JP2002207487A - Microporous soundproofing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a soundproofing material which is large in characteristic impedance, is clean, is light in weight, is highly flexible and may have fire retradance. SOLUTION: The microporous soundproofing material is composed of a foam which is formed by a process step of impregnating a thermoplastic polymer with inert gas, then decompressing the same and has an average cell diameter of 0.1 to 300 μm and relative density of <=0.3. The microporous soundproofing material is composed of the foam described above and may contain a fire retardant. The fire retardant is preferably the composite metal hydroxide expressed by the following formula (1): m(MaOb).n(QdOe).cH2O...(1) (In the formula, M and Q are metal elements different from each other; Q is the metal element belonging to the group selected from IVA, Va, VIa, VIIa, VIII, Ib and IIb of periodic table; m, n, a, b, c, d, e are positive numbers and may be the values which are the same as each other or different from each other).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microporous soundproofing material composed of a thermoplastic polymer and having excellent characteristic impedance, and more particularly, to a material having excellent characteristic impedance and having cleanness, flexibility and shape followability. The present invention relates to a microporous soundproofing material that may have flame retardancy and is suitable for a required electronic device application.

[0002]

2. Description of the Related Art It is known that the soundproofing performance of a conventional homogenous material used for a soundproofing material obeys the mass rule. Therefore,
Soundproofing can be improved by increasing the basis weight of the material, that is, by increasing the weight. However, if it is attempted to significantly improve the soundproofing properties, the weight of the soundproofing material becomes very heavy, and the operability and handleability are reduced due to an increase in cost and weight.

[0003] As a constituent material of the soundproofing material, an inorganic material is used. However, an inorganic material is not suitable for soundproofing a portion requiring shape followability, cushioning property, or the like because the material itself has no flexibility. In addition, the soundproofing material is made of an organic material, and has a foamed structure in which bubbles are formed inside, or a structure in which fibrous materials are laminated, thereby exhibiting soundproofing. Generally, when sound hits a foam having bubbles, the vibration of air is propagated inside.
This vibration is propagated to the air inside the bubble, and the sound energy is lost due to the viscous resistance between the air inside the bubble and the air. However, in a foam structure having a mechanism of expressing soundproofing by viscous resistance, soundproofing can be improved by increasing the material thickness of a material having a small flow resistance, but a material having a large flow resistance has a certain thickness. Unless the thickness is large, there is a problem that desired soundproofness cannot be obtained.

[0004] Physical foaming and chemical foaming are generally performed as a method of forming a foam having cells therein. Physical foaming refers to impregnating a polymer with a hydrocarbon-based or chlorofluorocarbon-based low-boiling liquid, and then heating the polymer to gasify the impregnated low-boiling liquid and use this as the driving force to drive the polymer. Is a method of foaming. Chemical foaming is a technique in which a resin composition obtained by adding a pyrolytic foaming agent to a polymer is heated and bubbles are formed by gas generated by decomposition of the decomposable foaming agent. However, in the technology based on physical foaming, there are concerns about the flammability and toxicity of a substance used as a foaming agent, and the impact on the environment such as destruction of the ozone layer. Further, in the chemical foaming method, a residue of the foaming gas remains in the foam, and therefore, particularly in an electronic device application where low pollution is required, contamination by corrosive gas or impurities in the gas becomes a problem. In any of these physical foaming methods and chemical foaming methods, it is difficult to form a fine cell structure in any case, and particularly, it is said that fine cells having a size of 300 μm or less cannot be formed.

In recent years, as a method for obtaining a foam having a fine cell structure, a method has been proposed in which an inert gas is dissolved in a polymer under high pressure, and then the pressure is rapidly lowered to form a foamed structure. For example, JP-A-6-322168 discloses a method in which a thermoplastic polymer is charged into a pressure vessel, high-pressure gas is charged while heating to a softening point of the polymer, and then the pressure is reduced to form bubbles. .
However, in this method, when the pressure is reduced, since the polymer is in a molten state, the polymer easily expands, and the bubble diameter of the obtained foam tends to increase. Further, since a polymer having a glass transition temperature of 150 ° C. or higher is usually used, flexibility is low at room temperature. Therefore, when used as a soundproofing material for electronic devices, there is a problem in terms of shape followability and cushioning properties. Japanese Patent Application Laid-Open No. 10-168215 discloses a method for producing a thermoplastic polyurethane foam sheet in which a sheet made of a thermoplastic polyurethane is impregnated with an inorganic gas under pressure, and then foamed by heating. .
However, these publications do not disclose or suggest any soundproofing material.

[0006] Further, foams are used in various parts for the purpose of watertightness, airtightness, heat insulation, soundproofing, cushioning, etc.
In applications such as electronic devices, the material may be required to have flame retardancy depending on the part used. for that reason,
Various studies have been made on flame retardancy as a foam.

[0007] In the foam, depending on the original material, generally, as a flame retardant, chlorinated polyethylene, chlorinated paraffin, decabromodiphenyl ether, antimony trioxide and the like are used in combination with aluminum hydroxide. I have. However, when a chlorine-based material is used as a flame retardant, the generation of chlorine ions from the foam causes corrosion of electronic devices. In addition, decabromodiphenyl ether is concerned about the generation of dioxin during incineration, and it is considered that its use is not desirable due to environmental problems. Furthermore, since antimony trioxide is an environmentally hazardous substance and a harmful substance, its use is not desirable.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a soundproofing material which has a large characteristic impedance, is clean and lightweight, and has excellent flexibility. Another object of the present invention is to provide a soundproofing material that can achieve high soundproofing even if the thickness is small. Another object of the present invention is to provide a soundproofing material which has a large characteristic impedance, is clean and lightweight, has excellent flexibility, and has flame retardancy. Still another object of the present invention is to provide a soundproofing material which has a high soundproofing property even with a small thickness and has excellent flame retardancy.

