WO1997027042A1 - Combination desiccant and heat source - Google Patents

Abstract

A porous polymer material mixed with a drying agent composes a desiccant which may be used proximate to a heat source or thermally cycling device, such as an automobile lamp (28, 40). Heat generated by the heat source regenerates the drying agent in the porous polymer material. The desiccant material may be formed into a variety of shapes for ease of placing or affixing the material proximate to the heat source.

Description

COMBINATION DESICCANT AND HEAT SOURCE

Field of the Invention The invention is directed to a desiccant in combination with a heat source, and more particularly a porous material containing a desiccant disposed proximate to a heat source

Background of the Invention Many items are susceptible to damage caused by excessive moisture

For instance, packaged food items and chemical reagents may be ruined or altered due to excessive moisture Similarly, devices which thermally cycle and are contained in a housing are susceptible to moisture related problems One means of dispersing moisture is to provide greater air flow across the device However, for items located in a package or housing, it can be very difficult to provide adequate or greater air flow, especially if the housing is a closed housing

Another means of managing moisture is to place a drying agent or desiccant proximate to the item or device to be preserved or protected Desiccants occupy an important role in the preservation of many items from damage caused by moisture, for instance moisture due to condensation As the terms "desiccants" or "drying agents" are used herein they are intended to mean any mateπal that adsorbs water vapor from air and is able to dry the atmosphere in containers, particularly closed or sealed containers One commonly known desiccant is a silica gel disposed in an air permeable package This type of desiccant is used, for instance, in shipping electronic devices, such as personal computers, in a sealed box Even though the box is sealed, the box is still permeable to moisture, and a desiccant or drying agent is thus necessary to protect the electronic device from being damaged by moisture

Devices which are thermally cycled, such as a light bulb, also often have a desiccant disposed nearby, especially when the bulb is located in a closed housing For instance, automotive head lamps located in a closed housing include a desiccant for preventing fog formation on the internal walls of the head lamp or its reflector The desiccant adsorbs water vapor which enters the housing when the head lamp is off When the head lamp is turned on heat generated by the bulb dries the air and the desiccant, thereby regenerating the desiccant As previously discussed, the desiccant is usually in the form of a housed or packaged silica gel or similar material Although this type of packaged desiccant provides adequate moisture adsorption under some conditions and is capable of being regenerated by the heat produced by the light bulb, the package is not easy to position within the housing, often requiring that a special sub-housing be provided within the head lamp housing In addition, this type of packaged desiccant subhousing cannot withstand the high temperatures generated by some light bulbs and accordingly, the desiccant must be located at least a minimum distance from a high temperature bulb and/or shielded from the bulb

It has been previously proposed to employ a silica material in a polytetrafluoroethylene material in order to serve as a drying aid in global positioning systems Such devices have not been accepted and generally fully covered packets of desiccants are used in such environments To date, no such devices have been employed in thermally cycling apparatus

Accordingly, there is a need in the art for a drying agent, such as a desiccant which adsorbs water vapor from the air, that can be located proximate to a bulb or heat source, can be regenerated by the thermal cycling of the heat source, does not require packaging or a special housing or heat shield, and can be shaped or formed with characteristics that are functional to installation and adsorbtion and desorbtion characteristics

Summary of the Invention

The invention provides a shaped desiccant material for adsorbing moisture from air and which can be regenerated According to one aspect of the invention, a desiccant material for use with a device which thermally cycles is provided wherein the material comprises a shaped porous polytetrafluoroethylene (PTFE) or similar material filled with a desiccant Heat generated by the device regenerates the desiccant

The preferred embodiment of the present invention comprises a drying agent mixed with a porous polymer formed or shaped into a predetermined configuration, such as a toroid shape, that can be installed without a cover and without risk of drying agent loss or contamination of surrounding environment Yet another aspect of the invention provides a desiccant material in combination with a heat source, the desiccant material comprising a porous polymer with a drying agent, wherein the member is disposed proximate to the heat source and heat generated by the heat source regenerates the drying agent

Yet another aspect of the invention provides a desiccant material in combination with a heat source, the desiccant material comprising a heat resistant porous polymer member with a drying agent, said porous polymer member designed to adsorb and desorb the adsorbate at rates which will minimize the formation of adsorbate condensation, wherein the member is disposed proximate to the heat source and heat generated by the heat source regenerates the drying agent

A further aspect of the invention comprises an electrical light bulb, an electrical socket for receiving the light bulb and supplying electrical current thereto, and a desiccant member made with filled PTFE or other packaging free desiccant materials such as composites comprising a formable substrate that can retain adsorbent materials affixed proximate to the bulb and the socket

The formed desiccant material of the invention is particularly useful in adsorbing moisture from the air within an enclosed or sealed container or housing for a device which thermally cycles, such as, but not limited to, an automotive head lamp

Description of the Drawings

The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred It should be understood, however, that the invention is not limited to the precise arrangement and instrumentalities shown In the drawings Fig 1 is a perspective view of a shaped material including a drying agent in accordance with a first embodiment of the present invention,

Fig 2 is a perspective view of a shaped material including a drying agent in accordance with a second embodiment of the present invention,

Fig 3A is a perspective view of a shaped material including a drying agent in accordance with a third embodiment of the present invention, Fig. 3B is a perspective view of a shaped material including a drying agent in accordance with a fourth embodiment of the present invention;

Fig. 4 is a perspective view of the shaped material of Fig. 3A in combination with a light socket; Fig. 5 is a side view, partially in cross-section, of the shaped material of

Fig. 1 in combination with a light bulb;

Fig. 6 is a sectional view of a vehicle head lamp including a shaped material including a drying agent in accordance with the present invention;

Fig. 7 is a sectional view of an alternate embodiment of a vehicle head lamp including a shaped material including a drying agent in accordance with the present invention;

Fig. 8 is a side exploded view of a shaped material of the present invention shown mounted around a bulb fixture;

Fig. 9 is a perspective view of ring shaped material similar to material in Fig. 1 ;

Fig. 10 is a graph plotting water gain against time of various embodiments of the present invention;

Fig. 11 is a graph plotting water gain against time of various embodiments of the present invention; Fig. 12 is a graph plotting water loss against time of various embodiments of the present invention;

Fig. 13 is a graph plotting water loss against time of various embodiments of the present invention;

Fig. 14 is a graph plotting water loss against time of various embodiments of the present invention; and

Fig. 15 is a graph plotting water loss against time of various embodiments of the present invention.

