JPH09111210A - Tacky sheet for protecting coating film of automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject sheet excellent in dimensional stability during production of a tacky, workability of adhesion to an automobile and durability after execution, not being broken during release and removal, by providing one side of a specific substrate film with a rubber-based tacky agent layer. SOLUTION: This tacky sheet for protecting a coating film of an automobile is obtained by coating (A) one side of a substrate film composed of a biaxially orientated polyolefin-based resin (e.g. a biaxially orientated film which is composed of a resin obtained by blending a polypropylene with a polyethylene in the ratio of 95:5 to 70:30 and has the ratio of the maximum value and the minimum value of transmitted microwave intensity by a microwave method of 4GHz measuring frequency expressed in terms of 50μm film thickness of <=3) with (B) a rubber-based tacky agent layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile coating film-protecting pressure-sensitive adhesive sheet, which is used to protect a coating film applied to the body of an automobile from acid rain, dust, dust and the like.

[0002]

2. Description of the Related Art Adhesive sheets have been widely used for commercial use, office use, process control, physical distribution control, household use, etc. in the form of labels, stickers, patches, delivery slips and the like. The general configuration of the pressure-sensitive adhesive sheet will be described below. The pressure-sensitive adhesive is sandwiched between a surface substrate and a release sheet, and paper, foil, film, or the like is used as the surface substrate. Further, as the release sheet, high density base paper such as glassine paper, clay coated paper, polyamid base paper obtained by laminating a resin film such as polyethylene on kraft paper or high quality paper, or polyvinyl alcohol, starch on kraft paper or high quality paper, etc. A resin-coated base paper having a coating layer containing a water-soluble polymer or the like and a pigment as a main component and coated with a release agent such as a silicone compound or a fluorine compound is used. As the pressure-sensitive adhesive, a rubber-based, acrylic-based, vinyl ether-based emulsion, or a solvent or solvent-free pressure-sensitive adhesive is used.

[0003] On the other hand, when a new automobile or its parts, etc., after painting are loaded on a ship or truck and transported to a remote place such as abroad, various floating matters such as dust, dust, acid rain, and colliding substances are encountered. There is a demand for a means for preventing damage to the coating film, gloss blurring, discoloration, and the like due to this. Conventionally, a method of providing a coating film of wax having a thickness of 5 to 20 μm has been known as such a preventive measure. However, it is difficult to apply a uniform wax coating film, and it is not possible to obtain a uniform protective film. It easily stains, is vulnerable to acid rain, easily stains, and penetrates into the coating film, causing discoloration. However, there is a problem in that a great deal of labor is required to apply and remove the wax, and environmental problems such as the use of a solvent and the treatment of a waste liquid are likely to occur.

Therefore, recently, a method of protecting a coating film of an automobile by using a pressure-sensitive adhesive sheet instead of a wax (Japanese Patent Laid-Open No. Hei 6-1994).
No. 73352, JP-A-6-128540, etc.)
Is gradually becoming popular.

[0005]

However, in the method using a protective pressure-sensitive adhesive sheet, since the film is often incinerated after use, a polyolefin-based film is used so as not to generate toxic gas and the like. These are usually as thin as 30 to 50 μm from the viewpoint of economy and workability, and solvent-based primers, adhesives,
When a release agent or the like is applied and dried and wound into a pressure-sensitive adhesive sheet, it easily expands and contracts. Therefore, it is necessary to take measures such as increasing the tension at the time of coating and controlling the temperature at the time of drying, which causes a problem in dimensional stability.

[0006] Further, when it is applied to an automobile, it is necessary to cut it accurately according to the complicated shape of the vehicle body. If you use a sharp knife for cutting, the car body may be damaged.Therefore, I usually use a tool that is somewhat unsuitable for cutting such as a bamboo horn, but when using such a tool, the shape that I think There is a problem that it doesn't cut well.

