JPH0313973B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composite film suitable for painting the surface of polyethylene-styrene copolymer foam, and a resin foam decorated using decorative materials such as blanks and labels printed on the surface of this composite film. The present invention provides a method for manufacturing a body. 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, the use of cardboard boxes increases the cost of packaging materials, so cardboard boxes are not used. Alternatively, there is a desire for a packaging material that can be used in pieces, rather than in the form of a box. 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 melt (Japanese Patent Publication No. 28-5036). No. 38-226119, No. 40-
(See Publications No. 12988, No. 46-9959, 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 printed on the surface of synthetic paper made of a stretched film of a resin composition containing high-impact polystyrene and an inorganic filler such as calcium carbonate, and fixed this as a blank in a mold. 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. Additionally, when the synthetic paper was thick, such as 60 microns or 150 microns, a phenomenon was observed where the blank curled and peeled off 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. The present inventors further investigated various decorative films and foamed polystyrene in order to solve the problem of poor thermal welding of these synthetic papers that can be printed with multicolor offset printing of minute letters and designs.・Multi-layered films made of polyethylene copolymer foam are used for gravure printing, in which a polyethylene film with a wall thickness of 1 to 30 microns is integrally bonded to the back side of these high-melting point resin synthetic papers for labels. Flexographic printing and offset printing are also possible, and even when used as a decorative film (including labels and blanks) for expanded styrene/polyethylene copolymer, that is, a decorative sheet, the print will not be blurred, and The inventors have discovered that it is possible to obtain painted molded products of expanded styrene/polyethylene copolymer with strong fusion bonding, and have arrived at the present invention. That is, in the present invention, the inorganic fine powder is contained in an amount of 8 to 65% by weight.
At least two layers: a paper-like layer consisting of a thermoplastic resin film containing a melting point of 145°C or higher, and a back layer consisting of a polyethylene film with a thickness of 1 to 30 microns forming the surface opposite to the paper-like layer. A decorative sheet such as a blank or label printed on the paper-like layer side of the structural 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 polyethylene-styrene copolymer beads obtained by pre-foaming resin particles obtained by the polymerization method described below, steam is introduced into the mold cavity to form these beads. A decorated polyethylene product characterized by fusing beads together to form a foam and adhering the formed foam to a decorative sheet.
A method of manufacturing a styrene copolymer foam is provided. Polymerization method: 100 parts by weight of polyethylene resin particles, 10 parts by weight of styrene
In a method of polymerizing styrene by heating an aqueous suspension containing ~400 parts by weight and a radical polymerization initiator of 0.01 to 1 part by weight per 100 parts by weight of styrene, an expanding agent is supplied to the suspension during polymerization of styrene. Alternatively, after polymerization of styrene, an expanding agent is supplied to an aqueous suspension in which polyethylene/styrene copolymer particles are dispersed to produce expandable polyethylene/styrene copolymer particles. 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 paper-like layer made of a crystalline thermoplastic resin film, with a wall thickness of 1 to 30 microns (μ), preferably 5 to 20μ, and a density of 0.92 to 20 μm.
The wall thickness is 0.96g/cc polyethylene as the back layer.
It is a composite film with a two-layer laminated structure of 30 to 300μ, preferably 35 to 100μ. The film of this paper-like layer is preferably a stretched film having orientation. 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 a sheet, cooled to 40-80℃, reheated to 134-164℃, preferably 145-160℃, and heated to 3.5-3.5℃ in longitudinal and transverse directions.
Biaxially stretched 10 times, simultaneously or sequentially, and if necessary, the resulting stretched film was stretched at 165 to 168°C for 5
Obtained by annealing for ~60 seconds. 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 polyethylene 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 an ethylene/acrylic acid copolymer (K, Na, Zn), maleic anhydride grafted polyethylene or polypropylene is blended with polypropylene, (C). Each piece of polyethylene 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. The sheet is produced by simultaneously or sequentially biaxially stretching the sheet at a temperature lower than the melting point of the polypropylene (A). Further, after longitudinally stretching a coextruded sheet of polyethylene of composition (C) of composition (B) described above, a sheet of polypropylene composition of (A) is placed on the surface side of the sheet of (B) of this coextrusion sheet. It can also be obtained by laminating and then laterally stretching. Furthermore, a sheet of the polypropylene composition of (A) and (C) are placed on each side of the sheet of (B) which has been longitudinally stretched in advance.
It can also be obtained by melt-laminating polyethylene sheets and then laterally stretching them. 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 polyethylene film (C). is also manufactured.
