JP7262268B2 - Foamed thermoplastic resin particles for cushion, cushion body and expandable thermoplastic resin particles for cushion - Google Patents

Description

TECHNICAL FIELD The present invention relates to foamed thermoplastic resin particles for cushions, cushion bodies, and expandable thermoplastic resin particles for cushions. More particularly, the present invention relates to foamed thermoplastic resin particles for cushioning which show little change in volume even after repeated use, a cushion body in which the expanded thermoplastic resin particles are enclosed as a filler , and expandable thermoplastic resin particles for cushioning.

2. Description of the Related Art Conventionally, there has been known a cushion body in which a bag made of cloth or leather is filled with cotton, polyurethane foam, foamed resin particles, or the like as a filler.
A cushioning body using cotton as a filling material exhibits cushioning properties by compressing the cotton like a sponge and deforming it so that its volume is reduced.
In addition, in a cushion body using foamed resin particles with a relatively large particle size as a filler, the foamed resin particles are simply compressed and deformed to reduce their volume, thereby exhibiting cushioning properties and being comparable to fillers. A cushioning body using foamed resin particles having a relatively small particle diameter develops cushioning properties as the foamed resin particles flow (move) in the bag.

For example, the applicant of the present application has found that a large number of foamed resin particles having an average particle diameter of 400 to 900 μm and a value obtained by dividing a partial compressive load of 3 Nmm ³ /g or less by the apparent specific gravity are filled in a bag. (International Publication No. WO2003/032783: Patent Document 1). In Patent Document 1, foamed resin particles having a relatively small particle size are used and the foamed resin particles are impregnated with a fluidity accelerator to provide particles that are easy to slide and that the foamed resin particles flow with very little force. To provide a cushion body which has improved touch and feel and suppresses the generation of abnormal noise.

In addition, the applicant of the present application has proposed a cushion body in which foamed resin particles having a volume 1.1 to 3.5 times the internal volume of the bag body are enclosed as a filler in a stretchable bag body. (Japanese Unexamined Patent Application Publication No. 2004-223002: Patent Document 2). In Patent Document 2, expanded resin particles having an average particle diameter of 0.4 to 1.4 mm are used, and 0.4 to 1.5 parts by weight of a flow accelerator is used in combination with 100 parts by weight of expanded resin particles. As a result, the cushion body is improved in touch feeling, prevents the occurrence of abnormal noise, and achieves both comfort in sitting without a feeling of bottoming out and prevention of deformation of the cushion.

International Publication No. WO2003/032783 Japanese Patent Application Laid-Open No. 2004-223002

However, the above prior art cushion body has a problem that it is gradually compressed due to long-term load from a specific direction, causing a large change in volume, that is, so-called "settling".
In order to disperse the load, a cushion body using foamed resin particles with a relatively small particle diameter as a filler and also using a fluidity promoter also has the problem of volume change.
Thus, conventionally, in order to disperse the force (load) applied to the cushion body, it has been necessary to use foamed particles as a filling material for the cushion, further reduce the range of the particles, and add a glidant.
Accordingly, it is an object of the present invention to provide cushioning foamed thermoplastic resin particles whose volume change is small even after repeated use, a cushion body in which the foamed thermoplastic resin particles are enclosed as a filler , and foamable thermoplastic resin particles for cushioning. .

Therefore, the inventors of the present invention have made intensive studies to solve the above problems. The inventors have unexpectedly found that it is possible to provide expanded thermoplastic resin particles, a cushion body in which the expanded thermoplastic resin particles are enclosed as a filler , and expandable thermoplastic resin particles for cushioning, and have completed the present invention.

Thus, according to the present invention, the expanded particles are formed by expanding expandable thermoplastic resin particles containing a thermoplastic resin and a blowing agent,
The expanded particles have a bulk expansion ratio of 20 times or more and less than 60 times, and the expanded particles are sieved on a JIS standard sieve (JIS Z8801-1: 2000 regulation) in 20 stages with a nominal mesh size of 5.60 to 0.212 mm. When sieved using a sieve of the following conditions:
(a) all expanded particles pass through a 5.60 mm nominal sieve and do not pass through a 0.212 mm nominal sieve;
(b) the coefficient of variation (CV value) of the particle size distribution obtained from the mass fraction of particles in the size range sieved between the sieves of each adjacent stage is 4 or less; and (c) the mass fraction of the particles is Foamed thermoplastic resin particles for cushioning, characterized by having a particle size distribution satisfying a mass ratio of 5 to 45% by mass of particles in a particle size range one step smaller or one step larger than the highest particle size range. is provided.

Further, according to the present invention, there is provided a cushion body in which the foamed thermoplastic resin particles for cushioning are enclosed as a filler in a bag body.
Further, according to the present invention, there is provided expandable thermoplastic resin particles for cushioning, which are composed of particles containing a thermoplastic resin and a foaming agent and are for the above foamed thermoplastic resin particles for cushioning. be.

Further, according to the present invention, the expandable beads for manufacturing expanded beads having a bulk expansion ratio of 20 times or more and less than 60 times, containing a thermoplastic resin and a blowing agent,
The expandable particles have an average particle diameter of 0.23 to 0.92 mm, and the expandable particles are sieved through a JIS standard sieve (JIS Z8801-1: 2000) with a nominal opening of 5.60 to 0.212 mm. When sieved using a 20-stage sieve, the following conditions:
(a′) all expandable particles pass through a sieve with a nominal opening of 5.60 mm and do not pass through a sieve with a nominal opening of 0.212 mm;
(b') the coefficient of variation (CV value) of the particle size distribution determined from the mass ratio of particles in the particle size range sieved between adjacent stages of sieves is 4 or less; and (c') the mass of the particles. Foaming heat for a cushion, characterized by having a particle size distribution satisfying a mass ratio of 5 to 45% by mass of particles in a particle size range one step smaller or one step larger than the highest particle size range. A plastic resin particle is provided.

ADVANTAGE OF THE INVENTION According to this invention, the foamed thermoplastic resin particles for cushioning whose volume change is small even after repeated use, the cushioning body and the foamable thermoplastic resin particles for cushioning in which the foamed thermoplastic resin particles are encapsulated as a filler can be provided.
The foamed thermoplastic resin particles for cushions of the present invention can be suitably used for cushions such as cushions, sofas, chairs, beds, mattresses, pillows and stuffed toys.

