US2030743A - Adhesive or binder - Google Patents

Description

Patented Feb. 11 1936 ADHESIVE on BINDER Richard P. Carlton, St. Paul, Minn., assignor to Minnesota Mining and Manufacturing Company, St. Paul, sota Minn., a corporation of Minne- No Drawing. Original application December 29, 19 23, Serial N0. 683,523. Divided and this 31)- pllcation May 23, 1925, Serial No. 32,445

13 Claims. (Cl. 134-23) This case is a division of my application filed December 29, 1923, Serial No. 683,523, Patent No. 1,736,964, issued Nov. 26, 1929.

This invention relates to abrasives and the like and more particularly to moistureproof flexible abrasive devices, and more especially with reference to improvements in moisture-proof, that is, water, oil and other wet proof abrasive material which is characterized by tenacity, and, pref erably, flexibility, and which is capable of use in the presence of dampness or wetness without immediate disintegration due thereto, and specifically to so-called cellulosic binders.

It will be understood by those'skilled in the art that cellulosic materials disclosed as employed by me is intended to include such cellulosic materials, treated or otherwise, which may be suitspecific modifying agent or agents are mentioned as this description proceeds, and while the invention is described for use as a moisture-proof binder for sandpaper or other abrasive devices, fabric or otherwise, that is, for securing the grit to the fabric and for rendering the whole moistureproof, if desired; it will be understood that they are set forth as illustrations of the employment of a particular ingredient or ingredients or proportions of such ingredients for my present purposes, and that the field of utility of the binder and the abrasive device is of wide application.

This invention has as one of its principal objects the employment of cellulosic materials such as cellulose nitrate, cellulose acetate, et cetera, as the basis for an improved binder for securing pulverulentpr comminuted abrasive material to a flexible backing formed either of similar material as thatof the binder or a derivative thereof, or formed of paper, cloth, or other suitable fabric, and this invention contemplates the use of a backing which may or may not be waterproof or moistureproof per se or of.

'a backing which may or may not be first rendered moisture-proof before receiving the binder and the abrasive. I contemplate the employment of my invention for one or more of the following purposes, viz: as an improved binder per se, and as a binder on paper or cloth which has previously been rendered moisture-proof, such as by oil saturation, varnish, moisture-proof glue, or the resulted in the production of a moisture-proof,

highly tenacious and flexible abrasive sheet, (socalled sandpaper) has been carried on with cellulosic materials in various forms, and various solutions and modifications. With the object in mind of producing the product in large quantities at a reasonable cost, I have employed among other things, the various nitro-cellulose products, including leather solutions that is, cellulosic materials used for making artificial leather and those commonly known as powder dopes, made by converting powder, of which latter there were large stocks remainingas surplus material after the recent great war. This powder dope, socalled, when reduced, affords a cellulose nitrate solution of low fiber content and as a bond for moisture-proof abrasive devices is capable of being rendered practicable if modified as hereinafter pointed out. The cellulosic materials are generally classifled according to their content of fiber and it will readily be understood that the better cellulosic solutions contain a greater quan tity of fiber, and therefore, a better body is imparted to the material. I do not reject the higher fiber content cellulosic solutions, but I have found that by my invention I am enabled to use the cheaper grades by combining therewith in suitable proportions a modifying agent which is in itself moisture-proof, flexible and tenacious for imparting to the cheaper grade-of cellulosic materials suitable body, tenacity, and adhesive quality without detracting from the flexibility of the product when set. I have found that where cellulosic materials is employed as a binder when applied with a suitable abrasive, to celluloid, the adhesiveness of the binder is materially increased as well as the tenacity if a modifying agent. is employed, and this is particularly true of the lower grades of cellulosic materials or its derivatives. For this reason, andothers to appear, I have employed cellulosic materialsin combination with a modifying agent such as resin, either natural resin or synthetic resin. This invention also has as a principal object thereof the employment of' cellulosic materials or the like and a modifying agent as a binder for attaching comminuted abrasive material to a sheet of fabric or the like.

Therefore, the principal objects and advantages of this invention reside in the provision of an improved moisture-proof binder including cellulosic materials; the provision of. an improved flexible moisture-proof binder including cellulosic materials and a modifying agent; the provision of an improved binder,- including cellulosic materials, for attaching grit to paper sheets or cloth or fabric; and the provision of an improved binder characterized by flexibility, tenacity, chemical inertness, that is, stability and imperviousness to moisture, which includes cellulosic materials and a modifying agent, for the purpose of increasing the tenacity of the binder without reducing the flexibility or durability thereof.

Certain cellulosic solutions produced from powder are in some cases very explosive and others are not of an explosive nature. They may be classified as cellulose mononitrate which contains a percentage of nitrogen to about 7 percent; cellulose dinitrate containing 11 to 12 percent nitrogen; and cellulose trinitrate containing from 14 to 14.15 percent nitrogen. I find that all these classes are readily soluble in suitable solvents nitrate, such as by boiling withldilute nitric acid,

thereby preventing explosion either'in manufacture or use.

The above classification of the cellulosic solutions merely serves to indicate these products as they are produced in their crude state, the finishe product now obtainable in the open market being a solution of these solid cellulosic materials. The quantity of the solid which is taken up by the solvent determines the fiber content of the cellulosic solution. A solution wherein the fiber content is about 50 to 55 percent is now readily ob tainable. This is called a ounce solution, that is 70 ounces of the solid are taken up per gallon of the'aggregate. It will be obvious to those skilled in the art that the higher the percentage of fiber content, the tougher the film and, therefore, the

more the substance becomes desirable for use as l a binder such as for sandpaper.

The usual solvents for nitrocellulose are amyl acetate, amyl alcohol, butyl alcohol, acetone and her of cellulosic solutions now in the market and as solvents thereof amyl acetate or amyl alcohol in combination with benzine may be employed,

the benzine serving as a thinner. In these cellulosic solutions the solvents mentioned above are solvent with hygroscopic tendencies such as acetone is employed, due to the tendency of such solvents toabsorb water from the air. It is, therefore, obvious that to make a moisture-proof binder it is preferable that the cellulosic solution be treated by either amylacetate, amyl alcohol or other non-hygroscopic solvent so as to prevent any absorption of moisture as explained.

I have, in the course of my practice, employed nitro cellulose varnishes, a particular one, for

duced by adding castor oil in small percentages, usually below 10 percent.

In addition to these materials; that is, gum camphor and castor oil, I have further modified the cellulosic solution by the addition thereto of gums such as shellac, kauri, dammar, pontianac, cumoron, and either natural or synthetic resins.

In my practice I have employed gum pontianac in quantity about 10 percent by weight to a quantity of cellulosic varnish and good results are obtained.- Any of the gums mentioned hereinbefore are readily soluble directly in the varnish since the amyl acetate used as a solvent for the cellulose nitrate is also a rapid solvent for the gum.

Under ordinary conditions the addition of any of the above mentioned gums to the higher fiber content cellulosic varnish is not so absolutely necessary as the addition of such gums to the cheaper cellulosic materials, such as that known as powder dope, but at all times materially improves the appearance, body and tenacity of the binder without interfering with the flexibility desired where the binder isapplied to a flexible sheet. The cheaper cellulosic dopes commercially available are usually dissolved in low boiling point alcohol andgive an insufficient body for supporting the abrasive material, but the gums added "to the cellulosic material retain their adhesive nature after the cellulosic film has had surface coagulation and thus improve the aggregate as a binder.

In the employment of cellulosic solutions wherein the fiber content is high, amyl acetate or amyl alcoholis employed by me as the solvent as this material dries comparatively slowly which makes it possible for the comminuted abrasive to penetrate the film applied to the paper or fabric be-- fore the same has had surface coagulation.

From the foregoing it will be seen that in the case of cheaper dopes it is necessary to modify gums hereinbefore mentioned may becombined other alcohol mixtures. There are a large numwith the-cellulosic solution for two purposes at least, the a principal purpose being to increase the tenacity of the solution and-the binder, and secondly toretard the drying'sufliciently to permit of. introduction-of the abrasive material into the binder before coagulation or skinning over preferred because the resultant films are clear as distinguished from the result obtained when has set in. The addition of either the natural or synthetic resins will accomplish this result very nicely and one example of a practicable application of this invention asto proportions by-weight' employed is as follows:

the gum camphor added above serves as a plasticizer further insuring flexibility of the adhesive when dry.

I also contemplate applying the binder ofthis Parts 30 oz. cellulose nitrate solution 10 Gum pontianac added directly to above solu- I tion Gum camphor A Castor oil invention to a base layer or member which is 1 formed of material ofthe same nature, such as or strip or disc, the arrangement in such a case preferably including first the celluloid sheet, secondly a coating of my improved binder, then a coating of the same binder containing grit applied thereto, and lastly a sizing coating. In this manner the continuity of the base layer is not disturbed by the grit and the base layer thus retains its original strength.

I also contemplate employing this invention in connection with oiled paper or with any other paper or fabric which has previously been rendered waterproof or moisture-proof by impregnation or partial impregnation or by applying a coating of waterproof material to the back thereof. Such waterproofing material may be my present binder suitably thinned.

After the product is set, I apply a sizing coat or coats which may be of the same solution as that used for carrying the grid but generally without thinning it, though, of course, where a very heavy body solution such as those referred to hereinbefore is employed it is necessary to thin such a solution to a sufficient extent to facilitate its handling and any of the solvents mentioned hereinbefore may be employed for this purpose.

Again, especially in employing the cheaper dopes, such as cellulosic solutions having a small fiber content, it is desirable that when applied to paper, the latter be sized to improve the bond between the base and the adhesive, and to prevent the base or making coat from penetrating too greatly, so that this making coat of the binder will not be unduly reduced in strength but will be thick enough to receive the abrasive substance.

'The application of a sizing coat to the base may be followed advantageously, even with the higher fiber content cellulosic solutions.

