JPH0261798B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention aims to prevent electrical and electronic products from impairing their electrical characteristics by being placed on the floor, etc.
Antistatic mat used to prevent the human body from being charged with static electricity, more specifically, for indoor use, it has excellent antistatic performance that requires a color other than black that does not contain carbon black for aesthetic reasons. This invention relates to antistatic mats. (Prior art) Conventionally, antistatic mats (hereinafter simply referred to as "mats") used for the above purposes have a higher coefficient of friction than resin, and can be placed on the floor to improve walking safety for people. Conductivity can be easily obtained by blending carbon black or metal powder, etc. alone or in combination as conductivity-imparting substances with rubber, which has excellent vibration-proof properties. A pine tree is known. In addition, the antistatic performance of such mats is as follows:
In order to prevent the human body from being charged with static electricity, it is required that the electrical resistance between the insulating plate and the surface of the mat placed on the insulating plate be 1×10 ⁷ Ω or less, and that this electrical resistance will change depending on the temperature or It is required that a predetermined value can always be maintained without being affected by changes in the environment such as humidity. (Problems to be solved by the invention) However, in the above conventional mat,
For example, when metal powder is blended as the main component of a conductivity-imparting substance, a large amount must be blended in order to impart the desired conductivity, which has the disadvantage of reducing the elasticity and strength of the rubber.On the other hand, carbon When black is blended as the main component of the conductivity-imparting substance, the mat itself becomes black, and there is a problem in that it cannot be met if a color other than black is required due to aesthetic problems. In particular, recently there has been an increasing demand for colored mats having colors other than black for aesthetic reasons. Under these circumstances, several means have been devised to impart a predetermined electrical conductivity without using carbon black. For example, matte is known, which is made of rubber mixed with an electrolyte. Although the specified conductivity is maintained initially by adding such an electrolyte, changes in the environment, such as drying conditions such as high temperature or reduced pressure, may cause the composition to lose or remove water content over time. However, there is a problem that the conductivity decreases. The present invention was invented based on the above-mentioned circumstances, and the present invention has been devised to prevent static electricity from being charged on the human body, and which can always maintain a predetermined conductivity (electrical resistance) even against changes in the environment such as temperature or humidity. The object of the present invention is to provide a mat that can meet the needs for colorization with excellent prevention performance. (Solution Means) In order to achieve the above object, the mat of the present invention contains a phosphate ester plasticizer and an ionic surfactant on a conductive rubber base layer containing carbon black. It is characterized by being constructed by laminating conductive rubber cover layers. As the rubber base material constituting each layer in the present invention, natural rubber or synthetic rubber may be used alone or in combination as necessary, but especially in the cover layer, nitrile rubber (NBR), chloroprene rubber (CR), etc. is preferred. The base layer of the present invention contains carbon black as a conductivity-imparting substance in the above-mentioned rubber, and therefore has a black color. The cover layer of the present invention is constructed by not using carbon black as a conductivity-imparting substance in the rubber, but instead containing a phosphate ester plasticizer and an ionic surfactant. Phosphate ester plasticizers include trioctyl phosphate (TOP), 2-ethylhexyl-diphenyl phosphate, tributoxyethyl phosphate (TBXP), cresyl diphenyl phosphate, isodecyl diphenyl phosphate, and trioxyethyl phosphate. Silenyl phosphate, alkylaryl phosphate, etc. are preferably used because of their low volatility. Examples of ionic surfactants include cationic surfactants such as salts of alkyl amines or quaternary ammonium with acids such as phosphoric acid, carboxylic acid, and sulfonic acid, or alkali metal salts of carboxylic acid and sulfonic acid. Anionic surfactants are used. The ionic surfactant is effective in imparting significant electrical conductivity in the initial stage, and is used in an amount of 2 to 20 parts by weight, preferably 5 to 15 parts by weight, per 100 parts by weight of the rubber base material. Phosphate ester plasticizers have the effect of imparting electrical conductivity to rubber compositions to some extent, but they also have the characteristic of not reducing the electrical properties of the rubber compositions, especially against changes in the environment such as under dry conditions. 5 to 30 parts by weight, preferably 10 parts by weight per 100 parts by weight of the rubber base material
~25 parts by weight are used. If it is less than 5 parts by weight, the above-mentioned effects will be poor, and if it exceeds 30 parts by weight, it will not have the effect of imparting conductivity or suppressing the deterioration of electrical properties, and will also have an adverse effect on the physical properties of the rubber. In the mat of the present invention, it is important to use the above-mentioned phosphate ester plasticizer and ionic surfactant in combination in the rubber constituting the cover layer; using each alone is not effective. Furthermore, among plasticizers, phosphate ester-based ones are particularly effective, and their effects are noticeable when combined with ionic surfactants, and the effects of ionic surfactants can be adjusted to changes in the environment. It acts so that it can be performed without being influenced. In addition, each layer in the present invention contains a vulcanizing agent in addition to the above-mentioned additives, and furthermore, reinforcing agents, fillers (calcium carbonate, talc, etc.), anti-aging agents, various pigments, etc. are appropriately selected as necessary. It is used as (Example) Next, an example of the present invention will be shown in comparison with a conventional example. First, a rubber composition constituting the base layer (the formulation is shown in Table 1) was kneaded based on a known method and separated into a sheet. On the other hand, a rubber composition constituting the cover layer (the formulation is shown in Table 1) was similarly kneaded according to a known method and separated into sheets.
Then, such sheets are stacked on top of each other and heated to 150°C.
Press vulcanization was carried out under vulcanization conditions of x30 minutes to produce mats each having a thickness of 1 mm for both the base layer and the cover layer. Next, the electrical properties (electrical resistance) of the pine thus obtained were investigated. This electrical resistance was tracked as a change over time when the pine was dried at 70°C. The results are shown in FIG. Regarding the numbers of Examples and Comparative Examples, the rubber composition code of the cover layer is indicated by A, Comparative Example 1, B, Comparative Example 2, and C, Example. The method for measuring electrical resistance was based on the antistatic mat electrical resistance test described in the Technical Guidelines of the Institute of Industrial Safety and RIIS-TR-84-1 Structural Standards for Static Electrical Appliances (1984 revised edition). The electrical resistance between the surface and the back surface (ground) was measured. For reference, Fig. 2 shows the results of changes over time in the volume resistivity of the cover layer and the base layer (drying at 70°C).

[Table] (Effects of the Invention) As explained above, the mat of the present invention has a black base layer that does not change its electrical properties over time due to changes in the environment (temperature or humidity) because it contains carbon black. By containing a phosphate ester plasticizer and an ionic surfactant,
It is composed of a laminated cover layer colored in a color other than black, which does not contain carbon black and whose electrical characteristics do not change over time due to changes in the environment. As a required antistatic mat, it exhibits excellent antistatic effects over a long period of time even in the face of environmental changes. In addition, since both the cover layer and the base layer of the mat of the present invention are made of rubber, they not only have excellent vibration-proofing and sound-absorbing properties, but also have a large coefficient of friction, making them excellent in terms of walking safety for people. It also has the additional effect of

[Brief explanation of the drawing]

1 and 2 are graphs for explaining the present invention, and FIG. 1 shows the electric resistance of the pine,
The figure is a graph showing changes in volume resistivity of rubber compositions over time.

Claims (1)

[Claims] 1. A conductive rubber cover layer containing a phosphate plasticizer and an ionic surfactant is laminated on a conductive rubber base layer containing carbon black. An antistatic mat characterized by: 2 The content of phosphate ester plasticizer and ionic surfactant is 5 to 5 parts by weight each per 100 parts by weight of rubber.
30 parts by weight and 2 to 20 parts by weight of the antistatic mat according to claim 1.