Rubber modified weatherable styrenic blends with improved transparency and colorability are disclosed. A matrix phase of poly(alkyl alkylacrylate) and vinyl carboxylic acid ester-vinyl aromatic-vinyl cyanide terpolymer is combined with a rubbery graft phase of a poly(alkyl acrylate) rubber substrate grafted with a vinyl aromatic-vinyl cyanide superstrate copolymer to provide acrylate-styrene-acrylonitrile type (ASA) compositions.

1. Field of the Invention
The present invention relates to weatherable styrenics with improved translucency. More particularly, the invention relates to modified acrylate-styrene-acrylonitrile (ASA) plastics with improved translucency for better colorability.
2. Description of the Related Art
ASA polymers (also known as AAS), which are rubber and thermoplastic composites, have long been known and used in various outdoor applications which take advantage of the weatherability of such resins. ASA polymers are in general terpolymers of acrylate, styrene, and acrylonitrile having an excellent combination of impact and weatherability properties. These ASA resins typically contain a grafted crosslinked alkylacrylate rubber phase. Most ASA products consist of a two phase system of a grafted elastomeric terpolymer, acrylate-styrene-acrylonitrile, dispersed in a glassy continuous matrix of styrene-acrylonitrile (SAN) copolymer. The graft typically consists of a polyalkylacrylate rubber core and grafted SAN shell, small amounts of styrene and acrylonitrile being grafted onto the rubber particles to compatibilize the two phases.
In the ASA manufacturing process, three distinct polymerization reactions or stages are involved. First the elastomeric component, typically a polyalkyl acrylate rubber or polyalkyl alkylacrylate rubber, is produced. This phase can be carried out either in a water-based emulsion or in a solution polymerization process. In the second stage, the styrene and acrylonitrile are copolymerized optionally with other monomers and grafted onto the elastomeric phase to achieve the desired compatibility. This stage can be performed either in emulsion, bulk/mass or via suspension and/or the emulsion-suspension process route. In the third stage, styrene and acrylonitrile (and, optionally, other monomers) are copolymerized, either simultaneously with the second (grafting) stage or separately in an independent operation, to form the rigid matrix. Again, this step may involve one or more of the following processes: emulsion, bulk or suspension.
In addition, the ASA materials may be produced by other process techniques such as batch, semibatch and continuous polymerization for reasons of either manufacturing economics or product performance or both.
To alter specific properties of the resulting polymers, other acrylate, monovinylidene aromatic, and ethylenically unsaturated nitrile monomers may be incorporated, either in addition to or in place of the various acrylate-styrene-acrylonitrile components. The physical properties of ASA plastics vary somewhat with their method of manufacture but more so with their composition. Specific performance requirements and extensive material differentiation are achieved by manipulation of monomer composition, microstructure, morphology and/or additives.
However, due to a high level of opacity, weatherable ASA materials are difficult to color match in bright colors and may lack depth of color. In addition, coloring costs are usually high when matches are possible. There remains a need for improved ASA materials which maintain desirable properties which allow matching of bright colors at reduced pigment cost or production of intense colors with better depth of color.
There is a particular need for weatherable ASA plastics which allow matching of bright colors at reduced pigment cost or production of bright intense colors with better depth of color with reduced pigment usage while maintaining other desirable properties. Weatherable ASA materials with improved translucency that reduces opacity, resulting in better colorability can be prepared from SAN copolymer grafted alkyl acrylate rubber, preferably butyl acrylate rubber, with a matrix rigid phase prepared from polymethyl methacrylate (PMMA) and methyl methacrylate-styrene-acrylonitrile (MMASAN) terpolymer.
In one embodiment the present invention generally provides for an acrylate-styrene-acrylonitrile type (ASA) composition comprising:
a) a matrix phase comprising (i) a terpolymer of a vinyl carboxylic acid ester monomer, a vinyl aromatic monomer and a vinyl cyanide monomer and (ii) a polymethylmethacrylate (PMMA); and
b) a graft copolymer comprising (i) a substrate rubber and (ii) a superstrate copolymer, wherein the substrate rubber comprises a rubber derived from a vinyl carboxylic acid ester monomer and wherein the superstrate copolymer comprises a copolymer derived from both a vinyl aromatic monomer and a vinyl cyanide monomer,
wherein the matrix phase is present at a weight percent level of from about 75 to about 25 weight percent of the total weight of the composition; and
wherein the graft copolymer is present at a level of from about 25 to about 75 weight percent of the total weight of the composition, and the substrate rubber is present at a level of from about 5 to about 55 weight percent of the total weight of the composition.
In another embodiment the present invention generally provides for an acrylate-styrene-acrylonitrile type (ASA) composition comprising:
a) a continuous phase or matrix, frequently denoted a xe2x80x9crigid matrix phase,xe2x80x9d comprising a mixture of:
1) MMASAN, a terpolymer of methyl methacrylate and styrene acrylonitrile ranging in weight percent composition of the continuous rigid phase of from about 90 weight percent to about 10 weight percent; and
2) PMMA, a homopolymer of methylmethacrylate, polymethylmethacrylate, ranging in weight percent composition of the continuous phase of from about 10 weight percent to about 90 weight percent; and
b) a discontinuous phase, dispersed in the continuous phase, comprising:
1) a core graft rubber where the core is butyl acrylate rubber comprising from about 15 to about 90 weight percent of the total core graft disperse phase and
2) a graft or superstrate polymer of styrene acrylonitrile (SAN) comprising from about 85 to about 10 weight percent of the total core graft disperse phase;
wherein the continuous or matrix phase comprises from about 90 to about 10 weight percent of the total composition; and
wherein the dispersed or discontinuous phase comprises from about 10 to about 90 weight percent of the total composition.
Weatherable ASA polymers with improved translucency, better colorability and color matching, reduced pigment costs and other desirable physical properties are prepared from poly (alkyl acrylate) rubber based ASA graft phase in combination with a vinyl aromatic/vinyl cyanide/vinyl carboxylic acid ester matrix phase.
As used herein, the terms xe2x80x9cweatherablexe2x80x9d and xe2x80x9cweatherabilityxe2x80x9d refer to the ability or property of a material to effectively withstand the conditions of an outdoor environment over a long period of time (years) with substantially no degradation or decomposition, that is, resistance to UV radiation and to exposure to cyclic variations in temperature and humidity.
The ASA polymers of the present invention comprise a two phase system. The two phase system comprises an acrylate rubber substrate, preferably poly (butyl acrylate) rubber, with a superstrate (or graft) copolymer of styrene-acrylonitrile (SAN) attached to it. This phase is commonly referred to as the xe2x80x9crubber graft phasexe2x80x9d because the SAN is physically attached or grafted to the rubber through chemical reaction. A xe2x80x9crigid matrix phasexe2x80x9d or continuous phase of PMMA/MMASAN is utilized. The rubber graft phase (or dispersed phase) is dispersed throughout the matrix phase PMMA/MMASAN which forms the polymer continuum. The rubber interface is the surface forming the boundaries between the graft and matrix phases. The grafted SAN acts as a compatibilizer between the rubber and the matrix phase PMMA/MMASAN at this interface and prevents the separation of these two otherwise immiscible phases.
It has been found that there is a synergistic effect in reducing opacity of the blend when PMMA/MMASAN mixture is used as compared to using PMMA or MMASAN alone. Weatherable ASA blends with bright intense colors, reduced usage of color pigments and/or achievement of better depth of the color are possible utilizing existing inorganic pigments, organic pigments and dyes. In addition to improved translucency with better colorability, an improved weathering performance can also be expected for the mixture compared to MMASAN alone and improved physical properties can be expected for the mixture compared to PMMA alone.
