MXPA01002139A - Powder slurry composition containing particulate carbamate functional compounds - Google Patents

Abstract

The invention provides a powder slurry composition having a particulate component (a) dispersed in a liquid component (b). Component (a) comprises a solid or particulate compound (i) comprising the reaction product of a polyisocyanate (A) and a compound (B). Polyisocyanate (A) is of the formula [R(NCO)y]x, where x=1 or higher, y=2 or higher, and R has Cn symmetry when n=2 or higher. Compound (B) comprises both an isocyanate-reactive group and a functional group selected from thegroup consisting of a carbamate group and groups convertible to a carbamate group after reaction of compound (B) with polyisocyanate (A). One or both of component (a) and (b) comprise a crosslinking agent (ii) reactive with particulate compound (i).

Description

' COMPOSITION OF POWDER SUSPENSION CONTAINING FUNCTIONAL COMPOUNDS OF CARBAMATE IN PARTICLES Field of the Invention The present invention relates to powdered suspension compositions containing solid, particulate carbamate functional compounds. The invention provides a powder suspension composition comprising a component (a) in particles dispersed in a liquid component (b).

BACKGROUND OF THE INVENTION Powder suspension compositions have been used to provide a variety of advantages in the 'coating of articles. Powder suspension compositions typically include a first component that is in solid particulate form and a second component that is liquid. The first component is dispersed in the second component to provide A suspension that can be applied using conventional spray application equipment and techniques, Aqueous powder slurry compositions provide the advantages of powder coating compositions with the ease of "application of coatings carried by traditional solvent. As a result. Powder suspension compositions have the potential for environmental and / or financial advantages. However, powder slurry compositions can present manufacturing, operation and / or application challenges. Traditional powder slurry compositions often utilize epoxy acid compound systems. These systems can sacrifice resistance to rapping and damage in order to obtain acceptable water resistance, chipping resistance and etch resistance. The nature of the powder coating composition used in the powder suspension composition requires the use of initial temperatures above the Tg of the powder resin, followed by temperatures sufficient to effect crosslinking. In this way, high cure programs are often required. It will be noted that application rates and energy costs encourage the use of powder slurry compositions having lower Tg resins. The use of lower Tg resins facilitates faster flow, improved appearance and lower cure temperatures. However, storage and fabrication problems can result when powder suspension compositions having lower Tg resins are used. Manufacturing is particularly challenging, especially with epoxy acid compound systems. The separation, precipitation and / or agglomeration of the solid particulate component during storage can also be observed. The lower film adhesion and / or cracking of the powder slurry film applied during curing is sometimes observed, particularly when the powder slurry is applied over a previously applied coating. These negative performance characteristics can be enlarged by accumulations of Superior film and storage stability. Finally, the finished films obtained from the powder slurry compositions may exhibit variable luster and / or lower performance characteristics, particularly when balancing scratch resistance and water resistance damage, chipping resistance and etch resistance. It is often difficult to achieve an acceptable balance of properties between these characteristics, especially with traditional epoxy acid / powder slurry compound systems.

In this way it is desirable to provide improved powder suspension compositions, wherein the above disadvantages are eliminated or reduced to a minimum. The efforts of the prior art so far have not been successful. It is expected that the use of one or more functional carbamate resins in particles will provide powder suspension compositions having an advantageous balance of properties.

SUMMARY OF THE INVENTION The invention provides a powder suspension composition having a particulate component (a) dispersed in a liquid component (b). Component (a) comprises a solid or particulate compound (i) comprising the reaction product of a polyisocyanate (A) and a compound (B). The polyisocyanate (A) TS of the formula [R (NCO) y] x, where x = 1 or higher, y = 2 or higher, and R has symmetry d, when n = 2 or higher. The compound (B) comprises both a reactive isocyanate group and a functional group selected from the group consisting of a carbamate group and groups convertible to a carbamate group after the reaction of the compound (B) with polyisocyanate (A) , One or both of component (a) and component (b) will comprise at least one crosslinking compound (ii).

