WO2002094534A1

WO2002094534A1 - Method for the production of castings from polyamide nanocomposites

Info

Publication number: WO2002094534A1
Application number: PCT/EP2002/005472
Authority: WO
Inventors: Walter Heckmann; Rainer Klenz; Christof Mehler; Falko Ramsteiner; Jens Rieger
Original assignee: Basf Aktiengesellschaft
Priority date: 2001-05-23
Filing date: 2002-05-17
Publication date: 2002-11-28
Also published as: DE10125560A1

Abstract

The invention relates to a method for the production of moulded parts by injection moulding using polyamide nanocomposites. Said moulded parts contain A) at least one polyamide A) and B) at least one delaminated phyllosilicate B). The inventive method involves injecting a melt containing A) and B) via a gate into an injection mould. The invention is characterized by the selection of injection moulding conditions in a manner known per se, allowing the melt to flow inside the injection mould in a substantially parallel manner so that a high orientation can be obtained therefor, said orientation exhibiting transition.

Description

Process for the production of molded parts from polyamide nanocomposites

description

The invention relates to a method for producing molded parts from polyamide nanocomposites, containing

A) at least one polyamide A), and

B) at least one delaminated layered silicate B)

in the injection molding process by introducing a melt containing A) and B) via a sprue into an injection molding tool.

In addition, the invention relates to the moldings obtainable by the process, and to a process for increasing the toughness of moldings made of polyamide nanocomposites containing at least one polyamide A) and at least one delaminated layered silicate B).

Polyamide nanocomposites are thermoplastic molding compounds containing polyamide and layered silicates delaminated as fillers and reinforcing materials.

Such materials and molded parts made therefrom are, for. B. from the documents WO-A 94/11430, WO-A 93/04118, WO-A 93/04117, WO-A 99/41299 and EP-A 940430 known. Although moldings have from those described there molding compositions for some applications adequate mechanical properties, but they are for specific applications too brittle, ie the total fracture energy W _tot according to DIN 53443 in the multiaxial impact test is comparatively small and the toughness is too low.

The task was to remedy the disadvantages described. In particular, the object was to provide a process for the production of moldings from polyamide nanocomosites, which provides moldings with improved toughness (reduced brittleness), in particular improved multiaxial toughness.

In particular, the task was to provide a method that delivers such molded parts with a higher total damage work W _g e _S (according to DIN 53443).

Accordingly, the process defined at the outset was found. It is characterized in that the injection molding conditions are selected in a manner known per se such that the melt in the injection molding tool flows essentially in parallel, as a result of which a high orientation of the melt is achieved, and that the high orientation of the melt is frozen when the melt solidifies.

Furthermore, the moldings obtainable by the process were found, as well as a process for increasing the toughness of moldings made of polyamide nanocomposites, containing at least one polyamide A) and at least one delaminated layered silicate B). Preferred embodiments of the invention can be found in the subclaims.

Surprisingly, molded parts with significantly improved toughness, in particular improved overall damage work W _total , are obtained if special injection molding conditions are set.

Component A)

20 As component A), the polyamide nanocomposites contain at least one polyamide A).

Polyamides with an aliphatic semi-crystalline or partially aromatic and amorphous structure of any kind and their 25 blends, including polyether amides such as polyether block amides, are suitable. For the purposes of the present invention, polyamides should be understood to mean all known polyamides.

Such polyamides generally have a viscosity number of 30 90 to 350, preferably 110 to 240 ml / g, determined in a 0.5% strength by weight solution in 96% strength by weight sulfuric acid at 25 ° C. according to ISO 307 ,

Semi-crystalline or amorphous resins with a molecular weight 35 (weight average) of at least 5,000, e.g. U.S. Patents 2,071,250, 2,071,251, 2,130,523, 2,130,948, 2,241,322, 2,312,966, 2,512,606 and 3,393,210 are preferred. Examples include polyamides derived from lactams with 7 to 13 ring members, 40 such as polycaprolactam, polycapryllactam and polylaurine lactam, and polyamides obtained by reacting dicarboxylic acids with diamines.

Alkanedicarboxylic acids with 6 to 12, in particular 45, 6 to 10 carbon atoms and aromatic dicarboxylic acids can be used as dicarboxylic acids. Here are adipic acid, azelaic acid, sebacin Suitable promoters are potassium, sodium, manganese, chromium, cobalt, tungsten, molybdenum, nickel, iron, magnesium, calcium or mixtures thereof, preferably potassium, manganese, chromium, molybdenum or mixtures thereof, particularly preferably potassium, chromium, molybdenum or their mixtures mixtures.

The shape and shape of the catalysts according to the invention can be selected as desired, such as tablets, rings, stars, wagon wheels, extrudates such as cylinders, pellets or strands, ring tablets or tablets are preferred.

The purification of ethylene with the catalysts according to the invention can be carried out as follows:

The ethylene to be cleaned can be processed in a two-step process

a) in the presence of hydrogen on the catalysts of the invention in the reduced state at a temperature of 70 to 110 ° C, preferably 75 to 100 ° C, particularly preferably 80 to 95 ° C and a pressure of 5 to 80 bar, preferably 10 to 70 bar, particularly preferably 20 to 60 bar and then

b) on the catalysts according to the invention in the oxidized state at a temperature of 70 to 110 ° C., preferably 75 to 100 ° C., particularly preferably 80 to 95 ° C. and a pressure of 5 to 80 bar, preferably 10 to 70 bar, particularly preferably 20 to 60 bar can be implemented.

The catalysts of the invention have a higher resistance to acetylenes than those catalysts which have not undergone inventive post-treatment by post-calcining the shaped bodies. The catalysts of the invention can be operated with a content of up to 200 [ppm] acetylenes in ethylene to be purified.

