【０００１】
【産業上の利用分野】
本発明は、道路、造成地等の地盤の補強や、軟弱地盤における盛土の沈下防止のために土中に埋設する土木用ネットとして好適に使用される高強度網体に関する。
【０００２】
【従来の技術】
土木用ネットとして使用される合成樹脂製の高強度網体には種々のタイプのものが開発、提案されており、本出願人も、一軸延伸した合成樹脂テープを縦糸及び横糸として、これらを所定間隔をあけて互いに交差させ、それぞれの交点部分を融着して成る高強度網体を既に提案した（実願平１−３２３８２号）。
【０００３】
この高強度網体は、引張強度が大きく、目崩れしにくい上に、適度の柔軟性と剛性を有し、取扱いや製造が容易であるなど、種々の長所を有するものであったが、その反面、次のような問題があった。
【０００４】
【発明が解決しようとする課題】
即ち、上記の高強度網体は、その縦糸及び横糸が偏平な合成樹脂テープであるため、土中に埋設したとき縦糸及び横糸が土と噛み合いにくく、網体と土砂との接触摩擦抵抗が小さいものである。そのため、この高強度網体の上に盛った土砂に横方向の圧力が加わると、比較的簡単に横滑りして土砂崩れを発生しやすいという問題があった。
【０００５】
また、縦糸及び横糸となる合成樹脂テープとして、一軸延伸した引張強度の極めて大きいポリプロピレンテープや超高分子ポリエチレンテープを使用すると、該テープの交点部分を超音波融着等の手段で融着するときに交点部分が劣化して引張強度の大幅な低下を生ずるため、満足な高強度網体を得ることが難しいという問題もあった。
【０００６】
本発明は上記問題に鑑みてなされたもので、その目的とするところは、土中に埋設したときの土砂との接触摩擦抵抗が大きくて土砂の横滑りを抑制することができ、しかも、一軸延伸したポリプロピレンや超高分子ポリエチレンよりなる芯材の優れた引張強度を実質的に損なうことなく縦糸と横糸の交点部分を強固に溶着できる高強度網体を提供することにある。
【０００７】
【課題を解決するための手段】
上記目的を達成するため、本発明の高強度網体は、一軸延伸したポリプロピレン又は超高分子ポリエチレンよりなる芯材の周囲又は上下両面に熱可塑性樹脂を押出被覆又は積層一体化した被覆テープを縦糸及び横糸とし、縦糸及び横糸を所定間隔をあけて互いに交差させると共に、縦糸及び横糸の少なくとも一方に捻りを与え、縦糸と横糸の交点部分を溶着したことを特徴とするものである。
【０００８】
そして、好ましくは延伸倍率が５〜２０倍の芯材を使用し、更に、被覆用の熱可塑性樹脂としてエチレン−酢酸ビニル共重合体を使用したものである。
【０００９】
【作用】
本発明の高強度網体は、縦糸及び横糸の少なくとも一方に捻りを与えてあるので、土中に網体を埋設すると、この捻りを与えた縦糸又は横糸が土砂に噛み合って接触摩擦抵抗が大きくなる。そのため、高強度網体の上の土砂に横方向の圧力が加わっても、土砂が容易に横滑りしないので、土砂崩れを充分抑制することができる。
【００１０】
しかも、縦糸及び横糸は、芯材の周囲又は上下両面に熱可塑性樹脂を押出被覆又は積層一体化した被覆テープであるから、縦糸と横糸の交点部分を溶着するとき、内部の芯材まで軟化溶融させない穏やかな加熱条件で外側の熱可塑性樹脂を軟化溶融させて溶着を行うことができる。従って、縦糸及び横糸の芯材は実質的に熱劣化を生じず、一軸延伸されたポリプロピレン又は超高分子ポリエチレンが有する優れた引張強度を維持するので、強度の極めて大きい網体となる。
【００１１】
特に、芯材の延伸倍率が５〜２０倍であると、分子配向による引張強度の向上が顕著であり、フィブリル化による引張強度の低下もみられないので、極めて高強度の網体が得られる。
【００１２】
また、被覆用の熱可塑性樹脂がエチレン−酢酸ビニル共重合体であると、超音波溶着及び高周波溶着のいずれの手段を採用しても縦糸と横糸の交点部分を溶着することができ、しかも、該重合体は融点が芯材よりも遥かに低いので、芯材を被覆するときや交点部分を溶着するときに芯材を熱劣化させる心配が全くない。
【００１３】
【実施例】
以下、図面を参照して本発明の実施例を説明する。
【００１４】
図１は本発明の高強度網体の一実施例を示す部分斜視図、図２は縦糸又は横糸の拡大断面図、図３は本発明の高強度網体の他の実施例を示す部分斜視図である。
