US3725286A - Detergent compositions - Google Patents

Abstract

FABRIC-WASHING DETERGENT COMPOSITIONS INCORPORATING, AS DETERGENCY BUILDERS, WATER-SOLUBLE OR WATER-DISPERSIBLE SALTS OF DICARBOXYLIC ACIDS HAVING THE GENERAL FORMULA:

R1-CH(-X)-CH(-Y)-R2-CH(-COOH)-(CH2)N-COOH

WHEREIN R1 IS A HYDROGEN ATOM OR AN ALKYL OR SUBSTITUTED ALKYL GROUP CONTAINING FROM 6 TO 20 CARBOON ATOMS, R2 IS AN ALKYLENE OR SUBSTITUTED ALKYLENE GROUP CONTAINING FROM 0 TO 4 CARBON ATOMS AND OPTIONALLY INCORPORATING HETERO ATOMS AS LINKING GROUPS, THE TOTAL NUMBER OF CARBON ATOMS IN GROUPS R1 AND R2 BEING FROM 6 TO 20, ONE OR BOTH OF X AND Y BEING NON-IONISABLE ATOMS OR GROUPS, ANY OTHER BEING HYDROGEN, AND N IS 0 TO 1, ARE DISCLOSED.

Description

United States Patent Int. 01. C11d 3/04 us. Cl. 252-89 ABSTRACT OF THE DISCLOSURE Fabric-washing detergent compositions incorporating, as detergency builders, water-soluble or water-dispersible salts of dicarboxylic acids having the general formula:

1|: Y lh-GH-JJH-Rz-CHUJOOH)-(CH2).,'COOH wherein R is a hydrogen atom or an alkyl or substituted alkyl group containing from 6 to 20 carbon atoms, R is an alkylene or substituted alkylene group containing from 0 to 4 carbon atoms and optionally incorporating hetero atoms as linking groups, the total number of carbon atoms in groups R, and R being from 6 to 20, one or both of X and Y being non-ionisable atoms or groups, any other being hydrogen, and n is O to 1, are disclosed.

5 Claims The present invention relates to detergent compositions, and particularly to detergent compositions adapted for fabric-washing.

Detergent compositions for heavy-duty fabric washing in fabric-washing machines normally comprise as major ingredients detergent-active compounds and detergency builders. The most commonly used detergency builders are the condensed phosphates, particularly sodium tripolyphosphate, although other inorganic or organic materials, such as sodium nitrilotriacetate and sodium copolyethylene-maleate, have been proposed.

It has been suggested that the use of condensed phosphates as detergency builders in detergent compositions contributes to the phenomenon of eutrophication. Considerable effort has been expended to find some other detergency builders not containing phosphorous which are at least as effective as the presently available materials whilst not being too expensive or having any deleterious properties.

In the complete specification of United Kingdom patent application No. 37,961/68 are described detergent compositions incorporating as detergency builders salts of dicarboxylic acids of the general formula:

R-CH(COOH) (CH -COOH wherein n is 0 or 1 and R is a primary or secondary straight-chain alkyl or alkenyl group containing from to 20 carbon atoms.

It has now been found that other water-soluble or dispersible salts of dicarboxylic acids are detergency builders and can be used to advantage in detergent compositions. Such other dicarboxylic acids have the general formula:

wherein R is a hydrogen atom or an alkyl or substituted alkyl group containing from 6 to 20, preferably from 10 "ice to 20, carbon atoms, R; is an alkylene or substituted alkylene group containing from O to 4, preferably 0 to 1, carbon atoms and optionally incorporating hetero atoms as linking groups, the total number of carbon atoms in groups R, and R being from 6 to 20, one or both of X and Y being non-ionisable atoms or groups, any other being a hydrogen atom, and n is 0 or 1.

For convenience, the detergency builders of the invention are hereinafter referred to as substituted dicarboxylic acid salts.

R and R are preferably linear.

The preferred non-ionisable atoms or groups are halogen atoms, particularly chlorine or bromine, and hydroxy groups; the presence of any additional ionisable groups in the substituted dicarboxylic acids tends to detract from the detergency building properties of the substituted dicarboxylic acid salts.

A detergent composition according to the invention comprises at least one detergent-active compound and at least one substituted dicarboxylic acid salt as defined above, the weight ratio of the detergent-active compound to the substituted dicarboxylic acid salt being within the range of about 10:1 to about 1:10.

