JPH0428007B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for kneading conductive rubber. High molecular weight polymers such as natural rubber or synthetic rubber are generally electrical insulators, but they have problems such as dust adhesion due to static electricity charging and accidents caused by sparks when charged static electricity is discharged, so it is necessary to add conductivity. Things have been done. In addition, by taking advantage of the elasticity, weather resistance, and other various characteristic functions of these polymeric substances, and adding functions by imparting conductivity, materials have been developed to be applied in new fields. Conventionally, the most commonly used composition for imparting electrical conductivity to a molecular polymer is a composition to which carbon black is added, and compositions to which various other chemicals are added are also known. All of these are materials used in fields that require electrical resistance of about 10 ² -10 ⁸ Ω-cm, and are generally called semiconductive materials. Polymers containing carbon black are conductive polymer compositions that are often used in this field. Because the composition has a conductive effect, it has the disadvantage that its conductivity rapidly decreases when stretched, so be prepared for unexpected changes in electrical resistance when used in places that are stretched or bent. I didn't have to. On the other hand, conductive compositions made by adding surfactants and similar antistatic agents to high-molecular polymers can be made into light-colored compositions, but surfactants are slightly harmful to the human body. Furthermore, when the composition is exposed to water or the like, chemicals such as surfactants are washed away, resulting in a decrease in conductivity. The applicant previously aimed to provide a semiconductive material by imparting conductivity to a high molecular weight polymer.
At the same time, in an attempt to improve the drawbacks of the conventional technology, a patent application
No. 58-170936 was filed. The above application discloses that the polymer contains magnesium,
At least one metal oxide of calcium or zinc, a chloride of the same metal, and water,
The present invention is directed to a conductive polymer composition characterized in that each of these components is added alone or as a reactant of two or more. Here, the chlorides of magnesium, calcium, and zinc also include hydrous compounds. The conductive polymer composition of the above-mentioned application by the present applicant provides a semiconductive material, that is, a light-colored polymeric material having an electrical resistance of about 10 ² -10 ⁸ Ω-cm and whose conductivity does not decrease even when exposed to water. I was able to get Among the above-mentioned polymeric materials, natural rubber, synthetic rubber, etc. are kneaded using a kneading roll machine (hereinafter referred to as "roll"), and in the process, vulcanizing agents, vulcanizing Various rubber compounding agents such as accelerators, vulcanization accelerating aids, anti-aging agents, softeners, fillers, and reinforcing agents; oxides of at least one metal among magnesium, calcium, and zinc; At least one of the metal chlorides and an agent imparting conductivity, such as water, are added. In this case, for example, when kneading with rolls, the various compounding agents mentioned above as well as magnesium, calcium,
Zinc oxide and the like are easily and uniformly dispersed when added onto the masticated rubber wrapped around a roll by a conventional method. However, since chlorides such as calcium, magnesium, and zinc are crystalline, they are difficult to disperse uniformly even if added with great care and time to the masticated rubber wound around a roll. If it is not added in small amounts, it will flow down from the top of the masticated rubber wrapped around the roll and it will not be possible to add the desired amount accurately. It also becomes impossible to obtain semiconductive materials with electrical resistance. In this case, the first thing to consider is to first dissolve the deliquescent chloride, which is extremely soluble in water, in water, and then add the solution onto the masticated rubber wrapped around a roll. Although the trouble of separately adding the crystalline chloride can be omitted,
Since the solution is extremely fluid, it is essentially the same as adding water, and must be carefully added in small amounts onto the masticated rubber wrapped around a roll. There is no change,
Also, it is not possible to prevent it from flowing down,
In any case, it could not be a fundamental solution. The present invention was invented in view of the above circumstances, and it eliminates the fluidity of the chloride aqueous solution and makes it muddy, so that it does not require special attention and does not flow down. The purpose is to facilitate the kneading of conductive rubber, and the purpose is to add required rubber compounding agents and at least one metal selected from magnesium, calcium, and zinc to masticated natural rubber or synthetic rubber. In the method of kneading conductive rubber, in which a chloride of at least one metal among calcium, magnesium, and zinc is added, an oxide of at least one metal among calcium, magnesium, and zinc, and water. This was achieved by a method of kneading conductive rubber, which is characterized in that water is made into a slurry with bentonite and added to masticated natural rubber or synthetic rubber in the slurry state. The bentonite used in the kneading method is composed of three-layer structure type sammolinite, and when such bentonite is added to an aqueous solution in which at least one metal chloride among calcium, magnesium, and zinc is dissolved. When an aqueous solution enters between the layers of bentonite, the lattice gaps widen, causing a so-called swelling phenomenon and forming a slurry. When bentonite is added to the aqueous solution, such a swelling phenomenon occurs, but the addition can be carried out by an extremely simple operation of just stirring, and the amount of bentonite added is 3% by weight relative to water. Optimal is at least 3 times, especially 3 to 5 times. And since the mixture is a slurry when the bentonite is 3 to 5 times the amount, it will float in the air like any other dry powder when it is added onto the masticated rubber wrapped around a roll. The bentonite is kneaded into the masticated rubber extremely smoothly, without causing any splatter or scattering.Also, even if the amount of bentonite exceeds 5 times, the moisture is sufficient, so it will not float or scatter in the air. Even if it tends to fall down a little, it can all be collected and added immediately, and the kneading operation can be carried out without any problems, allowing the kneading process to be completed reliably. Example

