EP1563009A1 - Polyamide molding material, molded articles that can be produced therefrom and the use thereof - Google Patents

Abstract

The invention relates to a novel polyamide molding material for highly lustrous and rigid polyamide molded articles that contains a polyamide mixture consisting of a semicrystalline linear polyamide, a special branched graft polyamide, an amorphous polyamide, reinforcing substances as well as conventional additives.

Description

 Polyamide molding compound, molded parts that can be produced therefrom and their use

The invention relates to reinforced polyamide molding compositions with improved processing behavior, increased flowability and molded articles produced therefrom with improved surface quality and improved mechanical properties, in particular in the conditioned state after moisture absorption. The molding compound according to the invention is suitable for the production of molded parts, in particular with large wall thicknesses, or other semi-finished or finished parts which, for example, can be produced by extrusion, extrusion blow molding, extrusion stretch blow molding, pultrusion, injection molding, micro injection molding, GIT injection molding, injection blowing or other shaping techniques.

Reinforced polyamides play an increasing role in the field of engineering construction materials in addition to high rigidity, toughness and heat resistance for use in the visible area, must show an optimal surface quality. Areas of application are interior and exterior parts in the automotive and other transport sectors, housing material for devices and apparatus for telecommunications, consumer electronics, household appliances, mechanical engineering, heating systems and fastening parts for installations. External parts that are exposed to the weather require additional stabilization in order to ensure the necessary function for several years.

The particular advantage of reinforced polyamides is the exceptionally good bond between the polymer matrix and reinforcing materials. This enables high levels of reinforcement, which lead to highly rigid products, which can be easily processed in an injection molding process due to the low melt viscosity of polyamides.

Disadvantages of reinforced polyamide molding compounds, such as glass fiber reinforced polyamide 6 (PA6), lie in the sharp drop in mechanical properties (rigidity, tensile stress at break) and the sharp increase in elongation at break due to water absorption in the standard atmosphere.

High proportions of reinforcing materials, such as glass fibers, carbon fibers or others, in a rapidly solidifying, partially crystalline polymer matrix reduce the flowability, for example in injection molding processing, and lead to reduced surface quality. For this reason, reinforced moldings made from semi-crystalline polyamides (PA6, PA66, PA6T / 66 etc.) result from the high melting temperature and a very high rate of crystallization to poor surfaces, especially with high reinforcement proportions and with molded parts with high wall thickness. In these cases, attempts are made to keep the degree of filling low and to achieve rigidity by ribbing.

It is known that the flowability of polymer melts can be increased and the solution viscosities / melt viscosities can be reduced by branched polymers. Branched polyamides for improving flow are also known and can be produced in various ways.

EP 1 120 443 A2 describes transparent polyamide mixtures in which a branched polyamide component based on the transparent polyamide is used to improve the flow. The resulting, unreinforced mixtures are stiffer but less impact-resistant than the purely transparent polyamides. The branched polyamide is made using a polyamine dendrimer. Transparent polyamides must be used as the basis of the mixtures and the mixtures must remain transparent.

EP 0 672 703 A1 also describes the structure of branched, star-shaped polyamides from linear polyamides with dendrimers as branching agents for improving the flow.

The structure of star-shaped polyamides from lac amen is described in EP 0 832 149 B1 by a two-stage process with a triazine derivative or a trifunctional amine as branching agent. The resulting star-shaped (3 arms) polyamides show a ne reduction of melt and solution viscosity. Lactam polymerization with the branching agents also provides a mixture of low molecular weight, linear polyamides and branched polyamides.

The production of H-shaped polyamides from lactaenes or aminocarboxylic acids with at least trifunctional amines (dendrimers) or trifunctional carboxylic acids as branching structures is known from DE 19 654 179 AI. The H-shaped polyamides show improved flow behavior with good mechanical properties. This document only deals with the production of the branched polyamides and does not describe any reinforced molding compounds.

