FI104092B - Electrostatically controlled piece - Google Patents

Description

104092

ELECTRICALLY CONTROLLED TRACK ^ TECHNICAL FIELD

The invention relates to material technology and relates to plastic bodies protected against static electricity generation, their manufacture and use. The invention can be utilized in the manufacture of plastics, for example, transport containers or enclosures for devices that require static electricity control.

TECHNICAL BACKGROUND

In many cases, the generation of static electricity is harmful or even a hazard list. When handling highly flammable or explosive materials, static discharge can cause accidents. They are prevented by using anti-static vessels and facilities. Static electricity discharges can also damage sensitive electronic equipment, both during manufacture and use, requiring the use of antistatic enclosures, transport equipment, and manufacturing facilities.

15 Highly conductive metal bodies do not generate static electricity. However, metals cannot be used in all applications.

In plastic parts, the generation of static electricity is a particular problem. Electricity generation can be prevented by increasing the conductivity of the body surface or the body.

Antistatic agents may be used to increase the surface conductivity of the body. The conductivity of these is usually based on ionic charge carriers. However, these substances are not always able to obtain sufficient conductivity. In addition, they tend to migrate to the surface of the piece and eventually disappear. They are also very sensitive to the humidity of the air and lose their function in extremely dry conditions.

»'· In order to increase the electrical conductivity, a conductive additive such as carbon or metal can be mixed with the plastic. In order to achieve conductivity, the additive is quite necessary, which accordingly degrades the properties of the mixture. The plastics filled in this way are not suitable for many applications. An additional problem is the difficult to adjust conductivity.

Internally conductive polymers are also known. Their electrical conductivity is based on polymer chain conjugated double bonds, ring structures, and 2,104,092 electron donating or receiving alloys. Known conductive polymers include, for example, polyacetylene, polyparaphenylene, polypyrrole, polythiophenes, polyphenylene vinylene and polyanilines. The major problem with conductive polymers * has been their poor stability. Another problem has been the poor processability of the melt.

»5 Conductive polymers can in principle be used with other polymers. However, the problem here is the poor compatibility of conductive polymers with conventional polymers of interest. Polymerization of a conductive polymer on the surface of a common plastic has also been used, but this method is also unsatisfactory.

10 Conductive polyanilines contain aniline or a derivative thereof as a monomer. In the polymer, the nitrogen atom is bonded to the para-carbon atom of the next unit benzene ring. Polyaniline can exist in many different forms, of which the so-called emeraldine form is commonly used for conductive polymer applications. Usually a protonic acid, in particular sulfonic acid, is used as the dopant. A suitable acid may be used to plasticize the mixture excess. A suitable metal compound may be used to compensate for the acidity caused by the excess acid. EP 582919 A discloses one such method for the production of an electrically conductive polyaniline resin.

DESCRIPTION OF THE INVENTION

20 General description

An electrostatic-controlled body according to claim 1 containing a conductive polymer has now been found. Certain preferred embodiments of the invention are set forth in the other claims.

It is most important in the invention that the surface resistivity of the surface, expressed in units of Ω / D, is at least a decade, preferably at least two decades, greater than the resistivity of the interior expressed in units of Qcm. Thus, the surface drains the charge slowly enough by controlling the electrostatic discharge, but due to the lower resistivity of the inner part, the charge is not stored in the body.

DETAILED DESCRIPTION 30 As used herein, a paragraph generally refers to any whole product, such as a sheet or case, or part of a product, such as a coating. The body may be made of a single alloy containing conductive polymer or may be made of a body in which the top layer and the inner layer are different. In addition to the doped conductive polymer, the article material may contain a matrix material such as a suitable plastic and suitable additives.

"f; The resistivity of the outer surface is, for example, about 10 ^ - 10 ^ Ω / ΕΙ, most preferably about 10 ^ - 1010 Ω / Π, and most preferably about 10 ^ - 10 ^ Q / Sis. 2 -10 ^ Ωαη, most preferably about 10 "2 - 106 Ωαη and most preferably about 10" 2 - 10 ^ Qcm.

According to one embodiment, the piece has a resistivity profile in which the resistance when first going inward from the surface first decreases and then rising inwardly increases to a substantially constant level.

10 The conductive polymer is preferably polyaniline (including polyaniline derivatives) which is very stable. The conductive dopant is preferably a functional dopant, which also provides good compatibility with non-polar matrix plastics. The acid may in particular be an organic sulfonic, phosphoric or phosphonic acid. Most preferably the acid is an aromatic sulfonic acid, especially al-15-alkylbenzenesulfonic acid, especially dodecylbenzenesulfonic acid. An excess of acid is best used to provide more plasticity. In addition, a metal compound such as zinc oxide is best used to compensate for the acidity, especially as described in EP-545 729 and EP-582 919 A (the references are incorporated herein by reference). It is also possible to add calcium compounds such as calcium carbonate. For example, the pH of the mixture is about 3-8, typically about 4-7.

Preferably, the composition comprises a melt-processable conductive polymer blend and a compatible melt-processable matrix resin. They can be mixed with each other using suitable machine tools such as mixers or knives to provide shear forces to the mixture. A screw mixer is best used.

The matrix resin may contain a thermoplastic such as polyolefin, polyvinyl chloride, styrene-butadiene polymer, polyester, polyamide, acrylonitrile-butadiene-styrene, rhenium polymer or polycarbonate, or a thermoset such as phenol-formaldehyde. Polyolefin such as polypropylene or polyethylene is best used. The conductive polymer blend comprises, for example, from about 0.1% to about 30% by weight, preferably from about 1% to about 20% by weight, and most preferably from about 5% to about 15% by weight.

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The bodies according to the invention may be made of a conductive polymer-containing plastic. The advantages of plastics are good processability, lightness and generally low cost.

Separate antistatic coating treatment is not required for the piece fabrication, but the fabrication can be done in one step. Conductive polymers also achieve lower resistivity than coatings. Surface wear does not increase resistance and under normal conditions the controlled electrostatic properties of the body are maintained for 5 to 10 years.

With conductive polymers, resistivity is easier to adjust than with carbon-10 or metal fillers, and sufficiently low resistivity for ESD and also EMI applications is reliably achieved.

With conductive polymers, the properties of the articles are also improved than with carbon or metal fillings because the mechanical properties of the conductive polymer, such as impact strength, are better matched to those of the matrix plastic.

Also, no dirty and electrically conductive carbon or metal dust is released from the product of the invention.

The dyeing capabilities of the product of the invention are better than with carbon-filled materials.

The inventive alloys also have the advantage that carbon or metal filler plastics have good processability. For example, the alloy does not consume hardware such as metal filled plastics. The alloy has a low viscosity whereby lower temperatures or higher speeds can be used. Due to its high processability, it is also possible to use different manufacturing processes, for example, to make a fiber or film, or to stretch the product.

The polyaniline alloy acts as a special process aid that lowers the required processing temperature. This shortens the production time and makes it possible to manufacture pieces with a difficult structure.

According to one embodiment of the invention, the entire body is made of a single plastic alloy, which is melt-processed and then solidified so that a desired resistivity profile is formed in the kappa sheet. According to another embodiment of the invention, the body is made of two different alloys with different conductivities. According to both embodiments, the body is best manufactured by injection molding.

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It is also possible, for example, to mold parts of the plastic alloy in a suitable manner by molding or coating.

The bodies according to the invention are particularly suitable for applications where protection against static electricity or electromagnetic interference (EMI) is required. Typical applications of the products of the invention include packaging for the electronics industry, articles for handling and transporting chemicals or explosive products, shipping containers, cases, e.g., diskette cases, copying machines, etc., and components for industrial painting such as, for example, automotive buffers. protective covers for computers and other sensitive electronic devices are an important application of the products of the invention specifically to provide EMI protection. Such items may include, for example, circuit boards for circuit board components, enclosures for equipment, containers, or even coke rooms in rooms.

