JP2017186422A - Foamable styrene resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamable styrene resin particle having good fusion property, surface property and strength in a low pressure molding condition.SOLUTION: There is achieved by a foamable styrene resin particle containing easily volatile foaming agent, a styrene resin of the foamable styrene resin particle contains 0.010 to 0.020 pts.wt. of divinyl benzene based on 100 pts.wt. of a styrene monomer, a xylene insoluble component of the foamable styrene resin particle is less than 1.5%, Z average molecular weight (Mz1) of a surface part of the foamable styrene resin particle is 600,000 to 1,000,000, whole Z average molecular weight (Mz2) is 700,000 to 1,150,000 and a ratio of Mz1 and Mz2 (Mz1/Mz2) is 0.85 to 0.95.SELECTED DRAWING: None

Description

  The present invention relates to expandable styrene resin particles and a method for producing the same. Furthermore, the present invention relates to pre-expanded particles obtained by foaming expandable styrenic resin particles, and foam-molded products obtained by in-mold molding of pre-expanded particles.

  Conventionally, foamed molded articles obtained from expandable styrene resin particles are excellent in lightness, heat insulation, strength, and hygiene, and are widely used for food containers, cushioning materials, heat insulating materials, residential building materials, and the like. For example, it is used for floor heating in the residential building materials field. In this floor heating application, there is a part where a pipe is embedded, and since it is necessary to make this part a thickness of several millimeters, high strength is required.

  On the other hand, recently, there has been an increasing demand for energy saving due to increased concern about environmental problems, and there is a demand for a resin that can be foamed with a small amount of steam used by lowering the temperature during molding. .

  However, if the temperature at the time of foaming is lowered, foaming is suppressed by the accumulation of vapor drain generated during heating, and in the obtained molded product, the pre-foamed particles are not sufficiently fused together. In this case, the strength such as bending strength and compressive strength tends to deteriorate. Furthermore, since the filling state of the pre-expanded particles in the vicinity of the mold wall surface is poor, the porosity is high, and the generation of drain in this part increases, and there is a problem that a particle gap is generated on the surface of the molded body.

  Patent Document 1 discloses a method in which the ratio (Mz1 / Mz2 = 1.05 to 1.5) of the resin particle surface layer part and the entire resin particle is adjusted by adding a crosslinking agent to improve the strength. However, since the molecular weight (Mz = 1.3 to 2 million) of the resin particle surface layer is higher than the molecular weight of the entire resin particle (Mz = 1.2 to 1.9 million), if the steam temperature during molding is low, the fusion deteriorates. The problem is that it is difficult to ensure sufficient strength.

  In Patent Document 2, in order to improve heat resistance, the ratio of the resin particle surface layer to the entire resin particle is adjusted by adding a crosslinking agent (Mz1 / Mz2 = 1.05 to 2.9) and the average cell diameter is 150 to 300 μm and the outermost wall A method is disclosed in which the grain boundary wall thickness is adjusted to 2.0 to 10.0 μm. In this method, the strength is increased, but the molecular weight of the resin particle surface layer (Mz = 115 to 2.5 million) is higher than the molecular weight of the entire resin particle (Mz = 85 to 1.1 million), and the grain boundary of the outermost wall is thick, When the steam temperature at the time of molding is low, the fusion deteriorates, and it is difficult to ensure sufficient strength.

  Patent Document 3 discloses a method for adjusting resin particles in which a crosslinking agent is added and the gel content is 10 to 50% by mass in order to suppress oil and pigment bleeding. In this method, the gel content: solvent insoluble content (10 to 50% by mass) specified in the literature is difficult to ensure sufficient strength because the fusion deteriorates when the steam temperature during molding is low. Was a problem.

  Patent Document 4 discloses an adjustment method in which the particle size is 200 to 600 μm, the amount of residual styrene is 1000 ppm or less, the amount of blowing agent is 2 to 6% by weight, and the expansion ratio is 3 to 30 times. Although this method has good formability at low pressure, there is room for improvement because sufficient strength cannot be obtained.

  As in Patent Documents 1 to 4, no material satisfying all of the fusion property, surface property and strength under low pressure molding conditions has been found.

JP2013-159683A Japanese Patent Laying-Open No. 2015-214641 JP 2007-31641 A JP 2004-155870 A

  An object of the present invention is to provide expandable styrenic resin particles having good fusion properties, surface properties, and strength under low pressure molding conditions.

  As a result of intensive studies, the present inventors have adopted a specific xylene-insoluble component, a surface layer and a molecular weight ratio of the whole, so that a foamable styrene system having good fusion properties, surface properties, and strength under low-pressure molding conditions. The inventors have found that resin particles can be obtained and have completed the present invention. That is, the present invention is as follows.

  [1] Expandable styrene resin particles containing a volatile foaming agent, wherein the styrene resin of the expandable styrene resin particles is 0.010 to 100 parts by weight of divinylbenzene. 0.020 part by weight, the xylene-insoluble content of the expandable styrene resin particles is less than 1.5%, and the Z average molecular weight (Mz1) of the surface layer of the expandable styrene resin particles is 600,000 to 1,000,000 A foamable polystyrene having an overall Z-average molecular weight (Mz2) of 700,000 to 1.15 million and a ratio of Mz1 to Mz2 (Mz1 / Mz2) of 0.85 to 0.95 Resin particles.

  [2] The volatile blowing agent is at least one member selected from the group consisting of propane, isobutane, normal butane, isopentane, normal pentane, and neopentane, and includes 2 to 7 parts by weight with respect to 100 parts by weight of the styrene resin particles. The expandable polystyrene resin particle according to the invention of [1], which is characterized in that

  [3] Pre-expanded particles obtained by foaming the expandable styrenic resin particles according to the invention of [1] or [2].

  [4] A foam molded article obtained by in-mold molding the pre-expanded particles according to the invention of [3].

[5] The foam molded article according to the invention of [4], wherein the density of the foam molded article is 0.05 to 0.2 g / cm ³ .

  [6] The method for producing expandable styrene resin particles according to the invention of [1] or [2].

  [7] 0.040 parts by weight to 0.180 parts by weight of the compound represented by the general formula (1) is used as a polymerization initiator with respect to 100 parts by weight of the total amount of the styrene resin seed particles and the styrene monomer. The method for producing expandable styrene resin particles according to the invention of [6], wherein

(In the formula, R ¹ represents a branched alkyl group, and R ² represents a branched or straight chain alkyl group.)
[8] The method for producing expandable styrenic resin particles according to [6] or [7], wherein after the addition of divinylbenzene, heat treatment is performed at 115 to 130 ° C. for 2 to 7 hours.

  [9] The expandable styrene system according to any one of [6] to [8], wherein divinylbenzene is added when 90% to 100% of the total amount of the styrene monomer is added. A method for producing resin particles.

  Under low-pressure molding conditions, expandable polystyrene resin particles having good fusing properties, surface properties, and strength can be obtained.

  Hereinafter, embodiments of the present invention will be described in more detail.

  The present invention relates to expandable styrene resin particles containing a volatile foaming agent, wherein the styrene resin of the expandable styrene resin particles contains divinylbenzene in an amount of 0.010 with respect to 100 parts by weight of styrene monomer. -0.020 parts by weight, the xylene-insoluble content of the expandable styrene resin particles is less than 1.5%, and the Z average molecular weight (Mz1) of the surface layer of the expandable styrene resin particles is 600,000-100 The foaming property is characterized in that the entire Z average molecular weight (Mz2) is 700,000 to 1,150,000, and the ratio of Mz1 to Mz2 (Mz1 / Mz2) is 0.85 to 0.95. Styrenic resin particles.

  The styrene resin particles used in the present invention are generally known styrene resin granules, and are styrene and styrene derivatives such as α-methylstyrene, paramethylstyrene, t-butylstyrene, chlorostyrene, and the like. In addition, components that can be copolymerized with styrene, such as esters of acrylic acid and methacrylic acid such as methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, cetyl methacrylate, acrylonitrile, dimethyl fumarate, ethyl fumarate, etc. And various functional monomers such as divinylbenzene and alkylene glycol dimethacrylate. One or more of these copolymerizable components may be used for copolymerization.

  The amount of phenylacetylene in styrene is preferably 0 to 250 ppm. When the amount of phenylacetylene exceeds 250 ppm, it is necessary to increase the amount of the initiator used. On the other hand, the molecular weight of the obtained expandable styrene resin particles tends to be greatly reduced. As a result, there is a problem that strength and formability are lowered.

  The styrene resin particles in the present invention are produced by a so-called suspension seed polymerization method in which a styrene monomer is added to styrene resin seed particles dispersed in an aqueous suspension and polymerized while impregnating the seed particles. Can be used.

  The resin seed particles used in the suspension seed polymerization method are (1) a normal suspension polymerization method, and (2) a polymerizable monomer is passed through a nozzle under regular vibration to form droplets in an aqueous medium. It can be obtained by a method of dispersing, polymerizing without causing coalescence and additional dispersion.

  The amount of the styrene resin seed particles is preferably 5 to 60% by weight with respect to the target amount of the styrene resin particles. When the amount is less than 5% by weight, the polymerizable monomer added to the aqueous suspension does not polymerize within the resin seed particles, and the proportion of polymerization alone tends to increase. When the amount exceeds 60% by weight, More monomers cannot be polymerized in one polymerization step, which is uneconomical.

