JPH058209B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a foam-shaped vibration damping material having excellent vibration damping performance, and more specifically to a foam-shaped vibration damping material with significantly improved vibration damping performance in the low and medium frequency range. The present invention relates to an extremely practical vibration damping material that has excellent sound absorption performance, is much lighter than conventional sheet-shaped vibration damping materials, and has a large cost reduction effect. Conventionally, vibration damping materials include various rubber-like substances, thermoplastic resins, thermosetting resins, kraftite,
A blend containing mica and carbon is used, and as a matter of course, the material has a high density, that is, a large weight. For this reason, as a result of the increased need for vehicle noise countermeasures in recent years, the development of lightweight vibration damping materials has been focused on, but damping performance is proportional to the square of the thickness of the damping material. There is a general rule that if the weight is reduced to 1/2 or 1/3, the damping performance becomes 1/4 or 1/9 respectively [edited by the Japan Acoustic Materials Association, Noise Countermeasures Handbook, p. 442] ] In the case of conventional damping materials, it has been extremely difficult to use them as lightweight damping materials. On the other hand, polyurethane foam, which is a typical lightweight material, has rarely been used as a vibration damping material due to its low damping performance. This is essentially due to the low damping performance of polyurethane itself, and it is clear considering that foaming results in a significantly lower density state. In fact, the present inventors evaluated the vibration damping performance of general commercially available foams while proceeding with the research of the present invention, and found that the vibration damping performance of polyurethane foam was generally at a low level, especially at low frequencies below 1000 Hz. , the performance is significantly poor in the medium frequency region.The damping performance shows a large frequency dependence.
We discovered this important phenomenon. By the way, as is well known, the oscillation frequency of many devices and equipment that require noise countermeasures is 1000Hz or less [Noise Countermeasures Handbook, Volume 1, Chapter 4, p. 97]
~171p], there is a strong demand for noise reduction in the low and medium frequency range below 500-600Hz, if possible. It is natural that general commercially available polyurethane foams are of little use in meeting these requirements, as mentioned above, and therefore vibration damping materials based on polyurethane foam materials do not improve the overall damping performance. Of course, it is essential to improve damping performance, especially in the low and medium frequency ranges. As a result of intensive research, the present inventors have found that it is possible to use a silicone foam stabilizer for rigid polyurethane foam with a specific composition as a foam stabilizer when manufacturing the soft polyurethane foam that forms the foam-shaped vibration damping material. We have discovered that this material plays an important role in achieving the above goals, and have obtained a foam-shaped damping material that has excellent damping performance in the low and medium frequency ranges, as well as excellent damping performance overall. Furthermore, the damping performance of conventional damping materials rapidly decreases as the temperature increases, so the practical temperature range is very narrow, whereas the foam-shaped damping material of the present invention has a temperature-dependent damping performance. is small, and therefore it is a material that provides excellent vibration damping effects over a wide temperature range from low temperatures to considerably high temperatures. Another advantage of the foam damping material of the present invention is that, in addition to the above-mentioned excellent damping performance, it also has the property of having excellent sound absorption performance in the low and medium frequency ranges. That is, conventional polyurethane foams have a sound absorption effect in the high frequency range, but have a drawback in that the sound absorption effect is very small in the low and medium frequency ranges, which are most important in practice. The foam-shaped vibration damping material of the present invention has greatly improved this drawback, and is an advantage that should be noted as a practical vibration damping/sound absorbing material. By the way, as is well known, it is already well-established that in order to carry out comprehensive and effective noise countermeasures, it is indispensable in many cases to exhibit both a vibration damping effect and a sound absorption effect. For this reason,
When commercially available polyurethane foam is used as a sound absorbing material, considering that its damping performance is particularly low in the low and medium frequency ranges as mentioned above, a practical solution is to use polyurethane foam with a solid damping material (sheet). By pasting and compounding,
We are trying to provide vibration damping and sound absorption performance. Therefore, in the case of a foam-shaped damping material that has both excellent damping performance and sound absorption performance by itself, as in the present invention, there is no need for an expensive damping sheet, and there is no need for the complicated Since manufacturing processes can be omitted, costs can be significantly reduced, leading to major industrial and academic developments. The vibration damping material of the present invention is a rigid polyurethane foam obtained by reacting a polyol, a polyisocyanate, a blowing agent, a catalyst, a foam stabilizer, a filler, etc., in which propylene oxide and ethylene oxide are added to a silicone foam stabilizer. A silicone foam stabilizer for rigid urethane foam, which is a polydimethylsiloxane polymer with a propylene oxide content of 5 to 35 mol% in the side chain, is used as a polyol.
It consists of a flexible polyurethane foam obtained by using 0.5 to 5 parts by weight per 100 parts by weight. The present invention will be explained in detail below. The polyol used in the present invention is a polyhydroxyl compound having a molecular weight of 500 to 10,000 and having at least two active hydrogens, and a polyether polyol having a hydroxyl group at its end;
These are called polyester polyols and polyether ester polyols, which are copolymers of ether and ester, and can be arbitrarily selected to suit the characteristics of the desired flexible polyurethane foam. In the present invention, poly(oxypropylene) obtained by reacting propylene oxide with glycerin having a molecular weight of 800 to 6,000 and ring-opening addition, which is commonly used in the production of general soft or semi-rigid polyurethane foams, is used in the present invention. Active polyols such as toluol or poly(oxyethylene-oxypropylene) toluol obtained by reacting propylene oxide and ethylene oxide to perform ring-opening addition are preferably used. Furthermore, as the polyisocyanate, tolylene diisocyanate is generally used. Among these, tolylene diisocyanate having a mixing ratio of 2,4- and 2,6-isomers of isocyanate groups of 80/20 or 65/35 (weight ratio) is preferred from the viewpoint of low cost and usefulness. The blending amount of this polyisocyanate with respect to the above polyol, that is, the isocyanate index (NCO index) is in the range of 60 to 130, but preferably in the range of 70 to 110 in consideration of the various properties of the resulting flexible polyurethane foam. The catalyst used in the present invention includes known catalysts commonly used in this field, such as tertiary amines and organotin compounds. The silicone foam stabilizer used in the present invention is a silicone foam stabilizer for rigid polyurethane foam made of propylene oxide and a polydimethylsiloxane polymer having propylene oxide in its side chain, and the content of propylene oxide is 5 to 35 moles. %, usually a poly(oxypropylene-oxyethylene)siloxane copolymer. Further, more preferable effects can be obtained by setting the propylene oxide content to 10 to 30 mol%. That is, when the content of propylene oxide is less than 5 mol%,
Foaming becomes unstable, cell roughness occurs, and a foam with a desired foam structure cannot be obtained.
The damping performance in the low frequency range is significantly reduced, making it impossible to achieve the object of the present invention. These silicone foam stabilizers are used in amounts of 0.5 to 100 parts by weight of polyol.
It is added in an amount of 5 parts by weight. If it is less than 0.5 parts by weight, the original function of the foam stabilizer, which is to generate uniform bubbles and adjust the size of the bubbles, cannot be obtained, and even if it is added in excess of 5 parts by weight, no further effect can be obtained. However, it is disadvantageous in terms of cost. As described above, the vibration damping material of the present invention can be produced by applying a specific silicone foam stabilizer for hard polyurethane foam to soft polyurethane foam.
It is designed to achieve excellent vibration damping and sound absorption effects in the low frequency range below 1000 Hz.The reason for this effect is due to the cell structure of the obtained foam. It has a special structure that is convenient for optimizing M25/d of
It is also presumed that this is due to (ii) a large amount of residual cell membrane and low air permeability. Furthermore, in the present invention, it is also possible to further improve the cell uniformity of the foam obtained by adding various organic or inorganic powder fillers. Powder fillers used for this include polyvinyl chloride, polyvinyl chloride-vinyl acetate copolymer, zinc oxide, antimony oxide, barium sulfate, calcium carbonate, mica, alumina, etc.
These can be used alone or in combination of two or more. And this filler is polyol
5 to 120 parts by weight per 100 parts by weight, more preferably
It can be used in an amount of 10 to 100 parts by weight; if it is less than 5 parts by weight, the above effects cannot be obtained, and if it exceeds 120 parts by weight, the viscosity of the mixed liquid mainly containing polyol increases, making it difficult to achieve good foaming. In addition, at this time, an appropriate amount of plasticizer such as phthalate esters and halogen-containing condensed phosphate esters (for example, polyol
By adding 50 parts by weight or less per 100 parts by weight, it is possible to suppress an increase in the viscosity of the liquid mixture, and by doing so, it is possible to further add the powder filler. Other additives that may be used in the practice of this invention include water or low boiling volatile liquids as blowing agents which have the effect of controlling the general physical properties and density of the resulting flexible polyurethane foam. The amount of water as a blowing agent is not particularly limited, but as described below, the amount of water used as a blowing agent is
% Ratio of stress at compression (M ₂₅ ) to specific gravity (d) (M ₂₅ /
In order to optimize d) and obtain high vibration damping and sound absorption properties, it is desirable to use 1.0 to 3.5 parts by weight per 100 parts by weight of the polyol. Furthermore, examples of low-boiling volatile liquids include methylene chloride, chloroform, monofluorotrichloromethane, monochlorodifluoromethane, and dichlorodifluoromethane, which can be used alone or in combination. In addition, appropriate colorants, flame retardants,
Plasticizers and the like may be used as appropriate without departing from the purpose of the present invention. The vibration damping material of the present invention can be obtained by a commonly used method for manufacturing rigid polyurethane foam. For example, there is a one-shot method in which polyisocyanate is added to a mixed solution of polyol, water, catalyst, foam stabilizer, foaming aid, etc. and foamed by reaction, or a one-shot method in which a part or all of the polyol is reacted with the entire amount of polyisocyanate in advance. It can be manufactured using a prepolymer method in which a prepolymer and other components are mixed and foamed. The soft polyurethane foam constituting the vibration damping material of the present invention has the above-mentioned formulation characteristics and the following physical properties, thereby exhibiting high vibration damping and sound absorption effects. That is, the foam material is 25
% stress (M ₂₅ ) when compressed is 1 g/cm ² or more, 60
g/cm ² or less, and the ratio of the above stress (M ₂₅ ) to specific gravity (d) (M ₂₅ /d) is 5 g/cm ² or more, 1500
A foam material having an air permeability of ² to 130 c.c./cm ² ·sec at a thickness of 20 mm has even better vibration damping and sound absorption effects. If the above stress (M ₂₅ ) is less than 1 g/cm ² , the rebound modulus of the foam is too low to function as a foam, and if it exceeds 60 g/cm ² , the desired vibration damping performance cannot be obtained. , preferably 40 g/cm ² or less, and further 30 g/cm 2 when improving vibration damping properties in the low frequency range.
It is desirable that it is less than g/cm ² . Further, the specific gravity (d) of the foam is preferably 0.02 or more and 0.5 or less,
Furthermore, 0.025 or more and 0.30 or less are desirable. If the specific gravity of the foam is too small, even if the modulus is small, the vibration damping performance will be low, while if the specific gravity is too large, stress will tend to become too high. Therefore, the ratio of stress (M ₂₅ ) to specific gravity (d) (M ₂₅ /d) is an important parameter for obtaining excellent damping performance in the low and medium frequency range, and the above
Considering the limited range of M ₂₅ and d, the value of M ₂₅ /d is larger than 2 g/cm ² and smaller than 3000 g/cm ² , but generally M ₂₅ /d is 5 to 1500 g/cm ² , more preferably , preferably in the range of 5 to 1000 g/cm ² . Also, when focusing on the low frequency range, 10 to 600 g/cm ²
is appropriate. The foam-shaped damping material of the present invention, whose stress, specific gravity, and the ratio thereof (M ₂₅ /d) are within the above-mentioned limit ranges, has the following characteristics in terms of vibration damping performance and sound absorption performance. In other words, regarding damping performance, as mentioned above, foam damping materials exhibit frequency dependence, and when the loss coefficient (η), which is a measure of the magnitude of damping performance, is plotted against frequency, the maximum η value There are one or more frequencies that give . Therefore, if the frequency that gives the maximum value among those maximum values is max, then max is
It is below 1000Hz, more preferably below 800Hz. On the other hand, regarding sound absorption performance, in order to have excellent sound absorption performance in the low and medium frequency range, it is necessary to
The air permeability in thickness should be in the range of 2 to 130 c.c./cm ² .sec, preferably 2 to 80 c.c./cm ² .sec. In this way, by satisfying the physical property conditions as described above, the vibration damping material of the present invention has both excellent vibration damping performance and sound absorption performance in the low and medium frequency ranges. Therefore, since the vibration damping material of the present invention has the above-mentioned excellent properties, it can be used as a vibration damping and sound absorbing material for the ceilings, floors, side walls, bonnets, etc. of various vehicles such as automobiles, trains, aircraft, and ships. , and various other industrial machinery such as construction machinery, agricultural machinery, and civil engineering machinery, as well as various noise sources in factories such as metal processing machinery, ducts, hoppers, and shoots, and roofs of residences and offices (especially iron plate roofs). , for noise sources such as ceilings, floors, and walls, for various office machines such as computers and printers, for various home appliances such as washing machines and vacuum cleaners, and for sound systems such as stereos and record players. It is widely used for pianos, organs, etc. Hereinafter, the present invention will be specifically explained based on Examples. Examples 1, 2, 3, Comparative Examples 1, 2 A 20 mm thick sheet specimen of a soft polyurethane foam obtained from the formulation shown in Table 1 was attached to a 1 mm thick iron plate. The loss coefficient (η) was measured as a test specimen at room temperature (30°C) using a vibration analysis device (mechanical impedance method) manufactured by Akashi Seisakusho Co., Ltd. The results are shown in Figure 1.
The loss coefficient (η) is a physical property value that is a measure of vibration damping performance, and the larger the loss coefficient, the higher the vibration damping performance. As a damping material, η is generally 0.05 or more, preferably
A value of 0.1 or higher is considered desirable.

[Table] Comparative Examples 1 and 2 are ordinary commercially available flexible polyurethane foams with propylene oxide content of 48 to 50%.
A silicone foam stabilizer for soft urethane foam is used in the amount of mol%, and the amount of water is also large. For this reason, the obtained foam has a large M ₂₅ /d and therefore f _nax is significantly reduced at high frequencies. As a result,
It is a general polyurethane foam with an overall low loss coefficient. In comparison, Examples 1 and 2 are ether-based polyurethane foams according to the present invention that use a silicone foam stabilizer for rigid urethane foam containing 20 mol% propylene oxide, contain a small amount of filler, and have a considerably lower water content. be. This urethane foam has a low M ₂₅ and a fairly low M ₂₅ /d. Therefore, it can be seen that f _nax shifts to the low frequency range, and a very excellent vibration damping effect can be obtained in the low and medium frequency ranges, which are the most important for soundproofing. On the other hand, in Example 3, the same silicone foam stabilizer as in Examples 1 and 2 was used, and a relatively low molecular weight polyol was used.
By lowering the NCO index and adding a significant amount of filler, it also has an excellent vibration damping effect. Example 4, Comparative Example 3 Soft urethane foam with the formulation of Example 1
Example 4 shows the temperature dependence of the loss coefficient at 300Hz.
Comparative Example 3 is shown in FIG. 2 as Comparative Example 3, which is a commercially available polyvinyl chloride sheet vibration damping material. It should be noted that the urethane foam of the present invention has a small temperature dependence of the loss coefficient, particularly the large loss coefficient at high temperatures. In addition, the foam of Example 1 has a weight approximately 1/1 that of the polyvinyl chloride sheet vibration damping material used in Comparative Example 3.
4, and it is understood that it is an extremely excellent lightweight vibration damping material. Example 5 The sound pressure level was measured when the foam damping material (20 mm thick) of Example 1 was attached to a steel plate (1 mm thick) and vibrated at 30°C, and compared with the case of only the iron plate. . The results are shown in Figure 3. It can be seen that the sound pressure level is significantly reduced in accordance with the frequency dependence of the loss coefficient in FIG. 1, indicating that it can be an excellent soundproofing material. Example 6, Comparative Example 4 Using 20 mm thick specimens of the foams of Example 1 and Comparative Example 1, the sound absorption coefficient was measured by placing them in close contact with a rigid wall at 30°C by the normal incidence method.The results are shown in Example 6 and Comparative Example, respectively. 4 in Figure 4. It can be seen that the foam of Example 1 has significantly improved sound absorption coefficient in the low and medium frequency ranges compared to the foam of Comparative Example 1. Thus, it can be seen that the foam-shaped vibration damping material of the present invention has excellent sound absorption performance and is a new sound insulation material that has both vibration damping performance and sound absorption performance.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the frequency dependence of the loss coefficient of the damping materials of Examples and Comparative Examples, and FIG.
A graph showing the temperature dependence of the loss coefficient at 300 Hz for the damping materials of Examples and Comparative Examples. Figure 3 shows the sound pressure level of the foam-shaped damping material of the present invention attached to an iron plate and only the iron plate. Graph showing frequency dependence. FIG. 4 is a graph showing the frequency dependence of the normal incidence sound absorption coefficients of the foams of Example 1 and Comparative Example 1.

Claims (1)

[Claims] 1. Polyol, polyisocyanate, blowing agent,
In a vibration damping material made of a soft polyurethane foam obtained by reacting a foam stabilizer, a foam stabilizer, a filler, etc., the foam stabilizer is a polydimethylsiloxane polymer having propylene oxide and ethylene oxide in its side chains. , a silicone foam stabilizer for rigid urethane foam having a propylene oxide content of 5 to 35 mol % is added to the above polyol.
Obtained using 0. to 5 parts by weight per 100 parts by weight, 25%
The stress during compression ( _M25 ) is 1 to 60 g/ ^cm2 , and the ratio of the above stress to specific gravity ( _M25 /d) is 5 to 1000.
A vibration damping material made of hard urethane foam with an air permeability of 2 to 130 c.c./cm ^{2 ·} sec. 2. The vibration damping material according to claim 1, wherein 5 to 120 parts by weight of an inorganic or organic powder filler is used per 100 parts by weight of the polyol. 3. The vibration damping material according to claim 1, wherein 1 to 3.5 parts by weight of water is used as a foaming agent per 100 parts by weight of polyol.