JP2001180704A - Resin cap and packaging container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin cap excellent in preservability of a container content when used as a cap. SOLUTION: A resin cap is composed of a high density polyethylene resin having a melt flow rate (JIS K7210-76; 190 deg.C-2.16 kg load) of 0.05-10 g/10 min and the density (JIS K6760-81) of 0.940-0.965/cm3, and the dispersion properties (weight-average molecular weight/number-average molecular weight) in the gel permeation chromatography measurement is in the range of 7 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin cap which, when used as a cap, has excellent long-term storage of the contents of the container, and a packaging container having this cap. More specifically, the resin cap is made of environmental stress crack resistance.
CKing Resistance (hereinafter referred to as ESCR) has a characteristic that the value is sufficiently high with respect to the performance of the cap. Due to such characteristics, the resin cap of the present invention prevents cracks generated in the cap for a long time against various environmental stresses such as cap tightening stress, environmental temperature, temperature of contents, pressure in the container and the like. It is useful regardless of the type of food and beverage content.

[0002]

2. Description of the Related Art In general, the material of a resin cap is a polypropylene resin, and the top surface of the cap is made of a special resin.
A resin cap having a structure provided with a cap liner as disclosed in JP-A-88608 has been suitably used. Why is a high-density polyethylene resin, which is a general-purpose resin similar to a polypropylene resin, not used for the resin cap material?
The reason that the polypropylene-based resin was suitably used is that the compression molding method (specifically, the resin cap composition is melt-extruded with an extruder and a fixed amount (about 3 g) is preferably used in the resin cap molding method. ) Is hot-cut and dropped into a cap-shaped mold.
Then, it is pressurized and cooled immediately by a pressing die to prepare a cap, and a cap is produced. ) And the moldability of the injection molding method, the fluidity of the high-density polyethylene resin is required to a certain extent, which will lower the ESCR of the high-density polyethylene resin and cause cracks. Because it could not be used. In addition, some resin caps for beverages and food products that do not apply much environmental stress use high-density polyethylene resin as a type of cap without a cap liner. There is also the problem of being done.

[0003] Therefore, a cap linerless type resin cap for products such as beverages and foods subject to environmental stress,
A high-density polyethylene resin cannot be used, and a polypropylene resin is employed. However, the resin cap made of polypropylene resin has a disadvantage in that the surface smoothness is a disadvantage of the polypropylene resin, so that the opening torque of the cap is higher than the proper opening torque. Such a slip agent must be added. For this reason, there is a demand for a resin cap that does not cause the slip agent to elute into the product contents and can prevent the inhibition of flavor by the slip agent.

As described above, the conventional resin cap has problems such as low ESCR of high-density polyethylene resin and impaired flavor of the resin cap made of polypropylene resin, and has a sufficient ESCR for the performance of the resin cap. There is a demand for a resin cap made of a high-density polyethylene resin.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a resin cap made of a high-density polyethylene resin having good cap moldability and a sufficient ESCR for the resin cap performance.

[0006]

The inventors of the present invention have conducted intensive studies and have found that a high-density polyethylene resin having a melt flow rate, density and monodispersity (weight average molecular weight / number average molecular weight) within a specific range. Was found to have good cap moldability and a sufficient ESCR for resin cap performance, and completed the present invention. That is, the present invention relates to a melt flow rate (JIS K7210-76; 190 ° C.-2.
16 kg load) 0.05 to 10 g / 10 min, density (JIS K6760-81) 0.940 to 0.965
A resin cap comprising a high-density polyethylene resin having a g / cm ³ and a monodispersity (weight average molecular weight / number average molecular weight) in gel permeation chromatography measurement of 7 or more. .

The high-density polyethylene resin used in the present invention has a melt flow rate (JIS K7210-7).
6; 190 ° C.-2.16 kg load) 0.05 to 10 g
/ 10 min, density (JIS K6760-81) of 0.940 to 0.965 g / cm ³ , and monodispersity (weight average molecular weight / number average molecular weight) of 7 or more in gel permeation chromatography measurement. is there.

