WO2000032715A1

WO2000032715A1 - Customized grip using a thermoreversible gel composition

Info

Publication number: WO2000032715A1
Application number: PCT/US1999/027434
Authority: WO
Inventors: Michael T. Nowak; Barry W. Chadwick; Lev Bromberg; Toyoichi Tanaka
Original assignee: Bic Corporation
Priority date: 1998-12-03
Filing date: 1999-11-18
Publication date: 2000-06-08
Also published as: AU1737300A

Abstract

The present invention relates to a unique, customizable grip comprising a thermoreversible gel and a thermally conductive container. This grip, which can be utilized on products such as writing instruments, power tools, razors, lighters, and sports equipment, among others, customizes to the user's grip. In use, heat provided by a hand gripping the container causes the thermoreversible gel to customize to the grip and to solidify in that shape, rendering the grip ergonomically correct. Once the user releases the grip, the gel cools, converts back to its original flowable state.

Description

CUSTOMIZED GRIP USING A THERMOREVERSIBLE GEL COMPOSITION

Background of the Invention: Field of the Invention:

This invention relates to temperature sensitive gels, and especially relates to gels which substantially solidify at body temperature and which are used as grips.

Brief Description of the Related Art:

Various designs of consumer products, such as lighters, razors, writing instruments, hand tools, power tools, sports equipment, among others, and techniques for their use have been explored to improve their look, design, geometry, size, etc., in order to improve their consumer appeal, usability and to make the tool or device more ergonomic (in the sense of putting less utrcin on bones (hand) and/or reducing carpal tunnel possibilities). For example, pens, whose barrel is typically tubular and formed of metal or plastic, may have various diameter barrels, an ergonomic shape, and even a rubber grip. Similarly, men's razors typically have a substantially square geometry handle with or without a grip, while women's razors may have a square or flat handle (i.e. somewhat rectangular or oval), triangular, other geometric cross-section to enhance maneuverability during use and to inhibit slipping.

There continues to be a need in the art for writing instruments, razors, lighters, and other consumer products with greater ease and comfort of handling. Summary of the Invention:

The above-described drawbacks and disadvantages of the prior art are alleviated by the customized grip of the present invention and method of making an article having the same. The customizable grip comprises: a thermoreversible gel composition disposed within thermally conductive container, wherein said container is disposed on a grip portion of an object which will be contacted with a hand.

The method for forming a writing instrument having a customizable grip, comprises: forming a barrel having a grip portion, disposing a writing composition concentrically within said barrel, forming a thermally conductive container, and disposing a thermoreversible gel composition within said container.

The above discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.

Brief Description of the Drawings: Referring now to the drawings, which illustrate some of the various embodiments of the present invention, such drawings are meant to be exemplary, not limiting; like elements are numbered alike in the several FIGURES:

Figure 1 is a frontal view of an embodiment of a writing instrument comprising the customizing grip of the present invention; Figure 2 is a combination of frontal and side views of another embodiment of a writing instrument comprising the customizing grip of the present invention;

Figures 3 and 4 are frontal views of other embodiments of writing instruments comprising the customizing grip of the present invention;

Figures 5 and 6 are side views illustrating embodiments of razors comprising the customizing grip of the present invention;

Figure 7 is a side view of an embodiment of a lighter comprising the customizing grip of the present invention;

Figure 8 is a graph of the effect of Carbolpol on the gelation of the gelling compound; and Figures 9 and 10 are graphs of the effect of Avicel on the gelation of the gelling compound.

Best Mode for Carrying Out the Invention:

The present invention relates to a unique grip, such as for use on a writing instrument, lighter, razor handle, hand tools, power tools, sports equipment, and other instruments or devices which would have grips in contact with a human body, which, upon being held, customizes, i.e. molds, to accommodate each individual's grip. Once the grip is no longer held (i.e. provided a temperature in the range of about 15°C to about 40°C), the grip returns to its original shape. Consequently, upon each use of the instrument the grip customizes to the individual's hold. This grip comprises a flexible container having a thermoreversible gel therein.

The thermoreversible gel of the present invention comprises an aqueous solution of about 1 weight percent (wt%) to about 50 wt% of a gelling compound having a liquid, or soft or viscous gel state wherein the liquid has a loss modulus (G") greater than its storage modulus (G') at temperatures below about 15°C, while being a gel having G' greater than G" by at least about 150% at temperatures above about 15°C. Furthermore, the gelling compound should be capable of forming temperature sensitive hydrogen bonds, a thermally reversible non-permanent physical association between polymer chains, or possess both water soluble and water insoluble segments. Possible gelling compounds which could be employed with the present invention include, but are not limited to, poly(vinyl alcohol) crosslinked by poly(ethylene oxide), boric acid and other hydrogen bonding agents; syndiotactic poly(methacrylic acid), and poly(vinyl alcohol); ethyl(hydroxyethyl)cellulose blended with cetyltrimethylammonium bromide; block-copolymers of poly(ethylene oxide) and poly(propylene oxide), among others, and combinations thereof, with gelling compounds which have a transition temperature range from the liquid to the gel states of 0.1 to 8°C preferred.

The thermoreversible gel of the present invention further comprises a rheology modifier which thickens the gelling compound such that at low temperatures, such as below about 17°C, the thermoreversible gel will retain a viscosity of at least about 1,000 centipoise (cps), such that it can more readily be incorporated into the various embodiments of the present invention including a writing instrument, razor handle, etc. Rheology modifiers include a material or combination of materials capable of increasing the viscosity of the gelling compound while not inhibiting the gelling compound's ability to form a gel upon the application of heat. Referring to Figures 8 - 10, it can be seen that the addition of a rheology modifier, a high molecular weight lightly cross-linked poly(acrylic acid), i.e. Carbopol (available from BF Goodrich Specialty Polymers, Cleveland, OH), inhibited the thermoreversible gel from attaining an elastic gel state at temperatures exceeding 20°C (Figure 8). Meanwhile, the addition of a water-swellable, insoluble excipient, i.e. macrocrystalline cellulose formulations, such as Avicel (a blend of microcrystalline cellulose and sodium carboxymethylcellulose available from FMC Co., Newark, DE), increased the storage modulus at body temperatures while not inhibiting gelation (Figures 9 - 10).

Typically, an amount of rheology modifier below a level which the modifier would prevent the transition from a viscous gel to an elastic gel upon the application of heat, can be employed. Consequently, up to about 20 weight percent (wt%) rheology modifier or more if other additives are employed can be used, with below about 20 wt% rheology modifier preferred.

The thermoreversible gel of the present invention can further comprise other additives, including, but not limited to, acids, alcohols, amines, surfactants, salts, anti- bacterial agents, dyes such as thermochronin dyes, pigments, ultraviolet absorbers, fluorescent agents, and others, such as a filler, and combinations thereof. The filler can be employed to render the gel white, opaque, or colored. As with the rheology modifier or any other additive, the filler must not prevent the viscous gel from transitioning to an elastic gel state. Some possible fillers include, but are not limited to, silica, polyacrylic acid, cellulosic polymers, polyurethane, associative thickeners, proteins, among others, and combinations thereof. The amount of filler is based upon the desired feel of the grip. Typically up to about 40 wt% of the total composition (gel, thickener, water, and filler) can be filler, with about 10 wt% to about 30 wt% filler preferred, and about 17 wt% to about 25 wt% especially preferred. In order to inhibit bacterial growth in the thermoreversible gel, it can either be sterilized in a conventional fashion, such as using heat (i.e. autoclaving), radiation, such as ultraviolet radiation, and/or chemicals, such as ethyl oxide, among others, or an antibacterial agent can be added to the composition. The anti-bacterial agent should not effect the gelation capabilities of the composition. Possible anti-bacterial agents include: azides, such as sodium azide, conventional biocides, or combinations thereof. Preparation of the composition comprises: mixing the various components under low shear. Preferably the components are mixed together at low temperature, preferably about 5°C, so as to form a substantially homogeneous, viscous gel. Once mixed, the composition can be disposed in any container having an appropriate geometry, a smooth or textured exterior surface, and sufficient structural integrity to restrain the composition under normal use conditions.

Possible containers have various sizes and geometries and should: (1) be flexible, capable of allowing the gel to conform to the individual's grip; (2) be inert with relation to the composition; (3) be moisture resistant for the given environment; (4) possess a low moisture vapor barrier, for example less than about 0.001 grams per square centimeter per 24 hours (g/cm²/24 hrs) at 50°C; (5) possess a high heat transfer rate, for example a rate similar to that of aluminum foil (247 watts per degree Kelvin (W/°K)), i.e., about 225 W/°K or greater; and (6) possess sufficient structural integrity to withstand normal use conditions, with a burst strength greater than about 800 pounds per square inch (psi) desired, and greater than about 1,000 psi preferred. Possible containers include, but are not limited to, bags, laminates, bladders such as doughnut bladders, toroid bladders, thermally weldable bladders, among others. These containers can be formed from materials including, but not limited to, polyvinylidene chlorides, polyethylenes, cellulose, acrylics, polyolefms, polyamides, polyethylene terephthalates, polystyrenes, ethylene vinyl alcohols, polyurethanes, polyesters, polypropylenes, polyvinyl acetates (including partially saponified polyvinyl acetate), polyvinyl alcohols, aluminum (or other metallic films), and mixtures and laminates thereof, among other materials which are inert with relation to the gel composition. Some examples of container materials include, but are not limited to, Surlyn^®, Bynel^®, Elvax^®, Nucrel^®, Appeel^®, and Saran^® (commercially available from E.I. duPont de Nemours and Company, Wilmington, DE) alone or in combination, and laminates thereof with materials such as papers, foils (including, but not limited to metal foils), ethylene vinyl alcohols, polyethylenes (high and/or low density), polyethylene terephthalates, polypropylenes, and others.

The container heat transfer characteristics can be improved by combining the container materials with high heat conductivity materials, such as metals, and/or by utilizing a metal lining within the container. Preferably, the metal liner is inert with respect to the thermoreversible gel composition and is located so as not to inhibit the flexibility of the container. For example, for a writing instrument, above-mentioned materials could form the portion of the container directly contacted by a hand, and the metal lining could form the opposite side of the container which is in intimate contact with the barrel of the writing instrument. The desired geometry, size, and specific orientation of the metal liner is dependent upon the heat transfer characteristics and the liner's effect on the container's flexibility.

Other container characteristics, such as structural integrity, can be adjusted through various techniques, including, but not limited to: (a) increasing the thickness of the polymer layer forming the container (the bladder thickness is based upon the type of item and the stresses associated with the item's normal use; typically the layer can be up to a few millimeters thick, with less than about 1 mm thick preferred); (b) introducing crystallinity into the polymer container as may be achieved by orientation, such as in a stretch blow molding process (biaxial stretching) or control of blow-up ratio in a film extrusion process; (c) utilization of various fillers and/or stabilizers; (d) utilization of polymer blends and/or copolymers; (e) coating of one polymer with another; and/or (f) lamination of one or more polymer layers together and/or with reinforcing layers, heat conducting layers, and others, in adhesive, extrusion, coextrusion or other processes. Disposed within the container is preferably a sufficient amount of thermoreversible gel composition to enable the grip to mold to the individual's hold, with the specific amount of thermoreversible gel composition being dependent on the size of the item and its grip. Typically up to about 30 grams of the composition will be employed for most hand-held items, with about 0.1 to about 20 grams per bladder preferred. The following examples are meant to be exemplary, not limiting.

EXAMPLES

Example 1 : Writing Instrument Applications

A. The writing instrument of Figure 1 illustrates a textured bladder 1 with a composition comprising 20 wt% Pluronic F127 (a block-copolymer of poly(ethylene oxide) and poly(propylene oxide) available from BASF Company, Mount Olive, NJ), 3 wt% Avicel, and 20 wt% silica gel (60 A pore, 35 - 75 micrometer particle available from Analtech, Newark, DE). In one embodiment, the bladder 1 is disposed around barrel 5, which houses an ink cartridge or lead (not shown). In another embodiment, the composition is disposed within bladders 1' (see Figure 2) having thicknesses "a" of about 25 millimeters (mm) and "b" of about 40 mm, and a width of about 8 mm. It should be noted that these bladders 1' can comprise the same or different container composition and/or the same or different thermoreversible gel composition. In other words, the exact container and thermoreversible gel chosen for each location can be tailored to the conditions typically encountered by that portion of the grip (e.g., temperature, pressures, stresses, etc.).

The composition could be prepared by combining Pluronic F127, deionized water having a temperature of water 5°C, silica gel, and Avicel in a paddle blade mixer (air or electric) with moderate agitation. In order to inhibit bacterial growth within the bladder, the composition can be sterilized under ionizing radiation for about 1 minute in an ultraviolet electron beam.

Figures 3 and 4 illustrate other writing instruments employing bladders having disposed in different locations on the writing instrument. As previously stated, the size, geometry, and location of the bladder on an item, and the amount of composition employed within the bladder is dependent upon the size and geometry of the item.

B. An alternative composition comprises 18 wt% Pluronic F127, Pluronic F68 (another block-copolymer of poly(ethylene oxide) and poly(propylene oxide available from BASF Company, Mount Olive, NJ), 2 wt% Avicel, 20 wt% silica gel, and 0.05 wt% sodium azide.

This composition could be prepared by combining Pluronic F127 and Pluronic F68, with water. Silica gel and Avicel can then be added to the aqueous Pluronic solution. In order to inhibit bacterial growth within the bladder, the composition can be sterilized in an autoclave.

Figures 5 and 6 show two different possible embodiments which can be employed with razors. In Figure 5, the bladder 1 " forms the majority of the handle of the razor 7. As can be seen from cut-away portion 9, however, a stem 11 can optionally be employed within the bladder 1" for additional structural integrity. In Figure 6, the bladder 1' is disposed on the handle 15 as desired.

Figure 7 illustrates yet another embodiment of the present invention where a bladder 1' is disposed in the frontal portion of a lighter 17.

Various articles incorporating the customizable grip with the thermoreversible composition can be formed using conventional techniques, such as molding and the like. For example, a writing instrument can be formed in a conventional fashion wherein a barrel having a grip portion is formed with a writing composition (e.g. lead, ink, or the like) concentrically disposed therein. A thermoreversible gel composition is then formed and disposed in a container located on the grip portion of the barrel. As can be seen from the above description and examples, the composition of the present invention can be used to form numerous customized grips for a variety of objects, including, but not limited to, writing instruments, golf club grips, bicycle grips, lighters, razors, stroller grips, steering wheels, fishing pole handles, lawn and garden equipment grips, power tool grips, and any other grips which are grasped with a hand or other object which will provide a sufficient amount of heat to render the composition in a state such that its storage modulus is greater than its loss modulus. Essentially, the composition of the present invention has a sufficient viscosity at low temperatures to substantially maintain its shape while being soft and somewhat malleable, and is stiff at slightly higher temperatures, rigidly retaining its shape, even under pressure. Heat provided by a hand gripping the container causes the thermoreversible gel to customize to the grip and to solidify in that shape, rendering the grip ergonomically correct. Once the user releases the grip, the gel cools, converts back to its original flowable state.

While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.

Claims

1. A customizable grip for hand held object, comprising: a thermoreversible gel composition disposed within thermally conductive container, wherein said container is disposed on a grip portion of an object which will be contacted with a hand.

2. A customizable grip as in Claim 1, wherein said thermoreversible gel composition has a loss modulus and a storage modulus, and wherein said loss modulus is greater than said storage modulus at temperatures below about 15°C.

3. A customizable grip as in Claim 2, wherein said storage modulus is greater than said loss modulus at temperatures above about 15°C.

4. A customizable grip as in Claim 3, wherein said storage modulus is at least about 3 times greater than said loss modulus at temperatures above about 15°C.

5. A customizable grip as in Claim 1, wherein said thermoreversible gel composition comprises a block-copolymer of poly(ethylene oxide) and poly(propylene oxide).

6. A customizable grip as in Claim 5, wherein said thermoreversible gel composition comprises Pluronic F127.

7. A customizable grip as in Claim 5, wherein said thermoreversible gel composition further comprises a rheology modifier.

8. A customizable grip as in Claim 7, wherein said rheology modifier is a water-swellable, insoluble excipient.

9. A customizable grip as in Claim 7, wherein said rheology modifier is a blend of cellulose and sodium carboxymethylcellulose.

10. A customizable grip as in Claim 9, wherein said thermoreversible gel composition further comprises an acid, alcohol, amine, surfactant, salt, anti-bacterial agent, dye, pigment, ultraviolet absorber, fluorescent agent, or a combination thereof.

11. A customizable grip as in Claim 7, wherein said thermoreversible gel composition further comprises an azide, biocide, or combination thereof

12. A customizable grip as in Claim 5, wherein said object is a writing instrument, golf club grip, bicycle grip, lighter, razor, stroller grip, steering wheel, fishing pole handle, equipment grip, or power tool grip.

13. A customizable grip as in Claim 1, wherein said container is a bag, laminate, bladder.

14. A customizable grip as in Claim 1, wherein said container comprises polyvinylidene chlorides, polyethylenes, cellulose, acrylics, polyolefms, polyamides, polyethylene terephthalates, polystyrenes, ethylene vinyl alcohols, polyurethanes, polyesters, polypropylenes, polyvinyl acetates, polyvinyl alcohols, metallic films, or mixtures thereof.

15. A customizable grip as in Claim 14, wherein said container comprises Surlyn^®, Bynel^®, Elvax^®, Nucrel^®, Appeel^®, Saran^®, or a mixture thereof.

16. A writing instrument, comprising: a barrel having a grip portion; a writing composition concentrically disposed within said barrel; a container disposed in said grip portion; and a thermoreversible gel composition disposed within said container.

17. A writing instrument as in Claim 16, wherein said thermoreversible gel composition comprises a block-copolymer of poly(ethylene oxide) and poly(propylene oxide).

18. A writing instrument as in Claim 17, wherein said thermoreversible gel composition comprises Pluronic F127.

19. A writing instrument as in Claim 18, wherein said thermoreversible gel composition further comprises a water-swellable, insoluble excipient.

20. A writing instrument as in Claim 18, wherein said thermoreversible gel composition further comprises a blend of cellulose and sodium carboxymethylcellulose.

21. A writing instrument as in Claim 16, wherein said thermoreversible gel composition further comprises an acid, alcohol, amine, surfactant, salt, anti-bacterial agent, dye, pigment, ultraviolet absorber, fluorescent agent, or a combination thereof.

22. A writing instrument as in Claim 16, wherein said thermoreversible gel composition has a loss modulus and a storage modulus, and wherein said loss modulus is greater than said storage modulus at temperatures below about 15°C.

23. A writing instrument as in Claim 22, wherein said storage modulus is greater than said loss modulus at temperatures above about 15°C.

24. A writing instrument as in Claim 23, wherein said storage modulus is at least about 3 times greater than said loss modulus at temperatures above about 15°C.

25. A method for forming a writing instrument having a customizable grip, comprising: a. forming a barrel having a grip portion; b. disposing a writing composition concentrically within said barrel; c. forming a thermally conductive container; and d. disposing a thermoreversible gel composition within said container.

26. A method for forming a writing instrument as in Claim 25, wherein said thermoreversible gel composition comprises a block-copolymer of poly(ethylene oxide) and poly(propylene oxide).

27. A method for forming a writing instrument as in Claim 26, wherein said thermoreversible gel composition comprises Pluronic F127.

28. A method for forming a writing instrument as in Claim 25, wherein said thermoreversible gel composition further comprises a water-swellable, insoluble excipient.

29. A method for forming a writing instrument as in Claim 25, wherein said thermoreversible gel composition further comprises a blend of cellulose and sodium carboxymethylcellulose.

30. A method for forming a writing instrument as in Claim 25, wherein said thermoreversible gel composition further comprises an acid, alcohol, amine, surfactant, salt, anti-bacterial agent, dye, pigment, ultraviolet absorber, fluorescent agent, or a combination thereof.

31. A method for forming a writing instrument as in Claim 25, wherein said thermoreversible gel composition has a loss modulus and a storage modulus, and wherein said loss modulus is greater than said storage modulus at temperatures below about 15°C.

32. A method for forming a writing instrument as in Claim 31 , wherein said storage modulus is greater than said loss modulus at temperatures above about 15°C.

33. A method for forming a writing instrument as in Claim 32, wherein said storage modulus is at least about 3 times greater than said loss modulus at temperatures above about 15°C.