JP4060452B2 - Method for producing foam blow molded article and foam blow molded article - Google Patents

Description

【００４１】
【表２】

【００４２】
本明細書中において、発泡層厚み、密度、平均気泡径、非発泡層の厚み、成形品の密度、連続気泡率、及び成形品の外観、発泡層を形成している樹脂のＭＴの測定方法、評価基準は以下の通りとする。
【００４３】
※１発泡層及び非発泡層の厚み
成形品のブロー成形時、過度に伸ばされていない部分（例えばボトル形状の成形品の場合は胴部）を押出方向に垂直な平面で切断し、得られた断面より発泡体層の厚みを測定する。
【００４４】
※２発泡層の密度
成形品からブロー成形時に過度に伸ばされていない、密度、厚みが均一な部分（例えば、ボトル形状の成形品の場合は側面中央部）を選んで、なるべく大きなサンプルを切り取り、サンプル面積：Ｓ（ｃｍ² ）、サンプル重量：Ｗ（ｇ）、発泡層厚み：Ｔ₁ （ｃｍ）、非発泡層厚み：Ｔ₂ （ｃｍ）、非発泡層の密度：Ｄ（ｇ／ｃｍ³ ）を測定し（各厚みはサンプル断面より測定する。）、次式により求める。
【００４５】
【数１】

【００４６】
※３平均気泡径
成形品からブロー成型時に過度に伸ばされていない部分（例えばボトル形状の成形品の場合は側面中央部）を選んでサンプルを切り取り、ＡＳＴＭ Ｄ３５７６に準拠した測定方法を採用し、発泡層断面を拡大投影し、投影画像上に直線を引き、その直線と交差する気泡数をカウントし、画像上の直線長さを気泡数で割ることによって求めた値を更に０．６１６で割って求められる、押出方向、幅方向及び厚み方向の平均径の算術平均値である。
【００４７】
※４成形品密度
得られた成形品重量（ｇ）を、該成形品をエタノール中に沈めて水位上昇分より求めた成形品体積（ｃｍ³ ）で割って求める。
【００４８】
※５連続気泡率
ＡＳＴＭ Ｄ２８５６（手順Ｃ）の手順により成形品サンプルの実容積（独立気泡部分の容積と樹脂部分の容積との和）：Ｖｘ（ｃｍ³ ）を求め、次式より算出した値である。
【００４９】
【数２】

【００５０】
※６成形品の外観
成形品外観を観察し、
◎・・・成形品の表面が平滑であり、穴、亀裂等がないもの。
○・・・表面に気泡の凹凸が若干あるものの概ね平滑であり、穴、亀裂等がないもの。
×・・・表面に穴、亀裂等が発生したり、非発泡樹脂層に極端に薄い部分が発生し、外観が著しく悪いもの。
として評価した。
【００５１】
※７発泡層を形成している樹脂のメルトテンション（ＭＴ）
成形品より発泡層を切り出し１２０℃で５時間乾燥後、ヒートプレスにより２８０℃、１００ｋｇ／ｃｍ² の条件により発泡層を構成している気泡を脱泡させシート状サンプルを得る。次に該サンプルを適当な大きさに切断し、前述の樹脂のメルトテンションの測定方法と同様の方法によりＭＴ（ｇｆ）を測定した。
【００５２】
【発明の効果】
以上説明したように本発明の発泡ブロー成形品は、ポリカーボネート樹脂を主体とし、２５０℃におけるメルトテンションが４ｇｆ以上の樹脂から形成されている発泡層を少なくとも有するパリソンをブロー成形して得たことにより、押出発泡が難しいとされているポリカーボネート樹脂を環状ダイスより押出発泡して得た発泡層を有するパリソンをブロー成形した成形品でありながら、充分な発泡倍率の発泡層とすることができ、また発泡層におけるセル破壊やセルの不均一という不具合がなく、外観にも優れている等の利点を有する。また発泡層の内外面に非発泡樹脂層を有する場合には、発泡層を形成している樹脂の２５０℃におけるメルトテンションが２ｇｆ以上であれば、上記した優れた発泡ブロー成形品となる。
【００５３】
更に本発明の発泡ブロー成形品は、ポリカーボネート樹脂を主体とするため、耐熱性、耐老化性、耐水性等に優れ、電気的性質、機械的性質等に優れる効果がある。
【００５４】
また本発明方法によれば、特定のメルトテンションを有するポリカーボネート樹脂を使用することにより優れた発泡ブロー成形品を得ることができ、発泡剤として沸点が−３０〜１００℃の物理発泡剤を用いると、より確実に優れた発泡ブロー成形品を得ることができる。
【図面の簡単な説明】
【図１】本発明の発泡ブロー成形品の一例を示す縦断面図である。
【図２】本発明の発泡ブロー成形品の製造法を示す断面略図である。
【図３】メルトテンションテスターのノズルから樹脂を紐状に押出し、この紐状物を一定の巻き取り速度で巻き取りローラーで巻き取った時の、張力と経過時間とを示すチャートである。
【図４】本発明の発泡ブロー成形品の他の例を示す縦断面図である。
【符号の説明】
１ 発泡ブロー成形品
２ 発泡層
３ 非発泡樹脂層
４ 環状ダイス
５ パリソン
６ 金型
７ 気体吹き込み口[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a foam blow molded article and a method for producing the same.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, as a method for obtaining a hollow foamed blow molded product, a resin and a foaming agent are melt-kneaded in an extruder, and the cylindrical foamed parison formed by extruding this from a die is sandwiched between molds. A method is generally used in which a pressurized gas is blown into the interior and the parison is molded along the inner shape of the mold.
