JP2001079874A - Composite molding and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a composite molding excellent in thermal insulation and small in change with the passage of time by thermoforming expandable resin particles after being subjected to vacuum treatment. SOLUTION: A composite molding which is used as an insulating material of a refrigerator, etc., is produced by a process in which expandable resin particles are packed in an aluminum bag, subjected to vacuum treatment to be sealed, and heated. A monomer mixture comprising styrene as a main component, styrene derivatives such as alpha-methyl styrene, acrylates such as methyl acrylate, methacrylates such as methyl methacrylate is used for the particles. In this way, the water content of the molding is minimized since steam, which has been used conventionally, is not used. The amount of air in a system is minimized by the vacuum treatment, thermal conductivity is decreased, and high thermal insulation is obtained. Moreover, due to closed structure, the diffusion of a foaming agent is reduced, and the composite molding small in the change of thermal conductivity can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a refrigerator, a freezer,
The present invention relates to a method for producing a composite molded product used for a heat insulating material such as a building material, and a composite molded product.

[0002]

2. Description of the Related Art Conventionally, a method for producing a foamed styrene resin particle molded product is carried out in two stages. The first stage is
Usually referred to as a pre-expansion step, this is a step in which raw resin particles containing a foaming agent are heated by steam to obtain pre-expanded particles having a desired density. Then, the obtained pre-expanded particles are cured for a predetermined time and supplied to the second stage process. The second stage is a so-called molding process. By filling the mold with the pre-expanded particles and heating with steam, an expandable styrenic resin molded article according to the mold is obtained. The molded article obtained in this way is considered to have excellent heat insulating properties, but the steam used in the pre-foaming and molding steps is condensed inside the molded article and becomes water content, so the molded article is formed. Immediately after, the heat insulating properties are reduced.
It is also believed that the thermal conductivity of the molded article is determined substantially by the thermal conductivity of the contained foaming agent, but the contained foaming agent escapes from the molded article over time. Therefore, there is a drawback that the thermal conductivity of the molded article increases with time and the heat insulating property decreases. In order to make up for the drawback, it is common practice to use a foaming agent having a low thermal conductivity and hard to escape. A typical blowing agent is a chlorofluorocarbon-based blowing agent. However, this type of blowing agent is mainly considered to be a substance that may destroy the ozone layer, and its use is regulated. In addition, although fluorocarbons have been proposed as substitutes, they are expensive and cause a great increase in cost when used as general-purpose products.

[0003]

SUMMARY OF THE INVENTION The present invention provides a method for producing a composite molded article which uses conventional expandable resin particles, has excellent heat insulating properties, and has little change over time, and a composite molded article.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a composite molded article in which expandable resin particles are subjected to a reduced pressure treatment in an aluminum bag, followed by heat molding, and a composite molded article obtained by this production method.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, known foamable resin particles are used as foamable resin particles. This foamable resin particles are filled in an aluminum bag and subjected to a decompression treatment,
After sealing, heating is performed to produce a composite molded article.

The expandable resin particles of the present invention contain styrene or styrene as a main component, styrene derivatives such as α-methylstyrene, chlorostyrene and vinyltoluene, and acrylics such as methyl acrylate, ethyl acrylate and butyl acrylate. It is preferable to use a mixed monomer with acid esters, methacrylic esters such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate.

[0007] The suspension polymerization of the styrene monomer in the present invention can be carried out by a conventionally known method. A styrene monomer or the like in which an organic peroxide is dissolved in an aqueous medium containing a dispersant is dispersed by radical polymerization. This is a method in which polymerization is carried out by generating In the present invention, such styrene resin particles can be used.

As the dispersant used in the suspension polymerization and the impregnation of the foaming agent in the present invention, a conventionally known method such as a method using a hardly soluble inorganic salt and a surfactant in combination or an organic dispersant such as polyvinyl alcohol is used. it can. The organic peroxide used in the suspension polymerization has a 10-hour half-decomposition temperature of 5
A conventionally known compound having a temperature of 0 to 100 ° C is preferred. For example, there are lauroyl peroxide, benzoyl peroxide, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate and the like.

As the chain transfer agent in the present invention, conventionally known ones such as octyl mercaptan, dodecyl mercaptan and α-methylstyrene dimer can be used.

The blowing agent used in the present invention is appropriately selected from aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane and normal pentane. Further, as a foaming aid, an alicyclic hydrocarbon such as cyclohexane or an aromatic hydrocarbon can be used in addition to an aliphatic hydrocarbon having 6 or more carbon atoms.

In the present invention, the amount of the foaming agent is preferably in the range of 3 to 10% by weight based on the expandable resin particles from the viewpoint of imparting expandability. The degree of decompression inside the bag is -760mmHg ~-
A range of 550 mmHg is preferred.

The foamable resin particles according to the present invention are impregnated with a foaming agent, dehydrated and dried, and then coated with a surface coating agent. As the coating agent, those applied to expandable polystyrene can be applied as they are. Examples include zinc stearate, triglyceride stearate, monoglyceride stearate, hardened castor oil, amide compounds, silicones, antistatic agents and the like. When depressurizing foamable resin particles in an aluminum bag, to obtain a molded product with a constant thickness, as shown in the examples, uniformly spread the foamable resin particles on both sides of the double-sided adhesive tape. It is preferable to fill this in a bag.

[0013]

By not using steam which has been conventionally used, the water content of the molded article is extremely small. Further, by the decompression treatment, the inside of the system is infinite, the presence of air is removed, and the thermal conductivity becomes low. Furthermore, because of the hermetically closed structure, a composite molded article can be obtained in which the escape of the foaming agent is small and the thermal conductivity is small over time.

Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[0015]

EXAMPLE 1 Into a 16 liter autoclave equipped with a stirrer, 6000 g of pure water, 9 g of tricalcium phosphate, 0.30 g of sodium dodecylbenzenesulfonate and 4.2 g of sodium sulfate were put, and at 200 rpm. It was charged while stirring. Then, 6000 g of styrene, 15.0 g of benzoyl peroxide, 2.4 g of t-butylperoxyisopropyl carbonate, and 3 g of ethylenebisamide were charged with stirring.

After the completion of the charging, the temperature was raised to 90 ° C., and 2 hours and 3 hours after the completion of the heating, tricalcium phosphate was added to each of 3
g and 6 g were added. Subsequently, the temperature was kept at 90 ° C. for 4 hours to advance the polymerization rate to 95%.

Subsequently, 90 g of cyclohexane and 480 g of butane were sequentially injected into the autoclave, and then
After the temperature was raised to 0 ° C., the temperature was further maintained for 4 hours, and then cooled to room temperature to complete the polymerization and the impregnation with the blowing agent, thereby obtaining a slurry.

<Post-treatment> The removed slurry was dehydrated and dried by centrifugal separation, passed through 14 mesh, classified with 22 mesh remaining, and further coated with 4.8 g of zinc stearate and 3 g of castor hardened oil to coat the surface and foam. Resin particles were obtained.

<Molding> 40 g of the obtained expandable resin particles
Was filled in a 35 cm square aluminum bag. At this time, a double-sided adhesive tape was used, and resin particles were uniformly attached to both surfaces of the tape so that the resin particle layer was filled so as to have a uniform thickness. Next, the inside of the bag was -650 mmHg by a vacuum pump.
, And the bag was sealed after decompression treatment for 10 minutes. The bag was placed in a dryer and heated at 110 ° C. for 5 minutes to obtain a composite molded product. The density of the obtained composite molded product is 60 kg /
m ³ , and the thermal conductivity one day after molding was 21.5 mW /
mK. The thermal conductivity three weeks after molding was 2
At 0.9 mW / mK, the change over time is small.

Example 2 In Example 1, the time for the decompression treatment was 5 minutes, and the degree of decompression was-
It carried out similarly to Example 1 except having set it to 550 mmHg. The density of the obtained molded product was 61 kg / m ³ , and the thermal conductivity was 23.0 mW / mK. The thermal conductivity three weeks after molding was 23.2 mW / mK.

Comparative Example 1 The pre-expanded particles obtained by pre-expanding the foamable resin particles produced in Example 1 with steam were placed in a mold and charged for 0.0 mm.
Heat and pressure molding was performed under the conditions of 8MP and 110 ° C to obtain a molded product. The density of the molded product is 58 kg / m ³ , and the thermal conductivity is
It was 29.0 mW / mK.

Comparative Example 2 In Comparative Example 1, the obtained molded article was put in a bag in the same manner as in Example 1, and subjected to a reduced pressure treatment under the same conditions as in Example 1 to obtain a composite molded article. The density of the molded product is 58 kg / m ³ , and the thermal conductivity is
It was 27.0 mW / mK.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4F074 AA32 AA48 BA36 BA37 BA38 BA39 BA40 CC10X CC22X CC26Z CC28Z CC30Z CC34Z CC42 CD04 CD20 CE16 CE33 CE43 DA47 DA50 DA54 4F212 AA13 AB02 AD03 AE02 AG20 AR02 UA01 UN27 UB01 UN01

Claims (5)

[Claims] 1. A method for producing a composite molded article, comprising subjecting expandable resin particles to a reduced pressure treatment in an aluminum bag and heat molding. 2. The method according to claim 1, wherein the expandable resin particles are expandable styrene resin particles. 3. The method according to claim 1, wherein the expandable resin particles contain a foaming agent in an amount of 3 to 10% by weight. 4. The method for producing a composite molded article according to claim 1, wherein the degree of reduced pressure in the bag is -550 mmHg or less and -760 mmHg or more. 5. A composite molded article obtained by the production method according to claim 1.