System and method for controlling water flow through ground with a ...

United States Patent [w]

Terry et al.

US005980996A [ii] Patent Number: [45] Date of Patent:

5,980,996 Nov. 9,1999

[54] SYSTEM AND METHOD FOR

CONTROLLING WATER FLOW THROUGH
GROUND WITH A GEOTEXTILE
COMPRISING WATER ABSORBING
MATERIAL

[75] Inventors: Mark Edward Terry, Rockmart;

Martin G. Hoskins, Brunswick;
Connie Hensler, Kennesaw, all ol Ga.

[73] Assignee: Interface, Inc., LaGrange, Ga.

[21] Appl. No.: 09/055,587 [22] Filed: Apr. 6, 1998

Related U.S. Application Data

[60] Continuation-in-part of application No. 08/822,675, Mar. 24, 1997, Pat. No. 5,756,159, which is a division of application No. 08/354,676, Dec. 13, 1994, Pat. No. 5,614,269.

[51] Int. CI. B05D 3/06

[52] U.S. CI 427/513; 427/519; 427/520

[58] Field of Search 427/508, 513,

427/517, 519, 520

[56] References Cited

U.S. PATENT DOCUMENTS

4,909,592 3/1990 Arroyo et al. .

4,990,373 2/1991 Kittle 427/244

5,082,347 1/1992 Akasaka et al. .

5,179,619 1/1993 Bosisio et al. .

5,182,786 1/1993 Kinaga et al. .

5,244,934 9/1993 Umeda et al 522/129

5,275,509 1/1994 Honeycutt 405/129

5,593,736 1/1997 Cowen et al 427/492

5,614,269 3/1997 Hoskins et al 427/512

5,756,159 5/1998 Hoskins et al 427/394

Bl 5,199,098 2/1995 Nolan et al. .

FOREIGN PATENT DOCUMENTS

2184047 2/1997 Canada .

62-225507 10/1987 Japan .

6-007759 1/1994 Japan .

9-052323 2/1997 Japan .

91/04786 4/1991 WIPO .

98/06570 2/1998 WIPO .

OTHER PUBLICATIONS

Castor, Innovative Hazard. Waste Treat. Technol.Ser. (1990), 2 (Phys./Chem. Processes), pp. 211-220, 1990. Heiser et al, Technol. Programs Radioact. Waste Manage. Environ. Restor. (1994), (vol. 2), pp. 1057-1062, 1994.

Primary Examiner—Erma Cameron

Attorney, Agent, or Firm—-Jones & Askew, LLP

[57] ABSTRACT

A water absorptive material comprising a fibrous substrate impregnated with a water absorptive, water insoluble polymer, wherein the polymer is intertwined and interlocked with fibers ol the fibrous substrate, and the use ol such water absorptive material to form a water control zone to prevent water egress from the water control zone into adjacent ground or water ingress into the water control zone from adjacent ground.

15 Claims, 1 Drawing Sheet

1

SYSTEM AND METHOD FOR
CONTROLLING WATER FLOW THROUGH
GROUND WITH A GEOTEXTILE
COMPRISING WATER ABSORBING
MATERIAL

CROSS REFERENCE TO RELATED
APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No. 08/822,675 filed on Mar. 24,1997, now U.S. Pat. No. 5,756,159 which is a divisional of U.S. application Ser. No. 08/354,676, filed Dec. 13,1994 which has issued as U.S. Pat. No. 5,614,269.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to water absorbing materials, particularly water absorptive polymeric materials, and use of such materials to control water flow through ground and to protect cables such as fiber optic cables.

BACKGROUND OF THE INVENTION

Commonly owned and related U.S. Pat. No. 5,614,269 discloses a method of making a water absorptive article comprising a water absorptive, water insoluble polymer and discloses the use of such a water absorptive article to protect cable, such as fiber optic cable, from water from the ingress of moisture and water into the cable. As explained in U.S. Pat. No. 5,614,269 ingress of water into cable is a substantial and persistent problem in the cable industry. Such ingress often results from changes in ambient conditions which cause differences in vapor pressure between the inside and the outside of a cable jacket. Consequently, moisture tends to diffuse in a unidirectional manner from the outside of the cable to the inside of the cable, resulting in an undesirably high moisture level inside the cable. High levels of condensed moisture inside a cable sheath system may have a detrimental effect on the transmission characteristics of a metallic conductor cable.