[0009]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted various studies on the structure of the soundproofing material, the constituent materials, and the like. As a result, even when the thickness is small, the bubbles formed in the foam are In a foam having a basically independent shape, when the cell diameter is in a specific range and the relative density is equal to or less than a specific value, an excellent soundproofing effect can be obtained even with a small thickness, and It has been found that a suitable foam can be obtained by impregnating a specific polymer with an inert gas under high pressure and then reducing the pressure. The present invention has been completed based on these findings.

That is, the present invention is formed by impregnating a thermoplastic polymer with a high-pressure inert gas and then reducing the pressure, and has an average cell diameter of 0.1 to 300 μm and a relative density of 0.3 or less. The present invention provides a microporous soundproofing material composed of a foam.

The present invention is also formed by impregnating a non-foamed molded article made of a thermoplastic polymer with a high-pressure inert gas and then reducing the pressure.
Provided is a microporous soundproofing material comprising a foam having a relative density of not more than 0.3 μm.

[0012] The present invention is further formed by impregnating a molten thermoplastic polymer with an inert gas under a pressurized state, and then subjecting the molten thermoplastic polymer to molding under reduced pressure.
Provided is a microporous soundproofing material made of a foam having a relative density of 300 μm and a density of 0.3 or less.

Each of the above-mentioned microporous soundproofing materials may be constituted by a foam formed by further heating after reducing the pressure. Carbon dioxide or the like can be used as the inert gas. The inert gas at the time of impregnation may be in a supercritical state. Preferred microporous soundproofing materials have a repulsion load of 20 N / cm ² or less when compressed by 50%.

Further, the present inventors have further achieved the above object of providing a soundproofing material having flame retardancy.
As a result of various studies on the structure of soundproofing materials, constituent materials, etc.,
Even in the case where the thickness is small, the bubbles formed in the foam are basically independent in shape, and when the bubble diameter is in a specific range and the relative density is equal to or less than a specific value, the thickness is small. Even a good soundproofing effect can be obtained, and such a foam can be obtained by impregnating a specific polymer with an inert gas under high pressure and then reducing the pressure, and furthermore, the foam and the flame retardant It has been found that flame retardancy can be achieved by combining. The present invention has been completed based on these findings.

That is, the present invention relates to a flame retardant comprising a foam formed by impregnating a thermoplastic polymer with a high-pressure inert gas and then reducing the pressure, and containing a flame retardant. The present invention provides a microporous soundproofing material.

Further, the present invention comprises a foam formed by impregnating an unfoamed molded article made of a thermoplastic polymer with a high-pressure inert gas and then reducing the pressure, and containing a flame retardant. The present invention provides a microporous soundproofing material having flame retardancy.

Further, the present invention comprises a foam formed by impregnating a molten thermoplastic polymer with an inert gas under a pressurized state, then subjecting the molten thermoplastic polymer to molding under reduced pressure and containing a flame retardant. To provide a microporous soundproofing material having flame retardancy.

In the present invention, it is preferable that the foam is constituted by a foam formed by further heating after decompression.

In the present invention, the flame retardant is preferably a hydrated metal compound and / or a brominated compound. Also,
It is preferable that the hydrated metal compound is a composite metal hydroxide represented by the following formula (1). _{m (M a O b) ·} n (Q d O e) · cH 2 O (1) [ in the formula, M and Q are different metal elements from each other, Q
Is a metal element belonging to a group selected from IVa, Va, VIa, VIIa, VIII, Ib and IIb of the periodic table. m,
n, a, b, c, d, and e are positive numbers and may have the same value or different values.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Foam] [Thermoplastic polymer] In the present invention, the thermoplastic polymer as a material of the foam (resin foam) is a polymer exhibiting thermoplasticity and impregnated with a high-pressure gas. There is no particular limitation as long as it is possible. As such a thermoplastic polymer, for example, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, a copolymer of ethylene and propylene, ethylene or propylene and other α-olefin Olefinic polymers such as copolymers with ethylene and vinyl acetate, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, vinyl alcohol and the like;
Styrene polymers such as polystyrene; polyamides; polyamide imides; polyurethanes; polyimides;

The thermoplastic polymer also includes a thermoplastic elastomer which exhibits properties as a rubber at room temperature and exhibits thermoplasticity at a high temperature. As such a thermoplastic elastomer, for example, ethylene-propylene copolymer,
Olefin elastomers such as ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polybutene, polyisobutylene, and chlorinated polyethylene; styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene Styrene-based elastomers such as isoprene-butadiene-styrene copolymers and hydrogenated polymers thereof; thermoplastic polyester-based elastomers; thermoplastic polyurethane-based elastomers;
Examples include thermoplastic acrylic elastomers. Since these thermoplastic elastomers have a glass transition temperature of, for example, room temperature or lower (for example, 20 ° C. or lower), when used as a soundproofing material, they have remarkably excellent flexibility and shape following properties.

The thermoplastic polymers can be used alone or in admixture of two or more. Further, as the foam material (thermoplastic polymer), any of thermoplastic elastomer, thermoplastic polymer other than thermoplastic, and a mixture of thermoplastic elastomer and thermoplastic polymer other than thermoplastic elastomer can be used.

As a mixture of the thermoplastic elastomer and a thermoplastic polymer other than the thermoplastic elastomer, for example,
Examples include a mixture of an olefin-based elastomer such as an ethylene-propylene copolymer and an olefin-based polymer such as polypropylene. When a mixture of a thermoplastic elastomer and a thermoplastic polymer other than the thermoplastic elastomer is used, the mixing ratio is, for example, the former / the latter = 1/99 to
It is about 99/1 (preferably about 10/90 to 90/10, more preferably about 20/80 to 80/20).

[Inert gas] The inert gas used in the present invention is not particularly limited as long as it is inert and impregnable to the thermoplastic polymer. For example, carbon dioxide, nitrogen gas, Air and the like can be mentioned. These gases may be used as a mixture. Of these, carbon dioxide, which has a large amount of impregnation into the thermoplastic polymer used as the material of the foam and has a high impregnation rate, is preferred.

The inert gas when impregnating the thermoplastic polymer is preferably in a supercritical state. In supercritical state,
The solubility of the gas in the polymer is increased and high concentrations can be incorporated. Also, at the time of rapid pressure drop after impregnation, since the concentration is high as described above, the generation of bubble nuclei increases, and the density of bubbles formed by the growth of the bubble nuclei is large even if the porosity is the same. Therefore, fine bubbles can be obtained. The critical temperature of carbon dioxide is 31 ° C., and the critical pressure is 7.4 MPa.

When forming the foam, the thermoplastic polymer
Additives may be added as needed. The type of the additive is not particularly limited, and various additives commonly used for foam molding can be used. Examples of such additives include a bubble nucleating agent, a crystal nucleating agent, a plasticizer, a lubricant, a coloring agent, an ultraviolet absorber, an antioxidant, a filler, a reinforcing agent, and an antistatic agent. The addition amount of the additive can be appropriately selected within a range that does not impair the formation of bubbles and the like, and the addition amount used for molding a thermoplastic polymer such as a usual thermoplastic elastomer can be adopted.

In particular, in the present invention, by using a flame retardant, a microporous soundproofing material having flame retardancy (hereinafter sometimes referred to as "flame retardant microporous soundproofing material") can be obtained.
The flame retardant can be used by mixing with a foam material (thermoplastic polymer) as shown below. As such a flame retardant, the following flame retardants can be used.

[Foam Forming Step] The foam is formed by impregnating a thermoplastic polymer with an inert gas under a high pressure, a pressure reducing step of reducing the pressure after the step to foam the resin, and Accordingly, it is formed through a heating step of growing bubbles by heating. In this case, a preformed unfoamed molded product may be impregnated with an inert gas, or the molten thermoplastic polymer may be impregnated with an inert gas under a pressurized state, and then subjected to molding at a reduced pressure. May be. These steps may be performed by any of a batch system and a continuous system.

According to the batch method, for example, a foam can be formed as follows. That is, first, a thermoplastic polymer such as a polyolefin resin or a thermoplastic elastomer is extruded using an extruder such as a single-screw extruder or a twin-screw extruder, so that an unfoamed molded product (such as a resin sheet for foam molding) is extruded. To form Alternatively, using a kneading machine provided with rollers, cams, kneaders, and Banbury type blades, a thermoplastic polymer such as a polyolefin resin or a thermoplastic elastomer is uniformly kneaded, and the mixture is heated using a hot plate press. To form an unfoamed molded product (such as a resin sheet for foam molding) containing a thermoplastic polymer as a base resin. Then, the obtained unfoamed molded product is put into a pressure-resistant container, a high-pressure inert gas is introduced, and the inert gas is impregnated into the unfoamed molded product. In this case, the shape of the unfoamed molded product is not particularly limited, and may be any of a roll shape, a plate shape, and the like. The introduction of the high-pressure inert gas may be performed continuously or discontinuously. The pressure is released (usually up to the atmospheric pressure) when the sufficiently high pressure inert gas is impregnated, and bubble nuclei are generated in the base resin. The bubble nucleus may be grown at room temperature as it is, or may be grown by heating if necessary. As a heating method, a known or commonly used method such as a water bath, an oil bath, a hot roll, a hot air oven, far infrared rays, near infrared rays, and microwaves can be adopted. After the bubbles are grown in this way, they are rapidly cooled with cold water or the like to fix the shape.

On the other hand, according to the continuous method, for example, a foam can be formed as follows. That is, high-pressure inert gas is injected while kneading the thermoplastic polymer using a single-screw extruder, an extruder such as a twin-screw extruder, and the gas is sufficiently impregnated into the thermoplastic polymer and then extruded. The pressure is released (usually to atmospheric pressure), and foaming and molding are performed simultaneously, and in some cases, heating is performed to grow bubbles. After the bubbles grow, they are rapidly cooled with cold water or the like to fix the shape.

The pressure in the gas impregnation step is, for example, 6 MPa or more (for example, about 6 to 100 MPa), preferably 8 MPa or more (for example, about 8 to 100 MPa). When the pressure is lower than 6 MPa, bubble growth during foaming is remarkable, and the bubble diameter becomes too large, so that the soundproofing effect tends to decrease. This is because when the pressure is low, the gas impregnation amount is relatively smaller than when the pressure is high, and the number of bubble nuclei formed is reduced due to the decrease of the bubble nucleation rate, so the gas amount per bubble increases conversely. This is because the bubble diameter becomes extremely large. Further, in a pressure range lower than 6 MPa, the bubble diameter and the bubble density are greatly changed only by slightly changing the impregnation pressure, so that it is easy to control the bubble diameter and the bubble density.

The temperature in the gas impregnation step depends on the type of the inert gas or the thermoplastic polymer to be used, and can be selected in a wide range. However, in consideration of the operability and the like, the temperature is, for example, about 10 to 350 ° C. For example, when impregnating an inert gas into an unfoamed molded product such as a sheet, the impregnation temperature is about 10 to 200 ° C. in a batch system, and preferably about 40 ° C.
~ 200 ° C. In the case where the molten polymer impregnated with the gas is extruded to simultaneously perform foaming and molding, the impregnation temperature is generally about 60 to 350 ° C. in a continuous system. When carbon dioxide is used as the inert gas, the temperature at the time of impregnation is 32 ° C. in order to maintain the supercritical state.
The temperature is preferably 40 ° C. or higher.

In the pressure reduction step, the pressure reduction rate is not particularly limited, but is preferably about 5 to 300 MPa / sec in order to obtain uniform fine bubbles. The heating temperature in the heating step is, for example, about 40 to 250 ° C.,
Preferably it is about 60 to 250 ° C.

[Properties of Foam] The foam of the present invention has an average cell diameter of 0.1 to 300 μm, preferably 5 to 300 μm.
It has a fine cell size of 250 μm, more preferably 30 to 200 μm, and a relative density (density after foaming / density in an unfoamed state) of 0.3 or less (for example, 0.002
~ 0.3), preferably 0.25 or less (for example,
About 0.005 to 0.25). Further, in a preferred foam, a rebound load when compressed by 50% (hereinafter, referred to as a “rebound load”)
"May be referred to as" 50% compression load ") of 20 N / c
m ² or less (e.g., about 0.1~20N / cm ^2), in particular 15N / cm ² or less (e.g., 0.3~15N / cm ² or so). Such a foam is particularly excellent in flexibility.

The above-mentioned average cell diameter, relative density and 50% compressive load are determined, for example, by controlling the temperature, pressure, time and the like in the gas impregnation step according to the type of the inert gas and the thermoplastic polymer or thermoplastic elastomer used. It can be adjusted by appropriately selecting and setting conditions, operating conditions such as a decompression rate, temperature, and pressure in the decompression step, and a heating temperature after decompression.

[Flame retardant] In the present invention, the flame retardant includes
There is no particular limitation, and various flame retardants can be used. As the flame retardant, for example, a hydrated metal compound, a brominated compound and the like are suitably used. Among them, a flame retardant which releases moisture by heating to extinguish the flame is particularly preferable. Such flame retardants include, for example, hydrated metal compounds. As the hydrated metal compound, for example,
Examples include aluminum hydroxide and magnesium hydroxide. Such a hydrated metal compound may be surface-treated.

The flame retardants can be used alone or as a mixture of two or more.

[Polyhedral Composite Metal Hydroxide] In the present invention, among the hydrated metal compounds as the flame retardant, the composite metal hydroxide represented by the following formula (1) is most suitable. _{m (M a O b) ·} n (Q d O e) · cH 2 O (1) [ in the formula, M and Q are different metal elements from each other, Q
Is a metal element belonging to a group selected from IVa, Va, VIa, VIIa, VIII, Ib and IIb of the periodic table. m,
n, a, b, c, d, and e are positive numbers and may have the same value or different values.

When the polyhedral complex metal hydroxide represented by the formula (1) is used as a flame retardant in combination with the foam, the properties of the foam (for example, fine foaming properties,
It is possible to obtain a soundproof material that can exhibit excellent flame retardancy while maintaining soundproofness and flexibility without impairing it.

In the polyhedral composite metal hydroxide represented by the above formula (1), M representing a metal element is represented by:
Aluminum (Al), magnesium (Mg), calcium (Ca), nickel (Ni), cobalt (Co),
Tin (Sn), zinc (Zn), copper (Cu), iron (F
e), titanium (Ti), boron (B) and the like.
Among them, magnesium and the like are preferable. M may be composed of one kind of metal element, or may be composed of two or more kinds of metal elements.

Further, Q represents another metal element in the polyhedral complex metal hydroxide represented by the above formula (1).
Are IVa, Va, VIa, VIIa, VIII, I of the periodic table
b and metals belonging to the group selected from IIb. For example, iron (Fe), cobalt (Co), nickel (N
i), palladium (Pd), copper (Cu), zinc (Zn)
And the like. Among them, nickel, zinc and the like are preferable. Q may be composed of one kind of metal element,
It may be composed of two or more metal elements.

Such a composite metal hydroxide having a polyhedral crystal shape can be produced by a known method (see JP-A-2000-53875). For example,
By controlling various conditions and the like in the production process of the composite metal hydroxide, a desired polyhedral shape, for example, approximately dodecahedral, approximately 8 A composite metal hydroxide having a shape such as a tetrahedron or a substantially tetrahedron can be obtained.

As a polyhedral composite metal hydroxide,
Crystals having a polyhedral structure with a crystal outline of approximately octahedron are particularly preferred. The aspect ratio of the polyhedral composite metal hydroxide is about 1 to 8, preferably about 1 to 7, particularly 1 to 7.
Those adjusted to about 4 are preferable. Here, the aspect ratio means the ratio between the major axis and the minor axis of the composite metal hydroxide. The polyhedral composite metal hydroxide has an average particle size of about 0.05 to 10 μm, preferably about 0.1 to 10 μm.
About 6 μm. The average particle size can be measured by, for example, a laser type particle size measuring device. If the aspect ratio exceeds 8, or the average particle size exceeds 10 μm, it becomes difficult to obtain a highly foamed resin foam.

As a specific representative example of the composite metal hydroxide having the polyhedral shape, sMgO. (1-s) N
iO · cH ₂ O [0 <s <1, 0 <c ≦ 1], sMgO
· (1-s) ZnO · cH ₂ O [0 <s <1, 0 <c ≦
_{1], sA1 2 O 3 ·} (1-s) Fe 2 O 3 · cH 2 O [0
<S <1, 0 <c ≦ 3]. Among these, sMgO · (1-s) Q 1 O · cH 2 O [ However, Q
¹ represents Ni or Zn, and 0 <s <1 and 0 <c ≦ 1], for example, a hydrate of magnesium oxide / nickel oxide, magnesium oxide
A hydrate of zinc oxide is particularly preferably used.

In the present invention, a brominated compound, a composite metal hydroxide having a thin plate shape or the like can be used together with the composite metal hydroxide having a polyhedral shape. The ratio of the polyhedral complex metal hydroxide represented by the formula (1) in the entire flame retardant is, for example, 10 to 1
It is about 00% by weight, preferably about 30 to 100% by weight. If the proportion of the polyhedral composite metal hydroxide is less than 10% by weight, it is difficult to obtain a highly foamed resin foam.

The brominated compounds include, for example, tetrabromobisphenol A (TBA), TBA-bis (2,3-dibromopropyl ether), TBA-bis (allyl ether), hexabromocyclododecane, tribromophenol , Ethylenebistetrabromophthalimide, dibromoethyldibromocyclohexane, tetrabromophthalic anhydride, ethylenebisdibromonorbornenedicarboximide, vinyl bromide, tetrabromocyclooctane, ethylenebispentabromodiphenyl and the like.

As such a bromine compound, when the bromine compound is in a powder form, its average particle size is, for example, 0.0%.
It can be selected from the range of about 5 to 10 μm, preferably about 0.1 to 6 μm.

[Soundproofing Material] The soundproofing material of the present invention is composed of the foam, and may contain a flame retardant as needed. That is, the soundproofing material may be a flame-retardant microporous soundproofing material (flame retardant microporous soundproofing material) containing the foam and a flame retardant. Such a microporous sound-insulating material that may contain a flame retardant (a microporous sound-insulating material that does not contain a flame-retardant, or a flame-retardant microporous sound-insulating material) may contain a flame retardant if necessary. After mixing with a foam material (thermoplastic polymer) and then forming the foam through a foaming step, the foam can be prepared by incorporating a flame retardant inside the foam as necessary. That is, a gas impregnation step of impregnating a thermoplastic polymer which may contain a flame retardant with an inert gas under high pressure, a pressure reduction step of reducing the pressure after the step to foam the resin, and heating as necessary. Thus, a foam as a microporous soundproofing material (a microporous soundproofing material that may contain a flame retardant) can be formed through a heating step of growing bubbles. Of course, in this case, a preformed unfoamed molded product made of a thermoplastic polymer that may contain a flame retardant may be impregnated with an inert gas and then molded through a step of reducing pressure, The molten thermoplastic polymer, which may contain a flame retardant, may be impregnated with an inert gas under a pressurized state, and then subjected to molding at a reduced pressure.

As described above, it is important that the flame-retardant microporous soundproofing material of the present invention is composed of a microporous foam containing a flame retardant inside the foam.

The content of the flame retardant (particularly, the above-mentioned polyhedral complex metal hydroxide) is about 10 to 70% by weight, preferably about 10 to 70% by weight of the whole foam (for example, the total weight of the thermoplastic polymer and the flame retardant). It is about 25 to 65% by weight. If this content is too small, the flame retarding effect will be small, and if it is too large, it will be difficult to obtain a highly foamed foam.

The soundproofing properties of the material (flame retardant microporous soundproofing material)
In general, the characteristic impedance of air: Z_c(= Ρ^air× c
^air), The characteristic impedance of the material: Z_c ^mat.Ratio
[Z _c ^mat./ Z_c], That is, [Z_c ^mat/ (Ρ^air×
c^air)] (Unit: dimensionless). here,
The unit of each physical quantity is as follows. Z_c ^mat.: Kg / s ・ m^Two Z_c: Kg / s ・ m^Two ρ^air(Air density): kg / m^Three c^air(Propagation velocity of air (sound)): m / s Z_c ^mat/ (Ρ^air× c^air): Dimensionless

In the microporous soundproofing material of the present invention, the ratio of the characteristic impedance of the material to the characteristic impedance of the ^air [Z _c ^mat / (ρ ^air × c ^air )] is, for example, 3 to 50.
(−), Preferably about 5 to 50 (−).

As the soundproofing material (microporous soundproofing material which may have flame retardancy) of the present invention, a foam which may contain a flame retardant may be used alone as a soundproofing material. . In addition, the above-mentioned foam is processed into a shape adapted to a device for installing a soundproofing material, an adhesive layer is provided on one or both sides of the foamy surface, or a molded body such as a film or sheet is attached to the foam as a soundproofing material. Is also good. The adhesive layer and a film or the like may be combined.

The microporous soundproofing material of the present invention, which may have flame retardancy, has very small bubbles and a low relative density. The number of times that acoustic energy incident on the material is reflected at the bubble interface is very large, so that part of the acoustic energy is lost in the bubbles, so that the soundproofing is improved. Therefore, even if the thickness of the soundproofing material is thin, excellent soundproofing can be exhibited. Moreover, it is highly foamed and lightweight.

