JP2015193694A - Foam body and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamed body that has a sound absorption peak performance in a low frequency band and moreover that can suppress the decrease in sound absorption performance in the high frequency band.SOLUTION: Provided is a foamed body H constituted of foamed cells S1 to S3 that are obtained by foaming pulp fiber component, synthetic resin component and starch component as adjuvant and in which a large number of spaces are formed, and in which the foamed cells S1 to S3 constitute a foamed cell layer 1 in which foamed cells S1 are densely disposed, and a surface membrane layer 2 that is disposed on the surface side of the foamed cell layer 1 and in which foamed cells S2 having a higher foam density than the foamed cell layer 1 are densely disposed, and in which the surface membrane layer 2 has, as foamed cell S2, ruptured cells S2b whose cell membrane is ruptured.

Description

  The present invention relates to a foam having a pulp fiber component, a synthetic resin component, and a starch component as an auxiliary agent as a foaming material, and a method for producing the same.

  Conventionally, a foam using paper as a part of a foam material has been proposed (see Patent Documents 1 and 2). Since this foam can use waste paper as a pulp fiber component, it is suitable for paper recycling. As shown in FIGS. 11 (a) and 11 (b), the foam 50 foams a paper powder component that is a pulp fiber component, a synthetic resin component, and corn starch that is a starch component as an auxiliary agent. It is comprised from foam cell S11, S12. Each foam cell S11, S12 has an internal space (air layer) covered with a cell coating. The foam 50 has different foam densities (foaming ratios) of the foam cells S11 and S12 depending on the position, and has a three-layer structure including a foam cell layer 51 and two surface coating layers 52 arranged on both surfaces. It is configured. In the foam cell layer 51, foam cells S11 having a foam density lower than that of the respective surface coating layers 52 are densely arranged. Each surface film layer 52 has an extremely thin thickness, and foam cells S12 having a foam density higher than that of the foam cell layer 53 are densely arranged.

  Next, an extrusion molding machine 60 for producing the foam 50 will be described. As shown in FIG. 12 (a), the extrusion molding machine 60 includes a charging port (not shown) for charging the foam material, kneading means (not shown) for kneading the charged foam material, and kneading foam. A heating means (not shown) for heating the material to a high temperature, a pressing means (not shown) for pressing the foam material, a base member 61 arranged so as to close the front end side of the pressing chamber, and the base member 61 And a regulation frame wall 70 arranged so as to surround the outside. As shown in FIG. 12B, the base member 61 has a plurality of discharge ports 62 arranged at equal intervals in the horizontal direction. The discharge port 62 is one stage. The restriction frame wall 70 restricts the foaming region of the foam material discharged from the plurality of discharge ports 62. The restriction frame wall 70 is a flat rectangular frame.

  Next, the manufacturing method of the foam 50 is demonstrated. A paper powder component, a polypropylene resin material, corn starch as an auxiliary agent, and water are supplied into the extrusion molding machine 60. The paper powder component, polypropylene resin material, corn starch and water are kneaded with heat, and this high-temperature foam material is discharged from the plurality of discharge ports 62 by pressing.

  Then, the water mixed in the high-temperature foam material is vaporized at the moment when the water is discharged from each discharge port 62, and the foam material composed of the paper powder component, the polypropylene resin material, and the corn starch is foamed by the water vapor pressure. Since the foaming is regulated by the regulation frame wall 70, the foam 50 having the regulation frame wall 70 as a cross-sectional area is continuously extruded. Each of the foamed cells S11 and S12 is hermetically sealed without being broken by the flexibility of the paper powder component and the adhesiveness of corn starch.

  The foam 50 having such a structure has sound absorption characteristics as shown in FIG. This sound absorption characteristic is considered to be a combination of the natural vibration and phase velocity and the porous type. In other words, the sound absorption performance by the natural vibration is due to the solid vibration of the foam at the natural frequency due to the incident vibration, and the cancellation of the incident vibration and the solid vibration. The sound absorption performance by the phase velocity is due to the cancellation of the surface reflected wave reflected by the surface coating layer 52 and the transmitted reflected wave that enters the inside of the foam 50 and returns as the reflected wave among the sound incident from the outside. Yes (see the characteristic diagram of natural vibration + phase velocity in FIG. 13). The sound absorbing performance due to the natural vibration and the phase velocity exhibits peak performance in a low frequency band of 1 kHz to 2 kHz. The sound absorption performance by the porous type is due to the energy absorption (thermal energy release) due to the vibration that the sound entering the inside of the foam 50 vibrates in the internal space of the foam cells S11 and S12 and the film of the foam cells S11 and S12. Yes (see the characteristic diagram of the porous effect in FIG. 13). The porous sound absorbing performance is not effective in the low frequency band and exhibits high sound absorbing performance in the high frequency band of 2 kHz or higher. The sound absorption performance of the porous type becomes higher as the frequency becomes higher even in the high frequency band.

