JP2000178518A - Adhesive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide adhesive films excellent in self-adhesiveness without the generation of peeling sound and static electricity when fed and without no reduction in adhesion after stretching, and further suitable for the adhesive layer of a pallet stretched film excellent in hygienic qualities and recycling. SOLUTION: This adhesive film having a peel tack strength at a peel angle of 180 deg. of 3-35 in the unstretched state, an average surface roughness Ra 1, measured by an atomic force microscope, of not greater than 6.5 nm and, at the same time, an average surface roughness Ra 2 of not greater than 5.5 nm when stretched is molded by using a copolymer of ethylene with a 3-18C α-olefin, and the film is used for the surface layer of a pallet stretched film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is excellent in self-adhesiveness, peels off smoothly at the time of unreeling (unstretched), has almost no peeling sound and static electricity, and is stretched and wound around a package (after stretching). The present invention relates to an adhesive film having good adhesive strength between films, and particularly suitable for an adhesive layer of a pallet stretch film.

[0002]

2. Description of the Related Art A typical example of a pallet stretch film for wrapping an article (packed object) while stretching is a copolymer of ethylene and vinyl acetate (hereinafter simply referred to as a surface layer (inner and outer layers)). An adhesive layer formed of a resin material in which an adhesive is blended is disposed on "EVA", and an intermediate layer is formed of linear low-density polyethylene (hereinafter simply abbreviated as "LLDPE"). There is a multilayer adhesive film having a three-layer structure in which a base layer is disposed.

Here, as one of the important qualities required for the pallet stretch film, when the product (stretch film itself) is fed, it has a relatively low adhesive strength and is smoothly peeled off, stretched and wound around the package. (Packed)
After that, the adhesive strength is required to be improved, to exhibit an appropriate adhesive strength, not to be peeled off, and for the packaged body not to be broken.

However, since the adhesive film having an adhesive layer using EVA has a considerably high adhesive force when the film is fed (ie, when not stretched), it cannot be peeled smoothly, and peeling sound and static electricity are easily generated. There are drawbacks. Peeling noise and static electricity are disliked by end users. For this reason, sorbitan oleate,
EVA is used for expensive surfactants such as diglycerindiolate
The generation of peeling noise and static electricity is suppressed by being compounded in the composition.

[0005] In addition, since the adhesive layer using EVA has a reduced adhesive strength after being stretched, the above-mentioned expensive surfactant, liquid polybutene and the like are blended in order to further increase the adhesive strength.

[0006] For this reason, even if expensive adhesives and surfactants are not used, problems such as peeling noise and static electricity generation at the time of feeding out do not occur, and the adhesive having an appropriate adhesive strength after stretching. The development of an adhesive film having a layer is desired.

[0007] In the formation of a film, usually,
2. Description of the Related Art Films that are not cut into products, such as both ends of a molded film, are re-pelletized and reused. Also in the above-mentioned formation of the multilayer adhesive film, the cut-off film pieces are repelletized, blended with LLDPE, and then directly put into a hopper of a forming machine for an intermediate layer to be subjected to film production again.

However, when the recycled pellets are mixed with LLDPE, the strength of the film tends to decrease by about 20%. This is considered to be due to the fact that EVA is mixed in the regenerated pellets. Therefore, development of a multilayer adhesive film in which all layers are formed by LLDPE without using EVA is desired.

Furthermore, a pallet stretch film in which an adhesive is blended in an adhesive layer is not hygienic because the adhesive or the like may adhere to a package. Further, even when the film removed from the packaged object is recycled, it is difficult to repellet a film containing an adhesive or the like. Therefore, development of a pallet stretch film that does not contain an adhesive or the like is desired.

[0010]

The present invention has a self-adhesive property without using an expensive pressure-sensitive adhesive or surfactant, and when peeled (unstretched), peels off smoothly and has almost no peeling noise and static electricity. On the other hand, even after stretching and winding the packaged body (at the time of stretching), the adhesive strength between the films does not decrease, and it is excellent in hygiene and recyclability, especially suitable for the adhesive layer of a pallet stretch film. It is an object to provide a film.

[0011]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the 180 ° peel adhesive strength in the unstretched state and the average surface roughness in the unstretched state and the stretched state measured by an atomic force microscope are lower. The present inventors have found that the above problems can be solved by using a film made of an ethylene / α-olefin copolymer having a specific value, and have completed the present invention.