The ASA type thermoplastic resins utilized by the present invention are graft copolymers of vinyl carboxylic acid ester monomers, vinyl aromatic monomers and vinyl cyanide monomers. Thus applicants define herein the phrase ASA type or acrylate-styrene-acrylonitrile type to include the group of polymers derived from vinyl carboxylic acid ester monomers, vinyl aromatic monomers and vinyl cyanide monomers as hereinafter defined. Vinyl carboxylic acid ester monomers (esters of alpha-, beta-unsaturated carboxylic acids) utilized in the present invention are herein defined by the following structural formula:
where J is selected from the group consisting of hydrogen, alkyl groups of from 1 to 8 carbon atoms, cycloalkyl, alkoxy and 1hydroxyalkyl and A is selected from the group consisting of alkyl groups of from 1 to 12 carbon atoms. Examples of vinyl carboxylic acid ester monomers include butyl acrylate, methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl methacrylate, propyl methacrylate, propyl acrylate, hexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, decyl methacrylate, methyl ethacrylate, butyl ethacrylate, cyclohexyl methacrylate, methoxyethyl acrylate, hydroxyethyl methacrylate and mixtures thereof. The vinyl aromatic monomers are herein defined by the following structural formula:
where each X is independently selected from the group consisting of hydrogen, alkyl groups of from 1 to 5 carbon atoms, cycloalkyl, aryl, alkaryl, aralkyl, alkoxy, aryloxy, hydroxy and halogen and where R is selected from the group consisting of hydrogen, alkyl groups of from 1 to 5 carbon atoms, bromine and chlorine. Examples of substituted vinyl aromatic monomers include styrene, 4-methyl-styrene, vinyl xylene, trimethyl-styrene, 3,5-diethyl-styrene, p-tert-butyl-styrene, 4-n-propyl-styrene, xcex1-methyl-styrene, xcex1-ethyl-styrene, xcex1-methyl-p-methyl-styrene, p-hydroxy-styrene, methoxy-styrenes, chloro-styrene, 2-methyl-4-chloro-styrene, bromo-styrene, xcex1-chloro-styrene, xcex1-bromo-styrene, dichloro-styrene, 2,6-dichloro-4-methyl-styrene, dibromo-styrene, tetrachloro-styrene and mixtures thereof. Vinyl cyanide monomers are herein defined by the following structural formula:
where R is selected from the group consisting of hydrogen, alkyl groups of from 1 to 5 carbon atoms, bromine and chlorine. Examples of vinyl cyanide monomers include acrylonitrile, methacrylonitrile, ethacrylonitrile, xcex1-chloroacrylonitrile and xcex1-bromoacrylonitrile.
It will be understood that by the use of xe2x80x9cmonomersxe2x80x9d are included all of the polymerizable species of monomers and copolymers typically utilized in polymerization reactions, including by way of example monomers, homopolymers of primarily a single monomer, copolymers of two or more monomers, terpolymers of three monomers and physical mixtures thereof.
Various monomers may be further utilized in addition to or in place of those listed above to further modify various properties of the compositions disclosed herein. In general, the components of the present invention may be compounded with a copolymerizable monomer or monomers within a range not damaging the objectives and advantages of this invention. For example, the rubber phase may in addition to or in place of butyl acrylate rubber be comprised of polybutadiene, styrene-butadiene or butadiene-acrylonitrile copolymers, polyisoprene, EPM (ethylene/propylene rubbers), EPDM rubbers (ethylene/propylene/non-conjugated diene rubbers) and other crosslinked acrylate and alkylacrylate rubbers based on C1-C12 acrylates and alkylacrylates, either alone or as a mixture of two or more kinds. Furthermore, the rubber may comprise either a block or random copolymer. In addition to or in place of the acrylate, styrene and acrylonitrile monomers used in the graft or matrix resins, monomers including vinyl carboxylic acids such as acrylic acid, methacrylic acid and itaconic acid, acrylamides such as acrylamide, methacrylamide and n-butyl acrylamide, alpha-, beta-unsaturated dicarboxylic anhydrides such as maleic anhydride and itaconic anhydride, imides of alpha-, beta-unsaturated dicarboxylic acids such as maleimide, N-methylmaleimide, N-ethylmaleimide, N-alkyl maleimide, N-aryl maleimide and the halo substituted N-alkyl N-aryl maleimides, imidized polymethyl methacrylates (polyglutarimides), unsaturated ketones such as vinyl methyl ketone and methyl isopropenyl ketone, alpha-olefins such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl stearate, vinyl and vinylidene halides such as the vinyl and vinylidene chlorides and bromides, vinyl-substituted condensed aromatic ring structures such as vinyl naphthalene and vinyl anthracene and pyridine monomers may be used, either alone or as a mixture of two or more kinds.
In one embodiment, the rubbers are cross-linked poly (alkyl acrylate) rubbers and poly (alkyl alkylacrylate) rubbers. In other embodiments, the rubbers are poly (butyl acrylate), poly (ethyl acrylate) and poly (2-ethylhexyl acrylate) rubbers. In yet another embodiment, the rubber is poly (butyl acrylate) rubber, particularly poly (n-butyl acrylate) rubber.
Various methods of preparation of suitable cross-linked poly (alkyl acrylate) rubbers are well known in the art, for example via aqueous emulsion or suspension processes. By way of illustration, one method of preparing a poly (alkyl acrylate) rubber suitable for use in the present invention is via continuous emulsion polymerization of a monoethylenically unsaturated vinyl carboxylic acid ester monomer, a polyethylenically unsaturated monomer, a surfactant and a polymerization initiator.
In one embodiment, the monoethylenically unsaturated vinyl carboxylic acid ester monomer utilized for preparation of the rubber graft phase is selected from (C1-C12) alkyl acrylate and (C1-C12) alkyl (C1-C8) alkylacrylate monomers and mixtures thereof. In another embodiment, it is selected from (C1-C12) alkyl acrylate monomers and mixtures thereof. As used herein, the terminology xe2x80x9cmonoethylenically unsaturatedxe2x80x9d means having a single site of ethylenic unsaturation per molecule and the terminology xe2x80x9calkyl acrylate monomersxe2x80x9d refers collectively to vinyl carboxylic acid ester acrylate monomers and alkylacrylate monomers and the terminology xe2x80x9c(Cx-Cy)xe2x80x9d, as applied to a particular unit, such as, for example, a chemical compound or a chemical substituent group, means having a carbon atom content of from x carbon atoms to y carbon atoms per such unit, for example, xe2x80x9c(C1-C12)alkylxe2x80x9d means a straight or branched alkyl substituent group having from 1 to 12 carbon atoms per group and includes, e.g., methyl, ethyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-propyl, isopropyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl and dodecyl.
As used herein, the terminology xe2x80x9cpolyethylenically unsaturatedxe2x80x9d means having two or more sites of ethylenic unsaturation per molecule. A polyethylenically unsaturated monomer is used in the alkyl, acrylate rubbers of the present invention to provide xe2x80x9ccrosslinkingxe2x80x9d of the poly (alkyl acrylate) rubber particles formed in the process and to provide xe2x80x9cgraftlinkingxe2x80x9d sites in the poly (alkyl acrylate) rubber for subsequent reaction with grafting monomers. In one embodiment, the polyethylenically unsaturated crosslinking monomers contain at least two ethylenically unsaturated sites per molecule that have a reactivity that is similar, under the polymerization conditions utilized, to that of the monoethylenically unsaturated alkyl acrylate monomer. In another embodiment, the graftlinking monomers include those monomers having at least one site of ethylenic unsaturation that have a reactivity that is similar, under the emulsion or other polymerization conditions used, to that of the alkyl acrylate monomer and at least one other site of ethylenic unsaturation having a reactivity that is substantially different, under the emulsion polymerization conditions used in the process of the present invention, from that of the monoethylenically unsaturated alkyl acrylate monomer, so that at least one unsaturated site per molecule of graftlinking monomer reacts during synthesis of the rubber latex and at least one other unsaturated site per molecule of graftlinking monomer remains unreacted following synthesis of the rubber latex and is thus remains available for subsequent reaction under different reaction conditions.
In yet another embodiment, the polyethylenically unsaturated monomers include, for example, butylene diacrylate, divinyl benzene, butene diol dimethacrylate, trimethylolpropane tri(meth)acrylate, allyl methacrylate, diallyl maleate, triallyl cyanurate and mixtures thereof. In a preferred embodiment, triallyl cyanurate is used as both a crosslinking monomer and a graftlinking monomer.
In various embodiments, the feed streams to the reactor vessel and the reaction mixture contain from about 0.01 to 4 pbw or from about 0.1 to 1.5 pbw, polyethylenically unsaturated monomer per 100 pbw monoethylenically unsaturated alkyl acrylate (vinyl carboxylic acid ester) monomer.
In various embodiments of the present invention, the monoethylenically unsaturated alkyl acrylate monomer utilized in the emulsion is selected to provide a poly(alkyl acrylate) rubber having a glass transition temperature (Tg) of less than or equal to 25xc2x0 C. or less than or equal to 0xc2x0 C. or less than or equal to xe2x88x9230xc2x0 C. As referred to herein, the Tg of a polymer is the Tg value of polymer as measured by differential scanning calorimetry (heating rate 20xc2x0 C./minute, with the Tg value being determined at the inflection point).
Minor amounts, such as, for example, up to about 25 pbw per 100 pbw of the total amount of monomers, of other unsaturated monomers that are copolymerizable with the alkyl acrylate monomer used in the present invention may optionally be included in the reaction mixture, provided that the limitation regarding the Tg of the rubber latex is satisfied. Suitable copolymerizable monomers include, for example, monoethylenically unsaturated carboxylic acids, hydroxy (C1-C12) alkyl methacrylate monomers, (C4-C12) cycloalkyl (meth)acrylate monomers, acrylamide monomers, maleimide monomers and vinyl esters. As used herein, the term xe2x80x9c(C4-C12) cycloalkylxe2x80x9d means a cyclic alkyl substituent group having from 4 to 12 carbon atoms per group and the term xe2x80x9cacrylamidexe2x80x9d refers collectively to acrylamides and methacrylamides. Also suitable are vinyl aromatic monomers such as, for example, styrene and substituted styrenes having one or more alkyl, alkoxy, hydroxy or halo substituent group attached to the aromatic ring.
