TWI749199B - Biaxially oriented polypropylene resin film - Google Patents

Abstract

The subject of the present invention is to provide a biaxially oriented polypropylene resin film that has sufficient heat-seal strength and airtightness for packaging heavy objects and is also suitable for automatic packaging processing.

The biaxially oriented polypropylene resin film of the present invention will be composed of the base layer (A), the intermediate layer (B) and the sealing layer (C) in the biaxially oriented polypropylene resin film. The melting point of the resin of) and the sealing layer (C) is set to a specific range, and the ratio of the thickness of each of the intermediate layer (B) and the sealing layer (C) to the thickness of the entire layer is set to a specific range.

Description

Biaxially oriented polypropylene resin film

The present invention relates to a biaxially oriented polypropylene resin film, and more specifically, to a biaxially oriented polypropylene resin film that has sufficient heat-seal strength and airtightness for packaging heavy objects and is also suitable for automatic filling and packaging. Resin film.

In the past, as a heat-sealing film for packaging, a laminated polypropylene resin film obtained by laminating a non-stretched polyethylene resin film or a non-stretched polypropylene resin film with a stretched polypropylene resin film has been widely used. A resin film, or a laminated polypropylene resin film obtained by co-extruding a low melting point polyolefin resin layer from a laminated layer composed of a high melting point polypropylene resin and then extending it.

However, with regard to the laminated polypropylene resin film obtained by laminating a non-stretched polyethylene resin film or a non-stretched polypropylene resin film and a stretched polypropylene resin film, although it has sufficient sealing strength, it is necessary to use an organic solvent or the like. The cascading steps are both unsatisfactory in terms of economics and impact on the global environment.

In addition, with regard to the laminated polypropylene resin layer obtained by co-extruding a low melting point polyolefin resin layer on a high melting point polypropylene resin layer and then extending it Although the lipid film has a certain degree of sealing strength, it does not reach the sealing strength of heavy objects such as packaged water content.

It is disclosed that by laminating an intermediate layer between a base layer composed of a polypropylene resin and a sealing layer composed of a low-melting polyolefin resin, the heat-seal strength and sealing properties are improved, even in the case of packaging heavy objects. In this case, the sealing portion does not peel off, and the content does not leak from the seal (for example, refer to Patent Document 1).

However, there is the following problem: after the packaging of the film, the bag-making process that is continuously heat-sealed, that is, the so-called automatic packaging process, produces folds in the bag-made product, or it cannot be smoothly performed in the automatic packaging process. Convey the film to the ground.

[Prior Technical Literature]

[Patent Literature]

Patent Document 1: Japanese Patent No. 4894340.

The purpose of the present invention is to solve the above-mentioned problems of the conventional laminated polypropylene film, and to provide a biaxially oriented polypropylene resin film that has sufficient heat-seal strength and airtightness for packaging heavy objects, and can be carried out smoothly. Automatic packaging processing, less wrinkles in the bag-made products obtained, and less air return to the bag-made products that have been vacuum degassed.

The inventors have made diligent studies to achieve the above-mentioned objects, and found that the biaxially oriented polypropylene resin film composed of the base layer (A), the intermediate layer (B), and the sealing layer (C) is used as the base The melting point of the resin of the material layer (A) and the sealing layer (C) is set to a specific range, and the thickness of each of the intermediate layer (B) and the sealing layer (C) is relative to the thickness of the total layer and the thickness of the entire film Set to a specific range, and have sufficient sealing strength and tightness for packaging heavy objects, can smoothly transport the film in automatic packaging processing, and it is not easy to produce wrinkles in the obtained bag-made product, and it is degassed by vacuum The air return in the bag-making product is less, thus completing the present invention.

That is, the present invention is as follows.

1. A biaxially oriented polypropylene resin film composed of a base layer (A), an intermediate layer (B) and a sealing layer (C), and satisfies the following (1) to (7).

(1) The resin composition constituting the base layer (A) is mainly made of polypropylene resin and has a melting point of 156°C or higher.

(2) The resin composition constituting the intermediate layer (B) contains at least one selected from the group consisting of propylene-ethylene-butene-1 copolymer, propylene-butene-1 copolymer, and propylene-ethylene copolymer One copolymer is 30% by weight or more.

(3) The resin composition constituting the sealing layer (C) is at least selected from the group consisting of propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, and propylene-ethylene copolymer One type of copolymer is the main body, and the melting point of the copolymer is 135°C or less.

(4) The thickness of the sealing layer (C) is 2% or more and 8% or less with respect to all layers of the film.

(5) The thickness of the intermediate layer (B) is 5% or more and 18% or less with respect to all layers of the film.

(6) The total of the thickness of the sealing layer (C) and the thickness of the intermediate layer (B) is 22% or less with respect to all layers of the film.

(7) The thickness of all layers of the film is 33 μm or less.

2. The biaxially oriented polypropylene resin film according to 1, wherein the sealing layer (C) contains an anti-fogging agent.

According to the present invention, a biaxially oriented polypropylene resin film can be provided, which has sufficient sealing strength and airtightness for packaging heavy objects, can smoothly perform automatic packaging processing, and has less wrinkles in the obtained bag-making product. In addition, there is less air backflow into the bag-making product that has been vacuum degassed.

