CA2066685A1 - Flowable, pressure-compensating material and process for producing same - Google Patents
Flowable, pressure-compensating material and process for producing sameInfo
- Publication number
- CA2066685A1 CA2066685A1 CA002066685A CA2066685A CA2066685A1 CA 2066685 A1 CA2066685 A1 CA 2066685A1 CA 002066685 A CA002066685 A CA 002066685A CA 2066685 A CA2066685 A CA 2066685A CA 2066685 A1 CA2066685 A1 CA 2066685A1
- Authority
- CA
- Canada
- Prior art keywords
- weight percent
- flowable
- pressure
- recited
- composition
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
- C08J3/09—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in organic liquids
- C08J3/091—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in organic liquids characterised by the chemical constitution of the organic liquid
- C08J3/095—Oxygen containing compounds
-
- A—HUMAN NECESSITIES
- A41—WEARING APPAREL
- A41D—OUTERWEAR; PROTECTIVE GARMENTS; ACCESSORIES
- A41D13/00—Professional, industrial or sporting protective garments, e.g. surgeons' gowns or garments protecting against blows or punches
- A41D13/05—Professional, industrial or sporting protective garments, e.g. surgeons' gowns or garments protecting against blows or punches protecting only a particular body part
- A41D13/06—Knee or foot
-
- A—HUMAN NECESSITIES
- A41—WEARING APPAREL
- A41D—OUTERWEAR; PROTECTIVE GARMENTS; ACCESSORIES
- A41D31/00—Materials specially adapted for outerwear
- A41D31/04—Materials specially adapted for outerwear characterised by special function or use
- A41D31/28—Shock absorbing
- A41D31/285—Shock absorbing using layered materials
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2300/00—Characterised by the use of unspecified polymers
- C08J2300/10—Polymers characterised by the presence of specified groups, e.g. terminal or pendant functional groups
Abstract
Abstract A flowable, pressure-compensating composition is provided comprising a liquid, a material for increasing the viscosity of the liquid and, preferably, spherical particles. A method for making such composition is also provided. The composition is especially suitable for use in padding devices.
Description
;~$},~
FLO~'1ABLE, PRESSURE;-COMPEMSATII'1G
M~ 3RI~L ~ND PROCRSS YOR PRODUCIl`IG SAME
Yield Or the Invention This inven-tion relates yenerally -to the field of padding materials, and in particular, to flowable, pressure-compensatiny materials and methods for producing such materials.
; Backqround of the Invention Various padding devices have been employed in the past. Examples include li~uid- or gas-filled bladders, e.y. water--filled cushions and pneumatic pads; and gases or liquids dispersed in a solid material, e.g. foams and gels. Generally, such padding devices operate on the principle of conformation to the shape of an object when placed under pressure. When a force, such as a person's mass, is placed on such a padding device, the device deforms so as to conform to the shape of the pressure applyiny object in order to distribute the force over as large ~n area as possible. These devices perform adequately when the object being padded has a relatively large, uniformly shaped surface area. However, when the object being padded includes a relatively small area of concen-trated force, such as that causea by a ~ protuberance, the majority of known padding devices do not perform to adequately reduce the discomEort of users in many applications. This is because SUCh paclding devices exert yreater responsive pressure on -the area oE
concentrateA force.
The reason for the greater pressure is that materials employed in prior art padding devices typically have a high degree of "memory." As used herein, the term "memory" will refer to that characteristic of a material in which the material returns to its original shape as a resul-t of internal restoring forces when an external force is removed.
Such materials deform to the shape of an object which applies an external force by compressing. I~owever, due ~?~
to ~lle inte-rnal restorincJ forces, a pressure which is proportion~l to the deyree of compression is exerted against the object which applies the ex-ternal force. A
sharp protube~ance compresses the padding device more than the surrounding areas and, as a result, the padding device presses back with greater pressure in these areas of high compression. Such areas of hiyh pressure ~re especially undesirable when the protuberance is a bone, such as an ankle or ischial tuberosity. The high 10 pressure can lead to discom~ort and, after periods of extende~ use, to actual damage to the tissue overlying the protruding bone.
The problem can be described with reference to a padding device comprising a gas dispersecl in a solid material/ e.g. foam. Tiny gas bubbles in foam act like millions o~ coil "springs." When required to conform to an irregular shape, such as a human hody, the "springs"
are compressed to varying degrees, each pushing back on the body with a force proportional to the amount of compression. Intimate conformity is best obtained with a relatively soft foam, which can be compared to weak "sprinys." The pressure on protuberances, where the Usprings'' are greatly compressed, will be relatively high, possibly causing pain and reduced circulation.
The problem is even more pronounced if a stiffer foam is employed, because the "springs" are stronger.
Deformable silicone gel padding devices are disclosed in U.S. Patent Mo. 3,449,844 by Spence, issued June 17, 1969; U.S. Patent No. 4,380,569 by Shaw, issued April 19, 1983; U.S. Patent No. 3,663,973 by Spence, issued May 23, 1972; U.S. Patent No. 3,548,420 by Spence, issued December 22, 1970; U.S. Patent No.
3,308,491 by Spence, issued March 14, 1967; U.S. Paten-t No. 4,019,209 by Spence issued April 26, 1977; and U.S.
Patent No. 4,668,564 by Orchard, issued May 26, 1987.
In U.S. Patent No. 4,380,569, a silicone gel containing glass microbeads is disclosed.
;,f~æ~
'L'he silicone gel disclosed in -these patents is described as having near total memory. In other words, it returns to i-ts or:iginal shape when an external force is remove~. The internal res-toring forces necessary to provide such memory are undesirable in some applications. In use, differential pressures will result depending upon the degree of deformation of the silicone gel material, with higher deformation resulting in localized areas of high pressure being exerted on the external pressure applying object.
In order to alleviate the problem of differential pressure inherent with many prior art materials, flowable, pressure-compensating materials were developed. Such materials and applications thereo are described in U.S. Patent No. 3,402,411 by Alden Hanson, issued September ~4, 1968; U.S. Patent No. 3,635,849 by Alden ~lanson, issued January 18, 1972; U.S. Patent No.
4,038,762 by Swan, Jr., issued August 2, 1977; U.S.
Patent No. 4,083,127 by Chris Hanson, issued April 11, 1978; U.S. Patent No. ~,108,92~ by Swan, Jr., issued August 22, 1978; U.S. Patent No. 4,144,65B by Swan, Jr., issued March 20, 1979; U.S. Patent No. 4,229,546 by Swan, Jr., issued October 21, 1980; and U.S. Patent No.
4,243,754 by Swan, Jr., issued January 6, 1981. These patents will collectively be referred to as the nflowable, pressure-compensating material patents."
The preferred materials disclosed in U.S. Patent No. 3,402,411 comprise ~rom 20 to 25 weiyht percent polyisobutylene, from 25 to 37.5 weight percent of an inert o.il, e.y. mineral oil or a saturated ester oil or a mixture thereof and from 42.5 to 50 weight psrcent inorganic filler. U.S. Patent No. 3,635,849 discloses a composition consisting essentially of from about 5 to about 45 weight percen-t oE a polyolefin, particularly polyisobutylene, from about 15 to about 70 weight percent of a paraffin and from about 5 to about 80 weight percent oil. Lightweight aggregate materials, for example, polystyrene beads or a heavy agyregate such as Fe.30~ can also be added.
The flowable, pressure-compensatiny materials disclosed in U.S. Patent Nos. 4,038,762, 4,108,928 and 5~,243,75~ include from 21.39 to 77.96 weight percent oil, 21.04 -to 69.62 weight percent wax and 1 to 9 weight percent microbeads. These patents teach away Erom the use of water in the finished product statiny that "Since water generally increases the specific gravity of the finished fitting material, and does not serve any functional or necessary purpose, as such, in the finished fitting material, it is very desirable tha-t if ; it is present in the finished fitting material, that it not be present in amounts or levels that exceed tolerable, minimal or residual levels (e.g. up to or not exceeding about 8~ by weight, preferably up to not exceediny about 3% or about 5% by weight)."
U.S. Patent Nos. 4,144,65~ and 4,229,546 disclose flowable, pressure-compensating materials comprising 10 ; 20to 60 weight percent hollow, ylass microbeads, 8.5 to 34 weight percent wax and 26.5 to 81 weight percent oil.
U.S. Patent No. ~,0~3,127 discloses a flowable, ; pressure-compensating fittiny material. consistiny essentially of discrete, lightweight, sturdy microbeads ; 25 distributed throughout a colltinuous phase of wax and oil.
In use, the flowable, pressure-compensating materials disclosed in the above-mentioned patents are ; typically placed in a pliable package, such as between 30. two leak-proof resinous sheets which are sealed at the edges. The flowable materials act hydraulically. An applied force causes flowable material to migrate from areas of higher pressure to areas of lower pressure until pressure throughout the package is uniform. Once conformity has been achieved, force is distributed substantially e~ually over the entire surface of the package thus alleviating the differential pressure problems associated with prior devices. The viscosity oE the Elowable materials can be varied. Iliyher visc05:ity does not decre~se the ability of the flowable materia:ls to conform to the shape of the pressure applyillc3 object, only -the rate at which they will migrate -to conform. Flowable materials are presently marketed under tlle trademark FLOLITEI~ by Alden Laboratories, Inc. of Boulder, Colorado U.S.A.
FLOLIl'E'~ brand materials have performed exceptionally well in a number of applications, and have gained wide commercial acceptance in the marketplace.
In spite of this commercial success, it would be ; advantageous to provide novel compositions which are useful as flowable, pressure-compensating materials.
For example, it would be advantageous to provide a composition which exhibits a higher degree of flame retardancy than present flowable, pressure~compensating materials. It would be advantageous if the number of components required to provide a flowable, pressure-compensating composition were reduced to a minimum. In this way, it would be possible to simplify manufacturing. It would be advantageous if the materials used in a composition were relatively inexpensive in order to reduce raw material costs. It would be advantageous if the composition were to be less prone to separation than currently-employed materials.
It would be advantageous if spherical particles included in a flowable, pressure-compensating composition would not "float out" of the composition. It would be advantageous if the viscosity of the composition was relatively stable over broad temperature ranges. It would be advantageous if the viscosity of the material could be controlled in such a way so as to ease manufacture of devices containing the composition.
Summar~ of the Invention In accordance with the present invention, a novel flowable, pressure-compensating composition is provided.
The composition comprises a li~uid and a material for
FLO~'1ABLE, PRESSURE;-COMPEMSATII'1G
M~ 3RI~L ~ND PROCRSS YOR PRODUCIl`IG SAME
Yield Or the Invention This inven-tion relates yenerally -to the field of padding materials, and in particular, to flowable, pressure-compensatiny materials and methods for producing such materials.
; Backqround of the Invention Various padding devices have been employed in the past. Examples include li~uid- or gas-filled bladders, e.y. water--filled cushions and pneumatic pads; and gases or liquids dispersed in a solid material, e.g. foams and gels. Generally, such padding devices operate on the principle of conformation to the shape of an object when placed under pressure. When a force, such as a person's mass, is placed on such a padding device, the device deforms so as to conform to the shape of the pressure applyiny object in order to distribute the force over as large ~n area as possible. These devices perform adequately when the object being padded has a relatively large, uniformly shaped surface area. However, when the object being padded includes a relatively small area of concen-trated force, such as that causea by a ~ protuberance, the majority of known padding devices do not perform to adequately reduce the discomEort of users in many applications. This is because SUCh paclding devices exert yreater responsive pressure on -the area oE
concentrateA force.
The reason for the greater pressure is that materials employed in prior art padding devices typically have a high degree of "memory." As used herein, the term "memory" will refer to that characteristic of a material in which the material returns to its original shape as a resul-t of internal restoring forces when an external force is removed.
Such materials deform to the shape of an object which applies an external force by compressing. I~owever, due ~?~
to ~lle inte-rnal restorincJ forces, a pressure which is proportion~l to the deyree of compression is exerted against the object which applies the ex-ternal force. A
sharp protube~ance compresses the padding device more than the surrounding areas and, as a result, the padding device presses back with greater pressure in these areas of high compression. Such areas of hiyh pressure ~re especially undesirable when the protuberance is a bone, such as an ankle or ischial tuberosity. The high 10 pressure can lead to discom~ort and, after periods of extende~ use, to actual damage to the tissue overlying the protruding bone.
The problem can be described with reference to a padding device comprising a gas dispersecl in a solid material/ e.g. foam. Tiny gas bubbles in foam act like millions o~ coil "springs." When required to conform to an irregular shape, such as a human hody, the "springs"
are compressed to varying degrees, each pushing back on the body with a force proportional to the amount of compression. Intimate conformity is best obtained with a relatively soft foam, which can be compared to weak "sprinys." The pressure on protuberances, where the Usprings'' are greatly compressed, will be relatively high, possibly causing pain and reduced circulation.
The problem is even more pronounced if a stiffer foam is employed, because the "springs" are stronger.
Deformable silicone gel padding devices are disclosed in U.S. Patent Mo. 3,449,844 by Spence, issued June 17, 1969; U.S. Patent No. 4,380,569 by Shaw, issued April 19, 1983; U.S. Patent No. 3,663,973 by Spence, issued May 23, 1972; U.S. Patent No. 3,548,420 by Spence, issued December 22, 1970; U.S. Patent No.
3,308,491 by Spence, issued March 14, 1967; U.S. Paten-t No. 4,019,209 by Spence issued April 26, 1977; and U.S.
Patent No. 4,668,564 by Orchard, issued May 26, 1987.
In U.S. Patent No. 4,380,569, a silicone gel containing glass microbeads is disclosed.
;,f~æ~
'L'he silicone gel disclosed in -these patents is described as having near total memory. In other words, it returns to i-ts or:iginal shape when an external force is remove~. The internal res-toring forces necessary to provide such memory are undesirable in some applications. In use, differential pressures will result depending upon the degree of deformation of the silicone gel material, with higher deformation resulting in localized areas of high pressure being exerted on the external pressure applying object.
In order to alleviate the problem of differential pressure inherent with many prior art materials, flowable, pressure-compensating materials were developed. Such materials and applications thereo are described in U.S. Patent No. 3,402,411 by Alden Hanson, issued September ~4, 1968; U.S. Patent No. 3,635,849 by Alden ~lanson, issued January 18, 1972; U.S. Patent No.
4,038,762 by Swan, Jr., issued August 2, 1977; U.S.
Patent No. 4,083,127 by Chris Hanson, issued April 11, 1978; U.S. Patent No. ~,108,92~ by Swan, Jr., issued August 22, 1978; U.S. Patent No. 4,144,65B by Swan, Jr., issued March 20, 1979; U.S. Patent No. 4,229,546 by Swan, Jr., issued October 21, 1980; and U.S. Patent No.
4,243,754 by Swan, Jr., issued January 6, 1981. These patents will collectively be referred to as the nflowable, pressure-compensating material patents."
The preferred materials disclosed in U.S. Patent No. 3,402,411 comprise ~rom 20 to 25 weiyht percent polyisobutylene, from 25 to 37.5 weight percent of an inert o.il, e.y. mineral oil or a saturated ester oil or a mixture thereof and from 42.5 to 50 weight psrcent inorganic filler. U.S. Patent No. 3,635,849 discloses a composition consisting essentially of from about 5 to about 45 weight percen-t oE a polyolefin, particularly polyisobutylene, from about 15 to about 70 weight percent of a paraffin and from about 5 to about 80 weight percent oil. Lightweight aggregate materials, for example, polystyrene beads or a heavy agyregate such as Fe.30~ can also be added.
The flowable, pressure-compensatiny materials disclosed in U.S. Patent Nos. 4,038,762, 4,108,928 and 5~,243,75~ include from 21.39 to 77.96 weight percent oil, 21.04 -to 69.62 weight percent wax and 1 to 9 weight percent microbeads. These patents teach away Erom the use of water in the finished product statiny that "Since water generally increases the specific gravity of the finished fitting material, and does not serve any functional or necessary purpose, as such, in the finished fitting material, it is very desirable tha-t if ; it is present in the finished fitting material, that it not be present in amounts or levels that exceed tolerable, minimal or residual levels (e.g. up to or not exceeding about 8~ by weight, preferably up to not exceediny about 3% or about 5% by weight)."
U.S. Patent Nos. 4,144,65~ and 4,229,546 disclose flowable, pressure-compensating materials comprising 10 ; 20to 60 weight percent hollow, ylass microbeads, 8.5 to 34 weight percent wax and 26.5 to 81 weight percent oil.
U.S. Patent No. ~,0~3,127 discloses a flowable, ; pressure-compensating fittiny material. consistiny essentially of discrete, lightweight, sturdy microbeads ; 25 distributed throughout a colltinuous phase of wax and oil.
In use, the flowable, pressure-compensating materials disclosed in the above-mentioned patents are ; typically placed in a pliable package, such as between 30. two leak-proof resinous sheets which are sealed at the edges. The flowable materials act hydraulically. An applied force causes flowable material to migrate from areas of higher pressure to areas of lower pressure until pressure throughout the package is uniform. Once conformity has been achieved, force is distributed substantially e~ually over the entire surface of the package thus alleviating the differential pressure problems associated with prior devices. The viscosity oE the Elowable materials can be varied. Iliyher visc05:ity does not decre~se the ability of the flowable materia:ls to conform to the shape of the pressure applyillc3 object, only -the rate at which they will migrate -to conform. Flowable materials are presently marketed under tlle trademark FLOLITEI~ by Alden Laboratories, Inc. of Boulder, Colorado U.S.A.
FLOLIl'E'~ brand materials have performed exceptionally well in a number of applications, and have gained wide commercial acceptance in the marketplace.
In spite of this commercial success, it would be ; advantageous to provide novel compositions which are useful as flowable, pressure-compensating materials.
For example, it would be advantageous to provide a composition which exhibits a higher degree of flame retardancy than present flowable, pressure~compensating materials. It would be advantageous if the number of components required to provide a flowable, pressure-compensating composition were reduced to a minimum. In this way, it would be possible to simplify manufacturing. It would be advantageous if the materials used in a composition were relatively inexpensive in order to reduce raw material costs. It would be advantageous if the composition were to be less prone to separation than currently-employed materials.
It would be advantageous if spherical particles included in a flowable, pressure-compensating composition would not "float out" of the composition. It would be advantageous if the viscosity of the composition was relatively stable over broad temperature ranges. It would be advantageous if the viscosity of the material could be controlled in such a way so as to ease manufacture of devices containing the composition.
Summar~ of the Invention In accordance with the present invention, a novel flowable, pressure-compensating composition is provided.
The composition comprises a li~uid and a material for
2~r~
increasilly the viscosity o~ the liquid. ~he composition may also include substantially spherical particles dispers~d throughout the composition. The liqui~ may include water, glycerin, or mixtures thereof.
~s used herein, the term "glycerinN refers to the trihydric alcohol haviny the chemical formula (C1l2OII~2CIIOH, which is also commonly refer~ed to as glycerol. Although ylycerin is the preferred liquid for use in connection with the present invention, alternative liquids such as other glycerols (i.e., other trihydric alcohols) and glycols (i.e., dihydric alcohols) can also be employed. For the sake of simplicity, the followi2lg description of the invention will refer to glycerin as the preferred liquid, however, it is to be expressly unders-tood that the other li~uids can be used, even thouyh glycerin is preferred.
Glycerin has a hygroscopic nature and may comprise a small amount oE water, e.g. about 4 percent.
When the liquid comprises water, the material for increasing the viscosity of the liquid is preferably selected from the group consisting of guar, agar, carboxymethylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, and polyethyleneoxide. When glycerin is included in the liquid, fumed silica, attapulgite clays and mixtures thereof may also be utilized as a visosity-increasing material. When the liquid is primarily glycerin, the viscosity-increasing material is most preferably an attapulgite clay.
Preferably, substantially spherical particles are also employed in the compositions of the present invention. Preferably, the substantially spherical particles have diameter of less than about 300 micrometers.
A process for producing the flowable, pressure-compensating compositions is also provided. The process ; includes the steps of preparing a slurry comprising a viscosity-increasi2lg material, a liquid and substantially spherical particles, and mixing the components toyether until the viscosity-increasiny agent and the particles are distributed substantially evenly throughout the liquid.
