This invention relates to paintable compositions. In one aspect, the invention relates to paintable compositions comprising polypropylene and at least one of (i) a substantially linear ethylene polymer, or (ii) an interpolymer of ethylene and an α,β-unεaturated carbonyl. In another aspect, the invention relates to paintable compositions in which one or both of the polypropylene and substantially linear ethylene polymer are grafted with an unsaturated organic compound containing a carbonyl group, for example maleic anhydride. In yet another aspect, the invention relates to articles fabricated from these paintable compositions.

Thermoplastic polyolefins (TPOS) have many desirable properties, for example light weight, durability, low cost, etc., that make them an attractive material of construction for many consumer goods, for example interior and exterior automotive parts, and decorative fascia for household appliances. However because of their nonpolar nature, TPOs do not readily accept paint or decorative print. Most paints and inks are polar in nature, and thus require a surface with some degree of polarity before it can adhere to the surface with any degree of desirable fastness.

In the past, this problem has been addressed from a number of different directions. One typical and effective method of applying a paint to a TPO is first to apply a primer to the TPO. Primer materials are typically compositions containing a halogenated polyolefin and an aromatic solvent. While widely recognized as effective, primers are expensive and their application is an extra step in the finishing of the TPO article.

Another effective approach is to subject the surface of a TPO article to a physical or chemical treatment, such as etching with a chemical abrasive or irradiating with a plasma. While generally effective, these methods are more complex in nature than the application of a primer, and thus more difficult to control in terms of quality and consistency from part to part. Another approach is to modify the physical and/or chemical properties of the TPO either by blending it with other thermoplastic

polymers, or by incorporating into one or more polar groups, or both. For example, USP 4,946,896 to Mitsuno, et al . teaches a paintable TPO comprising 20-80 weight percent (weight percent) polypropylene,- 5-38 weight percent of an ethylene copolymer consisting of ethylene, an ester unit of either alkyl acrylate or methacrylate, and an unsaturated dicarboxylic acid anhydride; and 5-70 weight percent ethylene-propylene rubber. USP 4,888,391 to Domine, et al . teaches a paintable polyolefin composition comprising a blend of a polyolefin as the continuous phase with an ethylene/acrylate/acrylic acid terpolymer as the discontinuous phase. USP 4,945,005 to Aleckner, Jr., et al . teaches paintable TPOs comprising 2-25 weight percent of a copolymer of an ethylenically unsaturated carboxylic acid and ethylene; 3-50 weight percent of an ethylene α,β-olefin copolymer; optionally a crystalline homopolymer or copolymer of propylene,- 5-50 weight percent of an inorganic filler; and 10-35 weight percent of a polyethylene or a copolymer of ethylene and an α-olefin.

While these and other modified TPO compositions all demonstrate some degree of efficacy, a continuing interest exists in identifying and developing new paintable TPOS. According to this invention, a paintable, thermoplastic polyolefin composition is characterized by, in weight percent, based upon the total weight of the composition:

A. 30 to 70 percent of at least one of polypropylene or graft-modified polypropylene; B. 0 to 40 percent of at least one of a nongrafted substantially linear ethylene polymer or graft-modified substantially linear ethylene polymer; and C. 0 to 50 percent of an interpolymer of ethylene and an α,β- unsaturated carbonyl; with the provisos that:

(i) the sum of Components B and C is from 30 to 70 weight percent of the composition, and (ii) the substantially linear ethylene polymer is characterized as having : (a) a melt flow ratio, Iιo' ^] -2' — 5.63;

(b) a molecular weight distribution, M _w /M _n defined by

the equation :

M _w /M _n < ( I ₁₀ / I ₂ ) " 4 . 63 ;

(c) a density greater than 0.850 g/cm ³ ,- and

(d) a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear olefin polymer having about the same I2 and M _w /M _n . Component A of the paintable TPO composition of this invention can comprise 100 weight percent polypropylene, or 100 weight percent graft-modified polypropylene, or a blend of the two in any proportion. Similarly, Component B of the paintable TPO composition can comprise 100 weight percent of the substantially linear ethylene polymer, or 100 weight percent of the graft-modified version of this polymer, or a blend of the two in any proportion. As here used, "graft-modi ied" means that the polypropylene or the substantially linear ethylene polymer is grafted with an unsaturated organic compound containing at least one ethylenic unsaturation and at least one carbonyl group.

The polypropylene component of this invention is a homopolymer or one or more copolymers of propylene and up to about 20 mole percent ethylene or other α-olefin having up to about 12 carbon atoms. If a copolymer, it can be random, block or graft. The polypropylene component of this invention has a typical melt flow rate (as determined by ASTM D-1238, Condition 230/2.16 (formerly Condition L) ) of from 0.1 to 30, and preferably from .8 to 30.

