JP4627637B2 - Surface protection film - Google Patents

Description

  The present invention relates to a surface protective film. More specifically, the present invention is temporarily attached to an adherend such as a synthetic resin plate, a metal plate, a decorative plywood, a coated coated steel plate, various nameplates, and the like. The present invention relates to a surface protective film used for preventing sticking.

Plasticized vinyl chloride is temporarily attached to the surface of synthetic resin plates, metal plates, decorative plywood, coated and coated steel plates, various nameplates, etc., to prevent scratches and dirt during processing, transportation and storage of these adherends. A surface protective film in which an adhesive layer is provided on one surface of a base film made of a resin or polyolefin resin has been widely used. The surface protective film is in close contact with the adherend during processing, transportation and storage of the adherend, and when it is no longer necessary, leave a part of the adhesive layer on the surface of the adherend. And moderate tackiness that can be easily peeled off is required.
As such a surface protective film, it consists of a composition of 60% by weight or more of a hydrogenated random copolymer consisting of 1 to 50% by weight of styrene and 99 to 50% by weight of a diene hydrocarbon and 40% by weight or less of polyolefin (A ) Layer (adhesive layer), and a composition comprising less than 60% by weight of a hydrogenated random copolymer consisting of 1 to 50% by weight of styrene and 99 to 50% by weight of a diene hydrocarbon and exceeding 40% by weight of polyolefin (B ) Layer (support layer) is disclosed.

However, the pressure-sensitive adhesive layer of the surface protective film tends to cause a so-called adhesive residue that is scraped off and part of the pressure-sensitive adhesive layer remains on the surface of the adherend when it is peeled and removed by adhesion progress after temporarily attached to the adherend. Moreover, although it is not so much adhesive residue, the peeling resistance unevenness that repeats strong peeling resistance and weak peeling resistance called slip stick occurs, peeling of the surface protective film becomes intermittent, and strong peeling resistance and weak In order to leave a very thin adhesive layer stripe pattern corresponding to the boundary line of the peeling resistance on the surface of the adherend, there is a problem that the commercial value of the adherend is reduced or eliminated (for example, patent document) 1).
JP-A-7-241960

  An object of the present invention is to provide a surface protective film having an appropriate temporary adhesion force to an adherend and little adhesion progress.

In order to achieve the above object, the present inventors have repeatedly studied. As a result, the base material made of thermoplastic resin,
1) Hydrogenated copolymer (1) obtained by adding hydrogen to a copolymer comprising a conjugated diene compound and a vinyl aromatic compound satisfying the following (a) to (e) and a block X comprising a vinyl aromatic compound and at block Y Tona Lube locking copolymer comprising a conjugated diene compound, vinyl aromatic compound content of 13 to 35 wt%, hydrogenated block more than 95% of the double bonds of the conjugated diene is hydrogenated adhesive composition containing a copolymer (2) is a front surface protective film is laminated to a substrate made of a thermoplastic resin ing,
In the hydrogenated block copolymer (2), when the block X composed of the vinyl aromatic compound is X and the block Y composed of the conjugated diene compound is Y, the hydrogenated block copolymer (2) has a structure of XYXY. A surface protective film characterized by being made.
(A) The content of the vinyl aromatic compound of component (1) is more than 60% by weight and 90% by weight or less.
(B) The proportion of the vinyl aromatic compound polymer block of component (1) is 40% by weight or less.
(C) The weight average molecular weight of component (1) is 10,000 to 300,000.
(D) 70% or more of the double bond based on the conjugated diene compound of component (1) is hydrogenated.
(E) In the viscoelasticity measurement chart obtained for the component (1), there is at least one tan δ (loss tangent) peak at -20 to 80 ° C.
2) The composition for adhesive which component (1) and component (2) are contained by the mass ratio of (1) :( 2) = 80: 20-20: 80 is laminated | stacked. 2. The surface protective film as described in 1 above, which is characterized by the following.

  Since the surface protective film of the present invention is configured as described above, it has moderate initial tackiness to the adherend, and even when placed in a severe heating environment, adhesion progress is suppressed, The surface protective film can be easily peeled off from the adherend, and the adherend surface is not contaminated with adhesive residue or cloudiness.

The pressure-sensitive adhesive used in the pressure-sensitive adhesive layer of the present invention comprises a hydrogenated copolymer (1) and a block copolymer (2).
The hydrogenated copolymer (1) of the present invention is a hydrogenated product of a copolymer comprising a conjugated diene compound and a vinyl aromatic compound.
In the present invention, the content of the vinyl aromatic compound in the hydrogenated copolymer (1) is more than 50% by weight, 90% by weight or less, preferably more than 60% by weight, 88% by weight or less, more preferably 62%. ~ 86% by weight. The use of a vinyl aromatic compound having a content within the range specified in the present invention is necessary for controlling an appropriate temporary adhesion force to the adherend and suppressing adhesion progress. In the present invention, the content of the vinyl aromatic compound in the hydrogenated copolymer may be grasped by the content of the vinyl aromatic compound in the copolymer before hydrogenation.

