GB2207139A - Impact-resistant and rigid polyamide alloys - Google Patents

Abstract

Moulding materials of thermoplastically-processable polyamide alloys, which contain both an elastomeric polymer as impact-resistance-modifier and a polyfunctional epoxide or glycidyl ether compound, exhibit especially low tendency to creep and shrink, with high impact-resistance, rigidity and dimensional stability, even though lower amounts of modifier are necessary than for comparable polyamides made impact-resistant without the addition of epoxide.

Description

Impact-resistant and rigid polyamide alloys Field of the Invention This invention relates to impact-resistant and rigid polyamide alloys.

Background of the Invention The preparation of shaped polyamide bodies having good impact properties and high rigidity is described in various publications. Thus, according to DE-A-1241606 (= GB-A-0998439), high impact resistance is achieved by mixing into rigid polyamides two polyolefines onto which unsaturated carboxylic acids have been grafted (the polyolefines themselves have poor compatibility with the polyamide matrix).

CH-A-0649566 describes polyamide mixtures in which, to the same end, polyolefines derived from ethylene, propylene and 1,4-hexadiene or 2,5-norbornadiene, which are activated with a, S-unsaturated dicarboxylic acids, anhydrides or esters, are mixed with various known polyamide types having high bending E-modulus. Shaped bodies prepared according to this procedure have very good impact and notched-bar impact properties and high ductility, but in general are insufficiently rigid and dimensionally stable, i.e. they have a high tendency to creep, own account of which they are unsuitable for many end uses.

US-A-4410661 and US-A-4536541 describe the provision of impact resistance for rigid amorphous copolyamides by admixture with core-sheath polymers or of grafted copolyolefines. These inherently highly viscous and rigid polymer mixtures exhibit considerable shrinkage after only short operation at elevated temperatures.

Shaped bodies produced from them are therefore unsuitable for many areas of use, such as thermally -stressed workpieces.

DE-A-3436362 discloses the impact-resistance modification of rigid polyamides derived from terephthalic acid, isophthalic acid and alkanediamines, b the admixture of copolymerisates of ethylene and/or acrylates which, after grafting, have carboxyl groups.

EP-A-0027198 describes impact-resistant polyamide materials in which the impact-resistance-modifier is a core-sheath polymer, in which acrylic acid derivatives are grafted on to a polybutadiene or butadiene/styrene core. The loss of stiffness is compensated by the addition of glass fibres.

US-A-4180494 describes impact-resistance modifiers which are used in the present invention.

DE-A-3339000 describes the introduction of similar core-sheath polymers into polyamides.

Moulding materials of this type are in general unsatisfactory, with respect to their stability, because they both tend to creep and also to be highly heat-shrinkable.

GB-A-1069176 describes an attempt to achieve high thermal stability and improved dimensional stability for moulded bodies, by the admixture to the polyamide melts of cross-linking diepoxides.

GB-A-1376537 and DE-A-2144687 describe the provision of rigidity and stability by the introduction of epoxide resins into plastomeric materials, which are therefore largely form-stable and rigid, but insufficiently impact-resistant. Further, on account of the high content cf fillers and reinforcing agents, these products have a high density which, in many cases, is undesirable.

US-A-4086295 describes polyamide compositions comprising 65-95% w/w polyamide and 35.5% w/w of a copolymer of ethylene series containing unsaturated carboxylic acid components (in salt form), to which 0.1-5% by weight of a carbonate or epoxy compound is added. Compounds having at least two epoxy groups are described in general terms; butyl glycidyl ether and 2-ethyihexyl glycidyl ether are exemplified (Experiments 23 and 24). Stiffness is provided by the use of fillers.

There is nevertheless, to an increasing extent, a great desire for polymeric materials from which impactresistant, rigid and dimensionally-stable workpieces can be prepared by simple injection moulding, e.g. for casing and protective parts in the construction of machines, apparatus and vehicle bodies.

There is therefore the problem of providing polyamide moulding materials which are impact-resistant and which also exhibit a high measure of rigidity and dlmensional stability, and which also have minimal creepage and shrinkage, without an associated excessively high increase of the specific weight.

Summary of the Invention The problem described above is reduced or obviated, in accordance with this invention, in that moulding materials of thermoplastical workable polyamide alloys contain an elastomeric polymer and an epoxide compound having more than one epoxide group.

An especial and unexpected advantage is provided according to the invention, in that, in the simultaneous use of epoxide compound and impact-resistance-modifier in the polyamide mass, the amount of the latter can be reduced, without thereby reducing the impact properties.

By virtue of this synergic effect, a substantially improved combination of high notch impact strength and, at the same time, high rigidity can be achieved. In addition, it is possible to achieve cost savings. A further advantage is that bodies shaped from these products are particularly stable and have low shrinkage.

Description of the Invention Among the polyamide moulding materials which can be used in the present invention are known crystalline and amorphous copolyamides, e.g. derived from optionally alkyl-substituted hexamethylenediamine, or a bis (4-aminocyclohexyl) methane homologue substituted adjacent to the amino groups, and isophthalic acid, terephthalic acid or another aromatic or aliphatic dicarboxylic acid; and also polyamide elastomers, such as polyetheramides and polyetheresteramides, and their mixtures and alloys with known homopolyamides, such as polyamide 6, polyamide 6,6, polyamide 6,10, polyamide 11, polyamide 12 and polyamide 6,12, in amounts of at least 40% by weight of the moulding materials.

The polyamide moulding materials according to the invention preferably contain at least 3% by weight, more preferably 5 to 30% by weight, most preferably 10 to 20% by weight, of the impact-resistance-increasing polymer, based on the total moulding material.

Known elastomeric copolymers are used as impactresistance-increasing components, e.g. copolyolefines derived from ethylene, propylene or 1-butene, activated with unsaturated dicarboxylic acids, or also so-called core-sheath homo- or copolmers. The former comprise no more than 90 mol % ethylene and no more than 1 mol %'of an a,B-unsaturated dibasic acid grafted thereon, so that the maximum carboxyl group content is 2 mol %. They should preferably not be introduced as metal salts, in ionic form, since binding to the polyamide is undesirably affected; the compostion is therefore substantially free of metal carbolate. The latter comprises, for example, a butadiene-containing or acrylate-containing copolyolefine core around which grafted vinyl compounds, e.g. acrylate compounds, are formed as sheath.

Suitable epoxide compounds for use according to the invention are those which have more than one preferably terminal-positioned epoxide group, especially more than one glycidyl ether group, in the molecule. They increase the molecular weight by connecting the polyamide macromolecules. Very small amounts are necessary.

Amounts below 1% often give maximum effect. Larger amounts lead to increased viscosity, even to the extent that the product is not workable. It is preferred to use diglycidyl compounds in amounts of at least 0.0018 by weight, based on the total moulding material. Amounts of 0.01 to 15% by weight, in particular 0.5 to 5% by weight, are especially preferred. It is also possible to use polymeric epoxide compounds, which contain at least two epoxide group, or, as the case may be, glycidyl groups per molecule.

The diglycidyl ethers which are preferably used have the general formula Y-O-X-O-Y wherein Y is an epoxide group and Y. is a divalent C2~10 alkyl or C7-20 arylkyl residue, examples of which are derived from neopentl glycol and/or Bisphenol A.

Polyamide moulding materials according to the invention are pre-mixed in conventional mixing apparatus, such as vibrating mixers, stirring mixers, mills or phase mixers, processed in the melt in screw machines, such as extruders or plasticorders, to give moulding materials or granulates, strands etc., and then formed, e.g. on injection moulding machines or extruders.

The given moulding materials can contain additives such as, e.g. stabilisers, pigments, lubricants, emulsifiers, release agents, colourants, flame-retardants, mineral or metallic fillers, or reinforcing agents.

The polyamide moulding materials according to the invention are illustrated by the following Examples.

Preparation of Polyamide Moulding Materials The polyamide was mixed sequentially with the impact-resistance-modifier and the epoxide compound, and the mixture homogenised on a Werner Pfleiderer ZSK 30 two-phase extruder at temperatures of 220-2900C, extruded to give a strand, and comminuted to a uniform granulate.

After drying the granulate under nitrogen at 80-900C and a vacuum of 30-50 mbar, test bodies were prepared using an Arburg extruder (type 320-210-250) and their mechanical properties were measured.

The following five Tables comprise Examples, listed in comparison to samples which contain no diepoxide compounds. In these five Tables, the number of the product under test is given in column 0, the weight proportion of the polyamide in column 1, the weight proportion of the impact-resistance-modifier of the copolyolefine type derived from ethylene, propylene, 1-butene modified with maleic acid anhydride (Tables I-IV) or of the core-sheath polymer type (Table V) in column 2, the weight proportion of neopentyl glycol diglycidyl ether in column 3, and the melt viscosity in Pas at 2700C and 122.6 N in column 4.

In the following columns, particular mechanical properties are given which were determined on test bodies: In columns 5 and 6, the impact-resistance and the notch impact resistance according to DIN 53453 (measured dry at 230C) are given. nb indicates no break.

In column 7 the bending E modulus and in column 8 the limit bending stress, both measured according to DIN Norm 53452 are given. In columns 9, 10, 11 and 12 the values of yield stress, elongation at yield, tensile strength and elongation at break according to DIN Norm 53455 (measured dry at 230C) are given.

In column 13, the shrinkage values in the longitudinal direction are given for DIN tension bars 53445/3, measured after storage for 24 hours in a circulating air oven at 1000C, and in column 14 the same for the test bodies after storage for 1 hour at 1400C in the same oven. Column 15 (Tables II and III) reports injection shrinkage values, measured for DIN tension bars 53445/3 after dry storage for 24 hours following inection. The values are given in percentages.

The polyamides used in Tables I-VI were of the following types: in Tables I, V and VI, polyamide 6, mp 221"C, in Table II, an amorphous copolamide derived from heamethylenediamine/isophthalic acid, having a glass transition point of 1400C, in Table III an amorphous copolyamide of the type Grilamid TR55, TG 1550C, and in Table IV, polyamide 12; mp 1780C.

The preferred epoxide compound used in the tests of Tables I-V is the neopentyl diglycidyl ether having the chemical name 2,2'-t(2,2-dimethyl-1,3-propanediyl)- bis(oxymethylene)]bisoxirane.

In Table II, test (1) (E 5867) , 1,4-butanediglycidyl ether was used.

Table VI gives results when using the diglycidyl ether of Bisphenol A, available as G 1302 (mw 385) from the company EMS-CHEMIE AG.

