US2405602A - Adhesive activation - Google Patents

Description

Aug. l, i946.

F.V{NUGENT VADHESIVE ACTIVATION Filed Sept. 23, 1944 A 1M/eww? i: Frederick Vfulgen Patented Aug. 13, 1946 UNITED STATES PATENT OFFICE ADHESIVE ACTIVATION Frederick V. Nugent, Abington, Mass., assigner to B. B. Chemical Co., Boston, Mass., a corporation of Massachusetts Application September 23, 1944, Serial No. 555,579

2 Claims.

This invention relates to improvements in the joining together of fibrous surfaces with cements or adhesives and more particularly to the joining of shoe parts, such as leather soles to shoe uppers by means of synthetic rubber-like adhesives.

In the manufacture of shoes in which the soles are attached to the uppers by means of adhesives it is conventional practice to apply a suitable adhesive to the over-lasted edge of the shoe upper from one hour to eighteen hours before the attachment and to cement the marginal portion of the shoe sole from five hours to one week prior to attachment. The adhesive on the uppers and soles is therefore hard and dry when it becomes convenient to join the parts together. When the parts are to be assembled the dry and hardened adhesive on the sole is activated or softened by a suitable solvent the volatility of which must be so adjusted as to allow the operator suiiicient time to assemble the parts before placing them in a pressure device. In the present practice for temporarily restoring normal adhesiveness it is customary to apply the activator or softener by means of a brush and in so doing the quantity of the solvent or activator applied is so excessive that the soles must be set aside for about an hour before they are applied to the shoe uppers, necessitating care in timing the operations of shoe manufacture and contributing to the uncertainty as to whether the cement is properly activated. If such delay preliminary to sole attachment is to be avoided, it is necessaryin alternative customary practice, for the shoes to remain in the pressure device for a considerable time to permit substantially complete removal of the volatile material in the softener or until the adhesive has set completely. In other words, a considerable delay has been heretofore essential in shoe manufacturing procedure either before or after sole laying. Another diiculty that has arisen is that when a machine is used to apply the activator or solvent to the margin of the soles the operator may not notice that the supply of solvent has given out or is irregular with the result that the attachment of the sole to the upper Vis neither secure nor reliable. Y

t .One object of this invention is the provision of an improved method of joining fibrous surfaces together with synthetic rubber-like adhesive cement previously applied to the surfaces and allowed to dry in which method no undue delay or interruption in manufacturing procedure need be encountered,

A further object of the invention is to provide that a cemented portion has been activated or softened prior to its assembly or joinder with another cemented part. l

The invention will be explained with reference to the accompanying drawing, in which Fig. 1 shows a perspective view of a shoe sole showing the marginal portion to which adhesive cement has been applied for attaching the sole to a shoe; and

Fig. 2 shows an elevation view of the main pory tion of a machine adapted to carry out the method of this invention.

I have discovered that by applying an activator or solvent lightly to hardened synthetic rubberlike adhesive cement by spraying, the cement is temporarily restored to attaching condition substantially immediately, that is to say, no waiting is required between the activation of the cement and the sole attaching operation (for example) even with ordinary activators such as toluene. When spraying is used it is possible to activate merely the surface of the cement and no excess solvent need be dissipated ,before the parts are ready for attachment. Ithas been found that in spray activation of neoprene or polymerized chloroprene cement, for example, an initial bond strength of 15 to 20 pounds may be obtained as compared with the five-pound bond ordinarily obtained with liquid solvent activation. The neoprene or chloroprene cement spoken of is of the type as described in United ,States Letters Patent No. 2,061,296, granted November 17, 1936, on an application filed in the name of W. H. Wedger'. By initial bond is meant the strength l tested immediately after a time dwell in an at- Similar copolymers may also be obtained commercially under the trade name Chemigum manufactured by Goodyear 'Iire and Rubber Company, Akron, Ohio, or under the trade name Perbunan manufactured by the Standard Oil a method for clearly indicating by means of color Company of New Jersey. For butadiene-acrylonitrile type cements, suitable illustrative solvents for application by spray are acetone and methyl ethyl ketone. With the use of any of these cements spray activation necessitates prompt joinder of the parts, that is, a period not in excess preferable that they be maintained under sole attaching pressure for at least 40 to 60 seconds, and this may be accomplished conveniently in a machine such as shown in UnitedStates Letters Patent No. 2,047,185, granted July 14, 1936, on an application filed in the namev of Milton H. Ballard et al.

