KR20070034418A - flexible tube - Google Patents

Abstract

The present invention in the manufacture of a flexible tube consisting of a thin aluminum plate and a plastic material used for tube containers such as toothpaste, cosmetics, food, pharmaceuticals, etc., the laminated structure of the present invention is injection of the injection hole using an insert mold mold It is a laminated structure to prevent the damage (cracking) of the aluminum thin plate generated by high heat and high pressure during molding, and also minimizes the thickness of the aluminum thin plate in the longitudial seam of the tube body, thereby inducing high frequency induction heating and ultrasonic friction heat. It is a laminated structure to selectively apply the joint.

High Frequency Induction Heating, Ultrasonic Friction Heat, Flexible Tube, Tube Body

Description

Flexible tube

1 is a cross-sectional view of the circular joint of the flexible tube,

2 is a cross-sectional view of a laminated structure of a sheet according to the present invention;

3 is a cross-sectional view showing an embodiment constituting the inner blocking layer of the sheet according to the present invention;

Figure 4 is a cross-sectional view showing an embodiment in which the polyethylene resin extrusion coating on the tube body bonded to the sheet according to the present invention.

<Explanation of symbols for main parts of drawing>

a: tube body b: circular joint of tube body

c: over-lap d: extrusion coating of polyethylene resin

e: boundary between injection resin and tube

10: inner surface layer 20: first adhesive resin layer

30: internal barrier layer 40: second adhesive resin layer

50: outer surface layer 301: aluminum thin layer

302: adhesive layer 303: plastic film layer

304: adhesive layer 305: adhesive plastic film layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to sheet structures in the form of flexible tubes, which are commonly used for filling paste products, and methods of manufacturing and circular joining of tube bodies. The tube body of a conventional flexible tube is composed of an inner and an outer heat adhesive layer, an adhesive resin layer and an inner barrier layer, and the base of the inner barrier layer is laminated with a single layer of aluminum to prevent ultraviolet rays, gas permeation, and moisture permeation. Used for the purpose of

As shown in Fig. 1, in the sheet structure of the flexible tube, the inner barrier layer was laminated with a thin aluminum sheet alone, and a plurality of polymers were laminated to the inner surface layer 10 (polyethylene) / first adhesive resin layer ( 20) A flexible sheet in which (ethylene acrylic acid copolymer) / inner blocking layer 30 (aluminum thin plate) / second adhesive resin layer 40 (ethylene acrylic acid copolymer) / outer surface layer 50 (polyethylene) is laminated It is commonly used.

The circular joint (b) method of the tube body (a) includes an external heating method using a heating heater bar and an internal heating method using high frequency induction heating or ultrasonic frictional heating, but are generally bonded by an internal heating method. In addition, the sealing method after filling the contents to seal the inner surface layer by a high frequency induction heating method or hot-air (hot-air) to exhibit the function of the tube container.

As described above, the high frequency induction heating bonding in the circular joining of the tube body heats the aluminum sheet, which is a metal layer, to melt the adhesive resin layer and the polyethylene film, which is a heat-adhesive layer, and press-bonds the tube body by heating temperature, time and pressure. In general, the thickness of the laminated base material is determined in consideration of the adhesive strength.

Ultrasonic frictional heat bonding, on the other hand, generates a frictional heat by applying ultrasonic vibration to the polyethylene interface of the inner and outer surface layers, and at the same time, a constant pressure must be applied to obtain adhesive strength by pressing and bonding.

In the injection mold of the opening using the tube body and the insert mold mold, the injection pressure of the injection molding using polyethylene resin is 28-50 kgf / cm 2, and the temperature of the injection resin is 260-310 ° C. When the inner surface layer of the melt is integrated by the injection heat, there is a problem that damage (crack) of the aluminum thin plate is caused by the injection pressure. In other words, the polyethylene surface of the inner surface layer bonded to the aluminum sheet and the ethylene acrylic acid copolymer resin of the adhesive resin layer have a softening point of 100 ° C. or less, which leads to loss of rigidity due to the heat of the injection resin and cracking of the aluminum sheet due to the injection pressure. have.

As described above, in insert molding molds, it is common to solve the problem by the strength (heat treatment change, alloy) and thickness of the aluminum sheet as an example for preventing damage to the aluminum sheet. As an example of an insert mold mold for producing a plurality of tubes, as in the case of Korea Patent Publication No. 10-0363996 registered a mold mold structure for producing a plurality of tubes, this is a plurality of tube molding for the purpose of mass production It is a structure commonly used to manufacture tube containers using mold molds.