Detailed Description of the Invention The powder suspension composition of the invention requires two components, a first component (a) in solid or particulate form which is dispersed in a liquid component (b). The first component (a) comprises a particulate compound (i) comprising the reaction product of a polyisocyanate (A) and a compound (B). The polyisocyanate (A) has a Tg _ < _ 30aC and is of the formula [R (NCO) y] x, where x =; 1 or higher, y = 2 or higher, and R has symmetry C when n = 2 or higher. The compound (i) of the invention is particularly suitable for use in powder suspension coating compositions. While not wishing to be limited to a particular theory, the particular advantages of the compound (i) are believed to be partly ST to the polyisocyanate (A), the polyisocyanate (A) is of the formula [R (NCO) and] " , where x = 1 or higher, y = 2 or higher, and R has symmetry Cn where n = 2 or higher. In this way, the isocyanate (A) is monomeric when x = 1, a dimer of urethretone or polyisocyanate if x = 2, an isocyanate when x = 3, or a polymorphic homopolymer if x is greater than 3. x can be 1 or higher, but is preferably 1, 2, or 3, more preferably x = 1 or 3, and more preferably, x = 3, and may be 2 or higher, but is preferably 2, 3, or 4 and it is more preferably 2. As indicated above, R must have a particular symmetry in order to provide a polyisocyanate (A) suitable for use in the present invention. As used herein, a molecule with symmetry means that certain parts of the molecule can be exchanged, through an operation of symmetry, with others without altering the identity or orientation of the molecule. Symmetry operations are geometrically defined ways of exchanging equivalent parts of a molecule. However, these operations are symmetry operations if, and only if, the appearance of the molecule is exactly the same in relation to the pre- and post-symmetry operation view. In this way, the term "symmetric" as used herein refers to a molecular having an appearance appears identical in relation to the views of pre- and post-symmetry operation, Put another way, "[a] The molecule has an element of symmetry if the application of the operation generated by the element leaves the molecule in a non-distinguishable state. " Molecular Symmetry and Group Theory, Alan Vincent, Wiley & Sons, NY, 1977, reprinted 1981, page 21, incorporated herein by reference. The present application relates only to the appropriate rotation symmetry operations. Appropriate rotation, also referred to as "CJJ refers to simple rotation about an axis that passes through the molecule by an angle 2 p / n 'or an angle of 360s / n. A molecule is said to have a symmetry element Cn if after undergoing a proper rotation Cn operation, its appearance is not distinguishable from its appearance before undergoing the Cn rotation itself, independently of the conformational isomers. Put another way, a molecule has an element of symmetry, in this case C ", when one or more of its conformational isomers has that element of symmetry. The highest symmetry element that belongs to any conformational isomer of the molecule is assigned to the molecule. Although it can be seen that all molecules have symmetry, where n is 1, the present application is only interested in groups R that also have symmetry Cb, where n is 2 or higher.

For example, .the two most common conformational isomers of cyclohexane they are the chair which has its own rotation axis C3, and the formation of a which has an own rotation E C? . As a result. the cyclohexane can be defined as having a molecular rotation axis C3 (C ", where n = 3) without having to define its conformation. Similarly, hexane; with the freedom of movement around its numerous simple links can exist in a large number of configurations such as the one that follows One of the isomers of hexane conformation (shown below) has its own rotation axis C-. Therefore, it can be said that hexane has a molecular symmetry element C (where n = 2). c, P is an alkyl or cycloalkyl group having at least four carbons and a particular symmetry as described in the present. Preferably, R will be an alkyl group having from four to 11 carbon; and more preferably R will be an alkyl group having four to eight carbons R preferably it will be an alkyl group of the formula CnH..D Examples of illustrative P groups include C, HB and C6H | 2 A particularly preferred group is C (, H, Illustrative examples of appropriate R groups include alkyl groups such as: -X where 'X' marks the location of an isocyanate group Examples of suitable polyisocyanates for use as a polyisocyanate (Aj include d-6-hexane dusocyanate d-m-tetramethyl xylene d? c? clohexylmethane dusocyanate -4 4'-diisocyanate, dusccianato -e 1,4-butane l-? Soc? Anato-2.2 '- (b? S? Soc? Ana or et? L) propar or 1 -d?? Soc? Anato-4 The respective dimers of the same, the respective trimers of the same and mixtures thereof, are preferred. The preferred polysaccharides DS (Á) are 1-? Soc? Anato-l, 1 '(bis The 1,6-hexapc dusocyanate of m-tetramet and Ixylene and the respective dimers thereof, the respective trimers thereof, are most preferred as the poly-isocyanate IA) is 1,6-hexane dusocyanate the respective dimers the respective trimers thereof Compound (B) is a compound containing an isocyanate-reactive group and either a carbamate group or a conv group ertible or capable of becoming a carbamate group after the reaction of the compound (B) is completed with polyisocyanate (A). The compound (B) is preferably a compound containing an isocyanate-reactive group and a carbamate group. The compounds containing an isocyanate-reactive group and a carbamate group are preferably hydroxyalkyl carbamates such as hydroxypropyl carbamate or hydroxybutyl carbamate. or aminoalkyl carbamate groups such as aminoethyl carbamate, aminopropyl carbamate and the like. The compounds that. contain a group reactive with isocianat? and a group convertible or capable of converting to a carbamate group after the reaction of the compound (B) with the polyisocyanate (A) is complete, includes cycloalcarbon carbonate containing compounds convertible to carbamate by reaction with ammonia (v. g ,, the reaction product of glycidol and C02), monoglycidyl ethers (e.g., glycidylpropyl ether convertible to carbamate by reaction with C02 and then ammonia), allyl alcohols wherein the alcohol group is reactive with NCO and the double bond can be converted into carbamate by reaction with peroxide, and vinyl esters wherein the ester group is reactive with NCO and the vinyl group can be converted to carbamate with reaction with peroxide, then C02, and then ammonia. Also suitable as compound (B) are compounds having a carbamate group as well as a group which can be converted to carbamate. The carbamate group can then be reacted with the isocyanate group to form an allophanate. The group convertible to carbamate can then be converted to a carbamate. An example of said compound is allyl carbamate. Preferably, the compound (B) will be a hydroxyalkyl carbamate compound having an alkyl group of 2 to 6 carbons, especially 2 to 4 carbons. More preferably, (B) will be hydroxypropyl carbamate. The compound (i) of the invention will preferably have a molecular weight of 350 to 1900 and more preferably of 460 to 900. The equivalent weight per carbamate functional group can vary from 175 to 450 and preferably from 175 to 350. The compound (i) will typically have no acid or hydroxy groups. Compound (i) is usually a solid at 252C. the term "solid" referring to a substance of defined shape and relatively large density, low internal enthalpy, and great cohesion of its molecules, Grant & amp;; Hackhs's Chemical Dictionary, Fifth Edition McGra-Hill, Inc. p, 541, Compound (i) will typically have a Tg _ > _ 30eC. The compound (i) of the invention will typically be processed in one or more solid masses, for example sheets, rolls, or drops, by accepted powder compound manufacturing techniques. After solidifying, the mass is broken into particles having the desired size and configuration. The size and configuration of the composite particles depends on the considerations of handling, processing and equipment. Preferably, the compound (i) will be in the form of flakes or flat discs having regular or irregular dimensions. Particles having an average particle size of 2.54 to 7.62 centimeters are preferred, with average particle sizes from 1 micron to 2.54 centimeters more preferred. The particle size as used herein refers to the average diameter of an object having irregular boundaries that can be determined with known test methods. It will be noted that the particulate component (a) is preferably a powder coating comprising the compound (i), before dispersion in the liquid component (b). component (a) must have an average particle size of 0.1 to 100 microns. A preferred average particle size scale for component (a) at this time is 3 to 60 microns. An average particle size of 30 to 45 microns as most preferred. Traditional extrusion and grinding processes can be used to obtain the component (a) in particles within these scales. Compound (i) may initially have an average particle size on or off this scale, resulting from known powder compound manufacturing techniques. The first solid particulate component (a) after mixing with component (b) liquid will typically be discussed subsequently in order to reduce the above particle sizes to those more desirable for a powder suspension composition. Once in combination with component (b), the powder suspension composition can be subjected to a particle size reduction treatment such as wet milling, microfluidization, cavitation, or other high-temperature, low-temperature cutting techniques