ES2256153T3 - LOW-DENSITY THERMOPLASTIC MATERIAL MATERIAL AND HIGH EMPTY INDEX, AND DEVICE AND PROCEDURE FOR PRODUCTION. - Google Patents

Abstract

Matting of interlaced and entangled filaments of low-density thermoplastic material, the matting having a high voids index and comprising a plurality of hollow protuberances arranged in several parallel rows; at least a part of said protuberances presents at least one open portion, defined by non-interlaced filaments, such as to create a chamber for receiving the material with which the matting is intended to be covered; a plant and process for producing said matting. <IMAGE>

Description

Blanket made of low density thermoplastic material and high void index, and device and procedure for its production.

The present invention relates to panels or flexible blankets that consist of a plurality of partially bonded thermoplastic polymer filaments each other at their contact points.

This type of article has been known for some time time and has found application in numerous technical sectors, such as soil drainage, protection against erosion, armed with concrete, support and reinforcement of thermosetting foams or polymer and reinforcement of resins, mixtures and conglomerates.

Such a blanket can be produced by two different procedures, specifically a procedure denominated in wet and a procedure called in dry, which give place to products of different geometry and different mechanical characteristics

These known procedures are described in Italian patents 883371, 1061875, 1257665 and in US Pat. No. 4,212,692, to which reference should be made for more information.

With the wet procedure, they are obtained monofilament blankets not stretched practically parallelepiped with flat sides, while with the procedure called dry, the blanket can have at least one profiled surface, for example with bumps.

The surface profiling is obtained by leaving drop the filaments on a surface provided with projections, by example a rotating cylindrical surface, or a tape of translation that presents a plurality of geometric highlights.

It has been observed that using the procedure dry, you get a blanket with mechanical characteristics substantially better than the blanket obtained by wet process and also the presence of said bumps in the final product is useful in all those applications in which the end of the blanket is substantially retain a material, such as soil or polymer foam, that is find over or partially embedded in it.

For these reasons, in the environmental field, it currently use the blanket obtained by the procedure in dry that has at least one profiled surface, which is placed usually on sloping ground and then covered with land.

To improve soil consolidation, it is a usual practice cover it with a layer of grass, so that the roots of the grass act as an additional element of soil retention.

However, such a blanket has shown various inconveniences in this application.

A first drawback is based on the fact that that the known products have a low capacity to copenetration by arable land, due to the fact that such Highlights are partially impervious to the passage of land.

Therefore, after installation, the product it presents practically empty spaces below each boss. In this way air cells are created within said spaces that are detrimental to the development of root system of the grass layer, whose roots become dry and die in contact with the air.

Also, depending on the inclination of the pending on which the blanket is used, it may happen that a side of said projections rest in a horizontal position or even tilted down, thereby endangering the soil retention capacity of the product, which is your requirement basic.

An objective of this patent is to overcome said drawbacks within the framework of a reliable solution of low cost.

This and other objectives are achieved according to the invention using a flexible blanket of low density and high index of voids, whose surface comprises a plurality of nearby bumps, said bumps being hollow and being provided with at least one open side such that define a pocket or camera to accommodate the material, such as ground, with which the blanket is covered when installed.

Such a blanket is obtained by a procedure in dry of the type mentioned above, using as a surface of receiving filaments a translation surface provided with Highlights

According to the invention, said projections present the minus an inclined part with respect to the direction of movement of the surface at the moment of impact by the filament.

Said inclined part is preferably flat, defining its inclination with respect to the direction of the movement by the angle? subtended between the surface and the direction perpendicular to the direction of movement.

In the case of a non-flat part, the angle α is the subtending between the tangential plane at the point considered and said perpendicular direction.

The translation surface that carries the Highlights is preferably a rotating cylindrical surface.

In this case, an angle β is defined subtended counterclockwise between the horizontal diametric plane of the cylinder and the diametric plane that passes through the point of impact of the filaments.

In the case of a flat translation surface horizontal, the angle? is obviously zero.

The filament drop speed is indicated by V_ {C} and the speed of surface translation and Relative highlights are indicated by V_ {P}.

These speeds are always considered as vectors.

For the required result to be achieved, the vector difference between V_ {C} and V_ {P} must be represented by a resulting vector

V_ {R} = V_ {C} - V_ {P}

which is addressed in a way that does not intersect at least with an inclined part of the surface of translation.

In other words, the vector V_ {R} that expresses the relative velocity of the filament that falls vertically with with respect to said inclined part it must be directed against said part inclined with a positive incidence angle close to zero or with An angle of negative incidence.

In this regard, if the angle of incidence is zero, the filaments slide parallel to the inclined part and they are arranged without entangling, this also happening for angles of Very small incidence, that is, close to zero.

The construction characteristics and operation of the invention will be clearly apparent from the following description of an embodiment preferred thereof provided by way of non-limiting example and illustrated in the accompanying drawings.

The described embodiment refers to a cylindrical translation surface provided with projections square-based pyramids, whose walls constitute parts inclined from the translation surface, but that is also suitable for a flat translation surface for which consider that the angle? is equal to zero.

Figure 1 is a perspective view of a First embodiment of the product of the invention.

Figure 2 is a perspective view Schematic of the production plant of the invention.

Figure 3 shows a first configuration Schematic of the plant of the invention.

Figure 4 shows a second configuration possible of the production plant of the invention.

Figure 5 is an enlarged diagram view showing filament and surface speeds of translation of figure 3 and figure 4 for various values of the angle β.

Figure 6 shows a possible configuration additional of the plant of the invention.

Figures 1 to 4 show blanket 1, whose surface is constituted by a plurality of protuberances 2, aligned along several parallel rows and inclined in a angle between 30º and 45º with respect to the sides of the blanket. Specifically, said protuberances 2 are hollow and have a open side that defines a chamber 3 to accommodate the material with the The blanket is usually covered when installed.

Blanket 1 is produced by plant 4 shown in figure 2, comprising a nozzle 5 provided with a plurality of holes aligned along several rows parallel, through which filaments are extruded from thermoplastic material The thermoplastic material is fed to the nozzle by means of a usual extruder, not shown, at a temperature between 160ºC and 270ºC.

Said extruder is in turn fed by a usual hopper, not shown as it is of known type.

The theoretical speed of filament extrusion it is between 10 and 15 m / min and, preferably it is approximately 12 m / min

However, the actual fall rate V_ {C} of the filament is from 1 to 1.5 times higher due to stretching of the filament and the consequent reduction in its cross section.

Below the nozzle 5 a rotating cylinder 8 presenting its axis parallel to the rows of holes in the nozzle, and presenting on its outer surface a plurality of pyramids 9 straight with a square base height preferably between 20 and 50 mm.

As can be seen from the figure, the pyramids are arranged in rows aligned with each other in the manner of a predetermined tilt propeller, preferably between 30º and 45º with respect to the horizontal axis of the cylinder 8.

To get blanket 1 with at least one side open for the passage of the material, the speed must be regulated V_ {C} of vertical drop of the filaments, in relation to the velocity V_ {P} of translation of the inclined wall of the pyramids, so that the vector difference between the two is a vector V_ {R} that presents a direction and a sense of way That does not meet the wall.

Figure 5 shows the speed diagrams for both cases of β = 90º and β = 120º in a roller 200 mm diameter with pyramidal cusps with a base square of 15 mm side and presenting a height of 25 mm, with an angle at its vertex of 40 ° and an angle α of 20 °.

It has been assumed that the speed V_ {C} of fall actual filament is 20 m / min and that the module of the speed V_ {P} is 4 m / min.

From the graphical calculation it has been observed that with β = 120 °, the resulting VR is substantially parallel to the front face of the pyramid in the direction of the movement, which means that said face does not meet the falling filaments and therefore, is substantially open.

If the speed V_ {C} of fall of the filaments decrease, or the velocity module V_ {P} of translation of the pyramid wall increases, the resulting V_ {R} He comes to the wall, which is therefore closed.

With β = 90º, the graphical calculation shows that V_ {R} cuts both the front wall and the back wall of the Pyramid, therefore, are closed.

In order for one of these walls, and in this if the back wall is open, V_ {C} must be lowered or V_ {P} must be increased; the graph shows with dashed lines the vector V ’R, from which the wall begins to stay open For this, the value of V_ {P} is 6 m / min

Figure 4 shows the particular case in which β = 0 °. In this case, since V_ {C} is perpendicular to V_ {P}, the relationship between the modules that must be respected is the next:

V_ {C} \ leq V_ {P} [cos \ alpha / sen \ alpha]

is tell,

V_ {C} \ leq V_ {P} .cotan \ alpha

Figure 6 shows the limiting case in which β = 180 °. In this case, as in the case where β = 0º, the front and rear walls in the direction of movement They are always empty.

The sloping parts of the highlights of which it distance

V_ {R} = V_ {C} - V_ {P}

they don't get the shock of filaments that are therefore deposited in a non-interlaced state and leave said parts substantially permeable to the passage of material.

On the contrary, in the parts of the projections opposite to the previous ones, a thickened structure of interlaced filaments that is impermeable to the passage of material. From this way, an open chamber is defined on one side, in the shape of a pocket, to accommodate the material with which the blanket 1.

It should be noted that blanket 1 of the invention It can also be obtained by replacing cylinder 8 with a translation surface on which a plurality of pyramids 9, or highlights of any kind, provided they are suitable for the purpose.

The appropriate speed diagram for this configuration is that of figure 4 referred to β = 0 °.

In the latter case, said surface of translation is preferably inclined with respect to the plane horizontal at an angle between 0º and α, to facilitate the phenomenon.

Claims (13)

1. Blanket of entangled and entangled filaments of low density thermoplastic material, the blanket having a high index of voids and comprising a plurality of hollow protrusions arranged in several parallel rows, characterized in that at least a part of said protuberances has at least a part open defined by non-interlaced filaments, so that a chamber is created to receive the material with which the blanket is intended to be covered. 2. Blanket according to claim 1, characterized in that said protuberances are devoid of their lower base. 3. Blanket according to claim 1, characterized in that said hollow protuberances are placed along one another in parallel adjacent rows. 4. Device for manufacturing a blanket of entangled monofilaments provided with protuberances that have at least one part not occupied by the filaments according to claim 1, comprising a vertical axis nozzle for extruding parallel alignments of said filaments, a rotating cylinder positioned by under said nozzle and having its horizontal axis and parallel to said alignments, and a series of projections distributed regularly on said cylinder that have at least a part inclined with respect to the direction of surface movement at the time of impact with the filament, characterized in that the distance between the axis of the cylinder and the average vertical plane in which the filaments fall is selected such that the vector V_ {R}, which results from the difference between the vector V_ {C}, specifically the velocity of the vertical drop of the filament, and the vector V_ {P}, specifically the translation speed of the inclined part , cut the inclined part at an angle equal to zero or at a negative angle, so that said inclined part does not meet the falling filaments. Device according to claim 4, characterized in that said projections are arranged in mutually aligned rows in the manner of a propeller. Device according to claim 5, characterized in that said propeller, along which the projections are arranged, has an inclination of between 30 ° and 45 ° with respect to the axis of the cylinder. 7. Device according to any of claims 4 to 6, characterized in that said projections are straight pyramids. 8. Device according to claim 7, characterized in that the base of said pyramids is square. 9. Device according to claim 8, characterized in that the bases of said pyramids have at least one side in common with the adjacent pyramids. 10. A method for producing a blanket of entangled and entangled filaments of low density thermoplastic material according to claim 1, comprising the steps of extruding a thermoplastic material through the nozzle and collecting the extruded filaments that fall vertically on a translation surface. provided with a plurality of profiled projections that have at least an inclined part with respect to the direction of surface movement at the moment of filament impact, characterized in that the vector V_ {R} expressing the relative velocity of the vertically falling filament , which results from the difference between the vector V_ {C}, specifically the speed of the vertical drop of the filament, and the vector V_ {P}, specifically the translation speed of the inclined part, with respect to said inclined part is directed against said inclined part with an angle equal to zero or at a negative angle, so that said part in Cloned does not meet the falling filaments. Method according to claim 10, characterized in that said translation surface is a flat conveyor belt on which a plurality of straight pyramidal projections are arranged. 12. Method according to claim 11, characterized in that the speed V_ {P} of the tape is related to the speed V_ {of vertical fall of the filament by the following relation: V_ {C} \ leq V_ {P} [cos \ alpha / sen \ alpha] where \ alpha is the half angle at the apex of the pyramids 13. Method according to claim 12, characterized in that said belt is preferably inclined with respect to the horizontal plane at an angle between 0 ° and α.