JPH0154189B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> This invention relates to a sheet for forming a shrinkable sleeve,
More specifically, the present invention relates to a sheet for forming a shrinkable sleeve as a material for a shrinkable sleeve that covers and protects a glass bottle or the like used for storing a liquid subject to internal pressure such as a carbonated beverage. <Prior Art and Problems to be Solved by the Invention> Conventionally, a sleeve made of a heat-shrinkable thermoplastic resin sheet is placed over the outer surface of a glass bottle, and the sleeve is shrunk by heating to conform to the outer shape of the glass bottle. Glass bottles are coated tightly to provide cushioning protection during transportation and storage of glass bottles. Particularly in the case of glass bottles that store items subject to internal pressure, such as carbonated drinks, it is an important safety issue to prevent bottle fragments from scattering in the event of damage. Therefore, as the above safety standard, JIS-S2306
(Test method for anti-scattering performance of glass bottles for carbonated beverages)
is applied to determine its suitability as a protective sleeve. In particular, if the sleeve does not break even if the glass bottle itself is broken when the bottle is broken, the pieces of the glass bottle will not be scattered, which is very desirable from a safety standpoint, and it will also be easier to dispose of the bottle pieces. In order to increase the safety in the event of breakage, it is important to improve the elongation rate and tensile strength of the material sheet, as well as the balance between the two. Furthermore, the protective sleeve is required not only to be safe in the event of breakage, but also to be durable against vibrations and impact forces during transport of the glass bottle. Furthermore, in order to mechanize or automate the process of winding material sheets into sleeves and coating bottles, it is necessary to have appropriate rigidity or strength so that the sheets do not locally deform or bend during handling. Is required. Among the various synthetic resin sheets conventionally used as materials for sleeves, non-foamed sheets such as polyvinyl chloride sheets and stretched polystyrene sheets have poor shock absorption and protection properties, while expanded polystyrene sheets have poor tensile strength and elongation. In addition, the foamed polyolefin sheet was too flexible and difficult to handle in an automatic bottle winding machine. Therefore, the present invention aims to eliminate the drawbacks of the conventional sleeve-forming sheets and provide a sheet that is excellent in cushioning properties, safety in the event of breakage, ease of handling, etc. <Means for Solving the Problems> The structure of the present invention for solving the above problems is as follows:
A shrinkable polystyrene foam sheet that becomes the inner layer,
A shrinkable polyolefin-based foam sheet serving as an intermediate layer and a shrinkable polyolefin-based non-foaming film or a shrinkable polystyrene-based non-foaming film containing a rubber component or ethylene-vinyl acetate copolymer resin serving as an outer layer are laminated. , above 3
A flexible adhesive is added to at least one of the adjacent layers, and each layer has a shrinkage rate larger than that of the middle layer and the outer layer. The resulting sheet has a shrinkage rate of 60% or less in the machine direction, a shrinkage rate of 10% or less in the width direction, and the shrinkage rate in the machine direction is greater than the shrinkage rate in the width direction. It is characterized by joining. <Function> According to the invention configured as described above, the foamed polyolefin sheet serving as the intermediate layer has excellent flexibility and a high elongation rate, so it has excellent cushioning properties against vibrations and shocks during transportation of glass bottles. The resulting product is excellent, and the safety when the bottle is broken is also very good. By laminating an inner layer made of a highly rigid polystyrene foam sheet and an outer layer made of a non-foamed film on both the inside and outside of the intermediate layer, the rigidity of the entire sleeve is increased, and a portion of the sleeve does not bend during handling. It is possible to eliminate the inconvenience of wobbling or deforming. Moreover, the non-foamed film of the outer layer can improve the smoothness and printability of the outer surface of the sleeve, improve the appearance, and also improve the strength because it is less likely to be scratched. Furthermore, since the above-mentioned non-foamed film improves the lubricity of the sleeve surface, glass bottles can be transported smoothly using a vibrating conveyor or chute. <Example> Next, examples of the present invention will be illustrated