Fig. 1 is a schematic diagram of a test piece for measuring the shape of the bag made in the embodiment and the heat-sealing strength.

Figure 2 is a schematic diagram of the sealing evaluation method.

The following describes the implementation of the biaxially aligned polypropylene resin film of the present invention form.

(Substrate layer (A))

The resin composition used in the base layer (A) is mainly made of polypropylene resin. The polypropylene resin referred to here is preferably selected from the group consisting of homopolymers of propylene which are insoluble in n-heptane and copolymers of propylene and other α-olefins containing 70 mol% or more of propylene. At least one kind of resin.

Such a polypropylene resin is preferably contained at 80% by weight or more, and more preferably at 90% by weight or more with respect to the resin composition constituting the base layer (A).

The polypropylene resin used in the base layer (A) needs to have a melting point of 156°C or higher. The melting point was measured by the method described in the examples described later. If the melting point is less than 156°C, the film cannot be transported more smoothly in the automatic packaging process, and wrinkles are more likely to occur in the obtained bag products.

The so-called n-heptane insolubility is based on the crystallinity of polypropylene as an indicator, and at the same time it indicates the safety properties when used as food packaging. No. 20 n-heptane-insoluble (the elution point at 25°C, 60 minutes of extraction is 150ppm or less [when the use temperature exceeds 100°C, it is 30ppm or less]) polypropylene resin.

As the α-olefin copolymerization component of the copolymer of propylene and other α-olefins, α-olefins having a carbon number of 2 to 8 are preferred, such as ethylene, butene-1, pentene-1, hexene-1, and 4 -Methyl-1-pentene, etc. Here, the so-called copolymer is preferably a combination of propylene and one or two of the above-exemplified α-olefins Random or block copolymer obtained by the above polymerization.

In the case of mixing propylene homopolymers and copolymers of propylene and other α-olefins containing 70 mol% or more of propylene, it is desirable that the resin composition used in the substrate layer (A) is The content of the copolymer of propylene and other α-olefins containing 70 mol% or more of propylene is set to 20% by weight or less, more preferably 10% by weight or less.

(Middle layer (B))

The resin composition constituting the intermediate layer (B) must contain at least one selected from the group consisting of propylene-ethylene-butene-1 copolymer, propylene-butene-1 copolymer, and propylene-ethylene copolymer The copolymer is 30% by weight or more. In this way, the ultimate sealing strength and sealing performance can be improved. It is preferably 65% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more.

More preferable forms of the propylene-butene-1 copolymer, the propylene-ethylene-butene-1 copolymer, and the propylene-ethylene copolymer are described in (1) to (3) below.

(1) Propylene-ethylene-butene-1 copolymer

The butene content in the propylene-ethylene-butene-1 copolymer is preferably 5% by weight or more. If the butene content is 5 mol% or more, the adhesion between the layers with the sealing layer (C) is improved, and the heat-sealing strength and/or sealing properties are easily improved.

The upper limit of the butene content is not particularly limited. If the butene content is too large, the crystallization is excessively suppressed and the crystallinity is lower than that of the propylene homopolymer. As a result, the toughness of the film is reduced.

As the above-mentioned propylene-ethylene-butene-1 copolymer with a large butene content, for example, "FSX66E8" manufactured by Sumitomo Chemical Co., Ltd. can be exemplified.

The propylene-ethylene-butene-1 copolymer is preferably blended at 65% by weight or more in the resin component constituting the intermediate layer (B). It is more preferably 70% by weight or more, still more preferably 99% by weight or less, and still more preferably 95% by weight or less. By adjusting the blending of the propylene-ethylene-butene-1 copolymer to 65% by weight or more, the interlayer strength with the sealing layer (C) is improved, the heat sealing strength is improved, or the sealing performance is further improved. On the other hand, by setting it to 95% by weight or less, the interlayer strength with the base material layer (A) can be improved.

(2) Propylene-butene-1 copolymer

The butene content in the propylene-butene-1 copolymer is preferably 20 mol% or more. If the butene content is 20 mol% or more, the adhesion between the layers with the sealing layer (C) is improved, and the heat-sealing strength and/or sealing properties are improved.

The upper limit of the butene content is not particularly limited. If the butene content is too large, the crystallization is excessively suppressed and the crystallinity is lower than that of the propylene homopolymer. As a result, the toughness of the film is reduced.

As the above-mentioned propylene-butene-1 copolymer with a large butene content, for example, "SPX78J1" manufactured by Sumitomo Chemical Co., Ltd., "XR110H" manufactured by Mitsui Chemicals Co., Ltd., and the like can be exemplified.

The propylene-butene-1 copolymer is preferably blended at 65% by weight or more in the resin component constituting the intermediate layer (B). It is more preferably 70% by weight or more, still more preferably 99% by weight or less, and still more preferably 95% by weight or less. Improve and seal by setting the blending of propylene-ethylene-butene-1 copolymer to 65% by weight or more The interlayer strength of the layer (C) can improve the heat-seal strength, or it is easy to improve the sealing performance. On the other hand, by setting it to 95% by weight or less, the interlayer strength with the base material layer (A) can be improved.

(3) Propylene-ethylene copolymer

The ethylene content in the propylene-ethylene copolymer is preferably 4 mol% or more. If the ethylene content is 4 mol% or more, the adhesion between the layers with the sealing layer (C) is improved, and the heat-sealing strength and/or sealing properties are improved.

The upper limit of the ethylene content is not particularly limited. If the ethylene content is too large, the crystallization is excessively suppressed, and the crystallinity is lower than that of the propylene homopolymer. As a result, the toughness of the film is reduced.

As the propylene-ethylene copolymer having a high ethylene content, for example, "PC540R" manufactured by SunAllomer Co., Ltd., "VM3588FL" manufactured by Mitsui Chemicals Co., Ltd., and the like can be exemplified.

The propylene-ethylene copolymer is preferably blended at 65% by weight or more in the resin component constituting the intermediate layer (B). It is more preferably 70% by weight or more, still more preferably 99% by weight or less, and still more preferably 95% by weight or less. By adjusting the blending of the propylene-ethylene:butene-1 copolymer to 65% by weight or more, the interlayer strength with the sealing layer (C) can be improved, the heat sealing strength can be improved, or the sealing performance can be easily improved. On the other hand, by setting it to 95% by weight or less, the interlayer strength with the base material layer (A) can be improved.

Preferably, the above-mentioned propylene copolymer has a propylene-α-olefin copolymer with a cold xylene soluble matter (CXS; cold xylene soluble matter) of 3 wt% or less Things. When a propylene-α-olefin copolymer with a cold xylene soluble content (CXS) exceeding 3% by weight is used, the toughness tends to disappear, so it is not good.

The above-mentioned "cold xylene soluble fraction" refers to the amount of amorphous parts contained in the α-olefin copolymer. The so-called "cold xylene soluble fraction 3% by weight or less" means that there are few amorphous parts and high crystallinity. The α-olefin copolymer.

Here, the so-called cold xylene solubles means that after 1 g of the sample is completely dissolved in 100 ml of boiling xylene, the temperature is lowered to 20°C, and after standing for 4 hours, the liquid is separated into precipitates and solutions by filtration, and the filtrate is dried and solidified by measurement. The weight when dried at 70°C under reduced pressure was used to determine the weight %.

At this time, the cold xylene soluble content (CXS) of the entire intermediate layer is preferably 2.5% by weight or less, more preferably 2.4% by weight or less, and still more preferably 2.2% by weight or less.

(Sealing layer (C))

The resin composition constituting the sealing layer (C) must be at least one selected from the group consisting of propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, and propylene-ethylene copolymer The copolymer is the main component, and the melting point of the resin composition is set to 135°C or lower. The melting point was measured by the method described in the examples described later. If the melting point exceeds 135°C, the heat sealing and heat sealing strength cannot be expected to increase.

More preferable forms of the propylene-butene-1 copolymer, the propylene-ethylene-butene-1 copolymer, and the propylene-ethylene copolymer are described in (1) to (3) below.

(1) The butene content in the propylene-butene-1 copolymer is preferably 20 mol% or more. By setting it as 20 mol% or more, the heat-seal strength can be improved, or the sealing performance can be easily improved.

The upper limit of the butene content is not particularly limited. If the butene content is too large, the film surface may become sticky and the sliding properties or blocking resistance may decrease. Therefore, it may be appropriately determined within a range that does not cause such defects. As the above-mentioned propylene-butene-1 copolymer with a large butene content, for example, "SPX78J1" manufactured by Sumitomo Chemical Co., Ltd., "XR110H" manufactured by Mitsui Chemicals Co., Ltd., and the like can be exemplified.

The propylene-butene-1 copolymer is preferably blended in the resin component constituting the sealing layer (C) at 65% by weight or more, more preferably 70% by weight or more. Preferably it is 99 weight% or less, More preferably, it is 95 weight% or less. By adjusting the blending of the propylene-butene copolymer to 65% by weight or more, the heat-seal strength can be improved, or the sealing performance can be easily improved. On the other hand, by setting it to 95% by weight or less, the interlayer strength with the intermediate layer (B) can be improved.

(2) Propylene-ethylene-butene-1 copolymer

The butene content in the propylene-ethylene-butene-1 copolymer is preferably 5 mol% or more. In addition, the upper limit of the butene content is not particularly limited. If the butene content is too large, the film surface may become sticky and the sliding properties or blocking resistance may decrease. Therefore, it may be appropriately determined within a range that does not cause such defects. As the above-mentioned propylene-ethylene-butene-1 copolymer with a large butene content, for example, "FSX66E8" manufactured by Sumitomo Chemical Co., Ltd. can be exemplified.

(3) Propylene-ethylene copolymer

The ethylene content in the propylene-ethylene copolymer is preferably 4 mol% or more. Furthermore, the upper limit of the ethylene content is not particularly limited. If the ethylene content is too large, the film surface may become sticky and the sliding properties or blocking resistance may decrease. Therefore, it may be appropriately determined within a range that does not cause such defects. As the propylene-ethylene copolymer having a high ethylene content, for example, "PC540R" manufactured by SunAllomer Co., Ltd., "VM3588FL" manufactured by Mitsui Chemicals Co., Ltd., and the like can be exemplified.

