JPS63230893A - Structural frame for electrochemical baths - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a structural frame for use in electrochemical tanks and special Kt gas chemical tanks.

BACKGROUND OF THE INVENTION The production of various chemical products in an electrochemical cell with an anode and a cathode is well established. For example, alkali metal chlorates such as sodium chlorate have been formed electrochemically from sodium chloride brine in an electrolytic cell without a separator between the anode and cathode.

When a separator, such as a liquid-permeable asbestos or polytetrafluoroethylene membrane or a substantially liquid-impermeable alpha-exchange membrane, is used in the cell for the electrolysis of sodium chloride brine, the electrolysis products are usually gaseous chlorine, It would be an aqueous solution containing gaseous hydrogen and sodium hydroxide.

For many years, gaseous chlorine was produced in electrolytic cells placed between finger-shaped anodes and cathodes sandwiched by asbestos membranes. Over the past few years, it has become clear that when higher purity products, e.g. lower sodium chloride content, higher sodium hydroxide products are desired, virtually liquid-impermeable membranes are preferred over the more well-established membranes. It has become clear that it is preferable to use an ion exchange membrane. It is more convenient to construct an ion-exchange electrochemical cell from a relatively flat or planar sheet of ion-exchange membrane than to sandwich the membrane between an anode and a cathode in an old-fashioned finger cell for use with an asbestos diaphragm. It turns out that there is something.

A so-called flat plate electrochemical cell is a multi-cell electrochemical cell configured to support an anode on one side and a cathode on the other. There are also solid, liquid-impermeable frames.

These frames have heretofore been constructed from materials such as metal and plastic, but it has become clear that neither material is completely satisfactory.

In electrochemical cells, including monopolar and bipolar, electrolyte may leak outward from the cell. If such a leak occurs in a vessel using a steel or other ferrous type of frame, the steel frame will corrode or itself become electrolytically attacked.

Although plastic frames are generally impervious to electrolytic attack, they typically do not withstand the anolyte and/or catholyte in the bath under long-term operating conditions, such as several years.

reduce corrosion problems and improve the relatively short useful life associated with those frames used in the prior art;
It is desirable to provide a structural frame for use in an electrochemical cell.

Structure of the Invention The present invention is particularly in the form of a substantially planar member made of a polymeric material, with horizontally and vertically spaced spacers projecting outwardly from at least one surface of the planar member. central cistern element having a plurality of spaced apart shoulders: at least one electrical conductor extending from the outer surface of the shoulder on one surface of the planar member through the planar member to the outer surface of the shoulder on the opposite surface of the planar member; an electrically conductive insert, provided that each of the wire shoulders annularly surrounds and supports each of the inserts; is in intimate contact with the surface of at least one of the planar members and is in contact with the electrolyte in the bath and the planar surface; an electrically conductive, substantially completely hydraulically impermeable liner that resists the corrosive effects of the electrolyte in the bath; This is a structural frame configured to be used in an electrochemical tank.

In one embodiment, the anolyte cover (liner) is secured flush against the anolyte side surface of the planar member and is configured to minimize contact between the anolyte and the planar side. The anolyte cover is resistant to the corrosive effects of the anolyte. The catholyte cover extends over the opposite, catholyte-side surface of the planar member and is flush and secured, and is structured to minimize contact between the catholyte and the planar member. The catholyte cover is resistant to the corrosive effects of the catholyte. Both the anolyte cover and the catholyte cover are metallic, or a metal insert embedded in the non-metallic liner at the point where the metal insert in the liner contacts the metal insert passing through the planar member. It can be made of some other material.

The present invention further utilizes a plurality of the above-described structural frames removably and sealably disposed in coplanar relationship with each other, and each of the planar members is arranged on one or opposite sides of the planar member. It includes an electrochemical cell spaced apart by an anode on one side of the planar member and a cathode on the opposite side of the planar member.

DETAILED DESCRIPTION OF THE EMBODIMENTS The accompanying drawings further illustrate the invention. Identical numerals separated by letter suffixes in the drawings indicate parts having similar functions within different embodiments.

FIG. 1 shows structural frames 10 and 10a that achieve the above objective. This indicates its use in an electrochemical cell for producing gaseous chlorine and aqueous alkali metal hydroxide solutions.

