CA1060599A - Padding and filling material therefor - Google Patents

Abstract

A method and product is disclosed relating to a filling material for padding. The material consists at least partially of unicellular bubbles the outer walls of which consist of at least one copolymer selected from the group consisting of vinylidene chloride copolymers and vinyl chloride copolymers, the inside of the bubble containing a gas.

Description

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This invention refers to a filling material for paddings, supports or the like, to a padding filled with such a filling material and to a process for the production of such a padding. The invention is particularly concerned with a filling for a padding or the like, as well as with a padding containing such a filling serving for the adaptation of various articles, such as trusses, corsets, girdles, pro- ~-tective helmets, artificial limbs and insertions, which are to be used on the human body as well as adapting pads, support pads, safety pads and sealing pads or the like, particularly I -for shoes.
Up till now, there has not been found a satisfactory method of comfortably and individually adapting hard objects to the shapes of the human body and for simultaneously cushion-ing the supported portion of the human body, as is, for example, required when adapting and cushioning the outer .::
shells of ski boots consisting of rigid cured or thermosetting synthetic resin. !~
It is known to fit shoes to the foot by pouring into i~
the cavity between the foot and the upper of the shoe a sili-cone rubber, and vulcanizing or curing said silicone rubber in presence of the foot (see U.S. Patent Specification !-3,325,919). Paddings produced in such a manner suffer from I the drawbacks that they are given a final unalterable shape and that they can be very heavy.
It is also known to provide pockets or shells in cavities between rigid objects and the human body and to fill ;
the pockets or shells with small balls of hard thermosetting phenolic resins to form a padding, the balls being practically incompressible and being coated with a lubricating agent -- 1 -- .

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(see U.S. Patent Specification 3,407,406; German published -Patent ApplicationsDT-OLS 1,485,772 and DT-OLS 2,211,718).
Such padding will assume a shape adapted to the shape of the cushioned body portion, but will not provide the desired yielding support because the padding is not elastically de-formable as is for instance the case with soft synthetic foamed material. Thus, it ~ecomes necessary to use an addi~
tional foam material in conjunction with the padding.
It has further been proposed to fill paddings, pock- ¦~
ets and other cavities with a paste-like thixotropic substance having a high viscosity and mainly consisting of polyisobutyl-ene having a high content of filler material (see German published Patent Application DT-OLS 1,685,307). Even with this padding, the padding effect is very slight because the filling material present in such a padding cannot be compressed 5 so as to be restored when dynamic pressure is applied to the padding. Thus, also in this case, a compressible padded layer is required in addition to the padding.
According to a further proposal, paddings for body portions are produced from polyurethane foam, thereby provid-ing the required adaptation by introducing the required reac-tants into the existing cavity (see German Patent Specifica-tion DT-PS 901,471). This proposal suffers from the drawback that any individual fitting must take place in situ, which is dangerous in view of the high toxicity of the isocyanates from which the polyurethane foam is made, and in view of the ¦;-heat of reaction wh~ch is evolved. Furthermore, this method often leads to faulty fittings which are difficult to remove.
A further disadvantage is that the polyurethane foam is sensi-tive to perspiration and hydrolysis and soon loses its resil ience under their influence. ''

