Method and apparatus for making a compartmentalized tire sealant strip

Abstract

A method for making a compartmentalized sealant strip and barrier assembly 10 has the steps of co-extruding a barrier strip 9 of non-sealant elastomeric material with a plurality of projecting linear extending walls 9c and a sealant strip 11 wherein the sealant strip 11 is formed on one side of the barrier strip 9 filling the space between the plurality of projecting walls 9c to form a plurality of linearly extending rows of sealant 11 across the transverse width of the co-extrusion to form the compartmentalized sealant strip and barrier assembly 10. The step of co-extruding may further include the step of: forming the projecting walls 9c on an inclined angle relative to a plane perpendicular to the width of the assembly 10. The step of co-extruding further has the step of forming the barrier strip 9 with lateral edges 9a and 9c that extend beyond the lateral outermost sealant strips 11 on each side of the assembly 10, the lateral edges 9a, 9b being bonding surfaces to seal the sealant strip and barrier assembly 10 into an uncured rubber layer when assembled into an unvulcanized tire 2.

Claims

1. A co-extruded compartmentalized sealant strip and barrier strip assembly comprising: a co-extrusion of a top or radially outer layer barrier strip of non-sealant elastomeric material and an underlying sealant strip formed in a dual extrusion of material flows, one flow forming the barrier strip and one flow forming the sealant strip, wherein the barrier strip has a plurality of inclined projecting linearly extending barrier walls formed on one side of the barrier strip, the barrier strip has a layer thickness of 1 mm to 4 mm and the plurality of inclined projecting linearly extending barrier walls having a thickness equal to or less than the barrier strip layer thickness and wherein the sealant strip is formed on one side of the barrier strip filling a space between the plurality of inclined projecting linearly extending barrier walls, the sealant strips having a thickness of 0.5 cm to 2.0 cm and the plurality of inclined projecting linearly extending barrier walls extend from one side of the barrier strip to a depth of 50 to 100 percent the thickness of the sealant to form a co-extrusion of a plurality of linearly extending rows of sealant across the transverse width of the co-extruded assembly to a thickness at least filling spaces between the plurality of inclined projecting linearly extending barrier walls of the barrier strip, to form the compartmentalized sealant strip, and the top or radially outer barrier strip has a pair of lateral extending edges, each lateral extending edge extends laterally beyond the lateral outermost sealant strip on each side of the assembly, the lateral extending edges having a width which provides a bonding surface to seal the sealant and the top or radially outer barrier strip assembly to an uncured rubber layer when assembled into an unvulcanized tire; wherein the co-extruded assembly has a center plane perpendicular to the width of the assembly and the plurality of inclined projecting linearly extending barrier walls are inclined from the barrier strip extending laterally outwardly away relative to the center plane to form a sealant barrier to prevent sealant migration toward the center plane of the assembly wherein the plurality of inclined projecting linearly extending barrier walls are configured to allow sealant to completely surround a nail or other sharp object from two compartments when the nail penetrates into one of the plurality of inclined projecting linearly extending barrier walls while entrapping the sealant in the other compartment, the combination forming the compartmentalized sealant strip and barrier assembly; and wherein the sealant is comprised of, based upon parts by weight per 100 parts by weight of said partially depolymerized butyl rubber exclusive of carbon black: (A) a partially organoperoxide-depolymerized butyl rubber as a copolymer of isobutylene and isoprene, wherein said butyl rubber, prior to such depolymerization, is comprised of about 0.5 to about 5 percent units derived from isoprene, and correspondingly from about 95 to about 99.5 weight percent units derived from isobutylene; (B) particulate reinforcing filler comprised of: (1) about 20 to about 50 phr of synthetic amorphous silica, or (2) about 15 to about 30 phr synthetic amorphous silica, preferably precipitated silica, and about 5 to about 20 phr of clay, or (3) about 15 to about 30 phr synthetic amorphous silica and about 5 to about 20 phr of calcium carbonate, or (4) about 15 to about 30 phr synthetic amorphous silica, about 5 to about 15 phr of clay and about 5 to about 15 phr of calcium carbonate; (C) from zero to 6 phr of short organic fibers; (D) a colorant of other than a black color wherein said colorant is selected from at least one of organic pigments, inorganic pigments and dyes; and (F) from zero to about 20 phr of rubber processing oil.