Although the present invention can be advantageously utilized in the production of chlorine and various alkali metal hydroxide solutions, it is preferred to use sodium chloride as the primary salt in the raw brine, since this particular salt is readily available on the market. There are many well-established uses for sodium hydroxide, which is readily available and produced electrolytically.

The tank structure 10 includes a planar barrier section, a periphery 7 flange section (34), an anode and a cathode for keeping the anodes and cathodes of adjacent tank structures at a predetermined distance from the planar barrier section. There is a horizontal member 12 having a standoff member or boss. The planar member is formed by industrially and conventionally known methods into a plurality of horizontally and vertically spaced apart shoulders (boss) 14 projecting outwardly from the cathode and anode sides 16 and 18, respectively. and 14a. The periphery 1fi20 of the planar member 12 forms the outer surface of the electrochemical cell when the illustrated plurality of planar members are arranged side by side. The peripheral contour of planar member 12 is optional and may be varied to suit the particular contour of the desired electrochemical cell shape.

The number, size, and shape of shoulders 14 and 14a are important considerations in both the design and operation of the present invention. When viewed in cross-section either parallel or perpendicular to the central portion, the shoulder can be square, rectangular (square), conical, cylindrical or any other convenient shape. The shoulder may have an elongated shape forming a series of spaced ribs distributed over the surface of the plastic member.

A number of polymeric materials are suitable for use in the present invention for rounding the configuration of planar members. Although not intended to be limited by the specific materials detailed below, examples of such suitable materials (substances) include:
Polyethylene; polypropylene; polyvinyl chloride: chlorinated polyvinyl chloride; acrylonitrile, polystyrene/, folysulfone, styrene; acrylonitrile, phthalene and styrene copolymers; epoxy;
Vinyl ethers; polyesters; and fluoroplastics and their copolymers.

It is preferred to use polymeric materials such as polypropylene for planar members because shapes with sufficient structural integrity are easily obtained at elevated temperatures and are relatively This is because it is cheap.

It is surprising that planar member 12 can be manufactured by any of a number of processes well known to those skilled in the plastic molding art. Such molding processes include, for example, injection molding, compression molding, transfer molding, and casting. In those processes, it has been found that structures with sufficient strength for use in electrochemical cells can be produced satisfactorily by injection molding. Preferably, the polymeric material is injected into a mold containing the desired number of inserts (described below). In this manner, the planar member is an integral member that fits around the inserts, holding them in place and providing them with elevated support. Such a configuration minimizes the possibility of the insert separating from the planar member and becoming loose. The ease of molding relatively complex shapes and the strength of the finished injection molded article make this process preferred for the purpose of manufacturing the planar parts described herein. This is a significant advantage over prior art techniques in which the polymeric member is first formed and then the electrical conductors are subsequently applied.

When the planar member is used in an electrochemical cell for chlorine production, the temperature of the cell and the planar member often reaches or remains at a temperature of 60° to 90° C. At this temperature, polymeric materials, like most substances, expand by a measurable amount. Expansion of the planar members and subsequent contraction upon cooling will result in seepage of electrolyte from within the cells when joined together or, more importantly, if the planar members are made of expanded mesh or perforated sheets of metal. distortion of the anode and cathode. Furthermore, the difference in expansion coefficients between the planar member 12 and the electrolyte liner or cover 22 and/or 24 is such that the indentations molded into the planar member are in the welds securing these covers. will cause stress.

In order to reduce, and preferably minimize, the difference in expansion rates between the covers 22 and 24 and the planar member 12, additives may be included to reduce thermally induced expansion of the planar member. preferable. Preferably, the additive also increases the structural strength of the finished article. Such additives can be, for example, glass fibers, goulphite fibers, carbon fibers, talc, glass beads, micronized mica, asbestos, etc., and combinations thereof. 5 to 75% by weight of polymer,
More preferably, it contains 10 to 40% by weight of additives.

Glass fibers can be easily mixed with polypropylene to produce an injectable material suitable for use in the present invention, which is a solid, physical material with a lower coefficient of expansion than polypropylene without glass fibers. produces a solid object. More important is to minimize the expansion (rate) differences between the planar members, electrodes, and current collectors, because these elements are welded together, and they This is because it is critical that they be substantially flat and parallel.

