JPS6153224B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a sheet for forming a printing sleeve,
The present invention aims to provide a material suitable for shrink sleeves used to cover and protect glass bottles, particularly for sleeves used after printing. Conventionally, the outer surface of a glass bottle, etc. is covered with a sleeve made of a heat-shrinkable synthetic resin sheet, and the sleeve is shrunk by heating to cover the outer surface of the glass bottle, etc., so as to protect the glass bottle, etc. things are being done. As the heat-shrinkable sheet forming the sleeve, for example, a foamed polystyrene sheet is widely used as it has excellent cushioning properties, but the foamed sheet has the drawback of poor surface smoothness and poor printability. In addition, the sheet surface was easily scratched. Furthermore, after shrink-covering the glass bottle with a sleeve, when the glass bottle is continuously transferred on a vibrating conveyor, etc., the glass bottle does not move smoothly because the surface is not smooth, and there is a risk that the glass bottle will stagnate in the middle of the travel path. Therefore, the present invention solves the above-mentioned conventional drawbacks and provides a sheet for forming a printing sleeve that has excellent printability and durability of the printed surface during use. The non-foamed film contains 0.03 to 6.0 parts of polyethylene wax per 100 parts of styrene resin, and the foamed sheet has a shrinkage rate lower than that of the non-foamed film. is large, and the skin layer is thicker on the non-laminated side than on the laminated side with the non-foamed film, and the shrinkage rate of the laminated sheets in the machine direction is 60% or less and the shrinkage rate in the width direction is 10% or less, and It is characterized in that the shrinkage rate in the machine direction is greater than the shrinkage rate in the width direction, and both ends in the machine direction are joined with the foam sheet side as the inner surface. Next, embodiments of the present invention will be illustrated below with reference to the drawings. The printing sleeve forming sheet S is a laminated sheet of a shrinkable foamed polystyrene sheet 1 and a shrinkable non-foamed polystyrene film 2, both of which are 1 and 2.
All of them have so-called heat shrinkability, which means that they shrink when heated. The shrinkability is added by stretching during extrusion molding, and the magnitude of the shrinkage force or shrinkage rate varies depending on the molding conditions such as the amount of stretching or the composition of the resin material. In the case of the foamed sheet 1, resin skin layers are formed on both sides by extrusion foaming, and the thickness thereof varies depending on the degree of cooling during molding. Therefore, the printing sleeve forming sheet S of the present invention can be formed by appropriately setting the above-mentioned molding conditions or the composition of the raw material. First, the polystyrene resin that is the material of the foamed sheet 1 is styrene, vinyltoluene, isopropylstyrene, α-methylstyrene, styrene polymers obtained by polymerizing vinyl aromatic monomers such as methylstyrene, chlorostyrene, and tertiary-butylstyrene. Coalescence, styrene monomer and alkyl acrylates such as 1,3-butadiene, butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, acrylonitrile, vinyl acetate, α-methylethylene, divinylbenzene, dimethyl maleate, diethyl maleate, A styrene copolymer containing 50% by weight or more of styrene monomer, which is obtained by copolymerization with maleic anhydride, is used, and the above resin contains propane, butane, isobutane, pentane, neopentane, isopentane, hexane, butadiene, etc. Aliphatic hydrocarbons, cycloaliphatic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane, and halogens such as methyl chloride, methylene chloride, dichlorofluoromethane, chlorotrifluoromethane, dichlorodifluoromethane, chlorodifluoromethane, and trichlorofluoromethane. A foaming agent such as hydrogenated hydrocarbons is added, and the foamed sheet 1 is formed by heating and foaming. The thickness of foam sheet 1 is 0.1~1mm
It can be used within a range of 1 mm or more, but if it exceeds 1 mm, it becomes difficult to wind the roll and cannot be shipped in roll form, which is not preferable. As the non-foamed film 2, the above foamed sheet 1
The same styrene resins as the materials can be used, and 0.03 to 6.0 parts of polyethylene wax is contained per 100 parts of these styrene resins. Polyethylene wax is an ethylene low polymer produced by polymerization of ethylene or thermal decomposition of polyethylene, and in the present invention, polyethylene waxes with a molecular weight in the range of 500 to 15,000 can be used, particularly those with a molecular weight of 1,000 to 10,000. is preferred. That is, when measuring the drop point (ASTM, D566 ² standard) that indicates the softening point of the polyethylene wax, if the molecular weight is less than 1000, the drop point becomes low, and the screw biting during extrusion molding decreases. However, only a small amount of polyethylene wax can be mixed into the styrene resin, which is not preferable. On the other hand, if the molecular weight exceeds 10,000, the drop point will become high and the miscibility with styrene resin will deteriorate, which is not preferable. When the above molecular weight range is expressed as a drop point value, it is approximately 50 to 150℃.
