EP0849746B1 - Thermoplastic moulding composition, process of its prouction and use thereof - Google Patents

Description

The invention relates to a thermoplastically processable molding compound for magnetic materials. It relates in particular to a molding compound made from thermoplastic polyamides and one filler homogeneously distributed therein, which is permanently magnetic or magnetizable.

Thermoplastic processable molding compounds with a high volume of magnetizable or permanent magnetic filler and a thermoplastic matrix are known. Important fillers are rare earth metal compounds such as Nd / Fe / B in polyamides such as Nylon-6, -11 and -12 or polyphenylene sulfide or polybutylene terephthalate, as a matrix.

To achieve good magnetic values, a volume fraction of over 30% is particularly important 50 or more% of magnetic or magnetizable filler is required. This prepares considerable problems in practice, so that in the patent literature many solutions are proposed.

For technical areas of application, e.g. in the engine compartment of vehicles, but are also the matrix properties of great importance.

In particular, matrix materials with good temperature resistance and methods are used wanted for sufficient mixing with the magnetic filler. Such methods are complex and expensive and take insufficient account of environmental aspects. Especially with the Nd / Fe / B compounds, the so-called neodymium types the problem of corrosion to it. The metallic neodymium particles corrode under the Exposure to moisture and / or oxygen. This reaction can even take place spontaneously and lead to self-ignition.

There are therefore many methods, especially in the patent literature, to delay or prevent the corrosion of the neodymium particles, in particular by means of a protective layer (coat),
to modify the matrix in a flowable and wetting-active manner via special additives, such as ester compounds or amide compounds of fatty acids,
to bring the matrix into a form that enables a high degree of filling, such as fine grinding of the matrix or dissolving of the matrix and coating of the magnetic particles with subsequent evaporation of the solvent,
to provide a matrix with special properties such as good chemical resistance.

JP 04257203-A contains , for example, magnetizable neodymium particles, specially coated and coated with adhesive, in a PA-12 matrix which contains magnesium stearate as an internal lubricant.
JP J03270201-A describes magnetic powder, such as Ba and Sr ferrite in linear polyamide, such as nylon-6, -66, -610, -11 and -12 as a matrix, which contain bishydroxycarboxamides to improve the processability.
No. 4,462,919 describes the application of a coating to ferromagnetic samarium / cobalt, which is then incorporated into a thermoplastic, such as polyamide-12.
DE-OS 27 36 642 describes the addition of thermoplastic to oxidation-sensitive magnetic material via a solution under protective gas.

DE 44 20 318 C2 describes compositions which contain partially aromatic thermoplastics of the polyester and polyamide type and permanently magnetic and / or ferromagnetic, metal-containing compounds.

With one exception, the thermoplastic compounds are polyesters, in particular polybutylene terephthalate, which is pure or as a polymer alloy. For example 3, a polymer called polyterephthalic acid hexamethylenediamide is used and described with a melting point of 236 ° C. However, the low melting point shows that it must be a heavily modified product, because all the common ones partially aromatic polyamides (polyaramides) melt at a temperature of approx. 300 ° C and above. Partly aromatic polyamide according to the teaching of this patent use it as an example if it is so modified that its melting point, as described in Application Example 3 at 236 ° C, is significantly reduced.

As already explained and confirmed in DE 44 20 318 C2 , the high-quality aromatic or partially aromatic thermoplastics can only be used as a matrix for magnetic materials via expensive or less environmentally compatible processes, such as through fine grinding or application in the form of a solution.
It is particularly difficult to manufacture and process thermoplastically processable magnetic materials with a high degree of filling, in particular of over 50% by volume of magnetic or magnetizable metal compound in a matrix of partially aromatic polyamide with a melting point of over 300 ° C.

This calls for thermoplastic plastic materials with a matrix Dimensionally stable, hydrolysis and chemical resistant polyamide of high rigidity and a high melting point, filled with a high volume fraction, especially of over 50%, of magnetic or magnetizable metal alloy and / or metal compound, which can be easily processed using the injection molding process and form-stable magnetic or magnetizable molded bodies result.

Also required are those based on thermoplastically processable polymer compositions Magnetic material molded parts for special applications, e.g. in electric motors, for Functions in automobiles or consumer electronics, especially when the continuous use temperature at 100 ° C or above and for a short time also temperature peaks of 200 ° C can be reached.

