JPH01275604A - Manufacture of polymer - Google Patents

Abstract

PURPOSE:To prevent gelation and to improve the color tone, by adding a semipolar boric acid ester compound and a stabilizer to a specific polymer solution and removing the solvent. CONSTITUTION:A conjugated diene compound (a) (e.g., 1,3-butadiene) and, if desired, an aromatic vinyl compound (b) (e.g., styrene) are polymerized in the presence of an initiator (c) comprising an organolithium compound in a hydrocarbon solvent (d) at 0-150 deg.C for 15min-5hr with the compositional ratio of (a) to (b) being 97-5:3-95, thereby producing a solution (A) of a polymer having a weight-average molecular weight of 10,000-1,000,000. A semipolar boric acid ester compound (B) (e.g., diglycerol borate) in an amount of 0.01-1.0pts.wt. for 100pts.wt. of the polymer in the component (A) and a stabilizer (C) in an amount of 0.005-10pts.wt. for 100pts.wt. of the polymer in the component (A) are added to the component (A), the mixture is mixed at 30-120 deg.C for a few min-a few hr, and the component (d) is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a method for producing a polymer which has excellent color tone and is stabilized against gel formation.

b. Conventional technology Conjugated diene polymers using organolithium compounds as initiators or random copolymers of conjugated diene compounds and aromatic vinyl compounds have extremely excellent practical physical properties such as wear resistance, low-temperature properties, and dynamic properties. Because of these properties, it is widely used in vulcanized rubber products such as tires and impact-resistant polystyrene resins.

When the copolymer of a conjugated diene compound and an aromatic vinyl compound is a block copolymer, it is widely used as a thermoplastic resin for plastic modifiers, footwear, and food packaging containers.

However, such polymers have poor color stability, become yellow or brown during storage, and their manufacturing process
In particular, there is a problem in that gel (crosslinked polymer) is generated during the finishing process (dehydration and drying process) and remains as a foreign substance in the product, significantly reducing the commercial value.

Therefore, several methods have been proposed to improve these problems.For example, Japanese Patent Application Laid-Open No. 168612/1983 describes a method of recovering a polymer by adding boric acid and then adding a stabilizer. There is. Furthermore, JP-A No. 60-231717 describes a method in which a stabilizer and a polymerization terminator are added, a solvent is removed from a polymer solution, and then a higher fatty acid or rosin acid and an oxycarboxylic acid are added. Showa 62-23
No. 2402 describes a method of adding an organic acid to a living polymer in the absence of water.

Problems that the C0 invention aims to solveHowever, although these methods improve the color tone of the polymer and the thermal stability during storage, they are still not sufficient and are particularly effective against gel formation during the finishing process of the polymer. In view of this situation, the present inventors have worked diligently to solve the above problems and provide a polymer that has excellent color tone and is stabilized against gel formation during the finishing process. As a result of research, it was discovered that the objective could be achieved by adding (1) a semipolar boric acid ester compound and (2) a stabilizer to a polymer solution, and the present invention was completed.

Means for Solving the d0 Problem The present invention involves polymerizing a conjugated diene compound or copolymerizing a conjugated diene compound and an aromatic vinyl compound in a hydrocarbon solvent using an organolithium compound as an initiator. A method for producing a polymer, which comprises adding (1) a semipolar boric acid ester compound and (2) a stabilizer, and then removing a solvent from the polymer solution.

I will provide a.

The present invention will be explained in detail below.

In the method of the present invention, first, a conjugated diene compound or a conjugated diene compound and an aromatic vinyl compound are anionically polymerized in a hydrocarbon solvent using an organolithium compound as an initiator to produce a polymer solution. A conjugated diene polymer or a copolymer of a conjugated diene compound and an aromatic vinyl compound can be produced by a known method.

In the case of a copolymer of a conjugated diene compound and an aromatic vinyl compound, the composition ratio of the conjugated diene compound and the aromatic vinyl compound is not particularly limited, but can generally be contained in a range of 97:3 to 5:95. Further, the bonding mode may be a random copolymer or a block copolymer.

For example, random copolymers can be prepared by feeding a mixture of a conjugated diene compound and an aromatic vinyl compound to a polymerization reactor at a rate slower than the polymerization rate, as described in US Pat. No. 3,094,514. In addition, 3 US patents
451988, by copolymerizing a mixture of a conjugated diene compound and an aromatic vinyl compound in the presence of a polar compound randomizing agent such as an ether or an amine to produce a random copolymer. I can do it.

On the other hand, methods for producing block copolymers include known methods (for example, Japanese Patent Publication No. 36-19286, Japanese Patent Publication No. 43-1
It can be produced by sequentially polymerizing an aromatic vinyl compound and a conjugated diene compound using an organolithium compound as an initiator in accordance with the method described in No. 7979, etc.). In this way (A
Various types of block copolymers can be obtained, such as -B), (AB), -A, (AB), -X, (where n is 1 or more).

Here, the conjugated diene compound is 1,3-butadiene,
1.3-pentadiene, isoprene, 1゜3-hexadiene, 2,4-hexadiene, 2゜3-dimethyl-1,
In addition to 3-butadiene and 2-ethyl-1,3-butadiene, there are various branched conjugated diene compounds having 4 to 7 carbon atoms, and 1,3-butadiene and isoprene are especially used.

In addition, aromatic vinyl compounds include styrene, α-methylstyrene, P-methylstyrene, vinyltoluene,
Examples include vinylnaphthalene, vinylethylbenzene, vinylxylene, and styrene is particularly preferred.

Examples of the hydrocarbon solvent used as the polymerization solvent include pentane, hexane, heptane, cyclohexane, methylcyclopenkune, benzene, toluene, and xylene.

These hydrocarbon solvents may be used alone or in combination of two or more.

Examples of organic lithium compounds include n-propyllithium, isopropyllithium, n-butyllithium, 5
ec-butyllithium, tert-butyllithium, n
-pentyl lithium, lithium toluene, benzyl lithium, 1,4-dilithio-n-butane, etc.,
-a, n-butyllithium and 5ec-butyllithium are used.

The polymerization temperature when producing the polymer in the method of the present invention is generally 0°C to 150°C, preferably 50°C to 120°C. The time required for polymerization varies depending on the conditions, but is usually 15 minutes to 5 hours, preferably is 30 minutes to 2 hours.

Coupling treatment with tin halide or the like can also be performed if necessary. In addition, the atmosphere of the polymerization reaction system is sufficiently replaced with an inert gas such as nitrogen gas to inactivate the catalyst and plating polymer. Care should be taken to avoid contamination with impurities such as water and oxygen.

The weight average molecular weight of the polymer thus produced is generally 1
0.000 to 1,000,000, preferably 50,
When the polymer is rubbery, the Mooney viscosity (ML, a at 100°C) is generally from 10 to 100, preferably from 20 to 80.

The present invention applies to the polymer solution obtained above. (1) Semipolar boric acid ester compound and (2) stabilizer Add.

The semipolar boric acid ester compound preferably used in the present invention is a reaction product of a polyhydric alcohol and boric acid, as described in Oil Chemistry, 29893 (1980), and is a semipolar boric acid ester compound that is a reaction product between a residual hydroxyl group and a boron atom. Compounds forming polar bonds include, for example, diglycerol borate, (mono- or di) fatty acid esters of diglycerol borate, and polyoxyethylene ethers of diglycerol borate.

The fatty acid mentioned here has 7 to 22 carbon atoms, and specific examples thereof include lauric acid, palmitic acid, stearic acid, and oleic acid. Further, polyoxyethylene having 1 to 30 +cuzcnzO+ chains is preferably used.

The amount of the semipolar boric acid ester compound added is 0.01 to 1.0 parts by weight, preferably 0.06 to 1.0 parts by weight, based on 100 parts by weight of the polymer.
02 to 0.9 parts by weight, more preferably o.

It is 3 to 0.8 parts by weight.

If it is less than 0.01 part by weight, the color stability of the polymer will be poor and gels will often occur during the finishing process. When the semi-polar boric acid ester is a transparent block copolymer such as styrene-butadiene-stynarene, the product becomes opaque, which is undesirable.The semipolar borate ester may be added after anionic polymerization or may be added together with a polymerization terminator, or It may be added after the polymerization terminator is added after the two-ion polymerization.

As the stabilizer, various known antioxidants such as hindered phenol type, organic phosphite type, sulfur type, amine type, etc. are used. It can be used as a species or a mixture of two or more.

The stabilizer is generally used in an amount of 0°005 per 100 parts by weight of the polymer.
It is used in a range of 10 parts by weight.

As the polymerization terminator, known terminators that can deactivate living polymers produced with organolithium compounds can be used, but suitable ones include water, alcohol (
methanol, ethanol, isopropanol, etc.) polyhydric alcohols (ethylene glycol, propylene glycol, glycerin, etc.) and mixtures thereof.

These terminators are generally used in amounts of 0 to 100 parts by weight of polymer.
．． It is used in a range of 0.005 to 1 part by weight.

In the present invention, since the semipolar boric acid ester compound itself acts as a polymerization terminator, it is not necessary to use a polymerization terminator if the amount used is sufficient to deactivate the living polymer.

Further, although the amounts of the semi-polar boric ester compound and the stabilizer may be added first, it is preferable that the semi-polar boric ester compound is added first.

The polymer solution, semi-polar boric acid ester compound, stopper, and stabilizer are brought into contact with each other in a conventional stirring tank, line mixer, static mixer, or the like. The mixing temperature is 30 to 120°C, preferably 50 to 110°C.
Temperatures of 0.degree. C. are used and mixing times of several minutes to several hours are sufficient.

