US3574047A - Composite filament having reduced stickiness - Google Patents

Abstract

COMPOSITE FILAMENTS HAVING LATENT CRIMPABILITY AND REDUCED STICKINESS WHICH CONSISTS ESSENTIALLY OF (1) A HOMOPOLYAMIDE DERIVED FROM POLYAMIDE FORMING COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF LACTAMS, OMEGA-AMINOCARBOXYLIC ACIDS AND SALTS OF DIAMINES AND DICARBOXYLIC ACIDS, AND (2) A COPOLYAMIDE DERIVED FROM ONE OF SAID POLYAMIDE FORMING COMPOUNDS AND AT LEAST ONE SAID POLYAMIDE FORMING COMPOUNDS DIFFERENT THEREFROM, SAID COPOLYLAMIDE CONTAINING FROM ABOUT 0.3 TO ABOUT 3% BY WEIGHT OF A MONO- OR DIMETAL SALT OF A MONO- OR DICARBOXYLIC ACIDS, SAID HOMOPOLYAMIDE AND COPOLYAMIDE COMPONENTS BEING ECCENTRICALLY DISPOSED RELATIVE TO EACH OTHER THROUGHOUT THE LENGTH OF THE FILAMENT.

Description

April 6, 1971 SATOSHI ANDO ETAL 3,574,047

COMPOSITE FILAMENT HAVING REDUCED STICKINESS Original Filed Dec. 14. .1966

Fig.

- Time (minute) Unwinding resistance (9) O 5 IO V I5 Time (minute) Fig. 2

5 go I I I l I I I I I I I I T I I INVENT()R$ 39mm: fiNDO yum/n4. 'mA mm ATV JRHI- VS United States Patent 3,574,047 COMPOSITE FILAMENT HAVING REDUCED STICKINESS Satoshi Audio and Yusaku Tanaka, Osaka, Minoru Kojima,

Osaka-fir, and Kyoichi Fujimura, Ibaraki, Japan, assignors to Kanegafuchi Boseki Kabushiki Kaisha, Tokyo, Japan, and Snia Viscosa Societa Nazionale Industria Applicazioni Viscosa S.p.A., Milan, Italy Original application Dec. 14, 1966, Ser. No. 601,757, now Patent No. 3,554,980, dated Jan. 12, 1971. Divided and this application Sept. 3, 1968, Ser. No. 798,208 Claims priority, application Japan, Dec. 23, 1965, 40/79,726 Int. Cl. D01d /28; D02g 1/00 US. Cl. 161173 1 Claim ABSTRACT OF THE DISCLOSURE Composite filaments having latent crimpability and reduced stickiness which consists essentially of (1) a homopolyamide derived from polyamide forming compounds selected from the group consisting of lactams, omega-aminocarboxylic acids and salts of diamines and dicarboxylic acids, and (2) a copolyamide derived from one of said polyamide forming compounds and at least one said polyamide forming compounds different therefrom, said copolyamide containing from about 0.3 to about 3% by weight of a monoor dimetal salt of a monoor dicarboxylic acids, said homopolyamide and copolyamide components being eccentrically disposed relative to each other throughout the length of the filament.

This application is a division of our copending application, Ser. No. 601,757, filed Dec. 14, 1966.

The present invention relates to a method for preventing stickiness of fibres produced from copolyamides.

The polyamide fibres have been heretofore used in a wide field owing to its excellent properties, but most of these fibres have been formed from homopolyamide's.

On the other hand, however, the homopolyamides have a number of disadvantages in dyeability, hygroscopicity, elastic recovering property etc. so that a large number of copolyamides copolymerized with at least two polyamide forming materials have been proposed in order to improve these disadvantages. It is considered that, in general, the fibres consisting of these copolyamides have excellent properties in dyeability, hygroscopicity, elastic recovering property etc. as compared with homopolyamide fibres and also the shrinking property in hot water is increased, so that they suit for particular uses. A large disadvantage to retard practice of the copolyamide fibres consists in an inherent stickness of the copolyamides, so that in spite of that said fibres have a large number of advantages, these fibres have heretofore not been produced commercially.

Namely, when the copolyamides are melt spun and then treated with an oil composition, such as, an aqueous emulsion and thereafter taken up on a bobbin, the fibres stick With each other, so that when said fibres are subjected to next processes, such as, drawing and the other processes an uneveness occurs in yarn tension when unwinding yarn from a bobbin and a uniform treatment cannot be effected and moreover in the worst case, the yarn is broken and the operatability is highly damaged.

Moreover, when a side-by-side type of composite filament having a latent crimpability, in which two or more polymers have been arranged highly eccentrically in the cross-section of a unitary filament has been heretofore produced, it has been necessary to use polymers having similar chemical configuration and property in order to 3,574,047 Patented Apr. 6, 1971 prevent separation of each component of the polymers after spinning, so that in general, copolyamide has been used in combination with a homopolyamide. In order to make the crystal structures of the both polymers in these fibres different as far as possible and to increase the difference of shrinking property, that is, to increase the latent crimpability, although it is preferable to increase a copolymerization ratio of the copolyamide, the stickiness phenomena are remarkably increased as the copolymerization ratio increases, so that the copolymerization ratio must be limited fairly, and therefore, it has been difficult to prepare a side-by-side type of polyamide composite fibres having a satisfactory crimp developability.

The inventors have made various invetsigations in order to solve the above described problems resulting in accomplishment of the present invention.

The object of the present invention is to provide fibre consisting of copolyamide, which has no stickiness without deteriorating the other excellent properties.

A further object is to provide a method of producing a practical fibre from polyamide having such a high copolymerization ratio that a practical fibre can not be obtained as such due to a high stickness.

The other object is to provide polyamide composite filaments having no stickiness but an excellent latent crimpability, which consist of a copolyamide and a homopolyamide.

The objects above described can be attained by previously mixing homogeneously a small quantity of metal salts of aliphatic mono or dicarboxylic acid to the copolyamide when melt spinning said copolyamide.

The copolyamides to be applied to the method of the present invention include polyamides obtained by copoly condensating two or more polyamide forming compounds selected from the group consisting of lactams, w-aminO- carboxylic acids and salts of diamines and dicarboxylic acids, for example, the polyamide forming materials such as, 'y-butyrolactam, fi-valerolactam, e-caprolactam, heptolactam, 6-aminocaproic acid, 7-aminoheptanoic acid, 9- aminononanoic acid, ll-aminoundecanoic acid or salts of diamines, such as, tetramethylenediamine, pentamethylenediamine hexamethylenediamine, heptamethylenediamine', octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, metaxylylenediamine, paraxylylenediamine, bis(y-aminopropyl)ether N,N'-bis(w-aminopropyl) piperazine, l,l1-diaminoundecanone-6 and dicarboxylic acids, such as, terephthalic acid, isophthalic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelac acid, sebacie acid, dodecandicarboxylic acid, hexahydrotereph- .thalic acid, diphenylene-4,4-dicarboxylic acid, diphenylmethane-4,4-dicarboxylic acid, diphenylether 4,4-dicarboxylic acid, diphenylpropane-4,4-dicarboxylic acid, or salts of diamines and diearboxylic acid derivatives or salts of diamine derivatives and dicarboxylic acids.

Furthermore, these copolyamides involve polyamide copolymers added with inorganic or organic substances of delustrants, pigments, dyestuffs, light stabilizers, heat resistants, antistatic agents and plasticizers.

The metal salts of aliphatic monoand di-carboxylic acid which may be used for the method according to the invention are aliphatic carboxylic salts in granular form of metals selected from the group consisting of lighium, beryllium, sodium, magnesium, aluminium, potassium, calcium, manganese, nickel, copper, zinc, silver, barium, mercury, thallium, lead, etc. and an aliphatic carboxylic acid forming the salts thereof is monoand dicarboxylic acid having three or more carbon atoms.

The monocarboxylic acid includes, for example, saturated aliphatic acids such as propionic acid, butylic acid, valeric acid, caproic acid, enanthylic acid, caprylic acid,

pelargonic acid, capric acid, undecylic acid, laulic acid, tridecylic acid, myristic acid, pentadecylic acid, palrnitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid, montanoic acid, nonacosanoic acid, melissylic acid, hentriacontanoic acid, dotriacontanoic acid, tetratriacontanoic acid, ceroplastic acid, hexatriacontanoic acid, octatriacontanoic acid, hexatetracontanoic acid, etc., and unsaturated aliphatic acids such as undecylenic acid, oleic acid, elaidic acid, cetoleic acid, erricic acid, brassidic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, stearolic acid, etc., whilst dicarboxylic acid includes, saturated dicarboxylic acid, such as malonic acid, succinic acid, glutaric acid,

adipic acid, pimelic acid, suberic acid, azelaic acid, etc. and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, etc.

An application of metal salts of carboxylic acid having less than two carbon atoms to the method according to the invention is not suitable because when said metal salts are mixed to copolyamide before and during the polymerization, said metal salts are disintegrated and act as a chain reaction inhibitor and moreover, when said metal salts are deposited to the fine flake or granules of copolyamide and supplied to a melting device, they are also disintegrated to very decrease a stability of the melt viscosity of copolyamide and deteriorate quality of fibres. As for the metal salts of aromatic monoand dicarboxylic acids other than those of aliphatic monoor dicarboxylic acid, not only some of them act as to vary the viscosity of copolyamide, but also in general the dispersibility thereof in the copolyamide melts is insufiicient, so that they are ineffective to prevent a stickiness between fibres of copolyamide and therefore not suitable to be used in the method according to the invention.

One or more than two of these metal salts of aliphatic carboxylic acid alone or more than two of them are added into starting materials of the copolyamide to effect the polycondensation thereof or these metal salts are added during or after the polycondensation reaction and mixed With agitation, whereby they are very homogeneously dispersed. The copolyamide containing the metal salts of aliphatic carboxylic acid in a homogeneous dispersed state is melt spun in a conventional process directly or after moulded into fine granules or fine flakes. Furthermore, to fine granules or fine flakes of the copolyamide free from metal salts of aliphatic carboxylic acid, are deposited or mixed powders of the metal salts and then the mass is melt spun and the metal salts of aliphatic carboxylic acid are incorporated homogeneously into the spun filament, whereby satisfactory results can be obtained.

In any case, it is essential that the metal salts incorporated in the copolyamide in molten state are to be homogeneously dispersed in the copolyamide and it is Well effected by a mechanical or physical mixing and dispersing operations such as stirring, shaking, etc., when required. The aforesaid operations may be attained by a screw or a pump housed in a melt extruder.

The content amount of the metal salts to perform the purpose of the invention is preferable within range from 0.03 to 3% by weight based upon the total weight of the copolyamide. [In the case of less than 0.03% by weight, the effect for preventing stickiness is insufficient whereas in the case of more than 3% by weight, yarn breakage is developed during the manufacture of fibre and the drawing step and therefore the quality of the fibre is deteriorated.

The greater the fine granule size of metal salts of aliphatic monoand dicarboxylic acid to be used in the method according to the invention, the less the dispersibility in the molten polymer will be resulting in unhomogeneous dispersion of the metal salts, so that the effect subjected by the invention is not exhibited sufficiently and 4 furthermore the breakage and unevenness of the yarn are developed during the spinning operation, hence it is desired to use fine granules having particle size of less than 50/! The mechanism of the sticking phenomena between the fibres of copolyamide have been hardly made clear, notwithstanding it may be presumed that the moisture contained in the oil composition contribute to the stickiness since a remarkable sticking phenomena are appeared when an aqueous emulsion is imparted to the spun filament.

It is therefore assumed that the metal salts of aliphatic carboxylic acid contained in the copolyamide according to the method of the invention disturb the mutual action between the fibre and water resulting in having an ability to prevent the stickiness, although the detailed mechanism and function thereof are not yet clear.

According to the addition of the metal salts of aliphatic monoor dicarboxylic acid the stickiness of the copolyamide may be never developed and moreover the copolymerization ratio which has heretofore been considerably restricted owing to the increase of the stickiness is relatively increased, whereby the polyamide fibre free from stickiness while having an extremely high heat shrinking property can be obtained. Furthermore, within the above range of the content an amount of the metal salts, the strength, elongation, dyeability, hygroscopicity, elastic recovering property and the other desired properties are not substantially decreased.

Moreover, composite filaments obtained by melting copolyamide containing metal salts of aliphatic carboxylic acid according to the invention and well known homopolyamide separately and by spinning them from the same orifice simultaneously have a good mutually bonding property of the both polymers and also the copolymer does not show any stickiness, the latent crimpability is increased use to the high heat shrinking property and the fibre having extremely excellent crimpability and bulky can be obtained by heat treatment.

The fibre consisting of the copolyamide melt spun according to the method of the invention can be treated uniformly and easily in a treatment with an oil composi tion, taking up, drawing after spinning and the succeeding knitting and weaving processes without accompanying any disadvantage, such as, bad unwinding from a bobbin or stickiness between fibres as in a conventional homopolyamide fibre and furthermore the treatment velocity can be further increased.

Furthermore, the fibres obtained by the method of the invention are provided with the excellent properties as described above which have never been seen in conventional homopolyamide fibres, so that they are preferable as raw material for producing various clothings, interior decorations, commercial articles, etc. by using solely or in combination with the other fibres. Particularly, if said fibres are mix-spun or mix-woven with the other fibres and then subjected to heat treatment by utilizing the high shrinking property, interesting fancy yarns or fancy fabrics can be manufactured.

For a better understanding of the invention reference is made to the accompanying drawings:

FIG. 1 is a graph showing a resistance of a well known and drawn copolyamide yarn in unwinding it from a bobbin; and

FIG. 2 is a graph showing a resistance of the undrawn copolyamide yarn improved by the method according to the invention in unwinding it from a bobbin.

The invention will be explained further in detail by the following examples, in which parts and means parts by weight and by weight unless any special reference provided.

EXAMPLE 1 To e-caprolactam was added 10% by weight of salt of N,N-bis(w-aminopropyl)piperazine with adipic acid, mol of acetic acid as a viscosity regulator and further 0.5% by weight of calcium stearate and the resulting mixture was heated with agitation in the nitrogen gas atmosphere at 250 C. for 7 hours under a normal pressure to conduct copolycondensation, whereafter the reacted product was extruded from bottom of a reactor in the form of strip to permit passing through water bath so as to be cooled and solidified, which was then cut into cpolyamide fine granules of 3 mm. x 3 mm. The thusly obtained fine granules were washed with hot water of approximately 80 C. to remove monomer therefrom and dried by a vacuum drier at 80 C. under 0.1 mm. Hg to reduce the water content to 0.065% and whereafter sup plied to a heat grid type of melt-spinning device. After residence for 40 minutes, the copolymer melted at 270 C. was extruded from nozzles and applied with the spinning oil composition consisting of an aqueous emulsion by means of the rotary roller and then taken up on a bobbin as an undrawn yarn having 412 d./ 28 filaments.

Moreover, the polymerization and the spinning were carried out under the same condition as the above, except that calcium stearate was not added, to produce an undrawn yarn consisting of copolyamide of the same denier filaments which was adapted as a control yarn. In any case, there perceived no yarn breakage and the other barriers on spinning.

The resulting two yarns were determined with respect to stickiness degree by the following means. That is, a bobbin was arranged at right angle to the bottom thereof. A tension meter (TI-80 type made by Toyo Sokki Co.) was located at a position right above the bobbin and separated from it 90 cm. along the extension line of the bobbin axis.

A guide was secured to a point separated 12 cm. from the tension meter along a line inclined by 20 from the bobbin axis. A winding machine was arranged at a position located horizontally with respect to the guide.

In the thus arranged apparatus, the yarn unwound from the bobbin was passed through the tension meter and taken up by the winder through the guide. The unwinding resistance of the yarn perceived on the tension meter was recorded on a chart by means of a pen writing recorder (WTR-211 type made by Watanabe Sokki Co.). In the determined conditions, the take-up velocity was 100 m./min. and the graduation of 1 cm. in the chart to record the unwinding resistance of yarn was adjusted so as to correspond to a resistance of 5 g. load.

The results obtained by determining the resistances of the above described two filaments from bobbin are shown in FIGS. 1 and 2, respectively.

FIG. 1 is a diagrammatical view of a control yarn containing no calcium stearate, which shows a stickiness corresponding to to 12 g.

On the other hand FIG. 2 illustrates a resistance of the sample used in the method according to the invention which exhibits the resistance of only 2 to 3 g. Moreover, these two yarns taken up on the bobbins were drawn four times their original length and as the results the control yarn was developed with the yarn breakage simultaneously with starting the drawing machine, so that the drawing could not be performed. On the contrary, the yarn containing calcium stearate was normally drawn without developing any yarn breakage.

