JPS6043859B2 - Polypropylene film with excellent transparency - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to polypropylene films with excellent transparency.

Polypropylene film has excellent moisture and oil resistance,
Depending on the strength etc., unstretched film (hereinafter P
(abbreviated as P-No) or biaxially stretched film (hereinafter referred to as P-No)
It is used in large quantities in the form of P-BO.

However, in the case of PP-No, polypropylene film tends to grow spherulites, so it has poor transparency both before and after molding, and in the case of PP-BO, although it has good transparency to some extent, In order to further improve the appearance of products and improve display effects, it is desired that they have even better transparency. Conventionally, adding dibenzylidene sorbitol to polypropylene or adding alkylene bisamide alone has been known as a method of improving such transparency, but adding such additives alone does not improve transparency one step further. I couldn't improve.

That is, such additives have the disadvantage that there is a limit to the extent to which they can improve transparency by themselves, and beyond that, transparency cannot be improved at all even if the amount added is increased or decreased. The present inventors conducted intensive studies to further improve the transparency of such polypropylene films, and were surprised to find that the transparency of polypropylene films was improved by combining specific additives among conventional additives. The present invention was achieved by discovering the fact that the That is, the present invention provides 1 in polypropylene resin.
・3・2.4 Dibenzylidene-D-sorbitol and alkylene bisamide are added to this polypropylene film with excellent transparency.

By adopting such a configuration, it was possible to provide a polypropylene film with excellent surface smoothness and excellent transparency evaluated by haze visible light transmittance and small angle scattered light transmittance.

The polypropylene resins used in the present invention include polypropylene homopolymers, copolymers of propylene and other olefins such as ethylene and butene, and polypropylene and other olefins such as polyethylene, ethylene-propylene copolymers, butene-propylene copolymers, etc. It is a polypropylene resin consisting of a mixture with polybutene, etc.

In the case of a copolymer, the propylene component accounts for 80% or more of the total weight%, preferably 90% or more, and in the case of a mixture, the polypropylene weight ranges from 20 to 80% depending on the other polymers to be mixed. However, in order to improve moldability when subjecting to molding, butene-propylene copolymer or ethylene-propylene copolymer is added to polypropylene.
Preferred examples include those containing a propylene copolymer. The alkylene bisamide of the present invention is a compound represented by the following general formula.

(However, R1 is an alkylene group having 1 to 20 carbon atoms, and R2 and R3 are an alkyl group, an allyl group, or an aryl group having 2 to 30 carbon atoms.

) Specific examples of such compounds include ethylene bis stearylamide, methylene bis octadecanamide, methylene bis hexadecanamide, 1◆4-phenylene bis octadecanamide, and the like.

From the viewpoint of colorability and transparency, such a compound is added in an amount of 0.1 to 0.6 parts by weight, preferably 0.15 to 0.5 parts by weight, per 100 parts by weight of the polypropylene resin.

1,3,2,4-dibenzylidene-D-sorbitol, which is another additive of the present invention, must be contained in the polypropylene resin at the same time as the alkylene bisamide (hereinafter referred to as additive B).

In terms of smoothness and transparency, the amount of sorbitol added is 0.1 to 0.1 to 100 parts by weight of the polypropylene resin.
6, preferably 0.15 to 0.5 parts by weight. Therefore, the total amount of such additives added is 0.2 to 1.2 parts by weight, and in the case of the present invention, the total amount added is more preferably 0.3 to 1.2 parts by weight.
0.4 to 0 for scolding. Parts of saliva (based on 100 parts by weight of resin)
It is effective to mix within this range. The composition of such additives may be such that both additives are mixed and contained at the same time, but 1.3◆2●4-dibenzylidene-D
- Sorbitol (hereinafter referred to as Additive A)-rich, that is, it is preferable to use Additive A as the main ingredient. Specifically, the amount of Additive A is 5% or more and particularly 54% or more and 75% by weight or less of the total amount of additives. A blended one is better.

In a more optimal embodiment, additive A is 60 to 75% by weight.
It is a combination. In this way, additive A. ．． When B is blended with a polypropylene resin, a film with excellent transparency can be obtained at any stage from unstretched to biaxially stretched polypropylene film due to the synergistic effect of both.

On the other hand, if Additive A is added alone in an amount exceeding 0.3 parts by weight to 100 parts by weight of polypropylene resin, (1) it will bleed out onto the film surface during melt extrusion, significantly impairing the surface smoothness of the film; , (2) The compatibility and dispersibility with the polypropylene resin deteriorates, and domains of additive A are formed, resulting in the cast PP-N
The overall transparency of the O film deteriorated significantly, and the PP-(1) film obtained by biaxially stretching it also had poor transparency.