  The particle diameter of the expandable styrene resin particles is preferably 200 to 600 μm. If the particle size is less than 200 μm, the yield during polymerization is extremely deteriorated and cost increase is unavoidable. In addition, the retention of the foaming agent tends to be lowered and the bead life tends to be shortened. Exceeding the range is not preferable because the mold filling property tends to deteriorate when the floor base material is molded. In order to set the particle diameter of the expandable styrene resin particles to 200 to 600 μm, the particle diameter of the styrene resin seed particles is preferably 200 to 300 μm.

  Examples of the dispersant used in the present invention include dispersants generally used for suspension polymerization, such as poorly water-soluble inorganic salts such as calcium phosphate, hydroxyapatite, and magnesium pyrophosphate. When these poorly water-soluble inorganic salts are used, the use of an anionic surfactant such as α-olefin sodium sulfonate or dodecylbenzene sodium sulfonate is effective because the dispersion stability increases. Further, the hardly soluble inorganic salt may be added one or more times during the polymerization in order to adjust the particle diameter of the resulting expandable styrene resin particles.

  In the production of expandable styrenic resin particles, generally, an initiator mainly for forming a resin and an initiator mainly for reducing the amount of residual styrene are generally used in combination. Here, as a polymerization initiator for forming a resin, organic oxides such as benzoyl peroxide, t-butyl peroxybenzoate, isopropyl t-butyl peroxycarbonate, butyl perbenzoate and azobisiso Examples include azo compounds such as butyronitrile. By using one or more of these polymerization initiators in combination, it is possible to obtain a good product in which the amount of residual styrene is reduced while further widening the selection range such as polymerization temperature, polymerization time, resin molecular weight and the like. Therefore, using together is a very preferable embodiment.

The polymerization initiator for reducing the residual styrene is a compound represented by the general formula (1), R ¹ is a branched alkyl group, and R ² has a branched or straight chain alkyl group structure. .

(In the formula, R ¹ represents a branched alkyl group, and R ² represents a branched or straight chain alkyl group.)
The R ¹ structure of the general formula (1) is preferably a t-butyl group or a t-amyl group, and the R ² structure is preferably a ² -ethylhexyl group or an isopropyl group from the viewpoint of reducing the amount of residual styrene.

  Specific examples include t-butyl peroxy-2-ethylhexyl monocarbonate, t-amyl peroxy-2-ethylhexyl monocarbonate, t-hexyl peroxyisopropyl monocarbonate, t-butyl peroxyisopropyl monocarbonate, and the like. .

  In particular, among the compounds of the general formula (1), t-butylperoxy-2-ethylhexyl monocarbonate (10 hour half-life temperature 99 ° C.) determines the residual styrene content of the expandable styrene resin particles as the final product. This is preferable because it can be reduced and is cheaper.

  The amount of the polymerization initiator used is 0.040 parts by weight or more and 0.180 parts by weight or less based on 100 parts by weight of the total amount of the styrene resin seed particles and the styrene monomer. When the amount of the polymerization initiator used is within this range, a resin having an appropriate molecular weight can be obtained, and the amount of residual styrene can be reduced. If the amount is less than 0.040 parts by weight, the amount of residual styrene tends to increase, and the heat resistance and strength tend to decrease due to the plastic effect of the amount of residual styrene. If it exceeds 0.180 parts by weight, the effect of reducing the amount of residual styrene monomer is sufficient, but the molecular weight of the resin tends to decrease, causing problems such as strength deterioration and narrowing of the condition range at the time of molding. Occurs.

  In the general formula (1), the 10-hour half-life temperature is preferably 96 ° C. or higher and 110 ° C. or lower. If it is this range, the amount of cleavage during superposition | polymerization can be suppressed as much as possible, and the amount of residual styrene can be reduced efficiently during the heat treatment which heat-processes at 115-130 degreeC, or a foaming agent impregnation process. A 10-hour half-life temperature of less than 96 ° C. is not preferable because the amount of cleavage during polymerization increases and the molecular weight of the resin decreases. As a solution to this problem, it is possible to lower the polymerization temperature. However, in this case, the polymerization time is extended, which is not preferable for industrial production. Conversely, when the 10-hour half-life temperature exceeds 110 ° C., the amount of initiator that cleaves during heat treatment or foaming agent impregnation is insufficient, and the amount of residual styrene cannot be reduced sufficiently.

  Moreover, when using the compound of General formula (1), it is preferable to heat-process at 115 degreeC or more and 130 degrees C or less after adding divinylbenzene.

  When the heating temperature during the heat treatment and the blowing agent impregnation step is 115 ° C. or higher and 130 ° C. or lower, in particular, a compound having a 10-hour half-life temperature of 96 ° C. or higher and 110 ° C. or lower is used. Well, styrene monomer can be reduced. However, when the temperature is lower than 115 ° C., radical generation of the compound of the general formula (1) is reduced and productivity is lowered. When the temperature exceeds 130 ° C., the internal pressure of the polymerization apparatus becomes high, and a polymerization apparatus having a pressure resistance of heavy equipment is required. Furthermore, the amount of decrease in molecular weight increases, resulting in problems such as deterioration in strength and narrowing of the condition range during molding.

