JP3888006B2 - In-mold foam molding method for polyolefin resin - Google Patents

Description

【０１０３】
表１に示すように、従来の充填法により予備発泡ビーズを充填して製作した成形品では、仕切壁４の基端部４ａから先端部４ｃ側へ行くに従って密度が低下しているのに対し、本発明の充填方法により予備発泡ビーズを充填して製作した成形品では、略一様な密度になっていることが判る。つまり、本発明の充填方法では、密度のバラツキの少ない品質の良い成形品を製作できることが判る。また、従来の成形品では、密度の低い部分においても十分な強度が得られるように、密度の低い部分を基準に成形品の設計を行う必要があり、成形品が重たくなるという問題があるが、本発明の成形品では、成形品の各部における密度が略一様になるので、成形品の強度を十分に確保しつつ、成形品を軽量に構成でき、しかも予備発泡ビーズの使用量を少なくして成形品の製作コストを低減できる。
【０１０４】
【表２】

【０１０５】
表２に示すように、本発明の充填方法で予備発泡ビーズを充填して成形すると、従来の圧縮充填法で充填して成形した場合よりも、成形ショット間における成形品の重量バラツキが小さくなり、所望の重量に精度よく成形されていることが判る。
【０１０６】
次に、成形サイクルの評価試験について説明する。
圧縮成形品として、図１、図２に示すような形状で、外寸で縦４５０ｍｍ、横３００ｍｍ、高さ１８０ｍｍの箱型、厚み８ｍｍの縦方向のリブ５本、厚み８ｍｍの横方向のリブ１本の成形品を製作するにあたり、本発明例として、予備発泡ビーズとして嵩密度が２０ｇ／Ｌのポリプロピレン製ビーズを用い、成形品の嵩密度を２８ｇ／Ｌ、２６ｇ／Ｌ、２４ｇ／Ｌに設定した実施例１〜３の成形品と、予備発泡ビーズとして嵩密度が２５ｇ／Ｌのポリエチレン製ビーズを用い、成形品の嵩密度を３３ｇ／Ｌ、３０ｇ／Ｌ、２９ｇ／Ｌに設定した実施例４〜６の成形品を製作した。
【０１０７】
また、比較例として、予備発泡ビーズとして嵩密度が２０ｇ／Ｌのポリプロピレン製ビーズを用い、成形品の嵩密度を３０ｇ／Ｌ、２８ｇ／Ｌ、２６ｇ／Ｌに設定した従来例１〜３の成形品と、予備発泡ビーズとして嵩密度が２５ｇ／Ｌのポリエチレン製ビーズを用い、成形品の嵩密度を４０ｇ／Ｌ、３８ｇ／Ｌ、３５ｇ／Ｌに設定した従来例４〜６の成形品を製作した。
そして、実施例１〜６と比較例１〜６の成形サイクルと成形品品質とを測定して表３，４を得た。但し、表３，４において、成形品品質は、ビーズ同士の密着状態を３段階評価したもので、十分に密着しているものを良品として「○」で表示し、使用には耐え得るが多少難のあるものを「△」で表示し、全く使用に耐えないものを「×」で表示した。
【０１０８】
【表３】

【０１０９】
【表４】

【０１１０】
表３，４に示すように、従来の成形方法では、予備発泡ビーズとしてポリプロピレン製ビーズを使用した場合には、比較例１のように成形品嵩密度を３０ｇ／Ｌ（圧縮比１．５）以上に設定しないと、品質の良い成形品が得られず、またポリエチレン製ビーズを使用した場合には、比較例４のように成形品嵩密度を４０ｇ／Ｌ（圧縮比１．６）以上に設定しないと、品質の良い成形品が得られない。それに対して、本発明の成形方法では、予備発泡ビーズとしてポリプロピレン製ビーズを使用した場合には、実施例２のように成形品嵩密度を２６ｇ／Ｌ（圧縮比を１．３に設定した場合でも、十分な品質の成形品が得られ、ポリエチレン製ビーズを使用した場合には、実施例５のように成形品嵩密度を３０ｇ／Ｌ（圧縮比１．２）以上に設定した場合でも、品質の良い成形品が得られる。また、成形サイクルは、成形品の嵩密度を予備発泡ビーズの嵩密度で除算して求めた圧縮比が増大するにしたがって長くなり、十分な品質の成形品が得られる比較例１，４では、１８０ｓｅｃ，２１０ｓｅｃであるのに対し、実施例２，３では１３０ｓｅｃ，１２０ｓｅｃであり、本発明の成形方法では、従来の成形方法と比較して、十分な品質を確保しつつ、成形サイクルを格段に短縮できることが判る。
【０１１１】
尚、本実施例では、成形品１の各部における密度が一様になるように、チャンバ１７，１８と型間空洞部４１と管内空間４５の内圧を調整したが、局部的に強度を高めたい部分における予備発泡ビーズの充填密度を高めることも可能である。また、成形品１以外の各種形状の成形品を成形する場合においても、本発明を勿論適用することが可能である。
【０１１２】
【発明の効果】
請求項１に係るポリオレフィン系樹脂の型内発泡成形方法によれば、３０〜５０℃の設定温度に温度調整した予備発泡ビーズを、この設定温度に適応する圧力であって大気圧よりも大きく、｛（７０−設定温度［℃］）／１０｝kg/cm²の式で得られる値以下の圧縮充填圧力で成形空間内に圧縮充填するので、予備発泡ビーズの嵩密度が各成形ショット間において予備発泡ビーズの移送時における分級等により変動しても、その悪影響を受けることなく一様な重量の成形品を製作できるので、成形品の品質安定性を格段に向上できる。
また、予備発泡ビーズの温度を設定温度±５℃の範内に設定するので、比較的容易に温度調整可能で、しかも各成形ショット間における成形品の嵩密度のバラツキを、成形品の品質に悪影響を及ぼさない程度に低減できるので好ましい。
更に、ポリオレフィン系樹脂からなる予備発泡ビーズは、素材自体が軟らかく、しかもガス透過性が高いことから、同一発泡倍率のポリスチレン系樹脂からなる予備発泡ビーズよりも格段に粒子形状が変形しやすく、充填性を一層向上できるので好ましい。
更にまた、３つのチャンバの無機ガス圧を個別に或いはいずれかの組み合わせにより制御し、圧縮した予備発泡ビーズを無機ガスの流れに乗せて成形空間内へ充填するので、例えば予備発泡ビーズが充填されにくい難充填部に対して先に予備発泡ビーズが充填されるように、各チャンバの無機ガス圧を制御することで、成形品の各部における充填密度を一様に設定できる。このため予備発泡ビーズが充填されにくい、厚さ２０ｍｍ以下の薄肉な仕切壁を有するような成形品でも、充填器の個数を増やすことなく、成形品の各部における充填密度を適正な値に設定できる。また、強度、剛性を高めたい部分に対して先に予備発泡ビーズを充填すると、該部分における充填密度を局部的に高めてその強度を高めることが可能となる。
【０１１３】
請求項２記載のように、圧縮充填開始前の予備発泡ビーズの温度条件で、成形品密度を予備発泡ビーズの嵩密度で除算して得られる予備発泡ビーズの圧縮比が１．２〜１．５となる圧縮充填圧力に設定すると、成形のサイクルタイムを短くして生産性を向上できるとともに、ビーズ同士が適正に密着した品質の良い成形品を成形できる。また、成形品の嵩密度と予備発泡ビーズの嵩密度とが接近するので、予備発泡ビーズの輸送効率や保管効率を高めることが可能となる。
【０１１４】
請求項３記載のように、予備発泡ビーズとして、ポリオレフィン系樹脂からなり、セル径が１００〜９００μｍ、発泡倍率が５〜６０倍、ＤＳＣ２’ｎｄピーク比が８〜６０％、独立気泡率が６５％以上のポリオレフィン系樹脂からなる予備発泡ビーズを用いると、成形品の表面性を向上し、その外観の見栄性を向上できるとともに、成形時の加熱条件に対する制約を緩和して、成形性及び省エネ性を向上できる。
【０１１６】
請求項４記載のように、第３チャンバとして、コア型とキャビティ型間のクリアランスを介して成形空間に連通するチャンバを備えると、クリアランスを介して成形空間の外周部に流入した充填用の無機ガスを効率的に外部へ排出できるので、例えば底の深い容器等を製作するときには、容器の開口縁に対応する位置にクリアランスが形成されるように構成することで、充填器の個数を増やすことなく、予備発泡ビーズの充填密度を適正に設定でき、容器の品質を向上することが可能となる。
【０１１７】
請求項５記載のように、第３チャンバとして、仕切壁成形部の奥部に連通するチャンバを備えると、充填密度を十分に確保できないことから、従来成形困難であると考えられていた厚さ２０ｍｍ以下の仕切壁を有するような複雑形状の成形品でも、仕切壁成形部に対して先に予備発泡ビーズを充填することで、仕切壁成形部における予備発泡ビーズの充填密度を高めて、適正な密度の品質のよい成形品を製作することが可能となる。
【０１１８】
請求項６記載のように、第３チャンバとして、予備発泡ビーズの充填器から離れている成形空間の遠隔部の奥部に連通するチャンバを備えると、予備発泡ビーズの充填密度が低下し易い遠隔部の充填密度を十分に確保でき、品質のよい成形品を製作することが可能となる。
【０１１９】
請求項７記載のような構成の仕切壁成形部を形成すると、高さＨ（ｍｍ）と厚さＴ（ｍｍ）とにＨ／Ｔ≧１０の関係式が成り立つような仕切壁を有する成形品を成形することが可能となる。このような成形部は、仕切壁成形部における予備発泡ビーズの充填密度を十分に確保できないことから従来成形困難であると考えられていたが、請求項１〜６のいずれか１項記載の成形方法、特に請求項５記載の成形方法により成形することで、品質よく成形することができる。
【０１２０】
予備発泡ビーズとしては、ポリオレフィン系樹脂からなるものであれば任意の素材からなるものを採用できるが、安価で且つ入手が容易なことから、請求項８記載のようにポリプロピレン系樹脂や、請求項９記載のようにポリエチレン系樹脂からなるものを採用することが好ましい。
【０１２１】
前記成形方法では、薄肉でしかも高さの高い仕切壁を有する成形体を成形できるが、請求項１０記載のように、仕切壁成形部に抜き勾配を形成すると、このような成形品であっても、離型時における破損を防止できるので好ましい。
【図面の簡単な説明】
【図１】 成形品の斜視図
【図２】 成形品の縦断面図
【図３】 型内発泡成形装置の縦断面図
【図４】 図３のIＶ−IＶ線断面図
【図５】 通気孔付近の縦断面図
【図６】 コアベントの正面図
【図７】 他の構成の型内発泡成形装置の図４相当図
【図８】 予備発泡ビーズの嵩密度と成形品重量との関係を示す線図
【図９】 予備発泡ビーズの嵩密度と成形品重量との関係を示す線図
【図１０】 予備発泡ビーズの嵩密度と成形品重量との関係を示す線図
【図１１】 予備発泡ビーズの嵩密度と成形品重量との関係を示す線図
【図１２】 予備発泡ビーズの嵩密度と成形品重量との関係を示す線図
【図１３】 従来技術に係る型内発泡成形装置の縦断面図
【図１４】 従来技術に係る他の構成の型内発泡成形装置の縦断面図
【符号の説明】
１ 成形品 ２ 本体部
３ 収容空間 ４ 仕切壁
４ａ 先端部 ４ｂ 途中部
４ｃ 基端部
１０ 型内発泡成形装置
１１ コア型 １２ キャビティ型
１１ａ，１２ａ フランジ部
１３ 成形空間 １３ａ 外周先端部分
１３ｂ 仕切壁成形部 １４ 枠状フレーム
１５ 裏板 １６ ハウジング
１７ 第１チャンバ １８ 第２チャンバ
２０ コアベント
２１ コアベントホール
２２ 通気孔 ２３ 取付孔
２２ａ 貫通孔 ２２ｂ 長孔
ＳＶ１〜ＳＶ３ 用役弁
ＳＷＶ１〜ＳＷＶ４ 切替弁
ＤＶ１〜ＤＶ４ ドレン弁
Ｖ１ 吸気弁 Ｖ２ 充填エア弁
Ｖ３ 調整エア弁
２５ 蒸気供給管 ２６ エア供給管
２７ ドレン管 Ｐ 真空ポンプ
２８ 減圧管 ２９ 原料タンク
３０ 吸気管 ３１ 充填器
３２ シャッター ３３ 充填管
３４ 充填エア供給管
３５ 調整エア供給管
３６ 温調手段
３７ａ 温度センサ ３７ｂ 温度センサ
３８ ビーズ温調槽 ３９ 加熱手段
４０ クリアランス ４１ 型間空洞部
４２ 隔壁 ４３ 貫通孔
４４ 排気管 ４５ 管内空間[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a method for in-mold foam molding of polyolefin resin.To the lawRelated.
