US2169277A - Composite sheet material - Google Patents

Description

Patented Aug. 15, 1939 UNITED STATES COMPOSITE 8m! Ismur.

llama-ignorlinnesotamningalianufacturingcompany,8t.laul,mnn.,aootporationofDeiaware No Drawing. Application November 80, ll, SerialNo. 755,445

, 1: Claim. My present invention relates in generalto the treatment of material preferably in sheet form,

and more particularly the treatment of material for the p p s of forming or attaining composite structures, of which well known forms of abrasives, such as what is commonly known'as sandpaper, is an example.

Although I hereinafter disclose the practice of my invention in connection with abrasives such as sandpaper, it will be understood that my invention, or certain features thereof, have a wider field of utility,.and, therefore, this invention contemplates and includes improvements in sheeted materials, such, for example, as paper, wherein one or more of the surfaces thereof are treated to render the same waterproof and relatively smooth without necessarily detracting from the fiexibility of the finished product.

This application is a continuation in part of my prior application Serial No. 338,022, filed February 6, 1929, now Patent No. 2,013,925, Sept. 10,

1935; the instant application being directed more particularly to the intermediate product employing the backing, coating or coatings according to the disclosure of the said prior application for producing waterproof sheets with relatively smooth exterior finishes, the invention being' adapted as well, without the abrasive grain, to

form with the backing, a highly lustrous waterproof article which may be provided on either plain or figured fabrics, paper or similar fiexible material.

This invention also contemplates the employment of the improved coatings as binders for abrasive articles. which latter generally include in the coating may serve as a binder for abrasivematerial functioning more efficiently than any known to me, either as such waterproofing coating or dressing, or as the binder for abrasives.

Further objects of my invention reside in the provision of an improved abrasive article wherein the binder is tougher than any prior binders known to me, whether used dry or in a water abrading operation; the provision of an improved composite fiexible waterproof sheeted material characterized by extensibility and compressibility toaccommodate itself to bending when in use or when applied as a composite surfacing material to irregular surfaces; the provision of such an article, either where used as an abrasive article or as the intermediate product, affording an increased cohesion between the binder and the backing and wherein a'good balance of drying is attained without any tendency to crack when subjected to bending after drying: the provision of an improved article of the character referred to wherein the waterproof coating may, for some purposes, penetrate into the backing sheets such as paper or cloth, and, for other purposes, may be excluded from penetration as desired, but, in either event, the treated backing or sheet is adequately water-resistant, either where employed with an abrasive material secured thereto or as a waterproof sheet per se; and the provision of improved c'oatings of the character referred to herein which tend to increase the life of the backing, such as paper or cloth, in use, without me.- terially decreasing the flexibility of the same when the coating or coatings are dry; and the provision of an improved binding and sizing material having moistureproofing characteristics and being quite flexible when dry.

This invention in one of its forms further includes the improvement which resides in incorporating soft oils-in the backing or sheet in sufficient quantity to load the sheet but in a degree insumcient to result in rendering the sheet brittle when dry, in combination with a sealing coat on the surface to increase the waterproofness of the sheet and wherein the employment of a harder binding coat, when dry, is compensated for by the inclusion in the sheet of a waterproofed material which maintains the flexibility of the binder and the sheet but results in the provision of a backing having greater resistance to abrasion, either where the material is employed as a smooth, lustrous, coated sheet or wherein the same is employed as an abrasive article.

It is, of course, desirable that the binder utilized have the functions and characteristics not only of great mechanical strength and of great binding strength, but also that it be non-hygroscopic, permeative, moisture-resistant, easily worked, readily obtainable, relatively inexpensive and capable of facile application to the sheet.

In the manufacture of waterproof sheeting of the character referred to herein, I have treated the backing or sheet with a waterproofing solution and then applied coats of the improved binder material of this invention, together with auxiliary coating or coatings, on either the back or the front or on both, this being carried out both where the article is to be of the intermediate type, that is, coated, glossy paper, or is to be employed as a finished abrasive product.

