JP2017031343A - Rubber composition and steering hole cover - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition improving molding quality without causing deterioration in appearance quality and dimensional accuracy, and in which the lightening characteristic of the same is attained.SOLUTION: Provided is a rubber composition obtained by kneading a glass balloon and a thermoexpansible micro capsule or an organic foaming agent into raw material rubber in the form of joint use, in which the addition amount of the glass balloon is 10 to 30 pts.wt., and a mixed ratio of both the glass balloon and the thermoexpansible micro capsule or organic foaming agent obtained by removing the addition amount of the glass balloon with the addition amount of the thermoexpansible micro capsule or organic foaming agent is 10 to 100. Desirably, the pressure strength of the glass balloon is controlled to 80 MPa or higher. The rubber composition part is used as the material, e.g., upon injection molding for an automobile steering hole cover with a die.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition and a steering hole cover using the rubber composition, and more particularly to a technique for reducing the weight of the rubber composition.

  Conventionally, as a means for reducing the weight of a rubber composition, a technique in which an organic foaming agent or a thermally expandable microcapsule is kneaded into a raw rubber is known, for example, in the field of extrusion molding.

  Further, for example, a technique for reducing the weight of the rubber composition similar to the above by kneading a hollow ceramic balloon typified by a glass balloon into a raw rubber instead of the organic foaming agent and the thermally expandable microcapsule, for example, This is proposed in Patent Document 1.

JP 2006-241335 A

  However, with the former technique using organic foaming agents and thermally expandable microcapsules, even if it is effective in the extrusion molding method, raw rubber is injected and injected into the sealed space of the mold and molded into a predetermined product shape. In the mold forming method, the expansion or foaming in the mold is not uniform, the dimensional accuracy of the product is insufficient, or the surface of the product is uneven. There is. These problems can be solved to some extent by using a so-called core back molding method in which a part of the mold (core) is actively moved in one molding cycle. This increases the cost of the mold apparatus, which is not preferable.

  In the latter technique using a hollow ceramic balloon, the hollow ceramic balloon is damaged or broken when the rubber material is injected and injected from the injection device into the mold under the injection molding method. There was a problem that the effect of weight reduction could not be obtained.

  The present invention has been made paying attention to such a problem, and without any modification of the mold apparatus, etc., to improve the molding quality so as not to bring about a decrease in appearance quality and dimensional accuracy. It is an object of the present invention to provide a rubber composition capable of reducing the original weight and a steering hole cover using the rubber composition.

  The present invention is based on the premise that a glass balloon and a thermally expandable microcapsule or an organic foaming agent are used in combination, and a glass balloon and a thermally expandable microcapsule or an organic foaming agent are kneaded in a raw rubber. The addition ratio of the glass balloon is 10 to 30 parts by weight, and the mixing ratio (compounding ratio) of the two obtained by dividing the addition amount of the glass balloon by the addition amount of the thermally expandable microcapsule or the organic foaming agent is 10 to 100. It is the rubber composition characterized by being as follows.

  The mixing ratio between the glass balloon and the thermally expandable microcapsule or the organic foaming agent is set to 10 to 100. If the mixing ratio is less than 10, unevenness or the like is likely to occur on the product surface, resulting in poor appearance, and the mixing ratio is This is because the expected weight reduction effect cannot be obtained when the number exceeds 100.

  More specifically, as described in claim 2, it is desirable that the pressure resistance of the glass balloon is 80 MPa or more.

  A preferable example of the use of such a rubber composition is a steering hole cover for an automobile. A steering hole cover (sometimes referred to as a steering shaft cover or grommet) is inserted into a shaft insertion hole formed in a partition wall (dash panel) that separates a vehicle body compartment and an engine room of an automobile body. In addition to covering the periphery of the sterling shaft, it has a function of sealing between the shaft insertion hole and the sterling shaft by pressing against the partition wall from the engine room side.