[0003]
Such foam blow-molded products are used for applications that require heat insulation, soundproofing, flexibility, and the like, and specifically include applications such as ducts, automobile parts, and containers. For these applications, those having an expansion ratio of 3 to 30 times are particularly preferably used. When the base resin is polystyrene or polyethylene, for example, as described in JP-B-3-59819 A foamed blow molded article having a foaming ratio of 4 to 12 is obtained.
[0004]
Polycarbonate resin, on the other hand, has excellent heat resistance, aging resistance, water resistance, etc., and also has excellent electrical and mechanical properties, so it can be widely used for interior materials, packaging materials, and various containers for automobiles and buildings. Is expected. In particular, since it is excellent in heat resistance, it is highly useful as a container material for microwave ovens and retort foods.
[0005]
Japanese Patent Publication No. 4-70974 discloses a foamed parison of a thermoplastic resin such as polycarbonate resin extruded and extruded from an extruder using a decomposable foaming agent. In this method, a pressurized blown gas is blown into the mold cavity until it is in close contact with the cavity of the mold, and the foaming ratio is controlled in the range of 1.01 to 2.5 times to obtain a foamed blow molded article. However, the polycarbonate resin has a very high melt viscosity in the vicinity of the extrusion foaming temperature compared to the polystyrene-based resin. Therefore, the polycarbonate resin is inferior in extrusion foamability and sheet forming processability. It is only about 3 times, and an excellent blow-molded product with a high expansion ratio is not obtained as in the case of polystyrene resins and polyethylene resins.
[0006]
On the other hand, in the production method of a polycarbonate extruded foam sheet, various devices have been conventionally used. For example, a method of using an organic substance having a solubility coefficient of 6.5 or more as a foaming agent (Japanese Patent Laid-Open No. 2-261636), A method of foaming using isoparaffin having a boiling point of 50 to 150 ° C. as a foaming agent (Japanese Examined Patent Publication No. 47-43283), a method of gelling a polycarbonate resin with a lower alkylbenzene and a low-boiling solvent (Japanese Patent Publication No. 46-31468). Publication) etc. are proposed.
[0007]
However, even if these methods are applied to foam blow molding, foam blow molding does not simply obtain foam by extrusion foaming, but the foam obtained as a parison is softened, drawn down, Since blow molding must be performed while considering crushing, etc., the appearance, heat insulation, moldability, etc. will be insufficient, and the foaming ratio, thickness, cell diameter of cells, open cell ratio, etc. shall be adjusted over a wide range. It was also difficult. For this reason, it is difficult to obtain a good molded product even if the technology of the polycarbonate resin extruded foam sheet is applied to the production of a foamed blow molded product.
[0008]
The present inventors solved the problem that, in the method of obtaining a foamed blow-molded product by blow-molding a foamed parison of polycarbonate resin, conventionally, only a low-foamed and insufficiently heat-insulated molded product as described above can be obtained. As a result of diligent research aimed at achieving this, it was found that the above problems can be solved by using a polycarbonate resin having a specific melt tension according to the layer structure of a parison formed by extruding a polycarbonate resin containing a foaming agent from a ring die. The present invention has been completed.
[0009]
[Means for Solving the Problems]
That is, one of the methods for producing a foamed blow molded product of the present invention is that the physical foaming agent is 0.05 to 0.00 per 1 kg of resin having a polycarbonate resin as a main component and a melt tension at 250 ° C. of 6 gf or more. A parison having at least a foamed layer formed by extruding and foaming a foamable melt obtained by melting and kneading in an extruder at a ratio of 5 moles from the extruder is sandwiched between molding dies and placed in the parison. It is characterized in that a pressurized gas is blown and a portion sandwiched between the parison dies is formed into a shape along the inner surface of the dies. Further, another method for producing the foamed blow molded article of the present invention is that the physical foaming agent is added in an amount of 0.05 to 0 per 1 kg of resin whose main component is polycarbonate resin and the melt tension at 250 ° C. is 3 gf or more. The foamable melt obtained by adding 5 mol and melt-kneading in the extruder and the non-foamable resin melt mainly composed of the polycarbonate resin are cylindrically bonded under a low pressure from the inside of the extruder. Extruded into a multi-layer parison with a non-foamed resin layer formed on the inner and outer surfaces of the foam layer, and the parison is sandwiched between molding dies and pressurized gas is blown into the parison, and the portion sandwiched between the parison molds It is characterized by being formed into a shape along the inner surface of the mold.
