JP2012184355A - Pre-foamed particle and foam molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide pre-foamed particles excellent in fluidity.SOLUTION: The pre-foamed particle satisfies formula (1): 1.0≤L/D≤1.5 (wherein L is a major axis (mm) of the pre-foamed particle; and D is a minor axis (mm) thereof), and formula (2): Y≤0.13X-1.0 (wherein X is a bulk foaming magnification (times) of the pre-foamed particle; and Y is a percentage (mass%) of moisture attached to the surface of the pre-foamed particle), and has a repose angle of 0 to 22 degrees.

Description

  The present invention relates to pre-expanded particles and a foam-molded product. More specifically, the present invention relates to pre-expanded particles having excellent fluidity and a foam-molded product obtained from the pre-expanded particles.

  Conventionally, foam molded articles obtained from expandable resin particles containing polystyrene resin, polypropylene resin or the like as a thermoplastic resin component are excellent in impact resistance, moldability, etc., so that cushioning materials for packaging, structural members for automobiles, etc. Is widely used.

  In addition, the foamed molded product is usually obtained by prefoaming expandable resin particles containing a resin component and a foaming agent, and then the obtained prefoamed particles are heated with heat such as water vapor in a foam molding machine. It is manufactured by foam molding using a medium.

  However, when the pre-expanded particles are sent to the in-mold foam mold during foam molding, depending on the shape, properties, etc. of the pre-expanded particles, the pre-expanded particles may become a feeder May stay in the mechanism) and may not be sufficiently filled into the foam molding machine.

  In this case, the obtained foamed molded product may cause defects in the foamed molded product due to partial filling failure, and the presence of such defects significantly impairs the commercial value of the foamed molded product. For this reason, as pre-expanded particles that solve the above-mentioned problems, for example, JP 2009-256477 A (Patent Document 1) discloses a pre-improved filling property in a mold containing a polypropylene resin as a resin component. Expanded particles are described.

JP 2009-256477 A

  However, the pre-expanded particles described in Examples and Comparative Examples of Patent Document 1 listed as specific embodiments have a large angle of repose (23 to 37 degrees), and the fluidity of the pre-expanded particles In terms of improvement, it was not satisfactory. Specifically, these do not show excellent fluidity such as substantially liquid, but from the viewpoint of improving the filling property of the pre-foamed particles to the foam molding machine and obtaining a foam molded article having excellent surface properties. It was not satisfactory.

  For this reason, in view of these problems, it is required to provide pre-expanded particles having excellent fluidity and a high-quality foam-molded product obtained from the pre-expanded particles.

Thus, according to the present invention, the following formula (1):
1.0 ≦ L / D ≦ 1.5 (1)
(In the formula, L is the major axis (mm) of the pre-expanded particles, and D is the minor axis (mm) of the pre-expanded particles)
And the following formula (2):
Y ≦ 0.13X−1.0 (2)
(In the formula, X is the bulk foaming ratio (times) of the pre-foamed particles, and Y is the surface adhering moisture content (mass%) of the pre-foamed particles)
And pre-expanded particles characterized by having an angle of repose of 0 to 22 degrees.

  Moreover, according to this invention, the foaming molding obtained from the said pre-expanded particle is also provided.

  According to the present invention, pre-expanded particles having excellent fluidity can be provided.

  Further, according to the present invention, when the pre-expanded particles have a major axis of 2.0 to 7.0 mm and a minor axis of 2.0 to 6.5 mm, the particle size of the pre-expanded particles can be suitably designed. Thus, it is possible to provide pre-expanded particles having more excellent fluidity.

  Further, according to the present invention, when the pre-expanded particles have a bulk expansion ratio of 20 to 60 times, the pre-expanded particles have a suitable bulk specific gravity, and thus can provide pre-expanded particles with more excellent fluidity. .

  Further, according to the present invention, when the pre-expanded particles have a surface-attached moisture content of 0 to 6.8% by mass, aggregation due to moisture present on the surface can be suppressed, so that the fluidity is more excellent. Pre-expanded particles can be provided.

  Further, according to the present invention, when the pre-expanded particles include at least 100 parts by mass of a polyolefin resin and 100 to 400 parts by mass of a polystyrene resin as resin components, the pre-expanded particles are preferably a polyolefin resin that can contribute to the strength. Therefore, pre-expanded particles having higher strength and fluidity can be provided.

  Moreover, according to this invention, when a pre-expanded particle contains a flame retardant, the pre-expanded particle more excellent in a flame retardance and fluidity | liquidity can be provided.

According to the invention, the pre-expanded particles are
In the aqueous suspension containing the dispersant, in the presence of 0.001 to 0.05 parts by mass of a surfactant with respect to 100 parts by mass of the aqueous medium, the polyolefin resin seed particles and the first styrene monomer Step A for dispersing the monomer and the first polymerization initiator;
Heating the obtained dispersion to a temperature at which the first styrenic monomer is not substantially polymerized to impregnate the seed particles with the first styrenic monomer; and
The step of obtaining the first particles by performing the first polymerization of the first styrene monomer at a temperature of (T-10) ° C. to (T + 20) ° C. when the melting point of the polyolefin resin is T ° C. C
Subsequent to Step C, the second particles are further added with a second styrene monomer and a temperature of (T-25) ° C. to (T + 10) ° C. Impregnation of the second styrenic monomer and the seed polymerization step through the second polymerization to obtain resin particles D (however, the amount of polyolefin resin and the first styrenic monomer) The total amount of the second styrenic monomer is 100: 100 to 400 (mass ratio));
An impregnation step of obtaining expandable resin particles by impregnating resin particles with a foaming agent;
A pre-foaming step for pre-foaming the expandable resin particles; and when the pre-foamed expandable resin particles are obtained by a production method including an aging step of standing at a temperature of room temperature or higher for 12 hours or longer Excellent pre-expanded particles can be easily provided.

  According to the present invention, since the pre-expanded particles have excellent fluidity, it is possible to provide a foamed molded article having excellent surface properties.

The feature of the present invention is the following formula (1):
1.0 ≦ L / D ≦ 1.5 (1)
(In the formula, L is the major axis (mm) of the pre-expanded particles, and D is the minor axis (mm) of the pre-expanded particles)
And the following formula (2):
Y ≦ 0.13X−1.0 (2)
(In the formula, X is the bulk foaming ratio (times) of the pre-foamed particles, and Y is the surface adhering moisture content (mass%) of the pre-foamed particles)
And pre-expanded particles having an angle of repose of 0 to 22 degrees.

  The pre-expanded particles of the present invention have a substantially spherical shape that satisfies the formula (1), and have a suitable relationship between the bulk expansion ratio and the surface adhering moisture content. And has a very small angle of repose of 0 to 22 degrees. In the present invention, the angle of repose refers to an angle (°) measured in accordance with JIS R 9301-2-2. Specifically, the pre-expanded particles are dropped from the lower end of the funnel container, and the height of the pre-expanded particles deposited on the disk-shaped table is measured, and the diameter of the disk-shaped table and the height of the deposited expanded particles are measured. From the relationship, the angle of repose of the deposited pre-expanded particles is calculated. The major axis and minor axis of the pre-expanded particles mean the longest and shortest diameters of the pre-expanded particles, and the major axis is a diameter equal to or greater than the minor axis. Furthermore, the substantially spherical shape means a spherical to egg-shaped shape. The repose angle measurement method and the like will be described in detail in Examples.

  Conventionally, since pre-expanded particles are manufactured using cylindrical resin particles or the like, it is expected that the obtained pre-expanded particles also have an irregular shape such as a column. For this reason, these pre-expanded particles had a large angle of repose and low fluidity.

  On the other hand, since the pre-expanded particles of the present invention are produced using substantially spherical resin particles, the obtained pre-expanded particles also have a substantially spherical shape that satisfies the formula (1). Specifically, in order to obtain the pre-expanded particles of the present invention, first, approximately spherical resin particles are similarly obtained by impregnating approximately spherical resin particles with a foaming agent. Next, pre-expanded particles are obtained by pre-expanding the substantially spherical expandable resin particles obtained. For this reason, the pre-expanded particles of the present invention have a substantially spherical shape and are extremely excellent in fluidity unlike the irregular-shaped pre-expanded particles.

  Moreover, since the pre-expanded particles of the present invention have a suitable relationship between the bulk expansion ratio and the surface adhering moisture content, it is possible to suppress agglomeration via moisture existing on the surface between the pre-expanded particles, As a result, the fluidity of the pre-expanded particles can be further improved.

Therefore, the pre-expanded particles of the present invention can realize an extremely small angle of repose of 0 to 22 degrees, which could not be realized with conventional pre-expanded particles, and as a result, stay in the feeder, etc. Therefore, the pre-expanded particles can be easily filled in the foam molding machine.
Hereinafter, the pre-expanded particles of the present invention will be described in detail.

<Resin particles>
The pre-expanded particles of the present invention are produced by impregnating resin particles with a foaming agent to obtain expandable resin particles, and then pre-expanding the obtained expandable resin particles. In the present invention, since the shape of the resin particles greatly affects the shape of the pre-foamed particles, the resin particles are also preferably substantially spherical.