[Table] In the above formulation, the rubber is styrene-butadiene copolymer rubber, the rubber is natural rubber, the rubber is acrylonitosol-butadiene copolymer rubber, the vulcanization accelerator is 2-mercaptobenzothiazole, and the vulcanization accelerator is 2-mercaptobenzothiazole. Benzothiazolyl disulfide, vulcanization accelerator Diphenylguanidine is used as the accelerator, and magnesium chloride, water, and bentonite are prepared by dissolving magnesium chloride in water and adding bentonite to the solution while stirring. It was used as a slurry. Here, formulation No. 1 was used as a control example. First, rubber was masticated with a roll (two 8-inch rolls), zinc leather, stearic acid, a vulcanization accelerator, and magnesium oxide were added and mixed, and then about half of the reinforcing agent and polyethylene glycol were added and mixed.
Furthermore, a solution of magnesium chloride dissolved in water was added to formulation No. 1, and a slurry obtained by adding bentonite to the solution was added and mixed to formulations No. 2 to No. 7, respectively.
Thereafter, about half of the remaining reinforcing agent and polyethylene glycol were added and mixed, and finally sulfur was added and mixed. In this kneading process, the kneading properties and kneading time were investigated. Using this kneaded material, press-type vulcanization was performed to prepare a specimen, and the volume resistivity R was measured.

[Table] In the above table, the x mark indicates that kneading was not easy because a highly fluid solution had to be added, and the ○ mark indicates that kneading was not very easy. shows. In this example, as shown in the table above, in the control example, a solution of magnesium chloride dissolved in water was added slowly over time to the masticated rubber on the roll. However, since the slurry was added to formulations No. 2 to No. 7, it was immediately kneaded into the rubber, and kneading was carried out smoothly and in a short time without special care. Ta. In addition, the volume resistivity of formulations No. 2 to No. 7 was not inferior to that of the control example, but was rather slightly decreased.

Claims (1)

[Scope of Claims] 1. Masturbated natural rubber or synthetic rubber, a necessary rubber compounding agent, an oxide of at least one metal among magnesium, calcium, and zinc, and at least one metal among magnesium, calcium, and zinc. In the method of kneading conductive rubber in which chloride and water are respectively added, the chloride of at least one metal selected from calcium, magnesium, and zinc and the water are made into a slurry with bentonite, and then mixed in the slurry state. A method for kneading conductive rubber, characterized by adding it to masticated natural rubber or synthetic rubber.