Coating processes – Solid particles or fibers applied – Plural particulate materials applied
Patent
1997-09-24
2000-01-25
Parker, Fred J.
Coating processes
Solid particles or fibers applied
Plural particulate materials applied
427352, 427353, 427366, 210504, 210507, B05D 310
Patent
active
060175834
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for the manufacture of a strip material in which on at least one side of a support a plastics layer is formed from a mixture of plastics material and particulate soluble corpuscles, the soluble corpuscles being leachable by a solvent to which the plastics material is stable and that thereafter the soluble corpuscles are at least in part leached out of the plastics layer with the formation of throughflow passages.
DESCRIPTION OF RELATED ART
A strip material of the aforesaid type for employment in a paper machine is described in EP-B-0 196 045. It comprises a support in the form of a liquid previous fabric onto which a layer, 1,3 to 5 mm thick, of an elastomeric Polymer resin has been applied. The plastics layer comprises throughflow passages which pass from the otherwise smooth and plane outside down to the support and which, in the paper machine, serve as de-watering passages.
The production of the throughflow passages is brought about in that textile fibres are homogeneously dispersed in the polymer resin, prior to the mixture of textile fibres and polymer resin being applied onto the support. As an alternative to the aforegoing, a fibre fleece may first be applied onto the support, whereafter the coating of polymer resin is applied. In both cases the textile fibres are composed of an organic material which can be dissolved by the application of a solvent, the plastics layer being resistant to this solvent. The leaching out of the textile fibres is carried out after the application of the polymer resin by the application of the solvent such that the throughflow passages are formed the configuration and orientation of which corresponds to the leached out textile fibres.
In a less preferred embodiment, particulate corpuscles are proposed instead of the textile fibres which are distributed homogeneously in the polymer resin. Inorganic salts or their hydrate or oxides are proposed as the material for those corpuscles. By appropriate solvents they can be leached out of the polymer resin in the same manner as the textile fibres and in the course thereof leave behind pore cavities.
In the manufacture of the above described paper machine belt difficulties are experienced with the uniform distribution of the soluble components--either fibres or particulate corpuscles--in the polymer resin and with the maintenance of this distribution when applying the mixture. The reason is that during the processing of the mixture of polymer resin and soluble components demixing takes place, so that there can be no certainty that throughflow passages are formed by the leaching out of the particles. For that reason it is also not possible to produce distributions of the soluble components which vary over the cross-section.
Apart from that, polymer resins have a tendency after curing to form a closed surface which inhibits the dissolving out of the soluble textile fibres or corpuscles contained in the polymer resin. In order to solve this problem, it has been proposed in EP-B-EPO 273 613 to so grind down the surface of the plastics layer, that a communication is formed to the soluble fibres and in addition a smooth surface is generated. Such a grinding procedure, however, is very time consuming. Moreover, it is first necessary to apply an appropriate excess of plastics material and during the grinding procedure dust is formed which must be sucked off and be either disposed of or be processed for reuse. Moreover, a smooth surface is formed which inhibits release of the paper strip from the paper machine belt. The reason is that paper strips are inclined to become firmly drawn against smooth surfaces.
Apart from the aforegoing disadvantages, paper machine belts of this genus are claimed to have a number of advantages as compared with known felt materials, according to the batt-on-base principle, more particularly an increased resistance against permanent deformation and thereby a longer operating life and resulting therefrom reduced maintenance costs, improved abrasion res
REFERENCES:
patent: 4482601 (1984-11-01), Hartigan, Jr.
patent: 5298124 (1994-03-01), Eklund et al.
patent: 5364504 (1994-11-01), Smurkashi et al.
Conrad Munzinger & Cie AG
Parker Fred J.
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