Specifically, when the resin particles of the present invention are substantially spherical, preferably the following formula (3):
1.0 ≦ A / B ≦ 1.5 (3)
(In the formula, A is the major axis (mm) of the resin particles, and B is the minor axis (mm) of the resin particles)
More preferably, the following formula (4):
1.0 ≦ A / B ≦ 1.3 (4)
Meet.

  In the present invention, since the fluidity of the pre-foamed particles can be more easily ensured, the resin particles are preferably 2.0 to 7.0 mm, more preferably 2.0 to 6.5 mm long diameter, Preferably it has a minor axis of 2.0 to 6.5 mm, more preferably 2.0 to 6.0 mm. The major axis is a diameter greater than the minor axis.

  The resin component which comprises the resin particle of this invention will not be specifically limited if foamable, A well-known thermoplastic resin, a thermosetting resin, etc. can be used. Specific examples include polystyrene resins, polyolefin resins, poly (meth) acrylic resins, polyphenylene ether resins, polycarbonate resins, polyester resins including polylactic acid resins, and chlorine resins. In addition, (meth) acryl means acryl or methacryl.

  As the resin component contained in the resin particles of the present invention, a polystyrene resin is preferable because rigidity and high foaming performance can be imparted.

  A polyolefin resin is also preferable because it can impart high heat resistance and impact resistance. Furthermore, since both of the characteristics can be included, it is more preferable that the resin particles of the present invention include both a polystyrene resin and a polyolefin resin. In the present invention, when a plurality of resin components are used as the resin component of the pre-expanded particles, the mass ratio between the monomers, the mass ratio between the monomer and the resin, and the resin The mass ratio is substantially the same as the mass ratio of the resin component contained in the resin particles, the pre-expanded particles, and the foamed molded product obtained therefrom.

  In the present invention, the polystyrene-based resin means a styrene homopolymer or a copolymer of styrene as a main component and another monomer copolymerizable with styrene. Here, styrene as a main component means that styrene accounts for 50% by mass or more of all monomers. Examples of other monomers include α-methylstyrene, p-methylstyrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, alkyl acrylate ester, alkyl methacrylate ester, divinylbenzene, and polyethylene glycol dimethacrylate. The In the examples, alkyl means alkyl having 1 to 8 carbon atoms. In the present invention, a styrene homopolymer capable of stably pre-foaming expandable resin particles is preferable.

  In the present invention, the polyolefin resin means an olefin homopolymer or a copolymer of an olefin monomer as a main component and another monomer copolymerizable with the olefin monomer. Here, having an olefin monomer as a main component means that the olefin monomer occupies 50% by mass or more of the total monomers.

Specifically, as the polyolefin resin, for example, branched low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer Polyethylene resins such as
Examples thereof include polypropylene resins such as propylene homopolymer, ethylene-propylene copolymer, propylene-1-butene copolymer, and ethylene-propylene-1-butene copolymer.

  In the present invention, since a higher level of heat resistance and impact resistance can be expected, a polypropylene resin is preferred as the polyolefin resin.

Moreover, as long as the desired physical properties are not affected, the polyolefin resin may be used alone or in combination of two or more. In addition, in the said illustration, it is preferable that low density is 0.91-0.94 g / cm < ³ >, and it is more preferable that it is 0.91-0.93 g / cm < ³ >. Preferably high density and is 0.95~0.97g / cm ^3, more preferably 0.95~0.96g / cm ^3. The medium density is an intermediate density between the low density and the high density.

  Polyolefin resins include talc, calcium silicate, calcium stearate, synthetic or naturally produced silicon dioxide, ethylene bis-stearic acid amide, methacrylic acid ester copolymer, etc., carbon black, iron oxide, graphite, etc. It may contain a coloring agent.

  Furthermore, the resin component of the present invention has a functional group such as a vinyl group, a carbonyl group, an aromatic group, an ester group, an ether group, an aldehyde group, an amino group, a nitrile group, and a nitro group as long as the desired physical properties are not affected. May be contained, may be crosslinked with a crosslinking agent having two or more vinyl groups, and may be used alone or in combination of two or more.

  Similarly, the resin particles of the present invention may contain other resin components as long as they do not affect the desired physical properties. Examples of other resin components include known thermoplastic resins and thermosetting resins. Specific examples include poly (meth) acrylic resins, polyphenylene ether resins, polycarbonate resins, polyester resins including polylactic acid resins, and chlorine resins.

  In the present invention, when a polystyrene resin and a polyolefin resin are used as the resin component, the polystyrene resin is preferably contained in the resin particles in an amount of 100 to 400 parts by mass with respect to 100 parts by mass of the polyolefin resin. More preferably, it is contained in an amount of 125 to 240 parts by mass. If the content of the polystyrene resin is more than 400 parts by mass, the polyolefin resin may be insufficient, and the heat resistance and impact resistance may be inferior. On the other hand, when the amount is less than 100 parts by mass, the polystyrene-based resin may be insufficient and desired foamability may not be obtained.

  Moreover, since the physical property which both have can be introduce | transduced into a foaming molding suitably, the resin particle is a resin component which combined both in 100 mass parts of resin particles, Preferably it is 70-100 mass parts, More preferably, it is 80. Contains 100 parts by mass. On the other hand, as a combination of a polyolefin resin and a polystyrene resin, a combination of a polypropylene resin and a styrene homopolymer is preferable.

  Moreover, as long as a desired foaming molding can be obtained, the resin particle may contain the other additive. Specific additives include flame retardants, flame retardant aids, coating agents, chain transfer agents, light stabilizers, UV absorbers, pigments, dyes, antifoaming agents, thickeners, heat stabilizers, leveling agents. , Lubricants, antistatic agents and the like. In addition, when the resin particle contains these additives, the pre-foamed particles and the foamed molded product obtained from the resin particles can also contain these additives.

<Method for producing resin particles>
A known polymerization method, that is, a suspension polymerization method, an emulsion polymerization method, a solution polymerization method, a seed polymerization method, or the like can be used as appropriate for the production of the resin particles used in the production of the expandable resin particles. The seed polymerization method is a method of obtaining resin particles by impregnating seed particles (seed particles) with a monomer component in an aqueous medium and polymerizing them. In the present invention, since a composite resin particle containing a plurality of resin components can be easily produced, a seed polymerization method is preferable. In this case, higher chemical resistance, impact resistance, strength, etc. may be introduced into the foamed molded product. Moreover, when the seed polymerization method is used as a production method, the obtained resin particles are likely to be substantially spherical. In this case, the expandable resin particles and the pre-expanded particles obtained from the resin particles are also preferably substantially spherical.

<Method for producing composite resin particles>
An example will be given below to describe a method for producing composite resin particles containing a polyolefin resin and a polystyrene resin as resin components by a seed polymerization method, but the present invention is not limited to these.

The composite resin particles of the present invention are, for example,
In the aqueous suspension containing the dispersant, in the presence of 0.001 to 0.05 parts by mass of a surfactant with respect to 100 parts by mass of the aqueous medium, the polyolefin resin seed particles and the first styrene monomer Step A for dispersing the monomer and the first polymerization initiator;
Heating the obtained dispersion to a temperature at which the first styrenic monomer is not substantially polymerized to impregnate the seed particles with the first styrenic monomer; and
The step of obtaining the first particles by performing the first polymerization of the first styrene monomer at a temperature of (T-10) ° C. to (T + 20) ° C. when the melting point of the polyolefin resin is T ° C. C
Subsequent to Step C, the second particles are further added with a second styrene monomer and a temperature of (T-25) ° C. to (T + 10) ° C. Impregnation of the second styrenic monomer and the seed polymerization step through the second polymerization to obtain resin particles D (however, the amount of polyolefin resin and the first styrenic monomer) The total amount of the second styrene monomer can be 100: 100 to 400 (mass ratio). In this case, the mass ratio of the polyolefin resin and the styrene monomer is substantially the same as the resin component ratio in the foamed molded product, the pre-foamed particles, and the composite resin particles.

  Each of the steps A to D can be carried out using an autoclave polymerization apparatus used when a known polymerization method such as a suspension polymerization method or a seed polymerization method is carried out, but the production apparatus used is limited to this. Not.

(Process A)
In the step A of the present invention, in the aqueous suspension containing the dispersant, in the presence of 0.001 to 0.05 parts by mass of a surfactant with respect to 100 parts by mass of the aqueous medium, In this step, the first styrene monomer and the first polymerization initiator are dispersed.

  The polyolefin resin particles used as seed particles in seed polymerization are, for example, a method in which a polyolefin resin is melted with an extruder and granulated into pellets by strand cutting, underwater cutting, hot cutting, etc. It can be obtained by a method in which resin particles are pulverized and pelletized. Further, examples of the shape include a true spherical shape, a substantially spherical shape, a cylindrical shape, and a prismatic shape. In this case, since the substantially spherical composite resin particles can be obtained more easily, the polyolefin resin particles are also preferably substantially spherical. Furthermore, from the same viewpoint, the preferred particle diameter of the polyolefin resin particles is in the range of 0.5 to 1.5 mm, and more preferably in the range of 0.6 to 1.0 mm.

