JPH0334482B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing styrenic resins, more particularly comprising (co)polymerizing monomers based on styrenic monomers using a specific trifunctional free radical initiator. The present invention relates to a method for producing resins with improved flowability and strength. Styrenic resins generally have excellent moldability, dimensional stability, colorability, electrical properties, and safety, so they are used in a wide variety of fields by taking advantage of these characteristics. However, in fields where a certain degree of durable strength is required, such as durable consumer goods and industrial parts, the need for improvement has become a major issue. As one measure to improve the strength of these styrene resins, it has been proposed to increase the molecular weight of the resin [Fujii, Plastic Materials Lecture 12, "Styrene Resin", p. 15]. However, it has been observed that when increasing the molecular weight to improve the strength of the resin, the fluidity of the resin deteriorates significantly;
Since strength and fluidity are contradictory properties, it can be said to be an extremely difficult task to improve both of these properties. For example, if we place too much emphasis on mechanical strength and sacrifice fluidity, even higher temperatures will be required during molding, which will not only consume energy but also cause residual distortion in the molded product. This can cause a decrease in strength due to an increase in the number of molded products, a decrease in transparency in molded products, and accelerated decomposition. Furthermore, it can also cause lengthening of the molding cycle and poor moldability when obtaining complex molded products. Become. As a result, despite the high molecular weight of the resin,
In reality, the strength of the molded product did not improve much;
It was not possible to obtain molded articles of the desired excellent quality. Furthermore, from the viewpoint of resin preparation, low-temperature reactions are essential for increasing the molecular weight, which may result in an abnormally long polymerization time, a significant increase in residual unreacted monomers in the product, or As the molecular weight increases, the viscosity of the resin increases, which places too much load on stirring power and transport pumps, making it difficult to manufacture the resin.
Achieving such a high molecular weight was extremely difficult. Furthermore, in the case of highly viscous resins, the thermal conductivity is significantly reduced, making it impossible to efficiently transfer or remove polymerization heat, which may result in partial accumulation of polymerization heat, leading to a runaway reaction. Therefore, the process of increasing the molecular weight has generally been considered to be very difficult. For these various reasons, increasing the molecular weight in order to obtain a styrenic resin that maintains excellent practical strength is difficult to achieve industrially due to technical and manufacturing process constraints. Ta. However, obtaining a resin with a high molecular weight and excellent fluidity has great industrial value, and if such a resin can be obtained, new uses can be expected from an application standpoint. For example, even though conventional styrene resins have excellent impact strength and toughness, they still have unsatisfactory performance in terms of durability such as creep resistance and fatigue resistance.・The use of plastics has been greatly restricted in fields where durable performance is required, such as durable consumer goods, light electrical parts, industrial materials, and industrial materials. However, if it is possible to make use of the excellent moldability characteristic of general-purpose styrene-based resins while also imparting durability, there is great promise for the development of applications in each of the above-mentioned fields. . On the other hand, regarding the fluidity mentioned above, it is well known that star-shaped branched polystyrene has superior fluidity compared to linear polystyrene of the same molecular weight [Nagazawa, Koka Shi 73 (7) P. 1264 ( 1970)]. However, although such star-branched polystyrene is generally produced by chemically bonding the ends of linear polystyrene synthesized by ionic polymerization, it is extremely difficult to commercialize it industrially. Ta. However, as a result of various studies aimed at industrially synthesizing such star-shaped branched polystyrene resins, the present inventors found that the general formula [However, R ₁ , R ₂ and R ₃ in the formula are an alkyl group or an alkanoyl group having 4 to 10 carbon atoms, which may be the same or different from each other. ] It was discovered that a styrenic resin synthesized using a free radical initiator having the following structure has good fluidity and extremely high practical strength, despite having a very high molecular weight. As a result, we have completed the present invention. That is, the present invention uses a trifunctional free radical initiator represented by the above general formula [], and injects styrene, substituted styrene, and/or these styrenic monomers in the presence or absence of a rubbery substance. The present invention provides a method for producing a styrenic resin, which comprises polymerizing other monomers that are copolymerizable with the styrenic resin.When the method of the present invention is followed, conventionally known monofunctional and/or difunctional Compared to any resin synthesized using free radical initiators, it has good fluidity, high strength, and has a wide molding temperature range, providing high-quality products with excellent transparency. can do. The method of the present invention will be described in detail below. Using one or more monomers selected from, if necessary,
Furthermore, a rubbery substance is also present, and a resin is obtained by polymerizing using a free radical initiator represented by the above general formula [] at a temperature of 50 to 180°C in the presence or absence of a solvent. If necessary, this resin is subjected to post-treatment steps such as dehydration, drying, demonomer removal, and/or desolvent removal.
