JPH0364521B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a polymer that has excellent color tone and transparency that does not whiten when immersed in hot water, and is excellent in preventing yellowing when heated at high temperatures. [Prior Art] A block copolymer composed of a conjugated diene and a vinyl aromatic hydrocarbon is transparent when the vinyl aromatic hydrocarbon content is relatively small, and can be used as a vulcanized natural rubber or vulcanized natural rubber without vulcanization. It has the same elasticity as synthetic rubber at room temperature and the same processability as thermoplastic resin at high temperatures, so it is widely used in the fields of footwear, plastic modification, asphalt, adhesives, etc. 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. However, such block copolymers have the disadvantage that the color tone is poor and the molded products exhibit a yellowish tinge. Therefore, several methods have been attempted to improve this drawback. For example, in Japanese Patent Publication No. 54-2679, in the hydrocarbon solvent of the activated block copolymer,
A method of directly removing the solvent by adding water/carbon dioxide/phenolic antioxidant and treating at a temperature in the range of 150 to 200°C is described.
No. 7459 describes a method in which a hydrocarbon solution of a block copolymer is heated or mixed with heated water and brought into contact with an aqueous solution of an organic acid compound before stripping the solvent. Also, JP-A-58-
Japanese Patent No. 168612 describes a method for recovering the polymer by adding boric acid to the polymer and then adding a stabilizer. [Problems to be solved by the invention] However, although the color tone is improved by these methods, the whitening resistance is poor, and the polymer obtained by the above method cannot be left in a humid atmosphere for a long period of time or immersed in water. As a result, it becomes cloudy and loses its transparency. Furthermore, there is a problem in that the yellowish tinge of the molded product increases due to the heat history of the extruder or injection molding machine. Under these circumstances, the inventors of the present invention have investigated methods for obtaining polymers with excellent color tone, resistance to whitening when immersed in hot water, and resistance to yellowing during high-temperature heating. The inventors have discovered that the objective can be achieved by using a specific amount of a specific compound as a quenching agent in the absence of water, and have completed the present invention. [Means for Solving the Problems] That is, the present invention provides a polymer solution obtained by polymerizing a conjugated diene and/or a vinyl aromatic hydrocarbon in a hydrocarbon solvent using an organolithium compound as an initiator. (i) for organolithium compounds using one or more organic acids as a polymer initiator in the absence of water as a polymerization terminator;
(ii) 0.005 to 5 parts by weight of one or more phenol compounds added to 100 parts by weight of the polymer;
The method for producing a polymer is characterized in that a stabilizer is then added to the polymer solution and the solvent is removed. The present invention will be explained in detail below. In the method of the present invention, a conjugated diene and/or vinyl aromatic hydrocarbon is polymerized in a hydrocarbon solvent using an organolithium compound as an initiator to produce a polymer solution. 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 can be prepared by any known method in an inert hydrocarbon solvent. It can be produced by anionic polymerization with a 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. 1984-28925, Special Publication No. 1971-
Examples include the method described in Publication No. 49567. By these methods, block copolymers can be produced with the general formula: (A-B) _o , A(-B-A) _o , B(-A-B) _o (in the above formula, A represents a vinyl aromatic hydrocarbon). B is a polymer block mainly composed of conjugated diene. The boundary between A block and B block does not necessarily have to be clearly demarcated. Also, n is an integer of 1 or more. ) 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 a residue of an initiator such as a polyfunctional organolithium compound. (m and n are integers of 1 or more). 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 copolymer portion may include a plurality of portions in which vinyl aromatic hydrocarbons are uniformly distributed and/or a plurality of 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 When the content exceeds 60% by weight, preferably 65% by weight or more, it exhibits properties as a thermoplastic resin. Vinyl aromatic hydrocarbons used in the method of the present invention include styrene, O-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3
Examples include -dimethylstyrene, α-methylstyrene, vinylnaphthalene, and vinylanthracene, with styrene being particularly common. These may be used not only alone, but also as a mixture of two or more. The conjugated diene used in the present invention is a diolefin having a pair of conjugated double bonds, for example, 1,3
-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, etc., but particularly common ones include Examples 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 with one or more lithium atoms 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 present invention, polar compounds and Randomizing agents can be used. Examples of polar compounds and randomizing agents include ethers, amines, thioethers, phosphoramides, alkylbenzene sulfonates, potassium or sodium alkoxides, 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 sulfonate, potassium or sodium butoxide, and the like. The polymerization temperature for producing the polymer in the method of the present invention is generally -40°C to 150°C, preferably
The temperature is between 40℃ and 120℃. The time required for polymerization varies depending on the conditions, but is usually within 48 hours.
Particularly preferred is 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 nature of the polymer, the polymer may be insoluble in the hydrocarbon solvent and may be obtained in a suspended state; however, in the present invention, these will also be referred to as a polymer solution. The present invention involves adding (i) one or more organic acids (hereinafter referred to as components) to the polymer solution obtained above in the substantial absence of water.
(i)); (ii) one or more phenolic compounds (hereinafter referred to as component (ii)) are used as a polymerization terminator. The organic acid of component (i) here refers to an organic compound having acidity in a broad sense, and includes, for example, a compound having a functional group such as carboxylic acid, sulfonic acid, phenol sulfinate, enol, imide, or oxime, but is preferred. is an organic compound containing a carboxyl group, and the following are preferred. (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, linolenic acid, ricinoleic acid,