The object of the present invention is to meet these requirements and the To overcome disadvantages of the prior art.

This object is achieved by the thermoplastically processable molding composition according to the Features of claim 2, by the method for producing the Molding composition according to claim 1 and by using the thermoplastically processable Molding compound for the production of magnetic or magnetizable molded parts according to claim 1.

The object is achieved in particular by a molding compound consisting of a two-phase Blend a) from at least one partially aromatic copolyamide and at least one aliphatic polyamide or copolyamide as a matrix, which has at least one permanent magnetic or magnetizable connection b) contains as a filler in homogeneous distribution.

a1) 70 - 97 Gew.% eines teilaromatischen Copolyamids mit einem Schmelzpunkt von mehr als 280° C
und

a2) 3 - 30 Gew.% eines aliphatischen Polyamids oder Copolyamids mit im statistischen Mittel mindestens 10-CH₂-Gruppen pro -CONH - Gruppe,
und

a3) 0 bis 10 Gew.% an eigenschaftsrelevanten und/oder verarbeitungsbedingten Additiven, wobei die Summe der Matrixkomponenten a1) bis a3) 100 Gew.% beträgt,

sind dafür bevorzugt, insbesondere wenn ihre Polyamid-Kettenenden einen Überschuss an NH₂-Gruppen aufweisen.
Weil die Polyaramide a1) üblicherweise im Endgruppen-Gleichgewicht sind, kann der NH₂-Endgruppen-Überschuss in der Matrix durch das aliphatische Polyamid a2) allein erreicht werden. In der Mischung bilden die beiden Polyamide a1) und a2) zwei Phasen.Matrices

a1) 70-97% by weight of a partially aromatic copolyamide with a melting point of more than 280 ° C
and

a2) 3 to 30% by weight of an aliphatic polyamide or copolyamide with a statistical average of at least 10 CH ₂ groups per -CONH group,
and

a3) 0 to 10% by weight of property-relevant and / or processing-related additives, the sum of the matrix components a1) to a3) being 100% by weight,

are preferred, especially if their polyamide chain ends have an excess of NH ₂ groups.
Because the polyaramides a1) are usually in the end group equilibrium, the excess of NH ₂ end groups in the matrix can be achieved by the aliphatic polyamide a2) alone. In the mixture, the two polyamides a1) and a2) form two phases.

In particularly preferred variants, the matrix consists of 80 to 97% by weight of partially aromatic copolyamide a1) and 3 to 20% by weight of aliphatic polyamide or copolyamide a2).
The partially aromatic copolyamides of the molding composition according to the invention are notable for the fact that a high proportion of the dicarboxylic acid component is aromatic acids, in particular terephthalic acid, but also isophthalic acid or naphthalenedicarboxylic acid. In addition, a proportion of less than 50 mol%, based on the total acid proportion, of aliphatic dicarboxylic acids, of which adipic acid is preferred, is advantageous. The amine component is preferably aliphatic, with hexamethylene diamine being the preferred diamine. Caprolactam is also often used as a comonomer.

Since the crystallizable, partially aromatic polyamides, the amine component of hexamethylenediamine and their acid component exclusively aromatic dicarboxylic acid, such as e.g. Terephthalic acid, has melting points well above 300 ° C and is exceptional have high melt viscosities, the comonomers are also used in order to to specifically change the properties, in particular to lower the melting point and to enable thermoplastic processing. Commercially available partially aromatic polyamides are e.g. the Ultramid®T types from BASF, Ludwigshafen (D), the Amodel® types from Amoco, Chicago (USA), Zytel® HTN, polyamides from Du Pont, Wilmington (USA), the Arlen® products from Mitsui Sekka, Tokyo (J) and the Grivory® HT polyamides from EMS-CHEMIE AG, Domat / Ems (CH).

Semi-aromatic copolyamides a1) in the sense of the invention are semi-crystalline products with a Melting point which is above 280 ° C, preferably above 300 ° C and particularly preferably in the range between 310 to 320 ° C is. The term polyaramides is a generic term for this class of polyamides.

A preferred and well suited for technical applications, and subsequently as "Polyamide T" called copolyamide consists of 55 mol% hexamethylene terephthalamide and 45 mol% hexamethylene adipamide units and melts at 310 to 315 ° C.

Aliphatic polyamides a2) in the context of the invention are, for example, polyamides 11 and 12, polyamides 1012, 1210 and 1212, copolyamides a2) are, for example, those which contain dimerized fatty acids with 36 to 44 C atoms and have a melting point above 170 ° C. , It is advantageous if these aliphatic polyamides or copolyamides have more NH ₂ end groups than COOH end groups. Highly free-flowing, aliphatic polyamides and copolyamides, which have, for example, 50-200 μAeq. / G amino end groups and 2-30 μAeq. / G carboxyl end groups, are particularly preferred.
The molding composition according to the invention contains at least 30% by volume of a permanently magnetic or magnetizable metal compound and / or alloy as a homogeneously distributed, finely divided filler b).

In preferred product variants, this filler fraction is at least 45% by volume and very particularly advantageously even at least 55% by volume of the total molding composition.
Preferred fillers are metals or alloys, in particular rare earth powder (including yttrium) of the rare earth / iron / boron type, with Nd / Fe / B, also referred to as "neodymium", being very particularly preferred. The alloys known as magnetic materials, samarium / cobalt and samarium / thulium, ferrites, such as barium and strontium ferrite, and carbonyl iron powder are also advantageous. Suitable metal powders are described, for example, in the company brochure DR 9632 MAG from Delco Remy, Anderson, IN 46013, USA and bear the name Magnequench® Products.

High quality magnetic products are in particular Nd / Fe / B; SmTm, e.g. Sm ₂ Tm ₁₇ ; SmCo, e.g. SmCo ₅ . In principle, however, all magnetic and / or magnetizable metal powders and metal compounds can be used. It is advantageous, but not necessary, that they be coated. Suitable coats for ferrites are state of the art.

The matrix of the molding composition according to the invention advantageously additionally contains up to 10% by weight. on processing and / or property-relevant additives a3) in order to erweitem.

These are in particular stabilizers e.g. Heat stabilizers, such as sterically hindered phenols, Sulfide derivatives or aromatic amines. Examples include Irganox® 1098, Irganox® 1076, Irganox® 245 or Irganox® 1010 as phenol derivatives and Irganox® PS800 as sulfide derivative. The manufacturer of these products is Ciba-Geigy, Basel. An example of a suitable, aromatic Amin is Naugard® 445 from Uniroyal, Herstal, Belgium.

Further advantageous additives are processing aids, such as metal stearates, partial glycerol esters, fatty acid esters and fatty acid amides and in particular alkylamines which carry a primary amino group and / or those of the formula I, R- (HN-CH ₂ CH ₂ CH ₂ ) _n -NH ₂

in which n = 1 to 3 and R is a C12 to C44 alkyl radical which can also contain heteroatoms. They are preferably present in proportions of 0.1 to 7% by weight, based on the weight of the matrix.

Examples of such processing aids, which in particular also improve the processability in injection molding, are, for example, calcium stearate, magnesium stearate, ethylene bisstearamide, stearyl stearate, glycerol monostearate and in particular amines, such as N-hexadecylamine, and diamines in which an amino function is secondary.
Examples of such diamines, which are derived from the corresponding natural products with the brand name Duomeen® from AKZO, are N-coco-1,3-diaminopropane with the coco radical (C ₈ to C ₁₈ with 50% C ₁₂ ) and N- Talc-1,3-diaminopropane with the talc residue (mainly C ₁₈ ). Furthermore, all non-oxidizing additives, such as those used for thermoplastically processable polyamide molding compositions, can also be used, such as waxes, light stabilizers and antioxidants, such as phosphites. This list can be expanded according to the known state of the art.

The corrosion-inhibiting effect of the amine-containing melt is particularly advantageous Molding composition according to the invention compared to metal compounds and alloys.

The production of the molding composition according to the invention is particularly advantageous and simple. No special and time-consuming preparation steps or solvents are required.

The process can be carried out in a simple manner for the production of polyamide molding compositions suitable device, e.g. a twin-screw extruder, especially a ZSK machine e.g. from Werner and Pfleiderer, Stuttgart, directly from a mixture of the matrix components carried out by incorporating the metal powder into the molten matrix molding compound become.

