JPH0468342B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a polymer composition having excellent color tone, transparency, and color fastness. [Prior Art] When a block copolymer consisting of a conjugated diene and a vinyl aromatic hydrocarbon has a relatively small content of vinyl aromatic hydrocarbon, it can be used to form vulcanized natural rubber or synthetic rubber without vulcanization. It has the same elasticity at room temperature as thermoplastic resin, and has the same processability as thermoplastic resin at high temperatures, so it is useful for footwear, plastic modification,
Widely used in asphalt, adhesive and other fields. In addition, when the vinyl aromatic hydrocarbon content is relatively high, a thermoplastic resin that is transparent and has excellent impact resistance can be obtained, so its usage has increased in recent years, mainly in the food packaging container field, and its applications have also expanded. It is becoming more diverse. Such block copolymers are generally produced using an organolithium compound as an initiator, and a polymer with good color tone cannot be obtained unless an appropriate reaction termination method is applied after the polymerization reaction is completed. Therefore, several methods have been attempted to improve this drawback. For example, Japanese Patent Publication No. 54-2679 discloses that after adding water/carbon dioxide/phenolic antioxidant to the hydrocarbon solvent of activated block copolymer,
A method for directly removing the solvent by treatment at a temperature in the range of 200°C is described, and Japanese Patent Publication No. 55-7459 describes a method in which the hydrocarbon solvent of the block copolymer is heated,
Alternatively, a method is described in which the organic acid compound is brought into contact with an aqueous solution of an organic acid compound before being mixed with heated water and stripped of the solvent. Furthermore, Japanese Patent Application Laid-Open No. 168612/1983 describes a method in which boric acid is added to a polymer, and then a stabilizer is added to recover the polymer. [Problems to be Solved by the Invention] However, although these methods improve the color tone immediately after production, after long-term storage, especially in containers such as kraft paper bags or cardboard boxes, the cause Although it is not necessarily clear, it has the problem of yellowing. Under these circumstances, the present inventors have proceeded with studies to obtain a polymer that has excellent color tone immediately after production and color fastness during long-term storage in containers such as kraft paper bags and cardboard boxes. As a result, by combining one or more inorganic acids and/or organic acids with a specific phenolic compound, the objective was achieved and the present invention was completed. [Means for solving the problems] That is, the present invention is as follows. (1) A polymer solution obtained by polymerizing a conjugated diene and/or a vinyl aromatic hydrocarbon using an organolithium compound as a polymerization initiator, or a polymer solution obtained by further adding a polymerization terminator to the polymer solution. , to a polymer solution substantially in the absence of water, (i) after adding one or more organic acids in an amount of 0.05 to 5 equivalents relative to the organolithium compound, (ii) following the general formula [], [ ] and [ ] at least one selected from the phenolic compounds shown in [ ] per 100 parts by weight of the polymer.
0.05-5 parts by weight (In the above formula, R ₁ is an alkyl group having 1 to 4 carbon atoms, R ₂ is an alkenyl group having 2 to 4 carbon atoms, and R ₃ is an alkenyl group having 2 to 4 carbon atoms.
tert-butyl group or cyclohexyl group, R ₄ represents hydrogen or an alkyl group having 1 to 18 carbon atoms. ) A method for producing a polymer composition, which comprises: (2) After adding one or more organic acids in (i), at least one phenolic compound selected from the general formulas [], [], and [] in (ii) is blended. , the method for producing a polymer composition according to item (1) above, which comprises removing the solvent. (3) After adding one or more organic acids in (i), remove part or all of the solvent, and then remove the phenols represented by the general formulas [], [], and [] in (ii). The method for producing a polymer composition according to item (1) above, which comprises blending at least one selected from the grouping compounds and removing the remaining solvent. The present invention will be explained in detail below. The polymer used in the present invention can be prepared in a hydrocarbon solvent.
