JPH0621135B2 - Method for producing rubber-modified styrene resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a rubber-modified styrene resin having excellent strength and colorability. More specifically, the present invention relates to a method for producing a rubber-modified styrene-based resin which has a practical impact resistance and is excellent in colorability with a coloring agent, by making the polybutadiene used as a toughening agent have a special molecular weight distribution.

(Prior Art) Conventionally, rubber-modified styrenic resin dissolves unvulcanized rubber in styrene-based monomer and polymerizes this solution in bulk, solution or bulk-suspension, or simply unvulcanized. It has been produced by mechanically mixing the rubber. In particular, rubber-modified styrenic resins obtained by bulk or bulk-suspension polymerization are widely used industrially. In this case, the unvulcanized rubber usually used as a toughening agent includes polybutadiene rubber and styrene-butadiene rubber. Polybutadiene rubber is most often used because it is superior to styrene-butadiene rubber in terms of low temperature impact resistance of the resulting rubber-modified styrene resin.

However, one of the drawbacks of the rubber-modified styrene resin using such a polybutadiene rubber as a toughening agent is poor coloring property due to a coloring agent. Styrene-based resins that do not contain a toughening agent, such as polystyrene, are originally resins that have better coloring properties than other resins such as polyethylene, but with the purpose of improving impact resistance, they are made tougher like rubber. When the agent is added, its coloring property is significantly impaired. This tendency is more remarkable when polybutadiene rubber is used as the toughening agent than when styrene-butadiene rubber is used.

Generally, the modified styrenic resin has a two-phase structure composed of a rubber phase and a polystyrene phase, and it is speculated that one of the causes of the decrease in the coloring property of the rubber-modified styrenic resin is the two-phase structure. . In other words, the presence of the rubber phase reduces the transparency, and the dispersed rubber phase has a so-called salami structure by containing a styrene-based polymer inside, but the polybutadiene portion has poor colorability, and as a result, as a whole. It has been considered that the coloring property of the rubber-modified styrenic resin is reduced.

On the other hand, rubber-modified styrenic resins are often used by injection molding of so-called home appliances such as TV outer frames, radio and video housings, etc. In that case, the physical properties required for the resins are not colored. Good and practical impact resistance is desired.

Even with polybutadiene rubber, conventionally, the cis-1,4 bond structure obtained by solution polymerization with a lithium-based catalyst is 25 to
A so-called low cis polybutadiene rubber having a content of 45% has a better coloring property than a so-called high cis polybutadiene rubber having a cis 1,4 bond structure of 90% or more obtained by solution polymerization using a Ziegler catalyst. On the contrary, it is generally known that the high-cis polybutadiene rubber is better in terms of practical impact resistance.

So far, it has not yet been clarified what can satisfy the practical impact resistance and colorability of the rubber-modified styrene resin.

As a disclosure of these improved techniques, JP-A-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 7-35% for 1,2-vinyl bond structure, 20-80% for cis-1,4 bond structure,
Ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw /
A polybutadiene rubber having a Mn) of 2.6 or more and a Williams recovery value of 2.6 mm or more is dissolved in styrene, and the solution is subjected to bulk polymerization or bulk-suspension polymerization to obtain low-temperature impact resistance and coloring property. It is said that impact-resistant polystyrene having both properties improved can be obtained.

However, when the method described in JP-A No. 53-130791 is examined in detail, it is true that there is some improvement in coloring property and low temperature impact resistance as compared with conventional polybutadiene rubber. The effect is not sufficient for practical use, and the boss strength that is important for practical use is not satisfactory.

(Problems to be Solved by the Invention) In order to solve the above problems and obtain a rubber-modified styrene-based resin having an excellent balance of practically important physical properties, the present inventors have earnestly studied, and as a result, as a toughening agent. The inventors have found that a rubber-modified styrene-based resin excellent in colorability and practical strength can be obtained by specifying the structure of the polybutadiene rubber to be used, and completed the present invention.

(Means for Solving Problems) That is, according to the present invention, polybutadiene rubber is dissolved in a styrene-based monomer, and the solution is polymerized to produce a rubber-modified styrene-based resin. The cis-1,4 bond structure is 90% or more, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn)
Shows a bimodal distribution curve at a value of 3.5 or more, and has a 5 wt% toluene solution viscosity (S.V.) measured at 25 ° C. of 1
It is intended to provide a method for producing a rubber-modified styrenic resin, which is a polyptadiene rubber in the range of 0 to 250 cps.

Hereinafter, the present invention will be described in more detail.

First, the polyptadiene 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 having a cis-1,4 bond structure of less than 90%, practical strength is not sufficient. Furthermore, the weight average molecular weight (M
It is necessary that the ratio (Mw / Mn) of w) and the number average molecular weight (Mn) is 3.5 or more and that the bimodal molecular weight distribution curve is exhibited. When Mw / Mn is less than 3.5, the coloring property is insufficient, and also when the molecular weight distribution curve does not exhibit bimodality but only one peak, the coloring property is also insufficient. Also, the practical strength is not sufficient. Furthermore, the 5 wt% toluene solution viscosity (SV) measured at 25 ° C. is 100 to 250.
cps should preferably be in the range 130-180 cps. When the SV is less than 100 cps, the strength is not sufficiently expressed, and when it exceeds 250 cps, a very large stirring power is required when industrially producing the rubber-modified styrene resin, which is not preferable in terms of a stirring device.

A method for producing such a polybutadiene rubber is preferably a method for polymerizing 1,3 butadiene using a catalyst obtained from a cobalt compound, a halogen-containing organoaluminum compound and a polyhydric alcohol, and detailed examples will be given below. As long as it is a polybutadiene satisfying the scope of the claims of the present invention, any conventionally known method may be used.

Examples of the cobalt compound include cobalt salts of organic carboxylic acids having 6 or more carbon atoms such as cobalt octoate, cobalt naphthoate, and cobalt benzoate, cobalt chloride pyridine complexes, cobalt halide complexes such as cobalt chloride ethyl alcohol complex, and cobalt aceto. Examples include cobalt β-keto acid ester complexes such as acetic acid ethyl ester complex.

Examples of the halogen-containing organoaluminum compound include dialkylaluminum halides such as diethylaluminum monochloride, diethylaluminum monobromide and diisobutylaluminum monochloride, and alkylaluminum sesquihalides such as ethylaluminum sesquichloride.

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

As in the present invention, Mw / Mn is as large as 3.5 or more, that is,
A preferred method for obtaining a broad molecular weight distribution and bimodal distribution is to carry out the polymerization reaction in two stages. For example, there is a method in which bulk polymerization is carried out up to a certain polymerization rate, and then a solvent is added to the system to carry out solution polymerization. In such a case, a known molecular weight regulator, for example, ethylene, propylene, styrene, α-olefins such as butene-1, cyclooctadiene, or non-conjugated dienes such as allene may be used in each polymerization step, By not using it, it is possible to increase the peak on the high molecular weight side or the peak on the low molecular weight side in the bimodal molecular weight distribution.

It is also possible to change SV by changing the molecular weight of such polybutadiene rubber.

The polybutadiene rubber used in the present invention includes the commonly used antioxidants such as 2,6-ditertiarybutyl-4-methylphenol (BHT), tri (nonylated phenyl) phosphite (TNP) and 2,2 '. Methylenebis (4-methyl-6-tertiarybutylphenol), octadecyl 3- (3 ', 5'ditertiarybutyl 4'hydroxyphenyl) propionate, tetrakis- [methylene- (3,5ditertiarybutyl-4)
-Hydroxyhydrocinnamate)] methane, tris (2,4-di-tert-butylphenyl) phosphite and the like are preferably blended 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 used is 2
-15 parts by weight to 85-98 parts by weight are preferred. When the polybutadiene rubber concentration is less than 2% by weight, the impact strength of the produced resin is insufficient, and when it exceeds 15% by weight, the strength is economically improved. The range of 2 to 15% by weight is most suitable because the degree is low and problems such as excessively high viscosity of the polymerization system tend to occur.

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 the case of the bulk-suspension polymerization method, the polybutadiene rubber of the present invention is dissolved in a styrene-based monomer, and the solution is treated with an azo compound such as azobisisobutyronitrile or azobiscyclohexanecarbonitrile, or a peroxide. In the presence or absence of a catalyst such as a peroxide such as benzoyl, t-butylperoxybenzoate, di-t-butylperoxide, dicumylperoxide, etc., this solution is heated under stirring to perform radical polymerization. , Polymerization rate 20-4
When 0% is reached, the polymerization solution is suspended in water to continue the polymerization, and the polymerization is completed. At this time, a molecular weight modifier such as mercaptan and a plasticizer such as white mineral oil can be appropriately used if necessary. It is also possible to add a catalyst and a molecular weight modifier separately during the polymerization.

In the present invention, the styrene-based monomer is styrene, paramethylstyrene, t-butylstyrene, α-methylstyrene, chlorostyrene, or the like, and these may be used alone or in combination. A part of the styrene-based monomer may be replaced with a monomer which can be radically copolymerized with them, for example, acrylonitrile, methyl methacrylate, methyl acrylate or the like.

The rubber-modified styrenic resin thus obtained is superior in practical impact resistance and colorability with a coloring agent as compared with the conventional ones.

The rubber-modified styrenic resin obtained by the method of the present invention has a participation inhibitor, if necessary, in addition to a coloring agent during processing.
An ultraviolet absorber, a lubricant, a release agent, and a filler may be added in advance and used for general injection molding, extrusion sheet molding and the like.

(Examples) Hereinafter, the present invention will be described more specifically with reference to 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 properties, and it can be seen that the one according to the present invention has a good physical property balance.