【００１５】
図１に示す実施例の高強度網体Ａは、方形網目を形成するように縦糸１と横糸２を所定間隔をあけて直角に交差させると共に、横糸２に捻りを与え、縦糸１と横糸２の交点部分３を溶着したものである。縦糸１の間隔及び横糸２の間隔は特に制限されないが、土木用ネットに適した強度を得るためには２０〜１５０ｍｍ程度の間隔とするのが望ましい。
【００１６】
この網体Ａは、縦糸１の相互間において、横糸２に右回り方向の１８０度の捻りを与えているが、これに限定されるものではなく、縦糸１の相互間隔に応じて（１８０×ｎ）度の捻り（但しｎは正数）を与えることができる。また、捻りの方向は左回り方向でもよく、更に、右回り方向に捻った横糸と左回り方向に捻った横糸を交互に配列するようにしてもよい。全ての横糸２に同じ方向の捻りを与えると、横糸２の復元力によって縦糸１が湾曲し、網体Ａに強い巻き癖を生じるが、上記のように捻り方向が反対の横糸を交互に配列すると、網体Ａに巻き癖が生じないので、網体Ａの取扱いや敷設作業等を容易に行えるという利点がある。
【００１７】
このような高強度網体Ａを土中に埋設すると、捻りを与えた横糸２が土砂と噛み合って接触摩擦抵抗が増大し、網体Ａの上の土砂に横方向の圧力が加わっても土砂が容易に横滑りしないので、土砂崩れを充分抑制することができる。
上記実施例の網体Ａでは横糸２に捻りを与えているが、縦糸１に捻りを与えてもよいし、縦糸１と横糸２の双方に捻りを与えてもよい。縦糸１と横糸２の双方に捻りを与えると、土砂との接触摩擦抵抗が一層増大するので、土砂崩れの抑制効果が更に大きくなる。
【００１８】
また、上記実施例の網体Ａでは、縦糸１の上に横糸２を重ねて直角に交差させているが、縦糸１の下に横糸２を重ねて直角に交差させてもよく、場合によっては図３に示す実施例の網体Ｂのように、各交点部分３で縦糸１と横糸２の上下関係を平織のように交互に逆転させて重ね合わせ、各交点部分３を溶着してもよい。このように縦糸１と横糸２の上下関係を交点部分で交互に逆転させると、縦糸１と横糸２が波形線状になるので、土砂との接触摩擦抵抗が更に大きくなる利点がある。
【００１９】
また、図１及び図３の網体Ａ，Ｂはいずれも、方形網目を形成するように縦糸１と横糸を直角に交差させているが、菱形網目を形成するように縦糸１と横糸２を網体の長さ方向に対して斜めに交差させてもよい。
【００２０】
上記の高強度網体Ａ，Ｂを構成する縦糸１及び横糸２は、図２に示すように、一軸延伸したポリプロピレン又は超高分子ポリエチレンよりなる帯状の芯材４の周囲を熱可塑性樹脂５で押出被覆した被覆テープである。
【００２１】
芯材４としては、ポリプロピレン又は超高分子ポリエチレンを溶融押出成形した帯状体を、９０〜１４０℃の温度域で５〜２０倍（好ましくは７〜８倍）に一軸延伸して得られる厚さ０．２ｍｍ以上（好ましくは０．５〜０．７ｍｍ）、幅５〜２０ｍｍ（好ましくは１０〜１５ｍｍ）程度の帯状の芯材が好適に使用される。延伸倍率が５倍より小さな芯材は、延伸による分子配向が不充分なため引張強度があまり大きくなく、一方、延伸倍率が２０倍より大きい芯材はフィブリル化による強度低下が大きくなるので、いずれも望ましくない。また、延伸倍率が５〜２０倍の芯材でも、厚さが０．２ｍｍより薄いものは、やはり絶対的な強度が不足するので望ましくない。なお、一軸延伸したポリプロピレン又は超高分子ポリエチレンの繊維を束ねたものや織成したものも、芯材４として使用することができる。
【００２２】
この芯材４を被覆する熱可塑性樹脂５としては、融点が１６０℃以下、好ましくは１４０℃以下で超音波溶着性が良い樹脂（例えばエチレン−酢酸ビニル共重合体、低密度ポリエチレン等）や、誘電率が高くて高周波溶着性が良い樹脂（例えばポリ塩化ビニル、エチレン−酢酸ビニル共重合体等）が好適に使用される。特に、エチレン−酢酸ビニル共重合体は融点が１４０℃以下と低いため、押出被覆時に芯材４を熱で傷めることがなく、また、該共重合体は超音波溶着性も高周波溶着性も良いため、どちらの溶着手段によって縦糸１と横糸２の交点部分を溶着する場合でも、穏やかな溶着条件を採用して芯材４を熱劣化させることなく溶着できるので最適である。
【００２３】