However, if additive B is present at the same time, the compatibility and dispersibility of both additives in the polypropylene resin will be greatly promoted, and the transparency will not only be improved, but also the film surface will be smoothed during melt extrusion. This has the effect of making the film form (edge molding tool and thickness unevenness) extremely good. Next, a method for manufacturing the film of the present invention will be illustrated.

Appropriate amounts of Additive A and Additive B are blended with a mixer to 100 parts by weight of polypropylene resin, pelletized if necessary, and heated and melted at 250 to 300°C using an ordinary extruder to obtain a thickness of 100 to 1000 PTT1. Make an unstretched film.

The transparent PP-NO obtained in this way may be used as it is as a sheet, or it may be formed by vacuum forming, pressure forming, etc. and used for food, frozen desserts, cakes, and pharmaceutical containers. . The PP-NO according to the present invention is
At the same time, it has excellent transparency before molding,
The transparency after molding is also extremely good. Such PP-N
The O film can further be uniaxially or biaxially stretched.

The stretching temperature is usually 100 to 160°C, and the stretching ratio is 4 to 12 times. A method of stretching in the direction and then stretching in the vertical direction,
Alternatively, one of two methods is adopted: stretching both vertically and horizontally at the same time.

After stretching, it is heat treated at 140-165°C for 2-1@.
This heat treatment may be carried out under tension, or may be carried out in the stretching direction, or by 3 to 15% in the stretching direction.
It may be done while providing some relaxation. Thus obtained 10~
100pm transparent PP-BO is suitable for packaging, albums,
Used for applications such as adhesive tape bases.

The PP film thus obtained is ASTM-D-10
The haze value of PP-NO with a thickness of 300 pm measured in 2003-61 was far below the maximum value of 19% shown by the mixture containing additive A or B alone, and even below 15%.
Improved to 0% or less, also ASTM-D-1746
The small-angle scattered light transmittance within 0.054 of scattered light for a stack of 8 sheets of PP-BO with a thickness of 40 μm measured in the -6th edition is at most 50% at the highest value of additive A or B alone.
On the other hand, the film of the present invention has significantly improved transparency, exceeding this 50% line, 60% and even 70%, and is an extremely practical film.

Examples and comparative examples are shown below, but the present invention is not limited thereto. Example 1 Polypropylene pellets FS-20 manufactured by Sumitomo Chemical Co., Ltd.
1,3,2,4-dibenzylidene-D-sorbitol manufactured by EC Chemical Industry Co., Ltd., ゜"EC-F" and Kao for 10 parts of saliva ([η] = 2.04) Soap Co., Ltd.
Ethylene bis stearylamide (hereinafter referred to as EBA) manufactured by Manufacturer Co., Ltd. was dry blended in a Henschel mixer with varying amounts of each, and after pelletizing at 2800C,
The melted product was heated to 300°C and discharged from the extruder nozzle, and then cast onto a cooling roll with a roll surface temperature of 60°C to a thickness of 3.
An unstretched sheet with a thickness of 00 μm was prepared.

To evaluate the transparency of these sheets, the haze of one sheet was measured using a haze meter SER-H model manufactured by Nippon Seimitsu Kogaku Co., Ltd. The results are shown in Table-1. From Table 1, it is clear that the effect of improving transparency due to the mutual action of the two additives. The haze value in Table 2 clearly shows the transparency effect of the additive.

Moreover, the measured value of gel fraction indicates that gelation, that is, three-dimensional crosslinking, is not performed in the present invention. Example 3 A PP chip used in Example 1゜"Fs-201r17
5 parts by weight and the ethylene-propylene copolymer (propylene component: 96% by weight) chips used in Example 2 "FA-"
641r' chips, 25 parts by weight were mixed by dry blending, and 1, 3, 2,
4-Dibenzylidene - Missing Example 2 To 10 parts of the raw material composition shown in Table 2, a fixed amount of the same two additives as in Blood Example 1 was added, and a case where they were not added. A sheet with a thickness of 300 μm was made in the same manner as in Example 1, and the haze and gel fraction were D-Sorbitol 0. 0.2 parts by weight of ethylene bis stearylamide was added and pelletized to 29
A sheet with a thickness of 300 μm was prepared by melt extrusion at 0°C.

As a comparative example of 3A, a sheet having a thickness of 300 pm was prepared using the same method as A without adding dibenzylidene sorbitol and ethylene bis stearylamide.

20 parts by weight of "FS-201" and 75 parts by weight of the butene-1-propylene copolymer ([η] = 2.18, propylene component: 92.5% by weight) chip "JSB-G" used in Example 2 The same additives as described in A were added in the same manner to 10 parts of the mixture with A to prepare a sheet with a thickness of 300 μm.

As a comparative example of DC, a sheet with a thickness of 300 prrL was prepared using the same raw materials as C above, but without the addition of additives.

The transparency of the above-mentioned four types of sheets (molded body raw fabrics) was evaluated by haze measurement, and then vacuum forming was performed using a vacuum pressure forming machine model C-3 manufactured by Kansai Automatic Forming Machinery Co., Ltd.

The molding mold has a diameter of 100Tnm and a depth of 30wr! A cup-shaped molded product was made using No. n, and after molding, the transparency of the center of the bottom of the cup was evaluated by haze measurement. In addition, for the appearance evaluation of the molded product, a comprehensive judgment was made regarding the thickness unevenness of the corner walls and bottom, and the presence or absence of vacuum holes. Table 2 of the results
It was shown to. According to Table 3, the examples of the present invention have excellent transparency after molding. Moreover, there is no disadvantage in terms of appearance due to the effect of adding transparency according to the present invention. Example 4 1, 3, 2, and 4 described in Example 1 were applied to 10 parts of isotactic polypropylene chip ゜゛JS-1429゛ ([η] = 2.25) manufactured by Mitsui Toatsu Co., Ltd. -dibenzylidene-D-sorbitol 0.4 parts by weight and ethylene bisstearylamide 0.4 parts by weight. weighing section, and betaine antistatic agent "TPA-5028"0 manufactured by Sanyo Chemical Co., Ltd.
．． Mixer blend 5 parts by weight at 100°C,
After petalizing at 60°C, this was melt-extruded at 280°C to form a sheet, which was cast into a cooling drum at 60'C and solidified by cooling.

This unstretched sheet was preheated to 115° C., and then stretched 5.0 times in the longitudinal direction while locally heated with an infrared heater. This uniaxially stretched film was fed into a stenter, preheated to 160°C, and then stretched at 165°C in the width (horizontal) direction.
It was stretched 5 times. Next, heat treatment was performed at 163°C for 2 seconds in a stenter while maintaining tension in the width direction, and then 8% in the width direction.
Heat treated at 164°C for 3 seconds while allowing relaxation to a thickness of 25
．． A 60 μm (7) PP-BO was made. After this film was pulled out from the stenter, both sides were subjected to corona discharge treatment at 70° C. to give a surface critical tension of 43 dynes/Cm. As a comparative example, a 25.60 prrL. I made a PP-BO.

The film thus obtained had the characteristics shown in Table 4. The results of haze and small-angle scattered light transmittance shown in Table 4 show that the examples of the present invention have extremely excellent transparency.

Furthermore, it was confirmed that none of the samples had undergone gelation (three-dimensional crosslinked structure). Also, slipperiness,
The anti-blocking property and antistatic property were so good that they did not detract from the properties of the conventionally treated product (comparative example). Example 5 A composite film was made using the following method.

A film uniaxially stretched in the longitudinal direction in the same manner as in Example 4 was
It was wound around a cooling drum at 0° C., and the following mixture was melt-extruded on one side of the drum at 270° C. from another extruder to form a composite layer. The two-layer sheet thus obtained was fed into a stenter, stretched in the width direction in the same manner as in Example 4, and subjected to tension heat treatment.
A two-layer composite stretched film was prepared by allowing relaxation heat treatment.

The thickness of the two layers was 20 μm for the biaxially stretched layer and 5 μm for the uniaxially stretched layer in the width direction, resulting in a total thickness of 25 μm.
As a comparative example, a two-layer composite resin having the same thickness as in the example was prepared without adding 1,3,2,4-dibenzylidene-D-sorbitol and ethylene bisstearylamide to both layers.

The film thus obtained had the characteristics shown in Table 5.

From Table 5, it is clear that the examples according to the present invention had extremely excellent transparency and a heat sealability of 30 minutes.

In addition, it was confirmed that gelation (three-dimensional crosslinked structure) was not formed in this example as well.

Example 6 Under the same film forming conditions as Example 4, the thickness was 40μ7TL3.
I made a PP-BO.

Claims (1)

[Claims] 1. A highly transparent polypropylene film made by adding 1,3,2,4-dibenzylidene-D-sorbitol and alkylene bisamide to a polypropylene resin.