JPH08333557A - Surface protecting film - Google Patents

Abstract

PURPOSE: To obtain a surface protecting film having slight plastic deformation in deformation, excellent in stress relaxation and elongation recovery, slightly causing increase in adhesion with time. CONSTITUTION: This surface protecting film is obtained by supplying a tacky agent layer to one side of base prepared by adding 3-30wt.% of a plasticizer having 300-1,000 molecular weight to a polyolefin which is composed of an ethylene-propylene copolymer and/or a copolymer of an α-olefin except ethylene- propylene and has <=45% degree of crystallization.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a surface protective film.

[0002]

2. Description of the Related Art A surface protective film has a structure in which an adhesive layer is formed on one surface of a base material such as a thermoplastic resin, has an appropriate adhesive force (temporary adhesion), and after use, a synthetic resin plate. , A part of the adhesive layer of the surface protective film is peeled off and left on the surface of various adherends such as a decorative plywood, a metal plate, and a coated steel plate, or a substance contained in the adhesive layer migrates to the surface. It must be easy to peel off without fouling.

Further, the surface protection film may be machined while it is temporarily attached to the adherend. In such a case, the temporary adhesion and removability which are originally required for the surface protection film are required. In addition, it is required to have machinability. Among the existing base film for surface protection film, since the soft vinyl chloride resin film is most suitable, the soft vinyl chloride resin film formed by the calendar molding method or the extrusion molding method is used as the base material, A surface protective film having an adhesive layer on one surface is widely used.

However, a soft vinyl chloride resin film is used as an alternative surface protection film because of the environmental problems of chlorine-based gas generated during waste incineration after use. The adoption of an olefin resin film, which is easy to use, has been considered.

As for the machinability of the surface protective film, it deforms following the deformation of the adherend during machining, but it does not deform further and does not float or peel off from the surface of the adherend. In the meantime, it is required that the above-mentioned load stress does not locally remain as it is and is immediately relaxed, in other words, plastic deformation is small at the time of deformation, and stress relaxation and elongation recovery are excellent.

The machinability of the surface protective film largely contributes to the performance of the base material layer, but is also related to the adhesive force at the interface of the adherend of the pressure-sensitive adhesive layer. If the adhesive force of the pressure-sensitive adhesive layer is increased in order to prevent the protective film from peeling off, there is a problem of so-called adhesion progressing property, which makes it difficult to peel off the surface protective film from the surface of the adherend after use.

As an attempt to improve the above problems, for example, in JP-A-52-62347, 0.001 part by weight of a phosphoric acid ester or / or its derivative is added to 100 parts by weight of an adhesive composition. A pressure-sensitive adhesive composition for a surface protection sheet, which was added in an amount of less than 0.5 parts by weight, was applied to a polyethylene film having one surface subjected to corona treatment so that the thickness after drying was 10 μm, and dried. A surface protection sheet is disclosed.

However, in the surface protective sheet disclosed in the above-mentioned Japanese Patent Laid-Open No. 52-62347, the adhesion promoting property may be improved depending on the type and blending amount of the phosphoric acid ester or / or its derivative used. However, since there is no detailed description about the polyethylene film, it is not suitable for the above machinability if it is understood as a general low density polyethylene film.

Further, in JP-A-54-133577, in a laminated film comprising a polyethylene resin layer and an adhesive resin layer, the polyethylene resin layer has a vinyl acetate content of 20 parts by weight per 100 parts by weight of low density polyethylene.
A composition comprising 3 to 60 parts by weight of an ethylene-vinyl acetate copolymer and 1 to 35 parts by weight of a plasticizer, wherein the adhesive resin layer is an ethylene-unsaturated ester copolymer. Laminated films of layers are disclosed.

However, in the laminated film disclosed in JP-A-54-133577, the low density polyethylene used for the polyethylene resin layer is not particularly limited, and any general commercially available low density polyethylene can be used. It is used with ethylene containing more than 20% by weight of vinyl acetate.
Since the vinyl acetate copolymer is blended, the adhesive strength at the interface between the polyethylene resin layer and the adhesive resin layer is improved, and the adhesive strength to the adherend is also improved, but the adhesion progresses over time, It is possible to meet the required quality that the surface protective film is difficult to peel off from the surface of the adherend after use, and the plastic deformation is small at the time of deformation during machining, stress relaxation and elongation recovery are large. is not.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and an object of the present invention is to reduce plastic deformation during deformation, to provide excellent stress relaxation and elongation recovery. In addition, the object is to provide a surface protective film with little progress of adhesion over time.