Table I - Polyamide 6 - moulding materials with impact-resistance-modifier derived from dicarboxylic acids-grafted copolyolefines 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Test Poly- Impact- Digly- Melt Impact Notch Bending Limit Yield Elong- Tensile Exten- Shrinkage Srinkage No. amid- Resist- cidyl Visco- Resist- Impact E Mod- Bending Stress ation Strength sion after after wt.% ance ether sity ance Resist. ulus Stress 23 C/ at 23 C/dry at 24h/100 C 1 h/140 C modifier wt.% (270 / 23 C/ 23 C/ N/mm dry Yield N/mm Break wt.% 122.6N) dry dry dry % % kJ/m kJ/m N/mm (a) PA 6 0 0 350 nb 6.0 2000 100 85 10 55 10 -0.36 -0.75 A28 100 pure (b) PA 6 0 0.4 403 nb 4.1 2645 109 - - - - -0.22 -0.32 E 5006 99.6 (c) PA 6 15 - 578 nb 35.4 1203 84 57.3 7.0 42 17.2 -0.38 -0.47 E 5179 85 (d) PA 6 15 0.2 1363 nb 38.1 1950 83 56.3 7.8 65.3 264 -0.30 -0.36 E 5178 84.8 (e) PA 6 15 0.4 1342 nb 44.7 1940 79.6 - - - - -0.28 -0.35 E 5005 84.6 (f) PA 6 15 0.5 1032 nb 53.3 1870 80 - - - - - E 5487 84.5 (g) PA 6 12 0.5 1177 nb 32 2160 90 42 7.3 53.3 144 -0.16 -0.33 E 5180 87.5 (h) PA 6 10 1.0 6071 nb 39 1243 91.3 - - - - - E 4913 89.0 (i) PA 6 10 3.0 > 10000 nb 69.5 2625 104 - - - - - E 4796 87.0 (k) PA 6 20 0.4 681 nb 14.3(-40 ) 1667 68.6 -0.28 -0.40 E 5007 73.6 50.4 (e) 75 20 5.0 > 10000 nb nb 2045 77.7 - - - - - E 4575 (1) nb 66.6 E 4574 77.7 19.4 2.9 2065 nb 30.6 2039 79.6 - - - - - (E 3752) (-20 ) (-20 ) (m) 80 20 - 136 nb 42 1517 62 45 5 50 150 -0.47 -0.58 A 28NZ Table II - Amorphous copolyamide (type XE 3038) derived from hexamethylenediamine/isophthalic acid with impact-resistance-modifier (impact-resistance-modifier as in Table I) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Test Poly- Impact- Digly- Melt Impact Notch Bending Limit Yield Elong.Tensile Exten- Login- Longi- % Injection No. amid- Resist- cidyl Visco- Resist- Impact E Mod- Bending Stress ation Strength sion tudinal tudinal Shrinkage wt.% ance ether sity ance Resis- ulus Stress 23 C/ at 23 C/dry at Shrink- after modifier wt.% (270 / 23 C 23 C/ 23 C/ N/mm2 dry Yield N/mm2 Break age after 24 h wt. % 122.6N) dry dry dry % % 24h/100 C 1h/140 C kJ/m2 kJ/m2 N/mm2 (a) A2771 100 0 0 1755 40% nb 1.5 2960 166 110 70 62 0.0132 -0.332 +0.218 XE 3038 60% 60 (b) 99.7 0 0.3 2643 40% nb 1.6 3120 125 - - - - -0.33 -1.1 E 6248 60% 58 (c) 86.8 13 0.2 2643 nb 47.0 2350 114 73 8 55 25 -0.05 -0.54 E 6248 (d) E4471 85 15 - - nb 38 1991 100.3 - - - - +.17 -2.0-4.0 E 6603 (e) 84.8 15 0.2 2994 nb 51.3 2238 110 68 9 55 46 -0.092 -3.8 E 5864 (f) 84.7 15 0.3 3407 nb 49.2 2241 112 70 7 57 61 -0.07 -3.1 +0.315 E 5864 (g) 84.6 15 0.4 4440 nb 49.9 2288 114 70 7 54 25 -0.03 -2.6 E 5866 (h) 80 20 - 4027 nb 42.2 1880 93 65 7 56 65 +0.188 -5.0-8.0 -0.5-0.7 E 5275 (i) 79.9 20 0.1 4801 nb 43.6 1920 92 - - - - +0.02 -3.9 +0.374 E 6753 (k) 79.8 20 0.2 - nb 45.6 2110 102 67 6.5 56 8 -0.071 -2.36 E 6601 (1) 84.7 15 0.3 4130 nb 47.1 2299 114 70 8.5 53 18 -0.04 -3.6 E 5867 Table III - Amorphous Copolyamide TR55 (impact-resistance-modifier as in Table I) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Test Poly- Impact- Digly- Melt Impact Notch Bending Limit Yield Elong. Tensile Exten- Login- Longi- % Injection No. amid- Resist- cidyl Visco- Resist- Impact E Mod- Bending Stress ation Strength sion tudinal tudinal Shrinkage wt.% ance ether sity ance Resis- ulus Stress 23 C/ at 23 C/dry at Shrink- after modifier wt.% (270 / 23 C 23 C/ 23 C/ N/mm2 dry Yield N/mm2 Break age after 24 h wt. % 122.6N) dry dry dry % % 24h/100 C 1h/140 C kJ/m2 kJ/m2 N/mm2 (a) 100 0 0 1200- nb 5.0 2100 118 8 60 30 -0.07 -0.09 0.8-1.0 TR55 1500 (b)E5428 99.7 0 0.3 2189 nb 5.26 2160 - - - - - - E5716 99.7 0 0.3 1241 nb 5.09 2080 119 80 11 55 24 (c) 99.6 0 0.4 1446 nb 5.03 2190 - - - - - -0.16 0.4 E 5482 (d) 90 10 - 1516 nb 21.9 1730 101 64 20 54 33 -0.30 -1.3 -0.5 F3-55 (e) 89.7 10 0.3 3511 nb 23.8 1860 98 64 10 50 50 -0.08 -0.36 -0.36 E 6180 (f) 85 15 - 1454 nb 30.9 1737 89 50.7 21 48 36 -0.50 -1.2 -0.53 F3-56 (g) 84.5 15 0.4 nb 34.9 1780 88 60 10 52 82 -0.23 -0.98 E 5255 (h) 80 20 - 1755 nb 37.7 1504 77 21 22 44 36 -0.58 -2.6 -0.69 F3-57 (i) 79.6 20 0.4 2815 nb 40.2 1800 95 68 18 57 28 -0.073 -0.24 -0.40 Table IV = Polyamide 12 with impact-resistance-modifier (impact-resistance-modifer as in Table I) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Test Poly- Impact- Digly- Melt Impact Notch Bending Limit Yield Elong. Tensile Exten- Login- Longi No. amid- Resist- cidyl Visco- Resist- Impact E Mod- Bending Stress ation Strength sion tudinal tudinal wt.% ance ether sity ance Resis- ulus Stress 23 C/ at 23 C/dry at Shrink- Shrink modifier wt.% (270 / 23 C 23 C/ 23 C/ N/mm2 dry Yield N/mm2 Break age after age after wt. % 122.6N) dry dry dry % % 24h/100 C 1h/140 C kJ/m2 kJ/m2 N/mm2 Grilamid 100 - - nb 14.4 1256 64 44 9 47 178 +0.25 +0.9 (a) L25 (b) 99.75 - 0.25 1853 nb 15.6 1420 65 45 7 44 126 +0.20 +0.82 E6413 (c) 99.6 - 0.4 - nb 23.2 1680 72 50 7 60 153 +0.13 +0.5 E5254 (d) 91.7 8 0.3 3698 nb 72.8 1350 60 40 8 44 120 -0.14 +0.8 E6424 (e) 89.7 10 0.3 3089 nb 65.3 1290 57 38 10 46 140 -0.24 -0.6 E6423 (f) 86 10 4 > 10000 nb nb 2243 122 - - - - - E3535 (g) 90 10 - 320 nb nb 380 58 38 23 42 280 -0.36 +1.15 Table V = Polyamide 6 with impact-resistance-modifier derived from core-steaht polymers 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Test Poly- Impact- Digly- Melt Impact Notch Bending Limit Yield Elong.Tensile Exten- Login- Longi No. amid- Resist- cidyl Visco- Resist- Impact E Mod- Bending Stress ation Strength sion tudinal tudinal wt.% ance ether sity ance Resis- ulus Stress 23 C/ at 23 C/dry at Shrink- Shrink modifier wt.% (270 / 23 C 23 C/ 23 C/ N/mm2 dry Yield N/mm2 Break age after age after wt. % 122.6N) dry dry dry % % 24h/100 C 1h/140 C kJ/m2 kJ/m2 N/mm2 (a) 100 - - 350 nb 4.0 2000 100 83 10 55 30 -0.36 -0.75 A28 pure (b) 91.6 8 0.4 372 nb 7.3 2570 106 73 7 54 10 -ss.28 -0.48 E 5253 (c) 89.6 10 0.4 454 nb 14.4 2360 97 - - - - -0.40 -0.50 E 5004 (d) 84.6 15 0.5 - nb 18.5 2380 91 63 7 51 123 -0.42 -0.34 E 5223 (e) 75 25 - 434 nb 38 1572 66.2 45 5 40 110 -0.65 -0.57 A28 NT (f) 74.6 25 0.4 2394 nb 60% nb 1698 69.6 - - - - -0.48 -0.39 E 5008 40% 50 (h) 72 25 3.0 5369 nb 42.8 2005 78.5 - - - - - E 4572 (i) 70 25 5.0 - nb nb 1974 76.8 - - - - - E 5473 Table VI = Polyamides 6 with impact-resistance-modifier (C elastomeric copolyolefine type) and diglycidyl ethter 0 1 2 3 4 5 6 7 8 9 10 11 12 Test Poly- Impact- Digly- Melt Impact Notch Bending Limit Yield Elong. Tensile Exten No. amid- Resist- cidyl Visco- Resist- Impact E Mod- Bending Stress ation Strength sion wt.% ance ether sity ance Resis- ulus Stress 23 C/ at 23 C/dry at modifier wt.% (270 / 23 C 23 C/ 23 C/ N/mm2 dry Yield N/mm2 Break wt. % 122.6N) dry dry dry % % kJ/m2 kJ/m2 N/mm2 A29NZ 80 20 - 136 nb 42 1517 62 45 5 50 150 E7716 84.2 15 0.8% G1302 814 nb 44.4 1951 78 56 6 62 150 E7718 79.2 20 0.8% G1302 2808 nb 53.8 1760 69 48 7 51 135

Claims (15)

1. A moulding material of a thermoplasticallyprocessable polyamide alloy, having improved impactresistance, rigidity and dimensional stability, characterised in that it contains an elastomeric copolymer and an epoxy compound having more than one epoxide group.

2. A moulding material according to claim 1, which comprises at least 40% by weight of the polyamide.

3. A moulding material according to claim 2, wherein the polyamide is an amorphous or partially crystalline polyamide, a polyetheramide, or a mixture or alloy of such a polyamide with a homopolyamide.

4. A moulding material according to any preceding claim, wherein the elastomeric copolymer is an impact-resistance-modifier known per se derived from modified polyolefines based on activated copolyolefines and/or mixtures thereof, and is present in an amount of at least 3% by weight of the moulding material.

5. A moulding material according to claim 4, which comprises 5 to 30% by weight of the elastomeric polymer.

6. A moulding material according to claim 5, which comprises 10 to 20% by weight of the elastomeric polymer.

7. A moulding material according to any of claims 4 to 6, wherein the modified polyolefine comprises a grafted carboxylic acid, substantially or wholly free of any salt form thereof.

8. A moulding material according to any of claims 1 to 3, wherein the elastomeric polymer is an impact-resistance-modifier known per se, of the core-sheath-polymer type, comprising a core of homo- or copolymers, which contain butadiene or an acrylic compound, and a grafted vinyl or acrylic compound as the sheath.

9. A moulding material according to any of claims 1to 3, wherein the elastomeric polymer comprises a mixture of a modified copolyolefine as defined in any of claims 4 to 7, with a core-sheath polymer as defined in claim 8.

10. A moulding material according to any preceding claim, wherein the epoxy compound contains at least two glycidyl ether groups.

11. A moulding material according to claim 10-, wherein the epoxy compound has the formula Y-O-X-O-Y wherein Y is an epoxide group and Z is a divalent C2 10 alkyl or C7 0 aralkyl residue.

12. A moulding material according to claim 11, wherein the epoxy compound is neopentyl diglycidyl ether and/or a Bisphenol A-derived diglycidyl ether.

13. A moulding material according to any preceding claim, which comprises 0.01 to 15% by weight of the epoxy compound.

14. A moulding material according to claim 13, which comprises 0.1 to 5% by weight of the epoxy compound.

15. A moulding material substantially as herein described with reference to any of the Examples in which an epoxy compound is present.