JP3365854B2 - Impact resistant styrenic resin composition and continuous production method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact-resistant styrenic resin composition and a method for producing the same. More specifically, it relates to improvement of impact strength of impact-resistant styrene resin composition produced by bulk continuous polymerization method.

[0002]

2. Description of the Related Art It has been widely known that various unvulcanized rubbers are used as a toughening agent for hard and brittle styrenic resins, and styrene resins using unvulcanized rubber generally have impact resistance. It is called polystyrene (HIPS). In particular, HIPS obtained by dissolving polybutadiene, butadiene-styrene copolymer, or the like as an unvulcanized rubber in a styrene-based monomer and performing random copolymerization by bulk-suspension polymerization or bulk polymerization is inexpensive and has various physical properties. It has been widely used due to its excellent balance. In order to further improve the impact strength in such HIPS, a means of increasing the rubber content in the product is generally used. However, if the rubber content is increased too much, the viscosity in the polymerization equipment will increase during production, which will hinder operations such as stirring and mixing, and the impact strength will increase only slightly, while the gloss and rigidity will decrease. Etc. are remarkable.

Without excessively increasing the rubber content,
In order to efficiently improve impact strength, a method is known in which rubber particles have a bimodal particle size distribution of small particles and large particles. The mechanism of impact strength improvement by making the rubber particle diameter bimodal is described in the literature (eg Macromolecules, Vol.24, 5639-5644, (1991)).
Is shown in. As a specific example of this method, Japanese Patent Publication No. 1-41177 proposes a method of newly adding a rubber liquid to a rubber liquid that has undergone phase inversion in a batch process. In addition, impact strength is improved by blending high-gloss HIPS having rubber particles with a single occlusion structure formed using styrene-butadiene copolymer rubber and ordinary HIPS having a small amount of rubber particles having a salami structure. Attempts to do so can be found in U.S. Pat. No. 4,493,922, Japanese Patent Laid-Open No. 63-112646, and the like.
In addition, after forming rubber particles in the first reaction tank, a raw material containing a styrene-butadiene block copolymer rubber is supplied to the liquid at the outlet of the first reaction tank, and then the styrene-butadiene block copolymer is loaded in the second reactor. Japanese Patent Laid-Open No. 3-199212 proposes a method in which a coalesced rubber is made into particles to make the rubber particle diameter bimodal. Further, Japanese Unexamined Patent Publication (Kokai) No. 3-263415 proposes a method in which the reaction system is made into two series, HIPS having different particle diameters are produced therein, and then both are merged to make bimodal. Although impact strength is certainly improved by these methods, the process is a batch process, or the resins produced separately are blended in an extruder,
Since it is necessary to mix the polymerization liquid of the small particle rubber and the large particle rubber in the reaction tank or to manufacture the production line in two lines, there are disadvantages that the manufacturing process becomes complicated and the manufacturing cost becomes high.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide an impact-resistant styrenic resin composition having an impact strength superior to that of the conventional impact-resistant styrene resin composition. It is an object of the present invention to provide a continuous process for producing a composition efficiently and in a simple process.

[0005]

That is, the present invention provides a rubber-modified styrene in which rubber particles obtained by polymerizing a styrene monomer in the presence of a rubbery polymer are dispersed in a styrene polymer resin phase. In the resin composition, (a) the particle size distribution of the rubber particles dispersed in the resin composition is monomodal, and the rubber particle size D measured with a Coulter counter is D.
When the number of [μm] particles is n [pieces], Dv = ΣD ⁴ n / ΣD ³ n (1), the volume average rubber particle diameter (Dv) is 1.5 ≦ Dv ≦ 5. .0 (2), and (b) the volume rubber particle size distribution (f
(D)) In f (D) = D ³ n / ΣD ³ n (3), the cumulative frequency fraction of (f (D)) from the large particle diameter side is 25, 50, 75%. D to D25 and D respectively
When 50 and D75, Cv = (D25-D75) / D50 (4) The Cv defined by (4) is in the range of 0.60≤Cv≤0.85 (5). The impact-resistant styrene resin composition is

Further, the present invention provides a method for producing the above impact resistant styrene resin composition. That is, the method for producing the impact-resistant styrene resin composition of the present invention comprises a raw material solution prepared by dissolving a rubber-like polymer in a styrene monomer, using an anchor type stirring blade or
Is continuously supplied to a complete mixing tank type reactor (A) having a paddle blade, and styrene is added so that the resin ratio in the complete mixing tank type reactor is at least twice the weight fraction of the rubber-like polymer. The system monomer is polymerized, and the reaction solution is continuously taken out from the reactor in an amount corresponding to the amount of the raw material solution supplied. Further, if necessary, the reaction mixture is placed in series at the subsequent stage of the complete mixing tank reactor.
Polymerization is carried out in a plug flow type reactor having a group or a plurality of groups, and the stirring rotation speed of the complete mixing tank type reactor is N [sec
-1], and when the diameter of the stirring blade is d [m], the polymerization is performed while maintaining 0.18≤N3d2≤0.90 (6).

Further, in this production method, instead of directly supplying the raw material solution to the complete mixing tank reactor (A), preferably upstream of the complete mixing tank reactor, preferably a complete mixing tank reactor or a plug. A prepolymerizer comprising a flow type reactor was provided, and a raw material solution in which a rubbery polymer was dissolved in a styrene-based monomer was continuously supplied to the prepolymerizer, and the resin in the prepolymerizer in the prepolymerizer was supplied. The prepolymerization is carried out in a range where the rate is less than twice the weight fraction of the rubbery polymer, and the prepolymerization reaction liquid continuously taken out from the prepolymerizer in an amount corresponding to the amount of the raw material solution supplied is anchored with stirring. It was continuously supplied to the complete mixing tank reactor (A) having blades or paddle blades, and the resin content in the complete mixing tank reactor was twice the weight fraction of the rubbery polymer. Polymerize the styrenic monomer as above and mix thoroughly. Type reaction vessel (A), the amount of the reaction solution corresponding to the supply amount of the prepolymerization reaction solution is continuously taken out from the complete mixing tank type reactor (A), and further, if necessary, the tank type reactor. Polymerization was carried out in one or a plurality of plug flow type reactors arranged in series in the subsequent stage, and the stirring rotation speed of the above complete mixing tank type reactor was N [sec-1] and the stirring blade diameter was d [m. ], 0.18≤N3d2≤0.90 (6) is maintained and polymerization is carried out, and a high-impact styrene-based resin composition is produced. Here, the resin ratio is the ratio of the rubber-like polymer, the polymer of the styrene-based monomer and the copolymer of the rubber-like polymer and the styrene-based monomer in the reaction solution. An example of the rubber particle size and volume rubber particle size distribution obtained with a Coulter counter and the cumulative frequency fraction from the large particle size side is shown in the figure. Shown in 1.

Examples of the styrenic monomer in the present invention include styrene and nuclear alkyl-substituted styrenes such as o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene and ethylstyrene, α
Α-alkyl substituted styrenes such as -methylstyrene, o
-Nucleohalogenated styrenes such as chlorostyrene, m-chlorostyrene and p-chlorostyrene, which are used alone or as a mixture of any two or more thereof.

The styrenic polymer in the present invention means a homopolymer or a copolymer of two or more kinds of the above-mentioned styrenic monomers.

The rubber-like polymer in the present invention is 1,
3-Butadiene alone or made by solution polymerization of isoprene, styrene, α-methylstyrene and the like copolymerizable with 1,3-butadiene with an organic lithium catalyst,
So-called low cis polybutadiene and high cis polybutadiene obtained by coordination polymerization are suitable.

The raw material solution in the present invention means a solution in which a rubber-like polymer is dissolved in a styrene-based monomer and a solvent in which a solvent is added if necessary. The proportion of the rubbery polymer to be dissolved is preferably 3 to 12% by weight based on the total raw material solution. When the proportion of the rubber-like polymer is 3% by weight or less, the impact strength is not improved so much.
It is disadvantageous for operations such as mixing. The amount of the solvent to be added is not particularly limited, but if the amount of the solvent exceeds 50% by weight of the total raw material solution, the effective reaction volume of the reaction tank decreases and it is very difficult to separate and recover the solvent from the product. Energy is required, which is not economically preferable.

In the present invention, the polymerization may be either thermal polymerization without addition of a catalyst or catalytic polymerization with addition of a catalyst. The catalyst is not particularly limited as long as the reaction proceeds by a free radical mechanism such as organic peroxide. Examples of such organic peroxides include peroxyketals such as 1,1-bis (tertiarybutylperoxy) 3,3,5-trimethylcyclohexane, dialkylperoxides such as ditertiarybutylperoxide, and tertiary. Examples thereof include peroxyesters such as tributyl peroxyisopropyl carbonate, and these can be used alone or in combination of two or more kinds.

In the present invention, the volume average rubber particle diameter Dv of the rubber particles is kept within the range of 1.5≤Dv≤5.0. D
When v is smaller than 1.5, the strength of the obtained resin is low and it is not practical as an impact resistant resin. Further, even if Dv is larger than 5.0, the improvement in strength due to the larger rubber particle size is small and ineffective, and the appearance is also poor.
If the stirring conditions in the complete mixing tank are made gentle to further increase the particle size, the mixing state in the complete mixing tank will deteriorate,
Even in this case, it is difficult to continue safe driving.

In the present invention, the rubber particle size distribution Cv of the rubber particles is maintained in the range of 0.60≤Cv≤0.85, but when Cv is smaller than 0.60, the conventional rubber particle size distribution is substantially the same. Since there is no difference from the monomodal impact-resistant styrene-based resin, the effect of the present invention is not exhibited, and a resin having excellent impact strength cannot be obtained. Also, as Cv is increased, the mixed state inside the complete mixing tank deteriorates, and Cv>
Under the condition of 0.85, it is difficult to keep the temperature of the complete mixing tank uniform, and it is difficult to continue stable operation.
An example of the rubber particle size and volume rubber particle size distribution obtained with a Coulter counter and the cumulative frequency fraction from the large particle size side is shown in the figure. Shown in 1.

The continuous production method of the impact resistant styrene resin composition of the present invention is carried out by using a complete mixing tank type reactor equipped with an anchor type stirring blade or paddle blade. Is characterized in that it is polymerized under a certain resin ratio and stirring conditions. In this reactor, a rubber-like polymer is dispersed as dispersed particles containing polystyrene (occluded polystyrene) in the styrene-based polymer resin phase. (Forming rubber particles) is essential. Although this will be described later, in order to prevent excessive shearing in the plug flow type reactor after the complete mixing tank type reactor, it is necessary to form rubber particles in the complete mixing tank type reactor so that the rubber particles will be formed in the subsequent process. This is because it cannot be formed and the desired resin cannot be obtained. The shape of the stirring blade is an anchor-type stirring blade for anchoring ships (anchor blade, anchor blade,
Horseshoe-shaped stirring blade) or paddle blade . Fig. 2 shows a specific example. Further, it is essential that the resin ratio in the complete mixing tank type reactor is at least twice the weight fraction of the rubber-like polymer, but the upper limit thereof is preferably 50% by weight, more preferably 40% by weight. . This is because if the resin ratio is excessively increased, it becomes difficult to make the inside of the tank uniform as the viscosity of the resin liquid in the reactor increases. Further, a prepolymerization vessel may be installed in front of this reactor. In this case, the prepolymerization vessel is preferably, for example, a complete mixing tank type reactor or a plug flow type reactor, but the resin ratio is set to 2% by weight of the rubbery polymer so that rubber particles are not formed at the prepolymerization vessel outlet. It is necessary to suppress the reaction to less than twice. After the rubber particles are formed, the reaction is allowed to proceed in a plug flow type reactor so that excessive shear is not applied. In this plug flow type reactor, it is necessary to eliminate the concentration distribution in the direction perpendicular to the fluid flow, but in this operation, a static mixer is built in, and shearing more than the necessary minimum is carried out. You have to make sure it doesn't happen. This is because excessive shear in the plug flow reactor may affect the morphology of the rubber particles formed in the complete mixing tank reactor. As static mixers, there are a static mixer manufactured by Sruzer, a static mixer manufactured by Kenix, and a static mixer manufactured by Toray.

Further, in the present invention, the anchor type stirring of the complete mixing tank
As the stirring condition of the blade, the stirring rotation speed of the reactor is N [sec.
^-1], N when the stirring blade diameter is d [m]³d²To 0.18
≦ N ³d²It is necessary to keep the range of ≦ 0.90. N³d²But
Below 0.18 keeps the reactor substantially completely mixed
Things become difficult. N³d²Is over 0.90, the reactor
Can be kept in a completely mixed state, but the average particle size of rubber particles
The particle size becomes smaller and the particle size distribution becomes sharper.
Therefore, the effect of the present invention is not exhibited.

In the present invention, the resin liquid obtained from the final plug flow reactor is continuously sent in a temperature range of 200 to 300 ° C. to a devolatilization tank for evaporating unreacted monomers and a solvent under a vacuum atmosphere, and the resin liquid is subjected to resistance. Recovered as impact styrene resin. The resin thus obtained is characterized in that it has a high impact strength as compared with resin compositions having the same average rubber particle diameter and rubber content, although the particle diameter distribution of the rubber particles is unimodal. There is.

EXAMPLES Examples of the present invention will be shown below.

With respect to the obtained resin, the rubber particle diameter, the rubber content and the Izod impact strength were measured. Hereinafter, these measuring methods will be described. The rubber particle size is dimethylformamide (DMF) and ammonium thiocyanate (NH ₄ SC) with a Coulter counter (TA-II type manufactured by COULTER).
Using the mixed electrolyte of N), 2 to 5 resin pellets are placed in about 5 ml of DMF and left for about 2 to 5 minutes, and then the DMF dissolved content is adjusted to an appropriate particle concentration in an aperture tube of 30 μm. To be measured. Rubber content is halogen addition (iodometric titration), Izod impact strength is ASTM-D
According to 256. The resin ratio was determined by dissolving an appropriate amount of resin solution (X grams) collected from a polymerization vessel with methyl ethyl ketone (MEK), precipitating the solution with a large excess of methyl alcohol, and then drying it at a constant weight (Y grams) in a dryer at 80 ° C. ) And dried according to the following formula. Resin ratio (%) = (Y / X) × 100

[0019]

Example 1 4.9% by weight of low-cis polybutadiene rubber as a rubber-like polymer (made by Asahi Kasei, trade name Diene 55A
S) was dissolved in 91.1% by weight of styrene and 4.0% by weight of ethylbenzene as a solvent to prepare a polymerization raw material. Further, 0.1 part by weight of a rubber antioxidant (manufactured by Ciba Geigy, trade name Irganox 1076) was added. This polymerization raw material was provided with a 14-liter jacketed reactor equipped with an anchor type stirring blade having a blade diameter d = 0.285 [m] (R-01, FIG.
2)) at 12.5 [kg / hr]. Reaction temperature is 1
40 ° C, N ³ d ² is 0.83 [m ² / S ³ ], and the resin rate is 25%
Met. The obtained resin liquid was introduced into two plug flow type reactors with an internal volume of 21 liters arranged in series. The first plug flow reactor (R-0
In 2), the reaction temperature is 120 ° C to 1 in the flow direction of the resin liquid.
40 ° C. In the second plug flow reactor (R-03), the reaction temperature was 130 ° C. to 160 ° C. in the resin liquid flow direction.
The jacket temperature was adjusted so as to have a gradient of. R-0
The resin rate at the 2 outlet was 50%, and the resin rate at the R-03 outlet was 70%. The obtained resin liquid is heated to 230 ° C.,
After being sent to a devolatilization tank with a vacuum degree of 5 [torr] to separate and collect unreacted monomer and solvent, it is extracted from the devolatilization tank with a gear pump, made into a strand through a die plate, and then pelletized through a water tank as a product. Recovered. The rubber content of the obtained resin was 7.1%, the particle size distribution was 0.79, and Iz
The od impact strength was 10.2 [kgf · cm / cm].

[0020]

[Comparative Example 1] Production was carried out under exactly the same conditions as in Example 1 except that the N ³ d ² of R-01 was 0.13 [m ² / S ³ ], the polymerization raw materials, the polymerization conditions, and the resin rate. Under such conditions, it was quite difficult to keep the polymerization temperature constant, and it was difficult to continue steady stable operation in a completely mixed state.

[0021]

[Comparative Example 2] Polymerization was carried out under exactly the same conditions as in Example 1 except that the N ³ d ² of R-01 was 2.19 [m ² / S ³ ]. The obtained resin had a narrow particle size distribution of 0.54 and an Izod impact strength of 7.6 [kgf · cm / cm], which was a considerably low value compared with Example 1.

[0022]

[Comparative Example 3] Production was carried out under exactly the same conditions as in Example 1 except that the N ³ d ² of R-01 was 1.51 [m ² / S ³ ], the polymerization raw materials, the polymerization conditions, and the resin rate. In this case as well, as in Comparative Example 2, the Izod impact strength was 7.5 [kgf · cm / cm], which was considerably lower than that in Example 1.

[0023]

Example 2 Production was carried out under the same conditions as in Example 1 except that the resin rate at the outlet of R-03 was set to 80%. The obtained resin has a rubber content of 5.8%, a particle size distribution of 0.78, and Izo.
d Impact strength was 8.9 [kgf · cm / cm].

[0024]

[Comparative Example 4] except that the N ³ d ² of R-01 and 2.19 [m ² / S ^3] Polymerization raw materials, the polymerization conditions, the resin ratio was produced in the same conditions exactly as in Example 2. The obtained resin has a narrow particle size distribution of 0.54. As a result, the Izod impact strength was 7.6 [kgf · cm / cm], which was a low value as compared with Example 2.

[0025]

Example 3 7.3 wt% high-cis polybutadiene rubber as a rubber-like polymer (trade name BR-15 manufactured by Ube Industries, Ltd.)
HL) 86.7% by weight of styrene, and 6.0 as a solvent.
It was dissolved in wt% ethylbenzene to obtain a polymerization raw material. Further, 0.1 part by weight of a rubber antioxidant (manufactured by Ciba Geigy, trade name Irganox 1076) was added. This polymerization raw material was fed into a 14-liter jacketed reactor (R-01) equipped with an anchor type stirring blade having a blade diameter d = 0.285 [m] as in Example 1 at 11.0 [kg / hr]. Supplied. The reaction temperature is 140 ° C., N ³ d ² is 0.83 [m ² / S ³ ], and the resin rate is 2
It was 5%. The obtained resin liquid was introduced into two plug flow type reactors with an internal volume of 21 liters arranged in series. The first plug flow reactor (R-
In 02), the reaction temperature is 120 ° C to the resin liquid flow direction.
150 ° C, second plug flow reactor (R-03)
Then, the reaction temperature is 140 ° C to 180 ° C in the flow direction of the resin liquid.
The jacket temperature was adjusted so as to have a gradient of ° C. R-
The resin rate at the 02 exit was 55%, and the resin rate at the R-03 exit was 82%. The resin obtained by removing the volatile matter had a rubber content of 9.4%, a particle size distribution of 0.66, and an Izod impact strength of 9.7 [kgf · cm / cm].

[0026]

[Comparative Example 5] except that the N ³ d ² of R-01 and 0.94 [m ² / S ^3] Polymerization raw materials, the polymerization conditions, the resin ratio was produced under completely the same conditions as in Example 3. The obtained resin had a particle size distribution of 0.57, which did not satisfy the formula (3) and had an Izod impact strength of 7.8 [kgf · cm / cm], which was a low value as compared with Example 3. .

[0027]

Example 4 Production was carried out under exactly the same conditions as in Example 1 except that the stirring blade of R-01 was changed to a paddle blade having a blade diameter of 0.184 [m] (see FIG. 3). As a result, the particle size distribution was 0.68 and the Izod impact strength was 9.0 [kgf · cm / cm].

[0028]

Comparative Example 6 A paddle blade similar to that of Example 4 was used and N ³ d ² was used.
Except for 5.63 [m ² / S ³ ].
The resin was manufactured under the same conditions as in Example 4.

[0029]

[Comparative Example 7] A paddle blade similar to that of Example 4 was used and N ³ d ² was used.
Except for 0.15 [m ² / S ³ ].
The resin was manufactured under the same conditions as in Comparative Example 7.
The results of Examples 1 to 4 and Comparative Examples 1 to 7 are shown in Table 1, Table 2 and Table 3.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

As described above, the styrene resin obtained by the method of the present invention is excellent in impact strength and has great industrial utility value in applications such as home electric appliances and food packaging materials. Further, in the present invention, an impact-resistant styrene-based resin having excellent impact strength can be obtained without requiring a complicated device or operation, which is advantageous in terms of energy and economy.

[Brief description of drawings]

FIG. 1 is an example of a rubber particle size and a volume rubber particle size distribution obtained by a Coulter counter and a cumulative frequency fraction from the large particle size side.

FIG. 2 is an example of a vertical cross-sectional view showing a reactor equipped with an anchor type stirring blade used in Examples 1 to 3 and Comparative Examples 1 to 5.

FIG. 3 is an example of a longitudinal sectional view showing a reactor equipped with paddle blades used in Example 4 and Comparative Examples 6 and 7.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-57-96006 (JP, A) JP-A-63-118315 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08F 279/02

Claims (3)

(57) [Claims] 1. A rubber-modified styrenic resin composition obtained by polymerizing a styrenic monomer in the presence of a rubbery polymer, wherein the rubber particles are dispersed in a styrenic polymer resin phase. ) When the particle size distribution of the rubber particles dispersed in the resin composition is monomodal and the number of rubber particle size D [μm] measured with a Coulter counter is n [pieces], Dv = The volume average rubber particle diameter (Dv) defined by ΣD ⁴ n / ΣD ³ n (1) is 1.5 ≦ Dv ≦ 5.0 (2), and (b) Volume rubber particle size distribution (f
(D)) In f (D) = D ³ n / ΣD ³ n (3), the cumulative frequency fraction of (f (D)) from the large particle diameter side is 25, 50, 75%. D to D25 and D respectively
When 50 and D75, Cv = (D25-D75) / D50 (4) The Cv defined by (4) is in the range of 0.60≤Cv≤0.85 (5). Impact resistant styrene resin composition. 2. A raw material solution in which a rubbery polymer is dissolved in a styrene-based monomer is continuously supplied to a complete mixing tank type reactor having an anchor type stirring blade or paddle blade, and the complete mixing tank type The styrene monomer was polymerized so that the resin ratio in the reactor was more than twice the weight fraction of the rubbery polymer, and the reaction liquid was continuously supplied from the reactor in an amount corresponding to the amount of the raw material solution supplied. After taking out, polymerization is carried out in one or a plurality of plug flow type reactors arranged in series in the latter stage of the tank type reactor, if necessary, and the stirring rotation speed of the complete mixing tank type reactor is N [ sec-1], and when the stirring blade diameter is d [m], the polymerization is carried out while maintaining 0.18 ≦ N ³ d ² ≦ 0.90 (6). Item 2. A method for producing the impact resistant styrene resin composition according to Item 1. 3. A raw material solution in which a rubbery polymer is dissolved in a styrene-based monomer is continuously supplied to a prepolymerizer, and the resin ratio in the prepolymerizer in the prepolymerizer is the weight of the rubbery polymer. Preliminary polymerization is performed in a range of less than twice the fraction, and the prepolymerization reaction liquid continuously taken out from the prepolymerizer in an amount corresponding to the amount of the raw material solution supplied has an anchor type stirring blade or paddle blade.
Continuously fed to a complete mixing tank type reactor, 2 resin ratio in said complete mixing tank type reactor of the weight fraction of the rubber-like polymer
Polymerize the styrene-based monomer so that it is more than double the amount, and continuously supply the amount of reaction solution equivalent to the supply amount of the prepolymerization reaction solution introduced into the complete mixing tank reactor from the complete mixing tank reactor. And, if necessary, polymerization is carried out in one or a plurality of plug flow type reactors arranged in series in the latter stage of the tank type reactor, and the stirring rotation speed of the complete mixing tank type reactor is set to N. [sec-1], which comprises polymerizing by maintaining the impeller diameter to satisfy the d [m] and the time ^{0.18 ≦ N 3 d 2 ≦ 0.90} ··· (6) The method for producing the impact resistant styrene resin composition according to claim 1.