US3578197A

US3578197A - Porous mass and a container therefor

Info

Publication number: US3578197A
Application number: US817206*A
Authority: US
Inventors: Leslie G Taylor; Donald S Withey
Original assignee: British Oxigen Ltd
Current assignee: BOC Group Ltd
Priority date: 1969-02-20
Filing date: 1969-02-20
Publication date: 1971-05-11
Anticipated expiration: 1988-05-11

Abstract

A porous mass having a high absorptive capacity for a liquefied gas is housed in a vented thermally insulated container, the porous mass having recesses therein for the reception of materials requiring refrigeration by said liquefied gas has been inserted.

Description

United States Patent Leslie G. Taylor Wimbledon;

Donald S. Withey, Beddington, England 817,206

Feb. 20, 1969 Division of Ser. No. 641,914, May 9, 1967 May 1 l, 1971 The British Oxygen Company Limited lnventors App]. No. Filed Patented Assignee POROUS MASS AND A CONTAINER THEREFOR 2 Claims, 1 Drawing Fig.

US. Cl 220/16,

62/372, 62/457, 312/31.04 Int. Cl 865d 25/00 Field of Search 220/ 16, 9

(A), 9 (B), 9 (C); 62/371, 372, 457, 464; 312/3101; l1/3l.04

[56] References Cited UNITED STATES PATENTS 665,925 1/1901 Nordtmeyer 252/449 1,623,169 4/1927 Dalen 252/449 3,238,002 3/1966 OConnell et al 220/9(C)X FOREIGN PATENTS 339,899 12/1930 Great Britain 252/449 Primary Examiner-Joseph R. Leclair Assistant Examiner-James R. Garrett Attorney-Townshend & Meserole ABSTRACT: A porous mass having a high absorptive capacity for a liquefied gas is housed in a vented thermally insulated container, the porous mass having recesses therein for the reception of materials requiring refrigeration by said liquefied gas has been inserted.

POROUS MASS AND A CONTAINER THEREFOR This is a division of the application, Ser. No. 64l ,9l4, filed May 29, 1967.

The present invention relates to a porous mass having high absorptive capacity for a liquefied gas and to a shaped porous mass housed in a vented thermally insulated container, the porous mass being recessed for the reception of materials requiring refrigeration by a liquefied gas of low boiling point. The invention is particularly concerned with, but not exclusively limited to, the storage and transporting of biological materials which undergo undesirable changes unless they are maintained at very low temperatures. One example of these biological materials is frozen bovine semen which tends to suffer considerable loss in viability unless maintained at a tum-- perature below 1 30 C.

It is important that the porous mass should have the following characteristics:

- 1. that it be relatively light in order to keep down the overall weight of the container; 2. that it be highly absorbent in order to absorb the maximum possible amount of liquefied nitrogen; 3. that it be mechanically strong, and it must not undergo any change at liquid nitrogen temperature which will impair its strength or absorbency.

lt is an object of the present invention to provide a porous mass which possesses the three above-mentioned charac teristics.

' According to one aspect of the present invention an absorbent for liquefied gas comprises a porous mass compounded of a mixture of kieselguhr and asbestos bonded with cement.

According to another aspect of the present invention a thermallyinsulated container for transporting material requiring refrigeration by a liquefied gas having a low boiling point comprises an outer shell and an inner vessel defining an evacuable space between them, and a porous mass disposed in the inner vessel and comprising a mixture of kieselguhr and asbestos bonded with cement, the porous mass being shaped to accommodate the material to be refrigerated.

Preferably the evacuable space between the outer shell and .inner vessel contains low heat conductivity material in powder, fibre or film form which may be interleaved with foil having high heat reflecting properties.

The term "kieselguhr" refers to a diatomaceous earth comprising the silica skeletons of diatoms in the form of a tine powder.

The term asbestos"asbestos refers to all forms of the fibrous siliceous mineral marketed under this name, such as chrysotile, amosite, or crocidolite. Asbestos is available commercially in varying fiber lengths, but it is preferred to use a medium length fiber, for example having an average length between one-fourth inch and one-half inch. A high proportion of short fiber material may lead to cracking of the mass during setting, whilst a high proportion of long-fibered material may cause some difficulty in mixing. Two or more types of asbestos may be used together in preparing the mix.

The term cement refers to a homogeneous inorganic material prepared by high-temperature calcination which reacts with water to give a solid mass. The preferred type of cement is Portland cement, but other types such as aluminous cement or pozzolanic cement may also be employed, either alone or in admixture.

The container is preferably cylindrical, and the porous mass may be cast with a single recess for the reception of the material to be refrigerated, or a number of recesses may be provided. ln general the material to be refrigerated will be contained in a phial or like receptacle of a standard size usually made of glass or plastic and generally cylindrical in shape. The recesses formed in the porous mass are preferably dimensioned to make an easy fit with the phial or like receptaa cle. An opening in the container provides access to the inner vessel, and a plug may be provided for sealing this opening when the container is closed. It is to be understood that the clearance between the plug and the container will be such that venting means is provided for the interior of the container to atmosphere.

The invention will now be particularly described with reference to the accompanying drawing which is aside elevation in section of a thermallyinsulated container.