On the other hand, examples of the dispersant used to obtain an aqueous suspension include organic dispersants such as partially saponified polyvinyl alcohol, polyacrylate, polyvinyl pyrrolidone, carboxymethyl cellulose, and methyl cellulose;
Examples include inorganic dispersants such as magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, calcium carbonate, magnesium phosphate, magnesium carbonate, and magnesium oxide. Among these, since a more stable aqueous suspension may be obtained, an inorganic dispersant is preferable, and magnesium pyrophosphate is more preferable.

  Moreover, since the substantially spherical composite resin particles can be obtained more easily, the dispersant is preferably 0.1 to 5 parts by mass, more preferably 1 to 4 parts by mass with respect to 100 parts by mass of the aqueous medium. Used in proportions. Examples of the aqueous medium constituting the aqueous suspension include water, a mixture of water and a water-soluble solvent (for example, lower alcohols such as methanol and ethanol), and the like. Furthermore, the aqueous medium may contain an additive such as an electrolyte as long as the desired physical properties are not affected.

  In the present invention, since seed polymerization can be performed more stably, the seed particles are preferably used in a proportion of 10 to 80 parts by mass, more preferably 20 to 50 parts by mass with respect to 100 parts by mass of the aqueous medium. Is done. Moreover, also when the resin particles are composite resin particles containing a flame retardant or the like, the seed particles are preferably used in a proportion of 10 to 80 parts by mass, more preferably 20 to 50 parts by mass with respect to 100 parts by mass of the aqueous medium. Is done.

  On the other hand, it is preferable to use a surfactant because substantially spherical composite resin particles can be obtained stably. As the surfactant, any of an anionic surfactant, a nonionic surfactant and a cationic surfactant can be used as long as the desired physical properties are not affected.

Specifically, anionic surfactants such as sodium oleate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, alkyl naphthalene sulfonate and alkyl phosphate ester salts;
Nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkylamine and glycerin fatty acid ester;
Examples include amphoteric surfactants such as lauryl dimethylamine oxide; and cationic surfactants such as aliphatic quaternary ammonium salts.

  In the present invention, since an approximately spherical composite resin particle can be obtained more stably, an anionic surfactant is preferable, and sodium dodecylbenzenesulfonate is particularly preferable. In addition, since the resin particles and pre-expanded particles having a substantially spherical shape can be obtained more easily, the surfactant used in the first polymerization is preferably 0.1% relative to 100 parts by mass of the aqueous medium. It is used at a ratio of 001 to 0.05 parts by mass, more preferably 0.005 to 0.05 parts by mass.

As the polymerization initiator used as the first polymerization initiator and the second polymerization initiator, conventionally known polymerization initiators widely used for the polymerization of styrene monomers can be used. For example, benzoyl peroxide, lauroyl peroxide, t-amyl peroxy octoate, t-butyl peroxybenzoate, t-amyl peroxybenzoate, t-butyl peroxybivalate, t-butyl peroxyisopropyl carbonate, t- Butyl peroxyacetate, t-butylperoxy-3,3,5-trimethylcyclohexanoate, di-t-butylperoxyhexahydroterephthalate, 2,2-di-t-butylperoxybutane, dicumyl peroxide Organic peroxides such as;
Examples include azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. In addition, a polymerization initiator may be used independently or may be used together. It is preferable that the usage-amount of a polymerization initiator is 0.1-5 mass parts with respect to the sum total of 100 mass parts of styrene-type monomers. Moreover, it is preferable that the usage-amount of a 1st polymerization initiator is 0.01-1 mass part with respect to 100 mass parts of 1st styrenic monomers. Furthermore, it is preferable that the usage-amount of a 2nd polymerization initiator is 0.05-4 mass parts with respect to 100 mass parts of 2nd styrene-type monomers.

  Moreover, you may use a crosslinking agent. As a crosslinking agent, 2,2-di-t-butylperoxybutane, 2,2-bis (t-butylperoxy) butane, dicumyl peroxide, 2,5-dimethyl-2,5-di-t -Organic peroxides such as butylperoxyhexane. Examples of the method of adding the crosslinking agent include a method of directly adding the crosslinking agent to the polyolefin resin, a method of adding the crosslinking agent after dissolving it in a solvent, a plasticizer or a styrene monomer, and a method of adding the crosslinking agent to water. The method of adding after dispersing is mentioned. Among these, a method of adding a crosslinking agent after dissolving it in a styrene monomer is preferable.

  In order to impregnate the polyolefin resin particles with the styrene monomer, it can be added continuously or intermittently to the aqueous medium. It is preferable to gradually add the styrenic monomer to the aqueous medium.

(Process B)
Step B of the present invention is a step in which the obtained dispersion is heated to a temperature at which the first styrenic monomer is not substantially polymerized to impregnate the seed particles with the first styrenic monomer.

  In the present invention, the temperature at which the first styrenic monomer is not substantially polymerized means a temperature not higher than the 10-hour half-life temperature of the polymerization initiator used, although it depends on the type of polymerization initiator used. . In addition, the temperature is preferably in the range of 45 to 70 ° C., because the first styrene monomer can be sufficiently absorbed and poured into the polyolefin resin. When the heating temperature is less than 45 ° C., the impregnation of the first styrene monomer may be insufficient, and a polystyrene polymer powder may be generated. On the other hand, when the heating temperature exceeds 70 ° C., polymerization may occur before the styrene monomer is sufficiently impregnated into the polyolefin resin particles. More preferably, the temperature is in the range of 50-65 ° C.

(Processes C and D)
In the step C of the present invention, when the melting point of the polyolefin resin is T ° C., the first polymerization of the first styrene monomer is performed at a temperature of (T−10) ° C. to (T + 20) ° C. This is a step of obtaining first particles. Moreover, the process D of this invention adds the 2nd styrene-type monomer and the 2nd polymerization initiator following the process C, and is the temperature of (T-25) degreeC-(T + 10) degreeC. Thus, the first particle is impregnated with the second styrenic monomer and the second polymerization is performed to obtain resin particles.

  In step C and step D, the polymerization temperature is an important factor. By performing polymerization in the above temperature range, composite resin particles having a large amount of polystyrene resin in the center and a large amount of polyolefin resin in the surface layer may be obtained in some cases. In this case, as a result of the uneven distribution of the polystyrene resin and the polyolefin resin, the foam molded article that has the advantages of the polyolefin resin and the polystyrene resin, and has excellent rigidity, foam moldability and chemical resistance. May be able to provide.

  When the polymerization temperature is lower than the above temperature range, the abundance of the polystyrene-based resin at the center is small, and a foamed molded article having good physical properties may not be obtained. In addition, when the polymerization temperature is higher than the above temperature range, the polymerization starts before the styrene monomer is sufficiently impregnated with the polyolefin resin particles, so that a foam molded article having good physical properties cannot be obtained. There is. Moreover, if it becomes high, the superposition | polymerization equipment excellent in heat resistance will be needed.

  The reason for dividing the polymerization of the styrenic monomer into two stages, Step C and Step D, is that if a large amount of styrene monomer is impregnated into the polyolefin resin at once, the styrene monomer The polyolefin resin may not be sufficiently impregnated and may remain on the surface of the polyolefin resin. If the polymerization process is divided into two stages, the styrene monomer is reliably impregnated in the center of the polyolefin resin in the process C, and the styrene monomer is impregnated in the process D toward the center of the polyolefin resin. May be.

  In the present invention, since the impregnation can be performed more efficiently, the amount of the polyolefin resin and the total amount of the first styrene monomer and the second styrene monomer are: Preferably it is 100: 100-400, More preferably, it is 100: 125-240 (mass ratio). Similarly, the amount of the polyolefin resin and the amount of the first styrene monomer are preferably 100: 10 to 100, more preferably 100: 30 to 70 (mass ratio).

  In Step D, a surfactant may be optionally added together with the second styrenic monomer or the second polymerization activator. Also in this case, since the substantially spherical composite resin particles can be obtained more stably as the surfactant to be used, an anionic surfactant is preferable, and sodium dodecylbenzenesulfonate is particularly preferable. Furthermore, the surfactant used in the second polymerization is preferably used in a ratio of 0.001 to 1 part by mass, more preferably 0.005 to 0.1 part by mass with respect to 100 parts by mass of the aqueous medium. The

  On the other hand, when the composite resin particles contain a flame retardant, the first particles or the composite resin particles in the second polymerization can be impregnated with the flame retardant. Furthermore, after the step D, the reaction vessel is cooled, and the composite resin particles can be isolated from the aqueous medium to isolate the composite resin particles. On the other hand, other temperatures, pressures, process times, and the like during the seed polymerization process are appropriately set according to manufacturing equipment and manufacturing conditions.

<Foaming resin particles>
The foamable resin particles mean resin particles that are foamed by heating, in which resin particles are impregnated with a foaming agent at a predetermined ratio.

