PROCESS FOR PRODUCING POROUS PARTICLES OF A POLYHYDROXYALKANOATE (PHA), POROUS PARTICLES OBTAINABLE FROM SAID PROCESS AND COSMETIC COMPOSITIONS COMPRISING THE SAME

Abstract

A process for producing porous particles of a polyhydroxyalkanoate (PHA) includes the following steps: providing a spray drying atomization chamber heated to an operating temperature comprised between 50° C. and 300° C.; providing an aqueous suspension having the PHA and an expanding agent which decomposes at the operating temperature of the atomization chamber, with the formation of at least one gaseous compound; and injecting the aqueous suspension into the atomization chamber provided at the operating temperature, so as to cause instantaneous evaporation of the aqueous suspension and decomposition of the expanding agent, with formation of the porous PHA particles. The particles obtained from said process can be used to obtain cosmetic compositions that are soft to the touch, with high oil absorbing capacities and high flow index, able to generate a uniform, filling effect for wrinkles and skin furrows, making the skin more glossy and compact.

Claims

1. A process for producing porous particles of a polyhydroxyalkanoate (PHA), which comprises the following steps: providing a spray drying atomization chamber heated to an operating temperature comprised between 50° C. and 300° C., providing an aqueous suspension comprising the PHA and an expanding agent which decomposes at the operating temperature of the atomization chamber, with formation of at least one gaseous compound, and injecting the aqueous suspension into the atomization chamber provided at the operating temperature, so as to cause instantaneous evaporation of the aqueous suspension and decomposition of the expanding agent, with formation of the porous PHA particles.

2. The process according to claim 1, wherein the expanding agent is a carbonate or bicarbonate of an alkali or alkaline earth metal or of ammonium.

3. The process according to claim 2, wherein the expanding agent is selected from: ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, calcium carbonate, magnesium carbonate, or mixtures thereof.

4. The process according to claim 1, wherein the operating temperature of the atomization chamber is comprised between 100° C. and 200° C.

5. The process according to claim 1, wherein the PHA is present in the aqueous suspension at a concentration comprised between 1% w/v and 50% w/v, the % being expressed by weight with respect to the total volume of the suspension.

6. The process according to claim 1, wherein the expanding agent is present in the aqueous suspension at a concentration comprised between 0.5% w/v and 30% w/v, the % being expressed by weight with respect to the total volume of the suspension.

7. Porous particles of a polyhydroxyalkanoate (PHA) obtainable by means of a process according to claim 1.

8. The particles according to claim 7, wherein the PHA is a polymer containing repetitive units of formula (I):
—O—CHR.sub.1—(CH.sub.2).sub.n—CO—  (I) wherein: R.sub.1 is selected from: C.sub.1-C.sub.12 alkyls, C.sub.4-C.sub.16 cycloalkyls, C.sub.2-C.sub.12 alkenyls, optionally substituted with at least one group selected from: halogen (F, Cl, Br), —CN, —OH, —COOH, —OR, —COOR (R=C.sub.1-C.sub.4 alkyl, benzyl); n is zero or an integer from 1 to 6.

9. The particles according to claim 8, wherein the PHA is a homopolymer, or a copolymer, or a terpolymer.

10. The particles according to claim 7, wherein the particles have an average diameter (d50) comprised between 1 μm and 150 μm.

11. The particles according to claim 7, wherein the particles have a ratio (d90-d10)/d50 (span) value comprised between 1 and 3.

12. The particles according to claim 7, wherein the particles have a bulk density value, measured by means of the method described in “European Pharmacopoeia 7.0-2.9.34”, comprised between 0.1 g/ml and 0.5 g/ml.

13. The particles according to claim 7, wherein the particles have a tapped density value, measured by means of the method described in “European Pharmacopoeia 7.0-2.9.34”, comprised between 5% and 15%.

14. The particles according to claim 7, wherein the particles have an oil (linseed oil) absorption value, measured according to ISO 787-5:1980, comprised between 1 ml/g and 4 ml/g, where ml/g is the amount of absorbed oil, expressed in ml, per gram of particles.

15. A cosmetic composition comprising porous particles of a polyhydroxyalkanoate (PHA) according to claim 7 and a cosmetically acceptable basic formulation.

Description

DETAILED DESCRIPTION OF THE DISCLOSURE

[0082] The following examples of embodiment are provided for the sole purpose of illustrating the present disclosure and are not to be understood to limit the scope of protection defined by the appended claims.

Example 1: Process for Producing Porous Particles of PHB by Means of Atomization (Spray Drying)

[0083] The atomization chamber of a spray dryer was heated to a temperature of 200° C. An aqueous suspension of PHB at 20% w/v was prepared, the % being expressed by weight in relation to the total volume of the suspension. Ammonium bicarbonate was added to the suspension in a quantity equal to 10% w/v, the % being expressed by weight in relation to the total volume of the suspension. Ammonium bicarbonate decomposes at 35° C., leading to the formation of carbon dioxide and ammonia, it therefore acts as an expanding agent in accordance with the present disclosure.

[0084] The PHB suspension containing ammonium bicarbonate was nebulized inside the atomization chamber through an injection nozzle. The nebulization obtained drops of PHB suspension. The drops were hit by an air flow with a temperature of 200° C., which assured the instantaneous evaporation of the water present in the suspension and the decomposition of the ammonium bicarbonate, with the formation of carbon dioxide and ammonia. The development of these gases led to the formation of a porous and hollow structure of the PHB particles. FIGS. 1A-1D show the PHB particles obtained according to the process described (microphotographs obtained by SEM electronic microscope).

Example 2: Characterisation of the Particles in Example 1

[0085] Apparent Density.

[0086] The analysis to determine the bulk density of the particles in Example 1 was performed three times. The particles in Example 1 were sieved using a sieve with 1.0 mm mesh. 50 g of particles in Example 1 were poured slowly into a 250 mL graduated glass cylinder (tolerance±2 mL). The analysis was conducted following the indications of the “European Pharmacopoeia 7.0-2.9.34” method. Table 1 gives the average values of the three analyses conducted; the bulk density is expressed as grams of particles in millilitres of volume occupied by the particles (g/mL) and the bulk density values are expressed in relation to the average diameter (d50) of the particles analysed.

TABLE-US-00001 TABLE 1 Average diameter (d50) Apparent density (g/mL) 5 μm 0.220 10 μm 0.280 20 μm 0.340 30 μm 0.380

[0087] Table 2 gives the bulk density values obtained by analysing samples of PHB particles obtained by spray drying according to the same procedure described in Example 1, but without any expanding agent (ammonium bicarbonate).

TABLE-US-00002 TABLE 2 Average diameter (d50) Apparent density (g/mL) 5 μm 0.240 10 μm 0.310 20 μm 0.380 30 μm 0.410

[0088] Comparing the values of the two tables, it is clear how the particles obtained from the process according to the present disclosure are characterised by a lower bulk density.

[0089] Tapped Density.

[0090] The analysis to determine the tapped density of the particles in Example 1 was performed three times. The particles in Example 1 were sieved using a sieve with 1.0 mm mesh. 50 g of particles in Example 1 were poured slowly into a 250 mL graduated glass cylinder (tolerance±2 mL). The analysis was conducted following the indications of the “European Pharmacopoeia 7.0-2.9.34” method. Table 3 gives the average values of the three analyses conducted; the tapped density is expressed as a percentage obtained by the following formula

[00001]$\frac{100\times \left(V_0-V_f\right)}{V_0}$

wherein V.sub.0 corresponds to the initial volume occupied by the particles in the cylinder, V.sub.f is the volume of the particles after tapping the cylinder that contains them.

TABLE-US-00003 TABLE 3 Average diameter (d50) Tapped density (%) 5 μm 10.4 10 μm 10.2 20 μm 10.0 30 μm 9.7

[0091] Table 4 gives the tapped density values obtained by analysing samples of PHB particles obtained by spray drying according to the same procedure described in Example 1, but without any expanding agent (ammonium bicarbonate).

TABLE-US-00004 TABLE 4 Average diameter (d50) Tapped density (%) 5 μm 11.3 10 μm 10.5 20 μm 10.2 30 μm 9.7

[0092] Comparing the values of the two tables, it is clear how the particles obtained from the process according to the present disclosure are characterised by a lower tapped density.

[0093] Oil Absorption (Linseed Oil).

[0094] The analysis to determine the oil absorption value of the particles in Example 1 was conducted two times in accordance with standard ISO 787-5:1980.

[0095] The analysis was conducted on a concave glass support, of a circular shape and with a diameter of approximately 17 cm on which 1 g of the particles in Example 1 was weighed. Cyclically, 4/5 drops of linseed oil were added to the particles using a 10 mL burette (with a measurement error equal to 0.02 mL) to obtain a compact, smooth and non-sticky paste, without lumps or cracks. The procedure then continued adding 1 drop at a time of oil until the consistency required by the standard was reached. After each addition of oil, the particles were mixed carefully to allow the oil to be absorbed appropriately.

[0096] The oil absorption value was expressed in terms of millilitres of oil absorbed per gram of particles (mL/g). The results are given in Table 5.

TABLE-US-00005 TABLE 5 Average diameter (d50) Oil absorption (mL/g) 5 μm 1.57 10 μm 1.73 20 μm 1.73 30 μm 1.66

[0097] Table 6 gives the linseed oil absorption values obtained by analysing samples of PHB particles obtained by spray drying according to the same procedure described in Example 1, but without any expanding agent (ammonium bicarbonate).

TABLE-US-00006 TABLE 6 Average diameter (d50) Oil absorption (mL/g) 5 μm 1.48 10 μm 1.37 20 μm 1.34 30 μm 1.27

[0098] Comparing the values of the two tables, we can see a net increase in the oil absorption values by the particles obtained with the process according to the present invention compared to the non-porous and non-hollow particles of the same grain size (d50).

[0099] A similar analysis was also conducted to assess the absorption capacity of another oil, isopropyl myristate.

[0100] The oil absorption value was expressed in terms of millilitres of oil absorbed per gram of particles (mL/g). The results are given in Table 7.

TABLE-US-00007 TABLE 7 Average diameter (d50) Oil absorption (mL/g) 5 μm 1.35 10 μm 1.65 20 μm 1.69 30 μm 1.77

[0101] Table 8 gives the isopropyl myristate absorption values obtained by analysing samples of PHB particles obtained by spray drying according to the same procedure described in Example 1, but without any expanding agent (ammonium bicarbonate).

TABLE-US-00008 TABLE 8 Average diameter (d50) Oil absorption (mL/g) 5 μm 1.35 10 μm 1.30 20 μm 1.29 30 μm 1.21

[0102] Comparing the values of the two tables, we can see a net increase in the oil absorption values by the particles obtained with the process according to the present disclosure compared to the non-porous and non-hollow particles of the same grain size (d50).

Example 3: Cosmetic Composition Comprising the Particles in Example 1

[0103] Table 9 shows the cosmetically acceptable basic formulation used to produce the cosmetic composition. The quantities are expressed as % p/p, in relation to the total weight of the composition.

TABLE-US-00009 TABLE 9 Excipients (% p/p) Water 73.3 Sepigel 305 0.5 Montanov 68 5 Lanol 99 20 Benzyl alcohol 1.2

[0104] After weighing, both the aqueous phase, composed of water and Sepigel 305, and the oily phase, composed of 99 and Montanov 68, were heated to a temperature of 80° C. Having reached the required temperature and once the substances reached the liquid state, the two phases were joined and homogenised using a turbo-emulsifier at 3200 rpm for 5 minutes. The emulsion obtained thus was allowed to cool slowly to a temperature of 40° C. Thereafter, benzyl alcohol (preservative) was added. The particles in Example 1 were added to this formulation in a quantity equal to 2% p/p, the % expressed in relation to the total weight of the cosmetic composition.

Example 4: Gloss Index of the Cosmetic Composition in Example 3

[0105] In cosmetics, the analysis for the determination of gloss index is used for the characterisation of cosmetic compositions comprising particles. According to its own chemical and physical characteristics, each particle may in fact interact differently to visible light radiation. The gloss index refers to the value obtained by using a glossmeter, an instrument that is able to determine light reflection, that is the light intensity defined within a restricted area around the angle of reflection, which is the same as incident light.

[0106] The gloss index is measured in accordance with standard BS EN ISO 2813:2014. A low index corresponds to a cosmetic composition that is able to cause the diffraction rather than the reflection of the light, thus contributing to creating a uniform and filling effect on wrinkles and skin furrows, making the skin more glossy and compact.

[0107] The gloss index was determined by measuring, with the glossmeter, a film of the cosmetic composition in Example 3 with a thickness of 150 μm, spread on a sheet of Byk Chart glossy paper (Byk-Gardner, Germany) using a film-applicator (Byk-Gardner, Germany). The analysis was carried out 2 hours after spreading the film on the sheet of paper. The glossmeter (Micro-TRI-gloss, Byk-Gardner, Germany) was set at an incidence angle firstly of 60° and then 85°. The gloss index value given in Table 10 is the average result of 5 measurements made on different points of the film, per different grain size (d50) of the particles. The gloss index was expressed as an average value with its standard deviation (STD) selecting the angle of incidence 60° for a first reading, and in the case of value lower than 10 GU (gloss unit), the measurement was repeated with an angle of incidence of 85°.

TABLE-US-00010 TABLE 10 60° 85° Cosmetic d50 Average Average composition particles value STD value STD Without particles — 6.5 0.8 18.3 1.3 With particles 5 μm 5.8 0.6 13.8 2.2 With particles 10 μm 5.6 0.1 8.0 0.8 With particles 20 μm 5.4 0.1 4.0 1.1 With particles 30 μm 5.0 0.1 3.8 0.7

[0108] Table 11 on the other hand gives the gloss index values obtained by analysing a cosmetic composition comprising particles of PHB free of porosity and cavities (therefore not obtained with the method according to the present disclosure).

TABLE-US-00011 TABLE 11 60° 85° Cosmetic d50 Average Average composition particles value STD value STD Without particles — 6.9 0.7 18.3 1.3 With particles 5 μm 3.4 0.3 10.1 1.3 With particles 10 μm 3.0 0.2 8.4 1.5 With particles 20 μm 2.6 0.1 6.2 0.4 With particles 30 μm 2.2 0.1 4.3 0.5

[0109] From the analysis of the results obtained at 60°, comparing the composition without particles with the composition in Example 3, a progressive reduction of the gloss index can be seen as the particle grain size (d50) increases.

[0110] In conclusion, the particles according to the present disclosure are used to obtain cosmetic compositions that are soft to the touch, with high oil absorbing capacities and high flow index, able to generate a uniform, filling effect for wrinkles and skin furrows, making the skin more glossy and compact.