【発明の詳細な説明】[Detailed description of the invention]
本発明は予備発泡粒子型内成型体の製造方法に
関する。
予備発泡粒子型内成型体（以下型内成型体また
は単に成型体と称する）は、予備発泡粒子を成型
用型内に充填し、次いで水蒸気等の加熱媒体によ
り加熱して予備発泡粒子を発泡融着せしめること
により製造されている。しかしながら従来の方法
によつて製造された型内成型体は表面に予備発泡
粒子形状模様が現われるため、成型に用いる予備
発泡粒子の大きさの違いにより成型体ごとに表面
模様が異なり、また予備発泡粒子の大きさが均一
でないと模様が乱れたものとなり外観上見苦しい
ものであつた。しかも成型体ごとの粒子形状模様
の違いや模様の乱れという問題に加えて、成型体
表面が水蒸気等の加熱媒体を供給するための蒸気
孔と接しているため成型体表面には蒸気孔の跡が
顕著に残り、成型体の外観を著るしく損なう欠点
があつた。また従来の製造方法により得られる成
型体では、成型体表面の予備発泡粒子の隣接部に
凹陥部が形成されることは避け難く、このため表
面側の予備発泡粒子の融着は比較的弱いものとな
り、成型体表面側の予備発泡粒子が欠け落ち易い
という欠点も有していた。更に、予備発泡粒子を
加熱する蒸気等を供給するため通常、型窩壁に設
けた貫通孔に、複数の孔またはスリツトを有し、
柱状に形成された別体の蒸気孔形成部品を打ち込
んで蒸気孔を形成しているが、従来の製造方法に
おいて予備発泡粒子を均一に加熱するには蒸気孔
（型窩壁に設ける貫通孔）を多数必要とし、この
ため多数の蒸気孔形成部品打ち込みのための手間
がかかり、また蒸気孔形成部品コストが高くつく
等の問題も有していた。
本発明は上記の点に鑑みなされたもので、外観
が良好で、表面の粒子融着性に優れた成型体を得
ることができるとともに、加熱効率に優れ少数の
蒸気孔によつても予備発泡粒子を均一に加熱して
成型体を得ることができる予備発泡粒子型内成型
体の製造方法を提供することを目的とする。
即ち本発明は多数の貫通小孔を有する金属製ス
クリーンを内壁に装着してなる成型用型内に予備
発泡粒子を充填し、次いで該予備発泡粒子を加熱
媒体により加熱し、予備発泡粒子を発泡融着せし
めて成型体を得ることを特徴とする予備発泡粒子
型内成型体の製造方法を要旨とする。
本発明に用いられる予備発泡粒子としては架橋
あるいは無架橋の、ポリプロピレン系樹脂、ポリ
エチレン系樹脂、ポリスチレン系樹脂等を基材樹
脂とする予備発泡粒子であるが、特にプロピレン
単独重合体、エチレン―プロピレンランダム共重
合体、エチレン―プロピレンブロツク共重合体等
を基材樹脂とする無架橋ポリプロピレン系樹脂予
備発泡粒子が好ましい。
本発明に用いられる、多数の貫通小孔を有する
金属製スクリーンとしては、ステンレス、銅等か
らなる金網、金属板に多数の小孔を穿設したいわ
ゆるパンチングメタル等が用いられる。上記スク
リーンは、金網の場合には通常30〜500メツシユ
程度のものが好ましく、またパンチングメタル等
の場合には、１cm2当り20〜3000個程度の貫通小孔
を穿設したものが好ましい。上記小孔の大きさが
大きすぎると成型体表面に予備発泡粒子形状模様
が現われ、従来の製造方法によつて得られる成型
体の有する前述の欠点を充分解決することができ
ず、また逆に小孔の大きさが小さすぎると水蒸気
等の加熱媒体の透過性が低下し、予備発泡粒子の
加熱効率に低下をきたす。
次に本発明の製造方法の一実施例を図面に基き
説明する。
第１図において１は、従来の型内成型体の製造
に用いられる成型用型で第１成型用型１ａと第２
成型用型１ｂとからなる。該成型用型１の内壁に
は多数の貫通小孔を有する金属製スクリーンとし
ての金網２，２が装着されている。上記、内壁に
金網２，２を装着してなる成型用型１内に予備発
泡粒子３を充填し、しかる後、該予備発泡粒子３
を加熱媒体により加熱する。加熱媒体としては通
常1.0Kg／cm2(G)〜5.0Kg／cm2(G)の水蒸気が用いら
れ、水蒸気等の加熱媒体は蒸気孔４より供給され
る。予備発泡粒子３は、加熱により発泡して粒子
相互が融着し、冷却後型１より取り出す（金網２
より剥離する）ことにより型通りの成型体が得ら
れる。
上記方法により得られる成型体の表面には予備
発泡粒子形状模様は形成されず、金網２の形状模
様のみが形成され、このため成型に用いる予備発
泡粒子の大きさの如何にかかわらず、成型体表面
には常に同一の模様が形成される。
上記実施例においてはスクリーンとしての金網
２を成型用型１の内壁全体に装着した場合を示し
たが、金網２は成型用型１の内壁の一部に装着し
てもよい。しかも金網２は一枚のみを装着する場
合に限定されず、メツシユの異なるものを複数枚
重ね合わせて用いることもでき、織模様を変えて
成型体の表面に変化を与えることも出来る。この
場合、熱媒体の透過性が更に良好となり、加熱効
率の向上を図ることができ、また成型体表面側
（金網と接する面）の予備発泡粒子の融着性を更
に向上することができる。また金網製スクリーン
としてパンチングメタル等を用いる場合には貫通
小孔は任意の形状、配設パターンに形成すること
ができ、貫通小孔の形状、配設パターンの異なる
スクリーンを用いて成型を行なうことにより、成
型体の表面模様はバラエテイーに富んだものとな
り、成型体の意匠性をも向上できる。
以上説明したように本発明によれば、成型体表
面の、成型時金属製スクリーンと接した面に予備
発泡粒子形状模様や蒸気孔跡が現われず、スクリ
ーン形状の模様のみを現わすことができ、成型に
用いる予備発泡粒子に大きさの違いや大きさのバ
ラツキが存在する場合でも成型体表面には常に同
一模様が形成されるため、成型体の外観が予備発
泡粒子形状に左右される不具合がなく、また成型
体表面に蒸気孔跡が現われることによる外観低下
を防止できる。しかも成型時に金属製スクリーン
と接する表面側の予備発泡粒子はスクリーンの貫
通小孔部と非貫通小孔部によつて形成される凹凸
により押圧されるため該発泡粒子相互の融着性が
向上し、表面側の予備発泡粒子が欠け落ちる等の
欠点のない優れた成型体を提供することができ
る。また形状、配設パターンの異なる貫通小孔を
有するスクリーンを用いて成型を行なうことによ
り表面模様の種々異なる成型体を得ることがで
き、意匠性に優れた成型体を提供することができ
る。更に本発明によれば、成型用型内壁に多数の
貫通小孔を有する金属製スクリーンを装着して用
いるため、スクリーンによつて加熱媒体の熱エネ
ルギーを型内の予備発泡粒子に均一に加えること
ができ、この結果、加熱効率向上ひいては生産性
向上が図れるとともに、成型用型に設ける蒸気孔
の数を少なくすることができ、蒸気孔形成部品の
取り付け作業の簡易化、蒸気孔形成部品にかかる
部品コスト低減化等を図ることができる等種々の
効果を有する。
而して本発明により得られる成型体は、外観良
好な意匠性に富んだものであるとともに表面強度
に優れ、包装材、家具、寝具、自動車船舶部材、
デイスプレイ等として利用価値の高いものであ
る。
以下具体的実施例を挙げて本発明を更に詳細に
説明する。
尚、実施例、比較例において、表面粒子の融着
強度、成型体の表面状態は以下の如く判定した。
表面粒子の融着強度：防衛庁規格（NDS）Z0503
に準じ、厚さ10mm、幅25mm、長さ300mm
の成型体を試料として、該試料片を直径
