WO1993020121A1

WO1993020121A1 - Novel crosslinker for use in acrylic-based urethane powder coatings

Info

Publication number: WO1993020121A1
Application number: PCT/US1993/000542
Authority: WO
Inventors: Melvin Kaplan; Rose Maria Trapasso; Stephen Craig Lapin; Frank Courtney Briden
Original assignee: AlliedSignal Inc
Current assignee: Honeywell International Inc
Priority date: 1992-03-31
Filing date: 1993-01-21
Publication date: 1993-10-14
Anticipated expiration: 1994-09-30
Also published as: MX9300962A

Abstract

The invention relates to novel crosslinkers which may be used to produce acrylic-based urethane powder coatings having improved flexibility and impact resistance. These coatings may be used in a variety of automotive, decorative and protective industrial and household applications including coatings for bathroom fixtures, furniture builders' hardware and cast aluminum wheels.

Description

NOVEL CROSSLDNKER FOR USE IN ACRYLIC- BASED URETHANE POWDER COATINGS

Fieldofthe Invention

The invention relates to novel crosslin ers which may be used to produce acrylic-based urethane powder coatings having improved flexibility and impact resistance. These coatings may be used in a variety of automotive, decorative and protective industrial and household applications including coatings for bathroom fixtures, furniture builders' hardware and cast aluminum wheels.

Backgroundofthe Invention

Although acrylic-based urethane powder coatings are superior to polyester or epoxy-based urethane coatings in a number of areas including clarity, durability, resistance to UV degradation and chemical and solvent resistance, their use has been limited by their brittleness. Impact resistance and flexibility are key concerns in many applications including automotive trim and outdoor furniture applications.

Currently available crosslinkers do not improve the limited flexibility and impact resistance of the acrylic-based systems. The crosslinkers that have traditionally been employed in acrylic-based powder coating applications either do not contain a polyol component or contain a low molecular weight polyol which when blended with the acrylic resin increase its hardness and ultimately makes the resulting coating somewhat brittle.

In order to compensate for this, some have experimented with such techniques as dual coat dry- over-dry powder coating systems while others have tried to introduce flexibility by adding a polyester resin to the acrylic resin of the coating formulation. These methods, however, have resulted in, at best, only modest improvements in flexibility and impact resistance.

The novel crosslinkers of the invention eliminate this brittleness problem and thus, for the first time, open the door to a range of applications in which acrylic-based urethane powder coatings have traditionally been excluded.

DetailedDescriptionofthe Invention

For purposes of this invention, "acrylic-based urethane powder coating" shall refer to any urethane powder coating in which the resin component of the coating composition comprises an acrylic resin.

A typical acrylic-based urethane powder coating contains an acrylic resin, a crosslinker, fillers or pigments and other additives like surfactants and flow modifiers.

Traditional crosslinkers containing polyols which have been used in acrylic-based urethane powder coatings contain from about 50 to about 60 weight percent polyisocyanate, from about 5 to about 15 weight percent polyol and from about 25 to about 40 weight percent blocking agent and typically have the following properties:

Softening point 100-ll5°C

% NCO, before deblocking < 1.0% % NCO, by wt. after deblocking 14-16% Equivalent weight 263-300

Traditionally, the polyol portion of the crosslinker, when present in the crosslinker, has included such low molecular weight polyols like 1,4- hexanediol, trimethylolpropane, 1,4- cyclohexanedimethanol, ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, dipropylene glycol and trimethylolethane.

As stated above, when these polyols have been used in traditional crosslinker formulations to produce acrylic-based urethane powder coatings, the resulting coatings have been unusually brittle.

We have discovered that by using an organic polyol of the invention in the crosslinker one is able to prepare acrylic-based urethane powder coatings that are unexpectedly flexible and impact resistant while retaining desirable processing and coating properties.

In a crosslinker composition comprising a polyol, polyisocyanate and blocking agent wherein the blocking agent is other than a 1,2-polyol or a monoethylenically unsaturated blocking agent, the improvement comprises utilizing as said polyol an organic polyol or mixture of polyols wherein each polyol has at least two hydroxyl groups, an equivalent weight greater than 250 to about 2500, an acid number of less than about 20 and functional groups solely selected from the group consisting of ester, other than lactones, ether, acrylic, carboxyl and hydroxyl wherein when an acrylic polyol is used, said acrylic polyol is used in combination with a polyol having a functionality solely selected from the group consisting of ester, other than lactones, ethers, carboxyl and hydroxyl which produces a crosslinker composition having less than about 1% by weight unblocked isocyanate, at least about 4% by weight available isocyanate after deblocking and a softening point of from about 75 to about 130*C.

In a preferred embodiment of the invention, the crosslinker has from at least 4 to about 12 weight percent available isocyanate after deblocking and a softening point of from about 85 to about 120°C.

In a more preferred embodiment of the invention, the crosslinker has from about 6 to about 11 weight percent available isocyanate after deblocking and a softening point of from about 105 to about 120°C.

In a still more preferred embodiment of the invention, the crosslinker has from about 7 to about 9 weight percent available isocyanate after deblocking.

In yet a still more preferred embodiment, the invention comprises an organic polyol or mixture of polyols wherein each polyol has an equivalent weight greater than 250 to about 2500, at least 2 hydroxyl groups per polyol, an acid number of less than about 20 and functional groups solely selected from the group consisting of ester, other than lactones, ether, acrylic, carboxyl and hydroxyl wherein when an acrylic polyol is used, said acrylic polyol is used in combination with a polyol having a functionality solely selected from the group consisting of ester, other than lactones, ethers, carboxyl and hydroxyl.

In yet another still more preferred embodiment of the invention, the blocking agent is a ketoxime, lactam or blend thereof.

In the most preferred embodiment, the organic polyol of the invention is selected from the group consisting of: Cargill 30-3000, FORMREZ«8009-146, F0RMREZ»55-225, RUCOTE«lll, RUCOTE«112, Cargill 30- 3016, Joncryl SCX-800 B and mixtures thereof.

In another embodiment of the invention, the organic polyol is prereacted with the isocyanate component of the crosslinker to form an NCO terminated prepolymer.

In still another embodiment of the invention, the organic polyol has an average hydroxyl functionality of at least 2 to about 4.

For purposes of this invention, hydroxyl number (for the organic polyols) was determined in accordance with ASTH D 4274-83. Acid number (for the organic polyols) was determined in accordance with ASTM D 4662- 87.

The most preferred organic polyols of the invention are commercially available. Cargill 30-3000 and Cargill 30-3016 may be purchased from Cargill Inc. of Minneapolis, Minnesota. F0RMREZ«8009-146 may be purchased from Witco Corporation, Organics Division of Melrose Park, Illinois. RUC0TE»111 and 112 may be purchased from Ruco Polymer Corporation of Hicksville, New York and Joncryl SCX-800 B may be purchased from S.C. Johnson & Son, Inc. of Racine, Wisconsin. Based on the instant disclosure, other suitable organic polyols will readily occur to those skilled in the art. For example, other polyester polyols useful in the invention may be obtained by the conventional condensation of a polybasic acid such as isophthalic acid with a polyol such as neopentyl glycol and/or 1,6- hexanediol or the like with an excess of hydroxyls. Other acrylic polyols useful in the invention may be obtained by copolymerizing a hydroxyl containing acrylic monomer such as hydroxy ethyl methacrylate with an acrylic monomer such as methyl methacrylate and styrene. Other suitable polyether polyols may be prepared by the condensation reaction of a polyol with propylene and/or ethylene oxide.

A variety of organic aliphatic or aromatic polyisocyanates or blends thereof may used in practicing the invention. They include isophorone diisocyanate, 4,4'-methylene bis-(cyclohexyl isocyanate) , toluene diisocyanate, hexamethylene diisocyanate, cyclohexylene-l,3-diisocyanate, m- phenylene diisocyanate, p-phenylene diisocyanate, 4,4'- diphenyl diisocyanate, 1,5-napthalene diisocyanate, toluene trisisocyanate, 1,4-xylene diisocyanate and 4,4^*-diphenyl methyl diisocyanate. Isophorone diisocyanate, toluene diisocyanate, l,3-bis-(l- isocyanato-1-methylethyl)-benzene, bis-(4-isocyanato cyclohexyl)methane are preferred. These materials are all commercially available. Isophorone diisocyanate is available, for example, through Hάls America Inc. Bis- (4-isocyanato cyclohexyl) methane, may be purchased, for example, through Miles Inc. of Pittsburgh, Pennsylvania under the name Desmodur W¹. l,3-bis-(l- isocyanato-1-methylethyl)-benzene may be purchased, for example, through American Cyanamid Company and toluene diisocyanate is available, for example, through Miles Inc. as Mondur TD-80².

Any of the blocking agents known in the art to be useful in acrylic-based powder coating applications other than 1,2-polyols (including, for example, ethylene glycol, 1,2-propylene glycol, 1,2-butane diol and hydrolyzed butyl glycidyl ether) and ethylenically unsaturated blocking agents (including, for example, butylaminoethyl methacrylate, methacrylamide, allyl alcohol and 4-(4-hydroxybutyl)-2-vinyl-l,3-dioxolane) may be used as the blocking agent in the invention, thereof are preferred. Ketoximes like acetone oxi e.

¹ Desmodur W is a liquid cycloaliphatic diisocyanate which is used in the manufacture of high performance specialty polymers such as light fast and color stable urethane coatings. It has the following typical properties:

Viscosity § 25°C, mPa's 30 + 10 % NCO 31.8min. Viscosity § 50°C, Pa's 12 + 4 Amine equiv. 132max. Weight per gallon, lbs ca 8.9 Total acidity 0.03max. Specific gravity θ 25/4°C 1.07 ± 0.02 Flash point (TCC) > 202°C

² Mondur TD-80 is an aromatic diisocyanate. Specifically it is a mixture of 2,4 and 2,6 toluene diisocyanate isomers in the ratio of 80% and 20% respectively. Mondur TD-80 has the following typical properties:

Appearance clear, colorless liquid Sp. gravity §25°C 1.22 Wt. per gallon, lbs 10.2 Total chlorides, % 0.05 Max Crystallizing point 13°C Refractive index § 25°C 1.566 Flash Point 127°C

(Pensky-Marten closed cup) lactams like e-caprolactam and mixtures thereof are commercially available and may be purchased, for example, through Allied-Signal Inc. of Morristown, New Jersey. Alternately, acetone oxime and other keto imes may be synthesized in accordance with U.S. Patent 4,323,706 to Bonfield et al.

In addition to an organic polyol, polyisocyanate and blocking agent, the crosslinker compositions of the invention may also contain an organometallic catalyst or a blend thereof. Of those known in the art, dibutyl tin dilaurate is preferred.

The proportions in which the organic polyol, polyisocyanate and blocking agent components of the crosslinker composition of the invention can be combined are well known to those skilled in the art. Generally, the composition is formulated such that the equivalents ratio of NCO groups to hydroxyl groups and blocking agents is about 0.85:1 to about 1:1.3. Preferably, to form a composition in which substantially all of the groups react, about a 1:1 to about a 1:1.03 ratio is used.

The preparation of acrylic-based urethane powder coatings is well known in the art. See, for example, U.S. Patents 4,093,674 to Tsutsui et al., 4,171,305 to Mochizuki and 3,931,117 to Leonard.

The present invention is more fully illustrated by the following non-limiting Examples.

In the following Examples, various physical properties of the crosslinkers prepared were measured. Softening point was determined using a Mettler Model ^ψ FP800 and FP83HT Dropping Point Apparatus using ASTM method D 3461-76. Equivalent weight was determined using the following formula:

fEquivalents KOH x 1000. or 56.000

Hydroxyl # Hydroxyl #

Percent NCO by weight before deblocking (or % free NCO) was determined using ASTM D1638. Percent NCO by weight after deblocking (or % NCO blocked) was determined using the following formula:

(equivalents blocking agent x 42. x 100 total weight of crosslinker (grams)

For example, the 5.9 % NCO after deblocking reported in Example 1 below was arrived at as follows:

(Q.69 * 4? ) x 100

490 Acrylic-based urethane powder coatings were prepared using the crosslinkers of the Examples. Various physical properties of these coatings were measured.

Average dry film thickness was determined using Model # 256FN from Elcometer of Birmingham, Michigan. Gloss was determined at two different angles, i.e., 60^s and 20° using a glossmeter. Model # 4411, from K. Chemie of Chicago, Illinois. Film hardness was determined using the procedure and equipment described in ASTM D3363-74 (reapproved 1989) . Cross-hatch adhesion was determined using the procedure and equipment described in ASTM D3359-90. Reverse and direct impact were determined using the apparatus and procedure described in ASTM D2794-90 using a 5/8 inch dia eter die/head. Conical mandrel was determined using the procedure and equipment described in ASTM D522-88. Solvent rub reported in certain Examples was determined in accordance with the procedure recommended by the Powder Coating Institute for solvent cure test 1988. Distinctness of image was determined using a distinctness of image meter from the Paul N. Gardner Company of Pompano Beach, Florida. Various coatings were visually rated within a series. "A" represents coatings which were uniform and smooth. "B" represents coatings which were not as uniform or smooth as the "A" coatings.

Example 1

Approximately 180 grams (1.62 equivalents NCO) of isophorone diisocyanate³ (IPDI) was charged to a one liter reactor equipped with an addition funnel, agitator, nitrogen purge gas, thermometer, heater and a vented water cooled condenser. Five drops of dibutyltin dilaurate were added and the mixture was warmed to about 60°C. A blend of 229.5 grams (0.93 equivalents OH) of FORMREZ* 55-225* and 80.4 grams (0.71 equivalents) of e-

³The isophorone diisocyanate (3-isocyanatomethyl- 3 , 5 , 5-trimethylcyclohexyl isocyanate) used herein was manufactured by Hύls America , Inc . It has the following typical properties :

% NCO 37.5-37.8 purity, % by wt. >99 . 0 total Cl₂, ppm <400 density 1.058- viscosity 15 ( 8 20°C, g/cm³) 1. 064

(§ 20°C, mPa.s) n²⁵o 1 . 483 flashpoint 155

(closed cup, °C)

'FORMREZ* is a registered trademark of witco Corporation Organics Division, Melrose Park, Illinois. FORMREZ® 55-225 is Witco^•s trademark for its poly(neopentyl adipate) . It has the following properties: OH # 25.3 % H₂0 0.017

Acid # 0. 6 M.W• « 500 caprolactam were heated at 90°C and added through the steam heated addition funnel to the reactor over a 30 minute period during which the temperature was maintained at between 60 and 130°C. After the addition was completed, the mixture was maintained for 20 minutes at a temperature of 120-130°C and then poured into a teflon- lined tray. The resulting crosslinker had the following properties:

Example2

Using the equipment described in Example 1 above,

114 grams (1.02 equivalents NCO) IPDI and 5 drops of

117.7 grams (0.103 equivalents OH) of Cargill⁵ 30-3000, dibutyltin dilaurate were charged to the reactor. This mixture was then heated to between 100 and 110^*C. Then,

⁵Cargill 30-3000 is manufactured by Cargill, Inc. of Minneapolis, Minnesota. It is a functional polyester resin having the following properties:

Eq. Wt. 1020 - 1250 Sp. gravity l.l - 1.2

ICI Viscosity 30-45 poise (Cone & Plate § 200°C) 79.7 grams (0.207 equivalents) of FORMREZ®⁶8009-146 and 81.9 grams (0.725 equivalents) of ε-caprolactam were blended in a flask and heated to 100"C. The polyol/caprolactam blend was then added to the agitated reactor over a 10-15 minute period in which the temperature was maintained at between 100 and 110'C. The reactor was then heated to between 130 and 140*C for 30 minutes and the product was poured on a teflon-lined tray. The resulting crosslinker had the following properties:

Example3

The procedure and equipment described in Example l above, were utilized in this experiment along with the following materials:

111 grams (1.00 equivalent NCO) IPDI 5 drops dibutyltin dilaurate 119.2 grams (0.105 equivalents OH) Cargill 30-3000 179.0 grams (0.466 equivalents OH) FORMREZ® 8009-146 50.7 grams (0.449 equivalents) ε-caprolactam

⁶FORMREZ« is a registered trademark of witco Corporations Organics Division, Melrose Park, Illinois. FORMREZ® 8009-146 is a linear adipate/isophthalate polyester resin otherwise known as poly 1,6- hexane/neopentyl adipate/isophthalate. It typically has the following properties:

OH # 146 Acid # 0.8 M.W. -800 Viscosity 650 (60'C,cps) The resulting crosslinker had the following properties:

NCO, % by weight after deblocking 4.0

NCO, % by weight before deblocking 0.36

Equivalent Weight 1045

Softening Point, "C 82

Each of the crosslinkers prepared in Examples 1-3 above, was formulated with Joncryl SCX-800B⁷ into an acrylic-based urethane powder coating at an NCO:OH ratio of 1:1 as follows: the Joncryl SCX-800B, the crosslinker, pigment and additives were ground to a powder individually and blended in a polyethylene bag prior to charging the mixture into a single screw extruder. The extruder temperature was maintained at 130°C by using cold water on the jacket. The effluent from the extruder was passed through rollers into a sheet. The resulting extrudate was broken up into small flat chips which were cooled with liquid nitrogen and ground into a powder. Subsequent sizing through a 40 mesh screen yielded a fine powder. The resulting composition was electrostatically sprayed onto metal sample panels. The panels were then baked for 25 minutes at 190°C. The resulting panel coatings were 1-2 mil

⁷Joncryl SCX-800B is an acrylic resin for use in powder coatings. It has the following typical properties:

Appearance solid, clear flake

Non-volatile content 98%

Acid # 16

Softening point(^*C) 107

Hydroxyl # 40

Equivalent wt. 1400

ICI Viscosity § 200^*C 40-50 poise

T_βCC) 43

Molecular wt. 21,000 thick and excellent in appearance.

⁸Degussa Special Black 4A pigment was the black pigment used in the coating formulation described herein. Benzoin is an additive to reduce surface imperfections. It may be purchased, for example, from Aldrich Chemical Company of Milwaukee, Wisconsin. It has the following typical properties:

Boiling point 194°C/12 mm Hg Melting point 134-136°C Appearance/odor It. yellow powder

"MODAFLOW® is a registered trademark of Monsanto Company. MODAFLOW® Powder III is a resin modifier developed to reduce surface imperfections in industrial powder coatings. It has the following typical properties:

Appearance Free-flowing, white pwdr.

% H₂0 (LOD) 4 Max.

Density(lb/ft³) 36 - 40

Odor No foreign odor

Active ingred. 65% wt. min. The resulting coatings had the following properties:

propert es:

Gardner viscosity S-W @ 65% in MIAK solvent %NCO ± 0.5 1.0 Specific gravity 1.1 - 1.2 T, (°C) 52 ± 2 Combining weight 240

Of the properties listed, direct and reverse impact and conical mandrel measure the flexibility of the Example coatings. The impact and conical mandrel results for this series of experiments demonstrate that the acrylic-based powder coatings prepared with the crosslinkers of the invention possess improved flexibility over the coating prepared using the prior art crosslinker (i.e. Cargill 24-2400) .

Example4

The procedure and equipment described in Example 2 above, were utilized in this experiment along with the following materials: 123 grams (0.94 equivalents NCO) Desmodur W 6 drops dibutyltin dilaurate 270 grams (0.13 equivalents OH) RUCOTE® 111¹¹ 93.8 grams (0.83 equivalents) ε-caprolactam The resulting crosslinker had the following properties:

"RUCOTE® is a registered trademark of Ruco Polymer Corporation of Hicksville, New York. RUCOTE® 111 is a polyester resin useful in powder coatings. It has the following typical properties:

Color (Gardner-Holt/50%in M-PYROL® (GAF) <2 Viscosity (ICI Cone and Plate § 200°C) , poise 60-75 Hydroxyl # 17-25 Acid # <7

T, (DCS) , °C >57

Hydroxyl Equivalent Wt., nominal 2800 Example 5

The procedure and equipment described in Example 2 above, were utilized in this experiment along with the following materials:

121.9 grams (0.97 NCO equivalents) TMXDI¹² 264 grams (0.16 OH equivalents) RUCOTE® 112¹³ 73 grams (0.83 equivalents) acetone oxime

The resulting crosslinker had the following properties:

The crosslinkers prepared in Examples 4 and 5 above, were formulated with Joncryl SCX-800B into an acrylic- based urethane powder coating at an NCO:OH ratio of 1:1 in accordance with the procedure outlined below:

¹²TMXDI® (META) aliphatic isocyanate or meta- Tetra ethylxylene diisocyanate is commercially available from American Cyanamid. It has the following typical properties:

Molecular wt. 244.3 viscosity, cps @ 0°c, 25 Equivalent wt. 122.1 20°C 9 Melting pt., °C -10 Flash Point (Closed Cup),³c 93 Boiling pt., °C 150

@ 3 mmHg Autoignition Point, °C 450 Specific gravity 1.05 % NCO (theo. by wt.) 34.4

¹³RUCOTE® is a registered trademark of Ruco Polymer Corporation of Hicksville, New York. RUCOTE® 112 is a polyester resin useful in powder coatings. It has the following typical properties: Color (Gardner-Holt/50%in M-PYROL (GAF) <2 Viscosity (ICI Cone and Plate @ 200°C) , poise 40-55 Hydroxyl # 28-35

Acid # <7

T_s (DCS) , °C >5⁷

Hydroxyl Equivalent wt., nominal 1810 Formulation Parts By Weight

Example Control*

Joncryl SCX-800B 118.5 98.6 100

Black Pigment

Benzoin

MODAFLOW® Powder III

Hύls 1530 B 25

Crosslinker/Ex.4 45.4

Crosslinker/Ex.5 44

*Hύls B 1530 crosslinker was the control. Hύls B 1530 is a standard crosslinker used to make acrylic-based urethane powder coatings. Applicants believe that this crosslinker does not contain a polyol. It has the following typical properties:

Blocked, NCO content approx. 15 wt . % Free NCO content <1 wt. % Splitting temp. 160-170°C Melting range 85-90°C 2nd order transition point by DTA approx. 50°C

Joncryl . SCX-800B, black pigment, benzoin, MODAFLOW® Powder III and crosslinker were premixed using a Vita-Mix blender Model 3600 from Vita-Mix Corporation of Cleveland, Ohio at high speed before melt mixing. Samples of the dry powder blend were then processed on a Brabender two-roll mill Type PM-3000, No. 128 B from c.w. Brabender Instruments, Inc. of E. Hackensack, New Jersey with the hot roll at 130°C and the cold roll chilled with tap water. The melt was processed for a total of 3 minutes at 130 rpm with sample rotation at 1 minute intervals. The resulting product was then ground using a Brinkman ultra centrifugal mill, Model ZM-l from Brinkman Instruments of Westbury, New^" York at 20,000 rp through a 0.5 screen. Samples were sieved through a 140 mesh vibratory sieve prior to electrostatic spray application over grounded steel panels pretreated with zinc phosphate. The coated panels were then baked at 190°C for 25 minutes to form hard glossy coatings.

The resulting coatings had the following properties:

The impact and conical mandrel results for this series of experiments demonstrate that the acrylic based powder coatings prepared with the crosslinkers of the invention possess improved flexibility over the coating prepared using the prior art crosslinker (i.e., Hύls B 1530) .

Example6

336.6 grams (2.55 equivalents NCO) Desmodur W 12 drops dibutyltin dilaurate

329 grams (0.273 equivalents OH) Cargill 30-3000 2019 grams (0.535 equivalents OH) FORMREZ®8009-146 136 grams (1.86 equivalents) acetone oxime

The resulting crosslinker had the following properties:

Example7

The procedure and equipment described in Example l above were utilized in this experiment along with the following materials:

185 grams (1.38 equivalents NCO) Desmodur W 6 drops dibutyltin dilaurate 182 grams (0.11 equivalents OH) RUCOTE® 112 149 grams (1.30 equivalents) ε-caprolactam

The resulting crosslinker had the following properties:

The cured crosslinker prepared in Example 7 was formulated with SCX-802 into an acrylic-based urethane powder coating at an NCO:OH ratio of 1:1 in accordance with the procedure outlined on pages 18-19 above.

grade acrylic resin designed for thermoset crosslinking with blocked isophorone diisocyanate. SCX-802 is manufactured by S.C. Johnson & Son Inc. of Racine, Wisconsin. It has the following typical properties:

OH≠

Acid#

Softening Point,°C

Tg,°C

ICI Melt Viscosity

(poise @200'C) 50

^**HύLS B 1530 was the control. See page 25 for control formulation.

The resulting coating had the following properties:

comparative data. The impact results for this Example demonstrate that the acrylic based powder coating prepared with crosslinker 7 of the invention possesses improved flexibility over the coating prepared using the prior art crosslinker (i.e., Hύls B 1530).

The cured crosslinkers prepared in Examples 6 and 7 were formulated with Joncryl 587 at an NCO:OH ratio of 1:1 in accordance with the procedure outlined on pages 18 and 19 above.

"Joncryl 587 is an acrylic polyol designed for use in high performance isocyanate-crosslinked urethane coatings. It has the following typical properties:

Non-volatile content 100% Color, Gardner-Holt <l Equivalent Wt. 600 OH ≠ (calc.) 94 Density,lb/gal. 9.7 The resulting coatings had the following properties:

HύT^B 15^0 was the control.

The impact results for this series of experiments demonstrates that the acrylic based powder coatings prepared with the crosslinkers of the invention possess improved flexibility over the coating prepared using the prior art crosslinker (i.e., Hύls B 1530).

Example8

204 grams (1.545 equivalents NCO) Desmodur W

12 drops dibutyltin dilaurate

426 grams (0.375 equivalents OH) Cargill 30-3000

57.6 grams (0.150 equivalents OH) FORMREZ«8009-146

124.5 grams (1.095 equivalents) ε-caprolactam The resulting crosslinker had the following properties:

Example9

344 grams (2.61 equivalents NCO) Desmodur W 12 drops dibutyltin dilaurate

278 grams (0.27 equivalents OH) Cargill 30-3016 199 grams (0.52 equivalents OH) FORMREZ®8009-146 214 grams (1.89 equivalents) ε-caprolactam The resulting crosslinker had the following properties:

Example 10

272 grams (2.06 equivalents NCO) Desmodur W 12 drops dibutyltin dilaurate 487 grams (0.47 equivalents OH) Cargill 30-3016 179 grams (1.55 equivalents) ε-caprolactam The resulting crosslinker had the following properties:

Each of the crosslinkers prepared in Examples 8-10 above, were formulated into an acrylic-based urethane powder coating. Specifically, the cured crosslinker prepared in Example was formulated with Joncryl SCX-802 at an NCO:OH ratio of 1:1 in accordance with the procedure outlined on pages 18 and 19 above.

The resulting coatings had the following properties:

The impact results for this experiment demonstrate that the acrylic based powder coating prepared with crosslinker from Example 8 of the invention possesses improved flexibility over the coating prepared using the prior art crosslinker (i.e., Hύls B 1530).

The cured crosslinkers prepared in Examples 9 and 10 were formulated with SCX-802 into an acrylic based urethane powder coating at a NCO:OH ratio of 1:1 in accordance with the procedure outlined on pages 18 and 19 above.

HΪTi-π^-5TO^{^}c"rosslinker was th^ -ontrol ^ee page 25 for control formulation. The resulting coatings had the following properties:

Example 10

Gloss, 60* 90 45

Pencil Hardness 2H 2H

X-hatch Adhesion (%) 5B 5B

Direct Impact (in.-lbs.) 120 120

Reverse Impact (in.-lbs.) 120 120

1/8" Conical Mandrel(mm to cracking) Pass Pass

Solvent Rub 100 100

Visual Rating B

Huls B 1530 crosslinker was the control, See page 26 for control comparative data.

The impact results for this series of experiment demonstrate that the acrylic based powder coatings prepared with the crosslinkers of the invention possess improved flexibility over the coating prepared using the prior art crosslinker (i.e., Hύls B 1530)

ExampleU

To a flask was added 276 grams (0.23 equiv. OH) Joncryl SCX-800B, 80.9 grams (0.21 equiv. CH; FORMREZ«8009-146 and 136 grams (1.20 equiv.) caprolactam. This mixture was heated to 140°C to achieve a uniform mixture and added to a warm (100°C) mixture of 8 drcps dibutyltin dilaurate and 214 grams (1.62 equiv. COi Desmodur W maintaining the reaction at 140°C. After the addition was complete (10-15 minutes) the reaction was heated to 150-160°C for 20 minutes. The resulting product was poured on a teflon-lined tray. The resulting crosslinker had the following properties:

The crosslinker prepared in Example 11 above was formulated with Joncryl SCX-802 into an acrylic-based urethane powder coating at an NCO:OH ratio of 1:1 in accordance with the procedure outlined on pages 18 and 19 above.

The resulting coating had the following properties:

The impact results for this experiment demonstrate that the acrylic based powder coating prepared with crosslinker from Example 11 of the invention possesses improved flexibility over the coating prepared using the prior art crosslinker (i.e., Hύls B 1530).

Claims

ww AT τ.ς PT ATMKTV

1. In a crosslinker composition comprising a polyol, polyisocyanate and blocking agent wherein the blocking agent is other than a 1,2-polyol or a monoethylenically unsaturated blocking agent, the improvement comprises utilizing as said poly an organic polyol or mixture of polyols wherein each polyol has at least two hydroxyl groups, an equivalent weight of greater than 250 to about 2500, an acid number of less than about 20 and functional groups solely selected from the group consisting of ester, other than lactones, ether, acrylic, carboxyl and hydroxyl wherein when an acrylic polyol is used, said acrylic polyol is used in combination with a polyol having a functionality solely selected from the group consisting of ester, other than lactones, ethers, carboxyl and hydroxyl which produces a crosslinker composition having less than about 1 % by weight unblocked isocyanate, at least about 4% by weight available isocyanate after deblocking and a softening point of from about 75 to about 130°C.

2. The crosslinker of claim 1 wherein said crosslinker has from at least 4 to about 12 weight percent available isocyanate after deblocking and a softening point of from about 85 to about 120°C.

3. In a crosslinker composition comprising a polyol, polyisocyanate and blocking agent wherein the blocking agent is other than a 1,2-polyol or a monoethylenically unsaturated blocking agent, the improvement comprises utilizing as said polyol an organic polyol or mixture of polyols wherein each polyol has an equivalent weight greater than 250 to about 2500, an acid number of less than about 20, at least 2 hydroxyl groups per polyol and functional groups solely selected from the group consisting of ester, other than lactones, ether, acrylic, carboxyl and hydroxyl wherein when an acrylic polyol is used, said acrylic polyol is used in combination with a polyol having a functionality solely selected from the group consisting of ester, other than lactones, ethers, carboxyl and hydroxyl.

4. The crosslinker of claim 1 wherein said blocking agent is a ketoxime, lactam or a blend thereof.

5. The crosslinker of claim 5 wherein said blocking agent is a ketoxime, lactam or a blend thereof.

6. In a crosslinker composition comprising a polyol, polyisocyanate and blocking agent wherein the blocking agent is other than a 1,2 polyol or a monoethylenically unsaturated blocking agent, the improvement comprises utilizing as said polyol a compound selected from the group consisting of Cargill 30-3000, FORMREZ»8009-146, FORMREZ»55-225, RUCOTE»lll, RUCOTE*112, Cargill 30-3016, Joncryl SCX-800 B and mixtures thereof as the polyol component of the crosslinker.

7. The crosslinker of claim 11 wherein said blocking agent is a ketoxime, lactam or blend thereof.

8. The crosslinker of claim 1 wherein said organic polyol is prereacted with the isocyanate component of the crosslinker to form an NCO terminated prepolymer.

9. The crosslinker of claim 5 wherein said organic polyol is prereacted with the isocyanate component of the crosslinker to form an NCO teπmnated prepolymer.

10. The crosslinker of claim 11 wherein said organic polyol is prereacted with the isocyanate component of the crosslinker to form an NCO terminated prepolymer.