Moreover, when at least one of the following requirements is satisfied, more excellent foamed thermoplastic resin particles for cushioning can be provided.
(1) The expanded particles have an average particle diameter of 0.5 to 2.8 mm, and the following conditions are met when the expanded particles are sieved through a JIS standard sieve:
(d) having a particle size distribution satisfying the condition that the mass ratio of particles in the particle size range with the highest mass ratio is 40 to 65% by mass;
(2) When the expanded particles are sieved through the JIS standard sieve, the following conditions are met:
(e) the mass fraction of particles in the particle size range having the highest mass fraction of particles is 65 mass % or less; It has a particle size distribution that satisfies a mass ratio of 0.1 to 10% by mass.
(3) When the expanded particles are sieved through the JIS standard sieve, the following conditions are met:
(g) the mass fraction of particles in the particle size range that is one step smaller or one step larger than the particle size range in which the mass fraction of the particles is the highest is 33 to 45% by mass; and (h) the mass fraction of the particles is It has a particle size distribution that satisfies that the mass ratio of particles in a particle size range two steps smaller or two steps larger than the highest particle size range is 0.1 to 10% by mass.

Further, when at least one of the following requirements is satisfied, it is possible to provide expandable thermoplastic resin particles for cushioning which are more excellent for producing foamed thermoplastic resin particles for cushioning.
(4) The expandable particles meet the following conditions when the expandable particles are sieved through a JIS standard sieve:
(d') having a particle size distribution satisfying the condition that the mass ratio of particles in the particle size range with the highest mass ratio is 35 to 70% by mass;
(5) When the expandable particles are sieved through a JIS standard sieve, the following conditions:
(e′) the mass fraction of particles in the particle size range with the highest mass fraction of particles is 70% by mass or less; and (f′) the particle size range one step larger than the highest mass fraction of particles It has a particle size distribution that satisfies a mass ratio of particles of 0.1 to 10% by mass.
(6) The expandable particles meet the following conditions when the expandable particles are sieved through a JIS standard sieve:
(g′) the mass ratio of particles in the particle size range that is one step smaller or one step larger than the particle size range in which the mass ratio of the particles is the highest is 28 to 32% by mass; and (h′) the mass of the particles. It has a particle size distribution that satisfies that the mass ratio of particles in the particle size range two steps smaller or two steps larger than the particle size range with the highest ratio is 3% by mass or less.

FIG. 2 is a diagram (overall diagram) showing the relationship between the particle size (mm) of 0.2 to 5.2 mm and the mass ratio x (mass %) of expanded beads of Examples 1 to 8 and Comparative Examples 1 to 3. FIG. FIG. 2 is a diagram (enlarged diagram) showing the relationship between the particle size (mm) of 0.45 to 1.95 mm and the mass ratio x (mass %) of expanded beads of Examples 1 to 8 and Comparative Examples 1 to 3. FIG.

(1) Expanded particles The thermoplastic resin expanded particles for cushioning of the present invention (hereinafter also referred to as "expanded particles") are made of expanded particles obtained by expanding expandable thermoplastic resin particles containing a thermoplastic resin and a blowing agent,
The expanded particles have a bulk expansion ratio of 20 times or more and less than 60 times, and the expanded particles are sieved on a JIS standard sieve (JIS Z8801-1: 2000 regulation) in 20 stages with a nominal mesh size of 5.60 to 0.212 mm. When sieved using a sieve of the following conditions:
(a) all expanded particles pass through a 5.60 mm nominal sieve and do not pass through a 0.212 mm nominal sieve;
(b) the coefficient of variation (CV value) of the particle size distribution obtained from the mass fraction of particles in the size range sieved between the sieves of each adjacent stage is 4 or less; and (c) the mass fraction of the particles is It is characterized by having a particle size distribution that satisfies that the mass ratio of particles in a particle size range one step smaller or one step larger than the highest particle size range is 5 to 45% by mass.
First, the particle size distribution and bulk expansion ratio, which are characteristics of the expanded beads of the present invention, will be explained, and then the constituent materials and the production method thereof will be explained.

(1-1) Particle size distribution Particle size distribution conditions (a) to (h) and the average particle size are the nominal openings of 5.60 to 0.212 mm of a JIS standard sieve (JIS Z8801-1: 2000). It is a value when sieving (classifying) using a 20-step sieve.
A specific method for measuring the particle size distribution will be described in detail in Examples.

[Condition (a)]
Condition (a) is that all the expanded particles pass through a sieve with a nominal opening of 5.60 mm and do not pass through a sieve with a nominal opening of 0.212 mm. less than 0.60 mm and greater than 0.212 mm.
If all the foamed particles contain particles that do not pass through a sieve with a nominal mesh size of 5.60 mm, the change in volume increases, and the touch and sitting comfort may deteriorate. On the other hand, if all the expanded particles include particles that pass through a sieve with a nominal opening of 0.212 mm, the volume change will increase and the filling amount will increase, which may increase the mass of the cushion.
All expanded particles preferably pass through a sieve with a nominal opening of 4.00 mm and do not pass through a sieve with a nominal opening of 0.355 mm, pass through a sieve with a nominal opening of 2.00 mm and have a nominal opening of 0.500 mm. more preferably does not pass through the sieve of
However, the expanded particles of the present invention may contain particles that do not pass through a sieve with a nominal opening of 5.60 mm and particles that pass through a sieve with a nominal opening of 0.212 mm, as long as the effects of the present invention are not impaired. .

[Condition (b)]
The condition (b) is that the coefficient of variation (CV value) of the particle size distribution obtained from the mass ratio x of the particles in the particle size range sieved between the sieves in each adjacent stage is 4 or less, and the particle size distribution is not too sharp and grains are not too uniform.
A CV value can be obtained from a standard deviation (σ) and an average value (μ) as in the following formula.
Deviation σ ² = (Σ (mass ratio x - average μ) ² )/number of sieves n
Standard deviation σ = √σ ²
Coefficient of variation CV = standard deviation σ / average μ
Note that the average value μ=100/19=5.26 and the number of sieves n=19.

If the CV value exceeds 4, the volume change may become large.
The expanded beads of the present invention have a peculiar sharp distribution as shown in condition (c), and the lower limit of the CV value is 1.5, and the range is 2.0 to 3.9. is preferred, and 2.5 to 3.5 is more preferred.

[Condition (c)]
Condition (c) is that the mass ratio of particles in the particle size range one step smaller or one step larger than the particle size range where the mass ratio of the particles is the highest is 5 to 45% by mass, and the particle size distribution It means that the mass ratio of particles in the particle size range of either one of the distributions on both sides of the peak is 5 to 45% by mass.
If the mass ratio of the particles is less than 5% by mass, the volume change may become large. On the other hand, when the mass ratio of the particles exceeds 45% by mass, the volume change may become large.
The mass ratio of the particles is preferably 19-45% by mass, more preferably 33-45% by mass.