range of 90 to 150℃ can be used, preferably 90 to 150℃
Implemented within the range of . The addition of the polyethylene wax to the non-foamed film 2 has the effect of improving the solvent resistance of the non-foamed film 2. That is, when simply printing on a shrinkable sheet in which a foamed sheet and a non-foamed film are laminated, the surface of the non-foamed film to be printed is partially eroded by the solvent of the printing ink. When this shrinkable sheet is used to form a sleeve and shrink-cover a bottle or the like, fine cracks will occur on the printed surface over time or due to changes in outside temperature. In this invention, the solvent resistance of the printing ink, which causes the cracking, is improved by containing the polyethylene wax. The composition of non-foamed film 2 is 0.03 parts of polyethylene wax per 100 parts of styrene resin.
It can be used containing up to 6.0 parts.
If it is less than 0.03 part, there will be little effect such as improving solvent resistance.
If it exceeds 6.0 copies, the surface of the film will deteriorate and printability will deteriorate, so both are undesirable.
It is most effective to use the content within the range of 0.03 to 4.0 parts. Further, the non-foamed film 2 can also contain a rubber component such as butadiene or butene, and by containing the rubber component, the non-foamed film 2 and the foamed sheet 1 can be simultaneously extruded using a co-extruder. When laminating the non-foamed film 2, the stretching of the non-foamed film 2 can be freely controlled, and it becomes easy to create a difference in stretching, that is, a difference in shrinkage rate, between the non-foamed film 2 and the foamed sheet 1. This is assumed to be a non-foamed film 2 and a foamed sheet 1.
If the shrinkage rate is the same as that of the non-foamed film, cracks will occur in the non-foamed film when this laminated sheet is used to form a sleeve and the bottle is covered with shrinkage. In order to prevent this, it is necessary to make the shrinkage rate of the non-foamed film 2 smaller than that of the foamed sheet 1, and for this reason, it is effective to contain a rubber component that can control the stretching of the non-foamed film 2. becomes. The amount of rubber contained in the non-foamed film 2 is not more than 20% by weight, preferably in the range of 2 to 10% by weight, and if it is more than 20% by weight, it is undesirable because it is easily attacked by the solvent of printing ink. In addition, if the non-foamed film 2 contains a pigment such as titanium white, it will reduce the light transmittance and increase the reflectance, so when laminated with the foamed sheet 1, the color will be better during printing and the surface will have a better luster or luster. It is effective, and the content of titanium white is preferably 5% by weight or less. The thickness of the non-foamed film 2 is preferably in the range of 2 to 160 .mu.m. If it is less than 2 .mu.m, the strength is weak and scratches are likely to occur during printing, and if it is 160 .mu.m or more, the winding property becomes poor, which is not preferable. The above-mentioned foamed sheet 1 and non-foamed film 2 are molded separately and then laminated by thermal bonding or the like to form the sheet S for forming a printing sleeve, and the foamed sheet 1 and non-foamed film 2 are molded by co-extrusion. Any method of laminating them simultaneously can be used. First, I will explain the method using coextrusion.
For example, in the case of inflation molding, the foamed sheet 1 is on the inside and the non-foamed film 2 is on the outside, and they are simultaneously extruded from an extrusion die, and cooling air is applied only to the inner foamed sheet 1 side, or the foamed sheet 1 side is Air the outer non-foamed film 2
By making the sheet particularly stronger than the outside, the inside and outside are stretched to a different degree of cooling, and then taken off and formed into a laminated sheet. The above-mentioned stretching causes the shrinkability of the sheet S for forming a printing sleeve, but the foamed sheet 1 that has been cooled to a high degree exhibits a higher shrinkage rate than the non-foamed film 2, and the foamed sheet 1 itself also has a shrinkability. A thicker skin layer is formed on the surface 11 that is hit by air and is not laminated with the non-foamed film 2 than on the surface 10 that is laminated with the non-foamed film 2, and the shrinkage rate is also increased. In addition, by appropriately setting the take-up speed and blow-up ratio during stretching,