Referring to the drawing, the container includes a sheet metal outer shell I joined to a recessed bottom plate 2 so as to form a strong circumferential rim upon which the container can stand. A sheet metal inner vessel 3 is joined to a base plate 4, and located inside the outer shell 1, The inner vessel 3 and outer shell 1 are joined at their upper ends to define a space 5 which can be evacuated through a tube 6 which is normally protected by a cap 7.

The space 5 is filled with a composite heat insulation material not shown and a porous mass 8 as hereinbefore defined is located in the lower portion of the inner vessel 3. The container is closed by a lid 9 of the lift-off type which is fastened by a locking pin 10 and socket 11. The lid 9 has attached'to it a plug'l2 of lightweight insulating material, such as expanded polystyrene, which fills the part of the inner vessel 3 above the porous mass 8 when the lid 9 is closed. The plug is of sufficient dimensionto provide venting means for the interior of the internal vessel to atmosphere.

Cylindrical holes 13 are formed in the porous mass 8 in order to accommodate tubes of the material to be refrigerated. I

The porous mass is made by mixing predetermined amounts of cement, kieselguhr, asbestos and water; the mixture then being introduced into the inner vessel 3, and allowed to set. The moisture is then driven off by gentle heat, leaving a dry monolithic mass in the container. Alternatively, the mass may be produced and shaped outside the container, and then introduced.

The dry ingredients may be mixed separately and the water then added, or the ingredients may be added separately, to the water while being stirred. The requirement is that the solid ingredients must be thoroughly mixed with each other, and with the water, to give a homogeneous product.

One method of preparing the mass is to introduce the solid constituents into a drum which is then rotated for 30--60 minutes to achieve thorough mixing. The mixed solids are then added to the required amount of water contained in a mixing vessel fitted with a stirrer. It is sometimes necessary,

using this method, to tease" the asbestos, i.e., to separate the fibers, particularly if it contains a high proportion of long-fiber material.

An alternative method, which obviates the need for teasing, is to employ a mixing vessel fitted with a stirrer, preferably of the type which has a lifting and stirring action. The dry ingredients are added separately, one after the other, to the required volume of water in the mixing vessel. The preferred order of addition is cement, followed by asbestos, and finally kieselguhr. Care must be taken to see that mixing is thorough, and, in particular, that there are no dry spots in the mix.

After the ingredients have been thoroughly mixed they may be introduced directly-into the inner vessel 3. Preferably, they are added in such a way that a minimumof air is entrapped during the addition. The mass may be assisted to settle by vibration of the container, or by tapping, and a vacuum may, if desired, be applied to remove air bubbles. The mass is then allowed to stand for a length of time sufficient for the cement to set; the time required will, of course, depend on the cement used, and may be up to 3 weeks or more.

After the cement has set, the water present in the mass is gently removed, for instance, by gently heating the container in a current of'air. It is, of course, necessary toensure that all Asbestos: 10-40 percent by weight Water: 2.55 times the combined weight of the solids For best results the preferred range is:

Cement: 25--50 percent by weight Kieselguhr: 30-65 percent by weight Asbestos: -40 percent by weight Water: 3-4 times the combined weight of the solids The ratio of water to total solids has a big influence on porosity; in general, the higher the proportion of water used, the greater is the porosity: Using the proportions given in the preferred range, of IO cm. cube. of the mass will absorb at least 800 ml. of liquid nitrogen.

The holes 13 in the mass, into which the material to be refrigerated are inserted, may be molded into the mass before the cement sets, but are preferably drilled in the mass after hardening. When drilling is employed, it is preferable that the asbestos content of the mass should not exceed 30 percent by weight of the dry solids.

It is possible to make the mass in a mold of dimensions similar to that of the inner vessel of the container and when the molded mass has been thoroughly dried, to introduce the mass into the vessel. Alternatively, the mass may be molded somewhat larger than the size required, and the surplus material removed prior to the insertion of the mass into the inner vessel.

In operation, liquefied nitrogen is added to the porous mass 8 until it is saturated with liquefied nitrogen. A tube containing the semen in a diluent is then inserted in one of the holes 13 in the porous mass; the tube being dimensioned so that only a very small part of the tube projects beyond the hole. The lid 9 is then closed, and the container is ready for storing and transporting the semen. It has been found that a container according to the invention can preserve semen at temperatures below l 30 C. for several days.

We claim:

1. In a thermally insulated container for material requiring refrigeration by a liquefied gas the combination comprising, a receptacle portion including an outer shell, an inner shell wholly within said outer shell and spaced therefrom to define an evacuable space therebetween, a porous mass disposed within a part of said receptacle portion configured to receive and support said material requiring refrigeration, said mass constituting a mixture of from 20 to 35 percent by weight of cement, from 25 to 45 percent by weight of kieselguhr, and from 20 to 30 percent by weight of asbestos, with water in an amount from 2.5 to 5 times the combined weight of cement, kieselguhr and asbestos, and a complementary cover portion including a lid and a plug, said plug affixed to said lid and configured to extend into said receptacle portion to an extent sufficient to substantially fill the part of said receptacle unoccupied by said porous mass and said material requiring refrigeration.

2. The container defined by claim I wherein said complementary cover portion including said lid and said plug are dimensioned with respect to said container to define vent passage means between the interior of said container and the atmosphere.

Claims

2. The container defined by claim 1 wherein said complementary cover portion including said lid and said plug are dimensioned with respect to said container to define vent passage means between the interior of said container and the atmosphere.