JP7178181B2 - Film for heavy duty packaging bags and heavy duty packaging bags - Google Patents

Description

The present invention relates to a heavy-duty packaging bag film containing ethylene-vinyl acetate copolymer (EVA) and a heavy-duty packaging bag using the film.

For heavy-duty packaging bags that mainly contain 5 to 30 kg of content, such as fertilizers and chemical products, it is required that the bag not break due to the weight of the content. ), which are mainly composed of a resin having high drop strength (see, for example, Patent Documents 1 and 2).

On the other hand, the applicant of the present application has proposed a packaging material that uses a low-density polyethylene resin (LDPE) as a main component to impart easy-openability (see, for example, Patent Document 3).

JP 2015-21112 A Japanese Patent Application Laid-Open No. 2008-230706 JP 2017-202641 A

However, heavy-duty packaging bags made mainly of LLDPE have high drop strength, but are not easy to open, requiring strong force to open with bare hands. There is a risk that the contents may pop out when the package is opened because the package is cut diagonally.

On the other hand, a packaging material containing LDPE as a main component has a weak drop strength, and although it can be easily opened, it may easily break when used as a heavy-duty packaging bag.

In other words, the falling bag strength and the easy-openability are contradictory, and it was difficult to make them compatible.

Heavy duty packaging bags containing ethylene-vinyl acetate copolymer (EVA) as a main component are available on the market, but they are not easy to open.

Moreover, in order to improve filling aptitude of the content, it is preferable to obtain a good stiffness.

It is an object of the present invention to provide a film for heavy duty packaging bags having both drop strength and easy openability, and a heavy duty packaging bag using the film.

In order to solve the above-mentioned problems, the present inventors conducted extensive studies and found that a heavy-duty packaging bag film containing, as a main component, an ethylene-vinyl acetate copolymer resin (EVA) containing a desired amount of vinyl acetate is used. Thus, the inventors have found that both the strength of the falling bag and the easy-openability can be achieved, leading to the present invention. Therefore, the means for solving the problems of the present invention are as follows.

<1> A heavy-duty packaging bag film characterized by containing 80% by weight or more of an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content of more than 1.5%.

<2> The film for heavy duty packaging bags according to <1>, wherein the vinyl acetate content in the EVA is less than 10%.

<3> The film for heavy duty packaging bags according to <2>, wherein the vinyl acetate content in the EVA is 3% to 9%.

<4> The film for heavy-duty packaging bags according to any one of <1> to <3>, which contains 0.942 g/cm ³ or more high-density polyethylene resin (HDPE) in a range of 5% by weight or more and less than 15% by weight. be.

<5> The film for heavy duty packaging according to <1>, wherein the EVA has a vinyl acetate content of 10% or more and contains 10% to 20% by weight of HDPE.

<6> The film for heavy duty packaging bags according to <4> or <5>, wherein HDPE has a melt flow rate (MFR) (g/10 minutes, 190°C) of 0.10 or more.

<7> The film for heavy duty packaging bags according to any one of <1> to <6>, which has a thickness of 50 μm to 200 μm.

<8> The film for heavy duty packaging bags according to <7>, which has a thickness of 150 μm or more.

<9> The film for heavy duty packaging bags according to any one of <1> to <8>, which is composed of a single layer.

<10> A heavy-duty packaging bag comprising the film for heavy-duty packaging bags according to any one of <1> to <9>.

The heavy-duty packaging bag film of the present invention contains 80% by weight or more of ethylene-vinyl acetate copolymer resin (EVA) having a vinyl acetate content of more than 1.5%, so that it achieves both drop-down strength and easy-openability. becomes possible.

Since the heavy-duty packaging bag of the present invention is made of the film for heavy-duty packaging bags of the present invention, it is possible to achieve both drop-bag strength and easy-openability.

1 is a photograph showing the results of the drop bag test of Comparative Example 5. FIG.

The film for heavy duty packaging bags of the present invention contains ethylene-vinyl acetate copolymer resin (EVA) as a main component.

