JP6176935B2 - Transverse heat-sealing film and easy-open packaging body using the same - Google Patents

Description

  The present invention relates to a transverse heat-sealing film and an easy-open packaging body using the same, and more particularly to a film having improved lateral tearability of the film and an easy-open packaging body formed from the film.

  Currently, in the packaging of articles, films and articles are supplied by an automatic packaging machine, and filling, packaging, and sealing are performed continuously. The performance required for such a packaging film is to have sufficient strength at the time of supply and processing of the film and further distribution and satisfy good heat sealability at the time of sealing. In addition to these requirements, easy opening is also required. An unstretched film, which is a general sealant film, is generally not stretched and therefore tends to have high tear strength as a whole. Further, in a general biaxially stretched heat seal film, the tear strength is lowered due to molecular orientation, but the directionality is not fixed. Therefore, tearing of the heat seal film is not always easy, and there are problems such as excessive resistance at the time of tearing and directionality not being determined.

  As a countermeasure against such tearability, a film formed by uniaxial stretching has been proposed (see Patent Documents 1, 2, and 3). Patent Document 1 is a transverse tearable laminated film in which a film of a propylene resin having a higher melting point than that of a heat seal layer of various olefin resins is laminated and stretched laterally uniaxially. In Patent Document 2, a propylene resin film having a higher melting point is laminated on a heat seal layer of various olefin resins, and a propylene resin film having a high melt index is further laminated thereon. It is a transversely easily tearable laminated film formed by uniaxial stretching. Patent Document 3 discloses a film formed by transversely uniaxially stretching a resin composition containing high-density polyethylene and low-density polyethylene.

  According to the films exemplified in Patent Documents 1 and 2, etc., a certain effect is exhibited in the tearability in the lateral direction of the film. Generally, an article to be packaged for a heat seal film is often a food, and the food is taken out by breaking the film of the packaging bag at the time of eating. Or often eat with a broken packaging bag. However, in the case of a packaging bag made from a conventional heat-seal film, as shown in the photograph of FIG. 6, there is a problem that strips or fibrous film strips are formed along the tearing direction of the film at the broken portion of the film. Had. Therefore, there is a concern that the food may be accidentally eaten with the food that is the content at the time of eating, and the advantage of tearability is not fully utilized.

  In Patent Document 3, although it is effective in suppressing film strips generated during tearing, it is not always sufficient. Moreover, since it is a stretched film mainly composed of high-density polyethylene, it does not have heat sealability and cannot be used alone as a heat seal film for packaging. Therefore, processing such as separately laminating a polypropylene film is required to provide heat sealability, and the division height is high.

  Thus, in the existing film, the heat seal film appropriately having the tear resistance in the direction orthogonal to the film forming direction and the generation of film strips at the time of tearing, and further the heat seal characteristics of the film itself. It still did not exist. Therefore, a suitable packaging heat-sealing film that satisfies all the required performances is desired.

Japanese Patent Publication No. 8-18416 Japanese Patent No. 2995869 Japanese Patent No. 5022585

  The present invention has been proposed in view of the above situation, and a film strip generated on a fracture surface at the time of tearing of the film, together with good tearability (openability and directionality) in a direction orthogonal to the film forming direction of the film. A transverse heat-sealing film that can be suppressed and further has heat-sealing characteristics due to the film itself is provided. And the easy-open packaging body which improved the ease of opening shape | molded using the said horizontal heat seal film is provided.

That is, the invention of claim 1 is a heat seal film that is provided with a heat sealable layer on one side of the base material layer and formed by biaxial stretching, and the base material layer contains a polypropylene resin . In addition, the alicyclic hydrocarbon resin is added in an amount of 5 to 30% by weight based on the total weight of the base material layer, and the heat seal layer includes an ethylene-propylene copolymer, an ethylene-propylene-1 butene copolymer, One or more of propylene-1 butene copolymers are contained, and when the heat seal film is biaxially stretched, the draw ratio in the machine direction (MD) of the heat seal film is 1.1. a ~ 1.5-fold, and the stretching ratio in the transverse direction (TD) is related to the transverse direction, heat-sealing film and satisfies the from 7 to 12 times.

The invention of claim 2 is a heat seal film that is formed by biaxial stretching with a heat sealable layer on one side of the base material layer , the base material layer containing a polypropylene resin, An alicyclic hydrocarbon resin is added in an amount of 5 to 30% by weight based on the total weight of the base material layer, and the heat seal layer comprises an ethylene-propylene copolymer, an ethylene-propylene-1 butene copolymer, a propylene- It contains any one or more of 1-butene copolymers, and when the heat seal film is biaxially stretched, the draw ratio in the machine direction (MD) of the heat seal film is 1.1 to 1. a .5 times, and stretching ratio in the transverse direction (TD) satisfies be 7-12 times, that the outer surface layer is provided which comprises an olefin-based resin on the other side of the base layer Special According to the transverse direction, heat-seal film to.

