JP2011074144A - Styrene polymer particle, manufacturing method for the same, expandable styrene polymer particle and foam-molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foam-molded product having a smooth cut surface after cut by a hot nichrome wire, and a method of manufacturing styrene polymer particle giving the foam-molded product, styrene polymer particles, expandable styrene polymer particles, and the like. <P>SOLUTION: The method of manufacturing the styrene polymer particles comprises effecting polymerization by previously causing a molecular weight modifier to be present in an aqueous medium and adding a styrene monomer continuously or stepwise to the system, where the temperature, A°C, at the time of the initiation of polymerization and the temperature, B°C, at the time of finish of the addition of the predetermined amount of the styrene monomer, are caused to satisfy A≤B≤A+15 and the temperature is kept at A°C over a period of at least 50% of the total polymerization time. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a styrene polymer particle, a method for producing the same, an expandable styrene polymer particle, and a foamed molded product. More specifically, the present invention relates to a styrene polymer particle for obtaining a foamed molded article having a smooth cut surface after nichrome cutting, its production method and expandable styrene polymer particle, and a cut surface after nichrome cutting is smooth. The present invention relates to a foamed molded article.

Block-shaped styrene resin foam molding in which foamable styrene polymer particles imparted with foaming performance are impregnated with styrene polymer particles by impregnating volatile foaming agents such as propane, butane and pentane. A body (also referred to as a foam molded body) is widely used as a building material panel, packaging material, and the like from the viewpoint of moldability.
In general, the method of cutting with nichrome wire (also referred to as nichrome cutting) is widely used as a method for processing a foamed molded product because the foamed molded product can be processed very easily into a desired size and shape. However, in this processing method, since the foamed molded product is exposed to high heat by the nichrome wire, large unevenness may be confirmed on the cut surface (processed surface) of the foamed molded product. In this case, the foamed molded article having a cut surface on which irregularities have been confirmed is not beautiful and may cause poor adhesion on the cut surface.
Therefore, provision of a processed product of a foamed molded article having a smooth cut surface is demanded.

A technique for providing a processed product having a smooth cut surface is reported in Japanese Patent Application Laid-Open No. 7-188453 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2007-246606 (Patent Document 2).
In JP-A-7-188453, when the reaction temperature at the start of polymerization of the styrene monomer is A ° C. and the reaction temperature at the end of the polymerization is B ° C., B ° C ≧ A ° C. + 15 ° C. Describes a process for producing expandable styrenic polymer particles in which a styrene monomer is supplied while raising the temperature. The foamed molded article derived from the obtained expandable styrenic polymer particles is said to have good fusion between the foamed particles, well filled gaps between the particles, and good appearance.

In JP 2007-246606 A, the weight average molecular weight of the entire styrene polymer particles is in the range of 330,000 to 500,000, and the weight average molecular weight of the styrene polymer particle surface layer is (X). When the weight average molecular weight of the whole particle is (Y), the molecular weight reduction rate (%) obtained by the following formula (1):
Molecular weight reduction rate (%) = (Y−X) / Y × 100 (1)
Expandable polystyrene-based resin particles are described in the range of 0.5 to 5%. In this publication, it is said that by using the expandable polystyrene resin particles having the above-described molecular weight reduction rate, a processed product having a smooth cut surface with few irregularities can be obtained.

JP-A-7-188453 JP 2007-246606 A

As for the foaming molding obtained by the technique of Unexamined-Japanese-Patent No. 7-188453, the unevenness | corrugation of a cut surface may be confirmed.
In Japanese Patent Application Laid-Open No. 2007-246606, the turtle shell height is cited as an index indicating the smoothness of the cut surface. In Example 3 of this publication, the smallest turtle shell height of 18 μm is obtained. However, there is a need for a foam molded body that has a smaller turtle shell height, in other words, that can provide a cut surface with higher smoothness.

Thus, according to the present invention, the molecular weight regulator is preliminarily present in the aqueous medium, and the styrene monomer is continuously or stepwise added to the system to carry out the polymerization. The temperature B ° C. when the predetermined amount of the styrenic monomer has been added is set to a temperature satisfying A ≦ B ≦ A + 15, and 50% or more of the total polymerization time is maintained at A ° C. A method for producing styrenic polymer particles is provided.
Moreover, according to this invention, the styrene-type polymer particle obtained by the said method is provided.
Furthermore, expandable styrene polymer particles obtained from the styrene polymer particles are provided.
Moreover, the foaming molding obtained by carrying out in-mold foaming molding of the said expandable styrene-type polymer particle is provided.

According to the production method of the present invention, it is possible to provide styrene polymer particles capable of giving a foamed molded article having a smooth cut surface after nichrome cutting. Moreover, the expandable styrene-type polymer particle and foaming molding which can give a smooth cut surface can be provided. Furthermore, the foaming molding which has a smooth cut surface can be provided.
Further, when the temperature A ° C. is within the range of ± 15 ° C. of the 10-hour half-life temperature of the molecular weight modifier, it is possible to provide styrene polymer particles that can give a foamed molded product with a smoother cut surface.

Furthermore, when suspension polymerization is maintained at A ° C. for 50 to 80% of the total polymerization time, it is possible to provide styrene polymer particles that can give a foamed molded product with a smoother cut surface.
In addition, when the styrene monomer is added to the aqueous medium in an amount of 1 to 10 hours, styrene polymer particles that can give a foamed molded article with a smoother cut surface can be provided.
Furthermore, when the expandable styrene polymer particles have an average particle diameter of 600 to 1500 μm, styrene polymer particles that can give a foam molded product with a smoother cut surface can be provided.