[0012]

The present invention relates to a polyolefin having a crystallinity of 45% or less, which comprises an ethylene-propylene copolymer and / or an α-olefin copolymer other than ethylene-propylene and has a molecular weight of 300 to 1,000. The surface protection film is characterized in that an adhesive layer is provided on one surface of a substrate formed by adding 3 to 30% by weight of the plasticizer.

In the present invention, the polyolefin having a crystallinity of 45% or less, which is used as the base material, is an ethylene-propylene copolymer and / or an α-other than ethylene-propylene.
-Although it is composed of an olefin copolymer, the above α-
Examples of the olefin include 1-butene, 1-hexene, 1-octene and the like. When the degree of crystallinity of the polyolefin exceeds 45%, plastic deformation is small at the time of deformation, and a base film having excellent stress relaxation property and elongation recovery property is not provided.

The above ethylene-propylene copolymer and /
Alternatively, a polyolefin having a crystallinity of 45% or less, which is composed of an α-olefin copolymer other than ethylene-propylene,
Any polymerization method may be adopted as long as the crystallinity is controlled to 45% or less, but it can be easily obtained by copolymerization by a reactor blending method. Here, the reactor blending method is a polymerization method in which a plurality of types of polymers can be continuously produced by performing multi-stage polymerization of two or more steps, instead of completing the polymerization once. It is a completely different method from the so-called ordinary polymer blending method in which a mixed resin composed of different polymers is obtained using a mechanical method, and it is a method of producing a blend type copolymer resin at the molecular level. is there. The polyolefin having a crystallinity of 45% or less obtained in this manner faithfully retains various properties of the mixed copolymer components, which are different from each other, by finely dispersing the copolymer components. You can get what you embody. As a specific manufacturing method, for example, there is a method described in JP-A-3-205439.

The plasticizer having a molecular weight of 300 to 1000 is not particularly limited, but for example,
Di- (2-ethylhexyl) phthalate, didecyl phthalate and other phthalate ester plasticizers, di- (2-ethylhexyl) adipate, didecyl adipate and other adipate ester plasticizers, di- (2-ethylhexyl)
Azelaic acid ester plasticizers such as azelaate and didecyl azelaate, sebacate ester plasticizers such as di- (2-ethylhexyl) sebacate and didecyl sebacate, oleic acid ester plasticizers such as 2-ethylhexyl oleate Agents, trimellitic acid ester-based plasticizers such as trioctyl trimellitate, tetraoctyl pyromellitate, pyromellitic acid ester-based plasticizers, adipic acid-based, azelaic acid-based, sebacic acid-based polyester plasticizers, chlorine Included are polyolefinized plasticizers and the like.

When the plasticizer has a molecular weight of less than 300,
When the plasticizer present in the base material layer remarkably migrates to the pressure-sensitive adhesive layer, the adhesive performance is deteriorated, and at the same time, the degree of contamination of the adherend is increased. On the contrary, when the molecular weight exceeds 1,000, the phase with the polyolefin is The solubility is lowered, sufficient base material performance cannot be obtained, diffusion to the pressure-sensitive adhesive layer is inhibited, and the effect of suppressing adhesion promotion cannot be sufficiently obtained.

The plasticizer having a molecular weight of 300 to 1000 is added in an amount of 3 to 30% by weight based on the polyolefin having a crystallinity of 45% or less.
If it is less than 10% by weight, the effect of the addition is not sufficiently exhibited, and if the addition ratio exceeds 30% by weight, the amount of the plasticizer transferred to the pressure-sensitive adhesive layer increases and the anchor of the pressure-sensitive adhesive layer decreases. As a result, the adhesion performance is deteriorated and at the same time, the degree of contamination of the adherend is increased.

In order to improve the practicality of the surface protective film, a release agent is used on the back surface of the base material, or the flexible base material prevents the surface from slipping. Within the range of not impairing the effect aimed at by the present invention, in the raw materials for laminating layers or constituting the base material, other compounds,
For example, a filler or a coloring agent can be used.

