JPH11115125A - Support film for surface protective pressure sensitive adhesive sheet and pressure sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of a crack, initial elastic modulus, wrinkle or bubble by forming a structure in which a linear low density polyethylene resin layer or a low density polyethylene resin layer at both sides is sandwiched between high density polyethylene resin layers, and forming its thickness at a specific value. SOLUTION: The surface protective pressure sensitive adhesive sheet has a support film for a thin surface protective pressure sensitive adhesive sheet and an adhesive layer at one side with the film as its support. The support film for the surface protective pressure sensitive adhesive sheet of the surface protective pressure sensitive adhesive sheet comprises an intermediate layer of a linear low density polyethylene resin (LLDP) layer or low density polyethylene (LDPE) layer and two high density polyethylene (HDPE) layers sandwiching the intermediate layer at both sides, and its thickness is set to 10 to 35 μm. As a method for manufacturing the support film, an inflation process or a T-die process of a general method for manufacturing a film is used, and the method is suitably selected in response to an amount of the film, applications and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin support film for a pressure-sensitive adhesive sheet for surface protection having a thickness of 10 to 35 μm, and a pressure-sensitive adhesive sheet for surface protection using the support film as a support.

[0002]

2. Description of the Related Art A pressure-sensitive adhesive sheet for surface protection in which a pressure-sensitive adhesive layer is provided on one side of a support of a polyolefin-based film is used as a pressure-sensitive adhesive sheet for surface protection. It is important that they can be attached without any problem.

[0003] Therefore, as a thin polyolefin-based film which can be attached without wrinkles and bubbles, a polypropylene (PP) film or polypropylene-
Polyethylene (PP-PE) blend films and the like have been used.

[0004] However, these polyolefin-based films containing PP as a main component tend to be torn due to the strong crystal orientation of the film, and cannot maintain sufficient properties as a film for a surface protective material.

When a high-density polyethylene (HDPE) having relatively high strength is formed as a single film, the initial elastic modulus and the tear strength are satisfactory, but the crystallization speed of HDPE is very high. Many wrinkles were formed during film formation, and the film could not be used as a film for a surface protective material.

Further, when a low-density polyethylene (LDPE) or a linear low-density polyethylene (LLDPE) is formed as a thin film as it is, the initial elastic modulus is not satisfactory, and the required characteristics at the time of lamination may be satisfied. I couldn't.

[0007]

In general, when considered as a film for a surface protective material, it is important to attain both easy adhesion and a tear strength that can withstand processing. Conventionally, this problem has been dealt with by increasing the film thickness (40 μm or more) using PP or LDPE.

However, as the flow of the entire industry, producing and supplying good products at lower cost is an eternal theme for each manufacturer, and the production of thin film as one of the themes is an important problem. However, a thin film for a polyolefin-based surface protective material that has solved the above-mentioned problems has not been put to practical use.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thin surface protection material having the property of being easy to stick and tearing strength capable of withstanding processing, and having the property of being able to be stuck to an adherend without wrinkles and bubbles. It is to provide a pressure sensitive adhesive sheet and a support film for such a sheet.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention focuses on the strength of HDPE,
The inventors have discovered that a balanced thin film can be produced by taking a multilayer structure with PE or LDPE, and further studied to complete the present invention.

[0011] The present invention provides a pressure-sensitive surface protective layer having a structure in which both sides of a linear low-density polyethylene resin layer or a low-density polyethylene resin layer are sandwiched between high-density polyethylene resin layers, and having a thickness of 10 µm to 35 µm. It is a support film for an adhesive sheet. In particular, the present invention relates to JIS K-
The initial elastic modulus measured under the conditions of 7127 is 80 kg /
mm ² or more, the Elmendorf tear values supporting the above surface protective pressure sensitive adhesive sheet is not less than 30g in the thickness 25μm film strength in the MD direction of the film. Another aspect of the present invention is a pressure-sensitive adhesive sheet for surface protection, comprising a pressure-sensitive adhesive layer formed on one side of the support film.

[0012]

In the past, HDPE has been applied only in applications where it is difficult to form a thin film and there is no practical problem even if there are some wrinkles like a shopping bag in a supermarket.

The present invention can be applied to a surface protection material which has been considered to be unusable by using HDPE by taking a multilayer structure with LLDPE having a low crystallization rate (compared to HDPE). This is a completely new finding.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a thin (10 μm to 35 μm)
m) A support film for a pressure-sensitive adhesive sheet for surface protection, and a pressure-sensitive adhesive sheet for surface protection comprising the film as a support and an adhesive layer provided on one side.

In the present invention, the structure of the polyolefin film is such that LLDPE or LDPE is provided in the intermediate layer, and both sides thereof are sandwiched by HDPE. HDPE has a thickness of usually 5 μm to 30 μm, preferably 15 μm to 20 μm. LLDPE or L
The thickness of the DPE is usually 2 μm to 15 μm, preferably 5 μm.
μm to 10 μm.

The density of HDPE is 0.94 g / cm ^3.
０．９0.965 g / cm ³ , preferably 0.95 g / cm 3
^{3 to} 0.965 g / cm ³ , melt flow index (MI) (190 ° C., 2 kg) 0.001 dg / min
~ 20 dg / min, preferably 0.1 dg / min ~
Generally, it is 20 dg / min, but is not limited to this.

LLDPE has a density of 0.91 g / c.
m ^{3 to} 0.925 g / cm ³ , preferably 0.91 g / cm ³
cm ^{3 to} 0.918 g / cm ³ , melt flow index (MI) (190 ° C., 2 kg) 1.0 dg / min
~ 4.0 dg / min, preferably 1.0 dg / min
It is generally 3.0 to 3.0 dg / min, but is not limited to this. LDPE has a density of 0.90 g / cm ³ to
0.925 g / cm ³ , preferably 0.91 g / cm
^{3 to} 0.925 g / cm ³ , melt flow index (MI) (190 ° C., 2 kg) 1.0 dg / min
10 dg / min, preferably 1.0 dg / min
It is generally 5.0 dg / min, but is not limited to this.

The support film of the present invention has an initial elastic modulus (J
ISK-7127) is 80 kg / mm^TwoAbove, preferably
Is 100 kg / mm^TwoAnd the upper limit is 200kg /
mm ^TwoIt is enough. Initial elastic modulus is 80kg / mm
^TwoIf less than, stick together when used as a tape
Poor performance and easy wrinkles during lamination
Not preferred.

The support film of the present invention is formed of a film MD.
Strength in the direction of elemendorf (JIS-P-8
116) is 30 g or more (at a film thickness of 25 μm), preferably 50 g or more, and an upper limit of 200 g is sufficient. If the Elmendorf tear strength is less than 30 g, the workability required for the surface protective material is extremely poor, and tearing frequently occurs when used as a tape, which is not preferable.

[0020] In addition to the above three layers, other layers may be laminated as long as they are thin and stipulated in the present invention and do not contradict the object of the present invention. Examples of such a layer include a polypropylene-polyethylene blend layer, a polyethylene (different in density and the like) blend layer, a printing layer, and the like.

Examples of the method for producing the support film of the present invention include a general film production method such as an inflation method and a T-die method. The method may be appropriately selected depending on the amount and use of the film. It is not limited.

The pressure-sensitive adhesive layer applied to the support may be an appropriate one. Generally, various pressure-sensitive adhesive layers of acrylic, natural rubber, synthetic rubber, Si, etc. are required. Not limited. The thickness of the adhesive layer is 0.1 μm to 2
Those having a thickness of 5 μm, especially 0.1 μm to 10 μm are used. The coating method of the adhesive includes solvent drying coating, emulsion drying coating, hot melt extrusion coating,
Various coating methods such as V polymerization may be mentioned, but not limited thereto.

[0023]

【Example】

Example 1 H having a density of 0.96 g / cm ³ and an MI of 0.1 dg / min
DPE, density 0.915 g / cm ³ , thickness 10μ
m, an intermediate layer of LLDPE having an MI of 1.0 dg / min is sandwiched, a 25 μm three-layer film is formed by an inflation-type extrusion molding machine, and a corona discharge treatment is performed on one side to obtain a 25 μm-thick three-layer film. Was.

Example 2 An acrylic pressure-sensitive adhesive (ethyl acrylate (EA) 6) was provided on the corona discharge treated side of the support film prepared in Example 1.
0 parts by weight, 2 ethylhexyl acrylate (2EHA)
40 parts by weight, an adhesive consisting of 5 parts by weight of hydroxyacrylate (HEA) and 5 parts by weight of tolylene diisocyanate (TDI)) is applied to a thickness of 5 μm to obtain a wound pressure-sensitive adhesive sheet for surface protection. Was.

Comparative Example 1 A homopolymer polypropylene (PP) having a density of 0.90 g / cm ³ and an MI of 3.0 dg / min was formed into a film having a thickness of 25 μm by a T-shaped extrusion molding machine, and one side was subjected to corona discharge treatment. To form a sheet.

Comparative Example 2 An acrylic pressure-sensitive adhesive (ethyl acrylate (EA) 6) was placed on the corona discharge treated side of the support film prepared in Comparative Example 1.
0 parts by weight, 2 ethylhexyl acrylate (2EHA)
An adhesive composed of 40 parts by weight, 5 parts by weight of hydroxy acrylate (HEA) and 5 parts by weight of tolylene diisocyanate (TDI)) was applied so as to have a thickness of 5 μm to obtain a wound pressure-sensitive adhesive sheet for surface protection.

Comparative Example 3 L having a density of 0.92 g / cm ³ and an MI of 5.0 dg / min
DPE was formed into a film having a thickness of 25 μm using an inflation-type extrusion molding machine, and a corona discharge treatment was performed on one side to form a sheet.

Comparative Example 4 An acrylic pressure-sensitive adhesive (ethyl acrylate (EA) 6) was provided on the corona discharge treated side of the support film prepared in Comparative Example 3.
0 parts by weight, 2 ethylhexyl acrylate (2EHA)
An adhesive composed of 40 parts by weight, 5 parts by weight of hydroxy acrylate (HEA) and 5 parts by weight of tolylene diisocyanate (TDI)) was applied so as to have a thickness of 5 μm to obtain a wound pressure-sensitive adhesive sheet for surface protection.

[Evaluation Test-1] The following evaluations were performed on the pressure-sensitive adhesive sheets for surface protection prepared in Example 2, Comparative Example 2, and Comparative Example 4. Table 1 shows the results. The pressure-sensitive adhesive sheets prepared in Example 2, Comparative Example 2, and Comparative Example 4 were subjected to a bender workability test to confirm that the film was torn, and to evaluate the ease of tearing. The bender workability test was performed by the following procedure using the apparatus shown in FIG. (1) The pressure-sensitive adhesive sheet is pressure-bonded to a 430BA plate (0.4 mm thick) serving as an adherend at a linear pressure of 8 kg / cm, and left for 24 hours without pressure. (2) Next, the plate 4 is placed on the measuring section 2 provided with the groove 1. (3) Pressure is applied to the installed plate 4 from above by the punch 3, and tearing of the film when the plate is bent is confirmed. The specifications of the apparatus shown in FIG. 1 are as follows. In the measuring section 2, the width W of the groove 1 is 12 mm, the depth d is 5 mm, and the R at the intersection of the surface forming the groove 1 and the upper surface 2a of the measuring section is 2m
m. In the punch 3, the width wd is 30 m
m, and the height h of the projection is 15 mm. The pressure-sensitive adhesive sheets (width: 300 mm) produced in Example 2, Comparative Example 2, and Comparative Example 4 were subjected to 430B using a small laminator.
Affix to the A plate, check the occurrence of wrinkles on the adhesive sheet,
The workability was evaluated.

[0030]

[Table 1]

As is clear from Table 1 above, and in both Examples, satisfactory results were obtained for both.
Was only a pressure-sensitive adhesive sheet for surface protection.

[Evaluation Test-2] The films formed in Example 1, Comparative Examples 1 and 3 were subjected to JIS K-712.
7 and JIS P-8116, the initial elastic modulus and the Elmendorf tear strength were measured. Table 2 shows the results
Shown in

[0033]

[Table 2]

As is apparent from Table 2, only the film obtained in Example 1 had an initial elastic modulus of 80 kg / mm ² or more and an elemental rupture strength of 30 g or more.

[0035]

According to the present invention, the problem of tearing and LD which could not be solved with a thin PP or blend film
It is possible to supply a thin polyolefin-based film that has solved the problem of initial elastic modulus that could not be solved by PE or LLDPE, wrinkles that could not be solved by HDPE, and the problem of bubbles.

[Brief description of the drawings]

FIG. 1 is a diagram showing an apparatus used for a bender workability test.

[Explanation of symbols]

 1 groove 2 measuring part 3 punch 4 plate

Claims (3)

[Claims] 1. A structure in which both sides of a linear low-density polyethylene resin layer or a low-density polyethylene resin layer are sandwiched between high-density polyethylene resin layers, and have a thickness of 10
A support film for a pressure-sensitive adhesive sheet for surface protection having a thickness of from 35 μm to 35 μm. 2. An initial elastic modulus of 80 kg / mm ² or more,
The pressure-sensitive adhesive sheet supporting film for surface protection according to claim 1, wherein the value of the elementeldorf tear strength in the MD direction of the film is 30 g or more at a thickness of 25 µm. 3. A pressure-sensitive adhesive sheet for surface protection obtained by forming a pressure-sensitive adhesive layer on one side of the support film for a pressure-sensitive adhesive sheet for surface protection according to claim 1.