JP3215054B2 - Molded sound absorbing material and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded sound absorbing material used as a ceiling material for automobiles and the like, and more particularly to a molded sound absorbing material having both high strength and rigidity and excellent sound absorbing characteristics, and the molded sound absorbing material. It is a proposal for a method of advantageously producing a material.

[0002]

2. Description of the Related Art In recent years, in order to reduce the noise inside a vehicle, an interior material having a sound absorbing function is used. Among such interior materials, the molded ceiling material particularly has a large occupied area in the vehicle, and therefore, it is extremely effective to improve the sound absorbing function of the ceiling material in reducing the noise in the vehicle.

As a material having such a sound absorbing function, a material obtained by treating a porous material such as glass wool or resin felt with a thermosetting resin is known. However, such a sound absorbing material has insufficient rigidity to be used as a car interior material, particularly as a ceiling material. On the other hand, in order to impart a predetermined rigidity to this material, there have been problems such as an increase in weight as a member, poor moldability, and generation of dust during handling.

On the other hand, as a sound absorbing material which can solve the above-mentioned problems, there is a material obtained by expanding a stampable sheet. The sound-absorbing material obtained by expanding and molding the stampable sheet is a kind of porous material having a fine void structure, which is composed of reinforcing fibers and a thermoplastic resin which bonds the fibers to each other. Therefore, this kind of sound-absorbing material is characterized in that it does not generate dust during handling, has excellent shape retention, is lightweight, has a wide sound-absorbing frequency range, and is inexpensive compared to other materials.

However, such a thin plate-shaped sound-absorbing material made of such a porous material is required to be excellent in both sound-absorbing characteristics and rigidity when used in products such as ceiling members for automobiles.

For example, a sound absorbing material obtained by expanding and forming a stampable sheet as described in Japanese Patent Application Laid-Open No. 8-6549 is large in the thickness direction because the sound absorbing property is expressed on the back air layer. Space is needed. For this reason, there has been a problem that this sound-absorbing material cannot obtain sufficient sound-absorbing characteristics as a ceiling material for automobiles that requires sound-absorbing characteristics in a narrow space. Even if a material exhibiting a predetermined sound absorbing property is obtained, it is necessary to extremely increase the weight per unit area (weight per unit area) in order to maintain the rigidity as a ceiling material for an automobile, and the weight cannot be reduced. There was a disadvantage that.

Japanese Patent Application Laid-Open No. 6-156161 proposes a technique for improving the sound absorbing properties of a sound absorbing material by laminating an inorganic fiber layer on a stampable sheet. However, the sound-absorbing material according to this proposal has disadvantages in that the cost of the inorganic fiber itself is high, and since the inorganic fiber is laminated after the stampable sheet is formed, the number of manufacturing steps increases and the material itself becomes heavy. .

[0008] On the other hand, in a ceiling material for an automobile, a skin material as a decoration is generally bonded to a surface inside the vehicle. When both the skin material and the car ceiling material have air permeability,
The ceiling itself functions as a filter for the air inside the vehicle, and there is a problem in that the surface of the skin material becomes extremely dirty. Such a problem arises, for example, when the sound-absorbing material described in the above-mentioned JP-A-8-6549 having air permeability is used as a ceiling material for automobiles.

In order to solve such a problem, for example, there are methods such as applying a non-air-permeable treatment to a skin material, and providing a non-air-permeable layer between an automobile ceiling material and a skin material. However, when such a non-ventilating process is performed, the interior noise is reflected by the non-ventilating layer, and there is a fatal problem that the ceiling material made of the sound absorbing material does not substantially absorb sound.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems relating to a molded sound absorbing material, and a main object of the present invention is to provide a lightweight material having high strength and rigidity and excellent sound absorbing characteristics. And to provide a molded sound-absorbing material which is not air-permeable. Another object of the present invention is to propose a method for advantageously producing the molded sound absorbing material.

[0011]

Means for Solving the Problems The above-described sound absorption of a porous material involves friction between the air and the material when the sound passes through a gap in the porous material, and the energy of the sound is converted into heat energy. It is said to be caused by conversion (for example, see Koyasu's "Sound Absorbing Material" Gihodo).

