JP3659928B2 - Block copolymer composition and heat shrinkable film thereof - Google Patents

Description

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【００５０】
【表２】

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【００５１】
表１に示した物性の測定は下記の方法により行った。
（１）オゾン分解
ブロック共重合体中組成物に組み込まれている芳香族炭化水素重合体ブロック群の分子量分布は、ブロック共重合体をオゾン分解〔Ｙ．ＴＡＮＡＫＡ，et al.，ＲＵＢＢＥＲ ＣＨＥＭＩＳＴＲＹ ＡＮＤ ＴＥＣＨＮＯＬＯＧＹ，５８，１６（１９８５）〕して得たビニル芳香族炭化水素重合体成分をＧＰＣで測定して求めた。
（２）重量平均分子量
重量平均分子量は下記記載のＧＰＣ測定条件で測定した。
装置名：ＳＹＳＴＥＭ−２１ Ｓｈｏｄｅｘ（昭和電工社製）
カラム：ＰＬ ｇｅｌ ＭＩＸＥＤ−Ｂを３本直列
温度：４０℃
検出：示差屈折率
溶媒：テトラヒドロフラン
濃度：２質量％
検量線：標準ポリスチレン（ＰＳ）（ＰＬ社製）を用いて作成し、分子量はＰＳ換算値で表した。
【００５２】
（３）伸び
ＪＩＳ Ｋ６８７１に準拠し、エー・アンド・デイ製テンシロン万能試験機（ＲＴＣ−１２１０Ａ）を用いて測定した。
（４）ミシン目切れ性
得られたフィルムに、カット０．７ｍｍ、ブリッジ１．４ｍｍで収縮率の高い方向と直交する方向にミシン目を入れた後、そのフィルムを台上に置き、ミシン目の片側を手で押さえて、反対側を指で掴んで、台と平行に引き裂いた時の状態を下記の基準で評価した。
○： ミシン目に沿って切れる
△： 途中でミシン目からずれる
×： ミシン目通りに切れない
（５）熱収縮率（％）
延伸フィルムを７０℃の温水中に３０秒間浸漬し、次式より算出した。
熱収縮率（％）＝｛（Ｌ１−Ｌ２）／Ｌ１ ｝×１００
Ｌ１：収縮前の長さ （延伸方向）
Ｌ２：収縮後の長さ （延伸方向）
【００５３】
（６）自然収縮率（％）
延伸フィルムを３０℃で３０日間放置し、次式より算出した。
自然収縮率（％）＝｛（Ｌ３−Ｌ４）／ Ｌ３｝×１００
Ｌ３：収縮前の長さ （延伸方向）
Ｌ４：収縮後の長さ （延伸方向）
（７）ブロック共重合体中に含まれるブタジエンの質量分率の測定：
０．１ｇの該ペレットをクロロホルム約５０ｍＬに溶解し、２５ｍＬの一塩化ヨウ素四塩化炭素溶液を加えて暗所に１時間放置後、さらに２．５％のヨウ化カリウム溶液７５ｍＬを加えた。このとき、過剰の一塩化ヨウ素を２０％のアルコール性Ｎ／１０チオ硫酸ナトリウム溶液で滴定して、ポリブタジエンの二重結合への付加反応で消費されたヨウ素量を逆算し、ブタジエン濃度を求めた。
【００５４】
【発明の効果】
本発明の熱収縮性フィルムは耐自然収縮性、伸び及びミシン目切れ性に優れるため、その製造方法も含めて特徴あるブロック共重合体として産業上有用である。[0001]
[Technical field to which the invention belongs]
  The present invention relates to a block copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene, which are excellent in resistance to natural shrinkage, elongation and perforation.CompositionAnd copolymers thereofCompositionIt is related with the heat-shrinkable film formed by extending | stretching.
[0002]
[Prior art]
  When a vinyl aromatic hydrocarbon and a conjugated diene are copolymerized in an organic solvent using an alkyllithium as an initiator by living anionic polymerization, various physical properties depend on the mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene and the structure of the copolymer. It is known that block copolymers having
  A block copolymer is generally a polymer having excellent impact resistance and transparency. If the content of the conjugated diene in the block copolymer is large, it becomes a thermoplastic elastomer, but it contains vinyl aromatic hydrocarbons. When the amount is increased, the properties as a thermoplastic are exhibited. Various manufacturing methods that make use of this excellent characteristic are disclosed in Japanese Patent Publication Nos. 36-19286 and 48-4106.
