JPS585772B2 - How do I know what to do? - Google Patents

Description

【発明の詳細な説明】 本発明は透明性の優れた二軸配向ポリプロピレン樹脂中
空成形品の吹込成形方法に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blow molding method for a biaxially oriented polypropylene resin blow molded product having excellent transparency.

本発明は特に同樹脂の筒状の予備成形品（パリソン）を
融点以下で吹込成形する方法に関するものである。The present invention particularly relates to a method for blow molding a cylindrical preform (parison) of the same resin at a temperature below its melting point.

結晶性の合成樹脂を融点以下で伸ばすと、その方向に分
子配向が生じ強度が大きくなる。When a crystalline synthetic resin is stretched below its melting point, molecular orientation occurs in that direction, increasing its strength.

ポリプロピレンの如き材料では融点以上の温度で吹込成
形を行なっても透明にはならないが、２軸延伸を行なう
さ機械的強度が大きくなる他に透明性が非常によくなる
。A material such as polypropylene does not become transparent even if blow molding is performed at a temperature above its melting point, but biaxial stretching increases mechanical strength and improves transparency.

そのため筒状のパリソンを融点以下で吹込成形すると、
特に降伏点のある温度状態では、通常の吹込成形（パリ
ソンが融点引上で行なわれる）の気体圧力では膨張が開
始し難く、かといって過大な圧力の気体を吹込むとパリ
ソンは側方に膨張するのみで製品にならない。Therefore, when a cylindrical parison is blow-molded below its melting point,
Particularly in a temperature state where the yield point is present, it is difficult for the parison to start expanding under the gas pressure of normal blow molding (where the parison is made by raising its melting point); It only expands and does not become a product.

そこで筒状のパリソンの一端を挾持するか、その底部を
ロツド等で軸方向の伸長を充分行なった後、圧力気体を
送入し吹き膨らます方法等が提案されている。Therefore, methods have been proposed in which one end of the cylindrical parison is clamped or the bottom of the parison is stretched sufficiently in the axial direction using a rod or the like, and then pressurized gas is introduced to inflate the parison.

この方法によってポリプロピレン樹脂から瓶を多数成形
してみた結果、瓶の壁に縦方向のこまかい亀裂が無数に
生じて、それ自体好ましくないし、透明性をも低下させ
る欠点がみられた。When a large number of bottles were molded from polypropylene resin using this method, numerous fine vertical cracks were formed on the walls of the bottles, which was not desirable in itself and also had the disadvantage of reducing transparency.

本発明者等はこの欠点を含めて成形法自体の改善の試み
の結果、パリソンの吹膨が容易で、歩留りもよく、上記
欠点を解消して透明で優美な、しかも強度のある新しい
ポリプロピレン樹脂の二軸延伸吹込成形方法を開発する
に到った。As a result of attempts to improve the molding method itself, including these drawbacks, the present inventors have discovered a new polypropylene resin that is transparent, elegant, and strong, eliminating the above drawbacks and making parison blowing easier and yielding better. We have developed a biaxial stretch blow molding method.

本発明は融点以下の筒状のポリプロピレン樹脂中空成形
用予備成形品を中空成形用割金型で挾持して、該パリシ
ンに軸方向の機械的伸長を加えて吹込成形する方法に於
いて、パリソンに加える軸方向の機械的伸長を該樹脂の
降伏点を越えネツキングの始まる未然に止め、その間若
しくはしかる後に圧力気体により吹膨成形を行なうポリ
プロピレン樹脂の二軸配向吹込成形法である。The present invention is a method for blow-molding a cylindrical polypropylene resin preform for blow molding having a temperature below the melting point by sandwiching it between split molds for blow molding and applying mechanical elongation in the axial direction to the parisin. This is a biaxially oriented blow molding method for polypropylene resin, in which mechanical elongation in the axial direction applied to the resin is stopped to prevent necking from exceeding the yield point of the resin, and blow molding is performed using pressurized gas during or after that time.