This two-stage process can be preceded by a hydrogenation stage, which conducts the ethylene to be purified in the presence of a sufficient amount of hydrogen over a hydrogenation catalyst, for example a noble metal hydrogenation catalyst, for example 0.3% by weight of Pd on an Al 0 _{3 support} . This is usually indicated if the ethylene to be cleaned contains large amounts of acetylenes, ie amounts of more than 200 [ppm]. Process for the production of molded parts from polyamide nanocompo sites

description

The invention relates to a process for the production of molded parts from polyamide nanocomposites containing

A) at least one polyamide A), and

B) at least one delaminated layered silicate B)

Such materials and molded parts made therefrom are, for. B. from the documents WO-A 94/11430, WO-A 93/04118, WO-A 93/04117, WO-A 99/41299 and EP-A 940430 known. Although moldings have from those described there molding compositions for many applications sufficient mechanical natural sheep s, but they are brittle for certain applications, the total fracture energy W _tot ie according to DIN 53443 in the multiaxial impact test is comparatively small and the toughness is too low.

In particular, the object was to provide a method which such molded parts having a higher overall fracture energy W _tot (according to DIN 53443) provides.

Surprisingly, molded parts with significantly improved 15 ter strength, especially improved overall fracture energy Wg _it when setting specific injection molding conditions.

Component A)

Alkanedicarboxylic acids with 6 to 12, in particular 45, 6 to 10 carbon atoms and aromatic dicarboxylic acids can be used as dicarboxylic acids. Here are adipic acid, azelaic acid, sebacin Acid, dodecanedioic acid (= decanedicarboxylic acid) and terephthalic and / or isophthalic acid are mentioned as acids.

Particularly suitable diamines are alkanediaes having 6 to 12, in particular 6 to 8, carbon atoms and -xylylenediamine, di- (4-aminophenyl) methane, di- (4-aminocyclohexyl) methane, 2,2-di- (4 -aminophenyl) propane or 2,2-di- (4-aminocyclohexyl) propane.

Preferred polyamides are polyhexamethylene adipic acid amide (PA 66) and polyhexa ethylene sebacic acid id (PA 610), polycaprolactam (PA 6) and copolyamides 6/66, in particular with a proportion of 5 to 95% by weight of caprolactam units.

PA 6, PA 66 and copolyamides 6/66 are particularly preferred. Polyamide 6 (PA 6) is very particularly preferred.

Polyamides may also be mentioned, e.g. can be obtained by condensing 1,4-diaminobutane with adipic acid at elevated temperature (polyamide-4, 6). Manufacturing processes for polyamides of this structure are e.g. in EP-A 38 094, EP-A 38 582 and EP-A 39 524.

Other examples are polyamides which are obtainable by copolymerizing two or more of the aforementioned monomers, or mixtures of two or more polyamides, the mixing ratio being arbitrary.

Furthermore, those partially aromatic copolyamides such as PA 6 / 6T and PA 66 / 6T have proven particularly advantageous, the triamine content of which is less than 0.5, preferably less than 0.3% by weight (see EP-A 299 444). The partially aromatic copolyamides with a low triamine content can be prepared by the processes described in EP-A 129 195 and 129 196.

The following non-exhaustive list contains the named ones, as well as further polyamides in the sense of the invention (the monomers are given in brackets):

PA 46 (tetramethylene diamine, adipic acid) PA 66 (hexamethylene diamine, adipic acid) PA 69 (hexamethylene diamine, azelaic acid). PA 610 (hexamethylene diamine, sebacic acid) PA 612 (hexamethylene diamine, decanedicarboxylic acid) PA 613 (hexamethylene diamine, undecanedicarboxylic acid) PA 1212 (1,12-dodecanediamine, decanedicarboxylic acid) PA 1313 (1, 13-diaminotridecane, undecanedicarboxylic acid)

PA MXD6 (m-xylylenediamine, adipic acid)

PA TMDT (Tri ethylhexamethylene diamine, terephthalic acid)

PA 4 (pyrrolidone) PA 6 (ε-caprolactam)

PA 7 (ethanolactam)

PA 8 (caprylic lactam)

PA 9 (9-aminopelargonic acid)

PA 11 (11-aminoundecanoic acid) PA 12 ((laurolactam)

These polyamides and their production are known. The person skilled in the art can find details on their production in Ullmann's Encyclopedia of Technical Chemistry, 4th edition, vol. 19, pp. 39-54, Verlag Chemie, Weinheim 1980, and Ullmann's Encyclopedia of Industrial

Chemistry, Vol. A21, pp. 179-206, VCH Verlag, Weinheim 1992, and Stoeckhert, Kunststofflexikon, 8th edition, pp. 425-428, Hanser Verlag München 1992 (keyword "Polyamide" and the following).

The production of the preferred polyamides PA6, PA 66 and copolyamide 6/66 is briefly discussed below.

The polymerization or polycondensation of the starting monomers is preferably carried out by the customary processes. For example, the polymerization of caprolactam can be carried out by the continuous processes described in DE-A 14 95 198 and DE-A 25 58 480. The polymerization of AH salt to produce PA 66 can be carried out by the customary batch process (see: Polymerization Processes pp. 424-467, in particular pp. 444-446, Interscience, New York, 1977) or by a continuous process , e.g. according to EP-A 129 196.

Conventional chain regulators can also be used in the polymerization. Suitable chain regulators are, for example, triacetone diamine compounds (see WO-A 95/28443), monocarboxylic acids such as acetic acid, propionic acid and benzoic acid, and bases such as hexamethylene diamine, benzylamine and 1,4-cyclohexyl diamine. Also C ₄ -C ~ dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acid; C ₅ -C ₈ cycloalkane dicarboxylic acids such as cyclohexane-1,4-dicarboxylic acid; Benzene and naphthalenedicarboxylic acids such as isophthalic acid, terephthalic acid and naphthalene-2, 6-dicarboxylic acid are suitable as chain regulators.

The polymer melt obtained is discharged from the reactor, cooled and granulated. The granules obtained are subjected to post-polymerization. This is done in a manner known per se Way by heating the granules to a temperature T- below the melting temperature T _s or crystallite melting temperature T _{k of} the polyamide. The final molecular weight of the polyamide (measurable as a viscosity number VZ, see details on the VZ above) is established by the post-polymerization. Postpolymerization usually lasts from 2 to 24 hours, in particular from 12 to 24 hours. When the desired molecular weight is reached, the granules are cooled in the usual way.

