JP3983116B2 - Expandable thermoplastic resin particles and foamed molded products - Google Patents

Description

【００３２】
表１中、＊１〜４は以下の事項を意味する。
＊１ カップにカレー粉を８分目まで入れ、カップをラッピングした後、６０℃のオーブン中に入れ、カレー粉の黄色色素がカップ外壁に滲み出すまでの時間を測定し評価した。評価基準は表２に示す。
【００３３】
【表２】

【００３４】
＊２ カップ成形品に温度２３℃の界面活性剤水溶液（エマルゲン８１０（花王社製）を０．１重量％、エリオクロムブラックＴを０．００５重量％溶解させた水溶液）を８分目まで入れ、温度２３℃、湿度５０％の雰囲気下で界面活性剤水溶液がカップ外壁に滲み出すまでの時間を測定し評価した。評価基準を表３に示す。
【００３５】
【表３】

【００３６】
＊３ カップの外側面と、その反対側の外側面から圧力をかけてカップを押しつぶして破断させ、破断した面において発泡粒子自身が破断している割合を測定し、評価した。評価基準を表４に示す。
【００３７】
【表４】

【００３８】
＊４ 平均最大長の測定は、マルチイメージアナライザー（ベックマン・コールター社製）を用いて行なった。マルチイメージアナライザーは、凝集体がアパチャーチューブを介してアパチャーを通過するとき、アパチャーチューブ後方のストロボにより光線を照射し、個々の凝集体の投影画像をＣＣＤカメラにより撮影する装置である。
【００３９】
本発明におけるマルチイメージアナライザーによる凝集体の平均最大長の測定には、アパチャーの直径が１００μｍのアパチャーチューブを使用し、ＣＣＤカメラの計測倍率が４０倍のレンズを使用した。また、画像処理における１画素の大きさは０．２１９μｍ、撮影範囲となるフレームサイズの設定値は３１４、二値化レベルの設定値は２００、ノイズカットの設定値は０．５とした。撮影された１０００枚の凝集体画像から、個々の粒径の最大値を測定し、その測定結果を平均することで平均最大長を算出した。なお、この測定に必要とする電解液は、アイソトンＩＩ−ＰＣ（ベックマン・コールター社製）を使用した。本発明におけるマルチイメージアナライザイーの測定設定値を表５に示す。
【００４０】
【表５】

