JPH0726212A - Surface protective film - Google Patents

Abstract

PURPOSE:To obtain a surface protective film which is transparent, excellent in weatherability, and produced by a simple process. CONSTITUTION:This surface protective film is produced by successively laminating a polyolefinic resin layer contg. titanium oxide with a mean particle size of 100nm or lower, a layer comprising a polyolefinic resin alone, a layer of a modified block copolymer formed by modifying a block copolymer of an A-B-A type and/or a block copolymer of an A-B type (wherein A is a styrenic polymer block; and B is an olefin polymer block formed by hydrogenating a butadiene polymer block) with an acid, and a self-adhesive layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to protect a surface of a coated steel plate, a metal plate, a synthetic resin plate, a decorative plywood or the like, which is temporarily adhered to the surface thereof so as not to be attached with dust or scratched. The present invention relates to a surface protection film to be used, and more specifically to a surface protection film having excellent weather resistance and being transparent.

[0002]

2. Description of the Related Art In order to prevent the surface of coated coated steel plates, metal plates, synthetic resin plates, decorative plywood, etc. from being damaged or soiled during processing and transportation, a surface protective film is attached to these surfaces. ing. The surface protective film has a structure in which a pressure-sensitive adhesive layer is formed on one surface of a base material layer made of a thermoplastic resin, paper, etc. It must be easy to peel off without contaminating the surface of the body with adhesive.

Conventionally, vinyl chloride resins and polyolefin resins (polyethylene resins, polypropylene resins, etc.) are known as thermoplastic resins used for the base material layer.
Coated steel plates and metal plates are often used as building materials, and at construction sites, they are often left outdoors for a long time with the surface protective film attached. When no ultraviolet absorbing substance is added to the polyolefin resin as the base material, the polyolefin resin undergoes a deterioration reaction (crosslinking and decomposition) due to the ultraviolet rays contained in the sunlight. Part of the light passes through the base material and reaches the pressure-sensitive adhesive layer.

The pressure sensitive adhesive is deteriorated by receiving such ultraviolet rays. Acrylic adhesive has a relatively slow reaction rate, but isoprene rubber (IR) and butyl rubber (B
R), ethylene-vinyl acetate copolymer (EVA), natural rubber, styrene-butadiene-styrene copolymer (hereinafter, SBS), styrene-isoprene-styrene copolymer (hereinafter, SIS), etc. It has an unsaturated double bond and therefore deteriorates faster than polyethylene or polypropylene. Since the decomposition reaction occurs earlier than the crosslinking reaction, the apparent molecular weight decreases and the adhesive strength increases. In some cases, cohesive failure (paste residue) occurs.

Therefore, a method is known in which an organic UV absorber such as a benzotriazole type, a benzophenone type, or a salicylate type is added to the adhesive and the base material.
Such an ultraviolet absorber converts light energy into heat energy. Also known is a method of adding a light stabilizer such as hindered phenol to an adhesive or a base material. The light stabilizer causes a reaction that inactivates the generated radicals. The effects of such an ultraviolet absorber and a light stabilizer gradually decrease with the progress of the reaction, that is, with the lapse of time.

In order to prevent such deterioration of the adhesive,
A method is known in which a metal salt such as titanium oxide, calcium carbonate or the like is added to a base material so that the pressure-sensitive adhesive does not transmit ultraviolet rays to make the base material opaque (JP-A-4-153287).
No. According to such a method, about 30% by weight of metal salts such as titanium oxide and calcium carbonate is added to the base material polyolefin to make it opaque, and the adhesive layer is cohesively destroyed even if it is left outdoors for one month. It can be peeled off without doing.

[0007]

However, there are cases in which scratches, stains, etc. on the article are confirmed while the surface protective film is still attached, and in such a case, one of the required performances of the surface protective film. It is necessary that the surface protection film be transparent. As described above, the method of adding titanium oxide or the like to make the film opaque has a problem that it is not possible to confirm such scratches and stains on the article.

An object of the present invention is to provide a surface protective film which solves the above-mentioned conventional problems, is transparent, has excellent weather resistance, and can be manufactured by a simple manufacturing process.

[0009]

The surface protective film of the present invention comprises a polyolefin resin layer (a) containing titanium oxide having an average particle size of 100 nm or less, a polyolefin resin single layer (b), and a general formula: A block copolymer represented by ABA and / or a block copolymer represented by the general formula A-B (where A is a styrene-based polymer block,
B means an olefin polymer block obtained by hydrogenating a butadiene polymer block. The acid-modified block copolymer layer (c) obtained by acid-denaturing the above) and the pressure-sensitive adhesive layer (d) are sequentially laminated.

