JPH06860B2 - Method for producing expandable resin particles having antistatic ability - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing expandable resin particles having an antistatic ability (prior art and problems to be solved). The foam is provided with an antistatic ability. The most usual method is to form an antistatic layer on the surface of the foam by immersing the foam in an antistatic agent solution or spraying the antistatic agent solution. However, this method has a drawback in that the number of steps of the molding maker increases as well as the inconvenience of treating a foam having a large volume because the foamed molded body is applied after manufacturing. In order to ameliorate this drawback, it is necessary to impart an antistatic ability before the foam is molded. That is, a method of adding an antistatic agent at the time of polymerization, a method of kneading into a resin at the resin stage after polymerization (kneading method), a method of adding a foaming agent to a resin at the time of a press-in reaction (addition method during reaction), or foam There is a method (blending method) of adding and blending to the obtained expandable thermoplastic resin particles after pressurizing the agent. However, among these methods, the kneading method does not form a spherical shape because the antistatic agent is kneaded by an extruder and cut into pellets, and therefore adversely affects the mold filling, and the machine Strength also decreases. With the blending method, the surface of the expandable resin particles is weakly bound to the antistatic agent, and during pre-expansion, when the expandable resin particles are fed into the foaming machine by the granulation hose, the antistatic agent adheres to the inside of the hose and the granulation operation is performed. In addition, in the reaction addition method in which a foaming agent is added during the press-fitting reaction, the antistatic agent does not break the resin dispersion system or is not absorbed by the polymer, resulting in poor addition efficiency and good antistatic performance. There is a drawback that it is difficult to obtain resin particles.

On the other hand, recently, there is a method of coloring a resin in which a pigment is mixed while giving a high shearing force to the resin, but a high shearing force has not yet been given when an antistatic agent is added to a foamable resin.

By the way, the present inventor added an antistatic agent to a foamable resin by utilizing a high shearing force in order to improve the above-mentioned drawbacks, and stirred and mixed the mixture. The present invention has been completed by finding that the dropping-off of the antistatic agent at the time of granulation of the functional resin particles is improved, the addition efficiency of the antistatic agent is improved, and the filling property of the foamed particles at the molding stage can also be improved.

(Means for Solving Problems) That is, in the present invention, an antistatic agent is added to thermoplastic synthetic resin particles, and both are stirred and mixed under a high shearing force, and the surface layer of the resin particles is in a softened state. Then, an antistatic agent is attached to the surface of the resin particles to form an antistatic agent-containing synthetic resin particle,
Thereafter, the synthetic resin containing antistatic agent is impregnated with a foaming agent in an aqueous medium to provide a method for producing foaming agent resin particles having antistatic ability.

The antistatic agent used in the present invention is a cationic type,
It may be anionic, nonionic or amphoteric, and
Both liquid and powder are possible, but it is desirable that the liquid is not viscous and the powder is fine powder. When the powder is viscous or has a large particle size, it may be dissolved in a solvent such as alcohol before use. Further, as the thermoplastic resin particles used in the method of the present invention, in addition to polystyrene, polyolefins such as polyethylene and polypropylene, polymers of methacrylic acid esters such as polymethylmethacrylate, or copolymers thereof, etc. is there. In the present invention, these antistatic agents and thermoplastic resin particles are agitated and mixed under a high shearing force. As means for agitating and mixing under a high shearing force, the peripheral speed is 20 m / s.
Both are agitated and mixed by a mixer having agitating blades at the above rotation speeds, and suitable examples of such mixers include fixed container high-speed fluidized mixers such as Henschel mixers and super mixers. By stirring and mixing under such a high shearing force, the surface layer of the thermoplastic resin particles becomes in a softened state, and in this state, the antistatic agent adheres to the surface layer of the resin particles.

The thermoplastic resin particles containing the antistatic agent obtained by the above method are impregnated with a foaming agent under pressure in an aqueous suspension. The suspending agent used in the aqueous suspension is added to prevent the thermoplastic resin particles containing the above-mentioned antistatic agent from binding or coalescing with each other during impregnation of the blowing agent. , For example, partially saponified polyvinyl alcohol, polyacrylic acid salt, polyvinylpyrrolidone, carboxymethylcellulose, methylcellulose, calcium stearate, ethylenebisstearoamide and other organic compounds, as well as magnesium pyrophosphate, magnesium phosphate, magnesium oxide, magnesium carbonate, pyro Inorganic compounds such as calcium phosphate, calcium phosphate, and calcium carbonate, which are fine powders that are poorly soluble in water, can be mentioned.
In the method of the present invention, when an inorganic compound is used as a suspending agent, it is desirable to use a surfactant such as sodium dodecylbenzenesulfonate together.

The blowing agent used in the method of the present invention is a volatile blowing agent, that is, propane, n-butane, i-butane,
Aliphatic hydrocarbons such as n-pentane, i-pentane and n-hexane, cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane, methyl chloride, ethyl chloride,
Examples thereof include halogenated hydrocarbons such as dichlorodifluoromethane and trichlorofluoromethane. These foaming agents are generally used in a proportion of 3 to 40% by weight based on the thermoplastic resin particles containing the antistatic agent. or,
A small amount (1 to 5% by weight) of an organic solvent such as toluene or xylene may be used together.

The foaming agent is impregnated by, for example, suspending the thermoplastic resin particles containing the antistatic agent in an aqueous suspension containing a suspending agent in an autoclave, heating and press-fitting the foaming agent. Thus, expandable thermoplastic resin particles are obtained.

The expandable thermoplastic resin particles obtained by the method of the present invention can be pre-expanded and then foam-molded in the mold cavity to obtain a foam-molded article having a desired shape. The surface of this foamed molded article has a good antistatic property due to the action of the antistatic agent.

Next, the present invention will be specifically described with reference to examples.

Example 7 kg of polystyrene resin particles and 70 g of quaternary ammonium salt type antistatic agent (1 wt% of polystyrene resin particles) were charged into Supermixer 20 (Kawata Manufacturing Co., Ltd.), and the peripheral speed was 24.
The blades of the super mixer were rotated at m / s, and mixing was performed while checking the flow state and temperature. Immediately before the temperature reached the softening point of the resin (100 ° C.), rotation was stopped and the polystyrene resin particles to which the antistatic agent was added were taken out.

100 parts by weight of the resin obtained by the above method was filled in a pressure resistant container together with 100 parts by weight of water, 0.25 parts by weight of magnesium pyrophosphate, 0.9 parts by weight of sodium alkylbenzene sulfonate, and 2 parts by weight of toluene, and 8 parts by weight of butane was injected under pressure. 4 at 80 ℃
After the time was maintained, cooling was taken out. Seven days after the obtained expandable polystyrene resin particles were taken out, they were pre-expanded 50 times and molded the next day to obtain a molded body.

The molded body was allowed to stand in a constant temperature and humidity room at 23 ° C and 55% RH for one day, and its surface resistivity was measured to be 2 x 10 ¹¹ Ω, and a molded body having good antistatic ability was obtained. .

(Effect) As described above, in the present invention, the thermoplastic resin particles and the antistatic agent are mixed under high shearing force without melt-kneading the resin particles, so that the surface layer of the resin particles is softened. Since the antistatic agent is attached to the surface of the resin particles in this state, the shape of the resin particles is maintained as it is, the filling of the foam particles is not adversely affected at the time of molding, and the antistatic agent is appropriately located near the surface. Incorporation of the antistatic agent is improved when the expandable thermoplastic resin particles are fed, as compared with the simple blending method.

Claims (1)

[Claims] 1. An antistatic agent is added to thermoplastic synthetic resin particles, and both are stirred and mixed under a high shearing force, and the antistatic agent is applied to the surface of the resin particles in a state where the surface layer of the resin particles is softened. To produce an antistatic agent-containing synthetic resin particle, and then impregnating the antistatic agent-containing synthetic resin with a foaming agent in an aqueous medium. .