A preferred process variant is that one known under inert gas in each case First melt the polyamide components of the matrix with the additives and mixes homogeneously and then adds the filler to this melt and therein also distributed homogeneously. The molding compound is then discharged, cooled and crushed and dried. Afterwards, it can be processed thermoplastically by any method become. The production of molded parts by the injection molding process is preferred.

In general, the process steps are carried out continuously and under protective gas.

A preferred variant is to run the process as a whole continuously, i.e. stage on a machine, e.g. on a twin-screw extruder.

Another preferred variant is that in a first step only the matrix is produced, and only later the granulated matrix on a second machine or in melted again in a second extrusion pass and filled continuously. At this In the second preferred variant, the process steps are also seen individually when viewed continuously carried out, but separated from the overall process. The advantage of the second varante is that you can be more flexible when using a standard matrix in production can respond to various requests regarding the type and amount of filling material. there the melt is advantageously kept under protective gas (inert gas).

A particularly preferred process variant is the production of the molding composition via the Mix the polyamide components and the additives in the molten state using a continuously operating twin-screw extruder, e.g. type ZSK from Werner and Pfleiderer and incorporation of the metal powder in a second extrusion pass each under inert gas.

It is of very particular advantage when carrying out the method according to the invention the high wettability of the amine-containing melt compared to the matrix according to the invention Metal alloys.

Another very big advantage is the simplicity and the environmental friendliness of the solvent-free Process.

The invention also includes the use of the thermoplastics processors according to the invention Molding compound for the production of permanent magnetic or magnetizable Molded parts through thermoplastic forming.

In addition, it is a further decisive advantage that the molding composition according to the invention can not only be processed further in a simple manner thermoplastic, but also that it and the moldings produced from it can also withstand particularly high, in particular thermal requirements, for example permanent loads at temperatures above 100 ° C. ,
Their short-term application range can even exceed 200 ° C, as HDT A values over 200 ° C can be reached.

Magnetic material molded parts can be easily made from the molding material according to the invention Create way. For high-quality precision parts with excellent magnetic and mechanical Properties are advantageously used in the injection molding process.

Preferred applications are, for example, rotors and stators of electric motors.

The molded parts according to the invention are preferably magnetized as a finished part. Alternative is but also magnetization during the production of molded parts according to the known methods of Technology possible.

The molded parts are rigid, dimensionally stable, excellent temperature and chemical resistant, especially against fats, oils, cleaning agents and neutral and basic media. she are corrosion-resistant when exposed to oxygen and moisture.

Examples

During the production of the molding compounds on the twin-screw extruder, nitrogen was used worked as an inert gas.

Examples 1 to 8

Partly aromatic polyamide T, consisting of 55 mol% hexamethylene terephthalamide and 45 mol% hexamethylene adipamide units, with a melting point of 310 to 315 ° C, (DSC maximum), was on a twin-screw extruder from Werner and Pfleiderer, Stuttgart, type ZSK 30 with different aliphatic polyamides, lubricants and Heat stabilizer compounded in a known manner. In Table 1 are the recipes and Process parameters summarized.

The compounds investigated in the DSC show that the melting point of polyamide T is reduced by the addition of PA6 and PA66, whose own melting band no longer occurs. The compounds are therefore are true alloys of its components with reduced fitness as a matrix, in particular because the heat resistance, such as the H eat D istortion T emperature is lowered.

In contrast, the compounds made of polyamide T and aliphatic polyamides with 10 and more CH ₂ groups per -CONH group are stable 2-phase systems, which are retained in two phases even after repeated melting with an increase in temperature up to 330 ° C. The DSC melting points in Table 1, measured in several melting cycles, prove this impressively.

Thus, in Examples 3 to 8, the melting band of polyamide T is hardly changed even during the third melting and the melting band of the aliphatic polyamides with 10 and more CH ₂ groups per -CONH group are retained and their maximum is hardly changed.

To check this surprising stability of the 2-phase polyamide matrix and its behavior, a reduced proportion of 10% by weight of PA12, each with high flowability, with COOH or with NH _{2 end} groups with polyamide T was used in Examples 7 and 8 compounding temperature of 320 ° C and compounded with increased residence time in the extruder. Even for these stricter manufacturing conditions, the melting bands of polyamide T and the reduced proportion of PA12 are practically unchanged even after the third melting cycle.

Examples 9 and 10

Under the same conditions and on the same extruder as in Examples 1-8 based on the semi-crystalline semi-aromatic polyamide T matrix components, including (analogous to Example 4) amine-terminated PA-12 of high flowability, amine and heat stabilizer manufactured.

For comparative measurement of the flowability, pure polyamide T and the blends from experiments 9 and 10 were melted in an injection molding machine and injected at 328 ° C melt temperature under identical machine settings into an injection mold designed as a long spiral in one plane and held at 140 ° C. Depending on its viscosity, the melt could flow at different distances until it solidified.
The flow path length reached could be measured directly on the solidified spiral injection molded part. It is also a measure of the processability of the molding compound into complex parts.

The formulation and results are shown in Table 2 (on the following page).

Examples 11 and 12

On a double-shaft kneader, matrix materials according to tests 9 and 10 were produced at melt temperatures of 320 - 330 ° C and their flowability via MFR measurement (according to DIN ISO 1133 on a measuring device type MP-D from Göttfert with a nozzle of 0.8 cm length and 0.21 cm diameter) and the density, furthermore the notched impact strength and the tensile values on test specimens produced by injection molding. The compositions and results are shown in Table 3 (on the following page).

It was shown that by increasing the proportion by weight of polyamide 12 (PA12 as in Example 4) The flowability and impact strength can be increased while the other mechanical values changed only insignificantly.

Example 13

On a co-rotating twin-screw extruder, type KF 540 from Berstorff, Hanover, with a screw diameter of 32 mm, neodymium powder, type Magnequench® MQP.B from Delco Remy, Anderson, USA, was placed in a non-pre-extruded matrix mixture of the components according to Examples 11 and 12 incorporated. Compositions and machine parameters are shown in Table 4.

Examples 14 to 17

In a matrix from Example 12, Magnequench® was placed on the extruder analogously to Example 13 MQP.B powder gradually increasing the concentration of 83, 87, 88 and 89 % By weight incorporated. The procedure was similar to that of Example 13, in addition however, with increasing filling level the temperature of the melt and the nozzle up to 325 ° C raised.

The incorporation of Magnequench® MQP.B powder into the prepared matrix was quite possible. 89% by weight of Magnequench® powder was found to be the upper addition limit under the conditions of these examples.
The composition of the molding composition can be found in Table 5 and its properties can be found in Table 6.

Example 18

Using the same extruder as in Example 13, a thermoplastically processable molding composition with the composition according to Table 7 was produced.

Example 19

Granules from Example 13 were at a melt temperature of 320 ° C and a mold temperature from 140 ° C to 80 x 10 x 4 mm flat bars. The sprues were regranulated and 10 and 30% by weight were added to the base granules and these The mixture again sprayed into flat bars. In addition, the bars were each completely shredded and so 1x, 2x and 3x sprayed to flat bars of the given dimension.

Measurement of the remanence and the energy product show no decrease in the magnetic values. The toughness also changes only slightly. It only drops from 3.2 to 2.7 kJ / m ² for 3x completely regranulated material.
Only in the module and tensile strength is there a slight drop in the values after the second complete regranulation because the metal particles are crushed when the molding compound is formed several times, in particular platelets of smaller diameter are formed.
The module drops from 19000 to 16600 N / mm ² and the tensile strength from 97 to 70 N / mm ² .

Example 20 Resistance in the salt spray test

4 mm thick tension rods, ISO 527, type 2, were subjected to a salt spray test as described in the pre-standard DIN 50021 for 8 hours, and the rods were then optically examined for signs of corrosion.
The results are summarized in Table 8.

With long-term treatment in salt spray, the rust formation intensifies with red coloring. Up to a treatment of 48 hours (end of test), the formulations according to Example 13 and Example 15 are lower than for the molding composition according to Example 18. This additionally proves that the thermoplastic plastic materials according to the invention by using linear polyamide containing amino end groups and Amine compounds, which are also excellent lubricants, also have an impact on the environment resist increased mass.

Claims (17)

1. Method for production of a thermoplastically processible moulding substance including a melt cycle with at least 30 vol.-%, relative to the total volume of the moulding substance, of at least one permanently magnetised or magnetisable metal compound embedded in a two-phase matrix and/or metal alloy as filler material in homogenous distribution in the matrix, and the two-phase matrix a) is made available of

   a1) 70 to 99 weight-% of a partially aromatic copolyamide with a proportion of aliphatic dicarboxylic acids of less than 50 Mol-% in the total acid monomer and a melting point above 280°C;

   a2) 1 to 30 weight-% of an aliphatic polyamide or copolyamide with, in a statistical average, at least 10 -CH₂-groups per -CONH-group; and

   a3) 0 to 10 weight-% of additives relevant to characteristics and/or processing; and
   the sum of the matrix components a1) to a3) is 100 weight-%, and

   matrix materials of good temperature resistance are used and mixed through with a magnetic filler material b).
2. Thermoplastically processible moulding substance comprising
   a two-phase matrix a) of

   a1) between 70 and 97 weight-% of a partially aromatic copolyamide with a proportion of aliphatic dicarboxyl acids of below 50 Mol-% of the entire acid monomers and a melting point above 280°C;

   a2) between 3 and 30 weight-% of an aliphatic polyamide or copolyamide with, in a statistical average, at least 10 -CH₂-groups per -CONH-group; and

   a3) between 0 and 10 weight-% of characteristically relevant and/or processing additives; and
   the sum of the matrix components a1) to a3) equals 100 weight-%; and

   b) relative to the total volume of the moulding substance at least 30 vol.-% of at least one permanently magnetic or magnetisable metal compound embedded in the matrix and/or metal alloy as filler material in homogenous distribution in the matrix.
3. Moulding substance according to Claim 2, characterised in that the matrix a) is composed of
   between 80 and 97 weight-% of partially aromatic copolyamide a1) and
   between 20 and 30 weight-% aliphatic polyamide or copolyamide a2).
4. Moulding substance according to Claim 2 or 3, characterised in that the partially aromatic copolyamide a1) has a melting point of at least 300°C.
5. Moulding substance according to one of Claims 2, 3 or 4, characterised in that the partially aromatic copolyamide a1) is composed of 55 Mol-% hexamethylenterephtalamide units and 45 Mol-% hexamethyleneadipamide units.
6. Moulding substance according to one of Claims 2, 3, 4 or 5, characterised in that the aliphatic copolyamide a2) also includes dimerised fatty acid with between 36 and 44 C-atoms as comonomers.
7. Moulding substance according to one of Claims 2 to 6, characterised in that the aliphatic polyamide or copolyamide a2) includes amino end group in surplus.
8. Moulding substance according to one of the above Claims 2 to 7, characterised in that the aliphatic polyamide or copolyamide a2) has a majority of amino end groups of type-NH₂ or -NHR', where R' is an alkyl residue or cyclohexyl residue or the amino group is part of a cycloaliphatic residue.
9. Moulding substance according to one of the above Claims 2 to 8, characterised in that the aliphatic polyamide or copolyamide a2) has between 50 and 200 µAeq./g amino end groups.
10. Moulding substance according to one of the above Claims 2 to 9, characterised in that additive a3) is at least an alkylamin.
11. Moulding substance according to Claim 10, characterised in that the alkylamin a3) is an amin of formula 1 where n = 1 to 3 and R is an alkyl residue with between 12 and 44 C-atoms, which can contain heteroatoms: R-(HN-CH₂-CH₂-CH₂)_n-NH₂
12. Moulding substance according to one of the above Claims 2 to 11, characterised in that the metal compound or metal alloy b) is contained in a volume proportion of at least 45%.
13. Moulding substance according to one of the above Claims 2 to 12, characterised in that the metal compound or metal alloy b) is contained in a volume proportion of at least 55%.
14. Method according to Claim 1, characterised in that, relative to the total volume of the moulding substance, at least 30 vol.-% of at least one permanently magnetic or magnetisible metal compound and/or metal alloy is as magnet filler material homogenously distributed in the matrix via a melt mixing process.
15. Method according to Claim 14, characterised in that in a conventional manner the mixture of the matrix components and the additives is melted under inert gas, homogenously mixed, and subsequently the metal compound and/or metal alloy is added and homogenously mixed in, and the melt is subsequently released, cooled, reduced and dried.
16. Method according to Claims 14 or 15, characterised in that coated metal compounds and/or metal alloys are used.
17. Use of thermoplastically processible moulding substance according to Claim 2 in the production of moulded parts by thermoplastic reshaping.