Further, since automobiles are stored outdoors for a long period of time, the base film is likely to deteriorate with time due to heat or ultraviolet rays. In some cases, the film is torn, leading to a reduction in the efficiency of the removing operation. At present, basic performances such as suitability for processing into an adhesive sheet, workability at the time of sticking to an automobile, and weather resistance are not satisfied.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, a base film made of a biaxially stretched polyolefin resin, particularly a film satisfying specific conditions, Is a film prepared by mixing polypropylene and polyethylene in a specific ratio, and by forming a rubber-based adhesive layer on one side of the film, suitability for processing into a protective adhesive sheet, workability when sticking to an automobile, and It was found that after the application, it has excellent weather resistance, and that it can be removed without tearing even if peeled from any direction at the time of removal.

(1) The present invention is a pressure-sensitive adhesive sheet for protecting automobile coating films, characterized in that a rubber-based pressure-sensitive adhesive layer is provided on one surface of a base film made of a biaxially stretched polyolefin resin. .

(2) Further, the ratio of the maximum value and the minimum value of the transmitted microwave intensity of the base film measured by the microwave method with the measurement frequency of 4 GHz is 50 μm.
The pressure-sensitive adhesive sheet for protecting automobile coating film according to (1), which is a film having a value converted to 3 or less.

(3) The pressure-sensitive adhesive sheet for protecting automobile coating film according to (1) or (2), wherein the polyolefin resin is a resin in which polypropylene and polyethylene are mixed in a ratio of 95: 5 to 70:30. is there.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a biaxially stretched polyolefin resin film. Examples of the polyolefin resin include polypropylene, a mixture of polypropylene and polyethylene, an ethylene-propylene copolymer, polybutylene, and various mixtures of the above substances.

The biaxial stretching means that a non-stretched film that has been melted by heat, extruded, and formed into a film is stretched in a temperature range below the melting point in two directions, lengthwise and widthwise, at a predetermined ratio to form a molecular chain. Is a film forming technology that orients, crystallizes, and heat-fixes,
For example, the tenter method sequential biaxial stretching and the tubular method homogeneous stretching can be exemplified. The tenter method extrudes molten polymer from a T-die onto a casting drum and cools it to produce a sheet. Subsequently, it is stretched in the machine direction through a group of heating rolls having different speeds, and then is stretched in the cross direction while holding both ends in a tenter. It is a method of heat-fixing and winding if necessary. On the other hand, the tubular method is a method in which a molten polymer is extruded from a circular die into a tube shape, cooled in a cooling tank and then heated again, while introducing compressed air into the tube to expand the tube by an internal pressure and to stretch it in the longitudinal and lateral directions. . The biaxially stretched film used in the present invention is not limited in its manufacturing method.

By using such a biaxially stretched film, mechanical properties such as tensile strength, tensile modulus (Young's modulus) and impact strength are improved, and
A pressure-sensitive adhesive sheet for protecting automobile coating films, which has improved heat resistance, cold resistance, glossiness, moisture resistance and the like can be obtained.

Among the biaxially stretched polyolefin resin films, a value indicating the degree of anisotropy of the base film, that is, the transmission micro-value, measured by a microwave method using a molecular orientation meter with a measurement frequency of 4 GHz. A value obtained by converting the ratio of the maximum value to the minimum value of the wave intensity to a film thickness of 50 μm (hereinafter, referred to as MOR value) is 3 or less, preferably 2 or less, in particular, there is little deviation of the property depending on the direction of the film, Treatment such as cutting is easy, and the protective pressure-sensitive adhesive sheet can be easily peeled off after attachment, which is preferable. By the way, when the MOR value is larger than 3, the film has a biased molecular orientation, and uniform performance cannot be obtained. In the case of such a film, there are problems that an easy cutting direction and a difficult cutting direction occur, and the strength of the film differs depending on the direction when the protective adhesive sheet is peeled off after application, so that the sheet is broken. Occurs. N
The method of adjusting the OR value is performed by controlling the stretching ratio. In the case of a film that has not been stretched, the MOR value is often 3 or less, but such a non-stretched film cannot be used because the desired effect of the present invention cannot be obtained.

