Mineral Filled Polyphenylene Ether Compositions Having Improved Properties

This invention is concerned with compositions coπprising a polyphenylene ether resin and a mineral filler. It has been discovered that mineral filled polyphenylene ether compositions can be further modified fay including certain selected additives, in one case to improve the impact_ strength, and in another case to improve the modulus without sacrificing ductility.

Background of the Invention. - The polyphenylene ether resins are well known in the art as comprising a family of thermoplastic materials which are suitable for various engineering purposes. These may be made by catalyzed and non-catalyzed processes which are described in the patent literature, such as in Hay. U.S. 3,306,374 and 3,306,875, and in Stamatoff, U.S. 3,257,357 and 3,257,358, which are incorporated herein by reference.

It is known that the polyphenylene ether resins may be admixed with polystyrene, both unmodified and modified, to produce compositions having properties which are better than those of either of the two polymers individually. Such compo¬ sitions are disclosed in Cizek, U.S. 3,383,435, the disclosure of which is incorporated herein by reference.

To reduce the cost, it has been proposed to add mineral fillers such as aluminum silicate, calcium carbonate, talc or zinc oxide, to compositions containing a polyphenylene ether resin and polystyrene. Compositions comprising a poly¬ phenylene ethe resin, a rubber modified high impact styrene resin and aluminum silicate are disclosed in U.S. 4,166,812. Such compositions are described as having improved toughness. Copendiπg application Serial No. 755,025, filed December 23, 1976, discloses compositions comprising a polyphenylene ether resin, alone, or in combination with an impact modifier which is not a high impact rubber modified polystyrene, a mineral filler and a plasticizer.

Inexpensive fillers are often added to olastics to

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reduce cost, but often result in reduced impact strength. It has now been discovered that the addition of a plasticizer to mineral filled, e.g., clay filled, composicions comprising a polyphenylene ether resin and a high impact rubber modified polystyrene results in improved impact strength, thus providing reduced cost as well as property improvement.

It has also been discovered that a new class of mineral fillers, namely iron oxides, provide good ductility in compo¬ sitions comprising a polyphenylene ether resin, i oact modifiers and a plasticizer. Because the iron oxides are useful as pig¬ ments, this invention provides the capability for producing a variety of colored mineral filled materials having good ductility.

Description of the Invention. - According to this invention, there are provided improved -thermoplastic compositions. com risin :

(a) a polyphenylene ether resin-,

(b) a high impact, rubber modified polystyrene;

(c) a mineral filler which is not an iron oxide; and

(d) an effective amount of a plasticizer.

The mineral filler can be selected from a wide variety of materials. Examples include talc, clay (hydratec or an¬ hydrous), zinc oxide, titanium dioxide, antimony oxide, barium sulphate, calcium carbonate and zinc sulfide. Among these, clay is preferred.

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The mineral filler is present in such compositions preferably in amounts in the range between 15 and 50 parts by weight, more preferably between 20 and 35 parts by weight, based on the weight of (a) , (b) and (d) combined.

In another aspect of this invention, there are providec compositions comprising:

(a) a polyphenylene ether resin;

(b) an impact modifier which is not a high impact, rubber modified polystyrene;

(c) iron oxide in an amount sufficient to give good retention of ductility; and

(d) ^* an effective amount of a plasticizer.

In the foregoing compositions, the iron oxide prefer¬ ably is present in amounts in the range between 15 and 50 parts by weight, based on the total weight of (a), (b) and (d .

The terra "polystyrene" is used herein in the same manner as defined in Cize , U.S. 3,383,435. Such styrene resins will be combinable with the polyphenylene ether and, in general, will be selected from those having at leas* 25 ^* by weight of the polymer units derived from a vinyl arcratic monomer, e.g., one having the formula

O PI

wherein R is hydrogen, (lower)alkyl, e.g., of from 1 to 4 carbon atoms or halogen; Z is hydrogen, vinyl, halogen or (lower)alkyl; and p is 0 or a whole number of from 1 to 5. Illustrative polystyrene resins include homopolymers of polystyrene; poly- chlorostyrene; poly-^-methyls yrene; and the like; styrene- containing copolymets, such as styrene-acrylonitrile copolymers; copolymers of ethylvinylbenzene and divinylbenzene; styrene- acrylonitrile-^-methylstyrene terpolymers, and the like. Pre¬ ferred polystyrene resins of this class are homopolystyrene; poly- -methylstyrene; styrene-acrylonitrile copolyπers-. scyrene- - -methylstyrene copolymer; styrene-raethyl methacrylate co- polymer; poly-^-chlorostyrene and styrene-maleic anhydride copolymers. Especially preferred is homopolystyrene.