Furthermore, water may enter the cable as a result of damage to the cable which perforates the external water barrier elements. For example, animal attacks and mechanical impacts often create openings in the sheath system of the cable, which allows water to enter the cable. Once inside the cable sheath system, the water tends to move longitudinally along the cable into splice closures, if not controlled.

In another field, water flow through ground (meaning "earth") can pose problems, if not controlled. Water naturally percolates through the ground and such percolation is normally desirable because it purifies water. Rain water normally percolates through the surface of the ground and eventually flows into the local ground water system.

It is desirable to prevent percolation of water through ground in some instances. For example, it is desirable to prevent water egress from waste disposal sites into the adjacent ground and water ingress into waste disposal sites from the adjacent ground to avoid contamination of the local ground water by toxins in the waste disposal site. A landfill is a specific example of such a waste disposal site.

Bentonite clay has been used to block water flow into and out of waste disposal sites, but bentonite clay tends to migrate during use, leaving water permeable areas, and is heavy and therefore expensive to transport.

Accordingly, in addition to controlling water ingress into cables, there is also a need to control water flow through the ground, and there is a particular need to control water egress

2

from a waste disposal site into the adjacent ground and water ingress from the adjacent ground into the waste disposal site.

SUMMARY OF THE INVENTION

5 The present invention solves the above described problems in the prior art by providing a water absorbent material comprising a fibrous substrate impregnated with a water absorptive, water insoluble polymer, wherein the polymer is intertwined and interlocked with fibers of the fibrous substrate. Advantageously, the water absorbing material of the present invention is not bulky or heavy. Furthermore, the water absorbent material of the present invention does not suffer from problems associated with delimitation or substantial loss of water absorbing material during handling and application, because the water absorbent material is polymeric in nature and is intertwined and interlocked with the fibers of the substrate such that water absorbing material becomes intimately and integrally associated with the substrate and is not easily moved from or within the fibrous

20 substrate.

The present invention further encompasses a method of making a water absorptive, water insoluble material comprising the steps of (1) impregnating a fibrous substrate with

25 a solution capable of polymerizing upon exposure to UV irradiation to form a water absorptive polymer; and (2) exposing the impregnated fibrous substrate to UV irradiation to polymerize the solution to form a substrate impregnated with a water absorptive, water insoluble polymer, wherein

30 the polymer is intertwined and interlocked with fibers of the fibrous substrate. Desirably, the water absorptive, water insoluble polymer is essentially non-toxic and does not expose of workers or the environment to hazardous material. Still another advantage of the present invention is that the

35 method of making the water absorbent material is rapid, straightforward, and economical. Furthermore, the add on weight of the water absorbing material of the present invention can be accurately controlled and the resulting material is highly water absorbent. Yet other features of the present

40 invention are that the residual free monomer concentration is very low, less than about 200 ppm and the polymerization is a single step.

The present invention further encompasses a cable comprising, a water absorptive composition comprising a

45 fibrous substrate impregnated with a water absorptive, water insoluble polymer, wherein the polymer is intertwined and interlocked with fibers of the fibrous substrate, and wherein the water absorptive composition is essentially non-toxic. Because the water blocking composition made by the dis

50 closed method is not bulky or heavy, the cable size and weight can be maintained at a minimum. In addition, the water blocking composition made by the disclosed method does not suffer from problems associated with delimitation or substantial loss of water absorbing material during han

55 dling and application to the cable.

The present invention still further encompasses a system and method for controlling the flow of water through ground, meaning earth. Generally described, this method is a method of controlling water egress from a water control

60 zone into ground adjacent the water control zone or water ingress into the water control zone from the adjacent ground and comprises the step of forming a water barrier in or on the ground adjacent the water control zone. The water barrier includes a layer of the above described water absorbent

65 material comprising a fibrous substrate impregnated with a water absorptive, water insoluble polymer, such that the polymer is intertwined and interlocked with fibers of the 3

fibrous substrate. The system of the present invention for controlling the flow of water through ground is a water control zone formed by the described method. When used as a water barrier in ground, the water absorbent material of the present invention can be described as a geotextile. 5

The foregoing system and method for controlling water is particularly effective, because the water absorptive, water insoluble polymer swells when contacted by water and blocks water passage through the absorbent material. This system and method of the present invention for controlling 1° water flow through ground is particularly suitable for waste disposal sites, such as landfills, because the system and method of the present invention blocks the flow of water in or out of the waste disposal site and prevents water from carrying contaminants from the waste disposal site into the :5 local ground water. Accordingly, the water absorptive, water insoluble polymer of this invention is desirably non-toxic to avoid any harm to the environment and those manufacturing and handling the water absorbent material.