  FIG. 13 shows a comparison of sound absorption characteristics between the foam 50 and Shinsalate (registered trademark). Synthalate is an intertwined fabric (nonwoven fabric) of synthetic fibers, and exhibits a sound absorption performance by a porous type. As shown in FIG. 13, since the foam 50 has a sound absorption peak due to natural vibration and phase velocity in a low frequency band (approximately 1 kHz to 2 kHz), it exhibits sound absorption characteristics superior to a synthesizer.

Japanese Patent No. 3326156 JP 2000-273800 A JP-A-8-207170

  However, the above-described conventional foam 50 is inferior in sound absorption performance by the porous mold to that of cinsalate. For this reason, there is a band where the sound absorption performance is extremely lower than that of the synthesizer in a frequency band higher than the frequency band of the sound absorption peak due to natural vibration and phase velocity, specifically, a high frequency band of approximately 2 kHz or more.

  Accordingly, the present invention has been made to solve the above-described problems, and has a sound absorption peak performance in a low frequency band, and a foam capable of suppressing a decrease in sound absorption performance in a high frequency band, and its production It aims to provide a method.

  The present invention is a foam comprising foam cells in which a pulp fiber component, a synthetic resin component and a starch component as an auxiliary agent are foamed to form a large number of spaces. A foam cell layer densely arranged, and a surface film layer arranged on the surface side of the foam cell layer, and foam cells having a foam density higher than the foam cell layer are densely arranged, the surface film layer, It is a foam characterized by having a bubble-breaking cell in which a cell coating is broken as the foamed cell.

  The foam cell layer may have a foam cell in which a cell film is torn as the foam cell. The synthetic resin component may be a polypropylene resin material J830HV (a kind of product name Prime Polypro of Prime Polymer Co., Ltd.).

  Another aspect of the present invention uses an extrusion molding machine provided with discharge ports arranged at intervals, and provided with a regulation frame wall for regulating a foaming region of a foam material discharged from each of the discharge ports, A pulp fiber component, a synthetic resin component, a starch component as an auxiliary agent and water are supplied to an extrusion molding machine, and the pulp fiber component, the synthetic resin component, the starch component and water are heated and kneaded, and the pulp fiber component and the synthetic resin are mixed. An extrusion molding process in which a foaming material having a component and the starch component is discharged from each of the discharge ports by a pressing force in a highly fluid state, and the foam produced by the extrusion molding is pressed after the extrusion molding process. It is a manufacturing method of the foam characterized by including a press process.

  The pressing process includes a process in which uniform pressure is applied to the entire surface of the foam to compress it in a lump. The pressing step includes a step of compressing the foam by locally applying pressure sequentially. The synthetic resin component may be a polypropylene resin material J830HV (a kind of product name Prime Polypro of Prime Polymer Co., Ltd.).

  According to the present invention, when sound is incident on the foam from the outside, the foam vibrates at a specific frequency by incident vibration, absorbs the sound by canceling the incident vibration and the solid vibration, and enters the inside from the surface of the foam. Sound absorption is also achieved by canceling the incoming incident wave and the transmitted reflected wave that is reflected after passing through the interior. That is, the sound absorption due to the natural vibration and the sound absorption due to the phase velocity have a sound absorption peak in the low frequency band, and sound absorption performance can be obtained. On the other hand, the foam has a porous form, and the sound incident on the foam from the outside easily enters the inside of the foam from the bubble-breaking cell of the surface film layer, so that it is absorbed by vibration energy inside. The amount increases, and the sound absorption characteristic in the high frequency band due to the porous type is improved as compared with the conventional foam. As described above, the sound absorption peak performance is obtained in the low frequency band, and the deterioration of the sound absorption performance in the high frequency band can be suppressed.

1 is an external perspective view of a foam according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention, in which (a) is a structural schematic diagram of a foam along the line AA in FIG. 1 shows an embodiment of the present invention, (a) is a perspective view of a main part of an extrusion molding machine, and (b) is a front view of a base member. 1 shows an embodiment of the present invention and is a schematic cross-sectional view of an essential part of an extrusion molding machine. 1 is a side view of a press according to an embodiment of the present invention. It is a sound-absorption characteristic diagram of a foam with a bubble-breaking cell (one embodiment), a foam only in a press, and a cinsalate. It is a side view of another press. It is a perspective view of the foam pressed with the other press. Foam (foam with broken bubbles (small holes)) pressed by full-surface compression, foam pressed with rollers (foam with broken bubbles (small holes) and cracks), and sound absorption characteristics of synthrate FIG. It is a sound-absorption characteristic diagram of the foam pressed by the roller. A prior art example is shown, (a) is an external appearance perspective view of a foam, (b) is a structural schematic diagram of a foam. A prior art example is shown, (a) is a principal part perspective view of an extrusion molding machine, (b) is a front view of a nozzle | cap | die member. It is a sound-absorption characteristic diagram of the foam of a conventional example, and a cinsalate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(One embodiment)
1 to 6 show an embodiment of the present invention. As shown in FIG. 1, the foam H is a flat rectangular plate-like foam. Foam H is composed of foam cells S1, S2, and S3 formed by foaming a paper powder component that is a pulp fiber component, a synthetic resin component, and corn starch that is a starch component as an auxiliary agent to form a large number of spaces. (See FIG. 2 (b)). As the paper powder component, used paper such as government postcards made into paper powder fiber is used.

  The synthetic resin component is a polypropylene resin material J830HV (a kind of product name Prime Polypro of Prime Polymer Co., Ltd.). J830HV is a block copolymer in the form of copolymer, melt flow rate (test condition: 230 ° C.) 30 g / 10 min, density 910 Kg / m 3, tensile yield stress 28.0 MPa, tensile fracture nominal strain 30%, tensile It has physical properties with an elastic modulus of 1450 MPa.

  As shown in FIGS. 2A and 2B, each of the foam cells S1, S2, and S3 has an internal space (air layer) covered with a cell coating. Each foam cell S1, S2, S3 has a different foam density (foaming ratio) depending on its position, and the foam H is formed in the following layer structure depending on the density of the foam cells S1, S2, S3.

  That is, the foam H is configured in a three-layer structure in the thickness direction: a foam cell layer 1 in which the foam cells S1 are densely arranged and a surface coating layer 2 arranged on both surfaces of the foam cell layer 1. Yes.

  In the foam cell layer 1, foam cells S1 having a foam density lower than that of each surface coating layer 2 are densely arranged. The foam cell S1 of the foam cell layer 1 has a sealed cell S1a in which the internal space (air layer) is completely covered with the cell coating, and a bubble-breaking cell S1b in which the cell coating is broken, and these are irregularly formed. It is mixed.

  Each surface coating layer 2 has an extremely thin thickness, and foam cells S2 having a foam density higher than that of the foam cell layer 1 are densely arranged. The foam cell S2 of each surface coating layer 2 has a sealed cell S2a in which the internal space (air layer) is completely covered with the cell coating, and a bubble-breaking cell S2b in which the cell coating is broken, and these are irregular. Are mixed. A number of small holes 6 are formed in each surface film layer 2, that is, on the surface of the foam H, due to the cell film of the bubble-breaking cell S <b> 2 b being broken. The small holes 6 are uniformly formed in the entire area of the surface of each surface coating layer 2 (foam H).

  Each foam cell layer 1 is formed with a plurality of vertical partition coating layers 5 at equal intervals along the direction perpendicular to the thickness direction. Each foam cell layer 1 is divided by a vertical partition coating layer 5. In the vertical partition coating layer 5, foam cells S3 having a foam density higher than that of the foam cell layer 1 are densely arranged. The foaming cell S3 of the vertical partition coating layer 5 also has a sealed cell S3a in which the internal space (air layer) is completely covered with the cell coating, and a bubble-breaking cell S3b in which the cell coating is broken, and these are irregular. Are mixed.

  Next, the extrusion molding machine 10 and the press apparatus 30 for producing the foam H will be described. As shown in FIGS. 3 (a), 3 (b) and 4, the extrusion molding machine 10 includes an inlet (not shown) for charging each foam material, and a kneading means (see FIG. 3) for kneading the charged foam material. (Not shown), a heating means (not shown) for heating the kneaded foam material to a high temperature, a pressing means (not shown) for pressing the foam material, and a front end side of the pressing chamber are arranged to be closed. A base member 11 and a regulation frame wall 20 disposed so as to surround the outside of the base member 11 are provided. The base member 11 has a plurality of discharge ports 12 arranged at equal intervals in the horizontal direction. The discharge port 12 is disposed at an intermediate position of the restriction frame wall 20 at the vertical position. The restriction frame wall 20 restricts the foaming region of the foam material discharged from the one-stage discharge port 12. The regulation frame wall 20 is a flat rectangular frame. The restriction frame wall 2 has an internal space whose vertical height is 10 mm.

  As shown in FIG. 5, the press device 30 includes a fixed press body 31 and a movable press body 32 that are arranged to face each other. The movable press body 32 can move in the proximity / separation direction of the fixed press body 31.

  Next, the manufacturing method of the foam H is demonstrated. The method for manufacturing the foam H includes an extrusion process using the extrusion molding machine 10 and a pressing process using the press device 30. First, the extrusion process will be described. A paper powder component, a polypropylene resin material J830HV (a type of Prime Polymer, a product of Prime Polymer Co., Ltd.), corn starch as an auxiliary agent, and water are supplied into the extrusion molding machine 10. Then, the paper powder component, polypropylene resin material J830HV (a type of Prime Polymer, a product of Prime Polymer Co., Ltd.), corn starch, and water are heated and kneaded at a temperature of 184 ° C. or more immediately before discharge, and this high temperature The foamed material is discharged from the single-stage discharge port 12 of the base member 11 by pressing.

  Then, the water mixed in the high-temperature foam material is vaporized at the moment when the water is discharged from each discharge port 12, and the foam material composed of the paper powder component, the polypropylene resin material and the corn starch is foamed by the vapor pressure of the water. As shown in FIG. 4, since the foaming is regulated by the regulation frame wall 20, the foam Ha (thickness T = 10 mm) having a regulation space of the regulation frame wall 20 as a cross-sectional area is continuously extruded.

  As described above, the foam material discharged from each discharge port 12 is restrained from being foamed by the restriction frame wall 20, and foamed cells are restrained from interfering with each other. Specifically, the foaming cell S <b> 2 located in the vicinity of the inner periphery of the regulation frame wall 20 is suppressed from being foamed by the regulation frame wall 20. Thereby, the surface film layer 2 is formed. In the foam cell S3 located between the upper and lower surface coating layers 2 and in the vicinity of the intermediate position between the discharge ports 12 adjacent in the horizontal direction, the foam cells S3 collide (interfere) with each other to suppress foam formation. Is done. Thereby, the vertical partition film layer 5 is formed. Between the upper and lower surface coating layers 2, the foam cell S <b> 1 located in the vicinity of each discharge port 12 has only a weak suppression force compared to the foam cells S <b> 2 and S <b> 3. Thereby, the foam cell layer 1 is formed.

  Here, J830HV is a highly flowable synthetic resin having a melt flow rate (test condition: 230 ° C.) of 30 g / 10 min. Therefore, the foam material is combined with the flexibility of the paper powder component and the adhesiveness of corn starch. Discharged with high fluidity. As described above, since the foam material is discharged in a state of high fluidity from the respective discharge ports 12, it expands and foams even under a situation where foam formation is suppressed by the regulation frame wall 20, and each of the foam cells S1, S2, S3. In addition to the closed cells S1a, S2a, and S3a having a thin cell coating, bubble-breaking cells S1b, S2b, and S3b having a broken cell coating are also formed.

  In particular, the foam cell S2 of each surface coating layer 2 is subjected to a foam suppression force larger than that of the regulation frame wall 20 and is easily broken by a temperature difference from the outside air temperature. As described above, the foamed body Ha is produced in which each of the foamed cells S1, S2, and S3 has the bubble breaking cells S1b, S2b, and S3b and the small holes 6 are formed on the surface. The foam Ha has a thickness of 10 mm.

  Next, the pressing process will be described. The foam Ha produced from the extrusion molding machine 10 is cut to a predetermined size. As shown in FIG. 5, the cut foam body Ha is stacked on the three sheets and set in the press device 30. The press device 30 compresses the foam Ha to about 1/10, and then releases the compression. In other words, uniform pressure is applied to the entire surface of the foam Ha to compress it all together (entire surface compression). The foam H whose compression has been released becomes thin by about 2 mm. Foam Ha containing polypropylene resin material J830HV as a synthetic tree component has a core portion (hard portion) on the coating of foamed cells S1, S2, and S3 only by extrusion production with the extrusion molding machine 10, and vibration due to sound. It is a foam structure that is difficult to break. When the foam (virgin material) 1 extruded from the extrusion molding machine 10 is once compressed and deformed, the core portion (hard portion) of the coating of the foam cells S1, S2, and S3 is destroyed, thereby forming a flexible coating. . Thereby, it processes into the flexible foam H which is easy to vibrate with a sound. Thus, the foam H is manufactured.

  As described above, the foam H manufactured in this way is subjected to solid vibration at a specific frequency by incident vibration when sound is incident from the outside, and absorbs sound by cancellation of the incident vibration and solid vibration. Sound absorption is also achieved by canceling the incident wave that enters the interior from the surface of H and the transmitted reflected wave that is reflected after passing through the interior. That is, the sound absorption due to the natural vibration and the sound absorption due to the phase velocity have a sound absorption peak in the low frequency band, and sound absorption performance can be obtained. On the other hand, the foam H is in a porous form, and the sound incident from the outside easily enters the inside of the foam H from the bubble breaking cell S2b of the surface coating layer 2, so that it depends on the vibration energy inside. The amount of absorption is increased, and the sound absorption characteristics in the high frequency band due to the porous type are improved as compared with the conventional foam. As described above, the sound absorption peak performance is obtained in the low frequency band, and the deterioration of the sound absorption performance in the high frequency band can be suppressed.

  In addition, since the film thickness of each foam cell S1, S2, S3 is thin, the film of each foam cell S1, S2, S3 is easy to vibrate, and the sound is also absorbed by the vibration of the film. As described above, the foam H is made of a foam having paper as a part of the foam material, and exhibits excellent sound absorption characteristics.

  The foam cell layer 1 has a foam cell S1b in which the cell coating is broken as the foam cell S1. Therefore, since the sound that has entered the foam cell layer 1 is more likely to enter the inside of the foam H than the foam cell S1b of the foam cell layer 1, the amount of absorption due to vibration energy inside increases further, and the sound absorption performance is improved. improves.

  The synthetic resin component is a polypropylene resin material J830HV (a kind of product name Prime Polypro of Prime Polymer Co., Ltd.). Not only the flexibility of the paper powder component and the adhesiveness of the starch component, but also the synthetic resin component (J830HV) has a high melt flow rate (about 30 g / 10 min), so the foaming material is high in the foaming process It exhibits fluidity, and the foam cells S1, S2, and S3 swell greatly, and bubble breakage is promoted. Thereby, the foam H which has the bubble breaking cell S1b, S2b, S3b can be manufactured reliably.

  The extrusion molding machine 10 is provided with discharge ports 12 arranged at intervals, and is provided with a regulation frame wall 20 that regulates the foaming region of the foam material discharged from each discharge port 12. A foam material having a pulp fiber component, a synthetic resin component, and a starch component, supplying the fiber component, the synthetic resin component, the starch component and water as an auxiliary agent, and kneading the pulp fiber component, the synthetic resin component, the starch component, and the water by heating. The foam H is obtained by performing an extrusion molding process for discharging the foam H from each discharge port 12 with a pressing force in a highly fluid state, and a pressing process for pressing the foam Ha produced by the extrusion molding after the extrusion molding process. Manufactured. Therefore, in the high-temperature foam material discharged from the discharge port 12, water mixed in the high-temperature foam material is instantly vaporized, and the foam material is foamed by the vapor pressure of the water. Here, the foamed material Ha has high fluidity at the time of foaming, the foamed cells Ha, S2b, S3b each having foamed cells S1, S2, S3, in which the foamed cells S1, S2, S3 are about to swell and break, and the cell coating is broken. Even if the produced foam Ha has a core portion (hard portion) in the cell coating of the foamed cells S1, S2, S3, the core portion (hard portion) of the cell coating is formed by compressive deformation by the pressing process. ) Is broken to form a flexible cell film, and a flexible foam H that is easily vibrated by sound is produced. From the above, it is possible to produce a foam H that has sound absorption peak performance in a low frequency band and that can suppress a decrease in sound absorption performance in a high frequency band.

  Since the cutting process of cutting the foam H into a desired shape includes a pressing process, the actual foam H manufacturing process does not involve an increase in the process.

  FIG. 6 shows a reverberation chamber in a foam without a small hole (press only foam) on the surface, a foam with a small hole 6 due to bubble breakage (foam with a small hole) 1 on the surface, and a synthalate. It is a sound absorption coefficient measurement result by the method. Each foam sample has a horizontal dimension of 100 cm, a vertical dimension of 50 cm, and a thickness dimension of 10 mm.

  As shown in FIG. 6, the foam H with the small holes 6 showed a higher sound absorption rate in the range of about 1000 to 2000 Hz, compared with the synthate. Therefore, it was confirmed that a high sound absorption characteristic is exhibited in the range of the speech intelligibility of 1000 Hz to 2000 Hz. For example, it is suitable as a sound absorbing material used in an automobile. Moreover, it was confirmed that the foam H with the small holes 6 can suppress the deterioration of the sound absorption performance in the high frequency band (2000 Hz or more) as compared with the foam only in the press without the small holes.

  Next, another pressing process different from the above will be described. As shown in FIG. 7, the pressing device 40 used in this separate pressing step includes a pair of rollers 41 and a conveying means (not shown) that conveys the foam Ha between the pair of rollers 41. A pair of roller 41 is arrange | positioned in the mutually opposing position. The dimension between the pair of rollers 41 is configured to be adjustable.

  The foam Ha produced from the extrusion molding machine 10 is passed between the pair of rollers 41 to compress the foam Ha. In other words, the pressing process of the entire surface batch compression described above compresses the foam Ha in a local and sequential manner while the uniform pressure is applied to the entire surface of the foam Ha to compress the entire surface.

  The difference between the whole surface batch compression and the compression by the roller 41 is as follows. In the whole surface compression, since uniform pressure acts on the entire surface of the foam Ha, cracks are hardly generated in the surface coating layer 2, but the direction of the compression force is broken or cracked, and a flexible structure is obtained. The foam H that is compressed all over is thinner by about 2 mm than before compression.

  In the compression by the roller 41, a crack 44 (see FIG. 8) is generated in the surface film layer 2 due to a pressure difference (a tensile force between a portion pressed by the roller 41 and an adjacent portion that is not), and bubble breakage is also promoted. This synergistic effect provides a structure with good air permeability to the inside. The foam H by the roller 41 is thinner than before compression, as in the case of full-surface compression, but the change in thickness (the amount of crushing) can be adjusted by dimensional management between the rollers 41.

  FIG. 9 shows a foam (foam with broken bubbles (small holes)) that has been pressed by batch compression, and a foam that has been pressed by rollers 41 (foam with broken bubbles (small holes) and cracks). It is a sound absorption coefficient measurement result by the reverberation room method in a synthesizer.

  It was confirmed that the rising characteristic in the region around 1 kHz depends on the change in thickness (crushing amount). As the thickness increases, the rising characteristic shifts to the low frequency side. Conversely, as the thickness decreases, the rising characteristic shifts to the high frequency side. That is, it was confirmed that the sound absorption performance due to the natural vibration and the sound absorption performance due to the phase velocity change depending on the thickness change of the foam H. Thereby, the amount of crushing of the foam Ha can be adjusted by the dimension d between the rollers 41, and the sound absorption characteristics around 1 kHz can be managed. Specifically, when the dimension d between the rollers 41 is 4 mm, the thickness T of the foam H is 10 mm (crushing amount 0 mm), and when the dimension d between the rollers 41 is 3 mm, the thickness of the foam H is When T is 9 mm (crushing amount 1 mm) and the dimension d between the rollers 41 is 2 mm, the thickness T of the foam H is 8.5 mm (crushing amount 1.5 mm), and the dimension d between the rollers 41 is 1 mm and 0 mm. In this case, the thickness T of the foam H is 7 to 6 mm (crushed amount 3 to 4 mm).

  Moreover, it was confirmed that the fall of the sound absorption performance in a high frequency band can further be suppressed. That is, the foaming cell S2b is generated in the surface film layer 2 and the like by the local crushing and the crack 44 is generated, and the air permeability of the foam H is improved. It is presumed that this is because it became easier to enter the inside of H. The ratio of the bubble breaking cell S2b and the amount / size of the crack 44 depend on the amount of crushing. If the amount of crushing is large, the ratio of the bubble breaking cell S2b and the amount / size of the crack 44 are increased. It was confirmed to improve. When the dimension d between the rollers 41 is 4 mm, the thickness after compression is 10 mm (crushing amount 0 mm), and the improvement in sound absorption is small. It was confirmed that the sound absorption characteristic in the high frequency band due to was inferior.

  It was confirmed that the foam H in the case where the dimension d between the rollers 41 is 2 mm exhibits the highest sound absorption characteristics in the region of conversation clarity of 1000 Hz to 2000 Hz.

  FIG. 10 shows sound absorption coefficient measurement results by a reverberation chamber method in a foam (3 samples) subjected to press processing by full-surface compression, a foam (10 samples) pressed by a roller 41, and a synthesizer. A large number (10) of samples were produced for each dimension between the rollers 41, and the sound absorption characteristics of each sample were examined. The foam H that has been pressed by batch compression over the entire surface is subjected to compression of 1.5 mm per sheet. The foam H pressed by the roller 41 has a dimension d between the rollers 41 of 2 mm and a thickness T of the foam H of 8.5 mm (crushed 1.5 mm).

  In the case of roller compression, the sound absorption coefficient variation of 1000 Hz to 5000 Hz was within (3σ) − (average value) = 0.05 for 10 samples, and it was confirmed that stable sound absorption characteristics were obtained.

  In the above embodiment, as a synthetic resin component, a polypropylene resin material J830HV (a kind of product name Prime Polypro of Prime Polymer Co., Ltd.) is used. The foam material is in a highly fluid state. However, if it is a resin that can discharge a foamed material in a foaming process in a highly fluid state and can form a bubble-breaking cell, it is a polypropylene resin material J830HV (a kind of product name Prime Polypro of Prime Polymer Co., Ltd.) Any other resin may be used, and the heating temperature is appropriately changed depending on the resin used.

H Foam 1 Foam cell layer 2 Surface coating layer 10 Extruder 12 Discharge port 20 Restriction frame wall S1, S2, S3 Foam cell S1b, S2b, S3b Foam break cell

Claims (7)

A foam comprising a foam cell in which a pulp fiber component, a synthetic resin component, and a starch component as an auxiliary agent are foamed, and a large number of spaces are formed,
The foamed cell comprises a foamed cell layer in which foamed cells are densely arranged, and a surface film layer in which foamed cells having a foaming density higher than the foamed cell layer are densely arranged on the surface side of the foamed cell layer. And
The said surface membrane | film | coat layer has a foam cell by which the cell membrane was torn as said foam cell. The foam according to claim 1,
The foamed cell layer has a foamed cell in which a cell coating is broken as the foamed cell. The foam according to claim 1 or 2,
The synthetic resin component is a polypropylene resin material J830HV (a kind of product name Prime Polypro of Prime Polymer Co., Ltd.). Using an extrusion machine provided with discharge ports arranged at intervals and provided with a regulation frame wall for regulating the foaming area of the foam material discharged from each of the discharge ports,
A pulp fiber component, a synthetic resin component, a starch component as an auxiliary agent, and water are supplied to the extrusion molding machine, and the pulp fiber component, the synthetic resin component, the starch component, and water are heated and kneaded, and the pulp fiber component and the synthesis are mixed. An extrusion molding step of discharging a foam material having a resin component and the starch component from each of the discharge ports in a highly fluid state by a pressing force;
A method for producing a foam, comprising a pressing step of pressing the foam produced by the extrusion molding after the extrusion molding step. A method for producing a foam according to claim 4,
The said press process is applying the uniform pressure to the whole surface of a foam, and compressing it collectively, The manufacturing method of the foam characterized by the above-mentioned. A method for producing a foam according to claim 4,
The method for producing a foam, wherein the pressing step compresses the foam by locally applying a pressure sequentially. It is a manufacturing method of the foam according to any one of claims 4 to 6,
The synthetic resin component is a polypropylene resin material J830HV (a kind of product name Prime Polypro of Prime Polymer Co., Ltd.).

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