Further, the polyolefin resin comprises polypropylene and polyethylene, and the compounding ratio thereof is 95: 5.
When it is from 70:30, it is preferable because it provides a protective pressure-sensitive adhesive sheet with further excellent weather resistance. This is because polyethylene has properties such as less deterioration by ultraviolet rays than polypropylene, while polypropylene has properties such as superior tensile strength to polyethylene. It is believed that the film having each of these advantages is obtained in this specific range of formulation, and that it is suitable for the base material of the pressure-sensitive adhesive sheet that protects the automobile coating film. If the content of polyethylene is less than 5% by weight, sufficient weather resistance cannot be expected. Further, if the blending amount of polyethylene exceeds 30% by weight, uneven mixing occurs, uniform physical properties are difficult to obtain, and deterioration tends to occur.

The film used is preferably colored white. This is because by coloring in white, sunlight rays can be reflected and the temperature rise of the coating film can be suppressed. As the colorant, titanium oxide, zinc oxide, lithopone, lead white, chalk, barium sulfate, alumina white, silica white, clay and the like, it is preferable to use titanium oxide having high whiteness, which is excellent in hiding, and these are preferably used. The effect is great when applied to or contained in the film.

The pressure-sensitive adhesive sheet for protecting automobiles of the present invention can be obtained by providing a pressure-sensitive adhesive layer on one surface of the above-mentioned substrate film. Further, in order to improve the adhesion between the base film and the pressure-sensitive adhesive and to prevent the pressure-sensitive adhesive component from migrating to the automobile coating film and causing fogging in the coating film, an undercoat is formed between the base film and the pressure-sensitive adhesive layer. It is also possible to provide layers. The undercoat layer is, for example, an undercoat agent such as a resin whose main component is an acrylate copolymer modified with an alkyleneimine compound, and a thickener, a wetting agent, a leveling agent, a defoaming agent, a crosslinking agent, a pigment, etc. It can be provided by applying an appropriately added coating liquid to the substrate.

Examples of the pressure-sensitive adhesive used in the pressure-sensitive adhesive sheet for protecting automobile coating film of the present invention include rubber-based pressure-sensitive adhesives. For example, natural rubber, polyisobutylene, isobutylene-isoprene copolymer, isobutylene-1-butene copolymer, a rubber-based polymer such as isobutylene-n-butene copolymer as a main component, if necessary, a tackifier, A softener, a filler, a release agent, a pigment, and an ultraviolet absorber are appropriately blended. It should be noted that non-rubber adhesives, such as acrylic and vinyl ether adhesives, cannot be used because they cannot be applied under severe temperature conditions.

Regarding the method for constructing the pressure-sensitive adhesive sheet for protecting automobile coating film of the present invention, the pressure-sensitive adhesive coating liquid or the heat-melting adhesive liquid is directly applied onto the substrate or the undercoat layer provided on the substrate according to a conventional method. The pressure-sensitive adhesive is applied onto the release agent layer of the sheet by a method and dried if necessary to form a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is bonded to the back surface of the base material or the undercoat layer surface provided on the base material to finish. As an apparatus for applying the adhesive, for example, a reverse roll coater, a knife coater,
A bar coater, a die coater, a gear-in die coater, a slot die coater, an air knife coater, a reverse gravure coater, a vario gravure coater, etc. are appropriately used. The amount of adhesive applied is 5 to 3 on a dry weight basis.
0 g / m ^2, and more preferably is adjusted from about 7~20g / m ^2. By the way, if the coating amount is less than 5 g / m ² , the adhesive performance of the resulting protective pressure-sensitive adhesive sheet will be insufficient, and if the coating amount exceeds 30 g / m ² , the adhesive will stick out or cause cohesive failure during peeling. There is a risk that

The pressure-sensitive adhesive sheet for protecting automobile coating film of the present invention comprises
In order to protect the pressure-sensitive adhesive layer, a structure in which a sheet having a release agent layer is attached to the surface of the pressure-sensitive adhesive layer, or a release agent layer is provided on the surface of the base film opposite to the pressure-sensitive adhesive layer, and is wound. Offered in a finished configuration.