[Average particle size]
The expanded particles of the present invention preferably have an average particle size of 0.5-2.8 mm.
The average particle size can be obtained from the mass ratio Rn (%) of particles in each particle size range obtained in the above particle size distribution measurement and each median particle size (mm), as shown in the following formula.
Average particle size = {Σ(D _n R _n )}/100
When the average particle diameter of the foamed particles is less than 0.5 mm, the volume change becomes large, and the filling amount becomes large, which may increase the mass of the cushion. On the other hand, when the average particle diameter of the expanded particles exceeds 2.8 mm, the volume change becomes large, and the touch and sitting comfort may deteriorate.
The average particle diameter of the expanded particles is preferably 0.7 to 2.1 mm, more preferably 0.8 to 1.4 mm.

[Condition (d)]
The expanded beads of the present invention meet the following conditions:
(d) It is preferable to have a particle size distribution that satisfies 40 to 65% by mass of particles in the particle size range where the mass ratio of particles is the highest.
This means that the mass proportion of particles in the particle size range of the peak of the particle size distribution is 40-65% by mass.
When the expanded particles have an average particle diameter of 0.5 to 2.8 mm and satisfy the condition (d), the effect of little change in volume, that is, little settling is obtained.
If the mass ratio of the particles in condition (d) is less than 40% by mass, the volume change may become large. On the other hand, when the mass ratio of the particles of condition (d) exceeds 65 mass %, the volume change may become large.
The mass ratio of the particles in condition (d) is preferably 45-60% by mass, more preferably 50-60% by mass.

[Conditions (e) and (f)]
The expanded beads of the present invention also meet the following conditions:
(e) the mass fraction of particles in the particle size range having the highest mass fraction of particles is 65 mass % or less; It preferably has a particle size distribution that satisfies a mass ratio of 0.1 to 10% by mass.
When the expanded beads satisfy the conditions (e) and (f), an effect of little change in volume, that is, little settling is obtained.
The condition (e) means that the mass ratio of particles in the particle size range of the peak of the particle size distribution is 65% by mass or less, and the condition (f) is the particle size on the side where the particle size of the peak of the particle size distribution is larger. It means that the mass fraction of the particles in the range is 0.1-10% by mass.
If the mass ratio of the particles in condition (e) exceeds 65 mass %, the volume change may become large.
The expanded particles of the present invention have a peculiar sharp distribution as shown in condition (e), and the lower limit of the mass ratio of the particles in condition (d) is 40% by mass, and the range is 45 to 60%. % by mass is preferable, and 50 to 60% by mass is more preferable.
If the mass ratio of the particles in the condition (f) is less than 0.1% by mass, the volume change may become large. On the other hand, when the mass ratio of the particles of condition (f) exceeds 10% by mass, the volume change may become large.
The mass proportion of the particles in condition (f) is preferably 0.2 to 9.5 mass %, more preferably 0.3 to 9 mass %.

[Conditions (g) and (h)]
In addition, the expanded particles of the present invention meet the following conditions:
(g) the mass fraction of particles in the particle size range that is one step smaller or one step larger than the particle size range in which the mass fraction of the particles is the highest is 33 to 45% by mass; and (h) the mass fraction of the particles is It is preferable to have a particle size distribution satisfying the mass ratio of particles in a particle size range two steps smaller or two steps larger than the highest particle size range is 0.1 to 10% by mass.
When the expanded beads satisfy the conditions (g) and (h), an effect of little change in volume, that is, little settling is obtained.
If the mass ratio of the particles in condition (g) is less than 33% by mass, the volume change may become large. On the other hand, when the mass ratio of the particles of condition (g) exceeds 45 mass %, the volume change may become large.
The mass ratio of particles in condition (g) is preferably 34 to 44% by mass, more preferably 35 to 43% by mass.
If the mass ratio of the particles in condition (h) is less than 0.1% by mass, the volume change may become large. On the other hand, when the mass ratio of the particles of condition (h) exceeds 10% by mass, the volume change may become large.
The mass proportion of the particles in condition (h) is preferably 0.5 to 9 mass %, more preferably 1 to 8 mass %.

(1-2) Bulk Density and Bulk Expansion Ratio [Bulk Expansion Ratio]
The expanded beads of the present invention have a bulk expansion ratio of 20 times or more and less than 60 times.
If the bulk expansion ratio is less than 20 times, the foamed particles lose cushioning properties and elasticity and become hard, and the volume becomes low, so that the mass of the cushion increases and handling becomes difficult. On the other hand, when the bulk expansion ratio exceeds 60 times, the expanded particles become soft and cannot withstand the load, and the volume tends to change in a short period of time.
Specifically, the bulk expansion ratio may be set in consideration of the physical properties required for the cushion body, and is preferably 25 to 55 times, more preferably 30 to 50 times.
The bulk expansion factor of the expanded beads can be obtained from the bulk density as shown in the following formula.
Bulk expansion ratio = 1/bulk density (g/cm ³ )

[The bulk density]
Accordingly, the expanded beads of the present invention have a bulk density exceeding 1/60 (0.017) g/cm ³ and not more than 1/20 (0.05) g/cm ³ .
Specific methods for measuring bulk density and bulk expansion ratio will be described in detail in Examples.

(1-3) Constituent Resins of Expanded Beads The types of thermoplastic resins constituting the expanded beads of the present invention are not limited, but examples include polystyrene-based resins, polyethylene-based resins, polypropylene-based resins, polyester-based resins, and vinyl chloride-based resins. , ABS resin, AS resin, etc. can be used singly or in combination of two or more.
It is also possible to use a recovered thermoplastic resin that has been recovered after being used as a resin product.
Among the above thermoplastic resins, polystyrene-based resins such as amorphous polystyrene (GPPS) are particularly preferably used.

Polystyrene-based resins are not particularly limited, and examples include homopolymers of styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene, or these. and the like. Among polystyrene resins, resins containing 50% by mass or more of styrene units are preferred.

Further, the polystyrene-based resin may be a copolymer of the styrene-based monomer and a vinyl monomer copolymerizable with the styrene-based monomer, the main component of which is the styrene-based monomer. Examples of such vinyl monomers include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate and cetyl (meth)acrylate, (meth)acrylonitrile, dimethyl maleate, In addition to monofunctional monomers such as dimethylfumarate, diethylfumarate and ethylfumarate, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate can be used.

Moreover, other resins may be included as long as the polystyrene resin is the main component. As other resins, diene-based rubber-like polymers such as polybutadiene, styrene-butadiene copolymers, and ethylene-propylene-nonconjugated diene three-dimensional copolymers are used as resins that improve the impact resistance of foamed moldings. A rubber-modified polystyrene resin containing a high-impact polystyrene resin such as so-called high-impact polystyrene is preferable.
Alternatively, other resins include polyethylene resins, polypropylene resins, acrylic resins, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, and the like.