EXAMPLE 2 To e-caprolactam were added 15% by weight of salt of metaxylylenediamine and adipic acid and mol of ethylenediamine as a viscosity regulator and the resulting mixture was heated with agitation in the nitrogen gas atmosphere at 260 C. for initial 2 hours and further retained for 5 hours to effect the polycondensation. The resultant mass was extruded through nozzles provided at the bottom of a reactor into the fine granule of 2 mm. x 2 mm. which was then washed off with warm water at 80 C. to remove the monomer therefrom, and were then dried in a vacuum drier under 0.1 mm. Hg. These polyamide fine granules with water content of 0.061% by weight were filled into a cubic type rotary mixer which was in turn added with 0.3% by weight of fine particle of aluminium palmitate having particle size of approximately 10p. and then the mixer was sealed and then revolved and mixed at a rate of the rotation of three revolutions per minute for 3 hours, whereafter supplied to a melt spinning apparatus to spin the yarn having 160 d./ 7 filaments.

The copolyamide fine granule which was not applied with aluminium palmitate, was treated in the same manner as described above to take up undrawn yarn having the same denier on a bobbin, which was a control yarn.

Moreover the stickiness degree of the samples was measured by the method according to Example 1, and as the result the control yarn showed an unwinding resistance of 8 to 9 g. whereas the sample containing aluminium palmitate recorded to resistance of only 1 to 2 g. When these samples were further cold drawn four times their original length, as for the control yarn the drawing operation at a high speed became impossible owing to the high stickiness of the control yarn, so that the winding rate was reduced to 50 m./min. to continue the cold drawings. Furthermore, comparative tests of the samples of the both 40- d./ 7 filaments were made with respect to the yarn properties such as dyeability, hygroscopicity, shrinkability, elastic recovering properties, etc. and the both yarns exhibited the same value and no influence due to an application of aluminium palmitate was perceived.

EXAMPLE 3 To the salt of undecamethylenediamine and terephthalic acid were added 20% by weight of salt of paraxylylenediamine and adipic acid, 0.3% by weight of titanium oxide, V mol of hexamethylenediamine based upon the total amount of the starting material of the polycondensation as a viscosity regulator and further 1% by weight of zinc cerotate. The resulting mixture was heated at 295 C. under an inert gas and polymerized with agitation for 6 hours and then processed into the fine particles of 3 mm. x 3 mm., washed with water and dried by the conventional process.

The resulting fine particles were fed into a melt extruder (YE4NT type manufactured by Yamakawa Tekko Seisakusho) to spin denier monofilament and furthermore the fine granules free from zinc cerotate were prepared and spun under the exactly same condition.

The resulting two 80 denier filaments were determined in respect of each stickiness degree according to the method as mentioned in Example 1 and as the result, the control yarn free from zinc cerotate suffered the frequent yarn breakages during the determination owing to its high stickiness degree resulting in rendering the determination impossible, while the yarn containing zinc cerotate exhibited an unwinding resistance of only 2 to 3 g.

EXAMPLE 4 To the salt of hexamethylenediamine and isophthalic acid were added 8% by weight of salt of paraxylylenediamine and dodecandicarboxylic and mol of acetic acid as a viscosity regulator, 0.3% by weight of titanium oxide and further 0.8% by weight of zinc laurate and the resulting mixture was heated to 260 C. in the presence of an inert gas, stirred for 7 hours to effect the polymerization, processed into the fine granules of 3 mm. x 3 mm. in the conventional process, washed with water, dried and then fed into the melt process, washed with water dried and then fed into the melt spinning apparatus to spin the yarn of 280 d./4 filaments which was finally taken up on a bobbin and employed as the sample for determining the stickiness.

Moreover, the copolyamide fine granules free from zinc laurate were prepared and spun under the exactly same condition.

The resulting two yarns were determined in respect of each stickiness degree according to the method as mentioned in Example 1 and as the result the control yarn free from zinc laurate showed the unwinding resistance of 6 to 8 g., while the yarn containing zinc laurate exhibited the unwinding resistance of only 1 to 2 g. and a remarkable effect of preventing the stickiness due to an application of zinc laurate was perceived. Furthermore, these two yarns were determined in respect of an amount of spinning oil composition deposited there to by the ether extraction process and as the result, both yarns showed the same amount.

