JPH03231837A - Ultraviolet light absorbable stretched film - Google Patents

Abstract

PURPOSE:To lessen the rate of volatilization of ultraviolet light absorber and its initial loadings by a method wherein skin layer, which contains no ultraviolet light absorber, is laminated onto both sides of ultraviolet light absorber- containing core layer and, after that, the resultant layer is stretched at least uniaxially into film. CONSTITUTION:Skin layer, which contains no ultraviolet light absorber, is laminated onto both sides of ultraviolet light absorber-containing core layer and, after that, the resultant layer is biaxially or longitudinally and laterally stretched so as to produce ultraviolet light absorbable stretched film. As the stock material constituting the core layer, concretely polypropylene, polyfethylene terephthalate, polyamide or the like is exampled. As the preferable ultraviolet light absorber added to the core layer, 2, 2'-dihydroxy-4- methoxybenzophenone or the like is exampled. The preferable loadings to the core layer are about 0.05 - 1.2 wt.%. As the stock material constituting the skin layer, concretely, polyethylene, polybutene or the like is exampled.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an ultraviolet absorbing stretched film having excellent ultraviolet ray blocking ability.

<Prior art> Many ultraviolet absorbing films made by adding ultraviolet absorbers have been seen here and there, but these are mainly single films, and these single films undergo a stretching process to reduce the heat generated during the stretching process. Due to this action, the ultraviolet absorber sublimates from the surface, making it impossible to obtain sufficient effects.

On the other hand, if the mixture is large enough to be effective, problems such as poor film-forming properties and staining caused by sublimable substances during stretching may occur.

Furthermore, there are some cases in which a UV-absorbing film is used in only one layer of a two-layer stretched film, but when a UV-absorbing film is used in only one layer, there may be some improvement over a single-layer film. Again, volatilization of the ultraviolet absorbent during the stretching process poses a problem.

<Means for Solving the Problems> The present inventors have solved these conventional problems, and have achieved maximum efficiency with the addition of a small amount of ultraviolet absorber, as well as excellent M film performance and no staining during stretching. The present invention was finally arrived at as a result of various studies on UV absorbing stretched films that do not generate UV light, and its feature is that surface layers that do not contain UV absorbers are laminated on both sides of a core layer that contains UV absorbers. It has a configuration in which it is stretched in at least the l-axis in the state.

Next, the means for solving the problem will be explained in more detail.

The ultraviolet absorber according to the present invention is added only to the core layer, and the amount added may be arbitrary, but it is generally 0.105 to 2%, preferably 0.1 to 0.0%, based on the resin weight.
It is about 8 yen amount%. In the case of a stretched film, at least about 11 to 2% by weight of O is generally required, and from this point of view as well, the present invention can reduce the preferred usage type. Of course, the amount added depends on the compatibility with the resin,
It should be determined in consideration of film forming performance, prevention effect, and other factors, and the following values are not particularly limited.

There are no particular restrictions on the ultraviolet absorber, but examples of organic UV absorbers include hesiphenones such as 2,2'-dihydroxy-4-methoxybenzophenone and 2-hydroxy-4-n-octoxybenzophenone, p- - Salicylates such as butylphenyl saleylate, 2.4
- C-1-butyl phenyl-35 - C-1-butyl-4
-benzoates such as hydroxybenzoate, 2-
Benzotriazole series such as (2'-hydroxy-3°,5°-di-amyluphenyl)hencytriazole, 25-bis-[5°-1,-butylbenzoxazolyl-(2)]-thiophene There are no particular limitations, and examples include thiophenes such as thiophenes, etc., and it is of course possible to use m products or a combination of two or more of these.

The material used for the core layer is not particularly limited, but examples include polypropylene, polyethylene terephthalate, polyamide, etc., and the thickness may be set arbitrarily, but is usually about 5 to 70 microns. As a preferable material, crystalline polypropylene can be exemplified, and in this case, the melt flow ratio is not particularly limited, but can be exemplified as O15 to 3.0.

There are no particular restrictions on the material used for the surface layer, but olefins such as ethylene-propylene copolymer, polyethylene, polybutene, modified polyethylene, ethylene-vinyl acetate copolymer, propylene-butene copolymer, ethylene-butene copolymer, etc. Examples include polymers having a melting point lower than that of the polymer used for the core layer. Preferred materials are based on ethylene-propylene random copolymers and/or propylene-butene random copolymers containing 1t to 10 mol% of ethylene, and if necessary, appropriate resins such as those olefin-based as mentioned above may be optionally added. I can list the things that are mixed in. On this occasion,
The above-described ethylene-propylene copolymer preferably has an ethylene content of 2 to 7 mol% and is random, and its melt flow ratio is also not particularly limited, but is 3 to 2 mol%.
An example of such a copolymer is 0 type, and a more preferred example of the propylene-butene random copolymer mentioned above is one with a propylene content of 55 to 80 mol% and randomness. One of the surface layers may be based on an ethylene-propylene random copolymer containing ethylene at 1-10 mol%, and the other surface layer may be based on a propylene-butene random copolymer, and the surface layer may also be based on a propylene-butene random copolymer containing ethylene at 1-10 mol%. A propylene-butene random copolymer may be included in the ethylene-propylene random copolymer base, or conversely, an ethylene-propylene random copolymer with an ethylene content of 1 to 10 mol% It may contain a copolymer as appropriate. Furthermore, the surface layer may function as a heat-sealing layer, and its thickness is not particularly limited, but is typically about 1 to 10 microns.

