JPH0313971B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for producing a decorated polystyrene foam using a decorative material such as a blank or label printed on the surface of a composite film. Foamed polystyrene molded products can be used in electric washing machines,
It is used as a cushioning material and packaging material for home appliances such as televisions and refrigerators, and as coffee and tea cups on bullet trains and airplanes. When used as the former cushioning material, a cardboard box is also used to package the cushioning material, and the product name, manufacturer's name, vendor's name, etc. are printed on the cardboard box. However, since the use of cardboard boxes increases the cost of the packaging material, there is a desire for packaging materials that do not use cardboard boxes, or even if they are used, they are not box-shaped but are used piecemeal. In addition, the latter cup-shaped containers are occasionally found to have adhesive labels attached to them, but the appearance of these containers is poor. Furthermore, high-quality instant katsupu noodles are on sale, but in order to differentiate them from conventional, inexpensive, popular katsupu noodles, more advanced decoration of expanded polystyrene containers is being considered. This is the reality. It has been known for a long time to decorate plastic molded articles with decorative sheets such as labels and blanks. For example, a thermoplastic resin film made of polyvinyl chloride, polypropylene, polyethylene, etc. printed with letters or designs is cut out, fixed in a mold by electrostatic adhesion or reduced pressure, and then a thermoplastic resin made of the same material as the film is melted. A method has been proposed in which a thermoplastic synthetic resin molded product with a label pasted or painted is produced by bringing an object into contact with a film under pressure or reduced pressure, and then cooling the molten material (Japanese Patent Publication No. 5036/1989). , No. 38-26119, No. 40-12988
No. 46-9959, Publication No. 48-12865, etc.). Injection molded products, blow molded products, vacuum molded products, etc. using these printed thermoplastic resin films as labels are attached at the time of molding, so the adhesion between the label and the molded product is strong. In addition, when the material of the label is made of a thermoplastic resin film with high water resistance, it is particularly useful as a liquid hollow container for detergents, shampoos, antifreeze, medicine bottles, and the like. By applying these painting methods to molded products made of polystyrene foam, the present inventors have created a high-impact product that is made of the same material as polystyrene foam for the purpose of eliminating cardboard boxes or decorating cup-shaped containers. Polystyrene synthetic paper (Special Publication 1977-
4320, Japanese Patent Publication No. 49-43115) and the surface of a synthetic paper made of a stretched film of a resin composition made of high-impact polystyrene mixed with an inorganic filler such as calcium carbonate, and fixed in a mold as a blank. Then, pre-expanded beads were then filled into the mold and heated and molded at 110-120°C to produce a foamed polystyrene molded product with these printed synthetic papers laminated on the surface.The synthetic paper melted during molding. However, it was found that the printing was slightly blurred. Also. When the synthetic paper had a thick wall thickness of 60 microns or 150 microns, a phenomenon was observed in which the blank curled and peeled from the foam product while the painted foam product was being stored. The present inventors have determined that this cause is due to the fact that the resin material of the decorative film and the molded product are the same polystyrene, and the molding temperature.
Next, a synthetic paper (made of a stretched film made by blending inorganic fine powder with a crystalline thermoplastic resin such as polypropylene, polyethylene terephthalate, or polyamide, which has a melting point higher than the molding temperature of polystyrene (110 to 120°C)) was used as a synthetic paper. Special Public Service 1977
40794, USP 3741841, USP 4318950, JP 56-118437, JP 56-141339), it was found that the fusion between the foamed polystyrene product and the synthetic paper was insufficient. In order to solve the problem of poor thermal welding of these synthetic papers on which delicate characters and designs can be printed in multicolor offset, the present inventors further investigated various decorative films and discovered that these synthetic papers made of high melting point resin The multi-layered film, which has a polystyrene film with a wall thickness of 1 to 30 microns bonded to the back side, can be used for gravure printing, flexographic printing, and offset printing. It has been discovered that even when used as a decorative sheet (including labels and blanks), it is possible to obtain a painted foamed polystyrene molded product that has no blurred print and has strong fusion bonding, and has developed the present invention. Reached. That is, in the present invention, the inorganic fine powder is contained in an amount of 8 to 65% by weight.