That is, the present invention provides a method for producing ethylene and
(18) A film comprising a copolymer with an α-olefin of (18) to (18), which has all of the following physical properties (a) to (c). (A) 180 ° peel adhesive strength when not stretched is 3-35 g. (B) The average surface roughness Ra1 when not stretched measured by an atomic force microscope is 6.5 nm or less. (C) The average surface roughness Ra2 at the time of stretching measured by an atomic force microscope is 5.5 nm or less.

Further, according to the present invention, the copolymer preferably has a melting peak of 72 to 1 obtained by a differential scanning calorimetry.
The pressure-sensitive adhesive film according to claim 1, wherein the pressure-sensitive adhesive film has one or more in the range of 18 ° C and not in the range of 120 ° C or more.

The present invention also relates to an unstretched average surface roughness Ra1 and an unstretched surface roughness Ra2 obtained by an atomic force microscope.
Satisfies the following formula (I).

[0015]

(Ra2−Ra1) / Ra1 × 100 ≦ −10 (I)

The present invention also provides a pallet stretch film which is a single-layer or multi-layer film using at least a layer made of any one of the above-mentioned pressure-sensitive adhesive films as a surface layer.

[0017]

Embodiments of the present invention will be described below. The pressure-sensitive adhesive film of the present invention has ethylene and carbon number 3
To 18 α-olefins (hereinafter referred to as “ethylene / α-olefin copolymer”).

(1) Ethylene / α-olefin copolymer The ethylene / α-olefin copolymer constituting the pressure-sensitive adhesive film of the present invention comprises an ethylene unit as a main component and an α-olefin as a subcomponent (comonomer unit). Consists of units.

The α-olefin used as a comonomer is a C 3-18, preferably C 4-12, monoolefin.
-Olefins, specifically, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene,
-Heptene, 4-methyl-pentene-1,4-methyl-
Hexene-1,4,4-dimethylpentene-1 and the like. The α-olefin used as a comonomer is not limited to one type, and a multi-component copolymer using two or more types such as a terpolymer is also included as a preferable one.

The proportion of ethylene units in the copolymer is as follows:
Preferably it is at least 80 mol% and the comonomer is less than 20 mol%. For example, as a known method for controlling the molecular weight and the distribution of crystallinity, a polymer having desired physical properties can be obtained by appropriately adopting a method of adjusting the polymerization temperature and the amount of comonomer.

The MFR of the copolymer is not particularly limited, but the MFR value measured according to JIS-K7210 (190 ° C., 2.16 kg load) is preferably 0.1.
10 to 10 g / 10 min, more preferably 0.3 to 8 g / 10 min
Minutes. There is no particular limitation on the density.
The value measured according to IS-K7112 (23 ° C.) is preferably about 0.885 to 0.920 g / cm ³ .

Specific examples of the ethylene / α-olefin used in the present invention include an ethylene / 1-butene binary copolymer, an ethylene / 1-hexene binary copolymer, and an ethylene / 1-octene binary copolymer. Coalesce, ethylene propylene
Examples thereof include 1-butene terpolymer.

The ethylene / α-olefin copolymer used in the pressure-sensitive adhesive film of the present invention has a melting peak obtained by differential scanning calorimetry (DSC) of 72 to 11
One or more, preferably one, in the range of 8 ° C;
It is preferred that there is no melting peak below.

When the melting peak is below 72 ° C.,
The blocking becomes intense, the films are fused together, and they do not come off, or even if they come off, the peeling sound is loud,
It is not preferable because static electricity is easily generated. If the melting peak is higher than the above temperature range, the self-adhesiveness becomes poor, and the adhesive strength is undesirably reduced.

The ethylene / α-olefin copolymer of the present invention has a melting peak of 12
Those not present in the range of 0 ° C. or higher are preferred. 120 ° C
The presence of a melting peak as described above is not preferred because the adhesive strength particularly during stretching decreases. Also, like this, 12
When a melting peak is present at 0 ° C. or higher, low-crystalline / low-molecular-weight components are often present, and this is not preferable because it causes peeling noise and static electricity during feeding.

