JP6450522B2 - Matte in-mold label film - Google Patents

Description

  The present invention relates to a matte tone in-mold label film, and more particularly to a matte tone in-mold label film that can increase the production efficiency of a molded product.

  After a molded product such as a container is molded from a resin such as polyethylene or polypropylene, a label made of paper or resin is usually attached to the body of the molded product with an adhesive for product name and component display. Although strong adhesion is possible, there is a risk of peeling. Further, when the shape of a molded product such as a container is complicated, the surface shape cannot be followed and the label may be lifted. In particular, the appearance of the product when displayed as a product greatly affects the sales of the product. Therefore, a processing method integrated with container molding using an in-mold label is spreading as a label that is more beautiful and has no fear of peeling or floating.

  In this case, the in-mold label is placed at a predetermined position of the mold, and a molding resin is introduced into the mold by injection molding or blow molding. Then, the label is integrated with the molding resin in the mold to complete a container which is a molded product. After completion as a molded product, there is almost no distinction between the label and the molded product. Then, the label is fixed in conformity with the surface of the molded product. For this reason, it is possible to cope with a relatively free shape design, and the design of a molded product such as a container is greatly improved. Further, since the in-mold label itself is a resin and integrated with the molded product, it has water resistance and is resistant to friction.

  In manufacturing using an in-mold label, the labels are placed one by one at a predetermined position in the mold using an appropriate automatic feeder. For this reason, if the apparatus grips two labels at a time, or if the labels are in close contact with each other and fail to grip, a molding failure occurs and production efficiency is impaired.

  Problems that occur when gripping in-mold labels are mainly due to the difficulty in separating the labels. In such a case, extremely shallow unevenness can be easily imparted to the entire film surface by making the one side surface of the label matt (matte). Further, the matte unevenness becomes a passage for air between the label and the molding resin at the time of forming the container, so that molding defects such as air remaining between the label and the molding resin can be suppressed. In addition, there is also a method in which appropriate fine particles are mixed in that it is simply provided with unevenness. However, the manufacturing tends to be expensive compared to the resin alone.

  As a film having a matte surface, for example, a resin laminated film in which a matte surface is formed from a propylene-based block copolymer having characteristics such as an ethylene content of 8 to 16% by mass has been proposed (Patent Document 1, etc.) reference).

  However, the film of Patent Document 1 has a layer structure and a resin composition that place importance on the heat sealability between the sealing surfaces of the film, and is exclusively used for packaging materials for bag making. Therefore, it is not always suitable for in-mold label applications. Then, while improving the film which exhibits a matte tone, the film suitable for the use of an in-mold label came to be desired.

Japanese Patent Laid-Open No. 2007-45050

  This invention is proposed in view of the said situation, and provides the resin film suitable for the in-mold label which formed the moderate matte uneven surface on the film surface by mixing | blending resin.

That is, the invention of claim 1 is an in-mold label film that is applied to a molded resin that is placed in a mold and melted, and is integrated with the molded resin. It has a matte surface layer part on at least one surface side of the layer part, and the matte surface layer part has a low content of 45 to 80% by weight of polypropylene resin and 15 to 35% by weight of high density polyethylene resin. The composition contains 5 to 20% by weight of a density polyethylene resin, and includes a composition in which the total of the polypropylene resin, the high density polyethylene resin, and the low density polyethylene resin satisfies 100% by weight , and the in-mold. The label film exhibits a haze value of 40% or more in the measurement based on JIS K 7136 (2000), and the following adhesion And the adhesive strength measurements in degrees measured I is 2.5N or higher, and the adhesive strength measurements in adhesive strength measurement II is according to the matte tone-mold label film which is characterized in that at least 4.0 N.
<Adhesive strength measurement I>
The matt in-mold label film of the prototype is cut into a test piece having a width of 25 mm or more and a length of 100 mm or more, and then the biaxially stretched homopolymer with a thickness of 40 μm is formed on the surface of the test piece on the matte surface layer side. A polypropylene film is stacked, and a cellophane (# 300) manufactured by Phutamura Chemical Co., Ltd. is placed on the polypropylene film, and a heating sealer (a thermal tilt tester manufactured by Toyo Seiki Seisakusho Co., Ltd., product name "HG-100-2") The three-layer film was heat-sealed under the conditions of a set temperature of 200 ° C., a seal pressure of 0.35 MPa, and a seal time of 1 second. After heat sealing, it is taken out from the apparatus and cut into a rectangle with a width of 15 mm and a length of 100 mm or more. The heat sealing part of this heat sealing piece is opened at both ends 180 ° and opposite to each other. Fixed to a chuck of a universal testing machine (Autograph (AG-1)) manufactured by Seisakusho, pulled up and down at a speed of 200 mm / min, and read the load (N) at the time when the heat seal part broke, and the prototype example It was set as the measured adhesive strength of a matte tone in-mold label film.
<Adhesive strength measurement II>
Adhesive strength measurement II assumed polyethylene as the resin to be molded, and evaluated the adhesion of the matte tone in-mold label film of each prototype. The heating sealer used the same apparatus as the adhesive strength measurement I. The matt in-mold label film of the prototype is cut into a test piece having a width of 25 mm or more and a length of 100 mm or more, and then a non-stretched LDPE film having a thickness of 40 μm is formed on the surface of the test piece on the matte surface side. Furthermore, cellophane (# 300) manufactured by Futamura Chemical Co., Ltd. is placed thereon, the set temperature of the heating sealer (the same device as the adhesive strength measurement I) is 160 ° C., the sealing pressure is 0.35 MPa, the sealing Three layers of films were heat sealed under the condition of time 1 second. After heat sealing, it is taken out from the apparatus and cut into a rectangle with a width of 15 mm and a length of 100 mm or more. The heat sealing part of this heat sealing piece is opened at 180 ° at both ends and opposite to each other. It fixed to the chuck | zipper of Shimadzu Corp. make and a universal testing machine (autograph (AG-1)), and it pulled up and down at the speed of 200 mm / min. And the load (N) at the time of a heat-seal | rupture part fracture | rupture was read, and it was set as the adhesive strength measurement value of the matte tone in-mold label film of the said prototype.

  The invention according to claim 2 relates to the matte tone-in-mold label film according to claim 1, wherein the base material layer portion is a resin mainly composed of a polypropylene resin.

  The invention according to claim 3 is the matte tone in-mold label according to claim 1, wherein the base material layer portion is a resin having the same composition as the matte tone surface layer portion, and the resin composition of the in-mold label film is uniform. Related to film.

  The invention according to claim 4 relates to the matte tone in-mold label film according to any one of claims 1 to 3, wherein a melt flow rate of the high-density polyethylene resin is 0.04 to 0.5 g / 10 min.

  The invention of claim 5 relates to the matte tone in-mold label film according to any one of claims 1 to 4, wherein the in-mold label film is formed by biaxial stretching.

According to the matte tone in-mold label film according to the invention of claim 1, the in-mold label film is attached to the molded resin placed and melted in a mold and integrated with the molded resin, The in-mold label film has a matte surface layer part on at least one surface side of the base material layer part, and the matte surface layer part contains 45 to 80% by weight of polypropylene resin and 15 high-density polyethylene resin. -35 wt% and low density polyethylene resin 5-20 wt%, and the composition of the polypropylene resin, the high density polyethylene resin, and the low density polyethylene resin satisfy 100 wt% together we are in the in-mold label film, 40% or more in the measurement conforming to JIS K 7136 (2000) Indicates the haze value, further, at which mentioned above, and the adhesive strength measurements 2.5N or higher in bond strength measurements I, and the adhesive strength measurements in adhesive strength measurement II is obtained by the above 4.0N Thus, a resin film suitable for an in-mold label in which an appropriate matte concavo-convex surface is formed on the film surface by blending the resins can be obtained.

  According to the matte in-mold label film according to the invention of claim 2, in the invention of claim 1, since the base material layer portion is a resin mainly composed of a polypropylene resin, the polypropylene resin is excellent in strength. In addition, the film is processed into an in-mold label, and the film has a slight strength and is easy to handle.

  According to the matte tone in-mold label film of the invention of claim 3, in the invention of claim 1, the base material layer portion is a resin having the same composition as the matte tone surface layer portion, and the resin of the inmold label film Since the composition is uniform, there is no need to distinguish between the front and the back, and even a single-layer extrusion apparatus can be used.

  According to the matte tone in-mold label film according to the invention of claim 4, in the invention of claims 1 to 3, the melt flow rate of the high-density polyethylene resin is 0.04 to 0.5 g / 10 min. It can have a matte tone.

  According to the matte tone in-mold label film of the invention of claim 5, in the invention of claims 1 to 4, since the in-mold label film is formed by biaxial stretching, the orientation of the resin in both the vertical and horizontal directions Therefore, the film thickness can be reduced and the strength can be improved. Moreover, it is excellent in mass productivity.

It is the schematic about the usage example of an in-mold label. It is a cross-sectional schematic diagram of the matte tone in-mold label film of this invention. It is a triangular figure which shows the compounding ratio of the resin of a matt surface layer part.

  The matte tone in-mold label film of the present invention is a resin film for a label that is carried into a molding die via a supply device in molding that is mainly integrated with a label such as insert molding or in-mold molding. Since the resin film has a matte surface, the surface is slightly uneven. Therefore, a gap into which air enters is generated, and excessive adhesion between the resin films is avoided. As a result, it becomes easy to peel off one by one.

  FIG. 1 is a schematic view when molding a resin cup manufactured using an in-mold label. An example of insert molding will be described with reference to FIG. First, an in-mold label 1 that is appropriately printed on the surface of the base material layer portion of the matte-type in-mold label film of the present invention is prepared. The in-mold labels 1 are placed one by one at a predetermined position in the fixed mold 2 which is a mold through a supply device 6. Thereafter, the movable mold 3 moves forward with respect to the fixed mold 2, and the cavity 4 is formed by joining both molds. Then, the resin injection device 5 is connected to the fixed mold 2, and molten resin to be molded is injected into the cavity 4.

  The in-mold label 1 in the cavity 4 is also melted by the heat of the resin to be molded, and both the resins are integrated. After the resin to be molded is cooled and solidified, the resin cup as the molded product 7 is taken out from the mold. In this way, the in-mold label is attached to and integrated with the surface of the cup, which is a molded product. In this case, when air remains between the in-mold label 1 and the resin to be molded and is solidified, a portion where the label is lifted is generated, and the cup becomes a defective product. However, since the surface of the in-mold label 1 that is integrated with the resin to be molded is matte, the slight irregularities serve as air passages during molding, making it difficult for air to remain.

  The present invention can be applied to blow molding, vacuum molding, or the like instead of the illustrated injection molding. Moreover, in the case of manufacturing a molded product such as a dish shape, in-mold molding in which the in-mold label 1 is continuously supplied can be used. In addition, illustration about any manufacture is abbreviate | omitted. The molding method and the like are appropriately combined in consideration of the shape, size, material, and the like of the article to be manufactured, as well as the size and shape of the label itself.

  Hereafter, the structure and resin composition of a matte tone in-mold label film are demonstrated. As shown in FIG. 2A, the in-mold label film 10 has a matte surface layer portion 11 formed on at least one surface side of the base material layer portion 12. The surface of the matte surface layer portion 11 of the in-mold label film 10 is matte (matte). And the matte surface layer part 11 is a surface which adheres to a to-be-molded resin. The surface on the base material layer portion 12 side is smooth and suitable for printing and bonding with other films. In addition, in order to set it as the structure which does not ask | require front and back, you may distribute a matt surface layer part on both surfaces of a base material layer part (not shown).

  The in-mold label film 10 is formed by melting the following resin and discharging it from a T-die coextrusion apparatus or the like. Generally, a method for producing a polyolefin film is used. The film formation may be unstretched or stretched. Of these, the film is formed by biaxial stretching as specified in the invention of claim 5. In the case of biaxial stretching, it is sequential or simultaneous stretching. In the case of film formation by biaxial stretching, resin orientation occurs in both the vertical (MD) and horizontal (TD) directions, so that the film thickness can be reduced and the strength can be improved. Moreover, mass productivity is also excellent.

  The matte surface layer portion 11 provided in the in-mold label film 10 is made by melt-kneading three different types of resins: polypropylene resin (J1), high density polyethylene resin (J2), and low density polyethylene resin (J3). Composition. Although each resin is an olefin resin, properties such as compatibility are different due to the difference in molecular structure between polypropylene and polyethylene. For this reason, the resin obtained by melt mixing is inhomogeneous, resulting in a loss of gloss.

  The polypropylene resin (J1) is selected from one or a plurality of types such as a random copolymer obtained by polymerization of polypropylene and α-olefin, a block copolymer, etc., in addition to homopolypropylene of polypropylene alone. Examples of olefins other than propylene include ethylene, and α such as 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, and 3-methyl-1-pentene having 4 to 18 carbon atoms. -Olefin. The polypropylene resin (J1) is a main resin constituting the matte surface layer portion 11.

The high density polyethylene resin (J2) is generally selected from polyethylene polymers having a density of 0.942 g / cm ³ or more. When the blending of the high-density polyethylene resin (J2) is lacking, it is not a homogeneous and fine matte surface. In addition, as defined in the invention of claim 4, for the high density polyethylene resin (J2), the melt flow rate measured in accordance with JIS K 7210 (1999) is in the range of 0.04 to 0.5 g / 10 min. A filling resin is used. When a melt flow rate (MFR) high-density polyethylene resin (J2) within the above range is used, a matte tone can be exhibited.

The low density polyethylene resin (J3) is generally selected from polyethylene polymers having a density of 0.910 to 0.930 g / cm ³ . Even when the blending of the low density polyethylene resin (J3) is lacking, it does not become a homogeneous and fine matt surface. Moreover, when the in-mold label of the mixing | blending which lacked the low density polyethylene resin (J3) is used, the adherence force with a to-be-molded resin becomes weak.

  Even if only one of the high density polyethylene resin (J2) and the low density polyethylene resin (J3) is blended, the matte tone is not good. This is because, as described above, it is necessary to satisfy both the expression of matte tone and the enhancement of the adhesion strength with the molding resin. Therefore, it is essential to blend both the high density polyethylene resin (J2) and the low density polyethylene resin (J3).

  The blending ratio established between the three types of resins (J1, J2, J3) constituting the matte surface layer portion 11 is 45 to 80% by weight of the polypropylene resin (J1) and the high density polyethylene resin (J2). The composition is 15 to 35% by weight and the low density polyethylene resin (J3) is 5 to 20% by weight. And the sum total of weight% of each resin (J1, J2, J3) satisfy | fills 100 weight% (J1 + J2 + J3 = 100 weight%). Reference is made to the triangular diagram of FIG.

  When the blend of the polypropylene resin (J1) in the composition of the matte surface layer portion 11 is less than 45% by weight, the haze value that is an index of the matte tone is lowered, and the matte feeling in the film is hardly expressed. When the blending of the polypropylene resin (J1) exceeds 80% by weight, there is an influence of a decrease in adherence with the resin to be molded. Therefore, the proportion of the polypropylene resin (J1) is in the range of 45 to 80% by weight.

  When the blending of the high-density polyethylene resin (J2) in the composition of the matte surface layer portion 11 is less than 15% by weight, there is relatively little high-density polyethylene resin, and a good matte tone is not exhibited. When the blending of the high-density polyethylene resin (J2) exceeds 35% by weight, the amount of the high-density polyethylene resin is relatively increased and a good matte tone is not exhibited. Therefore, the blending of the high density polyethylene resin (J2) is in the range of 15 to 35% by weight.

  When the blend of the low density polyethylene resin (J3) in the composition of the matte surface layer portion 11 is less than 5% by weight, the effect on the matte tone is small. However, there is an effect of a decrease in adherence with the molding resin. When the blending of the low density polyethylene resin (J3) exceeds 20% by weight, the matte tone is somewhat inferior although there is an influence of other blending. Therefore, the blending of the low density polyethylene resin (J3) is in the range of 5 to 20% by weight.

  About resin which comprises the base material layer part 12 of the in-mold label film 10, there is no special restriction | limiting as long as compatibility with the composition resin of the matte surface layer part 11 is ensured. For example, polyolefin resins such as polyethylene resins and polypropylene resins can be widely used.

  In the case of a two-layer in-mold label film 10, the base layer 12 other than the matte surface layer 11 affects the strength of the in-mold label film, the printability, the suitability for bonding with other films, and the like. Effect. Therefore, the efficiency at the time of label production and container formation is influenced.

  In this case, as defined in the invention of claim 2, it is particularly desirable to use a resin mainly composed of a polypropylene resin for the base layer 12. This is because the polypropylene-based resin is excellent in strength and has a strong strength in the film when processed into an in-mold label, and is easy to handle.

  The polypropylene resin is selected from one or a plurality of types such as a random copolymer obtained by polymerization of polypropylene and an α-olefin, a block copolymer, and the like, in addition to a polypropylene homopolymer alone. Examples of olefins other than propylene include ethylene, and α such as 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, and 3-methyl-1-pentene having 4 to 18 carbon atoms. -Olefin. It is possible to select from these various types. In the examples described later, homopolypropylene was used.

  In the in-mold label film 10, the ratio of the layer thickness of the matte surface layer portion 11 and the base material layer portion 12 is approximately 1: 1 to 1:20, and the strength of the whole film is increased by increasing the base material layer side. Is increasing. The total film thickness is 10 to 100 μm. When the thickness on the matte surface layer portion side is too thin, there are few uneven layers, and an appropriate matte tone is hardly exhibited.

  Although the example of the in-mold label film 20 in FIG. 2B has two parts of a matte surface layer part and a base material layer part, the base material layer part as defined in the invention of claim 3. 12 is formed as a resin having the same composition as the matte surface layer portion 11. Although the in-mold label film 20 is formally formed in two layers by ejection, the in-mold label film 20 is a single-layered substance that is substantially composed of only the matte surface layer portion 11 as a whole. When the entire in-mold label film is a matte surface layer part, it is not necessary to distinguish between the front and back sides. In addition, a single layer extrusion molding apparatus can be used.

In the in-mold label film described so far, the unevenness on the matte surface layer portion side can be easily grasped by the degree of matte tone (matte tone) using the haze value as an index. At the same time, the uniformity of the surface irregularities can also be judged indirectly through the matte surface. Therefore, the matte surface layer portion side of the in-mold label film is desired to exhibit a haze value of 40% or more in haze measurement in accordance with JIS K 7136 (2000). When the haze value is 40% or more, it can be determined that moderate irregularities on the surface exist due to the matte tone, which is preferable as an in-mold label film. On the other hand, when the haze value is less than 40%, it can be determined that the degree of matte tone is small and the desired surface irregularities are not obtained.

  In addition to the above resin, an appropriate additive is added to the matte surface layer portion or the base layer portion of the in-mold label film as necessary. For example, various antistatic agents such as aliphatic amine compounds such as lauryl diethanolamine, myristyl diethanolamine, oleyl diethanolamine, aliphatic amide compounds such as lauryl diethanolamide, myristyl diethanolamide, oleyl diethanolamide, polyhydric alcohol, etc. are added appropriately. Has been. Further, various additives such as an anti-blocking agent, a heat stabilizer, an antioxidant, a light stabilizer, a crystal nucleating agent, and an ultraviolet absorber are also contained.

  And it is preferable that the surface of the in-mold label film, mainly the base material layer side, is subjected to an appropriate surface treatment such as a corona treatment to improve the adhesion to printing ink and other films.

[Creation of matte tone in-mold label film]
The matte in-mold label films of Prototype Examples 1 to 17 are based on the blending ratios (% by weight) shown in Tables 1 to 3 below. Resin pellets or the like as raw materials were supplied to a single screw extruder, and the raw materials were melted and kneaded to form a film using a three-layer coextrusion T-die film forming machine and a subsequent biaxial stretching machine. The film was formed by successive biaxial stretching of the draw ratio (longitudinal (MD) 5.0 times and transverse (TD) 8.0 times).

  In the films other than the prototypes 5 and 17, “matte surface layer part / base material layer part / base material layer part” was used, and the film was substantially formed as a two-layer film. In the film of Prototype Example 5, “matte surface layer / matte surface layer / matte surface layer” and in Sample 17 film “base layer / base layer / base layer”. Created as a substantially single layer film.

[Measurement of thickness]
The matte tone in-mold label film of each prototype was measured using a thickness measuring instrument (B-1 manufactured by Toyo Seiki Seisakusho Co., Ltd.) to determine the total thickness (μm). The final film thickness was 30 μm. In addition, the layer thickness ratio of the three-layer coextrusion T-die film molding machine was defined as the layer thickness ratio. In films other than the prototypes 5 and 17, the thickness ratio of the matte surface layer portion to the base material layer portion was 1: 9.

[Raw materials]
The raw material resins used are as follows.
<Composition resin of base material layer part>
Resin 1: Homopolypropylene (Nippon Polypro Co., Ltd., trade name “FL203D”)
<Composition resin of matte surface layer>
Resin 2: Random polypropylene (Nippon Polypro Co., Ltd., trade name “NOVATEC WFX6”)
Resin 3: High density polyethylene (manufactured by Keiyo Polyethylene Co., Ltd., trade name “FX501”, MFR 0.04 g / 10 min)
Resin 4: High-density polyethylene (manufactured by Keiyo Polyethylene Co., Ltd., trade name “E8060”, MFR 0.5 g / 10 min)
Resin 5: Low density polyethylene (Nippon Polyethylene Co., Ltd., trade name “LF440HB”)
Resin 6: Block polypropylene (Nippon Polypro Co., Ltd., trade name “BC6C”)
In the present invention, the polypropylene resin (J1) corresponds to “resin 2 and 6”, the high-density polyethylene resin (J2) corresponds to “resin 3 and 4”, and the low-density polyethylene resin (J3) corresponds to “resin 5”. And corresponding.

[Fusion evaluation]
The matt in-mold label film of the prototype was assumed to be used for insert molding or in-mold molding, and a simple evaluation was made as to whether or not the resin can be fused well.

<Adhesive strength measurement I>
Adhesive strength measurement I assumed polypropylene as the resin to be molded, and evaluated the adhesion of the matte in-mold label film of each prototype. As the heating sealer, a thermal tilt tester manufactured by Toyo Seiki Seisakusho, product name “HG-100-2”) was used.

  First, the matte tone in-mold label film of each prototype was cut into test pieces having a width of 25 mm or more and a length of 100 mm or more. Next, a biaxially stretched homopolypropylene film having a thickness of 40 μm was layered on the surface of the matte surface layer portion of the test piece, and cellophane (# 300) manufactured by Futamura Chemical Co., Ltd. was further placed thereon. The cellophane is intended to prevent heat sealing between the heating platen of the heat sealer and the film.

  The set temperature of the heat sealer was 200 ° C., and the three-layer film was heat sealed under the conditions of a sealing pressure of 0.35 MPa and a sealing time of 1 second. After heat sealing, it was taken out from the apparatus and cut into a rectangle having a width of 15 mm and a length of 100 mm or more. The heat-sealed part of this heat-sealed piece is centered at 180 ° on both ends and opposite to each other. Both ends are fixed to a chuck of Shimadzu Corporation, universal testing machine (Autograph (AG-1)), 200 mm Pulled up and down at a speed of / min. And the load (N) at the time of a heat-seal | rupture part fracture | rupture was read, and it was set as the adhesive strength measurement value of the matte tone in-mold label film of the said prototype.

<Adhesive strength measurement II>
Adhesive strength measurement II assumed polyethylene as the resin to be molded, and evaluated the adhesion of the matte tone in-mold label film of each prototype. The heating sealer used the same apparatus as the adhesive strength measurement I. First, the matte tone in-mold label film of each prototype was cut into test pieces having a width of 25 mm or more and a length of 100 mm or more. Next, an unstretched LDPE film having a thickness of 40 μm was stacked on the surface of the test piece on the matte surface layer portion side, and cellophane (# 300) manufactured by Futamura Chemical Co., Ltd. was placed thereon.

  The set temperature of the heat sealer was set to 160 ° C., and the three-layer film was heat sealed under the conditions of a sealing pressure of 0.35 MPa and a sealing time of 1 second. After heat sealing, it was taken out from the apparatus and cut into a rectangle having a width of 15 mm and a length of 100 mm or more. Centered on the heat-sealed part of this heat-sealed piece, both ends are opened 180 ° opposite to each other, and both ends are fixed to the chuck of the above-mentioned Shimadzu Corporation universal testing machine (Autograph (AG-1)) And pulled up and down at a speed of 200 mm / min. And the load (N) at the time of a heat-seal | rupture part fracture | rupture was read, and it was set as the adhesive strength measurement value of the matte tone in-mold label film of the said prototype.

[Haze value]
In accordance with JIS K 7136 (2000), Nippon Denshoku Industries Co., Ltd., NDH-5000 was used, and the haze value of the matte tone in-mold label film of each prototype was measured.

[Evaluation of feel]
The matt in-mold label film of each prototype was visually observed, and the appearance of the matte (matte) surface was evaluated in three stages.
An example of a uniform surface with a matte finish and a fine surface was evaluated as “◯”.
Part of the matte tone is uneven. Alternatively, an example having a rough surface was evaluated as “Δ”.
An example where the matt finish was uneven overall and the surface was rough was evaluated as “x”.

〔Comprehensive evaluation〕
Regarding the matte-in-mold label film of each prototype, the following three stages are comprehensively judged based on the actual demand viewpoint based on the results of adhesive strength measurement I and II, haze value, and feel. Evaluation was made.
Evaluation A: “Especially excellent in all indicators”
Evaluation B: “Relatively excellent in all indicators”
-Evaluation C: “It is not suitable as a product from an unfavorable index”

〔Results and discussion〕
Tables 1 to 3 show the blending ratio (% by weight) of the resin of the base layer part, the resin of the matte surface layer part, the measured values (N) of the adhesive strength measurements I and II, the haze value (%), It is a result of evaluation of touch and comprehensive evaluation.

<Selection of resin>
Comprehensive evaluations suitable as products are “A” and “B”, and “C” is insufficient or ineligible. The matt in-mold label films of Prototype Examples 1 to 5 are all good, and Prototype Examples 1, 2, 3, and 5 are particularly excellent.

  In the composition of the matte surface layer part, it is good in the composition lacking any of the polypropylene resin (J1), the high density polyethylene resin (J2), and the low density polyethylene resin (J3) from the results of the prototype examples 9, 10, and 17. Since the results cannot be obtained, all of the three types of resins J1, J2, and J3 are essential. Further, among the good prototype examples 1 to 5, the melt flow rate (MFR) of the high-density polyethylene resin (J2) used is high and low. Among them, the haze value of Prototype Example 1 using the high-density polyethylene resin on the lower value side of MFR was higher than that of Prototype Example 4. Therefore, it is more preferable to select a resin having an MFR of 0.04 to 0.5 g / 10 min as the high density polyethylene resin.

<About resin and blending ratio>
About the polypropylene-based resin (J1), high-density polyethylene resin (J2), and low-density polyethylene resin (J3) constituting the matte surface layer part of the matte tone in-mold label film, the blending ratio established between the resins The performance varies greatly depending on (% by weight). Therefore, a triangular diagram (diagram) in FIG. 3 was created in order to clarify the range of blending ratios that are possible in performance among the three types of resins. Polypropylene resin (J1) {resin 2} on the left side, high density polyethylene resin (J2) {resin 3} on the bottom side, and low density polyethylene resin (J3) {resin 5} on the right side, The blending ratio was plotted. In the figure, the prototype example is indicated as [n]. For example, Prototype Example 1 is [1]. The numerical value of the scale is% by weight, each side is 0% by weight, and the top side is 100% by weight. In addition, the example from which the kind of resin differs and the example from which a structure differs are excluded and illustrated.

  In the triangular diagram of FIG. 3, the region is defined by the quality of the comprehensive evaluation of the prototype examples 1, 2, and 3 and others. The region of the blending ratio between the resins established in the good prototype example is the inner side of the thick parallelogram.

  With respect to the blending ratio of the polypropylene resin (J1), according to prototype examples 6, 7, and 8 having a small blending ratio of the resin, the adhesive strength and haze value were low, and a good matte tone could not be obtained. Moreover, in Prototype Example 11 with a large blending ratio, the ratio of other resins was too small, resulting in insufficient adhesive strength. Therefore, a suitable blending ratio of the polypropylene resin (J1) is 45 to 80% by weight, more preferably 60 to 80% by weight.

  With respect to the blending ratio of the high-density polyethylene resin (J2), according to Prototype Examples 12 and 13 with a small blending ratio of the resin, the haze value was low, and it was insufficient to achieve a good matte tone. Moreover, the haze value also became low also in prototype examples 15 and 16 with many compounding ratios. Therefore, a suitable blending ratio of the high density polyethylene resin (J2) is 15 to 35% by weight.

  With regard to the blending ratio of the low density polyethylene resin (J3), according to prototype examples 10 and 11 having a small blending ratio of the resin, the adhesive strength is low and the haze value is slightly low. Therefore, it was not enough to achieve a good matte tone. Moreover, the haze value was low also in the prototype example 14 with many compounding ratios. Therefore, a suitable blending ratio of the low density polyethylene resin (J3) is 5 to 20% by weight.

<Haze value>
As a result of visual observation of the matte in-mold label film of each prototype, the haze value was 40% or more in all cases where the examples of the surface appearance of a good matte tone (matte tone) were collected. Since the matte tone and the haze value are in a complementary relationship, a preferable haze value can be derived as 40% or more.

  The matte tone in-mold label film of the present invention is a film specialized for molding integrated with a label such as insert molding or in-mold molding. And by providing a moderate matte uneven surface, it is possible to suppress molding defects due to adhesion between films and air remaining at the time of container formation, which contributes to an improvement in the yield of container formation.

DESCRIPTION OF SYMBOLS 1 In-mold label 7 Molded product 10,20 Matte tone in-mold label film 11 Matte surface layer part 12 Base material layer part

Claims (5)

An in-mold label film that is placed in a molding die and attached to a molten molding resin and integrated with the molding resin,
The in-mold label film has a matte surface layer portion on at least one side of the base layer portion,
The matte surface layer portion contains 45 to 80% by weight of a polypropylene resin,
15-35% by weight of high density polyethylene resin,
While containing 5 to 20 wt% of low density polyethylene resin,
The total of the polypropylene resin, the high-density polyethylene resin, and the low-density polyethylene resin includes a composition that satisfies 100% by weight ,
The in-mold label film exhibits a haze value of 40% or more in measurement according to JIS K 7136 (2000);
Further, a matte tone in-mold label film characterized in that an adhesive strength measurement value in the following adhesive strength measurement I is 2.5 N or more and an adhesive strength measurement value in adhesive strength measurement II is 4.0 N or more .
<Adhesive strength measurement I>
The matt in-mold label film of the prototype is cut into a test piece having a width of 25 mm or more and a length of 100 mm or more, and then the biaxially stretched homopolymer with a thickness of 40 μm is formed on the surface of the test piece on the matte surface layer side. A polypropylene film is stacked, and a cellophane (# 300) manufactured by Phutamura Chemical Co., Ltd. is placed on the polypropylene film, and a heating sealer (a thermal tilt tester manufactured by Toyo Seiki Seisakusho Co., Ltd., product name "HG-100-2") The three-layer film was heat-sealed under the conditions of a set temperature of 200 ° C., a seal pressure of 0.35 MPa, and a seal time of 1 second. After heat sealing, it is taken out from the apparatus and cut into a rectangle with a width of 15 mm and a length of 100 mm or more. Fixed to a chuck of a universal testing machine (Autograph (AG-1)) manufactured by Seisakusho, pulled up and down at a speed of 200 mm / min, and read the load (N) at the time when the heat seal part broke, and the prototype example It was set as the measured adhesive strength of a matte tone in-mold label film.
<Adhesive strength measurement II>
Adhesive strength measurement II assumed polyethylene as the resin to be molded, and evaluated the adhesion of the matte tone in-mold label film of each prototype. The heating sealer used the same apparatus as the adhesive strength measurement I. The matt in-mold label film of the prototype is cut into a test piece having a width of 25 mm or more and a length of 100 mm or more, and then a non-stretched LDPE film having a thickness of 40 μm is formed on the surface of the test piece on the matte surface side. Furthermore, cellophane (# 300) manufactured by Futamura Chemical Co., Ltd. is placed thereon, the set temperature of the heating sealer (the same device as the adhesive strength measurement I) is 160 ° C., the sealing pressure is 0.35 MPa, the sealing Three layers of films were heat sealed under the condition of time 1 second. After heat sealing, it is taken out from the apparatus and cut into a rectangle with a width of 15 mm and a length of 100 mm or more. It fixed to the chuck | zipper of Shimadzu Corp. make and a universal testing machine (autograph (AG-1)), and it pulled up and down at the speed of 200 mm / min. And the load (N) at the time of a heat-seal | rupture part fracture | rupture was read, and it was set as the adhesive strength measurement value of the matte tone in-mold label film of the said prototype.   The matte tone in-mold label film according to claim 1, wherein the base material layer portion is a resin mainly composed of a polypropylene resin.   The matte tone in-mold label film according to claim 1, wherein the base material layer portion is a resin having the same composition as the matte tone surface layer portion, and the resin composition of the in-mold label film is uniform.   The matte in-mold label film according to any one of claims 1 to 3, wherein a melt flow rate of the high-density polyethylene resin is 0.04 to 0.5 g / 10 min.   The matte in-mold label film according to any one of claims 1 to 4, wherein the in-mold label film is formed by biaxial stretching.

Images