JPH09297539A - Film for stretch label - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film for a stretch label having excellent heat resistance, scratch resistance and printing effect as a stretch label to be mounted at a columnar or prism-shaped object. SOLUTION: This film for the stretch label is a film 1 of 30 to 150μm thickness consisting of straight chain low-density polyethylene which is polymerized by using a single site type metallocene catalyst and has density of 0.905 to 0.940g/cm<3> . The film is deformed at a velocity of 300m/min in a transverse direction. The stress 0 strain (d) obtd. by measuring a hysteresis curve of <=25% does not exceed 7% and, further, the permanent strain (e) does not exceed 1.5%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a label attached to the periphery of a cylindrical or prismatic bottle or the like, and more specifically, the self-stretchability of a film is used for labeling, and the label is heat resistant. , Which belongs to stretch label film with excellent scratch resistance and printing effect.

[0002]

A stretch label made of a film having a pattern layer and having excellent self-stretchability can be adhered / followed according to subtle deformation of the container after being attached to a plastic container or a glass container. There are features.
As a film for stretch labels, conventionally, a film of ethylene / vinyl acetate copolymer containing 3 to 10% of vinyl acetate has been used. However,
Films of ethylene-vinyl acetate copolymer have mechanical strength such as tear strength, and lose the stretchability of the label when filled with a hot solution, resulting in loss of label or wrinkling, which is a problem due to lack of heat resistance. However, there is a problem that the surface is easily scratched and the scratch resistance and oil resistance are poor.

The present invention not only improves the mechanical strength, heat resistance, scratch resistance that easily scratches the surface, and oil resistance, which are disadvantages of the ethylene-vinyl acetate copolymer film as a stretch label. It is an object to provide a stretch label film having an excellent printing effect.

[0004]

In order to solve the above problems, the present invention has a density of 0.905 to 0.940 g / cm ³ polymerized using a single site metallocene catalyst.
The linear low-density polyethylene having a thickness of 30 to 15
A film having a thickness of 0 μm and laterally deformed at a speed of 300 mm / min, a hysteresis curve of 25% or less (hereinafter,
In the present specification, it is referred to as an SS curve. In the stretch label film, 0 strain obtained by the measurement of 1) does not exceed 7% and permanent set does not exceed 1.5%. Further, linear low density polyethylene having a density of 0.880 to 0.940 g / cm ³ polymerized using a single-site metallocene catalyst is 55 to 98% by weight, and a polyolefin resin is 2 to 45% by weight. And a film having a thickness of 30 to 150 μm and laterally deformed at a speed of 300 mm / min.
It is a film for stretch labels in which the 0-strain obtained from the S curve does not exceed 7% and the permanent set does not exceed 1.5%. The film is a stretch label film containing one or more selected from a lubricant, an anti-blocking agent, an antioxidant, and / or an antistatic agent.

[0005]

2. Description of the Related Art A conventional label attached to a container is a tubular label made of a stretched film such as polystyrene or polyvinyl chloride provided with a pattern layer on the front surface of the film or the back surface of the transparent film, and heat-shrinked to adhere. Shrink label, glue or label attached to the paper surface of a paper or film or a layer of aluminum foil and paper laminated with a shrink layer, a method of sticking the above label with an adhesive, a pattern layer There is a stretch label or the like in which the provided tubular label made of a plastic film having excellent self-stretchability is stretched and inserted into a container to be in close contact therewith.

Among the above, the stretch label not only has the feature that it is rich in flexibility so that it can closely adhere to and follow the subtle deformation of the container even after being attached to the plastic container, and it has excellent water resistance and Simply adheres (in this specification, evenly attached, but when peeled,
The state in which neither the container nor the label can be peeled off at the interface without any broken deposits is described as adhesion. I'm just doing it. Therefore, polyethylene terephthalate (hereinafter,
It is described as PET. ), Polyvinyl chloride, etc., can be used for drinking water containers, and after crushing the collection container, the fragments and the label can be separated by the difference in specific gravity, and since heat and special adhesive are not required for mounting, the recycling container It is often used for labels.

[0007] Conventional stretch labels mainly use a film of a combined ethylene / vinyl acetate copolymer containing 3 to 10% of vinyl acetate. However, this ethylene / vinyl acetate copolymer film is inferior in mechanical strength such as tensile strength and tear strength, and the label does not stretch when it is filled with a hot liquid or heat-treated for sterilization after filling. There is a problem due to lack of heat resistance that it is lost and can not follow the shape change of the container and falls off, or wrinkles are generated, and the surface is easily scratched and the scratch resistance and oil resistance are poor. It was

When the content of vinyl acetate is increased in order to increase the elasticity of the ethylene / vinyl acetate copolymer, not only the heat resistance is further reduced, but also the film is easily tackified, and handling such as winding of a film is performed. A problem occurred that hindered. In order to solve this, if the amount of lubricant added is increased, the adhesion of the printing ink will be reduced and the printing ink will be repelled, which will not only reduce the printing effect but also form a stretch label from the film. In some cases, the adhesion state when processed into a sheet varied.

On the other hand, low-density polyethylene (hereinafter referred to as LDPE), which is a homopolymer of ethylene having low tackiness, may be used, but it is not possible to comprehensively solve stretchability, slipperiness, and printability. Did not. Also, the resin used to make the film has a density of 0.905 to 0.9.
A technique for a stretch label film comprising 50% by weight or more of linear low-density polyethylene having a Vicat softening point of 80 ° C. or more at 40 g / cm ³ is also disclosed (Japanese Patent Laid-Open No. 7-29200).
(See Japanese Patent Publication No. 234638). However, since the film made of linear low-density polyethylene has a stress 0 strain in the S-S curve of close to 10%, it does not have sufficient stretchability and is inferior in adhesiveness and heat-slip resistance after label insertion. there were.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In order to achieve the above object, the present invention has a linear low density polyethylene polymerized using a single site metallocene catalyst having a density of 0.905.
It is a film having a thickness of about 940 g / cm ^{3 and} a thickness of 30 to 150 μm. Then, the film was stretched and deformed in the transverse direction at a speed of 300 mm / min, the stress 0 strain d obtained by the SS curve of 25% or less shown in FIG. 1 did not exceed 7%, and the permanent strain e was 1.5. The film for stretch labels does not exceed%.

The stress 0 strain d and the permanent strain e of the present invention are, as shown in FIG. 1 (B), a stretch label film having a width H of 15 mm in the direction orthogonal to the film forming direction M thereof,
A strip-shaped test piece T having a length L of 100 mm or more is cut, and chucked at a distance of 100 mm, and then cut in the lateral direction (X-Y).
Direction) and stretched 25% at a speed of 300 mm / min, and then reversed at the same speed to measure the S-S curve to release the stress S stretched 25% to 0 as shown in FIG. The instantaneous strain d is (stress 0 strain), and the strain after 10 minutes is permanent strain e.

A second aspect of the invention is a polymerized using a single-site metallocene catalyst having a density of 0.880 to 0.94.
0-g / cm ³ linear low density polyethylene 55-98
It is a film having a thickness of 30 to 150 μm and composed of 2% by weight and 2 to 45% by weight of a polyolefin resin. Then, it is deformed at a speed of 300 mm / min and 25%.
Stress 0 strain d obtained by the following S-S curve is 7%
The film for stretch labels has a permanent strain e not exceeding 1.5%.

Used for stretch label film,
The metallocene catalyst for producing linear low-density polyethylene having a density of 0.880 to 0.940 g / cm ³ polymerized using a single-site metallocene catalyst is prepared from one having uniform active sites (single site). . This single-site metallocene catalyst is a metallocene-based transition metal compound and an organoaluminum compound or a boron compound, and may be used while being supported by an inorganic substance.

The metallocene-based transition metal compound is a transition metal selected from Group IVA of the periodic table of elements, that is, titanium, zirconium, hafnium, cyclopentadienyl group, substituted cyclopentadienyl group, indenyl group, substituted indenyl group. , A tetrahydroindenyl group, a substituted tetrahydroindenyl group, a fluorenyl group, or a substituted fluorenyl group 1 or 2 are bound, or two of these groups are linked by a covalent bond, In addition, hydrogen atom, oxygen atom, nitrogen atom, silicon atom, halogen atom, alkyl group, alkoxy group, aryl group,
It has a ligand such as an acetylacetonal group, a carbonyl group, a substituent containing a Lewis base, and an unsaturated hydrocarbon.

Organoaluminum compounds include alkylaluminum, chain or cyclic alumoxane, and the like. Examples of the alkylaluminum include triethylaluminum, triisobutylaluminum, dimethylaluminum chloride, diethylaluminum chloride, methylaluminum dichloride, ethylaluminum dichloride, dimethylaluminum fluoride, diisobutylaluminum hydride, diethylaluminum hydride, and ethylaluminum sesquichloride.

The chain or cyclic aluminoxane is produced by contacting an alkylaluminum with water. For example, it can be obtained by adding water after adding alkyl aluminum at the time of polymerization, or by reacting water of crystallization of a complex salt or water of adsorption of an organic / inorganic compound with alkyl aluminum.

Examples of the inorganic material carrying the single-site metallocene catalyst include silica gel, zeolite and diatomaceous earth. Polymerization method, for example, bulk polymerization, solution polymerization,
Examples include suspension polymerization and gas phase polymerization. These polymerizations may be of a batch type or a continuous type. Polymerization temperature,
Pressure and time conditions are -100 ~ 25 ° C, 1 ~ 50kg
/ Cm ² , 0.08 to 10 hours.

The linear low-density polyethylene polymerized using the single-site metallocene catalyst of the present invention has a melt flow rate of 1.0 to 9.05 g / 10 min and a density of 0.905 to 0.940 g / cm. ³ is preferable, and if the density is higher than the above range, the stretchability is insufficient, and if the density is low, the film has tackiness and winding is difficult, and wrinkles are likely to occur when the label is inserted and mounted in a container.
However, even if the density is 0.905 or less, tackiness can be prevented by including another polyolefin resin in an amount of 2 to 45% as described later. Also, MFR
If it is less than 1.0 g, there is a problem that it is difficult to flow and a film cannot be formed.

When the thickness of the film is 30 μm or less, wrinkles are apt to occur during printing and label processing for joining and cutting into a tubular shape, and when it is 150 μm or more,
Not only is the resource wasted, but the rigidity is increased, which may hinder the insertion and mounting work.

The polyethylene used in the stretch label film of the second invention comprises 98 to 55% of linear low-density polyethylene polymerized using a single-site metallocene catalyst, and another polyolefin resin. ~
A film can be formed by mixing in the range of 45%. The density of the linear low-density polyethylene produced using the single-site metallocene catalyst at this time is not always 0.905.
It is not necessary to be more than g / cm ³ , 0.880 g / cm
^{About 3} may be used, and the density of a mixture of other polyolefin resins is 0.905 to 0.970 g / cm.
³ is fine. Then, a film having a thickness of 30 to 150 μm is deformed at a speed of 300 mm / min as described above, and the strain of 0 stress obtained by measuring the SS curve of 25% or less does not exceed 7%. The type does not matter as long as the stretchability as a stretch label showing a value in which the permanent set does not exceed 1.5% is satisfied.

The polyolefin resin mixed with the linear low-density polyethylene polymerized by using the single-site metallocene catalyst includes LDPE, medium-density polyethylene,
Examples include high-density polyethylene, polypropylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, and ionomer. By mixing these resins, if the film density exceeds 0.970 g / cm ³ , even if the label is peeled from the container after being adhered and used as a label on a container such as PET or polyvinyl chloride, the density It becomes difficult to separate the resin due to the difference. Therefore, it is preferable to set the density of the film smaller than that of the container.

The stretch label film may be composed of two or three layers mainly composed of linear low density polyethylene polymerized by using the above-mentioned single site metallocene catalyst, and may be bonded between the respective layers, if necessary. A resin layer may be provided. A linear low-density polyethylene polymerized using the above single-site metallocene catalyst with a different density (for example, mainly the intermediate layer with a particularly low density, and the higher density as a thinner layer). It may be used for the surface layer, and may be a linear polyethylene comprising ethylene / α-olefin copolymer, LDPE, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic ester copolymer. It is possible to use a blended product of an ionomer and an ionomer.

The stretch label film is a liquid paraffin, a synthetic paraffin, an aliphatic hydrocarbon such as microcrystalline wax, an ester of a straight chain alcohol and stearic acid, in order to provide lubricity, if necessary.
Lubricants such as higher fatty acid amides, antiblocking agents, nonionic surfactants, anionic surfactants, antistatic agents such as amphoteric surfactants, and / or metal compounds that can be used in polyolefin resins, epoxy compounds One or more stabilizers that can be selected from nitrogen compounds, phosphorus compounds, sulfur compounds, phenol compounds and the like can be appropriately selected and added. Coloring with an inorganic or organic pigment can also be performed.

The stretch label film of the present invention comprises:
It can be formed by a normal film forming method using a T die and a circular die. Preferably, a T-die method in which the gloss of the surface can be freely selected by the surface shape of the cooling roll.

These films are subjected to an easy adhesion treatment such as a corona discharge treatment on the surface on which the pattern layer is provided,
If desired, the picture layer can be provided by winding of gravure printing, flexographic printing, silk screen printing or sheet-fed printing. Printing is usually done by so-called back printing, in which the picture layer is viewed through a transparent film and the picture layer of the label is protected by the film. It is also possible to perform printing on an unprocessed film that is not subjected to an easy-adhesion treatment and surface printing (for example, additional printing of quantity, price, etc.).

The printing ink for providing the pattern layer may be a usual printing ink for polyolefin film (in the case of back printing, gloss is not required), an inorganic or organic pigment is used as a colorant, and a binder having high elasticity is used. Composed of. The binder is appropriately selected from polyamides, polyesters, polyurethanes, cyclized rubbers and the like which can be dissolved in a usual solvent for gravure ink. And for these inks,
It is preferable to add a lubricant or an anti-blocking agent for imparting lubricity and preventing blocking.

However, the use of an excessive amount of an anti-blocking agent in the form of fine particles such as silica, talc, or calcium carbonate roughens the printed surface and, when wound, causes an embossing action on the non-printed surface of the film, and then the surface. It should be noted that the gloss may change. Further, when a large amount of a lubricant such as higher fatty acid, higher fatty acid amide, or silicone is used, the printing effect is deteriorated by hindering the adhesion of the printing ink or repelling the ink, so the addition amount is 0.5% or less. It is preferable.

The stretch label film of the present invention comprises:
Usually, as shown in FIGS. 2 (A), (B) and (C), the pattern layer 2 is provided by back printing on the corona-treated surface of the film 1 in the direction of looking at the film forming direction M from above and below, and the pattern layer 2 is provided on the inner surface. In this state, the end portion of the non-printing surface is subjected to corona discharge treatment, the adhesive 3 is applied and the front and back surfaces of the film are adhered to each other, and the joint portion 4 is provided to form the tubular stretch label 5. . In addition, the circumference of the stretch label is designed to have a length in the lateral direction of the film (direction orthogonal to the film forming direction M) so as to be 98 to 85% of the outer circumference of the container 6 to be mounted shown in FIG. Also, the top and bottom of the stretch label, that is, the direction of film flow is cut to the desired length of the label.

The cylindrical label 5 is shown in FIG.
As shown in (A), (B), (C), and (D), the stretcher stretches the stretch label in the stretching direction 7 by 15 to 25% with the label mounting machine, inserts it in the container 6 in the spread state, and then stretches it. Except that the label 5 is contracted and the label 5 is brought into close contact with the outer surface of the container 6.

When the stress 0 strain of the stretch label film exceeds 7% or the permanent strain exceeds 1.5%, the expansion and contraction recovery time of the film becomes long, so that the position of the adhesion after the label is attached may shift. Since the adhesion strength is weak locally, non-adhesion parts (air bubbles, wrinkles) may occur.

[0031]

EXAMPLES Next, the composition of the composition shown in Table 1 and the compositions of Comparative Examples were added with 0.2% of silica as an anti-blocking agent and 0.05% of stearic acid amide as a lubricant.
In addition, a film was formed with the T-die shown in FIG. Dice 11
From the above, the above resin composition was extruded at 230 ° C., brought into close contact with the mirror-like cooling roll 13A having a temperature of 60 ° C. in the air chamber 12, and the peripheral speed was set to the cooling rolls 13B and 13C which were quickly set so that the cooling roll ratio was 107%. Nip roll 1
Cooling is performed while stretching 7% in the film-forming direction at 4 and cooling roll 1
Corona discharge treatment is applied to the surface that does not come in contact with 3A to a thickness of 1
Stretch label films 1 of Examples 1 to 5 and Comparative Examples 1 to 7 having a thickness of 00 μm were prepared. (Below margin)

[0032]

[Table 1] S-PE: Linear low-density polyethylene polymerized using a single-site metallocene catalyst. M • PE: Linear low density polyethylene polymerized using a multi-site metallocene catalyst. * 1: S-PE density 0.895 * 2: M-PE density 0.916 * 3: M-PE density 0.935 * 4: LDPE density 0.920

With respect to the samples of Examples and Comparative Examples, stretchability, heat-resistant slip property, surface gloss and transparency were comprehensively evaluated by the following methods. The results are shown in Table 2. Stretchability: As shown in FIG. 1 (B), the sample was cut into strip-shaped test pieces T each having a width H in the longitudinal direction parallel to the film-forming direction M of 15 mm and a length L in the lateral direction crossing the film-forming direction. The film is chucked at a distance of 100 mm in a direction orthogonal to the film forming direction M, that is, in the XY direction, stretched by 25% at a speed of 300 mm / min, the stretching is released, and the S-S curve is measured to obtain no stress. The strain d and the permanent strain e after standing for 10 minutes were measured. Heat resistance slip resistance: A plate heater 21 was attached to the dynamic friction measuring device 20 shown in FIG. 5, and (JISK7125-198
7), a rectangular parallelepiped metal sliding piece 22 can be measured so that the lateral direction of the non-corona treated surface of the sample film 1 can be measured.
Then, the plate 21 heated to 40, 50, or 60 ° C. was pressure-bonded, and after 3 minutes, the metal sliding piece 22 was evaluated by using the load cell 25 as the dynamic friction coefficient as heat-resistant sliding property. Surface gloss: The 60 ° × 60 ° gloss of the non-corona treated surface was measured based on (JIS K7105-1981). Transparency: Haze was measured based on (JIS K7105-1981). (Below margin)

[0034]

[Table 2] -Measurement impossible, * Comparative Example 1 blocking during film formation

[0035]

The linear low density polyethylene having a density of 0.905 to 0.940 g / cm ³ polymerized using a single-site catalyst has a narrow molecular weight distribution range, and
It is possible to form a stretch label film having a low stretchability and a low density component that causes the film to stick. Further, even in the linear low-density polyethylene polymerized by using a single-site catalyst and having a relatively low density of about 0.880, it is possible to easily prepare the linear low-density polyethylene by blending another low-adhesive polymer. The effect of suppressing tackiness is exhibited. Therefore, there is an effect of constructing a stretch label that is mainly composed of linear low-density polyethylene that is highly stretchable and that makes the most of its characteristics.

[Brief description of drawings]

FIG. 1 (A) is a diagram showing an SS curve of a stretch label film. (B) It is a figure which shows the position of the sample which measures an SS curve.

FIG. 2 is a conceptual diagram showing an outline of a process of producing a stretch label of the present invention. (A) A film for stretch labels. It is a perspective view which shows the concept which provided the pattern layer in the (B) film. (C) It is a perspective view which shows the concept which joined the film in the shape of a cylinder.

FIG. 3 is a conceptual diagram showing an outline of a step of mounting a stretch label on a container. (A) It is a perspective view of the stretch label cut into one sheet. (B) It is a conceptual diagram which shows the state of the label extended for insertion. (C) It is a conceptual diagram which shows the state which inserted the label in the container. It is a conceptual diagram which shows the state where (D) the label was closely attached to the container.

FIG. 4 is a conceptual diagram of a film forming machine for explaining film forming. (A) A label cut into a tubular shape. (B) The label is stretched for insertion. (C) A label inserted in the container. (D) A label that expands and contracts and adheres closely to the container.

FIG. 5 is a conceptual diagram of a measuring device for explaining a method of evaluating heat resistant slip resistance.

[Explanation of symbols]

 1 Stretch Label Film 2 Design Layer 3 Adhesive 4 Joint 5 Stretch Label 6 Container 7 Stretching Direction 11 T Dice 12 Air Chamber 13A, 13B, 13C Cooling Roll 14 Nip Roll 20 Dynamic Friction Measuring Device 21 Plate Heater 22 Sliding Piece 25 Load Cell D Strain d Stress 0 Strain e Permanent strain H Width of test piece L Length of test piece M Film forming direction S Stress T Strip test piece

[Procedure amendment]

[Submission date] July 17, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4 is a conceptual diagram of a film forming machine for explaining film forming.

Claims (3)

[Claims] 1. The density polymerized using a single-site metallocene catalyst has a density of 0.905 to 0.940 g / cm ^3.
The linear low-density polyethylene having a thickness of 30 to 15
A film of 0 μm and laterally deformed at a speed of 300 mm / min, the stress 0 strain obtained by measuring a hysteresis curve of 25% or less does not exceed 7%, and the permanent strain does not exceed 1.5%. A film for stretch labels, which is formed from a film. 2. The density polymerized using a single site metallocene catalyst has a density of 0.880 to 0.940 g / cm ^3.
Of linear low density polyethylene of 55 to 98% by weight and polyolefin resin of 2 to 45% by weight,
The film has a thickness of 30 to 150 μm, is deformed in the lateral direction at a speed of 300 mm / min, and has a stress 0 strain of 7% obtained by measuring a hysteresis curve of 25% or less.
A film for stretch labels, which is formed from a film having a permanent strain of not more than 1.5% and a permanent set of not more than 1.5%. 3. The stretch label film according to claim 1, wherein the film contains one or more selected from a lubricant, an antiblocking agent, an antioxidant, and / or an antistatic agent.