JPH10171464A - Foam rubber composition for filling structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foam rubber composition which can stably foam without inducing problems like cracks of an obtained rubber foaming body or expansion or warp of a structure and whose expansion ratio is easily forecast. SOLUTION: This composition is arranged in a prescribed space in the structure and foams by heating to fill up the space in this structure. 10 to 50 pts.wt. sulfur or 1 to 40 pts.wt. sulfur and 5 to 100 pts.wt. rigidity giving agent are mixed with 100 pts.wt. diene rubber, and further, an expandable microcapsule- type foaming agent is used as the foaming agent, and 2 to 30 pts.wt. this foaming agent is mixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a foamable rubber composition for filling a structure, and more particularly to an improvement in a foamable rubber composition for filling a structure which is low in cost and excellent in storage stability.

[0002]

2. Description of the Related Art Generally, there is a hollow inside a cylindrical frame member (structure) such as a front pillar or a center pillar of an automobile, and a wind noise is generated when wind passes through the hollow. Alternatively, the vibration noise of the engine is transmitted to the inside of the vehicle through the hollow portion, thereby causing the noise in the vehicle. Therefore, the gaps of the structure such as the skeletal member, which causes the noise in the vehicle, are conventionally filled with a foam to suppress the passage of wind and the transmission of vibration noise. Therefore, measures such as improving sound insulation have been taken.

[0003] As a method of filling the foam with such a void, a foam formed in accordance with the shape of the void is inserted into the void through a working hole, or foamed by heating to reduce the volume. A method of processing an expanding foamable composition into a sheet as a spot seal material, disposing the sheet in a gap, foaming the sheet by heating or drying in a baking furnace for electrodeposition coating, and filling the gap. And various other methods are employed.

However, in the method of inserting the foam into the gap, since the foam is inserted from the work hole, the filling property varies, and it is difficult to completely fill the gap with the shape of the gap. In addition, since the working hole is a punched edge of a steel plate, there is an inherent danger of a worker's hand being hurt.

[0005] In recent years, in order to improve the strength of a structure as well as to improve the conventional interior noise,
Increasingly, foam filling of structures has been performed. As such a foamable composition for filling a structure, a foamable composition made of an epoxy resin is used in order to obtain high rigidity. However, in general, an epoxy resin is expensive, including a crosslinking agent, and a molded sheet of a foamable composition comprising such an epoxy resin is in a state after a curing agent is added to the epoxy resin. Even if it is not heated, the reaction proceeds steadily and is naturally (automatically) cured by steam in the atmosphere under the temperature condition of about 40 ° C. even if it is not formed in the so-called B-stage state. Therefore, there is a problem that storage stability is lacking. Therefore, the foamable composition made of such an epoxy resin must be stored in a sealed bag filled with silica gel in a cool and dark place, and stored with great care. It was very troublesome.

[0006] For this reason, the present applicant has previously filed Japanese Patent Application No.
No. 17738 discloses a foamable rubber composition for filling a structure which is inexpensive and excellent in storage stability. That is, it is placed in a predetermined space in the structure, foamed by heating,
A foamable rubber composition for filling voids in the structure, wherein 10 to 50 parts by weight of the diene rubber is used.
Parts by weight of sulfur and 5 to 40 parts by weight of a foaming agent, or 1 to 30 parts by weight of sulfur, 5 to 1 part by weight.
It is obtained by mixing 00 parts by weight of a stiffening agent and 5 to 40 parts by weight of a foaming agent.

As described above, in the foamable rubber composition previously proposed, a diene rubber is used as a main component, and a predetermined ratio of sulfur, or a predetermined ratio of sulfur and a stiffening agent are added thereto. In order to increase the rigidity of the obtained foam,
The major feature is that it is compounded, where sulfur is used as a cross-linking agent because a rubber material consisting of a diene rubber is used as the main component. Since the rubber material and sulfur are inexpensive, the foamable rubber composition for filling the obtained structure can be made inexpensive, and the rubber material used there is a cross-linking agent, sulfur. Even if stored in a blended state, if not heated, it does not cure naturally and has excellent storage stability, as in the case of a foaming composition using a conventional epoxy resin,
It has the feature that it is not necessary to adopt a very troublesome storage method.

In addition, a rubber foam obtained by heating and foaming such a foamable rubber composition has excellent toughness due to the elasticity derived from the rubber, since the rubber foam inherits the properties of rubber. Thus, the foam has a larger impact energy absorption characteristic than the conventional foam.

[0009] However, the present inventors have further studied the foamable rubber composition for filling a structure having such excellent characteristics, and found that the foamable rubber composition incorporated into the foamable rubber composition has a problem. It became clear that the new problem was raised.

That is, in this case, a predetermined ratio of sulfur, or a predetermined ratio of sulfur and a stiffness-imparting agent is added to the diene rubber, and a predetermined ratio of a blowing agent is further added to achieve foamability. In general, such foaming agents include organic foaming agents such as diazoamino derivatives and azodicarboxylic acid derivatives, and inorganic foaming agents such as sodium hydrogencarbonate and ammonium hydrogencarbonate. Will be used. Thus, for example, in a foamable rubber composition using an organic foaming agent, since the organic foaming agent itself is decomposed at a certain temperature at a certain time, its vulcanization and foaming Because of the high gas pressure and large amount of gas generated during the vulcanization and in the vulcanization and foaming operations within the structure, the temperature distribution of the rubber tends to be non-uniform, especially at a vulcanization atmosphere temperature of 200 ° C or higher. The problem is that the balance with the vulcanization rate of the rubber is lost, so that the occurrence of cracks in the obtained rubber foam, swelling in the structure, warpage, etc. is significantly increased. Thus, the organic blowing agent is
It is considered that it is not suitable as a foaming agent in a high-rigid rubber composition for filling a skeleton having a wide range (variation) in vulcanization temperature, since decomposition starts rapidly when a predetermined temperature and time are reached. It is done.

When an inorganic foaming agent is used, the gas pressure is low and the foaming is slow, but the generated gas escapes from the foam. This is similar to the case of the organic foaming agent, and therefore has an inherent problem that the expansion ratio cannot be calculated, thereby preventing the structure from expanding and deforming, and preventing the structure from undergoing expansion deformation. There is an inherent problem that it is difficult to perform a foaming operation to sufficiently fill the voids.

[0012]

Here, the present invention has been made in view of such circumstances, and the problem to be solved is to solve problems such as cracks in the obtained rubber foam, swelling and warpage in the structure, and the like. An object of the present invention is to provide a foamable rubber composition for filling a structure, which is capable of performing stable foaming without causing any problem and easily predicting a foaming ratio.

[0013]

In order to solve such a problem, the present invention provides a foamable rubber which is arranged in a predetermined space in a structure, foams when heated, and fills the space in the structure. A composition, in which 10 to 50 parts by weight of sulfur is blended with respect to 100 parts by weight of the diene rubber, and an expanding microcapsule type foaming agent is used as a foaming agent. A foamable rubber composition for filling a structure, wherein the foamable rubber composition is characterized in that parts are blended.

The present invention is also a foamable rubber composition which is arranged in a predetermined space in a structure, foams when heated, and fills the space in the structure. 1 to 40 parts by weight of sulfur and 5 to 100 parts by weight of a stiffener are added to 100 parts by weight, and an expanding microcapsule type foaming agent is used as a foaming agent. The present invention also provides a foamable rubber composition for filling a structure, wherein the foamable rubber composition is characterized in that parts are blended.

As described above, in the foamable rubber composition for filling a structure according to the present invention, a predetermined ratio of sulfur, or a predetermined ratio of sulfur and a stiffener can be obtained with respect to a diene rubber as a main component. A major feature is that it is blended for the purpose of increasing the rigidity of the foam, and that a predetermined amount of a microcapsule-type foaming agent is blended as a foaming agent in order to further impart foamability. In particular, such a microcapsule-type foaming agent foams (expands) slowly, has a low gas pressure, and can independently form a foamed portion (bubbles) of a certain size. It is easy to balance with the sulfurization rate, so that problems such as cracks in the obtained rubber foam, swelling in the structure, warping, etc. can be satisfactorily prevented. When the foaming agent expands, it becomes a balloon that gives bubbles of a predetermined size.The foaming agent itself does not burst, and since the rubber foam is formed, the gas does not escape. Therefore, it is very easy to predict the expansion ratio, and this has a feature that the operation of filling the voids in the structure with the foam can be advantageously performed.

The microcapsule-type foaming agent constituting the foamable rubber composition for filling a structure according to the present invention is advantageously formed by encapsulating a volatile liquid with a thermoplastic wall material. Microcapsules, thereby, by a heating operation at the time of vulcanization of the rubber, while gradually evaporating the volatile liquid in the microcapsules, plasticizing the thermoplastic wall material, and performing its expansion, The bubbles of a predetermined size can be independently present in the rubber.

[0017]

In the foamable rubber composition for filling a structure according to the present invention as described above, the diene rubber used as a rubber component includes natural rubber (NR),
Any of known diene rubbers such as butadiene rubber (BR) and styrene-butadiene rubber (SBR) can be adopted, and a blend of them can be used.

Sulfur is added to increase the rigidity of the foam obtained by heating and foaming the foamable rubber composition due to the crosslinking action of the sulfur. If you can not mix the agent,
In order to increase the rigidity only by crosslinking with sulfur, it is necessary to be blended in a larger amount, whereas, when a stiffening agent is blended, the rigidity is increased only by crosslinking with sulfur. Since it is not necessary, a small amount of the compound is sufficient.

Therefore, when the rigidity-imparting agent is not compounded, sulfur must be compounded in a proportion of 10 to 50 parts by weight with respect to 100 parts by weight of the diene rubber. If the blending ratio is less than 10 parts by weight, the resulting foam has insufficient crosslink density, resulting in too low rigidity. Also, if the blending ratio is more than 50 parts by weight, This is because the foaming of the rubber composition becomes insufficient because the cross-linking density of the foam obtained becomes too large.

On the other hand, when a stiffness-imparting agent is compounded, sulfur is added to 100 parts by weight of the diene rubber.
The mixing ratio is 1 to 40 parts by weight. In this case, if the mixing ratio of sulfur is less than 1 part by weight, the rigidity of the obtained foam is insufficient, and if it is higher than this, the rigidity of the obtained foam becomes too high and It causes problems such as fragility of the body.

The above-mentioned stiffening agent is added for the purpose of imparting rigidity to a foam obtained by heating and foaming the expandable rubber composition. The sulfur content can be reduced. Specific examples of such a rigidity imparting agent include thermosetting resins such as phenolic resins, epoxy resins, melamine resins, and urethane resins, and modified products thereof. And the compounding ratio of such a rigidity imparting agent is set to 5 to 100 parts by weight with respect to 100 parts by weight of the diene rubber. However, if the content is less than 5 parts by weight, the effect of the stiffening agent cannot be sufficiently exerted. If the content is more than 100 parts by weight, the resulting foam may not be obtained. This is because the rigidity of the body becomes too high, which is not preferable. In order to further enhance the action of the stiffness imparting agent, a curing agent such as hexamine is added to a thermosetting resin such as a phenol resin at a ratio of about 20 to 200% of the theoretical equimolar amount of the resin. May be added, whereby the rigidity can be further advantageously increased.

The foaming agent, which is added to the diene rubber together with the sulfur or the sulfur and the stiffener to make the rubber composition foamable, expands when the rubber composition is heated, A balloon body of a predetermined size is an inflatable microcapsule-type foaming agent that achieves a desired foamed structure by being present in rubber, and such a microcapsule-type foaming agent is an organic foaming agent. Unlike the agent, it does not rapidly decompose and foam at a predetermined temperature, but expands gradually over a certain wide temperature range,
The resulting rubber foam has a closed-cell foam structure because it becomes a balloon of a predetermined size, exhibits a foamed form, and does not break the capsule itself. Therefore, any of the microcapsule-type blowing agents having such a function can be used in the present invention. Generally, a volatile liquid such as a low-boiling organic solvent such as isopentane is used as an acrylic-based liquid. Microcapsules (microspheres) encapsulated with a thermoplastic wall material such as a resin, an EVA resin, and an acrylonitrile-based resin are advantageously used. And such a microcapsule type foaming agent is already commercially available, for example,
A product group named EXPANCEL sold through Nippon Ferrite Co., Ltd. will be advantageously used in the present invention.

Further, such a microcapsule type foaming agent stably foams (expands) under vulcanization conditions generally employed (160 to 200 ° C. × 20 minutes) when vulcanizing the diene rubber. ), The center of the expansion temperature is preferably between 140 and 180 ° C,
Further, due to such expansion (foaming), the microcapsule-type foaming agent has an average particle size of about 10 to 30 μm (before foaming), and exceeds 30 μm to 50 to 120 μm.
It has a mean particle size of about (after foaming). The microcapsule-type foaming agent is used in an amount of 2 to 30 parts by weight, preferably 4 to 100 parts by weight of the diene rubber.
It will be added at a compounding ratio of 〜20 parts by weight. However, if the compounding ratio is less than 2 parts by weight, the expansion ratio is low, and a sufficient foaming action cannot be exhibited, and if it is more than 30 parts by weight,
This is because the foaming efficiency is poor and the physical properties after foaming are difficult to obtain.

The foamable rubber composition for filling a structure according to the present invention contains, in addition to the diene rubber, sulfur (+ stiffness imparting agent) and microcapsule type foaming agent, which are essential components as described above, Various compounding agents known from, for example, vulcanization accelerators, vulcanization aids, processing aids, fillers and the like are added as necessary, and any of them inhibits the object of the present invention. It can be blended in the same manner as before in a quantitative range that does not occur. For example, a metal oxide such as zinc oxide is used as a vulcanization aid, and is generally blended at a ratio of about 3 to 15 parts by weight with respect to 100 parts by weight of the diene rubber. In addition, as a processing aid, a fatty acid such as stearic acid is used in an amount of about 0.5 to 5 parts by weight based on 100 parts by weight of the diene rubber. Further, examples of the softener include liquid rubber, paraffin-based, naphthene-based, and aroma-based process oils and ester-based plasticizers, and 0 to 100 parts by weight of diene-based rubber.
The filler is used in an amount of about 15 parts by weight, and further, as a filler, calcium carbonate, carbon black, silica, talc, or the like is used in an amount of 0 to 15 based on 100 parts by weight of the diene rubber.
It is used at a ratio of about 0 parts by weight.

The foamable rubber composition for filling a structure according to the present invention is prepared by adding a predetermined amount of sulfur or sulfur and a stiffener to a diene rubber material according to a mixing method similar to the conventional one, and a microcapsule type. Blending foaming agent,
Furthermore, by compounding various compounding agents as described above,
It will be prepared.

Further, the foamable rubber composition for filling a structure thus prepared is heated and heated to form a foamed rubber composition.
By curing, it becomes a highly rigid rubber foam which is effective for filling the target structure. Such a foam has a compression rigidity of 0.5 kN / mm per 25 cm ^2. Above, and the energy absorption amount is 25
It has physical properties of 100 kN · mm or more per cm ² . In addition, in order to obtain a foam giving such physical properties, generally, under a temperature condition of 160 to 210 ° C., 15 to 15 ° C.
A foaming and curing operation for heating for about 30 minutes will be adopted.

The compression stiffness referred to here is:
When compressing a pair of surfaces of a foam test piece formed into a cube having a side of 5 cm, a compression load: P is applied so that the test piece is compressed at a rate of 20 mm / min in the compression direction, and a displacement amount at that time: S
And the above-mentioned compressive load: P, and the value obtained by dividing the initial fine change in load (ΔP) by the initial fine change in displacement (ΔS). It is expressed as a value per ² . In addition, the amount of absorbed energy means that when the foam test piece is compressed as described above, the compression displacement of the test piece is 30 m from the start of compression.
m means the amount of energy absorbed by the test piece, which is expressed as a value per 25 cm ² of the test piece. Specifically, the displacement amount: S and the compression load: P
In the graph showing the relationship, the compression rigidity is represented by the displacement amount: S
And the initial load gradient (ΔP / ΔS) of the relationship curve between the compression load: P and the absorbed energy amount. The absorbed energy amount is represented by the relationship curve between the compression load: P and the displacement amount: S, and the x-axis (0 to 30).
mm).

By the way, the high-rigidity rubber foam obtained from the foamable rubber composition for filling a structure according to the present invention has a large compression rigidity and a large amount of energy absorption. Therefore, when it is applied to a structure such as a skeleton of an automobile, it can advantageously absorb the impact of an automobile collision or the like, and thereby provide a safety to the occupants. Sex can be effectively enhanced.

When the foamable rubber composition for filling a structure according to the present invention is actually applied to an automobile structure, first, the foamable rubber composition is processed into a sheet. Then, after it is fixedly arranged in the internal space of the structure, it is subjected to normal automobile manufacturing processes such as welding, degreasing / washing, and electrodeposition, and then is subjected to heat treatment in processes such as drying and paint baking. By foaming and curing such a sheet-like foamable rubber composition, and filling the voids in the structure with the resulting highly rigid rubber foam, the intended foam-filled structure By adopting such a process, it is possible to exhibit features such as no need to provide any special heating process.

In the foaming and curing operation of the foamable rubber composition for filling a structure according to the present invention by heating, the foaming is performed by the presence of a balloon generated due to the expansion of the microcapsule type foaming agent by the expansion of the diameter. It is made with a structure, and unlike a conventional organic foaming agent and inorganic foaming agent, the generated gas does not escape to the outside, so it is extremely easy to predict the expansion ratio, and Since there is no sudden foaming, the resulting rubber foam does not crack, nor does the structure cause deformation such as swelling or warping.

In addition, such a high-rigidity rubber foam has a foamed structure composed of inflated balloons of a microcapsule-type foaming agent, and has a closed-cell type.
Since it is excellent in water resistance and does not absorb water in its pores, the rusting resistance of the structure filled with such a rubber foam can be effectively improved. is there.

[0032]

EXAMPLES In order to clarify the present invention more specifically, representative examples of the present invention will be shown below.
It goes without saying that the present invention is not subject to any restrictions by the description of such embodiments. In addition, in addition to the following examples, the present invention, in addition to the above-described specific description, various changes, corrections, and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that improvements can be made.

First, foamable rubber compositions for filling various structures having the compositions shown in Table 1 below were prepared. In addition, as the vulcanization accelerator in Table 1, a thiazole vulcanization accelerator and a thiuram vulcanization accelerator are used in combination. Hexamine is used as a phenol curing agent, and azodicarbonamide is used as an organic foaming agent. A urea-based foaming aid was used as a foaming aid. As the microcapsule-type foaming agents A, B, and C, Expancel 053DU-80 (expansion temperature: starting temperature) obtained by wrapping isopentane in an acrylonitrile-based resin shell sold by Nippon Ferrite Co., Ltd. 90-95 ° C, center 140-150 ° C), Expancel 091DU-80 (expansion temperature: start 118-
126 ° C., center 171-181 ° C.) and EXPANCEL 054 WU (expansion temperature: onset 125-135 ° C., center 140-150 ° C.).

[0034]

[Table 1]

Next, using the various foamable rubber compositions obtained above, an initial unvulcanized rubber molded article having a shape of 50 mm × 50 mm × 28 mm ^t was formed.
It is housed and placed in a square hollow pipe
Heating and foaming were performed under foaming conditions of 20 ° C. × 20 minutes, 180 ° C. × 20 minutes, or 200 ° C. × 20 minutes to obtain corresponding rubber foams. Further, the obtained foam was cut into 50 mm × 50 mm × 50 mm ^t , and this was used as a compression block. The compression stiffness and the energy absorption amount were measured, and the results were used to evaluate the appearance of the foam. In addition, the results are shown in Table 2 below.

[0036]

[Table 2] * 1 Unit g / cm ³ * 2 Unit kN / mm * 3 Unit kN · mm

As is evident from the results shown in Table 2, the rubber foam obtained from the foamable rubber composition according to the present invention has a sufficient compression rigidity and energy absorption, and has a variable foaming temperature. However, the appearance is good, and no problems such as cracks are observed. On the other hand, when the organic foaming agent of Comparative Example 1 is used, the foaming temperature becomes high. As a result, problems such as cracking were observed, and it became clear that the balance between the foaming of the organic foaming agent and the vulcanization rate of the rubber was lost.

[0038]

As is apparent from the above description, the foamable rubber composition for filling a structure according to the present invention can advantageously reduce the cost and exhibit excellent storage stability. In addition, the use of the microcapsule type foaming agent makes it easy to predict the expansion ratio, causing cracks in the obtained rubber foam, and deformation such as swelling or warping of the structure due to the foaming pressure of the rubber. Thus, the occurrence of a problem such as the occurrence of the problem can be effectively avoided.

Claims (3)

[Claims] 1. A foamable rubber composition which is placed in a predetermined space in a structure and is foamed by heating to fill the space in the structure, wherein 100 parts by weight of diene rubber is used. On the other hand, 10 to 50 parts by weight of sulfur is compounded, and an expanding microcapsule type foaming agent is used as a foaming agent, and 2 to 30 parts by weight thereof is compounded. Foamable rubber composition for use. 2. A foamable rubber composition which is disposed in a predetermined space in a structure and foams by heating to fill the space in the structure, wherein 100% by weight of diene rubber is used. On the other hand, 1 to 40 parts by weight of sulfur and 5 to
100 parts by weight of a stiffness-imparting agent is blended, and an expanding microcapsule-type foaming agent is further used as a foaming agent, and 2 to 30 parts by weight thereof is blended. Rubber composition. 3. The foamable rubber composition for filling a structure according to claim 1, wherein the microcapsule-type foaming agent is a microcapsule obtained by encapsulating a volatile liquid with a thermoplastic wall material. Stuff.