[0008] The high-density polyethylene resin is prepared by melt flow rate (JIS K7210-76; 190 ° C-2.
16kg load, hereinafter referred to as MFR) 0.05-10g
/ 10 min, preferably 0.3 to 5 g / 10 m
in. If the MFR is less than 0.05 g / 10 min, an excessive extrusion load is applied during cap molding such as compression molding, resulting in poor moldability and 10 g / 1.
If it exceeds 0 min, the ESCR is inferior.

The density of the high-density polyethylene resin (JI
SK6760-81) is 0.940 to 0.965 g /
cm^ThreeAnd preferably 0.942 to 0.963 g /
cm ^ThreeIt is. 0.940 g / cm density^ThreeLess than rigid
0.965 g / cm^ThreeESCR
Inferior. The high-density polyethylene resin has a weight-average
It is expressed by the ratio between the molecular weight (Mw) and the number average molecular weight (Mn).
Monodispersity (Mw / Mn) is 7 or more, preferably
It has a characteristic of being 9 to 40. Monodispersity less than 7
In this case, the molecular weight distribution is too narrow, resulting in poor cap moldability.
Good, and ESCR is inferior.
The ethylene resin is difficult to manufacture and difficult to obtain.
The method for measuring Mw and Mn was determined by gel permeation.
・ Chromatography (Nippon Millipore Co., Ltd., device name "A
LC / GPC150C "(Column: manufactured by Tosoh Corporation,
3 trade names "GMHHR-H (S)", solvent: 1,2,2
4-trichlorobenzene, temperature: 140 ° C, flow rate 1.0
ml / min, injection concentration 1mg / 1ml, injection volume 300μ
1) was measured. Note that Tosoh Corporation's standard
Universal calibration using polystyrene
The column elution volume was calibrated by the method.

Further, an N value (melt flow rate (J
IS K7210-76: 190 ° C-21.6 kg load) / Melt flow rate (JIS K7210-7)
6: 190 ° C.-2.16 kg load)) is preferably 50 or more, more preferably 70 to 300 in consideration of cap moldability and ESCR. Further, it is more preferable that the volatile content of the molded resin cap in the head space gas chromatography (the total peak area in the chart for 1 to 35 seconds) is 500 mV / sec or less, because the flavor inhibition to the contents is small and the content is low. .

The high-density polyethylene resin can be produced by a known production method. Generally, a highly active Ziegler-based catalyst comprising a transition metal compound such as titanium or zirconium, a magnesium compound, and an organoaluminum compound, or a zirconium compound is used. , A metallocene catalyst having at least one cyclopentadienyl group and a substituted cyclopentadienyl group as a transfer metal such as hafnium and titanium as a polymerization catalyst, ethylene, or ethylene and α having 3 to 20 carbon atoms. -It can be suitably produced by copolymerizing an olefin at a ratio that gives a desired density.

Among the high-density polyethylene resins, high-density polyethylene resins produced by a metallocene catalyst which suppresses the generation of volatile components and has little hindrance to flavor and aeration (a high-density polyethylene resin is treated with a gas such as air for a certain period of time) It is more preferable to use those treated. Examples of the polymerization method include slurry polymerization, gas phase polymerization, and solution polymerization.

Here, the α-olefin used for copolymerization with ethylene includes propylene, 1-butene,
-Methyl-1-pentene, 3-methyl-1-butene, 1
-Pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene , 1-
Examples thereof include octadecene, 1-nonadecene, and 1-eicosene. One or two or more blends of a copolymer of ethylene and one or more α-olefins can be used.

As a specific production method, the number of carbon atoms is 6-1.
In a slurry polymerization using a polymerization medium of a saturated hydrocarbon of 0, for example, normal hexane, normal heptane, or the like, a multistage polymerization method may be employed. As the multi-stage polymerization process, the density and the low molecular weight component of 0.94~0.98g / cm ^3, densities of less high molecular weight component having a density than the low molecular weight in 0.92~0.95g / cm ³ bicomponent Wherein the ratio of the amount of polymerization formed between the two components is low-molecular-weight component: high-molecular-weight component =
A two-stage polymerization method in which the ratio is 20:80 to 80:20 can be exemplified.

