JP2006110982A - Foam molded sound absorber and method for producing the same - Google Patents

Abstract

[PROBLEMS] To achieve both a preferable pore structure and structural strength for a sound absorber without using an adhesive resin.
A foam molded body 1 constituting the foam molded sound absorbing body of the present invention has a myriad of foam cells 11 and 11 obtained by heating and foaming foamable resin particles filled in a mold having a predetermined shape. ,..., Wherein the adjacent foam cells 11, 11,... Are softened and melted together at the contact surfaces 11a, 11a. The foamed molded body 1 includes a continuous air hole formed by connecting a space 12 surrounded by at least three foamed cells 11 (in FIG. 1, a space 12 surrounded by five foamed cells 11 is illustrated). The three-dimensional fine pores have a volume porosity of 10 to 40%, which is the total volume ratio of the fine pores to the entire volume, and have a tear strength of at least 0.16 MPa.
[Selection] Figure 1

Description

  The present invention relates to a foam molded sound absorber obtained by heating and foaming expandable resin particles filled in a mold, and an improvement of a method for producing the same.

  Conventionally, expanded polystyrene resin and expanded polyolefin resin are expected as porous sound-absorbing materials, and their development has been demanded. However, this type of foamed resin molded product has become a substantially non-breathable material as a result of the emphasis on heat insulation and cold preservation, as represented by the fresh food storage and transport BOX such as “fish box”. It was finished and did not have a pore structure suitable for sound-absorbing materials.

  Therefore, research has been conducted to give an appropriate pore structure of the foamed resin molded body. However, in order to achieve a favorable pore porosity, it is necessary to lower the heating temperature condition, and as a result, the bond strength of the foamed cell As a result, the structural strength practical for the molded body could not be obtained, and the practical application was not successful. In order to improve such a point, a “sound absorber” as disclosed in Patent Document 1 has been proposed.

Japanese Patent No. 3268094 (Japanese Patent Laid-Open No. 7-168577): claims, paragraphs [0017] [0018] and the like.

  In the sound absorber of Patent Document 1, an adhesive resin that can be thermally bonded at a temperature lower than the softening foaming temperature of the particles is attached to the surface of the foamable resin particles that are raw materials, and the amount of foaming is adjusted during molding. The foamed cells are bonded and bonded together with this adhesive resin while leaving the pore structure, and this is intended to achieve both the preferred pore structure and structural strength for sound absorbers that could not be realized in the past. It is.

However, since this sound absorber uses an adhesive resin, it has the following problems to be solved and has become a practical problem.
1) Since an adhesive resin is added, material costs and processing costs are increased.
2) Due to the adhesive resin, the fluidity of the expandable resin particles decreases, the filling device is clogged, and the operability is inferior, for example, the degree of filling in the mold tends to be uneven.
3) Due to the low temperature softening properties of the adhesive resin, the heat resistance and long-term durability of the sound absorbing material are greatly reduced.

  The present invention has been made in order to solve the above-described problems, and is intended to achieve both a preferable pore structure and structural strength for a sound absorber without using an adhesive resin. The present invention provides a foam molded sound absorber that can prevent cost increase, operability, heat resistance, and long-term durability, and a method for producing the same.

  In the foam molding using foamable resin particles, the present invention controls the expansion amount of the foamable resin particles under the fusion temperature condition so that the particles soften and fuse with each other while providing a gap between the particles. This is based on the knowledge found by the present inventors that it binds to.

(Invention of foam molded sound absorber)
The above-mentioned problem is a foamed molded article composed of an infinite number of foamed cells obtained by heating and foaming foamable resin particles filled in a mold, which is an invention of a product, and adjacent foamed cells are in contact with each other A three-dimensional fine pore having a volume porosity of 10 to 40%, which is composed of continuous air holes formed by being connected with a space surrounded by at least three foamed cells while being softened and melted on the surface. It can be solved by the foam molded sound absorbing body of the present invention, characterized in that it comprises a foam molded body having a tear strength of at least 0.16 MPa.