known to those experienced in the art. In this way, the particle size of the powder suspension composition of the invention after a size reduction treatment of. The particle is typically 0.1 to 20 microns, more preferably 0.1 to 15 microns, and more preferably, it will have an average particle size of 0.1 to 12 microns. Component (a) can be obtained in accordance with techniques and conventional methods. The compositions of the invention are advantageous because the compound (i) allows the use of higher processing temperatures. In addition, during the preparation of the component (a) in solid particles, or after the same, pigments, pigment dispersions, modifiers, dispersion aids, regulators, flow modifiers, fillers, and / or additives can optionally be added as is desired The liquid component (b) can be one or more liquids or solvents suitable for the dispersion of the particulate compound (a). Examples of suitable liquids or solvents include water, water soluble solvents, and organic solvents and mixtures thereof. Illustrative water soluble solvents are alcohols. Examples of illustrative water soluble solvents and / or organic solvents are ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methanol, ethanol, isopropanol, n-butanol, secondary butanol, tertiary butanol, dimethylformamide, etc. Preferred liquids to be used are water, alcohols and mixtures thereof. A preferred liquid component (b) is water. Such solvents will typically be used in amounts of 0 to 10, based on the total passage of the powder suspension, and preferably from 0 to 1.0%. The weight ratio of component (a) and component (bj) is usually from 90:10 to 50.50, preferably from 75:25 to 60.40, in terms of solid component The powder slurry composition of the invention may further comprise components additional optionals such as one or more solvents or additives such as pigments, fillers, catalysts, corrosion inhibitors, modifiers, dispersants, flow additives, and mixtures thereof These materials can be incorporated into component (a), component (b) or the mixture thereof, For the preparation of the powder slurry composition of the invention, the required and optional components can be combined in an optional order and mixed well by conventional processes. it can be mixed with component (a) and a pigment and, if necessary, in addition with other optional components.Alternatively, the pigment can be mixed with component (b) for Ormar a pigment paste, which is then mixed with a mixture of component (a) and component (b). A grinding or milling operation can follow said mixture. A preferred method of manufacture is described in U.S. Patent 5,379,947, incorporated herein by reference. The powder slurry composition of the invention advantageously has low VOCs as a result of the unexpected benefits of the components of the invention. The powder slurry composition of the invention can be applied by spraying or by electrostatic deposition and are useful both as basecoat and topcoat applications. It is expected that the resulting coating compositions form uniform films with advantageous performance properties. One or both of component (a) and component (bi) will comprise a crosslinking agent (ii) reactive with the particulate compound (i) The crosslinking agent (ii) may be in-lye. liquid or solid form at the time of incorporation into component (a), component (b) or mixture thereof. The use of crosslinking agent (ii) in liquid form and incorporated into the liquid component (b) is most preferred. Illustrative examples of crosslinking agent (ii) include one or more compounds having a plurality of functional groups that are reactive with compound (a). Suitable reactive groups include active methylol or methylalkoxy groups on aminoplast crosslinking agents or on other compounds such as phenol / formaldehyde adducts, acrylamide groups, isocyanate groups, siloxane groups, cyclic carbonate groups, and anhydride groups, examples of at least one crosslinking compound (n) includes melamine formaldehyde compound (including monomorphous or polymorph melamine compound or partially or completely alkylated melamine resin), urea resins (e.g., methylol ureas such as urea formaldehyde resin) , alkoxy ureas such as butylated formaldehyde urea resin), polymers having acrylamide groups, polymers having methylol or alkoxymethyl groups, polyanhydrides (v. gr., polysuccinic anhydride), and polysiloxanes (v. gr, trimethoxy siloxane). Low monomeric and / or oligomeric aminoplast resins such as melamine formaldehyde resins or urea formaldehyde resins are especially preferred. The ratio of equivalents of compound (a) to equivalents of crosslinking agent (ii) is about 0.5.1.0 (a: b) to 1.5: 1.0, preferably from about 0.8: 1.0 to 1.2: 1.0, the compositions Powder suspension of the invention can be applied by spraying or by electrostatic deposition and are useful both as basecoat and topcoat applications. It is expected that the resulting coating compositions form films that have an acceptable appearance with advantageous performance properties. The powder slurry compositions of the invention can be applied to a variety of substrates for use in various end-use applications such as automotive, furniture, industrial, lawns and gardens, household appliances, electrical equipment and the like. Suitable substrates include metal, plastic, wood, ceramics, compounds and mixtures thereof. Metal and / or plastic substrates are preferred Substrates will preferably be cleaned prior to the application of the powder coating. The substrates can be pre-treated optionally with phosphating, chromatization and similar pretreatment methods to improve adhesion and / or appearance. It will be noted that the selection of pretreatment depends on the desired substrate and the end-use application. After application, the coated part is subjected to a curing program sufficient to effect flow and curing. As used in the present "curing program" it refers to the 'ratio of time / temperature required to effect the complete curing of a thermosettable powder coating. Typical curing schedules for the powder coatings of the invention involve part temperatures of 121 to 204SC (250 to 400aF) and part-time of 10 to 30 minutes. Preferred curing programs are from 121 to 2042C (250 to 400aF) and part-time from 10 to 20 minutes. The inventions are further described in the following non-limiting examples.

