JP2974533B2 - Surface protection film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective film which is adhered to a metal plate, a resin plate, a decorative plywood or the like to protect the surface.

[0002]

2. Description of the Related Art Conventionally, surface protection films have been made of metal plates such as stainless steel plates, aluminum plates, coated and coated steel plates, and the like.
It is used for the purpose of preventing the surface of the adherend from being contaminated or damaged during transportation, storage, or processing when bonded to a synthetic resin plate, decorative plywood, or the like.

As a surface protective film, a polyolefin resin film such as polyethylene is often used as a substrate film as a support, and natural rubber, ethylene-vinyl acetate copolymer, styrene-butadiene -Styrene copolymer, styrene-isoprene-
An adhesive layer formed of an adhesive containing a styrene copolymer or the like as a main component is formed (for example, Japanese Patent Publication No. 58-3).
0911, JP-A-61-103975, etc.).

The pressure-sensitive adhesive used for the surface protective film does not peel off from the adherend during transportation, storage, or processing, and is easily peeled off thereafter, leaving no adhesive residue on the adherend after peeling. It is required that the body is not contaminated. By the way, natural rubber as a main component of the pressure-sensitive adhesive, ethylene-vinyl acetate copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer and the like,
Since it has an unsaturated double bond in the molecule, it is easily deteriorated by ultraviolet rays or the like. This degradation occurs faster in the decomposition reaction than in the cross-linking reaction, so that the apparent molecular weight is reduced and the adhesive strength is increased, that is, so-called adhesion enhancement is caused.

[0005] On the other hand, adherends such as coated coated steel sheets and decorative plywood to which a surface protective film is adhered and protected are often used for building materials. Etc. are left outdoors for a long time. For this reason, the pressure-sensitive adhesive used for the surface protection film is decomposed by the ultraviolet light that has passed through the polyolefin-based resin film of the support, the apparent molecular weight is reduced, and the adhesion is promoted. When the adhesion is promoted in this manner, when the surface protective film is to be peeled off, it is difficult to peel off from the adherend, and when it is forcibly peeled off, there is a problem that glue remains or the base film stretches and breaks. .

Therefore, it is conceivable to add an organic UV absorber, a light stabilizer or the like to the adhesive or the support to prevent the deterioration due to UV rays. The UV absorber, however, has a reaction to convert light energy into heat energy. This is because the light stabilizer causes a reaction to inactivate the generated radical, and in any case, as the reaction progresses, that is, its effect decreases with time, Was not enough.

[0007]

By the way, when the particle size is between 0.
It is well known that when a metal salt such as titanium oxide or calcium carbonate having a thickness of about 2 to several μm is contained in a polyolefin resin film at about 30% by weight, ultraviolet rays can be blocked. It is conceivable to prevent the adhesive from increasing the adhesion of the adhesive. However, in this case, since the polyolefin resin film becomes white and becomes opaque, it is one of the performances required for the surface protection film that the scratches and dirt on the adherend can be confirmed while the surface protection film is adhered. There is a problem that certain transparency is impaired.

[0008] The present invention has been made in view of the above points, and in a surface protection film using a polyolefin-based resin film as a base film, without impairing transparency, excellent weather resistance, and little increase in adhesion. It is intended to provide a surface protection film.

[0009]

Means for Solving the Problems The surface protective film of the present invention is a surface protective film having a polyolefin resin film as a base film and an adhesive layer formed on one surface thereof, wherein the base film has three or more polyolefin layers. At least one layer of the polyolefin-based resin layer except for the layer adjacent to the adhesive layer and the outermost layer contains titanium oxide having an average particle diameter of 100 nm or less.

In the present invention, the polyolefin resin forming the base film includes low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene (LLDPE), 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 can be mentioned. Also, a mixture of two or more of these polyolefin-based resins may be used.

[0011] And, the base material when the polyolefin resin layer is not less than three layers forming the films, at least in more average particle size 100, except for the layers and the outermost layer adjacent to the adhesive layer
nm or less of titanium oxide . The reason is as follows
It is on the street. That is, a small amount except for the layer adjacent to the adhesive layer
At least one layer containing titanium oxide is used for the adhesive layer .
Compared to those containing titanium oxide in adjacent layers,
Excellent weatherability and can be used outdoors for a long time
Base film (for example, even in a weathering test for 1000 hours)
Is not broken. In addition, the surface protection film,
Although a plurality of sheets are often stored and transported in a pile, when a film is formed by adding a titanium oxide to a polyolefin-based resin, kneading defects may occur, or inorganic substances such as titanium oxide may be secondary aggregated. Fish eyes are easily generated, and titanium oxide is contained in the outermost layer of the base film.
Then, this fish eye has a nick mark on the surface protection film
(Small traces generated when a foreign object is strongly pressed)
This is because the appearance of the surface protective film becomes worse.