A paper-like layer is a uniaxially stretched thermoplastic resin film containing a melting point of 145°C or higher, and a polystyrene film with a wall thickness of 1 to 30 microns constitutes the surface opposite to the paper-like layer as a back layer. A blank or decorative sheet of a label printed on the paper-like layer side of a two-layer composite film is placed inside at least one of the molds consisting of a male mold and a female mold so that the paper-like layer side of the decorative material is in contact with the mold. Then, after filling the mold cavity of the mold with pre-expanded polystyrene beads, steam is introduced into the mold cavity to fuse these beads together to form a foam. A method of making a decorated polystyrene foam is provided, which comprises adhering the formed foam. In the practice of the present invention, the simplest structure of the composite film for multilayer labels and blanks before offset printing contains 8 to 65% by weight of inorganic filler, preferably 20 to 55% by weight. A stretched film of crystalline thermoplastic resin is used as a paper-like layer, and the thickness is 1~
Density 0.93 of 30 microns (μ), preferably 5-20μ
It is a composite film having a two-layer laminated structure with a thickness of 30 to 300 μm, preferably 35 to 100 μm, with a back layer of polystyrene of ~1.07 g/cc. Such a composite film is made of, for example, polypropylene containing an inorganic filler and a metal salt (Na, K,
Zn), maleic anhydride-grafted ethylene/vinyl acetate copolymer, and other adhesive resins are melted and kneaded in separate extruders, then fed into the same die, and laminated in the die. Coextruded into sheets, cooled to 40-80°C, then reheated to 134-164°C, preferably 145-160°C, 3.5% in longitudinal and transverse directions.
~10 times each, simultaneously or sequentially biaxially stretched,
It can be obtained by annealing the obtained stretched film at 165 to 168° C. for 5 to 60 seconds, if necessary. In addition, a polypropylene film containing an inorganic filler was preliminarily coated using the difference in circumferential speed of the roll group.
A film obtained by longitudinally stretching 3.5 to 7 times at ~155°C is subjected to corona discharge treatment, an isocyanate adhesive is applied, and after drying with hot air, the polystyrene film is dry laminated. It will be done. In the method for manufacturing these multilayer films as well as in the method for manufacturing a composite film having three or more layers described below, the corona discharge treatment and annealing treatment are performed as necessary after stretching. When the composite film has three or more layers, it can be manufactured in various ways. For example (A). 8 inorganic fine powders
Polypropylene containing ~65% by weight, (B). A composition in which 0.5 to 50% by weight of an adhesive resin such as a metal salt of ethylene/acrylic acid copolymer (K, Na, Zn), polyethylene, maleic anhydride grafted polyethylene or polypropylene is blended with polypropylene, (C). Each piece of polystyrene is melted and kneaded using separate extruders, the melt is transferred to one die, the film made of (B) is laminated in the die as an intermediate layer, and the laminated layer is coextruded. It is produced by stretching a sheet at a temperature below the melting point of (A) polypropylene but above the softening point of polystyrene. In addition, after longitudinally stretching the above-mentioned composition (B) and polystyrene coextrusion sheet (C) in advance,
This coextruded sheet is obtained by laminating a sheet of the polypropylene composition (A) on the surface side of the sheet (B), and then laterally stretching the sheet. Furthermore, a sheet of the polypropylene composition of (A) and a sheet of polystyrene of (C) are melt-laminated on each side of the sheet of (B), which has been longitudinally stretched in advance, and then laterally stretched. You can also get Furthermore, a synthetic paper (such as By applying isocyanate adhesive to the back side of the paper (sold under the trade name ``YUPO FPG'' by Oji Yuka Synthetic Paper Co., Ltd.), and then dry laminating the polystyrene film (C). is also manufactured. In these embodiments, the film of the base material layer (B) contains 55% by weight or less of inorganic fine powder, preferably 15 to 15% by weight.
It may be contained in a proportion of 50% by weight. In these multilayer films, a paper-like layer of polypropylene containing 8 to 65% by weight of inorganic fine powder is oriented only in one axis direction from the viewpoint of offset printability. By stretching, cracks are generated on the surface of the paper-like layer with the inorganic fine powder as the nucleus, and the adhesion and drying properties of the printing ink are improved. Biaxially stretched orientation increases the chances of inorganic fine powder falling off, and deep cracks formed by uniaxial stretching may disappear with further stretching, resulting in offset printability inferior to uniaxially oriented films. . In addition, the number of layers is determined by using biaxially oriented adhesive resin in the middle layer.
It is preferable to have three or more layers including a polypropylene film layer containing 0.5 to 50% by weight. This 2
The axially oriented polypropylene film provides stiffness to the label and facilitates paper feeding during offset printing. The wall thickness of the composite film is 30~300μ, preferably
45~100μ, and the thickness of the back layer is 1~100μ.
30μ, preferably 5-20μ. If the thickness of the composite film is thinner than 30μ, paper feeding and offset printing will be difficult. Further, the composite film may shrink during molding. If the wall thickness exceeds 300μ, it is economically disadvantageous. The thickness of the polystyrene film on the back layer is 1μ because the polystyrene film is melted by the heat of the steam during molding of the polystyrene foam, and the molded product and the composite film are firmly bonded.
The above is necessary. Further, if it exceeds 20μ, the composite film will curl, making offset printing difficult and making it difficult to fix the composite film to a mold, which is preferable. Above, polypropylene was used as an example of the thermoplastic resin for the paper-like layer of the composite film, but the resin may be any crystalline thermoplastic resin with a melting point higher than that of polystyrene, and propylene homopolymer (melting point 163-170℃), propylene-ethylene copolymer (melting point 145-160℃), propylene-ethylene-butene-1 copolymer (melting point 145-160℃)
160℃), propylene-butene-1 copolymer (melting point
Propylene copolymers such as (145-158°C), polyethylene terephthalate (melting point 236-248°C), nylon 6 (melting point 246-252°C), etc. can also be used. Also, as polystyrene, the density is 1.03 to 1.07.
g/cm ³ of styrene homopolymer, styrene/α-methylstyrene copolymer, styrene/methyl methacrylate copolymer, styrene/acrylonitrile copolymer, and up to 50% by weight of these resins, preferably 8 to 45% by weight % of styrene-butadiene copolymer rubber, low-density polyethylene, isoprene rubber, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer or its metal (Na, Zn) salt, ethylene・
(Meth) acrylic acid lower alkyl (C ₁ -C ₈ ) ester copolymer or the like can be used instead.
Polystyrene containing 10 to 50% by weight of polyethylene or ethylene/vinyl acetate copolymer is sold by Mitsubishi Yuka Co., Ltd. under the trade name "Diemilon". In this method, a styrene monomer in which a polymerization initiator such as benzoyl peroxide is dissolved is supplied to a suspension of resin particles such as polyethylene dispersed in water, and suspension polymerization is carried out at 80 to 130°C for 6 to 18 hours. Manufactured by
No. 50389, No. 52-50390, No. 49-85187, No. 49
−97884). As the inorganic fine powder, heavy calcium carbonate, clay, titanium oxide, diatomaceous earth, kaolin, talc, etc., having a particle size of 15 μm or less, preferably 0.1 to 3 μm, are used. In addition, as described above, adhesive resin is used for the biaxially stretched polypropylene film as the base layer resin.
A biaxially oriented film of polypropylene containing 0.5 to 50% by weight is used. This material may contain inorganic fine powder, in which case fine voids are also formed in the base material layer, making the composite film even lighter. This composite film is printed by offset printing, gravure printing, etc. on the paper-like layer side, and is used as a decorative sheet for a decorative film for foamed polystyrene type products. This decorative film is cut, cut out, and bent as necessary (especially when used as a blank), and then placed in a mold using conventional electrostatic adhesion methods, vacuum methods, etc. so that the printed surface is in contact with the mold. After filling the pre-expanded polystyrene particles into the cavity of the mold, the pre-expanded polystyrene particles are heated with steam at 100 to 130°C to fuse the pre-expanded polystyrene particles together and create a mold by this fusion. Bonding of the polystyrene foam product and the printed composite film, which is a decorative sheet, takes place. After cooling, the mold is opened and the product with the decorative sheet attached to the surface of the polystyrene foam is taken out. This mold foam molding is conventional polystyrene mold molding (Japanese Patent Publication No. 45-33316, British Patent No. 1392467, British Patent No. 1409285, USP 3461088), except that a composite film with a special structure is installed in the mold. ). In addition, the conventional method for obtaining a foamed polystyrene molded product encapsulated with a non-oriented polyethylene film (Japanese Unexamined Patent Application Publication No. 53-94375,
54-46269). The pre-expanded particles contain an expanding agent such as butane, pentane, heptane, dichlorodifluoroethane, etc.