  In the hydrogenated copolymer (1) used in the present invention, the content of the vinyl aromatic compound polymer block in the copolymer is 40% by weight or less in terms of temporary adhesive force of the protective film obtained, Preferably it is 3 to 40 weight%, More preferably, it is 5 to 35 weight%. In the case of obtaining a protective film of the present invention, if a hydrogenated copolymer having excellent blocking resistance is preferred, the block ratio of the vinyl aromatic compound (vinyl aromatic relative to the total vinyl aromatic compound content in the copolymer) It is recommended that the ratio of the content of the compound polymer block is called 10 to 60%, preferably 13 to 50%, more preferably 15 to 40%.

The weight average molecular weight of the hydrogenated copolymer (1) used in the present invention is 1 to 300,000, preferably 3 to 200,000, and more preferably 70 to 150,000. When the weight average molecular weight is less than 10,000, the mechanical strength and heat resistance are inferior, and when it exceeds 300,000, the molding processability is inferior.
In the present invention, the molecular weight distribution of the hydrogenated copolymer is 10 or less, generally 1.05 to 8, preferably 1.1 to 5, but 1.3 to 5 when molding processability is important. It is recommended that the ratio be 1.5 to 5, more preferably 1.6 to 4.5, and still more preferably 1.8 to 4.
The hydrogenated copolymer (1) used in the present invention is a hydrogenated product of a copolymer comprising a conjugated diene and a vinyl aromatic compound, and is conjugated diene in the copolymer in terms of weather resistance and thermal stability. 70% or more, preferably 75% or more, more preferably 80% or more, particularly preferably 85% or more of the double bonds based on the above are hydrogenated. The hydrogenation rate of the aromatic double bond based on the vinyl aromatic hydrocarbon in the hydrogenated copolymer is not particularly limited, but the hydrogenation rate is 50% or less, preferably 30% or less, more preferably 20 % Or less.

The hydrogenated copolymer (1) of the present invention has a tan δ (loss tangent) peak of −20 to 80 ° C., preferably −10 to 80 ° C. in the viscoelasticity measurement chart obtained for the hydrogenated copolymer. More preferably, at least one is present at 0 to 70 ° C, particularly preferably at 5 to 50 ° C. The peak of tan δ existing in the temperature range of −20 to 80 ° C. defined in the present invention is a hydrogenated polymer of a random copolymer of a conjugated diene and a vinyl aromatic compound in the polymer chain of the hydrogenated copolymer. It is a peak due to the block. The presence of at least one peak due to the hydrogenated polymer block in the range of −20 ° C. to 80 ° C. is necessary for suppressing adhesion progress.
In the present invention, the structure of the hydrogenated copolymer (1) is not particularly limited and any structure can be used, but a particularly recommended one is a copolymer having at least one structure selected from the following general formula. It is a hydrogenated product of a polymer. The hydrogenated copolymer used in the present invention may be any mixture composed of a hydrogenated copolymer having a structure represented by the following general formula. Moreover, the vinyl aromatic compound polymer may be mixed with the hydrogenated copolymer.

S, (HS) _n , H- (SH) _n , S- (HS) _n , [(SH) _n ] _m- X,
[(HS) _n ] _m- X, [(SH) _n- S] _m- X, [(HS) _n- H] _m- X,
(SH) _n -X- (H) p, (ES) _n , E- (SE) _n , S- (ES) _n ,
[(ES) _n ] _m- X, [(SE) _n- S] _m- X, [(ES) _n- E] _m- X,
E- (S-H) _n , E- (HS) _n , E- (HS-H) _n ,
E- (S-HS) _n , HE- (SH) _n , HE- (HS) _n ,
H-E- (S-H) _n- S, [(HS-E) _n ] _m- X,
[H- (SE) _n ] _m- X, [(HS) _n- E] _m- X,
[(HS-H) _n- E] _m- X, [(SH-S) _n- E] _m- X,
[(E-S-H) _n ] _m- X, [E- (S-H) _n ] _m- X,
[E- (HS-H) _n ] _m- X, [E- (S-HS) _n ] _m- X,
(Here, H is a vinyl aromatic compound polymer block, S is a random copolymer of a conjugated diene and a vinyl aromatic compound, or a random copolymer block of a conjugated diene and a vinyl aromatic compound, and E is a conjugate. Diene polymer block, the boundary of each block does not necessarily need to be clearly distinguished, m is an integer of 2 or more, preferably an integer of 2 to 10, and n and p are integers of 1 or more, preferably It is an integer of 1 to 10. X represents a residue of a coupling agent or a residue of a polyfunctional initiator, or a residue of a modifying agent described later.In the general formula, a random copolymer or a random copolymer block S The vinyl aromatic hydrocarbon may be uniformly distributed or tapered, and the vinyl aromatic hydrocarbon is uniformly distributed in the copolymer or the copolymer block S. A plurality of distributed portions and / or a plurality of portions distributed in a tapered shape may coexist, and the random copolymer or random copolymer block S has a vinyl aromatic hydrocarbon content. A plurality of different segments may coexist.When there are a plurality of blocks H and blocks S in the copolymer, their structures such as molecular weight and composition may be the same or different. The structure of the polymer chain bonded to may be the same or different.)

