CA1090722A - Lining for concrete water conduits - Google Patents
Lining for concrete water conduitsInfo
- Publication number
- CA1090722A CA1090722A CA315,379A CA315379A CA1090722A CA 1090722 A CA1090722 A CA 1090722A CA 315379 A CA315379 A CA 315379A CA 1090722 A CA1090722 A CA 1090722A
- Authority
- CA
- Canada
- Prior art keywords
- lining
- conduit
- concrete
- layer
- toxicant
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/50—Treatment of water, waste water, or sewage by addition or application of a germicide or by oligodynamic treatment
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
- F16L58/02—Protection of pipes or pipe fittings against corrosion or incrustation by means of internal or external coatings
- F16L58/04—Coatings characterised by the materials used
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
- F16L58/02—Protection of pipes or pipe fittings against corrosion or incrustation by means of internal or external coatings
- F16L58/04—Coatings characterised by the materials used
- F16L58/10—Coatings characterised by the materials used by rubber or plastics
- F16L58/1009—Coatings characterised by the materials used by rubber or plastics the coating being placed inside the pipe
- F16L58/1045—Coatings characterised by the materials used by rubber or plastics the coating being placed inside the pipe the coating being an extruded or a fused layer
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Laminated Bodies (AREA)
- Protection Of Pipes Against Damage, Friction, And Corrosion (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Fouling of seawater conduits by accumulating marine organisms is prevented, so that periodic cleaning is no longer required, by making the conduits of rein-forced concrete, in the inner surface of which is bonded a flexible lining provided with T-ribs cast into the concrete, and with an internal surface, in contact with the seawater, of an elastomer containing a very slowly diffusible repellant for marine organisms.
Fouling of seawater conduits by accumulating marine organisms is prevented, so that periodic cleaning is no longer required, by making the conduits of rein-forced concrete, in the inner surface of which is bonded a flexible lining provided with T-ribs cast into the concrete, and with an internal surface, in contact with the seawater, of an elastomer containing a very slowly diffusible repellant for marine organisms.
Description
109C~72~
The invention relates to a lining for a conduit,particularly for a concrete water conduit.
Various kinds of industrial installations --such as power plants using sea water for cooling, and chemical plants using sea water as a source for some of the materials naturally present in sea water -- transport the water from the open sea to the inland location where the water is to be used, in l-arge conduits most often made of Portland cement concrete. Such conduits tend to beco~e rapidly fouled with a variety of living organisms, including both animals and plants of a considerable variety of kinds whose habit of growth is to attach themselves to a stationary surface and feed on the materials contained in the water flowing past. Fouling by such organisms rather rapidly reduces the capacity of the conduits and has required periodic shutdown for the purpose of laborious scraping of the accumulated growths from the surfaces. This is a very expensive operation, not only because of the labor involved but more importantly because of the interference with pro-duction which results.
It has been known for many years that concreteconduits can be protected against corrosion by acids which eat away the material of the`conduit, by casting the concrete against a corrosion-resistant plastic lining having projections interlocking with the concrete, such as T-shaped ribs which become embedded in the surface of the concrete, as shown in the expired U.S. Patent 2,816,323, of Munger. However, such linings have not been shown to be useful in preventing attachment and growth of living organisms.
It has also been known that the attachment and growth of barnacles, seaweeds, and other living creatures which attach themselves to the exterior surfaces of boat hulls, buoys, piling, and other structures exposed to seawater, could be prevented by application of a poison, ~ such as metallic copper, or paints containing various ,~ , ,'' '.
- :- . . : ,: ,. ., ... - . :
.. , . ~ . , .. , , .. , ~ , .
.
,- ' . , ~L()9(~22
The invention relates to a lining for a conduit,particularly for a concrete water conduit.
Various kinds of industrial installations --such as power plants using sea water for cooling, and chemical plants using sea water as a source for some of the materials naturally present in sea water -- transport the water from the open sea to the inland location where the water is to be used, in l-arge conduits most often made of Portland cement concrete. Such conduits tend to beco~e rapidly fouled with a variety of living organisms, including both animals and plants of a considerable variety of kinds whose habit of growth is to attach themselves to a stationary surface and feed on the materials contained in the water flowing past. Fouling by such organisms rather rapidly reduces the capacity of the conduits and has required periodic shutdown for the purpose of laborious scraping of the accumulated growths from the surfaces. This is a very expensive operation, not only because of the labor involved but more importantly because of the interference with pro-duction which results.
It has been known for many years that concreteconduits can be protected against corrosion by acids which eat away the material of the`conduit, by casting the concrete against a corrosion-resistant plastic lining having projections interlocking with the concrete, such as T-shaped ribs which become embedded in the surface of the concrete, as shown in the expired U.S. Patent 2,816,323, of Munger. However, such linings have not been shown to be useful in preventing attachment and growth of living organisms.
It has also been known that the attachment and growth of barnacles, seaweeds, and other living creatures which attach themselves to the exterior surfaces of boat hulls, buoys, piling, and other structures exposed to seawater, could be prevented by application of a poison, ~ such as metallic copper, or paints containing various ,~ , ,'' '.
- :- . . : ,: ,. ., ... - . :
.. , . ~ . , .. , , .. , ~ , .
.
,- ' . , ~L()9(~22
- 2 ~
compounds of copper or other poisonous metals, or most advantageously sheets of flexible plastic or elastomer material containing poisons. The materials of greatest long term effectiveness appear to be elastomer materials containing poisons that are very slightly soluble in water but somewhat soluble in the elastomer, so that they diffuse slowly to the surface, and therefore are continuously present at the surface for many years in minute but effective quantity because of the very low solubility in water, as disclosed in Cardarelli U.S.
patents 3,417,181 and 3,426,473.
According to the present invention there is provided a corrosion-resistant conduit lining, repellant to living organisms, comprising a flexible corrosion-resistant layer provided with projecting keys capable of being key-bonded to a conduit, and united thereto another layer of flexible material for exposure to the fluid in the conduit, said another layer being characterized by the presence of a compound which is slightly soluble in the ~20 material of said another layer and is very slightly water-soluble and also is toxic~to organisms which tend to attach themselves to surfaces and;grow on such surfaces.
In another aspect of the invention there is provided the combination of a conduit lining of the invention, and a concrete conduit cast around the lining so that the lining is keyed to it.
The invention more particularly involves the discovery that a surface material which will repel the organisms which tend to attach themselves to conduit linings can easily be provided on the inner surfaces of concrete conduits and other concrete structures such as reservoirs by preparing the known plastic lining material with locking ribs on one surface, and applying to the other surface of the plastic lining material a layer of an elastomeric material containing a long term effective poison. The composite lining is applied to the building 10~072~
- 2a -, forms for the conduit with the locking ribs outward, and the concrete is poured so as to embed the locking ribs and hold the lining firmly in place. The lining pre-ferably covers the entire inner surface of the conduit, with essentially none of the concrete ultimately exposed to the seawater on the inside, when the building forms are removed. :
In the construction of such lined concrete conduits, it is preferred to preassem~le the plastic sheets, having locking ribs on one side, with a sub-stantial thickness, on the other side, of elastomer con-taining a suitable poison. However the same excellent results can be obtained by constructing the plastic lined conduit first, and then applying a further lining .. >, .. . , , :. .................................. . :
. . .: ., : . . : ::
~U907'ZZ
,, of a material containing a slowly released poison, but with a generally higher labor cost.
The backing or supporting layer i~ preferably made from a suitable flexible inert material such as 5 plasticized polyvinyl chIoride, fabricated in extruded strips provided with locking ribs of T-shaped cross section. To this flexible, plastic lining is then adhered material including an appropriate toxicant com-pound. The composite sheet is wrapped around the inner 10 concrete form with the toxicant-containing material against the form, and the concrete conduit material is poured so as to surround and embed the locking ribs and therefore to hold the lining immovably in place on all or most of the exposed inner surface of the conduit when 15 it is built.
THE DRAWINGS
In the accompanying drawings:
Fig. 1 is a cross-section on a small scale of a large diameter concrete conduit provided with a lining 20 in accordance with this invention.
Fig. 2 is a partial section on a larger scale of one embodiment of the invention.
Fig. 3 is a similar partial section of another embodiment.
DETAILED DESCRIPTION
The lining material of this invention is pre-ferably made of at least two somewhat different kinds of compositions because they perform somewhat different functions which are most advantageously performed by 30 different compositions.
The base which is mechanically bonded to the concrete structure should be a somewhat stretchable but chemically unreactive material, so that it will not suffer rro~ long tlme exposure to strongly alkaline con-35 crete or to the atmosphere or fresh water or seawater.Although vulcanized or unvulcanized natural rubber or , 109~72Z
.
synthetic rubber may be used, it ls much preferred to use a flexible thermoplastic such as polyethylene or preferably plasticized polyvinyl chloride, the latter being particularly inexpensive, strong, and highly re-sistant to change, especially if plasticized with abouthalf its weight of plasticizer of high molecular weight and therefore of extremely low volatility so that the base material will not change appreciably in physical properties over many years of time.
10The principal other material is that which makes up the exposed surface of the lining. It must -contain, and retain for years of time, a poison or toxicant which will prevent attachment and growth of living organisms. While it is conceivable that almost 15 any weather-resistant flexible or elastic material might be used, it is presently preferred to use a vulcanizable elastomer, and preferably one which is essentially hydro-carbon in nature or at most contains substituents in the molecular structure which are quite unreactive under or-20 dinary conditions, such as chlorine or nitrile. Conse-quently, such materials as neoprene (a polymer of chloro-butadiene), butyl rubber (a copolymer of isobutylene with a little isoprene), and EPDM rubbers (copolymers of -ethylene and propylene with a little diene) are preferred 25 materials, although many other elastomers could be used, such as natural rubber, nitrile rubbers, butadiene-sty-rene rubbers, polyether rubbers, etc., or even plasti-cized thermoplastics such as polyvinyl chloride or polyvinyl butyral, or inherently resilient polymers such 30 as flexible polyethers, polyesters, polysilanes, etc.
The specific materials chosen must be extremely resistant to weathering. If a vuicanizable rubber is chosen, it should preferably be vulcanized to a strong and at least somewhat resilient condition. The choice of vulcanizing 35 agents is generally unimportant, as long as they do not decompose the toxicant which is used, or react with it.
' .. . . .. .
,: .
~ : , , : , ~o9o~zz The other essential material is the actual poison or toxicant which either repels or prevents the growth of living organisms on the exposed surface. For effective long term function, this needs to be a material which can be dispersed in a moderately high pro-5 portion in the surface layer and which will dissolve inthe elastomer to a slight but appreciable extent. There will, of course, be poison or toxicant present in the surface layer as long as any of the toxicant remains, because the material chosen is one which is capable of lO diffusing throughout the elastomer at a rate dependent on its solubility and molecular weight. For long term effectiveness, the material must therefore be somewhat :
soluble in the elastomeric surface material and have a molecular weight sufficiently high that it will diffuse 15 throughout the mass, very slowly, and will be dissolved into seawater from the surface at a predetermined but extremely slow rate, so that there will be some toxi-cant continuously at the exposed surface, effective to repel unwanted organisms but so little that it will be 20 many years before the toxicant is exhaused and its effect ceases.
The toxicant can be any material which is ade-quately repellant and at the same time has a sufficiently low solubility in water to be retained for many years.
25 For this purpose the organotin compounds disclosed in Cardarelli U.S~ patent 3,426,~73 are preferred, because of their effectiveness, extremely low solubility in water, and freedom from hazard to warm-blooded animals including people, and to food fish, at the concentration in which 30 these toxicants would be present in the water. Specific-ally preferred is tributyl-tin oxide.
The conduit lining material of this invention ' can be made of a single material which will function both as the base for keying into the concrete, and as the res-35 ervoir for the toxicant, but since the toxicant is some-109()7ZZ
what expensive, it is greatly preferred to place it onlywhere it will be most effective and to use a different material for the base. For the same reason, it is pre-ferred to use a barrier film between the two materials, 5 to minimize loss of toxicant by diffusion away from the exposed surface into the base. It is also pre-ferred, although not always necessary, to use an ad-hesive to bond the elastomer surface material containing the toxicant to the base material.
EXAMPLE
Referring to the drawings, Fig. 1 shows a section of a concrete conduit of cylindrical shape and therefore having a circular cross-section. Such a con-duit consists of a concrete shell 10, usually but not 15 necessarily with conventional longitudinal and circum-ferential reinforcing rods (not shown) and a lining.
In accordance with this invention, the lining consists of at least two layers, as shown in Fig. 2.
The base layer 11 in direct contact with the 20 concrete shell 10 is preferably made of a polyvinyl chloride plasticized with about half its weight of non-fugitive plasticizers, such as one of the common soft resinous polyester plasticizers. One or more liquid plasticizers such as didecyl phthalate may also be 25 employed, along with the usual minor quantity of a stabilizer. Mineral fillers may also be present if desired, for reducing cost.
The base layer 11 of the liner is fabricated by extrusion of the vinyl composition in a thin sheet, 30 which may suitably be about 2 mm thick, having T-shaped ribs 12 extending about 1 cm from one surface, with the head of the T about 1 cm in width. Spacing of the ribs may be about 5 to 8 cm. Such a sheet can be produced in whatever width is conveniently handled in an extruder, 35 and joined edge to edge by heat sealing to form blankets of any desired width for wrapping around a form for a . ~: ,.
, ~ ' ' ' ' ' .. . .
i()907ZZ
concrete conduit.
The inner layer 15 of the lining, which faces the hollow space of the conduit, is made from a material which is preferably elastomeric, or at least easily flex-5 ible, and should have a consistency in the range fromvery firm but still flexible, to soft and rubbery. It is preferred to use a fairly resilent material having a high resistance to weather, and particularly to moisture.
Accordingly, synthetic elastomers essentially free from 10 proteins and fatty acids are most suitable. Particularly preferred are the rubbert polymers of chlorobutadiene, generally known as neoprene, since properly compounded and prepared neoprene is easily vulcanized and is strong, resilient, resistant to weather and to oils, and can be 15 mixed with relatively high proportions of suitable toxi-cants so as to release them at the surface in an effec-tive amount at an extremely slow rate.
Thus a water resistant type of neoprene such as Neoprene WRT may be mixed with conventional vulcanizing 20 materials for neoprene, and preferably with addition of a reinforcing pigment such as carbon black (for a black surface) or hydrated silica (for a white surface). For each 100 parts by weight of neoprene polymer at least about 5 parts and preferably from 10 to 20 parts of tributyl-tin oxide are added as a long term toxicant.
Such a composition is then vulcanized in sheets of about 2 mm to as much as 12 or 15 mm thickness depending on the duration of protection desired. The minimum thickness of 2 mm will protect against fouling by most organisms, and particularly barnacles and mollusks, for 5 to 10 years. The length of protection accorded by greater thicknesses can only be estimated, but should be as much as 30 years for 12 mm thickness.
The union of the neoprene surface with the vinyl backing which is interlocked into the concrete can be obtained in a very simple matter by coating each surface 109()7ZZ
with a neoprene solution such as is known as "contact cement", and pressing them firmly together when the coated surfaces are tacky.
For long term protection, it is desirable to 5 bond the toxicant-containing surface layer to the base material which is interlocked with the concrete with a bond of maximum attainable strength and durability. It is also desirable to assure retention of toxicant for as long a period as possible by avoiding loss by dif-10 fusion or otherwise in the direction away from theexposed surface. For obtaining these objectives it is preferred to interpose between the two materials a chemically set adhesive cement and also a diffusion resistant barrier layer.
A suitable barrier to retard loss of the tributyl-tin oxide, or other toxicant, by diffusion, is -chlorinated rubber, preferably a grade containing at least 66~ chlorine, such as can be obtained under the trade name Parlon 125. A uniform coat of a solution of 20 such chlorinated rubber is applied to the smooth face of the vinyl backing, to form a strongly adherent barrier film 13 as shown in Fig. 3.
A room-temperature setting waterproof epoxy adhesive 14 can then be used to bond the toxicant-25 containing inner layer 15 to the barrier film 13 on thevinyl outer lining layer 11.
Alternatively, a mixture of polymers can be used to form a strongly adhesive barrier layer~ For example, approximately equal quantities of neoprene and 30 chlorinated rubber, together with a somewhat smaller quantity of a 50:50 butadiene-styrene copolymer, suitably one-third as much as the sum of the other two ingredi-ents, can be used to function both as a ribbed backing and as a diffusion barrier, or for either one of these 35 purposes if a different material is chosen for the other purpose.
. ~ .
~ - . 10907Z~
The composite material, with a toxicant-containing face, and a ribbed backing for keying into the concrete, is made up in dimensions suitable for lining the concrete conduit which is to be constructed.
If the concrete conduit is to be made in cylin-drical sections subsequently assembled, the inner cylin-drical concrete form will be wrapped with the composite sheet, which can then be held in place by reinforcing wires encircling the sheet on the inner form. Addi-10 tional reinforcing wires or rods may be placed next to the sheet lining before the outer form is assembled around it. The concrete mix is poured in the form around the lining. When the concrete is properly distri-buted, it fills the spaces between the ribs 16 so as to 15 lock the outer layer 15 of the liner firmly in place inside of the concrete shell. When the concrete has set and the forms are removed, the conduit section can be joined to the next previous section.
If the shape is such that the lining cannot be 20 held in place on the inner forms by wrapping with wires, it can be held to wooden forms by finishing nails, which can then be pulled through the elastomeric lining when the forms are removed, with the nail holes essentially closed by the elasticity of the material.
Whatever the shape or manufacturing procedure for the conduit, it will be made by placing the lining against the inner form and casting concrete around it to interlock with the keying ribs to form an integrally lined conduit or section of conduit.
Such a conduit may be cast in situ as an inte-gral continuous structure, or can be made from prefabri-cated sections with the linings of each section firmly abutted against linings of the adjacent sections so that there will be essentially no part of the surface exposed 35 to the water except that which is made from toxicant-containing material.
compounds of copper or other poisonous metals, or most advantageously sheets of flexible plastic or elastomer material containing poisons. The materials of greatest long term effectiveness appear to be elastomer materials containing poisons that are very slightly soluble in water but somewhat soluble in the elastomer, so that they diffuse slowly to the surface, and therefore are continuously present at the surface for many years in minute but effective quantity because of the very low solubility in water, as disclosed in Cardarelli U.S.
patents 3,417,181 and 3,426,473.
According to the present invention there is provided a corrosion-resistant conduit lining, repellant to living organisms, comprising a flexible corrosion-resistant layer provided with projecting keys capable of being key-bonded to a conduit, and united thereto another layer of flexible material for exposure to the fluid in the conduit, said another layer being characterized by the presence of a compound which is slightly soluble in the ~20 material of said another layer and is very slightly water-soluble and also is toxic~to organisms which tend to attach themselves to surfaces and;grow on such surfaces.
In another aspect of the invention there is provided the combination of a conduit lining of the invention, and a concrete conduit cast around the lining so that the lining is keyed to it.
The invention more particularly involves the discovery that a surface material which will repel the organisms which tend to attach themselves to conduit linings can easily be provided on the inner surfaces of concrete conduits and other concrete structures such as reservoirs by preparing the known plastic lining material with locking ribs on one surface, and applying to the other surface of the plastic lining material a layer of an elastomeric material containing a long term effective poison. The composite lining is applied to the building 10~072~
- 2a -, forms for the conduit with the locking ribs outward, and the concrete is poured so as to embed the locking ribs and hold the lining firmly in place. The lining pre-ferably covers the entire inner surface of the conduit, with essentially none of the concrete ultimately exposed to the seawater on the inside, when the building forms are removed. :
In the construction of such lined concrete conduits, it is preferred to preassem~le the plastic sheets, having locking ribs on one side, with a sub-stantial thickness, on the other side, of elastomer con-taining a suitable poison. However the same excellent results can be obtained by constructing the plastic lined conduit first, and then applying a further lining .. >, .. . , , :. .................................. . :
. . .: ., : . . : ::
~U907'ZZ
,, of a material containing a slowly released poison, but with a generally higher labor cost.
The backing or supporting layer i~ preferably made from a suitable flexible inert material such as 5 plasticized polyvinyl chIoride, fabricated in extruded strips provided with locking ribs of T-shaped cross section. To this flexible, plastic lining is then adhered material including an appropriate toxicant com-pound. The composite sheet is wrapped around the inner 10 concrete form with the toxicant-containing material against the form, and the concrete conduit material is poured so as to surround and embed the locking ribs and therefore to hold the lining immovably in place on all or most of the exposed inner surface of the conduit when 15 it is built.
THE DRAWINGS
In the accompanying drawings:
Fig. 1 is a cross-section on a small scale of a large diameter concrete conduit provided with a lining 20 in accordance with this invention.
Fig. 2 is a partial section on a larger scale of one embodiment of the invention.
Fig. 3 is a similar partial section of another embodiment.
DETAILED DESCRIPTION
The lining material of this invention is pre-ferably made of at least two somewhat different kinds of compositions because they perform somewhat different functions which are most advantageously performed by 30 different compositions.
The base which is mechanically bonded to the concrete structure should be a somewhat stretchable but chemically unreactive material, so that it will not suffer rro~ long tlme exposure to strongly alkaline con-35 crete or to the atmosphere or fresh water or seawater.Although vulcanized or unvulcanized natural rubber or , 109~72Z
.
synthetic rubber may be used, it ls much preferred to use a flexible thermoplastic such as polyethylene or preferably plasticized polyvinyl chloride, the latter being particularly inexpensive, strong, and highly re-sistant to change, especially if plasticized with abouthalf its weight of plasticizer of high molecular weight and therefore of extremely low volatility so that the base material will not change appreciably in physical properties over many years of time.
10The principal other material is that which makes up the exposed surface of the lining. It must -contain, and retain for years of time, a poison or toxicant which will prevent attachment and growth of living organisms. While it is conceivable that almost 15 any weather-resistant flexible or elastic material might be used, it is presently preferred to use a vulcanizable elastomer, and preferably one which is essentially hydro-carbon in nature or at most contains substituents in the molecular structure which are quite unreactive under or-20 dinary conditions, such as chlorine or nitrile. Conse-quently, such materials as neoprene (a polymer of chloro-butadiene), butyl rubber (a copolymer of isobutylene with a little isoprene), and EPDM rubbers (copolymers of -ethylene and propylene with a little diene) are preferred 25 materials, although many other elastomers could be used, such as natural rubber, nitrile rubbers, butadiene-sty-rene rubbers, polyether rubbers, etc., or even plasti-cized thermoplastics such as polyvinyl chloride or polyvinyl butyral, or inherently resilient polymers such 30 as flexible polyethers, polyesters, polysilanes, etc.
The specific materials chosen must be extremely resistant to weathering. If a vuicanizable rubber is chosen, it should preferably be vulcanized to a strong and at least somewhat resilient condition. The choice of vulcanizing 35 agents is generally unimportant, as long as they do not decompose the toxicant which is used, or react with it.
' .. . . .. .
,: .
~ : , , : , ~o9o~zz The other essential material is the actual poison or toxicant which either repels or prevents the growth of living organisms on the exposed surface. For effective long term function, this needs to be a material which can be dispersed in a moderately high pro-5 portion in the surface layer and which will dissolve inthe elastomer to a slight but appreciable extent. There will, of course, be poison or toxicant present in the surface layer as long as any of the toxicant remains, because the material chosen is one which is capable of lO diffusing throughout the elastomer at a rate dependent on its solubility and molecular weight. For long term effectiveness, the material must therefore be somewhat :
soluble in the elastomeric surface material and have a molecular weight sufficiently high that it will diffuse 15 throughout the mass, very slowly, and will be dissolved into seawater from the surface at a predetermined but extremely slow rate, so that there will be some toxi-cant continuously at the exposed surface, effective to repel unwanted organisms but so little that it will be 20 many years before the toxicant is exhaused and its effect ceases.
The toxicant can be any material which is ade-quately repellant and at the same time has a sufficiently low solubility in water to be retained for many years.
25 For this purpose the organotin compounds disclosed in Cardarelli U.S~ patent 3,426,~73 are preferred, because of their effectiveness, extremely low solubility in water, and freedom from hazard to warm-blooded animals including people, and to food fish, at the concentration in which 30 these toxicants would be present in the water. Specific-ally preferred is tributyl-tin oxide.
The conduit lining material of this invention ' can be made of a single material which will function both as the base for keying into the concrete, and as the res-35 ervoir for the toxicant, but since the toxicant is some-109()7ZZ
what expensive, it is greatly preferred to place it onlywhere it will be most effective and to use a different material for the base. For the same reason, it is pre-ferred to use a barrier film between the two materials, 5 to minimize loss of toxicant by diffusion away from the exposed surface into the base. It is also pre-ferred, although not always necessary, to use an ad-hesive to bond the elastomer surface material containing the toxicant to the base material.
EXAMPLE
Referring to the drawings, Fig. 1 shows a section of a concrete conduit of cylindrical shape and therefore having a circular cross-section. Such a con-duit consists of a concrete shell 10, usually but not 15 necessarily with conventional longitudinal and circum-ferential reinforcing rods (not shown) and a lining.
In accordance with this invention, the lining consists of at least two layers, as shown in Fig. 2.
The base layer 11 in direct contact with the 20 concrete shell 10 is preferably made of a polyvinyl chloride plasticized with about half its weight of non-fugitive plasticizers, such as one of the common soft resinous polyester plasticizers. One or more liquid plasticizers such as didecyl phthalate may also be 25 employed, along with the usual minor quantity of a stabilizer. Mineral fillers may also be present if desired, for reducing cost.
The base layer 11 of the liner is fabricated by extrusion of the vinyl composition in a thin sheet, 30 which may suitably be about 2 mm thick, having T-shaped ribs 12 extending about 1 cm from one surface, with the head of the T about 1 cm in width. Spacing of the ribs may be about 5 to 8 cm. Such a sheet can be produced in whatever width is conveniently handled in an extruder, 35 and joined edge to edge by heat sealing to form blankets of any desired width for wrapping around a form for a . ~: ,.
, ~ ' ' ' ' ' .. . .
i()907ZZ
concrete conduit.
The inner layer 15 of the lining, which faces the hollow space of the conduit, is made from a material which is preferably elastomeric, or at least easily flex-5 ible, and should have a consistency in the range fromvery firm but still flexible, to soft and rubbery. It is preferred to use a fairly resilent material having a high resistance to weather, and particularly to moisture.
Accordingly, synthetic elastomers essentially free from 10 proteins and fatty acids are most suitable. Particularly preferred are the rubbert polymers of chlorobutadiene, generally known as neoprene, since properly compounded and prepared neoprene is easily vulcanized and is strong, resilient, resistant to weather and to oils, and can be 15 mixed with relatively high proportions of suitable toxi-cants so as to release them at the surface in an effec-tive amount at an extremely slow rate.
Thus a water resistant type of neoprene such as Neoprene WRT may be mixed with conventional vulcanizing 20 materials for neoprene, and preferably with addition of a reinforcing pigment such as carbon black (for a black surface) or hydrated silica (for a white surface). For each 100 parts by weight of neoprene polymer at least about 5 parts and preferably from 10 to 20 parts of tributyl-tin oxide are added as a long term toxicant.
Such a composition is then vulcanized in sheets of about 2 mm to as much as 12 or 15 mm thickness depending on the duration of protection desired. The minimum thickness of 2 mm will protect against fouling by most organisms, and particularly barnacles and mollusks, for 5 to 10 years. The length of protection accorded by greater thicknesses can only be estimated, but should be as much as 30 years for 12 mm thickness.
The union of the neoprene surface with the vinyl backing which is interlocked into the concrete can be obtained in a very simple matter by coating each surface 109()7ZZ
with a neoprene solution such as is known as "contact cement", and pressing them firmly together when the coated surfaces are tacky.
For long term protection, it is desirable to 5 bond the toxicant-containing surface layer to the base material which is interlocked with the concrete with a bond of maximum attainable strength and durability. It is also desirable to assure retention of toxicant for as long a period as possible by avoiding loss by dif-10 fusion or otherwise in the direction away from theexposed surface. For obtaining these objectives it is preferred to interpose between the two materials a chemically set adhesive cement and also a diffusion resistant barrier layer.
A suitable barrier to retard loss of the tributyl-tin oxide, or other toxicant, by diffusion, is -chlorinated rubber, preferably a grade containing at least 66~ chlorine, such as can be obtained under the trade name Parlon 125. A uniform coat of a solution of 20 such chlorinated rubber is applied to the smooth face of the vinyl backing, to form a strongly adherent barrier film 13 as shown in Fig. 3.
A room-temperature setting waterproof epoxy adhesive 14 can then be used to bond the toxicant-25 containing inner layer 15 to the barrier film 13 on thevinyl outer lining layer 11.
Alternatively, a mixture of polymers can be used to form a strongly adhesive barrier layer~ For example, approximately equal quantities of neoprene and 30 chlorinated rubber, together with a somewhat smaller quantity of a 50:50 butadiene-styrene copolymer, suitably one-third as much as the sum of the other two ingredi-ents, can be used to function both as a ribbed backing and as a diffusion barrier, or for either one of these 35 purposes if a different material is chosen for the other purpose.
. ~ .
~ - . 10907Z~
The composite material, with a toxicant-containing face, and a ribbed backing for keying into the concrete, is made up in dimensions suitable for lining the concrete conduit which is to be constructed.
If the concrete conduit is to be made in cylin-drical sections subsequently assembled, the inner cylin-drical concrete form will be wrapped with the composite sheet, which can then be held in place by reinforcing wires encircling the sheet on the inner form. Addi-10 tional reinforcing wires or rods may be placed next to the sheet lining before the outer form is assembled around it. The concrete mix is poured in the form around the lining. When the concrete is properly distri-buted, it fills the spaces between the ribs 16 so as to 15 lock the outer layer 15 of the liner firmly in place inside of the concrete shell. When the concrete has set and the forms are removed, the conduit section can be joined to the next previous section.
If the shape is such that the lining cannot be 20 held in place on the inner forms by wrapping with wires, it can be held to wooden forms by finishing nails, which can then be pulled through the elastomeric lining when the forms are removed, with the nail holes essentially closed by the elasticity of the material.
Whatever the shape or manufacturing procedure for the conduit, it will be made by placing the lining against the inner form and casting concrete around it to interlock with the keying ribs to form an integrally lined conduit or section of conduit.
Such a conduit may be cast in situ as an inte-gral continuous structure, or can be made from prefabri-cated sections with the linings of each section firmly abutted against linings of the adjacent sections so that there will be essentially no part of the surface exposed 35 to the water except that which is made from toxicant-containing material.
Claims (9)
1. A corrosion-resistant conduit lining, repellant to living organisms, comprising a flexible corrosion-resistant layer provided with projecting keys capable of being key-bonded to a conduit, and united thereto another layer of flexible material for exposure to the fluid in the conduit, said another layer being characterized by the presence of a compound which is slightly soluble in the material of said another layer and is very slightly water-soluble and also is toxic to organisms which tend to attach themselves to surfaces and grow on such surfaces.
2. A conduit lining as in claim 1, in which the keys have the form of parallel ribs which are T-shaped in cross-section.
3. A conduit lining as defined in claim 1, in which a diffusion-resistant barrier layer is interposed between the key-bonded layer and the layer containing a toxic compound.
4, A combination of a conduit lining as defined in claim 1, and a concrete conduit cast around the lining so that the lining is keyed to it.
5. The combination of a conduit lining as defined in claim 3, and a concrete conduit cast around the lining so that the lining is keyed to it.
6. The combination of a conduit lining and a concrete conduit as defined in claim 5, in which the keys have the form of parallel ribs which are T-shaped in cross-section.
7. A conduit lining as in claim 3, in which the toxic compound is an organotin compound.
8. A conduit lining as in claim 7, in which the keys have the form of parallel ribs which are T-shaped in cross-section.
9. The combination of a conduit lining as defined in claim 8, and a concrete conduit cast around the lining so that the lining is keyed to it.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US86000477A | 1977-12-12 | 1977-12-12 | |
| US860,004 | 1977-12-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1090722A true CA1090722A (en) | 1980-12-02 |
Family
ID=25332287
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA315,379A Expired CA1090722A (en) | 1977-12-12 | 1978-10-31 | Lining for concrete water conduits |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5489324A (en) |
| CA (1) | CA1090722A (en) |
| DE (1) | DE2851399A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103925456A (en) * | 2014-04-29 | 2014-07-16 | 刘杰 | Anticorrosion structure for inner wall of concrete pipeline |
| SE541235C2 (en) * | 2016-07-11 | 2019-05-07 | Tekniska Verken I Linkoeping Ab | Method of providing a liquid proof joint between parts and structure comprising such joint |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3114003A1 (en) * | 1981-04-07 | 1982-10-21 | Schlegel Lining Technology GmbH, 2000 Hamburg | CONCRETE PIPE WITH AN INTERNAL LINING |
| US5394932A (en) * | 1992-01-17 | 1995-03-07 | Howmet Corporation | Multiple part cores for investment casting |
-
1978
- 1978-10-31 CA CA315,379A patent/CA1090722A/en not_active Expired
- 1978-11-24 DE DE19782851399 patent/DE2851399A1/en active Pending
- 1978-12-12 JP JP15407778A patent/JPS5489324A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103925456A (en) * | 2014-04-29 | 2014-07-16 | 刘杰 | Anticorrosion structure for inner wall of concrete pipeline |
| SE541235C2 (en) * | 2016-07-11 | 2019-05-07 | Tekniska Verken I Linkoeping Ab | Method of providing a liquid proof joint between parts and structure comprising such joint |
| EP3270026B1 (en) * | 2016-07-11 | 2021-08-18 | Tekniska Verken I Linköping AB | Method of providing a liquid proof joint between parts and structure comprising such joint |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2851399A1 (en) | 1979-06-13 |
| JPS5489324A (en) | 1979-07-16 |
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| Date | Code | Title | Description |
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