JPH07110894B2 - Method for producing impact resistant styrene resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing an impact-resistant styrenic resin using a diblock copolymer composed of styrene and butadiene as a toughening agent, and more specifically, The present invention relates to a method for producing an impact-resistant styrene-based resin having excellent impact resistance, particularly Izod impact strength, and good rigidity.

(Prior Art) Polystyrene resins are widely used in various applications because they are excellent in transparency, rigidity, gloss, and the like and have good moldability. However, this polystyrene resin has the drawback of being inferior in impact strength and being brittle, which limits its use. In order to improve this drawback, a method of bulk polymerization or bulk-suspension polymerization using a styrene solution of a rubber-like polymer has been proposed, and is widely used industrially as a method for producing an impact-resistant styrene resin. The rubber-like polymer used for this purpose has a low glass transition temperature,
Polybutadiene rubber and styrene-butadiene random copolymer rubber, which are apt to undergo a graft reaction and to cause appropriate gel formation, are generally used, and polybutadiene rubber is particularly preferable.

In recent years, impact-resistant styrenic resins have a better balance of price and performance than competing resins, so their applications are expanding to household electric appliance housings and parts, automobile parts, office equipment, daily sundries and toys. There is. With the spread of such applications, demands for improvement of impact resistance and rigidity, which are inferior to those of ABS (acrylonyl tri-butadiene-styrene copolymer) resins, which are competing resins, are further increasing.

The impact resistance is improved by increasing the content of rubbery polymer, but the rigidity decreases with the content of rubbery polymer.

On the other hand, rigidity is improved by reducing the rubber-like polymer content or reducing the rubber particle size after graft copolymerization,
Impact resistance decreases. It is a technically very difficult task to improve impact resistance and rigidity at the same time or to maintain the performance of one while maintaining the performance of the other.

Conventionally, there has been proposed a method for improving impact resistance and rigidity by specifying a polymer structure of polybutadiene and a certain physical property value of the rubber and styrene resin (Japanese Patent Laid-Open No. Sho 52-52).
-152491, JP-A-60-250021). However, not necessarily
I haven't reached the point where I can be fully satisfied.

(Problems to be Solved by the Invention) As a result of intensive studies on the method for improving the impact resistance and rigidity of the impact-resistant styrene-based resin, the present inventors strengthened a specific styrene-butadiene diblock copolymer. It was found that this problem can be solved by using it as an agent, and the present invention has been completed based on this finding.

Therefore, it is an object of the present invention to provide a method for producing an impact resistant styrene resin having improved impact resistance and rigidity.

(Means for Solving the Problems) An object of the present invention is to provide a high impact styrene resin by bulk polymerization or bulk-suspension polymerization of a solution of a diblock copolymer of styrene and butadiene dissolved in styrene. (1) The styrene content is 15 to 35% by weight, the 1,2-vinyl bond content of the butadiene unit is 15 to 35 mol%, and the styrene-butadiene diblock copolymer is (2)% by weight. Average molecular weight (w) and number average molecular weight (
The ratio (w / n) of n) is 1.5 or less, (3) the viscosity of a 5% by weight styrene solution measured at 25 ° C. is 5 to 20 cps, and (4) a portion where styrene units and butadiene units are randomly copolymerized. This is accomplished by using a block copolymer that is substantially free of polymer chains.

The method of the present invention is carried out by using the known bulk polymerization method or bulk-suspension polymerization method in the production of impact-resistant styrenic resins, except that the above-mentioned styrene-butadiene diblock copolymer is used.

The styrene-butadiene diblock copolymer used as a toughening agent in the present invention is a polystyrene-polybutadiene diblock copolymer produced by conventional anionic polymerization using a catalyst based on an alkali metal such as lithium. .

The styrene content in the block copolymer is 15 to 35% by weight. When the styrene content is less than 15% by weight, the impact resistance is improved but the rigidity is not sufficiently improved. On the other hand, the styrene content is 35
When the content is more than 10% by weight, the rigidity is improved but the impact resistance is not sufficiently improved. Further, the 1,2-vinyl bond of the butadiene unit in the block copolymer is 15 to 35
The mol% is essential for improving the balance between impact resistance and rigidity of the impact resistant styrene resin. When the 1,2-vinyl bond is less than 15 mol% and more than 35 mol%,
Both have poor impact resistance. Furthermore, in order to balance impact resistance and rigidity, the ratio (w / n) of the weight average molecular weight (w) and the number average molecular weight (n) of the block copolymer is 1.
Must be 5 or less. Further, the viscosity of a 5% by weight styrene solution of the block copolymer measured at 25 ° C. is 5
It is also necessary to be in the range of up to 20 cps. If it is less than 5 cps, the impact resistance will be poor, and if it exceeds 20 cps, the rigidity will be poor.
It is preferably 10 to 15 cps.

Finally, it is important that the styrene-butadiene diblock copolymer chain used in the present invention does not substantially include a portion in which a styrene unit and a butadiene unit are randomly copolymerized. The effect of the present invention is not exhibited when the random copolymerization portion of the styrene unit and the butadiene unit is contained.

In the present invention, the molecular weight (w) of the block copolymer is not particularly limited as long as it is a styrene-butadiene diblock copolymer satisfying the above requirements, but it is usually 30,000 to
It is in the range of 200,000.

In the method of the present invention, the above-mentioned styrene-butadiene diblock copolymer is dissolved in a styrene-based monomer or a mixture of this monomer and a monomer copolymerizable therewith, and bulk polymerization or Bulk-suspension polymerization. The amount of the block copolymer used is usually 2 to 20% by weight in the mixture of the block copolymer and these monomers.

As the styrene-based monomer used in the present invention, at least one kind of styrene such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene and derivatives thereof is used. Examples of the monomer copolymerizable with the styrene-based monomer include unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile, acrylic acid esters such as acrylic acid methyl ester, and methacrylic acid esters such as methacrylic acid methyl ester. At least one type of vinyl-based monomer is used. Such a monomer is used in the range of 50% by weight or less based on the total amount of monomers including the styrene-based monomer.

In the case of producing an impact resistant styrene-based resin by a bulk polymerization method, usually, a solution of a toughening agent such as styrene, if necessary, a diluent such as toluene or ethylbenzene, an internal lubricant such as liquid paraffin or mineral oil, Antioxidants, chain transfer agents such as mercaptans and α-methylstyrene dimers, etc. are added, and in the case of no catalyst, heat polymerization is usually carried out at 80 to 200 ° C., and in catalyst polymerization, acetyl peroxide, lauroyl peroxide Oxide, benzoyl peroxide, isobutyryl peroxide, bis-3,5,5-
Trimethylhexanoyl peroxide, di-tert-butyl peroxide, 4,4-di-tert-butyl peroxyperoxide, normal butyl ester and other peroxide catalysts, azobisisobutyronitrile and other azo catalysts Polymerization is usually carried out at 20 to 180 ° C., etc., and the polymerization operation is continued until the polymerization rate of styrene is about 70% or the polymerization reaction is substantially completed. In this case, it is more preferable to use a peroxide catalyst or an azo catalyst.

During the polymerization reaction, stirring is carried out in the stage until the toughening agent rubber becomes fine particles and becomes dispersed in the polystyrene phase, usually in the stage until the polymerization rate of styrene becomes about 30%. The operation is very important in controlling the mechanical strength of the finally obtained impact resistant styrene resin, and appropriate stirring operation must be carried out depending on the polymerization conditions. And the polymerization rate of styrene is
After proceeding to 30% or more, it is preferable to moderate or stop stirring. After the completion of the polymerization operation, in order to remove the unreacted styrene and the above-mentioned diluent and the like in the polymerization solution containing the produced resin, a known method, for example, a heating / vacuum removal device or a design for removing volatile matter is designed. It is performed using the extruding device or the like.

The obtained impact resistant resin is pelletized or powdered as necessary for practical use.

Further, in the bulk-suspension polymerization method, similarly to the above-mentioned bulk polymerization method, while stirring a styrene solution of a toughening agent, non-catalytic heat polymerization or catalytic polymerization, the polymerization rate of styrene is usually 30 to 50%. It partially polymerizes until it reaches. Then, the partially polymerized syrup-like polymerization solution is treated with an aqueous medium in the presence of both a polyvinyl alcohol, a suspension stabilizer such as carboxymethyl cellulose, or a surfactant such as sodium dodecylbenzenesulfonate. It is dispersed in a suspension with stirring, and the reaction is completed by further stirring. The polymer composition produced is
Isolate by a method such as filtration and centrifugation, wash with water and dry, and pelletize or powder if necessary.