  Various known foaming agents can be used as the foaming agent. Examples thereof include propane, n-butane (normal butane), isobutane, n-pentane (normal pentane), isopentane, industrial pentane, petroleum ether, cyclohexane, cyclopentane, flon, and halon alone or in a mixture. Among these, propane, n-butane, isobutane, n-pentane, isopentane, and cyclopentane, which can introduce greater foaming performance into the foamable resin particles, are preferred, and n-butane and isobutane are more preferred. . A foaming agent may be used independently and may use 2 or more types.

  It is preferable that the content rate of a foaming agent is 20 mass parts or less with respect to 100 mass parts of expandable resin particles. When the amount exceeds 20 parts by mass, the bubble size in the pre-expanded particles tends to be excessive, and the moldability may be deteriorated and the strength characteristics such as compression and bending of the obtained foamed molded article may be deteriorated. A more preferable foaming agent content is in the range of 7.5 to 18 parts by mass.

  Furthermore, you may use the foaming auxiliary agent which can pre-expand foamable resin particles more uniformly. Examples of the foaming aid include solvents such as toluene, xylene, cyclohexane, and d-limonene, and plasticizers (high-boiling solvents) such as diisobutyl adipate, glycerin, diacetylated monolaurate, and palm oil.

<Method for producing expandable resin particles>
The production method of the expandable resin particles is not particularly limited, and any known method can be used.
For example, a V-type, C-type or DC-type rotary mixer, in which resin particles are placed in a sealed pressure-resistant container and flowed, and then a foaming agent is introduced to impregnate the resin particles with the foaming agent;
Examples include a method of suspending resin particles in an aqueous medium in an airtight pressure vessel equipped with a stirrer, then introducing a foaming agent, and impregnating the resin particles with the foaming agent (impregnation step). Moreover, it is preferable to impregnate a volatile foaming agent for about 0.5 to 6 hours in 50 degreeC-140 degreeC atmosphere. Further, the impregnation may be performed under atmospheric pressure or under pressure as long as a desired foamed molded article or the like can be obtained.

<Method for producing pre-expanded particles>
Pre-expanded particles mean resin particles obtained by heating and foaming expandable resin particles to a predetermined bulk magnification. The pre-expanded particles of the present invention can be produced using a known pre-expand method. As an example of the pre-foaming method, the pre-foamed particles can be obtained by heating the foamable resin particles using a heating medium such as water vapor and pre-foaming to a predetermined bulk density.

  In the present invention, when a seed polymerization method is used as a method for producing resin particles, the obtained resin particles tend to be substantially spherical. In this case, the expandable resin particles and the pre-expanded particles obtained from the resin particles are also preferably substantially spherical. On the other hand, when deformed resin particles such as a columnar shape are used as the resin particles, expandable resin particles and pre-expanded particles obtained from these resin particles are also likely to be deformed. In this case, if L is the long diameter (mm) of the pre-expanded particles and D is the short diameter (mm) of the pre-expanded particles, the L / D value becomes a larger value, and as a result, the angle of repose becomes large and the pre-expanded The fluidity of the conductive resin particles may deteriorate.

Also, pre-expanded particles
In the aqueous suspension containing the dispersant, in the presence of 0.001 to 0.05 parts by mass of a surfactant with respect to 100 parts by mass of the aqueous medium, the polyolefin resin seed particles and the first styrene monomer Step A for dispersing the monomer and the first polymerization initiator;
Heating the obtained dispersion to a temperature at which the first styrenic monomer is not substantially polymerized to impregnate the seed particles with the first styrenic monomer; and
The step of obtaining the first particles by performing the first polymerization of the first styrene monomer at a temperature of (T-10) ° C. to (T + 20) ° C. when the melting point of the polyolefin resin is T ° C. C
Subsequent to Step C, the second particles are further added with a second styrene monomer and a temperature of (T-25) ° C. to (T + 10) ° C. Impregnation of the second styrenic monomer and the seed polymerization step through the second polymerization to obtain resin particles D (however, the amount of polyolefin resin and the first styrenic monomer) The total amount of the second styrenic monomer is 100: 100 to 400 (mass ratio));
An impregnation step of obtaining expandable resin particles by impregnating resin particles with a foaming agent;
A pre-foaming step for pre-foaming the expandable resin particles; and when the pre-foamed expandable resin particles are obtained by a production method including an aging step of standing at a temperature of room temperature or higher for 12 hours or longer It is preferable because excellent pre-expanded particles can be easily obtained.

  As an example of the pre-foaming step, pre-foamed particles can be obtained by filling expandable resin particles in a known pre-foaming machine and heating to a predetermined bulk factor. Steam is preferably used as the heating medium for heating. In addition, the temperature, pressure, process time, and the like of the pre-foaming process are appropriately set as long as excellent fluidity of the pre-foamed particles can be secured.

  In the aging step of the present invention, the temperature is preferably room temperature or higher, more preferably 10 to 50 ° C, still more preferably 10 to 40 ° C, and preferably 12 hours or more, more preferably 24. The pre-expanded particles are allowed to stand for more than an hour and are aged. When the pre-expanded particles are allowed to stand and age within the above temperature and time ranges, the surface adhering moisture content of the pre-expanded particles can be suitably set. In this case, the fluidity of the pre-expanded particles can be further improved, and a foamed molded product with better surface properties can be obtained.

  In the present invention, the pre-expanded particles obtained after the aging step are further preferably at 50 to 90 ° C., more preferably at a temperature of 50 to 70 ° C., and preferably 12 hours or more, more preferably 24 Pre-expanded particles can be left and aged for longer than the time. In this case, the fluidity of the pre-expanded particles can be further improved, and a foamed molded article with even better surface properties can be obtained.

  In addition, the aging step may be performed under atmospheric pressure or under pressure as long as a desired foamed molded article can be obtained.

<Pre-expanded particles>
In the present invention, the pre-expanded particles mean expanded particles obtained by pre-expanding expandable resin particles for producing a foam molded article. The pre-expanded particles of the present invention can be used in any foam molding method, and can also be used as pre-expanded particles for in-mold foam molding.

Since the pre-expanded particles of the present invention are substantially spherical, the following formula (1):
1.0 ≦ L / D ≦ 1.5 (1)
(In the formula, L is the major axis (mm) of the pre-expanded particles, and D is the minor axis (mm) of the pre-expanded particles)
And preferably the following formula (5):
1.0 ≦ L / D ≦ 1.4 (5)
More preferably, the following formula (6):
1.0 ≦ L / D ≦ 1.3 (6)
Meet.

  For this reason, the pre-expanded particles of the present invention have an angle of repose of 0 to 22 degrees, preferably 0 to 20 degrees, more preferably 0 to 18 degrees. The angle of repose means that the pre-expanded particles of the present invention have extremely high fluidity. As a result, the use of the pre-expanded particles of the present invention greatly improves the filling properties of the pre-expanded particles into the foam molding machine. be able to. The angle of repose of 0 degrees means a state where the pre-expanded particles are substantially liquefied without having a substantial angle.

  In the present invention, since the fluidity of the pre-expanded particles can be more easily ensured, the pre-expanded particles preferably have a major axis of 2.0 to 7.0 mm, more preferably 2.0 to 6.5 mm. Preferably it has a minor axis of 2.0 to 6.5 mm, more preferably 2.0 to 6.0 mm.

  Further, when the pre-expanded particles have a surface adhering moisture content of preferably 0 to 6.8% by mass, more preferably 0 to 6.0% by mass, based on the mass of the pre-expanded particles, Aggregation through moisture can be suppressed. As a result, the pre-expanded particles can have higher fluidity.

  Furthermore, when the pre-expanded particles preferably have a bulk expansion ratio of 20 to 60 times, more preferably 25 to 55 times, and even more preferably 30 to 50 times, the pre-expanded particles have a bulk specific gravity suitable for fluidity. It becomes. As a result, also in this case, the pre-expanded particles can have higher fluidity. On the other hand, when the bulk foaming ratio is larger than 60 times, the strength of the obtained foamed molded product may be lowered. On the other hand, if it is smaller than 20 times, the weight of the obtained foamed molded product may increase. In the present invention, the bulk expansion ratio of the pre-expanded particles means the bulk expansion ratio of the pre-expanded particles measured after completion of the aging step.

On the other hand, the pre-expanded particles have the following formula (2):
Y ≦ 0.13X−1.0 (2)
(In the formula, X is the bulk foaming ratio (times) of the pre-foamed particles, and Y is the surface adhering moisture content (mass%) of the pre-foamed particles)
When satisfy | filling, the pre-expanded particle | grains can have still higher fluidity | liquidity by aiming at harmony with a bulk foaming ratio and a surface adhesion moisture rate.

  On the other hand, pre-expanded particles satisfying Y> 0.13X-1.0 have a large angle of repose and may cause poor filling. Moreover, since the surface adhering moisture content in a suitable range of the pre-expanded particles depends on the bulk expansion ratio, when the formula (2) is satisfied, the pre-expanded particles having excellent desired fluidity can be obtained.

  On the other hand, since suitable flame retardance can be imparted to the pre-expanded particles, the foamed molded article, etc., the resin particles preferably include a flame retardant, and more preferably include a flame retardant and a flame retardant aid. Moreover, since suitable flame retardance can be ensured, the pre-expanded particles are preferably 0.15 to 8 parts by mass, more preferably 0.2 to 4 parts by mass with respect to 100 parts by mass of the resin component. Contains flame retardant. Similarly, the pre-expanded particles preferably contain 0 to 4 parts by mass, more preferably 0 to 2 parts by mass of a flame retardant aid with respect to 100 parts by mass of the resin component. In addition, as long as a desired physical property can be obtained, the pre-expanded particles may optionally contain a flame retardant aid.

  Flame retardants include tris (2,3-dibromopropyl) isocyanurate, tetrabromocyclooctane, hexabromocyclododecane, decabromodiphenyl ether, tribromophenyl allyl ether, tetrabromobisphenol A diallyl ether, tetrabromobisphenol A dipropyl Brominated flame retardants such as ether, tetrabromobisphenol A diglycidyl ether, tetrabromobisphenol A di (hydroxyethyl) ether, tetrabromobisphenol A bis (2,3-dibromopropyl ether), chlorinated paraffin, triphenyl chloride, chloride Chlorine flame retardants such as diphenyl and perchlorpentacyclodecane, and chlorine odors such as 1,2-dibromo-3-chloropropane and 2-chloro-1,2,3,4-tetrabromobutane Containing flame retardants and the like. Only one type of flame retardant may be used, or multiple types of flame retardants may be used in combination. When used in combination of plural kinds, it is preferable that tris (2,3-dibromopropyl) isocyanurate is a main component (for example, 50% by mass or more).

  Examples of the flame retardant aid include 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide, cumene hydroperoxide, and the like. Only one flame retardant aid may be used, or a plurality of flame retardant aids may be used in combination. When using in combination of two or more kinds, it is preferable that 2,3-dimethyl-2,3-diphenylbutane is a main component (for example, 50 mass% or more).

  The average particle diameter of the pre-expanded particles is preferably 6.5 mm or less, and more preferably 6.0 mm or less. When the average particle diameter is larger than 6.5 mm, the filling property of the pre-expanded particles in the foam molding machine may be lowered, and the strength of the obtained foam molded product may be lowered.

  Since the pre-expanded particles of the present invention are excellent in fluidity, it is preferably 1.0 or less between the bulk expansion ratio (P) of the pre-expanded particles and the bulk expansion ratio (Q) of the foam molded product obtained after foam molding. Ratio (Q / P). When Q / P is higher than 1.0, poor filling of the pre-foamed particles may be caused due to insufficient fluidity of the pre-foamed particles. In this case, a defect occurs in the foamed molded product, and the weight of the obtained foamed molded product is reduced. As a result, the bulk foaming ratio of the foamed molded product is larger than the bulk foaming ratio of the pre-expanded particles used.

<Foamed molded product>
The foamed molded product of the present invention can be produced using a known foam molding method. For example, pre-expanded particles are filled in a mold and heated again. Next, the pre-foamed particles are foamed in-mold, the particles are thermally fused together, and cooled to obtain a foamed molded product. As the heating medium, water vapor having a gauge pressure of 0.05 to 0.45 MPa is preferably used, and the time for introducing water vapor is preferably 10 to 180 seconds.

  Further, when the foamed molded article preferably has a bulk foaming ratio of 20 to 60 times, more preferably 25 to 55 times, a desired bulk specific gravity can be obtained and desired physical properties such as impact resistance can be obtained. it can.

  The foamed molded article of the present invention has a suitable bulk foaming ratio and excellent surface properties. For this reason, the foaming molding obtained by this invention can be used conveniently as a cushioning material for packaging, a structural member for motor vehicles, etc.

  EXAMPLES Hereinafter, although an Example is given and this invention is further demonstrated, this invention is not limited by these Examples. Various measurement methods and production conditions described in the examples will be described below.

<Long diameter and short diameter and long diameter / short diameter (L / D) of pre-expanded particles and resin particles>
The ratio of the major axis to the minor axis of the particles (major axis / minor axis (L / D)) is 20 particles randomly selected at 10 to 1000 times using a scanning electron microscope JSM-6360LV (manufactured by JEOL Ltd.). Is the value obtained by measuring the major axis and minor axis of each particle, further determining the ratio, and averaging them.

<Repose angle of pre-expanded particles>
The angle of repose of the pre-expanded particles is measured by an injection method according to JIS R 9301-2-2. Specifically, the upper part is a cylindrical shape with a diameter of 300 mm, the lower part is a nozzle with a diameter of 40 mm and an opening / closing stopper is located near the center of the nozzle, and the funnel is connected to the upper cylinder and the lower nozzle by a conical object with a height of 160 mm. Put 2L of pre-expanded particles to be measured, and set a disk-shaped base with a diameter of 15cm and a height of 7cm 10cm below the lower end of the lower nozzle. Then, open the nozzle and drop all the pre-foamed particles. The height of the pre-expanded particles deposited on the surface is measured, and the angle of repose (°) of the deposited pre-expanded particles is calculated from the relationship between the diameter of the disk-shaped platform and the height of the deposited expanded particles.

<Bulk expansion ratio of pre-expanded particles>
About 5 g of sample weight (a) is weighed to the second decimal place. Next, the sample weighed is placed in a 500 cm ³ graduated cylinder with a minimum scale unit of 5 cm ³ , and this is a round resin plate slightly smaller than the caliber of the graduated cylinder. Apply a pressing tool fixed upright with a rod-shaped resin plate of about 30 cm to make the boundary surface uniform, read the volume (b) of the sample, and calculate the bulk density (g / g) of the sample by the formula (a) / (b) cm ³ ). The bulk foaming ratio (times) is the reciprocal of the bulk density, that is, the formula (b) / (a).

<Moisture adhering to the surface of pre-expanded particles>
First, the total moisture content of the pre-expanded particles, that is, the total amount of the internal moisture content and the surface adhesion moisture content is measured. In the method, the pre-expanded particles are put into a 500 cm ³ graduated cylinder, adjusted so that the volume becomes 500 cm ^3, and then the weight (W1) is measured. Subsequently, the pre-expanded particles were placed in a hot air circulating dryer at 60 ° C. for 168 hours and then taken out. The weight (W2) was measured by the same method as described above, and the total water content (W1- W2) is calculated.
Next, the internal moisture content of the pre-expanded particles is measured. In the method, 5 g of pre-foamed particles are immersed in 200 ml of methanol and stirred for about 1 minute to remove the adhering moisture on the surface. Thereafter, the particles and methanol are separated by a vacuum filtration device and air-dried for 5 minutes. 0.5 g of the obtained particles are precisely weighed and measured by a Karl Fischer method at a heating temperature of 150 ° C. using a trace moisture measuring device (AQ-2100 manufactured by Hiranuma Sangyo Co., Ltd.). A value obtained by subtracting the internal moisture content from the measured total moisture content is defined as a surface adhesion moisture content (W3).
Further, the surface adhering moisture content (H) of the pre-expanded particles is calculated by the following formula.
H (mass%) = W3 / W1 × 100

<Average particle diameter of pre-expanded particles>
About 50 g of the sample was sieved using a low-tap type sieve shaker (manufactured by Iida Seisakusho Co., Ltd.) with a sieve opening of 8.00 mm, an opening of 6.70 mm, an opening of 5.60 mm, an opening of 4.75 mm, and an opening of 4 0.000, Aperture 3.35 mm, Aperture 2.80 mm, Aperture 2.36 mm, Aperture 2.00 mm, Aperture 1.70 mm, Aperture 1.40 mm, Aperture 1.18 mm, Aperture 1.00 mm , Classifying with a standard sieve having an opening of 0.85 mm, an opening of 0.71 mm, an opening of 0.60 mm, and an opening of 0.50 mm, and measuring the sample weight on the sieve screen, and the cumulative result obtained from the results Based on the weight distribution curve, the particle diameter (median diameter) at which the cumulative weight is 50% is determined as the average particle diameter.

<Fillability of pre-expanded particles>
The ratio (Q / P) between the bulk foaming ratio (P) of the pre-foamed particles and the bulk foaming ratio (Q) of the foamed molded product obtained after foam molding is calculated.
In the present invention,
(1) Q / P ≦ 1.0 (good filling)
(2) Q / P> 1.0 ... × (poor filling)
Is determined.

<Bulk foaming ratio of foam molded article>
The bulk density of the foam-molded product was determined by measuring the apparent volume (cm ³ ) (c) and weight (g) (d) of the foam-molded product obtained after foam molding, and using the formula (d) / (c) The bulk density (g / cm ³ ) of the foamed molded product is determined. If the shrinkage after molding is not taken into account, the apparent volume of the foam molded body is equal to the volume in the mold cavity at the time when the foam molded body is obtained, and can be calculated from the dimensions of the mold drawing. The bulk foaming ratio is the reciprocal of the bulk density, that is, the formula (c) / (d).

Example 1
(Production process of polypropylene resin particles)
Supply 50 kg of polypropylene resin (manufactured by Prime Polymer Co., Ltd., trade name “F-744NP”, melting point: 140 ° C., propylene unit: 96 mass%) to an extruder, melt knead, and granulate pellets by hot cut. Thus, substantially spherical (egg-like) polypropylene resin particles were obtained. The polypropylene resin particles had a weight of 50 mg per 100 grains and an average particle diameter of about 1 mm.

(Production process of resin particles (seed polymerization process))
Next, 800 g of the polypropylene resin particles were placed in a 5 L autoclave with a stirrer, and 2 kg of pure water, 20 g of magnesium pyrophosphate, and 0.5 g of sodium dodecylbenzenesulfonate were added as an aqueous medium. The contents were suspended in an aqueous medium by stirring, held for 10 minutes, and then heated to 60 ° C. to obtain an aqueous suspension. Next, 350 g of a styrene monomer in which 0.7 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the mixture was held for 30 minutes to allow the polypropylene resin particles to absorb the styrene monomer. Next, the temperature of the reaction system is raised to 140 ° C., which is the same as the melting point of the polypropylene resin particles, and is maintained for 2 hours, and the styrene monomer is polymerized in the polypropylene resin particles (first polymerization) to obtain the first. Obtained particles. Next, the reaction liquid for the first polymerization was set to 120 ° C., which is 20 ° C. lower than the melting point of the polypropylene resin particles. Thereafter, 1.5 g of sodium dodecylbenzenesulfonate was added to the suspension, and then 850 g of a styrene monomer in which 3.6 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise over 4 hours. Polymerization (second polymerization) was carried out while absorbing the particles in one particle. After completion of dropping, the mixture was held at 120 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization, thereby obtaining resin particles. Thereafter, the temperature of the reaction system was set to 60 ° C., and 20 g of tris (2,3-dibromopropyl) isocyanurate (manufactured by Nippon Kasei Co., Ltd.) as a flame retardant and 2,3 as a flame retardant aid were added to this suspension. -10 g of dimethyl-2,3-diphenylbutane (manufactured by Kayaku Akzo) was added. After the addition, the temperature of the reaction system was raised to 130 ° C. and stirring was continued for 2 hours to obtain flame retardant-containing resin particles (major axis 1.35 mm, minor axis 1.34 mm, major axis / minor axis 1.01). .

(Process for producing expandable resin particles (impregnation process))
Next, it was cooled to room temperature, and the flame retardant-containing resin particles were taken out from the 5 L autoclave. 2 kg of the flame retardant-containing resin particles after removal and 2 L of water were again put into a 5 L autoclave with a stirrer, and 300 g of butane (isobutane: normal butane = 3: 7, mass ratio) as a blowing agent was injected into the 5 L autoclave with a stirrer. . After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out the foamable resin particle from the 5L autoclave, and made it dehydrated and dried.

(Pre-foamed particle production process (pre-foaming process and aging process))
Next, 1000 g of the obtained expandable resin particles was put into a PSX40 pre-foaming machine manufactured by Kasahara Kogyo Co., Ltd., and steam with a gauge pressure of 0.04 MPa was introduced into the PSX40 pre-foaming machine and heated, and the bulk foaming ratio was about 30 times. And pre-foamed particles were obtained. The average particle diameter of the obtained pre-expanded particles was 3.61 mm. Using the obtained pre-expanded particles, bulk expansion ratio, major axis (L), minor axis (D), (L / D), and the like were measured.
Further, the pre-expanded particles were allowed to stand at room temperature for 24 hours and then left in a hot air circulation dryer at 60 ° C. for 48 hours to measure the surface moisture content, the angle of repose, and the like.

(Manufacturing process of foamed molded product)
The pre-expanded particles were filled into a cavity having a size of 400 mm × 300 mm × 30 mm, and steam having a gauge pressure of 0.25 MPa was introduced into a mold including the cavity for 50 seconds and heated. After the introduction of water vapor, the foamed molded body was cooled until the maximum surface pressure was reduced to 0.001 MPa to obtain a foamed molded body, and the bulk foaming ratio and the filling property were evaluated. The results are shown in Table 1.

Example 2
In the same manner as in Example 1, flame retardant-containing resin particles (major axis 1.36 mm, minor axis 1.31 mm, major axis / minor axis 1.04) were obtained. 2 kg of the flame retardant-containing resin particles and 2 L of water were again charged into a 5 L autoclave with a stirrer, and 300 g of butane (isobutane: normal butane = 3: 7, mass ratio) as a blowing agent was injected into the 5 L autoclave with a stirrer. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out the foamable resin particle from the 5L autoclave, and made it dehydrated and dried.
Next, 1000 g of the obtained expandable resin particles was put into a PSX40 pre-foaming machine manufactured by Kasahara Kogyo Co., Ltd., and steam with a gauge pressure of 0.04 MPa was introduced into the PSX40 pre-foaming machine and heated, and the bulk foaming ratio was about 30 times. And pre-foamed particles were obtained. The average particle diameter of the obtained pre-expanded particles was 3.22 mm. Using the obtained pre-expanded particles, bulk expansion ratio, major axis (L), minor axis (D), (L / D), and the like were measured. Thereafter, the pre-expanded particles were allowed to stand at room temperature for 24 hours, and the moisture content on the surface, the angle of repose, etc. were measured. A foam molded article was obtained in the same manner as in Example 1 except that foam molding was performed using the pre-expanded particles.

Example 3
In the same manner as in Example 1, flame retardant-containing resin particles (major axis 1.38 mm, minor axis 1.38 mm, major axis / minor axis 1.00) were obtained. 2 kg of the flame retardant-containing resin particles and 2 L of water were again charged into a 5 L autoclave with a stirrer, and 300 g of butane (isobutane: normal butane = 3: 7, mass ratio) as a blowing agent was injected into the 5 L autoclave with a stirrer. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out the foamable resin particle from the 5L autoclave, and made it dehydrated and dried.
Next, 1000 g of the obtained expandable resin particles was put into a PSX40 pre-foaming machine manufactured by Kasahara Kogyo Co., Ltd., and steam with a gauge pressure of 0.04 MPa was introduced into the PSX40 pre-foaming machine and heated to a bulk foaming factor of about 55 times. And pre-foamed particles were obtained. The average particle diameter of the obtained pre-expanded particles was 6.05 mm. Using the obtained pre-expanded particles, bulk expansion ratio, major axis (L), minor axis (D), (L / D), and the like were measured. Further, the pre-expanded particles were allowed to stand at room temperature for 24 hours and then left in a hot air circulation dryer at 60 ° C. for 48 hours to measure the surface moisture content, the angle of repose, and the like. Then, it carried out similarly to Example 1, and obtained the foaming molding.

Example 4
In the same manner as in Example 1, flame retardant-containing resin particles (major axis 1.41 mm, minor axis 1.35 mm, major axis / minor axis 1.04) were obtained. 2 kg of the flame retardant-containing resin particles and 2 L of water were again charged into a 5 L autoclave with a stirrer, and 300 g of butane (isobutane: normal butane = 3: 7, mass ratio) as a blowing agent was injected into the 5 L autoclave with a stirrer. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out the foamable resin particle from the 5L autoclave, and made it dehydrated and dried.
Next, 1000 g of the obtained expandable resin particles was put into a PSX40 pre-foaming machine manufactured by Kasahara Kogyo Co., Ltd., and steam with a gauge pressure of 0.04 MPa was introduced into the PSX40 pre-foaming machine and heated to a bulk foaming factor of about 55 times. And pre-foamed particles were obtained. The average particle diameter of the obtained pre-expanded particles was 5.42 mm. Using the obtained pre-expanded particles, bulk expansion ratio, major axis (L), minor axis (D), (L / D), and the like were measured. Thereafter, the pre-expanded particles were allowed to stand at room temperature for 24 hours, and the moisture content on the surface, the angle of repose, etc. were measured. A foam molded article was obtained in the same manner as in Example 1 except that foam molding was performed using the pre-expanded particles.