20mmの円筒の外周面に沿わせて折り曲げ
た時の試料片表面に割れが生じるまでの
角度で示した。
成型体の表面状態：
〇……成型体表面に規則的なスクリーン形状の
模様が形成され、予備発泡粒子形状模様
や、蒸気孔跡が形成されない。
×……成型体表面に予備発泡粒子形状模様や蒸
気孔跡が明確に現われる。
実施例１〜６，比較例１〜６
エチレン―プロピレンランダム共重合体を基材
樹脂とする第１表に示す予備発泡粒子を50メツシ
ユの金網を内壁に装着した厚さ40mm、巾300mm、
長さ300mmの金型内に充填し、3.6Kg／cm2(O)の水蒸
気にて加熱し予備発泡粒子を発泡融着せしめた後
50℃まで冷却し、得られた成型体を金網より剥離
して金型より取り出した。比較例として実施例と
同一の金型に金網を装着せずに成型を行なつた。
得られた各成型体の表面粒子の融着強度測定、お
よび成型体表面状態の観察を行なつた。また実施
例３、比較例３については成型に要した時間を測
定した。結果を第１表に合わせて示す。
実施例７，比較例７
内壁をゴムライニングした金型内壁の壁側より
40メツシユ、次いで100メツシユの金網を重ねて
装着し、該金型に実施例３と同一の予備発泡粒子
を充填して実施例３と同一条件で成型を行なつ
た。比較例として金網を用いずに他は上記実施例
７と同一条件で成型を行なつた。得られた成型体
の表面粒子の融着強度の測定、成型体の表面状態
の観察を行なつた。また成型に要した時間およ
び、使用水蒸気量の測定を行なつた。結果を第２
表に示す。
The present invention relates to a method for manufacturing a pre-expanded particle in-mold body. Pre-expanded particle in-mold products (hereinafter referred to as in-mold products or simply molded products) are produced by filling pre-expanded particles into a mold, and then heating the pre-expanded particles with a heating medium such as steam to foam and melt the pre-expanded particles. Manufactured by dressing. However, in-mold molded products manufactured by conventional methods have a pre-foamed particle shape pattern on the surface, so the surface pattern differs depending on the molded product due to the difference in the size of the pre-foamed particles used for molding. If the particle sizes were not uniform, the pattern would be disordered and the appearance would be unsightly. Moreover, in addition to the problem of differences in particle shape patterns and disordered patterns for each molded product, there are traces of steam holes on the surface of the molded product because the surface of the molded product is in contact with steam holes for supplying a heating medium such as water vapor. There was a defect that the appearance of the molded product was significantly impaired. Furthermore, in molded bodies obtained by conventional manufacturing methods, it is difficult to avoid the formation of recesses adjacent to the pre-expanded particles on the surface of the molded body, and therefore the fusion of the pre-expanded particles on the surface side is relatively weak. Therefore, it also had the disadvantage that the pre-expanded particles on the surface side of the molded body were likely to chip off. Furthermore, in order to supply steam, etc. for heating the pre-expanded particles, the through hole provided in the wall of the mold cavity usually has a plurality of holes or slits,
Steam holes are formed by driving a separate column-shaped steam hole forming part, but in conventional manufacturing methods, steam holes (through holes provided in the wall of the mold cavity) are required to uniformly heat the pre-expanded particles. This requires a large number of steam hole forming parts, which requires a lot of time and effort, and also poses problems such as high costs for the steam hole forming parts. The present invention was developed in view of the above points, and it is possible to obtain a molded product with a good appearance and excellent particle fusion properties on the surface, and also has excellent heating efficiency and a small number of steam holes, making it possible to