JP2018158556A - Method for producing porous foamed resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a porous foamed resin excellent in productivity.SOLUTION: A foamed resin is produced by a bead method in which foamable resin particles are filled in a mold having a plurality of protrusions protruding to an inside thereof and heated and foamed, and by removing the protrusion from the foamed resin, a porous foamed resin forming a non-penetrating hole is produced. At least a part of the protrusion is made of a resin elastic body.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a porous foamed resin.

A vehicle such as an automobile is a machine that has a power source such as an engine and can be moved by a human operation, and generates various vibrations and noises. The sound transmitted to the vehicle is not only the sound generated by the power source, but also road noise, tire pattern noise (also simply referred to as pattern noise), wind noise, etc. Sounds generated in are also included. If these sounds are transmitted into the vehicle, it may cause discomfort to people, so sound-absorbing measures are taken using sound-absorbing materials in the engine, engine room, interior, body, and exhaust pipe area. It has been broken.

In Patent Document 1, a flexible porous foam formed by foam molding has an introduction passage that opens on one surface, and a hollow portion that is formed at the back of the introduction passage and has a larger cross-sectional area than the introduction passage. A sound-absorbing material having a large number of resonance chambers is disclosed. Further, it is disclosed that a sound absorbing material is obtained by foam molding using a molding die including an introduction passage and a hollow portion and taking out the molding die from a flexible foam molding.

JP 08-260589 A

In Patent Document 1, as a method of manufacturing a sound absorbing material, a molding die having a shape corresponding to the shape of a resonance chamber to be formed and having a protruding middle die having a large cross-sectional area at the tip is used. A method of obtaining a sound absorbing member by performing foam molding and taking out a mold from a flexible foam molded body is disclosed. Patent Document 1 also describes the use of urethane as a flexible foamed molded product. Furthermore, Patent Document 1 describes that the hollow portion forming the middle size that forms each resonance chamber is extracted from the introduction passage using the elasticity of urethane foam. The method for producing the material utilizes the properties of a flexible porous foam. Therefore, in the manufacturing method in which the protrusions are installed in the mold as described in Patent Document 1, it is usually estimated that the same hard material (that is, metal) as the mold is used for the mold that is the protrusion. . Even if the middle mold is a hard material, the mold can be removed by the flexible porous foam.
However, when the method for producing a sound-absorbing material having a resonance chamber described in Patent Document 1 was applied to a foamed resin produced by a bead method, the mold could not be removed. This is presumably because the foamed resin produced by the bead method does not have flexibility after foam molding and is a hard material.

Furthermore, even when a protrusion (columnar protrusion) that does not have a large cross-sectional area at the tip is used, the foam resin shrinks due to cooling after mold molding in the bead method, and the protrusion and foam Friction with the resin was increased, and the foam could not be removed from the mold.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for producing a perforated foamed resin having excellent productivity.

That is, in the method for producing a porous foamed resin of the present invention, a foamed resin is produced by a bead method in which foamable resin particles are filled in a mold formed by arranging a plurality of protrusions protruding inside and heated and foamed, A method for producing a perforated foamed resin in which a non-through hole is formed in the foamed resin by extracting the protrusion from the foamed resin, wherein at least a part of the protrusion is made of a resin elastic body. To do.

In the method for producing a perforated foamed resin of the present invention, the foamed resin is produced by a bead method in which foamed resin particles are filled in a mold and foamed by a method such as steam heating. At this time, if a plurality of protrusions protruding inside are arranged in the mold, the portion of the protrusion is not filled with the foamed resin particles. Therefore, by removing the protrusion from the foamed resin, the shape of the protrusion A non-through hole corresponding to is formed in the foamed resin.
And since at least one part of this protrusion is comprised with the resin elastic body, when extracting a protrusion from foamed resin, a protrusion deform | transforms and extraction becomes easy.

In the method for producing a porous foamed resin of the present invention, the foamed resin preferably has a 50% deformation compressive stress σ ₅₀ measured in accordance with JIS K 7220 (2006) of 100 to 1000 kPa.
50% deformation compressive stress σ ₅₀ means that when a compressive load is applied to the object to be measured, the thickness of the object to be measured reaches 50% of the thickness in the state where no load is applied ( The value obtained by dividing the load at the time of 50% deformation) by the cross-sectional area before compression of the object to be measured in the direction perpendicular to the compression direction of the object to be measured.
When the 50% deformation compressive stress σ ₅₀ of the foamed resin is in the range of 100 to 1000 kPa, the shape of the foamed resin and the shape of the non-through holes are easily maintained. And since it becomes difficult to change the shape of a foamed resin and a non-through-hole, it is excellent in durability with respect to long-term use.
When the 50% deformation compressive stress σ ₅₀ of the foamed resin is less than 100 kPa, the foamed resin is too soft, and the shape of the foamed resin and the shape of the non-through holes are likely to change. On the other hand, if the 50% deformation compressive stress σ ₅₀ of the foamed resin exceeds 1000 kPa, the foamed resin is too hard and it becomes difficult to extract protrusions from the foamed resin.
Since the urethane resin described in Patent Document 1 has a σ ₅₀ of 6.5 kPa, the porous foam and the resonance chamber are easily deformed and do not have durability for long-term use. It is done.

