JP2009275185A - Styrenic resin composition for plate-like extruded foam, and method for producing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a styrenic resin composition suitable for production of plate-like extruded foam enabling extrusion at such low temperature that a flame retardant may not be decomposed during a production of plate-like extruded foam especially using a hydrocarbon- or an inorganic-based foaming agent such as carbon dioxide and water, having good foamability, excellent in mechanical strength and flame retaradance; and a method for producing it. <P>SOLUTION: Using a styrenic resin composition having a particular range of fluidity (melt mass flow rate) and a melt-tension value, as well as a particular range of weight-average molecular weight (Mw), molecular weight distribution (Mw/Mn, Mz/Mw) enables production of plate-like foam excellent in flame retardance and mechanical strength. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a styrene-based resin composition for a plate-like extruded foam and a method for producing the same, and can be extruded at a low temperature so as not to decompose a flame retardant, and has good foamability and mechanical properties. A plate-like extruded foam having excellent strength and flame retardancy can be obtained.

  Plate-like extruded foam made of styrene resin composition has excellent heat insulation and mechanical strength, so it can be used in various fields such as flooring for general buildings, wall materials, ceiling materials, and tatami core materials. Has been.

As a method for producing an extruded foam of a styrenic resin composition, various methods have been conventionally used. Generally, after a styrene resin composition is heated and melt-kneaded with an extruder, a foaming agent is added, A method of manufacturing by cooling and extrusion foaming in a low-pressure atmosphere is adopted. Moreover, although a fluorocarbon foaming agent has been used as the foaming agent (Patent Document 1), the ratio of using an inorganic foaming agent typified by a hydrocarbon foaming agent, carbon dioxide, and water is increasing due to recent environmental problems. The number of styrenic resin compositions suitable for these foaming agents is increasing.
Japanese Patent Laid-Open No. 10-182870

  As the hydrocarbon-based foaming agent, saturated hydrocarbons having 3 to 5 carbon atoms are mainly used. However, since the dispersibility is poor compared to the fluorocarbon-based foaming agent, the foaming agent is poorly dispersed during extrusion foaming. May be. Further, since the hydrocarbon-based foaming agent is flammable, the flame retardancy is deteriorated, and it is necessary to increase the amount of the flame retardant added. In addition, the amount of foaming agent used has been reduced due to safety problems during extrusion foaming. However, when the amount of foaming agent decreases, the resin viscosity in the extruder increases, and as a result, the resin temperature increases. When the resin temperature rises, there is a problem that the flame retardant is decomposed, thereby causing deterioration of the styrene resin. In order to suppress decomposition of the flame retardant, a styrenic resin composition that can be extruded at a low temperature is required, but at the same time, foamability and mechanical strength of the foam must be maintained.

  The use of an inorganic foaming agent typified by carbon dioxide or water as a main component has also been studied, but these foaming agents have a lower dispersibility in styrene resins than hydrocarbon foaming agents. Therefore, there is a demand for a styrenic resin composition that has good dispersibility, can be extruded at a low temperature so as to increase the amount of dissolved inorganic foaming agent, and can maintain foamability and mechanical strength.

  The present invention makes it possible to extrude at a low temperature so that the flame retardant does not decompose in the production of a plate-like extruded foam using an inorganic foaming agent typified by a hydrocarbon foaming agent, carbon dioxide and water. It is another object of the present invention to provide a styrene resin composition suitable for producing a plate-like extruded foam having good foamability and excellent mechanical strength and flame retardancy, and a method for producing the same.