The EVA content in the entire film must be 80% by weight or more, preferably 85% by weight or more, and more preferably 90% by weight or more. If the content is less than 80% by weight, it becomes difficult to obtain the desired effect of the present invention by using EVA as the main component. For example, if a large amount of high-density polyethylene resin (HDPE) is contained, the tearing force of the film becomes too strong, making it difficult to obtain easy-to-open properties. It may become difficult.

The content of vinyl acetate in this EVA is more than 1.5%, usually 20% or less, preferably less than 10%, more preferably 3% to 9%, particularly preferably 4% to 6%. If the content of vinyl acetate is 1.5% or less, the desired drop bag strength cannot be obtained, and if the content is 20% or more, there is no significant effect. Also, when the content of vinyl acetate is less than 10%, the tensile modulus of elasticity is high, a feeling of stiffness suitable for a heavy-duty packaging bag can be obtained, and when the bag is made into a bag, it can be made into a good filling aptitude.

The melt flow rate (MFR) (g/10 minutes, 190° C.) of EVA is not particularly limited as long as inflation molding is possible, but is usually in the range of 0.3 to 3.0.

The film for heavy-duty packaging bags of the present invention may be formed from EVA alone, except for a trace amount of additives. It preferably contains 0.942 g/cm ³ or more of HDPE.

HDPE is generally contained in the range of 5% by weight or more and less than 15% by weight, preferably 5% by weight to 10% by weight, in the entire film. If the content is 15% by weight or more, the drop bag strength tends to decrease and the easy-opening property is difficult to obtain.

However, when the content of vinyl acetate in EVA is 10% or more, the drop strength is suppressed, and HDPE is increased to 10% to 20% by weight, preferably 15% to 20% by weight. By blending, it is possible to improve the firmness.

The MFR (g/10 minutes, 190° C.) of HDPE is preferably 0.10 or more, more preferably 1.0 or more, in order to obtain a film with good appearance. The upper limit of the MFR is usually about 3.0, considering the inflation molding. If the MFR is less than 0.10, small lumps of residual resin called gels or lumps may remain on the film, resulting in poor appearance.

Here, the content of vinyl acetate in EVA can be analyzed based on JIS K7192, for example. Also, the amount of EVA and HDPE in the film can be analyzed, for example, by subjecting the film to heat treatment using a pyrolyzer and then quantitatively analyzing the ratio of the two using a gas chromatograph mass spectrometer.

In addition, each evaluation of the film is based on tear strength (N) measured in accordance with JIS K7128-1 for easy openability, and impact breaking mass (g) measured in accordance with JIS K7124-1 for drop strength. , Firmness can be measured by tensile elastic modulus (MPa) measured according to JIS K7161-1.

In order for the heavy-duty packaging bag made of this film to achieve both easy-openability and drop-down strength, the tearing force must be less than 12.0 N in the TD direction, which corresponds to the opening direction of the bag. It is preferably 10.5N or less, more preferably 8.0N or less. In addition, the impact breaking mass is usually 100 g or more, preferably 150 g or more, at folds (edges) that tend to be relatively weak when molded.

Furthermore, in order to obtain good stiffness, the tensile modulus is preferably 100 MPa or more, more preferably 150 MPa or more.

The film for heavy duty packaging bags of the present invention may be a single layer or a laminate of a plurality of layers by a known method, but is preferably a single layer. In the case of multiple layers, the excellent drop-bag strength and easy opening property of the layer containing EVA may be weakened by other layers that do not contain EVA, and the lamination may increase the manufacturing cost.

The film for heavy-duty packaging bags of the present invention is usually produced by inflation molding, while considering various conditions such as blow ratio, MD/TD orientation ratio, film take-up speed, resin temperature, etc., while considering the performance of the molding machine. Produce it by adjusting it appropriately.

The thickness of the film for heavy-duty packaging bags of the present invention thus obtained is usually 50 μm to 200 μm, preferably 150 μm to 200 μm in order to obtain good stiffness. If the thickness is less than 50 µm, the bag may be too thin and drop strength may be lowered, while if the thickness exceeds 200 µm, it may be difficult to obtain easy-openability. The thickness can be measured using a commercially available dial gauge based on JIS Z1702.

Here, when the content of vinyl acetate in EVA is 10% or more, it is preferable to mold with a blow ratio of 1.0 to 1.5 and a thickness of 150 μm to 200 μm. By keeping the blow ratio low and increasing the thickness to 150 μm or more, the tensile elastic modulus per 100 μm of thickness is increased, and the stiffness can be improved.

On the other hand, when the content of vinyl acetate in EVA is less than 3%, it is preferable to mold with a blow ratio of 1.5 to 2.0 and a thickness of 50 μm to 100 μm. By increasing the blow ratio and thinning the thickness to 100 μm or less, the tearing force is lowered and the ease of opening can be easily improved. The blow ratio is more preferably close to 2.0 in order to further improve the ease of opening and the drop strength.

In addition, the heavy packaging bag of the present invention is produced by cutting a tube film, which is produced by inflation molding, into a desired length and processing it into a bag shape in the same manner as the film for heavy packaging bags of the present invention.
In that case, for example, known components that can be used, such as antistatic agents, heat stabilizers, antioxidants, lubricants, ultraviolet absorbers, colorants, etc., may be appropriately added depending on the purpose.

As described above, the film for heavy-duty packaging bags of the present invention is suitable for use in the heavy-duty packaging bags of the present invention because it can achieve both drop-bag strength and easy-openability. It can be applied to a variety of required uses, and can be widely used in packaging materials that require easy opening properties.

Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[Evaluation of physical properties of film for heavy packaging bag 1]
The following ethylene-vinyl acetate copolymer resin (EVA), high-density polyethylene resin (HDPE), low-density polyethylene resin (LDPE), and linear low-density polyethylene resin (LLDPE) were prepared. These are appropriately used so as to have the formulations of the following examples, and the thickness is 100 μm, the folding diameter is 200 μm, and the blow ratio is 1.0 with an inflation molding machine (manufactured by Placo Co., Ltd.: die diameter 120 mmφ, screw diameter 50 mmφ). Thus, a tube film for a heavy-duty packaging bag of each example was produced.

・EVA
(a) Nippon Polyethylene Co., Ltd.: Novatec LV1511, MFR (g/10 min, 190°C) 3.0, vinyl acetate content 1.5%
(b) Nippon Polyethylene Co., Ltd.: Novatec LV115, MFR (g/10 min, 190°C) 0.3, vinyl acetate content 4.0%
(c) Nippon Polyethylene Co., Ltd.: Novatec LV211A, MFR (g/10 min, 190°C) 0.3, vinyl acetate content 6.0%
(d) Nippon Polyethylene Co., Ltd.: Novatec LV342, MFR (g/10 min, 190°C) 2.0, vinyl acetate content 10%
(e) Nippon Polyethylene Co., Ltd.: Novatec LV430, MFR (g/10 min, 190°C) 1.0, vinyl acetate content 15%
(f) Ube Maruzen Polyethylene Co., Ltd.: UBE polyethylene VF120T, MFR (g/10 min, 190°C) 1.0, vinyl acetate content 20%

・HDPE
(a) Prime Polymer Co., Ltd.: Hi-Zex 7000F, MFR (g/10 min, 190°C) 0.04, density 0.952 g/cm ³
(b) Prime Polymer Co., Ltd.: Hi-Zex 3600F, MFR (g/10 min, 190°C) 1, density 0.958 g/cm ³
(c) Prime Polymer Co., Ltd.: Hi-Zex 2208J, MFR (g/10 min, 190°C) 5.2, density 0.964 g/cm ³
(d) Prime Polymer Co., Ltd.: Hi-Zex 2110JH, MFR (g/10 min, 190°C) 10.0, density 0.952 g/cm ³

・LDPE
Ube Maruzen Polyethylene Co., Ltd.: UBE polyethylene R-300, MFR (g/10 min, 190° C.) 0.35, density 0.920 g/cm ³

・LLPDE
ExxonMobil Corporation: Enable2005MC, MFR (g/10 min, 190°C) 0.50, density 0.920 g/cm ³

(Formulation of each example)
Example 1 EVA (a) 100% by weight
Example 2 EVA (c) 100% by weight
Example 3 EVA (a) 95% by weight, HDPE (b) 5% by weight
Example 4 EVA (a) 90% by weight, HDPE (b) 10% by weight
Example 5 EVA (a) 95% by weight, HDPE (c) 5% by weight
Example 6 EVA (a) 90% by weight, HDPE (c) 10% by weight
Example 7 EVA (a) 95% by weight, HDPE (d) 5% by weight
Example 8 EVA (a) 90% by weight, HDPE (d) 10% by weight
Example 9 EVA (d) 100% by weight
Example 10 EVA (o) 100% by weight
Example 11 EVA (F) 100% by weight
Example 12 EVA (a) 95% by weight, HDPE (a) 5% by weight
Example 13 EVA (a) 90% by weight, HDPE (a) 10% by weight
Example 14 EVA (a) 85% by weight, HDPE (d) 15% by weight
Reference Example 1 EVA (a) 85% by weight, HDPE (c) 15% by weight
Comparative Example 1 EVA (a) 100% by weight
Comparative Example 2 LDPE 100% by weight
Comparative Example 3 LLDPE 100% by weight

-evaluation-
The produced tube films of each example were tested for tear strength as an index of easy-openability, tensile modulus as an index of stiffness, impact rupture mass as an index of strength against falling bags, and appearance by the following methods. was evaluated. The results are shown in Table 1 for Examples 1-10 and Table 2 for Examples 11-13 and Comparative Example.

・Tear force According to JIS K7128-1, using a universal testing machine (manufactured by Shimadzu Corporation: Autograph AG-X500N), the test piece is pulled at a speed of 200 mm / min in the TD direction corresponding to the opening direction of the bag, The average test force when the displacement at that time was between 20 mm and 120 mm was taken as the tearing force (N).

・ Tensile modulus of elasticity According to JIS K7161-1, using the universal testing machine described above, the test piece is pulled in the MD direction, which is the width direction, at a speed of 5 mm / min, and the strain of the test piece is 0.05% to 0. The tensile modulus (MPa) was calculated from the slope of the test force when changing to 0.25%.

・Impact breaking mass In accordance with JIS K7124-1, a free fall dart impact tester (manufactured by Toyo Seiki Seisakusho) is used to vertically drop an arbitrary weight from a height of 66 cm, and the flat part and fold of the test piece (ear part) were made to collide with each other. When the test piece broke during this collision, the weight of the weight was reduced by 30 g and the weight was dropped again. On the other hand, when the test piece did not break, the weight was increased by 30 g, and the weight was dropped again. The test was performed until the total number of times of destruction was 10 times and the total number of times without destruction was 10 times, for a total of 20 times, and the impact breaking mass (g) was calculated from a predetermined formula.
In Example 11, the weight exceeded 1,472 g, which is the measurement limit of the free fall dart impact tester.

・Appearance The appearance of the folds of the film was visually observed.

According to the results in Tables 1 and 2, the tube films of Examples 1 to 13 of the present invention containing more than 85% by weight of EVA having a vinyl acetate content of more than 1.5% had a tear force of 10.5 N or less. In addition, the value of the impact breaking mass exceeded 150 g even at the fold portion, which is relatively low, and both easy-openability and drop-bag strength were achieved. In particular, the tube films of Examples 1 and 2, in which the vinyl acetate content was less than 10%, had a high tensile modulus and good stiffness.

Further, the tube films of Examples 3 to 6, 12 and 13, which contained HDPE in the range of 5% by weight or more and less than 15% by weight, had an improved tensile modulus and a better feeling of stiffness. In particular, the tube films of Examples 3 to 6 containing HDPE having an MFR (g/10 min, 190°C) of 0.10 or more can be used more preferably without affecting the appearance even when HDPE is added. It turned out to be

Here, the tube film of Example 14 containing 15% by weight of HDPE had good stiffness and drop strength, and the tearing force was less than 12.0 N for ease of opening, which was within the allowable range. However, the tube film of Reference Example 1, which also contained 15% by weight of HDPE, tended to have a lower impact breaking mass.