【００４１】
表１から、凝集体の使用割合及び平均最大長を本発明の範囲にすることで、融着性に優れ及び内容物の滲み出しを防ぎうる発泡成形品を製造できる発泡性熱可塑性樹脂粒子を提供することができる
【００４２】
【発明の効果】
本発明の脂肪酸金属塩粒子の凝集体で被覆された発泡性熱可塑性樹脂粒子によれば、内容物の滲み出しが防止された成形品を製造することができる。
【図面の簡単な説明】
【図１】実施例１で使用した凝集体の電子顕微鏡写真である。
【図２】実施例５で使用した凝集体の電子顕微鏡写真である。
【図３】比較例１で使用した凝集体の電子顕微鏡写真である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an expandable thermoplastic resin particle and an expanded molded article. In particular, the foamable thermoplastic resin particles of the present invention include foamed molded products such as instant noodles and oily foods such as fried chicken, fats and oils such as fat-containing foods, coffee, ice-box ice water, etc. It can use suitably for manufacture of the foaming molded product which can prevent that it exudes outside through the fusion | melting surface of an inside foaming particle.
[0002]
[Prior art]
The expandable thermoplastic resin particles are obtained by impregnating an easily volatile aliphatic hydrocarbon as a foaming agent in an aqueous suspension of resin particles, or an aqueous suspension containing a small amount of a solvent that is soluble in the resin particles. It is produced by a method of impregnating a foaming agent in a turbid liquid.
The foamable thermoplastic resin particles thus obtained are pre-foamed in advance, and the pre-foamed particles are filled in a mold of a molding machine having small holes, and heated above the softening point with pressurized steam. To obtain a foam molded product.
[0003]
When the foamed molded product is broken, the fused state of each particle is good, that is, the surface of each particle at the fracture surface does not appear at all, and even if it is fused 100%, it is not a surface adhesion and is fine. A capillary tube is open to the outside. For example, when dye water containing a surfactant is added, the dye water passes through the particle fusion surface and oozes out to the outside, so that a capillary opening to the outside can be confirmed.
[0004]
For example, even when a cup obtained by a normal molding method using expanded polystyrene particles, which is a kind of expandable thermoplastic resin particles, is in a normal fusion state, when an aqueous surfactant solution is added as described above, It can be observed that it passes through the gaps between the particles and oozes out of the cup. These cups have no practical problem as a drinking cup like coffee. However, oily foods such as salad oils such as donuts, hamburgers, fried chicken, margarine, foods containing fats and oils, etc., when stored for a long period of time, oils and fats gradually ooze out of the vessel wall. It was inappropriate.
[0005]
In addition, if you store instant noodles mixed with curry powder in a container, the yellow pigment of the curry powder will ooze out on the outer wall of the container and the container will be contaminated. Is significantly reduced.
Further, in the simple ice box, the ice water in the ice box oozes out to the outside of the container after a long period of time and the commercial value is lowered.
In order to prevent exudation of fats and oils using the foamable thermoplastic resin particles, it is necessary to increase the heating conditions during molding or to increase the heating time. Such treatment can prevent exudation of oils and fats, but since the heat resistance is not high, it is difficult to obtain a molded product with a beautiful appearance that can be expanded and contracted by expanded particles. Moreover, there exists a problem that productivity is inferior because a molding cycle becomes long.
[0006]
In order to prevent the fats and oils in the container from exuding to the outer wall of the container, a method of coating the surface of the expandable resin particles with an additive for preventing the exudation has been proposed. For example, JP-A-5-140364 and JP-A-10-298339 propose a surface coating method with a fluorine-containing vinyl polymer, and Japanese Patent Publication No. 56-34172 proposes a method of surface coating with a sucrose ester. Has been.
[0007]
[Problems to be solved by the invention]
Although the above proposal is an effective means for preventing bleeding, it is not sufficient. In addition, the method of surface coating with a fluorine-containing vinyl polymer has a problem in that it tends to cause a filling failure or a mold release failure due to static electricity of foamed particles. Furthermore, in the method of surface coating with sucrose ester, the foamed particles are sticky, so the flowability is poor and it takes time to feed, and the foamed particles adhere to the inside of the feed tube and become dirty later. As a result, there is a problem of being mixed into a molded product.
[0008]
[Means for Solving the Problems]
Thus, according to the present invention, at least a part of the surface of the foamable thermoplastic resin particles is coated with an aggregate in which a plurality of metal salt particles of fatty acid selected from stearic acid, oleic acid or palmitic acid are collected. The aggregate is used in an amount of 0.1 to 0.6 parts by weight with respect to 100 parts by weight of the expandable thermoplastic resin particles, and the average particle diameter of the expandable thermoplastic resin particles and the average maximum length of the aggregate are 0, respectively. Coated foamed thermoplastic resin particles characterized in that they are 2 to 2.0 mm and 0.5 to 30 μm are provided.
Furthermore, according to the present invention, there is provided a foam molded product obtained by foam molding of the coated foamable thermoplastic resin particles.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In general, it is known to use a fatty acid metal salt as an anti-blocking agent during preliminary foaming. As the fatty acid metal salt, one produced by a so-called direct method in which a fatty acid and a metal oxide are reacted to pulverize the reaction product has been used. Although this pulverized product of fatty acid metal salt is expected to be effective in preventing blocking, the effect of preventing the exudation of the contents to the outer wall of a molded container or the like was not sufficient. On the other hand, the inventors of the present invention, as a result of intensive studies on how to efficiently express the water repellency and oil repellency possessed by the fatty acid metal salt, are very good by using an aggregate of fatty acid metal salt particles. Surprisingly, the present invention has been found out that an effective anti-bleeding effect can be obtained.
The present invention will be described below.
[0010]
The expandable thermoplastic resin particles used in the present invention comprise at least a base resin and a foaming agent. The base resin is not particularly limited as long as it is a resin that can be foamed with an inorganic or organic foaming agent. For example, polystyrene, impact polystyrene, styrene- (meth) acrylic acid copolymer, polystyrene resin such as AS resin, methacrylate ester resin, vinylidene chloride resin, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, etc. Olefin homopolymers and copolymer resins, polymers such as polyphenylene ether, mixtures of these polymers (for example, mixed resins of polyphenylene ether and polystyrene), and vinyl monomers grafted onto part of the polyolefin. The composite resin etc. which are carrying out are mentioned. In addition, (meth) acryl means methacryl or acryl.
[0011]
Among the above-mentioned base resins, it is particularly preferable to use a polystyrene-based resin for the purpose of preventing bleeding of contents when using a foam molded product. Specifically, homopolymerized particles of styrene monomers such as styrene, α-methylstyrene, paramethylstyrene, t-butylstyrene, chlorostyrene, divinylbenzene, or a combination of two or more of these monomers Other than coalesced particles, esters of acrylic acid and methacrylic acid such as methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, cetyl methacrylate, or styrene monomers such as acrylonitrile, dimethyl fumarate, ethyl fumarate, alkylene glycol dimethacrylate And copolymer particles with other monomers. Furthermore, resin particles obtained by extrusion blending a styrene resin and other resins may be used. Examples of resins other than styrene resins include polyphenyl ether resins, polyolefin resins, rubber components, and the like.
[0012]
The blowing agent is not particularly limited, and easily volatile aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane and cyclopentane, freon compounds such as freon 11 and freon 12, carbon dioxide Examples thereof include foaming agents that are liquid or gas at room temperature, such as inorganic compounds such as nitrogen and water vapor. In addition to this, a decomposable foaming agent that decomposes by heating to generate gas can also be used.
The foamable thermoplastic resin particles may contain known additives such as ultraviolet absorbers, extenders, and colorants.
[0013]
The average particle diameter of the expandable thermoplastic resin particles used in the present invention is 0.2 to 2.0 mm. When the average particle size is larger than 2.0 mm, filling in the mold details such as the container becomes insufficient, which causes a decrease in commercial value and a decrease in leakage prevention. Since the strength of the molded article such as the above is inferior, it is difficult to use practically, and further, the vapor holes of the foaming machine and the molding machine are clogged. A more preferable average particle diameter is 0.3 to 1.2 mm.
The production method of the expandable thermoplastic resin particles is not particularly limited, and can be produced by a known method. For example, a method in which an easily volatile aliphatic hydrocarbon is impregnated in an aqueous suspension as a foaming agent, or an aqueous suspension containing a small amount of a solvent that is soluble in resin particles is impregnated with a foaming agent. Methods and the like. The content of the foaming agent is preferably 3 to 8 parts by weight with respect to 100 parts by weight of the thermoplastic resin particles.
[0014]
In the aggregate used in the present invention, fatty acid metal salts include fatty acid metal salts of oleic acid, stearic acid, and palmitic acid (magnesium, calcium, barium, aluminum, zinc, etc.). Among these, a metal salt of stearic acid is preferable, and zinc stearate and calcium stearate are particularly preferable.
The shape of the fatty acid metal salt particles is not particularly limited. Specific examples include various shapes such as a spherical shape, a rod shape, a scale shape, and an indefinite shape. In particular, scale-like or irregular-shaped fatty acid metal salt particles are preferred. In the present invention, the scale shape means a shape having a thickness of 1/10 or less with respect to the average maximum length of the scale. Here, the average maximum length means an average value of the maximum lengths in the upper and lower surfaces perpendicular to the thickness direction of the scale.
[0015]
In the present invention, an aggregate in which a plurality of the particles are aggregated is used. The number of particles constituting the aggregate is preferably 5 or more. By setting the number to 5 or more, it is possible to further improve the ability to prevent the contents of the foam molded product obtained therefrom from seeping out.
The average maximum length of the aggregate is 0.5 to 30 μm. When the average maximum length is larger than 30 μm, aggregates are unevenly distributed on the individual surfaces of the particles, and it tends to be covered. As a result, the leakage preventing effect is lowered, which is not preferable. Many fatty acid metal salts that do not correspond to the aggregates referred to in the invention are likely to be present, and as a result, the effect of preventing leakage is reduced, which is not preferable.
The method for forming the aggregate is not particularly limited, and any known method can be used, but among them, the metathesis method described below is preferable.
(Double decomposition method)
A metal salt aqueous solution (for example, zinc chloride) and an alkali soap (for example, a salt of sodium or potassium and a fatty acid) are reacted to produce a fatty acid metal salt and an alkali metal salt (for example, sodium chloride). After the reaction, the fatty acid metal salt layer and the aqueous layer are separated by standing, and after removing the aqueous layer, the produced fatty acid metal salt is washed by washing with water, and the remaining alkali metal salt is centrifuged, filter press, etc. And agglomerates of fatty acid metal salt particles can be obtained by removing moisture by vacuum drying, hot air drying or the like.
[0016]
The surface of the expandable thermoplastic resin particle is coated with the above-mentioned aggregate to form a coated particle. However, the expandable thermoplastic resin particle only needs to be at least partly coated, and is not necessarily the entire surface of the expandable thermoplastic resin particle. May not be coated.
The coating method is not particularly limited, and a known method can be used. For example, a method of mixing foamable thermoplastic resin particles and agglomerates using a mixer such as a super mixer, a Henschel mixer, or a Laedige mixer may be mentioned.
[0017]
The aggregate is used in an amount of 0.1 to 0.6 parts by weight based on 100 parts by weight of the expandable thermoplastic resin particles. When the amount used is less than 0.1 parts by weight, the ability to prevent the content of the foamed molded product from oozing out is inferior, and when it is more than 0.6 parts by weight, the fusion of particles during molding is hindered by aggregates. Therefore, it is not preferable. A more preferable use amount of the aggregate is 0.2 to 0.5 parts by weight.
Further, a fusion accelerator or an antistatic agent may be used. These agents can be present in the foamable thermoplastic resin particles or can be present by coating the surface, but it is preferable to be present on the surface because the amount of the agent used can be reduced.
[0018]
The fusion accelerator is not particularly limited, and known ones can be used. For example, fatty acid amides such as lauric acid amide and oleic acid amide, amidated natural fatty acids such as amide of rice sugar oil and hardened beef tallow amide, triglycerides of fatty acids such as stearic acid triglyceride and palmitic acid triglyceride, soybean hardened oil and And natural triglycerides such as hydrogenated castor oil.
As an antistatic agent, it does not specifically limit but a well-known thing can be used. For example, polyhydric alcohols such as polyethylene glycol, polypropylene glycol and glycerin can be mentioned.
[0019]
A method for coating the surface of the foamable thermoplastic resin particles with a fusion accelerator or an antistatic agent is not particularly limited, and a known method can be used. For example, the same method as that for coating the surface of the foamable thermoplastic resin particles with the aggregate can be used.
The coating order of the aggregate, the fusion accelerator and the antistatic agent is not particularly limited. For example, the order of an aggregate, a fusion accelerator, and an antistatic agent, and the order of an antistatic agent, an aggregate, and a fusion accelerator are mentioned.
[0020]
The coated particles can be made into a foam-molded product by foam-molding by a known method. For example, there is a method in which the coated particles are pre-foamed to obtain pre-foamed particles, and the pre-foamed particles are placed in a desired mold and foamed to obtain a foam-molded product.
Pre-foaming can be performed by placing the coated particles in a foaming machine and heating with a medium such as steam. The bulk density of the pre-expanded particles is preferably about 0.015 to 0.5 g / cm ³ .
[0021]
Foam molded products are filled with pre-expanded particles in a mold and blown steam into the mold to heat and expand the pre-expanded particles, but the space that can be expanded by the mold is limited. Therefore, the particles adhere to each other and are fused and integrated, and as a result, a desired shape can be obtained.
The shape of the foam molded product is not particularly limited, and various shapes can be adopted. Examples thereof include a cup shape, a dish shape, a bowl shape, a tray shape, and a box shape. In addition, the contents of the foam molded products are vegetable oils such as beef tallow, soybean oil, rapeseed oil, lard, instant noodles, stew, mayonnaise, dressing sauce, curry roux, butter, margarine, white sauce, yogurt, ice cream, donut, The present invention is particularly effective for oily foods such as hamburgers and fried chicken, fat foods, aqueous solutions containing surfactants, and the like. That is, it is possible to prevent the contents (oils and fats, aqueous solutions, pigments, etc.) from penetrating to the outside from between the expanded particles constituting the expanded molded article.
[0022]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these.
Example 1
1000 g of expandable polystyrene resin particles having an average particle diameter of 0.4 mm containing 5.5 parts by weight of n-pentane as a foaming agent, and a scale-like aggregate of zinc stearate formed by the metathesis method shown in FIG. 2.0 g of the maximum length (9.4 μm) was placed in a super mixer and stirred for 2 minutes to coat the surface. Thereafter, 0.05 g of cured beef tallow acid amide, 0.05 g of medium chain saturated fatty acid triglyceride, and 0.4 g of polyethylene glycol are put into a super mixer, and the surface of the expandable polystyrene resin particles is coated with aggregates by stirring for 5 minutes. Coated particles were obtained.
[0023]
The coated particles were put into a batch type pre-foaming machine and heated uniformly with water vapor to be foamed to a bulk density of 0.1 g / ml to obtain pre-foamed particles. The obtained pre-expanded particles were aged and dried in the atmosphere for 6 hours.
Next, the pre-expanded particles were filled into a cup-forming mold having an internal volume of 450 cc and a wall thickness of 2 mm, heated with 0.2 MPa (gauge pressure) of water vapor for 6 seconds, and cooled to obtain a cup.
The exuded state of the yellow pigment in the curry powder and the exuded state of the surfactant aqueous solution on the outer wall of the obtained cup were evaluated (evaluation method is described below). The results are shown in Table 1.
[0024]
Example 2
A cup was obtained in the same manner as in Example 1 except that 4.0 g of the aggregate was used. The obtained cup was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0025]
Example 3
Instead of 2.0 g of flaky zinc stearate aggregates (average maximum length 9.4 μm), 5.0 g of flaky calcium stearate aggregates (average maximum length 11.0 μm) formed by the metathesis method was used. A cup was obtained in the same manner as in Example 1 except that. The obtained cup was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0026]
Example 4
A cup was obtained in the same manner as in Example 1 except that 5.0 g of the aggregate was used and pre-expanded so that the bulk density of the pre-expanded particles was 0.033 g / ml. The obtained cup was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0027]
Example 5
1. Amorphous calcium stearate aggregates (average maximum length 3.5 μm) formed by the metathesis method shown in FIG. 2 instead of 2.0 g of flaky zinc stearate aggregates (average maximum length 9.4 μm) A cup was obtained in the same manner as in Example 1 except that 0 g was used. The obtained cup was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0028]
Comparative Example 1
Example except that 2.0 g of crushed zinc stearate (average maximum length 20 μm) shown in FIG. 3 was used instead of 2.0 g of scale-like zinc stearate aggregate (average maximum length 9.4 μm) A cup was obtained in the same manner as in 1. The obtained cup was evaluated in the same manner as in Example 1. The results are shown in Table 1.
Comparative Example 2
A cup was obtained in the same manner as in Example 1 except that 7.0 g of the aggregate was used. The obtained cup was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0029]
Comparative Example 3
A cup was obtained in the same manner as in Example 1 except that 0.05 g of the aggregate was used. The obtained cup was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0030]
Comparative Example 4
Except for using 2.0 g of flaky zinc stearate aggregate (average maximum length 9.4 μm) instead of 2.0 g of flaky zinc stearate aggregate (average maximum length 45.0 μm) A cup was obtained in the same manner as in Example 1. The obtained cup was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0031]
[Table 1]