The invention according to claim 3, JIS K 7128-1 (1998) to the tear strength (S _M) and the transverse direction of the longitudinal direction (MD) of the heat-sealing film, determined in accordance with the trouser tear method defined (TD) in the tear strength (S _T), according to the transverse direction, heat-sealing film according to claim 1 or 2 below (i) tear strength ratio obtained from equation (R _S) is 2 or more.

The invention according to claim 4 is an easy-open packaging body characterized in that the heat-sealing layers in the transverse heat-sealing film according to any one of claims 1 to 3 are heat-sealed to form a bag-like product. Concerning.

In the invention of claim 5, the bag-like product is manufactured by an automatic packaging machine along the longitudinal direction (MD) of the transverse heat-sealing film, and the longitudinal heat-sealing film in the bag-like material is longitudinally formed. It concerns on the easy-open packaging body of Claim 4 in which the fine hole is provided in the heat seal site | part of a direction (MD).

According to the transverse heat seal film according to the invention of claim 1, a heat seal film having a heat seal layer that can be heat sealed on one side of the substrate layer and formed by biaxial stretching, wherein the substrate The layer contains a polypropylene resin, and an alicyclic hydrocarbon resin is added in an amount of 5 to 30% by weight based on the total weight of the base material layer. The heat seal layer is an ethylene-propylene copolymer, ethylene-propylene. -1 butene copolymer and propylene-1 butene copolymer, one or more of them, and in the biaxial stretching of the heat seal film, the machine direction (MD) of the heat seal film stretch ratio in is 1.5 times 1.1, and the stretching ratio in the transverse direction (TD) is to satisfy the 7-12 fold, perpendicular to the film forming direction of the film It is possible to suppress the film strip occurring in fracture surface tear when good tear resistance and film to direction, it is possible to obtain a lateral, heat-seal film provided with the heat-sealing properties further by the film itself. Moreover, the directionality of tearing can be improved and the waist of the film can be strengthened.

According to the transverse heat seal film of the invention of claim 2, a heat seal film having a heat seal layer that can be heat sealed on one side of the substrate layer and formed by biaxial stretching, wherein the substrate The layer contains a polypropylene resin, and an alicyclic hydrocarbon resin is added in an amount of 5 to 30% by weight based on the total weight of the base material layer. The heat seal layer is an ethylene-propylene copolymer, ethylene-propylene. -1 butene copolymer and propylene-1 butene copolymer, one or more of them, and in the biaxial stretching of the heat seal film, the machine direction (MD) of the heat seal film stretch ratio in is 1.1 to 1.5 times, and stretching ratio in the transverse direction (TD) satisfies that a 7-12 fold, olefinic resin on the other side of the base layer Since the outer surface layer containing is provided, it is possible to suppress the film strip occurring in fracture surface tear when good tear resistance and the film to the film forming direction perpendicular to the direction of the film, according to yet the film itself A transverse heat-sealing film having heat-sealing properties can be obtained. Moreover, the directionality of tearing can be improved and the waist of the film can be strengthened. In addition , a functional material can be added to the outer surface layer to improve performance efficiently.

According to the transverse heat seal film of the invention of claim 3, in the invention of claim 1 or 2 , the heat seal film measured according to the trouser tear method defined in JIS K 7128-1 (1998). Since the tear strength ratio (R _S ) between the tear strength (S _M ) in the machine direction (MD) and the tear strength (S _T ) in the transverse direction (TD) is 2 or more, the directionality when tearing is good. .

According to the easy-open packaging body according to the invention of claim 4, since the heat-sealing layers in the transverse heat-sealing film according to any one of claims 1 to 3 are heat-sealed to form a bag-like product, packaging The ease of opening will increase and the product value will increase, which will be advantageous for differentiation from other products.

According to the easy-open packaging body according to the invention of claim 5, in the invention of claim 4 , the bag is manufactured by an automatic packaging machine along the longitudinal direction (MD) of the transverse heat seal film, Since fine holes are provided in the longitudinal (MD) heat seal portion of the transverse heat seal film in the bag-like material, the ease of opening the bag-like material is further improved by the breaks formed from the fine holes. .

It is a schematic cross-sectional schematic diagram of the transverse heat seal film of 1st Embodiment. It is a schematic cross-sectional schematic diagram of the transverse heat seal film of 2nd Embodiment. It is a schematic diagram at the time of packaging of a transverse heat seal film. It is a whole perspective view of an easy-open packaging body. It is the schematic which shows opening of an easy-open packaging body. It is the photograph at the time of tearing of the conventional film.

