JP7228334B2 - Foamed resin particles and foamed resin products - Google Patents

Description

TECHNICAL FIELD The present invention relates to foamed resin particles having a special shape, and resin foam molded articles having continuous voids obtained by fusing and molding foamed resin particles and having excellent sound absorbing performance.

Resin foam materials are used as materials for replacing conventional solid resin materials and metal materials, as members of automobiles and electronic devices, and as structural materials for containers. These resin foam materials are characterized by low density, high heat insulation, and cushioning properties, and these properties are mainly used effectively. On the other hand, sound absorption and sound insulation are expected properties of foamed resin materials, but their range of application has been limited in the past.

The reason for this is that sound absorption and sound insulation are not characteristics that are expressed in foams in general, but rather depend on the cell structure. While the body has excellent rigidity and mechanical strength, its sound absorption and sound insulation performance is extremely low. Each property tends to conflict with each other, such as being inferior to the other, and it is difficult to achieve both.

Examples of open-cell resin foams include urethane resins and melamine resins, and their main uses are as sponges that absorb fluids and cushioning materials that utilize flexibility and shock absorption. Because of their excellent sound absorption properties, they are widely used as sound absorbing materials that are lighter in weight than inorganic materials. It is used.

The main methods of manufacturing foams include the bead foaming method and the extrusion foaming method. In the bead foaming method, granular resin foam particles obtained by pre-expanding resin particles are molded into a desired shape. After being filled in a mold, it is formed by a mechanism that forms a molded product by fusion due to thermal expansion of resin foam particles. Molding of foam materials for various structural members This is a particularly preferred method. However, in the foam molding process of the bead foam molding method, the foam cells are independent cells separated by a resin film, and due to the mechanism of mutual fusion between the foam particles due to the expansion of the bubbles, the foam structure of the foam normally obtained Since it basically has a closed cell structure, it is generally inferior in sound absorption performance.

On the other hand, as exemplified below, a foam having a continuous pore structure, that is, a continuous pore structure, has been proposed in the foam by a bead foam molding method, and a method for producing the same has been proposed, and it is known that it can be used as a sound absorbing foam material. .

In the method described in Patent Document 1, columnar polyolefin-based resin foams are fused to each other in a state in which they are positioned in non-oriented, irregular directions to obtain a molded article having communicating voids, but the shape of the resin foam particles is elongated. However, it has been difficult to put it to practical use due to problems such as the tendency to cause poor filling when filling the foamed particles into the mold, and the difficulty in balancing the porosity of the molded body and the fusion bond strength of the molded body.

In the method described in Patent Document 2, a granular resin having a void structure is obtained by impregnating thermoplastic resin expanded particles satisfying specific bulk density and true density relationships and shape parameters satisfying specific conditions with a physical foaming material. It is described that a thermoplastic resin foam molded article having continuous voids formed by foaming expanded particles in a mold is excellent in water permeability and sound absorption. However, the exemplified foam is a foam in which voids are formed by hollow and cruciform cross-sectional granular foams of ethylene propylene random polymer and low density polyethylene, and there is no specific description of strength and sound absorption performance, and void structure. It is unknown whether it is suitable as a sound absorbing material.

In the method described in Patent Document 3, a large number of foamed resin beads are surface-bonded at a part of the surface of adjacent foamed resin beads and integrated with a volume porosity of 15 to 40% with respect to the total volume. , it is produced by attaching an adhesive resin that can be thermally bonded at a temperature lower than the softening temperature of the expandable resin particles to the surface of the expandable resin particles, but a step of attaching the thermally adhesive resin to the expanded resin particles is required. As a result, the productivity is lowered, the balance between the strength and the porosity is not sufficient, and the porosity is limited to 40% or less. The exemplified foam is only a vinylidene chloride copolymer and the structure of the foam for obtaining the claimed sound absorbing performance is not shown.

In the method described in Patent Document 4, the three-dimensional shape, size, and relationship between the bulk density and the true density of the expanded resin particles of a cylindrical polyolefin resin are fused and integrated. However, there is no disclosure of performance as a sound absorbing material, and the adequacy of the void structure is unknown.

In the method described in Patent Document 5, a molded body having excellent sound absorption in a wide frequency range is obtained by in-mold expansion of hollow cylindrical resin expanded particles having a specific range of porosity and bulk density of the molded body. It states that you can However, the sound absorbing performance is insufficient and the thickness of the molded body is required, and physical properties such as mechanical strength are not disclosed.

In the method described in Patent Document 6, the state of impregnation of resin particles with a foaming agent before pre-foaming is controlled, and after producing drum-shaped thermoplastic resin foamed beads, the foamed particles having voids are foam-fused in a mold. However, since the shape is limited to an hourglass shape, there are large restrictions on the structure of the voids in the foamed molded product, and there are drawbacks that it is difficult to control the state of impregnation of the foaming agent into the resin particles.

As in Patent Documents 1 to 6 above, foams formed by fusing granular foams forming continuous voids in general-purpose resins such as polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, and vinylidene chloride resins. Although there are prior literatures suggesting that the sound absorption effect of the foam is manifested, the relationship between the microstructure of the foam and the sound absorption performance is unclear. Also, it is not disclosed whether a suitable shape is suitable.

For other general resins, it is thought that foamed moldings with void structures and their manufacturing technology have not yet been established. Technology for producing resin foam particles that form interconnected voids made from so-called engineering resins with functions, foam molded products having interconnected voids formed by fusing them, and sound absorption performance of foam molded products are not known. was the current situation.

JP-A-3-224727 JP-A-7-137063 JP-A-7-168577 JP-A-8-108441 JP-A-10-329220 JP-A-2000-302909

The problem to be solved by the present invention is to provide foamed resin particles that can be molded by bead foaming to form a foamed resin article that is excellent in sound absorbing performance and also as a structural material.

As a result of intensive studies to solve the problem, the present inventor surprisingly found a novel resin foam molding having communicating voids of a specific structure, which is formed by a process of heat-sealing foamed resin particles having a specific shape. The foam exhibits high sound absorption performance and mechanical strength not found in conventional foams, and can be a suitable structural material with sound absorption and sound insulation performance. It was found that a self-supporting sound absorbing structural material having high sound absorption performance and performance selected from mechanical strength, heat resistance, heat deformation resistance, flame retardancy, solvent resistance, and rigidity can be obtained by selecting, and the present invention. completed.

That is, the present invention is as follows.
(1)
A resin foamed particle having a concave outer shape containing a resin,
The ratio _{ρ 0 /} ρ ₁ of the density ρ 0 of the resin to the true density ρ ₁ of the expanded resin beads is 2 to 20, and the true density ρ ₁ of the expanded resin beads and the bulk density ρ ₂ of the expanded resin beads The ratio ρ ₁ / ρ ₂ is 1.5 to 4.0,
The resin is a modified polyether resin,
The resin has a surface tension of 37 to 60 mN/m at 20° C.,
The resin has a glass transition temperature of 10° C. or higher and 280° C. or lower,
The average particle diameter of the expanded resin particles is 1.2 to 6.0 mm ,
Resin foam particles.
(2)
A resin foamed particle having a concave outer shape containing a resin,
The ratio ρ _{0 /} ρ ₁ of the density ρ 0 of the resin to the true density ρ ₁ of the expanded resin beads is 2 to 20, and the true density ρ ₁ of the expanded resin beads and the bulk density ρ ₂ of the expanded resin beads The ratio ρ ₁ / ρ ₂ is 1.5 to 4.0,
The resin is a polyamide resin or a modified polyether resin,
The resin has a surface tension of 37 to 60 mN/m at 20° C.,
The resin has a glass transition temperature of 10° C. or higher and 280° C. or lower,
The average particle diameter of the expanded resin particles is 1.2 to 6.0 mm,
Resin foam particles.
(3)
(1 ) or (2) is a molded body in which the foamed resin particles are fused to each other,
A foamed resin article having continuous voids between the fused resin foamed particles and having a porosity of 15 to 80%.
(4)
A soundproof member comprising the resin foam molded article according to (3) .

ADVANTAGE OF THE INVENTION According to this invention, the resin foaming bead which can shape|mold the resin expansion molding excellent in sound absorption performance, and is excellent also as a structural material can be provided by foaming bead molding.

It is a figure which shows an example of sectional drawing of the resin expansion particle of this embodiment. 1 is a perspective view of resin foam beads of the present embodiment. FIG. FIG. 4 is a cross-sectional view showing the shape of the discharge port of the profiled extrusion die used in Examples and the concave outer shape portion of the obtained foamed resin beads.

A resin foam molded article having interconnected voids obtained by fusing and foam-molding the specially shaped resin foam particles of the present embodiment has excellent sound absorbing performance, is excellent as a structural material, and can be used as various sound absorbing members. In addition, as a hard foam, it is highly suitable for automatic assembly lines and has excellent productivity as a member with excellent fitting and assembly properties between foam and other members. effectively used for
Furthermore, by using a specific raw material resin, it is also possible to obtain a novel foam-molded article having performance selected from mechanical strength, heat resistance, heat deformation resistance, flame retardancy, solvent resistance, and rigidity.

[Resin foamed particles]
The expanded resin bead of the present invention is required to have a concave outer shape portion (having a concave shape portion in the outer shape viewed from at least one direction).
In this specification, having a concave outer shape portion means that there is a direction in which the orthogonal projection image of the expanded resin bead is a concave figure. In this specification, a concave figure means that at least a part (preferably, the whole line segment) of a line segment connecting two points on the outer surface of the orthogonal projection image figure to be a concave figure forms an external region of the resin foam beads. It means that it is possible to choose two points that will be a line segment that passes through. An example of a concave figure is shown in FIG.
Further, the concave outer shape portion has a structure different from that of foamed cells formed during foaming.

There may be one or a plurality of concave outer portions.
The concave outer shape portion may be one or more through-holes that connect the surfaces of the foamed resin particles, one or more concave portions that do not penetrate the particles, or one or more Through holes and one or more recesses may be mixed. Here, the through-hole may be a cavity connecting two holes formed on the outer surface of the resin foamed bead. The structure may be such that a projection image (an orthographic projection image in which the cavity forms an isolated cavity within the foamed resin particles) can be obtained.

In the expanded resin bead of the present embodiment, the concave portion is defined as a straight line that circumscribes the region occupied by the expanded resin bead in an orthographic projection image in which the concave portion can be confirmed, and the outer surface of the expanded resin bead. The ratio of the area A surrounded by (area A/area occupied by the expanded resin particles) is preferably 10% or more, more preferably 30% or more. Above all, it is preferable that the orthogonal projection image including the deepest part of the concave portion satisfies the above range. Here, the deepest part of the recess may be the part where the distance to the intersection of the straight line perpendicular to the recess at least at two points or more and the outer surface of the recess is the longest.

When the concave outer portion is a through-hole, the area of the through-hole should be 10% or more of the total area of the orthographic projection image of the expanded resin bead, in which the through-hole can be confirmed in the expanded resin bead. is preferred, and more preferably 30% or more. Above all, it is preferable that the above range is satisfied in an orthographic image in which the area of the through-holes of the expanded resin beads is the largest. In addition, in the cross section where the hollow shape passing through the through hole can be confirmed, the area of the hollow shape is preferably 10% or more, more preferably 30%, with respect to the total area of the expanded resin beads on the cross section. % or more. The through-hole preferably has at least one cross-section in which the area of the hollow shape satisfies the above, and more preferably the entire cross-section satisfies the above range.

By selecting the shape of the foamed resin particles such that the recessed outer shape portion satisfies the conditions for the recesses and/or the conditions for the through holes, the communicating voids (continuous voids, communicating voids) can be formed satisfactorily.

In the present embodiment, the concave outer shape portion of the expanded resin bead may or may not be a through hole, but it is particularly preferable that the expanded resin bead has a shape having a concave portion. By adopting a shape with recesses, there is a filling state that conventional foamed resin beads did not have, and the structure of the communicating voids of the resin foamed molded product obtained after molding has a particularly excellent balance in both sound absorption performance and mechanical strength. can be realized.

A particularly excellent shape as the shape having the recesses is a structure in which groove-shaped recesses are provided in the foamed resin particles, and the groove-shaped recesses are adjacent when the resin foamed particles are heat-sealed during the production of the foamed resin article. The foamed resin particles are joined in a partially meshed filled state to form a foamed resin article having a large bonding area between the foamed resin particles and high strength, and at the same time, the grooves of the adjacent foamed resin particles are connected. Voids extending between the resin foam particles, that is, interconnected voids are formed when they are joined together.

As the groove-shaped concave portion, for example, a shape (FIGS. 2A and 2B) obtained by overlapping cross sections (FIG. 1) of a shape (C shape, U shape, etc.) obtained by cutting a part of a hollow substantially circle (FIGS. 2A and 2B), a hollow and a shape in which cross sections (FIG. 1) obtained by partially cutting out approximately polygons (triangles, quadrilaterals, etc.) of are overlapped. Here, the hollow in the hollow substantially circle and the hollow substantially polygon may be substantially circular or substantially polygonal, but preferably has the same shape as the shape surrounding the hollow. . Moreover, it is preferable that the center of the hollow shape and the center of the shape surrounding the hollow overlap (for example, a concentric circle).

Examples of the recess include, for example, a saddle-shaped shape formed by bending a disk shape having a certain thickness, a shape formed by bending or bending a disk in the out-of-plane direction, and a single or multiple recesses on the outer surface of a cylindrical shape. structure provided with a concave portion. Among the particle shapes, an example of a particle shape that is particularly preferable in terms of ease of production, excellent productivity, and easy control of the shape is a cylindrical shape having a common axis with an outer diameter smaller than the outer diameter. Examples include a shape (FIG. 2) obtained by cutting out and cutting out a portion within a certain angle when viewed from the axial direction of a cylinder obtained by cutting a column of height. Hereinafter, this shape will be referred to as a C-shaped cross-sectional partial cylindrical shape, and even if it is substantially the same shape that is slightly deformed based on this shape, it is possible to form the same voids in the resin foam molding. Therefore, if the above conditions are satisfied, it can be used within the scope of the present invention. FIG. 2 shows a preferred example of a C-shaped cross-section partial cylinder having different sizes of portions to be cut and cut.

It is preferable that the concave portions have the same shape when the cross section is continuously formed in one specific direction of the foamed resin beads. For example, as shown in FIG. 2, the shape of the concave portion in a cross section in one direction (vertical direction in FIG. 2, extrusion direction) of the foamed resin particle is the same as the shape of the concave portion in a different cross section formed by being shifted in the one direction. Preferably.
The expanded resin particles may have the same shape or different shapes when the cross section is continuously formed in one specific direction, and preferably have the same shape.

In this embodiment, whether or not the foamed resin beads have a concave outer shape portion can be confirmed by observing and judging transmission images of the foamed resin beads with an optical microscope while changing the observation direction of the particles.

In the expanded resin beads of the present embodiment, the ratio ρ ₀ /ρ ₁ between the density ρ ₀ of the resin contained in the expanded resin beads and the true density ρ ₁ of the expanded resin beads is required and preferably 2 to 20. is 2.2-18, more preferably 2.5-15. If ρ ₀ /ρ ₁ is less than 2, the sound absorption performance is not sufficiently developed, and if it exceeds 20, the mechanical strength is undesirably lowered.

In the expanded resin beads of the present embodiment, the ratio ρ ₁ /ρ ₂ between the true density ρ ₁ of the expanded resin beads and the bulk density ρ ₂ of the expanded resin beads is required to be 1.5 to 4.0, It is preferably 1.8-3.5, more preferably 2-3. If ρ ₁ /ρ ₂ is less than 1.5, the sound absorption performance of the resin foam molding is insufficient, and if it exceeds 4.0, the mechanical strength of the resin foam molding decreases, which is undesirable.

In this specification, the bulk density ρ ₂ is the value M/V ₂ obtained by dividing the resin foamed beads of a predetermined weight M by the bulk volume V ₂ of the resin foamed beads at the weight M, and the true density ρ ₁ is the predetermined weight It is a value M/ _V1 obtained by dividing M resin expanded beads by the true volume _V1 of the resin expanded beads at the weight M. The bulk volume V ₂ refers to the value obtained by filling a graduated cylinder with the foamed resin particles of the predetermined weight M, vibrating the graduated cylinder, and reading the scale when the volume reaches a constant weight. Further, the true volume V ₁ is the volume of the portion increased by the liquid when the foamed resin beads of the predetermined weight M are submerged in a graduated cylinder containing a liquid that does not dissolve the foamed resin beads.
The density ρ ₀ of the resin is the density of the raw material resin before foaming, and is the density measured by the submersion method using a weighing scale.
In this specification, ρ ₀ , ρ ₁ , and ρ ₂ all mean values obtained by measurement under an environment of 20° C. and 0.10 MPa.

The average particle size of the expanded resin beads of the present embodiment can be measured by classifying 100 g of expanded resin beads using a standard sieve defined by JIS Z8801. The average particle diameter of the expanded resin particles is preferably 0.5 to 6.0 mm, more preferably 0.7 to 5.0 mm, even more preferably 1.0 mm to 4.0 mm, particularly preferably 1 .2 mm to 3.0 mm. If the average particle size is less than 0.5 mm, it is difficult to handle in the manufacturing process, and if it exceeds 6.0 mm, the surface precision of complicated molded articles tends to decrease, which is undesirable.
The shape of the foamed resin particles of the present embodiment is not particularly limited, and various shapes may be used.

As a method for producing the resin foamed particles of the present embodiment, a method utilizing the thermoplasticity of a thermoplastic resin, a method using post-processing such as cutting of particles in a solid state, and the like are possible, and a desired external shape can be imparted to the particles. Any method is applicable. Among them, a profile extrusion method using a die having a discharge cross section of a special shape can be suitably used as a method that is excellent in productivity and capable of producing particles with a stable shape. Thermoplastic resin is melt extruded by an extruder equipped with a die with a specially shaped discharge cross section, and the pellets obtained by pelletizing by a commonly used industrial method such as strand cutting or underwater cutting are foamed to foam the resin. A method of obtaining particles, a method of injecting a foaming agent into an extruder from the middle of a barrel, foaming simultaneously with discharge, cooling and then underwater cutting or strand cutting to obtain resin foamed particles directly, a method of melting in an extruder to obtain a desired cross-sectional shape. and then cut to a predetermined length by a pelletizer after cooling to produce base resin pellets. The base resin pellets are impregnated with a foaming agent and heated to foam at a predetermined expansion ratio. It can be manufactured by applying any conventionally known method such as a method.

The expanded resin particles of the present embodiment contain a resin. Examples of the resin include thermoplastic resins.
Examples of the thermoplastic resin include polystyrene, polyα-methylstyrene, styrene maleic anhydride copolymer, blend or graft polymer of polyphenylene oxide and polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene terpolymer, styrene-butadiene. Copolymers, styrenic polymers such as high impact polystyrene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, post-chlorinated polyvinyl chloride, vinyl chloride polymers such as copolymers of ethylene or propylene and vinyl chloride, polyvinylidene chloride Copolymer resins, nylon-6, nylon-6,6, homo- and copolymer polyamide resins, polyethylene terephthalate, homo- and copolymer polyester resins, modified polyphenylene ether resins (phenylene ether-polystyrene alloy resins), polycarbonate resins, methacrylimide Resins, polyphenylene sulfides, polysulfones, polyethersulfones, polyester resins, phenolic resins, urethane resins, polyolefin resins, and the like.

Examples of the polyolefin resin include polypropylene polymerized using a Ziegler catalyst or metallocene catalyst, ethylene-propylene random copolymer, propylene-butene random copolymer, ethylene-propylene block copolymer, ethylene-propylene-butene. Polypropylene resins such as terpolymers, low density polyethylene, medium density polyethylene, linear low density polyethylene, linear ultra-low density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl Polyethylene-based resins such as methacrylate copolymers and ionomer resins may be used alone or in combination.

The resin preferably has a surface tension of 37 to 60 mN/m at 20° C., more preferably 38 to 55 mN/m. If the surface tension is within the above range, a sound-absorbing foamed resin article having high mechanical strength can be obtained, which is particularly preferable.
As the surface tension of the resin, the value measured by the method described in JIS K6768 "Plastics-Film and Sheet-Wet Tension Test Method" with the temperature changed to 20°C is used.

Examples of thermoplastic resins included in the preferred surface tension range include polyamide resins, polyester resins, polyether resins, methacrylic resins, modified polyether resins (phenylene ether-polystyrene alloy resins), etc., and the surface tension is within the above range. A thermoplastic resin is exemplified. Among them, polyamide resin has excellent heat resistance, chemical resistance, and solvent resistance, and is suitable for use as a highly heat-resistant foam structure material. Modified polyether resin (phenylene ether-polystyrene alloy resin).

By setting the surface tension of the resin within the above range, especially when the foamed resin is thermally expanded and fused by superheated steam, the affinity between the water vapor and the surface increases, resulting in a uniform foamed molded product with high fusion strength. be done. The surface tension of the resin may be the surface tension of the mixed resin of all the resins constituting the resin foamed beads, and the surface tension of at least one resin among all the resins constituting the resin foamed beads satisfies the above range. More preferably, the surface tension of all the resins satisfies the above range.

The resin preferably has a glass transition temperature of −10° C. or higher and 280° C. or lower.
As the glass transition temperature of the resin, a value measured by the DSC method in accordance with JIS K7121:1987 "Method for measuring transition temperature of plastics" is used. That is, after conditioning for at least 24 hours at a temperature of 23 ± 2°C and a relative humidity of 50 ± 5%, place the specimen in the container of the DSC instrument and, if amorphous, at a temperature at least about 30°C higher than the end of the glass transition. to at least about 30° C. above the end of the melting peak, if crystalline, and held at each temperature for 10 minutes, followed by quenching to about 50° C. below the glass transition temperature. The heating rate was maintained at a temperature about 50°C lower than the transition temperature until the device stabilized, and then heated at a heating rate of 20°C per minute to a temperature about 30°C higher than the end of the transition, and a DSC curve was drawn.

The lower limit of the glass transition temperature of the resin raw material is more preferably 0°C, still more preferably 10°C. By making the glass transition temperature equal to or higher than the above lower limit, it is possible to suppress deterioration of the sound absorbing performance due to long-term compressive force applied to the molded product, and it is preferable in that it can be used for sound absorbing members to which stress is applied.

The upper limit of the glass transition temperature is more preferably 260°C, still more preferably 240°C. When the glass transition temperature is not higher than the above upper limit, the temperature for foam molding can be set low, and the foam can be manufactured with high productivity, which is particularly preferable.

Examples of thermoplastic resins included in the preferred glass transition temperature range include polyamide resins, polyester resins, polyether resins, methacrylic resins, modified polyether resins (phenylene ether-polystyrene alloy resins), etc., and the glass transition temperature is Thermoplastic resins within the above range can be mentioned.
Among them, polyamide resin has excellent heat resistance, chemical resistance, and solvent resistance, and is suitable for use as a highly heat-resistant foam structure material. Modified polyether resin (phenylene ether-polystyrene alloy resin).
The glass transition temperature of the resin may be the glass transition temperature of the mixed resin of all the resins constituting the resin foamed beads, and at least one resin among all the resins constituting the resin foamed beads has the above glass transition temperature. It is preferable that the range is satisfied, and it is more preferable that the glass transition temperatures of all the resins satisfy the above range.

The above thermoplastic resin may be used in an uncrosslinked state, or may be used after being crosslinked by peroxide, radiation, or the like.

The foamed resin particles of the present embodiment may optionally contain conventional compounding agents such as antioxidants, light stabilizers, ultraviolet absorbers, flame retardants, coloring agents such as dyes and pigments, plasticizers, lubricants, and crystallization agents. Inorganic fillers such as nucleating agents, talc, and calcium carbonate may be included depending on the purpose.
As the flame retardant, a bromine-based, phosphorus-based, etc. flame retardant can be used, and as the antioxidant, a phenol-based, phosphorus-based, sulfur-based, etc. antioxidant can be used. Hindered amine-based and benzophenone-based light stabilizers can be used as the agent.
If it is necessary to adjust the average cell diameter of the expanded resin beads, a cell control agent may be added. Inorganic nucleating agents include talc, silica, calcium silicate, calcium carbonate, aluminum oxide, titanium oxide, diatomaceous earth, clay, sodium bicarbonate, alumina, barium sulfate, aluminum oxide, bentonite, and the like. The amount to be used is usually 0.005 to 2 parts by mass based on the total amount of raw materials for the expanded resin particles.

A volatile foaming agent or the like may be used as the foaming agent used in producing the foamed resin beads of the present embodiment. Examples of the volatile foaming agent include chain or cyclic lower aliphatic hydrocarbons such as methane, ethane, propane, butane, isobutane, pentane, isopentane, neopentane, hexane, heptane, cyclopentane, cyclohexane, and methylcyclopentane; Halogenated hydrocarbons such as dicyclodifluoromethane, trichloromonofluoromethane, 1-chloro-1,1-difluoroethane, 1-chloro-2,2,2-trifluoroethane; inorganics such as nitrogen, air, and carbon dioxide; A gas-based foaming agent and the like are included.

[Foam molding]
The foamed resin article of the present embodiment is a molded article in which the foamed resin particles are fused to each other. That is, the foamed resin article of the present embodiment is a molded article having at least a portion in which at least two or more of the foamed resin particles are fused to each other. There are fused parts and voids between the fused resin foam particles. The resin foam molded article of the present embodiment can be used as a member that shields various noises, such as a soundproof member for vehicles such as automobiles. The soundproof member preferably contains the foamed resin article of the present embodiment, and may consist of the foamed resin article of the present embodiment only.
Further, the resin foam molded article of the present embodiment preferably has continuous voids between the fused resin foam particles, and preferably has a porosity of 15 to 80% (more preferably 30 to 70%). .
The porosity can be measured by the method described in Examples below.

In the foamed resin article of the present embodiment, if the proportion of the resin foamed particles in the entire foamed resin article is 98% by weight or more, the performance of the foamed resin particles having a substantially concave outer shape can be obtained. preferable.

The foamed resin article of the present embodiment is a molded article obtained by fusion-bonding aggregates of the foamed resin particles, and is required to have continuous voids between the foamed resin particles. As used herein, the term “continuous void” refers to the formation of mutually continuous voids between the fused resin foam particles. ), which means that continuous voids are generated and the fluid can flow. The resin foam molded article of the present embodiment preferably has voids continuous in at least one direction, and preferably has voids continuous in the thickness direction. In the present embodiment, a plate-shaped resin foam molded sample with a thickness of 10 mm is used as the communicating void, and the unit length flow resistance measured in the thickness direction by the AC method specified in the international standard ISO 9053 is 1. ,000,000 N·s/m ⁴ or less, more preferably 500,000 N·s/m ⁴ or less.

The foamed resin article of the present embodiment is produced by filling the foamed resin particles into a closed mold and foaming them. A fusing method may be employed. A general-purpose in-mold foaming automatic molding machine can be used depending on the type of resin and molding conditions.

In the present embodiment, resin foamed particles having a concave outer shape and resin foamed particles having a general shape such as an elliptical sphere, a columnar shape, a polygonal columnar shape, or the like, having no concave shape, are mixed at an arbitrary ratio and used. A desired balance between sound absorption performance and mechanical strength can be adjusted by producing a foam molded article.

The resin foam molded article of the present embodiment may be used as a single molded article, or may be used by laminating other inorganic and organic woven fabrics, nonwoven fabrics, and other fiber assembly layers and inorganic and organic porous layers in an arbitrary form. can be done. The layer to be laminated is used as a skin material to improve the surface appearance and surface characteristics of the product.In addition to laminating and bonding with the foam molded product, foamed resin beads are filled with the skin material set inside the mold during bead molding. A method of heat-sealing by performing foam molding can also be used.

The embodiments of the present invention are illustrated by the following examples. However, the scope of the present invention is not limited by the examples.

Evaluation methods used in Examples and Comparative Examples are described below.

(1) Resin density ρ ₀ (g/cm ³ )
After measuring the mass W (g) of the resin before foaming, the volume V (cm ³ ) was measured by the submersion method, and W/V (g/cm ³ ) was defined as the density of the resin.

(2) True density ρ ₁ (g/cm ³ ) of foamed resin particles
After measuring the mass W (g) of the foamed resin beads, the volume V (cm ³ ) was measured by the submersion method, and W/V (g/cm ³ ) was defined as the true density of the foamed resin beads.
The density of the resin raw material pellets after pre-foaming was measured with a hydrometer.

(3) Bulk Density ρ ₂ (g/cm ³ ) of Expanded Resin Particles
Bulk volume V1 (cm ³ ) is obtained by reading the scale on the flattened upper surface when 100 g of the expanded resin particles are placed in a graduated cylinder and vibrated, and the volume reaches a constant weight, and the mass of the graduated cylinder containing the expanded resin particles is W ₁ (g) and the mass W ₀ (g) of the graduated cylinder were measured and obtained by the following formula.
ρ ₂ = [W ₁ -W ₀ ]/V ₁

(4) Average particle diameter D (mm) of expanded resin particles
100 g of foamed resin particles are defined by JIS Z8801 and have nominal dimensions of d ₁ =5.6 mm, d ₂ =4.75 mm, d ₃ =4 mm, d ₄ =3.35 mm, d ₅ =2.36 mm, d Classification is _carried out using standard sieves with ₆ = 1.7 mm, d ₇ = 1.4 mm, d ₈ = ₁ mm _. , the average particle diameter D of all particle aggregates was determined by the following equation.
D=ΣX _i (d _i ·d _i+1 ) ^1/2
(i represents an integer from 1 to 7)

(5) Porosity (%) of resin foam molding
The porosity of the foamed resin product was obtained from the following formula.
Porosity (%) of resin foam molding = [(BC) / B] × 100
However, B is the apparent volume (cm ³ ) of the resin foam molding, C is the true volume (cm ³ ) of the resin foam molding, and the apparent volume is the volume calculated from the outer dimensions of the molded body, and the true volume. C means the actual volume of the compact excluding voids. The true volume C can be obtained by measuring the increased volume when the foamed resin article is submerged in a liquid (for example, alcohol).

(6) Presence or Absence of Continuous Gaps Judgment was made as follows from the measurement of the unit length flow resistance.
As a method for measuring the unit length flow resistance value, the AC method of the international standard ISO9053 was applied, and the flow resistance measurement system AirReSys type manufactured by Nippon Onkyo Engineering Co., Ltd. was used. That is, using a flat resin foam molded product sample with a thickness of 10 mm, the differential pressure P (Pa) between the front and back surfaces of the material is measured in a uniform flow at a flow rate of F = 0.5 mm / s. It was obtained from the material thickness t (m) as P/(t·F) (N·s/m ⁴ ). When the unit length flow resistance value is 200,000 N·s/m ⁴ or less, it is evaluated as having continuous voids (○), and when it exceeds 200,000 N·s/m ⁴ , it is evaluated as having no continuous voids (x). bottom.

(7) Fusion strength of resin foam molding Tensile strength was measured based on JIS K6767A, and when the breaking elongation of the resin foam molding was 2% or more, the fusion strength was excellent (◎), and the breaking elongation was 1. % or more and less than 2%, the fusion bond strength was evaluated as good (O), and when the elongation at break was less than 1%, the fusion bond strength was evaluated as poor (X).

(8) Sound Absorption Characteristics of Resin Foam Molding The normal incident sound absorption coefficient at 23° C. was measured according to JIS A1405-2. A plate-shaped resin foam molding with a thickness of 30 mm was prepared, and a disk with a diameter of 41 mm and a thickness of 30 mm was cut out, and the normal incidence sound absorption coefficient at a frequency of 200 to 5000 Hz was measured to be 20 using a normal incidence sound absorption measurement system WinZac MTX manufactured by Nippon Onkyo Engineering Co., Ltd. °C. The measurement is the average sound absorption coefficient of 1/3 octave band with 11 points of 200Hz, 250Hz, 315Hz, 400Hz, 500Hz, 630Hz, 800Hz, 1000Hz, 1250Hz, 1600Hz and 2000Hz as the center frequency. Among them, when there are 5 or more frequencies with a sound absorption coefficient of 20% or more, the sound absorption characteristics are excellent (◎), and when the frequencies with a sound absorption coefficient of 20% or more are 3 or more and 4 or less, the sound absorption characteristics are good (○). When the number of frequencies with a sound absorption rate of 20% or more was 2 points or less, the sound absorption characteristics were evaluated as poor (x).

(9) Sound absorption properties after compression test A flat resin foam molded product with a thickness of 30 mm was subjected to a compression creep test under the conditions of 40 ° C. and a stress of 0.020 MPa according to JIS K6767. The 23° C. normal incident sound absorption coefficient of the foam molded product was evaluated in the same manner as the sound absorption property of the resin foam molded product (8) above.

[Example 1]
Polyamide 6 resin (UBE nylon "1022B", manufactured by Ube Industries, surface tension 46 mN / m at 20 ° C.) was melted using an extruder and extruded from a profile extrusion die having a cross-sectional shape shown in FIG. 3 (a1). The strand was pelletized with a pelletizer to obtain pellets with an average particle size of 1.4 mm. The obtained pellets were put into a pressure cooker at 10° C., and carbon dioxide gas of 4 MPa was blown thereinto for absorption for 3 hours. Next, the mini-pellets impregnated with carbon dioxide gas were transferred to a foaming device, and air at 240° C. was blown for 20 seconds to obtain aggregates of foamed polyamide resin particles. The average particle diameter of the expanded polyamide resin particles contained in the obtained aggregate of expanded polyamide resin particles was 2.0 mm. When the expanded polyamide resin beads were cut and observed, it was found that a large number of closed cells were evenly formed on the cut surface of the expanded polyamide resin beads. The cross section of the foamed polyamide resin beads had a concave outer shape portion in the shape shown in FIG. 3(a2).
The polyamide resin foamed particle aggregate thus obtained was placed in the pressure cooker again and allowed to absorb 4 MPa of carbon dioxide gas at 10° C. for 3 hours. Next, the foamed polyamide resin particles impregnated with carbon dioxide gas are filled in the mold of an in-mold foam molding apparatus, and air at 230° C. is blown in for 30 seconds to obtain a resin foam molded product A-1 in which the foamed polyamide resin particles are fused together. got The expansion ratio of the resin foam molding was 7.5 times. When the resin foam molded product was cut and observed, aggregates of polyamide resin foam particles having a large number of closed cells with a cell diameter of 200 to 400 μm were formed. It was confirmed from the measurement value of airflow resistance that it had continuous voids. Table 1 shows the evaluation results of the foamed polyamide resin particles and the foamed resin article.

[Examples 2 to 5]
Polyphenylene ether resin (trade name: Zylon TYPE S201A, Asahi Kasei Co., Ltd., surface tension 40 mN / m at 20 ° C.) 60% by mass, non-halogen flame retardant (bisphenol A-bis (diphenyl phosphate) (BBP)) 18% by mass, 10% by mass of impact-resistant polystyrene resin (HIPS) with a rubber concentration of 6% by mass (rubber content in base resin is 0.6% by mass), and general-purpose polystyrene resin (PS) (trade name : GP685, manufactured by PS Japan Co., Ltd.) was added at 12% by mass, and the strand discharged from the profile extrusion die shown in FIG. According to the method described in Example 1 of JP-A-4-372630, the pellets as the base resin are placed in a pressure-resistant container, the gas in the container is replaced with dry air, and then carbon dioxide ( gas) is injected, and the pellets as the base resin are impregnated with 7% by mass of carbon dioxide over 3 hours under the conditions of a pressure of 3.2 MPa and a temperature of 11 ° C., and the base resin pellets are stirred in a foaming furnace. Foaming was performed with pressurized steam while feathering. FIG. 3 shows the general shape of the obtained expanded resin beads.
3(b1) shows Example 2, FIG. 3(c1) shows Example 3, FIG. 3(d1) shows Example 4, and FIG. 3(e1) shows Example 5. be. 3(b2) is Example 2, FIG. 3(c2) is Example 3, FIG. 3(d2) is Example 4, and FIG. 3(e2) is Example 5. .
The obtained resin expanded beads were transferred to a pressure-resistant container, and the internal pressure was increased to 0.5 MPa over 1 hour with compressed air, and then held at 0.5 MPa for 8 hours to perform pressure treatment. This is filled into a mold having steam holes of an in-mold foam molding device, heated with pressurized steam of 0.35 MPa to expand and fuse the resin foam particles to each other, cooled, and released from the mold. It was taken out to obtain resin foam molded articles A-2 to A-5. A-2 is the resin foam molded article obtained from the expanded resin particles of Example 2, A-3 is the resin expanded molded article obtained from the expanded resin particles of Example 3, and A-3 is the expanded resin article obtained from the expanded resin particles of Example 4. The obtained resin foam molded product is A-4, and the resin foam molded product obtained from the resin foam beads of Example 5 is A-5. It was confirmed from the measurement value of airflow resistance that it had continuous voids. Table 1 shows the evaluation results of the foamed resin particles and the foamed resin article.

[Example 6]
100 parts by weight of a polycondensate of ethylene glycol, isophthalic acid, and terephthalic acid (isophthalic acid content: 2% by weight, surface tension: 43 mN/m at 20°C), 0.3 parts by weight of pyromellitic dianhydride, and sodium carbonate 0.03 parts by weight of the mixture was melted and kneaded by an extruder at 270 to 290° C., butane as a foaming agent was injected into the middle of the barrel at a rate of 1.0% by weight with respect to the mixture, and FIG. 3 (f1 ), it was immediately cooled in a cooling water bath and cut into small granules using a pelletizer to produce expanded resin particles. The cross section of the obtained expanded resin beads was shown in FIG. 3(f2).
The obtained foamed resin particles had a bulk density of 0.14 g/cm ³ and an average particle diameter of 1.5 mm.
The foamed resin particles were placed in a closed container, carbon dioxide was injected at a pressure of 0.49 MPa, and the resin foamed particles were held for 4 hours. and the mold is clamped, steam at a gauge pressure of 0.02 MPa is introduced into the mold for 10 seconds, then steam at a gauge pressure of 0.06 MPa is introduced for 20 seconds, and the resin foamed particles are water-cooled after holding the temperature for 120 seconds. A resin foam molded product A-6 in which the two were fused together was obtained. It was confirmed from the measurement value of airflow resistance that it had continuous voids. Table 1 shows the evaluation results of the foamed resin particles and the foamed resin article.

[Example 7]
Polyamide 6 resin (UBE nylon "1022B", manufactured by Ube Industries) is melted using an extruder, and a die with the same shape as the profile extrusion die used in Example 1 but with a size reduced to 1/3 times is used. The extruded strand was pelletized by a pelletizer to obtain pellets having an average particle size of 0.5 mm. The obtained pellets were expanded by the method described in Example 1 to obtain expanded polyamide resin particles. When the expanded polyamide resin beads were cut and observed, it was found that a large number of closed cells were evenly formed on the cut surface of the expanded polyamide resin beads. The cross section of the foamed polyamide resin beads had a concave outer shape portion in the shape shown in FIG. 3(a2).
The resulting polyamide resin foamed particle assembly was molded in the same manner as in Example 1 using an in-mold foam molding apparatus to obtain a resin foam molded article A-7. Table 1 shows the evaluation results of the foamed resin particles and the foamed resin article.

[Example 8]
Polyamide 6 resin (UBE nylon "1022B", manufactured by Ube Industries) was melted using an extruder, and a cross-sectional die with the same shape as the profile extrusion die used in Example 1 and three times the size was used. The extruded strand was pelletized with a pelletizer to obtain pellets having an average particle size of 6.0 mm. An aggregate of expanded polyamide resin particles expanded by the method described in Example 1 was obtained. The average particle size of the resulting expanded polyamide particles was 6.0 mm. When the expanded polyamide resin beads were cut and observed, it was found that a large number of closed cells were evenly formed on the cut surface of the expanded polyamide resin beads. The cross section of the foamed polyamide resin beads had a concave outer shape portion in the shape shown in FIG. 3(a2).
The resulting polyamide resin foamed particle assembly was molded in the same manner as in Example 1 using an in-mold foam molding apparatus to obtain a resin foam molded article A-8. Table 1 shows the evaluation results of the foamed resin particles and the foamed resin article.

[Example 9]
An ethylene-propylene random copolymer (MI = 10 g/10 min, ethylene content = 2.4 wt%, melting point 147°C) is melted using an extruder, and extruded from a profile extrusion die having the cross-sectional shape shown in Fig. 3(a1). After the extruded strand was quenched in water, it was pelletized with a pelletizer to obtain pellets having an average particle size of 1.4 mm. 2.5 parts by weight of carbon dioxide as a foaming agent, 0.4 parts by weight of kaolin as a dispersant, 0.004 parts by weight of sodium dodecylbenzenesulfonate as a surfactant, and 240 parts by weight of water for 100 parts by weight of the pellets obtained. The mixture was stirred and dispersed, heated to 150 ° C., held for 15 minutes, and then applied with a back pressure equal to the equilibrium vapor pressure in the closed container. were released at the same time to obtain foamed resin particles. When the resin foamed beads were cut and observed, it was found that a large number of closed cells were evenly formed on the cut surface of the resin foamed beads. The cross section of the foamed resin beads had a concave outer shape in the shape shown in FIG. 3(a2).
The foamed resin particles are filled in a mold having steam holes of an in-mold expansion molding device, heated with pressurized steam of 0.3 MPa to expand and fuse the resin foamed particles to each other, and then cooled to form a mold. It was taken out from the mold to obtain a resin foam molded article A-9. The molding temperature was 145°C. It was confirmed from the measurement value of airflow resistance that it had continuous voids. Table 1 shows the evaluation results of the foamed resin particles and the foamed resin article.

[Example 10]
After melt-kneading an aliphatic polyester resin (Bionol #1001) (manufactured by Showa High Polymer Co., Ltd.) mainly composed of 1,4-butanediol and succinic acid with an extruder, the melt-kneaded product is shown in FIG. After extruding through a die having a cross-sectional shape shown in (a1) and quenching, the strand was then cut to obtain porous resin particles having an average particle size of 1.4 mm.
Next, 100 parts by weight of the resin particles, 300 parts by weight of water (concentration of dissolved oxygen: 6 mg/l), 0.5 parts by weight of aluminum oxide, 0.004 parts by weight of sodium dodecylbenzenesulfonate, organic peroxide (Nyper FF) A 5-liter autoclave was charged with 1.5 parts by weight of benzoyl peroxide with a purity of 50% (manufactured by NOF Co., Ltd.) and 0.1 part by weight of methyl methacrylate. The oxygen concentration in the part was set to 0.3% by volume. Then, while stirring the contents in the autoclave, the temperature was raised to 75°C at a temperature increase rate of 1.7°C/min, held at the same temperature for 20 minutes, and then raised to 105°C at a temperature increase rate of 0.5°C/min. The content in the autoclave was stirred and held at the same temperature for 45 minutes at the same temperature as the heated chloroform-insoluble matter on the resin particles. An operation to develop a gel that appears (gelation) and an operation to impregnate the resin particles with the blowing agent are performed, after which the contents are cooled to 90°C at a temperature-lowering rate of 1.7°C/min and held at the same temperature for 5 minutes. After that, one end of the autoclave was opened and nitrogen gas was introduced into the autoclave to maintain the internal pressure of the autoclave while releasing the contents to atmospheric pressure to expand the resin particles and obtain expanded particles. Next, the foamed particles were pressurized with air in a closed container to give an internal particle pressure of 0.12 MPa. Next, after filling the foamed particles to which the internal pressure was applied into another container, the pressure inside the container was reduced to -0.02 MPa, and then heated with a heating medium of 94 ° C. mixed with steam and compressed air, and expanded and foamed. Thus, expanded resin particles were obtained. Table 1 shows the properties of the foamed resin particles obtained.
Next, the obtained resin foamed beads are filled in a closed container, pressurized with air, and an internal particle pressure of 0.12 MPa is applied to the resin foamed beads. Heat molded. The resulting molded product was cured at 40° C. under atmospheric pressure for 24 hours to obtain a resin foam molded product A-10. Table 1 shows the evaluation results of the foamed resin particles and the foamed resin article.

[Example 1B]
A foamed resin article A-11 was produced and evaluated in the same manner as in Example 1, except that the thickness of the foamed resin article was changed to 20 mm. The evaluation results are shown in Table 1.

[Comparative Examples 1 to 3]
Resin foam particles and resin foam moldings B-1 and B-2 were obtained under the same conditions as in Examples 1, 2, and 6, except that the profile extrusion die of the extruder was changed to a normal hollow circular cross-section die. , B-3. It was confirmed from the measurement value of airflow resistance that there was no continuous void. Table 2 shows the evaluation results of the foamed resin particles and the foamed resin article.

By fusing and molding the foamed resin particles having a special shape according to the present invention, it is possible to produce a foamed resin article having both sound absorption performance with continuous voids and excellent mechanical strength.
The present invention enables the production of foams with a controlled structure of continuous voids exhibiting high sound absorption, which has been difficult in the past. It is possible to manufacture
Examples of applications of the continuous-gap foam molded article produced from the expanded resin particles of the present invention having a specific structure include the reduction of drive noise in vehicles such as automobiles, trains, and trains, and aircraft, which require lightness and noise reduction. In particular, it can be suitably used for sound absorbing members such as automobile engine covers, engine capsules, engine room hoods, transmission casings, sound absorbing covers, motor casings for electric vehicles, and sound absorbing covers.
Furthermore, the continuous-gap foamed molded product manufactured from the resin foamed particles of the specific structure of the present invention can be used in air conditioning equipment such as air conditioners, refrigerators, heat pumps, etc., parts that form air passages such as ducts, washing machines, etc., where noise reduction is required. , dryers, refrigerators, vacuum cleaners and other household electrical appliances; printers, copiers, OA equipment such as FAX; .

Claims (4)

A resin foamed particle having a concave outer shape containing a resin,
The ratio _{ρ 0 /} ρ ₁ of the density ρ 0 of the resin to the true density ρ ₁ of the expanded resin beads is 2 to 20, and the true density ρ ₁ of the expanded resin beads and the bulk density ρ ₂ of the expanded resin beads The ratio ρ ₁ / ρ ₂ is 1.5 to 4.0,
The resin is a modified polyether resin,
The resin has a surface tension of 37 to 60 mN/m at 20° C.,
The resin has a glass transition temperature of 10° C. or higher and 280° C. or lower,
The average particle diameter of the expanded resin particles is 1.2 to 6.0 mm
, resin foam particles. A resin foamed particle having a concave outer shape containing a resin,
Density ρ of the resin ₀ and the true density ρ of the foamed resin particles ₁ ratio ρ ₀ /ρ ₁ is 2 to 20, and the true density ρ of the resin foam particles ₁ and the bulk density ρ of the foamed resin particles ₂ ratio ρ ₁ /ρ ₂ is 1.5 to 4.0,
The resin is a polyamide resin or a modified polyether resin,
The resin has a surface tension of 37 to 60 mN/m at 20° C.,
The resin has a glass transition temperature of 10° C. or higher and 280° C. or lower,
The average particle diameter of the expanded resin particles is 1.2 to 6.0 mm
, resin foam particles. A molded article in which the expanded resin particles according to claim 1 or 2 are fused to each other,
A foamed resin article having continuous voids between the fused resin foamed particles and having a porosity of 15 to 80%. A soundproof member comprising the resin foam molded article according to claim 3 .

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