[0010]
In the method of the present invention, the resin constituting the non-foamable resin layer is preferably a resin having a melt tension at 250 ° C. of 1 gf or more. Moreover, it is preferable to use a physical foaming agent having a boiling point of −30 to 100 ° C. as the foaming agent.
[0011]
One of the foamed blow molded products of the present invention is a hollow molded product formed by blow molding a parison having at least a foamed layer made of a resin mainly composed of a polycarbonate resin, and forms the foamed layer. The melt tension of the resin at 250 ° C. is 4 gf or more, and the density of the molded product is 0.06 to 0.9 g / cm. ^Three It is characterized by being. Another foam blow-molded product of the present invention is a multi-layer parison in which a non-foamed resin layer composed mainly of a polycarbonate resin is formed on both sides of a foam layer composed mainly of a polycarbonate resin. The resin forming the foamed layer has a melt tension at 250 ° C. of 2 gf or more, and the density of the molded product is 0.06 to 0.9 g / cm. ^Three It is characterized by being.
[0012]
In the foam blow molded product of the present invention, the open cell ratio of the foam layer is preferably 70% or less, and the average cell diameter of the foam layer is preferably 0.15 to 2.0 mm. Furthermore, the polycarbonate resin that is the main component of the foamed layer is preferably a resin having a branched structure.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of a foamed blow molded article 1 according to the present invention. In the figure, 2 is a foamed layer made of a resin mainly composed of a polycarbonate resin, and 3 is a non-foamed resin layer made of a resin mainly composed of a polycarbonate resin. It is. FIG. 2 conceptually shows a method for producing the foamed blow-molded product 1. As shown in FIG. 2 (a), the foam blow molded product 1 is sandwiched between molds 6 and 6 while the parison 5 extruded from the annular die 4 of the extruder is in a softened state. It can be obtained by blowing pressurized gas from the blowing port 7 and forming the portion sandwiched between the molds 6 and 6 of the parison 5 along the inner surface of the mold as shown in FIG.
[0014]
A foamed blow-molded product 1 shown in FIG. 1 combines a foamable melt for forming a foamed layer 2 and a resin melt for forming a non-foamed resin layer 3 in a die 4 (non-foamed). After the resin melt for forming the resin layer 3 is merged with the foamable resin melt so as to be located on the outer surface side of the parison 5, the resin melt is extruded from the annular die 4 to foam the foamable resin melt. Thus, the foamed parison 5 is formed, and the parison 5 is sandwiched between the molds 6 and 6 as described above, and is molded by blowing a pressurized gas into the parison 5. As a method for performing parison blow molding, in addition to the above-described method, a method in which a previously prepared parison is softened by heating and blow molded can be employed.
[0015]
As the resin for forming the foam layer, a resin having a melt tension (hereinafter abbreviated as MT) at 250 ° C. of 6 gf or more is used.
[0016]
FIG. 1 shows an example of a foamed blow molded product 1 configured such that the parison 5 formed by the above-described method is molded so that the inner surface side becomes the foamed layer 2 and the outer surface side becomes the non-foamed resin layer 3. However, the parison formed so that the non-foamed resin layer is located on the inner surface side of the foam layer may be molded, and the foam blow-molded product in which the inner surface side of the foam blow-molded product becomes the non-foamed resin layer and the outer surface side is the foam layer. Moreover, the parison 5 which consists only of the foaming layer which does not have a non-foaming resin layer is shape | molded, and it is good also as a foaming blow molded product which consists only of a foaming layer.
[0017]
In any of the above cases (that is, when the foamed blow-molded product is composed of only the foamed layer, when the foamed layer is shown in FIG. 1 having the non-foamed resin layer on the outer surface side, the foamed layer is located on the outer surface side, Even in the case where a non-foamed resin layer is formed on the inner surface side), the foamed layer and the non-foamed resin layer are not limited to each having a single-layer structure, either the foamed layer or the non-foamed resin layer, or Both can also have a multilayer structure.
