DE4123963A1 - Impact resistant compsn. used for technical articles - Google Patents

Abstract

An impact-resistant compsn. contains (a) 30-97 pts. wt. of partly crystalline polyamide, e.g. PA 6 and/or PA 6.6 and/or PA 6/6.6, and (b) 70-3 pts. of polyolefin comprising (i) 0-90 wt.% of non-functionalised olefin (co)polymer and 100-0% of a carboxylated polyolefin (mixt.) with 5-95% gel content of the carboxylated component w.r.t. 0.2-10% of COOH gps., obtd. by grafting alpha,beta-ethylenically unsatd. mono- and/or di-carboxylic acids or anhdrides onto an olefinic backbone, e.g. ethylene and/or propylene (co)polymers, pref. ethylene-vinyl acetate copolymers.

Description

The invention relates to impact-resistant polyamide molding compositions 30 to 90 parts by mass of a partially crystalline polyamide, preferably polycapronamide (PA 6) and poly (hexamethylene adipamide) (PA 6.6) or their mixed polycondensates PA 6 / 6.6 or PA 6-PA 6.6 mixtures, and 10 to 70 parts by mass of one Polyolefin or polyolefin mixture containing a by grafting α, β-ethylenically unsaturated mono- and / or dicarboxylic acids or their anhydrides funktionali containing polyolefin mass fraction of 10 to 90%.

For most applications of molding compounds based on semi-crystalline polyamides, in particular PA 6 and PA 6.6, The main component is a high use toughness in the dry or "splash-fresh" (unconditioned) state while ensuring a high strength Stiffness Neveaus over a wider temperature range required.

Generally, this requirement can be achieved by incorporating a suitable, d. H. acceptable impact strength component achieved become.

Having functionalized polyolefins with carboxyl groups as well "adherent" toughening modifiers in polyamide form take precedence.

(S. Cartasegna and W. Heider, Rubber Fibers Plastics 41 (1988) 3, 110-119 and 5, 224-226; W. Illing, Kunststoffe 80 (1990) 7, 838-842).  

In this case, carboxyl-containing unsaturated Ver compounds, in particular the low molecular weight α, β-ethyls unsaturated mono- and dicarboxylic acids or their Anhydrides, such as acrylic acid, methacrylic acid and maleic acid Anhydride in the olefinic main chain to form Olefin co- and terpolymers incorporated or in the form of Side chains (grafts) grafted onto these.

The production of various olefin / (meth) is known Acrylic acid or MSA copolymer (GB 9 98 439, DE 36 04 376, DD 1 61 136, DD 2 48 368) or the corresponding, partial metal ions neutralized ionomers (US 33 73 224, US 38 45 163, US 38 73 667, US 44 78 978) and of Ethylene / α-olefin or (meth) acrylate / (meth) acrylic acid or MSA terpolymers (E.P. 01 06 999, WO 86/06 397, WO 88/03 543, US 41 74 358), which as compatible impact resistance modifiers can be used in polyamide molding compositions.

Greater space takes the grafting of carboxyl monomers to an olefinic backbone polymer from the series Polyethylene (HDPE, LDPE, LLDPE) (DE 19 32 739, DE 24 20 942, US 29 70 129, US 31 77 269, US 31 77 270, US 39 87 122, US 36 46 165, E.P. 1 87 659), ethylene / vinyl or (meth) acrylic acid ester copolymers, such as. Ethylene-vinyl acetate, Ethylene-ethyl acrylate and ethylene-butyl acrylate copolymers (EVA, EEA, EBA) (DE 23 29 780, DE 23 42 486), ethylene / propylene Co- or terpolymers (EPM, EPDM) (E.P. 02 66 221, JA 6 21 77 065, JA 6 21 79 546, JA 62 43 456) and isotactic polypropylene (PP) (E.P. 2 35 876, JA 62 59 652, JA 62 59 653, WO 88/02 387, WO 88/06 174) on. As a polymer backbone and mixtures, in particular Polyethylene or PP with EVA and / or EPDM used (E.P. 1 28 775, E.P. 2 87 140, WO 88/06 174, JA 8 246/1 882).  

The carboxylated in this way polyolefins adhere very good at the polyamide matrix and act as Ver compatibilizer between the polyamide and the pure polyolefin component.

In addition to being an effective increase in impact resistance at the same time for the intended areas of application necessary strength and stiffness characteristics, a finally, by the strong repression of the Water absorption conditional dimensional stability, secured (F. Altendorfer and E. Seitl, Kunststoffberater 3 (1990), 33-37; R. J. M. Borggreve u. a., Macromol. Chem., Macromol. Symp. 16 (1988), 195-207).

This applies especially to polyamide / polyethylene blends whose Compatibility with a proportion of carboxylated, including acid anhydride or epoxy groups Polyethylene is achieved (US 33 73 222, US 33 73 223, US 33 73 224, US 38 73 667), and polyamide / polypropylene blends, the same way functionalized polypropylene or Propylenco- or -terpolymere included (F. Ide and A. Hasegawa, J. Appl. Polym. Sci. 8 (1974), 963-974; US 38 45 163, US 41 74 358, JA 59.1 49 940, JA 49 018 (1985), JA 2 32 135 (1984), JA 1 10 740 (1985)).

Used as adhesion promoters / impact modifiers in polyamide / Polyolefin molding compounds used carboxylated poly olefins are either by suspension or solution grafting method using one for the backbone polymerisate of suitable organic solvent (E.P.187,660; F. Ide et al., Kobunshi Kagaku 25 (1968), p. 167; N.G. Gaylord, J. Polym. Sci., Polym. Lett. Ed. 20 (1982), P. 481, ibid. 21 (1983), p. 23) or mostly in the polymer melt, optionally directly in the process of reactive Melt blend, prepared (E.P. 82,704, E.P. E.P. 2 35 876, E.P. 2 66 221, WO 88/06174, US 38 62 265, US 41 74 358).  

An improved impact resistance, especially for PA 6 or PA 6.6 / PP blend with higher total polyolefin share (F. Ide and A. Hasegawa, J. Appl. Polym. Sci (1974), 963-974), by adding a in the Melt graft carboxylated EP (D) M / PP blend (E.P. 2 35,876, E.P. 2 66,221, WO 88/06174), including possible other elasticizing components such as Rubber and / or mineral processing oils (US 43 38 413, US 45 55 546, WO 86/06 397, E.P. 2 66 221, DE 38 05 377).

Also by these carboxylated EP (D) M / PP and / or Polyethylene combinations (E.P. 2 35 876, E.P. 2 87 140) only achieved a very limited toughness increase.

The variants known from the prior art are complex multi-component systems. The described blend Properties, however, are for demanding applications where a balanced property picture regarding toughness, Strength / rigidity is required, not sufficient. This disadvantage is due to the limited impact sity of the carboxy used as impact modifiers lierten polyolefins, their preparation - generally in the melt or in an aqueous and / or organic Suspension / solution - very expensive.

Compared to the achievable increase in mechanical and thermal characteristic levels, the high technical technological effort to produce the carboxylated Polyolefins not justified.

The object of the invention is therefore in development of polyamide / polyolefin molding compounds with improved Dry impact strength and sufficient strength, Stiffness and heat resistance on the basis of compositions of 30 to 90 parts by mass, preferably 40 to 80 parts by mass, semi-crystalline polyamide, preferably PA 6 and / or PA 6.6 and / or their mixture polycondensates PA6 / 6.6, and 10 to 70 parts by mass, preferably 20 to 60 parts by mass, polyolefin, consisting from 10 to 90% by weight of unfunctionalized olefin homo- and / or Olefinmischpolymeren and to 10 to 90 Mass% of one by grafting of α, β-ethylenic unsaturated mono- and / or dicarboxylic acids or their Anhydrides obtained on olefinic backbone polymer carboxylated olefin homo- and / or -mischpolymeres or Olefin polymer mixture.

According to the invention the object is achieved in that in the molding compositions functionalized polyolefins or polyols be used in the case of carboxyl groups. Mass fractions between 0.2 and 10%, preferably between 0.5 and 6%, gel mass contents between 5 and 95%, preferably between 10 and 80%, own.

