.7% Ti0 2 by weight and 84.3% precipitated sil ica (S1O2) by weight. The average particle size of this composite pigment was 0.77 pm.
Example 3
The pore sizes and the pore size distributions of pigment samples OPA1 , OPA2, Ti02A ja Ti02C were determined based on the measurements of isothermal adsoption-desorption points in a temperature of liquid nitrogen and the computa- tional handling of thus received adsoption-desorption isoterms. The pigment sam- ples were analysed with N2-sorption at -196 C (TriStar 3000, Micromeritics). The porocity of the pigments was estimated based on the amount of N2 in a proportional pressure of p/pO = 0.97. Barrett-Joyner-Halenda (BJH) theory was used herein. The porocity of the pigments of the pigment samples OPA1 , Ti02A and Ti02C (Kronos 2971) is shown in Table 1. Sample Ti02A contained 6.5% in- organic finishing. Sample Ti02C contains no finishing.
Table 1.
Only the pore volume of the samples OPA1 and OPA2 were significant. The pore volumes of the samples Ti02A and Ti02C were so low, that they could be due to the agglomeration of the particles.
Example 4
A paint paste was prepared from the pigment dispersion prepared in Example
1. The paste contained 5% dried pigment and 5% latex (Acronal S728, BASF) based on the amount of dry pigment. The pH of this aquoeus slurry was kept above pH- value 8.3 with the additions of lye while adding a thickener (Sterocoll FS, BASF) until the viscosity of the dispersion of 800 - 850 cp (Brookfield, 100 rpm, Spindle LV-4) was achieved.
The opacity and tone of the coatings of both 2.5 g/m 2 and 5 g/m 2 were meas- ured with an opacimeter (Rhopoint Novoshade Duo+). The coating was spread with standard rods nos. 4 and 7 (K Bar) of the rod coating method (RK101 Control Coater) onto a plastic film (Leneta 1 mm, clear polyester sheets). The pigments used were OPA1 , OPA2 and Ti02A (SR5, Venator).The results are shown in Table 2.
Table 2.
Example 5
The pigments OPA2 and Ti02A (SR5, Venator) were tested also in an un- coated fine paper. Tha pulp contained bleached pine and bleached eucalyptus (40:60) refined to the value SR30. Medium-cationic starch, 0.5% based on dry pulp, and size (AKD) 0.2% based on dry pulp, were added to the thick pulp. The tests were done in a dynamic sheet former so that the targets for basis weight and ash were 80 g/m 2 and 20%. These target values were achieved by adjusting the amount of furnish and the retention aid (PAM) in the dynamic sheet former. The papers pro- duced were machine calandered and dried in a drying drum before the conditioning of paper and testing. The results are shown in Table 3.
Table 3.
Example 6
In this example, the sheets of the previous example were HPL-laminated which is needed for the preparation of decor-paper. Decor-paper is laminated with resins using temperature above 120°C and pressure of 5 mPa. Lamination takes normally 40-50 minutes.The optical characteristics of laminated paper are usually called“wet opacity” and L-value, since the pigment is surrounded by the resin. The results of the laminated papers are presented in Table 4.
Table 4.
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