Preferably, the flowable, pressure-compensating composition of the present inven-tion is placed within an enclosure. In a preferred embodiment, the composition is placed between two resinous sheets, which are subsequently heat sealed together. In one embodiment of the invention, the composition is treated to kill microorganisms and prevent their growth. The composition may also include an additive, preferably boric oxide, to increase the flame retardance of the composition.
The present compositions provide a number of advantayes. When wa-ter is used as the primary liquid component, the flame retardancy is greatly increased.
When a flame retardant such as boric oxide (B2O3) is used in the glycerin-containing compositions, they typically have a higher degree of flame retardancy than prior art materials which are oil and/or wax based.
Glycerin has the advantage oE not only lowerin~ the freezing point of the composition, but it also provides a Nviscosity bonus efEect", which is described in more detail hereinbelow, when used with certain viscosity-increasing materials. ~urther, the spherical particlesdispersad throughout the composition are not prone to float -to the top oE the composition (a condition termed "float out"), in spite of being less dense than the remainder of the composition. Also, the viscosities of the present compositions are stable over broad temperature ranges. Furthermore, some of the present composi-tions can have initially low viscosities for limited periods of time to ease workability. This is advantageous when manufacturing padding dPvices because it allows the compositions to be poured into an enclosure which is then sealed. Subsequently, the viscosity of the composition increases to the desired level.
l~etaiL~ escriptioll of -the Illve~tion In accord~nce with the present invention, a ; flowable, pressure-compensatiny composi-tion and process for ma~ing the same is provided.
The composition includes a liquid. The liquid may include water, a dihydric alcohol, a trihydric alcohol, or mixtures thereof. The composition further includes a viscosity-increasing material. Spherical particles may also be dispersed throughout the composition.
Additionally, flame retardants can be added and/or preservatives can be included to prevent microbiological attack and chemical degradation.
The process for producing the present composition generally involves mixing the liquid, the viscosi-ty-! 15 increasing material and, optionally, the sphericalparticles until a homogenous mixture is achieved. The specific process for producing compositions in accordance with the present invention will vary slightly ; depending upon the liquid and viscosity-increasing material employed. For example, one process is p r e f e r a b l y em pl oyed when guar, agar, carboxymethylcellulose, hydroxypropylcellulose, hydroxyethylcellulose and/or polyethyleneoxide (hereinafter collectively referred to as "organic viscosity-increasing materials") are employed. A
slightly different process is employed when fumed silica and/or attapulgite clays (hereinafter collectively referred to as "mineral viscosity-increasiny materials") are employed.
When the organic viscosity-increasing materials are employed, the pH of the composition can be adjusted in order to control the rate in which the viscosity of the fluid increases, i.e. the "viscosity buildup" rate.
Generally, if the pH is lowered, the viscosity buildup will proceed at a slower rate~ A low pH is also advantageous when using certain preservatives in the composition.
~ viscosi-ty~increasiny material is a material which, when mixed with the liquid, increases -the viscosity of the li~uid. Preferred oryanic viscosity-increasing materials fvr use with -the present composition include gums, cellulose-based materials, soluble oxide polymers and other polymers. Preferred viscosity-increasing materials of this type include g u a r , a g a r , h y d r o x y e t h y l c e l l u l o s e , carboxymethylcellulose, hydroxypropylcellulose and polyethyleneoxide. Preferably, the organic viscosity-increasing material is present in an amount from about 0.5 weight percent to about 10 wei~ht percent, and more preferably from about 1 weight percent to about 6 weight percent, and most preferably Erom about 1.2 weight percent -to about ~ weiyht percent. As used herein, all weight percents are based on the total composition weiyht, unless otherwise indicated.
Hydroxyethylcellulose, carboxymethylcellulose and hydroxypropylcellulose, as well as other cellulose-based materials, are available from Aqualon Company of Wilmington, Delaware, U.S.A. Carboxyme-thylcellulose is described in a report entitled "Aqualon (TM) Cellulose Gum, Sodium Carboxylmethylcellulose, Physical and Chemical Properties/' copyright 1988, available from Aqualon Company. ~Iydroxyethylcellulose is described in a report entitled "Na-trosol (TM), Hydroxyethylcellulose, A Mon--Ionic Water-Soluble Polymer, Physical and Chemical Properties,/' revised July 1987, available from Aqualon Company.
When using organic viscosity-increasing materials such as hydroxyethylcellulose with ylycerin, it is prefera~le that the organic material does not include a hydrolyzing retardant layer on its surfac,e, as many commercially available brands do. A hydrolyzing retardant layer slows down the viscosity-increasing process. When glycerin is uti]ized in the composition, the process can become too slow to be practical.
.1~
~ e preerred ~ uids for use toyeth~r with oryanic visco~ity-increasing materials in the presen-t composition include water or a mixture of water and glycerin. An important advantage gained from the use of water is that it increases the flame retardancy of the composition. An important advantage gained from the use of glycerin is that it lowers the freeziny point of the liquid. Additionally, another and important advantage gained from the use of glycerin is that it is much easier to contain within a resinous package, hecause glycerin is not likely to evaporate through the resinous material. An additional advantage gained from the use of glycerin with an organic viscosity-increasing agent is that it provides a "viscosity bonus efect", described below.
According to one embodiment of the present invention, the total liquid content of the composition is between about 20 weight percent and about 75 weight percen-t, more preferably between about 50 weight percent and about 60 weight percent. According to this embodiment, the liquid may consist essentially of water or a mixture of water and glycerin. When the liquid is a mixture of water and glycerin, the glycerin is preferably present in an amount up to about 30 weiyht percent, and more preferably between about 15 weight percent and about 30 weight percent.
According to another embodiment of the present invention, the total liquid content of the composition is between abou-t 50 weight percent and about 76 weight percent, more preferably between about 6~ weight percent and about 70 weight percent. In this embodiment, the composition preferably comprises a higher amount of glycerin. Thus, the glycerin is pre~erably,present in an amount between about 42 weight percent and about 74 weight percent, more preferably between about 57 weight percent and about 69 weight percent. Accordingly, the water is preferably present in an amount between about 1 weight percent and about 8 weight percent, more Z ~'1 ¢~
preferably between about ~ weigh-t percen-t and about 6 weight p~rcent.
Whi:Le the ~orec~oing discussion consti-tutes a descrip-tion of particular preferred embodiments of the present invention, it is to be expressly understood that the present invention includes the use of water and glycerin in any ratio, and tha-t the ratio and total liquid conten-t can be altered to fit the desired purpose.
The behavior of some viscosity-increasing mate rials, su ch as highly subs tituted carboxymethylcellulose, in mixed-solvent systems, such as glycerin-water, ls similar to its behavior in water alone. ~owever, in mixed systems, the viscosity of the solvent affects the viscosity of the solution. For example, if a 60:~0 mixture of glycerin and water (which ; is 10 times as viscous as water alone) is used as the solvent, the resu:Lting solution of well~dispersed carboxymethylcellulose will be ten times as viscous as the comparable solution in water alone. This behavior is commonly referred to as the "viscosity bonus effect./' The organic viscosity-increasing material containiny composition is preferably produced by initially mixing the oryanic viscosity-increasiny material and a por-tion of the glycerin, when glycerin is utilized. This slurry can then be mixed with a second slurry of water and/or glycerin and any remaining ingredients. When water alone is employed as the liquid, a portion o~ the water and the viscosity-increasing material can be mixed to form a first slurry,a second slurry including water and the remainder of the ingredients is prepared, and the two slurries are mixed together. Preferably the mixing is accomplished in a blender using an emulsifier or homogenization head. As will be appreciated by those skilled in the art, other mixing techniques can be employed.
In addition to organic viscosity-increasing materials, it is possible to use mineral viscosity-~r~ r ~2 increasing materials. Preferred mineral viscosity-increas:ing materials include fumed silica, such as Cab-0-Sil M5'~, available from the Cabot Corporation of Tuscola, Illinois, U.S.A~, and attapulyite clays, such as Attayell 40~ or ~ttagell 50'U, both available from the Englehard Corporation of ~t-tapulyus, Georyia, U.S.A.
~dvantages of usillg mineral viscosity-increasing materials include: the materials can be used with ylycerin alone, without any need to employ water; the ; 10 composition can be sealed within a resinous package using heat-sealing techniques which provide good clean seals; and the materials, particularly attapulgite clays, are relatively inexpensive. The advantage of using yly~erin with no added water, is that a composition is obtained having a very low freezing point and in addition, it is much easier to contain ylycerin within a resinous package. Additionally, it has been found that mineral viscosity-increasing materials, particularly attapulgite clay, have relatively stable viscosity charac-teristics over a wide range of temperatures and are not prone to separating duriny use.
The mineral viscosity-increasiny materials are preferably present in an amount from about 2 w~igh-t percent to about 30 weight percent, more preEerably from about 3 weight percent to about 20 weight percent, anA
most preferably from about ~ weight percent to about 15 weiyht percent.
In one embodiment of the present invention, the li~uid consists essentially of ylycerin. The ylycerin is preferably present in an amount from about 25 w~iyht percent to about 75 weight percent, and more preferably in an amount from about 50 weiyht percent to about 74 weight percent. Mineral viscosity-increasing materials are preferably utilized in this embodiment and when fumed silica is employed, it is preferable to also employ a surfactant, e.g. Trithon X 100~.
When mixing the mineral viscosity-increasing materials with the glycerin, it is preferable to mix a 1~ 2~
portion of the ylycerin with the mineral viscosit~~
increasing agen-ts to ~orm an initial slurry and then add the rest of the materials. The mixing can be accomplished using a blender with an emulsifier or a homogenization head. ~lternatively, all of the materials may be mixed together at once.
~ 11 of the viscosity-increasing materials of the presen-t invention have the important characteristic of increasing the viscosity of a fluid, while still permitting the fluid to flow. The typical composition of the present invention is flowable and does not have total memory. In other words, once deformed, it will not always return to its original shape. However, some compositions in accordance with the present invention can exhibit a small degree of gel strength. But the gel structure can be broken merely by applylng sufficient force.
The compositions of the present invention are non-Newtonian, because their viscosities change when the shear rate changes. In o-ther words, the ratio of shear rate (Elow) to shear stress (force) is not constant.
The compositions are typically either pseudoplastic or thixotropic. A pseudoplastic composition is one which appears to have a yield stress beyond which flow commences and increases sharply with increase in stress.
In practice, the compositions exhibit flow at all shear stresses, although the ratio of flow to force increases negligibly until the force exceeds the apparent yield ~ stress. The flow rate of a thixotropic substance increases with increasing duration of agitation as well as with increased shear stress. In other words, the flow rate is time dependent. When agitation is stopped, internal shear stress can exhibit hysteresis. Upon re-agitation, generally less force is required~to create a given flow than is required for the firs~ agitation.
The fact that the present materials flow more readily when higher shear stress is applied is advantageous in a number of applications.
~ ccordincJ -to the present invention, spherlcal particles c~n preferably be added to enhance the propPrt:ies of the composition. However, the use of spherical particles is optional. For example, one embodiment of the present invention includes a liquid ! consisting essentially of glycerin and a mineral viscosity-increaslng material. In this case, it is not necessary to add spherical particles to the composition.
When employed in the present invention, the particles are preferably spherical and hollow to lessen their density and lighten the overall weight of the flowable, pressure~compensating composikion, or, if desired, can be solid or cellular. Expandable microbeads, as described in U.S. Patent Nos. 4,243,754, 4,108,928, and I,038,762 can also be employed.
The spherical particles may be made from a number of suitable materials including for example silica glass, saran polymer, phenolic resin and carbon.
Detailed descriptions of suitable spherical particles can be found in the flowable, pressure-compensating material patents, described hereinabove. Glass beads are pre~erred in certain applications because of their relatively low cost. When higher bead s-trength is desired, phenolic resin or carbon beads are preferred.
When used in compositions where a low total ~eight is desired, the spherical particles are preferably within the size range of from about 10 micrometers to about 300 microme-ters in diameter. The density of spherical particles can be, for example, about 0.05 to about 0.70 grams per cubic centimeter. More particularly, glass spherical particles preferably have a density of from about 0.23 grams pPr cubic centimeter to about 0.37 grams per cubic centimeter ~nd phenolic resin spherical particles preferably have a density o~
about 0.15 grams per cubic centimeter.
Specific examples of suitablP spherical particles include "3M Glass Bubbles" available from 3M, St. Paul, Minneso-ta, U.S.A., and "Mlcroballoons" available from Union Carbide Speci~1-ty Chemicals Division, Danbury, Connec ticut, U.s~ A .
~ I'he spherical particles are preferably present in an amount from about 0.1 to about 32 weight percent based on the total composition weight, ancl more preferably in an amount from about 15 to about 31 weight percent and still more preferably in amount from about 25 weight percent to about 30 weight percent. T h e spherical particles of the present eomposition perform at least two important functions. First, the size, shape and quantity of the spherical partieles influenee the flow characteristics of the composition. Therefore, a eomposition can be tailored to have the desired flow characteristics by selecting the appropriate size, shape 15; and amount of particles. Second, because of particle-to particle contact, the spherical particles can enhance the distribution of loads placed on flexible packages containing the present eomposition.
Another advantage of the spherical partieles employed in the present invention is that they permit a degree of weight control. For example, in most applications, the composition should weigh as little as possible. In such instances, lightweight hollow particles are preferred, in order to lower the overall density of the composition. ~lowever, in some applieations a heavier composition is desired. Examples of such applications would include weight belts to be ~trapped around parts of a person's body (e.g., wrist and ankle weights) and padding devices where it is desired that the device's own weigh-t hold it firmly in place. When heavy compositions are desired, solid particles eomprising dense materials are preferred~ In such applieations, particles greater ! than 300 micrometers in diameter can be used effectively.
When employed in padding deviees, the flowable, pressure-compensating composition is gener~lly enclosed within a flexible, protective enelosure with a pre determined volume of the compositioll retained therein.
.
2~.?~ t~$5 lG
Preferabl.y, -the enclos~lre is formed of suitable flexible materi~l and desirably i5 a pliable, thermoplastic, resinous film th~t c~n be hea-t-sealed after the composition is inserted therewithin. Because of their relatively low cost and desirable strength and flexibility characteristics, polyurethane and polyvinylchloride materials are preferred ~or use as the enclosure film.
The composition is initially distributed substantially uniformly throuyhout the confines of the enclosure, which is provided by sealing (e.g., heat sealing) the film along the marginal edges. If desired, one can choose to heat seal the protective enclosure for the composition, but leave a small vent opening and a small filling port, so that a predetermined volume of the flowable composition may be injected into the enclosure through the filling port, followed by heat sealing both the vent opening and the filling port.
Alterna-tively, the composition may be placed on one sheet, a second sheet may be placed over the composition, and the outer edges sealed. As can be appreciated, internal sealing lines can also be formed to compartmentalize the composition within the enclosure.
One of the advantages of using mineral viscosity-increasing materials such as fumed silica or at-tapulgite clays as the viscosity-increasing material, is that the sealabili.ty of the film packaye is improved. When using cellulose based materials as the viscosity-increasing material, such as hydroxyethylcellulose, the composition may "plate-out" and contaminate t~e seal.
The desired final viscosity of the composition can be selected to suit a wide variety of applications.
Some applications require high viscosity composi-tions and others require compositions of much lower viscosity.
For use in padding devices, viscosities in the range of from about 30,000 centipoise to about 1,0n0,000 centipoise are preEerred. When the viscosity exc~eds 1~ r 000 centipoisc, the composition is often so viscous that separation and non-homogeneity resul-t.
The viscosity of the present compositions is generally provided by hydrogen bonding. This hydrogen bonding is sufficient to keep the spherical particles dispersed throughout the composition. In prior art materials, such as a silicone gel disclosed in U.S.
Patent No. 4,380,569, cross-linking reactions were believed necessary to prevent the microbeads from floating out.
In a preferred embodiment of the present invention, steps are taken in order to prevent microbiological attack and chemical degradation of the present compositions. For example, radiation sterilization can be performed. Preferably, the composition is subjected to radiation such as x-ray radiation or gamma radiation in order to destroy microorganisms present in the composition. An advantage of radiation treatment is that it can be performed after the composition has been placed in a package, such as between pliable sheets of resinous material.
An alternative method useful in preventing microbiological attack is the use of a heat sterilization step. For example, a padding device comprising the present composition placed in a polyvinylchloride package can be heated to about 180F
for more than about 30 mi.nutes, preferably between about 30 and about 45 minutes. Preferably, this method is employed in an autoclave having a nitrogen atmosphere.
Alternatively, preservatives can be added to the composition in order to prevent microbiological attack and chemical degradation. Examples of suitable preservatives include formaldehyde, methyl- and propylparabens, phenol, phenylmercuric salts, sodium benzoate, sodium propionate, sorbic acid and sorbates (sodium and potassium salts). Additionally, proprietary preservatives such as Busan llml, ~5 available from Buckman Laboratory, Dowicide A and Dowicil 75, 200 ~?~ .5 available from Dow Chemical Company, Proxel GXL and CRL
availa~le from :ICI ~mericas Inc., Merbac 35 and Tektamer 38 available from Merk/Calgon Corporation, 'rhimerosal available Erom Eli Lilly and Company and Vancide TH
available ~rom R.T. Vanderbil-t Co., Inc. can be used.
In order to function properly, certain preservatives (e.g. benzoates and sorbates) require a low p~l, i.e., acidic, environment. This can be achieved by adding an acid, e.g. citric acid to the composition.
Citric and/or other desirable acid is added in an amount sufficient to lower the pH to a range of about pH 4 to about pH 6 and preferably about pH 4.5 to about pH 5.5.
In certain instances, such as when silica glass particles are employed, the silica will raise the pH o~
the system. Therefore, more acid is generally necessary to achieve the desired pH range than for a composition not having silica particles. Preferably from about 0.1 weight percent to about 0.5 weight percent benzoate or sorbate is included in the present compositions.
Additionally, flame retardants such as boric oxide (B2O3), boric acid ~B(OH)3), borax (Na2B4O7 10}l2O) or mixtures thereof can be added to the composition, particularly when high levels of glycerin are used.
This is particularly advantageous since the use of glycerin tends to decrease the flame retardancy of the composition. Preferably, flame retardallt is added in an amoun-t from about 5 weiyht percent to about 15 weight percent, more preferably from about 7 weight percent to about ~ weight percent.
In accordance with the present invention, a process for producing the present composition is provided. A
preferred embodiment of the process includes an initial step of producing two slurries. For example, a first slurry of a mineral viscosity-increasing material and i 35 glycerin or a first slurry of organlc viscosity-; increasing material and glycerin can be provided. A
sacond slurry, comprising more liquid, e.g. glycerin and/or water, and, optionally, the spherical particles, 19 Z ~ Jlc~ 5 is then provided. ~ddi-tives such as acid, preservatives ~nd flame retardants can also be mixed with ~his second slurry. At the appropriate time, the two slurries are mixed together. Alternatively, all the components may be mixed together at one time. Mixing can take place in mechanical mixers such as blenders available from Lightnin and Waring. Alternatively, static mixers such as those available from Chemix and from Lightnin can be us~d.
As explained hereinbefore, it can be advantageous to lower the pH of the compositions to a range of about pH 4 to about pH 6. One reason for this is that the rate of viscosity buildup is slower at lower pl-l's for organic viscosity-increasing materials and water. This provides a greater amount of time for working with ~he composition before it fully sets up. For example, when the composition is placed in an enclosure, it is advantageous if the composition maintains a low viscosity for a period of time to allow its insertion 20 into the enclosure. The viscosity buildup rate can also be slowed by using a low temperature liquid and/or by the use of chemical retarders. Alternatively, excess waker can initially be employed to lower the viscosity.
After the composition is placed in the enclosure, the excess water can be allowed to evaporate until the desired viscosity is at-tained.
Examples Five compositions were prepared contalning the following materials:
Composition No. 1 ; Wei~ht Percent Material 54.1 Water 0.9 Citric Acid 0.3 Sorbate (SorbstateW
available from Pfizer . Chemicals) ~$~ ,5 0-3 Sodium Benzoate 27.6 SphQrical Particles (B-37 ~esignation for Glass Bubbles available from 3M~
14.8 Glycerin 2.0 Hydroxyethylcellulose (Natrasol'U available from Aqualon) - , Composition No. 2 Weiqht Percent Material 2.9 Water 0.1 Bactericide (Vancide TH~
available from Vanderbilt Co. ) 23.7 Spherical par-ticles tB-37 designation for Glass ` Bubbles available from 3M) ; 65.5 Glycerin 0.5 Hydroxyethylcellulose (Natrasol'~ available from Aqualon) .9 Borax 2.4 Boric Acid Composition No. 3 Weiyht Percent Material 7.8 Attapulgite Clay (A-ttayel 50~ available from Englehard Corporation) 64.9 Glycerin 19.5 Spherical particles (B-37 : designation for Glass Bubbles available from 3M) 7.8 Boric Oxide tB203) Composition No. ~
Wei~ht Percent Material 74.7 Glycerin J ~
.5 Fumed Silica (Cab-O-Sil M5~ available from Cabot Corporation) 1.5 Surfactant (Trithon X100'~) 519.4 Spherical particles (B-37 designation for Glass Bubbles available from 3M~
Composition No~ 5 Actual Wei~ht (Pounds! Material 100.5 Glycerin 0.2 Fumed Silica (Cab-O-Sil - M5~ available from Cabot Corporation) 0.03 Surfac-tant (I'rithon X100~) 150.04 Borax 0.02 Boric Acid 0.15 Spherical particles ~B-37 for Glass Bubbles from 3M) ~ (Alternatively, 0.06 pounds Boric Oxide could be substituted for the Borax and Boric Acid).
~ 11 five compositions were individually placed within a polyurethane package. The materials prepared according to the above formulations exhibited good uniformity, low separation of ma-terials after a length of time, and low freezing points. Additionally, compositions 3, 4 and 5 exhibited more uniform viscosit.y ovar a period of time due to the fact that the glycerin was effectively main-tained within a resinous package.
While various embodiments of the present invention have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However,lit is to be expressly understood that such modifications and adap-tations are within the spirit and scope of the present invention, as set forth in the following claims.
increasilly the viscosity o~ the liquid. ~he composition may also include substantially spherical particles dispers~d throughout the composition. The liqui~ may include water, glycerin, or mixtures thereof.
~s used herein, the term "glycerinN refers to the trihydric alcohol haviny the chemical formula (C1l2OII~2CIIOH, which is also commonly refer~ed to as glycerol. Although ylycerin is the preferred liquid for use in connection with the present invention, alternative liquids such as other glycerols (i.e., other trihydric alcohols) and glycols (i.e., dihydric alcohols) can also be employed. For the sake of simplicity, the followi2lg description of the invention will refer to glycerin as the preferred liquid, however, it is to be expressly unders-tood that the other li~uids can be used, even thouyh glycerin is preferred.
Glycerin has a hygroscopic nature and may comprise a small amount oE water, e.g. about 4 percent.
When the liquid comprises water, the material for increasing the viscosity of the liquid is preferably selected from the group consisting of guar, agar, carboxymethylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, and polyethyleneoxide. When glycerin is included in the liquid, fumed silica, attapulgite clays and mixtures thereof may also be utilized as a visosity-increasing material. When the liquid is primarily glycerin, the viscosity-increasing material is most preferably an attapulgite clay.
Preferably, substantially spherical particles are also employed in the compositions of the present invention. Preferably, the substantially spherical particles have diameter of less than about 300 micrometers.
A process for producing the flowable, pressure-compensating compositions is also provided. The process ; includes the steps of preparing a slurry comprising a viscosity-increasi2lg material, a liquid and substantially spherical particles, and mixing the components toyether until the viscosity-increasiny agent and the particles are distributed substantially evenly throughout the liquid.
Preferably, the flowable, pressure-compensating composition of the present inven-tion is placed within an enclosure. In a preferred embodiment, the composition is placed between two resinous sheets, which are subsequently heat sealed together. In one embodiment of the invention, the composition is treated to kill microorganisms and prevent their growth. The composition may also include an additive, preferably boric oxide, to increase the flame retardance of the composition.
The present compositions provide a number of advantayes. When wa-ter is used as the primary liquid component, the flame retardancy is greatly increased.
When a flame retardant such as boric oxide (B2O3) is used in the glycerin-containing compositions, they typically have a higher degree of flame retardancy than prior art materials which are oil and/or wax based.
Glycerin has the advantage oE not only lowerin~ the freezing point of the composition, but it also provides a Nviscosity bonus efEect", which is described in more detail hereinbelow, when used with certain viscosity-increasing materials. ~urther, the spherical particlesdispersad throughout the composition are not prone to float -to the top oE the composition (a condition termed "float out"), in spite of being less dense than the remainder of the composition. Also, the viscosities of the present compositions are stable over broad temperature ranges. Furthermore, some of the present composi-tions can have initially low viscosities for limited periods of time to ease workability. This is advantageous when manufacturing padding dPvices because it allows the compositions to be poured into an enclosure which is then sealed. Subsequently, the viscosity of the composition increases to the desired level.
l~etaiL~ escriptioll of -the Illve~tion In accord~nce with the present invention, a ; flowable, pressure-compensatiny composi-tion and process for ma~ing the same is provided.
The composition includes a liquid. The liquid may include water, a dihydric alcohol, a trihydric alcohol, or mixtures thereof. The composition further includes a viscosity-increasing material. Spherical particles may also be dispersed throughout the composition.
Additionally, flame retardants can be added and/or preservatives can be included to prevent microbiological attack and chemical degradation.
The process for producing the present composition generally involves mixing the liquid, the viscosi-ty-! 15 increasing material and, optionally, the sphericalparticles until a homogenous mixture is achieved. The specific process for producing compositions in accordance with the present invention will vary slightly ; depending upon the liquid and viscosity-increasing material employed. For example, one process is p r e f e r a b l y em pl oyed when guar, agar, carboxymethylcellulose, hydroxypropylcellulose, hydroxyethylcellulose and/or polyethyleneoxide (hereinafter collectively referred to as "organic viscosity-increasing materials") are employed. A
slightly different process is employed when fumed silica and/or attapulgite clays (hereinafter collectively referred to as "mineral viscosity-increasiny materials") are employed.
When the organic viscosity-increasing materials are employed, the pH of the composition can be adjusted in order to control the rate in which the viscosity of the fluid increases, i.e. the "viscosity buildup" rate.
Generally, if the pH is lowered, the viscosity buildup will proceed at a slower rate~ A low pH is also advantageous when using certain preservatives in the composition.
~ viscosi-ty~increasiny material is a material which, when mixed with the liquid, increases -the viscosity of the li~uid. Preferred oryanic viscosity-increasing materials fvr use with -the present composition include gums, cellulose-based materials, soluble oxide polymers and other polymers. Preferred viscosity-increasing materials of this type include g u a r , a g a r , h y d r o x y e t h y l c e l l u l o s e , carboxymethylcellulose, hydroxypropylcellulose and polyethyleneoxide. Preferably, the organic viscosity-increasing material is present in an amount from about 0.5 weight percent to about 10 wei~ht percent, and more preferably from about 1 weight percent to about 6 weight percent, and most preferably Erom about 1.2 weight percent -to about ~ weiyht percent. As used herein, all weight percents are based on the total composition weiyht, unless otherwise indicated.
Hydroxyethylcellulose, carboxymethylcellulose and hydroxypropylcellulose, as well as other cellulose-based materials, are available from Aqualon Company of Wilmington, Delaware, U.S.A. Carboxyme-thylcellulose is described in a report entitled "Aqualon (TM) Cellulose Gum, Sodium Carboxylmethylcellulose, Physical and Chemical Properties/' copyright 1988, available from Aqualon Company. ~Iydroxyethylcellulose is described in a report entitled "Na-trosol (TM), Hydroxyethylcellulose, A Mon--Ionic Water-Soluble Polymer, Physical and Chemical Properties,/' revised July 1987, available from Aqualon Company.
When using organic viscosity-increasing materials such as hydroxyethylcellulose with ylycerin, it is prefera~le that the organic material does not include a hydrolyzing retardant layer on its surfac,e, as many commercially available brands do. A hydrolyzing retardant layer slows down the viscosity-increasing process. When glycerin is uti]ized in the composition, the process can become too slow to be practical.
.1~
~ e preerred ~ uids for use toyeth~r with oryanic visco~ity-increasing materials in the presen-t composition include water or a mixture of water and glycerin. An important advantage gained from the use of water is that it increases the flame retardancy of the composition. An important advantage gained from the use of glycerin is that it lowers the freeziny point of the liquid. Additionally, another and important advantage gained from the use of glycerin is that it is much easier to contain within a resinous package, hecause glycerin is not likely to evaporate through the resinous material. An additional advantage gained from the use of glycerin with an organic viscosity-increasing agent is that it provides a "viscosity bonus efect", described below.
According to one embodiment of the present invention, the total liquid content of the composition is between about 20 weight percent and about 75 weight percen-t, more preferably between about 50 weight percent and about 60 weight percent. According to this embodiment, the liquid may consist essentially of water or a mixture of water and glycerin. When the liquid is a mixture of water and glycerin, the glycerin is preferably present in an amount up to about 30 weiyht percent, and more preferably between about 15 weight percent and about 30 weight percent.
According to another embodiment of the present invention, the total liquid content of the composition is between abou-t 50 weight percent and about 76 weight percent, more preferably between about 6~ weight percent and about 70 weight percent. In this embodiment, the composition preferably comprises a higher amount of glycerin. Thus, the glycerin is pre~erably,present in an amount between about 42 weight percent and about 74 weight percent, more preferably between about 57 weight percent and about 69 weight percent. Accordingly, the water is preferably present in an amount between about 1 weight percent and about 8 weight percent, more Z ~'1 ¢~
preferably between about ~ weigh-t percen-t and about 6 weight p~rcent.
Whi:Le the ~orec~oing discussion consti-tutes a descrip-tion of particular preferred embodiments of the present invention, it is to be expressly understood that the present invention includes the use of water and glycerin in any ratio, and tha-t the ratio and total liquid conten-t can be altered to fit the desired purpose.
The behavior of some viscosity-increasing mate rials, su ch as highly subs tituted carboxymethylcellulose, in mixed-solvent systems, such as glycerin-water, ls similar to its behavior in water alone. ~owever, in mixed systems, the viscosity of the solvent affects the viscosity of the solution. For example, if a 60:~0 mixture of glycerin and water (which ; is 10 times as viscous as water alone) is used as the solvent, the resu:Lting solution of well~dispersed carboxymethylcellulose will be ten times as viscous as the comparable solution in water alone. This behavior is commonly referred to as the "viscosity bonus effect./' The organic viscosity-increasing material containiny composition is preferably produced by initially mixing the oryanic viscosity-increasiny material and a por-tion of the glycerin, when glycerin is utilized. This slurry can then be mixed with a second slurry of water and/or glycerin and any remaining ingredients. When water alone is employed as the liquid, a portion o~ the water and the viscosity-increasing material can be mixed to form a first slurry,a second slurry including water and the remainder of the ingredients is prepared, and the two slurries are mixed together. Preferably the mixing is accomplished in a blender using an emulsifier or homogenization head. As will be appreciated by those skilled in the art, other mixing techniques can be employed.
In addition to organic viscosity-increasing materials, it is possible to use mineral viscosity-~r~ r ~2 increasing materials. Preferred mineral viscosity-increas:ing materials include fumed silica, such as Cab-0-Sil M5'~, available from the Cabot Corporation of Tuscola, Illinois, U.S.A~, and attapulyite clays, such as Attayell 40~ or ~ttagell 50'U, both available from the Englehard Corporation of ~t-tapulyus, Georyia, U.S.A.
~dvantages of usillg mineral viscosity-increasing materials include: the materials can be used with ylycerin alone, without any need to employ water; the ; 10 composition can be sealed within a resinous package using heat-sealing techniques which provide good clean seals; and the materials, particularly attapulgite clays, are relatively inexpensive. The advantage of using yly~erin with no added water, is that a composition is obtained having a very low freezing point and in addition, it is much easier to contain ylycerin within a resinous package. Additionally, it has been found that mineral viscosity-increasing materials, particularly attapulgite clay, have relatively stable viscosity charac-teristics over a wide range of temperatures and are not prone to separating duriny use.
The mineral viscosity-increasiny materials are preferably present in an amount from about 2 w~igh-t percent to about 30 weight percent, more preEerably from about 3 weight percent to about 20 weight percent, anA
most preferably from about ~ weight percent to about 15 weiyht percent.
In one embodiment of the present invention, the li~uid consists essentially of ylycerin. The ylycerin is preferably present in an amount from about 25 w~iyht percent to about 75 weight percent, and more preferably in an amount from about 50 weiyht percent to about 74 weight percent. Mineral viscosity-increasing materials are preferably utilized in this embodiment and when fumed silica is employed, it is preferable to also employ a surfactant, e.g. Trithon X 100~.
When mixing the mineral viscosity-increasing materials with the glycerin, it is preferable to mix a 1~ 2~
portion of the ylycerin with the mineral viscosit~~
increasing agen-ts to ~orm an initial slurry and then add the rest of the materials. The mixing can be accomplished using a blender with an emulsifier or a homogenization head. ~lternatively, all of the materials may be mixed together at once.
~ 11 of the viscosity-increasing materials of the presen-t invention have the important characteristic of increasing the viscosity of a fluid, while still permitting the fluid to flow. The typical composition of the present invention is flowable and does not have total memory. In other words, once deformed, it will not always return to its original shape. However, some compositions in accordance with the present invention can exhibit a small degree of gel strength. But the gel structure can be broken merely by applylng sufficient force.
The compositions of the present invention are non-Newtonian, because their viscosities change when the shear rate changes. In o-ther words, the ratio of shear rate (Elow) to shear stress (force) is not constant.
The compositions are typically either pseudoplastic or thixotropic. A pseudoplastic composition is one which appears to have a yield stress beyond which flow commences and increases sharply with increase in stress.
In practice, the compositions exhibit flow at all shear stresses, although the ratio of flow to force increases negligibly until the force exceeds the apparent yield ~ stress. The flow rate of a thixotropic substance increases with increasing duration of agitation as well as with increased shear stress. In other words, the flow rate is time dependent. When agitation is stopped, internal shear stress can exhibit hysteresis. Upon re-agitation, generally less force is required~to create a given flow than is required for the firs~ agitation.
The fact that the present materials flow more readily when higher shear stress is applied is advantageous in a number of applications.
~ ccordincJ -to the present invention, spherlcal particles c~n preferably be added to enhance the propPrt:ies of the composition. However, the use of spherical particles is optional. For example, one embodiment of the present invention includes a liquid ! consisting essentially of glycerin and a mineral viscosity-increaslng material. In this case, it is not necessary to add spherical particles to the composition.
When employed in the present invention, the particles are preferably spherical and hollow to lessen their density and lighten the overall weight of the flowable, pressure~compensating composikion, or, if desired, can be solid or cellular. Expandable microbeads, as described in U.S. Patent Nos. 4,243,754, 4,108,928, and I,038,762 can also be employed.
The spherical particles may be made from a number of suitable materials including for example silica glass, saran polymer, phenolic resin and carbon.
Detailed descriptions of suitable spherical particles can be found in the flowable, pressure-compensating material patents, described hereinabove. Glass beads are pre~erred in certain applications because of their relatively low cost. When higher bead s-trength is desired, phenolic resin or carbon beads are preferred.
When used in compositions where a low total ~eight is desired, the spherical particles are preferably within the size range of from about 10 micrometers to about 300 microme-ters in diameter. The density of spherical particles can be, for example, about 0.05 to about 0.70 grams per cubic centimeter. More particularly, glass spherical particles preferably have a density of from about 0.23 grams pPr cubic centimeter to about 0.37 grams per cubic centimeter ~nd phenolic resin spherical particles preferably have a density o~
about 0.15 grams per cubic centimeter.
Specific examples of suitablP spherical particles include "3M Glass Bubbles" available from 3M, St. Paul, Minneso-ta, U.S.A., and "Mlcroballoons" available from Union Carbide Speci~1-ty Chemicals Division, Danbury, Connec ticut, U.s~ A .
~ I'he spherical particles are preferably present in an amount from about 0.1 to about 32 weight percent based on the total composition weight, ancl more preferably in an amount from about 15 to about 31 weight percent and still more preferably in amount from about 25 weight percent to about 30 weight percent. T h e spherical particles of the present eomposition perform at least two important functions. First, the size, shape and quantity of the spherical partieles influenee the flow characteristics of the composition. Therefore, a eomposition can be tailored to have the desired flow characteristics by selecting the appropriate size, shape 15; and amount of particles. Second, because of particle-to particle contact, the spherical particles can enhance the distribution of loads placed on flexible packages containing the present eomposition.
Another advantage of the spherical partieles employed in the present invention is that they permit a degree of weight control. For example, in most applications, the composition should weigh as little as possible. In such instances, lightweight hollow particles are preferred, in order to lower the overall density of the composition. ~lowever, in some applieations a heavier composition is desired. Examples of such applications would include weight belts to be ~trapped around parts of a person's body (e.g., wrist and ankle weights) and padding devices where it is desired that the device's own weigh-t hold it firmly in place. When heavy compositions are desired, solid particles eomprising dense materials are preferred~ In such applieations, particles greater ! than 300 micrometers in diameter can be used effectively.
When employed in padding deviees, the flowable, pressure-compensating composition is gener~lly enclosed within a flexible, protective enelosure with a pre determined volume of the compositioll retained therein.
.
2~.?~ t~$5 lG
Preferabl.y, -the enclos~lre is formed of suitable flexible materi~l and desirably i5 a pliable, thermoplastic, resinous film th~t c~n be hea-t-sealed after the composition is inserted therewithin. Because of their relatively low cost and desirable strength and flexibility characteristics, polyurethane and polyvinylchloride materials are preferred ~or use as the enclosure film.
The composition is initially distributed substantially uniformly throuyhout the confines of the enclosure, which is provided by sealing (e.g., heat sealing) the film along the marginal edges. If desired, one can choose to heat seal the protective enclosure for the composition, but leave a small vent opening and a small filling port, so that a predetermined volume of the flowable composition may be injected into the enclosure through the filling port, followed by heat sealing both the vent opening and the filling port.
Alterna-tively, the composition may be placed on one sheet, a second sheet may be placed over the composition, and the outer edges sealed. As can be appreciated, internal sealing lines can also be formed to compartmentalize the composition within the enclosure.
One of the advantages of using mineral viscosity-increasing materials such as fumed silica or at-tapulgite clays as the viscosity-increasing material, is that the sealabili.ty of the film packaye is improved. When using cellulose based materials as the viscosity-increasing material, such as hydroxyethylcellulose, the composition may "plate-out" and contaminate t~e seal.
The desired final viscosity of the composition can be selected to suit a wide variety of applications.
Some applications require high viscosity composi-tions and others require compositions of much lower viscosity.
For use in padding devices, viscosities in the range of from about 30,000 centipoise to about 1,0n0,000 centipoise are preEerred. When the viscosity exc~eds 1~ r 000 centipoisc, the composition is often so viscous that separation and non-homogeneity resul-t.
The viscosity of the present compositions is generally provided by hydrogen bonding. This hydrogen bonding is sufficient to keep the spherical particles dispersed throughout the composition. In prior art materials, such as a silicone gel disclosed in U.S.
Patent No. 4,380,569, cross-linking reactions were believed necessary to prevent the microbeads from floating out.
In a preferred embodiment of the present invention, steps are taken in order to prevent microbiological attack and chemical degradation of the present compositions. For example, radiation sterilization can be performed. Preferably, the composition is subjected to radiation such as x-ray radiation or gamma radiation in order to destroy microorganisms present in the composition. An advantage of radiation treatment is that it can be performed after the composition has been placed in a package, such as between pliable sheets of resinous material.
An alternative method useful in preventing microbiological attack is the use of a heat sterilization step. For example, a padding device comprising the present composition placed in a polyvinylchloride package can be heated to about 180F
for more than about 30 mi.nutes, preferably between about 30 and about 45 minutes. Preferably, this method is employed in an autoclave having a nitrogen atmosphere.
Alternatively, preservatives can be added to the composition in order to prevent microbiological attack and chemical degradation. Examples of suitable preservatives include formaldehyde, methyl- and propylparabens, phenol, phenylmercuric salts, sodium benzoate, sodium propionate, sorbic acid and sorbates (sodium and potassium salts). Additionally, proprietary preservatives such as Busan llml, ~5 available from Buckman Laboratory, Dowicide A and Dowicil 75, 200 ~?~ .5 available from Dow Chemical Company, Proxel GXL and CRL
availa~le from :ICI ~mericas Inc., Merbac 35 and Tektamer 38 available from Merk/Calgon Corporation, 'rhimerosal available Erom Eli Lilly and Company and Vancide TH
available ~rom R.T. Vanderbil-t Co., Inc. can be used.
In order to function properly, certain preservatives (e.g. benzoates and sorbates) require a low p~l, i.e., acidic, environment. This can be achieved by adding an acid, e.g. citric acid to the composition.
Citric and/or other desirable acid is added in an amount sufficient to lower the pH to a range of about pH 4 to about pH 6 and preferably about pH 4.5 to about pH 5.5.
In certain instances, such as when silica glass particles are employed, the silica will raise the pH o~
the system. Therefore, more acid is generally necessary to achieve the desired pH range than for a composition not having silica particles. Preferably from about 0.1 weight percent to about 0.5 weight percent benzoate or sorbate is included in the present compositions.
Additionally, flame retardants such as boric oxide (B2O3), boric acid ~B(OH)3), borax (Na2B4O7 10}l2O) or mixtures thereof can be added to the composition, particularly when high levels of glycerin are used.
This is particularly advantageous since the use of glycerin tends to decrease the flame retardancy of the composition. Preferably, flame retardallt is added in an amoun-t from about 5 weiyht percent to about 15 weight percent, more preferably from about 7 weight percent to about ~ weight percent.
In accordance with the present invention, a process for producing the present composition is provided. A
preferred embodiment of the process includes an initial step of producing two slurries. For example, a first slurry of a mineral viscosity-increasing material and i 35 glycerin or a first slurry of organlc viscosity-; increasing material and glycerin can be provided. A
sacond slurry, comprising more liquid, e.g. glycerin and/or water, and, optionally, the spherical particles, 19 Z ~ Jlc~ 5 is then provided. ~ddi-tives such as acid, preservatives ~nd flame retardants can also be mixed with ~his second slurry. At the appropriate time, the two slurries are mixed together. Alternatively, all the components may be mixed together at one time. Mixing can take place in mechanical mixers such as blenders available from Lightnin and Waring. Alternatively, static mixers such as those available from Chemix and from Lightnin can be us~d.
As explained hereinbefore, it can be advantageous to lower the pH of the compositions to a range of about pH 4 to about pH 6. One reason for this is that the rate of viscosity buildup is slower at lower pl-l's for organic viscosity-increasing materials and water. This provides a greater amount of time for working with ~he composition before it fully sets up. For example, when the composition is placed in an enclosure, it is advantageous if the composition maintains a low viscosity for a period of time to allow its insertion 20 into the enclosure. The viscosity buildup rate can also be slowed by using a low temperature liquid and/or by the use of chemical retarders. Alternatively, excess waker can initially be employed to lower the viscosity.
After the composition is placed in the enclosure, the excess water can be allowed to evaporate until the desired viscosity is at-tained.
Examples Five compositions were prepared contalning the following materials:
Composition No. 1 ; Wei~ht Percent Material 54.1 Water 0.9 Citric Acid 0.3 Sorbate (SorbstateW
available from Pfizer . Chemicals) ~$~ ,5 0-3 Sodium Benzoate 27.6 SphQrical Particles (B-37 ~esignation for Glass Bubbles available from 3M~
14.8 Glycerin 2.0 Hydroxyethylcellulose (Natrasol'U available from Aqualon) - , Composition No. 2 Weiqht Percent Material 2.9 Water 0.1 Bactericide (Vancide TH~
available from Vanderbilt Co. ) 23.7 Spherical par-ticles tB-37 designation for Glass ` Bubbles available from 3M) ; 65.5 Glycerin 0.5 Hydroxyethylcellulose (Natrasol'~ available from Aqualon) .9 Borax 2.4 Boric Acid Composition No. 3 Weiyht Percent Material 7.8 Attapulgite Clay (A-ttayel 50~ available from Englehard Corporation) 64.9 Glycerin 19.5 Spherical particles (B-37 : designation for Glass Bubbles available from 3M) 7.8 Boric Oxide tB203) Composition No. ~
Wei~ht Percent Material 74.7 Glycerin J ~
.5 Fumed Silica (Cab-O-Sil M5~ available from Cabot Corporation) 1.5 Surfactant (Trithon X100'~) 519.4 Spherical particles (B-37 designation for Glass Bubbles available from 3M~
Composition No~ 5 Actual Wei~ht (Pounds! Material 100.5 Glycerin 0.2 Fumed Silica (Cab-O-Sil - M5~ available from Cabot Corporation) 0.03 Surfac-tant (I'rithon X100~) 150.04 Borax 0.02 Boric Acid 0.15 Spherical particles ~B-37 for Glass Bubbles from 3M) ~ (Alternatively, 0.06 pounds Boric Oxide could be substituted for the Borax and Boric Acid).
~ 11 five compositions were individually placed within a polyurethane package. The materials prepared according to the above formulations exhibited good uniformity, low separation of ma-terials after a length of time, and low freezing points. Additionally, compositions 3, 4 and 5 exhibited more uniform viscosit.y ovar a period of time due to the fact that the glycerin was effectively main-tained within a resinous package.
While various embodiments of the present invention have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However,lit is to be expressly understood that such modifications and adap-tations are within the spirit and scope of the present invention, as set forth in the following claims.
Claims (50)
1. A flowable, pressure-compensating composition, comprising:
a) a liquid selected from the group consisting of water, dihydric alcohol, trihydric alcohol, and mixtures thereof;
b) a material for increasing the viscosity of the liquid; and c) substantially spherical particles.
a) a liquid selected from the group consisting of water, dihydric alcohol, trihydric alcohol, and mixtures thereof;
b) a material for increasing the viscosity of the liquid; and c) substantially spherical particles.
2. A flowable, pressure-compensating composition as recited in Claim 1, wherein said material is a mineral viscosity-increasing material.
3. A flowable, pressure-compensating composition as recited in Claim 2, wherein said material is present in an amount from about 2 weight percent to about 30 weight percent.
4. A flowable, pressure-compensating composition as recited in Claim 2, wherein said mineral viscosity-increasing material is selected from the group consisting of fumed silica, attapulgite clays and mixtures thereof.
5. A flowable, pressure-compensating composition as recited in Claim 1, comprising:
a) between about 25 weight percent and about 75 weight percent glycerin;
b) between about 2 weight percent and about 30 weight percent of a mineral viscosity-increasing material; and c) between about 0.1 weight percent and about 32 weight percent substantially spherical particles.
a) between about 25 weight percent and about 75 weight percent glycerin;
b) between about 2 weight percent and about 30 weight percent of a mineral viscosity-increasing material; and c) between about 0.1 weight percent and about 32 weight percent substantially spherical particles.
6. A flowable, pressure-compensating composition as recited in Claim 1, wherein said material is an organic viscosity-increasing material.
7. A flowable, pressure-compensating composition as recited in Claim 6, wherein said organic viscosity-increasing material is selected from the group consisting of gums, cellulose-based materials, soluble oxide polymers and mixtures thereof.
8. A flowable, pressure-compensating composition as recited in Claim 6, wherein said organic viscosity-increasing material is selected from the group consisting of guar, agar, carboxymethylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, polyethyleneoxide, and mixtures thereof.
9. A flowable, pressure-compensating composition as recited in Claim 1, comprising:
a) between about 42 weight percent and about 74 weight percent glycerin;
b) between about 1 weight percent and about 8 weight percent water;
c) between about 0.5 weight percent and about 10 weight percent of an organic viscosity-increasing material; and d) between about 0.1 weight percent and about 32 weight percent substantially spherical particles.
a) between about 42 weight percent and about 74 weight percent glycerin;
b) between about 1 weight percent and about 8 weight percent water;
c) between about 0.5 weight percent and about 10 weight percent of an organic viscosity-increasing material; and d) between about 0.1 weight percent and about 32 weight percent substantially spherical particles.
10. A flowable, pressure compensating composition as recited in Claim 1, comprising:
a) between about 20 weight percent and about 75 weight percent water;
b) up to about 30 weight percent glycerin;
c) between about 0.5 weight percent and about 10 weight percent of an organic viscosity-increasing agent;
and d) between about 0.1 weight percent and about 32 weight percent substantially spherical particles;
wherein the total liquid content comprises between about 20 weight percent and about 75 weight percent of the total composition.
a) between about 20 weight percent and about 75 weight percent water;
b) up to about 30 weight percent glycerin;
c) between about 0.5 weight percent and about 10 weight percent of an organic viscosity-increasing agent;
and d) between about 0.1 weight percent and about 32 weight percent substantially spherical particles;
wherein the total liquid content comprises between about 20 weight percent and about 75 weight percent of the total composition.
11. A flowable, pressure-compensating composition as recited in Claim 1, wherein said liquid consists essentially of between about 20 weight percent and about 75 weight percent water.
12. A flowable, pressure-compensating composition as recited in Claim 1, further comprising a flame retardant.
13. A flowable, pressure-compensating composition as recited in Claim 12, wherein said flame retardant is selected from the group consisting of boric oxide, boric acid, borax and mixtures thereof.
14. A flowable, pressure-compensating composition as recited in Claim 1, further comprising an outer enclosure for containing said composition.
15. A flowable, pressure-compensating composition as recited in Claim 1 further comprising a preservative.
16. A flowable, pressure-compensating composition as recited in Claim 1, wherein said composition has been treated to kill microorganisms contained therein.
17. A padding device comprising a flexible enclosure and a flowable, pressure-compensating composition substantially filling said enclosure, said flowable, pressure-compensating composition comprising:
a) a liquid selected from the group consisting of water, dihydric alcohol, trihydric alcohol, and mixtures thereof; and b) a material for increasing the viscosity of the liquid.
a) a liquid selected from the group consisting of water, dihydric alcohol, trihydric alcohol, and mixtures thereof; and b) a material for increasing the viscosity of the liquid.
18. A padding device as recited in Claim 17, wherein said flowable, pressure-compensating composition further comprises substantially spherical particles in an amount from about 0.1 weight percent to about 32 weight percent.
