Fluid dispensation

Pressure generating gas-releasing compositions which are microcmulsions, siloxane or hydrocarbon greases or elastomers, are used to aid dispensation of a fluid from a reservoir without the composition itself being dispensed. Dispensers containing such compositions can include writing implements.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates to the dispensation of fluids from a reservoir and
 particularly, but not exclusively, to the dispensation of ink in writing
 implements.
 2. Description of Related Technology
 There are a number of conventional techniques for delivering ink from an
 ink reservoir to the tip of a pen. The simplest technique is to rely on a
 gravity feed; however, this will not work well, and may not work at all,
 if the pen is turned upside down or if the ink is too viscous.
 Another technique is to use a pressurised permanent gas, such as nitrogen,
 within the ink reservoir. The gas ensures that a sufficient pressure is
 maintained on the ink to push it towards the tip of the pen. However,
 there is a problem with this technique: as the ink is dispensed from the
 reservoir, the pressure in the reservoir drops, because there is a greater
 volume for the gas to occupy. In order to overcome this problem, the gas
 must be provided initially at high pressure, and must occupy a large part
 of the volume of the reservoir relative to the ink: in practice, up to 90%
 of the volume of the reservoir may initially be occupied by gas.
 SUMMARY OF THE INVENTION
 We have now found that the problems described above can be overcome and
 that fluids can advantageously be dispensed from a reservoir by using a
 pressure generating composition capable of releasing a volatile component,
 wherein the volatile component is released from the composition as the
 fluid is dispensed in order to maintain the pressure in the reservoir at a
 level sufficient to aid dispensation of the fluid, the pressure generating
 composition itself remaining in the reservoir and not being dispensed with
 the fluid.
 According to one aspect of the invention, therefore, there is provided the
 use of a pressure generating composition capable of releasing a volatile
 component to generate a pressure, to aid the dispensation of a fluid from
 a reservoir without the said composition itself being dispensed, wherein
 the pressure generating composition comprises an oil-in-water or
 water-in-oil microemulsion, or a siloxane or hydrocarbon grease, or an
 elastomer, containing said volatile component.
 The invention is particularly suitable for dispensing inks from a pen, but
 can be used for dispensing other fluids from containers thereof.
 According to another aspect, the invention provides a dispenser for
 dispensing a fluid, which dispenser comprises a reservoir containing said
 fluid, the reservoir having an outlet through which said fluid can be
 dispensed, and a pressure generating composition capable of releasing a
 volatile component to generate a pressure within the reservoir to aid
 dispensation of the fluid, wherein said composition is capable of
 releasing the volatile component as the fluid is dispensed, in order to
 maintain the pressure in the reservoir at a level sufficient to aid
 dispensation of the fluid, and wherein the said composition is not
 dispensed with the fluid, said pressure generating composition comprising
 water-in-oil or oil-in-water a microemulsion or a siloxane or hydrocarbon
 grease, or an elastomer, containing said volatile component.
 DETAILED DESCRIPTION OF THE INVENTION
 The fluid can be any flowable material, but the invention is particularly
 suitable for aiding the dispensation of viscous fluids that do not flow
 well under the influence of gravity. For example, dispensation of pastes
 such as toothpaste and the like, and gels such as deodorant- or
 antiperspirant-containing gels and the like, or wet shaving preparations
 such as soaps and shaving aids, can be assisted by the present invention.
 The invention is particularly (but not exclusively) useful for aiding the
 dispensation of fluid from writing or correction instruments, particularly
 such fluids which are viscous, e.g. inks as used in ballpoint pens and the
 like. The invention is also useful to aid in the dispensation of solvent
 and water-based inks.
 The pressure necessary to aid dispensation of the fluid from the reservoir
 depends upon a number of factors, such as the properties of the fluid, and
 the size and shape of the reservoir. A reservoir pressure above about 0.5
 psi (3.4 kPa), preferably above about 1 psi (6.89 kPa), is normally
 sufficient to aid dispensation of the fluid. The maximum reservoir
 pressure is dictated by the strength of the reservoir and the
 characteristics of the pressure generating composition. Generally, the
 pressure will not be greater than 60 psi (413 kPa), preferably from 1 to
 15 psi (6.9 to 103 kPa). In practice, it would not normally be necessary
 for the maximum reservoir pressure to be above about 10 psi (68.9 kPa).
 For most dispensers, the reservoir pressure is preferably in the range 1
 to 4 psi (6.9 to 27.6 kPa). However, the optimum conditions will depend on
 all the circumstances and can be determined in any particular case by
 routine trial and experiment.
 It will be understood that generally the pressure generating composition is
 not itself dispensed with the fluid from the reservoir. Rather, the
 composition remains in the reservoir as the fluid is dispensed, the
 composition serving to maintain a gas pressure to aid in dispensing the
 fluid. Thus, the pressure generating composition is normally used in a way
 in which it does not intimately mix with the fluid to be dispensed,
 although it may be in direct contact therewith at an interface.
 Ideally, the pressure generating composition should be immiscible with the
 liquid to be dispensed. For example, if the fluid to be dispensed is
 organic-based, then the pressure generating material should be
 aqueous-based; and if the fluid to be dispensed is aqueous-based, then the
 pressure generating material should be organic-based. Alternatively, a
 barrier may be provided between the fluid to be dispensed and the pressure
 generating material, in order to prevent contact therebetween especially
 when both are organic-based or aqueous-based. For example, in the case of
 an aqueous-based fluid and an aqueous pressure generating material, an
 organic-based barrier, such as a grease plug, can be provided between the
 fluid and the pressure generating material. The use of a barrier can be
 very important when dispensing low viscosity fluids, in order to prevent
 the formation of air bubbles.
 Over a period of time, it is possible for the fluid being dispensed, or for
 the barrier, to dissolve some of the volatile component from the
 atmosphere in the reservoir. This does not normally affect the operation
 of the invention although preferably the barrier material will be such as
 not to dissolve the volatile component to any significant extent.
 Another way of providing a barrier between the pressure generating
 composition and the fluid to be dispensed is to confine the composition in
 an expandable bladder, bag or other flexible container, for example, the
 container being disposed within the reservoir containing the fluid to be
 dispensed. As the composition releases the volatile component, the
 container expands to raise the pressure in the reservoir to aid
 dispensation of the fluid.
