JP7780332B2 - Filler beads and method for producing filler beads - Google Patents

Description

The present invention relates to stuffing beads and a method for manufacturing stuffing beads, which are used in cushioning materials such as bead cushions, sofas, and mattresses.

Expanded beads have traditionally been used as filler beads to manufacture cushioning materials such as bead cushions, sofas, and mattresses. For example, Patent Document 1 discloses a cushion body made by filling a bag with expanded styrene resin beads.

Japanese Patent Application Laid-Open No. 2004-223002

The above-mentioned styrene-based resin expanded beads can provide a desirable feel when filled inside a bag as stuffing beads for cushioning material. However, when a load is repeatedly applied to the styrene-based resin expanded beads due to repeated use of the cushioning material, there is a problem in that the expanded beads do not fully return to their pre-load state even after the load is removed. As a result, there is a risk that the cushioning properties and feel of the cushioning material will deteriorate over long-term use.

In contrast, expanded polyolefin resin beads generally have superior recovery properties compared to expanded styrene resin beads. However, when using expanded polyolefin resin beads as filler beads for cushioning materials, there is still room for improvement in the feel of the cushioning material.

The present invention was made in light of this background, and aims to provide stuffing beads for cushioning material that exhibit good feel and cushioning properties and that can maintain good feel and cushioning properties even after long-term use, as well as a method for manufacturing the stuffing beads.

The filling beads of the present invention are filling beads for cushioning material, and are polyolefin resin expanded beads in which the expanded bead body, which has a polyolefin resin as the base resin, is coated with a coating agent containing a fatty acid metal salt, and the expanded bead body contains a fatty acid amide , the amount of fatty acid metal salt coating on the polyolefin resin expanded beads is 0.05% by weight or more and 1% by weight or less relative to 100% by weight of the polyolefin resin expanded beads, and the weight ratio of the fatty acid amide to the fatty acid metal salt is 1:0.5 to 1:20 .

The method for manufacturing stuffing beads of the present invention is a method for manufacturing stuffing beads for the cushioning material of the present invention, which uses a polyolefin resin as the base resin and coats an expanded bead body containing a fatty acid amide with a coating agent containing a fatty acid metal salt to obtain the stuffing beads.

The filler beads of the present invention improve the cushioning properties and feel of the cushioning material, and can maintain these good cushioning properties and feel for a long period of time, even when the cushioning material is used repeatedly.

The filling beads of the present invention can be easily obtained using the method for manufacturing the filling beads of the present invention.

1 is a DSC curve obtained according to the method for measuring the heat of transition of plastics described in JIS K7122 (1987) for determining the total heat of fusion and the high-temperature peak heat of the expanded polyolefin resin beads according to one embodiment of the present invention.

The filler beads of the present invention will now be described.
The filler beads of the present invention are particulate fillers that are filled into a bag to form a cushioning material. Such cushioning material includes a bag and filler beads filled inside the bag. The material for the bag can be a stretchy material, such as a cloth made of synthetic fiber, silk, cotton, or the like.
In the present invention, the cushioning material is used in a state where foamed beads are stuffed inside, and can be widely used as a cushioning structure. Specific examples of the cushioning material include cushioning structures such as bead cushions, sofas, pillows, dolls, and mattresses. Among these, the stuffing beads of the present invention can be suitably used as stuffing beads for bead cushions.
The filler beads of the present invention are expanded polyolefin resin beads containing a fatty acid amide, and have an expanded bead body coated with a coating agent containing a fatty acid metal salt.
The filler beads of the present invention having the above-described configuration, when filled into a bag to form a cushioning material comprising the bag and the filler beads filled inside the bag, improve the cushioning properties and feel of the cushioning material, and can maintain these good cushioning properties and feel for a long period of time even after repeated use. The filler beads of the present invention will be described in detail below.

[Foam particle body]
The expanded bead bodies used in the filling beads of the present invention are composed of a polyolefin resin as a base resin. By using expanded bead bodies based on a polyolefin resin, the present invention improves the flexibility and recovery of the cushioning material, and as will be described later, by coating the expanded bead bodies with a coating agent containing a fatty acid metal salt and incorporating a fatty acid amide into the expanded bead bodies, the cushioning material will have a good feel to the touch even after long-term use.

The polyolefin resin may be a polypropylene resin and/or a polyethylene resin, and is preferably a polypropylene resin. These resins may be used alone or in combination.
Furthermore, when a polypropylene-based resin is used, the proportion of the polypropylene-based resin in the polyolefin-based resin is preferably 50% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and it is particularly preferable that it is substantially 100% by weight, i.e., the polyolefin-based resin is a polypropylene-based resin.
The expanded bead body may be formed by including other polymers such as resins other than the polyolefin resin base resin and elastomers, without departing from the spirit of the present invention. When the expanded bead body includes other polymers, the content of the other polymers is preferably approximately 30 parts by weight or less, more preferably 20 parts by weight or less, and even more preferably 10 parts by weight or less, per 100 parts by weight of the base resin.

When a polypropylene-based resin is used as the base resin constituting the expanded bead body, examples of the polypropylene-based resin include a propylene homopolymer and a polypropylene-based copolymer containing more than 50% by weight of structural units derived from propylene.
Examples of the polypropylene copolymer include copolymers of propylene and ethylene or α-olefins having 4 or more carbon atoms, such as propylene-ethylene copolymer, propylene-butene copolymer, and propylene-ethylene-butene copolymer, as well as propylene-acrylic acid copolymer and propylene-maleic anhydride copolymer. These copolymers may be block copolymers, random copolymers, or graft copolymers.
The base resin may be composed of one type of polypropylene resin or two or more types of polypropylene resins. The polymer may be crosslinked, but is preferably non-crosslinked.
From the viewpoint of being able to stably obtain expanded beads that are lightweight, have appropriate rigidity, and have good cushioning properties and recovery properties, the polypropylene-based resin is preferably a polypropylene-based copolymer, more preferably one or more polypropylene-based copolymers selected from a propylene-ethylene copolymer, a propylene-butene copolymer, and a propylene-ethylene-butene copolymer, and even more preferably a propylene-ethylene copolymer.
From the viewpoint of easily imparting appropriate rigidity to the expanded beads, the melting point of the polypropylene resin is preferably 135° C. or higher, more preferably 138° C. or higher, and even more preferably 140° C. or higher. From the viewpoint of easily improving the cushioning properties and recovery properties of the expanded beads, the melting point of the polypropylene resin is preferably 160° C. or lower, more preferably 155° C. or lower, and even more preferably 150° C. or lower.
The melting point of a polypropylene-based resin can be determined based on JIS K7121: 1987. In this case, the condition of the test piece is adjusted as follows: (2) Measuring the melting temperature after a certain heat treatment.
More specifically, using expanded beads as a test specimen, a DSC curve is obtained based on heat flux differential scanning calorimetry as described in JIS K7121:1987. The test specimen is heated from 23°C to 200°C at a heating rate of 10°C/min, cooled to 23°C at a cooling rate of 10°C/min, and then heated again from 23°C to 200°C at a heating rate of 10°C/min. The melting point of the polypropylene resin is determined as the apex temperature of the melting peak. When two or more melting peaks appear in the DSC curve, the apex temperature of the melting peak with the largest area is determined as the melting point. The melting peak with the largest area can be determined by distinguishing each melting peak at the valley temperature of the DSC curve located between the peak temperatures of the melting peaks and comparing the areas (heats of fusion) of each melting peak. The valley temperature of the DSC curve can be determined by referring to the DSC derivative curve (DDSC) and the temperature at which the value on the vertical axis of the derivative curve becomes 0.