  Therefore, in the present invention, by using the glass balloon and the thermally expandable microcapsule or the organic foaming agent in combination, when the raw rubber flows in the mold by injection, the thermal expandable microcapsule or the organic foaming agent is used. Foaming (expansion) is started, and the contact pressure between the mold wall surface and the raw rubber is reduced, so that breakage or damage of the glass balloon is suppressed.

  According to the present invention, by using a glass balloon and a thermally expandable microcapsule or an organic foaming agent in combination, breakage or damage of the glass balloon is suppressed, so that the weight reduction effect according to the addition amount of the glass balloon is achieved. In addition to being obtained efficiently, the amount of thermally expandable microcapsules or organic foaming agents added is relatively small, so there is no appearance defect such as dimensional accuracy of the product or surface irregularities, and molding quality is improved. .

  According to the invention of claim 2, by setting the pressure strength of the glass balloon kneaded to the raw rubber to 80 MPa or more, the glass balloon can be prevented from being damaged during the raw rubber kneading process in the injection device, The above-described weight reduction effect can be obtained more efficiently.

It is typical explanatory drawing at the time of injection molding of a steering hole cover, (A) is an explanatory view showing a conventional example, (B) is an explanatory view in the rubber composition concerning the present invention. Sectional explanatory drawing around the steering device of the motor vehicle to which the steering hole cover which concerns on this invention is applied. The perspective view which looked at the steering hole cover shown in FIG. 2 from the front side in the single-piece | unit state. The perspective view which looked at the steering hole cover shown in FIG. 2 from the back side in the single-piece | unit state. FIG. 3 is an enlarged cross-sectional view of the steering hole cover shown in FIG. 2 in an assembled state.

  More specific embodiments of the rubber composition according to the present invention are shown in Table 1 together with Comparative Examples 1-5 as Examples 1-9.

  EPDM (ethylene / propylene / diene copolymer) was used as the base material of the raw rubber. Here, “JSR EP57F” manufactured by JSR Corporation was used.

  Zinc white was used as a vulcanization aid. Here, two kinds of zinc oxide flower manufactured by Hakusui Tech Co., Ltd. were used.

  MAF carbon (carbon black) was used as the reinforcing agent. Here, “Niteron # 10” manufactured by Shin-Nikka Carbon Co., Ltd. was used.

  Paraffin oil was used as the softening agent. Here, “Process P-300” manufactured by JX Nippon Oil & Energy Corporation was used.

A hollow glass balloon was used as a filler. The hollow glass balloon is a glass micro hollow sphere powder made of a chemically stable insoluble glass (for example, soda lime borosilicate glass), and has a particle diameter of about 16 to 65 μm (median diameter) and a true density of 0.13 to 0.13. It is a true sphere of about 0.60 g / cm ³ . Here, 3M Glass Bubbles manufactured by 3M Japan Co., Ltd. (“3M” is a registered trademark) is used as the glass balloon A, and 3M Glass Bubbles manufactured by 3M Japan Co., Ltd. (“3M” is used as the glass balloon B). "Is a registered trademark) grade" K46 ".

  Here, when the glass balloon A and the glass balloon B are compared, they are relatively different in terms of particle diameter and pressure strength, and the particle diameter of the glass balloon A is about 20 μm and the pressure strength is about 110 MPa. On the other hand, the particle diameter of the glass balloon B is about 40 μm and the pressure resistance is about 41 MPa.

  Further, a thermally expandable microcapsule was used as a filler used in combination with the hollow glass balloon. As its name suggests, heat-expandable microcapsules are microcapsules with a microcapsule structure with an outer shell (shell) of thermoplastic resin and aliphatic hydrocarbons enclosed in the core (core). Therefore, it has a characteristic of expanding about 5 to 7 times. Here, “Dai Form V307-T” manufactured by Dainichi Seika Kogyo Co., Ltd. was used.

  Furthermore, an organic foaming agent was used as a filler used in place of the thermally expandable microcapsules on the premise that the hollow glass balloon was used in combination. Here, an organic foaming agent “Cermic Z-676” manufactured by Sankyo Kasei Co., Ltd. was used.