The substantially linear ethylene polymers used in the practice of this invention are known, and they and their method of preparation are fully described in USP 5,272,236 and USP 5,278,272. As here used, "substantially linear" means that the polymer backbone is substituted with from 0.01 long-chain branches/1000 carbons to 3 long-chain branches/1000 carbons, more preferably from 0.01 long chain branches/1000 carbons to 1 long-chain branch/1000 carbons, and especially from 0.05 long-chain branches to 1 long-chain branch/1000 carbons. Long-chain branching is here defined as a chain length of at least about 6 carbon atoms, above which the length cannot be distinguished using 13C nuclear magnetic resonance spectroscopy .

However, the long-chain branch can be about the same length as the length of the polymer backbone.

These unique polymers (subsequently referred to as "substantially linear ethylene polymers") are prepared by using constrained geometry catalysts (CGC) , and are characterized by a narrow molecular weight distribution. Other basic characteristics of these substantially linear ethylene polymers include a low residuals content (i.e. low concentrations in the substantially linear ethylene polymer of the catalyst used to prepare the polymer, unreacted comonomers, and low molecular weight oligomers made during the course of the copolymerization) , a narrow comonomer distribution with respect to substantially linear ethylene interpoly ers, and a controlled molecular architecture which provides good processability even though the molecular weight distribution is narrow relative to conventional olefin polymers.

While the substantially linear ethylene polymers used in the practice of this invention include substantially linear ethylene homopolymers, preferably these substantially linear ethylene polymers comprise from 95 to 50 weight percent ethylene, and from 5 to 50 weight percent of at least one α-olefin comonomer, more preferably from 10 to 25 weight percent of at least one α-olefin comonomer. Comonomer content may be determined using infrared spectroscopy according to ASTMD-2238 Method B.

Typically, the substantially linear ethylene polymers are copolymers of ethylene and an α-olefin of 3 to about 20 carbon atoms, (such as propylene, 1-butene, 1-hexene, 4-methyl-l-pentene, 1-heptene, and 1-octene) , preferably of 3 to about 10 carbon atoms. Most preferably these polymers comprise ethylene and 1-octene. The density of the substantially linear ethylene polymer is typically from 0.850 to 0.96 grams per cubic centimeter (g/cm ³ ), preferably to 0.855 to 0.92 g/cm ³ , and more preferably from 0.865 to 0.90 g/cm ³ , and even more preferably from 0.865 to 0.88 g/cm ³ . The melt flow ratio, measured as I10 I2 ( ^AS ™ D-1238) , is greater than or equal to 5.63, and is preferably from 6.5 to 15, more preferably from 7 to 10. The molecular weight distribution (M _w /M _n ) , measured by gel permeation chromatography (GPC) , is defined by the equation:

M _w /M _n ≤ (I ₁₀ /I ₂ ) - 4.63, and is preferably from 1.8 to 2.5. For these substantially linear ethylene polymers, the I10/---2 ^ra tio indicates the degree of long-chain branching, i.e. the larger the I*κ ₎ /I ₂ ^rat io, the more long-chain branching in the polymer.

The unique characteristic of the homogeneously branched, substantially linear ethylene polymers is a highly unexpected flow property where the Ii( ^* *7**-2 ^va -*- ^ue °f the polymer is essentially independent of the polydisperεity index (i.e., M _w /M _n ) Of the polymer. This is contrasted with conventional linear homogeneously branched and heterogeneously branched polyethylene resins having rheological properties such that to increase the I10 I2 ^a **- ^ue the polydispersity index must also be increased.

Substantially linear olefin polymers have a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear olefin polymer having about the same I ₂ and M _w /M _n

The preferred melt index, measured as I ₂ (ASTM D-1238, condition 190/2.16 (formerly condition E) ) , is from 0.5 g/10 min to 20 g/10 min, more preferably from 1 to 5 g/10 min. Typically, the preferred substantially linear ethylene polymers used in the practice of this invention are homogeneously branched and do not have any measurable high density fraction, i.e. short chain branching distribution as measured by Temperature Rising Elution Fractionation which is described in USP 5,089,321. Stated in another manner, these polymers do not contain a polymer fraction that has a degree of branching less than or equal to 2 methyls/1000 carbons. These preferred substantially linear ethylene polymers are also characterized by a single differential scanning calorimetry (DSC) melting peak. Any unsaturated organic compound containing at least one ethylenic unsaturation (for example at least one double bond), and at least one carbonyl group (-C=0) that will graft to polypropylene or a substantially linear ethylene polymer as described above can be used in the practice of this invention. Representative unsaturated organic compounds that contain at least one carbonyl group are the ethylenically unsaturated carboxylic acids, anhydrides, esters and

