JP6788428B2 - Manufacturing method of foamable styrene resin particles - Google Patents

Description

The present invention relates to a method for producing foamable styrene resin particles using recycled styrene resin particles.

Polystyrene-based foam made of foamable styrene-based resin particles has excellent cushioning and heat-insulating properties because it is a structure in which a large number of well-shaped cells are assembled. It is used in many fields such as heat insulating materials for houses. On the other hand, with the growing interest in environmental protection in recent years, attempts to recover and reuse polystyrene-based foams that are widely used are spreading. As a method of reuse, there are a method of recovering heat by incineration and a method of reusing as polystyrene after heat shrinkage, but it is very difficult to recycle into foamable styrene resin particles again, especially aiming at a recycling type recycling system. It is meaningful and of increasing interest.

However, since the styrene resin is melted, extruded, picked up, rapidly cooled, cut, etc., the stretching force remains as internal strain in the resin particles, and the styrene resin particles become flat during the production of the foamable styrene resin particles. There was a problem of becoming. Further, when a recycled product is used as a raw material, unspecified impurities are mixed and the internal water content fluctuates, so that the cell state of the obtained expanded styrene resin is large and non-uniform, or excessively fine. There was a drawback that it became.

In response to this problem, Patent Document 1 proposes a recovery pelletization granulation method in which water, styrene resin particles, salt, and an amide compound are placed in a reactor, a foaming agent is added at 90 ° C, and impregnation is performed at 120 ° C. .. However, since the amide compound is added without emulsification, it is difficult for the amide compound to secondarily aggregate and make the cell state uniform from the initial stage to a long period of time.

Further, in Patent Document 2, a method for producing a recovered recycled styrene resin in which water, columnar styrene resin particles, tricalcium phosphate, and salt are put into a reactor, a foaming agent is added at 95 ° C, and impregnation is performed at 120 ° C. Has been proposed. However, in order to make it spherical, it is necessary to raise the temperature before adding the foaming agent, and there is a problem that the productivity is deteriorated. Moreover, since the amide compound was not emulsified and added, it was difficult to homogenize the cells.

Further, in Patent Document 3, a liquid in which ethylene bisstearoamide is dispersed in water is added to a reactor containing styrene-based polymer particles, and then a foaming agent is added to raise the temperature to 100 ° C. A method for producing based resin particles has been proposed, but it has not used recycled polystyrene.

Further, in Patent Document 4, styrene resin and amide are melt-extruded and pulverized, styrene resin particles and metal salt are dispersed in an aqueous medium, a dispersion liquid of a flame retardant is added, and a foaming agent is added and impregnated at 110 ° C. A method for producing foamable styrene-based resin particles has been proposed. However, since the amide is pulverized and kneaded in an extruder, the amide is secondarily agglutinated, making it difficult to homogenize the cells.

JP-A-2009-235250 Japanese Unexamined Patent Publication No. 2009-242543 Japanese Unexamined Patent Publication No. 2011-074144 JP-A-2002-030175

In the present invention, using recycled styrene resin particles, foamable styrene resin particles that are spherical and can obtain a uniform and fine cell structure immediately after production and can obtain a styrene foam having excellent moldability. Regarding the manufacturing method of.

As a result of diligent studies to improve the above-mentioned problems of the prior art, the inventors carefully examined the conditions for the dispersant and the conditions for adding the nucleating agent. We have found a method for producing sex styrene resin particles.

That is, the first method of the present invention is a method for producing foamable styrene resin particles in which styrene resin particles are dispersed in an aqueous medium in a closed container and impregnated with a foaming agent, and there are two or more types in the aqueous medium. Styrene-based resin particles contain a recycled styrene-based resin obtained by reducing the volume of the styrene-based resin foam by heat shrinkage and / or heat melting, which contains the metal salt of the above and an emulsified amide compound. The present invention relates to a method for producing sex styrene resin particles.

The second aspect of the present invention is the effervescent styrene type according to the first invention, wherein the styrene resin particles contain 50% by weight or more of the recycled styrene resin and have a columnar shape that is strand-cut through an extruder. The present invention relates to a method for producing resin particles.