Such a foamed molded product can be realized by controlling the expansion amount of the expandable resin particles under the fusion temperature condition. Details thereof will be described later as a method of manufacturing a foam molded sound absorber.
Further, the present invention can be embodied in a form in which a surface layer portion having a smaller volume porosity is added to a part or all of the outer surface of the foam molded body. In this case, the surface layer portion is foamed of the foam molded body. It is preferable that they are integrally molded at the time of molding.

  Furthermore, the present invention can be preferably embodied in a form in which an enhanced foam having higher strength is added to a part of the above-described foamed molded article. In this case, it is preferable that the reinforcing foam is integrally formed at the time of foam molding of the foam molded body.

  Further, the present invention has such a configuration, and the thickness of the surface layer portion is 10 to 45% of the total thickness of the foam molded sound absorber, and the foam molded sound absorber used as an automobile interior member Embodied. Further, the present invention may be embodied as a foam molded sound absorber used as a vehicle floor flat material in which the surface layer portion is installed facing the vehicle compartment and the unevenness of the vehicle body floor surface is flattened by the foam molded sound absorber. In this case, the thickness of the surface layer portion is preferably 5 to 40 mm.

  Further, in the present invention, similarly, the thickness of the surface layer portion is 10 to 45% of the total thickness of the foam molded sound absorbing body, and the sound absorbing member for building, the road / railway noise preventing member, the sound absorbing member for housing, It is embodied as a foam molded sound absorber used as a sound absorbing member for industrial equipment. In this case, the thickness of the surface layer part is preferably 5 to 40 mm.

(Invention of production method of foam molded sound absorber)
Furthermore, the above problem is a method for producing a foam molded sound absorber composed of a foam molded article obtained by heating and foaming foamable resin particles filled in a mold, wherein the foamable resin particles are present in the presence of heated steam. Under the above, after heating to the fusing temperature of the expandable resin particles, the foamed cell is fused and cooled while controlling the amount of foaming, to obtain a foamed molded article as defined in the invention of the above-mentioned product The foam molded sound absorber of the present invention can be solved by the production method.

  In the present invention, the foaming amount can be controlled by controlling the pressure on the foamable resin particles. In this case, it is preferable to perform pressure control up to the fusion completion temperature of the expandable resin particles.

  Further, in the present invention, after heating to the above-mentioned fusion temperature, when cooling while controlling the pressure, the heating steam in the mold is replaced with air in advance, or the heating steam in the mold is replaced with air. Is preferred.

  According to the foam-molded sound absorber of the present invention, a pore structure having a volume porosity of 10 to 40% that is preferable for a sound absorber without using an adhesive resin, withstands handling and conveyance, and is practical as a structure. As a structural strength, it is composed of a foamed molded article having a tear strength of 0.16 MPa, so the cost increase caused by the adhesive resin can be suppressed, and the original properties of the expandable resin particles can be utilized. There is an advantage that problems of operability, heat resistance and long-term durability can be solved.

  In addition, a surface layer portion having a lower volume porosity is added to the outer surface of the foamed molded body, the surface layer portion functions as a protective layer, and the sound absorber functions as a sound insulating layer or a reflective layer. The advantage of enhancing the sound absorption effect is obtained. Furthermore, the addition of an enhanced foam having a higher structural strength to a part of the foamed molded product is not limited to a simple sound absorbing material, and can be applied to applications that also serve as a structural member that bears strength. Is obtained.

  Further, according to the method for producing a foam-molded sound absorber of the present invention, the above-described foam-molded sound-absorber can be used without using an adhesive resin by performing a new operation in the foaming / fusion process of the foamable resin particles. Can be manufactured. Moreover, when controlling the foaming amount by the pressure on the foamable resin particles, it is possible to achieve a preferable volume porosity by adjusting the foaming amount by balancing the internal pressure and the external pressure at the time of foaming of the foamable resin particles. There is an advantage that conventional foamed resin raw materials can be used as they are, and when cooling while controlling the pressure reduction speed, if the heated steam in the mold is replaced with air, it will cause fluctuations in temperature conditions due to the latent heat of the heated steam Therefore, there is an advantage that the foaming / fusion process conditions are stabilized.

