JP2006124023A - Biodegradable cap - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pull-open type cap showing superior biodegradability, as well as a well opening characteristic. <P>SOLUTION: This cap is made of biodegradable aliphatic polyester resin characterized in that it has a top wall, having a cut-off region defined by a thin-wall part that can be broken and a finger tip arranged at the cutting-off region, the wall thickness of the thin wall part that is breakable has 0.05 to 0.20 mm and, more preferably, the wall thickness of the thin wall part is to be 0.07 to 0.17 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a synthetic resin cap having biodegradability, and more particularly to a pull-open cap having biodegradability.

Conventionally, the cap is manufactured by a known molding means such as injection molding or compression molding using a synthetic resin such as polypropylene or polyethylene. The performance required for the cap includes hermeticity, tamper evidence, openability, and the like. As caps excellent in these performances, pull-open caps having breakable thin portions are widely used.

The pull open cap here refers to a cap provided with a cut-off area partitioned by a thin-walled portion on the top wall of the cap body so that it can be broken, and has a finger hook in the cut-out area of the top wall. A cap having a column extending upward from a cut region of the top wall and a pull ring connected to the column is exemplified, and the cap is mainly formed using polyethylene resin. In this type of cap, it is a well-known and commonly used technique to set the thickness of the breakable thin portion around 0.25 mm, but the thickness of the breakable thin portion using a biodegradable aliphatic polyester resin is known. Is set in the vicinity of 0.25 mm, it becomes difficult to open, and there is a problem that it cannot be used practically.

It is an object of the present invention to provide a cap having an openability equivalent to that of a conventionally used polyethylene pull-open cap and having excellent biodegradability under natural conditions and under composting conditions. To do.

As a result of intensive studies to solve the above problems, the present inventors have set the thickness of the ruptureable thin part of the pull-open cap to a specific range, thereby using a biodegradable aliphatic polyester resin. In addition, it has been found that a cap excellent in openability can be obtained, and that a cap excellent in openability can be provided by setting the bending elastic modulus of the biodegradable aliphatic polyester resin in a specific range. It came to.

According to the present invention, the cap is made of a biodegradable aliphatic polyester resin, and the cap includes a top wall in which a cut region is defined by a breakable thin portion, and a finger hook provided in the cut region. The cap is characterized in that it has a wall thickness of 0.05 to 0.20 mm. In the present invention, the thickness of the breakable thin portion is particularly preferably in the range of 0.07 to 0.17 mm from the viewpoint of sealing properties and unsealing properties. The biodegradable aliphatic polyester resin used for the cap of the present invention is characterized in that its bending elastic modulus is in the range of 100 to 700 MPa. The biodegradable aliphatic polyester resin used for the cap of the present invention preferably has a flexural modulus in the range of 120 to 500 MPa from the viewpoints of openability and deformation resistance. The biodegradable aliphatic polyester resin used for the cap of the present invention preferably has a flexural modulus in the range of 150 to 400 MPa from the viewpoint of openability and deformation resistance. The biodegradable aliphatic polyester resin used for the cap of the present invention is characterized by being a polyalkylene alkanoate, a copolymer thereof, or a mixture thereof. The biodegradable aliphatic polyester resin used for the cap of the present invention is characterized by being polybutylene succinate or a copolymer thereof, or a mixture thereof. The copolymer of polybutylene succinate used in the cap of the present invention is polybutylene succinate adipate. The biodegradable aliphatic polyester resin used for the cap of the present invention is characterized in that it has a high molecular weight using a chain extender. The copolymer of the biodegradable aliphatic polyester resin used for the cap of the present invention is polybutylene adipate terephthalate. The biodegradable aliphatic polyester resin mixture used for the cap of the present invention is characterized by comprising at least two selected from polybutylene succinate, polybutylene succinate adipate, and polybutylene adipate terephthalate. . The biodegradable aliphatic polyester resin used in the cap of the present invention contains 0.1 to 5 parts by weight of fatty acid, fatty acid amide, or a mixture of fatty acid and fatty acid amide per 100 parts by weight of biodegradable aliphatic polyester. It is characterized by blending. The biodegradable aliphatic polyester resin used for the cap of the present invention is characterized by blending 1 to 10 parts by weight of an antiblocking agent per 100 parts by weight of the biodegradable aliphatic polyester. The biodegradable aliphatic polyester resin used for the cap of the present invention is characterized by blending 0.1 to 10 parts by weight of a hydrolysis inhibitor per 100 parts by weight of the biodegradable aliphatic polyester.

