JPS62152838A - Laminated sheet for retort-resistant shrink-label and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a shrink label used to protect the coating of glass bottles, etc., and in particular, a retort-resistant volume threshold sheet for shrink labels that can sterilize the glass bottle together with its contents at high temperature after coating the shrink label, and the like. This relates to a manufacturing method.

[Conventional technology]

BACKGROUND OF THE INVENTION Conventionally, glass bottles have been protected using shrink labels, which are made by covering the outer surface of a glass bottle with a sleeve made of a heat-shrinkable synthetic resin sheet and shrinking the sleeve by heating. As the synthetic resin sheet, for example, a foamed polystyrene sheet is widely used as a material with excellent cushioning properties. However, the foamed polystyrene sheet described above has poor surface smoothness, making it difficult to perform precise printing, and also difficult to increase the printing speed during printing. In addition, since the softening temperature of polystyrene, which is the raw material for conventional foamed polystyrene sheets, is low, for example, the high temperature sterilization process using hot steam at 120°C for 30 minutes, which is currently applied to coffee drinks, is not suitable for the foamed polystyrene sheets. When a shrink label based on . Furthermore, due to the low solvent resistance of styrene resin, the composition of the vehicle resin of ink that can be used for printing is limited, and the low heat resistance of this vehicle resin causes Deterioration and deformation occur, and the surface quality deteriorates significantly. As a solution to the problems that occur during high-temperature sterilization treatment using heated steam, we have created a heat-resistant foamed polypropylene sheet made from heat-resistant and solvent-resistant polypropylene that is printed using heat-resistant ink. A heat-shrinkable sheet for shrink labels has been developed.
It shows good heat resistance even in high temperature sterilization treatment for 0 minutes.

[Problem to be solved by the invention 1] Although polypropylene has excellent heat resistance and solvent resistance, it has inferior foaming properties compared to polystyrene, and it is difficult to make the cells in the foam sheet fine, making it difficult to Since it is difficult to improve smoothness, precise printing cannot be performed. In addition, as a typical technique for forming a sleeve from a heat-shrinkable sheet and putting it on a bottle, it is used as a heat-shrinkable shrink label.
There is a technique described in No. 8371, but in the case of foamed polypropylene with a normal expansion ratio, the sleeve is deformed when covering the lath pin due to the low rigidity of the sheet. There are some drawbacks, such as the fact that it ends. On the other hand, if the foaming ratio is lowered to improve the rigidity of the foamed polypropylene sheet, the heat shrinkability of the foamed polypropylene sheet will decrease due to the high heat distortion temperature of polypropylene, so the sleeve, which corresponds to the bottom of a glass bottle, will Shrinkage becomes insufficient, resulting in poor adhesion between the glass bottle and the shrink label. The present invention solves the above-mentioned problems that occur in the case of foamed polypropylene sheets, and furthermore, even after the above-mentioned high-temperature sterilization treatment, a beautiful surface showing high gloss is maintained, and it has retort resistance with appropriate rigidity. The present invention provides a laminate sheet for shrink labels (hereinafter abbreviated as laminate sheet). [Means for Solving the Problem] In place of polypropylene, which has excellent heat resistance but low rigidity, the present invention is composed of a polystyrene resin alone or a mixture, which has a heat distortion temperature higher than that of ordinary polystyrene and has heat resistance. The base material is a heat-shrinkable foam sheet,
This invention relates to a laminated sheet obtained by laminating heat-shrinkable polypropylene films on both sides of the laminated sheet. Although the heat distortion temperature of the heat-resistant polystyrene resin is higher than that of ordinary polystyrene, it is lower than that of polypropylene, and its heat resistance is also inferior. Furthermore, when a foamed sheet is made from heat-resistant polystyrene resin by extrusion foaming, the foaming gas used during foaming remains in the sheet, and the heat resistance of the foamed sheet further decreases due to the plasticizing effect of this residual component. A foam sheet made of heat-resistant polystyrene resin alone cannot be expected to have good heat resistance in the above-mentioned high-temperature sterilization process, and secondary foaming may cause deformation of the shrink label and deterioration of the printed layer, so the product The value will drop significantly. However, in the present invention, by laminating heat-shrinkable polypropylene films on both sides of a heat-shrinkable foam sheet made of heat-resistant polystyrene resin, the laminated sheet has heat resistance that cannot be obtained with the heat-shrinkable foam sheet made of heat-resistant polystyrene resin alone. This is based on the discovery that it can be applied to The laminated sheet of the present invention is composed of three layers: a heat-shrinkable polypropylene film that forms an outer layer and a cabinet, and a heat-shrinkable foam sheet of a heat-resistant polystyrene resin that forms an intermediate layer when used as a shrink label. The heat-shrinkable foam sheet serving as the intermediate layer is obtained by adding and mixing an organic foaming gas and a foaming nucleating agent to a heat-resistant polystyrene resin, followed by extrusion and foaming. The heat-resistant polystyrene resin used in the present invention has a higher heat distortion temperature than ordinary polystyrene.
Styrene-methacrylic acid copolymer resins, styrene-maleic anhydride copolymer resins, styrene-maleimide copolymer resins, polyvaramethylstyrene, and the like can be suitably used. The heat-shrinkable foam sheet made of the heat-resistant polystyrene resin has an expansion ratio of 10 times or less, a thickness in the range of 50 to 500μ, and a shrinkage rate in the machine direction of 30 when heated to 140°C.
% or more. If the expansion ratio exceeds 10 times, the surface of the heat-shrinkable foam sheet made of heat-resistant polystyrene resin becomes brittle, resulting in surface breakage of the foam sheet and a decrease in adhesive strength with the polypropylene film. Further, the thickness of the foam sheet is set to 50 to 500μ because if the thickness is less than 50μ, the cushioning properties will be insufficient and the rigidity of the sleeve formed from the foam sheet will decrease.
This is because if it exceeds 00μ, the foamed sheet will easily break. Furthermore, if the foam sheet has a heat shrinkage rate of less than 30%, the shoulder and bottom portions of the bottle tend to shrink insufficiently when the foam sheet is coated onto a bottle and heat-shrinked. Next, the heat-shrinkable polypropylene non-foamed film that forms the outer layer has a thickness of 15 μm or more and 150 μm or less, and the shrinkage rate in the flow direction when heated to 14. It is desirable to have a film that is smaller than the heat-shrinkable foam sheet of 2008, and has better transparency and high gloss. The thickness of the heat-shrinkable polypropylene non-foamed film is 1
If it is less than 5μ, the rigidity of the polypropylene is low when it is laminated with a foamed sheet of heat-resistant polystyrene resin, so the surface of the foamed sheet will appear, deteriorating the smoothness of the surface of the laminated sheet, so use a non-foamed polypropylene film. It is difficult to obtain the effect of pasting. The present invention is characterized in that the above-mentioned heat-shrinkable non-foamed polypropylene film serving as the outer layer is printed on the back in advance and then laminated with a heat-shrinkable foamed sheet of heat-resistant polystyrene resin. Transparency is desired. Additionally, when pasting such polystyrene resin foam sheets and polyolefin resin films together, heat-sensitive adhesives such as ethylene/vinyl acetate copolymer were used because the adhesion between the two was extremely low. . However, heat-sensitive adhesives such as these have a low heat distortion temperature and melt during high-temperature sterilization with heated steam, so heat-sensitive adhesives such as ethylene-vinyl acetate copolymer cannot be used in the present invention. do not have. Therefore, in the present invention, in order to bond a heat-shrinkable foamed sheet of heat-resistant polystyrene-based resin and a heat-shrinkable non-foamed sheet of heat-shrinkable polypropylene, polypropylene and heat-resistant polystyrene-based resin are used instead of the above-mentioned heat-sensitive adhesive. Using a polyurethane resin that has adhesive properties and heat resistance for both, and using a laminating ink that uses Hoko's polyurethane resin as a vehicle resin,
After back printing is performed on the white side of the heat-shrinkable non-foamed polypropylene film, it can be bonded to a heat-shrinkable foamed sheet of heat-resistant polystyrene resin by thermocompression bonding. In order to heat-shrink a heat-shrinkable synthetic resin foam sheet to make a shrink label, it is first necessary to bond both ends of the synthetic resin foam sheet by heat sealing to form a sleeve. However, in the case of a sheet made by laminating a polystyrene resin sheet and a polyolefin resin film, the adhesion between the two is low, so it has conventionally been necessary to use a small amount of polystyrene resin and polyolefin resin (either polyvinyl acetate or ethylene/vinyl acetate on one side). A method has been adopted in which copolymers and other additives are used as additives to facilitate heat sealing.However, adding additives with low heat distortion temperatures such as copolymers causes a decrease in the heat resistance of shrink labels. Therefore, it is not possible to improve the heat sealability by adding polyvinyl acetate or ethylene/vinyl acetate copolymer to the foam sheet and polypropylene film that constitute the laminated sheet of the present invention. In the present invention, in order to enable the joining of both ends of the laminated sheet by heat sealing when forming a sleeve, a heat-shrinkable polypropylene non-foamed film serving as the outer layer and a layer of a heat-sealable material, that is, polypropylene, are attached to the laminated sheet. The inner polypropylene layer should be provided with a heat-shrinkable polypropylene film as well as the heat-shrinkable polypropylene non-foamed film that becomes the outer layer. It can be formed by bonding it to a foam sheet.The inner layer, a heat-shrinkable polypropylene film, has a thickness of 1.
It is desirable that the film has a shrinkage ratio of 5μ or more and 150μ or less, and a shrinkage rate in the machine direction when heated to 140° C. is larger than that of the heat-shrinkable polypropylene film. The thickness of the heat-shrinkable polypropylene film is 150μ
If it exceeds this value, when the laminated sheet is made into a sleeve and then placed over a glass bottle and heat-shrinked, the shrinkage of the inner layer of the sleeve is delayed and the shrink label is likely to wrinkle. The heat-shrinkable polypropylene film that will be the inner layer and the heat-shrinkable foam sheet made of heat-resistant polystyrene resin are bonded together in the same way as the heat-shrinkable polypropylene non-foamed film that will be the outer layer. This can be done by coating a heat-shrinkable polypropylene film and then heat-pressing it onto a heat-shrinkable foam sheet of a heat-resistant polystyrene resin. As described above, the stacked sheet is made by laminating a heat-shrinkable foamed sheet of heat-resistant polystyrene resin as an intermediate layer, a heat-shrinkable polypropylene non-foamed film on the outer side of a shrink label, and a heat-shrinkable polypropylene fill on the inner layer side. It exhibits good heat-sealability and can be easily formed into a heat-shrinkable sleeve. In addition, it exhibits better heat shrinkability than when the middle layer is made of a low-foam polypropylene sheet, so it can be easily attached to the shoulder and bottom of the bottle even when it is heat-shrinked and made into a shrink label. It is. In addition, heat resistance is greatly improved by laminating polypropylene film, and good surface properties are maintained even after high temperature sterilization, especially since polypropylene film with back printing on the outer layer is laminated. , a label exhibiting much higher gloss than conventional front-printed labels can be obtained. The structure of the laminated sheet obtained by the present invention will be explained with reference to the drawings. The figure is an enlarged side view for explaining the structure of the 81st sheet of the present invention, in which 1 is a heat-shrinkable polypropylene non-foamed film, 2 is a printed layer using laminating ink, and 3 is a heat-resistant polystyrene resin. 4 is an adhesive layer, and 5 is a heat-shrinkable polypropylene film serving as an inner layer. Example 1 0 Heat-resistant polystyrene resin (styrene-methacrylic acid copolymer resin Product name: T-
8005 manufactured by Asahi Kasei Co., Ltd.) 100 parts by weight 0 Foaming agent n-pentane (manufactured by Board-Solvent Co., Ltd.)
5 Heavy mouth part 0 Nucleating agent 1 Baking soda-Quen 11:1 mixture) 0
．． The 8-fold mouth part was put into a 40 mmφ extrusion molding machine and foamed and extruded to a thickness of 0.25 mm and a foaming ratio of 5.5 times.
A foamed sheet with a shrinkage rate of 70% in the machine direction when heated to 140°C was produced. After corona discharge treatment of a 30 μ thick polypropylene cast film, back printing was performed using a polyurethane laminating ink (trade name: i-AMITEC, manufactured by Tokyo Ink Co., Ltd.) using a gravure printing machine. After a 20 μm thick polypropylene blown film was subjected to a corona discharge treatment, it was coated with the medium of the above laminating ink using a gravure printing machine using a solid plate. The foamed sheet, the back-printed polypropylene film, and the adhesive-coated polypropylene film were combined and passed between heated rolls at 120°C to create a laminated sheet. The following margin Example 2 0 Heat-resistant polystyrene resin (styrene-methacrylic acid copolymer resin, trade name: RURETEX A-15. Manufactured by Dainippon Ink Co., Ltd.) 100 Multi-volume part 0
Foaming agent, n-pentane (manufactured by Board-Solvent Co., Ltd.) 5
Parts by weight 0 Foaming nucleating agent 1 Baking soda-citric acid (1:1 mixture) 0
．． A foam sheet was made from 8 parts by weight in the same manner as in Example 1,
A laminated sheet was then produced in the same manner as in Example 1. Example 3 100 parts by weight of heat-resistant polystyrene resin (styrene-maleic anhydride copolymer resin, trade name: Dylarc, manufactured by Arco Chem, Co.) 0 Foaming agent, n-pentane (manufactured by Bord-Solvent Co., Ltd.) 4.5 Weight part 0
A foaming sheet was prepared from 0.9 parts of foaming nucleating agent 2 baking soda and citric acid (1:1 mixture) in the same manner as in Example 1, and a laminated sheet was prepared in the same manner as in Example 1. did. Example 4 100 parts by weight of heat-resistant polystyrene resin (styrene-maleimide polymer resin, trade name: Superlex, manufactured by Mitsubishi Mobile Corporation), blowing agent, n-pentane (manufactured by Board-Solvent Co., Ltd.)
5 Weight parts 0 Foaming nucleating agent 1 A foam sheet was prepared from 0.8 parts by weight of baking soda and citric acid Pli (1:1 mixture) in the same manner as in Example 1. j
·It was created. Example 5 0 Heat-resistant polystyrene resin (polyparamethylstyrene, manufactured by Mobil Corporation) 100 Heavy hanging section O Foaming agent, n-pentane (manufactured by Board-Solvent Corporation)
A foamed sheet was prepared in the same manner as in Example 1 from 5 parts by weight of foaming nucleating agent, 1 part by weight of sodium bicarbonate and citric acid (1:1 mixture), and 0.8 parts by weight. I created a straddle sheet. Comparative Example 1 0 polystyrene (trade name HH-102.Mitsubishi Monsanto Company'!1) 100 parts 0 blowing agent, n-pentane (manufactured by Board-Solvent Co., Ltd.)
5 parts by weight 0 foaming nucleating agent 1 C-citric acid (1:1 mixture)
A foamed sheet was prepared from 0.4 parts by weight in the same manner as in Example 1, and a laminated sheet was then prepared in the same manner as in Example 1. Comparative Example 2 The foam sheet prepared in Example 1 was subjected to gravure printing using printing ink for polystyrene (trade name 5TR911, manufactured by Dainichiseika Kaisha, Ltd.) to produce a sleeve-forming sheet consisting of a single foam sheet. Example 1. Example 2. Example 3. Example 4. Example 5.
and Comparative Example 1. A specimen for sleeve molding was cut out from the FA straddle sheet or foamed sheet prepared in Comparative Example 2,
When sleeves were made by heat-sealing, both laminated sheets showed sufficient heat-sealing adhesive strength similar to the foam sheet alone. Furthermore, cover the glass bottle with a sleeve such as this and heat it to 250°C1.
Each sleeve was heated for 5 seconds to shrink to form a shrink label, but in this case as well, no peeling of the heat-sealed portion was observed in any of the samples. Each of the glass bottles covered with 1q of the above 7 types of shrink labels was filled with water, and the pressure was 1.5 atm. After heat treatment in steam at 120°C for 30 minutes, the glossiness of the shrink label covering each glass bottle was measured using a glossmeter (incidence angle 75°) according to JIS P8142.
) was measured. The results are shown in the table below. Table: Glossiness of shrink labels Before heat treatment, composite sheets made by laminating polypropylene films had a high glossiness of 85 or higher, whereas sheets printed directly on foam sheets had a high glossiness. The temperature was as low as 70. Even when subjected to heat treatment, the shrink label composed of a laminated sheet based on a foamed sheet of heat-resistant polystyrene resin exhibited sufficient heat resistance, and the gloss level after treatment was 85. On the other hand, in the case of laminated sheets that use polystyrene foam sheets as the base material, the heat resistance of the foam sheets is low, so while some of the foam sheets undergo secondary foaming, some of the foam sheets soften, causing the foam sheets to deteriorate. Since the air bubbles inside were crushed, the shrink label surface lost its smoothness and the gloss level decreased to 45. Furthermore, since the foam sheet was crushed, the cushioning properties of the shrink label were significantly reduced. Furthermore, if a polypropylene film is not laminated, even if a foamed sheet made of heat-resistant polystyrene resin is used, roughness occurs on the surface of the foamed sheet and between printings, and the gloss level drops to 10, resulting in a score of 7. [Effect of the invention 1] The stacking sheet of the present invention has heat resistance that cannot be obtained with the foam sheet alone by laminating a polypropylene film with back printing to a foam sheet of heat-resistant polystyrene resin. be. In addition, because of the tri-layer structure with polypropylene films bonded to both sides, heat-sealing is easy when used as a sleeve, and the brittleness of the foamed sheet of heat-resistant polystyrene resin that forms the intermediate layer is compensated for. It has appropriate flexibility and rigidity, and can be used to cover lath pins by forming sleeves and shrink labels using various methods.As described above, the laminated sheet of the present invention has many advantages. It has great industrial value.

[Brief explanation of drawings]

The figure is an enlarged sectional view for explaining the structure of a laminated sheet according to the present invention. In the figure 1...Heat-shrinkable polypropylene non-foamed film 2.
... Printing ink for lamination 13 ... Heat-shrinkable foam sheet of heat-resistant polystyrene resin 4 ... Adhesive layer 5 ... Heat-shrinkable polypropylene film procedural amendment April 1986 2 days

Claims (1)

[Claims] 1. Thickness 15-15 printed with adhesive ink on the inner surface side.
The outer layer is a heat-shrinkable non-foamed polypropylene film with a thickness of 0μ, a heat-shrinkable foam sheet made of heat-resistant polystyrene resin with a thickness of 50 to 500μ is laminated as an intermediate layer, and the inner layer is a heat-shrinkable polypropylene non-foamed film with a thickness of 15 to 150μ. A laminated sheet for retort-resistant shrink labels, in which shrinkable polypropylene films are bonded together with adhesive. 2 The heat-resistant polystyrene resin is a styrene-methacrylic acid copolymer resin, a styrene-maleic anhydride copolymer resin,
The laminated sheet for retort-resistant shrink labels according to claim 1, which is a single substance or a mixture of styrene-maleimide copolymer resin and polyparamethylstyrene. 3. The retort-resistant shrink label laminated sheet according to claim 1 or 2, wherein the resin of the adhesive ink is a polyurethane resin or a polyurethane prepolymer resin. 4. The retort-resistant shrink label laminated sheet according to any one of claims 1 to 3, wherein the adhesive resin is a polyurethane resin or a polyurethane prepolymer resin. 5 A heat-shrinkable foam sheet made of heat-resistant polystyrene resin is produced using an extrusion molding machine at a foaming ratio of 10 times or less and a thickness of 50 to
500μ, extrusion molding with a shrinkage rate of 30% or more, the other 15~
One side of a heat-shrinkable non-foamed polypropylene film with a thickness of 150μ is subjected to corona discharge treatment, then printed with adhesive ink, the printed side and the above-mentioned heat-shrinkable foam sheet are overlapped, and then the other side of the heat-shrinkable foam sheet is on the surface, thickness 10~1
A method for producing a retort-resistant laminate sheet for shrinkable labels, which comprises applying a corona discharge treatment to one side of a 50μ heat-shrinkable polypropylene film, then overlapping the adhesive-coated side and laminating the three layers using a heating roll. . 6 The heat-resistant polystyrene resin is a styrene-methacrylic acid copolymer resin, a styrene-maleic anhydride copolymer resin,
The method for producing a retort-resistant syringe label laminate according to claim 5, which is a single substance or a mixture of styrene-maleimide copolymer resin and polyparamethylstyrene. 7. The method for producing a retort-resistant shrink label laminated sheet according to claim 5 or 6, wherein the resin of the adhesive ink is a polyurethane resin or a polyurethane prepolymer resin. 8. The method for producing a retort-resistant shrink label laminated sheet according to any one of claims 5 to 7, wherein the adhesive resin is a polyurethane resin or a polyurethane prepolymer resin.