Corresponding polyamides are available under the trade name Ultramid® from BASF.

Component B)

5 As component B), the molding compositions contain at least one delaminated layered silicate B). Layered silicates are also called phyllosilicates.

Layered silicate is generally understood to mean silicates in which the SiO ₄ tetrahedra are connected to form two-dimensional infinite networks (layered grids). The empirical formula for the anion is (Siθ ₅ ² ") _n > The individual layers are connected to each other by the cations lying between them, whereby in the naturally occurring layered silicates mostly as cations Na, K, Mg, Al or / and Approx.

The layer thicknesses of such silicates before delamination are usually from 5 to 100 Å, preferably 5 to 50 Å and in particular 8 to 20 Å. 1 angstrom corresponds to 0.1 nanometer 0 (nm).

Examples of synthetic and natural layered silicates (phyllosilicates) are montmorillonite, smectite, illite, sepiolite, palygorskite, muscovite, allevardite, amesite, hectorite, fluorhectorite, saponite, beidellite, talc, nontronite, steimmerite, vermiculite, bentonite, bentonite Fluoromiculite, halloysite and fluorine-containing synthetic mica types called.

A delaminated layered silicate in the sense of the invention 0 is to be understood as meaning layered silicates in which the layer spacings are initially increased by reaction with so-called hydrophobizing agents and, if appropriate, subsequent addition of monomers (so-called swelling e.g. with so-called AH salts).

By subsequent polycondensation or mixture (for example by preparation) of the hydrophobic and optionally gequol ^¬ lenen phyllosilicate with polyamides delamination occurs of the layers which preferably lead to a layer spacing of at least 40 Å, preferably at least 50 Å in the molded body.

To increase the layer spacing (hydrophobization), the layered silicates are reacted with so-called hydrophobizing agents, which are often also referred to as onium ions or onium salts, before the molding compositions are produced.

The cations of the layered silicates are replaced by organic water repellents, the desired layer spacings being able to be set by the type (size) of the organic residue. The layer spacing depends on the type of monomer or polymer in which the layered silicate is to be incorporated.

The metal ions can be exchanged completely or partially. A complete exchange of the metal ions is preferred. The amount of exchangeable metal ions is usually given in milliequivalents (meq) per 100 g of layered silicate and referred to as the ion exchange capacity.

Layered silicates with a cation exchange capacity of at least 50, preferably 80 to 130 meq / 100 g are preferred.

Suitable organic water repellents are derived from oxonium, ammonium, phosphonium and sulfonium ions, which can carry one or more organic radicals.

Suitable hydrophobicizing agents are those of the general formula I and / or II:

II

where the substituents have the following meaning:

_Rl. R ² , R ³ , R ⁴ independently of one another are hydrogen, a straight-chain branched, saturated or unsaturated hydrocarbon radical having 1 to 40, preferably 1 to 25, carbon atoms, which optionally carry at least one functional group or 2 of the radicals are connected to one another, in particular to form a heterocyclic radical having 5 to 10 carbon atoms,

X phosphorus or nitrogen,

Y oxygen or sulfur,

^{n is} an integer from 1 to 5, preferably 1 to 3 and

Z an anion.

Suitable functional groups in R ¹ to R ⁴ are hydroxyl,

Carboxyl, nitro or sulfo groups, carboxyl groups being particularly preferred, since such functional groups improve the bond to the end groups of the polyamide.

Suitable anions Z are derived from proton-providing acids, in particular mineral acids, with halide anions such as chloride, bromide, fluoride and iodide, and sulfate, sulfonate, phosphate, phosphonate, phosphite and carboxylate, in particular acetate, being preferred.

The layered silicates used as starting materials are generally reacted in the form of a suspension or solution. The preferred suspending agent or solvent is water, optionally in a mixture with alcohols, in particular lower alcohols with 1 to 3 carbon atoms. It can be advantageous to use a hydrocarbon, for example heptane, together with the aqueous medium, since the hydrophobized phyllosilicates are usually more compatible with hydrocarbons than with water.

Other suitable examples of suspending agents are ketones and hydrocarbons. A water-miscible solvent is usually preferred.

When the hydrophobizing agent is added to the layered silicate, an ion exchange takes place, as a result of which the layered silicate usually becomes more hydrophobic and precipitates out of the solution. The metal salt formed as a by-product of the ion exchange is preferably water-soluble, so that the hydrophobized layered silicate can be separated off as a crystalline solid by, for example, filtering off. The ion exchange is largely independent of the reaction temperature. The temperature is preferably above the crystallization point of the suspension or solvent and below its boiling point. In aqueous systems the temperature is between 0 and 100 ° C, preferably between 20 and 80 ° C.

For .polyamides, alkylammonium ions are preferred, which are obtained in particular by reacting suitable ω-aminocarboxylic acids such as ω-aminododecanoic acid, ω-aminoundecanoic acid, ω-aminobutyric acid, ω-aminocaprylic acid or ω-aminocaproic acid with customary mineral acids, for example hydrochloric acid, sulfuric acid or phosphoric acid or methylating agents how to get methyl iodide.

Further preferred alkylammonium ions are laurylammonium, myristylammonium, palmitylammonium, stearylammonium, pyridinium, octadecylammonium, monomethyloctadecylammonium and dimethyloctadecylammonium ions, and the derivatives of these ions substituted with alkyl and / or hydroxyalkyl.

Quaternary ammonium compounds, e.g. Di (2-hydroxyethyl) methylstearylammonium chloride, dimethylstearylbenzylammonium chloride, and trimethylstrearylammonium chloride.

Suitable phosphonium methyltri- nonylphosphonium, Ethyltrihexadecylphosphonium, Dimethyldidecyl- phosphonium, Diethyldioσtadecylphosphonium, Octadecyldiethylal- lylphosphonium, Trioctylvinylbenzylphosphonium, Dioctydecylethyl- include for example Docosyltrime- thylphosphonium, Hexatriacontyltricyclohexylphosphoniu, octadecyl cyltriethylphosphonium, Dicosyltriisobutylphosphonium, hydroxyethylphosphonium, Docosyldiethyldichlorbenzylphosphonium, Octylnonyldecylpropargylphosphonium, Triisobutylperfluordecyl - phosphonium, Eicosyltrihydroxymethylphosphonium, Triacontyltris - called cyanethylphosphoniu and bis-trioctylethylenediphosphonium.

