JPH0533659B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a vibration damping material that exhibits excellent vibration damping action in a wide temperature range from low to high temperatures. [Prior Art] Generally, vibration damping materials, especially vibration damping steel plates, are constructed by interposing a viscoelastic material layer between two steel plates and integrating the whole structure, so that it resists steady vibrations or shocks applied to the steel plates. The vibration energy caused by the vibration is absorbed by the viscoelastic material layer and converted into thermal energy due to internal friction, thereby reducing noise (vibration damping effect). This type of damping steel plate is widely used in oil pans, cylinder head covers, shielding plates, motor cases, etc. of vehicles. As mentioned above, the damping action of a damping steel plate is based on the damping action of the viscoelastic material layer itself interposed between the two steel plates, and loss is generally used as a measure of the damping action. A coefficient (η) is used, and the damping effect is evaluated based on the value of the loss coefficient η. It is preferable that the loss coefficient η is large and does not change over a wide range from low temperatures to high temperatures. In other words, the above-mentioned vibration damping steel plates are used in a wide temperature range from low to high temperatures, and those for automobiles in particular are required to be compatible with areas from extremely cold to extremely hot.
It is required to exhibit excellent vibration damping effect from high temperature range to considerably high temperature range. As described above, the performance of a damping steel plate is greatly influenced by the loss coefficient η of the viscoelastic material layer itself, and conventionally, synthetic resin or rubber has been used as the viscoelastic material layer. . Synthetic resins have unique viscoelastic characteristics, that is, the elastic modulus and loss coefficient η have a large temperature dependence, so a damping steel plate made of such a synthetic resin as a viscoelastic material layer has the following characteristics: The disadvantage is that the loss coefficient η has a large temperature dependence, has a sharp peak near the glass transition temperature (usually in the room temperature or higher temperature range), and the temperature range in which the damping effect is exerted is narrow. have. This is mainly due to the sudden decrease in the elastic modulus of the synthetic resin. Moreover, when the temperature of the synthetic resin rises and exceeds its glass transition temperature, it becomes molten, and a damping steel plate made of such a synthetic resin as a viscoelastic material layer suffers from a rapid decrease in the loss coefficient η. . Therefore, it is not possible to exhibit an excellent vibration damping effect over a wide temperature range, and only exhibits an excellent vibration damping effect at temperatures near the glass transition temperature. In particular, when the glass transition temperature is exceeded, the above-mentioned η decreases rapidly, so that it cannot be used at high temperatures. On the other hand, the loss coefficient η of a damping steel plate with rubber as a viscoelastic material layer reaches its maximum near the glass transition temperature, but since the glass transition temperature of rubber is generally lower than 0°C, it cannot be heated at room temperature or at room temperature. In a high temperature range above room temperature, it cannot exhibit an excellent vibration damping effect. However, since rubber is three-dimensionally crosslinked, even if the temperature rises and exceeds the glass transition temperature, it does not become molten, and the loss coefficient η does not drop as suddenly as in synthetic resins. Loss coefficient η of this rubber vs. temperature curve and loss coefficient η of synthetic resin
-The temperature curve is shown in FIG. In the figure, the curve
Curve A' is that for synthetic resin, and curve B' is that for rubber. As is clear from Figure 1, although synthetic resins exhibit excellent vibration damping effects near the glass transition temperature in the temperature range of room temperature or higher, they are not suitable for use due to the high temperature dependence of the loss coefficient η. In the temperature range above, the damping effect decreases rapidly.
On the other hand, rubber has a low temperature dependence of its loss coefficient η, so the vibration damping effect changes relatively little due to temperature changes. Sufficient vibration damping action cannot be obtained in the temperature range. As described above, synthetic resins and rubber have advantages and disadvantages, and even if they are used alone, an excellent vibration-damping steel plate cannot be obtained. Therefore, it has been considered to blend synthetic resin and rubber to reduce the temperature dependence of the loss coefficient η and obtain a high value of the loss coefficient η over a wide range of regions. [Problems to be Solved by the Invention] However, damping materials using a blend of synthetic resin and rubber as a viscoelastic material layer have a large loss coefficient η at the peak, but at the same time have low temperature dependence. Because of this, the intended purpose cannot be achieved. In this invention, the temperature dependence of the loss coefficient η is low,
By developing a viscoelastic material that can maintain a high loss coefficient η within the operating temperature range of vibration damping materials, it exhibits excellent vibration damping effects over a wide temperature range from low to high temperatures, which is the operating temperature range of vibration damping materials. The purpose is to provide vibration damping materials that [Means for Solving the Problems] In order to achieve the above object, the damping material of the present invention is a damping material in which a viscoelastic material layer is formed on the substrate surface of a rigid substrate, The material layer is
The composition is substantially composed of a viscoelastic reaction product obtained by reacting 5 to 80 parts by weight of component (B) with 100 parts by weight of component (A). (A) A repeating unit derived from acrylonitrile
Nitrile rubber containing 10-60% by weight. (B) An acrylic acid compound represented by the following general formula (1) or (2).

【formula】 [In formulas (1) and (2), R is a monovalent organic group. ]

In other words, the viscoelastic substance in the vibration damping material is not a simple mechanical blend of rubber and resin, but a mixture of upper nitrile rubber and acrylic represented by the general formulas (1) and (2) above. It is mainly composed of a viscoelastic reaction product with an acidic compound (monomer). In this viscoelastic reaction product, the acrylic acid compound (monomer) itself polymerizes to form a chain structure, and bonds to the double bond in the nitrile rubber molecules to form the nitrile rubber. It is thought that it constitutes a graft polymer, and this structure and
By specifying the component ratio of the graft polymer by reacting the nitrile rubber and acrylic acid compound in the above ratio, the viscoelastic reaction product can be produced in a range from low to high temperatures, which is the operating temperature range of vibration damping materials. It is thought that the material has a high loss coefficient η over a wide temperature range. Therefore, a damping material using this material exhibits an excellent damping effect in the above temperature range. The nitrile rubber used in the synthesis of the above viscoelastic reaction product is acrylonitrile copolymer (NBR), acrylonitrile-isoprene copolymer (NIR), acrylonitrile-butadiene-isoprene terpolymer (NBIR), or a combination thereof. They must be appropriately combined and contain 10 to 60% by weight of repeating units derived from acrylonitrile. That is,
10 repeating units derived from acrylonitrile
By using a nitrile rubber with 60% by weight and the balance being repeating units derived from butadiene and isoprene, the double bonds in the nitrile rubber (present in the repeating units derived from butadiene and isoprene) ) becomes appropriate, and the acrylic acid compound chain is bonded thereto to obtain a desired graft polymer. As the acrylic acid compound (monomer) to be reacted with the nitrile rubber, those represented by the following general formula (1) or (2) are used.

【formula】 [In formulas (1) and (2), R is a monovalent organic group. ]

Specific examples of the above-mentioned monovalent organic group R include alkyl groups such as methyl group, ethyl group, butyl group,
cycloalkyl group, 2-hydroxyalkyl group,
Examples include tetrahydrofurfuryl group, allyl group, glycidyl group, and dimethylamino group. Also included are residues of polyhydric alcohols such as diethyllene glycol and tetraethylene glycol. As the polymerization initiator for the above acrylic acid compound (monomer), a thermal polymerization initiator consisting of a widely used organic peroxide such as dialkyl peroxide, hydroperoxide, peroxy ester, peroxy ketal, etc. is used. It will be done. Further, as a rigid substrate on which a viscoelastic substance layer mainly composed of the above-mentioned viscoelastic reaction product is formed, a commonly used steel plate can be used.
In addition, rigid plastic plates such as FRP are also used. The damping material of the present invention is manufactured using the above-mentioned raw materials, for example, in the following manner. That is, the above nitrile rubber and acrylic acid compound (monomer) were mixed in 100 parts by weight (hereinafter "parts") of the former.
(abbreviated as )), the latter is blended in an amount of 5 to 80 parts. By doing this, in the viscoelastic reaction product obtained, the repeating unit (a) derived from the nitrile rubber and the repeating unit (b) derived from the acrylic acid compound are (on a weight basis) ( a):(b)=100:
The ratio will be 5 to 100:80. If the proportion of acrylic acid compound used is less than the above proportion, the repetition unit
When (b) falls below the above range, the viscoelastic reaction product becomes more rubbery, its loss coefficient η becomes lower in the high temperature range, and the damping effect in the high temperature range becomes smaller. On the other hand, when it exceeds the above range, the viscoelastic reaction product increases the resin properties, and its loss coefficient η becomes low near room temperature, resulting in a decrease in the damping effect near room temperature. Therefore, the ratio of repeating units (a) and (b) is set as above.
It is important to set the ratio of (a):(b) = 100:5 to 100:80, and for that purpose, it is necessary to mix the nitrile rubber and acrylic acid compound in the above ratio. be. In this case, appropriate amounts of an organic peroxide, a reinforcing filler, an anti-aging agent, and a softener are simultaneously added as a thermal polymerization initiator for the acrylic acid compound (monomer). Next, the above compound is rolled to form a thin sheet, which is sandwiched between two steel plates whose surfaces to which the viscoelastic material layer is coated are coated with a vulcanizing adhesive, and then vulcanized ( heat press). Through this vulcanization heating, the thermal polymerization initiator acts and the acrylic acid compound (monomer) is thermally polymerized and chained, and at the same time, it bonds to the double bond in the nitrile rubber molecules and grafts with the nitrile rubber. Forms a polymer and becomes a viscoelastic reaction product. As a result, the desired vibration damping steel plate is obtained. In addition, the above compound was dissolved in a known solvent to form a paste, and the paste was applied to the adhering surface of one of two steel plates whose adhering surface had been coated with a vulcanized adhesive, and then dried. Thereafter, the remaining steel plate may be stacked on top of the steel plate, and the steel plate may be vulcanized (heat pressed) and crimped in this state. In this case, a damping steel plate having an extremely thin layer of viscoelastic material is obtained. Note that the viscoelastic material layer is not only formed between two steel plates as described above, but may also be formed on one steel plate. In this case as well, an excellent vibration damping effect can be obtained due to the action of the viscoelastic material layer. [Effects of the Invention] As described above, in this invention, the viscoelastic material layer for exerting a vibration damping effect is not composed of a simple blend of rubber and resin, but is composed of a nitrile rubber and an acrylic acid compound. Since it is constructed using a viscoelastic reaction product obtained by reacting with and in the above ratio, the loss coefficient η of the viscoelastic reaction product continues to maintain its peak from a low temperature to a high temperature. Therefore, a damping material using the viscoelastic reaction product exhibits the maximum damping effect at any temperature within the above temperature range. In particular, the loss coefficient η of the viscoelastic reaction product is 100
Since the peak is almost maintained up to a high temperature range exceeding ℃, the maximum vibration damping effect is exhibited over a wide temperature range from low to high temperatures. This can be said to be an extremely important effect considering that vibration damping materials are often used in automobiles and the like that are used in a wide temperature range from extremely cold regions to extremely hot regions. Furthermore, since the viscoelastic reaction product uses nitrile rubber, which is highly oil resistant, it is also highly oil resistant, and therefore, the vibration damping material of the present invention is highly practical. Further, since the viscoelastic reaction product has excellent mechanical strength, the damping material of the present invention can sufficiently withstand mechanical processing such as shearing. Next, examples will be described together with comparative examples. Examples 1 to 6, Comparative Examples 1 and 2 The raw materials shown in Table 1 below were blended in the proportions shown in the same table, and the blend was kneaded using a Banbury mixer and passed through a forming roll to a thickness of 0.4 It was formed into a sheet of mm. This is applied to two steel plates (thickness:
0.7 mm) and heat pressed (vulcanized) at 150°C for 10 minutes to obtain a vibration damping steel plate. The structure of the obtained damping steel plate is shown in Figure 2. In the figure, 1 is a steel plate, 2
is a viscoelastic material layer.

【table】

[Table] The damping steel plate obtained as above was
Cut into lengths of 300 mm and measure the loss coefficient η at each temperature (frequency 500 Hz) using the mechanical impedance method.
was measured, and the loss coefficient η-temperature curve is shown in FIG. In the figure, curve A represents Examples 1 and 4, curve B represents Examples 3 and 5, curve C represents Example 6, and curve D
are Comparative Examples 1 and 2, and curve E is that of a commercially available damping steel plate using an ethylene-vinyl acetate copolymer resin as the viscoelastic material layer. From the comparison between curves A and B and curves D and E, the vibration damping steel plates of Examples 1, 4, 3 and 5 are as follows:
Compared to the comparative example, it exhibits a peak or near-peak loss coefficient η over a wide temperature range from low to high temperatures (100°C), indicating that it can exhibit the maximum damping effect within that temperature range. . However, although the performance of Example 6 (curve C) is slightly inferior to the above-mentioned Examples 1, 4, 3, and 5 in the low temperature range, it is said that it can be put to practical use if the above-mentioned loss coefficient η is 0.03 or more. Therefore, it can be said that it maintains practicality.

[Brief explanation of the drawing]

Fig. 1 is a loss coefficient η vs. temperature curve diagram of rubber and resin, Fig. 2 is a sectional view explaining the structure of an example product of the present invention, and Fig. 3 is an explanatory diagram explaining its loss coefficient η vs. temperature curve. It is. 1... Steel plate, 2... Viscoelastic material layer.

Claims (1)

[Scope of Claims] 1. A vibration damping material in which a viscoelastic material layer is formed on the substrate surface of a rigid substrate, wherein the viscoelastic material layer has the following:
A vibration damping material characterized in that it is substantially composed of a viscoelastic reaction product obtained by reacting 5 to 80 parts by weight of component (B) with 100 parts by weight of component (A). (A) A repeating unit derived from acrylonitrile
Nitrile rubber containing 10-60% by weight. (B) An acrylic acid compound represented by the following general formula (1) or (2). [Formula] [Formula (1) and (2), R is a monovalent organic group. 2. The damping material according to claim 1, wherein the rigid substrate is a steel plate.