With respect to the method for producing the ethylene / α-olefin copolymer of the present invention, as long as a product satisfying the predetermined properties and physical properties required in the present invention can be produced.
The polymerization method and catalyst are not particularly limited. For example,
As the catalyst, a Ziegler type catalyst (based on a combination of a supported or unsupported halogen-containing titanium compound and an organoaluminum compound), a Phillips type catalyst (based on supported chromium oxide (Cr ⁶⁺ )), a Kaminski type catalyst ( Based on combinations of supported or unsupported metallocene compounds and organoaluminum compounds, especially alumoxanes)
And the like.

As the polymerization method, a slurry method in the presence of these catalysts, a gas phase fluidized bed method (for example,
No. 23011), a solution method, or a high-pressure bulk polymerization method at a pressure of 200 kg / cm ² or more and a polymerization temperature of 100 ° C. or more.

In the ethylene / α-olefin copolymer of the present invention, if the molecular weight distribution is wide, the film surface becomes rough at the time of molding, and the composition distribution is wide, and if a high crystalline component is present, crystallization easily proceeds. Since the film surface becomes rough, the self-adhesiveness is deteriorated, and the adhesive strength is reduced, it is preferable that the film has a relatively narrow molecular weight distribution, and it is particularly preferable to use a Kaminski type catalyst.

Ethylene / α using a Kaminski type catalyst
-Specific production methods for olefin copolymers include JP-A-58-19309, JP-A-59-95292,
JP-A-60-35005, JP-A-60-35006
JP-A-60-35007, JP-A-60-3500
No. 8, JP-A-60-35009, JP-A-61-130
No. 314, JP-A-3-1630088, European Patent Application Publication No. 420,436, U.S. Pat. No. 5,055,438, and International Publication WO
91/04257, etc., or a metallocene catalyst or a metallocene / alumoxane catalyst, or
For example, a catalyst composed of a metallocene compound as disclosed in International Patent Publication WO92 / 07123 and the like and a compound that reacts with the metallocene compound to form a stable ion is used to remove ethylene as a main component. Examples thereof include a method of copolymerizing the component with an α-olefin.

It should be noted that the ethylene.
The α-olefin copolymer includes an antioxidant, a crystal nucleating agent, a clarifying agent, a light stabilizer, an ultraviolet absorber, and a lubricant used in ordinary polyolefin resin materials as long as the effects of the present invention are not significantly impaired. , Antiblocking agents, antistatic agents, antifogging agents, neutralizing agents, metal deactivators, coloring agents, dispersants,
A peroxide, a filler, a fluorescent whitening agent and the like may be blended.

(2) Film Properties The pressure-sensitive adhesive film of the present invention is an unstretched film and is characterized by having all of the following properties (a) to (c).

(A) 180 ° Peeling Adhesive Strength: The pressure-sensitive adhesive film of the present invention has a 180 ° peeling adhesive strength before unstretching of 3 to 3.
35 g, preferably 5 to 30 g. If the 180 ° peel adhesive strength is larger than the above range, a large peeling sound or static electricity is generated at the time of feeding, which is not preferable. On the other hand, if the 180 ° peel adhesive strength is smaller than the above range, the self-adhesiveness becomes poor and the adhesive strength is reduced, so that when a relatively soft packaged object such as a PET bottle is wound without being stretched without being stretched, it is used as an adhesive layer. Is not preferable because it does not fulfill the role of. On the other hand, when the 180 ° peel adhesive strength is smaller than the above range, the adhesive strength is weak even when stretched, and an appropriate adhesive strength cannot be obtained as a pallet stretch film.

(B) Average Surface Roughness Unstretched Ra1: The pressure-sensitive adhesive film of the present invention has an average surface roughness (Ra1) unstretched measured by an atomic force microscope of 6.5 nm or less, preferably, It is less than 6.0 nm. The average surface roughness R
If a1 is larger than the above value, the self-adhesiveness when unstretched may be poor, and the adhesive strength of the film after stretching tends to decrease, which is not preferable.

(C) Average surface roughness Ra2 at the time of stretching: The pressure-sensitive adhesive film of the present invention is stretched at a stretch ratio of 50 to 300%, usually 2.5 times (150 times) as measured by an atomic force microscope.
%)) Is 5.5 nm or less, preferably 5.0 nm or less. The average surface roughness Ra
When the value of 2 is larger than the above value, the self-adhesiveness after stretching becomes poor, and the adhesive strength is undesirably reduced.

Further, in the pressure-sensitive adhesive film of the present invention, the relationship between the average surface roughness Ra1 when unstretched and the surface roughness Ra2 when stretched obtained by an atomic force microscope preferably satisfies the following formula (I). .

[0036]

(Ra2−Ra1) / Ra1 × 100 ≦ −10 (I)

If the value of (Ra2−Ra1) / Ra1 × 100 is larger than −10, the adhesive strength of the stretched film is undesirably reduced.

(3) Pallet stretch film The pallet stretch film of the present invention is a single-layer or multilayer film using the above-mentioned adhesive film at least as a surface layer. That is, the pressure-sensitive adhesive film of the present invention can be suitably used as a pressure-sensitive adhesive layer of a pallet stretch film, but can also be used as a single film as it is as a single-layer pallet stretch fill. And a pallet stretch film can be formed as a multilayer film including the adhesive film layer (adhesive layer) and a resin film layer (intermediate layer) made of another polyethylene resin.

In the case of a multilayer film, the adhesive layer is usually disposed on the surface layer (the innermost layer and / or the outermost layer), and the adhesive film is used for at least one of the innermost layer and the outermost layer.

The basic layer constitution of the multilayer film is as follows.
A two-layer structure of a surface layer (outermost layer or innermost layer) / intermediate layer, or a three-layer structure of surface layer (outermost layer) / intermediate layer / surface layer (innermost layer) can be given. The pressure-sensitive adhesive film of the present invention may be used for only one of the innermost layer and the outermost layer, or both may be formed of the pressure-sensitive adhesive film.
Therefore, the pressure-sensitive adhesive film layer need not be provided on the entire surface (both sides) of the multilayer film as long as the object of the present invention is achieved, and the present invention also includes such a film.

When the pressure-sensitive adhesive film layer is used for only one of the outermost layer and the innermost layer, a non-adhesive film such as a polyethylene resin having a high tear strength is formed on the other surface layer (the outermost layer or the innermost layer). Sometimes used.

Specific examples of the layer structure include [the adhesive film layer / an intermediate layer composed of another resin film], [the adhesive film layer (outermost layer) / an intermediate layer composed of another resin film / the adhesive film layer]. (Innermost layer)], [the adhesive film layer (outermost layer) / intermediate layer composed of other resin film / surface layer composed of other resin film (innermost layer)], [surface layer composed of other resin film (outermost layer)] / Intermediate layer composed of another resin film / the pressure-sensitive adhesive film layer (innermost layer)].

Examples of the polyethylene resin constituting the other polyethylene resin film layer (intermediate layer) in the multilayer film include an ethylene / 1-hexene binary copolymer and an ethylene / 1-octene binary copolymer. No. A plurality of such intermediate layers may be present in the multilayer film, or a plurality of layers composed of different types of polyethylene resins may be present.

As described above, the pressure-sensitive adhesive film of the present invention can sufficiently exhibit its performance even when used as a single film. Also performs even better as a pallet stretch film.

The thickness of the pressure-sensitive adhesive film of the present invention is preferably about 10 to 50 μm when used as a single film for a pallet stretch film. When used as a surface adhesive layer of a multilayer film, the thickness is preferably about 2 to 25 μm. The thickness of the pallet stretch film made of such a multilayer film is preferably about 10 to 50 μm.

(4) Formation of Pallet Stretch Film When the pallet stretch film of the present invention is a multilayer film of an adhesive film layer and another polyethylene resin layer, etc., the formation or lamination of each layer in the production method is purposeful. Can be arbitrary. According to a conventional method of forming a multilayer film, for example, a method in which each layer is separately formed in advance into a film shape, and then, they are bonded and laminated, and a method in which each layer is formed and laminated by an extrusion method in the same step, and the like. There is. In the former case, the film can be produced by air-cooled inflation molding, air-cooled two-stage cooling inflation, T-die film molding, water-cooled inflation molding, or the like. Examples of the latter extrusion method include extrusion lamination, dry lamination, sandwich lamination, and coextrusion (including coextrusion without an adhesive layer, coextrusion with an adhesive layer, and coextrusion with an adhesive resin). And so on. In the present invention, various multilayer films can be obtained by any of the methods.

When a pallet stretch film is formed by using the pressure-sensitive adhesive film of the present invention alone, the above-mentioned air-cooled inflation molding, air-cooled two-stage cooling inflation, T-die film molding, water-cooled inflation can be used. A molding method or the like can be adopted.

[0048]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. The methods for evaluating various physical properties and the method for forming a film in the following Examples and Comparative Examples are as follows.

1. Various Physical Property Evaluation Methods (1) 180 ° Peel Adhesive Strength Before and After Stretching A single film formed by T-die molding (two films with an inner surface and an outer surface combined) or a single film formed by inflation molding (molding) At the time, cut both ends and divide it into two pieces, then cut two pieces of film with the inner and outer faces wound on a paper tube into a size of 30 mm width and 200 mm length in a constant temperature room at 23 ° C. After the two films having the inner and outer surfaces joined together were once peeled off, they were laminated again (in a state where the inner and outer surfaces joined together), and a load of 5 kg was applied for 5 minutes.

Then, a 200 g load was applied to the tip of the smooth plate, and a slip tester (manufactured by Shinto Kagaku Co., Ltd., HEID
ON-14 type), and the 180 ° peel adhesive strength was measured. FIG. 1 shows a schematic diagram of a 180 ° peel adhesive strength measuring method using this slip tester.

Specifically, the above-mentioned two laminated films (1 in FIG. 1; the same applies hereinafter) are placed on a smooth plate, the lower film is fixed, and the upper film is sandwiched by clips 5. , The clip 5 and the load cell 3 were connected by a monofilament 4. In addition, the clip laid the paper 6 on the upper film, and was mounted on the paper. Next, the smooth plate 2 is loaded with a load of 7
, And the maximum strength when the two films were peeled at 180 ° was defined as the 180 ° peel adhesive strength when unstretched.

The 180 ° peel strength at the time of stretching was measured as follows. That is, the two films obtained by the above-mentioned molding, whose inner and outer surfaces are combined, are cut out to the above-mentioned size, and a C-type shopper testing machine (manufactured by Toyo Seiki Co., Ltd.) is used.
The film was stretched by 150% (2.5 times) at a stretching speed of 00 mm / min. After the two stretched films whose inner surface and outer surface were joined were once peeled off, they were laminated again (in a state where the inner surface and the outer surface were joined), and a load of 5 kg was applied for 5 minutes. Thereafter, the 180 ° peel strength during stretching was measured according to the above method.

(2) Average Surface Roughness Before and After Stretching Using an Atomic Force Microscope A cantilever DF-40 was attached to an SPI3700 (SPA300 unit) manufactured by Seiko Instruments Inc.
After measuring the unevenness in the range of m × 20 μm in the cyclic contact mode, the average surface roughness (Ra) was calculated by the data processing software attached to the apparatus.

More specifically, the fine irregularities on the surface can be measured by using an atomic force microscope cyclic contact mode, and the average surface roughness, that is, the surface roughness is calculated by the following formula (II). Of the three-dimensional unevenness can be quantitatively known.

[0055]

(Equation 4)

Here, in the formula (II), F (X, Y): the measurement surface,
S _0: measurement area, Y _T ~Y _B: Y-direction measurement range, X _L ~X _R: X
Direction measurement range, Z ₀ : reference plane. Z ₀ is the following formula (III)
It is represented by

[0057]

(Equation 5)

The average surface roughness of the unstretched film was determined by measuring the inner surface of the unstretched film used in the 180 ° peel adhesion measurement of the unstretched film. 15 used in the 180 ° peel adhesion measurement at the time
The inner surface of the film stretched 0% (2.5 times) was measured.

(3) Measurement of Melting Peak Temperature by Differential Scanning Calorimetry (DSC) Approximately 5 mg of a sample was weighed from a 100 μm film formed by a hot press, and the sample was weighed.
After setting the temperature to 170 ° C. and holding at that temperature for 5 minutes, the temperature was lowered at a rate of 10 ° C.
Cooled to -10 ° C at ° C / min. Next, after holding for 1 minute, the temperature was increased to 170 ° C. at a rate of 10 ° C./min, and the measurement was performed. The temperature was raised from -10 ° C to 170 ° C to obtain a DSC melting curve. From the melting curve, a gentle peak and a sharp peak were defined as a melting peak, and the temperature at that time was defined as a melting peak temperature.

(4) Peeling sound at the time of feeding out A peeling sound at the time of winding a film having an inner surface and an outer surface wound around a paper tube was observed, and the sound of peeling was observed. The result was indicated by Δ, and the result of peeling was indicated by ×. The peeling sound ○ means that no sound is produced at the time of feeding, and the peeling sound × means that a sound is generated at the time of feeding and is inferior as a pallet stretch film.

[0061] 2. Film Forming Method The ethylene / α-olefin copolymer was formed into a film using a T-die molding machine and an air-cooled inflation molding machine under the following conditions to obtain a single-layer film having a thickness of 25 μm. This film was evaluated.

[T-die forming conditions] Model: T-die film forming machine manufactured by Placo Co., Ltd. Screw diameter: 35 mmφ L / D; 28 temperature; 240 ° C die lip; 0.8 mm die temperature; 240 ° C Cooling roll temperature; 30 ° C air Gap: 45 mm Take-off speed: 20 m / min Film thickness: 25 μm

[Inflation molding conditions] Model: Air-cooled blown film molding machine manufactured by Tommy Co., Ltd. Screw diameter: 40 mmφ L / D; 24 temperature; 180 ° C die diameter; 75 mmφ die lip; 3 mm dice temperature; 180 ° C blow ratio; 2.1 Take-off speed: 20 m / min Film thickness: 25 μm

[0064]

[Example 1] "Kernel KF3" manufactured by Nippon Polychem Co., Ltd.
“60” (melting peak by DSC; 90 ° C.) was directly charged into a hopper of a T-die molding machine to form a film. The unstretched 180 ° peel adhesive strength of this film was 7.2 g, the average surface roughness Ra1 when unstretched obtained by an atomic force microscope was 1.9 nm, and the stretched surface roughness obtained by an atomic force microscope was 1.9 nm. The average surface roughness Ra2 was 1.1 nm. Table 1 shows the results of evaluating various physical properties of this film by the methods described above. This film is excellent as an adhesive layer of a pallet stretch film because the adhesive strength is improved after stretching and there is no peeling sound at the time of feeding.

[0065]

[Example 2] “Kernel KF3” manufactured by Nippon Polychem Co., Ltd.
70 "(melting peak by DSC; 94 ° C.) was directly charged into a hopper of a T-die molding machine to form a film. The unstretched 180 ° peel adhesive strength of this film is 6.3 g, the average surface roughness Ra1 when unstretched obtained by an atomic force microscope is 2.5 nm, and the stretched surface roughness obtained by an atomic force microscope is 2.5 nm. The average surface roughness Ra2 was 1.6 nm. Table 1 shows the results of evaluating various physical properties of this film by the methods described above. This film is excellent as an adhesive layer of a pallet stretch film because the adhesive strength is improved after stretching and there is no peeling sound at the time of feeding.

[0066]

Example 3 "Kernel KF2" manufactured by Nippon Polychem Co., Ltd.
“60” (melting peak by DSC; 93 ° C.) was directly charged into a hopper of a T-die molding machine to form a film. The unstretched 180 ° peel adhesive strength of this film is 7.3 g, the average surface roughness Ra1 when unstretched obtained by an atomic force microscope is 2.2 nm, and the stretched surface roughness obtained by an atomic force microscope is 2.2 nm. The average surface roughness Ra2 was 1.5 nm. Table 1 shows the results of evaluating various physical properties of this film by the methods described above. This film is excellent as an adhesive layer of a pallet stretch film because the adhesive strength is improved after stretching and there is no peeling sound at the time of feeding.

[0067]

[Comparative Example 1] "Dowlex 20" manufactured by Dow Chemical Company
47AC "(melting peak by DSC; 108, 11)
9, and 127 ° C.) were directly charged into a hopper of a T-die molding machine to form a film. The unstretched 180 ° peel adhesive strength of the film was 9.8 g, and the unstretched average surface roughness Ra1 obtained by an atomic force microscope was 6.8 n.
m, average surface roughness Ra at the time of stretching obtained by an atomic force microscope
2 was 3.4 nm. Table 2 shows the results of evaluating various physical properties of this film by the methods described above. This film is not preferred because the adhesive strength is reduced after stretching. In addition, a slight peeling sound is produced when feeding out, which is not preferable.