When it is desired that a sole be molded or..V

formed the cement coated sole is mulled or tem'- pered and shaped. If la relatively long period of time elapses between the sole forming or molding and the sole attaching operations the-sole may be brought again into temper just prior to the sole attaching operation. Before the application of an activator or softener to the sole, Whether or not the sole is formed or molded, the sole is preferably mulled or tempered in order to make the same more iiexible, and to reduce the tendency of the sole to pull away 'from the upper after the release of the scle-attaching pressure. The step of activation is not adversely affected by the prior tempering operation.

I have avoided uncertainties in the prior methods of activation, whether such methods be by brush or spray application of a solvent, by 'incorporating a color indicator in the activator or solvent. A small quantity of a substance is placed in the activator, which substance will react with an' ingredient such as a ller in the cement and thereby constitute a color indication of4 the cement activation. The use of a color indicator enables an operatorl by casual Vobservation to observe immediately whether or not a hardened cement'lias been activated andV jhe can therefore proceed immediately to carry out the attaching step (if spray activation is used) or can proceed with his timing `(if brush activation isV used) and with greater certainty of result.

The use of the color indicator of this invention is especially and peculiarly adapted for combination with the spray activation feature'for the reason that spray activation requires vsuch a small amount of activator or solvent that an indicator isV particularly advantageous to Warn an operator from proceeding'with cement attaching Without proper activation.

It is customary in the use of adhesive lcements to incorporate therewith a quantity of magnesium oxide which usually functions as a filler. Inthe use of such cements l have found it` aolvantageousto use an activator containing a small quantity of symmetrical diphenyl carbazone (CeHaN-N- CO -NH -NH' Cel-lla) Approximately three grams of this material is used per gallon of solvent when activation is by means of a spray. Approximately one gram per gallon of solvent is used for brush activation. A suitable solvent composition With a color indicator for the activation has been found to be as follows:

ASixrounces Denatured alcohol Six ounces 1 Ethyl acetate One or three grams Diphenyl carbazide Dilute to one gallon with toluene. This solution 'should be'subjected to -agingfor five days; the aging results in the oxidation of the carbazide to carbazone. The necessity for aging may be obviated by dissolving diphenyl carbazide in toluene and oxidizing the carbazide to carbazone by means of quinone. The formula for symmetrical diphenyl carbazide is as follows: (CsHsNH-NH-CO-NH-NH-CsHs). The indicator as dissolved in the solvent presents a bright red color but when this is sprayed on an Auncoated shoe sole it is practically invisible. Wherever the indicator contacts a hardened cement which includes magnesium oxide there is an instantaneous chemical reaction which imparts a distinct red color to the cement. This vcolor 'fades ina few days if the parts are not attached together by means of the cement. Use 'of the. indicator inthe activator does not hinder reactivation of the cement at a later date. In employing an indicator as set forth in this in- Vention it is necessary to omit any accelerators of curing from the activator because such accelerators would react with the cli-phenyl carbazone. The use of such indicator is greatly superior to the use of dyes as dyes tend to migrate and are apt to discolor the objects treated, such as the uppers or soles of shoes. There is no migration or discoloration in the use of diphenyl carbazone.

