WO2008015433A2

WO2008015433A2 - Reversible formation of a solid

Info

Publication number: WO2008015433A2
Application number: PCT/GB2007/002931
Authority: WO
Inventors: Paul Luckman; Marta Del Mar Ramos Tejada
Original assignee: Imperial Innovations Limited
Priority date: 2006-08-03
Filing date: 2007-08-01
Publication date: 2008-02-07
Also published as: WO2008015433A3; GB0615462D0

Abstract

The present invention provides a process for the temporary reversible solidification of a suspension comprising either silica and a long chain polymer, wherein the silica is provided at a level of at least 14% by weight and the polymer has a chain length of greater than 2 micrometres, or Bentonite and a long chain polymer, wherein the polymer has a chain length of greater than 2 micrometres.

Description

Reversible formation of a solid

The present invention provides a process for the formation of a solid comprising agitating a suspension of silica or Bentonite and a long chain polymer in water, wherein the silica is provided at a level of at least 14% by weight.

It has been known in the art that aqueous mixtures of clays and polyethylene oxide form gels when the mixture is shaken vigorously. Attempts have been made to provide alternative gels however the use of silica has not previously been exploited as the resulting gels were found to be insufficiently rigid.

The present invention provides a process for the formation of a solid comprising agitating a suspension comprising silica and a long chain polymer, wherein the silica is provided at a level of at least 14% by weight and the polymer has a chain length of greater than 2 micrometres.

In an alternative feature of the invention, there is provided a process for the formation of a solid comprising agitating a suspension comprising Bentonite and a long chain polymer, wherein the polymer has a chain length of greater than 2 micrometres.

The process of the first aspect provides the reversible formation of a solid. For the purposes of this invention, the suspension of a long chain polymer and silica or Bentonite is preferably in water.

Agitation of the suspension results in a temporary reversible solidification of the suspension. The suspension is preferably agitated by shaking the suspension either by hand or by mechanical means, preferably the suspension is vigorously shaken. The suspension is preferably vigorously shaken by hand for between 1 second and 1 minute, preferably up to 5, 10, 15, 20, 25 or 30 seconds. The suspension can be shaken 20 times a second, preferably 10 times a second, more preferably 5 times a second. Alternatively, the suspension can be extruded through an aperture to form a solid. Preferably the solid is extruded through an aperture having a diameter of from 0.1mm to 10cm, preferably from 1 mm to 1 cm. Alternatively, the suspension can be agitated by non-mechanical means, such as ultrasound or radio frequencies.

Agitation of the suspension results in an increase in the viscosity and turbidity of the suspension. Agitation of the suspension can be continued until the suspension forms a solid. For the purposes of this invention, the term solid includes solid or semi-solid forms having a higher viscosity than a liquid. In particular, the solid exhibits an elastic, plastic or elasto-plastic behaviour. The solid produced by the agitation of the suspension can be a plastic deformable solid. Alternatively, the solid may be provided in the form of a gel. It will be appreciated that the degree of solidification of the suspension will be depend on the composition of the suspension and the quality and quantity of agitation performed.

The resulting solid reverts to a suspension over time. The production of the solid of the invention is therefore temporary and reversible. The first aspect of the invention therefore comprises a process for the temporary formation of a solid comprising agitating a suspension of silica and a long chain polymer in water to form a solid, wherein the silica is provided at a level of at least 14% by weight, the polymer has a chain length of greater than 2 micrometres and wherein the solid reverts back to the suspension over time. The invention further provides a process for the temporary formation of a solid comprising agitating a suspension of Bentonite and a long chain polymer in water, to form a solid, wherein the polymer has a chain length of greater than 2 micrometres and wherein the solid reverts back to the suspension over time.

It will be appreciated that the step of agitating the suspension to form a solid can be repeated after the solid has reverted back to the suspension. The present invention therefore provides a process for repeatedly producing a solid and allowing it to revert to a solution.

The suspension comprises silica at a level of at least 14% by weight, preferably at least 15%, 16%, 17%, 18% 19%, 20%, 21%, 22%, 23%, 24% or 25% by weight. More preferably the silica is provided at a minimum level of 14%, 15% or 16% and a maximum level of 20%, 21%, 22%, 23%, 24% or 25 %. The silica preferably has an average particle size of 10 to lOOnm, preferably 20 to 80 nm, more preferably 50nm or around 50 nm.

The suspension comprises Bentonite at a level of 1 to 4 % by weight, preferably 1.5% to 3.5% by weight, more preferably 2% or 3% by weight.

The suspension comprises a long chain polymer having a chain length of greater than 2 micrometres. Preferably, the polymer has a chain length of greater than 5 micrometres. It will be appreciated that the chain length of the polymer will depend upon the degree of polymerisation of the polymer and the molecular weight of the polymer. The chain length of the polymer is preferably 2 micrometres to 100 micrometres, preferably 5 micrometres to 50 micrometres, more preferably 10 micrometres to 20 micrometres. The polymer can be a long chain linear polymer or a long chain branched polymer. It will be appreciated that when the suspension is at rest the polymer does not adsorb onto the surface of the silica or Bentonite particles. However, on agitation of the suspension, the polymer adsorbs onto the surface of the silica or Bentonite particles thereby increasing the viscosity of suspension to form the required solid.

This adsorption is understood to occur on agitation of the suspension due to the resulting kinetic energy being imparted to the polymer, forcing it to absorb on to the particle surface. The polymer then desorbs when the solid is left at rest, thereby decreasing the viscosity of the solid. The polymer should therefore not adsorb onto the particle surface at rest but adsorb onto the particle surface on agitation of the suspension.

The long chain polymer is preferably polyethylene oxide or polyvinyl alcohol- polyvinyl acetate co-polymer. The long chain linear polymer can be provided at a level of 0.1 to 2% by weight. When the suspension comprises silica, the long chain polymer can be provided at a level of 0.2 to 0.9% by weight, preferably 0.3 to 0.8% by weight, more preferably 0.4 to 0.6% by weight. When suspension comprises Bentonite, the long chain polymer can be provided at a level of 0.1 to 2% by weight, preferably 0.1 to 1 % by weight, more preferably around 0.5 % by weight.

The polyethylene oxide or the polyvinyl alcohol-polyvinyl acetate co-polymer is preferably provided with an average molecular weight of 200,000 to 4xlO⁶. In a preferred aspect of the invention, the polyethylene oxide is provided with aann aavveerraaggee mmoolleeccuull;ar weight of 200,000 to 1 x 10⁶, preferably 250,000, more preferably 400,000. The polyvinyl alcohol-polyvinyl acetate co-polymer is preferably provided as 70% to 99% hydrolysed polyvinyl alcohol-polyvinyl acetate co-polymer (i.e. 70-99% in alcohol form).

The pH of the silica/polymer suspension is preferably between pH 7.5 to 10, preferably between pH 8 to 9, more preferably around pH 8.5. The pH of the Bentonite/polymer suspension is preferably between 6.5 to 11, more preferably between pH 8 to 10.

The second aspect of the invention relates to a suspension comprising silica and a long chain polymer in water, wherein the silica is provided at a level of at least 14% by weight and the polymer has a chain length of greater than 2 micrometres.

In an alternative feature of the second aspect, the invention relates to a suspension comprising Bentonite and a long chain polymer in water wherein the polymer has a chain length of greater than 2 micrometres.

The suspension can be provided for many different applications. The suspension may therefore comprise one or more additional components such as a colour, a flavouring, a stabiliser, a fragrance, a sweetener (including sugar), salt, an alcohol, a surfactant, etc. The exact composition of the suspension and the level of the components will therefore depend on the application in which the suspension is used.

In a preferred feature of the second aspect of the invention, the suspension is provided as a foodstuff. In particular, the foodstuff is provided as a suspension which is converted to a solid by the process of the first aspect of the invention prior to being ingested or placed into the mouth. The suspension preferably comprises one or more additional components selected from flavourings including sweeteners, fragrance, colouring, preservatives, stabilisers, etc.

The foodstuff is preferably a chewable gum. The chewable gum is converted into a solid according to the process of the first aspect before being placed in the mouth. The chewable gum is preferably a chewing gum or a bubble gum. The suspension preferably comprises one or more additional components selected from a flavouring, a sweetener, a colouring, an elastomer, an elastomer plasticizer, an oil, a fat, a wax, a softener, an inorganic filler and a bulking agent. The flavouring can include any natural or synthetic flavour. It can be fruit, vegetable, mint, chocolate, nut such as almond or hazelnut, vanilla, coffee, aniseed, spice, herb or any other flavour. The fruit flavour can be any, such as apple, orange, banana, strawberry, raspberry, cherry, blueberry, lemon, lime, grapefruit, pineapple, pear, peach, apricot, grape, plum, mango or any other fruit flavour. The flavourings may include acids suitable for use in foods such as citric acid, malic acid, lactic acid, succinic acid, tartaric acid, etc. The sweetener can be a natural sugar such as sucrose, glucose, fructose or can be an artificial sweetener such as aspartame or saccharin.

The elastomers may include natural latexes, styrene butadiene copolymer, polyisobutylene and isobutylene-isoprene copolymer. The elastomer plasticisers may include turpine and polyvinyl acetate resins. Oils and fats may include any, such as vegetable oils. The fats may, in addition, or alternatively be animal fats such as lard and tallow. Waxes for inclusion in the insoluble gum base may include petroleum waxes, such as polyethylene wax, beeswax, candellia, carauba, natural waxes, microcrystalline wax and paraffin. The suspension may additionally comprise fillers such as calcium carbonate, magnesium carbonate, talc, dicalciumphosphate etc, softeners such as glycerolmonostearate, glyceroltriacetate, etc and emulsifiers. It will be appreciated that the solid obtained by agitating the suspension according to the process of the first aspect, will revert to the suspension over a specified time period. The foodstuff can be swallowed while in solid form or alternatively can be swallowed after it has reverted to a suspension. Alternatively, the foodstuff can be disposed of in a solid state.

As the foodstuff will revert to a suspension over a specified time period, the foodstuff can more easily be disposed of. This advantage is particularly relevant when the foodstuff is a chewable gum. The disposal of chewable gum such as chewing gum or bubble gum is a problem in urban areas, where antisocial disposal results in chewable gum being disposed of on pavements, under chairs and tables, etc. This results in the adhesion of this discarded gum to shoes and clothes, etc, with resulting damage to shoes, clothes, etc. Furthermore, removal of discarded gum is time consuming, unpleasant and costly. The chewable gum of the present application reverts to a liquid overcoming the problems associated with disposal of conventional gums.

The suspension may alternatively be provided as a toy. The suspension can be provided preferably in a container, preferably a resealable container. The suspension can be converted into a solid according to the process of the first aspect of the invention, said solid being removable from the container. If the solid is returned to or retained in the container or a different container prior to its reversal into the suspension, then the process of the first aspect can be repeated at will.

Alternatively the suspension can be provided in a container comprising an outlet through which the suspension can, in use, be extruded and an extrusion means such as a plunger. Preferably the container is a syringe. S

The suspension is optionally provided with instructions relating to the process of the first aspect of the invention.

For this feature of the invention, the suspension preferably comprises a colouring agent and/or a fragrancing agent. All components of the invention are preferably non-toxic and can be safely ingested.

The suspension may further be provided to smooth out or dampen a shock impulse by, for example, allowing the dissipation of kinetic energy. In particular, the suspension can be provided as an anti- vibrational mount, a shock absorber and/or a component of braking fluid. In this application, the application of a shock impulse to an apparatus comprising the suspension, causes the suspension to vibrate, resulting in an increase in viscosity of the suspension and a concurrent damping of the shock impulse.

The suspension of the present invention may be provided as a shock absorber, an anti- vibrational mount and/or a component of braking fluid in a vehicle such as a motor vehicle or aircraft. Alternatively, the suspension may be provided as a shock absorber in a building or other construction.

The third aspect of the invention comprises a solid produced by the process of the first aspect of the invention.

The fourth aspect of the invention provides the use of a suspension comprising silica and a long chain polymer in water in the production of a solid, by agitation of the suspension, wherein the silica is provided at a level of at least 14% by weight and the polymer has a chain length of greater than 2 micrometres. An alternative feature of the fourth aspect provides the use of a suspension comprising Bentonite and a long chain polymer in water wherein the polymer has a chain length of greater than 2 micrometres.

The fifth aspect of the invention provides a process for the production of a suspension of the second aspect of the invention comprising admixing silica at a level of at least 14% by weight with a long chain polymer in water wherein the polymer has a chain length of greater than 2 micrometres.

An alternative feature of the fifth aspect provides the use of a process for the production of a suspension of the second aspect of the invention comprising admixing Bentonite with a long chain polymer in water, wherein the polymer has a chain length of greater than 2 micrometres.

The suspension of the second aspect is preferably produced by the initial formation of a solution of the long chain polymer in water, followed by addition of the silica or Bentonite. The suspension can be gently agitated to allow thorough mixing of the components of the suspension.

Alternatively, the suspension of the second aspect can be produced by combining silica at a level of at least 14% by weight, a long chain polymer and water and agitating the mixture to form a solid of the first aspect of the invention. The solid is then left at rest to allow it to revert to a suspension of the second aspect of the invention.

The suspension of the second aspect can further be produced by combining Bentonite, a long chain polymer and water and agitating the mixture to form a solid of the first aspect of the invention. The solid is then left at rest to allow it to revert to a suspension of the second aspect of the invention.

All preferred features of each aspects of the invention apply to all other aspects mutatis mutandis.

The invention may be put into practice in various ways and a number of specific embodiments will be described by way of example to illustrate the invention with reference to the accompanying drawings, in which;

Figure 1 shows the formation of a solid using a Bentonite suspension at different percentages of polyethylene oxide and using polyethylene oxide with different molecular weights.

The present invention will now be illustrated by reference to one or more the following non-limiting examples.

EXAMPLES

Production of a suspension comprising polyethylene oxide and silica.

Polyethylene oxide (0.04g) is added to deionised water (4.996g) and is allowed to dissolve for 2 days. The polyethylene oxide- water mixture is kept out of UV light.