On the other hand, in the tube film of Comparative Example 1, in which the content of vinyl acetate was 1.5% or less, although easy-opening properties were obtained, the value of the impact breaking mass was less than 100 g at the crease, and there was a risk of bag breakage. Therefore, the desired drop bag strength could not be obtained.

Furthermore, in the tube film of Comparative Example 2 using LDPE, the value of the impact breaking mass was less than 100 g at the fold portion, and the falling bag strength was low, and there was a risk of bag breakage. The tube film of No. 2 had a tearing force of 12.0 N, requiring a large force for opening, and was not easy to open.

From the above, in order to achieve both easy opening property and drop strength in the film for heavy duty packaging bags, it is preferable that EVA with a vinyl acetate content of more than 1.5% is contained in an amount of more than 85% by weight, and good filling is achieved. It was found that the vinyl acetate content of EVA is more preferably less than 10% in order to obtain an appropriate stiffness.

In addition, as long as the vinyl acetate content of EVA is in the range of less than 10%, HDPE should be added in an amount of 5% by weight or more and less than 15% by weight in order to improve the feeling of elasticity without affecting the strength of the falling bag. It was found that it is preferable to contain HDPE within the range, and in order not to affect the appearance, it is more preferable to contain HDPE having an MFR (g/10 min, 190° C.) of 0.10 or more.

[Evaluation of physical properties of film for heavy duty packaging bag 2]
In order to further verify the effect of the present invention, the following EVA was further prepared, and the type of EVA, the blending amount of HDPE, or the thickness of the film were changed as in each example below, except that each was changed. Tube films having the same folding diameter and blow ratio were produced with the same molding machine, and the same evaluation was performed. Table 3 shows the results. The thickness is 100 μm in all cases except for the example (Example 22) in which the thickness is changed. Moreover, in Example 18, it exceeded 1,472 g, which is the measurement limit of the free fall dart impact tester.

・EVA
(g) Tosoh Corporation: Ultrathen 515, MFR (g/10 min, 190°C) 2.5, density 0.925 g/cm ³ , vinyl acetate content 6.0%
(h) Tosoh Corporation: Ultrasen 540, MFR (g/10 min, 190°C) 3.0, density 0.929 g/cm ³ , vinyl acetate content 10%
(i) Tosoh Corporation: Ultrathen 630, MFR (g/10 min, 190°C) 1.5, density 0.936 g/cm ³ , vinyl acetate content 15%
(Co) manufactured by Tosoh Corporation: Ultrathen 631, MFR (g/10 min, 190°C) 1.5, density 0.941 g/cm ³ , vinyl acetate content 20%

(Formulation of each example)
Example 15 EVA (ki) 100% by weight
Example 16 EVA (h) 100% by weight
Example 17 EVA (ke) 100% by weight
Example 18 EVA (co) 100% by weight
Example 19 EVA (d) 80% by weight, HDPE (d) 20% by weight
Example 20 EVA (h) 80% by weight, HDPE (c) 20% by weight
Example 21 EVA (h) 80% by weight, HDPE (d) 20% by weight
Example 22 EVA (a) 100% by weight, thickness 150 μm
Comparative Example 4 EVA (h) 50 wt%, HDPE (d) 50 wt%

According to the results in Table 3, the tube films of Examples 15 to 18, which consisted only of EVA with a vinyl acetate content of more than 1.5%, had a tear force of 10.5 N or less and an impact breaking mass value of Even the relatively low fold portions exceeded 250 g, and both easy-openability and drop-bag strength were achieved. In particular, the tube film of Example 15, which had a vinyl acetate content of less than 10%, had a high tensile modulus and good stiffness. From this, it has been clarified that if the vinyl acetate content is within a predetermined range, the same effect can be obtained even if the resin is changed.

Further, when comparing Examples 16 to 18 consisting only of EVA having a vinyl acetate content of 10% or more and Examples 19 to 21 containing 20% by weight of HDPE although the EVA has a vinyl acetate content of 10%, In the latter, the value of the tensile elastic modulus was five times or more at the maximum and two times or more at the minimum, as compared with the former, and the stiffness was dramatically improved. At that time, the tearing force was all less than 11.0 N, and the value of the impact breaking mass at the fold portion of Example 21, which was the weakest, was about 150 g. was For this reason, even in EVA with a vinyl acetate content of 10% or more, by blending a larger amount of HDPE than when using EVA with a vinyl acetate content of less than 10%, it is possible to achieve both easy opening property and drop bag strength. In addition, it was found that the firmness can be improved.

Furthermore, in Example 22, which is different from Example 1 described above only in thickness, the value of the impact breaking mass is twice or more and the value of the tensile elastic modulus is about 1.8 times that of Example 1. It is high, and the falling bag strength and the feeling of stiffness are dramatically improved. From this, it was found that when the thickness of the film is 150 μm or more, excellent falling bag strength and stiffness can be obtained.

On the other hand, in Comparative Example 4, which uses EVA with a vinyl acetate content of 10% and contains 50% by weight of HDPE, the feeling of stiffness is improved, but the falling bag strength is lowered, the tear strength is extremely high, and the easy-openability is lost. was broken

From the above, even when EVA with a vinyl acetate content of 10% or more is used in the film for heavy-duty packaging bags, in order to achieve both easy openability and drop strength, the blending amount of HDPE is 20%. It has been found that the limit is about weight percent, and it is necessary to contain 80 weight percent or more of EVA having a vinyl acetate content of more than 1.5%.

In addition, in this verification, the external appearance was good regardless of the difference in composition.

[Evaluation of physical properties of heavy duty packaging bags]
(Example 23)
A mixed resin was prepared by mixing 96.3% by weight of EVA having the composition (a) above, 1.2% by weight of the white masterbatch of (1) below, and 2.5% by weight of the antistatic agent of (3) below. Using this, a tube film having a thickness of 150 μm, a folding diameter of 500 μm and a blow ratio of 1.6 was produced using an inflation molding machine (manufactured by Placo Co., Ltd.; die diameter 200 mmφ, screw diameter 50 mmφ). This tube film was cut into a length of 750 mm, and the bottom surface was sealed by heat sealing to prepare a heavy-duty packaging bag of the present invention.
The resulting heavy-duty packaging bag was measured for tear strength in the TD direction, tensile modulus in the MD direction, and impact breaking mass by the same methods as described above, and was also subjected to a drop bag test by the method described below. Table 4 shows the results other than the results of the drop bag test.
In this example, the bag was not broken as a result of the drop test.

· White masterbatch and antistatic agent (1) Sumika Color Co., Ltd.: 7A1155
(2) Prime Polymer Co., Ltd.: TH-5
(3) Ube Maruzen Polyethylene Co., Ltd.: MUD

・Drop bag test Fill the obtained bag with 20 kg of chemical fertilizer, fold the film on the top, seal the bag with tape, and drop the bag vertically up to 5 times from a height of 1.2 m with the bottom down. rice field. When the bag broke, the number of times the bag broke and the location of the bag break were recorded.

(Comparative Example 5)
A mixed resin was prepared by mixing 97.0% by weight of the above LDPE resin, 1.0% by weight of the white masterbatch of the above (1), and 2.0% by weight of the antistatic agent of the above (2). Using this, the same inflation molding machine as in Example 14 was used to produce a tube film as a heavy duty packaging bag of the present invention having a thickness of 150 μm, a folding diameter of 460 μm, and a blow ratio of 1.5.
As in Example 1, the resulting heavy-duty packaging bag was subjected to measurement of tearing force in the TD direction, tensile modulus of elasticity in the MD direction, impact breaking mass, and a drop bag test. Table 4 shows the results other than the results of the drop-bag test, and FIG. 1 shows the results of the drop-bag test.
In this example, the bag was broken at the second drop in the drop test.

