In­dus­tri­al clean­ing rep­re­sents an eco­nom­i­cal­ly im­por­tant and ex­pand­able fu­ture mar­ket for clean­ing en­ter­pris­es. An ex­am­ple is the clean­ing of paint­ing lines: Sur­face paint­ing is an im­por­tant pro­duc­tion step in sev­er­al in­dus­tri­al fields. Es­pe­cial­ly in the au­to­mo­tive in­dus­try, but also in me­chan­i­cal en­gi­neer­ing, fur­ni­ture, build­ing de­vices and con­sumer goods in­dus­try, sur­face treat­ments are done in paint­ing lines. De­pend­ing on the paint­ing pro­ce­dure, part ge­om­e­try and di­men­sion, 10-90 % of the sprayed paint does not reach the work­piece. Resid­u­al paint, the so called over­spray, is given off to the sur­round­ings as haze. Al­though the over­spray is part­ly catched and then uti­lized or dis­posed, the paint­ing line sur­faces get high­ly soiled by paint haze. In order to guar­an­tee a high qual­i­ty of the paint­ing, the clean­li­ness of paint­ing lines and spray booths is of es­sen­tial im­por­tance. The cur­rent clean­ing pro­ce­dures show many dis­ad­van­tages. Nec­es­sar­i­ly more ef­fi­cient clean­ing pro­cess­es have to be de­vel­oped. An ap­pro­pri­ate ap­proach re­lies on the ap­pli­ca­tion of spe­cial soil-re­lease poly­mer­ic sys­tems. They pos­sess on the one hand cer­tain rhe­o­log­i­cal prop­er­ties (thixotropy), which allow them not to run-off on walls (ver­ti­cal sur­faces). On the other hand they show high affin­i­ty with water (high swelling ra­tios). These soil-re­lease sys­tems are ap­pli­ca­ble at room tem­per­a­ture and form on the sur­face a trans­par­ent pro­tec­tive film. After soil­ing with paint and sprin­kling with tape water this film swells be­cause of water take up and thus can be re­moved eas­i­ly from the sur­face with­out high pres­sure. Aim of the re­search pro­ject was there­fore the de­vel­op­ment of a clean­ing pro­ce­dure based on thixotrop­ic soil re­lease gels for the re­moval of strong­ly ad­he­sive in­dus­tri­al soil­ings. In order to meet the re­quire­ments in prac­tice, sev­er­al cri­te­ria have been con­sid­ered for the poly­mer se­lec­tion: com­pat­i­bil­i­ty with the var­nish­ing, con­ve­nient thixotrop­ic be­haviour as well as easy re­moval when get­ting in con­tact with water. As gelling agents were used both syn­thet­ic (polyethy­lene oxide/ polypropy­lene oxide copoly­mers) and nat­u­ral poly­mers (cel­lu­lose deriva­tives, xan­than gum, galac­toman­nanes). The thixotrop­ic prop­er­ties were de­ter­mined by means of a ro­ta­tion­al vis­cosime­ter. The de­vel­oped soil-re­lease gels were ap­plied on typ­i­cal sur­face ma­te­ri­als, like stain­less steel, gal­va­nized tin, alu­mini­um, float glass, glazed ce­ram­ic tile, poly­car­bon­ate and poly­methyl­methacry­late in a spray booth with a spray robot. The soil re­lease films formed after dry­ing were char­ac­ter­ized and op­ti­mized in terms of dry­ing time, film for­ma­tion, film ho­mo­gene­ity and ad­he­sion. The coat­ed ma­te­ri­als were af­ter­wards soiled well-de­fined with var­nish and in­ves­ti­gat­ed with re­gard to the mi­gra­tion and re­moval abil­i­ty. Be­side dif­fer­ent var­nish types and col­ors (sol­vent-based and wa­ter-based sys­tems, one- and two com­po­nent sys­tems, syn­thet­ic resins var­nish, acrylic var­nish, hard­en­er and thin­ner) were used also dif­fer­ent prac­tice ori­ent­ed soil­ing sce­nar­ios. Some of the anal­ysed poly­mer sys­tems showed an ad­e­quate func­tion­al­i­ty (film ad­he­sion, re­moval abil­i­ty, no mi­gra­tion) even after a longer res­i­dence time of the varn­sih on the soil-re­lease film. The re­sults show that al­ready short dry­ing times of the soil-re­lease poly­mer­ic dis­per­sion are suf­fi­cient to ful­fil the coat­ing func­tion­al­i­ty. Resid­u­al soils like soil-re­lease film or var­nish rest take no ef­fect on func­tion­al­i­ty (ad­he­sion and strip­ping be­haviour) of the soil-re­lease dry film, so in prin­ci­ple a mul­ti­lay­er coat­ing with soil-re­lease film and soiled film is pos­si­ble with­out in­ter­im clean­ing pro­cess. On the basis of the pro­ject re­sults the costs of the re­spec­tive clean­ing pro­ce­dures can be re­duced.

The IGF-pro­ject 15911 N of the re­search as­so­ci­a­tion Europäische Forschungs­ge­mein­schaft Reini­gungs- und Hy­gien­etech­nolo­gie e.V., Cam­pus Ficht­en­hain 11, D-47807 Krefeld, was sup­port­ed via the AiF with­in the fund­ing pro­gramme „In­dus­trielle Gemein­schafts­forschung und –en­twick­lung (IGF)“ by the Fed­er­al Min­istry of Eco­nom­ic Af­fairs and Tech­nol­o­gy (BMWi) due to a de­ci­sion of the Ger­man Par­lia­ment.

The re­search re­port is avail­able on re­quest from FRT.