RU2247179C1 - Nonwoven material for reinforcement of road coat and method for manufacture of such material - Google Patents

Abstract

FIELD: production of rolled road coat reinforcing materials.

SUBSTANCE: nonwoven material has two-axially oriented composite flexible structure comprising two groups of discretely arranged filaments held by binder. Said groups define three-layer structure in such a manner that group of transverse filaments is arranged between upper and lower subgroups divided by longitudinal filaments. Glass roving with linear density of at least 400 tex is used as source of filaments. Method involves, prior to laying of filaments, dividing group of longitudinal filaments into two subgroups; impregnating one of said groups of filaments with binder; laying transverse filaments between upper and lower subgroups of longitudinal filaments in mutually perpendicular direction; providing thermal processing, repeated impregnation with binder and drying to residual moisture content below 0.5 wt%. Resultant nonwoven material is in isotropic state.

EFFECT: stabilized physical and mechanical characteristics of nonwoven material under cyclic loading conditions.

5 cl, 1 tbl, 1 ex

Description

The invention relates to the field of non-woven web material and can be used for reinforcing road construction coatings. The invention can be used in facilities where increased demands are made on the strength of the material when the product is operated in a difficult stress state under the influence of significant cyclic loads.

It is well known that, depending on the method of forming the base, the materials are conditionally divided into textile and non-woven materials. Non-woven materials belong to the category of materials that are obtained by forming and fixing in one way or another a layer of fibers or threads. Unlike textile materials, which are made by weaving or knitting yarn, non-woven materials are relatively inexpensive to manufacture, however, they are characterized by uneven distribution of threads in the material in different directions, i.e. significant heterogeneity of the density of the material. This leads not only to heterogeneity of the mechanical properties of the flat material in various directions, but also to insufficient stability of the properties over time. Non-woven material can be irreversibly deformed as a result of the application of significant cyclic loads to it, which leads to unsatisfactory stability if it is used as a reinforcing road or building pavement. Making the basis of the material by weaving gives the material uniformity in various directions, which is lacking in nonwoven materials, which have a highly discrete arrangement of threads in the warp, however, the weaving methods are quite complex, slow and unsuitable for forming long reinforcing products. There is a need for a method that would provide the ability to quickly form extended flexible reinforcing coatings that are uniform and stable in their mechanical properties.

Well-known in the textile industry non-woven materials (RU, 2106441, class D 04 H 3/04, 2003), containing at least two layers, and the threads inside each layer are mainly parallel to each other, while maintaining the parallelism of the threads in each layer is carried out by quilting. Such materials are mainly used as hardeners in products made from plastic materials. Unfortunately, the use of needle-punched means leads to rupture of some of the fibers.

In patent RU, 1516547, cl. D 04 H 3/00, 1989 discloses a nonwoven material containing synthetic fibers aerodynamically formed from a polymer melt and also bonded by needle piercing. Known non-woven material made of polypropylene yarns is intended for road construction works, the construction of soil structures. The surface density of the material is 500 g / m ² , the breaking load is 412 N, the elongation at break is -110-130%, which does not provide the required stability of the operating characteristics due to the large relative elongation and low breaking load.

In patent RU, 2075563, cl. D 04 H 3/04, 1997, a non-woven material is disclosed and a method for producing it, which consists in pulling polyimide fibers, then fastening them in a needle-punched manner in the form of a non-woven material and heat treating. Obtained by a known method, the molded fibrous product, despite its fibrous structure, has such strength that it can be machined. Known fibrous material has a specific gravity of 60-3000 g / m. The low wear resistance of the known material is associated with the irregularity of its structure with respect to the direction of application of the abrasive effect.

As noted above, the need for a crosslinking operation to form a nonwoven material creates problems regarding the structural strength of the material and the productivity of the manufacturing process. The presence of seams increases the likelihood of reducing the mechanical strength of the material, which is a composite structure, obtained by impregnating the laid yarns in the form of a two-dimensional shape with hardening binders, for example, hardening resins. There is a need for a simpler method of preforming flat shapes from materials without the use of crosslinking. Such joints, as noted above, can lead to a risk of lowering the strength of composite structures.

For a long time, in the manufacture of nonwoven materials using threads from thermoplastic copolymers, the threads are joined during melting. Means for joining can be an adhesive, a solvent, a softening polymer of the yarn and allowing the yarn to join together (see, for example, RU, 2106442, class D 04 H 5/02, 1998).

Known non-woven fibrous material from synthetic threads, made according to patent RU, 2058453, class. D 04 H 3/00 and having single thermally glued threads in the longitudinal and transverse directions and sections of groups of threads thermally glued to the side surfaces in the longitudinal and transverse directions, and the sections of the groups of longitudinal glues in the underlying and overlying layers are oriented mainly in different directions, and the minimum the angle between the axes of the longitudinal gluing sections is 45-90 °. Known material can be used in objects where increased demands are made on the wear resistance of the fibrous material, when the product is operated in a difficult condition under the action of cyclic loads under conditions of simple loading, for example, during abrasion between two rotating or reciprocating working bodies contacting surfaces. The low wear resistance of the known material under conditions of complex mechanical stress is associated with the heterogeneity of its structure with respect to the direction of application of the abrasion.

In patent RU, 2008383, cl. D 04 H 3/00, 1994 discloses a method for manufacturing a nonwoven fabric from two types of plastic fibers — longitudinal and transverse, differing in material, cross-sectional shape, and temperature of plastic deformation. Longitudinal and transverse fibers can be made of glass, basalt, a combination thereof, glass and nylon or other plastics. Depending on the requirements of use, these canvases can be impregnated with varnishes, glues, resins and other substances. The known method includes the manufacture of fibers from plastic materials and the formation on their basis of a grid of longitudinally and transversely laid fibers. Longitudinal fibers are rolled between metal rolls before forming a mesh to give them the shape of a tape 3-4 microns thick and 10-15 microns wide. When forming the mesh, the cut transverse fibers are laid on the longitudinal fibers, after which this fiber network is passed between the metal rolls at the temperature of plastic deformation of the cut fibers, causing flattening of the transverse fibers and pressing them into the longitudinal fibers at the intersection sites.

The closest in technical essence and the achieved result to this material is a nonwoven material for reinforcing road surfaces, having a biaxial composite flexible structure containing two groups of discreetly arranged fibers held together by a binder, the fibers of each group being parallel to each other and separated from each other at regular intervals and cross at right angles with the fibers of another group (RU, 2145985, class D 04 H 3/04, 2000).

Closest to this method is a method of manufacturing the same non-woven material for reinforcing road surfaces, including discrete laying with a regular step of groups of longitudinal and transverse fibers at right angles to each other, impregnating them with a binder and heat treatment (RU, 2145985, class D 04 H 3/04, 2000). The known method allows the production of relatively high-quality non-woven material for reinforcing road surfaces, however, its production technology has the significant drawback that the material produced according to this technology has a two-layer structure characterized by heterogeneity and instability of properties under complex cyclic loading.

In the framework of this application, the problem of obtaining a non-woven material for reinforcing road-building coatings with enhanced stability of physico-mechanical properties by forming an isotropic state of the base material is solved. There is a need for a simple method by which it is possible to produce nonwoven structures of materials by discreetly laying yarns arranged in a deck so as to provide isotropic physical and mechanical properties under significant cyclic loads.

There is a need to achieve stable material strength while maintaining the flexibility of its filaments.

The problem is solved in that in a nonwoven material for reinforcing road surfaces containing two groups of fibers discretely arranged at right angles to each other in the longitudinal and transverse directions of the fibers held by a binder and separated from each other in a group with a regular step in which both groups of fibers form a three-layer structure so that a group of transverse fibers is laid between longitudinal fibers divided into upper and lower subgroups, while the fibers of each group are made of stack Loroving with a linear density of at least 400 tex.

Preferably, the fibers are made of aluminoborosilicate glass roving with a relative elongation of not more than 5%.

The problem is also solved by the fact that in the method of manufacturing a nonwoven material for reinforcing road surfaces, including discrete laying at right angles to each other of two groups of fibers in the longitudinal and transverse directions, impregnating them with a binder and heat treatment, glass fibers with linear density are not used as fibers less than 400 tex, while previously before laying the fibers, the group of longitudinal fibers is divided into upper and lower subgroups, create a controlled tension of the fibers in these subgroups uppah, impregnate at least one of the subgroups of longitudinal fibers with a binder, then a group of transverse fibers is laid between the upper and lower subgroups of longitudinal fibers, after which heat treatment is carried out at a temperature of 150-180 ° C, followed by re-impregnation of the fibers with a binder and drying until the residual fiber moisture content not more than 0.5 wt.%.

It is preferable to carry out the drying in the temperature range 150-220 ° C, and glass fibers with a relative elongation of not more than 5% should be used as fibers.

The essence of the invention is to establish a causal relationship between the physicomechanical properties of the nonwoven material for reinforcing road surfaces and its structure, obtained on the basis of the used fiber material within a given sequence of actions and modes of their execution. To identify this interdependence, the behavior of a nonwoven material made by this method using glass roving with a linear density of at least 400 tex was experimentally studied under cyclic loads. In the absence of the popularity of the general equation relating the physical and mechanical state of the nonwoven material under cyclic loads with the fiber material, the authors experimentally found those optimal values of the linear glass roving density that allow the formation of a stable structure of the material and its isotropic state.

Impregnation of one of the subgroups of longitudinal fibers and heat treatment at a temperature of 150-180 ° C are necessary to create a rigid material structure. After this heat treatment, the longitudinal and transverse fibers are held near each other until the formed structure is subjected to repeated impregnation with a binder and drying in a controlled tension of the fibers to achieve the desired degree of residual moisture.

Example. For the manufacture of a three-layer nonwoven material having a biaxial composite flexible structure for reinforcing a pavement with a cyclic load of 10 tons, bays of aluminoborosilicate glass roving with a linear density of 1200 tex are used. Glass roving bays are mounted on creel. From the creel, the first group of fibers is fed to a dividing comb, where it is divided into upper and lower subgroups of longitudinal fibers, and then sent to a tensioner. The creation of tension of the upper and lower longitudinal fibers is necessary for pinching between them another group of transverse fibers. The tension of the upper longitudinal fibers is maintained in the range of 3-8 kg / thread, and the tension of the lower ones is in the range of 5-10 kg / thread. The transverse fibers from the glass roving bay are fed to a chain conveyor distributor having a movable bearing surface to maintain the structure of the formed material. Using a spreader, lay transverse fibers on the thread holder of the chain conveyor, while ensuring their perpendicular arrangement relative to the longitudinal fibers. The upper longitudinal fibers from the tensioner are sent to the bath, where they are impregnated with an adhesive. The biaxial mesh structure of the material is formed on a forming cylinder mounted on the drive shaft of the chain conveyor. The transverse fibers are laid on the forming cylinder between the upper and lower longitudinal fibers, while the transverse fibers between the longitudinal fibers are pinched using the molding device in the controlled tension mode of the longitudinal fibers. After that, the ends of the transverse fibers are trimmed with a cutting device. The speed of laying the threads in two mutually perpendicular directions is controlled during the formation of the material. A material with a formed three-layer structure is sent to hot calendars, where, in order to create the rigidity of the fabric structure, heat treatment is carried out at a temperature in the range of 150-180 ° C, accompanied by bonding of glass fiber longitudinal fibers. After re-impregnating the structure with an adhesive composition, the material is squeezed out, and then dried at a temperature of 190 ° C to a residual moisture content of not more than 0.5% by weight of the material. The finished material is fed to the pulling device, with the help of which they ensure the material production speed in the range of 0.5-3.5 m / min. Using this method allows you to get a three-layer structure, where the fibers of both groups, longitudinal and transverse, form a discrete array and do not completely cover the surface. The resulting non-woven material is the target product, which can be made in the form of a roll material.

Table 1 shows the physico-mechanical properties of the nonwoven material obtained according to this method.

Tab. 1 Name
indicators Nonwoven fabric values 1 2 3 4 Mass per unit area, g / m 225 ± 30 320 ± 40 450 ± 50 540 ± 60 Residual humidity, not more than,% of the mass per unit area 0.5 0.5 0.5 0.5 Breaking load, kN / m not less than: longitudinal threads fifty 70 100 120 transverse threads 48 65 95 115 Elongation at break,% no more: by 4.0 4.0 4.0 4.0

longitudinal threads
along transverse threads 4.0 4.0 4.0 4.0 Strength loss when checking frost resistance (50 cycles of freezing-thawing),% no more 25 25 25 25

Sizes of cells, mm 25 × 25 37.5 × 37.5 50 × 50 25 × 25 37.5 × 37.5 50 × 50 25 × 25 37.5 × 37.5 50 × 50 25 × 25
37.5 × 37.5
50 × 50

The invention can be used in the manufacture of non-woven web materials based on glass roving for reinforcing road and building coatings. The invention provides for the production of an isotropic state of a nonwoven material characterized by the required stable physical and mechanical properties. This leads to a number of commercial advantages, including the ability to produce high-quality coatings at a low cost in a single technological cycle, characterized by structural strength under the influence of cyclic loads.

Claims (5)

1. Non-woven material for reinforcing road surfaces, containing two groups of fibers discretely located at right angles to each other in the longitudinal and transverse directions, held by a binder and separated from each other in a group with a regular step in which both groups of fibers form a three-layer structure so that a group of transverse fibers is laid between longitudinal fibers divided into upper and lower subgroups, while the fibers of each group are made of glass roving with a linear density of e 400 tex. 2. The nonwoven material according to claim 1, in which the fibers are made of aluminoborosilicate glass roving with a relative elongation of not more than 5%. 3. A method of manufacturing a nonwoven material for reinforcing road surfaces, including discrete laying at right angles to each other of two groups of fibers in the longitudinal and transverse directions, impregnating them with a binder and heat treatment, in which glass fibers with a linear density of at least 400 tex are used as fibers, in this case, before laying the fibers, a group of longitudinal fibers is divided into upper and lower subgroups, a controlled tension of the fibers in these subgroups is created, and at least impregnated , one of the subgroups of longitudinal fibers with a binder, then a group of transverse fibers is placed between the upper and lower subgroups of longitudinal fibers, then heat treatment is carried out at a temperature of 150-180 ° C, followed by re-impregnation with a binder and drying until the residual moisture content of the fibers is not more than 0.5 wt. . % 4. The method according to p. 3, in which the drying is carried out in the temperature range of 150 - 220 ° C. 5. The method according to PP. 3, 4, in which aluminoborosilicate glass roving with a relative elongation of not more than 5% is used as fiber.