EP0300176B1 - Band containing non-woven fabric, for drive and conveyor belts - Google Patents

Abstract

The invention seeks to provide a band containing non-woven fabric, for drive and conveyor belts, which band does not build up electric charges. The fibre mixture of the non-woven fabric contains about 1 to 10 % by weight of electrically conductive fibres. <IMAGE>

Description

The invention relates to a belt for drive and drive belts, conveyor and conveyor belts with metal fibers.

Driving and driving belts, conveyor and conveyor belts are manufactured using nonwovens, among other things, which have the least possible stretch and possibly a certain elasticity in order to avoid elongation of the conveyor belt during its use and the consequent re-tensioning.

One problem with this is the easily occurring electrical charging of the belt or belt, for example in the manner known from the way a van der Graff generator works. This effect is extremely undesirable, particularly for the transport of sensitive, for example electronic, parts.

It is already known to provide nonwovens with antistatic properties, so it has already been proposed to incorporate conductive fibers into them to avoid charging carpets and other materials, including synthetic fibers.

In DE-A-20 16 403 it was proposed to use a base fabric for tufted carpets and needle-punched nonwovens to avoid static charging of carpets, which has filament yarns or fiber yarns from a fiber mixture with metal fibers or metallized fibers.

DE-C-19 17 587 also describes the addition of metal, preferably steel fibers, to a laminate made of different fiber materials.

In order to avoid the static charging of turntables of turntables, DE-C-24 57 542 has already proposed Metal fibers, especially steel fibers, to be incorporated into the felt with which these plates were covered.

Conductive cloths made of a nonwoven with a metal fiber content for filter purposes have been described in "Textile Institute and Industry", 7 , 1972, p.199.

From FR-A-2 181 564 a conveyor belt made of a synthetic textile woven material is known, which is equipped to prevent electrostatic charging, whereby to reduce the electrical resistance at least the warp threads of the woven belt consist of metal threads that have a diameter in the They are of the order of 15/100 mm and have a mutual distance of the order of 1 cm. As already stated, fabrics have problems with stretchability.

In the prior art, nonwovens are used which were not subject to any special requirements with regard to resistance to linear expansion and are not suitable for conveyor belts.

It has also already been proposed to produce conveyor belts of this type to avoid charging with binders or coating compositions to which conductive substances, usually carbon black or metal dust, have been added. It was also disadvantageous that dark conveyor belts were always produced here, while as bright as possible belts are desired for many applications, such as in the electronics or food industry. The previous tapes were either too expensive to manufacture or disadvantageous due to a rapidly wearing coating. The problem was exacerbated by the increasing use of plastic fibers which are suitable for the purpose of length-constant conveyor belts due to their favorable properties and which have a particular tendency to become electrically charged.

It is therefore an object of the invention to equip belts with nonwoven fabric for drive and drive belts, conveyor belts and conveyor belts so that charging of the conveyor belts can be avoided.

The object is achieved according to the invention by a generic band material having metal fibers, in which the band is formed from a nonwoven fabric which contains 1 to 10% by weight of steel fibers, the steel fibers being arranged uniformly over the entire cross section of the nonwoven.

Various nonwovens can be used as fiber nonwovens, for example needled nonwovens, random fiber nonwovens or the like.

The fiber mixture of the nonwoven fabric can have synthetic and / or natural and / or regenerated fibers, such as, for example, polyester, polyamide, polypropylene, polyacrylic, cotton, coconut, rayon fibers or the like.

It is particularly preferred if the tape has one or more high-strength, low-stretch yarns, filaments, fabrics or scrims made of synthetic and / or natural and / or regenerated fibers. Suitable fibers can include polyester, polyamide, polypropylene, wool, polyaramid, glass and ceramic fibers or combinations thereof.

Those which have at least one metal or elementary carbon can be used as electrically conductive fibers.

E.g. Steel fibers or copper fibers are suitable for this purpose, but it is also possible to use metallized, for example copper-plated or silver-plated threads. Carbon here means conductive carbon modifications, such as graphite whiskers.

In a preferred embodiment, steel fibers with a titer of 0.8-18 dtex, preferably 3-10 dtex and a staple length of 20-80 mm have proven to be advantageous for these purposes.

It is preferred that the surface resistance of the nonwoven material at 100 V voltage is 10² to 10⁸, preferably 10⁴ to 10⁶ ohms.

Hydrophobic binders, such as nitrile-butadiene rubber and / or styrene-butadiene rubber latex, can be used.

A conductive nonwoven for drive belts, conveyor belts and conveyor belts is preferably made of a mechanically needled synthetic fiber fleece with incorporated conductive fibers and a binder with which the base nonwoven is impregnated. In the manufacture of the nonwoven, which may contain one or more fabrics or scrims, conductive fibers are added to the nonwoven, then the mechanically consolidated nonwoven is impregnated with a binder solution and then dried at a temperature of 100 ° C.

The fiber mixture of the nonwoven fabric can have synthetic and / or natural and / or regenerated fibers. For example, polyester fibers, polypropylene fibers or mixtures thereof have proven to be favorable as synthetic fibers, in particular because of their high durability, but also because of the low price.

Particularly preferred electrically conductive fibers are those which have at least one highly conductive and have flexible metal such as copper, iron, aluminum, or fibers or elemental carbon coated with a conductive metal.

Preferred binders are nitrile-butadiene rubber and / or styrene-butadiene rubber latex. Aqueous dispersions of nitrile-butadiene rubber, styrene-butadiene rubber latex or solvent-based binders such as polyurethane, polyvinyl chloride, polyacrylate or mixtures thereof can be used as binders.

The ratio of fiber to binder can preferably be 1: 2 to 2: 1, particularly preferably 1: 1 parts by weight.

The impregnated and dried nonwoven can then be sanded on one or both sides, for example with emery paper, to improve the surface.

A fleece suitable for the production of drive belts, conveyor and conveyor belts can have thicknesses of 1-8 mm, preferably 2-5 mm and a basis weight of 300-6,000, preferably 1,000-4,000 g / m².

A conductive nonwoven for drive belts, conveyor and conveyor belts according to the invention consists of a preferably synthetic nonwoven, which has been mechanically consolidated, binders and fillers, dyes and vulcanizing agents, in which the fiber mixture contains 1-10 percent by weight of conductive fibers made of steel, graphite, cellulose or contains silver-plated or copper-containing fibers.

• Fig.1: einen Teilabschnitt eineserfindungsgemäßen Bandes in der Draufsicht;
  und
• Fig.2: den Teilabschnitt des Bandes der Fig. 1 im Querschnitt.

Further features and advantages of the invention result from the following description, in which a preferred embodiment is explained with reference to the drawing, in which a tape according to the invention is shown. It shows:

• Figure 1: a partial section of a tape according to the invention in plan view;
  and
• Fig.2: the section of the tape of Fig. 1 in cross section.

As shown in FIG. 1, a band according to the invention is formed by a nonwoven layer 10, here with 10% by weight of steel fibers with 6 dtex. The cross section of FIG. 2 shows that the steel fibers are evenly distributed over the entire thickness of the fleece.

Example:

For a polyester fabric or scrim with a basis weight of approx. 100 g / qm from 6 threads 1100 dtex in the longitudinal direction and 3 threads 1100 dtex in the transverse direction, 950 g / qm polyester fibers each consisting of 2 parts 6.7 dtex are used on both sides and 1 part of 17 dtex, to which 2% by weight of steel fibers of 9 dtex had been added, so that the thickness of the fleece was 6 mm, the weight per unit area was 2000 g / m 2 and the density was 0. 33 g / cubic centimeter.

The base fleece is then impregnated with 100% by weight of nitrile-butadiene rubber latex, to which 25% by weight of calcium carbonate as filler and 5% by weight of vulcanizing agent made from sulfur and zinc oxide are added, coagulated in an infrared shaft, washed out, dewatered, and then dried and vulcanized at 150 degrees Celsius. Then the binder-strengthened nonwoven is sanded on both sides with emery paper, grain size 120, so that a uniformly smooth surface and a thickness of 5.5 mm are produced.

The product has a surface resistance of 1x 10⁵ Ohm at 100 V applied voltage.

Claims (5)

1. A belt for drive/transmission belts and forwarding/conveyor belts with metal fibres, characterised in that the belt has been formed from a fibre web which contains from 1 to 10% by weight of steel fibres, the steel fibres being uniformly arranged over the entire cross-section of the web.
2. A belt according to Claim 1, characterised in that the fibre mixture comprises synthetic and/or natural and/or regenerated fibres.
3. A belt according to either of the preceding claims, characterised in that the surface resistance at a voltage of 100 V is from 10² to 10⁸, preferably from 10⁴ to 10⁶, ohm.
4. A belt according to any one of the preceding claims, characterised in that the conductive fibres are based on at least one metal or elemental carbon.
5. A belt according to any one of the preceding claims, characterised in that it comprises one or more high-strength, low-stretch yarns, filaments, woven fabrics or laid fabrics composed of synthetic and/or natural and/or regenerated fibres.

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