According to the results in Table 4, the tube film of Example 23, which is a heavy-duty packaging bag of the present invention, has a weaker tearing force, is superior in easy-openability, and has a higher value of impact breaking mass than that of Comparative Example 5. It also had excellent strength. Moreover, the tensile modulus of elasticity exceeded 150 MPa, and it had a feeling of stiffness suitable for a heavy-duty packaging bag, that is, filling aptitude.

Further, as shown in FIG. 1, in the bag drop test, the tube film of Comparative Example 5 was broken at the crease when dropped for the second time, whereas the tube film of Example 23 was broken. The bag did not fall off, and had sufficiently high drop strength even in actual use.

From the above, it was found that the heavy-duty packaging bag using the film of the present invention can achieve both easy-openability and drop-bag strength, and has good filling aptitude.

[Evaluation of physical properties of film for heavy duty packaging bag 3]
In order to further verify the effect of the present invention, the following EVA was further prepared, and the same molding machine as in Part 1 above except that the type of EVA, blow ratio or thickness was changed as in each example below. A tube film was produced in and evaluated in the same manner. Table 5 shows the results. The folding diameter was changed as the blow ratio was changed. In addition, in the case of the thickness of 150 μm, the tensile modulus was calculated by multiplying the measured value by 2/3 to calculate a value converted per 100 μm of thickness.

・EVA
(S) Tosoh Corporation: Petrocene 10K06A, MFR (g/10 min, 190°C) 1.5, density 0.926 g/cm ³ , vinyl acetate content 2%

According to the results in Table 5, in the tube films of Examples 24 to 31 of the present invention, the tear force was 10.0 or less, and the value of the impact breaking mass exceeded 100 g even at the crease portion with a relatively low value. Therefore, it was possible to achieve both easy-openability and drop-bag strength.

Here, among Examples 24 and 26 to 30, which consist of only EVA with a high vinyl acetate content of 10%, the blow ratio is 1.0 and the thickness is 150 μm, which is the lowest blow ratio and the highest thickness. In Example 24, which is thick, the tensile elastic modulus in terms of thickness of 100 μm reached 100 MPa, and good stiffness was obtained. From this, it was found that EVA with a high vinyl acetate content of 10% or more can be molded with a blow ratio of 1.0 and a thickness of 150 μm to improve the stiffness.

On the other hand, among the tube films of Examples 25 and 31 and Reference Example 2, which consist of only EVA having a relatively low vinyl acetate content of 2% and a relatively thin thickness of 100 μm, the tube films of Examples 25 and 31 did not tear. The force was 10.0 N or less and had excellent easy opening property. Even in this example with a thickness of 100 μm, in Example 25, which has a relatively high blow ratio of 2.0, the tear force decreased and the impact breaking mass value increased. From this, it is preferable to mold EVA with a relatively low vinyl acetate content of 2% with a blow ratio of 1.5 or more and a thickness of 100 μm or less because it is easy to improve the easy-openability. It was found that it is more preferable to make it closer to 2.0 because it is possible to further improve the easy-openability and the drop strength.

INDUSTRIAL APPLICABILITY The present invention can be applied to packaging materials that require easy opening, such as heavy duty packaging bags.

Claims (4)

A heavy-duty packaging bag film containing 80% by weight or more of ethylene-vinyl acetate copolymer resin (EVA) and containing 0.942 g/cm ³ or more of high-density polyethylene resin (HDPE),
The content of vinyl acetate in EVA is 4% or more and 6% or less , and HDPE is contained in a range of 5% or more and less than 15% by weight,
A film for heavy duty packaging bags, characterized in that HDPE has a melt flow rate (MFR) (g/10 minutes, 190°C) of 1.0 or more and a film thickness of 50 µm or more and 200 µm or less. The film for heavy duty packaging bags according to claim 1 , which has a thickness of 150 µm or more. The film for heavy-duty packaging bags according to claim 1 or 2, comprising a single layer. A heavy-duty packaging bag comprising the film for heavy-duty packaging bags according to any one of claims 1 to 3 .

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