JP3033598B2 - Injection molding of ultra high molecular weight polyethylene - Google Patents
Injection molding of ultra high molecular weight polyethyleneInfo
- Publication number
- JP3033598B2 JP3033598B2 JP24975290A JP24975290A JP3033598B2 JP 3033598 B2 JP3033598 B2 JP 3033598B2 JP 24975290 A JP24975290 A JP 24975290A JP 24975290 A JP24975290 A JP 24975290A JP 3033598 B2 JP3033598 B2 JP 3033598B2
- Authority
- JP
- Japan
- Prior art keywords
- mold
- cavity
- molecular weight
- resin
- injection
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
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- Injection Moulding Of Plastics Or The Like (AREA)
Description
【発明の詳細な説明】 （産業上の利用分野） 本発明は超高分子量ポリエチレンの射出成形法に関
し、得に耐摩耗性、耐衝撃性等の性質を要求される脱穀
用受網等各種製品の射出成形品の成形法にかかるもので
ある。Description: TECHNICAL FIELD The present invention relates to an injection molding method for ultra-high molecular weight polyethylene, and various products such as a threshing receiving net which are required to have properties such as abrasion resistance and impact resistance. And a method for molding an injection molded article.
（従来の技術） 超高分子量ポリエチレンは流動性が悪いため、従来よ
り射出成形法による製品の製造は難しいものとされ、一
般には圧縮成形法、押出成形法による製品の製造が成さ
れていた。これらの成形法にあっては金型の加熱・冷却
等を繰り返さなければならず、成形のサイクルが長く熱
効率も良くなかった。(Prior Art) Since ultra-high molecular weight polyethylene has poor fluidity, it has been conventionally difficult to produce products by an injection molding method. In general, products have been produced by a compression molding method or an extrusion molding method. In these molding methods, heating and cooling of the mold had to be repeated, and the molding cycle was long and the thermal efficiency was not good.
しかるにこの成形法の改良法として特公昭57−30067
号、特開昭61−262113号にて改良手段の技術が提案され
ている。However, as an improved method of this molding method, Japanese Patent Publication No. 57-30067
And Japanese Unexamined Patent Publication No. Sho 61-262113 proposes a technique of improving means.
前者においては、例えば製品が格子状等を有する構造
のものにあっては、樹脂が非常に流れにくく、このため
ゲートを多数設置しなければキャビテイ内に充填不足の
部分が発生してしまい良好な成形品は得られない。In the former case, for example, when the product has a lattice-like structure, the resin is very difficult to flow, so if a large number of gates are not provided, insufficient filling will occur in the cavity and a good result will be obtained. No molded product is obtained.
特にホットランナーを使用した場合にはホットランナ
ー部のゲート一個当たり50万円前後の製作費がかかり、
このゲート数を減らすことは成形品のコストダウンの条
件である。Especially when a hot runner is used, it costs about 500,000 yen per hot runner gate,
Reducing the number of gates is a condition for reducing the cost of the molded product.
また後者にあっては、二次射出速度を一次射出速度よ
りも早く射出させることになっているが、製品の形状が
前記したような樹脂の流れの悪い格子状の形状等を有す
るものにあっては、キャビテイ内への樹脂の充填が進ん
だ時点で射出速度を高めることは一般の射出成形機では
不可能なことである。In the latter case, the secondary injection speed is set to be faster than the primary injection speed. However, the shape of the product has a lattice shape or the like in which the flow of resin is poor as described above. In other words, it is impossible with a general injection molding machine to increase the injection speed when the filling of the cavity into the resin has progressed.
（発明が解決しようとする課題） 本発明は生産性向上を目的とする超高分子量ポリエチ
レンの射出成形法を提供するものであり、キャビテイが
複雑な形状を有していても十分実施可能な成形法であ
る。(Problem to be Solved by the Invention) The present invention provides an injection molding method of ultra-high molecular weight polyethylene for the purpose of improving productivity, and the molding can be performed sufficiently even if the cavity has a complicated shape. Is the law.