It has been determined that the use of commercially available polypropylene with a special formulation capable of bonding with glass fibers works particularly well. This results in a composite material with a lower coefficient of expansion than a mixture of polypropylene and glass fibers. Such chemically combined glass fiber reinforced polypropylene is available from Hercules, Inc., Ilmington, PR, for example as Pro-fax PCO 72 polypropylene.
Available from Inc.).

At least one electrically conductive element, such as insert 26, is disposed within planar member 12 and is preferably embedded. The insert 26 extends through the planar member from one electrolyte-side surface, eg, catholyte-side surface 16, to an opposite electrolyte-side surface, eg, catholyte-side surface 18. Inserts 26 and 26a are preferably retained within the planar member by friction between the polymeric material and the inserts. More preferably, the friction between these two objects is increased by having an additional member to retain the insert within the polymeric material. Such additional components may include, for example, groove(s) around the circumference of the insert, keys welded to the insert, holes, slots, rings extending in and/or through the insert. , collar studs, or bosses.

Insert 26 may be any material capable of conducting electrical current between catholyte cover 22 and anolyte cover 24 . Since the covers 22 and 24 are preferably made of metal, it is advantageous for the insert to be made from a metal, such as aluminium, copper, iron, steel, nickel, titanium, etc., or an alloy or physical composition comprising such a metal. .

The shoulders and inserts must be spaced from other shoulders and inserts to provide a reasonably uniform and low potential gradient across the electrode surface to which they are attached. They should be spaced apart to allow free liquid circulation from an unoccupied point within each electrolyte chamber to another unoccupied point in that chamber. The shoulders will therefore be fairly evenly spaced apart from each other within each chamber.

To improve DC current flow between covers 22 and 24, insert 26 is preferably made of a material that is welding compatible with the particular cover with which it contacts. For example, the insert 26 is a welded assembly of a steel rod 261 with a vanadium disk 262 placed between the steel stud 261 and a titanium cup 263 on the anode-facing portion of the structure 10 and welded to both. It may be three-dimensional. A similar nickel cup 264 may be welded directly to rod 26 on the cathode-facing portion of the insert. The titanium and nickel members 263 and 264 are then easily chlorinated and hydroxided (respectively) into a titanium anolyte cover 24 and a nickel catholyte cover 22 and 22a, which are preferably used in an electrochemical cell for producing an aqueous IJ solution. Can be welded to

To prevent contact of the catholyte with planar members in the electrochemical cell and deterioration of the polymeric material and/or leakage of the electrolyte from the cathode chamber 30 to the anode chamber 32 between the polymeric material and the insert 26. In addition, cover 22 is in snug contact with catholyte side surface 16 and anode cover 24 is in snug contact with anolyte side surface 18. As shown, both the anolyte and catholyte covers are shaped to closely correspond to the outer surface of planar member 12. In some cases, cover 2
2 or 24 is frame 10 in one or more places
You can lean on it. The portions of both covers 22 and 240 that are exposed to the anolyte or catholyte and that span the planar members have openings through which the electrolyte or electrolysis products can pass during operation of the electrochemical cell. It is important that there is no The lack of openings through the cover minimizes the possibility of electrolyte leaking through the holes or spaces around gaskets or other seals and coming into contact with the planar member.

The vi4M liquid cover 24 is constructed from a material that is resistant to the anolyte during operation of the tank. Typically, this material is not electrolytically active, but the present invention can operate even if the material becomes or is electrolytically active. Suitable materials include, for example, titanium, tantalum, zirconium, tungsten and other materials that are suitable for the anolyte! It is a valve metal that does not undergo Titanium is preferred as the anode cover.

The catholyte cover 22 resists catholyte attack under the conditions that exist in an electrochemical cell. Suitable materials for the cathode cover include, for example, iron, steel, stainless steel, nickel, lead, molybdenum, and cobalt and alloys containing these metals as a major portion. Nickel, including nickel alloys, is preferred for use as catholyte covers because nickel and nickel alloys are generally resistant to the corrosive effects of catholytes, particularly aqueous catholytes containing up to at least 35 wt ls of sodium hydroxide. This is because there is. Steel has also been found to be suitable for use in cells as a catholyte cover where a rare (ie, less than about 22 weights) aqueous sodium hydroxide solution is present, and to be relatively inexpensive.