1. Melt mass flow rate (MFR) measured at 200 ° C. and 49 N load is 10-30 g / 10 min, melt tension value measured at 200 ° C. is 5-15 gf, and methanol soluble content is 0.2. The weight average molecular weight (Mw) is 150,000 to 250,000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) is 3.5 to 8.0. A styrene resin composition for a plate-like extruded foam, wherein the ratio (Mz / Mw) of the Z average molecular weight (Mz) and the weight average molecular weight (Mw) is 2.2 to 3.6.
2. 2. The styrene resin composition for a plate-like extruded foam according to 1, wherein the total amount of residual styrene monomer and polymerization solvent in the styrene resin composition is 250 μg / g or less.
3. The styrenic resin composition for a plate-like extruded foam according to any one of items 1 to 2, wherein a Vicat softening temperature measured at a load of 50 N is 99 to 104 ° C.
4). When 5-20% by mass of ethylbenzene is used as a polymerization solvent and a continuous radical polymerization of styrene monomer is carried out, a complete mixing tank reactor consisting of 1 to 2 units is connected in series until the polymer concentration reaches 25-45% by mass. Polymerization is carried out so that the weight average molecular weight (Mw) of the polymer produced at a temperature of 110 to 130 ° C. in the connected process is 350,000 to 500,000, and then 150 ° C. to until the polymer concentration reaches 65 to 90%. Any one of items 1 to 3, wherein the polymerization is performed at a temperature of 210 ° C. such that the ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) is 2.2 to 3.6. The manufacturing method of the styrene-type resin composition for plate-shaped extrusion foam of Claim 1.
5. In the devolatilization step to remove the styrenic resin, unreacted styrene monomer and polymerization solvent obtained by continuous radical polymerization, a vacuum devolatilization tank with a heater connected in two stages in series is used as the first stage vacuum The resin temperature in the devolatilization tank is adjusted to 200 to 240 ° C., and the degree of vacuum is adjusted to 6.0 kPa or less so that the total amount of unreacted styrene monomer and polymerization solvent at the outlet is 0.2% by mass or less. 0.2 to 2.0 mass% of water is added to the polymer solution exiting the vacuum devolatilization tank of the eye, and water is dispersed in a dynamic or static mixer, and the degree of vacuum is 0.5 to The styrene-based resin composition for plate-like extruded foam according to any one of 1 to 4, which is introduced into a second-stage vacuum devolatilization tank adjusted to a range of 3.0 kPa and devolatilized. Manufacturing method.
6. A method for producing a plate-like extruded foam, wherein the styrenic resin composition according to any one of items 1 to 3 is foam-extruded and the density is 10 to 50 kg / m ³ .
A plate-like extruded foam obtained by the production method according to 7.6.

  By using the styrene-based resin composition of the present invention, extrusion at a low temperature is possible so that the flame retardant does not decompose, and it is possible to produce a plate-like extruded foam excellent in mechanical strength and flame retardancy. Thus, the extrusion foamability is also excellent.

  The melt mass flow rate (MFR) measured under the conditions of 200 ° C. and 49 N load of the styrenic resin composition targeted by the present invention is 10 to 30 g / 10 minutes, preferably 12 to 20 g / 10 minutes. . If it exceeds 30 g / 10 minutes, the resin viscosity will be too low, the foamability will deteriorate, and extrusion will be difficult. On the other hand, if it is less than 10 g / 10 minutes, the resin viscosity of the styrene-based resin composition is excessively increased, making it difficult to extrude at a low temperature, and the flame retardant decomposes due to an increase in the resin temperature. Even if the cylinder temperature of the extruder is lowered, the resin temperature rises due to shearing heat generation. The melt mass flow rate under the conditions of 200 ° C. and 49 N load of the styrene resin composition was measured based on JIS K-7210. The melt mass flow rate of the styrene-based resin composition is a parameter indicating the fluidity at the time of melting, but can be adjusted by controlling the molecular weight and the molecular weight distribution. In addition, various additive components such as styrene oligomers (styrene dimer, styrene trimer) and white oil that are by-produced in the polymerization process and devolatilization process, and low molecular weight components such as residual styrene monomer and polymerization solvent have a plasticizer effect. Because of this, there is an effect of increasing the melt mass flow rate.