The substituted dicarboxylic acid salt is preferably an alkali-metal salt, such as a sodium, potassium or lithium salt, sodium salts being particularly preferred, but other cations, such as ammonium and substituted ammonium, may be used if desired.

Preferably the weight ratio of the detergent-active compound to the substituted dicarboxylic acid salt is within the range of about 2:1 to about 1:4.

The substituted dicarboxylic acid salt normally comprises at least about 5%, and preferably from about 20 to about 60%, by weight of the detergent composition,

' although even higher levels may be required if the detergent composition is to be used at low concentrations or in water which is particularly hard.

Substituted dicarboxylic acids according to the present invention can be prepared by addition to the double bond of an alkenyl malonic acid or its salt or an alkenyl succinic acid or its salt or anhydride. The addition reaction is accomplished using conventional techniques to give a variety of different groups X and Y in Formula I. X and Y may be the same group or different groups, and where they are different it will be appreciated that either of the different groups represented by X and Y in the Formula I may be nearer to the dicarboxylic head group in the molecule. Examples of different reagents which may be reacted with the appropriate starting materials, i.e. the alkenyl succinic or malonic acids or their salts or anhydrides, to give the various groups X and Y are shown in Table I below:

TABLE I-Continued Starting Product Reagent material group Bromine water Acid OH Br -JJH( J H- Hydrogcn chloride Anhydrido Cl -01-Izi:11

Hydrogen bromide -do Br -C H2( 3 H- Alkaline potassium permanganate" Sodium salt OH O H CHCH l Perbenzoic acid Anhydridc O -Cfi -CH Pcrformic acid Acid OH 3HCH- Hydration (e.g. H2804 addition fol- .do OH lowed by hydrolysis) CH2 ([J H- Nitric acid Anliydride .c N

( 3HCH2 The preferred starting materials which are used to prepare the substituted dicarboxylic acids of the present invention are alkenyl succinic acids or their salts or anhydrides which can be prepared by reaction between an olefin and maleic anhydride to give an alkenyl succinic anhydride, which can then be hydrolysed to give the acid and neutralised to give the salts if desired. In the alkenyl succinic acids, or their anhydrides or salts, the double bond in the alkenyl group is predominantly between the 5 and 6 carbon atoms, in which case R in Formula I contains only 1 carbon atom. However, a certain amount of migration of the double bond along the carbon chain can take place, either during the preparation of the alkenyl compound or during the reactions to form the compounds of the invention, so that R can contain up to about 4 carbon atoms.

Alternatively, the starting material can be an alkenyl malonic acid and its salts or anhydride. These can be prepared by standard malonic ester synthesis techniques in which a sodium malonic acid diester is reacted with an alkenyl halide, for example chloride, to give the alkenyl malonic ester followed by conventional treatment to form the acid, anhydride or salt as desired. In this case position of the double bond will depend on the position of the double bond in the alkenyl halide used. An alternative route for preparing an alkenyl malonic acid and its derivatives is by condensation of an aldehyde with a malonic acid diester in the presence of an amine; in this case the double bond is immediately adjacent to the malonic acid group.

Substituted dicarboxylic acids according to the invention may also be prepared by reaction of a halogen with an alkyl succinic acid or alkyl malonic acid, in which case substitution tends to occur in the Ot-POSitiQIlS on the carbon chain.

A detergent composition of the invention will contain at least one detergent-active compound. The substituted dicarboxylic acid salts of the invention themselves have some limited detergent-active properties, but as these salts are deliberately selected for use as precipitant detergency builders, for which purpose their parent substituted dicarboxylic acids must have water-insoluble calcium salts, these salts are not considered as detergentactive compounds for the purposes of this specification. The detergent-active content of the composition will generally be from about 5 to about 50%, preferably from about 5 to about 35%, and particularly preferably from about 10 to about by weight of the composition.

The nature of the detergent-active compound or compounds in the composition is not an essential feature of the invention: any of the detergent-active compounds conventionally incorporated in or proposed for use in detergent compositions may be used, and those skilled in the art of formulating detergent compositions will be familiar with these detergent-active compounds and the various amounts and combinations in which they may advantageously be used. The detergent-active compound or compounds may be anionic, nonionic, amphoteric or zwitterionic in character.

Typical anionic detergent-active compounds are watersoluble or water-dispersible salts of various organic acids. The cations of such salts are generally alkali-metals, such as sodium and, less preferably, potassium, but other cations, such as ammonium and substituted ammonium, can be used if desired. Examples of suitable organic acids are: alkyl benzene sulphonic acids, the alkyl chains of which contain from about 8 to about 20 carbon atoms, such as p-dodecyl benzene sulphonic acid and linear alkyl (C benzene sulphonic acid; the mixtures of sulphonic acids obtained by reacting linear and branched olefins, particularly linear cracked-wax or Ziegler alpha-olefins, containing from about 8 to 22 carbon atoms, sulphur trioxide; alkyl sulphonic acids obtained by reacting alkanes containing from about 8 to about 22 carbon atoms with sulphur dioxide/oxygen or sulphur dioxide/chlorine (followed by hydrolysis in the latter case), or by the addition of bisulphite to olefins, particularly linear cracked-wax or Ziegler alpha-olefins, containing from about 8 to about 22 carbon atoms; alkyl sulphuric acids obtained by reacting aliphatic alcohols containing from about 8 to about 22 carbon atoms with sulphur trioxide; alkyl ether sulphuric acids, obtained by reacting molar quantities of aliphatic alcohols containing from about 6 to about 18 carbon atoms with from about 1 to about 15 moles of ethylene oxide, or a suitable mixture of ethylene oxide and propylene oxide, and subsequently reacting the alkoxylated alcohol with sulphur trioxide to yield the required acid; and natural or synthetic aliphatic carboxylic acids, particularly those derived from natural sources such as tallows, coconut oil, palm oil, palm kernel oil and groundnut oil.

Examples of suitable nonionic detergent-active compounds are: condensates of alkyl-phenols having an alkyl group (derived, for example, from polymerised propylene, diisobutylene, octene, dodecene or nonene) containing from about 6 to 12 carbon atoms in either a straight chain or branched chain configuration, with about 5 to 25 moles of ethylene oxide per mole of alkyl-phenol; condensates containing from about 40% to about polyoxyethylene by weight and having a molecular weight of from about 5,000 to about 11,000 resulting from the reaction of ethylene oxide with the reaction product of ethylenediamine and excess propylene oxide; condensates of linear or branched-chain aliphatic alcohols containing from 8 to 18 carbon atoms with ethylene oxide, e.g. a coconut alcohol-ethylene oxide condensate containing about 6 to 30 moles of ethylene oxide per mole of coconut alcohol; long-chain tertiary amine oxides corresponding to the general formula R R R N- O, wherein R is an alkyl radical containing from about 8 to 18 carbon atoms and R and R are each methyl, ethyl or hydroxy ethyl radicals, such as dimethyldodecylamine oxide, dimethyloctylamine oxide, dimethylhexadecylamine oxide and N-bis (hydroxyethyl) dodecylamine oxide; long-chain tertiary phosphine oxides corresponding to the general formula RRRP O, wherein R is an alkyl, alkenyl or monohydroxyalkyl radical containing from 10 to 18 carbon atoms and R and R are each alkyl or monohydroxyalkyl groups containing from 1 to 3 carbon atoms, such as dimethyldodecylphosphine oxide, dimethyltetradecylphosphine oxide, ethylmethyltetradecylphosphine oxide, dimethylstearylphosphine oxide, ethylpropylcetylphosphine oxide, diethyldodecylphosphine oxide, bis (hydroxymethyl) dodecylphosphine oxide, bis (2-hydroxyethyl) dodecylphosphine oxide, Z-hydroxypropylmethyltetradecylphosphine oxide, dimethyloleylphosphine oxide and dimethyl-Z-hydroxydodecylphosphine oxide; and dialkyl sulphoxides corresponding to the general formula RRS- 0, wherein R is an alkyl, alkenyl, betaor gammamonohydroxyalkyl radical or an alkyl or betaor gammamonohydroxyalkyl radical containing one or two other oxygen atoms in the chain, the R groups containing from to 18 carbon atoms and wherein R is methyl, ethyl or alkylol radical, such as dodecyl methyl sulphoxide, tetradecyl methyl sulphoxide, 3-hydroxytridecyl methyl sulphoxide, 2-hydroxydodecyl methyl sulphoxide, 3-hydroxy-4-dodecyloxybutyl methyl sulphoxide, 2-hydroxy-3- decyloxypropyl methyl sulphoxide, dodecyl ethyl sulphoxide, 2-hydroxydodecyl ethyl sulphoxide and dodecyl-2- hydroxyethyl sulphoxide.

Examples of suitable amphoteric detergent-active compounds are: derivatives of aliphatic secondary and tertiary amines, in which the aliphatic radical may be straight chain or branched and wherein one of the aliphatic substitnents contains from about 8 to 18 carbon atoms and one contains an anionic water solubilising group, such as sodium-3-dodecylaminopropionate, sodium 3 dodecylaminopropanesulphonate and sodium N-Z-hydroxydodecyl-N-methyl-taurate.

Examples of suitable zwitterionic detergent-active compounds are: derivatives of aliphatic quaternary ammonium compounds, sulphonium compounds and phosphonium compounds in which the aliphatic radical may be straight chain or branched and wherein one of the aliphatic substituents contains from about 8 to 18 carbon atoms and one contains an anionic water solubilising group, such as 3-(N,N-dimethyl-N-hexadecyl-ammonium) propane-l-sulphonate betaine, 3-(N,N-dimethyl-N-hexadecyl-ammonium)-2-hydroxypropane 1 sulphonate be taine, 3- (dodecylmethyl-sulphonium) propane 1 sulphonate betaine, and 3-(cetylmethylphosphonium) ethane sulphonate betaine.

Further examples of suitable detergent-active compounds commonly used in the art are given in Surface Active Agents, volume I by Schwartz and Perry (Interscience 1949) and Surface Active Agents, volume II bySchwartz, Perry and Berch (Interscience 1958), the disclosures of which are included by reference herein.

The substituted dicarboxylic acid salts of the invention may comprise the whole of the detergency builder content of a detergent composition of the invention. However, if desired, mixtures of one or more of these salts with one or more known detergency builders may be used. As one of the objects of the invention is to provide an effective detergent composition containing either no phosphorus or at most only a low level of phosphorus, it is preferred that any such other detergency builders should not be phosphorus-containing compounds. Usually the total amount of detergency builders in a detergent composition of the invention will be from about 5 to about 70% by weight of the detergent composition. Many detergency builders are known, and those skilled in the art of formulating fabric-washing detergent compositions will he familiar with these materials. Examples of known detergency builders are sodium tripolyphosphate; sodium orthophosphate; sodium pyrophosphate; sodium trimetaphosphate; sodium ethane-l-hydroxy-1,1-diphosphonate; sodium carbonate; sodium silicate; sodium citrate; sodium oxydiacetate; sodium nitrilotriacetate; sodium ethylenediaminetetraacetate; sodium salts of long-chain dicarboxylic acids, for instance straight chain (C to C succinic acids and malonic acids; sodium salts of alpha-sulphonated longchain monocarboxylic acids; sodium salts of polycarboxylic acids; i.e. acids derived from the polymerisation or copolymerisation of unsaturated carboxylic acids and unsaturated carboxy acid anhydrides such as maleic acid, acrylic acid, itaconic acid, methacrylic acid, crotonic acid and aconitic acid, and the anhydrides of these acids, and

also from the copolymerisation of the above acids and anhydrides with minor amounts of other monomers such as vinyl chloride, vinyl acetate, methyl methacrylate, methyl acrylate and styrene; and modified starches such as starches oxidised, for example using sodium hypochlorite, in which some anhydroglucose units have been opened to give dicarboxyl units.

In addition to the detergent-active compounds and detergency builders, a detergent composition of the invention may contain any of the conventional detergent composition ingredients in any of the amounts in which such conventional ingredients are usually employed therein. Examples of these additional ingredients are lather boosters, such as coconut monoethanolamide and palm kernel monoethanolamide; lather controllers; inorganic salts such as sodium sulphate and magnesium sulphate; bleaching agents such as sodium perborate, sodium percarbonate, trichloroisocyanuric acid, and sodium and potassium dichloroisocyanurates; antiredeposition agents, such as sodium carboxymethylcellulose; and, usually present only in minor amounts, perfumes, colourants, fluorescers, corrosion inhibitors, germicides and enzymes.

A detergent composition of the invention can be prepared using any of the conventional manufacturing techniques commonly used or proposed for the preparation of detergent compositions, such as slurry-making followed by spray-drying or spray-cooling, and subsequent dry-dosing of sensitive ingredients not suitable for incorporation prior to the drying step. Other conventional techniques, such as noodling, granulation, and mixing by fluidisation in a fluidised bed, may be utilised as and when necessary. Such techniques are familiar to those skilled in the art of detergent composition manufacture.

By using such conventional manufacturing techniques, a detergent composition of the invention may be prepared in any of the common physical forms associated with detergent compositions, such as powders, flakes, granules, noodles, cakes, bars and, in some cases, liquids.

The invention is illustrated by the following examples, in which all parts and percentages are given by weight.

EXAMPLE 1 Preparation of disodium dichloro-hexadecyl succinate Chlorine was slowly bubled through a vigorously stirred solution of 250 g. of hexadecenyl succinic anhydride in the minimum volume of carbon tetrachloride containing 2% by weight of ferric chloride (based on the alkenyl succinic anhydride), at room temperature until an excess of chlorine was indicated in the flask head. The ferric chloride and solvent were then removed and the crude di-chloro compound was purified by percolation in light petroleum (B.P. '60-80 C.) solution down a silica column.

The product was hydrolysed by pouring it steadily into a 10% molar excess of a stirred solution of sodium hydroxide in alcohol (10% solution). The di-sodium salt which precipitated was filtered and washed with a little ethanol to remove excess base and coloured by-product to yield, on drying, a light brown product (226 g., 65% yield) of predominantly disodium 5,6-dichloro hexadecyl succinate, the carbon atoms being numbered along the longest chain.

EXAMPLE 2 Preparation of disodium dihydroxy hexadecyl succinate To a solution of hexadecenyl succinic acid, prepared by conventional saponification and then acidification of 250 g. of the corresponding anhydride, were added formic acid ('850 ml.) and 30% hydrogen peroxide (75 ml.). The solution was stirred at 40 C. for 4 hours and was then basified with sodium hydroxide and warmed for 1 hour to hydrolyse the formate ester intermediate. The free acid was precipitated from solution by acidification with concentrated HCl and was filtered and dried.

To the free acid was added the calculated quantity of aqueous sodium hydroxide and the water was then removed by distillation to yield 256 g. of the dry product, consisting predominantly of disodium 5,6-trans-dihydroxy hexadecyl succinate, numbering the carbon atoms along the longest chain.

EXAMPLE 3 Preparation of mixed disodium hydroxy hexadecyl succinates To a solution of -65 g. of hexadecenyl succinic anhydride in 200 ml. of 1,4-dioxane was slowly added, with stirring, 20 g. of concentrated H 80 the temperature being kept at 20 C. When the addition was complete the reaction was continued for a further 2 hours and then a solution of 32 g. of sodium hydroxide in water was added over /2 hour and the whole solution stirred for 2 hours at 60 C. A white solid formed which was filtered, washed with dioxane and then diethyl ether and then dried to yield 55 g. of product (68%), consisting predominantly of the and 6-hydroxy compounds, numbering the carbon atoms along the longest chain.

EXAMPLE 4 Preparation of disodium epoxy hexadecyl succinates 150 g. of m-chloroperbenzoic acid were dissolved in diethyl ether and this solution was added to a stirred solution of 250 g. of hexadecenyl succinic anhydride in ether/ chloroform (1:3) so that the temperature remained at 25 C. The reaction was continued for 17 hours (overnight) before the excess per-acid was destroyed by the addition of a aqueous solution of sodium bisulphite. The solution was then washed rapidly in turn with 5% aqueous sodium carbonate solution, water, and brine before drying the organic layer with anhydrous sodium sulphate and removing the solvent. The yield was 142 g. of predominantly disodium 5,6-epoxy hexadecyl succinic anhydride which was subsequently hydrolysed to the disodium salt.

EXAMPLE 5 Preparation of disodium bromo-hydroxy hexadecyl succinates The dicarboxylic acid formed by hydrolysis of 50 g. of hexadecenyl succinic anhydride was dissolved in water and a dilute solution of bromine (12.5 g.) in 500 ml. of water was added at 20 C. The whole solution was kept at 20 C. for 2 hours and was then neutralised with sodium hydroxide and evaporated to dryness. Analysis indicated the product was 70% bromohydrin and 30% dibromo compounds.

EXAMPLE 6 Preparation of disodium hydroxy hexadecyl malonate 23 g. of sodium was dissolved in 600 ml. of dry ethanol and 160 g. of diethyl malonate added at 50 C. The mixture was stirred for minutes then 240 g. of dry hexadecane 1,2-epoxide were added. The mixture was gently refluxed for 2 /2 hours and allowed to cool. The precipitated product was removed by filtration and was heated for 1 hour with a slight excess of aqueous caustic soda. The solution was filtered and the filtrate evaporated to dryness.

EXAMPLE 7 Preparation of disodium nitro hexadecyl succinates To a refluxing mixture of hexadecenyl succinic anhydride (14.8 g), nitric acid (13.5 g. of 70% AR quality) and water (18.0 g.) was added instantaneously to a solution of sodium nitrite equivalent to about 0.5 molar percent; based on the anhydride. The nitration was continued at reflux temperature until the generation of brown fumes had ceased (1 hour). The solution was cooled to allow two layers to form and the aqueous layer was separated and extracted with ether. The combined organic layers were washed with water and brine and were dried over magnesium sulphate and filtered. The solvent was removed to yield 13.0 g. of a mixture of mainly nitro hexadecyl succinic acid with some of the corresponding anhydride. The mixture was then fully hydrolysed and neutralised to form the disodium salt of predominantly 5- and 6-nitrohexadecylsuccinates.

EXAMPLES 8 to 14 The detergency-building capacities of the seven substituted alkyl succinates and malonates as prepared as described in Examples 1 to 7 were determined by the following procedure:

Discs of desized cambric cotton were solid with a radioactive synthetic sebum deposited on the discs to the level of 1.5% from diluted benzene solution. After drying, the soiled discs were washed in the detergent solution containing 0.05% weight by volume of sodium dodecyl benzene sulphonate (prepared from sulphonated DOB 055 ex Shell Chemicals Ltd.), 0.025% of alkaline silicate and an amount of a selected detergency builder at 45 C. for 10 minutes in 25 H water at pH 10 using a repeatable degree of agitation at 70 cycles per minute. The percentage detergency of each material was determined by counting the radio-activity of each washed cotton disc before and after washing and the detergency was calculated by the equation:

Detergency percent: A X

where A is the corrected radio-active count before washing and A is the corrected radio-active count after washing.

The results obtained for the detergency builders of the invention together with a comparative result using sodium tripolyphosphate are given in Table II below.

TAB LE II Dntergeney (percent) Detergcncy builder 0. 1% 0. 15%

Disodium dichlorohexndeeyl succinate of Example 1 57. 8 78. 5 Disodium dihydroxyhexadecyl succinate of Example 2.. 52. 6 74. 8 Disodium hydroxyhexadceyl suceinates of Example 3.. 34. 4 64. 8 Disodium epoxy hexadecyl succinates of Example 4... 37. 9 37. 3

Disodium bromohydroxyhexadecyl succinates of Example 5. 36. 3 52. 9 Disodium hydroxy hexadecyl malonate of Example 6. 59.0 72. 9 Disodium nitro hexadecyl succinate of Example 7 43. 0 61. 0 Sodium tripolyphosphate 69. 3 78. 8

wherein R is a linear alkyl group, R is an alkylene group containing either 0 or 1 carbon atom, R and R contain together 14 carbon atoms, X and Y are selected from the group of non-ionisable atoms or groups consisting of hydrogen, chlorine, bromine, hydroxy and nitro (provided that both X and Y cannot be hydrogen), and n is 0 or 1;

the weight ratio of said detergent-active compound and said dicarboxylic acid salt being from about 1: 10 to about 10:1.

2. A detergent composition according to claim 1 wherein X and Y are selected from the group consisting of hy- 5 drogen, chlorine, bromine and hydroxy.

3. A detergent composition according to claim 1 Wherein said weight ratio is from about 2:1 to about 1.4.

4. A detergent composition according to claim 1 wherein said dicarboxylic acid salt comprises from about 20 to about 60% by weight of the detergent composition.

5. A detergent composition according to claim 1 Wherein R contains 1 carbon atom.

10 References Cited UNITED STATES PATENTS 2,264,103 10/1941 Tucker 252-89 3,635,830 1/1972 Lambert et al 252-89 3,661,787 5/1972 Brown 252-89 LEON D. ROSDOL, Primary Examiner W. E. SCHULZ, Assistant Examiner US. Cl. X.R. 260-537