Because the water absorptive, water insoluble polymer of 20 the absorbent material used in the system and method of the present invention for controlling water flow through ground is interlocked and intertwined in the fibrous substrate, the polymer does not migrate during handling or use and therefore does not leave areas of the water barrier permeable 25 to water. As a result, the water barrier in this system and method of controlling water is durable and maintains its barrier properties throughout the extent of the water barrier.

Therefore, an object of the present invention is to provide 3Q an improved water barrier material and method for controlling water flow.

Another object of the present invention is to provide an improved system and method for controlling the flow of water through ground. 35

Still another object of the present is to provide a system and method for controlling water egress from a water control zone into adjacent ground or water ingress into the control zone from adjacent ground.

Yet another object of the present invention is to provide a 40 system and method for controlling water egress from a waste disposal site into adjacent ground or water ingress into the waste disposal site from adjacent ground.

Another object of the present invention is to provide a non-toxic water barrier which is durable and economical. 45

A further object of the present invention is to provide an absorbent material which is effective for blocking water and absorbing moisture in cables, yet is inexpensive and easy to handle, and a fast and economical method of making such 5Q cable.

These and other objects, advantages and features of the present invention are more fully described in the following description.

DETAILED DESCRIPTION OF THE 55
INVENTION

As summarized above, the present invention encompasses a water absorbing material comprising, a fibrous substrate impregnated with a water absorptive, water insoluble 60 polymer, wherein the water absorptive, water insoluble polymer is intertwined and interlocked with fibers of the fibrous substrate, and a method of making a water absorptive material comprising the steps of (1) impregnating a fibrous substrate with a solution capable of polymerizing upon 65 exposure to UV irradiation to form a water absorptive, water insoluble polymer and (2) exposing the impregnated fibrous

4

substrate to UV irradiation to polymerize the solution therein to form a polymer, wherein the water absorptive, water insoluble polymer is intertwined and interlocked with fibers of the fibrous substrate.

The present invention also relates to cables that contain a water absorbing material comprising, a fibrous substrate impregnated with a water absorptive, water insoluble polymer, wherein the polymer is intertwined and interlocked with fibers of the fibrous substrate.

This invention further encompasses a system and method for controlling water flow through ground. Ground as used herein means earth. Generally described, the method of the present invention for controlling water flow through ground includes controlling water egress from a water control zone into ground adjacent the water control zone or water ingress into the water control zone from the adjacent ground. More particularly, this method comprises the step of forming a water barrier in or on the ground adjacent the water control zone. The water barrier includes a layer of absorbent material comprising a fibrous substrate impregnated with a water absorptive, water insoluble polymer, such that the polymer is intertwined and interlocked with fibers of the fibrous substrate. In other words, this aspect of the invention involves the use of the absorbent material of the present invention as a geotextile.

This method of controlling water flow through ground is described in more detail below. First, the method of making the absorbent material is described in detail.

More particularly, the method of making the absorbent material of this invention relates to combining monomers of super absorbent polymers (SAPs) with ultraviolet lightdependent free-radical generators in solution, applying this solution to a fibrous substrate such as a woven or nonwoven fabric, and exposing the monomer impregnated fibrous substrate to UV light to initiate a polymerization reaction. Polymerization of the SAP monomers occurs in and among the interstices of the fibers of the fibrous substrate to form a polymeric structure wherein the polymer is intertwined and interlocked with fibers of the fibrous substrate. The method of this invention for making the absorbent material requires only a single irradiation step to polymerize and cure the water absorptive, water insoluble polymers in the composition. Accordingly, this method is rapid, straightforward and economical.

The water absorbing material thus formed is highly water absorptive—capable of absorbing at least 50 grams of distilled water per gram of polymer, more preferably at least 100 grams of distilled water per gram of polymer, and even more preferably at least 200 grams of distilled water per gram of polymer. Additionally, the water absorbing material is relatively thin and light weight because it is not laminated, and does not lose appreciable water absorbing material upon handling and application to the cable. These advantages are the direct result of the intimate structural relationship achieved by polymerizing SAP monomers in situ in the fibrous substrate. The water absorbing material made by this method is a single structure wherein the network of fibers of the substrate and the network of polymeric chains of water absorbing material are interlaced, intertwined and interlocked. The water absorbing material is therefore, integrally, tightly and permanently associated with the fibrous substrate.

The method of the present invention permits very accurate control of the add on weight of the water absorbing material to the fibrous substrate. Consequently, the water absorbing materials made thereby are uniform with respect to the