（課題を解決する手段） 本発明は以上の課題を解決するために次のような手段
を採用したものである。(Means for Solving the Problems) The present invention employs the following means to solve the above problems.
即ち、金型の可動側を予め型締め終了時におけるキャ
ビテイ容積の0.9〜1.1倍にセットし、当該成形キャビテ
イ内へ超高分子量ポリエチレンをキャビテイ入口での剪
断速度が15000sec-1以下で、好ましくは10sec-1以上の
ほぼ一定の速度で射出し、前記金型の可動側を型締め終
了時におけるキャビテイ容積の1.1〜1.3倍に射出樹脂の
押圧力によって順次後退させ、その後射出成形機の弁を
閉じ、次いで金型の可動側を所定のキャビテイ容積にま
で樹脂を押圧して型締めを終了し成形する超高分子量ポ
リエチレンの射出成形法である。That is, the movable side of the mold is set to 0.9 to 1.1 times the cavity volume at the end of the mold clamping in advance, and the ultrahigh molecular weight polyethylene is sheared at the cavity entrance at a shear rate of 15000 sec -1 or less in the molding cavity, preferably. Inject at an almost constant speed of 10 sec -1 or more, and gradually move the movable side of the mold by 1.1 to 1.3 times the cavity volume at the end of mold clamping by the pressing force of the injection resin, and then open the valve of the injection molding machine. This is an injection molding method of ultra-high molecular weight polyethylene in which the resin is pressed to a predetermined cavity volume on the movable side of the mold after the mold is closed and the mold is closed and molded.
ここで超高分子量ポリエチレンとしては分子量が約10
0万〜1000万程度の分子量のものを言い、これを主体と
して汎用ポリエチレン、ポリプロピレン、EVA等のオレ
フィン系樹脂を混合したものが含まれる。Here, the molecular weight of the ultra-high molecular weight polyethylene is about 10
It refers to those having a molecular weight of about 100,000 to 10,000,000, and includes those obtained by mixing olefin resins such as general-purpose polyethylene, polypropylene, and EVA.
ここで言う超高分子量ポリエチレン樹脂は一般の樹脂
と比べて熱を加えても溶融しにくく、このためキャビテ
イ内に射出しても空気を含んだ状態で充填されることに
なる。The ultrahigh molecular weight polyethylene resin referred to here is less likely to be melted even when heat is applied than a general resin, so that even if injected into the cavity, it is filled with air.
このために充填物中よりこの空気を追い出す必要があ
るもので、従ってキャビテイの一部を可動型としてお
き、この可動型の可動範囲を1.1〜1.3倍に設定するので
ある。特にかかる可動設定のために樹脂内からの空気の
追い出しと樹脂同士の加圧による融合を促進するもので
あって、この圧縮代が小さすぎると正規の厚さに対して
薄い成形品が出来てしまい、大きすぎると厚い成形品と
なってしまうので、かかる範囲内で他の射出条件との関
係で調整されることになる。For this purpose, it is necessary to expel this air from the packing, so that a part of the cavity is made movable, and the movable range of this movable type is set to 1.1 to 1.3 times. In particular, for such a movable setting, it expels air from inside the resin and promotes fusion by pressurization of the resins. If the compression allowance is too small, a molded product thinner than the normal thickness can be formed. If the size is too large, the molded product becomes thicker. Therefore, the size is adjusted in such a range in relation to other injection conditions.
（作用） 本発明は射出樹脂の剪断速度を15000sec-1以下に押さ
え、射出工程で金型のキャビテイ容積をコントロールす
ると共に、金型の可動側を所定の位置に閉じて型締めす
るものであって、例えば樹脂の充填完了直前に型締め工
程即ちキャビテイ内樹脂の圧縮に入り、その後射出終了
後弁を閉じ型締め（樹脂圧縮）を継続するもので、本発
明の方法によればゲート数を少なくすることができ、通
常の射出成形機で成形可能となったのである。(Function) The present invention controls the shear rate of the injection resin to 15000 sec -1 or less, controls the cavity volume of the mold in the injection process, and closes the movable side of the mold at a predetermined position to clamp the mold. Thus, for example, immediately before the completion of the filling of the resin, a mold clamping step, ie, compression of the resin in the cavity is started, and after the injection is completed, the valve is closed to continue the mold clamping (resin compression). According to the method of the present invention, the number of gates is reduced. It was possible to reduce the number, and it became possible to mold with a normal injection molding machine.
以下図面をもって本発明の好ましい例について更に詳
細に説明する。Hereinafter, preferred examples of the present invention will be described in more detail with reference to the drawings.
第１図は本発明の射出時の状態を示し、第２図は可動
型を押すことによりキャビテイ内に充填された樹脂を圧
縮している型締め終了時の状態を示している。FIG. 1 shows a state at the time of injection according to the present invention, and FIG. 2 shows a state at the end of mold clamping in which a resin filled in a cavity is compressed by pressing a movable mold.
金型Ａは固定型１と可動型２よりなり、固定型１には
ランナー部３とキャビテイＣに通じるゲート４が備えら
れている。そして射出装置Ｂにはバレル５内にスクリュ
ー６が配置され、樹脂を射出するノズル部７には開閉弁
８が備えられている。符号t1、t2は固定型１と可動型２
の隙間を表し、t1は可動型２が最大に後退した場合の隙
間であって、t2は型締め終了時の所定のキャビテイを保
持した際の両型の隙間である。The mold A includes a fixed mold 1 and a movable mold 2. The fixed mold 1 is provided with a runner 3 and a gate 4 communicating with the cavity C. A screw 6 is disposed in a barrel 5 of the injection device B, and an opening / closing valve 8 is provided in a nozzle portion 7 for injecting resin. Symbols t 1 and t 2 are fixed type 1 and movable type 2
Represents the clearance, t 1 is a gap when the movable die 2 is retracted to the maximum, t 2 is the gap between both types at the time of holding the predetermined cavity during the mold clamping completion.
先ず、型締め終了時におけるキャビテイ容積Ｖ即ち成
形品取り出し時のキャビテイ容積に対して0.9〜1.1倍と
なるように可動型２の位置をセットする。First, the position of the movable mold 2 is set so as to be 0.9 to 1.1 times the cavity volume V at the end of the mold clamping, that is, the cavity volume at the time of removing the molded product.
そして、その射出装置ノズル部７に設けた開閉弁８を
開き、バレル５内の溶融ポリエチレンをキャビテイＣ内
に剪断速度15000sec-1以下の速度で射出する。Then, the on-off valve 8 provided on the injection device nozzle portion 7 is opened, and the molten polyethylene in the barrel 5 is injected into the cavity C at a shear rate of 15000 sec -1 or less.
この射出中に、可動型２をキャビティ内に射出された
樹脂の押圧力により型締め終了時におけるキャビテイ容
積Ｖの1.1〜1.3倍になるまで後退させる。During the injection, the movable mold 2 is retracted by the pressing force of the resin injected into the cavity until the cavity volume V becomes 1.1 to 1.3 times the cavity volume V at the end of the mold clamping.
次いで射出が終了する直前に可動型２を前進即ち前記
ポリエチレンを圧縮し始め、その後素早く射出工程を完
了すると共に開閉弁８を閉じる。この間は可動型２は樹
脂を圧縮させた状態で固定型１と共に所定のキャビテイ
容積Ｖにし、即ち隙間t2迄圧縮し、その後冷却させて成
形品を金型内より取り出すことになる。Next, just before the injection is completed, the movable die 2 is advanced, that is, the polyethylene is started to be compressed. Thereafter, the injection process is completed quickly and the on-off valve 8 is closed. During this period the predetermined cavity volume V with the fixed mold 1 while the movable die 2 is compressed resin, i.e. compressed until the gap t 2, the molded article will be taken out from the mold and then allowed to cool.
この場合、可動型２の加圧直前におけるキャビテイ容
積が型締め終了時におけるキャビテイ容積Ｖに対して1.
3倍を越えると成形品の正規な厚さが得られなくなり、
正規の厚さを得ようと圧縮力を増すと、過圧縮を起こし
て成形品の物性が著しく低下する結果となってしまい好
ましくない。In this case, the cavity volume immediately before pressurization of the movable mold 2 is equal to the cavity volume V at the end of the mold clamping by 1.
If it exceeds 3 times, the regular thickness of the molded product cannot be obtained,
If the compressive force is increased in order to obtain a regular thickness, overcompression occurs and the physical properties of the molded article are remarkably reduced, which is not preferable.
なお、可動型２は通常は型締め終了後のキャビテイ容
積Ｖの0.9〜1.1倍の位置にセッされ、これが充填された
樹脂によって押圧されて1.1〜1.3倍にまでキャビテイ容
積が拡大する方法が取られるのである。The movable mold 2 is usually set at a position 0.9 to 1.1 times the cavity volume V after the mold clamping is completed, and is pressed by the filled resin to expand the cavity volume to 1.1 to 1.3 times. It is done.
また、開閉弁８は射出装置Ｂのノズル部７に設けるの
が通常ではあるが、ランナー部３のノズル付近に設けて
も良い。The on-off valve 8 is usually provided at the nozzle 7 of the injection device B, but may be provided near the nozzle of the runner 3.
（実施例） 一辺9mmの正方形の穴を格子状に形成する厚さ4mmの脱
穀用受網（350m×400mm）を成形した。穴の数は554個
で、ゲートの数は12個である。(Example) A threshing receiving net (350 m x 400 mm) having a thickness of 4 mm and forming square holes each having a side of 9 mm in a lattice shape was formed. The number of holes is 554 and the number of gates is 12.
超高分子量ポリエチレンとして三井石油化学社製ハイ
ゼックスミリオン（分子量約300万）を使用し、成形条
件として射出シリンダのノズル部７の圧力を1500kgf/cm
2、射出樹脂の剪断速度10000sec-1をもってキャビテイ
Ｃ内に射出充填した。射出樹脂温度は200〜300＝Ｃであ
った。Using Hi-Zex Million (molecular weight: about 3 million) manufactured by Mitsui Petrochemical Co., Ltd. as ultra-high molecular weight polyethylene, the pressure of the nozzle 7 of the injection cylinder was set to 1500 kgf / cm as molding conditions.
2. Cavity C was injected and filled at a shear rate of 10,000 sec -1 of the injected resin. The injection resin temperature was 200-300 = C.
ほぼ樹脂の充填完了時に、受網の厚さ方向に可動型２
が1mm充填圧力によって移動していた。When the resin is almost completely filled, the movable mold 2
Was moved by the 1 mm filling pressure.
その後開閉弁８を閉じ、この可動型２を製品面にして
圧縮圧力100kgf/cm2にて所定のキャビテイ容積Ｖにまで
可動型２を戻し、圧縮時間120経過後に成形品を型内よ
り取り出した。Thereafter, the on-off valve 8 is closed, and the movable mold 2 is returned to a predetermined cavity volume V at a compression pressure of 100 kgf / cm 2 with the movable mold 2 as a product surface, and the molded product is taken out from the mold after a lapse of 120 compression times. .
なお、ゲート４はダイレクトゲートを使用し、ランナ
ー部３はホットランナーを使用した。In addition, the gate 4 used the direct gate, and the runner part 3 used the hot runner.
得られた成形品は樹脂の充填不良のない耐摩耗性、強
伸度の良好な成形品が得られた。The molded article obtained was a molded article having good abrasion resistance and strong elongation without resin filling failure.
（効果） 以上本発明の成形法によれば、流動性の余り良くない
超高分子量ポリエチレンであっても、例えば小さな格子
状の網目を有する脱穀装置の受網等の複雑で大型形状物
を一般の射出成形機を利用して、最小限のゲート数で充
填不良を起こすことなく十分な製品を得ることができる
ことになったもので、その産業上のメリットは大きい。(Effects) As described above, according to the molding method of the present invention, even a very high-molecular-weight polyethylene having a poor flowability can be used to form a complicated and large-sized object such as a receiving screen of a threshing device having a small lattice-like mesh. By using this injection molding machine, sufficient products can be obtained with a minimum number of gates without causing defective filling, and the industrial advantage is great.
第１図は本発明の射出時の状態を示し、第２図は可動型
を押すことによりキャビテイ内に充填された樹脂を圧縮
している型締め終了時の状態を示す。 Ａ……金型、Ｂ……射出装置、 Ｃ……キャビテイ、 １……固定型、２……可動型、 ３……ランナー、４……ゲート、 ５……バレル、６……スクリュー、 ７……ノズル部、８……開閉弁、 t1、t2……固定型と可動型の隙間。FIG. 1 shows a state at the time of injection of the present invention, and FIG. 2 shows a state at the end of mold clamping in which a resin filled in a cavity is compressed by pushing a movable mold. A: Mold, B: Injection device, C: Cavity, 1 ... Fixed type, 2 ... Movable type, 3 ... Runner, 4 ... Gate, 5 ... Barrel, 6 ... Screw, 7 …… Nozzle part, 8 …… On-off valve, t 1 , t 2 … Gap between fixed type and movable type.
Claims (1)
キャビテイ容積の0.9〜1.1倍にセットし、当該成形キャ
ビテイ内へ超高分子量ポリエチレンをキャビテイ入口で
の剪断速度が15000sec-1以下のほぼ一定の速度で射出
し、前記金型の可動側を型締め終了時におけるキャビテ
イ容積の1.1〜1.3倍に射出樹脂の押圧力によって順次後
退させ、次いで金型の可動側を所定のキャビテイ容積に
まで樹脂を押圧して型締めを終了し、成形することを特
徴とする超高分子量ポリエチレンの射出成形法。1. The movable side of a mold is set in advance to 0.9 to 1.1 times the volume of a cavity at the end of mold clamping, and ultrahigh molecular weight polyethylene is introduced into the molding cavity at a shear rate of 15000 sec -1 or less at a cavity entrance. Injecting at a substantially constant speed, the movable side of the mold is sequentially retracted by the pressing force of the injection resin to 1.1 to 1.3 times the cavity volume at the end of mold clamping, and then the movable side of the mold is brought to a predetermined cavity volume. An injection molding method for ultra-high molecular weight polyethylene, characterized in that the resin is pressed until the mold is closed and the molding is completed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24975290A JP3033598B2 (en) | 1990-09-19 | 1990-09-19 | Injection molding of ultra high molecular weight polyethylene |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24975290A JP3033598B2 (en) | 1990-09-19 | 1990-09-19 | Injection molding of ultra high molecular weight polyethylene |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04128022A JPH04128022A (en) | 1992-04-28 |
| JP3033598B2 true JP3033598B2 (en) | 2000-04-17 |
Family
ID=17197697
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24975290A Expired - Fee Related JP3033598B2 (en) | 1990-09-19 | 1990-09-19 | Injection molding of ultra high molecular weight polyethylene |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3033598B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07137091A (en) * | 1993-09-20 | 1995-05-30 | Mitsubishi Gas Chem Co Inc | Production of molded product having pattern thereon |
| JP4148583B2 (en) * | 1999-01-21 | 2008-09-10 | 積水化学工業株式会社 | Method for producing difficult-to-mold resin molded body |
-
1990
- 1990-09-19 JP JP24975290A patent/JP3033598B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04128022A (en) | 1992-04-28 |
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