JP2001002808A - Degradable plastic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a degradable plastic film that has good adhesion to a printing ink and prevents the blocking which occurs when it is processed and whose transparency can be positively held by forming a coating film layer comprising a mixture of a thermoplastic polyester resin and a cellulose derivative on a surface of the film. SOLUTION: A mixing ratio (wt.%) of a polyester resin to a cellulose derivative is preferably 50:50-80:20. As a polyester resin, a thermoplastic saturated polyester resin produced by polycondensation of a dicarboxylic acid component and a diol component is preferable and especially, copolymerized polyester resin produced by copolycondensation thereof is more preferable but it is not necessarily limited to these resins. As a cellulose derivative, a nitrocellulose, an acetyl cellulose, a methyl cellulose, an ethyl cellulose or a mixture thereof can be used and among them a nitrocellulose is particularly preferable. The coating film layer is preferably as thin as possible, taking the environmental load at the time of its degradation into consideration and the film thickness of the coating film layer is preferably in a range of 0.1-5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a decomposable plastic film having good adhesion to various printing inks.

[0002]

2. Description of the Related Art The greatest advantage of plastic is that it is stable against heat and light and is hardly deteriorated. However, the advantage is disadvantageous when it becomes dust after use. When this is left in a natural environment, it remains semipermanently, and thus disposal is a problem. Degradable plastics have been attracting attention as a solution to this problem. This plastic can be used in the same way as conventional petit sticks.After use, it is degraded by microorganisms living in the soil and water when left in the natural environment and eventually decomposed into carbon dioxide and water. Have. Recently, films using this degradable plastic have been developed, and films made from 3-hydroxybutyric acid / 3-hydroxyvaleric acid copolymer, polycaprolactone, polyvinyl alcohol / starch complex, polylactic acid and the like are used. In particular, polylactic acid-based films, which are aliphatic polyesters made from fermented lactic acid and have excellent mechanical properties and processability, have attracted attention.

[0003] However, these degradable plastic films have limited applications because of their low adhesion to printing inks and the like. Lamination of a polyester resin layer or a polyester resin / isocyanate resin layer is also performed to improve the adhesiveness. However, since the decomposable plastic film has low thermal stability, it is necessary to dry these resin layers. The temperature could not be raised, and blocking occurred due to insufficient curing of the resin. An ink layer comprising a filler such as silica and an organic solvent is also formed on a thermoplastic saturated copolymerized polyester resin (see Japanese Patent Application Laid-Open No. 10-120811). There was an inconvenience that the feeling was reduced.

[0004]

The object of the present invention is to provide a degradable plastic film which has good adhesion to printing ink, prevents blocking during processing, and makes it possible to ensure the transparency of the film. is there.

[0005]

Technical means The technical means for solving this technical problem is to provide a coating layer made of a mixture of a thermoplastic polyester resin and a cellulose derivative on the surface of the film. As described above, the decomposable film has low thermal stability, and the drying conditions of the coating layer formed on the surface cannot be set high. Blocking due to insufficient drying is liable to occur with only a polyester resin alone. By mixing a cellulose derivative, the drying conditions of the coating film layer can be kept low, so that the resin can be cured at a low temperature. Therefore, blocking of the film can be prevented.

The polyester resin is preferably a thermoplastic saturated polyester formed by polycondensation of a dicarboxylic acid component and a diol component, particularly a copolymerized polyester resin to be subjected to copolycondensation, but is not limited thereto. Cellulose derivatives are compounds derived from polysaccharides / cellulose, which are the main components of plant cell walls, chemically modified to part or all of the hydroxyl groups of cellulose. Nitrocellulose, acetylcellulose, methylcellulose, ethylcellulose and the like and mixtures thereof are used. In particular, nitrocellulose which is a nitrate ester can be suitably used.

The mixing ratio (% by weight) of the polyester resin and the cellulose derivative in the coating layer formed on the surface of the decomposable plastic film is preferably from 50:50 to 80:20, more preferably from 60:40 to 50:50.
A range of 70:30 is more preferred. If the mixing ratio of the polyester resin exceeds 80% by weight, there is a risk that blocking occurs during processing and the like, and if the mixing ratio of the polyester resin is less than 20% by weight, the adhesiveness with a printing ink or the like may be reduced. . The film thickness of the coating layer is preferably as thin as possible in consideration of the environmental load at the time of decomposition, and is desirably kept within the range of 0.1 to 5 μm. When the thickness is less than 0.1 μm, the adhesiveness to the ink is insufficient, and when the thickness is 5 μm or more, the adhesion between the decomposable film and the coating layer may be weakened.

Various additives such as antioxidants, ultraviolet absorbers, lubricants, pigments, organic or inorganic fine particles,
Fillers, plasticizers, antistatic agents and the like can be added. In particular, those to which inorganic particles are added are preferable because surface lubricity and blocking resistance are improved, and silica, alumina, talc, mica, calcium carbonate and the like can be suitably used. These inorganic particles have an average particle size of 0.01 to
The mixing ratio to the resin in the coating layer is not particularly limited, but is preferably 0.01 to 1% by weight. When the compounding ratio is large, the transparency of the film may be deteriorated.

For forming the coating layer on the surface of the decomposable plastic film, various coating methods such as a reverse coating method, a gravure coating method, a bar coating method and a die coating method can be used. It is necessary to pay attention to the thermal stability of the decomposable film as the drying temperature condition of the coating film.
It is desirable to set the temperature to not more than ° C. As the degradable plastic film, a biaxially stretched one can be used.
By subjecting the surface of the decomposable film to a corona discharge treatment or the like before forming the coating layer, the adhesiveness between the coating layer and the decomposable film can be improved. The formation of the coating layer on the decomposable plastic film may be performed on one side or both sides. The thickness of the entire film is not particularly limited, but is 10 to 300 μm as in a normal film.
When m is used, workability is good.

<Test Example> A polylactic acid film (Mitsui Chemicals, Lacia 25 μm) was used as a degradable plastic film, a thermoplastic saturated copolymerized polyester resin (Toyobo: Byron 200) was used as a polyester resin, and nitrocellulose was used as a cellulose derivative. And a resin (Joint Ink Co., Ltd .: K-1 varnish) in a weight ratio (%) of 70:30, and silica (Mizusawa Chemical Industry Co., Ltd .: Silnex) as inorganic particles was contained at 0.05% by weight based on the resin. The solution was applied on one side of the film to form a coating layer having a thickness of 1 μm (Example 1). Further, the resin mixture ratio (% by weight) of the mixed solution forming the coating layer was 50:50 (Example product 2) and 60:50, respectively.
A degradable plastic film was obtained in the same manner as in Example 1 except that the ratio was set to 40 (Example 3) and 80:20 (Example 4). Embodiment 1 As a comparative example with respect to the above-mentioned embodiment, the embodiment 1 is the same as the embodiment 1 except that the resin of the solution for forming the coating film layer is formed of the polyester resin alone (Comparative Example 1) and the nitrocellulose resin alone (Comparative Example 2). A decomposable plastic film was formed in the same manner as described above. Further, a decomposable plastic film was formed in the same manner as in Example 1 except that the thickness of the coating layer was changed to 10 μm (Comparative Example 3).

An untreated film was added to the above-mentioned embodiment film and comparative example, and the following 1) blocking resistance test and
2) The results of the printing ink adhesion test are shown in [Table 1].
It became what was shown in. 1) Blocking resistance test A film cut to a width of 50 mm was prepared, and the coating layer was superimposed on the non-coating layer non-formed surface on the opposite side, and under a load of 4 kgf / cm2 at 40 ° C. and 90% RH. After processing for 24 hours, the film was peeled off and evaluated. (○: No change △: Sound
×: Film destruction) 2) Printing ink adhesion test 161 black ink for offset (T
& K) was applied with a thickness of about 1 µm, a cellophane tape (Nichiban 24 mm width) was applied, and after leaving for 3 minutes, it was peeled off at a stretch in the 90 ° direction, and the residual ratio of the ink was visually evaluated.
(○: 80% or more △: Less than 80% 50% or more ×: 50% or less) [Table-1]

[0102]

[Effect of the Invention] By providing a coating layer of a specific mixing ratio comprising a thermoplastic polyester resin and a cellulose derivative on the surface of a decomposable plastic film, it has good adhesion to printing ink and the like, and has a blocking property during processing. And decompose after use to obtain a degradable plastic film having a low environmental load. Further, since the adhesion to the printing ink can be ensured without mixing a filler or the like, there is an advantage that printing can be performed while maintaining the transparency of the film. It can be used for various purposes such as packaging, miscellaneous goods such as labels, and does not accumulate in the natural environment even if discarded after use.

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Claims (2)

[Claims] 1. A decomposable plastic film having on its surface a coating layer made of a mixture of a thermoplastic polyester resin and a cellulose derivative. 2. The decomposable plastic film according to claim 1, wherein the mixing ratio (% by weight) of the polyester resin and the cellulose derivative is 50:50 to 80:20.