In the method for producing a perforated foamed resin of the present invention, the shape of the protrusion is preferably a straight columnar shape or a tapered column shape.
By setting the shape of the protrusion to a straight columnar shape or a tapered columnar shape, it is possible to obtain a perforated foamed resin having a straight columnar shape or a tapered columnar non-through hole formed on the surface. The perforated foamed resin in which holes having such a shape are formed exhibits excellent soundproofing performance in a frequency band corresponding to the shape.

In the method for producing a perforated foamed resin of the present invention, it is preferable that the protrusion has a substantially mushroom shape including a shaft portion and an umbrella portion, and the shaft portion is fixed to the mold.
When the projection is a substantially mushroom shape consisting of a shaft portion and an umbrella portion, and the shaft portion is fixed to the mold, the foamed resin has a hole (introduction passage) that opens on the surface of the foam resin corresponding to the shape of the shaft portion. In other words, a hole corresponding to the shape of the umbrella portion and connected to the outside by the introduction passage (volume is larger than the introduction passage and also referred to as a hollow portion) is formed.
Such a hole is also called a Helmholtz resonance structure, and by adjusting the shape of the Helmholtz resonance structure (thinness of the introduction passage, the length, and the volume of the hollow portion), soundproof performance in a specific frequency band can be obtained. It is done.

In the method for producing a perforated foamed resin of the present invention, it is desirable that the shaft portion is made of a metal and the umbrella portion is made of the resin elastic body.
When the shaft part of the protrusion is made of metal, the mechanical strength is high, so that the protrusion is not easily damaged by repeated use, the life of the protrusion can be kept long, and a highly durable mold can be obtained. .
Furthermore, when the umbrella portion of the protrusion is made of a resin elastic body, only the umbrella portion can be deformed, and thus the protrusion can be easily extracted from the foamed resin.

In the method for producing a perforated foamed resin of the present invention, it is desirable that the heat resistance temperature of the resin elastic body is higher than the temperature of heat foaming of the expandable resin particles.
If the heat resistance temperature of the resin elastic body is higher than the heat foaming temperature of the expandable resin particles in the bead method, the shape of the protrusions is not easily deformed by the heat generated when the expandable resin particles are expanded, and durability against repeated use Is obtained.
Since the heating temperature of the expandable resin particles in the bead method is 80 to 150 ° C., it is desirable that the heat resistance temperature of the resin elastic body is higher than the above temperature, specifically 100 to 180 ° C. 155 to 180 ° C. is more desirable.

In the method for producing a porous foamed resin of the present invention, the A hardness of the resin elastic body is preferably 50 ° or less.
When the A hardness of the resin elastic body is 50 ° or less, the shape of the non-through hole can be sufficiently retained when the foamed resin is molded by heating and foaming. Deforms and becomes easy to extract.
In addition, A hardness means the hardness using the type A durometer measured based on JIS K 6253-3 (2012).

In the method for producing a porous foamed resin of the present invention, the resin elastic body is preferably a silicone resin or a silicone gel.
When the resin elastic body is a silicone resin or a silicone gel, the heat resistance temperature of the resin elastic body is high, so that the shape of the protrusion is difficult to deform during heating and foaming, and the durability is high in repeated use. Further, the protrusion is easily deformed when the protrusion is extracted from the foamed resin, and the protrusion from the foamed resin is easily extracted. Furthermore, even when a projection that has a shape that forms a Helmholtz resonance structure is used, the projection (umbrella) that forms the hollow portion is deformed so that it can pass through the introduction passage. The protrusion can be extracted from the foamed resin without damaging the Helmholtz resonance structure.

In the method for producing a porous foamed resin of the present invention, the porous foamed resin is preferably used for a sound absorbing member.
The perforated foamed resin produced by the method for producing a perforated foamed resin of the present invention has a large number of non-through holes on its surface, and therefore can be suitably used as a sound absorbing member.

Fig.1 (a) is a perspective view which shows typically an example of the metal mold | die used for the manufacturing method of the porous foamed resin of this invention, FIG.1 (b) is the AA line in Fig.1 (a). It is sectional drawing. Fig.2 (a) is a perspective view which shows typically another example of the metal mold | die used for the manufacturing method of the porous foamed resin of this invention, FIG.2 (b) is B- in FIG.2 (a). It is B line sectional drawing. FIG. 3A to FIG. 3C are perspective views schematically showing an example of protrusions installed on a mold used in the method for producing a porous foamed resin of the present invention. 4 (a) to 4 (c) are explanatory views schematically showing an example of a process of extracting protrusions from the foamed resin in the method for producing a porous foamed resin of the present invention.

(Detailed description of the invention)
Hereinafter, the porous foamed resin of the present invention will be described in detail.

The method for producing a perforated foamed resin of the present invention is to produce a foamed resin by a bead method in which foamable resin particles are filled in a mold having a plurality of protrusions projecting inside and heated and foamed, and the above foaming is performed. A method for producing a perforated foamed resin in which a non-through hole is formed in the foamed resin by extracting the protrusion from a resin, wherein at least a part of the protrusion is made of a resin elastic body.

In the method for producing a perforated foamed resin of the present invention, the foamed resin is produced by a bead method in which foamed resin particles are filled in a mold and foamed by a method such as steam heating. At this time, if a plurality of protrusions protruding inside are arranged in the mold, the portion of the protrusion is not filled with the foamed resin particles. Therefore, by removing the protrusion from the foamed resin, the shape of the protrusion A non-through hole corresponding to is formed in the foamed resin. And since at least one part of this protrusion is comprised with the resin elastic body, when extracting a protrusion from foamed resin, a protrusion deform | transforms and extraction becomes easy.

First, an example of the metal mold | die used for the manufacturing method of the porous foamed resin of this invention is demonstrated using Fig.1 (a) and FIG.1 (b).
Fig.1 (a) is a perspective view which shows typically an example of the metal mold | die used for the manufacturing method of the porous foamed resin of this invention, FIG.1 (b) is the AA line in Fig.1 (a). It is sectional drawing.
As shown to Fig.1 (a), the metal mold | die 1 has the some protrusion 10 in the inside. As shown in FIG. 1B, the protrusion 10 has a substantially mushroom shape including a shaft portion 12 and an umbrella portion 11, and the shaft portion 12 is fixed to the mold 1.

Another example of the mold used in the method for producing a porous foamed resin of the present invention will also be described.
Fig.2 (a) is a perspective view which shows typically another example of the metal mold | die used for the manufacturing method of the porous foamed resin of this invention, FIG.2 (b) is B- in FIG.2 (a). It is B line sectional drawing.
As shown in FIG. 2A, the mold 2 is provided with a plurality of protrusions 10 protruding inside. More specifically, as shown in FIG. 2 (b), a mold unit 2 is formed by mounting a projection unit 5 configured by arranging a plurality of projections 10 on a plate-like member 4 in a die holder 6. Is configured. The protrusion 10 has a substantially mushroom shape including a shaft portion 12 and an umbrella portion 11, and the shaft portion 12 is fixed to the plate-like member 4.
As shown in FIGS. 2 (a) and 2 (b), the protrusion does not need to be directly fixed to the mold, and may be fixed via another member such as a plate-like member.

The mold used in the method for producing a perforated foamed resin of the present invention has a configuration normally provided in a mold used for foam molding of expandable resin particles (for example, a raw material filling port, an alignment guide, a cooling pipe, an exhaust A valve or the like), which is omitted in FIGS. 1A, 1B, 2A, and 2B.

As a material constituting the mold, a material generally used for manufacturing a mold can be used, and examples thereof include steel, stainless steel, and an aluminum alloy.

The shape of the protrusion is not particularly limited, but is desirably a straight columnar shape, a tapered columnar shape, or a substantially mushroom shape.
The straight columnar shape is a columnar shape without a taper, and may be a columnar shape or a prismatic shape. A tapered columnar shape is a tapered columnar shape having a relatively large equivalent circle diameter closer to the mold and a relatively smaller equivalent circle diameter at the tip of the protrusion. .
The equivalent circle diameter is the diameter when the cross-sectional area of the protrusion when the protrusion is cut in a direction perpendicular to the protrusion direction of the protrusion is replaced with a perfect circle of the same area. When the cross-sectional shape of the protrusion is a perfect circle, the diameter is adopted as it is, and is simply referred to as a diameter.

The shape of the protrusion may be a reverse tapered column shape. In contrast to the tapered columnar shape, the reverse tapered columnar shape is a shape in which the equivalent circle diameter closer to the mold is relatively small and the equivalent circle diameter of the portion that becomes the tip of the protrusion is relatively large. The shape of the non-through hole formed by the inverted tapered columnar protrusion is close to the Helmholtz resonance structure and may have good soundproofing performance.

Hereinafter, an example of the shape of the protrusions installed in the mold used in the method for producing a perforated foamed resin of the present invention will be described with reference to FIGS.
FIG. 3A to FIG. 3C are perspective views schematically showing an example of protrusions installed on a mold used in the method for producing a porous foamed resin of the present invention.
FIG. 3A shows a substantially mushroom-shaped protrusion 10. The substantially mushroom-shaped projection 10 includes a shaft portion 12 and an umbrella portion 11, and the equivalent circle diameter (diameter) R ₂ of the shaft portion 12 is smaller than the equivalent circle diameter (diameter) R ₁ of the umbrella portion 11. In addition, as for the substantially mushroom-shaped processus | protrusion 10, as shown in FIG. 1, it is desirable that the axial part side is being fixed to the metal mold | die. By using the substantially mushroom-shaped projection 10 with the shaft portion 12 fixed to the mold, a non-through hole having a Helmholtz resonance structure can be formed in the foamed resin.
FIG. 3B shows a columnar protrusion 20. The projections 20 no tapers, a straight columnar circle equivalent diameter (diameter) R ₃ in circle equivalent diameter (diameter) R ₄ and the upper bottom surface 20b of the bottom surface 20a is the same.
FIG. 3C shows a tapered columnar protrusion 30. The projection 30 is equipped with a taper, circle equivalent diameter (diameter) _{R 6} is larger than the equivalent circle diameter (diameter) _{R 5} in the upper bottom surface 30b at the bottom surface 30a. By using the tapered columnar protrusion, the protrusion can be easily extracted from the foamed resin. In addition, the protrusion 30 shown in FIG.3 (c) becomes a taper columnar protrusion by fixing to a metal mold | die with the bottom face 30a.

