JP2002172693A - Polyethylene monoaxially stretched product and ground reinforcement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyethylene monoaxially stretched product which shows outstanding creep properties and the best suitability for a ground reinforcement such as banking in the civil engineering field. SOLUTION: The polyethylene monoaxially stretched product has a longitudinal strand part and a crosswise strand part which are connected in a lattice fashion through a crossing part. In case the minimum value of a measured intensity is given as a base intensity B and the difference in intensity between the measured peak intensity and the base intensity B is given as A through X-ray diffraction at a reflective azimuth angle to the crossing part (110), A/(A+B) is 0.5 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniaxially stretched polyethylene material and a ground reinforcement suitable for a ground reinforcement such as embankment in the field of civil engineering.

[0002]

2. Description of the Related Art In recent years,
In many cases, embankments are formed in wetlands and valleys to become residential lands, industrial lands, or road lands. Since a building or the like is built on this embankment, the embankment must not collapse. Therefore, at the time of embankment, a reinforcing net made of synthetic resin is laid horizontally with a predetermined interval, embankment of several tens of centimeters is laid on this, and embankment formation such as residential land is performed by repeating this embankment process. ing. In particular, the construction of houses has increased rapidly in recent years, and as a result, there are cases where residential areas are constructed by embankment or on soft ground. In these residential areas, landslides are not allowed at all. For this reason, a method has been adopted in which net bodies are arranged in layers in the soil to prevent landslides and stabilize embankments. As the net, a polyethylene is used which is usually uniaxially or biaxially stretched and molecularly oriented to increase the strength.

[0003] The above-mentioned ground reinforcing net is a net having a number of holes, through which upper and lower embankments are connected to each other to prevent collapse. In order to resist the collapse of the embankment, the net is formed by stretching a highly stretchable resin such as ultra-high molecular weight polyethylene in one or two directions of the sheet so that the molecular arrangement is linear. That is, the molecular arrangement direction of the net is matched with the direction in which the embankment is expected to collapse, and the strength can be maintained without the net extending when the embankment attempts to move.

FIG. 1 shows an outline of such a resin reinforcing net (polyethylene uniaxially stretched product) 1, which is formed, for example, by punching a round or rectangular hole 3 in a polyethylene sheet 2 shown in FIG. Is obtained, for example, by uniaxial stretching to obtain a resin reinforcing net 1. The hole 3 has an elongated elongated hole shape 3 'having a pair of stretched opposed sides and a non-stretched opposed side. Become. Here, a land portion between the extending sides, that is, a land portion that is parallel to the stretching direction and is highly stretched is the vertical strand portion 11, and a land portion between the non-extending sides, that is, perpendicular to the stretching direction, substantially. The land portion that is not stretched in the horizontal direction is the horizontal strand portion 12, and the land portion where these two strand portions 11 and 12 intersect is the intersection portion 13.

[0005] Such a net for reinforcing the ground is also called a geogrid, which is required to be excellent in strength, creep resistance and durability, and particularly excellent in creep resistance. Further, a uniaxially stretched polyethylene or a ground reinforcing material has been required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a uniaxially stretched polyethylene and a ground reinforcing material capable of imparting excellent creep resistance.

[0007]

Means for Solving the Problems and Embodiments of the Invention The present invention has made the following findings as a result of intensive studies in view of the above circumstances.

[0008] That is, the uniaxially stretched polyethylene is composed of a vertical strand portion in which crystals are oriented in a uniaxial direction and a horizontal strand portion in which crystals are almost not oriented. The degree of stretching of the uniaxially stretched polyethylene determines the degree of orientation of crystals in the vertical strand portion, and determines the tensile strength of the stretched product in the stretching direction.

However, the creep resistance is not controlled solely by the high crystal arrangement height of the vertical strands, but rather the physical properties of the intersections where the horizontal strands and the vertical strands intersect and the boundaries between the individual parts. However, it has not been possible to control the crystal orientation of each part quantitatively.

[0010] From such a point, X, about the vertical strand, the horizontal strand, and the intersection of the uniaxially stretched polyethylene.
As a result of performing the line diffraction, the intersection portion, which is the connection position between the vertical strand portion and the horizontal strand portion, is not as remarkable as the vertical strand portion, but has a complicated orientation, and is not biaxially oriented in the stretching direction. Focusing on the characteristic of the orientation, the structural analysis of the intersection revealed that the creep resistance of the uniaxially stretched polyethylene had a correlation with the orientation of the intersection.

That is, X-ray diffraction at an azimuth of (110) reflection of 0 to 360 ° is performed on the intersection, the minimum value of the measured intensity is defined as the base intensity B, and the measured peak intensity and the base intensity are compared. When the difference in strength is represented by A, it has been found that a uniaxially stretched polyethylene having A / (A + B) of 0.5 or more has excellent creep resistance and is particularly suitable as a ground reinforcing material. It is what led to.

Accordingly, the present invention provides the following uniaxially stretched polyethylene and ground reinforcement. [Claim 1] In a polyethylene uniaxially stretched product comprising a vertical strand portion and a horizontal strand portion, and each of these strand portions is connected in a lattice pattern through an intersecting portion,
Azimuth angle of (110) reflection with respect to the above intersection 0 to 360
° X-ray diffraction and determine the minimum value of the measured intensity as the base intensity B
And A / (A + B) is 0.5 or more, where A is the intensity difference between the measured peak intensity and the base intensity. [2] A ground reinforcement comprising the uniaxially stretched polyethylene according to [1].

