JP4775874B2 - Surface protection sheet and manufacturing method thereof - Google Patents

Description

【００３９】
表１の結果より、実施例では基材に発泡層を有することによって、基材ギレが防止され、しかも加工後においても製品からの表面保護シートの浮きの発生がないことがわかる。
【図面の簡単な説明】
【図１】支持基材の断面を拡大して模式的に示し、発泡倍率の測定法を示した図
【図２】ベンダー加工評価法を示した図[0001]
BACKGROUND OF THE INVENTION
The present invention can be applied to protect the surface of metal plates, painted metal plates, aluminum sashes, resin plates, decorative steel plates, vinyl chloride laminated steel plates, glass plates, etc. The present invention relates to a surface protective sheet having a use.
[0002]
[Prior art]
The characteristics required for the surface protection sheet are that the adherend is not damaged when it is subjected to processing such as bending after being attached to the adherend, and the surface protection sheet does not float or peel off. The surface protection sheet is not lifted or peeled off due to handling such as transportation or collision with other products, and no glue residue or the like is generated when peeled off.
[0003]
Conventionally, as a surface protection sheet that has been generally used, a pressure-sensitive adhesive in which an acrylic copolymer is cross-linked three-dimensionally with an isocyanate compound or a methylol compound on a supporting substrate such as soft polyvinyl chloride or a polyolefin resin to increase cohesion A surface protective sheet using a pressure-sensitive adhesive in which an appropriate amount of a tackifier is blended with natural rubber or modified natural rubber is known.
[0004]
However, it is said that the use of soft polyvinyl chloride is not preferable because it may cause generation of dioxins during incineration. In addition, the surface protection sheet using a polyolefin-based support base material causes damage or cutting of the support base material during bending of the metal plate, etc. There was a case where it becomes defective.
[0005]
[Problems to be solved by the invention]
In the course of earnest research to overcome the above problems, the present inventors tried to reduce the occurrence of scratches on the product by increasing the thickness of the support base material layer to suppress the base material distortion. By increasing the thickness, the texture of the surface protection sheet is impaired, and in the case of weak adhesion like the surface protection sheet, there was a problem that the surface protection sheet floats after processing or peels off during transportation. .
[0006]
Furthermore, the present inventors tried to improve the adhesiveness of the pressure-sensitive adhesive layer and prevent the surface protection sheet from floating and the like.
[0007]
However, the releasability is greatly impaired by improving the adhesiveness, causing a problem of peeling failure when peeling after construction, and causing a residue of adhesive on the product surface.
[0008]
The present invention does not cause scratches or dents on the surface of the base material or the metal plate even when bending is performed, and the surface protection sheet is not peeled off or lifted after processing. An object of the present invention is to provide a surface protective sheet that can be satisfactorily peeled even when stored for a long time.
[0009]
[Means for Solving the Problems]
The surface protective sheet of the present invention is provided with an adhesive layer on one side of a support base material, and the support base material has a multilayer structure composed of a plurality of layers each made of a polyolefin-based resin, Ri one layer foamed layer der, the thickness of the foam layer is characterized by a 1 / 2-1 / 20 to the supporting substrate total thickness in a state after foaming.
[0010]
According to the present invention, even if the support base layer is thickened to prevent the base material from being distorted, the curved base followability is improved because the support base material layer has the foam layer, and the support base material thickness is increased. Even if it does not float. Moreover, the metal mold | die at the time of a bending process of a foaming layer reduces stress concentration with respect to a metal plate, and generation | occurrence | production of the damage | wound etc. of a metal plate can be prevented.
[0011]
The foamed layer is preferably the outermost layer on the side opposite to the adhesive layer.
When the foamed layer is provided as the outermost layer, the surface of the surface protection sheet is greatly roughened, and blocking between the surface protection films can be prevented when they are collected after being attached to a metal plate.
[0012]
Another aspect of the present invention is a method for producing a surface protective sheet in which an adhesive layer is provided on one side of a support substrate,
The support base material has a multilayer structure composed of a plurality of layers each made of a polyolefin resin, at least one of which is a foam layer, and the support base material layer and the adhesive layer are co-extruded. And the thickness of the foam layer is set to 1/2 to 1/20 with respect to the thickness of the entire support substrate in the state after foaming .
[0013]
The surface protective sheet of the present invention may be manufactured by applying a pressure-sensitive adhesive to a support substrate, but by manufacturing by a co-extrusion method, there is no need to separately provide a pressure-sensitive adhesive coating step, which makes it easier. It can be manufactured at low cost.
