US2333779A - Waterproof adhesive composition and method of making same - Google Patents

Description

Patented Nov. 9, 1943 UNITED STATES WATERPROOF ADHESIVE COIWPOSITION AND METHOD OF MAKING SAME Edwin 0. Groskopi, Rutherford, N. 3. assignor to The Patent and Licensing Corporation, New York, N. Y., a corporation of Massachusetts Z'Claims. '(ci. 252-311.5\

This application is a division of my copending application Serial No. 52,345, filed November 30, 1935, now Patent No. 2,180,305, dated November 14, 1939.

This invention relates to waterproof adhesive compounds and to methods of manufacturing same and is concerned more particularly with adhesive compositions of an asphaltic or similar bituminous character, or of a rubber character.

The invention is more particularly concerned with adhesive compounds of the aforesaid character which can. be successfully employed under conditions which have heretofore presented considerable difficulty in the attainment of the desired adhesive eifect.

One example of the particular. conditions untended to adhere. Furthermore, the requirement that the fllm shall resist flow at temperatures considerably above the melting point of the bitumen contained in, the emulsion, is also essential in order that the insulating material remain in place and not move substantially from its fixed position upon the metal layer under the heat of summer temperatures to which automobiles are subjected in use.

Bituminous emulsions of the aforesaid character which have heretofore been successfully used for said purpose, and possessing the characteristics just mentioned, are those made with the use of bentonite or bentonite-like materials as the dispersing agent in accordance, for example, with Kirschbraun Patent No. 1,620,899.

der which the adhesive compounds made in accordance with my invention may be successfully employed are those which prevail in the application of sound deadening sheets or pads to the metal parts of vehicle bodies during the course of manufacture of the vehicle.

Various forms and types of sound insulating sheets or pads have been employed in the automotive industry for deadening the sound of the vibrating metal parts of car bodies, the sound deadening sheet or pad being attached, for. this purpose, to the inner surface of the metal parts, the vibrations of which it is desired to dampen. Thus, for example, sheets or pads of relatively heavy porous or bibulous unsaturated felts, have been used for deadening the vibrational sounds of metal parts of car bodies. Sound insulating material of this character has been successfully aflixed to the metal parts by the employment of bituminous emulsions of those types in which a mineral colloid constitutes the dispersing agent. It is essential, in the use of an aqueous emulsion of bitumen or the like, for the purpose of afilxing the sound deadening layer to the metal layer, that the emulsion be of a character such that when the water of the emulsion has been removed, the resultant adhesive film will not flow at temperature considerably in excess of the melting point of the bitumen contained in the emulsion. This requirement of the adhesive is made necessary by reason of the fact that in the application of the sound deadening material to the metal parts of 'the body, the adhesive must be able to withstand flow at the temperatures of the ovens through which the body of the car with the sound insulating material affixed thereto must pass, as otherwise the layer of the sound insulating material will slide off or be otherwise parted from the metal layer to which it is in While'emulsions of this type have, as stated, been successfully used for cementing unsaturated sheets or pads of fibrous felt to metal body parts, recent developments in the automotive industry have made it necessary to employ more or less Waterproofed sound deadening materials, such as felts saturated to various degrees of waterproofness with asphalt, or the like.

In the use of these more or less waterproofed types of sound deadening material, however, considerable difiiculty has been encountered in successfully cementing the same with bituminous emulsions of the character above described, to the metal parts of the body, under the conditions which necessarily prevail when this operation of amxing the sound deadening material to the metal parts must be performed. In. fact, in certain instances, the attempt to cement the more or less waterproof type of sound deadening material to the metal parts of the body have met with complete failure.

An object of the invention is to provide an improved form of composition for successfully cementing these types of materials to the metal p rts of a body.

Another object of the invention is to provide an adhesive composition of th character indicated which will at the same time possess the characteristics of resistance to flow under high heats which is obtained, as above stated, with the use of bituminous emulsions made with bentonite or similar mineral colloids as the dispersing agent.

In approaching this problem, I found that the reason that bituminous emulsions of the character described may be successfully used as a. cementing medium for unsaturated sound-deadening felts, whereas they are troublesome and in many instances completely unsatisfactory where a more or less waterproof sound-deadening material such as saturated felt is used, is that in the former case the porous or bibulous character of the unsaturated felt is so comparatively great as to enable a sumcient portion of the water content of the emulsion to escape through the layer of sound deadening material itself before encoimtering temperatures sufficiently high to convert water into steam in the oven through which the body with the attached layer of sound insulating material must pass in course of construction. Hence before encountering the water-boiling case when considerably less than 90% ,1 .the water content thereof has been eliminated, although this depends to some extent upon the rate at which the temperature-of the film is in-- creased. The film of the composition thus rapidly exerts a strong adhesive function due to the fact that the oily character of thesurface of felt saturated .with asphalt or the like is readily wetted by the composition which is itself also of temperature, the emulsion, in the first case, has

- ample opportunity to undergo sufilclent inversion or a sufilcient coalescence of the bituminous-particles to render the film thereof adequately adheforth, applied to a layer ofmetal, and then resive and thereby prevent any steam that may be formed from blowing or otherwise forcing the layer of insulating material away from the metal layer. On the other hand, where the insulating layer consists of more or less waterproofed material, a sufilcient amount of water to cause the film of emulsion to invert and take on an adhe sive condition cannot escape before temperatures sufilciently high to convert water into steam are reached in the passage of the united materials through the ovens; and consequently, at that stage, there is a lack of sufficient adhesion between the insulating layer and the metal layer, and the remaining water entrapped between the two layers results in a blowing off or forcing away of the layer of insulatingmaterial from the metal layer when temperatures of the order of 212 F. are reached. In this connection it may be noted that bituminous emulsions such as those made in accordance with the aforesaid Kirschan oily character. This is in marked distinction to the action of films of bituminous emulsion as ordinarily produced. This distinction can readily be observed by lightly pressing a pad of saturated felt into a fihn of the ordinary type of bituminous emulsions of the character herein set moving the pad from the metal layer. The pad will show only water on the surface thereof thus indicating that the film of the emulsion has not wetted the surface of .the pad with anything more than water. On the other hand, when a. similar test is applied to the compositions made in accordance with my invention, the removal of the pad from the metal layer will show that the parting takes place through the film of the bituminous portion of the composition, has selectively wetted the pad and adhered not only to the surface of the metal, but to the surface of the removed-pad as-weu.

braun patent, and which provide a water-freewith my invention I have found to be eminently satisfactory as a medium for cementing more or less waterproof insulating materials to the metal parts of car bodies under any of the aforesaid conditions of temperature and time of drying to which they may be subjected during the conof the asphalt, together with a material which will so act upon the emulsion system as to cause a film thereof to invert and the particles of dispersed bitumen to coalesce, enabling the film to take on a comparatively strong 'ad'hesivetaharacter, while the water content of the film is still substantially high. As a-matter of fact, in oertain embodiments of the invention, the film of the composition may be caused to take on this condition when only as little as 20%, and in any As one illustration-of an embodiment of the invention in a composition which meets the requirements hereinbefore set forth,'the following formula may be-given:

Parts Asphalt (51 to penetration) 56 Water 39 Bentonite (as dispersing agent) 2 Kerosene 3 Oxalic acid 0.02 ml acetate In the composition as represented by the above formula, the kerosene constitutes the activating agent which causes the emulsion to invert and the dispersed particles ofthe bitumen to coalesce while the film of the composition still contains substantial amounts of water, this action taking place in many instances when as much as of the original water content of the emulsion is still present, although as heretofore stated, this may vary with the rate at which the water is driven ofi. The kerosene may be employed in quantities varying from 3 to 10% by weight of the finished product. Essentially, however, the activating agent must, in order to attain the objects of the invention, be of a character and be employed in quantities sufilcient to cause the film of the emulsion to take on a condition of inver ion or sumcient adhesive capacity to enable t to hold material such as saturated felt to the metal surface to which it is applied, without blowing ofi, during the conversion of the remaining portions of the water inthe film into steam when water boiling temperatures are reached in the drying process.

In lieu of the kerosene as the activating agent specifically set forth in the above formula, other materials may be employed to function in the 1 way in which the kerosene does. Thus for example, theactivating agent may consist of relatively small amounts of-a solution of rubber in a solvent, or of a solution of certain gums and/or resins in a solvent; and in general, anyother substance which will not materially change the fluid character of the emulsion but will cause it ther 'reduced in size.

'to invert to the adhesive character specified, in

the presence of a much higher water content than if the activating substance is omitted.

The purpose of the oxalic acid in the formula above given is to lower and retain a lowered viscosity of the emulsion, while keeping it at substantially the same water content with which the emulsion is initially produced (1. e., without requiring large additional quantities of water for the thinning), and thereby to facilitate the incorporation of the kerosene or other activating agent into the emulsion. Substances other than oxalic acid, well known in the art for this purpose, may be employed in lieu of the oxalic acid, to retain the liquid character of the product; or this effect may be induced in other ways known to the art.

The amyl acetate in the formula above given serves merely as a deodorant to disguise or obliterate the odor of the kerosene.

In the manufacture of the adhesive compositions in accordance with my invention, as typi fied by the above stated formula, I prefer to proceed by first making a base emulsion of the asphalt or other waterproof material in water with the aid of the bentonite or other emulsifying agent suitable for the purpose, having in mind particularly the requirement that the water-free film of the emulsion must be capable of resisting fiow at temperatures greatly in excess of themelting point of the dispersed material. The base emulsion as thus produced in accordance with commercial practice in the art and containing approximately 37% water, 60% asphalt and 2 to 3% bentonlte, is one in which the particle size of the dispersed asphalt averages about 18 microns. The emulsifying temperature for the production of the base emulsion will range from approximately 130 to 140 F. for asphalt of about the penetration indicated.

The base emulsion as discharged ,from the emulsifying apparatus is then preferably cooled from the emulsifying temperature of 130 to 140 F. down to approximately 115 to 125 F., or a drop of approximately 15 F. The thus cooled emulsion is then subjected to the action of a pugmill or similar beater after treating the emulsion with about 0.02% to 0.05% by weight of an electrolyte such as potassium dichromate. The purpose of this treatment with the electrolyte is to thicken or flocculate the cooled emulsion so that under the beating action of the 9118 11 the particles of dispersed bitumen will be fur- This treatment of the emulsion is preferably such as to reduce the particle size of the emulsion to an average of about 7 microns. This greatly reduced average particle size also contributes to the ease with which the kerosene may be incorporated in the emulsion without premature breaking thereof.

The emulsion with the reduced particle size is still comparatively thick due not only to the fact that the water present must surround the greatly increased amount of surface area of the increased number of finer particles, but also to the thickening effect of the electrolyte present therein. In order therefore to thin out the emulsion of the reduced particle size and thereby facilitate the incorporation of the kerosene or other activating agent, the emulsion as discharged from the pugmill is then preferably cooled to a temperature of about 100 to 110 F. and is then led into a second pugmill operating at a relatively high speed, viz. of the order of 150 R. P. M. and the oxalic acid is trickled into the emulsion in this pugmill while the emulsion is being agitated at a high speed. The agitating action of the high Speed 1 118111111 as well as the introduction of the oxalic acid serves to greatly thin the emulsion of reduced particle size without requiring any substantial additional water. i

It will be appreciated that since the high speed pugmilling action and the oxalic acid both serve to thin the emulsion, these expedients may be used more or less interchangeably with one another, depending upon the operating conditions prevailing. which will determine the most economical mode of bringing about the thinning of the emulsion. Furthermore where the thinning action is attained by the incorporation of a thinning agent, materials other than oxalic acid may be used for this purpose in lieu of the oxalic acid.

After the emulsion with the reduced particle size has been thus greatly thinned in the manner described, it may be transferred to a separate mixing tank where the kerosene or other activating agent is added while the material is being stirred in the mixing'tank, the kerosene bein preferably fed into this tank simultaneously with the feeding of the emulsion thereinto. Durin this incorporation of the kerosene or similar.

activating agent into the emulsion, it is quite essential that a comparatively low temperature be maintained and that, as already stated, the emulsion be of a thin consistency and have the particles thereof in a state of subdivision of the order of magnitude specified, in order to avoid inverting of the emulsion by the kerosene or other activating agent With that in mind, it is desirable before feeding the emulsion into the final mimng tank, to run into this tank about 50 to 100 gallons of water per 2000 gallons of finished product. The effect of water introduced into the bottom of the tank before any of the emulsion is fed thereinto, is to greatly reduce the temperature of the emulsion, namely from about to prevailing in the second pugmill to about 80 F.; and also, to further thin the emulsion.

The water in the bottom of the final mixing tank also prevents any mechanical friction during the mixing of the kerosene with the emulsion. The objective in this final step of the process is to incorporate the kerosene in the emulsion in the form of final droplets of the kerosene uniformly dispersed in the aqueous phase of the emulsion. This result is attained by conducting this step of the process in the manner described, it having been found that by having the emulsion very thin and the asphalt particles in the emulsion very finely divided, any tendency for the emulsion to break upon the addition of the kerosene can be avoided. This danger of breaking of the emulsion is further minimized by reason of the fact that the additional quantities of water placed in the bottom of the mixing tank as aforesaid, prevents any substantial rubbing contact between the kerosene and the dispersed asphalt particles, which might, by accumulating to a sufiicient extent, cause the emulsion to break during the introduction of the kerosene.

Having thus described the invention and the advantages thereof, it will be evident to those parting from its scope as defined in the appended claims.

What I claim is:

1. A waterproof adhesive composition comprising an emulsion of between 50 and 60% asphalt in water, about 2 to 3% of an emulsifying agent comprising a mineral colloid oi the bentonite type, whereby to render the water free him of the emulsion capable of resisting flow at temperatures greatly in excess of the melting point of the asphalt, said emulsion containing a small amount of oxalic acid in solution in the aqueous phase, and also containing 3 to 10% of kerosene, by weight of the final composition, dispersed as -flne droplets in the aqueous phase of the emulsion whereby to cause the emulsion to invert and the dispersed particles of a film thereof to coalesce when the film still contains from 20 to 90% of its original water content.

2. The method of producing a composition suitable for use as an adhesive in cementing layers of waterproof felt to the vibrating metal parts of car-bodies, which comprises emulsifying between 50 and 60% of bitumen in water with the aid of about 2 to 3% or bentonite as a dispersing agent and under conditions such that the dispersed particles of the bitumen will be or an average size of about '1 microns and the emulsion will be of substantially viscid consistency, then greatly thinning the emulsion without adding any additional substantial quantities of water by pug-