 In one preferred embodiment of the invention, the fluid is an ink, and the
 fluid dispenser is part of a writing implement having a tip for delivering
 the ink to a surface to be written on, or otherwise marked. In this
 embodiment, the reservoir and the tip are in fluid communication, whereby
 ink can be fed from the reservoir to the tip.
 In another embodiment, the fluid is an ink, and the fluid dispenser
 comprises a refill for a writing implement. The ink may be a water-based
 or solvent-based ink and may be for use in ballpoint pens or other writing
 instruments.
 In further exemplary embodiments, the fluid is a paste such as toothpaste,
 or a gel material, or a fluid such as a correction fluid or shaving soap
 or a shaving aid.
 In use of the pressure generating compositions in the present invention,
 the compositions release a volatile component at ambient temperatures. In
 some embodiments, at least some of the volatile component will be in
 solution in a component of the composition, or it may be otherwise
 dispersed in the composition. In accordance with a feature of the
 invention, we prefer to use as pressure generating compositions in the
 invention, stabilised oil-in-water or water-in-oil microemulsions in which
 the oil phase acts as a reservoir for the volatile component. Examples of
 such compositions are known (but are used for quite different purposes
 from the present invention) and are described, for example, in U.S. Pat.
 No. 3,541,581. In U.S. Pat No. 3,541,581, the microemulsion is in the form
 of a stable post-forming gel comprising water, a soap, a volatile liquid,
 and a water-soluble gelling agent. The gel is stored in a container and,
 when dispensed, the volatile liquid therein evaporates and, as a result,
 the gel becomes foamed. The composition is useful as a personal care
 lather-producing soap composition.
 For use in the present invention, such microemulsions need to be formulated
 to give the desired pressure-generation effect and this will be within the
 skill of those skilled in the art, using routine trial and experiment to
 determine the optimum conditions in any particular case. Most preferably,
 the microemulsions are so formulated as to be of gel-like consistency,
 normally having a viscosity in the range 200 to 20,000 centipoise (cP). By
 "microemulsion", we mean an emulsion in which the disperse phase is of a
 diameter of less than about 0.05 micrometer.
 For the aqueous phase of the microemulsions, we prefer to use an aqueous
 soap solution (or the like). The soap is preferably the reaction product
 of a fatty acid and a metal compound or an amine. The metal compound is
 suitably a metal hydroxide. The metal of the metal compound may be, for
 example, an alkali metal, such as Li, Na or K, or an alkaline earth metal,
 such as Mg or Ca. The amine compound is preferably triethanolamine,
 monoethanolamine, diethanolamine, isopropanolamine, aminomethylpropanol,
 aminomethylpropane diol, or another organic amine. The fatty acid
 desirably has from 8 to 18, more desirably from 10 to 16, carbon atoms.
 Palmitic acid and lauric acid are particularly preferred fatty acids.
 The soap may be formed, for example, from 60 to 80 wt % fatty acid,
 preferably 65 to 75 wt % fatty acid. The aqueous soap solution typically
 contains 50 to 75 wt % water, preferably 65 to 75 wt % water.
 Instead of soaps, sarcosinates can be used. Examples are crodasinic O,L,M
 and C available from Croda Chemicals Ltd., Hull, England, and Hampsoyl
 L95,L,M,C,O and S from Hampshire Chemicals Ltd.
 The oil phase of the microemulsion is insoluble in the aqueous phase, eg.
 soap solution, and is preferably a mineral oil, corn oil, isopropyl
 myristate, dimethyl siloxane (or polydimethyl siloxane), isocetyl alcohol,
 lauryl lactate, or a synthetic oil such as polydecane, polyhexane or
 polyisobutane, or polybutene. We especially prefer the use of a mineral
 oil.
 Instead of using microemulsions, simple solutions or dispersions of a
 volatile component in a material may be used, such as in an elastomer, eg.
 polyisobutylene of molecular weight below about 4000. Also, it is possible
 to use greases to contain the volatile component and so form pressure
 generating compositions for use in the invention. Thus, in oil-containing
 greases such as Gilugel, the oil can act as a reservoir for the pressure
 generating agent. Examples of oils which can be used in this way are
 mineral oil, isopropyl myristate, isopropyl palmitate, cyclomethicone
 pentamer and castor oil.
 Advantageously, the volatile component in the pressure generating
 compositions will be at least partly soluble in any oil or aqueous phase
 of the compositions at 25.degree. C. It is especially preferred that the
 volatile component is a non-permanent gas. The volatile component
 preferably has a vapour pressure of 8 to 40 psi (55 to 276 kPa) at
 25.degree. C. The boiling point of the volatile component is preferably in
 the range 30 to 36.degree. C. Suitable volatile components include
 saturated aliphatic hydrocarbons, having 4 to 6 carbon atoms, and
 partially or wholly halogenated hydrocarbons. It is possible to use a
 mixture of two or more volatile components in a the pressure generating
 composition. One particularly suitable volatile component is isopentane
 which provides a pressure of 4.5 to 5.7 psi (31 to 39 kPa). A 25:75 blend
 of isobutane and isopentane gives a pressure of 10.5 to 11.0 psi (72 to 76
 kPa).
 One preferred form of the pressure generating microemulsion composition
 with the volatile component dissolved therein comprises:
 Water: 50-70 wt %
 Soap: 20-40 wt %
 Organic liquid: 5-20 wt %
 Volatile component: 1-10 wt %
 Additives: 0-10 wt %
 Among the additives which may be present are lauryl alcohol, cetyl alcohol,
 stearyl alcohol, Clarit PDP-200 (Pentadoxynol-200), propylene glycol, and
 preservatives such as methyl paraben and propyl paraben.
 A more preferred form of the pressure generating composition comprises:
 Water: 55-65 wt %
 Soap: 25-35 wt %
 Organic liquid: 5-10 wt %
 Volatile component: 3-5 wt %
 Additives: 0-10 wt %
 The amounts of each component should be selected, within the above ranges,
 so that the total is 100 wt %.
 The use of pressure generating compositions in accordance with the present
 invention makes it possible to dispense fluids reliably from a reservoir
 without the need for a high pressure permanent gas. This enables the
 reservoir to be manufactured more cheaply, because it does not need to
 withstand such high pressures. In addition, the reservoir does not need to
 be pressurised during the manufacturing process: the fluid and the
 pressure generating material can be placed in the reservoir at atmospheric
 pressure, using conventional manufacturing methods, and then the reservoir
 can be sealed. After sealing, the reservoir pressure will build up, over
 time, to the required working pressure as the pressure generating material
 releases gas into the reservoir. Whilst the actual time will depend on all
 the circumstances, it will normally only be a matter of minutes, e.g. from
 8 to 12 minutes.
 The ability of the pressure generating composition to release gas, in order
 to maintain a sufficient pressure within the reservoir, makes it possible
 to provide much more fluid in the reservoir than would be possible with
 the use of a pressurised permanent gas. For example, when the invention is
 applied to a writing implement, 80% of the volume of the reservoir may be
 occupied by ink and 5% occupied by the pressure generating material.