Process for the preparation of branched graft polyamides (AB type), which can be used as an unreinforced blend component or as a hot melt adhesive, from diamines and dicarboxylic acids via precondensates which appear to crosslink or via a hydrolytic degradation of e.g. PA66 with polyamines as a branching structure are described in EP 1065 232 A2.

Furthermore, EP 1 065 236 A2 discloses hydrolysis-stable, low-viscosity, branched polyamides which are produced in a batch process from caprolactam and a polyamine. The polyamides obtained are preferably used as unreinforced, solvent- and fuel-resistant molding compositions.

US Pat. No. 5,480,994 presents highly branched, hyper-branched polyamides / polyesters which are mixed with semi-crystalline or amorphous thermoplastics for molecular reinforcement. In the prior art listed above, however, no reinforced, polyamide molding compositions with branched polyamides are described, and the effect of the branched polyamides on the flowability of the reinforced molding compositions and the mechanical properties, even after moisture absorption, and the surface quality of molded parts produced therefrom is not described.

WO 0 068 298 describes the production of highly branched, hyperbranched, dendrimer-like polyamides (PA6) with short PA6 arms, from 2 -10 caprolactam units per arm, as an additive for improving the melt flow of reinforced, thermoplastic molding compositions. The molding compositions produced in this way are characterized by a higher breaking stress and a higher Tg.

Reinforced polyamide molding compositions are also presented in EP 1099 727 A2. They consist of mixtures of thermoplastic polyamides with highly branched, so-called hyperbranched, polyetherimides, which are obtained by the polymerization of 1-oxazolines. The molding compositions are characterized by improved flowability and a reduction in the crystalline content.

WO 0 196 474 describes the visual surface improvement of injection molded parts by mixing linear, partially crystalline polyamides with highly branched, polyamide 6, with short polyamide 6 arms, and reinforcing materials.

In this state of the art, too, there is no solution for molded articles made of reinforced polyamide mixtures with an appealing surface quality and good mechanical ani see properties given after moisture absorption. Furthermore, the production methods of the branched polyamides for improving the flow in the documents mentioned are usually very complex, in some cases with multi-stage processes, or they do not provide any defined structures, or the structures for branching are very expensive and have no relation to their use.

It is therefore the task to find polyamide molding compounds which, at high fill levels, have a high melt flowability and a high gloss on molded parts. In the dry and conditioned state, the molding compositions should have the smallest possible differences in the mechanical properties, the highest possible heat resistance and moderate processing temperatures.

This object is achieved in relation to the molding composition by the features of claim 1 and in relation to the

Moldings also solved the features of claim 15. The subclaims show advantageous developments.

Surprisingly, it was thus found that the addition of branched, highly flowable graft polyamides, which are derived from linear, semi-crystalline polyamides, to give linear semi-crystalline polyamides and amorphous polyamides, molding compositions which, with high reinforcement proportions, have a high stiffness, a high breaking stress, one show high impact strength even after absorption of moisture and have a high flowability of the melt or a low solution viscosity and molded articles produced therefrom have a high surface quality. What is important in the case of the polyamide mixture A) is not only that it has a combination of a semicrystalline linear polyamide a) with a branched graft polyamide b), but that the graft polyamide b) has to meet special conditions.

According to claim 1, the graft polyamide bl) is composed of a styrene-maleimide basic structural unit of the general formula 1

where m stands for 1-5 and n stands for 3-15, the molar mass of the basic structural unit being between S00 and 9000 g / mol and that a polyamic acid chain was grafted onto position x. Such a graft polyamide is basically known in the prior art. Reference is made to EP 0 409 115 B1 for this and to a related process for the production of such graft polyamides. Reference is expressly made to the disclosure content of this document. It is then preferred if the styrene-maleimide basic structural unit of the formula I is linked to the polyamic acid chains via imide bonds at x. The molecular weight is then very particularly preferably between 10,000 and 100,000 g / mol.

Another possibility is to use a graft polyamide b.2.) Which has been obtained by hydrolytic polymerization from amino acids and / or lactams as basic building blocks, where preferably have at least 50% by weight of the polymer molecules more than one chain branch. During production, branched components with the following composition are added to the melt of the basic monomers:

an at least trifunctional, from an amine or a carboxylic acid monomer existing and b.2.2) 2-100 .mu.mol / g Pol ^* ymeres an at least trifunctional b.2.1) 5-150 .mu.mol / g of polymer when b.2.1 an amine from a Carboxylic acid or if b.2.1 is a carboxylic acid, monomers consisting of an amine. If necessary, 5 to 450 μmol / g

Polymer of a monomer having a monofunctional action in a conventional polycondensation can be added.

Such graft polyamides are described in EP 0 345 648 A2, the disclosure content of which is therefore also expressly referred to.

It is particularly important here that the graft polyamide b) preferably differs from PA6, PA11 and / or

PA12 derives and has more than 3 arms. The molecular weights of the individual arms must be high enough to form a hooking network so as not to produce a drop in toughness. It is also preferred if the relative viscosity (1% in H ₂ SO ₄ , 23 ° C.) <2.2 and 30 ° C. above the melting temperature is a melt viscosity (γ = 500 / s) <50 Pas. It is also important that, in the case of mixtures, the number-average and weight-average molecular weight of the graft polyamide, determined via gel

Permeation Chromatography (GPC), roughly the mole corresponding to the linear weights of the linear polyamides and that the graft polyamide enables a significant flow improvement of the melt. It is also particularly important that the graft polyamide can be easily produced on polymerization plants customary for polyamides. The surface quality of moldings can be measured using the gloss value or assessed visually. From a material point of view, the polyamide mixture A) in the case of the semi-crystalline linear polyamides a) comprises those which are selected, for example, from PA6, PA66, PA12, PA6T, PA6T12, PA12T, the terephthalic acid (T) here also being partly by isophthalic acid (I) or a-dipinic acid can be replaced or mixtures thereof.

The polyamide mixture A) also contains an amorphous polyamide c). This is preferably selected from PA MACM12, PA PACM12 or mixtures of copolyamides thereof, and also PA6I, PA MXDI, PA6I / MXDI, where isophthalic acid (I) can be partly replaced by terephthalic acid (T) or adipic acid and MXDA partly by PXDA. The amorphous polyamide is very particularly preferably selected from PA6I / 6T and / or PAMX-DI / MXDT / 6I / 6T.

The polyamide mixture A) is constructed in such a way that the components linear polyamide a) graft polyamide b) and amorphous polyamide c) and optionally carbon black d) together make up 100% by weight.

The polyamide mixture A) contains 0.5-95% by weight of the semi-crystalline linear polyamide a) and 5-99% by weight of the branched graft polyamide b) and 0.5-40% by weight of the amorphous polyamide c). The graft polyamide is constructed as explained above. It is preferred if the polyamide mixture A) 0.5- Contains 80% by weight of the semi-crystalline linear polyamide a) and 15-98.5% by weight of the branched graft polyamide b) and 1-35% by weight of the amorphous polyamide c). The weight ratios are very particularly preferably in the range from 1 to 64.5% by weight for the semi-crystalline linear polyamide a and 18-79.5% by weight for the branched graft polyamide b) and 20-35% by weight. for the amorphous polyamide c). In this case, 0.5-2% by weight of carbon black is then contained.

In addition to the polyamide mixture A), the molding composition contains 40 to 235 parts, preferably 40 to 150 parts, based on 100 parts of matrix component of reinforcing materials B). The reinforcing materials B are selected from glass fibers, glass rovings, glass spheres, glass powder, polymer fibers, carbon fibers, metal fibers or minerals such as talc, kaolin, wollastonite, which preferably have small particle sizes, high tendency to disperse and high aspect ratios. Mixtures of these or suitable master batches can of course also be used.

In addition to the polyamide mixture A) and the reinforcing material B), the molding composition contains customarily known additives C). Such additives are e.g. stabilizers,

Lubricants, dyes, metal filters, metallic pigments, stamped metal filters, flame retardants, impact modifiers, antistatic agents, conductivity additives, anti-fogging agents, optical brighteners, fragrances, etc.

The molding composition of the invention shows u. a. an improved melt flow.

Due to the improved melt flow and the reduced crystallization speed, optically high-quality molded parts can be produced in larger dimensions. The moldings have an excellent surface quality, expressed by the surface-5 chenglanz at an angle of 60 ° bigger 75. A particular advantage of products with very smooth surfaces, made of the erfindungsggmässen molding material, manifests itself in an excellent Metal ^• lisierbarkeit according to galvanic as , Lamination and loading

10 steaming methods and also excellent paintability. Furthermore, high-quality products can be obtained from the molding composition according to the invention when using internal gas pressure (GIT) or internal water pressure processes.

• 15

The high reinforcement content of the molding composition according to the invention makes it possible to produce highly rigid end products.

For the production of the molding composition according to the invention, conventional polymerization plants can be used for the production of polyamides and kneaders and / or single-screw extruders, which contain suitable conveying and kneading elements 25, can be used for the production of the mixtures. The are preferred

Matrix components and all additives / additives are metered into the feed zone of the extruder and the reinforcing materials are fed in and mixed via side feeders, as close as possible to the discharge nozzle. suitable

30 melt temperatures are between 230 ° C and 300 ° C.

Individual additives can optionally also be used in the form of suitable masterbatch granules or as compactates.

35

The production of molded parts, semi-finished products, extrudates or hollow body is carried out on commercially available systems, the suitable processing temperatures being between 250 ° C and 300 ° C. During processing, individual components in the form of masterbatch granules or compactates can be added directly in the preprocessing machine.

Suitable regulators can be added in the preparation of the graft polyamides and the linear polyamides in order to maintain the viscosity in the desired range. Monoamines or monocarboxylic acids are preferably used. Regulators such as 4-amino-2, 2, 6, 6-tetraalkylopiperidine or 2, 6-dialkylphenols with methylamine or carboxyl group or types of regulators which are one or more of these are particularly preferred

Groups included. Suitable amounts are 0.5 to 5 mol% based on the amount of lactam or diamine used.

Furthermore, catalytically active compounds based on phosphorus compounds, such as hypophosphorous acid, phosphorous acid or phosphoric acid, can be added to the polycondensation batch in amounts of 10 to 500 ppm, and suitable antioxidants such as sterically hindered hydroxyphenols or HALS stabilizers in amounts of 0. 05-0.5 Ge. -%.

To prevent foam formation in the polymerization or polycondensation process, suitable defoamers on silicone or silicone derivatives, preferably in the form of stable aqueous emulsions with added silica in concentrations of 10 to 500 ppm, can be added to the polymerization batch. Another variant consists in the addition of layered silicates such as, for example, montmorillonite, bentonite or mica, preferably with high aspect ratios, which are added directly during the extrusion of the molding composition and which can be present in the end product in an exfoliated form.

The polymerization or polycondensation batch can optionally contain suitable release agents and lubricants, such as, for example, fatty acid esters, waxes or fatty acid amides.

Examples

The following examples are intended to illustrate the invention without restricting it.

Property measurements

The properties labeled "cond." Were measured on conditioned test specimens, the properties labeled "tro." were measured on dry test specimens. Conditioning was carried out in accordance with ISO 1110.

The measurements of the thermal data were carried out on dry granules (120 ° C / 24h) with a Perkin Elmer DSC device with heating rates of 20 ° C / min and cooling rates of 5 ° C / min.

The melting temperature was measured according to ISO 3146-C. The crystallization temperature, enthalpy of crystallization and rate of crystallization were determined in the first cooling cycle. To determine the glass transition temperature (Tg), the sample was heated to about Tg + 20 ° C, quenched and in one second heating cycle (20 ° C / min) measured.

The mechanical properties of tensile modulus of elasticity, tensile strength and elongation at break were measured by tensile tests on standard test specimens in accordance with ISO 527.

The impact and notched impact values were determined according to Charpy at 23 ° C according to ISO 179eü and ISO 179eA.

The heat resistance (HDT A and HDT C) were measured according to ISO 75.

The flow lengths were determined in a spiral form 1.5 x 10 mm at 290 ° C measuring temperature, 100 ° C mold temperature and 1000 bar.

The gloss measurements were determined using a Lange color measuring device (color pen) on color plates (FP) with a thickness of 3 mm.

Materials used:

Grilon A28 (from EMS-CHEMIE AG / CH) a linear, partially crystalline PA6 with a rel. viscosity

(1% in 98% H2S04 23 ° C) of 2.81 Grilon A23 (from EMS-CHEMIE AG / CH) a linear, partially crystalline PA6 with a rel. Viscosity (1% in 98% H2S04 23 ° C) from 2.44 - Grivory G21 (from EMS-CHEMIE AG / CH) an amorphous

CoPolyamid (PA6I / 6T) glass fibers from Vetrotex

PA6 carbon black masterbatch (from EMS-CHEMIE AG / CH) with 25% carbon black content, for example: Black Pearl 880 (from Camot) and different additives common for polyamides. origin.

Furthermore, the branched graft polyamide, a branched polyamide 6 (PA6v), which is relevant for the invention, is used according to EP 0 409 115 and is produced as follows.

1737 g of SMA 1000 (oligomeric styrene-maleic anhydride copolymer, Mn ~ 1000 g / mol with ~ 7-8 maleic anhydride units;

Atofina) filled with 40909.5 g of caprolactam, 2353.5 g of tridecylamine and 18 l of water, heated to 265 ° C. until a pressure of 22 bar developed and held at this pressure for 5 hours. The mass was then cooled to 260 ° C. and let down to normal pressure for 6 h. The branched PA6 was discharged, granulated, extracted with water to remove residual caprolactam and oligomers, and dried.

The branched PA6 (PA6v) has the following properties in comparison to Grilon A23 (Table 1)

Table 1 Properties of PA6v:

Preparation of Examples (B1-B4) and Comparative Examples (VB1-VB3):

In a ZSK25 twin-screw extruder (Werner & Pfleiderer / D), the components according to Table 2 were extruded as follows at an increasing cylinder temperature of maximum 260 ° C by introducing the polyamide mixture with additives into the feed at 100 ° C and the glass fibers over one Side defeeders (5-6 zones after moving in) were metered into the melt. The melt strand was cooled in a water bath, granulated and dried.

The molding compositions thus produced and the molded parts produced therefrom by injection molding have the properties listed in Table 3. Table 2 Composition of the molding compositions

Table 3 Properties of the molding compounds

Claims

claims Containing polyamide molding compound for high-gloss, rigid polyamide molded articles A) 100 parts of a polyamide mixture of a) 0.5-95% by weight of a semi-crystalline linear polyamide, b) 5-99% by weight of a branched graft polyamide b.l.) from a styrene-maleimide Basic structure of the general formula 1 where -m stands for 1-5 and -n stands for 3-15 and the molecular weight of the basic structural unit is between 600 and 9000 g / mol and consists of polyamic acid chains grafted on at position X and / or b.2.) obtained by hydrolytic polymerization from amino acids and / or lactams as basic building blocks, components having a branching action are added to the melt of the basic building blocks in the following compositions: b.2.1.) 5-150 μmol / g polymer of an at least trifunctional monomer consisting of an amine or a carboxylic acid and b.2.2.) 2-100 μmol / g polymer of an at least bi-functional if b.2.1.) an amine is a carboxylic acid or if b.2.1.) a carboxylic acid is an amine monomer c) 0.5 -40% by weight of an amorphous polyamide and d) 0-2% by weight of carbon black, where a + b + c + d together give 100% by weight and B) 40-235 parts of reinforcing materials and C) additives customary for polyamide molding compounds. 2. Polyamide molding composition according to claim 1, characterized in that the polyamide mixture A) 0.5-80% by weight of the semicrystalline linear polyamide a), 15-98.5% by weight of the branched graft Contains polyamides b), 1-35% by weight of amorphous polyamide c) and 0-2% by weight of carbon black d). 3. polyamide molding according to claim 2, characterized • indicates that it 1-64.5 wt .-% of the semicrystalline linear polyamide a), Contains 18-79.5 wt .-% of the branched graft polyamide b), 20-35 wt .-% amorphous polyamide c) and 0.5-2 wt .-% carbon black d). 4. Polyamide molding composition according to one of claims 1 to 3, characterized in that it has melt viscosities at processing temperatures at shear rates of γ = 200 / s <300 Pas and at γ = 1000s <150 Pas. 5. polyamide molding composition according to at least one of claims 1 to 4, characterized in that the semi-crystalline, linear polyamides a) are selected from PA6, PA66, PA12, PA6T, PA6T12, PA12T, with the terephthalic acid (T) partially can be replaced by isophthalic acid (I) or adipic acid or mixtures thereof. 6. polyamide molding composition according to at least one of claims 1 to 5, characterized in that Graft polyamides b) are used which are derived from PA6, PAll, PA12 and have more than 3 arms. 7. polyamide molding composition according to at least one of claims 1 to 6, characterized in that the graft polyamides b) a relative viscosity (1% in H2S04, 23 ° C) <2.2 and 30 ° C above the melting temperature, a melt viscosity (γ = 500 / s) <50 Pas. 8. polyamide molding composition according to claim 7, characterized in that the graft polyamide b) inherently lubricants such. B. contain long-chain n-alkylenes. 9. polyamide molding composition according to at least one of claims 1 to 8, characterized in that - The graft polyamides b) have a molecular weight distribution (GPC / standard polystyrene) which corresponds approximately to the distribution of the semicrystalline polyamide a). 10. Polyamide molding composition according to one of claims 1 to 9, characterized in that the amorphous polyamide c) is selected from PA MACM12, PA PACM12 or mixtures / copolyamides thereof and PA6I, PAMXDI, PA 6I / MXDI where isophthalic acid (I) partly by terephthalic acid (T) or A-dipinic acid and MXDA can be partially replaced by PXDA. 11. Polyamide molding composition according to claim 10, characterized in that the amorphous polyamide c) is selected from PA6I / 6T and or PAMXDI / MXDT / 6I / 6T. 12. Polyamide molding composition according to at least one of claims 1 to 11, characterized in that the reinforcing materials B) are selected from glass fibers, carbon fibers, minerals such as talc, Mica, kaolin, wollastonite, nanocomposites, whiskers and other reinforcing materials or mixtures thereof customary for polyamide. 13. Polyamide molding composition according to at least one of claims 1 to 12, characterized in that the polyamide molding composition A) contains customary additives C). 14. Polyamide molding composition according to claim 13, characterized in that the additives C) are selected from impact modifiers, UV, heat and processing stabilizers and lubricants which may also be inherent in the graft polyamide. 15. Molded parts produced with molding compositions according to at least one of claims 1 to 14, characterized in that the molded parts have an excellent surface quality expressed by the surface gloss at an angle of 60 ° greater than 75. 16. Use of the polyamide molding compositions according to at least one of claims 1 to 15 for the production of molded parts by processing methods such as injection molding, extrusion, extrusion blow molding, GIT, WIT, micro injection molding, injection blowing, pultrusion, deep drawing or other processing methods suitable for polyamides. 17. Use according to claim 16, characterized in that components for industrial, optical, electrical, sanitary applications and or components are produced in the automotive sector.