When the substrate of the surface protective film of the present invention is obtained using the above-mentioned raw materials, the thickness of the substrate layer is
Although it depends on the thickness of the adherend to be applied, it is usually 30
˜100 μm. The method for obtaining the base material of the surface protective film is not particularly limited, and examples thereof include an extrusion molding method using a T die and a circular die, a calender molding method, and a casting method.

The pressure-sensitive adhesive used in the surface protective film of the present invention is not particularly limited as long as it can fulfill the function of the surface protective film, and examples thereof include rubber-based and acrylic-based adhesives. Adhesive of. The means for forming the pressure-sensitive adhesive layer is not particularly limited, and examples thereof include a coating method and a coextrusion method.

[0021]

In the surface protective film of the present invention, a polyolefin having a crystallinity of 45% or less and comprising an ethylene-propylene copolymer and / or an α-olefin copolymer other than ethylene-propylene has a molecular weight of 300 to 1,000. Since the pressure-sensitive adhesive layer is provided on one surface of the base material formed by adding the plasticizer in an amount of 3 to 30% by weight, it is possible to perform bending or bending while the surface protection film is temporarily attached to the adherend such as a metal plate. Plastic deformation is small at the time of deformation during mechanical processing such as drawing, stress relaxation and elongation recovery are excellent, and adhesion progress over time is small.

The effect of the surface protective film of the present invention as described above is to use a polyolefin comprising an ethylene-propylene copolymer and / or an α-olefin copolymer other than ethylene-propylene and having a crystallinity of 45% or less. By suppressing the yield point strength to a low value and maintaining an appropriate elastic modulus, it deforms following the deformation of the adherend during machining of the adherend, but further deforms By the way, it does not float or peel off from the surface of the adherend, but rather, the above-mentioned load stress does not locally remain as it is and is immediately relaxed, in other words, plastic deformation is small during deformation, stress relaxation, elongation It can be said that recoverability is realized.

Further, the plasticizer molecules added to the amorphous portion of the polyolefin molecules of the above base material layer in a ratio within the above range are relatively stably dispersed and held, and the preferable physical properties of the above base material are realized. In addition, the plasticizer, which bleeds slightly but continuously during deformation in the machining, also provides appropriate slipperiness at the interface with the adherend, and in combination with the excellent machine described above. It is presumed to have processing characteristics.

[0024]

Embodiments of the present invention will be described below. (Example 1) Ethylene-α-olefin copolymer (manufactured by Mitsui Petrochemical Co., Ltd., trade name: ULTOZEX 1520) 10
5 parts by weight of dioctyl phthalate was added to 0 parts by weight,
A substrate having a thickness of 100 μm is prepared by a die method, one surface of the substrate is subjected to corona discharge treatment, and an acrylic adhesive (manufactured by Soken Chemical Co., Ltd., trade name: AG105) is dried on the treated surface. To give a surface protection film.

Example 2 Instead of the ethylene-α-olefin copolymer of Example 1, an ethylene-propylene copolymer (manufactured by Highmont, trade name: HYFAX NKS) was used.
A surface protective film was produced in the same manner as in Example 1 except that 021P) was used.

Example 3 A surface protective film was prepared in the same manner as in Example 2 except that 10 parts by weight of octyl trimellitate was used instead of 5 parts by weight of the plasticizer dioctyl phthalate of Example 2.

Example 4 A surface protective film was produced in the same manner as in Example 2 except that 5 parts by weight of chlorinated paraffin was used instead of 5 parts by weight of the plasticizer dioctyl phthalate of Example 2.

Comparative Example 1 Ethylene-α-olefin copolymer (manufactured by Mitsui Petrochemical Co., Ltd., trade name: ULTOZEX 3
520) 10 parts by weight of dioctyl phthalate was added to 100 parts by weight, and a substrate having a thickness of 100 μm was prepared by the T-die method, and then a surface protective film was prepared in the same manner as in Example 1.

(Comparative Example 2) Except that the addition amount of the plasticizer dioctyl phthalate in Example 1 was changed to 50 parts by weight,
A surface protective film was produced in the same manner as in Example 1.

Comparative Example 3 A surface protective film was prepared in the same manner as in Example 1 except that the amount of the plasticizer dioctyl phthalate added in Example 1 was changed to 1 part by weight.

Comparative Example 4 A surface protective film was produced in the same manner as in Example 1 except that 10 parts by weight of dibutyl phthalate was used instead of the plasticizer dioctyl phthalate of Example 1.

(Comparative Example 5) The plasticizer dioctyl phthalate of Example 1 was replaced with 10 parts by weight of an adipic acid polyester plasticizer having a molecular weight of 1000 or more.
A surface protective film was produced in the same manner as in Example 1.

The surface protection films obtained in the above Examples and Comparative Examples had crystallinity, initial adhesion, peeling strength after aging, yield point during deformation, elongation recovery rate, stress residual rate and bending workability. The stain resistance of the adherend was tested and evaluated by the following method. The results are shown in Table 1.

1. Film crystallinity: The film obtained by the T-die method was sampled before the corona discharge treatment, and the crystallinity was measured by a differential thermal analysis method (Differenntial Scanning Calorimetry).

2. Initial adhesive strength: A test piece having a width of 25 mm was cut out from the obtained surface protection film, and a stainless steel plate (manufactured by Nisshin Steel Co., Ltd., trade name: SUS # 304HL)
2kg on the surface under the environment of 23 ℃ × 65% RH
After sticking with a roller and leaving for 20 minutes, peeling speed 3
The 180-degree peel adhesive strength at 00 mm / min was measured.

3. Peeling force after aging: A test piece having a width of 25 mm was attached to a stainless steel plate in the same manner as that used in the initial adhesive strength test in the previous section, and exposed outdoors for 1 month, and then at 23 ° C. × 65.
The 180-degree peel force was measured under the environment of% RH.
When the surface protection film was peeled off before the measurement due to poor adhesion, "peeling" was displayed.

4. Presence or absence of yield point during deformation: A test piece having a length of 40 mm and a width of 10 mm was cut out from the film obtained by the T-die method and stretched at a tensile speed of 200 mm / min to confirm the presence or absence of a yield point during deformation. The display shows no yield point: none, a slight yield point is recognized: slight
Those with a clear yield point: Yes

5. Elongation recovery rate: A test piece with a width of 10 mm was cut out from the film obtained by the T-die method, and the chuck interval was 40 mm, and the tensile speed was 200 mm / in a tensile tester.
Immediately after stretching at min and doubling the length to 80 mm,
Release the tensile force and measure the length after 5 minutes, 80 mm
The measured length was subtracted from the above, and the percentage of the value obtained by dividing the original length by 40 mm was expressed as the elongation recovery rate.

6. Residual stress rate: Similar to the elongation recovery rate in the previous section, a test piece with a width of 10 mm was stretched at a tensile speed of 200 mm / min using a tensile tester with a chuck interval of 40 mm.
The tensile strength when the length was doubled to 80 mm was left for 5 minutes in the stretched state to the same length, and the percentage of the value obtained by dividing the tensile strength after 5 minutes was expressed as the stress residual rate.

7. Bending processability: The obtained surface protection film was attached to the above-mentioned stainless steel plate having a thickness of 1.5 mm, and bent by a bender at 90 degrees, and the film was broken, and the surface protection film was lifted or peeled. The bending workability was observed. The observation result is smoothly bent,
The surface protection film adhered tightly after processing: ○, the surface protection film floated or peeled off: ×, the film cut during processing: “cut” was displayed.

8. Contamination property of adherend: After the bending workability test of the previous section, the surface protective film was peeled off, and the state of adhesive residue on the surface of the stainless steel plate of the adherend was observed. The observation results were evaluated in three grades: no adhesive residue: none, very little adhesive residue: slight, and significant adhesive residue: yes.

[0042]

[Table 1]

[0043]

Since the surface protective film of the present invention is constructed as described above, mechanical processing such as bending and drawing can be performed while the surface protective film is temporarily attached to an adherend such as a metal plate. The plastic deformation is small at the time of deformation when applied, the stress relaxation property and the elongation recovery property are excellent, and the adhesion progress with time is small.

Claims (1)

[Claims] 1. A polyolefin comprising an ethylene-propylene copolymer and / or an α-olefin copolymer other than ethylene-propylene having a crystallinity of 45% or less and a plasticizer having a molecular weight of 300 to 1000 of 3 to 30. A surface protective film, wherein a pressure-sensitive adhesive layer is provided on one surface of a base material added by weight%.