A third aspect of the present invention is the foamable styrene resin particles according to the first or second invention, wherein the styrene resin foam is a foamed molded product obtained from the foamable styrene resin particles. Regarding the manufacturing method of.

A fourth aspect of the present invention is the method for producing foamable styrene-based resin particles according to any one of the first to third inventions, wherein the metal salts present in the aqueous medium are calcium phosphate tribasic and sodium chloride. Regarding.

A fifth aspect of the present invention is the fourth aspect of the present invention, wherein the amount of the tertiary calcium phosphate added is 0.25 parts by weight or more and 0.8 parts by weight or less with respect to 100 parts by weight of the recycled styrene resin particles. The present invention relates to a method for producing foamable styrene resin particles according to.

A sixth aspect of the present invention is the fourth or fifth aspect, wherein the amount of sodium chloride added is 0.7 parts by weight or more and 1.5 parts by weight or less with respect to 100 parts by weight of the recycled styrene resin particles. The present invention relates to a method for producing foamable styrene resin particles according to the present invention.

In the seventh aspect of the present invention, a foaming agent is added in a state where the closed container is heated to 95 ° C. or higher and 130 ° C. or lower, and then the closed container is heated to 100 ° C. or higher and 130 ° C. or lower to make the recycled styrene resin particles spherical. The present invention relates to the method for producing foamable styrene-based resin particles according to any one of the first to sixth inventions, which is characterized in that the plastic is formed.

The eighth aspect of the present invention is any of the first to seventh inventions, wherein the emulsified amide compound added to the aqueous medium is an amide compound represented by the following general formula (I) or (II). The present invention relates to a method for producing the foamable styrene resin particles described in the above.

According to the present invention, a styrene-based foam having a spherical shape and a uniform and fine cell structure immediately after production can be obtained by using recycled styrene-based resin particles, and has excellent moldability.

As a method for producing the effervescent styrene resin particles, the following methods and the like are conventionally known.

(1) A production method involving a polymerization reaction in which resin particles are obtained by suspension polymerization of a styrene-based monomer together with various additives, and foamable polystyrene-based resin particles are obtained by further impregnating with a foaming agent.

(2) A production method that does not involve a polymerization reaction to obtain foamable styrene resin particles by granulating a polystyrene-based polymer together with various additives to a desired size by an extruder or the like and further impregnating with a foaming agent.

In the regeneration into polystyrene-based foam, it is necessary to granulate using a polymer as a starting material, so the production method (2) above is often used. Further, although the production method of (2) above has lower production efficiency than that of (1), it can be said to be a production method having high utility value because various components can be mixed. However, as described in the background, in the method (2), the spheroidization of the particles and the uniform miniaturization of the cells become problems due to the residual strain and impurities inside the resin particles. The essence of the present invention is to add a metal salt for adjusting the internal water content for uniform miniaturization of the cell, and to add an emulsified nucleating agent. Further, as a result of scrutinizing the temperature and time of impregnation with the foaming agent for spheroidization, a production method capable of obtaining foamable styrene resin particles having good moldability has been found.

The method for producing foamable styrene resin particles of the present invention is a method for producing foamable styrene resin particles in which styrene resin particles are dispersed in an aqueous medium in a closed container and impregnated with a foaming agent, and is an aqueous medium. It contains two or more kinds of metal salts and an emulsified amide compound, and the styrene resin particles contain a recycled styrene resin obtained by reducing the volume of the styrene resin foam by heat shrinkage and / or heat melting. It is characterized by.

The recycled styrene-based resin of the present invention is obtained by reducing the volume of a styrene-based resin foam by heat shrinkage and / or heat melting. The styrene-based resin foam is not particularly limited, but is preferably a foam-molded product obtained from foamable styrene-based resin particles because it has few impurities and stable production is possible. The recovered foamed molded product is not particularly limited, and examples thereof include foamed molded products generated as scraps when used as a mold for food transportation boxes such as fish boxes and vegetable boxes, and castings.