It is produced by polymerizing a conjugated diene and/or a vinyl aromatic hydrocarbon using an organolithium compound as an initiator. Polymers of conjugated dienes or vinyl aromatic hydrocarbons can be produced by any known method, including anionic polymerization of conjugated dienes or vinyl aromatic hydrocarbons with an organolithium compound in an inert hydrocarbon solvent. It can be manufactured by. When a conjugated diene and a vinyl aromatic hydrocarbon are used as monomers, the composition ratio of the conjugated diene and the vinyl aromatic hydrocarbon in the resulting polymer is not particularly limited, but is generally 99.9:0.1 to 0.1:99.9, preferably
It can be changed within the range of 98:2 to 5:95. The polymer consisting of a conjugated diene and a vinyl aromatic hydrocarbon may be a random copolymer or a block copolymer, and may be prepared by any known method in an inert hydrocarbon solvent. It can be produced by anionic polymerization using an organic lithium compound. For example, random copolymers are covered by U.S. Patent 3094514.
It can be prepared by feeding a mixture of a conjugated diene and a vinyl aromatic hydrocarbon to a polymerization vessel at a slower than normal polymerization rate, as described in that application. Alternatively, as described in U.S. Pat. No. 3,451,988, a random copolymer is produced by copolymerizing a mixture of a conjugated diene and a vinyl aromatic hydrocarbon in the presence of a polar compound or a randomizing agent, which will be described later. be able to. On the other hand, as a method for producing block copolymers,
For example, Special Publication No. 36-19286, Special Publication No. 43-17979
Publication number, Special Publication No. 32415, Special Publication No. 1977-
Publication No. 36957, Special Publication No. 1972-2423, Special Publication No. 1973
-4106 Publication, Special Publication No. 56-28925, Special Publication Sho
Examples include the method described in Publication No. 51-49567. By these methods, block copolymers have the general formula: (AB)n, A(-B-A)n, B(-A-B)
n (In the above formula, A is a polymer block mainly composed of vinyl aromatic hydrocarbons, and B is a polymer block mainly composed of conjugated dienes. The boundary between A block and B block is not necessarily clearly distinguished. (Also, n is an integer greater than or equal to 1.) Or the general formula, [(B-A) _o ] _n+1 ---X, [(A-B) _o ] _n+1 --
--X [(B-A) _o B] _n+1 ---X, [(A-B) _o A] _n
+1 ---X (In the above formula, A and B are the same as above,
X represents, for example, a residue of a coupling agent such as silicon tetrachloride, tin tetrachloride, or epoxidized soybean oil, or a residue of an initiator such as a polyfunctional organolithium compound. m
and n is an integer of 1 or more. ) is obtained as a block copolymer. In the above formula, the polymer block mainly composed of vinyl aromatic hydrocarbons refers to copolymer blocks of vinyl aromatic hydrocarbons and conjugated dienes containing 50% by weight or more of vinyl aromatic hydrocarbons, and/or vinyl This refers to an aromatic hydrocarbon homopolymer block, and a polymer block mainly composed of conjugated diene refers to a copolymer block of a conjugated diene and a vinyl aromatic hydrocarbon containing more than 50% by weight of conjugated diene, and/or Or a conjugated diene homopolymer block. The vinyl aromatic hydrocarbons in the copolymer block may be uniformly distributed or tapered. Further, the polymer portion may coexist with a plurality of portions in which vinyl aromatic hydrocarbons are uniformly distributed and/or portions in which vinyl aromatic hydrocarbons are distributed in a tapered manner. The block copolymer thus obtained exhibits properties as a thermoplastic elastomer when the vinyl aromatic hydrocarbon content is 60% by weight or less, preferably 55% by weight or less, and the vinyl aromatic hydrocarbon If the content exceeds 60% by weight, preferably 65% by weight
In the above cases, the resin exhibits characteristics as a thermoplastic resin. In the present invention, vinyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, etc. A particularly common example is styrene. These may be used not only alone, but also as a mixture of two or more. In the present invention, a conjugated diene is a diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,
3-butadiene, 1,3-pentadiene, 1,3
-hexadiene, etc., and particularly common ones include 1,3-butadiene and isoprene. These may be used not only alone, but also as a mixture of two or more. Hydrocarbon solvents include aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, octane, isooctane, cyclopentane,
Alicyclic hydrocarbons such as methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane, or aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene can be used. These may be used not only alone, but also as a mixture of two or more. Organolithium compounds are organic monolithium compounds in which one or more lithium atoms are bonded in the molecule, such as ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium,
Examples include tert-butyl lithium, hexamethylene dilithium, butadienyl dilithium, and isoprenyl dilithium. These may be used not only alone, but also as a mixture of two or more. In the production of the polymer used in the present invention, the polymerization rate is adjusted, the microstructure (cis, trans, vinyl ratio) of the polymerized conjugated diene moiety is changed, and the reactivity ratio of the conjugated diene and the vinyl aromatic hydrocarbon is adjusted. Polar compounds and randomizing agents can be used for such purposes. As polar compounds and randomizing agents, ethers, amines, thioethers,
Examples include phosphoramide, alkylbenzene sulfonate, potassium or sodium alkoxide, and the like. Examples of suitable ethers are dimethyl ether, diethyl ether, diphenyl ether and tetrahydrofuran, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether. As the amines, in addition to tertiary amines such as trimethylamine, triethylamine, and tetramethylethylenediamine, cyclic tertiary amines can also be used. Phosphines and phosphoramides include triphenylphosphine and hexamethylphosphoramide. Randomizing agents include potassium or sodium alkylbenzene sulfonates, potassium or sodium butoxide, and the like. The polymerization temperature for producing the polymer used in the present invention is generally -10°C to 150°C, preferably 40°C.
to 120℃. The time required for polymerization varies depending on the conditions, but is usually within 48 hours, particularly preferably 1 to 10 hours. Further, it is desirable to replace the atmosphere of the polymerization system with an inert gas such as nitrogen gas. The polymerization pressure is not particularly limited as long as it is within a pressure range sufficient to maintain the monomer and solvent in a liquid phase within the above polymerization temperature range. Furthermore, care must be taken to avoid contamination of the polymerization system with impurities that would inactivate the catalyst and living polymer, such as water, oxygen, carbon dioxide, and the like. The weight average molecular weight of the polymer thus obtained is generally 5,000 to 5,000,000, preferably 10,000 to 5,000,000.
1000000. The amount of hydrocarbon in the polymer solution is generally 50 parts by weight to 100 parts by weight of the polymer.
2000 parts by weight. Depending on the properties of the polymer, the polymer may be insoluble in the hydrocarbon solvent and may be obtained in a suspended state. The polymer obtained above contains 0.05 to 5 equivalents, preferably 0.05 to 5 equivalents, based on the organolithium compound using one or more organic acids as an initiator for the polymer.
Add 0.2 to 2 equivalents. If the blending amount of the organic acid is less than the above range, the effect of improving the color tone which is the objective of the present invention will be insufficient, and conversely, if it exceeds the above range, the improvement effect beyond the range of the present invention will not be recognized. Moreover, this is not preferable because it causes a problem of deterioration in whitening resistance when immersed in hot water. The organic acid used in the present invention is an organic compound having acidity in a broad sense, and includes compounds such as carboxylic acid, sulfonic acid, sulfinic acid, and phenol, but is preferably an organic compound containing a carboxyl group and the following: Preferably. (1) Fatty acid having 8 or more carbon atoms (2) Rosin acid (3) Oxycarboxylic acid (4) Aromatic carboxylic acid Specific examples of fatty acids preferably used in the present invention include octylic acid, capric acid, lauric acid, and myristic acid. acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linoleic acid, ricinoleic acid, phenic acid, castor hydrogenated fatty acid, beef tallow fatty acid, or mixtures thereof. Rosin acid may also be a hydrogenated product thereof. The oxycarboxylic acid is a compound having at least one hydroxy group and at least one carboxyl group in the molecule, such as glycolic acid, lactic acid, tartaric acid, citric acid, malic acid, oxyvaleric acid, 2-hydroxystearic acid, Examples include salicylic acid, o-oxycinnamic acid, and mixtures thereof. Aromatic carboxylic acids include benzoic acid, chlorobenzoic acid, aminobenzoic acid,
Examples include cinnamic acid, phenyl acetic acid, and mixtures thereof. In the present invention, it is necessary to blend one or more organic acids substantially in the absence of water in order to obtain a composition with excellent hot water whitening resistance. Here, blending in the substantial absence of water means that the organic acid is not dissolved in a large amount of water and added. Specifically, it is used as an initiator for the polymer. 10 for organolithium compounds
This means that water is added in a state in which only an equivalent amount or less, preferably 5 equivalents or less, of water is present. In addition, when the organic acid coexists with water in the form of water of crystallization, etc., the addition state is assumed to be carried out in the substantial absence of water. In the present invention, before blending the organic acid,
Alternatively, a polymerization terminator may be added at the same time. As a terminator, a known terminator other than water that can deactivate a living polymer produced by an organolithium compound, such as a compound having active hydrogen, can be used, but preferred ones are alcohols (methanol, ethanol, propanol, etc.), polyhydric alcohols (ethylene glycol, propylene glycol, glycerin, etc.), primary amines, secondary
amines and mixtures thereof. these are,
It is generally used in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the polymer. Next, the phenolic compound used in the present invention is at least one selected from the phenolic compounds represented by the general formulas [], [], and [].