Further, since the foam is made of a thermoplastic polymer such as a thermoplastic elastomer, the foam is excellent in flexibility, and an inert gas such as carbon dioxide is used as a foaming agent, which is different from conventional physical foaming and chemical foaming. It is clean without any harmful substances and no contaminants remain. Therefore, it can be suitably used especially as a soundproofing material used inside an electronic device or the like.

In particular, the flame-retardant microporous sound-insulating material of the present invention has excellent flame-retardancy, so that it can be used as a sound-insulating material for parts where flame retardancy is required. Can be used in a wide range of applications.

The soundproofing material containing the polyhedral complex metal hydroxide does not use a chlorine-based resin or an antimony-based flame retardant, has high safety, and has a low environmental load.

The soundproofing material of the present invention may contain, if necessary, a vulcanizing agent, a pigment, a dye, a surface treating agent, an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, a surfactant, a plasticizer. And the like may be contained in an appropriate amount.

[0059]

The soundproofing material of the present invention has a large characteristic impedance, is clean and lightweight, and has excellent flexibility. In addition, even if the thickness is thin, high soundproofing can be exhibited. In particular, a soundproofing material (flame retardant microporous soundproofing material) combining the foam and a flame retardant can exhibit excellent flame retardancy.

[0060]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The relative density, 50% compression load, and average cell diameter of the foam were determined by the following methods.

(Relative density) The relative density was determined by the following equation. Relative density (−) = (density of foam) ÷ (density of sheet before foaming) (50% compression load) A plurality of test pieces cut into a circular shape having a diameter of 30 mm are stacked to have a thickness of about 25 mm, The stress when compressed to 50% at a compression speed of 10 mm / min was converted per unit area (cm ² ) to obtain a 50% compression load. (Average cell diameter) The formed foam sheet is frozen in liquid nitrogen and cut, and the cross section is scanned with a scanning electron microscope (SEM) (Hita
chi-570) at an accelerating voltage of 10 kV, and the average bubble diameter was determined from the obtained observation image by image processing.

Example 1 50 parts by weight of a polypropylene having a density of 0.9 g / cm ³ and a melt flow rate of 4 at 230 ° C. and JIS-A
A kneading machine (Toyo Seiki Co., Ltd.) in which 50 parts by weight of an ethylene propylene-based elastomer having a hardness of 69 is provided with roller-type blades
The product was kneaded at a temperature of 180 ° C. with a trade name “Laboplast Mill”), and then formed into a sheet having a thickness of 0.5 mm and a diameter of 80 mm using a hot plate press also heated to 180 ° C. This sheet was put in a pressure-resistant container and kept in an atmosphere at 150 ° C. under a pressure of 15 MPa for 10 minutes to impregnate carbon dioxide. After 10 minutes, the pressure was rapidly reduced to obtain a foam made of an olefin-based polymer. The foam has a relative density of 0.026, an average cell diameter of 124 μm, and a 50% compression load of 0.78 N / c.
m ² . Table 1 shows the results of evaluating the acoustic characteristics of this foam.

Example 2 50 parts by weight of polypropylene having a density of 0.9 g / cm ³ and a melt flow rate of 4 at 230 ° C. and JIS-A
A kneading machine (Toyo Seiki Co., Ltd.) in which 50 parts by weight of an ethylene propylene-based elastomer having a hardness of 69 is provided with roller-type blades
The product was kneaded at a temperature of 180 ° C. with a trade name “Laboplast Mill”), and then formed into a sheet having a thickness of 0.5 mm and a diameter of 80 mm using a hot plate press also heated to 180 ° C. This sheet was put in a pressure-resistant container, and was kept in an atmosphere of 150 ° C. under a pressure of 20 MPa for 10 minutes to be impregnated with carbon dioxide. After 10 minutes, the pressure was rapidly reduced to obtain a foam made of an olefin-based polymer. The foam has a relative density of 0.029, an average cell diameter of 110 μm, and a 50% compression load of 2.16 N / c.
m ² . Table 1 shows the results of evaluating the acoustic characteristics of this foam.

Example 3 A thermoplastic polyurethane (trade name "E660MZAA", manufactured by Nippon Milactran Co., Ltd.) was mixed in a batch type kneader (trade name, "Laboplast Mill", manufactured by Toyo Seiki Co., Ltd.) for 160 minutes.
After melt-kneading at ℃, it was formed into a sheet having a thickness of 2 mm and Φ80 mm by a hot press heated to 160 ° C. This sheet is placed in a pressure-resistant container and placed in a 70 ° C. atmosphere at 10 MPa.
The carbon dioxide was impregnated by holding for 90 minutes under pressure. After 10 minutes, the pressure was rapidly reduced, followed by heating in warm water of 80 ° C. for 30 seconds to obtain a foam made of thermoplastic polyurethane. The relative density of the foam is 0.131,
The average bubble diameter is 150 μm and the 50% compression load is 9.
It was 90 N / cm ² . Table 1 shows the results of evaluating the acoustic characteristics of this foam.

Example 4 A thermoplastic polyurethane (trade name "E660MZAA", manufactured by Nippon Milactran Co., Ltd.) was mixed with a batch type kneader (trade name, "Laboplast Mill", manufactured by Toyo Seiki Co., Ltd.) for 160.
After melt-kneading at ℃, it was formed into a sheet having a thickness of 2 mm and Φ80 mm by a hot press heated to 160 ° C. This sheet is placed in a pressure-resistant container and placed in a 60 ° C. atmosphere at 10 MPa.
The carbon dioxide was impregnated by maintaining the pressure for 60 minutes. After 10 minutes, the pressure was rapidly reduced, followed by heating in warm water of 80 ° C. for 30 seconds to obtain a foam made of thermoplastic polyurethane. The relative density of the foam is 0.217,
The average bubble diameter is 75 μm and the 50% compression load is 10.
It was 6 N / cm ² . Table 1 shows the results of evaluating the acoustic characteristics of this foam.

Comparative Example 1 A thermoplastic polyurethane (trade name “E660MZAA” manufactured by Nippon Milactran Co., Ltd.) was mixed with a batch-type kneader (trade name “Laboplast Mill” manufactured by Toyo Seiki Co., Ltd.) for 160 minutes.
After melt-kneading at ℃, it was formed into a sheet having a thickness of 2 mm and Φ80 mm by a hot press heated to 160 ° C. This sheet is placed in a pressure-resistant container and placed in a 40 ° C. atmosphere at 20 MPa.
The carbon dioxide was impregnated by holding for 90 minutes under pressure. After 90 minutes, the pressure was rapidly reduced to obtain a foam made of thermoplastic polyurethane. The relative density of the foam is 0.329, the average cell diameter is 4 μm,
The compression load was 22.04 N / cm ² . Table 1 shows the results of evaluating the acoustic characteristics of this foam.

Comparative Example 2 A polyurethane foam INOAC SC type produced by a general chemical foaming method had a relative density of 0.071, a cell diameter of 480 μm, and a 50% compressive load of 0.1%.
It was 70 N / cm ² . Table 1 shows the acoustic characteristic evaluation results of this sample.

Evaluation of Acoustic Characteristics For the foams of the examples and comparative examples, the characteristic
Measurement of the impedance
The ratio of the characteristic impedance of the material [Z_c ^mat/ (Ρ ^air× c
^air)] (Unit: dimensionless), and the soundproofing property was evaluated.

The characteristic impedance was measured using a two-microphone impedance measuring device. In addition, the value of the real part at 2000 Hz was used as the measured value of the characteristic impedance. Table 1 shows the results.

[0070]

[Table 1]

As is clear from Table 1, the foams according to Examples 1 to 4 show higher characteristic impedance than the foams according to Comparative Examples 1 and 2. Also, it can be seen that a foam having a small cell diameter and a large cell density gives high characteristic impedance.

Example 5 50 parts by weight of polypropylene having a density of 0.9 g / cm ³ and a melt flow rate of 4 at 230 ° C., 50 parts by weight of an ethylene propylene elastomer having a JIS-A hardness of 69, and polyhedral MgO. 100 parts by weight of ZnO.H ₂ O (average particle size 1.0 μm, aspect ratio 4) was used as a Labo Plast Mill (manufactured by Toyo Seiki Seisaku-Sho, Ltd.) with roller-type wings.
After kneading at a temperature of 180 ° C., a hot plate press heated to 180 ° C. was used to mold into a sheet having a thickness of 0.5 mm and a diameter of 80 mm. Place this sheet in a pressure vessel,
Carbon dioxide was impregnated in an atmosphere of 0 ° C. under a pressure of 15 MPa for 10 minutes. Then 1
After 0 minute, the pressure was rapidly reduced to obtain a foam made of an olefin polymer. The relative density of the foam is 0.0
It was 4. The average cell diameter (average cell diameter) was 175 μm, and the 50% compression load was 2.22 N / cm ² .

Example 6 50 parts by weight of polypropylene having a density of 0.9 g / cm ³ and a melt flow rate at 230 ° C. of 4; 50 parts by weight of an ethylene propylene elastomer having a JIS-A hardness of 69; ZnO.H ₂ O (average particle size 1.
0 μm, aspect ratio 4) 100 parts by weight, and ethylenebispentabromodiphenyl (average particle size 5.0 μm) 2
5 parts by weight was kneaded at a temperature of 180 ° C. by a Labo Plastomill (manufactured by Toyo Seiki Seisakusho) provided with roller-type wings, and then 0.5 mm thick using a hot plate press heated to 180 ° C.
mm, and formed into a sheet shape of φ80 mm. This sheet was put in a pressure-resistant container and kept in an atmosphere at 150 ° C. under a pressure of 15 MPa for 10 minutes to impregnate carbon dioxide. Then, 10 minutes later, the pressure was rapidly reduced to obtain a foam made of an olefin polymer. The relative density of the foam was 0.077. The average cell diameter (average cell diameter) was 80 μm, and the 50% compression load was 2.34 N / cm ² .

Example 7 50 parts by weight of polypropylene having a density of 0.9 g / cm ³ and a melt flow rate of 4 at 230 ° C., 50 parts by weight of an ethylene propylene elastomer having a JIS-A hardness of 69, and polyhedral MgO. 100 parts by weight of ZnO.H ₂ O (average particle diameter 0.5 μm, aspect ratio 4) was used as a Labo Plast Mill (manufactured by Toyo Seiki Seisaku-sho, Ltd.) provided with roller-type wings.
After kneading at a temperature of 180 ° C., a hot plate press heated to 180 ° C. was used to mold into a sheet having a thickness of 0.5 mm and a diameter of 80 mm. Place this sheet in a pressure vessel,
Carbon dioxide was impregnated in an atmosphere of 0 ° C. under a pressure of 15 MPa for 10 minutes. Then 1
After 0 minute, the pressure was rapidly reduced to obtain a foam made of an olefin polymer. The relative density of the foam is 0.0
52. The average bubble diameter (average cell diameter) is 10
3 μm, and the 50% compression load was 2.61 N / cm ² .

Comparative Example 3 The relative density of a polyurethane foam Inoac SC type prepared by a general chemical foaming method was 0.071,
The average cell diameter was 480 μm, and the 50% compression load was 0.1%.
It was 70 N / cm ² .

(Evaluation) The flame retardancy and acoustic characteristics of the foams according to Examples 5 to 7 and Comparative Example 3 were
The following flame retardancy evaluation method and acoustic characteristic evaluation method were used. The evaluation results are shown in Table 2.

(Method of Evaluating Flame Retardancy) The foams according to Examples 5 to 7 and Comparative Example 3 were each sliced to a thickness of 1 mm, and the flame retardancy was evaluated according to UL94HF-1. Those that passed the UL94HF-1 standard are "passed"
Those that failed were shown as "fail" in Table 1.

(Method of Evaluating Acoustic Characteristics) With respect to the foams of the examples and the comparative examples, the characteristic impedance of the material was measured, and the ratio of the characteristic impedance of the material to the characteristic impedance of ^air [Z _c ^mat / (ρ ^air × c ^air )] ](unit:
(Dimensionless), and the acoustic characteristics as soundproofing were evaluated.

The characteristic impedance was measured using a two-microphone impedance measuring device. In addition, the value of the real part at 2000 Hz was used as the measured value of the characteristic impedance.

[0080]

[Table 2]

As is clear from Table 2, the soundproofing materials of the foams according to Examples 5 to 7 corresponding to the present invention have better flame retardancy than the soundproofing material of the foam of the comparative example. Has,
It shows a high characteristic impedance. Further, in the soundproofing material, the smaller the average particle diameter of the contained flame retardant, the smaller the bubble diameter and the larger the bubble density, and it can be inferred that a high characteristic impedance is provided.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 101: 00 B29C 67/22 (72) Inventor Manabu Matsunaga 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Katsuhiko Tachibana Inventor 1-1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation (72) Noriyuki Baba 1-1-2 Shimohozumi Ibaraki City, Osaka Nitto Inside Electric Works Co., Ltd. (72) Inventor Yoshihiro Minamizaki 1-2-1, Shimohozumi, Ibaraki City, Osaka Nitto Electric Works Co., Ltd. In-company (72) Inventor Mitsuhiro Kaneda 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Tomohiro Taruno 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Hideyuki Kitai 1-2-1 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 4F074 AA24 AA25 AA78 AA97 AC17 AG10 BA32 BA86 CA21 CC03X CC04Z CC10X CC22X CC34Y DA02 DA03 DA08 DA18 DA57 4F212 AB05 AB16 AE06 AG20 UA01 UA09 UC05 UC06 UE26 UW06 5D061 AA06 AA11 AA16 AA26

Claims (14)

[Claims] 1. A foam formed by impregnating a thermoplastic polymer with a high-pressure inert gas and then reducing the pressure, and having an average cell diameter of 0.1 to 300 μm and a relative density of 0.3 or less. Microporous soundproofing material composed of 2. An unfoamed molded product made of a thermoplastic polymer is formed by impregnating a high-pressure inert gas with a high-pressure inert gas and then depressurizing, and has an average cell diameter of 0.1 to 300 μm and a relative density of 0.1 to 300 μm. A microporous soundproofing material comprising a foam of 3 or less. 3. A molten thermoplastic polymer is impregnated with an inert gas under a pressurized state, and then formed by molding under reduced pressure, and has an average cell diameter of 0.1 to 300 μm and a relative density of 0. A microporous soundproofing material composed of a foam of not more than 3. 4. The microporous soundproofing material according to claim 1, comprising a foam formed by further heating after decompression. 5. The method according to claim 1, wherein the inert gas is carbon dioxide.
The microporous soundproofing material according to any one of Items 4 to 4. 6. The microporous soundproofing material according to claim 1, wherein the inert gas at the time of impregnation is in a supercritical state. 7. A rebound load when compressed by 50% is 20N.
/ Cm ² microporous soundproofing material of the following according to any one of claims 1 to 6 is composed of foam. 8. The microporous soundproofing material according to claim 1, wherein the soundproofing material is made of the foam and contains a flame retardant. 9. A microporous sound insulating material comprising a foam formed by impregnating a thermoplastic polymer with a high-pressure inert gas and then reducing the pressure, and containing a flame retardant. 10. A microporous material comprising a foam formed by impregnating a high-pressure inert gas into an unfoamed molded product made of a thermoplastic polymer and then reducing the pressure, and containing a flame retardant. Soundproofing material. 11. A foam formed by impregnating a molten thermoplastic polymer with an inert gas under a pressurized state, and then subjecting the molten thermoplastic polymer to molding under reduced pressure and containing a flame retardant. Porous soundproofing material. 12. The microporous soundproofing material according to claim 9, which is constituted by a foam formed by further heating after decompression. 13. The microporous soundproofing material according to claim 8, wherein the flame retardant is a hydrated metal compound and / or a brominated compound. 14. The microporous soundproofing material according to claim 13, wherein the hydrated metal compound is a composite metal hydroxide represented by the following formula (1). _{m (M a O b) ·} n (Q d O e) · cH 2 O (1) [ in the formula, M and Q are different metal elements from each other, Q
Is a metal element belonging to a group selected from IVa, Va, VIa, VIIa, VIII, Ib and IIb of the periodic table. m,
n, a, b, c, d, and e are positive numbers and may have the same value or different values.