JPS6023691B2 - Method of manufacturing high-impact polystyrene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing impact-resistant polystyrene with excellent colorability.

More specifically, the present invention relates to an improved method for producing impact-resistant polystyrene that has excellent colorability with colorants and practical impact resistance. Conventionally, impact-resistant polystyrene has been produced by dissolving unvulcanized rubber in styrene and subjecting this solution to bulk polymerization or bulk/suspension polymerization.

In this case, unvulcanized rubbers that are usually used as strong rutting agents include polybutadiene rubber and styrene-butadiene rubber. In particular, polybutadiene rubber is used because the resulting high-impact polystyrene has excellent low-temperature impact resistance. Most commonly used. However, one of the drawbacks of impact-resistant polystyrene using polybutadiene rubber as a strong rutting agent is poor colorability with colorants. Polystyrene, that is, so-called general polystyrene that does not contain a toughening agent, is a resin that originally has better coloring properties than other resins such as polystyrene. When agents are added to it, its coloring properties are significantly impaired. This tendency is particularly noticeable when the toughening agent used is polybutadiene rubber, and is considerably alleviated when the toughening agent is styrene-butadiene rubber. Generally, high-impact polystyrene is said to have a two-phase structure consisting of a rubber phase and a polystyrene phase, and it is presumed that this two-phase structure is one of the reasons for the decline in colorability of high-impact polystyrene. In other words, the decrease in transparency due to the two-phase structure and the poor colorability of the dispersed rubber phase, especially the voributadiene moiety in the rubber phase, are considered to be the causes of the decrease in colorability of impact-resistant polystyrene. However, it can be said that these issues have not been fully elucidated. At present, regarding the coloring properties and impact resistance of high-impact polystyrene, when polybutadiene rubber is used as a toughening agent, it has excellent low-temperature impact resistance, but has poor coloring properties. When using styrene-butadiene rubber, it has good coloring properties but is inferior in low-temperature impact resistance, so these impact-resistant polystyrenes, which have excellent low-temperature impact resistance and coloring properties, are Haven't gotten it yet. Under these circumstances, the present inventors
In order to obtain impact-resistant polystyrene with excellent low-temperature impact resistance and strength, as well as excellent colorability, we have repeatedly investigated various rubber-like toughening agents. As a result, various polybutadiene rubbers conventionally known as strong whipping agents in this field, for example, Japanese Patent Publication No. 37-6977, Japanese Patent Publication No. 41-161
Publication No. 85, Special Publication No. 1973-331, Special Publication No. 1973
If the polybutadiene rubbers having various micron structures, viscosities, and molecular weight distributions described in Japanese Patent No. 13954 and Tokukan Sho 51-13159 were used as they were,
It was not possible to improve the colorability of impact-resistant polystyrene. Furthermore, various block styrene-butadiene rubbers and random styrene-butadiene rubbers described in Japanese Patent Publication No. 41-14234 and Japanese Patent Publication No. 46-15017 have improved low-temperature resistance. It was significantly inferior in terms of impact resistance. in the end,
If known rubbers were used as they were as strong rut-forming agents for these high-impact polystyrenes, it would have been impossible to achieve high-impact polystyrenes that met the objectives of the present invention. Therefore, the present inventors conducted further intensive research on the polymer structure of polyptadiene rubber used as a strong rutting agent, and found that the vinyl content was 7 to 35% and the cis content was 20 to 80%.
, a polybutadiene rubber having a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw/Mn) of 2.6 or more and a Williams recovery value of 2.6 or more is dissolved in styrene, and the It was discovered that impact-resistant polystyrene meeting the object of the present invention could be obtained by bulk polymerization or bulk/suspension polymerization of a solution, and the present invention was developed based on this finding.

The impact-resistant polystyrene obtained by the method of the present invention has extremely excellent properties of both low-temperature impact resistance and colorability with coloring agents, and this characteristic cannot be achieved by using conventionally known rubber-like toughening agents. It is completely unobtainable.

That is, the impact-resistant polystyrene obtained using the polybutadiene rubber of the present invention is extremely superior in terms of colorability compared to the case where conventionally known polybutadiene rubbers are used. It also surpasses this in terms of low-temperature impact resistance. Moreover, when compared with the case where conventionally known styrene-butadiene rubber is used, it is superior not only in low-temperature impact resistance but also in terms of colorability. Even more surprisingly, it has been found that the method of the present invention, in addition to the above-mentioned characteristics, also produces completely unexpected side effects. In other words, when the polybutadiene rubber of the present invention is used as a strong rutting agent,
The volume occupied by the rubber phase in high-impact polystyrene is significantly increased compared to when conventionally known rubbers are used.

In general, the amount of rubber itself present in high-impact polystyrene is usually on the order of a few percent, but the volume of the rubber phase in high-impact polystyrene measured as the insoluble content in solvents such as toluene is the same as that of the rubber itself. It is known to increase several times. This is thought to be the result of polystyrene being occluded into the rubber phase during the polymerization process of high-impact polystyrene. Therefore, when the polybutadiene rubber of the present invention is used, more polystyrene is occluded than when conventional rubbers are used, and as a result, it is thought that the volume of the rubber phase is increased. The feature of the present invention in which the volume of the rubber phase increases is that a small amount of rubber is required to obtain the same impact resistance, which reduces the viscosity of the polymerization solution and facilitates polymerization control. This is a major improvement over the conventional manufacturing method of impact-resistant polystyrene, such as being economical due to the small amount used and achieving extremely high practical impact resistance, and its industrial ripple effects. can be said to be large.

The present invention will be explained in more detail below.

First, the polybutadiene rubber used in the rice grain toughening agent of the present invention will be described.

The polybutadiene rubber used in the present invention is, for example, n-
It is solution polymerized in a hydrocarbon solvent such as hexane in the presence of an organolithium catalyst such as butyllithium. The vinyl content of the polybutadiene rubber used in the present invention is 7 to 3.
5%, preferably 10-25%, more preferably 1
It is 0-20%.

If the vinyl content is less than 7%, the coloring properties of the resulting impact-resistant polystyrene will be poor and the tendency for the rubber phase to increase will not be noticeable, and if the vinyl content exceeds 35%, the low-temperature impact resistance will be poor. The cis content J of the polybutadiene rubber used in the present invention is 20 to 80%, preferably 25 to 45%.

If the cis content is less than 20%, the resulting impact-resistant polystyrene will have poor low-temperature impact resistance, and if the cis content exceeds 80%, its colorability will be poor. The ratio of the weight average Z molecular weight to the number average molecular weight (Mw/M
n) is 2.6 or more, preferably 2.9 to 5.

If Mw/Mn is less than 2.6, the resulting impact-resistant polystyrene will have poor coloring properties. The Williams 2 Mus recovery value (R,) of the polybutadiene rubber used in the present invention is 26 or higher, preferably 3.0 to 5. He is an enemy.

If the Williams recovery value is less than 2.6, the resulting impact-resistant polystyrene will have poor coloring properties and the texture of the rubber phase will not be noticeable. Williams' recovery value is AST
This value was measured using a Williams parallel plate plasticity meter in accordance with the method described in M-D926-56, and is a measure of the viscoelasticity of polyptadiene rubber.
In addition, the polybutadiene rubber used in the present invention has a Mooney viscosity (ML, 100qo) of 20 to 80, and the viscosity of a 5% by weight styrene solution measured at 2yo may be in the range of 40 to 20 ps. is preferable from the viewpoint of the physical property balance of the resulting impact-resistant polystyrene.The method for producing such polybutadiene rubber may be any conventionally known method as long as it produces the above structure. Vinylizing agents such as ethers of
A branching agent such as silicon tetrachloride described in Japanese Patent No. 1-36957 may be used, or the molecular weight distribution may be adjusted using the method described in Hakama Kosho No. 49-18475. On the other hand, as an actual method for producing the impact-resistant polystyrene of the present invention, the known bulk polymerization method or bulk/suspension polymerization method described in Japanese Patent Publication No. 46-15017 and the like is advantageously used. For example, the polybutadiene rubber of the present invention is dissolved in styrene, and this solution is heated to undergo radical polymerization in the presence or absence of a catalyst such as peroxide, and then bulk polymerization is continued to substantially inhibit the polymerization. Alternatively, the polymerization solution may be suspended in water during the polymerization to continue the polymerization and substantially complete the polymerization. At this time, a molecular weight regulator such as mercaptan, a solvent such as toluene, and a plasticizer such as mineral oil may be used as appropriate. In addition to the above, modifications and improvements to these methods are possible without impairing the effects of the present invention.

For example, a part of 1,3-butadiene forming the polybutadiene rubber used in the present invention may be replaced with other monomers such as isoprene, or other rubbers may be used in combination with this polybutadiene rubber. is also possible. In addition, a part of the styrene forming the impact-resistant polystyrene of the present invention,
It may be replaced with a monomer capable of radical copolymerization with styrene, such as Q-methylstyrene, acrylonitrile, and methacrylonitrile.

The impact-resistant polystyrene of the present invention obtained in this way has extremely superior low-temperature impact resistance and colorability with coloring agents compared to conventional impact-resistant polystyrene, and is molded by processing methods such as injection molding and extrusion molding. It is suitable for a variety of applications, especially colored products used at low temperatures.

In addition to coloring agents, antioxidants, ultraviolet absorbers, thickening agents, mold release agents, fillers, and other thermoplastic resins are also mixed into the impact-resistant polystyrene of the present invention during processing. By doing so, it can be used for a wide variety of purposes.
In addition, it can also be suitably used in general injection molding applications, sheet applications, and foam applications in which no coloring agent is added. Furthermore, the method of the present invention is superior to conventionally known production methods in terms of polymerization controllability and economic efficiency, and its utility value is wide-ranging.

Therefore, it can be said that the industrial significance of the present invention is extremely large. 0 Some Examples are shown below to show specific embodiments of the present invention, but these are for more specifically explaining the gist of the present invention, and are not intended to limit the present invention.

Examples 1 to 3, Comparative Examples 1 to 6 Polybutadiene rubber (sample A) having the structure defined in the present invention was subjected to the following conditions by recycling a portion of the polymer solution after the polymerization reaction was completed. Obtained by continuous polymerization method.

Polymerization conditions Polymerization vessel: Internal volume: 10 with rope scaler and jacket Monomer solution: Cyclohexane solution containing 2% by weight of butadiene Catalyst: 0.0 part by weight of n-butyl lithium per 100 parts by weight of monomer supplied as monomer solution Speed: 300'/min Polymerization vessel temperature: 120-130°C Circulating polymerization liquid amount: 3% by weight Polymer solution treatment method: 0.5 parts by weight of di-t-butyl per 10 parts by weight of polymer -After adding p-cresol,
When the solvent-removed sample A was analyzed on a heating roll, the cis content was 35.3%, the pinyl content was 12.4%, Mw/Mn was 3.21, and R was 3.
．． It had 84 ribs.

The cis content and pinyl content were determined by measuring the infrared spectrum using an infrared spectrophotometer (manufactured by JASCO Corporation, model IRA-2) using carbon disulfide as a solvent, and by the Morello method [D. Morer
o et al., Chim. elnd. 41, 758 (1959
)] respectively.

Mw/Mn was measured using GPC (LC-1, manufactured by Shimadzu Corporation) under the following conditions.

Solvent: Tetrahydrofuran Column: Shimadzu HSG-60, HSG-50, H
1 each of SG-40 and SG-50 3-column temperature bath temperature: 50oo Liquid feeding pressure: 80k9' Sample concentration: 0.1% by weight Sample liquid volume: 0.5cm Detector: Differential refractometer 3 or R
, was measured as follows using a Williams parallel plate plastometer specified in ASTM-D-926-56.

5k on a cylindrical specimen with a diameter of 14.3 ribs and a height of 12.7 ribs.
After applying a load of 9 and measuring the height of the sample after 3 minutes,
Immediately remove the sample from the plasticity meter and measure the height of the sample after leaving it at room temperature for 1 minute.

The difference in height of the sample before and after leaving it for 1 minute is the recovery value (R,
) and is expressed in side units. In addition, sample B shown below,
I prepared C, D, E, F, G, day, 1, and J.

Table 2 shows the physical properties of these samples. Sample B: High cis polybutadiene rubber, Tactene 12028 (pol$e
(Manufactured by R Company) Sample C: Low cis polybutadiene rubber, Inten Shishu FA (Manufactured by ISR Company) Sample D: Emulsion polymerized polybutadiene rubber, Myriopol 100 (Manufactured by Hodogaya Chemical) Sample E
: Emulsion polymerized styrene-butadiene rubber Nipol 1006
(manufactured by Nippon Zeon Co., Ltd.) Sample F: Polybutadiene rubber obtained by polymerizing butadiene in a cyclohexane solvent using butyl lithium as a catalyst, and shampooing the active end with silicon tetrachloride. Sample G, 1, 1, and J: Sample A was obtained. Table 1 shows the physical property values of polybutadiene comb samples A to J obtained using the same polymerization method as above, but changing the circulation amount of the polymerization solution and the polymerization temperature.

Using these rubbers as strong rutting agents, impact-resistant polystyrene compositions of Examples 1 to 4 and Comparative Examples 1 to 6 were obtained by the bulk polymerization method described below.

Conditions for bulk polymerization Polymerization solution composition: 80 parts by weight of styrene, 7.5 parts by weight of styrene benzene, 5 parts by weight, 0.5 parts by weight of RT-butyl-p-cresol, Polymerization vessel: Internal volume: 5, with jacket and flywheel polymerization temperature : Toazusa number: Polymerization time 125q○: 4pm: 4 hours 150q0: 1pm: 2 hours 170pm○: 8pm: Removal of reactants at the end of 2 hours: Obtained under the conditions of 220°C reduced pressure and 1 hour or more The composition was pulverized and made into pellets using an extruder.

In addition, when the amount of toughening agent in these compositions was calculated from the recovered styrene and ethylbenzene, they were all 6.0 to 6.0. a% by weight. Table 2 shows the physical properties of these compositions. Physical properties were measured as follows. The resulting composition was compression molded, and its Izod impact strength, tensile strength, and elongation at break were measured according to JIS-K-6871.

Injection molding was also carried out using a mold with a single pin gate measuring 15 m. Coloring property was determined by adding 0.3 parts of micro carbon black to 10 pieces of resin and injection molding in a 150 rib x 150 rib mold with a single pin gate on the 2-sided thickness. A rating of 4 was given for the property with the best quality, a rating of 1 was given for the poorest coloring property, and a rating of 3 and 2 was given for those in between. Further, one night of the obtained composition was dissolved in 30 kg of toluene, and the insoluble portion was centrifuged to measure the amount of toluene insoluble portion. Note that the amount of toluene misalignment substantially corresponds to the volume of the rubber phase. Table 1 *BR: Polybutadiene rubber SBR: Styrene-butadiene rubber Table 2 From the bulk polymerization results in Table 2, the following is clear.

[11 The cis content is greater than the range limited by the present invention,
Furthermore, the composition of Comparative Example 1 using Sample B whose pinyl content is less than the range defined by the present invention has inferior coloring properties compared to the composition using Sample A whose cis content is within the range defined by the present invention. .

[2] The composition of Comparative Example 3 using Sample D, which has a cis content lower than the range defined by the present invention, has a higher temperature at low temperatures than the composition using Sample A, which has a cis content within the range of the present invention. Poor impact resistance {3; Comparative Examples 2 and 5 using samples C and F in which Mw and Mn are outside the range of the present invention even if the cis content and total vinyl content are within the range limited by the present invention The compositions of Comparative Examples 2 and 6 using Samples C and G, in which R, is outside the range of the present invention, are different from those in Sample A, R, which is within the range of the present invention. Compared to the compositions of Examples 1 to 4 using No. 1 and J, the colorability is inferior.

