JPH03210357A - Low resilient rubber composition - Google Patents

Abstract

PURPOSE:To provide good vibration-insulating properties over a wide temp. range from room temp. to high temp. by incorporating a high-styrene rubber into a low resilient rubber compsn. contg. a polynorbornene as the main component, a reinforcement, a filler, and a softener. CONSTITUTION:Ethylene and cyclopentadiene are caused to undergo the Diels- Alder reaction to give norbornene, which is subjected to a ring-opening polymn. to give polynorbornene. Then, polynornonene as the main component is compounded with a reinforcement (e.g. carbon black), a filler (calcium carbonate), a softener (a process oil), etc., and also with a high-styrene rubber, giving a lowly resilient rubber compsn. A pref. amt. compounded of the high-styrene rubber is such that 20-60 pts.wt. styrene is contained in the resulting compsn. based on 100 pts.wt. polynorbornene. The compsn. is suitably used as a vibration-insulating rubber for a computer hard disk.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a low-resilience rubber composition used as vibration-proof rubber for computer hard disks and the like.

[Prior art] -I is used as a vibration-proof rubber for computer hard disks, etc., which contains polynorbornene as the main component, and contains a reinforcing agent such as carbon black, a filler such as barium sulfate, and a softening agent such as process oil. A composition made of a low-resilience rubber composition containing a low-resilience rubber composition is used. In addition, anti-vibration rubber is also used which uses a low-resilience rubber composition obtained by blending ethylene propylene diene rubber (EPDM) into the above composition in consideration of weather resistance. This type of anti-vibration rubber has a high loss coefficient (tan δ) near room temperature and has high damping properties, and exhibits good anti-vibration performance near room temperature.

[Problems to be Solved by the Invention] However, in devices such as computers, the temperature is low at the time of startup, and as the device continues to operate, the overall temperature increases due to the heat generated by the device. This is also transmitted to the vibration isolating rubber, raising the temperature of the vibration isolating rubber itself. Conventional low-resilience rubber compositions exhibit good vibration damping performance near room temperature, but as the temperature rises, the vibration damping performance deteriorates. Therefore, anti-vibration rubber using this has the disadvantage that it cannot exhibit sufficient anti-kneading properties in high-temperature regions.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a low-resilience rubber composition that can exhibit good vibration-proofing performance over a wide temperature range from near room temperature to high temperature.

[Means for solving problems]

In order to achieve the above object, the low rebound elastic rubber composition of the present invention contains polynorbornene as a main component, a reinforcing agent,
This is a low-resilience rubber composition containing a filler and a softener, and contains high styrene rubber.

(Function) The present inventors have conducted a series of studies for the purpose of improving the vibration damping performance in the high temperature range of the low-resilience rubber composition containing the above-mentioned polynorbornene as a main component.As a result, the above-mentioned polynorbornene This invention was achieved by discovering that by incorporating high styrene rubber into the low-resilience rubber composition, which is the main component, it becomes possible to obtain high vibration-proofing performance in high-temperature regions in addition to vibration-damping performance near room temperature. did.

This effect can be obtained because conventional low-resilience rubber compositions containing polynorbornene as a main component exhibit a so-called single peak in which the loss coefficient reaches its maximum near room temperature, whereas high styrene This is thought to be due to the fact that when rubber is included, a loss coefficient peak also occurs in a high temperature range, so that the so-called loss coefficient peak becomes double.

Next, this invention will be explained in detail.

This invention produces a low resilience rubber composition using polynorbornene, a reinforcing agent, a filler, a softening agent, and high styrene rubber.

The above-mentioned polynorbornene is generally produced by ring-opening polymerization of norbornene synthesized from ethylene and cyclopentadiene by a Ziels-Alder reaction.

This polymer has a glass transition temperature of about 35°C,
At room temperature, it is in the form of a resin or powdered resin.

Generally, a softening agent such as petroleum oil is added to this to form a rubber and used as norbornene rubber.

The reinforcing agent used together with the polynorbornene is used to increase the hardness, tensile strength, etc. of the anti-vibration rubber, and carbon black is generally used. However, in addition to these, white carbon, clay, etc. can be mentioned and used alone or in combination. Most preferred is carbon black.

Further, the filler used together with the reinforcing agent and the like is used for the purpose of improving the workability of the anti-vibration rubber, and examples thereof include barium sulfate and calcium carbonate. These may be used alone or in combination. In particular, in compositions containing polynorbornene as a main component, it is preferable to use barium sulfate as a filler.

In addition, the softening agent used together with the filler etc. is mainly used for the purpose of converting the polynorbornene into rubber, and as mentioned earlier, the softening agent is used to make the polynorbornene rubber by absorbing the softening agent. Norbornene turns into rubber. Examples of such softeners include process oils distilled from petroleum and plant-based softeners, but process oils are preferably used in the low resilience rubber composition.

This invention uses high styrene rubber together with the above raw materials. High styrene rubber is produced by uniformly mixing high styrene resin latex consisting of 85 to 87% by weight of styrene (hereinafter abbreviated as "%") and 13 to 15% of butadiene and styrene-butadiene copolymer rubber latex and co-coagulating the mixture. The average styrene content is set to about 50 to 70%.

In addition to the above-mentioned raw materials, the composition of the present invention may appropriately contain a vulcanizing agent, a vulcanization accelerator, an auxiliary agent, and the like.

The low-resilience rubber composition of the present invention can be produced using the above-mentioned raw materials, for example, in the following manner. That is, the above-mentioned raw materials can be blended in a predetermined ratio, mixed in a mixer, and formed into a sheet. The low-resilience rubber composition thus obtained is in the form of a sheet, and by molding and vulcanizing it, a vibration-proof rubber of a predetermined shape can be made. The blending ratio is usually set as follows: 100 parts by weight of polynorbornene (hereinafter abbreviated as "parts")
The ratio of reinforcing agent such as carbon to 30 to 200 parts, filler such as barium sulfate to 100 to 400 parts, and softening agent such as process oil to 100 to 200 parts is set. The high styrene rubber has a styrene content of 20 to 100 parts based on the styrene content in the high styrene rubber, based on 100 parts of polynorbornene in the above compound.
It is used within the range of 60 parts. Furthermore, in the composition of the present invention, a synthetic rubber such as EPDM is optionally blended for the purpose of improving weather resistance.

In this case, the blending amount of EPDM is polynorbornene 10
It is set within the range of 15 to 70 copies with respect to 0 copies. 20 EPDM and polynorbornene constitute the rubber component in the composition of this invention. In such a low resilience rubber composition, especially the above polynorbornene EPDM
By setting the proportion of reinforcing agents, fillers, and softeners other than the rubber content to 300 parts or less per 100 parts of the rubber content, the maximum value of the double peak of the loss coefficient can be increased. It is preferable from the viewpoint of

[Effects of the Invention] As described above, the low resilience rubber composition of the present invention contains high styrene rubber in the low resilience rubber composition containing polynorbornene as a main component, so that the peak of the loss factor can be reduced. It occurs not only in the temperature region near room temperature but also in the high temperature region, resulting in a double peak shape. As a result, by using this, it becomes possible to manufacture vibration-proof rubber that can exhibit good vibration-proofing properties in a wide temperature range from around room temperature to high temperatures. Therefore, this anti-vibration rubber can be used as anti-vibration rubber for computer hard disks, etc., without degrading the anti-vibration performance even when the computer heats up, and can achieve almost complete anti-vibration over a wide temperature range from around room temperature to high temperatures. It becomes like this.

Next, an embodiment will be described together with a conventional example.

[Examples, Conventional Examples] The raw materials shown in the table below were blended in the proportions shown in the table, and the mixture was blended and mixed in the manner described above to obtain a sheet-like low-resilience rubber composition. Next, mold this.

Anti-vibration rubber was made by vulcanization, and the properties of the anti-vibration rubber were measured and shown in the same table.

(The following is a blank space) The measurement results of the loss coefficient of the above-mentioned anti-vibration rubber are shown in FIGS. 1 and 2. In FIGS. 1 and 2, curves A-F correspond to Examples 1 to 6, and curve G corresponds to Conventional Example 2. As is clear from the comparison between curves A-F and curve G, the loss coefficient of the example product has a double peak in the temperature/loss coefficient curve, which results in good vibration isolation in a wide temperature range from room temperature to high temperature. It can be seen that the performance is demonstrated. That is, in the conventional example, the peak of the loss coefficient is a single peak, and the range of the loss coefficient of 0.6 or more, which is an index of anti-vibration performance, is a relatively narrow range of 8 to 42°C. and in Example 7, 15°
It has a wide temperature range of about 63°C to 63°C. To explain in more detail, in conventional compositions, the peak of the loss coefficient is a single peak near room temperature and the peak value is high, so it exhibits extremely excellent vibration damping performance near room temperature, so to speak, it can be said to be of excessive quality. That's about it. However, 4
When the temperature exceeds 0°C, the loss coefficient suddenly decreases (becomes 60°C).
At this level, it is no longer possible to satisfy the loss coefficient of 0.6 or more required for anti-vibration rubber. On the other hand, in the example, although the loss coefficient near room temperature is not very high in the conventional example, it has a double peak, so the loss coefficient of the vibration isolating rubber is 0.6 or more in a wide temperature range from room temperature to high temperature. It can be seen that the value is definitely cleared.

[Brief explanation of drawings]

FIGS. 1 and 2 are temperature loss coefficient curve diagrams.

Claims (2)

[Claims] (1) A low-resilience rubber composition containing polynorbornene as a main component and containing a reinforcing agent, a filler, and a softener, and containing high-styrene rubber. Composition. (2) The low resilience rubber composition according to claim (1), wherein the high styrene rubber is contained in an amount of 20 to 60 parts by weight based on the styrene content and per 100 parts by weight of polynorbornene.