JP5759399B2 - Anti-vibration rubber composition and anti-vibration rubber member - Google Patents

Description

  The present invention relates to an anti-vibration rubber member suitable for an engine mount for automobiles and the like, and an anti-vibration rubber composition for producing the same.

  In a vehicle such as an automobile, a vibration-proof rubber member is disposed at a site that is a source of vibration and noise to reduce vibration transmission and noise diffusion. This type of anti-vibration rubber member is required to have a strength for supporting heavy objects such as an engine and an anti-vibration performance that absorbs and suppresses vibration. One of the characteristics showing the anti-vibration performance is dynamic magnification. The dynamic magnification is the ratio of the dynamic spring constant to the static spring constant (dynamic spring constant (Kd) / static spring constant (Ks)), and the smaller the dynamic magnification, the higher the anti-vibration performance.

  As a material for the vibration-proof rubber member, natural rubber is mainly used because of its high tensile strength and low heat generation due to vibration. And various improvement is made | formed about the composition (anti-vibration rubber composition) containing a natural rubber in order to aim at the intensity | strength improvement of a vibration-proof rubber member, or low dynamic magnification (for example, refer patent documents 1-4). ).

Japanese Patent Laying-Open No. 2005-187583 JP 2006-143859 A JP 2006-193617 A JP 2009-30037 A

  Usually, carbon black, silica and the like are blended in the vibration-proof rubber composition as a reinforcing material. The greater the compounding amount of the reinforcing material, the greater the hardness of the resulting crosslinked product (anti-vibration rubber member) and the greater the strength (static spring constant). However, as the blending amount of the reinforcing material increases, the friction of the reinforcing material due to vibration increases, so that the energy loss increases and the dynamic magnification increases.

  On the other hand, the dynamic magnification varies depending on the particle diameter of the reinforcing material to be blended. For example, when carbon black is blended, the dynamic magnification can be made relatively small by increasing the particle diameter without changing the blending amount. However, the reinforcing effect of carbon black is reduced by increasing the particle size. For this reason, it is difficult to obtain a desired strength. On the contrary, when the particle size of the carbon black is reduced, the reinforcing effect is increased. For this reason, the strength of the anti-vibration rubber member is improved. However, loss due to friction between carbon blacks or between carbon black and polymer increases, and the dynamic magnification increases. Thus, in the vibration-proof rubber member, the improvement in strength and the reduction in dynamic magnification are in a trade-off relationship, and it is difficult to realize both of them. That is, it is difficult to reduce the dynamic magnification without reducing the strength only by adjusting the blending amount and particle diameter of the reinforcing material.

  The present invention has been made in view of such circumstances, and provides a vibration-proof rubber member having a reduced dynamic magnification without reducing strength, and a vibration-proof rubber composition capable of producing the same. Let it be an issue.

  (1) In order to solve the above-mentioned problems, the vibration-proof rubber composition of the present invention is characterized by containing a solid natural rubber having a nitrogen content of 0.6% by mass or more, a reinforcing material, and a crosslinking agent.

  Generally, solid natural rubber distributed as a raw material for producing rubber products is roughly classified into visual rating rubber (VGR) and technical rating rubber (TSR). A representative example of VGR is a smoke sheet (RSS) based on a rating based on “International Quality Packaging Standard for Natural Rubber Grades (commonly called Green Book)”. For example, RSS is manufactured as follows. First, after adding acid such as formic acid or acetic acid to the field latex and coagulating it, it is placed on a work table and stretched with a stick to adjust the thickness. Subsequently, the water is squeezed while being stretched by a corrugated (rib-shaped) roll, and formed into a sheet shape. Next, the molded sheet is hung for several days and dried. Then, the dried smokeless sheet (USS) is washed with water, smoked and dried for several days. TSR is manufactured by washing raw materials such as cup lamps (field latex naturally solidified in a collection cup) with pulverization, repeatedly passing the pulverized product through a roll and squeezing out moisture, and then drying with hot air. The

  Thus, solid natural rubber is manufactured through processes such as coagulation of natural rubber latex, squeezing out water from the coagulum, and washing with water. On the other hand, natural rubber includes non-rubber components such as proteins and lipids in addition to rubber components. Among these non-rubber components, water-soluble ones such as proteins flow out together with moisture when squeezing out or washing with water. As a result of investigation by the present inventor, it has been found that when the amount of protein is small, the function inherent to natural rubber is not sufficiently exhibited when a rubber product is produced.

  In this regard, in the vibration-proof rubber composition of the present invention, a solid natural rubber having a nitrogen content of 0.6% by mass or more is used as the rubber component. In this specification, the value measured by "2400II fully automatic elemental analyzer (CHNS / O)" of Perkin Elmer is adopted as nitrogen content. Nitrogen in solid natural rubber is mainly derived from proteins. For this reason, it is thought that more protein is contained, so that there is much nitrogen content. Incidentally, the nitrogen content of the solid natural rubber obtained by the conventional method of washing with water or the like is about 0.5% by mass.

  In the vibration-proof rubber composition of the present invention, solid natural rubber having a large amount of residual protein is used. For this reason, according to the vibration-insulating rubber composition of the present invention, the function inherent to natural rubber can be sufficiently exerted. Specifically, when the vibration-insulating rubber composition of the present invention is crosslinked, the crosslinking rate and the crosslinking density are increased. There are two possible reasons for this. One is that when sulfur is used as the cross-linking agent, the protein becomes a vulcanization accelerator and accelerates the reaction between the rubber component and sulfur. The other is that the protein itself serves as a cross-linking agent and a new cross-linked structure is formed via the protein. Moreover, according to the vibration-insulating rubber composition of the present invention, the strength of the obtained cross-linked product (vibration-proof rubber member) is increased. The reason is considered that protein functions as a reinforcing material for natural rubber. That is, in addition to the reinforcing effect of the protein itself, it is considered that the protein is bridged between the carbon black blended as a reinforcing material and the natural rubber, thereby strengthening the bond between the two.

  Therefore, according to the anti-vibration rubber composition of the present invention, the anti-vibration rubber member having high strength even if the dynamic ratio is reduced by reducing the amount of the reinforcing material, for example, due to the reinforcing effect of the protein originally contained in the natural rubber. Can be manufactured. That is, the dynamic magnification can be reduced at the same strength as compared with the conventional vibration-proof rubber member. Further, the strength can be increased at the same dynamic magnification.

  (2) The anti-vibration rubber member of the present invention is obtained by crosslinking the anti-vibration rubber composition of the present invention having the constitution (1).

  As described in (1) above, according to the vibration-insulating rubber member of the present invention, it is possible to achieve a low dynamic magnification while maintaining a desired strength due to the reinforcing effect of the protein originally contained in the natural rubber.

It is a graph which shows the value of the dynamic magnification with respect to a static spring constant.

  Hereinafter, the anti-vibration rubber composition and anti-vibration rubber member of the present invention will be described in detail.

<Anti-Vibration Rubber Composition>
The anti-vibration rubber composition of the present invention includes a solid natural rubber having a nitrogen content of 0.6% by mass or more, a reinforcing material, and a crosslinking agent. Solid natural rubber is produced by drying natural rubber latex. As the natural rubber latex, a field latex collected by tapping or a latex (high ammonia latex) treated with ammonia added thereto may be used. Also, in order to increase the nitrogen content of the solid natural rubber to 0.6% by mass or more, unlike the conventional method, the natural rubber latex is not performed without coagulating the natural rubber latex, squeezing out the water of the coagulated product, and washing with water. Need to be dried. By doing so, the outflow of protein which is a water-soluble non-rubber component is suppressed. That is, the protein originally contained in the natural rubber can be left. It is more preferable that the nitrogen content of the solid natural rubber is 0.7% by mass or more.

  The method for drying the natural rubber latex is not particularly limited. For example, natural rubber latex may be heated in an oven and dried. In consideration of degradation of natural rubber due to heat and productivity, it is desirable to apply natural rubber latex to a heated substrate or to spray and dry it. In this way, the drying time can be shortened. Therefore, thermal degradation of natural rubber can be suppressed, and productivity is improved. Among these, a method of spraying natural rubber latex is desirable. The sprayed natural rubber latex adheres to the substrate surface in the form of dots. For this reason, compared with the case where it apply | coats to the base-material surface, a specific surface area becomes large and it is easy to dry. Therefore, the natural rubber latex can be dried in a shorter time.

  The shape of the substrate is not particularly limited. For example, a rotating member such as a drum may be used as the base material. In this case, natural rubber latex is sprayed onto the heated endless annular surface (for example, the outer peripheral surface of the drum) of the rotating member, and the coating liquid is dried while rotating the endless annular surface. And what is necessary is just to peel the obtained solid natural rubber from an endless annular surface in order. By doing so, it is possible to automate a series of steps of spraying natural rubber latex → drying → peeling solid natural rubber. Therefore, productivity is greatly improved.

  The temperature of the substrate surface is desirably in the range of 120 ° C. or higher and 200 ° C. or lower. If the temperature of the substrate surface is too low, the natural rubber latex cannot be sufficiently dried in a practical drying time. On the other hand, if the temperature of the substrate surface is too high, the attached natural rubber latex may be excessively heated and deteriorated.

  As the reinforcing material, carbon black, silica, or the like usually used for a vibration-proof rubber member may be used. As the carbon black, various grades such as SAF class, ISAF class, HAF class, MAF class, FEF class, GPF class, SRF class, FT class, MT class and the like can be used. Any of these may be used alone or in admixture of two or more. The blending amount of carbon black is desirably 10 parts by mass or more and 140 parts by mass or less. In consideration of the balance between strength and dynamic magnification, 20 parts by mass or more and 70 parts by mass or less is more preferable.

  As the cross-linking agent, sulfur (powder sulfur, precipitated sulfur, insoluble sulfur, etc.) or organic peroxide usually used for cross-linking of natural rubber may be used. When sulfur is used as the crosslinking agent, the amount of sulfur is preferably 0.2 parts by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the solid natural rubber. More preferably, it is 0.3 to 5 parts by mass. If the amount of sulfur is small, crosslinking cannot proceed sufficiently, and the dynamic magnification may increase. On the other hand, when the amount of sulfur is large, the number of crosslinking points increases and the crosslinking density increases. However, the crosslinking point is easily cut by heat. For this reason, when there is much compounding quantity of sulfur, there exists a possibility that the heat resistance of a crosslinked material (vibration-proof rubber member) may fall. In this respect, according to the solid natural rubber having a nitrogen content of 0.6% by mass or more, a cross-linked product having a high cross-linking density can be produced as the amount of residual protein is large. Therefore, while maintaining the crosslinking density, it is possible to improve the heat resistance of the vibration-proof rubber member by reducing the amount of sulfur as compared with the conventional one.

  The anti-vibration rubber composition of the present invention may further contain additives such as a vulcanization accelerator, zinc oxide, a processing aid, an antiaging agent, and a softening agent. As the vulcanization accelerator, known vulcanization accelerators such as thiazole, sulfenamide, thiuram, aldehyde ammonia, aldehyde amine, guanidine, thiourea, etc. may be used. Of these, sulfenamide-based vulcanization accelerators are preferred in that they have excellent crosslinking reactivity. As the processing aid, stearic acid, magnesium oxide or the like may be used. As the anti-aging agent, anti-aging agents such as carbamate-based, phenylene diamine-based, phenol-based, diphenylamine-based, quinoline-based, imidazole-based, etc., wax or the like may be used. As the softening agent, naphthenic oil, paraffinic oil, aroma oil or the like may be used.

  The anti-vibration rubber composition of the present invention, in addition to solid natural rubber, reinforcing material, and cross-linking agent, by blending additives as necessary, by kneading using a Banbury mixer, kneader, roll, etc. What is necessary is just to prepare.

<Anti-vibration rubber member>
The anti-vibration rubber member of the present invention is formed by crosslinking the anti-vibration rubber composition of the present invention. That is, the anti-vibration rubber member of the present invention is produced by crosslinking the prepared anti-vibration rubber composition by holding it at a temperature of, for example, 140 to 180 ° C. for 5 to 30 minutes. The anti-vibration rubber member of the present invention includes an engine mount, a mission mount, a body mount, a cab mount, a member mount, a differential mount, a connecting rod, a torque rod, a strut bar cushion, a center bearing support, and a torsional damper disposed in a vehicle such as an automobile. Suitable for steering rubber coupling, tension rod bush, bound stopper, FF engine roll stopper, muffler hanger, stabilizer ring rod, radiator support, control arm bush, suspension arm bush, etc.

  Next, the present invention will be described more specifically with reference to examples.

<Manufacture of solid natural rubber>
As the natural rubber latex, one obtained by adding 0.5% by mass of ammonia to a field latex collected by tapping from para rubber tree was used. First, natural rubber latex was sprayed on the outer peripheral surface of a rotating drum and dried. The rotation speed of the drum is about 1 rpm (about 1 rotation per minute), and the outer peripheral surface of the drum is heated to about 180 ° C. in advance. The sprayed droplets of natural rubber latex are bonded together while being dried with the rotation of the drum, and are solidified into a sheet. Next, when the drum was rotated about 3/4, the formed sheet was peeled from the outer peripheral surface of the drum. Thus, solid natural rubber was manufactured by repeating a series of steps of spraying natural rubber latex → drying → peeling the solid natural rubber sheet. The nitrogen content in the obtained solid natural rubber was measured by “2400II fully automatic elemental analyzer (CHNS / O)” manufactured by Perkin Elmer, and found to be 0.7% by mass.

<Preparation of anti-vibration rubber composition>
[Example 1]
First, 100 parts by weight of the manufactured solid natural rubber, 5 parts by weight of zinc oxide (made by Sakai Chemical Industry Co., Ltd.), and a processing aid stearic acid ("Lunac (registered trademark) S30" manufactured by Kao Corporation) ) 2 parts by weight, 1 part by weight of “Ozonon (registered trademark) 6C” (manufactured by Seiko Chemical Co., Ltd.), 1 part by weight of “Nonflex (registered trademark) RD (manufactured by the company)”, and “Sannokku” (Registered trademark) "(Ouchi Shinsei Chemical Co., Ltd.) 2 parts by mass, FEF grade carbon black (Tokai Carbon Co., Ltd." Seast SO ") 30 parts by mass, softener naphthenic oil (Idemitsu) 3 parts by mass of “Diana (registered trademark) process oil NM-300” manufactured by Kosan Co., Ltd. and 2 parts by mass of “Noxeller (registered trademark) CZ” (manufactured by Ouchi Shinsei Chemical Co., Ltd.) as a vulcanization accelerator , And "Sunseller (R) TT" ( 1 part by mass of Shin Kagaku Kogyo Co., Ltd. and 1 part by mass of sulfur (“Sulfax T-10” manufactured by Tsurumi Chemical Co., Ltd.) are kneaded using a roll to obtain an anti-vibration rubber composition. Prepared. The prepared anti-vibration rubber composition was used as the anti-vibration rubber composition of Example 1.

[Example 2]
An antivibration rubber composition of Example 2 was prepared in the same manner as in Example 1 except that the amount of carbon black was changed to 40 parts by mass.

[Example 3]
An antivibration rubber composition of Example 3 was prepared in the same manner as in Example 1 except that the amount of carbon black was changed to 50 parts by mass.

[Comparative Example 1]
The anti-vibration rubber of Comparative Example 1 was the same as Example 1 except that a solid natural rubber “RSS # 3” produced by a conventional method was used instead of the produced solid natural rubber. A composition was prepared. The nitrogen content in the solid natural rubber used was 0.5% by mass.

[Comparative Example 2]
An anti-vibration rubber composition of Comparative Example 2 was prepared in the same manner as Comparative Example 1 except that the amount of carbon black was changed to 40 parts by mass.

[Comparative Example 3]
An anti-vibration rubber composition of Comparative Example 3 was prepared in the same manner as Comparative Example 1 except that the amount of carbon black was changed to 50 parts by mass.

Table 1 shows the raw materials of the vibration-insulating rubber compositions of Examples 1 to 3 and Comparative Examples 1 to 3.

<Production and evaluation of cross-linked product>
The prepared anti-vibration rubber composition was crosslinked at 160 ° C. for 30 minutes to produce a crosslinked product. And the test piece which consists of the said crosslinked material was produced for every following evaluation items, and the characteristic of the crosslinked material was evaluated.

[Tensile properties]
The anti-vibration rubber composition was press-molded under the above conditions to produce a rubber sheet (crosslinked product) having a thickness of 2 mm. The rubber sheet was punched out to produce a dumbbell-shaped No. 5 test piece defined in JIS K 6251 (2010). Using the prepared test piece, the tensile strength at break (TS _b ) and the elongation at break (E _b ) were measured according to the tensile test method defined in the JIS. The measurement results are summarized in Table 1.

  As shown in Table 1, the cross-linked product prepared from the anti-vibration rubber compositions of Examples 1 to 3 (hereinafter referred to as “the cross-linked product of Examples 1 to 3”) is a comparison using conventional solid natural rubber. It was confirmed to have excellent tensile properties in the same manner as the cross-linked product prepared from the anti-vibration rubber compositions of Examples 1 to 3 (hereinafter referred to as “cross-linked product of Comparative Examples 1 to 3”).

[Hardness]
The anti-vibration rubber composition was press-molded under the above conditions to produce a rubber sheet (crosslinked product) having a thickness of 6 mm. Using the rubber sheet, the type A durometer hardness defined in JIS K 6253 (2006) was measured. The measurement results are summarized in Table 1.

  As shown in Table 1, in any of the examples and comparative examples, the hardness increased with an increase in carbon black. Moreover, when the thing with the same compounding quantity of carbon black was compared, it was confirmed that the hardness of the crosslinked material of Examples 1-3 is larger than that of the crosslinked material of Comparative Examples 1-3.

[Dynamic characteristics]
A cylindrical rubber piece (diameter 50 mm, height 25 mm) was produced from the vibration-proof rubber composition. By placing disc-shaped metal fittings (diameter 60 mm, thickness 6 mm) one by one on the two bottom surfaces of the rubber pieces and pressing them under the above conditions, the rubber pieces are vulcanized and the metal fittings are attached to both bottom surfaces. Glued. In this manner, a test piece in which a columnar cross-linked product was sandwiched between a pair of metal fittings was produced. Using the prepared test piece, the static spring constant and the dynamic spring constant of the crosslinked product were calculated according to the test method defined in JIS K6385 (2001). That is, a load was applied from the axial direction, the test piece was compressed by 7 mm, and then unloaded and restored. Then, the load was applied again and the test piece was compressed 7 mm. At that time, a load-deflection curve in the process of applying the load is created, and the static spring constant (Ks) is calculated by reading the load value when the deflection is 1.5 mm and 3.5 mm from the load-deflection curve. did. Further, in a state where the test piece was compressed 2.5 mm in the axial direction, constant displacement harmonic compression vibration having an amplitude of 0.05 mm centered on the compression position was applied at a frequency of 100 Hz. Then, the dynamic spring constant (Kd ₁₀₀ ) at ₁₀₀ Hz was calculated by a non-resonant method (cited JIS K6394) defined in the above JIS. The dynamic magnification was calculated by dividing the dynamic spring constant by the static spring constant (Kd ₁₀₀ / Ks). The measurement results are summarized in Table 1. FIG. 1 is a graph showing the value of the dynamic magnification with respect to the static spring constant.

  As shown in Table 1 and FIG. 1, in the examples and the comparative examples, when the same amount of carbon black is compared, the crosslinked product of the example is more static spring than the crosslinked product of the comparative example. The constant has increased. That is, the strength increased. Moreover, it can be seen from the graph of FIG. 1 that when the static spring constant is the same, the cross-linked product of the example has a smaller dynamic magnification than the cross-linked product of the comparative example.

  The cross-linked products of Examples 1 to 3 are made from an anti-vibration rubber composition containing a solid natural rubber having a nitrogen content of 0.7% by mass. For this reason, even if the blending amount of carbon black is small, the strength is increased due to the reinforcing effect of the protein originally contained in the natural rubber. Therefore, even when the strength was the same as that of the crosslinked products of Comparative Examples 1 to 3, the dynamic magnification was reduced because the amount of carbon black was small.

  From the above, it was confirmed that according to the vibration-proof rubber composition of the present invention, a crosslinked product (vibration-proof rubber member) having a small dynamic magnification can be produced without reducing the strength. Moreover, it was confirmed that the vibration-insulating rubber member of the present invention has both strength and low dynamic magnification.

Claims (4)

Solid natural rubber obtained by spraying natural rubber latex onto the heated substrate surface to adhere the natural rubber latex to the substrate surface in the form of dots and drying without causing the water-soluble non-rubber component to flow out , An anti-vibration rubber composition comprising a reinforcing material and a crosslinking agent.   The anti-vibration rubber composition according to claim 1, wherein the solid natural rubber is produced by drying without solidifying the natural rubber latex, squeezing out water from the coagulated product, and washing with water. The reinforcing material is carbon black,
The vibration-insulating rubber composition according to claim 1 or 2, wherein the amount of the carbon black is 10 parts by mass or more and 140 parts by mass or less with respect to 100 parts by mass of the solid natural rubber.   An anti-vibration rubber member obtained by crosslinking the anti-vibration rubber composition according to any one of claims 1 to 3.

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