Another suitable hydrophobizing agents are attributed, inter alia, in WO-A 93/4118, WO-A 93/4117, EP-A 398 551 and DE-A 36 32 865 be ^¬.

After the hydrophobization, the layered silicates have a layer spacing of 10 to 40 Å, preferably of 13 to 20 Å. The layer spacing usually means the distance from the lower layer edge of the upper layer to the upper layer edge of the lower layer. The length of the leaflets is usually up to 2000 Å, preferably up to 1500 Å. Hydrophobized bentonites, for example hydrophobized montmorillonite, are particularly preferably used as delaminated layered silicate B).

5 The polyamide nanocomposites can be produced, for example, by the in-situ or melt-intercalation method.

In-situ method: The layered silicate which has been rendered hydrophobic in the above manner is then mixed in suspension or as a solid 10 with the polyamide monomers or prepolymers and the polycondensation is carried out in the customary manner.

It is possible to further increase the layer spacing by using the layered silicate with polyamide monomers or pre-

15 polymers at temperatures of 25 to 300, preferably from 100 to 280 and in particular from 200 to 260 ° C over a residence time of 5 to 120 minutes, preferably from 10 to 60 minutes (so-called swelling). Depending on the duration of the residence time and the type of monomer chosen, the layer spacing increases by an additional 10 to

20 150, preferably around 20 to 50 Å. The polycondensation is then carried out in the customary manner. The polycondensation is carried out particularly advantageously with simultaneous shear, preferably under shear stresses in accordance with DIN 11443 of 10 to 10 ⁵ Pa, in particular 10 ² to 10 ⁴ Pa.

25

Any additives C) used can be added to the monomers or to the prepolymer melt (degassing extruder).

30 Melt-incalation method: The layered silicate B) hydrophobicized in the above manner is mixed as a solid with the finished polyamide polymer A) in a conventional manner on known devices, and the mixture is discharged, cooled and comminuted. For example, you can A) and B) in an extruder

35 Mix the melt of the polyamide intimately, and discharge the extrudate, cool and granulate.

If additives C) are used, they can also be introduced into the mixing device and thus produce a mixture of A), B) 40 and C).

The polyamide molding compositions can then be subjected to a further thermal treatment, ie a post-condensation in the solid phase. In tempering units such as a tumbler mixer or 5 continuously and discontinuously operated tempering tubes, the molding compound present in the respective processing mold is tempered until the desired viscosity number VZ or relative Viscosity ηrel of the polyamide is reached. The temperature range of the tempering depends on the melting point of the pure component A). Preferred temperature ranges are 5 to 50, preferably 20 to 30 ° C. below the respective melting point of the pure components A). The process is preferably carried out in an inert gas atmosphere, nitrogen and superheated water vapor being preferred as inert gases. The residence times are generally from 0.5 to 50, preferably from 4 to 20 hours. Then molded parts are produced from the molding compositions by means of injection molding.

The in-situ and the melt intercalation method are described in detail in DE-A 198 54 170, to which reference is hereby made.

Quantities of A) and B)

The polyamide nanocomposites from which the molded parts are produced by the process according to the invention preferably contain

A) 60 to 99.9, preferably 90 to 99 and particularly preferably 93 to 97% by weight of at least one polyamide A), and

B) 0.1 to 40, preferably 1 to 10 and particularly preferably 3 to 7% by weight of at least one delaminated layered silicate B).

Additives C)

As optional component C), the polyamide nanocomposites can contain further additives and processing aids, preferably in proportions of 0 to 70, in particular 0 to 50,% by weight.

Further additives are, for example, in amounts up to 40, preferably up to 30 wt .-% elastomeric polymers (often also termed as Schlagzähodifier, elastomers or rubbers ^¬ records).

In general, these are copolymers which are preferably composed of at least two of the following monomers: ethylene, propylene, butadiene, isobutene, isoprene, chloroprene, vinyl acetate, styrene, acrylonitrile and acrylic or methacrylic acid esters with 1 to 18 C atoms in the alcohol component.

Such polymers are described, for example, in Houben-Weyl, Methods of Organic Chemistry, Vol. 14/1 (Georg-Thie e-Verlag, Stuttgart, 1961). Pages 392 to 406 and in the monograph by CB Bucknall, "Toughened Plastics" (Applied Science Publishers, London, 1977).

Some preferred types of such elastomers are presented below.

Preferred types of such elastomers are the so-called ethylene-propylene (EPM) or ethylene-propylene-diene (EPDM) rubbers.

EPM rubbers generally have practically no more double bonds, while EPDM rubbers can have 1 to 20 double bonds / 100 carbon atoms.

Examples of diene monomers for EPDM rubbers are conjugated dienes such as isoprene and butadiene, non-conjugated dienes having 5 to 25 carbon atoms such as penta-1, 4-diene, hexa-1, 4-diene, hexa-1 , 5-diene, 2, 5-dimethylhexa-l, 5-diene and octa-1, 4-diene, cyclic dienes such as cyclopentadiene, cyclohexadienes, cyclooctadienes and dicyclopentadiene as well as alkenylnorbornenes such as 5-ethylidene-2-norbornene, 5- Butylidene-2-norbornene, 2-methallyl-5-norbornene, 2-isopropenyl-5-norbornene and tricyclodienes such as 3-methyl-tricyclo (5.2.1.0.2.6) -3, 8-decadiene or mixtures thereof. Hexa-1,5-diene-5-ethylidene-norbornene and dicyclopentadiene are preferred. The diene content of the EPDM rubber is preferably 0.5 to 50, in particular 1 to 8,% by weight, based on the total weight of the rubber.

EPM or EPDM rubbers can preferably also be grafted with reactive carboxylic acids or their derivatives. Here are e.g. Acrylic acid, methacrylic acid and their derivatives, e.g. Glycidyl (meth) acrylate, as well as maleic anhydride.