The surfactant is for example one or more compounds according to formula Rxe2x80x94SO3M or Rxe2x80x94SO4M wherein R is alkyl, and M is a hydrogen radical or a cation. In a preferred embodiment, R is (C1-C30)alkyl, more preferably (C6-C30)alkyl, and M is a metal cation, an ammonium cation, an alkyl ammonium cation or an alkoxy ammonium cation. Suitable metal cations include, for example, sodium, potassium, lithium and magnesium cations. Suitable alkyl ammonium cations include, for example, diethyl ammonium and tetraethyl ammonium cations. Suitable alkoxy ammonium cations, include, for example, diethanol ammonium and tetraethanol ammonium cations.
Suitable surfactants include, for example, sodium lauryl sulfate, sodium decyl sulfate, sodium 2-ethylhexyl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, diethanol ammonium lauryl sulfate, tetraethanol ammonium lauryl sulfate, sodium eicosyl sulfonate and sodium paraffin sulfonate. In one embodiment, the surfactants are non-ionic surfactants consisting of addition products of ethylene oxide disclosed in U.S. Pat. No. 4,357,270 (1982) to Pippa et al. The surfactants consist of adducts of ethylene oxide with various organic compounds containing in the molecule reactive hydrogen atoms, such as alkylphenols having from 8 to 12 carbon atoms in the alkyl, aliphatic alcohols having from 12 to 18 carbon atoms, long chain fatty acids and alicyclic carboxylic acids of the type of abietic acid, tall oil, esters of long chain fatty acids, such as mono- and diglycerides, castor oil and esters of 1,4-sorbitan. The number of ethylene oxide molecules present in the molecule of the adduct varies, in general, from 10 to 100; but may also be greater.
As non-ionic surfactants there may also be used ethylene oxide/propylene oxide copolymers containing a percentage by weight of ethylene oxide comprising between 30 and 95%. Examples of non-ionic ethylene oxide addition products surfactants include the addition products of nonylphenol with 9, 20, 40 and 100 moles of ethylene oxide, the addition product of oleyl alcohol with 55 moles of ethylene oxide and the addition product of 1,4-sorbitan stearate with 20 moles of ethylene oxide, and particularly the adducts of nonylphenol with more than 20 moles of ethylene oxide.
The one or more initiators used in the preparation of the acrylate rubber are preferably selected from a conventional free radical initiators such as, for example, an organic peroxide compound, such as, for example, benzoyl peroxide, a persulfate compound, such as, e.g., potassium persulfate, an azonitrile compound such as, for example, 2,2xe2x80x2-azobis-2,3,3-trimethylbutyronitrile, or a redox initiator system, such as, for example, a combination of a peroxide or hydroperoxide, such as for example, hydrogen peroxide, cumene hydroperoxide or t-butyl hydroperoxide, an oxidizing agent, such as for example, ferrous sulfate, a chelating agent such as, for example, tetrasodium pyrophosphate, ethylene diamine tetraacetic acid or a salt of ethylene diamine tetraacetic acid, and a reducing agent, such as for example, sodium formaldehyde sulfoxylate or a reducing sugar.
In one embodiment, the redox initiator system comprises a combination of cumene hydroperoxide, ferrous sulfate, a chelating agent, preferably, the disodium salt of ethylene diamine tetraacetic acid and sodium formaldehyde sulfoxylate as the polymerization initiator. In a second embodiment, the redox initiator system contains from 0.05 to 0.5 pbw cumene hydroperoxide per 100 pbw of the vinyl carboxylic acid ester monoethylenically unsaturated alkyl methacrylate monomer, an amount of sodium formaldehyde sulfoxylate effective to provide a sodium formaldehyde sulfoxylate:cumene hydroperoxide molar ratio of about 0.9:1 to 1:1.1, from 0.1 to 10 pbw of the disodium salt of ethylene diamine tetraacetic acid per 100 pbw cumene hydroperoxide and from 0.1 to 10 pbw ferrous sulfate per 100 pbw cumene hydroperoxide.
In one embodiment, the poly(butyl acrylate) rubber latex particles of the present invention have a weight average particle size of 2700 angstroms, as measured by light transmission. The size of emulsion polymerized rubber particles may optionally be varied according to known process techniques. The poly (butyl acrylate) in one embodiment has a weight average molecular weight of from about 100,000 to about 130,000.
Vinyl aromatic and vinyl cyanide monomers or copolymers are grafted to poly(alkyl acrylate) rubber particles made via the example process above or via one of the many other processes known to the art to thereby form a graft phase copolymer having a poly(alkyl acrylate) rubber chemically grafted to the vinyl aromatic-vinyl cyanide. Again, the many different processes known to the art may be utilized to form the graft phase copolymer, for example bulk, emulsion, emulsion-suspension or emulsion-mass polymerization. In one embodiment, a poly(butyl acrylate) rubber is grafted with styrene-acrylonitrile (SAN) to form the ASA rubber graft phase.
In one embodiment, the rigid matrix phase comprises a terpolymer derived from monomers selected from the group consisting of vinyl carboxylic acid ester monomers, vinyl aromatic monomers and unsaturated nitrile monomers. In another embodiment, the mixture comprises polymethyl methacrylate (PMMA) homopolymer and methyl methacrylate-styrene-acrylonitrile (MMASAN) terpolymer.
In one embodiment, the vinyl carboxylic acid ester for use as one component of the matrix phase of the present invention comprises methyl methylacrylate in the form of polymethyl methacrylate (PMMA). Use of commercially available, easily utilized PMMA in conjunction with MMASAN allows greater flexibility in adjusting the percentage composition of methyl methacrylate in the matrix phase as well as allowing use of PMMA with varying molecular weights, modifying monomers, etc.
As is well known in the art, PMMA may be produced by the polymerization of methyl methacrylate monomer to form a homopolymer. PMMA homopolymer exists in its pure form only theoretically and is generally available commercially as a mixture of the homopolymer and with one or more copolymers of methyl methacrylate with C1-C4 alkyl acrylates, such as ethyl acrylate. Such commercially available PMMA copolymers contain methyl methacrylate and from about 1 percent to about 30 percent by weight of one or more C1-C4 alkyl acrylates. Such PMMA homopolymers are suitable for use in the present invention as the vinyl carboxylic acid ester monomer component. Copolymers of PMMA with minor amounts of one or more copolymerizable monomers are also intended to be encompassed, e.g., the copolymer of methyl methacrylate with styrene and/or acrylonitrile. The molecular weight of the polymethylmethacrylate polymer can range from 50,000 to 450,000, preferably from about 100,000 to about 250,000 as a weight average molecular weight.
In various embodiments the ASA polymers comprises about 10 percent to about 40 percent or about 15 percent to about 30 percent or about 15 percent to about 25 percent of poly (butyl acrylate) rubber.
In one embodiment, the rubber graft phase comprises from about 20% poly(butyl acrylate) to about 70% poly(butyl acrylate). In another embodiment, the rubber graft phase comprises about 45% poly (butyl acrylate) rubber and 55% SAN, with the SAN portion of the graft phase made from styrene and acrylonitrile in amounts in a range of 65% styrene and 35% acrylonitrile to 75% styrene and 25% acrylonitrile. In yet another embodiment, the SAN portion of the graft phase comprises about 70-75% styrene and about 25-30% acrylonitrile.
It will be appreciated that, in general, the particle size of the rubber in the emulsion during the graft polymerization reactions has an effect upon the optimum grafting level for the graft copolymer. A given weight percentage of smaller size rubber particles will provide considerably greater surface area for grafting than the equivalent weight of a larger size rubber particle. Accordingly, the density of grafting will be varied depending upon the size of the rubber particle. Generally, the smaller rubber particles will tolerate a higher superstrate/substrate ratio than larger size particles to give generally comparable results.
In one embodiment, the MMASAN comprises 80% MMA, 15% styrene and 5% acrylonitrile. In another embodiment, the MMASAN comprises about 60% MMA, 30% styrene and 10% acrylonitrile. In a third embodiment, the MMASAN comprises about 45% methyl methacrylate, 40% styrene and 150/a acrylonitrile. In one embodiment, the PMMA/MMASAN ratio in the matrix phase copolymer ranges from about 20/80 to about 80/20; and in another embodiment, from 25/75 to about 75/25 including 50/50.
The ASA polymer in one embodiment comprises of ratios of graft phase to matrix phase of 15/85 to 75/25. and in another embodiment, about 45% graft phase and 55% matrix phase. The graft copolymer phase may be coagulated, blended and collided with the matrix phase homopolymers, copolymers and/or terpolymers by the various blending processes which are well known in the art to form the ASA polymer blend.