Example 1 Preparation of compound in accordance with. The invention A mixture of 139.9 parts of hydroxypropyl carbamate, 98.8 parts of 1,6-haxendiisocyanate (HDI), 10.5 parts of toluene and 0.8 parts of tin octoate was mixed and heated until a reaction occurred. Exothermic the maximum temperature for the reaction mixture was maintained below 100aC, 28.5 parts of butyl acetate were added to the resulting solid resin. The mixture was heated until the system was liquid (132gC). When cooled to room temperature, approximately 251C. a solid compound was obtained.

EXAMPLE 2 Prothromatic Preparation of a Powder Suspension Composition According to the Invention Three hundred grams of the compound made in Example # 1 are ground in an ACM mill to an average particle size of 25-35 microns and set aside. One gram of Baex EP-110 (a surfactant, commercially available from Rhodia), is added to 100 grams of Cymel 303 (a hexamyethoxymethyl melamine, commercially available from Cytec) and mixed for 5 minutes with a conventional mixing blade. A stainless steel container with a Cowles mixing blade is loaded with 200 grams of water, keeping the speed low, the following items are added in order: 5 grams of Disperse AYD W-22 (a dispersant, commercially available from Daniel Products), 0.1 grams of Triton XlOO (a nonionic surfactant, commercially available from Union Carbide), 2.5 grams of propylene glycol, and 3 grams of Acrysol RM-8W (a thickener, commercially available from Rhom &Haas). The speed of the mixer is increased to 4 - 500 rpm for 5 minutes before the addition of 132.5 grams of the ground resin. The vessel is allowed to mix for 10 minutes. Then, 43 grams of the above premixed Cymel 303 are added followed by 7 grams of Nacure 5225 (a sulfonic acid catalyst, commercially available from King Industries) and 110 grams of water. The container is mixed for 10 minutes - after which the Cowles blade is replaced by a medium disk mixing blade. Ceramic medium sufficiently small (1.1 - 1.4 mm) is added to the vessel to equal 50% of the volume of the mixture. The temperature of the mixture is maintained at 18-23 C, and it is stirred at 1200 rpm. The particle size is monitored during the time to reach a final average particle size of 4-5 microns. The disk is separated and the medium is removed. filter using 55 micron nylon filter. The viscosity is adjusted to 35-45"Ford cup # 4 with water.

The suspension is sprayed from a conventional siphon spray gun onto a base coat carried by water heated instantaneously but not cured, allowed to evaporate 5 minutes at room temperature and then baked for 20-30 minutes at 132 ° C (270 ° F).

Claims (4)

1. - A powder suspension coating composition comprising (a) a particulate component comprising (i) a particulate compound comprising the reaction product of a polyisocyanate (a) and a compound (B), dispersed in (b) ) a liquid component, wherein the compound (B) comprises an isocyanate-reactive group and a functional group selected from the group consisting of a carbamate group and groups convertible to a carbamate group after reaction of the compound (B) with polyisocyanate (A) and the polyisocyanate (A) has a Tg > _ 30SC and is of the formula [R) NCO) and], where x = 1 or higher, y = 2 or higher, and R has symmetry C where n = 2 or higher.

2. The powder suspension coating composition according to claim 1, wherein R has a molecular weight between 50 and 165.

3. The powder suspension coating composition according to claim 1, wherein x is l, 2, or 3 and y is 2 or 3

4. - The powder suspension coating composition according to claim 1, wherein n is 2. 5, - The powder suspension coating composition according to claim 1, wherein the polyisocyanate (A) is a diisocyanate monomorphic 6, - The powder suspension coating composition according to claim 1, wherein the polyisocyanate (A) is an isocyanurate. 7, - The powder suspension coating composition according to claim 1, wherein the polyisocyanate (A) is selected from the group consisting of 1,6-hexane diisocyanate, m-tetramethyl xylene diisocyanate, dicyclohexylmethane -4,4 '- diisocyanate, 1,4-butane diisocyanate, l-isocyanate-2,2' - (bisisocyanatomethyl) propane, 'respective dimers' thereof, - the respective trimers thereof, and mixtures thereof. 8. The powder suspension coating composition according to claim 1, wherein the compound (B) is a hydroxyalkyl carbamate. 9. The powder suspension coating composition according to claim 8, wherein the compound (B) is hydroxy propyl carbamate. 10. The powder suspension coating composition according to claim 1, wherein one or both of the component (a) and component (b) comprise at least one cross-linking agent (ii) that is reactive with the compound ( i) in particles. 11. The powder suspension coating composition according to claim 1, wherein the crosslinking agent (n) is one or more aminoplast resins. 12. The powder suspension coating composition according to claim 1, further comprising one or more members selected from the group consisting of thickening agents. surfactants, dispersants, and mixtures thereof.