[0018]
The foam blow molded product 1 shown in FIG. 1 above, or a foam blow molded product consisting of only a foam layer as described above, or a layer in which the foam layer is located on the outer surface side and the non-foamed resin layer is located on the inner surface side (not shown) Foam blow-molded product having a structure (as described above, the foamed layer and the non-foamed resin layer are not limited to a single layer, but may have a multi-layer structure. Since the non-foamed resin layer is provided only on one side, the case of only the foamed layer is referred to as a “single layer” for convenience, and the non-foamed resin layer is formed on one side of the foamed layer. The foam layer 2 is a resin having a polycarbonate resin as a main component and an MT at 250 ° C. of 6 gf or more (preferably 7 to 20 gf) as described above. Obtained by. Note that the upper limit of MT is approximately 30 gf. The density of the molded product is 0.06 to 0.9 g / cm. ^Three Is necessary. Moreover, also when the foaming layer 2 consists of a several foam layer, each foaming layer needs to satisfy | fill the above-mentioned conditions. However, if each foam layer satisfies the above-described conditions, the MT of the resin for forming the foam layer, the thickness, density, etc. of the foam layer do not have to be exactly the same in each foam layer.
[0019]
The polycarbonate resin constituting the foamed layer 2 and the non-foamed resin layer 3 is a resin formed from carbonic acid and glycol, or a compound such as bisphenol having a phenolic hydroxyl group, and an aromatic polycarbonate having a diphenylalkane in the molecular chain. Resins are preferred because they are excellent in heat resistance, weather resistance and acid resistance. Examples of such polycarbonate resins include 2,2-bis (4-oxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-oxyphenyl) butane, and 1,1-bis (4-oxyphenyl). And polycarbonate resins derived from bisphenols such as cyclohexane, 1,1-bis (4-oxyphenyl) isobutane and 1,1-bis (4-oxyphenyl) ethane.
[0020]
Some polycarbonate resins have a linear structure and a branched structure. In the case of a linear polycarbonate resin, those having a viscosity average molecular weight of 25,000 or more, particularly 30,000 or more are preferable. A commercially available linear polycarbonate resin having a viscosity average molecular weight of 25,000 or more and an MT at 250 ° C. of 6 gf or more is, for example, Iupilon E-1000 (viscosity average molecular weight 32 manufactured by Mitsubishi Chemical Corporation). , 000, MT = 6.5 gf).
[0021]
A branched polycarbonate resin can be obtained by using a compound having three or more phenolic hydroxyl groups. Examples of such a compound having three or more phenolic hydroxyl groups include phloroglicinol, 4,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) -2-heptene, 4 , 6-Dimethyl-2,4,6-tri (4-hydroxyphenyl) -heptane, 1,3,5-tri- (4-hydroxyphenyl) -benzene, 1,1,1-tri- (4-hydroxy Phenyl) -ethane, tri- (4-hydroxyphenyl) -phenylmethane, 2,2-bis- [4,4-bis- (4-hydroxyphenyl) -cyclohexyl] -propane, 2,4-bis- (4 -Hydroxyphenylisopropyl) -phenol, 2,6-bis- (2-hydroxy-5'-methylbenzyl) -4-methylphenol, 2- (4-hydroxyphenyl) Nyl) -2- (3,4-dihydroxyphenyl) -propane, hexa- (4- (4-hydroxyphenylisopropyl) -phenyl) -orthoterephthalic acid ester, tetra- (4-hydroxyphenyl) -methane, tetra- (4- (4-hydroxyphenylisopropyl) -phenoxy) -methane, 1,4-bis- (4 ′, 4 ″ -dihydroxytriphenyl) -methylbenzene and the like.
[0022]
Further, since the long-chain branched polycarbonate resin tends to have a higher MT, it is advantageous when a resin having a high MT is used. Examples of commercially available long-chain branched polycarbonate resins having MT of 6 gf or more include, for example, Macrolon 3118 (MT = 16 gf) manufactured by Bayer, Lexane 151-112 (MT = 9 gf) manufactured by GE Plastics, And Taflon IB-2500 (viscosity average molecular weight 25,000, MT = 14.5 gf) manufactured by Idemitsu Petrochemical Co., Ltd.
[0023]
The resin used to form the foamed layer 2 when producing a single-layer or single-sided multilayer foamed blow-molded product is composed of only the above polycarbonate resin having an MT of 6 gf or more at 250 ° C. Acrylic acid-based resins such as homopolymers that use acrylic acid or acrylic acid esters, methacrylic acid or methacrylic acid esters as monomers for polycarbonate resins, and copolymers of these monomers with other monomers, It is preferable to mix a methacrylic acid resin or the like. In addition, other synthetic resins such as polyethylene terephthalate, high impact polystyrene, and high molecular weight polyethylene can be mixed and used as long as the objects and effects of the present invention are achieved. It is necessary to be 6 gf or more.