The- term "rubber" as used herein includes polymeric materials, natural and synthetic, which are elastomers at room temperature, e.g., 20" to 25 ^β C. The term "rubber" Includes, therefore, natural or synthetic rubbers of the type generally used in preparing impact polymers . All such rubbers will form a two phase system with the resin, e.g., a polystyrene resin, and will comprise the discontinuous particulate phase in the impact resistant polystyrene resin composition. Illustrative rubbers for use in this invention are natural rubber and poly¬ merized diene rubbers, e.g., polybutadiene, polyisoprene, and the like, and copolymers of such dienes with vinyl monomers, e.g., vinyl aromatic monomers, such as styrene. Examples of suitable rubbers or rubbery copolymers are neutral crepe rubber, synthetic SBR type rubber containing from 40 to 9S~ by weight of butadiene and from 60 to 2 percent by weight of styrene pre¬ pared by either hot or cold emulsion polymerization, synthetic

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SUBSTITUTE SHEET O PI

GR-N type rubber containing from 65 to 32 percent by weight of butadiene and from 35 to 18 percent by weight of acrylonicrile, and synthetic rubbers prepared from, for example, butadiene, butadieήe-styrene or isoprene by methods, e.g., those employing heterogeneous catalyst systems, such as a trialkylaluπinum and a titanium halide. Among the synthetic rubbers which may be used in preparing the present compositions are elastcmeric modified diene hσmopolymers, e.g., hydroxy- and carboxy-terminated polybutadienes; poly-chlorobutadienes, e.g., neoprenes; poly- isobutylene, and copolymers of isobutylene with butadiene or isoprene; polyisoprene; copolymers of ethylene and propylene and interpolymers thereof with butadiene; thiokol rubbers; pcly- sulfide rubbers; acrylic rubbers; polyurethane rubbers; copoly¬ mers of dienes, e.g., butadiene and isoprene, with various comonα ers, such as alkyl unsaturated esters, e.g., methyl methacrylate; unsaturated ketones, e.g., methylisopropenyl ketone, vinyl heterocyclics, e.g., vinyl pyridine; polyether rubbers; epichlorohydrin rubbers and the like. The preferred rubbers comprise polybutadiene and rubber copolymers of butadiene wish styrene. Such preferred rubbers are widely used in forming rubber modified high impact polystyrene resins with the broad range of elasto eric particle sizes mentioned in the above- cited references.

The term "rubber modified polystyrene resin" defines a class of compounds comprising a two-phase system in which rubber is dispersed in a polystyrene resin matrix in the form of discrete particles. The particles can be formed by a mechanical blending of the rubber and the polystyrene resin and in this case the particles will comprise a dispersed ungellec

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_. ._ _ i O PI

elastomeric phase. On the other hand, and as is preferred, the two-phase system will consist of interpoly ers of a styrene monomer and an elastomer or rubber. Commercially, such high impact polystyrenes are usually made by grafting of rubber in the presence of polymerizing styrene. Such systems consist of a continuous phase of the polymerized styrene monomer in which the rubber or elastomer is dispersed in a discontinuous elastomeric gel phase, with or without grafted chains of poly¬ merized styrene monomer. The particles may contain occluded, polymerized styrene monomer, too, and this has some bearing on their size.

The impact modifiers other than high impact rubber modified polystyrenes are comprised of any one of a number of elastomeric polymerized diene blends, and copolymers comprising grafts, block, radial, etc., structures known in this art under the general term "resin impact modifiers". Illustratively, they will comprise a compound selected from

(i) an A-B-A block copolymer wherein terminal blocks A comprise a polymerized vinyl aromatic compound and center blocks B comprise a polymerized diene hydrocarbon, or a hydrogenated derivacive thereof;

(ii) a radial teleblock copolymer com¬ prising polymerized vinyl aromatic blocks and polymerized diene hydrocarbon blocks, or a hydrogenated derivative thereof;

(iii) an A-B block copolymer wherein block A comprises a polymerized vinyl aromatic

1

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s compound and block B comprises a polymerized diene hydrocarbon, or a hydrogenated derivative thereof;

(iv) a rubber modified styrene resin comprising at least 20 parts by weight of a polymerized diene hydrocarbon and graft polymerized vinyl aromatic compound, or a hydrogenated derivative thereof; and

(v) a graft copolymer of an acrylic ester, alone, or in combination with a vinyl aromatic compound and a polymerized diene hydrocarbon, or a halogenated derivative thereof.

The A-B-A block copolymers of vinyl aromatic hydro¬ carbon and a diene hydrocarbon (b) (i) ^' are well known in the art and commercially available. These are described, for instance, in "Polymer Chemistry of Synthetic Elastomers", edited by Kennedy et al, Interscience Publishers, Vol. 23, Part II (1969), pages 553-559, the disclosure of which is incortorated herein by reference. Other descriptions are given in Zelinski, U.S. 3.251,905 and Holden et al. U.S. 3.231,635 which are also incorporated herein by reference.

In general, component (b)(i) is a block copolymer of A-B-A type in which terminal blocks A, which can be the same or different, are thermoplastic homopolymers or polymers prepared from a vinyl aromatic compound wherein true aromatic moiety can be either mono- or polycyclic. Examples include styrene, alpha-methylstyrene, vinyl toluene, vinyl xylene,

ethyl vinyl xylene, vinyl naphthalene and the like, or mixtures thereof.

Center block B is an elastomeric polymer derived from a diene hydrocarbon, preferably a conjugated diene, e.g., 1,3- butadiene, 2,3-dimethyl butadiene, isoprene, 1,3-pentadiene and the like, or mixtures thereof.

If desired, the block polymers can be post-created to hydrogenate the rubber portion of the polymer.

Hydrogenation can be carried out with a variety of hydrogenation catalysts, such as nickel on Kieselguhr, Raney nickel, copper chromate, molybdynum sulfate and finely divided platinum or other noble metals on a low surface area catalyst.

The hydrogenated block polymers are described further tn Jones, U.S. 3,431,323 and De LaMare et al, U.S. 3,670,054, both of which are incorporated herein by reference.

In preferred compositions, component (d)(i) comprises an A-B-A block copolymer of polystyrene-polybucadiene-poly- styrene or polystyrene-polyisoprene-polystyrene type wherein the polybutadiene or polyisoprene portion can be either hydrogenated or non-hydrogenated.

The radial teleblock copolymers can be mace by mea s known in this art and they are also commercially available. As an illustration, they can be made by polymerizing conjugated dienes, e.g., butadiene, and vinyl aromatic compounds, e.g..

styrene in the presence of an σrganometallic initiator, e.g., n-butyllithium, to produce copolymers which contain an active metal acom, such as lithium, on one end of each of the polymer chains. These metal atom-terminated polymers are then reacted with a coupling agent which has at least three active sites capable of reacting with the carbon-metal atom bonds on the polymer chains and replacing the metal atoms on the chains. This results in polymers which have relatively long branches which radiate from a nucleus formed by the polyfunctional coupling agent.

Such a method of preparation is described in detail in Zelinski et al, U.S. 3,281,383, which is incorporated herein by reference.

The coupling agents for the teleblock copolymers can be chosen from among polyepoxides, polyisocyanates, polyi ines, pσlyaldehydes, pσlyketones, polyanhydrides, polyesters, poly- halides and the like. These materials can contain two or more types of functional groups, such as the combination of epσxy and aldehyde groups or isocyanate and halide groups. The coupl¬ ing agents are described in detail in the above-mentioned U.S. Pat. No. 3,281,383.

