KR100397529B1 - Method of Preparing Expandable Styrene Resin Bead Having Good Demolding Effect in the Molding Process - Google Patents

Abstract

The present invention provides a release property characterized by adding a solution obtained by mixing polydimethylsiloxane-polyoxyethylene copolymer with ammonium sulfonate sulfate and styrene monomer when the polymerization rate becomes 50 to 80% when suspension polymerization of styrene monomer. Provided is a method for producing the excellent expandable styrene resin particles.

Description

Method for preparing expandable styrene resin particles with excellent release property {Method of Preparing Expandable Styrene Resin Bead Having Good Demolding Effect in the Molding Process}

Field of invention

The present invention relates to a method for producing expandable styrene resin particles having excellent release properties. More specifically, the present invention provides a foamed styrene resin having excellent releasability by adding a polydimethylsiloxane-polyoxyethylene copolymer by a specific process at the time of polymerization of the foamed styrene resin particles by suspension polymerization, and as a result, product appearance quality is improved. It relates to a method for producing the particles.

Background of the Invention

Generally, the expandable styrene resin particles prepared by the suspension polymerization method are spherical particles that are used as a final product after undergoing expansion and molding. When the expandable styrene resin particles are used as agricultural and marine product packaging materials or home appliance packaging materials, since the commercial properties vary depending on the appearance quality of the product, the appearance quality is evaluated as a very important physical property.

Therefore, efforts have been made to improve the appearance quality of products in which the expandable styrene resin particles are used. There are two conventional methods for improving the appearance quality.

The first is to uniformize the morphology of the cell, called bubble structure. Using a variety of cell-controllers, uniform cell-morphology of 100-120 μm in size can be achieved. It is a method of manufacturing. The structure of the resin thus prepared is excellent in the heat resistance of the foam granules, so that expansion and contraction due to heating and cooling occurs finely, so that the interface between the foam granules and foam foams becomes indefinite. . The second method is to improve the releasability of the mold and the expandable styrene resin during the molding process. If the releasability is improved, the heating time can be extended, and the appearance of the entire product is improved as the interface between the foamed-foamed foam is unclear as the heating time is extended.

The present inventors added a polydimethylsiloxane-polyoxyethylene copolymer during suspension polymerization to improve the releasability of the expandable styrene resin particles, and as a result, to improve the overall appearance quality when applied to the product. The primary hydroxyl-functional polydimethylsiloxane polyoxyethylene copolymer has two hydroxyl (OH-) groups at its end and is a functional material having a very low surface activity and is a foamed styrene as in the present invention. When used in the production of the resin particles it was possible to effectively improve the release properties and product appearance quality.

However, since the polydimethylsiloxane-polyoxyethylene copolymer is added to a dispersion (monomer) or suspension (dispersion medium) by a conventional conventional method, the suspension stability is lowered. The development of a method of adding siloxane-polyoxyethylene copolymers through a specific method has begun.

It is an object of the present invention to provide a method for producing expandable styrene resin particles which is excellent in releasability and consequently improves the appearance quality of a product.

Another object of the present invention is to add a polydimethylsiloxane-polyoxyethylene copolymer during the polymerization of the expandable styrene resin particles by suspension polymerization method to provide a method for producing expandable styrene resin particles excellent in releasability and improved appearance quality of the product. It is for.

Still another object of the present invention is to provide a method in which suspension stability is not lowered when polydimethylsiloxane-polyoxyethylene copolymer is added during suspension polymerization in order to prepare expandable styrene resin particles having excellent release property.

The above and other objects of the present invention can be achieved by the following description. Hereinafter, the content of the present invention will be described in detail.

The present invention relates to a method for producing expandable styrene resin particles having excellent releasability, comprising adding a polydimethylsiloxane-polyoxyethylene copolymer at the time of polymerization of the expandable styrene resin particles by suspension polymerization method.

The method for preparing expandable styrene resin particles having excellent release property of the present invention includes adding a polydimethylsiloxane-polyoxyethylene copolymer when suspending the styrene monomer, which will be described in detail below.

The present invention adds a solution in which a polydimethylsiloxane-polyoxyethylene copolymer is mixed with an ammonium sulfonic acid sulfate salt and a styrene monomer when suspending the styrene monomer.

In addition, it is preferable that the mixed solution of the polydimethylsiloxane-polyoxyethylene copolymer, ammonium sulfonate sulfate and styrene monomer is added when the polymerization rate is 50 to 80%.

The styrene monomer used in the present invention is a styrene monomer or a mixture with acrylonitrile or α-methylstyrene mainly composed of styrene monomers.

