EP1848774A1

EP1848774A1 - Transparent moulding compound

Info

Publication number: EP1848774A1
Application number: EP06700749A
Authority: EP
Inventors: Harald HÄGER; Franz-Erich Baumann; Michael Beyer
Original assignee: Evonik Degussa GmbH; Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2005-02-19
Filing date: 2006-01-04
Publication date: 2007-10-31
Also published as: WO2006087248A1; CN1821305A; TW200806741A; JP2008530325A; US20080166529A1; DE102005007664A1

Abstract

The invention relates to a moulding compound containing the following components: (a) a partially crystalline copolyamide, and (b) an effective amount of a crystallisation auxiliary selected from nanoscale fillers and metal salts, metal oxides and metal hydroxides that can react with the carboxyl terminal groups of the copolyamide. The copolyamide can be produced from the following combination of monomers: α) 50 to 99 mol. % of a lactam or a corresponding ϖ-aminocarboxylic acid with 8, 9, 10, 11 or 12 carbon atoms or an essentially equimolar mixture of a diamine and a dicarboxylic acid, the diamine being selected from the group comprising 1.6-hexamethylene diamine, 1.8-octamethylene diamine, 1.10-decamethylene diamine and 1.12-dodecamethylene diamine and the dicarboxylic acid being selected from the group comprising sebacic acid and 1.12-dodecanedioic acid, and (ß) 1 to 50 mol. % of an essentially equimolar mixture of a diamine and a dicarboxylic acid, where either the diamine or the dicarboxylic acid or both differ from, respectively, the diamine used in α) and the dicarboxylic acid used in α), or of another lactam or the corresponding ϖ-aminocarboxylic acid. The moulding compound is transparent and readily workable, and can be decorated using screen printing techniques.

Description

Transparent molding compound

The invention relates to a transparent molding compound made from a copolyamide, which is suitable for producing transparent, printable articles.

The utility model DE 295 19 867 Ul describes a decorable film made from a copolyamide which is composed of the monomer units laurolactam and caprolactam and / or hexamethylenediamine / dicarboxylic acid.

Copolyamides of this type are generally transparent and, owing to their low crystallinity, are also easy to decorate by screen printing, but problems repeatedly arise in the production of films from such copolyamides by extrusion. The films crystallize very slowly and only at low temperatures, so that a long cooling section is necessary or only low extrusion speeds are possible. The slow crystallization also causes the film to warp and shrink. When printing on such films by means of screen printing, they easily become brittle due to stress cracking.

Part of the task was to develop transparent, partially crystalline copolyamide compositions for articles such as molded parts and foils that have a rapid crystallization. Another part of the task was to produce such articles from transparent, partially crystalline copolyamide compositions which have no warpage and do not shrink.

In itself, it would be obvious to solve this problem by adding one of the usual crystallization aids (nucleating agents). Such tools have long been known. Usually, however, they lead to the formation of cloudiness, under certain circumstances to specks and, in the case of low film thickness, to roughness on the film surface. This is not acceptable for the intended application.

DE 199 37 117 A1 discloses a film with a layer of a copolyamide with nanoscale nucleating particles dispersed therein; the copolyamide contains building blocks which are derived from aromatic monomers; the rest of the building blocks are based on PA6 or PA6 / 66. The nucleation reduces the post-shrinkage of the film. The script also shows that the film can be printed; the methods used to do this are not specified. This film is used as food packaging.

In the article by M. Beyer and J. Lohmar, Kunststoffe 90 (2000) 1, pp. 98-101, examples of printable films made from PA12 molding compounds are given. However, the transparency and printability by means of screen printing are still in need of improvement in the case of such films.

An essential aspect of the task on which this is based is that a polyamide molding compound should be made available which can be processed into articles such as molded parts or foils which can be easily printed by means of screen printing. This requires a low crystallinity of the polyamide so that the colorant can be anchored in the surface of the article to be decorated by dissolving the polyamide.

Surprisingly, this object was achieved by a molding composition which contains the following components: a) a partially crystalline copolyamide as indicated below and b) an effective amount of a crystallization aid which is selected from

- Nanoscale fillers and / or

- Metal salts, metal oxides or metal hydroxides, which can react with the carboxyl end groups of the copolyamide.

Surprisingly, despite the forced crystallization, molding compositions of this type can be decorated well by means of screen printing.

Copolyamides which can be used according to the invention can be prepared from the following monomer combination: α) 50 to 99 mol%, preferably 60 to 98 mol%, particularly preferably 70 to 97 mol% and particularly preferably 80 to 96 mol% of a lactam or the corresponding o> Aminocarboxylic acid with 8, 9, 10, 11 or 12 carbon atoms or an essentially equimolar mixture of a diamine with a dicarboxylic acid, diamine and dicarboxylic acid being counted individually when calculating the composition, and the diamine is selected from group 1.6 Hexamethylene diamine, 1.8 octamethylene diamine, 1.10 decamethylene diamine and 1.12 dodecamethylene diamine and the dicarboxylic acid is selected from the group of sebacic acid and 1.12 dodecanedioic acid and β) 1 to 50 mol%, preferably 2 to 40 mol%, particularly preferably 3 to 30 Mol% and particularly preferably 4 to 20 mol% of an essentially equimolar mixture of a diamine and a dicarboxylic acid, wherein either the diamine or the

Dicarboxylic acid or both differ from the diamine optionally used under α) or the dicarboxylic acid optionally used under α), or a lactam or the corresponding co-aminocarboxylic acid which differs from the optionally used lactam or the corresponding co-aminocarboxylic acid of component α ) differentiate. Diamine and dicarboxylic acid are also used here when calculating the

Composition counted individually. In one possible embodiment, either the diamine or the dicarboxylic acid or both are branched or cyclic.

Suitable diamines of component β) have 4 to 40 carbon atoms; For example, 1,6-hexamethylene diamine, 2-methyl-1,5-diaminopentane, 2,2,4- or 2,4,4-trimethyl hexamethylene diamine, 1,9-nonamethylene diamine, 1,10-decamethylene diamine, 4,4'-diamino-dicyclohexyl methane, 3,3 '-dimethyl-4,4 come '-diaminodicyclohexylmethane, 4.4' -diamino-dicyclohexylpropane, 1.4-diaminocyclohexane, 1.4-bis (aminomethyl) cyclohexane, 2.6-

Bis (aminomethyl) norbornane and 3-aminomethyl-3.5.5-trimethylcyclohexylamine in question. Mixtures of different diamines can also be used.

Suitable dicarboxylic acids of component β) also have 4 to 40 C atoms; Examples include adipic acid, 2.2.4- or 2.4.4-trimethyladipic acid, azelaic acid, sebacic acid, 1.12-dodecanedioic acid, cyclohexane-1,4-dicarboxylic acid, 4.4 '-dicarboxydicyclohexylmethane, S.S'-DimethyM ^' - dicarboxydicyclohexylmethane, 4.4'- Dicarboxydicyclohexylpropane and 1,4-bis (carboxymethyl) cyclohexane. Mixtures of different dicarboxylic acids can also be used. Suitable other lactams or corresponding co-aminocarboxylic acids are those with 6, 7, 8, 9, 10, 11 or 12 carbon atoms.

The copolyamide used has a certain crystallinity, so that a minimum degree of stress crack resistance is guaranteed. The enthalpy of melting of the molding composition, determined by DDK according to DIN 53765 in the 2nd heating curve with a heating rate of 20 K / min, is generally at least 10 J / g, preferably at least 15 J / g and particularly preferably at least 20 J / g. The melting peak associated with the crystallite melting point T _m is generally between 100 and 220 ° C., preferably between 120 and 210 ° C. and particularly preferably between 140 and 200 ° C.

In general, the copolyamide has a relative solution viscosity η _re i, measured in a 0.5% strength by weight solution in m-cresol at 23 ° C. according to ISO 307, from about 1.5 to about 2.5 and preferably about 1.7 to about 2.2. In a preferred embodiment, the melt viscosity, measured in a mechanical spectrometer (cone plate) according to ASTM D 4440 at 240 ° C. and a shear rate of 100 s ^" , is 1.250 to 10000 Pas, preferably 350 to 8000 Pas and particularly preferably 500 to 5000 Pas.

The crystallization aid is generally added to the copolyamide in an amount of 0.001 to 5% by weight.

Nanoscale fillers are modified layered silicates, for example. The aspect ratio (the quotient of lateral dimensions and layer thickness) is generally at least 20, preferably at least 30 and particularly preferably at least 50, the layer thickness being 0.5 to 50 nm, preferably 1 to 35 nm and particularly preferably 1 to 20 nm . Polymer nanocomposites made from organophilized phyllosilicates and polymers were first described in US Pat. No. 2,531,396. The organophilization of layered silicates is also known, for example, from US Pat. Nos. 2,531,472, 2,996,506, 4,105,578, 4,412,018, 4,434,075, 4,434,076, 4,450,095 and 4,874,728. An overview of phyllosilicates can be found in the textbook on inorganic chemistry, Arnold F. Holleman, Niels Wiberg, 91.-100. Edition, published by Walter de Gruyter, Berlin-New York, 1985, pages 764 to 786. Organic modified layered silicates are now available from various companies, for example from Südchemie AG (brand name: Nanofil), Southern Clay Products (brand name: Cloisite), Rheox GmbH (brand name: Bentone), Laporte (brand name: Laponite), COOP Chemical (brand name: Somasif ) and TOP (brand name: Planomer).

The production of polymeric nanocomposites from polyamides and pretreated layered silicates is known. An overview of this topic can be found in the following applications and articles: US 5 721 306, EP-AO 747 451, WO 93/11190, WO 93/04118, WO 93/04117, EP-AO 398 551, US 4 739 007 , US 4 810 734, DE-A-38 10 006, US 5 385 776; P. Reichert et al., Acta Polymer. 49, 116-223; A. Usuki et al., J. Mat. Res., 1993, 8, 1179; Y. Kojimma et al., J. Mat. Res., 1993, 8, 1185; Y. Kojimma et al., J. Appl. Sci., 1993, 49, 1259; L. Lin et al., J. Appl. Pole. Sci., 1999, 71, 1133-1138; B. Hoffinann et al., Colloid Pol. Sci., 2000, 278, 629-636.

EP-A-0 358 415 describes the production of polymeric nanocomposites by polymerizing lactams in the presence of pretreated layered silicates. This improves the barrier properties against gases, heat resistance and rigidity.

Quantities of 0.001 to 2% by weight, particularly preferably 0.01 to 1.5% by weight and particularly preferably 0.1 to 1% by weight of the nanoscale fillers are preferably introduced into the copolyamide matrix, as a result of polycondensation can be accomplished in the presence of the filler or by subsequent compounding. The layered silicates montmorillonite, hectorite, saponite and synthetic layered silicates are particularly suitable nanoscale fillers.

Suitable metal salts, metal oxides and metal hydroxides react with the end groups of the copolyamide, the resulting neutralized end groups having a nucleating effect. It is advantageous if the copolyamide has an excess of carboxyl end groups. Alkali or alkaline earth metal carbonates or hydrogen carbonates can be used particularly advantageously. The reaction produces water and carbon dioxide, which can be easily removed from the copolyamide melt. Of the metal salts, oxides or hydroxides, preferably 0.01 to 5% by weight, particularly preferably 0.1 to 4% by weight and particularly preferably 0.5 to 3% by weight, based on the copolyamide, used. For example, lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium hydroxide, magnesium hydroxide, calcium hydroxide, magnesium oxide, calcium oxide, strontium oxide and barium oxide. In order to ensure the desired transparency, generally only as much should be added as can be dissolved in the melt under reaction with the carboxyl end groups.

Corresponding compounds of heavy metals can of course also be used, e.g. B. zinc carbonate. However, such compounds are often ecologically questionable and often lead to a deterioration in the aging resistance of the molding composition.

The molding composition can contain auxiliaries and additives in the amounts customary for polyamide molding compositions, for example stabilizers or dyes.

The molding composition according to the invention can be used for the production of articles such as moldings or films, which are also the subject of the invention. In a preferred embodiment, the films have a thickness of 0.05 to 1 mm, particularly preferably from 0.1 to 0.8 mm and particularly preferably from 0.2 to 0.6 mm.

The film can also have a multi-layer design, the following embodiments being preferred:

1. The multilayer film contains a further layer of a polyamide elastomer molding composition, in particular a polyether amide or a polyether ester amide, and preferably a polyether amide or polyether ester amide based on a linear aliphatic diamine having 6 to 18 and preferably 6 to 12 carbon atoms, a linear aliphatic or an aromatic dicarboxylic acid with 6 to 18 and preferably 6 to 12 carbon atoms and a polyether with more than an average of 2.3 carbon atoms per Oxygen atom and a number average molecular weight of 200 to 2,000. The molding composition of this layer may contain further blend components such as. B. polyacrylates or polyglutarimides with carboxyl or carboxylic anhydride groups or epoxy groups, a functional group-containing rubber and / or a polyamide. Such molding compositions are state of the art; they are described, for example, in EP 1 329 481 A2 and DE-OS 103 33 005, to which express reference is made here. In order to ensure good layer adhesion, it is advantageous if the polyamide portion of the polyamide elastomer is built up from the same monomers as are used as the monomer combination a) in the copolyamide of the other layer.

2. The multilayer film contains a further layer of a molding composition based on the same or a similar copolyamide and / or a polyamide, which is preferably composed of the same monomers as are used as the monomer combination a) in the copolyamide of the other layer.

3. The multilayer film contains an adhesion promoter layer for binding to the substrate or for connection within the multilayer film structure, for example a polyolefin functionalized with carboxyl or acid anhydride groups or with epoxy groups, a blend of the material of the bottom layer and the substrate material or a thermoplastic polyurethane .

These embodiments can also be combined with one another. In any case, it is preferred that the layer of the molding composition used according to the invention forms the cover layer. However, it can also be used as an intermediate or underlying layer. If necessary, for example with increased requirements for scratch resistance, the cover layer can optionally also be provided with a protective layer, for example with a clear lacquer based on polyurethane. If necessary, it can also be covered with an assembly film which is removed after the finished part has been produced.

The second, lower layer or, in the case of more than two layers, one of the layers below can be colorless, transparent, colored or opaque to show special design variants in combination with the transparent top layer can. In such cases, the transparent cover layer can also be printed from the top.

The films can be used, for example, as a protective film against dirt, UV radiation, weather influences, chemicals or abrasion, as a barrier film on vehicles, in the household, on floors, tunnels, tents and buildings or as a decorative support for covering surfaces of sports equipment, interior or exterior decorations on motor vehicles, boats, in the household or on buildings. These possible uses also apply to cases in which the molding compound is opaque colored. The integral connection of the film to the substrate can be produced, for example, by gluing, pressing, laminating, coextrusion or back injection. To achieve improved adhesion, the film can be flame-treated or treated with a plasma beforehand, for example.

The invention is illustrated by way of example below.

Comparative Example 1:

A copolyamide composed of 80 mol% laurolactam and 20 mol% caprolactam is used; η _re i = 1.9; Amino group concentration 30 mmol / kg; Carboxyl group concentration 60 mmol / kg.

Comparative Example 2:

A copolyamide composed of 80 mol% laurolactam and 20 mol% of an equimolar mixture of hexamethylenediamine and dodecanedioic acid is used. η _re i = 1.89; Amino group concentration 37 mmol / kg; Carboxyl group concentration 60 mmol / kg.

Comparative Example 3:

A copolyamide of 85 mol% laurolactam, 7.5 mol% isophoronediamine and 7.5 mol% 1.12-dodecanedioic acid is used. η _re i = 1.85; Amino group concentration 45 mmol / kg; Carboxyl group concentration 42 mmol / kg.

Example 1 : The same copolyamide as in Comparative Example 1 was melt blended with 0.1 wt .-% Nanofil ^® 804, an organically modified phyllosilicate bentonite type of Südchemie AG, D-85368 Moosburg in a twin screw extruder, extruded and pelletized. η _re i = 1.9.

Example 2:

In the preparation of the same copolyamide as in Comparative Example 2 was 0.1% Nanofil ^® 804, based on the copolyamide produced, mixed with the laurolactam, and, after addition of the remaining monomers, the entire mixture was then polymerized. The product was discharged as a melt strand and granulated. η _re i = 1.76; Amino group concentration 35 mmol / kg; Carboxyl group concentration 67 mmol / kg.

Example 3:

In the preparation of the same copolyamide as in Comparative Example 3 was 0.1% Nanofil ^® 804, based on the copolyamide produced, mixed with the laurolactam, and, after addition of the remaining monomers, the entire mixture was then polymerized. The product was discharged as a melt strand and granulated. η _re i = 1.73; Amino group concentration 22 mmol / kg; Carboxyl group concentration 37 mmol / kg.

Example 4:

In the production of the same copolyamide as in Comparative Example 1, an amount of sodium carbonate which was equivalent to the carboxyl group content to be achieved of 60 mmol / kg was added from the start of the polymerization. The product was extruded as a melt strand and granulated. η _re i = 1.9.

Example 5:

In the production of the same copolyamide as in Comparative Example 2, an amount of sodium carbonate which was equivalent to a carboxyl group content of 75 mmol / kg to be achieved was added from the start of the polymerization. The product was extruded as a melt strand and granulated. η _re i = 1.76.

Example 6: When the same copolyamide as in Comparative Example 3 was produced, 0.1 wt.

(S)

% of the layered silicate BENTONE 38 (an organically modified hectorite from Rheox GmbH, D-51307 Leverkusen), based on the copolyamide to be prepared, mixed with the laurolactam, and after the addition of the remaining monomers, the entire mixture was polymerized. The product was discharged as a melt strand and granulated, η _re i = 1.76; Amino group concentration 25 mmol / kg; Carboxyl group concentration 31 mmol / kg.

Comparative Example 4: The same copolyamide as in Comparative Example 1 was melt-mixed, extruded and granulated with 0.1% by weight of the nucleating agent Mikrotalkum IT extrafine in a twin-screw extruder. η _re i = 1.9.

Films with a thickness of 0.4 mm were extruded and evaluated from the products of Examples 1 to 6 and Comparative Examples 1 to 4. The results are shown in the table below.

In the case of the molding compositions with poor processability, the slow recrystallization caused a considerable delay.

Table: Assessment of the molding compounds

All foils could be decorated well using screen printing.

Claims

Claims:

1. Molding composition which contains the following components: a) a partially crystalline copolyamide and b) an effective amount of a crystallization aid which is selected from nanoscale fillers and / or

Metal salts, metal oxides or metal hydroxides which can react with the carboxyl end groups of the copolyamide,

characterized in that the copolyamide can be prepared from the following monomer combination: α) 50 to 99 mol% of a lactam or a corresponding ω-aminocarboxylic acid having 8, 9, 10, 11 or 12 carbon atoms or an essentially equimolar mixture of a diamine and a dicarboxylic acid, the diamine being selected from the

Group 1.6-hexamethylenediamine, 1.8-octamethylenediamine, 1.10-

Decamethylenediamine and 1.12-dodecamethylenediamine and the dicarboxylic acid is selected from the group of sebacic acid and 1.12-dodecanedioic acid and β) 1 to 50 mol% of an essentially equimolar mixture of a diamine and a dicarboxylic acid, either the diamine or the dicarboxylic acid or both being different the diamine or the dicarboxylic acid optionally used under α) or a lactam or the corresponding co-aminocarboxylic acid which differ from the optionally used lactam or the corresponding co-aminocarboxylic acid of component α).

2. Molding composition according to claim 1, characterized in that its enthalpy of fusion is at least 10 J / g.

3. Molding composition according to one of the preceding claims, characterized in that its melting enthalpy is at least 15 J / g.

4. Molding composition according to one of the preceding claims, characterized in that its melting enthalpy is at least 20 J / g.

5. Molding composition according to one of the preceding claims, characterized in that its crystallite melting point T _{m is} between 100 and 220 ° C.

6. Molding composition according to one of the preceding claims, characterized in that its crystallite melting point T _{m is} between 120 and 210 ° C.

7. Molding composition according to one of the preceding claims, characterized in that its crystallite melting point T _{m is} between 140 and 200 ° C.

8. Molding composition according to one of the preceding claims, characterized in that the crystallization aid is added to the copolyamide in an amount of 0.001 to 5% by weight.

9. Molding composition according to one of the preceding claims, characterized in that the molding composition as a crystallization aid, based on the copolyamide, 0.001 to 2 wt .-% of a nanoscale filler and / or 0.01 to 5 wt .-%

Contains metal salt, metal oxide or metal hydroxide.

10. Molding composition according to one of the preceding claims, characterized in that a modified layered silicate is used as the nanoscale filler.

11. Use of the molding composition according to one of the preceding claims Production of a printable or printed article.

12. Use according to claim 11, characterized in that the printable or printed article is a molded part or a film.

13. Printable or printed article, produced from the molding composition according to one of claims 1 to 10.

14. Printable or printed article according to claim 13, characterized in that it is a molded part or a film.

15. A film according to claim 14, characterized in that it is 0.05 to 1 mm thick.

16. Film according to one of claims 14 and 15, characterized in that it is 0.1 to 0.8 mm thick.

17. Film according to one of claims 14 to 16, characterized in that it is 0.2 to 0.6 mm thick.

18. Foil according to one of claims 14 to 17, characterized in that it is designed in multiple layers.