  For example, JP-A-59-49938 discloses a specific polystyrene composition comprising a styrene-butadiene block copolymer, another styrene-butadiene copolymer, a polystyrene polymer, and a rubber-modified polystyrene polymer. In addition, it is described that, by promoting molecular orientation in a single operation, a heat-shrinkable film having high tensile strength, impact resistance and elongation, and suitable as a transparent and high gloss packaging material can be obtained. Japanese Patent Application Laid-Open No. 7-144365 discloses a styrene-butadiene block copolymer in which the butadiene block in the entire polymer is 4 to 35%, or a mixture of this and a polystyrene polymer under specific conditions. A styrene-based shrink film excellent in fracture resistance, shrinkage characteristics and rigidity, which is a biaxially stretched film and has a tensile elongation at break of 10% or more at 0 ° C. in the longitudinal direction, is described.
[0003]
[Problems to be solved by the invention]
  Although these block copolymers and polymer compositions are relatively transparent and have good impact resistance, when used as a heat-shrinkable film after being stretched, a phenomenon that the film shrinks during storage ( (Natural contraction) occurs.
  For this reason, since it has problems such as that labels cannot be attached to various bottles and printing is shifted, it has been desired to develop a block copolymer and a heat-shrinkable film that hardly cause natural shrinkage.
  Further, these block copolymers and polymer compositions have been increasingly used particularly as labels for PET bottle beverages in recent years. In particular, labels that have been previously provided with perforations have become a large percentage so that consumers can separate labels and bottles at the time of disposal and recycle the bottles. For this reason, it has been desired to develop a material with excellent perforation that can cleanly cut the label according to the perforation without detaching from the perforation line.
[0004]
[Means for Solving the Problems]
  In view of the current situation, the present inventors have intensively studied to obtain a heat-shrinkable film with improved natural shrinkage. As a result, vinyl aromatic hydrocarbons and conjugated dienes andA specific block copolymer comprising a specific ratio, and in the resulting block copolymer compositionBlock copolymer of molecular weight distribution of vinyl aromatic hydrocarbon polymer block group that satisfies specific conditionsCompositionAs a result, it has been found that not only the natural shrinkage resistance but also the elongation and the perforation are improved, and the present invention has been completed.
[0005]
  That is, the present invention
(1) A block copolymer composition comprising the following block copolymers (A) and (B) comprising a vinyl aromatic hydrocarbon and a conjugated diene, wherein the mass ratio is (A) / (B) = A vinyl aromatic hydrocarbon polymer block group having a molecular weight of less than 5,000 in the molecular weight measurement of the vinyl aromatic hydrocarbon polymer block group of the block copolymer composition; Is a block copolymer composition having a mass ratio of 60/40 to 90/10 with a vinyl aromatic hydrocarbon polymer block group of 5,000 or more,
(A) is a block copolymer having a mass ratio of vinyl aromatic hydrocarbon to conjugated diene of 70/30 to 90/10 and a weight average molecular weight of 172,000 to 500,000,
(B) is a block copolymer having a mass ratio of vinyl aromatic hydrocarbon to conjugated diene of 60/40 to 80/20 and a weight average molecular weight of 40,000 to 140,000,
(2) A sheet or film for producing a heat-shrinkable film comprising the block copolymer composition described in (1) above, and further
(3) A heat-shrinkable film using the block copolymer composition according to (1), or
(4) A heat-shrinkable multilayer film using the block copolymer composition according to (1) in at least one layer.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the present invention will be described in detail.
  Examples of the vinyl aromatic hydrocarbon used in the present invention include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, and 3,4-dimethyl. Styrene, α-methyl styrene, vinyl naphthalene, vinyl anthracene and the like are available, and styrene is particularly common.
[0007]
  Conjugated dienes include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3 butadiene, 1,3-pentadiene, 1,3-hexadiene, Particularly common are 1,3-butadiene and isoprene.
[0008]
  Delete
[0009]
  A vinyl aromatic hydrocarbon polymer block of a block copolymer composition comprising (A) and (B) As for the mass ratio of the vinyl aromatic hydrocarbon polymer block group having a molecular weight of less than 5,000 and the vinyl aromatic hydrocarbon polymer block group having a molecular weight of 5,000 or more in the molecular weight measurement of the group C, Identified.
[0010]
  The mass ratio of the vinyl aromatic hydrocarbon polymer block group having a molecular weight of less than 5,000 and the vinyl aromatic hydrocarbon polymer block group having a molecular weight of 5,000 or more is 60/40 to 90/10. If it is less than 60/40, the natural shrinkage resistance and the perforation are reduced, and if it exceeds 90/10, the film appearance is impaired. The vinyl aromatic hydrocarbon polymer block group means that the block copolymer is ozonolyzed [Y. Tanaka, et al. , RUBBER CHEMISTRY AND TECHNOLOGY, 58, 16 (1985)] refers to an aggregate of components of the obtained vinyl aromatic hydrocarbon polymer, and measurement of gel permeation chromatograph (hereinafter abbreviated as GPC) of the component. The mass ratio can be obtained from the area ratio.
[0011]
  (A), (B) Two typesBlock copolymerFavorPreferred examples include those having the following general formula.
  a. A-C-B
  b. A-B-C-B
  c. A-C-B-A
  d. A-B-C-B-A
  e. A-B-A-B-A
  f. A-C-B-C-B
  g. (A-C-B) n-X
  h. (A-C-B-A) n-X
  i. (A-C-B-C-B) n-X
[0012]
  The above general formula has a chemical structure, that is, a block-like polymer chain A substantially composed of vinyl aromatic hydrocarbons, a copolymer chain B composed of vinyl aromatic hydrocarbons and conjugated dienes, and a block shape substantially composed of conjugated dienes. The sequence of the polymer chain C is shown. Even if there are a plurality of A, B or C in the general formula, molecular weight, vinyl aromatic hydrocarbon block ratio, mass ratio of conjugated diene, distribution state of vinyl aromatic hydrocarbon and conjugated diene in copolymer chain, etc. Each is independent and need not be identical. The molecular weight and composition distribution of the copolymer chain B are controlled mainly by the addition amount and addition method of the vinyl aromatic hydrocarbon monomer and the conjugated diene monomer.
[0013]
  In the structural formula, X is a residue of a polyfunctional coupling agent or a residue of a polyfunctional organolithium compound used as an initiator, and n is an integer of 2 to 4. Examples of the polyfunctional coupling agent used in the present invention include silicon tetrachloride and epoxidized soybean oil. Examples of the polyfunctional organolithium compound include hexamethylene dilithium, butadienyl dilithium, and isoprenyl dilithium.
[0014]
  (The mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene of A) is 70/30 to 90/10, and the weight average molecular weight is172,000The mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene in (B) is 60/40 to 80/20, and the weight average molecular weight is 40,000 to140,000These mass ratios are (A) / (B) = 20/80 to 80/20.
  (A)When(B)WhenConsist ofBlock copolymerIn the composition, when the mass ratio of the vinyl aromatic hydrocarbon of (A) to the conjugated diene is less than 70/30,Of heat-shrinkable film obtained from block copolymer compositionThe effect of improving perforation is not sufficient, and when it exceeds 90/10, the impact resistance is poor, and the weight average molecular weight is172,000If the ratio is less than 500,000, the effect of improving the strength is not sufficient.ButSince it is inferior, it is not preferable. When the mass ratio of vinyl aromatic hydrocarbon and conjugated diene in (B) is less than 60/40Of heat-shrinkable film obtained from block copolymer compositionInferior in transparency and rigidity, if it exceeds 80/20, the effect of improving the strength is not sufficient, and if the weight average molecular weight is less than 40,000, it is inferior in rigidity and impact resistance.140,000In the case where it exceeds 1, the effect of improving perforation is not sufficient, which is not preferable. When (A) is less than 20 parts by massOf heat-shrinkable film obtained from block copolymer compositionThe effect of improving perforation is not sufficient, and when (A) exceeds 80 parts by mass, the effect of improving the strength is not sufficient, but the mass ratio of (A) to (B) is 20/80 to 80/20. In this case, both the perforation and the strength are improved, which is preferable.
[0015]
  TheThe lock copolymer can be produced by polymerizing vinyl aromatic hydrocarbon and conjugated diene monomers in an organic solvent using an organolithium compound as an initiator.
  As the organic solvent, aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, octane, isooctane, cycloaliphatic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, or benzene, Aromatic hydrocarbons such as toluene, ethylbenzene and xylene can be used.
[0016]
  An organic lithium compound is a compound in which one or more lithium atoms are bonded in the molecule, such as ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, and tert-butyl lithium. A monofunctional organic lithium compound, the polyfunctional organic lithium compound described above, or the like can be used.
[0017]
  TheThe molecular weight of the lock copolymer can be controlled by the amount of initiator added relative to the total amount of monomers added.
[0018]
  In the present invention, the mass ratio of the component having a molecular weight of less than 5,000 and the component having a molecular weight of 5,000 or more in the vinyl aromatic hydrocarbon polymer block group is the molecular weight, composition distribution and co-weight of A, B and C in the above structural formula. It can be adjusted by controlling the combined block rate.
[0019]
  The block ratio of the block copolymer can also be controlled by the addition amount of the randomizing agent when the vinyl aromatic hydrocarbon and the conjugated diene are polymerized.
[0020]
  Tetrahydrofuran (THF) is mainly used as the randomizing agent, but other ethers, amines, thioethers, phosphoramides, alkylbenzene sulfonates, potassium or sodium alkoxides, and the like can also be used.
  Suitable ethers include dimethyl ether, diethyl ether, diphenyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether and the like in addition to THF.
  As the amines, tertiary amines such as trimethylamine, triethylamine, tetramethylethylenediamine, and internal cyclic amines can be used. In addition, triphenylphosphine, hexamethylphosphamide, potassium or sodium alkylbenzenesulfonate, potassium, sodium butoxide, etc. can be used as the randomizing agent.
[0021]
  As addition amount, 0.001-10 mass parts is preferable with respect to 100 mass parts of all preparation monomers. The timing of addition may be before the start of the polymerization reaction or before the polymerization of the block portion. Moreover, it can also add as needed.
[0022]
  The block rate can also be controlled by the monomer supply rate.
[0023]
  The block copolymer thus obtained is inactivated by adding a polymerization terminator such as water, alcohol, carbon dioxide or the like in an amount sufficient to inactivate the active terminal. As a method of recovering the copolymer from the obtained block copolymer solution,(A)A method of precipitating with a poor solvent such as methanol,(B)A method of evaporating the solvent with a heating roll or the like (a drum dryer method),(C)A method of removing the solvent with a vented extruder after concentrating the solvent with a concentrator,(D)An arbitrary method such as a method of dispersing the solution in water, blowing water vapor and removing the solvent by heating to recover the copolymer (steam stripping method) is used.
[0024]
  In order to effectively use the block copolymer shown in the present invention in each field, it is preferable to add various additives as necessary. Examples of the additive include various stabilizers, lubricants, processing aids, antiblocking agents, antistatic agents, antifogging agents, weather resistance improvers, softeners, plasticizers, and pigments.
[0025]
  Examples of the stabilizer include 2,6-di-t-butyl-4-methylphenol, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [ 1- (2-hydroxy-3,5-di-t-pentylphenyl) -ethyl] -4,6-di-pentylphenyl acrylate, n-octadecyl-3- (4′-hydroxy-3 ′, 5′- Phenolic antioxidants such as di-t-butylphenyl) propionate, phosphorus antioxidants such as 2,2-methyleneville (4,6-di-t-butylphenyl) octyl phosphite, trisnonylphenyl phosphite, etc. Is mentioned.
  Examples of the antiblocking agent, antistatic agent, and lubricant include fatty acid amide, ethylene bisstearamide, sorbitan monostearate, saturated fatty acid ester of aliphatic alcohol, pentaerythritol fatty acid ester, and the like.
  These additives are desirably used in an amount of 5% by mass or less based on the block copolymer.
[0026]
  Other polymers can be blended for modifying the block copolymer shown in the present invention. For example, a polymer of the above-mentioned vinyl aromatic hydrocarbon, a block copolymer of a hydrocarbon and a conjugated diene outside the range specified in the present invention, the above-mentioned vinyl aromatic hydrocarbon and another vinyl monomer, such as ethylene, Examples thereof include copolymers with propylene, butylene, vinyl chloride, vinylidene chloride, vinyl acetate, acrylic acid esters such as (meth) acrylic acid and methyl acrylate, methacrylic acid esters such as methyl methacrylate, and acrylonitrile.
[0027]
  Other,For reformingRubber-modified impact-resistant styrene resin (HIPS), acrylonitrile-butadiene-styrene copolymer (ABS), methyl methacrylate-butadiene-styrene copolymer (MBS), polyphenylene ether resin, polyethylene, polypropylene, polycarbonate, polysulfone, Polyamide, polyester, polyvinyl chloride, polymethacrylate, and the like can also be used.
[0028]
  Delete
[0029]
  The heat shrink film of the present invention is a block copolymer.CompositionThe sheet or film extruded by the known T-die method or tubular method can be stretched uniaxially, biaxially or multiaxially. Examples of uniaxial stretching include a method of stretching an extruded sheet in a direction perpendicular to the extrusion direction with a tenter, and stretching an extruded tubular film in the circumferential direction. As an example of biaxial stretching, the extruded sheet is stretched in the extrusion direction with a roll, and then stretched in a direction perpendicular to the extrusion direction with a tenter or the like, and the extruded tubular film is simultaneously extruded in the circumferential direction. Or the method of extending | stretching separately is mentioned.
[0030]
  In the present invention, the stretching temperature is preferably 60 to 120 ° C. If it is less than 60 ° C., the sheet or film breaks during stretching, and if it exceeds 120 ° C., good shrinkage characteristics cannot be obtained, which is not preferable. Although there is no restriction | limiting in particular in a draw ratio, 1.5-8 times are preferable. If it is less than 1.5 times, the heat shrinkability is insufficient, and if it exceeds 8 times, stretching is difficult, which is not preferable. The thickness of the film is preferably 10 to 300 μm.
[0031]
  As the application of the heat-shrinkable film of the present invention, a heat-shrinkable label, a heat-shrinkable cap seal, etc. are particularly effective, but can also be appropriately used for packaging films and the like.
[0032]
  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following examples.
[0033]
  Reference Example 15And Comparative Examples 1-4
  In Reference Examples and Comparative Examples, cyclohexane solvents are used, styrene and butadiene are copolymerized using n-butyllithium as an initiator and tetrahydrofuran as a randomizing agent, and block copolymers having the characteristics shown in Tables 1 and 2 are used. A coalescence was produced. In addition, the weight average molecular weight (Mw) was adjusted with the addition amount of n-butyllithium.
[0034]
  Delete
[0035]
[Reference example1][Production method of (A)]
(1) A reaction vessel was charged with 490 kg of cyclohexane and 8.4 kg of styrene monomer as a polymerization solvent, and kept at 30 ° C.
(2) To this, 1240 mL of a 10% by mass cyclohexane solution of n-butyllithium was added as a polymerization catalyst solution to anionically polymerize the styrene monomer.
(3) After the styrene monomer is completely consumed, while maintaining the internal temperature of the reaction system at 80 ° C., a total amount of 115.5 kg of styrene monomer and a total amount of 14.1 kg of butadiene were respectively 77.0 kg / h, 9 Both were added simultaneously at a constant addition rate of 4 kg / h, and maintained for 5 minutes after the addition was completed.
(4) After the butadiene gas was completely consumed, 19.5 kg of butadiene was added all at once while maintaining the internal temperature of the reaction system at 75 ° C., and this was subsequently reacted.
(5) Further, 52.5 kg of styrene monomer was added all at once to complete the polymerization.
(6) A polymer having a polystyrene block part, a polybutadiene block part and a random structure part of styrene and butadiene, in which all polymerization active terminals are deactivated with water.
A polymerization solution containing was obtained.
[0036]
[Reference example2][Production method of (B)]
(1) 245 kg of a polymerization solvent and 4.2 kg of a styrene monomer were charged into a reaction vessel and kept at 30 ° C.
(2) The polymerization catalyst solution 980mL was added in this and the styrene monomer was anion-polymerized.
(3) After the styrene monomer has been completely consumed, a total amount of 65.1 kg of styrene monomer and a total amount of 5.8 kg of butadiene were respectively changed to 43.4 kg / h, while maintaining the internal temperature of the reaction system at 80 ° C. Both were added simultaneously at a constant addition rate of 85 kg / h, and the state was maintained as it was for 5 minutes after the addition was completed.
(4) After the butadiene gas was completely consumed, 25.8 kg of butadiene was added all at once while maintaining the internal temperature of the reaction system at 60 ° C., and this was subsequently reacted.
(5) An additional 4.2 kg of styrene monomer was added all at once to complete the polymerization.
(6) All polymerization active terminals were deactivated with water to obtain a polymerization liquid containing a polymer having a polystyrene block part, a polybutadiene block part, and a random structure part of styrene and butadiene.
[0037]
[Reference example3][Production method of (B)]
(1) 245 kg of cyclohexane and 4.2 kg of styrene monomer were charged in a reaction vessel as a polymerization solvent and kept at 30 ° C.
(2) 1195 mL of the polymerization catalyst solution was added thereto, and the styrene monomer was anionically polymerized.
(3) After the styrene monomer has been completely consumed, a total amount of 59.9 kg of styrene monomer and a total amount of 4.9 kg of butadiene are respectively added to 59.9 kg / h, while maintaining the internal temperature of the reaction system at 80 ° C. Both were simultaneously added at a constant addition rate of 9 kg / h, and the state was maintained for 5 minutes after the addition was completed.
(4) After the butadiene gas was completely consumed, 31.8 kg of butadiene was added all at once while maintaining the internal temperature of the reaction system at 60 ° C., and this was subsequently reacted.
(5) An additional 4.2 kg of styrene monomer was added all at once to complete the polymerization.
(6) All polymerization active terminals were deactivated with water to obtain a polymerization liquid containing a polymer having a polystyrene block part, a polybutadiene block part and a random structure part of styrene and butadiene.
[0038]
[Reference example4][Production method of (A)]
(1) A reaction vessel was charged with 490 kg of cyclohexane and 8.4 kg of styrene monomer as a polymerization solvent, and kept at 30 ° C.
(2) 1270 mL of the polymerization catalyst solution was added thereto, and the styrene monomer was subjected to anionic polymerization.
(3) After the styrene monomer has been completely consumed, a total amount of 157.5 kg of styrene monomer and a total amount of 21.0 kg of butadiene were respectively maintained at 63.0 kg / h, 8 Both were added simultaneously at a constant addition rate of 4 kg / h, and maintained for 5 minutes after the addition was completed.
(4) After the butadiene gas was completely consumed, 14.7 kg of butadiene was added all at once while maintaining the internal temperature of the reaction system at 75 ° C., and this was subsequently reacted.
(5) A further 8.4 kg of styrene monomer was added all at once to complete the polymerization.
(6) All polymerization active terminals were deactivated with water to obtain a polymerization liquid containing a polymer having a polystyrene block part, a polybutadiene block part and a random structure part of styrene and butadiene.
[0039]
  Delete
[0040]
  Delete
[0041]
[Reference example5][Production method of (B)]
(1) 245 kg of cyclohexane and 4.2 kg of styrene monomer were charged in a reaction vessel as a polymerization solvent and kept at 30 ° C.
(2) The polymerization catalyst solution 980mL was added in this and the styrene monomer was anion-polymerized.
(3) After the styrene monomer is completely consumed, the total amount of 70.4 kg of styrene monomer and the total amount of 8.4 kg of butadiene are 46.9 kg / h, 5% while maintaining the internal temperature of the reaction system at 80 ° C. Both were added simultaneously at a constant addition rate of 6 kg / h, and the state was maintained for 5 minutes after the addition was completed.
(4) After the butadiene gas was completely consumed, 17.9 kg of butadiene was added all at once while maintaining the internal temperature of the reaction system at 60 ° C., and this was subsequently reacted.
(5) An additional 4.2 kg of styrene monomer was added all at once to complete the polymerization.
(6) All polymerization active terminals were deactivated with water to obtain a polymerization liquid containing a polymer having a polystyrene block part, a polybutadiene block part and a random structure part of styrene and butadiene.
[0042]
[Comparative Example 1]
(1) As a polymerization solvent, 490 kg of cyclohexane and 69.9 kg of styrene monomer were charged in a reaction vessel and kept at 30 ° C.
(2) 1670 mL of the polymerization catalyst solution was added thereto, and the styrene monomer was anionically polymerized.