As particularly suitable backbone polymers for the herzu substituted carboxylated polyolefins are used:

• - Ethylene-vinyl acetate copolymers (EVA) with a mass share of polymerized vinyl acetate units between 5 and 25% and a melt index MFI (190 ° C, 2.16 kg) according to DIN 53735 between 0.1 and 20 g / 10 min.  
• Polyethylene having an average molecular weight between 1.5 × 10⁴ and 1.0 × 10⁶, a density between 0.92 and 0.97 g / cm³ and melt indices between MFI (190 ° C., 21.6 kg) of 5 g / 10 min and
  MFI (190 ° C, 2.16 kg) of 50 g / 10 min.
• Polypropylene with average molecular weights between 2.5 · 10⁴ and 5.0 · 10⁵, an isotactic index between 50 and 99% and melt indices MFI (190 ° C, 5.0 kg) between 1.0 and 50 g / 10 min and
• Ethylene-propylene-unconjugated diene (dicyclopentadiene and / or ethylidenenorbornene) terpolymers (EPDM) together reduction 60-85% by mass, ethylene / 15-40% by mass, Propylene / 0.2-2.5 mass% diene units and a Mooney viscosity (ML / 1 + 4/125 ° C) between 25 and 95, with the EPDM optionally in the form of a compound with an ethylene or Propylene homopolymer content between 2 and 20% by mass may be present.

The used in the polyamide / polyolefin molding compositions carboxyl group-free (non-functionalized) polyolefins can be selected from the group of polyethylenes (HDPE, LDPE, LLDPE), the isotactic polypropylene (PP) and the ethylene copolymer or terpolymers, preferably EVA with vinyl acetate compositions between 2 and 50% and EP (D) M with 5 to 40 masses proportions of propylene units.  

The as molding compound component and / or backbone polymer used polyethylenes as well as polypropylenes can also a small mass fraction of a copolymerized Comonomers, in particular 0.1 to 5.0% by mass of C3 bis C6 olefins.

The carboxylation of the aforementioned polyolefins and olefin copolymers which contain the carboxyl groups according to the invention and gel contents, can be included in a separate, d. H. graft independent of the compounding process polymerization in a dry, preferably powdery and / or granular fixed bed at temperatures between 30 and 100 ° C and generally at atmospheric pressure be made.

As important parameters for the characterization of the invention used carboxylated polyolefins are determined:

• - By an alkaline titration by means of appropriate normal solutions (KOH, HCl back titration) on the Graft product mass related carboxyl group content (-COOH), grafted maleic anhydride among these Present in hydrolyzed form, and
• - By extraction under defined conditions (2 g of product in 100 ml of xylene after 12 hours of treatment under reflux) of the residue as a percent of residue to be understood gel mass content (m _gel ).

The polyamides used should have a relative viscosity η _rel (measured in a 1% by weight solution in m-cresol at 25 ° C.) of between 1.5 and 5.0, preferably between 2.0 and 4.0.

Furthermore, conventional additives, such as lubricants and Mold release agents, fillers and reinforcing agents, pigments / dyes and heat stabilizers, antioxidant and / or light stabilizers, the molding compositions of the invention be added.

It has for various applications of molding compounds, the one carboxylated polyolefin component with high gel mass content, especially the addition of a higher filler content, generally from 10 to 50% by mass, based on the total molding composition, proved to be advantageous.

This reveals a surprising effect of means equipped solid phase graft products Polyamide / polyolefin blends: a high (notch) impact toughness reserve, the first Line one positive carboxyl group concentration gradient to the polyolefin particle surface assigned to functionalized graft products, so that with fill levels between 0.3 and 0.5 still increased (Notch) impact toughness values are achieved.

The preparation of the molding compositions according to the invention takes place by melt mixing under defined temperature and Shearing conditions expediently in conventional kneaders, Single or multi-screw extruders.

All components can be combined in one step mixed or even individual components first to one be added later.

The molding compositions according to the invention are according to their within wide limits "adjustable" property picture in Injection molding and extrusion sector, in particular for the Automotive sector, in electrical engineering and mechanical engineering, suitable.

embodiment

In a twin-screw extruder molding compounds on Base of dried PA 6 (relative viscosity of 2.7, further characteristics in Table 1)

• - generally in compliance with a Melt temperature of 220 ° C -

or of PA 6.6 (relative viscosity of 2.8, further characteristics in Table 1)

• - generally in compliance with a Melt temperature of 260 ° C -

and the addition of the non-functionalized polyolefin component (s) (characteristic values for HDPE, PP and EVA in Table 1) and the carboxylated polyolefin or polyolefin mixture (Characteristic values in Table 2).

The to the inventive carboxylated polyolefins leading grafting has been done in such a way that first the olefinic backbone polymer (Table 2 / Column 2) in the purified and under a nitrogen atmosphere standing reactor, then the carboxyl monomer or monomer mixture (acrylic acid and / or MSA) in one Amount between 2 and 10%, based on the backbone polymer composition, if appropriate in admixture with styrene (Table 2 / Column 3: acrylic acid / MSA / styrene mass ratio), and the Initiator or the initiator mixture, such as. Eg dilauroyl and / or dibenzoyl peroxide in one of the backbone polymer composition related concentration between 0.5 and 1.5%, added, following a shorter dispersion phase from approx. 30 min. the polymerization batch to a reaction Temperature between 70 and 90 ° C heated and up to  Achievement of a monomer conversion between 80 and 93% - corresponding to a total polymerization time between 3 and 5,5 h - is kept at this temperature.

By means of titration, the carboxyl group fraction (-COOH) based on the total amount of graft product was determined and by extraction of the _gel mass content m _gel (Table 2 / columns 4 and 5).

The listed in Table 2 for comparison "gel-free" comparative products were by melt grafting (Reaction temperatures between 165 and 220 ° C according to the olefinic backbone polymer used) under known conditions (polymerization times in an extruder between 5 and 20 min. as well as use of initiators, such as di-tert-butyl peroxide or dicetyl peroxide, in concentrations between 0.02 and 0.2 mass%).

Table 3 shows the molding composition compositions, for which the characteristics, including for analog blend compositions using the above-mentioned "gel-free" Melt graft products for comparison, listed in Table 4 are.

More specifically, the following has been done: From the molding compounds were on an injection molding machine of the Type KuASY 150/50 (tool: heated shut-off nozzle / 235 ± 10) ° C for PA 6 or / 265 ± 10) ° C PA 6.6 mixtures) ISO test bars made in the dimensions 80 mm × 10 mm × 4 mm.  

Measurements were made for those listed in Table 3 Molding compounds the characteristics given in Table 4:

- Charpy impact resistance as well (a _n ) - Charpy impact strength at 23 ° C and -20 ° C according to DIN 53 453 (a _k ) - 3.5% - bending stress according to DIN 53 452 (σ _{b 3.5} ) - Flexural modulus according to DIN 53 457 (E _b ) Tensile strength (50 mm / min) according to DIN 53 455 (σ _z ) - Ball impression hardness (30 ") according to DIN 53 456 (H _{K 30 "} ) - Vicat softening temperature (air, 5 kg) according to DIN 53 460 (T _VB )

Based on the comparison shown in Tables 4.1 and 4.2 between different inventive molding composition (use of carboxylated polyolefins with m _gel values between 10 and 80% by weight) and analogously assembled comparative blends using carboxylated polyolefins with m _gel values between 0.0 and 1.4% by mass, the advantageous processing and application properties of the inventive blends are evident.

Table 1

Characteristics of the polyamides and polyolefins (PO) used (the latter as direct blend component and / or backbone polymer for the graft carboxylation)

Table 2

Characteristics of the carboxylated polyolefins used

Claims (3)

1. impact-resistant polyamide molding compositions based on compositions from

• 30 to 90 parts by weight of semicrystalline polyamide, such as PA 6 and / or PA 6.6 and / or their mixed polycondensates PA 6 / 6.6, and
• 10 to 70 parts by mass of polyolefin, consisting of 10 to 90% by mass of non-functionalized olefin homo- and / or olefin copolymers and 10 to 90% by mass of a by grafting of α, β-ethylenically unsaturated mono- and / or dicarboxylic acids or their anhydrides obtained on olefinic backbone polymer carboxylated olefin Homo- and / or -mischpolymerisat or olefin polymer mixture,

characterized in that the gel mass content of the carboxylated components is between 5 and 95% for carboxyl group mass fractions between 0.2 and 10%. 2. impact-resistant polyamide molding compositions according to claim 1, characterized in that the gel mass content of the carboxylated components between 10 and 80% for carboxyl group mass fractions between 0.5 and 6.0%.