Therefore, the sound absorption characteristics of the porous material are reduced when the porosity of the material becomes extremely small, because it becomes difficult for sound to enter the inside of the material. The case where the air-impermeable layer exists on the surface of the porous material is also reduced. Further, when compared with materials having the same porosity, the finer the void structure of the material and the thicker the sound absorbing layer, the better. Therefore, in order to obtain a material having excellent sound absorption characteristics, it is necessary to use a porous material having a large porosity and a fine void structure. On the other hand, the strength and rigidity of the porous material necessarily decrease because the amount of the adhesive resin between the reinforcing fibers relatively decreases as the porosity increases.

Based on such findings, the inventors have conducted intensive studies for the development of a molded sound absorbing material having both high strength and rigidity and excellent sound absorbing characteristics. As a result, by forming a molded sound absorbing material having a three-layer structure as shown below,
It has been found that the above object can be realized. . The inner layer of the molded sound-absorbing material is made to have a high void content having a fine void structure by making the content of the reinforcing fiber relatively higher than that of the outer layer. As a result, this layer has a structure that improves the expandability and the sound absorbing properties. In the layer having a high porosity, a sound having a high frequency of about 2000 Hz is particularly well absorbed. . One of the outer layer portions sandwiching the inner layer portion is impregnated with a resin to increase the content of the thermoplastic resin, so that the content of the reinforcing fibers is relatively lower than that of the inner layer portion, and the porosity is low. Layer. Thus, this layer has a structure that improves rigidity, and has a structure in which sound is prevented from being reflected by absorbing air, and sound is absorbed by the inner layer portion. In this dense layer, sound in the frequency range of 500 to 1000 Hz is particularly well absorbed. . The other of the outer layers sandwiching the inner layer is a non-breathable layer formed by laminating and bonding a resin film. Thus, this layer had a non-breathable structure. Therefore, such 3
Layered molded sound-absorbing material has high strength and rigidity,
It has a structure that can absorb sound in a wide frequency range of Hz well, and is lightweight and non-breathable.

That is, the molded sound-absorbing material of the present invention is a stampable sheet mainly comprising a thermoplastic resin and reinforcing fibers.
Composed of a porous one side of the substrate is smaller resin impregnated layer porosity obtained by impregnating the following thermoplastic resin a having a fine void structure obtained by expanding molded
It is on the other surface of the substrate, characterized der Rukoto When the film following thermoplastic resin b is laminated (see FIG. 1). Note Thermoplastic resin a: Thermoplastic resin having a lower melt flow rate than the thermoplastic resin in the porous substrate Thermoplastic resin b: Melting point or softening point of the stampable sheet , which is lower than the material temperature during sheeting and expansion molding High thermoplastic resin

Here, in the molded sound-absorbing material according to the present invention, it is preferable that the thermoplastic resin in the porous substrate is polypropylene and the reinforcing fibers are glass fibers. The thermoplastic resin a preferably has a melt flow rate that is 1/30 to 1/3 of the melt flow rate of the thermoplastic resin in the porous substrate.

The method for producing a molded sound-absorbing material according to the present invention comprises:
A molded sound-absorbing material is produced by heating and pressing a web obtained by forming a main raw material comprising a thermoplastic resin and reinforcing fibers, and then reheating and expanding the stampable sheet thus obtained, followed by molding. In the method, when the web is heated and pressed to form a sheet, a film of a thermoplastic resin a having a smaller melt flow rate than the thermoplastic resin in the web is laminated on one surface of the web, and the other side of the web is formed. The surface is made of a thermoplastic resin b whose melting point or softening point is higher than the heating temperature of the web at the time of forming the sheet.
Are laminated.

Here, in the method for producing a molded sound-absorbing material according to the present invention, it is desirable to use polypropylene as the thermoplastic resin in the web and to use glass fiber as the reinforcing fiber in the web. As the thermoplastic resin a, the melt flow rate is 1/1/1 of the melt flow rate of the thermoplastic resin contained in the web.
It is desirable to use a resin that is 30 to 1/3.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, components (or elements) constituting a molded sound absorbing material according to the present invention and a method for manufacturing the same will be described. About thermoplastic resins The thermoplastic resins used for the web include polyolefins such as polyethylene and polypropylene, resins such as polystyrene, polyvinyl chloride, polyethylene terephthalate, polycarbonate, polyamide, and polyacetal, and copolymers containing these resins as main components. Examples include a coalesced product (for example, an ethylene-vinyl chloride copolymer, an ethylene-vinyl acetate copolymer, etc.), a graft compound, and a blended product of these resins. Among them, polypropylene is preferable in terms of strength and price,
For the present invention, there are no particular thermoplastic resins which are incompatible.