According to the present invention, the breakable thin portion of the pull open cap is designed to have a thickness of 0.05 to 0.20 mm, more preferably 0.07 to 0.17 mm, and a flexural modulus of 100 to 700 MPa. By using a biodegradable aliphatic polyester resin, preferably in the range of 120 to 500 MPa, more preferably in the range of 150 to 400 MPa, good openability can be realized while maintaining the sealing performance. In addition, by blending 0.1 to 5 parts by weight of a fatty acid, or a fatty acid amide, or a mixture of a fatty acid and a fatty acid amide as a lubricant per 100 parts by weight of the biodegradable aliphatic polyester, mold release in the cap molding process Can be improved. Moreover, the moldability in the cap molding process can be improved by blending 1 to 10 parts by weight of an antiblocking agent per 100 parts by weight of the biodegradable aliphatic polyester. In addition, by adding 0.1 to 10 parts by weight of a hydrolysis inhibitor per 100 parts by weight of the biodegradable aliphatic polyester, hydrolysis resistance is ensured even under severe conditions where the inner surface of the cap comes into contact with the contents. Can be improved.
Since the pull-open cap of the present invention is made of a resin excellent in biodegradability, it can be made into an environmentally friendly package.

The present invention will be described in detail below.
In the present invention, when a biodegradable aliphatic polyester resin is used, an excellent opening property can be imparted to the cap by setting the thickness of the breakable thin portion to 0.05 to 0.20 mm. . When the thickness of the breakable thin portion is larger than the above range, the unsealing property is remarkably deteriorated. Further, when the thickness of the breakable thin portion is smaller than the above range, it is difficult to obtain satisfactory performance as a product, for example, the breakable thin portion is broken at the time of mold release or a pinhole is generated. Preferably, a cap superior in sealing performance and unsealing performance can be obtained by setting the thickness of the breakable thin portion to 0.07 to 0.17 mm.

The biodegradable aliphatic polyester resin used in the present invention is characterized in that the flexural modulus according to JIS K7171 is in the range of 100 to 700 MPa. When the flexural modulus is 700 MPa or more, it is extremely difficult to tear the thin portion that can be broken. Preferably, the bending elastic modulus of the biodegradable aliphatic polyester resin is desirably in the range of 120 to 500 MPa, and more preferably, the bending elastic modulus of the biodegradable aliphatic polyester resin is in the range of 150 to 400 MPa. Is desirable.

The biodegradable aliphatic polyester resin used in the composition of the present invention is obtained by condensing one or more of each of the following aliphatic polyhydric alcohols and aliphatic polybasic acids (or derivatives thereof). Can be used arbitrarily. In the present invention, the “biodegradable aliphatic polyester resin” includes those synthesized from cycloaliphatic compounds.

Examples of the aliphatic polyhydric alcohol that is one of the raw materials of the biodegradable aliphatic polyester resin used in the present invention include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and 1,8- Examples include octylene glycol, 1,10-decamethylene glycol, and 1,4-cyclohexanedimethanol. Among these, ethylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol are preferable in view of physical properties of the resulting biodegradable aliphatic polyester resin.

Examples of the aliphatic polybasic acid (or a derivative thereof) that is one of the raw materials of the biodegradable aliphatic polyester resin used in the present invention include succinic acid, succinic anhydride, adipic acid, sebacic acid, and dodecanedicarboxylic acid. Examples include 1,4-cyclohexanedicarboxylic acid. Of these, succinic acid and adipic acid are preferable in view of the physical properties of the resulting biodegradable aliphatic polyester resin. Moreover, you may use together aromatic polybasic acids, such as a terephthalic acid, as a copolymerization component.

Biodegradable aliphatic polyester resins suitable for the present invention include polybutylene succinate, which is a dehydration condensate of 1,4-butanediol and succinic acid, 1,4-butanediol and succinic acid, and adipic acid. Examples thereof include polybutylene succinate adipate which is a dehydration condensate. These biodegradable aliphatic polyester resins are preferably those having a high molecular weight using a chain extender such as lactic acid, polyvalent isocyanate, or acid anhydride. Examples thereof include a mixture of polybutylene adipate terephthalate obtained by dehydration condensation of 1,4-butanediol, adipic acid, and terephthalic acid, and the polybutylene succinate and polybutylene succinate adipate. In addition, other biodegradable resins such as polylactic acid and starch can be used by mixing with the biodegradable aliphatic polyester resin exemplified above or a mixture thereof. In this case, it is desirable to blend so that the final flexural modulus of the mixture is in the range of 100 to 700 MPa, preferably in the range of 120 to 500 MPa, more preferably in the range of 150 to 400 MPa. As a method for mixing the mixture, known mixing means such as dry blending of pellets, melt kneading using an extruder or the like can be used.

In the cap of the present invention, it is desirable to blend 0.01 to 5 parts by weight of a lubricant per 100 parts by weight of the biodegradable aliphatic polyester for the purpose of improving the releasability at the time of molding the resin. When molding by injection molding using a cold runner, it is necessary to consider not only the mold releasability of the mold part forming the molded product but also the mold releasability from the sprue. For this reason, in the cap of this invention, the mold release property at the time of shaping | molding can be improved and a moldability can be improved by mix | blending the said specific amount of lubricant.

Further, as an advantage of containing a lubricant, it is possible to improve the biting property of the resin into the screw during molding. When a specific amount of lubricant is included when the resin is introduced into the molding machine, the resin flows smoothly through the screw. However, if a lubricant exceeding the specified range is added, the bite property is adversely affected, resulting in molding failure.

As the lubricant, a so-called internal lubricant for imparting internal lubricity and an external lubricant for imparting external lubricity can be used together, and these can be used in combination. As the lubricant used in the present invention, all those generally used for resin molding can be applied. However, particularly when the resin composition of the present invention is used for food packaging, as a food additive. It is desirable to use one that has been approved for use.
Specifically, fatty acids such as stearic acid proposed in JP-A-8-27363, erucic acid amide, methylene bis-stearic acid amide, ethylene bis-stearic acid amide, ethylene bis-palmitic acid amide, ethylene bis-oleic acid Fatty acid amides such as amides, or a mixture of the above fatty acids and fatty acid amides can be used.

In addition to the above-mentioned lubricant, it is necessary to improve the moldability by forming irregularities on the surface of the molded product of the cap, increasing the surface roughness, and adjusting the resin biting property to improve the moldability. The antiblocking agent is preferably added in an amount of 1 to 10 parts by weight per 100 parts by weight of the biodegradable aliphatic polyester. A conventionally well-known antiblocking agent can be used as an antiblocking agent, A talc particle can be used suitably.

The addition of the lubricant and the antiblocking agent may be an internal addition in which a master batch containing these at a relatively high concentration is prepared and blended with the master batch, or an external addition in which the lubricant is directly added to the pellet particles.

Further, in the present invention, for the purpose of suppressing hydrolysis, it is preferable to add 0.1 to 10 parts by weight of a hydrolysis inhibitor per 100 parts by weight of the biodegradable aliphatic polyester. Since the cap is frequently used for packaging a food seasoning solution containing water, hydrolysis resistance is required. In the present invention, by adding the specific amount of hydrolysis inhibitor, hydrolysis resistance can be improved without impairing the biodegradability inherent in the biodegradable aliphatic polyester resin. The type of the hydrolysis inhibitor is not particularly limited as long as hydrolysis can be suppressed.

Examples of the hydrolysis inhibitor include carbodiimide compounds, surface-treated inorganic fillers, layered silicates, hydrophobic waxes, hydrophobic plasticizers, and olefinic resins proposed in Japanese Patent No. 3514736 and Japanese Patent Application Laid-Open No. 2003-165917. At least one of the groups is selected.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, the bending elastic modulus of the biodegradable aliphatic polyester resin used for the Example was measured based on JISK7171 using the test piece created by injection molding.

A cap as shown in FIG. 1 was molded with an injection molding machine. Thereafter, the pull-open strength was measured, and the presence or absence of liquid leakage due to the pinhole in the breakable thin portion was examined.

(cap)
As shown in FIGS. 1 and 2, the cap has a top wall in which a cutout region is defined by a breakable thin portion, a support column extending upward from the cutout region, and a pull ring connected to the support column. The cap has an engaging projection that engages with an annular protrusion provided on the outer periphery of the mouth tube portion of the container (not shown) on the inner surface of the outer tube wall, and is sealed and attached to the mouth tube portion by a stopper. In addition, it replaces with the said pull ring, A well-known finger hook part can be employ | adopted, such as providing a press protrusion so that a cutting area can be fractured | ruptured by press. Further, the entire cut region may be cut off, or may be cut off with a part of the unbroken portion remaining. Moreover, the pouring hole formed by breaking the breakable thin wall portion can adopt a known shape as appropriate. However, as shown in FIG. Can also be narrowed. The mounting of the cap on the container is not limited to the above-described means, and a known means such as mounting with a screw can be employed.

(Measurement of pull open strength)
Using a tensile tester, the pull open strength was measured by the following procedure. After fixing the measurement sample that has passed 24 hours or more after molding with a jig, pull the pull ring at a speed of 300 mm / min in the direction 90 degrees above the top wall surface, and the initial peak value in the fracture process of the breakable thin part ( Maximum) was recorded. A pull-open strength of less than 60N was acceptable, a strength of 60N or more and less than 80N was acceptable, and a strength of 80N or greater was not acceptable.

(Leakage test)
Using a desiccator, the presence or absence of liquid leakage due to pinholes in the breakable thin wall portion was confirmed under reduced pressure.
The test procedure is as follows.
A glass container is filled with 50% aqueous ethanol solution in which a methylene blue solution is dissolved, and then a cap is attached to the container. The cap has an engagement projection on the inner surface of the outer cylinder wall that engages with an annular protrusion provided on the outer periphery of the mouth tube portion of the glass container, and the cap is liquid-tight on the container mouth tube portion by a stopper. Installed. A container equipped with a cap is laid down for 20 minutes in a desiccator set to an internal pressure of 200 hPa, and then the presence or absence of liquid leakage is confirmed. A cap that did not cause liquid leakage was marked with ◯, and a cap that caused liquid leakage was marked with ×.

Example 1
Using a resin having a flexural modulus of 300 MPa consisting of 100 parts by weight of polybutylene succinate adipate and 2 parts by weight of erucamide, a cap having a thin breakable wall thickness of 0.07 mm was injection molded. A leak test was performed in the desiccator, but no liquid leak from the thin breakable part was observed. When the pull-open strength was measured, it was 26 N, and the openability was good.

(Example 2)
The same polybutylene succinate adipate used in Example 1, 100 parts by weight of erucamide, 2 parts by weight of erucamide, 1.5 parts by weight of bis (dipropylphenyl) carbodiimide, and a resin having a flexural modulus of 300 MPa, A cap having a thickness of the breakable thin part of 0.10 mm was injection molded. A leak test was performed in the desiccator, but no liquid leak from the thin breakable part was observed. When the pull-open strength was measured, the openability was good at 40N. Further, in order to evaluate the hydrolysis resistance of the cap, the cap was molded, stored at room temperature for 3 days, and then immersed in warm water at 45 ° C. for 2 months. The appearance of the cap after immersion was confirmed, but no change was observed.

(Example 3)
Using a resin having the same composition as in Example 1, a cap having a breakable thin portion with a thickness of 0.15 mm (Example 3) was injection molded. A leak test was conducted in a desiccator, but no liquid leak was observed. Next, when the pull open strength was measured, it was found that the openability was 71 N.

Example 4
Breakable thin part using a resin with a flexural modulus of 400 MPa, comprising 60 parts by weight of polybutylene succinate, 40 parts by weight of polybutylene succinate adipate used in Example 1, and 2 parts by weight of erucamide A cap having a wall thickness of 0.10 mm was injection molded. A leak test was performed in the desiccator, but no liquid leak from the thin breakable part was observed. When the pull-open strength was measured, it was 52 N, and the openability was good.

(Comparative Example 1)
Using a resin having the same composition as in Example 1, a cap having a ruptureable thin portion having a thickness of 0.03 mm was injection-molded. However, since the ruptureable thin portion was broken at the time of release, a leak test and measurement of pull-open strength were performed. Canceled.

(Comparative Example 2)
Using a resin having the same composition as in Example 1, a cap having a ruptureable thin portion with a thickness of 0.25 mm was injection molded. A leak test was performed in the desiccator, but no liquid leak from the thin breakable part was observed. Next, an attempt was made to measure the pull-open strength, but the base of the support broke during the measurement, and the measurement was impossible.
The results are shown in Table 1.

(Example 5)
A flexural modulus of 250 MPa consisting of 75 parts by weight of the same polybutylene succinate adipate used in Example 1, 25 parts by weight of polybutylene adipate terephthalate, 0.3 parts by weight of erucamide, and 5 parts by weight of talc. A cap having a thin breakable wall thickness of 0.07 mm was injection molded. A leak test was performed in the desiccator, but no liquid leak from the thin breakable part was observed. When the pull-open strength was measured, it was 24 N, and the openability was good.

(Example 6)
A resin having the same composition as in Example 5 was used, and a cap having a thin breakable portion having a thickness of 0.15 mm was injection molded. A leak test was performed in the desiccator, but no liquid leak from the thin breakable part was observed. When the pull-open strength was measured, the openability was 63N.

(Comparative Example 3)
Using a resin having the same composition as in Example 5, a cap having a ruptureable thin portion of 0.03 mm was injection-molded, but the ruptureable thin portion was broken at the time of mold release. The measurement was stopped.

(Comparative Example 4)
Using a resin having the same composition as in Example 5, a cap having a ruptureable thin portion with a thickness of 0.25 mm was injection molded. A leak test was conducted in the desiccator, but no liquid leakage from the thin part was observed. However, when the pull-open strength was measured, it was as high as 98 N, and the openability was not possible.
The results are shown in Table 2.

(Comparative Example 5)
The same polybutylene succinate adipate used in Example 1, 80 parts by weight of polylactic acid, 20 parts by weight of polylactic acid, 0.5 parts by weight of erucic acid amide, using a resin having a flexural modulus of 800 MPa, and a thin part that can be broken A cap having a wall thickness of 0.10 mm was injection molded. A leak test was carried out in the desiccator, but no liquid leakage from the thin part was observed. However, the pull-open strength was as high as 95N, and the unsealing property was not possible.

(Comparative Example 6)
Using a resin having the same composition as in Comparative Example 5, a cap having a ruptureable thin portion having a thickness of 0.03 mm was injection-molded. However, since the ruptureable thin portion was broken at the time of release, a leak test and measurement of pull-open strength were performed. Canceled.
The results are shown in Table 3.

As is clear from the above results, the thickness of the breakable thin portion of the pull-open cap is designed to be 0.05 to 0.20 mm, more preferably 0.07 to 0.17 mm, and bending elasticity. By using a biodegradable aliphatic polyester resin having a rate of 100 to 700 MPa, preferably 120 to 500 MPa, more preferably 150 to 400 MPa, it is possible to achieve good opening while maintaining sealing performance. it can. By blending 0.1 to 5 parts by weight of a fatty acid, or a fatty acid amide, or a mixture of a fatty acid and a fatty acid amide as a lubricant per 100 parts by weight of the biodegradable aliphatic polyester, the releasability can be improved. . Moreover, a moldability can be improved more by using together 1-10 weight part antiblocking agent per 100 weight part of biodegradable aliphatic polyester. Moreover, hydrolysis resistance can be improved by mix | blending 0.1-10 weight part hydrolysis inhibitor with respect to 100 weight part of biodegradable aliphatic polyester.

It is a partial cross section side view of the pull open cap used for the Example of this invention. It is a bottom view of the cap shown in FIG. 1 of this invention. It is a reference view (bottom view) of a pull open cap having a cutout region having a shape suitable for the present invention.

Explanation of symbols

A Pull open cap 1, 1a Breakable thin part 2, 2a Cut-out area 3 Top wall 4 Finger hook (pull ring)
5 Strut 6, 6a Strut connection 7 Outer cylinder wall 8 Engagement protrusion

Claims (15)

A cap made of a biodegradable aliphatic polyester resin, the cap having a top wall in which a cut-out region is defined by a breakable thin-walled portion, and a finger hook provided in the cut-out region, A cap having a thickness of a breakable thin portion of 0.05 to 0.20 mm. A cap made of a biodegradable aliphatic polyester resin, wherein the cap has a top wall in which a cut region is defined by a breakable thin wall portion, a column extending upward from the cut region, and a pull ring connected to the column And the thickness of the breakable thin portion is 0.05 to 0.20 mm. The cap according to claim 1 or 2, wherein a thickness of the breakable thin portion is 0.07 to 0.17 mm. The cap according to any one of claims 1 to 3, wherein the biodegradable aliphatic polyester resin has a flexural modulus in the range of 100 to 700 MPa. The cap according to any one of claims 1 to 4, wherein the biodegradable aliphatic polyester resin has a flexural modulus in a range of 120 to 500 MPa. The cap according to any one of claims 1 to 5, wherein the biodegradable aliphatic polyester resin has a flexural modulus in the range of 150 to 400 MPa. The cap according to any one of claims 1 to 6, wherein the biodegradable aliphatic polyester resin is a polyalkylene alkanoate, a copolymer thereof, or a mixture thereof. 8. The cap according to claim 7, wherein the biodegradable aliphatic polyester resin is polybutylene succinate, a copolymer thereof, or a mixture thereof. 9. The cap according to claim 8, wherein the copolymer of polybutylene succinate is polybutylene succinate adipate. The cap according to claim 8 or 9, wherein the biodegradable aliphatic polyester resin or a copolymer thereof has a high molecular weight using a chain extender. The cap according to claim 7, wherein the copolymer of the biodegradable aliphatic polyester resin is polybutylene adipate terephthalate. The mixture of biodegradable aliphatic polyester resins comprises at least two selected from polybutylene succinate, polybutylene succinate adipate, and polybutylene adipate terephthalate. Cap. The biodegradable aliphatic polyester resin is characterized in that 0.01 to 5 parts by weight of a fatty acid, a fatty acid amide, or a mixture of a fatty acid and a fatty acid amide is blended per 100 parts by weight of the biodegradable aliphatic polyester. The cap according to any one of claims 1 to 12. 14. The biodegradable aliphatic polyester resin contains 1 to 10 parts by weight of an antiblocking agent per 100 parts by weight of the biodegradable aliphatic polyester. Cap. The biodegradable aliphatic polyester resin contains 0.1 to 10 parts by weight of a hydrolysis inhibitor per 100 parts by weight of the biodegradable aliphatic polyester. Crab cap.

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