The cross-sectional shape of the protrusion in the direction perpendicular to the protrusion direction of the protrusion is not particularly limited, but may be a circle, an ellipse, a triangle, a quadrangle, a hexagon, an octagon, or the like, and is preferably a circle or an ellipse. . Since these circular and elliptical shapes do not have corners, stress concentration does not occur starting from the corners, and the foamed resin is less likely to be damaged when the protrusions are extracted from the foamed resin.
The cross-sectional shape may be different for each protrusion. Further, when the protrusion has a substantially mushroom shape, the cross-sectional shape of the shaft portion and the cross-sectional shape of the umbrella portion may be the same or different.

The method for disposing the protrusion in the mold is not particularly limited, and may be a method in which the protrusion is formed as a part of the mold from the beginning, and a mechanism (for example, a hole or the like) capable of removing the protrusion in the mold. Alternatively, a method of attaching a protrusion prepared separately may be used.
The method for attaching the protrusion in the mold is not particularly limited, and examples thereof include a method in which a hole is provided in the mold and one of the protrusions is inserted and fixed, and a method in which the mold and the protrusion are fixed by welding. It is done. Alternatively, a screw hole may be provided inside the mold, and one of the protrusions may be processed into a screw shape and screwed together. Furthermore, a plate-like member (protrusion unit) in which a plurality of protrusions are fixed in advance may be attached in the mold. In the method using the projection unit, it is not necessary to prepare a new mold when changing the shape or arrangement pattern of the projection, and it is only necessary to replace the projection unit, so that the manufacturing cost can be suppressed.

In the mold used in the method for producing a perforated foamed resin of the present invention, the number of surfaces on which the protrusions are arranged is not particularly limited, and the protrusions may be arranged only on one surface of the mold, and the protrusions are formed on a plurality of surfaces. May be arranged.
For example, if the shape of the perforated foamed resin is a box shape (box shape with only the top surface open) consisting of a bottom surface and four side surfaces substantially perpendicular to the bottom surface, a mold that covers the outside of the box, and the inside of the box It is necessary to have a mold to cover, but by arranging protrusions on the entire surface (five surfaces) of the mold covering the outside of the box, a box-like shape in which non-through holes are formed on the outside of each surface A porous foamed resin can be obtained. Such a perforated foamed resin can be used as, for example, a tool box disposed in a luggage space of an automobile.
The shape of the perforated foamed resin may be other than the above, and can be used as a raising material, a partition member between the luggage room and the underfloor space below the luggage room, or the like. A plurality of the perforated foamed resins may be combined as necessary, or the perforated foamed resin may be attached to the surface of another structure.

The arrangement pattern of the protrusions in the mold may be matched to the shape of the non-through holes of the perforated foam resin to be manufactured. For example, the center of the protrusions is arranged at the apexes of the squares in the plane in which the squares are continuously arranged vertically and horizontally. It may be a square array, or may be a staggered array in which the centers of the protrusions are arranged at the vertices of the triangles on a plane in which regular triangles are arranged vertically and horizontally.
Among these, a staggered arrangement is desirable. When the protrusion arrangement pattern is a staggered arrangement, a perforated foamed resin in which all adjacent non-through holes are equally spaced is obtained, so that sound attenuation efficiency is good and soundproofing performance is excellent.

The resin elastic body constituting at least a part of the protrusion is an elastomer that can be elastically deformed. For example, silicone resin, silicone gel, polyethylene resin, polypropylene resin, AS resin, ABS resin, vinylidene chloride resin, natural rubber, isoprene Examples thereof include rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, nitrile rubber, chloroprene rubber, chlorosulfonated polyethylene rubber, polyvinylidene chloride resin, and epichlorohydrin rubber. Of these, silicone resins and silicone gels are desirable.

In the method for producing a perforated foamed resin of the present invention, it is desirable that the tip end portion of the protrusion is made of a resin elastic body.
When the projection is extracted from the foamed resin, if the tip of the projection is made of a hard material such as metal, the tip may not be deformed, and the foamed resin may be damaged when the projection is pulled out. On the other hand, when the tip portion of the projection is made of a resin elastic body, when the projection is extracted from the foamed resin, the tip portion of the projection is deformed and can be easily removed, and damage to the foamed resin can be prevented.

When the protrusion has a substantially mushroom shape, it is desirable that the shaft portion is made of metal and the umbrella portion is made of a resin elastic body.
If the shaft part of the protrusion is made of metal, the mechanical strength of the protrusion is high, so that the protrusion is not easily damaged by repeated use, the life of the protrusion can be kept long, and a highly durable mold can be obtained. can get.
Furthermore, when the umbrella portion of the protrusion is made of a resin elastic body, only the umbrella portion can be deformed, and thus the protrusion can be easily extracted from the foamed resin.

When the protrusion has a straight column shape, the cross-sectional area of the protrusion in a direction perpendicular to the protrusion direction of the protrusion (also simply referred to as the cross-sectional area of the protrusion) is preferably 0.70 to 20.0 mm ² .
If the cross-sectional area is less than 0.70 mm ² , it is difficult for sound to enter the non-through hole, and sufficient soundproofing performance may not be obtained. On the other hand, when the cross-sectional area exceeds 20.0 mm ² , the soundproofing performance against sound in the frequency region of 800 to 2000 Hz is lowered.

It is desirable that an average area (also referred to as a bonding area) of a portion of the protrusion that is in contact with the mold is 3 to 100 mm ² .
When the bonding area is less than 3 mm ² , the bonding strength between the protrusion and the mold is weak, and the protrusion may be damaged when the protrusion is extracted from the foamed resin. Moreover, when a joining area exceeds 100 mm < ² >, the circle equivalent diameter of the formed introduction channel | path may become large too much, and soundproof performance may fall.

When the protrusion has a substantially mushroom shape, the cross-sectional area of the shaft portion (also simply referred to as the cross-sectional area of the shaft portion) in a direction perpendicular to the protrusion direction of the protrusion is preferably 0.70 to 20.0 mm ² .
If the cross-sectional area is less than 0.70 mm ² , it is difficult for sound to enter the non-through hole, and sufficient soundproofing performance may not be obtained. On the other hand, when the cross-sectional area exceeds 20.0 mm ² , the soundproofing performance against sound in the frequency region of 800 to 2000 Hz is lowered.

When the protrusion has a substantially mushroom shape, it is desirable that the cross-sectional area of the umbrella portion (also simply referred to as the cross-sectional area of the umbrella portion) in the direction perpendicular to the protrusion direction of the protrusion is 2.80 to 200.0 mm ² .
If the cross-sectional area of the umbrella is outside the above range, the soundproof performance in the frequency region of 800 to 2000 Hz may be deteriorated.

When the protrusion has a substantially mushroom shape, the length of the shaft portion is desirably 5 mm or more. When using the obtained porous foamed resin for automobile applications, the length of the shaft portion is more preferably 5 to 20 mm.
When the protrusion has a substantially mushroom shape, the length of the umbrella portion is desirably 5 mm or more. When the obtained porous foamed resin is used for automobile applications, the length of the umbrella part is more preferably 5 to 20 mm.
When the protrusion has a substantially mushroom shape, the center of the shaft portion and the center of the umbrella portion may be shifted, but it is desirable that they match.

When the protrusion has a substantially mushroom shape, the volume of the shaft part is desirably 2.4 to 20% of the volume of the umbrella part.
When the length of the shaft portion and the length of the umbrella portion are the same, and the volume of the shaft portion is 2.4 to 20% of the volume of the umbrella portion, the perforated foam having excellent soundproof performance in the frequency region of 800 to 2000 Hz A resin is obtained.

When the protrusion has a substantially mushroom shape, the ratio of the length of the shaft portion to the length of the umbrella portion is not particularly limited, but is preferably 2: 1 to 1: 4, and more preferably 1: 1.

In the method for producing a perforated foamed resin of the present invention, it is desirable that the heat resistance temperature of the resin elastic body is higher than the temperature of heat foaming of the expandable resin particles.
If the heat resistance temperature of the resin elastic body is higher than the heat foaming temperature of the expandable resin particles in the bead method, the shape of the protrusions is not easily deformed by the heat generated when the expandable resin particles are expanded, and durability against repeated use Is obtained.
Since the heating temperature of the expandable resin particles in the bead method is 80 to 150 ° C., it is desirable that the heat resistance temperature of the resin elastic body is higher than the above temperature, specifically 100 to 180 ° C. 155 to 180 ° C. is more desirable.

In the method for producing a porous foamed resin of the present invention, the A hardness of the resin elastic body is preferably 50 ° or less.
When the A hardness of the resin elastic body is 50 ° or less, the shape of the non-through hole can be sufficiently retained when the foamed resin is molded by heating and foaming. Deforms and becomes easy to extract.

Subsequently, a foamed resin is produced by a bead method in which foamable resin particles are filled in the mold and heated and foamed. At this time, since the protrusion is buried in the foamed resin, a non-through hole is formed in the foamed resin by extracting the protrusion from the foamed resin after heat foaming.
In the step of producing the foamed resin, a known bead method can be employed.
Specifically, the foamable resin particles are first subjected to primary foaming and aging, and then filled into a mold, and foamed (also referred to as secondary foaming) while feeding heated steam. Since the surface of the foamed resin after heating and foaming is wet by the water used for heating, the protrusions are extracted from the mold and released from the mold at this stage.
The temperature of primary foaming and secondary foaming is usually 80 to 150 ° C.

By extracting the protrusions from the foamed resin, non-through holes corresponding to the shape of the protrusions are formed in the foamed resin, and soundproof performance can be exhibited.
In the method for producing a perforated foamed resin of the present invention, since at least a part of the protrusion is made of a resin elastic body, the protrusion is deformed when the protrusion is extracted from the foamed resin, and the extraction becomes easy.
In particular, when the protrusion has a substantially mushroom shape, a Helmholtz resonance structure can be formed, which will be described below with reference to FIGS. 4 (a) to 4 (c).

4 (a) to 4 (c) are explanatory views schematically showing an example of a process of extracting protrusions from the foamed resin in the method for producing a porous foamed resin of the present invention.
As shown to Fig.4 (a), the protrusion 10a which consists of the axial part 12a and the umbrella part 11a is embed | buried in the foamed resin 50 after foam molding, and the umbrella part 11a is comprised with the resin elastic body.
When the projection 10a is to be removed from the foamed resin 50, the umbrella portion 11a is deformed as shown in FIG. 4 (b). This is because the umbrella portion 11a is made of a resin elastic body and easily deforms, and the foamed resin 50 does not deform. The protrusion 10a can be extracted from the foamed resin 50 by passing the umbrella portion 11a while being deformed.
When the protrusion 10 a is extracted from the foamed resin 50, the shape of the umbrella portion 11 a returns to the original shape as shown in FIG. 4C, and the space where the protrusion 10 a is buried becomes the non-through hole 100. Of the non-through hole 100, the shape of the introduction passage 120 opened to the surface corresponds to the shape of the shaft portion 12a, and the shape of the hollow portion 110 connected to the outside through the introduction passage 120 corresponds to the shape of the umbrella portion 11a. To do.

The expandable resin particles filled in the mold will be described.
The expandable resin particles are particles containing a foaming agent inside the resin particles, and known ones can be suitably used.
Examples of the resin component constituting the expandable resin particles include olefin resins such as polyethylene and polypropylene, and styrene resins such as polystyrene.
Examples of the styrene resin include a styrene homopolymer, and a copolymer obtained by copolymerizing styrene and a monomer (or a derivative thereof) copolymerizable with styrene. The styrene copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer.
Examples of the blowing agent include hydrocarbons such as propane, butane and pentane.

If necessary, known additives such as flame retardants, flame retardant aids, processing aids, fillers, antioxidants, light-resistant stabilizers, antistatic agents and colorants are added to the expandable resin particles. May be. As an example of the use of the additive, if a black colorant is used, stains are not noticeable.

Flame retardants include hydrated metal flame retardants such as aluminum hydroxide and magnesium hydroxide, phosphate flame retardants such as red phosphorus and ammonium phosphate, tetrabromobisphenol A (TBBA), brominated polystyrene, chlorinated paraffin And halogen-based flame retardants such as ammonium carbonate and melamine cyanurate.
Examples of the flame retardant aid include antimony trioxide and antimony pentoxide.
Examples of processing aids include stearates, liquid paraffin, olefin waxes, stearylamide compounds, epoxy compounds and the like.
Examples of the filler include silica, talc, and calcium silicate.
Examples of the antioxidant include alkylphenols, alkylene bisphenols, alkylphenol thioethers, β, β-thiopropionic acid esters, organic phosphite esters, and phenol / nickel complexes.
Examples of the light resistance stabilizer include benzotriazole-based ultraviolet absorbers and hindered amine-based stabilizers.
Examples of the antistatic agent include low molecular weight antistatic agents such as fatty acid ester compounds, aliphatic ethanolamine compounds and aliphatic ethanolamide compounds, and high molecular weight antistatic agents.
Examples of the colorant include dyes and pigments.

The average particle diameter of the expandable resin particles is desirably 300 μm to 2400 μm, and more desirably 800 μm to 2000 μm.

When foaming the foamable resin particles, it is desirable to adjust the foamed resin so that the density of the foamed resin is 0.02 to 0.1 g / cm ³ .
When the density of the foamed resin is within the above range, it is easy to obtain the strength required for the porous foamed resin.
On the other hand, if the density of the foamed resin is less than 0.02 g / cm ³ , sufficient mechanical strength as a porous foamed resin may not be obtained. When the density of the foamed resin exceeds 0.1 g / cm ³ , the weight of the porous foamed resin increases.

The obtained foamed resin preferably has a 50% deformation compression stress σ ₅₀ measured in accordance with JIS K 7220 (2006) of 100 to 1000 kPa.
When the 50% deformation compressive stress σ ₅₀ of the foamed resin is in the range of 100 to 1000 kPa, the shape of the foamed resin and the shape of the non-through holes are easily maintained. And since it becomes difficult to change the shape of a foamed resin and a non-through-hole, it is excellent in durability with respect to long-term use.
When the 50% deformation compressive stress σ ₅₀ of the foamed resin is less than 100 kPa, the foamed resin is too soft, and the shape of the foamed resin and the shape of the non-through holes are likely to change. On the other hand, if the 50% deformation compressive stress σ ₅₀ of the foamed resin exceeds 1000 kPa, the foamed resin is too hard and it becomes difficult to extract protrusions from the foamed resin.
Note that a foamed resin in which non-through holes are not formed is used for a measurement sample (measurement object) when measuring 50% deformation compressive stress.

Although the expansion ratio at the time of foaming expandable resin particles is not particularly limited, it is preferably 10 to 60 times.
The expansion ratio can be controlled by adjusting the amount of the foaming agent in the expandable resin particles, the primary foaming conditions, and the temperature during foam molding.
By setting the expansion ratio to a range of 10 to 60 times, it becomes easy to adjust the 50% deformation compressive stress σ ₅₀ to a range of 100 to 1000 kPa. Furthermore, it becomes easy to adjust the density of a foamed resin to the range of 0.02-0.1 g / cm < ³ > by making a foaming ratio into the range of 10-60 times.
On the other hand, when the expansion ratio is less than 10 times, the porous foamed resin may be too hard or too heavy. When the expansion ratio exceeds 60 times, the strength of the porous foamed resin may be insufficient.

According to the above procedure, a porous foamed resin excellent in soundproofing performance and mechanical strength can be produced.

The perforated foamed resin obtained by the method for producing a perforated foamed resin of the present invention is preferably used for a sound absorbing member.
Since the porous foamed resin obtained by the method for producing a porous foamed resin of the present invention has a large number of non-through holes on its surface, it can be suitably used as a sound absorbing member.

(Example)
Specific examples illustrating the present invention more specifically are shown below, but the present invention is not limited to these examples.

Example 1
(Production of protrusion unit)
An aluminum substrate was prepared by drilling 10 holes (diameter 3 mm, depth 5 mm) on the surface of an aluminum plate having a thickness of 10 mm so as to form a staggered arrangement with a pitch of 15 mm.
Subsequently, an acrylic mold for preparing a protrusion to be attached to the aluminum substrate was prepared.
The acrylic mold can be divided into two parts (one is male and the other is female), and the inside has a [diameter of 3 mm as a shaft part, a cylinder with a length of 15 mm, and a diameter of 7 mm as an umbrella part. The shape of a cylinder having a length of 10 mm has a substantially mushroom-shaped cavity in which the central axes of the cylinders are aligned. In order to obtain the cavity having the shape, the surface of each divided mold was cut. Recesses (cavities) corresponding to shapes obtained by dividing the substantially mushroom shape into two along the length direction are formed on the surfaces of the male mold and the female mold, respectively.
0.5 parts of a curing agent [manufactured by Shin-Etsu Chemical Co., Ltd., CAT-RM] is mixed with 100 parts of a silicone resin main component [manufactured by Shin-Etsu Chemical Co., Ltd., KE-17], followed by vacuum defoaming Foaming time: 20 minutes), and then poured into the female mold and the female mold cavity. The female mold and the female mold were combined, fixed with rubber bands, and cured at 70 ° C. for 20 minutes. After curing, the female mold and the female mold are separated, the cured product is taken out, and burrs are removed so that a cylinder with a diameter of 7 mm and a length of 10 mm and a cylinder with a diameter of 3 mm and a length of 15 mm are aligned with the central axis of each cylinder. A connected mushroom-shaped shaped body was obtained. The A hardness of the resin elastic body constituting the molded body was 50 °. The same operation was performed 10 times in total.
Subsequently, a protrusion unit in which ten protrusions were fixed on the aluminum substrate was prepared by inserting an end of the molded body having a diameter of 3 mm to a depth of 5 mm into a hole in the aluminum substrate. The protrusion was composed of a cylindrical shaft portion having a diameter of 3 mm and a length of 10 mm, and a cylindrical umbrella portion having a diameter of 7 mm and a length of 10 mm.

(Foaming of foamed resin)
A projection unit is attached to a die holder to prepare a mold, and pre-foamed primary foam particles (polypropylene, average particle diameter 3.5 mm, foaming agent: carbon dioxide) are filled into the mold and foamed with heated steam. After molding (143 ° C., 10 seconds), removing from the mold, and drying at 80 ° C. for 12 hours, a plate-like perforated foamed resin was produced. At this time, the expansion ratio of the foamed resin was 30 times.

(Measurement of 50% deformation compressive stress σ ₅₀ )
From the obtained porous foamed resin, a portion having a size of 50 × 50 × 10 mm and having no non-through holes was cut out and used as a sample for strength measurement. In accordance with JIS K 7220 (2006), the compression test was performed using an electromechanical universal testing machine (manufactured by Instron, 5567), compression speed: 5 mm / min, deformation rate: 0 to 75% (0.00 to 0.00). 75), and the 50% deformation compressive stress σ ₅₀ of the sample for strength measurement was measured and found to be 259 kPa.

(Formability test for non-through holes)
After foam molding, the foamed resin and the protruding unit were taken out in an integrated state, and the foamed resin and the protruding unit were separated. The surface of the foamed resin separated from the protrusion unit was observed, and it was visually confirmed whether or not non-through holes were formed. The number of protrusions remaining inside or deformed due to breakage or the like was counted as the number of defects, and the number of defects of 1 or more was evaluated as x, and the number of defects was evaluated as ◯. The results are shown in Table 1.

(Example 2)
The same procedure as in Example 1 except that the silicone resin was changed to an A hardness of 30 ° [100 parts of main agent (KE-14) and 5 parts of curing agent (CLC-229, both manufactured by Shin-Etsu Chemical Co., Ltd.)]. A projection unit was prepared and a non-through hole moldability test was performed. The results are shown in Table 1.

(Example 3)
Except for changing the silicone resin to a product with A hardness of 10 ° [mixing main agent and curing agent at 1: 1 (weight ratio), both manufactured by Momentive Performance Materials Japan (go)], the same as in Example 1 Protrusion units were prepared according to the procedure, and a non-through hole moldability test was performed. The results are shown in Table 1.

Example 4
Same as Example 1, except that the silicone resin was changed to A hardness: 5 ° product [mixed main ingredient and curing agent at 1: 1 (weight ratio), both manufactured by Momentive Performance Materials Japan (go)] The protrusion unit was prepared by the procedure described above, and a non-through hole moldability test was performed. The results are shown in Table 1.

(Example 5)
An aluminum cylinder having a diameter of 3 mm and a length of 20 mm subjected to primer treatment from one tip to 7 mm was placed inside the acrylic mold used in Example 1. At this time, among the cavities formed in the mold, the position of one end of the aluminum cylinder is aligned with the end where the cavity corresponding to the cylinder having a diameter of 3 mm is disposed, and the primer The tip on the treated side was placed in a cavity corresponding to a cylinder having a diameter of 7 mm. Subsequent steps were performed in the same manner as in Example 1 to obtain a molded body in which an aluminum cylinder was inserted by a depth of 5 mm into the center of a cylindrical resin elastic body having a diameter of 7 mm and a length of 10 mm. The same process was performed 10 times in total. Subsequently, by inserting an aluminum cylinder of the molded body into a hole of the aluminum substrate, a cylindrical shaft portion having a diameter of 3 mm and a length of 10 mm and a cylindrical umbrella portion having a diameter of 7 mm and a length of 10 mm are formed on the aluminum substrate. A protrusion unit provided with 10 protrusions made of was prepared. Other procedures were the same as in Example 1, and a non-through hole moldability test was performed. The results are shown in Table 1.

(Example 6)
A projecting unit was prepared in the same procedure as in Example 5 except that the length of the aluminum cylinder was changed to 25 mm and the region to be treated with the primer was changed from 11 mm to 11 mm. Went. The results are shown in Table 1.

(Example 7)
A protrusion unit was prepared in the same procedure as in Example 1 except that the shape of the cavity formed in the acrylic mold was changed to a cylinder having a diameter of 3 mm and a length of 25 mm, and a non-through hole moldability test was performed. . The results are shown in Table 1.

(Comparative Example 1)
An aluminum cylinder having a diameter of 3 mm and a length of 25 mm was inserted and fixed in a hole in the aluminum substrate to prepare a protrusion unit having 10 straight columnar protrusions having a diameter of 3 mm and a length of 20 mm. A non-through hole moldability test was performed in the same procedure. The results are shown in Table 1.

(Comparative Example 2)
Comparative Example 1 except that the shape of the aluminum cylinder was changed to a shape in which a cylinder with a diameter of 3 mm and a length of 15 mm and a cylinder with a diameter of 7 mm and a length of 10 mm were connected with the center axes of the cylinders aligned. Protrusion units were prepared in the same procedure, and a non-through hole moldability test was performed. The results are shown in Table 1.

From the results shown in Table 1, it was found that the method for producing a perforated foamed resin of the present invention was excellent in manufacturability without causing a problem that protrusions remained inside the foamed resin.

1, 2 Mold 4 Plate member 5 Protrusion unit 6 Die holder 10, 10a Protrusion (substantially mushroom shape)
11, 11a Umbrella part 12, 12a Shaft part 20 Projection (straight column shape)
20a Bottom surface 20b Upper bottom surface 30 Protrusion (tapered columnar)
30a Bottom surface 30b Upper bottom surface 50 Foamed resin 100 Non-through hole 110 Hollow portion 120 Introduction passage

Claims (9)

A foamed resin is produced by a bead method in which foamable resin particles are filled in a mold having a plurality of protrusions protruding inside and heated and foamed, and the protrusion is removed from the foamed resin. A method for producing a perforated foamed resin that forms non-through holes,
A method for producing a perforated foamed resin, characterized in that at least a part of the protrusion is made of a resin elastic body. 2. The method for producing a porous foamed resin according to claim 1, wherein the foamed resin has a 50% deformation compression stress σ ₅₀ measured in accordance with JIS K 7220 (2006) of 100 to 1000 kPa. The method for producing a perforated foamed resin according to claim 1 or 2, wherein the shape of the protrusion is a straight columnar shape or a tapered columnar shape. The method for producing a perforated foamed resin according to claim 1, wherein the protrusion has a substantially mushroom shape including a shaft portion and an umbrella portion, and the shaft portion is fixed to the mold. The method for producing a perforated foamed resin according to claim 4, wherein the shaft portion is made of metal and the umbrella portion is made of the resin elastic body. The method for producing a perforated foamed resin according to any one of claims 1 to 5, wherein a heat resistant temperature of the resin elastic body is higher than a heat foaming temperature of the expandable resin particles. The method for producing a perforated foamed resin according to claim 1, wherein the resin elastic body has an A hardness of 50 ° or less. The method for producing a perforated foamed resin according to any one of claims 1 to 7, wherein the resin elastic body is a silicone resin or a silicone gel. The method for producing a perforated foamed resin according to any one of claims 1 to 8, wherein the perforated foamed resin is used for a sound absorbing member.

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