JP6805516B2 - Multilayer film - Google Patents

Description

The present invention relates to a multilayer film.

Decorative steel sheets include galvanized steel sheets, electrogalvanized steel sheets, Ni—Zn alloy plated steel sheets, iron plates, copper plates, aluminum plates, tin, stainless steel (SUS), electrolytic chromium acid-treated steel sheets (tin). A bonding plate in which a bonding film is laminated on the surface of free steel (TFS)) is used. Here, as decorative steel sheets for light electric power, etc., they are used for AV equipment covers, covers for personal computers, printers, copiers, etc., refrigerator outer panels, washing machine outer panels, and the like. Further, as decorative steel sheets for building materials and the like, they are used for unit baths, exterior members, decorative steel sheets for doors and the like. Further, as the container, it is used for a 3-piece can such as a coffee can, a 2-piece can formed by deep drawing, a DI can, a DRD can, a tea can, a pail can, a square can and the like.

For example, Patent Document 1 describes a two-component curable polyester adhesive layer, a pattern printing layer, and a transparent layer containing an opaque base sheet made of a polyolefin resin to which a pigment has been added and an ultraviolet absorber sequentially laminated on the opaque base sheet. A polyolefin-based decorative sheet for a decorative steel plate made of a polyester-based resin layer is disclosed.

Further, Patent Document 2 discloses a three-layer composite film having a carboxyl group-containing polyethylene copolymer as an inner and outer layers and a polypropylene / polyethylene block copolymer as an intermediate layer as a multilayer film.

Japanese Patent No. 49474479 Japanese Unexamined Patent Publication No. 58-20646

However, the sheet disclosed in Patent Document 1 is used for decorative steel sheets, for the inner wall of a unit bath, etc., but has a polyester resin layer on the surface layer and is a fixing member that closes a gap between a panel and a ceiling panel. There are problems that it is necessary to use a rubber-based packing and that the adhesion to the caulking material that closes the joint is low. Further, the polyester resin on the surface layer and the polyolefin resin on the base material have different melting points, and are not suitable for heat welding.

Further, in the three-layer composite film disclosed in Patent Document 2, a film made of the same resin is used as the inner layer and the outer layer, and the melting points are the same. Therefore, there is a problem that the film of the outer layer is deformed by heat when the three-layer composite film is bonded so that the metal plate and the inner layer face each other.

The present invention has been made in view of the above circumstances, and the multilayer films bonded to the surface of a metal plate can be heat-welded to fill the gaps between the plates, and wrinkles and the like during heating during welding can be filled. Provide a material that does not generate.

In order to solve the above problems, the present invention has the following configurations.
That is, the invention according to claim 1 is a multilayer film, in which a first film containing an adhesive resin made of a polyethylene-based resin and a second film containing a heat-welding resin made of a polyethylene-based resin are laminated. the melting point of the adhesive resin, the heat-fusible resin 2 to 50 ° C. lower than the melting point, the a dynamic friction coefficient of 0.3 or more and less than 2.5 on the front and back surfaces of the multilayer film, the in the multilayer film the surface roughness of the second film side of the surface state, and are the 0.3μm or 2μm or less the ten-point average roughness, the surface roughness of the second film-side surface of the multilayer film, the arithmetic average roughness It is a multilayer film having a maximum height of 0.5 μm or more and 2 μm or less with respect to the surface roughness of the surface on the second film side of the multilayer film of 0.05 μm or more and 0.3 μm or less .

The invention according to claim 3 is the multilayer film according to claim 1 or 2, wherein the adhesive resin has a melting point of 85 ° C. or higher and 120 ° C. or lower.

The invention according to claim 4 is the multilayer film according to any one of claims 1 to 3, wherein the adhesive resin contains a metal crosslinked resin.

The invention according to claim 5 is the multilayer film according to any one of claims 1 to 4, wherein the multilayer film has a tensile strength of 20 MPa or more.