It can also be produced by melt-extruding polyethylene (C) on the back side of the synthetic paper "YUPO FPG" and laminating it. 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. Among these multilayer films, from the viewpoint of offset printability, it is preferable that the paper-like layer of polypropylene containing 8 to 65% by weight of inorganic fine powder is oriented only in one axis direction. By stretching, cracks are generated on the surface 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. . Further, the number of layers is preferably three or more including a biaxially oriented polypropylene film layer as an intermediate layer. This biaxially oriented polypropylene film gives stiffness to the label and facilitates paper feeding during sheet 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 polyethylene film on the back layer must be at least 1 μm in order for the polyethylene film to be melted by the heat of steam during the molding of the styrene-polyethylene copolymer foam, and for the molded product and composite film to firmly adhere to each other. Moreover, if it exceeds 30 μm, the composite film will curl, making offset printing difficult or making it difficult to fix the composite film to a mold, which is not preferable. Above, polypropylene was used as an example of the thermoplastic resin of the composite film, but the resin may be any crystalline thermoplastic resin having a melting point higher than polystyrene, such as propylene homopolymer (melting point 163 to 170°C). , propylene-ethylene copolymer (melting point 145-160℃), propylene-ethylene copolymer (melting point 145-160℃),
Propylene copolymers such as butene-1 copolymer (melting point 145-160℃), propylene-butene-1 copolymer (melting point 145-158℃), polyethylene terephthalate (melting point 236-248℃), nylon 6 (melting point 246~
252℃) can also be used. As polyethylene, the density is 0.910 to 0.965
Although polyethylene having a density of 0.910 to 0.935 g/cm ³ can be used, preferably low to medium density polyethylene having a density of 0.910 to 0.935 g/cm ³ may be used in view of adhesion to the foam. Less than 50% by weight of this polyethylene, preferably 3 to 30%
Weight% is polystyrene, ethylene/vinyl acetate copolymer, ethylene/(meth)acrylic acid copolymer or its metal (Na, Zn) salt, ethylene/vinyl acetate copolymer, ethylene/(meth)acrylic acid copolymer or its metal (Na, Zn) salt,
(Meth) acrylic acid lower alkyl (C ₁ -C ₈ ) ester copolymers and the like can also be used instead. 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. The composite film of the present invention 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 molded products of expanded styrene/polyethylene copolymer. 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. The pre-expanded styrene/polyethylene copolymer beads are then filled into the cavity of the mold, and then heated with steam at 100-130°C, which causes the pre-expanded beads to fuse with each other and this fusion. The molded styrene-polyethylene copolymer foam product is bonded to a printed composite film, which is a decorative sheet. After cooling, the mold is opened and the product with the decorative sheet attached to the surface of the styrene-polyethylene copolymer foam is taken out. This type of foam molding is similar to conventional polystyrene molding (Tokuko Showa), except that a specially structured composite film is installed in the mold, and styrene-polyethylene copolymer beads are used instead of pre-expanded polystyrene beads. No. 45-33316, British Patent No. 1392467
No. 1409285, USP No. 3461088). Also, except that the composite film is a stretched film with a special structure and the pre-foamed beads are styrene-polyethylene copolymer beads,
Conventional method for obtaining expanded polystyrene molded products encapsulated with non-oriented polyethylene film
No. 94375, No. 54-46269). Expandable styrene/polyethylene copolymer particles that provide unique pre-expanded styrene/polyethylene copolymer beads are disclosed in JP-A-48-101457.
No. 49-97884, No. 49-85187, No. 50-50490,
As shown in Publications No. 52-32972, No. 53-23358, etc., 100 parts by weight of polyethylene particles are dispersed in water using a suspending agent, and styrene with a polymerization initiator dissolved in the aqueous dispersion is stirred. The resulting styrene/polyethylene copolymer particles are impregnated with a blowing agent such as butane or heptane, and then the styrene/polyethylene copolymer particles are foamed with water. Obtained by separating. The above-mentioned polyethylenes include ethylene polymers, ethylene copolymers of ethylene and α-olefins such as propylene, butene-1, hexane, etc., and copolymers of ethylene and vinyl acetate with a density of 0.91 to
0.935g/cm ³ is available. The blowing agent can also be introduced into the suspension system before the polymerization of styrene. The amount of foaming agent used is such that the resulting expandable copolymer particles are foamed 4 to 60 times, that is, the amount contained in the resulting copolymer particles is 4 to 10% by weight. These expandable copolymer particles are sold by Yuka Verdice Co., Ltd. under the trade name "Elenpol" and by Sekisui Chemical Co., Ltd. under the trade name "Piocelan." The expandable copolymer particles are heated to 90 DEG -120 DEG C. with hot water or steam, and are pre-expanded 4-60 times to obtain pre-expanded beads with a particle size of 1.8-6 mm. The foam product obtained using these pre-expanded polyethylene/styrene copolymer beads has a shape recovery property after being subjected to a compressive load that is similar to that of a foam product obtained using pre-expanded polystyrene particles. better than. When the composite film of the present invention is used as a decorative sheet for painting polyethylene-styrene copolymer foam, heat shrinkage and printing become unclear despite the use of a stretched film. A decorative sheet can be firmly attached to a polyethylene/styrene copolymer foam molded product without problems such as curling. Therefore, since this printed composite film (decorative sheet) protects the foam, it is possible to omit part or all of the cardboard box or decorative box used as the exterior material. 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). Mitsubishi Yuka Co., Ltd.'s polypropylene "Mitsubishi Noblen MA-6" (trade name, melting point = 164℃) 87 parts, Mitsubishi Yuka Co., Ltd.'s high-density polyethylene "Yukalon Hard"
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). Polypropylene “Mitsubishi Noblen MA-3” manufactured by Mitsubishi Yuka Co., Ltd. (trade name, melting point = 163℃) 57
2 parts of heavy calcium carbonate and 43 parts of heavy calcium carbonate.
Melt and knead using one extruder and then pass through two dies.
The melt of (A) was 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. After applying corona discharge treatment to this one side,
A mixture of isocyanate adhesive "AD-980A, 100 parts and AD-980B, 12 parts" manufactured by Toyo Morton Co., Ltd. was applied to a thickness of 15μ, and after semi-drying, (C) Density 0.910g/cm The corona discharge-treated low-density polyethylene film of No. ³ was dry laminated and cooled to obtain a composite film with a total thickness of 137μ. Examples 2 to 4 The same procedure as in Example 1 above was carried out except that the thickness of the polyethylene film was changed so that a laminated product of a composite stretched film and a polyethylene film in which the thickness of the polyethylene back layer of (C) was as shown in Table 1 was obtained. Laminated product of composite stretched film and polyethylene film [] ~
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 after being treated for seconds, immediately placed in methanol (30 seconds), and dried.
I got it. On the back side of this synthetic paper, there is a thickness of 20μ on the back side.
dry laminated polystyrene film,
A bonded product [ ] was obtained. 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 polyethylene film with a wall thickness of 20 μm was dry laminated. Production Examples 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 with a knife cutter at right angles to the film flow direction. Vertical 93.9
The multi-stretched film was cut into pieces of 63.6 cm wide and 63.6 cm wide, and the cut double-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 Multicolor offset printing was performed on the surface of polystyrene synthetic paper [ ] or clay coat paper [ ] to obtain a decorated film [ ] or decorated paper [ ]. Example of manufacturing pre-foamed polyethylene/styrene copolymer beads 1 In a pressure-resistant stirring vessel, a mixture of the following composition was heated at 90°C for 4 hours with stirring to soften the polystyrene, and then the 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, MI2.0 (average particle (diameter: 0.3 mm) 40 Next, the styrene monomer was polymerized by heating at 120°C for 10 hours. 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. The particles were divided into small particles with a diameter of 0.8 to 1.3 mm and pre-foamed in a stream of steam to an apparent weight of 20 g/min, and then left to dry at room temperature for 5 hours. Example 2 Polymerization and pre-foaming were carried out in the same manner as in Example 1 except that the amount of low-density polyethylene powder used was changed to 100 parts by weight to obtain pre-foamed beads with an apparent density of 20 g/w. Examples 1 to 4, Comparative Examples 1 to 2 Cut out the four corners of each painted film or paper, make creases, and electrostatically fix it on the entire surface of the cavity of the female mold so that the printed surface is in contact with the mold, Next, after fitting with a male mold having many steam holes,
Inside this mold cavity (length 200cm, width 150cm, depth 5cm),
The pre-foamed polyethylene-styrene copolymer beads obtained in Example 2 above were filled, and then 0.05Kg/cm ³ G
Steam 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 polyethylene-styrene copolymer foam molded product was taken out of 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 5 A painted foamed resin product was obtained in the same manner as in Example 1, except that the pre-foamed beads obtained in Example 1 were used as the pre-foamed polyethylene/styrene copolymer beads.

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

Claims (1)

[Scope of Claims] 1. Melting point containing 8 to 65% by weight of inorganic fine powder
A composite film having at least two layers, with a paper-like layer made of a thermoplastic resin film heated to 145°C or higher, and a polyethylene film with a thickness of 1 to 30 microns forming the back surface on the opposite side of the paper-like layer. A decorative sheet such as a blank or a label printed on the paper layer side is fixed to the inside of at least one of the male and female molds so that the paper layer side of the decorative material is in contact with the mold, and then the paper layer side of the decorative material is in contact with the mold. After filling the mold cavity of the mold with polyethylene/styrene copolymer beads pre-foamed with expandable resin particles obtained by the following polymerization method, steam is introduced into the mold cavity to fuse these beads together. 1. A method for producing a decorated resin foam using a composite film, which comprises forming a foam using a composite film and adhering the formed foam to a decorative sheet. Polymerization method: 100 parts by weight of polyethylene resin particles, 10 parts by weight of styrene
In a method of polymerizing styrene by heating an aqueous suspension containing ~400 parts by weight and a radical polymerization initiator of 0.01 to 1 part by weight per 100 parts by weight of styrene, an expanding agent is supplied to the suspension during polymerization of styrene. Alternatively, after polymerization of styrene, an expanding agent is supplied to an aqueous suspension in which polyethylene/styrene copolymer particles are dispersed to produce expandable polyethylene/styrene copolymer particles. 2. A method for producing a resin foam decorated with a composite film according to claim 1, wherein the thermoplastic resin of the composite film material 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 polyethylene film. A method for producing a resin foam decorated with a composite film according to claim 2, characterized in that: