JPS6261231B2 - - Google Patents

Description

[Detailed description of the invention]

Styrene polymers have excellent transparency, moldability, and rigidity, and are therefore widely used as molding materials for household goods, electrical appliances, and the like. Against the backdrop of the recent trend of switching from high-grade resins due to the soaring prices of raw materials and the trend toward energy saving during molding, there is a strong demand for simultaneous improvements in the impact strength, moldability, and heat resistance of styrene polymers. . Conventionally, impact resistance strength has been improved by increasing the average molecular weight of styrene polymers, but as the average molecular weight increases, moldability decreases, and plasticizers such as mineral oil are added to improve moldability. As a result, the rigidity and heat resistance decrease, and in addition, deposits caused by the plasticizer occur near the mold exhaust hole, which are transferred as scratches or adhere to the product surface as dirt, significantly reducing the value of the molded product. , it has been extremely difficult to improve the quality of multiple items at the same time. As a method for improving the moldability of styrene polymers without using plasticizers, methods of increasing the proportion of low molecular weight moieties are known, as disclosed in Japanese Patent Publication No. 33-6986 and Japanese Patent Publication No. 57-30843. As the proportion of molecular weight moieties increases, the impact strength decreases significantly. In addition, methods have been proposed to balance moldability and impact strength by adjusting the molecular weight distribution, but these methods have not yet satisfied market demands for improvement. The present inventors conducted intensive research to develop a styrene polymer with a well-balanced impact strength, moldability, and heat resistance, and found that by incorporating a very small amount of ultra-high molecular weight styrene polymer into the styrene polymer. ,
The present invention has been achieved, which significantly improves the impact strength of styrene polymers without affecting their moldability. That is, the present invention uses 0.8% to 3.0% by weight of styrene polymers with a molecular weight of 2 million or more, 10% by weight or less of styrene polymers with a molecular weight of 50,000 or less, and styrene polymers with a molecular weight of more than 50,000 and less than 2 million. is 87% to 99.2% by weight, and the viscosity of a 10% by weight solution of toluene is 30cp to 60cp at 25°C. The styrene polymer composition of the present invention has superior impact strength and heat resistance compared to conventional styrene polymers, for example, when the moldability is the same. , the balance of heat resistance has been significantly improved. 10% by weight of the styrene polymer composition according to the invention
The viscosity of the toluene solution is set in the range of 30 cp to 60 cp at 25°C, taking into account the shape of the molded product, the purpose of use, etc. If the viscosity of a 10% by weight toluene solution of the styrene polymer composition is less than 30 cp at 25°C, there will be little improvement in impact resistance even if an appropriate amount of the ultra-high molecular weight styrene polymer is contained. Moreover, if it exceeds 60 cp, the moldability deteriorates significantly and is not practical. The content of the ultra-high molecular weight styrene polymer with a molecular weight of 2 million or more is required to be in the range of 0.8% by weight to 3.0% by weight. More preferably 1.0% to 2.5% by weight
is within the range of If it exceeds 3.0% by weight, it is necessary to reduce the average molecular weight of the styrene polymer composition excluding the ultra-high molecular weight styrene polymer in order to obtain a styrene polymer composition having the viscosity of the set 10% by weight toluene solution. As a result, the degree of improvement in impact strength becomes smaller. Furthermore, the ultra-high molecular weight styrene polymer affects the fluidity and the degree of improvement in moldability is also reduced. On the other hand, 0.8% by weight
If it is less than 20%, the effect of improving impact resistance strength by the ultra-high molecular weight styrene polymer will not be achieved. Styrene polymers with a molecular weight of 50,000 or less have a positive effect on moldability, but have the effect of significantly reducing impact strength. Therefore, if it is 10% by weight or less, preferably 5% by weight or less, moldability and resistance Although it improves the balance of impact strength, if it exceeds 10% by weight, it is undesirable because it cancels out the improvement in impact strength of the ultra-high molecular weight styrene polymer. The narrower the molecular weight distribution of styrene polymers other than ultra-high molecular weight styrene polymers, the better for improving moldability and impact strength. Its molecular weight distribution is preferably less than 3.0. In addition, in the present invention, the molecular weight of the ultra-high molecular weight styrene polymer is determined by the GPC measurement method.
GPC (HLC-802A), GPC column manufactured by the same company (TSK-GEL G6000H6-TSK-GEL G5000H6)
Measured using In addition, for the molecular weight of styrene polymers of 50,000 or less, use the same company's GPC column (TSK-GEL).
GMH6 x 2). Content is calculated by area ratio. 10% by weight of styrene polymer
The viscosity of the toluene solution is measured using an Ostwald Canon Fuenske viscosity tube #350. The styrene polymer composition of the present invention is first subjected to bulk or solution polymerization at low temperature to produce an ultra-high molecular weight styrene polymer, or alternatively, a multi-tubular low temperature catalyst (3 to 30
A method in which an ultra-high molecular weight styrene polymer is produced using a functional compound, and then the polymerization is proceeded by a known method; or an ultra-high molecular weight styrene polymer is produced by anionic polymerization, emulsion polymerization, etc. It is manufactured by a method of mixing a styrene polymer in an appropriate ratio using a known mixing method such as a solution state or pellets. The styrene polymer referred to in the present invention includes styrene,
It includes polymers of α-methylstyrene, p-methylstyrene, etc. alone or in mixtures. The styrenic polymer of the present invention may contain additives such as
stearic acid, behenic acid, zinc stearate,
Ethylene bisstearamide, etc. can be added. In addition, as antioxidants, hindered phenols, hindered bisphenols, hindered trisphenols, etc., such as 2,6-di-
t-Butyl-4-methylphenol; Stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; Triethylene glycol-bis-3-(3-t-butyl-4-hydroxy -5-methylphenyl)propionate, etc.; Phosphorus compounds, such as tri(2,4-di-t)
-butylphenyl) phosphorite; 4,4'-butylidene-bis-(3-methyl-6-t-butylphenyl-di-tridecyl) phosphorite, etc. can be added. Furthermore, depending on the shape and use of the molded article, a plasticizer such as mineral oil, polyethylene glycol, etc. may be added. Hereinafter, the present invention will be specifically explained with reference to Examples. In addition, the physical property test method of the example is described below. Melt flow rate: According to ISO R1133. Vikatsu Softening Point: According to ASTM D1525. Unnotched Izo impact strength: Conforms to ASTM D256 except that the test piece is not notched. Cyclic impact strength: Compression molding method (200℃) thickness 2
A square test piece of 9 cm x 5 cm was prepared, fixed with metal fittings at a point 2.5 cm vertically from the center, and a 3/4R, 130 g missile was dropped from a height of 5 cm onto the center of the test piece. Find the number of times until a crack occurs. One-shot impact strength: Compression molding method (200℃) thickness 2
Create a disk-shaped test piece with a diameter of 10 cm and a diameter of 7 cm, fix the annular part with a radius of 7 cm to 10 cm with metal fittings, drop a 28 g steel ball into the center of the test piece, and 50% of the test piece is destroyed. Find the height. Examples 1, 2; Comparative Examples 1, 2, 3 First, 3 kg of the composition shown in Table 1 was charged into a 5 liter reactor equipped with a stirring blade, and after replacing the air present in the reactor with nitrogen, the composition shown in Table 1 was charged. Polymerization was carried out at the temperature shown in 1 for 10 hours. After that, remove the reaction solution and heat at 200℃ and 15mmHg.
Unreacted monomers were removed under reduced pressure to obtain a styrene polymer. Table 1 shows the viscosity of a 10% by weight toluene solution of the obtained styrene polymer at 25°C. Next, the obtained styrene polymers were mixed in the proportions shown in Table 2. In order to obtain a homogeneous mixture, the mixed styrene polymer was dissolved in toluene, methanol was added to precipitate the styrene polymer composition, and after drying, the physical properties were measured. The physical property values are shown in Table 2. The molecular weight distribution of the styrene polymers excluding the ultra-high molecular weight styrene polymers of Examples 1 and 2 is 2.7 and 2.7, respectively.
It was 2.9.

【table】

【table】

[Table] Examples 3, 4; Comparative Examples 4, 5, 6, 7, 8 As shown in Table 3, the raw material composition and polymerization temperature were changed, and Examples 1, 2; Comparative Examples 1, 2, The same operation as in 3 was performed to obtain a styrene polymer. Table 3 shows the viscosity of a 10% by weight toluene solution of the obtained styrene polymer at 25°C. The obtained styrene polymers were mixed in the proportions shown in Table 4, and Example 1,
2; The same operations as in Comparative Examples 1, 2, and 3 were performed to obtain a styrene polymer composition, and the physical properties were measured. The physical property values are shown in Table 4. The molecular weight distributions of the styrene polymer compositions excluding the ultra-high molecular weight styrene polymer compositions of Examples 3 and 4 were 2.5 and 2.7, respectively.

[Table] Hexane

【table】

[Table] Table 2 shows that the polymer of the present invention has excellent moldability and impact strength. When a plasticizer was used to make the moldability the same as that of the polymer of the present invention (Comparative Example-2), the heat resistance decreased significantly. Furthermore, it can be seen that when the low molecular weight styrene polymer (molecular weight 50,000 or less) is 10% or more (Comparative Example-3), the impact strength is significantly reduced. The same thing can be seen from Table 4.
That is, when the strength and heat resistance were made the same as the polymer of the present invention (Comparative Example-7), the moldability decreased significantly, but when the moldability was improved with a plasticizer (Comparative Example-8)
The heat resistance is significantly lowered, and the strength is also slightly lowered. It can be seen that when the content of the ultra-high molecular weight styrene polymer was increased (Comparative Example-6), no improvement in moldability or strength was observed. The polymer of the present invention has simultaneously improved moldability, impact strength, and heat resistance.

Claims (1)

[Claims] 1 0.8% to 3.0% by weight of styrene polymers with a molecular weight of 2 million or more, 10% by weight or less of styrene polymers with a molecular weight of 50,000 or less, 200% by weight or less of styrene polymers with a molecular weight of 2 million or more,
Less than 10,000 styrene polymers 87% to 99.2% by weight
A styrene polymer composition consisting of
A styrene polymer composition that is 60 cp.