The melting point of the polypropylene resin constituting the sealing layer (C) of the present invention must be 135°C or lower. The melting point was measured by the method described in the examples described later. If the melting point exceeds 135°C, the heat sealing and heat sealing strength cannot be expected to increase.

In the present invention, various additives and fillers can be added to the resin forming each layer as needed within a range that does not hinder the characteristics of each layer. For example, antifogging agents, heat stabilizers, antioxidants, light stabilizers, and antioxidants can be added. Electrostatic agents, lubricants, nucleating agents, flame retardants, pigments, dyes, calcium carbonate, barium sulfate, magnesium hydroxide, mica, talc, clay, zinc oxide, magnesium oxide, aluminum oxide, antibacterial agents, impart natural decomposability The additive materials and so on. Furthermore, other thermoplastic resins, thermoplastic elastomers, rubbers, hydrocarbon resins, petroleum resins, etc. may be blended within a range that does not impair the characteristics of the film of the present invention.

(Biaxial oriented polypropylene resin film)

The polypropylene resin film of the present invention is composed of the above-mentioned base layer (A) and the intermediate layer (B) And the sealing layer (C).

The thickness of the sealing layer (C) needs to be 2% or more and 8% or less with respect to all layers of the film.

Here, when the thickness of the sealing layer (A) is less than 5%, the heat-seal strength and sealing performance cannot be sufficiently obtained. When the thickness of the sealing layer (A) exceeds 8%, the film can be transported smoothly in the automatic packaging process, and it is not easy to produce wrinkles in the obtained bag products. More preferably, it is 2% or more and 5% or less.

The thickness of the intermediate layer (B) needs to be 5% or more and 18% or less with respect to all layers of the film.

Here, when the thickness of the intermediate layer (B) is less than 5%, the ultimate sealing strength and sealing performance cannot be sufficiently obtained. When the thickness of the middle layer (B) is less than 18%, the film can be transported smoothly in the automatic packaging process, and it is not easy to produce wrinkles in the obtained bag products. More preferably, it is 5% or more and 15% or less.

The total thickness of the intermediate layer (B) and the thickness of the sealing layer (C) needs to be 7% or more and 22% or less with respect to the thickness of all layers of the film. When the sum of the thickness of the intermediate layer (B) and the thickness of the sealing layer (C) is 7% or more with respect to the thickness of all the layers of the film, the return of air to the vacuum-deaerated bag-making product becomes less. When the total thickness of the intermediate layer (B) and the thickness of the sealing layer (C) is 22% or less relative to the thickness of all layers of the film, the film can be transported more smoothly in the automatic packaging process, and the obtained system The bag product is also less prone to wrinkles. Preferably it is 10% or more and 22% or less. More preferably, it is more than 10% and less than 20%, particularly preferably Above 15% and below 18%.

The thickness of the biaxially aligned polypropylene resin film of the present invention needs to be 15 μm or more and 33 μm or less. In the case of this range, the toughness is balanced with the reduction of air backflow into the vacuum degassed bag-making product. It is more preferably 15 μm or more and 30 μm or less, and particularly preferably 15 μm or more and 28 μm or less.

(Production method)

The biaxially oriented polypropylene resin film of the present invention can be produced by the following film forming methods, but it is not limited to these film forming methods.

For example, the following method can be exemplified: use an extruder corresponding to the number of layers, use the T-die method or the inflation method, etc. to melt the layer, and then cool it by the chill roll method, water cooling method, or air cooling method. Laminated films are stretched using successive biaxial stretching methods, simultaneous biaxial stretching methods, tubular stretching methods, etc.

Here, if the conditions for manufacturing by the sequential biaxial stretching method are exemplified, the resin melted and extruded from the T-die nozzle is cooled and solidified by a casting machine to produce a raw material sheet.

The temperature during fusion lamination is preferably in the range of 240°C to 300°C, and is set based on the melting point of the raw material resin used for each layer. In addition, for the purpose of suppressing crystallization of the resin and improving transparency, the temperature of the roll for casting is preferably set to be between 15°C and 40°C.

Next, the raw material sheet is heated to a temperature suitable for stretching, and then stretched along the direction of travel of the sheet using the speed difference between the stretching rolls. As for the stretching magnification at this time, if it is considered that there is no stretching unevenness and stable production, it is better. Best set Between 3 times and 6 times. Regarding the stretching temperature, in consideration of stable production without stretching unevenness, it is preferably set to be between 100°C and 150°C.

Next, the two sides of the longitudinally stretched sheet are held by a tenter clip, while being heated by hot air to a temperature suitable for stretching, the sheet is stretched in sequence along a direction at right angles to the travel of the sheet. Regarding the lateral stretch magnification at this time, considering thickness variation and productivity, it is preferably set to be between 7 times and 10 times.

Regarding the stretching temperature, in consideration of stable production without stretching unevenness, it is preferably set to be between 130°C and 180°C.

Finally, it is preferable to perform heat fixation in the range of 150°C to 200°C.

The biaxially oriented polypropylene resin film of the present invention may be surface treated to improve printability, lamination properties, and the like. As the method of surface treatment, corona discharge treatment, plasma treatment, flame treatment, acid treatment, etc. can be exemplified, and there is no particular limitation. It is preferable to perform corona discharge treatment, plasma treatment, and flame treatment. These treatments can be processed continuously and can be easily implemented before the winding step of the film manufacturing process.

(Film characteristics)

(Anti-fog)

The polypropylene resin film of the present invention is preferably rated as level 3 or higher, more preferably level 2 or higher, and even more preferably level 1 in the anti-fogging performance obtained by the measurement method described later.

(Heat sealing start temperature)

The biaxially oriented polypropylene resin film of the present invention preferably has a heat-seal start temperature obtained by the measurement method described later, 120°C or lower, more preferably 115°C or lower.

(Ultimate heat sealing strength)

The biaxially oriented polypropylene resin film of the present invention preferably has an ultimate heat seal strength of 4.5N/15mm or more, more preferably 5N/15mm or more, and still more preferably 6N/15mm or more, obtained by the measurement method described later.

(Tightness)

The biaxially oriented polypropylene resin film of the present invention preferably has a sealability evaluation obtained by the measurement method described later as grade 3 or higher, more preferably grade 2 or higher, and even more preferably grade 1.

(Toughness of bag-making products)

The biaxially oriented polypropylene resin film of the present invention preferably has a grade 3 or higher evaluation of the toughness of a bag-made product obtained by the measurement method described later, more preferably a grade 2 or higher, and even more preferably a grade 1.

(Automatic packaging suitability)

The biaxially oriented polypropylene resin film of the present invention is preferably evaluated as ○ or △ for automatic packaging suitability obtained by the measurement method described later, more preferably ○.

(Air return after degassing packaging)

The biaxially oriented polypropylene resin film of the present invention is preferably obtained by the measurement method described below. The evaluation of air recirculation after vacuum degassing packaging is ⊚ or ⊚, more preferably ⊚.

Air recirculation is related to the above-mentioned airtightness, and has become a practical evaluation of the suitability of vacuum packaging.

(use)

Of course, the biaxially oriented polypropylene resin film of the present invention has sufficient heat-seal strength for packaging heavy objects, and is also excellent in handleability and good sealing properties. Therefore, it can be preferably used for wheat flour, rice, and wheat. Other grains; potato, radish, ginseng and other root vegetables; slab konjac, silk konjac; pickled radish, soy sauce pickles, Nara pickles and other pickled vegetables; all kinds of miso; soups, noodles, soy sauce, sauces Packaging materials for various seasonings such as, ketchup, mayonnaise, etc;

In addition, since the film has excellent transportability, it can also be applied to packaging materials used for automatic packaging of vegetables and the like.

[Example]

Hereinafter, specific examples of the present invention will be further described with examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the present invention. Furthermore, the characteristics in this specification were evaluated by the following methods.

(1) Melting point Tm

According to JIS (Japanese Industrial Standard; Japanese Industrial Standard) K7121, the measurement is performed with a differential scanning calorimeter (DSC; Differential Scanning Calorimeter).

As a state adjustment, heat up from room temperature at 30°C/min to 200°C, hold at 200°C for 5 minutes, cool down to -100°C at 10°C/min, and hold at -100°C for 5 minutes, and then measure the endothermic curve , From -100°C to 200°C at 10°C/min.

In addition, in the case of the heat-sealing layer (C) in the case of having a plurality of melting peaks, the melting peak with the highest temperature is set as the melting point. In the case of the base material layer (A), the melting peak with the lowest temperature is set as the melting point.

(2) Layer thickness

The sample film was cut into a size of 1cm×1cm, embedded in a UV (ultraviolet) curable resin, and irradiated with UV for 5 minutes to cure the curable resin. Then, a cross-sectional sample was prepared with a microtome, and observed with a differential interference microscope, and the thickness of the intermediate layer (B) and the sealing layer (C) were measured. Five points are measured for the sample, and the average value is calculated.

(3) Anti-fog

1) Add 300cc of warm water at 50°C into a 500cc container with an upper opening.

2) With the measurement surface of the film as the inner side, the opening of the container is sealed with the film.

3) Place in a cold room at 5°C.

4) Under the condition that the warm water in the container is completely cooled to the ambient temperature, evaluate the adhesion condition of the film surface with 5 levels.

Level 1: No exposure on the whole surface (attachment area 0).

Level 2: A little dew adhesion (at most 1/4 of the adhesion area).

Level 3: Approximately 1/2 of the dew attachment (attachment area is at most 2/4).

Grade 4: Most exposed attachment (attachment area is at most 3/4).

Grade 5: Adhesion on the whole surface (attachment area is 3/4 or more).

(4) Heat sealing start temperature

The starting temperature of heat sealing refers to the following temperature: make the heat sealing layers of the sample film face each other and overlap each other, use a heat tilt test machine (manufactured by Toyo Seiki Co., Ltd.), heat sealing pressure 1kg/cm ² , time 1 second, temperature When heat-sealing is performed at a temperature of 5°C higher from 80°C, the heat-seal strength becomes 1N/15mm temperature, so that the heat-sealing layers of the 5cm×20cm film face each other, using heat-sealing rods set at 5°C intervals ( Sealing surface 1cm×3cm) 5 pieces are heat-sealed at the same time, the central part of the film is cut into a width of 15mm, installed on the upper and lower suction cups of the tensile testing machine, and the strength of each when being stretched at a tensile speed of 200mm/min is measured. Calculate the heat seal strength (in N/15mm).

Draw a linear curve with temperature on the horizontal axis and heat seal strength on the vertical axis, and set the temperature at which the heat seal strength exceeds 2.5N/15mm as the starting temperature of the heat seal.

(5) Heat sealing ultimate strength

The heat-sealing ultimate strength is calculated as follows: the heat-sealing layers of the sample film are overlapped with each other, using a heat tilt tester (manufactured by Toyo Seiki Co., Ltd.), with a heat-sealing pressure of 1 kg/cm ² , time of 1 second, and temperature Heat sealing at a temperature of 5°C each time from 80°C to 150°C, cut the central part of the film into a width of 15mm, and install it on the upper and lower suction cups of the tensile testing machine. Calculate the heat seal strength (unit: N/15mm).

The upper limit of the sealing temperature is set as the maximum strength at 150°C as the heat-sealing ultimate strength.

(6) Tightness

The red ink ( ink) (RECORDER INK manufactured by CHUGAI KASEI CO.LTD) to evaluate the leakage to the outside of the bag.

Level 1: The ink is accumulated on the inside of the bag, has not penetrated into the sealing part, and has not leaked to the outside of the bag.

Rank 2: The ink slightly penetrates into the sealing part, but does not leak to the outside of the bag.

Rank 3: Ink penetrates into the sealing part, but does not leak to the outside of the bag.

Level 4: Ink penetrates into the sealing part, and a small amount of ink leaks out to the outside of the bag.

Level 5: Ink leaks to the outside of the bag.

(7) Toughness of bag products

In a bag made in the same way as the heat-sealing strength measurement method described above, a polyethylene film with a thickness of 25μm, a size of 80mm×140mm, and a piece of roasted rice noodles with a weight of about 4g and a size of 25mm×75mm were packed into the bag, and evaluated The operability of the product.

Grade 1: The film has toughness and can be easily packed, unpacked, and displayed.

Level 2: When holding the bag, I feel more or less insufficient toughness, but the work can be carried out without any problems.

Level 3: Feeling lack of toughness, feeling more or less insufficient toughness when holding it, and the operation is not easy.

Level 4: No resilience, feels insufficient resilience when holding it, and the operation is not easy.

Level 5: Completely without toughness, difficult to work.

(8) Automatic packaging suitability

A horizontal pillow-shaped bag-making machine (manufactured by Gongrong Printing Machinery Material Co., Ltd.: PP500) is used to produce pillow-shaped packaging.

Conditions: Fuse cutter; cutter head angle 60°.

Sealing temperature: 370°C.

Number of shots: 120 bags/min.

According to the smoothness of film conveyance and the degree of wrinkles of the bag-made products, the following 3 levels are used for evaluation.

○: The film transportability is good, and the bag-made product has no wrinkles.

△: Any of film transportability and bag-making product wrinkles is poor.

×: The film transportability is poor and the bag-made product has wrinkles.

(9) Air return after degassing packaging

When making the bag in the same manner as the above-mentioned automatic packaging suitability measurement method, two glass marbles (diameter 1.5 cm) are enclosed. Then, use a syringe to remove the air inside, and stick tape on the needle hole to become a vacuum state. After 24 hours, the degree of air recirculation was evaluated by the ease of movement of the marbles.

◎: Keep the vacuum state without air backflow.

○: The vacuum state is maintained, but a small amount of air backflow is confirmed.

△: The vacuum state is partially maintained, but air backflow is confirmed.

×: The vacuum state is not maintained.

(Using polypropylene resin)

The polypropylene resin constituting each layer used in the examples is as follows.

[PP-1]: Propylene homopolymer: "FS2011DG3" manufactured by Sumitomo Chemical Co., Ltd., MFR (melt mass flow rate): 2.5 g/10 minutes, melting point: 158°C.

[PP-2]: Propylene-ethylene-butene random copolymer: "FSX66E8" manufactured by Sumitomo Chemical Co., Ltd., ethylene content: 2.5 mol%, butene content: 7 mol%, MFR: 3.1g/ 10 minutes, melting point: 133°C.

[PP-3]: Propylene-butene-1 copolymer: "SPX78J1" manufactured by Sumitomo Chemical Co., Ltd., butene content: 25 mol%, MFR: 8.5 g/10 minutes, melting point: 128°C.

(Example 1)

The resin composition constituting each layer used in Example 1 is as follows.

(1) Resin composition constituting the substrate layer (A)

[PP-1] is added as an anti-fogging agent glycerol monostearate (Matsumoto Oils and Fats Pharmaceutical (stock), TB-123) 0.16 wt%, polyoxyethylene (2) stearylamine (Matsumoto Oils and Fats Pharmaceutical ( Stock), TB-12) 0.2% by weight, polyoxyethylene (2) stearylamine monostearate (Matsumoto Oils and Fats Pharmaceutical (stock), Ellex 334) 0.6% by weight of the raw material is set to [PP-4], as The resin composition constituting the base layer (A) is used at 100% by weight.

(2) Resin composition constituting the intermediate layer (B)

In [PP-2], 1.5% by weight of organic polymer particles (CS30: Sumitomo Chemical Co., Ltd.: particle size: 3.5μm), and glycerol monostearate (Matsumoto Oils and Fats Pharmaceutical Co., Ltd.) as an anti-fogging agent, TB-123) 0.45% by weight, melted and mixed so that the resin temperature becomes 240°C, and made into pellets.

The raw material was set to [PP-5], and 100% by weight was used as the resin composition constituting the intermediate layer (B).

(3) Resin composition constituting the sealing layer (C)

In [PP-3], 1.5% by weight of organic polymer microparticles (CS30: Sumitomo Chemical Co., Ltd.: particle size 3.5μm), and glycerol monostearate (Matsumoto Oils and Fats Pharmaceutical Co., Ltd.) as an anti-fogging agent, TB-123) 0.50% by weight, melted and mixed so that the resin temperature became 240°C, and pelletized, and the obtained raw material was set to [PP-6].

A composition mixed with 50% by weight of [PP-3] and 50% by weight of [PP-6] was used as the resin composition constituting the sealing layer (C).

Using three melt extruders, the resin composition constituting the base material layer (A) was melt-extruded by the first extruder at a resin temperature of 280°C, and the middle layer was formed by the second extruder ( The resin composition of B) is melted and extruded at a resin temperature of 250°C, and the resin composition constituting the sealing layer (C) is melted and extruded at a resin temperature of 250°C by the third extruder, so as to come into contact with the cooling roll The order from the surface is surface layer (B)/base layer (A)/sealing layer (C), and the thickness ratio in the T-die becomes base layer (A)/intermediate layer (B)/sealing layer (C) )=21/3/1, laminating and extruding, using a 30°C cooling roll to cool and solidify to obtain an unstretched sheet. Then, between the metal rolls heated to 130°C, the peripheral speed difference is used to extend 4.5 times in the longitudinal direction, and then it is further introduced into the tenter stretcher to extend 9.5 times in the transverse direction.

The temperature of the preheating part of the tenter stretcher is 168℃, and the temperature of the stretching part is 155℃.

Furthermore, in the second half of the tenter stretcher, after heat-fixing at 163°C, the surface of the base material layer (A) was subjected to corona discharge treatment using a corona discharge treatment machine manufactured by Kasuga Electric Co., Ltd., and then sealed The layer (C) was subjected to corona discharge treatment in the same manner, and was wound up by a film winder to obtain a polypropylene resin film. The final film thickness is 25μm, and the thickness of each layer is base layer (A)/intermediate layer (B)/sealing layer (C)=21/3/1(μm).

The obtained film satisfies the requirements of the present invention, has sufficient heat-sealing strength and ultimate strength at low temperatures, and takes into account airtightness, automatic packaging suitability, and bag making Product toughness, air return after degassing packaging. In addition, the anti-fogging performance has also become a problem-free level for fruit and vegetable packaging. The results of the film composition and physical properties are shown in Table 1.

(Example 2)

The resin composition constituting the intermediate layer (B) was a mixture of 10% by weight of [PP-1] and 90% by weight of [PP-5]. The obtained laminated film has sufficient heat-seal strength and ultimate strength at low temperature as in Example 1, and takes into account the airtightness, the suitability for automatic packaging, the toughness of the bag-making product, and the air recirculation after degassing packaging. In addition, the anti-fogging performance has also become a problem-free level for fruit and vegetable packaging. The results of the film composition and physical properties are shown in Table 1.

(Example 3)

The resin composition constituting the intermediate layer (B) was a mixture of 50% by weight of [PP-1] and 50% by weight of [PP-5]. The obtained laminated film has sufficient heat-seal strength and ultimate strength at low temperature as in Example 1, and takes into account the airtightness, the suitability for automatic packaging, the toughness of the bag-making product, and the air recirculation after degassing packaging. In addition, the anti-fogging performance has also become a problem-free level for fruit and vegetable packaging. The results of the film composition and physical properties are shown in Table 1.

(Example 4)

The resin composition constituting the intermediate layer (B) was set to a mixture of [PP-1] 70% by weight and [PP-5] 30% by weight, except that the same as in Example 1 Way to obtain laminated film. The obtained laminated film had a slight decrease in airtightness, but had sufficient heat-sealing strength and ultimate strength at low temperatures as in Example 1, and had both the suitability for automatic packaging, the toughness of the bag-making product, and the return of air after degassing packaging. In addition, the anti-fogging performance has also become a problem-free level for fruit and vegetable packaging. The results of the film composition and physical properties are shown in Table 1.