It will be understood that the degree of resistance to permeation by water, orother liquid either where the invention is employed as an abrasive article in a wet sanding operation or subjected to moisture as the intermediate product depends in part on the" amount of waterproofing materials introduced into the sheet or backing, and in part upon the degree of dryingto which the materials employed may be sub- .iected.

Ordinarilywhereitisdesiredtoincreasethe moisture-resistance of a sheeted material, and prior to the present invention, it has been customary to put on additional waterproofing coats. However, the addition of such coats of waterproofing material of the same character as the first coat may increase the resistance to water absorption but necessarily detract from the ultimate fiexibility of the article produced, and one of the principal objects of this invention is to increase the resistance to moisture-absorption by the applicationof additional coats, but to do .so without detracting from the initial relative flexibility of the backing.

Thus, it will be understood that where the prior methods are employed, a relatively harder ultimate coating results and causes a softening of the sheet beyond the degree desired. In the present invention, 1' provide'sizing, binding and auxiliary coats which permit of the application of an external harder outer surface coat which, in the intermediate product described herein, may have a glossy or smooth external appearance, yet increasing the durability of the sheet but afi'ording sufilcient flexibility thereof so that by cooperation between the balanced coatings a desirable balance of flexibility is maintained in the sheet yet at the same time materially increasing the external toughness of the finished article and its resistance to moisture absorption.

This invention permits the production on a flexible base material, such as paper or the like, of an outer surface which is durable, may be washed, is smooth and highly lustrous, resistant to greases and to other moisture.

In producing a sheet of material of the character referred to, I have, for some purposes, applied a relatively thin top or front coating as a presizing designed not to permeate the sheet ms.-

terially but serving as a penetration controlling coating when the other finished coating or coatings are applied thereto. In the case of an abrasive article, I apply an external binder coat,

-- and then a layer of grit, and then apply a sizing coating to the grit layer. Where the product is to have a smooth finish, the grit is omitted and, if desired, for some purposes, the sizing coating may be omitted, the binder coat, however, being applied.

To the back of the sheet thus coated, I may apply in succession two relatively soft coatings, these coatings lending their flexibility to the relatively harder binder coating on the opposite side of the sheet. It is, for some purposes, to be preferred that the secondary auxiliary backsizing coat be of a relatively softer material, when set, than that of the first backsizing coat so as to not materially detract from the flexibility of the finished article, whether same be sandpaper or a composite waterproof sheet with a lustrous external finish.

The intermediate sizing coat for my purposes,

that is to say, the front sizing coat which is interposed between the binder or finishing coat and the backing, may act as a protective or barrier coat designed not to penetrate the surface to which it is applied, and, for this purpose, I have employed cellulosic materials, such, for example,

9,169,977 V as nitro-celhilose, cellulose xanthogenate, and thelike, as will be more particularly pointed out hereinafter.

If desired, the backing sheet may be either of a relatively waterproof character, that is, may contain relatively soft oils, waxes, and the like, or may be of the ordinary non-waterproof sized paper or the like, and, in either event, the intermediate-sizing will serve the function of controlling the penetration of the outer finishing or hinder coating into the backing.

I may employ a primary binding or finishing coat to the nitro-cellulose coating, which I have termed the intermediate sizing, and thereupon the backsising coats may be applied and a further sixingcoat applied to the outer binder or finishing coat. The application of an external sizing coat to the finishing coat tends to compensate for any undue absorption of the binderor finishing coat by the base or backing.

0 l'romthe foregoing itwillbeseenthat the sheeted material of this invention includes the following principal elements, namely: a backing sheet (conveniently of paper) may contain soft oils in such manner as to render the sheet substantially waterproof; a presising or intermediate sizing front coat of a material which does not tend to penetrate the backing, whether previously waterproofed or not; an external finishing coat applied to the presixing or intermediate sizing coat and controlled thereby against penetration unduly into the backing; and one or more backsizing coats which prevent the entrance of moisture into the back of the sheet; and, lastly, where desired, an external sizing coat applied to the binder or finishing coat in order to enhance the desired lustrous and smooth finish. This last named coating serves as a sandsizing coat where a grit material has either been incorporated in the binder coat or is retained by such binder coat.

I find that it is desirable that the external sizing coat be applied to the binder or finishing coat, and such finishing coat be composed of materials which are relatively hard when dry, and that the backsizlng coats-be of relatively soft materials. It will thus be seen that a relatively hard outer surface is attained which will protect not only the backing but also afford a protection for the hinder or finisher'coat, yet not materially detracting from the flexibility, this flexibility being maintained substantially uniform by the presence of the backsizing coats, and/or the presence of soft oils when so employed in thesheet. I thus attain a selection of relatively hard materials for forming the external finish of the sheet, or, in the case of sandpap r, for retaining the grit particles, and relatively soft materials to lend flexibility where it is most required and to compensate for any tendency in the relatively hard binding coats to render the sheet brittle by penetration of such coats into the sheet.

' As an example of the relative characteristics as to hardness, when set, of the various coatings employed, the binder coat and its outer sizing where employed, preferably include, as one of their ingredients, one of the oils which is of a harder character when dry and yet which does not crack when dry; a prcsizing coating which has a barrier interposed between the binder or finishrcoat and the backing, and serve! as a barrier "for controlling penetration of the hard oils into the backing, or, in some instances, prcventing penetration entirely of such hard oils. 'Iheprlmarycoatmaybeofasoft material, and the second backsisinglooating may be of a relatively softer material. rmsome purposes, I have employed a material for the outermost backsizing coat of such a degree of softness that when placed on a glass it may be scraped oil with the finger nail several days after application.

.It will thus be understood that I may control penetration or entirely prevent penetration of the binder or finisher coat into the backing and that where the coatings of this invention are employed in the manufacture of an abrasive article a controlled penetration of liquid employed in an abrading operation into the pores of the flexible backing through the backsizing coatings may be afforded for increasing the flexibility of the abrading article when used with water. It will be observed that this function of controlled penetration of a liquid into the backing may serve the useful purpose in applying the sheeted intermediate material, which is not an abrasive article, to irregular surfaces by enhancing the flexibility of the article during application, without, however. endangering cracking of the same. i

In this way it will be understood that I am enabled to provide for elongation of the backing and distensibility thereof, preventing the finished article from becoming brittle or cracking when bent.

In carrying out the process of manufacturing the improved abrasive article of this invention.

which process I believe,to be new, and in order to obtain the proper drying cycle and to reduce the time required, I prefer to apply both coats of the backsizing in the second operation, that is,

for example, the coated sheet is passed through a set of squeeze rolls which apply oil on the back side, and then the sealing coat is applied thereto. Instead of sending it two trips through the steps of receiving two backsizlng coats, I apply both coats of backsizing in the second operation. The second coat of the backsizing thus seals the surface so that oxidation is retarded in the center of the fibre cellulose sheet.

Whether the invention is employed as a finished abrasive article or the intermediate, sheeted article, I find that it is possible to employ a socalled clear binder or finisher coating, which, in the case of sandpaper, serves to retain the grits but which, in the absence of the grits, forms an externally smooth and glossy coating. This clear binder may, in the case of sandpaper, obviate the necessity of employing a pigment for controlling penetration into the paper stock, but such a pigment may be introduced, if desired, for lending color for certain purposes in the intermediate sheeted product.

Thus it will be seen that I provide a flexible paper product whereby the presence of the varnish outer surface affords a lustrous finish, and by the employment of the celiulosic under coating I provide a non-brittle layer which lends to the flexibility of the coated sheet.

The employment of a presizlng coat on the sheet beneath the binder coat prevents an undue penetration of the sheet by the clear binder. I have found that I can obtain control of the application of the clear binder so as to prevent the undue penetration into the sheet by applying the binder to raw paper stock, which has been presized on the face but not previously I have found that in doing this, less penetration of the sheet by the grit binding coat takes place, probably due to the fact that in the prior operations known to me, the backsizing thinners, in evaporating, apparently exert a auction or capillaryactiononthebinderappiiedtotheopposite sideoi'thesheettoholdgritsandthustendto 'pulltbebinderintothesheehbythesolvent acclear binder and a grit. The sheet thus treated and which may contain the waterproofing oils referred to, is then passed one trip through an oven maintained at a temperature of between 125 I". to 180 F. for 36 to 48 hours, the oven being zoned so that the sheet first gets the high heat, and the solvents employed are quickly driven off before they permeate the whole drying room. The major portion of the oven has a temperature of about 125 F. to 130' 1!. After this trip through the oven, the two backsizing coats and the sizing coat for the binder or finishing coating are applied, and the paper again passed one trip through an oven, maintaining substantially the same temperature cycle as in its first trip.

In order to give a hard finish to the paper, the sizing coat for the finishing coat may be applied before the second oven. In the article that passes two trips through an oven, the presizing coat, and clear binder are conveniently on the paper on the first trip, and the two backsizing coats and the finisher sizing coat are ap plied to the paper for the second trip through the oven.

I find it preferable, though not necessary. to employ a presizing coat on the backing which is of a different material than that of the binder or finishing coating so that these coatings will be relatively incompatible in the sense that the presizing or intermediate coating will serve to either prevent or control penetration of the hinder or finisher coat into the backing sheet, and I will now proceed to describe the character of the hinder or finishing coating.

I have discovered that gums and resins, natural or synthetic, having the desired characteristics such, for example, as rosin and other gums and resins, perform the functions desired, that is, of giving the necessary mechanical and binding strength and waterproofness which produces a binder or finishing coat suitable for my purposes, when employed with a suitable vehicle.

In preparing the binder for use, the gum or resin is employed in connection with a suitable vehicle which I prefer is of the type such, for e'x-"---- ample, as China-wood oil, linseed oil, or both. Certain other oils, such as semi-drying oil (soyabean oil) are suitable for that purpose.

In employing the gum or resin prepared with a vehicle such, for example, as China-wood oil, to one surface of the base or'backing, I have found that the action of a vehicle involves a penetration of the base and, in some instances, this results in a weakening of the binding action and,- while not sufficient to destroy the usefulness of thebinder for some purposes, it is undesirable. My experience with this binder has shown thatthe application of a sizing coat to the back of the sheet tends to create a suction or capillary action and in order to prevent an undue penetration, in other inventions I have employed a filler for preventing a too great penetration into the backing. However, by omitting the backsizing coats until after the binder is applied and fairly dry, I am enabled to employ a clear binder without the necessity of incorporating ingredients for preventing undue penetration. This func ion is further attained by the employment of a presize, that is, a sizing coat which is applied to one side of the sheet which is to receive the binder. I desire it to be understood that while for some purposes the presizing coating may be of a diiferent character than that of the binder or finishing coating, the selection of the presizing depends on the relative absorbency characteristics of the paper, as well as the ultimate viscosity of the binder which is to be later applied and, therefore, I include herein examples of presizing compositions which are applicable to backings and for association with binders which are of different characteristics.

For dense papers, which do not absorb readily, the following examples of solution used are representative.

Preferred Example No. 1

Parts China-wood 011--..- 20.5 Rosin 3.5 Ester gum 2.0 Lime 0.13 Manganese oxide 0.015 Litharge 0.035 Lead acetate 0.50 Cobalt 0.015 Oleum 70.805 Turpentine 1.50 Aluminum stearate 1.000

Preferred Example No. 2 Parts Oleum spirits 96.0

Metal soaps, such as aluminum stearate, aluminum, palmitate, magnesium oleate, etc 4.0

For papers which are quite absorbent, or to control more fluid binders, a pigment may be added to such solutions as represented in Examples No. 1 and No. 2.

A representative formula for a presizing solution containing a pigment is as follows:

Parts Formula No. 1 45 Formula No. 2 45 Blane iixe (magnesium silicate or the like) For'papers which are very absorbent I use a It is not intended that I should limit myself to the use of the above to obtain a great degree of fineness in the presizing principles.

I have further found that solutions such as cellulose acetate or cellulose acetate combined with other oils; other metal soap, such as caleium oleate, and the like; and combinations of these solutions, with pigment such as magnesium carbonate. blanc fixe, magnesium silicate, and the like; and synthetic resin solutions. such as phenol formaldehyde resins; may be used, depending on degree of control of binder penetration desired, and varying absorbency qualities of paper stock used.

It will be understood that a pigment may be introduced into the binder or finishing coating,

if desired, but that by the provision of the barrier coatings above described as presizing or intermediate sizing coatings. it is not necessary that pigments be employed, and at least these pigments, if introduced, while perhaps serving their function as a penetration controlling medium. may be, in the intermediate finished prod uct which is not sandpaper or abrasive, considered in a measure serving as penetration controlling elements.

In my preferred employment of a clear binder the same may include the following ingredients in proportions by parts.

General Parts Vegetable drying 011---, 58.4 Manganese oxide 0.38 Litharge 0.26 Limo 0,46

Resin 2 8.0 Ole m 12.5

Preferred Parts China-wood oil 27.0 Linseed oil 31.4 Manganese oxide 0.38 Litharge 0.26 Rosin 7.5 Kauri 13.3 Ester g m 7.2 Oleum 12.5

General Parts Vegetable drying oils 34 Resin 13 Lime 0.2 Manganese oxide 0.04 Litharge 0.09 Lead acetate 0.04 Cobalt acetate 0.001

Oleum e 45.629 Turpentine 7.0

Preferred Parts China-wood oil 34 Rosin 5.0 Ester gum 8.0 Lime 0.2 Manganese oxide 0.04 Litharge 0.09 Lead acetate 0.04 Cobalt acetate 0.001 Oleum 45.629 Turpentine 7.0

'Ihe baeksiz'lng coat which is softer than either the clear binder or the hard external sizing coat may include the following ingredients by parts:

. Preferred china-wood oil 21.00 Linseed oil. 9.00 last India nuba L00 cobalt acetate 0.25 Gllsonite 1.82 Soap chips 1.49

1.49 Alum 1.07 Water 15.00 Oleum e 36.88 Ethyl alcohol 5.00

The auxiliary backsizing coat, that is, the sec- Castor oil or lindol.

Second backsizing solutions may include the parts as in the formula hereinafter.

Parts Nitrocellulose 9.4 Raw or heat treated China-wood oil 10.5 Raw or blown castor oil.. 2.! Ester gum 3.8 Slica 19.5 Water 1.5 Butyl Cellosolve 24.0 Mineral spirits 28.8

It will be understood that the presize or in termediate size which is interposed between the binder or finishing coating and the backing may,

for some purposes, include flllers, and particularly may include such fillers for preventing penetration where it is desired to first apply the backsizing coatings to the paper, that is to say, to apply the backsizing coatings set out in Formulae D and E before applying the external binder or finishing coating.

After the presize, clear-binder adhesive have been applied to the paper, the article is suitably forced dried, that is, partially "baked", as it is said, to the desired extent by subjecting it in the usual manner to a temperature which I prefer to control at approximately about 125 to 180 F., depending upon the degree of hardness desired, and for a required period of time, preferably 36 to 48 hours. It will be obvious that the hardness of finish of the article may be varied, as desired, by obtaining variations in the temperature employed and the time which the article is subjected to heat.

The backsizing coats of the Formulae D and E applied. and the article'again subjected to the desired hardening temperature which may be the same as that previously pointed out.

The provision of the treatment and coatings hereinabove described are particularly useful in the intermediate product where a grit layer is not employed in imparting a highly glazed finish to a paper sheet so that the same may present a leather-like appearance, and this is attained by applying the coatings containing nitrocellulose, a vegetable oil and the pigments, if desired,

dispersed in the solvents herein referred to.

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent is:

1. In a flexible paper product, a paper base having a smooth lustrous flnish comprising a non-brittle undercoat of a modifled cellulosic composition, and a top coat of a drying oil resinous material which is less flexible than the undercoat.

2. In a flexible paper product, a paper base having a smooth lustrous finish comprising a non-brittle undercoat of a modified cellulosic composition, and a top coat of a drying oil resinous material which is harder and less flexible when set than said undercoat.

and thehard'sise coat ofl ormula C are then 3. A new article of manufacture in the nature of sheeted material comprising a backing member and a plurality of separate layers attached, one layer containing a drying oil-resinous material and serving as an outer relatively smooth finishing layer, and another of said layers containing a cellulosic compound said outercoat being harder and less flexible than the said other coat.

4. In a flexible paper or sheeted fabric product, a paper or fabric base having a non-brittle under coat of oil and cellulosic compound composition, in which the oil constitutes about 40% of the oil-cellulosic compound mixture and a smooth harder top-coat of a drying oil-resinous material in which resin constitutes more than about of the total oil-resin component.

5. In a flexible paper or sheeted fabric product, a paper or fabric base having a non-brittle under coat of drying oil and cellulosic compound composition in which the oil constitutes about of the oil-cellulosic compound mixture and a smooth harder top-coat of a drying oil-resinous material in which resin constitutes more than about 30% of the total oil-resin component.-

6. In a flexible paper or sheeted fabric product, a paper or fabric base havinga non-brittle under coat of oil and nitro-cellulosic composition in which the oil constitutes about 40% of the oilcellulosic compound mixture and asmooth harder top-coat of a drying oil-resinous material in whichfresin constitutes more than about 30% of the total oil-resin component.

7. In a flexible paper or sheeted fabric product, a paper or fabric base having a non-brittle under coat of drying oil and nitro-cellulosic composition in which the oil constitutes about 40% of the drying oil-cellulosic compound mixture and a smooth harder top-coat of a drying oil-resinous material in which resin constitutes more than about 30% of the total oil-resin component.

8. In a flexible paper or sheeted fabric product a paper or fabric base having a non-brittle under coat comprising about 80% of a drying oil and a smooth harder top coat of a drying oil-resinous material in which the resin constitutes more than about 30% of the oil-resin mixture.

0. In a flexible-paper or sheeted fabric product,

a paper or fabric base having a non-brittle under coat of a cellulosic derivative compound and a blown vegetable oil and a smooth harder top-coat of a drying oil-resinous material in which the resin constitutes more than 30% of the total oilresin component.

10. In a flexible paper or sheeted fabric prodnot, a paper or fabric base having a composition comprising a cellulosic derivative and sumcle'nt softening agents to yield a non-brittle film and a smooth top coating of harder character than said film, comprising a drying fatty oil-resinous material.

11. A proces of making a flexible paper for sheeted fabric product, which comprises applying over said paper or sheeted fabric, a non-penetrating composition to yield anon-brittle film, said composition comprising an oil and a celluloaic derivative, and then applying a coating of a drying fatty oil-resinous material to yield a harder outer coating and setting the same to leave said outercoating with a smooth finish.

12. In a flexible paper or fabric product, a paper or fabric base having a non-brittle under coat of a tenacious fllm forming oil mixture and a smooth harder top coat of a drying oil-resinous mixture.

13. In a flexible paper or fabric product a paper or fabric base having a non-brittle under coat of a drying oil mixture and a smooth harder top coat of a drying oil-resinous mixture.

FRANCIS GURNEY OKIE.