WO1999002931A1

WO1999002931A1 - Hydration and freezing plant for flexible refrigerant media

Info

Publication number: WO1999002931A1
Application number: PCT/US1998/014366
Authority: WO
Inventors: Joseph C. Murray; Lyman E. Gaude
Original assignee: Thermal Products, Inc.
Priority date: 1997-07-11
Filing date: 1998-07-10
Publication date: 1999-01-21
Also published as: IL133946A0; JP2001509583A; TR200000063T2; AU747273B2; EP1009960A4; BR9810864A; EP1009960A1; NO20000117L; AU8394298A; CA2294633A1; NO20000117D0; NO312486B1; CN1263590A; KR20010021754A; NZ502149A

Abstract

Apparatus for preparing packaging materials for use in shipment of heat sensitive materials, utilizes a hydration module (11), a freezing module (40), and a delivery module (45). Rolls of superabsorbent polymer-based refrigerant media (117) in the form of a continuous web of a selected length and width are maintained in dry storage. These may be cut to size along the web material which separates cells containing the superabsorbent polymer. The web or pad is advanced into the hydration module (11) which comprises a dip tank (17) or spray system (26) to provide an adequate supply of hydrating fluid to the superabsorbent polymer. The hydrated web is then conveyed through a freezing chamber (40) having a temperature of -10° Fahrenheit, or lower, where the fluid absorbed within the cells freezes. The small footprint of the modular system means that necessary handling, including cutting into a suitable size and shape, may be accomplished in the consumer's shipping area for placement around perishable materials in shipping containers.

Description

HYDRATION AND FREEZING PLANT FOR FLEXIBLE

REFRIGERANT MEDIA

TECHNICAL FIELD

The present invention relates generally to apparatuses and processes for hydrating and freezing a selected media used to keep a variety of objects cold. In greater particularity, the current apparatus and method relates to apparatuses and processes for hydrating and freezing refrigerant media containing superabsorbent polymer laminated in individual cells on continuous sheets of thermoformable media which may be placed into shipping cartons so that a selected cool temperature may be maintained within the carton during shipment to a selected destination.

BACKGROUND ART

The present invention is an apparatus and method for hydrating and freezing superabsorbent polymer-based refrigerant media similar to that disclosed in international patent application number PCT7TJS92/06486 (in reference to U.S. App. No. 07/738835), herein incorporated for reference, or similar media which is used to keep perishable materials at a controlled, cool or freezer temperature during shipment. Accordingly, discussion of the structure and properties of the media disclosed in the referenced patent shall be discussed in detail only to the extent necessary to explain the media's interaction with the components of the apparatus and method herein described, and inasmuch as a detailed understanding of the chemical properties of the media are not necessary for an understanding of the invention. Prior to using superabsorbent polymers laminated into individual cells, shipping containers utilized only a few substances to maintain a cool temperature inside a shipping container. These include: ice in sealed pouches, dry ice, and gel blocks. However, for reasons such as high cost, contamination and handling problems, and an inability to maintain critical temperatures in a .container during shipment, these shipping materials have begun to be replaced with frozen, superabsorbent polymer-based refrigerant media [hereinafter media]. One such media is ThermaFreeze® made by Thermafreeze, Inc. of Mobile, Alabama. ThermaFreeze® is manufactured in long rolls, typically in 15 or 30 inch widths, containing a matrix of laminated individual cells between elongated continuous sheets of thermoformable media, as disclosed in the referenced patent. Each cell contains a measured amount of superabsorbent polymer capable of absorbing water to many times its own weight and size, thereby filling each cell upon exposure to water. Prior to exposure of the cells to an aqueous environment, the cells in the rolls are filled with the superabsorbent polymer powder which occupies negligible space inside the cells. Therefore, prior to hydration the cells are unexpanded and the media consists of a flat sheet or web of cells typically 15 or 30 inches wide and of a preselected length (typically 300 feet).

In one preferred operation, a media roll must be unwound, exposed to an aqueous environment suitable to quickly hydrate the media, frozen, and cut into shapes and sizes suitable for arrangement within shipping containers. This preparation operation may be established "on-site" within a production facility for a user consuming the media in shipping operations. However, current methods for preparing the media are manually based and, therefore, time consuming; thereby increasing the overall cost of utilizing the media in shipping operations. Furthermore, the consumer may not have the necessary know how to optimize the preparation operation so that the media is suitably prepared for incorporation within shipping containers of varying sizes and shapes. In addition, a variety of other uses may be made of the product, but for the lack of proper knowledge and a feasible automation facility.

Therefore, there is a need in the shipping packaging, and other industries for an apparatus and method for automating the preparation of superabsorbent polymer refrigerant media prior to arrangement into shipping containers. Inasmuch as many facilities place a premium on the use of floor space, a modular unit which has a relatively small "footprint" is important.

DISCLOSURE OF THE INVENTION

It is the object of the present invention to provide an apparatus for automating the hydration and freezing of superabsorbent polymer-based refrigerant media.

A further object of the present invention is to provide a method for optimizing the hydrating and freezing of superabsorbent polymer-based refrigerant media.

Yet another object of the present invention is to provide a modular minimal footprint plant incorporating a method for hydrating and freezing superabsorbent polymer-based refrigerant media so that the media may be suitably prepared at a consumer's site prior to arrangement into shipping carriers.

In one embodiment, the invention includes a hydration module, a freezing module, and a delivery module. Superabsorbent polymer-based refrigerant media, in rolls or in the form of integral pads of a selected length and width are maintained in dry storage. Rolls may be cut to size along the web material which separates cells containing the superabsorbent polymer or may be precut by the manufacturer into pads of desired sizes. When ready for consumption, the stored rolls may be precut at the manufacturer's or customer's site to desired lengths or may be positioned on a delivery spindle from which the web may be spooled. The web or pad is advanced into the hydration module which comprises a dip tank or spray system to provide an adequate supply of water to the superabsorbent polymer. The absorbed water fills the cells of the web. The hydrated web or pad is then passed to a shaker conveyor for removal of external moisture. It is then conveyed into a freezing chamber having a temperature of -10° Fahrenheit, or lower, where the water absorbed within the cells freezes. The frozen web then exits the freezer. Necessary handling including cutting into a suitable size and shape may be accomplished in the consumer's shipping area for placement around perishable materials in shipping containers. When properly arranged with the perishable materials, such as food stuff, medical or chemical products, etc. the frozen media maintains a temperature within a predetermined temperature regime in the container during transport to a shipping destination.

In another embodiment, the invention includes a storage section, a hydration section, a freezing section, and a cutting section. The storage area stores rolls of superabsorbent polymer-based refrigerant media in the form of a continuous web of a selected length and width. When ready for consumption, the stored rolls are positioned on spindles so that the web may be spooled onto an adjacent conveying system consisting of a series of rollers positioned throughout the shipping trailer. As the media is unwound, it becomes entrained on the conveying rollers and driving rollers urge the web through other rollers in the conveying system. As the conveying system draws the web into the hydration area, which consists of a dip tank or overhead spray nozzles, the superabsorbent polymer absorbs water and fills the cells of the web. The hydrated web is then conveyed into a freezing chamber having a temperature of -10 degrees Fahrenheit, or lower, where the water absorbed within the cells freezes. The frozen media then is cut into a preselected size and shape in a laser cutting area and removed to the consumer's shipping area for placement around perishable materials in shipping containers. When properly arranged with the perishable materials, the frozen media maintains a temperature within a maximum/minimum window in the container during transport to a shipping destination.

Other features and objects and advantages of the present invention will become apparent from a reading of the following description as well as a study of the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Apparatus embodying features of the invention are depicted in the accompanying drawings which form a portion of this disclosure and wherein:

Fig. 1 is a sectional view of the hydration module taken along the longitudinal centerline thereof;

Fig. 2 is a sectional view of the refrigerant module taken along the longitudinal centerline thereof;

Fig 3. is a sectional view of the shaker module taken along the longitudinal centerline thereof;

Fig. 4 is a block diagram of the components in operative relation.

Fig. 5 is a diagrammatic view of the second embodiment of the hydration- freezing plant showing the major internal elements; Fig. 6 is an expanded view of the hydration tank and freezing chamber in the plant; and

Fig.7 is a detail view of a conveying roller showing tractor-feed type surface features on the exterior of the roller and cooperatively positioned perforations on the web.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the figures for a clearer understanding of the invention, it may be seen in Fig. 1 that the first module 11 is a hydration unit which may be used as a stand alone unit but is specifically designed for use as a module of the media preparation apparatus. Module 11 includes an external housing 12 having an entrance opening 13 through which pads or an uncut web may be fed along a slide 14. At the bottom of slide 14 is a conveyor 16 which runs longitudinally along the bottom of a tank 17. Conveyor 16 has an inclined portion which extends upwardly and over one wall of tank 17 serving as a discharge conveyor. Optionally, a secondary conveyor 18 may be mounted above conveyor 16 at a height within tank 17. A motor 19, which may be hydraulic or electric with appropriate speed controls is mounted to a support frame within housing 12 and has an output sheaf or sprocket 21 which is connected to a drive roller 22 on conveyor 16 and a drive roller 23 on conveyor 18 by an appropriate belt or chain.

Tank 17 serves as a basin for the accumulation of a hydrating fluid. As will be understood the media is a multicell layer having a superabsorbent polymer in each cell in sufficient quantity to absorb a fluid for later freezing. The preferred fluid is water which has been filtered to remove impurities; however, other fluids may be appropriate for certain uses with specific polymers. The hydrating fluid may be filled to a certain level as shown in Fig. 1 such that conveyor 18 submerges the media beneath the surface of the fluid and urges the media toward the discharge end of conveyor 16. In this instance the fluid level is monitored by a sensor 24 and additional hydrating fluid is introduced to the tank to replenish that which hydrates the superabsorbent polymer. For example, a small unit of this design may consume about ten gallons per hour of hydrating fluid. Alternatively, a series of spray nozzles 26 may be mounted above tank 17 and media carried by conveyor 16 may be sprayed with fluid, the excess fluid being accumulated and resprayed by appropriate tubing and pump mechanisms. In either event, the conveyor is a stainless steel mesh or plastic type conveyor which allows fluid to pass therethrough yet is capable of urging the media through tank 17. The hydrating fluid may require heating to about 100° Fahrenheit; thus, an external reservoir 31 of pre-heated may be employed as the source for make up fluid. The speed of the conveyors may be adjusted with conventional controls for motor 19 to ensure that the media is fully hydrated before it is removed from tank 17 on conveyor 16.

Upon exiting tank 17 the media is delivered to a drip conveyor 32 which is also a stainless steel open belt, mounted above a drip pan 33 and having a vibratory assembly associated therewith such that external surface moisture is removed from the media as it traverses the conveyor. The conveyor may be driven from a sprocket on motor 19 such that its speed is concomitant with conveyors 16 and 18. By way of example a plurality of eccentric rollers 35 as shown in Fig. 3 may be used to impart motion to the conveyor transverse to the direction of travel to assist in removing external moisture. Excess fluid may also be removed from the media by employing a high pressure air knife. Drip conveyor 32 terminates at an entrance 39 into a refrigerant module 40. Module 40 includes an insulated housing 41 within which a plurality of successive conveyors 42 are supported for concomitant motion, each being similar in nature to the conveyors used in the first module 11. Hydrated media moves successively from one conveyor to another until discharged from outlet 44. The interior of housing 41 is maintained at a temperature well below the freezing point of the hydrated polymer media. Entrance 39 has a secondary entrance 39' for the introduction of "dry ice" for instances where dry ice is the preferred method of maintaining the subfreezing temperature. A cap may be placed over the entrance when an alternative cooling method as described hereinafter is employed.

In some instances, conventional mechanical refrigeration technology may be employed to maintain the internal temperature. In these situations, the extracted heat may be used in a heat exchanger 50 to preheat the hydration fluid used in the first module. In other situations a liquefied inert gas such as carbon dioxide, nitrogen, or a fluorocarbon may be used as the cooling agent. An appropriate set of nozzles as shown at 51 may inject the gas at 0 psig, dramatically lowering the temperature. As the gas heats and rises it may be drawn off into recovery plenum 52 by inlet fan on a compressor for recompression and recirculation. Again the heat extracted from the recirculatable gas can be used to heat the hydration fluid. In any case, it would be preferable to include a baffle system or air curtain system at entrance 39 and outlet 44 to minimize ingress or egress of gas at these areas. Inasmuch as dry ice may be retained on or other external solids accumulate on the media as is frozen, outlet 44 directs the frozen hydrated media to a second vibratory screen conveyor 45 such that the particulate is removed. Provision may readily be made to recirculate this material

to entrance 39'. A system as described herein may occupy as little space as an area three feet wide and eight feet long, if the modules are stacked as shown in Fig 4. The standing height would be less than eight feet tall. A machine of this size could process up to 1200 pound of hydration fluid per hour, which would be sufficient to fully hydrate two rolls of polymer-laden web three hundred feet long and fifteen inches wide. This quantity of media would be sufficient to place a layer inside eighty cartons each having a two cubic foot capacity each hour; thus, making it ideal for small shipping operations where perishable or heat sensitive products are packaged for cold shipment.

Referring to Figs. 5 through 7, the second embodiment will be described. Fig.

5 shows the hydration- freezing plant 110 with the major elements of the invention. The critical components of the plant 110 are housed inside a conventional insulated refrigeration trailer 111. The trailer includes a standard air-conditioning unit 112 underneath the trailer which supplies cool, dry air to the plant interior. The trailer shell 113 includes insulation to protect the components in the trailer from being exposed to high ambient temperatures outside the trailer. An onboard power generator 114 supplies power to all the systems of the plant and includes connections 116 for external power hookups so that external AC power at a consumer's location may be utilized to power the plant. An external water connection 131 allows water to be utilized at the consumer's site as well.

The plant 110 includes three main compartments A, B, and C, separated by fore 115 and aft 120 bulkheads. Each bulkhead includes an access doorway (not shown) so that a worker may walk through the entire plant for servicing of all compartments. The forward compartment A is used for storage area 125 for rolls of media 117. ThermaFreeze® media, suitable for use in this type of plant, is provided in rolls of 15 inches or 30 inches wide by 300 feet in length. The rolls consist of a continuous web of media of a non-woven fabric such as a 2 oz. Polypropylene. The web is comprised of a plurality of "cells" typically having a dimension of approximately 2 inches by 2 inches with a seal margin of inch between each cell. A plastic Polypropylene film is laminated onto the non-woven fabric to make the 2 x 2 cells. With a VΛ inch seal margin between each cell, a standard web of 15 inches has 6 cells across yielding 9,000 cells in a 300 foot roll, double for a 30 inch wide roll. Each cell contains a superabsorbent polymer such as sodium polyacrylate, crosslinked, which complies with FDA guidelines. The process of laminating the film onto the non- woven fabric, and depositing the polymer inside each cell has been automated with apparatuses such as found in U.S. Patent No. 5,628,845, by Murray et al., herein incorporated by reference, thereby making the use of such media more economical. While these materials work well with the current invention, other materials having similar physical properties may work equally well with the current invention. The applicant anticipates that various types of media will be developed over time to suit shipping needs, and the invention herein described is designed, therefore, to accommodate various types of media dimensions as they evolve.

In preparation for plant operation, a roll of media 117 is loaded onto a motorized spindle 118 for unwinding into the conveying rollers 119 positioned throughout the plant. A motor on the spindle may facilitate the unwinding of the media roll onto the conveying rollers 119, and in fact the motor may be electrically integrated into the conveying system such that movement of the rollers 119 causes a cooperatively timed movement of the spindle motor; however it is contemplated that the conveying rollers 119 themselves would provide enough power to unwind the media roll as the web becomes entrained onto the conveying system and driving rollers 121 are activated. A majority of the conveying rollers 119 are passive, rotating in response to the entrained web being drawn through the plant by the driving rollers 121. As seen in the figure, driving rollers are positioned at various critical locations in the plant, depending upon the length of the conveying system installed which may vary with different consumer applications. In some applications, a single driving roller may be sufficient to draw the web through the plant if the conveying system is sufficiently shortened. In addition, although several rollers are shown in the figures, it is contemplated that roller density and positioning will vary with different media types. Referring to Fig. 7, it may be seen that each conveying 119 and drive roller

121 is typically surrounded by "Hi-Slip," patterned rubber or Teflon™ alloy 122 to support and carry the web through the plant. Each roller is rotatably supported in each compartment by conventional means well known in the industry, and inasmuch as the method of rotation is not critical to the operation of the plant and does not embody novel aspects of the invention, further discussion as to the mechanical aspects of the rollers and the conveyor system will not be made. Each roller includes a series of protrusions 123 positioned on the exterior of the roller, and the web has cooperatively positioned perforations 124 along the 2nd and 4th seal margins of the web for receiving corresponding protrusions on the roller as shown. This type of tractor- feed arrangement enhances the gripping and support capabilities of the rollers as the web is drawn through the plant.

Referring now to Fig. 6, within compartment B is a hydration tank 126 and a freezing chamber 127. Hydration tank 126 includes a pump/heater device 128 and float sensor 129 for controlling the water temperature and level in the tank 126. External water connection 131 allows for connection to a water supply at the consumer's site to fill the tank 126 via pump 128, and drain port 132 allows for quick drainage of the tank after the media preparation is complete. A heating element and temperature sensors in the pump 128 maintains the temperature of the tank water between 90^°-150^° F (i.e. lukewarm). A driving roller 121a adjacent bulkhead 115 draws the web 117 through a slit in the bulkhead 115 and into the aqueous environment of the enclosed tank 126 through opening 134. Rollers 119 within the tank 126 draw the web 117 below the surface of the water as shown and convey the web 117 through the tepid water at a controlled rate to optimize water absorption by the polymer within the cells. While a full immersion type tank is shown, alternative methods of hydration may be suitable to hydrate the media. For example, an overhead water nozzle configuration providing a constant supply of water being sprayed onto the web as it travels through the tank will provide suitable hydration results. Replacing the water reservoir with an overhead nozzle arrangement would simply require altering the distribution pipes of heating/pump 128 device to re-circulate water to the nozzles from a submerged position in the tank (shown in phantom in Fig. 3).

After hydration, web 117 rises above water level 136 and is drawn through an insulating portal 138 into freezing chamber 127 by driving roller 121b. Portal 138 consists of a series of vertical non-stick, rubberized flaps supported by a cowl of suitable size to allow passage of the web 117 through insulating panel 139, and panels 139 also surround freezing chamber 127 as shown. Conveying rollers 119 are positioned within the chamber 127 to increase the vertical travel of the web and thereby increase the exposure time of the web 117 to freezing conditions within the freezing chamber. The chamber 127 includes a dedicated refrigeration system. Twin CO₂ cylinders 142 supply gas to expansion nozzles 141 within the chamber 127. A

mechanically based refrigerator unit 143 contributes to cooling by the CO₂ system. The mechanical unit 143 is conventional, but may have a higher cooling capacity to achieve lower temperatures in the chamber (127). Conventional AC components, condenser 144, evaporator 145, compressor 146, expansion valve 147, refrigerant lines 148, air ducting 149, and blower fan 150 are shown positioned above the chamber 127; however various types of systems as are well known in the art may be positioned in alternate locations to achieve optimal performance and economy. Temperature sensors and control circuitry (not shown) control interaction and operation of the two cooling units so that a temperature of less than -10° F is maintained in the chamber. This temperature is not critical to the freezing process as long as temperatures below 20° F are maintained inside the chamber (127). However, tests have shown that rapid freezing of the cells is optimally achieved at temperatures below -10° F. Additionally, although two types of cooling systems are shown, applicant contemplates that a single system of one type or the other will be suitable to maintain freezing temperatures within the chamber. After freezing, driving roller 121c adjacent bulkhead 120 draws web 117 through chamber 127 and conveys the web through rear portal 151, of similar construction to portal 138, through a slot in bulkhead 120 and into the cutting area 150 of compartment C. While the entire media absorbs some moisture, water is concentrated in the cells of the media and the web 117 remains relatively flexible. This allows the web 117 to continue to flex around the conveying rollers without significantly inhibiting travel throughout the plant.

Referring back to Fig. 5, the cutting area of compartment C is more clearly seen. Table 153 supports a cutting laser 154 and servo-controlled mirrors 156 for directing the cutting beam. Touch screen display 157 allows an operator to select a preprogrammed cutting pattern to suit a particular consumer's packing needs. The table 153 also includes a vacuum retention system 158 to anchor the frozen web onto the cutting table 153 at a predetermined moment. In operation, as the leading edge of the frozen web 117 traverses the cutting table 153, a sensing rod 159 at the distal end of the table activates the vacuum system 158 to lock the web onto the table in a stationary position upon contact by the web's leading edge. The laser 154 then cuts the frozen web into cell groupings of suitable size and shape for packing per the dictates of a firmware program held by control logic (not shown) which also coordinates the interaction of the laser, vacuum system, and mirror servos. The firmware permits an operator to quickly select different cutting patterns from the touch screen display 157. The cutting patterns held in the firmware are programmed to cut the media along seal margins so as to not rupture the individual cells and includes the capability to cut shapes suitable for a multitude of different types of shipping containers. Upon completion of the cutting sequence, the vacuum system automatically disengages and an operator clears the table of the cut pad groupings of cells into containers for removal from the rear doors of the trailer to the consumer's shipping area. The next length of frozen web then advances onto the table 153 for cutting. Any laser of suitable cutting capability may be used; however tests indicate that high-powered, sealed CO₂ lasers in the 75-500 watt range are most effective. A Plexiglas® shield (not shown) surrounds the laser cutting table 153 so that an operator is protected from laser emanations. While a laser-based cutting system is shown, other suitable cutting method such as rotary knives or high pressure water jets may be utilized with equally effective results.

With optimal hydration and freezing conditions as described above, a selected web portion may be hydrated, frozen, and cut to size at a speed of approximately 5 feet per minute on a continuous basis. This allows for the creation of large amounts of frozen media to be arranged within shipping containers around perishable materials economically.

While I have shown the invention in various forms, these are intended as illustrations of the invention and are not intended to limit the scope of the invention as set forth in the appended claims.

Claims

What I claim is:

1. A refrigerant media preparation apparatus for hydrating and freezing a superabsorbent polymer captured in a web of flexible permeable material, comprising: a. first module means for hydrating said polymer including means for urging said web through said first module; and, b. refrigerant module means for freezing hydrated polymer as said web is urged through said refrigerant module means.

2. Apparatus as defined in claim 1 wherein said first module means includes a conveyor for moving said web through a sufficient quantity of hydration fluid at a speed appropriate to achieve substantially complete hydration of said superabsorbent polymer.

3. Apparatus as defined in claim 2 wherein said conveyor submerges said web in a pool of said hydration fluid.

4. Apparatus as defined in claim 3 further comprising means for maintaining a quantity of said hydration fluid in said first module for substantially continuous hydration of superabsorbent polymer in a web passing through said first module.

5. Apparatus as defined in claim 2 further comprising means for adjusting the speed of said conveyor to increase or decrease the length of time said superabsorbent polymer is exposed to said hydration fluid.

6. Apparatus as defined in claim 2 further comprising means for spraying said hydration fluid onto said web and conveyor as said web moves through said first module.

7. Apparatus as defined in claim 1 wherein said refrigerant module includes a conveyor mounted therewithin for moving a hydrated web through said module at a speed appropriate to facilitate freezing of the hydration fluid within said web.

8. Apparatus as defined in claim 7, wherein said refrigerant module has an entrance for receiving said hydrated web and an outlet for discharging said hydrated web after freezing, and including means for limiting the ingress and egress of gases through said entrance and outlet.

9. Apparatus as defined in claim 7 wherein said refrigeration unit includes mechanical means for maintaining the interior of said chamber at a temperature beneath the freezing point of said hydrated web.

10. Apparatus as defined in claim 1 further comprising shaker means operably positioned to a receive frozen hydrated web from said refrigerant module for dislodging external moisture and solids from said frozen hydrated web.

11. Apparatus as defined in claim 10 wherein said shaker means comprises an open conveyor for supporting and conveying said web thereon along a first direction and means for imparting vibrations to said web.

12. A modular packaging preparation apparatus for hydrating and freezing a superabsorbent polymer captured in a web of flexible permeable material, comprising: a. first module means for hydrating said polymer including means for urging said web through said first module including conveying means for moving said web through a sufficient quantity of hydration fluid at a speed appropriate to achieve substantially complete hydration of said superabsorbent polymer, means for maintaining a quantity of said hydration fluid in said first module for substantially continuous hydration of superabsorbent polymer in a web passing through said first module, means for adjusting the speed of said conveying means to increase or decrease the length of time said superabsorbent polymer is exposed to said hydration fluid; and, b. refrigerant module means for freezing hydrated polymer as said web is urged through said refrigerant module means including a chamber having an entrance for receiving said hydrated web and an outlet for discharging said hydrated web after freezing, and including means for limiting the ingress an egress of gases through said entrance and outlet, secondary conveying means mounted within said chamber for moving a hydrated web through said chamber at a speed appropriate to facilitate freezing of the hydration fluid within said web, means for maintaining the interior of said chamber at a temperature beneath the freezing point of said hydrated web.

13. Apparatus as recited in claim 1, further including means for cutting said web into individual portions of a preselected size and shape after said web is frozen in said freezing means.

14. An assembly plant for hydrating and freezing flexible refrigerant media, comprising: a. vehicle means for transporting said plant such that said plant is mobile and self-contained; b. means for hydrating said media; c. means for dispensing said media into said hydration means; d. means for freezing said media; and, means for conveying said media from said hydration means to said freezing means.