  In the present invention, the content of the vinyl aromatic compound can be known using an ultraviolet spectrophotometer, an infrared spectrophotometer, a nuclear magnetic resonance apparatus (NMR), or the like. The vinyl aromatic polymer block content can be measured by, for example, a method in which osmium tetroxide is used as a catalyst to oxidatively decompose a copolymer before hydrogenation with tertiary butyl hydroperoxide (IM KOLTHOFF, etal. , J. Polym. Sci. 1, 429 (1946)) weight of vinyl aromatic hydrocarbon polymer block component (however, vinyl aromatic hydrocarbon polymer having an average degree of polymerization of about 30 or less) Can be obtained from the following equation:

Block weight (% by weight) of vinyl aromatic hydrocarbon = (weight of vinyl aromatic hydrocarbon polymer block in copolymer before hydrogenation / weight of copolymer before hydrogenation) × 100
Furthermore, the vinyl bond content based on the conjugated diene in the copolymer before hydrogenation can be determined by using an infrared spectrophotometer (for example, the Hampton method) and the conjugated diene in the hydrogenated copolymer after hydrogenation. The vinyl bond content based can be determined using a nuclear magnetic resonance apparatus (NMR). The hydrogenation rate of the hydrogenated copolymer can be known using a nuclear magnetic resonance apparatus (NMR). In the present invention, the molecular weight of the hydrogenated copolymer is measured by gel permeation chromatography (GPC), and the molecular weight of the peak of the chromatogram is determined from a calibration curve (standard The weight average molecular weight determined using the peak molecular weight of polystyrene). Similarly, the molecular weight distribution of the hydrogenated copolymer can be determined from the measurement by GPC, and is the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn).

  In the present invention, a conjugated diene is a diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3- Examples thereof include butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, and particularly common ones include 1,3-butadiene and isoprene. These may be used alone or in combination of two or more. Examples of vinyl aromatic compounds include styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl- Examples thereof include p-aminoethylstyrene, and these may be used alone or in combination of two or more.

  In the present invention, the copolymer before hydrogenation is obtained, for example, by anion living polymerization using an initiator such as an organic alkali metal compound in a hydrocarbon solvent. Examples of the hydrocarbon solvent include aliphatic hydrocarbons such as n-butane, isobutane, n-pentane, n-hexane, n-heptane and n-octane, and alicyclic carbonization such as cyclohexane, cycloheptane and methylcycloheptane. Hydrogen, and aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene.

  Further, as the initiator, an aliphatic hydrocarbon alkali metal compound, an aromatic hydrocarbon alkali metal compound, an organic amino alkali, which are generally known to have anionic polymerization activity with respect to a conjugated diene compound and a vinyl aromatic compound. Examples of the alkali metal include lithium, sodium, and potassium. Suitable organic alkali metal compounds are aliphatic and aromatic hydrocarbon lithium compounds having 1 to 20 carbon atoms, a compound containing one lithium in one molecule, and a dilithium compound containing a plurality of lithiums in one molecule , Trilithium compounds, and tetralithium compounds. Specifically, n-propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, n-pentyllithium, n-hexyllithium, benzyllithium, phenyllithium, tolyllithium, diisopropenylbenzene and sec- A reaction product of butyllithium, a reaction product of divinylbenzene, sec-butyllithium and a small amount of 1,3-butadiene can be used. Furthermore, organic alkali metal compounds disclosed in US Pat. No. 5,708,092, British Patent 2,241,239, US Pat. No. 5,527,753, etc. are also used. be able to.

