JPS6065039A - Expandable styrene resin particle - Google Patents

Abstract

PURPOSE:The titled resin particles which give a short molding time, a low moisture content and excellent fusion bonding of moldings, made by fixing calcium acetate on the surface thereof. CONSTITUTION:Styrene resin particles, preferably containing about 50wt% or more styrene (derivatives), are impregnated with about 1-15wt% expanding agent (e.g. propane, dichlorodifluoromethane, or cyclopentane) (about 0.1-4wt% solvent such as benzene may be used together). The expandable styrene resin particles thus obtained and calcium acetate of a particle diameter of about 0.1mm. or less are mixed using a twin-cylinder mixer, Henschel mixer, etc. to fix about 0.001-5wt% calcium acetate on the surface of the expandable styrene resin particles.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to expandable styrene-based resin particles, and more specifically to expandable styrene-based resin particles that require a short molding time, have a low water content, and have an excellent degree of fusion in a molded product. It relates to resin particles.

Expandable styrenic resin particles are generally prepared by preparing a granular polymer by aqueous suspension polymerization, etc., and impregnating it with an easily volatile blowing agent 9 such as propane, butane, pentane, etc. that only slightly swells or dissolves the polymer. This will result in $1 being made. Expandable styrene (
ti4 fat particles are widely used as a raw material for manufacturing expandable styrenic resin molded bodies. The following process is generally used to industrially obtain a foamable styrenic resin molded article. That is, 9 expandable styrene resin particles are heated and expanded (
After allowing it to stand for a certain period of time (ripening), it is filled into a mold with small holes, heated with steam (secondary foaming), and the mold is cooled to reduce the foaming pressure inside the molded product. After that, the mold is opened and one foam molded product is taken out. In this process, the length of mold cooling time has the greatest impact on productivity.

Several methods have been attempted to shorten this cooling time. For example, US Pat. No. 2,989,782 discloses a liquid organic compound having a boiling point of 100° C. or higher on or on the surface of expandable styrenic resin particles.

For example, the molding time can be shortened by the presence of aromatic compounds such as benzene, chlorinated hydrocarbons such as chlorobenzene, alkyl esters of phthalic acid such as dimethyl phthalate, or linseed oil, monoglycerides of fatty acids having 12 to 2 o carbon atoms, etc. It describes what you can do. but.

According to this method, since the liquid organic compound has a strong affinity with the styrene resin, the liquid -FF image compound penetrates into the expandable styrenic resin particles and exerts a plastic action, resulting in total adhesion between the particles before foaming. Also, blocking tends to occur during primary foaming.

Furthermore, the liquid organic compound permeates into the inside of the expandable styrene resin particles during storage, resulting in a significant reduction in effectiveness. In the case of this invention, a foaming agent that is liquid at room temperature and normal pressure is used as the blowing agent, but when the liquid organic compound is applied to styrene resin particles containing a blowing agent that is gaseous at room temperature and normal pressure, In most cases, the above-mentioned drawbacks suddenly disappear, rendering the device impractical.

This is because, in the case of a blowing agent that is a gas at room temperature and pressure, the pressure exerted inside each particle is large and cracks are likely to occur, and the blowing agent quickly evaporates through the cracks, causing a loss of foaming performance.

Further, in West German Publication No. 2,133,253, the surface of expandable styrenic resin particles is coated with a lipophilic surfactant.

Specifically, it is described that by coating with a mixture of glycerin and mono-, di-, and tri-esters of saturated fatty acids, it is possible to shorten the cooling time during molding and achieve good fusion between expanded particles.

However, this method has the drawback that since the surfactant has a hydrophilic group portion, it tends to take in condensed water during molding, resulting in a high water content during molding.

The present invention solves these problems.

That is, the present invention relates to expandable styrenic resin particles formed by depositing calcium acetate on the bottom surface of styrenic resin particles impregnated with a blowing agent.

Styrenic resin particles used in the present invention include styrene homopolymers or copolymers of styrene conductors such as α-methylstyrene, vinyltoluene, chlorostyrene, acrylonitrile, methyl methacrylate, and ethyl methacrylate.

Methacrylic esters such as butyl methacrylate and cetyl methacrylate, and ethyl acrylate.

Acrylic acid esters such as butyl acrylate, vinylhyricine, vinylcarbazole, ethylene.

Examples include copolymers of monomers such as glopyrene and styrene or styrene derivatives. The styrenic resin of the present invention preferably contains 50 weight or more of styrene or a styrene derivative. The shape of the styrene resin particles may be arbitrary, such as a true sphere or a pellet shape.

Hydrocarbon blowing agents are those that do not dissolve styrene resin particles or only cause them to swell slightly, and have a boiling point lower than the softening point of the styrene resin particles and are normally liquid. Can be used in solid or gaseous form. Examples include aliphatic hydrocarbons such as propane, phthane, pentane, dichlorodifluoromethane and trichloromonofluoromethane, and cyclic aliphatic hydrocarbons such as cyclobutane and cyclopentane.

The styrenic resin particles are manufactured by a conventional method. For example, it can be produced by aqueous suspension polymerization (including suspension polymerization using a part of the bulk alloy and using Mono-7- after dissolving the polymer).

In addition, it can also be produced by molding a 7'ξ product obtained by solution polymerization or bulk W polymerization into a shape using an extruder.

As a method for impregnating the blowing agent, it is possible to adopt a method in which styrenic resin particles are produced by a suspension polymerization method (11), and then added during synthesis to perform polymerization and impregnation at the same time.
After completing the R combination step, 12 steps including one τ'1 pass may be performed. When a method other than suspended polymerization is employed, the latter method is used. When added during suspension polymerization, it is generally not preferable to add it in the first half of one polymerization step from the viewpoint of particle dispersion. It is usually preferable to impregnate the styrene resin particles with the blowing agent in an amount of 1 to 15 times.

Among the above blowing agents, when propane and butane are used alone or in combination, it is desirable to use a solvent necessary to soften the styrene resin to some extent. Examples of such solvents include benzene, toluene, xylene, ethylbenzene, dichloride, trichloroethylene, tetrachloroethylene, cyclohexane, and the like.

The amount used is 0.1 to 4 times the amount of styrene resin particles.

The calcium acetate used in the present invention is preferably in powder form, and preferably has a particle size of 0.1 mm or less. By attaching this calcium acetate to the surface of styrenic resin particles impregnated with a blowing agent, the molding cycle can be significantly improved in the molding process. That is, it is possible to shorten the steam heating time and the cooling time. Other effects include that blocking occurs when the particles are foamed, and that the water content in the molded product during molding is relatively low. The amount of calcium acetate deposited is preferably 0.001 to 5% by weight, particularly preferably 0.01 to 5% by weight, based on the styrene resin particles impregnated with the blowing agent.
It is 1% by weight. If the adhesion of calcium acetate is too small, the above-mentioned effect will be reduced.

If the amount is too large, the fusion of the foam particles during molding will be inhibited. Any method may be used to attach the foam resin particles to the surface of the resin particles. Henschel mixer, ribbon mixer, and other mixing methods can be used.

Even if it is included in the foamed styrenic resin particles, there is no effect at all.

Next, the present invention will be specifically explained with reference to Examples.

Examples 1 to 3 and Comparative Example 1 Styrenic resin particles (Hitachi Chemical industry■
, Product name Hibiniz SB-'rI0100Ky (10
0 parts) and 50 g of zinc stearate (mixed for 1 minute in a 0.05 L mixer. This expandable styrenic resin particle composition was mixed in a batch-type continuous pre-foaming machine (manufactured by Hitachi Kasei Sekisei Construction ■).
was placed inside the foaming tank.

Pre-expanded particles with an expansion ratio of 60 times were obtained by stirring with a rotating stirring blade using steam with an internal temperature of 98 to 101"C. After aging these pre-expanded particles in an aging silo for 24 hours, they were molded into fishing box molds. (390mm x 330mm x 250mm
Using a barrier 1ON automatic molding machine (manufactured by Seki Seisakusho ■) equipped with a barrier 1 ON automatic molding machine (manufactured by Seki Seisakusho ■) equipped with A box-shaped styrene resin foam molded product was obtained.

°' - This box was broken from the center and the fusion properties were examined. The degree of fusion was defined as the ratio of the number of broken particles in the expanded particles at the fracture surface. Also,
To determine the moisture content, measure the weight of the molded product immediately after molding, and then
It was dried for 24 hours in an 8-60'IC dryer, and the difference in weight is expressed as -.

In the above cycle, steam heating and water cooling.

Table 1 shows the time required for cooling and one cycle, as well as the degree of fusion and moisture content of the molded body.

In addition, steam heating involves heating the mold by passing steam through two steam chambers (attached to male and female molds), closing the steam outlet of one steam chamber, and closing the air outlet of the other steam chamber. This consists of heating on one side and heating with the steam inlets of both steam chambers open and the steam outlets fully closed.

(Note 1) Steam pressure during heating is 0.40 Kq/
cm2.

(Note 2): The steam pressure on the fixed side and moving side of the mold during double-sided heating is 0 = 6 Ky/cm2 and 0. (3K17
cm2.

(Note 3): The limit value of water cooling time was determined as follows. Initially, the water cooling time is increased to determine the moisture content of the molded product immediately after molding. Next, shorten the water cooling time and increase the moisture content. By repeating this operation, the point at which the water content was less than 10 cm was taken as the limit value of the water cooling time.

(Note 4): The limit value for cooling time was determined as described above. After first determining the water cooling time, the cooling timer was shortened, and the time limit was determined when the molded product was insufficiently cooled and began to partially expand.

From the data shown in Table 1, nine effects of the present invention are short heating time, short cooling time, and excellent fusion degree and moisture content.

The expandable styrenic resin particle composition according to the present invention is as follows.

(1) The steam heating time (mold heating, one side heating, one side heating) is short (2) The water cooling and cooling time is short +31 The molding time is shorter than the results of +11 and (2) (4) Molding The body exhibits excellent effects such as excellent fusion and low moisture content.

Claims (1)

[Claims] 1. Expandable styrenic resin particles formed by adhering calcium acetate to the surface of styrene resin particles impregnated with a blowing agent. 2. The expandable styrenic resin particles according to claim 1, wherein the amount of calcium acetate attached is 0.001 to 5% by weight based on the styrene resin particles impregnated with a blowing agent.