JP2022063453A - Hollow particles and cushion body - Google Patents

Abstract

To provide hollow particles comprising high rigidity and stability and being suitable for a cushion body, and a cushion body using the hollow particles as a filler.SOLUTION: Hollow particles 1 comprise: an outer shell layer 2 which has a resin film formed of a substrate resin and a plurality of air bubbles which is partitioned by the resin film, and whose average thickness is 30 μm or greater and 150 μm or smaller; and a hollow part 3 surrounded by the outer shell layer 2. A substrate resin of the resin film is a composite resin including a styrene-based component and a (meth)acrylate component. An average particle diameter of the hollow particles 1 is 2 mm or greater and 8 mm or smaller, and apparent density is 30 kg/m3 or greater and 80 kg/m3 or smaller, and a ratio of an average value of a total thickness of the resin film with respect to an average thickness of the outer shell layer 2 is 0.5 or greater.SELECTED DRAWING: Figure 1

Description

The present invention relates to hollow particles and a cushion body.

The foamed particles may be used as a filler in a cushion body including a bag body and a filler filled inside the bag body, such as a bean bag, a sofa, and a mattress. For this type of application, styrene-based resin foamed particles having relatively excellent rigidity are often used (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2004-223002

A load is repeatedly applied to the filler of the cushion body such as a bean cushion due to repeated use or the like. However, the foamed particles as described in Patent Document 1 have reduced resilience when a load is repeatedly applied, and it is difficult to return to the state before the load is applied. Therefore, when the foamed particles of Patent Document 1 are used as a filler, there is a problem that the cushioning property tends to deteriorate when the cushion body is used for a long period of time.

The present invention has been made in view of such a background, and a hollow particle which has high rigidity and resilience and is suitable as a filler for a cushion body and a cushion body in which the hollow particle is used as a filler are provided. It is what we are trying to provide.

One aspect of the present invention is hollow particles used as a filler in a cushion body including a bag body and a filler filled in the bag body.
An outer shell layer having a resin film and a plurality of bubbles partitioned by the resin film and having an average thickness of 30 μm or more and 150 μm or less.
It has a hollow portion surrounded by the outer shell layer and has.
The base resin of the resin film is a composite resin containing a (meth) acrylic acid ester component and a styrene-based component.
The average particle diameter of the hollow particles is 2 mm or more and 8 mm or less.
The apparent density of the hollow particles is 30 kg / m ³ or more and 80 kg / m ³ or less.
The hollow particles have a ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer of 0.5 or more.

Another aspect of the present invention is a cushion body including a bag body and a filler filled in the bag body.
The filler includes a resin film and a plurality of bubbles partitioned by the resin film, and has an outer shell layer having an average thickness of 30 μm or more and 150 μm or less.
Hollow particles having a hollow portion surrounded by the outer shell layer.
The base resin of the resin film is a composite resin containing a (meth) acrylic acid ester component and a styrene-based component.
The average particle diameter of the hollow particles is 2 mm or more and 8 mm or less.
The apparent density of the hollow particles is 30 kg / m ³ or more and 80 kg / m ³ or less.
The cushion body has a ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer of 0.5 or more.

The base resin of the resin film of the hollow particles is a composite resin containing a (meth) acrylic acid ester component and a styrene-based component. By using the specific composite resin as a base resin, the hollow particles have at least the average thickness of the outer shell layer, the average particle diameter, the apparent density, and the total thickness of the resin film with respect to the average thickness of the outer shell layer. A structure represented by a ratio of average values can be easily realized. Hollow particles having such a structure have excellent resilience derived from the outer shell layer and also have high rigidity.

Therefore, the hollow particles have properties suitable as a filler for a cushion body.

Further, the hollow particles are used as the filler of the cushion body. Therefore, the cushion body is lightweight, has excellent cushioning properties, and can maintain cushioning properties for a long period of time.

As described above, according to the above aspect, it is intended to provide hollow particles which have high rigidity and resilience and are suitable as a filler for a cushion body, and a cushion body in which the hollow particles are used as a filler. Can be done.

FIG. 1 is an electron micrograph (magnification magnification 30 times) of the hollow particles of Example 1 in a state of being divided into two. FIG. 2 is an electron micrograph (magnification of 1000 times) of the outer shell layer in FIG. 1. FIG. 3 is an electron micrograph (magnification magnification 30 times) of the hollow particles of Comparative Example 3 in a state of being divided into two. FIG. 4 is an electron micrograph (magnification of 1000 times) of the outer shell layer in FIG. FIG. 5 is an electron micrograph of the foamed particles of Comparative Example 7 in a state of being divided into two.

(Hollow particles)
The hollow particles have an outer shell layer and a hollow portion surrounded by the outer shell layer. The outer shell layer constitutes the outer shell of the hollow particles, and has a resin film made of a base resin and a plurality of bubbles partitioned by the resin film. The hollow particles preferably consist of an outer shell layer and a hollow portion surrounded by the outer shell layer. The detailed configuration of the outer shell layer will be described later. Further, the hollow particles of the present invention are hollow particles formed by foaming foamable composite resin particles described later. The hollow particles of the present invention have a structure different from that of foamed particles having a bubble structure in which a large number of bubbles are formed relatively uniformly over the entire particles. The hollow particles of the present invention are preferably spherical.

The hollow portion of the hollow particles is located closer to the central portion of the hollow particles than the outer shell layer. The hollow portion, that is, the region surrounded by the outer shell layer may be substantially hollow. Here, "substantially hollow" means that after cutting hollow particles in a cross section passing through the center thereof, the cut surface is observed at a magnification of 20 to 1000 times using a transmission electron microscope or the like. A state in which the structure of the outer shell layer and the structure of the hollow portion are clearly different.

For example, the hollow portion may be a single space separated from the outside of the hollow particles by an outer shell layer. Further, the hollow portion may have a space wall made of a base resin and partitioning the hollow portion into a plurality of spaces. In this case, the hollow portion may be formed with a space wall of the hollow portion, or several to several tens of spaces partitioned by the space wall of the hollow portion and the inner surface of the outer shell layer. From the viewpoint of facilitating the development of desired physical properties, it is preferable that the hollow portions are partitioned into 50 or less spaces in the cross section when the hollow particles are bisected, and are partitioned into 30 or less spaces. It is more preferable that it is partitioned into 10 or less spaces, and it is particularly preferable that it is partitioned into 5 or less spaces.

If the region surrounded by the outer shell layer is substantially hollow, the hollow particles can easily realize excellent resilience. The hollow portion of the hollow particles is preferably a single space separated from the outside of the hollow particles by an outer shell layer.

[Average particle size]
The average particle size of the hollow particles is 2 mm or more and 8 mm or less. Hollow particles having an average particle diameter in the specific range are suitable as a filler used for a cushion body such as a bean cushion. By filling the bag body with such hollow particles, a cushion body having excellent cushioning properties can be obtained. If the average particle size of the hollow particles is excessively small, the hollow particles are likely to be charged, which may lead to deterioration of workability when the hollow particles are filled inside the bag. Further, when the average particle diameter of the hollow particles is excessively large, the cushion body obtained by filling the hollow particles may have an unfavorable feel to the user.

From the viewpoint of more reliably avoiding the above-mentioned problems, the average particle diameter of the hollow particles is preferably 3 mm or more and 7 mm or less, and more preferably 4 mm or more and 6 mm or less.

The above-mentioned average particle size of the hollow particles is a value of a cumulative 63% diameter (that is, d63) calculated based on the particle size distribution in the volume reference of the hollow particles. The particle size distribution based on the volume of the hollow particles can be obtained by using a particle size distribution measuring device (for example, "Millitrack JPA" manufactured by Nikkiso Co., Ltd.).

[Apparent density]
The apparent density of the hollow particles is 30 kg / m ³ or more and 80 kg / m ³ or less. The hollow particles having an apparent density in the specific range are lightweight and excellent in both rigidity and resilience. If the apparent density of the hollow particles is too small, the rigidity of the hollow particles may decrease. Further, in this case, the hollow particles are easily crushed when a load is applied, which may lead to a decrease in stability. On the other hand, if the apparent density of the hollow particles is too large, the mass of the hollow particles per unit volume becomes large, which may lead to deterioration in lightness and handleability.

From the viewpoint of enhancing the rigidity and resilience of the hollow particles, the apparent density of the hollow particles is preferably 32 kg / m ³ or more, and more preferably 35 kg / m ³ or more. From the viewpoint of further improving the lightness of the hollow particles, the apparent density of the hollow particles is preferably 70 kg / m ³ or less, more preferably 60 kg / m ³ or less, and 50 kg / m ³ or less. It is more preferable to have.

The apparent density of the hollow particles described above is a value calculated by the following method. First, an arbitrary amount of hollow particle group whose condition is adjusted by leaving it for 10 days under the conditions of a relative humidity of 50% and a temperature of 23 ° C. and 1 atm is prepared. Prepare a graduated cylinder containing water at a temperature of 23 ° C., and submerge the hollow particles in the water in the graduated cylinder using a tool such as a wire mesh. Then, the apparent volume (unit: L) of the hollow particle group is calculated by reading the amount of water level rise in the graduated cylinder and subtracting the volume of a tool such as a wire mesh from the amount of water level rise. The apparent density of hollow particles (unit: kg / m ³ ) can be obtained by dividing the mass (unit: g) of the hollow particles placed in the graduated cylinder by the apparent volume and then converting the unit.

[Outer shell layer]
The outer shell layer of the hollow particles has a resin film made of a base resin and a plurality of bubbles partitioned by the resin film. The outer shell layer includes, for example, a solid lower layer facing the hollow portion, a solid upper layer exposed on the outermost surface of the hollow particles (that is, the outer surface of the outer shell layer), and lower and upper layers. It may have a multi-layer structure including a foam layer portion provided between the above and a plurality of bubbles. The solid state means a state in which the resin has substantially no bubbles.

The average thickness of the outer shell layer is 30 μm or more and 150 μm or less, and the ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer is 0.5 or more. By making the structure of the outer shell layer a structure specified by the ratio of the above-mentioned average thickness and the average value of the total thickness of the resin film to the average thickness of the outer shell layer, the durability of the outer shell layer against a load is improved. be able to. This makes it possible to enhance the resilience of the hollow particles to repeated loads.

If the average thickness of the outer shell layer is excessively thin, the rigidity of the hollow particles is lowered, and the hollow particles may be easily deformed excessively with respect to a load. In addition, when a load is applied, the bubble film of the hollow particles tends to buckle, which may lead to a decrease in stability. From the viewpoint of further enhancing the resilience of the hollow particles, the average thickness of the outer shell layer is preferably more than 50 μm, more preferably 60 μm or more.

The average thickness of the outer shell layer is preferably 140 μm or less, more preferably 120 μm or less, and further preferably 100 μm or less. In this case, the feel of the cushion body filled with the hollow particles can be further improved, and the cushion body having a favorable feel for the user can be more easily obtained.

Further, even when the ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer is excessively small, the resin film of the hollow particles tends to buckle when a load is applied, which causes a decrease in recoverability. There is a risk. From the viewpoint of further enhancing the resilience of the hollow particles, the ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer is preferably 0.50 or more, and more preferably 0.55 or more. ..

The ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer can be, for example, 0.90 or less, preferably 0.80 or less, and more preferably 0.75 or less. In this case, the surface of the hollow particles tends to be flexible, and it becomes easy to adjust the feel of the cushion body filled with the hollow particles to a more preferable one.

The above-mentioned average thickness of the outer shell layer is a value calculated by the following method. First, the hollow particles are divided into roughly two equal parts to expose the cut surface of the outer shell layer. Using a scanning electron microscope, three or more observation positions are randomly set in one region of the cut surface of the outer shell layer divided into approximately four equal parts. By observing these observation positions at an appropriate magnification (for example, a magnification of 1000 times), an enlarged photograph of the cut surface of the outer shell layer at each observation position is obtained.

A line segment extending in the thickness direction of the outer shell layer (that is, the radial direction of the hollow particles) is drawn on the outer shell layer in the obtained enlarged photograph from the outer surface to the inner surface of the outer shell layer. The above operation is performed at 10 or more positions randomly selected from each enlarged photograph, and the length of the line segment at a total of 30 or more positions is measured. The arithmetic mean value of the length of the line segment thus obtained is taken as the thickness of the outer shell layer of each hollow particle. Then, the thickness of the above-mentioned outer shell layer is calculated for five or more randomly selected hollow particles, and the arithmetic mean value of the thickness of these outer shell layers is taken as the average thickness of the outer shell layer.

In calculating the average value of the total thickness of the resin film, as in the method of calculating the average thickness of the outer shell layer, one region of the cut surface of the outer shell layer is roughly divided into four equal parts, and 3 is randomly selected. Set more than one observation position and acquire an enlarged photograph of the cut surface of the outer shell layer at each observation position. Next, a line segment extending in the thickness direction of the outer shell layer is drawn on the outer shell layer in each enlarged photograph from the outer surface to the inner surface of the outer shell layer.

The above operation is performed at 10 or more positions randomly selected from each enlarged photograph, and the length of the line segment extending in the thickness direction of the outer shell layer is measured, and among the line segments, bubbles and bubbles are measured. Calculate the length of the overlapping part. Next, the total thickness of the resin film of each hollow particle is calculated by subtracting the length of the portion overlapping the bubble from the length of each line segment and arithmetically averaging these values. Then, the total thickness of the resin films described above is calculated for five or more randomly selected hollow particles, and the arithmetic mean value of the total thickness of these resin films is taken as the average value of the total thickness of the resin films.

When the hollow particles are bisected, the apparent density of the bisected hollow particles is preferably 80 kg / m ³ or more and 200 kg / m ³ or less. In this case, the proportion of air bubbles in the outer shell layer of the hollow particles becomes smaller, and the rigidity of the hollow particles can be increased. Further, in this case, the durability of the outer shell layer against a load is enhanced, and the resilience can be further enhanced. From the viewpoint of further enhancing the resilience of the hollow particles, the apparent density of the bisected hollow particles is preferably 90 kg / m ³ or more, more preferably 100 kg / m ³ or more, and 120 kg / m. It is more preferably ³ or more. Further, from the viewpoint of further enhancing the resilience, the apparent density of the bisected hollow particles is preferably 180 kg / m ³ or less, more preferably 170 kg / m ³ or less, and 160 kg / m ³ or less. The following is more preferable. In the present specification, "dividing the hollow particles into two equal parts" means dividing the hollow particles in half so that the masses of the hollow particles are substantially equal to each other.

The ratio of the apparent density of the hollow particles bisected to the apparent density of the hollow particles is preferably 1.5 or more, more preferably 2.0 or more, and more preferably 2.5 or more. Is more preferable, and more than 3.0 is particularly preferable. In this case, the hollow particles can be more reliably formed into a desired structure, and hollow particles having suitable physical properties as a cushioning filler can be more easily obtained.

Further, the ratio of the apparent density of the hollow particles bisected to the apparent density of the hollow particles is preferably 5.0 or less, more preferably 4.5 or less, and 4.2 or less. Is even more preferable. In this case, the resilience of the hollow particles can be enhanced and the feel of the hollow particles can be improved.

It should be noted that the apparent density of the foamed particles bisected with respect to the apparent density of the foamed particles in the foamed particles having no hollow portion having a bubble structure in which a large number of bubbles are relatively uniformly formed over the entire particles. The ratio is usually less than 1.5.

The ratio of the apparent density of the bisected hollow particles to the density of the base resin constituting the resin film of the hollow particles is preferably 0.08 or more, and preferably 0.1 or more. In this case, hollow particles having physical properties suitable for a cushion filler can be more easily obtained. Further, the ratio of the apparent density of the bisected hollow particles to the density of the base resin constituting the resin film of the hollow particles is preferably 0.5 or less, and more preferably 0.3 or less. It is preferably 0.2 or less, and more preferably 0.2 or less. In this case, the feel of the hollow particles can be improved.

For the apparent density of the hollow particles divided into two equal parts, use the hollow particles divided into two equal parts instead of the hollow particles before the equal division, and use a measuring cylinder of an aqueous solution containing a surfactant instead of water. It is the same as the above-mentioned method for measuring the apparent density of hollow particles except that the particles are placed inside. As the aqueous solution containing the surfactant, an aqueous solution that easily penetrates into the ruptured bubbles in the outer shell layer or the hollow portion can be used. For example, sodium linear alkylbenzene sulfonate (sodium dodecylbenzene sulfonate) can be used. ) And an aqueous solution containing 0.2 to 1% by mass of a surfactant such as sodium alkyl ether sulfate can be used.

When the hollow particles divided into two equal parts are submerged in the aqueous solution, the aqueous solution infiltrates into the region that was the hollow portion before the division in the individual hollow particles and the bubble bubbles in the outer shell layer. Therefore, the volume read from the rise in the water level of the graduated cylinder is closer to the apparent volume of the outer shell layer.

The closed cell ratio of the hollow particles is preferably 90% or more. In this case, the durability of the outer shell layer with respect to the repeatedly applied load can be improved. This makes it possible to further enhance the resilience of the hollow particles. From the viewpoint of further enhancing the resilience of the hollow particles, the closed cell ratio of the hollow particles is more preferably 95% or more.