The thermoplastic resin preferably has a melt flow rate of 10 to 300 g / 10 minutes. The reason is that if the melt flow rate is less than 10 g / 10 min, the adhesiveness is poor, while if it is more than 300 g / 10 min, the strength of the resin itself is low. Is lower.

The thermoplastic resin may be used in combination with one modified with various compounds such as an acid and an epoxy in order to improve the adhesion to the reinforcing fiber. In particular, in the case of polypropylene, those modified with maleic acid, maleic anhydride, acrylic acid or the like are preferable, and the modified group is preferably an acid anhydride group, a carboxyl group, a hydroxyl group, or the like. There are no other modifying groups that are incompatible with the present invention. When such a modified resin is used in combination with a thermoplastic resin, a web may be manufactured using the respective resin particles, or a pellet obtained by melting and kneading these resins in advance using an extruder or the like. You may use what was ground. In addition, one obtained by coating one resin with another resin can also be used.

The shape of the thermoplastic resin used for the web is not particularly limited, and for example, a fibrous or flake-like thermoplastic resin may be used in addition to the particulate shape. In particular, in the case of particles, it is desirable to use particles having a particle diameter in the range of 50 to 2000 μm. This is because the particle size is 2000
If it exceeds μm, it is difficult to obtain a stampable sheet in which the resin is uniformly dispersed in the reinforcing fibers.
If the thickness is less than μm, the resin is likely to fall off the web.

Further, additives for improving weather resistance and heat resistance can be added to the thermoplastic resin in advance. Also in this case, similarly to the case of the modified resin, a web may be manufactured using each particle, or these particles may be previously melt-kneaded with an extruder or the like, and a crushed product may be used. . Alternatively, one obtained by coating one particle with another material can be used.

Reinforcing Fibers Reinforcing fibers used in webs include glass fibers, rock fibers, carbon fibers, metal fibers, and the like.
Various organic fibers and inorganic fibers can be used.

The fiber length of the reinforcing fiber is from 5 to 30 mm, preferably from 10 to 26 mm, from the viewpoint that the obtained molded sound-absorbing material has sufficient rigidity and ensures the formability during paper-forming.
It is desirable to be within the range. The reason is that if the fiber length is shorter than 5 mm, sufficient rigidity cannot be obtained, while if the fiber length exceeds 30 mm, the reinforcing fibers are not sufficiently opened in the paper making process, and the expansibility of the molded body is reduced. This is because, at the same time, the expansion becomes uneven and the shapeability at the time of molding deteriorates. In addition, it is also effective to mix fibers having different fiber lengths from the balance between expandability and strength.

The fiber diameter of the reinforcing fiber is preferably in the range of 7 to 25 μm, and more preferably 11 to 23 μm, from the viewpoint of ensuring sound absorbing properties and reinforcing and expanding effects of the fiber. The reason is that if the fiber diameter is smaller than 5 μm, a sufficient expansion ratio cannot be obtained, while the fiber diameter is 30 μm.
If it exceeds m, sufficient sound absorption characteristics and rigidity cannot be obtained. Mixing fibers having different fiber diameters is effective in improving the sound absorbing properties and the reinforcing and expanding effects of the fibers.

The reinforcing fibers are optionally treated with a coupling agent or a sizing agent. In particular, when the reinforcing fibers are glass fibers, a treatment with a silane coupling agent is performed to improve the wettability and adhesion with a thermoplastic resin as a binder component. As the silane coupling agent, it is preferable to use a vinylsilane-based, aminosilane-based, epoxysilane-based, methacrylsilane-based, chlorosilane-based, or mercaptosilane-based coupling agent. The treatment of the glass fiber with such a silane coupling agent is performed by a known method such as a method of spraying the silane coupling agent solution while stirring and mixing the glass fiber, and a method of dipping the glass fiber in the coupling agent solution. It can be carried out.

Further, in order to improve the rigidity and expandability of the molded sound absorbing material, it is desirable to open the reinforcing fibers into single fibers. Therefore, the reinforcing fiber is treated with a water-soluble sizing agent. Examples of the sizing agent include a polyethylene oxide type and a polyvinyl alcohol type.

