JP2002338918A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a surface protective film which has a proper degree of initial tack, which, when temporarily stuck to the surface of an object to be protected, undergoes little increase in tack with time even after the elapse of a long time under heat or pressure, and which is excellent in releasability after use and in weatherability. SOLUTION: This surface protective film is characterized in that it has a pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive composition containing 100 pts.wt. of an A-B-A block copolymer or a mixture of an A-B-A block copolymer with an A-B block copolymer (wherein A is a styrene polymer block; and B is a butadiene polymer block, or an isoprene polymer block, or an olefin polymer block obtained by hydrogenating these polymer blocks) and 0.05-10 pts.wt. of a specified higher alkyl ester of an oxycarboxylic acid, formed on one side of a base material layer comprising a polyolefin resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, a metal plate,
The present invention relates to a surface protection film suitable for surface protection of various materials such as a painted steel plate, a synthetic resin plate, a decorative plate, and a glass plate.
In addition, the surface protection film referred to in the present invention includes a surface protection sheet and a surface protection tape.

[0002]

2. Description of the Related Art Conventionally, the surface of various materials (protected bodies) such as a metal plate such as a steel plate, a stainless steel plate, and an aluminum plate, and a coated steel plate, a synthetic resin plate, a decorative plate, and a glass plate have been so-called surface protection. It is widely practiced to protect the film with a film to prevent the adhesion and damage of dust, which are likely to occur during transportation and construction.

As a general surface protective film, for example, as disclosed in JP-A-61-103975, a film composed of a polyolefin-based resin such as polyethylene or polypropylene is used as a substrate layer. A surface protection film in which an adhesive layer made of a rubber (elastomer) adhesive or an acrylic adhesive is formed on one surface of the layer is exemplified.

As described above, the reason why a polyolefin resin is particularly used as a material for forming a base material layer is as follows.
This is because not only is it excellent in moisture resistance, chemical resistance, electrical insulation and the like, but it does not generate toxic gas even if it is incinerated after use, and there are few problems in post-treatment.

Incidentally, the pressure-sensitive adhesive layer of the surface protective film disclosed in the above publication is an ABA type block copolymer (where A represents a styrene polymer block, and B represents a copolymer of ethylene and butylene). (Indicating a copolymer block) 10
It is formed using a pressure-sensitive adhesive composition containing 0 parts by weight and 0 to 80 parts by weight of a tackifying resin. The reason is that, by using a coextrusion molding method that has become widely used in recent years, by simultaneously molding the base material layer and the pressure-sensitive adhesive layer at the same time, a polyolefin-based This is because the anchoring force (adhesion force) of the pressure-sensitive adhesive layer to the base material layer made of a resin is excellent.

However, as disclosed in the above publication, a surface protective film having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing only a block copolymer and a tackifying resin is not limited to a metal plate or the like. After temporarily attaching to the surface of the protected object,
There is no problem if it is used again and it will be peeled off in a relatively short time, but many of them are stacked or coiled for storage while temporarily attached to the surface of the protected object After a long period of time in the form, a large load is applied to the pressure-sensitive adhesive layer, so that the adhesive force remarkably increases with time, and it is difficult to remove the used film after use, and the surface protective film itself is torn or damaged. Problems such as the surface protection film remaining partially on the protective body, and the phenomenon that the pressure-sensitive adhesive layer remains on the protected body (adhesive residue phenomenon) occur, thereby contaminating the surface of the protected body. . Particularly, in order to increase the efficiency of the re-peeling operation after use, if the peeling is performed quickly, the peeling force naturally increases, so that the above problem becomes more remarkable.

[0007]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to have a proper initial adhesive strength, temporarily adhere to the surface of a protected object, and elapse over a long period of time under heating or pressure. Even so, it is an object of the present invention to provide a surface protective film which is less likely to increase in adhesive force with time, has excellent removability after use, and has excellent weather resistance.

[0008]

According to the first aspect of the present invention, there is provided a surface protective film comprising an ABA type block copolymer or an ABA type on one surface of a base layer made of a polyolefin resin. A mixture of a block copolymer and an AB block copolymer (provided that A represents a styrene-based polymer block, B represents a butadiene polymer block or an isoprene polymer block, or obtained by hydrogenating them. Pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive composition containing 0.05 to 10 parts by weight of a higher alkyl ester of oxycarboxylic acid represented by the following general formula (1) per 100 parts by weight of an olefin-based polymer block) Is formed.

Embedded image (Where n represents an integer of 10 to 50)

The polyolefin resin used for the base layer constituting the surface protective film of the present invention includes, for example, low density polyethylene, linear low density polyethylene,
Polyethylene resins such as medium-density polyethylene, high-density polyethylene, and copolymers of ethylene with long-chain olefin monomers such as 1-butene and 1-pentene; propylene homopolymer, high crystallinity propylene homopolymer, propylene-ethylene random Copolymer, polypropylene-based resin such as propylene-ethylene block copolymer; ethylene-ethyl acrylate copolymer, ethylene-n-butyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer resin, and the like; It is preferably used. These polyolefin resins may be used alone or in combination of two or more.

The base material layer may contain an inorganic filler, an organic filler,
Various additives such as softener, plasticizer, surfactant, coupling agent, antioxidant (antiaging agent), heat stabilizer, light stabilizer, ultraviolet absorber, coloring agent, lubricant, antistatic agent, flame retardant, etc. One or more of the agents may be added, but it is preferable to select and use an additive that does not inhibit the weather resistance of the substrate layer or the obtained surface protective film.

As a method for forming the base layer constituting the surface protective film of the present invention, for example, a polyolefin-based resin composition comprising a polyolefin-based resin and various additives optionally added is prepared in advance by an ordinary method. After doing
This polyolefin-based resin composition is melt-kneaded and extruded with an extruder and formed into a film using a T-die or a circular die, or the polyolefin-based resin composition is dissolved or dispersed in a solvent such as an organic solvent. After letting
A method of forming into a film by a cast method, or by co-extrusion of a polyolefin-based resin composition and a pressure-sensitive adhesive composition used to form a pressure-sensitive adhesive layer described below, forming a base layer and forming a pressure-sensitive adhesive. A method in which the formation of the layer is performed simultaneously and the like may be mentioned. Either method may be adopted, but a co-extrusion method is preferred because of excellent productivity.

The thickness of the substrate layer thus obtained is not particularly limited, but is preferably 5 to 70 μm. Further, the base layer may be a single layer,
Two or more layers may be used.

If the thickness of the substrate layer is less than 5 μm, the mechanical strength and removability of the surface protective film may be insufficient. In some cases, the operability of attaching to the surface may be reduced.

In the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer constituting the surface protective film of the present invention, an ABA type block copolymer or an A-
It contains a mixture of a BA block copolymer and an AB block copolymer.

In the above-mentioned ABA type block copolymer and AB type block copolymer, A represents a styrene-based polymer block, and B represents a butadiene polymer block, an isoprene polymer block or a hydrogen-containing polymer block. The olefin polymer block obtained by the addition is shown.

The styrenic polymer block (A) is
Although not particularly limited, its weight average molecular weight is 4,000 to 4,000 in terms of polystyrene by GPC analysis.
It is preferably about 115,000, and more preferably about 8,000 to 60,000. Also,
Those having a glass transition temperature of 20 ° C. or higher are preferred.

The butadiene polymer block or isoprene polymer block or the olefin polymer block (B) obtained by hydrogenating the butadiene polymer block or isoprene polymer block is not particularly limited, but its weight average molecular weight is
20004 to 4 in terms of polystyrene by GPC analysis.
It is preferably about 50,000, more preferably about 50,000 to 300,000. Further, those having a glass transition temperature of −20 ° C. or less are preferable.