[0002]
[Prior art]
As shown in FIG. 13, as an in-mold foam molding apparatus for producing a molded product using pre-expanded beads made of a thermoplastic synthetic resin, a pair of facing molds 100 and 101 and pre-expanded beads are both molded. And a filling device 111 for filling the molding space 104 formed by the molds 100 and 101. The chambers 102 and 103 are formed on the back sides of the molding molds 100 and 101, respectively. A plurality of air holes 105 and 106 communicating with the chambers 102 and 103 and the molding space 104 are respectively formed, and working fluids such as steam, air, and cooling water necessary for molding are formed through the chambers 102 and 103. What was comprised so that it might supply to 104 is put in practical use. In this example, upper service ports 107 and 108 for supplying heated steam are provided at the upper portions of the respective chambers 102 and 103, and lower service ports 109 and 110 connected to a decompression pump or a drain pipe at the lower portion. Is provided so as to supply steam to the molding space 104.
[0003]
In addition, the large number of ventilation holes 105 and 106 provided through the molds 100 and 101 are actually provided with a plurality of through-holes comprising round holes of about 0.5 mmφ and slits of about 0.5 mm in width. A core vent made of a cylindrical body having a lid with an outer diameter of 7 to 12 mm is formed by fitting into a core vent mounting hole formed in a hole in the molds 100 and 101, and a core vent formed directly on the molds 100 and 101. The vent holes 105 and 106 are provided in the molds 100 and 101 at a pitch of 20 to 50 mm.
[0004]
In the case of molding a foam molded body using such a foam molding apparatus, first, a molding die is closed to form a molding space 104, and pre-foamed beads such as polystyrene are used as raw material tanks (illustrated). From the abbreviation) into the molding space 104 through the filling device 111, and then, the pre-expanded beads in the molding space 104 are heated with heated steam, foamed and fused, and then cooled and solidified. 101 is opened to take out the foamed molded product.
[0005]
On the other hand, in the molded product molded using the molding apparatus, there is a problem that the variation in the molded product weight increases. In order to solve this problem, for example, in Japanese Patent Publication No. 8-15746, the temperature of the pre-expanded beads is measured before the start of compression filling, and the compression filling pressure is set so as to adapt to it. A foam molding method configured to set the temperature of the expanded beads constant is described.
[0006]
[Problems to be solved by the invention]
By the way, in such a molding method, as one of the problems that are particularly desired to be improved, there is a large difference between the packing density of the pre-expanded beads in a specific part in the molding space 104 and the packing density in other parts. It is a problem that there are things. Specific parts include (1) the inner part of the molding space 104 for molding details of a molded product having a complicated shape, and (2) the outer peripheral tip 104a of the molding space 104.
[0007]
Hereinafter, the cause of the fluctuation of the packing density in (1) and (2) will be described in detail. Before that, the most commonly used filling method of pre-expanded beads will be briefly described.
As the filling method of the pre-expanded beads, [1] cracking filling method, [2] pressure filling method, [3] compression filling method and the like are widely adopted.
[0008]
[1] The cracking filling method is used when the air used for filling cannot be exhausted sufficiently from the vent holes arranged in the core mold and cavity mold. In this method, the mold is not completely closed (cracking), for example, only 10% of the bottom thickness of the molded product is opened, and air used for filling is discharged from the gap between the core mold and the cavity mold.
[0009]
[2] In the pressure filling method, the inside of the raw material tank containing the pre-expanded beads is 0.2 to 1.5 kg / cm.²A method in which pre-expanded beads are transported and filled in the molding space using the pressure difference between the raw material tank and the molding space in a state in which the molding space is opened to atmospheric pressure through the vents and the chamber. It is.
[0010]
[3] In the compression filling method, the pressure p in the raw material tank is higher than the pressure filling method by 1.0 to 5.0 kg / cm.²A method of transporting and filling pre-expanded beads while maintaining the differential pressure (p-p1) of the pressure p1 in the molding space communicating with each other through a vent hole by pressurizing to a certain level It is.
[0011]
Next, the cause of the fluctuation of the packing density will be described in detail.
(1) Regarding the inner part of the molding space for molding the details of molded products with complex shapes
In short, the above three filling methods provide an appropriate differential pressure between the raw material tank and the molding space, and send the pre-expanded beads on the air flow generated based on this differential pressure. In the case of the molding space 104 having a relatively simple shape as illustrated, the pre-expanded beads are filled in every corner and the state where the partial filling unevenness is small is obtained. Even in the foam molded article, there was little density unevenness and a relatively homogeneous quality could be obtained.
[0012]
However, as shown in FIG. 14 (a), a shape in which the central plane of the core mold 101 is provided with deep and narrow recesses 112 (two places in the top and bottom in FIG. 14) having a bag-like cross section, or FIG. In the case of a shape in which a concave and deep recess 113 (in the same way, two places in FIG. 14) is provided in the central plane of the cavity mold 100 as illustrated in FIG. The flow of air, which is the driving force for filling, stagnates in this part, and it is difficult to fill the pre-expanded beads up to the back of the cross-section bag-shaped recess 112 or 113. Problems such as inability to mold due to defects.
[0013]
In order to deal with such problems, it has also been attempted to arrange a dedicated filling device toward the recess, which is difficult to fill, but in addition to the problem of increased air usage, molding that can be molded with one mold The number of bodies had to be reduced, resulting in a problem that productivity was significantly reduced. The reason is that the number of fillers attached to one molding apparatus is usually fixed according to the capacity of the raw material tank or the ability to supply pressurized air. For example, in the most general-purpose model, the number of attached fillers is set to 18, and when the shape of the molded product is simple, three fillers are provided for one molding space, whereas the shape of the molded product is Assuming that 6 pieces are required because of the complexity of the mold, the mold space is originally designed to allow only 3 molds to be designed even though there is room for 6 molds. Because it does.
[0014]
Also, as the number of fillers increases, the amount of air per unit time supplied to the molding space increases, so that the air pressure in the molding space decreases instantaneously immediately after filling or the air from the molding space On the contrary, it may cause a change in packing density, for example, the discharge cannot catch up. For this reason, the number of fillers to be used and the arrangement of the fillers are troublesome for mold designers, and there are many trial and error factors, and standardization is very difficult. In particular, the filling density of the pre-expanded beads for a portion away from the filling device or a narrow bottomed portion such as the above-mentioned concave portion tends to be low, and the filling density for these difficult filling portions is set to an appropriate value. Therefore, it is necessary to increase the filling density as a whole, and the weight of the molded product becomes heavier than when the density is uniform.
[0015]
Furthermore, from the viewpoint of moldability, when the filled pre-expanded beads are heated with steam, the pre-expanded beads are expanded to a greater extent so that the pre-expanded beads in the portion with low packing density are sufficiently fused. Therefore, it is necessary to increase the heating steam pressure. However, when the heating vapor pressure is increased in accordance with the portion having a low filling density as described above, the portion having a high filling density is excessively heated, and the foaming pressure becomes higher than that in the normal molding. For this reason, when the molded product is cooled, it takes a long time to reduce the high foaming pressure to a foaming pressure at which the mold can be released, resulting in a long molding cycle and reduced productivity. In addition, when heating or cooling, the foaming pressure of each part of the molded product becomes non-uniform so that the releasability is poor, and the filling property is poor, so that there is a problem that productivity and yield are lowered.
[0016]
(2) Regarding the outer peripheral tip of the molding space
In the pressure filling method and the compression filling method, as shown in FIG. 13, the pre-expanded beads are filled into the molding space 104 in a state where both the molding dies 100 and 101 are completely closed. The tip portion 104a has a dead end shape. For this reason, the air flow generated by the differential pressure in the raw material tank (not shown) and the molding space 104 stagnates at the outer peripheral tip 104a, and the pre-expanded beads are difficult to be filled, and uneven density tends to occur.
[0017]
On the other hand, in the cracking filling method, the core mold and the cavity mold are not completely closed, and, for example, only 10% of the bottom wall thickness of the molded product is opened, so that the outer peripheral tip portion of the molding space becomes a dead end shape. However, there is another problem in that the density of the bottom of the molded product is higher than that of the other part due to the cracking gap due to the closing of the core mold and the cavity mold after filling.
[0018]
Also, in the cracking filling method, after filling the pre-expanded beads, if both molds are completely closed, the outer peripheral tip of the molding space becomes a dead end shape. The following problems occur during cooling and mold release.
[0019]
At the time of heating the pre-expanded beads, for example, by supplying heating steam from one chamber to the other chamber, the heating vapor is passed through the pre-expanded beads in the molding space. If the outer peripheral tip portion 104a of the molding space 104 has a dead end shape, it is difficult for heated steam to reach the outer peripheral tip portion 104a, and the amount of heat flows to the outer peripheral portions 100a and 101a of the molding die having a relatively large heat capacity. Therefore, since the temperature of the pre-expanded beads at the outer peripheral tip portion 104a is difficult to rise and the temperature rise is considerably delayed from the other portions, the time of the heating process has to be lengthened, and eventually the entire molding time becomes longer. was there.
[0020]
During cooling of the molded product, cooling water is sprayed onto the molds 100 and 101 from nozzles (not shown) arranged in the chambers 102 and 103, or the chambers 102 and 103 are decompressed to adhere to the mold and the molding space. The water in 104 is evaporated and the foamed molded body is cooled together with the mold by the heat of vaporization at that time. In this case, contrary to the heating of the pre-expanded beads described above, the outer periphery of the mold There is a problem that it is difficult to cool the outer peripheral tip portion 104a of the molding space 104 due to heat transfer from the portions 100a and 101a, and it takes time to sufficiently cool the portion located at the outer peripheral tip portion 104a of the molding space 104 of the foam molded body. It was.
[0021]
When the molded product is released, the foam molded body is extruded from the back side of the cavity mold 100 with an ejector pin (not shown) while the molds 100 and 101 are opened, and the foam molded body is taken out from the mold. When the core mold 101 is opened, the water accumulated in the mold cavity 116, which is surrounded by the outer peripheral portions 100a and 101a of the mold and the frames 114 and 115, which correspond to the joints of the mold apparatus, flows down and becomes a product. There was a problem that a foamed molded product was wetted.
[0022]
  The object of the present invention is to provide an in-mold foam molding method for polyolefin resin that can appropriately adjust the filling density of pre-expanded beads between molding shots and in each part of the molding space.The lawIt is to provide.
[0023]
[Means for Solving the Problem and Action]
  The in-mold foam molding method for polyolefin resin according to claim 1 comprises:A molding space having a partition wall molding portion for molding a partition wall having a thickness of 20 mm or less with respect to a molded product, and at least three chambers for controlling a working fluid in the molding space, A first chamber on the back side of the core mold that communicates, a second chamber on the back side of the cavity mold that communicates with the molding space, and a third chamber that communicates with a difficult-to-fill portion that is difficult to fill with the pre-expanded beads in the molding space. Using the in-mold foam molding equipment provided,The temperature of the pre-expanded beads made of polyolefin resin is adjusted to a constant temperature of ± 5 ° C. centered on the set temperature within a range of 30 to 50 ° C., and the compression filling pressure is a pressure adapted to the set temperature. Greater than atmospheric pressure, {(70−set temperature [° C.]) / 10} kg / cm²To a constant pressure below the value obtained byCompressed with inorganic gasIn state,While controlling the inorganic gas pressure of each chamber individually or in any combination with the compression filling pressure,Molding having a partition wall molding portion for molding a partition wall having a thickness of 20 mm or less on a molded productspaceWithinPre-expanded beadsAfter compressing and filling, and then heat-sealing with steam, cooling and taking out from the mold.
[0024]
In this molding method, the temperature is adjusted to a set temperature of 30 to 50 ° C., and the compression filling pressure (the internal pressure of the molding space at the time of compression filling) is a pressure adapted to this set temperature and is larger than the atmospheric pressure, {( 70-set temperature [° C]) / 10} kg / cm²Since the constant pressure is set to a value equal to or less than the value obtained by the above equation, the weight variation of the molded product between molding shots can be remarkably reduced. In other words, pre-expanded beads are difficult to foam one bead to the same bulk density due to restrictions in production, and a mixture of particles having a magnification distribution around the target bulk density. Become. For this reason, classification is inevitably generated in the transfer process from the silo to the molding space, so that the bulk density of the pre-expanded beads used for each molding shot varies, and the molded product weight varies for each molding shot. In the present invention, the temperature of the pre-expanded beads is controlled to a constant set temperature, and the compression filling pressure is set to a pressure adapted to the set temperature, thereby preventing variation in the weight of the molded product. . In particular, when a molded product having a partition wall with a thickness of 20 mm or less is molded, it is difficult to ensure a sufficient density of pre-expanded beads in the partition wall molding part, and thus the weight variation of the molded product tends to increase. Therefore, it is preferable.
[0025]
However, the compression filling pressure may be set according to the apparent density of the pre-expanded beads or according to the apparent density and the temperature, but the means for measuring the apparent density is a large one, Moreover, since the ability to adjust the variation in the bulk density (foaming ratio) is smaller than the temperature adjustment, it is preferable to adjust the temperature to be constant. It is also possible to adjust the compression filling pressure according to the temperature of the pre-expanded beads that fluctuate, but adjustment of the compression filling pressure requires more complicated control than temperature adjustment. It is preferable to adjust it to be constant.
[0026]
The temperature of the pre-expanded beads is most preferably adjusted precisely to the set temperature, but it is difficult to measure the temperature directly, so it will have a certain range with respect to the set temperature. Is within the range of the set temperature ± 5 ° C., the temperature can be adjusted relatively easily, and the variation in the bulk density of the molded product between the molding shots can be reduced to the extent that the quality of the molded product is not adversely affected. Therefore, it is preferable.
[0027]
  In addition, pre-expanded beads made of polyolefin resin are softer and more gas permeable, so the particle shape is much easier to deform than pre-expanded beads made of polystyrene resin with the same expansion ratio. It is preferable because the properties can be further improved.
  Furthermore, with the pre-expanded beads made of polyolefin resin compressed with inorganic gas, the inorganic gas pressure in the three chambers is controlled individually or in any combination, and the compressed pre-expanded beads are placed on the inorganic gas flow. Since the new compression filling method is used to fill the molding space, the inorganic gas pressure in each chamber is set so that, for example, the pre-expanded beads are first filled in the difficult-to-fill parts that are difficult to be filled with the pre-expanded beads. By controlling, the filling density in each part of the molded product can be set uniformly. For this reason, even in a molded product that is difficult to be filled with pre-expanded beads and has a thin partition wall with a thickness of 20 mm or less, the filling density in each part of the molded product can be set to an appropriate value without increasing the number of fillers. . Further, if the pre-expanded beads are first filled in the portion where the strength and rigidity are to be increased, the filling density in the portion can be locally increased to increase the strength. The operation of feeding the pre-expanded beads to the difficult-to-fill part may be performed in a plurality of times so that the pre-expanded beads are intensively filled in the difficult-to-fill part.
[0028]
In the molding method according to claim 2, the compression ratio of the pre-expanded beads obtained by dividing the density of the molded product by the bulk density of the pre-expanded beads under the temperature condition of the pre-expanded beads before the start of compression filling is 1.2 to 1. Is set to a compression filling pressure of .5.
In other words, when the compression ratio is less than 1.2, the pre-expanded beads are not sufficiently foamed, and the molded product contracts significantly after release, or a gap is formed between the beads, and a good product is obtained. There is no problem. In addition, when the compression ratio exceeds 1.5, the space between the bead particles in the molding space after filling becomes very narrow, and the heating steam does not pass between the bead particles, resulting in poor fusion. Only the part that has passed is excessively foamed, and there is a problem that cracks occur in the molded product and the cooling time becomes long, so the compression filling pressure can be set so that the compression ratio is 1.2 to 1.5. preferable.
[0029]
Further, in the conventional molding method, the compression ratio is generally set to 1.4 or more in order to ensure sufficient filling performance, and has a thin wall shape having a partition wall of 20 mm or less as in the present invention. In the case of molding the molded product, it is necessary to keep it at 1.5 to 1.6 or more. However, when the compression ratio is set to be high in this way, the resin foaming pressure becomes higher than the vapor temperature necessary for fusing the pre-expanded beads together, which requires a long cooling cycle and decreases the productivity. To do. In the present invention, since the compression ratio is set as low as 1.2 to 1.4, the productivity can be improved, and the bulk density of the molded product and the bulk density of the pre-foamed beads are brought close to each other, thereby pre-foaming. It becomes possible to increase the transport efficiency and storage efficiency of beads. In particular, by molding as described in claim 4, the filling density of the pre-expanded beads in each part of the molded product can be set uniformly, so that it is possible to improve productivity while ensuring sufficient quality of the molded product It becomes.
[0030]
The molding method according to claim 3 is made of a polyolefin resin as the pre-expanded beads, having a cell diameter of 100 to 900 μm, an expansion ratio of 5 to 60 times, a DSC 2′nd peak ratio of 8 to 60%, and a closed cell ratio. Using pre-expanded beads made of a polyolefin-based resin of 65% or more.
[0031]
In this molding method, pre-expanded beads having a cell diameter of 100 to 900 μm, an expansion ratio of 5 to 60 times, a DSC 2′nd peak ratio of 8 to 60%, and a closed cell ratio of 65% or more are used. Therefore, the surface property of the molded product can be improved as described below, the appearance of the molded product can be improved, and restrictions on heating conditions during molding can be relaxed to improve moldability and energy saving.
[0032]
If the cell diameter is less than 100 μm, there is a problem that the surface elongation is poor during molding, the sink is easy, and the appearance of the surface is inferior. If it exceeds 900 μm, the cell diameter tends to be uneven, Is large, the surface is rough and the surface appearance is inferior. Therefore, it is preferably set within the range of 100 to 900 μm.
The expansion ratio is not particularly limited, but is preferably about 5 to 60 times (bulk ratio of expanded beads).
[0033]
The DSC 2'nd peak ratio is preferably set to 8% to 60%. DSC 2'nd peak ratio is the total of two low temperature and high temperature DSC (differential scanning calorimetry) peaks formed due to the crystalline melting point of the base resin when the base resin is heated. When the DSC 2′nd peak ratio is less than 8%, the heating condition width at the time of molding is narrow, and the molded body tends to shrink and sink easily. On the other hand, if it exceeds 60%, it is necessary to significantly increase the heating conditions, the size of the molding machine needs to be increased, and it is negative from the viewpoint of energy saving, so it is preferably set to 8 to 60%.
