JPS5940110B2 - Method for manufacturing polyolef in film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a composite polyolefin film in which both sides of the film have different slipperiness and the slipperiness does not easily change over time.

Conventionally, in the field of packaging materials, the inner surface of the film has a suitable baseness to maintain packaging suitability, while the outer surface of the film has a base property that is difficult to maintain from the viewpoint of transportation and storage after packaging, as well as mechanical adaptability during packaging. Films with physical properties have been developed.

For example, when forming a film, the temperature of the die slip in contact with the inner surface of the film is made higher than that in contact with the outer surface, that is, the temperature of the die slip is changed to make the slipperiness of the front and back surfaces of the film different. A method of coextruding a resin with good slip properties on the side that corresponds to the outer surface and a resin with poor slip properties on the side corresponding to the outer surface to make the slip properties of the front and back sides of the film different, or printing with low slip properties on one side of a regular film. Methods such as applying a non-slip substance such as ink or hot melt adhesive to make the slipperiness of the front and back surfaces different have been used. However, the method of changing the temperature of the die slip causes roughness, for example, which is unfavorable for the appearance of the film, and the coextrusion method requires the use of different types of resin, making the film production complicated and costly. In addition, the method of applying a non-slip material increases the number of film manufacturing steps and requires the installation of special equipment, which does not necessarily mean that it can be used as a general packaging material. It couldn't have been a certain film.

In the present invention, by laminating a polyolefin resin film containing a slip agent and a polyolefin resin film not containing a slip agent, and then performing a simple treatment, the slip properties on both sides of the film are different, and this slip property changes over time. It was discovered that a composite polyolefin film that is difficult to change could be obtained, and the present invention was completed.

That is, the gist of the present invention is to provide a method for producing a polyolefin film, which comprises laminating a polyolefin resin containing a slip agent and a polyolefin resin not containing a slip agent into a film, and heat-treating the resulting composite film. Exists.

Generally, films obtained by laminating synthetic resins containing slip agents and synthetic resins that do not exhibit a phenomenon called bleed or blooming, in which the slip agent changes over time from the resin layer containing the slip agent to the resin layer not containing the slip agent. transition,
It was also known that when heated, the film transfers more quickly, and the film surface of the resin layer that does not contain a slip agent becomes extremely slippery, and that when left at room temperature for a long period of time, there is no difference in slipperiness between both sides of the film. The present invention is completely different from the conventional wisdom, and the present invention is to laminate a polyolefin resin containing a slip agent and a polyolefin resin without a slip agent into a film, and to apply the resulting composite film immediately or to a slippery film on both sides of the composite film. Even when the difference in properties disappears, heat treatment usually makes the resin layer containing a slip agent slippery, while the resin layer that does not contain a slip agent becomes extremely slippery, and the slipperiness of both surfaces of the film becomes relatively slippery. It was found that this difference in slipperiness did not change easily over time.

To explain the present invention in detail, polyolefin resins that can be used in the present invention include low density polyethylene, high density polyethylene, polypropylene, ethylene-propylene copolymer, ethylene monovinyl acetate copolymer, polybutene, polyolefin resin,
4-Methylbenzene-1 or a mixture of these resins, or a mixture of these resins with a small amount of other resin such as polyethylene, polyvinyl chloride, etc., can be used. In the present invention, these resins and a composition in which a slip agent is added to these resins are laminated in the form of a film, and each resin to be laminated is preferably the same resin, but is particularly limited to this. This is not the case, and the effects of the present invention can be expected even with different types of resins. Also, in the present invention, among these resins, lamination of low density polyethylene or ethylene monovinyl acetate copolymer, especially lamination of low density polyethylene is preferred. On the other hand, as the slip agent contained in the polyolefin resin, long-chain fatty acid amides are usually used, and among these, fatty acid amides having 12 to 22 carbon atoms are preferably used because they tend to produce a difference in slipperiness between both sides of the film.

Specifically, lauric acid amide, myristic acid amide,
Examples include palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, and the like. Of course, two or more of these slip agents can be used in combination. In particular, fatty acid amides having 18 or more carbon atoms are preferred. The amount of the slip agent contained in the polyolefin resin depends on the thickness of the resin layer containing the slip agent, but it is usually preferably 300 to 3000 PF.
Further, the slip agent may be incorporated into the polyolefin resin by any conventional method, for example, by kneading it during the production of polyolefin resin pellets or during film molding. Methods for laminating a polyolefin resin containing a slip agent and a polyolefin resin not containing the slip agent include an inflation method, a calendering method, or T.
- A method in which films are molded from a polyolefin resin containing a slip agent and a polyolefin resin not containing the same using a die method, and one of the molten resins is interposed between the two films to form a composite; A method in which a film is formed using an inflation method, a calendar processing method, or a T-die method, and the other resin is laminated onto the film using a T-die method to form a composite. - Various methods have been adopted, such as coextrusion using a die method, and compositing by melt bonding inside or outside the die.Among these, the coextrusion method is preferred in consideration of workability, ease of compositing, reliability, etc. This is the most preferred method. Although the thickness of the film cannot be determined depending on the various uses, it is selected from the range of 5 to 300μ, for example, 150 to 250μ for heavy bags for packaging fertilizers, etc., and 150 to 250μ for rice bags. The film used is 60 to 100 microns, and the film used for sugar bags and salt bags of about 1k9 is about 50 to 70 microns. The ratio of the thickness of the slip agent-containing resin layer to the total thickness of the film is preferably 11 to 70%, particularly 15 to 60%, since this creates a clear difference in the slipperiness on both sides of the film. The product of the film thickness and the slip agent content of the film forming the polyolefin resin layer is 4.
It is preferable that it is 500Pβ·μm and 15000PI10·μm.

In other words, since slip agents exhibit a blooming phenomenon, if the thickness of the resin layer containing the slip agent is thick, the slip agent will migrate to the film surface more often, resulting in a decrease in the amount of slip agent added; In some cases it may be necessary to increase the concentration of the slip agent. The present invention resides in heat-treating the composite film laminated in film form obtained as described above.

The degree of heat treatment is related to the heat treatment temperature and heat treatment time. For example, the higher the treatment temperature, the shorter the treatment time, but if the temperature is too high for productivity reasons, the molecular orientation during film forming may be affected. It disappears and becomes a film with weak strength.
In addition, the film may be partially melted and the appearance of the film may be impaired. On the other hand, if the heat treatment temperature is low, it will take an extremely long time and is not industrially advantageous. Therefore, the treatment temperature is preferably 40°C or higher and lower than the melting point of the polyolefin resin, preferably 50°C or higher and 10°C lower than the melting point of the polyolefin resin.
It is better to use a lower temperature. Specifically, for example, 4
At 0°C, for 5 hours or more, preferably for 10 hours or more, 5
At 0°C, the heating time is 30 minutes or more, preferably 1 hour or more, and at 80 to 120°C, the heating time is 10 seconds or more and 120 seconds or less. As a heat treatment method, the composite film is continuously introduced into a heating device maintained at a predetermined temperature, and passed through it for a predetermined time.

As the heating device, a hot air tank, a dry hot air tank, an infrared heater, a heat roll, etc. can be used, and the important thing is that it is a device that can uniformly heat the entire surface of the film. Although the reason for the composite polyolefin film obtained by the method of the present invention is not clear, the coefficient of static friction after heat treatment of the resin layer containing a slip agent becomes smaller, and the coefficient of static friction after heat treatment of the resin layer containing no slip agent becomes smaller. The coefficient of static friction after treatment, which once decreased over time, increases again, and the coefficient of static friction decreases over time.
The coefficient of static friction is greater than that of the subsequent resin layer that does not contain a slip agent.

As a result, there is a large difference in the slipperiness between the two surfaces of the polyolefin film. Moreover, even if this is left for a long period of time, the effect on the slipperiness is small. In addition, bags made from the polyolefin film obtained by the present return method have different slipperiness on the inside and outside surfaces of the bag, so the inside surface is slippery, making it suitable for packaging, for example, when packaging fertilizers. Its non-slip outer surface makes it extremely convenient for transportation and storage, and it has extremely high utility value as a material for various packaging bags.

The method of the present invention will be specifically explained with examples, but the method of the present invention is not limited to the following examples unless it departs from the gist thereof. In the Examples, evaluation of slipperiness was expressed in terms of coefficient of static friction (COF).

COF is a friction angle tester (Fricti)
The slip start angle θ was expressed as Tanθ using OnAngleTester (manufactured by Toyo Seiki). Examples 1 and 2 Two extruders connected to a die for coextrusion of low density polyethylene (density 0.924, MI 2.0) and the low density polyethylene to which oleic acid amide 900 pus was added A composite blown film of 30 μm was obtained which was bonded in the die at an extrusion temperature of 160° C. and a pull-up ratio of 1.5.

The thickness of each resin layer was adjusted by changing the extrusion rate. For the film obtained, CO for the following:
F was measured and shown in Table 1. 1 Film after 10 minutes of film formation Film No. 32 was left in a constant temperature room at 220°C for one week. Heat treated in a dryer at 50°C for 2 hours. After 10 minutes, film No. 43 was left in a constant temperature room at 20°C for one week. Film after being left to stand From these results, in Example 1, the COF was relatively high on both sides of the film immediately after film formation because the slip agent had not yet sufficiently migrated to both sides of the film, but when the film was left to stand at 20°C for a week, the slip agent It can be seen that the COF has shifted to both sides, and the difference in COF between both sides has disappeared.

This has a large absolute amount of slip agent (900 PPI [l×
This is thought to be due to the 12 μm 10800 PPI1 μ).
When this film is heat-treated, the COF of the layer that does not contain a slip agent increases and does not change much over time. In Example 2, the absolute amount of the slip agent is smaller than in Example 1 (900PFX5μ=4500ppIn・μ), so the change is small, but the difference in COF after heat treatment on both sides of the film is larger than in Example 1, which is also the case in Example 2. It can be seen that this shows the same tendency as 1.

Examples 3 to 7 Composite films were manufactured by repeating the same method as in Example 1, and heat treated under the heat treatment conditions shown in Table 2.
The coefficient of static friction was measured for the film in the case of .

Claims (1)

[Claims] 1. A method for producing a polyolefin film, which comprises laminating a polyolefin resin containing a slip agent and a polyolefin resin not containing a slip agent into a film, and heat-treating the resulting composite film.