JP2005112906A - Polyethylene terephthalate-based polyester shrink packaging material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce shrink films, shrink labels and the like from recovered PET bottle flakes, the flakes of blanked skeletons obtained after sheet making and the like as the raw materials and to eliminate the emission of the odor of solvents remaining in the packages. <P>SOLUTION: The shrink packaging material is printed with an aqueous ink at the back and comprises a polyethylene terephthalate-based polyester modified to have a long chain branched structure. The aqueous ink printing is made with aqueous gravure printing. The polyethylene terephthalate-based polyester having a long chain branched structure is obtained by mixing polyethylene terephthalates such as linear-structured recovered PET bottle flakes and the flakes of blanked skeletons obtained after sheet making, a binder and a catalyst and melt-reacting the mixture at a temperature higher than the melting point of the polyethylene terephthalate-based polyester. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a shrink film in which a packaged article is wrapped with a printed shrink film, melted and sealed, and then shrunk by applying heat with hot air or the like, and more specifically, printing on one side of a polyethylene terephthalate polyester film with water-based ink. The present invention relates to a shrink film that is applied, wrapped in an article to be packaged, sealed with a fusing seal, then passed through a shrink tunnel and shrunk with hot air or the like.

  Conventionally, as shrink film used for shrink wrapping, there are polyethylene, polypropylene, polystyrene, and polyvinyl chloride shrink films. Then, the shrink wrap is made by passing through the shrink tunnel and applying heat with hot air, steam, etc., and shrinking tightly. In addition, there are two types of shrink, a biaxially stretched shrink film that shrinks vertically and horizontally, and a uniaxially stretched film that shrinks in one direction.

  The polyvinyl chloride-based shrink film has been used since the early days, has excellent properties such as transparency and excellent heat shrinkage properties, but has chlorine in the molecule. There are problems of waste gas (generation of HCl gas) when burned, and problems of environmental hormone contamination such as generation of dioxins, which are gradually replacing other shrink films. Similarly, polystyrene-based shrink films have a problem of environmental hormone contamination, and in recent years, they are being replaced by polyethylene-based and polypropylene-based shrink films. However, polyethylene-based and polypropylene-based shrink films are inferior to polyvinyl chloride-based shrink films in terms of gloss and transparency.

  In addition to the above-described shrink film, there is a polyester-based shrink film. Similarly to the above, there are two-way and one-way shrink films, and fusing sealing is also possible. Furthermore, it has excellent shrinkage properties and glossy transparency equivalent to polyvinyl chloride shrink film, and there is no problem of environmental hormone contamination.

  By the way, the shrink film made of polyethylene terephthalate-based polyester is made of polyethylene terephthalate used as a raw material for PET bottles, PET films and PET sheets. Using PETG resin (reactant of terephthalic acid + ethylene glycol) (terephthalic acid + ethylene glycol + 1,4 cyclohexanedimethanol reaction product, for example, product name: Eastar PETG6763 made by Nagase Sangyo Co., Ltd.) as a raw material Heat sealing and fusing sealing are possible.

  However, since PETG resin is expensive, it is often used as a label for bottles of cosmetics, toiletries and the like that easily absorb the price rather than as a general shrink film.

  By the way, in recent years, collection of PET bottles has progressed, and various methods of using the collected products have been studied. However, the recovered resin of the PET bottle has a reduced molecular weight due to the thermal load at the time of molding, and as a raw material for the PET bottle again, the molding processability is poor and the molded product is also brittle and impact resistant. It could not be reused and could only be used for low-quality sheets such as fibers and egg packs that could be molded with low molecular weight.

On the other hand, a shrink film or label is often printed on the back side with a product display, a description, a design, and the like, and printing is usually performed with oil-based gravure printing using oil-based ink. However, oil-based gravure printing is a bad odor during printing work with oil-based ink solvent, work environment for health, danger of explosion and environmental pollution around the factory, problem of CO ₂ reduction, by volatilizing all solvents There are problems of wasteful use of solvent resources and residual solvent odor of printed matter. In particular, in the case of shrink film, this residual solvent is volatilized by heat at the time of fusing sealing and heating in the shrink tunnel, and it becomes odorous in the package. It is.

  In addition, the manufacturing method (for example, refer patent document 1) of a polyester resin foaming molded object, the masterbatch type manufacturing method (for example, refer patent document 2) of a polyester resin and its molded object, polyester-polyolefin which combined polyethylene terephthalate and polyolefin A broth copolymer and a production method thereof (for example, see Patent Document 3) have been proposed.

JP 2000-169613 A Japanese Patent Application No. 2000-205828 JP 2001-122955 A

  As described above, the polyethylene terephthalate-based shrink film has various excellent properties, but the raw material PETG resin is expensive, and it is inexpensive if recovered and used as a PET bottle or the like. However, it was unusable due to lack of fusing sealability. Furthermore, a residual solvent odor was generated in the package.

  The present invention solves the above problems, is free from environmental hormone contamination such as polyvinyl chloride shrink film and polystyrene shrink film, and has better gloss and transparency than polyethylene, shrink film and polypropylene shrink film. Provided a polyethylene terephthalate polyester shrink wrapping material having shrinkage characteristics of a vinyl chloride shrink film, and without using an expensive PETG resin or the like as a raw material. It is an object of the present invention to provide a polyethylene terephthalate-based polyester shrink packaging material having a fusing sealing property.

  Furthermore, there are no problems such as bad odor during work, work environment for health, danger of explosion, environmental pollution around the factory, CO2 reduction problem, wasteful use of solvent resources, etc. Another object of the present invention is to provide a polyethylene terephthalate-based polyester shrink wrapping material in which a residual solvent odor is not generated in the package by heat at the time of fusing and heating in the next shrink tunnel.

  As a result of diligent research to solve the above problems, the present inventors have found that polyethylene terephthalate used in packaging materials such as ordinary PET bottles and sheets is a linear structure with a narrow molecular weight distribution and when melted. The melt viscosity is low and free, and as a result, when the package is wrapped with a horizontal pillow wrapping machine and melted and sealed with a hot blade, the combined film is separated due to the tensile stress that wraps the package. There was found. As a result of further diligent research, the linear structure of the collected PET bottle is modified into a long-chain branched structure, so that the melt viscosity increases due to the shrinkage effect of the molecular chain, and the tensile stress during fusing sealing It was found that it solidified without leaving and could be sealed well. In addition, the present inventors have found that various problems caused by solvents can be solved by changing oil-based ink to water-based ink, and the present invention has been completed.

  That is, the polyethylene terephthalate-based polyester shrink wrapping material according to the present invention is characterized by comprising a polyethylene terephthalate-based polyester that has been printed with water-based ink on the back surface and modified to have a long-chain branched structure.

  In the present invention, since the polyethylene terephthalate polyester of a linear structure such as a recovered PET bottle is modified to a long-chain branched structure, the melt viscosity increases and the melt viscosity of the film increases at the time of fusing and sealing. It will surely melt and bond without leaving. Further, by using water-based ink, a residual solvent odor is not generated by heat at the time of fusing and sealing a shrink film or heat in the shrink tunnel.

  In the present invention, a polyethylene terephthalate polyester modified to have a long-chain branched structure is used. Polyethylene terephthalate polyester modified into this long-chain branched structure is obtained by mixing the collected PET bottle flakes and the polyethylene terephthalate having a linear structure of punched skeleton flakes after sheet molding with a binder and a catalyst and causing a melt reaction. Can be produced.

  That is, the polyethylene terephthalate-based polyester modified to have a long-chain branched structure contains 100 parts by weight of polyethylene terephthalate in a linear structure of a recovered polyethylene terephthalate bottle or a stamped skeleton flake after sheet molding, and 2 in the molecule as a binder. 0.1 to 2 parts by weight of a mixture of 0 to 100% by weight of a compound having 1 epoxy group and 100 to 0% by weight of a compound having at least 3 epoxy groups in the molecule, and 0 metal salt of an organic acid as a catalyst A mixture composed of 0.05 to 2 parts by weight can be obtained by a melt reaction at a temperature equal to or higher than the melting point of the polyethylene terephthalate.

