JPS61203112A - Production of rubber-modified styrene resin - Google Patents

Abstract

PURPOSE:To obtain a rubber-modified styrene resin excellent in impact strength and colorability with a coloring agent, by dissolving a polybutadiene rubber of a specified MW distribution in a styrene monomer and polymerizing this solution. CONSTITUTION:A polybutadiene rubber is dissolved in a styrene monomer and the obtained solution is polymerized to produce a rubber-modified styrene resin. Said polybutadiene rubber is one having a cis-1,4-bond structure content >=90%, a Mw/Mn ratio (wherein Mw is a weight-average MW and Mn is a number-average MW) >=3.5, a bimodal distribution curve and a solution viscosity (SV) as measured in a 5wt% toluene solution at 25 deg.C of 10-250cP. The ratio of said polybutadiene rubber to the styrene monomer is preferably 2-15pts. wt./85-95pts.wt.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a rubber-modified styrenic resin having excellent strength and colorability. More specifically, it describes a method for producing a rubber-modified styrenic resin that has practical impact resistance and excellent colorability with coloring agents by using polybutadiene used as a toughening agent with a special molecular weight distribution. .

(Prior art) Conventionally, rubber-modified styrenic resins are produced by dissolving unvulcanized rubber in styrenic monomers and subjecting this solution to bulk, solution or bulk-suspension polymerization, or by simply polymerizing unvulcanized rubber into styrenic monomers. It has been manufactured by mechanically mixing sulfur rubber. In particular, rubber-modified styrenic resins obtained by bulk or bulk-suspension polymerization are widely used industrially. In this case, unvulcanized rubbers commonly used as toughening agents include polybutadiene rubber and styrene-butadiene rubber. Polybutadiene rubber is most commonly used because it is superior to styrene-butadiene rubber in terms of the low-temperature impact resistance of the resulting rubber-modified styrenic resin.

However, one of the drawbacks of rubber-modified styrenic resins using polybutadiene rubber as a toughening agent is poor colorability with colorants. Styrenic resins such as polystyrene that do not contain toughening agents originally have better coloring properties than other resins such as polyethylene, but in order to improve impact resistance, rubber-like toughening resins When the agent is added, the coloring property is significantly impaired. This tendency is more pronounced when polybutadiene rubber is used as the toughening agent than when styrene-butadiene rubber is used.

Rubber-modified styrenic resins generally have a two-phase structure consisting of a rubber phase and a polystyrene phase, and it is speculated that this two-phase structure is one of the reasons why rubber-modified styrenic resins deteriorate in colorability. .

Transparency decreases due to the presence of a rubber phase,
In addition, although the dispersed rubber phase has a so-called salami structure containing a styrene polymer inside, it is thought that the polybutadiene portion has poor coloring properties, which in turn reduces the coloring properties of the rubber-modified styrenic resin as a whole. n has arrived.

On the other hand, rubber-modified styrene resins are often used to mold so-called home appliances such as TV frames, radio and video housings by injection molding, but in this case, the physical properties required of the resin are colorability. It is desired that the material has good and practical impact resistance.

Conventionally, even in cibolyptadiene rubber, the cis 1°4 bond structure obtained by solution polymerization with a lithium catalyst is 25 to
So-called low cis polybutadiene rubber, such as 45%, is obtained by solution polymerization using a Ziegler catalyst.
So-called high-cis polybutadiene rubber, which has a 4-bond structure of 90% or more, also has good coloring properties, but it is generally known that high-cis polybutadiene rubber is better in terms of practical impact resistance. This is where I am.

To date, no rubber-modified styrenic resin has been found that satisfies practical impact resistance and colorability.

As a disclosure of these improved techniques, Japanese Patent Application Laid-Open No. 53-13079
There is Publication No. 1. This specifies the polymer structure of polybutadiene rubber used as a toughening agent. That is, in JP-A-53-130791, the polymer structure of polybutadiene is 7 to 35% 1,2 vinyl bond structure, 20 to 80% cis 1,4 bond structure,
Weight average molecular weight (Mw) and number average molecular weight (Mn)
Polybutadiene rubber having a ratio (Mw/Mn) of 2.6 or more and a Williams recovery value of 2.6 or more is dissolved in styrene and the resulting solution is subjected to bulk polymerization or bulk-suspension polymerization. The company claims that it is possible to obtain high-impact polystyrene with improved low-temperature impact resistance and colorability.

