US2168024A - Cleaning composition - Google Patents

Description

Patented Aug. 1, 1939 UNETED fiTATES CLEANING COMPOSITION George R. Ensminger, New Brunswick, N. J., assignor to E. 1. du Pont de Nemours & Company, Wilmington, Del., a corporation oi Delaware No Drawing. Application November 12, 1936, Serial No. 110,473

'1 Claims.

This invention relates to an improved cleaning composition and more particularly to a cleaning composition which is particularly adapted for preparing previously coated surfaces for refinishing. Heretofore, particularly in refinishing automobiles, the old surface was subjected to the slow and tedious process of sanding with gasoline and water. This treatment is effective in removing grease, wax, tar, and the like from the surface, but has the disadvantage that the old paint or lacquer which remains is usually scratched. When the new coating is applied, the solvents attack the old finish more along the scratches than on the unscratched area. This produces uneven swelling of the old finish and causes so-called welts to appear. In order to eliminate this, a shellac or shellac substitute sealer coat is often applied to the sandpapered surface prior to the application of the enamel.

An object of the present invention is the provision of a cleaning composition which quickly and efliciently removes dirt, grime, tar, and 1101- lshing wax from the old surface without the use of abrasives.

Another object of this invention is the provision of a cleaner which promotes adhesion of the new finish to the old.

A still further object of the invention is the preparation of a surface for refinishing which is charadterized by exceptional smoothness and absence of irregularities such as scratches, welts and the like. Other objects of the invention will become apparent as the description proceeds.

' These objects are accomplished by the use of a cleaning composition which contains a plurality of ingredients of at least two or three different classes.

The main class of compounds in the composition with respect to volume is represented by solvents for grease. wax and tar. These may be xylol, toluol, high boiling naphtha, mineral spirits, chlorinated hydrocarbons, hydrogenated naphtha, and usually a solvent such as turpentine which has a relatively low rate of volatility. The second class is present in much smaller amounts and is usually a lacquer solvent having a relatively high boiling point although the compositions which are satisfactory cannot be satisfactorily defined by the range of their boiling points. It has been found that the class of compounds which are satisfactory may be defined by their penetration power into a dried nitrocellulose film and also their evaporation rates as will be more fully described hereinafter.

I prefer to designate compounds of this class as activators.

The third class in the composition is a blanketing agent which serves the purpose of holding the other constituents of the cleaner in contact with the surface as long as is needed. The ingredients representing this class are present in relatively small amounts; that is, of the order of about 1% and are usually solvent plasticizers for the cellulose derivative.

The following examples are given to illustrate how the invention may be carried out. The following compositions are prepared by mixing the ingredients in any convenient manner and in any order:

Example 1 Per cent by weight Xylol 30.0

High boiling naphtha (B. R., 160 to 180 C.) 10.0 Mineral spirits (B. R., 150 to 225 C.) 21.0 Hydrogenated naphtha (B. R... to 190 C.) 17.0 Turpentine 15.0 Butyl lactate 6.0 Dibutyl phthalate 1.0

100.0 Example 2 Xylol 25.0 Carbon tetrachloride 5.0 Hydrogenated naphtha (B. R., 135 to 190 C.) 14.0 Mineral spirits (B. R., to 225 C.) 22.0 High boiling naphtha (B. R.., to 180 C.) 10.0 Turpentine 15.0 Diethylene glycol monobutyl ether 9.0

The cleaners may be applied to the old surface by means of a brush, cloth pad, or any other convenient way, and particularly good results are obtained if a small area is treated at one time. After the surface has been wetted liberally with the cleaner, it is wiped dry with a clean cloth at once until the finish is dry and clean. Usually, one application-is sufiicient, but where the old finish is in very poor condition or where heavy coats of polishing wax have been used, a second application is sometimes necessary. The work is thenready for refinishing.

The cleaners are also valuable for preparing surfaces in which the old finish has disappeared entirely in places. In such cases, the cleaner may be used with sand paper in order. to remove the rust spots. In cases where this is necessary, it is advisable to go over the surface after sanding with a cloth saturated with the cleaner in order to fiow the sanding scratches together and thereby avoid the subsequent use of a sealer.

The above formulas are given to illustrate the invention. However, many of the ingredients may be varied both with respect to amount and kind. This is particularly true of the volatile tar and grease solvents. It is important how'- ever to have a relatively large percentage of such solvents present and a much smaller percentage of butyl lactate or its equivalent and a still smaller percentage of solvent plasticizer in the composition. The invention is illustrated by the use of butyl lactate as the typical second class ingredient since it is relatively easy to obtain and is not as expensive as some of the other solvents which may be used in this class. These compounds should represent between 5 and of the composition. In determining the equivalents which may be substituted for butyl lactate.

it has been found that the following test serves for a qualitative evaluation of the emciency of a given compound as an activator. A film composed of 10 parts of camphor and 90 parts of nitrocellulose having a viscosity characteristic of 16 seconds and a nitrogen content of 12.3% is cast on a glass plate from a solution in volatile solvents to give a dry film having a thickness of .003 inch. The film when dry is removed and cut into pieces. These pieces are placed on a felt pad saturated with the activator being tested and the finger is rubbed lightly but continuously over the surface of the film. In order to prevent loss of the liquid during the test, the felt pad is placed in a semi-closed container. The time for penetration of the activator is that at which the liquid has softened the dry film sufilciently to give it a soft tacky surface which is easily detected by the moving finger.

The following table represents results obtained according to this test using a number of activators:

Penetration time. seconds Ethylene glycol monomethyl ether 46 Amyl acetate Ethylene glycol monoethyl ether 61. Diacetone alcohol Butyl propionate Ethyl lactate 104 Ethylene glycol monobutyl ether 112 Butyl lactate 122 Methyl cyclohexanone 152 Ethylene glycol monomethyl ether adipate- 220 Diethylene glycol monoethyl ether 235 Diethylene glycol monobutyl ether 270 Di-n-butyl adipate 480 Tributyl phosphate 520 Dimethyl phthalate 1,080 Diethyl phthalate-no softening of film up to 1,800 Dibutyl phthalate-no softening of film up to 1,800

with reference to the above table. an activator possessing a penetration time within the range of 104 to 270 seconds may be utilized in the composition of this invention.

It is therefore apparent that the cellulose 2,1ee,o24 I nitrate solventjgor- {plurality 51 solvents which may be employed' 'in brder. that 'the composition be effective as described shouldha've a solvency power not substantl'allyi ln, excess of that e;- hibited by ethyl Iactateand-atleast as great as that exhibited by diethylene glycol monobutyl ether.

Another important factor ii -the. "evaporation rate of the activator. The following :test may be used in comparing the volatility..using"amyl acetate as an arbitrary standard: '2- cc;"' of the liquid to be tested are placed at roomatemp'erature in a tared, open metal cup 2 inchesglh diameter and 1 inch deep. These cupsi'a're placed on a turntable which revolves at about 1 R. P. M. The apparatus also includes a guard about 3 inches high around the perphery'of the turntable, and attached to it only at a few points to afford support, in order to prevent direct drafts. At regular intervals, weighings are made to determine the loss by evaporation. This loss is calculated on a percentage basis and compared with the loss of amyl acetate. It has been found convenient to assign the arbitrary figure of to amyl acetate.

The following table gives these values on this basis for some of the activators which have been tested:

On the basis of the above tests, it has been determined that the cellulose nitrate solvent should not have an evaporation rate substantially greater than that exhibited by ethyl lactate in order that the cellulose nitrate solvent ingredients of the composition remain on the film surface for a suflicient period to fulfill its expressed function of suitably activating and softening the old surface film to the extent that sufiicient surface flow takes place to smooth out irregularities which would otherwise give an unsightly finish. The solvency characteristic of this ingredient is defined above and provides an interdependent limitation for the specific class of cellulose nitrate solvents which have been found satisfactory in the present composition.

As "blanketing agents other materials possessing properties similar to the dibutyl phthalate may be substituted in whole or in part therefor. Dimethyl phthalate, diethyl phthalate, tributyl phosphate, dibutyl tartrate, dibutyl adipate, the phthalate ester of ethylene glycol mono-methyl ether, etc., are illustrative of the type of materials that may be utilized in place of the dibutyl phthalate or as a substitution in part therefor.

In certain cases where the solvent ingredient of the composition has a sufllciently low evaporation rate, approaching that of dibutyl phthalate, it is possible to eliminate the separate blanketing agent" ingredient, since under these conditions the solvent constituent may, in addition to providing the desired activating action on the old film, function as a blanketing agent.

If the so-called blanketing agent is omitted,

the amount of nitrocellulose organic solvent required varies between approximately 5 and 10%. If the amount of this ingredient is substantially less than 5%, neither the solvent action nor blanketing efiect' is adequate for best results and if the proportion of solvent is increased substantially above 10%, the old film is softened beyond the desired point because of the greater solvent action and longer period of exposure of the film to the cleaner. Ingeneral if no blanketing agent is provided. it is preferred to use proportions of a less active solvent near the upper limit of the range indicated, since under these conditions, the cleaner can be kept in contact with the old film for a sufiicient length of time to permit a more complete removal of the grease and tar without causing too great softening of the old film.

The cleaning composition described herein may be utilized for cleaning and preparing old lacquer, baked enamel and synthetic resin finishes for refinishing, and is particularly adaptable to the treatment of old cellulose nitrate composition surfaces prior to refinishing. It eliminates sanding of the old finish, which means a definite saving in time and labor, and also disposes of all possibility of swelling" of sandpaper scratches. It avoids the appearance of welts and the need for a sealer coat. It insures a clean surface for refinishing and, due to its slight solvent action, it activates the old lacquer and promotes adhesion of the new finish.

It is apparent that many different embodiments of this invention may be made without departing from the spirit and scope thereof and it is, therefore, not intended to be limited except as indicated in the appended claims.

I claim:

1. A cleaning composition for preparing coated surfaces for refinishing, comprising hydrocarbon diluents having a boiling range of about 135 C. to 225 C. in major proportion, about 5 to 10% by weight of an organic solvent for nitrocellulose having a solvent power at least equal to diethylene glycol monobutyl ether and less than ethyl lactate, said organic solvent having an evaporation rate not greater than that of ethyl lactate,

and about 1% of a substantially non-volatile liquid nitrocellulose plasticizer.

. 2. Composition of claim 1 in which the organic solvent is butyl lactate.

3. Composition of claim 1 in which the nitrocellulose plasticizer is dibutyl phthalatep 4. A cleaning composition for preparing coated old surfaces for refinishing comprising hydrocarbon diluents having a boiling range of about 135-225 C. in major proportion, and about 5 to 10% by weight of organic solvents for nitrocellulose having a solvent power at least equal to diethylene glycol monobutyl ether and less than ethyl lactate, said organic solvent having an evaporation rate not greater than that of ethyl lactate.

5. A cleaning composition for preparing coated surfaces for refinishing comprising about to 75 parts by weight of hydrocarbon diluents having a boiling range of about -225 C., 15 parts by weight of turpentine, and 5 to 10 parts by weight of an organic solvent fornitrocellulose having at least as great a solvent power as diethylene glycol monobutyl ether but not substantially greater than ethyl lactate, said solvent having an evaporation rate not greater than that of ethyl lactate.

6. A cleaning composition for preparing coated surfaces for refinishing comprising '76 parts by weight of hydrocarbon diluents having a boiling range of about 135-225 0., 15 parts by weight of turpentine and 9 parts by weight of diethylene glycol monobutyl ether.

7. A cleaning composition adapted for preparing old coated surfaces for refinishing having approximately the following formula:

Percent by weight Xylene 30.0 High boiling naphtha (boiling range to Mineral spirits (boiling range 150 to 225 C.) 21.0 Hydrogenated naphtha (boiling range 135 to C.) 17.0 Turpentine 15.0 Butyl lactate 6.0 Dibutyl phthalate 1.0

GEORGE R. ENSMINGER.