Referring to FIGS. 1 and 2, there is shown schematically a reservoir vessel
 1 having a neck portion 2 in which is formed an outlet passage 3
 connecting to an outlet tube 3a. The outlet passage 3 is normally closed
 (FIG. 1) by a valve member 4. Valve member 4 has an operating button 5 by
 which it can be moved to bring an orifice 7 in the member into alignment
 with outlet passage 3 (see FIG. 2) to allow fluid 6 in the vessel 1 to
 pass out of the vessel. The valve member may be spring-biased so as to
 return to the closed position when pressure on the operating button 5 is
 released.
 Within vessel 1 is an expansible closed container 8 immersed in fluid 6.
 Within container 8 out of direct contact with fluid 6 is a pressure
 generating composition. In use, the composition releases a gas 9 within
 the container 8 and the container expands until the gas pressure within it
 is exactly balanced by the fluid pressure in vessel 1. The fluid in vessel
 1 is thus pressurised so that, when valve member 4 is moved to the open
 position (FIG. 2), the fluid is driven out of vessel 1 through outlet
 passage 3 and outlet tube 3a.
 When a quantity of fluid 6 is dispensed from reservoir vessel 1, the
 pressure in the fluid 6 in vessel 1 is lower than it was immediately prior
 to the dispensing. As a result, the pressure generating composition in
 container 8 releases more gas so that container 8 expands (see FIG. 2)
 until the fluid 6 is again at the same pressure as the gas 9 in container
 8. Thus, the pressure in vessel 1 is regenerated ready for dispensing more
 fluid when valve member 4 is moved to the open position.
 As will be clear to those skilled in the art, there are many uses for such
 a system. One such use is to provide soap or another shaving aid fluid to
 the blade, for example, of a wet shaving system.
 Referring to FIG. 3, a writing implement is generally designated 10. The
 writing implement 10 comprises a housing 12, a tip 14 and a liquid
 dispenser in the form of a reservoir 16, which is disposed within the
 housing 12. The reservoir 16 contains an ink 18, and a plug 21 of a
 pressure generating composition. As illustrated, there is also a barrier
 plug 20 separating the ink 18 from the plug 21. A barrier plug 20 will
 normally only be present when the ink 18 and the pressure generating plug
 21 are both aqueous based or organic based.
 The pressure generating composition comprises a volatile component that can
 be released, eg. can evaporate, from the pressure generating composition
 at room temperature.
 Outlet passage 16a passes axially through tip 14 communicating reservoir 16
 with a ball 14a so that the ink 18 can flow from the reservoir to the ball
 14a. Ball 14a is adapted to be brought into contact with a surface 22,
 such as a sheet of paper, in order to write on, or otherwise mark, the
 surface 22. The structure of the illustrated tip 14 is entirely
 conventional. Other such tips include, for example, those which are
 connected to the reservoir via a valve, eg. a diaphragm valve.
 An end 16b of the reservoir 16, which is opposite to the tip 14, is
 provided with a crimp 16c; the crimp 16c provides the reservoir 16 with an
 air-tight seal. During manufacture of the liquid dispenser, the ink 18 and
 the plugs 20 and 21 are placed in the reservoir 16, at atmospheric
 pressure, then the end 16b is crimped to provide the crimp 16c. (Reservoir
 16 can be sealed in other ways, for example by use of a plug.)
 There is a volume 16d within the reservoir 16, between the plug 21 and the
 end 16b of the reservoir 16. The volume 16d contains a gas which has been
 released from the pressure generating composition 21; the gas in the
 volume 16d is typically at a pressure of 1 to 4 psig (105 to 129 kPa). The
 pressure of the gas in the volume 16d pushes plug 21 and the ink 18
 towards the outlet 16a. This aids the dispensation of the ink 18 to the
 ball 14a, and from the roller-ball 14a to the surface 22.
 As the ink 18 is dispensed from the reservoir 16, the volume 16d becomes
 larger. At the same time more of the volatile component is released from
 the composition, in order to maintain the pressure within the reservoir 16
 at a level sufficient to aid the dispensation of the ink 18.
 The reservoir 16, tip 14 and the contents 18,21 and (if present) 20,
 constitute a refill for the writing implement, and can be made and sold
 for insertion in a housing 12.
 It will be appreciated by the skilled person that modifications may be made
 to the writing implement described above. For example, the writing
 implement may be provided with many different types of tip, and may have
 means other than a roller-ball to deliver the ink to the surface.
 Furthermore, the end of the reservoir remote from the outlet may be sealed
 by any conventional means.
 In order that the invention may be more fully understood, the following
 Examples of pressure generating compositions, and of their preparation and
 use, are given by way of illustration only.
 EXAMPLE 1
 A composition was made of the following components:

wt. %
 Palmitic acid 10.57
 Triethanolamine 7.69
 Coconut fatty acid 7.5
 Mineral oil 6
 Propylene glycol 4.11
 Isopentane 4
 Methyl paraben 0.2
 Propyl paraben 0.1
 Water 59.8
 The water used in the composition was first heated to 95.degree. C. to
 remove air therefrom.
 All the fatty acids and the propylene glycol, methyl paraben, propyl
 paraben and water were placed in a vessel and heated with stirring under a
 vacuum to 75.degree. C. With the mixture at this temperature, the
 triethanolamine was added and the stirring continued. The mixture became
 viscous as the soap formed, and was allowed to cool. When it reached
 20.degree. C., the isopentane and mineral oil were added. Cooling was
 continued to 10.degree. C. with slow stirring. The resulting gel was
 stored below 10.degree. C. until required for use.
 Further compositions were made in which the amount of mineral oil was
 varied up to 16% and the amount of isopentane was varied up to 10%, the
 volume of water being adjusted accordingly q.s. 100%.
 All the compositions were very satisfactory as pressure generators when
 confined in a closed space and allowed to warm to ambient temperature
 (e.g. about 20.degree. to 25.degree. C.). In particular, they were
 satisfactory when used as small plugs in ballpoint pen ink reservoirs,
 above the ink column, the end of the reservoir being closed, as described
 elsewhere herein.
 EXAMPLE 2
 A composition was made of the formulation given in Example 1 except that it
 contained 8.25 wt. % lauric acid in place of the 10.57 wt. % palmitic
 acid, and 3 wt % isopentane instead of 4 wt. %, and the amount of water
 was correspondingly 63.15 wt. %.
 The composition was made in the same way as that of Example 1.
 Further compositions, in which the amount of mineral oil was varied up to
 16% and the amount of isopentane was varied up to 10%, the volume of water
 being adjusted accordingly q.s. 100%, were also made.
 All the compositions were very satisfactory as pressure generators when
 confined in a closed space and allowed to warm to ambient temperature.
 Like the Example 1 compositions, they were useful in ballpoint pens as
 described.
 EXAMPLE 3
 A ballpoint pen ink was made from:
 Papermate blue ballpen ink (28.8 g) from Formalals Iberica
 2-Phenoxyethanol &gt;99% (3.00 g) from Fluka
 Gilugel MIN (6.90 g) from Giuline Chemie GmbH.
 The ink was placed in a 50 ml beaker and the 2-phenoxyethanol was added. An
 Ultra-Turrax T25 mixer was lowered into the beaker to just above the
 bottom. Thin plastic film was wrapped around the beaker and the stirrer to
 reduce evaporation, and the mixture was stirred at 8000 rpm for one hour.
 During this time, the mixture became warm.
 At the end of the one hour, the Gilugel MIN was added and the mixture
 stirred at the same speed for a further 4 hours to form the ballpoint pen
 ink.
 A reservoir tube was filled with ink (about 1 ml) by syringing air from one
 end of the tube. The tube was then centrifuged at 7.5 cm from centre at
 4600 rpm for 10 minutes to remove any entrapped air. Then, a ballpoint was
 firmly attached to one end of the tube and a quantity (about 1.5 cm in
 length) of a pressure generating composition according to the present
 invention was into the open end of the tube. Finally, the open end of the
 tube was firmly closed with a size 5 bung.
 In use of the pen, the ink flowed very smoothly and provided excellent lay
 down, even when used upside down, without any discontinuity in the
 writing.
 The pressure generating composition was made up of:

Hampsoyl L 11.16%
 Coconut fatty acid 7.5%
 PEG 150 distearate 0.1%
 Triethanolamine 7.69%
 Empilan MAA 2.0%
 Propylene glycol 4.11%
 Isopentane 3.0%
 Methyl paraben 0.2%
 Propyl paraben 0.1%
 Mineral oil 6.0%
 Water q.s. 100%
 The pressure generated from this formulation was 4.8 psi.
 The water used in this composition was heated to 95.degree. C. to remove
 air therefrom. The Hampsoyl L, coconut fatty acid, propylene glycol,
 peg-150-distearate, methyl paraben, propyl paraben and water were placed
 in a vessel and heated with stirring under vacuum to 75.degree. C. With
 the mixture at this temperature, the triethanolamine was added and the
 stirring continued. The mixture became viscous as the soap formed, and was
 allowed to cool. When it reached 10.degree. C., the isopentane and mineral
 oil were added. The resulting gel was then stored at 4.degree. C. until
 required for use.
 EXAMPLE 4
 The following microemulsion was made by the procedure of Example 1. It had
 a soap content of approximately 40%.

Material % w/w
 Water 33.97
 Palmitic acid 21.14
 Triethanolamine 15.38
 Coconut fatty acid 15
 Mineral oil 6
 Propylene glycol 4.11
 Isopentane 4
 Methyl paraben 0.2
 Propyl paraben 0.1
 Peg-150-distearate 0.1
 The water used in this composition was heated to 95.degree. C. to remove
 air therefrom. All the fatty acids, propylene glycol, peg-150-distearate,
 methyl paraben, propyl paraben and water were placed in a vessel and
 heated with stirring under vacuum to 75.degree. C. With the mixture at
 this temperature, the triethanolamine was added and the stirring
 continued. The mixture became viscous as the soap formed, and was allowed
 to cool. When it reached 10.degree. C., the isopentane and mineral oil
 were added. The resulting gel was then stored at 4.degree. C. until
 required for use.
 EXAMPLE 5
 The following microemulsion was made by the procedure of Example 4. It had
 a soap content of approximately 20%.

Material % w/w
 Water 60.73
 Palmitic acid 10.57
 Triethanolamine 7.69
 Coconut fatty acid 7.5
 Mineral oil 6
 Propylene glycol 4.11
 Isopentane 3
 Methyl paraben 0.2
 Propyl paraben 0.1
 Peg-150-distearate 0.1
 EXAMPLE 6
 The following microemulsion was made by the procedure of Example 4. It had
 an organic liquid (mineral oil) content of 5%.

Material % w/w
 Water 61.73
 Palmitic acid 10.57
 Triethanolamine 7.69
 Coconut fatty acid 7.5
 Mineral oil 5
 Propylene glycol 4.11
 Isopentane 3
 Methyl paraben 0.2
 Propyl paraben 0.1
 Peg-150-distearate 0.1
 EXAMPLE 7
 The following microemulsion was made by the procedure of Example 4. It had
 an organic liquid (mineral oil) content of 20%.

Material % w/w
 Water 46.73
 Palmitic acid 10.57
 Triethanolamine 7.69
 Coconut fatty acid 7.5
 Mineral oil 20
 Propylene glycol 4.11
 Isopentane 3
 Methyl paraben 0.2
 Propyl paraben 0.1
 Peg-150-distearate 0.1
 EXAMPLE 8
 The following microemulsion was made by the procedure of Example 4. It had
 a volatile component (isopentane) content of 5%.

Material % w/w
 Water 58.73
 Palmitic acid 10.57
 Triethanolamine 7.69
 Coconut fatty acid 7.5
 Mineral oil 6
 Propylene glycol 4.11
 Isopentane 5
 Methyl paraben 0.2
 Propyl paraben 0.1
 Peg-150-distearate 0.1
 EXAMPLE 9
 The following microemulsion was made by the procedure of Example 4. It had
 a volatile component level (isopentane) of 10%.

Material % w/w
 Water 53.73
 Palmitic acid 10.57
 Triethanolamine 7.69
 Coconut fatty acid 7.5
 Mineral oil 6
 Propylene glycol 4.11
 Isopentane 10
 Methyl paraben 0.2
 Propyl paraben 0.1
 Peg-150-distearate 0.1
 EXAMPLE 10
 The following formulation was made by the procedure of Example 1. It had a
 water content of 50%.

Material % w/w
 Water 50
 Palmitic acid 10.57
 Triethanolamine 7.69
 Coconut fatty acid 7.5
 Mineral oil 15.73
 Propylene glycol 4.11
 Isopentane 4
 Methyl paraben 0.2
 Propyl paraben 0.1
 Peg-150-distearate 0.1
 The microemulsions of Examples 4 to 10 were very satisfactory pressure
 generators when confined in a closed space and allowed to warm up, eg. in
 ballpoint pens.
 EXAMPLE 11
 A pressure generating composition was made by dissolving or dispensing a
 gas in a grease. Gilugel CAO was mixed and cooled to 0.degree. C.
 Isopentane was then added and the mixture stirred until homogeneous. It
 was then stored at 4.degree. C. until required. As made, the mixture
 contained 94% by weight Gilugel CAO (from Giuline Chemie GmbH) and 6% by
 weight isopentane. The pressure developed from one gram of this
 formulation was measured with a Digitron manometer and found to be 3.8
 psi.
 EXAMPLE 12
 Example 11 was repeated using Gilugel MIN in place of Gilugel CAO (in the
 same amount). The pressure from one gram of composition was measured with
 a Digitron manometer and found to be 3.8 psi.
 EXAMPLE 13
 The following example is of a water-in-oil emulsion pressure generating
 composition of the invention.

% w/w
 Gilugel MIN 15
 Isopentane 4
 Isostearyl diglycerol succinate 5
 Mineral oil 5
 Water 70.7
 Methyl paraben 0.2
 Propyl paraben 0.1
 Gilugel MIN, isostearyl diglycerol succinate and mineral oil were mixed
 together and heated to 80.degree. C. Water, methyl paraben and propyl
 paraben were mixed together and heated to 80.degree. C. The water phase
 was then added slowly to the oil phase and homogenised well. The resulting
 cream was cooled to below 10.degree. C. The resulting composition was then
 stored at 4.degree. C. until required.
 The pressure generating compositions of Examples 11 to 13 were very
 satisfactory pressure generators when confined in a closed space and
 allowed to warm to ambient temperature, eg. in ballpoint pens as described
 herein.
 This invention also relates to ballpoint pens and to inks therefor.
 In a conventional ballpoint pen, a reservoir column of thick ink bears onto
 the rear side of the writing ball. As the ball is rotated in its seat, the
 thick ink in contact with the ball is conveyed on the ball surface to be
 deposited on the paper or other substrate. As ink is withdrawn, the
 reservoir column of ink will flow down to maintain contact with the ball.
 This is vital since, if contact is lost and the ink will not flow on its
 own to re-establish contact with the ball, the pen becomes useless.
 In the early days of ballpoint pens, the inks were oil-based. They suffered
 a number of disadvantages including bleed into paper, point bleed (oil
 separation) and messiness. The subsequent introduction of dye-based glycol
 inks, which contained resins to reduce smearing and improve temperature
 stability, gave a major improvement in performance. Currently, most
 ballpoint pen inks are based on organic solvents such as phenyl glycols,
 diethylene glycol ethyl ether, dipropylene glycol or benzyl alcohol, or
 mixtures of two or more thereof.
 There have recently been developed a family of aqueous pigmented inks many
 of which display bright and attractive colours. In order to provide these
 inks in ballpoint pens, the pigments have been formulated as aqueous
 suspensions containing a thickener such as xanthan gum, carageenan gum,
 guar gum, locust bean gum or hydroxyethyl cellulose. These suspensions
 show shear thinning and can serve as inks in ballpoint pens. However, in
 use, a number of problems arise. For example, the aqueous suspension does
 not lubricate the ball in its seat and, as a result, severe wear can occur
 over a period of use and the pens do not write very smoothly.
 One of the most important requirements of a ballpoint pen ink is that it
 should write very smoothly. The organic-based ballpoint inks generally
 (but not invariably) write much more smoothly than the recently developed
 aqueous-based inks, but even the organic based inks are not always as
 smooth in use as would be desired, and in addition they have the
 disadvantage of being somewhat sticky.
 We have now found a way of improving the smoothness of organic-based
 ballpoint pen inks. Furthermore, we have found a way of providing
 pigmented inks whereby smooth writing can be obtained as well as a reduced
 ball/seat wear as compared with known aqueous-based ballpoint pen inks.
 According to the present invention, we include a grease in a ballpoint pen
 ink.
 In a first aspect, the invention provides an ink for a ballpoint pen, which
 ink comprises a dispersion of an organic solvent having a colorant
 dissolved therein and a grease.
 The ink can be made by dispersing a grease in an organic solvent having a
 colorant dissolved therein. The grease can be preformed, or it may be made
 in situ by subjecting a mixture of its components (mobile phase and
 structural phase) to high shear.
 According to this first aspect of the invention, ballpoint pen inks
 comprising a solution of a colorant in an organic solvent can be
 substantially improved by incorporating therein a grease. The grease
 promotes smoother writing. The presence of the grease will normally
 thicken the ink, but its presence imparts a shear thinning quality to the
 ink so that, under the high shear conditions around the ball (in use of
 the pen) the ink is thinned to provide an elastohydrodynamic layer usually
 about 500 nm thick on the ball. An elastohydrodynamic layer is a
 structured layer which deposits at the interface between two bodies
 despite the presence of high shear and compressive forces.
 The nature of the organic solvent and the colorant are not critical. The
 solvent is preferably a phenyl glycol, diethylene glycol ethyl ether,
 dipropylene glycol, or benzyl alcohol, or any mixture of two or more
 thereof. The colorant can be any suitable ballpoint pen ink dye. We have
 found Solvent Blue 38, Basic Blue 7 and Solvent Violet 8 to be very
 suitable but other colorants can be used.
 The nature of the grease is not critical. We prefer to use soap-based
 mineral oil greases, but other greases can be used. Preferably, the soap
 in the grease is a higher (i.e. C.sub.12 and above) carboxylic acid salt
 of an alkali or alkaline earth metal, or an aluminium soap, an
 aluminium/magnesium mixed soap, or a complex soap. As stated, the
 preferred mobile phase is mineral oil, but castor oil and silicone oil
 greases, for example, can be used. It is also possible to use other
 greases such as perfluoropolyether greases, eg. Krytox.RTM. (from DuPont).
 The preferred mineral oils for the greases are 65/75 mineral oil (i.e. oil
 of a viscosity from 65 to 75 centipoise) and oils from the Gravex series,
 eg. Gravex 21 (available from Shell Oils) and similar oils from the
 Enerthene series (available from BP Oil). Mineral oil soap based greases
 are, of course, commercially available (eg. Gilugel from Giulini GmbH) but
 they can be produced by melting the soap in the oil and then cooling, as
 is known in the art.
 The amounts of the three main components of the ink are not particularly
 critical, but will usually be (in weight % based on the weight of the
 ink):

general preferred most preferred
 solvent 20-90 30-70 40-60
 colorant 5-60 15-50 20-45
 grease 0.5-50 2-40 5-30
 The inks of the invention can, of course, contain other ingredients as
 desired and as may be usual in the art.
 The invention further includes a ballpoint pen or refill therefore wherein
 the ink is an ink of the invention. To be suitable as ballpoint pen inks,
 the inks of the invention are formulated with an appropriate viscosity (at
 least 500 centipoise) as will be well understood by those skilled in the
 art.
 The use, in accordance with the present invention, of a grease in ballpoint
 pen inks has enabled the formulation of certain new ballpoint pen inks.
 These inks comprise a pigment suspended in grease, and they have proved
 very satisfactory ballpoint pen inks. In particular, they are very smooth
 in use, the grease lubricating the ball and providing an excellent
 suspension medium for the pigment.
 Printing inks which comprise a pigment suspended in a grease (or in
 grease-forming components) are known from, for example, U.S. Pat. Nos.
 1,237,126 and 5,158,606. In U.S. Pat. No. 1,237,126, a printing ink is
 made of an aluminium salt of a fatty acid, a hydrocarbon mineral oil and a
 pigment. The ink is used in roller printing. In U.S. Pat. No. 5,372,635, a
 printing ink is described which comprises a dispersion of a pigment in an
 oil and a tall oil fatty acid soap. The ink is especially for use in
 lithographic printing processes utilising tap water. These inks are not
 described as suitable for use in ballpoint pens nor would they be so since
 their viscosities would normally be well above the maximum acceptable in
 conventional ballpoint pens. Thus, the printing inks if placed in
 conventional ballpoint pens, would not write out because they would be too
 viscous.
 The preferred ballpoint pigment ink of the present invention comprises a
 pigment, a grease, an organic liquid which is the same as the mobile phase
 of the grease or is compatible therewith, and a dispersant.
 Any grease can be used but we prefer the mineral oil and other greases
 described hereinabove with reference to the first aspect of the invention.
 Reference should be made thereto for details.
 The pigment inks of the invention can be made by dispersing a pigment in an
 organic liquid with a dispersant, adding a grease and mixing, the organic
 liquid being the same as the mobile phase in the grease or compatible
 therewith.
 Alternatively, the inks can be made by dispersing a pigment in an organic
 liquid with a dispersant and the mobile phase and structural phase
 components of a grease; and subjecting the mixture to high shear to form
 the grease; wherein the organtic liquid is the same as the mobile phase of
 the grease or is compatible therewith.
 It is preferred that the organic liquid be the same as the mobile phase of
 the grease. If it is not identical, then it should certainly be compatible
 therewith. By "compatible therewith" we mean that once the grease and
 organic liquid are mixed, the mixture is stable and the microstructure of
 the grease is intact, for example, if a mineral oil grease is used, a
 compatible organic liquid could be a different mineral oil.
 The amounts of the components of the pigment inks of the invention can vary
 widely. Generally, however, the amounts will by (by weight of the ink):

general preferred most preferred
 grease 0.5-80 2-50 5-25
 organic liquid 10-85 30-80 45-75
 pigment 1-50 5-40 15-30
 dispersant 0.1-5 1-3 1.5-2.5
 In order to disperse the pigment in the grease and to provide a stable
 dispersion, it will usually be necessary to use one or more dispersants.
 Suitable dispersants will be soluble in the organic liquid or mobile phase
 and will thus normally contain a long chain hydrocarbon moiety, e.g. a
 stearyl or oleyl group with a functional head group. As the functional
 head group, the dispersants can, for example, have polyol derivatives such
 as glycerol or sorbitan derivatives, to provide the appropriate polarity
 to bind to the pigment. Suitable dispersants will be well known to those
 skilled in the art. We prefer to use Solsperse hyperdispersants eg.
 Solsperse 13940, and Solsperse 17000, optionally with Solsperse 5000 from
 Zeneca ("Solsperse" is a trademark). The effectiveness of Solsperse 17000
 is significantly improved by the use therewith of Solsperse 5000 as a
 synergist. Solsperse 5000 is essentially a pigment derivative that has a
 strong affinity for the particular pigment type and furnishes the surface
 with anchoring sites for the conventional polymeric Solsperse
 hyperdispersant. The amount of dispersant will vary depending on the
 system in which it is used, but the total amount will normally not exceed
 about 5% by weight of the ink.
 The pigments used in the inks of the invention must be of small particle
 size to prevent clogging of the pen ball. We prefer to use printing ink
 pigments which in use form a colloid or sol. In general, the pigment size
 should not be greater than 5 .mu.m, preferably 0.1 to 2.0 .mu.m, most
 preferably 0.2 to 1.0 .mu.m. In the manufacture of the inks of the
 invention, we prefer to treat the final ink to remove any particulate
 agglomeration. This may be done, for example, by suitably processing the
 ink in a triple mill or by filtering. Filtration can be effected, for
 example, with a stainless steel unit equipped with 5 to 30 micrometer
 pads. The unit is connected to an air line with maximum pressure of about
 70 psi (480 kPa). The selection of pad size and the pressure will depend
 on the filtration speed desired and the pigment particle size.
 Whilst the nature of the pigment is not critical, we prefer to use pigments
 designed for use in organic solvents, eg. BASF's Heliogen or Paliotol
 series pigments.
 The pigment inks of the invention are loaded into ballpoint pens or refill
 reservoirs in conventional manner. Thus, for example, 1 g of a pigment ink
 of the invention is injected into the reservoir barrel using a syringe and
 an appropriate dispensing needle. The ball point is fitted and the pen (or
 refill) is then placed point down in a centrifuge set at 4000 rpm for 5
 minutes. This ensures that there is no gap between the column of ink and
 the back of the ball.
 The inks of the invention can be used in the same way as conventional
 ballpoint pen inks or they can be used in a reservoir containing a
 pressure generating composition. In this arrangement, the ink is loaded in
 a conventional reservoir above a conventional ball, and then a pressure
 generating composition is provided above the ink. The reservoir is then
 closed and the composition generates a gas pressure on the ink column to
 maintain it continuously in good contact with the ball.
 The pressure generating composition used with a grease ink should
 preferably be aqueous based so as to be immiscible with the grease ink of
 the invention. If an organic-based composition is used, then a barrier may
 be provided between the ink and the pressure generating material, in order
 to prevent contact therebetween.
 The use of a pressure generating composition with the inks of the present
 invention makes it possible to dispense the inks reliably from the
 reservoir without the need for a high pressure permanent gas. This enables
 the reservoir to be manufactured more cheaply, because it does not need to
 withstand such high pressures. In addition, the reservoir does not need to
 be pressurised during the manufacturing process: the ink and the pressure
 generating material can be placed in the reservoir at atmospheric
 pressure, using conventional manufacturing methods, and then the reservoir
 can be sealed. After sealing, the reservoir pressure will build up, over
 time, to the required working pressure. Whilst the actual time will depend
 on all the circumstances, it will normally be a matter of minutes, e.g.
 from 8 to 12 minutes.
 Referring now to FIGS. 4 and 5 of the drawings, in which like numerals
 indicate like parts, there is shown an SEM photograph taken axially of the
 ball seat of a ballpoint pen, the ball having been removed. The ball seat
 comprises a concave cup-shaped member 24 having five radial grooves 26
 therein equispaced around the member 24. Centrally of member 24 is an
 orifice 28 which communicates with the ink reservoir and with grooves 26
 to feed ink thereto.
 The ball (not shown) seats on the cup-shaped member 24. In use of the pen,
 ink flows out of orifice 28 into grooves 26. The ball contacts the ink
 supplied in the grooves 26 and, as the ball is rotated in use, as the ball
 is rotated in use, ink passes onto its surface and is laid on the paper or
 other substrate on which the ball is rolled. Small quantities of ink will
 also pass onto concave cup-shaped member 24 to lie thereon between the
 ball and the cup-shaped member surface, thus lubricating the ball/seat.
 The ball is held in its seat on the cup-shaped member 26 by a top rim not
 shown but which will be well understood in the art.
 FIG. 4 shows a pen in which the cup-shaped member 24 is of nickel silver
 and which had been written with for 2200 m. The reservoir of the pen
 contained an ink of the invention of the following composition:

wt. %
 Palmitic acid 10.57
 Triethanolamine 7.69
 Coconut fatty acid 7.5
 Mineral oil 6
 Propylene glycol 4.11
 Isopentane 4
 Methyl paraben 0.2
 Propyl paraben 0.1
 Water 59.83
 The water used in the composition was first heated to 95.degree. C. to
 remove air therefrom.
 All the fatty acids and the propylene glycol, methyl paraben, propyl
 paraben and water were placed in a vessel and heated with stirring under a
 vacuum to 75.degree. C. With the mixture at this temperature, the
 triethanolamine was added and the stirring continued. The mixture became
 viscous as the soap formed, and was allowed to cool. When it reached
 20.degree. C., the isopentane and mineral oil were added. Cooling was
 continued to 10.degree. C. with slow stirring. The resulting gel was
 stored below 10.degree. C. until required for use.
 Further compositions were made in which the amount of mineral oil was
 varied up to 16% and the amount of isopentane was varied up to 10%, the
 volume of water being adjusted accordingly q.s. 100%.
 All the compositions were very satisfactory as pressure generators when
 confined in a closed space and allowed to warm to ambient temperature
 (e.g. about 20.degree. to 25.degree. C.). In particular, they were
 satisfactory when used as small plugs in ballpoint pen ink reservoirs
 containing inks of the present invention.
 EXAMPLE 17
 A ballpoint pen ink according to the invention was made from:
 Papermate Blue Ballpen Ink (28.8 g)
 2-phenoxyethanol&gt;99% (3.00 g) from Fluka
 Gilugel MIN (6.90 g) from Giulini Chemie GmbH.
 The ink was placed in a 50 ml beaker and the 2-phenoxyethanol was added. An
 Ultra-Turrax T25 mixer was lowered into the beaker to just above the
 bottom. Thin plastic film was wrapped around the beaker and the stirrer to
 reduce evaporation, and the mixture was stirred at 8000 rpm for one hour.
 During this time, the mixture became warm.
 At the end of the one hour, the Gilugel MIN was added and the mixture
 stirred at the same speed for a further 4 hours to form the ballpoint pen
 ink.
 A reservoir tube was filled with ink (about 1 ml) by syringing air from one
 end of the tube. The tube was then centrifuged at 3000 g for 10 minutes to
 remove any entrapped air. Then, a ballpoint was firmly attached to one end
 of the tube and a quantity (about 1.5 cm in length) of a pressure
 generating composition was syringed into the open end of the tube.
 Finally, the open end of the tube was firmly closed with a size 5 bung.
 In use of the pen, the ink flowed very smoothly and provided excellent lay
 down, even when used upside down, without any discontinuity in the
 writing.
 The pressure generating composition was made up of:

Papermate blue ballpen ink 19.64 g
 2-Phenoxyethanol 2.01 g
 Gilugel SIL5 4.74 g (from Giuline Chemie
 GmbH)
 The ballpen ink and 2-phenoxyethanol were stirred at 8000 rpm for 1 hour
 using an Ultra-Turrax T25 high shear mixer. Gilugel SIL5 was added and the
 mixing continued for 4 hours, external cooling being applied to the mixing
 vessel. The resulting ink of the invention (viscosity 50,000 cpoise) was
 placed in a ballpoint pen as described in Example 17. A plug of the
 pressure generating composition was also used as in Example 17. The
 ballpoint pen wrote extremely smoothly. (Gilugel SIL5 is a mineral oil
 based grease with aluminium-magnesium hydroxide stearate soap as
 thickener).
 EXAMPLE 19
 A ballpoint pen ink according to the invention was made from:

Papermate blue ballpen ink 10 g
 2-Phenoxyethanol 2 g
 Albida R2 2.12 g (from Shell U.K. Ltd)
 The Albida R2 was added to the ballpen ink and stirred at 8000 rpm using an
 Ultra-Turrax T25 high shear mixer. 2-Phenoxyethanol was added immediately
 and stirring continued for 2 hours. The resulting ink of the invention
 (viscosity 40,000 c poise) was placed in a ballpoint pen as described in
 Example 17. The pen wrote smoothly either with or without addition of the
 plug of pressure generating composition as described in Example 17.
 (Albida R2 is a mineral oil based grease with a lithium hydroxystearate
 complex soap as thickener.)
 EXAMPLE 20
 A ballpoint pen ink according to the invention was made from:

Papermate black ballpoint ink 19.61 g
 2-Phenoxyethanol 2.0 g
 Gilugel Min 4.73 g (from Giulini Chemie
 GmbH)
 The ballpen ink and 2-phenoxyethanol were stirred at 8000 rpm for 1 hour
 using an Ultra-Turrax T25 high shear mixer. Gilugel Min was added and the
 mixing continued for 4 hours, external cooling being applied to the mixing
 vessel. The resulting ink of the invention was placed in a ballpoint pen
 as described in Example 17. A plug of the pressure generating composition
 was also used as in Example 17. The ballpoint pen wrote extremely
 smoothly. (Gilugel Min is a mineral oil based grease with
 aluminium-magnesium hydroxide stearate soap as thickener.)
 EXAMPLE 21
 A ballpoint pen ink according to the invention was made from:

Papermate blue ballpen ink 19.6 g
 2-Phenoxyethanol 2.0 g
 Aluminium-Magnesium 0.94 g
 Hydroxide stearate
 65/75 Mineral Oil 3.7 g
 The ballpen ink, 2-phenoxyethanol and aluminium-magnesium hydroxide
 stearate were stirred at 8000 rpm for 1 hour using an Ultra-Turrax T25
 high shear mixer. External cooling was applied. Mineral oil was added and
 the mixing continued for 5 hours. The resulting ink of the invention was
 placed in a ballpoint pen as described in Example 17. A plug of the
 pressure generating composition was also used as in Example 17. The
 ballpoint pen wrote extremely smoothly.
 EXAMPLE 22
 A ballpoint pen ink according to the invention was made from:

Carbon black 7.44 g
 65/75 Mineral oil 28.2 g
 Solsperse 13940 0.45 g
 Gilugel Min 4.5 g
 The mineral oil and dispersant Solsperse 17000 were stirred at 8000 rpm for
 10 minutes using an Ultra-Turrax T25 high shear mixer. Carbon black was
 added and stirring continued at 25.degree. C./30 minutes and 70.degree.
 C./3.5 hours. Gilugel Min was added and stirring continued for 1.5 hours.
 The resulting ink of the invention (viscosity 40000 cpoise) was placed in
 a ballpoint pen as described in Example 17. A plug of the pressure
 generating composition was also used as in Example 17. The ballpoint pen
 wrote smoothly.