Pigments suitable for use in the present invention include, by way of example, furnace black, inorganic pigments including aluminates such as cobalt aluminate blues, ceramic pigments such as the manganese violets, chromates such as chrome yellow and orange (lead chromates, optionally with lead sulfate), zinc yellow (zinc chromate), molybdate orange (lead chromate and sulfide and lead molybdate), chrome greens (greenish chrome yellow pigments with iron blues), iron blues (based on ferric ammonium ferrocyanide), oxides such as iron oxide (from yellow to black, particularly the browns or buffs and reds), chromium oxide greens (anhydrous), sulfides or cadmiums such as cadmium sulfide (orange or yellow with zinc sulfide), cadmium sulfoselenide (reds and oranges), cadmium mercury (mercadmiums), cadmium-lithium compounds and lithopones (barium sulfate extended versions of cadmium sulfide and cadmium sulfoselenide), titanates such as nickel titanate (a yellow colorant), titanium dioxides (whites including the rutiles and the anatase pigments), zinc sulfide white, ultramarine blues (aluminosilicate complex containing sulfur) and cobalt blue (a mixture of ultramarine blue and zinc oxides).
Suitable organic dyes and pigments include, for example, quinophthalone, isodolines, perylenes for yellows, diketo-pyrrolo-pyrrole, a cadmium-type red, high temperature versions of organic pigments such as azoic reds and yellows including azo compounds and acid azo pigments, quinacridones, phthalocyanine blues or greens, anthraquinone dyes, scarlet 3b Lake, chromophthalocyanine pyrroles, halogenated phthalocyanines, quinolines, heterocyclic dyes, perinone dyes, anthracenedione dyes, thioxanthene dyes, pyrazolone dyes, polymethine pigments, blends of organic and inorganic mixed metal oxide pigments and others.
Suitable special effect colorants include metallics such as aluminum flake and gold bronzes, pearlescents, granites, fluorescents, phosphorescent pigments such as zinc sulfides or alkaline earth aluminate oxides, luminescents, thermochromics and photochromics. Such pigments may be utilized alone or as a mixture of two or more kinds, as dry colorants, liquid colorants, color concentrates, encapsulated pigments, pigment dispersions, universal concentrates, freeze-dried concentrates and multifunctional concentrates.
There may optionally be added to the resin phases, during or after formation, such additives as chain transfer agents, heat and ultraviolet light stabilizers, UV absorbers, antioxidants, lubricants, flow aids, mold or metal release agents, antistatic agents, flame and fire retardants, plasticizers, drip suppressants, mineral additives and fillers, reinforcing agents, and the like.
The present ASA compositions can be molded, extruded and/or otherwise formed into weatherable, impact resistant articles. For example, the present compositions can be used to produce articles such as window coverings, house sidings, exterior automotive parts and other articles which are resistant to the effects of weather on a long term basis and, therefore, can be employed out-of-doors. Such finished products can include only the compositions of the present invention alone or they can be composites of the present compositions with other materials, such as wood, glass, additional polymeric materials, other fillers and the like.
The following examples are presented as illustrations of the preparation and utility of the present compositions. The examples are not intended in any way to limit the spirit and scope of the invention.

Weatherable styrenic blends with improved translucency


A bandage 1 for the ankle joint, with a lower-leg part 20 and with a foot part 10 with two straps 11, 12, the lower-leg part 20 having at least one strap 21, 22, the foot part 10 having a first strap 11 on the medial side and a second strap 12 on the lateral side, the lower-leg part 20 and the foot part 10 being connected to one another in such a way that, when the bandage 1 is applied to the foot, the heel area is left open, and, with the bandage 1 applied, the lower-leg part 20 wraps round the posterior face of the lower leg in the distal lower-leg area and can be closed, particularly on the anterior face, and the foot part 10 lies under the sole and wraps round the foot with the medial strap 11 and the lateral strap 12, said straps 11, 12 starting from the plantar area, overlapping across the back of the foot and extending medially and laterally to the distal area of the lower leg.

The invention describes a bandage for injuries to the ankle joint, for example distortions, mild sprains, extension injuries in the fibular area and the lateral ligament structure, and incipient degenerative changes of the upper and/or lower parts of the ankle joint.
Depending on their design and on the indications for which they are intended, orthopedic bandages exert a fixing, guiding, bracing and/or supporting action on the extremities of the human body.
These medical bandages must have a shape which corresponds to the anatomical circumstances in order to be able to act externally on the human body with a form fit and a force fit.
Medical bandages of this kind are produced by cutting out blanks from planar material, for example neoprene, knitted fabrics or woven fabrics. The anatomically appropriate shape is obtained via the shape of the blanks or darts, for example with gussets, and subsequent joining together of the blanks, as is also customary in articles of clothing.
This joining together can be done by sewing, gluing or other conventional methods. The great disadvantage of these bandages is that the exact anatomical fit can be achieved only with difficulty and there are a large number of connection points, for example seams. These connection points change the properties of the material used, and there is the danger of pressure points on the skin.
Ankle joint ortheses or bandages are used preferably for the early functional treatment of recent fibular ligament ruptures and of mild and moderately severe tarsal distortions, and are also used in cases of chronic instability.
DE-A-38 40 714 discloses an ankle joint orthesis with a U-shaped support stirrup, the branches of which run together to form a bridge under the foot, reach upwards across the malleoli and are held together in their end region by a securing tape. The outer branch is in this case guided upward laterally in front of its malleolus, and the inner branch opposite the outer branch is guided upward in front of the Achilles tendon. Both branches, in the direction toward the bridge, are guided to a position in front of the heel, and, in the direction toward their ends, they extend upward in such a way that they ascend laterally along the lower-leg ridges and approximately parallel to these, and a holding tape is fitted in the lower area of the branches, which holding tape extends from the one branch obliquely upward across the instep to the other branch, and can be fastened thereon, engages above the malleoli about the Achilles tendon and, overlapping on the instep, ends on the other branch in a holding part. An ankle joint orthesis designed in this way is intended to prevent twisting, primarily in the lateral anterior direction, that is to say in the direction of a talipes equinus position. Since the U-shaped support stirrup of this ankle joint orthesis has its outer branch guided upward laterally in front of the malleolus and has its inner branch guided upward in front of the Achilles tendon, and is held together by a bridge running under the foot, the medial margin of the metatarsus is not gripped, with the result that the use of this ankle joint orthesis is limited.
DE-A-39 09 922 describes a foot fixation splint. This foot fixation splint is used in particular for the postoperative treatment of an injured ankle joint, with a foot part which surrounds the foot and to which there is joined a holding part extending upward into the calf area and provided with closure straps. The holding part is in this case divided into two side parts which are joined to the foot part and are of cup-shaped design. The area of each side part covering the malleolus is provided with a window-type recess. The area of the Achilles tendon on the foot part and on the holding part is in this case left open. The adjustable and fixable tape-like closure straps are made of an inextensible material, and one closure strap is arranged on the foot part in such a way that it engages over the back of the foot and so fixes the first radius of the metatarsus against supinatory elevation. A foot fixation splint of this kind is intended, on the one hand, to ensure a satisfactory immobilization of the foot that is to be treated, and, on the other hand, to avoid the disadvantages of a plaster cast, since after injuries and operations involving the external ligament apparatus the foot is often put in plaster in order to immobilize it, and postoperative treatment of operation wounds is not possible on account of a great many serious disadvantages. In the case of this foot fixation splint, the starting point is a U-shaped joint cuff with a full-surface sole part which covers the middle and front portions of the foot as far as the ball of the small toe, but which does not provide sufficient suppleness in the metatarsal area.
DE-C-43 18 588 likewise discloses an ankle joint orthesis consisting of a U-shaped joint cuff which is made of thermoplastic material and is composed of an outer malleolar splint and an inner malleolar splint. These malleolar splints are connected via a bridge running underneath the heel. The malleolar splints additionally have anatomically correct depressions for adaptation to the malleolar contours and for a correct anatomical fit. A further element of the orthesis is its metatarsal part, which is likewise made of thermoplastic material. This part of the orthesis runs obliquely under the sole of the foot, proximal to the capitula of metatarsals I-V, and is formed into a loop shape medially and laterally. The loops thus formed enclose the outer and inner margins of the foot. They guide the metatarsus on the one hand, and on the other hand serve for securing cross and transverse belts. The metatarsal part is in this case connected on the sole side by a bridge which is again made of thermoplastic material but is highly flexible. This bridge has the function of an articulation and acts analogously to an integral hinge. The pivot axis of this articulation formed in the highly flexible bridge runs from dorsomedial to anterolateral and forms with the long axis of the foot an angle of approximately 10xc2x0, in accordance with the anatomy of the lower part of the ankle joint.
DE 42 91 109 C2 discloses a support device for an ankle joint with a closable main support body, which has a lower-leg part and a foot part, and with an inner and/or outer support part in each case fitted on a side part of the main support body, the lower-leg part and the foot part being perpendicular to each other. The support parts are arranged on the main support body in such a way that they can be removed from it. Both the lower-leg part and the foot part have velcro-type fasteners which can be closed in order to apply the support device.
At their end toward the sole of the foot, the support parts also have the possibility of being connected via a connecting tape which runs under the sole. Finally, the foot part has at least one stretchable tape which is secured at one end on the outside of the sole area and can be guided away from the sole area via the back of the foot in order to be wound in a spiral formation around the lower-leg area.
It is an object of the invention to design a bandage which has a high degree of functionality with proprioceptive action, but which at the same time is easy and uncomplicated for the patient to apply and which, by means of dispensing with rigid elements, offers a high degree of dynamics. Moreover, the bandage should be inexpensive to produce.
This object is achieved by the bandage defined in accordance with the main claim. The subclaims relate to advantageous developments of the bandage.
Accordingly, the invention relates to a bandage for the ankle joint with a lower-leg part and with a foot part with two straps.
The lower-leg part has at least one strap, and the foot part has a first strap on the medial side and a second strap on the lateral side.
According to the invention, the lower-leg part and the foot part are connected to one another, in particular by sewing, in such a way that, when the bandage is applied to the foot, the heel area of the foot is left open.
With the bandage applied, the lower-leg part wraps round the posterior face of the lower leg in the distal lower-leg area and can be closed, particularly on the anterior face. The foot part lies under the sole and wraps round the foot with the medial and lateral straps, said straps, starting from the plantar area, overlapping across the back of the foot and extending medially and laterally to the distal area of the lower leg.
In a first preferred embodiment of the bandage, a connection part is connected, once again preferably sewn, to the lower-leg part and to the foot part, and, with the bandage applied, the connection part wraps round the anterior face of the lower leg in the distal lower-leg area and the dorsal face of the foot.
The connection part gives the bandage a tubular configuration, with the result that the bandage can be securely applied and positioned in the anterior area of the lower leg and in the dorsal area of the foot and treatment reliability is thereby enhanced.
The lower-leg part also preferably has a medial strap and a lateral strap which wrap round the posterior face of the lower leg in a circle and are closed on the anterior face.
In a further preferred embodiment, the lower-leg part and the foot part of the bandage are made of a material which is laminated at least on both sides and which has a VELCRO(copyright)-like velour on the outside and a skin-compatible textile material on the inside.
Moreover, spacer fabrics with corresponding laminations can be used or, in the case of technical machine finishing, also without laminations.
Such spacer fabrics are disclosed in EP 0 071 212 B1. Spacer fabrics are mat-like laminated articles with a top layer of nonwoven fiber or filament, a bottom layer, and, between these layers, individual or clustered holding fibers which, distributed across the surface of the laminated article, are needled through the particle layer and join the top layer and the bottom layer together. In an additional feature according to EP 0 071 212 B1, but not an essential one, particles of inert stone, for example sand, gravel or the like, are provided in the holding fibers.
The holding fibers needled through the particle layer maintain the top layer and the bottom layer at a distance from each other and they are connected to the top layer and the bottom layer.
Woven or knitted spacer materials are described inter alia in two articles, namely:
an article from the specialist journal xe2x80x9ckettenwirk-praxis 3/93xe2x80x9d, 1993, pages 59 to 63 xe2x80x9cRaschelgewirkte Abstandsgewirkexe2x80x9d [Raschel-knit spacers] and
an article from the specialist journal xe2x80x9ckettenwirk-praxis 1/94xe2x80x9d, 1994, pages 73 to 76 xe2x80x9cRaschelgewirkte Abstandsgewirkexe2x80x9d [Raschel-knit spacers]
and reference is hereby made to their content, and their content is part of this disclosure and invention.
Other, preferred materials are neoprene foam, polyurethane foam or polyester foam, and these are preferably perforated for better aeration.
In a further preferred embodiment of the bandage, the material has an elasticity of 30 to 150% in the X axis and of 5 to 70% in the Y axis, where the X axis runs in a circle round the lower leg and foot respectively in the applied state of the bandage, and the Y axis, again in the applied state of the bandage, runs vertically in the lower-leg part, i.e. longitudinally, and follows the longitudinal axis of the foot in the foot part.
In a further preferred embodiment of the bandage, the material for the connection part has an elasticity of 50 to 200% in the X axis and of 0 to 50% in the Y axis, where the X axis runs in a circle or horizontally round the lower leg and foot respectively in the applied state of the bandage, and the Y axis, again in the applied state of the bandage, runs vertically in the lower-leg part, i.e. longitudinally, and follows the longitudinal axis of the foot in the foot part.
Finally, an excellent configuration of the bandage is obtained if the lower-leg part or the straps on the lower-leg part and/or the straps of the foot part have VELCRO(copyright) hook and loop fasteners or press studs.
The circular arrangement in the distal area of the lower leg leads to an individually adjustable compression effect and follows the course of the anterior and posterior tibiofibular ligaments, the fibrous bands holding the tibia and fibula together and thereby supporting them.
The arrangement round the foot, formed by a medial strap and a lateral strap each starting from the plantar area and overlapping on the back of the foot and extending to the distal area of the lower leg, has a stabilizing effect on the upper and lower parts of the ankle, as active supination and pronation of the foot is limited and thus inversion of the foot is reduced. This has an advantageous effect on the lateral fibulocalcaneal ligament structure since eversion tends to damage this structure. As the straps of the arrangement round the foot are individually adjustable, it is possible to set the strength of support to meet the particular indication. The arrangement round the foot follows the anatomy of the so-called stirrup which is formed by the tendons of the anterior lower-leg muscle and the long peroneal muscle.
The bandage places hardly any restriction on the physiological gait pattern. The opening left in the heel area means that the risk of pressure points in the heel contact area is avoided and the sensation of contact with the ground is maintained.
The invention is explained in more detail with reference to five diagrammatic drawings of an illustrative embodiment, specifically the configuration for the right foot, without this implying any unnecessary limitation on the invention. The embodiment of the bandage for the left foot is the mirror image of the former.


Precooked and partially-dehulled masa flour for tortilla and the like is produced by pressure pre-cooking in a continuous process with saturated-steam. The precooking effects corn hull hydrolysis and partial cooking with a lime solution, reduced kernel washing and solid loss in wastewater. Next, moisture content is stabilized, and the corn is ground and dried in a super-heated stream of air to produce a partial cooking, cooling and further drying of the dried-ground particles. Separating and recovering yields the fine grind or masa flour from the coarse grind which is segregated to isolate a hull fraction as corn hull waste. Reground coarse grind is sieved to produce further yield of the instant masa flour. The flour is well suited for use in making tortilla and other corn-based snack foods.

1. Field of the Invention
The present invention relates to an accelerated thermal process by pressure cooking for the production of nixtamalized corn flour and, more particularly, it relates to a process involving continuous precooking of the corn under pressure and moist conditions with the use of a lime solution. The process is advantageously applied to the production of instant masa flour for the preparation of tortilla, snack foods and the like.
2. Description of Related Art
Nixtamalized corn flour (NCF) is conventionally produced by alkaline cooking of food-grade corn under atmospheric pressure, steeping and washing, grinding the partially cooked corn (nixtamal) and drying to give corn masa flour. This flour is sieved and blended for different food product applications and it is usually supplemented with food-grade additives before packaging for commercial table tortilla and snack production. Montemayor and Rubio (Sustain, 1997) described both batch and continuous processes for cooking corn to produce instant masa flour. In the modern continuous process, the lime used is from 0.6 to 1% by weight (based on corn) and mixed with equal parts of corn and potable water. The corn suspension is cooked by atmospheric steam injection (Bressani, 1990) and although the pericarp is partially removed during cooking and washing, there is still some fiber left from the corn (with an estimated 7 to 9% dry solid loss).
The traditional method of cooking maize with lime (1-2% by weight) at the rural level is time consuming (around 14 to 15 hours) and requires hard labor. From 70% to 80% of the time is taken by the cooking and steeping-washing operations (with a 1:3 corn to water ratio); that time can be decreased to 8-12 hours or less at the urban or cottage level (with a 11 to 13% dry matter loss; Bressani, 1990).
At the industrial or commercial level, the xe2x80x9cgrinding and dehydrationxe2x80x9d steps are major cost factors. In any case, the availability of an instant flour has many advantages such as convenience for the customer, less labor, lower water and energy use, a safe and stable product (3 to 4 months under normal conditions), and the possibility to use the corn flour as a carrier of a macronutrients (defatted soybean flour or wheat and amaranth flour) and micronutrients (amino acids, vitamins and minerals).
Corn and tortilla chips are the second most popular salted snack food in the USA, after potato chips. However, the new or expanding plants along the US-Mexico border, including the new sewage treatment plants in northern Mexico, have to comply with the environmental regulations imposed by the NAFTA agreement. Any method which may decrease both time and cost, and still yield an acceptable nixtamalized corn dough or masa flour product per kilogram or raw corn, would be advantageous to the final customer. The mature dent corn kernel (Watson, 1987) has four separable components, on a dry weight basis: tip cap (0.8-1.1%), pericarp or hull (5.1-5.7%),endosperm (81.1-83.5%) and germ (10.2-11.9%).
In this connection, reference is made to the following U.S. Pat. Nos: 4,513,018; 4,594,260 and 5,532,013. These prior art methods for the industrial production of masa flour involve accelerated cooking with reduced amounts of water along with short processing times as well as low energy requirements for a high yield of the end product; however an industrial process capable of making such a masa flour having a low-cost wastewater treatment was still unavailable in the market at the time of the present invention.
Having in mind the disadvantages of the prior art methods, several studies were conducted to improve the efficiency of the water consumption during the alkaline-cooking and steeping-washing operations. For example, Anderson, in U.S. Pat. No. 3,083,103, describes a method for preparing a corn masa dough suitable for deep-fat frying including the steps of cooking corn in calcium hydroxide under high pressure, steeping the processed kernel for at least 30 to 120 minutes, and metal grinding the steeped kernel thereby to form said dough. Cooking comprises heating the kernel in a supersaturated solution of aqueous lime (1.5% by weight of corn) at a pressure ranging from 5 to 25 psig for 5 to 40 minutes. The corn chip thus obtained has a new, unique limed flavor and a highly desirable short texture.
Rubio in U.S. Pat. No. 4,250,802, discloses another improved method and apparatus for processing corn into masa flour and dough for tortilla products. His invention includes a dry-preheating of corn (at 135xc2x0 to 150xc2x0 C. for 12 to 18 minutes), quenching the cracked corn in lime-water for 5-15 minutes, and to stabilize the moisture content for grinding, drying, separating the flour into particle size categories, mixing the flour into dough and completing the cooking of the dough with a hot-lime solution under controlled temperature, and forming the cooked and extruded dough into the desired end product such as chip, taco shell, tortilla or the like.
Although the above described prior art methods can be useful in producing an increased yield of nixtamalized corn dough with a low-cost drying and dry solid losses as well, a continuous process was still unavailable for the expanding masa flour market for the tortilla and snack industry.
Accordingly, the present invention provides a method for continuous production of nixtamalized corn flour using pressure cooking, which generates not only a minimum amount of wastewater and solid loss, but also a high yield of the product.
Another object of the invention is to provide an instant masa flour for tortilla and derivatives thereof wherein such flour is uniform and homogenous in its physicochemical and rheological properties.
The above and other objects and advantages of the invention are achieve through a continuous process and apparatus applied to the production of partially-dehulled masa flour or instant masa flour, embodiments of which include pressure precooking with a lime solution so as to effect corn hull hydrolysis and partial cooking, reduced washing of precooked kernel and reduced corn loss, stabilizing the moisture content to a desired optimum level for grinding, grinding and drying the preconditioned kernel to produce a uniform partial cooking, cooling and drying the dry-ground particle, separating and recovering the fine grind so produced from the coarse grind while the latter is further aspirated to remove a hull fraction as corn waste, and regrinding the isolated coarse grind and further sieving it to obtain an instant masa flour for tortilla and snack.

Method for the production of pressure precooked and dehulled corn flour for tortilla


The invention relates to a cleaning agent, particularly for cleaning sewers, for fat and/or protein-containing sewage from the home or having a municipal or industrial origin, with a content of urea, a urea derivative, a urea salt and/or a urea derivative salt, the cleaning agent containing approximately 50 to 90 wt. % urea, urea derivative, urea salt and/or urea derivative salt, based on dry substance, and an alkaline-acting agent, protease and fat-degrading microorganisms.

The invention relates to a cleaning agent, particularly or cleaning sewers, for fat containing and/or protein-containing sewage from the home or having a municipal or industrial origin having a content of urea, a urea derivative, a urea salt and/or a urea derivative salt.
A process of the aforementioned type is disclosed in EP-B-236 989, which prescribes the use of supplines, e.g. in the form of nitrogen-containing compounds. This known proposal is based on the finding that microorganisms are frequently so specialized that they require supplines for life. Supplines are essential substances belonging to the elementary constituents of the cell and which cannot be synthesized by individual organisms. They are e.g. amino acids, purines, pyrimidines, organic acids, carbohydrates, together with vitamins, particularly phenyl alanine, arginine, aspartic, oxalic, malic, malonic and propionic acids. With regards to their function and concentration, supplines differ clearly from nutrients. They correspond to vitamins in the animal and human diet. As nutrients, which fundamentally differ from supplines, the following compounds can be given: ammonium, nitrate and phosphate ions, glucose, polysaccharide, proteins and carbohydrates. For cleaning sewers for fat-containing sewage from the home or industrial enterprises the supply of supplines for fat-degrading or emulsifying bacteria prevents the formation of a plug in the sewer or if a plug of this type has already formed, easily brings about the dissolving thereof. Thus, according to the known proposal there is a biological decomposition of the fat through the bacteria present in the sewage. Suppline combinations for promoting fat-degrading or emulsifying bacteria are applied to the plug in the sewer either alone or combined with a detergent. The suppline combination permits a rapid growth of the desired bacteria, which leads to the dissolving of the disturbing fat plug in the sewer. The fat-degrading or emulsifying bacteria are constituted by a wide range of bacteria, which are normally present in the sewage. To promote the penetration of supplines into the fat plug and in order to assist the microbial dissolving of the fat, it is possible to add a detergent. The same purpose is served alone or in combination with the detergent, the addition of a CO2-developing powder, e.g. effervescing powder, which comprises approximately 50 wt. % sodium bicarbonate and approximately 50 wt. % tartaric acid.
The above proposal has proved very valuable in practice, but requires improvement. Another prior art process can be gathered from DE 44 17 809 A1. The latter describes a process for sanitary cleaning using a sanitary cleaner in liquid or solid form, which has a minimum content of germ-inhibiting, organic substances, together with conventional lime-dissolving, water-soluble acids, germ-promoting, organic substances and further additives and it contains e.g. urea as the germ-promoting, organic substance. This application discloses a two-stage action system, according to which in a first phase the germ-inhibiting substances and in a second phase the germ-promoting substances bring about the cleaning of the sewage.
EP 184 416 A2 discloses a cleaning block for toilets, which is dissolved in the water tank and has a composition of 5 to 85 wt. % of one or more anionic surfactants, 2 to 50 wt. % of one or more solubility control agents and 0.5 to 50 wt. % of at least one water-soluble, polyvalent metal salt, such as e.g. crystal water-containing magnesium sulphate.
PCT/EP 00/04135 offers a significant improvement compared with the above-described processes or cleaning agents. The teaching described therein seeks to improve the action on the sewer-blocking plug and parts thereof in such a way that there can be both an easier and faster physical and also biochemical dissolving of plugs or parts thereof in the sewer and sewage.
This prior art also provides a proposal in this direction. It consists of a process for cleaning sewers for fat-containing sewage from the home or industrial enterprises, in which to the fat-degrading and/or fat-emulsifying bacteria contained in the sewage are added nitrogen-containing compounds and which is characterized in that 1. to a liquid effluent cleaner are additionally added urea, a urea derivative, a urea salt and/or a urea derivative salt and 2. to a solid effluent cleaner are additionally added urea, a urea derivative, a urea salt and/or a urea derivative salt and/or anhydrous magnesium sulphate, growth factors in the form of supplines being largely excluded, and in 1. and 2. the quantity of germ-inhibiting, organic substance is below 0.5 g/kg, preferably below approximately 0.3 g/kg, particularly below approximately 0.1 g/kg sewer effluent cleaner. Preferably urea is used, particularly in a quantity of 0.1 to 20 wt. %, based on the solid content. Use can advantageously also be made of urea phosphate, particularly in a quantity of 0.2 to 40 wt. %, based on the solid content. It is generally stated that fat, protein and carbohydrate-degrading enzymes and/or microorganisms can be used.
However, it is a particular characteristic of this proposal that not only are growth factors in the form of supplines largely excluded, but that in a solid sewer cleaner the quantity of germ-inhibiting, organic substances must be below 0.5 g/kg, particularly below 0.3 g/kg and more especially below 0.1 g/kg effluent cleaner. These are in particular acid, organic substances or their salts or suitable derivatives and essential oils. These more particularly include aliphatic carboxylic acids, lower carboxylic acids with 1 to 7 carbon atoms, such as more particularly formic, acetic, propionic, caproic, malonic and oxalic acids, as well as various fatty acids with 6 to 12 carbon atoms, e.g. sorbic acid or undecenoic acid, provided that they are usable in the form of suitable, water-soluble salts. Suitable derivatives of the aforementioned carboxylic acids are hydroxy acids, such as glycolic, tartaric and citric acids, as well as oxo acids, such as acetoacetic and pyruvic acids. Particularly suitable are also adequately water-soluble, aromatic carboxylic acids, such as in particular benzoic, salicylic and also other phenocarboxylic acids. Thus, the proposal of PCT/EP 00/04135 aims to exclude such germ-inhibiting, organic substances. This does not apply to the subsequently described cleaning agent according to the invention. It has been found that the last-described, technical proposal for cleaning sewers requires improvement and in particular an improved plug dissolving capacity must be sought.
Therefore the object of the invention is a cleaning agent, particularly for cleaning sewers, for fat and/or protein-containing sewage from the home or having a municipal or industrial origin and having a content of urea, a urea derivative, a urea salt and/or a urea derivative salt, which is characterized in that the cleaning agent contains approximately 50 to 90 wt. % urea, urea derivative, urea salt and/or urea derivative salt, based on dry substance, and an alkaline-acting agent, protease and fat-degrading microorganisms.
Thus, in complete contradiction to the procedure according to the prior art, the agent according to the invention uses an unusually high proportion of urea, urea derivative, urea salt and/or urea derivative salt, based on dry substance, namely approximately 50 to 90, preferably approximately 60 to 80 and in particular approximately 65 to 75 wt. %. The urea is not only germ-promoting during the targeted use of the cleaning agent according to the invention, but also acts in solubility-increasing manner for the inventively used proteases and also acts as a nitrogen source for the fat-degrading bacteria. It also has a dissolving function on proteins which may have to be removed. The germ-promoting, organic substance in the form of urea or urea derivative can fundamentally be an open-chain or cyclic compound of formula (I) R1R2Nxe2x80x94COxe2x80x94NR3R4, in which R1 to R4, in each case independently of one another, can be present in open-chain or cyclized form and can have the following meanings: hydrogen, a lower alkyl group with 1 to 4 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, an aryl group in the form of a phenyl or naphthyl residue, an aralkyl group with 7 to 18 carbon atoms, or an O, S or N-containing heterocyclic group with 2 to 5 carbon atoms, the compound of formula (I) being wholly or partly present in the form of a salt.
Thus, the following urea derivatives are covered by the above formula (I):
R1R2Nxe2x80x94COxe2x80x94N Nxe2x80x94COxe2x80x94N
and
R1Nxe2x80x94COxe2x80x94NR2
In formula (I) the groups R1, R2, R3 and R4 are preferably hydrogen, because the corresponding starting compounds are commercially available or can be easily prepared. Suitable within the scope of the present invention are in particular the substituents, which are given in the above definition of the invention. As a lower alkyl group with 1 to 4 carbon atoms can in particular be used the methyl, ethyl, n-propyl, i-propyl and the different isomers of the butyl group. The cycloalkyl group with 3 to 6 carbon atoms more particularly covers the cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl group, whilst the aralkyl group with 7 to 18 carbon atoms particularly covers the benzyl and phenethyl group. The alkylaryl group with 7 to 18 carbon atoms particularly covers the tolyl group, whilst the heterocyclic group with 2 to 5 carbon atoms particularly covers those in which the heterocyclic ring thereof contains at least one oxygen, sulphur or nitrogen atom and as suitable examples can be given the radicals of oxiran, tetrahydrofuran, dioxan and pyran.
It is fundamentally possible to use the compounds of formula (I) in the form of their salts or other precursors, which can promote solubility. In individual cases only this can lead to the desired solubility. It is therefore possible to consider compounds which only release the compounds of formula (I) in the aqueous medium or allow the evolution of their activity there. The following quantity details relate to the compounds of formula (I) as such or their proportion within the suitable derivatives or compounds.
Within the scope of the invention, it is possible to use random suitable salts of the indicated ureas or urea derivatives, provided that they do not impair the desired action mechanism. It is e.g. possible to use chlorides, sulphates, particularly hydrogen sulphate, phosphates, particularly hydrogen phosphates. Urea phosphate is particularly effective. Crystallized in the pure form, urea phosphate are colourless, has a melting point of 118 to 119xc3x8 C., is soluble in water, alcohol, acetic acid, glycerin, ethylene glycol, etc. The aqueous solution reacts acid (1% solution pH value 1.8). Apart from widespread use as an artificial fertilizer (N/P source), it offers a further advantageous practical use as a result of its acid action in solders, melting fluxes, pickles, metal polishes and rust removers and as a catalyst for acid-catalyzed synthetic resins (cf. p 1723, Rxe2x80x3mpp Chemie-Lexikon, Thieme Verlag, vol. 3, 9th edition, 1990). A proposal to use it for solving the aforementioned set problem in a solid or liquid effluent cleaner does not appear in the prior art and no teaching is provided in this connection.
Therefore the essence of the invention is to add to the solid or liquid effluent cleaner urea or the indicated derivatives or salts thereof in conjunction with the fat-degrading microorganisms, protease and an alkaline-acting agent. To a certain extent the urea or urea derivative used acts as a filler, dissolves pH-neutral, has a good water solubility, is inexpensive and aids the protease dissolving process. It is also an easily exploitable nitrogen source for fat-degrading bacteria.
Proteases are enzymes catalyzing the hydrolytic cleaving of the peptide bond in proteins and peptides. Use is more particularly made of a protease, which has increased activity in an aqueous, alkaline medium. The cleaning agent according to the invention also aims at low alkinity through the binding in of an alkaline-acting agent, also in liquid form, the pH-value preferably being in the range 8 to 12 and in particular approximately 9 to 10. Thus, the latter range represents the optimum. The protease quantity in the cleaning agent according to the invention is at least approximately 0.3 wt. %, particularly at least approximately 0.7 wt. %, based on dry substance or the solid content. Particular preference is given to a range between approximately 0.7 and 4 wt. %.
In view of the fact that there are different proteins in the plug to be removed from the sewer making the use of different proteases appear appropriate, preferably the proteases are used in the form of a mixture of at least 3 and in particular at least 4 different proteases. Use is more particularly made of those proteases, which have a protease activity in the alkaline pH-range. In the cleaning agent according to the invention they are more particularly in granulated form with a long term stability.
An essential part of the cleaning agent according to the invention is the use of fat-degrading microorganisms, particularly in the form of a mixed bacterial culture. The fat-degrading microorganisms are preferably present in a quantity of at least approximately 0.3 wt. %, particularly at least 0.7 wt. %, based on dry substance. Particular preference is given to the range of approximately 0.7 to 4 wt. %. The fat-degrading microorganisms degrade triglycerides and fatty acids, eliminate fat deposits and putrefaction odours and have a prophylactic action. In addition to the fat-degrading microorganisms, use can be made of lipases, particularly in the form of a mixture of different lipases. Lipases are enzymes belonging to the group of hydrolases, which cleave specific fats (triglycerides) into glyceride and fatty acids.
For the sought objective of the invention, it is also important that the claimed cleaning agent contains an alkaline-acting agent. An alkaline medium must be ensured for use and this is essential for the effects sought by the invention. The alkaline-acting agent is preferably in the form of an alkali metal and/or alkaline earth hydroxide and/or an alkaline-acting salt of an alkali metal and/or alkaline earth hydroxide. Sodium is preferred as the alkali metal in these compounds. In particularly preferred manner the alkaline-acting agent contains a mixture of sodium hydrogen carbonate and sodium carbonate. Particularly advantageous results are obtained if the mixture of sodium carbonate and sodium hydrogen carbonate is composed in such a way that there are approximately 2 to 4, particularly approximately 2.8 to 3.3 parts by weight sodium carbonate per part by weight sodium hydrogen carbonate. This mixture then sets an advantageous pH-range of approximately 8 to 11, particularly approximately 9 to 10. This pH-optimum also has an advantageous effect on the proteases used according to the invention with optimum effectiveness in the alkaline range.
The effects sought by the invention are improved by incorporating a surfactant, particularly a biodegradable surfactant, preferably in the form of a mixture of different surfactants. Preferably the surfactant quantity in the cleaning agent according to the invention, based on dry substance, is at least approximately 0.3, particularly at least approximately 0.7 wt. %. Preference is given to the range approximately 0.7 to 2.5 wt. %.
Surfactants are solubilizers, virtually all of them being surface-active. The choice of the most suitable solubilizer for the aqueous systems considered is based on the HLB system. These can in particular be anionic surfactants, such as fatty alcohol sulphonates, cationic surfactants, such as quaternary ammonium compounds, nonionic emulsifiers or solubilizers, such as fruit acid esters of mono-diglycerides, e.g. citrates and the like. As with all the essential constituents of the cleaning agent according to the invention, the aim here is that they are biodegradable under the use conditions. The surfactants make an important contribution to the dissolving of fats in the deposits to be removed. They also have a dissolving action on the proteases in the solid, inventive cleaning agent following introduction into the liquid phase of the sewer.