The present invention will be described in detail below. Polyolefin resin layer (a) Polyolefin resin used for the polyolefin resin layer containing titanium oxide includes polyethylene (low density, medium density, high density, linear low density), ethylene-α olefin copolymer. , Ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, polypropylene (homopolymer, random copolymer, block copolymer) and the like. Also, a mixture of these can be preferably used. In particular,
It is preferable to use polyethylene or polypropylene as a main component.

Titanium oxide having an average particle size of 100 nm or less is, for example, "MT-500HD" (trade name, manufactured by Teika), "UF07" (trade name, manufactured by Thai Oxide).
Is mentioned. The average particle size as used herein is calculated by measuring the specific surface area and assuming that the titanium oxide is a sphere. When the average particle size is 100 nm or less, particularly 50 nm or less, the surface activity increases and the catalyst may be used as a catalyst for the oxidation reaction, so a surface treatment agent is required. Lauric acid, silica, alumina, zirconia and the like are known as surface treatment agents, and among these, weather resistance is improved by using alumina and zirconia together. The crystal structure is preferably rutile. If the average particle size exceeds 100 nm, it blocks visible light and becomes opaque. The concentration of titanium oxide varies depending on the thickness of the film, but in order to prevent ultraviolet rays from penetrating the adhesive, 0.5% by weight or more at a thickness of 50 μm,
0.25 weight% or more is required at 100 μm. To be transparent, the thickness is 50 μm and 5% by weight or less, 100 μm
2.5% by weight or less is required.

If desired, a stabilizer such as an antioxidant may be added. For example, "Irganox 1010" (trade name, manufactured by Ciba-Geigy) is effective against heat deterioration.
In addition, the surface protective film has sufficient adhesiveness (temporary adhesion) and can be easily peeled off after use without being contaminated with the adhesive on the surface of various adherends. In order to ensure the stability, it is preferable to add a substance that suppresses adhesion promotion. An example is polyethyleneimine having a higher alkyl group introduced.

The method of mixing the polyolefin resin and titanium oxide is not particularly limited, but, for example, the mixture may be kneaded in advance at a concentration higher than the desired concentration, and the polyolefin resin may be added to the mixture to obtain a predetermined mixture. Adjustment to the concentration is generally performed.

For example, when the final titanium oxide concentration is 1% by weight, a masterbatch having a titanium oxide concentration of 10% by weight is prepared, and the desired master batch is kneaded with a polyolefin resin. Adjust to 1% by weight.

For the single layer of polyolefin resin (b),
As the polyolefin resin, the polyolefin resin used in the above polyolefin resin layer containing titanium oxide can be used.

Regarding the acid-modified block copolymer layer (c), the acid-modified block copolymer used in the present invention is a block copolymer represented by the general formula A-B-A and / or a general formula A-B. The block copolymer represented by
"BS") to which an unsaturated dicarboxylic acid such as maleic acid, fumaric acid, or maleic anhydride or a derivative thereof is added. It is obtained by performing a graft reaction between SEBS and an unsaturated dicarboxylic acid or a derivative thereof under melt mixing conditions such that radicals are not substantially generated in an extruder or the like. S used in acid-modified SEBS
The styrene-based polymer block A in EBS preferably has an average molecular weight of about 4,000 to 115,000, and more preferably about 8,000 to 60,000. The glass transition temperature is preferably 20 ° C. or higher. The olefin polymer block B obtained by hydrogenating a butadiene polymer block preferably has an average molecular weight of about 20,000 to 450,000, more preferably about 50,000 to 300,000. The glass transition temperature is preferably −20 ° C. or lower. A preferable weight ratio of the A component and the B component is A / B = 2/98 to 50/50, and more preferably A / B.
B = 5/95 to 30/70. The weight ratio of the general formula A-B-A block copolymer to the general formula A-B block copolymer is preferably A-B-A / A-B = 100 / 0-20.
/ 80, and more preferably ABAA / AB = 100.
/ 0 to 50/50.

Regarding the pressure-sensitive adhesive layer (d), as the pressure-sensitive adhesive, those generally used can be used, but EVA, SIS, SBS, SEBS, acrylic acid, which are widely used as pressure-sensitive adhesives for surface protection films. Ester copolymers and the like are particularly preferable.