To aid in assembling the plurality of structural frames 10 into an electrochemical cell, there are optionally seven rungs 34 and 34a extending outwardly from the raw portion of the planar member 12 along the perimeter of the planar member. is desirable. In a preferred embodiment, the 7 langes are an equal distance from the planar member to the insert 26;
Extends outward. Alternatively, but less preferably,
Planar member 1 using a separate spacer*m (not shown)
2 is assembled, and a large number of planar members are combined to form a tank series in which neither the anolyte nor the catholyte leaks from the catholyte chamber and the anolyte chamber 30 and 32, respectively, to the outer part of the tank, with respect to the electrolyte. You can combine them to make something that works.

The figure also shows an anode 36, which can be easily accomplished by welding the anode 36 to the anode cover at the point where the bar is in physical contact with the insert 26 during operation of the vessel. Anode cover 24 is welded to insert 26 and anode 36 is welded to anode cover 24 adjacent insert 26 to improve electrical contact. Although a variety of welding methods can be used with the present invention, it has been found to be very satisfactory to use resistive or vivacitance discharge welding methods. The anode 36 can also be welded to the cover 24 at an anode distal portion 42, for example by resistance or capacitance discharge welding. Other suitable welding methods include tungsten inert gas (TIG) and metal inert gas (MIG) welding. The primary purpose of this welding is to hold the anode in place, not because of the current flow, which naturally passes through the welded area.

The anode 36 is a metal, such as a common film-forming metal, which resists the corrosive effects of the anolyte during cell operation.

Suitable metals are, as is well known, tantalum, tungsten, columbium, zirconium, molybdenum and preferably titanium and alloys containing major amounts of these metals, such as activated platinum group metals such as ruthenium, 6m of iridium, rhodium, platinum, palladium oxides alone or in combination with film-forming metal oxides.

Other suitable activators, alone or in combination with film-forming metal oxides. There is an oxide of cobalt.

An example of such an activating oxide is U.S. Pat. No. 3,632.49.
No. 8: No. 4142.005; No. 4061.549;
and No. 4214971.

The cathodes 38 and 38a, which have a negative potential during operation of the cell,
22 and 22a, respectively. The cathodes 38 and 38a must be constructed of a material that resists the corrosive effects of the catholyte during operation of the cell. Suitable materials for contacting the catholyte will depend on the concentration of alkali metal hydroxide in the bath fluid and can be readily determined by one skilled in the art.

Generally, however, materials such as iron, nickel, lead, molybdenum, cobalt, and alloys containing major amounts of these metals, such as low carbon stainless steel, are suitable for use as the cathode. The cathode electrode may optionally be coated with an activating substance to improve the performance of the cell. For example, a nickel substrate can be coated with an oxide of nickel and a platinum group metal, such as ruthenium, or with an oxide of nickel and a platinum group metal, such as ruthenium oxide, to reduce the hydrogen overpotential. US Pat. No. 4,465,580 describes the use of such a cathode.

As is clear from the figure, both the anode and the cathode are permeable to the electrolyte. I! The poles can be made permeable in a number of ways, including, for example, using perforated sheets or plates, expanded mesh, or woven wire. The anode is Il#! It needs to be inherently porous to allow the catholyte and chlorine to pass through it, and the cathode needs to be porous enough to allow the catholyte and hydrogen to pass through it.

The electrochemical cell of FIG. 1 also shows that the anode 36 and cathode 38 are separated by an ion exchange membrane 44 in contact with the anode 36. However, if desired, membrane 44 can be in contact with cathode 38 or suspended between the two electrodes, although this is not preferred. Ion exchange membrane 4
4 is 11! It is important that the electrode chamber 32 is separated from the cathode chamber 30a.

In order to combine multiple structural frames 10 to minimize leakage of electrolyte from subsequent vessels, at least one gasket 46 is placed between the frames 10 and 10a. During assembly of the frame, a compressive force is applied to the outside of the frame to compress the gasket material 46 and apply ion exchange H44 to it.
The electrolyte is sealed in a predetermined position and leakage of the electrolyte from the completed cell array to the outside of the slide is minimized. Preferably membrane 4
4 is arranged so as to substantially completely prevent electrolyte from leaking from inside the completed cell row to the outside of the cells. Nine different gasket materials can be used, including, for example, fluorocarbons, chlorinated polyethylene rubber, and ethylene propylene dienetropolymer rubber.

FIG. 2Fi insert 26a is wrapped therein and
FIG. 3 is a partial cross-sectional perspective view of a structural frame 10b that includes a planar member 12a having a plurality of frustoconical layers 14b extending out from a planar anolyte side surface 18a. An identical shoulder 14c extends outwardly from the catholyte side of planar member 12a in mirror image of shoulder 14b on the anolyte side surface. Conduits or openings 48 are provided in planar member 12a to allow for the discharge of products produced within the electrochemical cell during operation. Preferably, pipe, tubing or formed metal conduit is disposed within opening 48 and secured to cover 24b to facilitate substantially leak-free product removal from the vessel. A similar aperture and conduit (not shown) may be provided, for example, in the wall portion of the planar member diagonally opposite the aperture 48 to permit the passage of an aqueous sodium chloride solution into the anode chamber through the conduit.

Similar openings and conduits are provided on the cathode side of the planar element, for example for the introduction of water into the cathode chamber and the removal of products, such as solutions containing sodium hydroxide and optionally hydrogen, therefrom.

The anolyte cover 24b and the catholyte cover 22a are the planar member 1.
2a, and even if there is a space between the cover and the planar member, the structure prevents the electrolyte from entering into that space from the respective electrode groups. The covers 22a and 24b also have conduits therein for discharging the brine solution and the products produced in the respective electrolyte chambers, and for introducing the raw solution into the respective chambers. For example, a molded pipe 50 in cover 24b corresponds to opening 48 in the planar member to facilitate drainage of product chlorine and depleted anolyte from the cathode chamber. Expanded mesh anode 36a and expanded mesh cathode 38a are constructed to fit with extensions 9 within their respective anolyte and catholyte covers substantially as shown. The ion exchange membrane is shown as sheet 44a. Gasket material 46a to minimize leakage is placed between the structural frame members prior to assembly of the electrochemical rows.

FIG. 3 shows a partially assembled cell array with three sets of structural frame members 'II:' with an anode and a cathode separated by an ion exchange membrane as shown in the previous figure. There is. In this embodiment, inserts 26b, 26c, 26d and 26e are in a different arrangement than shown in FIGS. 1 and 2. especially,
Insert 26d is a tubular member with a roughened outer surface;
An electrically conductive distal portion 52 is physically and electrically connected thereto and covers the entire cross section of the tubular insert 26d. Such electrical and physical connections can be obtained by scraping or other known bonding methods known to those skilled in the art. The peripheral portion of the cover 24b may optionally have an expansion glove (not shown) to minimize the effects of thermal expansion of the cover during vessel operation.

In operation of a cell bank as an electrolytic cell bank for NaCt brine,
Certain operating conditions are preferred. It is desirable to maintain a pH of about 0.5 to about 5.0 in the single field chamber. The raw brine preferably contains a trace amount of it (approximately 8 Qpp expressed as calcium).
Contains only polyvalent cations (up to m). When the pH of the raw brine is lower than 3.5, the raw brine is about 70p
Higher polyvalent cation concentrations can be tolerated when containing less than pm carbon dioxide.

The operating temperature is between 0° and 110°C, preferably between 60°C and 80°C. Purification from polyvalent cations with ion exchange resins after conventional brine treatment is particularly effective in extending membrane life. Low iron content in the feed brine is desirable to extend membrane life. Preferably, hydrochloric acid is added to bring the pH of the brine raw material to 4.
Maintain a pl (lower than 0). Preferably the operating pressure is 7
Maintain below atmospheric pressure.

Typically, cells are operated at current densities of 1.0 to 4.0 amps/in'', but in some cases 4.0 amps/in''.
Operating above 102 is completely acceptable.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of the present invention. FIG. 2 is an exploded, perspective view of another embodiment of a structural frame in combination with an anode, a cathode, and an ion exchange membrane. FIG. 3 is a cross-sectional side view of another embodiment of the electrochemical cell of the present invention. Adviser: The Dow Chemical Company My Clean TIF (No change in content) Procedural Amendment April 20, 1985 Commissioner of the Patent Office - Kuro 1) Akio Yu Dan 1, Indication of Case 1988 Patent Application No. 64431, Name of the invention Structural frame for electrochemical tank 1 Relationship with the case of the person who made the amendment Patent applicant name The Dow Chemical Company 4, agent As shown in the appendix, however, there were no amendments to the contents of the description and drawings.

