JP2005307075A - Expandable styrenic resin particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an expandable styrenic resin particle capable of almost preventing the break of an upper end opening part by smoothly absorbing the stress for deforming the upper end opening part to a flat state. <P>SOLUTION: This expandable styrenic resin particle usable for forming a cylindrical foamed container having a bottom by being foamed is regulated so that the total weight of organic compounds comprising one or more kinds of aromatic compounds selected from a styrenic monomer, ethylbenzene, toluene, n-propylbenzene, i-propylbenzene and xylene may be 0-500 ppm based on the whole amount of the expandable styrenic resin particle, and the variation coefficient of Cv value of a size distribution and the average particle diameter may be 0-0.1 and 0.3-0.6 mm, respectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an expandable styrene resin particle for producing a bottomed cylindrical foam container for packaging and cooking such as instant cup noodles.

  Conventionally, a bottomed cylindrical foam container is used as a container for instant cup noodle packaging and cooking. This foaming container is manufactured by filling pre-expanded particles obtained by pre-expanding expandable styrene resin particles in a mold, and heating and foaming.

  As such expandable styrene resin particles, Patent Document 1 discloses that 3 to 6% by weight of pentane and 0.01 to 1% by weight of propane with respect to 100% by weight of expandable styrene resin particles as an essential component of the foaming agent. %. Expandable styrenic resin particles characterized in that it is contained, and a cup-shaped foamed molded article excellent in top and bottom compression strength can be obtained by foaming the expandable styrene resin particles. Is disclosed.

  On the other hand, in recent years, with increasing social interest in environmental health, there has been a great interest in the effects of various chemical substances on the human body. The same applies to the cup noodle container described above, and the content of aromatic compounds such as styrene monomer, toluene, xylene, ethylbenzene, and propylbenzene in the expandable styrene resin particles that are the raw material of the container. There is a demand for reduction.

  However, since the aromatic compound has the effect of plasticizing the styrene resin, when only reducing the aromatic compound contained in the expandable styrene resin particles of Patent Document 1, styrene is used. As a result of the reduced flexibility of the resin, the extensibility of the foamed particles obtained by foaming the expandable styrene resin particles is reduced, and the thickness of the foamed container is very low, about 1.5 to 3.0 mm. When the stress which deform | transforms this upper end opening part into a flat state is added to the upper end opening part of a foaming container, another problem that a crack generate | occur | produces easily in the upper end opening part of a foaming container occurred.

  Therefore, it is conceivable to reduce the expansion ratio of the foam container, but if the expansion ratio of the foam container is decreased, there arises a problem that the light weight of the foam container is impaired.

JP 2003-82149 A

  The present invention manufactures a bottomed cylindrical foam container that can smoothly absorb the stress that deforms the upper end opening into a flat state and substantially prevents the upper end opening from being damaged and that is excellent in light weight. Expandable styrenic resin particles that can be provided are provided.

  The expandable styrenic resin particles of the present invention are expandable styrene resin particles for pre-expanding, filling into a mold and foaming to form a bottomed cylindrical foam container, The total weight of the expandable styrenic resin particles is the total amount of the organic compound composed of one or two or more aromatic compounds selected from the group consisting of a series monomer, ethylbenzene, toluene, n-propylbenzene, i-propylbenzene and xylene It is 0 to 500 ppm with respect to the particle size, the coefficient of variation Cv of the particle size distribution is 0 to 0.1, and the average particle size is 0.3 to 0.6 mm.

 The styrene resin constituting the expandable styrene resin particles is not particularly limited. For example, styrene, α-methyl styrene, vinyl toluene, ethyl styrene, i-propyl styrene, t-butyl styrene, dimethyl styrene, bromo Examples thereof include homopolymers of styrene monomers such as styrene and chlorostyrene or copolymers thereof.