The method for producing the surface protective film of the present invention is not particularly limited, but is a polyolefin resin layer (a) containing titanium oxide, a polyolefin resin single layer (b), and an acid-modified block. The copolymer layer (c) is preferably formed by a coextrusion method. Further, when a material that can be extruded is the main component of the pressure-sensitive adhesive, it is usually preferable to integrally produce the surface protective film by a coextrusion method. The co-extrusion molding method is advantageous in that the steps are simple and the interlaminar strength is obtained.

In the surface protective film of the present invention, the thickness of the polyolefin resin layer (a) containing titanium oxide, the polyolefin resin single layer (b), and the acid-modified block copolymer layer (c) is 30 to 30. 100 μm is preferable. The thickness of the pressure-sensitive adhesive layer (d) is preferably 5 to 20 μm.

The quality of the surface protective film includes the number of fish eyes. The causes of the fish eyes include "foreign matter" and "dust" that enter during the manufacturing process, as well as unmelted materials, gels, deteriorated materials (kogation, carbides), etc. of the raw material resin. When a mixture of a polyolefin resin and titanium oxide is used as a raw material as in the present invention, defective kneading and secondary aggregation of inorganic substances also cause fish eyes. Therefore, when the mixture is used as a raw material as in the present invention, the incidence of fish eyes increases. In the case of a surface protection film, the surface protection film may be stacked in multiple layers with the surface protection film attached to the adherend.
A load of m ² or more may take a long time. In such a case, if fish eyes are present in the surface protective film, dent marks remain on the adherend. In order to prevent the occurrence of such a dent mark, a polyolefin resin surface layer may be further used as a surface protective layer on the polyolefin resin layer (a) containing titanium oxide. By providing such a polyolefin-based resin surface layer, it is possible to reduce the occurrence rate of fish eyes, and make it possible to prevent imperfections from remaining on the adherend. As such a polyolefin resin surface layer, the same material as the polyolefin resin single layer (b) can be used,
It is preferable to mold by the coextrusion method like the single layer (b) of the polyolefin resin.

[0021]

In the surface protective film of the present invention, the polyolefin resin layer (a) containing titanium oxide is provided outside the adhesive. The polyolefin resin layer (a) containing this titanium oxide scatters the irradiated ultraviolet rays and prevents the ultraviolet rays from entering the pressure-sensitive adhesive layer (d). Therefore, deterioration of the pressure-sensitive adhesive layer (d) can be prevented, and cohesive failure (paste residue) and the like due to an increase in adhesive strength can be prevented.

In the present invention, the polyolefin resin single layer (b) is provided below the titanium oxide-containing polyolefin resin layer (a). This polyolefin resin single layer (b) is provided. Also, since the ultraviolet ray is scattered by the polyolefin resin layer (a) containing titanium oxide, the ultraviolet ray is prevented from entering, the deterioration reaction does not occur, and stable film physical properties can be exhibited for a long time.

In the surface protective film of the present invention, an acid-modified block copolymer layer (c) is further provided between the polyolefin resin single layer (b) and the pressure-sensitive adhesive layer (d). The acid-modified block copolymer layer (c) is
The interlayer strength between the single layer polyolefin resin (b) and the pressure-sensitive adhesive layer (d) is increased. That is, the adhesive is EVA,
In the case of SIS, SBS, acrylic acid ester copolymer, etc., the interlaminar strength with polyethylene or polypropylene is not sufficient, and conventionally, a polyolefin film was subjected to corona treatment or the like to form a polar group on its surface, Methods such as increasing the interlayer strength with the agent have been used. The acid-modified block copolymer layer (c) has a high interlaminar strength with the polyolefin and has a high polarity, so that it functions as a so-called anchoring agent, and as a result, the polyolefin resin single layer (b) and the pressure-sensitive adhesive layer (d) are combined. Increase the interlayer strength between.

[0024]

The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Compounding material] -Polyolefin resin: low-density polyethylene (trade name "Mirason 12" density = 0.927 g / cm ³ , MI =
3.0, manufactured by Mitsui Petrochemical Co., Ltd. ・ Titanium oxide: trade name "MT-500HD", average particle diameter of about 30 nm, treated with alumina / zirconia, manufactured by Teika Co., Ltd. ・ Acid-modified block copolymer: trade name "Tuftec M19"
43 ", manufactured by Asahi Kasei Co., Ltd.-Adhesive: Acrylic ester copolymer (butyl acrylate / ethyl acrylate / acrylic acid = 89/10
/ 1, gel fraction 93%) Example 1 As the polyolefin resin layer (a) containing titanium oxide, low density polyethylene "Mirason 12" 95% by weight and titanium oxide "MT-500HD" 5% by weight The mixture was used. This mixing is pre-kneaded with a twin-screw extruder,
A masterbatch having a titanium oxide content of 10% by weight was prepared, and this masterbatch and polyethylene were put into a single-screw extruder and supplied to a mold.

