Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-12-27
2004-11-02
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S208000, C525S209000, C525S217000, C525S232000, C525S241000
Reexamination Certificate
active
06812288
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rubber composition, a vibration-isolating rubber and a vibration-isolating mount; and more specifically, the invention relates to a vibration-isolating rubber that has excellent vibration-isolating properties, not previously obtained, and a corresponding rubber composition, as well as a vibration-isolating mount comprising this vibration-isolating rubber.
2. Description of the Related Art
A vibration-isolating rubber having a low dynamic-to-static modulus ratio and a large loss factor is desired, but a vibration-isolating rubber which sufficiently satisfies such performance has not been obtained yet. In the automobile industry and the like, a vibration-isolating rubber mount encapsulating a liquid is known. This “liquid encapsulated-type” vibration-isolating rubber mount has a complicated structure, and its vibration-isolating effect shows only one direction. Furthermore, it is expensive. So a vibration-isolating rubber mount which does not encapsulate a liquid is desired. Hitherto, a vibration-isolating rubber having a low dynamic-to-static modulus ratio and high loss factor has been disclosed in JP-A-7-216136, JP-A-11-222536, and the like.
However, the performance of the disclosed vibration-isolating rubber is not superior to a liquid-encapsulated type vibration-isolating mount. That is, when the value of a loss factor is large, the value of the dynamic-to-static modulus ratio becomes large, and when the value of a dynamic-to-static modulus ratio is small, the value of the loss factor becomes small.
In addition, as described in the following paragraphs (1) to (3), it is extremely difficult to overcome a linear relationship between a loss factor and a dynamic-to-static modulus ratio by using a rubber mount encapsulating no liquid, and it is extremely difficult to realize a vibration-isolating rubber comparable to a liquid-encapsulated mount at present (see “Kogyo Zairyo (Industrial materials)”, November, 1997, (Vol. 45, No. 12), page 36, left column, lines 4 to 9, same page, left column, line 26 to same page, right column, line 4, same page, right column lines 9 to 14).
(1) “It can be said that a smaller dynamic-to-static modulus ratio and a higher damping property provides high performance engine mount. However since a conventional rubber shows an almost linear relationship between the dynamic-to-static modulus ratio and the damping property as shown in
FIG. 2
, both properties could not be improved at the same time.”
(2) “Although it is impossible to realize an excellent rubber mount comparable to a liquid-encapsulated type vibration-isolating rubber mount by itself, an efficient vibration isolating rubber mount encapsulating no liquid is a theme of development based on balance with the cost. As shown in
FIG. 2
, the conventional blending technique can not solve this theme.”
(3) “In the past, very few polymers have been developed for a vibration-isolating rubber, and a natural rubber is dominantly used currently. It is desired to realize a polymer for the vibration-isolating rubber which optimizes a low dynamic-to-static modulus ratio and a high damping.”
As mentioned above, it is desired that a vibration-isolating rubber and a vibration-isolating mount have higher performance than the abovementioned vibration-isolating rubbers.
The present invention provides a rubber composition which provides a vibration-isolating rubber, having a higher performance than that of the conventional rubbers, a vibration-isolating rubber and a vibration-isolating mount.
SUMMARY OF THE INVENTION
The present inventors have found that a high performance vibration-isolating rubber is obtained from a rubber composition comprising two or more rubbers having specific weight-average molecular weights and specific glass transition temperatures, leading to the present invention, which is based on such findings.
The present invention is based on the findings described above and can be described as follows.
[1]. A rubber composition characterized in comprising 5 to 40 parts by weight of a styrene-butadiene-based copolymer rubber (A), having a weight-average molecular weight of 200,000 or less, and a glass transition temperature of −35° C. or higher, and 95 to 60 parts by weight of a diolefin-based rubber (B), having a weight-average molecular weight exceeding 200,000 and a glass transition temperature of −20° C. or lower. The weights are based on 100 parts by weight of the total amount of (A) and (B).
[2]. The rubber composition according to [1] above, wherein the diolefin-based rubber (B) is at least one rubber selected from the group consisting of a styrene-butadiene copolymer rubber, a butadiene rubber, an isoprene rubber and a natural rubber.
[3]. The rubber composition according to [2] above, wherein a weight-average molecular weight of the styrene-butadiene-based copolymer rubber (A) is 500 to 80,000.
[4]. The rubber composition according to [3] above, further comprising 10 to 200 parts by weight of a filler, based on 100 parts of the total amount of the styrene-butadiene-based copolymer rubber (A) and the diolefin-based rubber (B).
[5]. The rubber composition according to [3] above, wherein the styrene-butadiene-based copolymer rubber (A) is hydrogenated at 50% or more.
[6]. The rubber composition according to [5] above, further comprising 10 to 200 parts by weight of a filler, based on 100 parts of the total amount of the styrene-butadiene-based copolymer rubber (A) and the diolefin-based rubber (B).
[7]. The rubber composition according to [2] above, wherein the diolefin-based rubber (B) is at least one rubber selected from the group consisting of a modified diolefin-based rubber having at least one functional group selected from the group consisting of amino group, alkoxysilyl group, epoxy group and hydroxyl group, and a modified diolefin-based rubber obtained by reacting a diolefin-based rubber with a tin compound or a silicon compound.
[8]. The rubber composition according to [7] above, further comprising 10 to 200 parts by weight of a filler, based on 100 parts of the total amount of the styrene-butadiene-based copolymer rubber (A) and the diolefin-based rubber (B).
[9]. A vibration-isolating rubber which is obtained by crosslinking a rubber composition comprising 5 to 40 parts by weight of a styrene-butadiene-based copolymer rubber (A), having a weight-average molecular weight of 200,000 or less and a glass transition temperature of −35° C. or higher, and 95 to 60 parts by weight of a diolefin-based rubber (B), having a weight-average molecular weight exceeding 200,000 and a glass transition temperature of −20° C. or lower; the weights based on 100 parts by weight of the total amount of (A) and (B).
[10]. The vibration-isolating rubber according to [9] above, wherein the diolefin-based rubber (B) is at least one rubber selected from the group consisting of a styrene-butadiene copolymer rubber, a butadiene rubber, an isoprene rubber and a natural rubber.
[11]. The vibration-isolating rubber according to [10] above, wherein a weight-average molecular weight of the styrene-butadiene-based copolymer rubber (A) is 500 to 80,000.
[12]. The vibration-isolating rubber according to [11] above, wherein the styrene-butadiene-based copolymer rubber (A) is hydrogenated at 50% or more.
[13]. The vibration-isolating rubber according to [12] above, wherein a relationship between a dynamic-to-static modulus ratio (Kd/Ks), which is a ratio of a dynamic spring constant (referred to also as “dynamic elasticity modulus”) (Kd) and a static spring constant (referred to also as “static elasticity modulus”) (Ks), and a loss factor (tan &dgr;) is shown by the following equation (1):
Kd/Ks≦
20 tan &dgr;−1.8 (1).
[14]. The vibration-isolati
Kobayashi Naokazu
Tadaki Toshihiro
Tsukimawashi Keisuke
JSR Corporation
Nutter Nathan M.
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