[0032]
In Table 1, * 1 to 4 mean the following matters.
* 1 Curry powder was put into a cup until the 8th minute, and after wrapping the cup, it was placed in an oven at 60 ° C., and the time until the yellow pigment of curry powder oozed out on the outer wall of the cup was measured and evaluated. The evaluation criteria are shown in Table 2.
[0033]
[Table 2]

[0034]
* 2 Put a surfactant aqueous solution (Emulgen 810 (manufactured by Kao Corporation) 0.1 wt% and Eriochrome Black T 0.005 wt%) in a cup-shaped product up to the 8th minute. The time until the aqueous surfactant solution exudes to the outer wall of the cup was measured and evaluated in an atmosphere of a temperature of 23 ° C. and a humidity of 50%. Table 3 shows the evaluation criteria.
[0035]
[Table 3]

[0036]
* 3 The cup was crushed and broken by applying pressure from the outer surface of the cup and the outer surface on the opposite side, and the rate at which the foamed particles were broken on the broken surface was measured and evaluated. Table 4 shows the evaluation criteria.
[0037]
[Table 4]

[0038]
* 4 The average maximum length was measured using a multi-image analyzer (Beckman Coulter, Inc.). The multi-image analyzer is a device that irradiates light rays with a strobe behind the aperture tube when the aggregate passes through the aperture tube, and takes a projected image of each aggregate with a CCD camera.
[0039]
In the measurement of the average maximum length of the aggregates by the multi-image analyzer in the present invention, an aperture tube having an aperture diameter of 100 μm was used, and a lens having a CCD camera measurement magnification of 40 times was used. In addition, the size of one pixel in the image processing is 0.219 μm, the setting value of the frame size that is the photographing range is 314, the setting value of the binarization level is 200, and the setting value of noise cut is 0.5. The average maximum length was calculated by measuring the maximum value of individual particle diameters from 1000 photographed aggregate images and averaging the measurement results. Note that Isoton II-PC (manufactured by Beckman Coulter, Inc.) was used as the electrolytic solution required for this measurement. Table 5 shows measurement setting values of the multi-image analyzer in the present invention.
[0040]
[Table 5]

[0041]
From Table 1, the foamable thermoplastic resin particles capable of producing a foamed molded article having excellent fusion property and preventing exudation of the contents by making the use ratio and average maximum length of the aggregates within the range of the present invention. Can be provided [0042]
【The invention's effect】
According to the expandable thermoplastic resin particles coated with the aggregates of fatty acid metal salt particles of the present invention, a molded product in which the contents are prevented from bleeding can be produced.
[Brief description of the drawings]
1 is an electron micrograph of an aggregate used in Example 1. FIG.
2 is an electron micrograph of the aggregate used in Example 5. FIG.
3 is an electron micrograph of the aggregate used in Comparative Example 1. FIG.

Claims (4)

Coated particles in which at least a part of the surface of the foamable thermoplastic resin particles is coated with an aggregate of a plurality of metal salt particles of fatty acid selected from stearic acid, oleic acid or palmitic acid, and the aggregate is foamable 0.1 to 0.6 parts by weight are used with respect to 100 parts by weight of the thermoplastic resin particles, and the average particle diameter of the expandable thermoplastic resin particles and the average maximum length of the aggregate are 0.2 to 2.0 mm and Coated expandable thermoplastic resin particles, characterized in that they are 0.5-30 μm. The particles according to claim 1, wherein the fatty acid metal salt particles are scaly particles. The particles according to claim 1 or 2, wherein the aggregate is obtained by a metathesis method. A foam-molded product obtained by foam-molding the coated foamable thermoplastic resin particles according to any one of claims 1 to 3.

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