JPH0790091A - Polyolefin soft film and surface protective pressure-sensitive adhesive sheet using the same - Google Patents

Abstract

(57) [Summary] [Purpose] A polyolefin film that does not cause necking during a pulling operation is provided, and an adhesive layer is provided on one side of the film, which does not uniformly stretch and break during drawing. To provide an excellent polyolefin-based surface protective pressure-sensitive adhesive sheet. [Structure] The weight average molecular weight is 100,000 to 450,
It is in the range of 000 and is 0 ° C or more by the cross fractionation method 20
Elution amount of resin below ℃ is less than total polyolefin resin amount 2
0 to 50% by weight, the amount of resin eluted above 20 ° C and below 75 ° C is 5 to 25% by weight of the total amount of polyolefin resin, and the amount of resin eluted above 75 ° C and below 125 ° C is total polyolefin system. A polyolefin soft film formed using a polyolefin resin that is 35 to 70% by weight of the resin amount. Further, a surface protective pressure-sensitive adhesive sheet can be obtained by providing a pressure-sensitive adhesive layer on one side of this polyolefin soft film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin soft film useful as a substrate for a surface protective pressure sensitive adhesive sheet, and a surface protective pressure sensitive adhesive sheet using the same. The surface-protective pressure-sensitive adhesive sheet is used for preventing stains and scratches during the drawing process of a stainless plate, an aluminum plate, a copper plate, a metal plate with a surface coated, and the like.

[0002]

2. Description of the Related Art As a surface protective adhesive sheet for a metal plate,
A sheet obtained by applying a coating material composed of an organochlorine chloride, drying it, and peeling it off, a laminate composed of two layers of an ethylene-vinyl acetate copolymer layer and a low-density polyethylene layer (JP-A-54-133577). ), A film obtained by providing an adhesive layer on one side of a polyolefin substrate (Japanese Patent Publication No. 59-49953). Among such surface-protective pressure-sensitive adhesive sheets, a sheet using a soft vinyl chloride film does not cause necking,
It stretches uniformly during drawing, so it is suitable for drawing. However, due to environmental problems in recent years, there is a strong demand for dechlorinated vinyl materials, and the use of polyolefin films has been actively studied.

Recently, in addition to the above, Japanese Patent Laid-Open No. 3-1488
A surface protective pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer provided on one surface of a polyolefin-based film made of a propylene-ethylene copolymer as described in JP-A No. 5 (1998), and JP-A-4-10.
As disclosed in Japanese Patent No. 6175, there is proposed a surface protective pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is provided on one surface of a base film formed by mixing polypropylene, polyethylene and an ethylene-propylene copolymer.

However, necking occurs when the surface-protecting pressure-sensitive adhesive sheet formed using the conventional polyolefin film is pulled. Therefore, for example, when drawing is performed, the film does not stretch uniformly and results in a constriction.As a result, the deformed metal plate has a pattern of a constricted part, or the thin part of the film is torn to scratch the metal plate. There was a problem to do.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to use a specific polyolefin resin without using plasticized PVC (polyvinyl chloride), so that the above-mentioned necking does not occur during a pulling operation. It is an object of the present invention to provide an excellent polyolefin-based surface-protective pressure-sensitive adhesive sheet, which is obtained by providing a base film and further providing an adhesive layer on one surface of the film, and which is uniformly stretched and does not break during drawing.

[0006]

Means for Solving the Problems The inventors of the present invention have earnestly studied a film useful as a substrate for a surface protection film, and as a result, have a specific weight average molecular weight and a resin elution amount at a specific temperature within a certain range. It was found that the above object can be achieved by using the polyolefin-based film described in (3) above, and the present invention has been completed based on the findings.

The polyolefin soft film of the present invention has a weight average molecular weight of 100,000 to 450,000.
And the resin elution amount at 0 ° C. or higher and 20 ° C. or lower by the cross fractionation method is 20 to 5 of the total polyolefin resin amount.
0% by weight, the resin elution amount above 20 ° C and 75 ° C is 5 to 25% by weight of the total polyolefin resin amount, and the resin elution amount above 75 ° C and 125 ° C is the total polyolefin resin amount. 35 to 70% by weight of the polyolefin resin.

The deformation recovery rate after the tensile deformation is preferably 70% or less.

