JPH08143838A - Sheet for protecting coated film - Google Patents

Abstract

PURPOSE: To obtain a sheet for protecting the coating film, excellent in adhesive workability to a curved surface, excellent in weather resistance, holding a sufficient sheet strength, even when left outdoors in the adhered state at a high temperature for a long period, and capable of being easily peeled without causing a trouble such as breakage. CONSTITUTION: This sheet for protecting a coating film is produced by disposing an adhesive layer on a support film containing 5-20wt.% of titanium dioxide, 0.1-2wt.% of a UV light stabilizer and 20-94.9wt.% of a propylene block copolymer containing 5-30wt.% of at least one of ethylene and propylene as a rubber component and having an initial yield point strength of 15-50N/25mm in a thickness of <=150μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to workability for bonding to a curved surface,
The present invention relates to a coating film protection sheet which is excellent in weather resistance and peelability after long-term adhesion and is suitable for surface protection of automobile bodies and parts, coated steel sheets and the like.

[0002]

2. Description of the Related Art Floating or colliding objects such as dust, rain, stone particles, etc. when a painted automobile or its parts are loaded on a truck or ship and transported to a remote place such as overseas There is a demand for means for preventing damage to the coating film, blurring of the gloss or discoloration.

Conventionally, as a preventive measure, a wax-based coating material coated with a thickness of 5 to 20 μm has been known. However, it is difficult to form a wax coating with a uniform thickness, it is difficult to obtain a uniform coating, it is easy to get dirty and it is vulnerable to acid rain, and much effort is required to apply and remove the wax coating. In short, there is a problem that it is easy to induce environmental problems such as use of solvent and treatment of waste liquid.

On the other hand, various surface protective sheets for adhering a coating film have been proposed in which an adhesive layer is provided on a supporting film such as polyester. According to such a sheet system, the above problems can be overcome. However, in applications where it is left outdoors for a long time under high temperatures such as in the summer, such as the above-mentioned automobile transportation application, the coating film may be deteriorated due to a decrease in flexibility and strength of the sheet and an increase in adhesive strength of the adhesive layer. There is a problem that it becomes more difficult to peel off the protective sheet.

Attempts have been made to increase the strength of the supporting film to overcome the problems of the flexibility and strength of the sheet under high temperature outdoors, but in that case, as the initial strength of the supporting film increases, the car body The workability of adhering to such curved surfaces is deteriorated, and the required basic performance is lost, which is not a satisfactory solution.

[0006]

In view of the above problems, the present invention has an excellent workability for adhering to a curved surface and also has excellent weather resistance, and is left for a long time in a high temperature outdoor condition. In addition, it is an object to develop a coating film protection sheet which can be easily peeled off without any trouble such as damage while maintaining sufficient sheet strength.

[0007]

According to the present invention, at least one of ethylene and propylene is used as a rubber component in an amount of 5 to 30.
Polypropylene block polymer containing 20% by weight
To 94.9% by weight, titanium oxide 5 to 20% by weight, and an ultraviolet stabilizer 0.1 to 2% by weight, at least 1
Initial yield strength of 15-
The present invention provides a coating film-protecting sheet comprising a 50 N / 25 mm support film and an adhesive layer.

[0008]

By using the support film having the above structure,
While maintaining good adhesion workability to curved surfaces of automobile bodies, etc., it shows weather resistance that retains sufficient flexibility and strength even if it is left outdoors under high temperature for a long time, and can be easily peeled off without trouble such as damage. A coating film protection sheet is obtained.

[0009]

Examples of constituent elements of the invention: The coating film-protecting sheet of the present invention comprises 20 to 94.9% by weight of a block polymer of polypropylene containing 5 to 30% by weight of at least one of ethylene and propylene as a rubber component, and titanium oxide. 5-2
0% by weight and at least 0.1 to 2% by weight of an ultraviolet stabilizer, and an adhesive layer provided on a support film having an initial yield strength of 15 to 50 N / 25 mm at a thickness of 150 μm or less. Consists of.

The support film used in the present invention contains 20 to 94.9% by weight of a polypropylene block polymer containing 5 to 30% by weight of at least one of ethylene and propylene as a rubber component. When the content of the rubber component is less than 5% by weight, the flexibility is poor and the curved surface adhesiveness is poor, and wrinkles are likely to occur during bonding,
If it exceeds 30% by weight, the strength is poor and the releasability after long-term adhesion is poor, and it tends to break during peeling and becomes difficult to peel off.

The support film used in the present invention has an initial yield point strength of 15 to 50 N / 25 mm, preferably 20 at a thickness of 150 μm or less in view of the balance between curved surface adhesion and peelability after long-term adhesion. ~ 35N / 25mm
It is adjusted to. Its yield strength is 15N / 25mm
When it is less than the above range, the strength is poor, the waist (self-supporting property) is weak, and the peeling workability is poor. On the other hand, 50N / 25mm
If it exceeds, the flexibility is poor and the workability of adhering to a curved surface becomes poor.

Therefore, from the viewpoint of achieving both the curved surface adhesiveness and the peelability after long-term adhesion, it is preferable to maintain the yield strength of 15 N / 25 mm or more even during the peeling. In the present invention, the evaluation of the yield strength at the time of peeling is preferably performed by a 500-hour exposure test using a sunshine weather meter. 15N after the exposure test
/ 25mm or more, especially 15-50N / 25mm, especially 20-35
A supporting film maintaining a yield strength of N / 25 mm can be preferably used in the present invention.

The above-mentioned yield strength properties are obtained by adding 20 to 94.9% by weight of the above polypropylene block polymer.
It can be achieved by using a composition containing at least 5 to 20% by weight of titanium oxide and 0.1 to 2% by weight of an ultraviolet stabilizer. The content of the block polymer is 20
If it is less than 10% by weight, the strength is poor, and if it exceeds 94.9% by weight, the strength is large and it is difficult to control the yield strength to the above range.

If the content of titanium oxide is less than 5% by weight, the hiding power becomes poor and the support film and the pressure-sensitive adhesive layer are easily deteriorated by ultraviolet rays. On the other hand, if it exceeds 20% by weight, the formability of the film by the extrusion molding method or the like becomes poor. The preferable blending amount of titanium oxide is 8 to 15% by weight, and it is preferable to use surface-treated titanium oxide from the viewpoint of preventing deterioration.

When the amount of the ultraviolet stabilizer is less than 0.1% by weight, the support film and the pressure-sensitive adhesive layer are easily deteriorated by UV, and when the amount exceeds 2% by weight, the surface of the support film is easily bleed. It becomes easy to cause dusting phenomenon. As the UV stabilizer, for example, a suitable one such as a benzotriazole-based UV absorber, a hindered amine-based UV stabilizer, or a benzoate-based UV stabilizer can be used.

Specific examples of the ultraviolet stabilizer include 2
-(3-t-Butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5
-Di-t-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, poly [{6- (1,1,3,
3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6 , 6-Tetramethyl-4-piperidyl)
Imino}], dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, 2,4-di-t-butylphenyl-3,5 Typical examples include -di-t-butyl-4-hydroxybenzoate.

The support film may be formed by an appropriate method such as the above-mentioned extrusion molding method. When forming the support film, one or more kinds of olefin-based polymers other than the block polymer and an oxidant may be used as necessary. One or two or more kinds of additives other than titanium and an ultraviolet stabilizer can be blended. The blending amount can be appropriately determined within a range of 74.9% by weight or less that satisfies the above-mentioned yield point strength.

Examples of the above-mentioned olefin-based polymer which can be blended as necessary are homopolymers of polypropylene, random polypropylene, polyethylene of low density, medium density, high density, etc., ethylene / vinyl acetate copolymer, ethylene / acrylic. Examples thereof include copolymers and α-olefin copolymers. Examples of additives include pigments, fillers, antioxidants, slip agents and the like.

The coating film-protecting sheet of the present invention can be formed, for example, by applying a solution-type or emulsion-type pressure-sensitive adhesive to one side of the support film, or by transferring the pressure-sensitive adhesive layer formed on the separator. It can be performed according to the known method for forming an adhesive sheet. It can also be carried out by a method such as melt coextrusion of the support film and the pressure-sensitive adhesive layer.

The thickness of the support film used and the thickness of the pressure-sensitive adhesive layer to be formed may be appropriately determined, and generally 10 to 15
0 μm, especially 20 to 70 μm, especially 20 to 50 μm, on one side of the support film 100 μm or less, especially 1 to 40 μm,
In particular, a form in which an adhesive layer having a thickness of 3 to 20 μm is provided is adopted. The back surface of the support film may be treated with a suitable long-chain alkyl-based, silicone-based, or fluorine-based release agent, if necessary.

Any suitable adhesive may be used as the adhesive, and there is no particular limitation. Preferably, an adhesive having excellent weather resistance such as an acrylic adhesive, a polyisobutylene adhesive, a butyl rubber adhesive, a hydrogenated styrene / diene block polymer adhesive such as hydrogenated styrene / butadiene / styrene. Agents are used.

The coating film protective sheet of the present invention is, for example, an automobile body or its parts coated with a coating film of polyester melamine type, melamine / alkyd type, melamine / acrylic type, or urethane type, or steel plate It is preferably used for collision of microscopic substances on an adherend composed of the metal plate or its molded product, surface protection from chemicals, and the like. In particular, it can be advantageously used when the temperature rises due to outdoor transfer or the like, or when bonding is performed for a long time.

Example 1 50 parts by weight of a block polymer of polypropylene of MFR4 containing 8% by weight of ethylene and propylene as rubber components (parts by weight; hereinafter the same), 39.7 parts of homopolypropylene of MFR5, 10 parts of titanium white and 2- Corona treatment of a 40 μm-thick support film molded by T-die method (die temperature 240 ° C.) with 0.3 part of (3-t-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole. A 20% by weight toluene solution of a polyisobutylene-based pressure-sensitive adhesive was applied to one side of the coated surface and dried at 80 ° C. for 3 minutes to obtain a coating film-protecting sheet having a pressure-sensitive adhesive layer having a thickness of 10 μm.

Example 2 MFR2 polypropylene block polymer 50 containing 15% by weight of ethylene and propylene as rubber components.
Parts, 19.7 parts of MFR5 homopolypropylene, 20 parts of low-density polyethylene, 10 parts of titanium white, and 2- (3-
t-butyl-5-methyl-2-hydroxyphenyl)-
A support film was obtained in the same manner as in Example 1 except that 0.3 part of 5-chlorobenzotriazole was used, and a coating film-protecting sheet was obtained using the support film.

Example 3 MFR2 polypropylene block polymer 70 containing 15% by weight of ethylene and propylene as rubber components.
Part, 19.7 parts of MFR10 random polypropylene,
A support film having a thickness of 40 μm formed by a T-die method with a mixture of 10 parts of titanium white and 0.3 part of 2- (3-t-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole. An acrylic pressure-sensitive adhesive was coated on one side subjected to corona treatment, and dried at 80 ° C. for 3 minutes to obtain a coating film-protecting sheet having a pressure-sensitive adhesive layer having a thickness of 5 μm.

The acrylic adhesive is 40 parts of 2-ethylhexyl acrylate / 5 parts of ethyl acrylate.
It was prepared by polymerizing 0 parts / 9 parts of styrene / 1 part of acrylic acid in ethyl acetate by a conventional method to obtain a polymer having a weight average molecular weight of 600,000, and adding 5 parts of trifunctional isocyanate to the solution. is there.

Comparative Example 1 MFR5 polypropylene block polymer 20 containing 3% by weight of ethylene and propylene as rubber components.
Parts, MFR6 low density polyethylene 74.7 parts, titanium white 5 parts, and 2- (3-t-butyl-5-methyl-2-)
A support film was obtained in the same manner as in Example 1 except that 0.3 part of hydroxyphenyl) -5-chlorobenzotriazole was used.
Using it, a coating film protection sheet was obtained.

Comparative Example 2 Polypropylene block polymer 70 of MFR2 containing 15% by weight of ethylene and propylene as rubber components.
Part, 26.7 parts of MFR10 random polypropylene,
A support film was obtained in the same manner as in Example 3 except that 3 parts of titanium white and 0.3 part of 2- (3-t-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole were used to prepare a support film. A coating film protection sheet was obtained by using the above.

Evaluation Test Yield Point Strength With respect to the coating film protective sheets (width 25 mm) obtained in Examples and Comparative Examples, a pulling speed of 300 mm / min and a chuck interval of 50 mm
The tensile strength was examined under the conditions of (MD direction). For the sample,
The initial product and the product subjected to outdoor exposure test in Thailand for 6 months (Thailand exposure) were used. The exposure test was carried out under the condition that the surface protective sheet was adhered to an acrylic clear coated plate, which was placed on an outdoor exposure test stand and left for a period from February to August 1994.

Curved Surface Adhesives The coating film-protecting sheets obtained in Examples and Comparative Examples have a radius of 500.
The workability in adhering to a cm painted plate was examined and evaluated according to the following criteria. ◯: Adhesion treatment is easy without wrinkles Δ: Wrinkles are easy to form, and it takes work habits to adhere without wrinkles ×: Wrinkles cannot be avoided and adhesion treatment is difficult

Long-term peelability The coating film-protecting sheets obtained in Examples and Comparative Examples were treated with a radius of 500.
A peeling workability after adhering to a cm painted plate and exposing it to the outdoors for 6 months was examined and evaluated according to the following criteria. ◯: When the sheet was peeled smoothly without being cut Δ: When the sheet was occasionally cut and difficult to peel ×: When the sheet was very easily cut

The above results are shown in the following table.

[0033]

EFFECTS OF THE INVENTION According to the present invention, it has excellent workability in bonding to curved surfaces, and also has excellent weather resistance, and retains sufficient sheet strength even when left in a high temperature outdoor condition for a long time in a bonded state. It is possible to obtain a coating film protection sheet that can be easily peeled off without trouble such as damage.

Front page continuation (72) Kenichi Shibata, 1-2, Shimohozumi, Ibaraki, Osaka Prefecture Nitto Denko Corporation (72) Kenichi Okada, 1-2, Shihohozumi, Ibaraki, Osaka Prefecture Nitto Denko Stock Company (72) Inventor Go Inoue 1-2-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation (72) Inventor Mitsuru Dota 1-21-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation (72) Inventor Koharu Matsui 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd. (72) Inventor Takeshi Eda 33-1 Kanzaki-cho, Amagasaki-shi, Hyogo Kansai Paint Co., Ltd. (72) Inventor Hiroshi Ueda 33-1 Kanzaki-cho, Amagasaki-shi, Hyogo Prefecture Kansai Paint Co., Ltd.

Claims (3)

[Claims] 1. A polypropylene block polymer containing 5 to 30% by weight of at least one of ethylene and propylene as a rubber component, 20 to 94.9% by weight, titanium oxide 5 to 20% by weight, and an ultraviolet stabilizer of 0.1. A coating film-protecting sheet comprising a support film containing at least 1 to 2% by weight and having an initial yield point strength of 15 to 50 N / 25 mm at a thickness of 150 μm or less and an adhesive layer. 2. The coating film-protecting sheet according to claim 1, which further comprises 74.9% by weight or less of at least one other olefin polymer or other additive. 3. The yield strength of the supporting film is 20 to.
The coating film protection sheet according to claim 1 or 2, which has a size of 35 N / 25 mm.