Cushion Structure

Abstract

An improved gel-type cushion structure comprising a polyvinylchloride gel containing from approximately 6 to 14 parts by weight of plasticizer for each part by weight of high molecular weight polyvinylchloride resin. Preferably, the cushion structure includes approximately 9 parts by weight of plasticizer for each part by weight of high molecular weight polyvinylchloride resin together with an effective amount of suitable vinyl stabilizers.

Description

The present invention generally relates to improved gel-type seat and body cushions, mattresses and the like. More particularly, this invention is directed to cushions composed of a polyvinylchloride gel.

The gel pads of the present invention are particularly suited for use as wheelchair seat cushions and mattresses which are intended for use by patients confined to wheelchairs or beds for substantial periods of time. It is important to note, however, that these novel gel pads also find advantageous utility in general body-support cushioning applications such as, for example, automobile and furniture cushions.

In the past, cushion structures of the so-called inner spring, foam rubber, and pneumatic types have commonly been employed as seat cushions and matresses. These devices have not met with complete success, particularly with respect to applications wherein prolonged confinement by the person using the same was present. One of the reasons why these prior art structures have been generally unsatisfactory in such uses is that they are not capable of permiting unrestrained lateral movement of that part of the patient's body which is adjacent the supporting surface. Such unrestrained lateral movement is essential in order to prevent damage to a patient's skin.

It is known that with bedridden patients and those confined to wheelchairs, subjecting the skin of such individuals to constant pressure tends to produce a breakdown which results in decubitus ulcers, commonly known as bed sores. To prevent such decubitus ulcers from forming, it is important to establish a reduction of pressure over the localized areas of bony prominences since the most acute cases of such decubitus ulcers occur where the bony structure of the patient is close to the supporting surfaces, for example, over the sacrum or ischial tuberosities, so that the support of the patient tends to be concentrated in relatively small pressure areas of the supporting surface.

Past efforts to solve these problems have generally involved using the softest and/or most resilient materials available. In general, however, the compressibility of these materials ultimately results in the development of decubitus ulcers or bed sores with patients requiring relatively long periods of confinement to a bed or chair.

Recently, efforts to solve this problem have resulted in the development of gel cushions composed of an organosiloxane gel material of the type which is generally disclosed in U. S. Pat. Nos. 3,308,491 and 3,548,420. These cushions, however, have not been entirely satisfactory for a number of reasons, among which is the fact that they are costly to produce, prone to tearing, and, after prolonged periods of time, subject to deterioration.

The present invention overcomes the disadvantages of the above mentioned prior art cushioning materials by providing an improved polyvinylchloride gel support structure or cushion which contains from approximately six to 14 parts by weight of plasticizer for each part of high molecular weight polyvinyl chloride resin. In a preferred embodiment, the cushion includes approximately nine parts plasticizer for each part of high molecular weight polyvinylchloride resin and an effective amount of suitable vinyl stabilizers. As such, the improved polyvinylchloride gel cushions of the present invention are particularly suited for application in all general cushioning applications and are particularly suited for use by patients requiring long periods of confinement to a bed or chair.

It is, therefore, an important object of the present invention to provide an improved support structure which is particularly suitable for use as a seat cushion or mattress.

Another object of the present invention is to provide an improved support structure of a polyvinylchloride gel construction for a human body whereby the support pressure can be substantially uniformly distributed over a relatively large surface so that the occurrence of decubitus ulcers is greatly reduced, if not totally eliminated.

Another object of the present invention is to provide a gel-type pad which is substantially less costly to produce than the heretofore available organosiloxane gel-type cushions.

Another object of the present invention is to provide a gel-type pad which is characterized by greater tear resistance than the heretofore available organosiloxane gel-type cushions.

Another object of the present invention is to provide a gel-type pad which does not evaporate, leak or change consistency with use or during shelf storage.

These and other objects of the present invention will be apparent from the following detailed description thereof, taken in conjunction with the following drawing wherein:

FIG. 1 is a perspective view of a cushion made in accordance with the present invention; and

FIG. 2 is a cross-sectional view of the cushion shown in FIG. 1 taken along the line 2--2.

Referring to the drawing, and with particular reference to FIG. 1, the numeral 10 generally designates a covered cushion structure embodying the present invention. As is shown, the covered cushion structure 10 includes a closely fitting removable cover 11 which, for example, can be composed of latex rubber, a suitable synthetic elastomeric material or natural materials such as fawn or kid leather. As shown, the cover 11 is provided with a closable access slot 12 which, in the illustrated embodiment, includes a suitable zipper closure.

Referring to FIG. 2, an inner stockinette 13, preferably composed of wool, cotton or a synthetic material exhibiting characteristics similar thereto, is provided in close fitting relationship to a polyvinylchloride gel cushion core 14. Inner cover 13 is provided with a slit type opening running along one edge thereof which can include a plurality of snap fasteners 15 of conventional construction. If desired, the cushion 10 can be provided with a suitable cloth slip cover (not shown) which can be equipped with handles for facilitating the transporting thereof. In this regard, it is important to note, however, that the various cover members shown and described in connection with the illustrated embodiment of this invention are not essential thereto and that the novel polyvinylchloride gel core 14 thereof can be advantageously employed in other cushion applications which do not require these particular cover members.

In accordance with the present invention, the polyvinylchloride gel core is produced within critical composition limits and comprises a high molecular weight polyvinylchloride resin, a plasticizer which is principally a high molecular weight ester plasticizer and a suitable heat stabilizer.

The following example describes, for illustrative purposes only, a preferred embodiment of the polyvinylchloride gel core of the present invention. As such, this example is not to be construed as a limitation either with respect to the precise process steps recited therein or with respect to the particular materials and amounts thereof which are described. As used herein, all parts are parts by weight, all ratios are ratios by weight, and all temperatures are in degrees Fahrenheit.

EXAMPLE

A base mixture is prepared by admixing the ingredients set forth in Table 1.

TABLE 1

1200 parts plasticizer [for example, dioctyl phthalate-bis(2-ethylhexyl)phthalate] 18 parts epoxidized soy bean oil 18 parts vinyl stabilizer [for example, tin SS'-bis(isooctyl mercapto acetate)] 600 parts high molecular weight polyvinylchloride resin

The ingredients listed in Table 1 were admixed for 15 minutes, deaerated, and filtered into drums through a 30 mesh screen.

A commercially available composition which is highly satisfactory for use as the plasticizer (dioctyl phthalate constituent) identified above is available under the trademark KODAFLEX DOP (trademark Eastman Chemical Products, Inc., a subsidiary of Eastman Kodak Co.). Similarly, a suitable epoxidized soy bean oil which can be advantageously used in the practice of the present invention is commercially available under the trademark FLEXOL (trademark Union Carbide Corporation). A suitable vinyl stabilizer of the type described above is commercially available under the product name ADVASTAB TN-188 from the Advance Division of Carlisle Chemical Works, Inc. of New Brunswick, New Jersey. Similarly, a suitable high molecular weight polyvinylchloride resin which can be used in the manufacture of the gel pads of the present invention is available under the trademark EXON 654 (trademark Firestone Plastics Company, a division of Firestone Tire & Rubber Company). This particular polyvinylchloride resin has the following reported polymer properties.

TYPICAL POLYMER PROPERTIES

EXON 654 Relative Viscosity (1% in Cyclohexanone at 25.degree.C.) 2.65 Inherent Viscosity 1.16 (ASTM D-1243-66) Hot Melt Viscosity, M-Kg 0.85 10 minutes at 174.degree.C (Firestone Control Test C-157a) Specific Gravity 1.4 Brookfield Viscosity Range 50 to 70 (Firestone Control Test C-15e) Extrusion Rheometer Viscosity 100 to 150 Range 10 to 80 psig, poises (Firestone Control Test C-66b) Ultimate Tensile Strength, psi (ASTM D-412), when fused at 120.degree.C. (248.degree.F.) 310 150.degree.C. (302.degree.F.) 820 180.degree.C. (356.degree.F.) 2380 210.degree.C. (410.degree.F.) 2550 Volume Resistivity, ohm-cm .times. 10.sup.8 At Room Temperature 76 At 60.degree.C. 35 (ASTM D-257-66) ASTM Classification (ASTM D-1755-66) D4-33

it will be appreciated by those skilled in this art that other high molecular weight vinyl chloride resins may be suitably used in place of, on in conjunction with, the EXON 654.

Approximately 130 parts of the Table 1 admixture is combined with 255 parts of the Table 1 plasticizer, dioctyl phthalate, and with 42.5 parts of 2,2,4-trimethyl-1,3-pentanediol, diisobutyrate (KODAFLEX TXIB, trademark Eastman Chemical Products, Inc., a subsidiary of Eastman Kodak Company). These ingredients are admixed at room temperature for approximately 10 minutes in high shear condition. They are then charged to a mixing drum in the sequence dioctyl phthalate, then 2,2,4-trimethyl-1,3-pentanediol, diisobutyrate, then the admixture of Table 1.

The resuling mixture is then heated until the temperature reaches 330.degree., which temperature is maintained until the resulting mixture is poured. Initially, the viscosity is somewhat reduced in the first stage of heating but thereafter the gel thickens and becomes clear.

The thus heated mixture is then poured into a suitable Teflon lined mold or a mold treated with a suitable equivalent release agent which will prevent sticking of the finished polyvinylchloride gel with the sides of the mold.

After cooling to approximately room temperature, the polyvinylchloride gel core is preferably sprinkled with talcum powder to facilitate handling during removal from the mold. The gel is then peeled from the mold in a conventional manner and talcum powder applied to the whole unit after it has been removed. Thereafter, the pad can be stored for subsequent use as a seat cushion in accordance with the teachings of the present invention.

In the above described example, approximately 9 parts of plasticizer were used for each part of high molecular weight polyvinylchloride resin. In this regard, however, the polyvinylchloride gel pad of the present invention can contain from approximately 6 to 14 parts of plasticizer for each part of high molecular weight polyvinylchloride resin.

The plasticizers which can be used in accordance with the present invention are generally characterized as high molecular weight esters and include, by way of example, dioctyl phthalate and 2,2,4-trimethyl-1,3-pentanediol, diisobutyrate which are described above, however, the 2,2,4-trimethyl-1,3-pentanediol, diisobutyrate is not preferred for use by itself because of its relatively high volatility. Nonetheless, when used in the quantities set forth above, it imparts advantageous properties to the polyvinylchloride gel pads of the present invention. Other useful plasticizers include diisooctyl phthalate, tricrecylphosphate, butyl benzyl phthalate, diisodecyl phthalate and the like. It is, of course, known that the polyvinylchloride plasticizers are divided into two general types, namely, monomeric and resinous. In the present invention, the plasticizers are of the monomeric type, although as shown in the above example, blends of resinous and monomeric plasticizers can be advantageously employed.

Since polyvinylchloride dispersions are affected by heat, stabilization of the polyvinylchloride gel used in the cushions of the present invention is achieved by the addition of compounds capable of reacting with hydrogen chloride as it is formed, to prevent the development of an acid condition in the resin. The state of the art relating to polyvinylchloride heat stabilization is highly developed and inorganic oxides, salts of inorganic bases with weak acids, complex organometallic compounds, and various glycidal compounds are widely known and used as heat stabilizers for polyvinyl chloride resins of the general type employed in the present invention. Accordingly, any of these various other vinyl stabilizers can be used in place of, or in conjunction with, the organo tin compound used in the example set forth above.

In the foregoing specification, a preferred embodiment of the present invention has been disclosed for illustrative purposes. It will be recognized by those skilled in this art, however, that various modifications can be made therefrom without departing from the spirit of the present invention. Accordingly, this invention still is to be limited in scope only by the appended claims.

Claims

I claim:

1. An improved cushion structure comprising a resiliently flexible core of a polyvinylchloride gel containing from approximately 6 to 14 parts by weight of plasticizer for each part by weight of polyvinylchloride resin.

2. The cushion structure of claim 1 wherein said polyvinylchloride gel core contains approximately 9 parts by weight of plasticizer for each part by weight of polyvinlychloride resin.

3. The cushion structure of claim 1 wherein said plasticizer is a high molecular weight ester.

4. The cushion structure of claim 3 wherein said high molecular weight plasticizer is selected from the group consisting of: dioctyl phthalate; 2,2,4-trimethyl-1,3-pentanediol, diisobutyrate; diisooctyl phthalate; tricrecylphosphate; butyl benzyl phthalate; diisodecyl phthalate; and, mixtures thereof.

5. The cushion structure of claim 1 wherein said polyvinylchloride resin is a high molecular weight type polyvinylchloride resin.

6. The cushion structure of claim 1 wherein said polyvinylchloride gel also includes an effective amount of a vinyl stabilizer.

7. A composition suitable as a cushion core material consisting essentially of a polyvinylchloride gel comprising a high molecular weight ester plasticizer and a high molecular weight type polyvinylchloride resin, wherein the plasticizer is present in an amount of from 6 to 14 parts by weight per part by weight of said resin.