JPH04216925A - Network structure - Google Patents

Abstract

PURPOSE:To provide a plastic network structure, which has excellent strength and rigidity, in which there is no protrusion of the intersections of networks substantially and the strength of the intersections is also increased and which is used for reinforcing a poor subsoil, etc. CONSTITUTION:Each side forming a network is joined in the same plate in a network structure. Said network structure is manufactured in such a manner that polymer molecules constituting sides in at least one direction of each side forming the network are oriented in said direction, and a plastic network structure, in which the polymer molecules organizing intersection sections, where each side is joined, are oriented in at least one direction, and an extrusion- molded resin sheet are passed through a roll rolling or press operation process before an orienting process.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic network structure that can be used as a civil engineering material for reinforcing soft ground, reclaimed land, steep slopes, etc., packaging material, and various other materials.

0002

BACKGROUND OF THE INVENTION Plastic mesh structures are buried in the soil to reinforce soft ground, reclaimed land, steep slopes, and the like. Such mesh structures have been known to be manufactured by various methods. For example, a method of extruding molten resin from an extruder and simultaneously forming a network of a desired size. Or JP-A-61-154833
There is known a method of forming a mesh of a desired size by stretching a resin sheet with a large number of holes formed by punching, as disclosed in Japanese Patent Publication No.

However, since the former is usually an unstretched molded product, its strength and rigidity are low, so it cannot be used in applications that require strength, such as steep slope embankments. On the other hand, since the latter is stretched, it has high strength and rigidity and is superior to the former for reinforcement purposes, and has been widely used in recent years. However, since it is stretched after punching, the mesh intersection C
remains unstretched, and this part becomes a raised shape. If the intersection point is unstretched, the strength of this portion will be low and the creep will be large. Also, because of the upheaval, earth pressure tends to concentrate at these intersections, which is a major factor in lowering the overall strength of the network structure. Furthermore, due to this protrusion, there was a problem in that the overall structure became bulky and the installation workability was poor.

0004

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has excellent strength and rigidity that could not be achieved with conventional manufacturing methods.
In addition, the present invention aims to provide an excellent network structure in which the strength of these intersection points, which have been inferior in strength, is increased.

[0005]

[Means for Solving the Problem] As shown in FIG. 3, when a resin sheet with holes is stretched by ordinary means, the portion (4) is preferentially stretched in the stretching direction, and the portion (5) is stretched preferentially in the stretching direction. The portion remains unstretched. Therefore, in the part (4), the molecular orientation effect due to stretching occurs and the strength and rigidity are improved, but in the unstretched part (5), the molecular orientation does not occur and the effect cannot be obtained, so the strength and rigidity are improved. Doesn't improve. moreover(
The portion (4) becomes thinner due to stretching, but the portion (5) remains unstretched, resulting in a difference in thickness between the two, and the portion (5) remains in a raised shape. Finally, the mesh structure (4
) portions form the sides, and portions (5) form the intersections of each side. Therefore, the present inventors focused on the unstretched portion of (5), and created a novel network structure in which molecular orientation was developed in this portion, the strength of this portion was improved, and the adverse effects of bumps were substantially eliminated. They discovered this and completed the present invention.

That is, the present invention is as follows. (1) A network structure in which each side forming the network joins in the same plane, and polymer molecules constituting at least one side of each side forming the network are oriented in that direction, and each A plastic network structure in which polymer molecules constituting intersection points where sides meet are oriented in at least one direction. (2) Plastics include polyolefin resins such as polyethylene and polypropylene, polyacetal resins such as polyoxymethylene homopolymers and polyoxymethylene copolymers, polyester resins such as polyethylene terephthalate, and polyamide resins such as nylon 6 and nylon 66. The plastic network structure according to claim 1, which is made of a crystalline thermoplastic resin such as. (3) A plastic network structure characterized by forming a large number of small holes in an extruded resin sheet either before or after rolling or pressing, and then stretching it in a heated atmosphere. How the body is manufactured.