[0034]
If the closed cell ratio is less than 65%, even if the heating pressure at the time of molding is increased and the beads are somehow fused together, shrinkage and sink marks of the molded body tend to increase, and the molded body of the target quality. Therefore, it is preferable to set it to 65% or more.
[0037]
  Claim4In the described molding method, the third chamber includes one or a plurality of chambers communicating with the molding space via a clearance between the core mold and the cavity mold. In this case, since the filling inorganic gas flowing into the outer peripheral portion of the molding space through the clearance can be efficiently discharged to the outside, for example, when manufacturing a container having a deep bottom, it corresponds to the opening edge of the container. By configuring so that the clearance is formed at the position, it is possible to appropriately set the filling density of the pre-expanded beads without increasing the number of fillers, and to improve the quality of the container.
[0038]
  Claim5The described molding method includes, as the third chamber, one or a plurality of chambers communicating with the inner part of the partition wall molding portion, and the pre-expanded beads are previously placed on the partition wall molding portion when filling the pre-expanded beads. The inorganic gas pressure in the three chambers is controlled so as to be filled. In this case, since the packing density cannot be sufficiently secured, even a molded product having a complicated shape having a partition wall with a thickness of 20 mm or less, which has been thought to be difficult to be molded in the past, is formed with respect to the partition wall molding portion. By filling the pre-expanded beads first, the filling density of the pre-expanded beads in the partition wall molding part is increased, and a good quality product with an appropriate density is manufactured.ThisIs possible.
[0039]
  Claim6The molding method described includes, as the third chamber, one or more chambers that communicate with the back of the remote portion of the molding space that is away from the pre-expanded bead filler, and when the pre-expanded beads are filled, In contrast, the inorganic gas pressure is controlled so that the pre-expanded beads are filled first. If comprised in this way, the filling density of the remote part where the filling density of a pre-expanded bead tends to fall can fully be ensured, and it becomes possible to manufacture a molded article with good quality.
[0040]
  Claim7The described molding method has a partition wall molding portion that satisfies the relational expression of H / T ≧ 10 when the height of the partition wall to be molded is H (mm) and the thickness is T (mm). It is what. A molded product having a partition wall having such a configuration has been considered difficult to form in the past because it cannot sufficiently secure the packing density of the pre-expanded beads in the partition wall molding portion.1~6The molding method according to claim 1, in particular, claim5By molding by the described molding method, the packing density of the pre-expanded beads in the partition wall molding part is increased, and a molded product with an appropriate density and quality is manufactured.ThisIs possible.
[0041]
  As the pre-expanded beads, those made of any material can be adopted as long as they are made of polyolefin resin, but they are inexpensive and easy to obtain.8Polypropylene resin as described, or claims9It is preferable to employ a polyethylene resin as described.
[0042]
  Claim 10In the described molding method, a draft is formed in the partition wall molding part. Since the partition wall that can be molded by this new molding method is thin and high in height, it is preferable to give a draft to the partition wall molding portion to prevent damage to the molded product at the time of mold release.
[0043]
PoMolded using pre-expanded beads made of reolefinic resin, the interior is partitioned into a plurality of receiving spaces through a partition wall having a thickness of 20 mm or less in order to divide and store a plurality of articles.CollectionThe combined package was considered to be difficult to form in the past because the density of the beads in the partition wall was much lower than the other parts and sufficient strength could not be secured.1~ 10By molding by the molding method according to any one of the above, it is possible to appropriately set the packing density of beads in the partition wall, and to realize a collective package having a uniform density as a whole.
[0044]
in frontA partition that satisfies the relational expression of H / T ≧ 10 when the height of the partition wall is H (mm) and the thickness is T (mm).WallHowever, since it was thin and high in height, it was difficult to form a sufficient packing density of beads, but it was difficult to mold.1~ 10By molding by the molding method according to any one of the above, it is possible to appropriately set the packing density of beads in the partition wall, and to realize a collective package having a uniform density as a whole.
[0046]
  like thisSince the partition wall of the collective package is thin and high as described above, it is preferable to give a draft to the partition wall molding portion to prevent damage to the molded product at the time of mold release.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the configuration of the molded product will be described.
As shown in FIGS. 1 and 2, the molded product 1 is integrally molded by using an in-mold foam molding apparatus 10 described later using pre-expanded beads made of polyolefin resin, and has a bottomed box-shaped main body. This is a collective packaging body that includes a portion 2 and a partition wall 4 that divides the inside of the main body 2 into a plurality of storage spaces 3 and that is configured to store various articles in the storage space 3 in an aligned manner. The size and shape of the molded product 1 and the number of storage spaces 3 are not limited to the configuration illustrated in FIGS. 1 and 2, and can be arbitrarily set according to the size, shape, and number of items to be stored. Can be set. Further, the in-mold foam molding apparatus 10 and the molding method described later are suitable for molding such a complex shaped molded product 1, but a simple box-shaped or plate-shaped molded product is molded. It is also possible to do.
[0048]
The thickness T of the partition wall 4 is set to 20 mm or less, and the height H (mm) and the thickness T (mm) of the partition wall 4 are configured such that a relational expression of H / T ≧ 10 holds. . The molded product 1 having the partition wall 4 having such a configuration is difficult to be molded by the conventional molding method, but can be molded by the molding method of the present invention described later without deteriorating the quality. In addition, a predetermined draft is formed in the partition wall 4 so that the partition wall 4 is not damaged when the molded product 1 is released.
[0049]
Next, the pre-expanded beads used in this in-mold foam molding apparatus will be described.
As the material of the pre-expanded beads, a material having physical properties corresponding to the usage conditions of the molded product 1 to be manufactured is selected. Polyolefin-based synthetic resin materials such as polyethylene-based resins and polypropylene-based resins, or synthesis of these materials Copolymers of resin materials are used. Specifically, ethylene propylene random polypropylene resin, ethylene propylene block polypropylene resin, homopolypropylene ethylene propylene butene random terpolymer, linear low density polyethylene (LLDPE), cross-linked low density polyethylene (cross-linked LDPE), etc. can be suitably used. . Although it is possible to use pre-expanded beads made of polystyrene resin as the pre-expanded beads, the pre-expanded beads of polyolefin resin are softer and more gas permeable, so the same expansion ratio Since the particle shape is much easier to deform than the pre-expanded beads made of polystyrene resin, it is preferable for exhibiting the effect of improving the filling property, which is the object of the present invention. In addition, since the polystyrene resin generally has a larger variation in the shape of the pre-expanded beads than the polyolefin-based resin and the filling property is inferior, the pre-expanded beads made of the polyolefin-based synthetic resin material are more suitable for this application. The effect of this filling method is likely to appear.
[0050]
When the cell diameter of the pre-expanded beads is less than 100 μm, there is a problem in that the surface elongation is poor during molding, there is a problem that it is easy to sink, and the appearance of the surface is inferior. When the cell diameter exceeds 900 μm, the cell diameter becomes uneven. Since the cell diameter is large and the surface texture is rough and the surface appearance is inferior, there is a problem that the cell appearance is in the range of 100 to 900 μm, more preferably 150 to 700 μm, and particularly preferably 170 to 550 μm.
The expansion ratio is not particularly limited, but is preferably about 5 to 60 times (bulk ratio of expanded beads).
[0051]
The DSC 2'nd peak ratio is preferably set to 8% to 60%. DSC 2'nd peak ratio is the total of two low temperature and high temperature DSC (differential scanning calorimetry) peaks formed due to the crystalline melting point of the base resin when the base resin is heated. When the DSC 2′nd peak ratio is less than 8%, the heating condition width at the time of molding is narrow, and the molded body tends to shrink and sink easily. On the other hand, if it exceeds 60%, it is necessary to greatly increase the heating conditions, and it is necessary to increase the size of the molding machine, and it is negative from the viewpoint of energy saving, so it is 8 to 60%, more preferably 10 to 50%. %, Particularly preferably 15 to 40%.
[0052]
If the closed cell ratio is less than 65%, even if the heating pressure at the time of molding is increased and the beads are somehow fused together, shrinkage and sink marks of the molded body tend to increase, and the molded body of the target quality. Is less than 65%, more preferably 75% or more, and particularly preferably 85% or more.
[0053]
Next, the configuration of the in-mold foam molding apparatus will be described.
As shown in FIGS. 3 and 4, the in-mold foam molding apparatus 10 includes a pre-expanded bead in a molding space 13 formed by a core mold 11 and a cavity mold 12, which are arranged to face each other, and the core mold 11 and the cavity mold 12. Bead filling means for filling the molding space 13, steam supply means for heating, foaming, and fusing the pre-expanded beads filled in the molding space 13, and cooling means for cooling the molded product 1. Yes. In addition, although inorganic gas, such as nitrogen gas other than air, may be used for the filling of the pre-expanded beads in the molding space 13, the case of filling with clean air will be described here.
[0054]
The core mold 11 and the cavity mold 12 are respectively attached to a housing 16 having a frame-shaped frame 14 and a back plate 15. A first chamber 17 is provided on the back side of the core mold 11, and a back side of the cavity mold 12 is provided. Second chambers 18 are respectively formed.
[0055]
As shown in FIGS. 3 to 6, the core mold 11 and the cavity mold 12 are formed with a vent hole 22 including a core vent 20 and a core vent hole 21, and the molding space 13 and the chambers 17 and 18 have the vent holes 22. It is communicated through. As shown in FIGS. 5 and 6, the core vent 20 is a member that is attached to the mounting hole 23 formed in the core mold 11 and the cavity mold 12, and has a through hole 22 a having a diameter smaller than the diameter of the pre-foamed beads on the bottom surface. Alternatively, it is a bottomed cylinder having a plurality of long holes 22b, and the core vent hole 21 has a smaller diameter than the diameter of the pre-expanded beads formed in the core mold 11 and the cavity mold 12 as shown in FIG. It is a simple through hole.
[0056]
In the present embodiment, the molds 11 and 12 each having a plurality of vent holes 22 are used. However, a mold in which the vent holes 22 are substantially completely or completely omitted may be used. When using such a mold, with the molds closed, the molding space communicates with the external piping around the joint between the molds and the vicinity thereof or around the filler and ejector pins. By forming slits and through holes for the purpose, the working fluid such as air or vapor for filling the pre-expanded beads is controlled. If such a mold is used, the traces of the air holes 22 are not formed in the molded product, so that a molded product with a beautiful surface can be obtained, and the work of forming the air holes becomes almost unnecessary or completely unnecessary. The manufacturing cost of the mold can be reduced, the mold can be made thin, the responsiveness such as heating by steam can be improved, and the working fluid such as steam in the molding space and the chambers 17 and 18 can be individually controlled. Therefore, it is possible to obtain excellent effects such as the ability to independently control the surface property of the molded product and the internal fusion rate and to expand the degree of freedom with respect to the molded product characteristics.