The desired product is obtained by pelletizing. Here, typical free radical initiators include tris(alkylperoxy)triazine or tris(alkanoylperoxy)triazine, which can be used alone or in conventional polymerization of vinyl monomers. used in combination with free radical initiators. Typical initiators used in combination in this way are benzoyl peroxide, 1,1-di(t-butylperoxy)-
3,3,5-trimethylcyclohexane, t-butyl hydroperoxide, t-butyl peroxybenzoate, di-t-butyl peroxide, t-butyl peroxypivalate, cumene hydroperoxide, p-menthane hydroperoxide , dicumyl peroxide, lauroyl peroxide, t-butylperoxyisopropyl carbonate, di-t-butylperoxyisophthalate, t-butylperoxylaurate, t-butylperoxy-3,5,5-trimethylhexa Noate, t-butylperoxy-
2-ethylhexanoate, t-butylperoxyacetate, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, octanoyl peroxide, decanoyl peroxide or stearoyl peroxide, etc. It is. Typical examples of the above-mentioned substituted styrene include styrene in which the hydrogen atom of the benzene nucleus is substituted with a halogen atom or an alkyl group having 1 to 4 carbon atoms, such as o-
Chlorstyrene, p-chlorostyrene, p-methylstyrene, 2,4-dimethylstyrene, t-butylstyrene, α-methylstyrene, etc., which are representative of the other monomers having copolymerizability mentioned above. (meth)acrylonitrile, α
-Acrylonitrile monomers such as chloroacrylonitrile or vinylidene cyanide; (meth)
Acrylic acid, (meth)methyl acrylate, (meth)
Ethyl acrylate, butyl (meth)acrylate,
(Meth)acrylic acid and its esters such as glycidyl (meth)acrylate, 2-ethylhexyl (meth)acrylate or hydroxyethyl (meth)acrylate; vinyl acetate, vinyl chloride, vinylidene chloride, vinylpyrrolidone, ( Examples include various vinyl monomers such as meth)acrylamide, dimethyl(meth)acrylamide, maleic anhydride, itaconic anhydride, maleimide, or vinyl ketones or vinyl ethers. Furthermore, typical rubber-like substances mentioned above include polybutadiene rubber, SBR, SBS rubber,
EPDM rubber; rubber obtained from conjugated 1,3-diene monomers such as isoprene or chloroprene; butadiene-acrylonitrile rubber, isoprene-acrylic acid ester copolymer rubber,
Butyl rubber, acrylic rubber or styrene
Examples include isobutylene-butadiene rubber, which may be used alone or in combination of two or more. Furthermore, typical solvents mentioned above are aromatic hydrocarbons such as benzene, toluene, xylene or ethylbenzene. The amount of the above-mentioned free radical initiator used varies depending on the polymerization temperature, monomer combination, polymerization method, etc., and is not uniform, but it is 1 ppm to 3% by weight based on the above-mentioned monomers. Preferably 50ppm~0.8
A range of % by weight is suitable. Although the polymerization temperature varies depending on the polymerization method and the combination of monomers, etc., it is suitably in the range of 50 to 180°C, preferably 100 to 160°C, as described above. Furthermore, when carrying out the method of the present invention, various polymerization methods are used depending on the intended use of the styrenic resin obtained. In addition to suspension polymerization using appropriate dispersion stabilizers such as methylcellulose and various surfactants, known methods such as bulk polymerization, solution polymerization, or emulsion polymerization can be used, but molecular weight adjustment is necessary in this case. It is also possible to add a coloring agent or a coloring agent. Thus, the styrenic resin obtained by the method of the present invention can be used as is or if necessary,