The method for producing the expandable styrene resin particles having excellent release property of the present invention improves the problem that the suspension stability is lowered when the polydimethylsiloxane-polyoxyethylene copolymer is added to the expandable styrene resin. That is, if a polydimethylsiloxane-polyoxyethylene copolymer is to be added to a dispersion (monomer) or a suspension (dispersion medium) by mixing, the interfacial tension of the polydimethylsiloxane-polyoxyethylene copolymer itself is very low, so that either of the suspension and dispersion Even if added, it lowers the surfactant power of the added solution and ultimately the suspension stability.

Therefore, in order to produce expandable styrene resin particles having excellent releasability, it is preferable to add the copolymer mixed with ammonium sulfonate sulfate and styrene monomer at a specific polymerization point as described above. When the polymerization rate of the styrene monomer, which is a monomer, to the polystyrene is 50% or older or the above addition method is not applied, dispersion stability is not maintained and dispersion is broken, and polymerization heat is not controlled. Will be raised. In addition, when the polymerization rate is added after 80%, the addition efficiency drops sharply, leading to a state in which it is not commercially easy.

Styrene-based polymers prepared according to the invention are styrene copolymers, such as styrene homopolymers or copolymers of styrene and acrylonitrile or copolymers of styrene and α-methylstyrene.

The molding characteristics of the expandable styrene resin particles produced according to the present invention are that the molded article does not stick to the mold during high temperature and high pressure molding, and surface deterioration does not occur, and the surface is beautiful due to the unclear boundary between particles. The physical properties implemented in this way improve the appearance quality of the expandable styrene resin to enhance the quality of the product.

The foamed styrene resin particles thus prepared are excellent in releasability during molding to ultimately improve product appearance quality, and thus may be used as various home appliance packaging materials and agricultural and marine product packaging materials.

As a method for producing such expandable styrene resin particles, suspension polymerization method and emulsion polymerization method are generally used. Among them, suspension polymerization method is widely used commercially, and suspension polymerization method is used in the present invention.

The invention can be better understood by the following examples, which are intended for the purpose of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

Example

Example 1

38 kg of styrene monomer was added to the preliminary bath 1 and stirred at 110 rpm to 40 g of polyethylene wax having an average molecular weight of 1000 g / mol, 130 g of benzoyl peroxide and 62 g of t-butylperbenzoate for 30 minutes. It was dissolved to prepare a dispersion.

In predissolution tank 2, a dispersion was prepared in advance by slowly stirring 2 kg of styrene monomer, 40 g of polydimethylsiloxane-polyoxyethylene copolymer, and 0.6 g of ammonium sulfonate sulfate.

Separately, 40 kg of pure water was added to a 100 L pressure reactor, 250 g of tricalcium phosphate and 110 g of hydroxyethyl cellulose were added as a dispersant to prepare a suspension, and then the dispersion made in the pre-dissolution tank 1 was added and then operated at 110 rpm for 60 minutes. Stirred. Thereafter, the polymerization was carried out until the polymerization rate reached 50% while maintaining the temperature of the reactor at 90 ° C.

Thereafter, the polydimethylsiloxane-polyoxyethylene copolymer solution prepared in advance in pre-dissolution tank 2 was slowly added until the polymerization rate reached 80%. Then, after closing the reactor, 3 kg of pentane was added at a rate of 5 g / min for 60 minutes while the temperature was raised to 110 ° C. When the addition was completed and the temperature reached 110 ℃ was maintained for 6 hours to the content of unreacted styrene monomer up to 3000 ppm or less. The blowing agent introduced at this time was impregnated into the glass-transitioned polystyrene resin particles to be made into expandable styrene resin particles. After cooling to 45 ° C or less, the residual blowing agent was VENT. At this time, when the pressure of the reactor drops to normal pressure, the resultant was discharged to obtain expandable styrene resin particles in a slurry state. The obtained polymer was separated from water by dehydration, and then the water on the surface of the particle was removed to 0.3% or less through fluid bed drying, and then sorted and stored by particle size. Among them, a polymer having a particle size of 0.60 to 0.90 mm was added to a mixer, and 0.03 phr of mineral oil and 0.05 phr of glyceryl tri-stearate were added, followed by stirring for 30 minutes. The particles were obtained.

The final product thus obtained was foamed at 50 times magnification using a foaming machine (model name: HLC-901) specially manufactured at Dae-Hong Co., Ltd., followed by vacuum molding machine (model name: DKM-90VS manufactured by Dae-Gong Co., Ltd.). Molding was recorded and the desired molded article was obtained. Then, after drying at 60 ° C. for 24 hours, fusion, moisture content, and appearance quality were relatively compared.

Comparative Example 1

40 kg of styrene monomer was added to the predissolution tank and 40 g of polyethylene wax having an average molecular weight of 1000 g / mol, stirring at 110 rpm, 130 g of benzoyl peroxide, 62 g of t-butylperbenzoate and polydimethylsiloxane- A dispersion was prepared by dissolving 40 g of polyoxyethylene copolymer for 30 minutes.

Separately, add 40 kg of pure water in a 100 L pressure vessel, add 250 g of tricalcium phosphate and 110 g of hydroxyethylcellulose as a dispersant, prepare a suspension, add the dispersion made in the pre-dissolution tank, and stir at 110 rpm for 60 minutes. It was. Thereafter, the polymerization was performed until the polymerization rate reached 80% while maintaining the temperature of the reactor at 90 ° C. It carried out similarly to Example 1 below.

Comparative Example 2

The polydimethylsiloxane-polyoxyethylene copolymer solution prepared beforehand in the preliminary dissolution tank 2 was not added slowly at 50 to 80% of the polymerization rate, but was added at a time when the polymerization rate reached 50%, and then until the polymerization rate reached 80%. The same procedure as in Example 1 was conducted except that the temperature was maintained.

Comparative Example 3

The preparation was carried out in the same manner as in Comparative Example 1 except that the dispersion was prepared without adding the polydimethylsiloxane-polyoxyethylene copolymer in the predissolution tank.

Table 1 shows the foamed styrene resin particles prepared in Example 1 and Comparative Examples 1 to 3 by mesh-screen analysis to compare particle distribution.

division Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Particle Size Distribution (%) ON 0.12 Distribution failure 10.01 0.20 1.25 mm 1.28 7.47 0.72 1.12 mm 1.00 10.37 1.05 0.90 mm 12.71 45.40 27.82 0.63 mm 62.28 25.88 62.66 0.45 mm 21.42 0.41 6.77 0.35 mm 0.40 0.35 0.86 PASS 0.71 0.11 0.46 Yield (%) between 1.25 and 0.35 mm 99.17 88.88 99.34

In Comparative Examples 1 and 2 as shown in Table 1, the expanded styrene resin particles were prepared, which are not commercially easy due to wide or unstable particle size distribution.

The physical property measurement results of the expandable styrene resin particles prepared in Example 1 and Comparative Examples 2 and 3 are summarized in Table 2 below.

division Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Foam property 5-minute foamability 78 - 77 78 Lumping (%) 0.01 - 0.02 1.45 Low pressure molding (0.5 / 0.7) Forming c / t 120 sec - 125 sec 118 sec Appearance (Releasability) A ⁺ - A ⁺ C General molding (0.6 / 0.8) Forming c / t 145 sec - 151 sec 140 sec Appearance (Releasability) A ⁺ - A ⁺ C High Pressure Molding (0.7 / 0.9) Forming c / t 180 sec - 198 sec 172 sec Appearance (Releasability) A ⁺ - A ⁺ C

0.5 / 0.7 of Table 2 indicates the steam pressure condition, and the fixed steam pressure 0.5 kgf / cm ² and the moving steam pressure 0.7 kgf / cm ² are expressed. As a result, A (+, 0,-) is excellent, B (+, 0,-) is good, C (+, 0,-) is moderate, and D (+, 0,-) is inferior. Divided by grade.

The present invention adds a polydimethylsiloxane-polyoxyethylene copolymer during polymerization of the expandable styrene resin particles by the suspension polymerization method, so that the molded article does not stick to the mold during high temperature and high pressure molding, and the surface degradation does not occur. It has a useful effect of providing a manufacturing method for producing expandable styrene resin particles having excellent releasability, having a beautiful effect on the surface due to the indefinite boundary of the liver.

Simple modifications and variations of the present invention can be easily made by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (4)

In the suspension polymerization of the styrene monomer, a polydimethylsiloxane-polyoxyethylene copolymer is added at a time when the polymerization rate is 50 to 80%, and the polydimethylsiloxane-polyoxyethylene copolymer is an ammonium sulfonate sulfate And a foamed styrene resin particle having excellent releasability, which is added to a solution made by mixing with a styrene monomer. delete delete The method according to claim 1, wherein the styrene monomer is a styrene monomer or a mixture of acrylonitrile or α-methylstyrene mainly composed of styrene monomers.