JP3104712B2 - Manufacturing method of polyacetal hollow body - Google Patents
Manufacturing method of polyacetal hollow bodyInfo
- Publication number
- JP3104712B2 JP3104712B2 JP15370891A JP15370891A JP3104712B2 JP 3104712 B2 JP3104712 B2 JP 3104712B2 JP 15370891 A JP15370891 A JP 15370891A JP 15370891 A JP15370891 A JP 15370891A JP 3104712 B2 JP3104712 B2 JP 3104712B2
- Authority
- JP
- Japan
- Prior art keywords
- polyacetal
- resin
- gas
- mold cavity
- hollow
- 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
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/1703—Introducing an auxiliary fluid into the mould
- B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
- Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は、ポリアセタール樹脂を
使用して射出成形をするに際し、ヒケ等がなく、外観性
に優れ、且つソリのない寸法精度に優れたパイプ形状等
の中空成形品の製法に関する発明である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow molded article having a pipe shape and the like, which is free from sink marks, is excellent in appearance, and is excellent in dimensional accuracy without warpage when injection molding is performed using a polyacetal resin. This is an invention relating to a manufacturing method.
【０００２】[0002]
【従来の技術】ポリアセタール樹脂を通常の射出条件下
で射出成形すると、フローマーク、湯ジワ及び光沢ムラ
が生じ易い。これらの外観不良を避けるために金型温度
を高くする方法もあるが、ヒケを防止するには高圧射出
が必要であったり、また金型温度を高温にすると成形サ
イクルの点から問題が生ずる。更に、厚肉成形の場合
は、収縮寸法が大きく、冷却時に成形品がキャビティか
ら離れて伝熱が悪くなり、その結果成形サイクルが長く
なり且つ変形も生じやすいという問題点がある。2. Description of the Related Art When a polyacetal resin is injection-molded under ordinary injection conditions, flow marks, hot water wrinkles and gloss unevenness are likely to occur. Although there is a method of increasing the mold temperature to avoid these appearance defects, high-pressure injection is required to prevent sink marks, and if the mold temperature is increased, a problem arises in terms of the molding cycle. Further, in the case of thick-wall molding, there is a problem that the shrinkage dimension is large, the molded article separates from the cavity upon cooling, and the heat transfer is deteriorated. As a result, the molding cycle becomes longer and deformation tends to occur.
【０００３】他方、厚肉部分の内部にガスを圧入して中
空部を形成し、ヒケを防止する方法も知られているが
（ＧＰ 2,139,548）、この方法でポリアセタール成形品
のヒケを防止することはできるが、外観のフローマーク
を避けることは困難である。又、ガスを圧入しても中空
部の樹脂の肉厚が５ｍｍ以上であると樹脂の冷却速度が
遅くなり、自重によって溶融樹脂が垂れ下がり、偏肉と
なってソリなどの変形を生ずる場合がある。On the other hand, a method is known in which gas is press-fitted into a thick portion to form a hollow portion to prevent sink marks (GP 2,139,548). However, this method prevents sink marks in a polyacetal molded product. It is possible, but it is difficult to avoid the appearance of flow marks. Also, even if gas is injected, if the thickness of the resin in the hollow portion is 5 mm or more, the cooling rate of the resin becomes slow, and the molten resin hangs down due to its own weight, resulting in uneven thickness and deformation such as warpage. .
【０００４】[0004]
【発明が解決しようとする課題】本発明の目的は、ポリ
アセタール樹脂を射出成形する際に上記フローマーク、
湯ジワ及、光沢ムラ、ヒケ及びソリ等が生ずる課題を解
決し、外観良好なポリアセタール製中空体の製法を提供
することにある。SUMMARY OF THE INVENTION An object of the present invention is to provide a method for injection-molding a polyacetal resin.
An object of the present invention is to solve the problems of hot water wrinkles, uneven gloss, sink marks and warpage, and to provide a method for producing a polyacetal hollow body having a good appearance.
【０００５】[0005]
【課題を解決するための手段】本発明者らは上記課題を
解決するために鋭意検討した結果、ガスの注入による保
圧を利用した中空構造を有する厚肉のポリアセタール射
出成形品を製造する方法において、溶融ポリアセタール
を射出する際、金型キャビティの温度を制御することに
より金型表面温度を一定温度以上とし、更に厚肉中空部
の肉厚を一定厚み以下とすることにより、ヒケを防止で
き、且つ自重によって溶融樹脂が垂れ下がりを防止で
き、ソリ等のない寸法安定性に優れた成形品が得られる
ことを見いだし、本発明を完成した。Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a method for producing a thick polyacetal injection molded article having a hollow structure utilizing a holding pressure by gas injection. In injection of molten polyacetal, by controlling the temperature of the mold cavity to keep the mold surface temperature above a certain temperature, and by making the thickness of the thick hollow portion below a certain thickness, sink marks can be prevented. In addition, it has been found that the molten resin can be prevented from sagging due to its own weight, and a molded article excellent in dimensional stability without warping can be obtained, and the present invention has been completed.
【０００６】すなわち、本発明は、射出成形装置を使用
して金型キャビティ内の少なくとも一部を溶融ポリアセ
タール樹脂で充填した後、ガス体注入口より加圧ガス体
を圧入して中空構造を有する厚肉の射出成形品を製造す
る方法において、金型キャビティの表面温度１１０〜１
４０℃とし、かつ中空部の樹脂の平均肉厚を５ｍｍ以下
とするポリアセタール製中空部の製法に関する発明であ
る。次に本発明のポリアセタール製中空成形品の成形法
について説明する。本発明で使用する成形装置は、通常
の射出成形装置、金型キャビティに中空部を形成させる
際に使用するガス体注入装置を備えた装置である。金型
キャビティにおけるガス体の注入ノズルの位置は、溶融
樹脂流路と同一でも良く、又溶融樹脂流路とは異なった
位置でもよい。That is, the present invention has a hollow structure in which at least a part of a mold cavity is filled with a molten polyacetal resin by using an injection molding apparatus, and then a pressurized gas body is press-fitted from a gas body inlet. In the method for producing a thick injection molded product, the surface temperature of the mold cavity is set to 110-1.
The present invention relates to a method for producing a polyacetal hollow portion in which the temperature is set to 40 ° C. and the average thickness of the resin in the hollow portion is 5 mm or less. Next, a method for molding the hollow molded article made of polyacetal of the present invention will be described. The molding apparatus used in the present invention is an ordinary injection molding apparatus or an apparatus provided with a gas injection device used when forming a hollow portion in a mold cavity. The position of the gas injection nozzle in the mold cavity may be the same as the molten resin flow path, or may be a different position from the molten resin flow path.
【０００７】本発明におけるポリアセタール製中空部の
製法は以下に記す通りである。 (1) 先ず、射出成形装置から溶融樹脂を金型キャビティ
に流入させ、少なくとも金型キャビティのガス体注入ノ
ズル部を含む部分を溶融樹脂で充填する。ここでガス体
の流路に溶融樹脂が逆流しないように、該流路に逆止弁
を設けるか、該流路のノズル部を溶融樹脂が流入しない
程度の小さい径とする。本発明において、溶融ポリアセ
タールを金型キャビティ内へ射出する際の金型キャビテ
ィの表面温度を１１０〜１４０℃、好ましくは１２５〜
１４０℃の範囲にして制御する。[0007] The preparation of polyacetal hollow portion in the present onset Akira is as described below. (1) First, a molten resin is caused to flow into a mold cavity from an injection molding apparatus, and at least a portion of the mold cavity including a gas injection nozzle is filled with the molten resin. Here, in order to prevent the molten resin from flowing back into the flow path of the gas body, a check valve is provided in the flow path, or the nozzle portion of the flow path has a small diameter such that the molten resin does not flow. In the present invention, the surface temperature of the mold cavity at the time of injecting the molten polyacetal into the mold cavity is 110 to 140 ° C. , preferably 125 to 140 ° C.
It is controlled within the range of 140 ° C.
【０００８】ここにおいて、金型キャビティの表面温度
とは中空部を形成する金型キャビティ部分の金型表面の
測定温度をいう。上記金型キャビティの表面温度が１１
０℃以下では、ジェッテング、湯ジワ及び光沢ムラ等の
不都合が生ずる場合が多い。Here, the surface temperature of the mold cavity refers to a measured temperature of the mold surface in the mold cavity forming the hollow portion. The surface temperature of the mold cavity is 11
Below 0 ° C., inconveniences such as jetting, hot water wrinkling, and uneven gloss often occur.
【０００９】(2) 次にガス体注入装置より、加圧された
ガス体をガス注入口より注入する。注入するガス体の量
は、予め計量された一定圧のガス量を注入することがが
望ましい。ガス体を注入することにより、中空成形体が
形成されるが、該中空体の厚肉中空部の平均肉厚を５ｍ
ｍ以下とする。ポリアセタール製中空成形体の平均肉圧
を５ｍｍ以下とする様な製品形状では断面形状が円形の
場合は外径を５０ｍｍφ以下、偏平形状の場合は（長
辺）／（短辺）の長さの比を（７）／（１以上）の形状
にすることが望ましい。樹脂の射出量、及びガスの注入
方法は製品形状により異なり、一義的に定められない。
厚肉中空部の樹脂の平均肉厚が５ｍｍ以下とすることに
より、重力によって溶融樹脂が垂れ下がり、偏肉となる
こと、及びソリ等の変形を生じることを防止できるはか
りでなく、樹脂の冷却効果を高めることもできる。(2) Next, a pressurized gas body is injected from a gas inlet through a gas body injection device. It is desirable to inject a predetermined amount of gas at a predetermined pressure as the amount of gas to be injected. By injecting the gas body, a hollow molded body is formed, and the average thickness of the thick hollow portion of the hollow body is 5 m.
m or less. In the case of a product shape in which the average wall pressure of the polyacetal hollow molded body is 5 mm or less, the outer diameter is 50 mmφ or less when the cross-sectional shape is circular, and the length is (long side) / (short side) when the cross-sectional shape is flat. It is desirable that the ratio be a shape of (7) / (1 or more). The injection amount of the resin and the method of injecting the gas differ depending on the shape of the product and cannot be uniquely determined.
By setting the average thickness of the resin in the thick hollow portion to 5 mm or less, it is possible to prevent the molten resin from sagging due to gravity, causing uneven thickness, and preventing deformation such as warpage. Can also be increased.
【００１０】(3) ガス体の注入終了後、引続き中空成形
体内部のガス体圧力を保持して、射出された溶融樹脂を
冷却する。中空成形体内部のガス体圧力を保持すること
により、樹脂がキャビティ表面に押しつけられることに
より外観性が向上するばかりでなく、成形品のヒケを防
止することこともできる。(3) After the gas injection is completed, the injected molten resin is cooled while maintaining the gas pressure inside the hollow molded body. By maintaining the gas pressure inside the hollow molded body, not only the appearance is improved by pressing the resin against the cavity surface, but also the sink of the molded product can be prevented.
【００１１】(4) 樹脂が冷却された後、離型する。通常
のポリアセタール樹脂を射出成形して、成形品を量産す
る際の金型温度は６０〜１００℃前後であるが、本発明
の方法により、１１０℃以上の金型表面温度でも厚肉品
の量産が可能となる。(4) After the resin is cooled, it is released from the mold. The mold temperature for mass production of molded products by injection molding of ordinary polyacetal resin is around 60 to 100 ° C. However, the method of the present invention enables mass production of thick products even at mold surface temperatures of 110 ° C or more. Becomes possible.
【００１２】[0012]
【発明の効果】本発明のポリアセタール製中空成形体の
製法を採用することにより、成形時の金型キャビティ表
面温度が１１０℃以上でも成形可能となり、得られた成
形品の外観性が改良されるばかりでなく、ヒケの防止、
及び樹脂の垂れ下がり、中空部の偏肉を防止することが
できる。According to the method for producing a hollow molded article made of polyacetal of the present invention, molding can be performed even at a mold cavity surface temperature of 110 ° C. or more at the time of molding, and the appearance of the obtained molded article is improved. Not only the prevention of sink marks,
Further, it is possible to prevent the resin from sagging and uneven thickness in the hollow portion.
【００１３】実施例１ 長径２５ｍｍ、短径１８ｍｍのほぼ楕円形の棒状製品
を、ポリアセタール（三菱瓦斯化学（株）製、商品名：
エピタール F30-02 黒）を用い、金型表面温度１２５
℃、樹脂温度２１０℃にて成形した。まず、金型キャビ
ティ内に未充填状態の量を射出し、窒素ガスをキャビテ
ィ端部に開口するようにセットされたガスノズルから樹
脂内部に注入加圧して、キャビティ未充填部分にも樹脂
を充填して中空化した。３分後に窒素ガスを大気中に開
放し、製品を取り出した。成形品は平均で約４ｍｍの肉
厚を残し中空化され、ヒケもなく、光沢も良好であっ
た。Example 1 An approximately elliptical rod-shaped product having a major axis of 25 mm and a minor axis of 18 mm was used as a polyacetal (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name:
Mold surface temperature of 125 using Epitar F30-02 black)
And a resin temperature of 210 ° C. First, an unfilled amount is injected into the mold cavity, nitrogen gas is injected into the resin from a gas nozzle set to open at the end of the cavity, and then pressurized. And hollowed out. After 3 minutes, the nitrogen gas was released to the atmosphere, and the product was taken out. The molded article was hollowed out with an average thickness of about 4 mm, had no sink marks, and had a good gloss.
【００１４】比較例１ 金型表面温度を１００℃にした以外は、実施例と同様に
成形した。樹脂の先端に近い方に帯状のフローマークが
残り、光沢も劣った。金型の転写性も不良であった。Comparative Example 1 Molding was carried out in the same manner as in the Example except that the surface temperature of the mold was 100 ° C. A band-like flow mark remained near the tip of the resin, and the gloss was poor. The transferability of the mold was also poor.
【００１５】比較例２ ガスを注入しない以外は比較例１と同様に成形した。取
り出した成形品は内部が固化していないため、離型時に
エジェクターピンで変形し、取り出し後に大きくヒケが
生じた。Comparative Example 2 Molding was performed in the same manner as in Comparative Example 1 except that no gas was injected. Since the inside of the molded product taken out was not solidified, it was deformed by the ejector pin at the time of release from the mold, and a large sink occurred after being taken out.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 大槻 良治 三重県四日市市日永東２丁目４番16号 三菱瓦斯化学株式会社 四日市工場内 審査官 加藤 友也 (56)参考文献 特開 平２−223420（ＪＰ，Ａ) 特公 昭58−40504（ＪＰ，Ｂ２) (58)調査した分野(Int.Cl.7，ＤＢ名) B29C 45/00 - 45/84 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryoji Otsuki 2-4-1-16 Hinagahigashi, Yokkaichi-shi, Mie Examiner, Mitsubishi Gas Chemical Co., Ltd. Yokkaichi Plant Tomoya Kato (56) References JP-A-2-2 223420 (JP, A) JP 58-40504 (JP, B2) (58) Fields investigated (Int. Cl. 7 , DB name) B29C 45/00-45/84
Claims (1)
内の少なくとも一部を溶融ポリアセタール樹脂で充填し
た後、ガス体注入口より加圧ガス体を圧入して中空構造
を有する厚肉の射出成形品を製造する方法において、金
型キャビティの表面温度を１１０〜１４０℃とし、かつ
中空部の樹脂の平均肉厚を５ｍｍ以下とするポリアセタ
ール製中空体の製法。After filling at least a part of a mold cavity with a molten polyacetal resin by using an injection molding apparatus, a pressurized gas body is press-fitted from a gas body injection port to inject a thick wall having a hollow structure. A method for producing a molded article, comprising: producing a polyacetal hollow body having a surface temperature of a mold cavity of 110 to 140 ° C. and an average thickness of a resin in a hollow portion of 5 mm or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15370891A JP3104712B2 (en) | 1991-05-30 | 1991-05-30 | Manufacturing method of polyacetal hollow body |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15370891A JP3104712B2 (en) | 1991-05-30 | 1991-05-30 | Manufacturing method of polyacetal hollow body |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05138678A JPH05138678A (en) | 1993-06-08 |
| JP3104712B2 true JP3104712B2 (en) | 2000-10-30 |
Family
ID=15568366
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15370891A Expired - Fee Related JP3104712B2 (en) | 1991-05-30 | 1991-05-30 | Manufacturing method of polyacetal hollow body |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3104712B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2741648B2 (en) * | 1993-05-20 | 1998-04-22 | 旭化成工業株式会社 | Polyacetal resin molded product |
| JPH08140881A (en) * | 1994-11-22 | 1996-06-04 | Mitsubishi Gas Chem Co Inc | Synthetic resin shower molded product and molding method thereof |
| EP0806272B1 (en) * | 1994-11-25 | 2002-06-05 | Asahi Kasei Kabushiki Kaisha | Improved injection molding method for producing hollow articles and mold used for said method |
| JP6490570B2 (en) * | 2015-12-14 | 2019-03-27 | 旭化成株式会社 | Polyoxymethylene resin molded body and method for producing the same |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5840504B2 (en) | 2012-01-11 | 2016-01-06 | 株式会社ミツバ | Electric motor |
-
1991
- 1991-05-30 JP JP15370891A patent/JP3104712B2/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5840504B2 (en) | 2012-01-11 | 2016-01-06 | 株式会社ミツバ | Electric motor |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05138678A (en) | 1993-06-08 |
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