US1659611A - Composite adhesive and process of making same - Google Patents

Description

Patented Feb. 21, 1928.

UNITED STAT ES PATENT OFFICE.

FRANCIS G. OKIE, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO MINNESOTA MINING & MANUFACTURING COMPANYX OF ST. PAUL, MINNESOTA, A CORPORA- TION OF MINNESOTA.

COMPOSITE ADIIESIVE AND PROCESS OF MAKING SAME.

No-Drawing.

thereof, have a wider field of utility.

Composite structures of the abrasive type such as sandpaper or emery cloth comprise generally (a) a backing of sheet material, which may be felted as in the case of paper or woven as in the case of cloth, (6) a more or less finely comminuted resistant material having abrading properties. such as garnet or corundum, and (c) a binder generally in the form of a glue which serves to bind the abrasive to the backing.

"The binders as produced at present have as incidents certain features among which are (1) defect of desired drying qualities, (2) aflinity for moisture rendering them substantially inutile in the presence of water or moisture, (3) the tendency to premature pulverization or disintegration of the binder when exposed to normal atmospheric conditions and other undesired drying qualities, and (6) cracking, with consequent exposure of the base, when bent.

The principal objects of my present invention are the provision of a binder which functions more efiicientlythan any known to me; the provision of a binder characterized by flexibility without cracking or other undesirable effects; the provision of a bindor characterized by extensibility and coin; pressibility to accommodate itself to fiexion of the backingrthe provision of a binder by means of which the desired adhesive action between it and the backing is attained not only efficiently but also with a desirable degree of acceleration, and more particularly the provision of a binder in which the drying action will be effective from the contact surface between it and the backing outwardly; the provision of a binder in which Application filed March 4, 1922. 'serial No. 541,249.

the drying action will be effective from the outer surface thereof inwardly; the provision of a binder characterized by a drying action that permits of handling the product with a minimum of delay and more particularly such handling without impairment of the su'perficies of the material; the provision of a binder characterized by an accelerated drying action; the provision of a binder the rate of speed of whose drying is subject to variation; and the rovision of a binder having moisture-proo ng functions.

In the employment of my present invention for the production of sand-paper and the like (which I cite for purposes of example) I use as the backing a. sheet of material (which may be paper) as will conveniently serve the employment contemplated. and as the abrasive such comminuted material (which may be crushed garnet) similarly adapted toserve the function in view.

It is 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, in-

expensive and facilely applied.

I have discovered that resins including some ,which are commonly called gums of such types as are used in the manufacture of the better grades of varnish are peculiarly adapted for the attainment of these ends and that resins such as kauri, copal, dammar are examples of these types. preferred by me as best attaining the desired ends, viewed fromcertain aspects. In preparing the binder for use. the resin is used in connection with a suitable vehicle which I prefer is of a type such as linseed oil or China wood oil, for reason which I will proceed to explain.

In applying a resin prepared with a vehicle such as linseed oil to one surface of a backing of pa er for example I have found that the action of the vehicle involves a penetration of the backing by the vehicle, for example linseed oil, to a point which approximates the opposite surface of the sheet but falls short of actual exudation of the vehicle upon such opposite surface there Gum dammar is by preventing starving of the joint between This results in a moisture-proofing of the material even against the absorption of moisture through the surface opposite to that to which the binder is applied, without at the same time defacingor otherwise undesirably affecting such opposite surface.

This penetration by the vehicle, particularly when coupled with the use of the character of resin pointed out above, carries with it in such penetration a certain amount of fine- 1y divided resin so that a coating and binding action is secured between the fibres or elemental portions of the backing which thus substantially retards, if it does not entirely prevent, disintegration of the backing, in

.addition to preventing access of moisture through the backing to the plane of contact between the backing and the main mass of the binder material.

The efficient action of the binder may be enhanced in the manufacture of sand-paper if the binder is applied to the backing by the use of pressure and the more or less finely divided abrasive is then applied in such a manner as to cause it to adhere to the binder.

In order to accelerate the adhesion between the binder and the backing, I have ers generally, difficulties are encountered in handling the abrasive structure, within a convenient period because of the soft and sticky character particularly of the exposed surfaces of the binder. This objection I mitigate by associating with the improved binder a substance the action of which is to produce an accelerated drying action effective primarily at the exposed surface and working inwardly, and for this purpose I incorporate in the binder a. modifying element peculiarly effective in its action as an oxidizing agent on such vehicles as linseed oil and as a retarding agent with reference to the excess absorption of the vehicle by the backing.

The substance I have discovered to be particularly adapted for this purpose is carbonate of lead or white lead which is a new electrolytic process white lead and which in my experience is found to be more satisfactory than any other known form ofcarbonate of lead.- I

' Whereas by itself "the aforementioned white lead adds but relatively little strength to thebinder, in association in the binder withthe borate of manganese it intensifies the action of the binder in holding the abrasive firmly against the backing.

For increasing the adhesive properties of the binder, and for hastening the drying thereof, I have discovered that it is desirable to employ a paste dryer (ed-called because it is formed in the nature of a paste) which is also efficacious in holding the mineral particles such as grit in suspension in the binder without loss of siccative properties and without appreciably reducing the desired fluidity -of the binder. This may comprise such metallic compounds as sugar of lead and borate of manganese suspended in a suitable vehicle such, for instance, as linseed oil or linseed oil with. a resin, but I find it preferable to form the paste dryer so as to have the metallic compounds contained therein in the form of acetate of lead and resinate of manganese. I have found by experience that the paste dryer should be somewhat in the nature of cheesy butter, rather softer, and of a light brownish grey color.

As an auxiliary in (1) accentuating the adhesion of the binder to the paper, (2) facilitating to a certain extent the spreading of the binder, and (3) modifying as desired the consistency of the binder as is usefill in cases where it is desired to render it more fluid, I have discovered that the use of a japan dryer is desirable. Such a dryer which is relatively free from rosin is to be preferred. One form of this contains shellac, red-lead, litharge, manganese oxid, burnt umber, resin, linseed oil, and turpentine quantum sufiicit.

In order to give thebinder the desired fluidity, viscosity and bulk I preferably employ a varnish consisting largely of linseed oil boiled until it reaches nearly a solid state.

As far as practicable and feasible uncombined' fatty acids and glycerin should be eliminated. I have employed a linseed oil successfully for this purpose having an iodine number as low as 185, but refer that of having an iodine number as high as 190.

The aforementioned resins, such as gum dammar are preferably employed in the form of a varnish which is substantially three parts Batavia dammar, steam kettle melted, with two parts kettle boiled linseed oil.

While gum co al and gum kauri in cer-' tain respects ma e more substantial binders than gum dammar, as they will carry more I oil and dry harder under certain conditions as may be useful for certain purposes, gen-' erally speaking th'epresent relatively greater expense does not ordinarily justify their use for most purposes, which are well served by gum dammar.

Though I have hereinabove disclosed cercharacteristics, and likewise, Lhave discovered that where it is advisable that the siccati ve action thereof be limited, or at least retarded, that it is desirable to incorporate in the binder a non-drying oil such as castor oil or the like, for suc purposes.

"sandpaper'made in accordance with the disclosure of n y present invention is characterized by great flexibility without any adfverse effects, such as cracking of the binder or backing, or loosening of one from the other'.

In my preferred practice, as will hereafter appearQI form batches which byweight and percentage j contain the" following ingredi-, ents:"

Lbs.

" Carbonate of ]ead l .1066

smooth."

J the composite batch is then milled until Parts I and II include the gum varnish in order to? attain not only a'fine subdivision of themetallic substance but also to render them readily miscible with Part III.-

The materials'used by meas hereinabove described may be varied in character so as to 4D .var yfthe characteristics-of the binder from I the stand-point 10f adhesiveness, xion-hygro:

,' scopy, and flexibility." Wheresuchvariation' in ,the use of materials is emp'l'oyed to produce, for instance, "increased adhesion be-' crease may be attained though oss'ibly at a jcerta'inexpensein its characteristic of flexibility,

H san -paper characterized by extraordinary tweenthe binder and the abrasive, such inthis process, I am enabled to obtain thinness and flexibility, in that I am able to Q Inthe preferred practive of my invention,

I I form sand-paper and the like witha backing Sdthln that such product could not be manufactured, 1f the backing originally used were of the thinness ultimately desired.

in forming Part I hereinabove referred to, I grmd the carbonate of. lead and the gum varnish to an exceedingfineness which may be accomplished, by passing them through a fine-grmdmg mill three or. four trips. The omaterlal grinds quickly and easily and may be conveniently mixedjin the mill. One of thefuncti'ons ofthe carbonate of lead'is to hasten the oxidization of the thinner (and and 'ingal Ycalled gums,

greasier) elements of the binder and limit or the like, rendering it among other t ings easier to handle before it becomes dry. Or

dinary white leads, even though of apparent equal purity and of similar analyses as that herein referred to, do notj unction as satisfactorily for chemical reasons not yet brought to light by my experience.