below with reference to the drawings. The sheet S for forming a shrinkable sleeve is a laminated sheet in which three layers, an inner layer 1, an intermediate layer 2, and an outer layer 3, are laminated in order, and each layer 1, 2, and 3 is a so-called heat shrinkable sheet that shrinks when heated. It has a sexual nature. The above heat shrinkability (hereinafter simply referred to as shrinkability) is imparted by stretching when manufacturing each layer 1, 2, and 3 by extrusion molding, or by a subsequent stretching process after molding. be. The inner layer 1 is made of a shrinkable polystyrene foam sheet such as a shrinkable polystyrene foam sheet. The polystyrene resin used as the material is a styrene polymer obtained by polymerizing vinyl aromatic monomers such as styrene, vinyltoluene, isopropylstyrene, α-methylstyrene, core methylstyrene, chlorostyrene, and tertiary-butylstyrene. , or styrene monomer and 1.3
- Alkyl acrylates such as butadiene, butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, alkyl methacrylates such as methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, acrylonitrile, vinyl acetate, α-methylethylene A styrene copolymer containing 50% by weight or more of styrene monomer, which is obtained by copolymerization with divinylbenzene, dimethyl maleate, or diethyl maleate, is used. Further, if the resin contains 1 to 25% by weight of rubber, it is suitable for improving and adjusting the tensile strength and elongation, which will be described later. Then, propane, butane, isobutane, pentane, neopentane, isopentane,
Aliphatic hydrocarbons such as hexane and butadiene, cycloaliphatic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane, and methyl chloride;
methylene chloride, dichlorofluoromethane,
A foamed sheet is made by adding a blowing agent such as halogenated hydrocarbons such as chlorotrifluoromethane, dichlorodifluoromethane, chlorodifluoromethane, trichlorofluoromethane, etc. in an extruder, heating and kneading, and then extruding and foaming at atmospheric pressure. Form. The thickness of the foam sheet that becomes the interior 1 above is 0.1 to 1.
mm can be used, but preferably 0.1 to 0.5. A thickness of 1 mm or more is not preferable because it is difficult to wind the sleeve-forming sheet S of the present invention into a roll and causes wrinkles to occur. In addition, a spreading agent, a plasticizer, and other additives may be added to the foamed sheet. Furthermore, if a rubber component is contained, the elongation rate and tensile strength are improved, and stretching control during molding becomes easier. Next, the intermediate layer 2 is a shrinkable polyolefin foam sheet such as a shrinkable polyethylene foam sheet. The polyolefin resin constituting the foam sheet may be a single or copolymer of polyolefin resins such as low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, polybutene-1, ethylene-vinyl acetate copolymer, etc. , or mixed resins can be used. Then, in addition to the foaming agent added to the polystyrene resin, reactive foaming agents such as baking soda and citric acid, and decomposed foaming agents such as azobisisobutyronitrile, dinitrosopentamethylenetetramine, and azodicarboxylic acid amide are added to the polystyrene resin. A foam sheet is obtained using a foaming agent. The thickness of the foam sheet thus obtained is 0.1~
A foam with a foaming ratio of about 0.45 mm and a foaming ratio of 1.3 to 3.0 times can be suitably used. In addition, the intermediate layer 2 may also contain appropriate additives in the same way as the inner layer 1. Next, the outer layer 3 is made of a shrinkable polyolefin non-foamed film such as a shrinkable polypropylene non-foamed film, or a shrinkable polystyrene non-foamed film containing a rubber component or an ethylene-vinyl acetate copolymer resin. . As the material for the shrinkable polyolefin non-foamed film, the various polyolefin resins exemplified for the intermediate layer 2 can be used. As the material for the shrinkable polystyrene non-foamed film, the various polystyrene resins exemplified for the inner layer 1 can be used, and the rubber content can include 1% by weight or more of butadiene, butene, etc. The thickness of the shrinkable non-foamed film constituting the outer layer 3 is preferably 0.01 to 0.15 mm, preferably 0.02 to 0.07 mm. Further, if the outer layer 3 contains a white pigment such as titanium white, whiteness can be obtained and color development during printing can be improved. In addition, other lubricants,
Additives such as weathering agents and antistatic agents are also added as necessary. The sleeve-forming sheet S is manufactured by laminating the three layers 1, 2, and 3 described above, and in order to improve the adhesion between each layer, a flexible adhesive is added. However, the adhesive component may be blended into at least one of the two adjacent layers.