Claims (1)

[Scope of Claims] 1. In the form of a substantially planar member made of a polymeric material, horizontally and vertically spaced apart projecting outwardly from at least one surface of the planar member; a central tank element having a plurality of shoulders; at least one electrically conductive conductor extending from the outer surface of the shoulder on one surface of the planar member through the planar member to the outer surface of the shoulder on the opposite surface of the planar member; an insert, wherein each of the shoulders annularly surrounds and supports each of the inserts; in mating contact with the surface of at least one of the planar members and in contact with the electrolyte in the bath and the planar member; having a structure that minimizes contact between the electrolyte and the electrolyte in the bath,
A structural frame suitable for use in an electrochemical cell, characterized in that it has an electrically conductive, substantially completely hydraulically impermeable liner. 2. The liner is in contact with the anolyte side surface of the planar member, and the anolyte liner is made of a metal selected from titanium, tantalum, zirconium, tungsten and alloys thereof. Structural frame as described in section. 3. The liner is in contact with the catholyte side surface of the planar member, and the catholyte liner is selected from iron, steel, stainless steel, nickel, lead, molybdenum, cobalt, and alloys thereof. The structure frame according to claim 1, which is made of metal. 4. The structure frame according to claim 1 or 2, wherein the liner is attached to opposing surfaces of the planar member, and both of the opposing surfaces are anolyte side surfaces. 5. The structure frame according to claim 1 or 3, wherein the liner is attached to opposing surfaces of the planar member, and both of the opposing surfaces are catholyte side surfaces. 6. Liners are attached to opposing surfaces of the planar member, such that one of the surfaces is an anolyte side surface and the opposite side is a catholyte side surface, Claims 1 and 2 The structure frame according to item 1 or 3. 7. the anolyte liner is titanium or an alloy thereof; at least some of the inserts are made of a ferrous metal; and the liner is made of at least some of the ferrous metal inserts; 3. A structural frame according to claim 2, wherein the structural frame is attached to the ferrous metal insert by welding via a weld-compatible intermediate metal. 8. Claims 1 to 7, wherein said insert is made of a metal selected from aluminum, copper, iron, steel, nickel, titanium, alloys of these metals, or physical compositions of said metals. The structure frame according to any one of the above. 9. The polymer material of the planar member is polyethylene, polypropylene, polyvinyl chloride, polystyrene, polysulfone, styrene acrylonitrile copolymer, chlorinated polyvinyl chloride, acrylonitrile butadiene and styrene copolymer, polyepoxide, polyvinyl ester, polyester and fluoroplastics. A structural frame according to any one of claims 1 to 8, which is selected. 10. Claims in which the polymeric material of the planar member contains 5 to 75% by weight of an additive selected from glass fibers, graphite fibers, carbon fibers, talc, glass beads, asbestos, and micronized mica. The structure frame according to any one of Items 1 to 9. 11. in the form of a substantially planar member of polymeric material having a plurality of horizontally and vertically spaced shoulders projecting outwardly from at least one surface of the planar member; at least one electrically conductive insert extending from the outer surface of the shoulder on one surface of the planar member through the planar member to the outer surface of the shoulder on the opposite surface of the planar member; each of the shoulders annularly surrounding and supporting each of the inserts); matingly contacting the surface of at least one of the planar members and providing contact between the electrolyte in the bath and the planar members; having a structure that minimizes and resists the corrosive effects of the electrolyte in the bath;
a plurality of structural frames configured for use in an electrochemical cell, characterized in that they have: an electrically conductive, substantially completely hydraulically impermeable liner; removably and sealably arranged in coplanar relationship, and each of said planar members being selected from an anode on one or both sides of each of said frames or a cathode on one or both sides of each of said frames. an electrochemical cell characterized in that it has: spaced apart electrodes; 12. The vessel of claim 9, wherein each of the liners is welded to at least a portion of the insert, and the electrode is welded to the respective liner at a location adjacent to the insert.