JPH06183305A - Minutely foamed weather strip - Google Patents

Abstract

PURPOSE:To facilitate the control of foaming and provide a required low specific weight and hardness by minute foaming. CONSTITUTION:Micro capsules 2 with 30-50mu of diameters are dispersed in the inside 1a of the main body of a weather strip 1 whose main component is EPDM. Each micro capsule 2, whose shell is constructed by acrylonitrile system copolymer (softening point 145-150 deg.C), is formed by a shell part 3 made of a resin described later and hydrocarbon with a low boiling point enclosed in this shell part 3. The hydrocarbon with the low boiling point enclosed in the shell is n-pemuntane, n-hexane and the like and its low boiling point temperature is below 100 deg.C which is below its vulcanization temperature. The size of this micro capsule 2 is 5-8mu at the time before it is exposed to the vulcanization temperature and expanded to a size of 30-50mu without the destruction of the shell by the expansion of the enclosed hydrocarbon with the low boiling point, when it is exposed to the vulcanization temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weather strip, and more particularly to a fine foam weather strip.

[0002]

2. Description of the Related Art In recent years, there has been a demand for weight reduction of automobiles in order to preserve the environment and improve fuel efficiency. As a means for reducing the weight of the weather strip, there is a reduction in specific gravity. As a conventional technique for lowering the specific gravity, a technique has been proposed in which paraffin oil having a low specific gravity is blended in a large amount by using highly oil-absorbing carbon.

[0003]

However, this conventional technique for reducing the specific gravity has a specific gravity of 1. When the hardness is JIS-A70 or more.
It was difficult to make it 0 or less. It is also possible to mix a foaming agent with the weather strip to foam it,
When a conventional thermal decomposition type foaming agent is used, it is difficult to control the foaming, and it is difficult to obtain the desired hardness because the hardness is largely reduced even though the specific gravity is low.

The object of the present invention is to eliminate the above-mentioned problems, and it is easy to control foaming,
Another object of the present invention is to provide a weather strip having a desired low specific gravity and hardness by finely foaming.

[0005]

In order to solve the above problems, the present invention provides a weather strip including a main body having a rubber or thermoplastic resin as a base material and microcapsules dispersed in the main body. The gist is that the microcapsules are low-boiling point hydrocarbons and are thermally expandable capsules that expand at a vulcanization temperature.

[0006]

According to the invention constructed as described above, the microcapsules are dispersed in the body of the weather strip.
The dispersed microcapsules are thermally expanded at the vulcanization temperature during vulcanization, and are thermally expanded by the low hydrocarbon compound contained therein, so that the weather strip has a low specific gravity and the hardness is not significantly reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view schematically showing a weather strip 1 in this embodiment.

As shown in the figure, EPDM (ethylene-
Inside the main body interior 1a of the weather strip 1 containing propylene-diene copolymer rubber as a main component, a diameter of 30 to 5
The microcapsules 2 of 0 μ are dispersed. The microcapsules 2 are formed of a shell wall 3 formed of a resin described below and a low boiling point hydrocarbon contained in the shell wall 3.

The shell wall 3 of the microcapsule 2 is composed of an acrylonitrile copolymer (softening temperature 145 to 150 ° C.). The microcapsules 2 used in this example are (Matsumoto Yushi-Seiyaku Co., Ltd., trade name Matsumoto Microsphere F-80VSD).
Other than this acrylonitrile copolymer, vinylidene chloride copolymer can be mentioned. Examples of the low boiling point hydrocarbon contained in the shell wall 3 include n-pentane, n-hexane and the like, and the low boiling point means 100 ° C. or lower below the vulcanization temperature. The microcapsules 2 had a size of 5 to 8 μ before being exposed to the vulcanization temperature, and when exposed to the vulcanization temperature, the contained low boiling point hydrocarbons were expanded to destroy the shell wall 3 thereof. Don't be 30
Expands to a size of ~ 50μ.

The production of the weather strip 1 will be described. This weather strip 1 is 100 parts by weight of EPDM (manufactured by Sumitomo Chemical Co., Ltd., trade name: E552), 140 parts by weight of carbon black, 60 parts by weight of paraffin-based process oil, 1 part by weight of stearic acid, 5 parts by weight of zinc white, and dehydrated. 6 parts by weight of the thermal expansion microcapsule was added to a rubber composition containing 5 parts by weight of an agent (calcium oxide), 15 parts by weight of polyethylene, 1.5 parts by weight of sulfur, and 2.2 parts by weight of a vulcanization accelerator. Then, the weather strip 1 as shown in FIG. 1 was molded from the kneaded state at 50 to 60 ° C. by a known extrusion molding method. Here, polyethylene is blended to further secure hardness and reduce specific gravity. The blending amount of polyethylene is preferably 30 parts by weight or less in terms of sag resistance.

Then, by vulcanization molding under the condition of 200 ° C. × 10 minutes, a weather strip 1 in which the microcapsules 2 as shown in FIG. 2 was thermally expanded was obtained. Next, weather strips of Comparative Examples 1 and 2 were manufactured for comparison with the examples of the present invention.

The weather strip of Comparative Example 1 is EPD.
M (Sumitomo Chemical Co., Ltd., trade name: E502) 100 parts by weight, carbon black 100 parts by weight, paraffinic process oil 60 parts by weight, stearic acid 1 part by weight, zinc white 5 parts by weight, calcium bicarbonate 20 parts by weight, It is formed from a general rubber composition containing 5 parts by weight of a dehydrating agent (calcium oxide), 1.5 parts by weight of sulfur, and 2.2 parts by weight of a vulcanization accelerator.

The weather strip of Comparative Example 2 is E
PDM (Sumitomo Chemical Co., Ltd., trade name: E502) 10
0 parts by weight, carbon black 140 parts by weight, paraffinic process oil 120 parts by weight, stearic acid 1 part by weight, zinc white 5 parts by weight, polyethylene 15 parts by weight, dehydrating agent (calcium oxide) 5 parts by weight, sulfur 1.5 parts by weight. Parts, and 2.2 parts by weight of a vulcanization accelerator are compounded.

The target value of each item in Table 1 is a value required for actual use of the weather strip. Table 1 below
As is clear from this, in this embodiment, the weather strip has a specific gravity of 1 or less, and achieves the target value required for each item.

Next, FIG. 3 is a characteristic diagram showing the relationship between hardness (HS) and specific gravity, in which the weather strip is manufactured by the current foaming technology and the weather strip according to the present invention. It is shown that the mixing amount of 2 is changed.

In FIG. 3, A, B, C, D on the characteristic straight line I
The mixing amounts of the microcapsules 2 in the constitution of the above-mentioned embodiment are 10 parts by weight, 6 parts by weight, 2 parts by weight, and 0 parts by weight, respectively. They are the same.

[0017]

[Table 1]

Further, a, b, on the characteristic curve II which is a comparative example.
c and d are weather strips using a conventional organic pyrolyzable foaming agent, which is prepared by mixing a sulfonyl hydrazide compound which is a known foaming agent at 200 ° C.
This is a type in which the decomposed gas foamed under the temperature conditions of (3) escapes from the weather strip. A on the characteristic curve II,
In the weather strips b, c and d, the amount of the foaming agent used instead of the microcapsules 2 is 10 parts by weight,
6 parts by weight, 2 parts by weight, and 0 parts by weight, and the weight parts of the other materials are the same as those in the above-mentioned embodiment.

From this figure, in the embodiment of the present invention, the hardness and the specific gravity become smaller as the amount of the microcapsules 2 added becomes larger, and the hardness and the specific gravity become larger as the amounts of the microcapsules 2 added become smaller. . On the other hand, the weather strip using the current foaming technology tends to have a smaller specific gravity and hardness as the amount of the foaming agent used increases, but when compared with the weather strip of the same specific gravity of the example of the present invention, Is too hard. That is, a weather strip having a hardness satisfying the value of hardness 70 ± 5 required for the weather strip has a higher specific gravity than the weather strip foamed by the current foaming technology. You can get a light one. Further, in the current foaming technology, as shown in FIG. 3, it is difficult to control foaming because the characteristics of specific gravity and hardness do not show linearity corresponding to the amount of the foaming agent used.

The present invention is not limited to the above embodiment, but may be embodied as follows. (1) For example, in the above embodiment, extrusion molding was performed at a vulcanization temperature of 200 ° C., but injection molding was performed at a vulcanization temperature of 180 ° C. to thermally expand the microcapsules. (2) As the thermally expanded microcapsules, 5 in the above embodiment
.About.8 .mu. Was used, and one having a particle size of 30 to 50 .mu. Was used at the time of thermal expansion, but the number is not limited to this value, and any material which does not break during thermal expansion may be used.

[0021]

As described in detail above, according to the present invention, it is easy to control foaming, and by finely foaming, it is possible to provide low specific gravity and necessary hardness required for a weather strip. It is possible to reduce the weight of the weather strip itself.

Further, since the microcapsules are not destroyed during foaming, uniform and dense foaming is possible. Further, since the microcapsules are not destroyed during foaming, the influence on the surface skin of the weather strip is small. Further, this weather strip has an excellent effect that it can be manufactured by a conventional vulcanization process such as extrusion or injection molding.

[Brief description of drawings]

FIG. 1 is a cross section of an example weather strip embodying an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a microcapsule.

FIG. 3 is a characteristic diagram showing a relationship between hardness and specific gravity of a comparative example and an example of the present invention.

[Explanation of symbols]

 1 ... weather strip, 2 ... microcapsules.

Claims (1)

[Claims] 1. A weather strip comprising a main body made of rubber or a thermoplastic resin as a base material, and microcapsules dispersed in the main body, wherein the microcapsules contain a low boiling point hydrocarbon and are vulcanized. A microfoam weatherstrip, which is a thermally expandable capsule that expands with temperature.