JPH09118864A - Production of surface-protecting film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a surface-protecting film good in appearance and excellent in adhesive characteristics without causing the gelation of an adhesive by a coextrusion method. SOLUTION: This method for producing a surface-protecting film comprises coextruding an adhesive layer consisting mainly of a block copolymer expressed by the general formula: A-B-A or a block copolymer of the general formulas A-B-A and A-B (A is a styrenic polymer block; B is an olefinic polymer block produced by hydrogenating a butadiene polymer block or an isoprene polymer block) and having an iodine value of <=1 (gBr2 /100g) measured by JIS K 2605 on one side of a substrate film produced from an olefinic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for temporarily adhering to a surface of a synthetic resin plate, a decorative plywood, a metal plate, a coated steel plate, etc., and protecting the surface so that dust is not attached or scratched. The present invention relates to a method for manufacturing a surface protection film.

[0002]

2. Description of the Related Art Conventionally, surface protection films have been used to prevent scratches and stains on the surfaces of decorative plywood, metal plates, painted steel plates, etc. during processing and transportation. This surface protection film has a structure in which an adhesive layer is formed on one side of a base material layer such as a thermoplastic resin or paper, has an appropriate adhesive force or adhesive force (temporary adhesion), and is adhered after use. It must be easy to peel off without contaminating its surface with adhesive.

As an example of such a surface protective film, for example, in Japanese Patent Publication No. 58-30911, a general formula A-is formed on a thermoplastic resin film such as polyethylene.
B-A (wherein A is a styrene polymer block, B is an elastomer block derived from at least one conjugated diene such as butadiene or isoprene) A layer-formed surface protection film is described. Further, in JP-A-61-103975, a general formula A-is formed on a polyolefin resin film such as polyethylene.
B-A (where A is a styrene polymer block and B is a copolymer block of ethylene and butylene) for surface protection on which an adhesive layer containing a block copolymer as a main component is formed. Adhesive films are described.

By the way, usually, in addition to the block copolymer represented by the general formula A-B-A, which is the above main component, a tackifier, etc., a small amount of a phenolic antioxidant is added to the pressure-sensitive adhesive composition. Are configured.

[0005]

However, in the surface protective film described in the above publication, the hydrogenation is insufficient and the olefin polymer block of B in the block copolymer represented by the general formula ABA. When the ratio of carbon-carbon double bonds remaining in the mixture exceeds a certain level and the presence of the antioxidant is small, the adhesive causes gelation when produced by coextrusion, The present inventor has confirmed such a phenomenon. Then, in order to prevent this gelation phenomenon, as a result of diligent studies, as long as the ratio of carbon-carbon double bonds remaining in the olefin polymer block is set to a predetermined level or less, in the pressure-sensitive adhesive composition It was confirmed that even if the amount of the antioxidant was small, the adhesive did not gel.

The present invention has been made in view of the above conventional problems, and when produced by coextrusion, the pressure-sensitive adhesive does not cause gelation, has a good appearance, and is a surface protective film having excellent pressure-sensitive adhesive properties. It is an object of the present invention to provide a manufacturing method capable of obtaining

[0007]

A method for producing a surface protective film according to the present invention according to claim 1 is a surface protective film in which a base film made of an olefin resin and an adhesive layer are formed by a coextrusion method. In the production method of, the pressure-sensitive adhesive layer is a block copolymer represented by the general formula ABA, or
The block copolymers represented by the general formulas A-B-A and the general formula A-B (where A is a styrene-based polymer block and B is a block copolymer).
Is an olefin polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block. ), And moreover, it is a manufacturing method using as a main component as bromine number by JIS K 2605 is 1 (gBr ₂ / 100g) or less.

(Function) In the method for producing the surface protective film of the present invention according to claim 1, as described above, the block copolymer represented by the general formula A-B-A or the general formula A-B-A is used. And a block copolymer represented by the general formula AB (where A is a styrene polymer block, and B is an olefin polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block). In addition, since the one having a bromine value according to JIS K 2605 of 1 (gBr ₂ / 100g) or less is the main component constituting the pressure-sensitive adhesive layer, the olefin resin forming the base film and the pressure-sensitive adhesive are When the surface protection film is produced by co-extrusion, the pressure-sensitive adhesive does not gel in the extruder or mold, and as a result, fish eyes do not occur. Therefore, the surface of the pressure-sensitive adhesive layer does not become rough, and the SP pressure-sensitive adhesive force does not decrease. Also, the melt extrusion characteristics during manufacturing are excellent.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The base film used in the present invention is made of an olefin resin. Examples of the olefin resin include ethylene homopolymer, propylene homopolymer, ethylene and α-olefin. And a copolymer of propylene and α-olefin can be used. Here, examples of the α-olefin as a copolymerization component include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like. Further, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer and the like may be used. Furthermore, a mixture of any of the above may be used. The thickness of the substrate film is not particularly limited, but is 20 to 200 μm, preferably 40 to 100 μm.

The main component of the pressure-sensitive adhesive layer used in the present invention is the block copolymer represented by the general formula A-B-A or the general formula A-B-A and the general formula A-B. (A is a styrene polymer block, B is an olefin polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block). The styrene-based polymer block A has an average molecular weight of 4,000 to 115,000.
It is preferably about 0, more preferably 8,000 to 60,
Those of about 000 are more preferable. The glass transition temperature is preferably 20 ° C. or higher.

The olefin polymer block B obtained by hydrogenating a butadiene polymer block or an isoprene polymer block has an average molecular weight of 20,000-.
It is preferably about 450,000, more preferably 50,
Those of about 000 to 300,000 are more preferable. The glass transition temperature is preferably −20 ° C. or lower.

The preferred weight ratio of the component A and the component B is A / B = 2/98 to 50/50, and more preferably A / B = 5/95 to 30/70. In addition, a block copolymer represented by the general formula ABA,
A preferable weight ratio with the block copolymer represented by the general formula AB is ABAA / AB = 100/0 to 20/8.
0, more preferably A-B-A / A-B = 10
It is 0/0 to 50/50.

The main component of the pressure-sensitive adhesive layer in the present invention, that is, the block copolymer represented by the general formula A-B-A and the block copolymer represented by the general formula A-B are the block copolymers. Hydrogen is added to the carbon-carbon double bonds existing or remaining in the polymer, and
Bromine number by K 2605 is 1 (gBr _2/100
g) The following were made. This bromine number is an index for quantifying carbon-carbon double bonds existing or remaining in the resin which is an adhesive, and specifically, resin 10
Expressed in weight of bromine consumed per 0 g. And, the larger the bromine number, the more double bonds are present. This is, bromine number is 1 (gBr _2/100
When it exceeds g), when the surface protective film is produced by the coextrusion molding method, gelation occurs in the extruder and the mold, and the gelled substance is mixed into the pressure-sensitive adhesive layer, so that the fish eye Occurs, the surface is roughened and the SP adhesive force is reduced.

In the present invention, the general formula A-
A block copolymer represented by BA or a general formula A-
You may add tackifying resin, antioxidant, a flame retardant, a pigment, etc. to the adhesive resin which has a block copolymer shown by BA and general formula AB as a main component. At that time, the block copolymer represented by the general formula ABA and the general formula A
Any component may be used as long as it is selectively compatible with the B component in the block copolymer represented by -B. For example, as a tackifier resin, it is generally used as a tackifier for aliphatic petroleum resin, aromatic petroleum resin, alicyclic petroleum resin, rosin resin, modified rosin resin, terpene resin, coumarone indene resin, etc. Any known one may be used. The thickness of the pressure-sensitive adhesive layer is preferably 5 to 40 μm.

In the production method of the present invention, the olefin resin and the pressure-sensitive adhesive forming the base film are heated and melted respectively, and preferably two layers are coextruded by the T-die method to obtain the base film and the pressure-sensitive adhesive layer. It is a method for producing a surface protection film in which and are laminated.

[0016]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

[Synthesis of Styrene-Butadiene-Styrene Block Copolymer (SBS)] 1.35 kg of dried styrene monomer was dissolved in 5 kg of dried benzene and charged into a stainless reaction vessel, and the solution temperature was adjusted to 40 ° C. , Butyllithium (0.15 mol) was added and reacted until all the styrene monomers were converted to a polymer having a lithium group at the end. Next, 12 kg of dried butadiene monomer was added to this reaction mixture, and the mixture was reacted until it was completely converted into a copolymer. Then, 1.35 kg of dried styrene monomer was added and reacted until the styrene monomer was completely consumed. The obtained styrene-butadiene-styrene block copolymer (SB
The styrene-converted weight average molecular weight of each block of S) by gel permeation chromatography (hereinafter referred to as GPC) was 9,000 for styrene blocks and 72,000 for butadiene blocks.

[Synthesis of Styrene-Isoprene-Styrene Block Copolymer (SIS)] 1.8 kg of dried styrene monomer was dissolved in 5 kg of dried benzene and charged into a reaction vessel made of stainless steel, and the solution temperature was adjusted to 40 ° C. , Butyllithium (0.15 mol) was added and reacted until all the styrene monomers were converted to a polymer having a lithium group at the end. Next, 27 kg of dried isoprene monomer was added to the reaction mixture, and the reaction was allowed to proceed until all the copolymer was converted into a copolymer. After that, 1.8 kg of dried styrene monomer was added and reacted until the styrene monomer was completely consumed. Obtained styrene-isoprene-styrene block copolymer (SIS)
The weight average molecular weight of each block converted to styrene by GPC was 12,000 for the styrene block and 160,000 for the isoprene block.

(SBS Hydrogenation Reaction-1) In a cyclohexane solution, 0.5 mol of nickel acetyl acetate and 1 mol of triisobutylaluminum were added at 25 ° C.
The hydrogenation catalyst was prepared by reacting for 15 minutes under a hydrogen pressure of 7 kg / cm ² . A 10% cyclohexane solution of SBS was prepared and added to the hydrogenation catalyst prepared above. The nickel equivalent amount was set to 1 g for each 1,600 g of SBS and SIS. And 40
After reacting at 35 ℃ / cm ² for 90 minutes, isopropyl alcohol was added, and then 200 ℃, 84kg.
/ Cm ² It was made to react for 1 hour. The hydrogenated SBS [SEBS (1)] thus obtained has a bromine number of 0.
Was 8 (gBr ₂ / 100g).

(Hydrogenation reaction of SIS-2) The hydrogenation reaction was carried out in the same manner as in the above SBS except that SIS was used instead of SBS. The resulting hydrogenated S
The bromine number of IS [SEPS (1)] is 0.7 (gBr ₂ /
It was 100 g).

(SBS Hydrogenation Reaction-3) A 10% cyclohexane solution of SBS was prepared, and 50 g of the nickel catalyst on diatomaceous earth was added to 100 g of SBS. And
The reaction was carried out at 150 ° C. and 35 kg / cm ² for 13 hours. The hydrogenated SBS thus obtained [SEBS
(2) bromine number] was 1.3 (GBR _2/100 g).

(Hydrogenation reaction-4 of SIS) A hydrogenation reaction was carried out in the same manner as the hydrogenation reaction-3 of SBS except that SIS was used instead of SBS. The bromine number of the obtained hydrogenated SIS [SEPS (2)] is 1.5.
It was (gBr ₂ / 100g). SEBS (1), SEBS (2), SEPS obtained by the hydrogenation reaction
Table 1 shows various characteristic values of (1) and SEPS (2).

[0023]

[Table 1]

(Example 1) 10 parts by weight of a tackifying resin (manufactured by Tonex Co., trade name: Escorets 5300) per 100 parts by weight of SEBS (1), an antioxidant (manufactured by Ciba-Geigy Japan, trade name: Irganox) 1010)
Low-density polyethylene (trade name: LC500, manufactured by Mitsubishi Chemical Co., density =
0.918 g / cm ³ , melt index = 4 g / 1
0 minutes) and two layers were coextruded to obtain a surface protection film in which a low-density polyethylene film having a thickness of 50 μm was laminated with an adhesive layer having a thickness of 20 μm on one surface.

Example 2 30 parts by weight of a tackifying resin (manufactured by Tonex Co., trade name: Escorets 5300), 100 parts by weight of SEPS (1), antioxidant (manufactured by Ciba-Geigy Co., Ltd., trade name: Irganox) 1010)
Low-density polyethylene (trade name: LC500, manufactured by Mitsubishi Chemical Co., density =
0.918 g / cm ³ , melt index = 4 g / 1
0 minutes) and two layers were coextruded to obtain a surface protection film in which a low-density polyethylene film having a thickness of 50 μm was laminated with an adhesive layer having a thickness of 20 μm on one surface.

(Comparative Example 1) S instead of SEBS (1)
A surface protective film was obtained in the same manner as in Example 1 except that EBS (2) was used, and a pressure-sensitive adhesive layer having a thickness of 20 μm was laminated on one surface of a low-density polyethylene film having a thickness of 50 μm.

(Comparative Example 2) S in place of SEPS (1)
A surface protective film was obtained in the same manner as in Example 2 except that EPS (2) was used, and a pressure-sensitive adhesive layer having a thickness of 20 μm was laminated on one surface of a low-density polyethylene film having a thickness of 50 μm.

With respect to the surface protection films obtained in Examples 1 and 2 and Comparative Examples 1 and 2, the adhesive strength, the number of fish eyes and the surface roughness were measured. The measuring method is as follows. Table 2 shows the pressure-sensitive adhesive compositions in the above Examples and Comparative Examples.

[0029]

[Table 2]

(Adhesive Strength) Adhesion was performed according to JIS Z 0237-8 (adhesive tape / adhesive sheet test method). The adhesive strength to the acrylic resin coated steel plate was that after attaching the surface protection film to the stainless steel plate, after 23 minutes at 30 ° C.,
The adhesive strength after 30 days was measured under a pressure of 500 ton / m ² . The peeling speed is 300 mm / min.
20 m / min. For the measurement of the peeling speed of 20 m / min, a high-speed peeling tester TF-70 (manufactured by Tester Sangyo Co., Ltd.) was used. The unit of the adhesive force is g / 25 mm width.

(Fish eyes) The number of fish eyes present on the surface of the surface protective film was visually inspected.
The unit is the number per 1 m ² .

(Surface Roughness) JIS B 0601-3.
It carried out according to 1. The measuring machine is JIS B0651.
SE-3H manufactured by Kosaka Research Institute Co., Ltd.
The cutoff value is 0.8 mm and the measurement length is 8 mm.

Table 3 shows the results of these measurements.

[Table 3] As is clear from Table 3, fish eyes were hardly present in Examples 1 and 2, and the surface condition was good. On the other hand, in Comparative Examples 1 and 2, the number of fish eyes was large, and therefore the surface condition was considerably uneven, and the adhesive strength was also reduced, which is unsuitable as a surface protective film.

[0034]

As described above, in the method for producing the surface protective film according to the present invention, the pressure-sensitive adhesive layer has the general formula A-
A block copolymer represented by BA or a general formula A-
B-A and a block copolymer represented by the general formula A-B (where A is a styrene polymer block, B is an olefin polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block). And a bromine number of 1 (gBr ₂ / 100g) or less according to JIS K 2605 is the main component constituting the pressure-sensitive adhesive layer. When the surface protective film is produced by coextrusion with the agent, gelation of the pressure-sensitive adhesive does not occur in the extruder or mold, and as a result, fish eyes do not occur. Therefore, the surface of the adhesive layer is not roughened, and SP
It is possible to manufacture a surface protective film having excellent adhesive properties such as adhesive strength, and at the same time, it has excellent melt extrusion properties during production.

Claims (1)

[Claims] 1. A base film made of an olefin resin,
In the method for producing a surface protective film in which a pressure-sensitive adhesive layer is formed by a co-extrusion method, the pressure-sensitive adhesive layer is a block copolymer represented by the general formula A-B-A, or a general formula A-B-A and a general formula. A block copolymer represented by the formula AB (where A is a styrene polymer block and B is an olefin polymer block obtained by hydrogenating a butadiene polymer block or an isoprene polymer block). Moreover, JIS
Bromine number according to K 2605 is 1 (gBr ₂ / 100g)
A method for producing a surface protective film, characterized in that the main components are as follows.