REINFORCED FLEXIBLE POLYMER MATERIAL STRIP, METHOD OF MANUFACTURING SAME AND THREE DIMENSIONAL STRUCTURE MADE USING SAME

Abstract

The flexible strip of a polymeric material includes reinforcing elements and protrusions located on a surface of the strip. The reinforcing elements are placed to contact the surface of the strip and embedded at intersections between the protrusions and the reinforcing elements. A method for producing the flexible strip of a polymeric material includes extruding the polymeric material for producing a flat preform, laying the reinforcing elements onto a preform surface, processing the preform in rolls for forming protrusions on the preform surface, cutting the preform into strips. In the step of processing the preform, the reinforcing elements are embedded into said protrusions at the intersections between the protrusions and the reinforcing elements.

Claims

1. A flexible strip of polymeric material for producing a three-dimensional cellular structure, comprising: reinforcing elements; and protrusions located on a surface of the strip, wherein the reinforcing elements are arranged so as to be in contact with the surface of the strip and are embedded into the protrusions at intersections between the protrusions and the reinforcing elements.

2. The flexible strip of claim 1, wherein the protrusions located on the surface of the strip form a regular relief in the form of embossment, and wherein the reinforcing elements are arranged longitudinally and are made in the form of reinforcing threads, a height of an embossment protrusion, a thickness of the reinforcing thread, and a thickness of the flexible strip being preferably related therebetween by the following ratio:
0.01≤(a+c)/d≤4, where: a—height of the embossment protrusions, a=0.01-2 mm, c—thickness of the reinforcing thread, c=0.01-2 mm, d—thickness of the flexible strip, d=1-2 mm.

3. The flexible strip of claim 2, further comprising: threads, as the reinforcing threads, with a fleecy surface, selected from the group consisting of laysan textured threads, cord threads, polyester threads, polyamide threads, polypropylene threads, polyethylene threads, viscose threads, polyester laysan-staple threads, or said threads combined with composite materials.

4. The flexible strip of claim 2, wherein a strength of the flexible strip and its reinforcement step are related therebetween by the following ratio:
0.005≤R×(h/b)×d≤12, where: R—strength of the flexible strip under tension at maximum load, kN/m, b—reinforcement step, b 0.002 m, d—thickness of the flexible strip, d=0.001-0.002 m, h—width of the flexible strip, h=0.05-0.3 m.

5. The flexible strip of claim 1, further comprising: oval through holes.

6. The flexible strip of claim 1, further comprising: round through drain holes, the drain holes having a diameter from 6 to 13 mm, and a total perforation area being from 3 to 25% for every 150 to 250 mm of a length of the strip.

7. The flexible strip of claim 1, being comprised of high density polyethylene (HDPE), or linear low density polyethylene (LLDPE), or a mixture of high density polyethylene (HDPE) and linear low density polyethylene (LLDPE) as the polymeric material.

8. The flexible strip of claim 1, being comprised of polypropylene (PP) or propylene homopolymer (PP HO) or metallocene polypropylene (MPP) or random propylene copolymer (PPCP) as the polymeric material.

9. A method for producing a flexible strip of a polymeric material for production of a three-dimensional cellular structure, wherein the strip comprises reinforcing elements and protrusions located on a surface of the strip, the method comprising the steps of: extruding a polymeric material to produce a preform, laying the reinforcing elements on a preform surface, processing the preform in rolls for forming the protrusions on the preform surface, and cutting the preform into strips, wherein, when the preform is processed in the rolls in the step of forming the protrusions, the reinforcing elements are additionally embedded into these protrusions at intersections of the protrusions and the reinforcing elements.

10. The method of claim 9, wherein, when the preform is processed in the rolls, the protrusions on the surface of the strip are formed by providing a regular relief in the form of embossment; the reinforcing elements are arranged longitudinally; and wherein reinforcing threads made from high-strength fibers, in particular twisted synthetic threads with a fleecy surface, are used as the reinforcing elements; the following ratio of a height of embossment protrusions, a thickness of the reinforcing threads and a thickness of the flexible strip being observed:
0.01≤(a+c)/d≤4, where: a—height of the embossment protrusions, a=0.01-2 mm, c—thickness of the reinforcing thread, c=0.01-2 mm, d—thickness of the flexible strip, d=1-2 mm.

11. The method of claim 9, wherein the preform is perforated to produce oval through holes.

12. The method of claim 9, wherein, before cutting into strips, the preform is perforated to produce round through drain holes, the drain holes being preferably made with a diameter from 6 to 13 mm, and a total perforation area being from 3 to 25% per every 150-250 mm of a length of the strip.

13. The method of claim 9, wherein, before laying the reinforcing elements on the preform surface, the reinforcing elements are impregnated with an adhesive formulation and/or a formulation that increases their resistance to adverse natural conditions.

14. A three-dimensional cellular structure being comprised of flexible polymeric strips, the structure comprising: reinforcing elements; and protrusions located on a surface of the strip, the strips being arranged in rows connected therebetween in a staggered order along their length to form a three-dimensional cellular structure when stretched in a direction normal to their surface, wherein the reinforcing elements are placed so as to contact the surface of the strip and are embedded in the protrusions located on the surface of the strip at intersections of the protrusions and the reinforcing elements.

15. The three-dimensional cellular structure of claim 14, wherein the flexible polymeric strips are provided with round through drain holes arranged longitudinally in rows between the reinforcing elements, with the exception of zones where the strips are connected, the drain holes having a diameter preferably from 6 to 13 mm, and a total perforation area being from 3 to 25% per every 150-250 mm of a length of the strip.

16. The three-dimensional cellular structure of claim 14, being comprised of oval through holes for quick mounting with the use of a key-type fastener, the holes being located in zones of connecting the strips, having an elongated shape extending in the direction of reinforcement and being provided in the interval between the reinforcing elements.

17. The three-dimensional cellular structure of claim 14, being comprised of oval through holes for quick mounting with the use of a key-type fastener, the holes being located near end regions of the strip and extended transversely.

18. The three-dimensional cellular structure of claim 14, being comprised of oval through holes for quick mounting with the use of a key-type fastener, the holes being located near end regions of the strip and extended longitudinally.

19. The three-dimensional cellular structure of claim 14, being a spatial geogrid.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0066] The drawings are provided for better understanding of the claimed invention, however, it will be obvious to a person skilled in the art that the disclosed group of inventions is not limited to the embodiment shown in the drawings.

[0067] FIG. 1 shows a segment of a flexible polymeric strip, a top schematic view.

[0068] FIG. 2 shows a fragment of the flexible polymeric strip, a 3D schematic view.

[0069] FIG. 3 shows, on an enlarged scale, the fragment of the flexible polymeric strip, shown in FIG. 2 as a schematic view.

[0070] FIG. 4 shows a general schematic view of the three-dimensional cellular structure made of the flexible strips shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0071] FIG. 1 shows a segment of a flexible polymeric strip 1, a top view. The flexible strip 1 comprises reinforcing elements 2 and round drain holes 3, which corresponds to one of its preferred embodiments. FIGS. 2 and 3 show on an enlarged scale that the surface of the claimed strip comprises projections 4 that form a regular relief in the form of embossment. FIGS. 2 and 3 show that the reinforcing elements 2 are placed in contact with the surface of the strip 1 and are embedded in the projections 4 at the intersections of the projections 4 and the reinforcing elements 2. Thus, the problem of limiting the reinforcing elements thickness is removed, since, being on the surface of the strip, the reinforcing elements do not reduce a critical cross-section of the strip, which is responsible for its shear strength under lateral load. The placement of reinforcing elements on the surface of the strip further improves its performance by increasing a coefficient of friction when the strip interacts with particles of soil or other filler of a three-dimensional cellular structure. The claimed invention not only provides high specific strength and cutting resistance of the strip under transverse loads, but also improves soil stabilization conditions when using the claimed strip as part of a three-dimensional cellular structure.

[0072] As shown in FIG. 1, the reinforcing elements 2 are located on the strip 1 in contact with the outer surface of the strip 1 in the longitudinal direction and, preferably, are made in the form of reinforcing threads. In this case, depending on the height of the embossment projections 4, retention of the reinforcing thread by the material of the projections 4 will change, and to provide a preset value of the operational reliability of the strip 1, the following condition must be fulfilled, according to which the height of the embossment projections 4, the thickness of the reinforcing elements 2 (reinforcing thread) and the thickness of the flexible strip 1, are related therebetween by the following ratio:

0.01≤(a+c)/d≤4, where [0073] a—height of the embossment protrusions, a=0.01-2 mm, [0074] c—thickness of the reinforcing thread, c=0.01-2 mm, [0075] d—thickness of the flexible strip, d=1-2 mm.

[0076] If this ratio is observed, the preset level of operational reliability of the claimed strip and a three-dimensional cellular structure made therefrom is provided; when the strip is bent, the reinforcing elements are not pulled out from it and are firmly held in the embossment protrusions along the strip entire length.

[0077] Preferably, the claimed flexible strip comprises, as the reinforcing elements 2, threads with a fleecy surface (not shown in the drawing), since after extrusion, when processing a hot strip preform in rolls to create an embossment relief, the hairs of the reinforcing thread additionally interact with the softened polymeric material of the preform, which results in an increase in the strength of adhesion of the reinforcing elements with the polymer matrix.

[0078] In a preferred embodiment, the strip 1 comprises, as the reinforcing elements 2, threads selected from the group consisting of laysan textured threads, cord threads, polyester threads, polyamide threads, polypropylene threads, polyethylene threads, viscose threads, polyester laysan-staple threads, or said threads combined with composite materials. The main advantages of the strips reinforced with threads of this group are uniformity of the thread material and increased adhesion to a polymer matrix, which simplifies the production technology due to the absence of the need to use adhesive solutions for processing the threads. Furthermore, the threads of this group are characterized by high chemical resistance, high performance characteristics at elevated operating temperatures, the ability to process the material of the threads into secondary raw materials, which helps to reduce pollution of the environment.

[0079] Further, the strength of the flexible strip 1 and its step of reinforcement in the preferred embodiment are related by the ratio that regulates the level of the strip's breaking strength safety factor:

0.005≤R×(h/b)×d≤12, where [0080] R—strength of the flexible strip under tension at maximum load, kN/m, [0081] b—step of reinforcement; b 0.002 m, [0082] d—thickness of the flexible strip, d=0.001-0.002 m, [0083] h—width of the flexible strip, h=0.05-0.3 m.

[0084] Compliance with this ratio in the production of the strip enables to predict its strength level more accurately, which enables to reliably provide a specified strength in the finished product. The strength of the flexible strip under tension at maximum load is at least R=5-40 kN/m.

[0085] In a preferred embodiment, the flexible strip 1 is provided with oval through holes 5 that are shown in FIG. 4. The main advantages of the production of the strip 1 with oval holes are an increase in drainage capacity, accelerated installation of sections of a three-dimensional cellular structure, as well as the possibility of replacing existing metal mounting clips with polymeric fasteners—key-type fasteners (abandoning expensive equipment). In addition, the provision of the holes makes a three-dimensional cellular structure composed of flexible strips lighter.

[0086] The flexible strip may be additionally provided with round through drain holes; in the claimed cellular structure, the drain holes of the strip preferably have a diameter from 6 to 13 mm, and the total perforation area is from 3 to 25% for every 150 to 250 mm of the length of the strip. A perforation area influences the drainage factor of a three-dimensional cellular structure, thus preventing moisture saturation of its filler material, which causes the risk of damaging the structure. Depending on a water flow rate, geometrical dimensions of the strip, and a perforation area, the drainage factor of a three-dimensional cellular structure changes.

[0087] The claimed flexible strip is additionally characterized in that it comprises high density polyethylene (HDPE), or linear low density polyethylene (LLDPE), or a mixture of high density polyethylene (HDPE) and linear low density polyethylene (LLDPE) as the polymeric material.

[0088] The main advantages of strips of linear low density polyethylene (LLDPE) are high chemical resistance of this polymer; high performance characteristics both at high and low temperatures; high resistance to cracking; improved puncture resistance, as well as increased resistance to damage during installation. The production of the strip 1 from this polymer ensures successful use of a three-dimensional cellular structure in the regions of the Far North.

[0089] The main advantages of strips made of a composition (mixture) of high density polyethylene (HDPE) and linear low density polyethylene (LLDPE) are high chemical resistance of a mixture of these polymers; high performance characteristics of welds both at rather high or low temperatures; high resistance to cracking, as well as increased resistance to damage during installation. The production of the strip 1 from a mixture of these polymers ensures successful use of a three-dimensional cellular structure in the regions of the Far North.

[0090] In another embodiment, the flexible strip may comprise polypropylene (PP), or propylene homopolymer (PP HO), or metallocene polypropylene (MPP), or random propylene copolymer (PPCP), or mixtures of different compositions as the polymeric material. The main advantages of strips made of polypropylene compositions are high chemical resistance; high performance characteristics at high temperatures in use; low unit elongation at elevated operating temperatures. The production of the strip 1 from compositions of the above types of polypropylene ensures successful use of a three-dimensional cellular structure in tropical countries and other places of use at high operating temperatures.

[0091] As a part of the proposed group of inventions, a method for producing a flexible strip for a three-dimensional cellular structure is claimed, wherein the strip 1 is made of a polymeric material and comprises the reinforcing elements 2 and the protrusions 4 located on the surface of the strip 1. The method comprises extrusion of a polymeric material to produce a flat preform, laying of the reinforcing elements 2 on the preform surface, processing of the preform in rolls for forming the projections 4 on the preform surface, cutting of the preform into strips. Moreover, when processing the preform in rolls in the step of forming the protrusions 4, the reinforcing elements 2 are additionally embedded therein at the intersections of the protrusions 4 and the reinforcing elements 2.

[0092] In a preferred embodiment, the method of producing the flexible strip 1 for subsequent production of a three-dimensional honeycomb structure is characterized in that, after the extrusion step, when processing the preform in rolls, e.g. in calenders, the protrusions 4 on the surface of the strip are formed by forming a regular relief in the form of embossment. Embossment in relation to the implementation of the claimed method means extrusion, by rolls, of regular relief comprising protrusions and depressions of a certain shape. For example, FIG. 2 shows, as regular relief, depressions shaped as rhombuses with partitions therebetween protruding above the surface of the strip, which are formed by embossment on the preform surface softened by heating the polymeric material. The polymer material is heated in advance for extrusion. Then, the hot preform coming from an extruder T-die, is cooled and stabilized in rolls (calenders) having the regular relief on their working surface that is imprinted on the surface of the polymeric preform with the formation of the relief having the protrusions 4.

[0093] The reinforcing elements 2 are placed longitudinally along the preform length on the surface of the preform produced in the result of extruding the polymeric material. Preferably, reinforcing threads of high-strength fibers, in particular twisted synthetic threads with a fleecy surface, are used as the reinforcing elements 2, the following ratio of a height of the embossment projections 4, a thickness of the reinforcing elements 2 in the form of threads and a thickness of the flexible strip 1 being observed:

0.01≤(a+c)/d≤4, where [0094] a—height of the embossment protrusions, a=0.01-2 mm, [0095] c—thickness of the reinforcing thread, c=0.01-2 mm, [0096] d—thickness of the flexible strip, d=1-2 mm.

[0097] As explained earlier, the above condition is observed, since retention of the reinforcing thread by the material of the projections 4 depends on the height of the embossment projections 4, which value is adjusted to ensure a preset value of the operational reliability of the strip 1.

[0098] In one embodiment of the claimed invention, when the method is carried out, the preform is perforated for producing oval through holes.

[0099] In another embodiment of the claimed invention, when the method is carried out, before cutting the extruded preform into strips, the preform is additionally perforated to provide round through drain holes; preferably, the drain holes being made with a diameter from 6 to 13 mm, a total perforation area being 3 to 25% per every 150-250 mm of the length of the strip.

[0100] When carrying put the claimed method, if necessary, before laying the reinforcing elements on the preform surface, the reinforcing elements may be impregnated with an adhesive formulation and/or a formulation that increases their resistance to adverse natural effects. Since the reinforcing threads partially lie on the outer surface of the strip and are exposed to effects of natural factors, impregnation is provided for protecting them against UV-radiation, moisture and microflora.

[0101] After extrusion, processing in rolls and perforation, the reinforced preforms are welded into blocks in ultrasonic welding units, and then they are cut into bands and strips.

[0102] As a part of the proposed group of inventions, a three-dimensional cellular structure made of the flexible polymeric strips 1 comprising the reinforcing elements 2 and the protrusions 4 located on the surface of the strips 1 is claimed, wherein the strips are arranged in rows connected therebetween in a staggered order along their length to form a three-dimensional cellular structure when stretched in a direction normal to their surface. The reinforcing elements are placed so as to contact the surface of the strip and are embedded in the protrusions 4 located on the surface of the strip at the intersections of the protrusions 4 and the reinforcing elements 2.

[0103] In a preferred embodiment, the three-dimensional cellular structure is composed of geocells or is a so-called spatial geogrid, being characterized by that the flexible polymeric strips 1 included therein are provided with round through holes 3 for drainage, placed in longitudinal rows between the reinforcing elements 2, with the exception of the zones where the strips are connected; preferably, the drain holes 3 have a diameter from 6 to 13 mm, and a total perforation area is from 3 to 25% for every 150 to 250 mm of the length of the strip 1.

