US20050197455A1

US20050197455A1 - Method of stabilizing an olefin-based block copolymer with a dispersing mechanism

Info

Publication number: US20050197455A1
Application number: US10/420,033
Authority: US
Inventors: Craig Schang; Paul Harris
Original assignee: BASF Corp
Current assignee: BASF Corp
Priority date: 2000-11-07
Filing date: 2003-04-21
Publication date: 2005-09-08
Also published as: EP1332190A2; MXPA03001299A; US20030229179A1; US6939916B2; WO2002038689A3; WO2002038689A2; CA2426039A1; AU2002215338A1

Abstract

An olefin-based block copolymer is stabilized with a dispersing mechanism. The olefin-based block copolymer is first provided and is then circulated though the dispersing mechanism. Upon circulation through the dispersing mechanism, a particle size of the olefin-based block copolymer is less than 15 microns and the olefin-based block copolymer is thixotropically stable.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. Ser. No. 09/707,513, filed Nov. 7, 2000, which is incorporated herein by reference.

FIELD OF THE INVENTION

The subject invention generally relates to a method of stabilizing an olefin-based block copolymer. More specifically, the subject invention relates to a method of stabilizing an olefin-based block copolymer with a dispersing mechanism wherein the olefin-based block copolymer has an olefin block that is substantially saturated and at least one (poly)ester or (poly)ether block.

BACKGROUND OF THE INVENTION

In the automotive and automotive coatings industries, when dealing with adhesion to a thermoplastic polyolefin (TPO) substrate, it is known that adhesion additives are necessary. As is understood by those skilled in the art, adhesion additives are used as components in solventborne primer surfacers, or other intermediate coating compositions, to promote adhesion between a substrate and a topcoat system for an automobile, such as a topcoat system including a flexible basecoat and flexible clearcoat. Adhesion additives are primarily used in solventborne primer surfacers that are applied to a bumper, i.e., facie, or other trim component as the substrate. Typically, these substrates are made up of thermoplastic polyolefin (TPO), and without the inclusion of example, the olefin-based block copolymer of the adhesion copolymer is polymerized at elevated temperatures (e.g. 145° C.) and one attempt at stabilizing the olefin-based block copolymer such that it does not settle out into the organic solvent requires a gradual cooling phase under vigorous agitation. Gradual cooling is time consuming and resource-intensive (e.g. utilities) and is therefore costly. Furthermore, the various agitation techniques that have been employed in these attempts have been unable to effectively reduce the particle size of the olefin-based block copolymer below 15 microns such that the shelf stability of the adhesion copolymer remains generally unacceptable.
Due to the deficiencies associated with the adhesion copolymers of the prior art, including those described above, it is desirable to provide a unique method of stabilizing an olefin-based block copolymer with a dispersing mechanism that achieves a particle size of the olefin-based block copolymer of less than 15 microns such that the olefin-based block copolymer is thixotropically stable.

SUMMARY OF THE INVENTION AND ADVANTAGES

A method of stabilizing an olefin-based block copolymer is disclosed. More specifically, the olefin-based block copolymer has an olefin block that is substantially saturated and at least one (poly)ester or (poly)ether block and a dispersing mechanism is utilized to stabilize the olefin-based block copolymer.
The method includes the steps of providing the olefin-based block copolymer and circulating the olefin-based block copolymer through the dispersing mechanism. As a result of the circulation of the olefin-based block copolymer through the dispersing mechanism, a particle size of the olefin-based block copolymer is less than 15 microns and the olefin-based block copolymer is thixotropically stable.
Accordingly, the method disclosed in the subject invention uses a dispersing mechanism to achieve a particle size of the olefin-based block copolymer of less than 15 microns such that the olefin-based block copolymer is thixotropically stable. Furthermore, it is advantageous that, because the olefin-based block copolymer is thixotropically stable, it can be stored over time and then used as a separate and stable additive that can be incorporated into various coatings and remain in solution or uniformly dispersed throughout such coatings.

DETAILED DESCRIPTION OF THE INVENTION

An adhesion copolymer according to the subject invention is used as an adhesion additive to promote adhesion to a substrate, preferably a TPO substrate. More specifically, this adhesion copolymer is preferably used as a component in a primer surfacer, or other intermediate coating composition, to promote adhesion between the substrate and a topcoat system for an automobile, such as a topcoat system including a flexible basecoat and flexible clearcoat. The adhesion copolymer is primarily used in solventborne primer surfacers that are applied to a bumper, i.e., facie, or other trim component as the substrate. Typically, these substrates are TPO. It is to be understood, however, that the adhesion copolymer of the subject invention may be used as a component in other intermediate coating compositions based on waterborne technology. It is to be further understood that this adhesion copolymer may be used with topcoat systems, both solventborne and waterborne, other than flexible basecoats and flexible clearcoats. As one example, this adhesion copolymer can be used in a solventborne primer surfacer that has been topcoated with a rigid waterborne basecoat and a solventborne clearcoat. The adhesion copolymer of the subject invention may be used in combination with other adhesion additives including, but not limited to, CPO, without varying the scope of the subject invention.
The adhesion copolymer according to the subject invention includes an olefin-based block copolymer and an organic solvent. More specifically, the olefin-based block copolymer has an olefin block that is substantially saturated and at least one (poly)ester or (poly)ether block, and the olefin-based block copolymer is present in the organic solvent. The adhesion copolymer may further include e-caprolactone and a catalyst including, but not limited to, stannous octoate. The e-caprolactone, prompted by the catalyst, reacts with the olefin-based block copolymer. Finally, the adhesion copolymer may further include additives including, but not limited to, CPO, epoxy resin, and combinations thereof. Preferably, the adhesion copolymer of the present invention is formed with the olefin-based block copolymer in combination with the organic solvent, the e-caprolactone, the catalyst, and the additive(s), prior to circulation of the olefin-based block copolymer through the dispersing mechanism.
By the terms “(poly)ester block” and “(poly)ether block” it is meant that the base polyolefin material is modified with one or more one monomer units through formation of, respectively, ester or ether linkages. For purposes of the present invention, “(poly)ester block” has a special meaning that, in the case of two or more monomer units, the monomer units are predominantly, preferably exclusively, arranged in head-to-an adhesion additive in an intermediate solventborne primer surfacer layer, the topcoat system may delaminate from the TPO substrate.
One example of an adhesion additive is chlorinated polyolefin (CPO). However, it is known that CPO is expensive, has poor shelf stability, and may be hazardous to the environment. Accordingly, the automotive coatings industry has developed other adhesion additives to replace CPO. More specifically, adhesion copolymers, used as an adhesion additive as a replacement for CPO, have been found to provide advantageous adhesion characteristics to the TPO substrate. Examples of such adhesion copolymers are disclosed in United States Patent Nos. 6,300,414 and 6,423,778.
Unfortunately, the various chemistries of the adhesion copolymers are very often unstable in solution. More specifically, these adhesion copolymers include olefin-based block copolymers that have an olefin block that is substantially saturated and at least one (poly)ester or (poly)ether block. The olefin-based block copolymer is typically present in a strong organic solvent such as xylene, toluene, and the like. The individual components of the adhesion copolymers, i.e., the olefin-based block copolymer, frequently settle out into the organic solvent. This settling renders the adhesion copolymer unstable, i.e., having poor shelf stability when isolated, and therefore, not suitable for use as a component of a solventborne primer surfacer or other intermediate coating composition. This settling is a direct result of a particle size of a molecule of olefin-based block copolymer. Typically, this particle size is in excess of 50 and even 100 microns.
Several attempts have been made to stabilize the olefin-based block copolymer. However, these attempts have been relatively unsuccessful and are cumbersome. For tail linkages. Thus, the arrangement of the ester linkages in the (poly)ester block or blocks may be represented by

in which n represents the number of monomer units, R represents the part of each monomer unit between the ester groups (which may be all the same if only one type of monomer is used or different for individual units if a mixture of different monomers is used), and Y represents the end group of the block. The monomer units should be arranged exclusively in the head-to-tail arrangement, although it is possible, particularly in longer blocks, for there to be some variation; in the latter case, the arrangement should still be predominantly head-to-tail. Preferred embodiments for n, R, and Y are described additionally below.
It is preferred that the olefin-based block copolymer has one block of the olefin to which is attached one or more of the (poly)ester and/or (poly)ether blocks. In one embodiment, the olefin-based block copolymer of the invention can be represented by a structure

in which A represents the olefin block, B represents a (poly)ester or (poly)ether block or combinations thereof, and m is on average from about 0.7 to about 10, preferably from about 1.7 to about 2.2, and particularly preferably about 1.9 or 2. The A block is more specifically a saturated or substantially saturated olefin polymer. The B block preferably contains, on average, from about 0.5 to about 25 monomer units, more preferably the B block has on average from about 2 to about 10, and even more preferably from about 2 to about 6, monomer units per hydroxyl group of the unmodified olefin block. The monomer units may be the same or there may be different monomer units in a single (poly)ester or (poly)ether block. For example, a (poly)ether block may have one or more ethylene oxide units and one or more propylene oxide units.
The olefin-based block copolymer of the adhesion copolymer that is stabilized in the present invention can be prepared by reacting a hydroxyl-functional, saturated or substantially saturated, olefin polymer with a chain-extension reagent that is reactive with hydroxyl groups and will polymerize in a head-to-tail arrangement of monomer units. Preferably, the olefin polymer has a number average molecular weight of from about 1000 up to about 5000, more preferably from about 1000 up to about 3500, and even more preferably from about 1500 up to about 3500.
The hydroxyl-functional olefin forms the A block and the chain-extension reagent forms the B block or blocks. Such chain-extension reagents include, without limitation, lactones, hydroxy carboxylic acids, oxirane-functional materials such as alkylene oxides, and combinations of these. Preferred chain-extension reagents are lactones and alkylene oxides, and even more preferred are epsilon caprolactone, ethylene oxide, propylene oxide, and combinations of these.
The hydroxyl-functional olefin polymer may be produced by hydrogenation of a polyhydroxylated polydiene polymer. Polyhydroxylated polydiene polymers may be produced by anionic polymerization of monomers such as isoprene or butadiene and capping the polymerization product with alkylene oxide and methanol, as described in United States Patent Nos. 5,486,570, 5,376,745, 4,039,593, and Reissue 27,145, each of which is incorporated herein by reference. The polyhydroxylated polydiene polymer is saturated or substantially saturated by hydrogenation of the double bonds that is at least 90 percent, preferably at least 95% and even more preferably essentially 100% complete to form the hydroxyl-functional olefin polymer. The hydroxyl equivalent weight of the hydroxyl-functional saturated olefin polymer may be from about 500 to about 20,000. The hydroxyl-functional olefin polymer is preferably a hydroxyl-functional ethylene/butylene polymer. Preferred olefin polymers may have a number average molecular weight of from about 1,000 to about 10,000. Preferably, the olefin polymer is a liquid poly(ethylene/butylene) polymer having at least one hydroxyl group. Preferably, the olefin polymer has from about 0.7 to about 10 hydroxyl groups on average per molecule, more preferably from about 1.7 to about 2.2 hydroxyl groups on average per molecule, and still more preferably about 2 hydroxyl groups on average per molecule. The hydroxyl-functional olefin polymer preferably has terminal hydroxyl groups and a hydroxyl equivalent weight of from about 1000 to about 3000.
The olefin polymer is preferably a low molecular weight polybutylene polymer having at least one hydroxyl group. In another preferred embodiment the polyolefin polyol is a hydrogenated polybutadiene. In forming the hydrogenated polybutadiene polyol, part of the butadiene monomer may react head-to-tail, i.e., by a 1,4 polymerization, and part may react by a 1,2 polymerization to yield a carbon-carbon backbone having pendent ethyl groups from the 1,2 polymerization. The relative amounts of 1,4 and 1,2 polymerizations can vary, with from about 80% to about 85% of the monomer reacting by the 1,4 polymerization and from about 15 to about 20% of the monomer reacting by the 1,2 polymerization.
Such preferred hydrogenated polyolefin polyol materials are commercially available under the trademark POLYTAIL™ from Mitsubishi Chemical Corporation of Japan, including POLYTAIL™ H and POLYTAIL™ HA. POLYTAIL™ H has a particle size in excess of 50 and even 100 microns.
While not intending to be bound by theory, it is believed that the mechanism that results in adhesion of the coating to the substrate involves a migration of the olefin-based block copolymer to the olefinic or TPO substrate interface and an interaction with the olefinic or TPO substrate. It is believed that the migration and/or interaction is facilitated by application of heat, such as the heat applied to cure the coating composition. It is also believed that the migration and/or interaction is facilitated by predominantly lower molecular weight molecules. Low molecular weight hydrogentated polyolefin polyols or olefin-based block copolymers having narrower polydispersity (i.e., closer to the ideal of 1), in which high molecular weight fractions are less than for materials having similar number average molecular weights but broader (higher) polydispersity, are believed to offer an advantage in either better adhesion at lower levels of incorporation or effective adhesion achieved under milder conditions (lower temperatures and/or shorter interaction times). “Polydispersity,” also known simply as “dispersity,” is defined in polymer science as the ratio of the weight average molecular weight to the number average molecular weight. Higher polydispersity numbers indicate a broader distribution of molecular weights, and in particular mean a larger fraction of higher molecular weight species.
The olefin-based block copolymer of the invention thus preferably has a narrow polydispersity. When the liquid olefin polymer is anionically polymerized it may have a very narrow polydispersity, such as on the order of only about 1.1. The ring-opening reactions of lactones and alkylene oxides or reactions of other materials that add head-to-tail like the hydroxy carboxylic acids tend to produce polymers that are more uniform and have narrow polydispersities. Modification of the olefin polymer by a head-to-tail reaction such as a ring-opening reaction of a lactone or alkylene oxide compound usually results in a product having a polydispersity of about 1.1 or 1.15, thus essentially preserving the narrow polydispersity of the hydroxyl-functional olefin starting material. Block copolymers of the invention preferably have polydispersities of about 1.2 or less, and more preferably have polydispersities of about 1.15 or less.
Again while not intending to be bound by theory, it is believed that the modification of the liquid olefin polymer by the (poly)ester or (poly)ether block or blocks offers significant advantages in providing adhesion of coatings to olefinic substrates because of increased compatibility of the resulting block copolymer toward materials commonly employed in such coatings. In addition, the imposition of the (poly)ester or (poly)ether block between the olefin block and the functional group, such as the hydroxyl group, makes that functional group more accessible for reaction during the curing of the coating composition. These principles can be used to optimize the olefin-based block copolymer of the invention for use under particular conditions or with or in particular coating compositions.
In a preferred embodiment, the olefin polymer is reacted with a lactone or a hydroxy carboxylic acid to form an olefin-based polymer having (poly)ester end blocks. Lactones that can be ring opened by an active hydrogen are well-known in the art. Examples of suitable lactones include, without limitation, ε-caprolactone, γ-caprolactone, β-butyrolactone, β-propriolactone, γ-butyrolactone, α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-decanolactone, δ-decanolactone, γ-nonanoic lactone, γ-octanoic lactone, and combinations of these. In one preferred embodiment, the lactone is ε-caprolactone. Lactones useful in the practice of the invention can also be characterized by the formula:

wherein n is a positive integer of 1 to 7 and R is one or more H atoms, or substituted or unsubstituted alkyl groups of 1-7 carbon atoms.
The lactone ring-opening reaction is typically conducted under elevated temperature (e.g., 80-150° C.). When the reactants are liquids a solvent is not necessary. However, a solvent may be useful in promoting good conditions for the reaction even when the reactants are liquid. Any non-reactive solvent may be used, including both polar and nonpolar organic solvents. Examples of useful solvents include, without limitation, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, and the like and combinations of such solvents. A catalyst is preferably present. Useful catalysts include, without limitation, proton acids (e.g., octanoic acid, Amberlyst® 15 (Rohm & Haas)), and tin catalysts (e.g., stannous octoate). Alternatively, the reaction can be initiated by forming a sodium salt of the hydroxyl group on the molecules that will react with the lactone ring.
A hydroxy carboxylic acid can also be used instead of a lactone or in combination with a lactone as the compound that reacts with the liquid olefin polymer to provide ester blocks. Useful hydroxy carboxylic acids include, without limitation, dimethylhydroxypropionic acid, hydroxy stearic acid, tartaric acid, lactic acid, 2-hydroxyethyl benzoic acid, N-(2-hydroxyethyl)ethylene di amine triacetic acid, and combinations of these. The reaction can be conducted under typical esterification conditions, for example at temperatures from room temperature up to about 1 50° C., and with catalysts such as, for example, calcium octoate, metal hydroxides like potassium hydroxide, Group I or Group II metals such as sodium or lithium, metal carbonates such as potassium carbonate or magnesium carbonate (which may be enhanced by use in combination with crown ethers), organometallic oxides and esters such as dibutyl tin oxide, stannous octoate, and calcium octoate, metal alkoxides such as sodium methoxide and aluminum tripropoxide, protic acids like sulfuric acid, or Ph₄SbI. The reaction may also be conducted at room temperature with a polymer-supported catalyst such as Amerlyst-150® (available from Rohm & Haas) as described by R. Anand in Synthetic Communications, 24(19), 2743-47 (1994), the disclosure of which is incorporated herein by reference.
While polyester segments may likewise be produced with dihydroxy and dicarboxylic acid compounds, it is preferred to avoid such compounds because of the tendency of reactions involving these compounds to increase the polydispersity of the resulting block copolymer. If used, these compounds should be used in limited amounts and preferably employed only after the lactone or hydroxy carboxylic acid reactants have fully reacted.
The reaction with the lactone or hydroxy carboxylic acid or oxirane compounds adds at least one monomer unit as the B block and-preferably provides chain extension of the olefin polymer. In particular, the (poly)ester and/or (poly)ether block is thought to affect the polarity and effective reactivity of the end group functionality during curing of the coating. The (poly)ester and/or (poly)ether block also makes the olefin-based block copolymer more compatible with components of a typical curable coating composition. The amount of the extension depends upon the moles of the alkylene oxide, lactone, and/or hydroxy carboxylic acid available for reaction. The relative amounts of the olefin polymer and the alkylene oxide, lactone, and/or hydroxy acid can be varied to control the degree of chain extension. The reaction of the lactone ring, oxirane ring, and/or hydroxy carboxylic acid with a hydroxyl group results in the formation of an ether or ester and a new resulting hydroxyl group that can then react with another available monomer, thus providing the desired chain extension. In the preferred embodiments of the present invention, the equivalents of oxirane, lactone, and/or hydroxy carboxylic acid for each equivalent of hydroxyl on the olefin polymer are from about 0.5 to about 25, more preferably from about 1 to about 10, and even more preferably from about 2 to about 6. In an especially preferred embodiment about 2.5 equivalents of lactone are reacted for each equivalent of hydroxyl on the olefin polymer.
In another embodiment of the invention, a polyolefin having terminal hydroxyl groups is reacted with an oxirane-containing compound to produce (poly)ether endblocks. The oxirane-containing compound is preferably an alkylene oxide or cyclic ether, especially preferably a compound selected from ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, and combinations of these. Alkylene oxide polymer segments include, without limitation, the polymerization products of ethylene oxide, propylene oxide, 1,2-cyclohexene oxide, 1-butene oxide, 2-butene oxide, 1-hexene oxide, tert-butylethylene oxide, phenyl glycidyl ether, 1-decene oxide, isobutylene oxide, cyclopentene oxide, 1-pentene oxide, and combinations of these. The hydroxyl group of the olefin-based polymer functions as initiator for the base-catalyzed alkylene oxide polymerization . The polymerization may be carried out, for example, by charging the hydroxyl-terminated olefin polymer and a catalytic amount of caustic, such as potassium hydroxide, sodium methoxide, or potassium tert-butoxide, and adding the alkylene oxide at a sufficient rate to keep the monomer available for reaction. Two or more different alkylene oxide monomers may be randomly copolymerized by coincidental addition and polymerized in blocks by sequential addition.
Tetrahydrofuran polymerizes under known conditions to form repeating units
[CH₂CH₂CH₂CH₂O ]
Tetrahydrofuran is polymerized by a cationic ring-opening reaction using such counterions as SbF₆, AsF₆, PF₆, SbCl6, BF₄, CF₃SO₃, FSO₃, and Cl₄. Initiation is by formation of a tertiary oxonium ion. The polytetrahydrofuran segment can be prepared as a “living polymer” and terminated by reaction with the hydroxyl group of the olefin polymer.
It is also highly desirable for the olefin-based block copolymer of the invention to have functional groups that are reactive with one or more film-forming components of the adhesion promoter, or of the coating composition applied over an adhesion promoter containing the olefin-based block copolymer, or of the coating composition to which the olefin-based block copolymer is added. The film-forming components with which the olefin-based block copolymer may be reactive may be a film-forming polymer or a curing agent. The reactive functional groups on the olefin-based block copolymer may include, without limitation, hydroxyl, carbamate, urea, carboxylic acid, and combinations of these. Following addition of the ether or ester blocks, the block copolymer of the invention has one or more hydroxyl groups, which may be reactive with the film-forming polymer or curing agent. If desired, the hydroxyl groups may be converted to other functional groups, including carbamate, urea, carboxylic acid groups and combinations of these. Carbamate groups according to the invention can be represented by the

structure
in which R is H or alkyl, preferably of 1 to 4 carbon atoms. Preferably R is H or methyl, and more preferably R is H. Urea groups according to the invention can be represented

by the structure
in which R′ and R″ are each independently H or alkyl, or R′ and R″ together form a heterocyclic ring structure. Preferably, R′ and R″ are each independently H or alkyl of from 1 to about 4 carbon atoms or together form an ethylene bridge, and more preferably R′ and R″ are each independently H. Hydroxyl groups can be converted to carbamate groups by reaction with a monoisocyanate (e.g., methyl isocyanate) to form a secondary carbamate group (that is, a carbamate of the structure above in which R is alkyl) or with cyanic acid (which may be formed in situ by thermal decomposition of urea) to form a primary carbamate group (i.e., R in the above formula is H). This reaction preferably occurs in the presence of a catalyst as is known in the art. A hydroxyl group can also be reacted with phosgene and then ammonia to form a primary carbamate group, or by reaction of the hydroxyl with phosgene and then a primary amine to form a compound having secondary carbamate groups. Finally, carbamates can be prepared by a transesterification approach where hydroxyl group is reacted with an alkyl carbamate (e.g., methyl carbamate, ethyl carbamate, butyl carbamate) to form a primary carbamate group-containing compound. This reaction is performed at elevated temperatures, preferably in the presence of a catalyst such as an organometallic catalyst (e.g., dibutyltin dilaurate). A hydroxyl group can be conveniently converted to a carboxylic acid by reaction with the anhydride of a dicarboxylic acid. It is possible and may be desirable to derivative the hydroxyl functional olefin-based block copolymer to have other functional groups other than those mentioned, depending upon the particular coating composition in which the olefin-based block copolymer is to interact. The hydroxyl groups of the low molecular weight polyolefin polyol may also be derivatized to hydroxyl, carbamate, urea, carboxylic acid, or other functional groups. For convenience, the term “polyolefin polyol” as used in the description of this invention is used to encompass such derivatives having different functional groups. The functional groups, whether hydroxyl or the other functional groups, react during curing to crosslink to a cured film.
As previously mentioned, the olefin-based block copolymer of the invention can be used to prepare an adhesion promoter for olefinic substrates like TPO that provides excellent adhesion of subsequent coating layers to the substrates. Alternatively, the olefin-based copolymers of the invention can be used as an additive in a curable coating composition to provide excellent adhesion to olefinic substrates like TPO. The adhesion promoter or coating composition of the invention is applied directly to an unmodified and untreated plastic substrate.
First, the olefin-based block copolymer can be used in an adhesion promoter. The olefin-based block copolymer can be used alone as an adhesion promoter layer, particularly when it is of a sufficiently low viscosity to flow out to form a substantially continuous layer on the substrate. In most cases, however, it will be desirable to combine the olefin-based block copolymer with other components, including for example and without limitation crosslinking agents reactive with the functionality on the olefin-based block copolymer, solvents including water and organic solvents, pigments, customary coatings additives, and combinations of these.
In one preferred embodiment, the adhesion promoter is a solution or dispersion that includes only the olefin-based block copolymer as the vehicle. In this embodiment, it is preferred to first apply the adhesion promoter directly to the plastic substrate and then to apply a layer of a coating composition that includes one or more components reactive with the olefin-based block copolymer of the adhesion promoter layer. Applying coating layers “wet-on-wet” is well known in the art.
In an alternative embodiment, the adhesion promoter includes, in addition to the olefin-based block copolymer, at least one crosslinking agent reactive with the block copolymer. The curing agent has, on average, at least about two crosslinking functional groups. Suitable curing agents for active-hydrogen functional olefin-based copolymers include, without limitation, materials having active methylol or methylalkoxy groups, such as aminoplast crosslinking agents or phenol/formaldehyde adducts, curing agents that have isocyanate groups, particularly blocked isocyanate curing agents; and combinations of these. Examples of preferred curing agent compounds include melamine formaldehyde resins (including monomeric or polymeric melamine resin and partially or fully alkylated melamine resin), blocked or unblocked polyisocyanates (e.g., TDI, MDI, isophorone diisocyanate, hexamethylene diisocyanate, and isocyanurate trimers of these, which may be blocked for example with alcohols or oximes), urea resins (e.g., methylol ureas such as urea formaldehyde resin, alkoxy ureas such as butylated urea formaldehyde resin), polyanhydrides (e.g., polysuccinic anhydride), polysiloxanes (e.g., trimethoxy siloxane), and combinations of these. Unblocked polyisocyanate curing agents are usually formulated in two-package (2K) compositions, in which the curing agent and the film-forming polymer (in this cased the block copolymer) are mixed only shortly before application and because the mixture has a relatively short pot life. The curing agent may be combinations of these, particularly combinations that include aminoplast crosslinking agents. Aminoplast resins such as melamine formaldehyde resins or urea formaldehyde resins are especially preferred. For this embodiment of the adhesion promoter, the applied adhesion promoter may be either coated “wet-on-wet” with a one or more additional coating compositions, and then all layers cured together, or the adhesion promoter layer may be partially or fully cured before being coated with any additional coating layers. Curing the adhesion promoter layer before applying an additional coating layer may allow the subsequent coating layer to be applied electrostatically when the adhesion promoter is formulated with a conductive carbon black, according to methods known in the art.
Secondly, the olefin-based block copolymer can be added to a variety of coating compositions to produce coating compositions that have excellent adhesion to plastic substrates, particularly to olefinic substrates including TPO. Compositions in which the olefin-based block copolymer may be used include primers, one-layer topcoats, basecoats, and clearcoats. The coating composition having the added block copolymer of the invention can then be applied directly to an uncoated and unmodified olefin-based substrate or other plastic to form a coating layer having excellent adhesion to the substrate. In the case of adding the block copolymer to a basecoat or one-layer topcoat composition, the use of an adhesion promoter or primer layer can be avoided. When the olefin-based block copolymer of the invention is added to a clearcoat composition, the clearcoat can be applied directly to a colored polyolefin substrate, particularly a colored TPO substrate, also known as color-in-mold. This method produces a colored part having better appearance, exterior durability, scratch resistance, and mar resistance as compared to the relatively soft uncoated TPO substrate.
The compositions of the invention preferably include at least about 0.001% by weight of the liquid olefin-based block copolymer, based upon the total weight of nonvolatile vehicle. In one preferred embodiment, the olefin-based block copolymer of the invention is included in the coating composition in an amount of from about 0.001% to about 4% by weight of the total weight of nonvolatile vehicle. In another preferred embodiment, the olefin-based block copolymer of the invention is included in the coating composition in an amount of from about 0.1% to about 10% by weight of the total weight of nonvolatile vehicle, more preferably from about 0.2% to about 5% by weight of the nonvolatile vehicle, and still more preferably from about 0.2% to about 3% of the nonvolatile vehicle of the coating composition. Vehicle is understood to be the resinous and polymer components of the coating composition, which includes film forming resins and polymers, crosslinkers, other reactive components such as the block copolymer of the invention, and other reactive or nonreactive resinous or polymeric components such as acrylic microgels.