Expandable polystyrene particles containing 10% by weight and having a particle size of 0.65 to 2 mm are pre-foamed with steam, and the bulk density is 0.015 g/~0.1 g/, and the particle size is 1~2 mm.
8mm can be used. The material of the expandable polystyrene particles is not limited to a styrene homopolymer, but may also be a styrene/methyl methacrylate copolymer or a styrene/α-methylstyrene copolymer. In addition, less than 50% by weight,
Preferably, 8 to 50% by weight may be replaced by polyethylene or ethylene/vinyl acetate copolymer. The latter was prepared in the same manner as the above-mentioned "Diemilon" except that it contained a swelling agent (JP-A-48-101457, JP-A No. 50-127964, JP-A No. 50-50).
No. 127965, No. 51-37980, No. 53-23358). Such products are sold by Yuka Verdice Co., Ltd. under the trade name "Ellenpol" and by Sekisui Plastics Co., Ltd. under the trade name "Piocelan." When using pre-expanded particles containing polyethylene, etc., the shape recovery properties of the resulting foam product after receiving a compressive load are lower than those obtained using pre-expanded particles that do not contain polyethylene, etc. Better than that. When the composite film is used as a decorative sheet for painting polystyrene foam, heat shrinkage occurs and printing becomes unclear despite the use of a stretched film. A decorative sheet can be firmly attached to a polystyrene foam molding without problems such as curling. Therefore, this printed composite film (decorative sheet) protects the foam, making it possible to omit part or all of the cardboard box or decorative box used as the exterior. Furthermore, in the case of cup-shaped containers, delicate multicolor offset printing gives the product a sense of luxury, which has the advantage of motivating consumers to purchase it. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example of manufacturing synthetic paper 1 (B) 87 parts of polypropylene "Mitsubishi Noblen MA-6" (product name, melting point = 164°C) manufactured by Mitsubishi Yuka Co., Ltd., high-density polyethylene "Yukalon Hard" manufactured by Mitsubishi Yuka Co., Ltd.
EY-40” (product name, melting point = 130℃, density 0.950g/
cc) A composition consisting of 10 parts and 8 parts of heavy calcium carbonate was melt-kneaded using an extruder, extruded into a sheet from a die at a temperature of 250°C, and the sheet was cooled to a temperature of approximately 50°C. did. Next, after heating this sheet to about 153℃,
A uniaxially stretched film was obtained by stretching 4 times in the longitudinal direction using the difference in peripheral speed between the roll groups. Separately, (A) a mixture consisting of 57 parts of polypropylene "Mitsubishi Noblen MA-3" (trade name, melting point = 163°C) manufactured by Mitsubishi Yuka Co., Ltd. and 43 parts of heavy calcium carbonate was prepared using two extruders. Melt and knead and pass through two dies (A)
The melts were extruded into sheets at a temperature of 250° C. and laminated on the front and back surfaces of the uniaxially stretched film to obtain a three-layer sheet. After cooling this three-layer sheet to 60℃, approx.
The film was reheated to a temperature of 163°C, stretched 8 times in the transverse direction using a tenter, and then passed through an oven set at 165°C to set the heat.
℃, and the edges were slit to give a biaxially stretched intermediate layer film with a thickness of 62 microns, and a surface layer and a back layer uniaxially stretched film made of the composition of (A) each with a thickness of 30 μm. Micron synthetic paper was obtained. On one side of this, add 100 parts of Toyo Morton Co., Ltd. isocyanate adhesive “AD-980A” and AD-980B.
After applying 12 parts of the mixed solution to a thickness of 15μ and semi-drying, (C) a corona-discharged film of styrene homopolymer with a density of 1.04 g/cm ³ was dry laminated, cooled, and the entire film was dried. A composite film with a wall thickness of 137 μm was obtained.Examples 2 to 4 Polystyrene was mixed so as to obtain a bonded product of a composite stretched film and a polystyrene film in which the thickness of the polystyrene back layer of (C) was as shown in Table 1. A laminated product of composite stretched film and polystyrene film was produced in the same manner as in Example 1 above except that the film thickness was changed.
I got []. Example 5 HI/PS (high impact polystyrene) unstretched film (manufactured by Mitsubishi Monsanto Chemical Co., Ltd. Styrene content approx. 92
%, butadiene content approximately 8%) original fabric (thickness 350μ),
Stretching temperature 120℃, stretching speed 110cm/sec, stretching ratio 4~
Sequential biaxial stretching at 14 times, then 10
Polystyrene synthetic paper with a wall thickness of 94 μ, whiteness of 88%, and Beck smoothness of 210 seconds.
I got it. Example 6 Instead of the synthetic paper in Example 1, clay coated paper manufactured by Company A with a wall thickness of 80 μm was used, and a polystyrene film with a wall thickness of 20 μm was laminated thereon. Manufacture of painted films or papers (decorative sheets). Examples 1 to 4 The edges of the composite stretched films obtained in Production Examples 1 to 4 were slit, and the composite stretched films were cut lengthwise by 93.9 mm using a knife cutter at right angles to the film flow direction.
The composite stretched film was cut into pieces of 63.6 cm and width 63.6 cm, and the cut composite stretched film was stored in a sheet stocker. After performing multicolor offset printing according to each purpose on the paper-like layer surface of the cut sheet-like synthetic paper, the printed part is trimmed and a painted film is made.
I got it. Examples 5 to 6 A decorated film or paper was obtained by multicolor offset printing on the surface of polystyrene synthetic paper or clay coated paper. Examples 1 to 3, Comparative Examples 1 to 3 Cut out the four corners of each painted film or paper, make creases, and fix the entire cavity of the female mold with static electricity so that the printed surface is in contact with the mold. After fitting with a male mold with many holes,
Inside this mold cavity (length 200cm, width 150cm, depth 5cm),
Expandable polystyrene particles (containing 6.8% by weight of butane) whose surface is coated with hydrogenated tallow oil (0.2% by weight)
The bulk density obtained by pre-foaming with 0.05Kg/cm ² G steam and aging for one day is
Filled with 15 g/pre-expanded particles, then 0.05
Steam of kg/cm ² G was introduced into the mold cavity for 1 minute to fuse the pre-expanded particles together, and then cooled for 3 minutes and the painted polystyrene foam molded article was removed from the mold. The painted products were examined for blurring of the print and the adhesive strength between the painted film or paper and the foam. The results are shown in Table 1. Example 4 A painted foam product was obtained in the same manner as in Example 1, except that expandable polystyrene particles containing low-density polyethylene produced by the following method were used as expandable polystyrene particles. Polymerization method: In a pressure-resistant stirring vessel, a mixture with the following composition is heated at 90°C for 4 hours while stirring to soften the polystyrene, and then add styrene monomer and N.
- Pentane was impregnated into polyethylene. Parts by weight Styrene monomer 100 Water 250 Sodium pyrophosphate 0.1 Polyvinylpyrrolidone 1.0 Dikymil peroxide 0.5 n-pentane 10 Low density polyethylene powder (Yukalon EH30 manufactured by Mitsubishi Yuka Co., Ltd. Density = 0.920, MI 2.0 (average particle size)
0.3mm)) 40 Then, the mixture was heated at 120°C for 10 hours to polymerize the styrene monomer. After cooling the obtained small spheres (particle size 0.85 to 1.3 mm),
It was separated from the aqueous phase, washed with water, and dried. The blowing agent was contained in the particles at 6.5% by weight.

【table】

[Table] * There were unevenness and wrinkles in the painted area.
** The space between the polystyrene film and the clay coated paper peeled off.

Claims (1)

[Scope of Claims] 1. Melting point containing 8 to 65% by weight of inorganic fine powder
It has at least a two-layer structure, with a paper-like layer made of a uniaxially stretched thermoplastic resin film heated at 145°C or higher, and a polystyrene film with a thickness of 1 to 30 microns, which forms the surface opposite to this paper-like layer, as the back layer. A blank or decorative sheet of a label printed on the paper-like layer side of the composite film is fixed to the inside of at least one of the molds consisting of a male mold and a female mold so that the paper-like layer side of the decorative material is in contact with the mold, Next, after filling the cavity of the mold with pre-expanded polystyrene beads, steam is introduced into the cavity to fuse these beads together to form a foam, and the foam formed with the decorative sheet is A method of producing a decorated polystyrene foam characterized by bonding the body. 2. The manufacturing method according to claim 1, wherein the thermoplastic resin is polypropylene. 3. The composite film has a composite structure of three or more layers, with a paper-like layer made of a uniaxially stretched film, and a base layer made of a biaxially stretched polypropylene film between the paper-like layer and the back layer of the polystyrene film. The manufacturing method according to claim 2, characterized in that: