JPH0649740B2 - Method for producing rubber-modified styrene resin - Google Patents

Description

The present invention relates to a method for producing a rubber-modified styrenic resin having excellent coloring properties. More specifically, the present invention relates to a method for producing a rubber-modified styrene-based resin having excellent coloring properties by a coloring agent, practical impact resistance, rigidity and gloss because polybutadiene used as a toughening agent has a special structure.

Conventionally, a rubber-modified styrenic resin dissolves an unvulcanized rubber in a styrenic monomer and polymerizes this solution in bulk, solution or bulk-suspension, or simply unvulcanized the rubber mechanically. It has been manufactured depending on whether it is mixed. 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 a polybutadiene rubber is used as a toughening agent than in the case of styrene-butadiene rubber. Furthermore, even with polybutadiene rubber, a cis-1,4 bond structure obtained by solution mixing with a lithium-based catalyst is obtained. Cis-1, which is obtained by solution polymerization using a Ziegler-based catalyst, rather than so-called low-cis polybutadiene rubber having a content of 25 to 45%.
The so-called high-cis polybutadiene rubber having a 4-bond structure of 90% or more is further inferior in colorability.

Generally, the rubber-modified styrenic resin has a two-phase structure composed of a rubber phase and a polystyrene phase, and it is speculated that this two-phase structure is one of the causes of the decrease in the coloring property of the rubber-modified styrene resin. . That is, the presence of the rubber phase reduces the transparency, and the dispersed rubber phase has a so-called salami structure in which the styrene-based polymer is contained therein, but the polybutadiene portion has poor colorability, and thus the rubber as a whole. It has been considered that the modified styrenic resin reduces the colorability.

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. Not only good and practical impact resistance, but also good gloss is desired. It is generally known that the size of a rubber phase dispersed in a resin having a two-phase structure of a rubber-modified styrenic resin is greatly related to gloss. That is, when the size of the rubber phase is reduced, the gloss is improved, but the impact resistance is inferior. On the contrary, when the size is increased, the impact resistance is enhanced, but the gloss is decreased.

To date, a satisfactory method for obtaining a rubber-modified styrenic resin excellent in low-temperature impact resistance, colorability, and gloss has not been clarified yet.

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, as a polymer structure of polybutadiene, 1,2-vinyl bond structure is 7 to 35%, and cis-1,4 bond structure is 20 to 80%.
%, The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2.6 or more, and the recovery value of Williams is 2.
It is said that impact-resistant polystyrene improved in both low-temperature impact resistance and colorability can be obtained by dissolving polybutadiene rubber having a size of 6 mm or more in styrene and subjecting such a solution to bulk polymerization or bulk-suspension polymerization. .

However, when the method described in JP-A-53-130791 is examined in detail, it is true that some improvement effects in colorability and low temperature impact resistance are recognized as compared with conventional polybutadiene rubber, but it is practical. As for the gloss, which is a further required physical property, satisfactory results cannot be obtained.

The present inventor has solved the above problems and has the above-mentioned 3
In order to obtain a rubber-modified polystyrene-based resin having an excellent balance of physical properties in points, as a result of intensive research, by using a specific rubber-like polymer, a rubber-modified styrene-based resin excellent in colorability, practical strength, and luster can be obtained. They have found that they can be obtained, and have completed the present invention.

That is, the present invention is (1) dissolving polybutadiene rubber in a styrene monomer,
In producing a rubber-modified styrenic resin by polymerizing such a solution, as polybutadiene, (A) 1,2-vinyl bond structure is 20 to 40%, cis 1,4-
The binding structure is 15 to 35%, (B) the molecular weight distribution region has at least two peaks of the low molecular weight region and the high molecular weight region, the peak of the low molecular weight region is 100,000 or more, and the low molecular weight region and the high molecular weight region are high. The boundary with the molecular weight region is between 100,000 and 1,000,000, and (C) the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 1.2 or more and less than 1.8. And (D) a polymer which is a coupled polymer and has a coupling degree of 50% or more, and is polymerized to provide a method for producing a rubber-modified styrene resin.

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

First, the polybutadiene rubber used as the toughening agent of the present invention will be described. Specific polybutadiene rubbers used in the present invention are organolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, n
Solution-polymerized with propyllithium, isopropyllithium, benzyllithium, trimethylenelithium, etc. as a catalyst.

The polybutadiene rubber used in the present invention has a 1,2-vinyl bond structure of 20 to 40%, preferably 23 to 35%, and a cis-1,4 bond structure of 15 to 35%, preferably 1.
Must be 8-27%. When polybutadiene having a microstructure out of this range is used, the rubber-modified styrene resin obtained is significantly inferior in colorability and inferior in practical value. Further, when the 1,2-vinyl bond structure exceeds 40%, the properties of the rubber as a toughening agent are poor, and the polybutadiene used in the method of the present invention has a molecular weight distribution curve having at least two peaks in a low molecular weight region and a high molecular weight region. Has a peak in the low molecular weight region at a molecular weight of 100,000 or more,
In addition, the boundary between the low molecular weight region and the high molecular weight region has a molecular weight of 10 to 10
It is between 0,000. Further, the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polybutadiene rubber must be 1.2 or more and less than 1.8. 1.2
When the amount is less than the above, the obtained rubber-modified styrene resin has excellent gloss, but the practical strength is weak, and when it is 1.8 or more, the practical strength is excellent, but no gloss appears. Also, the colorability is poor.

Furthermore, the polybutadiene should also have a branched shape with a high molecular weight of the polymer. That is, a polyfunctional binder having a shape that is capped with a trifunctional or tetrafunctional binder such as silicon tetrachloride, monomethyl silicon trichloride, tin tetrachloride, etc. ) Is required to be 50% or more. When the coupling degree is less than 50%, the obtained rubber-modified styrene resin is poor in coloring property, and particularly when the coupling degree is 30% or less, the coloring property is extremely poor and it cannot be put to practical use. In the method of the present invention, the coupling degree must be 50% or more, preferably 65% or more.

The method for producing such polybutadiene may be any conventionally known method, for example, by adding a vinylating agent such as ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, etc. to n-butyllithium, sec-
Using an organolithium compound such as butyllithium as a catalyst, solution polymerization is carried out as described above, and silicon tetrachloride, tin tetrachloride,
A coupling reaction is carried out with a polyfunctional binder such as halogen compounds such as carbon tetrachloride and diethyl esters such as diethyl adipate and dimethyl maleate [J. Polym.
Sci. Part A Vol.13 p. 93-103 ('65)]
However, any other conventionally known method may be used as long as it satisfies the scope of the claims of the present invention.

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 concentration of polybutadiene rubber is less than 2% by weight based on the total amount of the polybutadiene rubber and styrene-based monomer, the impact strength of the produced resin is insufficient, and when it exceeds 15% by weight, the strength is economically improved. Therefore, the range of 2 to 15% by weight is most suitable because problems such as a low degree and a high viscosity of the polymerization system are likely 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 coloring property by a coloring agent, practical impact resistance and rigidity and gloss as compared with conventional ones.

The rubber-modified styrenic resin obtained by the method of the present invention contains an antioxidant, if necessary, in addition to the coloring agent during processing.
An ultraviolet absorber, a lubricant, a release agent, a filler, etc. may be added in advance and used for general injection molding or extrusion sheet molding. Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The invention is not limited to these examples only.

Table 1 shows examples and Table 2 shows comparative examples. The rubber-modified styrene resins shown in the examples are excellent in all of the physical property items, and the one according to the present invention has a good physical property balance. I understand.

Example 1 [Synthesis of polybutadiene rubber] An autoclave having an internal volume of 100 was charged with 50 parts of dehydrated and purified benzene, 10 mmol of n-butyllithium, and 0.7 g of THF (tetrahydrofuran) as a vinylating agent. After adding 7,000 g of butadiene, polymerization was carried out at 60 ° C. for 2 hours. After adding tin tetrachloride as a coupling agent to the obtained polymer and reacting for 1 hour, 70 g of methanol was added to terminate the polymerization reaction, and then 4-methyl-2,6-diethanol was added as an antiaging agent. 50 g of each of sialy-butylphenol and trinonylphenylphosphite were added, and a polymer was precipitated by a steam stripping method. Table 1 shows various physical properties of the polybutadiene rubber obtained by drying by a usual drying method.

[Synthesis of rubber-modified styrene resin]

A rubber solution prepared by dissolving 8 parts by weight of the obtained polybutadiene in 92 parts by weight of styrene was charged into a 100 autoclave and 2,2 ditertiary butyl peroxybutane 0.05
Parts by weight and 0.05 parts by weight of tert-lead decyl mercaptan were added and stirred at 250 rpm. The inside of the autoclave was replaced with nitrogen gas, which was then sealed and heated. 6 at 100 ° C
After polymerization for a period of time, the mixture was cooled and then added to an autoclave having a capacity of 200, 100 g of pure water, 0.5 g of sodium dodecylbenzenesulfonate and 800 g of tricalcium phosphate, and a new 3,3 ditertiary peroxy was added while stirring at 130 rpm. 70 kg of the above prepolymerized solution containing 77 g of butyric acid citrate ethyl ester was added, and after nitrogen substitution, the temperature was sealed, the temperature was raised, polymerization was carried out at a temperature of 115 ° C. for 5 hours, and at 135 ° C. for 4 hours, followed by cooling. After neutralization, dehydration and drying according to a conventional method, the polymer was made into a usual pellet shape by an extruder to obtain a rubber-modified styrene resin. The results of measuring the physical properties are shown in Table 1.

Examples 2 to 5 and Comparative Examples 1 to 4 Polybutadiene rubber samples having different microstructures, coupling degree and Mw / Mn were obtained in the same manner as the polybutadiene rubber was obtained in Example 1.

Using these polybutadiene rubbers, rubber-modified styrenic resins of Examples 2 to 5 and Comparative Examples 1 to 4 were obtained by the bulk-suspension polymerization method similar to that of Example 1.

Table 1 and Table 2 show these measured physical properties.

Comparative Examples 5 to 7 Instead of the polybutadiene rubber used in Example 1, three types of commercially available polybutadiene rubber were used to obtain a rubber-modified styrene resin. Table 2 shows the brands of the commercially available polybutadiene rubber used and the measured physical properties.

Example 6 Using the polybutadiene rubber obtained in Example 1, bulk polymerization was carried out under the following conditions to obtain a rubber-modified styrene resin.

Polymerization liquid composition: Styrene 92 parts by weight Polybutadiene 8 parts by weight Irganox 1076 1.0 parts by weight t-dodecyl mercaptan 0.0002 parts by weight Polymerizer: equipped with a jacket and an agitator having an internal volume of 5, 10, 10 Polymerization conditions: 120 ° C. 70 rpm 2 Time 140 ° C. 25 rpm 4 hours 165 ° C. 10 rpm 4 hours Unreacted monomer removal 230 ° C. 45 minutes This was made into pellets with a 20 mmφ extruder.

Table 1 shows the physical property measurement results.

For the micro composition of the polybutadiene rubber, an infrared spectrophotometer (A-302 type manufactured by JASCO Corporation) was used to measure an infrared spectrum using carbon disulfide as a solvent, and then the Morello method [D. Morero
Et al., Chim. 6 Ind. , 41, 758 (1959)].

Polybutadiene has Mw / Mn and coupling degree of GPC
It was measured under the following conditions using [HLC-802A manufactured by Toyo Soda].

Solvent: Tetrahydrofuran (THF) Column: Two Toyo Soda GMH-6 2Fect Column constant temperature bath temperature: 38 ° C Solvent flow rate: 1.5 ml / min Sample concentration: 0.1% by weight Sample injection amount: 0.5 ml Detector: Differential refractometer data processor: cp-8000 manufactured by Toyo Soda Co., Ltd. The degree of coupling is on the GPC chart corresponding to the molecular weight of uncoupled rubber and the molecular weight of coupled rubber in the GPC data obtained under the above GPC measurement conditions. The peak area ratio is calculated and used as the coupling%.

The physical properties of the rubber-modified styrene resin were measured by the following methods.

(1) Tensile strength: According to JIS K-6871 (2) Izod impact strength: According to JIS K-6871 (3) Falling weight strength: Injection molded 2 mm thick 12 cm x 12 c
At the center of the square plate of m, weight tip 5R, weight diameter 14mmφ,
Drop a weight of 1 kg 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 in-line screw injection molding machine SN-51B manufactured by Niigata Iron Works Co., Ltd. at a molding temperature of 230 ° C. It should be noted that the injection-molded product is likely to receive directionality, and is easily cracked in the direction of the molding flow even when cracked by an external force. In this respect, the falling weight strength is the easiest to find the directionality.
In the present invention, the falling weight strength is adopted as a method of expression according to the actual situation.

(4) Gloss: According to JIS Z-8741 (5) Colorability: Add 0.5 parts of blue pigment PSD-B-871 from Nippon Pigment Co., Ltd. to 100 parts by weight of resin, and mold by injection molding to form a three-step step plate. The dark ultramarine blue,
The pigment closest to the color of the pigment itself and having the best coloring property was evaluated as A, the blue light grayish blue color and the one having the poorest coloring property were evaluated as E, and the middle thereof were evaluated as B, C and D in order.

[Brief description of drawings]

FIG. 1 is a molecular weight distribution curve by GPC of the polybutadiene rubber (A) used in Example 2 of the present invention and the commercially available polybutadiene rubber (B) used in Comparative Example 6, respectively. The horizontal axis represents the molecular weight (M) in logarithm and the vertical axis represents the weight%.

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Claims (2)

[Claims] 1. When a polybutadiene rubber is dissolved in a styrene-based monomer and the solution is polymerized to produce a rubber-modified styrene-based resin, the polybutadiene has (A) 1,2-vinyl bond structure of 20 to 40. %, Cis 1,4-
The binding structure is 15 to 35%, (B) the molecular weight distribution region has at least two peaks of the low molecular weight region and the high molecular weight region, the peak of the low molecular weight region is 100,000 or more, and the low molecular weight region and the high molecular weight region are high. The boundary with the molecular weight region is between 100,000 and 1,000,000, and (C) the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 1.2 or more and less than 1.8. And (D) a coupled polymer having a coupling degree of 50% or more, which is polymerized, to produce a rubber-modified styrene resin. 2. A polybutadiene rubber in an amount of 2 to 15 parts by weight and a styrene-based monomer in an amount of 85 to 98 parts by weight.
The method for producing a rubber-modified styrene resin according to the item.