In addition, when the suspension polymerization is a seed polymerization method using seed particles made of a styrene polymer, since the particle diameter of the styrene polymer particles can be made uniform, a foam molded product with a smoother cut surface can be obtained. Styrenic polymer particles can be provided.
Further, suspension polymerization of styrene monomer for seed particles in an aqueous medium in the presence of a salt particle selected from water-soluble phosphate, water-soluble sulfite and water-soluble persulfate. Can provide a styrenic polymer particle capable of giving a foamed molded article having a smoother cut surface.
Moreover, according to this invention, the styrene-type polymer particle which can manufacture the foaming molding with a smooth cut surface can be provided.

It is a schematic explanatory drawing of the measuring method of the turtle shell height of a foaming molding. It is an enlarged photograph of a part of foaming molding which measured the turtle shell height of Example 1 and comparative example 2.

  In the method for producing styrene polymer particles of the present invention, when a molecular weight modifier is present in an aqueous medium in advance and a styrene monomer is continuously or stepwise added to the system, polymerization is started. The temperature A ° C. and the temperature B ° C. when the predetermined amount of the styrenic monomer has been added are set to a temperature satisfying A ≦ B ≦ A + 15, and 50% or more of the total polymerization time is A ° C. It is a method to hold in.

(Styrene monomer)
As the styrene monomer, any of styrene and substituted styrene (substituent includes lower alkyl, halogen atom (especially chlorine atom) and the like) can be used. Examples of the substituted styrene include chlorostyrenes, p-methylstyrene, α-methylstyrene, and the like. Of these, styrene is generally preferred. The styrene monomer can be a mixture of other monomers copolymerizable with styrene. Other monomers include, for example, acrylonitrile, methacrylic acid alkyl ester (alkyl moiety having about 1 to 8 carbon atoms), maleic acid mono to dialkyl (alkyl moiety having about 1 to 4 carbon atoms), maleic anhydride, N -Phenylmaleide, allyl (meth) acrylate, divinylbenzene, alkylene glycol dimethacrylate (alkylene preferably has 2 to 4 carbon atoms). In these mixtures, the styrene monomer preferably occupies a dominant amount (for example, 50% by weight or more).

(Molecular weight regulator)
The molecular weight modifier is not particularly limited as long as the molecular weight of the styrene resin constituting the styrene resin particles can be adjusted. For example, benzoyl peroxide (73.6 ° C), lauryl peroxide (61.6 ° C), t-butylperoxy-2-ethylhexanoate (72.1 ° C), t-butylperoxybenzoate (104. 3 ° C), t-butylperoxy-2-ethylhexyl monocarbonate (99 ° C), t-butylperoxypivalate (54.6 ° C), t-butylperoxyisopropyl carbonate (98.7 ° C), t- Butyl peroxyacetate (101.9 ° C), 2,2-t-butylperoxybutane (103.1 ° C), t-butylperoxy-3,3,5-trimethylhexanoate (97.1 ° C) And azo compounds such as azobisisobutyronitrile (65 ° C.) and azobisdimethylvaleronitrile (51 ° C.). In the above examples, the temperature in () means the decomposition temperature for obtaining the 10-hour half-life of the molecular weight modifier (hereinafter referred to as 10-hour half-life temperature).

  The said molecular weight modifier can be used individually or in combination of 2 or more types. When using 2 or more types together, it is based on the lowest 10-hour half-life temperature. The molecular weight modifier is added in advance to the aqueous medium. However, if the molecular weight modifier is added directly to the aqueous suspension, the molecular weight modifier may be difficult to be uniformly absorbed by the styrene monomer droplets. The modifier is added in a state suspended or emulsified in another aqueous medium, or dissolved and added in a small amount of styrenic monomer, or dissolved in a small amount of styrenic monomer, and an inorganic suspension is added. You may add as an aqueous suspension which added the turbid stabilizer and / or the anionic surfactant.

(Production of styrene polymer particles)
The styrene monomer is polymerized by adding the styrene monomer continuously or stepwise to the aqueous medium containing the molecular weight modifier. Examples of the aqueous medium include water and a mixed medium of water and a water-soluble organic solvent (lower alcohol such as methanol and ethanol). Here, continuous means that the styrenic monomer is added to the aqueous medium seamlessly, and stepwise means that the added styrenic monomer is divided into a plurality of categories. It means that the styrenic monomer is added at a time during which no styrenic monomer is added.

Here, in the present invention, the temperature A ° C. at the start of polymerization and the temperature B ° C. when the addition of a predetermined amount of the styrenic monomer are completed are set to satisfy the temperature A ≦ B ≦ A + 15.
When the temperature B ° C. is lower than the temperature A ° C., it is necessary to cool or warm the reactor, so that the polymerization time may be extended or it may be difficult to adjust the molecular weight. When the temperature B ° C. is higher than the temperature (A + 15) ° C., the unevenness after the nichrome cut may become large. More preferably, the temperatures A ° C. and B ° C. satisfy A ≦ B ≦ A + 10.

  Furthermore, the temperature A ° C is preferably within a range of ± 15 ° C of the 10-hour half-life temperature. When the temperature A ° C. is low exceeding (10-hour half-life temperature −15 ° C.), the adjustment of the molecular weight may be difficult due to insufficient polymerization of the styrenic monomer. When the temperature A ° C is higher than (10-hour half-life temperature + 15 ° C), the reproducibility of the molecular weight of the resulting styrene polymer particles may be deteriorated due to the high polymerization rate.