  The schematic cross-sectional schematic diagram of FIG. 1 is a disclosure example of the simplest structure of the transverse heat seal film 10A. As specified in the invention of claim 1, a heat seal layer 12 capable of heat sealing is provided on one side of the base material layer 11. Furthermore, as shown in the schematic cross-sectional schematic diagram of the transverse heat seal film 10B of FIG. 2 and defined in the invention of claim 2, on the other side opposite to the side in contact with the heat seal layer 12 of the base material layer 11 An outer surface layer 13 is provided. The constituent resin of each layer is discharged from the T die by co-extrusion, and the film has a longitudinal direction MD (also referred to as a winding direction or a machine direction) and a predetermined direction described later in the transverse direction TD perpendicular to the longitudinal direction MD. The film is stretched at a magnification. The direction of MD and TD is shown in FIG. The thickness of the transverse heat-seal film finally obtained after stretching is 20 to 60 μm. The transverse heat seal film may be simply referred to as a heat seal film.

  The base material layer 11 is a part that maintains the structural strength of the heat seal films 10A and 10B itself, and a polypropylene resin is used as a main component. In addition to the homopolymer of propylene, the polypropylene resin may include a random or block copolymer of propylene and olefin. Examples of olefins other than propylene include ethylene, and α such as 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, and 3-methyl-1-pentene having 4 to 18 carbon atoms. -Olefin.

Furthermore , in the composition of the base material layer 11, an alicyclic hydrocarbon resin corresponding to 5 to 30% by weight of the total weight of the base material layer is added. The alicyclic hydrocarbon resin includes compounds such as C5 cyclopentadiene and derivatives thereof. Although blending of the alicyclic hydrocarbon resin is not essential, blending of the alicyclic hydrocarbon resin to the polypropylene resin forming the base layer improves the tear directionality and reduces the film's stiffness. Can be strengthened.

  When the amount of the alicyclic hydrocarbon resin added to the total weight of the base material layer is less than 5%, the effect of improving the directionality is not observed. For this reason, 5% is considered the lower limit. When the addition amount of the alicyclic hydrocarbon resin exceeds 30%, the amount of the alicyclic hydrocarbon resin is too large, which is an obstacle to proper stretching.

  The heat seal layer 12 comes into contact with the article when the article is packaged with the transverse heat seal film, and is fused by mutual heat sealing. Therefore, in addition to the stability of the resin of the layer itself, heat sealing performance at low temperature is required from the viewpoint of production efficiency when forming an easy-open package or the like described later.

  In addition to this, when selecting the resin for the heat seal layer 12, it is necessary to increase the compatibility between the resins in order to increase the interlayer strength with the base material layer 11. Therefore, it is a copolymer of propylene and another olefin resin such as an ethylene-propylene copolymer, an ethylene-propylene-1 butene copolymer, a propylene-1 butene copolymer, and any one of them Two or more kinds are blended. As in the examples described later, an ethylene-propylene copolymer alone, an ethylene-propylene-1 butene copolymer alone, an ethylene-propylene-1 butene copolymer and a propylene-1 butene copolymer are mixed in two kinds. Preferably used. The selection of the resin type and the blending ratio is stipulated in consideration of the adjustment of the heat seal temperature, the strength as the heat seal layer, the quality of stretching, and the like.

  The outer surface layer 13 disclosed in the transverse heat seal film 10B of FIG. 2 is not particularly limited as long as it is a resin type that does not peel from the base material layer 11, and is selected from general olefin-based resins. For example, it is desirable to match the resin type used for the base material layer 11. In the examples described later, the same kind of polypropylene resin as that of the base material layer 11 is used.

  The heat seal film of the present invention is completed through film formation by stretching, appropriate heat setting, and the like. And it winds up in the vertical direction MD and is shipped as a product. For winding, the heat seal layer 12 is always in contact with the base material layer 11 (outer surface layer 13). Therefore, there is a risk that blocking may occur due to strong adhesion between the layers during storage. As a countermeasure against such blocking, an anti-blocking agent is generally added. Although the antiblocking agent can be added to the base material layer 11 itself, it is diluted due to the layer thickness. Therefore, by further providing the outer surface layer 13 and adding a functional material such as an antiblocking agent to the same layer, the performance can be improved efficiently. Further, since printing as a packaging material is also performed on the outer surface layer, components such as corona treatment for printing suitability and adhesion of printing ink are added.

  For stretching the heat seal film 10A having a two-layer structure and the heat seal film 10B having a three-layer structure, a known stretching apparatus and stretching method are employed. For example, a tenter biaxial stretching apparatus or the like is used, and the film is formed by simultaneous or sequential stretching. The greatest point of stretching in the production of the heat seal film is to develop a desired tear property in the film through controlling the orientation of the heat seal film to be completed.