Another group of preferred rubbers are copolymers of ethylene with acrylic acid and / or methacrylic acid and / or the esters of these acids. In addition, the rubbers can

Dicarboxylic acids such as maleic acid and fumaric acid or derivatives of these acids, e.g. Contain esters and anhydrides, and / or monomers containing epoxy groups. These dicarboxylic acid derivatives or monomers containing epoxy groups are preferably incorporated into the rubber by adding monomers M containing dicarboxylic acid or epoxy groups to the monomer mixture.

Preferred dicarboxylic acid or epoxy monomers M are maleic acid, maleic anhydride and epoxy group-containing esters of acrylic acid and / or methacrylic acid, such as glycidyl acrylate, glycidyl methacrylate, and the esters with tertiary alcohols, such as t-butyl acrylate no free carboxyl groups, However, their behavior is close to that of free acids and are therefore referred to as monomers with latent carboxyl groups.

The copolymers advantageously consist of 50 to 98% by weight of ethylene, 0.1 to 20% by weight of monomers containing epoxy groups and / or monomers containing methacrylic acid and / or acid anhydride groups and the remaining amount of (meth) acrylic acid esters.

Further preferred esters of acrylic and / or methacrylic acid are the methyl, ethyl, propyl and i- or t-butyl esters. In addition, vinyl esters and vinyl ethers can also be used as comonomers.

The ethylene copolymers described above can be prepared by processes known per se, preferably by random copolymerization under high pressure and elevated temperature. Appropriate methods are generally known.

Preferred elastomers are also emulsion polymers, the production of which e.g. in Blackley, Emulsion Polymerization, Applied Science Publishers, London 1975. The emulsifiers and catalysts that can be used are known per se.

In principle, homogeneous elastomers or those with a shell structure can be used. The shell-like structure is determined by the order of addition of the individual monomers; The morphology of the polymers is also influenced by this order of addition.

Representative here are as monomers for the production of the rubber part of the elastomers acrylates such as n-Butyl acrylate and 2-ethylhexyl acrylate, corresponding methacrylates, butadiene and isoprene and mixtures thereof. These monomers can be combined with other monomers such as e.g. Styrene, acrylonitrile, vinyl ethers and other acrylates or meth acrylates such as methyl methacrylate, methyl acrylate, ethyl acrylate and propyl acrylate are copolymerized.

The soft or rubber phase (with a glass transition temperature of below 0 ° C) of the elastomers can be the core, the outer shell or a middle shell (in the case of elastomers with more than two shells); in the case of multi-layer elastomers, several shells can also consist of a rubber phase. If, in addition to the rubber phase, one or more hard components (with glass transition temperatures of more than 20 ° C) are involved in the construction of the elastomer, these are generally obtained by polymerizing styrene, acrylonitrile, methacrylonitrile, ^α -methylstyrene, p-methylstyrene, Acrylic acid esters and methacrylic acid esters such as methyl acrylate, ethyl acrylate and methyl methacrylate are produced as the main monomers. In addition, smaller proportions of further comonomers can also be used here.

In some cases, it has proven to be beneficial

To use emulsion polymers which have reactive groups on the surface. Such groups are e.g. Epoxy, carboxyl, latent carboxyl, amino or amide groups as well as functional groups by the use of monomers of the general formula

_R ιo _R ιι

CH ₂ = CXNCR ² 0 can be introduced,

where the substituents have the following meaning:

_R ιo is hydrogen or a C 1 -C ₄ -alkyl group,

Ri is hydrogen, a C 1 -C 6 -alkyl group or an aryl group, in particular phenyl,

R12 is hydrogen, a C ₁ -C 8 -alkyl, a C ₆ - to C ₁₂ -aryl group or -OR ¹³

R ¹³ is a Cι ~ to C ₈ -alkyl or C ₆ - may be substituted by Cι ₂ -aryl group which gege ^¬ appropriate, with 0- or N-containing groups,

X is a chemical bond, a Cχ ~ to Cio alkylene or C ₆ -C ₂ arylene group or

O-Z or NH-Z and

a Cι ~ to Cι ₀ alkylene or C ₆ ~ to C _i2 arylene group. The graft monomers described in EP-A 208 187 are also suitable for introducing reactive groups on the surface.

Further examples include acrylamide, methacrylamide and substituted esters of acrylic acid or methacrylic acid such as (Nt-butyla ino) ethyl methacrylate, (N, N-dimethylamino) ethyl acrylate, (N, N-dimethylamino) methyl acrylate and (N, N-diethylamino) ) called ethyl acrylate.

The particles of the rubber phase can also be crosslinked. Monomers acting as crosslinking agents are, for example, buta-1,3-diene, divinylbenzene, diallyl phthalate and dihydrodicyclopentadienyl acrylate, and the compounds described in EP-A 50 265.

So-called graft-linking monomers can also be used, ie monomers with two or more polymerizable double bonds which react at different rates during the polymerization. Compounds are preferably used in which at least one reactive group polymerizes at approximately the same rate as the other monomers, while the other reactive group (or reactive groups) polymerizes (polymerizes), for example, significantly more slowly. The different polymerization rates result in a certain proportion of unsaturated double bonds in the rubber. Is then grafted onto a rubber of a further phase, present in the rubber double bonds react at least partially with the graft monomers to form chemical bonds, ie, the grafted phase is at ^¬ least partly linked by chemical bonds with the graft base.

Examples of such graft-crosslinking monomers are monomers containing allyl groups, in particular allyl esters of ethylenically unsaturated carboxylic acids such as allyl acrylate, allyl methacrylate, diallyl maleate, diallyl fumarate, diallyl itaconate or the corresponding monoallyl compounds of these dicarboxylic acids. There are also a large number of other suitable graft-crosslinking monomers; for further details, reference is made here, for example, to US Pat. No. 4,148,846.

In general, the proportion of these crosslinking monomers in the impact-modifying polymer is 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. First of all, graft polymers with a core and at least one outer shell are to be mentioned, which have the following structure:

Instead of graft polymers with a multi-layer structure, homogeneous, i.e. single-shell elastomers of Bu-ta-l, 3-diene, isoprene and n-butyl acrylate or their copolymers are used. These products can also be prepared by using crosslinking monomers or monomers with reactive groups.

Examples of preferred emulsion polymers are n-Butylacry ^¬ lat / (meth) acrylic acid-copoly ere, n-butyl acrylate / glycidyl acrylate or _n-B utylacrylat / glycidyl methacrylate copolymers, graft - polymers with an inner core of n-butyl acrylate or based on butadiene and an outer shell of the above genann ^¬ th copolymers, and copolymers of ethylene with comonomers which provide reactive groups.

The elastomers described may also be prepared by other conventional processes, eg by suspension polymerization ^¬ 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 are also preferred.

Of course, mixtures of the types of cheeses listed above can also be used.

Furthermore, the polyamide nanocomposites can contain stabilizers, oxidation retarders, agents against heat decomposition and decomposition by ultraviolet light, lubricants and mold release agents, colorants such as dyes and pigments, nucleating agents, plasticizers, etc.

Examples of oxidation retarders and heat stabilizers are sterically hindered phenols, hydroquinones, copper compounds, aromatic secondary amines such as diphenylamines, various substituted representatives of these groups and mixtures thereof in concentrations of up to 1% by weight, based on the weight of the thermoplastic molding compositions.

Various substituted resorcinols, salicylates, benzotriazoles and Be zophenones may be mentioned as UV stabilizers, which are generally used in amounts of up to 2% by weight, based on the molding composition.

Inorganic pigments such as titanium dioxide, ultramarine blue, iron oxide and carbon black, furthermore organic pigments such as phthalocyanines, quinacridones, perylenes and dyes such as nigrosine and anthraquinones can be added as colorants.

Sodium phenylphosphinate, aluminum oxide or silicon dioxide can be used as nucleating agents.

Lubricants and mold release agents, which are usually used in amounts of up to 1% by weight, are preferably long-chain fatty acids (for example stearic acid or behenic acid), their salts (for example Ca or Zn stearate) and amide derivatives (for example ethylene-bis-stearylamide) ) montan waxes (mixtures of straight-ge ^¬ saturated carboxylic acids having chain lengths of from 28 to 32 carbon atoms) and low molecular weight polyethylene or polypropylene waxes, or.

Fibrous or particulate fillers are also suitable as additives C), for example in amounts of 0 to 50, preferably 5 to 40 and in particular 10 to 30% by weight. Carbon fibers, aramid fibers and potassium titanate fibers may be mentioned as preferred fibrous fillers, glass fibers made of E-glass being particularly preferred. These can be used as rovings or cut glass in the commercially available forms.

The fibrous fillers can be surface-pretreated with a silane compound for better compatibility with the polyamide.

Suitable silane compounds are those of the general formula III

(X- (CH ₂ ) _n ) _k ^_ Si (0-C _m H _{m +} ι) ₄ _ _{k χll}

m • the substituents have the following meaning:

n is an integer from 2 to 10, preferably 3 to 4 m is an integer from 1 to 5, preferably 1 to 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 a glycidyl group as substituent X.

The silane compounds are generally used in amounts of 0.05 to 5, preferably 0.5 to 1.5 and in particular 0.8 to 1% by weight (based on C)) for the surface coating.

Fibrous fillers are preferred having an average arith metic ^¬ fiber length of 150 to 300, preferably 200 to 270 and in particular to 220 to 250 to. The average diameter is generally from 3 up to 30 m, preferably from 8 to 20 microns to and from ^¬ particular 10 to 14. The desired fiber length can be adjusted by milling in a ball mill for example, wherein a fiber length distribution ^¬ formed.

If the average fiber length is <200 μm, a further reduction in the fiber length leads to a free-flowing bulk material that can be mixed into the polymer like a powder. Due to the short fiber length, there is only a slight further shortening of the fiber length during incorporation. The fiber content is usually determined after the polymer has been incinerated. To determine the fiber length distribution, the ash residue is generally taken up in silicone oil and photographed at 20x magnification of the microscope. The length of at least 500 fibers can be measured on the pictures and the arithmetic mean (d ₅₀ ) can be calculated from them.

Also suitable are needle-shaped mineral fillers, which are mineral fillers with a pronounced needle-like character. An example is needle-shaped wollastonite. The mineral preferably has an L / D (length / diameter) ratio of 8: 1 to 35: 1, preferably 8: 1 to 11: 1. The mineral filler can optionally be pretreated with the silane compounds mentioned above; however, pretreatment is not essential.

Amorphous silica, magnesium carbonate (chalk), kaolin (in particular calcined kaolin), powdered quartz, mica, talc, feldspar and in particular calcium silicates such as wollastonite are suitable as particulate fillers.

The moldings according to the invention generally have an A - [- B-A - πB layer structure, that is to say layer sequence ABABAB ..., A being the thermoplastic matrix and layer B being the delaminated layered silicate.

injection molding

In the process according to the invention, the molded parts are produced in an injection molding process by introducing a melt containing the polyamide A) and the delaminated layered silicate B) via a sprue into an injection molding tool.

In contrast to polyamide A), layered silicate B) generally does not melt during the injection molding process. Accordingly, the claim wording "melt" is to be understood as a mixture of molten (plastic) polyamide A) and solid layered silicate B).

The melt is introduced into the injection molding tool via a sprue in a manner known per se, for example by means of an injection molding machine (piston, screw or other injection molding machine). The injection molding process for the production of plastic molded parts has been known for a long time and requires no further explanation. The person skilled in the art finds details, for example, in the following monographs: Menges et al. , Instructions for the construction of injection molding tools, 2nd edition, Hanser Verlag, Munich 1983; Menges, introduction to plastics processing, Hanser Verlag, Munich 1979; Sarholz, injection molding: process flow, process parameters, process control, Hanser Verlag, Munich 1979.

The process according to the invention is characterized in that the injection molding conditions are selected in a manner known per se such that the melt in the injection molding tool flows essentially in parallel, as a result of which a high orientation of the melt is achieved and that the high orientation of the melt upon solidification of the Melt is frozen.

The wording of the claim "that the melt flows essentially parallel in the injection molding tool" is explained below.

An arbitrary point X of the melt flowing forward in the injection mold describes a flow path x, and an arbitrary point Y of the flowing melt describes a flow path y. The flow path is the path that the melt travels from the gate in the mold (the gate is the interface between the injection molded part and the sprue). According to the invention, the injection molding conditions are to be selected such that the two flow paths x and y are equidistant, and are therefore parallel in the case of straight lines.

The flow front of the flowing melt is therefore not just about substantially curved and the front and flows we ^¬ sentlichen at all points at the same speed.

The limitation "substantially" reflects the fact that a melt flows more slowly in the region directly adjoining the tool surface the edge region and directly on the work ^¬ imaging surface, the flow rate is zero, the flow front so that in this edge region is curved and possibly of the flow path is not parallel.

In other words: According to the invention, the flow paths of the melt are to be optimized in a manner known per se in such a way that the melt flows essentially parallel in the injection molding tool. The person skilled in the art, for example from the injection molding of glass fiber-containing thermoplastic molding compositions, knows how to choose the injection molding conditions so that the melt in the injection molding tool flows essentially in parallel.

The following are examples of injection molding conditions:

Design of the sprue, in particular the location of the sprue (e.g. in or outside the parting plane of the tool); Gating geometry, e.g. B. shape, cross section, volume; Geometry of any existing distribution channels, e.g. Length, cross section, volume; Geometry of the gate, e.g. Shape, cross-section, mold temperature (mold surface temperature) - melt temperature (melt temperature) melt pressure (injection pressure) hold pressure cycle time injection time and screw advance speed - cooling time

pressure time

Mold open time

Cross-sectional area of the tool cavity

Injection molding volume (molding volume) - locking force

Injection speed.

Reference is expressly made to the standard DIN EN ISO 294-1 (October 1998), in which the aforementioned parameters are defined.

Preferably, the parameters referred to within the following Be ^¬ are rich:

Tool surface temperature: from 15 to 140 ° C - melt temperature (melt temperature): from 240 to 320 ° C

Mass pressure (injection pressure): from 250 to 2500 bar

Holding pressure: from 250 to 1500 bar

Cycle time: from 3 to 300 s

Screw advance speed: from 20 to 1000 mm / s - holding time: from 0.5 to 60 s.

It goes without saying that in individual cases the numerical values to be selected strongly depend on the molded part to be produced (size, geometry) and on the composition and properties of the molding compound. The melt is preferably distributed in the sprue system in such a way that it enters the cavity of the tool with an approximately parallel flow front. The sprue system must be selected accordingly.

In a preferred embodiment, the sprue is designed as a tape gate (also referred to as a film gate or tape gate), i.e. the melt does not enter the tool at one point - as in the case of point sprue or rod or cone sprue - but at the same time on a surface. For example, you can spray directly into the parting surface of the tool during the gate.

The melt usually enters the mold on the whole side at the same time. Depending on the thickness of the molded part, the band gate can have different thicknesses. The gate in front of the gate (distribution channel, so-called belt distributor) should be significantly larger in cross-section so that the gate is evenly filled with the melt.

For the injection molding of tubular parts (e.g. pipes, rollers), a shield gate (also referred to as mushroom, plate or disc gate) or ring gate is used in a preferred embodiment.

The choice of the injection molding conditions in such a way that the melt flows in parallel in the mold ensures that the orientation is high

Melt (containing polyamide A) and layered silicate B)) reached, i.e. Due to the parallel flow, highly ordered structures are present in the melt.

One possible explanation for the emergence of high orientation, that a so-called shear profile is present. As mentioned above, the flow rate of the melt is directly on the tool press ^¬ goberfläche zero. If one assumes that the flow speed in the middle between the tool surfaces is maximum, then a speed ^graph is present when viewed over the melt cross section. This gradient causes the melt to be subject to shear forces which are maximum in the edge region of the melt (so-called shear profile). The shear forces lead to an orientation of the melt which is maximal in the edge areas.

Edge area means the area of the melt (more precisely: the melt cross-section) that borders on the tool surface, i.e. the area near the surface of the later molded part.

According to the invention, the injection molding conditions are to be selected so that the high orientation of the melt is frozen when the melt solidifies. This means that by solidifying the Melt to the finished solid molded part, the highly ordered structures made of polyamide and layered silicate are virtually "fixed".

The person skilled in the art knows, for example from the injection molding of glass fiber-containing thermoplastic molding compositions, how he uses the

Injection molding conditions must be selected so that the high orientation of the melt is frozen when it solidifies.

Important parameters for freezing the highly oriented melt are the temperatures of the melt and the tool surface.

The temperatures and the other injection molding conditions should preferably be selected in a manner known per se such that the tool is filled well and the high orientation generated by the parallel flow of the melt is frozen during solidification.

Another important parameter for freezing the highly oriented melt is the dimensioning of the mold cavity and thus the molded part: if the melt layer located between the opposite tool surfaces is thin, the melt orientation can generally be better frozen than with thick melt layers.

Based on the shear profile described above, there is the idea that with thin layers of melt - i.e. thin-walled molded parts - the highly oriented edge areas (areas close to the surface) are large compared to the less highly oriented interior of the melt or the molded part.

The method is therefore particularly suitable for the production of thin-walled moldings and in particular of moldings which essentially have a wall thickness of at most 2 mm, preferably at most 1 mm (so-called thin-walled moldings). By "substantially" is meant that the mold parts in the areas that are exposed to a loading stung ^¬, a wall thickness of not more than 2 mm have.

Examples of such thin-walled moldings with a wall thickness of at most 2 mm are shell-shaped moldings, for example for housing, in particular mobile phone housing, also bobbin, cable ties, Ge ^¬ housing for electrical installations and electrical or electronic devices. There is an idea that the frozen, highly oriented structures present in the molded part are the cause of the improved toughness and overall damage work of the molded parts.

The method according to the invention can be used to produce moldings of all types with improved toughness, including semi-finished products, pipes, profiles, plates, injection-molded foils, etc. In particular, thin-walled moldings can be produced with improved toughness. These molded parts are also the subject of the invention. Toughness means especially multiaxial toughness.

The invention also relates to molded parts, the molded part being produced by the process according to the invention and being a circular disc 60 mm in diameter and 1 mm thick, which is produced from 95% by weight of polyamide 6 and 5% by weight of hydrophobic bentonite, and the round disk in the puncture test according to DIN 53443 at 23 ° C has a total damage work W _tot of at least 30 J / mm.

The invention further relates to a process for increasing the toughness of molded parts made of polyamide nanocomposites containing at least one polyamide A) and at least one delaminated layered silicate B), characterized in that the molded parts are injection-molded by introducing a melt containing A) and B) via a sprue in an injection molding tool, and that the melt in the injection molding tool flows essentially in parallel, whereby a high orientation of the melt is achieved and that the high orientation of the melt is frozen when the melt solidifies.

The following examples illustrate the invention.

Examples

The following feedstocks were used.

Polyamide:

Polyamide 6 (polycaprolactam) having a viscosity number VN of 150 ml / g, measured as 0.5 wt .-% solution in 96 wt .-% hydrochloric pivot ^¬ ric acid at 25 ° C according to ISO 307. It has been Ultramid® B3 of BASF uses.

Delaminated hydrophobized layered silicate: 1 kg of purified sodium bentonite with an ion exchange capacity of 95 meq / 100 g was mixed with enough water in a stirred kettle that a 2% by weight suspension was removed. was standing. 397 g of di ⁽ 2-hydroxyethyl) methylstearylammonium chloride were added to the suspension at room temperature within 1 min. The precipitate which separated out was separated off by filtration, purified with water and spray-dried. •

The product is also available as Cloisite® 30B from Southern Clay Products, Texas, USA.

Production of the molding compound

95 parts by weight of polyamide and 5 parts by weight of delaminated hydrophobic layered silicate were intimately mixed on a twin-screw extruder at 250 ° C., 250 revolutions / min and 20 kg / h throughput, the mixture was discharged as strands and cooled in a water bath and granulated. A polyamide nanocomposite granulate was obtained.

Production of the moldings

Before the injection molding processing, the polyamide nanocomposite granules were dried in a vacuum at 100 ° C. for 16 hours.

In the following examples, the screw advance speed was selected so that the flow rate of the melt was identical at the point that corresponded to the tested point of the test specimen.

Example 1 (for comparison)

On an Arburg Allrounder 270S injection molding machine with 25 mm

Round disks with a thickness of 1 mm and a diameter of 60 mm were produced. The screw advance speed was 22 mm / s, the mold surface temperature 80 ° C and the melt temperature (melt temperature) 270 ° C. A simple tool was used as the injection molding tool. The sprue system consisted of a sprue with a sprue that lay in the parting plane of the tool. Due to this arrangement, the melt in the work ^¬ did not flow generating parallel but radially.

Example 2

Plates of 1 mm thickness and 100x100 mm edge length were produced on an Nestal Synergy 1200 injection molding machine with a 32 mm screw diameter. The screw advance speed was 50 mm / s, the tool surface temperature 80 ° C and

Melt temperature (melt temperature) 270 ° C. A double mold was used as the injection molding tool. The sprue system consisted of a bar sprue that was perpendicular to the two molded parts of the two-cavity mold, and a subsequent band gate for each molded part. The band cut caused the melt to flow essentially parallel in the tool. Round disks of 1 mm thickness and 60 mm diameter were machined from the plates.

Testing and properties of the test specimens

The total damage work W _{tot was} determined on the round disks in the multiaxial puncture test according to DIN 53443 at 23 ° C. The fracture behavior was determined visually.

The table summarizes the results.

The table shows that by choosing the injection molding conditions such that the melt flows in the mold in parallel (here: by changing from the point gate to the band gate) and that the melt orientation is frozen, the toughness of the thin-walled molded parts is significantly improved. The total damage capacity increases by more than half from 19.7 to 33.4 J / mm, and the fracture behavior is ductile-tough instead of brittle.

Claims

claims

1. Process for the production of molded parts from polyamide nanocomposites containing

A) at least one polyamide A), and

B) at least one delaminated layered silicate B)

in the injection molding process by introducing a melt containing A) and B) over a sprue into an injection molding tool, characterized in that the injection molding conditions are selected in a manner known per se such that the melt in the injection molding tool flows essentially in parallel, as a result of which a high orientation of the melt is achieved, and that the high orientation of the melt is frozen when the melt solidifies.

2. The method according to claim 1, characterized in that the sprue is designed as a band gate, umbrella gate or ring gate.

3. Process according to claims 1 to 2, characterized in that the polyamide nanocomposites contain 60 to 99.9% by weight of the polyamide A) and 0.1 to 40% by weight of the layered silicate B).

4. The method according to claims 1 to 3, characterized in ^¬ net in that polyamide A) is a polyamide 6 is used as.

5. The method according to claims 1 to 4, characterized in ^¬ net that as phyllosilicate B) hydrophobicized bentonites used.

6. The method according to claims 1 to 5, characterized in that the molded parts essentially have a wall thickness of at most 2 mm.

7. Molded parts, obtainable by the process according to claims 1 to 6.

8. Shaped parts according to claim 7, wherein the shaped part is a round disc of 60 mm in diameter and 1 mm thick, which is made of 95 wt .-% polyamide 6 and 5 wt .-% hydrophobic bentonite, and wherein the round disc in the puncture test according to DIN 53443 at 23 ° C has a total damage work W _tot of at least 30 J / mm.

9. Process for increasing the toughness of molded parts made of polyamide nanocomposites, containing at least one polyamide A) and at least one delaminated layered silicate B),

characterized in that the molded parts are produced in an injection molding process by introducing a melt containing A) and B) via a sprue into an injection molding tool, and in that the melt in the injection molding tool flows essentially in parallel, as a result of which a high orientation of the melt is achieved and that high orientation of the melt is frozen when the melt solidifies.