Detailed Description of Preferred Embodiments Certain terminology is used in the following description for convenience only and is not limiting. The words "inwardly" and "outwardly" refer to directions towards and away from, respectively, the geometric center of the shaped material and designated parts thereof. The terminology includes the words specifically mentioned, derivatives thereof and words of similar import. The present invention is directed to the use of a shaped member including a drying agent in combination with a heat source For instance, in a preferred embodiment of the invention, a shaped member, preferably formed of a porous polymer matrix, having a drying agent therein is disposed proximate to a light bulb or other heat source located within a housing As a result of the composition and method of manufacture of the shaped member, the member may be located very close to the bulb or heat source without the need for a package or special housing or heat shield to protect the member from the heat generated by the bulb In addition, because the member material can be shaped and formed, it may be located in a variety of positions within the housing The shaped member is able to maintain a dry atmosphere (i e , an atmosphere that is not saturated with moisture) within the housing and the drying agent is regenerated by the heat generated by the bulb when the bulb is

The drying agent or "desiccant" material of the present invention is constructed of materials such that the material can be formed or shaped, the desiccant is confined without a subhousing, and the mateπal is capable of adsorbing and desorbing water The material is further configured to be located and maintained in any desired manner, even when the material is subjected to temperature swings, shock and vibration, and high humidity The combination of materials allows the desiccant members to adsorb moisture without saturating and to shed the adsorbed moisture and regenerate when exposed to heat

Another feature of this shaped material is that the rate of adsorption and desorbtion of the shaped material can be influenced in a variety of manners

The means of altering the rate of adsorption and desorbtion beyond the shaped material's proximity to a thermally cycling device include variations of the shaped material's surface to volume ratio, variations of the shaped material's density, variations in the porosity or permeability of the shaped material, variations in the type of desiccant material used in the shaped material, variations in the size of the desiccant particles used in the shaped material, variations in the activity of the desiccant material used in the shaped material, masking or blocking of a part of the surface of the shaped material via coatings, adhesive, films, membranes, reflective materials, insulative materials, and/or contact with permeable, nonpermeable, or semi-permeable supports or covers and other similar means The ability to control the rate of adsorption and desorbtion of the adsorbate will permit more effective control over the formation of condensation within a housing or container as a device thermally cycles

The rate of adsorption and desorption of materials other than water by sorbents can also be controlled or modified via the processes and constructions described for moisture In some situations it may be valuable to control the rate of vapor desorption from an adsorbent material The rate of adsorption and desorption for an adsorbent member can be modified in the following ways variations of the shaped material's surface to volume ratio, variations of the shaped material's density, variations in the porosity or permeability of the shaped material, variations in the type of sorbmg material used in the shaped material, variations in the activity of the sorbmg material used in the shaped material, masking or blocking of a part of the surface of the shaped material via coatings, adhesive, films, membranes, reflective materials, insulative materials, and/or contact with permeable, nonpermeable, or semi- permeable supports or covers

Further examples of some of the processes that can be used to alter the rate of adsorption and desorption of sorbent materials are described below The surface to volume ratio of the sorbent member can be changed by alteπng the outer dimensions of the sorbent member Thickness of the sorbent material or height of the sorbent member can be increased while decreasing the radius of a disk, for example, or the length and width of a slab, for example, while keeping the weight of the member constant

The density and porosity or permeability of the sorbent material used in a sorbent member can also be altered Filled PTFE materials can be expanded or densified depending on the manner in which the material is processed after it is initially formed Methods of PTFE expansion are described later in the text Densification of filled PTFE materials can be accomplished by various processes including compressing the material with a press or rollers Masking or blocking a part of the sorbent members surface can be done in numerous ways Coating the surface can be accomplished by spraying, dipping, kiss coating, and numerous other known techniques The coating technique employed would be dependent on the coating mateπal used As an example, a urethane coating could be sprayed to block or mask the member surface Films could be applied using an adhesives such as the example using KAPTON® polyimide film Thermal bonding could be used to attach thermoplastic polymers such as polyethylene, polyester, etc , to the surface of the sorbent member or material Adhesives and/or coating techniques could also be used to attach reflective, insulating, permeable, nonpermeable, or semi-permeable layers in a manner described for KAPTON® polyimide film

It should be noted that in some situations where rate control is critical, it may be desirable to envelope all (i e , 100%), substantially all (e g , 99-95%), a significant part of (e g , 94-50%), a minor part of (e g , 49-1%), or none of the sorbent members surface The rate of adsorption and desorption required for a sorbent member in a specific application would be dependent on the design constraints imposed on the sorbent member by the application

It is desirable that the shaped mateπal of the present invention be sufficiently strong and resilient to prevent tearing when installed, such as over a light bulb or socket, or screwed or riveted to a wall In the preferred embodiment, the shaped material is constructed of a material which is sufficiently strong to avoid tearing and deterioration during prolonged use A number of composite mateπals comprising acceptable substrate that can retain adsorbant materials could be considered for use A sorbant material that is suitable for some applications is a multilayer biocomponent thermoplastic nonwoven incorporating adsorbant fillers such as that described in PCT Patent

Application WO 94/1 1556, incoφorated by reference, thermally induced phase separated polyethylene filled materials, or other similar polymer materials

Referring now to the drawings in detail, wherein like numerals indicate like elements throughout, there is shown in Fig 1 a perspective view of a shaped desiccant member 10 including a drying agent in accordance with a first embodiment of the present invention

As has been explained, the basic composition of the shaped material 10 according to the present invention may comprise a filled polymer, such as a polyethylene, a polytetrafluoroethylene (PTFE) or similar binder material that includes a drying agent therein It is particularly preferred that the material 10 employed in the present invention comprises a porous PTFE or, a porous expanded PTFE (ePTFE), such as that made in accordance with United States Patents 3,953,566, 3,962,153, 4,096,227, 4,187,390, and 4,902,423, all incorporated by reference This expanded PTFE material comprises a microporous structure of microscopic polymeric fibrils (i e , thread-like elements) interconnecting polymeric nodes (i e , particles from which fibrils emerge) Numerous microporous voids are provided within the material As the term "expanded PTFE" or "ePTFE" is used herein, it is intended to include any PTFE material having a node and fibril structure, including in the range from a slightly expanded structure having fibrils extending from relatively large nodes of polymeric or other material, to an extremely expanded structure having fibrils merely intersect with one another at nodal points

PTFE has a number of important properties that make it particularly suitable as a support material for drying agents of the present invention First, PTFE is a highly inert material that is hydrophobic Accordingly, the material is resistant to both water and a wide variety of other materials that could damage some of the reflectant surfaces Additionally, by expanding PTFE in the manner taught by United States Patent 3,953,566 to form the node and fibril structure, the material undergoes a significant increase in tensile strength and becomes highly flexible Moreover, expanded PTFE has proven to be an extremely effective support material that entraps drying agent particles and keeps them contained within the nodes and fibrils without the need for an outer cover or similar external package to contain the drying agent

