WO2000047669A1

WO2000047669A1 - Fiber reinforced syndiotactic monovinylidene aromatic polymer compositions having high gloss

Info

Publication number: WO2000047669A1
Application number: PCT/US1999/027896
Authority: WO
Inventors: Kevin L. Nichols; David H. Bank
Original assignee: The Dow Chemical Company
Priority date: 1999-02-09
Filing date: 1999-11-24
Publication date: 2000-08-17
Also published as: AU1921400A

Abstract

A fiber reinforced composition comprising (a) a syndiotactic monovinylidene aromatic polymer composition, (b) a ductility modifier (c) a fiber reinforcement, and (d) a mineral filler.

Description

FIBER REINFORCED SYNDIOTACTIC MONOVINYLIDENE AROMATIC POLYMER COMPOSITIONS HAVING HIGH GLOSS The present invention relates to syndiotactic monovinylidene aromatic polymer compositions. Glass fibers have frequently been used as reinforcement in polymer compositions such as syndiotactic monovinylidene aromatic polymers. However, the use of such fibers frequently presents a surface quality problem, in that the surface is roughened by the presence of the fiber. Mineral fillers have also been used as a reinforcement and produce a smooth surface. However, compositions containing only mineral filler have lower thermal properties, mechanical properties and the impact strength than those filled with glass fibers.

US-A-5,391 ,603 discloses a composition comprising a syndiotactic vinylaromatic thermoplastic, a rubbery, impact absorbing polymer, a nucleator, a mtfreral or glass reinforcing agent and a polyarylene ether. However, these compositions suffer from the same disadvantages as discussed above when using glass or mineral filler alone.

US-A-5,798,162 discloses a multilayered composite comprising an inner core layer of a crystalline polymer and a glass filler, and an outer skin layer of a crystalline polymer and a mineral filler. This composition maintains the strength of the glass in the inner layer while the outer mineral filled layer gives good surface quality. However, this requires the production of two filled systems and an expensive multistep process in order to produce the composite material.

Therefore, there remains a need for a reinforced syndiotactic monovinylidene aromatic polymer composition having good ductility, surface quality and gloss properties.

One aspect of the present invention is a composition comprising:

A) a syndiotactic monovinylidene aromatic polymer composition,

B) a ductility modifier,

C) a fiber reinforcement, and D) a mineral filler.

Surprisingly, it has been found that the surface quality of the composition is significantly improved with the presence of both mineral filler and ductility modifier in fiber reinforced compositions

Component A) of the composition of the present invention is a syndiotactic monovinylidene aromatic polymer composition. As used herein, the term

"syndiotactic" refers to polymers having a stereoregular structure of greater than 90 percent syndiotactic, preferably greater than 95 percent syndiotactic, of a racemic triad as determined by ¹³C nuclear magnetic resonance spectroscopy. The syndiotactic monovinylidene aromatic polymer composition is typically a syndiotactic monovinylidene aromatic polymer, although blends of syndiotactic monovinylidene aromatic polymers can also be used.

Monovinylidene aromatic polymers are homopolymers and copolymers of vinyl aromatic monomers, that is, monomers whose chemical structure possess both an unsaturated moiety and an aromatic moiety. The preferred vinyl aromatic monomers have the formula: H₂C=CR-Ar; wherein R is hydrogen or an alkyl group having from 1 to 4 carbon atoms, and Ar is an aromatic radical of from 6 to 10 carbon atoms. Examples of such vinyl aromatic monomers are styrene, alpha-methylstyrene, ortho-methylstyrene, meta- methylstyrene, para-methylstyrene, vinyl toluene, para-t-butylstyrene, vinyl naphthalene, and divinylbenzene. Syndiotactic polystyrene is the currently preferred syndiotactic monovinylidene aromatic polymer. Typical polymerization processes for producing syndiotactic monovinylidene aromatic polymers are well known in the art and are described in US-A-4,680,353, US-A-5,066,741 , US-A-5,206,197 and US-A-5,294,685. The Mw of the syndiotactic monovinylidene aromatic polymer used in the composition of the present invention is not critical, but is typically from 100,000 to 450,000.

Blends of syndiotactic monovinylidene aromatic polymers can comprise other polymers such as polyamides (nylons) and polypropylenes. Typical polyamides include polyamide-4; polyamide-6; polyamide-4,6; polyamide-6,6; polyamide-3,4; poiyamide-1 ,2; polyamide-1 ,1 ; polyamide-6,10; polyamide purified from terephthalic acid and 4,4' diaminocyclohexylmethane; polyamide purified from azelaic acid, adipic acid and 2,2,-bis(p-aminocyclohexyl)propane; polyamide purified from adipic acid and methaxylylenediamine; and polyamide purified from terephthalic acid and trimethylhexamethylene diamine. The syndiotactic monovinylidene aromatic polymer and polyamide or polypropylene are typically present in the composition of the present invention in ratios of from 5:95 to 95:5 based on only those two components. Preferably in ratios of 20:80 to 80:20, more preferably 30:70 to 70:30 and most preferably 40:60 to 60:40. The composition of the present invention typically comprises from 40 generally from 45 preferably from 50, more preferably from 55, and most preferably from 60 to preferably 88 and most preferably to 85 weight percent of the syndiotactic monovinylidene aromatic polymer composition.

Component B) of the composition of the present invention is a ductility modifier and can be any material which will improve the properties of the composition that relate to ductility such as tensile elongation or flexural elongation.

Suitable ductility modifiers include interpolymers of a vinyl aromatic and an aliphatic alpha-olefin monomer, elastomeric polyolefins, copolymers of a vinyl aromatic monomer and a conjugated diene monomer, and other copolymers of vinyl aromatic monomers such as styrene/ethylene-butylene/styrene (SEBS) and styrene/ethylene-propylene/styrene (SEPS) copolymers and mixtures thereof.

Interpolymers include any substantially random interpolymer of a vinyl aromatic and an aliphatic alpha-olefin monomer, wherein the interpolymer contains at least 40 weight percent vinyl aromatic monomer and elastomeric polyolefins. The term "interpolymer" as used herein refers to polymers prepared by the polymerization of at least two different monomers. The generic term interpolymer thus embraces copolymers, usually employed to refer to polymers prepared from two different monomers, and polymers prepared from more than two different monomers.

While describing in the present invention a polymer or inteφoiymer as comprising or containing certain monomers, it is meant that such polymer or inteφoiymer comprises or contains polymerized therein, units derived from such a monomer. For example, if the monomer is ethylene CH₂=CH₂, the derivative of this unit as incoφorated in the polymer is -CH₂-CH₂-.

The vinyl aromatic monomers contained in the inteφolymers useful as Component B) include those vinyl aromatic monomers described previously as monomers useful for preparing the syndiotactic monovinylidene aromatic polymers of Component A).

The aliphatic alpha-olefin monomers contained in the inteφolymers useful as Component B) include aliphatic and cycloaliphatic alpha-olef ins having from 2 to 18 carbon atoms, and preferably alpha-olefins having from 2 to 8 carbon atoms. Most preferably, the aliphatic alpha-olefin comprises ethylene or propylene, preferably ethylene, optionally together with one or more other alpha-olefins having from 3 to 8 carbon atoms, such as for example ethylene and propylene, or ethylene and octene, or ethylene and propylene and octene.

The inteφolymers suitable as Component B) are preferably a pseudo-random linear or substantially linear, more preferably a linear inteφoiymer comprising an aliphatic alpha-olefin and a vinyl aromatic monomer. These pseudo-random linear interpolymers are described in EP-A-0,416,815.

A particular distinguishing feature of pseudo-random inteφolymers is the fact that all phenyl or substituted phenyl groups substituted on the polymer backbone are separated by two or more methylene units. In other words, the pseudo-random inteφolymers comprising an a-olefin and vinyl aromatic monomer can be described by the following general formula (using styrene as the hindered monomer and ethylene as the olefin for illustration):

CH - - CH₂ — CH - CH 4-

where j, k and I > 1

The symbol > means equal to or greater than

It is believed that during the addition polymerization reaction of ethylene and styrene employing a catalyst as described hereinafter, if a hindered monomer (styrene) is inserted into the growing polymer chain, the next monomer inserted must be ethylene or a hindered monomer which is inserted in an inverted fashion. Ethylene, on the other hand, may be inserted at any time. After an inverted hindered monomer insertion, the next monomer must be ethylene, as the insertion of another hindered monomer at this point would place the hindering substituent too close to the previously inserted hindered monomer.

In one embodiment, Component B) is a pseudo-random linear inteφoiymer comprising ethylene and styrene.

The content of units derived from the vinyl aromatic monomer incoφorated in Component B), and preferably in the pseudo-random, linear inteφoiymer, preferably is greater than 40 weight percent, more preferably at least 50 weight percent, and most preferably at least 60 weight percent based on the total weight of the inteφoiymer. Preferably, the pseudo-random inteφoiymer useful as Component B) has a weight average molecular weight (Mw) of greater than 13,000. Also preferably such polymers possess a melt index (12), ASTM D-1238 Procedure A, condition E, of less than 125, more preferably from 0.01 - 100, even more preferably from 0.01 to 25, and most preferably from 0.05 to 6. While preparing the pseudo-random inteφoiymer, as will be described hereinafter, an amount of atactic monovinylidene aromatic homopolymer may be formed due to homopolymerization of the vinyl aromatic monomer at elevated temperatures. In general, the higher the polymerization temperature, the higher the amount of homopolymer formed. The presence of monovinylidene aromatic homopolymer is in general, not detrimental for the puφoses of the present invention and may be tolerated. The monovinylidene aromatic homopolymer may be separated from the inteφoiymer, if desired, such as by extraction with a suitable extracting agent, acetone or chloroform. For the puφose of the present invention it is preferred that the inteφoiymer contain no more than 20 percent by weight, based on the weight of the interpolymer, more preferably less than 15 weight percent of monovinylidene aromatic homopolymer.

The pseudo-random interpolymers may be modified by typical grafting, hydrogenation, functionalizing, or other reactions well known to those skilled in the art, provided their ductility modification function will not be substantially affected. The polymers may be readily sulfonated or chlorinated to provide functionalized derivatives according to established techniques. The inteφolymers may also be oil extended or combined with other lubricants.

The pseudo-random interpolymers can be prepared as described in E-A-0,416,815. Preferred operating conditions for such polymerization reactions are pressures from atmospheric up to 3000 atmospheres and temperatures from 30°C to 200°C.

Examples of suitable catalysts and methods for preparing the pseudo-random interpolymers are disclosed in EP-A-416,815; EP-A-468,651 ; EP-A-514,828; EP-A-520,732, WO 93/23412, US-A-5,347,024, as well as US-A-5,055,438, US-A-5,057,475, US-A-5,096,867, US-A-5,064,802, US-A-5, 132,380, and US-A-5,189,192.

The elastomeric polyolefins utilized as the ductility modifier of component B) can be any elastomeric polyolefin such as those described in US-A-5,460,818. Elastomeric polyolefins include any polymer comprising one or more C₂.₂o α-olefins in polymerized form, having Tg less than 25°C, preferably less than 0°C. Examples of the types of polymers from which the present elastomeric polyolefins are selected include homopolymers and copolymers of α-olefins, such as ethylene/propylene, ethylene/1 -butene, ethylene/1 -hexene or ethylene/1 -octene copolymers, and teφolymers of ethylene, propylene and a comonomer such as hexadiene or ethylidenenorbornene. Grafted derivatives of the foregoing rubbery polymers such as polystyrene-, maleic anhydride-, polymethylmethacrylate- or styrene/methyl methacrylate copolymer-grafted elastomeric polyolefins may also be used.

Preferred elastomeric polyolefins are such polymers that are characterized by a narrow molecular weight distribution and a uniform branching distribution. Preferred elastomeric polyolefins are linear or substantially linear ethylene inteφolymers having a density from 0.85 to 0.89 g/cm³ and a melt index from 0.5 to 20 g/10 min. Such polymers are preferably those prepared using a Group 4 metal constrained geometry complex by means of a continuous solution polymerization process, such as are disclosed in US-A-5,272,236 and US-A-5,278,272. Generally, the elastomeric polyolefins have a density of from 0.860 to 0.895 g/cm³, preferably less than 0.895, more preferably less than 0.885 and most preferably less than 0.88 g/cm³.

Where melt index values are specified in the present application without giving measurement conditions, the melt index as defined in ASTM D-1238, Condition 190°C/2.16 kg (formerly known as "Condition (E)" and also known as 12) is meant. The term "substantially linear" ethylene polymer or interpolymer as used herein means that, in addition to the short chain branches attributable to intentionally added α-olefin comonomer incorporation in interpolymers, the polymer backbone is substituted with an average of 0.01 to 3 long chain branches/1000 carbons, more preferably from 0.01 long chain branches/1000 carbons to 1 long chain branches/1000 carbons, and especially from 0.05 long chain branches/1000 carbons to 1 long chain branches/1000 carbons. In contrast to the term "substantially linear", the term "linear" means that the polymer lacks measurable or demonstrable long chain branches, that is, the polymer is substituted with an average of less than 0.01 long branches/1000 carbons. Long chain branching is defined herein as a chain length of at least 1 carbon less than the number of carbons in the longest intentionally added α-olefin comonomer, whereas short chain branching is defined herein as a chain length of the same number of carbons in the branch formed from any intentionally added α-olefin comonomer after it is incoφorated into the polymer molecule backbone. For example, an ethyiene/1 -octene substantially linear polymer has backbones substituted with long chain branches of at least 7 carbons in length, but it also has short chain branches of only 6 carbons in length resulting from polymerization of 1 - octene.

The presence and extent of long chain branching in ethylene inteφolymers is determined by gel permeation chromatography coupled with a low angle laser light scattering detector (GPC-LALLS) or by gel permeation chromatography coupled with a differential viscometer detector (GPC-DV). The use of these techniques for long chain branch detection and the underlying theories have been well documented in the literature, for example in Zimm, G.H. and Stockmayer, W.H., J. Chem. Phvs.. Vol. 17, p. 1301 (1949) and Rudin, A., Modem Methods of Polymer Characterization. John Wiley & Sons, New York (1991 ), pp. 103-1 12.

A. Willem deGroot and P. Steve Chum, both of The Dow Chemical Company, at the October 4, 1994 conference of the Federation of Analytical Chemistry and Spectroscopy Society (FACSS) in St. Louis, Missouri, U.S.A., presented data demonstrating that GPC-DV is a useful technique for quantifying the presence of long chain branches in substantially linear ethylene inteφolymers. in particular, deGroot and Chum found that the level of long chain branches in substantially linear ethylene homopolymer samples measured using the Zimm-Stockmayer equation correlated well with the level of long chain branches measured using ¹³C NMR.

Further, deGroot and Chum found that the presence of octene does not change the hydrodynamic volume of the polyethylene samples in solution and, as such, one can account for the molecular weight increase attributable to octene short chain branches by knowing the mole percent octene in the sample. By deconvoluting the contribution to molecular weight increase attributable to 1 -octene short chain branches, deGroot and Chum showed that GPC-DV may be used to quantify the level of long chain branches in substantially linear ethyiene/1 -octene copolymers. deGroot and Chum also showed that a plot of Log(l2, Melt Index) as a function of Log (GPC, Weight Average Molecular Weight) as determined by GPC-DV illustrates that the long chain branching aspects (but not the branching extent) of substantially linear ethylene polymers are comparable to that of high pressure, highly branched low density polyethylene (LDPE) and are clearly distinct from ethylene polymers produced using Ziegler-type catalysts such as hafnium and vanadium complexes.

The empirical effect of the presence of long chain branching in the substantially linear ethylene/α-oiefin inteφolymers used in the invention is manifested as enhanced rheological properties which are quantified and expressed herein in terms of gas extrusion rheometry (GER) results, and/or in terms of melt flow ratio (110/12) increase.

Substantially linear ethylene interpolymers as used herein are further characterized as having (i) a melt flow ratio, 110/12 ≥ 5.63, (ii) a molecular weight distribution or polydispersity, Mw/Mn, as determined by gel permeation chromatography and defined by the equation: (Mw/Mn)=(l10/l2)-4.63, (iii) a critical shear stress at the onset of gross melt fracture, as determined by gas extrusion rheometry, of greater than 4 x 10⁶ dynes/cm³, or a gas extrusion rheology such that the critical shear rate at onset of surface melt fracture for the substantially linear ethylene polymer is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture for a linear ethylene polymer, wherein the substantially linear ethylene polymer and the linear ethylene polymer comprise the same comonomer or comonomers, the linear ethylene polymer has an 12, Mw/Mn and density within 10 percent of the substantially linear ethylene polymer and wherein the respective critical shear rates of the substantially linear ethylene polymer and the linear ethylene polymer are measured at the same melt temperature using a gas extrusion rheometer, and

(iv) a single differential scanning calorimetry, DSC, melting peak between - 30°C and 150°C.