Example 5
800 g of polypropylene resin particles obtained in the same manner as in Example 1 was placed in a 5 L autoclave with a stirrer, and 2 kg of pure water, 20 g of magnesium pyrophosphate, and 1.0 g of sodium dodecylbenzenesulfonate were added as an aqueous medium. The contents were suspended in an aqueous medium by stirring, held for 10 minutes, and then heated to 60 ° C. to obtain an aqueous suspension. Next, 350 g of a styrene monomer in which 0.7 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the mixture was held for 30 minutes to allow the polypropylene resin particles to absorb the styrene monomer. Next, the temperature of the reaction system is raised to 140 ° C., which is the same as the melting point of the polypropylene resin particles, and is maintained for 2 hours, and the styrene monomer is polymerized in the polypropylene resin particles (first polymerization) to obtain the first. Obtained particles. Next, the reaction liquid for the first polymerization was set to 120 ° C., which is 20 ° C. lower than the melting point of the polypropylene resin particles. Thereafter, 1.5 g of sodium dodecylbenzenesulfonate was added to the suspension, and then 850 g of a styrene monomer in which 3.6 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise over 4 hours. Polymerization (second polymerization) was carried out while absorbing the particles in one particle. After completion of dropping, the mixture was held at 120 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization, thereby obtaining resin particles. Thereafter, the temperature of the reaction system was set to 60 ° C., and 20 g of tris (2,3-dibromopropyl) isocyanurate (manufactured by Nippon Kasei Co., Ltd.) as a flame retardant and 2,3 as a flame retardant aid were added to this suspension. -10 g of dimethyl-2,3-diphenylbutane (manufactured by Kayaku Akzo) was added. After the addition, the temperature of the reaction system was raised to 130 ° C. and the stirring was continued for 2 hours to obtain flame retardant-containing resin particles (major axis 1.76 mm, minor axis 1.16 mm, major axis / minor axis 1.52). . Next, it was cooled to room temperature, and the flame retardant-containing resin particles were taken out from the 5 L autoclave. 2 kg of the flame retardant-containing resin particles after removal and 2 L of water were again put into a 5 L autoclave with a stirrer, and 300 g of butane (isobutane: normal butane = 3: 7, mass ratio) as a blowing agent was injected into the 5 L autoclave with a stirrer. . After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out the foamable resin particle from the 5L autoclave, and made it dehydrated and dried.
Next, 1000 g of the obtained expandable resin particles was put into a PSX40 pre-foaming machine manufactured by Kasahara Kogyo Co., Ltd., and steam with a gauge pressure of 0.04 MPa was introduced into the PSX40 pre-foaming machine and heated to a bulk foaming factor of about 55 times. And pre-foamed particles were obtained. The average particle diameter of the obtained pre-expanded particles was 5.39 mm. Using the obtained pre-expanded particles, bulk expansion ratio, major axis (L), minor axis (D), (L / D), and the like were measured. Further, the pre-expanded particles were allowed to stand at room temperature for 24 hours and then left in a hot air circulation dryer at 60 ° C. for 48 hours to measure the surface moisture content, the angle of repose, and the like. Then, it carried out similarly to Example 1, and obtained the foaming molding.

Example 6
1000 g of polypropylene resin particles obtained in the same manner as in Example 1 was placed in a 5 L autoclave with a stirrer, and 2 kg of pure water, 20 g of magnesium pyrophosphate, and 0.5 g of sodium dodecylbenzenesulfonate were added as an aqueous medium. The contents were stirred and suspended in an aqueous medium, held for 10 minutes, and then heated to 60 ° C. to obtain an aqueous suspension. Next, 400 g of styrene monomer in which 0.8 g of dicumyl peroxide was dissolved was dropped into this suspension over 30 minutes. After dropping, the mixture was held for 30 minutes to allow the polypropylene resin particles to absorb the styrene monomer. Next, the temperature of the reaction system is raised to 140 ° C., which is the same as the melting point of the polypropylene resin particles, and is maintained for 2 hours, and the styrene monomer is polymerized in the polypropylene resin particles (first polymerization) to obtain the first. Obtained particles. Next, the reaction liquid for the first polymerization was set to 120 ° C., which is 20 ° C. lower than the melting point of the polypropylene resin particles. Thereafter, 1.5 g of sodium dodecylbenzenesulfonate is added to the suspension, and then 600 g of a styrene monomer in which 3 g of dicumyl peroxide is dissolved is added dropwise over 3 hours to be absorbed by the polypropylene resin particles. The polymerization (second polymerization) was carried out. After completion of dropping, the mixture was held at 120 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization, thereby obtaining resin particles. Thereafter, the temperature of the reaction system was set to 60 ° C., and 20 g of tris (2,3-dibromopropyl) isocyanurate (manufactured by Nippon Kasei Co., Ltd.) as a flame retardant and 2,3 as a flame retardant aid were added to this suspension. -10 g of dimethyl-2,3-diphenylbutane (manufactured by Kayaku Akzo) was added. After the addition, the temperature of the reaction system was raised to 130 ° C. and the stirring was continued for 2 hours to obtain flame retardant-containing resin particles (major axis 1.35 mm, minor axis 1.33 mm, major axis / minor axis 1.02). . Next, it was cooled to room temperature, and the flame retardant-containing resin particles were taken out from the 5 L autoclave. 2 kg of the flame retardant-containing resin particles after removal and 2 L of water were again put into a 5 L autoclave with a stirrer, and 300 g of butane (isobutane: normal butane = 3: 7, mass ratio) as a blowing agent was injected into the 5 L autoclave with a stirrer. . After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out the foamable resin particle from the 5L autoclave, and made it dehydrated and dried.
Next, 1000 g of the obtained expandable resin particles was put into a PSX40 pre-foaming machine manufactured by Kasahara Kogyo Co., Ltd., and steam with a gauge pressure of 0.04 MPa was introduced into the PSX40 pre-foaming machine and heated, and the bulk foaming ratio was about 30 times. And pre-foamed particles were obtained. The average particle diameter of the obtained pre-expanded particles was 3.91 mm. Using the obtained pre-expanded particles, bulk expansion ratio, major axis (L), minor axis (D), (L / D), and the like were measured. Thereafter, the pre-expanded particles were allowed to stand at room temperature for 24 hours, and the moisture content on the surface, the angle of repose, etc. were measured. A foam molded article was obtained in the same manner as in Example 1 except that foam molding was performed using the pre-expanded particles.

Example 7
400 g of the polypropylene resin particles obtained in the same manner as in Example 1 was placed in a 5 L autoclave equipped with a stirrer, and 2 kg of pure water, 20 g of magnesium pyrophosphate and 0.5 g of sodium dodecylbenzenesulfonate were added as an aqueous medium and stirred to obtain an aqueous medium. The suspension was suspended for 10 minutes and then heated to 60 ° C. to obtain an aqueous suspension. Next, 200 g of a styrene monomer in which 0.4 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the mixture was held for 30 minutes to allow the polypropylene resin particles to absorb the styrene monomer. Next, the temperature of the reaction system is raised to 140 ° C., which is the same as the melting point of the polypropylene resin particles, and is maintained for 2 hours, and the styrene monomer is polymerized in the polypropylene resin particles (first polymerization) to obtain the first. Obtained particles. Next, the reaction liquid for the first polymerization was set to 120 ° C., which is 20 ° C. lower than the melting point of the polypropylene resin particles. Thereafter, 1.5 g of sodium dodecylbenzenesulfonate was added to the suspension, and 1400 g of a styrene monomer in which 4.8 g of dicumyl peroxide was dissolved was dropped over 6.5 hours. Polymerization (second polymerization) was performed while absorbing the particles. After completion of dropping, the mixture was held at 120 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization, thereby obtaining resin particles. Thereafter, the temperature of the reaction system was set to 60 ° C., and 20 g of tris (2,3-dibromopropyl) isocyanurate (manufactured by Nippon Kasei Co., Ltd.) as a flame retardant and 2,3 as a flame retardant aid were added to this suspension. -10 g of dimethyl-2,3-diphenylbutane (manufactured by Kayaku Akzo) was added. After the addition, the temperature of the reaction system was raised to 130 ° C. and stirring was continued for 2 hours to obtain flame retardant-containing resin particles (major axis 1.58 mm, minor axis 1.53 mm, major axis / minor axis 1.03). . Next, it was cooled to room temperature, and the flame retardant-containing resin particles were taken out from the 5 L autoclave. 2 kg of the flame retardant-containing resin particles after removal and 2 L of water were again put into a 5 L autoclave with a stirrer, and 300 g of butane (isobutane: normal butane = 3: 7, mass ratio) as a blowing agent was injected into the 5 L autoclave with a stirrer. . After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out the foamable resin particle from the 5L autoclave, and made it dehydrated and dried.
Next, 1000 g of the obtained expandable resin particles was put into a PSX40 pre-foaming machine manufactured by Kasahara Kogyo Co., Ltd., and steam with a gauge pressure of 0.04 MPa was introduced into the PSX40 pre-foaming machine and heated to a bulk foaming ratio of about 60 times. And pre-foamed particles were obtained. The average particle diameter of the obtained pre-expanded particles was 6.04 mm. Using the obtained pre-expanded particles, bulk expansion ratio, major axis (L), minor axis (D), (L / D), and the like were measured. Thereafter, the pre-expanded particles were allowed to stand at room temperature for 24 hours, and the moisture content on the surface, the angle of repose, etc. were measured. A foam molded article was obtained in the same manner as in Example 1 except that foam molding was performed using the pre-expanded particles.

