JPS62232402A - Production of polymer - Google Patents

Abstract

PURPOSE:To obtain the polymer excellent in resistance to loss of transparency, hue, etc., by adding an organic acid and a stabilizer to a living polymer obtained by polymerizing a conjugated diene in a hydrocarbon solvent in the presence of an organolithium compound as an initiator and removing the solvent from the mixture. 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-butyllithium) as an initiator. An organic acid (e.g., stearic acid or benzoic acid) or a stabilizer (e.g., 4-methyl-2,6-di-t-butylphenol) and a shortstop (e.g., ethanol) are added to the obtained living polymer in the absence of water. The solvent is removed from the polymer solution to obtain a polymer which does not cloud when immersed in hot water and is suitable for food containers, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a polymer that does not whiten when immersed in hot water and has excellent transparency and color tone.

[Conventional technology]

A copolymer consisting of a conjugated diene and a vinyl aromatic hydrocarbon is transparent and can be vulcanized without vulcanization if the binding mode is a block copolymer or the vinyl aromatic hydrocarbon content is relatively low. It has the same elasticity as natural rubber or 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. There is. 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 poor color tone;
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 156 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, JP-A-58-1686
No. 12 describes a method in which boric acid is added to a polymer and then a stabilizer is added to recover the polymer.

〔problem〕

However, although these methods improve the color tone, they generally have poor transparency, and furthermore, they become cloudy and lose transparency when left in a humid atmosphere for a long time or immersed in hot water.

Under these circumstances, the present inventors have proceeded with studies on a method to solve the above problems and obtain a polymer with excellent color tone and transparency. The present inventors have discovered that the objective can be achieved by adding an organic acid and a stabilizer (or a stabilizer and a terminator), and have completed the present invention.

[Means for solving the problem] That is, the present invention provides a living polymer obtained by polymerizing a conjugated diene or a conjugated diene and a vinyl aromatic hydrocarbon in a hydrocarbon solvent using an organolithium compound as an initiator.
Provided is a method for producing a polymer, comprising: (a) adding an organic acid (BL stabilizer or a stabilizer and a terminator) in the substantial absence of water, and then removing the solvent from the polymer solution; do.

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 the same with an organolithium compound in a vinyl hydrocarbon solvent.

The composition ratio of conjugated diene and vinyl aromatic hydrocarbon in the obtained polymer is not particularly limited, but is generally 99.9:
0.1-0.1:99.9, preferably 98:2-
It can be varied within a range of 5:95.

A polymer consisting of a conjugated diene and a vinyl aromatic hydrocarbon is
It may be a random copolymer or a block copolymer, and these can be produced by anionic polymerization with an organolithium compound in an inert hydrocarbon solvent by any known method.

For example, random copolymers 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 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. 48-2423, Japanese Patent Publication No. 48-4106, 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). , A+B-A)n, B+A-B).

(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 the A block and the B block is not necessarily clearly distinguished. In addition, n is an integer of 1 or more.) or the general formula, [:(B-A)n+wrX, [(A-B)nkaFX
((B-A+nB te X' C(A-B÷n A
7
and n is an integer of 1 or more. ) is obtained as a radial block copolymer. In addition, the above formula "smell"
, a polymer block mainly composed of vinyl aromatic hydrocarbons is a copolymer block of a vinyl aromatic hydrocarbon and a conjugated diene containing 50% by weight or more of a vinyl aromatic raw hydrocarbon, and/or a vinyl aromatic carbonized ice cream alone. A polymer block mainly composed of a conjugated diene is a copolymer block of a conjugated diene and a vinyl aromatic hydrocarbon containing more than 50% by weight of a conjugated diene, and/or a conjugated diene homopolymer block. Shows a combined block. The vinyl aromatic hydrocarbons in the copolymer block may be uniformly distributed or tapered.

The block copolymer thus obtained exhibits properties as a thermoplastic elastomer when the content of vinyl aromatic hydrocarbon is 60% by weight or less, preferably 55% by weight or less,
When the vinyl aromatic hydrocarbon 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, 0-methylstyrene, p-methylstyrene, p-methylstyrene,
Examples include -tert-butylstyrene, 3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, and vinylanthracene, among which 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 isoprene. These may be used not only alone, but also in combination for 2 seconds or more.

Hydrocarbon solvents include aliphatic hydrocarbons such as butane, pentane, hexane, impentane, heptane, octane, and isooctane, alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane, or benzene. , aromatic hydrocarbons such as toluene, ethylbenzene, and xylene. 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, inglobillithium, n-butyllithium, 5
ee-butyllithium, tert-butyllithium,
hexamethylene dilithium, butadienyl dilithium,
Examples include isoprenyl dilithium. These are 1
You may use not only seeds but also a mixture of two or more kinds.

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 or sodium alkoxides, and the like. appropriate knee 9
= -Examples of thyls are dimethyl ether, diethyl ether,
They are diphenyl ether, tetrahydrofuran, diethylene glycol dimethyl ether, and diethylene glycol dibutyl ether. As the amines, in addition to tertiary amines such as trimethylamine, triethylamine, and tetramethylethylenediamine, cyclic tertiary amines and the like can also be used. Phosphines and phosphoramides include triphenylphosphine and hextemethylphosphoramide. 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. Although the time required for polymerization varies depending on the conditions, it is usually within 48 hours, and 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 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 1,000,000. The amount of hydrocarbon in the polymer solution is generally 5 parts by weight per 100 parts by weight of the polymer.
0 parts by weight to 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; however, in the present invention, these will also be referred to as a polymer solution.

In the present invention, a stabilizer or a stabilizer and a terminator are added to the polymer solution obtained above in the substantial absence of water.

The organic acid referred to here 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, Examples include listic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linoleic acid, ricinoleic acid, behenic acid, tallow fatty acid, or mixtures thereof. Rosin acid may also be a hydrogenated product thereof.

Oxycarboxylic acids include compounds having at least one hydroxyl group and at least one carboxyl group in the molecule, such as glycolic acid, lactic acid, tartaric acid,
Examples include citric acid, malic acid, oxyvaleric acid, 2-hydroxystearic acid, salicylic acid, 0-oxycinnamic acid, and mixtures thereof. Aromatic carboxylic acid and 1. Examples include benzoic acid, chlorobenzoic acid, aba)benzoic acid, cinnamic acid, phenylacetic acid, or mixtures thereof. The amount added is 0.01 to 0.5 parts by weight, preferably 0.03 to 0 parts by weight per 100 parts by weight of the polymer.
．． This is part 33ii. If the amount added is less than 0 parts, the improvement in color tone that is the objective of the present invention will be insufficient;
．． If the amount exceeds 5 parts by weight, the whitening property during immersion in hot water will be impaired.

The above fatty acids, rosin acids, and oxycarboxylic acids may be added to the polymer as a hydrocarbon solution, but in the present invention, it is preferable to add them as they are in order to obtain a polymer with good devitrification resistance.

The stabilizer may be any of the known stabilizers that have been used in the past, and extremely well-known antioxidants such as phenol-based, organic phosphate-based, organic phosphite-based, amine-based, and sulfur-based antioxidants are used. . The stabilizer is generally used in an amount of 0.001 to 10 parts by weight per 100 parts by weight of the polymer. As the terminator, known terminators that can deactivate living polymers produced with organolithium compounds can be used, but preferred ones are alcohols (methanol, ethanol, clobal, etc.) and polyhydric alcohols. (ethylene glycol, phlopylene gellicol, glycerin, etc.) and mixtures thereof. These are generally 0.01 to 10 parts by weight per 100 parts by weight of the polymer.
Used in parts by weight range.