  The styrenic resin may be a copolymer of the styrenic monomer having the styrenic monomer as a main component and a vinyl monomer copolymerizable with the styrenic monomer. Examples of vinyl monomers include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, alkyl (meth) acrylate such as cetyl (meth) acrylate, and (meth) acrylonitrile. In addition to dimethyl maleate, dimethyl fumarate, diethyl fumarate, and ethyl fumarate, bifunctional monomers such as divinylbenzene, alkylene glycol dimethacrylate, and polyethylene glycol di (meth) acrylate are exemplified. In addition, 200,000-400,000 are preferable and, as for the weight average molecular weight by GPC (gel permeation chromatography) method of the said styrene resin, 250,000-350,000 are more preferable.

  Here, as a method for producing the expandable styrene resin particles, a general-purpose production method is used. During the suspension polymerization of the styrene resin, a foaming agent is contained in the aqueous suspension, and foaming is performed in the styrene resin particles. For producing expandable styrene resin particles by impregnating with an agent, and for producing styrene resin particles by producing styrene resin particles by a general-purpose method and impregnating the styrene resin particles with a foaming agent Etc. In addition, when impregnating a foaming agent at the time of suspension polymerization of a styrene-type resin, it is preferable to contain a foaming agent in aqueous suspension, when the polymerization conversion rate of a monomer is 85% or more.

  In addition, a polymerization initiator is used at the time of suspension polymerization of the styrene resin. As the polymerization initiator, a general-purpose one is used, for example, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, orthochloro. Benzoyl peroxide, orthomethoxybenzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, cumene hydroperoxide, cyclohexanone peroxide, t-butyl hydroperoxide, t-butyl peroxybenzoate, t-butyl peroxybivalate , T-butylperoxyisopropyl carbonate, t-butylperoxyacetate, 2,2-t-butylperoxybutane, diisopropylbenzene hydroperio Peroxide-based polymerization initiators such as side, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,3- Dimethylbutyronitrile), 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (2,3,3-trimethylbutyronitrile), 2,2'-azobis (2-isopropyl) Butyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2- (carbamoylazo) isobutyronitrile 4,4′-azobis (4-cyanovaleric acid), dimethyl-2,2′-azobisisobutyrate and the like.

  In the foamable styrene resin particles of an organic compound composed of one or two or more aromatic compounds selected from the group consisting of the styrene monomer, ethylbenzene, toluene, n-propylbenzene, i-propylbenzene and xylene The total content (total weight) in is limited to 0 to 500 ppm, preferably 0 to 400 ppm, based on the total weight of the expandable styrenic resin particles.

  That is, the aromatic compound is not contained in the expandable styrene resin particles, or one kind selected from the group consisting of styrene monomers, ethylbenzene, toluene, n-propylbenzene, i-propylbenzene and xylene Or the organic compound which consists of 2 or more types of aromatic compounds is contained in an expandable styrene resin particle, The total amount of this organic compound is limited to 500 ppm or less with respect to the total weight of this expandable styrene resin particle, 400 ppm The following is preferred.

  Thus, by making the total content of the organic compound in the expandable styrene resin particles 0 to 500 ppm or less with respect to the total weight of the expandable styrene resin particles, the expandable styrene resin particles are obtained by foaming. The foamed container is less likely to generate volatile components, is excellent in environmental hygiene, and can be suitably used for food applications such as instant cup noodles that require cooking using hot water.

  And in order to make the total content of the organic compound in the expandable styrene resin particles 0-500 ppm with respect to the total weight of the expandable styrene resin particles, the above-mentioned organic is produced during the production of the expandable styrene resin particles. It is preferable not to add the compound separately as a plasticizer.

  However, in the production of expandable styrenic resin particles, a plasticizer is not separately added, but as an impurity in the styrene monomer used as a raw material for expandable styrene resin particles, ethylbenzene, toluene, i- The foamable styrene resin particles are plasticized by containing a large amount of propylbenzene, n-propylbenzene and xylene or by leaving a large amount of unreacted styrene monomer in the foamable styrene resin particles. There is a possibility that the chemical component is contained outside the above range.

