JPS62232401A - Improvement of hue - Google Patents

Abstract

PURPOSE:To improve the hue of a polymer, by adding a stabilizer to a polymer solution obtained by polymerizing a conjugated diene in a hydrocarbon solvent in the presence of an organolithium compound as an initiator, removing the solvent from the solution and adding a specified amount of an aromatic carboxylic acid to the obtained solid. CONSTITUTION:A conjugated diene (e.g., 1,3-butadiene) is polymerized or copolymerized with a vinyl aromatic hydrocarbon (e.g., styrene) in a hydrocarbon solvent such as hexane or toluene in the presence of an organolithium compound (e.g., n-butyllithim) as an initiator. A stabilizer (e.g., 4-methyl-2,6-di-t-butylphenol) or both of the stabilizer and a shortstop (e.g., ethanol) are added to the obtained polymer solution. After the solvent is removed from the polymer solution, 0.05-5 equivalent, per equivalent of the organolithium compound as the initiator, of an aromatic carboxylic acid (e.g., benzoic acid) is added to the product in the absence of water. In this way, the hue of the polymer can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for improving various color tones related to polymers, such as the color tone of the polymer itself, the color tone during processing and molding, or the color tone of final products.

[Conventional technology]

Block copolymers consisting of conjugated dienes and vinyl aromatic hydrocarbons are transparent and have the same properties as vulcanized natural rubber or synthetic rubber without vulcanization when the vinyl aromatic hydrocarbon content is relatively low. Because it has elasticity at room temperature and has processability similar to thermoplastic resin at high temperatures, it is suitable for footwear,
Widely used in plastic modification, asphalt, adhesive fields, etc., when the vinyl aromatic hydrocarbon content is relatively high, transparent thermoplastic resins with excellent impact resistance can be obtained. In recent years, its usage has been increasing, mainly in the field of food packaging and containers, and at the same time, its applications have been diversifying.

However, such block copolymers have poor color tone and
The disadvantage is that the molded product exhibits a yellowish tinge. 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 a hydrocarbon solvent of an active block copolymer, the solvent is treated at a temperature in the range of 150 to 200°C. A method for direct desolvation is described,
Japanese Patent Publication No. 55-7459 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, Japanese Patent Publication No. 58-16861
Publication No. 2 describes a method for recovering the polymer by adding boric acid to the polymer and then adding a stabilizer.

〔problem〕

However, although these methods improve the color tone of the polymer itself, it generally has poor transparency9, and furthermore, it becomes cloudy and loses its transparency when left in a humid atmosphere for a long time or immersed in hot water. has.

Furthermore, although the color tone of the polymer itself has been improved, the problem of coloring of the molded product during processing and molding again, or coloring of the molded product as a final product when stored for a long period of time, remains unsolved.

Under these current conditions, the inventors of the present invention have investigated these color-related problems and found that after adding a stabilizer to the polymer solution, the solvent is removed to reduce the amount of residual solvent to a specified amount or less, and after that, starting It has been found that the objective of F) can be achieved at once by blending and adding 0.05 to 5 equivalents of aromatic carboxylic acid to the organolithium compound used as the agent in the substantial absence of water. [Means for solving the problems] That is, the present invention involves polymerizing a conjugated diene or a conjugated diene and a vinyl aromatic hydrocarbon in a hydrocarbon solvent using an organolithium compound as an initiator. After a) adding a stabilizer, or a stabilizer and a terminator, to the polymer solution obtained, b) removing the solvent from the polymer solution, and then c) adding the stabilizer to the organolithium compound used as an initiator. Te 0.05
Provided is a method for producing a polymer, characterized in that ~5 equivalents of aromatic carboxylic acid are blended in substantially the absence of water.

The present invention will be explained in detail below.

In the method of the present invention, a conjugated diene or a vinyl aromatic hydrocarbon is polymerized with a conjugated diene using an organolithium compound as an initiator in a hydrocarbon solvent to produce a polymer solution.

It can be produced by anionically polymerizing a conjugated diene or n and a vinyl aromatic hydrocarbon with an organolithium compound in an inert hydrocarbon solvent.

When a conjugated diene and a vinyl aromatic hydrocarbon are used as monomers, the conjugated diene and vinyl aromatic hydrocarbon in the resulting polymer
There is no particular restriction on the composition ratio of i' to hydrogen, but in general K 9
It can be varied within the range of 9.9:0.1 to 0.1:99.9, preferably 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 subjecting a lithium compound to anionic polymerization.

For example, random copolymers can be made 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 U.S. Pat. No. 3,094,514. . 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, methods for producing block copolymers include, for example, Japanese Patent Publications No. 36-19286 and Japanese Patent Publication No. 43-17979.
Publication No. 46-32415, Special Publication No. 49-
Examples include the methods described in Japanese Patent Publication No. 36957, Japanese Patent Publication No. 4B-2423, Japanese Patent Publication No. 4106-1982, Japanese Patent Publication No. 28925-1982, Japanese Patent Publication No. 49567-1987, and the like. By these methods, block copolymers have the general formula: (A-B)n, A+B-A)n, BfA-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 diene. The boundary between the A block and the B block is not necessarily clear. There is no need to differentiate. Also, n is 1
is an integer greater than or equal to ), or −[(B
-A9Bactually (represents a residue of a ring agent or a residue of an initiator such as a polyfunctional organolithium compound.m and n are integers of 1 or more.).In the above formula, , a polymer block mainly composed of vinyl aromatic hydrocarbons is a copolymer block of vinyl aromatic hydrocarbons and a conjugated diene containing 50% by weight or more of vinyl aromatic hydrocarbons, or a vinyl aromatic hydrocarbon homopolymer. A polymer block mainly composed of a conjugated diene refers to a copolymer block of a conjugated diene and a vinyl aromatic hydrocarbon containing a conjugated diene in an amount exceeding 50% by weight, or a conjugated diene homopolymer block. The vinyl aromatic hydrocarbons in the copolymer block may be uniformly distributed or tapered.

The block copolymer thus obtained has a vinyl aromatic hydrocarbon content of 60% by weight or less, preferably 55% by weight or less.
When the content of vinyl aromatic hydrocarbon is less than 60% by weight, it exhibits properties as a thermoplastic elastic body, and when the content of vinyl aromatic hydrocarbon 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, 0-methylstyrene, I)-)f-styrene,
Examples include P-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, and styrene is 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, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene),
Examples include 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and particularly common ones include 1,3-butadiene and imprene. These may be used not only alone but also as a mixture of two or more. Examples of hydrocarbon solvents include aliphatic hydrocarbons such as butane, pentane, hexane, impentane, heptane, octane, and isooctane, cyclopentane, and methyl sulfate. Alicyclic hydrocarbons such as pentane, cyclohexane, methylcyclohexane, and ethylcyclohexane, or aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene can be used. These may be used not only for one meter, but also for a mixture of two or more types. Organolithium compounds are organic monolithium compounds in which one or more lithium atoms are bonded in the molecule, such as ethyllithium, n-propyllithium, inglobillithium, n-butyllithium, B
Examples include eQ-butyllithium, tert-butyllithium, hexamethylene dilithium, butadienyl dilithium, and imprenyl 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. Polar compounds and randomizing agents include ethers, amines, thioethers, phosphoramide,
Examples include alkylbenzene sulfonates, potassium/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 aminos, tertiary amines,
For example, in addition to 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 from -40°C to 150°C, preferably from 40°C to 120°C. The time required for polymerization varies depending on the conditions, but is usually within 48 hours, and is 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 ensure that there are no substances in the polymerization system that would inactivate the catalyst and living polymer.

The weight average molecular weight of the polymer thus obtained is generally t'c 5,000 to s, ooo, ooo, preferably 10,000 to 1,000,000. The amount of hydrocarbon in the polymer solution is generally from 50 parts by weight to 2000 parts by weight based on 100 parts by weight of the polymer. Depending on the properties 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.

A stabilizer or a stabilizer and a terminator are added to the polymer solution obtained above. Adding these at this stage is effective in preventing oxidative deterioration and thermal deterioration of the polymer when the solvent is removed in the next step. These may be added to the polymer solution as they are, or may be added after being dissolved in a hydrocarbon solvent. As the stabilizer, any of the known stabilizers that have been used conventionally may be used, and various known antioxidants such as phenol type, organic phosphate type, organic phosphite type, amine type, sulfur type, etc. are used. .

The stabilizer is generally 0.001 parts by weight per 100 parts by weight of the polymer.
~lO parts by weight.

As a terminator, a known terminator that can deactivate a living polymer produced with an organolithium compound can be used, but suitable ones include water, alcohol (methanol, ethanol, glopanol, etc.), polyhydric alcohol ( ethylene glycol, globylene glycol, glycerin, etc.) and mixtures thereof. These are generally polymeric Zo.

It is used in a range of 0.01 to 10 parts by weight. The terminator may be added before adding the stabilizer, or
It may be added at the same time as the stabilizer.

The solvent is then removed from the stabilizer, or the polymer solution to which the stabilizer and terminating agent have been added. At this time, the amount of the remaining solvent is 30 parts by weight or less, preferably 1 part by weight, based on 100 parts by weight of the polymer.
In order to obtain a polymer with excellent devitrification resistance, it is preferable to remove the amount until the amount becomes 0 parts by weight or less. 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), 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 of vacuum drying the solution, a method of evaporating a part of the solvent using a flash tower or the like, and then further removing the solvent using a vented extruder can be employed.

Next, the polymer from which the solvent has been removed by the above method is added in an amount of 0.05 to 5 equivalents, preferably 0.2 to 2 equivalents, more preferably 0.3 equivalents, based on the organic lithium compound used as an initiator.
~00 g equivalent of aromatic carboxylic acid is incorporated in the substantial absence of water. Examples of the aromatic carboxylic acid used here include benzoic acid, chlorobenzoic acid, aminobenzoic acid, cinnamic acid, phenylacetic acid, and mixtures thereof. If the blending amount of aromatic carboxylic acid is less than a predetermined amount, the various color tone improvement effects aimed at by the present invention will be insufficient.On the other hand, blending more than necessary will worsen the whitening property when immersed in hot water, and the polymer will It may lower the thermal stability of In the present invention, aromatic carboxylic acids and organic acids other than aromatic carboxylic acids can be used in combination. Examples of organic acids that can be used in combination include higher fatty acids having 10 or more carbon atoms, rosin acid, and oxycarboxylic acids. Specific examples of such higher fatty acids include capric acid, lauric acid, myristic acid, valmitic acid, stearic acid, oleic acid, linoleic acid, linolic acid, ricinoleic acid, behenic acid, 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, and 2-hydroxystearic acid. , salicylic acid, 0-oxycinnamic acid, or a mixture thereof. The amount of these acids that can be used in combination with the aromatic carboxylic acid must be equal to or less than the equivalent amount of the aromatic carboxylic acid used. Adding more than this is not preferable because it may cause a decrease in the thermal stability of the polymer or a deterioration in the whitening property when immersed in hot water.

Furthermore, in the present invention, the aromatic carboxylic acid must be added to the polymer solution in the substantial absence of water. For example, water is present in these additives in the form of impurities or crystallized water, but "substantially no water" here means that the amount of water is relative to the active living end in the polymer solution. 1/2 equivalent, preferably 1, more preferably 1/10
It means that it is less than the equivalent amount. The presence of more water than this will impair the effects of the present invention, especially the whitening property when immersed in hot water.

It is preferable to uniformly mix the above-mentioned aromatic carboxylic acid-added polymer using a conventional mixer.

Kneading machines include open call, intensive mixer, internal mixer, co-kneader, twin-screw rotor, -
A continuous kneader, an extruder, etc. attached to the polymer is used. However, if it is desired to further remove the solvent remaining in the polymer after adding the aromatic carboxylic acid in Method K of the present invention, the method described above may be used. The solvent may be removed by using any of the following solvent removal methods.

The most preferred embodiment of the method of the present invention is (1) to reduce the amount of residual solvent in the multipolymer by heating and evaporating the solvent from a polymer solution to which a stabilizer or a stabilizer and a terminator have been added, or by a steam stripping method. A method of reducing the amount to 5% by weight or less, preferably 1% by weight or less based on 100 parts by weight of the combined product, and then adding an aromatic carboxylic acid and kneading with an extruder (including a vented extruder), or (2) a stabilizer. Alternatively, in a method in which a part of the solvent is evaporated from a polymer solution to which a stabilizer and a terminator have been added in a 7-lush tower, the remaining solvent is further removed in a vented extruder to recover the polymer. One example is a method in which benzoic acid is added in a step in which the amount of residual solvent becomes 5 parts by weight or less, preferably 1 part by weight or less, based on 100 parts by weight of the polymer.

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 and inorganic fibers, reinforcing agents such as carbon black, and other thermoplastic resins. Can be used as an additive.

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

The block copolymers used in the examples were manufactured as follows. The weight ratio of the polymer to the solvent in each of the resulting polymer solutions was 1:4.

[Block copolymer (4)] In a nitrogen gas atmosphere, n-hexane solution containing 15 parts by weight of 1,3-butadiene and 20 parts by weight of styrene was added.
- Add 0.11 parts by weight of butyllithium and
After polymerization for an hour, an n-hexane solution containing 45 parts by weight of 1,3-butadiene and 20 parts by weight of styrene was further added, and the mixture was polymerized at 70° C. for 2 hours. The obtained polymer was a block copolymer having a B-A-B-A structure with a styrene content of 40% by weight.

[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. The mixture 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-B with a styrene content of 30% by weight.
It was a block copolymer with -A structure.

[Block copolymer (C)]

In a nitrogen gas atmosphere, 0.08 parts by weight of Kn-butyllithium, a cyclohexane solution containing 30 parts by weight of styrene and 0.3 parts by weight of tetrahydro7rane, was added, and the mixture was heated at 70°C.
After polymerization for 1 hour, a cyclohexane solution containing 20 parts by weight of 1,3-butadiene and 50 parts by weight of methylene fluoride was added and polymerized for 2 hours at 70°C. The obtained polymer was a block copolymer having an ABA structure with a styrene content of 80% by weight.

[Block copolymer]

In a nitrogen gas atmosphere, o, ovM parts of n-butyllithium were added to an n-hexane solution containing 15 parts by weight of 1,3-butadiene, 20M of styrene, and 20% of styrene. After polymerization at 70°C for 2 hours, n-hexane solution containing 15 parts by weight of l,3-butadiene and 50 parts by weight of styrene and n-
0.02 parts by weight of butyllithium was added and polymerized at 70°C for 2 hours. The resulting polymer had a styrene content of 70% by weight.
It was a mixture consisting of a block copolymer having a B-A-B-A structure and a block copolymer having a B-A structure, and the resulting polymer solution was in the form of a suspension.

[Block copolymer (g))]

In a nitrogen gas atmosphere, 0.15 parts of cyclohexane solution VCn-butyllithium containing 75 parts by weight of styrene was added.
After adding part by weight and polymerizing with 1:] at 70°C, 1,3
- A cyclohexane solution containing 25 parts by weight of 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 block copolymer with a radial structure having a styrene content of 75% by weight.

[Block copolymer (F)] In a nitrogen gas atmosphere, an n-hexane solution Vc containing 80 parts by weight of l,3-butadiene and 20 parts by weight of styrene.
1 o, os weight part of n-butyllithium was added, and the mixture was polymerized at 70°C for 2 hours. The resulting polymer had a styrene content of 20
It was a block copolymer with a B-A structure.

Examples 1 to 4 and Comparative Examples 1 to 4 A polymer of 4-methyl-2,6-tert-butylphenol and lysnonylphenyl phosphite was added as a stabilizer to the solution of the block copolymer (C) produced above. After adding 0.5 parts by weight of each to 100 parts by weight, the solvent was removed by heating until the amount of solvent remaining in the polymer reached the amount shown in Table 1.

Thereafter, aromatic carboxylic acid was added according to the formulation shown in Table 1, and the mixture was extruded into pellets using a 30 uφ extruder. If there was a large amount of residual solvent in the polymer, the solvent was removed by heating until the amount of residual solvent was reduced to about 1 weight or less, and then the polymer was applied to an extruder. The pellet was press-molded at 180°C and has a thickness of 2M as shown in the table.

*1: Indicates the amount of remaining solvent or blending amount based on 100 parts by weight of the polymer.

*2: The color tone was determined by measuring the b value using a comprehensive vision measuring device ND-V6B manufactured by Nippon Denshoku Industries Co., Ltd.

The larger the b value, the greater the apparent yellowness.

b value is 5 or less ◎ b value is 5 to 100 b value is more than 10 × * 3: Cloudiness was measured in accordance with ASTM D-1003.

Cloudiness is less than 5. ◎ Cloudiness is 5 to 0.0 Cloudiness is over 10. The degree of spearness of the test piece is A
The devitrification resistance was determined by determining the difference between the cloudiness of a test piece of each polymer obtained by adding only the stabilizer and removing the solvent. The larger this difference is, the worse the devitrification resistance is.

Difference in cloudiness is less than +5 ◎ Difference in cloudiness is +5 to +15 0 Difference in cloudiness exceeds +15 × *5: Extrude the pellet again using a 30Xφ extruder and change the color tone of the pellet was measured. The display was based on the same standards as *2.

Example 5-8 In Examples 1 to 4, except that 0.5 parts by weight of isopropyl alcohol was added in advance to 100 parts by weight of the block copolymer before adding the stabilizer to the solution of block copolymer C). Each test piece was prepared in the same manner as in Examples 1 to 4, and the obtained 7'Co test pieces exhibited color tone, transparency, and devitrification resistance equivalent to those in Examples 1 to 4, respectively.

Comparative Examples 5 and 6 In Example 1, benzoic acid was added to water at 0.2 and 1.0
parts by weight (8.9 and 44.4 equivalents relative to Li). All of the test pieces obtained had extremely poor whitening properties (evaluation rank: ×).

Examples 9 to 6 A polymer containing 0.5 parts by weight or less of residual solvent obtained in the same manner as in Example 1.2 was added according to the compounding procedure shown in Table 2.
Aromatic carboxylic acid was mixed in a 40wφ extruder at 200°C. Thereafter, the color tone, transparency, whitening property, and color stability of each polymer obtained were measured. The results are shown in Table 2.

Below is a blank space Example 17 0.07 parts by weight of n-butyllithium and 0.4 parts by weight of tetramethylethylenediamine were added to n-hexane containing 75 parts by weight of 1,3-butadiene and 25 parts by weight of styrene under a nitrogen gas atmosphere. The mixture was then polymerized at 50°C for 6 hours. 4-methyl-2,6-sheet was added to the obtained polymer solution.
After adding 1 part by weight each of rt-butylphenol and water, the polymer solution was heated to about 120°C, and the solvent was removed in a flash tower until the remaining solvent was 20 parts by weight (based on 100 parts by weight of the polymer). Removed. Thereafter, o and i parts by weight of benzoic acid were added to this polymer, and the polymer was extruded using a vent extruder, and at the same time, the remaining solvent was removed through the vent section. The thus obtained polymer had good color tone, transparency, and resistance to devitrification.

Example 18 0.0.0 of n-butyllithium was added to n-hexane containing 100 parts by weight of 1.3-butadiene in a nitrogen gas atmosphere.
5 parts by weight were added and polymerized for 4 hours at Ic. To the obtained polymer solution was added 4-methyl-2,6-ranol, di-tert-butylphenol, and an upper mold. After adding a total of 1 part by weight, the solvent was removed by heating until the remaining solvent was about 1 part by weight. 0.2 parts by weight of benzoic acid was added to 100 parts by weight of this polybutadiene, and the mixture was heated for 1 G with an 8φ inch roll at 60°C. As a result of kneading, polybutadiene with good color tone was obtained.

〔effect〕

Claims (1)

[Scope of Claims] A polymer solution obtained by polymerizing a conjugated diene or a conjugated diene and a vinyl aromatic hydrocarbon using an organolithium compound as an initiator in a hydrocarbon solvent is added with a) a stabilizer, or a stabilizer and a stopper. b) removing the solvent from the polymer solution, and then c) adding 0.05% of the solvent to the organolithium compound used as initiator;
A method for improving the color tone of a polymer, which comprises blending ~5 equivalents of an aromatic carboxylic acid in the substantial absence of water.