SURFACE-REACTED CALCIUM CARBONATE FOR STABILIZING MINT OIL

Abstract

The present invention refers to a surface-reacted calcium carbonate having a volume median particle size d.sub.50 from 0.1 to 90 μm, wherein mint oil is adsorbed onto and/or absorbed into the surface of the surface-reacted calcium carbonate as well as the use of such a surface-reacted calcium carbonate for stabilizing mint oil.

Claims

1. A surface-reacted calcium carbonate having a volume median particle size d.sub.50 from 0.1 to 90 μm, wherein mint oil is adsorbed onto and/or absorbed into the surface of the surface-reacted calcium carbonate, wherein the surface-reacted calcium carbonate is a reaction product of natural ground calcium carbonate or precipitated calcium carbonate with carbon dioxide and one or more H.sub.3O.sup.+ ion donors, wherein the carbon dioxide is formed in situ by the H.sub.3O.sup.+ ion donor treatment and/or is supplied from an external source.

2. The surface-reacted calcium carbonate of claim 1, wherein the surface-reacted calcium carbonate has a volume median particle size d.sub.50 from 0.5 to 50 μm, preferably from 1 to 40 μm, more preferably from 1.2 to 30 μm, and most preferably from 1.5 to 15 μm.

3. The surface-reacted calcium carbonate of claim 1, wherein the surface-reacted calcium carbonate has a specific surface area of from 15 m.sup.2/g to 200 m.sup.2/g, measured using nitrogen and the BET method.

4. The surface-reacted calcium carbonate of claim 1, wherein the natural ground calcium carbonate is selected from the group consisting of marble, chalk, limestone, and mixtures thereof, or the precipitated calcium carbonate is selected from the group consisting of precipitated calcium carbonates having an aragonitic, vateritic or calcitic crystal form, and mixtures thereof.

5. The surface-reacted calcium carbonate of claim 1, wherein the at least one H.sub.3O.sup.+ ion donor is selected from the group consisting of hydrochloric acid, sulphuric acid, sulphurous acid, phosphoric acid, citric acid, oxalic acid, an acidic salt, acetic acid, formic acid, and mixtures thereof.

6. The surface-reacted calcium carbonate of claim 1, wherein the surface-reacted calcium carbonate is in form of a powder.

7. The surface-reacted calcium carbonate of claim 1, wherein the surface-reacted calcium carbonate is in form of granules.

8. The surface-reacted calcium carbonate of claim 1, wherein the mint oil comprises two or more compounds selected from the group comprising menthol, isomenthone, menthone, limonene, menthylacetate, β-pinene, α-pinene, α-terpineol, isopulegol, terpinen-4-ol, neoisopulegol, pulegone, piperitone and caryophyllene.

9. The surface-reacted calcium carbonate of claim 1, wherein the mint oil is selected from mint oil, spearmint oil, peppermint oil and mixtures thereof.

10. A method of stabilizing mint comprising contacting the mint oil with a surface-reacted calcium carbonate having a volume median particle size d.sub.50 from 0.1 to 90 μm, wherein mint oil is adsorbed onto and/or absorbed into the surface of the surface-reacted calcium carbonate, wherein the surface-reacted calcium carbonate is a reaction product of natural ground calcium carbonate or precipitated calcium carbonate with carbon dioxide and one or more H.sub.3O.sup.+ ion donors, wherein the carbon dioxide is formed in situ by the H.sub.3O.sup.+ ion donor treatment and/or is supplied from an external source.

11. The method of claim 10, wherein at least one compound of the mint oil is stabilized against chemical conversion.

12. The method according to of claim 11, wherein the at least one compound is selected from β-pinene, α-pinene, limonene, isopulegol, neoisopulegol, pulegone and mixtures thereof.

13. The method of claim 10, wherein the stabilization of the mint oil comprises a recovery rate of same within 93 days of ≥96.0 wt.-%, as determined by GC-MS after storing the surface-reacted calcium carbonate at room temperature.

14. The method of claim 10, wherein the stabilization of the mint oil comprises a recovery rate of same within 30 days of ≥99.0 wt.-%, as determined by GC-MS after storing the surface-reacted calcium carbonate at room temperature.

15. The method of claim 10, wherein the stabilization of the mint oil comprises a recovery rate of same within 93 days, of ≥90.0 wt.-%, as determined by GC-MS after storing the surface-reacted calcium carbonate at a temperature of 40° C. (±2° C.).

16. The method according to claim 10, wherein the stabilization of the mint oil relates to comprises a recovery rate of same within 30 days, of ≥94.0 wt.-%, as determined by GC-MS after storing the surface-reacted calcium carbonate at a temperature of 40° C. (+2° C.).

17. The surface-reacted calcium carbonate of claim 7, wherein the granules have a volume median particle size of from 0.1 to 6 mm.

18. The surface-reacted calcium carbonate of claim 7, wherein the granules have a volume median particle size of from 0.3 to 4 mm.

19. The surface-reacted calcium carbonate of claim 7, wherein the granules have a volume median particle size of from 0.3 to 0.6 mm or 1 mm to 4 mm.

20. The surface-reacted calcium carbonate of claim 7, wherein the granules have a volume median particle size of from 0.6 to 1 mm or 1 to 2 mm.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0155] FIG. 1 shows a chromatogram of pure mint oil.

[0156] FIG. 2 shows a comparison of the results of the loaded samples and mint oil stored at room temperature over time.

[0157] FIG. 3 shows a comparison of the results of the loaded samples and mint oil stored at 40° C.

[0158] FIG. 4 shows a chromatogram after 93 days of storage at 40° C.

[0159] The scope and interest of the invention will be better understood based on the following examples which are intended to illustrate certain embodiments of the present invention and are non-limitative.

EXAMPLES

1. Measurement Methods

[0160] In the following, measurement methods implemented in the examples are described.

Particle Size Distribution

[0161] Volume determined median particle size d.sub.50 (vol) and the volume determined top cut particle size d.sub.98 (vol) was evaluated using a Malvern Mastersizer 2000 Laser Diffraction System (Malvern Instruments Plc., Great Britain). The d.sub.50 (vol) or d.sub.98 (vol) value indicates a diameter value such that 50% or 98% by volume, respectively, of the particles have a diameter of less than this value. The raw data obtained by the measurement was analyzed using the Mie theory, with a particle refractive index of 1.57 and an absorption index of 0.005. The methods and instruments are known to the skilled person and are commonly used to determine particle size distributions of fillers and pigments.

[0162] The weight determined median particle size d.sub.50 (wt) was measured by the sedimentation method, which is an analysis of sedimentation behaviour in a gravimetric field. The measurement was made with a Sedigraph™ 5120 of Micromeritics Instrument Corporation, USA. The method and the instrument are known to the skilled person and are commonly used to determine particle size distributions of fillers and pigments. The measurement was carried out in an aqueous solution of 0.1 wt.-% Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and supersonicated.

Specific Surface Area (SSA) The specific surface area was measured via the BET method according to ISO 9277 using nitrogen, following conditioning of the sample by heating at 250° C. for a period of 30 minutes. Prior to such measurements, the sample was filtered within a Buchner funnel, rinsed with deionised water and dried overnight at 90 to 100° C. in an oven. Subsequently, the dry cake was ground thoroughly in a mortar and the resulting powder was placed in a moisture balance at 130° C. until a constant weight was reached.
Intra-Particle Intruded Specific Pore Volume (in cm.sup.3/g)

[0163] The specific pore volume was measured using a mercury intrusion porosimetry measurement using a Micromeritics Autopore V 9620 mercury porosimeter having a maximum applied pressure of mercury 414 MPa (60 000 psi), equivalent to a Laplace throat diameter of 0.004 μm (˜nm). The equilibration time used at each pressure step was 20 seconds. The sample material was sealed in a 5 cm.sup.3 chamber powder penetrometer for analysis. The data were corrected for mercury compression, penetrometer expansion and sample material compression using the software Pore-Comp (Gane, P. A. C., Kettle, J. P., Matthews, G. P. and Ridgway, C. J., “Void Space Structure of Compressible Polymer Spheres and Consolidated Calcium Carbonate Paper-Coating Formulations”, Industrial and Engineering Chemistry Research, 35(5), 1996, p 1753-1764.).