The closed cell ratio of the hollow particles is a value calculated by the following method. First, a hollow particle group composed of a plurality of hollow particles is left in a constant temperature room at a relative humidity of 50% and 23 ° C. for 10 days under atmospheric pressure to adjust the state of the hollow particle group. A graduated cylinder containing water having a temperature of 23 ° C. is prepared, and the hollow particles after adjusting the state are submerged in the water in the graduated cylinder using a wire mesh or the like. Then, the water level rise of the measuring cylinder is read, and this value is taken as the apparent volume Va of the hollow particle group.

After sufficiently drying the hollow particle group after measuring the apparent volume, the value Vx of the true volume of the hollow particle group is measured according to the procedure C described in ASTM-D2856-70. An air comparison hydrometer (for example, an air comparison hydrometer 930 manufactured by Toshiba Beckman Co., Ltd.) may be used for measuring the true volume.

The closed cell ratio can be calculated by the following formula (1) using the apparent volume Va and the true volume Vx of the hollow particle group obtained as described above. The symbol W in the following formula (1) is the mass (unit: g) of the hollow particle group, and the symbol ρ is the true density of the hollow particles (unit: g / cm ³ ).
Closed cell ratio (%) = (Vx-W / ρ) x 100 / (Va-W / ρ) ... (1)

[Characteristics of hollow particles]
The resilience of the hollow particles to a load can be evaluated by performing repeated compression tests. The specific test method and conditions for the repeated compression test are as follows. First, hollow particles having a bulk volume of 330 mL are weighed using a measuring cylinder having a volume of 500 mL. A cylindrical container with a diameter of 78 mm is prepared, and hollow particles are placed in the container. Using a compression jig having a flat plate-like contact portion with the hollow particles, the hollow particles in the container are compressed by moving the compression jig downward at a speed of 10 mm / min. When the load applied to the hollow particles reaches 650 N, the compression jig is moved upward to completely remove the load on the hollow particles. With this cycle as one cycle, load application and unloading are repeated for 100 cycles.

The maximum value of the compression amount of the hollow particles in the above-mentioned repeated compression test is preferably 35 mm or less, more preferably 30 mm or less, and further preferably 28 mm or less. Hollow particles having such characteristics can maintain high rigidity for a longer period of time even when a load is repeatedly applied.

Further, after performing the above-mentioned repeated compression test, the volume reduction rate of the hollow particles is preferably 4% or less, preferably 3% or less, when the particles are allowed to stand for 24 hours in an environment of 25 ° C., humidity 50%, and 1 atm. Is more preferable. Hollow particles having such characteristics can maintain high resilience for a longer period of time even when a load is repeatedly applied.

The closed cell ratio of the hollow particles after the repeated compression test is preferably 85% or more, more preferably 90% or more. Hollow particles having such characteristics can maintain high resilience for a longer period of time even when a load is repeatedly applied. From the same viewpoint, the ratio of the closed cell ratio of the hollow particles after the repeated compression test to the closed cell ratio of the hollow particles before the repeated compression test is preferably 95% or more, preferably 96% or more. Is more preferable, and 98% or more is further preferable.

[Base resin]
The base resin of the resin film in the hollow particles contains a (meth) acrylic acid ester component derived from a (meth) acrylic acid ester monomer and a styrene-based component including a component derived from a styrene-based monomer. It is a composite resin. As will be described later, the composite resin is preferably a composite resin obtained by impregnating and polymerizing a (meth) acrylic acid ester and a styrene-based monomer into nuclear particles using a styrene-based resin as a base resin.

Examples of the (meth) acrylic acid ester component contained in the composite resin include components derived from acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and 2-ethylhexyl acrylate, and methacrylic acid. Examples thereof include components derived from methacrylic acid esters such as methyl, ethyl methacrylate, propyl methacrylate, butyl methacrylate and 2-ethylhexyl methacrylate. The composite resin may contain one kind of component selected from these (meth) acrylic acid ester components, or may contain two or more kinds of components.

It is preferable that the composite resin contains a component derived from methyl methacrylate as a (meth) acrylic acid ester component. In this case, the content ratio of the component derived from methyl methacrylate in the (meth) acrylic acid ester component is preferably 50% by mass or more, more preferably 60% by mass or more, and more preferably 80% by mass or more. It is more preferable, and it is particularly preferable that it is 90% by mass or more. In this case, the structure and physical properties of the hollow particles can be more reliably obtained into the desired structure and physical properties.

The styrene-based components contained in the composite resin include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, and p-methoxystyrene. , Pn-butylstyrene, pt-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4,6-tribromostyrene, divinylbenzene, styrenesulfonic acid and styrenesulfonicic acid. Components derived from styrene-based monomers such as sodium, components derived from homopolymers of styrene-based monomers such as polystyrene, rubber-modified polystyrenes, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers , Acrylonitrile-ethylene propylene rubber-styrene copolymer and the like, and examples thereof include components derived from a copolymer of a styrene-based monomer and another monomer or polymer. The composite resin may contain one kind of component selected from these styrene-based components, or may contain two or more kinds of components.

It is preferable that the composite resin contains a component derived from styrene as a styrene-based component. In this case, the content ratio of the styrene-derived component in the styrene-based component is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 80% by mass or more, and 90% by mass. It is particularly preferable that it is by mass or more. In this case, the structure and physical properties of the hollow particles can be more reliably obtained into the desired structure and physical properties.

The composite resin may contain components other than the (meth) acrylic acid ester component and the styrene-based component. Examples of such a component include carbon-carbon such as a vinyl compound containing a hydroxyl group, a vinyl compound containing a nitrile group, an organic acid vinyl compound, an olefin compound, a diene compound, a vinyl halide compound, a vinylidene halide compound, and a maleimide compound. Examples thereof include components derived from a monomer having a double bond.

Examples of the vinyl compound containing a hydroxyl group include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and the like. Examples of the vinyl compound containing a nitrile group include acrylonitrile and methacrylonitrile.

Examples of the organic vinyl acid compound include vinyl acetate and vinyl propionate. Examples of the olefin compound include ethylene, propylene, 1-butene, 2-butene and the like. Examples of the diene compound include butadiene, isoprene, chloroprene and the like.

Examples of the vinyl halide compound include vinyl chloride and vinyl bromide. Examples of the halogenated vinylidene compound include vinylidene chloride and the like. Examples of the maleimide compound include N-phenylmaleimide and N-methylmaleimide.

The composite resin may contain one kind of component selected from the components derived from these carbon-carbon double bond monomers, or may contain two or more kinds of components. ..

The amount of the components other than the (meth) acrylic acid ester component and the styrene-based component is preferably 20 parts by mass or less with respect to 100 parts by mass in total of the (meth) acrylic acid ester component and the styrene-based component. It is more preferably parts by mass or less, and even more preferably 5 parts by mass or less. In this case, the structure and physical properties of the hollow particles can be more reliably obtained into the desired structure and physical properties.

The composite resin can be obtained, for example, by impregnating and polymerizing a (meth) acrylic acid ester and a styrene-based monomer into nuclear particles using a styrene-based resin as a base resin. As the styrene-based resin that can be used for producing the composite resin, the above-mentioned homopolymer of the styrene-based monomer, a copolymer of the styrene-based monomer and another monomer or a polymer, or the like can be used. ..

The weight average molecular weight of the composite resin is preferably 30 × 10 ⁴ or more and 50 × 10 ⁴ or less, and more preferably 35 × 10 ⁴ to 45 × 10 ⁴ . In this case, the rigidity and resilience of the hollow particles can be further enhanced. The weight average molecular weight of the composite resin is a polystyrene-equivalent molecular weight measured by a gel permeation chromatography method using polystyrene as a standard substance.

The mass ratio of the (meth) acrylic acid ester component to the styrene-based component contained in the composite resin is preferably (meth) acrylic acid ester component: styrene-based component = 70:30 to 30:70. , (Meta) acrylic acid ester component: Styrene-based component = 60: 40 to 40:60 is more preferable. In this case, the yield of the hollow particles having the specific structure can be further increased.

The composite resin is obtained by impregnating and polymerizing the core particles composed of the base resin containing the (meth) acrylic acid ester component and / or the styrene-based component with the (meth) acrylic acid ester and / or the styrene-based monomer. In the case of production, the mass ratio of the (meth) acrylic acid ester component contained in the composite resin to the styrene-based component is the mass of each component in the nuclear particles and the mass of each monomer impregnated and polymerized. It can be obtained from the relationship of.