In the present invention, the titanium oxide contained in the polyolefin resin layer has an average particle size of 100 nm.
It must be: The particle size of titanium oxide is 10
This is because if it exceeds 0 nm, it also blocks visible light and becomes opaque. Here, the average particle size of the titanium oxide refers to a value calculated by measuring the specific surface area of the titanium oxide and assuming that the titanium oxide is a sphere. When the average particle size of titanium oxide is 50 nm or less, the surface activity increases and the catalyst becomes an oxidation reaction catalyst. Therefore, it is preferable to use surface-treated titanium oxide. Examples of the surface treatment agent include lauric acid, silica, alumina, and zirconia. When alumina and zirconia are used in combination, it is particularly preferable because the weather resistance is further improved.

The preferable content of the titanium oxide varies depending on the thickness of the film. However, from the viewpoint of the effect of blocking ultraviolet rays, the thickness of the film is 50 μm and 0.5% by weight or more.
The film thickness is 0.25% by weight or more at 50 μm and 5% by weight or less at 50 μm to maintain transparency.
It is preferably not more than 2.5% by weight at 00 μm. Therefore, when the film thickness is 50 μm, 0.5 to 5% by weight,
0.25 to 2.5% by weight at 00 μm is preferred. In addition,
Titanium oxide having a rutile crystal structure is more preferable.

The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is not particularly limited, and includes natural rubber, ethylene-vinyl acetate copolymer,
Styrene-butadiene-styrene copolymer, styrene-
Examples of the adhesive include an isoprene-styrene copolymer, a polyacrylate and the like as a main component. In particular, a pressure-sensitive adhesive that can be co-extruded with a polyolefin resin is preferably used.

However, as the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer, general formulas ABA and / or AB (where A represents a styrene polymer block, B represents a butadiene polymer block or isoprene polymer). (Indicating an olefin polymer block obtained by hydrogenating a coalesced block), which has no substantial unsaturated double bond. Few.

In the block copolymer represented by the general formula ABA or AB, the styrene polymer block A has a weight average molecular weight of 12,000 to 100,00.
The glass transition point is preferably about 0 ° C. or higher.

The olefin polymer block B obtained by hydrogenating a butadiene polymer block or an isoprene polymer block has a weight average molecular weight of 10,000.
The glass transition point is preferably -20 ° C or lower.

The preferred weight ratio of the component A and the component B is A / B = 5/95 to 50/50, and more preferably A / B = 10/90 to 30/70. When the block copolymer represented by the general formula ABA and the block copolymer represented by the general formula AB are used in combination, the weight ratio thereof is preferably ABA / A- B = 1
00/0 to 20/80, more preferably AB-
A / AB is 100/0 to 50/50.

A tackifier resin may be blended with the block copolymer. As the tackifying resin, general formula AB
-A and / or those which are selectively compatible with the B component in the block copolymer represented by the general formula AB are used. For example, an aliphatic hydrocarbon resin, a terpene resin, a coumarone-indene resin, an aromatic hydrocarbon resin, a rosin resin, and the like are suitably used. The adhesive includes a softener,
An ultraviolet absorber, an antioxidant and the like may be added as necessary.

In order to more completely suppress the increase in adhesion of the pressure-sensitive adhesive layer, a polyethyleneimine derivative having a higher alkyl group introduced therein can be added to the pressure-sensitive adhesive. The polyethyleneimine derivative into which the higher alkyl group is introduced preferably has an average molecular weight of 1,000 to 20,000, and the higher alkyl group is 0.5 to 1 equivalent, more preferably 0 to 1 equivalent to the imine group of the polyethyleneimine. .7-
It is recommended that one equivalent is introduced.

As the higher alkyl group, an alkyl group having 12 or more carbon atoms is generally preferred, and an octadecyl group is particularly preferred. In order to introduce a higher alkyl group into polyethyleneimine, for example, an excess higher alkylisocyanate can be added to polyethyleneimine and subjected to an addition reaction, whereby the higher alkyl group can be easily introduced.

The amount of the polyethyleneimine derivative into which the higher alkyl group is introduced is determined by the amount of the block copolymer 100
It is preferably 0.01 to 5 parts by weight based on parts by weight. 0.0
If the amount is less than 1 part by weight, the adhesive strength increases after heating and curing, and peeling after use becomes difficult. If the amount exceeds 5 parts by weight, bleed out to the surface of the pressure-sensitive adhesive layer and the adherend is contaminated. . More preferably, it is 0.1 to 2 parts by weight, further preferably 0.2 to 1.2 parts by weight.

The thickness of the base film and the pressure-sensitive adhesive layer constituting the surface protective film is appropriately determined depending on the application.
The thickness of the substrate film is generally 10 to 80 μm as a whole, and the thickness of the adhesive layer is usually 5 to 30 μm.

As a method for producing the surface protective film of the present invention, if a method of laminating each layer forming the base film and the pressure-sensitive adhesive layer by a co-extrusion method is employed, the process is simple and each layer is formed. It is preferable because they are integrated and the interlayer strength of each layer is improved.

[0025]

In the surface protective film of the present invention, the base film is composed of three or more polyolefin resin layers,
A layer adjacent to the adhesive layer in the polyolefin resin layer
And at least one layer excluding the outermost layer has an average particle size of 100 nm.
The following titanium oxide is contained, and the passage of ultraviolet rays is blocked by this titanium oxide-containing layer, does not reach the adhesive layer, and the deterioration of the adhesive layer due to ultraviolet rays is suppressed. And
Adhesion of natural rubber, ethylene-vinyl acetate copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, etc., which is the main component of the adhesive, does not degrade and the apparent molecular weight does not decrease. Increase can be suppressed. Also, multiple sheets of surface protection film are stacked and stored.
When transported, pipes and fittings caused by titanium oxide
Insufficient marks may remain on the surface protection film due to Shuai
Is prevented.

In a surface protective film in which the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive containing a block copolymer represented by the general formula ABA and / or AB as a main component, the pressure-sensitive adhesive itself is Since it has the adhesiveness required for the surface protective film and has a small increase in adhesion, it is further excellent in weather resistance in combination with the ultraviolet shielding effect of titanium oxide having an average particle diameter of 100 nm or less.

According to the method for producing a surface protective film of the present invention, the layers forming the base film and the pressure-sensitive adhesive layer are integrally laminated by the co-extrusion method, so that the process is simplified, and the The interlayer strength is improved.

[0028]

Embodiments of the present invention will be described below.

Examples 1 to 4, Reference Examples 1 to 4, Comparative Example 1,
2 and 4 to 11 1) Base film layer The base film layer was a single-layer, two-layer or three-layer polyolefin-based resin layer using a polyolefin-based resin as shown in Table 1. The polyolefin resins in the table are as follows. Mirason 12: manufactured by Mitsui Petrochemical Industries, Ltd., density = 0.92
7 g / cm ³ , MI = 3.0 Low density polyethylene Noblen WF825: manufactured by Sumitomo Chemical Co., Ltd., density = 0.
90 g / cm ³ , MI = 8.0 polypropylene (random copolymer)

In Examples 1 to 4 , the layer (first layer) and the layer (first layer) adjacent to the adhesive layer in the polyolefin resin layer were used.
And at least one layer (second layer) excluding the outermost layer (third layer)
Is a titanium oxide-containing polyolefin-based resin layer,
The titanium oxides in Table 1 are as follows, and the content ratios of polyolefin and titanium oxide were as shown in Table 2. MT-500HD: manufactured by Teica, average particle size about 30 nm,
Surface treated with alumina and zirconia UF07: manufactured by Tyoxide Corporation, average particle size of about 30 nm,
Surface treated with alumina / zirconia

As a method for incorporating titanium oxide into the polyolefin resin, first, a high-concentration master batch having a titanium oxide content of 10% by weight was prepared by preliminary kneading with a twin-screw extruder. This masterbatch is mixed with a required amount of polyolefin resin when forming the titanium oxide-containing polyolefin resin layer.

2) Pressure-sensitive adhesive layer A pressure-sensitive adhesive layer was formed from a copolymer as shown in Table 1. This copolymer is as shown below. EVA540: an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10% by weight, MI = 3, density = 0.927 g / cm ³ manufactured by Tosoh Corporation EVA603F: a vinyl acetate content = 15 manufactured by Tosoh Corporation
Ethylene-vinyl acetate copolymer with weight%, MI = 1.8, density = 0.940 g / cm ³ Clayton D1102: manufactured by Shell Chemical Company, styrene-butadiene-styrene copolymer (SBS) Clayton D1107: Shell Chemical Company Styrene-isoprene-styrene copolymer (SIS)

3) Preparation of Surface Protective Film The above polyolefin resin and pressure-sensitive adhesive were integrally laminated by a coextrusion method and extruded to prepare a surface protective film.
The thickness of each layer was as shown in Table 1. In the table, each layer of the polyolefin-based resin is represented as a first layer, a second layer, and a third layer in the order of proximity to the pressure-sensitive adhesive layer.