When a polyethylene-based resin is used as the base resin constituting the expanded bead body, examples of the polyethylene-based resin include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid ester copolymer, and ethylene-methacrylic acid ester copolymer. The base resin may be composed of one type of polyethylene-based resin, or two or more types of polyethylene-based resin. These copolymers may be block copolymers, random copolymers, or graft copolymers.

In addition to the resins including the base resin described above, the foamed bead body may contain any additives as appropriate within the scope of the present invention. Optional additives include flame retardants, flame retardant assistants, cell regulators, lubricants, crystal nucleating agents, colorants, conductive materials, antistatic agents, etc.

The method for manufacturing the expanded bead bodies used in the present invention is not particularly limited, but an example of a method for manufacturing the expanded bead bodies will be explained together with the explanation of the method for manufacturing the filler beads described below.

[Polyolefin resin expanded particles]
The expanded polyolefin resin beads (hereinafter simply referred to as expanded beads) constituting the filler beads of the present invention are mainly comprised of the expanded bead bodies coated with a coating agent and contain a fatty acid amide. The fatty acid amide contained in the expanded polyolefin resin beads of the present invention is mainly dispersed in the expanded bead bodies.

Coating:
The coating agent in the present invention coats the surface of the expanded bead body. By using expanded beads whose bodies are coated with a coating agent as filler beads for cushioning material, the fluidity of the expanded beads when filled into a bag is improved, thereby improving the feel of the cushioning material. In the present invention, fluidity refers to the ease of movement of each expanded bead in an aggregate of expanded polyolefin resin beads filled into a bag. The fluidity can be evaluated by sensory evaluation of the feel of the cushioning material, or by measuring the angle of repose of the expanded polyolefin resin beads.

The coating agent contains a fatty acid metal salt. From the perspective of consistently improving the feel of the cushioning material, the proportion of fatty acid metal salt in the coating agent is preferably 50% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 100% by weight.

The fatty acid metal salt is a salt of a fatty acid and a metal. Examples of the fatty acid metal salt include salts of a metal and a fatty acid (higher fatty acid) having from 12 to 30 carbon atoms, and more specifically, preferred examples include metal stearates, metal laurates, and metal palmitates.
Examples of metals constituting fatty acid metal salts include zinc, magnesium, calcium, barium, and aluminum.

From the perspective of significantly improving the feel of the cushioning material, the fatty acid metal salt preferably contains a metal stearate, and more preferably contains zinc stearate. Furthermore, when the fatty acid metal salt contains a metal stearate, the proportion of the metal stearate in the fatty acid metal salt is preferably 50% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more. In this case, too, it is preferable that the metal stearate is zinc stearate.

Examples of coating agents other than fatty acid metal salts that can be included in the coating agent include fatty acid esters such as glycerin monostearate, silicone oils such as dimethyl silicone oil, alkyldiethanolamines, and glycerin.

(Coating Amount of Fatty Acid Metal Salt on Expanded Polyolefin Resin Particles)
The coating amount of the fatty acid metal salt on the expanded polyolefin resin particles is preferably 0.05% by weight or more and 1% by weight or less, more preferably 0.08% by weight or more and 0.80% by weight or less, even more preferably 0.10% by weight or more and 0.60% by weight or less, and particularly preferably 0.15% by weight or more and 0.40% by weight or less, relative to 100% by weight of the expanded polyolefin resin particles.
Filling beads with a coating amount of the fatty acid metal salt of 0.05% by weight or more can reliably provide a cushioning material with a good feel, while filling beads with a coating amount of 1% by weight or less can effectively prevent excessive detachment of the fatty acid metal salt from the expanded polyolefin resin particles, improving workability when filling the filler beads into a bag and more reliably preventing the scattering of the fatty acid metal salt when the cushioning material is used.

(Method for measuring the amount of coating of fatty acid metal salt)
The method for measuring the coating amount of the fatty acid metal salt on the expanded polyolefin resin particles can be appropriately selected from known methods. Hereinafter, a method for measuring the coating amount of zinc stearate by chelate titration will be described as an example when zinc stearate is used as the fatty acid metal salt.
First, a predetermined amount of expanded polyolefin resin particles and methanol are placed in a flask or other container and stirred to elute the zinc stearate coated on the expanded polyolefin resin particles into the methanol. The methanol from which the zinc stearate has been eluted is then separated and mixed with an aqueous EDTA-Na ₂ -Cu(II) solution adjusted to a predetermined concentration and an NH ₄ Cl-ammonia buffer solution adjusted to a predetermined pH to prepare aqueous solution S1. Next, using an automatic potentiometric titrator equipped with an ion-selective electrode (copper ion electrode), an aqueous solution S2 containing EDTA-Na ₂ and MgCl ₂ adjusted to a predetermined concentration is added dropwise to aqueous solution S1 to perform chelate titration. The amount of copper ions (i.e., the amount of zinc ions) is calculated from this measurement, and the amount of zinc stearate contained in aqueous solution S1 is calculated by multiplying this amount by the molecular weight of zinc stearate (632 g/mol) for unit conversion. The amount of zinc stearate coated on the expanded polyolefin resin beads can be determined by dividing this amount by the amount of expanded polyolefin resin beads used in the measurement and expressing the result as a percentage.

(Average coating amount of fatty acid metal salt on expanded polyolefin resin beads)
The average coating amount of the fatty acid metal salt on the expanded polyolefin resin beads is preferably 0.01 μg or more and 0.3 μg or less per 1 mm ³ of the average volume of the expanded polyolefin resin beads.
When the average coating amount of the fatty acid metal salt is 0.01 μg or more per 1 ^mm3 of average volume of the expanded polyolefin resin beads, the cushioning material is likely to consistently exhibit a good feel to the touch. From this perspective, the average coating amount of the fatty acid metal salt is preferably 0.02 μg ^or more, more preferably 0.03 μg or more, even more preferably 0.04 μg or more, and particularly preferably 0.05 μg or more per 1 mm3 of average volume of the expanded polyolefin resin beads. Furthermore, by adjusting the average coating amount of the fatty acid metal salt to 0.3 μg or less per 1 ^mm3 of average volume of the expanded polyolefin resin beads, detachment of the fatty acid metal salt can be effectively prevented. From this perspective, the average coating amount of the fatty acid metal salt is preferably 0.20 μg or less, more preferably 0.18 μg or less, and even more preferably 0.16 μg or less per ¹ mm3 of average volume of the expanded polyolefin resin beads.
The average coating amount of fatty acid metal salt per 1 ^mm3 of average volume of expanded polyolefin resin beads is calculated by calculating the amount A (g) of fatty acid metal salt in a given amount (e.g., 100 g) of expanded polyolefin resin beads, the average volume a ( ^mm3 /bead) of each expanded polyolefin resin bead, and the number b (beads) of expanded polyolefin resin beads in the given amount (e.g., 100 g).Then, using the obtained values, it is calculated using the following formula (1):
[Equation 1]
Average coating amount (μg) of fatty acid metal salt per 1 ^mm3 of average volume of expanded polyolefin resin beads = Amount of fatty acid metal salt A (g) × ¹⁰⁶ / (Average volume a ( ^mm3 /particle) × Number of particles b (particles)) (1)

The method for coating the expanded bead body with a coating agent containing a fatty acid metal salt will be explained in the method for producing stuffing beads described below.

Fatty acid amides:
The expanded polyolefin resin particles constituting the filler beads of the present invention contain a fatty acid amide, which is realized by incorporating the fatty acid amide into the expanded particle bodies constituting the filler beads.
When a coating agent is applied to an expanded bead body having a polyolefin resin as a base resin, the coating agent tends to be more easily removed, resulting in a poorer feel of the cushioning material, compared to when a coating agent is applied to an expanded bead body having a polystyrene resin as a base resin. In contrast, the present invention not only coats the surface of the expanded bead body with a coating agent, but also incorporates a fatty acid amide into the expanded bead body, thereby achieving the excellent effect of enabling the cushioning material to maintain a good feel for a long period of time. The reason for this effect is unclear, but it is thought that a portion of the fatty acid amide contained in the expanded bead body migrates from the expanded bead body to the surface of the expanded bead body over time, and the affinity between the migrated fatty acid amide and the coating agent, such as a fatty acid metal salt, that coats the surface is good, thereby improving the fluidity of the expanded beads and making it easier to prevent the fatty acid metal salt from detaching.

In the present invention, fatty acid amide refers to a higher fatty acid amide having a hydrocarbon group with 12 or more carbon atoms. The number of carbon atoms in the hydrocarbon group of the fatty acid amide is preferably 12 to 30, more preferably 16 to 26, and even more preferably 18 to 24. The number of carbon atoms in the hydrocarbon group of the fatty acid amide is the number of carbon atoms in the hydrocarbon group excluding the carbon atoms constituting the amide group. For example, when the fatty acid amide is a primary amide, the fatty acid amide is represented by the general formula _RCONH2 and is a compound having a hydrocarbon group (specifically, a long-chain fatty acid group) and an amide group. In the general formula _RCONH2 , R is a hydrocarbon group.
The fatty acid amide may be a saturated fatty acid amide or an unsaturated fatty acid amide. From the viewpoint of easily maintaining the feel of the cushioning material for a long period of time, an unsaturated fatty acid amide is preferable. Furthermore, the fatty acid amide may be a primary amide, a secondary amide, or a tertiary amide. From the viewpoint of easily maintaining the feel of the cushioning material for a long period of time, a primary amide is preferable.

Specific examples of fatty acid amides include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide, and behenic acid amide; and unsaturated fatty acid amides such as oleic acid amide, erucic acid amide, and nervonic acid amide. The expanded bead body may contain one or more fatty acid amides. From the viewpoints of easily improving the feel of the cushioning material and easily maintaining the feel of the cushioning material over a long period of time, it is preferable that the fatty acid amide contains at least erucic acid amide.
Furthermore, when the fatty acid amide contains erucic acid amide, the proportion of erucic acid amide in the fatty acid amide is preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more.

(Fatty acid amide content in expanded polyolefin resin beads)
The content of the fatty acid amide in 100% by weight of the expanded polyolefin resin particles is preferably 0.01% by weight or more and 3% by weight or less, more preferably 0.02% by weight or more and 1% by weight or less, and even more preferably 0.03% by weight or more and 0.5% by weight or less. By setting the content of the fatty acid amide in the expanded polyolefin resin particles within the above range, the feel of the cushioning material can be improved and the feel of the cushioning material can be maintained for a longer period of time.
The content of fatty acid amide in the expanded polyolefin resin beads is equivalent to the amount of fatty acid amide used in the production of the expanded polyolefin resin beads, and therefore, the amount mentioned above is used as a reference. For example, when the expanded bead body is made to contain fatty acid amide during production, the amount of fatty acid amide used as a material at that time is recognized as the amount of fatty acid amide contained in the expanded polyolefin resin beads.
Alternatively, the content of fatty acid amide in the expanded beads can be determined by subjecting the expanded beads to gas chromatography-mass spectrometry (GC-MS) or the like.
When the content of fatty acid amide in the expanded beads is determined by gas chromatography mass spectrometry (GC-MS), the following method can be used, for example.
First, the frozen-pulverized expanded particles are subjected to Soxhlet extraction using chloroform as a solvent to remove chloroform-insoluble polymer components and the like. Next, the chloroform-soluble portion obtained by Soxhlet extraction is mixed with acetone, and the acetone-insoluble portion is removed. The solid obtained by removing the solvent from the acetone-soluble portion is used as a measurement sample and measured by gas chromatography-mass spectrometry (GC-MS). The content of fatty acid amide in the expanded particles can be determined from the relationship between this measurement result and a calibration curve created from a standard (internal standard sample) of known concentration.
As the gas chromatograph mass spectrometer, for example, a JMS-Q1500GCV model manufactured by JEOL Ltd. can be used.

(Average value of fatty acid amide content in expanded polyolefin resin beads)
The average content of fatty acid amide in the expanded polyolefin resin beads is preferably 0.002 μg or ^more and 0.5 μg or less, more preferably 0.005 μg or more and 0.3 μg or less, and even more preferably 0.008 μg or more and 0.1 μg or less per 1 mm3 of average volume of the expanded polyolefin resin beads.
When the average fatty acid amide content is 0.002 μg or more per 1 ^mm3 of average volume of polyolefin resin expanded beads, the cushioning material tends to maintain its good feel for a longer period of time. Furthermore, when the average fatty acid amide content is 0.5 μg or less per 1 ^mm3 of average volume of polyolefin resin expanded beads, a cushioning material with a good feel can be stably obtained. The average fatty acid amide content per 1 ^mm3 of average volume of polyolefin resin expanded beads is calculated by calculating the amount B (g) of fatty acid amide contained in a given amount (e.g., 100 g) of polyolefin resin expanded beads, the average volume a ( ^mm3 /bead), and the number b (beads) of expanded beads in the given amount (e.g., 100 g) of polyolefin resin expanded beads. The obtained values are then used to calculate the following formula (2):
[Equation 2]
Average value (μg) of fatty acid amide content per 1 ^mm3 of average volume of expanded polyolefin resin beads = Amount of fatty acid amide B (g) × ¹⁰⁶ / (Average volume a ( ^mm3 /particle) × Number of particles b (particles)) (2)

(Weight ratio of fatty acid amide to fatty acid metal salt)
In the expanded polyolefin resin beads, the weight ratio of the fatty acid amide content to the amount of coating of fatty acid metal salt is preferably 1:0.5 to 1:20, more preferably 1:1 to 1:15, even more preferably 1:2 to 1:10, and particularly preferably 1:3 to 1:8. By adjusting the weight ratio of fatty acid amide to fatty acid metal salt within the above range, detachment of the coating agent from the expanded beads is less likely to occur, the feel of the cushioning material becomes stable and good, and the good feel of the cushioning material can be maintained for a longer period of time.

Next, the average particle diameter, average volume, average weight, average L/D, and bulk density of expanded polyolefin resin beads will be described. The expanded polyolefin resin beads of the present invention differ from the expanded beads themselves in that the expanded beads themselves are coated with a coating agent. However, the average particle diameter, average volume, average weight, average L/D, and bulk density of the expanded polyolefin resin beads are nearly equivalent to those of the expanded beads themselves. Furthermore, the methods for measuring the average particle diameter, average L/D, average volume, average weight, and bulk density using expanded polyolefin resin beads can also be applied to the expanded beads themselves, as appropriate.

(Average particle size of expanded polyolefin resin particles)
The average particle size of the expanded polyolefin resin beads is not particularly limited, but is preferably 1 mm or more, more preferably 2 mm or more, and even more preferably 3 mm or more. When polyolefin resin beads with a relatively large particle size are used as padding beads for cushioning materials, the feel of the cushioning material tends to be poor. However, by using padding beads with the configuration of the present invention, a cushioning material with a good feel can be obtained. Furthermore, by using expanded polyolefin resin beads with a relatively large particle size, the ratio of the total surface area of the expanded polyolefin resin beads to the total volume of the expanded polyolefin resin beads filled in the cushioning material can be reduced. This reduces the amount of coating agent that coats the surfaces of the expanded polyolefin resin beads and also helps to prevent the coating agent (especially the powdered fatty acid metal salt) from scattering into the air during use of the cushioning material. On the other hand, from the viewpoint of improving fluidity within the cushioning material, the average particle size of the expanded polyolefin resin beads is preferably 12 mm or less, more preferably 10 mm or less, and even more preferably 8 mm or less.

The average particle size of the expanded polyolefin resin beads is calculated as the diameter of a hypothetical sphere having the same volume as the average volume per expanded polyolefin resin bead determined by the method described below.

(Average volume of expanded polyolefin resin beads)
The average volume per expanded polyolefin resin bead is preferably 0.5 mm ³ /piece or more and 1000 mm ³ /piece or less, more preferably 5 mm ³ /piece or more and 500 mm ³ /piece or less, and even more preferably 10 mm ³ /piece or more and 300 mm ³ /piece or less. Even when using expanded polyolefin resin beads with a relatively large volume as described above, a cushioning material with a good feel can be obtained by using filler beads having the configuration of the present invention.

The average volume per expanded polyolefin resin bead is determined by the submersion method. Specifically, water at 23°C is first poured into a measuring cylinder. Next, a predetermined number (e.g., 100) of expanded polyolefin resin beads are placed in the measuring cylinder, and the expanded polyolefin resin beads in the measuring cylinder are submerged in water using a wire mesh. The amount of rise in the water level in the measuring cylinder is then read, and the apparent volume (unit: L) of the expanded polyolefin resin beads is calculated by subtracting the volume of the wire mesh from the amount of rise in the water level. This apparent volume is then divided by the number of expanded polyolefin resin beads placed in the measuring cylinder, and the average volume (unit: ^mm3 /bead) of the expanded polyolefin resin beads can be calculated by converting the unit.
The average coating amount of the fatty acid metal salt per 1 mm ³ of the average volume of the expanded polyolefin resin beads can be calculated by the above-mentioned formula (1).

(Average weight of expanded polyolefin resin particles)
The average weight per expanded polyolefin resin bead is not particularly limited, but is preferably in the range of 0.1 mg or more and 5 mg or less, and more preferably 0.5 mg or more and 2 mg or less.
The average weight per polyolefin resin expanded particle is determined by measuring the total weight of 100 or more randomly selected polyolefin resin expanded particles and dividing the total weight by the number of selected polyolefin resin expanded particles.

(Average L/D of expanded polyolefin resin particles)
The shape of the expanded polyolefin resin beads is not particularly limited, but when the expanded beads are approximately cylindrical, the average L/D, which is the average ratio of the major axis (L) of the expanded beads to the minor axis (D) of the expanded beads, is preferably 0.8 or more and 1.3 or less, and more preferably 0.9 or more and 1.2 or less.
When the expanded bead bodies are produced by the direct expansion method described below, a substantially cylindrical expanded bead body is likely to be obtained. Comparing an embodiment using a substantially cylindrical expanded bead body with an embodiment using a substantially spherical expanded bead body, the embodiment using a substantially cylindrical expanded bead body generally tends to have inferior fluidity. However, by using an expanded bead body that is coated with a coating agent containing a fatty acid metal salt and also contains a fatty acid amide, a cushioning material with excellent fluidity and a pleasant feel can be easily realized, even with substantially cylindrical expanded polyolefin resin beads that have an average L/D within the above range.

The average L/D of the expanded polyolefin resin beads is determined as follows.
For 30 or more randomly selected expanded polyolefin resin beads, the maximum length (longer diameter of the expanded beads) L in the axial direction (height direction of the cylinder) of the expanded beads and the minimum diameter (minor diameter of the expanded beads) D at the center in the longitudinal direction of the maximum length L are measured with a vernier caliper, and the L/D of each expanded bead is calculated. The arithmetic mean value of the obtained values is taken as the average L/D of the expanded polyolefin resin beads.
In addition, when it is difficult to determine the axial direction of the expanded beads because the expanded beads are almost spherical, the maximum length of the expanded beads is taken as the major axis L of the expanded beads.

(Bulk density of expanded polyolefin resin particles)
The bulk density of the expanded polyolefin resin particles constituting the filler beads of the present invention is not particularly limited and can be appropriately determined taking into consideration the use of the cushioning material produced therefrom, etc. For example, from the viewpoint of reducing the weight of the cushioning material and providing good cushioning properties and feel, the bulk density is preferably 5 kg/ ^m3 or more and 200 kg/ ^m3 or less, more preferably 10 kg/ ^m3 or more and 100 kg/ ^m3 or less, even more preferably 12 kg/ ^m3 or more and 50 kg/ ^m3 or less, and particularly preferably 15 kg/ ^m3 or more and 30 kg/ ^m3 or less.

In order to adjust the bulk density to the above range, the bulk density of the expanded beads used in the expanded polyolefin resin beads may be adjusted.
The bulk density of the expanded bead body can be adjusted, for example, by appropriately changing the expansion conditions, such as the temperature and pressure in the sealed container when the content of the sealed container is released during the expansion process.
If a lower bulk density of the expanded bead body is desired, a step of expanding the expanded bead body in multiple stages (two-stage expansion step) may be carried out. For the two-stage expansion step, see the explanation of the method for producing filler beads described below.

The bulk density of the expanded polyolefin resin beads described above is measured by the following method. First, the expanded polyolefin resin beads to be measured are left to stand for 24 hours or more in an environment of 23°C temperature, 50% relative humidity, and 1 atm. The expanded beads having a weight W (g) thus obtained are filled into a measuring cylinder, and the bottom of the measuring cylinder is lightly tapped against the floor several times to stabilize the filling height of the expanded beads in the measuring cylinder. The bulk volume V (L) of the expanded beads indicated on the measuring cylinder scale is read, and the weight W of the expanded beads is divided by the bulk volume V of the expanded beads (W/V). The value thus obtained is converted into kg/ ^m3 to obtain the bulk density (kg/ ^m3 ) of the expanded beads.

[Manufacturing method of stuffing beads]
The method for producing the filler beads of the present invention is not particularly limited and can be appropriately determined within the range in which the expanded polyolefin resin beads having the above-mentioned configuration can be obtained. A preferred embodiment of the method for producing the filler beads will be described below.

Production of polyolefin resin particles:
Polyolefin resin particles are produced to obtain the expanded bead main body that constitutes the expanded polyolefin resin beads. The method for producing polyolefin resin particles is not particularly limited, but they can be produced, for example, by an extrusion method using an extruder. In the extrusion method, first, the polyolefin resin that constitutes the expanded bead main body is fed into the extruder, melted, and kneaded to obtain a resin melt. At this time, a fatty acid amide and, if necessary, other materials are blended with the polyolefin resin, which is the base resin.
The resin melt is then extruded from an extrusion die provided downstream of the extruder and pelletized to obtain cylindrical polyolefin resin particles.
The pelletizing method can be, for example, a method in which the molten resin is extruded through an extrusion die to form strands, and then the strands are cut into desired dimensions using a pelletizer or the like.

Manufacturing of the foamed particle body:
The expanded bead body can be produced by expanding the polyolefin resin beads prepared as described above. For example, the expanded bead body can be produced by a method for producing expanded beads including a dispersion step, a blowing agent impregnation step, and an expansion step.
The dispersing step is a step of dispersing polyolefin resin particles in an aqueous medium containing an inorganic dispersant in a container. The foaming agent impregnation step is a step of impregnating the polyolefin resin particles with a foaming agent in a container. The foaming step is a step of releasing the foaming agent-containing polyolefin resin particles (expandable resin particles) together with the aqueous medium from a sealed container to foam them.
In addition to these steps, any steps may be added to the production method of the present invention as appropriate within the scope of the present invention.

If necessary, a second-stage expansion process may be carried out after the expansion process. The second-stage expansion process involves first storing the expanded bead bodies in a pressurizable sealed container, and then pressurizing the container by injecting a gas such as air into it to increase the internal pressure within the cells of the expanded bead bodies. The expanded bead bodies are then removed from the sealed container and heated with steam or hot air to expand them. By carrying out this second-stage expansion process, it is possible to obtain expanded bead bodies (second-stage expanded beads) with a lower bulk density.

(high temperature peak)
Furthermore, in order to adjust the crystalline state of the resulting expanded bead body, adjustments such as adjusting the temperature rise rate of the container or holding the container at a predetermined temperature for a predetermined time may be made in the dispersion step and/or the blowing agent impregnation step described above. For example, it is possible to adjust the DSC curve obtained by heat flux differential scanning calorimetry (see FIG. 1 ) so that an endothermic peak (high-temperature peak) appears at a higher temperature than the endothermic peak (intrinsic peak) of the base resin constituting the expanded bead body. By making the expanded bead body exhibit such a high-temperature peak, it becomes easier to obtain filling beads that have good cushioning properties and good recovery properties.
The adjustment to obtain the above-mentioned high-temperature peak can be performed, for example, as follows. In the above-mentioned dispersion step and/or blowing agent impregnation step, a first-stage holding step is performed in which the temperature is held at a temperature of (the melting point of the polyolefin resin - 20°C) or higher but lower than the (end-of-melting temperature of the polyolefin resin) for about 10 to 60 minutes. Thereafter, the temperature is adjusted to a temperature of (the melting point of the polyolefin resin - 15°C) to lower than the (end-of-melting temperature of the polyolefin resin). If necessary, a second-stage holding step is performed in which the temperature is held for another 10 to 60 minutes. Next, the foaming step described below is performed, thereby producing expanded beads having a high-temperature peak.
From the viewpoint of stably obtaining padding beads having an excellent balance between cushioning properties and recovery properties, the total heat of fusion of the obtained expanded bead body or the polyolefin resin expanded beads using the expanded bead body is preferably 50 J/g or more and 90 J/g or less, more preferably 55 J/g or more and 80 J/g or less. Furthermore, the endothermic heat of the high-temperature peak (high-temperature peak heat quantity) of the obtained expanded bead body or the polyolefin resin expanded beads using the expanded bead body is preferably 5 J/g or more and 40 J/g or less, more preferably 8 J/g or more and 30 J/g or less, and even more preferably 10 J/g or more and 20 J/g or less.
The total heat of fusion and the high-temperature peak heat of the expanded beads themselves or the expanded polyolefin resin beads using the expanded beads are determined based on the method for measuring the heat of transition of plastics described in JIS K7122:1987 from a DSC curve (see FIG. 1 ) obtained by heating a test piece of 1 to 3 mg of the expanded beads from 23°C to a temperature 30°C higher than the end of the melting peak at a heating rate of 10°C/min.