The resin cap of the present invention is made of the above-mentioned high-density polyethylene resin. The composition for the resin cap used in the resin cap of the present invention may be a thermoplastic resin, a thermoplastic elastomer, a heat stabilizer, a weather resistance stabilizer, an antistatic agent, a slip agent, an organic peroxide, a surfactant, if necessary. , Anti-fog agent, dropping agent, nucleating agent, pigment, dye,
Silica, talc, mica, carbon, calcium carbonate,
Inorganic or organic additives and fillers such as magnesium carbonate, metal stearate, wood flour, cork powder, and cellulose powder may be added as long as the object of the present invention is not impaired. In particular, to prevent thermal deterioration, phenol-based, hindered phenol-based, phosphorus-based and sulfur-based heat-resistant stabilizers, and to adjust the viscosity of the composition, organic peroxides such as dialkyl peroxide-based and diacyl peroxide-based. Metal stearate such as calcium stearate and zinc stearate to deactivate the activity of substances and catalysts, and pigments such as titanium oxide and phthalocyanine blue to color resin caps are preferably used.

To obtain the resin cap molded product of the present invention,
Or use the high-density polyethylene resin alone,
Alternatively, when adding the above-mentioned inorganic or organic additives and fillers, various known methods, for example, Henschel mixer, V-blender, ribbon blender,
After mixing with a tumbler blender, etc., melt kneading with a single screw extruder, twin screw extruder, kneader, Banbury mixer, etc., and granulating or pulverizing, or blending method using dry blended product or auto feeder without prior melt kneading , A composition for a resin cap is obtained by a method of directly kneading, and a cap is formed by a compression molding method or an injection molding method to obtain a resin cap. In addition, the obtained resin cap is melt-extruded with an extruder using an in-shell mold method (a composition for a cap liner material, and a certain amount (about 30
0 mg) is hot-cut and dropped into the shell of the obtained resin cap. Immediately pressurize and cool with a pressing die,
Adjust to liner shape and make cap. )
A resin cap provided with a cap liner may be obtained.

The resin cap of the present invention is characterized by using a high-density polyethylene resin in which the melt flow rate, density and monodispersity (weight average molecular weight / number average molecular weight) are limited to specific ranges. In consideration of cap moldability, which is not in
It is a resin cap that has an SCR and is excellent in long-term storage of the contents of a container. From the above characteristics, by using the resin cap of the present invention as a cap for a packaging container filled with the following contents, a soft drink (carbonated beverage, fruit juice beverage,
Sports drinks), alcoholic drinks, coffee drinks, tea drinks, mineral water, dressings, sauces for grilled meats, sauces for seasoning, mayonnaise, salad oil, sesame oil, etc. Among them, it is particularly useful to use it for carbonated beverages where the internal pressure of the bottle is high and a high ESCR is required.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist thereof.

[0019]

