JPS6286388A - Heat shrinking label - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to heat-shrinkable labels, particularly heat-shrinkable polypropylene-based composite labels.

[Prior art]

In recent years, label stickers, cap stickers, etc. have been used for purposes such as exterior wrapping to improve the appearance of packaged goods, tight packaging to avoid direct impact on the inner container, and label packaging that serves both to protect glass bottles or plastic containers and to display products. is widely used.

Plastic films used for these purposes are required to have anisotropic heat shrinkability, printability, etc., and polyvinyl chloride, polystyrene, electron beam irradiated polyethylene, polyolefin films, etc. are used. There is.

However, although polyvinyl chloride film has a good heat shrinkage rate, it is not preferable because it generates chlorine gas when incinerated, causing problems such as corrosion and environmental pollution.

Moreover, polyethylene film does not have sufficient transparency and gloss, and it is difficult to obtain an anisotropic heat-shrinkable film.

On the other hand, polystyrene film is brittle and easily torn, so it has little protective effect on glass containers and the like.

In addition, polyolefin films have been developed using i! to overcome the above drawbacks. It began to be used in 2000, but is it sufficiently heat-shrinkable? '
In order to obtain this, a polymer with poor pJ511 resistance is used, which results in printing ink smearing due to the retort melting polymer.

[Purpose of the invention]

An object of the present invention is to provide a heat-shrinkable label which overcomes the drawbacks of the prior art and has excellent heat-resistance and sufficient heat-shrinkability.

[Structure of the invention]

” The present invention achieves the second object by forming an A/82 layer or an A/82 layer.
R/A Consisting of three layers of polyp 11 pyrene-based laminated film, the melting point tmA of the polymer having the form iii AN is 14
0 to 1 [10°C, the melting point t of the polymer forming the water layer]
mR is 150°C or higher, and the tmA is tmR
, the thickness of the heel is 8 μ or less and 1 to 20% of the thickness r7j of the entire laminated film, and the heat shrinkage rate at 100 ° C. of the laminated film when it is cylindrical is 15% in the circumferential direction. 1- above, and is characterized in that the A layer is printed.

The polypropylene film of layer A and layer B in the present invention is a film consisting of polypropylene in an amount of 50% or more by weight, specifically a propylene homopolymer, and a mixture of this and an α-olefin homopolymer such as polyethylene. It is a film made of a copolymer with α-olefin or α-olefin, and the copolymer is a random copolymer or a block copolymer.

The polymer forming ArfA is ethylene.
A propylene random copolymer is preferred, and a random copolymer with an ethylene component of 0.5 to 3.5% by weight is more preferred.

The polymer forming layer B is preferably a copolymer of propylene and ethylene and/or butene, particularly a random copolymer, or a mixture with a polyolefin such as polyethylene or polybutene.

More preferably, an ethylene/propylene random copolymer with an ethylene component of 3 to 8% by weight and a butene component of 2 to 1% by weight.
A propylene/butyne copolymer containing 5% by weight, and an ethylene/propylene/butene ternary random copolymer containing 0.5 to 15% by weight of an ethylene component and 1 to 15% by weight of a butene component.

Note that an inorganic filler may be added to BT@ to produce a film with internal voids.

That is, when the film is stretched with no filler added, many voids are generated inside the film, resulting in a film with excellent flexibility.

Examples of inorganic fillers include diatoms, calcium carbonate,
Kaolin, calcium silicate, talc, etc. are used.

Further, in the present invention, the melting point t of the polymer forming the A layer is
mA is 140-160°C, preferably 145-155
On the other hand, the melting point tmB of the polymer forming layer B is below 150°C, preferably below 140°C, and above 120°C.

If tmA is less than 140° C., heat resistance decreases, and when retort sterilization is performed, ink flow and printing distortion occur, resulting in poor appearance.

Also, if the temperature exceeds 160℃, the heat as a laminated film increases by +1
5j It becomes difficult to achieve a shrinkage ratio of 15% or more, and the surface becomes like a river, deteriorating the appearance.

- If the temperature exceeds 50°C for tmll months, the crystallinity of the 8-layer polymer increases and the heat shrinkage rate of layer B decreases.

Furthermore, in the present invention, the melting point tmA of layer A is higher than the melting point tmB of layer B, preferably 5 to 20°C higher than tmB.
expensive.

The thickness of AM is 1 to 2 times the thickness of the entire A/R layer film.
0% and 811 or less.

Further, in the case of three layers A/B/A, the total thickness of the two A layers is 1 to 20% of the total thickness, and the total thickness is 8 μm or less.

If the thickness of 1- is less than 1%, deterioration of appearance such as ink flow cannot be prevented.

On the other hand, if it exceeds 20% or 8μ, the heat shrinkage rate decreases, and the transparency and properties of the laminated film deteriorate.

Further, in the present invention, when the laminated film is formed into a cylinder, the heat shrinkage rate at 100°C in the circumferential direction is 15% or more.

In other words, in the present invention II, bonds! - When the film is made into a cylinder, it is better to have a high heat shrinkage rate only in the circumferential direction, and to have as low a heat shrinkage rate as possible in the direction that intersects with the circumferential direction. It is preferable that it is 5% or more).

Therefore, in the present invention, -axially stretched films are preferred.

If the heat shrinkage rate is less than 15%, the adhesiveness to the container will decrease.

In order to make this heat shrinkage rate 15% or more, tmB-
It is necessary to stretch at 5°C or higher, preferably Lmll-(30 to 50°C).

The lower the stretching temperature, the higher the temperature! Although the tiii ratio becomes large, since the film frequently breaks during the stretching process, tmR-(fin-70° (d) is 11 degrees).

The melting point of the A layer tmA is 4; the melting point of the B layer is higher than the melting point tmt of the A layer.

Therefore, the A layer is oriented much more strongly in the stretching direction than the B layer, and the heat resistance is improved.

The strength of the orientation in the stretching direction of A, 131 is expressed by the difference (birefringence) between the refractive index in the stretching direction and the refractive index in the direction perpendicular to it (birefringence).
It is preferably in the range of XIO to 35X10.

At this time, since tmA is higher than tmB, the birefringence of the A layer is greater than the birefringence of the 13th layer.

Note that the refractive index is a value measured at 20° C. using A-Ambe's refraction a1.

Furthermore, in the present invention, printing is applied to the surface of layer A.

Printing methods include jm regular, gravure, offset, and
/ A printing method such as Kutinki is employed, but the present invention is not limited thereto.

Next, a method for producing a heat-shrinkable label according to the present invention will be described, but the present invention is not limited thereto.

The treetop I-film used in the present invention is manufactured using a conventional composite film manufacturing method. Fi! Ji is accused.

That is, the polymers constituting layer A and layer 13 are co-extruded from one T-die, or laminated onto the solidly extruded polymer to form a laminated unstretched sheet. obtain.

This sheet is axially stretched in the longitudinal or transverse direction and relaxed as necessary.

The stretching temperature is as described above), and the stretching ratio is usually 5 to 15 times.

Note that it is also possible to preliminarily stretch the film by a factor of 2 or less in a direction perpendicular to this stretching direction.

Further, it is preferable that the No. 31 adhesive is not interposed between the A layer and the B layer, and that both layers are directly bonded.

The high melting point polymer layer side of the obtained laminated film, that is, A
The surface of the layer is subjected to surface activation treatment such as corona discharge, and then printed.

Alternatively, vapor deposition may be performed.

Next, the printed laminated film is formed into a cylindrical shape,
In the case of longitudinal-axial stretching, the transverse direction is the axis of the tube, and in the case of transverse uniaxial stretching, the longitudinal direction is the axis of the tube.

At this time, in the case of a transparent film, the printing surface is on the inside (of course, the printing is on the back side), and the printing surface is on the outside (1'', which is a film with an inorganic filler added to generate voids).

Next, the measurement method employed in this specification will be explained.

(1) Melting point Perkin - Differential scanning calorimeter model manufactured by former MER Corporation
Using the DSC-2 model, a 5 mg sample was heated to 280°C at a heating rate of 20°C/min, held for 5 minutes, cooled at the same rate, and then heated again. Take the melting curve.

When there is one apex of the melting peak, the temperature at the apex of the peak is taken as the melting point.

When there are two peaks of melting peaks, the heat of fusion of each peak is determined, and the value calculated by the following formula is taken as the melting point.

However, △Hi is the heat of fusion of the i-th peak, tIIli
indicates the temperature at the top of the i-th peak.

Examples of curves with two melting peaks are shown in Figures 1 and 2.
As shown in the figure. In these figures, among the melting peaks, the melting peak on the low temperature side is Pl, and the melting peak on the high temperature side is P2. In addition, the apex of each melting peak, the minimum point of the peak, and the minimum point of the peak are designated as A and B, and the temperature of this peak is ′r, respectively.
ml, Tm2.

Further, the heat of fusion of the peak on the low temperature side is Ill, and the heat of fusion of the peak on the high temperature side is H2.

The method for determining the heat of fusion is shown by the first peak Pl in FIG. First, the starting point TI and the ending point 'F2 of the absorption are connected by a straight line (broken line C in FIG. 1) to form a base line.

The intersection of the extrapolation line of the straight line part in the first half of the peak and the baseline is T5,
The intersection of the supplementary line 1 of the 1μ line in the latter half of the peak and the baseline is ′
(2) 6, and the area of the portion surrounded by the peak, extrapolation line, and base line (shaded portion) is heat of fusion 1-f 1 .

Similarly, the heat of fusion H2 at the second beam I)2 is determined. However, as shown in Fig. 2, the ending point of the first peak P1 is
and the starting point T3 of the second beak P2 becomes one point, and if it deviates from the base line C connecting T] and T4, the intersection with the base line C perpendicularly below the point is set as T9, and the second half of the peak Connect the straight line part of the peak (the first half of the peak in the case of the second bead P2) to '1'9, and calculate the area by considering that line as an extrapolation line.

(2) Shrinkage rate of nail A sample with a length of 200mm and a medium size of 10mm is heat treated in a hot air oven at 100°C for 15 minutes with a load of 3g applied.If the length after heat treatment is Lmm, the heat shrinkage rate is as follows. It is determined by the formula.

Heat shrinkage rate (%) = (200-L) /200 xlo
.

(3) Haze , TTS-67]4.

〔Effect of the invention〕

According to the present invention, the heat resistance of the laminated film is improved by making the A/13 or A/B/A laminated film higher than the melting point of the A layer polymer than that of the B layer. On the other hand, layer B, which has a low melting point, is made thicker than layer A to provide sufficient heat shrinkage.

Therefore, the heat-shrinkable label of the present invention can be subjected to tort sterilization after being brought into close contact with a container by heat treatment.

Next, examples of the present invention will be described.

〔Example〕

Example 1 Ethylene-propylene random copolymer with an ethylene content of 1.8% by weight (melting point 150"C, melt index 5g/10 min at 1230°C) A and an ethylene-containing if4
．． 5% by weight ethylene/propylene random copolymer (
Melting point 135℃, melt index 2g/1 at 230℃
0 minutes) B is coextruded from one T die at 260°C,
It was wound around a cooling drum at 40°C and rapidly cooled to produce a two-layer unstretched sheet.

This sheet was stretched 10 times in the transverse direction at 95°C and then 80°C.
A horizontally uniaxially stretched film having an A layer of 3 μm and a BN layer of 47 μm was obtained.

The properties of this film are shown in the table.

The surface of layer A was subjected to corona discharge treatment, the wetting tension of the film surface was set to 38 dyne/cm, and normal gravure printing was performed.

Next, cut it into predetermined dimensions, length 100 mm, circumference Wc
It was processed into a 200 mm cylindrical label. At this time, the lateral direction of the film was set to be the circumferential direction of the cylindrical label, and two types of labels were prepared: one with the printed surface on the inside and one with the printed surface on the outside.

A glass bottle with a height of 155 mm, a maximum diameter of the body of 56 mm, and a minimum diameter of 48 mm was inserted into this cylindrical label, and then the label was heat-shrinked in a tunnel oven at 100°C and retort sterilized at 120°C for 30 minutes. As a result, the adhesion of the label to the glass bottle was good, and no distortion of the print or ink flow occurred even after retort sterilization.

Comparative example 1 fli of Example 1 only with 131- without laminating AI-
Using F4i film, Haku carried out the same procedure.

As a result, although the adhesion of the label to the glass) 11r was good, distortion of the printing was observed in the first retort sterilization, and ink flow occurred especially in the front printed crystal C.

Comparative Example 2 The thickness of layer A is 15 mm! , 35 meters thick with 13 layers! The test was carried out in the same manner as in Example 1, except that the film was frequently torn in the tenter, and a poly-1 stretched film could not be obtained.

When the transverse stretching temperature was set to 110°C, stretching was possible, but the adhesion to the glass bottle was 111. was insufficient.

Comparative Example 3 Bolibu 1 cobylene homopolymer was used as layer A in Example 1, melting point 165'C, melt index at 1230°C 8g
/10 minutes) was used in the same manner.

The adhesion to Glass) 1 was somewhat insufficient at the smallest diameter portion, the surface condition of the film was also poor, and the appearance was not desirable.

(Margin below) *○: Good Ladle O: Good △: At the smallest diameter part of the bottle △: Printing distortion, insufficient adhesion Misalignment ×: Bad ×: Same and ink lk
Occurrence

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are explanatory diagrams each showing an outline of a melting spectrum measured by a differential scanning calorimeter. Pl...First (low temperature side) melting peak P2...Second (high temperature side) melting peak A...Vertex B of the first melting peak...Second The apex of the melting peak C.
...Baseline D...Start point of first melting peak Tn+]
... Temperature at point A Tm2 ... Temperature at point B H] ... Heat of fusion at P1

Claims (1)

[Claims] Consisting of a polypropylene laminated film with two A/B layers or three A/B/A layers, the melting point tmA of the polymer forming the A layer is 140 to 160°C, and the melting point tmB of the polymer forming the B layer is 150°C or less. In addition, the tmA
is higher than tmB, the thickness of the A layer is 8μ or less and 1 to 20% of the thickness of the entire laminated film, and the heat shrinkage rate at 100°C of the laminated film when it is cylindrical is 15 in the circumferential direction. % or more, and the A layer is printed.