2. A co-extruded compartmentalized sealant strip and barrier strip assembly of claim 1 wherein the projecting barrier walls are inclined relative to a plane perpendicular to a width of the strip and barrier assembly.

3. A co-extruded compartmentalized sealant strip and barrier strip assembly of claim 1 wherein the barrier strip of the assembly is a top or a radially outer layer or a radially outer layer of the compartmentalized sealant strip and barrier assembly when built into a tire.

4. A co-extruded compartmentalized sealant strip and barrier strip assembly of claim 1 wherein the barrier strip has a layer thickness of 1 mm to 4 mm and the projecting barrier walls have a thickness equal to or less than the thickness of the layer thickness.

5. A co-extruded compartmentalized sealant strip and barrier strip assembly of claim 1 wherein the barrier walls extend to the full thickness of the sealant strips and have exposed ends.

6. A sealant tire comprises: a pair of annular beads; a pair of elastomeric apexes, one apex above each bead; at least one carcass ply extending between and wrapped about each bead; a belt reinforcing structure overlaying the carcass; a tread overlaying the belt reinforcing structure; an air impervious inner liner extending between the beads underlying the carcass for forming an air chamber; and a compartmentalized sealant strip and barrier assembly positioned between the carcass and inner liner under the belt reinforcing structure, the compartmentalized sealant strip and barrier assembly characterized by: being a co-extrusion of a co-extrusion of a top or radially outer layer barrier strip of non-sealant elastomeric material and an underlying sealant strip formed in a dual extrusion of material flows, one flow forming the barrier strip and one flow forming the sealant strip wherein the barrier strip has a plurality of inclined projecting linearly extending barrier walls formed on one side of the barrier strip, the barrier strip has a layer thickness of 1 mm to 4 mm and the plurality of inclined projecting linearly extending barrier walls having a thickness equal to or less than the barrier strip layer thickness and wherein the sealant strip is formed on one side of the barrier strip filling a space between the plurality of inclined projecting linearly extending barrier walls, the sealant strips having a thickness of 0.5 cm to 2.0 cm and the plurality of inclined projecting linearly extending barrier walls extend from one side of the barrier strip to a depth of 50 to 100 percent the thickness of the sealant to form a co-extrusion of a plurality of linearly extending rows of sealant across the transverse width of the co-extruded assembly to a thickness at least filling spaces between the plurality of inclined projecting linearly extending barrier walls of the barrier strip to form the compartmentalized sealant strip, and the top or radially outer barrier strip has a pair of lateral extending edges, each lateral extending edge extends laterally beyond the lateral outermost sealant strip on each side of the assembly, the lateral extending edges having a width which provides a bonding surface to seal the sealant and the top or radially outer barrier strip assembly to an uncured rubber layer when assembled into an unvulcanized tire; wherein the co-extruded assembly has a center plane perpendicular to the width of the assembly and the plurality of inclined projecting linearly extending barrier walls are inclined from the barrier strip extending laterally outwardly away relative to the center plane to form a sealant barrier to prevent sealant migration toward the center plane of the assembly wherein the plurality of inclined projecting linearly extending barrier walls are configured to allow sealant to completely surround a nail or other sharp object from two compartments when the nail penetrates into one of the plurality of inclined projecting linearly extending barrier walls while entrapping the sealant in the other compartment, the combination forming the compartmentalized sealant strip and barrier assembly; and wherein the sealant is comprised of, based upon parts by weight per 100 parts by weight of said partially depolymerized butyl rubber exclusive of carbon black: (A) a partially organoperoxide-depolymerized butyl rubber as a copolymer of isobutylene and isoprene, wherein said butyl rubber, prior to such depolymerization, is comprised of about 0.5 to about 5 percent units derived from isoprene, and correspondingly from about 95 to about 99.5 weight percent units derived from isobutylene; (B) particulate reinforcing filler comprised of: (1) about 20 to about 50 phr of synthetic amorphous silica, or (2) about 15 to about 30 phr synthetic amorphous silica, preferably precipitated silica, and about 5 to about 20 phr of clay, or (3) about 15 to about 30 phr synthetic amorphous silica and about 5 to about 20 phr of calcium carbonate, or (4) about 15 to about 30 phr synthetic amorphous silica, about 5 to about 15 phr of clay and about 5 to about 15 phr of calcium carbonate; (C) from zero to 6 phr of short organic fibers; (D) a colorant of other than a black color wherein said colorant is selected from at least one of organic pigments, inorganic pigments and dyes; and (F) from zero to about 20 phr of rubber processing oil.

7. The sealant tire of claim 6 wherein the projecting barrier walls extend from the one side of the barrier strip to a depth between 50 to 100 percent of the thickness of the sealant strips.

8. The sealant tire of claim 6 wherein the barrier walls extend to the full thickness of the sealant strips and have exposed ends.

9. The sealant tire of claim 6 wherein the barrier strip has a layer thickness of 1 mm to 4 mm and the projecting barrier walls have a thickness equal to or less than the thickness of the layer thickness.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The structure, operation, and advantage of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings wherein:

(2) FIG. 1 is a schematic view of a cross section of tire with a sealant compartmentalized strip made in accordance with the present invention;

(3) FIG. 2 is a cross sectional view of a prior art sealant;

(4) FIG. 3a is a cross sectional view of a first embodiment of the compartmentalized sealant strip and barrier assembly;

(5) FIG. 3b is a cross sectional view of a second embodiment of the sealant and barrier assembly;

(6) FIGS. 4-7 are various views of an extruder die for forming the present invention sealant strip and barrier assembly

(7) FIG. 8 is a perspective view of the extruder die in a die head or holder showing the forming of the compartmentalized sealant strip and barrier assembly.

DETAILED DESCRIPTION OF THE INVENTION

(8) Referring now to FIG. 1, there is illustrated a cross-sectional view of a self-sealing pneumatic tire constructed in accordance with the invention. The tire may be any type of tire. For example, a truck tire, a light truck tire or a passenger tire. The tire 2 includes sidewalls 3, a supporting tire carcass 4, a pair of beads 5, an inner liner 6, a layer of the compartmentalized sealant strip and barrier assembly 10 of the present invention, and an outer circumferential tread 8. The sidewalls 3 extend radially inward from the axial outer edges of the tread portion 8 to join the respective beads. The carcass 4 acts as a support structure for the tread and sidewalls, and is comprised of one or more layers of cord reinforced ply 7. The compartmentalized sealant strip and barrier assembly 10 is shown disposed between the inner liner 6 and an elastomeric cover layer such as for example, a rubber layer, the ply layer 7 or an optional additional barrier layer. The barrier layer or strip 9 of the assembly 10 has a width sized to cover the sealant strip layers 11 such as from shoulder to shoulder, or may further extend down into the bead area between the ply and inner liner. The sealant assembly may also be disposed at different locations such as the sidewall region. The tread region 8 forms a crown region of the carcass. In the interior region of the tread, there is generally found one or more belts 18. The surface region of the tread forms a tread pattern.

(9) The sealant strips 11 may be made from any suitable sealant composition known to those skilled in the art, such as rubber or elastomer compositions and plastic compositions. One suitable polymer composition suitable for use is described in U.S. Pat. No. 4,895,610, the entirety of which is incorporated by reference. The polymer compositions described therein include the following composition by weight: 100 parts of a butyl rubber copolymer, about 10 to about 40 parts of carbon black, about 5 to about 35 parts of an oil extender, and from about 1 to 8 parts of a peroxide vulcanizing agent. A second polymer composition includes the following composition by weight: 100 parts of a butyl rubber copolymer, about 20 to about 30 parts of carbon black, about 8 to about 12 parts of an oil extender, and from about 2 to 4 parts of a peroxide vulcanizing agent.

(10) The sealant strips 11 may also comprise a colored polymer composition as described in U.S. Pat. No. 7,073,550, the entirety of which is incorporated herein by reference. The colored polymer composition is comprised of, based upon parts by weight per 100 parts by weight of said partially depolymerized butyl rubber exclusive of carbon black: (A) a partially organoperoxide-depolymerized butyl rubber as a copolymer of isobutylene and isoprene, wherein said butyl rubber, prior to such depolymerization, is comprised of about 0.5 to about 5, preferably within a range of from 0.5 to one, percent units derived from isoprene, and correspondingly from about 95 to about 99.5, preferably within a range of from 99 to 99.5, weight percent units derived from isobutylene; (B) particulate reinforcing filler comprised of: (1) about 20 to about 50 phr of synthetic amorphous silica, preferably precipitated silica, or (2) about 15 to about 30 phr synthetic amorphous silica, preferably precipitated silica, and about 5 to about 20 phr of clay, preferably kaolin clay, or (3) about 15 to about 30 phr synthetic amorphous silica, preferably precipitated silica, and about 5 to about 20 phr of calcium carbonate, (4) about 15 to about 30 phr synthetic amorphous silica, preferably precipitated silica, about 5 to about 15 phr of clay, preferably kaolin clay, and about 5 to about 15 phr of calcium carbonate; (C) from zero to 6, alternately about 0.5 to about 5, phr of short organic fibers (D) a colorant of other than a black color wherein said colorant is selected from at least one of organic pigments, inorganic pigments and dyes, preferably from organic pigments and inorganic pigments; (E) from zero to about 20, alternately about 2 to about 15, phr of rubber processing oil, preferably a rubber processing oil having a maximum aromatic content of about 15 weight percent, and preferably a naphthenic content in a range of from about 35 to about 45 weight percent and preferably a paraffinic content in a range of about 45 to about 55 weight percent.

(11) Another sealant polymer composition which may be utilized by the invention is described in U.S. Pat. No. 6,837,287, the entirety of which is hereby incorporated by reference.

(12) Further, any sealant polymer composition may also be used with the invention that has a polymer composition of butyl rubber and an organoperoxide vulcanizing agent which becomes activated at high temperatures above 100 degrees C.

(13) FIG. 1 illustrates one example of a sealant configuration for a tire. The sealant strips 11 are comprised of two or more zones, preferably two or more axially outer zones 20, 22 located between the shoulder portion and the center portion of the tire and one or more axially inner zones 21 located in the center portion of the tire 2.

(14) The thickness of the sealant in each of the zones 20, 21 and 22 can vary greatly in an unvulcanized puncture sealant-containing tire. Generally, the thickness of the sealant composition layer may range from about 0.13 cm (0.05 inches) to about 1.9 cm (0.75 inches). In passenger and truck tires it is normally desired for the sealant composition layer to have a thickness of about 0.32 cm (0.125 inches). The sealant width may vary depending upon the tire size, but may typically be in the range of 1 to 6 inches (2.5 cm to 15 cm).

(15) After the unvulcanized pneumatic rubber tires of this invention are assembled they are vulcanized using a normal tire cure cycle. The tires of this invention can be cured over a wide temperature range depending somewhat upon the size of the tire and the degree of desired depolymerization of the butyl rubber as well as the thickness of the sealant layer itself) and sufficient to at least partially depolymerize said sealant precursor layer to the aforesaid storage modulus (G′) physical property.

(16) With reference to FIG. 2, a prior art sealant is illustrated as a strip 100 which has been extruded having a width and a thickness sufficient to provide a puncture sealing layer in a tire to prevent air loss from nails or screws. As shown this prior art extrusion of the strip 100 would be formed as a single layer extrusion and then additional layers of material would be used to encapsulate it during the tire building process.

(17) With reference to FIG. 3a, the compartmentalized tire sealant strip and barrier assembly 10 is illustrated. The sealant strip and barrier assembly 10 is shown with a nail 1 puncturing the sealant strip 11. As shown, there is a barrier layer 9 extending from lateral edges 9a, 9b and above the sealant strips 20, 21, 22. This barrier layer or strip 9 has a plurality of barrier walls 9c shown extending from the barrier strip through and dividing various strips of sealant material. As shown, the axially outer sealant strips 20 and 22 are shown as well as the intermediate sealant strips 21. As illustrated, the barrier walls 9c are inclined relative to a center plane (cp) of the co-extrusion assembly 10. In such a way that the barrier walls 9c extend outwardly from the barrier layer 9 through the sealant strips 11 to an end 9d. As shown, the barrier walls 9c can be inclined extending the full depth of the sealant strip 11. Alternatively, it is sufficient if the barrier walls 9c only extend 50 to 100 percent of the thickness of the sealant material. This is true because during circumferential spinning and rotation of the tire sealant strips 11 become the semi-liquid or gelatinous sealant material after vulcanization, and when it is spun it tends to want to flow radially outwardly, as such shorter inclined barrier walls 9c are sufficient to entrap the sealant 11 in its location sufficiently to keep the sealant material in its proper compartmental strip zone 20, 21, 22. This is extremely important in that if the sealant is free to move as in the prior art of FIG. 2, all of the sealant during driving conditions would tend to rotate to the center of the tire as it revolves. This would result in a very minimal amount of sealant material being left in the shoulder regions of the tire. In order to prevent this, the inclined barrier walls 9c are formed as a part of co-extrusion of the barrier layer 9 and these barrier walls 9c keep each of the spaces sufficiently filled with sealant material that should a nail puncture the tire there will be sufficient sealant material to prevent air seepage from the tire. A careful review of the barrier strip 9 shows that by having the barrier walls 9c inclined as illustrated a nail 1 puncturing the sealant 11 would be able to receive sealant from two zones due to the inclination of the barrier walls 9c. This ability to receive a flow sealant as shown ensures that the tire 2 will be adequately sealed should a puncture occur that strikes near or adjacent the barrier walls 9c. If the barrier walls 9c were not inclined as shown, it would be possible for a nail to penetrate sliding against a barrier wall in such a fashion that the barrier wall would provide an open passage for air to escape from the tire 2 as the sealant 11 would be unable to get past the wall to completely surround the nail because the nail is rubbing against the barrier wall. By being inclined as illustrated it is impossible for the nail 1 not to be completely surrounded by sealant material should it puncture into the area of the inclined wall 9c. Alternatively, should the nail 1 puncture in the middle of the zone 21, the sealant strip 11 will perform more than adequately as it is directly in the path of the sealant material unobstructed by any walls or other surfaces. As shown, these zones 20, 21, 22 of sealant material formed as strips when wrapped around the tire create annular rings or hoops of sealant material. The compartmentalized barrier walls 9c enable the sealant strips 11 to stay in their proper position throughout the life of the tire. This means that the sealant material can have a thickness preferably between 0.5 cm and 4 cm or less. The less amount of sealant material used in the assembly 10 means that the tire 2 will provide sufficient nail puncture resistance while minimizing the amount of additional weight added to the tire 2. This enables the compartmentalized sealant strip barrier assembly 10 to be manufactured in a cost efficient manner in regards to its overall material usage.

(18) With reference to FIG. 3b, a second embodiment of the tire is shown where additional sealant strips 11 are employed. In this embodiment, the axially outer sealant strip zones 20 and 22 are illustrated with seven intermediate strip zones 21 provided. While this number can vary for each tire 2, it is sufficient to note that all of these can be assembled in a simple one step co-extrusion process that is described hereafter.

(19) The illustrated compartmentalized sealant strip and barrier assembly 10 is best manufactured by a dual co-extrusion process. This co-extrusion process requires a unique die 30 to be provided. This die 30 is best illustrated in FIGS. 4-7. With reference to FIG. 4 a perspective view of the die 30 is shown. A pair of lateral die ends 31, 32 are shown. In between the die ends 31, 32 is an upper surface 33, this upper surface 33 forms the barrier layer 9 profile as shown. This barrier layer profile also forms the pair of lateral edges 9a and 9b which are formed in depressions 34, 35 in the die. These depressions 34, 35 can step up to the flat surface 33 extending between the lateral depressions 34, 35 these features combined form the profile for overall barrier layer 9 in the die 30. At an outlet portion of the die 30 downstream the barrier material will pass over a plurality of openings or holes 40. These holes 40 project inwardly from the die surface 33 and allow barrier material to flow into them, each of these holes 40 extend to form channels or slots 41 that are inclined relative to the upper surface 33 of the die 30. These inclined channels 41 allow barrier material to flow in to form the barrier walls 9c of the co-extruded assembly 10 as the barrier material passes through the die 30 over the surface 33.

(20) With reference to FIG. 5, a frontal view of the die 30 is shown wherein the lower surface 50 of the die 30 is illustrated showing that forms the die profile where the sealant material will pass to form the sealant strips 11 as they pass through a plurality of spaces 51 and lateral extremes 52, 53. These lateral extremes 52, 53 are profile depressions that allow the axially outermost sealant strips 20, 22 to be formed wherein the intermediate zones 21 between the barrier wall 9c forming channels 41 are illustrated by the profile space 51 which form the intermediate sealant strips 21 in the finished assembly 10. In order to accomplish this co-extrusion of the barrier layer 9 with inclined barrier walls 9c it is important that the channels or slits 41 producing the barrier walls 9c be protected so they do not occlude with sealant material. To achieve this the die 30 is constructed with channel flow dividers 56 that project outwardly upstream of the slits 41 in such a fashion that the sealant material will be smoothly diverted around these carved projection surfaces of the flow diverters 56 as the sealant material flows past surrounding the downstream slit 41 directly below the flow divider 56 as the barrier walls 9c as they are being formed such that the sealant strips 11 simultaneously will fill the void spaces 51, 52 and 53 between the barrier layer 9 and the inclined walls 9c forming the plurality of sealant strips 11. These projections or flow dividers 56 are profiled as shown in an enlarged view in FIG. 7 of the die 30. As shown in FIG. 7, the barrier material will flow down into the holes 40 filling the channel or slit 41 and the sealant material coming from the lower side will be diverted around the flow divider 56 projections in such a fashion that the sealant 11 will flow back onto the inclined walls 9c as they are formed insuring that the entire assembly 10 is produced in a dual extrusion creating both the barrier layer 9 with inclined walls 9c and sealant strips 11 as a simple co-extruded compartmentalized strip and barrier assembly 10 according to the present invention.

(21) With reference to FIG. 8, the die 30 is shown encased in phantom lines representing the extrusion head holding the die 30. The extrusion head 60 has two feed nozzles 61, 62. One feed nozzle 61 for feeding the barrier material to form the barrier layer 9 within inclined barrier walls 9c as a top surface of the assembly 10 and the second extrusion nozzle 62 providing the sealant material which is shown feeding under the die 30 to form the sealant strips 11. As shown, the output end of the die head has an opening 63 through which a portion of the assembled co-extruded compartmentalized sealant and barrier assembly 10 is shown coming from the opening 63. This figure is exemplary of how the compartmentalized sealant strip and barrier assembly 10 is formed as a co-extrusion. Alternatively, it may be such that the die 30 is flipped to form the barrier as a lower surface during extrusion and then have the assembly 10 flipped at the tire building station to insure the barrier layer with inclined walls is the top or upper layer of the assembly 10.

(22) While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be appreciated there is still in the art various changes and modifications may be made therein without departing from the spirit or scope of the invention.