In the sheet structure of the tube body used in the manufacture of a conventional flexible tube container, the phenomenon as shown in Table 1 can be confirmed by comparing the bonding relationship between the injection pressure and the tube body with the thickness of the aluminum sheet.

<Table 1>

The results of <Table 1> show that the high frequency induction heating bonding does not damage the aluminum sheet in the welding method of the tube body, but in the case of the ultrasonic bonding, cracking occurs due to the thickness difference (BCD type) of aluminum. In case of type A, the cut portion exposed to the outer layer was precipitated in an aqueous solution of sodium hydroxide, and as a result, it was confirmed that the resin film layer was partially formed on the cut surface of the sheet and the aluminum sheet was eroded.

In the tube body welding as described above, in order to obtain a constant bond strength (0.31kg) in the state where the upper and lower overlapping portions of the joint are given 2 mm overlap, the joint pressure should be pressurized to 3.0 kgf / cm2 level, and the compression ratio is 20 to 30%. Maintaining this level can prevent leakage and achieve a certain burst strength.

In addition, in the production method using a plurality of insert mold molds for the purpose of mass production as shown in Table 1, it can be seen that cracks are generated due to the injection pressure as shown in Table 1 by the strength, or thickness, of the aluminum sheet. . In other words, the polyethylene of the inner surface layer laminated with the aluminum sheet and the ethylene acrylic acid copolymer of the first and second adhesive resin layers have a reduced strength due to the softening phenomenon caused by the injection temperature during injection molding, and thus the thermal transfer of the injection resin of the tube body. On the boundary line (e) of the part, it can be confirmed that the aluminum sheet is cracked by the injection pressure.

As described above, the flexible tube is composed of a thin aluminum sheet as an inner barrier layer and a plurality of polymers laminated, and is an example of a tube for improving chemical resistance, bending stability, gas barrier, moisture barrier, and the like. 1991-08844 (Application No. 1984-0001766) discloses multilayer flexible substrates in the form of flexible tubes commonly used for filling paste-like products and the use of these substrates.

In addition, Utility Model Publication No. 2004-0348800 filed by the present applicant discloses a flexible tube sheet structure for the ultrasonic welding method.

In the case of forming a gas barrier layer using a single layer of aluminum thin plate, it can be seen that there are many problems in storage resistance during the manufacturing process due to the change of injection molding and welding method, which adversely affects productivity and increases production cost. To provide them.

The present invention is suitable for mass production using a plurality of insert mold molds in the manufacture of a flexible tube laminated with a thin aluminum sheet and a plastic substrate, and provides a single sheet capable of high frequency induction heating bonding and ultrasonic friction heat bonding in a welding method. It is. In the fabrication of the tube using the sheet, a sheet having a laminated structure suitable for preventing the cracking of the aluminum sheet in the bonding process and the injection molding process, satisfying the gas barrier effect which is the highest object of laminating the aluminum sheet, and suitable for storage resistance To make it available.

In order to achieve the above object, the flexible tube sheet of the present invention is normally joined by an internal heating method in a tube body joining process, so that high frequency induction heating joining and ultrasonic friction heat joining are possible. The present invention provides a sheet having a laminated structure that not only prevents cracking of an aluminum thin plate that is devoted to the outside, but also prevents cracking of an aluminum sheet due to injection pressure due to the shape of a mold mold in injection molding.

The laminated structure of the sheet for realizing the object of the present invention is a multi-layered sheet structure having two outer surface layers and a plurality of inner blocking layers, which sheet structure is shown in Fig. 2 above to be suitable for circular bonding. Similarly, the stacking order of the sheets traps the stacking structure in the order of the inner surface layer 10 / the first adhesive resin layer 20 / the inner blocking layer 30 / the second adhesive resin layer 40 / the outer surface layer 50.

The inner blocking layer 30 of the flexible tube of the present invention is an aluminum thin film layer 301 / adhesive layer 302 / plastic film layer 303 / adhesive layer 304 / adhesive, as shown in Figure 3 The plastic film layer 305 is made of a multilayer composite substrate sequentially laminated using a dry lamination method. In bonding the aluminum thin film layer 301 and the plastic film layer 303, the peel strength is maintained to be 8 N / 15 mm or more.

The action of the plastic film layer 303 laminated on the inner blocking layer 30 is in the circular bonding (b) of the tube body (a), due to the ultrasonic welding pressure (2.5 ~ 3.5kgf / ㎠) of the aluminum sheet In order to prevent cracking and softening of the inner surface layer and adhesive resin layer due to heat of injection resin (280 ~ 310 ℃) during injection molding, aluminum sheet by injection pressure is formed on the joint boundary between injection resin and tube body (e). It laminates for the purpose of a reinforcement material in order to prevent this cracking phenomenon.

In order to realize this, the basic physical property of the plastic film layer 303 is ideally laminated with a film having a tensile strength of 1,000 kg / cm 2 or more, an elongation of 130% or less, and a softening point of 150 ° C. or more. It is preferable to selectively use the film which satisfy | fills phosphorus conditions.

<Table 2>

The action of the adhesive plastic film layer 305 laminated on the inner blocking layer 30 is the adhesion between substrates (bonding by the plastic film layer 303 and the dry lamination method, bonding by the outer surface layer 50 and the extrusion laminate) ), Due to frictional heat generated during ultrasonic welding, to prevent adhesion deterioration due to the difference in thermal strain stress between substrates (dilamination phenomenon), and to apply a gravure printing method to form a printed layer. In order to achieve this, the adhesive plastic film layer 305 may preferably use a polyethylene film having a softening point / melting point higher than that of the adhesive resin 40. For this purpose, in the present invention, a linear low density polyethylene (LLDPE.C-6) film, or A low density polyethylene (LDPE) film is laminated.

The adhesive layer 302.304 of the internal barrier layer is characterized by using a polyurethane-based adhesive having a heat resistance at 240 ℃ or more. This is to prevent the adhesive separation (delamination phenomenon) by heat of the injection resin during injection molding, and also to prevent the adhesive separation (delamination phenomenon) by the temperature of the heating element (190 ℃) during the high frequency induction heating bonding of the tube body. to be.

The inner surface layer 10 and the outer surface layer 50 of the present invention preferably use linear low density polyethylene (LLDPE-C6) among polyethylene resins excellent in heat-sealing strength and excellent in oil resistance and chemical resistance.

In addition, in order to diversify the printing method, the polyethylene laminated on the outer surface layer 50 is preferably laminated with an inflation film obtained by co-extrusion of high density polyethylene and linear low density polyethylene in order to maintain dimensional stability.

In the first and second adhesive resin layers 20 and 40 of the present invention, it is preferable to use a resin having a lower melting point than the polyethylene of the outer surface layers 10 and 50. In this case, the softened adhesive resin is pushed out by the pressure at the time of circular joining of the tube to form the molten resin and the resin film of the inner and outer surface layers 10 and 50. This is to allow the resin film to surround the cut portion and to prevent erosion of the aluminum sheet.

As the method of extrusion bonding the adhesive resin, a method of extrusion bonding with an inflation film and a method of coextrusion and coating a bonding resin and a polyethylene resin may be applied. The extrusion bonding resin of the aluminum thin plate layer 301 and the polyethylene of the inner surface layer 10 is made of an ethylene acrylic acid copolymer adhesive resin 20 so as to exert an ionic bond (hydrogen bond) by high temperature. In addition, in order to bond the polyethylene film of the adhesive plastic film layer 305 and the polyethylene of the outer surface layer 50, polyethylene resin can be used to exhibit melt bonding at high temperatures.

As described above, the present invention relates to a laminated structure of a sheet for preventing cracking of an aluminum thin plate in the joining and injection molding of a tube body in order to manufacture a flexible tube in which an aluminum thin plate and a plastic are laminated.

Hereinafter, the configuration and effects of the present invention will be described in more detail with reference to the following Table 3, but the scope of the present invention is not limited to the following examples.

<Table 3>

In the above embodiment, the internal barrier layer is laminated by a dry laminate method, and the polyethylene inflation films (LLDP, C6) are extruded and laminated on the inner and outer surface layers. In the embodiment of <Table 3>, the plastic film layer 303 formed in the internal barrier layer exhibits a function of preventing cracking of the aluminum thin plate and improving the restoring force of the tube.

According to the analysis of productivity and manufacturing cost among Example ABC, Example B can be selected as the best lamination structure.In another method, the inner barrier layer is laminated by dry lamination method, and the inner and outer surface layers are coextruded with adhesive resin and polyethylene resin. Lamination can also be carried out. As in the embodiment, the sheet of the final flexible tube had a gas barrier effect of 0.000 cm 3 / m 2, 24hrs, atm and a moisture permeability of 0.00g / m 2, 24hrs.

In another embodiment, the internal barrier layer 30 is laminated by a dry lamination method as in the laminated structure of <Table 3>, and the internal surface layer 10 and the aluminum thin layer layer 301 are extruded and laminated with ethylene acrylic copolymer resin. And bonded by high frequency induction heating or ultrasonic frictional heat, and selectively apply polyethylene and polypropylene resin to the surface of the adhesive plastic layer 305 with a thickness of 100 to 150 μm using an extrusion coating machine as shown in FIG. d) and cut to a practical standard according to the drawing direction. The extruded-coated tube body completes the processes of forming the opening, bonding the lead seal, and sealing the cap to complete the tube.

In the laminated structure, the thickness of the adhesive plastic layer 305 is most ideally laminated at a thickness of 300 to 350% of the thickness of the laminated aluminum thin film layer 301 / adhesive layer 302 / plastic film layer 303. to be. This is for the purpose of preventing erosion of the aluminum thin plate cut portion by melting the interface of the adhesive plastic layer to form a resin film on the sheet cut portion.

The flexible tube constructed and operated as described above is suitable for mass production using a plurality of insert mold molds, and provides a single sheet capable of high frequency induction heating bonding and ultrasonic friction thermal bonding in a welding method. This minimizes the thickness of the aluminum thin plate to improve the restoring force, and also to prevent the degradation of the contents retention due to the pinhole generation of aluminum due to bending of the tube body.

In particular, it is possible to significantly reduce the use of expensive aluminum sheet in terms of manufacturing cost while ensuring the same performance in terms of functional aspects of the conventional flexible tube sheet (aluminum thin sheet: 40 μm) and the sheet according to the present invention, which are capable of ultrasonic friction thermal bonding. It provides an economic advantage to reduce the cost.

Claims (8)

An inner surface layer forming an inner surface of the flexible tube, an outer surface layer forming an outer surface, an inner blocking layer preventing gas permeation into the tube, and first and second adhesive resin layers adhering the inner and outer surface layers and the inner blocking layer. In the flexible tube of the sheet consisting of, The inner surface layer and the outer surface layer are laminated with polyethylene, The resin of the first adhesive layer is laminated ethylene acrylic acid copolymer, The resin of the second adhesive layer is laminated ethylene copolymer or polyethylene, The inner blocking layer is a flexible tube of a sheet, characterized in that configured by sequentially laminating an aluminum thin plate layer, an adhesive layer, a plastic film layer, an adhesive layer, and an adhesive plastic film layer. The method of claim 1, A flexible tube of a sheet which is joined by high frequency induction heating or ultrasonic frictional heat for joining the flexible tube. The method of claim 1, The adhesive plastic film layer of the inner blocking layer is a flexible tube of a sheet, characterized in that laminated with an inflation film of linear low density polyethylene, or low density polyethylene. The method of claim 1, The plastic film layer of the inner barrier layer is a flexible tube of a sheet, characterized in that any one of a biaxially stretched polyester film, biaxially stretched nylon film, biaxially stretched polypropylene film. An inner surface layer forming an inner surface of the flexible tube, an outer surface layer forming an outer surface, an inner blocking layer preventing gas permeation into the tube, and first and second adhesive resin layers adhering the inner and outer surface layers and the inner blocking layer. In the flexible tube of the sheet consisting of, The inner surface layer was laminated with polyethylene, The outer surface layer is laminated with polyethylene or polypropylene by extrusion coating, The resin of the first adhesive resin layer is laminated with an ethylene acrylic acid copolymer, The inner blocking layer is a flexible tube of a sheet, characterized in that the laminated aluminum thin film layer, the adhesive layer, the plastic film layer, the adhesive layer and the adhesive plastic film layer sequentially laminated. The method of claim 5, A flexible tube of a sheet which is joined by high frequency induction heating or ultrasonic frictional heat for joining the flexible tube. The method of claim 5, And the adhesive plastic film layer of the inner blocking layer is laminated with an inflation film of linear low density polyethylene or low density polyethylene. The method of claim 5, The plastic film layer of the inner barrier layer is a flexible tube of a sheet, characterized in that any one of a biaxially stretched polyester film, biaxially stretched nylon film, biaxially stretched polypropylene film.

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