In the above ABA type block copolymer and AB type block copolymer, the composition ratio of the A block and the B block is not particularly limited. / B = 5/95 to 50/50 is preferable, and A / B = 10/90 to 3 is more preferable.
0/70.

Specific examples of the ABA type block copolymer include, for example, styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene -Butylene-styrene block copolymer (SEBS),
Styrene-ethylene-propylene-styrene block copolymer (SEPS) and the like are exemplified, and are preferably used.
Among the ABA type block copolymers, the adhesiveness and heat resistance of the pressure-sensitive adhesive layer constituting the surface protective film of the present invention to the base layer made of the polyolefin resin,
Since the weather resistance etc. is further improved, SEBS and SEPS
Is more preferably used. These ABA block copolymers may be used alone or in combination of two or more.

Specific examples of the AB block copolymer include, for example, styrene-butadiene block copolymer (SB), styrene-isoprene block copolymer (SI), and styrene-ethylene-butylene block copolymer. Polymer (SEB), styrene-ethylene-propylene block copolymer (SEP) and the like are exemplified, and are preferably used. Among the AB type block copolymers, the adhesiveness and heat resistance of the pressure-sensitive adhesive layer constituting the surface protective film of the present invention to the base layer made of the polyolefin resin,
Since the weather resistance and the like are further improved, SEB or SEP is more preferably used. These AB block copolymers may be used alone or in combination of two or more.

In the pressure-sensitive adhesive composition used in the present invention, only an ABA type block copolymer may be used as a main component, or an ABA type block copolymer and an ABA type block copolymer may be used. A mixture with a B-type block copolymer may be used.

The mixing ratio of the ABA type block copolymer and the AB type block copolymer is not particularly limited, but the mixing ratio of the ABA type block copolymer is not limited. It is preferable that the ratio of the copolymer / AB block copolymer is 99/1 to 20/80, more preferably, the ABA block copolymer / AB block copolymer = 99 / 1
５０50/50.

The pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer constituting the surface protective film of the present invention contains a higher alkyl ester of oxycarboxylic acid represented by the following general formula (1). .

Embedded image (Where n represents an integer of 10 to 50)

In the pressure-sensitive adhesive composition, the higher alkyl ester of oxycarboxylic acid represented by the general formula (1) functions as a so-called release agent, and effectively increases the adhesive force of the pressure-sensitive adhesive layer over time. Can be suppressed. Further, the higher alkyl ester of the oxycarboxylic acid is
It also has the advantage of being superior in weather resistance as compared with other organic release agents.

In the above general formula (1), n is 10 to 5
It is necessary to be an integer of 0, but among them, the higher alkyl ester of oxycarboxylic acid becomes solid at room temperature and melts and liquefies by heating at about 60 ° C., so that it is easy to use. Is preferably an integer around 30.

When the above n is an integer less than 10, the higher alkyl ester of oxycarboxylic acid becomes liquid at room temperature and the ABA type block copolymer or A-
Since the compatibility between the BA-type block copolymer and the mixture of the AB-type block copolymer is deteriorated, bleeding out from the pressure-sensitive adhesive layer is facilitated, and the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer is lost. Conversely, if n is an integer greater than 50, the molecular weight of the higher alkyl ester of oxycarboxylic acid will be too large, and will not be melted by heating at about 60 ° C., resulting in lower usability and higher oxycarboxylic acid. The effect of suppressing the increase in adhesive strength over time due to the inclusion of the alkyl ester cannot be sufficiently obtained.

In the pressure-sensitive adhesive composition used in the present invention, the ABA type block copolymer or AB-
With respect to 100 parts by weight of the mixture of the A-type block copolymer and the AB-type block copolymer, 0.05 parts of the higher alkyl ester of oxycarboxylic acid represented by the above general formula (1) is used.
-10 parts by weight, preferably 0.1-5 parts by weight.