About the compounding ratio of the reinforcing fiber and the thermoplastic resin,
Web after papermaking Te content ratio of the reinforcing fibers occupying in (after drying) (content) varies depending on the addition of the specific gravity and other raw materials of reinforcing fibers and a thermoplastic resin is used, glass as the reinforcing fibers When fibers are used and polypropylene is used as the thermoplastic resin, it is desirable that the compounding ratio of the reinforcing fibers be 50 to 80 wt% with respect to the total weight of the dry web. The reason is that the compounding ratio of the reinforcing fiber is 50wt%
If the amount is smaller than the above, sufficient rigidity cannot be expected, the sound absorbing property is insufficient, and the porous molded article having a high porosity cannot be obtained due to poor expandability. On the other hand, the compounding ratio of reinforcing fibers was 80
If the content exceeds wt%, the web after papermaking becomes brittle and the handling property deteriorates. In addition, when expanded, the thermoplastic resin as a binder component becomes insufficient, and the resin is uniformly spread on the reinforcing fiber joint. This is because impregnation becomes difficult, and the rigidity of the obtained molded sound absorbing material is reduced.

About the Thermoplastic Resin a The thermoplastic resin a is a thermoplastic resin having a lower melt flow rate than the thermoplastic resin contained in the porous substrate or the web. This thermoplastic resin a is impregnated into one surface of the porous substrate when the web is formed into a sheet,
The surface layer portion of the porous substrate has a smaller amount of reinforcing fibers than the inner layer portion and forms a resin-impregnated layer having a small porosity. As a result, the portion of the resin impregnated layer has a small springback amount and does not expand sufficiently. For this reason, the surface layer of the porous substrate impregnated with the thermoplastic resin a has a structure with few voids, and the rigidity of the entire molded sound absorbing material is improved. On the other hand, the portion of the porous base material other than the resin-impregnated layer (the inner layer portion of the molded sound-absorbing material) has a higher content of the reinforcing fiber than the resin-impregnated layer portion, so that the springback amount is large and sufficient. Swell. For this reason, the desired sound absorbing characteristics can be exhibited in the portion of the porous substrate other than the resin-impregnated layer. In order to achieve the desired sound absorbing properties, it is desirable that the specific gravity of the portion other than the resin-impregnated layer is less than 0.3. As described above, by forming a structure having the resin impregnated layer having a small porosity obtained by impregnating the thermoplastic resin a on one surface of the porous base material, the obtained molded sound absorbing material has excellent sound absorbing properties. The rigidity is excellent while maintaining the characteristics.

What is important here is that one outer layer of the molded sound absorbing material impregnated with the thermoplastic resin a must have air permeability. This is because it is indispensable to maintain the sound absorption characteristics. In order for the outer layer to have air permeability, the melt flow rate of the thermoplastic resin a is important. In the present invention, the thermoplastic resin a contained in the porous substrate or in the web is used as the thermoplastic resin a. Therefore, a thermoplastic resin having a lower melt flow rate is employed. More preferably, the thermoplastic resin a has a melt flow rate (hereinafter simply referred to as “MFR”) of the resin of 1/30 to 1/30 of the MFR of the thermoplastic resin contained in the porous substrate or the web. Preferably, it is 1/3. The reason for this is that if the ratio of the MFR is larger than 樹脂, the resin impregnates the inner layer portion of the web when the sheet is formed, resulting in insufficient expansion in the subsequent expansion molding and the obtained molded sound absorption. The load capacity of the material does not improve. On the other hand, when the ratio of the MFR is smaller than 1/30, it becomes difficult to impregnate the resin into the web, and the layer of the thermoplastic resin a completely remains in the surface layer in the expansion molding performed later, and the obtained molded sound absorbing material becomes This is because, as a result, a resin layer having no ventilation is formed, and as a result, noise is reflected by this layer, and the sound absorption characteristics are significantly reduced. As described above, the thermoplastic resin a does not impregnate the inner layer portion of the porous base material but remains on the surface layer portion of the porous base material.

