JP2014167074A - Adhesive for surface protective material and surface protective material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive for a surface protective material having excellent adhesiveness and extensibility, further being favourably suppressed increase of adhesiveness, and capable of providing the surface protective material hardly leaving adhesive residues when peeling from a protection target.SOLUTION: There is provided an adhesive for a surface protective material containing a block copolymer composition consisting of a block copolymer A represented by the formula (A) and a block copolymer B represented by the formula (B), and a tackifier resin, and having a weight ratio (A/B) of the block copolymer A and the block copolymer B in the block copolymer composition of 10/90 to 90/10. Ar1-D-Ar2(A) (Ar-D)n-X (B), where Ar1, Ar2and Arare each a specific aromatic vinyl polymer block, Dand Dare specific conjugated diene polymer blocks, X is a single bond or a residue of a coupling agent and n is an integer of 2 or more.

Description

  The present invention relates to a pressure-sensitive adhesive for a surface protective material and a surface protective material. More specifically, the present invention has excellent pressure-sensitive adhesiveness and developability, and further, the progress of pressure-sensitive adhesiveness is well suppressed and peeling from a protected object. The present invention relates to a pressure-sensitive adhesive for a surface protective material that can give a surface protective material that hardly causes adhesive residue, and a surface protective material having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive.

  Surface protection such as surface protection films, surface protection sheets, and surface protection tapes for the purpose of protecting the surface of various articles from damage caused by dirt, dust, and contact with other objects during storage and transportation. The material is widely used. The surface protective material generally has a structure in which an adhesive layer made of an adhesive is laminated on a substrate such as a resin, and the surface protective material is attached to the article so that the adhesive layer is in contact with the surface of the article to be protected. Used by pasting.

  Various adhesives are used as the material constituting the adhesive layer of the surface protective material, and as one of representative examples thereof, for example, styrene-isoprene-styrene trichloride as described in Patent Document 1 is used. The adhesive which mix | blends tackifier resin, such as a terpene resin, with a block copolymer can be mentioned. Adhesives using styrene-isoprene-styrene triblock copolymers are widely used as materials constituting the adhesive layer of the surface protective material because they have the feature of high adhesion.

  However, the surface protective material having an adhesive layer of an adhesive using a styrene-isoprene-styrene triblock copolymer is a phenomenon in which the adhesive force gradually increases as time passes in a state of being attached to an article (so-called adhesive). In order to strongly show the property of causing the development of force, there is a problem that it is not easy to peel off the article after sticking for a long time, and it is easy to cause adhesive residue on the article at the time of peeling. In addition, the surface protective material having an adhesive layer of an adhesive using a styrene-isoprene-styrene triblock copolymer is easy to rewind the roll when used as a roll because the adhesive layer has high adhesiveness. That is, it also has a tendency to be inferior in so-called developability.

  Therefore, various studies have been conducted on pressure-sensitive adhesives using styrene-isoprene-styrene triblock copolymers in order to eliminate these difficulties. For example, Patent Document 2 discloses a developability that is suitably used for a surface protective film by blending a tackifier resin and an olefin resin with a block copolymer such as a styrene-isoprene-styrene triblock copolymer. It is disclosed that an excellent adhesive can be obtained.

  However, the improvement effect by the method of blending the olefin resin disclosed in Patent Document 2 is still insufficient, and the adhesive using the styrene-isoprene-styrene triblock copolymer has adhesiveness, developability, adhesive strength. There is a need for a technology that can achieve a high balance between the suppression of progress and prevention of adhesive residue.

JP 54-126243 A JP-A-5-194923

  The present invention has excellent adhesiveness and developability, and further, surface protection that can suppress the progress of adhesive force and can provide a surface protective material that is less likely to remain glue when peeled off from the protection target. It aims at providing the adhesive for materials.

  As a result of intensive studies to achieve the above object, the present inventors have found that an asymmetric aromatic vinyl-conjugated diene-aromatic vinyl block copolymer in which two aromatic vinyl polymer blocks have different weight average molecular weights, and If an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer having a specific configuration different from the above is blended at a specific ratio, an adhesive having excellent adhesiveness and less adhesive strength is obtained. It was found that a block copolymer composition can be obtained. And, when an adhesive obtained by blending a tackifying resin with this block copolymer composition is used as a material for the adhesive layer of the surface protective material, it has excellent adhesiveness and developability, and further, adhesive strength It has been found that a surface protective material can be obtained in which the progress of the film is suppressed well and the adhesive remains difficult to leave when peeled from the object to be protected. The present invention has been completed based on this finding.

  Thus, according to the present invention, a block copolymer composition comprising a block copolymer A represented by the following formula (A) and a block copolymer B represented by the following formula (B), and an adhesive A pressure-sensitive adhesive for a surface protective material comprising an imparting resin, wherein the weight ratio (A / B) of the block copolymer A to the block copolymer B in the block copolymer composition is 10/90 to A pressure-sensitive adhesive for a surface protective material that is 90/10 is provided.

^{Ar1 a -D a -Ar2 a (A} )
(Ar ^b -D ^b ) n-X (B)

(In the formulas (A) and (B), Ar 1 ^a and Ar ^b are aromatic vinyl polymer blocks having a weight average molecular weight of 6000 to 20000, respectively, and Ar 2 ^a is an aromatic having a weight average molecular weight of 22,000 to 400,000. A vinyl polymer block, D ^a and D ^b are each a conjugated diene polymer block having a vinyl bond content of 1 to 20 mol%, X is a single bond or a residue of a coupling agent, n is an integer of 2 or more.)

  In the above-mentioned pressure-sensitive adhesive for surface protective material, the proportion of the aromatic vinyl monomer unit in the block copolymer composition is based on the total monomer units constituting the polymer component in the block copolymer composition. It is preferable that it is 13 to 85 weight%.

  In the above-mentioned pressure-sensitive adhesive for surface protective material, the content of the tackifying resin is preferably 1 to 100 parts by weight with respect to 100 parts by weight of the block copolymer composition.

  Moreover, according to this invention, the surface protection material formed by laminating | stacking the adhesion layer which consists of said adhesive for surface protection materials, and the base material layer which consists of resin is provided.

  According to the present invention, it has excellent adhesiveness and developability, and further, it is possible to provide a surface protective material in which the progress of adhesive force is satisfactorily suppressed and it is difficult for adhesive to remain when peeled off from the protection target. A pressure-sensitive adhesive for a surface protective material can be provided.

  The pressure-sensitive adhesive for surface protective material of the present invention comprises a block copolymer composition composed of at least two block copolymers and a tackifying resin. The block copolymer A which is one of the two block copolymers constituting the block copolymer composition used in the present invention has different weight average molecular weights represented by the following formula (A). An aromatic vinyl-conjugated diene-aromatic vinyl block copolymer having two aromatic vinyl polymer blocks.

^{Ar1 a -D a -Ar2 a (A} )

In the above formula ^(A), Ar1 ^a is an aromatic vinyl polymer block having a weight average molecular weight of 6,000 to 20,000, Ar @ 2 ^a is an aromatic vinyl polymer block having a weight average molecular weight of 22000-400000, ^Da is a conjugated diene polymer block having a vinyl bond content of 1 to 20 mol%.

  The block copolymer B, which is the other of the two block copolymers constituting the block copolymer composition used in the present invention, is an aromatic vinyl-conjugated diene represented by the following formula (B). -Aromatic vinyl block copolymer.

(Ar ^b -D ^b ) n-X (B)

In the above formula (B), Ar ^b is an aromatic vinyl polymer block having a weight average molecular weight of 6000 to 20000, and D ^b is a conjugated diene polymer block having a vinyl bond content of 1 to 20 mol%. X is a single bond or a residue of a coupling agent, and n is an integer of 2 or more.

The aromatic vinyl polymer blocks (Ar1 ^a , Ar2 ^a , Ar ^b ) of the block copolymer A and the block copolymer B are polymer blocks composed of aromatic vinyl monomer units. The aromatic vinyl monomer used for constituting the aromatic vinyl monomer unit of the aromatic vinyl polymer block is not particularly limited as long as it is an aromatic vinyl compound, but styrene, α-methylstyrene, 2 -Methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 4-bromostyrene, 2-methyl-4,6-dichlorostyrene, 2,4-dibromostyrene, vinyl And naphthalene. Of these, styrene is preferably used. These aromatic vinyl monomers can be used alone or in combination of two or more in each aromatic vinyl polymer block. Further, in each aromatic vinyl polymer block, the same aromatic vinyl monomer may be used or different aromatic vinyl monomers may be used.

Each of the aromatic vinyl polymer blocks (Ar1 ^a , Ar2 ^a , Ar ^b ) of the block copolymer A and the block copolymer B may contain a monomer unit other than the aromatic vinyl monomer unit. Good. Monomers constituting monomer units other than aromatic vinyl monomer units that can be included in the aromatic vinyl polymer block include 1,3-butadiene and isoprene (2-methyl-1,3-butadiene). Examples thereof include conjugated diene monomers such as α, β-unsaturated nitrile monomers, unsaturated carboxylic acid or acid anhydride monomers, unsaturated carboxylic acid ester monomers, and non-conjugated diene monomers. . The content of monomer units other than aromatic vinyl monomer units in each aromatic vinyl polymer block is preferably 20% by weight or less, more preferably 10% by weight or less, and substantially Particularly preferred is 0% by weight.

The conjugated diene polymer block (D ^a , D ^b ) of the block copolymer A and the block copolymer B is a polymer block composed of conjugated diene monomer units. The conjugated diene monomer used for constituting the conjugated diene monomer unit of the conjugated diene polymer block is not particularly limited as long as it is a conjugated diene compound. For example, 1,3-butadiene, isoprene, 2, Examples include 3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Among these, it is preferable to use 1,3-butadiene and / or isoprene, and it is particularly preferable to use isoprene. By constituting the conjugated diene polymer block with isoprene units, the obtained pressure-sensitive adhesive for surface protective materials is particularly excellent in adhesiveness. These conjugated diene monomers can be used alone or in combination of two or more in each conjugated diene polymer block. In each conjugated diene polymer block, the same conjugated diene monomer may be used, or different conjugated diene monomers may be used. Furthermore, you may perform hydrogenation reaction with respect to a part of unsaturated bond of each conjugated diene polymer block.

The conjugated diene polymer blocks (D ^a , D ^b ) of the block copolymer A and the block copolymer B may each contain a monomer unit other than the conjugated diene monomer unit. Monomers constituting monomer units other than the conjugated diene monomer unit that can be included in the conjugated diene polymer block include aromatic vinyl monomers such as styrene and α-methylstyrene, α, β-unsaturated monomers. Examples include saturated nitrile monomers, unsaturated carboxylic acid or acid anhydride monomers, unsaturated carboxylic acid ester monomers, and non-conjugated diene monomers. The content of monomer units other than the conjugated diene monomer unit in each conjugated diene polymer block is preferably 20% by weight or less, more preferably 10% by weight or less, and substantially 0% by weight. % Is particularly preferred.

The block copolymer A constituting the block copolymer composition is an aromatic vinyl polymer block (Ar1 ^a ) having a relatively small weight average molecular weight as represented by the above formula (A), a specific An asymmetric aromatic vinyl having a conjugated diene polymer block having a vinyl bond content (D ^a ) and an aromatic vinyl polymer block having a relatively large weight average molecular weight (Ar 2 ^a ) connected in this order It is a conjugated diene-aromatic vinyl block copolymer. The weight average molecular weight (Mw (Ar1 ^a )) of the aromatic vinyl polymer block (Ar1 ^a ) having a relatively small weight average molecular weight is 6000 to 20000, preferably 7000 to 18000, preferably 8000 to 16000. More preferably. If Mw (Ar1 ^a ) is too small, the resulting surface-protective material pressure-sensitive adhesive tends to remain adhesive, and if it is too large, the surface-protective material pressure-sensitive adhesive may become insufficient. is there. The weight average molecular weight of the aromatic vinyl polymer block (Ar @ 2 ^a) having a relatively large weight average molecular weight (Mw ^(Ar2 a)) is 22,000 to 400,000, preferably from 25000 to 370000, 30,000 to More preferably, it is 350,000. If Mw (Ar2 ^a ) is too small, the resulting pressure-sensitive adhesive for surface protective material tends to have a strong adhesive force, and may become adhesive residue at the time of peeling, and Mw (Ar2 ^a ) is too large. The block copolymer A may be difficult to produce.

  In the present invention, the weight average molecular weight of the polymer or polymer block is determined as a value in terms of polystyrene as measured by high performance liquid chromatography.

In the block copolymer A, the weight average molecular weight (Mw (Ar2 ^a )) of the aromatic vinyl polymer block (Ar2 ^a ) having a relatively large weight average molecular weight and the aromatic vinyl weight having a relatively small weight average molecular weight. the ratio of the weight average molecular weight of polymer block ^{(Ar1 a) (Mw (Ar1} a)) (Mw (Ar2 a) / Mw (Ar1 a)) is not particularly limited but is usually from 1.5 to 67, 2 It is preferable that it is -40, and it is more preferable that it is 3-35. By constituting the block copolymer A in this way, the obtained pressure-sensitive adhesive for surface protective material has excellent adhesiveness and developability.

The vinyl bond content of the conjugated diene polymer block (D ^a ) of the block copolymer A (the ratio of 1,2-vinyl bonds and 3,4-vinyl bonds in all conjugated diene monomer units) is 1 It is -20 mol%, it is preferable that it is 2-15 mol%, and it is more preferable that it is 3-10 mol%. If the vinyl bond content is too high, the resulting adhesive for a surface protective material may have insufficient tackiness.

The weight average molecular weight (Mw (D ^a )) of the conjugated diene polymer block (D ^a ) of the block copolymer A is not particularly limited, but is usually 20000 to 200000, preferably 30000 to 150,000, preferably 35000. More preferably, it is ˜120,000.

  The content of the aromatic vinyl monomer unit relative to all the monomer units of the block copolymer A is not particularly limited, but is preferably 35% by weight or more, more preferably 41% by weight or more, More preferably, it is 45-87 weight%, Most preferably, it is 50-85 weight%. By making the content of the aromatic vinyl monomer unit relative to all the monomer units of the block copolymer A within this range, the resulting pressure-sensitive adhesive for surface protective materials is particularly well-suppressed. In addition, it is difficult for adhesive residue to remain during peeling.

  Although the weight average molecular weight as the whole block copolymer A is not specifically limited, Usually, it is 70000-500000, It is preferable that it is 80000-470000, and it is more preferable that it is 90000-450,000.

The block copolymer B constituting the block copolymer composition used in the present invention is an aromatic vinyl polymer block (Ar ^b ) having a specific weight average molecular weight, as represented by the above formula (B). Two or more diblock bodies (Ar ^b -D ^b ) formed by binding to a conjugated diene polymer block (D ^b ) having a specific vinyl bond content are directly single bonds or residues of a coupling agent It is a block copolymer constituted by bonding via. The weight average molecular weight (Mw (Ar ^b )) of the aromatic vinyl polymer block (Ar ^b ) constituting the block copolymer B is 6000 to 20000, preferably 7000 to 18000, preferably 8000 to 16000. More preferably. If Mw (Ar ^b ) is too small, the resulting surface-protective pressure-sensitive adhesive may be liable to remain, and if it is too large, the surface-protective pressure-sensitive adhesive may be insufficiently tacky. is there. The weight average molecular weights (Mw (Ar ^b )) of the aromatic vinyl polymer blocks that the block copolymer B has may be equal or different from each other as long as they are within the above range. Good, but preferably substantially equal. Moreover, the weight average molecular weight (Mw (Ar ^b )) of these aromatic vinyl polymer blocks is the weight average of the aromatic vinyl polymer block (Ar 1 ^a ) having a relatively small weight average molecular weight of the block copolymer A. molecular weight (Mw ^(Ar1 a)), and more preferably substantially equal.

The vinyl bond content of the conjugated diene polymer block (D ^b ) of the block copolymer B is 1 to 20 mol%, preferably 2 to 15 mol%, and preferably 3 to 10 mol%. More preferred. If the vinyl bond content is too high, the resulting pressure-sensitive adhesive for surface protective material may be insufficient in tackiness. The vinyl bond content of the conjugated diene polymer block (D ^b ) of the block copolymer B is substantially equal to the vinyl bond content of the conjugated diene polymer block (D ^a ) of the block copolymer A. Is preferred.

The block copolymer B, aromatic vinyl polymer block (Ar ^b) a conjugated diene polymer block ^{(D b)} and formed by bonding diblock body ^{(Ar b} -D b) is a direct single bond, Alternatively, they are bonded via a residue of a coupling agent. In addition, what is mentioned later is mentioned as an example of the coupling agent which comprises the residue of a coupling agent. The number of diblock bodies (Ar ^b -D ^b ) to be bonded (that is, n in formula (B)) is not particularly limited as long as it is 2 or more. May be mixed. Although n in Formula (B) will not be specifically limited if it is an integer greater than or equal to 2, Usually, it is an integer of 2-8, Preferably it is an integer of 2-4.

The weight average molecular weight (Mw (D ^b )) of the conjugated diene polymer block (D ^b ) of the block copolymer B is not particularly limited, but is usually 20000 to 200000, preferably 30000 to 150,000, preferably 35000. More preferably, it is ˜120,000. The weight average molecular weight (Mw (D ^b )) of the conjugated diene polymer block (D ^b ) of the block copolymer B is the weight average molecular weight of the conjugated diene polymer block (D ^a ) of the block copolymer A ( Mw (D ^a )) is preferably substantially equal. In addition, when using the aromatic vinyl-conjugated diene-aromatic vinyl block copolymer manufactured without using a coupling agent as the block copolymer B, the conjugated diene polymer block contained in it is all single quantities. The body unit is directly bonded, and cannot be said to be actually composed of two conjugated diene polymer blocks (D ^b ). However, in the present invention, even such a conjugated diene polymer block is conceptually one in which two conjugated diene polymer blocks (D ^b ) having substantially the same weight average molecular weight are bonded by a single bond. As such, it shall be handled. Therefore, for example, in the block copolymer B which is an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer produced without using a coupling agent, the weight average molecular weight of the conjugated diene polymer block as a whole is 100,000. , The Mw (D ^b ) shall be handled as being 50000.

  The content of the aromatic vinyl monomer unit with respect to all the monomer units of the block copolymer B is not particularly limited, but is usually 10 to 35% by weight, preferably 12 to 32% by weight, More preferably, it is -30 wt%. Moreover, the weight average molecular weight as the whole block copolymer B is not specifically limited, However, Usually, it is 50000-400000, It is preferable 60000-350,000, It is more preferable that it is 70000-300000.

  Ratio of weight average molecular weight (Mw) and number average molecular weight (Mn) of each polymer block constituting block copolymer A and block copolymer B constituting the block copolymer composition used in the present invention (Mw) The molecular weight distribution represented by / Mn) is not particularly limited, but is usually 1.1 or less, preferably 1.05 or less.

  The weight ratio (A / B) of the block copolymer A and the block copolymer B contained in the block copolymer composition used in the present invention is 10/90 to 90/10, and 25/75 to 85/15 is preferable, and 36/64 to 80/20 is more preferable. When each block copolymer is contained at such a ratio, the obtained pressure-sensitive adhesive for surface protective material is excellent in adhesiveness and developability. On the other hand, if this ratio is too small, the adhesive force is likely to increase, and there is a possibility that the adhesive remains easily at the time of peeling. If this ratio is too large, the adhesiveness may be insufficient.

  The block copolymer composition used in the present invention may contain only the block copolymer A and the block copolymer B as polymer components, but other than the block copolymer A and the block copolymer B. It may contain a polymer component. Examples of the polymer component other than the block copolymer A and the block copolymer B that can be included in the block copolymer composition used in the present invention include aromatic vinyl other than the block copolymer A and the block copolymer B. Conjugated diene-aromatic vinyl block copolymer, aromatic vinyl-conjugated diene block copolymer, aromatic vinyl homopolymer, conjugated diene homopolymer, aromatic vinyl-conjugated diene random copolymer, and branches thereof Type polymers, thermoplastic elastomers such as polyurethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyethylene, polypropylene, polyvinyl chloride, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers Coalescence, polyphenylene ether And thermoplastic resins such as Le, and the like. However, the tackifier resin to be described later is distinguished from the polymer component constituting the block copolymer composition. In the block copolymer composition used in the present invention, the content of the polymer component other than the block copolymer A and the block copolymer B is preferably 20% by weight or less based on the entire polymer component. More preferably, it is 10% by weight or less.

  In the block copolymer composition used in the present invention, the ratio of the aromatic vinyl monomer unit to the total monomer units constituting the polymer component in the block copolymer composition (in the following description, the whole It is possible to adjust the balance between the adhesiveness and developability of the resulting surface-protective pressure-sensitive adhesive. The total aromatic vinyl monomer unit content is not particularly limited, but is preferably 13 to 85% by weight, more preferably 18 to 70% by weight, and 20 to 60% by weight. % Is more preferable. If the total aromatic vinyl monomer unit content is too small, the resulting surface-protective material pressure-sensitive adhesive is likely to have an increased adhesive force, and the adhesive residue may easily remain during peeling. If the aromatic vinyl monomer unit content is too large, the resulting pressure-sensitive adhesive for surface protective material may be insufficient in tackiness. The total aromatic vinyl monomer unit content is determined by the block copolymer A, the block copolymer B and the other polymer components constituting the block copolymer composition, and the respective aromatic vinyl monomers. It can be easily adjusted by taking into account the content of the units and adjusting their blending amount. In the case where all the polymer components constituting the block copolymer composition are composed only of aromatic vinyl monomer units and conjugated diene monomer units, Rubber Chem. Technol. , 45, 1295 (1972), ozonolysis of the polymer component of the block copolymer composition, followed by reduction with lithium aluminum hydride, decomposes the conjugated diene monomer unit portion, Since only the aromatic vinyl monomer unit portion can be taken out, the entire aromatic vinyl monomer unit content can be easily measured.

  Although the weight average molecular weight of the whole polymer component which comprises the block copolymer composition used by this invention is not specifically limited, Usually, it is 50000-500000, It is preferable 60000-450,000, It is 70000-400000 Is more preferable. Further, the molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the entire polymer components constituting the block copolymer composition used in the present invention is particularly limited. Although it is not carried out, it is 1.01-10 normally, it is preferable that it is 1.03-5, and it is more preferable that it is 1.05-3.

  Further, the melt index of the block copolymer composition used in the present invention is not particularly limited, but is usually 1 to 70 g / in as a value measured in accordance with ASTM D-1238 (G condition, 200 ° C., 5 kg). 10 minutes, preferably 2 to 65 g / 10 minutes, and more preferably 3 to 60 g / 10 minutes.

  The method for obtaining the block copolymer composition used in the present invention is not particularly limited. For example, according to the conventional block copolymer production method, block copolymer A and block copolymer B are produced separately, and if necessary, after blending other polymer components and the like, It can manufacture by mixing according to conventional methods, such as kneading | mixing and solution mixing. However, from the viewpoint of obtaining a block copolymer composition having a particularly desirable configuration with higher productivity, the following production method is preferred.

  That is, the block copolymer composition used in the present invention is preferably produced using a production method comprising the following steps (1) to (5).

(1): Step of polymerizing an aromatic vinyl monomer using a polymerization initiator in a solvent (2): A solution containing an aromatic vinyl polymer having an active terminal obtained in the step (1) above Step (3) of adding a conjugated diene monomer to the solution containing an aromatic vinyl-conjugated diene block copolymer having an active end obtained in the step (2) above with respect to the active end Step (4) of adding a coupling agent to form a block copolymer B in such an amount that the functional group is less than 1 molar equivalent: The aromatic vinyl monomer is added to the solution obtained in the step (3). Step 5 for forming block copolymer A: step for recovering the block copolymer composition from the solution obtained in step (4) above

  In the above method for producing a block copolymer composition, first, an aromatic vinyl monomer is polymerized using a polymerization initiator in a solvent. The polymerization initiator used is generally an organic alkali metal compound, an organic alkaline earth metal compound known to have anionic polymerization activity for an aromatic vinyl monomer and a conjugated diene monomer, Organic lanthanoid series rare earth metal compounds and the like can be used. As the organic alkali metal compound, an organic lithium compound having one or more lithium atoms in the molecule is particularly preferably used. Specific examples thereof include ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, Organic monolithium compounds such as sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, stilbenelithium, dialkylaminolithium, diphenylaminolithium, ditrimethylsilylaminolithium, methylenedilithium, tetramethylenedilithium, hexamethylene Organic dilithium compounds such as dilithium, isoprenyl dilithium and 1,4-dilithio-ethylcyclohexane, and further organic trilithium compounds such as 1,3,5-trilithiobenzene It is. Among these, an organic monolithium compound is particularly preferably used.

  Examples of the organic alkaline earth metal compound used as a polymerization initiator include n-butyl magnesium bromide, n-hexyl magnesium bromide, ethoxy calcium, calcium stearate, t-butoxystrontium, ethoxy barium, isopropoxy barium, ethyl mercapto barium, Examples thereof include t-butoxybarium, phenoxybarium, diethylaminobarium, barium stearate, and ethylbarium. Specific examples of other polymerization initiators include lanthanoid series rare earth metal compounds containing neodymium, samarium, gadolinium, etc./alkylaluminum/alkylaluminum halides / alkylaluminum hydrides, titanium, vanadium, samarium, gadolinium. Examples thereof include those having a uniform system in an organic solvent such as a metallocene-type catalyst containing a living polymer and the like and having living polymerizability. In addition, these polymerization initiators may be used individually by 1 type, and may mix and use 2 or more types.

  The amount of the polymerization initiator used may be determined according to the molecular weight of each target block copolymer, and is not particularly limited, but is usually 0.01 to 20 mmol, preferably 100 g per 100 g of all monomers used. Is from 0.05 to 15 mmol, more preferably from 0.1 to 10 mmol.

  The solvent used for the polymerization is not particularly limited as long as it is inert to the polymerization initiator. For example, a chain hydrocarbon solvent, a cyclic hydrocarbon solvent, or a mixed solvent thereof is used. Chain hydrocarbon solvents include n-butane, isobutane, 1-butene, isobutylene, trans-2-butene, cis-2-butene, 1-pentene, trans-2-pentene, cis-2-pentene and n-pentane C 4-6 linear alkanes and alkenes such as, isopentane, neo-pentane, n-hexane and the like can be exemplified. Specific examples of the cyclic hydrocarbon solvent include aromatic compounds such as benzene, toluene and xylene; alicyclic hydrocarbon compounds such as cyclopentane and cyclohexane. These solvents may be used alone or in combination of two or more.

  The amount of the solvent used for the polymerization is not particularly limited, but the concentration of the entire block copolymer in the solution after the polymerization reaction is usually 5 to 60% by weight, preferably 10 to 55% by weight, more preferably 20 to 50%. Set the weight%.

  In obtaining a block copolymer composition, a Lewis base compound may be added to a reactor used for polymerization in order to control the structure of each polymer block of each block copolymer. Examples of the Lewis base compound include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether and diethylene glycol dibutyl ether; tetramethylethylenediamine, trimethylamine, triethylamine, pyridine, quinuclidine and the like. Tertiary amines; alkali metal alkoxides such as potassium-t-amyl oxide and potassium-t-butyl oxide; phosphines such as triphenylphosphine; and the like. These Lewis base compounds are used alone or in combination of two or more, and are appropriately selected within a range not impairing the object of the present invention.

  Further, the timing of adding the Lewis base compound during the polymerization reaction is not particularly limited, and may be appropriately determined according to the structure of each target block copolymer. For example, it may be added in advance before the polymerization is started, or may be added after polymerizing a part of the polymer block. You may add further, after superposing | polymerizing a polymer block.

  The polymerization reaction temperature is usually 10 to 150 ° C, preferably 30 to 130 ° C, more preferably 40 to 90 ° C. The time required for the polymerization varies depending on the conditions, but is usually within 48 hours, preferably 0.5 to 10 hours. The polymerization pressure is not particularly limited as long as it is carried out within a range of pressure sufficient to maintain the monomer and solvent in the liquid phase within the above polymerization temperature range.

Under the conditions as described above, a solution containing an aromatic vinyl polymer having an active terminal can be obtained by polymerizing an aromatic vinyl monomer using a polymerization initiator in a solvent. The aromatic vinyl polymer having an active end is composed of an aromatic vinyl polymer block (Ar1 ^a ) having a relatively small weight average molecular weight of the block copolymer A and a block copolymer. The aromatic vinyl polymer block (Ar ^b ) of the combined B will be constituted. Therefore, the amount of the aromatic vinyl monomer used at this time is determined according to the target weight average molecular weight of these polymer blocks.

The next step is a step of adding a conjugated diene monomer to a solution containing an aromatic vinyl polymer having an active end obtained as described above. By adding this conjugated diene monomer, a conjugated diene polymer chain is formed from the active end, and a solution containing an aromatic vinyl-conjugated diene block copolymer (diblock) having an active end is obtained. The amount of the conjugated diene monomer used here is determined so that the resulting conjugated diene polymer chain has the weight average molecular weight of the conjugated diene polymer block (D ^b ) of the target block copolymer B. .

  In the next step, in the solution containing the aromatic vinyl-conjugated diene block copolymer having an active terminal (diblock) obtained as described above, the functional group is less than 1 molar equivalent with respect to the active terminal. Add the coupling agent in such an amount.

  The coupling agent to be added is not particularly limited, and any bifunctional or higher functional coupling agent can be used. Examples of the bifunctional coupling agent include bifunctional halogenated silanes such as dichlorosilane, monomethyldichlorosilane, and dimethyldichlorosilane; bifunctional alkoxysilanes such as diphenyldimethoxysilane and diphenyldiethoxysilane; dichloroethane and dibromoethane. Difunctional tin halides such as dichlorotin, monomethyldichlorotin, dimethyldichlorotin, monoethyldichlorotin, diethyldichlorotin, monobutyldichlorotin, dibutyldichlorotin, etc. Dibromobenzene, benzoic acid, carbon monoxide, 2-chloropropene and the like. Examples of the trifunctional coupling agent include trifunctional halogenated alkanes such as trichloroethane and trichloropropane; trifunctional halogenated silanes such as methyltrichlorosilane and ethyltrichlorosilane; methyltrimethoxysilane, phenyltrimethoxysilane, And trifunctional alkoxysilanes such as phenyltriethoxysilane; Examples of the tetrafunctional coupling agent include tetrafunctional halogenated alkanes such as carbon tetrachloride, carbon tetrabromide, and tetrachloroethane; tetrafunctional halogenated silanes such as tetrachlorosilane and tetrabromosilane; tetramethoxysilane, Tetrafunctional alkoxysilanes such as tetraethoxysilane; tetrafunctional tin halides such as tetrachlorotin and tetrabromotin; and the like. Examples of the pentafunctional or higher functional coupling agent include 1,1,1,2,2-pentachloroethane, perchloroethane, pentachlorobenzene, perchlorobenzene, octabromodiphenyl ether, decabromodiphenyl ether, and the like. These coupling agents may be used alone or in combination of two or more.

  The amount of the coupling agent added is determined according to the ratio of the block copolymer A and the block copolymer B constituting the block copolymer composition, and is a coupling agent with respect to the active terminal of the polymer. Is not particularly limited as long as the amount of the functional group is less than 1 molar equivalent, but is usually in the range where the functional group of the coupling agent is 0.10 to 0.90 molar equivalent with respect to the active terminal of the polymer. , 0.15 to 0.70 molar equivalent is preferable.

  As described above, in a solution containing an aromatic vinyl-conjugated diene block copolymer having an active end (diblock body), a functional group (a functional group capable of reacting with the active end of the polymer) with respect to the active end ) Is less than 1 molar equivalent, and when a coupling agent is added, in some of the aromatic vinyl-conjugated diene block copolymers (diblock bodies) having active ends, The polymer blocks are bonded to each other through a residue of the coupling agent, and as a result, a block copolymer B of the block copolymer composition is formed. And the remaining part of the aromatic vinyl-conjugated diene block copolymer (diblock body) which has an active terminal will remain in a solution with unreacted.

In the next step, an aromatic vinyl monomer is added to the solution obtained as described above. When an aromatic vinyl monomer is added to the solution, the aromatic vinyl polymer from the end of the aromatic vinyl-conjugated diene block copolymer (diblock body) having an active terminal remaining without reacting with the coupling agent. A chain is formed. This aromatic vinyl polymer chain constitutes an aromatic vinyl polymer block (Ar2 ^a ) having a relatively large weight average molecular weight of the block copolymer A constituting the block copolymer composition. It is. Therefore, the amount of the aromatic vinyl monomer used at this time is determined in accordance with the target weight average molecular weight of the aromatic vinyl polymer block (Ar2 ^a ). By the step of adding the aromatic vinyl monomer, an asymmetric aromatic vinyl-conjugated diene-aromatic vinyl block copolymer constituting the block copolymer A is formed. As a result, the block copolymer is formed. A solution containing the polymer A and the block copolymer B is obtained. In addition, before the step of adding the aromatic vinyl monomer, a solution containing an aromatic vinyl-conjugated diene block copolymer (diblock body) having an active terminal that has not reacted with the coupling agent is conjugated. A diene monomer may be added. When the conjugated diene monomer is added in this way, the weight average molecular weight of the conjugated diene polymer block (D ^a ) of the block copolymer A can be increased as compared with the case where the conjugated diene monomer is not added. In addition, a polymerization terminator (water, methanol, etc.) is added to the solution containing the aromatic vinyl-conjugated diene block copolymer having an active end that has not reacted with the coupling agent in an amount less than the equivalent of the active end. Also good. When the polymerization terminator is added in this manner, the active terminal of the aromatic vinyl-conjugated diene block copolymer (diblock body) is deactivated, and the resulting aromatic vinyl-conjugated diene block copolymer (diblock) is obtained. Body) will be contained in the block copolymer composition.

  In the next step, the target block copolymer composition is recovered from the solution containing the block copolymer A and the block copolymer B obtained as described above. The recovery method may be any conventional method and is not particularly limited. For example, after completion of the reaction, if necessary, a polymerization terminator such as water, methanol, ethanol, propanol, hydrochloric acid, citric acid is added, and if necessary, an additive such as an antioxidant is added. The solution can be recovered by directly applying a known method such as a drying method or steam stripping to the solution. When the block copolymer composition is recovered as a slurry by applying steam stripping or the like, it is dewatered using an arbitrary dehydrator such as an extruder-type squeezer, and a crumb having a moisture content of a predetermined value or less. In addition, the crumb may be dried using any dryer such as a band dryer or an expansion extrusion dryer. The block copolymer composition obtained as described above may be processed into a pellet shape or the like according to a conventional method, and then used for production of a pressure-sensitive adhesive for a surface protective material.

  According to the above production method, since the block copolymer A and the block copolymer B can be obtained continuously in the same reaction vessel, when each block copolymer is produced and mixed individually, In comparison, the target block copolymer composition can be obtained with extremely excellent productivity. Moreover, the resulting block copolymer composition has a particularly desirable balance for obtaining the pressure-sensitive adhesive for the surface protective material of the present invention, in which the weight average molecular weight of each polymer block of each block copolymer is obtained. In particular, it is possible to obtain a pressure-sensitive adhesive for a surface protective material having excellent adhesiveness.

  The pressure-sensitive adhesive for surface protective material of the present invention comprises a tackifying resin in addition to the above block copolymer composition. The pressure-sensitive adhesive for a surface protective material of the present invention exhibits excellent tackiness by containing a tackifier resin. The kind of tackifying resin contained in the pressure-sensitive adhesive for a surface protective material of the present invention is not particularly limited. For example, rosin; modified rosins such as disproportionated rosin and dimerized rosin; glycol, glycerin, pentaerythritol, etc. Esterified product of polyhydric alcohol and rosin or modified rosin; terpene resin; aliphatic, aromatic, alicyclic or aliphatic-aromatic copolymer hydrocarbon resin or hydride thereof; Phenol resins; coumarone-indene resins and the like can be used as tackifying resins. Among them, aliphatic, aromatic, alicyclic or aliphatic-aromatic copolymer hydrocarbon resins or these Hydrides are preferably used. In addition, a tackifier resin may be used individually by 1 type, and may be used in combination of 2 or more type.

  The softening point of the tackifying resin contained in the pressure-sensitive adhesive for surface protective material of the present invention is not particularly limited, but is preferably 10 to 160 ° C, and more preferably 20 to 150 ° C. By using a tackifier resin having a softening point in this range, the resulting pressure-sensitive adhesive for surface protective material is particularly excellent in tackiness.

  The content of the tackifier resin in the pressure-sensitive adhesive for surface protective material of the present invention is not particularly limited, but is preferably 1 to 100 parts by weight with respect to 100 parts by weight of the block copolymer composition, and is preferably 5 to 90 parts. More preferably, it is 10 parts by weight, and still more preferably 10 parts by weight. When the content of the tackifying resin is in this range, the resulting pressure-sensitive adhesive for a surface protecting material is particularly well-suppressed in the adhesive force, and it is difficult for adhesive residue to remain during peeling.

  An antioxidant may be added to the surface protective material pressure-sensitive adhesive of the present invention as necessary. The kind is not specifically limited, For example, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,6-di-t-butyl-p-cresol, di Hindered phenolic compounds such as t-butyl-4-methylphenol; thiodicarboxylate esters such as dilauryl thiopropionate; phosphites such as tris (nonylphenyl) phosphite; it can. Although the usage-amount of antioxidant is not specifically limited, It is 10 weight part or less normally with respect to 100 weight part of block copolymer compositions, Preferably it is 0.5-5 weight part. In addition, an antioxidant may be used individually by 1 type and may be used in combination of 2 or more type. Further, the timing of adding the antioxidant to the surface protective material pressure-sensitive adhesive is not particularly limited. For example, it may be added in advance to the block copolymer composition used to constitute the surface protective material pressure-sensitive adhesive. It may be added when the block copolymer composition and the tackifying resin are mixed.

  Other additives such as a softening agent, a heat stabilizer, an ultraviolet absorber, and a filler can be further added to the pressure-sensitive adhesive for a surface protective material of the present invention.

  In obtaining the pressure-sensitive adhesive for a surface protective material of the present invention, the method of mixing the block copolymer composition with the tackifier resin and various additives is not particularly limited. For example, each component is dissolved in a solvent and mixed uniformly. Then, a method of removing the solvent by heating or the like, and a method of heating and mixing the respective components with a kneader can be exemplified.

  Although the glass transition temperature of the adhesive for surface protection materials of this invention is not specifically limited, It is preferable that it is -50-30 degreeC, and it is more preferable that it is -40-25 degreeC. When the glass transition temperature is within this range, the balance between the tackiness and the spreadability of the pressure-sensitive adhesive for surface protective materials is particularly good. In addition, the glass transition temperature of the adhesive for surface protective materials can be easily adjusted according to a conventional method, and can be adjusted by adjusting the content of the tackifying resin, for example.

  The pressure-sensitive adhesive for a surface protective material of the present invention is used for forming pressure-sensitive adhesive layers of various surface protective materials such as a surface protective film, a surface protective sheet, and a surface protective tape. By forming the pressure-sensitive adhesive layer with the pressure-sensitive adhesive for surface protecting material of the present invention, it has excellent pressure-sensitive adhesiveness and developability, and further, the progress of the pressure-sensitive adhesive force is suppressed well, and the paste is peeled off when it is peeled from the object to be protected. It is possible to obtain a surface protective material that does not easily remain. The base material and use of the surface protective material in which the pressure-sensitive adhesive for surface protective material of the present invention is used are not particularly limited, and can be applied to various base materials and uses. In addition, the aspect and use of the surface protective material in which the pressure-sensitive adhesive for surface protective material of the present invention is suitably used will be described in detail below as an explanation of the surface protective material of the present invention.

  The surface protective material of the present invention is a surface protective material in which an adhesive layer made of the pressure-sensitive adhesive for surface protective material of the present invention and a base material layer made of resin are laminated. The material constituting the base material layer of the surface protective material of the present invention is not particularly limited as long as it is a resin. However, from the viewpoint of ease of molding, a thermoplastic resin is preferable, and an olefin resin is particularly preferable. It is. The olefin resin used as the material of the base material layer is not particularly limited. For example, polyethylene (low density, medium density, high density), polypropylene, polymethylpentene, polybutene, ethylene-propylene copolymer, propylene-butene copolymer. A polymer can be used. In addition, resin which comprises a base material layer may be used individually by 1 type, and 2 or more types may be mixed and used for it. In addition, additives such as an antioxidant, a colorant, a foaming agent, a flame retardant, a lubricant, an ultraviolet absorber, a light stabilizer, and a filler are added to the resin constituting the base layer as necessary. can do.

  Although the thickness of the adhesion layer in the surface protection material of this invention is not specifically limited, Usually, it is the range of 1-50 micrometers, Preferably it is the range of 2-30 micrometers. The thickness of the base material layer is not particularly limited, but is usually in the range of 10 to 50 μm, preferably in the range of 15 to 45 μm.

  The surface protective material of the present invention may be a laminate composed of only two layers of the above-mentioned pressure-sensitive adhesive layer and base material layer, or may be further disposed between these two layers or at any position such as one of the surfaces. It may be a laminate of three or more layers having other layers. Each layer may be subjected to a surface treatment such as a corona discharge treatment, an ultraviolet irradiation treatment, or a plasma treatment as necessary.

  Although the thickness in the whole surface protection material of this invention is not specifically limited, Usually, it is the range of 11-100 micrometers, Preferably it is the range of 12-75 micrometers. Moreover, the surface protection material of this invention can be used as surface protection materials of arbitrary forms, such as a surface protection film, a surface protection sheet, and a surface protection tape.

  The method for producing the surface protective material of the present invention is not particularly limited, and a conventionally known method for producing a surface protective material can be applied. As a production method suitably used, there can be mentioned a method of forming a laminate by co-extrusion of materials of each layer such as the pressure-sensitive adhesive for surface protective material of the present invention and a resin constituting the base material layer. .

  The surface protective material of the present invention can be stored in an arbitrary form after production. For example, it can be wound into a so-called roll body. Since the surface protective material of the present invention uses the pressure-sensitive adhesive for surface protective material of the present invention that is excellent in developability, the surface protective material can be easily developed and used from a roll body.

  The surface protective material of the present invention is a protective layer for the purpose of protecting the surface of various articles from the damage caused by adhesion of dirt and dust and contact with other objects during storage and transportation. It is used by being affixed to an article so as to be in contact with the surface of the article. Specific examples of articles to be protected include, but are not limited to, metal plates, synthetic resin plates, wood decorative plates, displays, optical films, and building materials.

  Since the surface protective material of the present invention uses the pressure-sensitive adhesive for surface protective material of the present invention that is excellent in adhesiveness, unintended peeling is unlikely to occur when it is attached to an article. Further, since the surface protective material of the present invention uses the pressure-sensitive adhesive for surface protective material of the present invention in which the progress of the adhesive force is satisfactorily suppressed, the surface protective material is peeled off from the product even after being attached to the product for a long time. It is easy to do, and it is hard to produce adhesive residue at the time of peeling.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, unless otherwise indicated, the part and% in each example are a basis of weight.

  Various measurements were performed according to the following methods.

[Weight average molecular weight of block copolymer and block copolymer composition]
Molecular weight in terms of polystyrene was determined by high performance liquid chromatography using tetrahydrofuran as a carrier at a flow rate of 0.35 ml / min. The apparatus is an HLC8220 manufactured by Tosoh Corporation, the column is a combination of three Shodex KF-404HQ manufactured by Showa Denko (column temperature 40 ° C.), the detector is a differential refractometer and an ultraviolet detector, and the molecular weight is calibrated by a polymer laboratory. The test was carried out using 12 standard polystyrenes (500 to 3 million).

[Weight ratio of each block copolymer in the block copolymer]
It calculated | required from the area ratio of the peak corresponding to each block copolymer of the chart obtained by said high performance liquid chromatography.

[Weight average molecular weight of styrene polymer block]
Rubber Chem. Technol. 45, 1295 (1972), the block copolymer was reacted with ozone and reduced with lithium aluminum hydride to decompose the isoprene polymer block of the block copolymer. Specifically, the procedure was as follows. That is, 300 mg of the sample was dissolved in a reaction vessel containing 100 ml of dichloromethane treated with molecular sieves. After putting this reaction container into a cooling tank and making it -25 degreeC, the ozone generated with the ozone generator was introduce | transduced, supplying oxygen at the flow volume of 170 ml / min to the reaction container. After 30 minutes from the start of the reaction, it was confirmed that the reaction was completed by introducing a gas flowing out of the reaction vessel into the potassium iodide aqueous solution. Next, 50 ml of diethyl ether and 470 mg of lithium aluminum hydride were charged into another reaction vessel purged with nitrogen, and the solution reacted with ozone was slowly added dropwise to the reaction vessel while cooling the reaction vessel with ice water. Then, the reaction vessel was placed in a water bath, gradually heated, and refluxed at 40 ° C. for 30 minutes. Thereafter, dilute hydrochloric acid was added dropwise to the reaction vessel little by little while stirring the solution, and the addition was continued until almost no generation of hydrogen was observed. After this reaction, the solid product formed in the solution was filtered off, and the solid product was extracted with 100 ml of diethyl ether for 10 minutes. The extract and the filtrate obtained by filtration were combined and the solvent was distilled off to obtain a solid sample. For the sample thus obtained, the weight average molecular weight was measured according to the above-described method for measuring the weight average molecular weight, and the value was taken as the weight average molecular weight of the styrene polymer block.

[Weight average molecular weight of isoprene polymer block]
Subtract the weight average molecular weight of the corresponding styrene polymer block from the weight average molecular weight of the block copolymer obtained as described above, and obtain the weight average molecular weight of the isoprene polymer block based on the calculated value. It was.

[Styrene unit content of block copolymer]
It calculated | required based on the detection intensity ratio of a differential refractometer and an ultraviolet detector in the measurement of said high performance liquid chromatography. In addition, the copolymer which has different styrene unit content was prepared previously, and the analytical curve was created using them.

[Styrene unit content of block copolymer composition]
It calculated | required based on the measurement of proton NMR.

[Vinyl bond content of isoprene polymer block]
It calculated | required based on the measurement of proton NMR.

[Melt index of block copolymer composition]
The measurement was made according to ASTM D-1238 (G condition, 200 ° C., 5 kg).

[Softening point of tackifying resin]
According to JIS K2531, it measured by the ring and ball method.

[Glass transition temperature of adhesive]
A dynamic viscoelasticity measuring device “ARES-II” manufactured by TA Instruments is used as a measuring device, and a pressure sensitive adhesive serving as a 2 mm thick sample is placed on a parallel plate having a diameter of 8 mm to perform dynamic viscoelasticity measurement. went. The measurement conditions were a frequency of 1 Hz and a temperature increase rate of 4 ° C./minute, from −80 ° C. to 150 ° C., and the temperature at the peak top of the obtained low temperature Tangent δ was taken as the glass transition temperature of the adhesive.

[Initial peeling force (low speed peeling)]
The surface protective material was bonded to a polypropylene plate by pressure bonding at a speed of 300 mm / min using a 2 kg rubber roller under the condition of 23 ° C., and a sample to be measured after 30 minutes was pasted. For this measurement sample, the peel adhesive strength (N / m) at 23 ° C. was measured according to PSTC-1 (180 ° peel adhesive test by the US adhesive tape committee), and “PA-1000” manufactured by Chem Instruments as a measuring instrument. The peel force was evaluated by measuring the peel speed at 0.3 m / min using -180 ". The larger this value, the better the adhesiveness.

[Initial peeling force (high speed peeling)]
The surface protective material was bonded to a polypropylene plate by pressure bonding at a speed of 300 mm / min using a 2 kg rubber roller under the condition of 23 ° C., and a sample to be measured after 30 minutes was pasted. With respect to this measurement sample, the peel adhesive strength (N / m) at 23 ° C. is measured according to PSTC-1 (180 ° peel adhesive test by the US adhesive tape committee) as a measuring device. Using a tester “TE-701-S”, the peeling force was evaluated by measuring the peeling speed at 15 m / min. The smaller this value, the better the developability.

[Aging force over time]
The surface protective material was bonded to a polypropylene plate by pressure bonding at a speed of 300 mm / min using a 2 kg rubber roller under the condition of 23 ° C., and then left to stand in a gear oven at 60 ° C. for 7 days. Then, it was allowed to cool and used as a measurement sample. For this measurement sample, the peel adhesive strength (N / m) at 23 ° C. was measured according to PSTC-1 (180 ° peel adhesive test by the US adhesive tape committee), and “PA-1000” manufactured by Chem Instruments as a measuring instrument. The peel force was evaluated by measuring the peel speed at 0.3 m / min using -180 ". It can be said that the smaller the difference between this value and the value of the initial peel force (low speed peel), the better the progress of the adhesive force is suppressed.

[Glue residue at the time of peeling]
The polypropylene after evaluating the initial peeling force (high-speed peeling) was visually observed, and the adhesive residue that was visually recognized was evaluated as “remaining” and the adhesive residue that was not visually recognized was evaluated as “no adhesive residue”.

[Reference Example 1]
To the pressure-resistant reactor, 23.3 kg of cyclohexane, 2.6 mmol of N, N, N ′, N′-tetramethylethylenediamine (hereinafter referred to as TMEDA) and 1.43 kg of styrene were added and stirred at 40 ° C. Thereto, 176.2 mmol of n-butyllithium was added, and polymerization was performed for 1 hour while raising the temperature to 50 ° C. The polymerization conversion of styrene was 100% by weight. Subsequently, 6.50 kg of isoprene was continuously added to the reactor over 1 hour while controlling the temperature so as to maintain 50 to 60 ° C. After completing the addition of isoprene, polymerization was continued for an additional hour. The polymerization conversion rate of isoprene was 100%. Next, 61.7 mmol of dimethyldichlorosilane was added as a coupling agent, and a coupling reaction was performed for 2 hours to form a styrene-isoprene-styrene triblock copolymer to be a block copolymer B. Thereafter, 2.07 kg of styrene was continuously added over 1 hour while controlling the temperature so as to maintain 50 to 60 ° C. After completion of the addition of styrene, polymerization was further performed for 1 hour to form a styrene-isoprene-styrene triblock copolymer to be a block copolymer A. The polymerization conversion of styrene was 100%. Thereafter, 352.4 mmol of methanol was added as a polymerization terminator and mixed well to stop the reaction. The amount of each reagent used in the reaction is summarized in Table 1. A part of the obtained reaction solution is taken out, the weight average molecular weight of each block copolymer and block copolymer composition, the weight ratio of each block copolymer in the block copolymer, the weight of each styrene polymer block The average molecular weight, the weight average molecular weight of each isoprene polymer block, the styrene unit content of each block copolymer, the styrene unit content of the block copolymer composition, and the vinyl bond content of the isoprene polymer block were determined. These values are shown in Table 2. To 100 parts of the reaction solution (containing 30 parts of the polymer component) thus obtained, 0.3 part of 2,6-di-tert-butyl-p-cresol was added as an antioxidant and mixed. The mixed solution was added dropwise to warm water heated to 85 to 95 ° C. little by little to volatilize the solvent to obtain a precipitate. The precipitate was pulverized and dried with hot air at 85 ° C. The block copolymer composition was recovered. The melt index was measured about the obtained block copolymer composition. The measured values are shown in Table 2.

[Reference Examples 2 and 3]
The blocks of Reference Example 2 and Reference Example 3 were the same as Reference Example 1 except that the amounts of styrene, n-butyllithium, TMEDA, isoprene, dimethyldichlorosilane and methanol were changed as shown in Table 1, respectively. The polymer composition was recovered. About the block copolymer composition of the reference example 2 and the reference example 3, the same measurement as the reference example 1 was performed. The results are shown in Table 2.

[Reference Example 4]
To a pressure-resistant reactor, 23.3 kg of cyclohexane, 2.2 mmol of TMEDA, and 1.85 kg of styrene were added, and 148.2 mmol of n-butyllithium was added to the mixture while stirring at 40 ° C., and the temperature was raised to 50 ° C. The polymerization was carried out for 1 hour. The polymerization conversion of styrene was 100%. Subsequently, 6.30 kg of isoprene was continuously added to the reactor over 1 hour while controlling the temperature so as to maintain 50 to 60 ° C. After completing the addition of isoprene, polymerization was continued for an additional hour. The polymerization conversion rate of isoprene was 100%. Further, 1.85 kg of styrene was continuously added over 1 hour while controlling the temperature so as to maintain 50 to 60 ° C. After completing the addition of styrene, polymerization was continued for an additional hour to form a styrene-isoprene-styrene triblock copolymer. The polymerization conversion of styrene was 100%. Thereafter, 296.4 mmol of methanol was added as a polymerization terminator and mixed well to stop the reaction. A part of the obtained reaction solution was taken out and subjected to the same measurement as in Reference Example 1. These values are shown in Table 2. The following operation was carried out in the same manner as in Reference Example 1, and the block copolymer composition of Reference Example 4 was recovered.

[Reference Example 5]
The block copolymer composition of Reference Example 5 in the same manner as Reference Example 1 except that the amounts of styrene, n-butyllithium, TMEDA, isoprene, dimethyldichlorosilane and methanol were changed as shown in Table 1, respectively. Was recovered. For the block copolymer composition of Reference Example 5, the same measurement as in Reference Example 1 was performed. The results are shown in Table 2.

[Example 1]
100 parts of the block copolymer composition obtained in Reference Example 1 was charged into a stirring blade type kneader, and ZEON Corporation, an aliphatic hydrocarbon resin having a softening point of 100 ° C., was used as a tackifier resin. 50 parts of “Quinton A100” manufactured by the company and 1 part of pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (“Irganox 1010” manufactured by BASF) which is an antioxidant After the addition and replacement of the system with nitrogen gas, the pressure-sensitive adhesive of Example 1 was prepared by kneading at 160 to 180 ° C. for 1 hour. About the obtained adhesive, the glass transition temperature was measured. Next, by using the pressure-sensitive adhesive of Example 1 and a linear low-density polyethylene resin “Nipolon-LF14” manufactured by Tosoh Corporation, co-extrusion molding by the T-die method is performed, whereby the pressure-sensitive adhesive of Example 1 is used. A surface protective material obtained by laminating two layers of a 10 μm thick adhesive layer made of an agent and a 25 μm thick base material layer made of a linear low density polyethylene resin was obtained. About this surface protection material, initial peel force (low speed peel), initial peel force (high speed peel), peel strength with time, and adhesive residue at the time of peel were evaluated. The results are shown in Table 3.

[Examples 2-6, Comparative Examples 1-4]
The pressure-sensitive adhesives of Examples 2 to 6 and Comparative Examples 1 to 4 were the same as Example 1 except that the types and amounts of the block copolymer composition and tackifying resin used were changed as shown in Table 3. And surface protective materials of Examples 2 to 6 and Comparative Examples 1 to 4 were obtained. The alicyclic hydrocarbon resin shown in Table 3 is “Escollet 5320” manufactured by ExxonMobil Chemical, which is an alicyclic hydrocarbon resin having a softening point of 125 ° C. The obtained pressure-sensitive adhesive and surface protective material were evaluated in the same manner as in Example 1. The results are shown in Table 3.

  Table 3 shows the following. That is, the pressure-sensitive adhesive for a surface protective material of the present invention has a high initial peel strength at the time of low-speed peeling and a relatively low initial peel strength at the time of high-speed peeling, and thus has excellent adhesiveness and spreadability. . Furthermore, in the pressure-sensitive adhesive for surface protective material of the present invention, the peel force with time does not increase significantly from the initial peel force (low-speed peel), so it can be said that the progress of the adhesive force is well suppressed. Since the adhesive residue at the time of peeling is not recognized, it can be said that the adhesive residue hardly remains (Examples 1-6). On the other hand, the block copolymer composition of Reference Example 4 consisting only of a symmetric styrene-isoprene-styrene triblock copolymer, or an asymmetric aromatic vinyl different from the block copolymer A used in the present invention Adhesion using the block copolymer composition of Reference Example 5 comprising a block copolymer comprising a conjugated diene-aromatic vinyl block copolymer and a symmetric aromatic vinyl-conjugated diene-aromatic vinyl block copolymer When the tackifier resin is not blended, the agent exhibits an extremely large increase in tack (Comparative Examples 1 and 2). When the tackifier resin is blended, the developability is inferior (initial peel force at high speed stripping). Is large), and adhesive residue was generated (Comparative Examples 3 and 4).

Claims (4)

A block copolymer composition comprising a block copolymer A represented by the following formula (A) and a block copolymer B represented by the following formula (B), and a tackifying resin. A pressure-sensitive adhesive for a surface protective material,
A pressure-sensitive adhesive for a surface protective material, wherein the weight ratio (A / B) of the block copolymer A to the block copolymer B in the block copolymer composition is 10/90 to 90/10.
^{Ar1 a -D a -Ar2 a (A} )
(Ar ^b -D ^b ) n-X (B)
(In the formulas (A) and (B), Ar 1 ^a and Ar ^b are aromatic vinyl polymer blocks having a weight average molecular weight of 6000 to 20000, respectively, and Ar 2 ^a is an aromatic having a weight average molecular weight of 22,000 to 400,000. A vinyl polymer block, D ^a and D ^b are each a conjugated diene polymer block having a vinyl bond content of 1 to 20 mol%, X is a single bond or a residue of a coupling agent, n is an integer of 2 or more.)   In the block copolymer composition, the ratio of the aromatic vinyl monomer unit to the total monomer units constituting the polymer component in the block copolymer composition is 13 to 85% by weight. The pressure-sensitive adhesive for a surface protective material according to claim 1.   The pressure-sensitive adhesive for a surface protecting material according to claim 1 or 2, wherein the content of the tackifying resin is 1 to 100 parts by weight with respect to 100 parts by weight of the block copolymer composition.   A surface protective material obtained by laminating a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive for surface protective material according to claim 1 and a base material layer made of resin.