(3) After the styrene monomer was completely consumed, 98.1 kg of styrene monomer and 42.0 kg of butadiene were added all at once while maintaining the internal temperature of the reaction system at 45 ° C., and this was subsequently reacted.
(4) All the polymerization active terminals were deactivated with water to obtain a polymerization liquid containing a polymer having a polystyrene block part and a tapered structure part of styrene and butadiene.
[0043]
[Comparative Example 2]
(1) A reaction vessel was charged with 490 kg of cyclohexane and 79.8 kg of styrene monomer as a polymerization solvent, and kept at 30 ° C.
(2) 1960 mL of the polymerization catalyst solution was added thereto, and the styrene monomer was anionically polymerized.
(3) After the styrene monomer was completely consumed, 50.4 kg of butadiene was added all at once while maintaining the internal temperature of the reaction system at 50 ° C., and this was subsequently reacted.
(4) After the butadiene gas was completely consumed, 79.8 kg of styrene monomer was added all at once while maintaining the internal temperature of the reaction system at 60 ° C. to complete the polymerization.
(5) All polymerization active terminals were deactivated with water to obtain a polymerization solution containing a polymer having a polystyrene block portion and a polybutadiene block portion.
[0044]
[Comparative Example 3]
(1) 490 kg of cyclohexane and 26.9 kg of styrene monomer were charged as a polymerization solvent in a reaction vessel, and kept at 30 ° C.
(2) 1720 mL of the polymerization catalyst solution was added thereto, and the styrene monomer was anionically polymerized.
(3) After the styrene monomer was completely consumed, 52.3 kg of styrene monomer and 6.7 kg of butadiene were added all at once while maintaining the internal temperature of the reaction system at 50 ° C., and this was allowed to react.
(4) Further, while maintaining the internal temperature of the reaction system at 60 ° C., 89.5 kg of styrene monomer and 34.7 kg of butadiene were added all at once to complete the polymerization.
(5) All the polymerization active terminals were deactivated with water to obtain a polymerization liquid containing a polymer having a polystyrene block part and a tapered structure part of styrene and butadiene.
[0045]
[Comparative Example 4]
(1) 490 kg of cyclohexane and 2.1 kg of styrene monomer were charged in a reaction vessel as a polymerization solvent and kept at 30 ° C.
(2) 1820 mL of the polymerization catalyst solution was added thereto, and the styrene monomer was anionically polymerized.
(3) After the styrene monomer was completely consumed, a total amount of 126.0 kg of styrene monomer and a total amount of 10.5 kg of butadiene were respectively maintained at 252.0 kg / h, 21 while maintaining the internal temperature of the reaction system at 80 ° C. Both were added simultaneously at a constant addition rate of 0.0 kg / h, and the state was maintained for 5 minutes after the addition was completed.
(4) After the butadiene gas was completely consumed, 33.6 kg of butadiene was added all at once while maintaining the internal temperature of the reaction system at 70 ° C., and this was subsequently reacted.
(5) Further, 37.8 kg of styrene monomer was added all at once to complete the polymerization.
(6) All polymerization active terminals were deactivated with water to obtain a polymerization liquid containing a polymer having a polystyrene block part, a polybutadiene block part and a random structure part of styrene and butadiene.
[0046]
  In addition, each polymer of the reference example and the comparative example in a solution state was devolatilized by a vent type extruder after preliminarily concentrating the polymerization solvent to form a pellet.
[0047]
  Reference example1-5Each polymer obtained in, tableOnce melted and kneaded with the formulation of 1Block copolymer groupAfter preparing the composition, it was subjected to the test described below, and the results are shown in Table 1 as examples.
  Each polymer obtained in Comparative Examples 1 to 4 was melt-kneaded alone and then subjected to the test described below, and the results are shown in Table 2 as Comparative Examples.
[0048]
  Each block copolymerBodyTables 1 and 2 show the thermal shrinkage, natural shrinkage, tensile elongation at break, and perforation of the film made of the composition. The film was first extruded into a sheet having a thickness of 0.3 mm at 210 ° C. and then stretched uniaxially at 90 ° C. using a biaxial stretching apparatus manufactured by Toyo Seiki Seisakusho Co., Ltd. ( Thickness about 60 μm). From the physical properties shown in Table 1, the present inventionHeat shrinkable filmIt can be seen that is excellent in resistance to natural shrinkage, elongation and perforation.
[0049]
[Table 1]

?
[0050]
[Table 2]

?
[0051]
  The physical properties shown in Table 1 were measured by the following methods.
(1) Ozone decomposition
  In block copolymerCompositionAromatic hydrocarbon polymer block group incorporated inMinutesThe molecular weight distribution is determined by ozonolysis of the block copolymer [Y. TANAKA, et al., RUBBER CHEMISTRY AND TECHNOLOGY, 58, 16 (1985)], and the vinyl aromatic hydrocarbon polymer component obtained by GPC was measured.
(2)Weight averageMolecular weight
    Weight averageThe molecular weight was measured under the GPC measurement conditions described below.
  Device name: SYSTEM-21 Shodex (manufactured by Showa Denko)
  Column: 3 series PL gel MIXED-B
  Temperature: 40 ° C
  Detection: Differential refractive index
  Solvent: Tetrahydrofuran
  Concentration: 2% by mass
  Calibration curve: prepared using standard polystyrene (PS) (manufactured by PL), and the molecular weight was expressed in terms of PS.
[0052]
(3) Elongation
  In accordance with JIS K6871, measurement was performed using an A & D Tensilon universal testing machine (RTC-1210A).
(4) Cutting perforation
  Put the perforation in the direction perpendicular to the direction of high shrinkage with cut 0.7mm, bridge 1.4mm on the obtained film, put the film on the table, hold down one side of the perforation by hand The state when the opposite side was grasped with a finger and torn parallel to the table was evaluated according to the following criteria.
    ○: Cut along perforations
    Δ: Deviation from perforation on the way
    ×: Not perforated
(5) Thermal shrinkage (%)
  The stretched film was immersed in warm water at 70 ° C. for 30 seconds and calculated from the following formula.
       Thermal contraction rate (%) = {(L1-L2) / L1} × 100
           L1: Length before shrinkage (stretching direction)
          L2: Length after shrinkage (stretching direction)
[0053]
(6) Natural shrinkage rate (%)
  The stretched film was allowed to stand at 30 ° C. for 30 days and calculated from the following formula.
        Natural shrinkage (%) = {(L3−L4) / L3} × 100
           L3: Length before shrinkage (stretching direction)
           L4: Length after shrinkage (stretching direction)
(7) Measurement of mass fraction of butadiene contained in block copolymer:
  0.1 g of the pellet was dissolved in about 50 mL of chloroform, and 25 mL of iodine tetrachloride carbon tetrachloride solution was added and left in the dark for 1 hour, and then 75 mL of a 2.5% potassium iodide solution was further added. At this time, excess iodine monochloride was titrated with 20% alcoholic N / 10 sodium thiosulfate solution, and the amount of iodine consumed in the addition reaction of polybutadiene to the double bond was calculated backward to obtain the butadiene concentration. .
[0054]
【The invention's effect】
  Of the present inventionHeat shrinkable filmIs excellent in spontaneous shrinkage resistance, elongation and perforation, and is industrially useful as a characteristic block copolymer including its production method.

Claims (4)

A block copolymer composition comprising the following block copolymers (A) and (B) comprising a vinyl aromatic hydrocarbon and a conjugated diene, wherein the mass ratio is (A) / (B) = 20/80 The vinyl aromatic hydrocarbon polymer block group having a molecular weight of less than 5,000 in the molecular weight measurement of the vinyl aromatic hydrocarbon polymer block group of the block copolymer composition; A block copolymer composition having a mass ratio of 000 or more vinyl aromatic hydrocarbon polymer block group of 60/40 to 90/10.
(A) A block copolymer having a mass ratio of vinyl aromatic hydrocarbon to conjugated diene of 70/30 to 90/10 and a weight average molecular weight of 172,000 to 500,000.
(B) A block copolymer having a mass ratio of vinyl aromatic hydrocarbon to conjugated diene of 60/40 to 80/20 and a weight average molecular weight of 40,000 to 140,000. A sheet or film for producing a heat-shrinkable film comprising the block copolymer composition according to claim 1. A heat-shrinkable film using the block copolymer composition according to claim 1. A heat-shrinkable multilayer film using the block copolymer composition according to claim 1 as at least one layer.