JPH09157598A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface protective film which has suitable initial tack, does not undergo an increase in pressure-sensitive adhesiveness with the lapse of time, and can easily be peeled from the substrate without leaving much adhesive on the substrate even when exposed to high temperature or applied to a substrate for a long time by forming a pressure-sensitive adhesive layer comprising a specified resin on either surface of a base film made of a polyolefin resin. SOLUTION: This film is prepared by forming a pressure-sensitive adhesive layer based on a hydrogenated styrene random copolymer on either surface of a base film made of a polyolefin resin. It is desirable that the pressure- sensitive adhesive resin is one based on a hydrogenated styrene random copolymer and an ethylene/α-olefin copolymer. It is also desirable that the pressure- sensitive adhesive layer is one based on a hydrogenated styrene random copolymer and a tackifying resin. It is more desirable that the pressure-sensitive adhesive layer it one based on a hydrogenated styrene random copolymer, an ethylene/α-olefin copolymer and a tackifying resin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a surface protection film such as a metal plate such as a stainless plate and an aluminum plate, a coated metal plate, a synthetic resin plate, a glass plate, a vinyl chloride laminated steel plate, and the like. The present invention relates to a surface protective film which protects the surface processed into an embossed board or matte board or the surface subjected to hairline processing.

[0002]

2. Description of the Related Art Conventionally, as a surface protective film, polyvinyl chloride has been used to prevent scratches on the surface of metal plates, synthetic resin plates, decorative plates, etc. during cutting, transportation and transportation.
A surface protective film in which an adhesive layer containing ethylene / vinyl acetate copolymer, acrylic resin, natural rubber or the like as a main component is provided on one surface of a base film such as polyethylene or polypropylene or paper is often used.

Further, one or both surfaces of a metal plate, a synthetic resin plate, a decorative plate, etc. are subjected to hairline processing, mat processing,
For embossed resin plates with irregularities on the surface, a natural rubber that is said to be glued as an adhesive that easily plastically deforms at room temperature and a tackifier are dissolved in a solvent to form a base film by bar coating or the like. The applied surface protection film is used.

By the way, it has an appropriate adhesive force to a surface having irregularities having different surface roughness, and is exposed to a high temperature,
Even if it is applied for a long period of time, the adhesive strength does not change with time, it can be easily peeled off when not needed, there is no adhesive residue, the base material does not break, or chlorine gas is not released even when incinerated, or A surface protection film that does not use a solvent has been desired.

Therefore, in order to solve the above problems, Japanese Patent Publication No. 58-30911 and Japanese Patent Laid-Open No. 61-103975.
On one side of the base film such as polyolefin,
A block copolymer of the general formula AB (wherein A represents a styrene polymer block, B represents a butadiene polymer block, an isoprene polymer block, or an ethylene / butylene copolymer block) and a tackifier resin. There is disclosed a surface protective film having a pressure-sensitive adhesive layer formed by mixing and.

However, when a pressure-sensitive adhesive layer composed of a block copolymer and a tackifying resin is attached to the surface protective film, the content of the block copolymer in the pressure-sensitive adhesive composition is large, and therefore the pressure-sensitive adhesive after the attachment is adhered. The strength is already high, and there is a problem that the adhesive strength is further increased and peeling is difficult when the adherends are changed over time during transportation and storage, when the adherends are stacked, and when the adherends are left at a high temperature of about 40 ° C.

As a method of improving them, Japanese Patent Laid-Open No. 6-
In JP-A-240216, a pressure-sensitive adhesive layer containing an ethylene-α-olefin copolymer and / or a propylene-α-olefin copolymer, a block-type styrene-based copolymer, and a tackifying resin as main components is exposed to a high temperature or is exposed for a long time. There is disclosed a surface protective film which does not cause an increase in the adhesive force with time even when it is adhered to the surface protective film.

However, this surface protection film is
It is effective for a mirror plate such as a metal plate, a synthetic resin plate, a decorative plate or a surface having a small center average roughness (for example, less than 1 μm) and a comparatively smooth surface, but the surface is hairline processed, matted, Metal plate or resin plate having embossed unevenness (for example, center line average roughness (JIS-B06
01) Ra having a thickness of 1 to 3 μm) has a problem that it is difficult to stick.

[0009]

DISCLOSURE OF THE INVENTION As a result of intensive studies aimed at solving the above-mentioned drawbacks, the present invention has a suitable initial adhesive force (100 g to 400 g / 50 mm) and is exposed to high temperatures. To provide a surface protective film which does not increase in adhesive strength with time even when applied for a long period of time, and can be easily peeled off when not needed, has no adhesive residue on an adherend, and does not cause breakage of a substrate. With the goal.

[0010]

Means for Solving the Problems In accordance with the present invention, an adhesive layer is formed on one surface of a base film made of a polyolefin resin, and the main component of the adhesive layer is a styrene random copolymer. A surface protective film comprising a hydrogenated resin.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as the polyolefin resin forming the base film, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene (LLD-PE), ethylene-
α-olefin copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-
Methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, polypropylene and the like can be used, and a mixture of two or more of these polyolefin resins may be used.

The hydrogenated resin of the styrene-based random copolymer used in the pressure-sensitive adhesive layer of the present invention is 7-45% by weight of styrene-based monomer, preferably 7-35% by weight and 93-55% by weight of butadiene, Preferred is a copolymer hydrogenated resin with 93 to 65% by weight. When the amount of the styrene-based monomer is less than 7% by weight, the handleability as a resin is deteriorated, and when the amount of the styrene-based monomer exceeds 45% by weight, the resin becomes hard. Furthermore, the hydrogenation rate of the copolymer is 95%
Or more, preferably 97% or more. Further, these resins include a block type and a random type depending on the polymerization method,
The random type is preferable in terms of adhesiveness to the embossed plate having irregularities and the mat plate.

The block type of the styrene copolymer hydrogenated resin is a hydrogenated block copolymer of styrene or α-methylstyrene and butadiene. Hydrogenated block copolymers of styrene and butadiene are commonly called SEBS (styrene / ethylene / butadiene / styrene) resins. Further, the random type of the hydrogenated resin of the styrene-based copolymer means a block (a) of polystyrene or α-methyl polystyrene and a random copolymer block (b) of styrene or α-methylstyrene and butadiene, if necessary. Is a block copolymer composed of a tapered block (c) of styrene or α-methylstyrene and butadiene, and these are block-bonded.

The difference between the random type and the block type of the styrene-based copolymer hydrogenated resin is that the block type is a glass near 100 ° C. corresponding to the block (a) of polystyrene or α-methyl polystyrene. While the transition temperature is detected, the random type is in that the glass transition temperature corresponding to (a) is not detected.

Ethylene used in the pressure-sensitive adhesive layer of the present invention
The α-olefin copolymer has an ethylene content of 30% by weight or more, preferably 40% by weight or more, more preferably 50% by weight or more, and propylene, butene-1, and hexene-.
It is a copolymer of 1,4-methylpentene-1 and octene-1. Among them, propylene, butene-1, octene-1
The copolymer with the above may be a single substance or a mixture, but is non-crystalline,
Low crystallinity copolymers are preferred.

The amount of the ethylene-α-olefin copolymer added is preferably less than 50% by weight because the cohesive force is too small when it exceeds 50% by weight with respect to the hydrogenated resin of the styrene random copolymer.