Styrene-based resins used as raw materials include ordinary commercially available polystyrene-based resins, polystyrene-based resins newly prepared by suspension polymerization and other methods, and non-recycled polystyrene-based resins (virgin polystyrene). In addition, a recycled polystyrene resin obtained by recycling a used polystyrene resin foam molded product can also be used.
Recycled polystyrene resins are polystyrene resins that are recycled from used polystyrene resin foam moldings, such as fish boxes, cushioning materials for home appliance packaging, food packaging trays, etc. Resin can be used. In addition, the recycled polystyrene resin that can be used is not only obtained by recycling used polystyrene resin foam moldings, but also home appliances (for example, televisions, refrigerators, washing machines, air conditioners, etc.). and office equipment (for example, copiers, facsimile machines, printers, etc.), pulverize, melt-knead, and re-pelletize non-foamed polystyrene-based resin moldings separately collected to use recycled polystyrene-based resins.
In addition, the resin may contain additives other than the resin, if necessary. Additives include plasticizers, flame retardants, flame retardant aids, antistatic agents, spreading agents, cell control agents, fillers, coloring agents, weathering agents, anti-aging agents, lubricants, anti-fogging agents, fragrances, etc. mentioned.

(1-4) Method for Producing Expanded Beads The expanded beads of the present invention are produced by impregnating thermoplastic resin particles (hereinafter also referred to as “resin particles”) produced using the above constituent resin material with a blowing agent. It can be produced by obtaining elastic thermoplastic resin particles (hereinafter also referred to as "expandable particles") and expanding them.
As the resin particles, those produced by known methods can be used. (2) supplying an aqueous medium and thermoplastic resin seed particles into an autoclave to disperse the thermoplastic resin seed particles in the aqueous medium; Thereafter, while heating and stirring the inside of the autoclave, the monomer is continuously or intermittently supplied, and the thermoplastic resin seed particles are allowed to absorb the monomer while being polymerized in the presence of the polymerization initiator. A seed polymerization method for producing plastic resin particles and the like can be mentioned. The thermoplastic resin seed particles may be obtained by classifying the particles after they are produced by the suspension polymerization method (1).
Examples of the above monomers include the monomers described in (1-3) Constituent resin of foamed beads.

The polymerization initiator used in the suspension polymerization method and seed polymerization method is not particularly limited, and examples thereof include benzoyl peroxide, lauryl peroxide, t-butyl peroxybenzoate, di-t-butyl peroxide, t-butyl Peroxypivalate, t-butyl peroxy isopropyl carbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy acetate, 2,2-bis organic peroxides such as (t-butylperoxy)butane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, azobisisobutyronitrile, and azo compounds such as azobisdimethylvaleronitrile. One of these polymerization initiators may be used alone, or two or more of them may be used in combination.

The aqueous medium is mainly composed of water and may contain small amounts of water-soluble organic solvents such as alcohols, ketones and ethers.
In the suspension polymerization method or the seed polymerization method, a suspension stabilizer may be added in advance to the aqueous medium in order to stabilize the dispersibility of the droplets of the monomer or the seed particles of the thermoplastic resin.
Examples of suspension stabilizers include water-soluble polymers such as polyvinyl alcohol, methylcellulose, polyacrylamide and polyvinylpyrrolidone, and poorly water-soluble inorganic salts such as tribasic calcium phosphate and magnesium pyrophosphate. When using a sparingly water-soluble inorganic salt, an anionic surfactant is usually used in combination.
Examples of anionic surfactants include alkyl sulfates such as sodium lauryl sulfate, alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, higher fatty acid salts such as sodium oleate, and β-tetrahydroxynaphthalenesulfonates. and particularly preferred are alkyl benzene sulfonates.

As a method for incorporating the foaming agent into the resin particles, there is a known method of impregnating the thermoplastic resin particles with the foaming agent. For example, a slurry in which thermoplastic resin particles are dispersed in an aqueous medium is placed in a pressure-resistant container such as an autoclave, and then the foaming agent is supplied to the pressure-resistant container and held for a certain period of time.

The expandable particles may also be produced by a melt extrusion method in which a molten resin containing a thermoplastic resin and a foaming agent is molded into granules.
Examples of the melt extrusion method include the following methods.
First, a foaming agent is injected and kneaded into a molten resin containing a thermoplastic resin to obtain a molten resin containing the foaming agent. While extruding the obtained molten resin containing the blowing agent directly from the small holes into the cooling liquid, the extrudate is cut in the obtained cooling liquid, and the extrudate is cooled by contact with the cooling liquid. solidify.
By using the melt extrusion method, expandable particles in which the foaming agent is uniformly dispersed in the thermoplastic resin can be obtained.

Blowing agents include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, 1,1-dichloro-1-fluoroethane (HCFC-141b), 1,1-dichloro-2 chlorofluorocarbons such as , 2,2-trifluoroethane (HCFC-123), chlorodifluoromethane (HCFC-22), 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124), 1, 1-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a), difluoromethane (HFC-32), etc. Physical blowing agents such as fluorocarbons, various alcohols, carbon dioxide, water, and nitrogen can be mentioned, and one or more of these can be used in combination. Among these, preferred blowing agents include n-butane, isobutane, n-pentane, and isopentane.
The content of the foaming agent is preferably in the range of 1 to 20 parts by mass, more preferably in the range of 2 to 15 parts by mass, based on 100 parts by mass of the thermoplastic resin.

The thermoplastic resin foamed particles of the present invention are used in order to prevent coalescence of the foamed particles during the foaming process, to prevent charging between the foamed particles, or to promote the flow of the foamed particles. Salts of fatty acids (stearic acid, lauric acid, palmitic acid) with metals (magnesium, calcium, zinc, barium, aluminum), carbonates (calcium carbonate), polyethylene wax, polyethylene glycol, N-hydroxyethyl-N- At least one or more selected from 2-hydroxyalkylamine, stearic acid monoglyceride and the like may be used. The amount used is 0.001 to 5 parts by mass, preferably 0.01 to 2 parts by mass, per 100 parts by mass of the thermoplastic resin.

When producing resin particles by a suspension polymerization method, the average particle diameter and particle size of the resin particles are generally adjusted by changing the stirring power (for example, the type of stirring blade of a stirrer and its rotation speed) during suspension polymerization. Distribution can be controlled.
When producing resin particles by the seed polymerization method, generally, by changing the particle diameter of the seed, and by changing the stirring power (for example, the type of stirring blade of the stirrer and its rotation speed) during seed polymerization. , the average particle size and particle size distribution of the resin particles can be controlled.
For both the expandable particles and the expanded particles, in order to obtain particles having a desired particle size distribution, separately produced particles may be mixed in the production process, or particles obtained by a single production process may be mixed. It may be sieved (classified) or the particles obtained from a single controlled manufacturing process may be used as is.

(2) Expandable particles As described above, the expandable thermoplastic resin particles for cushioning of the present invention (also referred to herein as "expandable particles") are particles containing a thermoplastic resin and a blowing agent, It is characterized by being for the foamed thermoplastic resin particles for cushioning.

The expandable beads of the present invention comprise expandable beads for manufacturing expanded beads having a bulk expansion ratio of 20 times or more and less than 60 times, containing a thermoplastic resin and a blowing agent,
The expandable particles have an average particle diameter of 0.23 to 0.92 mm, and the expandable particles are sieved through a JIS standard sieve (JIS Z8801-1: 2000) with a nominal opening of 5.60 to 0.212 mm. When sieved using a 20-stage sieve, the following conditions:
(a′) all expandable particles pass through a sieve with a nominal opening of 5.60 mm and do not pass through a sieve with a nominal opening of 0.212 mm;
(b') the coefficient of variation (CV value) of the particle size distribution determined from the mass ratio of particles in the particle size range sieved between adjacent stages of sieves is 4 or less; and (c') the mass of the particles. It is characterized by having a particle size distribution that satisfies a mass ratio of 5 to 45% by mass of particles in a particle size range one step smaller or one step larger than the particle size range in which the ratio is the highest.

The particle size distribution conditions (a′) to (h′) and the average particle size were determined by sifting the expandable particles through a JIS standard sieve (JIS Z8801-1: 2000) with a nominal opening of 5.60 to 0.212 mm in 20 steps. It is a value when sieving (classifying) using a sieve.
A specific method for measuring the particle size distribution will be described in detail in Examples.

[Average particle size]
The expandable particles of the present invention have an average particle size of 0.23-0.92 mm.
The average particle size can be obtained from the mass ratio Rn (%) of particles in each particle size range obtained in the above particle size distribution measurement and each median particle size (mm), similarly to the expanded particles.
Average particle size = {Σ(D _n R _n )}/100
If the average particle diameter of the expandable particles is less than 0.23 mm, the resulting expanded particles may have a large change in volume, and the filling amount may increase, resulting in an increase in the mass of the cushion. On the other hand, if the average particle diameter of the expandable particles exceeds 0.92 mm, the volume change of the obtained expanded particles may increase, and the touch and sitting comfort may deteriorate.
The average particle diameter of the expandable particles is preferably 0.25-0.90 mm, more preferably 0.30-0.85 mm.

[Condition (a')]
Condition (a′) is that all the expandable particles pass through a sieve with a nominal opening of 5.60 mm and do not pass through a sieve with a nominal opening of 0.212 mm, which means that the diameter of all the expandable particles is It means that the range is less than 5.60 mm and greater than 0.212 mm.
If all the expandable particles contain particles that do not pass through a sieve with a nominal mesh size of 5.60 mm, the resulting expanded particles may have a large volume change, and the texture and sitting comfort may be deteriorated. On the other hand, if all the expandable particles include particles that pass through a sieve with a nominal mesh size of 0.212 mm, the volume change of the obtained expanded particles may be large, and the filling amount may increase, resulting in an increase in the mass of the cushion. .
Preferably, all expandable particles pass through a sieve with a nominal opening of 4.00 mm and not through a sieve with a nominal opening of 0.212 mm, pass through a sieve with a nominal opening of 1.70 mm and pass through a sieve with a nominal opening of 0.21 mm. More preferably it does not pass through a 212 mm sieve.
However, the expandable particles of the present invention may contain particles that do not pass through a sieve with a nominal opening of 5.60 mm and particles that pass through a sieve with a nominal opening of 0.212 mm, as long as the effects of the present invention are not impaired. good.

[Condition (b')]
The condition (b') is that the coefficient of variation (CV value) of the particle size distribution obtained from the mass ratio x of the particles in the particle size range sieved between the sieves in each adjacent stage is 4 or less, and the particle size It means that the distribution is not too sharp and the particles are not too uniform.
The CV value can be determined from the standard deviation (σ) and the average value (μ) in the same manner as for the expanded particles.
Deviation σ ² = (Σ (mass ratio x - average μ) ² )/number of sieves n
Standard deviation σ = √σ ²
Coefficient of variation CV = standard deviation σ / average μ
Note that the average value μ=100/19=5.26 and the number of sieves n=19.

When the CV value exceeds 4, the volume change of the obtained expanded beads may become large.
The expandable particles of the present invention have a peculiar distribution as shown in condition (c′), the lower limit of the CV value is 1, and the range is preferably from 1.5 to 3.8. , 1.8 to 3.4.

[Condition (c')]
Condition (c′) is that the mass ratio of particles in the particle size range one step smaller or one step larger from the particle size range where the mass ratio of particles is the highest is 5 to 45% by mass, and the particle size distribution It means that the mass ratio of particles in the particle size range of either one of the distributions on both sides of the peak of is 5 to 45% by mass.
If the mass ratio of the particles is less than 5% by mass, the volume change of the obtained expanded particles may be large. On the other hand, when the mass ratio of the particles exceeds 45% by mass, the volume change of the obtained expanded beads may become large.
The mass ratio of the particles is preferably 6-43% by mass, more preferably 7-42% by mass.

[Condition (d')]
The expandable particles of the present invention meet the following conditions:
(d') It is preferable to have a particle size distribution that satisfies that the mass ratio of particles in the particle size range where the mass ratio of particles is the highest is 35 to 70% by mass.
This means that the mass proportion of particles in the particle size range of the peak of the particle size distribution is 35-70% by mass.
When the expandable particles have an average particle diameter of 0.23 to 0.92 mm and satisfy the condition (d'), the obtained expanded particles have a particularly small volume change, that is, little settling.
If the mass ratio of the particles in condition (d') is less than 35% by mass, the resulting expanded beads may have a large volume change. On the other hand, when the mass ratio of the particles in the condition (d') exceeds 70% by mass, the resulting expanded beads may have a large volume change.
The mass ratio of the particles of condition (d') is preferably 36 to 69.5% by mass, more preferably 37 to 69.0% by mass.

[Conditions (e') and (f')]
Also, the expandable particles of the present invention meet the following conditions:
(e′) the mass fraction of particles in the particle size range with the highest mass fraction of particles is 70% by mass or less; and (f′) the particle size range one step larger than the highest mass fraction of particles It is preferable to have a particle size distribution that satisfies that the mass ratio of particles is 0.1 to 10% by mass.
When the expandable beads satisfy the conditions (e') and (f'), the obtained expanded beads have an effect of little change in volume, that is, less settling.
The condition (e') means that the mass ratio of particles in the particle size range of the peak of the particle size distribution is 70% by mass or less, and the condition (f') means that the particle size of the peak of the particle size distribution is larger. It means that the mass proportion of particles in the particle size range is 0.1 to 10% by mass.
If the mass ratio of the particles in condition (e) exceeds 70% by mass, the volume change of the obtained expanded beads may become large.
The expanded particles of the present invention have a peculiar distribution as shown in condition (e'), and the lower limit of the mass ratio of the particles in condition (d) is 40.5% by mass, and the range is 40.5% by mass. It is preferably 8 to 64% by mass, more preferably 41 to 63% by mass.
If the mass ratio of the particles in the condition (f') is less than 0.1% by mass, the volume change of the obtained expanded beads may be large. On the other hand, when the mass ratio of the particles in the condition (f') exceeds 10% by mass, the resulting expanded beads may have a large volume change.
The mass ratio of the particles in condition (f′) is preferably 0.1 to 9% by mass, more preferably 0.2 to 8% by mass, and 0.3 to 5% by mass. More preferred.

[Conditions (g') and (h')]
Additionally, the expandable particles of the present invention meet the following conditions:
(g′) the mass ratio of particles in the particle size range that is one step smaller or one step larger than the particle size range in which the mass ratio of the particles is the highest is 28 to 32% by mass; and (h′) the mass of the particles. It is preferable to have a particle size distribution that satisfies that the mass ratio of particles in the particle size range two steps smaller or two steps larger than the particle size range with the highest ratio is 3% by mass or less.
When the expanded beads satisfy the conditions (g') and (h'), the obtained expanded beads have an effect of little change in volume, that is, little settling.
If the mass ratio of the particles in condition (g') is less than 28% by mass, the resulting expanded beads may have a large volume change. On the other hand, when the mass ratio of the particles in the condition (g') exceeds 32% by mass, the resulting expanded beads may have a large volume change.
The mass ratio of the particles in condition (g') is preferably 28.5 to 31.5% by mass, more preferably 28.8 to 31.0% by mass.
When the mass ratio of the particles in condition (h') exceeds 3% by mass, the volume change of the obtained expanded beads may become large.
The mass ratio of the particles of condition (h') is preferably 0 to 2.9% by mass, more preferably 0 to 2.8% by mass.

(3) Cushion body The cushion body of the present invention is constructed by sealing the foamed particles of the present invention as a filler in a bag body.
The material of the bag of the cushion body of the present invention is not particularly limited, and examples thereof include cloth made from chemical fibers, silk, cotton, etc. Materials having elasticity are particularly preferable. Specifically, a bag made of a stretchable material is preferable. As the stretchable material, elastic materials such as spandex (polyurethane elastic thread) and polyester are most preferable.
By using a bag body made of a material having elasticity as described above, when a part of the cushion body is compressed, the filled particles move from the compressed part to another part, and the volume of the moved particles can be tolerated by the expansion and deformation of the bag located at other sites, the allowable range of movement of the particles can be increased. Therefore, the touch and feel of the cushion body can be dramatically improved. In addition, the synergy of these effects of the foamed resin particles and the bag makes it possible to provide a cushion with a better feel.
Moreover, in order to satisfy the permanent cushioning property, it is more preferable to adopt a structure in which two zippers that can be opened and closed are provided so as to prevent the filler from leaking out of the bag. It is also effective to make the bag itself a double structure.
Furthermore, a configuration may be adopted in which a plurality of bags each containing a filler are placed in one large bag.

The foamed particles of the present invention can be suitably used not only for palm-sized cushions but also for cushions such as large cushions, sofas, chairs, beds, mattresses, pillows, and stuffed toys.

The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples. First, the measurement methods and evaluation methods used in Examples and Comparative Examples will be described.
In addition, "%" means "mass %" and "part" means "mass part" below.

[Particle size distribution]
The particle size distribution of expanded particles was measured as follows.
A low-tap sieve shaker equipped with 20 stages of JIS standard sieves with a nominal mesh size of 5.60 to 0.212 mm as shown in Table 1, sequentially stacked from a small sieve to a large sieve from the bottom to the top ( (manufactured by Iida Seisakusho Co., Ltd.), put about 2 to 50 g of weighed expanded particles into the uppermost sieve, shake (classify) for 10 minutes, and measure the mass of the expanded particles remaining on each sieve. , the particle size distribution of the expanded particles was obtained by plotting the obtained data.
Table 1 shows the relationship between the nominal mesh size of each sieve, the particle size range between each sieve, and the center particle size.
In the table, "X pass Y on" means that the foamed particles passed through a sieve with a nominal opening of X mm and remained on the sieve without passing through a sieve with a nominal opening of Y mm.
The "median particle size" is the arithmetic mean value of the nominal mesh size of each sieve that indicates the particle size range. asked to
(0.850+0.710)/2=0.780mm

A CV value can be obtained from a standard deviation (σ) and an average value (μ) as in the following formula.
Deviation σ ² = (Σ (mass ratio x - average μ) ² )/number of sieves n
Standard deviation σ = √σ ²
Coefficient of variation CV = standard deviation σ / average μ
Note that the average value μ=100/19=5.26 and the number of sieves n=19.

[Bulk Density and Bulk Expansion Ratio]
The bulk density of the expanded particles was measured according to JIS K6911: 1995 "General Test Methods for Thermosetting Plastics".
The mass W (g) of the foamed beads is weighed to two decimal places, and the foamed beads are filled into a graduated cylinder by free fall ^. The density was measured using a density measuring instrument, and the bulk density of the expanded particles was obtained based on the following formula.
Bulk density (g/cm ³ )=mass of measurement sample (W)/volume of measurement sample (V)
The bulk expansion ratio of the expanded beads was obtained from the bulk density as shown in the following formula.
Bulk expansion ratio = 1/bulk density (g/cm ³ )

[Slowness evaluation]
JIS K 7100: 1999 symbol "23/50" (temperature 23 ° C., relative humidity 50%), expanded particles left for 24 hours in a standard atmosphere of class 2, placed in a cylindrical container with an inner diameter of 50 mm and a height of 100 mm. 120 mL was filled and the volume V1 (mL) before compression was measured. After that, it was repeatedly compressed 100 times with a compression plate having a diameter of 49 mm at a speed of 10 mm per minute with a lower limit of 1 N and an upper limit of 267 N, and the volume V2 (mL) after compression was measured. A volume change rate (%) was calculated by the following formula. Evaluation is as follows. For the measurement, "Tensilon UCT-10T" universal testing machine manufactured by Orientec Co., Ltd. and "UTPS-458C" universal testing machine manufactured by Softbrain Co., Ltd. were used for data processing.
<Volume change rate>
Volume change rate (%) = V2/V1 x 100
<Slow evaluation>
A: Volume change rate is over 95% and 100% or less B: Volume change rate is over 90% and 95% or less C: Volume change rate is over 85% and 90% or less D: Volume change rate is 85% the following