Further, the invention according to claim 6 shows a dimensional change when the temperature is raised to 25 to 100 ° C. at a heating rate of 2 ° C./min while a load of 9.8 mN / mm is applied by thermomechanical analysis (TMA). The multilayer film according to any one of claims 1 to 5, wherein the rate is 8% or less.

Further, the invention according to claim 7 is the multilayer layer when the temperature is raised to 25 to 130 ° C. at a heating rate of 2 ° C./min while a load of 9.8 mN / mm is applied by thermomechanical analysis (TMA). The multilayer film according to any one of claims 1 to 6, wherein the film does not shrink and change.

The invention according to claim 10 is the invention according to any one of claims 1 to 9, wherein at least one of the first film and the second film contains either one or both of an antiblocking agent and a slipping agent. The multilayer film described.

The invention according to claim 11 is the multilayer film according to any one of claims 1 to 10, wherein the thickness of the multilayer film is 20 μm or more and 400 μm or less.

Since the multilayer film of the present invention has a structure in which a first film containing an adhesive resin and a second film containing a heat-welding resin are laminated, a plate made of wood or metal and the first film face each other. By laminating in this way, it is possible to prevent the second film on the side opposite to the adhesive surface from being thermally deformed.

It is a schematic cross-sectional view which shows an example of the structure of the multilayer film which is one Embodiment to which this invention is applied. It is a graph which shows the dimensional change rate by TMA of the multilayer film which is one Embodiment to which this invention is applied.

Hereinafter, a multilayer film according to an embodiment to which the present invention is applied will be described in detail. In the drawings used in the following description, in order to make the features easier to understand, the featured parts may be enlarged for convenience, and the dimensional ratios of each component may not be the same as the actual ones. Absent.

<Multilayer film>
First, an example of the configuration of the multilayer film 1 according to the embodiment to which the present invention is applied will be described with reference to FIG.
FIG. 1 is a schematic cross-sectional view of a multilayer film 1 according to an embodiment to which the present invention is applied. As shown in FIG. 1, the multilayer film 1 of the present embodiment includes a first film 2 and a second film 3, and the first film 2 and the second film 3 are laminated to be roughly configured. The multilayer film 1 of the present embodiment can be used as a surface protective film by laminating.

The thickness of the multilayer film 1 of the present embodiment is not particularly limited and can be appropriately selected. Here, as the upper limit value of the thickness of the multilayer film 1 of the present embodiment, specifically, for example, it is preferably 400 μm, and more preferably 100 μm. When the thickness is not more than the upper limit value, it is preferable that heating at the time of bonding can be suppressed, so that the deterioration of the metal plate can be prevented, and distortion of the film at the time of bonding can be suppressed.

On the other hand, the lower limit of the thickness of the multilayer film 1 of the present embodiment is, for example, preferably 20 μm, more preferably 30 μm, and even more preferably 50 μm. When the thickness is at least the lower limit value, it is preferable in that it prevents holes through which the film penetrates due to rubbing or the like, stabilizes the heat adhesiveness of the joint portion, and imparts corrosion resistance.

(1st film)
The first film 2 is a film containing an adhesive resin made of a polyethylene-based resin. With the first film 2, the multilayer film 1 can be bonded to the surface of a board made of wood, metal, or the like.

The polyethylene-based resin used for the adhesive resin is not particularly limited as long as it can be bonded to the surface of a metal plate, but specifically, for example, a low-density polyethylene resin (LDPE resin) or a straight chain. Low density polyethylene resin (L-LDPE resin), medium density polyethylene resin (MDPE resin), high density polyethylene resin (HDPE resin), ethylene-acrylic acid copolymer (EAA resin), ethylene-methacrylate copolymer ( Examples thereof include EMAA resin and ethylene-ethyl acrylate copolymer (EEA resin).

Further, the polyethylene-based resin used for the adhesive resin may be an ionomer resin containing metal ions in the polyethylene-based resin. Examples of the metal ion include transition metal ions such as zinc, manganese and cobalt, alkali metal ions such as lithium, sodium and potassium, and alkaline earth metal ions such as calcium. The ionomer resin contains at least one of the above metal ions.

The adhesive resin contains at least one of the polyethylene-based resin and the ionomer resin. The metal adhesive resin preferably contains an ionomer resin. Thereby, when the multilayer film 1 is attached to the surface of the metal plate, the adhesive force with the metal plate can be improved.

The melting point of the adhesive resin is preferably lower than the melting point of the thermosetting resin described later. Specifically, for example, the melting point of the adhesive resin is preferably 2 to 50 ° C. lower than the melting point of the thermosetting resin, more preferably 5 to 40 ° C. lower, and more preferably 10 to 35 ° C. lower. .. Here, the "melting point" refers to the melting point having the highest temperature in the case of a resin having two or more melting point peaks. The same applies hereinafter. As a result, it is possible to prevent the second film 3 from being deformed by heat due to heating when the multilayer film 1 is bonded to the surface of a plate such as wood or metal, and further, it is wound around a crimping roll at the time of bonding. Can also be suppressed.

Specifically, the upper limit of the melting point of the adhesive resin is preferably, for example, 120 ° C., more preferably 110 ° C. When the melting point is not more than the upper limit value, sufficient adhesive strength can be obtained even when the heating temperature at the time of bonding to the surface of a plate such as wood or metal is low.
On the other hand, as the lower limit of the melting point of the adhesive resin, specifically, for example, 85 ° C. is preferable, and 90 ° C. is more preferable. When the melting point is at least the lower limit value, thermal deterioration of the resin during film formation can be suppressed, and the slipperiness can be maintained in a good state.

The thickness of the first film 2 is not particularly limited and can be appropriately selected. Here, the lower limit of the thickness of the first film 2 is, specifically, for example, preferably 3%, more preferably 5%, and 7% of the thickness of the multilayer film 1. Is even more preferable. When the thickness is at least the lower limit value, sufficient adhesive strength and stability can be obtained when the multilayer film 1 is adhered to a plate such as wood or metal. As a result, for example, when the multilayer film 1 is crimped in the step of bonding to the surface of a plate such as wood or metal, even if the thickness of the first film 2 changes due to the resin flow due to the pressure variation, the first film 2 The thickness of the film can be kept favorable. As a result, the adhesive strength of the first film 2 can be maintained even when the film is bent or reheated.

On the other hand, the upper limit of the thickness of the first film 2 is, for example, preferably 40%, more preferably 25%, of the thickness of the multilayer film 1. When the thickness is not more than the upper limit value, the multilayer film 1 can be made thinner while maintaining sufficient adhesive strength.

(2nd film)
The second film 3 is a film containing a thermosetting resin made of a polyethylene-based resin having a melting point higher than that of the adhesive resin.

The polyethylene-based resin used for the heat-welding resin is not particularly limited as long as it is a resin that can be bonded by heat welding, and specific examples thereof include LDPE resin, L-LDPE resin, MDPE resin, HDPE resin and the like. Can be mentioned. Specifically, the thermosetting resin is preferably a resin having a slow crystallization rate, for example, an LDPE resin is preferable, and an L-LDPE resin is more preferable. As a result, since it does not crystallize excessively at the time of bonding or welding, the bonding strength is maintained and cracking at the bonded portion can be prevented.

Specifically, as the upper limit of the melting point of the thermosetting resin, for example, 170 ° C. is preferable, 140 ° C. is more preferable, and 130 ° C. is further preferable. When the melting point is below the upper limit, it softens during bonding and has the effect of making the pressure uniform, the joint can be fused at low temperature, high corrosion resistance can be obtained, and flexibility is easy to process. It is preferable in that it can be obtained.

On the other hand, as the lower limit of the melting point of the thermosetting resin, specifically, for example, 90 ° C. is preferable, and 105 ° C. is more preferable. When the melting point is at least the lower limit value, it is preferable that the generation of whiskers due to the elongation of the film in the punching process can be suppressed, and uneven welding and perforation can be suppressed.

Either one or both of the anti-blocking agent and the slip agent may be added to the second film 3. As a result, it is possible to prevent the films from adhering to each other during handling of the multilayer film 1, improve slippage, stabilize the tension applied to the films, and prevent loosening and stretching during bonding.

Specific examples of the antiblocking agent include inorganic particles such as silica and aluminum silicate, and organic particles such as polyethylene beads, acrylic beads and polytetrafluoroethylene particles. Specifically, for example, the amount of the antiblocking agent added is preferably 0.001 to 5% by mass, more preferably 0.05 to 3% by mass, based on the thermosetting resin of the layer to be added.

Examples of the slip agent include saturated fatty acid amide (saturated fatty acid amide) and unsaturated fatty acid amide (unsaturated fatty acid amide), and specific examples thereof include erucic acid amide and oleic acid amide. Specifically, the amount of the slip agent added is preferably 0.0005 to 3% by mass. For example, 0.001 to 2% by mass is preferable, and 0.001 to 1% by mass is more preferable with respect to the thermosetting resin.

The multilayer film 1 may be subjected to a decorative treatment. Examples of the method include laminating a colored second film 3 on the first film 2, printing a pattern on the surface of the second film 3 and laminating it on the first film 2. .. Further, the surface of the second film 3 on the side opposite to the adhesive surface with the first film 2 may be embossed to provide an uneven pattern.

As a method of laminating the colored second film 3 on the first film 2, a pigment or a dye is directly added to the second film using a heat-welding resin made of a polyethylene resin, or the pigment or the dye is contained. The resin to be used can be added as a masterbatch to extrude and form a uniform and colored resin to form a film.

The colorant is not particularly limited, and known colorants such as pigments and dyes can be used. For example, inorganic pigments such as titanium oxide, zinc flower, petals, vermilion, ultramarine, cobalt blue, titanium yellow, chrome yellow, carbon black; isoindolinone, Hansa yellow A, quinacridone, permanent red 4R, phthalocyanine blue, induslen. Organic pigments (including dyes) such as blue RS and aniline black; metal pigments such as aluminum and brass; titanium dioxide-coated mica, pearl pigments made of foil powder such as basic lead carbonate, and the like. It is preferable that it does not dissolve in water, and titanium oxide is particularly preferable.

The thickness of the second film 3 is not particularly limited and can be appropriately selected. Here, the lower limit of the thickness of the second film 3 is, specifically, for example, preferably 60%, more preferably 75%, and 80% of the thickness of the multilayer film 1. Is even more preferable. When the thickness is at least the lower limit, the pressure at the time of bonding can be uniformly transmitted, and the film can be prevented from traversing and wrapping around the roll.
On the other hand, the upper limit of the thickness of the second film 3 is preferably, for example, 95% of the thickness of the multilayer film 1. When the thickness is not more than the upper limit value, it is possible to suppress the variation in the adhesive strength due to the outflow of the first film 2 at the time of bonding.

The tensile strength of the multilayer film 1 of the present embodiment is preferably 20 MPa or more, more preferably 25 MPa or more. As a result, it is easy to adjust the tension at the time of bonding.

Further, when the multilayer film 1 of the present embodiment is heated to 25 to 100 ° C. at a heating rate of 2 ° C./min while a load of 9.8 mN / mm is applied by thermomechanical analysis (TMA). The rate of change is preferably 8% or less, and more preferably 5% or less. As a result, the dimensional change of the multilayer film 1 at the time of bonding is small, so that the bonding is excellent.

Further, the multilayer film 1 of the present embodiment does not have to be stretched in the manufacturing method described later. If there is no stretch orientation, shrinkage of the multilayer film 1 can be prevented in the above-mentioned TMA. As a result, the dimensional change is stable and the bonding is excellent.

The dynamic friction coefficient (measured based on JIS K7125) of the front and back surfaces of the multilayer film 1 of the present embodiment is preferably 0.3 or more and less than 2.5, and more preferably 0.3 or more and less than 1.0.

The wetting index of the surface of the multilayer film 1 of the present embodiment on the side of the second film 3 is, for example, 25 dynes / cm or more and 50 dynes / cm or less, preferably 30 dynes / cm or more and 43 dynes / cm. It is less than cm. As a result, when the multilayer film 1 is handled, adhesion between the films is prevented and slippage is improved.
In order to adjust the wetting index, corona treatment, plasma treatment, frame treatment, and ultraviolet irradiation treatment may be performed.

Further, the surface of the multilayer film 1 of the present embodiment on the side of the second film 3 may be embossed as described above. Specifically, the surface roughness is, for example, an arithmetic average roughness of 0.05 μm or more and 0.3 μm or less, a maximum height of 0.5 μm or more and 2 μm or less, and a ten-point average roughness of 0. .3 μm or more and 2 μm or less.

As a result, the amount of the anti-blocking agent and the slip agent added to the second film 3 can be reduced.

Further, when the surface roughness becomes smaller than the above maximum value, the variation in the content resistance due to the thickness variation can be suppressed. In addition, it is possible to prevent poor welding due to air entrapment at the joint during welding.
Further, when the surface roughness is larger than the above minimum value, sufficient slipperiness can be obtained and the bonding suitability is excellent.

The object to be adhered may be a plate on which the multilayer film 1 is laminated. Further, for example, in the case of construction, the multilayer film can be cut out into a required shape and heat-welded to a wood frame or a metal frame forming a window frame.

<Manufacturing method of multilayer film>
Next, the method for producing the multilayer film 1 described above will be described.
The multilayer film 1 of the present embodiment may be manufactured by separately manufacturing the first film 2 and the second film 3 described above and then joining them by a laminating machine or the like. Further, the multilayer film 1 of the present embodiment is manufactured by a method of forming the above-mentioned first film 2 and second film 3 by, for example, an air-cooled or water-cooled coextrusion inflation method or a coextrusion T-die method. You may. Among them, the method of forming a film by the coextrusion T-die method is excellent and preferable in that the thickness of each layer is controlled. Further, the surface of the multilayer film 1 may be embossed by bringing the film into close contact with the embossed roll having irregularities during film formation.

As described above, according to the multilayer film 1 of the present embodiment, since the first film 2 containing the adhesive resin and the second film 3 containing the heat-welding resin are laminated, wood or the like. By laminating the multilayer film 1 so that the plate of metal or the like and the first film 2 face each other, it is possible to prevent the second film 3, which is the surface opposite to the adhesive surface, from being deformed by heat. it can.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and the design and the like within a range not deviating from the gist of the present invention are also included. For example, in the above-mentioned multilayer film 1, the configuration in which the first film 2 and the second film 3 are laminated has been described as an example, but the position adjacent to the second film 3 and the opposite side of the first film 2 , The third film may be further laminated.

Further, in the above-mentioned multilayer film 1, an example in which either one or both of the antiblocking agent and the slipping agent are added to the second film 3 has been described, but similarly, the antiblocking agent and the antiblocking agent and the first film 2 Either one or both of the slip agents may be added.

Further, in the above-mentioned multilayer film 1, an example of heat bonding at the time of bonding to a plate to be bonded has been described, but an adhesive may be used.
The adhesive is not particularly limited, and examples thereof include acrylic type, isocyanate type, urethane type, polyester type, and amide type. Further, as a classification, a dry laminate adhesive, a curable adhesive, or a hot melt adhesive may be used.

<Manufacturing of multilayer film>
(Example 1)
As the first film, Hymilan (registered trademark) (registered trademark), which is a polyethylene-based ionomer resin (manufactured by Mitsui / DuPont Polychemical Co., Ltd., brand: 1652, melting point: 98 ° C., melt flow rate (MFR): 5.5 g / 10 min, density: 0 .94 g / cm ³ ) was prepared. In addition, as the second film, Umerit (registered trademark) (manufactured by Ube Maruzen Polyethylene, brand: 1520F, melting point: 114 ° C., MFR: 2 g / 10 min, density: 0.915 g / cm ³ ), which is an L-LDPE resin, is used. I prepared it.

The melting point of each resin was measured by differential scanning calorimetry (DSC) based on JIS K-7121. When two or more melting point peaks were detected, the high temperature side was defined as the melting point. The same applies below.

A multilayer film was produced by forming a film of Hymilan and Umerit by a coextrusion T-die method. Further, the surface of the multilayer film on the second film side was embossed by bringing the second film into close contact with the embossed roll having irregularities during film formation. The thickness of the produced multilayer film was 70 μm, the thickness of the first film was 10 μm, and the thickness of the second film was 60 μm.

(Example 2)
As the first film, Hymilan (registered trademark), which is a polyethylene-based ionomer resin (manufactured by Mitsui / DuPont Polychemical Co., Ltd., brand: 1652, melting point: 98 ° C., MFR: 5.5 g / 10 min, density: 0.94 g / cm ³ ) I prepared. In addition, as the second film, Mirason (registered trademark) (registered trademark) (manufactured by Mitsui / DuPont Polychemical Co., Ltd., brand: F997, melting point: 108 ° C., MFR: 5 g / 10 min, density: 0.92 g / cm ³ ), which is an LDPE resin, is used. I prepared it.

A multilayer film was produced by forming a film of Hymilan and Mirason by a coextrusion T-die method. Further, the surface of the multilayer film on the second film side was embossed by bringing the second film into close contact with the embossed roll having irregularities during film formation. The thickness of the produced multilayer film was 70 μm, the thickness of the first film was 11 μm, and the thickness of the second film was 59 μm.

(Example 3)
As the first film, Hymilan (registered trademark), which is a polyethylene-based ionomer resin (manufactured by Mitsui / DuPont Polychemical Co., Ltd., brand: 1652, melting point: 98 ° C., MFR: 5.5 g / 10 min, density: 0.94 g / cm ³ ) Was prepared. Further, as the second film, Elite (registered trademark) which is an L-LDPE resin (manufactured by Dow Chemical Co., Ltd., brand: 5220G, melting point: 121 ° C., MFR: 3.5 g / 10 min, density: 0.915 g / cm ³ ) I prepared. In addition, an LDPE-based masterbatch containing 10% by mass of natural silica as an anti-blocking agent and 1.5% by mass of erucic acid amide as a slip agent added to the second film, Ube-Maruzen Polyethylene Co., Ltd. Made, brand: 82105M) was prepared.

A multilayer film was produced by forming a film of Hymilan and an elite containing 3% by mass of Umerit (82105M) by a coextrusion T-die method.
Further, the surface of the multilayer film on the second film side was embossed by bringing the second film into close contact with the embossed roll having irregularities during film formation.

The thickness of the produced multilayer film was 70 μm, the thickness of the first film was 11 μm, and the thickness of the second film was 59 μm.

(Example 4)
As the first film, Hymilan (registered trademark), which is a polyethylene-based ionomer resin (manufactured by Mitsui / DuPont Polychemical Co., Ltd., brand: 1652, melting point: 98 ° C., MFR: 5.5 g / 10 min, density: 0.94 g / cm ³ ) Was prepared. Further, as the second film, Evolu (registered trademark) which is an L-LDPE resin (manufactured by Prime Polymer Co., Ltd., brand: SP3530, melting point: 122 ° C., MFR: 3.2 g / 10 min, density: 0.931 g / cm ³ ) I prepared. In addition, an LLDPE-based masterbatch containing 10% by mass of synthetic zeolite having an average particle size of 5 μm as an anti-blocking agent added to the second film, Evolu (registered trademark) (manufactured by Prime Polymer Co., Ltd., brand: EAZ-10, MFR). : 3.5 g / 10 min) was prepared.

A multilayer film was produced by forming a film of Hymilan and Evolu (SP3530) containing 3% by mass of Evolu (EAZ-10) by a coextrusion T-die method. Further, the surface of the multilayer film on the second film side was embossed by bringing the second film into close contact with the embossed roll having irregularities during film formation.

The thickness of the produced multilayer film was 70 μm, the thickness of the first film was 11 μm, and the thickness of the second film was 59 μm.

(Example 5)
As the first film, L-LDPE resin Ultzex (registered trademark) (manufactured by Prime Polymer Co., Ltd., brand: 2520F, melting point: 118 ° C., MFR = 2.5 g / 10 min, density: 0.922 g / cm ³ ) is used. I prepared it. As the second film, Ultozex (registered trademark) (manufactured by Prime Polymer Co., Ltd., brand: 2022 L, melting point: 120 ° C., MFR = 2.0 g / 10 min, density: 0.919 g / cm ³ ), which is an L-LDPE resin, is used. I prepared it.
Further, in Example 5, the third film was laminated on the opposite side of the first film at a position adjacent to the second film. As the third film, Ultozex (registered trademark) (manufactured by Prime Polymer Co., Ltd., brand: 2022 L, melting point: 120 ° C., MFR = 2.0 g / 10 min, density: 0.919 g / cm ³ ), which is an L-LDPE resin, is used. I prepared it.
Furthermore, an LLDPE-based masterbatch containing 10% by mass of synthetic zeolite having an average particle diameter of 5 μm as an anti-blocking agent to be added to the first and third films, Evolu (registered trademark) (Prime Polymer Co., Ltd., brand: EAZ- 10, MFR: 3.5 g / 10 min) was prepared.

Ultozex (2520F) containing 3% by mass of Evolu (EAZ-10) as the first film, Ultozex (2022L) as the second film, and 2% by mass of Evolu (EAZ-10) as the third film. A multilayer film was produced by forming a film of Ultzex (2022L) by a coextrusion T-die method and stretching the film. After film formation, the first film was subjected to corona treatment.

The thickness of the produced multilayer film was 70 μm, the thickness of the first film was 10 μm, the thickness of the second film was 50 μm, and the thickness of the third film was 10 μm. The wettability index of the corona-treated first film surface was 42 dynes.

(Comparative Example 1)
As the first film and the second film, polypropylene resin (PP resin) Noblen (registered trademark) (manufactured by Sumitomo Chemical Co., Ltd., brand: FS2011DG3, melting point: 158 ° C., MFR: 2.5 g / 10 min, density: 0.9 g / Cm ³ ) was prepared.

A multilayer film was produced by using Noblen (FS2011DG3) as the first film and the second film, forming a film by a coextrusion T-die method, and stretching the film. Here, when the film was formed, the first film was subjected to corona treatment. The thickness of the produced multilayer film was 70 μm.

<Lasting test>
The multilayer films of Examples 1 to 5 and Comparative Example 1 were heat-laminated on the steel sheet so that the steel sheet and the first film faced each other. The bonding temperature was 190 ° C.
Table 1 shows the results of bonding. The "difference in melting point" indicates how many times the melting point of the adhesive resin contained in the first film is lower than the melting point of the thermosetting resin contained in the second film. In the "results", the multilayer film in which the second film was hardly deformed after bonding was marked with "◎", and the multilayer film in which the second film was slightly deformed after bonding was marked with "○", and after bonding, the film was marked with "○". A multilayer film in which the second film was significantly deformed or had low adhesive strength was designated as "x".

In the multilayer film in which the melting point of the adhesive resin is lower than the melting point of the thermosetting resin by 2 to 50 ° C. as in Examples 1 to 5, the second film was hardly deformed after bonding. On the other hand, in the multilayer film in which the melting point of the adhesive resin is substantially the same as the melting point of the thermosetting resin as in Comparative Example 1, the second film is significantly deformed after bonding.
From the above results, it was confirmed that by lowering the melting point of the adhesive resin to 2 to 50 ° C. lower than the melting point of the thermosetting resin, it is possible to suppress the second film from being deformed by heat during bonding. did.

<Pull test>
A tensile test was performed on the multilayer films of Examples 1 to 5 and Comparative Example 1. The tensile test was performed in both the MD direction and the TD direction based on JIS Z1702.
Table 2 shows the tensile strength of each multilayer film. The tensile strength of the multilayer films of Examples 1 to 5 was 20 MPa or more.

<Thermomechanical analysis>
Thermomechanical analysis (TMA) was performed on the multilayer films of Examples 1 to 5 and Comparative Example 1. TMA was performed using EXSTAR6000 manufactured by Seiko Instruments Inc. TMA was carried out by raising the temperature to 25 to 130 ° C. at a heating rate of 2 ° C./min while applying a load of 9.8 mN / mm.
FIG. 3 shows the dimensional change rate of each multilayer film at each temperature. The multilayer films of Examples 1 to 5 had a dimensional change rate of 8% or less when the temperature was raised to 25 to 100 ° C. Moreover, the multilayer films of Examples 1 and 3 to 5 did not shrink during TMA.

<Measurement of dynamic friction coefficient>
The dynamic friction coefficient was measured for the multilayer films of Examples 1 to 5 and Comparative Example 1. The coefficient of dynamic friction was measured based on JIS K7125 (weight: 201 g, speed: 100 mm / mim). For the measurement of the dynamic friction coefficient, the dynamic friction coefficient on the front and back surfaces of the multilayer film was measured.
Table 3 shows the dynamic friction coefficients on the front and back surfaces of each multilayer film. In the multilayer films of Examples 1 to 5, the coefficient of dynamic friction was 0.3 or more and less than 2.5.

<Measurement of surface roughness>
The surface roughness of the surface on the second film side of the multilayer films of Examples 1 to 5 and Comparative Example 1 was measured. The surface roughness was measured using HandySurf E35B manufactured by Tokyo Seimitsu Co., Ltd.
Table 4 shows the arithmetic average roughness (Ra), the maximum height (Ry), and the ten-point average roughness (Rz) of the surface roughness of the surface on the second film side of each multilayer film.

The surface roughness of the surface of the multilayer film of Examples 1 to 5 on the second film side is in the range of Ra of 0.05 to 0.3 μm, Ry of 0.5 to 2 μm, and Rz of 0.3 μm to 2 μm. It was confirmed.

1 ... Multilayer film 2 ... 1st film 3 ... 2nd film

Claims (8)

It ’s a multilayer film,
A first film containing an adhesive resin made of a polyethylene resin and a second film containing a heat-welding resin made of a polyethylene resin are laminated.
The melting point of the adhesive resin is 2 to 50 ° C. lower than the melting point of the thermosetting resin.
The dynamic friction coefficient of the front and rear surfaces of the multilayer film is less than 0.3 to 2.5,
Wherein the surface roughness of the the multilayer film second film side of the surface, the average roughness ten points Ri der 0.3μm or 2μm or less,
Regarding the surface roughness of the surface on the second film side of the multilayer film, the arithmetic mean roughness is 0.05 μm or more and 0.3 μm or less.
A multilayer film having a maximum height of 0.5 μm or more and 2 μm or less with respect to the surface roughness of the surface on the second film side of the multilayer film. The multilayer film according to claim 1, wherein the adhesive resin has a melting point of 85 ° C. or higher and 120 ° C. or lower. The multilayer film according to claim 1 or 2 , wherein the adhesive resin contains a metal crosslinked resin. The multilayer film according to any one of claims 1 to 3 , wherein the multilayer film has a tensile strength of 20 MPa or more. According to a thermomechanical analysis (TMA), the dimensional change rate is 8% or less when the temperature is raised to 25 to 100 ° C. at a heating rate of 2 ° C./min while a load of 9.8 mN / mm is applied. The multilayer film according to any one of 1 to 4 . According to the thermomechanical analysis (TMA), the multilayer film does not shrink and change when the temperature is raised to 25 to 130 ° C. at a temperature rising rate of 2 ° C./min while a load of 9.8 mN / mm is applied. 5. The multilayer film according to any one of 5 . The multilayer film according to any one of claims 1 to 6 , wherein at least one of the first film and the second film contains either one or both of an antiblocking agent and a slipping agent. The multilayer film according to any one of claims 1 to 7 , wherein the thickness of the multilayer film is 20 μm or more and 400 μm or less.

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