Composition comprising interactive ingredients

Abstract

A composition comprising titanium dioxide and additives useful for enhancing the optical performance of titanium dioxide or for allowing substitution of at least part of the titanium dioxide in said composition for additives. At least two additives are added, wherein a first additive comprises a composite pigment and a second additive comprises a reactive polymer. The invention also provides a method for enhancing the optical properties of titanium dioxide compositions.

Claims

1. An composition comprising a combination of titanium dioxide and additives useful for allowing substitution of at least a part of the titanium dioxide in said composition by said additives while maintaining the contrast ratio achieved by a composition comprising titanium dioxide without said additives, the additives comprising a composite pigment and a reactive polymer, wherein said composite pigment comprises titanium dioxide at least partly embedded in a shell formed by precipitated calcium carbonate and wherein the combination of titanium dioxide and said additives comprises 55 to 75 wt % titanium dioxide and the remainder the composite pigment and the reactive polymer.

2. The composition according to claim 1, wherein said composition is a coating material composition.

3. The composition according to claim 1, wherein said composition is selected from the group consisting of coating material compositions; paints; filling material compositions for paper or board, plastics or printing inks; and webs of paper or board or films, wherein said webs or films are coated with the aforementioned coating material composition or filled with the aforementioned filling material composition.

4. The composition according to claim 3 wherein the coating material compositions comprise coatings for paper or board.

5. The composition according to claim 1, wherein the reactive polymer comprises polymeric latex particles capable of adsorbing onto the titanium dioxide.

6. The composition according to claim 1, wherein the reactive polymer comprises polymer particles capable of forming covalent bonds with titanium dioxide.

7. The composition according to claim 6, wherein the covalent bonds are formed directly between titanium dioxide and the reactive polymer.

8. The composition according to claim 6, wherein the covalent bonds are formed between titanium dioxide and reacted coupling agents bound to the reactive polymer.

9. The composition according to claim 1, wherein the reactive polymer is formed from acrylic, polyurethane, vinyl acetate, VA/Veo Va, or poly(vinyl acetate).

10. The composition according to claim 1, wherein the reactive polymer is an acrylic-based pre-composite polymer.

11. The composition according to claim 1, which comprises from 8.7 to 9.43 wt % titanium dioxide, from 1.45 to 2.17 wt % composite pigment and 3.625 wt % reactive polymer.

12. The composition according to claim 11 which comprises 9.43 wt % titanium dioxide, 3.625 wt % reactive polymer, and 2.175 wt % composite pigment.

13. The composition according to claim 11 wherein the wt % of titanium dioxide is selected from 9.43 wt % and 8.7 wt %.

14. The composition according to claim 11 which comprises 9.43 wt % titanium dioxide, 3.625 wt % reactive polymer, and 1.45 wt % composite pigment.

Description

DETAILED DESCRIPTION

(1) The “composition” according to this invention shall be understood to include coating material compositions, particularly coatings for paper or board; paints; filling material compositions for paper or board, plastics or printing inks; and webs of paper or board or films, wherein said webs or films are coated with the aforementioned coating material composition or filled with the aforementioned filling material composition.

(2) Preferably, the composition is a coating material composition.

(3) The “composite pigment” comprises a shell-forming component and a pigment affecting the optical properties of the composition (in the following called optical pigment), wherein said optical pigment is at least partly embedded in the shell formed by the shell-forming component.

(4) Composite pigments of this kind are described in WO 2009/109705, FP-Pigments Oy.

(5) The “optical pigment” is a light-scattering and/or absorbing pigment, such as, but not limited to titanium dioxide, aluminium hydroxide, barium sulphate, kaolin, gypsum, ground or precipitated calcium carbonate, chalk, a silicate such as mica, magnesium carbonate, dolomite, talc, aluminium silicate, silica, or mixtures thereof, or organic pigment materials, such as plastic pigments and furnace black, or mixtures thereof.

(6) Advantageously, the optical pigment comprises titanium dioxide.

(7) The “shell-forming component” comprises an inorganic compound, preferably a synthetic, i.e. a precipitated inorganic compound, preferably an inorganic compound with low water solubility, such as precipitated calcium carbonate, calcium sulphate, barium sulphate, magnesium carbonate, magnesium silicate, aluminium hydroxide or aluminium silicate, most preferably precipitated calcium carbonate.

(8) Preferably, the composite pigment comprises a shell-forming component, which is precipitated calcium carbonate and an optical pigment, which is titanium dioxide or a mixture of optical pigments, where one of the pigments is titanium dioxide.

(9) The shell, which is formed of the calcium carbonate particles or other shell-forming components encases, partly or totally, approximately 1-20, especially approximately 1-10, preferably 1-6 optical pigment particles. The calcium carbonate structure is formed of calcium carbonate particles, the original size of which, before they are carbonated in order to attach them to other particles, is on average approximately 20-250 nm. When the calcium carbonate particles coalesce, they form an essentially continuous surface.

(10) The weight ratio between the optical pigment particles and the calcium carbonate particles or other shell-forming components is approximately 90:10 . . . 5:95, preferably approximately 60:40 . . . 5:95, and especially approximately 40:60 . . . 10:90.

(11) The composite pigment may comprise, besides the optical pigment particles and the calcium carbonate particles or other shell-forming components, also other elements, such as dispersants, surface modifying agents and stabilizing agents or mixtures thereof. However, the total amount of these is at maximum approximately 20 weight-% of the total weight of the composition, typically below 10 wt-%.

(12) When the shell-forming component is precipitated calcium carbonate, the composite pigments are produced by atomizing a calcium hydroxide-bearing aqueous slurry comprising optical pigment particles into a carbon dioxide-bearing gas, wherein the calcium hydroxide was converted to calcium carbonate. In case the shell-forming component is another precipitated inorganic compound, the composite pigments can be prepared in a similar manner.

(13) In this method, calcium carbonate particles are precipitated from calcium hydroxide and carbon dioxide in such a way that calcium carbonate particles adhere to the surface of optical pigment particles and are carbonated in order to attach them to other calcium carbonate particles, in which case essentially opaque and stable pigment-calcium carbonate aggregates are formed, which are at least partly covered with calcium carbonate particles.

(14) Typically, carbonation is carried out continuously in such a way that the aqueous slurry undergoes at least one atomizing. The light-scattering and calcium hydroxide-bearing aqueous slurry which comprises optical pigment particles is then led through a high energy mixing zone, in which zone the aqueous slurry is broken up into drops or even into nebulous drops, and then dripped into a carbon dioxide-bearing gas. If necessary, dispersants, surface modifying agents or stabilising agents or mixtures thereof are added to the composite pigment to be manufactured during or after manufacturing.

(15) Essentially, all of the calcium hydroxide-bearing aqueous slurry can be added to the carbonation together with the optical pigment particles. However, it is also possible to introduce the calcium hydroxide-bearing aqueous slurry into the carbonation gradually and in several batches, in which case most suitably at least part of the calcium hydroxide-bearing aqueous slurry is free of optical pigments when it is fed into the carbonation.

(16) Suitable reactive polymers are described for example in U.S. Pat. Nos. 5,385,960A, 7,081,488B2 and US 2013/0085222A1.

(17) In one embodiment, the reactive polymer comprises polymeric latex particles capable of adsorbing onto the titanium dioxide.

(18) In another embodiment, the reactive polymer comprises polymer particles capable of forming covalent bonds with titanium dioxide. The covalent bonds can be formed directly between titanium dioxide and the reactive polymer. Alternatively, the covalent bonds are formed between titanium dioxide and reacted coupling agents bound to the reactive polymer.

(19) According to a particularly preferred embodiment, the reactive polymer is a pre-composite polymer, for example of the kind wherein the polymer matrix is formed from a binder. The binder can be a polymer of pre-polymeric material. Thus, the polymer can be a homopolymer, a copolymer, or a blend of at least two polymers or copolymers. Specific examples of suitable polymer matrices include acrylic based pre-polymers, such as acrylic (co)polymers. The polymer matrices can incorporate vinyl acetate polymers, vinyl/acrylic copolymers, styrene/acrylic copolymers, polyurethanes, polyureas, polyepoxides, polyvinyl chlorides, ethylene/vinyl acetate polymers, styrene/butadiene polymers, polyester polymers, polyethers, and similar, as well as mixtures thereof. Preferred binders of the matrices are acrylic, polyurethane, vinyl acetate, VA/Veo Va, poly(vinyl acetate) and pressure polymer binders.

(20) Particularly preferred embodiments are represented by EVOQUE™ pre-composite polymers supplied by Dow Coating Materials.

(21) In addition to the three essential components (the reactive polymer, the composite pigment and TiO.sub.2), the presence of an opaque polymer may also assist in the development of the final dry hide of the coating.

(22) It is further possible to improve the dispersion of the TiO.sub.2 in the dry film by using emulsions with smaller droplet sizes (e.g. of the EVOQUE™ type). The smaller the droplet size the better the TiO.sub.2 is spaced during drying, thus helping to prevent pigment—pigment flocculation. This “spacing” is further enhanced by the reactive nature of the binder, which associates with the TiO.sub.2 unspecific conditions.

(23) Another way to improve the pigment performance is to “lock-in” the dispersion in such a way that, regardless of the drying conditions (or emulsion droplet particle size), the pigment cannot flocculate.

(24) The use of both technologies (reactive polymer and composite pigment) in the same coating results in optimized and more efficient use of TiO.sub.2 than if either technology is used alone or in conjunction with other TiO.sub.2 enhancers/spacers/extenders.

(25) The surface structure of the composite pigment used in the invention has been developed to allow the composite pigment to combine with both TiO.sub.2 and the reactive polymer, e.g. an acrylic-based pre-polymer, e.g. EVOQUE™ (Dow). We believe that this may be the reason for the unexpected synergistic effect in the coating whereby up to 45 wt-% of the TiO.sub.2 in a coating can be removed whilst maintaining the optical and mechanical properties of the coating.