  In the present invention, more than 50% of the total polymerization time is maintained at A ° C. By holding, it can be adjusted to a desired molecular weight efficiently. Moreover, it is preferable that suspension polymerization is hold | maintained at A degreeC for 50 to 80% of time in all the polymerization time. Thus, it can adjust to desired molecular weight more efficiently by hold | maintaining at A degreeC for a fixed time. After being held at A ° C for a certain time, it is usually heated to a temperature about 0 to 15 ° C higher than A ° C.

Moreover, it is preferable that the whole quantity of a styrenic monomer is added to an aqueous medium within 1 to 10 hours. By adding within this time, there is an effect that a stable foaming property can be obtained. A more preferable addition time is 1 to 3 hours.
By the way, although the end point of superposition | polymerization can also be made at the time of completion | finish of addition of a styrene-type monomer, it is usually about 1 to 8 hours after the completion of addition.

(Seed polymerization method)
As described above, the method of the present invention can be applied to an ordinary suspension polymerization method. However, when it is desired to obtain styrenic polymer particles having a sharp particle size distribution, the method of the present invention can be applied to the seed polymerization method. By sharpening the particle size distribution, it is possible to provide styrene polymer particles that can give a foamed molded product with a smoother cut surface. The seed polymerization method is a method of obtaining styrene polymer particles by absorbing styrene monomers in seed particles in an aqueous medium and polymerizing the styrene monomers while or after absorption.

(1) Seed particles As seed particles, a homopolymer of styrene, a copolymer of styrene and another copolymerizable monomer, or the like is used. Examples of the copolymerizable monomer include α-methylstyrene, acrylonitrile, acrylic or methacrylic acid and an ester having 1 to 8 carbon atoms, maleic anhydride, N-vinylcarbazole and the like. In the case of a copolymer, the polystyrene component is preferably contained at 50% by weight or more, more preferably 80% by weight or more.

  In the seed polymerization method, if the particle diameter of the seed particles is within a narrow range, the particle diameters of the styrene polymer particles obtained are well aligned. That is, by performing seed polymerization using seed particles having a uniform particle diameter, styrenic polymer particles having a desired particle diameter according to the application are obtained, for example, 300 to 500 μm, 500 to 700 μm, 700 to 1200 μm, It can be divided into narrow ranges such as 1200-1500 μm and 1500-2500 μm, and each segment can be obtained with a yield of almost 100%. Therefore, as the seed particles, polymer particles obtained by once classifying the polymer particles obtained by the suspension polymerization method and adjusting the particle diameter to be within a range of ± 20% of the average particle diameter can be used. When obtained by a bulk polymerization method, pellets having a desired particle diameter can be used.

When seed particles are obtained by the suspension polymerization method, in the presence of a poorly water-soluble phosphate and water-soluble sulfite and / or water-soluble persulfate in an aqueous medium without using a surfactant. A method of polymerizing styrene monomers (so-called soap-free polymerization method) is preferred.
Examples of the poorly water-soluble phosphate include tricalcium phosphate, hydroxyapatite, and magnesium phosphate. Of these, tricalcium phosphate is preferred. Further, the poorly water-soluble phosphate can be used in the form of a powder or an aqueous slurry. The amount of the hardly water-soluble phosphate is preferably 0.03% by weight or more in terms of solid content with respect to the styrene monomer for forming seed particles. When the amount is less than 0.03% by weight, the dispersion state of droplets made of styrene monomer may not be maintained. In addition, suspension polymerization is possible even when the amount used is more than 1% by weight, but there is no effect due to the increased amount used, and in addition, it is not economical, so the upper limit of the amount used is 1% by weight. It is preferable.

Examples of water-soluble sulfites include sodium bisulfite, potassium bisulfite, and ammonium bisulfite. In addition to these salts, precursors that dissolve in water and react in the polymerization reaction system to become sulfites can also be used. Examples of such precursors include water-soluble pyrosulfites, pyrosulfates, dithionites, thiosulfates, sulfoxylates, sulfates, and the like. Of these water-soluble sulfites and precursors, sodium hydrogen sulfite, sodium pyrosulfite, sodium dithionite, and sodium formaldehyde sulfoxylate are preferred.
Examples of the water-soluble persulfate include sodium persulfate, potassium persulfate, and ammonium persulfate. Of these salts, potassium persulfate is particularly preferred.
Further, the weight average molecular weight of the seed particles is preferably 200000-350,000, more preferably 220,000-300000.

(Seed polymerization conditions)
A suspension stabilizer may be used to suspend the seed particles in the aqueous medium. Examples of the suspension stabilizer include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly soluble inorganic compounds such as tricalcium phosphate and magnesium pyrophosphate. When using a hardly soluble inorganic compound, an anionic surfactant such as sodium dodecylbenzenesulfonate may be used in combination.
Various conditions such as the temperature at the start of polymerization of the styrenic monomer in the seed polymerization method, the temperature at the end of the addition of the predetermined amount of the styrenic monomer, are as described in “Manufacturing styrene polymer particles” above. The conditions described in the column can be adopted.

  By the way, when using seed particles, the molecular weight modifier may be absorbed in the seed particles by adding a mixed solution obtained by dissolving or dispersing in the styrene monomer in advance to the aqueous medium. Good. By making it absorb, the molecular weight of the styrene-type polymer particle by a molecular weight modifier can be adjusted efficiently. In this case, the starting point of the polymerization means the point at which the addition of a styrene monomer that dissolves or disperses the molecular weight modifier is started.

  The use ratio of the seed particles used in the seed polymerization method is preferably 10 to 75% by weight, more preferably 15 to 50% by weight, based on the total amount of the styrene polymer at the end of the polymerization. When the amount of seed particles used is less than 10% by weight, it is difficult to control the polymerization rate of the styrene polymer particles within an appropriate range when adding the styrene monomer, and the resulting polymer has a high molecular weight. In addition, the production efficiency may be reduced due to the generation of a large amount of fine powder polymer, which may be industrially disadvantageous. Conversely, when it exceeds 75% by weight, it is difficult to obtain excellent foam moldability.

(Styrene polymer particles)
The styrene polymer particles obtained by the above method preferably have an average particle diameter of 600 to 1500 μm. By having an average particle diameter within this range, it is possible to provide styrenic polymer particles that can give a foamed molded product with a smoother cut surface.
Furthermore, when the present invention is applied to the seed polymerization method, the range of the particle diameter of the styrene polymer particles can be, for example, ± 20% or less with respect to the median diameter.

(Expandable styrene polymer particles)
The expandable styrenic polymer particles can be obtained by impregnating the above styrene polymer particles with a foaming agent. The styrene polymer particles may be impregnated with a foaming agent after the styrene polymer particles are taken out from the aqueous medium, or may be impregnated with the foaming agent by press-fitting the foaming agent into the aqueous medium without taking out the styrene polymer particles. .

  As the blowing agent, the boiling point is easily volatile with a polymer softening point or less, for example, propane, butane, pentane, cyclopentane, hexane, HCFC-141b, HCFC-142b, HCFC-124, HFC-134a, HFC -152a etc., and these foaming agents may be used alone or in combination of two or more. The amount of the blowing agent used is preferably 1 to 10% by weight, more preferably 2 to 7% by weight, based on the polymer particles obtained. The blowing agent may be added at any time before, during or after the polymerization, but it is usually added by press-fitting after the latter stage or after the polymerization to impregnate the styrenic polymer particles.

  A foaming aid can be used together with the foaming agent. Examples of the foaming aid include aromatic organic compounds such as styrene, toluene, ethylbenzene and xylene, cycloaliphatic hydrocarbons such as cyclohexane and methylcyclohexane, ethyl acetate, butyl acetate and the like having a boiling point of 200 at 1 atm. A solvent having a temperature of 0 ° C. or lower is exemplified.

  Further, in the expandable styrene polymer particles, a plasticizer having a boiling point of more than 200 ° C. under 1 atm, in order to maintain good foam moldability even when the pressure of water vapor used at the time of heat foaming is low, for example, Contains less than 2.0% by weight of plasticizers such as phthalic acid esters, glycerin diacetomonolaurate, glycerin tristearate, glycerin fatty acid esters such as glycerin diacetomonostearate, adipic acid esters such as diisobutyl adipate, and palm oil. May be.

In the present invention, in addition to a solvent and a plasticizer, it is used for producing expandable styrene polymer particles such as a foamed cell nucleating agent, a filler, a flame retardant, a flame retardant aid, a lubricant, a colorant, and a crosslinking agent. You may use an additive suitably as needed.
The expandable styrenic polymer particles in the present invention may be surface-coated as long as the physical properties are not impaired. Examples of the coating agent include powdered metal soaps such as zinc stearate, stearic acid triglyceride, stearic acid monoglyceride, castor oil, amide compound, silicones, and polyethylene glycol.

(Foamed molded product)
The foamed molded body is obtained by pre-foaming the expandable styrene polymer particles by using a heating medium such as water vapor to obtain pre-foamed particles, filling the pre-foamed particles in the mold of the molding machine, and heating. Then, secondary foaming is performed, and the pre-foamed particles are fused and integrated to obtain a desired shape. As the molding machine, there can be used an EPS molding machine or the like used when producing a foam molded body from pre-expanded particles.

  When the foamed molded product obtained by the present invention is processed by nichrome cutting, the smoothness of the cut surface is extremely excellent. Here, the smoothness can be evaluated by the height of the turtle shell, and the foam molded body obtained by the present invention can have a turtle shell height of preferably 30 μm or less, more preferably 20 μm or less. Since the foam-molded article obtained by the present invention has a smooth cut surface, it can be suitably used in the field of panels for building materials and the like that require smoothness of the surface. In addition, a process is not limited to the process by a nichrome wire, What is necessary is just a process using a well-known electrical resistance heating wire.

Hereinafter, the present invention will be further described with reference to examples. However, the present invention is not limited to these examples. Various manufacturing conditions and measurement methods will be described below.
<Average particle diameter of styrene polymer particles and expandable styrene polymer particles>
The average particle size is measured by the following method. That is, JIS standard sieve opening 2360 μm (7.5 mesh), opening 2000 μm (8.6 mesh), opening 1700 μm (10 mesh), opening 1400 μm (12 mesh), opening 1180 μm (14 mesh), opening Opening 1000 μm (16 mesh), opening 850 μm (18 mesh), opening 710 μm (22 mesh), opening 600 μm (26 mesh), opening 500 μm (30 mesh), opening 425 μm (36 mesh), opening 355 μm (42 mesh), mesh opening 300 μm (50 mesh), mesh opening 250 μm (60 mesh), mesh opening 212 μm (70 mesh), mesh opening 180 μm (83 mesh) and classification based on cumulative weight distribution curve , Average particle size (median) with a cumulative weight of 50% And child size.

<Bulk multiple of pre-expanded particles>
The bulk density of the pre-expanded particles is measured as follows.
First, the pre-expanded particles 500 cm ^3, filled into the graduated cylinder to the scale of 500 cm ^3. When the graduated cylinder is visually observed from the horizontal direction and any pre-expanded particles reach a scale of 500 cm ³ , the filling of the pre-expanded particles into the graduated cylinder is terminated at that point.
Next, the mass of the pre-expanded particles filled in the graduated cylinder is weighed with two significant figures after the decimal point, and the mass is defined as W (g).
Then, the bulk density of the pre-expanded particles is calculated by the following formula.
Bulk density (g / cm ³ ) = W / 500
The bulk foaming factor is the reciprocal of the bulk density.

<Turtle shell height of foam molding>
The turtle shell height of the Nichrome cut surface of the obtained foamed molded product is measured and evaluated by the following method.
Using a scanning electron microscope (JEOL JSM-6360LV, manufactured by JEOL Ltd.), the Nichrome cut surface was magnified 20 to 30 times in the vertical direction, and the indentation depth of the particles was measured for 10 particles as shown in FIG. The average value is defined as the turtle shell height.
Rating:
○: Tortoise shell height is 30 μm or less, there is no unevenness, and the surface is smooth and good.
X: Tortoise shell height exceeds 30 μm, unevenness is slightly seen, and surface smoothness is slightly inferior.

<Weight average molecular weight of styrene polymer particles and expandable styrene polymer particles>
The weight average molecular weight of the styrene polymer particles and the expandable styrene polymer particles is measured by gel permeation chromatography (hereinafter referred to as “GPC”).
GPC measurement condition model: HLC-8320GPC (manufactured by Tosoh Corporation)
Guard column: TSK guardcolumn Super HZ-H 4.6 ml. D. × 2cmL 1 (Tosoh Corporation)
Column: TSK gel Super HZM-H 4.6 ml. D. × 15cmL 2 (Tosoh Corporation)
Column temperature: 40 ° C
Detector: RI
Solvent: Reagent primary tetrahydrofuran flow rate: 0.175 ml / min.
Sample concentration: 0.03% by weight
Injection volume: 50 μl

Example 1
<Preparation of styrene polymer seed particles>
120 g of tricalcium phosphate (manufactured by Ohira Chemical Co., Ltd.), 0.2 g of sodium hydrogen sulfite and 0.2 g of potassium persulfate are added to an autoclave with a stirrer (hereinafter referred to as a reactor) having an internal volume of 100 liters. 75%) 140 g, 30 g of t-butylperoxy-2-ethylhexyl monocarbonate, 40 kg of ion-exchanged water, and 40 kg of styrene monomer were added and dissolved and dispersed with stirring to form a suspension.

  Next, the styrene monomer was polymerized at 90 ° C. for 6 hours and further at 120 ° C. for 2 hours under stirring at 200 rpm. After completion of the reaction, the reaction mixture is cooled to 25 ° C., the contents are taken out from the autoclave, dehydrated, dried and classified, and the styrene weight having an average particle size of 550 μm (distribution of 425-600 μm) and 660 μm (distribution of 500-710 μm) Combined seed particles were obtained. Each weight average molecular weight was 300,000.

<Preparation of styrene polymer particles>
Next, 11 kg of styrene polymer seed particles having an average particle diameter of 550 μm, 32 kg of distilled water, 128 g of magnesium pyrophosphate, 8.3 g of sodium dodecylbenzenesulfonate (25% purity, the same applies hereinafter) to an autoclave with a stirrer having an internal volume of 100 liters. The mixture was stirred and suspended, and the temperature inside the reactor was raised to 80 ° C.

  Next, 3000 g of distilled water, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbenzenesulfonate, and 1540 g of styrene were stirred with a homomixer to prepare a suspension, and this suspension was added to a reactor maintained at 80 ° C. Then, 1140 g of styrene was fed to the reactor at 228 g / min, and styrene was absorbed by the styrenic polymer seed particles for 15 minutes from the end of the feeding.

  Subsequently, 220 g of benzoyl peroxide with a purity of 75% (10-hour half-life temperature: 73.6 ° C.) as a molecular weight modifier was dissolved in 1890 g of styrene and stirred with a homomixer with 2000 g of distilled water and 3 g of sodium dodecylbenzenesulfonate. The suspension prepared above was fed to a reactor maintained at 80 ° C.

After 10 minutes from the end of the supply of the suspension containing the molecular weight modifier to the reactor, the styrene polymer seed particles absorb styrene and the molecular weight modifier, and then 28.43 kg of styrene is 9.48 kg in the reactor. The reactor temperature was continuously increased at a rate of 5 hr / hr for 3 hours, and the reactor temperature was continuously increased at a rate of 5 ° C./hr for 1 hour 2 hours after the start of the styrene feed. C.
Subsequently, styrene polymer particles were obtained by maintaining at 85 ° C. for 1 hour.

<Preparation of expandable styrene polymer particles>
In a reactor containing the styrene polymer particles, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbezene sulfonate, and 13.2 g of ethylene bisstearamide are added to 2000 g of distilled water, and the mixture is stirred with a homomixer. Prepared and added this dispersion. Then, 880 g of normal butane (trade name normal butane manufactured by Koike Chemical Co., Ltd.) and 1088 g of pentane as the foaming agent were injected and heated to 100 ° C. After maintaining at 100 ° C. for 3 hours, the mixture was cooled to 20 ° C., and the expandable styrene polymer particles were taken out from the reactor, washed, dehydrated and dried to obtain expandable styrene polymer particles. The average particle size of the expandable styrene polymer particles was 850 μm and had a distribution of 600 to 1000 μm. The weight average molecular weight was 210,000.