EXAMPLE 5 To e-caprolactam, where added 10% by Weight of salt of bis(' -aminopropyl)ether and terephthalic acid, mol of acetic acid as a viscosity regulator and further 0.5% by weight of calcium adipate and the resulting mixture was heated to 250 C. in the presence of an inert gas, stirred for 7 hours to effect the polymeriaztion and processed into the copolyamide fine granules of 3 mm.4 x 3 mm. Moreover, the copolyamide fine granules free from calcium adipate were prepared under the same condition.

Furthermore, to e-caprolactam was added 5% by weight of aminocaproic acid and mol of acetic acid and the resulting mixture was polymerized at 250 C. for 7 hours in the presence of an inert gas to form polycapramide fine granules of 3 mm. x 3 mm. The resulting fine granules were washed with Water and dried, whereafter the polycapramide fine granules and copolymeric fine granlues were fed into the melt spinning apparatus for producing composite filaments to from two side-by-side type composite filaments having 60 d./monofilament with the conjugating ratio of 1:1.

The thusly obtained two filaments where determined in respect of each stickiness according to the method as mentioned in Example 1 and as the result, the filament free from calcium adipate showed the unwinding resistance of 2 to 3 g., while the filament containing calcium adipate exhibited that of only 0.5 to 1 g. Furthermore, the two samples were subjected to the drawing process in which the filaments free from calcium adipate suffered the frequent breakages owing to its high stickiness. The resultant two drawn filaments were determined comparatively in respect of the yarn properties and crimpability, but no substantial difference was perceived.

EXAMPLE 6 To E-ca'prolactam were added 12% by weight of salt consisting of hexamethylenediamine and isophthalic acid and mol of acetic acid as a viscosity regulator, which was further added or not added with 1% by weight of beryllium propionate, 1% by Weight of barium undecylenate, 1% by weight of zinc melissate, 1% by weight of magnesium sebacate and 1% by weight of calcium fumarate. The resulting six starting materials of polymerization were heated respectively to 250 C. in the presence of an inert gas, stirred to 7 hours to effect polymerization, processed into copolyamide fine granules of 2 mm. x 2 mm., washed with water and dried in the conventional process. The thusly obtained fine granules were fed into a melt spinning apparatus to form the yarn having 268 d./ 18 filaments.

The resulting six bobbin filaments were determined in respect of respective stickiness according to the method as mentioned in Example 1 and as the result, the sample filament free from metal salt suffered the yarn breakage simultaneous with the starting of a winding device arranged in a measuring apparatus owing to its violet stickiness, resulting in rendering the determination impossible.

On the contrary, the sample containing beryllium propionate exhibited the unwinding resistance of 2 to 3 g., that containing barium undecylenate showed 2 to 3 g., that containing zinc melissate showed 1 to 2 g., that containing magnesium sebacate showed 3 to 4 g. and that containing calcium fumarate recorded the unwinding resistance of 1 to 2 g.

Furthermore, five sample filaments free from metal salt but having high stickiness were subjected to the cold drawing process for 3.8 times and the drawing operations were all finished without developing any yarn breakage.

What we claim is:

1. A composite filament having latent crirnpability and reduced stickiness which consists essentially of 1) a homopolyamide derived from polyamide forming compounds selected from the group consisting of lactams, omega-aminocarboxylic acids and salts of diamines and dicarboxylic acids, and (2) a copolyamide derived from one of said polyamide forming compounds and at least one other of said polyamide forming compounds different therefrom, said copolyamide containing from about 0.3 to about 3% by weight of a monoor di-crnetal salt of a monoor dicarboxylic acids, said homopolyamide and copolyamide components being eccentrically disposed relative to each other throughout the length of the filament.

References Cited UNITED STATES PATENTS 2,345,700 4/1944 Dreyfus 260-78 3,260,689 7/ 1966 Kibler et a1 260-22 3,399,108 8/1968 Olson 16 1-175X 3,418,199 12/1968 Anton et al 161-l77X ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner US. Cl. X.R.

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