  The melt tension value measured at 200 ° C. of the styrene resin composition targeted by the present invention is 5 to 15 gf. When the melt tension value is less than 5 gf, the foaming properties at the time of producing the plate-like extruded foam deteriorate, and there are adverse effects such as an increase in open cells. Moreover, the compressive strength of the plate-like extruded foam decreases. In addition, melt mass flow rate (MFR) in the range of 10 to 30 g / 10 min is difficult to achieve a melt tension exceeding 15 gf, the molecular weight distribution is too wide, and the strength and heat resistance are affected by the low molecular weight components. Such physical properties are reduced. The melt tension value is “Capillograph 1B type” manufactured by Toyo Seiki, barrel temperature 200 ° C., barrel diameter 9.55 mm, capillary length: L = 10 mm, capillary diameter: D = 1 mm (L / D = 10), The resin is extruded at an extrusion speed of 10 mm / min in the barrel, the load measuring part is set 60 cm below the die, the strand-shaped resin flowing out from the capillary is set in the winder, and the winding line speed is 4 m / min. From the minute to 200 m / min, the winding linear velocity is increased at a rate of 20 m / min per minute, and the load until the strand breaks is measured. As the winding line speed is increased, the load increases and stabilizes to a certain fluctuation range, but since the load has a fluctuation range, the range from when the load stabilizes until it breaks is averaged, and the melt tension value did. The winding line speed when the strand broke was defined as the thread break speed (m / min). The melt tension value is a parameter that represents the elastic properties of the styrene resin composition at the time of melting, but it can be adjusted by controlling the molecular weight and molecular weight distribution, and the higher the molecular weight, the higher the melt tension value. Can do. However, simply increasing the molecular weight will cause the melt mass flow rate to decrease at the same time, reducing the productivity of the plate-like extruded foam. To increase the melt tension value while maintaining the melt mass flow rate, there is a method of widening the molecular weight distribution. Specifically, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3 The melt mass flow rate and the melt tension of the present invention are such that the ratio (Mz / Mw) of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) is in the range of 2.2 to 3.6. It is possible to achieve a balance of values. In addition, various additive components such as styrene oligomers (styrene dimer, styrene trimer) and white oil that are by-produced in the polymerization process and devolatilization process, and low molecular weight components such as residual styrene monomer and polymerization solvent have a plasticizer effect. Therefore, there is an effect of lowering the melt tension value.

The methanol soluble part of the styrene resin composition targeted by the present invention is 0.2 to 1.5% by mass, preferably 0.2 to 1.3% by mass. When the methanol-soluble content exceeds 1.5% by mass, the heat resistance decreases. Moreover, it is difficult to make it less than 0.2 mass% by radical polymerization, and productivity falls remarkably. The methanol-soluble component means a component soluble in methanol in the resin composition. For example, in addition to styrene oligomer (styrene dimer, styrene trimer) by-produced in the polymerization process or devolatilization process of styrene resin, Various additives such as oil and silicone oil, and low molecular weight components such as residual styrene monomer and polymerization solvent are included. Methanol-soluble matter suppresses the amount of styrene oligomer (styrene dimer, styrene trimer) generated as a by-product in the polymerization process as much as possible, refrains from using various additives such as white oil, and reduces the amount of residual styrene monomer and polymerization solvent This can be reduced.
The methanol-soluble component is precisely weighed (mass P) of 1 g of the resin composition, 40 mL of methyl ethyl ketone is added and dissolved, and 400 mL of methanol is rapidly added to precipitate and precipitate the methanol-insoluble component (resin component). After leaving still for about 10 minutes, it is gradually filtered through a glass filter to separate methanol-insoluble matter, dried in a vacuum dryer at 120 ° C. under reduced pressure for 2 hours, and then allowed to cool for about 25 minutes without a desiccator. By measuring the mass N of the dried methanol-insoluble matter, it was determined by the following formula.
Methanol-soluble content (mass%) = (P−N) / P × 100

The weight average molecular weight (Mw) of the styrene resin composition targeted by the present invention is 150,000 to 250,000, preferably 200,000 to 240,000. Moreover, the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) is 3.5 to 8.0, preferably 4.0 to 6.0. The ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) is 2.2 to 3.6, preferably 2.3 to 2.9. When the weight average molecular weight (Mw), Mw / Mn, and Mz / Mw are out of the above ranges, the balance between the melt mass flow rate of the present invention and the melt tension value cannot be achieved.
The weight average molecular weight (Mw), Z average molecular weight (Mz), and number average molecular weight (Mn) in the present invention were measured under the following conditions using gel permeation chromatography (GPC).
GPC model: Shodex GPC-101 manufactured by Showa Denko KK
Column: Polymer Laboratories PLgel 10 μm MIXED-B
Mobile phase: Tetrahydrofuran Sample concentration: 0.2% by mass
Temperature: 40 ° C oven, 35 ° C inlet, 35 ° C detector
Detector: Differential refractometer The molecular weight of the present invention is calculated as the molecular weight in terms of polystyrene by calculating the molecular weight at each elution time from the elution curve of monodisperse polystyrene.