Additives commonly used in styrenic resins such as molecular weight regulators, plasticizers, internal lubricants, modifiers, flame retardants, fillers, blowing agents, blowing aids or colorants are added. May be used. Next, the present invention will be specifically explained using Examples and Comparative Examples. The physical properties of the resin were evaluated using the test method shown below. Test method Spiral flow test - Using "SAV-30A" injection molding machine (manufactured by Yamashiro Seiki Seisakusho), molding temperature 240℃ or 260℃, injection time 10 seconds, cooling time 20 seconds, injection pressure 590Kg/cm ² (Ram pressure 40Kg/
cm ² ), the mold temperature was 60° C., and the spiral cross-sectional area of the mold was 9.82 mm ² . Indentation strength test - Using "225MVXL-20 type Mitsubishi Natco" injection molding machine (manufactured by Mitsubishi Heavy Industries, Ltd.),
Molding temperature 240℃ or 260℃, injection time 7-10
molding was carried out under conditions of a cooling time of 40 seconds and a mold temperature of 60°C. Note that the injection pressure depends on the weight of the molded product.
The weight was adjusted appropriately so that it weighed 208 g. 216 molded items
This molded product, which was a lid-type container with dimensions of mm x 323 mm x 25 mm and a thickness of 2 mm, was left at a constant temperature of 23° C. for 4 days and then subjected to an indentation strength test. Here, this indentation strength test was performed using "Autograph IS-2000" [manufactured by Shimadzu Corporation].
A round bar with a cross-sectional area of 450 mm ² is moved at a speed of 50 mm/min.
The indentation strength was defined as the load at which the molded product broke when the molded product was pressed into the central gate portion placed on a horizontal plane. Example 1 A 200 reactor equipped with a stirrer and a thermometer was
80Kg of water, 80Kg of styrene, 1Kg of tricalcium phosphate
and 80 g of tris(t-butylperoxy)triazine were charged, the temperature was raised with stirring, and suspension polymerization was carried out at a polymerization temperature of 110° C. for 10 hours and then at 130° C. for 5 hours. The pearl-shaped styrene resin thus obtained was washed with dilute hydrochloric acid, dehydrated, and then dried at 60° C. for a day and a night. Next, this pearl-shaped resin is heated to cylinder temperature.
It was pelletized at 260°C using an extruder with a diameter of 50 mm. As a result of measuring the properties of the obtained resin, the melt flow rate was 0.30 and the weight average molecular weight was 570000.
It was hot. In addition, in order to know the flow characteristics of this resin, the spiral length and the indentation strength as practical strength were measured. Furthermore, using the same reaction apparatus as above, and
Under the above polymerization conditions, the amount of tris(t-butylperoxy)triazine was 240g and 190g, respectively.
The weight average molecular weight is 360,000, 410,000, 430,000 and
500,000 resins were obtained, and the spiral length and indentation strength of each of these resins were similarly measured. The results are summarized in Table 1 and Figure 1. Comparative Example 1 Tris(t-butylperoxy)triazine was replaced with benzoyl peroxide as a monofunctional free radical initiator and 1, as a difunctional free radical initiator.
1-di(t-butylperoxy)-3,3,5-
Use in the range of 70 to 300 g with or without mixing with trimethylcyclohexane,
The same procedure as in Example 1 was repeated except that the polymerization conditions were changed to 80 to 110°C for 15 hours to obtain a resin with a weight average molecular weight of 300,000 to 560,000, and the spiral length and indentation strength were measured. . The results are summarized in Table 1. Example 2 100 kg of water and styrene were placed in the same reactor as in Example 1.
80Kg, tricalcium phosphate 1.2Kg, mineral oil 0.8Kg and tris(t-butylperoxy)triazine
Pour 144g and raise the temperature while stirring, and raise the temperature to 110℃.
Suspension polymerization was further carried out at 130° C. for 5 hours to obtain a pearl-like styrene resin. Thereafter, the same operations as in Example 1 were repeated to pelletize. The resulting resin was molded at 240°C and 260°C, and the indentation strength and spiral length were measured. The results are summarized in Table 2. Comparative Example 2 1,1-di(t-butylperoxy)-3, instead of tris(t-butylperoxy)triazine
Using 192g of 3,5-trimethylcyclohexane,
A resin was obtained in the same manner as in Example 2, except that the conditions were changed to 85° C. for 15 hours and 120° C. for 3 hours, and the indentation strength and spiral length of the resin were measured. The results are shown in Table 2. Example 3 Using the same reactor as in Example 1, 90 kg of water, 70 kg of styrene, 10 kg of methyl methacrylate, 2 kg of tribasic calcium phosphate, and 112 g of tris(t-butylperoxy)triazine were charged and heated while stirring. Suspension polymerization was carried out at 95°C for 10 hours and then at 125°C for 5 hours to obtain pearl-like styrene resin.
Thereafter, the same operations as in Example 1 were repeated to measure the indentation strength and spiral length. The results are summarized in Table 3. Comparative Example 3 60g of di-t-butylperoxyhexahydroterephthalate was used instead of tris(t-butylperoxy)triazine, and the polymerization conditions were 85°C.
A resin was obtained in the same manner as in Example 3 except that the temperature was changed to 10 hours at 120° C. and 5 hours at 120° C., and the indentation strength and spiral length of the resin were measured. The results are summarized in Table 3. Example 4 Continuous bulk polymerization was carried out using three reactors of No. 5 equipped with a stirrer and a thermometer. First, 5% by weight of ``NF-35'' (Asahi Kasei Corporation) was added to styrene.
Butadiene Rubber Co., Ltd.) was dissolved and 2 kg/
hr. to the first reactor. In parallel with this,
Toluene solution of tris(t-butylperoxy)triazine [triazine/toluene = 10/90
(weight ratio)] was supplied to the first reactor at a rate of 2 kg/hr. These feed solutions were heated to 120°C for 1 hour in the first reactor.
Continuous polymerization was carried out at 130℃ for 1 hour in the second reactor, followed by 1.5 hours at 170℃ in the third reactor, and the resulting resin was continuously sent to a tank-type devolatilization tank under a reduced pressure of 100 mmHg. Then, unreacted monomers and low-boiling substances were devolatilized at 190°C, and then pelletized while devolatilizing in an extruder with a reduced pressure of 5 mmHg.
Resin pellets were obtained in Kg/hr. Table 4 shows the measurements of the indentation strength and spiral length of the obtained resins. Comparative Example 4 Instead of a toluene solution of tris(t-butylperoxy)triazine, a toluene solution of di(t-butyl)peroxide [di(t-butyl)peroxide/toluene = 10/90 (weight ratio)] was used. The same operation as in Example 4 was repeated except that the solution] was used to obtain resin pellets of 1.70 kg/hr. Table 4 shows the measurements of the indentation strength and spiral length of the obtained resins.

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[Table] From the above results, the product of the present invention obtained using the free initiator represented by the general formula [] It is known that the fluidity of the resin is better than that obtained using a resin, and the practical strength is also very superior.

[Brief explanation of the drawing]

Figure 1 is for explaining the flow characteristics of the resin obtained by the method of the present invention, and shows the relationship between the spiral length and the indentation strength. The dotted line is for the resin obtained in Comparative Example 1.

Claims (1)

[Claims] 1. General formula [However, R ₁ , R ₂ and R ₃ in the formula are an alkyl group or an alkanoyl group having 4 to 10 carbon atoms, which may be the same or different from each other. ] Polymerization of styrene, substituted styrene and/or other monomers copolymerizable with these styrenic monomers in the presence or absence of a rubbery substance using a free radical initiator shown in A method for producing a styrenic resin, characterized by: