JPH0564590B2 - - 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 noise 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 extremely cold and extremely hot regions. ) is required to exhibit excellent vibration damping effects even in extremely high temperature ranges. 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. Synthetic resin is
Since it has a unique viscoelastic characteristic, that is, the elastic modulus and the loss coefficient η have a large temperature dependence, a damping steel plate composed of such a synthetic resin as a viscoelastic material layer has a large temperature dependence of the elastic modulus and the loss coefficient η. It has a large temperature dependence, has a sharp peak near the glass transition temperature (usually at room temperature or higher), and has the disadvantage that the temperature range in which it exhibits a damping effect is narrow. . 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 substance 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. [Problems to be solved by the invention] As described above, since synthetic resins and rubber have the loss coefficient η-temperature characteristics as described above, conventional vibration damping steel plates using them as viscoelastic substances have However, the damping effect could not be achieved over a wide temperature range from low to high temperatures, and could only be achieved within a relatively narrow temperature range. An object of the present invention is to provide a vibration damping material that exhibits an excellent vibration damping effect in a wide temperature range from low to high temperatures. [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
A viscoelastic reaction product obtained by reacting 5 to 80 parts by weight of component (B) to 100 parts by weight of component (A), and 5 to 80 parts by weight of component (A) in the above viscoelastic reaction product.
The non-thermosetting phenolic resin is blended in proportions of parts by weight. (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). [In formulas (1) and (2), R is a monovalent organic group. ] In other words, the viscoelastic material layer in the damping material is made of a viscoelastic reaction product of the nitrile rubber and the acrylic acid compound (monomer) represented by the general formulas (1) and (2) above, as well as non-containing material. Mainly composed of thermosetting phenolic resin. This viscoelastic reaction product is produced by the polymerization and chaining of the acrylic acid compound (monomer) during the production reaction, and the bonding of the resulting chain to the double bond in the nitrile rubber molecular chain. As a result, it is a graft polymer, and due to this molecular structure and the specification of the component ratio of the graft polymer by reacting the nitrile rubber and acrylic acid compound at the above ratio, it has a high loss from low to high temperatures. Indicates the coefficient η. By blending the non-thermosetting phenolic resin, which is highly compatible with the viscoelastic reaction product, in the specific ratio described above, the absolute value of the loss coefficient η at each of the temperatures described above is improved. , the peak temperature of the loss coefficient η shifts to the high temperature side, and at the same time, the temperature dependence of the loss coefficient η at high temperatures decreases, making it possible to obtain the effect of keeping the value of η constant in the high temperature range. Therefore, a damping material using this material exhibits a strong damping effect throughout the above temperature range, especially in the high 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. [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 diethylene 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. The non-thermosetting phenolic resin to be blended with the viscoelastic reaction product is a novolac type phenolic resin or a modified resin thereof. This type of resin has good compatibility with the viscoelastic reaction products mentioned above, and when thermosetting phenolic resin (resol type phenolic resin) is used, curing is accelerated by heating, making the viscoelastic body hard. However, by blending the viscoelastic reaction product in the above ratio, the elastic modulus can be increased appropriately, and the peak temperature of the loss coefficient η can be lowered. This shifts the temperature to the high temperature side and at the same time reduces the temperature dependence of the loss coefficient η at high temperatures. Among various novolak type phenolic resins and their modified resins, the expression of such effects is
In particular, cashew-modified novolak type phenolic resin is notable, and it is preferable to use this. Further, as the rigid substrate on which the viscoelastic substance layer is formed, a commonly used steel plate may be used, but a rigid plastic plate such as FRP may also be used. The vibration 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.
5 to 80 parts of the latter to 100 parts of nitrile rubber. By setting the mutual ratio of the nitrile rubber and the acrylic acid compound as described above, the repeating unit (a) derived from the nitrile rubber is contained in the viscoelastic reaction product obtained by the reaction of the two. and the repeating unit (b) derived from an acrylic acid compound in a ratio of (a):(b)=100:5 to 100:80 on a weight basis. When the proportion of the acrylic acid compound used is below the above range, the repeating unit (b) is below the above range, the viscoelastic reaction product becomes more rubbery, and its loss coefficient η becomes lower in the high temperature range. Therefore, the damping effect in high temperature range becomes smaller. On the other hand, when the temperature exceeds the above range, the viscoelastic reaction product becomes more resinous, its loss coefficient η becomes lower near room temperature, and the damping effect at room temperature becomes smaller. Therefore, the repetition unit (a)
and (b) as above, (a):(b)=100:5 ~
It is important to set the ratio to 100:80, and for that purpose, it is necessary to mix the nitrile rubber and the acrylic acid compound in the above ratio.
In addition, by blending a non-thermosetting phenolic resin in the above ratio, repeating units derived from nitrile rubber in the molecular chain of the viscoelastic reaction product can be obtained.
For (a), the amount of non-thermosetting phenolic resin is 5 to 5.
It becomes 80% by weight (hereinafter abbreviated as "%"). When blending the nitrile rubber, acrylic acid compound, and non-thermosetting phenolic resin as described above, at the same time, an organic peroxide and a reinforcing filler, which serve as a thermal polymerization initiator for the acrylic acid compound (monomer), Add appropriate amounts of anti-aging agents and softeners.
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. A polymer is formed, and a viscoelastic material layer is formed together with the non-thermosetting phenolic resin coexisting therewith. As a result, the desired vibration damping steel plate is obtained. In addition, two sheets are prepared by dissolving the above-mentioned compound of nitrile rubber, acrylic acid compound, non-thermosetting phenolic resin, etc. in a known solvent to form a paste, and then applying a vulcanized adhesive to the adhering surface. One of the steel plates of
After the coating is applied to the adherend surface of the sheet and dried, the remaining steel sheet may be stacked on top of the sheet and vulcanized (heat pressed) and pressure bonded in that 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, the present invention provides a viscoelastic material layer for exhibiting a vibration damping effect with a viscoelastic material layer having a graft structure in which a nitrile rubber and an acrylic acid compound are reacted in the above ratio. It is mainly composed of a mixture of a reaction product and a non-thermosetting phenolic resin at a predetermined ratio, and the viscoelastic reaction product exhibits a high loss coefficient η from low to high temperatures, and the non-thermosetting phenolic resin Since the resin improves the absolute value of the loss coefficient η at each temperature, shifts the peak temperature of the loss coefficient η to higher temperatures, and reduces the temperature dependence of η at high temperatures, the value of the loss coefficient η increases. becomes higher overall, and continues to maintain its peak in a wide temperature range from the low temperature side to the high temperature side. Therefore, a vibration damping material using the above compound exhibits a strong vibration damping effect at any temperature within the above temperature range. In particular, the loss coefficient η of the above-mentioned compound uniformly shows a peak value or a value near it in a wide temperature range on the high temperature side.
The strong resonance effect is maximized in the high temperature range, and this is because the damping material is used in automobile engine compartments, etc.
This can be said to be an extremely important effect considering that it is often used in areas where temperatures reach around 120°C. Furthermore, since the above-mentioned compound contains 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 above-mentioned compound has excellent mechanical strength, etc., the vibration 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 9, 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. It was formed into a sheet with a thickness of 0.4 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] 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 curves are shown in FIGS. 3 and 4. In these figures, curves A to I correspond to Examples 1 to 9, curve J corresponds to Comparative Example 1, curve K corresponds to Comparative Example 2, and curve L corresponds to Comparative Example 2 using ethylene-vinyl acetate copolymer resin as the viscoelastic material layer. This is a commercially available damping steel plate. Comparison of curves A to I and curves J to K shows that the damping steel plates of the examples all have high loss coefficients in a wide temperature range from low to high temperatures (150°C), unlike those of the comparative examples. η, and its loss coefficient η is uniform, especially in the high temperature range, and shows a value at or near the peak, indicating that it can exhibit a particularly strong vibration damping effect within that temperature range. It is said that the above-mentioned loss coefficient η of 0.03 or more is usable for practical use, and the example products far exceed this value in all temperature ranges.

[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 this invention, and Figs. 3 and 4 are loss coefficient η.
- It is an explanatory diagram explaining a temperature curve. 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 viscoelastic reaction product obtained by reacting 5 to 80 parts by weight of component (B) to 100 parts by weight of component (A), and 5 to 80 parts by weight of component (A) in the above viscoelastic reaction product.
1. A vibration damping material, characterized in that it is substantially composed of a non-thermosetting phenolic resin blended in proportions of parts by weight. (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). [In formulas (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. 3. The damping material according to claim 1 or 2, wherein the non-thermosetting phenolic resin is a cashew-modified novolac type phenolic resin.