US3579453A - Alkali-soluble surfactant consisting of substituted succinic acid-nonionic ethoxylate blends - Google Patents

Abstract

NONIONIC ETHOXYLATES SURFACTANTS, WHICH ARE KNOWN TO BE VERY DESIRABLE COMPONENTS IN HEAVY DUTY CLEANING PRODUCTS, SUFFER FROM THE FACT THAT THEY HAVE LIMITED SOLUBILITY IN SOLUTION OF ALKALINE ELECTROLYTES AND THUS ARE NOT SOLUBLE OF ALKALINE BUILDER CONCENTRATES. ADDITION OF MODERATE AMOUNTS OF SUBSTITUTED SUCCINIC ACIDS OVERCOMES THIS DEFECT AND PERMITS THE INCLUSION OF THESE NONIONICS IN BUILT LIQUID DETERGENT CONCENTRATES.

Description

3,579,453 Patented May 18, 1971 3,579,453 ALKALI-SOLUBLE SURFACTANT CUNSISTING F SUBSTITUTED SUCCINIC ACID-NONIONIC ETHGXYLATE BLENDS Jean Dupre, Levittown, and Harrison Scott Killam, Holland, Pa., assignors to Rohm and Haas Company, Philadelphia, Pa. N0 Drawing. Filed Nov. 12, 1968, Ser. No. 775,137 Int. Cl. Clld 1/66 US. Cl. 252-89 8 Claims ABSTRACT OF THE DISCLOSURE Nonionic ethoxylated surfactants, which are known to be very desirable components in heavy duty cleaning products, sulfer from the fact that they have limited solubility in solutions of alkaline electrolytes and thus are not soluble in alkaline builder concentrates. Addition of moderate amounts of substituted succinic acids overcomes this defect and permits the inclusion of these nonionics in built liquid detergent concentrates.

This invention relates to surfactant compositions which can be incorporated into built liquid detergent concentrates, and at the same time possess useful performance characteristics in dilute cleaning baths,

Broadly stated, the invention pertains to surfactant compositions that are soluble in solutions of alkaline builders having a high solids content.

An object of the invention pertains to surfactant compositions that are soluble in solutions of alkaline builders having a high solids content.

An object of the invention is to provide means for solubilizing polyethylene oxide containing nonionic surface active compositions into builder solutions.

A further object is to provide homogeneous built liquid detergents and alkaline cleaners containing polyethylene oxide nonionic surfactants and alkaline builders, characterized by the possession of low foaming properties even when used in high pressure automatic cleaning operations.

Alkaline cleaners are the most widely used means in industry for cleaning meal, glass, certain plastics, etc. In the metal-forming field, in particular, such cleaners are used to remove various types of soils such as cutting oils, grinding( buffing, stamping and drawing compounds. The alkaline cleaning solutions may be used in various types of cleaning methods and apparatus, e.g. soaking, spraying, electrolytic, et al.

Currently, the trend in industrial use of alkaline cleaners is in the direction of automated operations as a means of reducing manpower and time requirements. The preferred detergent products for these operations are aqueous built liquids containing surfactants and high levels of alkaline builders. The preferred surfactants are the nonionic ethoxylated type, for they have some or all of various desirable features such as superior detergent action, rapid wetting, low foaming capacity, soil defoaming capacity, emulsifying properties, free rinsing, etc.

All nonionic surfactants based on polyethylene oxide units as the hydrophilic portion, however, suffer from a basic deficiency, They have poor tolerance in solutions for alkaline electrolytes, and thus are not soluble at the levels of alkaline builders required for a practical liquid detergent concentrate. It is believed that this is due to the fact that the other oxygen atoms of the polyethoxy chain lose Water of hydration excessively in alkaline builder solutions. In any event, the nonionic surfactants exhibit a cloud point whereby above this temperature the surfactant separates into a second phase.

Alkaline builders cause the cloud point to be lowered to a point where phase separation occurs at ambient temperature. Increasing the number of ethoxy groups in the molecule does raise the cloud point in water or in builder solutions of low concentrations, but solubility at high builder levels cannot be achieved regardless how many ethylene oxide units are present. Moreover, to modify the nonionic structure as by incorporating ionic groups may improve alkali tolerance but will also alter the performance undesirably as well as increase the costs.

A particularly difiicult part of the general problem of incorporating nonionic ethoxylated surfactants into aqueous alkaline builder concentrates is that of using lowfoaming nonionic surfactants. This group of ethoxylates must have relatively low cloud points in dilute solutions in order to exhibit low foaming properties at use temperatures. Consequently, they have not heretofore been capable of being incorporated into builder solutions even at relatively low alkaline builder levels. Nonetheless, low foaming nonionics are especially desirable for incorporation into built liquid detergents since many of the automated cleaning machines employ a power washing cycle. Although their greater mechanical action enables power washers to give quicker and better cleaning action than is achieved by still soaking and the like, their one big drawback is their tendency to generate excessive foam, the air content of which reduces the cleaners density and mechanical impact. The use of low foaming nonionic surfactants not only avoids this problem, but also serves to reduce the foam caused by certain soils such as proteinaceous matter.

The present invention has made it possible to incorporate nonionic polyethylene oxide type nonionics, such as the well known, commercially available Triton X-lOO, into alkaline builder solutions. This has been accomplished by blending together with those nonionics, in certain ratios of one to the other, certain substituted succinic acids. The effectiveness of such blends in making soluble in builder solutions nonionics which heretofore had no such properties is remarkably good. The presence of the substituted succinic acids raises the cloud point of the nonionics in the builder solutions to such an extent that clear, homogeneous solutions are obtained at ambient temperatures. Other hydrotropes are known to have some solubilizing activity for nonionics in builder solutions, but are unsatisfactory for most industrial applications because they require either too high a ratio of hydrotrope to nonionic or permit only such a relatively low concentration of builder as to make the resulting products have too little economic utility.

Another advantage derived from our novel utilization of the substituted succinic acids as part of the surfactant compositions of the present invention resides in the surprising fact that, unlike other hydrotropes, they do not adversely affect the properties or performance characteristics of the nonionics in the end-use baths. This particular characteristic is extremely important in power washing operations because any significant contribution of foam by the hydrotrope would make those materials useless.

The compositions of the present invention, which so effectively combine the property of solubility in highly built liquids with the performance properties of ethoxylated nonionics, essentially consist of blends of the following constituents:

25-90% of a substituted succinic acid,

R is an alkyl or alkenyl group, branched or straight chain, of 7 to 12 carbon atoms, and

-75% of a nonionic polyethoxylated surfactant. Illustrative of the nonionic surfactants which may be employed are those from the group consisting of;

R CHzO-O R where R is an alkoxy group whose alkyl portion has 818C atoms, an alkyl amine whose alkyl portion has 818 C atoms, or an alkyl phenoxy group whose alkyl portion has 6 to 12 C atoms,

R is H, a C alkyl group, benzyl, acetate, ethyl acetyl,

acetal, or chloro group,

R2 is H, CH3, or C2H5, and

(2) Ethylene oxide-propylene oxide block copolymer. A preferred novel blend in accordance with the present invention is one in which the substituted succinic acid is the n-octenyl adduct, the nonionic polyethoxylate is a low-foaming polypropylene oxide terminated ethoxylated linear primary alcohol, and the ratio of the former to the latter varies between 1.5 and 2.

Optional materials which may be employed as the hydrotrope in place of the substituted succinic acids are compounds which can form the dicarboxylate ion upon addition to alkaline builder solutions as does substituted succinic acid. Such materials, for example, would include monoor disalts, alkyl esters, amides, and the anhydrides of alkyl or alkenyl succinic acids.

The nonionic surfactant component of the novel blends may be selected from compositions containing a hydrophobic portion and a hydrophilic portion, the latter portion consisting principally or entirely of polyethylene oxide units and characterized by the fact that the molecule does not ionize in alkaline solutions. Included in these compositions are ethylene oxide adducts containing amine groups which sometimes are classed as cationics but actually are nonionics in alkaline solutions, and modified ethylene oxide adducts such as those terminated with benzyl groups and polypropylene oxide chains.

The effectiveness of the above-described hydrotropes in solubilizing the polyethoxylated nonionic surfactants can readily be demonstrated by comparing them with a number of prior art solubilizers for nonionics in alkaline builder solutions. In making such comparisons it should be kept in mind that the objective is to provide a solubilizing agent which will allow the highest concentrations of alkaline builders, and which can be present at the minimum level for a given amount of nonionic surfactant. Accomplishing this objective is paramount for practical economic considerations. Built liquid detergents with low builder levels and consequently high water contents have excessively high packaging, shipping and handling costs per part of active ingredient. Secondly, it is desirable to have present a minimum amount of any component that does not directly contribute to cleaning action; hence the need to keep the amount of hydrotrope present down to the minimum possible consistent with its required solubilizing activity.

A striking illustration of the effectiveness of the present invention is had by comparing the solubilizing activity of various substituted succinic acids when blended with the benzyl ether of an ethoxylated higher alcohol. This low-foaming nonionics solubility in alkaline builder is so poor that, for example, it is not soluble in solutions of potassium hydroxide having as little as 5% KOH present. Yet, when this same nonionic is blended with 80% n-octenyl succinic acid in accordance with the present invention the blend is soluble in as much as 35% KOH solutions, as indicated in Table I below which contains data regarding the solubility of 80/20 blends of potential hydrotropes and the benzyl terminated ethoxylate in KOH solution.

In obtaining the data reported in Table I the comparison standard employed called for a test composi tion to be considered as having adequate solubility in a system if a clear, homogeneous solution was obtained over the temperature range of 19-450 C. It will be noted from Table I that not all of the substituted succinic acid compositions are satisfactory hydrotropes. Whereas, under the conditions of test there shown, straight chain alkenyls of 8, 10 and a blend of 7 and 9 carbon atoms, branched chain alkenyls of 9 and 12 carbon atoms and a straight chain alkyl of 8 carbon atoms are effective solubilizers, straight chain alkenyls having 6 carbon atoms are not suitable and neither are compositions with an alkyl amino group or an aromatic group. The data further indicate that an alkyl chain above 12 carbon atoms will not be active at concentrations of 20% KOH or higher, and therefore would be considered unsatisfactory.

Numerous materials besides those listed in Table I were tested, including compositions with previously recognized hydrotropic activity as well as many experimental compositions. None of those materials, other than the substituted succinic acids, gave adequate solubilization of the nonionic surfactant when subjected to this screening. The unsatisfactory materials, which includes Na benzene sulfonate, Na toluene sulfonate, Na xylene sulfonate, sodium methyl naphthalene sulfonate, sodium dodecyl diphenylether disulfonate, and n-decvl monophosphate ester, the results obtained therewith, are reported in Table :11 below. Other compositions found to be ineffective solubilizers include Na butyl sulfonate, Na heptyl sulfonate, succinic acid, di-sodium phthalate, di-sodium alpha sulfo octanoic acid, di-sodium alpha sulfo stearic acid, Na ndecyl monophosphate, Na benzoate, Na nonanoate, and sulfonated naphthalene-formaldehyde condensate.

TABLE I.SOLUBILIZATION OF BENZYL ETHER OF ETHOXYLATED ALCOHOL 1 IN ALKALINE SOLUTIONS BY VARIO US HYDROTROPES HAVIN G FORMULA- R-CH-CO O11 CHz-C O OH Maximum percent KOH in which mate- 1Saialugility p57 rial shows en in -0 solubili l Substttucnt R in acid formula KOH solutioii semi/ii? Hydrogen 4 20 n-Hexenyl. 20

n-Heptenyl-noncnyl (1/1). 30

n-O ctcnyl E 35 n-Octyl 35 Branched n0ncny1 Clear, 0-45" C... 30

n-Decenyl Clear, 075 C-.- 30

Branched dodcccnyl. Clear, 0-88 C 20 t-Butyl amino Insoluble 3 20 Alpha methyl benzyl Clear, 025 C... 20

Solution contained 5% surfactant, consisting of an /20 ratio of substltuted succinic acid to the nonionic of footnote 1.

3 Insoluble indicates no clear solution from 0-100 0.; mixture scparates at ambient temperature into two strata.

4 20% was set as an arbitrary floor below which the product was considered inadequate.

5 The di-mcthyl ester, di-sodium salt, di-potassium salt, (Ii-amide, and the anhydride of n-octenyl succinic acid may be substituted with cssentially the same results.

TABLE II.SOLUBILIZATION OF BENZYL ETHER OF ETHOXYLATED ALCOHOL IN ALKALINE SOLUTIONS BY VARIOUS HYDROTROPES TABLE II.Coutinued produce a terminal hydroxyl group, an example being an Maximum acetate ester such as the last nonionic listed in Table III. zffi if TABLE III.SOLUBILIZATION OF VARIOUS NONIONIG which bllelnd 3 ETHOXYLATES IN ALKALINE SOLUTIONS l S OW'S solubilizing 5 Solubility of Hydrotrope 2 actlvlty Nonionic compositions 2 blend 3 n-CoH1 OE1OHgOO0Na 20 t-Oetylphenol Em Clear, 0100 C. n-CaHmOEgGHzGOONB. 20 D0, 1130. 0. OE CHgOO ONa 20 Linear primary C12 alcohol Es"- Do. C1215 alkyl amine E15 Do. Polydimethyl siloxane-E adduc Clear, 095 0.

Cu acetylenic glycol plus 10 E un Clear, 0- 00H:000H 100 0.

Etllilygznlo )oxide-propylene oxide block copolymer Clear, 0-80 C.

a 28 a Linear primary 010-12 alcohol E4P3 Clear, 059 C. COONa 20 10 Linear primary Co-m alcohol E3P3- Clear, 0-46 0. Linear primary 01o alcohol E1001 Clear, 0-54 0. Linear primary C1042 alcohol E4P3 acetate ester Clear, 0-59" 0. Na naphthenate 20 Nag phthalate 20 1 5% surfactant into 20% KOH; surfactant is a 60/40 blend of n-octenyl Na OOCGHeCHCO0Na 20 succinic acid/nonionic. Na OOC(CHg)5CO0Na 20 Illustrative of other nonionic surfactant compositions which could Na OOOHQOEQOHZCOONQ, 20 20 be blended with he same or other substituted succinic acids, at various Amino carboxylate hydrotropes: ratios (and naturally with varied performance), to give an alkali soluble n-C H NHOH2OH2COONa 20 product are: t-oetyl phenol E5, t-octyl phenol E30, hexyl phenol E9, H-CQHZNHOHZOOONB 20 t-octyl phenyl Em t-butyl ether, n-octyloxy E3, oetadecyloxy E12, 012 (CH3)2CHCH2CH(NH2)COON3. 0 amine EaoPno, S80. Cn-qsHza-nOEm ethyl 8.061331, and Sulfonate hydrotropes:

Na benzene sulionate 20 C2H5 Na p-toluene sulfonate.. 20 Na xylene sulionate 20 20 C1u-i2E1oCH2CHO H C HgOE2OHzOHzCHzSOaNa 20 Still other nonionics which are suitable are polyethylene oxide adducts of OOH2OH2OCH2CH2CH2SO3N& 20 polypropylene oxide where the molecular weight of the propylene oxide chain, and the weight percent of ethylene oxide, are respectively: 1,001 1 1,200 and 40%, 1,501-1,s00 and 20%, 1,5011,800 and 80%, 3,200-3,500 and t-C4H NHCH2CH2GH SO3NS. 20 30 30%.

t-OeHmNHOH OH CHzSOaNE. 20 3 N onionics alone are insoluble in 20% KOH. tC8H11NHCH2OH2OH2sO3Na- 20 Nora-E refers to ethylene oxide units, and P refers to units of Phosphate hy r p propylene oxide.

n-CrHgOEz phosphate 20 zgag E zglgsrgiat Egg The effective ratios of hydrotrope to IlOlllOIllCS have g g j gg lg g 1 20 been investigated, with the conclusion that any ratio would ResorcinolEz hosphate 39 have some nonionic solubilizing effect in builder solu- 1 CIHEEHO(CH,CH,O),,OH,C5H5 tions, so that the ratio of choice almost becomes an {:E in certain of the examples of hydrotropes refers to ethylene oxide bit Selection Th upper li it f Course, i di d 11111 S.

a 5% oiablend consisting oilpart of C 2-15H25-31O(CH2CH2 )11CH2C5H5 p m p ly y conom1cs. The hy r p portlon, 1t and 4 pa s of the y 40 should be noted, essentially is a diluent since the basic goal Since the data in Table I illustrate the ability of various is to obtain the performance of the nonionic portion. As substituted succinic acids to solubilize a particular nona practical matter, a 9/1 ratio is considered to be the efionic in builder solution, it naturally will be of interest fective maximum; and the lower effective limit depends to compare data which illustrate the ability of at least on the nonionic chosen together with the particular one of the substituted succinic acid hydrotropes to soluuilder system of interest. Actually, any amount of hybilizg examples of a number of nonionics under the same 4'0 drotrope added to a IlOIliOIllC Will raise ltS Cl0lld point conditions. Since polyethoxylated alcohols are the non- Somewhat; the higher the ratio the greater the level of ionics of principal interest, due to their well-known ulld r whlch can be tolerated. reputation for being among the most effective of all A a l We v found, a m m 0f 1 p r hy roknown detergents, major types of those ethoxylates were pe t0 3 parts nonionic are needed for solubility at screened i h h results set f rth i T bl 111 b l reasonable builder levels. In Table IV, which contains Using a /40 ratio (hydrotrope/nonionic) the ethoxdata regarding results obtained with different ratios of l t hi h were l bili d i t 20% KOH i l d d substituted succinic acid to noniomc, the system chosen adducts of alkylphenol, higher alkyl (as much as C for llustration resulted in ratlos of 9 to 0.33 (25/75) alcohols, alkyl amine, polysiloxane, and alkyl acetylenic Fr p g to be Soluble, a Clear Sohlholl being Obtained at glycol; other ethoxylated nonionic surfactants include a a least f In thls System a Tatlo Proved block copolymer of propylene oxide and ethylene oxide, to be lnadequately Solubletwo P YP PY olde termmlated h% ethoxylates Table IV.Effect of varying the ratio of substituted and a chloro-termmated ethoxy ated alco o succinic acid to nonionic Th data in able III clearl indicate that the effect of th e T 60 Ratio of n-octenyl Solubility in 20% e hydrotropes of the present invention is quite a general succinic acid at 5% surfactant one for all polyethoxylate nonionics, although it should to IIOIIIOIIICZ KOH solution be understood that not all such nonionics will be effective 90/10 Clear 0 100 C under the conditions described for the examples given 60/40 C1 a 3 C in that table. Likewise, it should be understood that not 30/70 2; (5 all nonionics are equal with regard to their ease of solu- 25/75 Clear bilization, and the minimum amount of hydrotrope re- 20/80 clear 1 quired to effect their solubilization will therefore vary. n

. v u n In general, the nonionic surfactants which will be most Octyl pheml E *ethylene Oxlde umts) readily solubilized into builder solutions by the substituted The solubility of the blends of alkyl or alkenyl succinic succinic acid hydrotropes of the present invention are acids and nonionic ethoxylates is, of course, not limited those which have a terminal hydroxyl group. Thus, those to potassium hydroxide solutions. To demonstrate this fact nonionics would certainly be the preferred types of surexamples are given in Table V below of several blends in factants. Included in this category would also be comsodium metasilicate, tetrapotassium pyrophosphate positions which, upon addition to alkaline builders, would (TKPP) and mixed builder solutions.

TABLE V.-EFFEOTIVENESS OF VARIOUS HYDROTROPES IN VARIOUS ALKALINE SOLUTIONS Alkaline builder solutions 2 in which blend is soluble CH3 2 Percent alkali in water. 3 5% surfactant. 4 SiO /NazO ratio of 1.86.

Various ones of the blends in Table V have been tested to determine their particular utility in a number of use situations. These formulations were added to cleaning baths at levels of 1 part of formulation to 50-1000 parts of water. Example No. 5 shows very low foam and effectively removes oils from steel under industrial spray metal cleaning conditions. Example No. 7 exhibits good detergency, low foam, and the ability to defoam proteinaceous food soils in mechanical dishwashing operations. Example No. 3 is a suitable for use in commercial laundering, particularly with heavily soiled cotton and polyester-cotton fabrics.

Regarding the methods of preparation of the components of the novel blends described above, it should be noted that any of the many conventional techniques for preparing the nonionics and the substituted succinic acids may be employed. Preferably, the substituted succinic acids may be prepared by heating a mixture of olefin and maleic anhydride in a closed vessel for a suitable period of time. The alkenylsuccinic acid anhydride so formed can be purified by distillation or, if a light color is not required and some loss in effectiveness can be tolerated, the reaction mixture can be used without distillation. Although in some applications the anhydride can be used directly, in others it is more advantageous to use the acid. Conversion of the anhydride to the acid can be effected by merely contacting the anhydride with the required amount of Water at elevated temperatures. Other derivatives of the anhydride, such as esters, amides, salts and saturated alkyl substituted derivatives can be used but are not as convenient to formulate and are more expensive to obtain.

From the foregoing specification it will be apparent to those skilled in the art that the compositions of the present invention are wide in their scope, both with regard to their formulation and their use, and are not necessarily limited by the examples hereinabove disclosed.

We claim:

1. A surface active composition consisting essentially of:

(a) 25-90% of a substituted succinic acid,

where R the sole substituent is an alkyl or alkenyl group, branched or straight chain, of 7 to 12 C atoms, and

(b) -75 of a nonionic polyethoxylated surface active agent.

2. The composition of claim 8 in which the agent is selected from one of a linear primary C1042 alcohol E 1 a linear primary C alcohol E P a linear primary C alcohol E Cl, a linear primary C alcohol E P acetate ester, and ethylene oxide and propylene oxide 8 block copolymer E P E and E P designation representing ethylene oxide and propylene oxide.

3. The composition of claim 8 in which the nonionic polyethoxylated surface active agent is selected from the group consisting of:

R2 R(OH2+O)R R is an alkoxy group whose alkyl portion has 8-18 0 atoms, an alkyl amine Whose alkyl portion has 8-18 C atoms, or an alkyl phenoxy group Whose alkyl portion has 6 to 12 C atoms,

R is H, a C alkyl group, benzyl, 'acetyl, ethyl acetal, or

chloro group,

R is H, CH or C H and (b) ethylene oxide-propylene oxide block copolymers. 4. A surface active composition consisting essentially of a blend containing (a) 25-90% of a substituted succinic acid,

Where where R is an alkyl or alkenyl group, branched or straight chain of 7 to 12 C atoms, and

(b) 10-75% of a low foaming polypropylene oxide terminated ethoxylated linear primary alcohol of 8- 12 carbons or the acetate ester thereof.

5. The composition of claim 4 in which the ratio of the substituted succinic acid to the nonionic surfactant is between about 1.5 and 2.

6. The composition of claim 4 in which R is selected from the group consisting of n-heptenyl-nonenyl (1/ 1), 'n-octenyl, n-octyl, branched nonenyl, n-decenyl, and branched dodecenyl.

7. The composition of claim 3 in which the nonionic polyethoxylated surface active agent is selected from the group. consisting of t-octylphenyl E t-octylphenyl E t-octylphenyl E hexylphenyl E nonylphenyl E dodecylphenyl E t-octylphenyl E t-butyl ether, n-octyloxy E octadecyloxy E C amine E P ethyl acetal, linear secondary alkyl alcohol E adduct in which the alkyl group has 11-15 C atoms, linear primary alkyl alcohol E adduct in which the alkyl group has 12 C atoms, alkyl amine B in which the alkyl group has 12-15 C atoms, polydimethyl siloxane-ethylene oxide adduct, alkyl acetylenic glycol B in which the alkyl group has 14 C atoms, ethylene oxide-propylene oxide block copolymers where the propylene oxide block(s) has at least 15 units and the ethylene oxide block(s) would represent between 10 and Weight percent of the total, linear primary alkyl alcohol E P in which the alkyl group has 10- 12 C atoms, linear primary alkyl alcohol B' P in which the alkyl group has 8-10 C atoms, linear primary alkyl alcohol E Cl in which the alkyl group has 10 C atoms, linear primary alkyl E P acetate ester in which the alkyl group has 10-12 C atoms, the E and P designations respectively representting ethylene oxide and propylen oxide.

8. A surface active composition consisting essentially (a) 25 to of a substituted alkyl or alkenyl succinic acids of 7-12 carbons selected from the group consisting of the monoand di-sodium and potassium salts, dimethyl esters, and the anhydrides of said acids, which upon addition to alkaline solutions gives the corresponding dicarboxylate ion of said acids, and

9 10 (b) 10-75% of a nonionic polyethoxylated surface ac- 3,231,587 1/1966 Reuse 252-356 tive agent. 3,288,772 11/1966 Becker et a1 252-356 References Cited UNITED STATES PATENTS LEON D. ROSDOL, Pnmary Eliiammer 2,182,178 12/1939 Pinkernelle 260-326.5F 5 SCHULZ Asslstant Exammel 2,283,214 5/1942 Kyrides 252-356 Us Cl XR 2,878,190 3/1959 Dvorkovitz et a1. 252-161 252 356 3,156,655 10/ 1964- Bright 252-89