[Compression test of palm-sized cushion]
JIS K 7100: 1999 symbol "23/50" (temperature 23°C, relative humidity 50%), bag made from stretchable fabric left for 24 hours in a class 2 standard atmosphere A cushion with a diameter of 15 cm filled with 18 g of foamed particles was put into a cylindrical container with an inner diameter of 158 mm and a height of 150 mm, and the height H1 (mm) under a load of 5 N was measured. After that, a compression plate with a diameter of 106 mm was repeatedly compressed 100 times at a speed of 20 mm/min with a lower limit of 2 N and an upper limit of 637 N (65 kgf), and a load of 5 N was applied again to measure the height H2 (mm). The dimensional change rate was calculated by the following formula. Evaluation is as follows. For the measurement, "Tensilon UCT-10T" universal testing machine manufactured by Orientec Co., Ltd. and "UTPS-458C" universal testing machine manufactured by Softbrain Co., Ltd. were used for data processing.
<Dimensional change rate>
Dimensional change rate (%) = (H1-H2)/H1 x 100
<Evaluation of compression test>
A: Dimensional change rate is 0% or more and less than 10.0% B: Dimensional change rate is 10.0% or more and less than 12.0% C: Dimensional change rate is 12.0% or more and less than 14.0% D: Dimensional change rate is 14.0% or more

[Compression test of sofa-sized cushion]
A sofa-sized cushion filled with foam particles in a bag (65 cm long, 65 cm wide, 45 cm high) made of stretchable fabric, and filled with foam particles so that the total weight of the fabric is 6 kg. was made.
This cushion was placed in a wooden case having a length of 65 cm, a width of 65 cm and a height of 65 cm, and the height H3 (mm) from the bottom of the case to the top of the cushion was measured. A weight of 65 kg was placed on the upper surface of the cushion, and was dropped from a height of 10 cm into the center of the cushion 4,000 times through the backing plate for the seat surface. . The heights H3 and H4 are the average heights at the four corners of the case. The dimensional change rate was calculated by the following formula. Evaluation is as follows.
<Dimensional change rate>
Dimensional change rate (%) = (H3-H4)/H3 x 100
<Evaluation of compression test>
A: The dimensional change rate is 0% or more and less than 18.5% B: The dimensional change rate is 18.5% or more and less than 20.0% C: The dimensional change rate is 20.0% or more and less than 21.5% D : Dimensional change rate is 21.5% or more

<Cloth fabric>
The fabrics used in the palm-sized cushion compression test and the sofa-sized cushion compression test are as follows.
1) The fabric material used was 100% polyester.
2) JIS K 7100: 1999 symbol "23/50" (temperature 23 ° C, relative humidity 50%), after curing for 24 hours in a standard atmosphere of class 2, width 25 mm in any direction of the fabric, length N=10 samples of 200 mm were sampled.
3) "Tensilon UCT-10T" universal testing machine manufactured by Orientec Co., Ltd., "UTPS-458X" universal testing machine manufactured by Softbrain Co., Ltd. Data processing is performed at a speed of 300 mm per minute. A tensile test was performed. The tensile test method complied with JIS L1096:2010 (Tensile strength test method for woven and knitted fabrics-A cut strip method of JIS method). The initial load of 0.4 N was used as the test starting point for the displacement origin. The average maximum point load of 10 samples was 131 (N/2.5 cm width).

[comprehensive evaluation]
Based on the evaluation results of the settling evaluation, the compression evaluation of the palm-sized cushion, and the compression evaluation of the sofa-sized cushion, a comprehensive evaluation was made based on the following criteria.
A: All three evaluation results are A evaluation.
B: Three evaluation results consist of A evaluation or B evaluation, and there is one or more B evaluations.
C: Three evaluation results have no D evaluation and one or more C evaluations.
D: Among the three evaluation results, there is one or more D evaluations.

(Example 1)
<Production of styrene-based resin particles>
82 g of magnesium pyrophosphate, 2.4 g of sodium dodecylbenzenesulfonate, 106 g of benzoyl peroxide (purity: 75%), 24 g of t-butylperoxy-2-ethylhexyl monocarbonate, and 40 kg of deionized water were placed in a 100-liter autoclave equipped with a stirrer. and 40 kg of a styrene monomer were supplied, and a suspension was prepared by stirring by rotating a stirring blade at a rotational speed of 230 rpm.
Next, while maintaining the rotation speed of the stirring blade at 230 rpm and stirring the suspension, the temperature of the autoclave is raised to 90° C. and maintained at 90° C. for 6 hours and 50 minutes. The temperature in the autoclave was raised to 125°C and maintained at 125°C for 2 hours. Thus, the styrene monomer was subjected to suspension polymerization.
After that, the temperature inside the autoclave was cooled to 25° C., and the polymer was taken out from inside the autoclave. The polymer was washed and dehydrated several times, dried and sieved to obtain styrene resin particles having a mass average molecular weight of 300,000.

<Production of expandable styrene resin particles>
Next, 2 kg of ion-exchanged water, 12 g of magnesium pyrophosphate, 0.3 g of sodium dodecylbenzenesulfonate, 0.6 g of dilauryl-3,3'-thiodipropionate, and 0.8 g of ethylenebisstearic acid amide were placed in a 5-liter autoclave. was charged as an aqueous medium. 2 kg of the styrene-based resin particles were added to the aqueous medium and stirred at 300 rpm.
Next, the temperature of the aqueous medium was raised to 110° C., and while maintaining this temperature, 55 g of butane and 151 g of pentane were pressurized and impregnated for 1 hour and 30 minutes, followed by cooling to obtain expandable styrene resin particles.
Thereafter, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Tables 2 and 3.

<Production of expanded styrene resin particles>
The obtained expandable styrene resin particles exhibiting the desired particle size distribution were supplied to a cylindrical batch-type foaming machine and uniformly heated with steam to obtain expanded styrene resin particles. The obtained expanded styrene resin particles had a bulk density of 0.0263 g/cm ³ (bulk expansion ratio of 38 times).
The particle size distribution of the obtained expanded styrene resin particles was measured, and the properties as a cushion body were evaluated based on the evaluation method described above. Table 6 shows the results obtained.

(Example 2)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 200 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 3. Next, expanded styrene resin particles having a bulk expansion ratio of 38 were obtained in the same manner as in Example 1. Table 6 shows the evaluation results of the obtained expanded beads.

(Example 3)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 235 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 3. Next, expanded styrene resin particles having a bulk expansion ratio of 38 were obtained in the same manner as in Example 1. Table 6 shows the evaluation results of the obtained expanded beads.

(Example 4)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 250 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 3. Next, expanded styrene resin particles having a bulk expansion ratio of 38 were obtained in the same manner as in Example 1. Table 6 shows the evaluation results of the obtained expanded beads.

(Example 5)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 65 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 4. Next, expanded styrene resin particles were obtained in the same manner as in Example 1 except that the bulk expansion ratio was 58 times. Table 7 shows the evaluation results of the obtained expanded beads.

(Example 6)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 220 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 4. Next, expanded styrene resin particles were obtained in the same manner as in Example 1, except that the bulk expansion ratio was 31 times. Table 7 shows the evaluation results of the obtained expanded beads.