[0024]
In the case of producing a single-sided multilayer foamed blow molded product, it is preferable to use a resin having a polycarbonate resin as a main component and an MT at 250 ° C. of 1 gf or more as a resin for forming a non-foamed resin layer. In order to form the non-foamed resin layer, the acrylic resin, methacrylic resin, polyester resin, and the like are preferable as the resin used by mixing with the polycarbonate resin. In addition, other resins such as polystyrene resin can be mixed.
[0025]
The above single-layer foamed blow-molded product is prepared by adding 0.05 to 0.5 mol of a physical foaming agent to 1 kg of resin having MT of 6 gf or more mainly composed of polycarbonate resin, and melt-kneading in an extruder. It is obtained by molding a parison obtained by extruding the foamable melt thus formed from an annular die. The single-sided multi-layer foamed blow-molded product is obtained after a foamable melt similar to the above and a non-foamed resin are joined in a die so that a non-foamed resin layer is formed on one surface of the foamed layer. It is obtained by extruding from a die, foaming a foamable melt to obtain a single-sided multilayer parison, and molding the parison.
[0026]
When obtaining a single-layer or single-sided parison, if the resin MT for forming the foam layer is less than 6 gf, cell breakage occurs in the process of forming the foam layer, resulting in foam blow molding with excellent heat insulation, etc. I can't get the goods.
[0027]
The MT of the resin can be measured by, for example, a melt tension tester type II manufactured by Toyo Seiki Seisakusho Co., Ltd. Specifically, using a melt tension tester having an orifice with an orifice inner diameter of 2.095 mm and a length of 8 mm, the resin is extruded in a string shape from the orifice at a resin temperature of 250 ° C. and an extrusion piston speed of 10 mm / min. This string-like material is hung on a tension detection pulley having a diameter of 45 mm, and then it is scraped by a scraping roller having a diameter of 50 mm at a scraping speed of 100 rpm.
[0028]
In the present invention, MT is obtained by measuring the MT of the string-like object detected with a detector connected to the tension detecting pulley at a constant take-off speed of 100 rpm over time, If a chart with MT (gf) on the axis and time (seconds) on the horizontal axis is shown, a graph with amplitude as shown in FIG. 3 is obtained. MT in the present invention is the median value (X) of the amplitude of the stable portion in FIG. However, if the string-like material is cut before the lashing speed reaches 100 rpm, the value at the lashing speed is defined as MT. Note that the specific amplitude that occurs infrequently is ignored.
[0029]
FIG. 4 shows a foamed blow molded article 1 having a non-foamed resin layer 3 on the inner and outer surfaces of the foamed layer 2. The foamed blow molded product 1 includes a foamable melt formed by melting and kneading a resin and a foaming agent in an extruder so that a non-foamed resin layer is formed on both the inner and outer surfaces of the foamed layer, and a non-foamed resin. It is obtained by molding a parison formed by joining the melt in a die and then extruding it from an annular die. The structure in which the non-foamed resin layer is formed inside and outside the foamed layer is hereinafter referred to as “double-sided multilayer” for convenience. In the case of a double-sided multilayer, as described above, the foamed layer and the non-foamed resin layer provided on both sides of the foamed layer may further have a multilayer structure.
[0030]
In the case of forming the double-sided multilayer parison, the foamable melt for forming the foamed layer is the same as in the case of the single-layer parison or single-sided multilayer parison. It can be obtained by adding 0.05 to 0.5 mol of a foaming agent and melt-kneading, but when forming a double-sided multilayer parison, the resin for forming the foamed layer has an MT of 250 ° C. What is necessary is just 3 gf or more (preferably 4-20 gf). Note that the upper limit of MT is approximately 30 gf. When the MT of the resin used to form the foamed layer is less than 3 gf, cell breakage occurs in the process of forming the parison foamed layer, and a foamed blow molded article having excellent heat insulation and the like cannot be obtained. As the resin for forming the non-foamed resin layer, it is preferable to use a resin mainly composed of a polycarbonate resin and having an MT at 250 ° C. of 1 gf or more (preferably 1 to 12 gf).
[0031]
Also in the case of forming a double-sided multilayer parison, the same polycarbonate resin as described above is used as the polycarbonate resin used for forming the foamed layer and the non-foamed resin layer.
[0032]
As described above, when the foamed blow molded article of the present invention is produced, it is necessary to add 0.05 to 0.5 mol of a physical foaming agent per 1 kg of the resin for constituting the foamed layer. When the addition amount of the foaming agent is less than 0.05 mol, a foamed layer having excellent heat insulation and rigidity cannot be formed. In addition, if an amount of foaming agent exceeding 0.5 mol is added, the foaming agent may not be sufficiently dissolved in the resin, or the foaming speed may become too high, resulting in cell destruction or non-uniformity. There is.
[0033]
As the foaming agent, it is preferable to use a physical foaming agent having a boiling point of −30 to 100 ° C., particularly −5 to 80 ° C. When a physical foaming agent having a boiling point of less than −30 ° C. is used, the foaming speed becomes too fast and cell destruction tends to occur. When a foaming agent having a boiling point of more than 100 ° C. is used, foaming power is insufficient or There is a possibility that liquefaction occurs and the foam layer shrinks.
Examples of such physical foaming agents include aliphatic hydrocarbons such as butane, pentane and hexane, chlorinated hydrocarbons such as methyl chloride and ethyl chloride, 1,1,1,2-tetrafluoroethane, 1,1- Examples thereof include physical foaming agents such as fluorinated hydrocarbons such as difluoroethane. These physical foaming agents can be used as a mixture, and liquids such as various alcohols having a boiling point equal to or lower than the extrusion temperature, or inorganic gases such as carbon dioxide and nitrogen can be used in combination. Further, a decomposable foaming agent such as sodium hydrogen carbonate, sodium citrate, azodicarbonamide or the like can be contained in the resin constituting the foamed layer and used.
[0034]
In the foamable melt for forming the foamed layer and / or in the non-foamable melt for forming the non-foamed layer, there are bubble regulators, flame retardants, fluidity improvers, weathering agents, colorings. Various additives such as an agent, a heat stabilizer, a filler, an antistatic agent, and a conductivity imparting agent can be appropriately blended as necessary.
[0035]
The foamed blow molded product of the present invention has a molded product density of 0.06 to 0.9 g / cm in any of the above-mentioned single layer, single-sided multilayer, and double-sided multilayer. ^Three (Preferably 0.06-0.45 g / cm ^Three )belongs to. The density of the molded product is 0.06 g / cm ^Three If it is less than 1, the mechanical strength and the appearance are insufficient, and the density is 0.9 g / cm. ^Three If it exceeds 1, the heat insulating property and light weight will be insufficient. The melt tension of the resin forming the foamed layer of the foamed blow molded product of the present invention is 4 gf or more (preferably 5 to 20 gf) in the case of a single layer and a single-sided multilayer, and preferably 2 gf or more in the case of a double-sided multilayer (preferably Is 2.5 to 20 gf). The melt tension of the resin forming the foam layer is equal to or slightly lower than the melt tension of the resin used to form the foam layer. Therefore, the melt tension of the resin forming the foamed layer can be generally controlled by adjusting the melt tension of the resin used to form the foamed layer, and the melt tension of the resin forming the foamed layer can be controlled. When each of the above values is the above value, the molded article is a good molded product for the same reason as the case where the melt tension of the resin for forming the foamed layer is the value specified in the present invention as described above. The open cell ratio of the molded product is preferably 70% or less, more preferably 50% or less. If the open cell ratio of the molded product exceeds 70%, the airtightness, heat insulating property, appearance, and mechanical strength of the molded product may be deteriorated. On the other hand, a high open cell ratio may be preferable depending on applications such as for sound absorption. The thickness of the foam layer 2 is preferably 0.5 to 15 mm, more preferably 1.0 to 8.0 mm, and the density is preferably 0.06 to 0.8 g / cm. ^Three More preferably, 0.06 to 0.4 g / cm ^Three It is. If the thickness is less than 0.5 mm, the appearance may be deteriorated and the heat insulation may be deteriorated. If the thickness is more than 15 mm, the mold reproducibility at the time of blow molding may be deteriorated, and the open cell ratio of the molded product may be too high. . The density of the foam layer is 0.06 g / cm ^Three If the ratio is less than 0.8 g / cm, the open cell ratio of the molded product may be too high. ^Three If it exceeds 1, there is a possibility that deterioration of formability at the time of blow molding, heat insulation of the molded product, and reduction in lightness due to an increase in the drawdown amount.
[0036]
Moreover, it is preferable that the average bubble diameter of the bubble of the foaming layer 2 of a molded article is 0.15-2.0 mm. If the average cell diameter is less than 0.15 mm, the appearance of the molded product may be deteriorated. On the other hand, if the average bubble diameter exceeds 2.0 mm, the heat insulating property may be lowered. In addition, the average bubble diameter of the bubbles in the foam layer 2 employs a measurement method based on ASTM D3576, enlarges and projects the cross section of the foam layer, draws a straight line on the projected image, and counts the number of bubbles intersecting the straight line. The arithmetic average value of the average diameters in the extrusion direction, the width direction, and the thickness direction is obtained by further dividing the value obtained by dividing the linear length on the image by the number of bubbles by 0.616.
[0037]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The resins used in Examples and Comparative Examples are as follows.
[0038]
PC-1: Mitsubishi Chemical Corporation: Iupilon E-1000 (linear polycarbonate resin, viscosity average molecular weight 32,000, MT = 6.5 gf)
PC-2: Mitsubishi Chemical Corporation: Iupilon E-2000 (linear polycarbonate resin, viscosity average molecular weight 27,000, MT = 3 gf)
PC-3: Idemitsu Petrochemical Co., Ltd .: Taflon IB-2500 (branched polycarbonate resin, viscosity average molecular weight 25,000, MT = 14.5 gf)
PC-4: Bayer Co., Ltd .: Macrolon 3118 (branched polycarbonate resin, MT = 16 gf)
PC-5: Mitsubishi Chemical Corporation: Iupilon H-3000 (linear polycarbonate resin, viscosity average molecular weight 18,000, MT = 0.5 gf)
PC-6: Mitsubishi Chemical Corporation Iupilon S-3000 (linear polycarbonate resin, viscosity average molecular weight 22000, MT = 1.5 gf)
[0039]
Examples 1-7, Comparative Examples 1-3
In an extruder having a diameter of 65 mm, the resin and the foaming agent are melted so that the foaming agent shown in the same table has the addition amount (number of moles) shown in the same table per 1 kg of the raw material resin of the foaming layer shown in Table 1. A foamable melt was prepared by kneading. Furthermore, in Examples 2 to 7 and Comparative Examples 2 and 3, in order to form a non-foamed resin layer on the inner and outer surfaces of the foamed layer, the raw material resins for the inner and outer layers shown in Table 1 were each provided in two units having a diameter of 40 mm. It was separately supplied to an extruder and melted to obtain a non-foamable melt. Next, in the foamable melt, Examples 2 to 7, and Comparative Examples 1 and 2, the above-mentioned diameter is further adjusted so that the non-foamable resin layer is formed on the inner surface side and the outer surface side of the foam layer. The foamable melt in the 65 mm extruder and the non-foamed melt in the two extruders having a diameter of 40 mm are merged in an annular die, adjusted to the temperature shown in Table 1, and then extruded from the annular die to obtain a foamed layer. A single-layer parison consisting of a single layer or a three-layer parison of non-foamed resin layer / foamed layer / non-foamed resin layer was formed. This parison is sandwiched between 4 liter bottle molds with handshakes located directly under the die, and the pressure is 500 g / cm in the parison. ² The compressed air was blown to form a parison into a shape along the inner surface of the mold. Table 2 shows the properties of the obtained foamed blow-molded product.
[0040]
[Table 1]

[0041]
[Table 2]

[0042]
In this specification, foam layer thickness, density, average cell diameter, non-foam layer thickness, molded product density, open cell ratio, appearance of molded product, MT measurement method for resin forming foam layer The evaluation criteria are as follows.
[0043]
* 1 Thickness of foam layer and non-foam layer
During blow molding of the molded product, the part that is not stretched excessively (for example, the barrel in the case of a bottle-shaped molded product) is cut in a plane perpendicular to the extrusion direction, and the thickness of the foam layer is measured from the obtained cross section To do.
[0044]
* 2 Density of foam layer
Select a portion with a uniform density and thickness that is not excessively stretched during blow molding from the molded product (for example, the center of the side surface in the case of a bottle-shaped molded product), cut out as large a sample as possible, and sample area: S ( cm ² ), Sample weight: W (g), foam layer thickness: T ₁ (Cm), non-foamed layer thickness: T ₂ (Cm), density of non-foamed layer: D (g / cm ^Three ) (Each thickness is measured from the cross section of the sample), and determined by the following formula.
[0045]
[Expression 1]

[0046]
* 3 Average bubble diameter
Select a part from the molded product that is not stretched excessively during blow molding (for example, the center of the side surface in the case of a bottle-shaped molded product). Projecting, drawing a straight line on the projected image, counting the number of bubbles intersecting the straight line, and dividing the straight line length on the image by the number of bubbles, further dividing by 0.616, the extrusion It is an arithmetic average value of average diameters in the direction, width direction and thickness direction.
[0047]
* 4 Molded product density
The obtained molded product weight (g) was determined by submerging the molded product in ethanol to obtain the molded product volume (cm ^Three )
[0048]
* 5 Open cell ratio
The actual volume of the molded product sample according to the procedure of ASTM D2856 (Procedure C) (the sum of the volume of the closed cell portion and the volume of the resin portion): Vx (cm ^Three ) And calculated from the following equation.
[0049]
[Expression 2]

[0050]
* 6 Appearance of molded product
Observe the appearance of the molded product,
A: The surface of the molded product is smooth and has no holes or cracks.
○: Although the surface has some irregularities of bubbles, it is generally smooth and has no holes or cracks.
×: Holes, cracks, etc. are generated on the surface, or extremely thin portions are generated in the non-foamed resin layer, and the appearance is extremely bad.
As evaluated.
[0051]
* 7 Melt tension (MT) of the resin forming the foam layer
The foamed layer is cut out from the molded product, dried at 120 ° C. for 5 hours, and then heated at 280 ° C. and 100 kg / cm. ² Under the conditions, the bubbles constituting the foam layer are defoamed to obtain a sheet sample. Next, the sample was cut into an appropriate size, and MT (gf) was measured by the same method as the method for measuring the melt tension of the resin.
[0052]
【The invention's effect】
As described above, the foamed blow-molded article of the present invention is obtained by blow-molding a parison having at least a foamed layer mainly composed of a polycarbonate resin and having a melt tension at 250 ° C. of 4 gf or more. In addition, it is a molded product obtained by blow molding a parison having a foam layer obtained by extruding and foaming a polycarbonate resin that is difficult to be extruded and foamed from an annular die. There are no defects such as cell breakage or cell non-uniformity in the foam layer, and there are advantages such as excellent appearance. Further, when the foamed layer has a non-foamed resin layer on the inner and outer surfaces, if the melt tension at 250 ° C. of the resin forming the foamed layer is 2 gf or more, the above-described excellent foamed blow-molded product is obtained.
[0053]
Furthermore, since the foamed blow molded article of the present invention is mainly composed of polycarbonate resin, it is excellent in heat resistance, aging resistance, water resistance, etc., and has excellent effects in electrical properties, mechanical properties, and the like.
[0054]
According to the method of the present invention, an excellent foamed blow molded product can be obtained by using a polycarbonate resin having a specific melt tension. When a physical foaming agent having a boiling point of −30 to 100 ° C. is used as the foaming agent. Thus, an excellent foamed blow molded product can be obtained more reliably.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example of a foam blow molded product of the present invention.
FIG. 2 is a schematic cross-sectional view illustrating a method for producing a foamed blow molded article of the present invention.
FIG. 3 is a chart showing tension and elapsed time when resin is extruded in a string form from a nozzle of a melt tension tester and the string-like article is wound up by a winding roller at a constant winding speed.
FIG. 4 is a longitudinal sectional view showing another example of the blow-molded foamed product of the present invention.
[Explanation of symbols]
1 Foam blow molding
2 Foam layer
3 Non-foamed resin layer
4 ring die
5 Parisons
6 Mold
7 Gas inlet

Claims (9)

Obtained by adding a physical foaming agent in a ratio of 0.05 to 0.5 mol and melting and kneading in an extruder per 1 kg of resin having a polycarbonate resin as a main component and a melt tension at 250 ° C. of 6 gf or more. A parison having at least a foam layer formed by extruding and foaming the foamable melt from inside the extruder is sandwiched between molding dies and pressurized gas is blown into the parison, and the portion sandwiched between the parison molds is A method for producing a foamed blow-molded product, comprising molding into a shape along an inner surface of a mold. Obtained by adding a physical foaming agent in a ratio of 0.05 to 0.5 mol and melting and kneading in an extruder per 1 kg of resin whose main component is polycarbonate resin and the melt tension at 250 ° C. is 3 gf or more. A multi-layer in which a non-foamed resin layer is formed on the inner and outer surfaces of a foamed layer by coextruding a foamable melt and a non-foamable resin melt mainly composed of a polycarbonate resin in a cylindrical shape under a low pressure from within the extruder. A foam blow characterized by sandwiching the parison between molding dies and blowing a pressurized gas into the parison to mold the portion sandwiched between the parison molds into a shape along the inner surface of the mold. Manufacturing method of molded products. The method for producing a foamed blow molded article according to claim 2, wherein the resin for forming the non-foamed resin layer is a resin having a melt tension of 1 gf or more at 250 ° C. The method for producing a foamed blow molded article according to any one of claims 1 to 3, wherein a physical foaming agent having a boiling point of -30 to 100 ° C is used. A hollow molded article formed by blow molding a parison having at least a foamed layer made of a resin mainly composed of a polycarbonate resin, and the melt tension at 250 ° C. of the resin forming the foamed layer is 4 gf or more. A foamed blow-molded product having a density of the molded product of 0.06 to 0.9 g / cm ³ . A hollow molded product formed by blow-molding a multi-layer parison in which a non-foamed resin layer composed of a resin mainly composed of a polycarbonate resin is formed on both surfaces of a foam layer composed mainly of a polycarbonate resin, A foam blow molded product, wherein the resin forming the foamed layer has a melt tension of 2 gf or more at 250 ° C. and the density of the molded product is 0.06 to 0.9 g / cm ³ . The foamed blow-molded article according to claim 5 or 6, wherein the open cell ratio of the foamed layer is 70% or less. The foamed blow molded article according to any one of claims 5 to 7, wherein the foamed layer has an average cell diameter of 0.15 to 2.0 mm. The foamed blow-molded product according to any one of claims 5 to 8, wherein the polycarbonate resin as a main component of the foamed layer is a resin having a branched structure.

Images