[0164] The total pore volume seen in the cumulative intrusion data can be separated into two regions with the intrusion data from 214 μm down to about 1-4 μm showing the coarse packing of the sample between any agglomerate structures contributing strongly. Below these diameters lies the fine inter-particle packing of the particles themselves. If they also have intra-particle pores, then this region appears bi-modal, and by taking the specific pore volume intruded by mercury into pores finer than the modal turning point, i.e. finer than the bi-modal point of inflection, the specific intra-particle pore volume is defined. The sum of these three regions gives the total overall pore volume of the powder, but depends strongly on the original sample compaction/settling of the powder at the coarse pore end of the distribution.

[0165] By taking the first derivative of the cumulative intrusion curve the pore size distributions based on equivalent Laplace diameter, inevitably including pore-shielding, are revealed. The differential curves clearly show the coarse agglomerate pore structure region, the inter-particle pore region and the intra-particle pore region, if present. Knowing the intra-particle pore diameter range it is possible to subtract the remainder inter-particle and inter-agglomerate pore volume from the total pore volume to deliver the desired pore volume of the internal pores alone in terms of the pore volume per unit mass (specific pore volume). The same principle of subtraction, of course, applies for isolating any of the other pore size regions of interest.

Loose Bulk density

[0166] 120 g of the respective carrier material were sieved through a 0.5 mm screen by means of a brush. 100±0.5 g of this sample were carefully filled through a powder funnel into the 250 mL measuring cylinder and the volume was read off to the nearest 1 mL. The loose bulk density was the calculated according the formula:

Loose bulk density [g/mL]=bulk volume [mL]/weighed sample [g]

and the result was recorded to the nearest 0.01 g/mL.

2. Carrier Materials

[0167] The carrier materials set out in table 1 have been used for the present invention.

TABLE-US-00001 TABLE 1 Specification of carrier materials Particle Surface Intra Particle size Area Bulk Specific Pore (d.sub.50) (BET) Density Volume Carrier material μm m.sup.2/g g/ml cm.sup.3/g SRCC powder 7.68 56.8 0.18 0.807 (for pore diameter range of 0.004 to 0.47 μm) SRCC granules 560 52 0.47 0.897 (for pore diameter range of 0.004 to 4.9 μm) Silica granules 248 118 0.25 1.899 (for pore diameter range of 0.004 to 4.0 μm)

[0168] SRCC powder was obtained by preparing 350 litres of an aqueous suspension of ground calcium carbonate in a mixing vessel by adjusting the solids content of a ground limestone calcium carbonate from Omya SAS, Orgon having a weight-based median particle size of 1.3 μm, as determined by sedimentation, such that a solids content of 10 wt.-%, based on the total weight of the aqueous suspension, was obtained.

[0169] Whilst mixing the slurry at a speed of 6.2 m/s, 11.2 kg phosphoric acid were added in form of an aqueous solution containing 30 wt.-% phosphoric acid to said suspension over a period of 20 minutes at a temperature of 70° C. After the addition of the acid, the slurry was stirred for additional 5 minutes, before removing it from the vessel and drying using a jet-dryer.

[0170] a) Granulation of Surface Reacted Calcium Carbonate (SRCC)

[0171] The SRCC powder obtained above was compacted in a Fitzpatrick roller compactor CCS220. The conditions for the dry granulation were roll speed 8 rpm, roll force 5 kN/cm, roll gap 0.9 mm (set 0.6 mm), vertical screw speed 250 rpm, horizontal screw speed 25 rpm (set to 30 rpm), mill speed 500 rpm (perforated 1 mm screen with knife rotor).

[0172] The outcome of the dry granulation was sieved through 90, 180, 250, 355, 500, 710 μm sieves in a Retsch tower sieve AS300 with a 1.00 mm amplitude with 10 sec. interval, for 3 minutes. The 0-90 and 90-180 μm fractions were emptied and all fractions re-sieved at the same conditions for another 6 minutes. The sieving was done in 300 g steps.

[0173] The Fraction 90 μm to 710 μm was used in the experiments.

[0174] b) Loading of Mint Oil on Powder and Granules

[0175] The mint oil was obtained from FREY & LAU (“Minzöl EuAB”; Product number P01422029).

[0176] The loading of mint oil on powder and granules (also mentioned as granulates) was done on plough shear mixer from Loedige. Mint oil was poured on the powder or granules with help of an Isotech peristaltic pump, the addition rate appx 10 gram/min.

[0177] The plough of the mixer was rotated at rate of 250 rpm and the chopper was on at all time to avoid clumps while loading of powder or granules with the oil.

[0178] 85 grams of mint oil were loaded on 100 grams of each carrier material set out in table 1 above. Silica granules were used instead of silica powder due to the teaching of U.S. Pat. No. 4,603,143 that discloses that substances are more chemically stable on silica granules compared to fine silica powder.

[0179] c) Analysis of Chemical Stability of Mint Oil

[0180] The samples loaded with mint oil were extracted and analyzed right after the loading (day 0) and after 30 and 93 days. Pure mint oil was analyzed (without extraction) with all the samples (SRCC powder, SRCC granules, and silica granules) to evaluate the change in time of the mint oil itself. One set of samples was stored at room temperature and the other one at 40° C. (±2° C.) all in air tight glass jars. Some of pure mint oil from day 0 was stored in the refrigerator (in a glass jar) to produce the calibrations on each analyzing day. Pure mint oil was analyzed with GC-MS and a base line chromatogram was obtained (see FIG. 1). Based on the area of peaks the amount of specific components of mint oil was determined as described in table 2.

TABLE-US-00002 TABLE 2 Substances contained in mint oil (see also FIG. 1) Substance CAS GC-Area % Peak at Rt 7.8 min α-Pinene 7785-26-4  3.90% Peak at Rt 8.6 min β-Pinene 18172-67-3  4.10% Peak at Rt 9.4 min Limonene 138-86-3  5.40% Peak at Rt 12.1 min Isopulegol 89-79-2  1.10% Peak at Rt 12.3 min Isomenthone 491-07-6 21.20% Peak at Rt 12.6 min Menthone 89-80-5 14.40% Peak at Rt 12.8 min Menthol 2216-51-5 40.50% Peak at Rt 13.0 min Terpinen-4-ol 562-74-3  0.40% Peak at Rt 13.1 min Neoisopulegol 29141-10-4  0.30% Peak at Rt 13.3 min a-Terpineol 98-55-5  2.90% Peak at Rt 14.8 min Pulegone 89-82-7  0.60% Peak at Rt 15.3 min Piperitone 89-81-6  0.30% Peak at Rt 15.9 min Menthylacetate 89-48-5  4.30% Peak at Rt 19.5 min Caryophyllene 87-44-5  0.50%

[0181] Mint oil was extracted from the carrier materials after the storage (at room temperature or at 40° C.) for 30 days and 93 days, respectively. Gas chromatography was used to analyze the composition of mint oil after storage (see FIGS. 2 and 3). The composition of mint oil has been slightly changing over time in the sample with silicate granules. The first three peaks were smaller and new small peaks were detected between 13 and 15 min (see FIG. 4). The amount of mint oil in these samples decreased slightly over time. There was no change in the composition of the mint oil in the samples with SRCC (powder and granules). The GC-MS chromatograms were still very similar to the ones of the standards (see FIG. 4). The amount of mint oil in the SRCC samples stayed constant.