JP4523398B2 - Method for producing a heat insulating foamed paper container - Google Patents

Description

  The present invention relates to a heat insulating foamed paper container having a heat insulating layer made of a foam resin on an outer surface.

  A paper container having a heat insulating layer made of foamed resin on the outer surface of the container has recently been used as a container for beverages and cup noodles. As the container which printed the outer surface of the container, the outer surface of the base paper constituting the container body is directly printed, and the outer surface is coated with foamed resin (Patent Document 1), or the outer surface of the foamed resin Are printed (Patent Documents 2 to 5). If the outer surface of the base paper is directly printed, the printed surface is unclear due to the presence of the foamed resin layer to be coated, and the appearance is inferior. Also, if the outer surface is printed, foaming is not sufficient. In most cases, the surface is uneven.

  As an invention related to the above technology, in Patent Document 2, printing is performed using a specific synthetic resin content (ink) having a specific synthetic resin content on a lower part of a container rim, a specific part such as a character, a figure, or a pattern. Thus, a technique for suppressing foaming of the printed portion is disclosed. Patent Document 3 discloses a technique for partially controlling the thickness of the foamed layer by a printing pattern (variation in the thickness of the printing layer) to form an uneven decorative appearance. In Patent Document 4 and Patent Document 5, printing is performed by using a special ink that synchronizes (does not suppress) the expansion of the resin during foaming of the thermoplastic synthetic resin. A technique for forming a smooth printed surface as compared with the case where there is no (part) is disclosed.

Japanese Patent Laid-Open No. 7-232774 Japanese Patent Laid-Open No. 9-95368 JP-A-10-34690 Japanese Patent Laid-Open No. 11-189279 JP 2001-270571 A

  The present invention solves the above-mentioned problems in the prior art. In a paper container having a heat insulating layer made of a foamed resin on the outer surface, the entire foamed layer is uniform using a conventionally known printing ink and printing method. Another object of the present invention is to provide a method for producing a heat-insulating foamed paper container that can be foamed smoothly and sufficiently and that can form a smooth and clean printed surface having no irregularities on the surface of the foamed resin layer.

  As a result of intensive studies to solve the above problems, the present inventors have been able to obtain the following knowledge. First, the entire surface of the thermoplastic synthetic resin to be foamed is printed on a single color and dried, so that when the synthetic resin is heated and foamed, the entire surface of the printing surface is uniformly distributed due to the presence of the printing layer. Since foaming is suppressed and controlled, foaming does not vary and a smooth foamed surface can be formed. Furthermore, when printing designs such as characters and figures on the printing surface of the single color, after the printing and drying of the single color, the characters are printed, and the ink used for the printing is in a softened state. By heating and foaming, it is possible to form a smooth foamed surface without affecting the foaming of printed portions such as characters, while suppressing and controlling the entire foaming by a single color printing layer. Based on the above findings, the present inventors have completed the present invention.

  That is, the present invention provides a base material in which a high-melting point thermoplastic synthetic resin layer is provided on one side of a base paper, and a low-melting point thermoplastic synthetic resin layer having a printing layer of a single color ink on the other side on the other side. A cylindrical body member having an upper and lower opening is molded with paper so that the printed layer is on the outside, and a bottom member is integrated with the body member to form a container body, and the container body is heated to produce a low-melting thermoplastic synthetic resin. This is a method for manufacturing a heat insulating foamed paper container in which a heat insulating layer is formed on the outer surface of the container by foaming the layer, and the foaming of the outer surface of the container is completely suppressed and controlled by the single color printing layer in the foaming process. By doing so, a smooth foamed outer surface is formed.

  According to the present invention, it is possible to provide a heat insulating foamed paper container in which a foamed resin layer having a uniform, smooth and sufficient thickness is formed on the outer surface of the container using a conventionally known printing ink and printing method. it can.

  Further, the present invention is the method for manufacturing a heat insulating foamed paper container, wherein after the container body is molded, a design such as letters and figures is printed on the outer surface, and then the ink for forming the printed layer is in a softened state. A method for producing a heat insulating foamed paper container, wherein the low-melting thermoplastic synthetic resin layer is foamed by heating.

  According to the present invention, on the outer surface of the single color heat insulating foamed paper container, the design of characters, figures, and the like is further made entirely by the single color printing layer using conventionally known printing ink and printing method. It is possible to form a foamed resin layer having a smooth and clean printing surface with no irregularities on the outer surface of the container without inhibiting the foaming of the printed part without affecting the foaming of the printed part such as characters.

  In addition, when printing the design of characters and patterns on the outer surface of the container, it is possible to print and use the required quantity for each product on the container. There is no waste and manufacturing loss can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail.

  The heat insulating foamed paper container according to the present invention includes a container body member and a bottom plate member. The manufacturing method of the heat insulating foamed paper container in the present invention includes a base paper manufacturing process, a primary printing process, a container body molding process, a secondary printing process, a heating foaming process, and a drying process. .

(1) Base paper manufacturing process A base paper of the present invention is manufactured by laminating a high melting point thermoplastic synthetic resin on one side of a base paper and a low melting point thermoplastic synthetic resin on the other side by a method such as lamination. To do.

  As the base paper and the thermoplastic synthetic resin used in the present invention, conventionally known ones can be used, but they are appropriately adopted in consideration of the strength of the container, the heat insulation by foaming of the synthetic resin layer, and the production suitability.

A base paper having a basis weight of 150 to 350 g / m ² and a moisture content of 5 to 9% is preferable for production.

The thermoplastic synthetic resin having a high melting point is preferably a medium density or high density polyethylene having a density of 0.93 to 0.95 g / cm ³ , a melting point of 130 to 135 ° C., and an MFR (Melt flow rate) of 4 to 8 g / 10 minutes. On the other hand, the low-melting thermoplastic synthetic resin is preferably low-density polyethylene having a density of 0.91 to 0.92 g / cm ³ , a melting point of 105 to 110 ° C., and an MFR (Melt flow rate) of 8 to 15 g / 10 minutes.

  By extruding these thermoplastic synthetic resins, a high-melting thermoplastic synthetic resin is laminated on both sides of the base paper in a thickness of 15 to 50 μm and a low-melting thermoplastic synthetic resin in a thickness of 30 to 70 μm.

(2) Primary printing step Next, the entire surface of the low-melting thermoplastic synthetic resin layer of the base paper is subjected to gravure printing with a single color ink and dried. The composition and color of the single color ink is not particularly limited as long as it is usually used for gravure printing. As for colors, when printing designs such as characters and figures in a later step, light colors, particularly white, are preferably used in order to minimize the influence on the colors.

(3) Container body molding step The base paper is punched into a blank plate in the shape of a container body trunk, and the bottom part is formed so that the low melting point synthetic resin layer is on the outside using a normal paper container molding machine. A cylindrical body member with an upper and lower opening having a shape that expands outward from the top is formed, and a bottom member is integrated with the body member to form a cup-shaped container body.

(4) Secondary printing step Next, when a design such as characters and figures is printed on the outer surface of the container body obtained in the molding step, printing is performed by an offset printing method.

  The ink used in the secondary printing process is not particularly limited as long as it can maintain the softened state of the ink for a certain period of time after printing, as long as it can be used for conventional offset printing. It is not something. For example, an oxidation polymerization type ink or a reaction curable ink that can be dried by irradiation with infrared rays, ultraviolet rays, or an electron beam can be employed. In the present invention, ultraviolet curable inks that are widely used in offset printing are preferred.

  The term “softened state” in the present invention means a state where the ink after printing is not completely cured and dried. For example, in the case of the oxidation polymerization type ink, the time until heating and foaming after printing is appropriately adjusted according to the environment such as the room temperature and humidity and the components of the ink. In the case of a reaction curable ink such as an ultraviolet curable ink, the softened state can be maintained for several days unless irradiation with ultraviolet rays or the like is performed.

  The composition of the ink is appropriately adjusted according to the type of the base paper and thermoplastic synthetic resin used in the present invention, the drying conditions, and the like. For example, when using oxidative polymerization type inks, a main agent composed of a pigment such as organic and inorganic pigments and a synthetic resin, a vehicle such as vegetable oil (drying oil) and a solvent, a viscosity modifier such as a diluted varnish, and a drying adjustment. It can be appropriately adjusted and employed from an auxiliary agent comprising an agent and other waxes. In addition, when an ultraviolet curable ink is used as a reaction curable ink, a coloring pigment (disazo yellow, carmine 6B, cyanine blue, carbon black, etc.) is used as a coloring component, and a photosensitive resin (polyester resin, ketone resin, Epoxy resin or the like), photosensitive monomer (acrylate type or methacrylate type), photopolymerization initiator (benzophenone type, benzoin type, acetophenone type, thioxanthone type) as a catalyst, and wax as an auxiliary agent can be appropriately adjusted and employed.

  As a printing method, for example, there is offset printing, and dry offset printing is preferable among them. Further, printing on a container having a curved surface such as a cup can be performed by performing curved surface printing.

(5) Heating and foaming step The thermoplastic synthetic resin layer having a low melting point is foamed by heating the molded container subjected to the primary printing or primary / secondary printing.

  The heating temperature and heating time in the heating and foaming step are appropriately set according to the moisture content of the base paper to be used and the components of the low-melting thermoplastic synthetic resin, the melting point, the density, the thickness of the printed ink, etc. The temperature is 110 ° C. to 200 ° C., and the heating time is 20 seconds to 12 minutes. Arbitrary methods, such as a hot air, electric heating, and an electron beam, can be used for a heating means, and oven etc. may be used. If it is heated by hot air or electric heat in a tunnel equipped with conveyor means, it can be mass-produced at low cost.

  In addition, when secondary printing is performed, it is essential that the ink used for the printing is heated and foamed in a softened state.

  In the heating and foaming step, since the entire outer surface of the thermoplastic synthetic resin layer on the outer surface of the container body is covered with a printing layer of a single color ink, foaming of the entire surface of the foamed layer is caused when the synthetic resin layer is foamed by heating. Is uniformly suppressed and a smooth foamed surface is formed. Furthermore, the secondary printing of the design of characters, figures, etc. is performed and the ink forming the printing layer is heated and foamed in the softened state, so that the secondary foam is suppressed and controlled by the single color printing layer. A smooth foamed surface can be formed without affecting the foaming of the printed part.

(6) Drying step When the second printing is performed and then heated and foamed, the ink forming the printed layer may be in a softened state even after foaming, and it is usually necessary to dry the printed ink. is there. The drying means varies depending on the ink used, and can be dried according to the characteristics of the ink used. For example, in the case of an ultraviolet curable ink, the ink can be cured and dried by irradiating with ultraviolet rays.

  The present invention will be specifically described based on examples, but the present invention should not be construed in a limited manner based on the disclosure of these examples.

Example 1
Low-density polyethylene (density 0.92 g / cm ³ ) was extruded and laminated to a thickness of 60 μm on one side of a base paper (basis weight 300 g / m ² , moisture content 8%). On the opposite side of the base paper, medium density polyethylene (density 0.94 g / cm ³ ) was extruded and laminated to a thickness of 40 μm. White ink was printed by gravure printing on the entire surface of the low melting point polyethylene film and dried to obtain a base paper. A blank for the container body member was punched out from this base paper, a blank for the bottom member was punched out from another base paper, and the container body 1 was formed by molding with a conventional cup molding machine.

  On the other hand, the container body 1 was further subjected to two-color curved surface printing by dry offset printing using an ultraviolet curable ink (“UV ink FD series” manufactured by Toyo Ink Co., Ltd.) to obtain a container body 2. Moreover, the container which carried out the cup shaping | molding without giving the white printing by the said gravure printing to the said base paper was made into the comparison goods.

  The container body 1 and the comparative product were placed in an oven and heated at 120 ° C. for 5 minutes to cause foaming, whereby a foamed container 1 and a comparative product 1 were obtained. As a result of measuring the thickness of each container body member, the total thickness of the foam layer of the foam container 1 and the comparative product 1 was about 0.9 mm and about 1.2 mm.

  On the other hand, the container body 2 was heated and foamed in the same manner while the ultraviolet curable ink was in a softened state, and then the ink was dried by ultraviolet irradiation to obtain a foamed container 2. Further, after the ink was dried by irradiating the container main body 2 with ultraviolet rays, the ink was put in an oven and heated and foamed under the heating conditions to obtain a foamed container 3. As a result of measuring the thickness of each container body member, the total thickness of the foam layers of the foam container 2 and the foam container 3 was about 0.9 mm.

The foamed resin layer of the comparative product 1 was fully foamed without any foaming being suppressed, whereas the foamed container 1, the foamed container 2 and the foamed container 3 had a printing surface due to the presence of a single color printing layer. Foaming was uniformly controlled over the entire surface, and a smooth foamed surface was formed. In addition, when the foamed container 2 and the foamed container 3 subjected to curved surface printing are compared on the outer surface of the container, foaming is suppressed in the portion of the foamed container 3 subjected to curved surface printing, and the outer surface of the container becomes concave. The printed part of the container 2 formed a foamed resin layer having a smooth and clean printing surface without affecting foaming.

Claims (1)

The printed layer is made of a base paper provided with a high-melting point thermoplastic synthetic resin layer on one side of the base paper and a low-melting point thermoplastic synthetic resin layer having a printing layer of a single color ink on the other side on the other side. After forming the cylindrical body member with the upper and lower openings so that the outer side is the outside , integrating the bottom member with the body member to form the container body, and after the container body is molded, the design of characters, figures, etc. is printed on the outer surface Manufacturing of a heat insulating foamed paper container that forms a heat insulating layer on the outer surface of the container by heating the container main body while the ink forming the printed layer is in a softened state and foaming a low melting point thermoplastic synthetic resin layer A method for forming a heat-insulating foamed paper container, wherein the foamed outer surface is formed by completely suppressing and controlling the foaming of the outer surface of the container by the single color printing layer in the foaming process. Production method.