JP2005036028A - Expandable styrene resin particle and expansion-molded article obtained using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an expandable styrene resin particle exhibiting an excellent balance among properties which, even when it is used for a container or the like for some specific contents having high permeability, hardly allows the contents to permeate into an outer wall of the container or the inside of the molded article, hardly causes mold stains, assures good operating efficiencies, and can be molded in a short time, and an expansion-molded article. <P>SOLUTION: The expandable styrene resin particle comprises an expandable styrene resin particle as the main body having the surface thereof coated with gluconic acid or a gluconate salt represented by general formula (1) (wherein R is a hydrogen atom or a metal, and when the metal is bivalent or higher, R is bonded to the part other than R in general formula (1) in the number corresponding to the valence). The expansion-molded article is obtained by expansion molding the particle. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

（式中、Ｒは、水素原子又は金属を示し、金属が２価以上の場合、一般式（１）のＲ以外が価数に応じた数だけ結合。）
一般式における金属として、Ｎａ、Ｋ、Ｃａ、Ｃｕ、Ｚｎ等を挙げることができる。
【００１３】
これらグルコン酸又はグルコン酸塩は、構造式を見ても明らかなように、分子中に水酸基を多く含むことから水との親和性が高い。成形後の樹脂粒子表面及び粒子間にこれらグルコン酸又はグルコン酸塩が存在することにより一種の保水層が形成され、これにより浸透性が高い油性の内容物について「水と油」の原理により浸透を妨げ、優れた遮蔽効果を発現するものと考えられる。
【００１４】
発泡性スチレン系樹脂粒子を構成するにあたり、これらグルコン酸又はグルコン酸塩の被覆量は、発泡性スチレン系樹脂粒子本体１００重量部に対して、０．００１〜０．５重量部の範囲内の値とするのが好ましい。このような範囲の被覆量であれば、作業性が良好であり、成形時間への影響が少ない発泡性スチレン系樹脂粒子及び発泡成形品を提供することが可能となる。また、内容物の遮蔽性及び生産性の効率とのバランスにより優れている観点から、被覆量を、発泡性スチレン系樹脂粒子本体１００重量部に対して、０．００５〜０．３重量部の範囲とするのがより好ましい。
【００１５】
また、本発明は、前記の発泡性スチレン系樹脂粒子を発泡成形して得られる発泡成形品に関する。
【００１６】
本発明の発泡成形品を加熱成形するにあたり、発泡性スチレン系樹脂粒子を、加熱温度が９０〜１５０℃及び加熱時間が１〜６０秒の条件で発泡成形するのが好ましい。このような加熱条件であれば、内容物の遮蔽性と生産性の効率とのバランスに優れた発泡成形品を製造することができる。また、内容物の遮蔽性と生産性の効率とのバランスに優れた発泡成形品を製造することができる観点から、加熱温度を１００〜１４０℃、加熱時間を３〜６秒で発泡成形することがより好ましい。
【００１７】
【発明の実施の形態】
次に、本発明の実施の形態を具体的に説明する。すなわちグルコン酸又はグルコン酸塩を発泡性スチレン系樹脂粒子本体の表面に被覆してなる本発明の発泡性スチレン系樹脂粒子において、以下のような発泡性スチレン系樹脂粒子を使用して、発泡成形品を加熱成形することができる。
【００１８】
１．発泡性スチレン系樹脂粒子
本発明の発泡性スチレン系樹脂粒子は、発泡性樹脂粒子本体の表面に対して、グルコン酸又はグルコン酸塩を被覆剤（被覆層と称する場合もある）として被覆することにより得られるものである。
（１） 発泡性スチレン系樹脂粒子本体
発泡性スチレン系樹脂粒子本体は、上述のようにスチレン系樹脂粒子に、発泡剤を含浸させることにより調製することができる。
１）スチレン系樹脂粒子
スチレン系樹脂粒子としては、特に制限はないが、例えばスチレンホモポリマ、又はスチレンモノマと共重合可能な成分、例えばアクリロニトリル、メタクリル酸メチル、メタクリル酸ブチル等のメタクリル酸エステル類、アクリル酸メチル、アクリル酸エチル、アクリル酸ブチル等のアクリル酸エステル類、α−メチルスチレン、クロルスチレン、ビニルトルエン等のスチレン誘導体のモノマ等との一種又は二種以上の共重合体を挙げることができる。
また、当該スチレン系樹脂粒子の粒子径についても特に制限されるものではないが、例えば、平均粒子径が０．８〜０．２５ｍｍの範囲内の値であるスチレン系樹脂粒子であれば、適度に発泡して緻密な成形品とすることができる。
２）発泡剤の種類
発泡剤の種類としては、特に制限はないが、例えばプロパン、ブタン、ペンタン、ヘキサン等の脂肪族系炭化水素等の、一般的に発泡性スチレン系樹脂粒子の製造に用いられている、常温（２５℃）で液体又は気体状の化合物を挙げることができる。
３）発泡剤の含浸方法及び含浸量
発泡剤の含浸方法としては、特に制限はなく、従来一般的に使用されてきた方法を採用することができる。また、スチレン系樹脂への発泡剤の含浸量を１〜１０重量％の範囲内の値とすることが好ましい。このような範囲で発泡剤を含浸すれば、発泡性スチレン系樹脂粒子（スチレン系樹脂粒子）を適度に発泡させて緻密な成形品とすることができる。
【００１９】
（２） その他の被覆剤
発泡性スチレン系樹脂粒子本体の被覆においては、グルコン酸又はグルコン酸塩の他に従来公知の被覆剤を併用することができる。例えば、一次発泡における集塊化防止のために使用されるステアリン酸亜鉛、ステアリン酸カルシウムなどの金属石鹸、エチレンビスアミド、ステアリン酸アミドのような高級脂肪酸アミドを挙げることができる。これらの集塊化防止剤は発泡性スチレン系樹脂粒子本体１００重量部に対して、０．０５〜０．８重量部の範囲内で使用することが好ましい。中でも集塊化防止効果に特に優れており、また経済的観点から安価なステアリン酸亜鉛が好ましい。
また、成形工程において、この発泡性樹脂粒子本体の融着促進効果のある添加剤も使用可能である。例えばステアリン酸グリセライド、オレイン酸グリセライド等の高級脂肪酸のトリエステル、ジエステル、モノエステル類、蔗糖エステル類等の一種又は二種以上が使用できる。
更に、発泡性スチレン系樹脂粒子本体の静電防止剤として使用されるグリセリン、ソルビトール、ポリエチレングリコール、ポリプロピレングリコール等の多価アルコール類、ソルビタンエステル、高級脂肪酸のエチレングリコール付加物等のノニオン系界面活性剤の一種または二種以上の併用も可能である。これら静電防止剤は発泡性スチレン系樹脂粒子本体１００重量部に対し、０．００５〜０．２重量部の範囲内で使用することが好ましい。
【００２０】
（３） 被覆層の形成
本発明における発泡性スチレン系樹脂粒子本体の表面へのグルコン酸又はグルコン酸塩の被覆層の形成方法は、特に制限はなく従来既知の手段で行うことができる。例えば、リボンブレンダー、Ｖ型ブレンダー、ヘンシェルミキサー、レディゲミキサー等の混合機を用い、室温、１００〜１０，０００ｒｐｍの回転数、及び１０秒〜１時間の撹拌時間の条件で、発泡性スチレン系樹脂粒子本体、グルコン酸又はグルコン酸塩及び前述の被覆剤各成分等をそれぞれ混合することによって被覆形成することができる。ただし、発泡性スチレン系樹脂粒子本体、グルコン酸又はグルコン酸塩、及び前述の被覆剤各成分等をそれぞれ個別に層状に被覆形成することもできる。
【００２１】
（４） 発泡成形品
本発明の発泡成形品は、前述の発泡性スチレン系樹脂粒子を成形することによって得ることができる。すなわち、上述した発泡性スチレン系樹脂粒子を使用することにより、短い成形加熱時間で発泡粒子同士が強固に融着し、かつその粒子界面が優れた撥油性を有する発泡成形品を得ることができる。
ここで具体的な成形加熱条件は特に制限されるものではないが、前述したとおり、金型等を用いて、加熱温度が９０〜１５０℃、加熱時間が１〜６０秒の条件で発泡成形するのが好ましい。従って、このように本発明の発泡成形品を製造すれば、例えば発泡成形品（容器）内に、ラード、即席ラーメン類、カレールウ、マヨネーズ、マーガリン等の浸透性の高い油性及び脂肪性の食品あるいは機械油等を直接包装あるいは収容しても、当該発泡成形品を構成する発泡性スチレン系樹脂粒子間から容器外へ油脂等が浸透するのを有効に防止することができ、発泡成形品の製品寿命を長くすることも可能となる。
【００２２】
【実施例】
以下、実施例によって本発明を更に詳細に説明するが、本発明はこれらの記載に制限されるものではない。
【００２３】
［実施例１］
（１）試料の作製
発泡剤として５．５重量％のペンタン（ｉｓｏ−ペンタン／ｎ−ペンタンの重量＝３０／７０）を含む平均径（直径）０．３５〜０．６０ｍｍの発泡性ポリスチレン粒子（日立化成工業株式会社製ハイビーズ５ＳＧ）２０００ｇをヘンシェルミキサーに入れた。次いで、５００〜１０００ｒｐｍの回転数で撹拌しながらステアリン酸亜鉛 ７．０ｇ、ポリエチレングリコール（三洋化成工業株式会社製 ＰＥＧ−４００）１．０ｇ、及びグルコン酸ナトリウム（藤沢薬品工業株式会社製 ヘルシャスＡ）１．０ｇを順次加え、約９０秒間撹拌を続けた後、撹拌を止めて原料とした。次いで、バッチ式一次発泡装置を用い、当該固形分を熱風とスチームの混合気を熱媒として嵩密度１０ｍｌ／ｇになるよう発泡させ、一次発泡樹脂粒子を得た。
その後、この一次発泡樹脂粒子を常温（２５℃）、常圧下で１６時間熟成した後、内容積５００ｃｃ、肉厚２．０ｍｍの成形品を得るための金型に充填し、加熱温度１４０℃、加熱時間４秒の条件で発泡成形品（カップ）を加熱成形した。なお、このとき加熱時間以外に、原料充填時間、金型を室温から加熱温度（１４０℃）に到達するまでの予備加熱時間、及び発泡成形品を取り出すために金型を所定温度以下まで冷却する必要があるが、そのための時間を別途、約８秒要した。
【００２４】
（２）性能評価方法
１）融着度の測定
発泡成形品（カップ）を手で割り、破断面を露出させ、当該破断面を光学顕微鏡で観察し、単位面積当たりの凝集破壊している部分の面積割合を融着度（％）として測定した。なお、発泡性スチレン系樹脂粒子同士の融着が不十分な場合には、粒子界面で破壊される。
２）界面活性剤入り水溶液の遮蔽性テスト
加速試験として、界面活性剤入りの水溶液を用いて遮蔽性テストを行った。すなわち、界面活性剤水溶液（花王株式会社製スコアロール７００、濃度０．１重量％）を約３００ｇ入れ、常温で放置し、カップの外壁に界面活性剤水溶液が浸透してくるまでの時間を測定した。
３）油脂成分の遮蔽性テスト
油脂成分に対する遮蔽性の確認として、得られた発泡成形品（カップ）にカレールウ２００ｇを入れた後、当該カップをサラン樹脂製ラッピングフィルムで包装した。そして、包装したカップを、６０℃雰囲気下のオーブン中に放置し、カップの外壁にカレールウが浸透してくるまでの時間を測定した。
それらの結果をまとめて表１に示した。
【００２５】
（３）評価結果
表１の結果から明らかなように、加熱時間が４秒と極端に短いにもかかわらず、融着度は７０％という良好な値を示した。また、界面活性剤の浸透時間は５０分、油脂成分としてのカレールウの浸透時間は２４時間であった。
したがって、本発明の発泡性スチレン樹脂粒子は、発泡成形品（カップ）に成形した場合に、浸透性の高い内容物であっても、当該内容物が発泡成形品の外壁まで浸透する時間（浸透時間）を著しく長くして、水性成分の内容物に対する浸透時間と同等かそれ以上の浸透時間を得ることができ、また、本発明の発泡性スチレン系樹脂粒子は短時間で発泡成形品を加熱成形することが可能であることが確認された。
【００２６】
［実施例２及び３］
実施例１において、加熱時間を５秒（実施例２）及び６秒（実施例３）にした以外は、実施例１と同様の条件で発泡成形品（カップ）を得た。そして実施例１と同様に性能評価を行った。
それぞれの測定結果を表１に示す。この結果から明らかなように、加熱時間が５秒及び６秒と長くなったため、融着度は９０％以上と良好であった。また、界面活性剤の浸透時間は６０分以上（５及び６秒加熱）、油脂成分としてのカレールウの浸透時間は３６時間（５秒加熱）あるいは６０時間（６秒加熱）と優れた内容物に対する遮蔽性を示した。
したがって、本発明の発泡性スチレン系樹脂粒子は、実施例１で示したように、加熱時間が４秒でも発泡成形品（カップ）として、実用に十分な内容物の遮蔽性と発泡成形品の加熱成形性とを得ることができるが、より長い加熱時間（５又は６秒加熱）を採ることにより、更に優れた内容物の遮蔽性と、発泡成形品の加熱成形性とが得られることが確認された。
【００２７】
［比較例１〜３］
実施例１〜３において、それぞれグルコン酸ナトリウムを除いて発泡性スチレン系樹脂粒子としたこと以外は、実施例１〜３と同様の条件で発泡成形品（カップ）を得た。そして、実施例１〜３と同様に性能評価を行った結果を表１に示した。
この結果から明らかなように、グルコン酸ナトリウムを使わないと、加熱時間が４秒の場合の融着度は７０％であり、加熱時間が５秒及び６秒の場合の融着度は９０％以上であった。すなわち融着度に関しては、グルコン酸ナトリウムを使用しない場合であっても、使用した場合と大差ない結果が得られる傾向を示した。
それに対して、界面活性剤の浸透時間は、加熱時間が４秒の場合には１５分であり、加熱時間が５秒の場合には２５分であり、加熱時間が６秒の場合では３５分であった。また、油性成分としてのカレールウの浸透時間は、加熱時間が４秒及び５秒の場合には３時間未満であり、加熱時間が６秒の場合でも４時間であった。したがって、内容物の遮蔽性に関しては、グルコン酸系化合物の存在が大きく寄与しており、これらを使用しないと、内容物の遮蔽性は著しく低下する傾向が見られた。
【００２８】
【表１】

【００２９】
【発明の効果】
本発明により、発泡成形品（カップ）を成形した場合に、浸透性の高い内容物であっても、当該内容物が発泡成形品の外壁まで浸透する時間（浸透時間）を著しく長くすることができるようになった。そして、特にカレールウのような浸透性の高い内容物に対しても優れた遮蔽性を示し、当該内容物を著しく長い間保持することができるようになった。
また、このように発泡性スチレン系樹脂粒子を構成することにより、上記の優れた遮蔽性を有しながら、当該発泡性スチレン系樹脂粒子の生産性を損なうことがない。
よって本発明により、浸透性の高い内容物の遮蔽性と加熱成形性とのバランスに優れた発泡性スチレン系樹脂粒子及び発泡成形品を提供することができるようになった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an expandable styrene resin particle and an expanded molded article using the same. More specifically, the present invention relates to expandable styrene resin particles suitable for use as a container for a highly permeable content, for example, a content in which an emulsifier component and an oil and fat component are mixed, and a foam molded product using the same.
[0002]
[Prior art]
In general, expandable styrenic resin particles can be pre-expanded with steam or the like to prepare pre-expanded particles, and the pre-expanded particles are filled into a mold having small holes and then heated again to be molded into a predetermined shape. . The molded product thus obtained has excellent properties such as economy, light weight, and hygiene, and is used in many fields as a packaging material, a heat insulating material, a container, and the like.
[0003]
Expandable styrenic resin particles are obtained by dispersing a foaming agent (generally a liquid or gaseous aliphatic hydrocarbon such as propane, butane, pentane, hexane, etc. at room temperature) together with styrenic resin particles in an aqueous medium, and foaming into particles. For example, a method of impregnating a foaming agent in an aqueous suspension containing a small amount of a solvent such as toluene or cyclohexane having solubility in styrene-based resin particles. And the expandable styrene resin particle obtained in this way is shape | molded through the above-mentioned process.
[0004]
However, since the obtained molded product is obtained by stacking expandable styrene resin particles in a stone wall shape and fusing them with foaming pressure and heat, the resin particles may not be integrated. As a result, depending on the type of contents stored when used as a container, the contents may permeate into the outer wall of the container or the inside of the molded product. In order to prevent such contents from penetrating, a method of minimizing voids inside the molded product that becomes a path when the contents penetrate the inside of the container, and the surface energy of the particle surface is reduced. By doing this, it is possible to generally adopt a method of increasing the contact angle of the surface of the molded product with respect to the permeating contents.
[0005]
In general, the former method is to strengthen the heating conditions during molding. To obtain a molded product with fewer defects, the molding temperature is set lower, and the expandable styrene resin particles are longer. The method of heating for a time is taken. However, this method requires a long time for molding and heating the expandable styrene-based resin particles, and it is difficult to say that this method is useful because it significantly reduces productivity industrially.
[0006]
On the other hand, as the latter method, the amount of metal soap (higher fatty acid salt) generally used for preventing agglomeration of expandable styrene resin particles in the pre-foaming is increased. ing. However, even in this method, it is necessary to lengthen the molding heating time in order not to exhibit the property of inhibiting the fusion of the expandable styrene resin particles due to the metal soap, and it is difficult to say that this is an industrially useful method. .
[0007]
Accordingly, various foamable styrene resin particles with less permeability of the contents in a shorter molding heating time have been proposed. For example, in Japanese Examined Patent Publication No. 56-34172, expandable styrenic resin particles whose surface is coated with sucrose ester or a derivative thereof are disclosed in Japanese Patent Laid-Open No. 2-115242. Styrenic resin particles are each disclosed.
[0008]
However, the expandable styrenic resin particles disclosed in JP-B-56-34172 and JP-A-2-115242 are excellent in shielding properties for general aqueous (including emulsified) or oil-based contents ( Although it is possible to exhibit a permeation prevention property, there is a risk that the permeation prevention performance may be insufficient depending on the type of contents contained in the molded product when processed into a molded product.
[0009]
Containers molded with the above-mentioned expandable styrene resin particles have a wide range of uses due to their economic efficiency, heat retention, etc., but when used for a long time as containers for some highly permeable contents, etc. There was a risk that the contents would permeate. The expandable styrenic resin particles disclosed in these publications can be used for a relatively long period of time even for some highly permeable oily contents (eg, curry roux, machine oil, etc. in which an emulsifier component and an oil component are mixed). By heat molding, excellent shielding properties (penetration prevention properties) can be exhibited. However, it is undeniable that productivity is lowered by long-time heat forming. That is, in the expandable styrenic resin particles disclosed in any of the above-mentioned patent publications, the balance between the shielding properties (penetration prevention properties) for the highly permeable contents and the productivity represented by the molding heating time. It was not always satisfactory.
[0010]
[Patent Document 1]
Japanese Patent Publication No. 56-34172 [Patent Document 2]
Japanese Patent Laid-Open No. 2-115242
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and even when a specific part of the highly permeable content is used for a container or the like, the content to be stored penetrates into the outer wall of the container or the inside of the molded product. It is an object of the present invention to provide an expandable styrene resin particle and an expanded molded product that are less likely to cause mold contamination, have good workability, and have an excellent property balance that can be molded in a short time.
[0012]
[Means for Solving the Problems]
The present invention relates to expandable styrene resin particles obtained by coating the surface of an expandable styrene resin particle body with gluconic acid or gluconate represented by the following general formula (1).
[Chemical 2]

(In the formula, R represents a hydrogen atom or a metal, and when the metal is divalent or higher, bonds other than R in the general formula (1) are combined according to the valence.)
Examples of the metal in the general formula include Na, K, Ca, Cu, and Zn.
[0013]
As is apparent from the structural formula, these gluconic acid or gluconate salts have a high affinity for water because they contain many hydroxyl groups in the molecule. The presence of these gluconic acids or gluconates between the resin particle surface and the particles after molding forms a kind of water-retaining layer, which infiltrates oily contents with high permeability by the principle of “water and oil”. It is considered that an excellent shielding effect is exhibited.
[0014]
In constituting the expandable styrene resin particles, the coating amount of these gluconic acid or gluconate is within the range of 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the expandable styrene resin particles main body. A value is preferred. When the coating amount is in such a range, it is possible to provide expandable styrene resin particles and a foam-molded product having good workability and little influence on molding time. In addition, from the viewpoint of excellent balance between the shielding properties of the contents and the efficiency of productivity, the coating amount is 0.005 to 0.3 parts by weight with respect to 100 parts by weight of the expandable styrene resin particle body. The range is more preferable.