The present invention will be described below with reference to the drawings. The uniaxially stretched polyethylene of the present invention is shown in FIGS.
As shown in FIG. 2, the polyethylene sheet 2 is manufactured by punching out a polyethylene sheet in a lattice shape and stretching the sheet in a predetermined stretching direction. Lattice-shaped polyethylene sheet 2 before stretching
Can be manufactured using a known material. For example, it can be manufactured by appropriately mixing a known additive such as carbon black with high-density polyethylene. The shape and thickness of the obtained sheet and the method of punching it into a lattice can be performed according to a conventional method, and are not particularly limited.

The stretched product of the present invention can be formed into a stretched product by uniaxially stretching the above-mentioned polyethylene sheet punched in a lattice by a predetermined method. In this case, the stretching ratio can be appropriately selected. , Usually 3 to 20 times, especially 5 to 1 times
Preferably it is 5 times.

[0015] Of the two pairs of lattice sides opposed to each other in the polyethylene sheet by the above-mentioned stretching, a pair of lattice sides that are elongated vertically in the stretching direction pass through the vertical strand portion 11 and another pair of lattice sides that are hardly affected by the stretching. The side becomes the horizontal strand portion 12. Further, the connecting portion of each strand portion is a portion affected by both the vertical strand portion 11 and the horizontal strand portion 12, and this portion becomes the intersection portion 13.

In this case, when the X-ray diffraction pattern is measured by a photographic method, the diffraction lines corresponding to the 110 plane in the crystal lattice of polyethylene are almost spot-shaped in the vertical strand portion. The crystals are highly oriented. On the other hand, in the horizontal strand portion, the diffraction lines are ring-shaped and are hardly oriented, but the intersections are not ring-shaped and have an intensity distribution in the circumferential direction. When the sample was set on a fiber sample stage, rotated in the azimuthal direction by 0 to 360 °, and the intensity distribution of 110 diffraction lines was measured by the scintillation counter method, two sharp peaks were found in the vertical strand as shown in FIG. The horizontal strand portion has almost no peak, and the intersection portion has four peaks.

In the uniaxially stretched polyethylene of the present invention, the portion near the center of the intersection is placed on a fiber sample table, and the azimuth angle is 0 to 0.
When the X-ray diffraction measurement of polyethylene is performed by rotating the film to 360 °, the diffraction intensity distribution curve of the 110 plane in the azimuth direction shows four peaks, and as shown in FIG. (A), the distance between the axis of diffraction intensity 0 and the baseline of the intensity distribution curve (B)
Is required to be 0.5 or more, especially 0.7 or more. The upper limit is preferably 1.0 or less, particularly preferably 0.95 or less. If the orientation parameter is too low, sufficient creep resistance cannot be obtained. The base strength B is the strength at which only the non-oriented portion contributes, and the intensity difference A between the peak intensity and the base strength is the strength attributable only to the oriented portion.

Further, the orientation parameter of the intersection in the present invention can be used as an index for evaluating the creep resistance. For example, the orientation parameter of the intersection is calculated for a uniaxially stretched polyethylene product. By
It can be easily determined whether or not the creep resistance of the uniaxially stretched product is good.

[0019]

Industrial Applicability The uniaxially stretched polyethylene of the present invention has excellent creep resistance and can be suitably used in the field of civil engineering as a ground reinforcement such as embankment.

[0020]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to the following Examples.

[Examples and Comparative Examples] As an example, a polyethylene sheet was punched out in a lattice and stretched by a stretching machine. X-ray diffraction of the (110) reflection azimuth angle of 0 to 360 ° is performed on the crossed portion after stretching, and the minimum value of the measured intensity is defined as the base intensity B, and the difference between the measured peak intensity and the base intensity is determined. A and A / (A +
The orientation parameter shown in B) was 0.75.

The creep elongation of the obtained stretched product after 1000 hours was measured and found to be 9%.

On the other hand, as a comparative example, the creep elongation of the stretched uniaxially stretched product having the orientation parameter of the intersection of 0.21 was measured in the same manner as in the above example. %Met.

From the above results, it was confirmed that the uniaxially stretched product having the specific orientation parameter of the present invention has excellent creep resistance.

[0025]

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a uniaxially stretched polyethylene product.

FIG. 2 is a schematic plan view of a polyethylene sheet before stretching.

FIG. 3 shows an example of an X-ray diffraction pattern of a vertical strand portion, an intersection portion, and a horizontal strand portion of the uniaxially stretched polyethylene according to the present invention, wherein (A) is a diffraction intensity distribution, and (B) is 110.
3 shows an intensity distribution in a surface reflection azimuth direction.

FIG. 4 is an explanatory diagram of orientation evaluation of an intersection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Uniaxially stretched polyethylene 11 Vertical strand part 12 Horizontal strand part 13 Intersection

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2D044 CA04 4F210 AA04 AG01 AG15 AG28 AH43 QC01 QG01 QG08 QG18

Claims (2)

[Claims] 1. A uniaxially stretched polyethylene product having a vertical strand portion and a horizontal strand portion, wherein each of these strand portions is connected in a grid pattern through an intersection portion. ) Reflection azimuth angle 0-3
When X-ray diffraction at 60 ° is performed and the minimum value of the measured intensity is defined as the base intensity B and the intensity difference between the measured peak intensity and the base intensity is defined as A, A / (A + B) is 0.5 or more. A uniaxially stretched polyethylene product. 2. A ground reinforcing material comprising the uniaxially stretched polyethylene according to claim 1.