pre-foam the product. An object of the present invention is to provide a method for producing a pre-expanded particle molded body in a mold, which can obtain a molded body by uniformly heating particles. That is, in the present invention, pre-expanded particles are filled into a mold having a metal screen with a large number of through holes attached to the inner wall, and then the pre-expanded particles are heated with a heating medium to foam the pre-expanded particles. The gist of the present invention is a method for producing an in-mold pre-expanded particle molded body, which is characterized by obtaining a molded body by fusing. The pre-expanded particles used in the present invention include cross-linked or non-cross-linked pre-expanded particles whose base resin is polypropylene resin, polyethylene resin, polystyrene resin, etc., but in particular propylene homopolymer, ethylene-propylene Pre-expanded particles of a non-crosslinked polypropylene resin having a base resin such as a random copolymer or an ethylene-propylene block copolymer are preferred. As the metal screen having a large number of through holes used in the present invention, a wire mesh made of stainless steel, copper, etc., a so-called punching metal in which a large number of small holes are punched in a metal plate, etc. are used. In the case of a wire mesh, the screen preferably has about 30 to 500 meshes, and in the case of punched metal, it preferably has about 20 to 3000 small through holes per cm 2 . If the size of the small pores is too large, a pattern of pre-expanded particle shapes will appear on the surface of the molded product, and the above-mentioned drawbacks of the molded product obtained by conventional manufacturing methods cannot be sufficiently solved, and vice versa. If the size of the small pores is too small, the permeability of heating media such as water vapor will decrease, resulting in a decrease in heating efficiency of the pre-expanded particles. Next, an embodiment of the manufacturing method of the present invention will be described based on the drawings. In FIG. 1, numeral 1 denotes molding molds used in the production of conventional in-mold molded bodies; a first molding mold 1a and a second molding mold 1a
It consists of a mold 1b for molding. The inner wall of the mold 1 is equipped with wire meshes 2, 2 as metal screens having a large number of small through holes. The pre-expanded particles 3 are filled into the mold 1 having the wire meshes 2, 2 attached to the inner walls, and then the pre-expanded particles 3 are filled with the pre-expanded particles 3.
is heated by a heating medium. Steam of 1.0 Kg/cm 2 (G) to 5.0 Kg/cm 2 (G) is normally used as the heating medium, and the heating medium such as steam is supplied from the steam hole 4 . The pre-expanded particles 3 are foamed by heating, the particles are fused to each other, and after cooling they are taken out from the mold 1 (wire mesh 2
By further peeling off), a molded body according to the mold can be obtained. No pre-foamed particle shape pattern is formed on the surface of the molded product obtained by the above method, only the shape pattern of the wire mesh 2 is formed, and therefore, regardless of the size of the pre-foamed particles used for molding, the molded product The same pattern is always formed on the surface. In the above embodiment, a case is shown in which the wire mesh 2 as a screen is attached to the entire inner wall of the mold 1, but the wire mesh 2 may be attached to a part of the inner wall of the mold 1. Moreover, the wire mesh 2 is not limited to the case where only one piece is attached, but a plurality of wire meshes with different meshes can be stacked and used, and the surface of the molded body can be changed by changing the weaving pattern. In this case, the permeability of the heat medium becomes even better, the heating efficiency can be improved, and the fusion properties of the pre-expanded particles on the surface side of the molded body (the surface in contact with the wire mesh) can be further improved. In addition, when punching metal or the like is used as the wire mesh screen, the through holes can be formed in any shape and arrangement pattern, and molding can be performed using screens with different shapes and arrangement patterns of the through holes. As a result, the surface pattern of the molded body becomes rich in variety, and the design of the molded body can also be improved. As explained above, according to the present invention, no pre-expanded particle shape pattern or steam hole traces appear on the surface of the molded product that is in contact with the metal screen during molding, and only the screen shape pattern appears. , Even if the pre-expanded particles used for molding have different sizes or variations in size, the same pattern is always formed on the surface of the molded product, so the appearance of the molded product is affected by the shape of the pre-expanded particles. Moreover, it is possible to prevent deterioration in appearance due to the appearance of steam hole marks on the surface of the molded product. Furthermore, during molding, the pre-foamed particles on the surface side that contacts the metal screen are pressed by the unevenness formed by the through-holes and non-through-holes of the screen, which improves the fusion properties of the foamed particles with each other. , it is possible to provide an excellent molded article free from defects such as chipping of the pre-expanded particles on the surface side. Further, by performing molding using a screen having through holes of different shapes and arrangement patterns, molded bodies with various surface patterns can be obtained, and molded bodies with excellent design properties can be provided. Further, according to the present invention, since a metal screen having a large number of through holes is attached to the inner wall of the mold for use, the thermal energy of the heating medium can be uniformly applied to the pre-expanded particles in the mold by the screen. As a result, it is possible to improve heating efficiency and productivity, and also to reduce the number of steam holes provided in the molding mold, simplifying the installation work of steam hole forming parts, and reducing the cost of installing steam hole forming parts. It has various effects such as being able to reduce parts costs. The molded product obtained by the present invention has a good appearance and is rich in design, has excellent surface strength, and can be used as packaging materials, furniture, bedding, automobile and ship parts, etc.
It is highly useful as a display, etc. The present invention will be explained in more detail below with reference to specific examples. In Examples and Comparative Examples, the fusion strength of surface particles and the surface condition of molded bodies were determined as follows. Fusion strength of surface particles: Defense Agency Standard (NDS) Z0503
According to , thickness 10mm, width 25mm, length 300mm
The molded body of is used as a sample, and the diameter of the sample piece is
The angle shown is the angle at which a crack appears on the surface of a sample piece when it is bent along the outer circumferential surface of a 20 mm cylinder. Surface condition of molded product: 〇...A regular screen-shaped pattern is formed on the surface of the molded product, and no pre-expanded particle shape pattern or steam hole traces are formed. ×...The pre-expanded particle shape pattern and steam hole marks clearly appear on the surface of the molded product. Examples 1 to 6, Comparative Examples 1 to 6 Pre-expanded particles shown in Table 1 using ethylene-propylene random copolymer as the base resin were attached to the inner wall with a wire mesh of 50 meshes, thickness 40 mm, width 300 mm,
After filling into a mold with a length of 300 mm and heating with 3.6 Kg/cm 2 (O) steam to foam and fuse the pre-expanded particles.
After cooling to 50°C, the obtained molded body was peeled off from the wire gauze and taken out from the mold. As a comparative example, molding was carried out in the same mold as in the example without installing a wire mesh.
The fusion strength of the surface particles of each of the obtained molded bodies was measured and the surface condition of the molded bodies was observed. Further, for Example 3 and Comparative Example 3, the time required for molding was measured. The results are also shown in Table 1. Example 7, Comparative Example 7 From the wall side of the mold inner wall whose inner wall is rubber-lined
A wire mesh of 40 meshes and then 100 meshes was stacked on top of each other, and the mold was filled with the same pre-expanded particles as in Example 3, and molding was carried out under the same conditions as in Example 3. As a comparative example, molding was carried out under the same conditions as in Example 7 except that a wire mesh was not used. The fusion strength of the surface particles of the obtained molded product was measured, and the surface condition of the molded product was observed. The time required for molding and the amount of steam used were also measured. Second result
Shown in the table.
【表】【table】
【表】【table】
【表】【table】
【図面の簡単な説明】[Brief explanation of the drawing]
図面は本発明の実施例を示すもので第１図は本
発明製造方法に用いられる成型用型の一実施例を
示す縦断面略図である。
１……成型用型、２……金網、３……予備発泡
粒子。
The drawings show embodiments of the present invention, and FIG. 1 is a schematic vertical cross-sectional view showing an embodiment of a mold used in the manufacturing method of the present invention. 1... Molding mold, 2... Wire mesh, 3... Pre-expanded particles.