JP2914723B2 - Heat resistant cap - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-resistant cap, and more particularly, to a heat-resistant cap whose inner surface is liner-treated with a liner material mainly composed of a synthetic resin.

[Conventional technology]

Conventionally, heat-resistant caps lined on the inside with synthetic resin include low-density polyethylene or ethylene
A heat-resistant cap treated with a liner such as a vinyl acetate copolymer is known.

Such a liner-treated heat-resistant cap is used for storing and transporting beverage liquid, but is subjected to a heat treatment for sterilization at the time of injecting and filling the beverage liquid or after sealing. Heating of beverage liquid is generally 85 ° C
That is all.

The opening torque of the closure is generally 5 to 15 kg.
-Cm, especially 6 to 9 kg-cm, is suitable. Peel strength is 4kgf
It is necessary that the temperature exceeds 4 kgf, and if it is 4 kgf or less, the liner may fall off when the plug is opened, which may lead to liquid leakage.

[Problems to be solved by the invention]

By the way, recently, the demand for a liner-treated heat-resistant cap that can be filled with a liquid for beverage in a higher temperature range is increasing, in association with the fact that it has become possible to mold a synthetic resin bottle having high heat resistance. .

Despite this demand, however, conventional liner-treated heat-resistant caps, if heat-treated at a temperature of 90 ° C or higher, cause a change in thermal composition, lowering the opening torque, leaking liquid, and cracking. This causes a problem that the sealing performance of the cap is reduced.

An object of the present invention is to provide a heat-resistant cap capable of sufficiently withstanding a high temperature of 90 ° C. or more, in particular, in order to solve such a conventional technical problem.

[Means for solving the problem]

In order to solve the problems described above, the heat-resistant cap of the present invention is a heat-resistant cap in which the inside is lined with a liner material, and the liner material is a mixed resin containing a homopolymer and a copolymer as main components. The homopolymer is a linear low-density polyethylene having a specific gravity of 0.91 to 93, and the copolymer contains α-olefin and ethylene as main monomers, and has a specific gravity of 0.9045 to 0.9055 ( Hereinafter, sometimes referred to as "ultra low density polyethylene copolymer")
When the ratio of the homopolymer in the mixed resin is a, the ratio of the copolymer is b, and the mixing ratio between the two is represented by the weight ratio a: b, 30:70 to 8
0:20.

 Hereinafter, the present invention will be described in more detail.

In the heat-resistant cap of the present invention, a mixed resin containing a homopolymer and a copolymer as main components is used for the inner liner material.

In the present invention, the homopolymer used together with the copolymer is a linear low-density polyethylene, and the linear low-density polyethylene generally has an MFR of 7.0 to 8.0 g / 10 min and a softening point of 93 to 90 ° C.
Is common. These are obtained by anionic polymerization or polycondensation of ethylene.

In the present invention, the copolymer used together with such a linear low-density polyethylene is a linear polymer containing ethylene and α-olefin as main monomers and has physical properties as shown in Table 1. It can be obtained, for example, from Sumitomo Chemical Co., Ltd. under the trade name “Excellen VL700”.

In the heat-resistant cap of the present invention, the proportion of the homopolymer is a,
When the ratio of the copolymer is represented by b and the mixture ratio of both is represented by the weight ratio a: b, a mixed resin having a ratio of 30:70 to 80:20 is used as the liner material for the liner treatment.

In the mixed resin of the liner material, the peel strength becomes weaker when the ratio a of the homopolymer and the ratio b of the copolymer are 100 and the sum 100 of the copolymer b, and the liner material falls off when the plug is opened. There is a fear that the impact resistance is weakened. In addition, cracks easily occur due to stress caused by the environment, leaks occur when subjected to thermal shock, or cracks occur when subjected to stress, which is undesirable.If a exceeds 80, peel strength is weak. When opening, the liner may fall off. Also, the impact resistance tends to be weak.

In the present invention, the cap body is lined with the liner material as described above.

In the liner material made of the mixed resin as described above, besides, a white pigment such as titanium dioxide, a lubricant, an antioxidant,
A heat stabilizer, an adhesion promoter and the like may be included in a range that does not impair the purpose of the present invention.

The thickness of the liner material in such a cap is usually
500 μm to 1500 μm is preferable.

〔Example〕

 Hereinafter, embodiments of the present invention will be described.

In the practice of the present invention and the practice of the comparative technique, the substances shown in Table 2 below were used.

<Examples 1 to 8> The substances shown in Table 2 were used and mixed as shown in each Example column of Table 3, and 0.03 parts by weight of erucamide and 2 parts by weight of titanium dioxide were further blended as a lubricant. A liner material was prepared, and ten heat-resistant caps 1 as shown in FIG. 1 were manufactured for each example.

The numbers in the circles are in accordance with Table 2, the mixing ratio column indicates the weight ratio, and the proportioning order is in accordance with the notation in the liner material column.

 The heat-resistant cap 1 was manufactured as follows.

The outer surface of an aluminum plate having a thickness of 0.23 mm is coated with a roll coat on the outer surface 3 and the inner surface 4 is coated on the inner surface, and the liner 12 is pressed onto the inner surface of the coated inner coat in a ring shape having an inner diameter of 18 mm from the center point. Masking printing on the inner surface of aluminum plate
13 were provided.

Next, the cap body 2 is press-formed from an aluminum plate provided with a masking print 13, a perforation 6 is opened at the periphery of the mouth of the cap by knurling, and the locking ring 8 and the cap body 2 are connected to the opening of the cylinder 10. The pill fur proof mechanism 5 connected by the plurality of connecting pieces 7 on the side peripheral edge was formed on the cap body 2.

The liner material in a molten state is put into the inner surface of the top plate 9 of the cap body 2 and pressed to form the inner coat 4.
A heat-resistant cap 1 was manufactured by molding a liner 12 of a fixed shape that was adhered and fixed to the main body 2 through the above.

Next, the heat-resistant cap 1 produced above was put on the mouthpiece 11 of a polyethylene terephthalate resin bottle filled with 1.5 liter of hot and cold water at 98 ° C., and roll-on capping was performed while applying a top pressure of 180 kg · f. The screw portion was formed with a machine, the bottle with the heat-resistant cap 1 attached was turned over for 45 seconds, and then sterilized by setting it upright for 5 minutes and 15 seconds. After that, water cooling with tap water,
The following tests were performed.

Opening torque test (Unit: Kg-cm) Fill the 1.5 liter heat-resistant bottle made of polyethylene terephthalate resin with hot water of 98 ° C, leave it at room temperature for one month after capping, and measure the opening torque value with a torque meter. did.

After the measurement of the environmental stress crack test, the presence or absence of cracks in the liner was checked with a microscope.

Peel Strength Test (Unit: Kgf) The peel strength of the liner from the main body was measured at an angle of 90 ° at 10 mm / s using an autograph.

Stress cracking resistance test A 10% Igepearl aqueous solution of crack accelerator was immersed in a 90 ° bent so that the side of the cap was removed and the liner was exposed. ₅₀ ) was measured.

Thermal shock test After heating to 65 ° C and leaving it for 4 hours, immerse in ice water for 30 minutes.
Thereafter, the liquid leakage and the degree of reduced pressure (mmHg) were measured.

Impact Test A sealed bottle was dropped upside down from a height of 50 cm onto a 30 ° inclined steel surface to confirm liquid leakage.

 The results are shown in Table 4.

In addition, liquid leak test, impact test, environmental stress crack test
The number (unit: books) of the caps in which the change was recognized among the ten heat-resistant caps 1 was indicated by a fraction.

<Comparative Examples 1 to 15> The procedure of Example 1 was repeated, except that the substances shown in Table 2 were used and mixed as shown in each Comparative Example column of Table 5 to prepare a liner material.

In Comparative Example 14, LDPE (low density polyethylene) conventionally used as a liner material was used. In Comparative Example 15, EVA (ethylene / vinyl acetate copolymer) conventionally used as a liner material was used.

In the same manner as in Example 1, heat-resistant cap 1 was used for each comparative example.
Each was manufactured and the same test as in Example 1 was performed.

 Table 6 shows the results of each test.

From the above results, all of the liner materials of the examples were compared with any of the comparative examples, all of which were opened torque test, environmental stress crack test, peel strength test, stress crack resistance test, thermal shock test, impact It was found that proper values were maintained in the test and heat resistance was exhibited.

That is, the heat-resistant cap 1 obtained in the embodiment not only prevents the lowering of the opening torque and the prevention of liquid leakage, but also is effective in generating the stress cracking in the environment of contact with steam and hot water due to the pressure applied during capping and high-temperature filling. It was found that the sealability of the conventional developed liner material was further improved.

[Effect of the Invention] Since the present invention has the above-described configuration, it is possible to obtain a heat-resistant cap that can sufficiently withstand a high temperature of 90 ° C or more.

In addition, since it is possible to seal a content liquid that needs to be heat-treated at 90 ° C. or higher, the field of use of a polyethylene terephthalate resin biaxially stretched blow molded bottle having high performance can be expanded.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an embodiment of the heat-resistant cap of the present invention. 1 ... heat resistant cap

Claims (1)

(57) [Claims] 1. A heat-resistant cap having an inner surface treated with a liner material, wherein the liner material is a mixed resin containing a homopolymer and a copolymer as main components, and the homopolymer has a specific gravity of 0.91 to 0.93. Is a linear low-density polyethylene whose copolymer contains α-olefin and ethylene as main monomers, and has a specific gravity of 0.9045 to 0.9055, and the proportion of the homopolymer in the mixed resin is a When the ratio of the copolymer is b and the mixing ratio between the two is represented by the weight ratio a: b, 30:70 to 8
Heat resistant cap that is 0:20.