(26) The following non-limiting examples illustrate further embodiments.

Example

(27) Various amounts of titanium dioxide in a coating composition were replaced by a reactive polymer only, by a composite pigment only and by a combined addition of a reactive polymer and a composite pigment. The results are presented in Table 1. The results show the potential synergy between a reactive polymer and the composite pigment. One can see that the use of both technologies together to replace TiO.sub.2 is always better (in Contrast Ratio (CR) and Tint Strength (TS)) than just using the reactive polymer by itself. Table 2 shows the standard formulation.

(28) TABLE-US-00001 TABLE 1 TiO.sub.2 TiO.sub.2 replaced by g per We Reactive 100 g top Gloss polymer (RP)/ of TiO.sub.2 Contrast Tint a- (degree of Functional Coating redn. Ratio strength city gloss) pigment (FP) comp. wt-% (CR) L* a* b* (TS) WO Stain 20 60 85 Standard 0/0 14.5 0 96.3 96.1 −0.52 2.84 61.1 Std Std 1 2 5 RP only 25/0  10.87 25.0 96.1 95.9 −0.49 2.92 60.0 − ++ 1 2 6 FP only  0/25 10.87 25.0 96.2 96.0 −0.51 2.94 60.5 −− ++ 1 2 5 RP only 35/0  9.43 35.0 95.9 96.0 −0.45 3.02 59.7 − + 1 2 3 RP + 25/10 9.43 35.0 96.3 96.0 −0.47 2.9 60.8 − − 1 2 6 1.1 wt-% FP460 RP only 40/0  8.7 40.0 96.0 96.0 −0.45 3.02 59.7 − + 1 2 3 RP + 25/15 8.7 40.0 96.2 96.0 −0.45 2.86 60.6 − + 1 2 6 1.6 wt-% FP460

(29) In Table 1 above RP means “reactive polymer” and is EVOQUE™ (Dow); FP is a “composite pigment”; FP460 is a composite pigment supplied by FP-Pigments, comprising calcium carbonate and titanium dioxide. The composition of the standard formulation “Standard” is shown in Table 2. Pvc means particle volume concentration. CR=Contrast Ratio (a measure of hiding power). RIB=Reflectance over a black substrate—a measure of reflected light also important. L*=Brightness (scale 0 to 100. 0 is black, 100 is pure white). a*=Red/Green shift a −ve value indicates a green colour, a +ve value indicates a red colour. b*=Blue/Yellow shift a −ve value indicates a Blue colour, a +ve value indicates a Yellow colour. TS=Tint strength or tint reducing power, the higher the better in most cases. This is a measure of the ability of the pigments to reduce (make paler) the strength of the colour added—in this case a blue tint, WO=Wet opacity, the hiding power of the paint when first applied and still wet. This is important and should be similar to the standard. An indication of one −ve sign suggests it is slightly lower in wet hide but not easy to see, 2 −ve's suggest well down and easily seen, 3 −ve's would be an obvious difference. Stain=A measure of the porosity of the film. The stain level should be the same as the standard or within one +. The higher the stain the more porosity there is in the film and more hiding is gained from air rather than the pigment. Comparing the performance of any two paints should ideally be done at the same porosity/stain level. 20=20 degree gloss value; 60=60 degree gloss value; 85=85 degree gloss value

(30) TABLE-US-00002 TABLE 2 Standard formulation STD Water 170.25 Cellosize QP4400H 2.70 Ammonia (25%) 1.02 CHP-805 1.26 Texanol 4.86 Foamaster NXZ 0.90 Acticide MV 14 1:10 3.60 pH 10.0 TIOXIDE ® TR92 87.10 Queensfil 25 85.36 Polestar 200P 85.36 Water 70.13 Mowilith LDM 2383 86.56 Total 599.10 W. Solids 52.03 Vol. Solids 32.00 TiO2vc 17.00 Evc 51.00 pvc 68.00

(31) The experiment shows an unexpected interaction between the three components, namely titanium dioxide, reactive polymer and composite pigment, which allows for the greater substitution of TiO.sub.2 than if either the reactive polymer or the composite pigment were used alone with TiO.sub.2.

(32) Used alone both technologies can help to replace up to 25 wt-% TiO.sub.2 without significant detriment to the coating properties by improving the “spacing” of the TiO.sub.2. Since both products improve the efficiency of the TiO.sub.2 in a similar way, a person skilled in the art would not expect their effects to be additive.

(33) However, when using a reactive polymer together with the composite pigment there is a synergy, which allows the replacement of far more TiO.sub.2 than expected, up to 40 wt-% or more. This synergy has been demonstrated in the Example, Table 1. In Table 1 one can see that when 35 or 40 wt-% of TiO.sub.2 was replaced by either reactive polymer only (RP) or by a combination of reactive polymer and composite pigment (RP+FP460), a better contrast ratio and a better tint strength was observed for the replacement with a combination of reactive polymer and composite pigment (RP+FP460), compared to the values obtained for replacement with reactive polymer (RP) alone.

(34) While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.