The polyolefin surface protective pressure-sensitive adhesive sheet is
It can be obtained by providing a pressure-sensitive adhesive layer on one surface of the polyolefin-based soft film.

The present invention will be described in detail below.

The polyolefin resin used in the present invention has a weight average molecular weight of 100,000 to 45 as described above.
It is 50,000 polyolefin resin. Polypropylene resin is most preferable, and other olefin resins may have insufficient heat resistance or strength. This weight average molecular weight is, for example, high temperature GP manufactured by WATERS.
It can be measured at C (150 CV). The weight average molecular weight of this resin is preferably 150,000 to 400,000. If the weight average molecular weight is less than 100,000, the ductility or strength of the film is insufficient, and if it exceeds 450,000, sufficient moldability cannot be obtained during drawing.

The amount of resin eluted by this cross fractionation method is measured as follows. First, a polyolefin resin is dissolved in o-dichlorobenzene at 140 ° C or a temperature at which the polyolefin resin is completely dissolved, cooled at a constant rate, and a thin polymer layer is formed on an inert carrier surface prepared in advance in order of high crystallinity and It is generated in descending order of molecular weight. Next, the temperature is raised continuously or stepwise, the concentration of the eluted components is detected in sequence, and the composition distribution (crystallinity distribution) is measured <temperature rising elution fractionation> and the molecular weight and molecular weight of the component by high temperature GPC. Measure the distribution. For example, the temperature rising elution fractionation (TREF = Temperatur
e Rising Elution Fractionation) and high temperature GPC
A cross fractionation chromatograph device <CFC-T150A type: manufactured by Mitsubishi Petrochemical Co., Ltd.> having a (SEC = Size Exclution Chromatograph) part as a system can be used.

The polyolefin resin used in the present invention is
The amount of resin eluted at 0 ° C. or higher and 20 ° C. or lower by the above cross fractionation method is preferably 20 to 50% by weight, more preferably 25 to 45% by weight, based on the total amount of polyolefin resin. If this amount is less than 20% by weight, the film lacks flexibility, and if it exceeds 50% by weight, the strength is insufficient.

This resin is 20% by the above-mentioned cross fractionation method.
The resin elution amount at a temperature higher than 75 ° C. and lower than or equal to 75 ° C. is preferably 5 to 25% by weight, and more preferably 5 to 20% by weight based on the total amount of the polyolefin resin. If it is less than 5% by weight, the formability of the pressure-sensitive adhesive sheet at the time of drawing is poor, and if it exceeds 25% by weight, the deformation recovery rate of the film becomes excessively low, and problems such as necking occur.

Further, the resin elution amount by the cross fractionation method at a temperature higher than 75 ° C. and lower than 125 ° C. is preferably 35 to 70% by weight, more preferably 35 to 68% by weight, based on the total amount of polyolefin resin. If it is less than 35% by weight, the deformation recovery rate of the film becomes high, and problems such as peeling from the product and the film not following during molding occur. If it exceeds 70% by weight, the flexibility of the film becomes insufficient.

The polyolefin-based resin used in the present invention is 0 ° C. or higher and 20 ° C. or lower, 20 ° C.
The weight average molecular weight of each elution resin at a temperature higher than 75 ° C. and lower than 75 ° C. and higher than 75 ° C. and lower than 125 ° C.
00, 50,000-900,000, 50,000-
It is preferably in the range of 750,000.

In the polyolefin resin of the present invention,
It is very important that the elution amount and the weight average molecular weight in each temperature range are within the above ranges in order to control the physical properties of the film such as elastic modulus, strength and ductility. Since the surface protection film formed by using the polyolefin resin satisfying the above requirements does not cause necking, the surface protection pressure-sensitive adhesive sheet obtained by providing the pressure-sensitive adhesive layer on one surface of the film has excellent drawability, and Good balance of sticking and peeling.

Necking here means "mechanical properties of polymer and composite material" (pp.183-188: LLNIEL).
As described in SEN, translated by Shigeharu Onoki, published by Kagaku Dojin Co., Ltd., when the sample is stretched, a constriction occurs at a limited point on the sample film, and the constriction becomes long as the sample is stretched. It is to grow. The cross section of the waist is much smaller than the cross section of the rest. In the case of drawing, it is considered that when the constriction occurs, a difference in thickness of the pressure-sensitive adhesive sheet occurs, and the sheet is cut, or a metal plate whose surface is protected by the sheet is damaged such as streaks.

