JP6995840B2 - Substrate for coating film surface protective film and coating film surface protective film using it - Google Patents

Description

The present invention relates to a base material for a coating film surface protective film and a coating film surface protective film having an adhesive layer on one side of the base material.

Metal plates, decorative plates, resin plates, glass plates, etc. or home appliances, automobiles, electronic parts, etc. processed using them are protected on the surface to prevent scratches, stains, etc. during transportation or storage. The film is attached.

In particular, unstretched PP (polypropylene) is used because a coating film surface protective film is generally used to protect the coating film of an automobile during transportation or storage of an automobile, and it is expected that the temperature will be high during transportation or storage. ) Film is used. However, the unstretched PP film has a weak tear strength in the film winding direction (MD direction) in the film forming process, and when the attached protective film is peeled off, the film tears and cannot be peeled off at one time, resulting in reduced work efficiency. There is a problem of doing.

On the other hand, as PPs generally used for a base material for a coating film surface protective film (a base material before providing an adhesive layer), there are homo PP, random PP or block PP, and these PPs include the following. There are challenges. That is, when homo-PP is used, the unfolding force after the adhesive processing (after forming the adhesive layer) is heavy, and it cannot be easily unfolded at the time of use, which impairs workability. Further, when random PP or block PP is used, it swells due to the solvent used during the adhesive processing, the film curls during drying, the flatness is impaired, and the workability during use is affected.

As a known coating film surface protective film, for example, in Patent Document 1, "a coating film surface protective film made of a three-layer laminated film of a polyethylene resin, both outer layers of the three-layer laminated film have a melt flow rate of 0. The intermediate layer is made of a polyethylene resin having a density of 0.930 to 0.945 g / cm ³ at 1 to 3 g / 10 minutes, and the intermediate layer is made of a polypropylene resin having a melt flow rate of 0.1 to 3 g / 10 minutes. The resin elution amount measured by the cross fractionation method of the polypropylene resin is 40 to 70% by weight of the total polypropylene resin amount at 0 ° C. or lower, and 10 to 30% by weight of the total polypropylene resin amount at 0 ° C. or higher and 70 ° C. or less. , 20 to 40% by weight of the total polypropylene resin at over 70 ° C., and the total component of the polyethylene resin and the polypropylene resin is 50 to 95% by weight of the polyethylene component and 5 to 50 of the α-olefin component other than ethylene. A coating surface protective film comprising a weight% by weight. ”Is disclosed. The coating film surface protective film of Patent Document 1 is said to be able to efficiently perform affixing work and peeling work after use while maintaining necessary qualities such as heat resistance.

Japanese Unexamined Patent Publication No. 2001-121662

The coating film surface protective film of Patent Document 1 is said to be able to efficiently perform affixing work and peeling work after use, but has a problem that curl occurs during adhesive processing. In this respect, if the coating film surface protective film has curls, it affects the work efficiency of the pasting work, so there is room for improvement. Further, from the viewpoint of improving the work efficiency during the adhesive processing, it is also required that the coating film surface protective film base material before the adhesive processing has good flatness.

In view of the problems of the prior art, the present invention provides a coating film surface protective film base material in which curling is suppressed before and after adhesive processing, and a coating film surface protective film having good tear strength and excellent adhesiveness. The purpose is to provide.

As a result of diligent research to achieve the above object, the present inventors have found that the above object can be achieved when a substrate for a coating film surface protective film having a specific layer structure of three or more layers is used. The invention was completed.