[Additive]
The hollow particles may contain additives such as a bubble regulator, a catalyst neutralizer, a lubricant, a crystal nucleating agent, and an antistatic agent as long as the above-mentioned effects are not impaired. The content of the additive in the hollow particles is, for example, preferably 20% by mass or less, more preferably 15% by mass or less, and preferably 10% by mass or less with respect to the total mass of the hollow particles. It is more preferably 5% by mass or less, and particularly preferably 5% by mass or less.

[Use]
The hollow particles are used as a filler in a cushion body including a bag body and a filler filled inside the bag body. Examples of this type of cushion body include bean cushions, sofas, mattresses and the like. As described above, the hollow particles are lightweight and have excellent rigidity and resilience. Therefore, the hollow particles are suitably used as a filler for a cushion body, which is desired to be excellent in these characteristics. In particular, the hollow particles are suitably used as a filler for a bean cushion. As the material constituting the bag body, it is preferable to use a material having elasticity, and for example, a cloth formed of chemical fiber, silk, cotton or the like can be used. The cushion body using the hollow particles as the filler is lightweight, has excellent cushioning properties, and can maintain excellent cushioning properties for a long period of time.

(Manufacturing method of hollow particles)
As a method for producing the hollow particles, for example, a method can be adopted in which the composite resin is used as a base resin, foamable resin particles containing a foaming agent are prepared, and then the foamable resin particles are foamed.

As a method for producing foamable resin particles, for example, styrene-based resin nuclei particles (hereinafter, appropriately referred to as “nucleus particles”) using a styrene-based resin as a base resin are impregnated with (meth) acrylic acid ester and styrene-based particles. A method of impregnating the (meth) acrylic acid ester with the styrene-based monomer and impregnating the foaming agent can be adopted.

More specifically, the method for producing the effervescent resin particles includes a dispersion step of dispersing the nuclear particles in an aqueous medium.
The dispersed nuclear particles in the aqueous medium are impregnated with the (meth) acrylic acid ester and the styrene-based monomer, and the (meth) acrylic acid ester and the styrene-based monomer are polymerized to obtain resin particles. The reforming process and
It has an impregnation step of impregnating the nuclear particles or the resin particles with a foaming agent at least once before, during the reforming step, and after the completion of the reforming step. May be. The dispersion step, the reforming step, and the impregnation step may be continuously performed in a single closed container, or may be performed using separate containers. Hereinafter, each process will be described in detail.

[Dispersion process]
In the dispersion step, the nuclear particles are dispersed in an aqueous medium to prepare a suspension. As the aqueous medium, for example, deionized water or the like can be used. In addition to the nuclear particles, a suspending agent, a surfactant, or the like can be added to the aqueous medium, if necessary.

The base resin of the nuclear particles used in the dispersion step is preferably a styrene resin. As the styrene-based resin, the above-mentioned homopolymer of the styrene-based monomer, a copolymer of the styrene-based monomer and another monomer or a polymer, and the like can be used. More specifically, as the styrene-based resin, for example, a homopolymer of a styrene-based monomer such as polystyrene, a copolymer containing 50 mol% or more of a component derived from the styrene-based monomer, or the like is used. be able to. Further, the nuclear particles may contain additives such as a bubble modifier, a pigment, a slip agent, an antistatic agent, and a flame retardant as long as the above-mentioned effects are not impaired.

The nuclear particles may contain a resin other than the styrene resin, such as an acrylic resin. From the viewpoint of making the structure of the hollow particles more surely desired, the content of the resin other than the styrene-based resin in the nuclear particles shall be 30 parts by mass or less with respect to 100 parts by mass of the styrene-based resin. Is more preferable, and it is more preferably 20 parts by mass or less, and further preferably 10 parts by mass or less.

The method for producing the nuclear particles is not particularly limited. For example, as a method for producing nuclear particles, a strand cut method, an underwater cut method, a hot cut method, or the like can be adopted. Further, the nuclear particles may be produced, for example, by a suspension polymerization method in which a styrene-based monomer is polymerized in an aqueous medium.

The average particle size of the nuclear particles is preferably 0.6 to 1.5 mm, more preferably 0.7 to 1.2 mm. In this case, the polymerization stability in the reforming step is enhanced, and the weight average molecular weight of the hollow particles can be easily increased. Further, in this case, the structure of the finally obtained hollow particles can be more reliably obtained as a desired structure.

The average particle size of the nuclear particles is a cumulative 63% diameter (that is, d63) value calculated based on the particle size distribution based on the volume of the nuclear particles, and is a particle size distribution measuring device (for example, "Millitrack" manufactured by Nikkiso Co., Ltd. It can be measured using "JPA") or the like.

Examples of the suspending agent used in the dispersion step include tricalcium phosphate, hydroxyapatite, magnesium pyrophosphate, magnesium phosphate, aluminum hydroxide, ferric hydroxide, titanium hydroxide, magnesium hydroxide, and phosphoric acid. Inorganic suspending agents consisting of fine particles of inorganic substances such as barium, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, talc, kaolin and bentonite, and organic suspensions such as polyvinylpyrrolidone, polyvinyl alcohol, ethyl cellulose and hydroxypropylmethyl cellulose. Examples include turbidants. These suspending agents may be used alone or in combination of two or more. The suspending agent is preferably one or more of tricalcium phosphate, hydroxyapatite and magnesium pyrophosphate.

The amount of the suspending agent added is preferably 0.05 parts by mass or more and 10 parts by mass or less, and more preferably 0.3 parts by mass or more and 5 parts by mass or less, based on 100 parts by mass of the aqueous medium. preferable. When the (meth) acrylic acid ester and the styrene-based monomer are added in the subsequent reforming step by adding the suspending agent in an amount of 0.05 parts by mass or more, more preferably 0.3 parts by mass or more. In addition, it becomes easier to maintain a state in which nuclear particles, monomers, etc. are suspended in an aqueous medium. Further, by setting the addition amount of the suspending agent to 10 parts by mass or less, more preferably 5 parts by mass or less, the particle size distribution of the finally obtained hollow particles can be narrowed.

As the surfactant, for example, an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant and the like can be used. Examples of the anionic surfactant include sodium alkylsulfonate, sodium alkylbenzenesulfonate, sodium laurylsulfate, sodium α-olefin sulfonate, sodium dodecylphenyl ether disulfonate and the like. Examples of the nonionic surfactant include polyoxyethylene dodecyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether and the like.

Examples of the cationic surfactant include alkylamine salts such as coconutamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride and stearyltrimethylammonium chloride. Examples of the amphoteric tenside include alkyl betaines such as lauryl betaine and stearyl betaine, and alkylamine oxides such as lauryl dimethylamine oxide. These surfactants may be used alone or in combination of two or more.

The surfactant is preferably an anionic surfactant, more preferably an alkyl sulfonic acid alkali metal salt having 8 or more and 20 or less carbon atoms, and more preferably sodium alkyl sulfonic acid having 8 or more and 20 or less carbon atoms. Is even more preferable. By using these surfactants, when the (meth) acrylic acid ester and the styrene-based monomer are added in the subsequent reforming step, the nuclear particles, the monomer, etc. are suspended in the aqueous medium. It will be easier to maintain.

If necessary, an electrolyte composed of inorganic salts such as lithium chloride, potassium chloride, sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, and sodium bicarbonate can be added to the suspension.

[Modification process]
In the modification step, (meth) acrylic acid ester and styrene-based monomer are added to the suspension, and the nuclear particles are impregnated with (meth) acrylic acid ester and styrene-based monomer, and these are impregnated. Polymerize the monomer. As a result, composite resin particles using a composite resin containing a styrene-based component and a (meth) acrylic acid ester component as a base resin can be obtained.

The total of the amount of the (meth) acrylic acid ester added in the reforming step and the amount of the styrene-based monomer added is, for example, 200 parts by mass or more and 700 parts by mass or less with respect to 100 parts by mass of the nuclear particles. It is preferably 250 parts by mass or more and 600 parts by mass or less. Further, the ratio of the amount of the (meth) acrylic acid ester added to the amount of the styrene-based monomer added may be appropriately set according to the desired composition of the composite resin. From the viewpoint of facilitating the acquisition of good hollow particles, the ratio of the amount of (meth) acrylic acid ester added to the amount of styrene-based monomer added is the mass ratio of (meth) acrylic acid ester: styrene-based single amount. The body = 50:50 to 85:15 is preferable, and the (meth) acrylic acid ester: styrene-based monomer = 60:40 to 75:25 is more preferable.