In carrying out the method a shoe, to which a sole is `to be applied, may have its upper llasted over its insole in any usual manner. YFor example, the heel seat portion may be lasted `with tacks and at the shank portion the upper may be Worked over the last and secured in position with staples by means of a machine such as the staple lasting machine disclosed in Letters Pat ent of the United States No. 1,815,295, granted J uly 21, 1931, on an application led in the name of George Goddu. The Iforepart may be similarly lasted or the upper may be held in lasted position by cement alone. The overlasted margin of the upper is preferably roughened before synthetic rubber-like adhesive cement is applied thereto by hand or byv means of a cement applying machine such as disclosed in Letters Patent No. 2,100,341, granted November 30, 1937, on an application filed in the name of Wilbur L. Mac- Kenzie. i

An outsole llll is prepared as shown in Fig. 1, the marginal portion of its inner -face being roughened at I2 for the receptiony of synthetic rubber-like cement which is shown `as having been applied to the margin. The roughing may be done by any of the usual roughing machines employed in themanufacture of cemented shoes. The, cement may be applied to the outsole by hand but preferably bya'machine such 'as disclosed in Letters Patent of the United States No. 2,042,479, granted June 2, 1936, on an application led in the name of Carl A. Newhall.

After the outsole and shoe -have been coated with adhesive cement they are aliowed'to dry in the-customary manner and the outsole may then be mulled and formed before the use of a softener' or-activator for the cement.

The application of the softener `or activator may be done by a spray gun mounted in place of a brush- Von a coating applying machine as disclosed inlLetters Patent of the United States No. 2,073,647 granted March 15, 1937, on an application filed-in the name of Carl A. Newhall. The substitution of a spray gun on such a machine is shown in Fig. 2 in which a spray gun 20 is shown mountedat an angle to the horizontal on an-arm 22 extending from `the machine frame and'inposition to direct a light spray of activator material on the margin of the outsole as the outsole is manipulated between the upper and lower feed rolls 24 and 26, Customary air and liquid feed connections 3l and 33 are shown. The spray gun is so adjusted that there is a ow of approximately four-tenths of one cubic centimeter of the activator to each sole. The spray may easily be maintained light by adjusting the gun to retain a large volume of air as compared with the amount of activator. 'Ihe trigger 30 of the spray gun may be operated by connecting it through arm 32 to the horizontal and sectional rod 34 which is rotated by the rod and lever system 36 upon depression of a foot treadle (not shown) to which a vertical rod 38 is attached. The feeding of an outsole and application of an activator to the outsole during feeding are both under the control of the treadle.

The activating medium preferably includes a` small quantity of diphenyl carbazone and in such case the cement on the outsole is a cement containing a quantity of magnesium oxide.

Prcmptly after activation of the outsole cement (preferably evidenced by the color produced in the cement), the outsole and shoe bottom are brought into juXtaposition and under attaching pressure in a sole attaching machine of a type before referred to. The pressure is maintained for 50 seconds and then the shoe may be removed from the machine as the strength of the initial bond is suiciently great to be reliable even though the last be immediately pulled from the shoe.

Having described my invention, what I claim `the United States is:

l. In the art of adhering fibrous materials together, that improvement which comprises adding a filler material yto a synthetic rubber-like adhesive, applying the adhesive to areas of the parts to be joined and permitting the adhesive to harden, providing a solvent activator for said adhesive and adding thereto an agent capable of subsequent reaction with said filler material for producing a color, applying the agent carrying activator to the hardened adhesive on at least one of said areas to render the adhesive tacky and with a resulting reaction between the agent and the filler giving a visual indication of the condition of the adhesive, and thereafter pressing the parts together to effect an adhesive bond.

2. In the art of adhering brous materials together, that improvement which comprises adding magnesium oxide to a synthetic rubber-like adhesive, applying the adhesive to areas of the parts to be joined and permitting the adhesive to harden, providing a solvent activator solution for said adhesive, said solution containing diphenyl carbazone, lightly spraying the said activator solution on the hardened adhesive of at least one of said areas to render the adhesive tacky and with a resulting Vreaction between the diphenyl carbazone and the magnesium oxide giving a visual indication of the condition of the adhesive, and thereafter pressing the parts together to effect an adhesive bond.

FREDERICK V. NUGENT.

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