There is a considerable quantity of cellulosic dopes of other kinds manufactured and in the applied to produce a composite film so as to attain the desired penetration, thickness and strength and tenacity, whether for the binding coat or for the sizing coats.

In the production of cellulosic materials acetate dope, cotton fiber, for example, may be subjected to the action of acetic anhydrid, and the resultant solid cellulose acetate dissolved in suitable solvents, such as nitrobenzol, chloroform, etc. In the production of cellulose xanthogenate, the cellulose may be subjected to the action of caustic soda, and then dissolved in suitable solvents such as carbon bisulphide.

The following formula by weight is suggested for a cellulose acetate solution applicable as a bond for sandpamr:

1 Parts Saturated solution cellulose acetate in acetone 10 Shellacgum 1 Castor oil The following formula by weight is suggested for the production of cellulose xanthogenate but is only a making process for this substance:

. Parts Cotton fiber 2 15% caustic soda solution 30 Steep for 24 to 36 hours. Add 1 part carat bisulphide. Stir from time to time until dissolved. Thin to a working consistency with water or additional carbon bisulphide.

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

1'. A waterproof binder for sandpaper which includes substantially forty parts of a solution of a cellulosic compound, threeparts of resin, and

one part of gum camphor and two parts of an oil.

2. A water-proof binder for sandpaper which includes a cellulosic solution as an ingredient thereof which is substantially between eighty and ninety per cent of the whole volume and combined with said cellulosic solution in an amount phor two per cent of the whole and an oil four per cent.

4. A water-proof binder for sandpaper which includes as ingredients thereof a cellulosic solution in amount substantially between eighty and. ninety per cent of the whole volume, a resin to substantiallv six per cent of the whole, gum camphor two per cent of the whole and a non-drying oil four per cent.

5. A water-proof binder for sandpaper which includes substantially forty parts of a solution of cellulosic material, three parts of resin, two parts of gum camphor, and two parts of a non-drying oil.

6. A water-proof binder for sandpaper and the like which includes as ingredients thereof ten parts of a saturated solution of cellulose acetate in acetone, one part shellac gum and threefourths of a part of non-drying oil.

7. A water-proof binder for sandpaper and the like which includes as ingredients thereof ten parts of a saturated solution of cellulose acetate in acetone, one part shellac gum and threefourths of a part of castor oil.

8. A water-proof binder including ten parts of a thirty-ounce cellulose nitrate solution, threefourths part gum pontianac, one-fourth part gum camphor, and one-half part non-drying oil. 9. A water-proof binder including ten parts of a thirty ounce cellulose nitrate solution, threefourths part gum pontianac, one-fourth part gum camphor, and one half part castor oil.

10. A waterproof adhesive for bonding grit to a grit abrading surface, forming with such grit a.

flexible waterpr of'abrasive article, said adhesive including a. cel ulosic compound and a solvent in proportion for spreadingthe abrasive thereon, and including a modifying agent which retards the setting of the cellulosic compound and separation of said solvent, permitting incorporation of said abrasive, and which lends tenacity, flexibility and solidity-to said cellulosic compound when set, so that the adhesive retains its bondin effect even when subjected to moisture and friction.

11. A waterproof adhesive for bonding grit to a surface, forming a backing to form with such backing and grit a flexible waterproof abrasive article, said adhesive "including a cellulosic compound, and a solvent in proportions for spreading the abrasive thereon, and including a resinous modifying agent which retards the setting and separation of said solvent and which lends tenacity, flexibility and solidity to said cellulosic compound when set, so that said adhesive retains its bonding effect even when subjected to moisture --and friction.

12. A waterproof adhesive for bonding grit to form a grit abrading surface, said adhesive including a cellulosie material, a flexibility modifying agent which is incorporated in said compound in proportion to the mass, sumcient to increase the tenacity of. the cellulosic material, otherwise inoperative for the 'purpose without rendering the same inflexible when set, the adhesive being thus rendered so as to be tough and flexible, when set and having tenacity sufllcient to retain grit.

foruse as a flexible waterproof abrasive article.

13. A waterproof adhesive for bonding grit to a surface forming a backing, said adhesive being the residuum of a cellulosic material, a solvent and a flexible modifying agent therefor including a resin, the proportion of resin retarding the setting and separation of the solvent, to permit introduction of the abrasive before coagulation and skinning over sets in, and a plasticizer combined with said cellulosic'material in proportion to the mass formed by the residuum sufiicient to increase the tenacity of they cellulosic material, otherwise inoperative as an effective binder for grit, without rendering the adhesive inflexible when set, the plasticizer and resin rendering the said residuum cellulosic material tough and flexible and of required tenacity to retain grit on a backing for use as a waterproofing abrasive 20 CERTIFICATE OF CORRECTION,

Patent No. 2,050,743. February 11, 1936 RICHARD P. CARLTON.

It is hereby certified that errorappears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 19, for "grid" read grit; line 57; for "cellulosic materials" read cellulose; and line 62-63, for "cellulose" read cellulosic materials; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office. v a

Signed and sealed this 51st day of March, A. D. 1936.

. Leslie Frazer (Seal) Acting Commissionerof Patents.