That is, it is sufficient to mix it only in the intermediate layer 2, or only the inner layer 1 and the outer layer 3, but it is of course possible to mix it in the remaining layers as well. As for the adhesive component, ethylene-vinyl acetate copolymer resin is suitable because it has good adhesion to the resins that make up each layer 1, 2, and 3. It is also excellent in flexibility, so it can be easily used during stretching processing during molding. Even when used as a sleeve, the layers 1, 2, and 3 are difficult to peel off, which is preferable. Further, by blending the above resin into each layer 1, 2, and 3, it has the effect of improving the elongation rate and tensile strength. In addition to the above-mentioned ethylene-vinyl acetate copolymer resin, adhesives made of various thermoplastic resins can also be used as the flexible adhesive. In order to manufacture the shrinkable sleeve forming sheet S in which the three layers 1, 2, and 3 having the composition described above are laminated, each layer, which has been extruded separately in advance, is laminated and integrated by means such as thermal bonding. However, it is more efficient to laminate the layers simultaneously with the molding of each layer by coextrusion. In the co-extrusion method, the raw material resins for each layer are melt-kneaded separately in three extruders, combined into one in an extrusion mold and extruded simultaneously, and then passed through a take-off plug or roll while being stretched. The stacked sheets are picked up by a pulling machine. At this time, the cooling air is applied to the inner surface of the laminated sheets, that is, the inner layer 1.
By applying cooling air only to the inner layer 1 side or by making the cooling air stronger on the inner layer 1 side than on the outer surface, that is, the outer layer 3 side, the stretching is performed with a difference in the degree of cooling between the inner and outer surfaces. The stretching causes shrinkage in each of the layers 1, 2, and 3 of the sleeve-forming sheet S, and the inner surface, which has a higher degree of cooling, exhibits a larger shrinkage rate than the outer surface. Therefore, among the three layers, the shrinkage rate of the inner layer 1 is greater than that of the intermediate layer 2 and the outer layer 3. Further, by appropriately setting the take-up speed and blow-up ratio during the above-mentioned stretching to control the amount of stretching in the machine direction and the width direction, the shrinkage rate in both directions can be adjusted. As a result, the shrinkage percentage in the machine direction of the produced sleeve-forming sheet S was 60% or less, the shrinkage percentage in the width direction was 10% or less, and the shrinkage percentage in the machine direction was larger than the shrinkage percentage in the width direction. Adjust to. In addition, as a manufacturing method for the sleeve-forming sheet S, when three layers 1, 2, and 3, which have been separately molded in advance, are laminated by thermal bonding or the like, the amount of stretching is controlled in advance when extruding each layer. The shrinkage rate in the machine direction and the width direction is adjusted so that the shrinkage rate of the inner layer 1 is larger than that of the intermediate layer 2 and the outer layer 3. In particular, during the extrusion molding of the inner layer 1 and the intermediate layer 2, the cooling degree is changed on both the front and back surfaces to create a difference in shrinkage rate, and when laminating, the inner layer 1 or the intermediate layer 2 is placed on the side closer to the outer layer 3. It is more preferable to laminate the layers so that the surface with the smaller shrinkage rate is arranged. Of the sleeve-forming sheet S manufactured as described above, the amount of residual gas due to the foaming agent contained in the foamed sheets of the inner layer 1 and intermediate layer 2 is determined at the time of post-operative use, that is, at the time of heat shrinkage of the sleeve. Keep it below 0.3mol/Kg. This is to prevent the printing surface of the non-foamed film of the outer layer 3 from peeling off or cracking due to the increase in thickness of the sleeve due to expansion due to heating if there is a large amount of residual gas when the sleeve contracts. After extrusion molding, the residual gas will gradually dissipate over time even if it is left to stand naturally, but it may also be adjusted by heating and pressing with hot rolls to actively dissipate, or it may be contained in the foam sheet in advance. The amount of blowing agent can also be adjusted. The sleeve-forming sheet S formed as described above is printed on the surface of the non-foamed film of the outer layer 3, and then cut into an appropriate size to form a cylindrical sleeve A. At this time, the inner layer 1 side of the sleeve S for forming the sleeve is made the inner surface, and the sheet is wound into a cylindrical shape so that the flow direction is in the cylindrical direction of the sleeve A, and both ends in the flow direction are bonded by means such as thermal bonding. The sleeve A is formed by joining the sleeves. After this sleeve A is placed over a glass bottle G for carbonated drinks, etc., the sleeve A is shrunk by heating and tightly covers the glass bottle G, thereby protecting the glass bottle G. .
The size of the sleeve A is approximately 0.6 to 1.2 mm when the diameter of the glass bottle G is subtracted from the diameter of the sleeve A when the sleeve A is placed over the glass bottle G. The glass bottle G when the one formed so as to occur between
This is preferable from the viewpoint of adhesion to or appearance. In addition, the sleeve A shrinks in the circumferential direction and becomes thicker in the thickness direction at the same time, but if this thickness change becomes extreme, the inner layer 1 or the middle layer 2 and the outer layer 3
Due to the difference in degree of shrinkage from non-foamed film,
The printed surface may bulge or cracks may appear on the surface. Therefore, the change in thickness mentioned above is before and after shrinkage.
Adjust the size of sleeve A relative to glass bottle G so that it is 2.0 times or less. In addition, the shrinkable sleeve forming sheet S of this invention
In addition to glass bottles G for carbonated beverages, it can also be used to cover and protect various glass bottles, ceramic products, synthetic resin pipes, etc. <Effects of the Invention> According to the shrinkable sleeve forming sheet S of the present invention configured as described above, three types of materials having different properties, the inner layer 1, the intermediate layer 2, and the outer layer 3, are combined and laminated. By doing so, it is possible to completely satisfy the various properties required of a shrinkable sleeve. In other words, the foamed polyolefin sheet that forms the intermediate layer 2 has excellent flexibility and a high elongation rate, so it has excellent cushioning properties against vibrations and shocks during transportation of glass bottles, and also provides safety when the bottle breaks. It will be very good. To explain in detail the above-mentioned improvement in safety when a bottle breaks, when a glass bottle protected by a sleeve is broken due to a drop impact or the like, first a crack or a crack appears in the glass bottle G, causing the bottle to break. This breaking energy is then transmitted from the inner layer 1 to the outer layer 3 via the intermediate layer 2. Among them, the polystyrene foam sheet of the inner layer 1 breaks due to the above-mentioned breaking energy. However, the fracture energy transmitted to the intermediate layer 2 is dispersed and absorbed by the flexible polyolefin foam sheet and the elongation of the outer layer 3, and the inner polyolefin foam sheet partially stretches and deforms, causing local tearing. arise. However, the breaking energy per unit area transmitted to the non-foamed film of the outer layer 3 becomes smaller, making it difficult for the non-foamed film to break. In particular, outer layer 3
Since the non-foamed film is made of a polyolefin resin or a polystyrene resin containing a rubber component or an ethylene-vinyl acetate copolymer resin, it has a good elongation rate.
The destructive energy transmitted to the surface is well absorbed. Therefore, if the outer layer 3 does not break, the entire sleeve A will not break and glass bottle fragments will not scatter, resulting in extremely high safety when the bottle breaks. If a polystyrene foam sheet were used as the intermediate layer 2, the intermediate layer 2 would not be able to sufficiently absorb fracture energy due to its low flexibility, and a large amount of fracture energy would be applied to the outer layer 3.
This is inappropriate because the non-foamed film of the outer layer tends to break easily. As mentioned above, the polyolefin foam sheet that forms the middle layer 2 has a great effect on improving safety when a bottle breaks, but it is too flexible and difficult to handle when forming a sleeve or coating a glass bottle. is difficult to do. Therefore, in this invention, on both the inside and outside of the intermediate layer 2,
By laminating the inner layer 1 made of a polystyrene foam sheet with good rigidity and the outer layer 3 made of a non-foamed film, the rigidity of the entire sleeve A is increased,
A part of sleeve A may be bent during handling.
The inconvenience of deformation can be eliminated. In addition, the non-foamed film of the outer layer 3 is the sleeve A
The smoothness and printability of the outer surface can be improved, the appearance is improved, and since it is less likely to be scratched, the strength is also improved. In addition, since the non-foamed film improves the lubricity of the surface of the sleeve A, the glass bottle G can be smoothly transferred by a vibrating conveyor or chute. Therefore, according to the present invention, it is possible to provide a sleeve-forming sheet that eliminates all of the drawbacks of conventional sheet materials and has excellent performance such as safety in the event of breakage, cushioning performance, and ease of handling. Become. <Experimental Examples> Next, the effects of the present invention are shown in the table below along with detailed data regarding specific experimental examples.

【table】

[Table] (Sheet composition) Each abbreviation indicates the resin name below. PSP...Polystyrene foam resin PS...Polystyrene resin EVA...Ethylene-vinyl acetate copolymer resin PE...Polyethylene resin PP...Polypropylene resin rubber...Rubber content such as butadiene Unitless numbers after the resin name are compounds Represents a ratio, %
The numerical value represents the blended weight %. Furthermore, the vinyl acetate (VA) content in all EVA is 25% by weight. (Elongation rate and tensile strength) A dumbbell test piece was prepared, and when it was pulled along the width direction of the sheet at a take-up speed of 50 mm/min using a Tensilon tester, the elongation rate (%) and tensile load (Kg) were measured. (Falling ball impact value) Sample size 70 x 70 mm Clamp 45 mm diameter steel ball Ball 28.6 mm diameter 95 g The test was conducted under the above conditions and the height at which breakage occurred was measured. (Crashing strength) Conforms to JIS P8126-1976 (Scattering performance) Conducts bottle breakage test in accordance with JIS S2306. After the bottle was broken, the location of the sleeve breakage was measured. 1 or less fracture locations...◎ 〃 2 locations...○ 〃 3 or more locations...× In the above test results, the falling ball impact value indicates the shock absorbing performance, the crush strength indicates the ease of handling of the sleeve, and the scattering performance indicates safety in the event of a broken bottle. In general, the higher the elongation rate, the higher the scattering performance and falling impact value, but this is also influenced by the balance between tensile strength and elongation rate.

[Brief explanation of drawings]

The figure illustrates an embodiment of the invention,
FIG. 1 is a sectional view, FIG. 2 is a perspective view of the sleeve, and FIG. 3 is a sectional view of the sleeve in use. S...Shrink sleeve forming sheet, 1...Inner layer, 2...Middle layer, 3...Outer layer, A...Sleeve, G...Glass bottle.

Claims (1)

[Scope of Claims] 1 A shrinkable polystyrene foam sheet serving as an inner layer, a shrinkable polyolefin foam sheet serving as an intermediate layer, and a shrinkable polyolefin non-foaming film or rubber component or ethylene acetate-vinyl copolymer serving as an outer layer. A shrinkable polystyrene non-foamed film containing a composite resin is laminated, and at least one of the three layers adjacent to each other contains a flexible adhesive. In addition, the shrinkage rate of each layer is such that the inner layer is larger than the middle layer and the outer layer, and the laminated sheets have a shrinkage rate of 60% or less in the machine direction, a shrinkage rate of 10% or less in the width direction, and A sheet for forming a shrinkable sleeve, characterized in that the shrinkage rate is greater than the shrinkage rate in the width direction, and the inner layer side is the inner surface and both ends in the flow direction are joined. 2. Claim 1 above, in which the flexible adhesive component is comprised of an ethylene-vinyl acetate copolymer resin
A sheet for forming a shrinkable sleeve as described in Section 1.