[0068]

[Comparative Example 2] "Novatech LL-" manufactured by Nippon Polychem Co., Ltd.
SF240 "(melting peak by DSC; 125 ° C)
Was directly charged into a hopper of a T-die molding machine to form a film. The unstretched film has a 180 ° peel adhesive strength of 37 g, an unstretched average surface roughness Ra1 of 11.6 nm obtained by an atomic force microscope, and an average surface of stretched film obtained by an atomic force microscope. The roughness Ra2 was 6.9 nm. Table 2 shows the results of evaluating various physical properties of this film by the methods described above. This film is not preferred because the adhesive strength is significantly reduced after stretching. Also, a peeling sound is generated at the time of feeding, which is not preferable.

[0069]

[Comparative Example 3] "Novatech LL-" manufactured by Nippon Polychem Co., Ltd.
SF941 "(melting peak by DSC; 128 ° C)
Was directly charged into a hopper of a T-die molding machine to form a film. The unstretched 180 ° peel adhesive strength of this film is 1.4 g, the average surface roughness Ra1 when unstretched obtained with an atomic force microscope is 18.2 nm, and the stretched surface strength obtained with an atomic force microscope is 18.2 nm. The average surface roughness Ra2 was 14.6 nm. Table 2 shows the results of evaluating various physical properties of this film by the methods described above. This film does not generate a peeling sound at the time of feeding, but has a low adhesive strength before and after stretching and is not practical.

[0070]

Comparative Example 4 "Kernel KF2" manufactured by Nippon Polychem Co., Ltd.
“60” (melting peak by DSC; 93 ° C.) was directly charged into a hopper of an air-cooled inflation molding machine to form a film. The unstretched 180 ° peel adhesive strength of this film was 13 g, the average surface roughness Ra1 when unstretched obtained by an atomic force microscope was 26.3 nm, and the average surface when stretched obtained by an atomic force microscope. The roughness Ra2 is 30.6 nm
Met. Table 2 shows the results of evaluating various physical properties of this film by the methods described above. Although this film does not generate a peeling sound when it is fed, it is not preferable because the adhesive strength is considerably reduced after stretching.

[0071]

[Table 1]

[0072]

[Table 2]

[0073]

The pressure-sensitive adhesive film of the present invention is self-adhesive without using expensive pressure-sensitive adhesives and surfactants, peels off smoothly at the time of feeding (unstretched), has almost no peeling sound and static electricity, and is stretched. After winding the packaged object (after stretching)
The adhesion between the films is good. Therefore, it can be suitably used especially for the adhesive layer of the pallet stretch film. In addition, the pallet stretch film not using the above-mentioned pressure-sensitive adhesive does not adhere the pressure-sensitive adhesive or the like to the packaged object, and is excellent in hygiene. Furthermore, the film removed from the packaged body is easy to re-pelletize because it does not contain an adhesive or the like, and is environmentally excellent.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a 180 ° peel adhesive strength measurement method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Film 2 ... Smooth board 3 ... Load cell 4 ... Monofilament 5 ... Clip 6 ... Paper 7 ... Load

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Etsushi Akashige 1 Toho-cho, Yokkaichi-shi, Mie F-term (reference) 4F071 AA15X AA21X AH04 BB05 BB06 BB09 BC01 BC16 4J004 AA07 AB01 BA02 BA03 BA04 EA06 FA06

Claims (4)

[Claims] 1. A film comprising a copolymer of ethylene and an α-olefin having 3 to 18 carbon atoms, wherein the film has all of the following physical properties (a) to (c): Adhesive film. (A) 180 ° peel adhesive strength when not stretched is 3-35 g. (B) The average surface roughness Ra1 when not stretched measured by an atomic force microscope is 6.5 nm or less. (C) The average surface roughness Ra2 at the time of stretching measured by an atomic force microscope is 5.5 nm or less. 2. The copolymer has one or more melting peaks obtained by differential scanning calorimetry in the range of 72 to 118 ° C. and does not have one in the range of 120 ° C. or higher. The pressure-sensitive adhesive film according to claim 1. 3. The relationship between the average surface roughness Ra1 in an unstretched state and the surface roughness Ra2 in a stretched state obtained by an atomic force microscope satisfies the following formula (I). Or 2
The adhesive film according to the above. (Ra2−Ra1) / Ra1 × 100 ≦ −10 (I) 4. A pallet stretch film, which is a single-layer or multilayer film using at least a surface layer of the pressure-sensitive adhesive film according to claim 1.