Examples include behenic acid, tallow fatty acid, or a mixture 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. The phenol compound of component (ii) is a compound having at least one phenolic hydroxyl group in the molecule, such as butylated hydroxytoluene, butylated anisole, 4-hydroxymethyl-2,6-
di-t-butylphenol, n-octadecyl-
β-(4′-hydroxy-3′,5′-di-t-butylphenyl)propionate, triethylene glycol bis3(2-t-butylhydroxy-5-methylphenyl)propionate, 2-n-octyl-thio-4 ,6-di(4'-hydroxy-3',5'-di-t-butylphenoxy)
1,3,5-triazine, 2,4,5-trihydroxybutyrophenone, 2-(2'-hydroxy-
5'-methylphenyl)benzotriazole, propyl gallate, octyl gallate, dodecyl gallate, 2-(2'-hydroxy-3'-t-butyl-
5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3-5'-di-t
-butylphenyl)-5-chlorobenzotriazole, tetrakis[methylene-3-(3'-5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, tocopherol, 1,3,5
-Tris(4-t-butyl-3-hydroxy-
2,6-dimethylbenzyl)isocyanuric acid, methyl-P-hydroxybenzoate, 2,2'-methylenebis(4-methyl 6-t-butylphenol), 2,2'-methylenebis(4-ethyl 6-t
-butylphenol), 2,2'-dihydroxy-
3,3'-dicyclohexyl-5,5'-dimethyldiphenylmethane, bis-{3,3'-bis(4'-hydroxy-3'-t-butylphenyl)butylphenyl)butyric acid} glycol ester, 4,4'-butylidene bis -(6-t-butyl-m-cresol), tris(2-methyl-4-hydroxy-5-t-butylphenylbutane), 1,3,5-trimethyl-2,4,6-tris(3 , 5-di-t-butyl-4-hydroxybenzene, P-t-butylphenyl nalicisate, 2,4-di-t-butylphenyl-3,5-di-t-butyl 4-hydroxybenzoate, 2- t-Butyl-6-(3-t-butyl5-methyl-2-hydroxybenzyl)-4-methylphenyl acrylate, 2,4,-bis-(noctylthio)-6-(4-hydroxy-3, 5-G-t
-butylanilino)-1,3,5-triazine, etc., but phenolic stabilizers having two or more hindered phenols in the molecule are preferred because of their low volatility and prevention of yellowing during high-temperature heating. preferable. Specific examples are 2,2'-methylenebis(4-methyl-6-t-butyl-phenol), 2,2-methylenebis(4-ethyl-6-t-butyl-phenol), 4,4'-butylidenebis( 6-t-butyl-m-cresol), 4,4'-thiobis(6
-t-butyl-m-cresol), 1,1,3-
Tris(2-methyl-4-hydroxy-5-t-
butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 2,
2'-dihydroxy-3,3'-dicyclohexyl-
Examples include 5,5'-dimethyl-diphenylmethane. The amount of component (i) added is 0.05 to 5 equivalents, preferably 0.2 to 2 equivalents, and more preferably 0.3 to 0.9 equivalents of the organic acid based on the organic lithium compound used as an initiator in the absence of substantially water. Mix below. If the amount of organic acid added is less than the specified amount, the effect of improving various color tones, which is the objective of the present invention, will be insufficient.On the other hand, if it is added more than necessary, the whitening resistance during immersion in hot water will deteriorate, and the polymer will be damaged by heat. This is undesirable because it reduces stability and may even cause a bad odor during processing. The amount of component (ii) added is based on 100 parts by weight of the polymer.
0.005 to 5 parts by weight, preferably 0.01 to 3 parts by weight,
More preferably, it is 0.03 to 1 part by weight. If the amount added is less than 0.005 parts by weight, the yellowing prevention effect during high-temperature heating will be insufficient, and if it exceeds 5 parts by weight, no further improvement effect can be expected. The above components (i) and (ii) may be added to the polymer solution as they are, or may be added as a hydrocarbon solution, but in the present invention, components (i) and (ii) are used as terminators. and the addition to the polymer solution must be carried out in the substantial absence of water. Adding component (i) and component (ii) in the presence of water is not preferred because it impairs the whitening resistance during immersion in hot water. In the present invention, adding to the polymer solution in the substantial absence of water means adding the components (i) and (ii) by dissolving or dispersing them in a large amount of water. Specifically, it means no more than 10 equivalents to the active living ends in the polymer solution,
Preferably it is added in a state in which less than 5 equivalents of water, more preferably less than 1 equivalent, of water is present. In addition, when component (i) or component (ii) coexists with water in the form of crystal water, etc., these additions are performed in the substantial absence of water. The stabilizer may be any of the known stabilizers conventionally used, and various known antioxidants such as phenol type, organic phosphate type, organic phosphite type, amine type, and sulfur type are used. The stabilizer is generally used in an amount ranging from 0.001 to 10 parts by weight per 100 parts by weight of the polymer. Mixing and contacting of the polymer solution with the terminator component (i) and component (ii) is carried out using a conventional stirring tank, line mixer, or the like. Also, the temperature is 0℃~
A temperature of 120°C, preferably 50°C to 100°C is used. Further, a few minutes to several hours is sufficient. The next step in the present invention is to add component (i) and component
This is the step (ii) of removing the solvent from the polymer solution to which the terminator and stabilizer have been added. The solvent may be removed from the polymer solution by 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 solvent. stripping method), adding a large amount of precipitant such as methanol to precipitate the polymer and separating it from the solvent, vacuum drying the solution, and evaporating part of the solvent using 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 obtained by the method of 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 an additive. [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,
A cyclohexane solution containing 70 parts by weight of 1,3-butadiene 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 was a block copolymer having an ABA structure with a styrene content of 30% by weight. [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, further A cyclohexane solution containing 20 parts by weight of 1,3-butadiene and 50 parts by weight of styrene was added and polymerized at 70°C for 2 hours.
The obtained polymer had a styrene content of 80% by weight.
It was a block copolymer with a B-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, 0.08 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 4 and Comparative Examples 1 to 5 Components (i) and (ii) were added to the polymer solution of block copolymer (C) produced above according to the formulation method shown in Table 1. did. Thereafter, 0.5 parts by weight of each of 4-methyl-2,6-di-tert-butylphenol and trisnonylphenyl phosphite were added as stabilizers to 100 parts by weight of the polymer, and the solvent was removed by heating. The obtained pellets of each polymer were press-molded at 180°C to create a sheet with a thickness of 2 mm, and the color tone of a 3 cm long and 4 cm wide test piece, whitening resistance when immersed in hot water, and color stability during extrusion were evaluated. was measured. The results are shown in Table 1.

【table】

[Table] Comparative Example 6 Benzoic acid and 2,2'-methylenebis(4-methyl-6-t-butylphenol) in Example 1
Addition of 0.2 and 1.0 parts by weight of water (8.9 and
44.4 equivalents). All of the test pieces obtained had extremely poor whitening properties (evaluation rank: ×). Examples 5 to 12 Each test piece was prepared in the same manner as in Example 1, except that the polymer solution and compounding method shown in Table 2 were followed. The color tone, whitening resistance during hot water immersion, and color tone stability during extrusion of the obtained test piece were measured. The results are shown in Table 2.

〔Effect of the invention〕

The polymer obtained by the method of the present invention is transparent and has excellent color tone, so it can be used to make a wide variety of molds such as sheets, films, injection molded products of various shapes, blow molded products, pressure molded products, and vacuum molded products. It can be used as a product. In particular, the polymer obtained by the method of the present invention is
Because it has excellent whitening resistance when immersed in hot water, it can be used effectively in humid environments and in applications that come into contact with water, such as food containers, food packaging materials, toys, medical supplies, etc. Furthermore, the method of the present invention can be applied to block copolymers of conjugated dienes and vinyl aromatic hydrocarbons, as well as conjugated diene polymers, vinyl aromatic hydrocarbon polymers, and random copolymers of conjugated dienes and vinyl aromatic hydrocarbons. It can also be used in polymers.

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 an initiator in a hydrocarbon solvent in the substantial absence of water. As a terminator (i) For organolithium compounds using one or more organic acids as polymer initiators;
(ii) 0.005 to 5 parts by weight of one or more phenol compounds added to 100 parts by weight of the polymer;
A method for producing a polymer, which comprises subsequently adding a stabilizer to the polymer solution and removing the solvent.