In the modification step, a polymerization initiator is used to polymerize the (meth) acrylic acid ester and the styrene-based monomer. The polymerization initiator is not particularly limited as long as it is a polymerization initiator applicable to suspension polymerization of styrene-based monomers. As the polymerization initiator, for example, a polymerization initiator that is soluble in vinyl monomer and has a 10-hour half-life temperature of 50 ° C. or higher and 120 ° C. or lower can be used. Examples of such polymerization initiators include cumene hydroxy peroxide, dicumyl peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxybenzoate, benzoyl peroxide, and t-butyl peroxyisopropyl carbonate. , T-amylperoxy-2-ethylhexyl carbonate, hexylperoxy-2-ethylhexyl carbonate, organic peroxides such as lauroyl peroxide, azo compounds such as azobisisobutyronitrile, and the like. These polymerization initiators may be used alone or in combination of two or more.

The polymerization initiator may be added to an aqueous medium in a state of being dissolved in a solvent or a monomer, and impregnated into nuclear particles together with a (meth) acrylic acid ester and a styrene-based monomer. In this case, as the solvent, for example, aromatic hydrocarbons such as ethylbenzene and toluene, aliphatic hydrocarbons such as heptane and octane, and the like are used. The amount of the polymerization initiator added is preferably 0.01 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass in total of the (meth) acrylic acid ester added in the reforming step and the styrene-based monomer. ..

In the reforming step, a bubble adjusting agent, a plasticizer, an oil-soluble polymerization inhibitor, a flame retardant, a dye and the like can be added, if necessary. The bubble conditioner is added to the aqueous medium, for example, in a state of being dissolved or dispersed in a monomer and / or a solvent. Examples of the bubble adjusting agent include fatty acid monoamide, fatty acid bisamide, talc, silica, polyethylene wax, methylene bisstearic acid, methyl methacrylate-based copolymer, and silicone. Examples of the fatty acid monoamide include oleic acid amide and stearic acid amide. Examples of the fatty acid bisamide include ethylene bisstearic acid amide.

Plasticizers, oil-soluble polymerization inhibitors, flame retardants and dyes can be added, for example, in an aqueous medium in a state of being dissolved or dispersed in a (meth) acrylic acid ester and / or a styrene-based monomer. Examples of the plasticizer include fatty acid esters such as glycerin tristearate, glycerin trioctate, glycerin trilaurate, sorbitan tristearate, sorbitan monostearate, and butyl stearate, and acetylation of glycerin diacet monolaurate and the like. Examples thereof include fats and oils such as monoglyceride, hardened beef fat and hardened castor oil, and organic compounds such as cyclohexane and liquid paraffin. Examples of the oil-soluble polymerization inhibitor include para-t-butylcatechol, hydroquinone, benzoquinone and the like.

The heating temperature in the reforming step and the time required for the addition of the (meth) acrylic acid ester and the styrene-based monomer are determined by the chemical structure of the styrene-based resin of the nucleus particles and the chemistry of the (meth) acrylic acid ester and the styrene-based monomer. It may be appropriately set according to the structure, the characteristics of the polymerization initiator, the degree of polymerization of the desired composite resin, and the like.

It is considered that the composite resin particles obtained from the modification step have a structure in which the surface layer portion of the resin particles contains a large amount of (meth) acrylic acid ester component, while the inside of the resin particles contains a large amount of styrene-based component. In the foaming step, the foamable resin particles in which the (meth) acrylic acid ester component and the styrene-based component are distributed as described above are foamed to promote foaming inside the resin particles and the surface layer portion of the resin particles. It is considered that hollow particles having an outer shell layer and a hollow portion can be obtained by suppressing the progress of foaming in the plastic.

[Immersion process]
In the impregnation step, the nuclear particles or the composite resin particles are foamed by impregnating the nuclear particles or the composite resin particles with a physical foaming agent at least once before the reforming step, during the reforming step, or after the completion of the reforming step. Obtain sex resin particles. That is, the impregnation step may be performed on the nuclei particles before impregnation with the (meth) acrylic acid ester and the styrene-based monomer, or the (meth) acrylic acid ester and the styrene-based monomer may be performed in the modification step. This may be performed on the composite resin particles in the process of being polymerized with, or on the composite resin particles after the polymerization of the (meth) acrylic acid ester and the styrene-based monomer is completed. Further, among these timings, the nuclear particles or the composite resin particles may be impregnated with the physical foaming agent at two or more timings. From the viewpoint of sufficiently impregnating the inside of the composite resin particles with the physical foaming agent to facilitate the desired structure of the hollow particles, the impregnation step is preferably performed at least before the modification step. From the same viewpoint, it is more preferable that the impregnation step is performed before the reforming step and at least one of the timings during the reforming step and after the completion of the reforming step.

As the physical foaming agent, for example, an organic compound having a boiling point of 90 ° C. or lower at atmospheric pressure such as propane, normal butane, isobutane, normal pentane, isopentane, neopentane, hexane, cyclobutane, cyclopentane, dimethyl ether, and diethyl ether is used. be able to. These volatile organic compounds may be used alone or in combination of two or more. When the impregnation steps are performed a plurality of times, the physical foaming agents used in each impregnation step may be the same or different from each other.

In impregnating the physical foaming agent, for example, the physical foaming agent may be supplied into a closed container containing nuclear particles or composite resin particles to increase the pressure in the closed container. By maintaining this state, the nuclear particles and the composite resin particles can be impregnated with the physical foaming agent.

If necessary, the inside of the closed container may be heated while being impregnated with the physical foaming agent. By heating the inside of the closed container, the impregnation of the physical foaming agent into the nuclear particles or the composite resin particles can be further promoted. The temperature and time for impregnating the foaming agent may be appropriately set according to the timing of the impregnation step. For example, in the impregnation step performed before the reforming step, it is preferable to impregnate the physical foaming agent by keeping the temperature at about 40 to 90 ° C. for 0.5 to 3 hours. In the impregnation step performed during the reforming step and / or after the completion of the reforming step, it is preferable to impregnate the physical foaming agent by keeping the temperature at about 80 to 120 ° C. for 3 to 5 hours.

The blending amount of the physical foaming agent in the impregnation step is, for example, preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 3 parts by mass or more and 9 parts by mass or less with respect to 100 parts by mass of the composite resin particles. It is more preferably 5 parts by mass or more and 8 parts by mass or less.

By performing the impregnation step as described above, foamable resin particles can be obtained. After performing the impregnation step, it is preferable to dehydrate and dry the obtained foamable resin particles. Further, when drying the foamable resin particles, it is preferable to dry the foamable resin particles by blowing hot air onto the foamable resin particles using an air flow dryer. In this case, the amount of water contained in the foamable resin particles can be reduced, and the excess foaming agent contained in the surface layer portion of the foamable resin particles is dissipated while maintaining the foamability of the foamable resin particles. It will be easier. As a result, even if the hollow particles have a low apparent density, a good outer shell layer is likely to be formed on the hollow particles. When an air flow dryer is used, the hot air temperature is preferably 30 to 60 ° C., and the drying time is preferably 0.5 to 4 hours.

Even if the hollow particles have a low apparent density, the water content of the foamable resin particles is preferably 0.01 to 0.5% by mass from the viewpoint of facilitating the formation of a good outer shell layer on the hollow particles. It is more preferably 0.03 to 0.4% by mass, and even more preferably 0.05 to 0.3% by mass. Further, after performing the impregnation step, a coating step of coating the surface of the foamable resin particles with a surface coating agent may be carried out, if necessary.

Examples of the surface coating agent used in the coating step include zinc stearate, triglyceride stearate, monoglyceride stearate, and castor oil. Further, an antistatic agent or the like can be used as the surface coating agent in the coating process. The amount of the surface coating agent added is preferably 0.01 to 2 parts by mass with respect to 100 parts by mass of the foamable resin particles.

Hollow particles can be obtained by foaming the effervescent resin particles. As a method for foaming the effervescent resin particles, for example, a method of heating the effervescent resin particles with a heating medium can be adopted. Specifically, the effervescent resin particles can be foamed by introducing a heating medium such as steam into a prefoaming machine to which the effervescent resin particles are supplied.

In foaming the foamable resin particles, for example, the foamable resin particles may be foamed in one step or in a plurality of steps so that hollow particles having a desired apparent density of 30 to 80 kg / m ³ can be obtained. The effervescent resin particles may be foamed separately. In the latter case, for example, foamable resin particles are foamed to produce one-stage hollow particles having an apparent density larger than the desired apparent density, and the one-stage hollow particles are further foamed to obtain hollow particles having the desired apparent density. Just do it.

A specific embodiment of the hollow particles and a method for producing the hollow particles will be described. The specific embodiment of the hollow particles according to the present invention is not limited to the embodiments of Examples 1 to 4 described below, and the configuration is appropriately changed as long as the gist of the present invention is not impaired. be able to.

(Example 1)
This example is an example of a method of producing hollow particles using the obtained nuclear particles after producing nuclear particles containing a styrene resin by a suspension polymerization method.

[Preparation of nuclear particles]
765 g of deionized water, 0.84 g of a suspending agent and 3.2 g of a surfactant were put into an autoclave having an internal volume of 3 L equipped with a stirrer. As the suspending agent, calcium phosphate tertiary (manufactured by Taihei Kagaku Sangyo Co., Ltd.) was used, and as the surfactant, sodium dodecylbenzene sulfonate (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was used.

Then, while stirring the contents of the autoclave, the polymerization initiator, the plasticizer and 848 g of styrene were put into the autoclave. As the polymerization initiator, 2.2 g of t-butylperoxy2-ethylhexanoate (“Perbutyl (registered trademark) O” manufactured by NOF CORPORATION) and 0.44 g of t-butylperoxy2-ethylhexyl It was used in combination with monocarbonate (“Perbutyl (registered trademark) E” manufactured by NOF CORPORATION). As the plasticizer, 12.7 g of cyclohexane and 6.2 g of hardened beef tallow were used in combination. The plasticizer was put into the autoclave in a state of being dissolved in styrene.

After stirring the contents of the autoclave at room temperature for 30 minutes, the temperature inside the autoclave was raised to 90 ° C. over an hour and a half. After the temperature in the autoclave reached 90 ° C., the inside of the autoclave was further heated to raise the temperature in the autoclave to 100 ° C. over 5 and a half hours. After the temperature in the autoclave reached 100 ° C., the inside of the autoclave was further heated to raise the temperature in the autoclave to 110 ° C. over an hour and a half. After maintaining this temperature for 2 hours, the inside of the autoclave was cooled to 30 ° C. over 4 hours. By the above operation, core particles using polystyrene as a base resin were produced.

After the cooling was completed, the nuclear particles in the autoclave were taken out, and nitric acid was used to remove the tricalcium phosphate adhering to the surface of the nuclear particles. After dehydrating and washing the nuclear particles using a centrifuge, the water adhering to the surface of the nuclear particles was removed using an air flow drying device. The nuclear particles obtained as described above had a particle size distribution having an average particle diameter of about 0.95 mm. The average particle size of the nuclear particles is a value of the cumulative 63% diameter (that is, d63) in the volume-based particle size distribution obtained by using a particle size distribution measuring device (“Millitrack JPA” manufactured by Nikkiso Co., Ltd.).

[Preparation of foamable resin particles]
965 g of deionized water and 6.0 g of sodium pyrophosphate were put into an autoclave having an internal volume of 3 L equipped with a stirrer. Next, 12.9 g of powdered magnesium nitrate hexahydrate was put into the autoclave, and the contents of the autoclave were stirred at 40 ° C. for 30 minutes. As a result, the contents of the autoclave became a slurry of magnesium pyrophosphate as a suspension agent.

Next, a surfactant, 200 g of nuclear particles and a polymerization initiator were put into the autoclave. As the surfactant, a 1% by mass aqueous solution of sodium laurylsulfonate was used, and the amount of the surfactant added was 0.04 g of sodium laurylsulfonate. Further, as a polymerization initiator, 2.4 g of benzoyl peroxide (NOF Corporation "Niper (registered trademark) BW") was used.

After replacing the inside of the autoclave with nitrogen, 18 g of the physical foaming agent was added into the autoclave over 10 minutes. As the physical foaming agent, a mixture of about 70% by mass of normal butane and about 30% by mass of isobutane was used.

After the addition of the foaming agent, the temperature in the autoclave was maintained at 40 ° C. for 1 hour. The temperature in the autoclave was then raised to 80 ° C. over 1 hour. While maintaining this temperature, a mixture of 200 g of styrene, 400 g of methyl methacrylate and a polymerization initiator was added into the autoclave over 6 hours while stirring the inside of the autoclave at a stirring speed of 450 rpm. As the polymerization initiator, 1.2 g of t-butyl peroxybenzoate (“Perbutyl Z” manufactured by NOF CORPORATION) was used.

Thirty minutes after the addition of styrene and methyl methacrylate, 80 g of pentane as a physical foaming agent was added into the autoclave over 30 minutes. Further, 30 minutes after the addition of styrene and methyl methacrylate, the temperature in the autoclave was raised to 110 ° C. over 1.5 hours, and this temperature was maintained for 4 hours. Then, the inside of the autoclave was cooled to 35 ° C. over about 6 hours. By the above operation, foamable resin particles containing a physical foaming agent were prepared using a composite resin containing a component derived from styrene and a component derived from methyl methacrylate as a base resin.

After the cooling was completed, the effervescent resin particles in the autoclave were taken out, and nitric acid was used to remove the tertiary calcium phosphate adhering to the surface of the effervescent resin particles. After dehydrating and washing the foamable resin particles using a centrifuge, the moisture adhering to the surface of the foamable resin particles was removed using an air flow drying device. The foamable resin particles obtained as described above had a particle size distribution having an average particle diameter of about 1.7 mm. The average particle size of the foamable resin particles is the cumulative 63% diameter (that is, d63) in the volume-based particle size distribution obtained by using a particle size distribution measuring device (“Millitrack JPA” manufactured by Nikkiso Co., Ltd.). be.

In this example, the surface of the foamable resin particles obtained as described above was coated with a surface coating agent. Specifically, 0.11 parts by mass of zinc stearate, 0.053 parts by mass of glycerin monostearate, 0.004 parts by mass of talc and 0.065 parts by mass with respect to 100 parts by mass of foamable resin particles. By adding a mixture of antistatic agents (“Regist® PE132” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., the surface of the foamable resin particles was coated with a surface coating agent containing these.

Further, after coating the surface of the foamable resin particles with a surface coating agent, the foamable resin particles are further heated at a temperature of 40 ° C. for 90 minutes using an air flow dryer to remove excess water and the foaming agent. Was done.

[Preparation of hollow particles]
The effervescent resin particles obtained by the above method were put into a normal pressure batch foaming machine having a volume of 30 L, and steam was supplied into the foaming machine. The temperature of the steam was 120 ° C. and the heating time was 90 seconds. As a result, the effervescent resin particles were foamed to obtain hollow particles having an apparent density of 39 kg / m ³ .

(Example 2-Example 4, Comparative Example 1-Comparative Example 2 and Comparative Example 5-Comparative Example 6)
In the method for producing hollow particles of Example 2-Example 4, Comparative Example 1-Comparative Example 2 and Comparative Example 5-Comparative Example 6, the average particle size of the nuclear particles was changed to the value shown in Table 1 or Table 2. In Example 1, except that the heat treatment time after coating the surface of the foamable resin particles with the surface coating agent was changed to the value shown in Table 1 or Table 2, and the heating time in the foaming step was changed. It is the same as the method for producing hollow particles.

(Comparative Example 3, Comparative Example 4)
In the method for producing hollow particles of Comparative Example 3 and Comparative Example 4, 213 g of seed particles containing 6.1% of butane (a mixed butane of about 70% by mass of normal butane and about 30% by mass of isobutane) were used as nuclear particles. Point, the point that the average particle size of the nuclear particles was changed to the value shown in Table 2, the point that the heat treatment time after the surface of the foamable resin particles was coated with the surface coating agent was changed to the value shown in Table 2, and in the foaming step. It is the same as the method for producing hollow particles of Example 1 except that the heating time is changed.

(Comparative Example 7)
Comparative Example 7 is an effervescent polystyrene resin particle (foamed particles produced by foaming "Styrodia PA100" manufactured by JSP Co., Ltd. "Styrodia" is a registered trademark of JSP Co., Ltd.

[Moisture content of foamable resin particles]
The method for measuring the water content in the effervescent resin particles of Examples and Comparative Examples is as follows. First, 0.28 g of foamable resin particles were weighed. Moisture in the effervescent resin particles was vaporized by heating the effervescent resin particles to a temperature of 160 ° C. using a heated moisture vaporizer. The amount of water in the foamable resin particles was measured by guiding the vaporized water to a Karl Fischer water measuring device (“AQ-6” manufactured by Hiranuma Sangyo Co., Ltd.) connected to the heated water vaporizing device.

The method for evaluating various characteristics of the hollow particles obtained above will be described below.

[Structure of hollow particles]
After dividing the hollow particles into roughly two equal parts, the cut surface of the hollow particles was observed using an electron microscope. As an example, the cut surface of the hollow particles of Example 1 is shown in FIGS. 1 and 2. As shown in FIG. 1, the hollow particles 1 of the first embodiment have an outer shell layer 2 provided with a resin film 221 and a hollow portion 3 surrounded by the outer shell layer 2.