EXAMPLES In Examples and Comparative Examples, commercially available products or high-density polyethylene obtained by the following production method was used. <Production Example of High Density Polyethylene Resin> Except for the commercial grade products used in some of the comparative examples, production was performed by a two-stage slurry polymerization method. In the first-stage polymerization, nitrogen is sufficiently substituted, and n-
A polymerization vessel equipped with a stirrer having an internal volume of 370 L and charged with hexane was adjusted to an internal temperature of 85 ° C., an internal pressure of 30 kg / cm ² G, 100 kg / h of n-hexane, and 15 to 150 g of ethylene.
25 kg / h, hydrogen to ethylene concentration ratio 0.6-0.8
Mol / mol, 0.5 g / h of Ziegler-based catalyst, and tri-i-butylaluminum as co-catalyst were continuously supplied at 75 mmol / h, and the density was 0.9.
Low molecular weight ethylene butyne of 6 to 0.98 g / cm ^3-
One copolymer was obtained. After removing unreacted hydrogen and ethylene in a flash tank, the hexane slurry containing the first-stage polymer was charged with n-hexane and the content was 545 L.
Continuously into a polymerization vessel equipped with a stirrer of
° C, the internal pressure was adjusted to 20 kg / cm ² G, 95 kg / h of n-hexane, 15 to 25 kg / h of ethylene, hydrogen to ethylene concentration ratio of 0.05 to 0.08 mol / mol, and butyne-1. 0.5 to 3 kg / h are continuously supplied so that the weight ratio of the polymerized ethylene-butene-1 copolymer to the low molecular weight ethylene / butene-1 copolymer component: high molecular weight ethylene / butene -1 copolymer component =
The high molecular weight ethylene / butene-1 copolymer was polymerized in the second stage so that the ratio became 35:65 to 65:35 to obtain a high-density polyethylene resin. Various molding methods and evaluation methods in Examples and Comparative Examples are shown below.

<Measurement of Mw / Mn (monodispersity)>
Permeation chromatography (manufactured by Nippon Millipore Co., Ltd., device name "ALC / GPC150C" (column: Tosoh Corporation, trade name "GMHHR-H (S)" 3)
Book, solvent: 1,2,4-trichlorobenzene, temperature: 1
40 ° C, flow rate 1.0ml / min, injection concentration 1mg / 1m
1, injection volume 300 μl). The column elution volume was calibrated by universal calibration using standard polystyrene manufactured by Tosoh Corporation.

<Resin Cap Forming Method> The resin cap was formed by a compression molding method generally used for cap forming. Specifically, L / D =
Using a single-screw extruder manufactured by Tanabe Plastics Machine Co., Ltd. of 25 mm and 65 mmφ, the resin cap material was heated at a resin temperature of 210 ° C., a screw rotation speed of 100 rpm, and a discharge amount of 50 k
g / h, and melted and kneaded at 15 g
Take out one strand from the hole of mmφ. The strand coming out of the die head portion is hot-cut using a cutter so that it becomes 3 g as it is. The hot-cut molten pellet is dropped into the center of a molding die for a 28 mmφ resin cap, and immediately cooled under pressure at a pressure of 3 kg / cm ² to prepare a resin cap shape, thereby producing a resin cap.

<ESCR> A test was conducted in accordance with the method of constant strain environmental stress crack test described in JIS K6760. Nonionic NS21 which is a surfactant is used as a test solution.
A 10% by weight aqueous solution of 0 was used. The ESCR value was obtained by writing the crack initiation time of 10 test pieces on log probability paper, and calculating the 50% crack initiation time from the graph.

<Cap liner molding method>
Inner molding is generally used for cap liner molding.
This was performed by the in-shell mold method described below. Specifically
Is L / D = 25mm, 40mmφ Tanabe Plastic
Polypropylene 3 using a single screw extruder manufactured by Sugi Machine Co., Ltd.
0% by weight (Chisso Polypro K180 manufactured by Chisso Corporation)
0), 40% by weight of thermoplastic elastomer (Shell Japan
Clayton G1651), liquid paraffin
29.5% by weight (Christole J manufactured by Esso Oil Co., Ltd.)
262) and a 0.5% by weight slip agent (Nippon Seika Co., Ltd.)
Composition for cap liner consisting of Neutron S)
The resin is discharged at a resin temperature of 200 ° C, a screw rotation speed of 30 rpm,
Melt and knead at an output of 8 kg / h and open it at the die head.
Take out one strand from the 8mmφ hole. Daihe
300mg of the strand coming out of the pad
Hot cut using a cutter so that hot
28mmφ resin obtained earlier from the cut molten pellets
Drop to the center of the inner top surface of the cap and immediately pressurize 2 kg
/ Cm ^TwoAnd pressurize and cool to form a cap liner shape.
A resin cap provided with a cap liner is produced. Ma
The test and measurement methods used in the present invention are as follows.

<Evaluation of Cap Moldability> The success rate of 1,000 resin caps produced based on the resin cap molding method to be accurately shaped caps is measured.

<Long-term storage test> In a 500 ml PET bottle having a carbon dioxide concentration of 500 ml, 5.0 vol
500 ml of carbon dioxide gas water, which is used as ume, was filled under the condition of 5 ° C., and using the prepared sample resin cap, the cap was tightened with a torque of 18 kg-cm to prepare a bottle for a long-term storage test. The bottle is erected at 5 ° C. for 24 hours, and then immersed in a 55 ° C. hot water bath to perform a long-term storage test. Visually check the occurrence of cracks in the resin cap and leakage of the internal solution. Maximum time for long-term storage test is 50
0 hours.

<Measurement of Cap Opening Torque> After storing the bottle for long-term storage test at 5 ° C. for one week, immediately, a cap opening torque measuring device (TNK-6 manufactured by Shinpo Kogyo Co., Ltd.)
0B), the opening torque of the cap wound around the test PET bottle was measured. In addition, the measured value of the cap opening torque is an average value of ten test PET bottles. The appropriate value of the cap opening torque is 8 to 15 kg-cm.

<Measurement of Volatile Content> Headspace gas chromatography (manufactured by Shimadzu Corporation, device name "GC9
A)), an appropriate amount of a sample obtained by finely pulverizing the resin cap was set, heated at 150 ° C. for 30 minutes, and its volatile content was measured. The total peak area for 1 to 35 seconds on the measurement chart was determined, and this was defined as the amount of volatile components.

<Flavor test> A 500 ml PET bottle was filled with 500 ml of distilled water at 80 ° C., and the sample resin cap was used.
cm. Then, 9 from the top of the cap
Hot water at 0 ° C. was showered for 5 minutes and sufficiently cooled to room temperature to obtain a flavor test bottle. After the flavor test bottle is laid down and stored at 50 ° C. for 2 weeks, the distilled water
By a taste sensory test, a change in flavor with distilled water before filling was observed. The test was performed by indicating ○ for no change in flavor, △ for slight change, and x for clear change. In addition, 5
It was performed by a human sensory test. And, as a comprehensive evaluation, for those in which flavor inhibition was not recognized,
For all (when there is no X, when there is no X, and when Δ is 2 or less and the others are ○), and when some flavor inhibition was observed, Δ (when there was no X, and Δ was 3) And x (when at least one person has x).

Example 1 A high-density polyethylene resin (melt flow rate (JI
SK7210-76; 190 ° C.-2.16 kg load, hereinafter referred to as MFR) 0.8 g / 10 min, density (JIS K6760-81) 0.956 g / cm ³ ,
Monodispersity 15, N value 98, hereinafter 99% by weight of HDPE-1) and 1% by weight of titanium oxide (Taipe CR-60 manufactured by Ishihara Sangyo Co., Ltd.) were mixed for 15 minutes by a tumbler blender, and then L / D = 36 mm, 57 mmφ, melt-kneaded and granulated at 210 ° C. with a twin screw extruder manufactured by Toshiba Machine Co., Ltd. to obtain a resin cap material. Using the material, evaluation of cap formability, long-term storage test, and measurement of cap opening torque were performed.

Example 2 In Example 1, HDPE-1 was replaced with a high-density polyethylene resin (MFR 2 g / 10 min, density (JIS K6).
760-81) 0.950 g / cm ³ , monodispersity 25,
N value 185, hereinafter referred to as HDPE-2), and a resin cap material was obtained in the same manner as in Example 1. Table 1 shows the test results.

Example 3 In Example 1, HDPE-1 was replaced with a high-density polyethylene resin (MFR 2 g / 10 min, density (JIS K6).
760-81) 0.943 g / cm ³ , monodispersity 25,
The N value was changed to 212 (hereinafter referred to as HDPE-3), and a resin cap material was obtained as in Example 1. Table 1 shows the test results.