In the present invention, when an organic alkali metal compound is used as a polymerization initiator and a conjugated diene compound and a vinyl aromatic compound are copolymerized, a vinyl bond (1, 2 or 3, 4 bond) resulting from the conjugated diene compound incorporated into the polymer A tertiary amine compound or an ether compound can be added as an adjusting agent in order to adjust the content of and to adjust the random copolymerizability between the conjugated diene compound and the vinyl aromatic compound.
In the present invention, the method of copolymerizing a conjugated diene compound and a vinyl aromatic compound using an organic alkali metal compound as a polymerization initiator may be batch polymerization, continuous polymerization, or a combination thereof. In particular, when adjusting the molecular weight distribution to a relatively wide range, a continuous polymerization method is recommended. The polymerization temperature is generally 0 ° C. to 180 ° C., preferably 30 ° C. to 150 ° C. Although the time required for the polymerization varies depending on the conditions, it is usually within 48 hours, particularly preferably 0.1 to 10 hours. The polymerization atmosphere is preferably an inert gas atmosphere such as nitrogen gas. The polymerization pressure is not particularly limited as long as the polymerization pressure is in a range sufficient to maintain the monomer and solvent in a liquid phase within the above polymerization temperature range. Furthermore, care must be taken so that impurities that inactivate the catalyst and living polymer, such as water, oxygen, and carbon dioxide, do not enter the polymerization system.

In the present invention, a coupling reaction can be performed by adding a necessary amount of a bifunctional or higher functional coupling agent at the end of the polymerization. Any known coupling agent may be used and is not particularly limited. For example, carboxylic acid esters, divalent or higher polyvalent epoxy compounds, general formula R _4-n SiXn (where R is a hydrocarbon group having 1 to 20 carbon atoms, X is halogen, and n is an integer of 2 to 4) A halogenated silicon compound represented by Dimethyl carbonate or diethyl carbonate can also be used.

  In the present invention, a modified hydrogenated copolymer in which a functional group-containing atomic group is bonded to at least one polymer chain end of the polymer can be used as the copolymer. Examples of the functional group-containing atomic group include a hydroxyl group, a carboxyl group, a carbonyl group, a thiocarbonyl group, an acid halide group, an acid anhydride group, a carboxylic acid group, a thiocarboxylic acid group, an aldehyde group, a thioaldehyde group, and a carboxylic acid ester group. Amide group, sulfonic acid group, sulfonic acid ester group, phosphoric acid group, phosphoric acid ester group, amino group, imino group, nitrile group, pyridyl group, quinoline group, epoxy group, thioepoxy group, sulfide group, isocyanate group, iso Examples thereof include an atomic group containing at least one functional group selected from a thiocyanate group, a silicon halide group, a silanol group, an alkoxysilicon group, a halogenated tin group, an alkoxytin group, and a phenyltin group. The modified hydrogenated copolymer is prepared by reacting a modifier having these functional group-containing atomic groups or a modifier forming these functional group-containing atomic groups at the end of polymerization of the copolymer, and then performing a hydrogenation reaction. Is obtained. Specific examples of the modifier include those described in JP-B-4-39495 (corresponding to US Pat. No. 5,115,035) and JP-A-2002-201333.

Specific modifiers include tetraglycidyl metaxylenediamine, tetraglycidyl-1,3-bisaminomethylcyclohexane, ε-caprolactone, 4-methoxybenzophenone, γ-glycidoxyethyltrimethoxysilane, γ-glycidoxy Butyltrimethoxysilane, γ-glycidoxypropyltriphenoxysilane, bis (γ-glycidoxypropyl) methylpropoxysilane, 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidi Non, N, N′-dimethylpropylene urea, N-methylpyrrolidone and the like can be mentioned.
As another method for obtaining a modified copolymer, an organic alkali metal compound such as an organolithium compound is reacted (metalation reaction) with a copolymer having no living end, and the copolymer is modified with an organic alkali metal added thereto. The method of making an addition reaction of an agent is raised. In the latter case, it is possible to obtain a modified hydrogenated copolymer by obtaining a hydrogenated product of the copolymer and then subjecting it to a metalation reaction and reacting with the above modifier.

The modifier is generally used in an added amount of 0.3 to 3 equivalents, preferably 0.5 to 2 equivalents as a functional group of the modifier per equivalent of initiator used for the polymerization of the copolymer. is there. Depending on the type of modifier, the hydroxyl group and amino group may generally be an organometallic salt at the stage of reaction of the modifier, but in that case, treatment with a compound having active hydrogen such as water or alcohol. By doing so, a hydroxyl group, an amino group, or the like can be obtained.
The hydrogenated copolymer used in the present invention can be obtained by hydrogenating the copolymer obtained above. The hydrogenation catalyst is not particularly limited and is conventionally known (1) A supported heterogeneous hydrogenation in which a metal such as Ni, Pt, Pd, or Ru is supported on carbon, silica, alumina, diatomaceous earth, or the like. A catalyst, (2) a so-called Ziegler-type hydrogenation catalyst using a transition metal salt such as an organic acid salt such as Ni, Co, Fe, Cr or an acetylacetone salt and a reducing agent such as organic aluminum, (3) Ti, Ru, A homogeneous hydrogenation catalyst such as a so-called organometallic complex such as an organometallic compound such as Rh or Zr is used. Specific examples of the hydrogenation catalyst include Japanese Patent Publication No. 42-8704, Japanese Patent Publication No. 43-6636, Japanese Patent Publication No. 63-4841, Japanese Patent Publication No. 1-337970, Japanese Patent Publication No. 1-53851, The hydrogenation catalyst described in Japanese Utility Model Publication No. 2-9041 can be used. Preferred hydrogenation catalysts include mixtures with titanocene compounds and / or reducing organometallic compounds.

As the titanocene compound, compounds described in JP-A-8-109219 can be used. Examples of the reducing organometallic compound include organic alkali metal compounds such as organolithium, organomagnesium compounds, organoaluminum compounds, organoboron compounds, and organozinc compounds.
In the present invention, the hydrogenation reaction is generally carried out in a temperature range of 0 to 200 ° C, more preferably 30 to 150 ° C. The pressure of hydrogen used in the hydrogenation reaction is 0.1 to 15 MPa, preferably 0.2 to 10 MPa, more preferably 0.3 to 5 MPa. The hydrogenation reaction time is usually 3 minutes to 10 hours, preferably 10 minutes to 5 hours. The hydrogenation reaction can be any of a batch process, a continuous process, or a combination thereof.

  In the hydrogenated copolymer solution obtained as described above, the catalyst residue can be removed if necessary, and the hydrogenated copolymer can be separated from the solution. Solvent separation methods include, for example, a method in which a polar solvent that is a poor solvent for a hydrogenated copolymer such as acetone or alcohol is added to the reaction solution after hydrogenation to precipitate and recover the polymer, and the reaction solution is stirred. Examples thereof include a method in which the solvent is removed by steam stripping and recovered by steam stripping, or a method in which the solvent is distilled off by directly heating the polymer solution. In addition, stabilizers, such as various phenol stabilizers, phosphorus stabilizers, sulfur stabilizers, amine stabilizers, can be added to the hydrogenated copolymer of the present invention.

  In the present invention, the modified hydrogenated copolymer is preferably an atomic group having at least one functional group selected from a hydroxyl group, an epoxy group, an amino group, a carboxyl group, an acid anhydride group, a silanol group, and an alkoxysilane group. It is a modified hydrogenated copolymer having at least one bond. The modified hydrogenated copolymer having at least one atomic group having at least one carboxyl group or acid anhydride group is bonded to at least one functional group selected from a hydroxyl group, an epoxy group, an amino group, and a silanol group. A compound having an acid anhydride group, such as maleic anhydride, itaconic anhydride, pyromellitic anhydride, cis-4-cyclohexane-1, a modified hydrogenated copolymer having at least one atomic group bonded thereto 2-dicarboxylic anhydride, 1,2,4,5-benzenetetracarboxylic dianhydride, 5- (2,5-dioxytetrahydroxyfuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic A method obtained by reacting a secondary denaturant such as an acid anhydride is recommended.

  The hydrogenated copolymer used in the present invention may be graft-modified with an α, β-unsaturated carboxylic acid or a derivative thereof such as an anhydride, esterified product, amidated product or imidized product thereof. Specific examples of α, β-unsaturated carboxylic acid or derivatives thereof include maleic anhydride, maleic anhydride imide, acrylic acid or ester thereof, methacrylic acid or ester thereof, endo-cis-bicyclo [2,2,1 ] -5-heptene-2,3-dicarboxylic acid or an anhydride thereof. The addition amount of the α, β-unsaturated carboxylic acid or derivative thereof is generally 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight per 100 parts by weight of the hydrogenated copolymer.

In the present invention, the reaction temperature for graft modification is preferably 100 to 300 ° C, more preferably 120 to 280 ° C. For details of the graft modification method, reference can be made to, for example, JP-A No. 62-79211.
Next, the hydrogenated block copolymer (2) of the present invention is a hydrogenated block copolymer comprising a vinyl aromatic compound and a conjugated diene.
The weight average molecular weight of the block copolymer (2) of the hydrogenated block copolymer is 5,000 or more from the problem of adhesive residue on the non-adherent, and 100,000 or less from the viewpoint of melt kneading properties, preferably 10,000. ˜80,000, more preferably 10,000 to 50,000.

