JPH08300389A - Production of resin molded product composed of styrene polymer composition - Google Patents

Abstract

PURPOSE: To provide a styrene polymer(GPPS) resin molded product excellent in practical strength. CONSTITUTION: 1-20 pts.wt. of styrene polymer resin master batch pellets (B) obtained by mixing 100 pts.wt. of a styrene polymer resin (l), 0.1-20 pts.wt. of one or more kind of an inorg. filler (2) with an average particle size of 0.001-0.5μm selected from calcium carbonate, barium sulfate and zinc oxide and 0.1-10 pts.wt. of a dispersant are added to and mixed with 100 pts.wt. of styrene polymer resin pellets (A) and the resulting mixture is subjected to injection molding to obtain an injection-molded product containing 0.01-3wt.% of the inorg. filler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a styrene polymer resin molded article excellent in transparency, moldability, practical strength and cost performance.

[0002]

BACKGROUND OF THE INVENTION Styrene polymers are excellent in transparency and moldability and inexpensive and are used in a wide range of fields such as food containers and light electric appliances. However, styrene polymers are not compatible with other transparent resins (especially styrene-acrylonitrile copolymers,
There is a problem that it is inferior in practical strength as compared with a styrene-based polymer such as a styrene-methyl methacrylate copolymer. Particularly, in the case of a deep-bottomed box-shaped molded product, a problem often occurs that the molded product is cracked at the time of release from the injection molding die.

Generally, in order to increase the practical strength of a styrene polymer, the molecular weight of the polymer is increased. However, if the molecular weight is increased, the fluidity deteriorates. Therefore, a plasticizer such as mineral oil is generally added for the purpose of improving the fluidity. Addition of a plasticizer improves the fluidity but decreases the heat resistance. As described above, the current styrene polymer is insufficient in terms of the balance of practical strength, moldability and heat resistance. Considering the balance of practical strength, moldability and heat resistance, the current styrene polymer alone is used. In the case of injection molding, a sufficiently satisfactory molded product could not be obtained.

[0004]

Therefore, an object of the present invention is to provide an injection molding method for molding a styrene polymer composition having an excellent balance of practical strength, moldability and heat resistance. In particular, it is to provide a styrene polymer composition molded article excellent in practical strength.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted diligent studies to solve the above problems, and as a result, have found that a molded product of a styrene polymer composition having a good balance of practical strength, moldability and heat resistance. The manufacturing method has been completed.

That is, according to the present invention, (A) 100 parts by weight of styrene polymer resin pellets, (B) (1) 100 parts by weight of styrene polymer resin, and (2) an average particle size of 0.001 to 0.5 micron. 0.1 to 20 parts by weight of one or more inorganic fillers selected from calcium carbonate, barium sulfate and zinc oxide,
And (3) a mixture of 0.1 to 10 parts by weight of a dispersant, 1 to 20 parts by weight of styrene polymer resin masterbatch pellets obtained by mixing, and injection-molded to obtain a mixture of the above-mentioned inorganic substances in an injection-molded molded product. It relates to a method for producing a styrene polymer composition resin molded product, characterized in that an injection molded product containing 0.01 to 3% by weight of a filler is obtained.

In general, styrene polymer resins are often colored during injection molding using master pellets. The present invention, when a general styrene polymer resin is molded, by blending a small amount of a very fine inorganic filler in a molded product using the master pellet, the resin is very easily and almost without impairing the transparency. It is to improve the practical strength of the molded product. In particular, when a master pellet containing an inorganic filler is used to mold a heat-resistant styrene polymer having a relatively low molecular weight, the fluidity and moldability of the resin (short molding cycle and few deposits on the mold) The heat resistance of the molded product is excellent and the practical strength is also excellent, resulting in a very balanced molding.

The inorganic fillers used in the present invention are calcium carbonate, barium sulfate and zinc oxide, which may be used alone or in combination.

In the present invention, the average particle size of the inorganic filler is 0.001 to 0.5 micron. Preferably 0.01-0.5
Micron. If the average particle size is less than 0.001 micron, the dispersibility is so poor that it cannot be uniformly dispersed in the resin. Further, if the average particle size of the inorganic filler exceeds 0.5 micron, improvement in practical strength is not observed. On the other hand, if the average particle size exceeds 0.5 micron, the haze value of the styrene polymer molded product becomes large even if the amount of the inorganic filler added is extremely small, which is not preferable. Thus, considering the balance between practical strength and transparency, the average particle size of the inorganic filler is 0.01 to 0.
It is 5 microns, preferably 0.001-0.5 microns.

In the present invention, the content of the inorganic filler in the molded product is 0.01 to 3% by weight. It is preferably 0.1 to 2% by weight. If the amount added is less than 0.01% by weight, the effect of improving practical strength cannot be obtained. On the other hand, if it exceeds 3% by weight, the haze value of the styrene polymer molded product becomes large, which is not preferable. Thus, considering the balance between practical strength and transparency, the addition amount of the inorganic filler is 0.01 to 3% by weight.

Regarding the content of the inorganic filler (2) in the masterbatch pellet (B), the styrene polymer resin
Inorganic filler (2) 0.1 to 20 parts by weight per 100 parts by weight of (1). If it is less than 0.1 part by weight, there is a problem in dispersibility, and in order to obtain a sufficient practical strength improvement effect, the amount of the master batch pellets (B) mixed with the main styrene polymer resin pellets (A) is large. It is not preferable because the cost becomes too high. On the other hand, if it exceeds 20 parts by weight, the dispersibility is deteriorated, which is not preferable.

Dispersant in Masterbatch Pellets (B)
The amount of (3) is 0.1 to 10 parts by weight based on 100 parts by weight of the styrene polymer resin (1). If it is less than 0.1 part by weight, the dispersibility of the inorganic filler is deteriorated, which is not preferable. If it exceeds 10 parts by weight, the amount of deposits on the mold increases, and defects such as flashing tend to occur during molding, which is not preferable. As the dispersant, ethylenebisstearylamide,
Examples thereof include metal soaps (zinc stearate, magnesium stearate, calcium stearate, etc.).

The ratio of the masterbatch pellet (B) to the styrene polymer resin pellet (A) is 1 to 20 parts by weight of the masterbatch pellet (B) based on 100 parts by weight of the styrene polymer resin pellet (A). If it is less than 1 part by weight, the dispersibility of the inorganic filler is deteriorated, which is not preferable. Further, if it exceeds 20 parts by weight, it is not preferable in terms of cost.

The styrene polymer in the present invention is preferably a heat-resistant styrene polymer. Its properties are the Vicat softening temperature (V
SP (° C) and melt index (MI (g / 10
Min)). Here, the Vicat softening temperature is JIS
The temperature is evaluated according to K-7206, and the load is 5 kg. The melt index is a value evaluated according to JIS K-7210, and the conditions are 200 ° C. and 5 kg. The styrene polymer needs to have a specific molecular weight and a specific plasticizer amount. If the added amount of the plasticizer changes, the optimum range of the molecular weight changes, and if the molecular weight changes, the optimum range of the added amount of the plasticizer changes. Further, if the kind of the plasticizer is changed, the range of the optimum addition amount of the plasticizer is changed. Therefore, the molecular weight and the plasticizer amount cannot be specified as values. In the present invention, it has been found that the optimum styrene polymer composition can be defined by VSP and MI of the final styrene polymer composition.
That is, the inorganic filler-containing styrene polymer composition,
1) VSP ≧ 98, 2) 3 ≦ MI ≦ 8, 3) VSP ≧ −3.
It is preferable to satisfy the range of 5 × MI + 111. The Vicat softening temperature (VSP) is preferably 98 ° C or higher, more preferably 100 ° C or higher. If the temperature is less than 98 ° C, that is, the amount of plasticizer is large, the amount of deposits on the mold during injection molding increases,
It is not preferable because a problem such as deterioration of heat resistance of the resin occurs. The decrease in heat resistance of the resin leads to an increase in molding cycle time. The melt index (MI) is preferably 3 to 8 g / 10 minutes, more preferably 3 to 6 g / 10 minutes. If the MI is less than 3, literally the fluidity is not so good, and it cannot be said that the physical property balance is very excellent.
When the MI exceeds 8, the molecular weight is too low and the practical strength is low, and the amount of the plasticizer is too high, which causes problems such as increase of deposits on the mold during injection molding process and deterioration of heat resistance of resin. Is not so preferable. Also, VSP ≧ −3.5 × MI
It is preferable to satisfy the range of +111. VSP <-3.5
× MI + 111 is not very preferable in terms of the balance between fluidity and heat resistance. In this range, the molecular weight is too high,
Further, the amount of the plasticizer is too large, which is not preferable in terms of the balance of physical properties.

Styrene polymer resin pellets (A) and styrene polymer resin masterbatch pellets according to the present invention
In (B), if necessary within the above range, stabilizers against heat, light and oxygen (for example, antioxidants such as phenol compounds and phosphorus compounds; benzotriazole compounds, benzophenone compounds, salicylic acid). UV absorbers such as phenyl compounds; hindered amine stabilizers)
Alternatively, additives such as a lubricant such as liquid paraffin, a release agent, an antistatic agent, and a coloring agent may be added.

The method for producing the styrene polymer resin masterbatch pellets (B) in the present invention (the method for adding an inorganic filler or the like) may include adding an inorganic filler or the like during the polymerization of the styrene polymer. It can also be produced by melt-kneading the coalesced pellets or powder and the inorganic filler and the like with a molding machine such as an extruder.

Further, in order to improve the dispersibility of the inorganic filler, the inorganic filler may be surface-treated or a dispersant may be added.

[0018]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Examples 1 to 4 and Comparative Examples 1 to 5 Blends were made according to the formulation shown in Table 1 and melt-kneaded at 220 ° C. in a twin-screw extruder to produce various styrene polymer resin master batch pellets. The masterbatch pellets and the styrene polymer resin pellets were dry blended according to the formulation shown in Table 2 and directly injection-molded to obtain a test piece molded product.
The cylinder temperature is 220 ℃ and the mold temperature is 50 ℃. The following physical properties were measured using the test piece. Table 3 shows the results.

(1) Melt index: Measured according to JIS K-7210 under the conditions of a temperature of 200 ° C. and a load of 5 kg. (2) Vicat softening temperature: Measured under a load of 5 kg in accordance with JIS K-7206. (3) Haze value: measured according to ASTM D1003. The thickness of the test piece was 3 mm. (4) Izod impact strength: Measured according to JIS K-6871. (5) Falling ball impact test: Color plate molded product (width 100 mm
(Length x 350 mm x thickness 3 mm) was molded, placed on a table in which a concave portion was formed, and a 50 g steel ball was dropped toward the concave portion, and the presence or absence of breakage of the molded product was visually observed. From the height of the drop at which the probability of breaking the molded product is 50%, it was converted to the energy standard and displayed as 50% breaking energy. (6) Deflection temperature under load: According to ASTM D648, measurement was performed with a test piece wall thickness of 6.4 mm and a load of 18.6 kg / cm ² . (7) Appearance evaluation: The injection molded color plate molded product was visually evaluated.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

Claims (2)

[Claims] 1. (B) (1) 100 parts by weight of styrene polymer resin, based on 100 parts by weight of (A) styrene polymer resin pellets,
(2) Selected from calcium carbonate, barium sulfate and zinc oxide having an average particle size of 0.001 to 0.5 micron 1.
0.1 to 20 parts by weight of at least one inorganic filler, and (3) dispersant
A mixture of 0.1 to 10 parts by weight of a styrene polymer resin masterbatch pellet obtained by mixing 1 to 20 parts by weight is injection-molded, and the inorganic filler is added in an amount of 0.01 to 3 in the injection-molded product. A method for producing a resin-molded product of a styrene polymer composition, characterized in that an injection-molded product containing 10% by weight is obtained. 2. The styrene polymer composition resin molded article has a Vicat softening temperature (VSP (° C.)) and a melt index (MI (g / 10 min)) in the following ranges. A method for producing a resin molded article of the styrene polymer composition described. 1) VSP ≧ 98 2) 3 ≦ MI ≦ 8 3) VSP ≧ −3.5 × MI + 111