[0015]
The present invention also relates to a foam-molded product obtained by foam-molding the expandable styrene resin particles.
[0016]
In thermoforming the foam-molded article of the present invention, it is preferable to foam-mold the expandable styrene resin particles under the conditions of a heating temperature of 90 to 150 ° C. and a heating time of 1 to 60 seconds. Under such heating conditions, it is possible to produce a foam molded article having an excellent balance between the shielding properties of the contents and the efficiency of productivity. In addition, from the viewpoint of producing a foam molded article having a good balance between the shielding properties of the contents and the efficiency of productivity, foam molding is performed at a heating temperature of 100 to 140 ° C. and a heating time of 3 to 6 seconds. Is more preferable.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be specifically described. That is, in the foamable styrene resin particles of the present invention formed by coating the surface of the foamable styrene resin particles main body with gluconic acid or gluconate, the following foamable styrene resin particles are used for foam molding. The product can be thermoformed.
[0018]
1. Expandable styrene resin particles The expandable styrene resin particles of the present invention coat gluconic acid or gluconate as a coating agent (sometimes referred to as a coating layer) on the surface of the foamable resin particle body. Is obtained.
(1) Expandable styrene resin particle main body The expandable styrene resin particle main body can be prepared by impregnating a styrene resin particle with a foaming agent as described above.
1) Styrene resin particles The styrene resin particles are not particularly limited. For example, styrene homopolymer, or a component copolymerizable with styrene monomer, for example, methacrylic acid esters such as acrylonitrile, methyl methacrylate, butyl methacrylate, etc. , One or two or more copolymers with acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, monomers of styrene derivatives such as α-methylstyrene, chlorostyrene, vinyltoluene, etc. Can do.
Further, the particle diameter of the styrene resin particles is not particularly limited. For example, if the average particle diameter is a styrene resin particle having a value in the range of 0.8 to 0.25 mm, it is appropriate. To form a dense molded product.
2) Types of foaming agent The type of foaming agent is not particularly limited, but is generally used for producing expandable styrene resin particles such as aliphatic hydrocarbons such as propane, butane, pentane and hexane. A liquid or gaseous compound at room temperature (25 ° C.).
3) The impregnation method and the impregnation amount of the foaming agent The impregnation method of the foaming agent is not particularly limited, and conventionally used methods can be employed. Moreover, it is preferable to make the impregnation amount of the foaming agent into the styrene-based resin a value within the range of 1 to 10% by weight. If the foaming agent is impregnated in such a range, the foamable styrene resin particles (styrene resin particles) can be appropriately foamed to form a dense molded product.
[0019]
(2) Other coating agents In the coating of the foamable styrene resin particle main body, conventionally known coating agents can be used in addition to gluconic acid or gluconate. Examples thereof include metal soaps such as zinc stearate and calcium stearate used for preventing agglomeration in primary foaming, and higher fatty acid amides such as ethylenebisamide and stearamide. These agglomeration inhibitors are preferably used within a range of 0.05 to 0.8 parts by weight with respect to 100 parts by weight of the expandable styrene resin particle body. Of these, zinc stearate is particularly excellent in the effect of preventing agglomeration, and inexpensive zinc stearate is preferable from an economical viewpoint.
In the molding step, an additive having an effect of promoting fusion of the expandable resin particle main body can also be used. For example, one or two or more of higher fatty acid triesters, diesters, monoesters, sucrose esters such as stearic acid glyceride and oleic acid glyceride can be used.
Furthermore, nonionic surfactants such as polyhydric alcohols such as glycerin, sorbitol, polyethylene glycol and polypropylene glycol, sorbitan esters, and ethylene glycol adducts of higher fatty acids used as antistatic agents for the foamable styrene resin particles. One or two or more agents can be used in combination. These antistatic agents are preferably used in the range of 0.005 to 0.2 parts by weight with respect to 100 parts by weight of the expandable styrene resin particle body.
[0020]
(3) Formation of coating layer The method for forming the coating layer of gluconic acid or gluconate on the surface of the expandable styrenic resin particle main body in the present invention is not particularly limited and can be carried out by conventionally known means. For example, using a blender such as a ribbon blender, a V-type blender, a Henschel mixer, a Redige mixer, etc., under conditions of room temperature, a rotational speed of 100 to 10,000 rpm, and a stirring time of 10 seconds to 1 hour, The coating can be formed by mixing the resin particle main body, gluconic acid or gluconate, and the respective components of the aforementioned coating agent. However, the foamable styrenic resin particle main body, gluconic acid or gluconate, and the respective components of the above-mentioned coating agent can be individually coated in layers.
[0021]
(4) Foam molded article The foam molded article of the present invention can be obtained by molding the above-mentioned expandable styrene resin particles. That is, by using the above-mentioned expandable styrene resin particles, it is possible to obtain a foam-molded product in which the foam particles are firmly fused with each other in a short molding heating time and the particle interface is excellent in oil repellency. .
Here, the specific molding heating conditions are not particularly limited, but as described above, foam molding is performed using a mold or the like under the conditions of a heating temperature of 90 to 150 ° C. and a heating time of 1 to 60 seconds. Is preferred. Therefore, when the foamed molded product of the present invention is produced in this way, for example, in a foamed molded product (container), highly permeable oily and fatty foods such as lard, instant ramen, kaleau, mayonnaise, margarine, etc. Even if machine oil or the like is directly packaged or stored, it is possible to effectively prevent the penetration of oils and fats from between the expandable styrenic resin particles constituting the foam molded product to the outside of the container. It is also possible to extend the life.
[0022]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited to these description.
[0023]
[Example 1]
(1) Preparation of sample Expandable polystyrene particles having an average diameter (diameter) of 0.35 to 0.60 mm containing 5.5% by weight of pentane (weight of iso-pentane / n-pentane = 30/70) as a foaming agent 2000 g (Hi-Beads 5SG manufactured by Hitachi Chemical Co., Ltd.) was put in a Henschel mixer. Next, 7.0 g of zinc stearate, 1.0 g of polyethylene glycol (PEG-400 manufactured by Sanyo Chemical Industries, Ltd.), and sodium gluconate (Health A manufactured by Fujisawa Pharmaceutical Co., Ltd.) while stirring at a rotational speed of 500 to 1000 rpm. 1.0 g was sequentially added and stirring was continued for about 90 seconds, and then stirring was stopped to obtain a raw material. Subsequently, using a batch type primary foaming apparatus, the solid content was foamed to a bulk density of 10 ml / g using a mixture of hot air and steam as a heat medium to obtain primary foamed resin particles.
Thereafter, the primary foamed resin particles were aged at room temperature (25 ° C.) and normal pressure for 16 hours, and then filled into a mold for obtaining a molded product having an internal volume of 500 cc and a wall thickness of 2.0 mm, and a heating temperature of 140 ° C., The foamed molded product (cup) was heat-molded under the condition of a heating time of 4 seconds. At this time, in addition to the heating time, the raw material filling time, the preheating time until the mold reaches the heating temperature (140 ° C.) from room temperature, and the mold are cooled to a predetermined temperature or less in order to take out the foam molded product. Although it is necessary, it took about 8 seconds for the time.
[0024]
(2) Performance evaluation method 1) Measurement of the degree of fusion The part where the foamed molded product (cup) is divided by hand, the fractured surface is exposed, and the fractured surface is observed with an optical microscope. Was measured as the degree of fusion (%). In addition, when the fusion | melting of expandable styrene resin particles is inadequate, it destroys at a particle | grain interface.
2) Shielding test of aqueous solution containing surfactant As a accelerating test, a shielding test was conducted using an aqueous solution containing a surfactant. That is, about 300 g of a surfactant aqueous solution (score roll 700 manufactured by Kao Co., Ltd., concentration 0.1% by weight) is added and left at room temperature, and the time until the surfactant aqueous solution penetrates into the outer wall of the cup is measured. did.
3) Shielding property test of oil / fat component As a confirmation of the shielding property against the oil / fat component, 200 g of curry roux was added to the obtained foamed molded product (cup), and then the cup was wrapped with a wrapping film made of Saran resin. Then, the packaged cup was left in an oven at 60 ° C., and the time until curry rose permeated into the outer wall of the cup was measured.
The results are summarized in Table 1.
[0025]
(3) Evaluation results As is clear from the results in Table 1, the degree of fusion showed a good value of 70% despite the extremely short heating time of 4 seconds. Further, the penetration time of the surfactant was 50 minutes, and the penetration time of Kara Leu as an oil and fat component was 24 hours.
Therefore, when the expandable styrene resin particles of the present invention are molded into a foam molded product (cup), even if the content is highly permeable, the time for the content to penetrate to the outer wall of the foam molded product (penetration) Time) can be significantly lengthened to obtain a penetration time equal to or longer than the penetration time of the aqueous component content, and the expandable styrenic resin particles of the present invention heat the foamed molded product in a short time. It was confirmed that molding was possible.
[0026]
[Examples 2 and 3]
In Example 1, a foamed molded article (cup) was obtained under the same conditions as in Example 1, except that the heating time was 5 seconds (Example 2) and 6 seconds (Example 3). And performance evaluation was performed similarly to Example 1.
Each measurement result is shown in Table 1. As is apparent from the results, the heating time was as long as 5 seconds and 6 seconds, and the degree of fusion was as good as 90% or more. In addition, the penetration time of the surfactant is 60 minutes or more (heating for 5 and 6 seconds), and the penetration time of Kara Leu as an oil and fat component is 36 hours (heating for 5 seconds) or 60 hours (heating for 6 seconds). Showed shielding properties.
Therefore, the expandable styrenic resin particles of the present invention, as shown in Example 1, can be used as a foam molded product (cup) even when the heating time is 4 seconds. Although heat moldability can be obtained, by taking a longer heating time (5 or 6 seconds heating), it is possible to obtain more excellent shielding properties of contents and heat moldability of foam molded products. confirmed.
[0027]
[Comparative Examples 1-3]
In Examples 1 to 3, foamed molded articles (cups) were obtained under the same conditions as in Examples 1 to 3 except that sodium gluconate was removed to obtain expandable styrene resin particles. And the result of having performed performance evaluation similarly to Examples 1-3 was shown in Table 1.
As is clear from this result, when sodium gluconate is not used, the degree of fusion when the heating time is 4 seconds is 70%, and the degree of fusion when the heating time is 5 seconds and 6 seconds is 90%. That was all. That is, with respect to the degree of fusion, even when sodium gluconate was not used, there was a tendency to obtain results that were not significantly different from those when it was used.
In contrast, the penetration time of the surfactant is 15 minutes when the heating time is 4 seconds, 25 minutes when the heating time is 5 seconds, and 35 minutes when the heating time is 6 seconds. Met. Moreover, the penetration time of curry roux as an oil component was less than 3 hours when the heating time was 4 seconds and 5 seconds, and was 4 hours even when the heating time was 6 seconds. Therefore, the presence of gluconic acid compounds greatly contributes to the shielding properties of the contents, and if these are not used, the shielding properties of the contents tend to decrease significantly.
[0028]
[Table 1]

[0029]
【The invention's effect】
According to the present invention, when a foam molded product (cup) is molded, even if the content is highly permeable, the time (permeation time) for the content to permeate to the outer wall of the foam molded product can be significantly increased. I can do it now. And the shielding property which was excellent also with respect to the content with especially high permeability | transmittance, such as Kalerou, was able to be hold | maintained for the said remarkably long time.
In addition, by configuring the expandable styrene resin particles in this way, the productivity of the expandable styrene resin particles is not impaired while having the above-described excellent shielding properties.
Therefore, according to the present invention, it is possible to provide expandable styrene-based resin particles and a foam-molded product excellent in the balance between the shielding property of the highly permeable content and the heat moldability.

Claims (3)

Expandable styrene resin particles obtained by coating the surface of the expandable styrene resin particle main body with gluconic acid or gluconate represented by the following general formula (1).

(The dotted line in general formula (1) should be a solid line.)
(In the formula, R represents a hydrogen atom or a metal, and when the metal is divalent or higher, bonds other than R in the general formula (1) are combined according to the valence.) The expandable styrene resin particles according to claim 1, comprising 0.001 to 0.5 parts by weight of the gluconic acid or gluconate with respect to 100 parts by weight of the expandable styrene resin particles. A foam-molded product obtained by foam-molding the expandable styrene-based resin particles according to claim 1.