As the release agent, water, solvent type or non-solvent type silicone resin, fluororesin, long-chain alkyl compound, etc. can be used, and the dry weight thereof is from 0.05 to
After coating about 3 g / m ² , a release agent layer is formed by heat curing, ionizing radiation curing or the like. Further, when the release agent layer is directly provided on the support and the adhesion between the support and the release agent is poor, it is desirable to subject the release agent coated surface to a surface activation treatment such as corona discharge treatment.

[0023]

The present invention will be described in more detail with reference to the following examples, but of course the present invention is not limited thereto. All parts and weights in the examples are shown by solid weight unless otherwise specified.

Example 1 [Manufacture of support] Polypropylene resin (trade name "FG3D", manufactured by Mitsubishi Chemical) 89 parts Rutile titanium oxide (trade name "R-25", manufactured by Sakai Chemical Industry) 10 parts Lubricant (trade name) "SZ-PG", manufactured by Sakai Chemical Industry) 0.5 part Antioxidant (trade name "Irganox 1010", manufactured by Ciba Geigy) 0.1 part Ultraviolet absorber (trade name "Seesorb 102", manufactured by Shiraishi Calcium) 4 parts The resin mixture having the above composition was supplied to an extruder, melt-kneaded in the extruder, and then biaxially stretched by a tenter method to give a thickness of 40.
A μm white film was obtained. This film is a molecular orientation meter by microwave method (Shin Oji Paper Co., MOA-500
1A), and the ratio of the maximum value and the minimum value of the obtained transmitted microwave intensity (maximum value /
Value (MOR) converted from the minimum value to a film thickness of 50 μm
Value) was 1.2 to 1.5.

[Production of Protective Adhesive Sheet] Both sides of this film were subjected to corona discharge treatment, and one side was coated with a long-chain alkyl release agent with a bar coater to a dry weight of 0.1 g / m ² and dried. Then, a release agent layer was formed. And
An adhesive containing polyisobutylene (trade name "Opanol B50SF, manufactured by BASF") as the main component was applied to the surface of the above film opposite to the release agent layer with a knife coater so that the dry weight was 20 g / m ^2, and dried. An adhesive sheet for protecting automobile coating film of the invention was obtained.

Example 2 [Production of support] Polypropylene resin (trade name "FG3D", manufactured by Mitsubishi Chemical) 79 parts Low density polyethylene resin (trade name "EH-30", manufactured by Mitsubishi Chemical) 10 parts Rutile titanium oxide (Brand name "R-25", Sakai Chemical Co., Ltd.) 10 parts Lubricant (Brand name "SZ-PG", Sakai Kagaku Co., Ltd.) 0.5 part Antioxidant (Brand name "Irganox 1010", Ciba Geigy Co.) 1 part Ultraviolet absorber (trade name "Seesorb 102", made by Shiraishi calcium) 0.4 part An adhesive sheet for protecting automobile coating film of the present invention was obtained in the same manner as in Example 1 except that the above resin mixture was used. It was The MOR value of the film was 1.3 to 1.7.

Example 3 [Production of support] Polypropylene resin (trade name "FG3D", manufactured by Mitsubishi Chemical) 64 parts Low density polyethylene resin (trade name "EH-30", manufactured by Mitsubishi Chemical) 25 parts Rutile titanium oxide (Brand name "R-25", Sakai Chemical Co., Ltd.) 10 parts Lubricant (Brand name "SZ-PG", Sakai Kagaku Co., Ltd.) 0.5 part Antioxidant (Brand name "Irganox 1010", Ciba Geigy Co.) 1 part Ultraviolet absorber (trade name "Seesorb 102", made by Shiraishi calcium) 0.4 part An adhesive sheet for protecting automobile coating film of the present invention was obtained in the same manner as in Example 1 except that the above resin mixture was used. It was The MOR value of the film was 1.3 to 1.8.

Example 4 [Production of support] Polypropylene resin (trade name "FG3D", manufactured by Mitsubishi Chemical) 54 parts Low density polyethylene resin (trade name "EH-30", manufactured by Mitsubishi Chemical) 35 parts Rutile titanium oxide (Brand name "R-25", Sakai Chemical Co., Ltd.) 10 parts Lubricant (Brand name "SZ-PG", Sakai Kagaku Co., Ltd.) 0.5 part Antioxidant (Brand name "Irganox 1010", Ciba Geigy Co.) 1 part Ultraviolet absorber (trade name "Seesorb 102", made by Shiraishi calcium) 0.4 part An adhesive sheet for protecting automobile coating film of the present invention was obtained in the same manner as in Example 1 except that the above resin mixture was used. It was The MOR value of the film was 1.6 to 2.0.

Example 5 When biaxially stretching by the tenter method, the stretching ratio in the transverse direction was 5
An adhesive sheet for protecting automobile coating films of the present invention was obtained in the same manner as in Example 2 except that the amount was reduced by 0%. The film M
The OR value was 3.1 to 3.4.

Comparative Example 1 The same as Example 2 except that the molten mixed resin was extruded from a T die onto a casting drum, cooled and wound as it was, without using a tenter method, to obtain an unstretched white film having a thickness of 40 μm. A pressure-sensitive adhesive sheet for protecting automobile coating films was produced in the same manner. The MOR value of the film is 1.2 to 1.4.
Met.

Comparative Example 2 The same as Example 3 except that the molten resin mixture was extruded from a T-die onto a casting drum, cooled and wound as it was, without using the tenter method, to obtain an unstretched white film having a thickness of 40 μm. A pressure-sensitive adhesive sheet for protecting automobile coating films was produced in the same manner. The MOR value of the film is 1.3 to 1.6.
Met.

The support thus obtained and the pressure-sensitive adhesive sheet for protecting automobile coating film were evaluated as follows, and the obtained results are shown in Table 1.

[Evaluation] [Processability] "Expansion / contraction degree by solvent" In order to judge the dimensional stability of the support at the time of adhesive processing, the expansion / contraction degree by the solvent of the obtained support was evaluated. The test piece was immersed in toluene for 1 minute using a Fencel elasticity tester (manufactured by Kumagai Riki Kogyo Co., Ltd.), and the maximum expansion and contraction rates in the vertical and horizontal directions were measured. The smaller the value, the more stable the dimension.

[Workability] "Tear strength" After the pressure-sensitive adhesive sheet for protecting automobile coating film was attached to the vehicle body, the tear strength in the longitudinal and transverse directions of the obtained support was used to judge the ease of cutting. evaluated. JIS P
According to 8116, the tear strength was measured in the machine direction and the transverse direction. The smaller the numerical value and the smaller the difference between the strength in the vertical direction and the strength in the horizontal direction, the easier the cutting process is.

[Weather Resistance] In order to evaluate the weather resistance, the following long-term exposure test was performed and each evaluation was performed. (Long-term exposure test) Put the test piece in Sunshine Inksenon long life weather meter (manufactured by Suga Test Instruments) and
Cycle (temperature 63 ° C, RH 40% condition: 6 hours, rain condition: 20 minutes, temperature 23 ° C, RH 65)
% Condition: 1 hour) was repeated 140 times.

"Adhesion" A steel sheet having a black alkyd melamine coating film having a glass transition point of 95 ° C. was applied with the obtained adhesive film for protecting automobile coating film at 23 ° C. and a reciprocating 2 kg rubber roller once. It adhered and left for 30 minutes to obtain a test piece. The test piece was subjected to a long-term exposure test. After the test, the test piece was placed at room temperature of 23 ° C. H. In a 65% atmosphere, with a tensile tester, in the direction of 180 ° C with respect to the test plate,
The adhesive strength when peeled off at a speed of 25 mm in width and 300 mm / min was measured. High adhesive strength means that the pressure-sensitive adhesive layer was exposed to high temperature, and it can be judged that the weather resistance is poor.

"Discoloration" A long-term exposure test was carried out in the same manner as in the evaluation of the adhesive strength, and the discolored state of the peeled protective pressure-sensitive adhesive sheet was evaluated. (Evaluation criteria) ○: Almost no change △: Some yellowing ×: Yellowing

[Tensile Strength] The tensile strength of the support was evaluated in order to determine the ease with which the pressure-sensitive adhesive sheet for protecting automobile coating films was peeled from the vehicle body. After performing the above-mentioned long-term exposure test on the obtained support, the tensile strength was measured in the longitudinal direction and the transverse direction according to JIS C 2318. If the numerical value is small, the film may be broken at the time of peeling, so the larger the numerical value, the better. Also, the smaller the difference in tensile strength between the longitudinal direction and the lateral direction, the less directivity there is when peeling,
It can be said that it is easier to remove the protective film from the vehicle body.

[Comprehensive Evaluation] The above test results were comprehensively evaluated. Comprehensive Evaluation Criteria A: Excellent. ○: Excellent. Δ: There is some problem, but there is no practical problem. X: Cannot be used for protecting automobile coating film.

[0040]

[Table 1]

It can be seen from Table 1 that each of the examples using the biaxially stretched polyolefin film as the surface substrate is excellent in processability, workability and weather resistance. The comparative examples using unstretched polyolefin films are inferior in all evaluations, and in particular, not only the adhesive strength after the weather resistance test is significantly increased but also adhesive residue is generated, resulting in an automobile coating film. It cannot be used for protection.

Among the Examples, in Example 5 in which the MOR value exceeded 3, there was a slight difference in the values in the longitudinal and transverse directions in tear strength and tensile strength after the weather resistance test. Is inferior to the other examples. That is, it is understood that a biaxially stretched film having a MOR value of 3 or less is preferable.

In addition, the one produced only from polypropylene of Example 1 has a higher adhesive force than the other Examples 2 and 3, and discoloration occurs. This indicates that polypropylene alone tends to have poor weather resistance. On the other hand, also in the case of Example 4 in which a large amount of polyethylene was mixed with polypropylene, the adhesive force was increased,
It can be seen that the weather resistance tends to be poor. It can be seen that Examples 2 and 3 in which polypropylene and polyethylene are mixed in the ratio of 95: 5 to 70:30 are excellent as the pressure-sensitive adhesive sheet for protecting automobiles.

[0044]

As is apparent from the examples, the pressure-sensitive adhesive sheet for protecting automobiles according to the present invention comprises forming a rubber-type pressure-sensitive adhesive layer on one surface of a base film made of a biaxially stretched polyolefin resin, In particular, it has excellent dimensional stability during production of the PSA sheet, and when it is applied to the vehicle body, it is easy to cut according to the shape regardless of the directionality.It also has excellent weather resistance after execution and peels off from all directions during removal. Can be removed without breaking.

Claims (3)

[Claims] 1. A pressure-sensitive adhesive sheet for protecting an automobile coating film, comprising a rubber-based pressure-sensitive adhesive layer provided on one surface of a base film made of a biaxially stretched polyolefin resin. 2. The substrate film is a film having a ratio of the maximum value and the minimum value of the transmitted microwave intensity converted to a film thickness of 50 μm, which is measured by a microwave method with a measurement frequency of 4 GHz, and is 3 or less. Item 1. An adhesive sheet for protecting automobile coating film according to item 1. 3. The pressure-sensitive adhesive sheet for protecting automobile coating film according to claim 1, wherein the polyolefin resin is a resin in which polypropylene and polyethylene are mixed in a ratio of 95: 5 to 70:30.