The hollow portion 3 of the hollow particles 1 is a single space separated from the external space of the hollow particles 1 by the outer shell layer 2. As shown in FIG. 2, the outer shell layer 2 of the hollow particles 1 includes a lower layer portion 21 facing the hollow portion 3, an upper layer portion 23 exposed on the outermost surface of the hollow particles 1, and a lower layer portion 21 and an upper layer portion 23. It has a foam layer portion 22 interposed between the two. The lower layer portion 21 and the upper layer portion 23 are solid layers made of the resin film 221. A plurality of bubbles 222 partitioned by the resin film 221 are formed in the foam layer portion 22.

The hollow particles of Examples 2 to 4 and Comparative Examples 1 to 6 also have an outer shell layer and a hollow portion surrounded by the outer shell layer, similarly to the hollow particles of Example 1. .. As an example, the cut surface of the hollow particles of Comparative Example 3 is shown in FIGS. 3 and 4. The hollow portion of the hollow particles of Examples 1 to 4 is composed of a single space, but the hollow portion may be divided into several to several tens of spaces by a space wall.

On the other hand, in the foamed particles 8 of Comparative Example 7, as shown in FIG. 5, bubbles are formed relatively uniformly over the entire inside of the particles, and no hollow portion is present.

[Apparent density]
A group of particles consisting of 1.5 g of hollow particles or foamed particles was left to stand for 10 days under the conditions of a relative humidity of 50% and a temperature of 23 ° C. and 1 atm to adjust the state. Next, a graduated cylinder having a volume of 200 mL was prepared, and 100 mL of water having a temperature of 23 ° C. was put in the graduated cylinder. After submerging the particle swarm in the water in the graduated cylinder using a wire mesh, the amount of water level rise in the graduated cylinder was read. Then, the apparent volume (unit: L) of the particle group was calculated by subtracting the volume of the wire mesh from the amount of water level rise. The apparent density of hollow particles or foamed particles (unit: kg / m ³ ) was calculated by dividing the mass of the particle group placed in the graduated cylinder by the apparent volume and converting it into units. The apparent densities (A) of the hollow particles or foamed particles of Examples and Comparative Examples were as shown in Table 1 or Table 2.

[Weight average molecular weight]
Chromatograms of hollow particles were obtained by gel permeation chromatography (GPC) using polystyrene as a standard material, and the weight average molecular weight calculated from the obtained chromatograms was taken as the weight average molecular weight of the base resin.

Specifically, HLC-8320GPC EcoSEC manufactured by Tosoh Corporation was used to obtain the chromatogram. Hollow particles as a measurement sample were dissolved in tetrahydrofuran (THF) to prepare a sample solution having a concentration of 0.1 wt%, and then TSKgradechrome SuperH-H x 1 and TSK-GEL SuperHM-H x 2 were connected in series. Using a column, measurement samples were separated by gel permeation chromatography (GPC) under the separation conditions of eluent: tetrahydrofuran (THF) and THF flow rate: 0.6 ml / min to obtain chromatograms. Then, the retention time in the chromatogram was converted into the molecular weight by the calibration curve prepared using the standard polystyrene, and the differential molecular weight distribution curve was obtained. The weight average molecular weight of the measured sample was calculated from this differential molecular weight distribution curve.

The weight average molecular weights of the composite resins in the hollow particles or foamed particles of Examples and Comparative Examples were as shown in Table 1 or Table 2.

[Average particle size]
A particle size distribution based on the volume of hollow particles was obtained using a particle size distribution measuring device (“Millitrack JPA” manufactured by Nikkiso Co., Ltd.). The value of the cumulative 63% diameter (that is, d63) in this particle size distribution was taken as the average particle diameter of the hollow particles. The average particle diameter (B) of the hollow particles or the foamed particles of Examples and Comparative Examples was as shown in Table 1 or Table 2.

[Average thickness of outer shell layer]
First, the hollow particles were divided into roughly two equal parts to expose the cut surface of the outer shell layer. Using a scanning electron microscope, three observation positions were randomly set in one region of the cut surface of the outer shell layer divided into approximately four equal parts. At each observation position, the cut surface of the outer shell layer was observed at a magnification of 1000 times to obtain an enlarged photograph of the cut surface of the outer shell layer. On the outer shell layer in the obtained enlarged photograph, a line segment extending in the thickness direction of the outer shell layer (that is, the radial direction of the hollow particles) was drawn from the outer surface to the inner surface of the outer shell layer. ..

The above operation was performed at 10 randomly selected positions in each enlarged photograph, and the lengths of 30 line segments per hollow particle were measured. The arithmetic mean value of the length of the line segment thus obtained was taken as the thickness of the outer shell layer of each hollow particle. Then, the thickness of the outer shell layer described above was calculated for five randomly selected hollow particles, and the arithmetic mean value of the thickness of these outer shell layers was taken as the average thickness (C) of the outer shell layer. The average thickness (C) of the outer shell layer in the hollow particles of Examples and Comparative Examples was as shown in Table 1 or Table 2. Further, Tables 1 and 2 show the values of the ratio (C) / (B) of the average thickness (C) of the outer shell layer to the average particle size (B).

In the measurement of the thickness of the outer shell layer, there may be a huge bubble having a length of 100 μm or more in the thickness direction of the outer shell layer near the inner surface of the outer shell layer or the like. In this example, such bubbles are treated as hollow portions. Specifically, when the above-mentioned huge bubbles are present near the inner surface of the outer shell layer, the length of the line segment from the outer surface of the hollow particles to the above-mentioned bubbles is set to the outside. The thickness of the shell layer was used.

Further, in the foamed particles of Comparative Example 7, since uniform bubbles are formed over the entire cut surface, the thickness of the outer shell layer cannot be measured. Therefore, the symbol “−” is described in the “Average thickness (C) of outer shell layer” column of Comparative Example 7. In the foamed particles of Comparative Example 7, the thickness of the resin film existing on the outermost surface is about 2 μm.

[Average value of the total thickness of the resin film in the outer shell layer]
Similar to the above-mentioned measurement of the average thickness of the outer shell layer, three observation positions are randomly set for one region of the cut surface of the outer shell layer divided into four equal parts, and the outside at each observation position is set. An enlarged photograph of the cut surface of the shell layer was obtained. A line segment extending in the thickness direction of the outer shell layer was drawn from the outer surface to the inner surface of the outer shell layer on the cut surface of the outer shell layer in each enlarged photograph. Then, the length of the line segment and the length of the portion of the line segment overlapping with the bubble were calculated, and the value obtained by subtracting the length of the portion overlapping with the bubble from the length of the line segment was calculated.

The above operation was performed at 10 randomly selected positions for each enlarged photograph, and the lengths of 30 line segments and the length of the portion overlapping the bubbles were measured for each hollow particle. Then, the arithmetic mean value of the value obtained by subtracting the length of the portion overlapping the bubble from the length of the line segment was calculated, and this value was taken as the total thickness of the resin film of the hollow particles. The total thickness of the resin films described above was calculated for five randomly selected hollow particles, and the arithmetic mean value of the total thickness of these resin films was taken as the average value (D) of the total thickness of the resin films.

The average value (D) of the total thickness of the resin film in the hollow particles of Examples and Comparative Examples was as shown in Table 1 or Table 2. Further, Tables 1 and 2 show the ratio (D) / (C) of the average value (D) of the total thickness of the resin film to the average thickness (C) of the outer shell layer.

[Apparent density of bisected hollow particles]
A particle group consisting of about 1 g of hollow particles or foamed particles was prepared and left to stand for 10 days under the conditions of a relative humidity of 50% and a temperature of 23 ° C. and 1 atm to adjust the state. The hollow particles or foamed particles contained in the state-adjusted particle group were roughly divided into two equal parts, and then the mass (unit: g) of the particle group was measured. Next, sodium dodecylbenzenesulfonate was dissolved in water so as to have a concentration of 0.3% by mass, and an aqueous surfactant solution having a temperature of 23 ° C. was prepared. A graduated cylinder containing this aqueous surfactant solution was prepared, and the particles after being divided into two equal parts were submerged in the water in the graduated cylinder using a wire mesh. Then, the amount of water level rise in the graduated cylinder was read, and the value obtained by subtracting the volume of the wire mesh from the amount of water level rise was taken as the apparent volume (unit: L) of the particle group. The mass of the particle group placed in the graduated cylinder is divided by the apparent volume of the bisected particles, and the unit-converted value is the apparent density (unit: kg / m ³ ) of the bisected hollow particles or foamed particles. bottom.

The apparent densities (E) of the bisected particles in the hollow particles or foamed particles of Examples and Comparative Examples were as shown in Table 1 or Table 2. Further, in Tables 1 and 2, the ratio (E) / (A) of the apparent density (E) of the bisected particles to the apparent density (A) of the hollow particles or the foamed particles, and the base material. The value of the ratio (E) / (F) of the apparent density (E) of the bisected particles to the density (F) of the resin is described. The density (F) of the base resin constituting the resin film of the hollow particles of Examples 1 to 4 and the hollow particles of Comparative Examples 1 to 6 is 1.1 × 10 ³ kg / m ³ , and Comparative Example 7 The density of the base resin constituting the foamed particles was 1.0 × 10 ³ kg / m ³ .

[Maximum compression amount and volume reduction rate in repeated compression test]
Hollow particles or foamed particles having a bulk volume of 330 mL were weighed using a measuring cylinder having a volume of 500 mL, and the hollow particles or foamed particles were placed in a cylindrical container having a diameter of 78 mm. Using a compression jig having a flat plate-like contact portion with the particles, the hollow particles or foamed particles in the container were compressed by moving the compression jig downward at a speed of 10 mm / min. When the load applied to the particles reached 650 N, the compression jig was moved upward to completely unload the load on the particles. This cycle was set as one cycle, and the compression test was repeated by repeating compression and unloading for 100 cycles. Tables 1 and 2 show the maximum compression amount of hollow particles or foamed particles during the repeated compression test.

Further, the hollow particles or foamed particles after the repeated compression test was completed were placed in a measuring cylinder having a volume of 500 mL, and the bulk volume at 25 ° C., humidity 50%, and standing for 24 hours in an environment of 1 atm was measured. Then, the reduction rate of the bulk volume after the repeated compression test with respect to the bulk volume of the particles before the repeated compression test was calculated, and this value was taken as the volume reduction rate (unit:%). The volume reduction rate 24 hours after the repeated compression test was as shown in Table 1 or Table 2, respectively.

[Initial closed cell ratio]
The apparent volume Va (unit: cm ³ ) of the hollow particle group or the foamed particle group was measured by the same method as the above-mentioned method. After sufficiently drying the particle swarm after measuring the apparent volume, the true volume value Vx (unit: cm ³ ) of the particle swarm is measured according to procedure C described in ASTM-D2856-70. bottom. An pneumatic hydrometer (air comparative hydrometer 930 manufactured by Toshiba Beckman Co., Ltd.) was used to measure the true volume value Vx.

Using the apparent volume Va and true volume Vx of the particle group obtained above, and the mass W (unit: g) and true density ρ (unit: g / cm ³ ) of the particle group, the following equation (1) is used. Based on this, the closed cell ratio of the particle group was calculated.
Closed cell ratio (%) = (Vx-W / ρ) x 100 / (Va-W / ρ) ... (1)

Then, the above operation was performed 5 times, and the average value of these was taken as the closed cell ratio of the hollow particles or the foamed particles. The initial closed cell ratio (G) of the hollow particles or the foamed particles in Examples and Comparative Examples was as shown in Table 1 or Table 2.

[Closed cell ratio after repeated compression test]
The closed cell ratio of the particles after the repeated compression test was calculated by the same method as described above except that the hollow particles or the foamed particles after the repeated compression test were used. The closed cell ratio (H) of the hollow particles or the foamed particles after the repeated compression test in Examples and Comparative Examples was as shown in Table 1 or Table 2. In addition, Tables 1 and 2 show values (H) / (G) in which the ratio of the closed cell ratio (H) after the repeated compression test to the initial closed cell ratio (G) is expressed as a percentage.

As shown in Table 1, FIG. 1 and FIG. 2, the hollow particles of Examples 1 to 4 have an outer shell layer having a plurality of bubbles and a hollow portion surrounded by the outer shell layer. There is. Further, these hollow particles have a structure specified by the ratio of the average thickness of the outer shell layer, the average particle diameter, the apparent density and the average value of the total thickness of the resin film to the average thickness of the outer shell layer in the specific range. Have. As shown in Table 1, the hollow particles of Examples 1 to 4 having such a structure have a small maximum value of the amount of compression during the repeated compression test and a high volume reduction rate before and after the repeated compression test. It has rigidity and resilience.

On the other hand, as shown in Table 2, the average thickness of the outer shell layer in the hollow particles of Comparative Example 1 is thinner than the specific range. Therefore, the hollow particles of Comparative Example 1 have a larger maximum value of the amount of compression during the repeated compression test than the hollow particles of Examples 1 to 4, and are inferior in rigidity. Further, the hollow particles of Comparative Example 1 have a larger volume reduction rate before and after the repeated compression test than the hollow particles of Examples 1 to 4, and are inferior in resilience.

The apparent density of the hollow particles of Comparative Example 2 is smaller than the specific range, and the ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer is smaller than the specific range. Therefore, the hollow particles of Comparative Example 2 have a larger maximum value of the amount of compression during the repeated compression test than the hollow particles of Examples 1 to 4, and are inferior in rigidity. Further, the hollow particles of Comparative Example 2 have a larger volume reduction rate before and after the repeated compression test than the hollow particles of Examples 1 to 4, and are inferior in resilience.

The ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer in the hollow particles of Comparative Example 3 is smaller than the above-mentioned specific range. Therefore, the hollow particles of Comparative Example 3 have a larger maximum value of the amount of compression during the repeated compression test than the hollow particles of Examples 1 to 4, and are inferior in rigidity.

The ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer in the hollow particles of Comparative Example 4 and Comparative Example 5 is smaller than the above-mentioned specific range. Therefore, the hollow particles of these comparative examples have a larger volume reduction rate before and after the repeated compression test than the hollow particles of Examples 1 to 4, and are inferior in resilience.

The average particle size of the hollow particles of Comparative Example 6 is larger than the specific range. Therefore, the hollow particles of Comparative Example 6 tend to have low workability when filled inside the bag body. Further, the apparent density of the hollow particles of Comparative Example 6 is smaller than the specific range. Therefore, the hollow particles of Comparative Example 6 have a larger maximum compression amount in the repeated compression test than the hollow particles of Examples 1 to 4, and are inferior in rigidity.

The foamed particles of Comparative Example 7 do not have a hollow portion and have a structure different from that of the hollow particles of Examples 1 to 4. Therefore, the foamed particles of Comparative Example 7 have a larger volume reduction rate before and after the repeated compression test than the hollow particles of Examples 1 to 4, and are inferior in resilience.

1 Hollow particles 2 Outer shell layer 221 Resin film 3 Hollow part

Claims (7)

Hollow particles used as a filler in a cushion body including a bag body and a filler filled in the bag body.
An outer shell layer having a resin film and a plurality of bubbles partitioned by the resin film and having an average thickness of 30 μm or more and 150 μm or less.
It has a hollow portion surrounded by the outer shell layer and has.
The base resin of the resin film is a composite resin containing a (meth) acrylic acid ester component and a styrene-based component.
The average particle diameter of the hollow particles is 2 mm or more and 8 mm or less.
The apparent density of the hollow particles is 30 kg / m ³ or more and 80 kg / m ³ or less.
Hollow particles in which the ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer is 0.5 or more. The hollow particles according to claim 1, wherein the ratio of the apparent density of the hollow particles divided into two equal parts to the apparent density of the hollow particles is 1.5 or more and 5.0 or less. The hollow particles according to claim 1 or 2, wherein the average thickness of the outer shell layer is more than 50 μm and 150 μm or less. The hollow particle according to any one of claims 1 to 3, wherein the composite resin has a weight average molecular weight of 30 × 10 ⁴ or more and 50 × 10 ⁴ or less. The hollow particle according to any one of claims 1 to 4, wherein the closed cell ratio of the hollow particle is 90% or more. The claim that the mass ratio of the (meth) acrylic acid ester component and the styrene-based component contained in the composite resin is (meth) acrylic acid ester component: styrene-based component = 70: 30 to 30:70. The hollow particle according to any one of 1 to 5. A cushion body including a bag body and a filler filled in the bag body.
The filler includes a resin film and a plurality of bubbles partitioned by the resin film, and has an outer shell layer having an average thickness of 30 μm or more and 150 μm or less.
Hollow particles having a hollow portion surrounded by the outer shell layer.
The base resin of the resin film is a composite resin containing a (meth) acrylic acid ester component and a styrene-based component.
The average particle diameter of the hollow particles is 2 mm or more and 8 mm or less.
The apparent density of the hollow particles is 30 kg / m ³ or more and 80 kg / m ³ or less.
A cushion body in which the ratio of the average value of the total thickness of the resin film to the average thickness of the outer shell layer is 0.5 or more.

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