融点以下のパリソンに圧力気体を送入しても、軸方向へ
の伸長する分力が小さいため機械的に伸長しなければな
らない。Even if pressurized gas is introduced into the parison at a temperature below its melting point, the force required to stretch it in the axial direction is small, so it must be stretched mechanically.

しかし従来のように成形品を軸方向に金型底端までの全
長を伸長したのでは透明性のよい塩化ビニル樹脂や塩化
ビニリデン樹脂等では問題がないが、ポリプロピレン樹
脂では前記の欠点を生ずる。However, if the molded product is extended along its entire length in the axial direction to the bottom end of the mold as in the past, there is no problem with highly transparent vinyl chloride resin or vinylidene chloride resin, but polypropylene resin has the above-mentioned drawbacks.

パリソンの軸方向に与える機械的伸長力は軸方向の気体
による伸長分力を補なうものであるが、ネツキング延伸
開始点の前までは機械的手段のみでもよく、同時に圧力
気体を供給するときはそれらの合力が材料の降伏点を越
えるように行なわれる。The mechanical stretching force applied in the axial direction of the parison is to supplement the stretching force due to the gas in the axial direction, but up to the start point of netting stretching, only mechanical means may be used, and when pressurized gas is supplied at the same time. is carried out so that the resultant force exceeds the yield point of the material.

パリソンの圧力気体による二軸配向はパリソンの軸方向
の伸長と同時を含め降伏点をわずかに過ぎる初期の段階
に行なうのが好ましい。Biaxial orientation of the parison by means of pressurized gas is preferably carried out at an early stage just past the yield point, including simultaneously with the axial elongation of the parison.

そしてパリソンが軸方向の機械的伸長によってネツキン
グを起す未然に圧力気体を主体とする二軸配向への移行
を済ませてしまうのが好ましい。It is preferable that the parison completes the transition to a biaxial orientation mainly using pressurized gas before netting occurs due to mechanical elongation in the axial direction.

ポリプロピレンのパリソンを軸方向への伸長を行なって
から吹膨した成形品の、軸方向への伸長と成形品のこま
かい亀裂の発生との関係を調べた結果、パリソンの伸長
がネツキング開始点を越え伸長すると、その後圧力気体
で全方向に吹膨しても亀裂が発生し、パリソンのもとの
長さに対して伸長する割合が大きくなるほど亀裂の発生
が甚しくなることがわかった。As a result of investigating the relationship between the axial elongation and the occurrence of fine cracks in the molded product of a molded product in which a polypropylene parison was expanded in the axial direction and then blown, it was found that the elongation of the parison exceeded the netting starting point. It was found that when the parison is stretched, cracks occur even if the parison is subsequently blown in all directions with pressurized gas, and the cracks become more severe as the ratio of stretching to the original length of the parison increases.

第３図のグラフに示すごとく、成形に用いる材料を成形
時と同じ温度で引張力と伸びの関係を表わした際、始め
引張力に比例し材料が伸びる区間ａがあり、降伏点Ａと
呼ばれるピークを過ぎると材料の断面積は減少しやがて
ネックと呼ばれるくびれが生じ、引張に要する力がやや
減少しその後はなだらかな線部分Ｃを描く引張力で試験
片のみが伸びて行く。As shown in the graph in Figure 3, when we express the relationship between tensile force and elongation of a material used for forming at the same temperature as during forming, there is a section a where the material initially stretches in proportion to the tensile force, which is called the yield point A. After passing the peak, the cross-sectional area of the material decreases, and eventually a constriction called a neck occurs, the force required for tension decreases slightly, and after that, only the test piece stretches with the tensile force that draws a gentle line C.

ネツキング開始点とは引張力と伸びのカーブが降伏点を
過ぎた区間ｂとなだらかなネツキング延伸部分Ｃとが急
激に変曲する点Ｃを呼称するものとする。The netting start point is the point C where the tensile force and elongation curve sharply changes the section b past the yield point and the gentle netting stretching section C.