Determination of the critical shear rate and the critical shear stress in regards to melt fracture as well as other rheology properties such as the "rheological processing index" (PI) is performed using a gas extrusion rheometer (GER). The gas extrusion rheometer is described by M. Shida, R.N. Shroff and L.V. Cancio in Polymer Engineering Science. Vol. 17, No. 1 1 , p. 770 (1977), and in Rheometers for Molten Plastics, by John Dealy, published by Van Nostrand Reinhold Co. (1982) on pp. 97- 99. The processing index is measured at a temperature of 190°C, at nitrogen pressure of 2500 psig (17 Mpa) using a 0.0296 inch (0.0117 cm) diameter, 20:1 UD die with an entrance angle of 180°. The GER processing index is calculated in millipoise units from the following equation:

PI = 2.15x10⁶ dynes/cm²/(1000 x shear rate), where: 2.15x10⁶ dynes/cm² is the shear stress at 2500 psi, (17 Mpa) and the shear rate is the shear rate at the wall represented by the following equation: 32Q'/(60 sec/min)(0.745)(diameter x 2.54 cm/in)³, where Q' is the extrusion rate (g/min), 0.745 is the melt density of the polyethylene (g/cm³), and diameter is the orifice diameter of the capillary (inches).

The PI is the apparent viscosity of a material measured at apparent shear stress of 2.15x10⁶ dyne/cm².

For the substantially linear ethylene polymers described herein, the PI is less than or equal to 70 percent of that of a comparative linear olefin polymer having an 12 and Mw/Mn each within 10 percent of the substantially linear ethylene polymers. The rheological behavior of substantially linear ethylene polymers can also be characterized by the Dow Rheology Index (DRI), which expresses a polymer's "normalized relaxation time as the result of long chain branching." (See, S. Lai and G.W. Knight "ANTEC '93 Proceedings, INSITE™ Technology Polyolefins (ITP) - New Rules in the Structure/Rheology Relationship of Ethylene/α-Olefin Copolymers," New Orleans, Louisiana, U.S.A., May 1993.) DRI values range from 0, for polymers which do not have any measurable long chain branching (for example, TAFMER™ products available from Mitsui Petrochemical Industries and EXACT™ products available from Exxon Chemical Company), to 15 and is independent of melt index. In general, for low- to medium-pressure ethylene polymers (particularly at lower densities), DRI provides improved correlations to melt elasticity and high shear flowability relative to correlations of the same attempted with melt flow ratios. For the substantially linear ethylene polymers useful in this invention, DRI is preferably at least 0.1 , and especially at least 0.5, and most especially at least 0.8. DRI can be calculated from the equation:

DRI = 3652879 x τo^{1 00649}/(ηo-1 )/10 where τo is the characteristic relaxation time of the material and ηo is the zero shear viscosity of the material. Both τo and are the "best fit" values to the Cross equation, that is,

where n is the power law index of the material, and η and γ are the measured viscosity and shear rate (rad sec^"1), respectively. Baseline determination of viscosity and shear rate data are obtained using a Rheometric Mechanical Spectrometer (RMS-800) under dynamic sweep mode from 0.1 to 100 rad/sec at 190°C and a Gas Extrusion Rheometer (GER) at extrusion pressures from 1000 psi to 5000 psi (6.89 to 34.5 MPa), which corresponds to shear stress from 0.086 to 0.43 MPa, using a 0.0754 mm diameter, 20:1 IJD die at 190°C. Specific material determinations can be performed from 140°C to 190°C as required to accommodate melt index variations. An apparent shear stress versus apparent shear rate plot is used to identify the melt fracture phenomena. According to Ramamurthy in Journal of Rheology. Vol. 30(2), pp. 337-357, 1986, above a certain critical flow rate, the observed extrudate irregularities may be broadly classified into two main types: surface melt fracture and gross melt fracture.

Surface melt fracture occurs under apparently steady flow conditions and ranges in detail from loss of specular gloss to the more severe form of "sharkskin." In this disclosure, the onset of surface melt fracture (OSMF) is characterized as the beginning of losing extrudate gloss at which the surface roughness of extrudate can only be detected by 40x magnification. The critical shear rate at onset of surface melt fracture for the substantially linear ethylene polymers is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having about the same 12 and Mw/Mn.

Gross melt fracture occurs at unsteady flow conditions and ranges in detail from regular (alternating rough and smooth or helical) to random distortions. The critical shear rate at onset of surface melt fracture (OSMF) and onset of gross melt fracture (OGMF) will be used herein based on the changes of surface roughness and configurations of the extrudates extruded by a GER.

Substantially linear ethylene polymers useful as ductility modifiers in the composition of the present invention are also characterized by a single DSC melting peak. The single melting peak is determined using a differential scanning calorimeter standardized with indium and deionized water. The method involves 5 to 7 mg sample sizes, a "first heat" to 150°C which is held for 4 minutes, a cool down at 10°C/minute to -30°C which is held for 3 minutes, and heated at 10°C/minute to 150°C for the "second heat." The single melting peak is taken from the "second heat" heat flow versus temperature curve. Total heat of fusion of the polymer is calculated from the area under the curve.

The term "polydispersity" as used herein is a synonym for the term "molecular weight distribution" which is determined as follows: The polymer or composition samples are analyzed by gel permeation chromatography (GPC) on a Waters 150°C high temperature chromatographic unit equipped with three mixed porosity columns (Polymer Laboratories 103, 104, 105, and 106), operating at a system temperature of 140°C. The solvent is 1 ,2,4-trichlorobenzene, from which 0.3 percent by weight solutions of the samples are prepared for injection. The flow rate is 1.0 milliliters/minute and the injection size is 200 microliters.

The molecular weight determination is deduced by using narrow molecular weight distribution polystyrene standards (from Polymer Laboratories) in conjunction with their elution volumes. The equivalent polymer molecular weights are determined by using appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described by Williams and Word in Journal of Polvmer Science. Polymer Letters. Vol. 6, p. 621 (1968), to derive the following equation: polyethylene = °-^{431 6} (^Mpolystyrene)- Weight average molecular weight, Mw, is calculated in the usual manner according to the following formula:

Mw = ∑i wi • Mi, where wi and Mi are the weight fraction and molecular weight, respectively, of the ith fraction eluting from the GPC column. Optionally, the elastomeric polyolefin of B) can be extended by incoφoration of an aliphatic oil. The extending oils, also referred to as paraffinic/naphthenic oils, are typically fractions of refined petroleum products having less than about 30 percent by weight of aromatics (by clay-gel analysis) and having viscosities between about 100 and 500 SSU at 100°F (38 °C). Commercial extending oils include SHELLFLEX® oils, numbers 310, 371 and 311 (which is a blend of 310 and 371 ), available from Shell Oil Company or Drakeoil™, numbers 34 or 35, available from Penreco division of Pennzoil Products Company. The amount of extending oil employed varies from 0.01 to 35 percent by weight of the elastomeric polyolefin, preferably from 0.1 -25 weight percent. Optionally, a compatibilizing rubbery polymer may also be used in combination with the elastomeric polyolefin of Component B). The desirable characteristic of the compatibilizing rubbery polymer is to provide compatibility between the syndiotactic monovinylidene aromatic polymer, component A), and the elastomeric polyolefin of component B), so as to minimize interfacial tension between the molten phases and to develop satisfactory adhesion between the solid phases to promote impact adsoφtion. Decreased interfacial tension in the melt promotes smaller rubber droplet formation due to the driving force to reduce surface area of the rubber particles in contact with the matrix. Representative compatibilizing polymers include multi-block copolymers of styrene and olefin such as styrene-butadiene-styrene (SBS) triblock copolymer and styrene-butadiene diblock copolymer; block copolymers of styrene and isoprene, such as styrene-isoprene diblock copolymers and hydrogenated versions thereof, and copolymers with greater numbers of blocks such as styrene-ethylene- propylene-styrene copolymers. Preferably, the multi-block copolymers contain from 45 to 80 weight percent styrene. Such block copolymers and methods for their preparation are well known in the art. Most preferably, the block copolymer is a

SEPS block copolymer. Typically, compatibilizing polymers are present in amounts of from 2 to 20 weight percent, based on the total weight of B).

Additionally, the elastomeric polyolefin of Component B) may also optionally comprise one or more domain forming rubbery polymers. Such additional rubbery polymers are suitably chosen in order to impart additional impact absorbing properties to the polymer composition. Generally, it is desirable to provide a domain forming rubbery polymer having extremely high melt viscosity, that is, very low melt flow. Such polymers having high melt viscosity are not drawn into extremely thin sections by the shear forces of the compounding process, and retain greater ability to reform discrete rubber particles more closely resembling spherical particles upon discontinuance of shearing forces. Additionally, the domain forming rubbery polymer beneficially should retain sufficient elastic memory to reform droplets in the melt when shearing forces are absent. The domain forming mbbery polymer is selected to be compatible with the elastomeric polyolefin of B) into which it mostly partitions under processing conditions, and therefore, the shearing forces are not as detrimental to the rubber domain. Most preferred domain forming rubbery polymers are those having a melt flow rate, (Conditions 315°C, 5.0 Kg) from O to 0.5 g/10 min. Representative polymers include block copolymers of styrene and olefin such as styrene-butadiene-styrene (SBS) triblock copolymer and styrene-butadiene diblock copolymer; block copolymers of styrene and isoprene, such as styrene-isoprene diblock copolymers, block copolymers of styrene and ethylene-butylene such as styrene/ethylene-butylene/styrene block copolymers (SEBS) and hydrogenated versions thereof. Preferably, the block copolymers contain from 15 to 45 weight percent styrene. Such block copolymers and methods for their preparation are well known in the art. Most preferably, the block copolymer is a SEBS block copolymer. Additionally, an ethylene-styrene inteφoiymer or another polyolefin as described above can act as the domain forming rubbery polymer.

Generally, higher molecular weight domain forming mbbery block copolymers possess increased melt viscosity. Accordingly, preferred domain forming rubbery block copolymers are those having Mw from 100,000 to 400,000 Daltons, more preferable from 150,000 to 300,000 Daltons, and having Tg less than 25°C, more preferably less than 0°C. Weight average molecular weights recited herein are apparent values based on a polystyrene standard, derived from gel permeation chromatography data, and not corrected for hydrodynamic volume differences between polystyrene and other polymeric Components. Preferred quantities of the domain forming mbbery polymer is from 2 to 40, most preferably 5 to 25 parts by weight per 100 parts of the elastomeric polyolefin.

The domain forming mbbery polymer may also be used in combination with the compatibilizing mbbery polymer described previously, in addition to the elastomeric polyolefin of Component B). Other components can also be used to enhance the ductility properties of the composition of the present invention. In another embodiment of the present invention the composition also comprises from 0 to 35 weight percent of an alpha-olefin/vinyl aromatic interpolymer, wherein the inteφoiymer contains from 25 to 40 weight percent vinyl aromatic monomer. The vinyl aromatic monomers and alpha-olefins are as previously defined in Component B), however the vinyl aromatic content is preferably less than or equal to 40, more preferably less than or equal to 35 and most preferably less than or equal to 30 weight percent of the inteφoiymer.