  “Noxeller CZ” manufactured by Ouchi Shinsei Chemical Co., Ltd. as the vulcanization accelerator (CBS), “Accel TRA” manufactured by Kawaguchi Chemical Industry Co., Ltd. as the vulcanization accelerator (DPTT), and vulcanization accelerator (TMTD) ) “Noxeller TT” manufactured by Ouchi Shinsei Chemical Co., Ltd. was used.

  Sulfur (S) was used as a vulcanizing agent, and here, finely powdered sulfur 200 mesh manufactured by Hosoi Chemical Co., Ltd. was used.

  In Table 1, the blending ratio of each blending material when EPDM as the base material is 100 is shown in parts by weight. In each of Comparative Examples 1 to 5 and Examples 1 to 9 in Table 1, a steering hole cover sample as a product to be described later was molded by injection molding using a mold, and the filler mixture ratio, appearance (unevenness) Evaluation was made on each item of quality and specific gravity.

  Here, the filler mixing ratio is a thermally expandable microcapsule or organic that is added as a filler by the addition amount of glass balloon A or the addition amount of glass balloon B added as a filler to EPDM as a base material. The mixing ratio of the two divided by the added amount of the foaming agent.

  Appearance quality is the result of visually observing the presence or absence of irregularities on the outer surface as well as the dimensional accuracy of the molded sample.

  Further, the specific gravity is an important index for evaluating weight reduction, and it is naturally desirable that the specific gravity is less than 1.

  As is clear from Table 1, in Comparative Example 1, none of glass balloon A, glass balloon B, thermally expandable microcapsule, and organic foaming agent was added as a filler. Even if it is good, the specific gravity exceeds 1, and it is a matter of course that the intended weight reduction has not been achieved.

  In Comparative Example 2, although 20 parts by weight of thermally expandable microcapsules are added as a filler, the appearance quality is poor and the specific gravity exceeds 1, and the amount of thermally expandable microcapsules added is small. Has not been lightened sufficiently.

  In Comparative Example 3, 10 parts by weight of glass balloon A was added as a filler, the appearance quality was good, and the specific gravity was less than 1, but it was light enough for the amount of glass balloon A added. It is not planned.

  In Comparative Example 4, 20 parts by weight of glass balloon A was added as a filler, and similarly 4 parts by weight of thermally expandable microcapsules were added as a filler. The specific gravity was less than 1, and the weight was reduced. However, the appearance quality is poor.

  In Comparative Example 5, 20 parts by weight of glass balloon A was added as a filler, and 0.16 parts by weight of thermally expandable microcapsules were added. At first glance, both the appearance quality and the weight reduction (specific gravity) required performance. I get the impression that On the other hand, the specific gravity is less than 1 as apparent from comparison with Example 2 described later in which the filler mixing ratio is extremely high as 125, and 20 parts by weight of the same glass balloon A is added as the filler. However, the effect of reducing the specific gravity is slow for the added amount of the glass balloon A, and the weight reduction is not necessarily achieved efficiently.

  In Example 1 of Table 1, 10 parts by weight of glass balloon A and 0.2 parts by weight of thermally expandable microcapsules are added as fillers, respectively, and the appearance quality is good and the specific gravity is less than 1. Thus, a corresponding weight reduction is achieved according to the amount of glass balloon and thermally expandable microcapsules added.

  In Example 2, 20 parts by weight of glass balloon A and 0.5 parts by weight of thermally expandable microcapsules were added as fillers, respectively, and the appearance quality was good and the specific gravity was even lower than in Example 1. In the same manner as in Example 1, the weight of the glass balloon and the thermally expandable microcapsule is reduced accordingly.

  In Example 3, 20 parts by weight of glass balloon B and 0.5 parts by weight of thermally expandable microcapsules were added as fillers, respectively, and the appearance quality was good and the specific gravity was less than 1. As in Example 1, the weight of the glass balloon and the thermally expandable microcapsule is reduced accordingly.

  In Example 4, 20 parts by weight of glass balloon A and 0.25 parts by weight of thermally expandable microcapsules were added as fillers, and only the amount of the thermally expandable microcapsules added was different from that of Example 2. ing. In this Example 4, the appearance quality is good and the specific gravity is less than 1. As in Example 2, the weight can be reduced corresponding to the addition amount of the glass balloon and the thermally expandable microcapsule. ing.

  In Example 5, 20 parts by weight of glass balloon A and 0.2 parts by weight of thermally expandable microcapsules are added as fillers, and only the amount of the thermally expandable microcapsules added is different from that of Example 2. ing. In this Example 5, the appearance quality is good and the specific gravity is less than 1. As in Example 2, the weight can be reduced corresponding to the addition amount of the glass balloon and the thermally expandable microcapsule. ing.

  In Example 6, 20 parts by weight of glass balloon A and 2 parts by weight of thermally expandable microcapsules are added as fillers, and only the addition amount of these thermally expandable microcapsules is different from that of Example 2. . In Example 6, the appearance quality is good and the specific gravity is less than 1, and, as in Example 2, the weight can be reduced corresponding to the amount of glass balloon and thermally expandable microcapsules added. ing.

  In Example 7, 30 parts by weight of glass balloon A and 1.5 parts by weight of thermally expandable microcapsules were added as fillers, respectively, and the appearance quality was good and the specific gravity was less than 1. As in Example 1, the weight of the glass balloon and the thermally expandable microcapsule is reduced accordingly. In particular, in Example 7, the amount of glass balloon A added is the largest compared to the other examples, and therefore the specific gravity, which is an index for weight reduction, is the smallest compared to the other examples. It can be understood that the most efficient weight reduction is achieved according to the amount of addition.

  In Example 8, 20 parts by weight of glass balloon A and 2 parts by weight of organic foaming agent were added as fillers, the appearance quality was good, the specific gravity was below 1, and the glass balloons and organic Appropriate weight reduction is achieved according to the amount of the foaming agent added.

  In Example 9, 20 parts by weight of glass balloon A and 0.25 part by weight of organic foaming agent were added as fillers, respectively, and only the amount of addition of this organic foaming agent was different from Example 8. . In Example 9, the appearance quality is good, the specific gravity is less than 1, and the weight reduction corresponding to the addition amount of the glass balloon and the organic foaming agent is achieved.

  As is clear from Comparative Examples 1 to 5 and Examples 1 to 9 described above, in order to satisfy both of the required qualities with respect to specific gravity, which is an index of appearance quality and weight reduction of the product, a glass balloon as a filler In addition to the use of A or glass balloon B, it is essential to use a heat-expandable microcapsule or an organic foaming agent in combination. It must be ~ 30 parts by weight.

  At the same time, in order to satisfy the required quality of both of the appearance quality of the product and the specific gravity, which is an index of weight reduction, the filler mixing ratio in Table 1 is set to a hollow glass balloon (glass balloon A as described above). Alternatively, when the addition ratio of glass balloon B) is defined as the mixing ratio of both divided by the addition amount of thermally expandable microcapsules or organic foaming agent, the filler mixing ratio must be 10-100. become.

  Here, when the glass balloon A and the glass balloon B used as a hollow glass balloon as a filler are compared, the pressure resistance of the glass balloon B is about 110 MPa, whereas the pressure resistance of the glass balloon B is 41 MPa. The degree is as described above. In this case, in order to prevent damage or breakage of the glass balloon in the molding process, it is desirable that the pressure strength is high, and it is also assumed that glass balloons made by other companies with different specifications are used. Even in this case, the pressure resistance of the glass balloon to be used is desirably 80 MPa or more.

  Moreover, in the said Examples 1-9, in addition to a hollow glass balloon (glass balloon A or glass balloon B), the advantage of using together a thermally expansible microcapsule or an organic type foaming agent demonstrates as follows. Can do.

  FIG. 1 schematically shows a state at the time of injection injection of raw material rubber from an injection device into a mold during injection molding using a mold. As shown in FIG. 5A, when only the glass balloon was kneaded into the raw rubber, the raw rubber was kneaded into the raw rubber under injection pressure during injection / injection of the raw rubber into the mold M. There is a tendency that breakage is likely to occur when the glass balloon collides with the mold wall surface.

  On the other hand, when the thermally expandable microcapsule is kneaded together with the glass balloon into the raw rubber by the combined use of the thermally expandable microcapsule, as shown in FIG. The expansion of the microcapsule at the time of injection / injection of the raw rubber reduces the impact pressure of the raw rubber against the mold wall surface, and as a result, damage to the glass balloon in which the raw rubber is kneaded is alleviated or Will be suppressed. This means that the amount of glass balloon that remains in the product as a hollow body without breakage is relatively large, and the specific gravity is less than 1 and can greatly contribute to weight reduction of the product. In addition, there is no unevenness exposed on the outer surface of the product, which can contribute to the improvement of the appearance quality.

  In addition, it is not necessary to adopt the conventional core back molding method to improve the appearance quality, so it can be handled with existing molds without difficulty, and the cost of the mold apparatus can be increased by adding a core moving mechanism. Will not be invited.

  2-5 has shown the example at the time of applying the steering hole cover 6 which is an example of the product shape | molded using the rubber composition of the said Examples 1-9 to a steering device.

  FIG. 2 is a longitudinal sectional view around the steering device of an automobile. 1 is a steering wheel, 2 is an upper shaft 2a, an intermediate shaft 2b, a lower shaft 2c, and joints 3a and 3b interposed therebetween. A steering shaft 4 is a steering gear box linked to the steering shaft 2. Reference numeral 5 denotes a dash panel as a partition wall that separates the vehicle compartment R1 and the engine room R2. A shaft insertion hole 5a is formed in the dash panel 5, and the lower shaft 2c penetrates the dash panel 5. Thus, the shaft is inserted into the shaft insertion hole 5.

  The steering hole cover 6 covers a portion on the engine room R2 side of the lower shaft 2c inserted through the shaft insertion hole 5a, and the steering hole cover 6 is pressed against the dash panel 5 from the engine room R2 side to contact the shaft. The space between the insertion hole 5a and the lower shaft 2c is watertightly sealed.

  As shown in FIGS. 3 to 5, the steering hole cover 6 has a substantially deformed cup shape or a deformed dish shape as a whole, and includes a cylindrical base portion 7 that covers the outer periphery of the lower shaft 2 c, and the cylindrical base portion 7. A first seal portion 8 provided on one end side and fitted on a cylindrical portion 4a provided on an upper end portion of the steering gear box 4 and the other end of the cylindrical base portion 7 is extended to the outer peripheral side of the other end to bend and deform. And a second seal portion 10 provided through a relatively thin flexible portion 9 that is freely configured and abutting a seal surface 5b that is a peripheral edge of the shaft insertion hole 5a on the engine room R2 side. . The steering hole cover 6 shown in FIGS. 2 to 5 is disclosed in Japanese Patent Application Laid-Open No. 2015-55326 related to the applicant's application.

  The steering hole cover 6 having such a structure is molded as a one-piece structure from the rubber composition of any one of the first to ninth embodiments described above.

  The rubber composition according to the present invention can be applied to molding of other elastic parts that require the same elastic characteristics as the steering hole cover 6 in addition to the steering hole cover 6 exemplified above. Needless to say.

6 ... Steering hole cover M ... Mold

Claims (3)

Glass balloon and thermally expandable microcapsule or organic foaming agent are kneaded in the raw rubber,
The addition amount of the glass balloon is 10 to 30 parts by weight,
A rubber composition characterized by having a mixing ratio of 10 to 100 obtained by dividing the amount of glass balloon added by the amount of thermally expandable microcapsules or organic foaming agent.   2. The rubber composition according to claim 1, wherein the pressure resistance of the glass balloon is 80 MPa or more. Covers the periphery of the steering shaft that is inserted into the shaft insertion hole formed in the partition that separates the compartment and engine compartment of the automobile body, and press-contacts the partition from the engine compartment side to the shaft insertion hole and the sterling A steering hole cover for sealing between the shaft and
A steering hole cover comprising the rubber composition according to claim 1 or 2.

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