  Recovered PET bottle flakes and stamped skeleton flakes after sheet formation absorb moisture in the air and leave a moisture content of 1,000 to 5,000 ppm when left in the air. In particular, since the recovered PET bottle flakes absorb as much as 10,000 ppm of moisture since it is finally washed with water, it is dried in advance with hot air or dehumidified air at 120 to 140 ° C. to a moisture content of 50 ppm or less. It is preferable.

  After mixing 100 parts by weight of this dried PET, 0.1 to 2 parts by weight of a binder, and 0.05 to 2 parts by weight of a catalyst with a Henschel mixer or the like, the mixture is put into an extruder and melted at a melting point or higher. The linear structure of recovered PET bottle flakes is modified into a long-chain branched structure by extruding.

  In addition, the undried recovered PET bottle flakes and the skeleton flakes after punching of the sheet molded product are put into an extruder having 2 or more vents, and the recovered PET bottle flakes or the like are melted, and -750 mmHg or more from the first vent. Moisture evaporated by high evacuation may be removed, a predetermined amount of binder and catalyst may be added after the second vent, and extrusion may be performed by melting reaction above the melting point.

  The compound having two epoxy groups in the molecule as the binder is aliphatic ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, hexamethylene diglycidyl ether, alicyclic hydrogenated bismuth. The compound containing at least one or more selected from the group of enol A · diglycidyl ether and aromatic bisphenol A · diglycidyl ether, and containing three or more epoxy groups in the molecule as the binder, Aliphatic trimethylolpropane / triglycidyl ether, glycerin / triglycidyl ether, epoxidized soybean oil, epoxidized linseed oil, heterocyclic triuricidyl isocyanurate, aromatic phenol novolac epoxy resin, cresol novolac epoxy Resin group It is preferably at least one selected et.

  As the binder, it is sufficient to use at least one of a compound having two epoxy groups and a compound having three epoxy groups in the molecule. Preferably, the compound having three epoxy groups has more branched structures than the compound having two epoxy groups, and the ratio can be selected as appropriate.

  The metal salt of an organic acid as the catalyst is a composite containing at least two or more selected from the group consisting of lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt, calcium salt, and manganese salt of stearic acid or acetic acid. It is preferable that

  For the binder and the catalyst, it is preferable to prepare a masterbatch and to add them, because a uniform melting reaction can be performed. The binder master batch is manufactured by kneading 95 to 98 parts by weight of polyethylene terephthalate having a linear structure such as recovered PET bottle flakes and 2 to 5 parts by weight of a binder with an extruder or the like. Similarly, the catalyst master batch is prepared by kneading 7 to 12 parts by weight of the catalyst into 88 to 93 parts by weight of polyethylene terephthalate having a linear structure.

  The resin that has been melt-reacted and modified in the extruder is formed into a film by a T-die or inflation method. The melting reaction temperature is suitably about 260 ° C. to 300 ° C. of the melting point, preferably 280 ° C. suitable for extrusion of PET. Subsequently, the film is stretched in two directions (biaxial stretching) or one direction (uniaxial stretching) while maintaining a predetermined stretching temperature. The stretching temperature is suitably from 80 to 180 ° C, and preferably from 100 to 160 ° C. The stretching ratio is preferably 1.5 × 1.5 times to 6.0 × 6.0 times, preferably 2.0 × 2.0 times to 5.0 × 5.0, as long as it is biaxially stretched. Double is more preferred. If it is uniaxial stretching, 1.5 to 6.0 times are preferred, and 2.0 to 5.0 times are more preferred.

  Shrink wrapping material is produced as described above, but when this shrink wrapping material is used for shrink labels such as shrink film used for shrink wrapping, PET bottles, etc., the back side is printed and used. To do. A water-based ink is used for this printing. For printing, gravure printing is preferable because it can reproduce details of the design, and gradation (gradation) is possible and photographic printing is possible.

  The solvent of the oil-based ink was methyl ethyl ketone (40%)-acetic acid ethyl ester (40%)-isopropyl alcohol (20%) latent heat of vaporization; (105.0 × 0.4) + (88.2 × 0.4) + Compared to (159.2 × 0.2) = 109.1 cal / g, the solvent of the water-based ink is water (70%)-ethanol (30%) latent heat of vaporization; (586.9 × 0.7) + As high as (199.2 × 0.3) = 470.7 cal / g, it requires 470.7 / 109.1 = 4.3 times the amount of heat to dry, compared to conventional oil-based inks.

  It is most preferable to raise the hot air temperature to give heat without reducing the printing speed. However, if the hot air temperature is raised, the temperature of the shrink film also rises, and heat is accumulated by passing through multiple printing units from the first color. Finally, there is a risk of shrinking. That is, in aqueous multicolor gravure printing of two or more colors, heat is gradually accumulated in the second color, the third color, and so on, and the temperature of the shrink film is gradually increased. Particularly in the case of a shrink film, when the temperature reaches about 70 ° C., partial shrinkage starts.

  In order to prevent this, in the printing unit comprising the printing process-drying process-cooling process, the capacity of the cooling process is increased from that of oil-based gravure printing, and the amount of heat given in the drying process of each color printing unit is increased. This can be done by completely erasing in the cooling process in the printing unit, not bringing heat to the next printing unit, and eliminating heat accumulation.

  Specifically, the printed surface is cooled with cold air and a cooling roll, and the opposite surface is coated with a cooling liquid, then blown with cold air to vaporize the cooling liquid, and rapidly cooled with the latent heat of evaporation. This can be done by erasing the amount of heat given by the printing unit. For example, a liquid of water (70%) + methanol (30%) is applied almost uniformly with a rubber roll, a molton roll, etc., and then the cooling capacity is improved by spraying cold air and evaporating latent heat (evaporation latent heat) by evaporation of the cooling liquid. Can be increased.

  As described above, in the present invention, a linear chain structure is melt-reacted with a binder and a catalyst while using recovered PET bottle flakes and the like that have recently advanced, and a tangled effect is obtained. The melt viscosity is increased by the above, enabling fusing and sealing, forming a shrink film by biaxial or uniaxial stretching after film formation, and applying water-based printing instead of conventional oil-based printing, A package without residual solvent odor can be obtained by heating the shrink tunnel.

  The biaxial extruder TEX-30 (L / D = 32, 2 vent holes, discharge amount 60Kg) manufactured by Nippon Steel Co., Ltd. was charged with 100 parts by weight of PET bottle flakes from Yono PET Bottle Recycle Co., Ltd. Water is removed from the first vent hole by vacuuming at -750 mmHg at a barrel set temperature of 260 ° C. From the second vent hole, 50 parts by weight of ethylene glycol diglycidyl ether having two epoxy groups (Epolite 40E manufactured by Kyoeisha Chemical Co., Ltd.) and trimethylolpropane triglycidyl ether having three epoxy groups ( A mixture with 50 parts by weight of Epolite 100MF manufactured by Kyoeisha Chemical Co., Ltd. was extruded by injecting 15 parts by weight using a metering pump.

  The strand coming out from the hole (diameter: 3.0 mmΦ) of the die was water-cooled and cut with a rotary cutter to produce a pellet. The obtained pellets were dried at 120 ° C. for 12 hours, and hermetically sealed in a moisture-proof bag made of paper / aluminum foil / polyethylene film to prepare a binder masterbatch.

  In addition, 100 parts by weight of PET bottle flakes from PET Bottle Recycling Co., Ltd., dried by hot air at 120 ° C. for 12 hours, and 2.5 parts by weight of lithium stearate were separately fed into an extruder TEX-30 manufactured by Nippon Steel Co., Ltd. Then, 2.5 parts by weight of sodium stearate and 5.0 parts by weight of calcium stearate were mixed with a tumbler mixer and then added.

