JPS5834349B2 - twist packaging film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new twist packaging film containing a styrene-butadiene block copolymer and polystyrene that satisfies all practical twist packaging suitability.

BACKGROUND ART Conventionally, cellophane, paraffin paper, -axially stretched polyethylene film, unstretched polypropylene film, etc. have been used to wrap confectionery such as candy, chocolate, and millet cakes one by one.

Twist packaging is wrapped using a twist packaging machine, and the properties required in this process are twist fixation, mechanical suitability for high-speed packaging, breaking strength, impact resistance, moisture resistance, transparency, bulkiness, and crispness. and odorless.

However, cellophane, paraffin paper, and other papers lack moisture resistance and heat retention, and also have insufficient impact resistance, so they have the drawback of being easily damaged during high-speed packaging or transportation of packaged items.

Although unstretched polypropylene film is almost satisfactory in terms of twist fixation, it has no stiffness and is difficult to work with, and the twist part is easily damaged.Furthermore, the package lacks bulk and crispness, compared to conventional cellophane. Because the value of the product is inferior compared to that of 2018, it is currently only used for some twist packaging applications.

Furthermore, biaxially oriented polypropylene film, which has excellent mechanical properties, moisture resistance, transparency, etc., has a fatal drawback of poor twist fixation.

Furthermore, uniaxially stretched polyethylene film has twist fixation,
Although it is excellent in packaging workability, mechanical properties, moisture resistance, etc., it has a disadvantage that it has poor transparency and can only be used for so-called vertical twist packaging in which it is twisted parallel to the stretching direction.

In contrast, the present inventors have focused on the packaging suitability required for practical twist packaging, that is, twist fixability, packaging workability,
Various studies have been conducted to provide a twist packaging film that satisfies all mechanical properties, moisture resistance, etc.

As a result, we used a styrene-butadiene block copolymer with a styrene content of more than 70 wt% and less than 90 wt% and a butadiene content of 10 wt% or more and less than 30 wt%, and polystyrene with a heat distortion temperature of a specific temperature or higher, and the content ratio of both was controlled within a specific range. By doing so, and by setting the stretching direction and magnification within a specific range, we have succeeded in providing a packaging film that satisfies all practical twist packaging suitability, which is the objective of the present invention, and this is the gist of the present invention. The styrene content is more than 70wt% and 90wtφ or less, butadiene content i
o wt % or more and less than 30 wt % styrene-butadiene block copolymer 50 to 98 Wi %, and a heat distortion temperature of 90 ° C or more containing polystyrene 50 to 2 wt %,
In addition, it is stretched five times or less in the warp direction.

The present invention will be explained in detail below.

The above styrene content exceeds 70wt% and does not exceed 90wt%,
A styrene-butadiene block copolymer having a butadiene content of 1 wt% or more and less than 30 wt% means an MI (melt index) of lO to 10.0, preferably 1.0 to
The power is in the range of 2.0.

In this case, if the styrene content is 70% or less and the butadiene content is 30% or more, the obtained film will have weak stiffness (low twisting stability) and will not be suitable as a wrapping film for twisting.

In addition, the styrene content exceeds 90% and the butadiene content exceeds 10%.
If the amount is less than 50%, the resulting film may tear when applied to twist packaging, which is not preferable.

The above-mentioned 0 polystyrene is preferably a heat-resistant grade with a heat distortion temperature of 90°C or higher (according to test method JIS K-6871), preferably in the range of 92 to 95°C. It is essential to contain a styrene-butadiene block copolymer and a specific amount of polystyrene, with a styrene content of more than 7 owt% and 90 wt% or less, and a butadiene content of iowt% or more of 3 owt.
If less than t% of the styrene-butadiene copolymer is used alone, the stiffness will be weak and the workability will be poor.

On the other hand, polystyrene alone does not have impact resistance, and the twisted portions are damaged, making it impossible to use as a practical twisting film.

The materials used in the present invention are 50 to 95 wt% of styrene-butadiene block copolymer, 50 to 2 wt% of polymethylene
It is in the t-diagonal range.

Here, the styrene-butadiene block copolymer is 5
If the polystyrene is less than 2 wt%, there is no impact resistance and the twisted portion is likely to be damaged.

Conversely, 98wt% styrene-butadiene block copolymer
As mentioned above, if polystyrene is less than 2 wt%, it becomes weak and has poor workability, and the packaged product lacks bulk and crispness, and can only be used in certain twist packaging applications.

In the present invention, well-known antistatic agents and lubricants may be added as necessary.

As this antistatic agent, glycerin fatty acid ester, sorbitan fatty acid ester, etc. are preferable, and other well-known ones can be used.

As the lubricant, well-known lubricants such as ethylene bisamide can be used.

In order to achieve the present invention, the styrene content is 70wt.
% but not more than 90 wt%, butadiene content 10 wt%
50 to 95 wt% of styrene-butadiene block copolymer and less than 30 wt%, and a heat distortion temperature of 90°C
A composition consisting of the above-mentioned 50 to 2 wt polymethyl fluoride and, if necessary, a small amount of an antistatic agent and a lubricant is applied to an extruder, and the sheet extruded from a T-die is longitudinally stretched using a stretching machine.

At this time, if necessary, heat treatment is performed at a temperature lower than the stretching temperature, so that shrinkage of the film can be suppressed, which is preferably 0.

As an example of the stretching means, stretching is carried out in the warp direction at a temperature of 100-130°C using a metal roll or the like, and the magnification is 5 times or less.
Preferably it is around 3 times.

Here, the reason why the stretching ratio is limited to 5 times or less in the present invention is because twist fixation deteriorates outside this range.

The above is a preferred example for achieving the present invention, and although the present invention is limited to this example, it goes without saying that it is not limited to Q.

In addition, in the present invention, as described above, a material stretched in the warp direction is used, and this shows the most preferable effect, but a material without stretching may cause pinholes, and a material stretched biaxially is This is not preferable because it may cause shrinkage.

The film obtained in this way has excellent twist fixing properties compared to conventional twist packaging films, can be twisted vertically and horizontally, and has good slipperiness and stiffness, making it suitable for high-speed packaging by machines. It has properties such as excellent packaging workability, breaking strength, impact resistance, and bulkiness.
It is highly economical and has a high commercial value, and can be expected to find many uses in the twist packaging field.

Next, examples of the present invention will be given to clarify its features.

<Example> Styrene-butadiene block copolymer 75 parts (styrene content: approx. 75, butadiene content: approx. 25%) Polystyrene (heat distortion temperature: 93°C) 25 parts Lubricant
Some amount of antistatic agent
A small amount of the above components were blended and extruded to form a film using a T-die extruder, followed by stretching twice in the warp direction using a roll-type stretching machine, followed by heat treatment to obtain a stretched film with a thickness of 25 μm.

In order to investigate the twisting stability of this film, I immediately tried 1.
5.2.0.2.5 turns each twisted package,
Table 1 below shows the residual twist angle when left for 24 hours after twist-wrapping and the rate at which the contents of the package pop out of the package when the twist-wrap is left on a plate for 1 hour, that is, the shedding rate.

Furthermore, as a comparative example, twist packaging was performed using an unstretched polypropylene film with a thickness of 25μ, a biaxially stretched polypropylene film with a thickness of 25μ, and cellophane #300 with a thickness of 22μ, and the same measurements as in the examples were performed. .

The results are shown in Table 1 below.

As is clear from the above results, the film of the present invention has
In terms of twist fixation, it has better twist fixation than cellophane, which has been considered the best in the past, and it also has excellent moisture resistance and storage stability, and has satisfactory impact resistance (O), as well as being able to withstand vibrations, etc. Objects come off better than cellophane,
It is a twist packaging film with high durability (0).

In this respect, cellophane is not satisfactory in terms of durability because it is inferior in moisture resistance, storage stability, and impact resistance.

Furthermore, compared to conventionally used unstretched and biaxially oriented polypropylene films, the film of the present invention not only has exceptional twist fixing properties, but also has better resistance to vibration than the conventional film.
In contrast, the contents tend to fall off, making it difficult to transport, etc., whereas the present invention can withstand considerable vibration and is a beautiful and durable twisted packaging film. .

Claims (1)

[Claims] 1. A styrene-butadiene block copolymer having a styrene content of more than 70 wt% and 9 wt% or less, and a butadiene content of 10 wt% or more and less than 30 wtφ, 50 to 98 wt%;
Polystyrene 750-2wt% with heat distortion temperature of 90℃ or higher
What is claimed is: 1. A twisted packaging film comprising: