Thermoplastic molding compositions comprise

The invention relates to thermoplastic molding compositions comprising
A) from 30 to 96% by weight of a polyester
B) from 1 to 30% by weight of melamine cyanurate
C) from 1 to 30% by weight of at least one phosphorus-containing flame retardant
D) from 0.01 to 5% by weight of at least one ester or amide derived from a saturated or unsaturated aliphatic carboxylic acid having from 10 to 40 carbon atoms and a saturated aliphatic alcohol or amine having from 2 to 40 carbon atoms
E) from 0 to 60% by weight of other additives and processing aids
where the total of the percentages by weight of components A) to E) is 100%.
The invention also relates to the use of the novel molding compositions to produce fibers, films or shaped articles, and to the shaped articles of any type thus obtained.
The market shows increasing interest in halogen-free flame-retardant polyesters. Important requirements of the flame retardant are: pale intrinsic color, sufficient thermal stability for incorporation in thermoplastics, and its efficacy in reinforced and non-reinforced polymers (wicking effect of glass fibers).
In addition, the UL 94 flammability test should also be passed at the V-0 level.
In principle, besides halogen-containing systems, four halogen-free FR systems are used in thermoplastics:
Inorganic flame retardants which must be employed in large amounts to be effective.
Nitrogen-containing FR systems, such as melamine cyanurate, which has limited efficacy in thermoplastics, eg. polyamide. In reinforced polyamide, it is effective only in combination with shortened glass fibers. In polyesters, melamine cyanurate is not effective.
Phosphorus-containing FR systems, which are generally not effective in polyesters.
Phosphorus/nitrogen-containing FR systems, eg. ammonium polyphosphates or melamine phosphates, which have insufficient thermal stability for thermoplastics processed above 200xc2x0 C.
JP-A 03/281 652 discloses polyalkylene terephthalates containing melamine cyanurate and glass fibers and also a phosphorus-containing flame retardant. These molding compositions contain phosphoric acid derivatives, such as phosphoric acid esters (valence state +5), which tend to xe2x80x9cbloomxe2x80x9d when subjected to thermal stress.
These disadvantages are also apparent for the combination of melamine cyanurate with resorcinol bis(diphenylphosphate) disclosed in JP-A 05/070 671.
It is an object of the present invention to provide flame-retardant polyester molding compositions which achieve the UL 94 classification V-0 and pass the glowing wire test. In doing so, mold deposit should be minimized, ie. xe2x80x9cbloomingxe2x80x9d of the flame retardants should be substantially prevented. Furthermore, the mechanical properties should be maintained as far as possible.
We have found that this object is achieved by means of the thermoplastic molding compositions defined at the outset. Preferred embodiments are given in the subclaims.
The novel molding compositions comprise, as component (A), from 30 to 96%, preferably from 40 to 93%, and in particular from 50 to 85%, of a thermoplastic polyester.
Polyesters which are used are generally based on aromatic dicarboxylic acids and an aliphatic or aromatic dihydroxy compound.
A first group of preferred polyesters consists of polyalkylene terephthalates having from 2 to 10 carbon atoms in the alcohol moiety.
Polyalkylene terephthalates of this type are known per se and are described in the literature. They contain, in their main chain, an aromatic ring which derives from the aromatic dicarboxylic acid. The aromatic ring may also be substituted, for example with halogen, such as chlorine or bromine, or with C1-C4-alkyl, such as methyl, ethyl, isopropyl or n-propyl, n-butyl, isobutyl or tert-butyl
These polyalkylene terephthalates can be prepared by reaction of aromatic dicarboxylic acids, their esters or other ester-forming derivatives with aliphatic dihydroxy compounds, in a manner known per se.
Preferred dicarboxylic acids are, for example, 2,6-naphthalenedicarboxylic acid, terephthalic acid and isophthalic acid or mixtures of these. Up to 30 mol %, preferably not more than 10 mol %, of the aromatic dicarboxylic acids may be replaced by aliphatic or cycloaliphatic dicarboxylic acids, such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acids and cyclohexanedicarboxylic acids.
Preferred aliphatic dihydroxy compounds are diols with from 2 to 6 carbon atoms, in particular 1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethylanol and neopentyl glycol, and mixtures of these.
Particularly preferred polyesters (A) are, for example, polyalkylene terephthalates derived from alkanediols having from 2 to 6 carbon atoms. Of these, especial preference is given to polyethylene terephthalate and polybutylene terephthalate or mixtures of these.
The viscosity number of the polyesters (A) is generally in the range from 70 to 220, preferably from 80 to 160 (measured in a 0.5% strength by weight solution in a mixture of phenol and o-dichlorobenzene (weight ratio 1:1) at 25xc2x0 C.
Particular preference is given to polyesters whose content of carboxyl end groups is up to 100 mval/kg, preferably up to 50 mval/kg, and especially up to 40 mval/kg of polyester. Polyesters of this type may be prepared, for example, by the process of DE-A-44 01 055. The content of carboxyl end groups is generally determined by titration methods (eg. potentiometry).
Particularly preferred molding compositions contain, as component A), a mixture of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). he proportion of the polyethylene terephthalate in the mixture is preferably up to 50% by weight, in particular from 10 to 30% by weight, based on 100% by weight of A).
Novel molding compositions of this type have very good flame retardance and improved mechanical properties.
It is moreover advantageous to use recycled PET materials (also termed scrap PET) in a mixture with polyalkylene terephthalates, such as PBT.
For the purposes of the invention, recycled materials are generally:
1) Post-industrial recycled materials: these are production wastes from polycondensation or processing, eg. injection-molding sprues, start-up material from injection molding or extrusion or edge cuts from extruded sheets or films.
2) Post-consumer recycled materials: these are plastic items which are collected and reprocessed after use by the final consumer. The items which, in terms of quantity, predominate by a wide margin are blow-molded PET bottles for mineral water, soft drinks and juices.
Both types of recycled material may be in the form either of regrind or of pellets. In the latter case, the raw recycled materials, after separation and cleaning, are melted in an extruder and pelletized. This usually makes the material easier to handle, more free-flowing and easier to meter out for further processing steps.
The recycled materials used may be either pelletized or in the form of regrind; the maximum edge length should be 6 mm, preferably below 5 mm.
Because polyesters can be cleaved by hydrolysis during processing (by traces of moisture), it is advisable to predry the recycled material. The residual moisture content after drying is preferably from 0.01 to 0.7%, in particular from 0.2 to 0.6%.
A further group which may be mentioned is that of the fully aromatic polyesters derived from aromatic dicarboxylic acids and aromatic dihydroxy compounds.
Suitable aromatic dicarboxylic acids are the compounds described above in relation to polyalkylene terephthalates. Preference is given to mixtures of from 5 to 100 mol % of isophthalic acid and from 0 to 95 mol % of terephthalic acid, in particular mixtures of from about 80 to about 50% of terephthalic acid with about 20 to about 50% of isophthalic acid.
where Z is alkylene or cycloalkylene having up to 8 carbon atoms, arylene having up to 12 carbon atoms, carbonyl, sulfonyl, an oxygen or sulfur atom, or a chemical bond, and where m is from 0 to 2. Compounds I may also carry C1-C6-alkyl or -alkoxy and fluorine, chlorine or bromine as substituents on the phenylene groups.
Examples of parent compounds are
dihydroxydiphenyl,
di(hydroxyphenyl)alkane,
di(hydroxyphenyl)cycloalkane,
di(hydroxyphenyl) sulfide,
di(hydroxyphenyl) ether,
di(hydroxyphenyl) ketone,
di(hydroxyphenyl) sulfoxide,
xcex1,xcex1xe2x80x2-di(hydroxyphenyl)dialkylbenzene,
di(hydroxyphenyl) sulfone,
di(hydroxybenzoyl)benzene,
resorcinol and
hydroquinone and their ring-alkylated and ring-halogenated derivatives.
Of these, preferred compounds are
4,4xe2x80x2-dihydroxydiphenyl,
2,4-di(4xe2x80x3-hydroxyphenyl)-2-methylbutane,
xcex1,xcex1xe2x80x2-di(4-hydroxyphenyl)-p-diisopropylbenzene,
2,2-di(3xe2x80x2-methyl-4xe2x80x2-hydroxyphenyl)propane and
2,2-di(3xe2x80x2-chloro-4xe2x80x2-hydroxyphenyl)propane,
and in particular
2,2-di(4xe2x80x2-hydroxyphenyl)propane,
2,2-di(3xe2x80x2,5-dichlorodihydroxyphenyl)propane,
1,1-di(4xe2x80x2-hydroxyphenyl)cyclohexane,
3,4xe2x80x2-dihydroxybenzophenone,
4,4xe2x80x2-dihydroxydiphenyl sulfone and
2,2-di(3xe2x80x2,5xe2x80x2-dimethyl-4xe2x80x2-hydroxyphenyl)propane and mixtures of these.
It is also possible, of course, to employ mixtures of polyalkylene terephthalates and fully aromatic polyesters. These generally include from 20 to 98% by weight of the polyalkylene terephthalate and from 2 to 80% by weight of the fully aromatic polyester.
For the purposes of the present invention, polyesters are also intended to include polycarbonates which can be obtained by polymerization of aromatic dihydroxy compounds, in particular 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) and its derivatives, for example with phosgene. Corresponding products are known per se and are described in the literature, and are mostly also commercially available. The amount of the polycarbonates is up to 90% by weight, preferably up to 50% by weight, based on 100% by weight of component (A).
Polyester block copolymers, such as copolyether esters, may, of course, also be used. Products of this type are known per se and are described in the literature, for example in US-A-3 651 014. corresponding products are also commercially available, for example Hytrel(copyright) (DuPont).
The novel thermoplastic molding compositions comprise, as component B), from 1 to 30% by weight, preferably from 1 to 20% by weight, and in particular from 5 to 20% by weight, of melamine cyanurate as flame retardant.
The melamine cyanurate used in the invention (component B) is a reaction product of preferably equimolar amounts of melamine (formula I) and cyanuric acid or isocyanuric acid (formulae IIa and IIb).
It is obtained, for example, by reaction of aqueous solutions of the starting materials at from 90 to 100xc2x0 C. The commercially available product is a white powder with a mean particle size d50 of from 1.5 to 7 xcexcm.
Suitable flame retardants C) are present in the novel molding compositions in amounts of from 1 to 30% by weight, preferably from 1 to 25% by weight, and in particular from 10 to 20% by weight, based on the total weight of components A) to E).
Component C) is an organic or inorganic phosphorus-containing compound in which the phosphorus has a valence state from xe2x88x923 to +5. The term valence state is taken to mean oxidation state, as given in xe2x80x9cLehrbuch der Anorganischen Chemiexe2x80x9d by A. F. Hollemann and E. Wiberg, Walter des Gruyter and Co. (1964, 57th to 70th Edition), pp. 166-177. Phosphorus compounds of valence states from xe2x88x923 to +5 are derived from phosphine (xe2x88x923), diphosphine (xe2x88x922), phosphine oxide (xe2x88x921), elemental phosphorus (+0), hypophosphorous acid (+1), phosphorous acid (+3), hypodiphosphoric acid (+4) and phosphoric acid (+5).
From the large number of phosphorus-containing compounds, only a few examples are mentioned.
Examples of phosphorus compounds of the phosphine class, having the valence state xe2x88x923, are aromatic phosphines, such as triphenyl phosphine, tritolyl phosphine, trinonyl phosphine, and trinaphthyl phosphine. Triphenyl phosphine is particularly suitable.
Examples of phosphorus compounds of the diphosphine class, having the valence state xe2x88x922, are inter alia tetraphenyldiphosphine and tetranaphthyldiphosphine. Tetranaphthyldiphosphine is particularly suitable.
Phosphorus compounds of the valence state xe2x88x921 are derived from phosphine oxide.
Suitable phosphine oxides are those of the formula I
where R1, R2 and R3 are identical or different alkyl, aryl, alkylaryl or cycloalkyl having from 8 to 40 carbon atoms.
Examples of phosphine oxides are triphenylphosphine oxide, tritolylphosphine oxide, trisnonylphenylphosphine oxide, tricyclohexylphosphine oxide, tris(n-butyl)phosphine oxide, tris(n-hexyl)phosphine oxide, tris(n-octyl)phosphine oxide, tris(cyanoethyl)phosphine oxide, benzylbis(cyclohexyl)phosphine oxide, benzylbisphenylphosphine oxide, phenylbis(n-hexyl)phosphine oxide. Particular preference is given to using triphenylphosphine oxide, tricyclohexylphosphine oxide and tris(n-octyl)phosphine oxide.
Compounds which are likewise suitable are triphenylphosphine sulfide and its derivatives corresponding to the phosphine oxides described above.
Phosphorus of the valence state xc2x10 is elemental phosphorus. Examples are red and black phosphorus, red phosphorus being preferred.
Examples of phosphorus compounds of the oxidation state +1 are hypophosphites. They may have the character of salts or be purely organic. Examples are calcium hypophosphite and magnesium hypophosphite, in addition double and complex hypophosphites, organic hypophosphites, such as cellulose hypophosphite esters, diol esters of hypophosphorous acids, for example those of 1,10-dodecyldiol. Substituted phosphinic acids and their anhydrides, for example diphenylphosphinic acid, may also be employed. Further examples are di-p-tolylphosphinic acid and di-cresylphosphinic anhydride, and also inter alia compounds such as bis(diphenylphosphinic acid) esters of hydroquinone, ethylene glycol and propylene glycol. Other suitable compounds are aryl(alkyl)phosphinic amides, such as diphenylphosphinic dimethylamide and sulfonamidoaryl(alkyl)phosphinic acid derivatives, such as p-tolylsulfonamidodiphenylphosphinic acid. Preference is given to using the bis(diphenylphosphinic acid) esters of hydroquinone and of ethylene glycol and hydroquinone bisdiphenylphosphinate.
Phosphorus compounds of the oxidation state +3 are derived from phosphorous acid. Suitable compounds are cyclic phosphonates derived from pentaerythritol, neopentyl glycol or pyrocatechol. Phosphorus of the valence state +3 is also present in triaryl(alkyl)phosphites, such as triphenyl phosphite, tris(4-decylphenyl) phosphite, tris(2,4-di-tert-butyl-phenyl) phosphite or phenyl didecyl phosphite inter alia. Further examples are, however, diphosphites, such as propylene glycol 1,2-bis(diphosphite) and cyclic phosphites derived from pentaerythritol, neopentyl glycol or pyrocatechol.
Particular preference is given to neopentyl glycol methylphosphonate and methyl neopentyl glycol phosphite, and pentaerythritol dimethyl diphosphonate and dimethyl pentaerythritol diphosphite.
Examples of phosphorus compounds of the oxidation state +4 are primarily hypodiphosphates, for example tetraphenyl hypodiphosphate and bisneopentyl hypodiphosphate.
Examples of phosphorus compounds of the oxidation state +5 are primarily alkyl- and aryl-substituted phosphates, such as phenyl bisdodecyl phosphate, phenyl ethyl hydrogen phosphate, phenyl bis(3,5,5-trimethylhexyl) phosphate, ethyl diphenyl phosphate, 2-ethylhexyl ditolyl phosphate, diphenyl hydrogen phosphate, bis(2-ethylhexyl)-p-tolyl phosphate, tritolyl phosphate, bis(2-ethylhexyl) phenyl phosphate, dinonyl phenyl phosphate, phenyl methyl hydrogen phosphate, di(dodecyl) p-tolyl phosphate, p-tolyl bis(2,5,5-trimethylhexyl) phosphate and 2-ethylhexyl diphenyl phosphate. Phosphorus compounds in which every radical is aryloxy are particularly suitable. very particularly suitable compounds are triphenyl phosphate and resorcinol bis(diphenyl) phosphate and its ring-substituted derivatives of the formula
where
R4-R7 are each an aromatic radical having from 6 to 20 carbon atoms, preferably phenyl, which may be substituted with alkyl having from 1 to 4 carbon atoms, preferably methyl,
R8 is a bivalent phenol, preferably
and n is from 1 to 100, preferably from 1 to 5.
Cyclic phosphates may additionally also be employed, diphenyl pentaerythritol diphosphate and phenyl neopentyl phosphate being particularly suitable.
Besides the abovementioned low-molecular-weight phosphorus compounds, oligomeric and polymeric phosphorus compounds are also suitable.
Halogen-free polymeric organic phosphorus compounds of this type, having phosphorus in the polymer chain, are formed, for example, in the preparation of pentacyclic unsaturated phosphine dihalides, as described, for example, in DE-A-20 36 173. The molecular weight of the polyphospholine oxides measured by vapor-pressure osmometry in dimethylformamide is claimed to be in the range from 500 to 7,000, preferably from 700 to 2,000.
Here phosphorus has the oxidation statexe2x88x921.
Inorganic coordination polymers of aryl(alkyl)phosphinic acids, such as poly-xcex2-sodium(I) methylphenylphosphinate, may also be employed. Their preparation is given in DE-A-31 40 520. Phosphorus has the oxidation number +1.
Halogen-free polymeric phosphorus compounds of this type can furthermore result from the reaction of a phosphonic acid chloride, such as phenyl-, methyl-, propyl-, styryl- or vinylphosphonic acid dichloride, with dihydric phenols, such as hydroquinone, resorcinol, 2,3,5-trimethylhydroquinone, bisphenol A, or tetramethylbisphenol A.
Other halogen-free polymeric phosphorus compounds which may be present in the novel molding compositions are prepared by reacting phosphoryl chloride or phosphoric ester dichlorides with a mixture of mono-, di- and trihydric phenols and other hydroxyl-containing compounds (cf. Houben-Weyl-Mxc3xcller, Thieme-Verlag Stuttgart, Organische Phosphorverbindungen Part II (1963)). Furthermore, polymeric phosphonates can be prepared by transesterification of phosphonates with dihydric phenols (cf. DE-A-29 25 208) or by reaction of phosphonates with diamines, diamides or hydrazides (cf. U.S. Pat. No. 4,403,075). The inorganic compound poly(ammonium phosphate) is, however, also suitable.
Use may also be made of oligomeric pentaerythritol phosphites, phosphates and phosphonates according to EP-B 8 486, for example Mobil Antiblaze(copyright) 19 (registered trademark of Mobil Oil).
The novel molding compositions comprise, as component D), from 0.01 to 5% by weight, preferably from 0.05 to 3% by weight, and in particular from 0.1 to 2% by weight, of at least one ester or amide derived from a saturated or unsaturated aliphatic carboxylic acid having from 10 to 40 carbon atoms, preferably from 16 to 22 carbon atoms, and a saturated aliphatic alcohol or amine having from 2 to 40 carbon atoms, preferably from 2 to 6 carbon atoms.
The carboxylic acid can be mono- or dibasic, for example nonanoic acid, palmitic acid, lauric acid, 1-heptadecanoic acid, dodecanedioic acid, docosanoic acid, and particularly preferably stearic acid, decanoic acid and montanic acid (a mixture of fatty acids having from 30 to 40 carbon atoms).
The aliphatic alcohols may be mono- to tetrahydric, examples being n-butanol, n-octanol, stearyl alcohol, ethylene glycol, propylene glycol, neopentyl glycol and pentaerythritol, glycerol and pentaerythritol being preferred.
The aliphatic amines may be mono- to trihydric, examples being stearylamine, ethylenediamine, propylenediamine, hexamethylenediamine and di(6-aminohexyl)amine, ethylenediamine and hexamethylenediamine being particularly preferred. Preferred esters and amides are correspondingly glycerol distearate, glycerol tristearate, ethylenediamine distearate, glycerol monopalmitate, glycerol trilaurate, glycerol monodocosanoate and pentaerythritol tetrastearate.
Mixtures in any desired ratio of different esters or amides or esters in combination with amides may also be employed.
The novel molding compositions may contain, as component E), from 0 to 60% by weight, in particular up to 50% by weight, of conventional additives and processing aids.
Conventional additives E) are, for example, elastomeric polymers (often also referred to as impact modifiers, elastomers or rubbers) in amounts of up to 40% by weight, preferably up to 30% by weight.
These are very generally copolymers, preferably built up from at least two of the following monomers: ethylene, propylene, butadiene, isobutene, isoprene, chloroprene, vinyl acetate, styrene, acrylonitrile and (meth)acrylates having from 1 to 18 carbon atoms in the alcohol component. Polymers of this type are described, for example, in Houben-weyl, Methoden der organischen Chemie, Vol. 14/1 (Georg-Thieme-Verlag, Stuttgart, 1961), pp. 392 to 406 and in the monograph by C. B. Bucknall, xe2x80x9cToughened Plasticsxe2x80x9d (Applied Science Publishers, London, 1977).
Some preferred types of such elastomers are listed below.
Preferred types of such elastomers are the ethylene-propylene rubbers (EPM) and the ethylene-propylene-diene rubbers (EPDM).
EPM rubbers generally have virtually no residual double bonds, whereas EPDM rubbers may have from 1 to 20 double bonds per 100 carbon atoms.
Examples of diene monomers for EPDM rubbers are conjugated dienes, such as isoprene and butadiene, non-conjugated dienes with from 5 to 25 carbon atoms, such as penta-1,4-diene, hexa-1,4-diene, hexa-1,5-diene, 2,5-dimethylhexa-1,5-diene and octa-1,4-diene, cyclic dienes, such as cyclopentadiene, cyclohexadienes, cyclooctadienes and dicyclopentadiene, and alkenylnorbornenes, such as 5-ethylidene-2-norbornene, 5-butylidene-2-norbornene, 2-methallyl-5-norbornene, 2-isopropenyl-5-norbornene, and tricyclodienes, such as 3-methyltricyclo(188.8.131.52.2.6)-3,8-decadiene or mixtures of these. Preference is given to hexa-1,5-diene, 5-ethylidenenorbornene and dicyclopentadiene. The diene content of the EPDM rubbers is preferably from 0.5 to 50% by weight, in particular from 1 to 8% by weight, based on the total weight of the rubber.
EPM or EPDM rubbers may preferably also be grafted with reactive carboxylic acids or their derivatives, for example acrylic acid, methacrylic acid or their derivatives, such as glycidyl (meth)acrylate, or maleic anhydride.
Copolymers of ethylene with acrylic acid and/or methacrylic acid and/or the esters of these acids are a further group of preferred rubbers. The rubbers may also include dicarboxylic acids, such as maleic acid and fumaric acid, or derivatives of these acids, eg. esters and anhydrides, and/or epoxy-containing monomers. These dicarboxylic acid derivatives or epoxy-containing monomers are preferably incorporated in the rubber by addition to the monomer mixture of monomers containing dicarboxylic-acid and/or epoxy groups and having the formula I, II, III or IV
where R1 to R9 are hydrogen or alkyl having from 1 to 6 carbon atoms, and m is an integer from 0 to 20, g is an integer from 0 to 10, and p is an integer from 0 to 5.
R1 to R9 are preferably hydrogen, where m is 0 or 1 and 9 is 1. The corresponding compounds are maleic acid, fumaric acid, maleic anhydride, allyl glycidyl ether and vinyl glycidyl ether.
Preferred compounds of the formulae I, II and IV are maleic acid, maleic anhydride and epoxy-containing (meth)acrylates, such as glycidyl (meth)acrylate, and the esters with tertiary alcohols, such as tert-butyl acrylate. Although these latter have no free carboxyl groups, their behavior approaches that of the free acids, and they are therefore referred to as monomers with latent carboxyl groups.
The copolymers advantageously consist of from 50 to 98% by weight of ethylene, from 0.1 to 20% by weight of epoxy-containing monomers and/or monomers containing methacrylic acid and/or acid anhydride groups, the residual amount being (meth)acrylates.
Particular preference is given to copolymers of
from 50 to 98% by weight, in particular from 55 to 95% by weight, of ethylene,
from 0.1 to 40% by weight, in particular from 0.3 to 20% by weight, of glycidyl acrylate and/or glycidyl methacrylate, (meth)acrylic acid and/or maleic anhydride, and
from 1 to 45% by weight, in particular from 10 to 40% by weight, of n-butyl acrylate and/or 2-ethylhexyl acrylate.
Other preferred acrylates and/or methacrylates are methyl, ethyl, propyl, isobutyl and tert-butyl (meth)acrylates.
Besides these, vinyl esters and vinyl ethers may also be employed as comonomers.
The ethylene copolymers described above may be prepared by processes known per se, preferably by random copolymerization under elevated pressure and temperature. Corresponding processes are well known.
Other preferred elastomers are emulsion polymers whose preparation is described, for example, by Blackley in the monograph xe2x80x9cEmulsion Polymerizationxe2x80x9d. The emulsifiers and catalysts which may be used are known per se.
In principle, both elastomers with a homogeneous construction and those with a shell construction may be employed. The shell-type construction results from the addition sequence of the individual monomers; the morphology of the polymers is also influenced by this addition sequence.
Compounds which may be mentioned here merely as examples of monomers for preparing the elastic part of the elastomers are acrylates, for example n-butyl acrylate and 2-ethylhexyl acrylate, the corresponding methacrylates, butadiene and isoprene and mixtures of these. These monomers may be copolymerized with other monomers, such as styrene, acrylonitrile, vinyl ethers and other acrylates or methacrylates, such as methyl methacrylate, methyl acrylate, ethyl acrylate and propyl acrylate.
The soft or elastic phase (with a glass transition temperature of less than 0xc2x0 C.) of the elastomers can be the core, the outer shell or an intermediate layer (in elastomers having a construction involving more than two layers); multishell elastomers may also have more than one layer formed from an elastic phase.
If one or more hard components (with glass transition temperatures of greater than 20xc2x0 C.) are also involved, besides the elastic phase, in the construction of the elastomer, these are generally prepared by polymerization of styrene, acrylonitrile, methacrylonitrile, a-methylstyrene, p-methylstyrene, or acrylates or meth-acrylates, such as methyl acrylate, ethyl acrylate and methyl methacrylate, as main monomers. Besides these, smaller amounts of other comonomers may also be employed here.
In a number of cases, it has proven advantageous to employ emulsion polymers having reactive groups at the surface. Groups of this type are, for example, epoxy, carboxyl, latent carboxyl, amino and amido, and functional groups which can be introduced by additional use of monomers of the formula
where
R10 is hydrogen or C1-C4-alkyl,
R11 is hydrogen, C1-C8-alkyl or aryl, in particular phenyl,
12 is hydrogen, C1-C10-alkyl, C6-C12-aryl or xe2x80x94OR13
R13 is C1-C8-alkyl or C6-C12-aryl, each of which may be substituted with oxygen- or nitrogen-containing groups,
X is a chemical bond, C1-C10-alkylene or C6-C12-arylene or
Y is Oxe2x80x94Z or NHxe2x80x94Z and
Z is C1-C10-alkylene or C6-C12-arylene.
The graft monomers described in EP-A 208 187 are also suitable for introducing reactive groups at the surface.
Further examples are acrylamide, methacrylamide, and substituted acrylates and methacrylates, such as (N-tert-butylamino)ethyl methacrylate, (N,N-dimethylamino)ethyl acrylate, (N, N-dimethylamino)methyl acrylate and (N,N-diethylamino) ethyl acrylate.
The constituents of the elastic phase may also be crosslinked. Monomers which act as crosslinkers are, for example, buta-1,3-diene, divinylbenzene, diallyl phthalate, dihydrodicyclopentadienyl acrylate and the compounds described in EP-A 50 265.
Use may, furthermore, also be made of graft-linking monomers, ie. monomers having two or more polymerizable double bonds which react at different rates during polymerization. Preference is given to these compounds in which at least one reactive group polymerizes at about the same rate as the remaining monomers, whereas the other reactive group(s), for example, polymerize(s) significantly more slowly. The different polymerization rates give rise to a certain proportion of unsaturated double bonds in the elastomer. If a further phase is then grafted onto an elastomer of this type, at least some of the double bonds in the elastomer react with the graft monomers to form chemical bonds, ie. the grafted phase is, at least to some extent, linked to the graft base via chemical bonds.
Examples of such graft-linking monomers are allyl-containing monomers, in particular allyl esters of ethylenically unsaturated carboxylic acids, such as allyl acrylate, allyl methacrylate, diallyl maleate, diallyl fumarate, diallyl itaconate, and the corresponding monoallyl compounds of these dicarboxylic acids. In addition, there are a wide variety of other suitable graft-linking monomers; further details may be seen, for example, in U.S. Pat. No. 4,148,846.
The proportion of these crosslinking monomers in the impact-modifying polymer is generally up to 5% by weight, preferably not more than 3% by weight, based on the impact-modifying polymer.
Some preferred emulsion polymers are listed below, beginning with graft polymers which have a core and at least one outer shell, and which have the following construction;
The graft polymers, in particular ABS and/or ASA polymers in amounts of up to 40% by weight, are preferably employed for impact modification of PBT, if desired as a mixture with up to 40% by weight of polyethylene terephthalate. Blends of this type are obtainable under the trademark Ultradur(copyright)S (previously ultrablend(copyright)s of BASF AG). ABS/ASA mixtures with polycarbonates are commercially obtainable under the trademark Terblend(copyright) (BASF AG).
Instead of graft polymers with a multishell construction, homogeneous, ie. single-shell, elastomers of buta-1,3-diene, isoprene and n-butyl acrylate or copolymers of these may also be employed. These products may also be prepared with additional use of crosslinking monomers or monomers with reactive groups.
Examples of preferred emulsion polymers are n-butyl acrylate-(meth)acrylate copolymers, n-butyl acrylate-glycidyl acrylate and n-butyl acrylate-glycidyl methacrylate copolymers, graft polymers with an inner core of n-butyl acrylate or based on butadiene and an outer shell of the abovementioned copolymers and copolymers of ethylene with comonomers which provide reactive groups.
The elastomers described may also be prepared by other conventional processes, for example by suspension polymerization.
Preference is likewise given to silicone rubbers, as described in DE-A-37 25 576, EP-A 235 690, DE-A-38 00 603 and EP-A 319 290. Mixtures of the rubber types mentioned above may, of course, also be employed.
Examples of fibrous or particulate fillers are carbon fibers, glass fibers, glass beads, amorphous silica, asbestos, calcium silicate, calcium metasilicate, magnesium carbonate, kaolin, chalk, quartz powder, mica, barium sulfate and feldspar, employed in amounts of up to 50% by weight, in particular up to 40% by weight.
Examples of preferred fibrous fillers are carbon fibers, aramide fibers and potassium titanate fibers, glass fibers made from E glass being particularly preferred. These may be employed as rovings or as chopped glass in the forms which are commercially available.
The fibrous fillers may be pretreated on their surfaces with a silane compound, for better compatibility with the thermoplastics.
Suitable silane compounds are those of the formula III
(Xxe2x80x94(CH2)n)kxe2x80x94Sixe2x80x94(Oxe2x80x94CmH2m+1)2-kxe2x80x83xe2x80x83III
where:
n is an integer from 2 to 10, preferably 3 or 4,
m is an integer from 1 to 5, preferably 1 or 2,
k is an integer from 1 to 3, preferably 1.
Preferred silane compounds are aminopropyltrimethoxysilane, aminobutyltrimethoxysilane, aminopropyltriethoxysilane, aminobutyltriethoxysilane and the corresponding silanes which contain glycidyl as substituent x.
The silane compounds are usually employed for surface coating in amounts of from 0.05 to 5% by weight, preferably from 0.5 to 1.5% by weight and in particular from 0.8 to 1% by weight (based on D).
Acicular mineral fillers are also suitable.
For the purposes of the invention, acicular mineral fillers are mineral fillers of strongly developed acicular character, for example acicular wollastonite. The mineral preferably has an L/D (length to diameter) ratio of from 8:1 to 35:1, preferably from 8:1 to 11:1. The mineral filler may, if desired, be pretreated with the abovementioned silane compounds, but the pretreatment is not essential.
Examples of other fillers are kaolin, calcined kaolin, wollastonite, talc and chalk.
The novel thermoplastic molding compositions may contain, as component E), conventional processing aids, such as stabilizers, oxidation inhibitors, thermal and UV stabilizers, lubricants, demolding aids, colorants, such as dyes and pigments, nucleating agents, plasticizers, etc.
Examples of oxidation inhibitors and thermal stabilizers are sterically hindered phenols and/or phosphites, hydroquinones, aromatic secondary amines such as diphenylamines, and various substituted representatives of these groups, and mixtures of these in concentrations of up to 1% by weight, based on the weight of the thermoplastic molding compositions.
Examples of UV stabilizers, generally used in amounts of up to 2% by weight, based on the molding composition, are various substituted resorcinols, salicylates, benzotriazoles and benzophenones.
Inorganic pigments, such as titanium dioxide, Ultramarine blue, iron oxide and carbon black, and organic pigments, such as phthalocyanines, quinacridones and perylenes, and dyes, such as nigrosin and anthraquinones, may be added as colorants.
Sodium phenylphosphinate, alumina or silica and preferably talc may be added as nucleating agent.
Lubricants and demolding aids, which are usually employed in amounts of up to 1% by weight, are preferably long-chain fatty acids (eg. stearic acid and docosanoic acid), salts of these (eg. calcium and zinc stearates) or amide derivatives (eg. ethylenebisstearylamide) or montan waxes (mixtures of straight-chain, saturated carboxylic acids with chain lengths of from 28 to 32 carbon atoms) or low-molecular-weight polyethylene waxes or polypropylene waxes.
Examples of plasticizers are dioctyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, hydrocarbon oils and N-(n-butyl)benzenesulfonamide.
The novel molding compositions may also include from 0 to 2% by weight of fluorine-containing ethylenic polymers. These are ethylenic polymers with a fluorine content of from 55 to 76% by weight, preferably from 70 to 76% by weight.
Examples of these are polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymers and tetrafluoroethylene copolymers with smaller proportions (generally up to 50% by weight) of copolymerizable ethylenically unsaturated monomers. These are described, for example, by Schildknecht in xe2x80x9cVinyl and Related Polymersxe2x80x9d, Wiley-Verlag, 1952, p. 484 to 494 and by Wall in xe2x80x9cFluoropolymersxe2x80x9d (Wiley Interscience, 1972).
These fluorine-containing ethylenic polymers are homogeneously distributed in the molding compositions and preferably have a particle size d50 (number average) in the range from 0.05 to 10 xcexcm. in particular from 0.1 to 5 xcexcm. These low particle sizes may particularly preferably be achieved by the use of aqueous dispersions of fluorine-containing ethylenic polymers and by incorporating these in a polyester melt.
The novel thermoplastic molding compositions can be prepared by processes known per se, by mixing the starting components in conventional mixing apparatus such as screw-extruders, Brabender mixers or Banbury mixers, and then extruding them. After extrusion, the extrudate can be cooled and comminuted. It is also possible to premix individual components and then to add the remaining starting materials, either individually or mixed. The mixing is generally carried out at from 230 to 290xc2x0 C.
In a preferred method of operation, components B) to D) and, if desired, conventional additives E) can be mixed with a polyester prepolymer, compounded and granulated. The resultant granules are then subjected in solid phase to continuous or batch condensation under inert gas at a temperature below the melting point of component A), until the desired viscosity is reached.
The novel thermoplastic molding compositions have good mechanical properties and good flame retardancy and at the same time pass the glowing-wire test. Processing can be carried out without any significant modification of the polymer matrix, and mold deposit is sharply reduced. The molding compositions are suitable for producing fibers, films and shaped articles, in particular for applications in the electrical and electronics sectors. Particular applications are lamp parts, such as lamp sockets and lamp holders, plugs and multipoint connectors, coil formers, casings for capacitors or connectors, and circuit-breakers, relay housings and reflectors.

Abstract: D) from 0.01 to 5% by weight of at least one ester or amide derived from a saturated or unsaturated aliphatic carboxylic acid having from 10 to 40 carbon atoms and a saturated aliphatic alcohol or andmine having from 2 to 40 carbon atoms


The invention concerns an oil supply system for an automatic transmission of a motor vehicle having one hydrodynamic starting element. It has one oil pump (2) to convey oil to a variator (9, 10) and/or to shifting elements (12, 13), to a converter unit (19) that can be supplied with oil via two oil lines (23, 25), especially a hydrodynamic torque converter (20) having a converter lock-up clutch (21), and to a lubrication device (28), the same as at least one filter device (3, 31) and one oil cooling device (17). Here are provided one prioritized primary circuit (6) with a main pressure adjusted by a main pressure valve (3) for pressure supply of the variator (9, 10) and/or of the shifting elements (12, 13) and a secondary circuit (7) for oil supply of the lubrication device (28). It is proposed according to the invention that the converter unit (19) be tied to the primary circuit (6) and to the secondary circuit (7) so that the converter lock-up clutch (21) be supplied with a minimum pressure required for torque transmission via the primary circuit (6) parallel to the supply of the lubrication device (28) via the secondary circuit (7) when on the converter lock-up clutch (21) a closing or slipping state is adjusted and that otherwise the converter unit (19) is supplied with oil via the secondary circuit (7).

The invention concerns an oil supply system for an automatic transmission of a motor vehicle with one hydrodynamic starting device.
It is known that automatic transmission in motor vehicles use oil for the hydrodynamic transmission of force and power, hydrostatic transmission of force and power, for information processing, for modulation of friction values, lubrication, heat emission and power consumption. As oil supply system serves here an oil circuit which, as a rule, is comprised of an oil sump, an oil filter, an oil pump, control valves, actuators of servoelements, seals, an oil cooler and connecting lines. Via the oil circuit oil volume is passed as pressure medium to shifting elements or for adjustment of variator disks of a variator in CVT transmission, to a converter unit consisting of a hydrodynamic torque converter and a converter lock-up clutch and to a lubrication device by means of which are lubricated or cooled, for example, the bearings of the many shafts, hollow shafts and webs of the planetary sets and servo-organs.
In the automatic transmissions known from the practice, the oil circuit is divided by a main pressure valve in a prioritized primary circuit and a secondary circuit. In a CVT transmission, the primary circuit contains here the pressure supply of the variator disks and shifting elements; in a multi-step transmission usually only the pressure supply of the shifting elements. The pressure of the primary circuit is determined by the main pressure valve, the consumers of the primary circuit being mutually equalized. Compared to the consumers of the primary circuit, the consumers of the secondary circuit have a lower priority in the provision of pressure.
On the primary side of the main pressure valve, when there is an excess of oil volume, the excess oil is sprayed off to the secondary circuit. The secondary circuit usually contains, together with the supply of the lubrication and the pressure supply of the torque converter, the pressure supply of the converter lock-up clutch when the torque converter is attached with its lock-up clutch to the oil supply in the two-line technique. In the known automatic transmissions, the pressure of the secondary circuit is determined by a converter safety valve designed as pressure-limiting valve. The consumers of the secondary circuit are mutually equalized to a pressure level above the predetermined lubrication pressure which is usually adjusted by a separate pressure-limiting valve. In such an arrangement, the main pressure cannot be below the maximum pressure level of the secondary circuit.
The pressure level of the secondary circuit is determined by the required pressure of the converter lock-up clutch when maximum torque is to be transmitted. It is disadvantageous here that in certain operating ranges the minimum main pressure in the primary circuit is determined by the pressure level of the secondary circuit even though for pressure supply of the consumers in the primary circuit a lower pressure level would suffice, for example, in case of small load or open drive train. Deterioration in effectiveness and consumption disadvantages accordingly result.
Although, as a rule, there is an oil oversupply of the primary circuit in operating situations needing a large oil volume in the primary circuit, such as in the case of large adjustment gradients of the variator in a CVT transmission, a brief undersupply in oil volume of the secondary circuit can occur so that the pressure level required does not build up in the secondary circuit. In the case of such an undersupply of the secondary circuit, the pressure in the converter lock-up clutch can drop to lubrication pressure which entails a slipping of the converter lock-up clutch. Due to the high rotation of the primary mover, a loss of comfort also results together with an undesirable wear of the converter lock-up clutch.
Together with the provision of a sufficient oil volume flow for building up a required pressure, the oil supply system in the automatic transmission also has the important function of taking care that the oil in the transmission is cooled in order to be able to remove as heat the power loss generating in the transmission. For this purpose, an oil-cooling device is, as a rule, situated before the lubrication in the secondary circuit wherefore the transmission elements are usually cooled via the supply of lubrication oil. The converter unit is conveniently disposed before the lubrication, since it needs a higher pressure level than the lubrication. To prevent an overpressure in the converter unit, the converter safety valve usually has an oil spray-off edge for discharging excessive oil volume in the oil sump. Consequently, the excessive oil is not cooled which results in a corresponding increase of temperature in the oil sump.
Therefore, the problem on which this invention is based is to make an oil supply system available for an automatic transmission of a motor vehicle, having one oil circuit divided by a main pressure valve into one primary circuit and one secondary circuit with which system can be effectively implemented by adjustment of the lowest possible main pressure, the pressure supply of a converter unit being always ensured. In addition, the oil supply system must make an effective cooling of the circulating oil possible.
According to the invention this problem is solved by an oil supply system.
Therefore, according to the invention, it is proposed to supply the converter lock-up clutch in the operating situations in which it is to be brought to a closing or slipping state with oil, via the primary circuit, with a required minimum pressure while oil is fed to the lubrication device, via the secondary circuit. Otherwise, the converter unit is bound to the secondary circuit.
In a especially advantageous manner, the pressure to be adjusted for the converter unit during the supply through the secondary circuit can be reduced to the cavitation limit of the converter. The inventive tying of the converter lock-up clutch to the primary circuit makes an optimum pressure design on the secondary circuit in the operating states possible with open converter lock-up clutch.
The converter unit is, therefore, always conveniently suppled with enough oil volume while the main pressure in the primary circuit can be below the pressure needed for the closing of the converter clutch, for example, in case of small load. An improved degree of efficiency can be conveniently implemented and thus an economy in fuel.
At the same time, the inventive oil supply system can be used both in multi-step automatic transmissions and in CVT transmission. The inventive oil supply system can, likewise, be used for any hydrodynamic starting elements in combination with an appertaining lock-up clutch, such as a torque converter with integrated lock-up clutch.
For the effective cooling of the oil circulating in the transmission, it is proposed to situate the inventive oil supply system in the secondary circuit in flow direction behind the main pressure valve and before the converter unit, before the lubrication device and before an oil spray-off device for discharging excess of oil volume in the secondary circuit. The cooling of the whole system is hereby improved in the sense that the oil already sprayed off in the oil sump during the pressure adjustment on the converter unit also has passed through the cooling device.

Oil supplying system for an automatic transmission with a hydrodynamic starting device


A steam grill includes a body, an upper lid, a water-storing member positioned on the upper lid, a beating section provided in the interior of the body, a dripping controller, and a grilling section under the heating section. The dripping controller is positioned within the water-storing member and controls the water volume dropping in the heating section. The heating section has a plurality of heating tubes for heating up water into steam to be supplied in the grilled section to moisten the food put on a grill plate therein to the proper degree so that the grilled food may have proper moisture and texture.

This invention relates to a steam grill, particularly to one supplying steam to different foods to be grilled positioned in a grilling section, and specifically to a steam grill where water is supplied via a dripping section into a heating section to be vaporized, with the water volume flowing into the heating section being controlled. The heating section heats up water to create steam to flow into a grilled section for moistening food to be grilled therein in various degrees according to different materials of food so as to grill foods to have proper resilience, moisture and texture.
A conventional steam grill generally has a grill plate placed on an inner bottom of a steam grill, a heating member positioned under the grill plate, and an upper lid pivotally connected to the grill housing. In the grilling process, the heating member electrically heats up food placed on the grill plate, but water in the food may be substantially evaporated out to cause the food to become very dry and have inferior texture.
This invention has been devised to offer a steam grill supplying steam for grilling food so as to let the grilled food have proper moisture, resilience and texture when eaten.
The feature of the invention is an upper lid provided with a recess for placing a water-storing member thereon and a transparent cover closing the water-storing member. The water-storing member and the transparent cover have a filling hole, and a dripping controller is provided in a chamber formed in the water-storing member. The dripping controller has a turning cap extending out of the transparent cover for manually turning to adjust water volume dropping down into the heating section. A shaft fits in a tubular portion of the turning cap and is always kept resiliently pushed downward.
A gap is formed between a hole in the bottom of the water-storing member and a lower tapered end of the shaft to allow water to flow down into the heating section for heating tubes to heat the water into steam. The steam flows down through holes in a bottom wall of the heating section to moisten food to be grilled. The gap can be adjusted by turning the turning cap to let different volumes of water flow through the gap into the heating section according to different foods to be grilled.


A system and method is provided for sensing information (e.g., voltage, current, data, etc.) that is being transmitted through a connector. Preferred embodiments of the present invention operate in accordance with a connector and at least one sensor. In one embodiment of the present invention, the connector comprises a plug, a receptacle, and a sensor assembly for housing at least one circuit board, at least one sensor, and at least one sensor housing, wherein the sensor is configured to sense (or sample) information that is being communicated over a conductor. The sensor may be a torroidal coil that includes a core (e.g., ferrite, etc.) and at least one wire (e.g., copper, etc.) wound around the core. Alternatively, the sensor may be a MEMS sensor, a Hall Effect sensor, a capacitive sensor, a resistive sensor and/or a direct (or physical) connection between the at least one wire and either the at least one circuit board or an external circuit. In one embodiment of the present invention, the at least one circuit board may include circuitry for storing, processing and transmitting the sensed information.

1. Field of the Invention
The present invention relates to a connector or, more particularly, to a connector (e.g., in-line connector, plug, receptacle, etc.) with (i) at least one sensor for sensing information that is being communicated on at least one conductor and/or (ii) at least one circuit for processing, storing and/or transmitting said information and/or a resultant thereof.
2. Description of Related Art
Connectors are used in many applications, including commercial, consumer and military applications. Connectors are typically used to transmit information (e.g., a voltage, current, etc.) from a first device to a second device. For example, a connector may be used to provide power from a power supply to a circuit. By way of another example, a connector may be used to provide analog and/or digital information from a first circuit to a second circuit. There are times, however, when a device in communication with a connector is either malfunctioning or needs to be monitored. Traditionally, this is done using a multi-meter (e.g., volt meter, ohm meter, etc.) or an oscilloscope.
There are several drawbacks, however, of using a multi-meter or an oscilloscope to measure and/or monitor a device. For example, it may be difficult to physically place a probe of the multi-meter on a conductor (or lead) of the device if the conductor is either too small, closely located to another conductor, or located in a concealed environment. Further, a user may have to hold the probe on the conductor, thereby preventing the user from performing other tasks. Such a system can also make it difficult for the device to be monitored over an extended period of time. There is even a chance that the multi-meter, itself, can alter or effect the signal that is being measured, thereby resulting in a false measurement.
Thus, it would be advantageous to provide a system and method that overcomes at least some of the foregoing drawbacks.

System and method for sensing information that is being communicated through a connector

Deutsch Engineered Connecting Devices, Inc.


Apparatus in a transceiver for broadcasting priority rated messages on a channel shared by a multiplicity of similar transceivers, converts an analog audio frequency message to compressed digitalized format which is stored, encrypted, and encoded with a priority rating and recipient identity code. A central data processor prevents broadcast of the message while any other message of higher priority rating is being broadcast, or interrupts broadcast of the message when broadcast of another message of higher priority is detected, or interrupts broadcast of any other message of lower priority than that of a message waiting to be broadcast. Received messages bearing the recipient's identity code are stored and played back in order of their priority rating.

1. Field of the Invention
This invention relates to the art of radio transceiver systems and more particularly concerns transceiver apparatus and a method for broadcasting priority rated messages on a communication channel of a multiple transceiver system.
2. Description of the Prior Art
Vehicles in fleets currently communicate with each other via radio transceivers or two-way radios as they are popularly known. These radio transceivers share the same narrow communication channel or assigned broadcast frequency. In operation, it is necessary that the channel be clear and free from any communication signals in order for a message to be sent by any one transceiver to any one or more other transceivers. The operator of a sending transceiver must wait until the channel is clear before his transmission begins. This waiting is required regardless of the urgency of the message to be sent, and is not only objectionable, but it also can create a hazardous, emergency condition. If the operator does not wait, and he initiates boradcast of a message while a prior message already occupies the available channel, loss of comprehensibility of both messages occurs. In emergency service situations this mixing and consequent garbling of messages can constitute a serious safety hazard. This hazard is particularly objectionable in emergency service fields such as police, fire, ambulance, rescue, military, etc . . . The hazard of a message "traffic jam" also exists in related services and applications employing two-way radio communication systems, such as air traffic control, construction projects, road building, truck convoys, etc . . .

Apparatus and method for broadcasting priority rated messages on a radio communications channel of a multiple transceiver system


The present invention provides a fluidized bed for dispensing small quantities of powders. The fluidized bed is made using a porous housing to permit injection and removal of fluid through the surrounding walls to improve the operation of the bed particularly for small particles of the group C size, including significantly reducing powder adhesion to the walls. In one aspect of the invention the fluidized bed housing is rotated about its longitudinal axis, which may be oriented at any suitable angle. A system for changing the volume of the bed is described as is a system for incorporating injection nozzles within the bed for constant agitation and prevention of powder adhering to the walls of the housing.

The present invention relates to devices for the metering of small quantities of powder from fluidized beds through a volumetric measuring device.
Accurate metering of a given quantity of powder is often required in various processes including chemical engineering and pharmaceutical processes. When the metered quantity is large, this is relatively easily achieved. However, when the required quantity is very small, this becomes very difficult if high accuracy is required at the same time. In addition, if very fine powder is used, strong interparticle forces cause the powder to agglomerate, thus making the precise metering even more difficult.
Pulmonary drug delivery represents a new drug administration method that provides many advantages. It provides direct and fast topical treatments to respiratory and lung diseases. It has less first-pass GI (gastrointestinal) metabolism and can provide targeted delivery to heart and brain. Drugs such as peptides can be systemically delivered using the pulmonary channel. Pulmonary drug delivery also allows the use of drugs with low solubility. Antibiotics and even vaccines can be delivered in this manner. Compared to oral in-take, it provides a fast and much more efficient adsorption. Typically, only a few percent of the medication of the oral in-take is required for pulmonary delivery. Compared to intravenous injection, it provides a painless and safe alternative.
To facilitate pulmonary delivery, drug powders should normally be less than 5 xcexcm so that they become airborne during inhalation. However, powders of such small sizes (typical group C powder in the Geldart classification) have very strong interparticle forces that make them agglomerate and cohesive, and thus very difficult to handle. Since the required dosage for pulmonary delivery is also very small (usually in the order of 1 xcexcg-100 mg), this makes it very difficult to accurately meter such a small quantity and fill them into packages.
To overcome the interparticle forces, current industrial practice applies two different methods; one involves mixing the ultrafine drug powders with large amounts of coarser powder, and the other the suspension of the powder in liquid. The first method uses a large quantity of excipient (filler) particles that are much larger (normally group A or group A-C powders in the Geldart classification). This makes the small-large powder mixture fluidize and flow easily so that they can be handled more easily. It also significantly increases the volume of each dosage so that the dispensing becomes more accurate when the drug powder is packaged into the Dry Powder Inhaler (DPI). However, only a small fraction of the small drug particles can detach effectively from the large excipient particles during inhalation and the rest stay with the large particles and land in the mouth, limiting the efficiency of final delivery to about 10-15%.
The second method involves suspending the ultrafine drug powders into liquids such as hydrocarbon propellants and storing them in Metered Dose Inhalers (MDI). When a metered quantity of the propellant is released from the storage canister, the propellant evaporates and expands quickly to disperse the powdered drug into the patients"" mouth. The key problem with this method is that the quick expansion of the propellant causes the drug to impact in the back of the throat and other places in the mouth, reducing the amount being inhaled into the lung to less than 10-15%. This method also needs good breath coordination, since it is difficult to predict the amount of drug inhaled if the patients"" inhalation does not coincide with the drug releasing.
Thus both currently practiced methods have significant limitations. It would be ideal if the required small quantity of the fine drug powder could be accurately dispensed alone, without any other chemical or physical constituents. When only the pure drug powder is packaged into the inhaler, the delivery efficiency is expected to increase significantly. However, this tends to be fairly difficult if the quantity to be packaged is extremely small. For example, if each dose contains 0.5 mg or 500 xcexcg of drug powder and the bulk (packed) density of the powder is 0.5 mg/mm3(=500 kg/m3), the total volume of the powder withdrawn for each dose is only 1.0 mm3.
Fluidization occurs when particulate materials of sub-micrometers to several millimeters are suspended by up-flowing gas in a vessel or column to form a gas-solid suspension more commonly referred to as a fluidized bed. The fluidized beds formed with the gas-solid suspension are specifically referred to as gas-solid fluidized beds. The term xe2x80x9cfluidized bedxe2x80x9d applies because the gas-solid suspension formed by the solid particles and the upflowing gas behaves like a fluid. Although primarily gas is used as fluidizing fluid, liquid can also be used. In some cases, both gas and liquid are used together. Those are called liquid-solid fluidized beds and gas-liquid-solid three-phase fluidized beds.
A gas-solid fluidized bed can operate in several fluidization regimes: particulate, bubbling, slugging and turbulent fluidization regimes (conventional fluidized beds), and fast fluidization and pneumatic transport regimes (high-velocity fluidized beds). In a conventional fluidized bed, there are usually two distinct regions: the upper dilute region (also called the freeboard region) and the bottom dense region which has most of the particles and also contains many more particles per volume than the dilute region. In a high-velocity fluidized bed, almost all particles are carried upwards by the high-velocity upflow gas and almost the entire bed is in a dilute suspension region. There is also a downflow fluidization regime where gas and particles flow co-currently downward in a dilute suspension form.
A typical design of a fluidized bed includes a gas distributor at the bottom of the fluidized bed column, the main function of which is to uniformly distribute the gas into the fluidized bed. The vessel that contains the fluidized bed can have any suitable shape, but those with cylindrical or rectangular cross-sections and oriented on a substantially vertical axis are commonly used. The vertical walls are usually of solid materials to prevent the gas and solids from escaping from the fluidized beds.
Sometimes, it is necessary to have solid feeds and withdrawal ports and/or heat transfer tubes or panels mounted on the wall(s) of a fluidized bed. At the top of the bed, there is usually a plate or similar structure that seals the top of the fluidization column. There is usually at least one exit port through the top plate and/or the side wall not far below the top plate that allow gas and entrained solids to leave the fluidized bed and enter into gas-solid separation devices or other vessels or other process units. Those particles that leave the fluidized bed are entrained out by the gas flow, i.e. by solids entrainment.
Powders may be classified into four groups in gas-solid fluidized systems, according to Geldart""s classifications. Groups B and D powders comprise large particles that typically result in large bubbles when fluidized. Group A powders comprise particles that first experience a significant expansion of the powder bed when fluidized before bubbles begin to appear. Group C powders comprise very small particles for which the interparticle forces significantly affect the fluidization behaviour. As the particle size reduces, interparticle forces increase significantly. Those strong interparticle forces cause the fine particles to agglomerate and make them very cohesive. Typical Group C powders comprise particles under 30-45 xcexcm in size, although some very sticky powders larger than these sizes may also belong to Group C powders. Due to strong interparticle forces, Group C powders are either very difficult to fluidize (with channeling and/or very poor fluidization) or mainly fluidize with the large agglomerates as pseudo-particles rather than as individual particles. In either case, fluidization of individual particles cannot be achieved easily so that handling of Group C powders becomes a difficult problem.
Different measures can be taken to assist the fluidization of Group C powders. Those methods are usually referred to as fluidization aids. Fluidization aids include mechanical stirring, mechanical, acoustic or ultrasonic vibration, addition of much larger particles or other objects to provide extra stirring, addition of finer particles to act as xe2x80x9clubricantxe2x80x9d, pulsation of fluidization gas, etc. Some aids are more effective than others for a given Group C powder, but the effectiveness of almost all aids tends to diminish as the powder becomes finer.
Group C powders also tend to clog up in certain areas of the fluidized bed, such as above the gas distributor, around internals and at exit port(s), and to stick to the internal wall or the ceiling of the bed. Large chunks of powder form in those places and then break from time to time as they grow and become unstable. As those chunks of particles from the ceiling or upper portion of the bed fall back into the fluidized bed, they disturb the flow hydrodynamics inside the bed, causing periodical variation of the bed density and other properties in both the bottom dense phase region and the upper dilute phase region.
Key characteristics of fluidized beds include easy handling of particles, excellent contact between gas and solids, excellent heat and mass transfer between gas and solids and between gas-solid suspensions and the column wall, good gas and solids mixing, etc. These and other useful characteristics have led to the wide application of fluidized beds in process and other industries. The xe2x80x9ceasy handling of particlesxe2x80x9d is due to the uniform solids suspension inside the bed and the relatively free movement of the particles within the gas-solids suspension and of the suspension itself.
Several well known problems currently exist with the fluidized beds pertaining to the metering of fine particles, especially Group C particles. Solids entrainment can sometimes cause problems to the maintenance of a uniform suspension, since entrained particles may flow out of the fluidized bed with the gas stream from the top exit. In order to maintain a constant suspension, escaped particles must be separated from the gas stream (by cyclone, bag filter and/or other devices) and returned. Because there is limitation on the separation efficiency, some particles may be lost even with several stages of separation, leading to a reduction of the powder inventory. This presents a serious problem in some cases where it is essential not to lose particles, such as in the case where expensive drug powder is handled. In this case, a filter may be installed inside or just at the exit port to stop the entrained particles from flowing out of the bed in the first place. However, such filters are plugged very quickly that periodical purging is essential. In addition, such filters also produce a high pressure drop that a very large filter area has to be created to allow enough gas to flow through.
The main problem associated with particle loss and with the gradual decrease of solids inventory due to continuous metering out of particles, is the reduction of solids suspension density. Such variations in solids suspension density may reduce the accuracy of powder metering from the fluidized bed. One measure is to continuously add additional particles into the fluidization column. An alternative measure proposed in this invention and discussed hereinafter is to gradually decrease the volume of the fluidized bed by moving one or more side of the column wall inwards.
Another problem with fluidized beds is that local dead zones or defluidization may occur due to the non-uniform gas distribution at the bottom or due to other reasons such as agglomeration of fine or ultrafine (Group C) particles. This can result in non-uniform and unpredictable suspension density, and other undesirable consequences. For greater certainty, particle agglomeration happens when very fine powder, such as the drug powder for pulmonary drug delivery, is fluidized. Such agglomeration causes non-uniform solids suspension and solids flow, greatly reducing the accuracy of powder metering from the fluidized bed.
Yet another problem is that some particles tend to stick on the inner wall or the top plate of the fluidization vessel/column. This is especially true when very fine particles are fluidized. This can lead to unwanted solids accumulation on the wall. Accumulation of particles on the wall reduces the solids holdup (=concentration) in the bed, making it difficult to precisely control the fluidized bed density, as desired in some processes. Those particles stuck on the wall may also fall periodically back to the bed (for example, when the accumulation is too thick), changing suddenly the bed density, that is, the solids concentration in the bed. A rotating fluidized bed can be used to overcome this problem. The concept of rotating fluidized bed with porous walls is known, however such beds are rotated to generate centrifugal force to the particles in the bed and are known as centrifugal fluidized beds. In these devices, the cylindrical wall is porous. The porous wall is used as gas distributor for the fluidizing gas to flow inward in all radial directions into the bed and the gas exits through the axial end(s) of the cylinder. The purpose of rotating the cylindrical (horizontal or vertical) vessel is to create a centrifugal force to hold the particles towards the cylindrical wall so that higher fluidization velocity can be used without producing large bubbles in the bed and/or without having significant solids entrainment. This allows the same bed to be operated at higher gas velocity so that the process capacity is increased. Example references that provide the details of such rotating fluidized beds include R Pfeffer, G I Tardos and E Gal, xe2x80x9cThe use of a rotating fluidized bed as a high efficiency dust filterxe2x80x9d, in Fluidization V, eds., K. Ostergaard and A. Sorensen, Eng. Foundation, New York, pages 667-672, 1986; J. Kao, R Pfeffer and G I Tardos, xe2x80x9cOn partial fluidization in rotating fluidized bedsxe2x80x9d, American Institute of Chemical Engineering Journal, Volume 33, pages 858-861, 1987; Qian G-H, I Bagyi, R Pfeffer, H Shaw and J G Stevens, xe2x80x9cA parametric study on a horizontal rotating fluidized bed using slotted and sintered metal cylindrical gas distributorsxe2x80x9d, Powder Technology, Volume 100, pages 190-199, 1998; Qian G-H, I Bagyi, R Pfeffer and H Shaw, xe2x80x9cParticle mixing in rotating fluidized beds: inferences about the fluidized state xe2x80x9d, American Institute of Chemical Engineering Journal, Volume 45, pages 1401-1410, 1999; and U.S. Pat. No. 6,197,369.
However, the key design concepts and the purpose of such prior art centrifugal fluidized beds are significantly different from the rotating and porous fluidized bed dispenser proposed in this invention.
U.S. Pat. No. 5,826,633 issued to Parks et al. is directed to a powder filling apparatus which uses gravity to assist filling of a metered chamber. The metered chamber is placed below a convergent passageway containing the powder that is being dispensed. While the method and device involves xe2x80x9cfluidizingxe2x80x9d the powder to overcome inter-particle cohesive forces, they defined fluidizing powder as xe2x80x9cthe powder is broken down into small agglomerates and/or completely broken down into its constituents or individual particlesxe2x80x9d. In their definition, upflowing gas is not essential to cause the powder to be fluidized. This is significantly different from the conventional definition of fluidization, as followed in this patent application, that powder is fluidized when it is suspended in an upflowing gas (or liquid). As a result, the device is not per se a fluidized bed since in this device all particles fall unassisted by gravity. In conventional fluidized beds particles are suspended by the fluidizing gas and very few, if any, particles can fall unassisted by gravity. Further, some typical components of a fluidized bed such as an air distributor is missing in this device. In addition, other problems as described above in this invention, such as sticking of particles to the inner surface of the convergent chamber is still problematic with this type of device.
U.S. Pat. No. 6,183,169 issued to Zhu et al. is directed to a device for precision dispensing of fine powders. This device includes two fluidized bed chambers communicating with each other and operates by first fluidizing a fine powder in one chamber and then using a pressure differential between the chambers to draw the fluidized particles into the second chamber. A solenoid valve attached to the second chamber is opened for a selected period of time to dispense the powder in the form of gas-solid suspension to a collection area. The two-chamber concept utilized by Zhu et al. in U.S. Pat. No. 6,183,169 is different from the one used in the current invention. It uses a two-stage method to dilute and control the gas-solids suspension and a Venturi mechanism to control the powder flow and to transport the powder from one stage to another, while the current invention only has one stage and does not require a Venturi or anything of such kind to control powder flow. In the device disclosed in Zhu et al. powder withdrawal is from the dilute phase in the second chamber.
Obviously, the key concepts of both U.S. Pat. Nos. 5,826,633 and 6,183,169 are different from the current invention.
In view of the difficulties and complexities with the prior art, it would be advantageous to provide a single fluidized bed which can dispense quantities of fine powder in an accurate and controlled manner which can be used for either batch or continuous processing of the fine powders. It would also be very advantageous to provide a fluidized bed system that significantly reduces solids accumulation on the walls of the fluidized bed, achieves total solids containment in the bed except for targeted particle withdrawal through selected ports, reduces or eliminates dead zones, and/or allows for the addition and removal of gas at various locations in the fluidized bed.
This invention utilizes the uniform solids suspension and easy mobility of particles inside the fluidized bed, from which particles are uniformly withdrawn to a fixed-volume cavity so that a definite quantity of particles can be metered out from the fluidized bed. To ensure consistency and accuracy of such powder metering, it is essential to maintain a constant and consistent gas-solids suspension inside the fluidized bed.
The method disclosed herein involves metering the powder flow from a fluidized bed where the particle suspension has a much lower density than that of packed (bulk) particles so that the withdrawal volume is significantly increased to increase metering accuracy, and where the particles are completely mobile so that a consistent withdrawal can be maintained.
The present invention also discloses rotating the porous fluidized bed to alternately switch the gas distributor, the bed wall and/or the top gas exit plate, so that particles stuck onto the wall can be continuously back purged off the wall when they are rotated to the bottom of the bed where the gas is introduced in the bed.
The current invention proposes the following alternatives to provide further agitation to the powder to enhance uniform fluidization: (1) rotating the fluidized bed, with or without adding large beads in the bed; (2) injecting additional gas into the bed at various locations in the bed through gas nozzles; and (3) using gas nozzles with flexible tube that can move randomly inside the bed.
An object of the present invention is to provide accurate volumetric metering of powder, either by filling a receptacle of given volume or by timing the powder flow at a given volumetric flow-rate, from a fluidized bed. In particular, this invention addresses the problems associated with metering of extremely small quantities (1 xcexcg-100 mg) of ultrafine ( less than 10 xcexcm) powders. To ensure precise metering, the invention provides fluidized bed structures that intend to ensure uniform and relatively constant gas-solids suspension inside the fluidized bed, by minimizing the problems associated with maintaining uniform gas-solids suspension and uniform fluidization. This invention also provides effective means to volumetrically meter and withdraw the required small quantities of powder in a very accurate and controlled manner.
It is a further object of the present invention to provide a fluidized system that may be used for reduction of solids accumulation on the walls, to provide a system that may be used for reduction or elimination of dead zones, and to provide a system that may be used to add and remove gas at various locations (e.g., along the axial direction).
Broadly, the present invention relates to metering a small quantity of powder from a fluidized bed using a volumetric method. It can be just any fluidized bed that can provide a steady gas-solid suspension and the withdrawal can be either from the dense phase or the dilute phase of the bed. An element of some suitable shape that has one or more cavities and that can be easily engaged and disengaged to the said fluidized bed with the cavities exposed to the fluidized bed is used for the metering and withdrawal.
Furthermore, the present invention relates to a fluidized bed structure comprising having a housing defining a fluidized bed chamber, means for introducing primary fluidizing fluid through one or more portion(s) of the surrounding walls into the chamber at one or more side(s) of the chamber and means for permitting the escape of the fluid through one or more portion(s) of the surrounding walls from the chamber at other one or more side(s) of said chamber. At least some of the walls of the chamber have a significant area that is porous, the porous area comprising pores having a size sufficiently small to prevent significant loss of particles from the fluidized bed.
This invention further relates to a powder metering and withdrawal mechanism that is attached to the fluidized bed. This mechanism includes an element of some suitable shape that has one or more small cavities (pockets, holes) and means (withdrawal port) to engage and disengage such element easily to/from the fluidized bed with the cavities exposed to the gas-solid suspension inside the fluidized bed.
In one aspect the present invention provides a fluidized bed for dispensing powders, comprising:
a) a housing defining an enclosure for containing particulate matter, said housing including a fluid injection means for injecting a fluid into said enclosure for fluidizing particulate matter contained within said housing for forming a dilute phase and a dense phase of fluidized powder in said housing; and
b) volumetric metering means connected to said housing and in flow communication with said enclosure through an outlet passageway for withdrawing pre-selected amounts of said particulate matter from said housing.
In another aspect of the invention there is provided a fluidized bed for dispensing powders, comprising:
a) a housing defining an enclosure for containing particulate matter, said housing including at least one porous wall having a suitable porosity to allow flow of fluid through said porous wall while preventing most of the particulate matter contained within said housing from passing through said porous wall, a fluid injection means for injecting a fluid into said enclosure for fluidizing particulate matter contained within said housing for forming either a dilute phase only or a dilute phase and a dense phase of fluidized powder in said housing; and
b) time controlled powder withdrawal means connected to said housing and in flow communication with said enclosure through an outlet passageway for withdrawing particulate matter from said housing for a pre-selected period of time.

Apparatus for volumetric metering of small quantity of powder from fluidized beds


A semiconductor module and a method for producing the same is disclosed. In one embodiment, the semiconductor module has adjacent regions on a common wiring substrate in a common plastic housing composition. The regions are thermally decoupled by a thermal barrier. Semiconductor chips whose evolution of heat loss differs are arranged in these thermally separate regions, the thermal barrier ensuring that the function of the more thermally sensitive semiconductor chip is not impaired by the heat-loss-generating semiconductor chip.

The invention relates to a semiconductor module including semiconductor chips in a plastic housing in separate regions, and to a method for producing the same.
In order to produce multichip semiconductor modules, thermally sensitive semiconductor chips together with thermally more robust semiconductor chips are often enclosed in a common plastic housing composition.
For thermal reasons, however, it would be expedient to accommodate these semiconductor chips in separate housings and therefore to mount them in dedicated housings. The separate construction of individual housings has the disadvantage, however, that a rapid and interference-free data exchange between the individual semiconductor chips is impeded by the mounting of the separate housings on a superordinate printed circuit board. Therefore, despite the thermal coupling, mounting in common plastic housings of a multichip package may be preferred. For the heat transfer from one semiconductor chip to the adjacent semiconductor chip, it is relatively unimportant whether the semiconductor chips are accommodated in the multichip housing of the semiconductor module using flip-chip technology or are electrically coupled to one another with the aid of bonding technology. The problem of the thermal coupling and the heating of a thermally sensitive semiconductor chip by an adjacent semiconductor chip having a high heat loss still remains.
In this case, the heat conduction through the common plastic housing composition is one of the most important thermal paths on which the mutual adverse thermal influencing of the semiconductor chips of the semiconductor module is based. Semiconductor modules which accommodate individual semiconductor chips in separate plastic housing compositions but have a common wiring substrate also likewise have the disadvantage of impeding a rapid and low-interference communication between the individual semiconductor chips. Moreover, the connecting lines on the common substrate are not mechanically protected perfectly in the way that is possible with a common plastic housing composition.
For these and other reasons, there is a need for the present invention.
It is an embodiment of the invention to overcome the disadvantages in the prior art and to provide a semiconductor module in which the thermal coupling in a common plastic housing composition between two separately arranged semiconductor chips is reduced.
The invention provides a semiconductor module including semiconductor chips, in a plastic housing in separate regions, wherein the semiconductor chips are embedded in a common plastic housing composition and are arranged on a common wiring substrate in adjacent regions. The wiring substrate has a thermal barrier between the regions, which thermal barrier impedes the heat transfer from one region to an adjacent region. In this case, the thermal barrier, the semiconductor chips and the substrate are surrounded by the common plastic housing composition.
This semiconductor module has one advantage that the heat conduction path via the common plastic composition is interrupted by the thermal barrier, such that thermally sensitive semiconductor chips, such as e.g., dynamic memories, the recovery time of which would be impaired at high temperature, are now protected from a semiconductor chip, e.g., a processor, having a significantly higher evolution of heat loss. For a semiconductor module equipped with a thermal barrier as claimed in the invention, this affords the possibility of the recovery time of a dynamic memory not being impaired despite a high heat loss e.g., of a processor, such that the memories can be utilized with a correspondingly high data transfer rate.
In one embodiment, the material of the thermal barrier has a specific heat conduction WB of less than ⅓ of the specific heat conduction WK of the common plastic housing composition where WK≧3 WB. This difference in the specific heat conduction has the effect of ensuring a considerable decoupling between the two regions of the semiconductor module for the semiconductor chips arranged in the corresponding regions. In order to position the thermal barrier stably and effectively on the wiring substrate, the thermal barrier has a width B that is at least five times the thickness D of the semiconductor chips where B≧5D.
The thermal barrier can be formed in various ways. It can first of all thermally shield a region to be protected from an adjacent region just on one side or else surround the region to be protected on two sides. Furthermore, there are possibilities available, depending on the size of the substrate, for surrounding the region to be protected on three sides or providing it with a thermal barrier completely on all four sides.
A thermal barrier of this type can have a prefabricated thermal barrier element which is prepositioned in the injection mold during the injection-molding of the plastic housing composition. On the other hand, the prefabricated thermal barrier element can also be adhesively bonded onto the top side of the substrate before the plastic housing composition is applied onto the substrate. Secure positioning of the thermal barrier element is possible in both cases. The thermal barrier element itself can be composed of a plastic material with a filler material different from the plastic housing composition.
The different filler material makes it possible to achieve the abovementioned difference in thermal conductivity. Other thermal barrier materials have ceramic prefabricated thermal barrier elements, which, given correspondingly high polycrystalline structuring, have a correspondingly lower heat conduction in comparison with the heat-conducting plastic. In principle, it is possible both to arrange the thermal barrier around the region of a heat-loss-generating semiconductor chip and to construct it around the region of a thermally sensitive semiconductor chip. However, the thermal barrier is moved into the vicinity of the thermally sensitive semiconductor chip in order not to impede the heat loss emission of the heat-loss-generating semiconductor chip via the plastic housing composition of the semiconductor module and in order only to prevent the introduction of heat into the region of the thermally sensitive semiconductor chip.
A method for producing a semiconductor module, including semiconductor chips in a plastic housing in separate regions, has the following method processes. The first process involves producing semiconductor chips which are characterized by different thermal sensitivities and are provided for a semiconductor module. This is followed by applying a thermal barrier between adjacent regions which are to be thermally decoupled onto a wiring substrate.
The semiconductor chips are subsequently accommodated onto the common wiring substrate, but in distributed fashion, in the thermally decoupled regions. Finally, the device components, namely the semiconductor chips, the wiring substrate and the thermal barrier, are packaged into a common plastic housing composition while embedding the thermal barrier. This method has the advantage that externally it cannot be seen from the semiconductor module whether a thermal barrier is integrated into the plastic housing. Consequently, a semiconductor device of this type can be packaged into a plastic housing composition with the aid of known injection-molding technology without changing the standardized housing types.
An alternative to this method provides for preparing a thermal barrier element and positioning and fixing it in an injection mold. Finally, when packaging the components in a plastic housing composition, the thermal barrier element prepositioned in the injection mold is arranged on the substrate. The fixing of a thermal barrier of this type in an injection mold can be effected in force-locking fashion, such that a fixing consists in the thermal barrier element being pressed into the injection mold.
When applying the thermal barrier element onto the substrate, there is the risk of the high injection-molding pressure causing the thermal element to shift on the substrate. Therefore, in a further embodiment of the method, it is provided that the thermal barrier has passage openings in order to ensure a uniform distribution of the plastic housing composition during injection-molding. This is employed particularly when the thermal barrier, or the thermal barrier element, completely surrounds the thermally sensitive semiconductor chip, such that through the openings in the thermal barrier element it is possible for the region surrounded by the thermal barrier to be completely filled with plastic housing composition without the position of the thermal barrier element being shifted.
To summarize, it can be established that the solution as claimed in the invention makes it possible to incorporate semiconductor chips whose evolution of heat loss differs in a common plastic housing composition within a semiconductor module. In this case, the thermal barrier has a plastic material having a significantly lower thermal conductivity than the plastic housing composition. In this case, the thermal barrier element can surround the semiconductor chip which is to be thermally insulated in ring-shaped fashion.
For the efficacy of the thermal barrier it is not critical, however, whether the IC having the highest evolution of heat loss or the IC having the lower evolution of heat loss is enclosed by the thermal barrier. For the thermal management it is advantageous, however, for the semiconductor chip having the lower evolution of heat loss to be surrounded by the thermal barrier. The thermal barrier preferably has a smaller height than the plastic housing composition, such that both the semiconductor chips and the thermal barrier are enclosed by the plastic housing composition on three sides.
FIG. 1 illustrates a schematic cross section through a semiconductor module 9 of a first embodiment. The semiconductor module 9 has two semiconductor chips 1 and 2, which are embedded in a common plastic housing composition 6. The semiconductor chips 1 and 2 are arranged on a wiring substrate 7 and electrically connected to a wiring structure 13 of the wiring substrate 7 by using flip-chip contacts 12. The wiring structure 13 is connected to external contact areas 14 of the semiconductor module 9 on the underside 15 of the wiring substrate 7 by using through contacts (not shown) through the wiring substrate 7, the external contact areas 14 carrying external contacts 16 in the form of solder balls.
In this embodiment, the semiconductor module 9 has two regions 4 and 5, wherein one region 4 thermally decouples the thermally sensitive semiconductor chip 2, which is a dynamic memory in this case, by using a thermal barrier 8 from the region 5 containing the semiconductor chip 1, which is a microprocessor having a high evolution of heat loss in this embodiment. The thermal barrier 8 completely surrounds the semiconductor chip 2, wherein, in this embodiment of the invention, the thermal barrier 8 has a typical thermal conductivity of 0.2 W/mK and the plastic housing composition 6 has a thermal conductivity of 0.7 W/mK. In this embodiment of the invention, the width B of the thermal barrier 8 is 6 mm, while the thickness D of the semiconductor chips 1 and 2 is just 0.55 mm.
The distance between the two adjacent semiconductor chips 1 and 2 is approximately 10 mm. A rough calculation reveals that the thermal resistance is increased by a factor of 1.8 by the thermal barrier 8 in comparison with a semiconductor module not provided with a thermal barrier 8. Consequently, the heat transfer between the individual semiconductor chips in this multichip semiconductor module is curbed by the thermal barrier made of plastic, wherein the plastic body of the thermal barrier 8 is completely embedded into the plastic housing composition 6 and, consequently, this semiconductor module cannot be differentiated externally from conventional semiconductor modules. The size of the thermal barrier becomes visible only from an X-ray photograph or from a cross section through the semiconductor module.
FIG. 2 illustrates a sectional view through the semiconductor module 9 in accordance with FIG. 1 along the sectional plane A-A. In this embodiment of the invention, the areal extent of the semiconductor chips 1 and 2 is identical in magnitude, the thermally sensitive semiconductor chip 2 being arranged in a region 4 completely surrounded by a thermal barrier 8. The thermal barrier 8 was adhesively bonded onto the top side 17 of the wiring substrate 7 in the form of a thermal barrier element 10 prior to the application of the plastic housing composition 6. The semiconductor chips 1 and 2 are connected to the wiring structure 14 on the top side 17 of the wiring substrate 7 by using flip-chip contacts, which cannot be seen in this sectional plane. The plastic housing 3 has a plastic housing composition 6, the areal extent of which is smaller than the areal extent of the top side 17 of the wiring substrate 7. Moreover, the plastic housing 3 is formed such that it is slightly inclined relative to the sectional plane in its edge sides 18, 19, 20 and 21.
The thermal barrier element 10 has in the section plane openings 22 which are arranged in the lateral regions of the thermal barrier 8 which are not arranged adjacent to the heat-loss-generating semiconductor chip 1. The openings 22 ensure that, during the introduction of the plastic housing composition 6, the region 4 surrounded by the thermal barrier 8 is completely filled with plastic housing composition 6.
FIG. 3 illustrates a plan view of a semiconductor module 11 of a second embodiment. Components having the same functions as in the previous figures are identified by the same reference symbols and are not discussed separately. The difference between the second embodiment in accordance with FIG. 3 and the embodiment in accordance with FIG. 1 is that the semiconductor chips 1 and 2 have a different areal extent, wherein the heat-generating chip 1, the contour of which is identified by a dashed line 23, takes up a larger area than the thermally sensitive semiconductor chip 2, which is surrounded on two sides by a thermal barrier element 10, the contour of which is marked by a dash-dotted line 24. In this case, no openings are provided in the thermal barrier 8 since no obstacle is present on two sides of the semiconductor chip 2, such that the plastic housing composition 6 can completely embed the semiconductor chip 2 and the thermal barrier 8 during injection-molding.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.

Semiconductor module including semiconductor chips in a plastic housing in separate regions