<Preparation of pre-expanded particles>
40 kg of expandable styrene polymer particles are charged into a tumbler mixer, followed by 20 g of polyethylene glycol having a weight average molecular weight of 300, 12 g of liquid paraffin having an average molecular weight of 378, and 8 g of dimethylpolysiloxane having a 100 cs, and a tumbler for 15 minutes. The mixer was rotated. Next, 32 g of zinc stearate, 12 g of stearic acid triglyceride, 20 g of stearic acid monoglyceride, and 28 g of 12 hydroxystearic acid triglyceride were put into a tumbler mixer and rotated for 15 minutes to coat the surface of the expandable styrene polymer particles.

  After the surface-coated expandable styrenic polymer particles were aged at 15 ° C. for 3 days, JPO Gazette 57 (1982) -133 [3347] Known and Conventional Techniques (Foam Molding) The pre-expanded particles were obtained by charging into a cylindrical batch type pressure pre-foaming machine having a volume of 350 liters up to the foam layer upper surface detector described in 39 and heating with steam. The pre-expanded particles had a bulk expansion ratio of 60 times.

<Preparation of foam molded article>
After leaving the pre-expanded particles in a room temperature atmosphere for 24 hours, using a block molding machine (PEONY-205DS manufactured by Kasahara Kogyo Co., Ltd.) having a mold of cavity size: height 1840 mm, width 930 mm, depth 530 mm, the mold cavity The pre-expanded particles are filled in, heated at a vapor pressure of 0.06 MPa (gauge pressure) for 20 seconds, then cooled until the internal pressure of the mold becomes −0.01 MPa, released from the mold, and blocked. A foamed molded product was produced and stored in a 60 ° C. drying room for 3 days.

  The foam molded body is placed on the base of a nichrome cutting machine with the plane of length 1840 mm x width 930 mm down, and ten 0.4 mm diameter nichrome wires are stretched in parallel at intervals of 50 mm to feed the foam molded body. Nichrome cutting was performed under the conditions of 600 mm / min and current of 3 A / line to obtain a flat sliced product.

Example 2
The reactor was charged with 11 kg of styrene polymer seed particles having an average particle diameter of 660 μm obtained in Example 1, 32 kg of distilled water, 128 g of magnesium pyrophosphate, and 8.3 g of sodium dodecylbenzenesulfonate, and the mixture was stirred and suspended. The reactor internal temperature was raised to 82 ° C.

  Next, 3000 g of distilled water, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbenzenesulfonate, and 1540 g of styrene were stirred with a homomixer to prepare a suspension, and this suspension was added to a reactor maintained at 82 ° C. Then, 1140 g of styrene was fed to the reactor at 228 g / min, and styrene was absorbed by the styrenic polymer seed particles for 15 minutes from the end of the feeding.

  Subsequently, 220 g of benzoyl peroxide having a purity of 75% as a molecular weight regulator was dissolved in 1890 g of styrene, and a suspension prepared by stirring with a homomixer with 2000 g of distilled water and 3 g of sodium dodecylbenzenesulfonate was maintained at 82 ° C. Feeded to the reactor.

After 10 minutes from the end of the supply of the suspension containing the molecular weight modifier to the reactor, the styrene polymer seed particles absorb styrene and the molecular weight modifier, and then 28.43 kg of styrene is 9.48 kg in the reactor. The reactor internal temperature was continuously increased at a rate of 5 ° C./hr for 2 hours, and the reactor internal temperature was increased to 87 hours. C.
Subsequently, styrene polymer particles were obtained by maintaining at 87 ° C. for 1 hour.

In a reactor containing the styrenic polymer particles, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbezene sulfonate, 6.6 g of ethylene bisstearamide, 13.2 g of toluene and 6.6 g of cyclohexane are added to 2000 g of distilled water. The mixture was stirred with a homomixer to prepare a dispersion, and this dispersion was added to the reactor. Thereafter, 3696 g of normal butane (trade name normal butane, manufactured by Koike Chemical Co., Ltd.) and 1320 g of pentane as a foaming agent were injected and heated to 100 ° C. After maintaining at 100 ° C. for 3 hours, the mixture was cooled to 20 ° C., and the expandable styrene polymer particles were taken out from the reactor, washed, dehydrated and dried. The average particle size of the expandable styrene polymer particles was 1100 μm, and there was a distribution of 710 to 1180 μm. The weight average molecular weight was 240,000.
Subsequent steps were performed in the same manner as in Example 1 to obtain a flat slice product.

Example 3
The reactor was charged with 22 kg of styrene polymer seed particles having an average particle diameter of 660 μm obtained in Example 1, 32 kg of distilled water, 128 g of magnesium pyrophosphate, and 8.3 g of sodium dodecylbenzenesulfonate, and the mixture was stirred and suspended. The reactor internal temperature was raised to 80 ° C.

  Next, 3000 g of distilled water, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbenzenesulfonate, and 858 g of styrene were stirred with a homomixer to prepare a suspension, and this suspension was added to a reactor maintained at 80 ° C. Then, 5500 g of styrene was supplied to the reactor at 275 g / min, and styrene was absorbed by the styrene polymer seed particles for 15 minutes from the end of the supply.

  Subsequently, 77 g of benzoyl peroxide having a purity of 75% as a molecular weight modifier was dissolved in 2000 g of styrene, and the suspension prepared by stirring with a homomixer with 2000 g of distilled water and 3 g of sodium dodecylbenzenesulfonate was maintained at 80 ° C. Feeded to the reactor.

The styrene polymer seed particles are allowed to absorb styrene and the molecular weight modifier for 55 minutes from the start of supply of the suspension containing the molecular weight modifier to the reactor, and then 13.64 kg of styrene is continuously fed into the reactor. Feeded in 1 hour.
Subsequently, styrene polymer particles were obtained by holding at 80 ° C. for 40 minutes.