Block copolymers of styrene and olefin can also be used as Component B). Such block copolymers include copolymers of styrene and diene monomers such as styrene-butadiene-styrene (SBS) triblock copolymer and styrene-butadiene diblock copolymer; block copolymers of styrene and isoprene, such as styrene-isoprene diblock copolymers, block copolymers of styrene and ethylene-butylene or ethylene- propylene such as styrene/ethylene-butylene/styrene (SEBS) and styrene/ethylene- propylene/styrene (SEPS) block copolymers and hydrogenated versions thereof. Such block copolymers and methods for their preparation are well known in the art. Preferably, the block copolymers contain from 15 to 45 weight percent styrene. Most preferably, the block copolymer is a hydrogenated SEBS block copolymer. The preferred mbbery block copolymers are those having Mw from 100,000 to 400,000 Daltons, more preferable from 150,000 to 300,000 Daltons, and having rubbery phase Tg less than 25°C, more preferably less than 0°C. Weight average molecular weights recited herein are apparent values based on a polystyrene standard, derived from gel permeation chromatography data, and not corrected for hydrodynamic volume differences between polystyrene and other polymeric components.

The ductility modifier of B) is typically present in amounts of from 2, preferably from 3, more preferably from 4 and most preferably from 5 to 30, preferably to 25, more preferably to 20 and most preferably 15 weight percent, based on the total weight of the composition.

The composition of the present invention also comprises from 5 to 50 weight percent of a fiber reinforcing agent, Component C), preferably from 10 to 45 weight percent, and most preferably from 15 to 40 weight percent based on the total weight of the composition. Suitable fiber reinforcing agents include, but are not limited to, glass fibers. Typically, suitable glass fibers have a length to diameter ratio (LJD) of greater than 5. Preferred particle diameters are from 0.1 micrometers to 1 millimeter. Preferred glass reinforcing agents include glass fibers, glass roving or chopped glass fibers having lengths from 0.1 to 10 millimeters and L/D from 5 to 100. Three such suitable glass fibers are available from Owens Coming Fiberglas under the designation OCF-187A or 497 or from PPG under the designation 3540. The reinforcing fiber may include a surface coating of a sizing agent or similar coating which, among other functions, may promote adhesion between the reinforcing agent and the remaining components, especially the matrix, of the composition. Suitable sizing agents may contain amine, aminosilane, epoxy, and aminophosphine functional groups and contain up to 30 nonhydrogen atoms. Preferred are aminosilane coupling agents and Ci alkoxy substituted derivatives thereof, especially 3-amιnopropyltrιmethoxysιlane.

The composition of the present invention also comprises a mineral filler, Component D Suitable mineral fillers typically have a plate-like physical structure having average equivalent spherical diameters of less than 10ππm, more preferably less than 5 Qm and most preferably less than 2 Dm Such mineral fillers include, but are not limited to mica, talc, clay, wollastonite, and glass flakes Preferred fillers are talcs with number average diameter less than 1 micron such as MP 10-52 available form Mineral Technologies and wollastonite with number average diameter less than 5 microns such as Jilin™ 2000 available from GLS Minerals, inc.

The mineral filler of D) is typically present in amounts of from 5, preferably from 7, more preferably from 8 and most preferably from 10 to 30, preferably to 28, more preferably to 25 and most preferably to 20 weight percent, based on the total weight of the composition. Optionally, the composition of the present invention can also comprise from 0 to 10 weight percent of a lubricant, based on the total weight of the composition. Exemplary lubricants include steaπc acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, ethylene bis-stearamide, pentaerythntol tetrastearate, organo phosphate, mineral oil, tπmellitate, polyethylene glycol, sihcone oil, epoxidized soy bean oil, tπcresyl phosphate, polyethylene glycol dimethyl ether, dioctyl adipate, di-n-butyl phthalate, paimityl palmitate, butyiene glycol montanate (Wax OP available from Hoechst Celanese), pentaerythntol tetramontanate (TPET 141 available from Hoechst Celanese), aluminum mono-stearate, aluminum di-stearate, montanic acid wax, montanic acid ester wax, polar polyethylene waxes, and non-polar polyethylene waxes.

Polyarylene ethers can also be optionally included in the composition of the present invention and are a known class of polymer having been previously descπbed in US-A-3,306,874, 3,306,875, 3,257,357, and 3,257,358. A preferred polyarylene ether is poly(2,6-dιmethyl-1 ,4-phenylene)ether. The polyphenylene ethers are normally prepared by an oxidative coupling reaction of the corresponding bisphenol compound. Preferred polyarylene ethers are polar group functionalized polyarylene ethers, which are a known class of compounds prepared by contacting polar group containing reactants with polyarylene ethers. The reaction is normally conducted at an elevated temperature, preferably in a melt of the polyarylene ether, under conditions to obtain homogeneous incoφoration of the functionalizing reagent. Suitable temperatures are from 150°C to 300°C.

Suitable polar groups include the acid anhydrides, acid halides, acid amides, sulfones, oxazolines, epoxies, isocyanates, and amino groups. Preferred polar group containing reactants are compounds having up to 20 carbons containing reactive unsaturation, such as ethylenic or aliphatic ring unsaturation, along with the desired polar group functionality. Particularly preferred polar group containing reactants are dicarboxylic acid anhydrides, most preferably maleic anhydride. Typically the amount of polar group functionalizing reagent employed is from 0.01 percent to 20 percent, preferably from 0.5 to 15 percent, most preferably from 1 to 10 percent by weight based on the weight of polyarylene ether. The reaction may be conducted in the presence of a free radical generator such as an organic peroxide or hydroperoxide agent if desired. Preparation of polar group functionalized polyarylene ethers have been previously described in US-A-3,375,228, 4,771 ,096 and 4,654,405.