  Accordingly, a styrene monomer having a small amount of impurities is selected so that the total content of the organic compound in the expandable styrene resin particles is 0 to 500 ppm with respect to the total weight of the expandable styrene resin particles. It is necessary to adjust the production conditions of the styrene resin particles. As a method for adjusting the production conditions of the expandable styrene resin particles in order to suppress the content of the organic compound within a predetermined range, for example, the decomposition temperature of the polymerization initiator used for suspension polymerization of the styrene resin Two different types of polymerization initiators are used. First, suspension polymerization of the styrene resin is performed using a polymerization initiator having a low decomposition temperature, and then the suspension of the styrene resin is performed using a polymerization initiator having a high decomposition temperature. Examples thereof include a method of continuously performing polymerization. In the above method, among the two types of polymerization initiators having different decomposition temperatures, the polymerization initiator having a high decomposition temperature is preferably a polymerization initiator having a half-life of 10 hours at a temperature of 90 to 120 ° C. Examples of such a polymerization initiator include t-butyl peroxybenzoate, t-butyl peroxybivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2,2-t-butyl peroxy Examples include butane.

  In addition, content of the organic compound in an expandable styrene-type resin particle is measured in the following way. That is, 1 g of expandable styrene resin particles was precisely weighed, and 1 ml of a dimethylformamide solution containing 0.1% by volume of cyclopentanol was added as an internal standard solution to the precisely weighed expandable styrene resin particles. Thereafter, dimethylformamide solution is further added to dimethylformamide solution to prepare a measurement solution of 25 ml, and 1.8 μl of this measurement solution is supplied to a sample vaporization chamber at 230 ° C., and an organic compound to be measured from a gas chromatograph The amount of the organic compound is calculated from the above chart based on the calibration curve of the organic compound to be measured that has been measured in advance.

In addition, content of the organic compound in an expandable styrene-type resin particle can be measured on the following measurement conditions using a gas chromatograph (Shimadzu Corporation brand name "GC-14A").
Detector: FID
Column: GL Sciences Co., Ltd. (3mm diameter x 2.5m)
Liquid phase: PEG-20M PT 25% by weight
Carrier: Chromosorb W AW-DMCS
Mesh: 60/80
Column temperature: 100 ° C
Detector temperature: 230 ° C
Inlet temperature: 230 ° C
Carrier gas: Nitrogen Carrier gas flow rate: 40 ml / min

  And as a foaming agent used by this invention, if it is conventionally used for manufacture of an expandable styrene-type resin particle, it will not specifically limit, For example, aliphatic hydrocarbons, such as propane, butane, and pentane 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b), 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-); 124), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a) and the like, and aliphatic hydrocarbons are preferable. In addition, a foaming agent may be used independently or may be used together.

  If the content of the foaming agent in the expandable styrenic resin particles is small, the mechanical strength of the foam container may be lowered due to insufficient fusion between the foam particles constituting the foam container. If the amount is too large, the size of the foamed particles obtained by foaming the expandable styrene resin particles becomes too large, and the depth of the recesses appearing on the surface of the foamed container and occurring at the heat fusion interface between the foamed particles becomes large. Since the smoothness of the surface of the foam container is impaired and the appearance of the foam container and the appearance when printing is performed on the surface of the foam container may be reduced, 2 to 6% by weight is preferable, and 4 to 5% by weight is more preferable. preferable.

  Here, the content of the foaming agent in the expandable styrene-based resin particles refers to that measured in the following manner. That is, the foamable styrene resin particles are supplied to a heating furnace at 180 ° C. to obtain a chart of the foaming agent to be measured from the gas chromatograph, and based on the calibration curve of the foaming agent to be measured that has been measured in advance. Then, the amount of the foaming agent in the expandable styrene resin particles is calculated from the chart.

In addition, content of the foaming agent in an expandable styrene-type resin particle can be measured on condition of the following using a gas chromatograph (Shimadzu Corporation brand name "GC-14B").
Detector: FID
Heating furnace: Product name “PYR-1A” manufactured by Shimadzu Corporation
Column: Shinwa Kako Co., Ltd. (3mm diameter x 3m)
Liquid phase: Squalane 25% by weight
Carrier: Shimalite 60-80 NAW
Heating furnace temperature: 180 ° C
Column temperature: 70 ° C
Detector temperature: 110 ° C
Inlet temperature: 110 ° C
Carrier gas: Nitrogen Carrier gas flow rate: 60 ml / min

  As described above, the content of the organic compound that exhibits the plasticizing action of the styrene resin is limited to a predetermined amount or less, or the organic compound is added to the expandable styrene resin particles. Since it is made not to contain, the softness | flexibility of a styrene resin is falling. Therefore, in the expandable styrene resin particles of the present invention, in order to compensate for the decrease in flexibility of the styrene resin, the variation coefficient Cv value of the particle size distribution is set to 0 to 0.1, and the average particle diameter is set to 0.3 to 0. The variation coefficient Cv value of the particle size distribution is preferably 0 to 0.05.

The variation coefficient Cv value of the particle size distribution in the expandable styrene resin particles is obtained by dividing the standard deviation of the particle diameter of the expandable styrene resin particles by the average particle diameter of the expandable styrene resin particles. Is calculated by
Variation coefficient Cv value of particle size distribution in expandable styrene resin particles = standard deviation / average particle diameter

  That is, by restricting the coefficient of variation Cv value of the particle size distribution and the average particle size in the expandable styrene resin particles, the size of the expanded particles obtained by expanding the expandable styrene resin particles is substantially equal overall. In addition, the foaming particles are integrated substantially uniformly and firmly in the entire heat-sealing interface so that the foaming pressure between the pre-foamed particles filled in the mold is not biased. The average particle diameter of the expandable styrenic resin particles is within a predetermined range, the size of the expanded particles obtained by foaming the expandable styrene resin particles is appropriate, and the forward stress that the expanded particles are superior to the stress It is adjusted to be able to demonstrate.

  Therefore, for example, a stress (hereinafter referred to as “flat stress”) that deforms the opening into a flat state is applied to the upper end opening of the foamed container obtained using the expandable styrene resin particles, as shown in FIG. Even if the upper end opening of the foam container C is deformed into a flat oval shape, the foam particles constituting the foam container concentrate the flat stress applied to the foam particles in part. It absorbs effectively without causing breakage and is hardly broken or separated from each other at the heat fusion interface.

  Therefore, the foam container obtained using the expandable styrenic resin particles exhibits excellent adaptability to the flat stress applied to the upper end opening thereof, and the upper end opening due to the flat stress applied to the upper end opening of the foam container. It is possible to generally prevent the occurrence of breakage such as cracks in the part.

  And as a method of obtaining expandable styrene resin particles having a coefficient of variation Cv value of particle size distribution of 0 to 0.1, expandable styrene resin particles produced in the above-described manner are obtained with different sizes. A method of classifying using two sieves having an opening, and classifying styrene resin particles before impregnating with a foaming agent using two sieves having openings of different sizes, and this classified styrene system A method of impregnating resin particles with a foaming agent can be mentioned.

  The coefficient of variation Cv of the particle size distribution in the styrene resin particles classified using two sieves as described above is measured in the following manner. Here, the variation coefficient Cv value of the particle size distribution is calculated from the average particle size and standard deviation of the classified resin particles as described above. First, as a method for measuring the average particle size of the resin particles, first, In addition, a plurality of types of sieves having different openings defined in JIS (aperture 3.35 mm, opening 2.80 mm, opening 2.36 mm, opening 2.00 mm, opening 1.70 mm, opening 1) .40 mm, Aperture 1.18 mm, Aperture 1.00 mm, Aperture 0.850 mm, Aperture, 0.710 mm, Aperture 0.600 mm, Aperture 0.500 mm, Aperture 0.425 mm, Aperture 0. 355 mm, opening 0.300 mm, opening 0.250 mm, opening 0.212 mm, opening 0.180 mm), and the expanded styrene resin particles or styrene resin classified as described above Child (hereinafter, collectively referred to as "resin particles") 25 g, sieved with a sieve so mesh becomes smaller sieve from a large sieve. Then, the resin particles cannot pass through a sieve having a predetermined opening according to the particle size of each particle, and remain on each sieve.

  Then, the average particle diameter of the resin particles remaining on each sieve is as shown in Table 1 based on the size of the openings of the sieves. For example, the openings remain on the sieve having an opening of 0.355 mm. The average particle diameter of the obtained resin particles is 0.390 mm.

  The average particle size of the resin particles remaining on each sieve was the arithmetic average value of the sieve openings and the sieve openings having the next largest openings. In the case of a sieve having an opening of 3.35 mm, the opening of the sieve defined by JIS having the next largest opening is 4.00 mm, so that the opening of the sieve is 4.00 mm. The arithmetic average value of was adopted.

Next, the weight W of the resin particles remaining on the sieve is measured for each sieve, and the weight ratio R (% by weight) of the resin particles remaining on the sieve to the total resin particles is calculated for each sieve. Every time, a value obtained by multiplying the average particle diameter D of the resin particles by the weight ratio R of the resin particles is calculated, and the sum of the values is defined as the average particle diameter of the resin particles.
Average particle diameter of resin particles = Σ (average particle diameter D of resin particles on each sieve × weight ratio R of resin particles)

  The standard deviation of the resin particles is the average particle diameter D of the resin particles for each sieve obtained in the above-described measurement procedure of the average particle diameter of the resin particles, and the total resin particles of the resin particles remaining on the sieve. It is calculated based on the weight ratio R (% by weight).

  When the styrene resin particles are classified, the styrene resin particles after classification are impregnated with a foaming agent to obtain expandable styrene resin particles. Before and after impregnating the styrene resin particles with the foaming agent, the resin Since the variation coefficient Cv value of the particle size distribution of the particles hardly changes, in the present invention, the variation coefficient Cv value of the particle size distribution of the styrene resin particles is used as the variation coefficient Cv of the particle size distribution of the expandable styrene resin particles. It may be a value.

  Next, a procedure for forming a bottomed cylindrical foam container using the above expandable styrene resin particles will be described. First, expandable styrene resin particles are pre-expanded in a pre-foaming machine to form styrene resin pre-expanded particles, and the obtained pre-expanded particles are filled in a mold of a foam molding machine and then heated with heating steam or the like. A bottomed cylindrical foam container can be manufactured by heating and foaming with a medium, and heat-sealing with each other by foaming pressure.

  The expansion ratio of the foamed container obtained by foaming the expandable styrene resin particles of the present invention is not particularly limited, but is preferably 5 to 15 times, more preferably 8 to 12 times. In addition, the foaming ratio of a foaming container means what remove | divided the specific gravity of the styrene resin which comprises a foaming container by the specific gravity of a foaming container.

  If the thickness of the bottomed cylindrical foam container is thin, the mechanical strength of the foam container may be reduced. On the other hand, if the thickness is thick, the lightweight property of the foam container may be reduced or the upper end opening of the foam container may be reduced. Since the adaptability when the above-described flat stress is applied, which is deformed into a flat state, may be reduced and the upper end opening of the foamed container may easily crack, 1.5 to 3.5 mm is preferable. More preferably, it is 7 to 2.5 mm.

  Moreover, since the expandable styrene resin particles have a very small content of the organic compound of 0 to 500 ppm, the foam container can be suitably used for food applications, and can be developed for various applications. is there.

  The expandable styrenic resin particles of the present invention are expandable styrene resin particles for pre-expanding, filling into a mold and foaming to form a bottomed cylindrical foam container, The total weight of the expandable styrene resin particles is the total amount of the organic compound composed of one or two or more aromatic compounds selected from the group consisting of a series monomer, ethylbenzene, toluene, n-propylbenzene, i-propylbenzene and xylene The content of the organic compound is characterized by being 0 to 500 ppm based on the particle size distribution coefficient Cv value of 0 to 0.1 and an average particle size of 0.3 to 0.6 mm. The particle size distribution coefficient of variation Cv value and the average particle diameter are limited within a predetermined range in spite of being suppressed, and thus obtained by foaming the expandable styrene resin particles. The foam container exhibits excellent forward stress against the flat stress that compresses the upper end opening into a flat state, and even when a flat stress is applied to the upper end opening, the upper end opening cracks. Can be generally prevented.

  Moreover, since the expandable styrenic resin particles of the present invention suppress the organic compound content, the resin can be suitably used for food applications, while the resin produced by suppressing the organic compound content. The reduction in the flexibility of the particles is effectively complemented by limiting the coefficient of variation Cv value of the particle size distribution and the average particle size. Therefore, according to the expandable styrenic resin particles of the present invention, the inclusion of organic compounds A foamed container excellent in lightness and adaptability to flat stress can be reliably obtained while suppressing the amount.

(Examples 1 to 3, Comparative Example 1)
40 kg of ion exchange water is supplied into a 100 liter autoclave equipped with a stirrer, and 40 kg of styrene monomer, 40 g of calcium triphosphate, 0.5 g of potassium persulfate, A suspension was prepared by supplying 105 g of benzoyl oxide and 30 g of t-butyl peroxybenzoate.

  Next, the suspension was heated to 90 ° C. over 1 hour while being stirred at a stirring speed of 200 rpm, and was further maintained at 90 ° C. for 6 hours for suspension polymerization. After adding 40 g of tribasic calcium phosphate and 0.4 g of α-olefin sulfonate (product name “Lipolane PJ-400” manufactured by Lion Corporation) to the suspension, 1600 g of n-pentane and 400 g of i-pentane were injected. The suspension was heated to 130 ° C. over 40 minutes and then left at 130 ° C. for 3 hours.

  Thereafter, the suspension was cooled, and hydrochloric acid was added to the suspension until the pH was 2, to decompose tricalcium phosphate. Then, the suspension was supplied to a dehydrator, washed with water for 10 minutes, dehydrated and air-dried to obtain expandable styrene resin particles.

  Next, a sieve A (manufactured by Sakakura Wire Mesh Co., Ltd.) having an opening a, a wire diameter b, a pitch c, and an aperture ratio d shown in Table 2 is used as a sieve machine (trade name “Gyroshifter GS-AIH” manufactured by Tokuju Kogakusha Co., Ltd.). The foamable styrene resin particles were sieved with a sieve A, and only the foamable styrene resin particles that passed through the sieve A were collected.

  Subsequently, a sieve B having an opening a, a wire diameter b, a pitch c, and an opening ratio d shown in Table 2 was attached to a sieve machine (trade name “Gyroshifter GS-AIH” manufactured by Tokuju Kogakusha Co., Ltd.). The expandable styrene resin particles that passed through A were sieved with sieve B, and only the expandable styrene resin particles remaining on sieve B were collected. Note that the openings of the sieves A and B are in the form of a square plane, the sieve openings a and pitch c shown in Table 2 are the dimensions of the parts shown in FIG. It is the diameter of the wire which comprises.

  In addition, 20 g of the expandable styrene resin particles collected from the sieve B was taken out as a measurement sample, and the variation coefficient Cv value of the particle size distribution of this measurement sample was measured. Here, looking at the particle size distribution of the measurement sample, resin particles having a particle size smaller than the opening of the sieve B may be mixed. This is because the foamable styrenic resin particles having a particle size smaller than the opening of the sieve B could not be completely removed even if they were sieved.

  The surface of 100 parts by weight of the foamable styrene resin particles thus obtained is coated with 4 parts by weight of zinc stearate obtained from palm oil by a direct method and 0.8 parts by weight of polyethylene glycol having a weight average molecular weight of 300. did. The foamable styrene resin particles were pre-foamed using a rotary stirring pre-foaming machine to obtain pre-foamed particles having a bulk ratio of 9 times.

  The obtained pre-expanded particles were allowed to stand at room temperature for 24 hours, and then the pre-expanded particles were filled in a mold cavity and heat-molded with water vapor at a gauge pressure of 0.2 MPa for 7 seconds. .

  Next, after the inside of the mold cavity was cooled, a bottomed cylindrical foam container C having the cross-sectional shape shown in FIG. 3 was obtained from the inside of the mold. The foam container C has a flat circular bottom surface portion 1 having a diameter of 68 mm and a thickness of 2.8 mm, and a cylindrical peripheral wall portion 2 that gradually increases in diameter from the outer peripheral edge of the bottom surface portion 1 obliquely upward. (Open end inner diameter: 178 mm, height: 100 mm, thickness 2 mm). In addition, a planar annular flange 21 having a thickness of 3 mm is projected in the horizontal direction at the upper end of the peripheral wall 2, and the outer diameter of the upper end of the cylindrical peripheral wall 2 including the flange 21 is as follows. It was 192 mm.

  Further, pre-expanded particles are produced by pre-expanding expandable styrene resin particles at a bulk magnification of 10 times instead of a bulk magnification of 9 times, and a foam container C is obtained in the same manner as described above using the pre-expanded particles. It was.

  Particle size distribution, average particle size, standard deviation, organic compound content (indicated as “organic compound amount” in Table 4) and foaming agent content (in Table 4, “foaming”) The amount of lip) was measured as described above, and the lip strength of the foamed container was measured as shown below. The results are shown in Tables 3 and 4.

(Lip strength)
A pressing tool 3 was prepared in which a groove portion 31 having a width of 4 mm, a depth of 4 mm, a length of 60 mm and an opening at both ends was formed on a flat lower end surface (see FIG. 4). Then, the foam container C was placed on the support plate in a state where the bottom surface portion 1 faced the vertical direction. Thereafter, the uppermost portion of the flange portion 21 in the horizontally placed foam container C is fitted with the central portion in the length direction of the groove portion 31 of the pressing tool 3, and then the pressing tool 3 is moved at a speed of 50 mm / min. Then, the flat plate was moved vertically downward to apply a flat stress to the opening of the foaming container in the vertical direction, thereby deforming the opening of the foaming container into a flat state.

  The pressing tool was moved vertically downward until a crack penetrating inward and outward at the opening end of the foam container C, and the maximum pressing strength at this time was defined as the lip strength. Ten foaming containers C were prepared, and among the lip strengths of the ten foaming containers C, the arithmetic average value of the lip strengths excluding the maximum value and the minimum value was defined as the lip strength of the foaming container C.

It is the top view which showed the state which deform | transformed the upper end opening part of the foaming container into the flat state. It is the model top view which showed the opening part of the sieve. It is sectional drawing which showed the foam container obtained in the Example. (A) It is the bottom view which showed the pressing tool. (B) It is the longitudinal cross-sectional view which showed the pressing tool.

Explanation of symbols

A, B Sieve C Foaming container

Claims (1)

Expandable styrene resin particles for pre-foaming, filling into a mold and foaming to form a bottomed cylindrical foam container, which is a styrene monomer, ethylbenzene, toluene, n-propylbenzene The total amount of the organic compound consisting of one or two or more aromatic compounds selected from the group consisting of i-propylbenzene and xylene is 0 to 500 ppm with respect to the total weight of the expandable styrene resin particles, Expandable styrene resin particles having a distribution coefficient of variation Cv of 0 to 0.1 and an average particle size of 0.3 to 0.6 mm.

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