The tackifying resin used in the pressure-sensitive adhesive layer of the present invention is one that is selectively compatible with the hydrogenated resin of the styrene random copolymer and the ethylene-α-olefin copolymer. For example, aliphatic hydrocarbon resins, terpene resins, coumarone-indene resins, aromatic hydrocarbon resins, rosin resins and the like are preferably used. A terpene resin is preferable from the viewpoint of good compatibility with a hydrogenated resin of a styrene-based random copolymer and development of adhesiveness to an adherend having irregularities. The addition amount of tackifying resin in the adhesive is 1
If the amount is less than 10% by weight, the adhesiveness to the adherend having irregularities will not be exhibited. On the contrary, if the amount exceeds 30% by weight, the adhesive force will be easily increased due to temperature and aging, and the adhesive residue on the adherend will remain. Since it tends to occur, it is limited to 1 to 30% by weight, and more preferably 1 to 20% by weight. If the glass transition temperature and the softening point of the tackifier resin are lower, the molecular weight is smaller and the tackiness is easily imparted, but the heat stability of the extrusion film formation is inferior. Therefore, the softening point is preferably in the range of 100 to 140 ° C. Further, in the problem that the adhesive strength increases when the surface protective film is adhered to an adherend and then left at high temperature, and peeling is difficult, depending on the content of the tackifying resin in the adhesive, the tackifying resin The glass transition temperature is preferably 50 ° C. or higher, more preferably 60 ° C. or higher in consideration of exposure to the outside air temperature in the summer, since the glass transition temperature is easily affected and the lower the glass transition temperature, the higher the adhesive strength. Is.

Regarding the phenomenon that the adhesive strength is likely to increase due to temperature / aging and the adhesive residue is likely to be left on the adherend, the glass transition temperature of the tackifying resin mixed in the adhesive layer is exposed. If the temperature is sufficiently higher than the temperature, problems do not easily occur, but if a tackifying resin having a glass transition temperature lower than the exposed temperature is mixed, the tackifying resin easily viscously flows to the surface of the pressure-sensitive adhesive layer, and thus the surface of the adherend The cause is considered to be coating. When the temperature for peeling off the surface protective film is equal to or higher than the glass transition temperature of the tackifying resin, the adhesive force is hard to increase, but conversely, when the temperature for peeling is equal to or lower than the glass transition temperature of the tackifying resin, It is presumed that the tackifying resin that coats the adherend is liable to increase in adhesive strength by cooling and solidifying, and problems such as adhesive residue on the adherend are likely to occur, but it is not clear.

The hydrogenated resin of the styrene-based random copolymer, the ethylene-α-olefin copolymer and the tackifying resin of the pressure-sensitive adhesive layer of the present invention are added to the adherends having different central average roughnesses. Therefore, it can be appropriately determined. For example, for an adherend having a large central average roughness (Ra), the addition amount of the ethylene-α-olefin copolymer may be reduced or the addition amount of the tackifier may be increased. Adhesive strength (100-400g / 50mm)
Can be provided.

The surface protective film of the present invention is one in which the above-mentioned pressure-sensitive adhesive composition is laminated on one surface of the above-mentioned substrate film, and any method may be adopted as the laminating method, for example, the above-mentioned pressure-sensitive adhesive composition. It may be a method of dissolving the substance in a solvent and applying it to a base film by bar coating or the like to laminate it, but a method of laminating by co-extruding the polyolefin resin and the pressure-sensitive adhesive composition forming the base film from the viewpoint of cost. Is preferred.

The thickness of the base material film and the pressure-sensitive adhesive layer constituting the surface protective film is appropriately determined depending on the application, but the thickness of the base material film is 10 to 80 μm, and the thickness of the pressure-sensitive adhesive layer is 5 to 30 μm. Is.

Further, to the pressure-sensitive adhesive layer, low-density polyethylene, medium-density polyethylene, as long as the effect of the present invention is not impaired,
High-density polyethylene, linear low-density polyethylene (LL
D-PE), ethyl acrylate copolymer, ethylene-
Vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer,
One or more polyolefin resins such as polypropylene may be added. Also, if necessary, a softening agent, an ultraviolet absorber, a heat resistance stabilizer, an antioxidant,
It can be used in combination with additives usually added to resins such as weather resistance stabilizers, antistatic agents, antiblocking agents, slip agents, pigments, dyes, and inorganic / organic fillers.

[0023]

[Characteristic measuring method and evaluation criteria]

(1) Glass transition temperature Using a differential scanning calorimeter (DSC, SII type manufactured by Seiko Denshi Kogyo Co., Ltd.), a glass state was obtained when 10 mg of a sample was heated from 0 ° C. at a heating rate of 5 ° C./min. The glass transition temperature was read by reading the center point between the start point and the end point of the specific heat change from the chart in which the change in the specific heat with the second transition from the rubber to the rubber state was measured.

(2) Adhesive strength A surface protective film is applied to a mat plate (center average roughness JIS-B
0601, Ra = 1.0 μm), embossed plate (Ra =
It was stuck on the surface of 2.1 μm) at 23 ° C. using a pressure roller of 2 kg, and the adhesive force in each case of 23 ° C. × 30 minutes and 60 ° C. × 7 days was measured according to JIS-Z0237.

(3) Contamination property of adherend surface A surface protective film is used as a mat plate (center average roughness JIS-B).
0601, Ra = 1.0 μm), embossed plate (Ra =
It was attached to a surface of 2.1 μm) at 23 ° C. by using a pressure roller of 2 kg, and the contamination of the mat plate after peeling was visually determined in each case of 23 ° C. × 30 minutes and 60 ° C. × 7 days. The sample which was not contaminated at all was evaluated as ○, the sample in which some stains were visible but practically usable was evaluated as Δ, and the sample in which stains were visible and unusable was evaluated as ×.

[0026]

Next, the effects of the present invention will be described with reference to examples.

(1) Preparation of pressure-sensitive adhesive composition Examples 1 to 6 As a hydrogenated resin of a styrene-based random copolymer in the pressure-sensitive adhesive layer, "Dyalon" 1320P manufactured by Japan Synthetic Rubber Co., Ltd. as an ethylene-α-olefin copolymer , Ethylene-octene-1 copolymer (“ENGAGE” manufactured by Dow Chemical Co., Ltd.
EG8200), terpene resin "Clearon" P125 manufactured by Yasuhara Chemical Co., Ltd. is used as a tackifying resin,
The addition amount of each is shown in Tables 1 and 2, 1.0 parts by weight of "Irganox" 1010 manufactured by Ciba-Gaigi Co., Ltd. as an antioxidant, and 0.5 parts by weight of "Tinuvin" 327 manufactured by Ciba-Gaigi Co., Ltd. as an ultraviolet absorber. The pressure-sensitive adhesive composition was prepared by blending.

Comparative Examples 1 and 3-5 A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that "Tuftec" H1052 manufactured by Asahi Kasei Kogyo Co., Ltd. was used instead of the hydrogenated resin of the styrene random copolymer.

Comparative Example 2 Ethylene-1 as an ethylene-α-olefin copolymer
Butene Copolymer ("Tahuma" A408 manufactured by Mitsui Petrochemical Co., Ltd.
5) A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that 90% by weight was used.

Examples 7 to 10 and Comparative Examples 6 to 8 As the tackifying resin, Examples 7, 9 to 10 and Comparative Example 8 are "Clearon" P12 manufactured by Yasuhara Chemical Co.
5 and Example 8 used "ALCON" P115 manufactured by Arakawa Chemical Co., Ltd., "Clearon" P85 manufactured by Yasuhara Chemical Co., Ltd. used in Comparative Example 6, and no tackifying resin added in Comparative Example 7. Further, Examples 7 to 10 have a ratio of the hydrogenated resin of the styrene-based random copolymer to the ethylene-α-olefin copolymer of 2
With respect to the composition of / 1, the pressure-sensitive adhesive composition was prepared in the same manner as in Example 4, except that the above tackifying resin, antioxidant and ultraviolet absorber were used.

In Comparative Examples 6 to 8, "Tuftec" H1052 manufactured by Asahi Kasei Kogyo Co., Ltd. was used in place of the hydrogenated resin of the styrene-based random copolymer, and the ratio with the ethylene-α olefin copolymer was 2/1. The above tackifying resin was added to the above composition, and an adhesive composition was prepared in the same manner as in Example 4 for the antioxidant and the ultraviolet absorber.

(2) Preparation of Surface Protective Film High-density polyethylene (“Showflex” F6080 manufactured by Showa Denko KK) / low-density polyethylene (“Sumikasen” L70 manufactured by Sumitomo Chemical Co., Ltd.) for the above-mentioned pressure-sensitive adhesive composition and substrate layer
5) = 50/50 is extruded by a two-layer coextrusion method,
A surface protection film having a thickness of 60 μm was prepared so that the thickness of the base material layer was 50 μm and the thickness of the adhesive layer was 10 μm.

The obtained surface protective film was attached to a mat plate or an embossed plate having different center average roughness, and the characteristics of the film were evaluated. The results are shown in Table 1, Table 2 and Table 3.

[0034]

[Table 1] As can be seen from Table 1, Examples 1 to 6 have an appropriate adhesive force to any adherend having irregularities, and show little change with time due to high temperature (60 ° C.). It was Further, no contamination of the surface of the adherend was observed after sticking to or peeling from the adherend.

[0035]

[Table 2] In comparison with this, as shown in Table 2, Comparative Examples 1 to 4
Although the surface of the adherend was not observed, the adhesive strength was insufficient for the adherend having irregularities. In Comparative Example 5, the adhesive strength was too strong, the surface of the adherend was soiled, and the change with time at high temperature was large.

[0036]

[Table 3] Further, as seen in Table 3, Examples 7 to 10 also have an appropriate adhesive force to any adherend having irregularities, and the change with time of the adhesive force at 60 ° C is small. Met.

On the other hand, Comparative Example 6 had an appropriate adhesive force to any adherend having irregularities, but the adhesive force at 60 ° C. increased and the change with time was large. In addition, Comparative Example 7 in which the tackifying resin was not added had insufficient adhesion. Furthermore, the content of the tackifying resin in the adhesive is 5
In Comparative Example 8 of 0%, the adhesive strength was too strong, and adhesive residue was left on the adherend.

The surface protective film of the present invention has an adhesive property to an adherend having an uneven mat plate or an embossed plate as shown in the examples, and the adhesive force does not increase due to temperature and aging, It can be seen that there is no adhesive residue on the adhered body, which is significantly superior.

[0039]

The surface protective film obtained by the present invention is
Styrene-based random copolymer hydrogenated product and ethylene-
A film obtained by melt-extruding a pressure-sensitive adhesive layer containing an α-olefin copolymer and a tackifying resin as a main component and a base material layer by a two-layer coextrusion method, and having unevenness of hairline processing, mat processing, and embossing processing. With respect to adherends such as metal plates and synthetic resin plates that it has, it has a suitable initial adhesive force, does not increase with time even if it is exposed to high temperatures or adhered for a long time, Further, it can be easily peeled at the time of peeling, there is no adhesive residue on the adherend, and the base film is not broken.

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Claims (5)

[Claims] 1. A surface protection characterized in that a pressure-sensitive adhesive layer is formed on one surface of a base film made of a polyolefin resin, and the main component of the pressure-sensitive adhesive layer is a hydrogenated resin of a styrene random copolymer. the film. 2. The surface protective film according to claim 1, wherein the main components of the pressure-sensitive adhesive layer are a hydrogenated resin of a styrene-based random copolymer and an ethylene-α-olefin copolymer. 3. The surface protective film according to claim 1, wherein the main components of the pressure-sensitive adhesive layer are a hydrogenated resin of a styrene-based random copolymer and a tackifying resin. 4. The pressure-sensitive adhesive layer is mainly composed of a hydrogenated resin of a styrene-based random copolymer, an ethylene-α-olefin copolymer and a tackifying resin. The surface protective film according to any one of the above. 5. The tackifying resin is contained in the pressure sensitive adhesive in an amount of 1 to 30% by weight, and the glass transition temperature of the tackifying resin is 50 ° C. or higher. Surface protection film.