The conjugated dienes of the radial teleblock copoly¬ mer include compounds such as 1,3-butadiene, isoprene, 2,3- dimethyl-l,3-butadiene, 1,3-pentadiene, 3-butyl-l,3-octadiene, and the like. The vinyl aromatic polymers may be prepared from vinyl aromatic compounds which include styrene, 1-vinyl- naphthalene, 2-vinylπaphthalene and the alkyl, cyclo-

i

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SUBSTITUTE SHEET ' ^OMπ -

alkyl, aryl, alkaryl and aralkyl derivatives thereof. Examples include 3-methylstyrene, 4-n-propylstyrene, 4-cyclohexylstyrene, 4-4-(4-phenyl-n-butyl) styrene, and the like.

Preferred radial teleblock copolymers are Solprene 406 (containing about 60 parts of weight of butadiene units and about 40 parts by weight of styrene units), Solprene 411 (containing about 70 parts by weight of butadiene units and about 30 parts by weight of styrene units) , Solprene 414 (con¬ taining about 60 parts by weight of butadiene units and about 40 parts by weight of styrene units) , and S&ll? (containing about 70 parts by weight of butadiene units and about 30 parts by weight of styrene units). These materials also include a relatively minor amount of coupling agent, e.g., less than 1 part by weight of coupling agent per 100 parts of polymer.

The graft copolymers or acrylic ester and diene rubber can be made by means known in the art and they are also commercially available, e.g., from Rohm & Haas Co., Philadelphia, Pa. , under the trade designation Acryloid KM 611.

The graft polymerization product of an acrylic mono¬ mer and a diene rubber preferably comprises (1) from about 20-807. by weight of a backbone polymer of the unitr of buta-

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diene or butadiene styrene, wherein the butadiene units are present in quantities of at least 40" by weight of the backbone polymer, (2) 80-20 by weight of an acrylic monomer graft polymerized to (1) ; said acrylic monomer units being selected from the group consisting of lower alkyl methacrylates, alicyclic methacrylates and alkyl aerylaces, and (3) 0 to 60^ by weight of a styrene monomer graft polymerized to (1) or (2) ; sequentially or simultaneously with the polymerization of (2) .

The graft polymerization product of an acrylic monomer alone or with styrene monomer and the rubbery diene polymer or copolymer may be prepared by known techniques, typically by emulsion polymerization. They may be formed from a styrene- butadiene copolymer latex and a onomeric material such as methyl methacrylate alone or with another compound having a single vinylidene group copoly erizable therewith, e.g., styrene. For example, in the preparation of a representative material, 85-65 parts by weight of monomeric methyl methacylate or monomeric methyl methacrylate to the extent of at least 5a7. and preferably as much as 757. by weight in admixture wish another monomer which copolymerizes therewith, such as ethyl aerylate, acrylonitrile, vinylidene chloride, styrene, and similar un¬ saturated compounds containing a single vinylidene group, is added to 15-35 parts by weight of solids in a styrenebutadiene copolymer latex. The copolymer solids in the latex comprise about 10-50" by weight of styrene and about 90-50 by weight of butadiene and the molecular weight thereof is within the ranee of about 25,000 to 1,500,000. The copolymer latex of solids in water contains a dispersing agent such as sodium oleate or the like to maintain the copolymer in emulsion. Interpolymerization

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SUBSTITUTE SHEET

13 of the monomer or monomeric mixture with the copolymer solids emulsified in water is brought about in the presence of a free- radical generating catalyst and a polymerization regulator which serves as a chain transfer agent, at a temperature of the order of 15°C. to 8Q"C. Coagulation of the interpoly erized product is then effected with a calcium chloride solution, for instance, whereupon it is filtered, washed and dried. Other graft co¬ polymers and differing from the above only in Che ratio of monomeric material solely or preponderantly of methyl mechacrylate to the butadlene-styrene copolymer latex in the presence of which it is polymerized extends from 85-25 parts by weight of the former to 15-75 parts by weight of the latter. These materials may extend in physical properties from relatively rigid compositions to rubbery compositions. A preferred com¬ mercially available material is Acryloid KM 611 which is sold, by Rohm ^' Haas. Also, U.S. Pat. Nos. 2,943,074 and 2,857.360, which are incorporated by reference, contain additional informa¬ tion as to the preparation of these materials . A preferred material is described in U.S. 2,943,074, column 4, preparation "D" and converted to emulsified polymer "3" as described therein.