In addition to the above, the impact-resistant styrene-based resin of the present invention can be obtained by a method obtained by modifying or improving these polymerization methods.

(Effects of the Invention) Thus, according to the present invention, it is possible to manufacture a resin having excellent Izod impact strength and good rigidity as compared with the conventional impact-resistant styrene resin.

The impact-resistant styrenic resin of the present invention can be manufactured into various practically useful products by processing methods such as injection molding and extrusion molding. Further, in processing, if necessary, a flame retardant, an antioxidant,
It can be used as a mixture with an ultraviolet absorber, a lubricant, a release agent, a filler, and other thermoplastic resins such as general-purpose polystyrene and methacrylic resin.

(Example) Hereinafter, the present invention will be described in more detail with reference to Examples.

Examples 1 to 3 and Comparative Examples 1 to 8 Styrene-butadiene diblock copolymers A to J and polybutadiene K of Table 1 (all of which use butyl lithium as a catalyst and tetrahydrofuran as a vinylating agent, Each of those obtained by polymerization in a cyclohexane solvent) was used as a toughening agent to obtain an impact-resistant polystyrene resin by the following bulk-suspension polymerization method.

230 g of rubber and 2070 g of styrene were placed in a polyethylene wide-mouthed bottle having an internal volume of 5 l, and dissolved by shaking at room temperature for 16 hours.

Next, after washing the styrene polymerization reactor having an internal volume of 4 liters, the entire amount of the above solution was transferred. Then, bulk polymerization was carried out at 140 ° C. for 40 minutes, and the contents were taken out after cooling.

After washing the stainless steel polymerization reactor with an internal volume of 4 liters, the bulk polymerization solution (contents above) 625 g, polyvinyl alcohol 0.2
% Aqueous solution (1875 g) was added and the temperature was raised to 70 ° C. Next, 1.25 g of benzoyl peroxide and dicumyl peroxide
0.63 g was dissolved in 20 g of styrene and added. Then 70
1 hour at ℃, 1 hour at 90 ℃, 1 hour at 110 ℃, 1 at 130 ℃
Suspension polymerization was carried out at 140 ° C. for 3 hours. After cooling
The resulting high impact polystyrene resin was overseparated. The separated resin was washed with water and dried under reduced pressure at 60 ° C. for 6 hours.

The impact-resistant polystyrene resin thus produced was pelletized by using an extruder, and a test piece was prepared from the compression-molded plate by machining.

In addition, the styrene content of the rubber and the vinyl bond content of the butadiene part shown in Table 1 are determined by infrared spectroscopy [Hampton, An.
al, Chem, 21 , 923 (1949)]. The w / n was calculated by gel permeation chromatography (GPC) by calculating w and n converted into standard polystyrene. The measurement conditions are as follows.

Column: Two Toyo Soda GMH-6 Temperature: 38 ° C Flow rate: 1.2 ml / min Table 2 shows the test results. From these results, the impact-resistant polystyrene produced by the method of the present invention has Izod impact strength and It is clear that both the rigidity is improved.

Claims (1)

[Claims] 1. When producing a high-impact styrene resin by bulk polymerization or bulk-suspension polymerization of a solution obtained by dissolving a diblock copolymer of styrene and butadiene in styrene, the styrene-butadiene diblock copolymer is used. As a polymer (1) Styrene content is 15 to 35 wt%, 1,2-vinyl bond amount of butadiene unit is 15 to 35 mol%, (2) Weight average molecular weight (w) and number average molecular weight (
The ratio (w / n) of n) is 1.5 or less, (3) the viscosity of a 5 wt% styrene solution measured at 25 ° C. is 5 to 20 cps, and (4) the styrene unit and the butadiene unit are randomly copolymerized. A method for producing an impact-resistant styrene-based resin, which comprises using a block copolymer which is substantially not included in a coalescence chain.