US2668781A - Antistick coated, steel building sheet - Google Patents

Description

Feb. 9, 1954 P. w. JENKINS ANTISTICK COATED, STEEL BUILDING SHEET Filed Sept. 22, 1951 IN VEN TOR. 2:0/ hz dwz/m6 BY Patented Feb. 9, 1954 Paul W. Jenkins, Pittsburgh, Pa., assigner to H. H. Robertson Company, Pittsburgh, Pa., a corporation of Pennsylvania Application September 22, 1951, Serial No. 247,853

2 Claims. (Cl. 117-85) -This invention relates to building materials and more particularly to a building material having a bituminous or similar surface which is normally characterized by some degree of tacklness and by a tendency to adhere to other surfaces placed in contact therewith.

One object of the invention is to provide a building material of the character specified with a novel and highly efficient antistick layer covering and adhering to a normally tacky surface of the building material.

` More specifically, an object of the invention is to provide a protected metal article of the type illustrated in the United States Patents to Robertson and to Coffman Nos. 1,277,755 and 2,073,334, having an antistick coatingmaterial possessing novel and superior characteristics which render such protected metal articles more suitable for their intended purposes than prior commercial forms of such articles.

With these general objects in View and such others as may hereinafter appear, the invention consists in the building material, in the protected metal sheets, and in the antistick compositions hereinafter described and particularly defined in the claims at the end of this specification.

In the drawing, Figs. 1 and 2 represent sectional views illustrating building sheets of the type shown in said Robertson and Coffman patents, each being provided with the present antistick layer.

In order to successfully ship and handle the protected metal building sheets forming the subject matter of the Robertson and Coffman patents above referred to, it has been the practice to provide the outer bituminousweatherproofing coatings with antistick layers in order to prevent the sheets from adhering together during shipment, and particularly during shipment in warmer climates, and in practice, these prior antistick compositions have comprised either the coating composition forming the subject matter of United States Patent No. 1,904,341, or the antistick coating composition disclosed in the United States patent to Young and Jenkins No. 2,440,626.

While the water-soluble antistick coating compositions disclosed in said Patents Nos. 1,904,341` and 2,440,626 are capable of performing their primaryantistick function in an efficient manner and without deleterious effects upon the underlying bituminous weatherproong coatings of the protected metal sheets, nevertheless, after such sheets have been erected it has been found from experience `that those exposed surfaces, such as the outer surfaces of the building sheets erected upon thefbuilding, 'whether as roofing or siding,

y remain in `a much better condition than the inner surfaces of the sheets which are not exposed to the weather. This has been found to be due to the fact that the effect of the weather upon the outer surfaces of the sheet has been to wash away the water-soluble antistick film from the outer surface of the sheet so that after a shortperiod of time the outer surfaces or sheets become free from the antistick lm.

In contrast therewith, experience has proved that those surfaces of the sheets which are not exposed to the weather, such as the undersurface of the sheets employed as the roof or the inner surfaces of the sheets employed as siding, do not remain in as satisfactory condition as do the outer or exposed surfaces of the sheets. This has been found due to the fact that in industrial buildings, such inner or undersurfaces of the sheet are normally subject to wide variations of temperature and variations in the humidity of the atmosphere within the building, both of which tend to induce strain between the antistick lm and the underlying bituminous coatings tov which the film is attached, and eventually checking, cracking, and alligatoring of the bituminous coatings result.

Because of the fact that it is impractical to wash off the antistick film or otherwise remove the same from such inner surfaces of the sheets prior to or after erection of the sheets on the building, it is extremely desirable to produce an antistick coating composition which not only is capable of functioning as a satisfactory antistick during shipment and handling of the sheet but which also possesses a minimum tendency to disrupt the bituminous coating on the under or inner surface of the sheet after the same has been erected upon the building. Prior attempts to control the plasticity of water-soluble films, such as the alginates and the cellulose ethers referred to in said U. S. Patents 1,904,341 and 2,440,626, so as to minimize the tendency of the films to induce strains in the bituminous coatings, have relied upon the use of plasticizers of the class of the polyhydric alcohols, such as glycerine, all characterized by a relatively high degree of hygroscopicity. Changes in moisture content in response to changes in humidity have been accompanied by variations in physical properties and dimensions of the films, all of which have been conducive to setting up stresses between the film and the underlying coatings. Furthermore, such fllmvcompositions have been subject to leaching l out of the plasticizer by movement of moisture into and out of the film, and' gradual reduction to the unplasticized stata` and as a result checking, alligatoring, and cracking of the bituminous coatings have resulted, diminishing the durability and impairing the appearance of the inner surfaces of the sheets.

The present invention contemplates an improved antistiek composition andv an improved building sheet providedl With the antistick composition and is based upon the recognition of the importance of holding the moisture content l of the antistick lm to as constant a value as possible. hlm-forming material, such as an alginate, either sodium or ammonium alginate,- or one of the cellulose ethers or the like, and. prelerablymethyl.

cellulose, is combined with a plasticizing agent of Very low hygroscopicity and in suchproportions that the moisture contentof' the resulting film over the normal range of humidity tobe encountered in the building is no greater than that oi the film-forming material under such conditions. v4In practica plasticizing agent. which may be used for thisv purposel may com- Prise one of the water-soluble polyalliiylenev glyeols arid/or the. mono-ether or mono-ester,y derivatives thereof. The principal elyeolsofthis class which I may use comprise, the polyethylene elyeols and. the Water-soluble copolymers of.' ethylene and propyleue slyools which are the subject oi U, S.. Patent. No. 2,425,845.. Among the. derivatives oi., suehrolyelyools which may be used, I prefer to employ tbemouo-ethersof. such polyglyools with the C to Ci ellrauols. The ud Water-soluble copolymers of ethylene and propylene elyools, and derivatives thereof, are found, to ollera particularly advantageous oombinarios4 of properties, to wit, 4low hyeroseopioity.. low'vapor pressure, low solubilltyiu end lor bi,- tuminous rrlaterialsv low pour point', and high viscosity index. Typical of these copolymers which may be employed are vthe members. ofthe 75-Hserle's (-dlols)y and they lio-HB series (meriobutyl ethers) of fluids, marketed under the trade. llame ofv Uoort Members of this water-solubleseries arecharacterized-.by low-vapor press sure, lowsolubility in or for aliphatic hydrocarbone, and are only slightly hysrosoopio.v

The film deposited from. a. water solution. of` equal partsby weight of methyl cellulose and Ucon fluidrQf-HB-GGD. is cited as an example of aneleotive autistick which. is reletively'ilree from tendency to distort the bituminous surfaces forl which intendedr even after-long periods of. oouteetuiider.adverseconditions.

vA somewhat` lower, ratio oi. the "Ueon," fluid to methyl cellulose might be employed and some. advantage is gained by increasing` theratio to, as',A much as vtwo parts-A of'plasticzer to1 011e. partl of methyl cellulose. Variations `in, ratio of this, order have Lnotbeen found to. make any appreciable difference ineiectiveness of the films in preventing sticking. While the Ucon fluid has. been rreferred to, asN a plasticiaer flor the methyl. cellulose, it is. rather obvious froxn the,propor-4v tions that may be employed that both` ingredients. are effective-in fullling the antistiek. iiinet.ibmL andthat. it would; be. equally proper to refer tor theeellulose ether as a thickeningfor bodying. agent for the. polyalkylene glycol derivative,

Reierring new to tbe drawing, in Fie. 1 1 have illustrated fa building` material oi the, type., illus:l trailed iu. the Robertson. patent, above referred to.l vvhereirilc represents tliefmetal core sheet; l2.,l the enveloping asphaltie. .uroteetive-ffcoatinsi 14, the, adhering klayers .0i blouslllaterial.i Such as; asbestos felt; lo. the bituminous,weatherbroong coating; and. I8A the'V present antistick iilm. In

Accordingly, a Water-soluble antistickV 4 Fig. 2, I have illustrated the building sheet of the type illustrated in the Coffman patent above referred to wherein I0 represents the metal core sheet having a layer 20 of zinc or equivalent metal coating upon the core sheet I0, and by whichthelayers I4 of*v asbestos felt arebonded to the metal core sheet. l0. The` asbestos felt layers I4 are provided With the enveloping bituminous Weatherproong coating I6 and the latter with the present antistick lm I8.

The polyalkylene glycols and derivatives thereof of low hygroscopicity would not ordinarily be selectedy asplastiolzers for water-soluble celluloseethers or alginates because of their relatively poorcompatibility with such materials and the results obtained by their use have been quite unexpected; Y

inefficient antistick solution may be made by dissolving the following in Water:

The alginates used maybe single salts, such as' sodium, potassium, or ammonium alginatesor double salts, such as copper ammonium alginate or zinc ammonium alginate.

An example of an eflicient antistick composittion embodying a,v cellulose ether, such as methyl cellulose, may comprise the following:

Parts by' Weighty Methyl cellulose .V "7.7 2; A, polyallyleneglycol or derivative charac terizedv by low hygroseopicity 1, toe,

This antistiek composition may be applied inany convenient and desired dilution, even as low as 3% solids, and operatesnotforily as a satisfactory and efficient antistick but also one in which the disadvantages above-enumerated with respectv to checking, all'igatoring, and cracking ofthe bituminous coating lli' are reduced to a mirlirrium,` and in practice eliminated'.

Having thus described vthe invention, wfhatfis claimed is:-

l. A- building sheet forr roofing andsiding-pur,-v poses, comprising a protected steel core sheetA having-an outer protective waterprooiing.ebituminous coating characterized by a normally tacky' surface,- rand av film coveringv said tacky surface and comprising a water-soluble cellulose-ether and a plasticizer-therefor consistingA of `armoric-` alkyl ether of a, polyalkylene glycol, the alkyl? grouprhavingl-l to lY carbon atoms.

2. A building material as definedin claim l wherein the water-soluble cellulose etherand thet water-soluble polya-lk-ylene glycoliic material areA in the rati'ooii from l to 1/27-2 parts by weight.

PAUL W; JENKINS@ lteferences,` Cited in. the iile, ofy this patent,`

UNITED STATES s

Claims (1)

1. A BUILDING SHEET FOR ROOFING AND SIDING PURPOSES, COMPRISING A PROTECTED STEEL CORE SHEET HAVING AN OUTER PROTECTIVE WATERPROOFING, BITUMINOUS COATING CHARACTERIZED BY A NORMALLY TACKY SURFACE, AND A FILM COVERING SAID TACKY SURFACE AND COMPRISING A WATER-SOLUBLE CELLULOSE ETHER AND A PLASTICIZER THEREFOR CONSISTING OF A MONOALKYL ETHER OF A POLYALKYLENE GLYCOL, THE ALKYL GROUP HAVING-1 TO 4 CARBON ATOMS.

Images