JPS61115944A - Stretch label - Google Patents

Abstract

PURPOSE:To provide a stretch label which is inexpensive, has excellent elastic recovery and meets requirements as label, by using a compsn. consisting of two linear polyethylenes. CONSTITUTION:A compsn. consists of 3-50wt% linear polyethylene contg. short branched chains and having a density of 0.850-0.905/cm<3> and 97-50wt% linear polyethylene contg. short branched chains and having a density of 0.910-0.940g/cm<3>. The compsn. has a melt index of 0.3-5.0g/10min. The compsn. is extruded into a film having thickness accuracy within average thickness + or -10%, and the film is processed to obtain the titled stretch label.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to stretch labels that are applied to the sides of containers and articles of various shapes by utilizing the elasticity of a synthetic resin film.

(Prior Art) Various articles, including containers such as bottles, have traditionally been provided with labels for the purpose of displaying marks, contents, manufacturers, distributors, etc.

Labels are usually made of paper or synthetic resin films, and those made of paper are attached using adhesives, and those of synthetic resin films are attached using adhesive or the heat-shrinkable properties of the film. ing.

(Problems to be solved by the invention) The problems when attaching labels to containers etc. by adhesive are as follows.
An adhesive layer must be placed on the back of the label, and if the adhesive is pressure-sensitive, protective paper or the like is required to cover the adhesive layer until it is attached to a container, etc., making the label costly. This is likely to be high. In addition, with labels made of heat-shrinkable films such as polyvinyl chloride and foamed polyethylene, simply forming the label into a cylindrical shape, placing it over the body of a container, and heating it allows it to shrink and adhere tightly around the body. This saves the time and effort required for adhesion, but requires a heating device to heat-shrink the label, and although it is only for a short time, it cannot be used for containers made from materials that do not like heating or containers filled with similar contents. have difficult problems.

Therefore, there has been a desire to develop a label that can be easily attached to a container or the like without using an adhesive or heat shrinkage or other means.

Under these circumstances, labels that utilize the elasticity of synthetic resin films, called stretch labels (elastic recovery labels), have recently been developed and are being used.

Due to their nature, stretch labels are made of highly elastic synthetic resin films, such as polyethylene films that are crosslinked by irradiation with radiation, or crosslinked polyethylene that is formed by adding a crosslinking agent such as an organic peroxide to polyethylene. Films are used, and labels made of these films are formed into a cylindrical shape. After the label is expanded, a container, etc. is inserted into the label, and then the expansion of the label is released and the restoring force due to the elasticity of the label itself is applied. Hold it tightly around the container, etc.

Stretch labels like this can solve the problems caused by adhesion and heat shrinkage, but as mentioned above, a special manufacturing method is used to crosslink polyethylene film, so it is difficult to use heat shrink films for labels. It is difficult to use it for purposes such as labels in the current situation because it is more expensive than conventional films, and unless inexpensive stretch labels are developed, it is said that it will not be possible to use it in the same way as conventional labels. There is.

(Means for Solving the Problems) Therefore, an object of the present invention is to provide inexpensive and excellent elastic restoring force.
Another object of the present invention is to provide a stretch label that also meets the requirements for a label.

Another object of the present invention is to provide a new stretch label made of a composition that can satisfy the conditions for a stretch label without crosslinking using special means.

Generally, the following conditions are required for stretch labels.

■It must have excellent transparency and gloss.

■ Possess a certain degree of self-adhesiveness.

■ Must have a certain degree of lubricity to accommodate packaging machines.

■ Highly safe in terms of food hygiene.

■ Possess elastic restoring force.

The present inventors have conducted various studies in order to obtain a synthetic resin film that satisfies the above conditions. He discovered that he could achieve his goal.

The above-mentioned linear polyethylene having two types of short chain branches is
Density is 0.850g/cm or more, 0.905? 7c
Copolymer of ethylene and α-olefin less than m3, density 0.910? /crn or more, 0.940g/cm
A copolymer of ethylene and an α-olefin with a density of less than 0.
850? /crn or more, the proportion of linear polyethylene having short chain branches of less than 0.905 g/cm is 3 to 50
% by weight, preferably 5-40% by weight, especially 7-30% by weight were preferred. Note that a straight chain having short chain branches means that the former has 140 or less branches and the latter has 140 or less branches per 1000 carbon atoms in the main chain, and the latter has no more than the open side.

The proportion of the former in this composition is necessary in order to satisfy the above conditions as a stretch label, and if the proportion of the former is less than 3% by weight, the elasticity will be insufficient and the product will not form in a cylindrical shape. When the container is expanded in this state, depending on the shape of the container, it may not be possible to bring it into close contact with the side surface of the container due to a lack of elastic restoring force.

If the proportion of the former exceeds (%) by weight, the elasticity and self-adhesiveness will increase, but the slipperiness will decrease, making it difficult to apply labels smoothly using a packaging machine.

Similarly, the former density also affects the conditions for use as a stretch label, and if the density is 905f/ar+ or higher, the elastic restoring force will decrease and no effect of adhesion to the container can be expected. Furthermore, the density of the latter is also 0.910g/c
If it is less than 0.940 m, the slipperiness will decrease and it will be difficult to apply the label smoothly using a packaging machine. P/
If crn3 or more, the elastic restoring force decreases, and it is difficult to obtain the effect of adhesion to the container.

The melt index (hereinafter referred to as MI) of the composition as the stretch label is due to problems in extrusion molding.
In the range of 0.3 to 5.02/10 m1n, especially 0.5 to 2
．． Oy/lQmin is preferred. MI is 0.3 r/1
If it is less than 0 m1n, the melt viscosity of the composition will increase, which will put too much load on the machine during extrusion molding, making molding difficult, and if the MI exceeds 5.0 f /10 min,
This is because it lacks molding stability due to its melt viscosity.

The above-mentioned two-component composition is extruded into a film using an inflation die, a T-type die, etc., but a T-die is used to achieve thickness accuracy for a stretch label, and a T-die is used to achieve transparency and gloss. The cooling means is preferably water cooling.

In addition, the thickness accuracy of the obtained film is such that, over the entire cylindrical film forming one stretch label, the minimum thickness is 90% or more of the average thickness of the cylindrical film, preferably 95 inches or more. . Further, the maximum thickness is preferably 110 inches or less, more preferably 105% or less of the average thickness of the cylindrical film.

A cylindrical stretch label made of the above composition is usually stretched and expanded by 10 to 30%, although it depends on the shape of the container and the like. If there is a part of the film that is less than 90% of the average thickness, the stress during expansion will be concentrated in that thin part, and this thin part will be stretched more significantly than other parts, and will not return to its original state even after the expansion is stopped. In addition, the characters, patterns, etc. printed in that area may become distorted, resulting in an unsightly appearance.

Furthermore, if the haze value (ASTMD1003) exceeds 4 inches or the gloss value (J-K5Z8741) is less than 115 inches, the label lacks aesthetic appeal and the range in which it can be used is narrowed.

Next, the present invention will be explained in detail with reference to examples.

(Example, Comparative Example) The following copolymer of ethylene and α-olefin (a
) (b) were triblended and mixed at room temperature for 10 minutes at the composition ratios shown in Table 1 using an ordinary tumbler. The obtained mixture was heated by an extruder for 200 m
After kneading and extruding at a temperature of ~220°C to make a hard red, the pellet was made using a water-cooled inflation film forming machine (screw span φ%, die diameter 150%, lip gap 7' 2.0%), It was molded into a film at a cooling water temperature of 4°C.

The film obtained as described above was slit to a width of 223%, the longitudinal side edges of the film were overlapped, and heat sealed at a temperature of 160° to 1800°C using a pillow type heat sealer. A cylindrical stretch label with 100% thickness was created.

This stretch label was expanded by approximately 20% in the radial direction, and a cylindrical container with a diameter of 76% was inserted inside while maintaining this state, and then the expansion was released and the stretch label was brought into close contact with the side of the container. .

a) Copolymer of ethylene and α-olefin O-density 0
．． 89717 ethylene-hexene-1 copolymer [number of ethyl groups per 1000 carbon atoms in the main chain, MI0.7 f/10 min:) (hereinafter LLD)
-a-1).

Ethylene-hexene-1 with O density & Ka 0.907 r/α
Copolymer [additional number of ethyl groups to 1000 carbon atoms in the main chain, MI1.2 t /10 min) (hereinafter referred to as I, L
D-IL-2).

b) Copolymer of ethylene and α-olefin Ethylene-hexene-1 copolymer with a zero density of 920 f/α [number of side chains per 1000 carbon atoms in the main chain: 15,
MI1. Oy/10 min:] (hereinafter referred to as LLD-
b −1).

Ethylene-hexene with zero density of 0.9425 f/cm
1 copolymer [number of side chains n per 1000 carbon atoms in the main chain,
MI 1. Or/10 min) (hereinafter referred to as LLD-
1)-2).

Table 1 below also lists, as comparative examples, compositions that were molded according to the same process as in the examples, but whose compositions or composition ratios were outside the conditions of the present invention. Also, the * mark represents permanent strain.

"Residual elongation" in Table 1 above refers to a strip-shaped specimen cut from a stretch label at a length of 100% in the circumferential direction and 20% in a direction perpendicular to the length, and then tested using a tensile tester. The distance between the chucks was set to 50% on the tensile testing machine, the above specimen was attached, and the distance between the chucks was set to 70% at a tensile speed of 10 n+m/min. After stretching the sample until it becomes , the distance between the chucks is narrowed at the same speed, and the elongation is measured when the stress in the sample becomes O.

Also, the "average thickness" is 5' in the circumferential direction of the stretch label.
The average thickness is shown when the thickness is measured in % intervals, and the "accuracy" is shown by measuring the maximum thickness and minimum thickness.

Next, Table 2 shows the results of the Examples and Comparative Examples listed in Table 1.

Table 2 o Haze value (ASTMD 1003) O Gloss value (J Engineering S Z8741) (Effects of the invention) The present invention having the above structure has good adhesion regardless of the shape of the container or article, and can be used as a label. Since it satisfies various conditions, it is more effective as a stretch label than conventional ones, and also has features such as being able to be manufactured at a low cost.

Claims (1)

[Claims] Density is 0.850g/cm^3 or more, 0.905g/c
linear polyethylene having short chain branches of less than m^3;
Density is 0.910g/cm^3 or more, 0.940g/c
linear polyethylene having short chain branches of less than m^3, and the density occupied in the composition is 0.8
The composition ratio of the linear polyethylene which is 50 g/cm^3 or more and less than 0.905 g/cm^3 is 3% by weight or more,
consisting of a composition having a melt index of less than 50% by weight and a melt index of 0.3 to 5.0 g/10 min,
A stretch label characterized in that the thickness accuracy is within ±10% of the average thickness.