their salts, both metallic and nonmetallic. Preferably, the organic compound contains a site of ethylenic unsaturation conjugated with the carbonyl group. Representative compounds include maleic, fumaric, acrylic, methacrylic, itaconic, crotonic, α-methyl crotonic, cinnamic acids and their anhydride, ester and salt derivatives, if any. Maleic anhydride is the preferred unsaturated organic compound containing at least one site of ethylenic unsaturation and at least one carbonyl group.

The unsaturated organic compound content of the grafted polypropylene or substantially linear ethylene polymer is at least

0.01 weight percent, preferably at least 0.1 weight percent, and more preferably at least 0.5 weight percent, based on the combined weight of the polymer and the organic compound. The maximum amount of unsaturated organic compound content can vary to convenience, but typically it does not exceed 10 weight percent, preferably it does not exceed 5 weight percent, and more preferably it does not exceed 2 weight percent. The unsaturated organic compound can be grafted to the polypropylene or substantially linear ethylene polymer by any known technique, such as those taught in USP 3,236,917 and USP 5,194,509. For example, in the '917 patent the polymer is introduced into a two-roll mixer and mixed at a temperature of 60 C. The unsaturated organic compound is then added along with a free radical initiator, such as benzoyl peroxide, and the components are mixed at 30 C until the grafting is completed. In the '509 patent, the procedure is similar except that the reaction temperature is higher, for example 210 to 300 C, and a free radical initiator is not used.

An alternative and preferred method of grafting is taught in USP 4,950,541 by using a twin-screw devolatilizing extruder as the mixing apparatus. The polypropylene or substantially linear ethylene polymer and unsaturated organic compound are mixed and reacted within the extruder at temperatures at which the reactants are molten and in the presence of a free radical initiator. Preferably, the unsaturated organic compound is injected into a zone maintained under pressure within the extruder. Representative of the interpolymers (which include copolymers and terpolymers) of ethylene and an α,β-unsaturated carbonyl comonomer

are copolymers of ethylene and acrylic acid or methacrylic acid (EAA or EMAA) and their ionomers (for example their metal salts), ethylene and vinyl acetate (EVA) and its derivative ethylene vinyl alcohol (EVOH) , ethylene and carbon monoxide (ECO) , ethylene/propylene and carbon monoxide (EPCO) , and ethylene/carbon monoxide/acrylic acid terpolymer (ECOAA) . With respect to EAA and EMAA (and their derivatives), these materials are usually produced by the free radical copolymerization of ethylene with acrylic acid or methacrylic acid. The resulting copolymers have carboxylic acid groups along the backbone and/or side chains of the copolymer which in the case of their ionomers, can be subsequently neutralized or partially neutralized with a base. Preferably, these copolymers contain from 3 to 20, more preferably from 5 to 15, and most preferably from 8 to 12 percent by weight of acrylic acid or methacrylic acid monomer units in the polymer chain. The melt index of these copolymers is in the range of from 0.5 to 1500, preferably in the range of from 5 to 300.

With respect to ECO and EPCO polymers, the classes of materials described in USP 4,916,208 to Klingensmith are illustrative of the classes of ECO and EPCO polymers that can be used in the practice of this invention. Such polymers can be linear altenating copolymers or random copolymers.

Preferably, the polypropylene or graft-modified polypropylene comprises from 40 to 60 weight percent, more preferably from 45 to 55 weight percent, of the paintable thermoplastic composition. Preferably, this component of the composition is at least 50 weight percent, based on the weight of this component, graf -modified polypropylene, more preferably at least 75 weight percent graft- modified polypropylene. Most preferably, this component of the composition is 100 percent graft-modified polypropylene. Preferably the substantially linear ethylene polymer component of the composition is from 10 to 30 weight percent, more preferably from 15 to 25 weight percent, of the composition. Like the polypropylene component, the respective amounts of substantially linear ethylene polymer and graft-modified substantially linear ethylene polymer can vary to convenience although a preponderance (i.e. greater than 50 weight percent) of nongrafted substantially

linear ethylene polymer is preferred. The more preferred composition of this component is at least 75 percent, on a weight basis, nongrafted substantially linear ethylene polymer, and a composition of 100 percent nongrafted substantially linear ethylene polymer is most preferred.

The preferred amount of the interpolymer of ethylene and an α,β-unsaturated carbonyl is from 10 to 40 weight percent, more preferably from 20 to 30 weight percent, based on the weight of this component. One preferred embodiment of this invention comprises a paintable, thermoplastic composition characterized by, in weight percent based upon the weight of the composition, about:

A. 40 to 60 percent graft-modified polypropylene;

B. 10 to 30 percent nongrafted substantially linear ethylene polymer; and

C. 10 to 40 percent interpolymer of ethylene and an α,β- unsaturated carbonyl comonomer, preferably one or more of EAA, EMAA, EVA, ECO, EPCO and ECOAA; with the proviso that the sum of Components B and C is from 40 to 60 weight percent of the composition.

Another preferred embodiment of this invention is a paintable thermoplastic composition characterized by, in weight percent based upon the weight of the composition, about:

A. 45 to 55 percent of graft-modified polypropylene; B. 15 to 25 percent nongrafted substantially linear ethylene polymer; and C. 20 to 30 percent of interpolymer of ethylene and an α,β- unsaturated carbonyl comonomer, preferably one or more of EAA, EMAA, EVA, ECO, EPCO and ECO; with the proviso that the sum of Components B and C is from 45 to 55 weight percent of the composition.

The components of the composition of this invention are mixed with one another in any conventional manner that ensures the creation of a relatively homogenous blend. If the blend is molded into a finished article by extrusion, the individual components are typically introduced into the extruder separately and mixed within it prior to

extrusion. If the blend is molded by a compression or injection technique, then the three components are first well mixed by any conventional means, for example, roller mill, agitator, etc., and then introduced as a homogenous mass into the mold. In another embodiment of this invention, the graft-modified polypropylene or substantially linear ethylene polymer is "let down" or diluted with virgin (i.e. nongrafted) polypropylene or substantially linear ethylene polymer prior to its use as a blend component. For example, after the graft-modified substantially linear ethylene polymer has been prepared as described in USP 4,950,541, it is then back-blended in an extruder with virgin substantially linear ethylene polymer to a predetermined dilution. Let down or dilution ratios will vary with the ultimate application of the thermoplastic composition, but weight ratios between 1:10 and 10:1 are typical. The paintable thermoplastic compositions of this invention exhibit several desirable properties. First, these compositions are paintable with conventional paints without prior application of a primer or prior surface treatment of the molded article.

Second, these materials demonstrate excellent heat resistance which is an important corollary property to paintability. In commercial applications, such as molded automobile parts, paints are often cured in an oven at temperatures in excess of 200°F (93°C) . The molded article must not only demonstrate good adhesion to the paint, but it must also demonstrate good resistance to the cure temperature. Third, molded articles made from the compositions of this invention demonstrate good low temperature impact resistance. Again, this is an important property in certain commercial applications, such as molded, exterior automobile parts.

Fourth, the recyclability of fabricated articles made from the compositions of this invention is enhanced relative to the recyclability of fabricated articles made from similar but conventional compositions. Recycled articles, for example automobile fascia, are ground into relatively small particles, and then blended with virgin polymer. With conventional compositions, the paint attaches to the article through the action of a primer or a surface pretreatment, which surface treatment is removed under conditions of

recycling. Once removed, compatibility between the TPO and the paint is lost (due to the polar nature of the paint and the nonpolar nature of the polymer) and the integrity of the recycle melt (i.e. paint, primer (perhaps) , recycled polymer and virgin polymer) , and any articles made from the melt, is degraded.

With the compositions of this invention, however, the paint and polymer are compatible (both are polar in nature) and as such, the conditions of recycling are not detrimental to the integrity of the recycle melt or the articles made from the melt. In other words, the compositions of this invention have compatibility with respect to both the surface and bulk matrix of the polymer formulation, while the conventional compositions have compatibility with the surface but not the bulk matrix of the polymer formulations. This compatibility characteristic is particularly useful in the recycling of painted automobile fascia fabricated from compositions comprising graft- modified substantially linear polymers and polypropylene-based TPO.

The fabricated articles of this invention can be prepared by known thermoplastic fabrication methods, and particularly by known thermoplastic molding methods, such as injection, compression, blow, rotational, reaction injection and molding techniques. Also, the fabricated articles of this invention can be painted by known coating methods, including spray paint applications and in-mold coating techniques.

The following examples are illustrative of certain specific embodiments of this inventions. All parts and percentages are by weight unless otherwise noted.

Table 2: Paintability Tests

SAMPLE INITIAL ADHESION AFTER 96 DIME SCRAPE AFTER ADHESION HOURS IN HUMIDITY 96 HOURS IN CHAMBER HUMIDITY CHAMBER

C-l Fail

C-2 Pass* Pass Pass

C-3 Pass*

C-4 Pass* Pass Pass

C-5 Pass Fail Fail

C-6 Fail

1 Pass Pass Pass

2 Pass Pass Pass

The testing sample shriveled after baking in the 250 F (121 C) oven for 40 minutes.

Sample C-l demonstrates that graft-modified polypropylene by itself is not paintable. Samples C-2, C-3 and C-4 are paintable, but these low density materials shriveled after 40 minutes in an oven at 250 F (121 C) . Sample 1 combines the excellent heat resistance of graft-modified polypropylene and the paintability of EAA. Sample C-5 demonstrates that a one-to-one blend of graft- modified polypropylene and graft-modified substantially linear ethylene polymer has good initial paint adhesion, but the adhesion will fail after 96 hours in a humidity chamber. Sample 2 shows that a blend of graft-modified polypropylene with graft-modified substantially linear ethylene polymer and EAA retains the initial paintability even after 96 hours in a humidity chamber. Sample C-6 demonstrates, however, that a blend of nongrafted polypropylene with graft-modified substantially linear ethylene polymer and EAA is not paintable.

To obtain the necessary thermal resistance to withstand the heat of a paint curing oven, the addition of a blend of a graft-modified and nongrafted polypropylene is beneficial. Moreover, blending graft- modified polypropylene with a blend of EAA and graft-modified substantially linear ethylene polymer demonstrates dramatically better

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paintability than the blending of nongrafted polypropylene with a blend of EAA and graft-modified substantially linear ethylene polymer.

Impact Properties

In addition to the properties of heat resistance and paintability, the property of impact resistance is also important in many applications. Table 3 reports the measured IZOD impact properties at room temperature and at -30 C.

Table 3: Impact Properties and Flex Modulus

Among the test samples, Sample 2 demonstrates a superior balance of low temperature impact resistance with excellent paintability and heat resistance. Although the invention has been described in detail by the preceding examples, such detail is for the purpose of illustration only, and it is not to be construed as a limitation upon the invention. Many variations can be made upon the preceding examples without departing from the spirit and scope of the following claims.

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Table 2: Paintability Tests

SAMPLE INITIAL ADHESION AFTER 96 DIME SCRAPE AFTER ADHESION HOURS IN HUMIDITY 96 HOURS IN CHAMBER HUMIDITY CHAMBER

C-l Fail

C-2 Pass* Pass Pass

C-3 Pass*

C-4 Pass* Pass Pass

C-5 Pass Fail Fail

C-6 Fail __

1 Pass Pass Pass

2 Pass Pass Pass

The testing sample shriveled after baking in the 250 F (121 C) oven for 40 minutes.

Sample C-l demonstrates that graft-modified polypropylene by itself is not paintable. Samples C-2, C-3 and C-4 are paintable, but these low density materials shriveled after 40 minutes in an oven at 250 F (121 C) . Sample 1 combines the excellent heat resistance of graft-modified polypropylene and the paintability of EAA. Sample C-5 demonstrates that a one-to-one blend of graft- modified polypropylene and graft-modified substantially linear ethylene polymer has good initial paint adhesion, but the adhesion will fail after 96 hours in a humidity chamber. Sample 2 shows that a blend of graft-modified polypropylene with graft-modified substantially linear ethylene polymer and EAA retains the initial paintability even after 96 hours in a humidity chamber. Sample C-6 demonstrates, however, that a blend of nongrafted polypropylene with graft-modified substantially linear ethylene polymer and EAA is not paintable.

To obtain the necessary thermal resistance to withstand the heat of a paint curing oven, the addition of a blend of a graft-modified and nongrafted polypropylene is beneficial. Moreover, blending graft- modified polypropylene with a blend of EAA and graft-modified substantially linear ethylene polymer demonstrates dramatically better

paintability than the blending of nongrafted polypropylene with a blend of EAA and graf -modified substantially linear ethylene polymer. Impact Properties

In addition to the properties of heat resistance and paintability, the property of impact resistance is also important in many applications. Table 3 reports the measured IZOD impact properties at room temperature and at -30 C.

Table 3: Impact Properties and Flex Modulus

Among the test samples, Sample 2 demonstrates a superior balance of low temperature impact resistance with excellent paintability and heat resistance. Although the invention has been described in detail by the preceding examples, such detail is for the purpose of illustration only, and it is not to be construed as a limitation upon the invention. Many variations can be made upon the preceding examples without departing from the spirit and scope of the following claims.