The styrene-based resin particles used in the present invention preferably contain 50% by weight or more of recycled styrene-based resin and are columnar cut by strand cutting through an extruder. By using the recycled styrene resin, it is more preferable that the styrene resin particles contain 80% by weight of the recycled styrene resin, and 100% by weight should be used because of the low environmental load and the realization of recycling material recycling. Is particularly preferable. The columnar shape used here is not particularly limited as long as it is a columnar shape, but the length / diameter ratio is preferably 0.8 or more and 3.0 or less, and more preferably 0.9 or more / 2.5 or less. ..

In the present invention, a foaming agent is added in a state where the closed container is heated to 95 ° C. or higher and 130 ° C. or lower, and then the recycled styrene resin particles are sphericalized by keeping the closed container at 100 ° C. or higher and 130 ° C. or lower. It is characterized by.

The temperature at which the foaming agent is added in the present invention is 95 ° C. or higher and 130 ° C. or lower, preferably 100 ° C. or higher and 110 ° C. or lower. If the addition temperature is less than 95 ° C., agglomerates tend to increase and the yield tends to deteriorate.

The temperature at which the recycled styrene resin particles in the present invention are sphericalized and impregnated with the foaming agent is 100 ° C. or higher and 130 ° C. or lower. Preferably, it is 110 ° C. or higher and 120 ° C. or lower. When the impregnation temperature is less than 100 ° C., the foamable styrene-based resin particles are difficult to be spherical and tend to be close to a columnar shape.

The styrene-based resin particles in the present invention are resins containing a styrene-based monomer as a main component, and are resin particles granulated by any of the methods described below.

Examples of the monomer composition constituting the styrene-based resin particles dispersed in the aqueous medium include styrene and various substituted styrenes such as α-methylstyrene, chlorostyrene, paramethylstyrene, and t-butylstyrene. The monomer component is composed of one kind or two or more kinds. Further, as a component capable of copolymerizing with these constituent monomer compositions, for example, an ester of acrylic acid and methacrylic acid such as methyl acrylate, butyl acrylate, methyl methacrylate and ethyl methacrylate, or acrylonitrile, dimethyl fumarate and ethyl fuma. Examples thereof include a composition containing one or more of these various monomers partially, and a composition containing a polyfunctional monomer such as divinylbenzene or alkylene glycol dimethacrylate. Can be done.

Examples of the method for producing the styrene-based resin particles of the present invention include a method of directly obtaining polymer particles by suspension polymerization, bulk polymerization, emulsion polymerization, etc., and reusable foam molding recovered after being used for the original purpose. It can be obtained by reducing the dissolution of the body with an extruder or the like.

As a method of granulating the styrene resin after melting and kneading, there is a strand cut method in which pellets are obtained by extruding the styrene resin into a strand shape from a die having small holes attached to the tip of the extruder, cooling the resin, and then cutting the pellet with a pelletizer. , A generally known pelletized granulation method such as a hot cut method that extrudes from a die and cuts before forced cooling, an underwater cut method that extrudes from a die into water and cuts, and after extruding into a lump. It can be obtained by a method of crushing with a crusher or the like.

The present invention is characterized in that the aqueous medium contains two or more kinds of metal salts. The metal salt added to the aqueous medium is used as a dispersant for dispersing the styrene resin particles in the aqueous medium and as a moisture adjusting agent for adjusting the internal moisture in the foamable styrene resin particles in order to uniformly stabilize the cell. It has two roles. It is essential to add one type of metal salt having each of these roles.

As the dispersant referred to here, for example, a poorly water-soluble inorganic salt such as calcium phosphate, hydroxyapatite, magnesium pyrophosphate, kaolin and the like can be used. Of these, tricalcium phosphate is preferable from the viewpoint of economy and dispersion stability. The amount of the tertiary calcium phosphate used is preferably 0.25 parts by weight or more and 0.8 parts by weight or less, more preferably 0.30 parts by weight or more and 0.7 parts by weight or less with respect to 100 parts by weight of the styrene resin particles. is there. If the amount of the tertiary calcium phosphate is less than 0.25 parts by weight, the dispersion becomes unstable and the particles tend to aggregate with each other and the yield tends to deteriorate. Further, if it exceeds 0.8 parts by weight, it is not preferable from the viewpoint of economy.

When a poorly water-soluble inorganic salt is used, an anionic surfactant such as α-olefin sulphonic acid sodium and dodecylbenzene sulphonic acid soda, and a polymer dispersant such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylamide are used in combination. It is effective because it increases dispersion stability.

Further, it is necessary to add a metal salt as a water content adjusting agent in order to adjust the internal water content in the effervescent styrene resin particles and uniformly stabilize the cell. For example, metal salts such as sodium chloride and sodium sulfate can be used. In particular, it is preferable to add sodium chloride. The amount of sodium chloride used is preferably 0.7 parts by weight or more and 1.5 parts by weight or less with respect to 100 parts by weight of the styrene resin particles. When the amount of sodium chloride is less than 0.7 parts by weight, the internal water content increases, the cell becomes finer, and the surface property deteriorates. If the amount of sodium chloride exceeds 1.5 parts by weight, it is not preferable from the viewpoint of economy.

In the present invention, the styrene resin particles are impregnated with an emulsified amide compound together with a foaming agent in order to obtain a uniform and fine cell structure immediately after production. The amide compound referred to here is preferably a fatty acid bisamide, an aliphatic dicarboxylic acid diamide, or an aliphatic monoamide. In particular, an amide compound represented by the following general formula (I) or (II) is preferable from the viewpoint of forming a stable cell.

As the alkyl group represented by R _{1 to} R ₄ , an alkyl group having 8 to 24 carbon atoms, preferably 10 to 22 carbon atoms is preferable. Further, this alkyl group may contain an unsaturated carbon bond. Further, n is preferably 1 or 2, and more preferably 2.

Examples of such amide compounds include aliphatic bisamides such as methylene bislauric acid amide, methylene bisstearic acid amide, ethylene bisstearic acid amide, hexamethylene bispalmitic acid amide, and ethylene bisoleic acid amide, and N-lauryl stearate. Acid amide, N-palmityl stearate amide, N-oleyl stearate amide, N-stearyl stearate amide, N-behenyl stearate amide, N-erkyle stearate amide, N-lauryl oleate amide, N-pal Examples thereof include fatty acid monoamides such as mityloleic acid amide, N-palmityloleic acid amide, oleic acid amide, erucic acid amide, palmitate amide and stearic acid amide. These amide compounds can be used alone or in combination of two or more. Further, among the above compounds, ethylene bisstearic acid amide or stearic acid amide has a remarkable effect in forming stable cells.

The amount of the amide compound used is preferably 0.03 parts by weight or more and 0.10 parts by weight or less with respect to 100 parts by weight of the styrene resin particles. If the amount of the amide compound used is too small, the effect of forming a stable cell becomes small, and if the amount used is too large, the size of the obtained cell becomes too small and becomes sensitive to heat during molding, and the surface of the molded product melts. It is easy to show a similar appearance.

The shape of the amide compound is not particularly limited, but the impregnation efficiency is better when the size of the primary particles is not too large. The size of the primary particles of the amide compound is preferably 1 mm or less, more preferably 0.5 mm or less.

The method for emulsifying the amide compound is not particularly specified, but a method of dispersing the amide compound, the surfactant and water with a homomixer is preferable. For example, as the surfactant, it is preferable to use 0.002 parts by weight of an anionic surfactant such as α-olefin sulfonic acid sodium for 100 parts by weight of the styrene resin particles, and the rotation speed is 2600 rpm with a homomixer. Is preferably stirred for 30 minutes.

The foaming agent used in the present invention is an easily volatile organic compound having a boiling point equal to or lower than the softening point of the polymer. Examples of such a foaming agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane and hexane, and alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane.

These foaming agents may be used alone or in combination of two or more. Among these easily volatile organic compounds, butane or pentane is preferable, and pentane is more preferable, and a uniform and fine cell structure can be easily obtained.

The amount used is preferably 2 parts by weight or more and 12 parts by weight or less, and more preferably 3 parts by weight or more and 8 parts by weight or less. If it is 2 parts by weight or less, it is difficult to obtain the foaming power after forming the foamable styrene resin particles, and if it is 12 parts by weight or more, the foaming power becomes excessive and the suspension stability in the impregnation step is lowered.