There are no particular restrictions on the lamination method for the core layer and surface layer (e.g. coextrusion method or extrusion lamination method) After lamination by an appropriate method, it is necessary to stretch at least in the l-axis, preferably the core layer is biaxially stretched. In addition, it is desirable that the surface layer is stretched at least in the l-axis.

As a specific embodiment, after laminating both surfaces of the 037 layer and the surface layer, biaxial stretching is carried out in the longitudinal and lateral directions.After laminating one of the surface layers on the 097 layer, stretching in the longitudinal direction, and then laminating the other surface layer. Examples include a structure in which the core layer is stretched in the longitudinal direction, and then a surface layer is laminated on both surfaces and stretched in the transverse direction, but the present invention is not limited to these.
Other appropriate aspects may be adopted in accordance with the spirit of the present invention.
rJ Noh. At this time, in the embodiments (1) and (2) above, one or both sides of the core layer are directly exposed to the stretching process during longitudinal stretching, but even in such cases, the surface area becomes particularly large.
Since it has a surface layer on both sides during horizontal stretching when the ultraviolet absorber is likely to volatilize, it has a special effect compared to the 11-film type.
This does not change the scope of the present invention.

The film of the present invention is effective for packaging films for foods, medicines, cosmetics, etc., which deteriorate or change in quality due to ultraviolet rays, but is not particularly limited and can be used in all fields.

The above description has only described the preferred embodiments of the present invention, and it goes without saying that the present invention is not limited to these descriptions.

Next, examples of the present invention will be described.

<Example> Density 01903g/cm5, melt flow ratio 1.45
(g/lomin, 230°C) 2-(3'-t,-butyl-5'methyl-2'-hydroxyphenyl)-5-chlorohencytriazole to crystalline polypropylene relative to the polymer (resin amount) 013 double world% and 2-(5°
-Methyl-2°-hydroxyphenyl)-benzotriazole, which also contains an ultraviolet absorber containing 55% by weight of O, and a blended composition containing a small amount of a well-known antistatic IF agent, lubricant, and antiblocking agent, is extruded to form a film, An unstretched sheet of 1040μ was obtained.

On one side of this sheet, an ethylene-propylene random copolymer with an ethylene content of 4.7 mol%, a density of 01895, and a melt flow ratio of 9.0 was laminated by melt extrusion to a thickness of 1120μ.
A sheet was obtained, stretched 4 times in the longitudinal direction using a 150'c roll stretching machine, and then melt extrusion laminated with the same ethylene-propylene random copolymer as above on the opposite side to obtain a 300μ laminated sheet. Thereafter, the film was stretched 10 times in the transverse direction in a tenter at 170° C. to obtain a 30 μm ultraviolet absorbing stretched film.

At this time, the thickness of the core layer is 26μ, and the thickness of both surface layers is 2μ.
It was μ.

<Comparative Example> A biaxially stretched film having a thickness of 26 μm and consisting only of a core layer was obtained in the same manner as in the example.

Table 1 shows the volatilization rate of the ultraviolet absorber during the stretching process of the film thus obtained. As is clear from this result, the effects of the present invention are clear. In addition, the films of Examples did not show any stains due to the sublimation phenomenon of the ultraviolet absorber during stretching, but the films of Comparative Examples showed some stains during stretching.

(Hereinafter referred to as "Jiba") Table ■ <Effects of the invention> As described above, the present invention has a low volatilization rate of the ultraviolet absorber despite being a stretched film, so the initial addition amount can be greatly reduced, etc. It has a special effect. In particular, reducing the amount of ultraviolet absorber used improves film formability and has the advantage of preventing stains caused by sublimation of the ultraviolet absorber during stretching.

Claims (1)

[Scope of Claims] 1) An ultraviolet absorbing stretched film having a structure in which a core layer containing an ultraviolet absorber is laminated with surface layers not containing an ultraviolet absorber on both sides thereof, and the film is stretched in at least one axis. 2) The core layer is a biaxially stretched polypropylene film, and the surface layer is an ethylene-based film with an ethylene content of 1 to 10 mol%.
at least one based on a propylene random copolymer and/or a propylene-butene random copolymer
The ultraviolet absorbing stretched film according to claim 1, which is an easily heat-sealable layer stretched axially. 3) The ultraviolet absorbing stretched film according to claims (1) and (2), which has a configuration in which it is uniaxially stretched at least in the transverse direction.