Examples of the polyolefin resin having the above properties include propylene-ethylene or propylene-α-olefin copolymer. Specifically, it is prepared by the following method. First, in the first stage, polymerization is carried out in the presence of a titanium compound catalyst and an aluminum compound catalyst using a propylene monomer and, if necessary, an α-olefin monomer other than propylene to obtain a first propylene-based polyolefin. The polyolefin can be a propylene polymer, a propylene-ethylene copolymer, a propylene-α-olefin copolymer, and the like. In the second step, the titanium-containing propylene-based polyolefin and the olefin monomer (for example, propylene or α
-Olefin) to obtain a second polyolefin. The second polyolefin obtained by this two-step reaction can be a propylene-ethylene copolymer, a propylene-α-olefin copolymer, or an ethylene-α-olefin copolymer. Similarly, a multi-step copolymerization reaction can be performed depending on the purpose.

As a method for producing such a polyolefin resin, for example, there is a method described in Japanese Patent Laid-Open No. 4-224809. Here, as the titanium compound, for example, titanium trichloride and magnesium chloride are co-ground, and n-butyl orthotitanate, 2-ethyl-1-
Spherical average particle size 1 treated with hexanol, ethyl p-toluate, silicon tetrachloride, diisobutyl phthalate, etc.
A solid Ti catalyst of 5 μm is used, and an alkylaluminum such as triethylaluminum is used as the aluminum compound. Further, a silicon compound, preferably diphenyldimethoxysilane, is added as an electron donor in the polymerization tank. In addition to that, ethyl iodide is also added. In the above production method, the polymerization reaction is carried out in two or more steps. After the second stage, the monomer is further copolymerized with the polymer produced in the previous stage. Therefore, a plurality of types of polymers are formed, and a blend type copolymer at a molecular level which is completely different from a normal polymer blend is produced. Further, by using such a polymer blend, in such a case, a compound which cannot be finely dispersed in terms of resin viscosity in kneading with an ordinary extruder can be prepared. In addition to the above, JP-A-4-96912 and JP-A-4-96
No. 907, No. 3-174410, No. 2-170803, No. 2-170802, No. 61-42553, No. 3-205.
A similar method is described in Japanese Patent No. 439, by which a polyolefin resin can be prepared. JP-A-3-
It can also be prepared by the titanium compound described in 97747, in which the adduct of magnesium chloride and alcohol is first formed and then treated with titanium tetrachloride and an electron donor. Thus, the polyolefin resin used in the present invention can be produced by any of these methods. Examples of commercially available resins obtained by the above-described production method include "PER" manufactured by Tokuyama Soda Co., Ltd. and "Cataloy" manufactured by Himont Co., Ltd.

The deformation recovery rate after tensile deformation of the polyolefin soft film of the present invention is preferably 70% or less. When the deformation recovery rate is 70% or less, the phenomenon that the obtained surface protection sheet floats above the material to be protected such as a metal plate over time during drawing is eliminated. If it exceeds 70%, the floating sheets will overlap during drawing, and the metal plate that should have been surface-protected will be scratched, such as dented. The deformation recovery rate here means that the film to be tested (width (width) 10 mm × length 100 mm) is 23
Deformation recovery rate (%) = [1 − {(L _5min −L ₀ ) / L ₀ }], where L _5min is the length of the film when the load is released after 100 minutes of stretching at 100 ° C.
× 100 (however, L ₀ : initial (before stretching) film length).

A film is formed using the above polyolefin resin. This film can be formed by a conventional inflation method, extrusion method, or the like. This film is preferably used as a base material for a surface protective adhesive sheet,
The thickness is usually 30 to 70 μm. The surface protective pressure-sensitive adhesive sheet of the present invention can be obtained by using this film as a substrate and providing a pressure-sensitive adhesive layer on the surface thereof.

The pressure-sensitive adhesive used in the surface protective pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it is a commonly used pressure-sensitive adhesive, and examples thereof include acrylic pressure-sensitive adhesives and rubber-based pressure-sensitive adhesives. Providing a pressure-sensitive adhesive layer on the surface of the base film, by applying a pressure-sensitive adhesive solution to the polyolefin-based film of the present invention and drying, or coextruding the pressure-sensitive adhesive and the polyolefin-based film base component of the present invention. By doing so, a base / adhesive two-layer type surface protective adhesive sheet is obtained. The thickness of the adhesive layer is 3 to 20.
It is suitable that the thickness of the base material layer is 30 to 70 μm.
m is suitable.

The surface protective pressure-sensitive adhesive sheet thus obtained is attached to a desired material to be protected, such as a metal plate.

Since this polyolefin-based surface protective pressure-sensitive adhesive sheet is highly flexible, necking does not occur during stretching,
Very good drawability. The reason for such a result is not clear, but the following may be considered.

The polyolefin resin used in the present invention is
Generally, a low crystalline polyolefin polymer is uniformly dispersed during polymerization in a propylene-based polyolefin,
It is a polymer alloy material. As a result, in the polyolefin surface protective film and the surface protective pressure-sensitive adhesive sheet using the same in the present invention, the copolymer component such as ethylene is uniformly present in the polymer chain, so that polypropylene or EPR rubber (ethylene-propylene) is used. Necking does not occur during a tensile test, as compared to a film formed of polypropylene or the like blended with (rubber). The performance of this film is comparable to that of plasticized PVC.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

(Example 1) The molecular weight was 288,000, and the elution amount at each temperature by the cross fractionation method was 0 ° C or more 2
It is 39.1% by weight below 0 ° C, 6.9% by weight above 20 ° C and below 75 ° C, 54.0% by weight above 75 ° C and below 125 ° C, and the weight average of the eluted resin in each temperature range. Molecular weight of 420,000, 654,0
A polypropylene resin having a size of 00, 224,000 was used to form a 40 μm film by an inflation method. This film did not neck during the tensile test and showed uniform elongation. This tensile test is performed on the film to be tested (100 mm long × 10 m wide)
m) was measured by stretching 100% at 23 ° C. and releasing the load after 5 minutes. The tensile deformation recovery rate used here is expressed according to the above. The tensile deformation recovery rate of the film was 23% in the longitudinal direction and 25.3% in the lateral direction.
One surface of this film was first treated with a primer, and then an acrylic pressure-sensitive adhesive was applied so that the thickness after drying was 5 μm, and dried at 100 ° C. for 5 minutes to obtain a surface-protective pressure-sensitive adhesive sheet.

(Example 2) The molecular weight was 203,000, and the elution amount at each temperature by the cross fractionation method was 0 ° C or more 2
It is 29.0% by weight below 0 ° C, 6.3% by weight above 20 ° C and below 75 ° C, 64.7% by weight above 75 ° C and below 125 ° C, and the weight average of the eluted resin in each temperature range. Molecular weight is 191,000, 117,0
A polypropylene resin having a size of 00, 199,000 was used to prepare a 40 μm film in the same manner as in Example 1. This film did not neck during the tensile test and showed uniform elongation. The recovery rate of tensile deformation of the film is 29% in the longitudinal direction and 31% in the lateral direction.
%Met. One surface of this film was first treated with a primer, and then an acrylic pressure-sensitive adhesive was applied so that the thickness after drying was 5 μm, and dried at 100 ° C. for 5 minutes to obtain a surface-protective pressure-sensitive adhesive sheet.

(Example 3) The molecular weight was 370,000 and the elution amount at each temperature by the cross fractionation method was 0 ° C. or more 2
It is 42.2% by weight at 0 ° C or lower, 15.7% by weight at 20 ° C or higher and 75 ° C or lower, and 42.1% by weight at 75 ° C or higher and 125 ° C or lower, and the weight average molecular weight in each temperature range is 403. 4,000, 445,000, 3
07,000 polypropylene resin and SEBS
(Styrene-based triblock copolymer, trade name Tuftec 1052, manufactured by Asahi Kasei Co., Ltd.) and a tackifier resin (trade name Alcon P-125, manufactured by Arakawa Chemical Co., Ltd.) mixed in a ratio of 100/30, and two layers. Using a co-extrusion T-die, a substrate layer having a thickness of 60 μm and an adhesive layer having a thickness of 7 μm were co-extruded to obtain a surface protective adhesive sheet. The recovery rate of tensile deformation of the base film was 51% in the longitudinal direction and 54% in the lateral direction. The film did not neck during the tensile test and showed uniform elongation.

(Comparative Example 1) The molecular weight is 253,000, and the elution amount at each temperature by the cross fractionation method is 0 ° C. or more 2
It is 70.2% by weight below 0 ° C, 9.8% by weight above 20 ° C and below 75 ° C, and 20.0% by weight above 75 ° C and below 125 ° C, and the weight average molecular weight in each temperature range is 178. 2,000, 266,000, 40
Using a polypropylene resin of 6,000, a film having a base material layer of 60 μm was obtained. Of the base film at this time,
Recovery rate of tensile deformation is 78% in the vertical direction and 80.3% in the horizontal direction.
Met. The film exhibited no uniform necking and uniform elongation during the tensile test. Further, a surface protective pressure-sensitive adhesive sheet having a thickness of 7 μm was obtained on the substrate film in the same manner as in Example 3.

(Comparative Example 2) The molecular weight was 530,000, and the elution amount at each temperature by the cross fractionation method was 0 ° C or more 2
2.7% by weight below 0 ° C, 3.7% by weight above 20 ° C and below 75 ° C, 9% above 75 ° C and below 125 ° C
It is 3.6% by weight, and the weight average molecular weight in each temperature range is 136,000, 148,000, 40.
A 40 μm film was prepared in the same manner as in Example 1 by using 7,000 polypropylene resin.
This film caused necking during the tensile test and did not show uniform elongation. The recovery rate of tensile deformation of the film was 3% in the longitudinal direction and 5.1% in the lateral direction. One surface of this film was first treated with a primer, and then an acrylic pressure-sensitive adhesive was applied so that the thickness after drying was 5 μm, and dried at 100 ° C. for 5 minutes to obtain a surface-protective pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive sheet 1 obtained in each of the examples and comparative examples was prepared as follows: length 150 mm × width 150 mm × thickness 0.5 mm
1 is attached to a stainless steel plate (SUS304BA) 2 and is drawn into a tubular shape having a depth of 50 mm (L ₁ ) and a bottom diameter of 85 mm (L ₂ ) as shown in FIG. 1, and then the sheet is pulled. After peeling, the surface state of the SUS plate was observed.

Table 1 below shows the weight average molecular weights and cross-fractionation results of the resins of Examples and Comparative Examples, and the deformation recovery rates of the obtained films.

[0035]

[Table 1]

The evaluation results of the films and pressure-sensitive adhesive sheets obtained in each of the examples and comparative examples are shown in Table 2 below. In the drawability here, if the result is good,
Displayed with ○.

[0037]

[Table 2]

From Table 2, the polyolefin-based surface protective films obtained in the examples did not cause necking during the tensile test, and the surface protective pressure-sensitive adhesive sheets obtained from this film were higher than those in the comparative examples. It can be seen that the drawability and the SUS surface state are excellent.

[0039]

The polyolefin-based surface protective film of the present invention and the polyolefin-based surface protective pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer provided on one side of the film have a weight-average molecular weight of the polyolefin-based resin and cross-fractionation of the polyolefin-based resin. By specifying the elution amount and molecular weight of the resin by the method, a polyolefin-based surface protective pressure-sensitive adhesive sheet exhibiting excellent drawability can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a drawn sample in a drawing test of the surface protective pressure-sensitive adhesive sheets obtained in this example and a comparative example.

[Explanation of symbols]

 1 Surface protection adhesive sheet 2 Stainless steel plate

Claims (2)

[Claims] 1. A soft film formed by using a polyolefin resin, wherein the polyolefin resin has a weight average molecular weight of 100,0.
It is in the range of 0 to 450,000, and the resin elution amount by the cross fractionation method at 0 ° C. or higher and 20 ° C. or lower is 20 to 50% by weight of the total amount of the polyolefin-based resin, and is more than 20 ° C. and 75 ° C.
The resin elution amount below is 5 to the total polyolefin resin amount.
25% by weight, and the polyolefin soft film having a resin elution amount of more than 75 ° C and 125 ° C or less of 35 to 70% by weight of the total amount of polyolefin resin. 2. A surface-protective pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer provided on one surface of the soft polyolefin film according to claim 1.