WO2015004641A1 - Method for the preparation of micrometric or nanometric hollow particles - Google Patents

Method for the preparation of micrometric or nanometric hollow particles Download PDF

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Publication number
WO2015004641A1
WO2015004641A1 PCT/IB2014/063044 IB2014063044W WO2015004641A1 WO 2015004641 A1 WO2015004641 A1 WO 2015004641A1 IB 2014063044 W IB2014063044 W IB 2014063044W WO 2015004641 A1 WO2015004641 A1 WO 2015004641A1
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WO
WIPO (PCT)
Prior art keywords
particles
barrier film
preparation
polymer
hollow
Prior art date
Application number
PCT/IB2014/063044
Other languages
French (fr)
Inventor
Silvia ORSI
Ernesto Di Maio
Paolo Antonio Netti
Original Assignee
Orsi Silvia
Ernesto Di Maio
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Orsi Silvia, Ernesto Di Maio filed Critical Orsi Silvia
Publication of WO2015004641A1 publication Critical patent/WO2015004641A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/16—Making expandable particles
    • C08J9/18—Making expandable particles by impregnating polymer particles with the blowing agent
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/12—Powdering or granulating
    • C08J3/126—Polymer particles coated by polymer, e.g. core shell structures
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/22—After-treatment of expandable particles; Forming foamed products
    • C08J9/224—Surface treatment
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2325/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
    • C08J2325/02—Homopolymers or copolymers of hydrocarbons
    • C08J2325/04—Homopolymers or copolymers of styrene
    • C08J2325/06—Polystyrene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2429/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
    • C08J2429/02—Homopolymers or copolymers of unsaturated alcohols
    • C08J2429/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids

Definitions

  • the present invention relates to a method for the preparation of micrometric or nanometric hollow particles.
  • Hollow particles of micrometric or nanometric dimension have attracted industrial attention in recent years for their numerous applications.
  • these particles can be used as carriers for encapsulation of drugs, enzymes, proteins and genes, as contrast agents in diagnostics, as reactors in chemistry and chemical engineering, as transducers and dielectrics in electronics and as absorbent systems of sound ultrasound and microwaves.
  • the methods known from the prior art for the preparation of hollow polymeric micro- and nano-particles include: emulsion polymerization, suspension polymerization, core- shell precursors, self-assembly, spraying, electro-spraying and template-directed synthesis.
  • emulsion polymerization suspension polymerization
  • core- shell precursors self-assembly
  • spraying electro-spraying
  • template-directed synthesis template-directed synthesis.
  • Each of these methods is rather complex, mainly in the fine chemical synthesis, and is limited in terms of particle dimensions and nature of utilizable materials, not being sufficiently versatile to cover all of the different, very specific, application needs.
  • current methods do not easily achieve non-spherical particles, which has been reported to be a critical need, for instance in drug delivery, to enhance the specificity of delivery and in chemistry, to enhance the specificity of catalysis. In effect, each of these methods is able to produce particles in a narrow range of dimensions, with a limited nature of materials and with s
  • micrometric or nanometric hollow particles obtained with the method of the present invention.
  • PS polystyrene
  • PS spherical particles 50-5-0.5-0.2 ⁇ in diameter
  • PVA poly (vinyl alcohol)
  • glycerol 5% (wt/vol) poly (vinyl alcohol)
  • the film embedding the particles is then subjected to a foaming process, as follows.
  • a pressure vessel having a volume of 0.3 L, (model BC-1, HiP Erie, US-PA) was used.
  • the pressure discharge system consists of a discharge valve, an electromechanical actuator and an electro-valve.
  • the samples (barrier film-embedded PS spheres) were loaded into the vessel, pressurized with a mixture of N2 and CO2 as the blowing agent at 14.0 MPa and 100°C for two hours and then pressure quenched at 100 MPa/s (foaming process) . PS Particles were then recovered by dissolving the PVA film in water at room temperature and washed centrifuging with water five times.
  • Particle morphology was observed by SEM, TEM, Dual Beam SEM/FIB and STED, showing that particles foamed when embedded in the PVA film presented hollows with morphologies depending on the different experimental conditions, as reported in Figure 1 and 2.
  • particles foamed when embedded in the PVA film have a slightly larger diameter with respect to unfoamed particles, as a consequence of the formation of the hollow.
  • Those of 5, 0.5 and 0.2 ⁇ have open hollows and are characterized by a bowl shape.
  • Bare polystyrene spheres (without being embedded in the barrier film - poured on lab paper) were also analyzed and subjected to the foaming process for proper comparison. Bare particles did not present any morphological modification after being subjected to the foaming process reported above, not presenting any hollow.
  • Figure 2 reports SEM images of particles characterized by open hollow and particles characterized by closed hollow obtained by means of the present invention.
  • Figure 3 shows an SEM image of kayak-shaped hollow nanometric particles, where the elongated shape was obtained by mechanical stretching at elevated temperature of the particles-embedded barrier film, followed by foaming .
  • the method of the present invention allows modifying the shape of the particles by inducing a deformation or a stress on the barrier film. This chance is offered by the presence of the barrier film completely embedding the total amount of particles, conferring to the method of the present invention a very large versatility.
  • Hollow particles can be obtained from any thermoplastic polymer (other than PS, reported in the example) and the barrier film could be made of a material different from PVA, standing it has the capability of allowing particle deformation/expansion and of keeping the blowing agent concentration in the particle sufficiently high (barrier effect) to induce the hollow formation, after the pressure release during the foaming process.
  • the blowing agent is solubilized into the particles after they have been embedded in the barrier film.
  • foaming can be conducted not only by releasing the pressure, but also by increasing the temperature of the blowing agent-laden particles at the glassy state. In other words, the foaming process can be conducted with techniques different from the pressure release technique described in the example.
  • the key point of the present invention is embedding the total amount of thermoplastic polymer particles in a single, continuous barrier film, which, during expansion, avoids blowing agent escape from the particles and manages to keep the blowing agent concentration within the particles sufficiently high to allow the hollow formation within the particles. Furthermore, the barrier film has to allow the particle deformation during foaming.
  • the method described in the present invention has the great advantage to produce hollow particles without making use of complex techniques like fine chemical synthesis and, at the same time, may be used on particles without dimensional constraints and made of different polymers.
  • the present invention it is possible, by modifying the blowing agent composition, the barrier film composition and by manipulating the barrier film itself, to achieve hollow particles of several shapes, with one ore more hollows per particle, with hollows of several shapes, of different open/closed feature and eccentricity with respect to the particle center.

Abstract

A method for the preparation of hollow polymeric micrometric or nanometric particles comprising, in sequence, a solubilization step, where a gas or a vapor is solubilized as the blowing agent in thermoplastic polymer bulk particles and a foaming step in order to produce one or more bubbles in said particles. The method comprises an embedding step, at least before the foaming step, where said bulk particles are embedded in a single and continuous barrier film made of a water-soluble polymer and, after the foaming step, a solubilization step where said barrier film polymer is washed out.

Description

METHOD FOR THE PREPARATION OF MICROMETRIC OR NANOMETRIC HOLLOW PARTICLES
FIELD OF THE INVENTION
The present invention relates to a method for the preparation of micrometric or nanometric hollow particles.
BACKGROUND OF THE INVENTION
Hollow particles of micrometric or nanometric dimension have attracted industrial attention in recent years for their numerous applications. In effect, these particles can be used as carriers for encapsulation of drugs, enzymes, proteins and genes, as contrast agents in diagnostics, as reactors in chemistry and chemical engineering, as transducers and dielectrics in electronics and as absorbent systems of sound ultrasound and microwaves.
The methods known from the prior art for the preparation of hollow polymeric micro- and nano-particles include: emulsion polymerization, suspension polymerization, core- shell precursors, self-assembly, spraying, electro-spraying and template-directed synthesis. Each of these methods is rather complex, mainly in the fine chemical synthesis, and is limited in terms of particle dimensions and nature of utilizable materials, not being sufficiently versatile to cover all of the different, very specific, application needs. Furthermore, notably, current methods do not easily achieve non-spherical particles, which has been reported to be a critical need, for instance in drug delivery, to enhance the specificity of delivery and in chemistry, to enhance the specificity of catalysis. In effect, each of these methods is able to produce particles in a narrow range of dimensions, with a limited nature of materials and with spherical shape.
There is, hence, an increased need for a simple method that allows the production of hollow particles from a wide range of particle dimensions, from a wide range of polymers and characterized by non-spherical shapes.
DISCLOSURE OF INVENTION
Therefore, it is an object of the present invention to provide a method for the preparation of hollow micrometric or nanometric particles of a large variety of materials, dimensions, shapes and hollow attributes, as described in CLAIM 1 and in the preferred and/or auxiliary CLAIMS 2 to 9.
Further objects of the present invention are the micrometric or nanometric hollow particles obtained with the method of the present invention.
In the following, examples on how to produce those particles are reported, provided that these are not restrictive as to the generality of the approach.
BRIEF DESCRIPTION OF THE DRAWINGS
In Figure 1 four SEM images at variable magnification of hollow particles with diameters of 50 μπι, 5 μπι, 500 nm and 200 nm produced by the method of the present invention are reported .
In Figure 2, low-magnification SEM images of hollow particles of different dimensions and high-magnification SEM images of hollow particles characterized by both "open" and "closed" hollow are reported.
In Figure 3, a high-magnification SEM image of ellipsoidal hollow particles obtained by deformation of the barrier film embedding the particles and by foaming is reported. BEST MODE FOR CARRYING OUT THE INVENTION EXAMPLES
The method of the present invention was applied to polystyrene (PS) particles of diameters of 50 μπι, 5 μπι, 500 nm and 200 nm. The procedure reported below was applied, separately, for the different particles.
0.1% (wt/vol) of PS spherical particles (50-5-0.5-0.2 μπι in diameter) were dispersed in aqueous solutions of 5% (wt/vol) poly (vinyl alcohol) (PVA) and 2% (wt/vol) of glycerol. The obtained mixtures were carefully poured in Teflon molds with flat surfaces and left to dry at room temperature for 72h. As a result of the drying, a solid single and continuous PVA film embedding the total amount of PS particles is obtained.
The film embedding the particles is then subjected to a foaming process, as follows. For the production of foamed samples, a pressure vessel, having a volume of 0.3 L, (model BC-1, HiP Erie, US-PA) was used. The pressure discharge system consists of a discharge valve, an electromechanical actuator and an electro-valve.
The samples (barrier film-embedded PS spheres) were loaded into the vessel, pressurized with a mixture of N2 and CO2 as the blowing agent at 14.0 MPa and 100°C for two hours and then pressure quenched at 100 MPa/s (foaming process) . PS Particles were then recovered by dissolving the PVA film in water at room temperature and washed centrifuging with water five times.
Particle morphology was observed by SEM, TEM, Dual Beam SEM/FIB and STED, showing that particles foamed when embedded in the PVA film presented hollows with morphologies depending on the different experimental conditions, as reported in Figure 1 and 2. In particular, particles foamed when embedded in the PVA film have a slightly larger diameter with respect to unfoamed particles, as a consequence of the formation of the hollow. Those of 5, 0.5 and 0.2 μπι have open hollows and are characterized by a bowl shape.
Bare polystyrene spheres (without being embedded in the barrier film - poured on lab paper) were also analyzed and subjected to the foaming process for proper comparison. Bare particles did not present any morphological modification after being subjected to the foaming process reported above, not presenting any hollow.
Authors of the present invention verified that, by modifying the blowing agent composition and other foaming process parameters such as pressure and temperature, it is possible to prepare particles with open or closed hollows, that is particles with a cavity that communicates with the external environment or not, respectively. It is possible, furthermore, by tuning the processing conditions, to modulate the hollow dimension, the hollow number within a single particle, and the eccentricity of the hollow with respect to the center of the particle.
Figure 2 reports SEM images of particles characterized by open hollow and particles characterized by closed hollow obtained by means of the present invention.
Furthermore, it has been verified that, by modulating the properties of the barrier film material and/or manipulating the barrier film itself, it is possible to modify the shape of the hollow particles.
For instance, Figure 3 shows an SEM image of kayak-shaped hollow nanometric particles, where the elongated shape was obtained by mechanical stretching at elevated temperature of the particles-embedded barrier film, followed by foaming . In effect, the method of the present invention allows modifying the shape of the particles by inducing a deformation or a stress on the barrier film. This chance is offered by the presence of the barrier film completely embedding the total amount of particles, conferring to the method of the present invention a very large versatility. Hollow particles can be obtained from any thermoplastic polymer (other than PS, reported in the example) and the barrier film could be made of a material different from PVA, standing it has the capability of allowing particle deformation/expansion and of keeping the blowing agent concentration in the particle sufficiently high (barrier effect) to induce the hollow formation, after the pressure release during the foaming process.
In the example provided, the blowing agent is solubilized into the particles after they have been embedded in the barrier film. Alternatively, it is also possible to embed blowing agent-laden particles in the barrier film (the blowing agent is solubilized in the particles before the particles are embedded in the barrier film) . Furthermore, foaming can be conducted not only by releasing the pressure, but also by increasing the temperature of the blowing agent-laden particles at the glassy state. In other words, the foaming process can be conducted with techniques different from the pressure release technique described in the example.
As it may result evident, the key point of the present invention is embedding the total amount of thermoplastic polymer particles in a single, continuous barrier film, which, during expansion, avoids blowing agent escape from the particles and manages to keep the blowing agent concentration within the particles sufficiently high to allow the hollow formation within the particles. Furthermore, the barrier film has to allow the particle deformation during foaming.
As it has been reported in the provided example, in case no barrier film is used (bare particles), during the foaming process the blowing agent evolution towards the outside of the particles (blowing agent loss) is so fast that there is no chance for the bubble to nucleate and grow to form the hollow .
The method described in the present invention has the great advantage to produce hollow particles without making use of complex techniques like fine chemical synthesis and, at the same time, may be used on particles without dimensional constraints and made of different polymers.
Furthermore, by means of the present invention, it is possible, by modifying the blowing agent composition, the barrier film composition and by manipulating the barrier film itself, to achieve hollow particles of several shapes, with one ore more hollows per particle, with hollows of several shapes, of different open/closed feature and eccentricity with respect to the particle center.