The polar group modified polyarylene ethers beneficially act as compatibilizers to improve adhesion between the reinforcing agent and the syndiotactic monovinylidene aromatic polymer. Thus, their use is particularly desirable when a filler or reinforcing agent is additionally utilized. The amount of polyarylene ether employed in the present resin blend is beneficially from 0.1 to 50 parts by weight, preferably from 0.2 to 10 parts by weight based on 100 parts glass and polyarylene ether. In one embodiment, the polar group modified polyarylene ether may be in the form of a coating applied to the outer surface of the reinforcing agent to impart added compatibility between the reinforcing agent and the polymer matrix. The polar group modified polyarylene ether so utilized may be in addition to further amounts of polyarylene ether or polar group modified polyarylene ether also incorporated in the blend. The surface coating is suitably applied to the reinforcing agent by contacting the same with a solution or emulsion of the polar group functionalized polyarylene ether. Suitable solvents for dissolving the polar group functionalized polyarylene ether to form a solution or for use in preparing an emulsion of a water-in-oii or oil-in- water type include methylene chloride, trichloromethane, trichloroethylene and trichloroethane. Preferably the concentration of polar group functionalized polyarylene ether in the solution or emulsion is from 0.1 weight percent to 20 weight percent, preferably 0.5 to 5 percent by weight. After coating of the reinforcing agent using either a solution or emulsion, the liquid vehicle is removed by, for example, evaporation, devolatilization or vacuum drying. The resulting surface coating is desirably from 0.001 to 10 weight percent of the uncoated reinforcing agent weight. Nucleators may also be included in the present invention and are compounds capable of reducing the time required for onset of crystallization of the syndiotactic vinylaromatic polymer upon cooling from the melt. Nucleators provide a greater degree of crystallinity in a molding resin and more consistent distribution of crystallinity under a variety of molding conditions. Higher levels of crystallinity are desired in order to achieve increased chemical resistance and improved heat performance. In addition crystal moφhology may be desirably altered. Examples of suitable nucleators for use herein are monoiayer of magnesium aluminum hydroxide, calcium carbonate, mica, wollastonite, titanium dioxide, silica, sodium sulfate, lithium chloride, sodium benzoate, aluminum benzoate, talc, and metal salts, especially aluminum salts or sodium salts of organic acids or phosphonic acids. Especially preferred compounds are aluminum and sodium salts of benzoic acid and d-₁₀ alkyl substituted benzoic acid derivatives. A most highly preferred nucleator is aluminum tris(p-tert-butyl)benzoate. The amount of nucleator used should be sufficient to cause nucleation and the onset of crystallization in the syndiotactic vinylaromatic polymer in a reduced time compared to compositions lacking in such nucleator. Preferred amounts are from 0.5 to 5 parts by weight.

Other additives may also be included in the composition of the present invention including additives such as flame retardants, pigments, and antioxidants, including IRGANOX™ 1010, 555, 1425 and 1076, IRGAFOS™ 168, CGL-415, and G ALVINOXYL™ available from Ciba Geigy Coφoration, SEENOX™ 412S available from Witco, ULTRANOX™ 626 and 815 available from GE Specialty Chemicals, MARK PEP™ 36 available from Adeka Argus, AGERITE™ WHITE, MA and DPPD, METHYL ZIMATE, VANOX™ MTI and 12 available from R.T. Vanderbilt, NAUGARD™ 445 and XL-1 available from Uniroyal Chemical, CYANOX™ STDP and 2777 available from American Cyanamid, RONOTEC™ 201 (Vitamin E available from Roche, MIXXIM CD-12 and CD-16 available from Fairmount, Ethanox™ 398, DHT-4a, SAYTEX™ 8010, 120, BT93 and 102 available from Ethyl, Hostanox™ PAR 24, 03, and ZnCS1 available from Hoechst Celanese, cesium benzoate, sodium hydroxide, SANDOSTAB™ PEPQ available from Sandoz, t-butyl hydroquinone, and SANTOVAR™ A available from Monsanto, phenothiazine, pyridoxine, copper stearate, cobalt stearate, MOLYBDENUM TENCEM™ available from Mooney Chemicals, ruthenium (III) acetylacentonate, boric acid, citric acid, MARK™ 6000 available from Adeka Argus, antimony oxide, 2,6-di-t-butyi-4-methylphenol, stearyl-β- (3,5-di-tert-butyl-4-hydroxyphenol)propionate, and triethylene glycoi-bis-3-(3-tert- butyl-4-hydroxy-5-methylphenyl)propionate, tris(2,4-tert-butylphenyl)phosphite and 4,4'-butylidenebis(3-methyl-6-tert-butylphenyl-di-tridecyl)-phosphite; tris nonyl phenyl phosphite, carton black, PYROCHEK™ PB68 available from Ferro Corporation, decabromodiphenyl oxide, antiblock agents such as fine particles composed of alumina, silica, aluminosiiicate, calcium carbonate, calcium phosphate, and silicon resins; light stabilizers, such as a hindered amine-based compounds or benzotriazole- based compounds; plasticizers such as an organopolysiioxane or mineral oil; blowing agents, extrusion aids, stabilizers such as bis(2,4-di-tertbutylphenyl)pentaerythritol and tris nonyl phenyl phosphite.

The compositions of the present invention are prepared by combining the respective components under conditions to provide uniform dispersal of the ingredients. For best results, the polymer(s), fillers, and all additives except reinforcing agents are usually melt mixed under harsh mixing conditions to maximize dispersion and distribution of ingredients and then reinforcing agents are added to the melt mixture under gentler mixing conditions to allow dispersion without causing attrition of the reinforcing agent. Alternatively, where a polar group modified polyarylene ether is used, this Component of the blend may be prepared in situ by reacting the polar group reactant with the polyphenylene ether and further incorporating the molten product directly into the finished blend. Mechanical mixing devices such as extruders, internal mixers, continuous mixers, ribbon blenders, solution blending or any other suitable device or technique may be utilized.

In one embodiment, the composition of the present invention comprises:

A) from 40 to 88 weight percent of a syndiotactic monovinylidene aromatic polymer composition,

B) from 2 to 30 weight percent of a ductility modifier, C) from 5 to 50 weight percent of a fiber reinforcement, and

D) from 5 to 30 weight percent of a mineral filler, wherein all weight percents are based on the total weight of the composition.

The composition of the present invention is typically prepared by compounding

Components A, B, C, and D and other optional additives on a plasticating extmder. It is preferable that the compounding be conducted such that little attrition of the reinforcing fibers occurs. A common practice is to melt mix the polymer Components A and B, the mineral filler (Component D), and other additives and then subsequently introduce the reinforcing fiber, Component C, to this melt mixture in the compounding equipment. Another acceptable procedure would be to melt mix Components A and B, and other additives, and then to add mineral filler (Component D) and reinforcing fiber (Component C) either sequentially or together to the melt mixture in the processing equipment.

The following examples are provided as further illustration and are not to be constmed as limiting. Unless stated to the contrary, parts and percentages are based on weight. EXAMPLE I

Samples are prepared by dry blending all components except the glass fiber in a polyethylene bag. This mixture is then fed to a 30 mm co-rotating twin screw extruder and the glass fibers are fed downstream after the mixture is sufficiently melt mixed. The extrudate strands from the extmder are pelletized, and the pellets are injection molded into tensile bars on a 100 ton injection molding machine. The tensile bars are then measured for gloss as described. Results are listed in Table I.

TABLE I

fumaric acid.

²PO is an ethylene/octene copolymer having a density of 0.863 g/cc and melt index of 30 extended with oil (25 weight percent).

³SEBS is a styrene/ethylene-butylene/styrene copolymer containing 32 weight percent styrene.

⁴SEPS is a styrene/ethylene-propylene/styrene copolymer containing 65 weight percent styrene.

Carbon black concentrate is 25 percent carbon black with 75 percent SPS. ⁶lrganox 1010 is 3,5-di-tert-butyl-4-hydroxy-neopentanetetraylester of hydrocinnamic acid

⁷pTBBA-AI is aluminum tris(p-tert-butyl)benzoate

⁸Micro Talc MP 10-52 is a 1 mm average particle size talc available from Mineral Technologies.

⁹Drakeoil 32 is mineral oil available from Drakeoil. ¹⁰Glass Fiber PPG 3540 is a glass fiber filler available from PPG. ¹¹The 60^Q Gardner Gloss is measured at five locations along the length of a tensile bar. The value given is the average of the five measurements. The gloss is measured with a micro gloss meter. 'COMPARATIVE EXAMPLES

As shown in Table I, the presence of mineral filler (talc) and ductility modifier, significantly increase the gloss properties of the composition when compared to fibers alone (A), fibers and talc (B), and fibers and ductility modifier (C).

Claims

CLAIMS:

1 . A composition comprising:

A) a syndiotactic monovinylidene aromatic polymer composition,

B) a ductility modifier, C) a fiber reinforcement, and

D) a mineral filler.

2. The composition of Claim 1 wherein the syndiotactic monovinylidene aromatic polymer composition comprises a syndiotactic polystyrene.

3. The composition of Claim 1 wherein the ductility modifier is an ethylene-octene copolymer.

4. The composition of Claim 1 wherein the fiber reinforcement is glass fibers.

5. The composition of Claim 1 wherein the mineral filler is a talc.

6. The composition of Claim 1 wherein A) a syndiotactic monovinylidene aromatic polymer is present in an amount of from 40 to 88 weight percent,

B) a ductility modifier is present in an amount of from 2 to 30 weight percent,

C) a fiber reinforcement is present in an amount of from 5 to 50 weight percent, and

D) a mineral filler is present in an amount of from 5 to 30 weight percent, wherein all weight percents are based on the total weight of the composition.

7. The composition of Claim 1 wherein B) is an elastomeric polyolefin which is extended with an aliphatic oil.

8. The composition of Claim 1 wherein B) additionally comprises a compatibilizing rubbery polymer.

9. The composition of Claim 8 wherein the compatibilizing mbbery polymer is a styrene/ethylene-propylene/styrene copolymer.

10. The composition of Claim 1 wherein B) additionally comprises an alpha-olefin/vinyl aromatic inteφoiymer, wherein the inteφoiymer contains from 25 to 40 weight percent vinyl aromatic monomer.

11. The composition of Claim 1 which additionally comprises up to 10 weight percent of a lubricant.

12. The composition of Claim 1 which additionally comprises a polyarylene ether.

13. The composition of Claim 1 which additionally comprises a nucleator.

14. The composition of Claim 1 wherein the syndiotactic monovinylidene aromatic polymer composition comprises a syndiotactic monovinylidene aromatic polymer and a polyamide.

15. The composition of Claim 1 wherein the syndiotactic monovinylidene aromatic polymer composition comprises a syndiotactic monovinylidene aromatic polymer and a polypropylene.