More specifically, on the DSC curve shown in Fig. 1, a straight line is drawn connecting point I on the DSC curve, which corresponds to 80°C, and point II, which corresponds to the melting end temperature of the expanded beads. The melting end temperature is the high-temperature end point of high-temperature peak b, and is the intersection point of high-temperature peak b and a baseline on the higher temperature side of high-temperature peak b on the DSC curve.
As shown in FIG. 1 , a line is drawn connecting points I and II, and then a line passing through the maximum point III between the intrinsic peak a and the high-temperature peak b and parallel to the vertical axis of the graph intersects with the line connecting points I and II at point IV.
The area of the straight line connecting points I and IV, the straight line connecting points III and IV, and the DSC curve connecting points I and III are defined as the area of intrinsic peak a. The area of the portion (shaded portion) surrounded by the straight line connecting points IV and II, the straight line connecting points III and IV, and the DSC curve connecting points III and II is defined as the area of high-temperature peak b. The total heat of fusion of the expanded beads is calculated from the sum of the areas of intrinsic peak a and high-temperature peak b determined as described above, and the high-temperature peak heat of the expanded beads is calculated from the area of high-temperature peak b.

Production of filler beads (polyolefin resin expanded particles):
Filling beads are produced by coating the foamed bead bodies, which are prepared as described above and have a polyolefin resin as the base resin and contain a fatty acid amide, with a coating agent containing a fatty acid metal salt. The coating method is not particularly limited, but for example, an appropriate amount of foamed bead bodies and a powdery coating agent containing a fatty acid metal salt are mixed in a mixer such as a drum tumbler, and the coating agent is thereby attached to the surface of the foamed bead bodies to coat them.
This manufacturing method involves a simple process in which a typical expanded bead body is obtained by a manufacturing method for the expanded bead body, and then the expanded bead body is coated with a coating agent, thereby obtaining stuffing beads that can improve the feel of the cushioning material and maintain the feel of the cushioning material for a longer period of time.
According to the inventors' investigations, when a coating agent is applied to the expanded bead body having a polyolefin resin as the base resin, the coating agent tends to be more easily removed than when a coating agent is applied to the expanded bead body having a polystyrene resin as the base resin. However, the above-mentioned production method makes it possible to adhere the coating agent well to the expanded bead body having a polyolefin resin as the base resin.

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In Table 1, expanded polyolefin resin beads are simply referred to as "expanded beads."
Example 1
(Preparation of Resin Particles)
A production apparatus was prepared, which was equipped with an extruder having an inner diameter of 50 mm and a strand-forming die attached to the downstream side of the extruder.
Polypropylene resin, erucic acid amide ("Fatty Acid Amide E" manufactured by Kao Corporation, added to achieve the content shown in Table 1) as a fatty acid amide, and zinc borate (0.1 part by weight per 100 parts by weight of polypropylene resin) as a cell regulator were fed into an extruder and melt-kneaded. The resulting molten resin was introduced into a strand-forming die to extrude strands. The extruded strands were water-cooled and cut with a pelletizer to obtain resin particles with an average weight of 1.0 mg per piece.

(Preparation of Expanded Bead Body)
1 kg of the obtained resin particles was supplied together with 3 L of water as an aqueous dispersion medium into a sealed container having an internal volume of 5 L. Furthermore, 0.3 parts by weight of kaolin as an inorganic dispersant and 0.004 parts by weight (as an active ingredient) of a surfactant (trade name: NEOGEN, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) were added to the sealed container relative to 100 parts by weight of the resin particles.
Next, carbon dioxide was injected into the sealed container as a blowing agent and pressurized to a gauge pressure of 2.0 MPa (G). The pressures indicated with (G) are gauge pressures, i.e., pressure values based on atmospheric pressure. The contents of the sealed container were then heated to the foaming temperature (149.5°C) at a rate of 2°C/min while stirring, and maintained at this temperature for 15 minutes. This adjustment allowed the endothermic curve of the resulting expanded beads to exhibit a high-temperature peak when measured by DSC.
Thereafter, the contents of the sealed container (resin particles and water) were released under atmospheric pressure to obtain expanded particles (first-stage expanded particles) having a bulk density of 60 kg/m ³ .
The first-stage expanded beads obtained as described above were left to cure for 24 hours in an environment of 23°C temperature, 50% relative humidity, and 1 atm. The cured first-stage expanded beads were then filled into a pressurizable sealed container, and the pressure inside the sealed container was increased from normal pressure to pressurize the expanded beads. The pressurized state of the expanded beads was maintained for a predetermined time, allowing air to penetrate into the cells of the expanded beads. The first-stage expanded beads were then removed from the sealed container, and first-stage expanded beads with an internal cell pressure of 0.5 MPa (G) were obtained. The first-stage expanded beads were then fed into a second-stage expansion device. Steam was supplied into the device to expand the first-stage expanded beads, resulting in expanded bead bodies with a bulk density of 18 kg/ ^m3 .
The total heat of fusion of the expanded beads obtained was 65 J/g, and the heat of fusion of the high-temperature peak was 15 J/g.

Preparation of Filling Beads
The expanded bead bodies obtained as described above and zinc stearate as a fatty acid metal salt were fed into a drum tumbler having a volume of 100 L so as to obtain the coating amounts shown in Table 1. The expanded bead bodies and the coating agent were then mixed by stirring at a temperature of 23°C for 15 minutes to adhere the coating agent to the surfaces of the expanded bead bodies, thereby producing approximately cylindrical expanded polyolefin resin beads whose particle body surfaces were coated with the coating agent.

<Examples 2 to 4, Comparative Examples 1 and 2>
Filler beads of Examples 2 to 4 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except for the changes shown in Table 1.

For each of the Examples and Comparative Examples carried out as described above, the average particle size, average L/D, average volume (a), average weight, and bulk density of the expanded polyolefin resin beads were measured by the following methods.
The coating amount (A) of fatty acid metal salt per 100 g of expanded polyolefin resin beads for each Example and Comparative Example was calculated by the following method, and the average coating amount of fatty acid metal salt per ^mm3 of average volume of expanded beads was calculated using the above formula (1) and shown in Table 1. The content (B) of fatty acid amide per 100 g of expanded polyolefin resin beads was calculated from the amount of fatty acid amide blended with the resin beads and shown in Table 1, and the average content of fatty acid amide per ^mm3 of average volume of expanded beads was calculated using the above formula (2) and shown in Table 1. The weight ratio of fatty acid metal salt to fatty acid amide in the expanded polyolefin resin beads was also determined.
The results of these measurements are shown in Table 1. The average weight of the expanded polyolefin resin beads obtained in the Examples and Comparative Examples was 1.0 mg, and the average L/D was 1.1.

<Average particle size of expanded beads>
From the average volume of the expanded beads determined as described below, the diameter of a virtual sphere having the same volume as the average volume of the expanded beads was calculated, and this was taken as the average particle size of the expanded beads.

<Average L/D of expanded beads>
For 30 randomly selected expanded beads, the maximum axial length L of the expanded beads (the major axis of the expanded beads) and the minimum diameter D of the central portion in the length direction of the maximum length L of the expanded beads (the minor axis of the expanded beads) were measured with a vernier caliper. The L/D ratio for each expanded bead was calculated, and the arithmetic mean value was taken as the average L/D of the expanded beads.

<Average volume a of expanded beads>
A measuring cylinder with a volume of 200 mL was prepared, and 100 mL of water at 23°C was placed in the measuring cylinder. Next, 100 expanded beads were placed in the measuring cylinder and submerged in the water in the measuring cylinder using a wire mesh, and the amount of rise in the water level in the measuring cylinder was read. The apparent volume (unit: L) of the expanded beads was then calculated by subtracting the volume of the wire mesh from the amount of rise in the water level. This apparent volume was divided by the number of expanded beads placed in the measuring cylinder and converted into units to calculate the average volume of the expanded beads (unit: ^mm3 /piece).

<Average weight of expanded beads>
The total weight of 100 randomly selected expanded beads was measured, and this was divided by 100 to determine the average weight (mg) per expanded bead.

<Bulk density of expanded beads>
First, the expanded beads to be measured were left for 24 hours or more in an environment of 23°C, 50% relative humidity, and 1 atm. Then, a weight W (unit: g) of expanded beads was filled into a measuring cylinder, and the bottom of the measuring cylinder was lightly tapped against the floor several times to stabilize the filling height of the expanded beads in the measuring cylinder. The bulk volume V (unit: L) of the expanded beads indicated on the measuring cylinder's scale was read, and the weight W of the expanded beads was divided by the bulk volume V of the expanded beads (i.e., W/V). The value thus obtained was converted into units to obtain the bulk density (unit: kg/ ^m3 ) of the expanded beads.

<Coating Amount A of Fatty Acid Metal Salt>
The coating amount of the fatty acid metal salt (zinc stearate) used as the coating agent was determined by the following method (chelate titration method).
First, 6 g of expanded polyolefin resin particles and 100 mL of methanol were placed in a 500 mL flask and stirred to elute the zinc stearate coated on the expanded polyolefin resin particles into the methanol. Next, the expanded polyolefin resin particles were removed, and the methanol into which the zinc stearate had been eluted was transferred to a container (a plastic cup).
Next, 5 mL of an EDTA-Na ₂ —Cu(II) aqueous solution (concentration: 2.0×10 ⁻² mol/L) and 5 mL of an NH ₄ Cl-ammonia buffer solution (pH 10.7) were placed in the container to prepare an aqueous solution S1.
Next, using an automatic potentiometric titrator (Kyoto Electronics Manufacturing Co., Ltd. "AT-710", copper ion electrode: I-371) equipped with an ion-selective electrode (copper ion electrode), an aqueous solution S2 containing EDTA-Na ₂ and MgCl ₂ (EDTA-Na ₂ concentration: 1.0 × 10 ^-2 mol/L, MgCl ₂ concentration: 1.0 × 10 ^-3 mol/L) was dropped into a container containing the aqueous solution S1, and chelate titration was performed. The amount of aqueous solution S2 dropped at the equivalence point determined by this measurement was multiplied by the EDTA-Na ₂ concentration of the aqueous solution S2 to calculate the amount of copper ions (mol) in the aqueous solution S1 (i.e., the amount of zinc ions (mol)), and this ion amount was multiplied by the molecular weight of zinc stearate (632 g/mol) to calculate the amount of zinc stearate contained in the aqueous solution S1. This amount of zinc stearate was divided by the amount of expanded polyolefin resin beads used in the measurement, and the result was expressed as a percentage to determine the coating amount (wt %) of zinc stearate on the expanded polyolefin resin beads.
Furthermore, based on the coating amount of zinc stearate, the coating amount A per 100 g of expanded beads was calculated.

<Average coating amount (μg) of fatty acid metal salt per 1 ^mm3 of average volume of expanded beads>
The average coating amount (μg) of the fatty acid metal salt per 1 ^mm3 of average volume of the expanded beads was calculated using the above-mentioned formula (1). Since the weight of the expanded beads used in the examples and comparative examples was 1.0 mg/piece, the number of expanded beads per 100 g of expanded bead body was calculated as 1.0 × ¹⁰⁵ pieces.

<Fatty Acid Amide Content B>
The content B of fatty acid amide per 100 g of expanded beads was calculated from the amount of fatty acid amide blended in the resin beads used to produce the expanded beads.

<Average content (μg) of fatty acid amide per 1 ^mm3 of average volume of expanded beads>
The average content (μg) of fatty acid amide per 1 ^mm3 of average volume of expanded beads was calculated using the above-mentioned formula (2). Since the weight of the expanded beads used in the examples and comparative examples was 1.0 mg/piece, the number of expanded beads per 100 g of expanded beads was calculated as 1.0 × ¹⁰⁵ pieces.

The cushioning materials filled with each example and comparative example were evaluated or measured for their recovery rate from repeated compression, angle of repose, feel, and feel after repeated compression tests, and the results are shown in Table 1.

<Recovery rate from repeated compression>
A bulk volume of 330 mL of expanded polyolefin resin beads was measured using a 500 mL measuring cylinder and placed in a cylindrical container with an inner diameter of 78 mm. Using a compression tool with a flat contact area with the expanded polyolefin resin beads, the expanded polyolefin resin beads in the container were compressed by moving the compression tool downward at a speed of 10 mm/min. When the load applied to the expanded polyolefin resin beads reached 650 N, the compression tool was moved upward, and the load on the expanded polyolefin resin beads was completely released. This cycle constituted one cycle, and a repeated compression test was performed by repeating compression and release 100 times.
After the repeated compression test, the expanded polyolefin resin particles were placed in a 500 mL measuring cylinder and left to stand for 24 hours at 25°C, 50% humidity, and 1 atm, after which the bulk volume was measured. The ratio of the bulk volume after the repeated compression test to the bulk volume of the expanded polyolefin resin particles before the repeated compression test was calculated, and this value was taken as the repeated compression recovery rate (unit: %).

<Angle of repose>
To evaluate the flowability of the expanded polyolefin resin beads, the angle of repose was determined. Specifically, the angle of repose of the expanded polyolefin resin beads was determined by the cylindrical rotation method using a "Flow Surface Angle Measuring Instrument FSA-100S" manufactured by Tsutsui Scientific Instruments Co., Ltd.
First, 200 mL of expanded polyolefin resin beads in terms of bulk density were placed in a cylindrical container (volume 500 mL) for measurement. Next, the cylindrical container was rotated for 3 minutes at a rotation speed of 26 seconds per revolution. The rotation of the container was then stopped just before the upper part of the expanded polyolefin resin beads collapsed. A goniometer was set to align with the upper and lower ends of the slope of the expanded polyolefin resin beads formed by this operation, and the angle of the slope was measured. The measured angle was taken as the angle of repose of the expanded polyolefin resin beads. A repose angle of 35° or less can be determined to indicate good fluidity. From the viewpoint of improving the fluidity of the expanded polyolefin resin beads, the angle of repose is preferably 34° or less, more preferably 33° or less. The lower limit of the angle of repose is approximately 25°, and may be 28°.

<Texture>
A cushioning material was prepared by filling and sealing a 2.5 L bulk volume of expanded polyolefin resin particles into a stretchable bag (2 L internal volume) made of spandex fabric (200 g/ ^m2 basis weight). The following feel evaluation was carried out on this cushioning material to evaluate the feel of the expanded polyolefin resin particles.
(Touch evaluation)
Ten randomly selected panelists checked the feel of the cushioning materials prepared as described above and evaluated the feel of the cushioning materials according to the following criteria.
3 points: High fluidity and smooth feel 2 points: Fluidity is good, but occasionally feels rough 1 point: Low fluidity and feels rough The feel of the cushioning material was evaluated using the following criteria: a total score of 27 points or more by 10 people was given an "A" rating, a total score of 20 to 26 points by 10 people was given a "B" rating, and a total score of 19 points or less by 10 people was given a "C" rating. In the above evaluations, an "A" rating means that the feel is the best.

<Feel after repeated compression test>
A bulk volume of 5 L of expanded polyolefin resin beads was placed in a cylindrical container with an inner diameter of 500 mm. Using a compression tool with a flat contact area with the expanded polyolefin resin beads, the expanded polyolefin resin beads in the container were compressed by moving the compression tool downward at a speed of 10 mm/min. When the load applied to the expanded polyolefin resin beads reached 10 kN, the compression tool was moved upward, and the load on the expanded polyolefin resin beads was completely released. This cycle was counted as one cycle, and a repeated compression test was performed by repeating compression and release 100 times.
The expanded polyolefin resin particles after the repeated compression test were filled into the bag in a bulk volume of 2.5 L to prepare a cushioning material. The feel of the cushioning material was evaluated in the same manner as in the evaluation of feel described above, except that this cushioning material was used, and the feel (durability of the feel of the expanded polyolefin resin particles) after the repeated compression test was evaluated. If the feel of the cushioning material was evaluated as "A," it can be determined that the expanded polyolefin resin particles are capable of maintaining a good feel even after long-term use.

The above embodiment encompasses the following technical ideas.
(1) Filling beads for use as a cushioning filler,
The filler beads are expanded polyolefin resin beads, the expanded beads having a polyolefin resin as a base resin and a coating agent containing a fatty acid metal salt.
Filling beads characterized in that the expanded bead body contains a fatty acid amide.
(2) The filling beads according to (1), wherein the content of fatty acid amide in the expanded polyolefin resin beads is 0.01% by weight or more and 3% by weight or less.
(3) Filling beads according to (1) or (2) above, wherein the weight ratio of the fatty acid amide to the fatty acid metal salt is 1:0.5 to 1:20.
(4) Filler beads according to any one of (1) to (3) above, wherein the fatty acid amide comprises erucamide.
(5) The average volume of the expanded polyolefin resin beads is 0.5 mm ³ /piece or more and 1000 mm ³ /piece or less,
the average coating amount of the fatty acid metal salt on the expanded polyolefin resin particles is
The filler beads according to any one of (1) to (4) above, wherein the average weight of the expanded polyolefin resin beads is 0.01 μg or more and 0.3 μg or less per 1 ^mm3 of average volume.
(6) Filling beads according to any one of (1) to (5) above, wherein the fatty acid metal salt comprises zinc stearate.
(7) Filler beads according to any one of (1) to (6) above, wherein the expanded polyolefin resin particles have an approximately cylindrical shape and an average L/D of 0.8 or more and 1.3 or less.
(8) Filling beads according to any one of (1) to (7) above, wherein the bulk density of the expanded polyolefin resin particles is 5 kg/m ³ or more and 200 kg/m ³ or less.
(9) Filling beads according to any one of (1) to (8) above, wherein the coating amount of the fatty acid metal salt on the expanded polyolefin resin particles is 0.05% by weight or more and 1% by weight or less.
(10) The average content of the fatty acid amide in the expanded polyolefin resin beads is:
The filler beads according to any one of (1) to (9), wherein the weight of the expanded polyolefin resin particles is 0.002 μg or more and 0.5 μg or less per 1 ^mm3 of average volume.
(11) A method for producing fill beads for cushioning, comprising:
A foamed bead body containing a polyolefin resin as a base resin and a fatty acid amide is
A method for producing stuffing beads, comprising coating the stuffing beads with a coating agent containing a fatty acid metal salt.

Claims (8)

Filling beads for cushioning, comprising:
The filler beads are expanded polyolefin resin beads, the expanded beads having a polyolefin resin as a base resin and a coating agent containing a fatty acid metal salt.
The expanded bead body contains a fatty acid amide ,
the coating amount of the fatty acid metal salt on the expanded polyolefin resin particles is 0.05% by weight or more and 1% by weight or less, based on 100% by weight of the expanded polyolefin resin particles;
Filling beads characterized in that the weight ratio of said fatty acid amide to said fatty acid metal salt is 1:0.5 to 1:20 . 2. The filler beads according to claim 1, wherein the content of fatty acid amide in said expanded polyolefin resin beads is 0.01% by weight or more and 1 % by weight or less. 3. Filling beads according to claim 1 or 2 , wherein said fatty acid amide comprises erucamide. the average volume of the expanded polyolefin resin beads is 0.5 mm ³ /piece or more and 1000 mm ³ /piece or less;
the average coating amount of the fatty acid metal salt on the expanded polyolefin resin particles is
4. Filling beads according to claim 1, wherein the polyolefin-based resin expanded beads have an average volume of 0.01 ^μg or more and 0.3 μg or less per 1 mm3 of the expanded polyolefin-based resin beads. 5. Filling beads according to any one of claims 1 to 4 , wherein the fatty acid metal salt comprises zinc stearate. 6. Filler beads according to claim 1 , wherein the expanded polyolefin resin particles have a substantially cylindrical shape and an average L/D ratio of 0.8 to 1.3. 7. Filling beads according to any one of claims 1 to 6 , wherein the expanded polyolefin resin particles have a bulk density of 5 kg/ ^m3 or more and 200 kg/ ^m3 or less. 8. A method for producing fill beads for a cushioning material according to any one of claims 1 to 7, comprising the steps of :
A foamed bead body containing a polyolefin resin as a base resin and a fatty acid amide is
A method for producing stuffing beads, comprising coating said stuffing beads with a coating agent containing a fatty acid metal salt.