Comparative Example 1 In Example 1, HDPE-1 was replaced with a high-density polyethylene resin (Nipolon Hard 5700, manufactured by Tosoh Corporation).
FR1g / 10min, density (JIS K6760-8
1) Changed to 0.953 g / cm ³ , monodispersity 6, N value 35, hereinafter referred to as HDPE-4), and a resin cap material was obtained in the same manner as in Example 1. Table 1 shows the test results.

Comparative Example 2 In Example 1, HDPE-1 was replaced with a high-density polyethylene resin (MFR 20 g / 10 min, density (JIS K
6760-81) 0.951 g / cm ³ , monodispersity 1
5, N value 61, hereinafter referred to as HDPE-5), and a resin cap material was obtained as in Example 1. Table 1 shows the test results.

Comparative Example 3 In Example 1, HDPE-1 was replaced with a high-density polyethylene resin (Nipolon Hard 5400, manufactured by Tosoh Corporation).
FR 0.85 g / 10 min, density (JISK6760
-81) 0.958 g / cm ³ , monodispersity 5, N value 3
7, hereinafter referred to as HDPE-6), and a resin cap material was obtained as in Example 1. The test results are shown in Table 1. As a result, the extrusion load was large at the time of forming the cap, the cap could not be formed, and no cap molded product was obtained.

Comparative Example 4 In Example 1, HDPE-1 was replaced with a polypropylene-based resin (Chisso Polypro K7014 manufactured by Chisso Corporation, melt flow rate (JIS K7210-76; 230 ° C.)
−2.16 kg) 3 g / 10 min, hereinafter referred to as PP-1), and a resin cap material was obtained as in Example 1. Table 1 shows the test results.

Example 4 HDPE-2 used in Example 2 was aerated (exposed to air at a temperature of 50 ° C. for 48 hours).
The resin was replaced with a high-density polyethylene resin (hereinafter referred to as HDPE-7), and a resin cap material was obtained as in Example 1. Table 1 shows the test results.

Example 5 A long-term storage test and cap opening torque measurement were performed using a resin cap obtained by applying a cap liner to the resin cap formed in Example 2 based on the cap liner molding method. The test results are shown in Table 1. .

Comparative Example 5 A test was performed in the same manner as in Example 5 except that the resin cap was changed to the one molded in Comparative Example 1. Table 1 shows the test results.

[0039]

[Table 1]

[0040]

The resin cap of the present invention is useful because it has features that are not found in conventionally known resin caps, such as good cap moldability and excellent long-term storage of container contents.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroaki Tsutsumi 148 Nogi, Nogi-cho, Shimotsuga-gun, Tochigi Prefecture F-term in Shibasaki Manufacturing Co., Ltd. (Reference) 3E084 CC04 DC04

Claims (6)

[Claims] 1. Melt flow rate (JIS K721)
0-76; 190 ° C.-2.16 kg load) 0.05-
10g / 10min, density (JIS K6760-8
1) 0.940 to 0.965 g / cm ³ , and a high-density polyethylene resin having a monodispersity (weight average molecular weight / number average molecular weight) of 7 or more in gel permeation chromatography measurement. A resin cap, characterized in that: 2. An N value (melt flow rate (JIS) represented by a ratio of melt flow rates under different measurement conditions.
K7210-76; 190 ° C-21.6 kg load) /
Melt flow rate (JIS K7210-76; 19
2. The resin cap according to claim 1, comprising a high-density polyethylene resin having a temperature of 0 ° C. and a load of 2.16 kg) of 50 or more. 3. The method according to claim 1, wherein the amount of volatile matter (all peak areas in the chart for 1 to 35 seconds) in the headspace gas chromatography is 500 mV / sec or less. Resin cap. 4. The resin cap according to claim 1, which is used for a carbonated beverage cap. 5. The resin cap according to claim 1, wherein the cap is formed by a compression molding method. 6. A packaging container using the resin cap according to claim 1.