Gum varnish may be No. 1 gum kauri, gum copal, or gum dammar or more or less numerous similar suitable resins commonly called gums melted in'boiled or raw linseed oil, with or without the presence of dryers, suchasred lead, litharge, black oxid of manganese, burnt umber, and the like. The gum varnish preferably used by me in Parts I, II. and III above referred to, is substantially equal parts Batavia dammar gum, steam kettle melted, and kettle boiled linseed oil. While I preferably use gum dammar, as just indicated, I have formed a. um dammar varnish made from three arts atavia dammar, melted by itself un er gentle heat, as is preferable thoughrit may be used cold, and two parts of a hydrocarbon (which maybe one of the etroleum series)obviously added after tile heat, if used, is discontinued. The hydrocarbon referred to preferably takes, the a following form Color, water white; Beaum, 4849; initial boiling point, not below 2759 .F.; not more than 50% over, at 340 F.; recovery, at least 95%; residue, colorless; end point, below 475 F. I

As the hydrocarbon evaporates, it may be advisable to add more to the mixture in order to preserve the desired degree of fluidity. The hydrocarbon dammar varnish thus formed makes a more brittle binder than the linseed oil gum dammar varnish above described. 1 Although gum copal and gum kauri each make a more substantial binder than um dammar, as they carry more oil ry harder, the are more expensive. Gum dammar, thoug not oxidizing to such a degree of hardness and toughness as other gums mentioned, is preferab e for my purpose because it ap roximates as nearly as ossible the desira le properties of kauri, ut a preaches in cost rosin without includthe undesirable characteristics thereof and goes as far in the direction of the employment of common rosin as I am at present advised is safe to do.

I have found that synthetic resins can also be used in place of natural resins, sometimes to good advantage in making a binder for my purposes.- An example of sucha synthetic resln' is that known to the trade as bakelite resin, or commercial phenol resin produced by a condensation process. In using borate of manganese I have found that awell known borate of manganese, readily obtainable in the open market combines best siccative properties with susceptibility to fine rinding and to form Part II referred to above it should be ground in the varnish until it may be spread on a glass without being mealy under ones finger. It should be ground until experience shows that it can be ground no finer.

It will be understood from the foregoing reference to drying intensifiers that the siccative properties of the borate of manganese constituent are such as to include facilitating drying outwardly of the binder from the surface in contact with the backing, and that the carbonate of" lead constituent includes causing drying inwardly of the binder from the surface thereof which is in contact with.

the air. L

While I prefer to employ manganese compounds in the form of borate of manganese, it is to be observed that although black oxide of manganese contains certain-desirable siccative elements for my purposes, it does not readily lend itself to grinding in such a manner as is desired by me. At times, advantage may be taken of the characteristics of black oxide of manganese as a drier by heating it in linseed oil and using this mixture.

Similarly, cobalt derivatives, (such as me tate of cobalt) may be employed for their siccative qualities, but I have found that due care should be employed in using such highly concentrated dryers so as to avoid any tendency toward deterioration and relative inactivity with the other dryers; failing such care such cobalt derivatives do not give such excellent effects as borate of manganese.

In forming Part II accordin to my pre ferred practice, I find it desirable to grind the borate of manganese by itself, ten or twelve trips if necessary, as this is relatively a very hard substance to grind, and the varnish may be mixed therewith in the mill.

The form of japan-dryer preferably employed by me is a well-known japan which contains about 2% (two percentum) of shellac, preferably the best obtainable, besides substances such as red lead (Pb O litharge PbO) manganeseoxid (MnO) burnt umber which has a manganese and oxygen con-- 7 tent) and resins in linseed oil and turpentine. It aids in the binding action and acts to some extent as a thinner whose turpentine content evaporates after the binder is spread on the paper and somewhat facilitates the spreading process. I have the pro portion of japan dryer indicated in Part III as ordlnarily adequate but yet capable of increase with safety when larger quantities are desirable. Although to an unaccustomed observer a rosin content in the japan may, due to its rapidity of action, appear to be advantageous, such a content, is within my experience undesirable, and to. be avoided.

solid. While this is more difiicult to handle,

I find that it possesses to a high degree the ideal balance between fatty acids and glycerides, so that it neither overoxidizes nor does it dry sticky.

In preparing the paste-dryer of Part III above referred to, which preferably incorporates two separately prepared compositions, I first form the initial portion of the dryer by stirring 200 pounds of litharge (PhD) and 200 pounds of hot water (120 F.), the agitation of the water being sufliciently violent .during and after the addition of the litharge to keep it from settling. After, say, two to five minutes of this sustained. agitation, 45 pounds of 80% acetic acid is dashed into the hot-water and litharge composition without cessation of the violent stirring, which may be mechanical agitation, and which should continue until the milky white liquid that develops as soon as the acid strikes the waterand litharge, sets to a consistency resembling soft cottage cheese or bonny clabber and offers resistance enough to tend to slow up a strong man using a paddle.

In cases where a mechanical agitator'is used, it should be shut off at this stage which is ordinarily reached within a minute after the acetic acid is dashed in. It is advisable to have the agitation sufiicicntly violent to cause suspension of all of the litharge and to dash in the acetic acid suddenly, as otherwise a quantity of uncombined litharge will be found at the bottom of the mixer, and the mass, which-is now basic acetate of lead. will not set stifi. This resultant Inass should be undisturbed for about 15 hours and then pounds kettle boiled linseed oil is added to the mass, which by. this time has become somewhat stiffer. The whole mass is then mixed preferably in a mechanical mixer. The mixer should be run until a large percentage of the original water may be poured off. At this time the basic acetate of lead has a greater afiinity for the oil than for the water. When further agitation separates out no more water, the compound should be ground. This may be done on 3 roller ink mill until no more water can be discerned, and when substantially all ofit can be accounted for by weighing the water that has beenpoured off. The strength of the acetic acid may be varied below providedthe proportionsare changed correspondingly to the strength of the acetic acid. This forms the first part or composition of the paste dryer.

While the second part of the paste dryer I mix thoroughly 100 pounds of kettle boiled linseed oil, with 75 pounds of. resinate of manganese (powdered form) and then grind the mixture two or three trips until fine and smooth.

I then add 225 pounds kettle boiled linseed oil to the acetic acid treated litharge formed in the mixer as above set forth, and then ouicklv mix the resulting mass of the second resinate manganese composition with the modified first or lead compound ortion by resinate of manganese; then certain modilication of the portion A is afforded tojget AC; namely, adding linseed oil to the part A. When this is accomplished I add AC to B and thus obtain the complete mixture D.

This mixing of the two'portions should be done quickly because there is a nicely balanced proportion between the two, and an excess of either portion in long contact with the other portion, imperfectly mixed, causes a livering and sometimes a separation therebetween. After this mixture of the two portions has stood for substantially an hour, they should be'milled one trip. This completes the paste dryer. It should flow down the apron-of the mill about one inch deep, (more or less, depending partly on tightness of rollers and consequent heat,) and it should be kept in stock in a consistency about like cheesy butter, but rather softer,

pro erties.

and of a light brownish gray color.

The manganese compoundmay be'made from a resin other than rosin Wl'llCll for my purpose may be dammar, kauri or similar compounds which inthe paste drier will in the final product render the same more tenacious, stable and of augmented physical rom the foregoin a parent that one o the general functions 0? the carbonate of lead is to serve primarily as a filler; and of the borate of manganese as well as of the japan composition referre to, is toserve primarily as a dryer, and that the rest of my improved binder is made up of varnishes.

The gross formula of the binder produced b my method considered from this'ust re- 0! ed aspect of the invention, there ore involves the use, generally, of four parts filler three arts dryer, and seventeen parts varnish, referably associated together in the specific manner set forth.

The binder is formed, in my preferred practice, by runnin together through the mill Parts I and I ound finel as de- 05 scribed, together with t e items of art III,

description it will be all three parts being milled together until the whole mass is uniform and smooth. The

binder thus formed should be kept carefully covered preferably in contact with oiled paper to prevent the formation of surface skin through exposure. Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent is- 1. The process of producing a binder for sandpaper which includes admixing lead carbonate as an oxidizing agent with a varnish, combinmg the same with a varnlsh ineluding a compound of manganese as a siccativeand adding a drying oil and a drier thereto, whereby the whole is adapted to harden or congeal into a substantially stable, flexible form or condition for forming a coating which will adhere both to the supporting backing and abrasive particles.

2. The "process of producing a binder for sandpaper whichincludes admixing a com,

pound of a heavy metal as "an oxidizing agent with varnish,'combining the same with a varnish including a compound of manganese, adding a drier and linseed oil varnish, whereby the whole is adapted to harden or congeal into a substantially stable, flexible form or condition for forming a coating which will adhere both to the supporting backin and abrasive particles. V g',

3. T e process of producing a binder for sandpaper which includes admixing a compound of a heavy metal as an oxidizing agent with a gum varnish, combining the same withlinseedoil including a drier and adding a varnish including linseed oil, a resinate of manganese and basic acetate of lead,

whereby the whole is adapted to harden or congeal into a substantially stable, flexible form or condition for forming a coating which will adhere both to the supporting backin and abrasive particles.

4. T e process of producing a binder for sandpaper which includes admixing lead carbonate with a gum varnish, combining the same with a gum varnish including a siccative and with linseed oil varnish together with the reaction product of basic lead acet ate and resinate of manganese whereby the a substantially stable, flexible form or condition for forming a coating which will adhere both to the supporting backing and abrasive particles. r

5. The process of producing a binder for sandpaper which includes preliminarily forming individual batches of varnish eac including respectively, a compound of a heavy metal as an oxidizing agent, a siccative, and a paste drier comprising the reaction product of basic lead acetate and manganese resinate, combining said batches ada ted to harden or congeal into a substantia y stable,

whole is adapted to harden or congeal into sandpaper which lncludes admixin form or conditionfor forming a coating which will adhere both to the supporting backing and abrasive particles.

6. The process of producing a binder for sandpaper which includes preliminarily forming individual batches of varnish,'eac of said batches including, respectively, a filler having oxidizing properties and a siccative, combining said batches, then adding a linseed oil varnish whereby the whole is adapted to harden or congeal in a substantially stable or flexible form or condition for forming a coating which will adhere both to the supporting backing and abrasive particles. v

7. In the process of preparing a binder for sandpaper including a gum varnish, the step which includes preparing a basic acetate of lead in an aqueous medium and separating the basic acetate of lead from the mev dium in which it is formed by the addition thereto of a vehicle soluble in the varnish.

8. The process of producing a binder for lead carbonate with a varnish therefor com ining the same with a varnish material including borate of manganese, adding a paste drier including the reaction product of basic acetate of lead and a resinate in linseed oil whereby a composition is obtained adapted to form a substantially stable, flexible coating which will adhere both to the supporting backing and abrasive particles.

' 9. The process of making a binder including metallic compounds serving as a filler and an oxidizer, gum, varnish, linseed oil varnish and a drier which includes the steps of preparing individual batches of said comadhere both to the supporting backing and abrasive particles.

10. The process of producing a binder for sandpaper which includes combining with a gum varnish, a mixture comprising a powdered, body augmenting agent in a vehicle soluble in the varnish and lneluding' a gum, adding a drier thereto and an additional quantity of gum varnish, whereby the whole is adapted to harden or congeal into a substantially stable, flexible form or condition for forming a coating which will adhere both to the supporting backing and abrasive particles. l

11. The process of producing a binder for sandpaper which includes combining with an oil varnish, a mixture comprising a normally dry, powdered body augmenting a cut in a vehicle soluble in said varnish, ad ing a drier thereto and an additional quantity of a drying oil varnish whereby the whole is adapted to harden or eongeal in a substantially stable, flexible form or condition for forming a coating which will adhere both to the supporting backing and abrasive par-- tieles.

signed my name.

FRANCIS G. OKIE.