  In biaxial stretching of the heat seal film, specifically, the stretching ratio in the machine direction MD is 1.1 to 2 times, preferably 1.1 to 1.5 times, and the stretching ratio in the transverse direction TD. Is 5 to 30 times, preferably 7 to 12 times. In the present invention, the stretching ratio in the machine direction MD and the transverse direction TD must satisfy the specified values in both directions. It has also been clarified that if only one of them is satisfied, the performance corresponding to the object of the invention cannot be exhibited.

  As will be apparent from the following examples, when the stretching ratio in the machine direction MD is less than 1.1 times, stretching in the machine direction is not substantially performed, and stretching is performed only in the transverse direction. Therefore, there are many film strips (see the photograph in FIG. 6) generated on the fractured surface when the film is torn, which is not suitable for use. When the stretching ratio in the machine direction MD exceeds 2, the generation of film strips is suppressed, but the direction of tearing the film is deteriorated. Therefore, the stretching ratio in the longitudinal direction MD described above is appropriate.

  Next, when the stretching ratio in the transverse direction TD is less than 5 times, uneven stretching occurs and the film thickness becomes non-uniform, which is not suitable as a product. When the stretching ratio in the transverse direction TD exceeds 30 times, a film is not formed because a hole is formed in the film during the stretching or a fracture occurs. Also from this, the draw ratio in the transverse direction TD described above is appropriate. As will be described in detail in the examples, the evaluation of the film strip means the presence or absence of the strip generated at the fracture site when the film is actually torn.

The heat seal film formed in accordance with the above resin composition and stretching conditions is used as a sealant film or the like that is laminated with other films or the like and takes advantage of the heat seal performance in addition to being used alone. In any case, packaging materials for articles are assumed as the main application. In this case, the improvement of the ease of opening the package is greatly related to the good tearability of the film. Therefore, the tear strength S _T tear strength S _M and lateral TD in the longitudinal direction MD in the heat-sealing film is measured. Each tear strength is measured in accordance with the trouser tear method defined in JIS K 7128-1 (1998).

In carrying out the trouser tearing method, in the heat seal film to be measured, a predetermined long test piece is cut out in each of the longitudinal direction MD and the transverse direction TD. A cut is formed in the longitudinal direction, and both pieces are pulled in opposite directions. The load (N) required for tearing at this time is the tear strength. The heat seal film of the present invention is mainly adjusted mainly for the good tearability in the transverse direction TD. The factor that changes the tearability (tear strength S _T ) in the transverse direction TD of the heat seal film is that the transverse stretching is excessively larger than the longitudinal direction. For this reason, the orientation of the constituent resins of the respective layers is changed during stretching in the lateral direction to facilitate alignment in the lateral direction.

Specifically, the tear strength S _T tear strength S _M and lateral TD longitudinal MD, can be found the relative relationship supra formula (i). Therefore, it is possible to index the value obtained by dividing the tear strength S _T of the tear strength S _M in the longitudinal direction MD transverse direction TD as tear strength ratio R _S. When the tear in the lateral direction TD is improved, the value of the tear strength S _T becomes small. Accordingly, the tear strength ratio R _S is increased, and the directionality of the film is improved. As can be seen from the examples below, the tear strength ratio R _S is 2 or more, preferably 4 or more, thereby improving the directionality. On the other hand, when the tear strength ratio R _S is less than 2, the lateral direction is not sufficient.

  Synthetic silica etc. are illustrated as an antiblocking agent used for the transverse heat seal film of the present invention. In addition to the base material layer 11 and the outer surface layer 13, it is also added to the heat seal layer 12 due to blocking resistance. Further, in addition to the antistatic agent for suppressing static electricity of the heat seal film, a predetermined amount of additives such as an antioxidant, a neutralizing agent and a colorant may be added if necessary.

As shown in FIGS. 3 and 4, the transverse heat-sealing films 10 </ b> A and 10 </ b> B are heat-sealed with the heat-sealing layers 12 (see FIG. 3B), and the bag-like material 20 ( Easy-open packaging) (see FIG. 4). The type of the contents C is not particularly limited, and is various articles such as household goods, pharmaceuticals, and foods. Among these, the transverse heat-sealing film and the bag-like product are mainly used for food packaging. Improving the ease of opening the package is directly linked to the ease of eating. For this reason, packaging materials play a large role in increasing product value and differentiating from other products.

The illustrated bag 20 is a film packaging form generally called pillow packaging or the like. At the time of bag making , the roll-shaped wound transverse heat seal films 10A and 10B are supplied to various automatic wrapping machines such as a horizontal pillow wrapping machine and a vertical pillow wrapping machine along the vertical direction MD. Filling and bag making are carried out continuously with the supply. Examples thereof include automatic packaging machines such as JP-A-6-179420 and JP-A-8-91307. In the pillow package bag 20, the center seal portion 23 is formed along the longitudinal direction MD, and the sealing portions 21 and 22 are formed at both ends thereof. Reference numeral 24 denotes a main body portion of the bag-like object. In an automatic packaging machine, the formation of a sealing part by heat sealing and the separation (cutting) of individual bag-like materials are performed simultaneously.

  In addition, in the bag-like product 20, fine holes 25 are provided in the center seal portion 23 corresponding to the heat seal portion in the longitudinal direction MD of the heat seal films 10A and 10B. The micro holes 25 are formed by an appropriate method such as drilling with a needle-shaped mold. Since the fine hole 25 is provided in the center seal portion 23, the film easily breaks at the center seal portion 23. For this reason, the cut | interruption which arose in the center seal part becomes a trigger of opening.

  Normally, when taking out an article (contents) from a pillow-shaped bag, the sealing part 21 or 22 is pulled while the center seal part 23 and the main body part 24 are picked with fingers. By doing so, the encapsulated article can be taken out by releasing the heat seal of the sealing portion. Although there is no problem in such an unsealing operation itself, it may be assumed that the removal of the article is not easy depending on the shape and size of the article. For example, when roll cakes, churros, long confectionery breads, and the like are assumed as articles to be packaged, it takes time and effort to extrude the articles in addition to pulling out with fingers when taking out from the opened sealing portion. In addition, there is a risk that the shape may be lost during eating, resulting in a poor appearance.

  Such a problem is simply caused by the fact that only the heat-sealed sealing portion and the center seal portion are opened. Moreover, it is also possible to tear and open in the longitudinal direction of a bag-shaped object along longitudinal direction MD by cutting off the shape of the edge part of a sealing part in a mountain shape. However, since the opening of the bag-like material becomes large, it is difficult to say that it is satisfactory in terms of the holding property of the article and the ease of eating the food.

  On the other hand, according to the transverse heat-sealing films 10A and 10B and the bag-like product 20 made from now on, the film is torn at the main body 24 other than the heat-sealed part, and the packaging is unwound and the ease of taking out the article is improved. To do. In particular, the ease of eating of the food content is greatly improved. The mechanism will be described with reference to FIG. When trying to open around the trunk of the bag-like object 20, as shown in FIG. 5 (a), it exists at the time of bag making by pulling the center seal portion 23 of the bag-like object 20 while picking an arbitrary position by hand. An unbroken cut K occurs.

  As shown in FIG. 5B, the center seal portion 23 can be torn at the boundary K. The tearing direction is different in the direction before and after the page as shown by the thick arrow in the figure. The direction in which the break K enters is the transverse direction TD of the heat seal film. In addition, since the center seal portion 23 is provided with the fine hole 25, the cut is more easily made and the cut K is easily generated.

  In FIG. 5C, the cut K reaches the film of the main body 24 beyond the center seal portion 23, and the body portion of the bag 20 is cut along the lateral direction TD of the heat seal film. Thus, the opening Op is generated from the cut K. The center seal portion 23 in the vicinity of the cut K is pulled in the direction of the thick arrow so as to widen the opening portion Op.

  Finally, as shown in FIG. 5 (d), the opening Op reaches the entire periphery of the film of the main body 24, and the bag 20 is divided into two parts. By doing so, the contents C can be easily taken out. In particular, in the case of the above-mentioned bread and confectionery, the bag-like material can be easily opened without smearing hands and nails (fingertips) during eating, and therefore, it greatly advances in ease of eating. Moreover, since the film strip produced by tearing of a film (opening of a bag-like thing) is also suppressed very much, when eating in the state of the same figure, a possibility that a film strip may be accidentally eaten is also reduced. When proceeding with eating, a cut is made in another center seal portion, and the film of the main body portion 24 can be opened in a ring shape as before. Accordingly, it is possible to fundamentally review the ease of opening a bag-like product for packaging a long food through improvement of the heat seal film, and propose an easy-open packaging body having a new way of eating.

(Creation of transverse heat seal film)
Resins used as raw materials for the transverse heat seal films (heat seal films) of Examples 1 to 10 and Comparative Examples 1 to 9 based on the blending ratio (parts by weight) of each layer shown in Tables 1 to 4 below. Were melted and kneaded, and a film was formed by adjusting the stretching ratio (longitudinal direction MD and transverse direction TD) of each table with a coextrusion T-die film forming machine and a sequential biaxial stretching machine. Regarding the raw materials used, the blending ratio is 100% by weight in total in each of the outer surface layer, the base material layer, and the heat seal layer. However, Examples 1, 4, 8, 9, and 10 are used as reference examples.

  Example 10 was two-layer coextrusion, and all other than this was three-layer coextrusion. In each Example and Comparative Example, the film thickness after stretching was controlled under the condition of 30 μm. The ratio of the layer thicknesses of the outer surface layer, the base material layer, and the heat seal layer was approximately 1: 8: 1. For Example 10, the base material layer and the heat seal layer had a layer thickness ratio of 9: 1.

[Raw materials]
The following raw materials were used as the raw material resin for forming each layer.
(Raw material 1) Polypropylene homopolymer (manufactured by Nippon Polypro Co., Ltd., trade name “FL100A”, melting point 160 ° C.)
(Raw material 2) Ethylene-propylene copolymer (manufactured by Nippon Polypro Co., Ltd., trade name “WFX4”, melting point 125 ° C.)
(Raw material 3) Ethylene-propylene-1 butene copolymer (manufactured by Nippon Polypro Co., Ltd., trade name “FX4G”, melting point 129 ° C.)
(Raw material 4) Propylene-1 butene copolymer (Mitsui Chemicals, trade name “Toughmer XM7070”, melting point 75 ° C.)

The following raw materials were also used as other additives and blending components.
(Raw material 5) Powdered synthetic silica as an anti-blocking agent (Fuji Silysia Chemical Co., Ltd., trade name “Silicia 430”)
(Raw material 6) Alicyclic hydrocarbon resin (Arakawa Chemical Industries, trade name “Arcon P-125”)
(Raw material 7) Antistatic agent (trade name “Anstex SA-300F” manufactured by Toho Chemical Industry Co., Ltd.)

[Film occurrence rate]
The heat-seal film that was formed under the conditions of the example and the comparative example was torn 50 times by hand in the transverse direction TD while changing the place. As shown in FIG. 5, the lateral direction of the film is the direction of opening when the bag is made into a bag. And the frequency | count that the film strip (refer the photograph of FIG. 6) generate | occur | produced was counted. The number of occurrences of film strips occupying the total number of tears (50 times) was determined and expressed as a percentage. That is, film strip generation rate (%) = {(number of film strips generated) ÷ (total number of tears)} × 100 ”.

[Tear Strength Ratio (R _S )]
To heat seal the film made of a film under conditions of examples and comparative examples, JIS K 7128-1 (1998) to the provisions of the tear strength S _M and transverse direction TD in the longitudinal direction MD in compliance with the trouser tear method to measure the tear strength S _T. In the heat-seal film to be measured for the trouser tear method, a long test piece having a length of 150 mm in the longitudinal direction MD and a length of 50 mm in the transverse direction TD is cut out, and a notch of 75 mm is made in the longitudinal direction. The load (N) (longitudinal MD tear strength S _M ) was measured by pulling in the direction. Similarly, a long test piece of 50 mm in the vertical direction MD and 150 mm in the horizontal direction TD is cut out, a notch of 75 mm is made in the longitudinal direction, and both pieces are pulled in opposite directions to load (N) (horizontal The tear strength S _T ) in the direction TD was also measured.

Then, the tear strength S _M in the longitudinal direction MD divided by the tear strength S _T in the transverse direction TD, and the value and tear strength ratio R _S. The numerical value in the table is the tear strength ratio R _S. In the table, “*” is an example in which tearing in the horizontal direction TD is strong and tearing in the vertical MD is not possible. Therefore, because the tear strength S tear strength ratio not _M can be obtained R _S is not indeterminate.

[Heat sealability]
About the heat-seal film which was able to be formed on the conditions of an Example and a comparative example, it was bag-formed into the pillow-shaped bag-like material of FIG. 4 by heat sealing using an automatic packaging machine (Fujikikai Co., Ltd., FW3400). As bag making conditions, the bag making speed was set to 120 rpm, and two types of heat seal temperatures of 145 ° C. and 190 ° C. were set. Therefore, a film that could be made by heat sealing at 145 ° C. was evaluated as “◎”. About the film which was able to make a bag by heat sealing at 190 degreeC, since heat sealing temperature rose, it evaluated as "(circle)". Films that could not be heat sealed even at 190 ° C. were evaluated as “x”.

〔productivity〕
In making the heat seal films of the examples and comparative examples, the quality of the product was judged from the difficulty of film production and bag making. An example of producing a uniform heat seal film without any problem in the production of the bag-like product was evaluated as “◎”. Although it was possible to create a bag-like product, an example of creating a heat seal film in which unevenness slightly occurred in the film thickness was evaluated as “◯”. About the example of preparation of the heat seal film which became the tear at the time of extending | stretching, the film thickness nonuniformity, or the creation of the bag-like thing became impossible, it evaluated as "x".

〔Comprehensive evaluation〕
Comprehensive evaluation comprehensively considered the quality of each index of film strip generation rate, tear strength ratio, heat seal suitability, and productivity. Evaluation of “A” is an extremely excellent heat seal film. The evaluation of “B” is a good heat seal film. The “C” rating is a heat seal film that cannot be used.

Tables 1 to 4 show the raw materials used, the measurement results, and the evaluation results of Examples and Comparative Examples. The raw material used in order of the outer surface layer (13), the base material layer (11), and the heat seal layer (12) and the weight blending ratio (parts by weight, weight percent) for each layer are shown. And longitudinal stretch ratio (times), transverse stretch ratio (times), film strip generation rate (%), tear strength ratio (R _S ), heat seal suitability (three-stage evaluation), productivity (three-stage evaluation) ) And comprehensive evaluation (three-level evaluation). In the table, “-” is an example in which film formation itself was not possible and measurement was impossible, or the film thickness accuracy (thickness stability) was poor, and sufficient reliability was not obtained in the evaluation results.

[Results and discussion]
In all examples and comparative examples, Example 10 is a film formation by two-layer coextrusion. Since Example 10 also has the same performance as Example 9, the heat seal film can have either two layers or three layers. In general, an anti-blocking agent can be added to the outer surface layer 13 to improve the performance efficiently. Therefore, in many embodiments, film formation by three-layer coextrusion is employed.

(Alicyclic hydrocarbon resin)
In the heat seal films of the examples, the blending of the alicyclic hydrocarbon resin is selective in terms of performance evaluation. However, in the composition of the base material layer, 5.0% by weight (Example 2), 10.0% by weight (Examples 3 and 5), 20.0% by weight (Example 6), 30.0% by weight ( It can be blended up to Example 7). With the blending of the alicyclic hydrocarbon resin, the tear directionality was improved. In addition, the waist of the film became stronger. As disclosed in the examples, 5 to 30% by weight is an appropriate range. In addition, when the blending of the alicyclic hydrocarbon resin exceeds 30% by weight, the blending ratio becomes too high, which is an obstacle to proper stretching. Therefore, 30% by weight is considered the limit.

(Longitudinal draw ratio)
When the draw ratio in the machine direction MD of Comparative Examples 1 and 2 is 1.0, the film is formed as a film, but the occurrence rate of film strips generated at the time of transverse tearing is high. It is inappropriate as the target film. Therefore, the lower limit is 1.1 times the draw ratio in the machine direction MD of Examples 1 to 4. The stretching ratios in the machine direction MD of Comparative Examples 7 and 8 are both 2.5 times. Although Comparative Example 7 was capable of forming a film from the relationship with stretching in the transverse direction, the thickness accuracy was poor, and in Comparative Example 8, film formation itself was not possible. On the other hand, in Examples 8 to 10, the draw ratio in the machine direction MD is 2.0 times, and film formation and bag making are good. Therefore, the upper limit is defined as a draw ratio of 2 in the machine direction MD. In addition, when taking the comprehensive evaluations “A” and “B” into consideration, the draw ratio in the machine direction MD is more preferably 1.1 to 1.5 times.

(Stretch ratio in the transverse direction)
When the draw ratio in the transverse direction TD of Comparative Examples 3 and 5 was 4.0 times, even if the draw ratio in the longitudinal direction was within the range, the thickness accuracy was poor and film formation was poor. On the other hand, when the draw ratio of Examples 1 and 8 is 5.0 times or more, the properties of the film are improved. From this, the lower limit is a draw ratio of 5.0 times in the transverse direction TD. Comparative Examples 4 and 6 had a transverse draw ratio of 35.0 times, and film formation was impossible even if the longitudinal draw ratio was within the range. In Examples 4, 9, and 10, film formation was possible at a transverse draw ratio of 30.0 times, and good properties were exhibited. Therefore, the upper limit can be 30 times the draw ratio in the transverse direction TD. Considering the transverse stretch ratios of Examples 2, 3, 6 and 7 with better evaluation, 7 to 12 times can be derived.

(Film strip incidence)
The occurrence of film strips in the examples is generally suppressed to a low rate. Since Examples 5 to 10, especially Examples 5 to 7 have not occurred, it can be said that they are extremely good. In consideration of other indicators and the actual opening of the bag-like material, it is appropriate that the film strip generation rate is at most 10%.

(Tear strength ratio)
When the tear strength ratio is 1.8 in Comparative Example 7, it cannot be said that the tear directionality in the transverse direction TD is good. When the tear strength ratio of Example 8 is 2.7, the directionality of tearing in the transverse direction TD becomes better. Therefore, it can be said that the tear strength ratio required for the heat seal film is at least 2 or more. Considering Example 6 with more desirable properties, the desired tear strength ratio is 4 or more. In the example in which the tear strength ratio is “*”, the tearing in the transverse direction TD itself is good. From this, it can be said that there is no problem in tearing performance in the heat seal film.