Comparative Example 1
In the same manner as in Example 1, flame retardant-containing resin particles (major axis 1.35 mm, minor axis 1.33 mm, major axis / minor axis 1.02) were obtained. 2 kg of the flame retardant-containing resin particles and 2 L of water were again charged into a 5 L autoclave with a stirrer, and 300 g of butane (isobutane: normal butane = 3: 7, mass ratio) as a blowing agent was injected into the 5 L autoclave with a stirrer. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out the foamable resin particle from the 5L autoclave, and made it dehydrated and dried.
Next, 1000 g of the obtained expandable resin particles was put into a PSX40 pre-foaming machine manufactured by Kasahara Kogyo Co., Ltd., and steam with a gauge pressure of 0.04 MPa was introduced into the PSX40 pre-foaming machine and heated, and the bulk foaming ratio was about 30 times. And pre-foamed particles were obtained. The average particle diameter of the obtained pre-expanded particles was 3.10 mm. Using the obtained pre-expanded particles, bulk expansion ratio, major axis (L), minor axis (D), (L / D), and the like were measured. Thereafter, the pre-expanded particles were allowed to stand at room temperature for 6 hours, and then the surface adhering moisture content and the angle of repose were measured. A foam molded article was obtained in the same manner as in Example 1 except that foam molding was performed using the pre-expanded particles.

Comparative Example 2
In the same manner as in Example 1, flame retardant-containing resin particles (major axis 1.37 mm, minor axis 1.37 mm, major axis / minor axis 1.00) were obtained. 2 kg of the flame retardant-containing resin particles and 2 L of water were again charged into a 5 L autoclave with a stirrer, and 300 g of butane (isobutane: normal butane = 3: 7, mass ratio) as a blowing agent was injected into the 5 L autoclave with a stirrer. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out the foamable resin particle from the 5L autoclave, and made it dehydrated and dried.
Next, 1000 g of the obtained expandable resin particles was put into a PSX40 pre-foaming machine manufactured by Kasahara Kogyo Co., Ltd., and steam with a gauge pressure of 0.04 MPa was introduced into the PSX40 pre-foaming machine and heated to a bulk foaming factor of about 55 times. And pre-foamed particles were obtained. The average particle diameter of the obtained pre-expanded particles was 5.53 mm. Using the obtained pre-expanded particles, bulk expansion ratio, major axis (L), minor axis (D), (L / D), and the like were measured. Thereafter, the pre-expanded particles were allowed to stand at room temperature for 6 hours, and then the surface adhering moisture content and the angle of repose were measured. A foam molded article was obtained in the same manner as in Example 1 except that foam molding was performed using the pre-expanded particles.

Comparative Example 3
800 g of polypropylene resin particles obtained in the same manner as in Example 1 was placed in a 5 L autoclave with a stirrer, and 2 kg of pure water, 20 g of magnesium pyrophosphate, and 2.5 g of sodium dodecylbenzenesulfonate were added as an aqueous medium. The contents were suspended in an aqueous medium by stirring, held for 10 minutes, and then heated to 60 ° C. to obtain an aqueous suspension. Next, 350 g of a styrene monomer in which 0.7 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the mixture was held for 30 minutes to allow the polypropylene resin particles to absorb the styrene monomer. Next, the temperature of the reaction system is raised to 140 ° C., which is the same as the melting point of the polypropylene resin particles, and is maintained for 2 hours, and the styrene monomer is polymerized in the polypropylene resin particles (first polymerization) to obtain the first. Obtained particles. Next, the reaction liquid for the first polymerization was set to 120 ° C., which is 20 ° C. lower than the melting point of the polypropylene resin particles. Thereafter, 1.5 g of sodium dodecylbenzenesulfonate was added to the suspension, and then 850 g of a styrene monomer in which 3.6 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise over 4 hours. Polymerization (second polymerization) was carried out while absorbing the particles in one particle. After completion of dropping, the mixture was held at 120 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization, thereby obtaining resin particles. Thereafter, the temperature of the reaction system was set to 60 ° C., and 20 g of tris (2,3-dibromopropyl) isocyanurate (manufactured by Nippon Kasei Co., Ltd.) as a flame retardant and 2,3 as a flame retardant aid were added to this suspension. -10 g of dimethyl-2,3-diphenylbutane (manufactured by Kayaku Akzo) was added. After the addition, the temperature of the reaction system was raised to 130 ° C., and stirring was continued for 2 hours to obtain flame retardant-containing resin particles (major axis 1.83 mm, minor axis 1.14 mm, major axis / minor axis 1.61). . Next, it was cooled to room temperature, and the flame retardant-containing resin particles were taken out from the 5 L autoclave. 2 kg of the flame retardant-containing resin particles after removal and 2 L of water were again put into a 5 L autoclave with a stirrer, and 300 g of butane (isobutane: normal butane = 3: 7, mass ratio) as a blowing agent was injected into the 5 L autoclave with a stirrer. . After the injection, the temperature was raised to 70 ° C. and stirring was continued for 4 hours. Then, it cooled to normal temperature, took out the foamable resin particle from the 5L autoclave, and made it dehydrated and dried.
Next, 1000 g of the obtained expandable resin particles was put into a PSX40 pre-foaming machine manufactured by Kasahara Kogyo Co., Ltd., and steam with a gauge pressure of 0.04 MPa was introduced into the PSX40 pre-foaming machine and heated, and the bulk foaming ratio was about 30 times. And pre-foamed particles were obtained. The average particle diameter of the obtained pre-expanded particles was 3.03 mm. Using the obtained pre-expanded particles, bulk expansion ratio, major axis (L), minor axis (D), (L / D), and the like were measured. Thereafter, the pre-expanded particles were allowed to stand at room temperature for 24 hours, and the moisture content on the surface, the angle of repose, etc. were measured. A foam molded article was obtained in the same manner as in Example 1 except that foam molding was performed using the pre-expanded particles.

Comparative Example 4
Expanded polypropylene resin with an expansion ratio of 30 times and an average particle diameter of 2.64 mm [(1) Random copolymer of propylene and ethylene, (2) MFR when loaded with 2.16 kg is 7.0 g / 10 min, (3) MS (Melt tension (mN) at 160 ° C.)> 90-130 × log (MFR)] was allowed to stand at room temperature for 24 hours, and surface adhering moisture content, angle of repose, etc. were measured. Using the pre-expanded particles, foam molding was performed to obtain a foam having the same shape as in Example 1.

  In Table 1, the raw material seed | species and evaluation result of an Example and a comparative example are explained in full detail.

All examples showed good filling properties, i.e. excellent flowability. On the other hand, there was a case where the above results could not be obtained for the comparative example.
Therefore, the pre-expanded particles of the present invention can be suitably used for the production of foamed molded articles such as packaging cushioning materials and automobile structural members.

Claims (8)

Following formula (1):
1.0 ≦ L / D ≦ 1.5 (1)
(In the formula, L is the major axis (mm) of the pre-expanded particles, and D is the minor axis (mm) of the pre-expanded particles)
And the following formula (2):
Y ≦ 0.13X−1.0 (2)
(In the formula, X is the bulk foaming ratio (times) of the pre-foamed particles, and Y is the surface adhering moisture content (mass%) of the pre-foamed particles)
And having an angle of repose of 0 to 22 degrees.   The pre-expanded particles according to claim 1, wherein the pre-expanded particles have a major axis of 2.0 to 7.0 mm and a minor axis of 2.0 to 6.5 mm.   The pre-expanded particles according to claim 1 or 2, wherein the pre-expanded particles have a bulk expansion ratio of 20 to 60 times.   The pre-expanded particle according to any one of claims 1 to 3, wherein the pre-expanded particle has a surface adhering moisture content of 0 to 6.8% by mass.   The pre-expanded particles according to any one of claims 1 to 4, wherein the pre-expanded particles include at least 100 parts by mass of a polyolefin resin and 100 to 400 parts by mass of a polystyrene resin as a resin component.   The pre-expanded particles according to any one of claims 1 to 5, wherein the pre-expanded particles include a flame retardant. The pre-expanded particles are
In the aqueous suspension containing the dispersant, in the presence of 0.001 to 0.05 parts by mass of a surfactant with respect to 100 parts by mass of the aqueous medium, the polyolefin resin seed particles and the first styrene monomer Step A for dispersing the monomer and the first polymerization initiator;
Heating the obtained dispersion to a temperature at which the first styrenic monomer is not substantially polymerized to impregnate the seed particles with the first styrenic monomer; and
When the melting point of the polyolefin resin is T ° C., the first polymerization of the first styrene monomer is performed at a temperature of (T−10) ° C. to (T + 20) ° C. Obtaining step C;
Subsequent to the step C, the second styrene monomer and the second polymerization initiator are further added, and the temperature is set to (T−25) ° C. to (T + 10) ° C. A seed polymerization step through the step D of impregnating the particles of the second styrene monomer and performing the second polymerization to obtain resin particles (however, the amount of the polyolefin resin and the first styrene type) The total amount of the monomer and the second styrene monomer is 100: 100 to 400 (mass ratio));
An impregnation step of obtaining expandable resin particles by impregnating the resin particles with a foaming agent;
The pre-foaming step of pre-foaming the foamable resin particles; and a aging step of leaving the foamable resin particles after pre-foaming at room temperature or higher for 12 hours or longer. Pre-expanded particles.   The foaming molding obtained from the pre-expanded particle as described in any one of Claims 1-7.