The thickness of the film used for impregnation with the thermoplastic resin a depends on the required rigidity and sound absorption coefficient, but is usually preferably 30 to 300 μm. The reason is that if the thickness of the film is less than 30 μm, the strength of the sound absorbing material is not sufficiently improved, while if it exceeds 300 μm, the expandability and the air permeability deteriorate. Examples of the thermoplastic resin a include resins such as polyolefins such as polyethylene and polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, polycarbonate, polyamide, and polyacetal, and copolymers containing these resins as main components ( For example, an ethylene-vinyl chloride copolymer, an ethylene-vinyl acetate copolymer, etc.), a graft compound, or a blend of these resins may be used.

Regarding the Thermoplastic Resin b The thermoplastic resin b is a thermoplastic resin having a higher melting point or softening point than the heating temperature of the web when it is formed into a sheet. The thermoplastic resin b is not particularly limited as long as the resin satisfies the above conditions. For example, polyolefin such as polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, polycarbonate,
Resins such as polyamide and polyacetal, and copolymers containing these resins as main components (for example, ethylene-
Vinyl chloride copolymers, ethylene-vinyl acetate copolymers, etc.), graft compounds, and blends of these resins. Here, the reason why such a film of the thermoplastic resin b is laminated and adhered to the porous substrate or the other surface of the web is that, while maintaining excellent sound absorption characteristics with respect to in-vehicle noise, it is not suitable for automotive ceiling materials. If the melting point or the softening point of the thermoplastic resin b is lower than the heating temperature of the web at the time of forming the sheet, the thermoplastic resin b is formed at the time of forming the sheet or the expansion molding.
This is because the melt viscosity of the film becomes low, cracks are easily formed on the film surface, and air permeability cannot be ensured.

The thickness of the film of the thermoplastic resin b is:
It depends on the required rigidity and air permeability, but usually 10 to 10
The thickness is desirably 0 μm, more preferably 15 to 60 μm. The reason for this is that if the thickness of the film is less than 10 μm, the film is easily torn during expansion molding, while
If the value exceeds, the sound absorbing material becomes heavy, which is economically disadvantageous. If the film has poor adhesion to the thermoplastic resin contained in the porous substrate or web, the film is laminated with one or more adhesive resin (adhesive layer) to form a multilayer film. Can be laminated and bonded to the web.

The above-mentioned molded sound-absorbing material according to the present invention contains, in addition to the above-mentioned various components, additives such as an antioxidant, a light-resistant stabilizer, a metal deactivator, a flame retardant, and a carbon black. Etc. can be contained. These additives and coloring agents can be contained in a product by, for example, previously blending or coating with a granular thermoplastic resin, or adding them to a web by spraying or the like.

Next, a method for producing the molded sound absorbing material according to the present invention will be described. (1) Preparation of web (papermaking method) In a foaming liquid in which an aqueous solution containing a surfactant was previously foamed,
A raw material mainly composed of a reinforcing fiber and a thermoplastic resin is dispersed. Next, the obtained dispersion is sucked and defoamed on a porous support to deposit solids in the dispersion, and the deposit is dried to obtain a nonwoven fabric-like intermediate product. The non-woven intermediate product is called a web. The thickness of this web is usually 1 to 30 mm.

Here, the surfactants that can be used include:
Any of anionic, nonionic and cationic types may be used. In particular, sodium dodecylbenzelsulfonate, coconut oil fatty acid diethanolamide, and the like are advantageously used because they are excellent in uniformly dispersing a reinforcing fiber and a raw material mainly composed of a thermoplastic resin.

The web manufactured by the papermaking method using foam has a uniform distribution of the raw materials in the width direction and the thickness direction, and the reinforcing fibers are spread to almost single fibers.

(2) Preparation of stampable sheet The web prepared in the paper making step of (1) is heated and pressed so that the reinforcing fibers and the thermoplastic resin are sufficiently impregnated.
Then, the sheet is cooled and solidified under pressure to produce a dense sheet (a stampable sheet).

In the present invention, in particular, in this sheeting step, a film of a thermoplastic resin a having a smaller melt flow rate than the thermoplastic resin contained in the web is laminated on one side of the web, and the other side of the web is formed. It is characterized in that a film of a thermoplastic resin b having a higher melting point or softening point than the heating temperature of the web at the time of forming a sheet is laminated on the surface and formed into a sheet. As a result, the outer layer side of the web on which the thermoplastic resin a film is laminated is impregnated with the thermoplastic resin a and has a structure having a small number of voids and air permeability. The web portion excluding the outer layer side has a fine void structure. Thus, a three-layer molded sound-absorbing material can be obtained in which a structure having a high porosity and a portion where the thermoplastic resin b film is laminated and bonded has a structure having no air permeability.

Here, it is desirable that the preheating temperature of the web at the time of forming the sheet be equal to or higher than the melting point of the thermoplastic resin in the web and lower than the decomposition temperature. In particular, when the thermoplastic resin is polypropylene, the preheating temperature is 170 to 230.
C., preferably 190-220.degree. The reason for this is that if the temperature exceeds 230 ° C., coloration and strength decrease due to thermal decomposition and deterioration of polypropylene are caused.

In order to sufficiently impregnate the reinforcing fiber with the thermoplastic resin, it is desirable that the pressure applied to the web at the time of forming the sheet be in the range of 0.5 to 50 kgf / cm ² . This is because, the pressure is less than 0.5 kgf / cm ^2,
Insufficient impregnation makes it impossible to obtain the desired rigidity. on the other hand,
If the applied pressure exceeds 50 kgf / cm ² , the reinforcing fibers will be damaged, and the desired rigidity and expandability cannot be obtained.

As a method for forming the web into a sheet, any known method such as a usual batch type intermittent pressing method and a continuous pressing method using Teflon or a steel belt can be applied.

The stampable sheets thus obtained are stacked in a state where the reinforcing fibers are opened to single fibers. Therefore, when the thermoplastic resin is melted again,
Due to the rigidity of the reinforcing fibers that are trying to return to the original web state, the thickness recovers to approximately the thickness of the web. This phenomenon is peculiar to a stampable sheet produced by a papermaking method, and is called springback. Since the driving force that causes the springback is the rigidity of the reinforcing fiber, the size of the springback depends on the amount and characteristics of the reinforcing fiber.

(3) Production of Molded Sound Absorbing Material (Expansion Molding) The stampable sheet produced in the above (2) is melted again with a thermoplastic resin, expanded by the above-mentioned springback force of the reinforcing fiber, and molded into a mold. The molded sound-absorbing material according to the present invention is manufactured by compressing, cooling and solidifying so that the specific gravity becomes smaller than the specific gravity when the porosity is zero (this is called expansion molding).

Here, the heating temperature for expanding the stampable sheet is desirably equal to or higher than the melting point of the thermoplastic resin and lower than the decomposition temperature. In particular, when the thermoplastic resin is polypropylene, the heating temperature is 170 to 230 ° C.,
Preferably, the temperature is 190-220 ° C. The reason for this is that if the temperature exceeds 230 ° C., coloring and strength reduction due to decomposition of polypropylene are caused. The temperature of the mold or the temperature of cooling and solidifying the expansion sheet at the time of compression molding may be lower than the freezing point of the thermoplastic resin, and is usually 60 ° C. or lower from the viewpoint of handling properties and productivity.
Further, the expansion molding pressure varies depending on the product shape, but is usually 50 kgf / cm ² or less. The reason for this is that excessive pressure will break the reinforcing fibers.

In the method for producing a molded sound-absorbing material according to the present invention, the step of applying heat and pressure to the web to impregnate the reinforcing fibers with the thermoplastic resin (the step of producing a stampable sheet) comprises the steps of: A film, a sheet, a nonwoven fabric, etc. other than the films of the resins a and b can be simultaneously bonded or combined with other materials to impart design properties and other functions.

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. (Example 1) The reinforcing fibers and thermoplastic resin used in this example are as follows. -Thermoplastic resin: polypropylene particles (MFR; 20, average particle size; 500 µm, melting point: 160 ° C)-Reinforcing fiber: glass fiber (length: 25 mm, diameter;
(13 μm) (treated with an aminosilane-based coupling agent and a polyethylene oxide-based sizing agent) (1) In a foam solution in which an aqueous solution containing a surfactant is foamed in advance, 30% of polypropylene particles and glass Raw materials having a component composition of 70% of fibers were mixed, defoamed and dried to a total weight of 960 g / m ² to produce a web. (2) On the surface of the web prepared in (1) above, a polypropylene film (200 μm
Thickness, MFR = 2), and a two-layer film of a nylon 6 film (melting point: 233 ° C., 25 μm thickness) and a polypropylene film (melting point: 160 ° C., 40 μm thickness, MFR = 8) as a thermoplastic resin b film, Each was laminated. At this time, the film of the thermoplastic resin b was laminated with the polypropylene film on the web side. (3) The laminate obtained in the above (2) is heated to 210 ° C.
Pressurized at a pressure of kgf / cm ² , the heated and pressed laminate was placed between cooling boards at 25 ° C., and pressed and solidified at a pressure of 3 kgf / cm ² to produce a dense stampable sheet . (4) The stampable sheet prepared in (3) is heated to 210 ° C. by a far-infrared heater, compressed and cooled by a flat plate mold with a clearance set to 4.2 mm, and formed into a good plate-shaped sound absorbing material. Was manufactured. The thickness of the molded sound absorbing material at this time is
4.0 mm.

As a result of observing the cross section of the molded sound absorbing material thus obtained with a microscope, resin impregnation with a low content of reinforcing fibers and a low porosity near the surface compared to the inside of the molded product. The layer was found to be present. Also, when the air permeability of the obtained molded sound absorbing material was examined, the surface on which the film of the thermoplastic resin a was laminated and impregnated had air permeability, but the surface on which the film of the thermoplastic resin b was bonded was There was no breathability.

(Example 2) A two-layer film of a polyethylene terephthalate film (melting point: 256 ° C., 25 μm thickness) and a polypropylene film (melting point: 168 ° C., 40 μm thickness, MFR = 8) as a film of thermoplastic resin b on the back surface of the web Except that was laminated in the same manner as in Example 1.
A molded sound absorbing material having a thickness of 4.0 mm was manufactured.

As a result of observing the cross section of the molded sound absorbing material thus obtained with a microscope, resin impregnation with a low content of reinforcing fibers and a low porosity near the surface compared to the inside of the molded product. The layer was found to be present. Also, when the air permeability of the obtained molded sound absorbing material was examined, the surface on which the film of the thermoplastic resin a was laminated and impregnated had air permeability, but the surface on which the film of the thermoplastic resin b was bonded was There was no breathability.

(Comparative Example 1) (1) A raw material having a component composition consisting of 30% of polypropylene particles and 70% of glass fiber was mixed in a foaming liquid in a dry weight% so that the total weight per unit area was 1140 g / m ^2. And dried to prepare a web. (2) Nylon 6 film (melting point: 233 ° C.,
(25 μm thickness) alone. (3) The laminate obtained in the above (2) is heated to 210 ° C.
Pressurized at a pressure of kgf / cm ² , the heated and pressed laminate was placed between cooling boards at 25 ° C., and pressed and solidified at a pressure of 3 kgf / cm ² to produce a dense stampable sheet . (4) The stampable sheet prepared in (3) is heated to 210 ° C. by a far-infrared heater, compressed and cooled by a flat mold having a clearance set to 4.2 mm, and has a thickness of 4.0 mm.
Was produced.

The cross section of the molded sound absorbing material thus obtained was observed with a microscope.
It was found that the surface on which the film was laminated was a layer having no voids, but the other portions had a structure having uniform voids. When the air permeability of the obtained molded sound absorbing material was examined, the surface on which the film was not laminated had air permeability, but the surface on which the thermoplastic resin b film was laminated did not have air permeability.

(Comparative Example 2) A stampable sheet was prepared without laminating films on both sides of a web, except that
In the same manner as in Comparative Example 1, a molded sound absorbing material having a thickness of 4.0 mm was manufactured.

Observation of the cross section of the molded sound absorbing material thus obtained with a microscope showed that the sound absorbing material had a structure having uniform voids. When the air permeability of the obtained molded sound absorbing material was examined, it was found that both surfaces had air permeability.

From the molded sound-absorbing materials of Examples 1 and 2 and Comparative Examples 1 and 2 manufactured as described above, 50 mm width × 120 m
A test piece having a length of m was cut out, and the test piece was subjected to a bending test in which a punch was pressed from the surface on which the thermoplastic resin a film was bonded (for the comparative example, the surface on which the film was not bonded). 50 mm / min, distance between spans 100 mm). The elastic gradient at this time is the gradient of the load (kgf) and the amount of deflection (mm) when the distance between the spans is 100 mm. Further, the normal incidence sound absorption coefficient was measured according to JIS A 1405. When the normal incidence sound absorption coefficient is 1.0, the sound is completely absorbed. As a result, the results of bending characteristics are shown in Table 1, and the results of sound absorption coefficient measurement are shown in FIG.

[0056]

[Table 1]

As is clear from the results shown in Table 1 and FIG. 2, when the structure according to the present invention is used, the molded sound absorbing material has a high maximum load and an elastic gradient, and exhibits excellent strength characteristics. It was found that the sound absorption characteristics in a wide frequency range from 500 to 2000 Hz were excellent.

[0058]

As described above, according to the present invention, it is possible to provide a lightweight, non-breathable molded sound absorbing material having high strength, rigidity and excellent sound absorbing characteristics. Thereby, the molded sound-absorbing material according to the present invention can be effectively used as a sound-absorbing material requiring rigidity, for example, an automobile ceiling material, an engine room, and a dash panel.

[Brief description of the drawings]

FIG. 1 is a schematic partial sectional view showing the structure of a molded sound absorbing material according to the present invention.

FIG. 2 is a diagram illustrating a relationship between a normal incidence sound absorption coefficient and a frequency.

[Explanation of symbols]

Reference Signs List 1 Resin-impregnated layer formed by impregnating a porous base material with thermoplastic resin a 2 Layer of porous base material containing thermoplastic resin and reinforcing fibers as main components 3 Layer of thermoplastic resin b

──────────────────────────────────────────────────続 き Continuing from the front page (72) Katsuhiro Nagayama, 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (72) Shigeru Takano 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Inside the Technical Research Institute Co., Ltd. (72) Inventor Yukio Nagashima 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Inside the Technical Research Institute Co., Ltd. Co., Ltd. (72) Inventor: Hiroshige Yamamura 5-33-8, Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor: Yasushi Yasuharu 5-33-8, Shiba, Minato-ku, Tokyo Mitsubishi Motors (72) Inventor Details Togo Togo 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Yutaka Araki 1,000 Chiba Prefecture No. 1, Kawasaki-cho, Chuo-ku, Ha-shi, Japan (56) References JP-A-64-63112 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00- 35/00 G10K 11/16 B60R 13/00-13/08

Claims (8)

(57) [Claims] 1. A one surface of the porous base material having a fine porous structure obtained by stampable sheet mainly composed of reinforcing fibers and thermoplastic resin expands molding, impregnating the following thermoplastic resin a It is composed of a resin impregnated layer with a small porosity obtained by allowing the other surface of the base material,
Forming sound absorbing material which film follows thermoplastic resin b is characterized in that it is laminated. Note Thermoplastic resin a: Thermoplastic resin having a lower melt flow rate than the thermoplastic resin in the porous substrate Thermoplastic resin b: Melting point or softening point of the stampable sheet , which is lower than the material temperature during sheeting and expansion molding High thermoplastic resin 2. The molded sound absorbing material according to claim 1, wherein the thermoplastic resin in the porous substrate is polypropylene. 3. The molded sound absorbing material according to claim 1, wherein the reinforcing fibers are glass fibers. 4. The thermoplastic resin a according to claim 1, wherein the melt flow rate of the thermoplastic resin a is 1/30 to 1/3 of the melt flow rate of the thermoplastic resin in the porous substrate. Molded sound absorbing material. 5. A web obtained by forming a main material comprising a thermoplastic resin and a reinforcing fiber is heated and pressurized, and the obtained stampable sheet is reheated and expanded, and then molded. In the method for producing a sound absorbing material, when the web is heated and pressed to form a sheet, a film of a thermoplastic resin a having a smaller melt flow rate than the thermoplastic resin in the web is laminated on one surface of the web. A method of manufacturing a molded sound-absorbing material, comprising laminating a film of a thermoplastic resin b having a higher melting point or softening point than the heating temperature of the web at the time of forming a sheet on the other surface of the web. 6. The method according to claim 5, wherein polypropylene is used as the thermoplastic resin in the web. 7. The method according to claim 5, wherein glass fibers are used as reinforcing fibers in the web. 8. The method according to claim 5, wherein a resin whose melt flow rate is 1/30 to 1/3 of the melt flow rate of the thermoplastic resin contained in the web is used as the thermoplastic resin a. The manufacturing method as described.