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It is also known to fill paddings with scraps of soft resilient foam in the form of sheets or discs having a large surface area (see German published Patent Application DT-AS 1,010,825). The desired individual adaptation to exist~
ing shapes of body portions cannot be effected with such a padding because the soft foamed material, in this case a poly-urethane foam, is neither thermoplastic nor thermoelastic.
Furthermore, also in this case the padding is subject to -~
deterioration under the action of perspiration and hydrolysis 0 80 that the polyurethane foam used will soon lose its elasticity.
It has also been proposed to fill paddings with 1:
extruded cord, skein or rope-like fillings consisting of foam-ed thermoplastic or thermosetting material. E~owever, with !
such paddings it is not possible to effect the desired adapta-tion to the existing shape of the body portion and at the same time provide an elastic support for the body portion.
It is further known to use foamed polystyrene in the ~.!
form of flakes, granules or powder as a filling for padded ,i~
cushions and mattresses (see French Patent Specification 1,302,015). Such a foamed polystyrene will lose its elasticity after being compressed for a long time, so that it cannot be re-fitted and then no longer has the property of a padding. l.
It is an object of the present invention to avoid the drawbacks of known filling materials and, respectively, of paddings filled with such known filling materials, and to provide a filling for a padding which can be individually .::1 .. .
adapted to a certain shape as often as required and is elasto- -~meric to the desired extent so that a resilient support may be ~
provided without additional measures. ^
The padding according to the present invention is .
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based on a filling for paddings and supports which consists of particles of a thermoplastic synthetic resin, preerably hav-ing a density of 0.02 to 0.3 gm/cc, and according to the inven-tion the particles are formed, at least in part, of unicellular bubbles whose outer wall consists of a copolymer of vinylidene chloride and/or vinyl chloride copolymer, and the hollow inner core thereof contains a gas, and a skin enclosing said parti- -cles. It has been found that a filler consisting at least in part of such bubbles can be easily, for example by supplying heat, connected into a microfoam-like structure with thermo-plastic properties, and can be shaped in such a way that the shape of this structure can be accurately adapted to a certain form, for example to parts of the body, and the structure also has the desired elasticity so that it gently pads these parts of the body. The shape of the filling of the padding according to the present invention which is formed at first need not be permanently maintained, but can be varied as desired, so that thi5 filling can be adapted as frequently as desired, for example, to certain parts of the body, without any physiologi- ~`
cal harm. Furthermore, the filling of the padding according -to the invention is light in weight and, in addition, is resistant against perspiration and hydrolysis. ~ -The filling of the padding according to the invention thus is particularly suitable for manufacturing paddings for patients and invalids, for example, for artificial limbs and orthopaedic articles of any kind, paddings for wheel-chairs, sick beds, seats, cushions, beds, supports and so on, and is also suitable for manufacturing paddings or padded parts for test drivers, astronauts, racing drivers, sportsmen and sensitive persons, thus for example for seats, beds or supports ., ... , :

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1060s99 in spacecraft, test vehicles, cars~ in particular sport cars, racing boats and aircraft, and also for paddings for shoes of all kinds, arch supports, chairs and Eeclining furniture, .... .
knee pads, pads for helmets, diver's goggles, breast prothesis, and bra paddings.
The bubbles whose resilient outer walls consist of a -copolymer of vinylidene chloride or of a copolymer of vinyl chloride are, in contrast to most of the other filling mater-ials for paddings, non-combustible, so that when combined with non-combustible padding covers, as for instance asbestos ;
fabric, the filling is particularly suitable for use in disasters. The non-combustible foam-like filling which is -thermally insulating, together with the light weight and exellent padding effect, make it particularly advantageous. -It has been proved to be of particular convenience if the outer walls of the bubbles consist of a copolymer of vinyl chloride and ethylene or of a copolymer of vinylidene chloride -and acrylonitrile.
According to a further feature of the invention, the thin casing of the bubbles may consist of copolymers having an essentially lower softening point than homopolymers whose -monomers form the main component in terms of volume in the formation of the copolymer.
In one aspect of this invention there is provided a conforming padding comprising a material consisting of a cohered mass formed of discrete hollow resilient thermoplastic synthetic resin particles and a bonding agent; said discrete particles having a density of about 0.02 to 0.3 gm/cc and formed into intact hollow microbubbles having a thin, resi-lient, gas-impermeable shell enclosing and confining a gas, said shell consisting of a copolymer of vinylidene chloride ~ -5-~060599 ~:
or of vinyl chloride; said bonding a~ent adherently inter--connecting said discrete particles into a mobile, resilient, coherent, plastically deformable mass at body temperature, said bonding agent having a softening point lower than that of said shell copolymer and said bonding agent being flowably plastic at about body temperature and having little plastici~
zing action on said bubble-forming copolymer In another aspect, the present invention resides in the combination of a filling material consisting of a padding as defined in the immediately preceding paragraph, with a flexible sheath or envelope enclosing said filling material in a cushion.
In another aspect of this invention there is provided a method for the production of a padding comprising particles of a thermoplastic resin having a density of about 0.02 to 0.3 gm/cc., wherein the particles are formed into intact hollow microbubbles having a thin, resilient, gas-impermeable shell enclosing and confining a gas, said shell consisting of a copolymer of vinylidene chloride or of vinyl chloride, and a material bonding said particles together, and a covering :
~ enclosing said particles, said method comprising introducing :;j said bubbles into the covering by means of a carrier substance via an opening provided in the covering.
The gas present within tbe bubbles may simply be air.
However, in some cases, it may be convenient to use as the gas ethylene and/or a halogenated hydrocarbon, such as carbon tetrachloride, and/or a hydrocarbon other than ethylene.
Since vinylidene chloride copolymers and vinvl chloride copolymers have an extremely low gas permeability, it is practically impossible for the gas to escape from the closed bubbles whose -5a~

.: ' outer walls consist of such a plastics material. This property is, above all, of great importance for the rapid xeturn to shape of the pad after compression and is a pre-requisite for obtaining the desired comfort of the padding filled with the filling according to the invention.
For paddings, which in practice will not be subject-ed to high pressure and which in the first instance are soft and elastically deformable, it is merely sufficient to fill the casings or cavities to be padded with the particles form-ing the filling. However, in the case of paddings which areto retain their shape under normal pressure loads, it is ex-pedient to join the individual bubbles together. This may be effected, as already mentioned, by supplying heat wherein, by suitably selecting the materials for the casing of the bubbles, the casings may be joined together by body heat supplied to the bubbles (owing to the position of the padding next to the !
parts of the body to be padded), so that at the same time the shape of the padding is adapted to these parts of the body.
In order that the bubbles may be more easily joined together, these bubbles may, according to a further feature of the invention, be connected by means of an adhesive agent to form one unit which can preferably be separated again. The soften-ing point of the adhesive agent is preferably lower than that of the material of the outer walls of the bubbles, whereby the outer walls of the bubbles will sinter under the influence of heat and pressure to produce on cooling a foam-like struc-ture which can be converted again into individual bubbles by the application of heat. To provide the desired adhesive -action, the bubbles may be impregnated with a melt, a solution, an emulsion or a dispersion of any suitable adhesive substance :.

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~0599 provided it has a broad softening range, such as, for example, low molecular weight polymers or copolymers, natural or synthetic resins, natural and synthetic waxes and, above all, those substances which are used for the preparation of glue and adhesive melts. Since the melting point of the synthetic resin materials used for the bubbles of the padding according to a preferred embodiment of this invention lies in the range from about 140 to about 195C, depending upon the mixing proportions of the monomers, the softening range and the melting point of the adhesive agent should preferably be con-siderably below this temperature. Particularly suitable ad-hesive agents are mixed polyamides containing plasticizers and having a melting point of approximately 68C. It has been found that most of the known so-called external plasticizers for pla~tics, lacquers, resins and rubbers meet these require-ments. Particularly suitable external plasticizers are diethyl-glycolphthalate, diisooctyl adipate, dibutyl phthalate, dioctyl ;
phthalate, dioctyl sebacate, dibutyl adipate, epoxidized oleic acid esters, epoxy plasticizers having a molecular weight up to 2,000, glycerol and polyglycerol, castor oil as well as many low molecular weight polymers having a molecular weight ;
up to 3,000 such as polyesters of adipic acid and ethylene glycol or polyethers of triols and propylene oxide, polysilox-anes, polyolefins, higher alcohols and so on. m ese substan-ces, which to a certain extent have a slight plasticizing effect, can be used alone or in mixtures with each other or with water or with other substances having similar properties as adhesive agents for joining the individual particles. ¦;
The adhesive agent preferably consists of a sub-stance which is fluid or paste-like at body temperature, and ~060599 ~
which exerts a slightly softening effect on the bubbles so that only at body temperature do the bubbles join together as desired to form a foam-like structure.
In certain fields of application, it is expedient if the filling according to the invention consists only in part of the unicellularbubbles with the thin casing of a resilient vinylidene chloride copolymer or vinyl chloride copolymer, which are mixed with other synthetic resin particles.
In this case, according to a preferred embodiment of the inven~
10 tion, the bubbles are surrounded by another polymer matèxial. i Furthermore, larger particles of foam, for example foamed spherical particles consisting of amorphous synthetic resins and having a closed-cell structure, may be added together with the bubbles as a filling for the padding. The minute uni-cellular bubbles thus fill up practically all the cavities ,; ..
; which are formed between the larger particles, and in the li`
event of a mechanical pressure being applied from the outside, ;~
the thin casing of the bubbles will be subjected to a uniform pressure from all sides. The effect of forming an uneven texture on the surface of the thin padding covers, which dis-advantageously occurs when using the abovementioned iarger spherical foam particles consisting of amorphous synthetic resin, i8 removed by using the minute bubbles. 1~`
In addition to synthetic resin particles, other materials such as fibres, rubber particles or the like may ~`~
also be used as filling in conjunction with the bubbles.
~; Different materials such as leather, synthetic leather, fabrics or fleeces may also be considered as casings ~; or coverings for the filling of the padding according to this invention, depending upon the purpose for which it is to be ' ~060599 used. The bubbles are preferably surrounded by a cover which is at least partially permeable to air and water.
This filling of the padding according to the inven- ;
tion can obviously be introduced through an opening in the casing of the padding, whereupon the opening is closed.
According to a method of the invention for producing a padding according to this invention, the bubbles and, if required, other additives, are inserted through an opening in the padding cover by means of a preferably fluid carrier substance.
In this case, the filling material can, for example, be intro-duced into the cover of the padding together with the fluid carrier substance by means of a thin hollow needle, as is for instance used as an injection needle for medical purposes.
The cover may be pierced at any desired location by means of this hollow needle.
After the bubbles have been introduced into the padding cover, the carrier substance, if liquid, is preferably evaporated off. This can, for example, be effected in a i`
circulating warm air oven.
It is of particular advantage to use as the carrier substance an adhesive agent which, after the bubbles have ¦;
been added, causes them to combine in the desired shape into a micro-foam. The carrier substance used can, for instance, be a higher alcohol or an epoxy plasticizer.
According to a further feature of the inventive process, the bubbles may be formed after being introduced by li means of the carrier subst2rce, as particles containing an expanding agent which are inflated, preferably by the applica-tion of heat.
After having been introduced into the padding cover, the particles which have not been foamed and containing, as a _ g _ "'' ' . : . ~ ' ' ' : . '' ' , ' i . . ' , ' . ' ' ', ' ,:, . ' ~ 60599 rule, as an expanding agent carbon tetrachloride, ethylene or a hydrocarbon other than ethylene, can be made to expand by means of a heat source between +75C and +160C, and thus changed ~nto bubbles. For this purpose, fluid baths heated to a temperature between +85C and +110C are most suitable in view of their capacity of rapid heat transfer to the particles which have not been foamed, and particularly in those cases in which -- as is preferred -- the padding casings used are permeable to fluids.
Parts of normal thickness, such as parts for artifi-cial legs or sports shoes, with a thickness of 1.5 to 3.5 cm in the finished foam state, are ready in less than 20 seconds.
In the case of permeable casings, hot steam is proposed for a partial foaming, as for example in the case of large articles, and infrared irradiators are proposed in the case of non-permeable padding casings.
According to a further feature of the inventive procbss, the carrier substance may consist of an inert liquid, for example water, preferably including hygroscopic additives. ~
When using water, the water may contain a plasticizing com- $
ponent, for example glycerol acting as an adhesive agent.
The padding of this invention has the advantage of ~-having a low density, so that, in the event of a dynamic load, the low density causes reduced inertia forces since the ;`
kinetia energy and the centrifugal force are directly propor- , tional to the mass moved. ~he reduced forces of inertia result in reduced wear and a saving in drive energy so that it is possible to provide a padding of simpler construction as well as a padding of lighter weight -- an advantage which is particularly appreciated by persons who wear artificial `
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106~599 limbs and also sportsmen and athletes.
A further advantage of the padding according to this invention is that, in the event of compression, the filling behaves in a similar manner to air enclosed in a gas-tight resilient covering. This effect results from the fact that the gas-filled bubbles first try, on exertion of pressure, to escape sideways away from the point of compression, before they themselves are elastically compressed. This property is desired in numerous paddings and becomes of still greater importance if it is considered that the padding casings need not be impermeable as is the case with an alr or liquid ;
filling, but can be constructed so as to be permeable and therefore breathe. The softness, adaptability, reversible compressibility, density and numerous other properties of the filling of the padding according to this invention can be varied extensively by varying the type and ~uantity of the ~ ~
adhesive agent used. In general, 65 to 450 grams of adhesive ~ -agent are used for a finished padding volume of 3,500 cc.
The filling of the padding according to this invention pre-ferably has a density of 0.02 to 0.3 gm/cc, but can, in certain cases, also have a higher density, particularly in those cases in which, in addition to the bubbles, other particles of larger size are provided within the filling.
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Claims (25)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A conforming padding comprising a material consist-ing of a cohered mass formed of discrete hollow resilient thermoplastic synthetic resin particles and a bonding agent;
said discrete particles having a density of about 0.02 to 0.3 gm/cc. and formed into intact hollow microbubbles having a thin, resilient, gas-impermeable shell enclosing and confining a gas, said shell consisting of a copolymer of vinylidene chloride or of vinyl chloride; said bonding agent adherently interconnecting said discrete particles into a mobile, resilient, coherent, plastically deformable mass at body temperature, said bonding agent having a softening point lower than that of said shell copolymer and said bonding agent being flowably plastic at about body temperature and having little plasticizing action on said bubble-forming copolymer.