By controlling the stretching amount in the machine direction and the width direction, the shrinkage rate in the machine direction of the laminated sheets can be kept below 60% and the shrinkage rate in the width direction is below 10%, and the shrinkage rate in the machine direction can be reduced to below 60%. The shrinkage rate should be greater than the shrinkage rate in the width direction. The difference in shrinkage rate between the foamed sheet 1 and the non-foamed film 2 is adjusted by adjusting the strength of the cooling air and by increasing or decreasing the amount of rubber contained in the non-foamed film 2. Next, in the method of laminating by thermal adhesion, the foamed sheet 1 and the non-foamed film 2 are extruded separately in advance, and the shrinkage rate of the molded foamed sheet 1 is adjusted by adjusting the stretching amount etc. The shrinkage rate should be greater than that of the foamed film 2. Furthermore, during extrusion molding of the foamed sheet 1, the thickness and shrinkage rate of the skin layer are made different on the front and back sides of the foamed sheet 1 by making a difference in the degree of cooling on both sides. Furthermore, by forming the foamed sheet 1 with a difference in the amount of stretching in the flow direction and the width direction, the shrinkage rate in both directions can be adjusted. If the foamed sheet 1 and non-foamed film 2 thus formed separately are laminated by thermally adhering the non-foamed film 2 to the surface 10 of the foamed sheet 1 with a thin skin layer, a printing sleeve forming sheet S is formed. ,
Instead of thermal adhesion, it is also possible to laminate both 1 and 2 by adhesion using a binder such as ethylene-vinyl acetate copolymer. In the printing sleeve forming sheet S formed as described above, the amount of residual gas due to the foaming agent contained in the foamed sheet 1 is kept at 2% by weight or less at the time of use, that is, at the time of heat shrinkage of the sleeve, which will be described later. This is to prevent the printed surface of the non-foamed film 2 from peeling off or cracking due to a large increase in the thickness of the sleeve due to expansion due to heating if there is a large amount of residual gas when the sleeve contracts. Although the residual gas gradually diffuses over time after extrusion, it is preferable to actively diffuse it using a hot roll or the like to control the residual gas. Sheet S for forming a printing sleeve in which the foamed sheet 1 and the non-foamed film 2 are laminated as described above.
After printing on the non-foamed film 2 side, it is cut into an appropriate size to form a cylindrical sleeve. At this time, the foamed sheet 1 side of the printing sleeve forming sheet S is placed on the inner surface, and the sheet is wound into a cylindrical shape so that the direction of flow of the sheet is in the circumferential direction of the sleeve, and both ends in the direction of flow are bonded by heat bonding, etc. Sleeve A is formed by joining by the following means. This sleeve A is placed over a glass bottle G, etc., and then heated to shrink the sleeve A and tightly cover the glass bottle G.
This is to protect the people. The size of the above-mentioned sleeve A is determined so that when it is placed over the glass bottle G, there is a gap of about 1 mm between the glass bottle G and the sleeve A, and the adhesion when the sleeve A shrinks.
It is also preferable in terms of 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 change in thickness becomes extreme, the printing surface may bulge due to the difference in the degree of shrinkage between the foamed sheet 1 and the non-foamed film 2. There is a risk of cracks forming on the surface. Therefore, the size of the sleeve A relative to the glass bottle G is adjusted so that the change in thickness is 2.0 times or less before and after shrinkage. In addition to the glass bottle G, the sleeve A can be used for various purposes such as protecting fragile articles such as various glass products and ceramics. Next, properties such as solvent resistance were measured for the above printing sleeve forming sheet, and the results were compared for sheets having different raw material compositions. The sheet is manufactured using an inflation extrusion method using simultaneous extrusion, using two extruders, one extruder (screw diameter: 65 mm).
φ) to melt and knead the raw materials for foamed sheet 1, and the other extruder (screw diameter 45 mmφ) to melt and knead the raw materials for non-foamed film 2 (extruder temperature 130-190 mm).
°C), connect the tip of one extruder to the die of the other extruder, coat the outer periphery of the other melt-kneaded material with one melt-kneaded material, and then cut the slit with a diameter of 75 mmφ and a slit width.
Output amount 30-33Kg/H from 0.4mm annular tip die
It was extruded into a cylindrical shape, passed over a plug with a diameter of 145 mm, and taken off at a speed of 16 m/min. After passing through the plug, the sheet is cut into two pieces, and then passed through a hot roll (diameter: 100 mmφ) with a surface temperature of 92° C. to obtain a sheet S for forming a printing sleeve. Then, printing is performed on the printing sleeve forming sheet S using a printing ink normally used for foamed polystyrene sheets. Composition of printing ink and solvent Alcohol 40% Toluene 12% Ethyl acetate 6% Pigment 20% Acrylic resin 15% Cellulose resin 7% Next, both ends of the printing sleeve forming sheet S in the flow direction are joined to form sleeve A. A glass bottle G for coating is preheated at 68°C, and the sleeve A is placed on the glass bottle G, and then heated in an oven at 160°C for 10 seconds to shrink and cover the sleeve A. Various tests were conducted during the above process and on the finished shrink coating, and the results are shown in the table below. However, the composition of the foam sheet is polystyrene.
For 100 parts, a blowing agent containing 0.345 mol of butane per 1 kg of polystyrene was used, and the non-foamed film was formulated using 75 parts of polystyrene and styrene-butadiene copolymer (containing 6% butadiene)25. 50 parts of high-impact polystyrene resin (HI), which is a polystyrene-based resin containing 100 parts of polystyrene and 5 parts of titanium white, and 50 parts of polystyrene resin (PS), which contains 100 parts of polystyrene and 5 parts of titanium white, was mixed with polyethylene wax. Comparisons were made using various PEwax contents, and in the example of . Comparisons are made using materials with different contents. Furthermore, the polyethylene wax (PEwax) used in the above formulations has a molecular weight of 2000 and a drop point of 118°C.

【table】

【table】

[Table] From each of the above tables, the effect of containing polyethylene wax in the non-foamed film 2 and the preferable range of the content of the polyethylene wax (Examples ~) are clear. According to the sheet for forming a printing sleeve of the present invention constructed as described above, a shrinkable foamed polystyrene sheet and a shrinkable non-foamed polystyrene film are laminated, and when formed into a sleeve, the non-foaming material that becomes the outer surface. The foamed film has a smooth surface and very good printability, and requires less printing ink. Furthermore, since the above-mentioned film has excellent strength and is resistant to scratches, combined with the excellent cushioning properties of the inner foam sheet, it provides extremely excellent protection against glass bottles and the like. Therefore, even if the thickness of the glass bottle itself is made thinner, it can still withstand use, making it possible to reduce the weight to approximately 1/2 of that of conventional bottles, which is highly effective in reducing costs and transportation weight. It is something. Furthermore, since the above-mentioned film improves the surface lubricity, when glass bottles shrink-covered with sleeves are transferred by a vibrating conveyor, chute, etc., there is less frictional resistance when the glass bottles come into contact with each other, allowing smooth transfer. This eliminates the drawbacks of conventional foam sheet sleeves in which glass bottles tend to get clogged or stagnate in the middle of the travel path. In addition, the shrinkage rate of the foam sheet that forms the inner surface of the sleeve is greater than that of the non-foamed film that forms the outer surface, so when shrink-covering a glass bottle, the inner foam sheet that requires a larger amount of shrinkage is It can be coated tightly, eliminating the occurrence of gaps or warping or curling at the shoulder or bottom of the bottle, and the bonding force to the glass bottle is sufficiently large. Furthermore, since the foamed sheet itself has a thicker skin layer on the non-laminated side than on the laminated side with the non-foamed film, it has even better adhesion to glass bottles and can exhibit good effects in terms of shrinkage. The shrinkage rate of the laminated sheets as a whole in the flow direction is greater than the shrinkage rate in the width direction, and when formed into a sleeve, the sheets are wound into a cylindrical shape so that the flow direction is in the circumferential direction of the sleeve, and both ends are joined. Then, when the sleeve is placed over a glass bottle and contracted, the sleeve mainly contracts only in the circumferential direction and hardly contracts in the axial direction, so that a predetermined range of the glass bottle can be sufficiently covered. Furthermore, in this invention, since the non-foamed film contains polyethylene wax, it has solvent resistance that is not easily attacked by the solvent of the printing ink used when printing on the surface of the non-foamed film. Even after the sleeve is shrink coated, cracks do not occur on the printed surface even with time or changes in outside temperature, and a beautiful exterior surface can always be maintained, resulting in extremely high commercial value. As described above, it is possible to provide a sheet that is very suitable for forming printing sleeves that can exhibit excellent performance as a sleeve for shrink-coating glass bottles and the like.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the present 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. 1... Shrinkable expanded polystyrene sheet, 10...
... Laminated surface, 11... Non-laminated surface, 2... Shrinkable non-expanded polystyrene film, S... Sheet for forming a printing sleeve, P... Sleeve, G... Glass bottle.

Claims (1)

[Claims] 1. A shrinkable foamed polystyrene sheet and a shrinkable non-foamed polystyrene film are laminated, and the non-foamed film contains 100 parts of styrene resin.
Containing 0.03 to 6.0 parts of polyethylene wax, the foamed sheet has a higher shrinkage rate than the non-foamed film, and its skin layer is thicker on the non-laminated surface than on the laminated surface with the non-foamed film, and The shrinkage rate in the machine direction of the sheet is 60% or less, the shrinkage rate in the width direction is 10% or less, and the shrinkage rate in the machine direction is greater than the shrinkage rate in the width direction, and both ends in the machine direction with the foam sheet side inside. A sheet for forming a printing sleeve, characterized by joining. 2. A sheet for forming a printing sleeve according to claim 1, wherein the non-expanded polystyrene film contains 5% by weight or less of white titanium.