Example 1 A polybutadiene rubber having an Mw / Mn of 4.2 and a bimodal molecular weight distribution curve as shown in FIG. 1, an SV of 193 cps and a cis-1,4 bond structure of 97.8% ( Ube Industries
8 parts by weight of Ubepol BR100 Co., Ltd. was dissolved in 92 parts by weight of styrene. This rubber solution was charged into an autoclave of 100, and 0.08 part by weight of dicumyl poxoxide and 0.04 part by weight of linear dodecyl mercaptan were added,
Stirred at 150 rpm. The inside of the autoclave was replaced with nitrogen gas, which was then sealed and the temperature was raised. After polymerizing at 105 ° C for 6 hours, the mixture was cooled and then added to an autoclave having a capacity of 200, pure 100, 0.5 g of sodium dodecylbenzenesulfonate, and 800 g of tribasic calcium phosphate,
70 g of 2,2 bis (tert-butylperoxy) butane and 28 g of dicumyl peroxide were newly added while stirring at 30 rpm.
After adding Kg and purging with nitrogen, the mixture was sealed and heated to polymerize at a temperature of 115 ° C. for 5 hours and at 135 ° C. for 4 hours, and cooled. After neutralization, dehydration and drying according to a conventional method, a rubber-modified styrene resin was obtained by forming the polymer into an ordinary pellet shape by an extruder. The results of measuring the physical properties are shown in Table 1.

Example 2 shows a bimodal molecular weight distribution curve with Mw / Mn of 3.6, and SV
Of 153 cps and cis-1,4 bond structure of 97.8% (Ubepol BR10 manufactured by Ube Industries, Ltd.)
A rubber-modified styrene resin was obtained in the same manner as in Example 1 except that 1) was used. The results of measuring the physical properties are shown in Table 1.

Comparative Example 1 Mw / Mn is 3.7, and it is a molecular weight distribution curve showing no bimodality, SV is 156 cps, and cis-1,4 bond structure is 95.
9% polybutadiene rubber (BR from Nippon Synthetic Rubber Co., Ltd.
The same procedure as in Example 1 was carried out except that (01) was used to obtain a rubber-modified styrene resin. The results of measuring the physical properties are shown in Table 1.

Comparative Example 2 Mw / Mn is 4.1 and is a bimodal molecular weight distribution curve.
A rubber-modified styrene resin was obtained in the same manner as in Example 1 except that a polybutadiene rubber having a V. of 60 cps and a cis-1,4 bond structure of 35.4% (Asaprene 760, Asahi Kasei Corporation) was used.

The results of measuring the physical properties are shown in Table 1.

For the micro composition of polybutadiene, an infrared spectroscopic clock (Model A-302 manufactured by JASCO Corporation) was used to measure an infrared spectrum using carbon disulfide as a solvent, and the Morello method [D. Morero et al., Chi.
m.61nd., 41, 758 (1959)].

Mw / Mn of polybutadiene is GPC [HLC made by Toyo Soda
-802A] was used and measured under the following conditions.

Solvent: Tetrahydrofuran (THF) Column: Toyo Soda GMH-6 2Feet 2 columns Constant temperature bath temperature: 38 ° C Solvent flow rate: 1.5 ml / min Sample concentration: 0.1 wt% Sample injection amount: 0.5 ml Detector: Differential refractometer Data processing device: The physical properties of CP-8000 rubber-modified styrene resin manufactured by Toyo Tanso Co., Ltd. were measured by the following methods.

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

(2) Izod impact strength: According to JIS-K-6871.

(3) Drop weight strength: 12mm x 12c with 2mm thickness by injection molding
At the center of the square plate of m, the tip of the weight is 5R, the diameter of the weight is 14mm, and φ1K.
Drop the weight of g and express the strength by multiplying the height (cm) at which cracking does not occur and the weight of the weight.

The molding machine was a 2 ounce line screw injection molding machine SN-51B manufactured by Niigata Iron Works Co., Ltd. and molded at a molding temperature of 230 ° C. It should be noted that injection-molded products are susceptible to directionality,
Even when it is cracked by an external force, it is easily cracked in the direction of the molding flow. In this respect, since the falling weight strength is most easily found in the directionality, in the present invention, the falling weight strength is adopted as a way of expressing it according to the actual situation.

(4) Colorability: To 100 parts by weight of resin, 0.5 part of Nippon Pigment Co., Ltd. blue pigment PSD-B-871 was added, and a three-step step plate was formed by injection molding to give a deep ultramarine blue color, and the color of the pigment itself. Was closest to, and the best coloring property was A, the blue color was a pale grayish blue, and the poorest coloring property was E, and the intermediate positions were evaluated as B, C, and D in that order.

[Brief description of drawings]

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

Claims (2)

[Claims] 1. A polybutadiene rubber having a cis-1,4 bond structure of 90% or more is prepared by dissolving a polybutadiene rubber in a styrene-based monomer and polymerizing the solution to produce a rubber-modified styrene-based resin. Yes, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3.5.
The above shows a bimodal distribution curve, and the 5 wt% toluene solution viscosity (S.V.) measured at 25 ° C. is 100 to 25.
A method for producing a rubber-modified styrenic resin, which is a polyptadiene rubber in the range of 0 cps. 2. The method for producing a rubber-modified styrene resin according to claim 1, wherein the polybutadiene rubber is 2 to 15 parts by weight and the styrene monomer is 85 to 98 parts by weight.