It is a seed. Specific examples of substituent R ₁ include methyl group,
Examples include ethyl group, propyl group, isobutyl group, tert-butyl group, but especially methyl group or tert-butyl group.
Butyl group is preferred. R ₂ is an alkenyl group having 2 to 4 carbon atoms, and specific examples include an ethenyl group, an isopropenyl group, a propenyl group, an isobutenyl group, a butenyl group, and the like. Particularly preferred is an ethenyl group. Preferred R ₃ is tert-butyl. Specific examples of substituent R ₄ include hydrogen methyl group,
Examples include ethyl group, propyl group, and butyl group, with hydrogen or methyl group being particularly preferred. The above phenol compound is 0.05 parts by weight per 100 parts by weight of the polymer.
It is used in an amount of 5 parts by weight, preferably 0.1 to 2 parts by weight. The amount of the above phenolic compound is
If it is less than 0.05 parts by weight, it is not preferable because stability during high-temperature processing is poor and gelation and deterioration of color tone occur. On the other hand, even if the amount exceeds 5 parts by weight, the improvement effect in terms of stability and color tone during high-temperature processing beyond the scope of the present invention will not be exhibited. In the present invention, at least one kind selected from phosphorus stabilizers and sulfur stabilizers may be added in an amount of 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight, per 100 parts by weight of the polymer. A specific example of a phosphorus stabilizer is tris (nonylphenyl).
Phosphite, Cyclic neopentanetetrylbis(octadecyl phosphite), Tris(2,4-di-tert-butylphenyl) phosphorite, 4,4-butylidene-bis(3-methyl-6-tert-butylphenyl-di-tridecyl) ) Phosphite, 4,4'-biphenylene diphosphinic acid tetrakis (2,4-di-tert-butylphenyl), cyclic neopentanetetraylpis (2,4-di-tert-butylphenyl)
Examples include phosphite. Specific examples of sulfur stabilizers include dilauryl-3,3'-thiodipropionic acid ester, dimyristyl-3,3'-thiodipropionic acid ester, and distearyl-3,3'-thiodipropionic acid ester. , laurylstearyl-3,3'-thiodipropionic acid ester, pentaerythritol-
Tetrakis-(β-lauryl-thio-propionate), 3,9-bis-(2-dodecylthioethyl)-2,4,8,10-tetraoxaspiro[5,
5] Examples include undecane. A preferred method for obtaining the composition of the present invention is a polymer solution obtained by polymerizing a conjugated diene and/or a vinyl aromatic hydrocarbon using an organolithium compound as an initiator in a hydrocarbon solvent, or A method in which one or more organic acids are first added to the polymer solution to which the agent has been added, and then at least one of the phenolic compounds specified in the present invention is added, and then the solvent is removed, or the polymer solution This is a method in which one or more organic acids are added to the mixture, a portion or the entire amount of the solvent is removed, and then at least one of the phenolic compounds specified in the present invention is added, and the remaining solvent is removed. . The method for removing the solvent from the polymer solution may be any known method, such as heating the solution to evaporate the solvent, dispersing the solution in water or hot water, and blowing water vapor to evaporate the solution (steam). stripping method), a method in which a large amount of a precipitant such as methanol is added to precipitate the polymer and separate it from the solvent, a method in which the solution is vacuum dried, and a part of the solvent is evaporated in a flash tower, etc. Furthermore, a method of removing the solvent using a vented extruder can be adopted. Various additives can be added to the polymer composition obtained in the present invention depending on the purpose. For example, softeners such as oil, plasticizers, antistatic agents, lubricants, ultraviolet absorbers, flame retardants, pigments, inorganic fillers,
Organic fibers, inorganic fibers, reinforcing agents such as carbon black, and other thermoplastic resins can be used as additives. The polymer composition obtained in the present invention can be used for various purposes as described below, but a particularly suitable use is the heat-shrinkable material obtained by uniaxially, biaxially or multiaxially stretching the polymer composition. Applications include films, sheets, etc., which are printed with characters or designs and then used by being tightly attached to the surface of a packaged object such as a plastic molded product, metal product, glass container, porcelain, etc. by heat shrinking. It can be used as a material for so-called heat-shrinkable labels. Polymers used for such purposes include (i) a polymer block containing at least one vinyl aromatic hydrocarbon as a main component and at least one conjugated diene as a main component; ,
The main component is a block copolymer resin in which the weight ratio of vinyl aromatic hydropolymer and conjugated diene is 60/40 to 95/5, and the impact resistance, rigidity, (ii) has at least one polymer block mainly composed of vinyl aromatic hydrocarbon and at least one polymer block mainly composed of conjugated diene, for the purpose of improving slipperiness, stretching properties, etc.;
A block copolymer elastomer in which the weight ratio of vinyl aromatic hydrocarbon and conjugated diene is 10/90 or more and less than 60/40 (iii) Non-rubber modified styrenic polymer (iv) Rubber modified styrenic polymer A block copolymer composition in which at least one type of polymer is combined can also be suitably used. Block copolymer resins generally have a number average molecular weight of
50,000 to 500,000, preferably 80,000 to 350,000 can be used. Block copolymer elastomers can also be used as impact modifiers, and generally have a number average molecular weight of 20,000 to 250,000, preferably 40,000 to 250,000.
200000 items can be used. The non-rubber-modified styrenic polymer is obtained by polymerizing the vinyl-substituted aromatic hydrocarbon compound or a monomer copolymerizable therewith. Examples of monomers copolymerizable with the vinyl-substituted aromatic hydrocarbon compound include α-methylstyrene, acrylonitrile, acrylic esters, methacrylic esters, and maleic anhydride. Particularly preferred non-rubber modified styrenic polymers include polystyrene, styrene-α-methylstyrene copolymer, acrylonitrile-styrene copolymer, styrene-methacrylic acid ester copolymer, and styrene-maleic anhydride copolymer. These can be used alone or in a mixture of two or more. Rubber-modified styrenic polymers are obtained by polymerizing a mixture of a vinyl-substituted aromatic hydrocarbon compound or a monomer copolymerizable therewith with an elastomer, and polymerization methods include suspension polymerization, emulsion polymerization, bulk polymerization, and bulk polymerization. -Suspension polymerization etc. are commonly carried out. Monomers copolymerizable with vinyl-substituted aromatic hydrocarbon compounds include α-methylstyrene, acrylonitrile, acrylic ester,
Examples include methacrylic acid ester and maleic anhydride. Further, as the elastomer, natural rubber, synthetic isoprene rubber, butadiene rubber, styrene-butadiene rubber, high styrene rubber, etc. are used. These elastomers are generally 2 to 70 parts by weight, more generally 3 to 50 parts by weight per 100 parts by weight of the vinyl-substituted aromatic hydrocarbon compound or a monomer copolymerizable therewith, or dissolved in the monomer. In latex form, it is subjected to bulk polymerization, bulk-suspension polymerization, emulsion polymerization, etc. Particularly preferred rubber-modified styrenic polymers include high impact rubber-modified styrenic polymers (HIPS). Non-rubber-modified styrenic polymers can be used as stiffness improvers, and rubber-modified styrenic polymers can be used as stiffness, impact resistance, and slip property improvers. The blending amount of polymers (i) to (iv) is generally 100 parts by weight or less, preferably 0.5 to 50 parts by weight, each based on 100 parts by weight of polymer (i). In order to obtain a heat-shrinkable uniaxial, biaxial or stretched film from the block copolymer resin or block copolymer composition described above, the block copolymer or block copolymer composition is processed by a conventional T-die or cyclic process. From die to flat or tube shape 150~
Extrusion molding is carried out at 250°C, preferably 170 to 220°C, and the resulting unstretched product is substantially uniaxially, biaxially or multiaxially stretched. For example, in the case of uniaxial stretching, in the case of a film or sheet, it is stretched in the extrusion direction using a calendar roll, etc., or in the direction perpendicular to the extrusion direction using a tenter, etc., and in the case of a tube shape, it is stretched in the extrusion direction of the tube or in the circumferential direction. Stretch. In the case of biaxial stretching, in the case of a film or sheet, the extruded film or sheet is stretched in the longitudinal direction with a metal roll, etc., and then stretched in the transverse direction with a tenter, etc., and in the case of a tube shape, the extruded film or sheet is stretched in the longitudinal direction with a tenter, etc. They are stretched simultaneously or separately in the circumferential direction of the tube, that is, in the direction perpendicular to the tube axis. Stretching temperature is 60-110℃, preferably 80-100℃
The stretching ratio is 1.5 to 1.5 in the longitudinal and/or transverse directions.
It is preferred to stretch 8 times, preferably 2 to 6 times. If the stretching temperature is lower than 60°C, breakage will occur during stretching, making it difficult to obtain the desired heat-shrinkable film.
If the temperature exceeds 110°C, it is difficult to obtain a product with good shrinkage characteristics. The stretching ratio is selected within the above range to correspond to the shrinkage rate required depending on the application, but if the stretching ratio is less than 1.5 times, the heat shrinkage rate is low and it is not suitable for heat-shrinkable packaging. Further, a stretching ratio exceeding 8 times is not preferable in terms of stable production in the stretching process. In the case of biaxial stretching, the stretching ratios in the machine direction and the transverse direction may be the same or different. After uniaxial stretching or biaxial stretching, the heat-shrinkable film, etc., is then cooled and then heated for a short time at 60 to 105°C, preferably 80 to 95°C, if necessary.
For example, it is also possible to carry out a heat treatment for 3 to 60 seconds, preferably 10 to 40 seconds, to prevent natural shrinkage at room temperature. In order to use the heat-shrinkable film etc. obtained in this way as a heat-shrinkable packaging material or heat-shrinkable label material, the heat shrinkage rate at 80°C in the stretching direction is 15% or more, preferably 20%. It should be ~70%, more preferably 30-80%. If the heat shrinkage rate at 80℃ in the stretching direction is less than 15%, the shrinkage characteristics are poor, so it is necessary to adjust the process to a high and uniform temperature in the shrink packaging process, or to heat it for a long time. This is undesirable because it becomes impossible to package such products and shrink-wrapping processing capacity decreases. Note that the heat shrinkage rate at 80℃ refers to the thermal shrinkage rate at 80℃ for uniaxially stretched or biaxially stretched films, etc.
This is the heat shrinkage rate in each stretching direction of a molded product when immersed for 5 minutes in a heat medium such as hot water, silicone oil, or glycerin that does not inhibit the properties of the molded product. Furthermore, a heat-shrinkable film that has been uniaxially or biaxially stretched has a tensile modulus in the stretching direction.
It is suitable for the heat-shrinkable packaging material to be 5,000 Kg/cm ² or more, preferably 7,000 Kg/cm ² or more, and more preferably 10,000 Kg/cm ² or more. If the tensile modulus in the stretching direction is less than 5000 Kg/cm ² , it is not preferable because it causes sagging during the shrink wrapping process and normal packaging cannot be performed. When using a uniaxially stretched or biaxially stretched film as a heat-shrinkable packaging material, the temperature is 130 to 300°C, preferably 150 to 250°C to achieve the desired heat shrinkage rate.
It can be heat-shrinked by heating at a temperature of from several seconds to several minutes, preferably from 1 to 60 seconds, more preferably from 2 to 30 seconds. In addition, when using a heat-shrinkable film obtained by uniaxially stretching a block copolymer resin or a block copolymer composition as a heat-shrinkable label material, heat at 80°C in a direction perpendicular to the stretching direction. The shrinkage rate is
It is preferably less than 15%, preferably less than 10%, more preferably less than 5%. Therefore, substantially uniaxial stretching for heat-shrinkable labels means that the heat shrinkage rate at 80°C in the stretching direction is 15% or more, and the heat shrinkage rate at 80°C in the direction perpendicular to the stretching direction is 15%.
% or less. As the heat-shrinkable film, one whose thickness is generally adjusted to a range of 10 to 300 microns, preferably 30 to 100 microns is suitably used. [Example] The present invention will be explained in more detail with reference to Examples below. The block copolymers used in the examples were produced as follows. The weight ratio of polymer to solvent in each of the obtained polymer solutions was 1:4. [Block copolymer (A)] In a nitrogen gas atmosphere, 0.11 parts by weight of n-butyllithium was added to an n-hexane solution containing 15 parts by weight of 1,3-butadiene and 20 parts by weight of styrene, and the mixture was heated at 70°C for 2 hours. After polymerization for a period of time, an n-
A hexane solution was added and polymerization was carried out at 70°C for 2 hours. The obtained polymer had a styrene content of 40% by weight.
It was a block copolymer with an ABA structure. [Block copolymer (B)] In a nitrogen gas atmosphere, 0.11 parts by weight of n-butyllithium was added to a cyclohexane solution containing 15 parts by weight of styrene, and after polymerization at 70°C for 1 hour, 70% of 1,3-butadiene was added. A cyclohexane solution containing parts by weight was added and polymerized at 70°C for 2 hours. Thereafter, a cyclohexane solution containing 15 parts by weight of styrene was further added, and polymerization was carried out at 70°C for 1 hour. The obtained polymer had a styrene content of 30% by weight.
The structure was a block copolymer. [Block copolymer (C)] In a nitrogen gas atmosphere, 0.08 parts by weight of n-butyllithium was added to a cyclohexane solution containing 30 parts by weight of styrene and 0.3 parts by weight of tetrahydrofuran, and after polymerization at 70°C for 1 hour, A cyclohexane solution containing 20 parts by weight of , 3-butadiene and 50 parts by weight of styrene was added and polymerized at 70°C for 2 hours. The resulting polymer was A-B with a styrene content of 80% by weight.
It was a block copolymer with -A structure. [Block copolymer (D)] In a nitrogen gas atmosphere, 0.07 parts by weight of n-butyllithium was added to an n-hexane solution containing 15 parts by weight of 1,3-butadiene and 20 parts by weight of styrene, and the mixture was heated at 70°C for 2 hours. After polymerization for an hour, an n-hexane solution containing 15 parts by weight of 1,3-butadiene and 50 parts by weight of styrene and 0.02 part by weight of n-butyllithium were further added, followed by polymerization at 70 DEG C. for 2 hours. The obtained polymer is a mixture of a B-A-B-A structure block copolymer and a B-A structure block copolymer with a styrene content of 70% by weight, and the obtained polymer solution is It was in a suspension state. [Block copolymer (E)] In a nitrogen gas atmosphere, 0.15 parts by weight of n-butyllithium was added to a cyclohexane solution containing 75 parts by weight of styrene, and after polymerization at 70°C for 1 hour,
A cyclohexane solution containing 25 parts by weight of 1,3-butadiene was added and polymerized at 70°C for 2 hours. Thereafter, 5 parts by weight of epoxidized soybean oil was added to obtain a radial structure block copolymer having a styrene content of 75% by weight. [Block copolymer (F)] In a nitrogen gas atmosphere, 0.08 parts by weight of n-butyllithium was added to an n-hexane solution containing 80 parts by weight of 1,3-butadiene and 20 parts by weight of styrene, and the mixture was heated at 70°C for 2 hours. Polymerized for hours. The obtained polymer was a block copolymer of BA structure with a styrene content of 20% by weight. Examples 1 to 10 and Comparative Examples 1 to 7 For n-butyllithium compounds in which the organic acids shown in Table 1 were used as polymer initiators in the solution of the block copolymer (C) produced above. After 1.0 equivalent of each was added, the phenolic compounds shown in Table 1 were added, and then the solvent was removed by heating. Each of the obtained polymer compositions was extruded into pellets using a 30 mmφ extruder. The color tone, transparency, color fastness and whitening resistance of the obtained pellets were measured and the results are shown in Table 1. As is clear from Table 1, the polymer composition of the present invention has excellent color tone, transparency, color fastness, and whitening resistance. In addition, in Example 1, the amount of benzoic acid added was n
A polymer composition similar to Example 1 was obtained except that the amount was 10 equivalents relative to the -butyllithium compound. The resulting polymer composition had the same performance as the composition of Example 1 in terms of color tone, transparency, and discoloration resistance, but was slightly inferior in whitening resistance with a difference in cloudiness of about 10. Also, Example 1
A polymer composition similar to that of Example 1 was obtained except that the amount of AO-1 added was 10 parts by weight. The performance of the obtained polymer compositions was equivalent to that of the composition of Example 1.

【table】

【table】

[Table] Examples 11 to 17 and Comparative Examples 8 to 10 After adding the inorganic acid and/or organic acid shown in Table 2 to the block copolymer shown in Table 2, 100 parts by weight of the block copolymer 0.5 parts by weight of AO-1 and 1.0 parts by weight of AO-9 were added thereto, and then the solvent was removed by heating. 30 mm of each obtained polymer composition
It was extruded into pellets using a φ extruder. The properties of the pellets obtained are shown in Table 2. In addition, Comparative Example 8~
In No. 10, the amount of water contained in the inorganic acid was more than 10 equivalents relative to n-butyllithium used in the polymerization.

〔Effect of the invention〕

The polymer composition obtained by the present invention is transparent and has excellent color tone and discoloration resistance, especially yellowing resistance when stored for a long period of time in containers such as kraft paper bags or cardboard boxes. Take advantage of the sheet,
Films, injection molded products of various shapes, hollow molded products,
In addition to being used as a wide variety of molded products such as air pressure molded products and vacuum molded products, it can also be used as a modification material for various thermoplastic resins, as a material for footwear, as a material for adhesives and adhesives, as a modification material for asphalt, as a material for electric wires and cables, etc. Materials for vulcanized rubber, modifying materials for vulcanized rubber, home appliances, automobile parts,
It can be used as a material for industrial parts, household goods, toys, etc. In particular, the polymer composition of the present invention, in which an organic acid is blended with substantially no water, has excellent whitening resistance when immersed in hot water, so it is used in a humid atmosphere or in application fields where it comes into contact with water. For example, it can be effectively used in food containers, food packaging materials, packaging materials for food containers, toys, medical supplies, etc. In particular, the polymer composition obtained by the present invention has excellent color tone, color fastness,
Suitable for use in heat-shrinkable labels that require whitening resistance.

Claims (1)

[Scope of Claims] 1. A polymer solution obtained by polymerizing a conjugated diene and/or a vinyl aromatic hydrocarbon using an organolithium compound as a polymerization initiator, or a polymer solution obtained by further adding a polymerization terminator to the polymer solution. and after (i) adding one or more organic acids in an amount of 0.05 to 5 equivalents relative to the organolithium compound to a polymer solution substantially in the absence of water, (ii) the following general formula [] , [ ] and [ ] in an amount of 0.05 to 5 parts by weight per 100 parts by weight of the polymer.
Weight part (In the above formula, R ₁ is an alkyl group having 1 to 4 carbon atoms, R ₂ is an alkenyl group having 2 to 4 carbon atoms, and R ₃ is an alkenyl group having 2 to 4 carbon atoms.
tert-butyl group or cyclohexyl group, R ₄ represents hydrogen or an alkyl group having 1 to 18 carbon atoms. ) A method for producing a polymer composition, which comprises: