U.S. patent application number 09/155257 was filed with the patent office on 2002-03-07 for method of encapsulation.
Invention is credited to BROWN, MALCOLM DAVID.
Application Number | 20020026771 09/155257 |
Document ID | / |
Family ID | 10791058 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020026771 |
Kind Code |
A1 |
BROWN, MALCOLM DAVID |
March 7, 2002 |
METHOD OF ENCAPSULATION
Abstract
A method of encapsulation is characterized by supplying to an
encapsulation unit (22) two films (14, 16) of like material capable
of deforming elastically at least when partially solvated, and
applying solvent to at least one of the films prior to
encapsulation to cause partial solvation of the material surface,
such that the partially solvated surface can adhere to and seal
with the film material. In the encapsulation unit, the substance to
be encapsulated e.g. a cosmetic oil or vitamin preparation is
supplied between the films, the films are formed, typically by a
molding process, into suitably shaped capsule portions which can
adhere to each other as a result of the adhesive action of the
partially solvated surface(s), and which seal together
encapsulating the supplied substance, forming a capsule. The
invention enables encapsulation using materials other than gelatin,
such as polyvinyl alcohol. Also disclosed is encapsulation
apparatus and the resulting capsules.
Inventors: |
BROWN, MALCOLM DAVID;
(MUNDFORD, GB) |
Correspondence
Address: |
MORGAN & FINNEGAN
345 PARK AVENUE
NEW YORK
NY
10154
|
Family ID: |
10791058 |
Appl. No.: |
09/155257 |
Filed: |
September 24, 1998 |
PCT Filed: |
March 25, 1997 |
PCT NO: |
PCT/GB97/00838 |
Current U.S.
Class: |
53/454 |
Current CPC
Class: |
A61K 8/8129 20130101;
A61Q 19/10 20130101; C08J 5/122 20130101; A61K 8/11 20130101; A61J
3/07 20130101; A61K 9/4816 20130101 |
Class at
Publication: |
53/454 |
International
Class: |
B65B 047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 26, 1996 |
GB |
9606371.4 |
Claims
1. A method of encapsulation, characterised by supplying to an
encapsulation unit two films of like material capable of deforming
elastically at least when partially solvated, and applying solvent
to at least on of the films prior to encapsulation to cause partial
salvation of the material surface, such that the partially solvated
surface can adhere to and seal with the film material.
2. A method of encapsulation, comprising supplying two films of
like material capable of deforming elastically at least when
partially solvated; applying solvent to at least one of the films
to cause partial solvation of the material surface; supplying
substance to be encapsulated between the films; forming the films
into suitably shaped capsule portions which can adhere to each
other as a result of the adhesive action of the partially solvated
surface(s); and sealing the capsule portions together,
encapsulating the supplied substance, to form a capsule.
3. A method according to claim 2, wherein a vacuum is applied
during capsule portion formation to assist deformation of the film
material.
4. A method according to claim 1, 2 or 3, wherein the film material
is selected from polyvinyl alcohol, alginate, hydroxypropyl methyl
cellulose, polyethylene oxide, polycaprolactone and gelatinized
starch based materials.
5. A method according to claim 4, wherein the film material is
polyvinyl alcohol and the solvent is water.
6. A method according to any one of the preceding claims, wherein
the film material becomes more flexible on partial solvation.
7. A method according to any one of the preceding claims, wherein
the solvent is applied just prior to encapsulation.
8. A method according to any one of the preceding claims, wherein
the solvent applied by means of a gravure or flexo printing
process.
9. Encapsulation apparatus comprising means for supplying two films
of material to an encapsulation unit; an encapsulation unit; and
means for supplying a solvent for the film material to at least one
of the films upstream of the encapsulation unit.
10. Apparatus according to claim 9, wherein the encapsulation unit
comprises a pair of counter-rotating moulding drums, and an
associated arrangement for coordinated supply of substance to be
encapsulated.
11. Apparatus according to claim 10, including means for applying a
vacuum inside the moulding drums.
Description
FIELD OF INVENTION
[0001] This invention concerns encapsulation and relates to a
method of encapsulation, encapsulation apparatus and the resulting
capsules.
BACKGROUND TO THE INVENTION
[0002] The provision of water soluble and digestible capsules
containing pharmaceutical or cosmetic preparations is well
established. Typically oils are encapsulated in gelatin shells
designed to release their contents when subjected to immersion in
water or exposure to digestive juices. These oils include dietary
enhancement substances or, in the case of cosmetic preparations,
fragrant oils for release into bath water. A substantial industry
has been built up around this principle, based primarily on the use
of gelatin for the capsule shells. This gelatin is derived from the
bones and skins of animals.
[0003] With concern for the environment and animal welfare and fear
of animal related diseases such as Bovine Spongiform Encephalopathy
(BSE) increasing, the number of individuals adopting a serious
stance on the use of animals and animal-derived products in food
substances and cosmetic applications has risen dramatically. As a
result, the sales of such gelatin capsules are very limited among
such individuals. There exists therefore the need for the provision
of a suitable substitute for gelatin in order to provide water
soluble or digestible capsules which are not derived from animals.
Whilst this is a desirable aim, few materials lend themselves to
such use and the machinery currently creating such capsules has
been specifically designed to suit the properties of gelatin. As a
result, a change in material for the capsule shell requires a
redesign of the machinery if it is to have the capability of
efficiently producing capsules from the replacement material. It is
a change in material and the commensurate machine requirements
needed to enable successful processing which this invention
addresses.
SUMMARY OF THE INVENTION
[0004] In one aspect, the present invention provides a method of
encapsulation, characterised by supplying to an encapsulation unit
two films of like material capable of deforming elastically at
least when partially solvated, and applying solvent to at least one
of the films prior to encapsulation to cause partial solvation of
the material surface, such that the partially solvated surface can
adhere to and seal with the film material.
[0005] In the encapsulation unit, the substance to be encapsulated
is supplied between the films, the films are formed, typically by a
moulding process, into suitably shaped capsule portions which can
adhere to each other as a result of the adhesive action of the
partially solvated surface(s), and which seal together
encapsulating the supplied substance, forming a capsule.
[0006] In a further aspect, the invention provides a method of
encapsulation, comprising supplying two films of like material
capable of deforming elastically at least when partially solvated;
applying solvent to at least one of the films to cause partial
solvation of the material surface; supplying substance to be
encapsulated between the films; forming the films into suitably
shaped capsule portions which can adhere to each other as a result
of the adhesive action of the partially solvated surface(s); and
sealing the capsule portions together, encapsulating the supplied
substance, to form a capsule.
[0007] Conventional gelatin encapsulation relies upon heat as the
mechanism for sealing the two portions of the shell together to
enclose the contents. The capsules made by this invention do not
use heat as the primary means of securing the two portions of the
capsule together, but instead make use of the adhesive effects
manifested when suitable films are partially solvated at their
surface.
[0008] The films may be of a range of different materials. Suitable
materials soluble in water (hot or cold) include polyvinyl alcohol
(PVA), alginate, hydroxypropyl methyl cellulose and polyethylene
oxide. In this case it is simply necessary to apply water at a
suitable temperature to the film or films to cause partial
solvation. The resulting capsules release their contents when
immersed in water or exposed to digestive juices and thus lend
themselves to such uses as the release of fragrant oil in a bath or
the release of dietary supplements after ingestion. If the material
is only soluble in hot water then it is necessary to apply water at
appropriately elevated temperatures, but the partial solvation and
the subsequent adhesive effects are still effective to seal the
capsule.
[0009] Non-water soluble film materials may also be used, such as
polycaprolactone and gelatinized starch based materials. In this
case it is necessary to apply a suitable solvent such as N-methyl
pyrrolidone rather than water to at least one film surface to
induce partial solvation. The partial solvation of such films
causes them to soften, enabling them to take up the internal
dimensions of a mould used to create a capsule. Capsules made from
films which are biodegradable but not water soluble release their
contents as a result of microbial action instead of immersion in
water, and can find use in agricultural and industrial
applications.
[0010] The currently preferred film material is PVA, preferably
plasticised with glycerin. Suitable films are commercially
available in a range of different grades, types and thicknesses. An
appropriate film can be readily selected having regard to the
intended use, capsule contents and desired capsule properties. For
example, PVA film is available in thicknesses ranging between 20
and 1000 microns. For cosmetic applications, good results have been
obtained with 80 micron PVA film, eg Hi-Selon (Hi-Selon is a Trade
Mark) cold water soluble PVA B9, obtainable from British Traders
and Shippers, 429-431 Rainham Road South, Dagenham, Essex.
[0011] It is preferred to use film material that becomes more
flexible when in partially solvated conditions as this assists
capsule formation. PVA has this property.
[0012] Instead of using pre-formed films, the films may be formed
during the encapsulation method, eg by being cast from
solution.
[0013] In practising the invention it is appropriate to use two
films of like material. The films should be chemically alike but
need not be identical in terms of factors such as grade, thickness
etc.
[0014] The solvent is selected having regard to the film material,
and is conveniently water in the case of water soluble materials.