The next step in the present invention is the step of removing the solvent from the polymer solution to which the semipolar boric acid ester compound, terminator, and stabilizer have been added.The method for removing the solvent from the 6-polymer solution can be any known method. For example, a polymer solution is often dispersed in hot water, steam is blown in to evaporate the solvent to obtain a crumb-like polymer, and then the polymer is dehydrated and dried using a screw dryer or the solvent is directly removed using a vent extruder. methods can be adopted.

e. Examples Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Polybutadiene rubber (A)) 1,3-Butadiene 10 from the bottom of the polymerization reactor equipped with a stirrer
0 parts by weight, 600 parts by weight of cyclohexane, and 0.06 parts by weight of n-butyllithium were continuously fed into the reactor using a metering pump so that the average residence time in the reactor was 2 hours. The temperature was maintained at 100° C. throughout, and the polymer solution was continuously drawn out from the top of the reactor. The obtained polymer was a polybutadiene rubber having a Mooney viscosity (MLM4100°C) of 60.

(Random copolymer (B)) 1,3-butadiene 7 was added to a reactor equipped with a stirrer under a nitrogen atmosphere.
5 parts by weight, 25 parts by weight of styrene, 500 parts by weight of cyclohexane
0.07 parts by weight of n-butyllithium was added to a mixed solution obtained by adding 1.5 parts by weight of tetrahydrofuran. After polymerization at 85°C for 50 minutes, tin tetrachloride 0
．． A polymer solvent was obtained by adding 03 parts by weight. The obtained polymer was a starter rubbery styrene-butadiene random copolymer having a Mooney viscosity (MLwal O0°C) of 50, a styrene content of 25%, and a coupling efficiency of 50%.

(Block copolymer (C)) Add 0.12 parts by weight of n-butyllithium to a mixed solution obtained by adding 30 parts by weight of styrene and 500 parts by weight of cyclohexane to a polymerization reactor equipped with a stirrer under a nitrogen atmosphere. did. After polymerizing for 30 minutes at 70°C, 1,3-butadiene 40
Parts by weight were added and polymerized at 70°C for 40 minutes. Thereafter, 30 parts by weight of styrene was further added and polymerized at 70°C for 30 minutes to obtain a polymer solution. The obtained polymer has a weight average molecular weight of 1
50,000, and was an ABA type block copolymer with a styrene content of 60%.

(Examples 1 to 3, Comparative Examples 1 to 4) A diglycerol borate compound, boric acid, and stearic acid were added in the amounts shown in Table 1 to the solution of the polybutadiene rubber (A) produced above, and then As a stabilizer, 0.5 parts by weight of 4-methyl-2,6-tert-butylphenol was added to 100 parts by weight of the polymer.

Thereafter, the solvent was removed from the polymer solution by a steam stripping method to obtain a crumb-like polymer.

This crumb-like polymer was heated at 170 to 180°C and 200 rp+
A dry polybutadiene rubber having a moisture content of 0.1 to 0.3% was obtained by applying the mixture to a screw type Exvandigon dryer operated at m.m.

The obtained dried polybutadiene rubber was evaluated for color tone and gel content.

The color tone was evaluated both immediately after drying and after being left in a gear oven at 80° C. for 7 days.

Regarding the gel content, 10 g of dried polybutadiene was dissolved in 200 ml of toluene by standing for a day and night, then 200 w
The mixture was filtered through an esh wire mesh, and the undissolved content remaining on the wire mesh was measured as the gel content.

Table 1> *1 Amount based on 100 parts by weight of polymer (Examples 4 to 5, Comparative Example 5) A diglycerol borate compound was added to the solution of the random copolymer (B) produced above as shown in Table 2. Add the indicated amount,
Then, 4-methyl-2,6-tert was used as a stabilizer.
-butylphenol in an amount of 0.0% per 100 parts by weight of the polymer.
5 parts by weight was added.

Thereafter, solvent removal and drying were performed in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 4 to obtain dry random copolymers.

The color tone and gel content of the obtained dried random copolymer were evaluated. The results are shown in the second example (Examples 6 to 7).
, Comparative Examples 6-7) The solution of the block copolymer (C) produced above was also evaluated in the same manner as in Example 1.

Additionally, we added an evaluation of transparency. Regarding transparency, the dry polymer was heated with a hot roll at 120°C to remove residual moisture, and then press-molded at 180°C and 150 kg/ai to create a sheet with a thickness of 2ms+, and the transparency was visually evaluated. did. The results are shown in Table-3.

Table 3 f. Effect The polymer obtained by the method of the present invention has excellent color tone and less gel, so it can be used in rubbers such as conjugated diene polymers and random copolymers of conjugated diene and aromatic vinyl compounds. In the case of block copolymers, they are used in vulcanized products such as tires and canvas, and as base rubber for impact-resistant polystyrene resins, while block copolymers are used as thermoplastic resins in sheets, films, and various injection molded products. It is suitable for various uses, and its industrial significance is extremely large.

Patent applicant: Japan Synthetic Rubber Co., Ltd.

Claims (2)

[Claims] (1) Semipolar borate ester is added to a polymer solution obtained by polymerizing a conjugated diene compound or copolymerizing a conjugated diene compound and an aromatic vinyl compound in a hydrocarbon solvent using an organolithium compound as an initiator. compound and (2) A method for producing a polymer, which comprises adding a stabilizer and then removing the solvent from the polymer solution.