The coating compositions of the invention may contain a wide variety of film-forming resins. At least one crosslinkable resin is included. The resin may be self-crosslinking, but typically a coating composition includes one or more crosslinking agents reactive with the functional groups on the film-forming resin. Film-forming resins for coating compositions typically have such functional groups as, for example, without limitation, hydroxyl, carboxyl, carbamate, urea, epoxide (oxirane), primary or secondary amine, amido, thiol, silane, and so on and combinations of these. The film-forming resin may be any of those used in coating compositions including, without limitation, acrylic polymers, vinyl polymers, polyurethanes, polyesters, polyethers, epoxies, and combinations and graft copolymers of these. Also included are polymers in which one kind of polymer is used as a monomer in forming another, such as a polyester-polyurethane or a polyether-polyurethane in which a dihydroxy functional polyester or polyether is used as a monomer in the urethane polymerization reaction. One preferred film-forming resin is a hydroxy-functional acrylic resin. Many references describe film-forming polymers for curable coating compositions and so these materials do not need to be described in further detail here.
When the coating composition includes a curing agent, or crosslinker, the crosslinker is preferably reactive with both the olefin-based block copolymer and the polymeric film-forming resin. The curing agent has, on average, at least about two crosslinking functional groups, and is preferably one of the crosslinking materials already described above. Aminoplast resins such as melamine formaldehyde resins or urea formaldehyde resins are especially preferred for resin functional groups that are hydroxyl, carbamate, and/or urea. The coating compositions of the invention can be formulated as either one-component (one-package or 1K) or two-component (two-package or 2K) compositions, as is known in the art.
The adhesion promoter or coating composition used in the practice of the invention may include a catalyst to enhance the cure reaction. For example, when aminoplast compounds, especially monomeric melamines, are used as a curing agent, a strong acid catalyst may be utilized to enhance the cure reaction. Such catalysts are well-known in the art and include, without limitation, p-toluenesulfonic acid, dinonylnaphthalene disulfonic acid, dodecylbenzenesulfonic acid, phenyl acid phosphate, monobutyl maleate, butyl phosphate, and hydroxy phosphate ester. Strong acid catalysts are often blocked, e.g. with an amine. Other catalysts that may be useful in the composition of the invention include Lewis acids, zinc salts, and tin salts.
A solvent may optionally be included in the adhesion promoter or coating composition used in the practice of the present invention, and preferably at least one solvent is included. In general, the solvent can be any organic solvent and/or water. It is possible to use one or more of a broad variety of organic solvents. The organic solvent or solvents are selected according to the usual methods and with the usual considerations. In a preferred embodiment of the invention, the solvent is present in the coating composition in an amount of from about 0.01 weight percent to about 99 weight percent, preferably for organic solventborne compositions from about 5 weight percent to about 70 weight percent, and more preferably for topcoat compositions from about 10 weight percent to about 50 weight percent.
In another preferred embodiment, the solvent is water or a mixture of water with any of the typical co-solvents employed in aqueous dispersions. When the olefin-based block copolymer is to be used in a waterborne composition, it is advantageous to include in the block copolymer at least one polyethylene oxide segment to aid in dispersing the material. When modified with a polyethylene oxide segment, the block copolymer of the invention may be dispersed in water, optionally with other components (crosslinkers, additives, etc.) and then applied as an adhesion promoter or added to an aqueous coating composition as an aqueous dispersion of the block copolymer. Alternatively, the block copolymer may be blended with the film-forming polymer and then dispersed in water along with the film-forming polymer. In the latter method, it is contemplated that the block copolymer need not be modified with a hydrophilic segment, and instead the affinity of the block copolymer for the film forming vehicle can be relied upon to maintain the components in a stable dispersion.
Additional agents known in the art, for example and without limitation, surfactants, fillers, pigments, stabilizers, wetting agents, rheology control agents (also known as flow control agents), dispersing agents, adhesion promoters, UV absorbers, hindered amine light stabilizers, silicone additives and other surface active agents, etc., and combinations of these may be incorporated into the adhesion promoter or coating composition containing the olefin-based block copolymer.
The adhesion promoter and coating compositions can be coated on the article by any of a number of techniques well-known in the art. These include, without limitation, spray coating, dip coating, roll coating, curtain coating, and the like. Spray coating is preferred for automotive vehicles or other large parts.
The olefin-based block copolymer can be added to a topcoat coating composition in amounts that do not substantially change the gloss of the topcoat. In one application, for example, the olefin-based block copolymer is utilized in a topcoat composition, in particular a clearcoat composition which produces a high-gloss cured coating, preferably having a 20° gloss (ASTM D523-89) or a DOI (ASTM E430-91) of at least 80 that would be suitable for exterior automotive components. In another application, the olefin-based block copolymer may be added a topcoat composition that produces a low gloss coating, such as for coating certain automotive trim pieces. Typical low gloss coatings have a gloss of less than about 30 at a 60° angle.
When the coating composition of the invention is used as a high-gloss pigmented paint coating, the pigment may include any organic or inorganic compounds or colored materials, fillers, metallic or other inorganic flake materials such as mica or aluminum flake, and other materials of kind that the art normally names as pigments. Pigments are usually used in the composition in an amount of 0.2% to 200%, based on the total solid weight of binder components (i.e., a pigment-to-binder ratio of 0.02 to 2). As previously mentioned, adhesion promoters preferably include at least one conductive carbon black in an amount that makes the coating produced suitable for electrostatic applications of further coating layers.
The adhesion promoters and coating compositions can be applied at thicknesses that will produce dry film or cured film thicknesses typical of the art, such as from about 0.01 to about 5.0 mils. Typical thicknesses for adhesion promoter layers are from about 0.1 to about 0.5 mils, preferably from about 0.2 to about 0.3 mils. Typical thicknesses for primer layers are from about 0.5 to about 2.0 mils, preferably from about 0.7 to about 1.5 mils. Typical thicknesses for basecoat layers are from about 0.2 to about 2.0 mils, preferably from about 0.5 to about 1.5 mils. Typical thicknesses for clearcoat layers or one-layer topcoats are from about 0.5 to about 3.0 mils, preferably from about 1.5 to about 2.5 mils.
The adhesion promoters and coating compositions described herein are preferably thermally cured. Curing temperatures will vary depending on the particular blocking groups used in the cross-linking agents, however they generally range between 225° F. and 270° F. The curing temperature profile must be controlled to prevent warping or deformation of the TPO substrate or other plastic substrate. The first compounds according to the present invention are preferably reactive even at relatively low cure temperatures. Thus, in a preferred embodiment, the cure temperature is preferably between 230° F. and 270° F., and more preferably at temperatures no higher than about 250° F. The curing time will vary depending on the particular components used, and physical parameters such as the thickness of the layers, however, typical curing times range from 15 to 60 minutes, and preferably 20-35 minutes. The most preferred curing conditions depends upon the specific coating composition and substrate, and can be discovered by straightforward testing.
The coating compositions of the invention are particularly suited to coating olefinic substrates, including, without limitation, TPO substrates, polyethylene substrates, and polypropylene substrates. The coating compositions may also be used, however, to coat other thermoplastic and thermoset substrates, including, without limitation, polycarbonate, polyurethane, and flexible substrates like EPDM rubber or thermoplastic elastomers. Such substrates can be formed by any of the processes known in the art, for example, without limitation, injection molding and reaction injection molding, compression molding, extrusion, and thermoforming techniques.
The materials and processes of the invention can be used to form a wide variety of coated articles, including, without limitation, appliance parts, exterior automotive parts and trim pieces, and interior automotive parts and trim pieces.
The method of the subject invention stabilizes the olefin-based block copolymer. More specifically, the method of the subject invention stabilizes the olefin-based block copolymer with a dispersing mechanism. To adequately stabilize the olefin-based block copolymer, the method includes the steps of providing the olefin-based block copolymer, and circulating the olefin-based block copolymer through the dispersing mechanism such that a particle size of the olefin-based block copolymer is less than 15 microns and the olefin-based block copolymer is thixotropically stable. The dispersing mechanism imparts shear and work on the olefin-based block copolymer to reduce its particle size. This method, and particularly the step of circulating the olefin-based block copolymer through the dispersing mechanisms described below, surprisingly provided an olefin-based block copolymer having the particle size of less than 15 microns and suitable thixotropic stability, which were both unexpected results. The terminology thixotropic stability is described below.
In addition to thixotropic stability, the olefin-based block copolymer processed according to the method of the subject invention has superior shelf stability. That is, after circulation of the olefin-based block copolymer through the dispersing mechanism, the olefin-based block copolymer has a shelf stability, at temperatures ranging from 66° F. to 77° F., of from 1 to 365 days. As such, the olefin-based block copolymer processed according to the subject invention is sufficiently stable as it is present in the organic solvent. That is, the olefin-based block copolymer does not settle out into the organic solvent. More specifically, the olefin-based block copolymer, reacted with the e-caprolactone, and the CPO and epoxy resin, do not settle out into the organic solvent.
Typical organic solvents that are utilized in the adhesion copolymer include, but are not limited to, xylene, toluene, methyl ethyl ketone, methyl isobutyl ketone, and the like, including combinations of such organic solvents. However, it is a further objective of the present invention to ensure that the olefin-based block copolymer remains stable in alternative organic solvents which are generally ‘weaker’ than the organic solvents set forth above. Examples of these alternative organic solvents include, but are not limited to, aromatic 100, SC150, and the like.
Preferably, the dispersing mechanism is further defined as an inline dispersing mechanism. As such, the step circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer through the inline dispersing mechanism. To circulate the olefin-based block copolymer through the inline dispersing mechanism, a pump is utilized to continuously pump the olefin-based block copolymer into and out of the inline dispersing mechanism. In this particular embodiment, where an inline dispersing mechanism is utilized, the olefin-based block copolymer is preferably circulated through the inline dispersing mechanism at a flow rate of from 30 to 120, more preferably from 40 to 60, and most preferably from 50 to 54, ml/min. At the flow rate of from 30 to 120 ml/min, the preferred inline dispersing mechanisms rotate at from 11,000 to 24,000, most preferably 24,000, revolutions per minute (RPMs). Suitable inline dispersing mechanisms, include, but are not limited to, the Ultra-Turrax® 25 and the Ultra-Turrax® 50 Basic Inline Dispersers, which are both commercially available from IKA-Werke GmbH & Co. KG, Staufen, Germany or IKA Works, Inc., Wilmington, N.C. These inline dispersing mechanisms typically utilize the S 25 KV G IL dispersing tool or element.
Although the preferred dispersing mechanism is an inline dispersing mechanism, it is to be understood that the dispersing mechanism is not limited to inline dispersing mechanism. Instead, it is possible that the dispersing mechanism is further defined as a batch dispersing mechanism. In this case, the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block through the batch dispersing mechanism. To circulate the olefin-based block copolymer through the batch dispersing mechanism, the pump is utilized to pump the olefin-based block copolymer into and out of the batch dispersing mechanism. Suitable batch dispersing mechanisms, include, but are not limited to, the Ultra-Turrax® T 25 and T 65 D batch dispersers, which are both commercially available from IKA-Werke GmbH & Co. KG and IKA Works, Inc.
Because the olefin-based block copolymer is prepared at an approximate temperature of 145° C., the olefin-based block copolymer is provided, prior to circulation through the dispersing mechanism, at a temperature greater than 60° C. As a result, when the olefin-based block copolymer is circulated through the dispersing mechanism, the temperature of the olefin-based block copolymer decreases and ranges from 60° C. to 38° C. This cooling of the olefin-based block copolymer can be passive or can be active. That is, the temperature can decrease gradually based on the time that the olefin-based block copolymer is circulated through the dispersing mechanism, or the temperature can be actively decreased by the inclusion of a cooling mechanism, such as an ice bath and the like, prior to the dispersing mechanism. If the cooling mechanism is included, it is preferred that the olefin-based block copolymer is circulated through the cooling mechanism prior to circulation of the olefin-based block copolymer through the dispersing mechanism.
As initially described above, circulation of the olefin-based block copolymer through the dispersing mechanism of the subject invention provides an olefin-based block copolymer that is less than 15 microns. However, it is more preferred that the olefin-based block copolymer is circulated through the dispersing mechanism such that the particle size of the olefin-based block copolymer is less than 10 microns, and it is most preferred that the olefin-based block copolymer is circulated through the dispersing mechanism such that the particle size of the olefin-based block copolymer is less than 5 microns. A particle size of less than 5 microns is ideal because a solventborne primer surfacer is typically spray applied on a substrate, such as a TPO substrate, to a film build of 6 to 9 microns and it would be undesirable for the particle size of the olefin-based block copolymer to be greater than the film build.
Overall, it is an objective to reduce the particle size of the olefin-based block copolymer by at least 50%, as compared to a particle size of the olefin-based block copolymer prior to circulation through the dispersing mechanism. Of course, with particle sizes of the preferred olefin-based block copolymer, POLYTAIL™ , in excess of 50 and even 100 microns, the particle size of the olefin-based block copolymer is frequently reduced by well over 50%. As understood by those skilled in the art, the particle size of the olefin-based block copolymer is evaluated by a ‘grind check’ with a standard Hegrnan Gauge.
The reduction in the particle size guarantees thixotropic stability. For purposes of the subject invention, the terminology thixotropic describes a physical property of the olefin-based block copolymer wherein the copolymer becomes increasingly fluid upon being disturbed, for example, as by stirring, agitation, or circulation through the dispersing mechanism. Therefore, the olefin-based block copolymer has a viscosity which is shear dependent. When the olefin-based block copolymer is at rest, or subjected to relatively low agitation, the viscosity of the olefin-based block copolymer tends to be very high. On the other hand, the same copolymer, when subjected to more work in the form of stirring, agitation, or circulation through the dispersing mechanism, has a much lower viscosity. As is known to those skilled in the art, the relationship between the degree of work introduced upon the copolymer and the viscosity has a time dependency. A thixotropic system, such as the olefin-based block copolymer stabilized in the method of the subject invention, can be rapidly disturbed thus lowering the viscosity a substantial amount. Then, if the disturbance is removed and the thixotropic system is allowed to rest, the system will rebuild its internal association structure and the viscosity will increase. This is a cyclic process that can be repeated indefinitely.
For purposes of the subject invention, the terminology thixotropic stability describes an olefin-based block copolymer that has been circulated through the dispersing mechanism and has a thixotropic index ranging from 0.1 to 4.0 at 25° C. for particle sizes of less than 15 microns. More specifically, it is believed that the thixotropic indices outlined in the following table for specific particle sizes are necessary for thixotropic stability.

Particle Size of Expected Thixotropic Index

Olefin-Based Block Copolymer Necessary for Thixotropic Stability

0 to 4 0.1 to 1.4

5 to 9 1.5 to 1.9

10 to 15 2.0 to 3.5

Of course, as understood by those skilled in the art, the degree of thixotropic stability, i.e., the value of the thixotropic index, that is necessary to maintain particles of the olefin-based block copolymer in solution with the organic solvent may vary depending on the particle size of the olefin-based block copolymer. However, as the above table reveals, it is unlikely that a thixotropic index of 3.5 or less will be sufficient to maintain thixotropic stability when the particle size of the olefin-based block copolymer exceeds 15 microns.
As understood by those skilled in the art, the thixotropic index is a value that is obtained by dividing a viscosity of a particular system, such as the olefin-based block copolymer, obtained at a low shear rate, by the viscosity of the same system, obtained at a high shear rate. The larger the thixotropic index is, the more thixotropic stability a system will have.
The example included in the following table generally illustrates the thixotropic index and thixotropic stability:

System A System B

Shear Rate Viscosity Shear Rate Viscosity

LOW 1 RPM 75 dPas 1 RPM 120 dPas

HIGH 100 RPM 15 dPas 100 RPM 100 dPas

Thixotropic Index 5.0 1.2

Based on Systems A and B in the above table, System A has a larger the thixotropic index and is, therefore, more thixotropically stable.
As a result of the method of the subject invention, the adhesion copolymer, specifically the olefin-based block copolymer in the solvent, is thixotropically stable and can, therefore, be stored over time and subsequently used as a separate additive to be incorporated into various coating compositions, including solventborne primer surfacers as well as other intermediate coating compositions. As the adhesion copolymer is stored, it remains a thixotropic gel and then, upon subsequent stirring, agitation, shaking, or other mixing, a viscosity of the adhesion copolymer decreases, i.e., the adhesion copolymer ‘thins down’, and the thinned-down adhesion copolymer can be incorporated into the intermediate coating composition.
In the various embodiments of the subject invention, it is to be understood that the olefin-based block copolymer can be circulated, in one, discrete pass through the dispersing mechanism. This is referred to as a batch process. Alternatively, the olefin-based block copolymer can be circulated through the dispersing mechanism in more than one pass. This is referred to as a re-circulation process. Although the re-circulation process is easier to run, the batch process is more preferred because the ultimate particle size of the olefin-based block copolymer is more uniform and can be more effectively controlled.
The following examples illustrating the stabilization of the adhesion copolymer, more specifically illustrating the stabilization of the olefin-based block copolymer, with the dispersing mechanism according to the subject invention, as presented herein, are intended to illustrate and not limit the invention.

EXAMPLES

The method of stabilizing according to the subject invention, as disclosed in Examples 2-4, was applied to the following adhesion copolymer, which is defined by the olefin-based block copolymer, an organic solvent, and other components including CPO. Examples 1 and 5 are comparative examples as described below.

Amount

Component (grams)

Polytail ™ H 502.35

E-Caprolactone 214.70

Aromatic 100 4,425.00

Stannous Octoate 1.26

CPO 358.52

Epoxy Resin 7.17

Total 5,509.00
This adhesion copolymer was made as described above.

Example 1



			Post Grind
Initial Grind		Rotation of	Temperature of
Temperature of	Initial	Dispersing	Adhesion	Post
Adhesion Copolymer	Grind	Mechanism	Copolymer	Grind
(° C.)	(μm)	(RPM)	(° C.)	(μm)

23	˜40	24K	23	˜24

In Example 1, the adhesion copolymer was circulated through the dispersing mechanism, specifically an Ultra-Turrax® 25 Basic Inline Disperser, for one pass, i.e., in a batch process. The particle size, as evidenced by a grind check with a Hegman Gauge, decreased from approximately 40 microns to approximately 24 microns.
After only one pass and with the particle size at approximately 24 microns, the adhesion copolymer of Example 1 did not demonstrate thixotropic stability. In this, and the following examples, thixotropic stability was determined as described immediately below.
After circulating the adhesion copolymer, including the olefin-based block copolymer, through the inline dispersing mechanism, the adhesion copolymer is generally of a very low viscosity, e.g., 30 centipoise. A 20 cc retain vial was then filled ¾ by volume with the adhesion copolymer that had been dispersed. Consequently, an air bubble was trapped within the remaining volume of the 20 cc retain vial. This retain vial was allowed to set at rest for at least 18 hours. Following this 18 hour rest period, two steps were conducted to determine if a thixotropically stable adhesion copolymer and olefin-based block copolymer were present. In the first step, the retain vial was inverted and visually evaluated to determine the flow behavior of the adhesion copolymer. If the air bubble in the vial does not travel freely through the adhesion copolymer, due to an increase in the viscosity generally up to approximately 150 centipoise, over the 18 hour period, then the second step was conducted. In the second step, the retain vial is shaken vigorously to simulate work put into the adhesion copolymer including the olefin-based block copolymer within it. The retain vial is again inverted and visually evaluated to determine the flow behavior of the adhesion copolymer and the olefin-based block copolymer within it. If the air bubble in the vial travels more freely in the second step, then the viscosity of the adhesion copolymer has decreased as a result of the inputted work. Finally, when the adhesion copolymer is again rested for an extended period of time, the viscosity of the adhesion copolymer increases, thereby exhibiting thixotropic stability.
As described above, after only one pass and with the particle size at approximately 24 microns, the adhesion copolymer of Example 1 did not demonstrate thixotropic stability according to the evaluation criteria outlined immediately above.

Example 2



			Post Grind
Initial Grind		Rotation of	Temperature of
Temperature of	Initial	Dispersing	Adhesion
Adhesion Copolymer	Grind	Mechanism	Copolymer	Post Grind
(° C.)	(μm)	(RPM)	(° C.)	(μm)

23	˜40	24K	29	˜13

In Example 2, the adhesion copolymer was continuously circulated through the dispersing mechanism, specifically an Ultra-Turrax® 25 Basic Inline Disperser, for approximately 30 minutes in a re-circulation process. The particle size, as evidenced by a grind check with a Hegman Gauge, decreased from approximately 40 microns to approximately 13 microns. After circulation for approximately 30 minutes, the adhesion coplymer of Example 2 demonstrated thixotropic stability according to the evaluation above.

Example 3



			Post Grind
Initial Grind		Rotation of	Temperature of
Temperature of	Initial	Dispersing	Adhesion	Post
Adhesion Copolymer	Grind	Mechanism	Copolymer	Grind
(° C.)	(μm)	(RPM)	(° C.)	(μm)

23	˜40	24K	30	˜12

In Example 3, the adhesion copolymer was continuously circulated through the dispersing mechanism, specifically an Ultra-Turrax® 25 Basic Inline Disperser, for approximately 60 minutes in a re-circulation process. The particle size, as evidenced by a grind check with a Hegman Gauge, decreased from approximately 40 microns to approximately 12 microns. After circulation for approximately 60 minutes, the adhesion colploymer of Example 3 demonstrated thixotropic stability according to the evaluation above.

Example 4



			Post Grind
Initial Grind		Rotation of	Temperature of
Temperature of	Initial	Dispersing	Adhesion	Post
Adhesion Copolymer	Grind	Mechanism	Copolymer	Grind
(° C.)	(μm)	(RPM)	(° C.)	(μm)

70	˜50	24K	33	<10
(Example 4A)
33	<10	24K	29	0
(Example 4B)

In Example 4A, the adhesion copolymer was continuously circulated through the dispersing mechanism, specifically an Ultra-Turrax® 25 Basic Inline Disperser, for approximately 40 minutes in a re-circulation process. The pump setting for the Ultra-Turrax® 25 Basic Inline Disperser was set to 5 which is equivalent to approximately 54 mi/mn. The particle size, as evidenced by a grind check with a Hegman Gauge, decreased from approximately 50 microns to less than 10 microns. The thixotropic stability of Example 4A was not investigated.
In Example 4B, the adhesion copolymer was continuously circulated through the dispersing mechanism, specifically an Ultra-Turrax® 25 Basic Inline Disperser, for an additional 60 minutes in a re-circulation process. The pump setting for the Ultra-Turrax® 25 Basic Inline Disperser was set to 5 which is equivalent to approximately 54 ml/min. The particle size, as evidenced by a grind check with a Hegman Gauge, decreased from<10 microns to 0 microns. In other words, the grind check was clean. After this additional circulation for 60 minutes, the adhesion copolymer of Example 4B was investigated and demonstrated thixotropic stability according to the evaluation criteria outlined above. Furthermore, the adhesion copolymer of Example 4B processed according to the method of the subject invention had a shelf stability with no settling at Room Temperature of 365 days.

Example 5



			Post Grind
Initial Grind		Rotation of	Temperature of
Temperature of	Initial	Dispersing	Adhesion	Post
Adhesion Copolymer	Grind	Mechanism	Copolymer	Grind
(° C.)	(μm)	(RPM)	(° C.)	(μm)

Room Temperature	50-100	Not	Not	Not
(appx. 20-21° C.)		Applicable	Applicable	App.

In Example 5, the adhesion copolymer was not circulated through any dispersing mechanism. The particle size, as evidenced by a grind check with a Hegrnan Gauge, ranged anywhere from 50 to 100 microns. Without circulation and with the particle size ranging from 50 to 100 microns, the adhesion copolymer of Example 5 did not demonstrate thixotropic stability according to the evaluation criteria outlined above. The adhesion copolymer of Example 5 had unacceptable shelf stability with significant settling (visual) within 20 to 60 days.
As alluded to above, Examples 1 and 5 are comparative examples. In Example 5, the adhesion copolymer was not circulated through any dispersing mechanism and the results were unacceptable as described immediately above. On the other hand, in Example 1, although the adhesion copolymer was circulated through the for one pass, the particle size of the adhesion copolymer was above 15 microns at 24 microns. Consequently, the adhesion copolymer of Example 1 did not demonstrate thixotropic stability.
The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings, and the invention may be practiced otherwise than as specifically described.

Claims

1. A method of stabilizing an olefin-based block copolymer with a dispersing mechanism wherein the olefin-based block copolymer has an olefin block that is substantially saturated and at least one (poly)ester or (poly)ether block, said method comprising the steps of:

providing the olefin-based block copolymer; and

circulating the olefin-based block copolymer through the dispersing mechanism such that a particle size of the olefin-based block copolymer is less than 15 microns and the olefin-based block copolymer is thixotropically stable.

2. A method as set forth in claim 1 wherein the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer through the dispersing mechanism at a temperature of from 60° C. to 38° C.

3. A method as set forth in claim 1 wherein the step of providing the olefin-based block copolymer is further defined as providing the olefin-based block copolymer at a temperature greater than 60° C.

4. A method as set forth in claim 3 wherein the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer through the dispersing mechanism at a temperature of from 60° C. to 38° C.

5. A method as set forth in claim 1 wherein the dispersing mechanism is further defined as an inline dispersing mechanism and the step circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer through the inline dispersing mechanism.

6. A method as set forth in claim 5 wherein the step of circulating the olefin-based block copolymer through the inline dispersing mechanism is further defined as continuously pumping the olefin-based block copolymer through the inline dispersing mechanism.

7. A method as set forth in claim 5 wherein the step of circulating the olefin-based block copolymer through the inline dispersing mechanism is further defined as circulating the olefin-based block copolymer through the inline dispersing mechanism at a flow rate of from 30 to 120 ml/min.

8. A method as set forth in claim 1 wherein the dispersing mechanism is further defined as a batch dispersing mechanism and the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block through the batch dispersing mechanism.

9. A method as set forth in claim 8 wherein the step of circulating the olefin-based block copolymer through the batch dispersing mechanism is further defined as pumping the olefin-based block copolymer into and out of the batch dispersing mechanism.

10. A method as set forth in claim 1 wherein the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer through the dispersing mechanism such that the particle size of the olefin-based block copolymer is less than 10 microns.

11. A method as set forth in claim 1 wherein the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer through the dispersing mechanism such that the particle size of the olefin-based block copolymer is less than 5 microns.

12. A method as set forth in claim 1 wherein the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer through the dispersing mechanism such that the particle size of the olefin-based block copolymer is reduced by at least 50%, as compared to a particle size of the olefin-based block copolymer prior to circulation through the dispersing mechanism.

13. A method as set forth in claim 1 wherein the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer in one, discrete pass through the dispersing mechanism.

14. A method as set forth in claim 1 wherein the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer through the dispersing mechanism in more than one pass.

15. A method as set forth in claim 1 further comprising the step of circulating the olefin-based block copolymer through a cooling mechanism prior to the step of circulating the olefin-based block copolymer through the dispersing mechanism.

16. A method as set forth in claim 1 wherein the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer through the dispersing mechanism such that a thixotropic index of the olefin-based block copolymer ranges from 0.1 to 4.0 at 25° C. for particle sizes of less than 15 microns.

17. A method as set forth in claim 1 wherein the step of circulating the olefin-based block copolymer through the dispersing mechanism is further defined as circulating the olefin-based block copolymer through the dispersing mechanism such that a shelf stability of the olefin-based block copolymer ranges from 1 to 365 days at 66° F. to 77° F.

18. A method as set forth in claim 1 further comprising the step of providing a solvent in combination with the olefin-based block copolymer prior to circulation of the olefin-based block copolymer through the dispersing mechanism.

19. A method as set forth in claim 18 further comprising the step of providing e-caprolactone and a catalyst in combination with the olefin-based block copolymer and the solvent prior to circulation of the olefin-based block copolymer through the dispersing mechanism.

20. A method as set forth in claim 19 further comprising the step of providing an additive in combination with the olefin-based block copolymer, the solvent, the e-caprolactone, and the catalyst prior to circulation of the olefin-based block copolymer through the dispersing mechanism, wherein the additive is selected from the group consisting of chlorinated polyolefin, epoxy resin, and combinations thereof.