JPH0341101B2 - - Google Patents

Description

[Detailed description of the invention]

<Technical Field> This invention relates to an antistatic agent for foamed polyolefin sheets, and relates to an antistatic agent that is mixed in advance with raw material resin and used for foamed polyolefin sheets used as molding materials for various packaging containers, etc. There is. <Prior art> Conventionally, when manufacturing a synthetic resin sheet, an antistatic agent is mixed into the raw resin in advance, and after the foamed sheet is molded, a conductive layer of the antistatic agent bleeds onto the surface of the synthetic resin. Measures are being taken to prevent the sheet from being charged. However, when using a foamed polyolefin sheet such as a foamed polyethylene sheet as a synthetic resin sheet, the foamed sheet itself has flexibility, and the surface of the foamed sheet has fine irregularities, so bleeding may occur on the sheet surface. It is difficult for antistatic agents to form a uniform conductive layer. This tendency was particularly strong when the antistatic agent was solid, since it had no fluidity. Therefore, a necessary condition for the antistatic agent is that it be a liquid with an appropriate viscosity. However, in the case of ordinary antistatic agents, even though they are liquid at room temperature, when exposed to temperatures below the freezing point of the antistatic agent in low-temperature environments such as winter, they form a uniform conductive layer at room temperature. The antistatic agent begins to solidify, becomes finely cracked, and some parts peel off, making the conductive layer non-uniform and significantly reducing the antistatic effect. Especially when used with flexible foamed polyolefin sheets,
The conductive layer could not keep up with the flexible deformation of the foam sheet, and there was a very high possibility that the above-mentioned cracks would occur. Therefore, when using a conventional foamed polyolefin sheet containing an antistatic agent as a charging sheet, it is necessary to warm it to a certain temperature before use as a measure against winter, which is extremely time-consuming and troublesome. It was hot. Therefore, in the case of foamed polyolefin sheets used as packaging containers, etc., conventional antistatic agents are extremely inconvenient, as their antistatic effect is extremely reduced at low temperatures, and improvements are not yet possible. It was requested. <Purpose> Therefore, it is an object of the present invention to provide a practical antistatic agent that solves the problems of the above-mentioned conventional techniques and can exhibit a sufficient antistatic effect even at low temperatures. <Structure> In order to achieve the above objective, the main component is polyoxyethylene alkylamine, which is compatible with the above main component, and contains non-volatile additives with a freezing point of 20°C or lower. It is characterized by what it does. <Example> Next, an example of the present invention will be described below. First, polyoxyethylene alkylamine is used as the main component of the antistatic agent. This is a nonionic surfactant that creates a uniform conductive layer on the surface of the foam sheet, absorbs moisture in the air well, and due to its own conductivity, it creates a uniform conductive layer on the surface of the sheet. Static electricity can be quickly discharged. It also has the effect of reducing frictional electrification itself. As an additive to the main component, it is compatible with the main component and is non-volatile.
Contains substances with freezing points below 20℃. The above-mentioned compatibility is necessary for the additive to be mixed uniformly with the main component and to work effectively. A low freezing point is a necessary condition for lowering the freezing point of the entire antistatic agent and exhibiting effective antistatic properties even at low temperatures. Specific additives that meet the above conditions include:
Ethylene glycol (EG), tetraethylene glycol dimethyl ether (TEGM), diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, etc., and o-dichlorobenzene (freezing point -17℃, boiling point
Halogenated hydrocarbons such as (179.5℃), higher alcohols such as n-heptanol (freezing point -34.6℃, boiling point 175.8℃), ketones such as acetophenone, and other substances that meet the above conditions. If so, it can be used. The mixing ratio of the main component and the additive is usually about 4:1, but the amount of the additive may vary depending on the freezing point of the main component and the additive, the intended use of the foam sheet, and the operating environment temperature. Adjust and implement as appropriate. However, if the blending ratio of additives to the entire antistatic agent exceeds 40%, the antistatic effect of the main component cannot be sufficiently exerted and the cost will be high, which is inappropriate. Further, if the amount is less than 5%, the additive cannot be mixed uniformly with the main component, and the effect of the present invention of lowering the freezing point of the entire antistatic agent cannot be fully exhibited, so it is unsuitable. In order to blend an antistatic agent consisting of the above-mentioned main components and additives into a foamed polyolefin sheet, first add the usual additives for foamed sheets, such as a foaming agent and a cell control agent, to the polyolefin resin raw material. At the same time as blending, a certain amount of the antistatic agent of the present invention is added, and a foamed sheet is molded by a conventional extrusion molding method or the like. Then, the antistatic agent blended into the foam sheet bleeds onto the sheet surface.
A uniform conductive layer will be formed. Examples of the polyolefin resin forming the foamed polyolefin sheet include low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, polypropylene-polyethylene random copolymer, ethylene-vinyl acetate copolymer, and other polyolefin resins. Copolymers or mixed resins of resins and other thermoplastic resins can also be used. In the case of the above-mentioned foamed polyolefin sheet, even if an antistatic agent containing an ethylene oxide adduct, a glyceride of a higher fatty acid, or an alkylamine derivative is used as in the present invention, it will not bleed onto the surface after molding. Since it is easy to use, the effects of the antistatic agent of the present invention can be effectively exhibited. Note that the higher the content of the antistatic agent contained in the foamed polyolefin sheet, the higher the antistatic effect, but if the content is too large, the difference in antistatic effect will become less noticeable and the cost will be high. Therefore, it is not preferable to increase the content too much. <Effects> According to the antistatic agent of the present invention configured as described above, as an antistatic agent used in a foamed polyolefin sheet, it can exhibit an excellent antistatic effect at room temperature; By adding an additive with a freezing point of 20°C or lower to polyoxyethylene alkylamine, which has poor antistatic effect, the freezing point of the entire antistatic agent is lowered, without reducing the antistatic effect even at low temperatures. , it has become possible to consistently exhibit good antistatic effects over a wide range of temperatures from room temperature to low temperatures. In addition, by using additives that have good compatibility with the main component polyoxyethylene alkylamine, the additives can be uniformly blended into the entire antistatic agent, and therefore can be applied to the entire foam sheet. This makes it possible to uniformly and favorably exhibit the antistatic effect. Furthermore, by using non-volatile additives, the effects of the additives can be satisfactorily exhibited over a long period of time, and the sustainability of the antistatic effect is also increased. As described above, it is possible to provide an excellent antistatic agent that can exhibit good antistatic properties for foamed polyolefin sheets not only at room temperature but also at low temperatures. <Example> In order to demonstrate the effects of the present invention described above, a foamed polyolefin sheet containing an antistatic agent was specifically manufactured, and the antistatic performance and the like were measured. § Experiment 1 After adding the antistatic agent of the present invention and a conventional antistatic agent to a blend of polyethylene resin and ordinary additives such as blowing agents and cell control agents, the mixture was extruded to a thickness of approximately A 1.1mm foamed polyethylene sheet was manufactured and various experiments were conducted.
The results are shown in the table and FIG. In addition, as the polyoxyethylene alkylamine which is the main component of the antistatic agent, Elegan S-
100 (manufactured by Nippon Oil & Fats) was used. In addition, ethylene glycol (EG) has a freezing point of -11.5℃,
Tetraethylene glycol dimethyl ether (TEGM) is used with a boiling point of 197℃.
Uniotx MM-200 (manufactured by Nihon Yushi), which has a freezing point of -27°C and a boiling point of about 200°C, was used. As the antistatic agent, the main ingredient Elegan S-100 and the additive EG or
A 4:1 solution with TEGM was prepared and compounded into expanded polyethylene sheets.