[0104] The three-dimensional cellular structure may be provided with additional oval through holes 5, as shown in FIG. 4, for quick mounting with the use of a key-type fastener, the holes being located in the strip connection zones, having an elongated shape extending in the direction of the reinforcement and being provided in the interval between the reinforcing elements 2.

[0105] In another embodiment, the three-dimensional cellular structure may be provided with oval through holes for quick mounting with the use of a key-type fastener so that the holes that are located near the end portions of the strips may be extended both in the transverse direction and in the longitudinal direction.

EXAMPLE

[0106] A three-dimensional cellular structure (spatial geogrid) is produced from flexible strips of a thermoplastic polymeric material of HDPE type, in particular that based on gas-phase high density polyethylene in accordance with GOST 16338-85 in the form of a composition based on high density polyethylene with the addition of a dye, a stabilizer and other additives modifying the properties of the polymeric material of the strip according to applicable technical requirements. When producing the strip, crushed waste—internally produced regranulate—may be added into the original polymer composition.

[0107] A polymeric reinforced preform was produced by extrusion on an extrusion line; the production process included incoming control of raw materials, preparation of a polymer composition based on high density polyethylene with the addition of a dye, a stabilizer and modifying additives, feed of the polymer composition into the extruder feed box, extrusion of a polymeric preform with the use of a T-die, while ensuring the preform thickness d=0.001-0.002 m (1-2 mm).

[0108] Upon leaving the extruder, the preform was reinforced with reinforcing elements in the form of high-strength viscose threads 1 mm thick, in particular, with the use of textured cord threads with a fleecy surface. The threads were laid on the surface of the hot preform in three groups of three filaments each with a pitch of 2 mm between the threads in the group, as shown in FIG. 1. The hot preform with the reinforcing threads laid thereon was introduced into rolls—calenders with a relief surface, where the preform polymeric material was cooled and stabilized. Under pressure of the rolls, the relief was imprinted on the surface of the polymeric preform, the relief had depressions and protrusions approximately 1 mm in height, so that the reinforcing threads 1 mm thick were captured by the material of the protrusions throughout their entire thickness at the points of their mutual intersection, and after cooling, the threads were firmly held on the surface of the polymeric preform.

[0109] After cooling, the preform was perforated to form longitudinal rows of round drain holes located between the groups of reinforcing elements, as shown in FIG. 1.

[0110] After the perforation of the drain holes was complete, the preform was longitudinally cut into strips of a given width h=0.05-0.3 m (5-30 cm). Then, the strips were transversely cut along a predetermined length into strips, the strips were laid in blocks according to a predetermined number of pieces, controlled, packaged and tested for acceptance. The tensile strength of the flexible strip under maximum load was R=40 kN/m.

[0111] The economic efficiency and environmental friendliness of the production process of the claimed product is ensured by complete processing of resulting wastes and their reuse in production.

[0112] If necessary, oval holes may be additionally punched in the finished strip for a new type of geogrid connector, for example, for a key-type fastener of the “FAST-lock” type.

[0113] To prepare sections of a cellular structure from the produced strips, the reinforced strips are welded into blocks in ultrasonic welding units. The production of the product is completed by carrying out acceptance tests of each section of the three-dimensional cellular structure, followed by strapping and packing them on pallets.

[0114] The claimed invention is further advantageous in that it expands the range of means in the form of three-dimensional cellular structures, which are widely used for reinforcing building structures and strengthening weak foundations of industrial and civil facilities as well as slopes of coastlines and beds of water reservoirs.

[0115] The invention enables to produce high-quality three-dimensional cellular structures having increased strength, operational reliability and stability under transverse loads due to the use of a new design of a flexible strip of polymeric material comprising reinforcing elements located on the outer surface of the strip, which are fixed to the strip by the claimed production method. Strength of the flexible strip under tension at maximum load is at least R=5-40 kN/m, depending on a reinforcement volume.

[0116] The technical effect is achieved by producing three-dimensional cellular structures from flexible strips based on a polymeric material and comprising reinforcing elements firmly fixed on the surface of the strip in the embossment protrusions, so that the strip is characterized by high specific strength and high resistance to polymeric material cutting by reinforcing elements under transverse loads. The method for producing the strip is characterized by simplicity, reliability, economy and environmental friendliness as well as by a wide range of possibilities for optimal selection of materials for the production of a flexible strip polymer matrix and its reinforcing elements.