Claims

1. A method for the preparation of hollow particles of a thermoplastic polymer, with micrometric or nanometric dimensions, and comprising, one after the other, a solubilization step for the solubilization of a gas or a vapor acting as the blowing agent into thermoplastic polymeric bulk particles with micrometric or nanometric dimensions, and a foaming step for the expansion of the blowing agent in order to produce one or more bubbles inside said particles; said method being characterized by comprising, at least before said foaming step, an embedding step to include said bulk particles in a single and continuous polymeric barrier film and, after the foaming step, a washing step where the polymeric barrier film is washed out in a proper solvent; said embedding step including :
- a mixing operation, in which the thermoplastic polymer bulk particles and a barrier polymer are dispersed in a proper solvent wherein the polymer of said polymeric barrier film is soluble and at a concentration such that the polymer of said polymeric barrier film is at least five times higher than that of the thermoplastic polymer bulk particles, and
- a drying operation, wherein the solution coming from the mixing operation is dried obtaining a single and continuous polymeric barrier film embedding the total amount of thermoplastic polymer bulk particles;
- said polymeric barrier film being made of a polymer that allows, during the foaming step, the particles to dilate and the blowing agent concentration within the particles to be kept sufficiently high to induce bubble nucleation and growth; said polymeric barrier film being made of a polymer which is soluble in solvents wherein the thermoplastic polymer bulk particles are not soluble.
2. A method for the preparation of hollow particles according to claim 1, characterized in that said polymeric barrier film is made of a water-soluble polymer and in that, in said mixing operation, the solvent is water.
3. A method for the preparation of hollow particles according to claim 2, characterized in that said barrier polymer film is made of poly (vinyl alcohol) .
4. A method for the preparation of hollow particles according to any of the previous claims, characterized in that in said mixing step the barrier film polymer quantity is at least ten times higher than that of the thermoplastic polymer bulk particles.
5. A method for the preparation of hollow particles according to any of the previous claims, characterized in that said embedding step precedes said solubilization step, which is conducted via a high-pressure treatment with the blowing agent gas or vapor.
6. A method for the preparation of hollow particles according to any of the previous claims, characterized in that said foaming step is performed via a blowing agent pressure release.
7. A method for the preparation of hollow particles according to any of the previous claims, characterized in that said blowing agent is nitrogen, carbon dioxide or their mixture.
8. A method for the preparation of hollow particles according to any of the previous claims, characterized in that said thermoplastic polymer bulk particles are made of polystyrene .
9. A method for the preparation of hollow particles according to any of the previous claims, characterized in that it comprises a deformation and/or stress transfer step of the polymeric barrier film in order to achieve a deformation of said particles to obtain non-spherical particles and/or hollows.
10. Hollow polymeric micrometric or nanometric particles prepared with the method described according to any of the previous claims.
PCT/IB2014/063044 2013-07-12 2014-07-11 Method for the preparation of micrometric or nanometric hollow particles WO2015004641A1 (en)

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ITRM2013A000410 2013-07-12
IT000410A ITRM20130410A1 (en) 2013-07-12 2013-07-12 METHOD FOR THE PREPARATION OF MICROMETRIC OR NANOMETRIC CAVE PARTICLES

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Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS54153869A (en) * 1978-05-26 1979-12-04 Dainichi Seika Kogyo Kk Heat expansive resin composition
JPS63183943A (en) * 1986-08-25 1988-07-29 Sekisui Plastics Co Ltd Production of expanded particle for insulating material of lpg stockpiling tank
EP0306877A2 (en) * 1987-09-08 1989-03-15 BASF Aktiengesellschaft Use of polystyrene foam beads for mobile heat insulation and shadowing of transparent parts of buildings
JPH0867762A (en) * 1994-08-31 1996-03-12 Sekisui Plastics Co Ltd Pre-expanded thermoplastic resin particle having low thermal conductivity and molding made thereof
JPH11181141A (en) * 1997-12-25 1999-07-06 Hitachi Chem Co Ltd Expandable styrene resin particle and expanded molding made therefrom
JPH11263868A (en) * 1998-03-17 1999-09-28 Hitachi Chem Co Ltd Foamable styrene resin particle and molded foam
JP2003138055A (en) * 2001-10-31 2003-05-14 Hitachi Chem Co Ltd Foamable styrenic resin particle and foam-molded product
US20050187307A1 (en) * 2002-05-08 2005-08-25 Makoto Kunimi Expandable styrene resin particles, expandable beads, and foamed article
JP2006152029A (en) * 2004-11-25 2006-06-15 Sekisui Plastics Co Ltd Expandable styrene-based resin particle
EP2452969A1 (en) * 2010-11-11 2012-05-16 Basf Se Method for producing expandable thermoplastic particles by means of re-impregnation

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS54153869A (en) * 1978-05-26 1979-12-04 Dainichi Seika Kogyo Kk Heat expansive resin composition
JPS63183943A (en) * 1986-08-25 1988-07-29 Sekisui Plastics Co Ltd Production of expanded particle for insulating material of lpg stockpiling tank
EP0306877A2 (en) * 1987-09-08 1989-03-15 BASF Aktiengesellschaft Use of polystyrene foam beads for mobile heat insulation and shadowing of transparent parts of buildings
JPH0867762A (en) * 1994-08-31 1996-03-12 Sekisui Plastics Co Ltd Pre-expanded thermoplastic resin particle having low thermal conductivity and molding made thereof
JPH11181141A (en) * 1997-12-25 1999-07-06 Hitachi Chem Co Ltd Expandable styrene resin particle and expanded molding made therefrom
JPH11263868A (en) * 1998-03-17 1999-09-28 Hitachi Chem Co Ltd Foamable styrene resin particle and molded foam
JP2003138055A (en) * 2001-10-31 2003-05-14 Hitachi Chem Co Ltd Foamable styrenic resin particle and foam-molded product
US20050187307A1 (en) * 2002-05-08 2005-08-25 Makoto Kunimi Expandable styrene resin particles, expandable beads, and foamed article
JP2006152029A (en) * 2004-11-25 2006-06-15 Sekisui Plastics Co Ltd Expandable styrene-based resin particle
EP2452969A1 (en) * 2010-11-11 2012-05-16 Basf Se Method for producing expandable thermoplastic particles by means of re-impregnation

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Title
DATABASE WPI Week 198003, Derwent World Patents Index; AN 1980-04329C, XP002717222 *
DATABASE WPI Week 199620, Derwent World Patents Index; AN 1996-196616, XP002717221 *
DATABASE WPI Week 200409, Derwent World Patents Index; AN 2004-084847, XP002717220 *

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