(Example 7)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 180 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 4. Next, expanded styrene resin particles were obtained in the same manner as in Example 1, except that the bulk expansion ratio was 35 times. Table 7 shows the evaluation results of the obtained expanded beads.

(Example 8)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 190 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 4. Next, expanded styrene resin particles were obtained in the same manner as in Example 1 except that the bulk expansion ratio was 36 times. Table 7 shows the evaluation results of the obtained expanded beads.

(Comparative example 1)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 225 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 5. Next, expanded styrene resin particles having a bulk expansion ratio of 38 were obtained in the same manner as in Example 1. Table 8 shows the evaluation results of the obtained expanded beads.

(Comparative example 2)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 70 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 5. Next, expanded styrene resin particles were obtained in the same manner as in Example 1 except that the bulk expansion ratio was 60 times. Table 8 shows the evaluation results of the obtained expanded beads.

(Comparative Example 3)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 50 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 5. Next, expanded styrene resin particles were obtained in the same manner as in Example 1 except that the bulk expansion ratio was 18 times. Table 8 shows the evaluation results of the obtained expanded beads.

(Comparative Example 4)
Expandable styrene resin particles were obtained in the same manner as in Example 1, except that the rotation speed of the stirring blade was maintained at 60 rpm to obtain the styrene resin particles. Then, the mixture was sieved to obtain expandable styrene resin particles having a particle size distribution shown in Table 5. Next, expanded styrene resin particles were obtained in the same manner as in Example 1 except that the bulk expansion ratio was 60 times. Table 8 shows the evaluation results of the obtained expanded beads.

From the results in Tables 6 to 8, the expanded beads of Examples 1 and 2 have the most excellent physical properties (characteristics) as thermoplastic resin expanded beads for cushions, and the expanded beads of Examples 3 and 4 and Examples 5 to 8 It can be seen that the order of the foamed particles follows. On the other hand, it can be seen that the expanded particles of Comparative Examples 1 to 4 are inferior as thermoplastic resin expanded particles for cushions.

Claims (9)

Consists of expanded particles obtained by expanding expandable thermoplastic resin particles containing a thermoplastic resin and a blowing agent,
The expanded particles have a bulk expansion ratio of 20 times or more and less than 60 times and an average particle diameter of 0.5 to 2.8 mm, and When sieving using a 20-stage sieve with an opening of 5.60 to 0.212 mm, the following conditions:
(a) all expanded particles pass through a 5.60 mm nominal sieve and do not pass through a 0.212 mm nominal sieve;
(b) the coefficient of variation (CV value) of the particle size distribution obtained from the mass fraction of particles in the size range sieved between the sieves of each adjacent stage is 4 or less; and (c) the mass fraction of the particles is Having a particle size distribution that satisfies that the mass ratio of particles in a particle size range one step smaller or one step larger than the highest particle size range is 5 to 45% by mass,
The thermoplastic resin is a polystyrene resin,
The foamed thermoplastic resin particles for a cushion, wherein the foamed particles are a filling material for a cushioning body which is formed by enclosing a filling material in a bag body. When the expanded particles are sieved through the JIS standard sieve, the following conditions are met:
2. The foamed thermoplastic resin particles for cushioning according to claim 1, having a particle size distribution that satisfies (d) the mass ratio of particles in the range of particle diameters in which the mass ratio of particles is the highest is 40 to 65% by mass. When the expanded particles are sieved through the JIS standard sieve, the following conditions are met:
(e) the mass fraction of particles in the particle size range having the highest mass fraction of particles is 65 mass % or less; The foamed thermoplastic resin particles for cushioning according to claim 1 or 2, having a particle size distribution satisfying a mass ratio of 0.1 to 10% by mass. When the expanded particles are sieved through the JIS standard sieve, the following conditions are met:
(g) the mass fraction of particles in the particle size range that is one step smaller or one step larger than the particle size range in which the mass fraction of the particles is the highest is 33 to 45% by mass; and (h) the mass fraction of the particles is Any one of claims 1 to 3, having a particle size distribution satisfying the mass ratio of particles in a particle size range two steps smaller or two steps larger than the highest particle size range is 0.1 to 10% by mass. The foamed thermoplastic resin particles for the cushion according to 1. A cushion body in which the foamed thermoplastic resin particles for cushioning according to any one of claims 1 to 4 are enclosed as a filler in a bag body. Composed of expandable particles for producing expanded beads containing a thermoplastic resin and a blowing agent and having a bulk expansion ratio of 20 times or more and less than 60 times and an average particle diameter of 0.5 to 2.8 mm,
The expandable particles have an average particle diameter of 0.23 to 0.92 mm, and the expandable particles are sieved through a JIS standard sieve (JIS Z8801-1: 2000) with a nominal opening of 5.60 to 0.212 mm. When sieved using a 20-stage sieve, the following conditions:
(a′) all expandable particles pass through a sieve with a nominal opening of 5.60 mm and do not pass through a sieve with a nominal opening of 0.212 mm;
(b') the coefficient of variation (CV value) of the particle size distribution determined from the mass ratio of particles in the particle size range sieved between adjacent stages of sieves is 4 or less; and (c') the mass of the particles. It has a particle size distribution that satisfies that the mass ratio of particles in a particle size range one step smaller or one step larger than the particle size range with the highest proportion is 5 to 45% by mass,
The thermoplastic resin is a polystyrene resin,
The expandable thermoplastic resin particles for a cushion, wherein the foamed particles are a filling material for a cushion body which is formed by enclosing a filling material in a bag body. When the expandable particles are sieved through the JIS standard sieve, the expandable particles meet the following conditions:
7. The expandable thermoplastic resin particles for cushioning according to claim 6 , having a particle size distribution satisfying (d') the mass ratio of particles in the range of particle diameters having the highest mass ratio of particles of 35 to 70% by mass. When the expandable particles are sieved through the JIS standard sieve, the expandable particles meet the following conditions:
(e′) the mass fraction of particles in the particle size range with the highest mass fraction of particles is 70% by mass or less; and (f′) the particle size range one step larger than the highest mass fraction of particles 8. The expandable thermoplastic resin particles for cushioning according to claim 6 or 7, having a particle size distribution satisfying a mass ratio of the particles of 0.1 to 10% by mass. When the expandable particles are sieved through the JIS standard sieve, the expandable particles meet the following conditions:
(g′) the mass ratio of particles in the particle size range that is one step smaller or one step larger than the particle size range in which the mass ratio of the particles is the highest is 28 to 32% by mass; and (h′) the mass of the particles. In any one of claims 6 to 8, having a particle size distribution satisfying that the mass ratio of particles in a particle size range two steps smaller or two steps larger than the particle size range with the highest proportion is 3% by mass or less. The foamable thermoplastic resin particles for cushioning described.

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