Patent Application
20110196098
The invention relates to polyester mixtures, comprising
The prior art has previously disclosed approaches to improvement of the mechanical properties and the flow behavior of polyesters, such as PBT.
WO 2004/078844 describes polyester mixtures composed of PBT (component A) and of an aliphatic-aromatic polyester (component C) for improvement of flexural stiffness, in particular of bristles. WO 2004/078844 does not use flow improvers.
WO 2005/075565 discloses improved-flow polyester mixtures. Flow improvers used are highly branched and hyperbranched polycarbonates (component B1). The improved-flow polyester mixtures are, however, not always entirely satisfactory with regard to their mechanical properties, for example with regard to elongation or to tensile strain at break.
Finally, WO 2006/018127 describes polyester mixtures which comprise not only flow improvers but also rubbers as impact modifiers (component D1). Mechanical properties can be improved in these mixtures, but addition of the rubbers in turn impairs flow behavior.
An object was therefore to find a highly flowable polyester with markedly improved rheological properties which simultaneously has excellent mechanical properties.
Surprisingly, the object was achieved via the inventive polyester mixtures, which use a combination composed of flow improvers (component B) and of aliphatic-aromatic polyesters (component C).
In one preferred embodiment, impact modifiers (component D1) can be added. It is interesting that the flow behavior of the polyester mixtures is not significantly impaired by the addition of impact modifiers, and in the presence of the aliphatic-aromatic polyesters.
In another preferred embodiment, fiber-reinforced polyester mixtures are provided.
The inventive polyester mixtures are described in more detail below.
The inventive molding compositions comprise, as component A), from 30 to 98% by weight, preferably from 50 to 98% by weight, and in particular from 90 to 97% by weight, of at least one thermoplastic polyester which differs from components B2) and C).
Polyesters A) based on aromatic dicarboxylic acids and on an aliphatic or aromatic dihydroxy compound are generally used. Preference is given to poly-C2-C10-alkylene terephthalates, and particular preference is given to polybutylene terephthalate (PBT).
These polyalkylene terephthalates are known per se and are described in the literature.
The specifications WO 2005/075565 and WO 2006/018127, which are expressly incorporated herein by way of reference, give a very detailed description of component A with regard inter alia to
The inventive molding compositions comprise, as component B), from 0.01 to 15% by weight, preferably from 0.3 to 15% by weight, and in particular from 0.5 to 10% by weight, of B1) at least one highly branched or hyperbranched polycarbonate with an OH number of from 1 to 600 mg KOH/g of polycarbonate, preferably from 10 to 550 mg KOH/g of polycarbonate, and in particular from 50 to 550 mg KOH/g of polycarbonate (to DIN 53240, Part 2), or of at least one hyperbranched polyester, as component B2), or a mixture of these, as explained below.
For the purposes of this invention, hyperbranched polycarbonates B1) are non-crosslinked macromolecules having hydroxy groups and carbonate groups, these having both structural and molecular non-uniformity. Their structure may firstly be based on a central molecule in the same way as dendrimers, but with non-uniform chain length of the branches. Secondly, they may also have a linear structure with functional pendant groups, or else they may combine the two extremes, having linear and branched molecular portions. See also P. J. Flory, J. Am. Chem. Soc. 1952, 74, 2718, and H. Frey et al., Chem. Eur. J. 2000, 6, no. 14, 2499 for the definition of dendrimeric and hyperbranched polymers.
Component B1) preferably has a number-average molar mass Mn of from 100 to 15 000 g/mol, preferably from 200 to 12 000 g/mol, and in particular from 500 to 10 000 g/mol (GPC, PMMA standard).
The glass transition temperature Tg is in particular from −80° C. to +140° C., preferably from −60 to 120° C. (by DSC, to DIN 53765).
Viscosity (mPas) at 23° C. (to DIN 53019) is in particular from 50 to 200 000, in particular from 100 to 150 000, and very particularly preferably from 200 to 100 000.
The specifications WO 2005/075565 and WO 2006/018127, which are expressly incorporated herein by way of reference, give a very detailed description of component B1 with regard inter alia to
The inventive molding compositions can comprise, as component B2), at least one hyperbranched polyester of A×By type, where
x is at least 1.1, preferably at least 1.3, in particular at least 2
y is at least 2.1, preferably at least 2.5, in particular at least 3.
It is, of course, also possible to use mixtures as units A or B.
An AxBy-type polyester is a condensate composed of an x-functional molecule A and a y-functional molecule B. By way of example, mention may be made of a polyester composed of adipic acid as molecule A (x=2) and glycerol as molecule B (y=3).
For the purposes of this invention, hyperbranched polyesters B2) are non-crosslinked macromolecules having hydroxy groups and carboxy groups, these having both structural and molecular non-uniformity. Their structure may firstly be based on a central molecule in the same way as dendrimers, but with non-uniform chain length of the branches. Secondly, they may also have a linear structure with functional pendant groups, or else they may combine the two extremes, having linear and branched molecular portions. See also P. J. Flory, J. Am. Chem. Soc. 1952, 74, 2718, and H. Frey et al., Chem. Eur. J. 2000, 6, no. 14, 2499 for the definition of dendrimeric and hyperbranched polymers.
Component B2) preferably has an Mn of from 300 to 30 000 g/mol, in particular from 400 to 25 000 g/mol, and very particularly from 500 to 20 000 g/mol, determined by means of GPC, PMMA standard, dimethylacetamide eluent.
B2) preferably has an OH number of from 0 to 600 mg KOH/g of polyester, preferably from 1 to 500 mg KOH/g of polyester, in particular from 20 to 500 mg KOH/g of polyester to DIN 53240, and preferably a COOH number of from 0 to 600 mg KOH/g of polyester, preferably from 1 to 500 mg KOH/g of polyester, and in particular from 2 to 500 mg KOH/g of polyester.
Tg is preferably from −50° C. to 140° C., and in particular from −50 to 100° C. (by DSC, to DIN 53765).
Preference is particularly given to those components B2) in which at least one OH or COOH number is greater than 0, preferably greater than 0.1, and in particular greater than 0.5.
Inventive component B2) can be obtained via the processes described in WO 2006/018127, by
WO 2006/018127, which is expressly incorporated herein by way of reference, gives a very detailed description of component B2 with regard inter alia to
The inventive polyesters have a molar mass Mw of from 500 to 50 000 g/mol, preferably from 1000 to 20 000 g/mol, particularly preferably from 1000 to 19 000 g/mol. Polydispersity is from 1.2 to 50, preferably from 1.4 to 40, particularly preferably from 1.5 to 30, and very particularly preferably from 1.5 to 10. They usually have good solubility, i.e. clear solutions can be prepared using up to 50% by weight, indeed in some cases up to 80% by weight, of the inventive polyesters in tetrahydrofuran (THF), n-butyl acetate, ethanol, and numerous other solvents, without any gel particles detectable by the naked eye.
The inventive high-functionality hyperbranched polyesters are carboxy-terminated, terminated by carboxy groups and by hydroxy groups, and preferably terminated by hydroxy groups.
The ratios of the components B1) to B2) are preferably from 1:20 to 20:1, in particular from 1:15 to 15:1, and very particularly from 1:5 to 5:1, if these are used in a mixture.
In principle, component C used can comprise polyesters based on aliphatic and aromatic dicarboxylic acids and on an aliphatic dihydroxy compound, these being known as semiaromatic polyesters. Mixtures of a plurality of these polyesters are, of course, also suitable as component C.
According to the invention, polyester derivatives, such as polyetheresters, polyesteramides, or polyetheresteramides, are also understood to be semiaromatic polyesters. Among the suitable semiaromatic polyesters are linear non-chain-extended polyesters (WO 92/09654). Preference is given to chain-extended and/or branched semiaromatic polyesters. The latter are disclosed in the specifications WO 96/15173 and WO 2006/074815, which are expressly incorporated herein by way of reference. Mixtures of different semiaromatic polyesters can likewise be used. Semiaromatic polyesters also include in particular products such as Ecoflex® (BASF Aktiengesellschaft), Eastar® Bio, and Origo-Bi (Novamont).
Among the particularly preferred semiaromatic polyesters are polyesters which contain, as essential components,
HO—[(CH2)n—O]m—H (I)
In one preferred embodiment, the acid component a) of the semiaromatic polyesters comprises from 35 to 70 mol %, in particular from 40 to 60 mol %, of a1, and from 30 to 65 mol %, in particular from 40 to 60 mol %, of a2.
Particular preference is given, as component C), to a copolymer composed of
The semiaromatic polyesters C mentioned are generally biodegradable.
For the purposes of the present invention, a substance or a mixture of substances complies with the feature termed “biodegradable” if this substance or mixture of substances has a percentage degree of biodegradation of at least 60% in at least one of the three processes defined in DIN V 54900-2 (preliminary standard, as at September 1998).
The preferred semiaromatic polyesters are characterized by a molar mass (Mn) in the range from 1000 to 100 000 g/mol, in particular in the range from 9000 to 75 000 g/mol, preferably in the range from 10 000 to 50 000 g/mol, and a melting point in the range from 60 to 170° C., preferably in the range from 80 to 150° C.
The semiaromatic polyesters mentioned can have hydroxy and/or carboxy end groups in any desired ratio. The semiaromatic polyesters mentioned can also be end-group-modified. By way of example, therefore, OH end groups can be acid-modified via reaction with phthalic acid, phthalic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, or pyromellitic anhydride.
The inventive thermoplastic molding compositions comprise, as component (D1), from 1 to 20% by weight, preferably from 1 to 15% by weight, of an impact-modifying polymer (often also termed elastomeric polymer or elastomer).
Preferred elastomeric polymers are the polymers described in WO 2006/018127 and based on olefins and composed of the following components:
A first preferred group that may be mentioned is that of what are known as ethylene-propylene (EPM) rubbers or ethylene-propylene-diene (EPDM) rubbers, whose ratio of ethylene units to propylene units is preferably in the range from 40:60 to 90:10.
WO 2006/018127, which is expressly incorporated herein by way of reference, describes these rubbers in detail.
Examples of particularly preferred components D1) are MBS rubbers composed of:
from 65 to 99% by weight of a core composed of
WO 2006/018127, which is expressly incorporated herein by way of reference, describes these rubbers in detail.
Another group of preferred olefin polymers is provided by copolymers of α-olefins having from 2 to 8 carbon atoms, in particular of ethylene, with C1-C18-alkyl esters of acrylic acid and/or methacrylic acid.
WO 2006/018127, which is expressly incorporated herein by way of reference, gives a more detailed specific description of these olefin polymers, and also of the individual components d3 to d8.
Particular preference is given to olefin polymers composed of:
Preference is further given to acrylate rubbers D1) composed of:
WO 2006/018127, which is expressly incorporated herein by way of reference, gives a more detailed description of the acrylate rubbers D1.
A thermoplastic elastomer based on TPEE (thermoplastic polyester elastomers) can also be used as component D1. These products are marketed inter alia with trademark Pibiflex®, for example E4090, from P-Group, Italy, or Hytrel® (DuPont), or Arnitel® (Akzo), or else Pelprene® (Toyobo Co. Ltd). These products have a crystalline PBT fraction and a polyethylene glycol fraction as soft segment, and are described in detail in the specification WO 2007/009930, which is expressly incorporated herein by way of reference.
TPEE has short-chain units of the formula:
—O-D-O—CO—R—CO (I)
and long-chain units having the formula:
—O-G-OCO—R—CO— (IIa)
—O-D-O—CO—R—CO (IIb)
where
Further preferred impact modifiers D1 that can be used are thermoplastic elastomers of TPU type as by way of example available with trademark Elastollan® from Elastogran. The elastomers generally have a soft segment formed from a diisocyanate and from a long-chain diol, where the latter in turn can comprise ether or ester groups, and a hard segment, formed from diisocyanates and from short-chain diols. As a function of the constitution of the long-chain diol, the term polyester polyols or polyether polyols is used.
The preferred quantitative proportion of the impact modifier D1 introduced into the thermoplastic polymer is in the range from 1 to 20% by weight and preferably from 1 to 15% by weight, based on 100% by weight of the thermoplastic polymer used.
Fibrous or particulate fillers D2) that can be used are carbon fibers, glass fibers, glass beads, amorphous silica, asbestos, calcium silicate, calcium metasilicate, magnesium carbonate, kaolin, chalk, powdered quartz, mica, barium sulfate, and feldspar, their amounts being up to 50% by weight, in particular up to 30%.
Preferred fibrous fillers that may be mentioned are carbon fibers, aramid fibers, and potassium titanate fibers, particular preference being given to glass fibers in the form of E glass. These can be used as rovings or chopped glass in the forms commercially available. The thickness of the glass fibers is generally about 10 μm.
To improve compatibility with the thermoplastic, the fibrous fillers may have been pretreated on the surface with a silane compound. WO 2006/018127, which is expressly incorporated herein by way of reference, gives a more detailed description of the silane-modification process.
The inventive molding compositions can moreover comprise conventional processing aids, such as stabilizers, oxidation retarders, agents to counteract decomposition by heat and decomposition by ultraviolet light, lubricants and mold-release agents, colorants, such as dyes and pigments, plasticizers, nucleating agents, and compatibilizers.
Examples mentioned of oxidation retarders and heat stabilizers are sterically hindered phenols and/or phosphites, hydroquinones, aromatic secondary amines, such as diphenylamines, and various substituted representatives of these groups, and mixtures thereof, in concentrations up to 1% by weight, based on the weight of the thermoplastic molding compositions.
UV stabilizers which may be mentioned, and are generally used in amounts of up to 2% by weight, based on the molding composition, are various substituted resorcinols, salicylates, benzotriazoles, and benzophenones.
Colorants which may be added are inorganic pigments, such as titanium dioxide, ultramarine blue, iron oxide, and carbon black, and also organic pigments, such as phthalocyanines, quinacridones and perylenes, and also dyes, such as nigrosine and anthraquinones.
Nucleating agents which may be used are sodium phenylphosphinate, alumina, silica, and preferably talc.
Other lubricants and mold-release agents are usually used in amounts of up to 1% by weight. Preference is given to long-chain fatty acids (e.g. stearic acid or behenic acid), salts of these (e.g. calcium stearate or zinc stearate) or montan waxes (mixtures of straight-chain saturated carboxylic acids having chain lengths of from 28 to 32 carbon atoms), or calcium montanate or sodium montanate, or low-molecular-weight polyethylene waxes or low-molecular-weight polypropylene waxes.
Examples of plasticizers which may be mentioned are dioctyl phthalates, dibenzyl phthalates, butyl benzyl phthalates, hydrocarbon oils and N-(n-butyl)benzene-sulfonamide.
The inventive molding compositions may also comprise from 0 to 2% by weight of fluorine-containing ethylene polymers. These are polymers of ethylene with a fluorine content of from 55 to 76% by weight, preferably from 70 to 76% by weight.
Examples of these are polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymers and tetrafluoroethylene copolymers with relatively small proportions (generally up to 50% by weight) of copolymerizable ethylenically unsaturated monomers. These are described, for example, by Schildknecht in “Vinyl and Related Polymers”, Wiley-Verlag, 1952, pages 484-494 and by Wall in “Fluoropolymers” (Wiley Interscience, 1972).
These fluorine-containing ethylene polymers have homogeneous distribution in the molding compositions and preferably have a particle size d50 (numeric average) in the range from 0.05 to 10 μm, in particular from 0.1 to 5 μm. These small particle sizes can particularly preferably be achieved by the use of aqueous dispersions of fluorine-containing ethylene polymers and the incorporation of these into a polyester melt.
The inventive thermoplastic molding compositions may be prepared by methods known per se, by mixing the starting components in conventional mixing apparatus, such as screw extruders, Brabender mixers or Banbury mixers, and then extruding them. The extrudate may be cooled and comminuted. It is also possible to premix individual components and then to add the remaining starting materials individually and/or likewise in a mixture. The mixing temperatures are generally from 230 to 290° C.
In another preferred procedure, components A and C, and also, if appropriate, D1 can be charged, premixed, to the extruder, and component B can preferably be added dropwise by a hot-feed method, and component D2 can likewise be added at a later juncture to the extruder by a hot-feed method. The final extrudate can, if appropriate, be compounded and pelletized.
A feature of the inventive thermoplastic molding compositions is good flowability simultaneously with good mechanical properties.
In particular, processing of the individual components is possible without difficulty (without clumping or caking), and in short cycle times, a particular possible application therefore being thin-walled components.
The use for an improved-flow polyester is conceivable in almost any injection-molding application. The improved flow can give a lower melt temperature and can therefore lead to a marked lowering of the total cycle time for the injection-molding process (lowering of production costs for an injection molding!). Furthermore, lower injection pressures are needed during processing, and a lower total clamping force is therefore needed on the injection mold (lower capital expenditure for the injection-molding machine).
Alongside the improvements in the injection-molding process, the lowering of melt viscosity can lead to marked advantages in the actual design of the component. By way of example, thin-walled applications which hitherto, for example, were not achievable using filled grades of polyester, can be produced by way of injection molding. By analogy with this, it is conceivable that the use of reinforced grades of polyester that have improved flow will reduce wall thicknesses in existing applications, and therefore reduce component weights.
These materials are suitable for production of fibers, of foils, and of moldings of any type, in particular for applications as plugs, switches, housing parts, housing covers, headlamp bezels, shower heads, fittings, smoothing irons, rotary switches, stove controls, fryer lids, door handles, (rear) mirror housings, (tailgate) screen wipers, or sheathing for optical conductors.
Electronic and electrical applications which can be produced using the improved-flow polyesters are plugs, plug components, plug connectors, cable harness components, circuit mounts, circuit mount components, three-dimensionally injection-molded circuit mounts, electrical connectors, mechatronic components, or optoelectronic components.
Possible uses in automobile interiors are for dashboards, steering column switches, seat components, headrests, center consoles, gearbox components, and door modules, and possible automobile exterior components are door handles, headlamp components, exterior mirror components, windshield washer components, windshield washer protective housings, grilles, roof rails, sunroof frames, and exterior bodywork parts.
Possible uses of the improved-flow polyester in the kitchen and household sector are production of components for kitchen equipment, e.g. fryers, smoothing irons, buttons, and also garden and leisure sector applications, such as components for irrigation systems or garden equipment.
In the medical technology sector, it becomes simpler to produce inhaler housings and components of these via improved-flow polyesters.
General operating specification for production of inventive polyester mixtures:
Each of the compounding materials described in the examples was produced in a ZSK 30 twin-screw extruder using a processing temperature of 260° C. PBT was premixed here with the additives C and, if appropriate, D1 in the form of a premix, and charged to the extruder feed. The glass fiber (D2) was charged to the middle of the extruder by a hot-feed method. The flow improver (B) was added dropwise to the polymer melt by a hot-feed method, by means of a pump. The additive B can also optionally be concomitantly added dropwise to the intake, or can be applied in a mixing drum to the premix. To test mechanical properties, dumbbell specimens were produced to ISO 527-2 and the tensile test was carried out to ISO 527-2 (exception: Inventive Example 3, see description). Impact resistance was also determined to ISO179-2, as were viscosity number (VN: ISO 1628 in phenol/o-dichlorobenzene, 1:1, 25° C.), and flowability by means of MVR (ISO 1133).
The mechanical data shown in Table 3 were obtained from tensile tests to ISO 527-2 on tensile specimens of thickness 2 mm, which had been cut out from sheets.
The results listed in Table 1 show that the mechanical properties of injection moldings can be decisively improved via addition of semiaromatic polyesters C, such as Ecoflex. The improved tensile strain at break behavior due to addition of semiaromatic polyesters C is particularly noticeable (see Inventive Example 2), when comparison is made with PBT which comprises merely flow improver (Example comp 1).
The data collated in Table 2 show that the use of impact modifiers D1 (comp 6 and comp 9) impairs the flowability of the polyester mixtures (comp 5). There is a marked attenuation of this effect in the presence of the semiaromatic polyesters C (see Inventive Examples 7, 8, 10, and 11). Moldings produced from these mixtures moreover have excellent mechanical properties.
The data shown in Table 3 show that the addition of semiaromatic polyesters C brings about a similar favorable effect in glassfiber-reinforced PBT.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07114384.6 | Aug 2007 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP08/60626 | 8/13/2008 | WO | 00 | 2/12/2010 |
