JP2014125519A - Prefoamed particle and foamed molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylonitrile-styrene resin prefoamed particle which has resistance to blocking, can shorten the cooling time of the molding in a mold and can produce a foamed molded article excellent in weldability, and to provide a molded article thereof.SOLUTION: A prefoamed particle is obtained by adhering paraffin-based wax and a fatty acid amide to the surface of the prefoamed particle using an acrylonitrile-styrene resin as a base material. In the prefoamed particle, the adhesion amount of the paraffin-based wax is 1 to 20 pts.mass based on 100 pts.mass of the prefoamed particle, and the adhesion amount of the fatty acid amide is 2 pts.mass or less (excluding 0) based on 100 pts.mass of the prefoamed particle.

Description

  The present invention relates to acrylonitrile / styrene resin pre-foamed particles and a foamed particle molded body obtained by molding these in-mold.

  It is known that acrylonitrile / styrene resin (hereinafter referred to as “AS resin” as appropriate) is superior in oil resistance, chemical resistance, heat resistance and the like as compared with polystyrene. Therefore, taking advantage of this feature, AS resin pre-expanded particles are used for applications that require oil resistance, chemical resistance, heat resistance, etc., which were difficult to use with polystyrene resin pre-expanded particles. ing.

  The AS resin pre-expanded particles are molded by the same apparatus as the polystyrene resin pre-expanded particles. In the molding process, the cooling time occupies 50% or more of the molding time. Therefore, shortening the cooling time shortens the molding time, leading to an improvement in productivity. However, in general, the AS resin pre-foamed particles are superior to the polystyrene resin pre-foamed particles in the retention of the foaming agent, and the foaming agent remaining in the foamed particles is increased. The cooling time tends to be longer.

  As a method of shortening the cooling time, a method of coating a certain additive on the surface of the resin particles has been proposed. For example, a method of coating fatty acid glyceride on expandable styrene resin particles (see Patent Document 1) and a method of coating acetylated monoglyceride on expandable AS resin particles (see Patent Document 2) are known.

JP 52-127968 A JP 2002-161163 A

However, when fatty acid glyceride is coated on polystyrene-based pre-expanded particles, a sufficient cooling shortening effect can be obtained. However, AS resin pre-expanded particles having excellent oil resistance have a cooling time shortening effect. Very small. Therefore, the conventional method using fatty acid glyceride cannot sufficiently shorten the cooling time for in-mold molding of pre-expanded particles based on AS resin.
On the other hand, acetylated monoglyceride has an effect of shortening the cooling time even in the pre-expanded particles based on AS resin. However, when acetylated monoglyceride is used, blocking that causes foamed particles to adhere to each other at the time of foaming of foamable resin particles tends to occur. When the blocking increases, the filling property of the expanded particles into the mold may be lowered, and a good molded article may not be obtained.

  The present invention has been made in view of such a background, and is capable of producing a foamed particle molded body having excellent anti-blocking property, reducing the cooling time in in-mold molding, and excellent in fusion property. An object of the present invention is to provide pre-expanded acrylonitrile / styrene resin particles, and molded articles thereof.

One aspect of the present invention comprises a paraffin wax and a fatty acid amide attached to the surface of pre-expanded particles based on acrylonitrile / styrene resin.
The amount of the paraffin wax attached is 1 to 20 parts by mass with respect to 100 parts by mass of the pre-expanded particles,
The amount of the fatty acid amide attached is 2 parts by mass or less (excluding 0) based on 100 parts by mass of the pre-expanded particles (excluding 0). .

  Another aspect of the present invention lies in a foamed particle molded body obtained by molding the acrylonitrile / styrene resin pre-foamed particles in a mold (Claim 7).

  In the AS resin pre-expanded particles, paraffinic wax and fatty acid amide adhere to the surface of the pre-expanded particles based on the AS resin in the specific amounts. Therefore, the cooling time can be shortened when the AS resin pre-expanded particles are molded in the mold. As a result, the molding time can be greatly shortened, and the productivity of the foamed particle molded body can be improved.

In general, when a large amount of an additive having a cooling shortening effect is adhered to the surface of the pre-foamed particles in order to shorten the cooling time, the blocking during foaming increases as described above, and into the mold. There is a tendency that the filling property of the pre-expanded particles is lowered.
On the other hand, in the said pre-expanded particle, the said fatty acid amide has adhered to the surface of the pre-expanded particle with the said paraffinic wax. Therefore, the occurrence of blocking between the pre-expanded particles can be suppressed, and the pre-expanded particles are excellent in handleability. Moreover, in the said pre-expanded particle, the outstanding meltability which the pre-expanded particle originally has can be exhibited, without inhibiting the melt property of the pre-expanded particle at the time of in-mold shaping | molding. Therefore, a foamed particle molded article having excellent mechanical strength can be obtained without impairing mechanical strength such as bending strength.
That is, in the pre-expanded particles, it is possible to obtain a foamed particle molded article having excellent mechanical strength without inhibiting blocking and impairing the fusibility, and shortening the cooling time during molding. .

  The foamed particle molded body can be produced by in-mold molding of AS resin pre-foamed particles having a specific amount of the paraffinic wax and fatty acid amide adhered to the surface. And the said expanded particle molded object can exhibit the outstanding mechanical strength using the above-mentioned outstanding fusion property of the said AS resin pre-expanded particle.

Next, preferred embodiments of the pre-expanded particles and the expanded particle molded body will be described.
The said pre-expanded particle consists of the pre-expanded particle which uses AS resin as a base material, and the paraffin wax and fatty acid amide adhering to the surface.

AS resin is a copolymer (copolymer) of acrylonitrile and styrene, and is also called styrene acrylonitrile copolymer (SAN).
The AS resin pre-foamed particles can be obtained by foaming expandable AS resin particles. The expansion ratio can be appropriately adjusted according to desired physical properties.

  The paraffinic wax and the fatty acid amide are not only attached to the surface of the AS resin pre-foamed particles, but a part thereof may be impregnated in the vicinity of the surface of the particles.

  As a method of attaching paraffin wax to the AS resin pre-expanded particles, there is a method in which paraffin wax is added to the expandable AS resin particles at the time of pre-foaming and pre-foaming is performed in the presence of paraffin wax. Alternatively, the paraffin wax may be heated to the melting point or higher to be in a liquid state, and this may be applied to the pre-foamed AS resin pre-expanded particles.

  Among these methods, paraffin wax is added at the time of pre-foaming, and foaming is performed in the presence of paraffin wax, particularly from the viewpoint that the manufacturing process is simple, and that a superior cooling shortening effect and fusion property can be obtained. A method of pre-foaming AS resin particles is preferred.

  Moreover, as a method for attaching fatty acid amide to the surface of the AS resin pre-expanded particles, there is a method in which fatty acid amide is previously attached to expandable AS resin particles and then expandable AS resin particles are pre-expanded. In addition, there is a method in which fatty acid amide is added to expandable AS resin particles at the time of preliminary foaming, and preliminary foaming is performed in the presence of fatty acid amide. Furthermore, the method etc. of apply | coating a fatty acid amide to the AS resin pre-expanded particle after foaming may be used.

  Among these methods, a method of preliminarily foaming expandable AS resin particles by attaching fatty acid amide to expandable AS resin particles in advance from the viewpoint that the production process is particularly simple and a more excellent cooling time shortening effect can be obtained. Alternatively, a method in which fatty acid amide is added at the time of preliminary foaming and foamable AS resin particles are pre-foamed in the presence of fatty acid amide is preferable.

  When the pre-foamed particles are prepared, when the method of pre-foaming the foamable AS resin particles in the coexistence of the fatty acid amide and the paraffin wax as described above is adopted, foaming is performed at a stage before being supplied to the foaming tank. It is possible to employ a method in which the functional AS resin particles, the fatty acid amide and the paraffinic wax are allowed to coexist and then supplied into the foaming tank. Alternatively, a method of supplying the fatty acid amide and the paraffin wax simultaneously or separately after supplying the foamable resin particles into the foaming tank may be employed. In addition, when supplying fatty acid amide and paraffin wax separately, which may be supplied first.

As the paraffin wax, a single type may be used, or a plurality of types may be mixed and used.
If the melting point of the paraffin wax is too low, the stickiness of the paraffin wax becomes large and its handling becomes difficult. On the other hand, if the melting point is too high, when the pre-foamed particles are prepared by pre-foaming the expandable AS resin particles in the presence of paraffin-based wax, the paraffin-based wax becomes difficult to melt and adheres to the pre-foamed particles. Can be difficult. Further, if the melting point of the paraffin wax is too high, the inside of the tank of the foaming machine may be significantly contaminated when the paraffin wax adheres to the AS resin pre-expanded particles in the foaming machine. Therefore, the melting point of the paraffin wax is preferably 40 to 100 ° C. (Claim 2), and more preferably 50 to 80 ° C.

  In the pre-expanded particles, the adhesion amount of the paraffin wax is 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the AS resin pre-expanded particles excluding the paraffin wax and the fatty acid amide. When it falls below this range, the fusibility of the pre-expanded particles decreases, and when it exceeds this range, blocking increases. From the same viewpoint, the adhesion amount of the paraffinic wax is preferably 5 parts by mass or more and 18 parts by mass or less, more preferably 10 parts by mass or more and 18 parts by mass or less.

Moreover, as said fatty acid amide, C12-24 fatty acid amides, such as an oleic acid amide, an erucic acid amide, a stearic acid amide, can be used, for example. As the fatty acid amide, a single type may be used, or a plurality of types may be mixed and used.
Preferably, the fatty acid amide is an unsaturated fatty acid amide having 14 to 24 carbon atoms (Claim 3).
In this case, the above-described operation and effect that the effect of shortening the cooling time can be obtained without impairing the fusibility of the pre-expanded particles becomes more remarkable. More preferably, the fatty acid amide is oleic acid amide and / or erucic acid amide (claim 4).

  In the pre-expanded particles, the adhesion amount of fatty acid amide is 2 parts by mass or less (excluding 0) with respect to 100 parts by mass of AS resin pre-expanded particles excluding paraffinic wax and fatty acid amide. When exceeding this range, the meltability is lowered, the appearance of the foamed particle molded body obtained by molding the pre-foamed particles in the mold is deteriorated, and the strength is lowered. From the same viewpoint, the adhesion amount of fatty acid amide is preferably 1 part by mass or less, more preferably 0.5 part by mass or less. Moreover, from the viewpoint of further improving the cooling time shortening effect, the fatty acid amide adhesion amount is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and further preferably 0.2 parts by mass or more.

The amount of paraffinic wax and fatty acid amide adhering to the pre-expanded particles can be measured as follows.
That is, first, the weight of the pre-expanded particle group to which an arbitrary amount of paraffinic wax and fatty acid amide are attached is measured. Next, the pre-expanded particles are dissolved in a sufficient amount of a solvent such as tetrahydrofuran, and the paraffin wax and fatty acid amide adhering to the surface of the pre-expanded particles are extracted, and the amount of paraffin wax and fatty acid amide attached is determined by gas chromatography. Can be requested.

The content of the acrylonitrile component of the AS resin constituting the AS resin pre-expanded particles is preferably 10 to 50% by mass (Claim 5).
When the content of acrylonitrile is within the above range, the cooling time shortening effect by attaching a specific amount of paraffinic resin and fatty acid amide becomes more remarkable. More preferably, the content of acrylonitrile is 20 to 35% by mass.

  The AS resin pre-foamed particles can be obtained by foaming the foamable AS resin particles as described above, but the foamable AS resin particles can be obtained by impregnating the AS resin particles with a foaming agent. The AS resin particles may contain additives such as a bubble regulator, a pigment, a slip agent, an antistatic agent, and a flame retardant, as long as the effects of the present invention are not impaired.

  The AS resin particles can be produced by suspension polymerization of an acrylonitrile monomer and a styrene monomer. The AS resin particles can be produced by melt-kneading commercially available resin pellets with an extruder and then finely pulverizing them by a strand cut method, a hot cut method, an underwater cut method, or the like. In the case of suspension polymerization, the particle diameter of AS resin particles can be adjusted as appropriate by adjusting the amount of suspending agent added and the stirring power. Moreover, when using an extruder, it can adjust suitably by adjusting melt kneaded material, discharge amount, and the speed which cuts it. Any other method can be used as long as the desired particle size can be obtained.

Next, the pre-expanded particles preferably have an average particle diameter of 1.5 to 6.0 mm and a bulk expansion ratio of 5 to 70 times (Claim 6).
When the average particle diameter of the pre-expanded particles is too small, there is a risk of adversely affecting blocking and fusion properties. From this viewpoint, the average particle diameter of the pre-expanded particles is preferably 1.5 mm or more as described above. More preferably, it is 2.0 mm or more. On the other hand, when the average particle diameter of the pre-expanded particles is too large, the filling property into the mold is deteriorated when the expanded particle molded body is produced by in-mold molding. From this viewpoint, the average particle size of the pre-expanded particles is preferably 6.0 mm or less as described above. More preferably, it is 4.0 mm or less, and more preferably 3.0 mm or less.
The average particle diameter of the pre-expanded particles can be controlled by adjusting the particle diameter of the expandable AS resin particles and the expansion ratio.

Moreover, when the bulk foaming ratio of the pre-foamed particles is too low, there is a possibility that the light weight inherently possessed by the foamed-particle molded body formed by in-mold molding of the pre-foamed particles may not be sufficiently exhibited. From this viewpoint, the bulk magnification of the pre-expanded particles is preferably 5 times or more as described above. More preferably, it is 20 times or more, and more preferably 30 times or more. On the other hand, if the bulk foaming ratio of the pre-expanded particles is too large, there is a possibility that desired mechanical strength cannot be obtained. From this viewpoint, the bulk expansion ratio of the pre-expanded particles is preferably 70 times or less as described above. More preferably, it is 50 times or less, and more preferably 40 times or less.
The bulk expansion ratio of the pre-expanded particles can be adjusted mainly by increasing / decreasing the content of the foaming agent in the expandable resin particles, and can be finely adjusted by the temperature and time at the time of foaming. The content of the foaming agent in the foamable resin particles is adjusted by the amount of the foaming agent impregnated into the resin particles, the aging time after impregnation with the foaming agent, and the like.

The average particle diameter of the pre-expanded particles to which the paraffinic wax and the fatty acid amide are attached can be measured as follows.
That is, first, a graduated cylinder containing water at a temperature of 23 ° C. was prepared, and an arbitrary amount of pre-expanded particle group (pre-expanded particle group of the pre-expanded particle group) left for 2 days under the conditions of 50% relative humidity, 23 ° C. and 1 atm. The mass W1) is submerged in water in the graduated cylinder using a tool such as a wire mesh. Then, taking into account the volume of a tool such as a wire mesh, the volume V1 [L] of the pre-expanded particle group read from the rise in the water level is measured, and the number of pre-expanded particles (N) in which this volume V1 is placed in the measuring cylinder. The average volume per pre-expanded particle is calculated by dividing by (V1 / N). And let the diameter of the virtual sphere which has the same volume as the obtained average volume be the average particle diameter [mm] of the pre-expanded particles.

The bulk expansion ratio of the pre-expanded particles to which the paraffin wax and the fatty acid amide are attached can be measured, for example, as follows.
That is, first, a graduated cylinder containing water at a temperature of 23 ° C. was prepared, and an arbitrary amount of pre-expanded particle group (pre-expanded particle group of the pre-expanded particle group) left for 2 days under the conditions of 50% relative humidity, 23 ° C. and 1 atm. The mass W1) is submerged in water in the graduated cylinder using a tool such as a wire mesh. Then, taking into account the volume of a tool such as a wire mesh, the volume V1 [L] of the pre-expanded particle group read from the rise in the water level is measured, and the mass W1 [g] of the resin pre-expanded particle group placed in the measuring cylinder Is divided by the volume V1 (W1 / V1) to obtain the apparent density ρ1 of the pre-expanded particles. By dividing this density ρ1 by the density of the AS resin constituting the pre-expanded particles and further multiplying by 1.6, the bulk expansion ratio of the pre-expanded particles can be determined.

A foamed particle molded body (acrylonitrile / styrene resin foamed particle molded body) can be obtained by in-mold molding of the pre-expanded particles to which the paraffinic wax and the fatty acid amide are attached. In other words, the pre-expanded particles can be obtained by filling the pre-expanded particles into a mold and introducing the heating medium into the mold to fuse the pre-expanded particles to each other.
In-mold molding is a suitable method for filling foam particles in a mold and obtaining a foam molded product (foamed particle molded body) with a uniform density distribution.

As a heating medium for obtaining the foamed particle molded body, for example, saturated steam, inorganic gas, and a mixed gas thereof can be used.
As the inorganic gas, air, nitrogen, carbon dioxide, argon, helium, oxygen, neon, or the like can be used. From an economical viewpoint, it is most preferable to use air as the inorganic gas.

  The foamed particle molded body is preferably used for applications that require heat resistance, oil resistance, and chemical resistance, such as automobile interior materials, packaging materials, and heat insulating members for electrical appliances.

Hereinafter, examples and comparative examples of the pre-foamed particles and the foamed particle molded body will be described.
(Examples 1 to 11)
The pre-expanded particles according to the examples are obtained by attaching paraffin wax and fatty acid amide to at least the surface of the pre-expanded particles based on AS resin, and the amount of paraffin wax attached is 100 parts by mass of the pre-expanded particles. The pre-expanded particles are 1 part by mass or more and 20 parts by mass or less, and the adhesion amount of the fatty acid amide is 2 parts by mass or less (excluding 0) with respect to 100 parts by mass of the pre-expanded particles. . The foamed particle molded body is formed by in-mold molding of prefoamed particles. In addition, the adhesion amount of paraffinic wax and fatty acid amide is based on the mass of 100 parts by mass obtained by subtracting the adhesion amount of paraffinic wax and fatty acid amide from the mass of the pre-expanded particles to which these paraffinic wax and fatty acid amide are adhered. Value.

The pre-expanded particles of this example can be prepared by expanding expandable AS resin particles in the presence of wax and fatty acid amide. Hereinafter, the manufacturing method will be specifically described.
First, “HA300” manufactured by JSP Co., Ltd. was prepared as expandable AS resin particles. The monomer component constituting the AS resin of the expandable AS resin particles is 28% by mass of acrylonitrile and 72% by mass of styrene, and the average particle diameter of the expandable AS resin particles is 1 mm. The average particle diameter of the expandable AS resin particles was measured by the same method as the above-described method for measuring the average particle diameter of the pre-expanded particles, except that the expandable AS resin particles were used as a measurement sample. In addition, about 500 cc foamable resin particle group was used for the measurement.

  As the paraffin wax, as shown in Table 1 and Table 2 described later, paraffin wax “PALVAX 1230” (melting point 65 ° C.), “PALVAX 1330” (melting point 64 ° C.), “POLYCOTE 3030” manufactured by Nippon Seiwa Co., Ltd. (Melting point 75 ° C.) was used. As fatty acid amides, oleic acid amide (die wax OA, melting point 75 ° C.) manufactured by Dainichi Chemical Co., Ltd., erucic acid amide (amide E, melting point 80 ° C.) manufactured by Kao Corporation, manufactured by Dainichi Chemical Co., Ltd. Of stearic acid amide (die wax SA-200, melting point 100 ° C.) was used.

  Next, paraffin wax and fatty acid amide were added to and mixed with each blending ratio shown in Tables 1 and 2 with respect to 100 parts by mass of expandable AS resin particles. And by a batch type foaming machine with a volume of 60 L, the expandable AS resin particles were expanded 40 times with a bulk expansion ratio not containing paraffinic wax and fatty acid amide, and the pre-expanded particles with paraffinic wax and fatty acid amide adhered to the surface Got. Next, the pre-expanded particles obtained were aged by allowing them to stand at room temperature in a silo for 1 day. Thus, 11 types of pre-expanded particles of Examples 1 to 11 were obtained.

Tables 1 and 2 show the types and blending amounts of the expandable AS resin particles, the paraffinic wax, and the fatty acid amide used in the preparation of the pre-expanded particles according to each example.
About each pre-expanded particle, the average particle diameter [mm] and the bulk expansion ratio [times] were measured by the method described above. The results are shown in Tables 1 and 2. In addition, the pre-expanded particle group of about 500cc was used for the measurement of an average particle diameter and a bulk expansion ratio, and 1 g / cm < ³ > was employ | adopted as the density of AS resin for calculation of a bulk expansion ratio. Further, Tables 1 and 2 show the bulk expansion ratio (bulk ratio) of the pre-expanded particles in a portion excluding the paraffinic wax and the fatty acid amide for reference.

  Moreover, about each pre-expanded particle, the adhesion amount of paraffin wax and fatty acid amide was measured by the gas chromatography as follows. Then, the results are shown in Tables 1 and 2 described later as adhesion amounts [parts by mass] of paraffinic wax and fatty acid amide to 100 parts by mass of AS resin pre-expanded particles.

[Pre-processing conditions]
About 100 mg of pre-expanded particles to which paraffin wax and fatty acid amide are attached are diluted with 3 ml of tetrahydrofuran, and this is used as a sample for gas chromatography.
[Gas chromatography conditions]
Apparatus: GC-2010 manufactured by Shimadzu Corporation
Injection volume: 1.0 μL
Vaporization chamber temperature: 280 ° C
Column: HP-5MS (30 m × 0.25 mm × 0.25 μm) manufactured by Agilent Technologies
Column tank: 100 ° C. (5 min hold) to 280 ° C., heated at 15 ° C./min Column flow rate: He 1.0 ml / min (split ratio 1/50)
Detector: FID

Next, each pre-expanded particle was evaluated for blocking resistance as follows.
"Blocking resistance"
Pre-expanded particles with paraffinic wax and fatty acid amide adhered to each other in a silo, and the fluidity of the pre-expanded particles with no paraffinic wax and fatty acid amide adhered to each other was marked as “×” ”, Those with no problems in fluidity were evaluated as“ ◯ ”. The results are shown in Tables 1 and 2.

Next, each of the pre-expanded particles of each example was molded using an MDX-10VS automatic molding machine (manufactured by Hitachi Chemical Co., Ltd.) to prepare a foamed particle molded body (AS resin foamed particle molded body).
Specifically, the pre-expanded particles were filled in a mold having dimensions of 700 mm × 500 mm × 25 mm. And the vapor | steam of 0.08 Mpa (G) of original pressure was introduce | transduced in the metal mold | die, and it heated for 15 second, and the secondary foaming particle was secondary-foamed and fused. Subsequently, water cooling was performed for 8 seconds, and then vacuum cooling was performed until the foam pressure became 0.01 MPa to obtain a foamed particle molded body. In addition, said (G) means a gauge pressure. The vacuum cooling time at this time was set as the cooling time [second], and the results are shown in Tables 1 and 2. Further, cooling of the foamed particle molded body of each Example with respect to the cooling time of the foamed particle molded body (Comparative Example 1 described later) obtained by in-mold molding of pre-foamed particles to which paraffinic wax and fatty acid amide are not attached. The time reduction rate (cooling time reduction rate;%) was calculated. The results are shown in Tables 1 and 2. Moreover, the original pressure of the steam was changed from 0.08 MPa (G) to 0.07 MPa (G) and 0.09 MPa (G), and expanded particle molded bodies were obtained under the same conditions as above.

Next, for the obtained foamed particle molded body, the fusion rate and the bending strength were measured as follows, and the bending strength retention rate was further determined.
"Fusion rate"
Each foamed particle molded body was divided in the vicinity of the center (350 mm position) in the longitudinal direction (700 mm direction), and the fracture surface thereof was visually observed. Then, the ratio (percentage) of the number of expanded particles broken from the inside of the expanded particles to the total number of expanded particles in the fracture surface was calculated, and this was defined as the fusion rate (%). The fusion rate was calculated for each foamed particle molded body produced using steam at a molding pressure (original pressure) of 0.07 MPa (G), 0.08 MPa (G), and 0.09 MPa (G). . The results are shown in Tables 1 and 2.

"Bending strength and bending strength retention"
The bending strength was measured according to JIS K7221-2: 2006. In the measurement, without removing the molding skin (25 mm) from the foamed particle molded body produced with steam having a molding pressure (original pressure) of 0.08 MPa (G), the obtained foamed particle molded body was adjusted to 100 × 350 mm. A test piece was prepared by cutting. The distance between fulcrums was 300 mm, the speed of the pressure wedge was 20 mm / min, the test temperature was 23 ° C., and the test humidity was 50% relative humidity.
In addition, the bending strength retention rate was determined by measuring the bending strength of a foamed particle molded body prepared at a magnification of 40 times without using paraffin wax and fatty acid amide, and using this as a reference value. It showed in. Specifically, the bending strength of the foamed particle molded body of Comparative Example 1 described later was used as a reference value. The comparison with respect to the reference value was performed using the same foaming magnification in terms of the magnification not including paraffinic wax and fatty acid amide. The lower the fusion property of the expanded particles, the lower the value of bending strength retention. The results are shown in Tables 1 and 2.

(Comparative Examples 1-10)
Next, pre-expanded particles and expanded particle molded bodies for comparison with Examples 1 to 11 were produced.
Comparative Example 1 was prepared in the same manner as in the above Example except that it was prepared without using paraffin wax and fatty acid amide, as shown in Table 3 below.

  Comparative Examples 2 and 3 were produced in the same manner as in the Examples, except that, as shown in Table 3 described later, only the paraffin wax was used without using the fatty acid amide. Comparative Examples 2 and 3 are examples in which the amount of paraffin wax adhered to the pre-expanded particles was changed by changing the amount of paraffin wax added to each other.

  Comparative Examples 4 and 5 were produced in the same manner as in the Examples except that, as shown in Table 3 described later, only the fatty acid amide was used without using paraffin wax. Comparative Examples 4 and 5 are examples in which the type of fatty acid amide was changed.

  Comparative Examples 6 to 9 are examples of pre-foamed particles and foamed particle molded bodies produced using both paraffinic wax and fatty acid amide as in Examples, as shown in Table 4 below. Comparative Examples 6 to 9 were prepared in the same manner as in Examples except that the addition amount of the paraffin wax and the fatty acid amide was changed to change the adhesion amount of the wax and the fatty acid amide of the pre-expanded particles. In Comparative Examples 6 and 7, the amount of paraffinic wax is increased as compared with the Examples, and in Comparative Examples 8 and 9, the amount of fatty acid amide is increased as compared with the Examples, so that the pre-expanded particles and the expanded particle molding are formed. The body was made.

  As shown in Table 4 to be described later, Comparative Example 10 was the same as in Example except that expandable polystyrene particles (FB250 average particle diameter 0.9 mm manufactured by JSP Corporation) were used instead of expandable AS resin particles. In this example, pre-expanded particles are produced.

About the pre-expanded particles of Comparative Examples 1 to 9 obtained as described above, the adhesion amount [parts by mass] of paraffinic wax and fatty acid amide to 100 parts by mass of AS resin pre-expanded particles, the average particle diameter [mm], and The bulk foaming ratio [times] was measured in the same manner as in the above examples, and the blocking resistance was evaluated in the same manner as in the above examples. The results are shown in Tables 3 and 4.
Moreover, about the foamed particle molded object of Comparative Examples 1-9, it carried out similarly to the above-mentioned Example, measured cooling time [second], and calculated | required the shortening rate [%] of cooling time. Moreover, about the foamed particle molded object of Comparative Examples 1-9, bending strength [kPa] was measured and bending strength retention [%] was calculated | required. The results are shown in Tables 3 and 4.
In Comparative Example 10, the foamable AS resin particles contracted during foaming and could not reach a predetermined foaming ratio. Therefore, in Comparative Example 10, various measurements relating to the pre-expanded particles and the expanded particle molded body could not be performed.

  As known from Tables 1 and 2, pre-expanded particles in which 1 to 20 parts by mass of paraffin wax and 2 to less than 2 parts by mass of fatty acid amide (except 0) are attached to the surface of AS resin expanded particles. It turns out that (Examples 1-11) is excellent in blocking resistance. It can also be seen that such pre-expanded particles have a short cooling time during molding. Furthermore, it can be seen that the foamed particle molded body produced using these pre-expanded particles is excellent in the fusion property between the expanded particles and in the bending strength.

  On the other hand, as is known from Table 3, Comparative Example 1 in which both the paraffinic wax and the fatty acid amide are not adhered, and Comparative Examples 2 and 3 in which only the paraffinic wax is adhered, have a long cooling time during molding. became.

  Further, as is known from Table 3, the foamed particle molded body produced using the pre-expanded particles of Comparative Examples 4 and 5 using only fatty acid amide has a lower fusion strength between the expanded particles, and has a bending strength. It was insufficient.

  Further, as is known from Table 4, the pre-expanded particles of Comparative Examples 6 and 7 in which the amount of the paraffin wax attached was too large were inferior in blocking resistance.

  Moreover, as is known from Table 4, the foamed particle molded body produced using the pre-expanded particles of Comparative Examples 8 and 9 having too much fatty acid amide attached has reduced the fusibility between the expanded particles, and has a bending strength. Was insufficient.

  Further, as is known from Table 4, in Comparative Example 10 using expandable polystyrene particles, when paraffin wax and fatty acid amide were adhered, the particles contracted in the preliminary foaming step, and the predetermined expansion ratio was not reached. It was.

  Thus, according to this example, the surface of the pre-expanded particles based on AS resin is 1 part by mass or more and 20 parts by mass or less of paraffinic wax and 2 parts by mass or less of fatty acid amide (except 0). It can be seen that the pre-expanded particles to which are attached have excellent blocking resistance and handleability. Furthermore, it can be seen that when these pre-expanded particles are used, the cooling time at the time of molding can be shortened, and a foamed particle molded body having excellent mechanical strength such as bending strength can be produced.

Claims (7)

Paraffin wax and fatty acid amide adhere to the surface of pre-expanded particles based on acrylonitrile / styrene resin,
The amount of the paraffin wax attached is 1 to 20 parts by mass with respect to 100 parts by mass of the pre-expanded particles,
The acrylonitrile / styrene resin pre-expanded particles, wherein the adhesion amount of the fatty acid amide is 2 parts by mass or less (excluding 0) with respect to 100 parts by mass of the pre-expanded particles.   The acrylonitrile / styrene resin pre-expanded particles according to claim 1, wherein the paraffin wax has a melting point of 40 ° C. to 100 ° C.   The acrylonitrile / styrene resin pre-expanded particles according to claim 1 or 2, wherein the fatty acid amide is an unsaturated fatty acid amide having 14 to 24 carbon atoms.   The pre-expanded acrylonitrile / styrene resin pre-expanded particle according to claim 1, wherein the fatty acid amide is erucic acid amide and / or oleic acid amide. .   5. The acrylonitrile / styrene resin pre-expanded particles according to claim 1, wherein the content of the acrylonitrile component in the acrylonitrile / styrene resin is from 10 to 50% by mass. Pre-expanded particles.   The pre-expanded acrylonitrile styrene resin particles according to any one of claims 1 to 5, wherein the pre-expanded particles have an average particle size of 1.5 to 6.0 mm and a bulk expansion ratio of 5 to 70 times. Pre-expanded particles of acrylonitrile / styrene resin,   A foamed particle molded body obtained by molding the acrylonitrile / styrene resin pre-foamed particles according to any one of claims 1 to 6 in a mold.