A preferred PTFE material for use in the present invention is made in the following manner A fine powder PTFE resm is blended with a lubricant, such as odorless mineral spirits, until a coagulated compound is formed The volume of lubricant used should be sufficient to lubricate primary particles of the PTFE resin so as to minimize the potential of the shearing of the particles prior to extruding The compound is then compressed into a billet and extruded, such as through a ram type extruder, to form a coherent sheet of extrudate A reduction ratio of about 30 1 to 300 1 may be used (i e , reduction ratio = cross- sectional area of extrusion cylinder divided by the cross-sectional area of the extrusion die) For most applications, a reduction ratio of 75 1 to 100 1 is preferred

The lubricant may then be removed, such as through volatilization, and the dry coherent extrudate sheet is expanded rapidly in at least one direction about 1 1 to 50 times its original length (with about 1 5 to 2 5 times being preferred) Expansion may be accomplished by passing the dry coherent extrudate over a series of rotating heated rollers or heated plates at a temperature of between about 100 and 325°C, such as through the method taught in United States Patent 3,953,566 Alternatively, the extruded sheet may be expanded in the manner described in United States Patent 4 902,423 to Bacino, prior to removal of the lubricant In either case, the material may be further expanded at a ratio of 1 1 1 to 50 1 (with 5 1 to 35 1 being preferred) to form a final microporous sheet Preferably the sheet is biaxially or multi-axially expanded so as to increase its strength in both its longitudinal and transverse directions Finally, the material may be subjected to an amorphous locking step by exposing it to a temperature in excess of 340°C

According to the present invention, the shaped material 10 also includes a drying agent or "desiccant " Suitable drying agents which may be included in the shaped material include, but are not necessarily limited to, Al₂0₃, CaCI₂, CaS0₄, K₂C0₃, molecular sieves, Na₂S0 , activated carbon, and silica gel The amount of the drying agent required is dependent on the type of device being used and the environment the device is exposed to The drying agent may be included in the shaped material by mixing the drying agent with the PTFE dispersions during coagulation of the dispersion

For instance, a concentration range of 30 to 90 wt% drying agent was mixed with ePTFE Generally, when the amount of drying agent is less than

0 1%, then minimal beneficial sorb g capacity is obtained Generally, when the drying agent amount exceeds 98 wt%, the physical properties of the formulation is believed to become commercially undesirable More desirable drying agent concentrations are from about 5 % to about 95 %, even more preferred concentrations are from about 10 % to about 90 % The preferred range for use with sorbent filled thermally induced phase separated polyethylene and like materials is 5 to 90 wt% sorbent material mixed with polyethylene or a like material The most preferred range for thermally induced phase separated polyethylene and like materials is believed to be 10 to 90 wt% sorbent material mixed with polyethylene or a like material

The preferred range for multilayer thermoplastic nonwoven materials incorporating sorbent materials is 10 to 90 wt% sorbent material with the thermoplastic material The most preferred range for multilayer thermoplastic nonwoven materials incorporating sorbent materials is believed to be 20 to 90 wt% sorbent material with the thermoplastic material Packaged sorbents in which sorbents are retained by various polymeric and/or fibrous materials in a pouch or envelope can have very high sorbent loadings The preferred range for packaged sorbent materials is 20 to 99 wt% sorbent material contained by the packaging material The most preferred range for packaged sorbent materials is believed to be 30 to 99 wt% sorbent material contained by the packaging material

As improvements are made in each of the materials and methods of processing the materials described above, it can be envisioned that improvements in the physical properties of the filled materials will be made With improved physical properties at higher sorbent loadings, it can be envisioned that materials with sorbent loadings greater than the ranges described for the sorbent member could be used for the present invention with potentially beneficial effects

The invention thus provides a method of forming a shaped material including a drying agent or desiccant from a variety of porous polymer compositions Where PTFE is employed, the method includes the steps of (a) mixing a PTFE dispersion, (b) processing the mixture, and (c) forming a predetermined shape from the processed mixture The predetermined shape may be formed by a variety of methods, such as die cutting, extruding or various molding and forming methods

The ability to form the composition into a vaπety of shapes without the use of packaging or a subhousing is an important aspect of the invention Again, referring to Fig 1 , the shaped material 10 comprises a toroid or πng shaped member 12, including a center hole 14 For some applications it may be further useful to provide an adhesive layer 15, such as a pressure sensitive adhesive, on at least one face of the desiccant member 10 of the present invention to aid in holding the member in position during use The dimensions, i e , diameter of the ring shaped member 12, the thickness, and the size of the center hole 14, etc , may all vary depending upon the particular application for which the ring shaped member 12 is to be used and the amount of moisture which the ring shaped member 12 will be required to adsorb Each of these variables may be readily determined by one of ordinary skill in the art

The dimensions of the desiccant member can also be manipulated to change the surface to volume ratio Changes in the surface to volume ratio of the desiccant member can effect the rate of adsorption and desorption by the desiccant member As mentioned previously, the rate of adsorption and desorption of the desiccant member can be an essential part of the desiccant member design

Fig 2 is a perspective view of a shaped material 10 including a drying agent in accordance with a second embodiment of the present invention In Fig 2, the material 10 comprises a rectangular shaped member 16, which also includes a rectangular center hole 18 Referring to Figs 3A and 3B, the shaped material 10 comprises a plug or cylinder shaped member 20 The cylindπcal shaped member 20 shown in Fig 3A also includes a pair of vertical channels 22 extending from a top surface 24 thereof through to a bottom surface 26 thereof Although the vertical channels 22 are shown extending through cylindrical member 20, the vertical channels 22 could extend only partially through the member 20 In addition, although the embodiment shown includes only two vertical channels, more or less vertical channels could be provided Alternatively, horizontal channels or holes (not shown) could be placed or cut into the member 20 Thus, it will be apparent to those of ordinary skill in the art that the shape of the material 10 may vary depending upon the desired shape suitable for the application in which the material will be used Although, particular applications in which particular shapes are desirable are described below, it will be apparent to those of ordinary skill in the art that most any shape, size or configuration is possible and within the scope of the invention

Forming or shaping the desiccant member into shapes that are functional for a specific application is an advantage of the desiccant members described by this invention For automotive lighting, attaching a desiccant material to the bulb, bulb socket, bulb socket conductors, or bulb supports (bulb assembly) can provide advantages over pπor drying devices Attaching or locating the desiccant materials on the bulb assembly allows the desiccant material to be installed as a part of the bulb assembly as opposed to the desiccant material being installed into the housing in a separate operation A desiccant material installed on the bulb assembly can also be placed such that the desiccant material does not interfere or minimally interferes with reflective surfaces of the light The toroid or ring shape located between the bulb and socket illustrates this concept. The disk shape installed in a socket recess is another example of this idea Attaching the desiccant material to a heat shield or other structure required in a lamp assembly can provide the same advantages as attaching the desiccant to the bulb assembly The desiccant material can be installed into the housing as part of the heat shield installation and the desiccant material can be placed such that there is no interference or minimal interference with the reflective surfaces of the light These general locations and shapes, in the case of lighting, have advantages over prior art locations and shapes These general shapes and locations could be used with many forms of desiccant materials including porous polymer matrices with or without covering materials, desiccants contained in various packages or housings, fibrous matrices, or desiccant materials made from other known techniques

As previously discussed, one use of the shaped material 10 is for use in combination with a device which thermally cycles, such as an electronic device or a light bulb, especially a device or bulb which is confined within a housing Referring now to Fig 4, a perspective view of the cylindrical member 20 of Fig 3A having a pair of vertical channels 22 is shown in combination with a light bulb 28 and a light bulb socket 30 When an electrical light bulb, such as light bulb 28, is energized, heat is generated by electπcal current passing through a filament 32 in the bulb 28 When light bulb 28 is de-energized, the bulb 28 no longer generates heat and thus, cools to an ambient temperature This process is repeated each time the light bulb is turned on and off The light bulb 28 may therefore be characterized as a device which "thermally cycles "

The light bulb socket 30 includes a recess 34 and a pair of conductive blades 36 of the light bulb 28 As is well known, the conductive blades 36 conduct electπcal current between the light bulb 28 and the light bulb socket 30 According to one embodiment of the present invention, the cylindrical member 20 is placed in the recess 34 of the socket 30 The light bulb 28 with the blades 36 pass through the vertical channels 22 in the cylindrical member 20 In this embodiment, it can be seen that the member 20 is located proximate to the heat source (i e , the light bulb) As the term "proximate to the heat source" is used herein, it is intended to include mounting an embodiment of the present invention in direct contact with, directly next to, or in close proximity to the heat source It is further apparent that a special housing or added member is not required for mounting the member 20 proximate to the light bulb 28 Even further, a heat shield is not required to protect the member 20 from the heat generated by the bulb 28 Thus, the member 20 is advantageous over pπor art desiccants which must be shielded from excessive heat and/or located within a separate housing Referring now to Fig 5, a side view, partially in cross-section, of the ring shaped member 12 of Fig 1 in combination with a light bulb 28 is shown In this embodiment, the ring shaped member 12 may be slipped over the light bulb 28 and placed between the light bulb 28 and the socket 30 Due to the conformable nature of the material 10 from which the ring shaped member 12 is constructed, the member 12 may be stretched over the bulb 28 Thereafter, since the member 12 has a smaller internal ring diameter than the diameter of the light bulb 28, the member 12 remains in position between the socket 20 and the bulb 28 Alternatively, the nng shaped member 12 can be placed between a socket and a bulb prior to inserting a bulb into a socket As with the previously described embodiment (Fig 4), the ring shaped member 12 is disposed proximate to the heat source, i e , the bulb 28, without the necessity of a heat shield or a special housing or bracket for securing the ring shaped member 12 It will also be apparent to those of ordinary skill in the art, that the rectangular shaped member 16, instead of the πng shaped member 12 could be placed over the bulb 28

It should be appreciated that the device of the present invention may be quite useful in applications where excessive heat may not be encountered For instance, even with lower temperature bulbs, the ability to correctly mount the device around the base of the bulb, and the ability of the device to be designed to adsorb and desorb moisture at carefully controlled rates are considered extremely beneficial

Referring now to Fig 6, a sectional view of a vehicle head lamp 38 is shown The vehicle head lamp 38 is meant to be exemplary of known vehicle lamps (e g , headlamps, tail lamps, dπving lamps, signal lamps, fog lamps, etc ), which, as is well known, generally include an incandescent light bulb 40 housed in a reflective housing 42 capped with a lens 44 The light bulb 40 is plugged or otherwise mounted into a light bulb receiving socket 46 and mounted in the reflective housing 42 Often, a sealing ring 48 is disposed between the socket 46 and the housing 42 to seal the interior of the housing 42 from outside air In addition, it is known to include a vent 50 and any number of means for minimizing the entry of liquid water into the housing while permitting air flow to and from the housing to allow pressure equalization An air permeable membrane 52 is one means to allow airflow into and out of the housing 42 A number of other means have been found to allow pressure equalization for automotive lamps and other thermally cycling devices In many prior art head lamp designs, a small housing or channel (not shown) is also included for holding a desiccant, the housing or channel being attached to an inner wall of the reflective housing 42 proximate the vent hole 50 However, using the compositions of the present invention, a separate housing or channel for a desiccant is no longer required As shown in Figs 4 and 5, a desiccant material member, such as members 12, 16 or 20, may be located proximate to the light bulb 40 for maintaining a dry atmosphere within the housing 42 Alternatively, as shown in Fig 6, if the housing 42 also includes a reflector/heat dissipator 54, a desiccant member 56 formed according to the present invention may be secured or attached thereto The formed desiccant member 56 is shown attached to an outer surface 55 of the reflector/heat dissipator 54 with a screw or rivet attachment means 58 Alternatively, the desiccant member 56 could be attached to an inner surface 57 of the reflector/heat dissipator 54 with a mechanical attachment means 58 If the desiccant member 56 is in the shape of a ring, as previously described and shown in Fig 1 , then the attachment means 58 may pass through the inner hole of such a ring shaped member Alternatively, the desiccant member 56 could be formed as a solid rectangular member (or circular member) without any holes or openings therein and could be attached to the reflector/heat dissipator 54 with an adhesive The adhesive could be formed as a separate layer on the desiccant member 56 during manufacturing and preserved with a peelable tab or release paper layer prior to installation, as is well known to those of ordinary skill in the art The desiccant member 56 could thus be secured proximate to the light bulb 40 with either mechanical attachment means 58, as shown, or with an adhesive means, or a combination of both mechanical means and adhesive means

Fig 7 is a sectional view of the housing 42 including a reflector/heat dissipator 60 proximate to the light bulb 40 A formed desiccant member 62 is attached to an interior surface 64 of the reflector/heat dissipator 60 by an adhesive attachment means, i e , an adhesive composition which bonds the desiccant member 62 to the heat dissipator 60 Alternatively, the desiccant member 62 could be attached to the reflector/heat dissipator 60 by other adhesive attachments means, such as tape (not shown), or by mechanical attachment means, such as a screw, rivet, thermally bond, mechanical clip, mechanical pinch, velcro, needle point, hook, or the like In addition, although shown attached to the interior surface 64, the desiccant member 62 could also be attached to an outer surface 66 of the reflector/heat dissipator 60 However, by disposing the desiccant member 62 proximate to the heat source, i e , the light bulb 40, the desiccant member 62 is more completely regenerated when the lamp is lit Attachment to the bulb socket, light bulb, conductors, and/or interior surface of the housing would also be feasible using the methods and devices outlined above

As previously mentioned, the rate of adsorption and desorption of the shaped material can be modified by a number of methods In the case of a housed thermally cycling device exposed to environmental temperature and humidity fluctuations, the rate of adsorption and desorption of the adsorbate during the heating and cooling cycles will affect the formation of condensation within the housing For example, when the adsorbent is heated rapidly and the adsorbate is expelled rapidly, the surrounding air temperature increase may not be sufficient to accommodate all the adsorbate and the saturation point for the adsorbate is reached resulting in condensation In this situation, the rate of desorption of the adsorbate could be slowed allowing the air in the housing to achieve a higher temperature and a greater capacity for adsorbate The air will carry the adsorbate out of the housing as it thermally expands and the vapor volume of the adsorbate increases during the desorption process

Use of the present invention in a vehicle head lamp 38 minimizes the formation of condensation The present invention also minimizes condensation on the reflective surface of the housing 42 of the lens 44, which could damage the reflective surface (e g , via corrosion) or interfere with the reflection of light While this invention is particularly applicable for use with automotive or vehicle head lamps, it can be beneficially used in other applications where moisture control is desired For example, the present invention may be readily employed in a wide variety of light devices, such as street lamps, transportation lighting in general, and other outdoor lights, etc It is contemplated that the device of the present invention may be used, for instance, in an airplane equipped with electronic devices maintained in a closed box for protecting the electronic device from drastic atmospheric conditions The present invention may be included in such a closed box for maintaining a dry atmosphere (i e , an atmosphere that is not saturated with moisture) therein

The invention may also be used in other automotive electronic devices, such as engine control units Engine control units have components that thermally cycle within a vented or sealed housing The invention could be used to eliminate or minimize condensation within this type of unit as well as other devices which are housed and thermally cycled, such as motors, capacitors, displays, lamps, heat exchangers, heat sinks, etc

Finally, formed desiccant material of the present invention may be provided in lieu of a typical silica gel package commonly used for drying One particular example would be to place a formed shape of desiccant material, such as the shape shown in Fig 3B, in a shipping package containing a fragile device, such as an electronic device packed in cushioning materials

Figure 8 demonstrates that the member 10 of the present invention may be mounted into a lamp fixture 70 prior to insertion of a bulb 40 From this drawing it can be appreciated that the member 10 can be proportioned to fit closely around the base of the bulb so that the member 10 will not displace by sliding over the bulb once the light fixture is assembled

For some lamp applications it will be possible to use packaged desiccant materials In cases where a packaged desiccant material will provide acceptable performance with regard to temperature resistance and rate of adsorption and desorption, the ring shape, disk shape, and other shapes that are functional to installation, and can be placed proximate to the light bulb, could be made using a packaged desiccant material Figure 9 is a perspective view of a ring shaped material 72 similar to material 10 in Figure 1 This material has a fibrous outer layer that retains the desiccant material within an envelope or pouch The fibrous material can be sealed or closed at the perimeter of the part using numerous techniques The shapes and locations previously described as improvements over prior art can be used with packaged desiccant materials in some instances From the foregoing description, it can be seen that the preferred embodiment of the invention comprises a shaped material including a drying agent that requires no cover or subhousing for use in protecting a thermally cycling device from moisture The shaped material exhibits excellent drying properties, can be regenerated, and can be placed so that the material is very close to or in direct contact with the thermally cycling device, the material can also be modified to effect rates of adsorption and desorption which can be critical for some applications

There are a number of materials from which the shaped desiccant member of the present invention can be made For the most part, the polymeric or fibrous materials of the desiccant member will determine the maximum temperature to which the desiccant member could be exposed The maximum temperature that the member withstands is dependent on the temperature at which the polymeric or fibrous material begins to degrade if it is a thermoset material or significantly soften if it is a thermoplastic material The maximum continuous use temperature for PTFE is approximately 300 °C "Polyethylene" describes a wide range of materials with various molecular weights and corresponding melting points Generally, 130 °C represents the high end of temperature range for a polyethylene material Other polymeric and/or fibrous materials such as polyesters, polyolefins, polypropylenes, nylons, cellulose fibers, cellulosic plastics, etc , have functional temperature limits based on the degradation or softening temperatures of the individual polymer, polymer blends, or fibrous materials

The adsorptive capacity of the desiccant members is related to the temperature change that occurs as a result of a thermal cycle A change of 5°C in the desiccant members temperature during a thermal cycle of a heat source or thermal cycling device permits the desiccant member to absorb and desorb an absorbent For most desiccant materials, this temperature change may not allow the most efficient use of the desiccant It should be noted, however, that in some situations design constraints, such as space or locations available proximate a heat source or device, or the maximum temperature change achieved by the thermal cycling heat source or device, may limit the temperature change of the desiccant member It would be more desirable if the temperature change that occurred in the desiccant member were 10 °C Still more desirable would be a temperature change of 15 °C in the desiccant member Further capacity utilization of the desiccant would result when the desiccant member has a temperature increase of 20 °C Automotive lamp temperature changes can vary significantly depending on the type of lamp and lamp design, as well as the type of light bulb and light bulb design

Temperature increases of greater than 30 °C have been observed proximate to incandescent bulbs near the bulb base Temperature increases of greater than 90 °C have been observed proximate to the base of halogen bulbs Temperatures for high intensity discharge bulbs are anticipated to be greater than the temperatures of halogen bulbs

It is a particular benefit of the present invention that the desiccant device can be made to release moisture at a controlled rate suitable for particular applications As the term "controlled rate" is used in this application, it is intended to denote any instance where the desiccant device of the present invention releases moisture at a rate different from the rate of moisture evaporation from an uncovered dish containing the same quantity of water and exposed to the same environmental conditions via the options disclosed above or other similar processes It is particularly preferred that the desiccant device of the present invention releases moisture at a gradual rate over time, closely approximating the normal cycling time and expected environmental conditions of the thermal cycling device In this regard, moisture release should be slow enough that noticeable condensation does not occur

For some lamp applications it will be possible to use packaged desiccant materials In cases where a packaged desiccant material will provide acceptable performance with regard to temperature resistance and rate of adsorption and desorption, the ring shape, disk shape, and other shapes that aid in installation and positioning during use, and can be placed proximate to the light bulb, could be made using a packaged desiccant material Figure 9 is a perspective view of one such ring shaped member 72 This member 72 has a porous outer cover 74 that retains a desiccant material 76 within an envelope or pouch The cover 74 can be sealed or closed along its perimeter 78 using any suitable technique, such as sealing edges of the cover (as shown), providing a non-permeable coating along the edge, using a binder on the desiccant mateπal, etc The desiccant contained in the cover may be loose or may be bound in a porous polymer, as previously described herein

Without intending to limit the scope of the present invention, the following examples illustrate how the present invention may be made and used

Example 1

In this Example 900 grams of Sι0₂ solids were added to 18000 cc of deionized water in a 38 liter baffled stainless steel container The SιO₂ was Syloid 53 obtained from Grace Davidson After agitating 5 minutes, 2100 g of PTFE solids in the form of a 28 6% solids dispersion was rapidly poured into the mixing vessel The PTFE was AD-059 dispersion obtained from ICI Americas, Inc After 1 minute of mixing, 2727 grams of a 0 44% solution of Sedipur 803 was added The Sedipur 803 was obtained from BASF The mixture coagulated immediately and was mixed for 1 5 minutes

The co-coagulum was placed in trays and dried in a convection oven for 24 hours at 165°C The compound was chilled to -10°C and screened through a coarse mesh screen Approximately 0 45 grams of lubricant was added per gram of screened compound The lubricant was a mixture of 1/3 IPA and 2/3 propylene glycol The lubricated compound was frozen, tumbled, and screened Then the lubricated compound sat at 65°F (18°C) for 16 hours The compound was tumbled again and pelletized under vacuum in a cylinder

The pellet was heated to 49°C and ram extruded through a 4" x 0 125" (10 2 cm x 0 318 cm) tape die The extrudate was calendered through heated rollers to 125 mils The tapes were then soaked in a 25 gallon bath of water and sonicated for 2 hours Spacer layers were placed between layers to aid diffusion This procedure was repeated 3 times The tapes were then dried using two zone convection ovens set at 155°C and 270°C The oven was approximately 20 feet (6100 mm) long and the tap traveled at 1 ft/minute (305 mm/minute)

This process resulted in a material with the following typical properties Thickness 0 125 inch (0 318 cm)

Width 3 2 inches (8 13 cm)

Weight Percent SιO₂ 30% Example 2

In this Example 900 grams of SιO₂ solids were added to 18000 cc of deionized water in a 38 liter baffled stainless steel container The Sι0₂ was Syloid 53 obtained from Grace Davidson After agitating the container for 5 minutes, 2100 grams of PTFE solids in the form of a 28.6% solids dispersion was rapidly poured into the mixing vessel The PTFE was AD-059 dispersion which was obtained from ICI Americas Inc After 1 minute of mixing, 2727 grams of a 44% solution of Sedipur 803 was added The Sedipur 803 was obtained from BASF The mixture coagulated immediately and was mixed for 1 5 minutes

The co-coagulum was placed in trays and dried in a convection oven for 24 hours at 165°C The compound was chilled to -10°C and screened through a coarse mesh screen. Approximately 0.45 grams of lubricant was added per gram of screened compound The lubricant was a mixture of 1/3 IPA and 2/3 propylene glycol. The lubricated compound was frozen, tumbled, and screened Then the lubricated compound sat at 65°F (18°C) for 16 hours The compound was tumbled again and pelletized under vacuum in a cylinder.

The pellet was heated to 49°C and ram extruded through a 4" x 0 125" (10.2 cm x 0.318 cm) tape die The extrudate was calendered through heated rollers in three passes to 60 mils The tapes were then soaked in a 25 gallon bath of water and sonicated for 2 hours. Spacer layers were placed between layers to aid diffusion. This procedure was repeated 3 times The tapes were then dried using two zone convection ovens set at 155°C and 270°C The oven was approximately 20 feet (6100 mm) long and the tap traveled at 5 ft/minute (1.520 mm/minute).

This process resulted in a material with the following typical properties Thickness 0 061 inch (0 155 cm)

Width 3.2 inches (8 13 cm)

Weight Percent SiO₂ 30%

Example 3

In this Example 1500 grams of SiO₂ solids were added to 18000 cc of deionized water in a 38 liter baffled stainless steel container The SiO₂ was Syloid 53 obtained from Grace Davidson After agitating the container for 5 minutes, 1500 grams of PTFE solids in the form of a 28 6% solids dispersion was rapidly poured into the mixing vessel. The PTFE was AD-059 dispersion which was obtained from ICI Americas Inc. After 1 minute of mixing, 693 grams of a 4% solution of Sedipur 803 was added. The Sedipur 803 was obtained from BASF. The mixture coagulated immediately and was mixed for 1.5 minutes.

The co-coagulum was placed in trays and dried in a convection oven for 24 hours at 165°C. Approximately 0.73 g of lubricant was added per gram of screened compound. The lubricant was a mixture of 1/3 IPA and 2/3 propylene glycol. The lubricated compound was frozen, tumbled, and screened. Then the lubricated compound sat at 65°F (18°C) for 16 hours. The compound was tumbled again and pelletized under vacuum in a cylinder.

The pellet was heated to 49°C and ram extruded through a 4" x 0.125" (10.2 cm x 0.318 cm) tape die. The extrudate was calendered through heated rollers to 125 mils. The tapes were then soaked in a 25 gallon bath of water and sonicated for 2 hours. Spacer layers were placed between layers to aid diffusion. This procedure was repeated 3 times. The tapes were then dried using two zone convection ovens set at 155°C and 270°C. The oven was approximately 20 feet (6100 mm) long and the tap traveled at 1 ft/minute (305 mm/minute). This process resulted in a material with the following typical properties:

Thickness 0.128 inch (0.325 cm)

Width 3.0 inches (7.62 cm)

Weight Percent SiO₂ 50%

Example 4

In this Example 1500 grams of SiO₂ solids were added to 18000 cc of deionized water in a 38 liter baffled stainless steel container. The Si0₂ was Syloid 53 obtained from Grace Davidson. After agitating the container for 5 minutes, 1500 grams of PTFE solids in the form of a 28.6% solids dispersion was rapidly poured into the mixing vessel. The PTFE was AD-059 dispersion which was obtained from ICI Americas Inc. After 1 minute of mixing, 693 grams of a 4% solution of Sedipur 803 was added. The Sedipur 803 was obtained from BASF. The mixture coagulated immediately and was mixed for 1.5 minutes. The co-coagulum was placed in trays and dried in a convection oven for 24 hours at 165°C The compound was chilled to -10°C and screened through a coarse mesh screen Approximately 0 73 g of lubricant was added per gram of screened compound The lubricant was a mixture of 1/3 IPA and 2/3 propylene glycol The lubricated compound was frozen, tumbled, and screened Then the lubricated compound sat at 65°F (18°C) for 16 hours The compound was tumbled again and pelletized under vacuum in a cylinder

The pellet was heated to 49°C and ram extruded through a 4" x 0 125" (10 2 cm x 0 318 cm) tape die The extrudate was calendered through heated rollers in three passes to 60 mils The tapes were then soaked in a 25 gallon bath of water and sonicated for 2 hours Spacer layers were placed between layers to aid diffusion This procedure was repeated 3 times The tapes were then dried using two zone convection ovens set at 155°C and 270°C The oven was approximately 20 feet (6100 mm) long and the tap traveled at 5 ft/minute (1520 mm/minute)

This process resulted in a material with the following typical properties Thickness 0 060 inch (1 52 cm)

Width 3 0 inches (7 62 cm)

Weight Percent SιO₂ 50%

Example 5

The silica gel material in this example is produced by way of thermally induced phase separation of polyethylene The equipment used is a Zsk28 twin screw extruder manufactured by Werner and Pfleiderer, along with an 8 inch (20 3 cm) flex lip sheeting die The silica gel is Syloid 53 from Grace

Davidson and is metered into the throat of the extruder using an accurate powder feeder at the rate of 2 ounces per minute Likewise, polyethylene with an average molecular weight of 500,000 is fed into the extruder throat, but at a rate of only 0 2 ounces per minute The powders are conveyed through the extruder and mixed with a petroleum oil that is injected at the first barrel at a rate of 2 ounces per minute At an elevated temperature, the polyethylene dissolves in the petroleum oil and becomes uniformly mixed with the silica gel and oil The mixture is then extruded through the 8 inch (20 3 cm) sheeting die at a thickness of 0 03 inches (0 08 cm), and subsequently fed through calendaring rolls and chilled rolls. The petroleum oil is then extracted out of the resulting sheet using hexane as a solvent.

This process results in a material with the following typical properties: Thickness 0.030 inch (0.08 cm) Width 8.2 inches (20.8 cm)

Weight percent SiO₂ 90%

Experimental Part Manufacture

The desiccant filled PTFE sheet materials from the processes outlined above and multilayer biocomponent thermoplastic nonwoven adsorbant filled materials were used in the manufacture of parts for concept validation purposes. The washer and disk shaped parts were die cut from the desiccant filled PTFE sheet stock using machined steel punches. Any slits formed in the parts were made with scissors or razor blades. Rectangular parts were made by cutting the materials with razor blades.

Adhesive materials placed on a release film was first laminated to the desiccant filled PTFE sheet materials. The part shape was then manufactured as explained above. When the parts were used, the release film was removed from the adhesive material exposing the adhesive. The desiccant filled PTFE parts were placed on a substrate with the adhesive material against the substrate.

Example 6

Test samples were cut from rolls of material comprising the following: 0.125" (3.18 mm) thick porous PTFE with a 30% loading of silica gel

0.061" (1.55 mm) thick porous PTFE with a 30% loading of silica gel 0.128" (3.25 mm) thick porous PTFE with a 50% loading of silica gel 0.060" (1.52 mm) thick porous PTFE with a 50% loading of silica gel

KAPTON® polyimide film is used as an example of a nonporous layer used to block a part of the surface of the shaped material and thereby alters the rate of desorbtion and adsorption of the shaped member.

All samples were cut to fit into 3.68" (93.5 mm) diameter sample pans for use with the Mettler Infrared Dryer and Moisture Analyzer. Samples were not treated or altered in any way except as noted below. Samples with KAPTON® polyimide film were made by bonding KAPTON® polyimide film acquired from E I du Pont de Nemours and Co with adhesive to one surface of the sample The KAPTON® polyimide film covered side of the samples were facing the Mettler infrared heat source during the testing The adhesive used to attach the KAPTON® polyimide film to the sample surface was SCOTCH™ Brand 9188MP Laminating Adhesive acquired from Minnesota Mining & Manufacturing Co

Adsorption testing was done as follows 1 ) Four sample groups with three samples each were tested

2) The sample groups were the following

A) 30 weight % silica gel with a surface to volume ratio of 17 1 (3 68" OD (93 5 mm) x 0 125" (3 18 mm) thick)

B) 30 weight % silica gel with a surface to volume ratio of 33 9 (3 68" OD (93 5 mm) x 0 061" (1 55 mm) thick)

C) 50 weight % silica gel with a surface to volume ratio of 16 7 (3 68" OD (93 5 mm) x 0 128" (3 25 mm) thick)

D) 50 weight % silica gel with a surface to volume ratio of 34 4 (3 68" OD (93 5 mm) x 0 060" (1 52 mm) thick) 3) Samples were dried in an air circulating oven for 20 hours at 160 °C

4) Samples were individually removed from the oven, weighed and placed in a container at greater than 95% relative humidity and 21 ±2 °C

5) Samples were removed from the humidity chamber, weighed, and returned to the humidity chamber 6) Samples were weighed at the following time periods after removal from the oven 30 minutes, 120 minutes, 240 minutes, 480 minutes, and 1440 minutes

Desorption testing was done as follows 1 ) Four sample groups with three samples each were tested for all tests except the testing with the KAPTON® polyimide film Only one sample from each group was used in the KAPTON® polyimide film tests

2) The sample groups were the following A) 30 weight % silica gel with a surface to volume ratio of 17 1 (3 68" OD (93 5 mm) x 0 125" (3 18 mm) thick)

B) 30 weight % silica gel with a surface to volume ratio of 33 9 (3 68" OD (93 5 mm) x 0 061" (1 55 mm) thick) C) 50 weight % silica gel with a surface to volume ratio of 16 7

(3 68" OD (93 5 mm) x 0 128" (3 25 mm) thick) D) 50 weight % silica gel with a surface to volume ratio of 34 4 (3 68" OD (93 5 mm) x 0 060" (1 52 mm) thick)

3) Samples were stored in a container at greater than 95% relative humidity and 21 ±2 °C for 48 hours

4) Samples were individually removed from the humidity chamber and placed in a Mettler LP16 Infrared Dryer and LJ16 Moisture Analyzer This device was used to heat the samples and measure the weight loss of the samples 5) Samples were heated to 160 °C or 80 °C for the measurement period

6) Samples were continuously weighed and weight loss was recorded via a printer attached to the Mettler every 30 seconds

The weight gam or weight loss of the samples is expressed as the percentage of weight gained or lost at the time of the sample weight measurement, divided by the total weight gam or loss of the sample during the duration of test This unit of measurement was used for comparison in all the graphs Adsorption test results are contained in the graph of Figure 10 The graph of Figure 11 provides for closer inspection of the test results over a shortened time period

Three test conditions were chosen for the collection of desorption data from the four sample groups The graph of Figure 12 contains data collected at 160°C for the four groups of samples The graph of Figure 13 contains data for samples covered with KAPTON® polyimide film on one side and then heated to 160°C The graph of Figure 14 displays the data on Figures 12 and 13 together for convenient comparison The graph of Figure 15 contains data collected at 80°C for the four groups of samples The test results demonstrate that the rate of adsorption and desorption of silica gel filled PTFE can be significantly affected by the following 1 ) Weight percent Silica Gel in the filled PTFE material 5 2) Surface to volume ratio of the filled PTFE material

3) Films (KAPTON® polyimide film) adhered to the surface of the filled PTFE material

4) Temperature that the filled PTFE material is exposed to

l o This data indicates that the adsorption and desorption rates of desiccant filled materials can be significantly modified permitting desiccant filled member design for particular applications

It will be appreciated by those skilled in the art that changes and modifications could be made to the embodiments described above without

15 departing from the broad inventive concept thereof It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims

Claims

1 A desiccant member in combination with a heat source comprising a heat source that thermally cycles, and a desiccant member composed of a porous polymer matrix and a drying agent for adsorbing moisture from air, wherein said member is disposed proximate to said heat source, wherein heat generated by said heat source regenerates the drying agent

2 The combination of claim 1 wherein the drying agent is selected from the group consisting of Al₂0₃, CaCI₂, CaS0₄, K₂C0₃, molecular sieves,

Na₂S0 , silica gel, and activated carbon

3 The combination of claim 1 wherein said desiccant member further compπses an adhesive layer for attaching the desiccant member proximate said heat source 4 The combination of claim 1 wherein said heat source comprises a light bulb

5 The combination of claim 1 wherein said desiccant member is generally ring shaped

6 The combination of claim 1 wherein said desiccant member releases moisture at a controlled rate when heated

7 The combination of claim 1 wherein said desiccant member is mounted proximate to the heat source by mechanical attachment means

8 The combination of claim 1 wherein the porous polymer matrix comprises a PTFE structure of polymeric nodes and fibrils; and wherein the drying agent is entrapped within the node and fibril structure of the PTFE so that the drying agent is held therein without the need for a cover surrounding the desiccant member

9 The combination of claim 1 wherein the porous polymer matrix comprises a polyethylene structure of polymeric fibrils, and wherein the drying agent is entrapped within the fibril structure of the polyethylene so that the drying agent is held therein without the need for a cover surrounding the desiccant member 10 The combination of claim 1 wherein the porous polymer matrix comprises a multilayer thermoplastic nonwoven structure of polymeric fibrils, and wherein the drying agent is entrapped within the fibril structure of the multilayer thermoplastic polymer so that the drying agent is held therein without the need for a cover surrounding the desiccant member

11 A desiccant member in a device that thermally cycles, the member comprising a porous polymer matrix filled with a drying agent for adsorbing moisture from air proximate the device, wherein heat from the device regenerates the drying agent

12 The desiccant member of claim 11 wherein the drying agent is selected from the group consisting of Al₂0₃, CaCI₂, CaS0₄, K₂C0₃ molecular sieves, Na₂SO₄, silica gel, and activated carbon

13 The desiccant member of claim 11 wherein said desiccant member further comprises an adhesive layer for attaching the desiccant member proximate said device

14 The desiccant member of claim 11 wherein said device compπses a light bulb having a base and the desiccant member comprises a ring shape adapted to fit around the base of the light bulb 15 The desiccant member of claim 1 1 wherein said desiccant member is generally ring shaped

16 The desiccant member of claim 11 wherein said desiccant member releases moisture at a controlled rate when heated

17 The thermal cycling device of claim 11 wherein said desiccant member is mounted proximate the device by mechanical attachment means

18 The desiccant member of claim 11 wherein the porous polymer matrix comprises a PTFE structure of polymeric nodes and fibrils, and wherein the drying agent is entrapped within the node and fibril structure of the PTFE so that the drying agent is held therein without the need for a cover surrounding the desiccant member

19 The desiccant member of claim 11 wherein the porous polymer matrix comprises a polyethylene structure of polymeric fibrils, and wherein the drying agent is entrapped within the fibril structure of the polyethylene so that the drying agent is held therein without the need for a cover surrounding the desiccant member

20 The desiccant member of claim 11 wherein the porous polymer matrix comprises a multilayer thermoplastic nonwoven structure of polymeric fibrils, and wherein the drying agent is entrapped within the fibril structure of the multilayer thermoplastic polymer so that the drying agent is held therein without the need for a cover surrounding the desiccant member 21 A lamp comprising an electric light bulb, a socket for receiving said light bulb and supplying electπcal current thereto, a housing at least partially surrounding the socket and the light bulb, and a desiccant member comprising a combination of a heat resistant polymer and a drying agent contained therein, the desiccant member being affixed within the housing proximate to said bulb, whereby the desiccant member adsorbs moisture from air within the housing, and heat generated by the bulb dries the desiccant member, thereby regenerating the drying agent

22 The desiccant member of claim 21 wherein the drying agent is selected from the group consisting of Al₂0₃, CaCI₂, CaS0₄, K₂C0₃, molecular sieves, Na₂SO , silica gel, and activated carbon 23 The lamp of claim 21 wherein further comprising a vent for allowing air to pass to and from an interior of the housing

24 The lamp of claim 21 wherein said desiccant member comprises a shaped member filled with drying agent

25 The lamp of claim 21 wherein said desiccant member is mounted proximate said light bulb by mechanical attachment means

26 The lamp of claim 21 wherein said desiccant member includes an adhesive attached thereto

27 The lamp of claim 21 wherein said desiccant member is mounted proximate said light bulb by adhesive means 28 The lamp of claim 21 further comprising a heat shield located within said housing and proximate to the light bulb, wherein said desiccant member is mounted to the heat shield

29 The lamp of claim 21 wherein said desiccant member within said housing is mounted on the light bulb

30 The lamp of claim 21 wherein the desiccant member comprises generally a ring shape positioned around the base of the bulb

31 The lamp of claim 21 further comprising conductors for the light bulb located within said housing and proximate to the light bulb, wherein said desiccant member is mounted on the conductors

32 The lamp of claim 21 further comprising supports for the light bulb located within said housing and proximate to the light bulb, wherein said desiccant member is mounted on the supports

33 The lamp of claim 21 wherein said desiccant member within said housing is mounted on the interior of the housing proximate the light bulb

34 The lamp of claim 21 wherein said desiccant member within said housing is mounted on the bulb socket

35 The lamp of claim 21 wherein said desiccant member comprises a disk located within said socket 36 The lamp of claim 21 wherein said desiccant member releases moisture at a controlled rate when heated

37 The desiccant member of claim 21 wherein the heat resistant polymer comprises a PTFE structure of polymeric nodes and fibrils, and wherein the drying agent is entrapped within the node and fibril structure of the PTFE so that the drying agent is held therein without the need for a cover surrounding the desiccant member

38 The desiccant member of claim 21 wherein the heat resistant polymer comprises a polyethylene structure of polymeric fibrils; and wherein the drying agent is entrapped within the fibril structure of the polyethylene so that the drying agent is held therein without the need for a cover surrounding the desiccant member

39 The desiccant member of claim 21 wherein the heat resistant polymer comprises a multilayer thermoplastic nonwoven structure of polymeric fibrils, and wherein the drying agent is entrapped within the fibril structure of the multilayer thermoplastic polymer so that the drying agent is held therein without the need for a cover surrounding the desiccant member 40 A process for controlling rate of target chemical exchange from an adsorbent material that comprises providing a substrate mateπal, placing into the substrate material an adsorbent material, suitable for holding and releasing the target chemical, to form a porous composite material, treating the composite mateπal by coating the composite material with a non-porous layer that reduces the rate of exchange of the target chemical from the composite material to the surrounding environment 41 The process of claim 40 that further comprises modifying the porous composite material by expanding the composite to increase the porosity of the composite material