[0057]
The chambers 17 and 18 are connected to the steam supply pipe 25 and the air supply pipe 26 via the service valves SV1 and SV2 and the switching valves SWV1 and SWV2, respectively, and via the drain valves DV1 and DV2 and the switching valves SWV3 and SWV4. The drain pipe 27 and the vacuum pump P are connected to the decompression pipe 28. Then, by operating the service valves SV1 and SV2, the drain valves DV1 and DV2, and the switching valves SWV1 and SWV2, the service fluid such as steam and compressed air can be individually supplied to or discharged from the chambers 17 and 18. It is configured.
[0058]
The bead filling means will be described. As shown in FIG. 3, a raw material tank 29 for storing pre-expanded beads is provided, an intake pipe 30 is connected to the raw material tank 29, and an intake pipe 30 is in the middle of the intake pipe 30. The internal pressure of the raw material tank 29 is adjusted by interposing the valve V1 and controlling the intake valve V1.
[0059]
The back plate 15 on the cavity mold 12 side is provided with a filling device 31 that opens into the molding space 13, and the raw material tank 29 is provided with a shutter 32, and the filling device 31 is provided with a shutter 32 for the raw material tank 29 through a filling pipe 33. The pre-expanded beads filled in the raw material tank 29 are connected to the air and are supplied to the molding space 13 from the filler 31 by riding on the air flow. A filling air supply pipe 34 is connected to the filling device 31, and a filling air with an appropriate pressure is supplied by a filling air valve V <b> 2 interposed in the middle of the filling air supply pipe 34.
[0060]
The raw material tank 29 is set to a pressurized state that is equal to or higher than the internal pressure of the chambers 17 and 18, and the pre-expanded beads stored in the raw material tank 29 are compressed into the air flow from the raw material tank 29 to the molding space 13. It is configured to ride and fill the molding space 13.
[0061]
An adjustment air supply pipe 35 is connected between the shutter 32 and the filling pipe 33, and an appropriate pressure is adjusted with respect to the filling pipe 33 by an adjustment air valve V <b> 3 interposed in the middle of the adjustment air supply pipe 35. Air is supplied, and the pre-expanded beads are supplied from the raw material tank 29 to the filling pipe 33 while being diluted with adjustment air. Further, by changing the supply amount of the adjustment air, the supply amount per unit time of the pre-expanded beads supplied to the filling tube 33, that is, the final dilution degree described later is adjusted. However, it is also possible to supply the pre-expanded beads from the raw material tank 29 to the filling pipe 33 by supply means such as a screw conveyor. In this case, the adjustment air valve V3 and the adjustment air supply pipe 35 are omitted, By changing the rotational speed of the screw conveyor, the supply amount of the pre-expanded beads per unit time to the molding space 13 is adjusted.
[0062]
The first configuration, which is a feature of the present invention, is provided with a third chamber that communicates with a difficult filling portion in the molding space 13 that is difficult to be filled with the pre-expanded beads, and the filling air is discharged through the third chamber. Thus, the inflow of the pre-expanded beads into the hardly filled portion is promoted, and the filling density of the pre-expanded beads in the hardly filled portion is appropriately set.
[0063]
Examples of the difficult filling portion include an outer peripheral tip portion 13 a of the molding space 13, a flange portion of the partition wall molding portion 13 b that molds the partition wall 4, and a remote portion of the remote portion of the molding space 13 that is away from the filler 31. Can be considered.
[0064]
A slit-like clearance 40 is formed between the core mold 11 and the cavity mold 12 in a state in which the mold is closed in order to improve the filling performance in the difficult filling portion of the outer peripheral tip portion 13a, and the flanges of the core mold 11 and the cavity mold 12 are formed. An inter-mold cavity portion 41 as a third chamber is formed between the portions 11 a and 12 a, and the hardly filled portion of the outer peripheral tip portion 13 a is communicated with the inter-mold cavity portion 41 through a clearance 40. The inter-cavity portion 41 is connected to the steam supply pipe 25 and the air supply pipe 26 via the service valve SV3 and the switching valves SWV1 and SWV2, respectively, and to the drain via the drain valve DV3 and the switching valves SWV3 and SWV4. The pipe 27 and the vacuum pipe 28 interposing the vacuum pump P are connected to each other, and the internal pressure of the difficult-to-fill portion of the outer peripheral tip portion 13a can be adjusted by controlling the internal pressure of the mold cavity 41. Yes. However, the inter-cavity portion 41 need only be connected to the drain pipe if it only improves the fillability of the pre-expanded beads, and is not necessarily connected to the steam supply pipe 25, the air supply pipe 26, or the decompression pipe 28. However, by connecting to these tubes, the working fluid other than the filling air in the inter-mold cavity 41 is controlled as will be described later, so that the pre-foamed beads are heated and the molded product 1 is cooled and separated. It is preferable because various merits at the time of molding can be obtained.
[0065]
The opening width of the clearance 40 is set to be smaller than the diameter of the pre-expanded beads, and when filling the pre-expanded beads, only the filling inorganic gas supplied to the molding space 13 together with the pre-expanded beads passes, and the pre-expanded beads Is configured to remain in the molding space 13. However, the clearance 40 may be formed over the entire circumference of the core mold 11 and the cavity mold 12 or may be provided locally only at a necessary portion. In addition, as shown in FIG. 7, the clearance 40 is divided into a plurality (two in the illustrated example) by the partition wall 42, and an inter-mold cavity 41 is provided corresponding to the plurality of clearances 40, and the plurality of inter-mold cavities 41 may be configured such that filling air and other service fluids can be individually controlled.
[0066]
In order to improve the filling property in the difficult filling part of the flange part of the partition wall molding part 13b, a through hole 43 is formed in the collar part of the partition wall molding part 13b, and the exhaust pipe 44 connected to the through hole 43 is It is connected to a drain pipe 27 and a pressure reducing pipe 28 via a drain valve DV4 and switching valves SWV3 and SWV4, respectively. In this case, the in-pipe space 45 of the exhaust pipe 44 functions as a third chamber, and the filling air that has flowed into the flange portion of the partition wall forming portion 13b is discharged through the through hole 43 and the exhaust pipe 44. It is configured. The through-hole 43 may be connected only to the drain pipe 27 if only the fillability is improved, as with the clearance 40, but the steam supply pipe 25, the air supply pipe 26, and the decompression pipe 28. It may be connected to other pipes or the like to control the working fluid more finely.
[0067]
The through hole 43 can be formed in an arbitrary shape such as a round hole shape or a slit shape, but in any case, the pre-foamed beads do not flow into the exhaust pipe 44 through the through hole 43. The opening width is formed. In addition, when it is difficult to fill the pre-expanded beads in the remote part or other parts separated from the filling device 31, a through hole is formed in the same manner as the collar part of the partition wall forming part 13b and connected to the exhaust pipe. It can be configured to discharge the filling air.
[0068]
The second configuration, which is a feature of the present invention, adjusts the temperature of the pre-expanded beads to be supplied to the molding space 13 to a predetermined set temperature, and adapts this to the compression filling pressure (internal pressure of the molding space during compression filling). Is in the point set.
Specifically, the raw material beads are heated to a set temperature in the bead temperature control tank 38 and supplied to the raw material tank 29 via the raw material supply valve V4. Here, the bead temperature control tank 38 is provided with a heating means 39 for heating the pre-expanded beads and a temperature sensor 37a, and the heating temperature by the heating means 39 is controlled based on a signal from the temperature sensor 37a. Then, the temperature of the pre-expanded beads is adjusted to the set temperature. However, the inner wall of the bead temperature control tank 38 is made of a heat insulating material or the outer wall is made of a heat insulating material to improve the heat retaining property of the bead temperature control tank 38 and the atmosphere temperature in the bead temperature control tank 38 is uniform. Thus, it is preferable to use, for example, a hot air blower as the heating means 39 and adjust the temperature while stirring the beads. Further, in order to more precisely adjust the temperature of the pre-expanded beads, a plurality of temperature sensors 37a may be provided and the average temperature may be used as the temperature of the pre-expanded beads. It is preferable that the piping for transporting the pre-expanded beads from the bead temperature control tank 38 to the raw material tank 29 is kept warm, and the temperature of the air for transporting the raw material is also adjusted in advance. The raw material tank 29 is provided with a temperature control means 36 and a temperature sensor 37b for measuring the atmospheric temperature in the raw material tank 29. Based on a signal from the temperature sensor 37b, the temperature setting of the bead temperature control tank 38 is changed. Alternatively, the temperature of the pre-expanded beads before filling can be made constant by controlling the temperature of the temperature adjusting means 36.
[0069]
As the heating means 39, a heating means having an arbitrary configuration can be adopted. However, since heating steam is used at the time of molding, it is preferable in terms of equipment economy to provide a heating means using heating steam. In addition, an electric heater etc. are mentioned as a heating means, You may use together the heating means using heating steam, and heating means, such as an electric heater. As the temperature control means 36, it is preferable in terms of equipment economy to perform temperature control using this cooling water because the cooling water temperature is controlled at 30 to 50 ° C. in the molding factory.
The heating temperature of the pre-expanded beads can be set to any temperature between the normal temperature and the melting point, but considering the deterioration of the beads in the high temperature range or the temperature control in the summer time in the low temperature range, and the energy saving in the winter season, Considering the control accuracy of the compression filling pressure in the low compression pressure region or the high compression pressure region of the molding machine and the bead compression characteristics, it is preferably set to 30 ° C. to 50 ° C. Further, in order to stabilize the mechanical strength and weight of the molded product, the temperature of the pre-expanded beads is preferably adjusted within the range of the set temperature ± 5 ° C.
[0070]
Further, the compression filling pressure of the pre-expanded beads is set in advance by performing the following test, for example.
First, a description will be given of a test performed to obtain an optimum compression filling pressure with respect to the set temperature.
As a molded article, a core material of an automobile bumper having an outer size of 1158.6 mm, a width of 144.3 mm, and a thickness of 114.3 mm was manufactured as follows using pre-expanded beads made of polypropylene.
[0071]
First, a plurality of types of pre-expanded beads having different bulk densities were used and maintained at a set temperature of 24 ° C. to 4.0 kg / cm.²The pre-expanded beads were heat-fused with steam, and a plurality of types of molded products having different bead bulk densities were manufactured. Also, changing only the compression filling pressure, 3.5kg / cm², 3.0kg / cm²In the same way, the molded product was set in the same manner. Then, the relationship between the bead bulk density of the pre-expanded beads and the weight of the molded product after drying at each compression filling pressure was obtained, and the results shown in FIG. 8 were obtained.
[0072]
Next, a plurality of types of pre-expanded beads having different bulk densities were used and maintained at a set temperature of 40 ° C. to 3.5 kg / cm.²The pre-expanded beads were heat-fused with steam, and a plurality of types of molded products having different bead bulk densities were manufactured. Also, only the compression filling pressure is changed to 3.0 kg / cm², 2.5kg / cm²2.0kg / cm²In the same way, the molded product was set in the same manner. Then, the relationship between the bead bulk density of the pre-expanded beads and the weight of the molded product after drying at each compression filling pressure was obtained, and the results shown in FIG. 9 were obtained.
[0073]
Next, a plurality of types of pre-expanded beads having different bulk densities were used and maintained at a set temperature of 55 ° C. to 3.0 kg / cm.²The pre-expanded beads were heat-fused with steam, and a plurality of types of molded products having different bead bulk densities were manufactured. Also, change only the compression filling pressure, 2.5kg / cm²2.0kg / cm²1.5kg / cm²1.0kg / cm²In the same way, the molded product was set in the same manner. Then, the relationship between the bead bulk density of the pre-expanded beads and the weight of the molded product after drying at each compression filling pressure was obtained, and the results shown in FIG. 10 were obtained.
[0074]
The most preferable molding conditions in the present invention are molding conditions such that the weight of the molded product is uniform even if the bulk density of the pre-expanded beads varies due to classification in the process of transferring the pre-expanded beads from the silo to the molding space. As can be seen from the test results shown in FIGS. 8 to 10, when the pre-expanded bead temperature is set to 24 ° C., the compression filling pressure is 3.5 kg / cm.²When the pre-expanded bead temperature is set to 40 ° C., the compression filling pressure is set to 2.0 kg / cm.²When the pre-expanded bead temperature is set to 55 ° C., the compression filling pressure is 1.0 kg / cm.²When set to, the graphs are almost horizontal, and it can be seen that the weight of the molded product hardly changes even if the bulk density of the pre-expanded beads changes.
[0075]
In other words, by setting the compression filling pressure according to the temperature of the pre-expanded beads filled in the molding space, it is possible to produce a molded product so that the weight of the molded product does not change even if the bulk density of the pre-expanded beads changes. I understand. In addition, since it is easier to control the temperature of the pre-expanded beads than to adjust the compression filling pressure, the temperature of the pre-expanded beads to be filled in the molding space is adjusted to a preset temperature, The compression filling pressure is preferably fixed to the compression filling pressure corresponding to the set temperature.
[0076]
The set temperature is preferably set in the range of 30 to 50 ° C. in order to reduce the energy consumption for temperature adjustment and reduce the running cost. In addition, since it is difficult to measure the temperature of the pre-expanded beads directly, the temperature is measured by attaching a temperature sensor to the raw material tank filled with the pre-expanded beads. When the temperature difference from the temperature increases, the weight of the molded product varies greatly depending on the bulk density of the pre-expanded beads. Therefore, the measurement temperature is preferably set within the set temperature ± 5 ° C.
[0077]
The compression filling pressure is set to a pressure suitable for the set temperature. Specifically, it is larger than the atmospheric pressure, and as can be seen from FIGS. 8 to 10, {(70−set temperature [° C.]) / 10} kg / cm.²It will be set below the value obtained by the equation. More preferably, 0.5 kg / cm²Above, {(70−set temperature [° C.]) / 10} kg / cm²It will be set below the value obtained by the equation.
[0078]
Next, a verification test performed for verifying the test result will be described.
In order to produce a molded product having the same size as the molded product, a plurality of types of pre-expanded polypropylene beads having a bulk density of 59 to 64 g / L are used, and the pre-expanded beads are kept at a set temperature of 40 ° C. .5kg / cm²The pre-expanded beads were heated and fused with steam, and 100 molded products with different bead bulk densities were manufactured. Then, the relationship between the bead bulk density of the pre-expanded beads of these molded products and the weight of the molded product was obtained, and the results shown in FIG. 11 were obtained.
[0079]
Next, in order to produce a molded product having the same size as the molded product, a plurality of types of polypropylene pre-expanded beads having a bulk density of 51 to 58 g / L were used, and this was maintained at a set temperature of 40 ° C. 2.0kg / cm in state²The pre-expanded beads were heated and fused with steam, and 900 molded products with different bead bulk densities were manufactured. Then, the relationship between the bead bulk density of the pre-expanded beads of these molded products and the weight of the molded product was obtained, and the results shown in FIG. 12 were obtained.
[0080]
As shown in FIG. 11 and FIG. 12, by properly setting the relationship between the temperature of the pre-expanded beads to be filled in the molding space and the compression filling pressure, the weight of the molded product depends on the bulk density of the pre-expanded beads. Although it tends to increase somewhat, it does not increase greatly, and there is less variation in the weight of the molded product, indicating that the test results are compatible with mass production.
[0081]
Further, the compression ratio of the pre-expanded beads obtained by dividing the density of the molded product by the bulk density of the pre-expanded beads under the temperature condition of the pre-expanded beads before the start of compression filling is 1.2 to 1.5, preferably 1. The compression filling pressure is set to 25 to 1.45. In other words, when the compression ratio is less than 1.2, the pre-expanded beads are not sufficiently foamed, and the molded product contracts significantly after release, or a gap is formed between the beads, and a good product is obtained. There is no problem. In addition, when the compression ratio exceeds 1.5, the space between the bead particles in the molding space after filling becomes very narrow, and the heating steam does not pass between the bead particles, resulting in poor fusion. Only the part that has passed is excessively foamed, and there is a problem that cracks occur in the molded product and the cooling time becomes long, so the compression filling pressure can be set so that the compression ratio is 1.2 to 1.5. preferable.
[0082]
Next, an example of a pre-expanded bead filling method using the in-mold foam molding apparatus 10 will be described.
First, pre-expanded beads are filled in a containing tank (not shown) and 0.3 to 2.0 kg / cm.²Inorganic gas is pressed into the pre-expanded beads. That is, the pre-expanded beads used in the present invention are made of a polyolefin resin, and generally have a weaker foaming power than polystyrene resins. Therefore, even if heated with steam, the pre-expanded beads do not sufficiently expand, It is conceivable that the quality of the molded product is deteriorated, for example, the adhesiveness is lowered, or the gap between the beads is increased and the appearance is lowered. For this reason, it is preferable to press-fit inorganic gas into the pre-expanded beads in advance to increase the foaming power. However, although this composition process may be used depending on the raw material to be used, it is generally omitted.
[0083]
The pre-expanded beads thus obtained are supplied to the bead temperature control tank 38, while the temperature of the pre-expanded beads in the bead temperature control tank 38 is measured, the inside of the bead temperature control tank 38 is heated by the heating means 39, and the pre-expansion is performed. After adjusting the temperature of the beads to a predetermined set temperature of 30 to 50 ° C., the pre-expanded beads are supplied to the raw material tank 29 that has been kept warm.
[0084]
Next, after closing the core mold 11 and the cavity mold 12, the chambers 17, 18 and the inter-cavity 41 are used to adjust the inside of the molding space 13 to a compression filling pressure adapted to the set temperature of the pre-expanded beads. The inside space 45 is pressurized to a preset compression filling pressure, and the inside of the raw material tank 29 is set slightly lower than the pressure in the molding space 13. In this way, the temperature of the pre-expanded beads at the time of compression filling is set to the set temperature, and the compression filling pressure is set to a pressure adapted to this set temperature. Even if there is a variation, it is possible to produce a molded product having a uniform weight.
[0085]
Next, the filler of the filling device 31, the shutter 32, the filling air valve V2, and the regulating air valve V3 are opened, and filling of the pre-expanded beads is started. The filling air pressure in the filling air valve V2 is at least 2 kg / cm from the internal pressure of the raw material tank 29.²More than 4kg / cm in absolute value²Set to above.
[0086]
During filling, the pre-expanded beads flow into the molding space 13 while being diluted with the compressed air in the raw material tank 29, the compressed air from the adjustment air valve V3, and the compressed air from the filling air valve V2. At this time, the volume ratio between the air flowing into the molding space 13 and the pre-expanded beads is defined by defining the numerical value obtained by dividing the volume of the air supplied to the molding space 13 by the volume of the pre-expanded beads as the final dilution degree. The final dilution degree is set to 5 or more, preferably 10 to 50.
[0087]
If the final dilution degree of the pre-expanded beads is larger than 50, the amount of the pre-expanded beads to be filled per unit time is lowered, so that it takes time to fill, the molding cycle time is extended, and the air consumption is large. There is a problem of becoming. Further, if the final dilution degree is less than 10, the number of contacts or collisions between the pre-expanded beads in the filling tube 33, the filling device 31 or the molding space 13 increases, so that the resistance to prevent the filling of the pre-expanded beads increases. In addition, since the pre-expanded beads obstruct the air flow, there is a problem that the filling cannot be performed satisfactorily. However, when the pre-expanded beads are supplied by a supply means such as a screw conveyor, the rotation speed of the screw conveyor is controlled so that the final dilution degree becomes a desired value, and the unit of the pre-expanded beads with respect to the molding space 13 The supply amount per hour will be set.
[0088]
Thus, the compressed air that has flowed into the molding space 13 increases the pressure in the chambers 17, 18, the mold cavity 41, and the in-pipe space 45 through the vent hole 22, the clearance 40, and the through hole 43. At this time, by controlling the pressures of the chambers 17 and 18, the mold cavity 41, and the pipe inner space 45 individually or in combination using the drain valves DV1 to DV4, the pre-expanded beads are hardly filled. On the other hand, the pre-expanded beads can be filled first to suppress the density variation in each part of the molded product 1 or to ensure the filling density appropriately.
[0089]
For example, the drain valves DV1 to DV4 are sequentially opened when the internal pressures of the chambers 17 and 18, the mold cavity 41, and the pipe space 45 become equal to or higher than the set pressure, and the set pressure is set to the second chamber 18>. If the first chamber 17> the mold cavity 41> the in-pipe space 45, first, the drain valve DV4 is opened, and the pre-expanded beads are filled in the difficult-to-fill part 40. When the filling is substantially completed and the internal pressure of the chambers 17 and 18 and the inter-mold cavity 41 is increased, the drain valve DV3 is opened, and the outer edge of the molding space 13 is filled with the pre-expanded beads. In this way, the drain valve is opened in order from the smallest set pressure, and the molding space 13 is filled with the pre-expanded beads.
[0090]
As another control method, the filling process is divided into four, the air pressure in the pipe space 45 is controlled using only the drain valve DV4 in the first process, and the drain valves DV3 and DV4 are used in the second process. Is used to control the air pressure in the inter-cavity 41 and the pipe inner space 45, and in the third step, the air in the first chamber 17, the inter-cavity 41 and the pipe inner space 45 using the exhaust valves DV1, DV3 and DV4. The pressure is controlled, and in the fourth step, the pre-expanded beads are sequentially placed in the molding space 13 while controlling the air pressure in the chambers 17 and 18, the mold cavity 41 and the pipe space 45 using the exhaust valves DV 1 to DV 4. Fill.
[0091]
Thus, after filling the pre-expanded beads, the filler of the filler 31 is closed and the adjustment air valve V3 is closed, and the pre-expanded beads remaining in the filler 31 and the filling pipe 33 are filled into the raw material tank 29 using the filling air. Then, the filling air valve V2 and the shutter 32 are closed to complete the filling cycle, and a series of normal molding steps of heating, cooling and mold release are sequentially performed to obtain the predetermined molded product 1.
[0092]
In the in-mold foam molding apparatus 10, since the clearance 40 and the inter-mold cavity 41 are formed, the working fluid in the clearance 40 and the inter-mold cavity 41 is used as follows. It is also possible to perform heating, cooling, and mold release while controlling the temperature.
[0093]
That is, in the heating process, steam is introduced into the inter-cavity portion 41 and the clearance 40 to heat the peripheral portion of the clearance 40 and also into the molding space 13, and the outer peripheral tip portion 13 a of the molding space 13. The operation to supplement the heating of the pre-expanded beads is performed.
[0094]
In this case, the flange portions 11a and 12a constituting the outer peripheral portions of both molds 11 and 12, which have conventionally had a relatively large heat capacity and did not easily rise in temperature, are directly heated. Since the temperature of the pre-expanded beads can be rapidly increased, the advantage that the total molding time can be shortened is obtained.
[0095]
In addition, since the air purge of the outer peripheral tip portion 13a by steam is ensured or an independent pressure adjustment operation is possible through the clearance 40, the mold pressure is controlled by controlling the steam pressure to plus or minus the chamber pressure. The temperature balance in 13 can be set to the most preferable state, and a significant cycle time reduction or energy saving effect can be expected.
[0096]
In the cooling step, in addition to cooling water injection, the inside of the molding space 13 is depressurized through the clearance 40 to promote cooling due to vaporization of water that has entered the molding space 13 by water injection, and drain operation is performed. .
Even in this case, the temperature drop of the flange portions 11a and 12a of the molds 11 and 12 that have a large heat capacity and are difficult to decrease in temperature can be promoted, which can greatly contribute to the reduction of cycle time.
[0097]
In the mold releasing step, an operation of discharging the drain accumulated in the clearance 40 and the inter-mold cavity 41 is performed. As a result, since the clearance 40 and drainage accumulated in the inter-mold cavity 41 can be removed due to the water injection during cooling, problems such as making the workplace wet with the mold even when the mold is opened for mold release can be solved. .
[0098]
In the description so far, the case where the partition wall forming portion 13b is provided in the core mold 11 has been described. However, when the partition wall forming portion 13b is provided on the cavity mold 12 side, By adopting a method in which the chambers 17 and 18 in the description are read in reverse, exactly the same operations and effects can be obtained.
[0099]
For example, the molded product 1 molded in this way has a wall thickness of the partition wall 4 of 20 mm or less, preferably 3 to 15 mm, more preferably 5 to 10 mm, or the partition wall 4 of the molded product 1. Even in the molded product 1 that has been thought to be difficult to fill, such as those with 3 or less beads arranged in the thickness direction, the density in each part is within ± 5% of the average density Therefore, the molded article 1 is preferably a good quality molded article 1 having a small density variation set within ± 4%, more preferably within ± 3%. Further, since molding is performed in a state in which the temperature of the pre-expanded beads is maintained at the set temperature and the compression filling pressure is maintained at a pressure adapted to the set temperature, for example, when the molded product of 900 g is molded, the weight variation 3σ of the molded product is What is 10% in the conventional molding method can be adjusted to 3% or less, and there is little variation in the weight of the molded product between the molding shots, and the molded product has good molded product quality and yield.
[0100]
INDUSTRIAL APPLICABILITY The present invention is effective and useful when molding a package having a relatively large and complicated shape, such as a molded product 1 having a small and simple shape such as a cup noodle container. . In particular, it is useful for a collective package having both a thick part and a thin part. In addition, since there is less variation in weight between molding shots, it can be suitably used for molded products that are severely limited in mechanical strength and weight, such as a core material for automobile bumpers.
[0101]
Next, a quality evaluation test of the molded product 1 filled with pre-expanded beads and molded by this filling method will be described.
In the production of the molded product 1 having the shape shown in FIGS. 1 and 2, as the filling method of the pre-expanded beads, the pre-expanded beads are filled by the cracking filling method, the pressure filling method and the compression filling method, Four kinds of molded products were manufactured by filling the pre-expanded beads by the four filling methods when the pre-expanded beads were filled by the filling method of the present invention. And as shown in FIG. 2, the density in the front-end | tip part 4a of the partition wall 4 of the molded article 1, the middle part 4b, and the base end part 4c was measured, respectively, and the result as shown in Table 1 was obtained. Also, the filling method of the present invention and the conventional compression filling method are each performed 100 times, and the weight of each molded shot is measured to determine the average weight, maximum and minimum weight, and maximum weight difference. Then, the weight variation 3σ of the molded product was obtained, and the results shown in Table 2 were obtained.
[0102]
[Table 1]

[0103]
As shown in Table 1, in the molded product manufactured by filling the pre-expanded beads by the conventional filling method, the density decreases as it goes from the base end portion 4a of the partition wall 4 to the tip end portion 4c side. It can be seen that the molded product produced by filling the pre-expanded beads by the filling method of the present invention has a substantially uniform density. That is, according to the filling method of the present invention, it can be seen that a high-quality molded product with less variation in density can be produced. Further, in the conventional molded product, it is necessary to design the molded product based on the low density portion so that sufficient strength can be obtained even in the low density portion, and there is a problem that the molded product becomes heavy. In the molded product of the present invention, since the density in each part of the molded product is substantially uniform, the molded product can be configured to be lightweight while sufficiently securing the strength of the molded product, and the amount of pre-expanded beads is reduced. Thus, the manufacturing cost of the molded product can be reduced.
[0104]
[Table 2]

[0105]
As shown in Table 2, when the pre-expanded beads are filled and molded by the filling method of the present invention, the variation in the weight of the molded product between molding shots is smaller than the case of filling and molding by the conventional compression filling method. It can be seen that the desired weight is accurately formed.
[0106]
Next, the molding cycle evaluation test will be described.
As a compression-molded product, it has a shape as shown in FIGS. 1 and 2 and is an outer dimension of 450 mm in length, 300 mm in width, 180 mm in height, five ribs in the vertical direction with thickness of 8 mm, and ribs in the horizontal direction with thickness of 8 mm In producing one molded product, as an example of the present invention, polypropylene beads having a bulk density of 20 g / L are used as pre-expanded beads, and the bulk density of the molded product is 28 g / L, 26 g / L, and 24 g / L. Using the molded products of Examples 1 to 3 and polyethylene beads having a bulk density of 25 g / L as the pre-expanded beads, the bulk density of the molded products was set to 33 g / L, 30 g / L, and 29 g / L. The molded articles of Examples 4 to 6 were produced.
[0107]
Further, as comparative examples, moldings of Conventional Examples 1 to 3 using polypropylene beads having a bulk density of 20 g / L as pre-expanded beads and setting the bulk density of the molded product to 30 g / L, 28 g / L, and 26 g / L. And molded products of Conventional Examples 4 to 6 with bulk density of 40 g / L, 38 g / L, and 35 g / L using polyethylene beads having a bulk density of 25 g / L as pre-expanded beads. did.
And the molding cycle of Examples 1-6 and Comparative Examples 1-6 and the molded product quality were measured, and Table 3, 4 was obtained. However, in Tables 3 and 4, the quality of the molded product is a three-stage evaluation of the state of adhesion between the beads. Those with difficulty were indicated by “△”, and those that could not be used at all were indicated by “x”.
[0108]
[Table 3]

[0109]
[Table 4]

[0110]
As shown in Tables 3 and 4, in the conventional molding method, when polypropylene beads were used as the pre-expanded beads, the bulk density of the molded product was 30 g / L (compression ratio 1.5) as in Comparative Example 1. Otherwise, good quality molded products cannot be obtained, and when polyethylene beads are used, the molded product bulk density is 40 g / L (compression ratio 1.6) or more as in Comparative Example 4. If not set, good quality molded products cannot be obtained. In contrast, in the molding method of the present invention, when polypropylene beads are used as the pre-expanded beads, the bulk density of the molded product is 26 g / L as in Example 2 (when the compression ratio is set to 1.3). However, when a molded product with sufficient quality is obtained and polyethylene beads are used, even when the bulk density of the molded product is set to 30 g / L (compression ratio 1.2) or more as in Example 5, A molded product with good quality can be obtained, and the molding cycle becomes longer as the compression ratio obtained by dividing the bulk density of the molded product by the bulk density of the pre-expanded beads increases, so that a molded product with sufficient quality can be obtained. In the comparative examples 1 and 4 obtained, they are 180 sec and 210 sec, whereas in the examples 2 and 3, they are 130 sec and 120 sec. The molding method of the present invention has a sufficient quality as compared with the conventional molding method. Secure While, it can be seen that can be significantly shortened molding cycle.
[0111]
In the present embodiment, the internal pressures of the chambers 17 and 18, the inter-mold cavity 41 and the pipe space 45 are adjusted so that the density in each part of the molded product 1 is uniform, but it is desired to increase the strength locally. It is also possible to increase the packing density of the pre-expanded beads in the part. In addition, the present invention can of course be applied to the molding of various shapes other than the molded product 1.
[0112]
【The invention's effect】
  According to the in-mold foam molding method for polyolefin resin according to claim 1, the pre-expanded beads whose temperature is adjusted to a set temperature of 30 to 50 ° C. are pressures adapted to the set temperature and larger than the atmospheric pressure, {(70-set temperature [° C.]) / 10} kg / cm²Since the molding space is compressed and filled with a compression and filling pressure equal to or less than the value obtained by the above formula, even if the bulk density of the pre-expanded beads fluctuates due to classification during the transfer of the pre-expanded beads between the respective molding shots, its adverse effect Since a molded product having a uniform weight can be manufactured without being subjected to the above, the quality stability of the molded product can be remarkably improved.
  In addition, since the temperature of the pre-expanded beads is set within the range of the set temperature ± 5 ° C, the temperature can be adjusted relatively easily, and the variation in the bulk density of the molded product between the molding shots can be improved. Since it can reduce to the extent which does not exert a bad influence, it is preferable.
  In addition, pre-expanded beads made of polyolefin resin are softer and more gas permeable, so the particle shape is much easier to deform than pre-expanded beads made of polystyrene resin with the same expansion ratio. It is preferable because the properties can be further improved.
Furthermore, the inorganic gas pressures in the three chambers are controlled individually or in any combination, and the compressed pre-expanded beads are loaded into the molding space on the inorganic gas flow so that, for example, the pre-expanded beads are filled. By controlling the inorganic gas pressure in each chamber so that the pre-expanded beads are filled in the difficult filling portion first, the filling density in each portion of the molded product can be set uniformly. For this reason, even in a molded product that is difficult to be filled with pre-expanded beads and has a thin partition wall with a thickness of 20 mm or less, the filling density in each part of the molded product can be set to an appropriate value without increasing the number of fillers. . Further, if the pre-expanded beads are first filled in the portion where the strength and rigidity are to be increased, the filling density in the portion can be locally increased to increase the strength.
[0113]
The compression ratio of the pre-expanded beads obtained by dividing the density of the molded product by the bulk density of the pre-expanded beads under the temperature condition of the pre-expanded beads before the start of compression filling as in claim 2. When the compression filling pressure is set to 5, productivity can be improved by shortening the molding cycle time, and a molded product with good quality in which beads are closely adhered can be molded. Further, since the bulk density of the molded product and the bulk density of the pre-expanded beads are close to each other, it becomes possible to increase the transport efficiency and storage efficiency of the pre-expanded beads.
[0114]
As described in claim 3, the pre-expanded beads are made of a polyolefin resin, the cell diameter is 100 to 900 μm, the expansion ratio is 5 to 60 times, the DSC 2′nd peak ratio is 8 to 60%, and the closed cell ratio is 65. Using pre-expanded beads made of more than 100% polyolefin-based resin can improve the surface quality of the molded product and improve the appearance of the molded product, and also eases the restrictions on the heating conditions during molding, thereby improving moldability and energy saving. Can be improved.
[0116]
  Claim4As described, when the third chamber has a chamber communicating with the molding space through the clearance between the core mold and the cavity mold, the filling inorganic gas that has flowed into the outer peripheral portion of the molding space through the clearance is efficiently obtained. For example, when manufacturing a container having a deep bottom, for example, a clearance is formed at a position corresponding to the opening edge of the container, so that the number of filling devices is not increased. The filling density of the expanded beads can be set appropriately, and the quality of the container can be improved.
[0117]
  Claim5As described, if a chamber communicating with the inner part of the partition wall molding part is provided as the third chamber, the filling density cannot be ensured sufficiently, so that a thickness of 20 mm or less, which has been conventionally considered difficult, can be formed. Even for a molded product with a complicated shape such as a partition wall, by filling the pre-expanded beads in the partition wall molding part first, the filling density of the pre-expanded beads in the partition wall molding part can be increased, Producing high-quality molded productsThisIs possible.
[0118]
  Claim6As described, when the third chamber is provided with a chamber communicating with the inner part of the remote part of the molding space away from the pre-expanded bead filling device, the filling of the remote part is likely to decrease the packing density of the pre-expanded beads. It is possible to secure a sufficient density and manufacture a molded product with good quality.
[0119]
  Claim7When the partition wall forming portion having the structure as described above is formed, a molded product having a partition wall in which the relational expression of H / T ≧ 10 is established between the height H (mm) and the thickness T (mm) is formed. It becomes possible. Such a molded part has been conventionally considered difficult to be molded because the filling density of the pre-expanded beads in the partition wall molded part cannot be sufficiently secured.6The molding method according to claim 1, in particular, claim5By molding by the described molding method, it can be molded with good quality.
[0120]
  As the pre-expanded beads, those made of any material can be adopted as long as they are made of polyolefin resin, but they are inexpensive and easy to obtain.8Polypropylene resin as described, or claims9It is preferable to employ a polyethylene resin as described.
[0121]
  In the molding method, a molded body having a thin wall and a high partition wall can be molded.0As described, it is preferable to form a draft in the partition wall molding portion because even such a molded product can be prevented from being damaged during mold release.
[Brief description of the drawings]
FIG. 1 is a perspective view of a molded product.
[Figure 2] Longitudinal section of molded product
FIG. 3 is a longitudinal sectional view of an in-mold foam molding apparatus.
4 is a cross-sectional view taken along line IV-IV in FIG.
[Fig.5] Longitudinal section around the vent
[Figure 6] Front view of core vent
FIG. 7 is a view corresponding to FIG. 4 of an in-mold foam molding apparatus having another configuration.
FIG. 8 is a diagram showing the relationship between the bulk density of pre-expanded beads and the weight of the molded product
FIG. 9 is a diagram showing the relationship between the bulk density of pre-expanded beads and the weight of the molded product.
FIG. 10 is a diagram showing the relationship between the bulk density of pre-expanded beads and the weight of a molded product
FIG. 11 is a diagram showing the relationship between the bulk density of pre-expanded beads and the weight of a molded product
FIG. 12 is a diagram showing the relationship between the bulk density of pre-expanded beads and the weight of a molded product
FIG. 13 is a longitudinal sectional view of an in-mold foam molding apparatus according to the prior art.
FIG. 14 is a longitudinal sectional view of an in-mold foam molding apparatus having another configuration according to the prior art.
[Explanation of symbols]
1 Molded product 2 Body
3 accommodation space 4 partition wall
4a tip 4b midway
4c Base end
10 In-mold foam molding equipment
11 Core type 12 Cavity type
11a, 12a Flange
13 Molding space 13a Outer peripheral tip
13b Partition wall forming part 14 Frame-shaped frame
15 Back plate 16 Housing
17 First chamber 18 Second chamber
20 Core vent
21 Core vent hole
22 Vent hole 23 Mounting hole
22a Through hole 22b Long hole
SV1 to SV3 service valves
SWV1 to SWV4 selector valve
DV1 to DV4 drain valve
V1 Intake valve V2 Filling air valve
V3 adjustment air valve
25 Steam supply pipe 26 Air supply pipe
27 Drain pipe P Vacuum pump
28 Pressure reducer 29 Raw material tank
30 Intake pipe 31 Filler
32 Shutter 33 Filling tube
34 Filling air supply pipe
35 Adjustment air supply pipe
36 Temperature control means
37a Temperature sensor 37b Temperature sensor
38 Bead temperature control tank 39 Heating means
40 Clearance 41 Cavity between molds
42 Bulkhead 43 Through-hole
44 Exhaust pipe 45 Inner space

Claims (10)

A molding space having a partition wall molding portion for molding a partition wall having a thickness of 20 mm or less with respect to a molded product, and at least three chambers for controlling a working fluid in the molding space, A first chamber on the back side of the core mold that communicates, a second chamber on the back side of the cavity mold that communicates with the molding space, and a third chamber that communicates with a difficult-to-fill portion that is difficult to fill with the pre-expanded beads in the molding space. Using the in-mold foam molding equipment provided, the temperature of the pre-expanded beads made of polyolefin resin is adjusted to a constant temperature of ± 5 ° C., centered on the set temperature within the range of 30 to 50 ° C., and the compression filling pressure is adjusted. greater than atmospheric pressure to a pressure to adapt to the set temperature, {(70-set temperature [℃]) / 10} in a compressed state by an inorganic gas obtained value below a predetermined pressure by the equation kg / cm ² While controlling an inorganic gas pressure individually or in any combination of each chamber to the compression filling pressure, the molding space having a partition wall forming portion for forming a thickness of 20mm or less of the partition wall against the molded article A method for in-mold foam molding of polyolefin resin, in which pre-expanded beads are compressed and filled, and then heat-sealed with steam, and then cooled and taken out from the mold.   Under the pre-expanded bead temperature conditions before the start of compression filling, the compression filling pressure is set so that the compression ratio of the pre-expanded beads obtained by dividing the density of the molded product by the bulk density of the pre-expanded beads is 1.2 to 1.5. The method for in-mold foam molding of a polyolefin resin according to claim 1.   The pre-expanded beads are made of a polyolefin resin and have a cell diameter of 100 to 900 μm, an expansion ratio of 5 to 60 times, a DSC 2′nd peak ratio of 8 to 60%, and a closed cell ratio of 65% or more. The method for in-mold foam molding of a polyolefin resin according to claim 1 or 2, wherein the pre-expanded beads are used. The in-mold foam molding of a polyolefin-based resin according to any one of claims 1 to 3, wherein the third chamber includes one or a plurality of chambers communicating with the molding space via a clearance between the core mold and the cavity mold. Method. As the third chamber, there is provided one or a plurality of chambers communicating with the inner part of the partition wall molding part, and when the pre-expanded beads are filled, the pre-expanded beads are previously filled in the partition wall molded part. The method for in-mold foam molding of a polyolefin resin according to any one of claims 1 to 4, wherein the inorganic gas pressure in one chamber is controlled. The third chamber is provided with one or a plurality of chambers communicating with the inner part of the remote part of the molding space away from the pre-expanded bead filling device. The method for in-mold foam molding of a polyolefin resin according to any one of claims 1 to 5 , wherein the inorganic gas pressure is controlled so that the foam beads are filled. The height of the molded as a partition wall H (mm), the thickness is taken as T (mm), according to claim 1 relationship of H / T ≧ 10 had a partition wall forming portion as true 6 The method for in-mold foam molding of a polyolefin resin according to any one of the above. The method for in-mold foam molding of a polyolefin resin according to any one of claims 1 to 7 , wherein the pre-expanded beads are made of a polypropylene resin. The method for in-mold foam molding of a polyolefin resin according to any one of claims 1 to 8 , wherein the pre-expanded beads are made of a polyethylene resin. The method for in-mold foam molding of a polyolefin-based resin according to any one of claims 1 to 9 , wherein a draft is formed in the partition wall molding portion.

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