(Heat sealability)
Comparative Example 9 is an example in which a polypropylene homopolymer was used for the heat seal layer in the same manner as the base material layer. As expected from the melting point of the polypropylene resin, Comparative Example 9 was defective in heat sealing with an automatic packaging machine. From this point of view, it is important to select a resin type having a lowered melting point and the like from the viewpoint of heat sealability. Therefore, it is desirable to select the composition of the heat seal layer from ethylene-propylene copolymer, ethylene-propylene-1 butene copolymer, and propylene-1 butene copolymer.

  In the constituent resin raw materials of the heat seal layer, only ethylene-propylene copolymer (Example 1), ethylene-propylene-1 butene copolymer only (Examples 4, 8, 9, 10), ethylene-propylene-1 butene It is roughly classified into two types of mixtures of copolymers and propylene-1 butene copolymers (Examples 2, 3, 5, 6, 7). As a general tendency, the propylene-1 butene copolymer is not essential, but the low temperature heat sealability is improved by blending the same resin.

[Summary]
Considering productivity and comprehensive evaluation, the transverse heat-sealed film converged on the formulation and conditions of the examples is better than the comparative examples. In particular, also in the heat seal of the examples, the comprehensive evaluation “A” is the winding direction of the polypropylene resin film formed by biaxial stretching by controlling the stretching ratio in the longitudinal direction and the transverse direction to an appropriate range. A suitable tearability in the orthogonal transverse direction could be realized. In addition, not only the tearability was improved, but also the generation of film strips during tearing could be suppressed.

  As described above, the transverse heat-sealing film containing the elements defined in the present invention has good tearability and heat-sealing properties, and further has the property of reducing film fragments during tearing. Then, since the said transverse heat seal film can implement | achieve simple opening, it is very convenient as a packaging material of various articles | goods, such as a foodstuff.

10A, 10B Transverse heat seal film (heat seal film)
DESCRIPTION OF SYMBOLS 11 Base material layer 12 Heat seal layer 13 Outer surface layer 20 Bag-shaped thing 21,22 Sealing part 23 Center seal part 24 Main body part 25 Fine hole C Contents K Cut Op Opening MD The longitudinal direction (winding direction) of a heat seal film )
TD Transverse direction of heat seal film (direction perpendicular to winding direction)

Claims (5)

A heat seal film formed by biaxial stretching with a heat seal layer capable of heat sealing on one side of the base material layer,
The base material layer contains a polypropylene resin, and an alicyclic hydrocarbon resin is added in an amount of 5 to 30% by weight based on the total weight of the base material layer ,
The heat seal layer contains one or more of ethylene-propylene copolymer, ethylene-propylene-1 butene copolymer, propylene-1 butene copolymer,
Upon biaxial stretching of the heat seal film, the stretch ratio in the machine direction (MD) of the heat seal film is 1.1 to 1.5 times, and the stretch ratio in the transverse direction (TD) is 7 to 12 times. A transverse heat-seal film characterized by satisfying A heat seal film formed by biaxial stretching with a heat seal layer capable of heat sealing on one side of the base material layer,
The base material layer contains a polypropylene resin, and an alicyclic hydrocarbon resin is added in an amount of 5 to 30% by weight based on the total weight of the base material layer,
The heat seal layer contains one or more of ethylene-propylene copolymer, ethylene-propylene-1 butene copolymer, propylene-1 butene copolymer,
In biaxial stretching of the heat seal film, the stretch ratio in the machine direction (MD) of the heat seal film is 1.1 to 1.5 times, and the stretch ratio in the transverse direction (TD) is 7 to 12 times. Be satisfied,
An outer surface layer containing an olefin resin is provided on the other side of the base material layer.
A transverse heat-sealing film characterized by that. JIS K 7128-1 (1998) to the tear strength of the longitudinal tear strength in the direction (MD) of the heat-sealing film, determined in accordance with the trouser tear method defined (S _M) and transverse direction (TD) (S _T) 3. The transverse heat seal film according to claim 1, wherein the tear strength ratio (R _S ) obtained from the following formula (i) is 2 or more.

The easy-open packaging body characterized by heat-sealing heat-seal layers in the transverse heat-sealing film of any one of Claims 1 thru | or 3 , and making it into a bag-shaped object. The bag-like product is made by an automatic packaging machine along the longitudinal direction (MD) of the transverse heat seal film, and the longitudinal (MD) heat seal of the transverse heat seal film in the bag-like product. The easy-open packaging body according to claim 4 , wherein the portion is provided with a fine hole.

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