19. A padding device as recited in Claim 17, wherein said flowable, pressure-compensating composition comprises:
a) between about 20 weight percent and about 75 weight percent water; and b) between about 0.5 weight percent and about 10 weight percent of an organic viscosity-increasing material.
a) between about 20 weight percent and about 75 weight percent water; and b) between about 0.5 weight percent and about 10 weight percent of an organic viscosity-increasing material.
20. A padding device as recited in Claim 19, wherein said composition further comprises between about 15 weight percent and about 30 weight percent glycerin.
21. A padding device as recited in Claim 17, wherein said flowable, pressure-compensating composition comprises:
a) between about 25 weight percent and about 75 weight percent glycerin; and b) between about 2 weight percent and about 30 weight percent of a mineral viscosity-increasing material.
a) between about 25 weight percent and about 75 weight percent glycerin; and b) between about 2 weight percent and about 30 weight percent of a mineral viscosity-increasing material.
22. A padding device as recited in Claim 21, wherein said flowable, pressure-compensating composition further comprises between about 15 weight percent and about 31 weight percent of substantially spherical particles having a diameter less than about 300 micrometers.
23. A padding device as recited in Claim 21, wherein said flowable, pressure-compensating composition further comprises between about 5 weight percent and about 15 weight percent of a flame retardant.
24. A padding device as recited in Claim 17, wherein said flowable, pressure-compensating composition comprises:
a) between about 42 weight percent and about 74 weight percent glycerin;
b) between about 1 weight percent and about 8 weight percent water;
c) between about 0.5 weight percent and about 10 percent of an organic viscosity-increasing material; and d) between about 5 weight percent and about 15 weight percent of a flame retardant.
a) between about 42 weight percent and about 74 weight percent glycerin;
b) between about 1 weight percent and about 8 weight percent water;
c) between about 0.5 weight percent and about 10 percent of an organic viscosity-increasing material; and d) between about 5 weight percent and about 15 weight percent of a flame retardant.
25. A process for producing a flowable, pressure-compensating composition, comprising the steps of:
a) preparing a first slurry comprising a liquid and a viscosity-increasing material;
b) preparing a second slurry comprising substantially spherical particles; and c) mixing said first slurry and said second slurry until said material and said spherical particles are distributed throughout said liquid.
a) preparing a first slurry comprising a liquid and a viscosity-increasing material;
b) preparing a second slurry comprising substantially spherical particles; and c) mixing said first slurry and said second slurry until said material and said spherical particles are distributed throughout said liquid.
26. A process as recited in Claim 25, wherein said first slurry comprises glycerin and a mineral viscosity-increasing material.
27. A process as recited in Claim 26, wherein said mineral viscosity-increasing material is selected from the group consisting of fumed silica and attapulgite clays.
28. A process as recited in Claim 25, wherein said first slurry comprises glycerin and an organic viscosity-increasing material.
29. A process as recited in Claim 25, wherein said second slurry comprises water and said viscosity-increasing material is selected from the group consisting of gums, cellulose-based materials, soluble oxide polymers, and mixtures thereof.
30. A process as recited in Claim 28, wherein said organic viscosity-increasing material is selected from the group consisting of guar, agar, carboxymethylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, polyethyleneoxide, and mixtures thereof.
31. A process as recited in Claim 25, further comprising the step of adding a preservative.
32. A process as recited in Claim 25, further comprising the step of sealing said pressure-compensating composition within an enclosure.
33. A process as recited in Claim 25, further comprising a step of treating said composition to kill microorganisms contained within said composition.
34. A process as recited in Claim 25, wherein said second slurry further comprises a flame retardant.
35. A flowable, pressure-compensating composition, comprising:
a) between about 50 weight percent and about 60 weight percent water;
b) between about 1 weight percent and about 6 weight percent of an organic viscosity-increasing material; and c) between about 15 weight percent and about 31 weight percent substantially spherical particles.
a) between about 50 weight percent and about 60 weight percent water;
b) between about 1 weight percent and about 6 weight percent of an organic viscosity-increasing material; and c) between about 15 weight percent and about 31 weight percent substantially spherical particles.
36. A flowable, pressure-compensating composition as recited in Claim 35, further comprising an outer enclosure for containing said composition.
37. A flowable, pressure-compensating composition, comprising:
a) between about 20 weight percent and about 60 weight percent water;
b) up to about 30 weight percent glycerin;
c) between about 1 weight percent and about 6 weight percent of an organic viscosity-increasing material; and d) between about 15 weight percent and about 31 weight percent substantially spherical particles.
a) between about 20 weight percent and about 60 weight percent water;
b) up to about 30 weight percent glycerin;
c) between about 1 weight percent and about 6 weight percent of an organic viscosity-increasing material; and d) between about 15 weight percent and about 31 weight percent substantially spherical particles.
38. A flowable, pressure-compensating composition as recited in Claim 37, further comprising an outer enclosure for containing said composition.
39. A flowable, pressure-compensating composition, comprising:
a) between about 2 weight percent and about 6 weight percent water;
b) between about 57 weight percent and about 69 weight percent glycerin;
c) between about 1 weight percent and about 6 weight percent of a viscosity-increasing material; and d) between about 15 weight percent and about 31 weight percent substantially spherical particles.
a) between about 2 weight percent and about 6 weight percent water;
b) between about 57 weight percent and about 69 weight percent glycerin;
c) between about 1 weight percent and about 6 weight percent of a viscosity-increasing material; and d) between about 15 weight percent and about 31 weight percent substantially spherical particles.
40. A flowable, pressure-compensating composition as recited in Claim 39, further comprising an outer enclosure for containing said composition.
41. A flowable, pressure-compensating composition as recited in Claim 39, further comprising between about 5 weight percent and about 15 weight percent of a flame retardant.
42. A flowable, pressure-compensating composition, comprising:
a) between about 42 weight percent and about 7 weight percent glycerin;
b) between about 3 weight percent and about 20 weight percent of a viscosity-increasing material; and c) a flame retardant.
a) between about 42 weight percent and about 7 weight percent glycerin;
b) between about 3 weight percent and about 20 weight percent of a viscosity-increasing material; and c) a flame retardant.
43. A flowable, pressure-compensating composition, as recited in Claim 42, further comprising between about weight percent and about 31 weight percent substantially spherical particles.
44. A flowable, pressure-compensating composition, as recited in Claim 42, comprising between about 5 weight percent and about 15 weight percent of said flame retardant.
45. A flowable, pressure-compensating composition, as recited in Claim 42, further comprising between about 1 weight percent and about 8 weight percent water.
46. A flowable, pressure-compensating composition as recited in Claim 42, wherein said viscosity-increasing material is an organic viscosity-increasing material.
47. A flowable, pressure-compensating composition as recited in Claim 42, wherein said viscosity increasing material is a mineral viscosity-increasing material.
48. A flowable, pressure compensating composition as recited in Claim 42 further comprising an outer enclosure for containing said composition.
49. A flowable, pressure-compensating composition, comprising:
a) between about 50 weight percent and about 7 weight percent glycerin;
b) between about 4 weight percent and about 15 weight percent of a mineral viscosity increasing agent;
and c) between about 5 weight percent and about 15 weight percent of a flame retardant.
a) between about 50 weight percent and about 7 weight percent glycerin;
b) between about 4 weight percent and about 15 weight percent of a mineral viscosity increasing agent;
and c) between about 5 weight percent and about 15 weight percent of a flame retardant.
50. A flowable, pressure-compensating composition as recited in Claim 49, further comprising between about weight percent and about 31 weight percent substantially spherical particles.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US410,610 | 1989-09-21 | ||
| US07/410,610 US5100712A (en) | 1989-09-21 | 1989-09-21 | Flowable, pressure-compensating material and process for producing same |
| US53734490A | 1990-06-13 | 1990-06-13 | |
| US537,344 | 1990-06-13 | ||
| US07/573,452 US5093138A (en) | 1989-09-21 | 1990-08-27 | Glycerin-containing flowable, pressure-compensating material and process for producing same |
| US573,452 | 1990-08-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2066685A1 true CA2066685A1 (en) | 1991-03-22 |
Family
ID=27410857
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002066685A Abandoned CA2066685A1 (en) | 1989-09-21 | 1990-09-21 | Flowable, pressure-compensating material and process for producing same |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0493505A4 (en) |
| AU (1) | AU6513690A (en) |
| CA (1) | CA2066685A1 (en) |
| WO (1) | WO1991004290A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5362543A (en) * | 1993-02-23 | 1994-11-08 | Jay Medical, Ltd. | Pressure-compensating compositions and pads made therefrom |
| US5421874A (en) * | 1993-06-22 | 1995-06-06 | Genesis Composites, L.C. | Composite microsphere and lubricant mixture |
| US8932692B2 (en) | 2008-10-03 | 2015-01-13 | Edizone, Llc | Cushions comprising deformable members and related methods |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3810265A (en) * | 1971-08-04 | 1974-05-14 | Castleman C | Viscosity control additive for water beds and other aqueous-filled furniture |
| US4243754A (en) * | 1978-09-05 | 1981-01-06 | Hanson Industries Incorporated | Viscous, flowable, pressure-compensating fitting compositions |
| EP0045185A1 (en) * | 1980-07-25 | 1982-02-03 | Hempex Corporation | Tyre sealing and balancing composition |
| US4534767A (en) * | 1980-09-08 | 1985-08-13 | Hollister Incorporated | Protective sealing composition in molded form |
| US4664909A (en) * | 1980-12-29 | 1987-05-12 | Colgate-Palmolive Company | Stable suspension of powder in alcoholic media |
| US4748978A (en) * | 1984-09-27 | 1988-06-07 | Kamp Herman F | Therapeutic dressing having mineral components |
-
1990
- 1990-09-21 AU AU65136/90A patent/AU6513690A/en not_active Abandoned
- 1990-09-21 EP EP19900914868 patent/EP0493505A4/en not_active Withdrawn
- 1990-09-21 CA CA002066685A patent/CA2066685A1/en not_active Abandoned
- 1990-09-21 WO PCT/US1990/005399 patent/WO1991004290A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| WO1991004290A1 (en) | 1991-04-04 |
| EP0493505A1 (en) | 1992-07-08 |
| AU6513690A (en) | 1991-04-18 |
| EP0493505A4 (en) | 1993-01-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 19980921 |