JP3145132B2 - In-mold labels with good slipperiness - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-mold with good slipperiness used for a label (including a blank) which is adhered to a synthetic resin container manufactured by differential pressure molding and hollow molding at the same time as container molding. For labels, in particular, by setting the label in the mold in advance, and then from the thermoplastic resin by hollow molding or vacuum molding or air pressure molding,
The present invention relates to a label for in-molding, which is capable of decorating a container by integrally molding a resin-molded container with a label, and which prevents blocking during printing, cutting, and punching and has good slipperiness.

[0002]

2. Description of the Related Art Conventionally, in order to integrally mold a resin-molded container with a label, a blank or a label is inserted in a mold in advance, and then the mold is formed by injection molding, hollow molding, differential pressure molding, foam molding or the like. A container is formed inside the container, and the container is painted or the like (see JP-A-58-69015 and European Patent Publication No. 254923). Such in-mold labels include a gravure printed resin film and offset multicolor printed synthetic paper (for example, Japanese Patent Publication No. 46-40794, Japanese Patent Publication No. 54-31030, British Patent No. 1090059).
Or an aluminum label obtained by laminating polyethylene on the back surface of an aluminum foil and performing gravure printing on the surface of the foil.

[0003]

However, such an in-mold label had good suitability for blistering and label bonding, but it was difficult to perform printing (offset, flexo, etc.) in the label manufacturing process which was the preceding process. , UV
(Offset, letterpress) and the cutting / cutting and punching are likely to cause blocking at the cut / cut and punching operations, and to easily cause blocking when the labels are overlaid. In addition, even when gravure printing is performed using a roll, there is a case where the sheet is not evenly arranged and the cutting has to be interrupted due to poor slipperiness in a sheeting (sheet-sheet cutting) process after printing.

[0004]

[Means for Solving the Problems]

[Summary of the Invention] The present inventors have conducted intensive studies in view of the above problems, and as a result, in a resin constituting an adhesive layer of an in-mold label, a specific amount of a lubricant selected from a specific compound was added. The present invention has been completed based on the finding that the above-mentioned problems can be solved by blending. That is, the in-mold label with good slipperiness of the present invention is selected from the group consisting of fatty acid amides and fatty acid metal salts having 12 to 19 carbon atoms in the resin constituting the adhesive layer of the in-mold label. At least one lubricant is blended in a ratio of 0.5 to 5% by weight.

DETAILED DESCRIPTION OF THE INVENTION [I] In-mold label (1) Structure The in-mold label of the present invention having good slip properties is a label having good slip properties before being attached to a container. However, when a synthetic resin container is manufactured by injection molding, differential pressure molding, or hollow molding, it is a label that can be adhered to the container in a molding die to be integrated. Such an in-mold label basically has 12 to 19 carbon atoms.
A resin adhesive layer having a low melting point (for example, having a melting point of 85 to 130 ° C.) containing at least one lubricant selected from the group consisting of fatty acid amides and fatty acid metal salts at a ratio of 0.5 to 5% by weight; One consisting of a two-layer structure adhered to a base layer made of a higher temperature resin, or further, a paper-like layer made of a stretched resin film containing an inorganic fine powder is formed on the surface, and a base layer is formed in between. There is a three-layer structure in which the low-melting-point resin adhesive layer is formed on the back surface side, or a multi-layer structure in which the low-melting-point resin adhesive layer is further formed.

(2) Constituent Materials Specific examples of the materials used for each constituent layer of the basic in-mold label having the above structure include the following. (a) Substrate layer As the material used for the substrate layer of the in-mold label having good slipperiness of the present invention, a melting point of 135 to 264 such as polypropylene, high-density polyethylene, polyvinyl chloride, polyethylene terephthalate, and polyamide is used. C. thermoplastic resin, a resin film containing 8 to 65% by weight of an inorganic fine powder, or a film in which an inorganic filler-containing latex (coating agent) is coated on the surface of the resin film;
Alternatively, a material obtained by depositing aluminum on the resin film can be used. Such a base material layer may be a single layer or a laminated structure of two or more layers.

(B) Adhesive layer The adhesive layer to be adhered to the back surface side (the side in contact with the resin container) of the resin film of the base material layer is a resin obtained by blending a compounding material component with the following resin component. There is a film layer of the composition, or a heat-sealing resin layer formed by applying and drying an emulsion of these resin compositions or a solution of these resin compositions in a solvent and drying. Resin component Materials used for the resin film of such an adhesive layer include low-density polyethylene, vinyl acetate / ethylene copolymer, ethylene / acrylic acid copolymer, and metal salts of ethylene / methacrylic acid copolymer. Melting point 85-135
° C, preferably 90 to 125 ° C, and a film layer made of these resins is laminated on the resin film of the base material layer. Alternatively, an emulsion of these resins or a solution dissolved in a solvent may be applied and dried to form an adhesive layer. Lubricant component As the lubricant component to be blended in the resin component, a blended material selected from the group consisting of the following components alone,
Alternatively, a mixture obtained by mixing two or three or more kinds and kneading with an extruder or a kneader is used. Fatty acid amides Examples of the fatty acid amides having 12 to 19 carbon atoms to be blended in the resin component include erucic acid amide, stearic acid amide, purmitic acid amide, and methylenebisstearamide. Fatty acid metal salt The fatty acid metal salt to be blended in the resin component preferably includes a fatty acid having 12 to 22 carbon atoms,
Group 4 metals, preferably salts with Group 2 and the like, specifically, calcium stearate, magnesium stearate, zinc stearate, aluminum stearate,
Zinc palmitate and the like can be mentioned. Amount ratio These lubricants are contained in the resin forming the adhesive layer in an amount of 0.5 to 0.5%.
5% by weight, preferably 1 to 3% by weight.

(3) Surface Structure Such an in-mold label is in the form of a piece of paper before being attached to a container in a mold, but is integrated with the container after being attached. Such an in-mold label can be used as an in-mold label such as differential pressure molding such as vacuum molding and pressure molding, and hollow molding in which a parison is pressed against the inner wall of a mold by air pressure. Of course, it can be used as an in-mold label for injection molding. However, when the in-mold label is adhered to a container, blisters are likely to be generated. In order to prevent the blister, the label has an adhesive layer on the back side (side adhered to the container). In particular, after the number of rolls is set to 80 to 200 lines / inch and embossing is performed with a reverse gravure type pattern, stretching is performed 4 to 8 times in the vertical direction and / or 4 to 12 times in the horizontal direction. The surface area of the convex portion from the center line of the amplitude of the peaks and valleys of the unevenness on the film surface after stretching is 50 to 90 of the entire label.
%, Preferably 55 to 80%, and the average depth of the concave portion from the center line is 0.5 to 10 μm, preferably 1 to 8
It is preferable to form the structure having a μm. The formation of such a surface structure is preferable because the slipperiness can be further improved.

[II] Manufacture of In-Mold Label The in-mold label with good slidability of the present invention having the above structure is manufactured by various methods. This will be described specifically. (1) Embossing The in-mold label with good slipperiness of the present invention comprises a heat-sealing resin film kneaded with a compounded material obtained by mixing and kneading a lubricant with a base layer at a ratio of 0.5 to 5% by weight. By laminating the adhesive layer, the in-mold label and the resin container are firmly adhered to each other when the in-mold molding is performed, and printing and cutting are performed in the manufacturing process of the in-mold label before being attached to the container. Although it is possible to prevent blocking at the time of punching processing, in order to further prevent blocking or to prevent the occurrence of blisters at the time of sticking, the surface of the heat-sealing resin film layer which is the adhesive layer, The number of points or lines in the gravure pattern is 80 to 80 per inch (2.54 cm).
The embossing as shown in FIG. 5 is performed by a metal roll and a rubber roll formed in an embossed pattern of 200 pieces. It is important that the emboss is a reverse gravure type pattern as shown in FIG. 5 having a large number of independent concave structures surrounded by a twill line, and a convex in which gas in each room can move freely as shown in FIG. In the case of the regular gravure type pattern, the effect of the present invention cannot be sufficiently exerted even in the stretched state as shown in FIG.

(2) Stretching However, since the effect of preventing the generation of blisters is small when the laminated structure film after the embossing is used alone, the film is further added in at least one direction, usually 4 to 12 times, preferably 4 to 8 times.
It is stretched twice. The stretching is performed at a temperature lower than the melting point of the resin of the base material layer and at a temperature equal to or higher than the melting point of the heat sealing resin as the adhesive layer. Although the base material layer is oriented by this stretching, the surface of the heat seal layer as the adhesive layer is deformed as shown in FIG. 6 without being oriented. (3) Other treatments If necessary, the stretched laminated structure film (synthetic paper) is subjected to corona discharge machining, flame treatment, plasma treatment or the like to improve its surface printability and adhesiveness. You can also put it. Usually, printing is performed on the surface side of the base material layer, for example, on a paper-like layer. Examples of such printing include gravure printing, offset printing, flexographic printing, screen printing, and the like, whereby the product name, manufacturer, sales company name, character, bar code, usage, and the like can be printed. (4) Stamping The container label printed and embossed as described above is separated into a label having a required shape and dimensions by stamping. This label may be a partial label attached to a part of the container surface, but it is usually used as a blank surrounding the side of the cup-shaped container in differential pressure molding, and the front and back of the bottle-shaped container in hollow molding. Manufactured as a label to be adhered to.

[III] Label for In-Mold The label for in-mold having good slippage of the present invention produced as described above preferably has the above-mentioned structure, It can be used as an in-mold label such as differential pressure molding such as molding or hollow molding in which a parison is pressed against the inner wall of a mold by compressed air. Hereinafter, as a typical example of the in-mold label having good slipperiness of the present invention, a blank for a hollow molded container will be described more specifically. FIG. 1 shows a cross-sectional view of a two-layered in-mold label used for blow molding, which is mentioned as an example of the in-mold label with good slipperiness of the present invention. In FIG. 1, reference numeral 1 denotes an in-mold label, reference numeral 2 denotes a thermoplastic resin film base layer constituting the label, reference numeral 3 denotes printing, and reference numeral 4 denotes an adhesive layer formed from a heat-sealing resin film. . Reference numeral 5 denotes a twill (convex portion) in which an adhesive layer made of the heat-sealing resin film is provided with a lattice pattern by embossing using an inverse gravure roll.
6 indicates a trough (recess) of a lattice pattern. FIG. 2 is a plan view of the in-mold label 1 on the side of the adhesive layer 4 made of a heat-sealable resin film (the back side of the in-mold label), and FIG.
1 is a cross-sectional view of a laminated structure film before stretching and before printing to obtain an in-mold label shown in FIG. FIG. 4 is a partially enlarged view of the laminated structure film shown in FIG.
In the embossed pattern of the laminated structure film shown in FIG. 3, the number of points or lines of the roll is set to, for example, 1 inch (2.54c
m), the number of which is 80 to 200. If it is less than the above range, the groove of the concave portion 6 becomes too deep, and an embossed pattern is likely to appear on the label surface (printed side) after sticking. On the other hand, if it exceeds the above range, the groove of the concave portion 6 becomes too shallow, so that the volume for containing gas and air is insufficient, and the effect of preventing blisters is reduced. Further, when the amount exceeds the above range, in the case of a part of the low melting point resin during the embossing, the phenomenon of sticking to the roll due to insufficient cooling occurs, and there is a problem in processing.
The number of lines per inch is referred to as the number of lines, and is a measure of the fineness of the embossed pattern. In the present invention, it is important that such an embossed pattern is a reverse gravure type pattern.

As shown in FIG. 4, the depth (h) of the embossed valley is preferably the thickness (h) of the heat seal resin layer.
₀ ) or more, and preferably １ ／ or more of ( ₀ ), and may penetrate into the substrate layer (h> h ₀ ). By stretching the laminated structure film embossed into the reverse gravure pattern in this manner, the thickness of the laminated structure film is reduced, the emboss pattern is widened, and the depth of the embossed valleys is reduced. Then, the surface area S of the protrusion 5 is 50% of the area of the entire label from the center line (position of h / 2) L of the peaks and valleys 5 of the unevenness of the film surface after the transverse stretching.
About 90%, preferably 55 to 80%, and furthermore, a structure having an average depth L1 of the concave portion from the center line L of 0.5 to 10 μm, preferably ₁ to 8 μm.
When the surface area of the convex portion is less than 50%, blisters are easily generated, and when the surface area exceeds 90%, the adhesive strength is reduced.
When the average depth of the concave portion is less than the above range, blisters are easily generated, and when the average depth is more than the above range, the adhesive strength is reduced. The surface Beck smoothness (JIS-P8119) of the heat-sealing resin layer is 20 to 800 seconds, preferably 30 to 400 seconds, and the average surface roughness (Ra) is 0.5 to 800 seconds.
5 μm is preferred in terms of adhesive strength. The dynamic friction coefficient of such in-mold label base paper is 0.3.
０．５0.5 (TAPPI T-816), and the paper feeding / discharging property is good. Since the in-mold label of the present invention is configured as described above, it is particularly formed in a reverse gravure type, so that the unevenness of the surface of the adhesive layer 4 of the stretched film is higher than the center line L. 5, the area per unit area can be greatly increased by increasing the area S to be bonded to the low-melting-point resin. In addition, since it is an inverse gravure type, the accumulation of gas and air at one location under high-temperature molding conditions is reduced, and it is possible to prevent the generation of blisters by dispersing and enclosing in many concave portions 6.

[IV] Adhesion The in-mold label of the present invention having good slipperiness is provided by placing the label in the cavity of the mold so that the printing side is in contact with the wall of the mold, and then sucking the mold. The container is fixed to the inner wall, and then a melt of the container molding material resin sheet is guided to a mold and molded by a conventional method to form a container in which the label is fused to the outer wall of the container. Specific manufacturing conditions for the resin molded container decorated with such a label include a high pressure of about ²⁰ to 200 kg / m ^{2 in} injection molding,
2-7 kg / m ² or -50 to -650 m for differential pressure molding
It is molded at a low pressure of about 1 to 10 kg / m ^{2 in} hollow molding at about mHg. In the container molded in this way, after the label is fixed in the mold, the label and the resin container are integrally molded, so that there is no deformation of the label, and the adhesion strength between the container body and the label is strong. This is a container which has no appearance of blisters and has a good appearance decorated with a label.

[0014]

The present invention will be described more specifically with reference to the following examples and comparative examples. In addition, the evaluation method in an Example and a comparative example is as showing below. (1) Friction coefficient Static friction coefficient Measured according to TAPPI standard T-816. Dynamic friction coefficient Measured according to TAPPI standard T-816. (2) Offset continuous printing: Using a diamond-II printing machine manufactured by Mitsubishi Heavy Industries, Ltd., a chrysanthemum plate (636 mm x 939 mm)
The maximum number of sheets that can be supplied and ejected was determined for each paper size. (3) Generation of blisters suitable for in-mold molding The evaluation was performed according to the following criteria. It was classified into the following five stages according to the state of label attachment. 5: Adhesion on entire surface 4: Less than 100% to 90% of the label is attached. 3: Less than 90% to 70% of the label is stuck. 2: Less than 70% to 50% of the label is stuck. 1: Less than 50% of the label adheres. Label Adhesive Strength The adhesive strength of a 15-mm-wide adhesive label (T-peeling) was measured by Tensilon, Shimadzu Corporation. (4) Suitability for label punching: 100 sheets on which labels were printed were stacked, punched out with a rectangular blade of 60 mm × 90 mm, and the blocking state of the cut was observed. Is x). (5) Measurement of Surface Layer The surface structure of the adhesive layer was measured based on the figure measured and displayed by a surf coder SE-30K manufactured by Kosaka Laboratory Co., Ltd.

Example 1 (1) Production of in-mold labelSubstrate layer Melt flow rate (MFR) 0.8, melting point 164 ° C
High density of homopolypropylene 70% by weight, melting point 134 ° C
Heavy weight of polyethylene 12% by weight and average particle size 1.5μm
Combine 18% by weight of calcium carbonate (A) and reach 270 ° C
After kneading with the set extruder, extruding into a sheet,
It was cooled by a cooling device to obtain a non-stretched sheet. Next
Then, after heating this sheet to 145 ° C, it is 5 times in the longitudinal direction.
It was stretched to obtain a (A layer) 5-fold stretched sheet in the machine direction.Adhesive layer On the other hand, 58% by weight of homopolypropylene having an MFR of 4.0
And 42% by weight of calcium carbonate having an average particle size of 1.5 μm.
The mixture (B) is mixed with ethylene methyl alcohol having a melting point of 90 ° C.
Using a different extruder for each of the relevant copolymers (C)
After melt-kneading at a temperature of 270 ° C, supply to one die
Then, after lamination (B layer-C layer) in the die, this lamination
The product (layer B-layer C) is extruded from a die into a film,
The C layer is on the back side of the 5-fold stretched sheet in the longitudinal direction of the A layer.
And extrude it into a metal roll and rubber roll.
Through the embossing roll consisting of
0.3mm interval (80 lines), valley depth 3
Engraving a reverse gravure pattern with 0 μm dots
Boss processed.Surface layer  On the other hand, the mixture of (B) was mixed
Laminated on the surface side to form a paper-like layer (layer B), four layers
A laminated film having the structure was obtained. Then, this laminated film
After reheating to about 155 ° C., stretched 7 times in the transverse direction,
Next, after performing corona discharge treatment on the paper-like layer (layer B),
After cooling this to 55 ° C, the ears are slit,
The thickness of each layer of (B) / (A) / (B) / (C) is respectively
Synthesis of a four-layer structure consisting of 30/70/30/10 μm
I got the paper.

(2) Manufacture of a label Then, after continuous offset printing is performed on the paper-like layer (layer B) side of this synthetic paper at a speed of 8,000 sheets / hour, it is further cut and punched. And in-mold label 1
(Width 60 mm, length 110 mm). The label was evaluated for in-mold suitability and label punching suitability by measuring the coefficient of friction, offset continuous printability, blister generation and adhesive strength. The surface structure of the embossed reverse gravure pattern on the surface of layer (C) of this label was measured using a surface roughness meter (Surfcoder SE-3 manufactured by Kosaka Laboratory Co., Ltd.).
0), the surface area S of the protrusion projecting from the center line L which is the middle of the peaks 5 and valleys 6 of the unevenness of the surface occupies 65% of the entire label. The average depth of the concave portion 6 recessed from the center line L is 6 μm, the Beck smoothness is 30 seconds, and the surface average roughness (R
a) is 1.2 μm, the Daver hardness measured by the method of JIS-P8125 is 1.8 g-cm in the MD direction, TD
The direction was 3.5 g-cm.

(3) Adhesion After fixing the in-mold label 1 to one of the blow mold split dies so that the printing surface side (layer B) is in contact with the mold by using vacuum, the high-density polyethylene ( A parison having a melting point of 134 ° C.) is melt-extruded at 205 ° C., and then the split mold is clamped. Then, 4.2 kg / cm ² of compressed air is supplied into the parison to expand the parison into a container and to form a container. After being fused with the label and then cooling the mold, the mold was opened and the hollow container was taken out. In this hollow container, there was no discoloration of printing, and no shrinkage of the label or generation of blister was observed. Also, the supply of labels to the blow mold split mold by the automatic label feeder was performed continuously for 100 sheets, but an error (two labels overlapped and supplied to the mold,
Label was dropped from the mold). Table 1 shows the results of measuring the adhesive strength of the label.

Examples 2 and 3 and Comparative Examples 1 and 2 The same procedure as in Example 1 was carried out except that the types and the mixing ratios of the components of the adhesive layer of the in-mold label were as shown in Table 1. . Table 2 shows the results.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

The in-mold label with good slipperiness of the present invention can be supplied and discharged during printing (offset, flexo, UV offset, letterpress) in the label manufacturing process before in-mold molding. Blocking does not occur on the cut surface during paper processing and cutting and punching, and blocking does not occur when the labels are overlapped. In addition, even when gravure printing is performed with a roll, the slippage is poor in the sheeting (sheet-sheet cutting) process after printing, so that it is not necessary to interrupt the cutting due to uneven paper. In addition, the in-mold label with good slipperiness of the present invention can be obtained by setting an in-mold label in a mold in advance when hollow or vacuum forming or pressure forming a thermoplastic resin, and melting the mold. By supplying the thermoplastic resin, the thermoplastic resin is pressed against the mold wall,
By adhering the in-mold label to a thermoplastic resin, a resin molded container with a label is integrally molded.At this time, the label is not deformed, and the adhesion strength between the container body and the label is strong, There is no blister, and a container with a good appearance decorated with a label can be obtained. In particular, in the case where the adhesive surface of the in-mold label with good slipperiness of the present invention is embossed to form an inverse gravure type, the area of the convex portion (the adhesive surface between the container and the label) is a majority of the label area. The adhesive strength per unit area is higher than that of a conventional label having a convex pattern obtained by using a positive gravure pattern embossing roll. Further, by forming the embossed portion of the adhesive layer into an inverse gravure type, the concave portion has an independent room structure, and furthermore, the concave portion is dispersed and present on the entire surface of the label, so that gas and air can be sealed in a small amount dispersedly. Also, by setting the depth of the concave portion to be 0.5 to 10 μm, which is an extremely small value as compared with the thickness of the entire label, the rising of the label in a state where gas or air is partially collected ( Blistering) can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an in-mold label having a two-layer structure according to the present invention.

FIG. 2 is a plan view of the back side of the in-mold label.

FIG. 3 is a cross-sectional view of a laminated structure film before stretching and before printing to obtain the label for in-mold shown in FIG.

FIG. 4 is a partially enlarged view of the laminated structure film shown in FIG.

FIG. 5 is a view showing the surface of a film on which a 100-line inverted trapezoidal gravure embossing according to an embodiment of the present invention is formed.

FIG. 6 is a diagram showing a film surface after the film of FIG. 5 has been stretched in the horizontal direction.

FIG. 7 is a view showing a film surface on which a conventional 100-line regular trapezoidal gravure emboss is formed.

FIG. 8 is a diagram showing a film surface after the film of FIG. 7 is stretched in the transverse direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 In-mold label 2 Thermoplastic resin film base material layer 3 Printing 4 Heat-sealable resin layer (adhesive layer) 5 Top of a twill (convex part) provided with a dot-like lattice pattern by emboss processing 6 Valley of lattice pattern part (recess) area of the projection above the average depth of the L center line L ₁ recess S L

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G09F 3/00-3/10 B29C 49/24 B29C 65/48

Claims (1)

(57) [Claims] 1. A resin constituting an adhesive layer of an in-mold label, comprising at least one lubricant selected from the group consisting of fatty acid amides having 12 to 19 carbon atoms and fatty acid metal salts in an amount of 0.5 to 5% by weight. %. An in-mold label having good slipperiness, characterized in that the label is blended at a ratio of 0.1%.