In order to increase the activity of the fat-degrading bacteria, it is particularly advantageous to incorporate into the inventive cleaning agent a carbon source for the same, particularly in the form of an organic acid, but which largely limits its acid functionality in the alkali medium, so that here its possible germ-inhibiting action does not come fully to bear or is excluded. These can be the organic acids mentioned hereinbefore in connection with the prior art, particularly citric acid, e.g. in the form of the aldehyde in the solid cleaning agent according to the invention.
The citric anhydride not only has the function of a carbon source, but in conjunction with the preferred alkali medium sodium hydrogen carbonate/sodium carbonate leads to dissolving, accompanied by gas production, which aids the complete operational sequences of the cleaning agent according to the invention when used. Thus, there is a bubbling action, the dissolving process of the constituents of the agent and an acoustic feedback are assisted and also constitutes an easily exploitable carbon source for the fat-degrading bacteria.
In order to increase the effects sought by the invention it is possible to add fat, protein and carbohydrate-degrading enzymes to the cleaning agent, particularly in the form of carbohydrate-degrading enzymes, preferably cellulase. The alkaline medium assists the fat and protein-dissolving properties of the enzymes and microorganisms contained in the product.
With a view to special applications, it is also possible to incorporate fillers with additional characteristics, e.g. in the form of sodium sulphate, sodium chloride and/or saccharose. As is conventional, to the cleaning agent according to the invention can also be added perfumes and/or dyes. These are in particular limonene/orangene terpenes. A suitable quantity range is between approximately 0.1 and 0.001 wt. %, based on dry substance. Thus, limonene/orangene terpenes produce a pleasant odour and a different perfume oil can also be used. It is optionally possible to use amino acids, such as cysteine.
From the technical standpoint the invention can be explained as follows:
All the indicated constituents which must or which are preferably used according to the invention reveal a functional interaction on achieving the sought technical result, which is not referred to in the prior art. With regards to the individual, technical processes, reference is made to the above statements. It is particularly necessary to stress the high proportion of urea or urea derivative or salt. Compared with the standard, prior art cleaning agents, the cleaning agent according to the invention is highly superior. With such a high urea quantity it virtually reaches the action of caustic soda (30 minutes), namely a dissolving of the comparison plug within 4 hours. Accompanied by the addition of water at 50xc3x8 C., there is a further improvement to the action. It is also possible to bring about the heating in that prior to the use of the cleaning agent according to the invention anhydrous magnesium sulphate is introduced into the sewer. As a result of hydration energy this leads to a desired, high heating.
The invention is further illustrated hereinafter by means of an example.


This invention presents Normalized Amplitude Hilbert Transform (NAHT) and Normalized Hilbert Transform(NHT), both of which are new methods for computing Instantaneous Frequency. This method is designed specifically to circumvent the limitation set by the Bedorsian and Nuttal Theorems, and to provide a sharp local measure of error when the quadrature and the Hilbert Transform do not agree. Motivation for this method is that straightforward application of the Hilbert Transform followed by taking the derivative of the phase-angle as the Instantaneous Frequency (IF) leads to a common mistake made up to this date. In order to make the Hilbert Transform method work, the data has to obey certain restrictions.

The term 'Instantaneous Frequency (IF)' has elicited strong opinions amongst the data analysis community. The range covers from 'banishing it forever from the dictionary of the communication engineer (Shekel, 1953)' to being a 'conceptual innovation' in assigning physical significance to the nonlinearly distorted waveforms (Huang et al 1998)'. In between these extremes, there are plenty of more moderate opinions stressing the frustration of finding an acceptable definition. In general, most of the investigators accept the definition of classical wave theory, the derivative of the phase (see, for example, Cohen, 1995). But questions of its validity persist.
Yet the need for instantaneous frequency is a real one for data from nonstationary and nonlinear processes. Certainly, the non-stationarity is a key feature here, but IF is even more important for nonlinear processes. If the process is non-stationary, the frequency should be ever changing, albeit at a slow rate. Then, there is a need for frequency value as a function of time, for the value will not be constant throughout. For the nonlinear cases, the oscillation can be viewed as intra-wave frequency modulation (Huang et al, 1998, 1999). Therefore, it is compelling to clarify the concept of, to settle these arguments on, and to provide a workable method for implementing the IF.
To date the most popular and direct method to define Instantaneous Frequency is through the Hilbert Transform (HT). Yet practical difficulties of implementation make it not only useless, but also controversial. Straightforward application of HT and then taking the derivative of the phase-angle as the instantaneous frequency is the common mistake made up to this date (Hahn, 1995). In order to make the HT method work, the data has to obey certain restrictions.
Some publications relating to Instantaneous Frequency are listed below:    Bedrosian, E., 1963: On the quadrature approximation to the Hilbert Transform of modulated signals. Proc. IEEE, 51, 868-869.    Boashash, B., 1992a: Estimating and interpreting the instantaneous frequency of a signal. Part I: Fundamentals, Proc. IEEE, 80, 520-538.    Boashash, B., 1992a: Estimating and interpreting the instantaneous frequency of a signal. Part I: Algorithms and Applications, Proc. IEEE, 80, 540-568.    Cohen, L., 1995: Time-frequency Analysis, Prentice Hall, Englewood Cliffs, N.J.    Daubechies, I., 1992: Ten Lectures on Wavelets, Philadelphia SIAM.    Flandrin, P., 1999: Time-Frequency/Time-Scale Analysis, Academic Press, San Diego, Calif.    Gabor, D., 1946: Theory of communication, J. IEE, 93, 426-457.    Goldstein, H., 1980: Classical Mechanics, 2nd Ed., Addison-Wesley, Reading, Mass.    Hahn, S., 1995: Hilbert Transforms in Signal Processing, Artech House, Boston, Mass.    Huang, et al. 1998: The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis. Proc. Roy. Soc. Lond., 454, 903-993.    Huang, N. E., Z. Shen, R. S. Long, 1999: A New View of Nonlinear Water Waves—The Hilbert Spectrum, Ann. Rev. Fluid Mech. 31, 417-457.    Kaiser, J. F., 1990: On Teager's energy algorithm and its generalization to continuous signals. Proc. 4th IEEE Signal Processing Workshop, Mohonk, N.Y.    Landau, L. D. and E. M. Lifshitz, 1976: Mechanics, 3rd Ed. Pergamon, Oxford.    Maragos, P., J. F. Kaiser, and T. F. Quatieri, 1993a: On amplitude and frequency demodulation using energy operators, IEEE Trans. Signal Processing, 41, 1532-1550.    Maragos, P., J. F. Kaiser, and T. F. Quatieri, 1993b: Energy separation in signal modulation with application to speech analysis, IEEE Trans. Signal Processing, 41, 3024-3051.    Meville, W. K., 1983: Wave modulation and breakdown, J. Fluid Mech., 128, 489-506.    Nuttall, A. H., 1966: On the quadrature approximation to the Hilbert Transform of modulated signals, Proceedings of IEEE, 54, 1458-1459.    Rice, S. O., 1944a: Mathematical analysis of random noise, Bell Sys. Tech. Jl., 23, 282-310.    Rice, S. O., 1944b: Mathematical analysis of random noise, III. Power spectrum and correlation functions, Bell Sys. Tech. Jl., 23, 310-332.    Rice, S. O., 1945a: Mathematical analysis of random noise, III. Statistical properties of random noise currents, Bell Sys. Tech. Jl., 24, 46-108.    Rice, S. O., 1944a: Mathematical analysis of random noise, IV. Noise through nonlinear devices, Bell Sys. Tech. Jl., 24, 109-156.    Infeld, E. and G. Rowland, 1990: Nonlinear waves, solutons and chaos, Cambridge University Press, Cambridge.    Shekel, J., 1953: Instantaneous Frequency. Proc. I.R.E. 41, 548.    Van der Pol, B., 1946: The fundamental principles of frequency modulation, Proc. IEE, 93, 153-158.    Whitham, G. B., 1975: Linear and Nonlinear Waves, New York, Wiley.
The following U.S. Patents are incorporated by reference:    U.S. Pat. No. 5,983,162 "Computer Implemented Empirical Mode Decomposition Method, Apparatus and Article of Manufacture"    U.S. Pat. No. 6,381,559 "Empirical Mode Decomposition Apparatus, Method and Article of Manufacture for Analyzing Biological Signals and Performing Curve Fitting"    U.S. Pat. No. 6,311,130 "Computer Implemented Empirical Mode Decomposition Method, Apparatus and Article of Manufacture for Two-Dimensional Signals"

Computing Instantaneous Frequency by normalizing Hilbert Transform

The United States of America as represented by the Administrator of the National Aeronautics and Space Administration