[0034]

[Table 1]

[0035]

[Table 2]

4) Physical Properties of Surface Protective Film The obtained surface protective film was adhered to an acrylic plate, and was applied at 23 ° C. × according to JIS Z0237-8.
The 180 ° peel adhesion at 30 minutes was measured.
Further, the obtained surface protective film was attached to an acrylic plate, and a weather resistance test was performed in accordance with JIS A1415.
The 180 ° peeling adhesive force was measured in the same manner as above. As a weather resistance tester, a sunshine super long life weatherometer WEL-SUN-TC type (manufactured by Suga Test Instruments Co., Ltd.) was used. The black panel temperature: 63
± 3 ° C., rain cycle: 18 minutes out of 120 minutes. These results were as shown in Table 3. Reference Example 1
Surface protection off Irumu of to 4, the surface protection off of Examples 1 to 4
This film has the same level of weather resistance as the
If you wrap the system around a paper core and store it later,
Small notch marks were observed on the surface protective film. Example
In the surface protective films of Nos. 1 to 4, no nicks are observed.

[0037]

[Table 3]

Examples 5 to 7, Reference Examples 5 to 7 , Comparative Examples 3 and 12 to 17 1) Base film layer As the base film layer, a polyolefin resin as shown in Table 4 was used. It was used as a single-layer, two-layer or three-layer polyolefin resin layer. The polyolefin resin and titanium oxide in the table are all the same as in Examples 1 to 4 , and the content ratio of polyolefin and titanium oxide in the titanium oxide-containing polyolefin resin layer is as shown in Table 5. did.

2) Pressure-sensitive adhesive layer A pressure-sensitive adhesive layer was formed using a pressure-sensitive adhesive composition having the following composition, using a copolymer as shown in Table 4 as a main component and a tackifying resin as shown in Table 4. did. Copolymer 100 parts by weight Tackifying resin 20 parts by weight PEIO 1 part by weight (addition reaction product of polyethyleneimine and octadecyl isocyanate) Antioxidant (Irganox 1010, manufactured by Ciba Geigy) 1 part by weight

The above copolymer is as follows. Septon 2043: a hydrogenated product of a styrene-isoprene-styrene block copolymer manufactured by Kuraray Co., Ltd. Tuftec H1052: hydrogenated styrene-butadiene-styrene block copolymer manufactured by Asahi Kasei Corporation. Clayton G1657: a hydrogenated product of a styrene-butadiene-styrene block copolymer manufactured by Shell Chemical Company.

3) Preparation of Surface Protective Film The above-mentioned polyolefin resin and pressure-sensitive adhesive were integrally laminated by a coextrusion method and extruded to prepare a surface protective film.
The thickness of each layer is as shown in Table 4. In addition,
In Table 4, each layer of the polyolefin-based resin is indicated as a first layer, a second layer, and a third layer in the order of proximity to the pressure-sensitive adhesive layer.

[0042]

[Table 4]

[0043]

[Table 5]

4) Physical Properties of Surface Protective Film The obtained surface protective film was adhered to a stainless steel plate and peeled off at 180 ° in the same manner as in Examples 1-4 . Further, the obtained surface protective film was subjected to a weather resistance test in the same manner as in Examples 1 to 4, and then the 180 ° peel adhesion was measured. In addition, the weather resistance test was extended to 1000 hours, assuming that the product was left outdoors for a long time. The results are as shown in Table 6. The surfaces of Reference Examples 5 to 7
The protective film was the same as the surface protective film of Examples 5 to 7.
Degree of weather resistance, but this surface protection film
If the product is wound up and stored and later rewound, the surface protection
A small nick was found on the film. Table of Examples 5 to 7
No notch marks are observed on the surface protection film.

[0045]

[Table 6]

[0046]

As described above, the surface protective film of the present invention has an appropriate initial adhesive strength, and does not cause a time-dependent increase in adhesive strength even when exposed to a high temperature or applied over a long period of time. Furthermore, at the time of peeling, it can be easily peeled off, there is no adhesive residue on the adherend, and the base film is not broken. In addition, the surface protection film of the present invention,
When stored and transported, use titanium oxide on the surface protection film.
Nicks due to fish eye caused by
Prevents leaving small traces generated when pressed)
Thus, the appearance of the surface protective film does not deteriorate.

Claims (1)

(57) [Claims] 1. A surface protective film comprising a polyolefin-based resin film as a base film and an adhesive layer formed on one surface thereof, wherein the base film is composed of three or more polyolefin-based resin layers. A surface protective film characterized in that at least one layer excluding the layer adjacent to the adhesive layer and the outermost layer contains titanium oxide having an average particle size of 100 nm or less.