  The heating time is preferably 2 to 7 hours. If it is this range, a styrene-type monomer can be reduced efficiently. However, when the heating time is less than 2 hours, radical generation of the compound of the general formula (1) decreases and the amount of residual styrene tends to increase. When the heating time exceeds 7 hours, the amount of decrease in the molecular weight increases, resulting in problems such as deterioration in strength and narrowing of the condition range during molding.

  The method for adding the compound of the general formula (1) for reducing the residual styrene may be added before the start of polymerization or may be added in the latter half of the polymerization as long as the seed resin is dispersed in water. For example, when it is added before the temperature rise to the polymerization step, or when it is added at the 5th polymerization time in a prescription in which the polymerization time is 6 hours, the residual styrene amount is sufficiently reduced. However, when adding the compound of the general formula (1), an inorganic dispersant such as calcium phosphate needs to be present in water. Without the inorganic dispersant, the polymerization initiator becomes a medium, and the seed resins agglomerate. Or dispersion | distribution of the compound of General formula (1) deteriorates, and the content variation of the compound of General formula (1) between particle | grains becomes large. In this case, the amount of residual styrene tends to increase, which is not preferable.

  The obtained expandable styrene resin particles of the present invention have a residual styrene monomer content of 300 ppm or less, preferably 250 pm or less. The lower limit is practically less than 0 ppm, so it is 1 ppm or more if dare to display.

  The compound of the general formula (1) generates many radicals during heating at 115 to 130 ° C., and the radical species cuts the polymer and lowers the molecular weight in addition to reducing the residual styrene. Therefore, it is necessary to control the amount of decrease in the Z average molecular weight of the entire resin particles between 5 and 30 in the heat treatment and the blowing agent impregnation step. In order to achieve this reduced amount, the additional amount of the general formula (1) described above is 0.040 parts by weight or more and 0.000 part by weight with respect to 100 parts by weight of the total amount of the styrene resin seed particles and the styrene monomer. 180 parts by weight or less. When the molecular weight decrease is less than 5 in Mz, the foaming property is lowered, and therefore, when the steam temperature at the time of molding is low, surface elongation and fusion tend to be deteriorated. When the amount of decrease in molecular weight exceeds 30 in Mz, the strength tends to decrease.

  The Z-average molecular weight (Mz2) of the entire expandable styrene resin particles of the present invention is 700,000 to 1,150,000. If it is less than 700,000, the strength tends to decrease. Moreover, when the vapor pressure at the time of molding becomes high, the resin on the surface tends to be melted and the surface appearance tends to be impaired. If it exceeds 1.15 million, the foaming property will be low, so if the steam temperature at the time of molding is low, surface elongation and fusion will deteriorate, and as a result, sufficient strength will not be obtained.

  The Z average molecular weight (Mz1) of the surface layer portion of the expandable styrene resin particles is 600,000 to 1,000,000. If it is less than 600,000, the strength tends to decrease. Moreover, when the vapor pressure at the time of molding becomes high, the resin on the surface tends to be melted and the surface appearance tends to be impaired. If it exceeds 1,000,000, the foaming property will be low, so if the steam temperature at the time of molding is low, surface elongation and fusion deteriorate, and as a result, sufficient strength cannot be obtained.

  In addition, since it is difficult to measure the molecular weight of the surface layer portion of the expandable styrene resin particles from the particles themselves, in the present specification, a foam molded product obtained by pre-foaming the resin particles and molding in-mold (expanding ratio 10 times) The surface layer portion (0.3 mm) of is the molecular weight of the surface layer portion of the expandable polystyrene resin particles.

  The ratio Mz1 / Mz2 between the Z average molecular weight (Mz1) of the resin particle surface layer and the entire Z average molecular weight (Mz2) is 0.85 to 0.95. If it is less than 0.85, the resin on the surface tends to melt during molding, and the surface appearance tends to be impaired. If it exceeds 0.95, the foaming property will be low, so if the steam temperature at the time of molding is low, surface elongation and fusion will deteriorate, and as a result, sufficient strength will not be obtained.

  The xylene-insoluble matter in the resin particles of the present invention is adjusted by adding a crosslinking agent. Examples of the crosslinking agent include divinylbenzene, alkylene glycol dimethacrylate, polyethylene glycol dimethacrylate, and the like. Among these, divinylbenzene is preferable because it is inexpensive and increases the strength when added. As a method for adding the crosslinking agent, it is preferable to add divinylbenzene when 90% to 100% of the total amount of the styrenic monomer is added. When the crosslinking agent is added and the amount is less than 90% of the total amount of the styrenic monomer, the layer of the expandable styrene resin particles obtained by crosslinking the polymer molecules by the crosslinking agent tends to be too thick. In this case, the foaming power is reduced, and the moldability at low pressure tends to deteriorate.

  The expandable styrene resin particles obtained by the above method have a xylene insoluble content of less than 1.5%. If it is less than 1.5%, good fusing property, surface property and strength can be maintained even under low pressure molding conditions. As described in JP-A-2007-31641, when the insoluble content of the solvent (xylene) is 1.5% or more, the foamability becomes low, and the moldability at low pressure is likely to deteriorate (the vapor during molding). If the temperature is low, the fusion deteriorates, and as a result, sufficient strength cannot be obtained. In order to obtain the xylene-free component, the amount of crosslinking agent added is 0.010 to 0.020 parts by weight. More preferably, it is 0.012 to 0.016 part by weight. When the amount is less than 0.010 parts by weight, good strength cannot be obtained. When it exceeds 0.020 weight part, an insoluble content will be 1.5% or more, and the moldability in low pressure will deteriorate easily.

As volatile blowing agents used in the present invention, aliphatic hydrocarbons such as hydrocarbons having 3 to 5 carbon atoms such as propane, isobutane, normal butane, isopentane, normal pentane and neopentane, and difluoroethane and tetrafluoroethane And volatile foaming agents such as fluorinated hydrocarbons having zero ozone depletion coefficient. These foaming agents can be used in combination. These volatile blowing agents are at least one member of the group consisting of isobutane, normal butane, isopentane, normal pentane, and neopentane, which increases the retention in the styrenic resin particles and provides a high foaming power for a long time. It is preferable in that it can be maintained.
Of these foaming agents, butane is preferred because it is inexpensive and has good foaming power. The ratio of butane is preferably normal butane: isobutane of 80:20 to 40:60. The higher the normal butane ratio, the larger the air bubble diameter, and the more difficult it is to fuse. As a result, it is difficult to obtain sufficient strength. The higher the normal butane ratio is, the smaller the average bubble diameter becomes, and surface melting tends to occur during molding, and the surface appearance tends to be impaired. Further, the fusion tends to deteriorate, and as a result, the strength also tends to decrease.

The amount of the volatile foaming agent used is preferably 2 to 7 parts by weight, more preferably 3 to 6 parts by weight, based on 100 parts by weight of the styrene resin particles. If it is less than 2 parts by weight, the pre-foaming time becomes longer and the fusion rate at the time of molding tends to decrease, which is not preferable. If it exceeds 7 parts by weight, it is relatively 0.05 to 0.2 g / cm ^3. When foaming at a low magnification, there is a tendency for the variation in magnification between particles to increase, such being undesirable.

  As the additive used in the present invention, a plasticizer, a bubble adjusting agent, a flame retardant, a flame retardant aid and the like can be used depending on the purpose. Examples of the plasticizer include stearic acid triglyceride, palmitic acid triglyceride, lauric acid triglyceride, stearic acid diglyceride, stearic acid monoglyceride and other fatty acid glycerides, palm oil, palm oil, palm kernel oil and other vegetable oils, dioctyl adipate, dibutyl sebacate And the like, and aliphatic hydrocarbons such as liquid paraffin, and organic hydrocarbons such as cyclohexane. These may be used in combination. Examples of the air conditioner include aliphatic bisamides such as methylene bis stearic acid amide and ethylene bis stearic acid amide, polyethylene wax, and the like. Flame retardants include brominated styrene, brominated butadiene-vinyl aromatic copolymer, brominated novolak resin allyl ether, brominated poly (1,3-cycloalkadiene) and brominated poly (4? Vinylphenol allyl ether). And low molecular weight compounds such as polyglycerin dibromopropyl ether, tetrabromobisphenol A, tetrabromobisphenol-A-bis (2,3-dibromo-2-methylpropyl ether), and the like. Examples of the flame retardant aid include high-temperature decomposition type organic substances such as cumene peroxide, dicumyl peroxide, t-butyl hydroperoxide, and 2,3-dimethyl-2,3-diphenylbutane.

  In the present invention, higher fatty acid amides such as stearic acid amide having an effect of promoting fusion at the time of molding, higher fatty acid glycerides such as hardened castor oil and hardened soybean oil, zinc stearate having an effect of preventing agglomeration during pre-foaming, etc. Fatty acid metal salts can be used. These additives can be coated or adhered to the surface of the expandable styrene resin particles by mixing with the expandable styrene resin particles for a predetermined time in a mixer such as a Henschel mixer, a super mixer, or a universal mixer. Furthermore, one type or two or more types of glycerin, polyethylene glycol, polypropylene glycol, fatty acid monoglyceride, sodium alkyl sulfonate, etc. generally used as an antistatic agent can be used.

  The expandable styrene resin particles of the present invention can be foamed by a known method to obtain a styrene foam molded article. For example, a method of once preparing pre-expanded particles and then filling and molding the pre-expanded particles in a mold (in-mold molding), a method of directly filling expandable styrenic resin particles into a mold and performing foam molding, etc. It is done. The styrenic foam molded article of the present invention is produced by an in-mold molding method. That is, by heating the expandable styrene-based resin particles at about 80 to 110 ° C. with water vapor using a rotary stirring pre-foaming device, pre-foamed particles having a bulk ratio are obtained, and the obtained pre-foamed particles are desired. The styrenic foamed molded article can be obtained by filling in a mold having the shape and heating at a lower water vapor pressure of 0.05 to 0.11 MPa (conventional water vapor pressure 0.07 to 0.1 MPa). it can. The average cell diameter of the styrene foam molded article is preferably 40 to 70 μm. If it is this range, the foaming molding with favorable melt | fusion property and surface beauty will be obtained.

  The styrene foam molded article of the present invention thus obtained has a small amount of residual styrene and has good strength.

The expandable styrene resin particles in the present invention preferably have a density of 0.05 to 0.2 g / cm ³ when formed into a foamed molded product. When the density exceeds 0.2 g / cm ³ , not only the amount of resin used per unit volume is increased and the cost is increased, but also the fusion rate between particles tends to decrease, which is not preferable. Less than / cm ^{3 This} is not preferable because the compressive strength is lowered.

  Examples and Comparative Examples are given below, but the present invention is not limited thereby. The molecular weight, xylene insoluble content, average cell diameter, molding (fusibility, surface property) and strength evaluation in the examples and comparative examples were measured by the following methods. “Parts” and “%” are based on weight unless otherwise specified.

(Molecular weight measurement method)
Mz of the surface layer portion of the resin particle is calculated as the surface layer portion of the foamed molded product (foaming ratio 10 times). That is, since the foam molded body is obtained by pre-foaming resin particles and molding in-mold, the resin particle surface layer portion corresponds to the foam molded body surface layer portion. In the present invention, the average molecular weight of the resin particle surface layer portion is expanded. The average molecular weight of the surface layer of the molded product is taken. After drying the foamed molded product at 35 ° C. for 24 hours, the surface layer of the foamed molded product is cut by 0.3 mm using a vertical slicer to obtain a sample for the surface layer part.

  In addition, Mz of the whole resin particle makes the thing cut in the thickness direction of the foaming molding into the sample for whole.

  0.02 g of the obtained sample was dissolved in 20 ml of tetrahydrofuran, and GPC (HLC-8020 manufactured by Tosoh Corporation, column: TSKgel Super HZM-H, column temperature: 40 ° C., flow rate: 0.35 ml / 1 min.). The molecular weight was measured.

(Measurement of insoluble matter in xylene)
The xylene-insoluble matter in the expandable styrene resin particles of the present invention is measured by using 80 g of xylene per 1 g of expandable styrene resin particles and extracting with boiling xylene. After 2 hours from the start of boiling, filter through a 200 mesh wire mesh, remove the filtrate, extract the filtrate again with boiling xylene for 2 hours from the start of boiling, filter again through a 200 mesh wire mesh, and remove the filtrate. The remaining filtrate is again extracted with boiling xylene for 1 hour from the start of boiling, filtered through a 200 mesh wire mesh, the filtrate not extracted into boiling xylene is regarded as insoluble matter, and the obtained insoluble matter is heated to 150 ° C. Dry with a dryer for 1 hour and weigh (assum W2). The ratio of the original expandable styrene resin particles to the weight W1 is defined as xylene unnecessary content.

  Xylene insoluble matter (%) = 100 × W2 / W1.

(Residual styrene measurement method)
Expandable styrenic resin particles are dissolved in methylene chloride (internal standard cyclopentanol), and gas chromatography GC-2014 (capillary column: Rtx-1, manufactured by GL Sciences, Inc.), column temperature condition: 50 → 80 ° C. After (3 ° C./min), the amount of residual styrene (ppm) contained in the expandable styrene resin particles was quantified using 80 → 180 ° C. temperature rise (10 ° C./min), carrier gas: helium.

(Fusability evaluation)
The foam molded body (foaming ratio 10 times) obtained by molding at a low pressure of 0.05 MPa was broken, the fracture surface was observed, and the ratio of the broken particles rather than the particle interface was determined. The fusing property was determined based on the standard.
A: The ratio of particle breakage is 90% or more.
○: The ratio of particle breakage is 80% or more and less than 90%.
(Triangle | delta): The ratio of particle | grain fracture | rupture is 70% or more and less than 80%.
X: The ratio of particle breakage is less than 70%.

(Surface property evaluation)
The surface state of the foam molded body (foaming ratio 10 times) obtained by molding at a low pressure of 0.05 MPa was visually observed, and the surface properties were evaluated according to the following criteria.
A: There is no melting of the surface, no intergranularity, and it is very beautiful.
○: Melting of the surface, little intergranularity, and beautiful.
Δ: Surface melted, intergranular, appearance somewhat poor.
X: Surface melting, intergranularity, and poor appearance.

(Measurement of average bubble diameter)
The average cell diameter of the foamed molded product was determined by observing the cut surface of the foamed molded product (foaming ratio 10 times) with a microscope and measuring the average cell diameter from the number of cells applied on a straight line (60 mm) of the cut surface. Moreover, the average bubble diameter obtained by this measurement is called average chord length.

  Average bubble diameter (t) = line length / (number of bubbles × photo magnification).

(Strength measurement: bending strength)
A sample piece obtained by molding a foamed molded article (foaming ratio 10 times) obtained by molding at a low pressure of 0.05 MPa to 300 × 750 × 20 (t) mm is stored in a constant temperature and humidity chamber for 24 hours, and then bending strength is obtained. Was measured. . In addition, it evaluated by the foaming molding obtained by the water vapor pressure at the time of shaping | molding: 0.05MPa.
A: Bending strength is 3.0 MPa or more. B: Bending strength is 2.5 MPa or more and less than 3.0 MPa. Δ: Bending strength is 2.0 MPa or more and less than 2.5 MPa. X: Bending strength is less than 2.0 MPa.

Example 1
<Manufacture of expandable styrene resin particles>
In a 6 L autoclave attached to a stirrer, 85 wt. Parts of pure water, 0.57 wt. Parts of tricalcium phosphate, 0.00476 wt. Parts of α-olefin sodium sulfonate, 0.1 wt. Stirring was started after charging 15 parts by weight of styrene resin seed particles having a weight of 2 to 0.3 mm, a residual styrene amount of 70000 to 90000 ppm, and a weight average molecular weight of 180,000. Thereafter, 0.04 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate was charged as an initiator. Subsequently, after the temperature was raised to 92 ° C., 0.257 parts by weight of a 30% benzoyl peroxide solution was added for 4 hours and 50 minutes, and 85 parts by weight of a styrene monomer having a phenylacetylene concentration of 80 ppm was added to the reactor over 5 hours and 45 minutes. Polymerized while charging inside. Further, 0.012 part by weight of divinylbenzene was charged just before the addition of styrene. Thereafter, after maintaining at 92 ° C. for 30 minutes, the temperature was immediately raised to 120 ° C. and held for 1 hour. After cooling to 95 ° C., 5.7 parts by weight of normal butane 70% concentration (isobutane 30% concentration) was charged into the system, and further maintained at 120 ° C. for 3 hours, and then cooled. The suspension was taken out, dehydrated, dried, and classified. After the particle size was 400 to 600 μm, the suspension was cooled to room temperature, and the polymerization slurry was taken out from the autoclave. The taken-out polymerization slurry was washed, dehydrated and dried to obtain expandable styrene resin particles having a residual styrene content of 300 ppm.

<Production of pre-expanded particles>
This was put into a rotary stirring type pre-foaming apparatus and foamed for about 2 minutes in water vapor at about 95 ° C. until the bulk density reached 100 g / L (foaming ratio: 10 times) to obtain pre-foamed particles.

<Manufacture of foam molding>
The pre-expanded particles obtained were cured and dried at room temperature for about 24 hours, then filled into a flat mold having a length of 450 mm × width of 300 mm × thickness of 20 mm, and taken out by heating and cooling with 0.05 MPa steam for 30 seconds. The molded body was cured in a 30 ° C. soaking dryer for 24 hours and then stored in a constant temperature and humidity room for another 24 hours to obtain a flat foam molded body. The evaluation results are shown in Table 1.

(Example 2)
In <Manufacture of expandable styrene-based resin particles>, expandable styrene having a residual styrene content of 250 ppm was obtained by the same operation as in Example 1 except that t-butylperoxy-2-ethylhexyl monocarbonate was changed to 0.08 parts by weight. System resin particles, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

(Example 3)
In <Manufacture of expandable styrene resin particles>, expandable styrene having a residual styrene content of 70 ppm was the same as in Example 1 except that the amount was changed to 0.18 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate. System resin particles, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

Example 4
<Production of expandable styrenic resin particles> In the same operation as in Example 1, except that 0.08 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate and 0.016 parts by weight of divinylbenzene were used. Expandable styrene resin particles having a residual styrene content of 260 ppm, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

(Example 5)
<Production of expandable styrenic resin particles> In the same operation as in Example 1, except that 0.08 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate and heating at 115 ° C. were changed to 7 hours in total. Thus, expandable styrene resin particles having a residual styrene content of 220 ppm, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

(Example 6)
<Production of expandable styrenic resin particles> In the same operation as in Example 1, except that 0.18 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate and heating at 125 ° C. were changed to 2 hours in total. Thus, expandable styrene resin particles having a residual styrene content of 140 ppm, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

(Example 7)
<Production of expandable styrenic resin particles> In the same operation as in Example 1, except that 0.18 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate and heating at 115 ° C. were changed to 7 hours in total. Thus, expandable styrene resin particles having a residual styrene content of 100 ppm, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

(Comparative Example 1)
In <Manufacture of expandable styrene resin particles>, expandable styrene having a residual styrene content of 50 ppm was obtained by the same operation as in Example 1 except that t-butylperoxy-2-ethylhexyl monocarbonate was changed to 0.22 parts by weight. System resin particles, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

(Comparative Example 2)
In <Manufacture of expandable styrenic resin particles>, except that t-butyl peroxy-2-ethylhexyl monocarbonate 0.18 parts by weight, divinylbenzene 0.016 parts, heating at 110 ° C. was changed to a total of 7 hours. By the same operation as in Example 1, expandable styrene resin particles having a residual styrene content of 890 ppm, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

(Comparative Example 3)
<Production of expandable styrenic resin particles> In the same operation as in Example 1, except that 0.18 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate and heating at 120 ° C. were changed to 8 hours in total. Thus, expandable styrene resin particles having a residual styrene content of 10 ppm, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

(Comparative Example 4)
<Production of expandable styrenic resin particles> In the same operation as in Example 1, except that 0.08 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate and 0.150 parts by weight of divinylbenzene were used. Expandable styrene resin particles having a residual styrene content of 200 ppm, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

(Comparative Example 5)
<Manufacture of expandable styrene-based resin particles> In the same manner as in Example 1 except for changing to 0.16 parts by weight of 1,1-bis (t-butylperoxy) cyclohexane and 0.0160 parts by weight of divinylbenzene. By the operation, expandable styrene resin particles having a residual styrene content of 300 ppm, pre-expanded particles, and in-mold expanded molded articles were obtained. The evaluation results are shown in Table 1.

(Comparative Example 6)
In <Manufacture of Expandable Styrenic Resin Particles>, expandable styrene resin particles, pre-expanded particles, and in-mold foam molded articles were obtained in the same manner as in Example 1 of JP-A No. 2004-155870. The evaluation results are shown in Table 1.

  In the embodiment of the present invention, not only a molded body molded under normal conditions but also a molded body molded under low pressure conditions, not only the fusion and surface properties but also excellent strength can be obtained.

Claims (9)

発 泡 Expandable styrene resin particles containing a volatile foaming agent, wherein the styrene resin of the expandable styrene resin particles is 0.010 to 0.020 with respect to 100 parts by weight of divinylbenzene. The xylene-insoluble content of the expandable styrene resin particles is less than 1.5%, and the Z average molecular weight (Mz1) of the surface layer of the expandable styrene resin particles is 600,000 to 1,000,000. Expandable polystyrene resin particles having an overall Z average molecular weight (Mz2) of 700,000 to 1,150,000 and a ratio of Mz1 to Mz2 (Mz1 / Mz2) of 0.85 to 0.95 . 昜 The volatile blowing agent is at least one member of the group consisting of propane, isobutane, normal butane, isopentane, normal pentane, and neopentane, and contains 2 to 7 parts by weight with respect to 100 parts by weight of the styrenic resin. The expandable polystyrene resin particle according to claim 1. Pre-expanded particles obtained by expanding the expandable styrenic resin particles according to claim 1 or 2. A foam-molded product obtained by in-mold molding of the pre-expanded particles according to claim 3. The density of a foaming molding is 0.05-0.2 g / cm < ³ >, The foaming molding of Claim 4 characterized by the above-mentioned. The manufacturing method of the expandable styrene resin particle of Claim 1 or 2. 0.040 parts by weight to 0.180 parts by weight of the compound represented by the general formula (1) is used as a polymerization initiator with respect to 100 parts by weight of the total amount of styrene resin seed particles and styrene monomer. The method for producing expandable styrene resin particles according to claim 6.

(In the formula, R ¹ represents a branched alkyl group, and R ² represents a branched or straight chain alkyl group.) The method for producing expandable styrene resin particles according to claim 6 or 7, wherein after the addition of divinylbenzene, heat treatment is performed at 115 to 130 ° C for 2 to 7 hours. The method for producing expandable styrene resin particles according to any one of claims 6 to 8, wherein divinylbenzene is added when 90% to 100% of the total amount of the styrene monomer is added. .