降伏点を過ぎると材料は分子配向が始まり、ネツキング
開始点では材料が局部的に分子配向がほぼ完了した状態
になり、ネツキング延伸部分Ｃでは材料はネツクのくび
れがきつくはならずネック領域が伸びてネツキング延伸
が行なわれて行く。After passing the yield point, the material begins to have molecular orientation, and at the necking start point, the material is in a state where the local molecular orientation is almost completed, and at the necking extension area C, the neck of the material is no longer tight and the neck area is stretched. Then, netsking stretching is performed.

降伏点とネツキング開始点の間ｂでは、配向分子と未配
向分子が混在するものと思われる。It is thought that oriented molecules and unoriented molecules coexist in the region b between the yield point and the netting start point.

本発明は、ポリプロピレンパリソンの圧力気体による軸
方向の伸長の不足を材料の降伏点を越える程度に機械的
な手段で補ない、この区間の未配向分子が残留しており
、未配向分子が消失するネツキング延伸開始点に到る未
然に機械的延伸を制限するが中止し過剰な軸方向の機械
的伸長が生じてネツキング延伸するのを避け、未配向分
子が消失する段階の前に圧力気体を主体とする吹膨成形
への移行を終了させることを特徴とする。The present invention compensates for the lack of axial elongation of the polypropylene parison by pressurized gas to an extent that exceeds the yield point of the material, and the unoriented molecules in this section remain and the unoriented molecules disappear. The mechanical stretching is limited but stopped before reaching the netting stretching start point to avoid excessive axial mechanical stretching and netting stretching, and the pressurized gas is applied before the stage where unoriented molecules disappear. It is characterized by ending the transition to mainly blow molding.

次に実施例により本願の発明を説明する。Next, the invention of the present application will be explained with reference to Examples.

１ 第１図は射出成形したポリプロピレン樹脂の有底パ
リソンを融点以下で分子配向のし易い温度まで加熱し、
吹込成形用割金型６，６に挾んだところの断面図である
。1 Figure 1 shows an injection-molded polypropylene resin parison heated to a temperature below its melting point that facilitates molecular orientation.
It is a sectional view of the part sandwiched between split molds 6, 6 for blow molding.

１はパリソン、２はパリソン保持金型、３はパリソン部
を内部より抑える吹込コア金型、４はパリソンを軸方向
に伸長する伸長ロツド、５は吹込用圧力気体の通路、６
，６は所望の製品の形状に彫刻した吹込成形用割金型で
ある。1 is a parison, 2 is a parison holding mold, 3 is a blowing core mold that suppresses the parison portion from the inside, 4 is an extension rod that extends the parison in the axial direction, 5 is a passage for pressure gas for blowing, 6
, 6 are split molds for blow molding engraved into the shape of the desired product.

所望の温度に加熱され、吹込金型で挾まれたパリソンは
始めｌの位置にある。The parison, heated to the desired temperature and sandwiched between blow molds, is initially in position 1.

次に伸長ロツド４を伸長させパリソンをその方向に分子
配向の不完全な１′の位置にある間に圧力気体を送入し
第２図の説明図に示すようにパリソンを全方向に膨らま
し吹込金型６，６の内壁に押しつけられるまで膨張し瓶
等の容器Ｔを製造する。Next, the extension rod 4 is extended, and while the parison is in the 1' position where the molecular orientation is incomplete in that direction, pressure gas is introduced to inflate the parison in all directions as shown in the explanatory diagram in Figure 2. It expands until it is pressed against the inner walls of the molds 6, 6 to produce a container T such as a bottle.

この際パリソンが心ずれを起さないように、伸長ロツド
でパリソン先端をわずかに先導させ金型底端８まで到達
させるのが好ましい。At this time, in order to prevent the parison from being misaligned, it is preferable to slightly lead the tip of the parison with an extension rod so that it reaches the bottom end 8 of the mold.

ポリプロピレン（ＭＦＩ−１，密度−０．９０〜０．
９ １ ｇ／ｃｍ’、融点１５０℃附近、昭和油化株式
会社製、商品名ショウアロマーＥＧＩ ｌ Ｏ ）を用
いて第１図の何き形状のパリソンを射出成形した。Polypropylene (MFI-1, density -0.90~0.
9 1 g/cm', melting point around 150° C., manufactured by Showa Yuka Co., Ltd., trade name Showaromer EGI 1 O) was used to injection mold a parison in the hollow shape shown in FIG.

