GB2170502A

GB2170502A - Thermoplastic polymer blends

Info

Publication number: GB2170502A
Application number: GB08530606A
Authority: GB
Inventors: Yoshimitsu Tani; Eduard Schmid
Original assignee: EMS Inventa AG; Inventa AG fuer Forschung und Patentverwertung
Current assignee: Inventa AG fuer Forschung und Patentverwertung; Uhde Inventa Fischer AG
Priority date: 1984-12-21
Filing date: 1985-12-12
Publication date: 1986-08-06
Also published as: FR2575167A1; JPS61215655A; IT8548942A0; DE3545033A1; GB8530606D0; GB2170502B; DE3545033C2; IT1182093B; FR2575167B1; CH665648A5

Abstract

A thermoplastically processable composition comprises a mixture consisting of 5 to 90% by weight of a thermoplastic polyamide, 5 to 90% by weight of a thermoplastic polyurethane, and 5 to 50% by weight of a thermoplastic, activated polyolefin.

Description

SPECIFICATION Thermoplastic polymer blends This invention relates to blends of thermoplastic polymers.

Polyamides are exceptionally suited to thermoplastic processing. Many fields of use are known for polyamides, hitherto generally in relation to stiff, stable construction parts. Disadvantages associated with most aliphatic polyamides are insufficient dimensional stability and loss of stiffness during use, as the result of moisture uptake. Their resistance to abrasion is relatively good, but often insufficient for practical demands.

Flexible polyamides have recently become available. The flexibility is achieved by the addition of monomeric plasticisers and also through the formation of segmented polymer structures in which elastomer blocks are introduced between normal polyamide blocks. These generally consist of polytetramethylene oxide with a molecular weight of 600 to 3000.

Monomeric plasticisers can be extracted from polyamides on contact with water or organic solvents.

Segmented polyamides are expensive to prepare, despite being very easily processable. Disadvantages lie with respect to abrasion resistance, elastic resilience and generally with respect to hydrolysis-resistance.

Thermoplastic polyurethanes have a wide spectrum of properties. Their hardness can cover a broad range, from 80 Shore A to 75 Shore D. Their abrasion resistance and their elastic resilience, particularly after annealing, are outstanding. Their low-temperature flexibility and toughness can be partially influenced by choosing suitable amounts of elastomer segments, of which there are three principal kinds: 1. Tetramethylene oxide polyether 2. Poly-w-caprolactone 3. Adipic acid-polyester with ethylene glycol or mixed ethylene glycol/butanediol or hexanediol as diol components The hard segments are generally based on aromatic diisocyanates, in particular the diphenylmethanediisocyanate-types (MDI) or the isophoronediisocyanate (IPDI) or the toluenediisocyanate (TDI), which are often prereacted with butanediol.The principal disadvantage of the thermoplastic polyurethanes is their poor processability in injection moulding and particularly in extrusion.

The class of polyamides is described, e.g. in the Kunststoff-handbuch, Volume VI (1966), and the class of the polyurethanes in the Kunststoffhandbuch, Volume VII (1983), both published by the Carl Hanser Verlag, Munich.

There has been no shortage of attempts to combine the properties and the good processability of polyamides with the properties of the thermoplastic polyurethanes.

Org. Coat. Plast. Chem., 40 (1979) 664-668, describes blends of TPUR with a variety of thermoplasts.

Extensive non-compatibility was found with pure polyamide 6, and a partial compatibility with polyamide 12.

The theromplastic PA-TPUR blends described in the patent literature are distinguished by the use of a particular copolyamide of low softening temperature and containing, in generai, dimerised tall oil fatty acid having 36 C atoms. This is the case, for example, in EP-A-0109342, US-A-4384083 and DE-A-2431984, in which such products are generally suitable as melt-adhesives.

Owing to low compatibility, the TPUR proportion is often considerably restricted, e.g. in US-A-4369285 and SU-A-0352915. In FR-A-2207955, JP-A-7278673 and JP-A-7434947, the addition of monomeric plasticizers is described, which,in addition to reducing the stiffness of the final products, improve the plasticity, miscibility and compatibility.

By the choice of soft, low-melting copolyamides, the stiffness, strength and heat-resistance are reduced. The possibility of adding only a little TPUR reduces the possibility of desired standardisation of combinations of properties. Monomeric plasticizers can sweat out during processing or in use, leading to undesirable side-effects.

Blends of polyamide with thermoplastic polyurethane, with a range of miscibility between the polyamide and polyurethane which is as broad as possible, which are easily processable and which allow new combinations of properties, are therefore desired.

It has now been found that a thermoplastically processable composition of: a) 5-90% by weight of a thermoplastic polyamide b) 5-90% by weight of a thermoplastic polyurethane c) 5-50% by weight of a thermoplastic, activated polyolefin has a good thermoplastic processability and leads to products with new combinations of properties. The compositions are particularly easily processable when the a:b ratio is 0.2-5, when at least 10% by weight of component c) is present.

Suitable polyamides comprise all linear, thermoplastically processable polyamides which have a softening range below about 235"C. Linear aliphatic polyamides such as polyamide 6, polyamide 6.9, po lyamide 6.10, polyamide 6.12, polyamide 11 and polyamide 12 are particularly suitable.

The polyamide compositions can also comprise copolyamides principally of aliphatic monomers or al loys of two polyamides. If this involves the use of polyamide 66, a depression in melting point can be achieved, in the case of true alloys, so that the softening temperature is reduced to 2350C and below or, if polyamide 66 is not the principal component, it can be present as a disperse phase, e.g. in the matrix of the other polyamide (for instance polyamide 6), so that the composition is nevertheless processable at 235"C and below. The same is true for mixtures of other, e.g. also amorphous, polyamides.

All types of thermoplastic polyurethanes which, on account of their heat stability, can be processed with polyamides, are suitable. Particularly easily processable compositions are obtained by the use of socalled polyether-polyurethanes. Polyurethanes with polycaprolactone as the soft segment also render easily processable products. It is of particular interest, howoever, that easily processable compositions, with new combinations of properties, are obtained from the hydrolysis-sensitive and poorly processable adipate types by mixture according to the given process.

The so-called activated copolyolefins are copolymers of ethylene with at least one a-olefin with 3 and more carbon atoms, on which organic carboxylic acid or a derivative of a carboxylic acid which has 1 or more -COOH groups or their derivatives is grafted. The grafting should be such that about 0.05-2% by weight acid or its derivative is grafted.

Most preferably, maleic acid anhydride or fumaric acid is used for the grafting. Copolymeres of ethylene with propylene, butene, hexene and octene are used as copolyolefins. Copolyolefins with a predominant proportion of ethylene are usual, but it can also be the case that the copolyolefin proportion of, e.g., propene and octene, predominates. In addition to the a-olefin, the copolyolefin can contain additionally an amount suitable for further grafting of a non-conjugated diene such as, say, 1,4-hexadiene or diethylidene-norbornene.

The technology of the grafting of these copolyolefins is state of the art and is widely described. DE-A2722720 and JP-A-7801291, for example, relate to grafting with the use of organic peroxide, and US-A4026967 and EP-A-0109342 to peroxide-free grafting which requires high temperatures, and copolyolefins which are prepared together with a diolefin with non-conjugated double bonds.

The activated copolyolefins can have properties varying over a wide range, e.g. in which their crystalline proportion is 1-35% and their so-called MFI (melt flow index according to ASTM D 1238) is 0.1-50 gl 10 minutes.

The thermoplastically processable compositions of the invention can- of course be further modified, according to the state of the art, in which they contain, e.g., further additives such as fillers such as glass and/or minerals, plasticizers, in lower amounts other thermoplasts, processing aids such as internal and external lubricants, mould release agents, stabilisers (heat, light, oxidation), carbon black, dyes, pigments, flame retardant agents etc. as well as combinations of these additives, as required.

The invention will now be described in more detail with reference to examples.

Examples 1-9 Comparative experiments are marked in Table 1 with an asterisk (*), and the proportions of the individual components are parts by weight. The materials used are more closely characterised in the addendum to Table 1.

For the purpose of the experimental procedure, the dry components (water content lower than 0.05% by weight) of polyamide, TPUR and, according to the experiment, activated- polyolefin, were mixed, and then the additives, in premixed form introduced and further mixed, until the added materials were distributed uniformly in a thin layer on the granulate particles. This mixture was then introduced in to the feed hopper of a double screw extruder of the type ZSK-30 from Werner und Pfleiderer, Stuttgart, and the temperature in the six heat zones in the range of 180-230"C so regulated, at a screw speed of 150 rpm, that a strand as homogeneous as possible and easily granulable was obtained using a 4 mm nozzle.

The throughput in this case was about 8 kg/hour. A typical initial temperature profile of the six heat zones is, for example, 180/190/220/230/220 (each "C). The extrusion strand was passed through a water bath, and granulated, and the granules were dried to a water content of less than 0.05% by weight.

The measured melt temperatures in the nozzle are given in Table 1.

Examination of the melt strands from the nozzle gave an initial interesting result: In all cases, the addition of the activated polyolefin gave a homogeneous strand with a smooth surface, while this is often knotted and rough and leaves the nozzle in a pulsing manner, as described in the invention, if the inventive blend component c), the activated polyolefin, is absent.

So the addition of an activated polyolefin to the mixture of polyamide and TPUR gives already a clearly favourable behaviour even at the preparation stage of the polymer alloy.

The preparation of test pieces (small DIN bars, DIN 53453, tensile test bars, DIN 53455/3) was conducted on an injection moulding machine available from Netstal, Niederurnen, Switzerland, of the Neomat N 110/565-type, which includes an efficient melt extruder.

The processing parameters such as temperature profile of the screw, troughput etc. were adapted in each case, as satisfactorily as possible to the particular blend formulation.

As the observations on the injection-moulding procedure in Table 1 show, problems appeared in all cases in the comparative tests. By contrast, the formulations according to the invention allowed processing to homogeneous test pieces with a smooth surface. Only in the case of blends with TPUR proportions above 50%, does the moulding time have to be extended somewhat.

In addition to the improved processability, the blends according to the invention also possess a clearly improved toughness according to DIN 53453. In Table 1, oB indicates: the test bodies do not break on testing.

The tensile strength at yield according to DIN 53455 gives also a favourable result. While, e.g. polyamide 12 blends with a high polyurethane content, cannot be prepared and processed (comparative test 7), without the addition of an activated polyolefin, the stress/strain curve of the corresponding blends according to the invention exhibits high tensile strength and elongation at break without any yield point being visible.

If the stress/strain curve gives no defined yield point, no values for yield strength and elongation at yield are given in Table 1.

TABLE 1 Test No. 1 2 3 4 5 6 7 8 9 *Comparative Test * * * * Composition: -PA 12, Type 1 80 70 80 70 25 25 25 - PA 12, Type 2 80 70 - TPUR, Type 1 20 20 20 20 - TPUR ,Type 2 20 20 80 65 55 -Activated 10 10 10 10 20 Polyolefin - Additives 1 1 1 1 1 1 1 1 Extrusion: - Melt temperature 216 223 231 222 216 225 - 191 184 ( C) Processing: - Observed prob- 1) 1) 1) 5) 4) 4) lems (s.) 3) Mechanical proper ties:: - Notched impact strength, DIN 53'453 23OC(kJ/m2) 11 oB 27 oB 16 oB - oB oB -20 C (kJ/m2) 5 8 7 8 5 9 - oB oB -40 C (kJ/m2) 5 5 5 5 5 6 - oB oB Tensile test, DIN 53'455/3, 23"C - Tensile strength 34.8 27.7 - - 23.4 - at yield (N/mm2) - Tensile strength 27.2 38.8 27.0 30 25.0 17.8 16.3 at break (N/mm2) - Elongation at 7.7 15.8 - - 18.5 - yield (%) - Elongation at 34.7 198.2 3.2 66.5 31.5 250 225 break (%) Flexural moduius, DIN 53452: 23 C (N/mm2) 1215 791 1045 823 1302 677 - 78.1 67.4 0 C (N/mm2) 1630 980 -20 C (N/mm2) 1887 1122 -40 C (N/mm2) 2104 1192 1550 1182 Flexural strength at yield, DIN 53452:: 23"C (N/mm2) 57.4 39.8 47 39.4 58 32.6 - 5.1 4.5 0 C (N/mm2) 86 55 -20 C (N/mm2) 104 65 -40 C (N/mm2) 121 71 94 70 Addendum to Table 1: Abbreviations have the following meanings: - PA 12, type 1: Medium viscosity, injection-moulding-type, chain-length regulated so that it has the following terminal groups (each expressed as me-glkg polymer): -COOH = 49,-NH2 = 27 - PA 12, type 2: Medium viscosity, injection-moulding-type, chain-length regulated so that it has the following terminal groups: -COOH = 20,-NH2 = 57 - TPUR, type 1: Pellethane 2102-80a, Polyester-type - TPUR, type 2 Pellethane 2103-80AE, Polyether-type from Upjohn Europe SA, St.Galleon, Switzerland - Additives: Mixture of processing aids and stabilisers which is formulated from (in % by weight): 20% Tinuvin P, 20% Irganox 1076, 20% Irganox 1098 (stabilisers from Ciba-Geigy AG, Basel, Switzerland), 20% lubricant PAT-712/11 from Wurtz GmbH, Bingen-Sponsheim, West Germany, and also 10% of each of zinc stearate and magnesium stearate from 0. Baerlocher, 8000 Munich, 50, West Germany - Activated Polyolefin: APO,AP712 T from Mitsubishi Chemical, Tokyo - In the injection-moulding procedure, the observations have the following meanings: 1) Non-homogeneous blend, skin separation from surface of strand 2) Tensile test bars DIN 53455/3 cannot be moulded 3) Apparent decomposition of the melt on injection; test bodies have blistered surfaces.Tensile test bars (DIN 53455/3) cannot be prepared 4)Test pieces having good, smooth surfaces; minor adhesion in the mould 5) Even the preparation of the blends in the double-screw extruder was impossible because of incompatibility of the components and indications of decomposition Examples 10-14 and Comparative Examples 15-19 After having shown in Examples 1-9, that by the addition of an activated polyolefin, the ease of preparation, the processability and several mechanical properties are improved, only blends containing activated polyolefin are described in the examples which follow, and they are comared with the pure polyamide and polyurethane types.

The preparation and processing of the blends were conducted according to the parameters described above, but instead a single-screw extruder with an efficient mixing zone was used in the blend preparation. The exact processing-parameter for each formulation was thus optimised to the best possible extent.

The comparative materials according to tests 15-19 were processed in accordance with the conventional parameters for these thermoplasts. For most of the tests, polyamide 12 injection-moulding grade, GRILAMID L 20 G, from EMS-CHEMIE AG, Domat/Ems, Switzerland 7013, was used, which already contains lubricants and stabilisers, so that for the blend-preparation no additives besides the base polymeres, are used.

The composition of the blends and their mechanical properties are summarized in Table 2.

TABLE 2 TEST Examples Comparative Examples 10 11 12 13 14 15 16 17 18 19 Composition (% by weight) Polyamide 12, 20 20 35 60 100 GRILAMID L 20 G Polyamide elastomer, 35 100 GRILAMID ELY-60 Polyamide 6, 20 15 GRILON A-28 TPUR: - Adipate-type, 70 30 100 Pellethane 2355-90A - Lactone-type, 70 35 100 Elastollan E 590 FNAT -Polyether-type, 30 100 Elastollan E 190 FNAT - Activated polyolefin, 10 10 15 15 10 APO AP 712 T TABLE 2 (Continued) Test Examples Comparative Examples 10 11 12 13 14 15 16 17 18 19 Mechanical properties Test: Norm:Unit: ASTM D Tensile strenght 638 kg/cm 200 410 270 280 350 610 350 440 450 450 at break Elongation at 638 % 450 585 390 570 450 310 300 550 500 550 break Hardness, Shore A 2240 - 92 87 96 92 90 - - 90 90 90 E-Modulus 790 kg/cm 1000 1000 2800 3200 11000 2750 - - Resilience 2632 % 57 58 60 44 50 75 60 45 50 45 Density 792 g/cm 1.10 1.11 1.01 1.02 1.03 1.01 1.01 1.20 1.18 1.22 Notched impact kg/cm/ strenght (oB = 256 cm oB oB oB oB oB 8 8 oB oB oB no break) Addendum to Table2: The raw materials are commercial products from the following companies:: - The polyamide types used from EMS-CHEMIE AG, 7013 Domat/Ems, Switzerland - Pellethane 2355-90/A from Upjohn, La Porte, USA - Elastollan E 590 FNAT and E 190 FNAT from Elastogran- Chemie, GmbH, 2844 Lemförde, West Germany - APO, AP 712 T from Mitsubishi Chemical, Tokyo To make evident the new combinations of properties of the blends according to the invention, a range of special comparative tests was conducted. The results of these tests are summarized in Table 3.

Instead of numerical values, the overall properties are represented by symbols, with the aim of good clarity.

The symbols are on a decreasing scale of values: + 0 8 -, i.e. in which + = very favourable properties and - = comparatively poor properties.

TABLE 3 Test No. Test Examples Comparative Examples 1 Flexibility at low + + + + + - 0 - - + temperatures (-20 to -40 C) 2 Flexural fatigue + + + + + - + 0 0 + resistance 3 Adhesive strength of + + 0 0 0 - 6 + + + bonds performed with a polyurethane adhesive-system 4 Kink resistance + + 0 0 0 - - + + + 5 Tack on tool during + + + + + + + 6 (3 8 injection moulding 6 Hydrolysis-resistance + + + + + + + - - 0 Test Nos. 1-6 in Table 3 will now be briefly described: - No. 1: The E-moduli of formulations according to the invention are in Tables 1 and 2. For a favourable flexibility-performance at low temperatures, the value of the E-modulus at -40 C should increase as little as possible from the value at 23"C. This is clearly better achieved by the blends according to the invention in comparison with the pure polyamide-TPUR blends.

- No. 2: Test pieces according to Table 2 were provided with a 2 mm deep notch and subjected to an extended blending test of 105 cycles: formulations according to the invention and also Comparative Examples 16 and 19 = no determinable chance Comparative Example 18 and also polyamide 6, injection-moulding material = break after 800 cycles Comparative Example 17 or 18 = break after 117,000 respectively 20,000 cycles - No. 3: In order to examine the adhesive strength of urethane adhesive systems, a peel strength test was conducted. In this, test bodies according to Table 2, in the form of strips, were bonded to synthetic leather using a polyurethane adhesive, Bostic 4120 H and an isocyanate hardener, mixed in a ratio of 100:5, were used as the adhesive. The peeling speed was 200 mm/min.

Tearing-apart of the test body occurred as follows: Example 10 and 11 and also pure polyurethane in the leather or in the test bodies, but not at the adhesive join Example 12, 13, 14, to 70% in the leather or test bodies and onyl to 30% as the result of peeling off the adhesive joint, in which the peeling strength was 13 mg/25 mm In Comparative Example 15, using polyamide 12, the peeling strength was only 5 kg/25 mm (the same applies for polyamide 6); it was 12 kg/25 mm in Comparative Example 16 It is apparent from these results that, if blends according to the invention are used as the material for shoe soles, it is no longer necessary that the shoe upper material is sewn on to it, as the adhesion with the given adhesive provides sufficient strength.By contrast, shoe soles of pure nylon must be sewn on to the shoe upper material.

- No. 4: In order to test the kink resistance, tubes of 18 mm outer and 17 mm inner diameter were prepared and subjected to a prolonged kink test.

For Example 10 and 11, no kinks could be detected even after prolonged testing For Example 12, 13 and 14, the first kinks appeared only after 50 cycles . For Comparative Examples 15 and 16, kinks were already immediately apparent after the beginning of the test . From Comparative Example 17, 18 and 19, and also pure polyurethane, no tubes of the given dimensions could be prepared on account of their poor processability (adhesion in the nozzle). It is however known from the tests on flat bars that polyurethanes have a good kink resistance - No. 5: Tendency to adhesion in the mould.It is apparent from preparation of test pieces corresponding to Table 2 and also preparation of tubes that test pieces or tubes without a tendency to adhesion in the mould or nozzle can only be prepared using blends according to the invention or pure polyamides. It was also quite impossible to prepare thin-walled tubes for the kink test for example, using the pure TPUR-types (as in comparative tests 17-19).

- No. 6: Hydrolysis-resistance For this test, tubes having an outer dimension of 6 mm and an inner diameter of 4 mm were prepared and subjected to a burst pressure test of 15 kg/cm2, which all passed. They were then filled with water, sealed and stored for 20 days at about 60"C. They were then subjected to a burst-pressure test of 15 kg/ cm2 at room temperature.

The tubes corresponding to Example 10-14 and according to Comparative Example 15 and 16 (pure nylon tubes) remained undestroyed The TPUR-tubes corresponding to Comparative Example 17-19 all burst.

This shows that the formulations according to the invention have a clearly improved hydrolysis-resistance.

Claims

1. A thermoplastically processable composition which comprises a mixture consisting of 5 to 90% by weight of a thermoplastic polyamide, 5 to 90% by weight of a thermoplastic polyurethane, and 5 to 50% by weight of a thermoplastic, activated polyolefin.

2. A composition according to claim 1, wherein the mixture comprises 0.2 to 5 parts by weight of the polyamide per part by weight of the polyurethane, and at least 10% by weight of the polyolefin.

3. A composition according to claim 1 or claim 2, wherein the polyamide is a homopolyamide, a copolyamide, a segmented polyamide (elastomer polyamide) or a mixture or alloy of different polyamides, and the polyamide has a softening point below 235 C.

4. A composition according to claim 3, wherein the polyamide is polyamide 12 or polyamide 11.

5. A composition according to claim 3, wherein the polyamide is polyamide 6.

6. A composition according to claim 3, wherein the polyamide is the condensation product of diaminohexane and a dicarboxylic acid having at least 9 carbon atoms.

7. A composition according to claim 3, wherein the polyamide is a polyamide elastomer or a polyamide blend which contains a- polyamide elastomer.

8. A composition according to any preceding claim, wherein the polyurethane is of the polyester-type.

9. A composition according to any of claims 1 to 7, wherein the polyurethane is of the polyether-type.

10. A composition according to any preceding claim, wherein the polyolefin comprises an olefin copolymer on to which is grafted 0.1 to 2% by weight of an unsaturated carboxylic acid or a derivative of such a carboxylic acid.

11. A composition according to claim 10, wherein the olefin copolymer is derived from ethylene and at least one higher a-olefin, and the grafting is achieved radically by the use of a peroxide.

12. A composition according to claim 10, wherein the olefin copolymer is derived from ethylene, at least one higher a-olefin, and a non-conjugated diene, and the grafting is achieved without peroxide, at high temperature.

13. A composition according to claim 10, wherein the olefin copolymer is derived from ethylene, at least one higher o-olefin, and a non-conjugated diene, and the grafting is achieved by the use of a peroxide.

14. A composition according to any of claims 10 to 13, wherein the acid or acid derivative is a dicarboxylic acid or a derivative thereof.

15. A composition according to claim 14, wherein the dicarboxylic acid or derivative isfumaric acid, maleic acid anhydride, bicyclo[2.2.2]-2,3: 5,6-dibenzooctadiene-2,5-dicarboxylic acid-7,8-anhydride or a mixture thereof.

16. A composition according to any preceding claim, wherein the polyolefin has a glass transition temperature below -20 C, a degree of crystallisation of 1 to 35%, and a melt index of 0.2 to 50 g/10 minutes at 190 C and 2.16 kp load.

17. A composition according to any preceding claim, wherein the polyolefin is a mixture of graft copolyolefin as defined in any of claims 10 to 15 and non-grafted copolyolefin, and in which the proportion of the graft copolyolefin in the mixture is at least 30% by weight.

18. A composition according to claim 1, substantially as described in any of Examples 2, 4, 6 and 8 to 14.