Example 15 An emeraldine base form of polyaniline prepared by Y. Cao, A. Andreatta, A.J. Heeger & P. Smith, Polymer 30 (1989) 2305, but using sulfuric acid instead of hydrochloric acid in the polymerization.

Sulfosoft, a commercial grade of dodecylbenzenesulfonic acid (DBSA), was used as the polyaniline dopant.

Prepared by solidification screw mixing at 150 ° C with polyaniline / DBSA complex (PANI), which additionally contained zinc oxide and calcium carbonate.

This complex was mixed with polypropylene (PP) at 170 ° C in the same apparatus. The following compositions (ingredients by weight, based on the total mixture) were prepared: 25 __P1__P2__P3 polyaniline__1,77__1,11__1,77 DBSA__IM__10j3__10,2

ZnO__U6__0 * 98__1.06 lcaC03 1.15 1.14 1.14

The mixtures were prepared by injection molding (200-220 ° C, dwell time less than 3 min); 100x100x50 mm- * boxes with a wall thickness of 2 mm. The boxes had a 6 104092 witch lid. For comparison, boxes were also made of two commercial carbon-containing polypropylene blends (PP / CB; Cl, C2). The boxes were otherwise similar in appearance, except that the PP / PANI boxes were green and the PP / CB boxes black. PP / PANI boxes were about 8% lighter. The bending-5 durability of the PP / PANI box lids was significantly better: the lids could be bent thousands of times without breaking, while the lids of the PP / CB boxes had broken a little more than ten times.

The surface resistivity (R $) was measured according to DIN 53 482 using a 100 V potential and a ring electrode.

The resistivity profile was measured using a 2-point sensor moving in the depth of the piece. For some specimens, resistivity was also measured on thinly sliced slices that were cut parallel to the surface using a 4-point transducer. The latter method is more laborious, but provides more accurate and accurate values, since 4-point measurement eliminates contact resistance. Values obtained with 2-point measurement are too small.

Figure 1 shows a typical resistivity profile of a PP / PANI body. The resistivity decreases as the surface goes inward, but then increases again. However, the material is homogeneous throughout the article. The resistance of the CB block is constant throughout the block.

Figure 1 also shows the mean resistances pc and pr. pc is calculated from the average of the conduk-20 dances and describes the resistivity that an electromagnetic field sees as it passes through a song. pr is calculated from the average of the resistances and represents the resistivity that the current sees as it attempts to pass through the object. The lower the pq, the better the electrostatic properties.

ESD protection features were measured according to IEC 801-2. Inside the box, either a ring (diameter 28 mm) or dipole (length 50 mm) antenna was used to detect interference. The antenna was connected to an oscilloscope to detect the difference between maximum and minimum voltage. The boxes were tested using 4 kV direct and indirect charges. The direct charge was applied to the surface of the box. Indirect charge was applied 10 cm from the box.

The results of β 30 ESD measurements are shown in Table 1.

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table 1

Alloy Rs (Ω / Π) Direct Charge (V) pc (Qcm) Indirect Charge (V) __ ring dipole__ ring dipole, P1_ 2.7 * 108 3.7 5.4 6.5 * 10 ^ 1.9 2.6 P2_ 3.3 * 108 3.0 5.8 8.3 * 10 ^ 2.9 4.5 P3_ 2.3 * 108 1.2 2.2 2.6 * 106 3.8 6.8

Cl_ 1.1 * 104 4.2 8.6 7.7 * 10 ^ 2.3 3.5 C2 19.7 * 103 | 4> 6 6.8 | 6.8 * 105 1.9 3.3

In the bodies according to the invention, pq is small enough that the charge cannot be stored. Measurements showed that the 1000 V charge discharged to 50 V in less than 2 5 s. However, a high Rs prevents charging by discharging by sparking. However, the PR is also high (see Figure 1), which prevents, for example, the batteries from discharging through the box.

§

Claims (12)

104092 O 1. An electrically conductive electrostatic-controlled melt-machined article, characterized in that it contains a conductive polymer component and a compatible matrix resin, made by first mixing the conductive polymer component at 150 ° C and then together with the matrix resin at 170 ° C. and forming the body of the mixture thus obtained by a molding process and having an outer surface resistivity, expressed in units of Ω / D, of at least a decade and preferably of at least two decades greater than the resistivity of the interior in units of Ωαη. Piece according to Claim 1, characterized in that the outer surface has a surface resistivity of about 10 ^ - 10 ^ 2 Ω / D, preferably about 10 ^ - 10 ^ Ω / D and most preferably about 10 ^ - 10 ^ Ω / D and the resistivity of the inner part is about 10 * 2. io ^ Ωαη, preferably about 10 * 2 - 10 ^ Ωαη and most preferably about 10 * 2 - 10 ^ Ωαη. Piece according to Claim 1 or 2, characterized in that the piece 15 has a resistivity profile in which the resistance from the surface first decreases and then increases further to a constant level when going inward. Body according to Claim 3, characterized in that the body is made by injection molding. Piece according to one of Claims 1 to 4, characterized in that the whole piece is made of a single material. Piece according to Claim 5, characterized in that the piece is a box. Piece according to one of Claims 1 to 6, characterized in that the conductive polymer component is a blend containing a conductively doped polyaniline or a polyaniline derivative, preferably an acid doped polyaniline or polyaniline derivative. Piece according to Claim 7, characterized in that the mixture contains an acid doped polyaniline or a polyaniline derivative which is a functional doping acid such as an organic, preferably aromatic sulfonic acid such as alkylbenzenesulfonic acid and especially dodecylbenzenesulfonic acid. Body according to claim 7, characterized in that the conductive polymer alloy contains a metal compound such as zinc oxide. 104092 Body according to one of Claims 1 to 9, characterized in that the matrix plastic contains a thermoplastic such as polyolefin, polyvinyl chloride, styrene-butadiene polymer, polyester, polyamide, acrylonitrile-butadiene-styrene polymer or polycarbonate. 11. A body according to claim 10, characterized in that the matrix resin contains polyolefin, preferably polypropylene or polyethylene, most preferably polypropylene. Piece according to one of Claims 1 to 9, characterized in that the matrix resin contains a thermoset, such as a phenol-formaldehyde polymer or a melamine-formaldehyde polymer. 13. A process for the production of an electrically conductive electrostatic-controlled body by a melt-working process, characterized in that first a mixture of a conductive polymer component containing a conductive doped polyaniline or polyaniline derivative is mixed at 150 ° C, and then at 170 ° C. with a matrix resin which is compatible with the matrix resin and which is manufactured by injection molding a part containing a conductive polymer and having an outer surface resistivity in units of vähintään / Ό greater than or equal to at least two decades greater than the internal resistivity in units. Method according to Claim 13, characterized in that the residence time in injection molding is less than 3 min. The process according to claim 14, characterized in that the injection molding temperature is 200 to 220 ° C. 16. A method for preventing electrostatic or electromagnetic interference from a body, characterized in that a body according to any one of claims 1 to 12 or manufactured according to one of claims 13 to 15, having a surface resistivity of about 10 to 10 10 Q / d, preferably about 10l ° Ω / Π and most preferably about 10 ^ - 10 ^ Ω / ΕΙ and the resistivity of the inner part is about 10 "2 - 10 ^ Ωαη, most preferably about 10'2 - 10 ^ Ω ^ and most preferably about 30 ΙΟ - 2 - ΙΟ4 Ωαη. 17. A method for protecting a product from electrostatic or electromagnetic interference, characterized in that the article is applied to an article si, 0 104092 according to any one of claims 1 to 12 or manufactured according to one of claims 13 to 15, wherein the outer surface has a surface resistivity of about 10 ^ - 10 ^ 2 D, preferably about 10 ^ - 1010 Ω / Π and most preferably about 10 ^ - 10 ^ Ω / D and the resistivity of the inner part is about 10 "2 - 10 ^ Qcm, most preferably about 10'2 - 10 ^ Qcm and most preferably about ΙΟ -2 -104 Qcm. 5 Patent claims