JPH11130916A - Light weight rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition which shows little volume change during vulcanization and forming to give predetermined dimensions and has high tenacity by mixing a rubber with a hollow polymer sphere obtained in advance by heating of a polymer microcapsule including a hydrocarbon having a low boiling point and expanding thereof by evaporating the low boiling point hydrocarbon. SOLUTION: A rubber is mixed with a hollow polymer sphere obtained in advance by heating at about 120-200 deg.C of a polymer microcapsule containing a hydrocarbon having a low boiling point (for example an isobutane) inside a separate wall made of a polymer selected from homopolymers of a vinilydene chloride, an acrylonitrile or a methacrylonitrile and copolymers thereof and expanding the microcapsule by evaporating the low boiling point hydrocarbon. The hollow polymer sphere preferably has an expanded separate wall without any unevaporated hydrocarbon and has a lubricant agent on the surface thereof. The amount of the hollow polymer sphere is preferably 5-80 vol.%. Thus obtained composition gives light weight and shows no breakage even under heavy duty applications.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight rubber composition, and more particularly, to a lightweight rubber composition which, when vulcanized and formed, has a small volume change and can be finished to an intended size.

[0002]

2. Description of the Related Art Flexible lightweight rubber compositions include:
Sponge is well known. However, sponges are not only low in elongation, strength, modulus, hardness, tear strength, etc., but they are not suitable for high-performance applications due to large variations in their physical properties. there were.

Further, recently, partition walls have been made of phenolic resin, polyamide resin, polyurethane resin, methyl methacrylate, vinylidene chloride resin, polyacrylonitrile,
Rubber containing organic microcapsules, such as polyvinylidene chloride / acrylonitrile copolymer, which contains a substance that evaporates by heat and expands the partition material, such as low-boiling hydrocarbons, inside the rubber, and vulcanizes the rubber At the same time, a lightweight rubber obtained by expanding the partition material is known, and is disclosed in, for example, JP-A-8-53567 and JP-A-4-246440.

Further, a rubber laminate obtained by laminating the above-mentioned lightweight rubber and non-lightweight rubber is also used, for example, in a crop harvesting belt in which a lightweight rubber layer is attached to the back of a belt main body in which a core wire or a core is embedded. in use. In this case, after the lightweight rubber layer and the non-light rubber are separately vulcanized and formed, the lightweight rubber layer and the non-light rubber are bonded together using an adhesive.

[0005]

However, a rubber laminate in which a lightweight rubber and a non-lightweight rubber are bonded and laminated using an adhesive has insufficient adhesion, and the interface between the lightweight rubber and the non-lightweight rubber is insufficient. There is a problem that peeling is likely to occur and the bonding step is complicated, and it has been strongly desired that the lightweight rubber and the non-lightweight rubber be simultaneously vulcanized and bonded. However, when a foamed rubber composition containing an inorganic foaming agent, a nitroso compound, an azo compound, a hydrazine compound-based foaming agent or the above microcapsules and a non-foamed rubber composition are simultaneously vulcanized and molded, the foamed rubber is vulcanized. Since the non-foamed rubber composition does not change in volume while large volume expansion occurs before and after, the obtained laminate is greatly curved and deformed with respect to the shape of the molding die, and the desired shape cannot be obtained. There were difficulties.

[0006] In addition, when sponge rubber is used as a lightweight rubber, the strength is low, and when the sponge rubber is used for an application receiving a relatively large load, such as a belt for transporting agricultural products, the lightweight rubber is liable to be broken and its life is shortened. was there.

In view of these points, the present invention takes into account these points, and when vulcanization molding is performed, the volume change is small and finished to the intended size, and since the enclosed hollow portion is independent, the strength is high and the load is high. It is an object of the present invention to provide a lightweight rubber composition which is hardly damaged even in use.

[0008]

That is, according to the present invention, a low-boiling hydrocarbon is contained in a partition wall material selected from vinylidene chloride, polyacrylonitrile, methacrylonitrile, and a copolymer thereof. A lightweight rubber composition in which a microcapsule is preliminarily heated to evaporate and reduce the weight of the low-boiling hydrocarbon by vaporizing the low-boiling hydrocarbon is kneaded in rubber, and in particular, the low-boiling hydrocarbon is included in the partition wall material. In order to use a rubber composition obtained by kneading a polymer hollow body expanded in advance to evaporate the low-boiling hydrocarbon by heating the microcapsules that have been kneaded in the rubber,
Even when vulcanization is performed, the volume change of the lightweight rubber layer is small, the finished dimensions are as intended, and a vulcanized product with good dimensional accuracy can be obtained.

In the invention according to the second aspect of the present invention, since the partition wall material is expanded so that the low-boiling-point hydrocarbon is completely vaporized as the polymer hollow body to be added, the non-vulcanized non-polymerized body is used. The change in volume of the lightweight rubber is small, and a vulcanizate with good dimensional accuracy can be obtained.

[0010] In the invention according to claim 3 of the present application, the polymer hollow body to be added has a lubricant attached to its surface, so that the expanded polymer hollow body is mixed with the rubber at the time of kneading the rubber composition. Is good and puncture is difficult.

In the invention according to claim 4 of the present application, the volume fraction of the hollow polymer body to be added is 5 to 80%.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber used in the present invention includes:
Natural rubber, polyisoprene rubber, polybutadiene rubber,
Ethylene-α- such as styrene-butadiene copolymer rubber, chloroprene rubber, ethylene-propylene rubber
Olefin copolymer rubber, nitrile rubber (NBR),
Hydrogenated nitrile rubber (H-NBR), hydrogenated nitrile rubber (H-NBR) to which an unsaturated carboxylic acid metal salt is added, alkylated chlorosulfonated polyethylene (A
CSM), chlorosulfonated polyethylene rubber (CS
M) or the like as a main component, and a reinforcing agent such as carbon black, a filler, a softening agent, an antioxidant, a vulcanization aid, a vulcanizing agent such as sulfur, and the like are added and mixed.

The hollow polymer body to be added to the lightweight rubber composition of the present invention is a relatively heat-resistant polymer selected from vinylidene chloride, polyacrylonitrile, methacrylonitrile, and a copolymer thereof, polyacrylonitrile methacrylonitrile copolymer. Isobutane, n
-A microcapsule containing a low-boiling hydrocarbon such as pentane, previously heated at 120 to 200 ° C to vaporize the low-boiling hydrocarbon, thereby expanding the polymer hollow to tens of times the original volume. It is preferably a body which hardly expands during vulcanization. If the hollow polymer body expands during vulcanization, the change in volume of the molded body becomes large, so that it is impossible to finish it to the intended dimensions and to improve the dimensional accuracy. The microcapsules referred to here are those in which the low-boiling hydrocarbon contained in the partition wall material is hardly vaporized.

It is preferable to use the above-mentioned hollow polymer body having a lubricant previously attached to the surface thereof. This is because the polymer hollow body to which the lubricant is adhered has a good sliding property with the rubber at the time of kneading the rubber composition, which makes it difficult to puncture. The lubricant used here is an oil such as process oil, DOP or paraffin wax or a plasticizer. The lubricant can be attached by immersing the hollow polymer body in a liquid lubricant or by mixing the hollow polymer body and the lubricant.

The addition amount of the hollow polymer body is 5 to 80% by volume, preferably 20 to 80%. 8
If the amount exceeds 0% by weight, kneading of the polymer hollow body into rubber becomes difficult, and the mechanical strength such as tensile strength and elongation decreases, which is not preferable. Can not do it.

The above lightweight rubber composition is prepared by kneading a rubber and a filler, a softening agent, an antioxidant and the like, which are added as necessary, with a roll, kneader, Banbury mixer, etc. There is a method of mixing a sulfurizing agent, and a method of kneading rubber and a polymer hollow body, a vulcanizing agent, and a filler, a softening agent, an antioxidant, and the like, which are added as needed, with an open roll.

The rubber composition thus obtained is formed into a sheet using a roll such as a calender roll, and then vulcanized. As the vulcanizing device, mold heating, hot air heating,
A rotary drum type vulcanizer, an injection molding machine or the like can be used.

[0018]

The present invention will be described in more detail with reference to the following examples. Example 1, Comparative Examples 1-2 Light weight rubber 1, light weight rubber 2, light weight rubber 3 and non-light weight rubber in the compounding table shown in Table 1 are kneaded with a Banbury mixer, and a 5 mm thick sheet is extruded with a roll. Was. In this case, the polymer hollow body used for the lightweight rubber 1 was a heat-treated one minute at 160 ° C., and the polymer hollow body used for the lightweight rubber 2 was a microcapsule which had not been heat-treated in advance. For the lightweight rubber 3, a chemical foaming agent was used.

Then, the lightweight rubber 1, the lightweight rubber 2, and the lightweight rubber 3 are each superimposed on the non-lightweight rubber to obtain 1
The thickness was 0 mm. This is 25mm in width, 100mm in length,
The mixture was filled into a mold engraved to a depth of 10 mm, vulcanized at 153 ° C. for 20 minutes, and the apparent specific gravity and hardness of the lightweight rubber layer of the laminate and the presence or absence of deformation were examined. Table 2 shows the results.

[0020]

[Table 1]

[0021]

[Table 2]

As a result, it can be seen that when a lightweight rubber layer using a polymer hollow body expanded by heating in advance is used, there is no deformation of the vulcanized integrated laminate. But,
When a lightweight rubber layer for expanding the microcapsules during vulcanization was used, or when a chemical foaming agent was used, the surface of the lightweight rubber layer was deformed in a convex shape.

[0023]

As described above, according to the first aspect of the present invention, a microcapsule containing a low-boiling hydrocarbon in a partition material selected from vinylidene chloride, polyacrylonitrile, methacrylonitrile, and a copolymer thereof. Is preliminarily heated to vaporize the low-boiling hydrocarbon to evaporate the polymer hollow body, which is kneaded in rubber in a lightweight rubber composition, and in particular, a microcapsule containing a low-boiling hydrocarbon in a partition wall material. In order to use a rubber composition obtained by kneading a polymer hollow body that has been expanded by heating in advance to evaporate the low-boiling hydrocarbon into rubber, the volume change of the lightweight rubber layer is small even when vulcanized. In addition, there is an effect that a vulcanized product having a good dimensional accuracy can be obtained by finishing to a target size.

In the invention according to the second aspect of the present invention, since the partition wall material is expanded so that the low-boiling hydrocarbon is completely vaporized, the polymer hollow body to be added is used. In the case of integration, there is an effect that the volume change of the non-lightweight rubber becomes smaller and a laminate with good dimensional accuracy can be obtained.

According to the third aspect of the present invention, since a polymer hollow body to which a lubricant is attached is used as the polymer hollow body to be added, the polymer hollow body expanded without concern for the viscosity of rubber is used. When the rubber composition containing the rubber composition is kneaded, the rubber composition has a good sliding property, and the hollow polymer body is less likely to be punctured.

In the invention according to claim 5 of the present application, the volume fraction of the hollow polymer body to be added is 5 to 80%.

Claims (4)

[Claims] 1. A microcapsule in which a low-boiling hydrocarbon is encapsulated in a partition wall material selected from vinylidene chloride, polyacrylonitrile, methacrylonitrile, and a copolymer thereof, is heated in advance to vaporize the low-boiling hydrocarbon. A lightweight rubber composition characterized in that the polymer hollow body expanded by the above method is kneaded in rubber. 2. The lightweight rubber composition according to claim 1, wherein the low-boiling hydrocarbon is completely vaporized and the partition wall material is expanded in the polymer hollow body to be added. 3. The lightweight rubber composition according to claim 1, wherein the lubricant is attached to the surface of the hollow polymer body to be added. 4. The polymer hollow body to be added has a volume fraction of 5
The lightweight rubber composition according to claim 1, wherein the content is from 80 to 80%.