  The barrel set temperature is 260 ° C, both the first vent hole and the second vent hole are extruded while evacuating -750mmHg, and the strand coming out from the hole of the die (diameter: 3.0mmΦ) is cooled with water. A pellet was prepared by cutting. The obtained pellets were dried at 120 ° C. for 12 hours and sealed in a moisture-proof bag made of paper / aluminum foil / polyethylene film to prepare a master batch of catalyst.

  100 parts by weight of PET bottle flakes from Yono PET Bottle Recycle Co., Ltd., dried at 120 ° C. for 12 hours, 6.0 parts by weight of binder masterbatch and 2.0 parts by weight of catalyst masterbatch were mixed with a Henschel mixer, A single-screw extruder manufactured by Hitachi Zosen Co., Ltd. was connected to this mixture by a twin screw extruder TEX-30 (caliber 30 mm, L / D = 32, 2 vent holes, discharge amount 60 kg / hr) manufactured by Nippon Steel Co., Ltd. Into the machine SHT-90 (caliber 90mm, L / D = 32, discharge rate 250Kg / hr), Nippon Steel Corporation twin screw extruder barrel set temperature 280 ° C, first and second vent hole vacuum degree- Extruded under conditions of 750mmHg, discharge rate 40Kg, barrel setting temperature 280 ° C, discharge rate 40Kg / hr of Hitachi Zosen Co., Ltd., width 4 by T-die method 0mm, it was formed into a film having a thickness of 135μm.

  This film was continuously subjected to a stretching machine (stretching temperature: 130 ° C.) and subjected to simultaneous biaxial stretching of length (3 times) × width (3 times) to produce a shrink film having a width of 1000 mm and a thickness of 15 μm.

  This shrink film is set in a 5-color gravure printing machine (FM-5S type) manufactured by Fuji Machine Co., Ltd., and water-based ink hydric PRP-401 manufactured by Dainichi Seika Kogyo Co., Ltd. is water (70%) and ethanol (30%). To adjust yellow (solid content 12%), red (solid content 12%), green (solid content 12%), blue (solid content 12%), black (solid content 12%) 5 colors were printed. The printing speed was set to 200 m / min, the same printing speed as oil gravure printing, and the temperature of hot air was increased from 60 ° C. to 120 ° C. for oil gravure printing.

  For cooling after drying, the printing surface is the same cold air and cooling roll as oil-based gravure printing, and the opposite surface is coated with water (70%) and methanol (30%) cooling liquid using a rubber roll and sprayed with cold air. The cooling capacity was increased and the heat given by the printing unit was erased in the unit. Thus, heat accumulation due to passing through the printing unit from the first color was eliminated, and the temperature of the film after drying of each printing unit was prevented from reaching 70 ° C. at which shrinkage started. Table 1 shows the film temperature immediately after the drying process of each printing unit. The temperature was measured using a radiation thermometer.

  Further, the state and printing of the shrink film after printing was observed with the naked eye. However, the shrink film was not shrunk, and the printing was free from occurrence of color misregistration and the like, and was a glossy and excellent cosmetic.

  Next, this printed shrink film was placed in a cup-shaped container (upper diameter 10 cm, lower diameter 7 cm, height 10 cm) made by polystyrene bead foam molding, and an L-shaped sealing machine VT-450 made by Kyowa Denki Co., Ltd. After using and overlapping and performing fusing sealing, shrinking was performed at a tunnel temperature of 135 ° C. using a shrink tunnel VS-500 manufactured by Kyowa Denki Co., Ltd. The seal strength of the fusing seal part of this shrink package and the residual solvent odor inside the package were evaluated.

The seal strength was about 0.8 kgf / 15 mm width, which was sufficient as the fusing seal strength of the shrink film. The seal strength was measured by cutting a film including a fusing seal part with a width of 15 mm, and sandwiching both ends with a chuck, and using a tensile tester STA-1150 manufactured by Orientec Co., Ltd., at a pulling speed of 100 mm / min.
Table 2 shows the fusing seal strength.

  The residual solvent odor was evaluated by breaking the shrink film of the package, and evaluating the residual solvent odor inside by a sensory test by five panelists. As a result, no residual solvent odor was felt in all five persons.

  In the same manner as in Example 1, a film having a width of 400 mm and a thickness of 75 μm was formed, and this was continuously applied to a stretching machine, and the film was stretched by 3.0 times a horizontal axis, and a stretched film having a width of 1000 mm and a thickness of 25 μm. Was made. The stretching temperature was 130 ° C. This stretched film was subjected to five-color aqueous gravure printing in the same manner as in Example 1.

  This printed film is cut into a uniaxial stretching direction of 230 mm × a non-stretching direction of 115 mm, folded back in the uniaxial stretching direction, overlapped at both ends, and heat-sealed with a stacking width of 3 mm, and a cylindrical shape with a diameter of 71 mmΦ × height of 115 mm A film was produced and folded to produce a label with a folding diameter of 112 mm. This label is put on a PET bottle (diameter 63 mmΦ x shoulder height 110 mm x overall height 160 mm) containing beverage (tea), and the tunnel temperature is 135 ° C using Kyowa Denki Co., Ltd. Shrink Tunnel VS-500. Shrinking was performed and the appearance was observed.

  As a result of the observation, the label is in close contact with the PET bottle, and the portion where the diameter of the upper part from the height of 110 mm to the shoulder gradually decreases (115 mm to 110 mm as the label portion) is also properly contracted and closely attached to the pitet. It was. Moreover, the cosmetics and gloss of printing were not impaired, and the solvent odor was not felt by the five panelists.

Claims (6)

A polyethylene terephthalate-based polyester shrink wrapping material comprising a polyethylene terephthalate-based polyester that has been printed with water-based ink on the back surface and modified into a long-chain branched structure. 2. The polyethylene terephthalate-based polyester shrink packaging material according to claim 1, wherein the water-based ink is printed by water-based gravure printing. The polyethylene terephthalate-based polyester having the long-chain branched structure is composed of 100 parts by weight of polyethylene terephthalate in the linear structure of the recovered polyethylene terephthalate bottle flakes or stamped skeleton flakes after sheet molding, and two in the molecule as a binder. 0.1 to 2 parts by weight of a mixture of 0 to 100% by weight of a compound having an epoxy group and 100 to 0% by weight of a compound having at least three epoxy groups in the molecule, and a metal salt of an organic acid as a catalyst 0.05 The polyethylene terephthalate-based polyester shrink according to claim 1 or 2, which is obtained by melting and reacting a mixture consisting of ~ 2 parts by weight at a temperature equal to or higher than the melting point of the mixed polyethylene terephthalate-based polyester. Packaging material. The compound having two epoxy groups in the molecule as the binder is aliphatic ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, hexamethylene diglycidyl ether, alicyclic hydrogenated bismuth. A compound containing at least one selected from the group of enol A · diglycidyl ether and aromatic bisphenol A · diglycidyl ether, and containing three or more epoxy groups in the molecule as the binder is aliphatic. Of trimethylolpropane / triglycidyl ether, glycerin / triglycidyl ether, epoxidized soybean oil, epoxidized linseed oil, heterocyclic triurisidyl isocyanurate, aromatic phenol novolac epoxy resin, cresol novolac epoxy resin Select from group Polyethylene terephthalate polyester shrink wrapping material according to claim 3, wherein the at least one element. The composite in which the metal salt of the organic acid as the catalyst contains at least two or more selected from the group consisting of lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt, calcium salt and manganese salt of stearic acid and acetic acid The polyethylene terephthalate-based polyester shrink packaging material according to claim 3. The polyethylene terephthalate-based polyester shrink packaging material according to claim 1, wherein the polyethylene terephthalate-based polyester shrink wrapping material is formed by a T-die method or an inflation method and stretched in two directions or one direction of a vertical direction and a horizontal direction.