直径は２０ｍｍ、高さ７０ｍｍ（そのうち２ｍｍは頚部
で残り５０ｍｍが吹膨される）肉厚は３． ０ ｍｍで
あった。The diameter is 20mm, the height is 70mm (of which 2mm is the neck and the remaining 50mm is inflated), and the wall thickness is 3. It was 0 mm.

射出成型の条件は２１０℃、射出圧力９７０ｖ／ｃｍ’
，射出時間ｌ０秒、冷却時間Ｉ０秒で、射出金型は１８
０℃の水１，０００ＣＣ／分で冷却した。Injection molding conditions are 210℃, injection pressure 970v/cm'
, injection time is 10 seconds, cooling time is 10 seconds, the injection mold is 18
Cooled with 1,000 CC/min of 0°C water.

このパリソンは８０℃ぐらいに冷却されており、射出成
形の終了後射出コア金型（射出成形系統は図示せず）を
パリソンから外ずし、続いてパリソン保持金型２ととも
にパリソンを射出凹金型より取外ずす。This parison is cooled to about 80°C, and after the injection molding is finished, the injection core mold (injection molding system is not shown) is removed from the parison, and then the parison is injected together with the parison holding mold 2. Remove from mold.

次にパリソン１の口部から吹込コア金型３を挿入し、ｌ
３２゜Ｃまでパリソンを加熱した後（加熱機構は図示せ
ず）、吹込割金型６，６で挾持する。Next, insert the blowing core mold 3 from the mouth of the parison 1, and
After heating the parison to 32°C (heating mechanism not shown), it is held between blow molds 6, 6.

ここで試験的に圧縮空気を供給したが１．２ｋｇ／ｃｍ
’ぐらいまではパリソンの膨張が起らなかった。Compressed air was supplied here on a trial basis, but it was 1.2 kg/cm.
The parison did not expand until about '.

そして２。Ｏ ｋｇ ／ｃｍ’以上の圧力の空気を吹込
んだところパリソンは腹部に側方向の局部的な膨張を起
したが、軸方向には膨らまず製品にはならなかった。And 2. When air was blown at a pressure of 0 kg/cm' or more, the parison locally expanded in the lateral direction in the abdomen, but did not expand in the axial direction and did not become a product.

次に１３２℃まで加熱した第１図の形状のパリソン１を
金型６，６で挾持し、伸長ロツド４を用いて伸長し、パ
リソンの種々の伸び率のところで２．０ｋｇ／ｃｍ’の
圧力の空気を吹き込んで全方向に吹膨させて第２図に示
す如き高さ８０ｍｍ、直径５０ｍｍ ： １５０ｃｃの
瓶を成形した。Next, the parison 1 having the shape shown in Fig. 1 heated to 132°C is held between the molds 6, 6, and stretched using the extension rod 4, and a pressure of 2.0 kg/cm' is applied at various elongation rates of the parison. Air was blown into the flask to inflate it in all directions to form a 150 cc bottle with a height of 80 mm and a diameter of 50 mm as shown in FIG.

このとき用いた材料の１３２℃に於ける引張力と伸びの
関係のグラフはほぼ第３図のグラフの通りである。The graph of the relationship between tensile force and elongation at 132° C. for the material used at this time is approximately as shown in the graph in FIG.

前記パリソンの伸び部は５０ｍｍで、各試料を５ｍｍの
段階でロツド４で変化させて伸ばし、その各段階で圧力
空気を吹込み始めた。The extension of the parison was 50 mm, and each sample was stretched in 5 mm steps with a rod 4, and pressure air was started to be blown at each step.

そのときの成形品のヘイズの値は後記の表の如く、降伏
点を過ぎてからは段階的に増し、ネツキング開始点へ近
ずくと少しずつこまかい亀裂さえ発生しはじめ、ネツキ
ング開始点以上に軸方向に伸した後には圧力空気で膨ら
ましても、もはや透明な商品とは言い難いものとなる。As shown in the table below, the haze value of the molded product increases step by step after passing the yield point, and as it approaches the netting starting point, small cracks begin to appear little by little, and the haze value of the molded product increases gradually beyond the netting starting point. Even if it is inflated with pressurized air after being stretched in that direction, it can no longer be called a transparent product.

次にこの実験結果の実施例と比較例をまとめて表に示す
。Next, examples and comparative examples of the experimental results are summarized in a table.

パリソンを軸方向に伸 ヘイズ ％ 長す、圧力気体の吹込 厚さ０．３８ｍｍを始めた時の
パリソン のもとの長さに対する 伸び ％ パリンン温度１３２°Ｃ 実施例１ ０ ３．４実施例２
１０ ３．６／／３
２０ ８．６／／４ ３０
１７．３わずかにこまかい亀裂発 生 ／／５ ４０ ２１．０こまかい亀
裂が増えはじ める 比較例１ ５０（ネツキング ２８．７こまかい開
始点超４） 亀裂が多くヘイ ズが犬で透明品 として不向 比較例２ 吹込圧力２．０ｋｇ 軸方向の伸長なしで は側方には膨らむが 軸方向にパリソンが 伸びず製品ができな い。Stretching the parison in the axial direction Haze % Lengthening, blowing pressure gas Elongation relative to the original length of the parison when the thickness started at 0.38 mm % Paring temperature 132°C Example 1 0 3.4 Example 2
10 3.6//3
20 8.6//4 30
17.3 Slightly small cracks occur//5 40 21.0 Comparative example 1 where small cracks start to increase 50 (Netsking 28.7 Fine crack starting point > 4) Comparative example 2 with many cracks and haze, unsuitable as a transparent product Blow pressure: 2.0 kg Without stretching in the axial direction, the parison will expand laterally, but the parison will not stretch in the axial direction, resulting in no product.

軸方向の伸長がおくれると始めに金 型に接触した部分が 厚くなり、後で伸長 した部分は薄くなる。When the axial elongation slows down, gold initially appears. The part that came into contact with the mold thickens and later elongates The affected area becomes thinner.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明を説明するための、パリソンを吹込成形
金型に挾持したところの断面図、第２図は吹込成形を終
了したところの断面図、第３図は成形に用いる樹脂の成
形時の温度の引張力と伸びの関係を示したグラフである
。 １・・・・・・パリソン、２・・・・・・パリソン保持
金型、３・・・・・・吹込コア金型、４・・・・・・伸
長ロツド、５・・・・・・吹込用圧力気体通路、６，６
・・・・・・吹込成形用割金型、７・・・・・・成形品
、８・・・・・・金型底端。Figure 1 is a cross-sectional view of a parison clamped in a blow molding die to explain the present invention, Figure 2 is a cross-sectional view of the finished blow molding, and Figure 3 is a molding of the resin used for molding. It is a graph showing the relationship between tensile force and elongation at different temperatures. 1... Parison, 2... Parison holding mold, 3... Blowing core mold, 4... Extension rod, 5... Pressure gas passage for blowing, 6, 6
...Split mold for blow molding, 7... Molded product, 8... Bottom end of the mold.

Claims (1)

【特許請求の範囲】[Claims] １ ポリプロピレン樹脂からなりパリソンを融点以下で
軸方向に機械的伸長を加えて吹込成形する方法に於いて
、パリソンに加える軸方向の機械的伸長を該樹脂の降伏
点を越えネツキング延伸の始まる未然に止め、その間若
しくはしかる後に圧力気体により吹膨成形を行なうポリ
プロピレン樹脂の二軸配向吹込成形法。1 In a method of blow molding a parison made of polypropylene resin by applying mechanical elongation in the axial direction below its melting point, the mechanical elongation applied to the parison in the axial direction exceeds the yield point of the resin and prevents netting stretching from starting. A biaxially oriented blow molding method for polypropylene resin, in which blow molding is performed using pressurized gas during or after stopping.