The resulting polyethylene oxide solution is added to silica (Ludox TM-50) (5g) and mixed by gently tilting the mixture back and forth to ensure complete mixing. The mixture is placed into a closed vessel with a greater volume than that of the mixture.

Production of a solid from a suspension comprising polyethylene oxide and silica

The mixture is vigorously shaken by hand, several times per second. Within the period of 1 to 10 seconds, the viscosity and turbidity of the mixture increases. The shaking can be continued until the mixture is solid or until the desired degree of solidity is required.

Relaxation of the solid back to a suspension occurs over time when the solid is kept at rest.

Alternative production of a solid from polyethylene oxide and silica

Polyethylene oxide (0.04g) is added to deionised water (4.996g) and is allowed to dissolve for 2 days. The polyethylene oxide-water mixture is kept out of UV light. The resulting polyethylene oxide solution is added to silica (Ludox TM-50) (5g) and shaken vigorously such that the viscosity and turbidity of the mixture increases. The shaking can be continued until the mixture is solid or until the desired degree of solidity is required.

A suspension comprising polyethylene oxide and silica can be produced from the solid by allowing the relaxation of the solid back to a suspension over time.

Production of a solid from polyethylene oxide and Bentonite

A 2% dispersion of Bentonite is prepared in water and polyethylene oxide. The polyethylene oxide is present at between 0.1 and 1.5%. Polyethylene oxide with varying molecular weights are investigated as illustrated in Figure 1. Solids are observed on agitation using polyethylene oxide with a molecular weight above 200,000.

Similar data is observed for a 3% dispersion of Bentonite

Claims

1. A process for the formation of a solid comprising agitating a suspension comprising silica and a long chain polymer, wherein the silica is provided at a level of at least 14% by weight and the polymer has a chain length of at least 2 micrometres.

2. A process for the formation of a solid comprising agitating a suspension comprising Bentonite and a long chain polymer wherein the polymer has a chain length of at least 2 micrometres.

3. A process as claimed in claim 1 or claim 2 wherein the long chain polymer is polyethylene oxide.

4. A process as claimed in claim 3, wherein the polyethylene oxide is provided at a level of 0.1 to 2% by weight.

5. A process as claimed in claim 3 or claim 4 when the polyethylene oxide has an average molecular weight of 200,000 to 4xlO⁶.

6. A process as claimed in any one of claims 1 or 3 to 5 wherein the silica has an average particle size of 10 to lOOnm.

7. A process as claimed in any one of claims 1 to 6 wherein the solution is agitated by shaking.

8. A process as claimed in any one of claims 1 to 6 wherein the solution is agitated by extrusion through an aperture.

9. A suspension comprising silica and a long chain polymer in water, wherein the silica is provided at a level of at least 14% by weight and the polymer has a chain length of at least 2 micrometres.

10. A suspension comprising Bentonite and a long chain polymer in water, wherein the polymer has a chain length of at least 2 micrometres.

11. A foodstuff comprising a suspension as claimed in claim 9 or claim 10 and optionally comprising one or more of a flavouring, a sweetener or a colouring.

12. A toy comprising a suspension as claimed in claim 9 or claim 10 and optionally comprising instructions regarding the formation of a solid as set out in claim 1 or claim 2.

13. An anti- vibrational mount comprising a suspension as claimed in claim 9 or claim 10.

14. A shock absorber comprising a suspension as claimed in claim 9 or claim 10.

15. Braking fluid comprising a suspension as claimed in claim 9 or claim 10.

16. A solid produced by the process of any one of claims 1 to 8.

17. The use of a suspension comprising silica and a long chain polymer in water to produce a solid, wherein the suspension is agitated, the silica is provided at a level of at least 14% by weight and the polymer has a chain length of at least 2 micrometres.

18. The use of a suspension comprising Bentonite and a long chain polymer in water to produce a solid, wherein the suspension is agitated, the polymer having a chain length of at least 2 micrometres.

19. A process for the formation of a suspension as claimed in claim 9 comprising admixing silica with a long chain polymer in water, wherein said silica is provided at a level of at least 14 % by water and the polymer has a chain length of at least 2 micrometres.

20. A process for the formation of a suspension as claimed in claim 10 comprising admixing Bentonite with a long chain polymer in water, wherein said polymer has a chain length of at least 2 micrometres.

21. A process as substantially described herein with reference to one or more of the drawings or one of more of the examples.

22. A suspension as substantially described herein with reference to one or more of the drawings or one of more of the examples.

23. A foodstuff, toy, anti- vibrational mount, shock absorber or braking fluid as substantially described herein with reference to one or more of the drawings or one of more of the examples.

24. A solid as substantially described herein with reference to one or more of the drawings or one of more of the examples.

25. A use as substantially described herein with reference to one or more of the drawings or one of more of the examples.