In addition, in the present invention, the organic acid itself is also a terminator, and its usage amount (b) is sufficient to deactivate the IJ ping polymer, or if the stabilizer used in conjunction with it has a deactivating effect, The use of agents is not necessary.

The organic acid, stabilizer, and terminator may be added in any order, or may be added at the same time.

In the present invention, the addition of organic acids and the like to the polymer solution must be carried out substantially in the absence of water.

For example, water is present in the form of impurities or water of crystallization in these additives, but the substantial absence of water here means that the amount of water is less than the amount of active living terminals in the polymer solution. It means each equivalent, preferably 2.0 equivalents, more preferably 2.0 equivalents or less. The presence of more water than this is the effect of the present invention,
In particular, the whitening property during immersion in hot water will be impaired.

Mixing of polymer solution with organic acid, stabilizer, and terminator, -14
= Contact is made using a normal stirring tank or line mixer. Further, the temperature used is 0 to 120°C, preferably 50°C to 100°C, and the time is sufficient within several minutes to several hours.

The next step in the invention is to remove the solvent from the polymer solution to which the organic acid and stabilizer or stabilizer and terminator have been added. At this time, the amount of solvent remaining is 10% of the polymer.
In order to obtain a polymer with excellent devitrification resistance, it is preferable to remove it until it becomes 30 parts by weight or less, preferably 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 in which the solution is vacuum-dried, a method in which a part of the solvent is evaporated in a flash tower, etc., and then further A method such as removing the solvent using a vented extruder can be adopted.

When a method in which the solvent is removed substantially in the absence of water, such as a flash method, this step may be performed simultaneously with or prior to the addition of the organic acid.

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 living block copolymer used in the examples was produced as follows. of the obtained polymer solution,
The weight ratio of polymer to solvent was 1:4 in both cases.

[Block copolymer (A)]

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 with n.
- 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]

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 703i 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 block copolymer having an ABA structure with a styrene content of 30% by weight.

[Block copolymer (C5)] In a nitrogen gas atmosphere, 17 parts by weight of n-butyllithium O,OS was added to a cyclohexane solution containing 30 parts by weight of styrene and 0.3 parts by weight of tetrahydrofuran, and the mixture was heated at 70°C for 1 hour. After the polymerization, a cyclohexane solution containing 20 parts by weight of 1,3-butadiene and 50 parts by weight of styrene was added and polymerized for 2 hours at 70°C.The obtained polymer had a styrene content of 80% by weight. It was a block copolymer with A structure.

[Block copolymer position]

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 with n.
- Add 0.07 parts by weight of butyllithium and
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° C. for 2 hours. The obtained polymer is a mixture consisting of a block copolymer with a B-A-B-A structure and a block copolymer with a B-A structure with a styrene content of 70% by weight! However, the obtained polymer solution was in the form of a suspension.

[Block copolymer (E)] In a nitrogen gas atmosphere, 1,3-butadiene = 1
8- Add o, osmit parts of Kn-butyllithium to an n-hexane solution containing 80 parts by weight and 20 M parts of methylene chloride, and
Polymerization was carried out at 0°C for 2 hours. The obtained polymer was a block copolymer having a BA structure with a styrene content of 20% by weight.

Examples 1 to 4 and Comparative Examples 1 to 3 Stearic acid and benzoic acid in the amounts shown in Table 1 were added as organic acids to the solution of the block copolymer particles prepared above, and 4-methyl-2 as a stabilizer was added. , 0.5 parts by weight of each of 6-tert-butylphenol and trisnonylphenyl osphite were added to 100 parts by weight of the polymer, and after stirring at 80°C for 5 minutes, the remaining solvent in the polymer was removed by heating, It was extruded using a 30rrxφ extruder to form a pellet. Press mold the pellets at 180℃ to a thickness of 2m+1
A sheet was prepared, and the color tone, transparency, and devitrification resistance of the test piece of 3 m in length and 4 m in width were measured. The results are shown in Table 1.

(Less than small margin) Table 1 *l: Indicates the blending amount based on 100 parts by weight of the polymer.

*2: Nippon Denshoku Kogyo Co., Ltd.* The b value was measured using an ND-VSB comprehensive vision measuring device to examine the color tone. The larger the b value, the greater the apparent yellowness.

b value is less than 5 ◎ b value is 5 to 100 b value is more than 10 × *8: Origin was measured in accordance with ASTM D-1003.

Origin is less than 5 ◎ Origin is 5-10 0 Origin is more than 10 × *4: Completely immersed in a constant temperature bath filled with 60℃ warm water
After allowing the test pieces to stand still for 150 minutes, the identity of each test piece was determined by AS.
Measurement was carried out in accordance with TM D-1003, and the difference between the degree of purity of a test piece of each polymer obtained by adding only the stabilizer and removing the solvent was determined, and evaluation was made based on this difference.

Difference is less than 5 ◎ Difference is 5 to 15 0 Difference is more than 15 Each test piece was created in the same manner as in Examples 1 to 4 except for the following. The obtained test pieces each showed the same color tone, transparency, and devitrification resistance as Examples 1 to 4.

Comparative Example 4 In Example 3, benzoic acid was added as an aqueous solution. The obtained polymer had poor IJIi properties and whitening properties when immersed in hot water. (Evaluation rank is ×.) Examples 9 to 14. Comparative Examples 5-8 Polymers shown in Table 2, other than Example 1 according to the compounding treatment
Each test piece was prepared in the same manner as above.

Table 2 shows the color tone, transparency, and whitening property of the obtained test piece when immersed in hot water.

(Leaving space below) -28 Example 15 In a nitrogen gas atmosphere, 0.07 i part of n-butyllithium and tetramethylethylenediamine were added to n-hexane containing 75 parts by weight of 1.3-butadiene and 25 parts by weight of styrene. 0.4 part by weight was added and polymerized at 50°C for 6 hours. After adding 0.1 part by weight of benzoic acid and 1 part by weight of 4-methyl-2,6-tert-butylphenol to the obtained polymer solution and mixing and stirring, the polymer solution was heated to about 120°C and the solvent was removed. The polymer thus obtained at °C had good color tone, transparency, and resistance to devitrification.

Example 16 Adding n-butyllithium 0,0 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 at 70°C for 4 hours. 0.05 parts by weight of benzoic acid and 4-methyl-2,
After adding 1 part by weight of 6-sheeter L-butylphenol and stirring, the solvent was removed by heating, and polybutadiene with a good color tone was obtained. [Effect] The polymer obtained by the method of the present invention is transparent and has a good color tone. Due to its excellent characteristics, it can be used as sheets, films, injection molded products of various shapes, and hollow molded products. In particular, the polymer obtained by the method of the present invention has excellent resistance to whitening and devitrification when immersed in hot water, so it can be used in a humid atmosphere or in fields where it comes into contact with water, such as food containers and food packaging materials. , toys, medical supplies, etc. In addition to the block copolymer of a conjugated diene and a vinyl aromatic hydrocarbon, the method of the present invention can also be used to produce a block copolymer of a conjugated diene and a vinyl aromatic hydrocarbon, a conjugated diene polymer, a vinyl aromatic hydrocarbon polymer, and a random copolymer of a conjugated diene and a vinyl aromatic hydrocarbon. It can also be used for merging.

Patent applicant: Asahi Kasei Industries, Ltd. =25=

Claims (1)

[Claims] A living polymer obtained by polymerizing a conjugated diene or a conjugated diene and a vinyl aromatic hydrocarbon in a hydrocarbon solvent using an organolithium compound as an initiator, in substantially the absence of water. A method for producing a polymer, which comprises adding (a) an organic acid, and (b) a stabilizer or a stabilizer and a terminator, and then removing the solvent from the polymer solution.