In this example, a polyolefin resin surface layer was further formed outside the polyolefin resin layer (a) containing titanium oxide. The thickness of the polyolefin resin surface layer is 20 μm, the thickness of the polyolefin resin layer (a) containing titanium oxide is 10 μm, the thickness of the polyolefin resin single layer (b) is 20 μm, and the acid-modified block copolymer layer (c). To have a thickness of 5 μm by a coextrusion method, and the pressure-sensitive adhesive layer (d) has a thickness of 10
The surface protection film according to the present invention was produced by laminating the layers to have a thickness of μm.

Regarding the obtained surface protection film, SP
After the adhesive strength and the weather resistance test, the SP adhesive strength was measured and the peeled state at that time was observed. The results are shown in Table 1. The measuring method is as follows. -SP adhesive strength; based on JIS Z0237-8.・ SP adhesive strength after weather resistance test: Stick to SP plate, JI
After performing a weather resistance test by a method based on SA1415, the adhesive strength was measured. As a tester, Sunshine Super Long Life Weatherometer WEL-
Using a SUN-TC type (manufactured by Suga Test Instruments Co., Ltd.), the black panel temperature was 63 ± 3 ° C. and the rain cycle was performed for 18 minutes in 120 minutes. -Peeling state: The state when the SP adhesive strength was measured after the weather resistance test was observed to see if the adhesive remained on the SP plate.

Comparative Example 1 A surface protective film was prepared in the same manner as in Example 1, except that the surface layer, the polyolefin resin layer (a) containing titanium oxide and the acid-modified block copolymer layer (c) were removed. The thickness of the single layer polyolefin resin (b) was 50 μm, and the thickness of the adhesive layer (d) was 10 μm. The SP adhesive strength and the like were measured in the same manner as in Example 1, and the results are shown in Table 1.

[0029]

[Table 1]

The unit of adhesive force in Table 1 is g /
It is 25 mm. As is clear from Table 1, the surface protective films of the examples according to the present invention have stable adhesive strength even after the weather resistance test, and peel off without leaving any adhesive residue, whereas the surface protective films of the comparative examples. , The adhesive strength increased after the weather resistance test, and adhesive residue was generated. Further, as a result of visually observing the fish eyes of the surface protective film of the example, the number of counts of 0.5 mm or more was less than 1 piece / m ² .

[0031]

According to the present invention, the average particle size is 100 nm.
The following polyolefin-based resin layer (a) containing titanium oxide is provided, and the irradiated ultraviolet ray is scattered by the polyolefin-based resin layer (a) containing titanium oxide, and the ultraviolet ray to the adhesive layer (d) is obtained. Is prevented from entering.
Therefore, the deterioration reaction in the pressure-sensitive adhesive layer (d) is prevented, the adhesive force does not change, and the surface protective film having excellent weather resistance can be obtained.

In the surface protective film of the present invention, the acid-modified block copolymer layer (c) is provided between the polyolefin resin homogenous layer (b) and the pressure-sensitive adhesive layer (d),
The interlayer strength between the polyolefin resin homogenous layer (b) and the pressure-sensitive adhesive layer (d) is higher than that of the acid-modified block copolymer layer (c). Therefore, it can be peeled off without causing cohesive failure (adhesive residue).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B32B 27/00 104 8413-4F 27/08 8413-4F 27/20 A 8413-4F 27/28 8413 -4F 27/32 Z 8115-4F

Claims (1)

[Claims] 1. A polyolefin resin layer containing (a) titanium oxide having an average particle size of 100 nm or less, (b) a polyolefin resin single layer, and (c) represented by the general formula A-B-A. Block copolymer and / or block copolymer represented by the general formula AB (where A means a styrene polymer block and B means an olefin polymer block obtained by hydrogenating a butadiene polymer block). The acid-modified block copolymer layer obtained by acid-denaturing the above) and the adhesive layer (d) are sequentially laminated.