  The molecular weight of the styrene resin composition targeted by the present invention is controlled by the reaction temperature, residence time, type and amount of polymerization initiator used in radical polymerization of styrene, type and amount of solvent used during polymerization, and the like. be able to. The molecular weight can be increased by suppressing the polymerization rate, such as by performing polymerization at a low temperature, but it is not efficient by itself, and a polyfunctional organic peroxide can be used as a polymerization initiator. Preferably, 2,2-bis (4,4-t-butylperoxycyclohexyl) propane (tetrafunctional) and 1,1-bis (t-butylperoxy) cyclohexane (bifunctional) can be suitably used. . On the other hand, the molecular weight can be lowered by increasing the polymerization rate such as by performing polymerization at a high temperature, but a monofunctional organic peroxide may be used in order to further increase the polymerization rate. Further, the molecular weight can be lowered by adding a chain transfer agent. The polymerization method is preferably a commercially continuous polymerization, and in the first half of the polymerization where the concentration of styrene monomer is high, it is more advantageous to use a complete mixing tank type reactor in terms of increasing the molecular weight. Regarding the control of Mw / Mn and Mz / Mw representing the molecular weight distribution, the molecular weight distribution can be broadened by generating a high molecular weight component in the first half of the polymerization and generating a low molecular weight component in the second half of the polymerization.

  About the manufacturing method of the styrene resin composition of this invention, it is preferable that it is continuous radical polymerization of a styrene monomer, and it is preferable to use 5-20 mass% of ethylbenzene as a polymerization solvent. Further, toluene may be used in place of ethylbenzene. Until the polymer concentration reaches 25 to 45% by mass, the weight average molecular weight (Mw) of the polymer produced at a temperature of 110 to 130 ° C. in a process in which 1 or 2 complete mixing tank reactors are connected in series. It is preferable to carry out the polymerization so that becomes 35 to 500,000. Next, the ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) is 2.2 to 3.6 at a temperature of 150 to 210 ° C. until the polymer concentration reaches 65 to 90%. Polymerization is preferably performed so that At this time, the type of the reactor is not particularly limited, but a plug flow reactor or a combination of a complete mixing tank reactor and a plug flow reactor can be used. In the case of a plug flow reactor, since a temperature gradient is formed in the flow direction, the temperature may be controlled to be 150 ° C. to 210 ° C. after the middle portion of the reactor, and the vicinity of the inlet may be less than 150 ° C.

The total amount of residual styrene monomer and polymerization solvent in the styrene-based resin composition of the present invention is preferably 250 μg / g or less, more preferably 150 μg / g or less. When the total amount of residual styrene monomer and polymerization solvent in the styrene-based resin composition is large, problems such as odor may occur in the obtained plate-like extruded foam, and it is preferable to reduce as much as possible.
The amount of the residual styrene monomer and the polymerization solvent in the present invention was measured under the following conditions using gas chromatography by dissolving 500 mg of the resin composition in 10 ml of DMF containing cyclopentanol as an internal standard substance.
Gas chromatograph: HP-5890 (manufactured by Hewlett-Packard Company)
Column: HP-WAX, 0.25 mm × 30 m, film thickness 0.5 μm
Injection temperature: 220 ° C
Column temperature: 60 ° C to 150 ° C, 10 ° C / min
Detector temperature: 220 ° C
Split ratio: 30/1
The residual styrene monomer and the polymerization solvent can be reduced by the configuration of the devolatilization step and the operating conditions of the devolatilization step.

  When a styrene resin is produced by continuous radical polymerization, a devolatilization step is required to remove the obtained styrene resin, unreacted styrene monomer and polymerization solvent, but a vacuum devolatilization tank with a heater is connected in series. It is preferable to use one connected in two stages. The resin temperature in the first stage vacuum devolatilization tank is adjusted to 200 to 240 ° C., and the degree of vacuum is 6.0 kPa so that the total amount of unreacted styrene monomer and polymerization solvent at the outlet is 0.2 mass% or less. Adjust to the following, 0.2 to 2.0 mass% of water is added to the polymer solution exiting the first-stage vacuum devolatilization tank, and the water is dispersed in a dynamic or static mixer, It is preferable to introduce into a second-stage vacuum devolatilization tank adjusted to a vacuum degree of 0.5 to 3.0 kPa and perform devolatilization. The water added at the outlet of the first-stage vacuum devolatilization tank is gasified when it enters the second-stage vacuum devolatilization tank. At this time, if the devolatilization interface increases due to foaming, the devolatilization efficiency increases. Conceivable. Regarding the total amount (A) of unreacted styrene monomer and polymerization solvent at the first stage vacuum devolatilization tank outlet and the concentration of water added at the first stage outlet (B), the ratio of B to A, B / A is 1 It is preferable that it is -30, and it is more preferable that it is 4-20.

  The molten resin that has undergone the devolatilization process is transferred to the flow forming process by a gear pump or the like. In the granulation step, the molten resin is extruded in a strand form from a porous die and processed into a pellet shape by a cold cut method, an air hot cut method, or an underwater hot cut method.

  In the polymerization method of the present invention, in addition to 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane and 1,1-bis (t-butylperoxy) cyclohexane, polymerization is started as necessary. Agents and chain transfer agents can be used. As polymerization initiators, organic oxides such as benzoyl peroxide, t-butylperoxybenzoate, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, t-butylperoxy Isopropyl carbonate, dicumyl peroxide, t-butyl cumyl peroxide, t-butyl peroxyacetate, t-butyl peroxy-2-ethylhexanoate, polyether tetrakis (t-butyl peroxycarbonate), ethyl-3 , 3-di (t-butylperoxy) butyrate, t-butylperoxyisobutyrate and the like. As the chain transfer agent, for example, aliphatic mercaptan, aromatic mercaptan, pentaphenylethane, α-methylstyrene dimer, terpinolene and the like can be used, and α-methylstyrene dimer is preferable in consideration of odor and the like.

  In the styrenic resin composition targeted by the present invention, a metal soap such as zinc stearate, calcium stearate, magnesium stearate, stearic acid, ethylene bisstearyl amide or the like is used as an internal lubricant or external lubrication as necessary. It may be used as an agent. Moreover, although plasticizer components, such as white oil, can also be added, heat resistance falls. In addition, an antioxidant may be added to suppress thermal deterioration in the extruder.

  The Vicat softening temperature of the styrenic resin composition of the present invention measured at 50 N load is preferably 99 to 104 ° C, more preferably 100 to 104 ° C. If the Vicat softening temperature is less than 99 ° C., the heat resistance is insufficient and there is a risk of deformation in a high temperature environment. In addition, 104 ° C. is a structural limit in radical polymerization polystyrene. The Vicat softening temperature was determined according to JIS K-7206 at a heating rate of 50 ° C / hr and a test load of 50N.

The styrenic resin composition of the present invention is particularly suitable for producing a plate-like extruded foam by extrusion molding. The plate-like extruded foam is obtained by heating and melting a styrene resin composition, injecting a foaming agent, kneading, and adjusting the foaming optimum temperature to extrusion foaming in a low-pressure atmosphere (usually atmospheric pressure). Can be manufactured. The pressure at the time of injecting the blowing agent is not particularly limited, and the gas may be not gasified at a pressure higher than the internal pressure of an extruder or the like. In addition, the plate-like extruded foam targeted by the present invention has a density of 10 to 50 kg / m from the viewpoint of heat insulation, bending strength and compressive strength as a heat insulating material for buildings, a cold storage or a cold insulation vehicle. ³ and the thickness is preferably 10 to 150 mm.

  Moreover, when manufacturing a plate-like extrusion foam, a flame retardant can be used and inorganic fillers, such as a silica, a talc, and a calcium carbonate, can be used as a foaming nucleating agent as needed. The density, expansion ratio, and average cell diameter of the foam can be changed by adjusting the amount of the foaming agent and the amount of the foam nucleating agent. Furthermore, an antioxidant, a plasticizer, a lubricant, a dye / pigment, an antistatic agent, and the like can be added as long as the effects of the present invention are not impaired. Known blowing agents such as lower hydrocarbons such as propane, butane, pentane and hexane, ethers such as dimethyl ether and diethyl ether, ketones such as dimethyl ketone and methyl ethyl ketone, alcohols such as methanol, ethanol and propyl alcohol Arbitrary foaming agents such as halogenated hydrocarbons such as trichloromonofluoromethane and methyl chloride, inorganic gases such as carbon dioxide and water can be used alone or in combination, but the main component is lower hydrocarbons It is preferable. Known flame retardants can be used, such as hexabromocyclododecane, dibromoneopentyl glycol, decabromodiphenyl oxide, tetrabromobisphenol A, tetrabromophthalic acid diol, tetrabromophenol, polypentabromobenzyl acrylate, etc. Examples of the flame retardant include phosphoric flame retardants such as phosphoric acid guanene urea, polyphosphazene, ammonium phosphate, ammonium polyphosphate, and red phosphorus.

  The styrenic resin composition of the present invention can be extruded at a low temperature, and is excellent in flame retardancy and mechanical strength of the obtained plate-like extruded foam. Suitable for manufacturing.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these Examples.

(Method for producing styrene resin compositions PS-1 to PS-9)
The polymerization reactor was configured by connecting in series a first reactor that was a complete mixing tank, a second reactor, and a third reactor that was a plug flow reactor with a static mixer. The capacity of each reactor was 39 liters for the first reactor, 39 liters for the second reactor, and 16 liters for the third reactor. A raw material solution was prepared with the raw material composition described in Table 1, and the raw material solution was continuously supplied to the first reactor at a flow rate described in Table 1. The polymerization initiator was added and mixed with the raw material solution at the inlet of the first reactor or the third reactor so as to have the addition concentration shown in Table 1 (concentration based on mass relative to the raw styrene). The polymerization initiator and chain transfer agent described in Table 1 are as follows. As the white oil, ExxonMobil Cristol N352 was used.
Polymerization initiator-1: 1,1-bis (t-butylperoxy) cyclohexane (Perhexa C manufactured by NOF Corporation was used.)
Polymerization initiator-2: 2,2-bis (4,4-t-butylperoxycyclohexyl) propane (Pertetra A manufactured by NOF Corporation was used.)
Polymerization initiator-3: t-butyl cumyl peroxide (Perbutyl C manufactured by NOF Corporation was used.)
Chain transfer agent-1: α-methylstyrene dimer (Nofmer MSD manufactured by NOF Corporation) was used.
Polymerization initiators-1 and 2 and chain transfer agent-1 were added at the inlet of the first reactor, and polymerization initiator-3 was added at the inlet of the third reactor.
In the third reactor, a temperature gradient was provided along the flow direction, and the temperature in Table 1 was adjusted at the intermediate part and the outlet part.
Subsequently, the solution containing the polymer continuously taken out from the third reactor was introduced into a vacuum devolatilization tank with a preheater constituted by two stages in series, and the preheater was adjusted to the resin temperature shown in Table 1. By adjusting the temperature and adjusting to the pressure shown in Table 1, unreacted styrene and ethylbenzene are separated and then extruded into a strand form from a perforated die, and the strand is cooled and cut by a cold cut method. Pelletized. PS-1 to 5 were used in the examples, and PS-6 to 9 were used in the comparative examples.

  Table 2 shows the characteristics of the obtained styrene-based resin composition. Moreover, the measuring method in an Example is shown below.

The foam density (kg / m ³ ) was calculated from the weight (kg) of the foam and the volume (m ³ ) of the foam (foam density = foam weight / foam volume).

The cell diameter of the foam was measured by observing the cross section of the plate-like extruded foam with a microscope. At the same time, foamability was determined according to the following criteria.
○: The bubble size is uniform and independent.
(Triangle | delta): The bubble size is somewhat non-uniform | heterogenous and a part continuous bubble exists.
X: The bubble size is non-uniform, and some continuous bubbles are present.

The flame retardancy of the foam was determined by a method in accordance with JIS A 9511, in which five test pieces having a thickness of 10 mm, a length of 200 mm, and a width of 25 mm were prepared from the foam that had passed 2 weeks after production.
A: All five flames disappear within 3 seconds.
○: 1 to 2 out of 5 flames do not disappear within 3 seconds, but the rest disappear within 3 seconds.
Δ: 3 to 4 out of 5 flames do not disappear within 3 seconds, but all the others disappear within 3 seconds.
X: The flame does not disappear within 3 seconds for all five.

  The compressive strength of the foam was measured by a method according to JIS K 7220 from the foam after 2 weeks of production.

(Examples 1-5, Comparative Examples 1-4)
To 100 parts by mass of the styrenic resin composition described in Table 2, 2.5 parts by mass of hexabromocyclohexane and 0.5 parts by mass of talc as a foam regulator were added and blended. After feeding to a 40 mm diameter single screw extruder (cylinder temperature 200 ° C.) and melt mixing, 5 parts by mass of butane gas was injected as a blowing agent. Thereafter, it is transferred to a 65 mm diameter single-screw extruder (cylinder temperature 120 ° C.), extruded from a die having a rectangular cross section with a thickness of 2 mm and a width direction of 40 mm at the tip of the extruder, and a plate shape having a thickness of about 40 mm. A foam was produced. About each composition, the quantity of the foaming agent and the quantity of the bubble regulator were adjusted so that it might become the foam density of Table 2, and a bubble diameter. Table 2 shows the foamability, compressive strength, and resin temperature at the exit of the extruder.

  By using the styrenic resin composition of the example, low-temperature extrusion becomes possible, and a plate-like extruded foam excellent in flame retardancy and compressive strength can be obtained. Moreover, since it is excellent also in the foamability at the time of extrusion, the manufacture of the stable plate-like extrusion foam becomes possible.

  By using the styrenic resin composition of the present invention, extrusion at a low temperature is possible, a plate-like extruded foam excellent in flame retardancy and compressive strength can be obtained, and the foamability is also excellent. Suitable for use in extruded extruded foam. In addition, the method for producing a styrene resin composition of the present invention makes it possible to produce a styrene resin composition suitable for plate-like extruded foam applications at low cost.

Molecular weights obtained by gel permeation chromatography (GPC) measurement of the styrene resin compositions PS-1 and PS-3 used in the examples and the styrene resin compositions PS-6 and PS-8 used in the comparative examples. It is a figure which compares distribution.

It is a figure explaining one structural example of a superposition | polymerization process.

It is a figure explaining one structural example of a superposition | polymerization process.

It is a figure explaining one structural example of a superposition | polymerization process.

It is a figure explaining 1 structural example of a devolatilization process.

Claims (7)

  The melt mass flow rate (MFR) measured under the conditions of 200 ° C. and 49 N load is 10 to 30 g / 10 minutes, the melt tension value measured at 200 ° C. is 5 to 15 gf, and the methanol soluble content is 0.2 to 1. 0.5 mass%, the weight average molecular weight (Mw) is 150,000 to 250,000, the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) is 3.5 to 8.0, Z A ratio of average molecular weight (Mz) to weight average molecular weight (Mw) (Mz / Mw) is 2.2 to 3.6.   The total amount of residual styrene monomer and polymerization solvent in the styrene-based resin composition is 250 µg / g or less, and the styrene-based resin composition for plate-like extruded foam according to claim 1.   The Vicat softening temperature measured at a load of 50 N is 99 to 104 ° C, The styrenic resin composition for plate-like extruded foam according to any one of claims 1-2.   When 5-20% by mass of ethylbenzene is used as a polymerization solvent and a continuous radical polymerization of styrene monomer is carried out, a complete mixing tank reactor consisting of 1 to 2 units is connected in series until the polymer concentration reaches 25-45% by mass. Polymerization is carried out so that the weight average molecular weight (Mw) of the polymer produced at a temperature of 110 to 130 ° C. in the connected process is 350,000 to 500,000, and then 150 ° C. to until the polymer concentration reaches 65 to 90%. The polymerization is carried out at a temperature of 210 ° C. so that the ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) is 2.2 to 3.6. The manufacturing method of the styrene-type resin composition for plate-shaped extrusion foams of any one.   In the devolatilization step to remove the styrenic resin, unreacted styrene monomer and polymerization solvent obtained by continuous radical polymerization, a vacuum devolatilization tank with a heater connected in two stages in series is used as the first stage vacuum The resin temperature in the devolatilization tank is adjusted to 200 to 240 ° C., and the degree of vacuum is adjusted to 6.0 kPa or less so that the total amount of unreacted styrene monomer and polymerization solvent at the outlet is 0.2% by mass or less. 0.2 to 2.0 mass% of water is added to the polymer solution exiting the vacuum devolatilization tank of the eye, and the water is dispersed in a dynamic or static mixer, and the degree of vacuum is 0.5 to It introduce | transduces into the 2nd step | paragraph vacuum devolatilization tank adjusted to the range of 3.0 kPa, and devolatilizes, The styrene resin for plate-like extrusion foam of any one of Claims 1-4 characterized by the above-mentioned. A method for producing the composition. A method for producing a plate-like extruded foam, wherein the styrenic resin composition according to any one of claims 1 to 3 is foam-extruded and has a density of 10 to 50 kg / m ³ .   A plate-like extruded foam obtained by the production method according to claim 6.

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