Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2001-10-18
2004-06-22
Kiliman, Leszek B (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S402200, C428S402210, C428S402220, C428S402240, C428S403000, C428S407000, C427S212000, C427S213300, C427S213310, C427S213320, C427S213340
Reexamination Certificate
active
06753083
ABSTRACT:
The present invention relates to particulate compositions which comprise particles that have a hydrophobic polymeric core within a shell, which comprises a membrane and processes for making said particles. The invention also relates to stable uniform dispersions of polymer particles and methods for making same. The invention further relates to methods of controlling the release of active substances from particles.
It is known to make particles having a core shell configuration. One method involves coacervation of a polymer around the core. Methods of forming a coacervate coating from a polymer solution around an aqueous core, and which are suitable for the manufacturer of micro capsules that can be included in a liquid detergent concentrate, are described in, for instance, the EP-A-356239 and WO-A92/20771. It is difficult to obtain by this technique a product in which the enzyme is retained satisfactorily in the particles while in the concentrate but is reliably released from the particles when the concentrate is diluted into wash water.
WO-A-97/24179 describes a particulate composition comprising particles having a hydrophilic core within a shell comprising a membrane comprising an association product of (a) an IFC condensation product formed by reaction between a first IFC reactant having at least two first condensation groups and a second IFC reactant having at least two second condensation groups, and (b) an amphipathic polymeric stabiliser which will concentrate at the interface between oil and water and which has recurring hydrophobic groups and recurring reactive hydrophilic groups which associate with the second condensation groups
U.S. Pat. No. 4,708,816 describes a method for preparing microcapsules which are stable in that the microcapsules have a controlled density to be closely similar to that of an aqueous bleaching solution into which they are dispersed. The microcapsules comprise an inner core and a polymeric outer shell which is used to vary the density to be compatible with the liquid medium into which the particles are dispersed. This process therefore requires that the shell wall needs to be synthesised precisely such that the density of the microcapsules will match the density of a given liquid medium. In practice it may be difficult to consistently produce microcapsules with a precise density by a microencapsulation process in which the density of the microcapsule is determined solely by the amount of density adjusting polymer in the outer shell. Thus the carrier phase is inevitably more dense that the wall forming material.
U.S. Pat. No. 3,676,363 describes producing weighted microcapsules, by incorporating a finely divided weighting compound in the capsular material. The amount of weighting compound incorporated will depend upon the desired weight of the capsules, which depends upon the specific gravity of the liquid. This reference appears to deal specifically with increasing the density of particles for use with high density liquids such as brine.
U.S. Pat. No. 5,723,059 discloses improving a dispersion of a microencapsulated phase change material in a poly alpha olefin electronic coolant fluid by modifying the density of the fluid to match the density of the dispersed particles. This would only be applicable to systems in which altering the density of the oil based continuous phase is feasible.
It is also known to prepare microparticles which have pre-determined densities in order to form a uniform dispersion in a hydrocarbon liquid.
However, there exists a need for particles which can readily and consistently form a uniform dispersion in a liquid. There also exists a need for an improved method of forming such dispersions in which particles or microcapsules are uniformly distributed, and which avoids any surface stratifying of particles, “creaming” and also avoids sedimentation of the particles. In particular there is a need to achieve this for dispersions in non-aqueous liquids, especially hydrocarbons.
Furthermore there is also a need for improvements to particles containing active substances and improved methods for releasing said active substances.
According to a first aspect of the present invention we provide a particulate composition comprising particles having a core within a shell, in which the core comprises a hydrophobic polymer, characterised in that the shell comprises a semi-permeable membrane.
It is important to the functionality of the particles of the present invention that the core comprises at least some hydrophobic polymer. In one form of the invention the core comprises an aqueous liquid containing particles of hydrophobic polymer particles dispersed throughout the aqueous liquid. In another form the core may comprise agglomerates of hydrophobic polymer particles. In a further form the core comprises a matrix of hydrophobic polymer. In all of these forms of the invention, the core is regarded as a hydrophobic polymeric core.
The particles may comprise a core which is essentially a single intact matrix of polymer core material. Alternatively the core material comprises voids or vesicles distributed throughout the matrix polymer. In addition it may also be possible for the core to comprise other components, which are for instance distributed throughout the hydrophobic polymeric core.
Desirably the hydrophobic polymeric core is any suitable material that is capable of absorbing, imbibing or dissolving in a hydrophobic or water immiscible liquid.
In one form of the invention the core also comprises a hydrophobic liquid. Desirably the hydrophobic liquid has been absorbed or imbibed by the hydrophobic polymeric core material.
This preferred form of the invention relates to particles which comprise a core that contains absorbed or imbibed hydrophobic liquid and a semipermeable membrane shell wherein the core comprises i) an aqueous liquid containing dispersed hydophobic polymer particles, ii) agglomerates of hydrophobic polymer particles or iii) a hydrophobic polymer matrix. In each case the hydrophobic liquid is desirably absorbed by or imbibed into the hydrophobic polymer. This preferred form of the invention may be achieved by dispersing the particles in said hydrophobic liquid for sufficient time to allow the hydrophobic liquid to pass through the semi-permeable membrane and into the hydrophobic polymeric core.
In one preferred form the particles comprise an active substance. The active substance can be any active ingredient that is either released slowly as part of a controlled release mechanism or alternatively may perform some function by remaining within the particles. Such an active substance which remains within the particle could be a pigment, dye or colour former and the particle may be used in a colour forming application. Typically the active substance may be any selected the group consisting of fragrance oils, lubricant oils, essential oils, wax inhibitors, corrosion inhibitors, colorants, oxygen scavengers, antioxidants and vitamins.
The hydrophobic polymeric core material may be any polymeric material which exhibits hydrophobic properties. It may be a natural polymer but preferably it is a synthetic polymer. Desirably the polymer can be a condensation polymer, for instance a polyester or polyamide. The polymer may be a condensation polymer of formaldehyde for instance a phenolic resin. Other suitable polymers include polyurethanes. Preferably the hydrophobic polymer core is formed by polymerisation of ethylenically unsaturated monomer or monomer blend. Generally the monomer or blend of monomers are hydrophobic, but may include some hydrophilic monomer, provided that the resulting polymer is hydrophobic. By hydrophobic we mean that the hydrophobic monomer has a solubility in water of less than 5 g in 100 cm
3
of deionised water at 25° C. By hydrophilic monomer we mean that the hydrophilic monomer has a solubility in water of at least 5 g in 100 cm
3
of deionised water at 25° C. Typically the monomers include monomers which do not possess ionic or hydrophilic functional groups. Suitable monomers are for instance acryl
Mistry Kishor Kumar
Preston Janine Andrea
Symes Kenneth Charles
Ciba Specialty Chemicals Water Treatments Ltd.
Kiliman Leszek B
Villamizar JoAnn
LandOfFree
Particles does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Particles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Particles will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3304757