That is, the present invention relates to the following base material for a coating film surface protective film and a coating film surface protective film using the same.
1. 1. A base material for a coating film surface protective film that is used as a coating film surface protective film after the pressure-sensitive adhesive is applied to the layer to be coated with the adhesive to form the pressure-sensitive adhesive layer.
(1) The base material contains 50% by mass or more of polyethylene resin and is composed of three or more layers.
(2) Of the pair of outermost layers, the layer to be coated with the pressure-sensitive adhesive contains 50 to 90% by mass of a random copolymerized polypropylene resin having an ethylene content of 5% by mass or less, and 10 to 10 to 90% by mass of a homopolypropylene resin. Contains 50% by mass,
(3) The other outermost layer, the non-coated adhesive layer, contains 90 to 100% by mass of a random copolymerized polypropylene resin having an ethylene content of 5% by mass or less, and 0 to 10% by mass of a homopolypropylene resin. %contains,
A base material for a coating film surface protective film.
2. 2. Item 2. The base material for a coating surface protective film according to Item 1, wherein the base material comprises three layers, that is, a layer to be coated with an adhesive, an inner layer, and a non-coating layer with an adhesive.
3. 3. The thickness of the pressure-sensitive adhesive coating layer and the pressure-sensitive adhesive non-coating layer are the same, and the ratio of the random copolymerized polypropylene in the pressure-sensitive adhesive coating schedule layer is A%, and the pressure-sensitive adhesive non-coating layer is used. The base material for a coated surface protective film according to claim 1 or 2, wherein the ratio of the random copolymerized polypropylene in the layer is B%, and the absolute value of AB is 50 or less.
4. A coating film surface protective film having an adhesive layer in contact with the pressure-sensitive adhesive coating layer of the coating film surface protective film substrate according to any one of Items 1 to 3.

The base material for a coating film surface protective film of the present invention has a specific layer structure of three or more layers, so that curling is suppressed before and after the adhesive processing and the flatness is excellent, and the adhesive processing and the adhesive processing are performed. Excellent post-stickability. That is, the generation of curl is suppressed at both the time of forming the base material (before the pressure-sensitive adhesive processing) and the time of forming the pressure-sensitive adhesive layer (after the pressure-sensitive adhesive processing). In addition, the coating film surface protective film also has good tear strength, and is more useful than the conventional coating film surface protective film. Such a coating film surface protective film of the present invention is particularly useful as a coating film surface protective film used for protecting an automobile coating film during transportation or storage of an automobile.

(A) It is a layer composition schematic diagram of one aspect of the base material for a coating film surface protective film of this invention. (B) It is a layer structure schematic diagram of one aspect of the coating film surface protection film of this invention. In Test Example 1, it is a schematic diagram which shows pulling at 250 mm / min in the 90 ° direction when measuring the back surface peeling force of the sample of the coating film surface protection film. It is a schematic diagram which shows the measurement state of the curl resistance of the base material for a coating film surface protective film, and the sample of a coating film surface protective film in Test Example 1.

Substrate for coating film surface protective film The substrate for coating film surface protective film of the present invention is used as a coating film surface protective film after the pressure-sensitive adhesive is applied to the layer to be coated with the pressure-sensitive adhesive to form the pressure-sensitive adhesive layer. It ’s a base material,
(1) The base material contains 50% by mass or more of polyethylene resin and is composed of three or more layers.
(2) Of the pair of outermost layers, the layer to be coated with the pressure-sensitive adhesive contains 50 to 90% by mass of a random copolymerized polypropylene resin having an ethylene content of 5% by mass or less, and 10 to 10 to 90% by mass of a homopolypropylene resin. Contains 50% by mass,
(3) The other outermost layer, the non-coated adhesive layer, contains 90 to 100% by mass of a random copolymerized polypropylene resin having an ethylene content of 5% by mass or less, and 0 to 10% by mass of a homopolypropylene resin. % Is contained.

The base material for a coating film surface protective film of the present invention having the above-mentioned characteristics has a specific layer structure of three or more layers, so that the generation of curls is suppressed before and after the adhesive processing (adhesive layer is applied). It has excellent flatness and excellent adhesiveness and stickability after adhesive processing. In addition, the coating film surface protective film also has good tear strength, and is more useful than the conventional coating film surface protective film. Further, it is particularly useful as a coating film surface protective film used for protecting the coating film of an automobile during transportation or storage of the automobile.

The base material for a coating film surface protective film of the present invention (hereinafter, also referred to as “base material”) is composed of three or more layers, and contains 50% by mass or more of polyethylene resin as the whole base material. That is, the base material is mainly composed of polyethylene resin in that polyethylene resin occupies more than half of the mass of the resin component. The content of the polyethylene resin in the entire base material is preferably 60% by mass or more, more preferably 60 to 70% by mass. By containing 50% by mass or more of the polyethylene resin as the whole base material, a coating film surface protective film having good tear strength can be obtained.

In the base material of the present invention, one of the pair of outermost layers is a layer to be coated with an adhesive, and is a layer to which an adhesive layer is applied by adhesive processing. The other is an adhesive non-coated layer. The central layer sandwiched between the adhesive-coated layer and the non-adhesive-coated layer can be composed of one layer or two or more layers, but usually, as illustrated in FIG. 1 (a), a single inner layer is used. It should be configured. FIG. 1A shows a configuration in which an inner layer 2 is provided between a layer 1 to be coated with an adhesive and a layer 3 not coated with an adhesive. An adhesive layer can be included between the layers as needed.

In the substrate of the present invention, the adhesive coating layer contains 50 to 90% by mass of a random copolymerized polypropylene resin having an ethylene content of 5% by mass or less and 10 to 50% by mass of a homopolypropylene resin. do.

The ethylene content of the random copolymerized polypropylene resin may be 5% by mass or less, preferably 3 to 5% by mass, more preferably 3.5 to 4.5% by mass. The content of the random copolymerized polypropylene resin may be 50 to 90% by mass, preferably 60 to 90% by mass, and more preferably 70 to 80% by mass. The content of the homopolypropylene resin may be 10 to 50% by mass, preferably 10 to 40% by mass, more preferably 20 to 30% by mass. When the content of homopolypropylene is within such a range, it is possible to suppress swelling due to the solvent contained in the coating liquid during adhesive processing (formation of the adhesive layer) and curl during drying.

In the substrate of the present invention, the pressure-sensitive adhesive non-coated layer contains 90 to 100% by mass of a random copolymerized polypropylene resin having an ethylene content of 5% by mass or less, and contains 0 to 10% by mass of a homopolypropylene resin. do.

The ethylene content of the random copolymerized polypropylene resin may be 5% by mass or less, and the lower limit is not particularly limited as long as it exceeds 0% by mass. The content of the random copolymerized polypropylene resin may be 90 to 100% by mass, preferably 92 to 100% by mass, more preferably 95 to 100% by mass. The content of the homopolypropylene resin may be 0 to 10% by mass, preferably 0 to 8% by mass, more preferably 0 to 5% by mass. By reducing the content of the homopolypropylene resin to 10% by mass or less (including 0% by mass), the content of the randomly copolymerized polypropylene is relatively increased, so that after the adhesive processing (adding the adhesive layer). Good expandability (stickability) of the coating film surface protective film can be ensured.

Explaining the case where the central layer has an inner layer as shown in FIG. 1A, the resin component contained in the inner layer is not limited as long as the condition that the polyethylene resin is contained in an amount of 50% by mass or more as the whole base material is satisfied. However, polyethylene alone or a mixture of polyethylene and a random copolymerized polyethylene can be preferably used. Here, as the random copolymerized polyethylene, the same ones as described above can be used.

The polyethylene resin is not particularly limited, and a commercially available polyethylene resin can be appropriately used.

As the polyethylene resin, for example, LDPE (low density polyethylene), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE) and the like can be used. These polyethylene resins can be used alone or in combination of two or more, but in the present invention, LLDPE is preferably used because it has an excellent balance between tensile strength and tear strength.

LDPE is a polyethylene-based resin (homopolyethylene) having a density in the range of 0.910 to 0.930 g / cm ³ , and among them, the range of 0.920 to 0.930 g / cm ³ is preferable. Examples of the method for producing LDPE include those produced by high-pressure radical polymerization using a radical initiator. The density in the present specification is a value measured under the conditions of JIS K7112: 1999 underwater substitution method (method A) and 25 ° C.

The melt flow rate (MFR) of LDPE is preferably 0.5 to 6.0 g / 10 minutes, more preferably 1.0 to 4.0 g / 10 minutes. When the MFR is within this range, good formability by the T-die method can be easily obtained. The MFR in the present specification is a value measured under the conditions of JIS K7210: 1999, A method, 190 ° C., and a load of 21.18N, unless otherwise specified.

There is no clear distinction between LLDPE and MDPE, but they may be distinguished for convenience by density. LLDPE and MDPE can be obtained by copolymerizing ethylene and α-olefin using a single-site catalyst such as a Ziegler catalyst or a metallocene catalyst, and the density can be adjusted by adjusting the type and amount of α-olefin. The range can be controlled.

Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like. These α-olefins can be used alone or in combination of two or more.

A wide range of products with a density of LLDPE of 0.870 to 0.945 g / cm ³ are commercially available, and the range of 0.925 to 0.935 g / cm ³ is preferable. The MFR of LLDPE is preferably 0.5 to 6.0 g / 10 minutes, more preferably 1.0 to 4.0 g / 10 minutes. When the MFR is within this range, it is easy to obtain the effect of good moldability by the T-die method.

MDPE refers to LLDPE having a density of about 0.930 to 0.945 / ^cm3 , and MFR is preferably about 1.0 to 4.0 g / 10 minutes.

The HDPE is not particularly limited, but the density is preferably 0.940 to 0.960 g / cm ³ , and more preferably 0.945 to 0.960 g / cm ³ . The MFR of HDPE is preferably 0.5 to 6.0 g / 10 minutes, more preferably 1.0 to 4.0 g / 10 minutes. When the MFR is within this range, it is easy to obtain the effect of good moldability by the T-die method.

When using a mixture of polyethylene and random copolymerized polyethylene, it is assumed that the content of polyethylene resin in the entire substrate is 50% by mass or more, depending on the physical characteristics of the coating surface protective film of the final product. Adjust the blending ratio as appropriate.

The thickness of each layer constituting the base material of the present invention is not limited, but when it is composed of three layers, that is, a layer to be coated with an adhesive, an inner layer, and a non-applied adhesive layer, the thickness is 1: 2 to 8 in order. It is preferably in the range of the thickness ratio of 1, and more preferably in the range of the thickness ratio of 1: 4 to 6: 1.

Specifically, the thickness of the layer to be coated with the adhesive is preferably 3 to 10 μm, more preferably 4 to 7 μm. The thickness of the inner layer is preferably 6 to 80 μm, more preferably 16 to 42 μm. The thickness of the non-adhesive-coated layer is preferably 3 to 10 μm, more preferably 4 to 7 μm.

The base material of the present invention is effective in ensuring a layer to be coated with an adhesive that has the effect of suppressing swelling during adhesive processing and curling during drying, and good expandability (stickability) after adhesive processing. By including the above-mentioned inner layer between the non-coated layer of the adhesive, the difference in thermal properties of the pair of outermost layers is alleviated, and curl is generated during the formation of the base material and after the pressure-sensitive adhesive treatment on the base material. Can be suppressed.

In the substrate of the present invention, the ratio of the predetermined random copolymerized polypropylene in the layer to be coated with the adhesive is set to A%, particularly when the thickness of the layer to be coated with the adhesive and the layer not to be coated with the adhesive are the same. When the ratio of the predetermined random copolymerized polypropylene in the non-coating layer of the adhesive is B% and the absolute value of AB is 50 or less, it is easy to suppress the generation of curl during the formation of the substrate. The absolute value of A (%)-B (%) is preferably 50 or less, more preferably 25 or less, and most preferably 0.

When forming the base material of the present invention, conventionally known methods such as an inflation method and a T-die are preferably used, but each layer may be separately prepared and then formed by dry laminating using an adhesive.

Coating film surface protective film The substrate for a coating film surface protective film of the present invention forms an adhesive layer by applying and drying a coating liquid for forming an adhesive layer on a layer to be coated with an adhesive. , Can be a coating film surface protective film.

The coating liquid for forming the pressure-sensitive adhesive layer can be selected from various known materials, for example, a solvent for a rubber-based polymer such as natural rubber; styrene-butadiene rubber (SBR); polyisoprene; butyl rubbers; polyisoprene. Can be prepared by adding.

The thickness of the pressure-sensitive adhesive layer is not limited and can be appropriately set depending on the type of the coating film surface protective film, but is preferably 3 to 30 μm, more preferably 5 to 20 μm.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to the examples.

Examples 1 to 4 and Comparative Examples 1 to 8
Depending on the conditions such as the raw material composition, the layer thickness ratio, and the thickness of the entire base material shown in Table 1, the base materials for the coating film surface protective film of Examples 1 to 4 and Comparative Examples 1 to 8 (adhesive coating planned layer / A three-layer film composed of an inner layer / an adhesive non-coated layer: "/" indicates an interlayer) was prepared. As a result, a base material for a coating film surface protective film was obtained.

Test Example 1
Regarding the base material for the coating film surface protective film produced above, the tear strength, the back surface peeling force, the degree of curl of the base material, and the degree of curl after the adhesive processing were investigated. The method and evaluation criteria for each test are shown below, and the results of each test are shown in Table 1.

≪Tear strength≫
The tear strength (N) of each substrate in the MD direction was examined according to JIS K7128-2 (Elmendorf tearing method).

≪Back surface peeling force (N / 25mm) ≫
A release agent was thinly applied (mold release treatment) to the adhesive non-coated layer of the base material, and a polyisobutylene-based adhesive was applied to the layer to be coated with the adhesive to form a pressure-sensitive adhesive layer. The coating film surface protective film on which the adhesive layer was formed was wound around a 3-inch paper tube and slit into a tape having a width of 25 mm.

The above tape sample was set in the tensile tester used in JIS K7127, and the force when pulling in the 90 ° direction at a tensile speed of 250 mm / min was measured as shown in FIG.

≪Degree of curl of base material≫
After preparing each base material, it was cut into a length of 25 mm and a width of 100 mm. As shown in FIG. 3, the glass plate 6 was set vertically on the horizontal floor surface 5, and the sample 7 was fixed using the sample fixing tape 8 so that the length of 100 mm was perpendicular to the floor surface.

The gap between the sample 7 and the glass plate 6 was measured and evaluated as follows.
◯: Gap is less than 5 mm ×: Gap is 5 mm or more

≪Degree of curl after adhesive processing≫
A mold release agent is thinly applied (release treatment) to the adhesive non-coated layer of the base material, and then polyisobutylene-based adhesive is applied to the planned adhesive coating layer at a ratio of 10 g / m ² . Formed a layer. Then, it was cut into a sample having a length of 25 mm and a width of 100 mm.

In the same manner as in FIG. 3, the glass plate 6 was set vertically on the horizontal floor surface 5, and the sample 7 was fixed with the sample fixing tape so that the glass plate 6 and the mold release processing surface were in contact with each other.

The gap between the sample 7 and the glass plate 6 was measured and evaluated as follows.
◯: Gap is less than 5 mm ×: Gap is 5 mm or more

(Consideration)
As can be seen from the results in Table 1, the substrate for the coating film surface protective film and the coating film surface protective film of Examples 1 to 4 having a specific layer structure of three or more layers specified in the present invention (collectively referred to as "sample"). The generation of curl is suppressed before and after the adhesive processing, and the tear strength is good and the adhesiveness is excellent. On the other hand, the samples of Comparative Examples 1 to 8 having no specific layer structure of three or more layers specified in the present invention were carried out in any of curl generation, tear strength or stickability before and after the adhesive processing. Performance is inferior to the example sample.

a. Substrate for coating film surface protective film b. Coating film surface protective film 1. Adhesive coating planned layer 2. Inner layer 3. Adhesive non-coated layer 4. Adhesive layer 5. Floor surface 6. Glass plate 7. Sample 8. Sample fixing tape

Claims (4)

A base material for a coating film surface protective film that is used as a coating film surface protective film after the pressure-sensitive adhesive is applied to the layer to be coated with the adhesive to form the pressure-sensitive adhesive layer.
(1) The base material contains 50% by mass or more of polyethylene resin and is composed of three or more layers.
(2) Of the pair of outermost layers, the layer to be coated with the pressure-sensitive adhesive contains 50 to 90% by mass of a random copolymerized polypropylene resin having an ethylene content of 5% by mass or less, and 10 to 10 to 90% by mass of a homopolypropylene resin. Contains 50% by mass,
(3) The other outermost layer, the non-coated adhesive layer, contains 90 to 100% by mass of a random copolymerized polypropylene resin having an ethylene content of 5% by mass or less, and 0 to 10% by mass of a homopolypropylene resin. %contains,
A base material for a coating film surface protective film. The base material for a coated surface protective film according to claim 1, wherein the base material comprises three layers of the adhesive coating planned layer, the inner layer, and the pressure-sensitive adhesive non-coating layer. The thickness of the pressure-sensitive adhesive coating layer and the pressure-sensitive adhesive non-coating layer is the same, and the ratio of the random copolymerized polypropylene in the pressure-sensitive adhesive coating schedule layer is A%, and the pressure-sensitive adhesive non-coating layer is used. The base material for a coated surface protective film according to claim 1 or 2, wherein the ratio of the random copolymerized polypropylene in the layer is B%, and the absolute value of AB is 50 or less. A coating film surface protective film having an adhesive layer in contact with the pressure-sensitive adhesive coating layer of the base material for a coating film surface protective film according to any one of claims 1 to 3.

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