JP2009125767A - Method of manufacturing container which is easily broken and opened - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a weakened part with a breaking strength uniform as on the whole as possible even when burrs are present in the portion to be a weakened part when forming the weakened part in the boundary between the container body and an enclosed body by emitting a laser beam as to the container made of polyester resin which is easily broken and opened. <P>SOLUTION: While the container 6 is relatively rotated not less than six times to the irradiation of the laser beam from a laser beam gun 11 as detecting the burrs with a placement meter 12 to the portion to be the weakened part in the boundary between the container body 2 and the enclosing body 3, the laser is emitted at the energy density of 1.41-2.02 J/mm<SP>3</SP>. In sections where the burrs are detected with the displacement meter 12, a groove to be the weakened part 4 is formed in the boundary between the container body 2 and the enclosed body 3 by emitting the laser beam by increasing the energy density more than the above value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a so-called twist-off in which a container main body having an opening and a sealing body that seals the opening of the container main body are integrally formed via a weakly breakable portion formed at the boundary between the two. Regarding a container that can be easily opened by breakage, called a container or a snap-off container, in particular, a polyester resin container having a burr at the boundary between the container body and the sealed body is irradiated with a laser at the boundary between the container body and the sealed body. The present invention relates to a method for forming a weakened portion that is easily broken.

The container main body having the opening and the sealing body for sealing the opening of the container main body are integrally formed through a weakly fragile portion formed at the boundary between the two, and the sealing body is picked and twisted. Or opening the opening of the container body by breaking the weakened part and detaching the sealing body from the container body by pushing down the sealing body. Conventionally, according to the following patent document 1 relating to the application of the present applicant, a weakened portion that is easily broken is formed by irradiating a laser at a boundary between a container main body and a sealed body of a container made of polyester resin. It is publicly known.
Japanese Patent No. 3929065

  By the way, in Patent Document 1 described above, as a specific method for forming the weakened portion by irradiating the boundary between the container main body and the sealed body, the container is rotated about the axis of the container as the rotation axis. A method of irradiating a laser having an output of 1.0 to 100 W and a light diameter of 0.1 to 5 mm while rotating the container once in one second is disclosed. If the rotating container vibrates during the laser irradiation, the laser irradiation position in the container shifts, and the weakened part is not irradiated with the laser. There is a possibility that an excessively irradiated portion is formed, the rupture strength of the entire weakened portion is uneven, and it is difficult to break the portion where the laser is not irradiated, and the portion is excessively irradiated.

  On the other hand, when a container is manufactured from a synthetic resin such as a polyester resin, for example, an elliptical parison extruded from an extruder is sandwiched between two molds each having a plurality of container molds, and a vacuum molding method or a blow process is performed. When molded by the molding method, burrs may remain in the container at the joint of the two-part molds. However, in such a container with a rupture that easily breaks open, the part that becomes a weakened part (container body and sealing) When the weakened part is formed by the laser irradiation as described above, the weakened part is insufficiently formed in the burr part, and the weakened part in the part. Since it becomes difficult to be broken, the container may be difficult to open.

  An object of the present invention is to solve the above-described problems. Specifically, for a polyester resin container that is easily opened by breakage, a weakened portion is formed at the boundary between the container body and the sealed body by laser irradiation. It is an object of the present invention to make it possible to form the weakened portion with as uniform overall breaking strength as possible even if burrs exist in the portion that becomes the weakened portion.

In order to solve the above-described problems, the present invention provides a container body having an opening and a sealing body that seals the opening of the container body via a weakly fragile portion that is formed at the boundary between the two. It is easy to break by irradiating a laser at the boundary between the container body and the sealing body for a container having a burr at least at the boundary between the container body and the sealing body. As a method for forming a weakened portion, while rotating the container relative to the laser irradiation more than 6 rotations, with respect to the portion that becomes the weakened portion at the boundary between the container body and the sealed body, while detecting the burr by a displacement meter, by irradiating a laser at an energy density of 1.41~2.02J / mm ^3, at the section where displacement meter detects the burr, by increasing the energy density than laser Irradiate And forming a groove that becomes a weakened portion at the boundary between the container main body and the sealed body, and lowering the intrinsic viscosity of the resin without changing the density of the resin at the groove and its peripheral part, It is characterized in that the ratio between the maximum value and the minimum value of the amount of decrease in intrinsic viscosity at that portion is 1.5 or less.

According to the method for manufacturing a container with an easy break opening according to the present invention as described above, a weakened portion is irradiated with a laser to form a groove due to resin sublimation. By reducing the intrinsic viscosity of the resin without changing the density, the portion becomes brittle, and the weakened portion is remarkably easily broken. Further, even if the rotating container vibrates during laser irradiation and the laser irradiation position is shifted momentarily, while the container is rotated more than 6 times, 1.41 to 2.02 J / By irradiating the laser with an energy density of mm ³ , the laser irradiation to the weakened portion is made uniform so that the maximum amount of decrease in the intrinsic viscosity in the groove that is the weakened portion and the surrounding portion The minimum ratio can be 1.5 or less, and the weakened portion can be formed with a uniform uniform breaking strength.

And even if there is a burr in the weakened part at the boundary between the container body and the sealed body, while the laser is being irradiated, the displacement meter In the section where burrs are detected, the energy density is increased from that of the previous energy density (1.41 to 2.02 J / mm ³ ), and the laser is irradiated, so a weakened portion is sufficiently formed even in the burrs. Thus, the weakened portion can be formed with a uniform breaking strength as a whole.

When a weakened part is formed at the boundary between the container body and the sealed body by laser irradiation, even if there are burrs in the weakened part, the entire weakened part is as much as possible. As shown in the following examples as the best mode, the purpose of enabling formation with a uniform breaking strength can be easily broken by irradiating the boundary between the container body and the sealed body. As a method for forming the weakened portion, the container is displaced relative to the portion that becomes the weakened portion at the boundary between the container main body and the sealing body while the container is rotated more than six times relative to the laser irradiation. While detecting burrs, irradiate the laser at an energy density of 1.41 to 2.02 J / mm ³ and increase the energy density to irradiate the laser in the section where the displacement meter detects burrs. You By forming a groove that becomes a weakened portion at the boundary between the container body and the sealing body, and reducing the intrinsic viscosity of the resin without changing the density of the resin at the groove and its peripheral portion. This is realized by making the ratio of the maximum value and the minimum value of the decrease amount of the intrinsic viscosity in the part to be 1.5 or less.

  In addition, about the polyester resin used as the material of the container in the present invention, for example, as an acid component, adipic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4-biphenylcarboxylic acid, succinic acid, succinic acid, glutar It consists of one or more selected from acids, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecadioic acid, trans-1,4-cyclohexanedicarboxylic acid, and isophthalic acid. Selected from methylene glycol (1,3-propanediol), tetramethylene glycol (1,4-butanediol), pentamethylene glycol, hexamethylene glycol, 1,4-hexanedimethanol, bisphenol A, spiroglycol 1 or 2 or more types A polyester resin or a copolymerized polyester, the (preferably 0.8~1.3dl / g) intrinsic viscosity 0.8~1.5dl / g polyester resins suitable for blow molding.

  One example of the method for producing a container having an easy break opening according to the present invention, which is carried out using the polyester resin as described above, will be described below.

  In the production method of this example, as the polyester resin as the material of the container, the acid component is terephthalic acid, and the glycol component is 4 mol of 1,4-cyclohexanedimethanol or bisphenol A with respect to 96 mol% of ethylene glycol. % Added polyester resin. This polyester resin has an intrinsic viscosity of about 1.0 dl / g, does not draw down during direct blow molding, has a melting point of about 235 to 245 ° C., and is 10 to 30 ° C. than a general polyester resin. Since it is low and can be molded at a low temperature, rapid cooling is possible. Furthermore, since the crystallization rate is low, the moldability is good.

  In the case of producing a container from such a polyester resin, in this example, first, the molten polyester resin is extruded from the nozzle of the extruder as an elliptical parison having a major axis of about 140 mm and a thickness of about 0.8 mm. Next, this parison is blow-molded by sandwiching it between two molds in which three container molds are formed, so that first, three container intermediate products with the upper end opened (the neck upper part is unmolded). The container body).

  Next, each container intermediate product is filled with content liquid (beverages, chemicals, etc.) from the upper opening, and then the upper end part (unformed neck upper part) of each container intermediate product is formed into three container molds The container main body for storing contents and the sealing body for sealing the container main body are integrally formed by forming the top plate portion of the container main body and the sealing body above the top plate portion between the two split molds. After forming into three formed containers, each container taken out from the mold is irradiated with a laser at the boundary between the container main body and the sealed body, so that the weakened part (part to be broken) ) Is formed.

  In the case of the present embodiment, as shown in FIGS. 1 and 2, the container body 2 has a cylindrical body 22 formed upward from the circular plate-shaped bottom 21 in the case of this embodiment. A neck portion 24 having a smaller diameter than the trunk portion 22 and slightly bulging at the center is formed through a shoulder portion 23 inclined from the upper end of the trunk portion 22, and a top plate portion 25 is formed inward from the upper end of the neck portion 24. Is formed.

  Moreover, in the sealing body 3, as a sealing part which seals the opening part of the container main body 2, the small diameter cylindrical part 31 which stands | starts up from the top-plate part 25 of the container main body 2, the large diameter cylindrical part 32, and the upper end of the upper part The conical portion 33 is integrally formed, and the flat plate portion 34 that is a knob portion when the container is opened is integrally formed so as to straddle the cylindrical portion 32 and the conical portion 33 of the sealing body 3. Has been.

  In the container 1 as described above, when the intermediate product of the container is formed by being sandwiched between the two molds, a burr 5 is formed at a portion that becomes a joint between the molds. 3 is left in the container 1 in the vertical direction so as to cross the boundary between the container body 2 (top plate part 25) and the sealing body 3 (small diameter cylinder part 31) so as to extend downward from the three flat plate parts 34.

  As such, the container body 2 and the sealing body 3 are integrally formed and the container 1 having the burr 5 is present at the boundary between the container body 2 and the sealing body 3, that is, the top plate portion of the container body 2. As shown in FIG. 1, a laser (carbon dioxide laser light) is irradiated by a laser gun 11 to the lower end of the small-diameter cylindrical portion 31 of the sealing body 3 at the inner end of the sealing body 3. A weakened portion 4 that is easy to break is formed on the boundary of, so as to form an annular shape when viewed from above.

  In the polyester resin container 1 in which the container main body 2 and the sealing body 3 are integrally formed through the weakened portion 4 as described above, the flat plate portion 34 of the sealing body 3 is picked with a fingertip and twisted or pushed down. Thus, the weakened portion 4 that connects the container body 2 and the sealed body 3 is broken, whereby the sealed body 3 is separated from the container body 2, so that the sealed portion of the sealed body 3 (the small diameter cylindrical portion 31 and the cylindrical portion). 32 and the conical portion 33), the opening of the container body 2 (inside the top plate portion 25) is opened.

  In the production of a container having an easy break opening as described above, in the case of forming the weakened portion 4 that is easily broken by laser irradiation, in the method of this embodiment, the parison is sandwiched between molds and blow molded (direct blow). The container body 2 (the top plate portion 25) and the sealing body 3 (the molding body) are molded using the mold used when the upper neck portion of the container intermediate product is molded into the top plate portion 25 and the sealing body 3. By making the mold bite into the boundary portion with the small-diameter cylindrical portion 31), the portion is made a thin wall portion thinner than the wall thickness obtained by normal blow molding. The laser is irradiated.

  In this way, a mold is digged into the boundary between the container body 2 and the sealing body 3 to form a thin wall portion sinking inward from the upper surface of the top plate portion 25, and then a laser is irradiated toward the thin wall portion. By doing so, the laser to be irradiated is irradiated at an angle of 45 ° to 60 ° with respect to the axial direction (vertical direction) of the container so as not to interfere with the laser irradiation at such an angle. In addition, both sides of the lower end of the flat plate portion 34 of the sealing body 3 are shaped to be cut at an angle of 45 ° to 60 ° with respect to the axial direction of the container. The laser tilt angle may be any angle as long as the laser reaches the weakened portion 4.

  By the way, about the weakening part 4 formed in the boundary of the container main body 2 and the sealing body 3, while forming a groove | channel so that it may become annular | circular shape seeing from upper direction by irradiation of the above lasers, The peripheral part is a resin whose intrinsic viscosity is lowered without changing the density of the resin, and the part is made brittle. Such a weakened part 4 is made uniform over the entire annular shape. In the method of this example, the laser is irradiated under specific conditions as described below so that the film can be formed with a sufficient breaking strength.

  That is, in the method of the present embodiment, a displacement gauge 12 that detects the presence of a burr 5 by laser irradiation is provided in addition to a laser gun 11 that emits laser, and the container 1 is irradiated by laser irradiation from the displacement gauge 12. While detecting the presence / absence of the burr 5 and the height of the burr 5 present in the portion that becomes the weakening part 4 of the light source, the presence / absence of the burr 5 detection signal from the displacement meter 12 and the signal of the burr 5 height are synchronized. In addition, the energy density of the laser (carbon dioxide laser) irradiated from the laser gun 11 is changed.

Specifically, while the container is rotated (spinned) by an appropriate means at a rotational speed of 6 times / sec or more (preferably 6 to 9 times / sec) with the central axis of the container as the rotation axis. While detecting the burr 5 by the displacement meter 12, the laser is irradiated so that the energy density of the laser irradiation per unit volume in the portion irradiated with the laser is 1.41 to 2.02 J / mm ³ (for example, 7-10W output, laser period of 100μsec or more and laser spot diameter of 200-400μm is irradiated for 1 second), and in the section where burr 5 is detected, it is proportional to burr 5 height The laser is irradiated to increase the energy density.

The energy density of laser irradiation is defined by (laser output × laser irradiation time) ÷ (peripheral length of weakened portion × laser spot diameter × container wall thickness). At 10 W, when the laser spot diameter is 300 μm, the laser irradiation time is 1 second, the container thickness is 0.75 mm, and the diameter of the weakened portion is 7 mm (perimeter is 7 mm × 3.14), When the energy density is calculated, the energy density when the laser output is 7 W is 1.41 J / mm ³ , and the energy density when the laser output is 10 W is 2.02 J / mm ³ .