  Thus, the foam-molded sound absorber of the present invention and the method for producing the same solve the problem that has heretofore been difficult to obtain a preferable pore structure and structural strength for the sound absorber without using an adhesive resin. Thus, there are excellent effects that the increase in cost, operability, heat resistance and long-term durability caused by the adhesive resin can be prevented. Therefore, the present invention has an extremely great industrial value as a foam molded sound absorber and a method for producing the same which have solved the conventional problems.

Next, an embodiment according to the foam molded sound absorbing body and the manufacturing method thereof of the present invention will be described with reference to FIGS.
(Foam molded sound absorber)
The foam molded sound absorbing body of the present invention is characterized in that it is first composed of the foam molded body 1 described below illustrated in FIG. The foam molded body 1 is a foam molded body composed of a myriad of foam cells 11, 11,... Obtained by heating and foaming expandable resin particles filled in a mold configured in a predetermined shape. , Adjacent foam cells 11, 11,... Are bonded to each other at the contact surfaces 11a, 11a by softening and melting. That is, the fusion bonded portion literally has the same resin properties as the foamed resin material because the foamed resin material is fused.

  Next, the foam molded body 1 is formed by connecting a space 12 surrounded by at least three foam cells 11 (in FIG. 1, a space 12 surrounded by five foam cells 11 is illustrated). It has three-dimensional fine pores composed of continuous ventilation holes and has at least the following physical properties.

That is, the three-dimensional fine pores have a volume porosity of 10 to 40%, which is the total volume ratio of the fine pores to the entire volume, and have a tear strength of at least 0.16 MPa.
The three-dimensional pores have a complicated spatial path in which a large number of branches, zigzags, and windings, and the inner diameter of the three-dimensional fine pores irregularly repeats expansion and contraction. It exhibits the basic sound absorbing function of attenuating effects such as interference and resonance.

  When this volume porosity is less than 10%, it is convenient to obtain high strength, but it is not preferable as a sound absorber because the sound absorbing effect is insufficient. On the other hand, if it exceeds 40%, the sound absorption effect tends to decrease, and the mechanical strength is difficult to obtain, which is not preferable. In addition, as the strength of the sound absorber of the present invention, it is necessary to have a shape retention strength that can withstand handling at a minimum, and it is preferable to have a mechanical strength as a structure. From this point, it is appropriate to evaluate the tear strength as a measure representative of mechanical strength, and it is preferably at least 0.16 MPa, preferably 0.22 MPa or more.

The shape of the foam cell constituting the foam molded article of the present invention also has the following characteristics. That is, the cut cross section of the foam cell is a granule having a substantially circular or oval cross section, and the size thereof is preferably 1.5 to 5.5 mm on the basis of the major axis. If it is outside this range, it is difficult to obtain a fine pore volume necessary for the sound absorbing action.
In addition, it is preferable that each foam cell has a substantially oval cross-sectional particle having a major axis / minor axis range of up to 3.0, because a fine pore volume necessary for sound absorption is easily obtained.

  Further, in the present invention, as shown in FIG. 2, it is preferable to integrally provide a surface layer portion 2 having a small volume porosity on one side of the foam molded body 1. In addition to functioning as a protective layer for the foam molded body 1, the surface layer portion 2 functions as a sound insulating layer or a reflective layer as a sound absorbing body to enhance the sound absorbing effect, and therefore has a lower volume porosity than the foam molded body 1. Depending on the purpose, it may be a non-breathable strong resin layer.

  In addition, this surface layer part 2 can be arrange | positioned according to the objective like one part of one side like FIG. Further, the surface layer portion 2 may be affixed separately to the foam molded body 1, but is preferably integrally molded at the time of foam molding of the foam molded body from the viewpoint of manufacturing cost. In addition, in order to manufacture the foam-molded sound absorber having such a structure, it is possible to adjust the heating conditions of the portion corresponding to the surface layer portion 2.

Furthermore, as shown in FIG. 3, the present invention, when embodied as a part of the foam molded body 1 provided with the enhanced foam 3 having a higher tear strength, is not only a sound absorbing material, The range of application is also widened for applications that also serve as a structural member that bears strength, which is preferable.
In the example of FIG. 3, the reinforcing foam 3 is arranged at the corner portion of the foam molded body 1 having a bending angle, and the surface layer portion 2 is also provided. As in the case of the surface layer portion 2, a material having a reduced volume porosity and improved strength can be applied. Also in this case, it is preferable from the viewpoint of manufacturing cost that the reinforcing foam 3 is integrally formed by adjusting the heating conditions at the time of foam molding of the foam molded body 1.

  Next, the present invention will be supplemented from the application aspect. The present invention is suitable not only as a sound-absorbing material but also as a structural member that bears strength, and is therefore suitable for automobile interior members that require moderate sound-absorbing properties and strength. As shown in FIG. 5, it can be used for the dashboard 51, the vehicle interior wall 52, the floor 53, etc. In this case, the thickness of the surface layer portion 2 is 10 to 45% of the total thickness of the foam molded sound absorber, It is appropriate that the thickness of one part of the foamed molded product is the remainder (90 to 55%). In particular, when used for the floor 53, as schematically shown in FIG. 6, the surface layer portion 2 is installed toward the vehicle compartment side, and the foam molded body 1 is interposed between the vehicle body floor and the It is preferably used as a vehicle floor flat material for flattening the unevenness of the surface of the vehicle body floor 53a by the foam molded sound absorber. In this case, the thickness of the surface layer portion is preferably 5 to 40 mm.

  Furthermore, it goes without saying that the present invention can be widely used as a sound absorbing interior member such as a building wall or a ceiling, a road / railway noise preventing member, a residential sound absorbing member, or an industrial equipment sound absorbing member. In this case, the surface layer portion 2 constitutes a decorative face having strength, but the thickness is preferably 10 to 45% of the total thickness of the foam molded sound absorbing body, more specifically. The surface layer 2 preferably has a thickness of 5 to 40 mm.

(Method for producing foam molded sound absorber)
The method for producing a foam molded sound absorber of the present invention will be described with reference to FIGS. 4A and 4B. FIG. 4 shows a cavity filled with expandable resin particles, which is an important operating condition in the foam molding method. FIG. 4 is a graph schematically showing the behavior slightly exaggerated, with the pressure (pressure curves 4 and 5) and the temperature (temperature curves 4a and 5a) in the vertical axis and the passage of time as the horizontal axis. (A) is the case of the conventional air-impermeable foam molding method, and FIG. 4 (B) is the case of the method of the present invention.

The method of the present invention is not different from the conventional basic method in that the foamed resin particles filled in a predetermined mold are heated and foamed to produce a foamed molded article.
First, the production process of a non-breathable foamed molded article having no pore structure as in the present invention, which has been conventionally produced, will be described with reference to FIG. 4 (A) based on the knowledge of the present inventors. Then, it is roughly divided into the following A1) temperature raising step, A2) fusion temperature heating step, A3) foam fusion step, and A4) cooling / removal step.

(Contrast conventional method)
A1) Temperature raising step: In the step of heating and raising the temperature inside the cavity, following filling of the foamed resin particles, the inside is made of water vapor by exhausting in the chamber, one-way exhausting by the heating steam in the cavity, or reverse exhausting in the same way. Heat up and fill with steam. The pressure curve 4 and the temperature curve 4a actually increase in a zigzag manner, but the temperature curve 4a is delayed and follows the pressure curve 4.

  A2) Fusion temperature heating step: In order to foam (expand) and fuse the foamed resin particles into a predetermined shape along the cavity shape, the whole is heated with heated steam to fuse evenly. Heating to temperature. In this step, the foamed resin particles are pressed and compressed with a vapor pressure corresponding to the fusing temperature, and are kept in a freely flowable state in the cavity.

  A3) Foam fusion process: A process of stopping the supply of steam and opening the exhaust valve to release the pressure at point a heated to the fusion temperature uniformly. In this case, since the compressed foamed resin particles are exposed to a rapid decompression at the fusion temperature, the foam is expanded (expanded) suddenly by the internal pressure to crush the gaps between them and further press each other to form a boundary surface. It will be fused. Here, although the pressure rapidly decreases as shown by the pressure curve 4, the temperature in the cavity does not follow the expanded foamed resin particle (foamed cell) because it is adiabatic, as in the temperature curve 4a. Fusion completion temperature: Decreases with delay until point b. Here, the fusion completion temperature is a temperature at which the fusion phenomenon does not proceed.

A4) Cooling / removing step: A step of cooling the inside of the mold with cold water or the like and taking out a molded product foam-molded into a predetermined shape. The temperature drops rapidly.
Thus, the adjacent foam cells are fused together to obtain a substantially air-impermeable foam molding.

(Method of the present invention)
Next, a method for producing the foam molded sound absorbing body of the present invention will be described with reference to FIG.
The foamed molded product, which is the main point of the present invention, can be roughly divided into B1) a temperature raising step, B2) a fusion temperature heating step, B3) a foam fusion step, and B4) a cooling / removal step. Here, B1) temperature raising step and B2) fusing temperature heating step are steps in which the expandable resin particles are uniformly heated to the fusing temperature of the expandable resin particles in the presence of heated steam. It is the same as A1 process and A2 process which were explained in 1.

  B3) Foam fusion process: This is a process characterized by the present invention, and is a process of fusing foam cells while controlling the amount of foaming (expansion) of the expandable resin particles following the process B2. Specifically, the pressure curve 5 changes from the point a to the point c shown in FIG. 4B by adjusting the supply and exhaust of steam instead of reducing the pressure rapidly as in the previous step A3. In addition, it is important to finally reduce the pressure while controlling the pressure along a certain pressure path.

  In the case of FIG. 4 (B), the pressure in the cavity is controlled to the end point of control: point c from the point a where the inside of the cavity has a uniform set fusion temperature to the point b where the temperature is the fusion completion temperature. The pressure is reduced while controlling. The purpose of this pressure control is to expand (expand) foamable resin particles in the fusion temperature range while balancing the internal pressure (particle internal pressure) and external pressure (cavity internal pressure) of the particles. The amount of foaming (expansion) is adjusted to leave the space (volume porosity) between the foamable resin particles, and to press and press the contact surface to be fused. Thus, from the foam cell which is a substantial constituent material of the foam-molded sound absorber of the present invention and has the above-mentioned three-dimensional fine pores having a predetermined volume porosity and fusion-bonded to a strength represented by a predetermined tear strength. Thus, a foamed molded product is obtained.

  In general, if the decompression speed is increased, the expansion is promoted and the volume porosity is decreased, and if the decompression speed is decreased, the expansion is suppressed and the volume porosity is increased. Since the foaming characteristics of the resin vary depending on the type of resin and the prefoaming treatment, the degree of decompression speed, the decompression curve, and the value of the control end pressure c are determined by conducting a preliminary test based on the foamable resin particles used in advance. To do.

Further, it is appropriate to perform this pressure control until reaching the point b of the fusion completion temperature of the expandable resin particles to be used. Since the fusion completion temperature is a temperature at which the fusion of the foamed cells does not proceed, the desired effect cannot be expected even if the pressure is controlled below this temperature.
The fusing temperature and the fusing temperature in the present invention are values determined mainly by the resin type of the expandable resin particles to be used. For example, in the case of polyolefin resin, the lower fusing temperature is 130 to 135. The upper limit is preferably up to 160 ° C. The fusion completion temperature is 125 to 129 ° C. Accordingly, the set fusion temperature at point a is set between the upper limit and the lower limit fusion temperature.

After the foam molding method fusion process described above, B4) a cooling / removal process is performed, which is the same as the previous A4 process.
Thus, the adjacent foam cells themselves constituting the foam molded sound absorber of the present invention are softened and melted and bonded, and three-dimensional fine pores having a volume porosity of 10 to 40% and at least 0.16 MPa. A foamed molded article having a tear strength of 5% is obtained.

  In controlling the pressure in the foaming and fusion process, it is preferable to replace the heated steam filled in the mold with air in advance, or replace the heated steam with air while controlling the pressure. The reason for this is that during the pressure control, most of the water vapor usually changes to condensed water. In this case, the temperature and pressure during the process are accompanied by a large volume change and sensible heat of liquefaction. This is because an unexpected influence may be exerted, and the stability of pressure control may be impaired. In addition, when air is used, there is an advantage that temperature raising and lowering control can be easily performed as compared with water vapor.

Next, examples of the production method of the present invention and the characteristics of the foamed molded article thus obtained will be described.
The specifications of the manufacturing conditions were as follows.
a) Used foamed resin:
Type: Polyolefin resin, particle size: 2.5-3.5 mm, pre-foaming treatment: finished.
b) Mold:
A normal heating type open / close mold using heated steam with vent holes on both sides of the cavity.

c) Temperature raising step up to the fusion temperature heating step:
The filling of the foamed resin particles, the exhaust in the chamber, the one-way exhaust by the heating steam in the cavity, and the reverse exhaust in the same manner are performed under the conditions conventionally known.
d) Fusion temperature heating process:
Heated water vapor of 0.3 to 0.35 MPa is introduced into the chambers on both sides for 20 seconds, and the foamed resin particles in the cavity are heated to the set fusion temperature (143 to 149 ° C.).

e) Foaming / fusion process:
The supply of water vapor is stopped at point a after the heating is completed, the air is supplied, the exhaust valve is opened, and the pressure reduction rate is adjusted while replacing the water vapor and the air. The pressure reduction control is performed along the pressure curve 51 from the point a to the point b as shown in FIG. 4B until the point corresponding to the point b (129 ° C.) of the fusion completion temperature confirmed in advance. The pressure reduction control is terminated at the pressure point c (0.18 MPa). In addition, it shall be previously determined by a preliminary test so as to be applied to specifications such as the pressure curve 51, the foamed resin particles used, the heating conditions, the planned volume porosity, and the planned strength.

  f) Cooling / removal step: The supply of air to the chamber is stopped, the exhaust valve is opened, the gas is exhausted inside, and at the same time, cold water is poured into the chamber for cooling. Thereafter, the mold is opened and the molded body is taken out.

  The foamed molded body thus obtained was a structure having a volume porosity of 20% and a tear strength of 0.22 MPa, and it was confirmed that the foamed molded body has a strength that can be used as a structural member as well as handling. In addition, as a result of observation of the cut cross section, it is recognized that the foam cell is a granule having a substantially circular or oval cross section, and each of the adjacent foam cells is softened and melted and bonded to each other at the contact surface. It was. The tear strength in the present invention is measured by the method defined in JIS-K6767.

Moreover, it is observed that the space surrounded by such foam cells constitutes pores communicating like a mesh in the molded body, and a three-dimensional pore structure is formed as a whole, and its sound absorption characteristics are ,
In the measurement of a sample thickness of 15 mm and a frequency range of 100 to 3000 Hz (JIS (A) 1405), it was confirmed that the sound absorption coefficient was excellent in bass sound absorption with a peak of 30% or more.

  Thus, the sound absorber made of the foamed molded product of the present invention has a sound absorbing effect by such a three-dimensional pore structure and a sound absorbing material for noise prevention utilizing the original material strength, heat resistance, and durability possessed by the foamed resin, For example, it has been confirmed that it is widely useful for automobile interior members, vehicle floor flat materials, sound absorbing materials for buildings such as residential walls, industrial equipment, road noise prevention, and exhaust silencers for factories and subways. .

The typical sectional view of the foaming fabrication object of the present invention. The typical sectional view showing another form of the foaming fabrication object of the present invention. Typical sectional drawing which shows the other another form of the foaming molding of this invention. The typical progress graph (B) which shows the relationship between the pressure, temperature, and time for demonstrating the manufacturing method of this invention, and the conventional reference graph (A). The cross-sectional illustration which shows a motor vehicle interior. The cross-sectional schematic of the interior member for motor vehicles of this invention.

Explanation of symbols

1: foamed molded body, 11: foamed cell, 11a: contact surface, 12: space

Claims (15)

  A foam-molded article composed of an infinite number of foam cells obtained by heating and foaming foamable resin particles filled in a mold, and adjacent foam cells are softened and melted and bonded to each other at the contact surface. A foam having three-dimensional narrow pores having a volume porosity of 10 to 40% and having a tear strength of at least 0.16 MPa, comprising continuous vents formed by connecting spaces surrounded by at least three foam cells. A foam molded sound absorber comprising a molded body.   A foam molded sound absorber, wherein a surface layer portion having a smaller volume porosity is added to a part or all of the outer surface of the foam molded body according to claim 1.   The foam molded sound absorbing body according to claim 2, wherein the surface layer portion is integrally formed at the time of foam molding of the foam molded body.   A foam-molded sound absorber, wherein an enhanced foam having a higher strength is added to a part of the foam-molded body according to claim 1, 2 or 3.   The foam-molded sound absorber according to claim 4, wherein the reinforcing foam is integrally formed when the foam-molded body is foam-molded.   A method for producing a foam-molded sound absorber comprising a foam-molded product obtained by heating and foaming foamable resin particles filled in a mold, wherein the foamable resin particles are heated in the presence of heated steam. The foam molded sound absorber according to claim 1, wherein the foam molded body according to claim 1 is obtained by heating to the fusion temperature of the particles and then fusing and cooling the foamed cells while controlling the amount of foaming. .   The method for producing a foam-molded sound absorber according to claim 6, wherein the amount of foaming is controlled by controlling the pressure on the foamable resin particles.   The method for producing a foam molded sound absorber according to claim 7, wherein the pressure control is performed up to a fusion completion temperature of the expandable resin particles.   The method for producing a foam-molded sound absorber according to claim 7 or 8, wherein the heating steam in the mold is replaced with air in advance when cooling while controlling the pressure after heating to the fusion temperature.   The method for producing a foam-molded sound absorber according to claim 7 or 8, wherein the heating steam in the mold is replaced with air when cooling while controlling the pressure after heating to the fusion temperature.   The foam molded sound absorber according to any one of claims 2, 3, 4, and 5, wherein the thickness of the surface layer portion is 10 to 45% of the total thickness of the foam molded sound absorber. Foam molded sound absorber used as a member.   The foam molded sound absorber according to any one of claims 2, 3, 4, and 5, wherein the surface layer portion is disposed toward a vehicle compartment side, and the unevenness of the vehicle body floor surface is flattened by the foam molded sound absorber. Foam molded sound absorber used as a vehicle floor flat material.   The foam-molded sound absorber according to claim 12, wherein the thickness of the surface layer portion is 5 to 40 mm.   The foam-molded sound absorber according to any one of claims 2, 3, 4, and 5, wherein the thickness of the surface layer portion is 10 to 45% of the total thickness of the foam-molded sound absorber. A foam molded sound absorber used as a member, a road / railway noise prevention member, a residential sound absorbing member, or a sound absorbing member for industrial equipment.   The foam-molded sound absorber according to claim 14, wherein the surface layer portion has a thickness of 5 to 40 mm.

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