WO2000020512A1

WO2000020512A1 - Polyketone polymer blends

Info

Publication number: WO2000020512A1
Application number: PCT/GB1999/003045
Authority: WO
Inventors: James Graham Bonner
Original assignee: Bp Chemicals Limited
Priority date: 1998-10-01
Filing date: 1999-09-14
Publication date: 2000-04-13

Abstract

A polymer blend consisting of a linear polyketone, a polyolefin and a thermoplastic polyurethane compatibiliser where the thermoplastic polyurethane is present in the blend in an amount of from 0.5 to 25 % by weight. The polymer blend may be fabricated into articles, films, sheets, coatings, liners, fibres or monofilaments having improved mechanical properties.

Description

POLYKETONE POLYMER BLENDS

The present invention relates to a polymer blend composition comprising a polyketone, a polyolefin and a thermoplastic polyurethane, in particular, to a polymer blend composition comprising a polyketone, a polyethylene and a thermoplastic polyurethane. For the purposes of this patent, polyketones are defined as linear polymers having an alternating structure of (a) units derived from carbon monoxide and (b) units derived from one or more olefinically unsaturated compounds. Such polyketones have the formula:

O II [(CR₂-CR₂)C]_m where the R groups are independently hydrogen or hydrocarbyl groups, and m is a large integer; they are disclosed in several patents e.g. US 3694412. Processes for preparing the polyketones are disclosed in US 3694412 and also in EP 181014 and EP 121965. Although for the purposes of this patent polyketones correspond to this idealised structure, it is envisaged that materials corresponding to this structure in the main but containing small regimes (i.e. up to 10 wt %) of the corresponding homopolymer or copolymer derived from the olefinically unsaturated compound, also fall within the definition.

Polymeric blends of thermoplastic polyurethane elastomers and polyolefins are known. Thus, EP 0354431 describes a polymeric blend composition comprising a mechanically compatible blend of a thermoplastic polyurethane elastomer and a polyolefin wherein the polyolefin is a homopolymer or copolymer of a C₂ to C₆ alpha- olefin and is present in the blend in an effective amount to improve the low temperature toughness of the thermoplastic polyurethane (preferably 3.5 to 20 % wt). However, EP

0354431 does not disclose a blend of a thermoplastic polyurethane elastomer, a polyolefin and a polyketone. US 4,851,482 relates to a blend of (a) a linear alternating polymer of carbon monoxide and an ethylenically unsaturated hydrocarbon and (b) a polyurethane polymer.

However, US 4,851,482 does not suggest that a further polymeric component may be added to the blend.

EP 0569101 describes a composite part comprising a first polymer section and a second polymer section, wherein the first polymer section comprises a linear alternating polyketone polymer and the second polymer section comprises a thermoplastic polymer selected from the group consisting of thermoplastic polyurethanes, phenoxy resins and polyamides which contain units of polymerised hexamethylenediamine/adipic acid, and wherein the second polymer section is directly neighbouring upon the first polymer section and exhibits interactive adhesion therewith. However, EP 0569101 does not teach that a thermoplastic polyurethane can act as a compatibiliser for a blend of a polyketone and a polyolefin.

Surprisingly, it has now been found that when a minor amount of a thermoplastic polyurethane is blended with a mixture of a polyketone and a polyolefin that the resulting blend has improved mechanical properties (e.g. elongation to break and impact strength) when compared with polyketone/polyolefin blends.

Thus, according to the present invention there is provided a polymer composition comprising a polymer blend and optionally conventional additives, the polymer blend consisting of: (A) a linear polyketone having an alternating structure of (a) units derived from carbon monoxide and (b) units derived from one or more olefinically unsaturated compounds;

(B) a polyolefin; and

(C) a thermoplastic polyurethane in an amount of from 0.5 to 25 % by weight based on the total weight of the polymer blend. Without wishing to be bound by any theory it is believed that the thermoplastic polyurethane acts as a compatibiliser allowing improved mixing and interfacial adhesion of the polyketone and polyolefin components of the polymer blend. Further advantages of the polymer composition of the present invention include improved paintability, chemical resistance, and barrier properties, when compared with polyketone/polyolefin blends.

As noted above, the polyketone component of the blend is a linear polymer having an alternating structure of (a) units derived from carbon monoxide and (b) units derived from one or more olefinically unsaturated compounds. Suitable olefinic units are those derived from C₂ to Cι₂ alpha-olefins or substituted derivatives thereof or styrene or alkyl substituted derivatives of styrene. It is preferred that such olefin or olefins are selected from C to Cβ normal alpha-olefins (straight chain alpha-olefins) and it is particularly preferred that the olefin units are either derived from ethylene or most preferred of all from a mixture of ethylene and one or more C₃-Cβ normal alpha-olefin(s) especially propylene or butylene. In these most preferable materials it is further preferred that the molar ratio of ethylene derived units to C₃-Cβ normal alpha-olefin derived units is greater than or equal to 1 most preferably between 2 and 30. Typically, the polyketone component of the polymer blend will be a terpolymer of ethylene/propylene/CO or ethylene/butylene/CO where, preferably, the amount of units derived from propylene or butylene is in the range 0.5-10 mole % e.g. 6 mole % of the polymer. The polymer blend may comprise two or more polyketones.

The Melt Flow Rate of the polyketone (5kg load at 240°C, 2.095 mm diameter die) is typically in the range 5-200 preferably 10-150, more preferably 20-100, for example 40-80g/10mins.

The polyketone component of the blend will suitably have a number average molecular weight of between 10,000 and 500,000 preferably between 15,000 and 300,000, more preferably between 20,000 and 200,000, for example, 25,000 to 250,000. The polyolefin component of the polymer blend may be a homopolymer of an olefin e.g. ethylene or propylene, in particular high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE) or very low density polyethylene (VLDPE), preferably LLDPE, or a copolymer of an olefin e.g. propylene with ethylene, butene, or other unsaturated aliphatic hydrocarbons or a terpolymer of an olefin e.g. ethylene with propylene and a diene. Such homopolymers, copolymers and terpolymers are known and any such polymer can be used.

The polyolefin component of the polymer blend may also be a graft copolymer having a polyolefin backbone grafted with 0.001 to 30% by weight of at least one polymerisable ethylenically unsaturated carboxylic acid or derivative thereof.

The polyolefin used as the backbone of the graft copolymer can be a homopolymer of an olefin or a copolymer of an olefin. Suitable homopolymers of an olefin or copolymers of an olefin include those described above. Blends of two or more polyolefins can be used. It is preferred that the backbone of the graft copolymer is polypropylene or polyethylene; where the polyolefin backbone is a copolymer it is preferred that it comprises at least 80% of polymerised ethylene or 80% of polymerised propylene units. Polymerisable ethylenically unsaturated carboxylic acids and derivatives thereof include, for example, acrylic acid, methacrylic acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, maleic anhydride, 4-methyl cyclohex-4-ene-l,2-dicarboxylic acid anhydride, bicyclo (2.2.2) oct-5-ene-2,3-dicarboxylic acid anhydride, 1,2,3,4,5,8,9,10- octahydronaphthalene-2,3 dicarboxylic acid anhydride, 2-oxa-l,3-diketospiro (4.4) non- 7-ene, bicyclo (2.2.1) hept-5-ene-2,3 -dicarboxylic acid anhydride, maleopimaric acid, tetrahydrophthalic anhydride, x-methyl-bicyclo (2.2.1) hept-5-ene -2,3 -dicarboxylic acid anhydride, x-methyl-norborn-5-ene-2, dicarboxylic acid anhydride, norborn-5-ene-2,3- dicarboxylic acid anhydride. Preferably, maleic anhydride is used. When maleic anhydride is used as the polymerisable ethylenically unsaturated carboxylic acid anhydride, the amount which is graft copolymerised with a polyolefin backbone is preferably from 0.1 to 10% more preferably from 0.15 to 5 % by weight of the grafted copolymer.

The polymer blend of the present invention may comprise a mixture of polyolefins selected from the group consisting of a homopolymer of an olefin, a copolymer of an olefin, a terpolymer of an olefin and a graft copolymer having a polyolefin backbone.

Where the physical properties (e.g. toughness, impact strength and melt processability) of the polyketone are to be improved, then it is preferred that the blend comprises 1 to 20% by weight of polyolefin, more preferably 5 to 15%, for example 10% by weight of polyolefin based upon the total weight of the polymer blend. On the other hand, if other properties such as thermal characteristics (e.g. Vicat softening point and heat distortion temperature) and gaseous or liquid barrier properties (e.g. oxygen, water and hydrocarbon) of the polyketone are to be improved, then it is preferred that the blend comprises 0.5 to 25% by weight of polyketone, more preferably 1 to 20%, most preferably 5 to 20%, for example, 15% by weight of polyketone, based upon the total weight of the polymer blend. The thermoplastic polyurethane component of the blend may be a polyether- based polyurethane or a polyester-based polyurethane (as described in US 4,851,482 or EP 0569101 which are herein incorporated by reference). Such thermoplastic polyurethane polymers may be prepared from long chain polyols reacted with polyisocyanates and chain extenders. The polyols may be of two basic types, either polyether-type or polyester-type.

Polyether-type polyols usable herein include poly(oxypropylene) glycols and poly(oxytetramethylene) glycols. Polyester-type polyols usable herein can be hydroxyl terminated polyesters prepared from, e.g. adipic acid and an excess of glycol, such as ethylene glycol, neopentyl glycol, hexanediol-1,6-, and the like or mixtures thereof. The thermoplastic polyurethanes are preferably prepared from polyols having a molecular weight between 750 and 10,000, more preferably between 750 and 3500. In the preparation of the thermoplastic polyurethanes the polyols can be mixed with a molar excess of an organic diisocyanate to form urethane linkages in a linear polymer. This linear polymer can be reacted with a chain extending agent, such as water, diamine, or hydroxy-amine.

Any of a wide variety of diisocyanate compounds may be used in the polymerisation to prepare the thermoplastic polyurethanes usable herein. Aromatic diisocyanates, such as toluene-2,4-diisocyanate (and its dimers), A, 4'-methylene- bis(phenyl isocyanate), 1,5-naphthylene diisocyanate and 4-tertbutyl m-phenylene diisocyanate are usable herein. Diphenyl methane diisocyanate may be particularly advantageous for use herein. Aliphatic compounds such as hexamethylene diisocyanate and tetramethylene diisocyanate, and the alicyclic compounds such as 1,4-cyclohexylene diisocyanate may be operable. It is to be understood that these diisocyanates may be used either singly or in combination. The chain-extending agent can contain a plurality of active hydrogen atoms, with up to two atoms in the molecule having active hydrogen attached thereto. A preferred chain-extending agent is 1,4-butanediol. Suitable chain-extending agents include ethylene diamine, m-tolylene diamine, benzidine, diethylene glycol, hydrazine, succinic acid and 1,4-butanedisulfonic acid.

The polymer blend may comprise two or more thermoplastic polyurethanes. Preferably, the thermoplastic polyurethane comprises 1 to 15, more preferably 2 to 10 %, most preferably 3 to 7, for example 5 % by weight of the polymer blend.

Other polymers may be blended with the polymer composition of the present invention; the nature and amount of such a polymer will depend upon what modifications of the polymer properties are required. Furthermore, the polymer compositions of the present invention may contain conventional polymer additives such as anti-oxidants, stabilisers, impact modifiers, fillers, mould release agents, colorants, fire resistant materials and internal or external lubricants.

It is to be understood that when in the specification and claims herein, the amounts of the individual components of the polymer blend are expressed in terms of percent by weight, it is meant, unless otherwise indicated, percent by weight based on the total weight of the polymer blend, excluding further components.

The polymer composition of the present invention can be prepared using conventional techniques and equipment for batch or continuous blending such as a two- roll mill, a Banbury mixer, or a single/twin screw compounding extruder.

The scope of the present invention extends to polymer-based articles (for example, mouldings, containers, pipes, tubes and receptacles such as containers, bowls and trays), and to polymer-based films, sheets, coatings, liners, fibres and monofilaments comprising the polymer compositions as defined hereinbefore.

Methods of fabricating the compositions into articles, films or other applications are standard in the art, for example extrusion, coextrusion, injection moulding, blow- moulding and thermoforming. Preferred methods of fabricating the compositions are those where orientation of the polymer is likely e.g. extrusion (film extrusion), blow- moulding and thermoforming.

The articles comprising the polymer composition as defined above may be made at least in part from a monolayer of the composition of the present invention. Alternatively, the articles may be of a multi-layer construction at least one layer of which is a composition according to the present invention.

The invention will now be illustrated by the following Examples. Materials

The materials in the blending experiments were:

Polyethylene (PE): Rigidex HD5502XA supplied by BP Chemicals Limited which is a general purpose grade used for blow moulding and packaging applications. Thermoplastic polyurethane (TPU): Estane 58630 ™ supplied by BF Goodrich

Company.

Polyketone (PK): an ethylene/butylene/CO terpolymer having a melting point of 214°C and a melt flow rate (MFR) of 12 g/10 minutes (at 250°C, 2.16kg load). Melt Flow Rate The melt flow rate (MFR) of the polyketone (PK) was measured using a

Davenport Melt Index Tester. Tests were carried out at a temperature of 250°C and an applied load of 2.16 kg. The MFR was calculated from the mass of extrudate pushed through a die (2.095 mm diameter) over a 30 second period on application of the load 4 minutes after charging the polymer into the barrel of the instrument at a temperature of 250°C. Otherwise, standard MFR procedures were followed (e.g. ISO 1133). Materials Preparation

The materials used in the following experiments were prepared using a Prism 16mm co-rotating, laboratory, twin screw extruder. The feed, barrel and die sections of the extruder were set to the following temperatures: 200, 215, and 225°C respectively. A screw speed of 250 rpm and a torque of 30-50% were used throughout production runs. The materials were passed through the extruder a second time to ensure good mixing. Examples

A polyethylene/polyketone/thermoplastic polyurethane blend containing 80% w/w polyethylene, 15% w/w polyketone and 5% w/w thermoplastic polyurethane was prepared using a Prism 16mm co-rotating twin screw extruder as described above. In addition, a sample of the polyethylene and a polyethylene/polyketone blend (85% w/w polyethylene, 15% w/w polyketone) were also processed under the above conditions. Compression Moulded Sheets A compression moulded sheet of the polyethylene/polyketone/thermoplastic polyurethane (PE/PK TPU) blend was produced using a 20 tonne Moore press under the following conditions: a l5 cm x l5 cm x l mm "picture frame" mould was preheated for 5 minutes at a temperature of 235°C (platen temperature), pressed at 15 tonnes for 5 minutes at this temperature and then crash cooled to room temperature.

A polyethylene (PE) sheet and a sheet of the polyethylene/polyketone (PE/PK) blend were made using the same procedure to that given above. Blend Characterisation

Scanning electron microscopy (SEM) was used to examine the phase structure of the blends and hence the degree of compatibilisation. Samples were prepared by cryo polishing a surface of a sheet which surface was then coated with gold.

SEM showed that the blends according to the present invention had very small phase sizes, a property associated with good compatibility. Where the blends contain high amounts of polyethylene, the polyketone was found to be distributed in a polyethylene matrix. Tensile Properties

Tensile properties were determined in accordance with ISO 527-1966 (ASTM D 638M-93) using the compression moulded sheets. The test conditions were as follows:

23 °C

50% RH (relative humidity); and

50 mm/min (cross head speed). Measurements were carried out using an Instron 1122 Universal Testing Machine.

The polymer blends according to the present invention had a high tensile elongation to break, a further property associated with good compatibility. The polymer blends according to the present invention showed a slight decrease in yield stress compared with the non-compatibilised blend which is believed to arise from the rubbery nature of the TPU compatibiliser.

The results of the tensile tests are given in Table 1. TABLE 1 - TENSILE TESTS

CD

Claims

Claims: 1. A polymer composition comprising a polymer blend and optionally conventional additives, the polymer blend consisting of:

(A) a linear polyketone having an alternating structure of (a) units derived from carbon monoxide and (b) units derived from one or more olefinically unsaturated compounds; (B) a polyolefin; and

(C) a thermoplastic polyurethane in an amount of from 0.5 to 25 % by weight based on the total weight of the polymer blend.

2. A polymer composition as claimed in claim 1 wherein the polymer blend comprises 2 to 10 % by weight of thermoplastic polyurethane.

3. A polymer composition as claimed in claims 1 or 2 wherein the polymer blend comprises 3 to 7 % by weight of thermoplastic polyurethane.

4. A polymer composition as claimed in any one of the preceding claims wherein the polymer blend comprises 1 to 20% by weight of polyolefin.

5. A polymer composition as claimed in claim 4 wherein the polymer blend comprises 5 to 15% by weight of polyolefin.

6. A polymer composition as claimed in any of claims 1 to 3 wherein the polymer blend comprises 0.5 to 25% by weight of polyketone.

7. A polymer composition as claimed in claim 6 wherein the polymer blend comprises 1 to 20% by weight of polyketone.

8. A polymer composition as claimed in any one of the preceding claims wherein the polyketone component of the polymer blend is a terpolymer of ethylene/propylene/CO or ethylene/butylene/CO.

9. A polymer composition as claimed in any one of the preceding claims wherein the polyolefin component of the polymer blend is selected from the group consisting of a high density polyethylene, a low density polyethylene, a linear low density polyethylene, very low density polyethylene, a polypropylene, a copolymer of ethylene and propylene, and a terpolymer of ethylene, propylene and a diene.

10. A polymer composition as claimed in any one of the preceding claims wherein the thermoplastic polyurethane component of the blend is a polyether-based polyurethane or a polyester-based polyurethane.

11. A polymer-based article wherein the polymer comprises a polymer composition as defined in any one of the preceding claims.

12. A polymer-based article as claimed in claim 11 wherein the article is of a multilayer construction at least one layer of which is a polymer composition as defined in any one of claimed 1 to 10.

13. A polymer-based film, sheet, coating, liner, fibre or monofilament wherein the polymer comprises a polymer composition as defined in any one of claims 1 to 10.