However, when we examine the method described in JP-A-53-130791 in detail, we find that it does show some improvement in colorability and low-temperature impact resistance compared to conventional polybutadiene rubber. However, the effect is insufficient for practical use, and although the boss strength, which is important in practical use, is satisfactory, it has not been achieved.

(Problems to be Solved by the Invention) In order to solve these problems and obtain a rubber-modified styrenic resin with an excellent balance of physically important physical properties, the present inventor has conducted extensive research and found that The present inventors have discovered that by specifying the structure of the polybutadiene rubber used, it is possible to obtain a rubber-modified styrenic resin with excellent colorability and practical strength, and have completed the present invention.

(Means for Solving the Problems) That is, the present invention involves dissolving polybutadiene rubber in a styrene monomer and polymerizing the solution to produce a rubber-modified styrenic resin. However, if the cis 1,4 bond structure is 90X or more, and the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw/Mn) is 3.5 or more, a bimodal distribution curve is obtained. A method for producing a rubber-modified styrenic resin, characterized in that the polybutadiene rubber has a 5 wt% toluene solution viscosity (S, V,) measured at 25° C. of 100 to 250 cp8. It provides:

The present invention will be explained in more detail below.

First, the polybutadiene rubber used as the toughening agent of the present invention will be described. The specific polybutadiene rubber used in the present invention needs to be a so-called high-cis polybutadiene rubber having a cis 1,4 bond structure of 90% or more. In the case of so-called low-cis polybutadiene rubber in which the cis-1,4 bond structure is less than 90%, the practical strength is insufficient. Furthermore, the weight average molecular weight (Mw
) and number average molecule! (Mn) ratio (Mw/
Mn ) is required to be 3.5 or more and to exhibit a bimodal molecular weight distribution curve.

If Mvr/Mn is less than 3.5, the coloring property is insufficient, and if the molecular weight distribution curve does not show bimodality but only one peak, the coloring property is also insufficient. In addition, the practical strength is not sufficient. Furthermore, the 5 wt% toluene bath solution viscosity (S, V, ) measured at 25°C is 100~
It should be in the range of 250 cps preferably 130-180 eps.

If S, V, is less than 100 cps, the strength will not be sufficiently developed, and if it exceeds 250 cps, a very large stirring power will be required when industrially producing rubber-modified styrenic resin, and the stirring equipment will not be sufficient. Undesirable.

A method for producing such polybutadiene rubber is preferably a method of polymerizing 1.3-butadiene using a catalyst obtained from a cobalt compound, an organic aluminum compound, and a polyhydric alcohol. Detailed examples will be given below, but any conventionally known method may be used as long as the polybutadiene satisfies the scope of the claims of the present invention.

Examples of the cobalt compounds include cobalt salts of organic carboxylic acids having 6 or more carbon atoms such as cobalt octoate, cobalt naphtonite, and cobalt benzoate; halogenated cobalt complexes such as cobalt chloride pyridine complexes and cobalt chloride ethyl alcohol complexes; Examples include cobalt β-keto acid ester complexes such as cobalt acetoacetate ethyl ester complexes.

Examples of the halogen-containing organoaluminum compounds include dialkylaluminum halides such as diethylaluminum monochloride, diethylaluminium hepthanopromide, and diisobutylaluminum monochloride, and alkyl/I/fluminium sesquihalides such as ethylaluminum sesquichloride. can be mentioned.

As the polyhydric alcohol, ethylene glycol,
Examples include dihydric alcohols such as phlopylene gellicol, α-butylene glycol, and tetramethylene glycol, and trihydric alcohols such as glycerin.

In order to obtain a large My/Mn of 3.5 or more as in the present invention, that is, a broad molecular weight distribution and a bimodal distribution, a preferred method is to carry out the superimposition reaction in two stages. It is. For example, there is a method in which bulk polymerization is performed up to a certain polymerization rate, and then a solvent is added to the system to perform solution polymerization.

In such cases, known molecular weight modifiers, such as α-olefins such as ethylene, propylene, styrene, and butene-1, and nonconjugated dienes such as cyclooctadiene and arene, are used in each polymerization step. By not using it, it is possible to increase the peak on the high molecular weight side or increase the peak on the low molecular weight side of the bimodal molecular weight distribution.