While rotating the container 6 times or more as described above, the displacement meter detected the burrs by irradiating the laser at an energy density of 1.41 to 2.02 J / mm ³ while detecting the burrs with the displacement meter. In the section, as a specific example of the method of the present embodiment in which the laser is irradiated with the energy density increased more than that, for the container 1 having a wall thickness of 0.75 mm and a weakened portion diameter of 7 mm, While rotating (spinning) the container at a rotation speed of 6 times / sec, a laser spot diameter of 300 μm is irradiated for 1 second at an output of 8 W, and in the section where the displacement meter detects burrs, for example, If the thickness of the part is double, when the energy density is increased according to the height of the burr, such as doubling the energy density of the laser irradiation, the weakened part is the whole including the burr part. A groove having a remaining thickness of about 0.25 mm was formed in a uniform state.

When the intrinsic viscosity of the resin at the groove and its peripheral portion was measured along the circumferential direction of the annular weakened portion where the groove was formed, the intrinsic viscosity of the resin was 0.85 dl / g on average. , 15% lower than the original intrinsic viscosity. Further, at the place where the intrinsic viscosity was reduced most, it was 0.82 dl / g (the amount of decrease in the intrinsic viscosity was 0.18 dl / g), and at the place where the intrinsic viscosity was not lowered most, 0.88 dl / g ( The decrease amount of the intrinsic viscosity was 0.12 dl / g), and the ratio of the maximum value and the minimum value of the decrease amount of the intrinsic viscosity was 0.18 / 0.12 = 1.5. In addition, about the density of resin, it was hardly changing from the value before laser irradiation, and the value of the non-crystallized state of 1.38 g / cm < ³ > or less was exhibited.

  As described above, the weakened portion is formed so that the intrinsic viscosity of the resin at the groove and its peripheral portion is reduced, and the ratio between the maximum value and the minimum value of the reduced amount of the intrinsic viscosity of the resin is 1.5 or less. In addition, according to the container having a break opening easily according to the method of the present embodiment, a groove is formed in the weakened portion and the wall thickness is thinned, and the intrinsic viscosity of the resin is reduced while the resin density remains unchanged. Since the resin is brittle, the weakened part can be easily broken by twist-off or snap-off operation that twists or pushes down the sealing body, and the amount of decrease in the intrinsic viscosity of the resin in the weakened part is reduced. Since the ratio between the maximum value and the minimum value is 1.5 or less, the weakened portion can be broken uniformly throughout the entire circumference, and as a result, it is weakened smoothly with a small force of 70 to 80 N · cm. Easy to open the container by breaking the part Door can be.

  As mentioned above, although one Example of the manufacturing method of the container with easy break opening of this invention was described, the method of this invention is not limited only to the above Examples, For example, the part used as a weakening part Is not limited to the method of biting the mold as shown in the above embodiment, and a method of moving a part of the mold upward and extending it is also possible. In some cases, the thin wall portion may be omitted.

  In addition, as for rotating the container during laser irradiation, it is only necessary to rotate the container relative to the laser irradiation. In addition to the method of rotating (spinning) the laser irradiation, the laser irradiation may be moved around the fixed container, and the rotation speed of the container during the laser irradiation is shown in the embodiment. The rotation speed is not limited to 6 rotations / sec or more, and may be a slower rotation speed. In such a case, laser output is performed so that the laser is irradiated with a predetermined energy density while rotating 6 rotations or more. Needless to say, it can be changed as appropriate.

The front view which shows the state which is irradiating the laser with respect to the rotating container in the method of this invention. The side view which shows the state seen from the side of the container shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container where break opening is easy 2 Container body 3 Sealed body 4 Weakened part 11 Laser gun 12 Displacement meter

Claims (1)

A container main body having an opening and a sealing body that seals the opening of the container main body are integrally formed via an easily breakable weakening formed at the boundary between the two, and at least the container main body and the sealing body As a method for forming a weakened part easily breakable by irradiating a laser to the boundary between the container main body and the sealed body, a container made of polyester resin having a burr at the boundary is used for laser irradiation. On the other hand, while relatively rotating the container 6 or more times, while detecting a burr with a displacement meter for the portion that becomes the weakened portion at the boundary between the container main body and the sealed body, 1.41-2. In the section where the displacement meter detects burrs by irradiating the laser with an energy density of 02 J / mm ³ , weakening the boundary between the container body and the sealed body by irradiating the laser with an increased energy density. Department and In addition to reducing the intrinsic viscosity of the resin without changing the density of the resin in the groove and the surrounding area, the maximum value and the minimum value of the decrease amount of the intrinsic viscosity in the part are formed. The ratio of the ratio is 1.5 or less.

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