[0014]
In the manufacturing method described above, the foamed layer is preferably formed as an outermost layer on the side opposite to the adhesive layer.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the support substrate having a multilayer structure composed of a plurality of layers each made of a polyolefin-based resin is a multilayer structure of two layers or three or more layers, and at least one layer of which is foamed. Say. Moreover, at least 1 layer of a support base material layer is an unfoamed layer from a viewpoint of the base material prevention at the time of peeling, and a base material strength. The non-foamed layer refers to a layer that is not foamed by adding a foaming agent, and even if there are air entrained bubbles, it is not called a foamed layer.
[0016]
Examples of olefin resins that can be used for the support substrate include olefin homopolymers, multiple olefins, and copolymer resins such as block polymers and random polymers using other monomers. Specifically, propylene Polymers, low density polyethylene, high density polyethylene, medium density polyethylene, linear low density, etc. ethylene polymers, ethylene / propylene copolymers, ethylene-α-olefin copolymers, olefin polymers such as reactor TPO, ethylene Examples include olefin copolymers of olefin and other monomers such as vinyl acetate copolymer and ethylene / methyl methacrylate copolymer. These olefin-based resins may be used alone, or two or more of them may be used to constitute the support substrate. The foamed layer and the unfoamed layer may be different olefin resins.
[0017]
For the purpose of preventing deterioration or the like, a light stabilizer such as an antioxidant, an ultraviolet absorber, or a hindered amine light stabilizer may be added to the support substrate. In addition, an antistatic agent and other suitable additives such as fillers such as calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide, pigments, anti-tarnish agents, lubricants, antiblocking agents, and the like can also be blended.
[0018]
The thickness of the supporting substrate layer is generally 20 to 300 μm, particularly 30 to 250 μm, and preferably 40 to 200 μm, but is not limited thereto.
[0019]
As a foaming agent to be added to the olefin resin to form a foamed layer, a known polyolefin resin foaming agent can be used without limitation. For example, propane, n-butane, i-butane, n-pentane, Volatile organic blowing agents such as hydrocarbons and halogenated hydrocarbons such as hydrocarbons such as i-pentane, cyclopentane, pentene and hexane, halogenated hydrocarbons, inorganic gas blowing agents such as carbon dioxide, air and nitrogen, azodicarbonamide, N, N -Decomposable organic foaming agents such as dinitrosopentamethylenetetramine and azobisisobutyronitrile, and decomposable inorganic foaming agents such as sodium hydrogen carbonate and calcium carbonate. These foaming agents can be used alone or in admixture of two or more. A commercially available foamable masterbatch may also be used. As a commercially available foamable masterbatch, for example, trade name Polyslen (manufactured by Eiwa Kasei Co., Ltd.) can be used.
[0020]
The form of the bubbles in the foamed layer may be closed cells, open cells, or a mixture of these. However, closed cells are more preferable from the viewpoint of improving the scratch resistance of the product coated with the surface protective sheet. In addition, the expansion ratio of the foam layer may be determined appropriately. It is preferably 2 to 6 times. 3 to 4 times is more preferable, and 1 is more preferable. 5 to 3 times. The expansion ratio is 1. If it is less than 2, the effect of improving the texture and scratch resistance is poor, and if it exceeds 6 times, the strength of the foamed layer decreases. The foamed layer can be an appropriate layer such as an intermediate layer, outermost layer, innermost layer, etc. of the support substrate having a multilayer structure, but as described above, from the viewpoint of preventing blocking of the surface protective sheet, the outermost layer, that is, the adhesive layer More preferably, it is a layer on the opposite side.
[0021]
The thickness of the foamed layer is 1/2 to 1/20, more preferably 1/3 to 1/10, still more preferably 1/4 to 1/8, relative to the thickness of the entire support substrate in the state after foaming. It is. When the thickness of the foamed layer exceeds 1/2 of the entire supporting substrate, the strength of the supporting substrate is significantly reduced, and the surface protective sheet may be torn during peeling and cannot be peeled off. Moreover, when it is less than 1/20, the texture improving effect is poor, and the workability may be reduced, or the protective sheet may be lifted from the product.
[0022]
As a material constituting the adhesive layer, for example, a known adhesive such as rubber, acrylic or urethane may be used. Examples of rubber-based polymers include diene polymers such as natural rubber, polyisobutylene, butyl rubber, polyisoprene, polybutadiene and their hydrogenated products, ethylene propylene rubber, ethylene-α-olefin, ethylene-propylene-α-olefin, and propylene. -Olefin-based rubbers such as α-olefin, styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene (SEPS) ABA type block polymer such as styrene / butadiene (SB), styrene / isoprene (SI), styrene / ethylene / butylene copolymer (SEB), styrene / ethylene / propylene copolymer (SEP), etc. A-B type Copolymer, styrene random copolymer such as styrene / butadiene rubber (SBR), hydrogenated styrene random copolymer (HSBR), styrene / ethylene-butylene copolymer / AB, such as olefin crystal (SEBC) Examples include those based on O-type styrene / olefin crystal block polymers and C / B / C type olefin crystal block polymers such as olefin crystals / ethylene-butylene copolymers / olefin crystals (CEBC). These can be used alone or in combination of two or more.
[0023]
When forming the adhesive layer, for example, softening agent, olefin resin, silicone polymer, liquid acrylic copolymer, phosphate ester compound, tackifier, anti-aging, etc. An appropriate additive such as a filler, a pigment such as an agent, a hindered amine light stabilizer, an ultraviolet absorber, and other calcium oxide, magnesium oxide, silica, zinc oxide, titanium oxide, and the like can be blended.
[0024]
The surface of the adhesive layer may be subjected to surface treatment for the purpose of adhesiveness control or pasting workability, such as corona discharge treatment, ultraviolet irradiation treatment, flame treatment, plasma treatment or sputter etching treatment, as necessary. This is a preferred embodiment.
[0025]
The support substrate is formed by coextrusion molding of a foam layer forming material composed of a mixture of an olefin resin and a foaming agent masterbatch and an olefin resin not containing a foaming agent, or by using an organic gas or an inorganic olefin resin. It can be performed by a method of co-extrusion molding of a foam layer forming material in which a gas agent is injected in an extruder and a base material layer made of an olefin resin not containing a foaming agent.
[0026]
The surface protective sheet can be formed by, for example, applying a solution or emulsion of the adhesive layer forming material in a hot melt or solvent to the support substrate, or applying a solution or emulsion of the adhesive layer forming material in a hot melt or solvent on the separator. A method of transferring a coated adhesive layer to a supporting substrate, a method of extruding an adhesive layer forming material onto a supporting substrate, a method of co-extruding the supporting substrate layer and the adhesive layer in two layers or multiple layers, etc. It can carry out according to the formation method of well-known surface protection sheet.
[0027]
In particular, from the viewpoint of productivity and cost, a preferable method for forming a surface protective sheet is preferably produced by a multilayer coextrusion method of an olefin resin layer containing a foaming agent, a base material layer not containing a foaming agent, and an adhesive layer.
[0028]
The thickness of the pressure-sensitive adhesive layer to be formed may be appropriately determined according to the adhesive force and the like, and is generally 1 to 50 μm, preferably 2 to 40 μm, particularly preferably 5 to 20 μm. If necessary, the adhesive layer can be protected by temporarily attaching a separator or the like until practical use.
[0029]
The surface of the support substrate with the adhesive layer is subjected to a surface treatment for the purpose of improving the adhesive strength of the adhesive layer, such as corona discharge treatment, flame treatment, plasma treatment, sputter etching treatment, primer undercoating treatment, etc. It can also be applied as necessary. In addition, for the surface of the supporting substrate that is not provided with an adhesive layer, for example, a fatty acid amide, a fatty acid ester, polyethyleneimine, or the like is added to the supporting substrate for the purpose of forming a wound body that can be easily rewound. A coating layer made of an appropriate release agent such as silicone, long chain alkyl, or fluorine can also be provided.
[0030]
【Example】
Examples and the like specifically showing the configuration and effects of the present invention will be described below.
[Production of surface protection sheet]
Example 1
A foam layer containing 3 parts by weight of Polyslene EE105 (manufactured by Eiwa Kasei Co., Ltd.) as a foaming agent masterbatch with 100 parts by weight of low-density polyethylene (Tosoh Corp., Petrocene 180) and white with respect to 100 parts by weight of low-density polyethylene An intermediate layer composed of 4 parts by weight of pigment HCM2035W (manufactured by Dainichi Seika Co., Ltd.) and an innermost layer composed of low-density polyethylene were extruded at a die temperature of 200 ° C. by a T-die method. At that time, the foam layer was 30 μm, the intermediate layer was 70 μm, and the innermost layer was 20 μm.
[0031]
Thereafter, 10 parts by weight of a petroleum resin (Arakawa Chemical Co., Alcon P-100) was mixed with 100 parts by weight of styrene / ethylene-butylene / styrene copolymer (SEBS) (Asahi Kasei Co., Ltd., Tuftec HI042) and dissolved in a toluene solution. The applied pressure-sensitive adhesive was applied so that the thickness after drying was 10 μm, and after drying, a surface protective sheet was prepared. At this time, the expansion ratio of the foam layer was 1.5 times.
[0032]
(Example 2)
A foam layer containing 3 parts by weight of Polyslene EE105 (manufactured by Eiwa Kasei Co., Ltd.) as a foaming agent masterbatch with 100 parts by weight of low-density polyethylene (Tosoh Corp., Petrocene 173) and white with respect to 100 parts by weight of low-density polyethylene Pigment HCM2035W (manufactured by Dainichi Seika Co., Ltd.) An intermediate layer composed of 4 parts by weight, an innermost layer composed of low-density polyethylene, and a styrene / ethylene-butylene / styrene copolymer (manufactured by Asahi Kasei Co., Ltd., Tuftec H1221) as an adhesive layer by the T-die method Multi-layer coextrusion was performed at a die temperature of 230 ° C. to obtain a surface protective sheet. At that time, the foamed layer (1) was 40 μm, the intermediate layer was 50 μm, the innermost layer was 20 μm, and the adhesive layer was 7 μm. At this time, the expansion ratio of the foam layer was 2.0 times.
[0033]
(Comparative Example 1)
A surface protective sheet was prepared according to Example 1 except that the foaming agent master batch of Example 1 was not added and the thickness of the outermost layer was changed to 30 μm.
[0034]
(Comparative Example 2)
A surface protective sheet was prepared according to Example 2 except that the foaming agent master batch of Example 2 was not added. Due to non-foaming, the outermost layer was 20 μm.
[0035]
〔Evaluation test〕
<Measurement of expansion ratio>
The expansion ratio was measured as follows.
The cross section of the measurement sample was cut with a microtome, and the measurement was performed as follows with respect to the foamed layer of the electron microscopic cross-section photograph taken at 10 arbitrarily selected locations.
A cross section of the supporting substrate is schematically shown in FIG. The support substrate 1 is composed of a foam layer 3 and a non-foam layer 5. The adhesive layer is provided on the surface 7.
Let A be the length of an arbitrary place (a straight line between arrows) of an arbitrarily set portion. Let B be the total of the straight unfoamed lengths. For example, at the measurement position P shown in FIG. 1, B = b ₁ + b ₂ + b ₃ is calculated. The expansion ratio was determined by the following formula. In addition, the measurement measured 10 points (n = 10) at intervals of 10 mm, and calculated as an average value.
Foaming ratio = A / B
[0036]
<Vendor processability evaluation>
After a surface protective sheet was attached to a 3 mm thick stainless steel plate (2D finish), the upper protective mold and the lower mold shown in FIG. 2 were used, and bender processing was performed with the surface protective sheet attached surface facing downward. . In FIG. 2, L = 12 mm, R = 1.5 mm, and the bending angle θ is 88 degrees.
After the bender processing, the stainless steel plate was taken out, and the presence or absence of a base material in the surface protective sheet was visually confirmed.
[0037]
<Confirmation of bent part>
The presence or absence of lifting of the surface protective sheet of the curved portion after the bender processing was visually confirmed.
The results of the evaluation are summarized in Table 1.
[0038]
[Table 1]

[0039]
From the results shown in Table 1, it can be seen that, in the examples, the base material has a foam layer to prevent the base material from being creased, and the surface protection sheet does not float from the product even after processing.
[Brief description of the drawings]
FIG. 1 is an enlarged schematic view of a cross-section of a support substrate, and shows a method for measuring the expansion ratio. FIG. 2 shows a bender processing evaluation method.

Claims (2)

A method for producing a surface protective sheet in which an adhesive layer is provided on one side of a support substrate,
The support base material has a multilayer structure composed of a plurality of layers each made of a polyolefin resin, at least one of which is a foam layer, and the support base material layer and the adhesive layer are co-extruded. The method for producing a surface protective sheet is characterized in that the foam layer is formed to have a thickness of 1/2 to 1/20 with respect to the thickness of the entire support substrate in the state after foaming. The method for producing a surface protective sheet according to claim 1 , wherein the foamed layer is formed as an outermost layer on the side opposite to the adhesive layer.

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