The structure of the hydrogenated block copolymer (2) comprising a vinyl aromatic compound and a conjugated diene used in the present invention is at least one polymer block X mainly composed of a vinyl aromatic compound and mainly composed of a conjugated diene. This is a hydrogenated block copolymer comprising a polymer block X having at least one polymer block Y and having at least one terminal mainly composed of a conjugated diene.
The vinyl aromatic compound content of the hydrogenated block copolymer (2) is 5 to 50% by weight, preferably 10 to 40% by weight, more preferably 13 to 35% by weight, in terms of the balance between cohesive strength and adhesive strength. It is.
In the hydrogenated block copolymer (2) of the present invention, 70% or more of the double bond of the conjugated diene is hydrogenated, preferably 90% or more, from the viewpoint of heat resistance during processing and weather resistance during use. More preferably, it is 95% or more.

The added amount of the hydrogenated block copolymer (2) is 20% by weight or more from the viewpoint of adhesive strength to the adherend, 80% by weight or less, preferably 40 to 80% by weight from the possibility of causing adhesive residue at the time of peeling. .
The pressure-sensitive adhesive layer of the present invention comprises a pressure-sensitive adhesive composition containing a hydrogenated copolymer (1) and a hydrogenated block copolymer (2), and the following substances can be used as other components. . Although not particularly limited, for example, low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, An ethylene-ethyl (meth) acrylate copolymer, an ethylene-methyl (meth) acrylate copolymer, etc. are mentioned, These may be used independently and 2 or more types may be used together. The α-olefin is not particularly limited as long as it can be copolymerized with ethylene and propylene. For example, propylene, 1-pentene, 1-heptene, 1-hexene, 4-methyl-1 -Pentene, 1-octene, etc. are mentioned.

If necessary, the thermoplastic resin used for the base material may include fillers and lubricants such as talc, stearamide and calcium stearate, reinforcing agents composed of inorganic hollow particles such as glass balloons and silica balloons, and organic polymers. Microspheres, antioxidants, UV absorbers, UV stabilizers and the like may be added.
The means for laminating the base material made of the thermoplastic resin and the pressure-sensitive adhesive layer is not particularly limited. For example, the base material layer made of the thermoplastic resin and the hydrogenated copolymer and the hydrogenated block Multi-layer extrusion method in which the two layers are laminated and integrated using a multi-layer extruder such as a T-die method or an inflation method, and the base material made of the thermoplastic resin is formed into an extruder or the like. Examples thereof include a laminating method in which the pressure-sensitive adhesive layer is laminated and integrated using appropriate laminating means such as an extrusion laminating method and a thermal laminating method after being molded using the means.

The thickness of the base material layer and the pressure-sensitive adhesive layer to be laminated is appropriately set according to the use of the surface protective film to be obtained. Usually, the base material layer is 10 to 100 μm, and the pressure-sensitive adhesive layer is about 3 to 50 μm. Set to
Since the surface protective film of the present invention is configured as described above, it has moderate initial tackiness to the adherend, and even when it is placed in a heating environment, the adhesion progress is suppressed, and the surface is covered. The surface protective film can be easily peeled off from the adherend, and the adherend surface is not contaminated by adhesive residue or cloudiness. Since the surface protective film of the present invention has the above-described structure, it is very easy to manufacture by coextrusion, and the surface protective film thus manufactured particularly includes a base material layer and an adhesive layer. However, since the physical anchor effect is taken into account in addition to the chemical bond due to the polarity unique to the pressure-sensitive adhesive composition, the two layers peel even under severe use conditions. No contamination due to adhesive residue or cloudiness.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these examples.
In the following examples, the characteristics and physical properties of the polymer were measured as follows.
A. Characteristics and physical properties of polymer 1) Styrene content The styrene content was measured using an ultraviolet spectrophotometer (manufactured by Shimadzu Corporation, UV-2450).
2) Polystyrene block content A polymer before hydrogenation was used. M.M. Kolthoff, et al. , J .; Polym. Sci. 1, 429 (1946).
3) Amount of vinyl bond and hydrogenation rate Measured using a nuclear magnetic resonance apparatus (manufactured by BRUKER, DPX-400).
4) Molecular weight and molecular weight distribution Measurement was performed by GPC (apparatus, manufactured by Waters), tetrahydrofuran was used as a solvent, and measurement conditions were performed at a temperature of 35 ° C. The molecular weight is a weight average molecular weight obtained by using a calibration curve (created using the peak molecular weight of standard polystyrene) obtained by measuring the molecular weight of the peak of the chromatogram from measurement of commercially available standard polystyrene.
5) Peak temperature of tan δ (loss tangent) Viscoelasticity spectrum was measured and determined using a viscoelasticity measurement analyzer (model DVE-V4 manufactured by Rheology Co., Ltd.). The measurement frequency is 10 Hz.

B. Preparation of hydrogenation catalyst Hydrogenation catalyst I used in the hydrogenation reaction was prepared by the following method.
Charge 1 liter of dried and purified cyclohexane to a nitrogen-substituted reaction vessel, add 100 mmol of bis (η ⁵ -cyclopentadienyl) titanium dichloride, and mix n-hexane solution containing 200 mmol of trimethylaluminum with thorough stirring. The mixture was added and allowed to react at room temperature for about 3 days.

C. Preparation of hydrogenated copolymer (1) Using a stirrer having an internal volume of 10 liters and two jacketed tank reactors, first, continuous polymerization of the non-hydrogenated copolymer was carried out by the following method.
4.51 liter / hr of cyclohexane solution having a butadiene concentration of 24% by weight, 5.97 liter / hr of cyclohexane solution having a styrene concentration of 24% by weight, and 100 parts by weight of monomers (total of butadiene and styrene) A cyclohexane solution of n-butyllithium adjusted to a concentration of 0.077 parts by weight is supplied to the bottom of the first reactor at 2.0 liter / hr, and N, N, N ′ N, N, N ′, N′-tetramethylethylenediamine in cyclohexane solution at a feed rate of 0.44 mol per mol of n-butyllithium, Was continuously polymerized. The reaction temperature was adjusted by the jacket temperature, the temperature near the bottom of the reactor was about 88 ° C., and the temperature near the top of the reactor was about 90 ° C. The average residence time in the polymerization reactor was about 45 minutes, the conversion of butadiene was almost 100%, and the conversion of styrene was 99%.

The polymer solution from the first group is fed to the bottom of the second group, and at the same time, a cyclohexane solution having a styrene concentration of 24% by weight is fed to the bottom of the second group at a feeding rate of 2.38 liters / hr, Continuous polymerization was performed at 90 ° C. to obtain a copolymer (non-hydrogenated copolymer). The conversion of styrene at the second outlet was 98%.
When the non-hydrogenated copolymer obtained by continuous polymerization was analyzed, the styrene content was 67% by weight, the polystyrene block content was 20% by weight, the vinyl bond content in the butadiene portion was 14% by weight, and the weight average molecular weight was 20%. The molecular weight distribution was 1.9.
Next, 100 ppm of titanium as titanium per 100 parts by weight of the non-hydrogenated copolymer was added to the non-hydrogenated copolymer obtained by continuous polymerization, and water was added at a hydrogen pressure of 0.7 MPa and a temperature of 65 ° C. Addition reaction was performed. After completion of the reaction, methanol was added, and then octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate as a stabilizer was added in an amount of 0.3 part by weight based on 100 parts by weight of the polymer. A hydrogenated copolymer (Polymer 1) was obtained.
The hydrogenation rate of polymer 1 was 99%. As a result of viscoelasticity measurement, the peak of tan δ was present at 10 ° C.

D. Preparation of Hydrogenated Block Copolymer (2) While maintaining an autoclave with a stirrer and a jacketed internal volume of 5 l at 50 ° C., 100 g of pre-purified styrene and 1000 g of cyclohexane were supplied. Next, 0.5 g of a butyllithium hexane solution was supplied in terms of butyllithium to initiate the polymerization reaction. One hour after adding the catalyst, 700 g of butadiene that had been purified and dried in advance and 1000 g of cyclohexane were added and polymerized at 50 ° C., and after 1 hour, 100 g of styrene and 1000 g of cyclohexane were added, and polymerization was performed for 1 hour. Polymerization was carried out for 1 hour by adding 100 g of butadiene and 500 g of cyclohexane. In the polymerization reaction, tetramethylethylenediamine was used as a regulator of the 1,2 bond amount in the polybutadiene block part.
The obtained block copolymer solution was diluted with cyclohexane to 5% by weight. To this block copolymer solution, 1.175 g of hexane solution of nickel octenoate was converted to nickel as a catalyst, and hexane solution of triethylaluminum was added. 6.85 g in terms of triethylaluminum was added and reacted at 50 ° C. for about 6 hours under hydrogen pressure. The obtained hydrogenated block copolymer solution was washed with an aqueous hydrochloric acid solution three times. The hydrogenated copolymer solution thus washed with water was precipitated with an excess of methanol, and the precipitate was dried under reduced pressure. The resulting hydrogenated block copolymer (2) had a styrene content of 20%, a 1,2-bond content of the polybutadiene block of 41%, and a hydrogenation rate of 97%.

(Examples 1-3, Comparative Examples 1-2)
Polyethylene (trade name “Mirason 12”, manufactured by Mitsui Petrochemical Co., Ltd., MFR = 3.0 g / 10 minutes, 190 ° C.) constituting the base material layer has a thickness of 40 μm and the hydrogenated copolymer constituting the adhesive layer (1) and hydrogenated block copolymer (2) are blended in the mixing amount shown in Table 1, and supplied to each extruder so as to have a thickness of 20 μm, and both layers are integrated by an inflation-type coextrusion method. And coextruded to produce a surface protective film.
In order to evaluate the performance of the surface protective films obtained in Examples 1 to 3 and Comparative Examples 1 and 2, initial adhesive strength, temporal adhesive strength, adherend contamination degree, and interlayer strength were measured by the following methods. The measurement results are shown in Table 1.

1. Initial adhesive strength: The obtained surface protective film was cut to a width of 25 mm, and this was 300 mm / mm using a 2 kg pressure roller on the surface of a 1 mm thick polycarbonate plate (trade name “Iupilon NF2000” manufactured by Mitsubishi Gas Chemical Co., Inc.). After sticking at a rate of minutes and making a test piece and leaving it in a measurement environment for 30 minutes, in accordance with JIS Z0237, at 23 ° C. × 65% RH, the peel strength was measured by 180 degrees, and this was the initial adhesion. Power.
2. Adhesive strength with time (1): The same test piece as used in the test of the previous item was heated in a gear oven at 70 ° C. for 30 minutes to accelerate deterioration, and left in a measurement environment for 30 minutes. Then, in accordance with JIS Z0237, 23 At 180 ° C. and 65% RH, the 180 ° peel adhesive strength was measured, and this was defined as the temporal adhesive strength (1).
3. Adhesive force with time (2): Adhesive force with time (2) was measured in the same manner as the adhesive force with time (1) except that the deterioration promoting condition was 90 ° C. × 30 minutes.
4). Substrate contamination level: Observe the presence or absence of contamination on the polycarbonate plate adherence surface used as the adherend during the initial adhesive strength measurement described in Item 1, and indicate the result as ○: None, X: Existence. did.
5. Interlaminar strength: At the time of measuring the initial adhesive strength in the first item, the presence or absence of delamination at the interface between the base material layer and the adhesive layer of the surface protective film peeled off from the adherend was visually observed to evaluate the interlaminar strength. did. The evaluation was performed with ○: None and ×: Yes.

  Since the surface protective film of the present invention is configured as described above, it has moderate initial tackiness to the adherend, and even when placed in a harsh heating environment, adhesion progress is suppressed, The surface protective film can be easily peeled off from the adherend, and the adherend surface is not contaminated with adhesive residue or cloudiness. It can be temporarily attached to the surface of synthetic resin plates, metal plates, decorative plywood, coated coated steel plates, various nameplates, etc., and can be used to prevent scratches and stains during processing, transportation and storage of these adherends.

Claims (2)

Hydrogenated copolymer (1) obtained by adding hydrogen to a copolymer comprising a conjugated diene compound and a vinyl aromatic compound satisfying the following (a) to (e), and a block X comprising a vinyl aromatic compound. in block Y Tona Lube lock copolymer of a diene compound, with the vinyl aromatic compound content of 13 to 35% by weight, the hydrogenated block copolymerization of more than 95% of the double bonds of the conjugated diene is hydrogenated polymer (2) an adhesive composition comprising a can, a front surface protective film is laminated to a substrate made of a thermoplastic resin ing,
In the hydrogenated block copolymer (2), when the block X composed of the vinyl aromatic compound is X and the block Y composed of the conjugated diene compound is Y, the hydrogenated block copolymer (2) has a structure of XYXY. A surface protective film characterized by being made.
(A) The content of the vinyl aromatic compound of component (1) is more than 60% by weight and 90% by weight or less.
(B) The proportion of the vinyl aromatic compound polymer block of component (1) is 40% by weight or less.
(C) The weight average molecular weight of component (1) is 10,000 to 300,000.
(D) 70% or more of the double bond based on the conjugated diene compound of component (1) is hydrogenated.
(E) In the viscoelasticity measurement chart obtained for the component (1), there is at least one tan δ (loss tangent) peak at -20 to 80 ° C.   Component (1) and component (2) are laminated | stacked by the composition for adhesives contained (contained) by the mass ratio of (1) :( 2) = 80: 20-20: 80, It is characterized by the above-mentioned. The surface protective film according to claim 1.