2. A padding as claimed in claim 1, wherein the outer walls of the microbubbles consist of a vinylidene chloride-ethylene copolymer.

3. A padding as claimed in claim 1, wherein the outer walls of the microbubbles consist of a vinylidene chloride-acrylonitrile copolymer.

4. A padding as claimed in claim 1, 2 or 3 wherein the copolymer of which the outer walls of the microbubbles are formed has a softening point lower than that of a homopolymer of the monomer which, in combined form, is the main constituent by volume of the copolymer.

5. A padding as claimed in claim 1, 2 or 3 wherein the gas in the microbubbles is at least one member selected from the group consisting of hydrocarbons including ethylene, and halogenated hydrocarbons including carbon tetrachloride.

6. A padding as claimed in claim 1, 2 or 3, wherein the microbubbles are embedded within another polymer.

7. A padding as claimed in claim 1, wherein, in addition to the microbubbles, additives are provided.

8. A padding as claimed in claim 7, wherein the additives are formed particles.

9. me padding as claimed in claim 1, 2 or 3, wherein the gas in the bubbles is ethylene or carbon tetrachloride.

10. The padding as claimed in claim 1, 2 or 3, wherein the thermoplastic resin has a melting point in the range from about 140 to about 195°C.

11. The padding as claimed in claim 1, wherein the adhesive agent is mixed polyamides containing plasticizers and having a melting point of approximately 68°C.

12. The combination of a filling material with a flexible sheath or envelope enclosing said filling material in a cushion, said filling material consisting of the padding defined in claim 1.

13. A method for the production of a padding comprising particles of a thermoplastic resin having a density of about 0.02 to 0.3 gm/cc., wherein the particles are formed into intact hollow microbubbles having a thin resilient, gas-impermeable shell enclosing and confining a gas, said shell consisting of a copolymer of vinylidene chloride or of vinyl chloride, and a material bonding said particles together, and a covering enclosing said particles, said method comprising introducing said bubbles into the covering by means of a carrier substance via an opening provided in the covering.

14. A method as claimed in claim 13, wherein the carrier substance is a liquid.

15. A method as claimed in claim 13, wherein the bubbles are used in combination with additives.

16. A method as claimed in claim 13, 14 or 15 wherein the carrier substance is removed after the bubbles have been introduced into the covering.

17. A method as claimed in claim 13, 14 or 15 wherein the carrier substance is an adhesive agent.

18. A method as claimed in claim 13, wherein the bubbles are formed by expanding particles containing an expanding agent after introducing said particles by means of said carrier substance.

19. A method as claimed in claim 18, wherein the particles containing expanding agents are expanded through a heat supply.

20. A method as claimed in claim 13, wherein the carrier substance is an inert fluid.

21. A method as claimed in claim 20, wherein the inert fluid is water.

22. A method as claimed in claim 20 or 21, wherein the inert fluid contains at least one hygroscopic additive.

23. A method as claimed in claim 20 wherein a softening component is added to the inert fluid as an adhesive agent, said softening component softening the outer walls of the bubbles.

24. A method as claimed in claim 23, wherein the softening component is glycerol.

25. A method as claimed in claim 23 or 24 wherein the inert liquid is water.