[Table] 〓 Half-life Measured according to JIS L-1094-1980 "Electrostatic test method for woven and knitted fabrics". Test conditions: Temperature: 22±2°C Humidity: 50-55% Test equipment: Stateik Honest Meter (manufactured by Shishido Shokai) Resistance value (surface specific resistance value) Measured according to the reference test method in JIS L-1094-1980. Test conditions: Temperature: 21±1℃ Humidity: 70% Test device: Electrometer TR8651 (manufactured by Takeda Riken) From the above results, at room temperature (22±2℃), experimental examples 1 and 2, which are the products of this invention, and the conventional product Although there is not much difference in antistatic performance from a certain comparative example, the lower the storage temperature from 15℃ to 5℃, the more remarkable the difference in antistatic performance between Experimental Examples 1 and 2 and the comparative example. The effects of the invention are obvious. § Experiment 2 Under substantially the same experimental conditions as in Experiment 1 above, foamed polyolefin sheets were produced by varying the amount of antistatic agent added. However, ethylene glycol (EG) was used as an additive. The results are shown in the table and FIG.

[Table] From the above results, when the amount of antistatic agent added to the foamed polyolefin sheet is small (Comparative Example 1), sufficient antistatic effect cannot be achieved.
It has been demonstrated that the greater the amount incorporated, the greater the antistatic effect.However, even if the amount incorporated is too large, the improvement in the antistatic effect accompanying the increase in amount is small, and there is little economic merit. § Experiment 3 Diethylene glycol monobutyl ether (freezing point -68.1°C, boiling point 230.4°C) was used as an additive, and an antistatic agent consisting of a 4:1 solution of the above Elegan S-100 and the above additive was added to the same resin as in the previous experiment. A foamed polyethylene sheet with a thickness of approximately 1.2 mm was manufactured by blending 0.25 parts with the raw materials. After storing the above foam sheet at a temperature of 5±2°C for one month, the antistatic performance was measured. From the results of half-life 0.5 sec or less and resistance value 3.3×10 ¹⁰ Ωcm or more, it was demonstrated that the above-mentioned diethylene glycol monobutyl ether is effective as an additive. § Experiment 4 Triethylene glycol monoethyl ether (freezing point -18.7°C, boiling point 255.9°C) was used as an additive, and 0.2 parts of an antistatic agent consisting of a 9:1 solution of the above Elegan S-100 and the above additive was added. A foamed polyethylene sheet with a thickness of 1.1 mm was produced by blending. After storing the foamed sheet at a temperature of 5±2° C. for one month, the antistatic performance was measured. The half-life was 0.5 sec or less and the resistance was 1.9×10 ¹⁰ Ωcm or more, which demonstrated that the above triethylene glycol monoethyl ether was effective as an additive. § Experiment 5 As an additive, acetophenone (freezing point 19.6
℃, boiling point 202.1℃), and the Elegan S-
A foamed polyethylene sheet having a thickness of about 1.2 mm was manufactured by adding 0.25 parts of an antistatic agent consisting of a 4:1 solution of 100 and the above additive. The antistatic performance of the foamed sheet after being stored for one month is shown in the table below.

[Table] From the above results, acetophenone has a storage temperature of 15
It is effective at ±2°C, but ineffective at 5±2°C. Furthermore, as an antistatic agent, it has been confirmed that it maintains a fluid state up to around 10℃ due to the lowering of the freezing point by mixing the main ingredient and additives, and is effective up to storage temperatures of around 10℃. It can be estimated that § Experiment 6 (comparative example using volatile additives) Ethanol (freezing point -114.4℃,
(boiling point 78.3°C), using a 4:1 solution of the above Elegan S-100 and the above additive as an antistatic agent,
A foamed polyethylene sheet with a thickness of about 1.2 mm was produced by blending 0.25 parts. The table shows the antistatic performance of the foamed sheet after storage at different storage temperatures and storage periods.

[Table] From the above results, it can be seen that ethanol, which has a low boiling point and is volatile, deteriorates in antistatic performance and is less practical when stored for a long period of one month or more. § Experiment 7 0.25 parts of an antistatic agent consisting of a 9:1 solution of Elegan S-100 and ethylene glycol was added to a polypropylene resin blended with ordinary foaming agents and cell regulators, and the mixture was extruded. Thickness approx. 0.9
A foamed polypropylene sheet with an expansion ratio of approximately 20 times was produced. The antistatic performance of the foamed sheet was measured after storage at a storage temperature of 5±2° C. The results are shown in the table.

[Table] From the above results, it was demonstrated that the antistatic agent of the present invention is also effective for foamed polypropylene sheets.

[Brief explanation of drawings]

FIGS. 1 and 2 are graphs demonstrating the effects of this invention.

[Claims]

1 0.05 to 0.7 weight of a metal salt of resin acid and cobalt as a metal element content per 100 parts by weight of rubber containing 70 parts by weight or more of one or two of natural rubber and synthetic polyisoprene rubber. In the rubber composition formed by blending the metal salts, an alkali metal salt of a resin acid and a cobalt salt of a monovalent acid are metathesized at 50°C or lower, separated without solvent extraction, and dried at 60°C or lower. did
The melting point is within the range of 140 to 180℃, the degree of oxidation by gas chromatography is 60% or less, the sulfur concentration in the metal salt is 2000ppm or less, and the toluene/water insoluble part of the metal salt has infrared absorption. It has a characteristic absorption near 3600cm ^-1 in the spectrum, and when heated at 5℃/min using a differential scanning calorimeter, it has a characteristic absorption of 250cm -1
A rubber composition characterized by using cobalt resin acid having endothermic peaks in the range of 350°C and 300 to 420°C.