The preferred polyphenylene ether resins are chose havinp Che formula

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wherein the oxygen ether atom of one unit is connected to the benzene nucleus of the next adjoining unit, n is a positive integer and is at least 50, and each Q is a monovalent sub- stituent selected from the group consisting of hydrogen, halogen, hydrocarbon radicals free of a tertiary alpha-carbon atom, halo- hydrocarbon radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus, hydrocarbonoxy radicals, and halohydrocarbonoxy radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus.

The preparation of polyphenylene ether resins corre¬ sponding to the above formula is described in the above- mentioned patents of Hay and Sta atoff.

The most preferred polyphenylene ether resin for use in this invention is pol (2,6-dimethyl-1,4-phenylene)ether.

The styrene resin should have at least 25 percent of its units derived from an alkenyl aromatic monomer of the formula

CR ¹ -CHR ²

wherein R~ ¹ and R2 are selected from the group consisting of hydrogen and lower alkyl or alkenyl groups of from 1 to 6

SUBSTITUTE SHEET

~ A. carbon atoms; R and R are selected from the group consisting of chloro, bromo, hydrogen, and lower alkyl groups of from 1 to 6 carbon atoms and and R are selected from the group consisting of hydrogen and lower alkyl and alkenyl grouos of from 1 to 6 carbon atoms.

Specific examples include styrene, bromostyrene, chlorostyrene and rJL-methylstyrene. Especially preferred for use herein is styrene.

The olasticizer can be selected from among any material known to impart flexibility. Preferably, the plasticizer is an aromatic phosphate, and especially a compound having the formula:

0R ^S

wherein R 7, R8 and 9 are the same or di erent and are alkyl , haloalkyl, cycloalkyl, halocycloalkyl, aryl, haloaryl, alkyl substituted aryl, haloalkyl substituted ar l, aryl substituted alkyl, haloaryl substituted alkyl, hydroxyalkyl, hydroxyaryl, hydroxyalkaryl, halogen and hydrogen, provided that at least

7 8 9 one of R , R and R is always aryl.

Examples include cresyl diphenyl phosphate, 2-ethyl- hexyl diphenyl phosphate, tricresyl phosohate, triisooropyl- phenyl phosphate, triphenyl phosphate, dibutyl phenyl phosphate,

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cresyl diphenyl phosphate, isooctyl diphenyl phosohate, 2- ethylhexyl diphenyl phosohate, isodecyl diphenyl phosphate, isodecyl dicresyl phosphate, didecyl cresyl phosphate, di-π_- octyl phenyl phosphate and di-2-ethyl-hexyl phenyl, or mixtures thereof. Especially preferred is triphenyl phosphate.

In all of the foregoing compositions of this invention, the plasticizer is preferably present in an amount in the range between 5 and 35, more preferably, 15 to 30 parts by weight, based on (a) , (b) and (c) combined.

The polyphenylene ether resin and the high impact, ^• rubber modified polystyrene or other impact modifier can be present in virtually any amount _r &. ^~ . , from 1 to 99 parts by weight of polyphenylene ether to 99 to 1 part by weight of polystyrene.

Other ingredients, such as stabilizers, flame retardant agents, drip retardants ^' , antioxidants, colorinz agents, pigments, mold release agents, and the like, can also be included in the compositions for their conventionally employed purposes.

The compositions of this invention are prepared con¬ ventionally in any manner. Usually, however, the ingredients are formed into a preblend by tumbling in a mixer, the preblend is extruded at a temperature of from 450 to 600"?., the extrudate is cut into smaller pieces, and the pieces are injection molded at a temperature of from 425 to 550"F.

Description of the Preferred Embodiments. - The com-

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SUBSTITUTE SHEET OMH

positions of this invention are illustrated in the following examples, which are not intended to be limiting.