The solvent should be applied in an appropriate amount, either in
isolation or as part of a formulation containing materials such as
thickening and/or wetting agents, to cause a suitable degree of
partial solvation of the film material surface: this can be readily
determined by experiment.
[0015] The solvent is preferably applied just prior to
encapsulation at an appropriate location to obtain optimum speed of
capsule production.
[0016] The solvent can be applied in a variety of different ways,
including by atomisation such as in the form of a spray or jet, by
dipping, electrostatic coating, roller, air knife or Meyer bar, or
with a sponge. The currently preferred technique is by means of a
gravure or flexo printing process as this enables ready control and
regulation of the amount and uniformity of solvent application.
[0017] Solvent may be applied to one or both films as
appropriate.
[0018] A vacuum is conveniently applied during capsule portion
formation to assist deformation of the film material.
[0019] The invention may be used to encapsulate a wide range of
substance in the form of solids, liquids or gases. The invention
may, for example, be used to encapsulate all of the substances
currently encapsulated in gelatin, such as drugs, vitamins,
powders, oils, cosmetic preparations, drug delivery systems, paint
etc. A typical cosmetic application is encapsulation of bath oils
to produce capsules intended to be used in the bath, where the
capsule shell dissolves releasing the oil into the bath water.
[0020] The capsules may have a variety of different sizes and
shapes, usually determined by the shape of the mould employed.
Typically the capsules are spherical or oval, but more elaborate
forms eg based on fruit, animal or abstract shapes may be produced,
usually for cosmetic applications.
[0021] In a further aspect the invention provides encapsulation
apparatus comprising means for supplying two films of material to
an encapsulation unit; an encapsulation unit; and means for
supplying a solvent for the film material to at least one of the
films upstream of the encapsulation unit.
[0022] The encapsulation unit may be based on those used in
conventional apparatus currently used for gelatin encapsulation. In
typical conventional apparatus, two separate ribbons of gelatin
film are first produced by pouring heated liquid gelatin at a
controlled rate onto the peripheral faces of two cylinders each
rotating about a horizontal axis. The liquid gelatin cools on the
cylinders and forms two ribbons which are fed from opposed sides to
an encapsulation unit.
[0023] The encapsulation unit typically comprises a pair of similar
moulding drums. The outer cylindrical face of each drum is formed
with a plurality of indentations of desired form, eg hemispherical,
arranged in a series of axially extending rows with, say, 5 or 6
indentations in each row. The drums are supported in side by side
relationship, with a small gap there between, and are arranged for
coordinated rotation in opposed directions (the left hand drum
clockwise, and the right hand drum anticlockwise). A similar
arrangement may be used in the present invention. Means for
applying a vacuum inside the drums are conveniently included, to
help pull the partially solvated films into the indentations and so
assist capsule portion formation.
[0024] The encapsulation unit typically also comprises a reservoir
of the substance to be encapsulated, eg bath oil, and an associated
supply arrangement adapted simultaneously to supply a plurality of
metered doses (one for each indentation in a row on the moulding
drums) of the substance to the moulding drums at predefined time
intervals. The arrangement may employ syringe pumps or the like.
Again, a similar arrangement may be used in the present
invention.
[0025] The metered doses are initially supplied to a heated
injection segment located above the nip between the moulding drums,
and including a row of a plurality of injectors aligned with the
rows of indentations in the drums. A similar arrangement may again
be used in the present invention although there is no need for the
injection segment to be heated.
[0026] In use in conventional encapsulation, two gelatin ribbons
are formed and fed over appropriate guide rollers etc to pass below
the injection segment and into the nip between the counter-rotating
rollers. Metered doses of the substance to be encapsulated are
injected into the nip in synchronism with the drum rotation. The
heating segment also acts to heat the gelatin films, which has the
effect of making the films capable of sealing to each other and
also makes the films more elastic. As the doses of substance are
injected between the heated films, the films deform to line the
indentations, forming series of pairs of opposed capsule halves
containing the substance. The pairs of capsule halves are brought
together, sealed and cut from the gelatin ribbons on continued
rotation of the drums, thus forming capsules containing the
substance. A typical production rate is one row of capsules every 2
seconds. Instead of cutting the capsules from the ribbons, they may
be left integral with the ribbons. The resulting capsules are
collected below. The capsules are then typically tumbled in a hot
air dryer and then kept in a controlled humidity environment for
about 2 days to stabilise the capsules. The capsules are then ready
for use or sale.
[0027] As noted above, the present invention may use an
encapsulation unit generally as described. It is not necessary for
the injection segment to be heated, as the present invention does
not rely on heating for sealing, as in the prior art, so processing
costs may be reduced somewhat and faster processing may be
possible. However, the films of the present invention may
optionally be heated: in some cases this may enhance film
elasticity and sealing.
[0028] Conventional encapsulation apparatus would, of course, also
need modification by removal of the gelatin ribbon formation
equipment and substitution of equipment for supplying (and possibly
also forming) the films of material used in the present invention.
In a simple case this could just be a pair of spindles each for
receiving a roll of the film, to be fed to the encapsulation unit
in known manner.
[0029] A further necessary modification is addition of mean for
applying solvent to one or both of the films, preferably located
just upstream of the encapsulation unit. As noted above these means
could be a spray or jet arrangement, a bath for dipping, an
electrostatic coating unit, a roller, an air knife, a Meyer bar, a
sponge etc. Preferably, however, a gravure or flexo printing unit
is used.
[0030] Means for applying a vacuum within the moulding drums are
conveniently also incorporated.
[0031] The invention also covers capsules formed in accordance with
a method or by use of apparatus in accordance with the
invention.
[0032] The invention also includes within its scope a capsule
having a shell comprising material capable of adhering to and
sealing with itself when in partially solvated condition.
[0033] In a preferred aspect the invention covers a capsule having
a shell comprising polyvinyl alcohol.
[0034] The invention will further be described, by way of
illustration, in the following Example and with reference to the
accompanying drawing, in which:
[0035] FIG. 1 is a schematic illustration of one embodiment of
apparatus in accordance with the invention.
DETAILED DESCRIPTION OF THE EMBODIMENT
[0036] The apparatus illustrated in FIG. 1 comprises two rolls 10,
12 of film 14, 16 of like material rotatably supported on spindles
18, 20, with associated means (not shown) for feeding film from the
rolls to an encapsulation unit 22. The films first pass over
respective support rollers 24, 26 and then through respective
flexographic printing units 28, 30 with associated backing rollers
32, 34 for supply to a surface of the film, in an adjustable
manner, of accurately metered quantities of solvent for the film
material. In an experimental apparatus, laboratory scale narrow
flexographic heads from RK Print Coat Instruments Limited,
Litlington, Royston, U.K. were used for this purpose.
[0037] The encapsulation unit 22 is based on the encapsulation unit
of conventional apparatus, as discussed above, and comprises a
reservoir containing the substance to be encapsulated and an
associated supply arrangement for supplying metered doses of the
substance. The reservoir and supply arrangement are represented
schematically at 36.
[0038] The encapsulation unit further comprises a pair of similar
moulding drums 38, 40. The outer cylindrical face of each drum is
formed with a plurality of hemispherical indentations 42 arranged
in a series of axially extending rows with 6 indentations in each
row. Vacuum means (not shown) may optionally be included for
applying a vacuum inside the drums to assist deformation of the
film material. The drums are supported in side by side relationship
with a small gap therebetween, and are arranged for coordinated
rotation in opposed directions (the left hand drum 38 clockwise,
and the right hand drum 40 anticlockwise). An injection segment 44
is located above the nip between the moulding drums to receive
substance from reservoir and supply arrangement 36, as illustrated
schematically by line 46. Injection segment 44 includes an array of
6 injectors (not shown) aligned with the rows of indentations in
the drums.
[0039] In use, film 14, 16 is supplied at an appropriate rate to
the encapsulation unit 22, passing over support rollers 24, 26 and
through printing units 28, 30 where solvent is applied to the film
surface in appropriate amount. The films then pass below the
injection segment 44 and into the nip between drums 38, 40 which
are counter-rotating at an appropriate speed. Metered doses of the
substance to be encapsulated are injected into the nip from
injection segment 44 in synchronism with the drum rotation. As the
doses of substance are injected between the films, the films deform
to line the indentations 42 of one row in each of the drums,
possibly assisted by application of a vacuum, forming a series of 6
pairs of opposed capsule halves containing the substance. On
continued rotation of the drums the pairs of capsule halves are
brought together and seal because of the adhesive effect caused by
partial solvation of the film surface, producing a row of
surface-containing capsules which are cut from the films. One row
of 6 capsules is produced approximately every 2 seconds. The
resulting capsules 48 are collected in a tray 50, and the waste
film remaining is disposed of. The capsules are dried and
stabilised in generally conventional manner.
EXAMPLE
[0040] Using the apparatus of FIG. 1 encapsulation of a typical
bath oil cosmetic product was carried out using Hi-Selon cold water
soluble plasticised polyvinyl alcohol (B9) film, 80 micron thick,
with partial solvation carried out by application of water. This
resulted in production of good quality capsules, suitable for
cosmetic use.
* * * * *