By changing the molecular weight of such polybutadiene rubber, it is also possible to change S and V.

The polybutadiene rubber used in the present invention contains commonly used anti-aging agents, such as 2,6-ditertiary-butyl-4-methylphenol (BHT), tri(nonylated phenyl)phosphite (TNP), 2. 2'methylenebis(4-methyl-6-tert-butylphenol)
, octadecyl 3-(3',5'ditert-butyl-4' hydroxyphenyl)gropionate, tetrakis-[methylene-(3,5 ditert-butyl-4-
Hydroxyhydrocinnamate)] Methane, Tris (
It is preferable that 2,4-ditertiary-butylphenyl) phosphite or the like be used alone or in combination of two or more.

In the method for producing a rubber-modified styrenic resin of the present invention, the ratio of polybutadiene rubber to styrene monomer is preferably 2 to 5 parts by weight to 85 to 98 parts by weight. If the concentration of polybutadiene rubber is less than 2% by weight with respect to the content of polybutadiene rubber and styrene monomer, the impact strength of the resulting resin will be insufficient, and if it exceeds 15% by weight, the economic efficiency will be reduced. Since problems such as the degree of strength improvement is small and the viscosity of the polymerization system becomes too high tend to occur, a range of 2 to 15% by weight is most appropriate.

The method for producing the rubber-modified styrenic resin of the present invention includes:
Bulk, solution or bulk-suspension polymerization methods are advantageously used.

For example, in Yang Kai using the bulk-suspension polymerization method, the polybutadiene rubber of the present invention is dissolved in a styrene-based single F, and the solution is mixed with an azo compound such as azobisisobutyronitrile, azopiscyclohexanecarponitrile, etc. , benzoyl peroxide, by heating the solution with stirring in the presence or absence of a catalyst such as peroxide such as butyl peroxybenzoate, di-t-butyl peroxide, dicumyl peroxide, etc. Radical polymerization, polymerization rate 20-4
When the concentration reaches 0%, the polymerization solution is suspended in water to continue polymerization and complete the polymerization. At this time, a molecular weight regulator such as mercaptan and a plasticizer such as white mineral oil may be used as appropriate. It is also possible to separately add a catalyst and a molecular weight regulator during the polymerization.

In the present invention, the styrenic monomer includes styrene, paramethylstyrene, t-butylstyrene, α-methylstyrene, chlorostyrene, etc., singly or in combination. Further, a part of the styrenic monomer may be replaced with a monomer that can radically copolymerize with these monomers, such as acrylonitrile, methyl methacrylate, and methyl acrylate.

The rubber-modified styrenic resin obtained in this manner has excellent practical impact resistance and colorability with coloring agents compared to conventional resins.

The rubber-modified styrenic resin obtained by the method of the present invention may be treated with antioxidants, antioxidants,
Add UV absorbers, lubricants, mold release agents, fillers, etc. in advance,
It can be used for general injection molding, extrusion sheet molding, etc.

(Examples) The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to these Examples.

Table 1 shows Examples and Comparative Examples. The rubber-modified styrenic resins shown in Examples are excellent in all physical property items, and it can be seen that the products according to the present invention have a good balance of physical properties.

Example I Mw/M n is 4.2, exhibits a bimodal molecular weight distribution curve as shown in FIG. 1, and S, V, and l 93 cp
s, cis 1,4 bond structure is 97.8 Add this rubber solution to 1
00t autoclave, 0.08 parts by weight of dicumyl peroxide, 0.0 part by weight of linear dodecyl mercaptan.
4 parts by weight were added and stirred at 150 rpm. After purging the inside of the autoclave with nitrogen gas, it was sealed and the temperature was raised. After polymerization at 105°C for 6 hours, it was cooled and then reduced to a volume of 2
100 t of pure water and 0.5 t of sodium dodecylbenzenesulfonate in a 00 t autoclave. , 80 Qf of tricalcium phosphate was added, and while stirring at 130 rpm, the prepolymerization solution 70 K9 to which 701 of 2,2-bis(tertiary-butylperoxy)butane and 28 t of dicumyl peroxide were newly added was added. , After replacing with nitrogen, seal, raise temperature, and heat at 115°C for 5 hours at 135°C.
Polymerization was carried out at ℃ for 4 hours and cooled. Neutralization according to conventional methods,
After dehydration and drying, the polymer was shaped into ordinary pellets using an extruder to obtain a rubber-modified styrene resin. The results of this physical property measurement are shown in Table 1.

Example 2 A polybutadiene rubber (manufactured by Ube Industries, Ltd.) having an Mw/M n of 3.6, a bimodal molecular weight distribution curve, S, V, 153 cps, and a cis 1,4 bond structure of 97.8%. (2) A rubber-modified styrenic resin was obtained in the same manner as in Example 1, except that Ubepol BRIOI) was used. The results of this physical property measurement are shown in Part 1.

Comparative Example I Mw/Mn was 3.7, and the molecular weight distribution curve did not show bimodality.
.

The same procedure as in Example 1 was carried out except that polybutadiene rubber (Nippon Synthetic Rubber BROI) having a 4M composite structure of 95.9% was used, and a rubber-modified styrene resin was used. The results of this physical property measurement are shown in Table 1.

Comparative Example 2 Polybutadiene rubber (Asahi Kasei ■) with Mw/M n of 4.1, a bimodal molecular weight distribution curve, S, V, 60 cps, cisl, 4-bond structure of 35.4X A rubber-modified styrenic resin was obtained in the same manner as in Example 1 except that Asaprene 760) was used.

The results of this physical property measurement are shown in Table 1.

The microcomposition of polybutadiene rubber can be determined using an infrared spectrophotometer (
Using JASCO [Model A-302], the infrared spectrum was measured using carbon disulfide as a solvent, and the Morero method (D, More
ro et al., Chim, 61 nd, , 41.758 (
(1959)).

Mw/Mn of polybutadiene was measured using GPCC Toyo Ida fiHLc-802A] under the following conditions.

Solvent: Tetrahydrofuran (THF) Column: Toyo Soda GMH-62F-set 2 columns Constant temperature bath Temperature: 38°C Solvent flow rate: 1.5 d/m Sample concentration: 0.1% by weight Sample injection amount 20, 5- Detection Instrument: Differential refractometer Data processing device: CP-8000 manufactured by Toyo Soda The physical properties of the rubber-modified styrenic resin were measured by the following method.

(1) Tensile strength: According to JIS-6871.

(2) Izot impact strength: JIS-ni-6
According to 871.

(3) Falling weight strength: 12 strokes x 12 2m thick by injection molding
The tip of the weight is 5R in the center of the square plate.

A weight with a weight diameter of 14mmφIkg is dropped, and the strength is determined by the product of the height (prepared to prevent cracking) and the weight of the weight.

The molding machine was a 2-ounce in-line screw injection molding machine 5N-51B manufactured by Niigata Iron Works at a molding temperature of 230°C. In addition, molded products made by injection molding are easily susceptible to directionality.
Even when cracking occurs due to external force, it tends to break in the direction of the molding flow. In this respect, since the falling weight strength is the easiest to find the direction of, the present invention adopts the falling weight strength as an expression that suits the actual situation.

(4) Colorability: 0.5 parts of Nippon Pigment's evening color pigment PSD-B-871 was added to 100 parts by weight of the resin, and a 3-step step plate was formed by injection molding, showing a deep group color, and the pigment itself The one closest to the color and the best in colorability was rated A, the one with a pale gray-blue color and the poorest coloring was rated E, and the intermediate ones were rated BIC and D in order.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a molecular weight distribution curve of the polybutadiene rubber used in Example 1.

Claims (2)

[Claims] (1) Polybutadiene rubber is dissolved in a styrene monomer and the solution is polymerized to produce a rubber-modified styrenic resin.
The 4-bond structure is 90% or more, and the weight average molecular weight (Mw
) and the number average molecular weight (Mn) (Mw/Mn) is 3.
5 or more, it shows a bimodal distribution curve, and the 5 weight % toluene solution viscosity (S.V.) measured at 25°C is 100 to 2.
A method for producing a rubber-modified styrenic resin, characterized in that the polybutadiene rubber is within a range of 50 cps. (2) Claim 1 in which the polybutadiene rubber is 2 to 15 parts by weight and the styrene monomer is 85 to 98 parts by weight.
A method for producing a rubber-modified styrenic resin as described in .