[0007] The network structure of the present invention can be applied to both thermoplastic resins and thermosetting resins, which are generally referred to as plastics, but thermoplastic resins that can be easily stretched and oriented are preferred. In addition, molecular orientation tends to occur by stretching,
Crystalline thermoplastic resins are preferred, and their orientation significantly improves strength and rigidity. Specifically, for example, polyolefin resins such as polyethylene and polypropylene, polyacetal resins such as polyoxymethylene homopolymers and polyoxymethylene copolymers, polyester resins such as polyethylene terephthalate, and nylon 6.
and polyamide resins such as nylon 66. Such materials are inexpensive and widely used for general purposes, and in that sense, they are preferable materials. Furthermore, it is of course possible to mix a fibrous material such as glass fiber or other additives with the above resin.

The shape of the mesh is not particularly limited, such as elliptical, quadrangular, hexagonal, etc., but it is easy to manufacture, the strength in the vertical and horizontal directions can be uniformly strengthened, and the size of the mesh can be controlled as necessary. A rectangular shape, ie, a grid shape, is usually preferable because it can be easily formed. Furthermore, the size of the mesh is determined depending on the purpose for which it will be used, taking into consideration the required strength, type of resin, etc.

As a method for manufacturing the network structure of the present invention, for example, a method using the apparatus shown in FIG. 4 can be applied. FIG. 4 shows an example of an apparatus for manufacturing the structure of the present invention. The molten resin is extruded from an ordinary extruder (6) and formed into a sheet. This sheet is then rolled by a roll mill (7). This rolling stretches the sheet in the roll direction and orients the polymer molecules in that direction. This rolled sheet is then punched with holes of a uniform, fixed shape by a punching device (8). The shape of the hole is usually circular. The resin is then guided to a transverse stretching machine (tentter) (9) set at a stretching temperature appropriate for the resin, and stretched in the transverse direction. Lateral stretching machine (9
) consists of a preheating zone (12) and a stretching zone (13). By this lateral stretching, the circular hole is stretched into an elliptical shape. Next, this horizontally stretched sheet is passed through a roll longitudinal stretching machine (1
0) and further stretched in the longitudinal direction. Longitudinal stretching machine (10)
consists of a plurality of rolls, and stretching is performed by the difference in rotational speed between the low-speed roll (15) and the high-speed roll (16). Note that (14) is a heating zone for heating the atmosphere during longitudinal stretching as necessary, and is used as appropriate depending on the type of resin. By the stretching described above, the sheet as a whole is stretched in two axes, ie, the longitudinal direction and the transverse direction. Furthermore, if necessary, mechanical properties etc. can be improved by applying heat treatment after this stretching. Next, this biaxially stretched sheet is wound up by a winding machine (11). By the above operations,
By stretching the perforated sheet in two directions, a lattice-like network structure in which each part has a uniform rectangular shape as shown in FIG. 1 is obtained. In this method, rolling is performed prior to stretching, so that the intersection points of the meshes are also in a state where molecular orientation is likely to occur due to stretching, and in the subsequent stretching step, this region is also stretched and molecular orientation occurs. In the network structure obtained here, the polymer molecules are oriented mainly in the vertical direction on the vertical side (1) and mainly in the horizontal direction on the horizontal side (2), and each side joins. Intersection (3)
However, it has a molecular orientation structure in which the molecules are oriented. Depending on the type of resin, the size and spacing of the pores, the stretching ratio in the vertical and horizontal directions, the molecular orientation at the intersection point may be the same in the vertical and horizontal directions, or it may be stronger in either the vertical or horizontal directions, depending on the application, etc. These conditions are selected as appropriate. The mesh structure obtained here has virtually no protrusions at the intersections of the meshes, so
Stress concentration due to earth pressure etc. is reduced in this part and it can withstand large earth pressure. In addition, since the molecules on each side are oriented, the structure has high strength.

[0010] In the above manufacturing example, holes were formed after roll rolling, but this hole forming operation can also be performed before roll rolling. In addition, in the above example, roll rolling is
Although an example was shown in which rolling was performed only in one direction, it is also possible to perform rolling in two directions, including a direction perpendicular to this direction. Further, instead of this rolling operation, a stretching orienting operation using a pressing method disclosed in Japanese Patent Application Laid-Open No. 63-191616 may be performed. Although the pressing method has some difficulties in making it continuous, it is an excellent method for uniformly orienting the molecules of crystalline resin etc. in a plane.

[0011]Also, in the above-mentioned example, a sequential biaxial stretching method of transverse stretching and then longitudinal stretching was used for the stretching performed after rolling or press operation, but a simultaneous biaxial stretching method may also be employed if longitudinal and transverse stretching is performed simultaneously. You can also do it. On the other hand, uniaxial stretching may be performed in only one direction, either the transverse direction or the longitudinal direction. That is, a method of rolling followed by longitudinal stretching or rolling followed by transverse stretching can be adopted. In this case, considering that molecular orientation has already been applied in the longitudinal direction due to rolling, it is better to uniaxially stretch in the transverse direction after rolling, as this allows for molecular orientation in both the longitudinal and transverse directions, resulting in a more balanced structure. You can get a body.

The structure of the present invention can be manufactured by various methods as described above, but it is possible to manufacture it continuously in an industrial manner easily and inexpensively, and it also has better balance of vertical and horizontal characteristics. In addition, for resins such as crystalline thermoplastic resins whose crystals or molecules are easily oriented in the stretching direction and whose stretching stress is high, holes may be added before or after rolling as first exemplified in the present invention. A preferred method is to open the film and then stretch it horizontally and then stretch it longitudinally.

[0013] When producing the structure of the present invention, the production conditions, particularly the rolling and stretching conditions, must be appropriately selected depending on the type of resin used and the properties required depending on the intended use. For example, the following conditions are preferable for polypropylene and polyoxymethylene. For polypropylene, the rolling temperature is room temperature or higher and 120°C or lower, the rolling ratio is 1.5 times or more and 5 times or less, and the stretching temperature is 140°C or higher and 170°C or higher.
℃ or less, the stretching ratio is preferably 1.5 times or more and 10 times or less, and for polyoxymethylene, the rolling temperature is room temperature or more and 150 degrees Celsius.
The rolling ratio is 1.5 times or more and 5 times or less, and the stretching temperature is 1.
The stretching ratio is 1.5 times or more and 15 times at a temperature of 50°C or higher and 180°C or lower.
Preferably, the amount is less than twice that.

[0014] The molecular orientation referred to in the present invention is the in-plane direction of the structure (
This can be easily confirmed by analyzing the orientation pattern by wide-angle X-ray diffraction (edge direction or end direction). This molecular orientation can be easily caused by rolling or stretching, and the degree of orientation generally increases in proportion to the rolling or stretching ratio.

[0015]

EXAMPLES Next, the present invention will be explained in more detail by way of examples.

[0016]

[Example 1] Extruding polypropylene resin from an extruder,
It was molded into a sheet with a width of 200 mm and a thickness of 3 mm. Next, it was passed through rolling rolls with a roll diameter of 250 mm and a roll temperature of 70° C., and a rolling force was applied so that the thickness became 1.5 mm. This rolling stretched the sheet twice in the machine direction. Next, this rolled sheet was subjected to a continuous punching device to uniformly punch holes with a diameter of 5 mm and a distance between the centers of adjacent holes of 15 mm over the front surface of the sheet as shown in FIG. 3. Next, this sheet was subjected to a tenter transverse stretching machine set at a stretching temperature of 155° C. and a stretching ratio of 5 times. Subsequently, the film was subjected to longitudinal stretching at a stretching ratio of 2.5 times using a longitudinal stretching machine with a stretching roll temperature set at 157°C. Through the above steps, the sheet as a whole was biaxially stretched 5×5 times. As a result of this stretching, a mesh structure having a substantially uniform shape in each part and having a rectangular shape with a vertical side of 12 mm and a horizontal side of 25 mm was obtained. The vertical sides of each mesh have strong molecular orientation in the vertical direction, and the horizontal sides have strong molecular orientation in the horizontal direction, and the intersection of each side has a structure in which molecular orientation is slightly stronger in the vertical direction than in the horizontal direction. there were. Furthermore, the thickness of this intersection was approximately equal to the thickness of each side, and no protuberance was observed in this area.

[0017]

[Example 2] In the sheet extruded in Example 1, the diameter of the holes was 5 mm, and the distance between the centers of adjacent holes was 15 mm, as in Example 1.
A hole of 1.0 mm in diameter was made, and then the material was similarly rolled twice in the longitudinal direction, and then biaxially stretched by 5 times in the transverse direction and 2.5 times in the longitudinal direction. As a result, a mesh structure having a rectangular shape with each length and width of 25 mm was obtained. Similarly to Example 1, the obtained network structure had a structure in which each side had strong molecular orientation, and the intersections thereof had a structure in which molecular orientation was also applied. Of course, no bumps at the intersections were seen.

[0018]

[Comparative Example 1] The sheet extruded in Example 1 had the same hole diameter as Example 1, and the distance between the centers of adjacent holes was 15 mm.
A hole of mm in diameter was made, and then the film was stretched 5 times in the longitudinal direction, and then stretched 5 times in the transverse direction to perform biaxial stretching. As a result, a mesh structure having a rectangular shape with length and width sides of 25 mm was obtained. Each side of the resulting network structure was strongly molecularly oriented, but the intersections were almost unstretched, ie, not molecularly oriented. As a result, this intersection remained in a raised hump-like state. The apex was approximately 1.2 mm higher than each side.

[0019]

Example 3 A polyoxymethylene homopolymer was extruded in the same manner as in Example 1, and formed into a sheet having a width of 200 mm and a thickness of 3 mm. Next, rolling was performed in the same manner as in Example 1, followed by hole punching. Next, it was applied to a tenter transverse stretching machine with a stretching temperature of 172° C. and a stretching ratio of 6 times. Subsequently, the film was subjected to longitudinal stretching at a stretching ratio of 3 times using a longitudinal stretching machine with a stretching roll temperature set at 173°C. Through the above steps, the sheet as a whole was biaxially stretched 6×6 times. By this stretching, the vertical side is 15 mm and the horizontal side is 30 m.
A mesh body having a rectangular shape of m was obtained. The vertical sides of each mesh have strong molecular orientation in the vertical direction, and the horizontal sides have strong molecular orientation in the horizontal direction, and the intersection of each side has a structure in which molecular orientation is slightly stronger in the vertical direction than in the horizontal direction. there were. Also, the thickness of this intersection is approximately equal to the thickness of each side,
No protuberance was observed in this area.

[0020]

Effects of the Invention: The mesh structure of the present invention has excellent strength and rigidity, has virtually no bulges at the intersections of the meshes, and has increased strength at these intersections, so it has a reinforcing effect on the ground, etc. Of course, it also has excellent handling and workability, such as not being bulky when wound into a roll. Therefore, soft ground
It is suitable as a plastic mesh structure for reinforcing the ground of reclaimed land, steeply sloped land, residential development land, etc., or for reinforcing road surfaces to prevent cracks in asphalt pavement.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing a network structure of the present invention.

FIG. 2 is a diagram schematically showing a conventional plastic network structure.

FIG. 3 is a schematic diagram showing a resin sheet with holes.

FIG. 4 is a schematic diagram showing an example of the manufacturing method of the present invention.

[Explanation of symbols]

1 Vertical side of the network structure 2 Horizontal side of the network structure 3 Intersection of each side of the network structure 4 Stretched portion when stretched by conventional method 5 Unstretched portion when stretched by conventional method 6 Extrusion Machine 7 Rolling machine 8 Punching device 9 Horizontal stretching machine 10 Longitudinal stretching machine 11 Winding machine 12 Preheating zone 13 of the horizontal stretching machine Stretching zone 14 of the horizontal stretching machine Heating zone 15 of the longitudinal stretching machine Low speed roll 16 High speed roll

Claims (3)

[Claims] Claim 1: A network structure in which each side forming the network joins in the same plane, wherein polymer molecules constituting at least one side of each side forming the network are oriented in that direction. A plastics network structure in which the polymer molecules constituting the intersection points where each side joins are oriented in at least one direction. 2. The plastics are polyolefin resins such as polyethylene and polypropylene, polyacetal resins such as polyoxymethylene homopolymers and polyoxymethylene copolymers, polyester resins such as polyethylene terephthalate, and nylon 6 and nylon 66.
The plastic network structure according to claim 1, which is made of a crystalline thermoplastic resin such as a polyamide resin such as. 3. A plastics sheet characterized in that a large number of small holes are formed in the extruded resin sheet either before or after roll rolling or pressing operation, and then stretched in a heated atmosphere. Method for manufacturing a mesh structure.