EXAMPLES 1-4

CoTTOosirions according to this invention are prepared by fumbling the ingredients, extruding at a temperature of 550"F. and injection molding at a temperature of 500 ^β F. , mold temperatur 190 ^β F.

The compositions after molding are evaluated for physical properties using standard ASTM procedures. The com¬ positions and physical properties are summarized in Table 1.

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SUBSTITUTE SHEET '

TABLE I. Compositions Comprising a Polyphenylene Ether Resin, a High Impact Rubber Modi¬ fied Polystyrene, a Mineral Filler and a PlastLclzer

Ingredients, parts by weight I 2 3 4 A*

(ft c Poly(2,6-dimethyl-

01 1,4-phenylene)ether 40 40 40 40 40 0)

^~ i High impact, rubber- _ modified polystyrene 60 60 60 60 60 c ^~ i

Plasticizer (triphenyl

H phosphate) 3 6 9 12 -- Pl 25 25 25 ω I Mineral filler (clay) ^c 25 25 x Polyethylene 1.5 1.5 1.5 1.5 1.5

Pl Trldecyl phosphite 0.5 0.5 0.5 0.5 0.5

Zinc aulflde 0.15 0.15 0.15 0.15 0.15

Zinc oxide 0.15 0.15 0.15 0.15 0.15

* comparison experiment a General Electrlc's PP0, having an Intrinsic viscosity of 0.46 deciliters per gram in chloroform at 30 ^* C. b Foster Grant's FG 834, a polystyrene containing about 9 percent by weight of polybutadiene c Freeport Kaolin, NCF

TABLE 1. (cont'd.)

Physical Properties I 2 3 4 A*

Tensile yield, pal xlO ^"3 9.1 8.3 7.5 7.2 9.0 c (ft Tensile elongation, 7. 38 48 66 62 42 in Motched Izod impact strength, ft. Ilia./In. 1.3 1.4 1.4 1.4 1.3

Gardner impact strength, In. lbs. 30 95 90 100 30 c

H Flexural modulus, psl xlO -3 582 557 511 478 535 Pl Flexural strength, psl xlO ^" 3.0 11.9 10.β 10.1 13.1

(ft a:

Pl l comparison experiment

O tni

It can be seen that the addition of an aromatic phosphate in amounts of 6 parts by weight or more results in a marked improvement in the Gardner impact strength, which is surprising.

EXAMPLES 5 and 6

Using the procedures described in Examples 1-4, additional compositions according to this invention are pre¬ pared, molded and evaluated for physical properties after molding. The compositions and physical properties are summarized in Table 2.

SUBSTITUTE SHEET

O FI ^'

TABLE 2. Compositions Comprising a Polyphenylene Ether Resin, an Impact Modifier, a Plasticizer and Iron Oxide

Ingredients, parts by weight 5

Poly(2,6-dlmethyl-

(ft l,4-phenylene)ether 78 78 c Impact Improver 5 5

CO

(ft Plasticizer (triphenyl ^~ i phosphate) 22 22 c Iron oxide (I) 43

H Iron oxide (II) ^f -- 43 Pl

Polyethylene 1.5 1. 5

(ft X Trldecyl phosphite 0.5 0. 5 l PI Zinc sul lde 0.15 0. 15

^~ i Zinc oxide 0.15 0.15

TABLE 2. (cont ' d . )

Physical Properties 5 6

Tensile yield, pal xlO ^-3 9.7 8.5

(ft _ ^• ] c Tensile strength, pal xlO B.6 8.3 in Tensile elongation, 7. 49 79 (ft

H Notched Izod Impact strength, ft.lbs./in. 1.7 2.7 c -I

Gardner impact strength,

H in.-lbs. 150. 250 l _] Flexural modulus, pel xlO 445 358

(ft

Flexural strength, pal xlO ^" 13.8 12.0

Pl

Other modifications and variations of the present invention are possible in view of the foregoing description. It is to be understood, therefore, that changes may be raade in the particular embodiments of the invention without departing from the principles or scope of the i vention defined in the appended claims and without sacrificing the chief benefits .

QMPI