In a reactor containing the styrenic polymer particles, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbezene sulfonate, 13.2 g of ethylene bisstearamide, and 176 g of toluene are added to 2000 g of distilled water, and the mixture is stirred with a homomixer. A dispersion was prepared and this dispersion was added into the reactor. Then, 1276 g of normal butane (trade name normal butane manufactured by Koike Chemical Co., Ltd.) and 2948 g of pentane as the foaming agent were injected and heated to 100 ° C. After maintaining at 100 ° C. for 3 hours, the mixture was cooled to 20 ° C., and the expandable styrene polymer particles were taken out from the reactor, washed, dehydrated and dried. The average particle size of the expandable styrene polymer particles was 850 μm and had a distribution of 600 to 1000 μm. The weight average molecular weight was 290,000.
Subsequent steps were performed in the same manner as in Example 1 to obtain a flat slice product.

Example 4
The reactor was charged with 11 kg of styrene polymer seed particles having an average particle diameter of 550 μm obtained in Example 1, 32 kg of distilled water, 128 g of magnesium pyrophosphate, and 8.3 g of sodium dodecylbenzenesulfonate, and the mixture was stirred and suspended. The reactor internal temperature was raised to 75 ° C.

  Next, 3000 g of distilled water, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbenzenesulfonate, and 1540 g of styrene were stirred with a homomixer to prepare a suspension, and this suspension was added to a reactor maintained at 75 ° C. Then, 1140 g of styrene was fed to the reactor at 228 g / min, and styrene was absorbed by the styrenic polymer seed particles for 15 minutes from the end of the feeding.

  Subsequently, 220 g of benzoyl peroxide having a purity of 75% and 40 g of t-butylperoxy-2-ethylhexyl monocarbonate were dissolved in 1890 g of styrene as a molecular weight modifier and stirred with a homomixer together with 2000 g of distilled water and 3 g of sodium dodecylbenzenesulfonate. The suspension thus prepared was fed to a reactor maintained at 75 ° C.

After 10 minutes from the end of the supply of the suspension containing the molecular weight modifier to the reactor, the styrene polymer seed particles absorb styrene and the molecular weight modifier, and then 28.43 kg of styrene is 9.48 kg in the reactor. The reactor internal temperature was continuously increased at a rate of 13 ° C./hr for 1 hour at a rate of 13 ° C./hr. C.
Subsequently, styrene polymer particles were obtained by maintaining at 88 ° C. for 1 hour.

In a reactor containing the styrenic polymer particles, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbezene sulfonate, 13.2 g of ethylene bisstearamide, 13.2 g of toluene, and 6.6 g of cyclohexane are added to 2000 g of distilled water. The mixture was stirred with a homomixer to prepare a dispersion, and this dispersion was added to the reactor. Then, 880 g of normal butane (trade name normal butane manufactured by Koike Chemical Co., Ltd.) and 1088 g of pentane as the foaming agent were injected and heated to 100 ° C. After maintaining at 100 ° C. for 3 hours, the mixture was cooled to 20 ° C., and the expandable styrene polymer particles were taken out from the reactor, washed, dehydrated and dried. The average particle size of the expandable styrene polymer particles was 850 μm and had a distribution of 600 to 1000 μm. The weight average molecular weight was 280,000.
Subsequent steps were performed in the same manner as in Example 1 to obtain a flat slice product.

Comparative Example 1
The reactor was charged with 11 kg of styrene polymer seed particles having an average particle diameter of 550 μm obtained in Example 1, 32 kg of distilled water, 128 g of magnesium pyrophosphate, and 8.3 g of sodium dodecylbenzenesulfonate, and the mixture was stirred and suspended. The reactor internal temperature was raised to 75 ° C.

  Next, 3000 g of distilled water, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbenzenesulfonate, and 1540 g of styrene were stirred with a homomixer to prepare a suspension, and this suspension was added to a reactor maintained at 75 ° C. Then, 1140 g of styrene was fed to the reactor at 228 g / min, and styrene was absorbed by the styrenic polymer seed particles for 15 minutes from the end of the feeding.

  Subsequently, 220 g of benzoyl peroxide having a purity of 75% as a molecular weight regulator was dissolved in 1890 g of styrene, and a suspension prepared by stirring with a homomixer with 2000 g of distilled water and 3 g of sodium dodecylbenzenesulfonate was maintained at 75 ° C. Feeded to the reactor.

After 10 minutes from the end of the supply of the suspension containing the molecular weight modifier to the reactor, the styrene polymer seed particles absorb styrene and the molecular weight modifier, and then 28.43 kg of styrene is 9.48 kg in the reactor. The reactor internal temperature was continuously increased at a rate of 17 ° C./hr for 1 hour at a rate of 17 ° C./hr. C.
Subsequently, styrene polymer particles were obtained by maintaining at 92 ° C. for 1 hour.

In a reactor containing the styrenic polymer particles, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbezene sulfonate, 13.2 g of ethylene bisstearamide, 13.2 g of toluene, and 6.6 g of cyclohexane are added to 2000 g of distilled water. The mixture was stirred with a homomixer to prepare a dispersion, and this dispersion was added to the reactor. Then, 880 g of normal butane (trade name normal butane manufactured by Koike Chemical Co., Ltd.) and 1088 g of pentane as the foaming agent were injected and heated to 100 ° C. After maintaining at 100 ° C. for 3 hours, the mixture was cooled to 20 ° C., and the expandable styrene polymer particles were taken out from the reactor, washed, dehydrated and dried. The average particle size of the expandable styrene polymer particles was 850 μm and had a distribution of 600 to 1000 μm. The weight average molecular weight was 290,000.
Subsequent steps were performed in the same manner as in Example 1 to obtain a flat slice product.

Comparative Example 2
The reactor was charged with 11 kg of styrene polymer seed particles having an average particle diameter of 550 μm obtained in Example 1, 32 kg of distilled water, 128 g of magnesium pyrophosphate, and 8.3 g of sodium dodecylbenzenesulfonate, and the mixture was stirred and suspended. The reactor internal temperature was raised to 75 ° C.

  Next, 3000 g of distilled water, 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbenzenesulfonate and 220 g of styrene were stirred with a homomixer to prepare a suspension, and this suspension was added to a reactor maintained at 75 ° C. The styrene polymer seed particles were allowed to absorb styrene for 15 minutes.

  Subsequently, 160 g of benzoyl peroxide having a purity of 75% as a molecular weight modifier was dissolved in 1860 g of styrene, and a suspension prepared by stirring with a homomixer with 2000 g of distilled water and 3 g of sodium dodecylbenzenesulfonate was maintained at 75 ° C. Feeded to the reactor.

After the styrene polymer seed particles have absorbed styrene and the molecular weight modifier for 10 minutes from the end of the supply of the suspension containing the molecular weight modifier to the reactor, 31.42 kg of styrene is 11.8 kg in the reactor. Was continuously supplied at a rate of 2 hours and 40 minutes at a rate of / hr, and the temperature was continuously increased at a rate of 17 ° C / hr from the start of styrene supply, and the temperature in the reactor at the end of the styrene supply was set to 108 ° C. .
Subsequently, styrene polymer particles were obtained by maintaining at 108 ° C. for 1 hour.

In the reactor containing the styrenic polymer particles, the temperature in the reactor is cooled to 100 ° C., 13 g of magnesium pyrophosphate, 3 g of sodium dodecylbezene sulfonate, 13.2 g of ethylene bisstearamide, 2000 g of distilled water, 13.2 g of toluene and 6.6 g of cyclohexane were added and stirred with a homomixer to prepare a dispersion. The dispersion was press-fitted into the reactor. Then, 880 g of normal butane (trade name normal butane manufactured by Koike Chemical Co., Ltd.) and 1088 g of pentane as the foaming agent were injected. After maintaining at 100 ° C. for 3 hours, the mixture was cooled to 20 ° C., and the expandable styrene polymer particles were taken out from the reactor, washed, dehydrated and dried. The average particle size of the expandable styrene polymer particles was 850 μm and had a distribution of 600 to 1000 μm. The weight average molecular weight was 310,000.
Subsequent steps were performed in the same manner as in Example 1 to obtain a flat slice product.

  In Table 1, the evaluation result of the sliced product of the foaming molding obtained by the Example and the comparative example is shown. Moreover, the one part enlarged photograph which measured the turtle shell height of the foaming molding of Example 1 and Comparative Example 2 is shown in FIG. 2A is an enlarged photograph of the first embodiment, and FIG. 2B is an enlarged photograph of the second embodiment. In FIG. 2A, a turtle shell height portion of 18 μm is shown, and in FIG. 2B, a turtle shell height portion of 76 μm is shown.

  From Table 1, from the example and the comparative example, by setting the temperature B ° C. at the end of the addition of styrene to the temperature A ° C. to (A + 15) ° C. at the start of polymerization, foaming with extremely high cut surface smoothness. It turns out that a molded object can be obtained.

Claims (11)

  In carrying out the polymerization by adding a molecular weight modifier to the aqueous medium in advance and adding a styrenic monomer continuously or stepwise to the system, a temperature A ° C. at the start of polymerization and a predetermined amount of the styrenic monomer are used. Styrenic polymer particles characterized in that the temperature B ° C. at the end of addition of the monomer is set to a temperature satisfying A ≦ B ≦ A + 15, and a time of 50% or more of the total polymerization time is maintained at A ° C. Manufacturing method.   The method for producing styrene-based polymer particles according to claim 1, wherein the temperature A ° C at the start of the polymerization is within a range of ± 15 ° C of a decomposition temperature for obtaining a 10-hour half-life of the molecular weight modifier.   The method for producing styrene polymer particles according to claim 1 or 2, wherein the suspension polymerization is maintained at A ° C for 50 to 80% of the total polymerization time.   The method for producing styrene polymer particles according to any one of claims 1 to 3, wherein the styrene monomer is added to the aqueous medium in an amount of 1 to 10 hours.   The method for producing styrene polymer particles according to any one of claims 1 to 4, wherein the styrene polymer particles have an average particle size of 600 to 1500 µm.   The method for producing styrene polymer particles according to any one of claims 1 to 5, wherein the suspension polymerization is a seed polymerization method using seed particles made of a styrene polymer.   The seed particles are obtained by suspension polymerization of a styrene monomer for seed particles in an aqueous medium in the presence of a poorly water-soluble phosphate and a salt selected from a water-soluble sulfite and a water-soluble persulfate. The method for producing styrenic polymer particles according to claim 6 obtained.   Styrenic polymer particles obtained by the method according to any one of claims 1 to 7.   Expandable styrene polymer particles obtained by impregnating the styrene polymer particles according to claim 8 with a foaming agent.   A foam molded article obtained by in-mold foam molding of the expandable styrenic polymer particles according to claim 9.   The foamed molded product according to claim 10, wherein the foamed molded product has a cross section cut by an electric resistance heating wire.