(Example 5)

Except for setting the thickness of the base layer (A) to 22.5 μm and the thickness of the intermediate layer (B) to 1.5 μm, a laminated film was obtained in the same manner as in Example 2. The obtained laminated film had a slight decrease in airtightness, but had sufficient heat-sealing strength and ultimate strength at low temperatures as in Example 2, and had both automatic packaging suitability, bag-making toughness, and air recirculation after degassing packaging. In addition, the anti-fogging property has also become a problem-free level for fruit and vegetable packaging. The results of the film composition and physical properties are shown in Table 1.

(Example 6)

Except that the thickness of the base layer (A) was set to 20.5 μm and the thickness of the intermediate layer (B) was set to 3.5 μm, a laminated film was obtained in the same manner as in Example 2. The obtained laminated film has a slight decrease in the toughness of the bag-making product, but it has sufficient heat-seal strength and ultimate strength at low temperature as in Example 2, and takes into account the sealing performance, the suitability for automatic packaging, the toughness of the bag-making product, and outgassing. The air returned after packaging. In addition, the anti-fogging performance has also become a problem-free level for fruit and vegetable packaging. The results of the film composition and physical properties are shown in Table 1.

(Comparative example 1)

The thickness of the base layer (A) was 24 μm, and the intermediate layer (B) was not provided, except that the laminated film was obtained in the same manner as in Example 1. The airtightness of the obtained laminated film and the air return after degassing packaging are poor. The results of the film composition and physical properties are shown in Table 2.

(Comparative example 2)

The thickness of the base layer (A) was 22 μm, the intermediate layer (B) was not provided, and the thickness of the sealing layer (C) was 3 μm, except that the laminated film was obtained in the same manner as in Example 1. The airtightness of the obtained laminated film and the air return after degassing packaging are poor. The results of the film composition and physical properties are shown in Table 2.

(Comparative example 3)

The thickness of the base layer (A) was set to 15 μm, the thickness of the intermediate layer (B) was set to 4 μm, and the thickness of the sealing layer (C) was set to 1 μm, except that the build-up layer was obtained in the same manner as in Example 2. membrane. The bag-making product of the obtained laminated film had poor toughness. The results of the film composition and physical properties are shown in Table 2.

(Comparative example 4)

Except that the resin composition constituting the base material layer (A) was set to 100% by weight of [PP-5], a laminated film was obtained in the same manner as in Example 2. The bag-making product of the obtained laminated film had poor toughness. The results of the film composition and physical properties are shown in Table 2.

(Comparative Example 5)

Except that the resin composition constituting the intermediate layer (B) was set to 100% by weight of [PP-4], a laminated film was obtained in the same manner as in Example 1. The obtained laminated film has poor airtightness and suitability for automatic packaging, and poor air return after degassing packaging. The results of the film composition and physical properties are shown in Table 2.

(Comparative Example 6)

The thickness of the base layer (A) was set to 23 μm, the thickness of the intermediate layer (B) was set to 1 μm, and the thickness of the sealing layer (C) was set to 1 μm, except that the build-up layer was obtained in the same manner as in Example 1. membrane. The obtained laminated film has poor airtightness and suitability for automatic packaging, and poor air return after degassing packaging. The results of the film composition and physical properties are shown in Table 2.

(Comparative Example 7)

The thickness of the base layer (A) was set to 35 μm, the thickness of the intermediate layer (B) was set to 5 μm, and the thickness of the sealing layer (C) was set to 2 μm, except that the build-up layer was obtained in the same manner as in Example 1. membrane. The airtightness of the obtained laminated film and the air return after degassing packaging are poor. The results of the film composition and physical properties are shown in Table 2.

(Industrial availability)

The polypropylene resin film of the present invention can provide a biaxially oriented polypropylene resin film, which has sufficient sealing strength and airtightness for packaging heavy objects, and can smoothly perform automatic packaging processing. There are few middle wrinkles, and in addition, there is little air backflow into the vacuum degassed bag-making product.

Claims (2)

A biaxially oriented polypropylene resin film composed of a base layer (A), an intermediate layer (B) and a sealing layer (C), and satisfies the following (1) to (7): (1) constitutes the base material The resin composition of layer (A) is mainly made of polypropylene resin with a melting point of 156°C or higher; (2) the resin composition constituting the intermediate layer (B) contains selected from propylene-ethylene-butene-1 copolymer, propylene -Butene-1 copolymer and at least one copolymer in the group consisting of propylene-ethylene copolymer 30% by weight or more; (3) The resin composition constituting the sealing layer (C) is selected from propylene-butylene At least one copolymer in the group consisting of ene-1 copolymer, propylene-ethylene-butene-1 copolymer, and propylene-ethylene copolymer as the main body, and the melting point of the resin composition is 135°C or less; 4) The thickness of the sealing layer (C) is 2% or more and 8% or less relative to all layers of the film; (5) The thickness of the intermediate layer (B) is 5% or more and 18% or less relative to all the layers of the film; (6) Sealing layer The total of the thickness of (C) and the thickness of the intermediate layer (B) is 22% or less with respect to all layers of the film; (7) the thickness of all layers of the film is 33 μm or less. The biaxially oriented polypropylene resin film according to claim 1, wherein the sealing layer (C) contains an anti-fogging agent.

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