JP2016179685A - Multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer film capable of suppressing deformation caused by heat, of a surface on the opposite side to an adhesive surface, when being laminated on the surface of a metal plate.SOLUTION: A multilayer film 1 is selected, which is formed by laminating a first film 2 containing an adhesive resin comprising a polyethylene-based resin and a second film 3 containing a heat-fusible resin comprising a polyethylene-based resin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multilayer film.

  For decorative steel plates, etc., steel plates, iron plates, copper plates, aluminum plates, tinplate, stainless steel (SUS), electrolytic chromic acid treated steel plates (tin), such as zinc plating, electrogalvanization, Ni-Zn alloy plating, etc. A bonded plate in which a film for bonding is laminated on the surface of free steel (TFS) is used. Here, as a decorative steel plate for weak electricity, it is used for AV equipment covers, covers for personal computers, printers, copying machines, etc., refrigerator outer plates, washing machine outer plates and the like. Further, decorative steel sheets for building materials are used for decorative steel sheets for unit baths, exterior members, doors, and the like. Furthermore, as a container, it is used for 3 piece cans, such as a coffee can, the deep drawing 2 piece can, DI can, DRD can, tea can, pail can, square can.

  For example, Patent Document 1 discloses a two-component curable polyester adhesive layer comprising an opaque base material sheet made of a polyolefin resin to which a pigment is added and an ultraviolet absorber sequentially laminated thereon, a pattern printing layer, a transparent A polyolefin-based decorative sheet for decorative steel sheet comprising a polyester resin layer is disclosed.

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

Japanese Patent No. 4947479 JP 58-20646 A

  However, although the sheet | seat disclosed by patent document 1 is used for decorative steel plates, and is used for unit bath inner walls etc., there is a polyester resin layer on the surface layer, and a fixing member that closes a gap between the panel and the ceiling panel In addition, there is a problem that a rubber-based packing must be used and that the adhesiveness with the caulking material that closes the joint is low. Further, the polyester resin of the surface layer and the polyolefin resin of the base material have a melting point difference and are not suitable for heat welding.

  In the three-layer composite film disclosed in Patent Document 2, films made of the same resin are used as the inner layer and the outer layer, and the melting points are the same. For this reason, when bonding a three-layer composite film so that a metal plate and an inner layer may oppose, there existed a problem that the film of an outer layer deform | transforms with a heat | fever.

  The present invention has been made in view of the above circumstances, and multilayer films bonded to the surface of a metal plate can be thermally welded to fill a gap between the plates, and wrinkles in heating at the time of welding, etc. Provide materials that do not generate.

In order to solve the above problems, the present invention comprises the following arrangement.
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 resin and a second film containing a heat-welding resin made of a polyethylene resin are laminated. .

  Moreover, the invention which concerns on Claim 2 is a multilayer film of Claim 1 whose melting | fusing point of the said adhesive resin is 2-50 degreeC lower than melting | fusing point of the said heat welding resin.

  Moreover, the invention which concerns on Claim 3 is a multilayer film of Claim 1 or 2 whose melting | fusing point of the said adhesive resin is 85 degreeC or more and 120 degrees C or less.

  Moreover, the invention which concerns on Claim 4 is a multilayer film as described in any one of Claims 1 thru | or 3 in which the said adhesive resin contains metal crosslinking resin.

  Moreover, the invention which concerns on Claim 5 is a multilayer film as described in any one of Claims 1 thru | or 4 whose tensile strength of the said multilayer film is 20 Mpa or more.

  Further, in the invention according to claim 6, when the temperature is increased from 25 to 100 ° C. at a rate of temperature increase of 2 ° C./min while applying a load of 9.8 mN / mm, the dimensional change is determined by thermomechanical analysis (TMA). It is a multilayer film as described in any one of Claims 1 thru | or 5 whose rate is 8% or less.

  Further, the invention according to claim 7 is the multilayer when the temperature is increased from 25 to 130 ° C. at a temperature increase rate of 2 ° C./min while applying a load of 9.8 mN / mm by thermomechanical analysis (TMA). The multilayer film according to any one of claims 1 to 6, wherein the film does not change in shrinkage.

  Moreover, the invention which concerns on Claim 8 is a multilayer film as described in any one of Claims 1 thru | or 7 whose dynamic friction coefficients of the front and back of the said multilayer film are 0.3-2.5.

  The invention according to claim 9 is any one of claims 1 to 8, wherein the ten-point average roughness of the surface of the multilayer film on the second film side is not less than 0.3 μm and not more than 2 μm. The multilayer film according to one item.

  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 includes one or both of an antiblocking agent and a slip agent. It is a multilayer film of description.

  Moreover, the invention which concerns on Claim 11 is a multilayer film as described in any one of Claims 1 thru | or 10 whose thickness of the said multilayer film is 20 micrometers or more and 400 micrometers or less.

  The multilayer film of the present invention has a configuration in which a first film containing an adhesive resin and a second film containing a heat-welding resin are laminated, so that a board made of wood or metal and the first film are opposed to each other. By sticking together as described above, it is possible to suppress thermal deformation of the second film on the side opposite to the bonding surface.

It is a schematic cross section which shows an example of a 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, the multilayer film which is one embodiment to which the present invention is applied will be described in detail. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

<Multilayer film>
First, an example of the structure of the multilayer film 1 which is one 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 which is an embodiment to which the present invention is applied. As shown in FIG. 1, the multilayer film 1 of this embodiment is equipped with the 1st film 2 and the 2nd film 3, and the 1st film 2 and the 2nd film 3 are laminated | stacked, and it is schematically comprised. The multilayer film 1 of this embodiment can be used for the use of a surface protection film by bonding together.

  The thickness of the multilayer film 1 of this embodiment is not specifically limited, It can select suitably. Here, specifically as an upper limit of the thickness of the multilayer film 1 of this embodiment, specifically, it is preferable to set it as 400 micrometers, for example, and it is more preferable to set it as 100 micrometers. When the thickness is equal to or less than the upper limit value, it is preferable in that the heating at the time of bonding can be suppressed to prevent the deterioration of the metal plate and the 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 specifically preferably 20 μm, more preferably 30 μm, and still more preferably 50 μm, for example. When the thickness is equal to or more than the lower limit, it is preferable in terms of preventing perforation through the film due to rubbing or the like, in terms of stabilizing the heat adhesiveness of the joint, and in providing corrosion resistance.

(First film)
The first film 2 is a film containing an adhesive resin made of a polyethylene resin. The first film 2 allows the multilayer film 1 to be bonded to the surface of a plate such as wood or metal.

  The polyethylene resin used for the adhesive resin is not particularly limited as long as it is a resin that can be bonded to the surface of a metal plate. Specifically, for example, a low-density polyethylene resin (LDPE resin), 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-methacrylic acid copolymer ( Examples include EMAA resin, ethylene-ethyl acrylate copolymer (EEA resin), and the like.

  The polyethylene resin used for the adhesive resin may be an ionomer resin containing metal ions in the polyethylene resin. Examples of the metal ions 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 resin and the ionomer resin. The metal adhesive resin preferably contains an ionomer resin. Thereby, when bonding the multilayer film 1 on the surface of a metal plate, the adhesive force with a metal plate can be improved.

  The melting point of the adhesive resin is preferably lower than the melting point of the heat-welding 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 heat-welding resin, more preferably 5 to 40 ° C., and more preferably 10 to 35 ° C. . Here, “melting point” refers to the melting point with the highest temperature in the case of a resin having two or more melting point peaks. The same applies hereinafter. Thereby, it can suppress that the 2nd film 3 is deform | transformed with a heat | fever by the heating at the time of bonding the multilayer film 1 to the surface of board | plates, such as a timber and a metal, and also it winds around the crimping | compression-bonding roll at the time of bonding. Can also be suppressed.

Moreover, specifically as an upper limit of melting | fusing point of adhesive resin, 120 degreeC is specifically preferable, for example, and 110 degreeC is more preferable. When the melting point is not more than the upper limit value, sufficient adhesive force 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, the lower limit of the melting point of the adhesive resin is specifically preferably, for example, 85 ° C., more preferably 90 ° C. When the melting point is equal to or higher than 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 1st film 2 is not specifically limited, It can select suitably. Here, specifically, the lower limit value of the thickness of the first film 2 is, for example, preferably 3% of the thickness of the multilayer film 1, more preferably 5%, and 7%. More preferably. When the thickness is equal to or greater than the lower limit value, sufficient adhesion and stability can be obtained when the multilayer film 1 is bonded to a board such as wood or metal. Thereby, for example, even when the thickness of the first film 2 changes due to resin flow due to pressure variation when the multilayer film 1 is bonded in the step of laminating to the surface of a plate such as wood or metal, the first film 2 The thickness of can be kept preferable. Thereby, even if it is a case where it is a case where it is bent and is reheated, the adhesive force of the 1st film 2 can be maintained.

  On the other hand, the upper limit value of the thickness of the first film 2 is specifically preferably 40% of the thickness of the multilayer film 1, and more preferably 25%. When the thickness is not more than the upper limit value, the multilayer film 1 can be thinned while maintaining a sufficient adhesive force.

(Second film)
The 2nd film 3 is a film containing the heat-welding resin which consists of a polyethylene-type resin whose melting | fusing point is higher than the said adhesive resin.

  The polyethylene resin used for the heat-welding resin is not particularly limited as long as it is a resin that can be joined by heat welding. Specifically, for example, LDPE resin, L-LDPE resin, MDPE resin, HDPE resin, etc. Can be mentioned. Specifically, the heat-welding resin is preferably a resin having a low crystallization rate, such as an LDPE resin, and more preferably an L-LDPE resin. Thereby, since it does not crystallize excessively at the time of bonding or welding, it is possible to maintain the bonding strength and prevent cracking at the bonded portion.

  The upper limit of the melting point of the heat-welding resin is specifically preferably, for example, 170 ° C., more preferably 140 ° C., and further preferably 130 ° C. Because the melting point is below the upper limit, the effect of softening at the time of bonding and the effect of making the pressure uniform can be obtained, the joint can be fused at a low temperature, high corrosion resistance can be obtained, and flexibility that is easy to process It is preferable at the point obtained.

  On the other hand, the lower limit of the melting point of the heat-welding resin is specifically preferably 90 ° C., and more preferably 105 ° C., for example. When the melting point is not less than the lower limit, it is preferable in that the generation of whiskers due to the elongation of the film in the punching process can be suppressed, and in that welding unevenness and hole opening can be suppressed.

  One or both of an antiblocking agent and a slip agent may be added to the second film 3. Thereby, adhesion of films can be prevented at the time of handling of the multilayer film 1 and slipping can be improved, tension applied to the film can be stabilized, and loosening and elongation at the time of bonding can be prevented.

  Specific examples of the anti-blocking agent include inorganic particles such as silica and aluminum silicate, and organic particles such as polyethylene beads, acrylic beads, and polytetrafluoroethylene particles. Specifically, the addition amount of the antiblocking agent is preferably 0.001 to 5 mass%, more preferably 0.05 to 3 mass%, for example, with respect to the heat-welding resin of the layer to be added.

  Examples of the slip agent include saturated fatty acid amides (saturated fatty acid amides) and unsaturated fatty acid amides (unsaturated fatty acid amides). Specific examples include erucic acid amides and oleic acid amides. Specifically, the addition amount of the slip agent is preferably 0.0005 to 3% by mass. For example, 0.001 to 2 mass% is preferable with respect to the heat-welding resin, and 0.001 to 1 mass% is more preferable.

  The multilayer film 1 may be subjected to a decoration process. As the method, a processing method such as laminating the colored second film 3 on the first film 2, printing a pattern on the surface of the second film 3, and laminating the first film 2 is used. . The second film 3 may be embossed on the surface opposite to the adhesive surface with the first film 2 to provide a concavo-convex pattern.

  As a method of laminating the colored second film 3 on the first film 2, a pigment or dye is added directly to the second film using a heat-welding resin made of polyethylene resin, or a pigment or dye is contained. The resin to be added can be added as a master batch, and a uniformly colored resin can be formed by extrusion to form a film.

  It does not specifically limit as a coloring agent, Well-known coloring agents, such as a pigment and dye, can be used. For example, inorganic pigments such as titanium oxide, zinc white, petal, vermilion, ultramarine, cobalt blue, titanium yellow, yellow lead, carbon black; isoindolinone, Hansa Yellow A, quinacridone, permanent red 4R, phthalocyanine blue, indanthrene Organic pigments (including dyes) such as blue RS and aniline black; metal pigments such as aluminum and brass; pearlescent pigments made of foil powder such as titanium dioxide-coated mica and basic lead carbonate. Preferably, those that do not dissolve in water are preferable, and titanium oxide is particularly preferable.

The thickness of the 2nd film 3 is not specifically limited, It can select suitably. Here, the lower limit value of the thickness of the second film 3 is specifically preferably 60% of the thickness of the multilayer film 1, more preferably 75%, and 80%, for example. More preferably. When the thickness is equal to or greater than the lower limit value, the pressure at the time of bonding can be transmitted uniformly, and film trailing and winding around the roll can also be suppressed.
On the other hand, the upper limit value 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 equal to or less than the upper limit value, it is possible to suppress variations in adhesive strength due to the flow of the first film 2 during bonding.

  The tensile strength of the multilayer film 1 of the present embodiment is preferably 20 MPa or more, and more preferably 25 MPa or more. Thereby, it is easy to adjust the tension when bonding.

  In addition, 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 applying a load of 9.8 mN / mm by thermomechanical analysis (TMA), the dimensions The rate of change is preferably 8% or less, and more preferably 5% or less. Thereby, since the dimensional change of the multilayer film 1 at the time of bonding is small, it is excellent in bonding suitability.

  Moreover, the multilayer film 1 of this embodiment does not need to perform an extending | stretching process in the manufacturing method mentioned later. If there is no stretch orientation, shrinkage of the multilayer film 1 can be prevented in the above-described TMA. Thereby, the dimensional change is stable and the bonding is excellent.

  Moreover, 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.

Further, the wetting index of the surface on the second film 3 side in the multilayer film 1 of the present embodiment is specifically, for example, 25 dynes / cm or more and 50 dynes / cm or less, preferably 30 dynes / cm or more and 43 dynes / cm. cm or less. Thereby, adhesion of films is prevented at the time of handling of multilayer film 1, and slipping is improved.
In order to adjust the wetting index, corona treatment, plasma treatment, flame treatment, or ultraviolet irradiation treatment may be performed.

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

  Thereby, the quantity of the antiblocking agent and slip agent added to the 2nd film 3 can be reduced.

Further, since the surface roughness is smaller than the above maximum value, variation in resistance to physical properties due to thickness variation can be suppressed. Further, it is possible to prevent welding failure due to air entrapment at the time of welding at the joint.
Furthermore, when the surface roughness is larger than the above minimum value, sufficient slipperiness is obtained, and the bonding property is excellent.

  The object to be bonded may be a plate on which the multilayer film 1 is laminated. For example, in the case of building use, the multilayer film can be cut into a required shape and thermally welded to a wooden frame or a metal frame forming a window frame.

<Method for producing multilayer film>
Next, the manufacturing method of the multilayer film 1 mentioned above is demonstrated.
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 using a laminating machine or the like. In addition, the multilayer film 1 of the present embodiment is manufactured by a method in which the first film 2 and the second film 3 described above are formed by, for example, an air-cooled or water-cooled coextrusion inflation method or a coextrusion T-die method. May be. Especially, the method of forming into a film by a coextrusion T-die method is excellent and preferable at the point which controls the thickness of each layer. Moreover, you may emboss the surface of the multilayer film 1 by sticking the film and the embossing roll which has an unevenness | corrugation in the case of film forming.

  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, By laminating the multilayer film 1 so that a plate of metal or the like and the first film 2 face each other, the second film 3 which is the surface opposite to the adhesive surface is prevented from being deformed by heat. it can.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention. For example, in the multilayer film 1 described above, the configuration in which the first film 2 and the second film 3 are laminated is described as an example, but the position is adjacent to the second film 3 and on the opposite side of the first film 2. The third film may be further laminated.

  Moreover, in the multilayer film 1 mentioned above, although the example in which any one or both of the antiblocking agent and the slip agent was added to the 2nd film 3 was demonstrated, the antiblocking agent and the Either one or both of the slip agents may be added.

Moreover, in the multilayer film 1 mentioned above, in the case of bonding to the board used as bonding object, the example of bonding by heat was demonstrated, However, You may use an adhesive agent.
The adhesive is not particularly limited, and examples thereof include acrylic, isocyanate, urethane, polyester, and amide. Moreover, as a classification, a dry laminate adhesive, a curable adhesive, or a hot-melt adhesive may be used.

<Production of multilayer film>
Example 1
As a first film, Hi-Iran (registered trademark), a polyethylene 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. Further, as a second film, Umerit (registered trademark) which is an L-LDPE resin (manufactured by Ube Maruzen Polyethylene Co., Ltd., brand: 1520F, melting point: 114 ° C., MFR: 2 g / 10 min, density: 0.915 g / cm ³ ) Prepared.

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

  A multi-layer film was manufactured by forming high-milan and Umerit by coextrusion T-die method. Moreover, the 2nd film and the embossing roll which has an unevenness | corrugation were stuck in the case of film forming, and the embossing was given to the surface by the side of the 2nd film of a multilayer film. The manufactured multilayer film had a thickness of 70 μm, the first film had a thickness of 10 μm, and the second film had a thickness of 60 μm.

(Example 2)
HiMilan (registered trademark) which is a polyethylene ionomer resin as a first film (Mitsui / DuPont Polychemical Co., Ltd., brand: 1652, melting point: 98 ° C., MFR: 5.5 g / 10 min, density: 0.94 g / cm ³ ) Prepared. As the second film, LDPE resin Mirason (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 ) Prepared.

  A multi-layer film was manufactured by forming high-milan and mirason by co-extrusion T-die method. Moreover, the 2nd film and the embossing roll which has an unevenness | corrugation were stuck in the case of film forming, and the embossing was given to the surface by the side of the 2nd film of a multilayer film. The manufactured multilayer film had a thickness of 70 μm, the first film had a thickness of 11 μm, and the second film had a thickness of 59 μm.

Example 3
As a first film, Hi-Iran (registered trademark) which is a polyethylene 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 Company, brand: 5220G, melting point: 121 ° C., MFR: 3.5 g / 10 min, density: 0.915 g / cm ³ ) Prepared. Also, LDPE-based masterbatch, Umerit (registered trademark) (Ube Maruzen Polyethylene Co., Ltd.) containing 10% by mass of natural silica as an antiblocking agent added to the second film and 1.5% by mass of erucamide as a slip agent. Manufactured, brand: 82105M).

A multilayer film was manufactured by forming a film of high Milan and elite containing 3% by mass of Umerit (82105M) by a coextrusion T-die method.
Moreover, the 2nd film and the embossing roll which has an unevenness | corrugation were stuck in the case of film forming, and the embossing was given to the surface by the side of the 2nd film of a multilayer film.

  The manufactured multilayer film had a thickness of 70 μm, the first film had a thickness of 11 μm, and the second film had a thickness of 59 μm.

Example 4
As a first film, Hi-Iran (registered trademark) which is a polyethylene 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. In addition, as the second film, Evolue (registered trademark) which is an L-LDPE resin (manufactured by Prime Polymer, brand: SP3530, melting point: 122 ° C., MFR: 3.2 g / 10 min, density: 0.931 g / cm ³ ) Prepared. Also, an LLDPE-based masterbatch containing 10% by mass of synthetic zeolite having an average particle size of 5 μm as an antiblocking agent added to the second film, Evolue (registered trademark) (manufactured by Prime Polymer Co., Ltd., brand: EAZ-10, MFR) : 3.5 g / 10 min).

  A multilayer film was manufactured by film-forming Himiran and Evolue (SP3530) containing 3% by mass of Evolue (EAZ-10) by the coextrusion T-die method. Moreover, the 2nd film and the embossing roll which has an unevenness | corrugation were stuck in the case of film forming, and the embossing was given to the surface by the side of the 2nd film of a multilayer film.

  The manufactured multilayer film had a thickness of 70 μm, the first film had a thickness of 11 μm, and the second film had a thickness of 59 μm.

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

  Ultex (2520F) containing 3% by mass of Evolue (EAZ-10) as the first film, Ultozex (2022L) as the second film, and 2% by mass of Evolue (EAZ-10) as the third film. Ultra-Zex (2022L) was formed into a film by a coextrusion T-die method and subjected to a stretching treatment to produce a multilayer film. After film formation, the first film was subjected to corona treatment.

  The manufactured multilayer film had a thickness of 70 μm, the first film had a thickness of 10 μm, the second film had a thickness of 50 μm, and the third film had a thickness of 10 μm. The wetting index of the first film surface subjected to the corona treatment was 42 dynes.

(Comparative Example 1)
As the first film and the second film, Noblene (registered trademark) which is a polypropylene resin (PP resin) (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 manufactured by forming and stretching the first film and the second film using no-brene (FS2011DG3) by the coextrusion T-die method. Here, when the film was formed, the first film was subjected to corona treatment. The thickness of the produced multilayer film was 70 μm.

<Bonding test>
The multilayer films of Examples 1 to 5 and Comparative Example 1 were heat laminated to a steel plate so that the steel plate and the first film face each other. The bonding temperature was 190 ° C.
Table 1 shows the result of pasting. “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 heat-welding resin contained in the second film. In “Results”, “◎” indicates a multilayer film in which the second film hardly deformed after bonding, and “◯” indicates that the second film slightly deformed after bonding. The multilayer film in which the second film was greatly deformed or the adhesive strength was low was designated as “x”.

As in Examples 1 to 5, in the multilayer film in which the melting point of the adhesive resin was 2 to 50 ° C. lower than the melting point of the heat-welding resin, the second film was hardly deformed after bonding. On the other hand, as in Comparative Example 1, in the multilayer film in which the melting point of the adhesive resin is substantially the same as the melting point of the heat-welding resin, the second film was greatly deformed after bonding.
From the above results, it is confirmed that the second film can be prevented from being deformed by heat when bonding by making the melting point of the adhesive resin 2-50 ° C. lower than the melting point of the heat-welding resin. did.

<Tensile 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 performed by raising the temperature to 25 to 130 ° C. at a rate of temperature rise of 2 ° C./min while applying a load of 9.8 mN / mm.
In FIG. 3, the dimensional change rate in each temperature of each multilayer film is shown. 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. In addition, 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 dynamic friction coefficient was measured based on JIS K7125 (weight: 201 g, speed: 100 mm / mim). The dynamic friction coefficient was measured by measuring the dynamic friction coefficient on the front and back surfaces of the multilayer film.
Table 3 shows the dynamic friction coefficient on the front and back surfaces of each multilayer film. In the multilayer films of Examples 1 to 5, the dynamic friction coefficient was 0.3 or more and less than 2.5.

<Measurement of surface roughness>
For the multilayer films of Examples 1 to 5 and Comparative Example 1, the surface roughness of the surface on the second film side was measured. The surface roughness was measured using Handy Surf 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) for the surface roughness of the surface on the second film side in each multilayer film.

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

DESCRIPTION OF SYMBOLS 1 ... Multilayer film 2 ... 1st film 3 ... 2nd film

Claims (11)

  A multilayer film in which a first film containing an adhesive resin made of polyethylene resin and a second film containing a heat-welding resin made of polyethylene resin are laminated.   The multilayer film according to claim 1, wherein the melting point of the adhesive resin is 2 to 50 ° C. lower than the melting point of the heat welding resin.   The multilayer film of Claim 1 or 2 whose melting | fusing point of the said adhesive resin is 85 degreeC or more and 120 degrees C or less.   The multilayer film according to claim 1, wherein the adhesive resin contains a metal cross-linked resin.   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.   The rate of dimensional change is 8% or less when the temperature is increased from 25 to 100 ° C at a rate of temperature increase of 2 ° C / min while applying a load of 9.8 mN / mm by thermomechanical analysis (TMA). The multilayer film as described in any one of 1 to 5.   The multilayer film does not undergo shrinkage change when the temperature is increased from 25 to 130 ° C at a rate of temperature increase of 2 ° C / min while applying a load of 9.8 mN / mm by thermomechanical analysis (TMA). The multilayer film as described in any one of 6.   The multilayer film as described in any one of Claims 1 thru | or 7 whose dynamic friction coefficients of the front and back of the said multilayer film are 0.3-2.5.   The multilayer film according to any one of claims 1 to 8, wherein the ten-point average roughness of the surface of the multilayer film on the second film side is not less than 0.3 µm and not more than 2 µm.   The multilayer film according to any one of claims 1 to 9, wherein at least one of the first film and the second film contains one or both of an antiblocking agent and a slip agent.   The multilayer film according to any one of claims 1 to 10, wherein the multilayer film has a thickness of 20 µm or more and 400 µm or less.

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