PROCESS FOR PRODUCING MICROPARTICLES LADEN WITH A VOLATILE ORGANIC ACTIVE

Abstract

The present invention relates to a process for producing microparticles laden with at least one active, wherein the microparticles are formed from a thermoplastic organic, polymeric material and in the unladen state, in their interior, have at least one cavity connected via pores to the surface of the microparticles, wherein (a) a composition of unladen microparticles are impregnated with a liquid comprising the active, whereby laden microparticles are obtained, which contain in the interior cavity the liquid, and (b) subjecting the laden microparticles to thermal treatment by passing a stream of free flowing laden microparticles in a carrier gas through a heated zone at a temperature of at least 20 K, in particular at least 40 K, e.g. 20 to 250 K especially 40 to 200 K above the softening temperature of the thermoplastic organic polymeric material, where the average residence time of the laden microparticles in the heated zone is not more than 60 s, in particular not more than 30 s, especially not more than 20 s or not more than 10 s, e.g. in the range of 0.1 to 60 s, in particular in the range of 0.1 to 30 s, more particularly in the range of 0.5 to 20 s and especially in the range of 1 to 10 s. The present invention further relates to compositions of microparticles filled with at least one active, in particular with at least volatile organic active, which is obtainable by a process of the invention, and to the use thereof, especially in a product selected from perfumes, washing and cleaning compositions, cosmetic compositions, personal care compositions, hygiene articles, foods, food supplements, fragrance dispensers and fragrances. The present invention further relates to products comprising an inventive composition of microparticles filled with at least one active, in particular with at least one volatile organic active, and to the use thereof, especially for controlled release of actives of low molecular weight and specifically for controlled release of aroma chemicals.

Claims

1.-16. (canceled)

17. A process for producing microparticles laden with at least one active, wherein the microparticles are formed from a thermoplastic organic, polymeric material and in the unladen state, in their interior, have at least one cavity connected via pores to the surface of the microparticles, wherein (a) a composition of unladen microparticles are impregnated with a liquid comprising the active, whereby laden microparticles are obtained, which contain in the interior cavity the liquid, and (b) subjecting the laden microparticles to thermal treatment by passing a stream of free flowing laden microparticles in a carrier gas through a heated zone at a temperature of at least 20 K above the softening temperature of the thermoplastic organic polymeric material, where the average residence time of the laden microparticles in the heated zone is not more than 60 s.

18. The process according to claim 17, where the temperature in the heated zone is in the range from 130 to 350° C.

19. The process according to claim 17, where the softening temperature of the thermoplastic organic polymeric material is in the range from 50 to 160° C.

20. The process according to claim 17, where the heating zone has a straight tubular geometry.

21. The process according to claim 17, where the mass density of the stream of free flowing laden microparticles passed through the heated zone is in the range from 5 to 500 g/m.sup.3.

22. The process according to claim 17, where the stream of free flowing laden microparticles is quenched immediately after leaving the heated zone.

23. The process according to claim 17, wherein the thermoplastic organic, polymeric material comprises at least one polymer having a glass transition temperature or melting point in the range from 45 to 140° C.

24. The process according to claim 17, wherein the thermoplastic organic, polymeric material has a solubility in dichloromethane of at least 50 g/L at 25° C.

25. The process according to claim 17, wherein the thermoplastic polymeric material comprises at least one aliphatic-aromatic polyester or a combination of at least one aliphatic-aromatic polyester with at least on thermoplastic polymer which is not an aliphatic-aromatic polyester.

26. The process according to claim 25, wherein the thermoplastic organic, polymeric material, besides the aliphatic-aromatic polyester, additionally comprises at least one further polymer which is different from aliphatic-aromatic polyesters and which is in particular selected from the group consisting of aliphatic polyesters, polyanhydrides, polyesteramides, modified polysaccharides and proteins and mixtures thereof.

27. The process according to claim 17, wherein the active is liquid at 22° C. and 1013 mbar or has a melting point below 100° C.

28. The process according to claim 27, wherein the active is an aroma chemical which is liquid at 22° C. and 1013 mbar, or a mixture of aroma chemicals which is liquid at 22° C. and 1013 mbar.

29. A composition of microparticles filled with at least one active, obtainable by a process according to claim 17.

30. A product comprising a composition according to claim 29 in a proportion by weight of 0.01% to 80% by weight based on the total weight of the product.

31. The use of the composition according to claim 29 in a product selected from perfumes, washing and cleaning products, cosmetic products, personal care products, hygiene articles, foods, food supplements, fragrance dispensers and fragrances.

32. The use of the composition according to claim 29 for controlled release of actives.

Description

FIGURES

[0450] FIG. 1a shows a scanning electron micrograph of the microparticles from production example 1 before thermal treatment.

[0451] FIG. 1b shows a scanning electron micrograph of the microparticles from production example 1 after thermal treatment at 250° C.

[0452] FIG. 1c shows a scanning electron micrograph of the microparticles from example 1 after thermal treatment at 300° C.

[0453] FIG. 2 shows a scanning electron micrograph of the microparticles from production example 2 before thermal treatment.

EXAMPLES

[0454] Materials

[0455] Unless stated otherwise, the following materials and components were used: [0456] Polybutylene sebacate terephthalate (PBSeT): Ecoflex™ FS Blend A1300, melting point in the range of 100-140° C., glass transition temperature of −33° C. (BASF SE), VST/A50=91° C.; [0457] Amorphous polylactic acid (PLA-a): glass transition temperature of 55-60° C., VST/A50=56° C.; [0458] Crystalline polylactic acid (PLA-a): melting point of 150° C. (BASF SE), VST/A50=56° C.; [0459] Polyvinylalkohol: degree of hydrolysis of 88 mol %, a viscosity of a 4% by weight aqueous solution at 20° C. of 25 mPa*s and proportion of carboxyl groups of 3 mol %; [0460] aroma chemical composition: mint aroma consisting of 2.3 wt.-% L-isopulegol, 3.1 wt.-% L-menthyl acetate, 36.4 wt.-% L-methone and 58.2 wt. % L-menthol characterized by the following evaporation rate at 25° C. and 1 bar:

TABLE-US-00001 Time [hours] Aroma chemical mixture Δ M [%]* 0 0 3 15 10 45 19 87 33 99.1 *Decrease in mass of the aroma chemical mixture in % by weight normalized to the starting value

[0461] Methods

[0462] Determining the average particle diameter in aqueous suspension/emulsion by light scattering (laser diffraction).

[0463] The particle diameter of the w/o/w emulsion or the particle suspension is determined with a Malvern Mastersizer 2000 from Malvern Instruments, England, Hydro 2000S sample dispersion unit, by a standard test method documented in the literature. The value D[4,3] is the volume-weighted average.

[0464] Determining the average particle diameter of the solid:

[0465] The particle size distribution of the microparticles are determined as powder with a Malvern Mastersizer 2000 from Malvern Instruments, England, including Scirocco 2000 powder feed unit, by a standard test method documented in the literature. The value D[4,3] is the volume-weighted average.

[0466] Determining melting points: The melting temperature was determined by means of dynamic differential calorimetry (DSC) to DIN EN ISO 11357-3:2018-07 in open crucibles applying a heating rate of 10 K/min.

[0467] Determining glass transition temperature: The glass transition temperature was determined by means of dynamic differential calorimetry (DSC) to DIN EN ISO 11357-1:2017-02 in open crucibles applying a heating rate of 10 K/min.

[0468] Determining VST/A50: The Vicat softening Temperature was determined in accordance with the protocol of DIN EN ISO 306:2014-03 with a heating rate of 50° C./h and a force of 10 N.

[0469] Scanning electron microscopy: Close-up images were taken from a probe of the microparticles these were retrospectively automatically measured using the ProSuite (FibreMetric) software from Phenom.

[0470] Determining the Pore Diameter:

[0471] The pore diameters were determined by means of scanning electron microscopy as described above. The pores of a selected region of a particle were identified using the difference in contrast and the surfaces thereof were automatically measured. The diameter for each surface was calculated with the assumption that the surfaces were circular. (Sample size 100 pores).

[0472] In the context of the evaluation, only those pores whose pore diameter was at least 20 nm were taken into consideration. Depending on the particle size, the images were recorded, for larger particles with 1600- to 2400-times magnification, and for smaller particles with up to 8000-times magnification.

[0473] In order to determine the size of at least 10 pores, only those microparticles, whose particle diameter does not deviate from the mean particle diameter of the composition of microparticles by more than 20% were taken into consideration.

[0474] The following assumptions were made for evaluation of the number of pores based on the total surface area of the microparticle: Since these are spherical particles, the image only shows half the surface of the particle. If the image of a microparticle shows at least 5 pores whose diameter is at least 20 nm and whose diameter is in the range from 1/5000 to 1/5 of the mean particle diameter, then the total surface comprises at least 10 pores.

[0475] The evaluation was carried out according to the following procedure: [0476] 1. The mean particle diameter D[4,3] of the microparticles was already determined in the microparticle dispersion, using light scattering. The upper and lower limits of the particle diameter of the microparticles which are taken into consideration for determining the pores (±20%) can be calculated from this. [0477] 2. The microparticle dispersion was dried. [0478] 3. From a sample, in each case 20 images showing multiple microparticles were taken by means of scanning electron microscopy. [0479] 4. 20 microparticles were selected whose particle diameter is in the range ±20% of the mean particle diameter of the microparticles. The particle diameter thereof was thus measured with the ProSuite (FibreMetric) software from Phenom. [0480] 5. The pores of each of these 20 microparticles were measured. For this purpose, the surface areas of the visible pores were measured automatically and the diameter thereof was calculated. [0481] 6. The individual values of the pore diameters were checked as to whether their diameter met the condition of being in the range from 1/5000 to 1/5 of the mean particle diameter and being at least 20 nm. [0482] 7. The number of pores meeting this condition was determined and multiplied by two. [0483] 8. It was verified whether at least 16 microparticles had on average at least 10 pores.

Production Example 1: Production of Spherical Fillable Microparticles

[0484] Spherical fillable microparticles were produced analogously to example 8 of WO 2018/065481. The matrix-forming polymer used was a polymer blend of 70% by weight of polybutylene sebacate terephthalate and 30% by weight of amorphous polylactic acid (PLA-a) (PBSeT; Ecoflex™ FS Blend A1300 product from BASF SE). This blend has a Vicat softening temperature VST/A50 of about 58.5° C. The procedure was as follows:

[0485] Pore former solution: 0.54 kg of ammonium carbonate was dissolved in 53.5 kg of water (pore former).

[0486] Solution of the aliphatic-aromatic polyester: 15.1 kg of PBSeT and 6.5 kg of PLA-a were stirred into 270.0 kg of dichloromethane and dissolved at 25° C. while stirring.

[0487] The w/o emulsion was produced by emulsifying the pore former solution in the solution of the aliphatic-aromatic polyester at 170 rpm with a twin-level cross-beam stirrer for 15 minutes.

[0488] The w/o emulsion thus obtained was transferred into 423 kg of a 0.8% b.w. solution of polyvinyl alcohol in water and likewise emulsified with shear and energy input (one minute at 120 rpm with an impeller stirrer).

[0489] Stirring of the w/o/w emulsion thus created was then continued with an impeller stirrer at 120 rpm, while reducing the pressure to 800 mbar and gradually increasing the jacket temperature to 40° C. and keeping it at this temperature for 4 hours. Thereafter, the microparticle suspension was cooled to room temperature, filtered and dried at 37° C.

[0490] The mean particle diameter D[v, 0.5] determined from the aqueous suspension was 270 μm. Bulk density was effected to DIN EN ISO 60:1999 and was 0.15 g/cm.sup.3. The pore size was 5.6 μm and was determined by means of mercury porosimetry. Visual evaluation was carried out as described above and showed than each of the microparticles within the size range of 210 to 325 μm had more than 10 pores at their surface, wherein the pores had a diameter within the range of 0.1 to 50 μm.

Production Example 2: Production of Spherical Fillable Microparticles

[0491] The microparticles were prepared in accordance to the protocol of production example 1, where amorphous polylactic acid (PLA-a) was completely replaced by the same amount of crystalline polylactic acid (PLA-c). This blend has a Vicat softening temperature VST/A50 of about 57.2° C.

[0492] The mean particle diameter D[v, 0.5] determined from the aqueous suspension of the microparticles was 160 μm. Bulk density was effected to DIN EN ISO 60:1999 and was 0.15. g/cm.sup.3. The pore size was 5.0 μm and was determined by means of mercury porosimetry. Visual evaluation was carried out as described above and showed than each of the microparticles within the size range of 125 to 195 μm had more than 10 pores at their surface, wherein the pores had a diameter within the range of 0.1 to 30 μm.

Production Example 3: Loading of the Microparticles with Aroma Chemical

[0493] The microparticles of production example 2 were loaded with the aroma chemical composition according to the following protocol.

[0494] 4.0 g of the microparticles of production example 2 were placed in a plastic beaker equipped with a stirring bar. 8.0 g of the aroma chemical composition were dripped onto the microparticles at 23° C. while stirring for 10 min. to obtain the laden microparticles M P1. Any adherent liquid was removed by means of tissue and the obtained microparticles were weighed. The thus obtained microparticles contained about 60% by weight of the aroma chemical.

Examples 1a, 1b, 2a and 2b

[0495] The heating zone was a vertically mounted steel pipe with a length of 3000 mm and an inside diameter of 55 mm, which was heated by means of an electric heating jacket over a length of 2000 mm. The temperature inside the pipe (internal temperature) was set to the desired temperature and controlled by a temperature sensor. The lower opening of the pipe was connected to a solids separator, which was a flask filled with cold water, the flask having an outlet just above the water surface, which was connected to a vacuum pump. An air flow was sucked downwards through the pipe by applying a slight vacuum to the solids separator. The flow rate was about 30 cm/s. By means of a funnel 5 g of the microparticles of production example 1 and 2, respectively were fed into the upper opening of the pipe. By this procedure a free flowing powder was obtained. The microparticles subjected to a heat treatment at an internal temperature of 250° C. showed only a few open pores (Example 1a and 2a respectively). At an internal temperature of 300° C. the pores were closed completely. No significant agglomeration was observed (Example 1 b and 2b).

Example 3

[0496] The microparticles of production example 3 were subjected to a heat treatment according to the protocol of examples 1 and 2 at a temperature of 200° C. (example 3a) and 220° C. (sample 3b). At an internal temperature of 220° C. at least 80% of the pores of the particles were closed. Only slight agglomeration was observed.

[0497] The microparticle compositions from production example 3, example 3a and example 3b were stored together at 25° C. and a relative air humidity of 50% in a climate-controlled cabinet. The decrease in mass of the aroma chemical mixture was determined via the decrease in weight of the sample. The results are summarized in Table 1.

TABLE-US-00002 TABLE 1 Time Production example 3 Example 3a Example 3b [hours] Δ M [%]* Δ M [%]* Δ M [%]* 0 0 0 0 10 86.7 81.2 70.8 33 99.9 83.7 85.7 *weight loss, based on the amount of perfume contained in the particles