[4} Cis content, vinyl content, Mw limited in the present invention
The compositions of Examples 1 to 4 using Samples A, 1, and J having /Mn,R, used Sample E, which is a styrene-butadiene rubber that was said to have excellent secondary coloring properties. The coloring property was equal to or better than that of the composition of Comparative Example 4, and the impact resistance at low overflow was far superior. ■ The compositions of Examples 1 to 4 using polyptadiene having the structure defined by the present invention are compared to other compositions despite having the same rubber content, as shown in the value of toluene dropout area. and the volume of the rubber phase is large.

{6' The compositions of Examples 1 to 4 using polyptadiene having the structure defined in the present invention are superior to the compositions of the comparative examples in both Izod impact strength and slender weight impact strength.

As described above, it is extremely important to limit the cis content, vinyl content, Mw/Mn, and R of the polyptadiene used in the present invention in order to achieve the object of the present invention.

As described above, the impact-resistant polystyrene composition obtained by the method of the present invention is a composition with excellent colorability and impact resistance at low temperatures.

Example 5, Comparative Examples 7-9 Impact-resistant polystyrene compositions of Example 5 and Comparative Examples 7-8 were obtained by the bulk suspension polymerization method shown below using Samples A, B, C, and E. .

Inner volume: 20 In the polymerization vessel, 9 parts by weight of styrene, 5 parts by weight of rubber.
．． 5 parts by weight, 0.5 parts by weight of di-butyl-p-cresol.
Using a polymerization solution having a composition of 42 parts by weight and 0.08 parts by weight of TS-dodecyl mercaptan, polymerization was carried out at a temperature of 115 DEG C. and a clearness number of 5 pm until the styrene reaction rate reached about 40%.

Next, 0.1 parts by weight of di-tert-butyl peroxide was added per 10 parts by weight of this solution, and further 0.15 parts by weight of polyvinyl alcohol and 0.05 parts by weight of dodecyl were added as suspension stabilizers. Add 100 parts by weight of water containing sodium benzenesulfonate and suspend under the water. The suspended mixture was heated under heating at 120 qo for 3 hours, at 140° C. for 3 hours, and finally at 150 oo for 2 hours to substantially complete the polymerization of styrene. The resulting bead-like composition was separated from the reaction mixture by centrifugation, washed with water, dried, and measured for physical properties in the same manner as in Example 1. The results are shown in Table 3. Table 3 As is clear from the results in Table 3, even by the bulk-suspension polymerization method, the cis content, vinyl content, Mw/Mn,
The composition of Example 5 using sample A of polybutadiene rubber having R,
Compared to the compositions of Comparative Examples 7 and 8 using C polybutadiene rubber, the colorability was lower and the volume of the rubber phase was larger,
Further, it has the same coloring properties as the composition of Comparative Example 9 using the styrene-butadiene rubber of Sample E, and has far superior impact resistance at low temperatures.

Claims (1)

[Claims] 1. When polybutadiene rubber is dissolved in styrene and the solution is subjected to bulk polymerization or bulk/suspension polymerization, (1) the vinyl content of the polybutadiene rubber is 7 to 35%;
Cis content is 20-80% (2) Weight average molecular weight (Mw
) and number average molecular weight (Mn) (Mw/Mn) is 2.6
Above (3) Williams recovery value (R_1) is 2.6
A method for producing impact-resistant polystyrene, characterized in that the polystyrene has a polystyrene impact resistance of 1 mm or more. 2. The method for producing impact-resistant polystyrene according to claim 1, wherein the polybutadiene rubber has a cis content of 25 to 45%. 3. The method for producing high-impact polystyrene according to claim 2, wherein the vinyl content of the polybutadiene rubber is 10 to 25%. 4. The method for producing high-impact polystyrene according to claim 2, wherein the polybutadiene rubber has a ratio of weight average molecular weight to number average molecular weight of 2.9 to 5. 5 Williams recovery value of polybutadiene rubber is 3.
The method for producing impact-resistant polystyrene according to claim 2, which has a thickness of 0 to 5.0 mm.