ABA type block copolymer or A-
When the content of the higher alkyl ester of oxycarboxylic acid is less than 0.05 part by weight based on 100 parts by weight of the mixture of the BA block copolymer and the AB block copolymer, the adhesive force over time When the effect of suppressing the increase is not sufficiently obtained, and when the content exceeds 10 parts by weight, the tackiness (tack) of the pressure-sensitive adhesive layer becomes poor, and the temporary adhesion to the protected object is reduced, and the pressure-sensitive adhesive layer is used as a surface protective film. The function cannot be performed sufficiently.

The pressure-sensitive adhesive composition used in the present invention may contain, if necessary, a tackifying resin, a stabilizer, a filler, a softener, a plasticizer, and a surfactant within a range not to impair the achievement of the object of the present invention. , Coupling agents, crosslinking agents, coloring agents, antistatic agents,
One or more of various additives such as a flame retardant, an organic solvent, and water may be added, but an additive that does not inhibit the weather resistance of the pressure-sensitive adhesive layer and the obtained surface protective film is selected and used. Is preferred.

Examples of the tackifying resin include a hydrogenated petroleum resin, an aliphatic hydrocarbon resin, an alicyclic hydrocarbon resin, an aromatic hydrocarbon resin, a rosin resin, a terpene resin, and a resin. Malon indene-based resin and the like,
It is preferably used. These tackifying resins may be used alone or in combination of two or more.

Examples of the stabilizer include hindered phenol stabilizers, hindered amine stabilizers, phosphite stabilizers, benzotriazole stabilizers, and triazine stabilizers, and are preferably used. . These stabilizers may be used alone,
Two or more types may be used in combination.

The form of the pressure-sensitive adhesive composition used in the present invention is not particularly limited. For example, any of a solvent-type pressure-sensitive adhesive composition, an emulsion-type pressure-sensitive adhesive composition, and a hot-melt-type pressure-sensitive adhesive composition can be used. May be used. The pressure-sensitive adhesive composition may be a non-cross-linked pressure-sensitive adhesive composition, a cross-linked pressure-sensitive adhesive composition, or a one-pack pressure-sensitive adhesive composition. A two-part or more multi-part adhesive composition may be used.

The preparation method of the pressure-sensitive adhesive composition used in the present invention is not particularly limited. For example, the pressure-sensitive adhesive composition may be prepared using a conventional stirring kneader such as a mixer, a kneader, a roll, an extruder or the like. A-type block copolymer or AB-
A mixture of the A-type block copolymer and the AB-type block copolymer and a predetermined amount of each of the higher alkyl esters of oxycarboxylic acid represented by the general formula (1) and various additives to be added as necessary; Is uniformly stirred and kneaded at room temperature or under heating to obtain a desired pressure-sensitive adhesive composition.

As a method for preparing the surface protective film of the present invention, for example, a pressure-sensitive adhesive composition is directly applied to a predetermined surface (one surface) of the base material layer using a usual coating machine such as a roll coater. After coating, passing through drying and cooling steps as necessary, forming an adhesive layer, and then adhering the release treated surface of a release material such as release paper (release paper) or release film as necessary. A method of laminating on a pressure-sensitive adhesive layer (direct coating method), after forming an adhesive layer on the release-treated surface of the release material by the same method as described above, and laminating this pressure-sensitive adhesive layer on a predetermined surface of the base material layer. A method of transferring the pressure-sensitive adhesive layer to a predetermined surface of the base material layer (transfer method), co-extrusion of the polyolefin resin composition for the base material layer and the pressure-sensitive adhesive composition for the pressure-sensitive adhesive layer, A method of simultaneously forming the material layer and forming the pressure-sensitive adhesive layer simultaneously (co-extrusion method), etc. Good, because of excellent productivity, it is preferable to adopt a coextrusion method. The predetermined surface of the base material layer is preliminarily subjected to a base treatment (pretreatment) such as a corona discharge treatment, a plasma discharge treatment, and a primer (undercoat) coating to further enhance the adhesiveness of the pressure-sensitive adhesive layer. It may be.

The thickness of the surface protective film of the present invention thus obtained varies depending on the type and use of the object to be protected and is difficult to determine uniquely, but is generally 10 to 100 μm because of good usability. Is preferred. Also,
The thicknesses of the base material layer and the pressure-sensitive adhesive layer constituting the surface protective film are not particularly limited, but are generally preferably 5 to 70 μm for the base material layer and 5 to 30 μm for the pressure-sensitive adhesive layer.

If the thickness of the surface protective film is less than 10 μm, the mechanical strength and the removability may be insufficient, while if it exceeds 100 μm, the workability of sticking to the protected object may be reduced. There is.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Low-density polyethylene (trade name “Mirason 1”) was used as a polyolefin resin for the base material layer.
6 ", manufactured by Mitsui Chemicals, Inc.). In addition, 100 parts by weight of a hydrogenated product of a styrene-butadiene-styrene block copolymer (SEBS, trade name “Clayton G1657”, manufactured by Clayton Polymer Japan Ltd.) as the ABA type block copolymer, and the above-mentioned general formula ( As the higher alkyl ester of the oxycarboxylic acid represented by 1), n is 30
0.1 parts by weight of a higher alkyl ester of oxycarboxylic acid (trade name “Kaowax 220”, manufactured by Kao Corporation), hydrogenated petroleum resin (trade name “Escolets 5300”, manufactured by Tonex Corporation) as a tackifying resin 100
0.5 parts by weight of a hindered phenol-based stabilizer (trade name "Irganox 1010", manufactured by Ciba Specialty Chemicals) as a stabilizer, and uniformly kneading the mixture, to thereby form an adhesive composition for the adhesive layer. Was prepared.

Next, using a co-extruder, co-extrusion of the low-density polyethylene “Mirason 16” for the base material layer and the pressure-sensitive adhesive composition for a pressure-sensitive adhesive layer obtained above was performed. The surface protective film having a thickness of 60 μm, a thickness of the pressure-sensitive adhesive layer of 10 μm, and a total thickness of 70 μm was prepared.

(Examples 2 to 4) and (Comparative Example 1)
And Comparative Example 2) A surface protective film was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive composition for the pressure-sensitive adhesive layer had the composition shown in Table 1.

Comparative Example 3 The pressure-sensitive adhesive composition for a pressure-sensitive adhesive layer did not contain a higher alkyl ester of oxycarboxylic acid, "Kaohax 220", but instead used polyoxy as another organic release agent. A surface protective film was produced in the same manner as in Example 1 except that 3 parts by weight of ethylene-hardened castor oil (trade name “Emanon 440”, manufactured by Kao Corporation) was included.

The performances of the surface protective films obtained in Examples 1 to 4 and Comparative Examples 1 to 3 (initial adhesive strength, adhesive strength with heating, adhesive strength with pressure A, adhesive strength with pressure over time B) And weather resistance) were evaluated by the following methods. The results are shown in Table 1.

Initial adhesive strength: A surface protective film was stuck to a coated steel sheet using a laminator, left for 30 minutes in an atmosphere of 23 ° C., and then subjected to a tensile speed of 300 mm / mm using a tensile tester in the same atmosphere. A 180 degree angle peel test was performed in minutes, and the initial adhesive strength was measured. Adhesion over time with heating: Using a laminator, a surface protective film was attached to a coated steel plate, left for 1 week in an atmosphere of 60 ° C., taken out, and left for 30 minutes in an atmosphere of 23 ° C. Using a tensile tester, a 180-degree square peel test was performed at a tensile speed of 300 mm / min, and the adhesive force with time was measured. Pressure Aging Adhesion A: A surface protective film was stuck to a coated steel plate using a laminator, left under an atmosphere of 23 ° C. under a load of 4.9 MPa for 3 days, and then pulled under the same atmosphere. Using a testing machine, pulling speed 300mm
Per minute, a 180-degree angle peel test was performed, and the pressure-sensitive adhesive force A over time was measured. Pressure-dependent adhesive strength B: A surface protective film was stuck to a coated steel plate using a laminator, left under an atmosphere of 23 ° C. under a load of 4.9 MPa for 3 days, and then pulled under the same atmosphere. Using a testing machine, a pulling speed of 20 mm /
A 180-degree angle peel test was performed in minutes, and the pressure-sensitive adhesive force B over time was measured. Weather resistance: Using a laminator, a surface protective film was stuck to the coated steel plate, and subjected to ultraviolet irradiation for 48 hours in an ultraviolet carbon type auto fade meter (model “U48AU”, manufactured by Suga Test Instruments Co., Ltd.), and then taken out. After being left for 30 minutes in an atmosphere of 23 ° C., a 180 ° angle peel test was performed at a tensile speed of 300 mm / min using a tensile tester in the same atmosphere to measure weather resistance (adhesion after ultraviolet irradiation). .

In the above performance evaluation, if the adhesive force generally exceeds 2.94 N / 25 mm, peeling becomes difficult (poor removability), and conversely, the adhesive force becomes 0.49 N / 25 mm.
If it is less than the above value, the adhesion becomes insufficient (temporary adhesion is poor).

[0045]

[Table 1]

As is clear from Table 1, all the surface protective films of Examples 1 to 4 according to the present invention have an appropriate initial adhesive strength and are capable of undergoing aging under heating and pressing conditions. The increase in adhesion was small, and the weather resistance was also good.

On the other hand, the surface protective film of Comparative Example 1 using the pressure-sensitive adhesive composition containing no higher alkyl ester of oxycarboxylic acid represented by the general formula (1)
Under the heating condition and the pressurizing condition, the adhesive strength increased with time, and the weather resistance was extremely poor. Also, AB-
The surface protective film of Comparative Example 2 using a PSA composition in which the content of the higher alkyl ester of the oxycarboxylic acid was more than 10 parts by weight based on 100 parts by weight of the A-type block copolymer was evaluated in all the evaluation items. Adhesion was too low. Furthermore, the surface protective film of Comparative Example 3 using the pressure-sensitive adhesive composition containing polyoxyethylene hydrogenated castor oil instead of the higher alkyl ester of oxycarboxylic acid was inferior in weather resistance.

[0048]

As described above, the surface protective film of the present invention is an ABA block copolymer or an AB block copolymer.
A mixture of an A-type block copolymer and an A-B type block copolymer as a main component, with respect to a specific amount of the main component,
Since it has a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing a specific amount of the higher alkyl ester of oxycarboxylic acid represented by the general formula (1), the higher alkyl ester of oxycarboxylic acid is exhibited. Due to the function as a release agent, the adhesive force can be effectively prevented from increasing with time even under a long period of time under heating or under pressure, and the weather resistance is also excellent.

That is, the surface protective film of the present invention has an appropriate initial adhesive strength, and the adhesive strength is temporally adhered to the surface of the object to be protected even if the adhesive is applied for a long time under heating or pressure. It has little remarkable increase, is excellent in removability after use, and is also excellent in weather resistance. For example, various materials such as a metal plate, a coated steel plate, a synthetic resin plate, a decorative plate, and a glass plate ( It is suitably used for protecting the surface of the object to be protected.

Claims (1)

[Claims] An ABA type block copolymer or an AB-type block copolymer is provided on one side of a base layer made of a polyolefin resin.
A mixture of an A-type block copolymer and an AB-type block copolymer (where A represents a styrene-based polymer block,
B represents a butadiene polymer block or an isoprene polymer block or an olefin polymer block obtained by hydrogenating the butadiene polymer block or 100% by weight of a higher alkyl group of an oxycarboxylic acid represented by the following general formula (1). A surface protective film comprising a pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive composition containing 0.05 to 10 parts by weight of an ester. Embedded image (Where n represents an integer of 10 to 50)