The foamable styrene-based resin particles thus obtained can have a uniform and fine cell structure immediately after production, and a foamed styrene-based molded product having excellent foamability and moldability can be obtained.

The foamable styrene resin particles obtained by the production method of the present invention can be obtained as a foam molded product having good moldability and surface properties by forming stable cells immediately after production. Further, since it is a batch production process, unlike a continuous production process in which a nucleating agent needs to be kneaded in advance at the time of granulation, the amide compound conditions of the next batch can be adjusted while checking the resin fluctuation. Can produce effervescent styrene-based resin particles that exhibit stable quality.

Examples and comparative examples will be given below, but the present invention is not limited thereto. Of the operations, measurements, and evaluation methods, items other than those described above were carried out as follows.

<Manufacturing of recycled styrene resin particles by an extruder>
A styrene resin obtained by reducing and crushing a foamed molded product obtained from a foamable styrene resin (trade name: Kanepearl MK) manufactured by Kaneka Co., Ltd. is put into a 50 mmφ single-screw extruder and heated. After melting, it is extruded into a strand shape from a die with small pores, rapidly cooled in water, and then cut into a size of about 0.7 mg / grain, length of about 1.1 mm, and diameter of about 0.9 mm with a pelletizer to make recycled styrene. Resin particles were obtained.
The extrusion conditions are as follows.

[Extruder conditions]
・ Cylinder temperature [W / 160/160/140/140/160/160/210/215/220/210/210/215 (F) / 220 (S / C) / 225 (D)]
・ Discharge rate: 300kg / Hr
・ Screw rotation speed: 450 rpm
[Pelletizer conditions]
・ Pick-up speed: 52.5m / min
-Cutter rotation speed: 1280 rpm.

<Yield calculation method>
Prepare a sieve with a mesh opening of 1.7 mm and a mesh of 1.0 mm, pass the obtained foamable styrene resin particles through the sieve, pass through 1.7 mm, and leave the product on the sieve of 1.0 mm. And said. The product yield was calculated by the following formula.

(Yield [%] = weight of resin that passed 1.7 mm and remained on 1.0 mm / weight of total resin obtained * 100).

<Measurement of the ratio between the length and diameter of resin particles>
Twenty grains were randomly selected from each sample, and the size was measured using a caliper capable of measuring up to 1/100 mm, and calculated as a number average value. In addition, the measured size was calculated by the following formula and used as an index for spheroidization.

Ratio of length to diameter = length (L) / diameter (D).

<Measurement of water content>
Add 50 ml of new dehydrating solvent to the cell and remove the water in the cell. Weigh 0.5 g of the resin to be measured, and quickly add the resin from the upper stopper of the cell using a funnel. After confirming that the resin has melted, perform titration with Karl Fischer's reagent and measure the water content of the resin.
Model (manufacturer): AQV-2100 piece (Hiranuma Sangyo Co., Ltd.)
Reagent: Dehydrating Solvent: Mitsubishi Chemical Aquamicron Dehydrating Solvent CM
Karl Fischer's Reagent: Mitsubishi Chemical Aquamicron Titrate SS 3mg
Standard water methanol: Mitsubishi Chemical Standard water methanol 2 mg.

<Surface evaluation>
The effervescent polystyrene-based resin particles are heated by a pre-foaming machine (manufactured by Daikai Kogyo Co., Ltd .: CH-100) with steam of 0.1 MPa to obtain pre-foamed particles having a bulk ratio of 50 ml / g. Next, the pre-foamed grains were cured at room temperature for one day, and then a flat foam was molded by a KR-57 molding machine manufactured by Daisen Kogyo Co., Ltd.

The surface condition of the obtained thermoplastic resin foam was visually observed, and the surface condition was evaluated according to the following criteria.
◎: Very beautiful with no melting of the surface and no intergrains.
◯: The surface is melted and there are few intergrains, and it is beautiful.
Δ: The surface is melted and there are intergrains, and the appearance is slightly poor.
X: Surface melts, there are many grains, and the appearance is poor.

<Evaluation of fusion property>
The obtained thermoplastic resin foam was broken, the fracture surface was observed, the rate at which the particles were broken, not the particle interface, was determined, and the fusion property was determined according to the following criteria.
⊚: The rate of particle breakage is 90% or more.
◯: The rate of particle breakage is 80% or more and less than 90%.
Δ: The rate of particle breakage is 70% or more and less than 80%.
X: The rate of particle breakage is less than 70%.

(Example 1)
In a reactor equipped with a stirrer, 200 parts by weight of pure water, 0.3 parts by weight of calcium phosphate, 0.008 parts by weight of α-olefin sulphonate, 1 part by weight of salt, and 100 parts by weight of recycled styrene resin particles were added. Added under stirring. There, 0.05 parts by weight of ethylene bisstearic acid amide (average particle size 0.24 mm, manufactured by Nichiyu, Alflo H50-S) was added as an amide compound in advance with a homogenizer to 0.002 parts by weight of sodium α-olefin sulfonate. And water were stirred at 2600 rpm for 30 minutes to prepare an emulsion, which was added under stirring.

Then, after raising the temperature to 100 ° C., 6 parts by weight of pentane (a mixture of 80% by weight of normal and 20% by weight of iso) was added, and the temperature was further raised to impregnate at 118 ° C. for 5 hours. After cooling to room temperature, the particles were taken out from the reactor, washed, dehydrated, and dried to obtain effervescent styrene resin particles.

The obtained effervescent styrene-based resin particles were pre-foamed with a pressure-type pre-foaming machine (manufactured by Daikai Kogyo Co., Ltd., CH-100) at a bulk ratio of 50 times, and left at room temperature for 1 day for curing and drying. Next, the obtained styrene-based resin pre-foamed particles were molded into a foam-molded product using a molding machine (manufactured by Daisen Kogyo Co., Ltd., KR-57) using a mold having a size of 300 × 450 × 20 (t) mm. Evaluation was performed using the obtained preliminary foamed particles and the foamed molded product, and the results shown in Table 1 were obtained.

(Examples 2 to 8, 10, 12, Reference Examples 9 and 11, Comparative Examples 1 to 4)
As shown in Table 1, the foamable polystyrene resin particles and pre-foaming were carried out in the same manner as in Example 1 except that the amount of the dispersant, the type and amount of the amide compound, the addition temperature of the foaming agent, and the impregnation temperature were changed. Particles and foam molded products were obtained, and the same evaluation was carried out.

Claims (7)

A method for producing effervescent styrene resin particles in which styrene resin particles are dispersed in an aqueous medium in a closed container and impregnated with a foaming agent. An amide compound emulsified with two or more types of metal salts in the aqueous medium. hints, styrene resin particles, see contains recycled styrenic resin obtained was reduced by heat shrinking and / or thermal melting a styrene resin foam,
A foaming agent is added while the closed container is heated to 95 ° C or higher and 130 ° C or lower.
After that, a method for producing foamable styrene resin particles, which comprises spheroidizing recycled styrene resin particles by lowering the temperature of the closed container to 110 ° C. or higher and 130 ° C. or lower . The method for producing foamable styrene-based resin particles according to claim 1, wherein the styrene-based resin particles contain 50% by weight or more of recycled styrene-based resin and have a columnar shape that is strand-cut through an extruder. The method for producing foamable styrene-based resin particles according to claim 1 or 2, wherein the styrene-based resin foam is a foamed molded product obtained from foamable styrene-based resin particles. The method for producing effervescent styrene resin particles according to any one of claims 1 to 3, wherein the metal salt present in the aqueous medium is calcium tertiary phosphate and sodium chloride. The effervescent styrene resin according to claim 4, wherein the amount of the tertiary calcium phosphate added is 0.25 parts by weight or more and 0.8 parts by weight or less with respect to 100 parts by weight of the recycled styrene resin particles. How to make particles. The effervescent styrene type according to claim 4 or 5, wherein the amount of sodium chloride added is 0.7 parts by weight or more and 1.5 parts by weight or less with respect to 100 parts by weight of the recycled styrene resin particles. Method for producing resin particles. The effervescent styrene-based compound according to any one of claims 1 to 6 , wherein the emulsified amide compound added to the aqueous medium is an amide compound represented by the following general formula (I) or (II). Method for producing resin particles.