この熱可塑性樹脂５の被覆厚さは０．１ｍｍ以上、好ましくは０．５〜０．８ｍｍ程度であり、０．１ｍｍより薄くなると縦糸１と横糸２の交点部分の溶着強度が不足するため、網体に大きい引掛力が作用したときに交点部分が剥離して目崩れし易くなる。また、この熱可塑性樹脂５の表面には、テープの縦裂け防止と溶着性を良くするための凹凸皺５ａを形成することが望ましい。
【００２４】
図１及び図３に示す実施例の高強度網体Ａ，Ｂでは、上記のように一軸延伸した芯材４の周囲に熱可塑性樹脂５を押出被覆した被覆テープを縦糸１及び横糸２として使用しているが、一軸延伸した芯材４の上下両面に熱可塑性樹脂５を積層一体化した被覆テープを縦糸１及び横糸２として使用してもよい。また、押出成形した未延伸のポリプロピレン又は超高分子ポリエチレンよりなる帯状体の周囲又は上下両面に熱可塑性樹脂を押出被覆又は積層一体化してから一軸延伸して得られる被覆テープを縦糸１及び横糸２として使用してもよい。
【００２５】
縦糸１と横糸２の交点部分３は、熱可塑性樹脂５の種類に応じて超音波溶着又は高周波溶着のいずれかを選択して溶着すればよい。即ち、熱可塑性樹脂５が超音波溶着性の良いものである場合には超音波溶着すればよく、高周波溶着性の良いものである場合には高周波溶着すればよく、超音波溶着性も高周波溶着性も良い場合には、超音波溶着及び高周波溶着のどちらでもよい。但し、いずれの場合も、縦糸１及び横糸２の芯材４まで熱劣化を生じさせない穏やかな溶着条件を採用して、交点部分３の縦糸と横糸の熱可塑性樹脂５同士を強固に溶着することが必要である。
【００２６】
図１及び図３の高強度網体Ａ，Ｂは、上記のように縦糸１と横糸２の交点部分３で芯材４を熱劣化させることなく縦糸１と横糸２の熱可塑性樹脂５同士を強固に溶着したものであるから、縦糸１及び横糸２の芯材４は、一軸延伸されたポリプロピレン又は超高分子ポリエチレンの優れた引張強度をそのまま維持している。従って、この網体Ａ，Ｂに大きいテンションが作用しても、縦糸１や横糸２が切断して網体Ａ，Ｂが簡単に破れる心配はなく、また、交点部分３の溶着強度が大きいので、網体Ａ，Ｂに引掛力が作用しても、交点部分３が剥離して簡単に目崩れを生じることがない。
【００２７】
次に、本発明の更に具体的な実施例と比較例を説明する。
【００２８】
［実施例１］
約８倍の延伸倍率で一軸延伸した厚さ０．５ｍｍ、幅９ｍｍのポリプロピレンの帯状芯材を作成した。この帯状の引張強度を測定したところ、１１８．３ｋｇｆであった。
【００２９】
次に、この帯状芯材の周囲にエチレン−酢酸ビニル共重合体（日本ユニカ株式会社製の商品名ＮＵＣ３１１９５）を約１４０℃の樹脂温度で０．７５ｍｍの厚さに押出被覆して、全体の厚さが２．０ｍｍの被覆テープを作製した。この被覆テープの引張強度を測定したところ、下記の表１に示すように１１９．０ｋｇｆであった。ポリプロピレンの帯状芯材の引張強度（１１８．３ｋｇｆ）を基準にして、この被覆テープの強度保持率を算出すると、下記の表１に示すように１００．６％であり、樹脂被覆による強度低下は見られず、わずかに向上していた。
【００３０】
この被覆テープを縦糸及び横糸とし、５０×５０ｍｍの間隔をあけて直角に交差させると共に、縦糸と縦糸の間で横糸に右回り方向の１８０度の捻りを与え、高周波溶着装置（精電舎電子工業株式会社製のＫＷ−３０００ＴＲ）を用いて、周波数２７ＭＨｚ、出力３Ｋｗ、発信時間３．０秒、加圧力２ｋｇｆ／ｃｍ２ の条件下に、縦糸と横糸の交点部分を高周波溶着して、網体を製造した。そして、この網体の縦糸の引張強度を測定したところ、下記の表１に示すように１１８．１ｋｇｆであった。ポリプロピレンの帯状芯材の引張強度（１１８．３ｋｇｆ）を基準にして、高周波溶着後の縦糸の強度保持率を算出すると、下記の表１に示すように９９．８％であり、高周波溶着による強度低下は実質的に見られなかった。また、交点部分の溶着強度を、交点間引掛け引張試験法で測定したところ、下記の表１に示すように３８．２ｋｇｆと大きかった。
【００３１】
［実施例２］
実施例１で作製した被覆テープを縦糸及び横糸とし、５０×５０ｍｍの間隔をあけて直角に交差させると共に、縦糸と縦糸の間で横糸に右回り方向の１８０度の捻りを与え、超音波溶着装置（精電舎電子工業株式会社製のＳＯＮＯＰＥＴ４５００Ｐ−２０７）を用いて、超音波発信時間０．５秒、加圧時間１．８秒、超音波ホーンと基台との間隔３．０ｍｍの条件下に、縦糸と横糸の交点部分を超音波溶着して網体を製造した。
【００３２】
そして、この網体の超音波溶着後の縦糸の引張強度、強度保持率、交点部分の溶着強度を求めたところ、下記の表１に示すように、それぞれ１１６．４ｋｇｆ、９８．４％、２７．０ｋｇｆであり、超音波溶着による強度低下は実質的に見られず、交点部分の溶着強度も良かった。
【００３３】
［実施例３］
実施例１で作製したポリプロピレンの帯状芯材の周囲に、ポリ塩化ビニル（鐘淵化学工業株式会社製のＳ１００３）を約１７０℃の温度で０．７５ｍｍの厚さに押出被覆して、全体の厚さが２．０ｍｍの被覆テープを作製した。この被覆テープの引張強度は下記の表１に示すように１０６．３ｋｇｆ、また、ポリプロピレンの帯状芯材の引張強度（１１８．３ｋｇｆ）を基準にした強度保持率は８９．９％であり、強度が少し低下していた。
【００３４】
この被覆テープを縦糸及び横糸とし、高周波発信時間を２秒に変更した以外は実施例１と同様にして縦糸と横糸の交点部分を高周波溶着し、網体を製造した。そして、この網体の超音波溶着後の縦糸の引張強度、強度保持率、交点部分の溶着強度を求めたところ、下記の表１に示すように、それぞれ１１４．４ｋｇｆ、９６．７％、３８．０ｋｇｆであり、超音波溶着による強度低下は極めて少なく、交点部分の溶着強度は大きかった。
【００３５】
［比較例］
実施例１で作製したポリプロピレンの帯状芯材を樹脂被覆しないでそのまま縦糸及び横糸とし、超音波発信時間を１秒、超音波ホーンと基台との間隔を０．８ｍｍに変更した以外は実施例２と全く同様に超音波溶着して網体を製造した。
【００３６】
この網体の超音波溶着後の縦糸の引張強度を測定したところ４２．９ｋｇｆであり、溶着前の引張強度（１１８．３ｋｇｆ）を基準にした強度保持率は下記の表１に示すように３６．３％で約１／３に強度が低下していた。また、交点部分の溶着強度を実施例１と同様に測定したところ、５ｋｇｆ以下と極めて小さかった。
【００３７】
【表１】
【００３８】
この表１から、ポリプロピレンの帯状芯材を樹脂被覆した被覆テープを縦糸及び横糸として作製した実施例１〜３の網体はいずれも、溶着後の縦糸の強度保持率が９５％以上と極めて高く、実質的に強度低下をきたしていないことが分かる。そして、交点部分の溶着強度も２５ｋｇｆ以上と大きいことが分かる。また、被覆樹脂としてエチレン−酢酸ビニル共重合体を使用したものは、実施例１のように高周波溶着しても、実施例２のように超音波溶着しても、実質的に強度低下をきたすことなく強固に交点部分を溶着できることが分かる。
【００３９】
これに対し、ポリプロピレンの帯状芯材を樹脂被覆しないでそのまま縦糸及び横糸として作製した比較例の網体は、溶着後の強度保持率が３６．３％で強度低下が著しく、交点部分の溶着強度も５ｋｇｆ以下で剥離しやすいことが分かる。
【００４０】
【発明の効果】
以上の説明から明らかなように、本発明の高強度網体は、土中に埋設したときの土砂との接触摩擦抵抗が大きいため、土砂の横滑りによる土砂崩れを充分に抑制することができ、しかも、縦糸と横糸の引張強度及び交点部分の溶着強度が大きいため、網体に大きいテンションや引掛力が作用しても、網体が簡単に破れたり目崩れを生じたりする心配がないといった顕著な効果を果する。
【図面の簡単な説明】
【図１】本発明の高強度網体の一実施例を示す部分斜視図である。
【図２】縦糸又は横糸の拡大断面図である。
【図３】本発明の高強度網体の他の実施例を示す部分斜視図である。
【符号の説明】
Ａ，Ｂ 高強度網体
１ 縦糸
２ 横糸
３ 交点部分
４ 芯材
５ 熱可塑性樹脂[0001]
[Industrial applications]
The present invention relates to a high-strength mesh body suitably used as a civil engineering net to be buried in soil for reinforcing a ground such as a road or a constructed ground, and for preventing settlement of an embankment in soft ground.
[0002]
[Prior art]
Various types of synthetic resin high-strength nets used as civil engineering nets have been developed and proposed, and the present applicant has also determined that uniaxially stretched synthetic resin tapes are used as warp and weft yarns, and these are specified. A high-strength net formed by intersecting each other at intervals and fusing each intersection has already been proposed (Japanese Utility Model Application No. 1-32382).
[0003]
This high-strength net has various advantages, such as high tensile strength, not easily collapsed, moderate flexibility and rigidity, and easy handling and manufacture. On the other hand, there were the following problems.
[0004]
[Problems to be solved by the invention]
That is, since the warp and the weft are flat synthetic resin tapes, the warp and the weft are hardly engaged with the soil when buried in the soil, and the contact friction resistance between the mesh and the sand is small. Things. Therefore, there is a problem that when a lateral pressure is applied to the earth and sand piled up on the high-strength mesh, the earth slides relatively easily and landslides easily occur.
[0005]
Further, when a uniaxially stretched polypropylene tape or an ultra-high-molecular polyethylene tape having an extremely large tensile strength is used as the synthetic resin tape to be the warp and the weft, when the intersection of the tapes is fused by means such as ultrasonic fusion, etc. In addition, there is a problem that it is difficult to obtain a satisfactory high-strength net because the intersection portion is deteriorated and the tensile strength is greatly reduced.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object the purpose of the present invention is to have a large contact friction resistance with earth and sand when buried in the soil, thereby suppressing the side slip of the earth and sand, and furthermore, the uniaxial stretching. It is an object of the present invention to provide a high-strength net body capable of firmly welding the intersection of the warp and the weft without substantially impairing the excellent tensile strength of the core material made of polypropylene or ultra-high-molecular-weight polyethylene.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the high-strength mesh body of the present invention is a warp yarn obtained by extrusion-coating or laminating a thermoplastic resin on or around both sides of a core material made of uniaxially stretched polypropylene or ultra-high-molecular-weight polyethylene. The warp and the weft are intersected with each other at a predetermined interval, and at least one of the warp and the weft is twisted to weld the intersection of the warp and the weft.
[0008]
Preferably, a core material having a draw ratio of 5 to 20 times is used, and an ethylene-vinyl acetate copolymer is used as a thermoplastic resin for coating.
[0009]
[Action]
Since the high-strength net of the present invention has twisted at least one of the warp and weft, when the net is buried in the soil, the twisted warp or weft meshes with the earth and sand to increase the contact friction resistance. Become. For this reason, even if lateral pressure is applied to the earth and sand on the high-strength net, the earth and sand do not easily slide, and the landslide can be sufficiently suppressed.
[0010]
Moreover, since the warp and weft are coated tapes in which the thermoplastic resin is extrusion-coated or laminated and integrated around the core material and on both upper and lower surfaces, when welding the intersection of the warp and weft, the inner core material is softened and melted. Welding can be performed by softening and melting the outer thermoplastic resin under mild heating conditions that do not allow it. Therefore, the core material of the warp and the weft does not substantially undergo thermal deterioration and maintains the excellent tensile strength of uniaxially drawn polypropylene or ultra-high-molecular-weight polyethylene, resulting in a net having extremely high strength.
[0011]
In particular, when the stretching ratio of the core material is 5 to 20 times, the tensile strength is significantly improved by molecular orientation, and the tensile strength is not reduced by fibrillation, so that an extremely high-strength net can be obtained.
[0012]
Further, when the thermoplastic resin for coating is an ethylene-vinyl acetate copolymer, the intersection of the warp and the weft can be welded by using any of the ultrasonic welding and the high frequency welding, and Since the melting point of the polymer is much lower than that of the core material, there is no fear that the core material is thermally degraded when coating the core material or welding the intersection.
[0013]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
FIG. 1 is a partial perspective view showing one embodiment of the high-strength net of the present invention, FIG. 2 is an enlarged sectional view of a warp or weft, and FIG. 3 is a partial perspective view showing another embodiment of the high-strength net of the present invention. FIG.
[0015]
The high-strength mesh A of the embodiment shown in FIG. 1 has a warp 1 and a weft 2 which intersect at right angles at a predetermined interval so as to form a square mesh, and a twist is given to the weft 2 so that the warp 1 and the weft 2 Is welded at the intersection 3 of The interval between the warp yarns 1 and the interval between the weft yarns 2 are not particularly limited. However, in order to obtain strength suitable for civil engineering nets, it is desirable to set the interval to about 20 to 150 mm.
[0016]
The mesh A gives the weft 2 a 180-degree twist in the clockwise direction between the warp yarns 1, but is not limited to this, and (180 × n) degrees of twist (where n is a positive number). Further, the twisting direction may be the counterclockwise direction, and the weft thread twisted clockwise and the weft thread twisted counterclockwise may be alternately arranged. When all the weft yarns 2 are twisted in the same direction, the warp yarns 1 are bent by the restoring force of the weft yarns 2 and a strong winding habit occurs in the net A, but the weft yarns having the opposite twisting directions are alternately arranged as described above. Then, since there is no curl in the net A, there is an advantage that the net A can be easily handled and laid.
[0017]
When such a high-strength mesh A is buried in the soil, the twisted weft yarns 2 mesh with the earth and sand to increase the contact frictional resistance. Does not slide easily, and landslides can be sufficiently suppressed.
In the net A of the above embodiment, the weft 2 is twisted, but the warp 1 may be twisted, or both the warp 1 and the weft 2 may be twisted. When twisting is applied to both the warp yarn 1 and the weft yarn 2, the contact friction resistance with the earth and sand is further increased, and the effect of suppressing the landslide is further increased.
[0018]
Further, in the mesh body A of the above embodiment, the weft yarn 2 is superposed on the warp yarn 1 and intersects at right angles. However, the weft yarn 2 may be superimposed under the warp yarn 1 and intersect at right angles. Like the net B of the embodiment shown in FIG. 3, the vertical relationship between the warp yarn 1 and the weft yarn 2 may be alternately reversed and overlapped at each intersection point 3 like a plain weave, and the intersection points 3 may be welded. . When the vertical relationship between the warp yarn 1 and the weft yarn 2 is alternately reversed at the intersection, the warp yarn 1 and the weft yarn 2 have a wavy line shape, so that there is an advantage that the contact friction resistance with earth and sand is further increased.
[0019]
1 and 3, the warp yarns 1 and the weft yarns intersect at right angles so as to form a square mesh, but the warp yarns 1 and the weft yarns 2 form a rhombic mesh. It may cross obliquely with respect to the length direction of the net.
[0020]
As shown in FIG. 2, the warp yarns 1 and the weft yarns 2 constituting the high-strength nets A and B are made of a thermoplastic resin 5 around a belt-shaped core material 4 made of uniaxially drawn polypropylene or ultra-high-molecular-weight polyethylene. Extruded coated tape.
[0021]
As the core material 4, a thickness obtained by uniaxially stretching a belt-like body obtained by melt-extruding polypropylene or ultra-high-molecular polyethylene 5 to 20 times (preferably 7 to 8 times) in a temperature range of 90 to 140 ° C. A band-shaped core material having a width of about 0.2 mm or more (preferably 0.5 to 0.7 mm) and a width of about 5 to 20 mm (preferably 10 to 15 mm) is suitably used. A core material having a draw ratio of less than 5 times has insufficient tensile strength due to insufficient molecular orientation by stretching, while a core material having a draw ratio of more than 20 times has a large decrease in strength due to fibrillation. Is also undesirable. Further, even if the core material has a draw ratio of 5 to 20 times, a core material having a thickness of less than 0.2 mm is not desirable because the absolute strength is still insufficient. In addition, what bundled or woven the fiber of the uniaxially drawn polypropylene or ultra high molecular polyethylene can also be used as the core material 4.
[0022]
As the thermoplastic resin 5 covering the core material 4, a resin having a melting point of 160 ° C. or less, preferably 140 ° C. or less and having good ultrasonic welding properties (for example, ethylene-vinyl acetate copolymer, low-density polyethylene, etc.), A resin having a high dielectric constant and good high-frequency welding properties (for example, polyvinyl chloride, ethylene-vinyl acetate copolymer, etc.) is preferably used. In particular, since the melting point of the ethylene-vinyl acetate copolymer is as low as 140 ° C. or less, the core material 4 is not damaged by heat during extrusion coating, and the copolymer has good ultrasonic welding properties and high-frequency welding properties. Therefore, even when the intersection of the warp 1 and the weft 2 is welded by either welding means, mild welding conditions can be adopted and the core material 4 can be welded without thermal deterioration, which is optimal.
[0023]
The coating thickness of the thermoplastic resin 5 is 0.1 mm or more, preferably about 0.5 to 0.8 mm. If the thickness is less than 0.1 mm, the welding strength at the intersection of the warp 1 and the weft 2 becomes insufficient. When a large hooking force is applied to the net, the intersections are peeled off and are easily collapsed. Further, it is desirable to form uneven wrinkles 5a on the surface of the thermoplastic resin 5 for preventing longitudinal tearing of the tape and improving the weldability.
[0024]
In the high-strength nets A and B of the embodiment shown in FIGS. 1 and 3, the coating tape obtained by extrusion-coating the thermoplastic resin 5 around the uniaxially stretched core material 4 as described above is used as the warp 1 and the weft 2. However, a covering tape in which a thermoplastic resin 5 is laminated and integrated on both upper and lower surfaces of a uniaxially stretched core material 4 may be used as the warp 1 and the weft 2. Further, a coating tape obtained by extrusion-coating or laminating a thermoplastic resin on the periphery or both upper and lower surfaces of an extruded unstretched polypropylene or ultra-high-molecular-weight polyethylene belt and then uniaxially stretching is applied to warp 1 and weft 2. You may use as.
[0025]
The intersection 3 between the warp 1 and the weft 2 may be welded by selecting either ultrasonic welding or high-frequency welding according to the type of the thermoplastic resin 5. That is, when the thermoplastic resin 5 has good ultrasonic welding properties, it is sufficient to perform ultrasonic welding, and when the thermoplastic resin 5 has good high-frequency welding properties, it is sufficient to perform high-frequency welding. In the case where the property is good, either ultrasonic welding or high frequency welding may be used. However, in any case, the thermoplastic resin 5 of the warp yarn and the weft yarn at the intersection 3 is firmly welded to each other by using a mild welding condition that does not cause thermal deterioration to the core material 4 of the warp yarn 1 and the weft yarn 2. is necessary.
[0026]
The high-strength nets A and B shown in FIGS. 1 and 3 form the thermoplastic resin 5 between the warp 1 and the weft 2 without thermally deteriorating the core 4 at the intersection 3 of the warp 1 and the weft 2 as described above. Since they are firmly welded, the core material 4 of the warp yarn 1 and the weft yarn 2 maintains the excellent tensile strength of uniaxially drawn polypropylene or ultra high molecular weight polyethylene as it is. Therefore, even if a large tension acts on the meshes A and B, there is no fear that the warp 1 and the weft 2 are cut and the meshes A and B are easily broken, and the welding strength of the intersection 3 is large. Even when the hooking force acts on the nets A and B, the intersection 3 does not separate and easily collapse.
[0027]
Next, more specific examples and comparative examples of the present invention will be described.
[0028]
[Example 1]
A 0.5 mm thick, 9 mm wide belt-shaped core material of polypropylene was uniaxially stretched at a stretching ratio of about 8 times. When the tensile strength of this band was measured, it was 118.3 kgf.
[0029]
Next, an ethylene-vinyl acetate copolymer (trade name: NUC31195, manufactured by Nippon Unica Co., Ltd.) was extrusion-coated to a thickness of 0.75 mm at a resin temperature of about 140 ° C. around the belt-shaped core material. A coated tape having a thickness of 2.0 mm was produced. When the tensile strength of this coated tape was measured, it was 119.0 kgf as shown in Table 1 below. When the strength retention of the coated tape was calculated based on the tensile strength (118.3 kgf) of the polypropylene core material, it was 100.6% as shown in Table 1 below. Not seen, slightly improved.
[0030]
This coated tape is made into a warp and a weft, crossed at right angles at an interval of 50 × 50 mm, and a 180 ° twist in the clockwise direction is given to the weft between the warp and the high-frequency welding device (Seidensha Electronics Co., Ltd.). Using a KW-3000TR (manufactured by Kogyo Co., Ltd.), the intersection of the warp and weft yarns was subjected to high frequency welding under the conditions of a frequency of 27 MHz, an output of 3 Kw, a transmission time of 3.0 seconds, and a pressure of 2 kgf / cm 2 , Body manufactured. When the tensile strength of the warp of this net was measured, it was 118.1 kgf as shown in Table 1 below. The strength retention of the warp after high-frequency welding was calculated based on the tensile strength (118.3 kgf) of the polypropylene band core material, as shown in Table 1 below, and was 99.8%. Substantially no decline was seen. Further, the welding strength at the intersections was measured by a hook tension test between the intersections and found to be as high as 38.2 kgf as shown in Table 1 below.
[0031]
[Example 2]
The coated tape produced in Example 1 was made into a warp and a weft, crossed at a right angle at an interval of 50 × 50 mm, and a 180 ° twist in the clockwise direction was given to the weft between the warp and the ultrasonic welding. Using an apparatus (SONOPET 4500P-207 manufactured by Seidensha Electronics Co., Ltd.), the conditions of an ultrasonic transmission time of 0.5 seconds, a pressurization time of 1.8 seconds, and a distance of 3.0 mm between the ultrasonic horn and the base were used. Below, the intersection of the warp and the weft was ultrasonically welded to produce a net.
[0032]
Then, when the tensile strength, strength retention, and welding strength of the intersections of the warp after ultrasonic welding of the mesh body were determined, as shown in Table 1 below, 116.4 kgf, 98.4%, 27 0.0kgf, the strength was not substantially reduced by ultrasonic welding, and the welding strength at the intersection was good.
[0033]
[Example 3]
Polyvinyl chloride (S1003 manufactured by Kanegafuchi Chemical Industry Co., Ltd.) was extrusion-coated to a thickness of 0.75 mm at a temperature of about 170 ° C. around the belt-shaped core material of polypropylene produced in Example 1. A coated tape having a thickness of 2.0 mm was produced. As shown in Table 1 below, the tensile strength of this coated tape was 106.3 kgf, and the strength retention rate based on the tensile strength (118.3 kgf) of the polypropylene strip core material was 89.9%. Was a little lower.
[0034]
This coating tape was made into a warp and a weft, and the intersection of the warp and the weft was welded by high-frequency welding in the same manner as in Example 1 except that the high-frequency transmission time was changed to 2 seconds to produce a net. Then, when the tensile strength, strength retention, and welding strength of the intersections of the warp after ultrasonic welding of this mesh body were determined, as shown in Table 1 below, they were 114.4 kgf, 96.7%, and 38, respectively. 0.0kgf, the strength decrease due to ultrasonic welding was extremely small, and the welding strength at the intersection was large.
[0035]
[Comparative example]
Example 1 except that the belt-shaped core material of polypropylene produced in Example 1 was used as warp and weft without resin coating, the ultrasonic transmission time was changed to 1 second, and the interval between the ultrasonic horn and the base was changed to 0.8 mm. Ultrasonic welding was performed in exactly the same manner as in Example 2 to produce a net.
[0036]
The tensile strength of the warp of this net after ultrasonic welding was measured to be 42.9 kgf, and the tensile strength before welding (118.3 kgf) was 36 as shown in Table 1 below. At 0.3%, the strength was reduced to about 1/3. When the welding strength at the intersection was measured in the same manner as in Example 1, it was extremely low at 5 kgf or less.
[0037]
[Table 1]
[0038]
From Table 1, all of the nets of Examples 1 to 3 in which the coated tape obtained by resin-coating the belt-shaped core material of polypropylene as the warp and the weft have extremely high strength retention of the warp after welding of 95% or more. It can be seen that the strength did not substantially decrease. And it turns out that the welding intensity | strength of an intersection part is as large as 25 kgf or more. In the case where the ethylene-vinyl acetate copolymer is used as the coating resin, the strength is substantially reduced even when the high frequency welding is performed as in Example 1 or the ultrasonic welding is performed as in Example 2. It can be seen that the intersection portion can be welded firmly without any problem.
[0039]
On the other hand, the mesh of the comparative example, which was prepared as a warp and a weft as it was without coating the polypropylene band-shaped core material with the resin, had a significantly reduced strength at a strength retention rate of 36.3% after welding, and the welding strength at the intersections. It can also be seen that peeling is easy at 5 kgf or less.
[0040]
【The invention's effect】
As is clear from the above description, the high-strength net of the present invention has a large contact friction resistance with earth and sand when buried in the soil, and thus can sufficiently suppress landslides caused by skidding of the earth and sand, and Since the tensile strength of the warp and weft yarns and the welding strength at the intersections are high, there is no danger of the net being easily torn or collapsed even if a large tension or hooking force acts on the net. It works.
[Brief description of the drawings]
FIG. 1 is a partial perspective view showing one embodiment of a high-strength net of the present invention.
FIG. 2 is an enlarged sectional view of a warp or a weft.
FIG. 3 is a partial perspective view showing another embodiment of the high-strength net of the present invention.
[Explanation of symbols]
A, B High strength net 1 Warp 2 Weft 3 Intersection 4 Core material 5 Thermoplastic resin
