Isosorbide-based degassing agent

Abstract

A non-toxic isosorbide-based degassing agent producible from biorenewable sources for addition to paints and coatings, powder coatings in particular, to prevent pinholing and minimize yellow discoloration during cure without use of potentially harmful VOCs or predominant proportions of benzoin.

Claims

1. An isosorbide-based degassing agent comprising: 15 to 35 weight percent isosorbide; 60 to 80 weight percent vegetable oil and/or wax; 0 to 5 weight percent high surface area, inorganic powder; and 0 to 10 weight percent benzoin; wherein the said degassing agent reduces incidences of pinholing during cure.

2. The isosorbide-based degassing agent of claim 1 wherein the high surface area inorganic powder is silica.

3. The isosorbide-based degassing agent of claim 2 wherein the vegetable oil and/or wax is castor oil and/or wax.

4. An isosorbide-based degassing agent comprising: 15 to 35 weight percent isosorbide; 60 to 80 weight percent vegetable oil and/or wax; and 0 to 10 weight percent high surface area inorganic powder; wherein the said degassing agent reduces incidences of pinholing during cure.

5. The isosorbide-based degassing agent of claim 4 wherein the high surface area inorganic powder is silica.

6. The isosorbide-based degassing agent of claim 5 wherein the vegetable oil and/or wax is castor oil and/or wax.

7. An isosorbide-based degassing agent comprising: 28.5 weight percent 1,4,3,6-dianhydro-D-glucitol; 68.5 weight percent castor oil and/or wax; and at least one selected from 3 weight percent silica; and 3 weight percent 2-hydroxy-1,2-diphenyl ethenone wherein the said degassing agent reduces incidences of pinholing during cure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a block chart showing Threshold Film Thickness (“TFT”) of various degassing agents at 0.5 weight percent of powder coating formulations.

(2) FIG. 2 is a block chart showing the TFT of a preferred embodiment of the present invention, known by the trade name “Oxymelt A-8”, measured at different loadings in power coating formulations.

(3) FIG. 3 is a block chart showing the color change (yellowing) index at 180° C. over 10 minutes for various degassing agents compared to Oxymelt A-8.

(4) FIG. 4 is a side elevation, diagrammatic view exemplifying a method of Threshold Pinhole Detection to measure the Threshold Film Thickness of various degassing additives.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) Table 1, below, presents the composition of a preferred embodiment of the instant invention known by the trade name “Oxymelt A-8”:

(6) TABLE-US-00001 TABLE 1 Raw Material Chemical Name Name CASRN Supplier Polysorb PBA, PB, 1,4,3,6- 662-67-5 Roquette Frères; P; Novosorb P Diarhydro-D- Novaphene gluciol Specialties Pvt Ltd Castor Wax Hydrogenated 8001-78-3 Nexeo Castor Oil Supernat 22 or other Silicon Dioxide 112928-00-8 Evonik precipitated silicas Benzoin 2-Hydroxy-1,2- 119-53-9 Miwon Diphenyl Ethanone

(7) Chemical formulations of the various degassing agents used in the instant experiments are provided in Table 2 below:

(8) TABLE-US-00002 TABLE 2 Recommended Degassing Additive Name Loading Suppliers Benzoin 0.3-1.5% Miwon (2-Hydroxy-1,2-Diphenyl Ethanone) Powdermate 542 DG 0.5-2.0% Troy Co. (Amide Modified Phenolated Urea Surfactant) Crayvallac PC 0.5-2.0% Arkema (Micronized Hydrogenated Castor Oil) Oxymelt A-4 0.5-4.0% Estron (Bisphenol A and Epoxy) Oxymelt A-8 0.3-1.5% Estron (Isosorbide-Castor Wax-Silica-Benzoin Mixture)

(9) In generating the results depicted herein, each degassing agent tested was admixed to standard, white β-hydroxyl-alkyl amide (“HAA”) polyester powder coating at 0.5 weight percent of total formulation (FIG. 1) and at 1 weight percent for yellow color change measurement (FIG. 3). An example powder coating formulation is set forth in Table 3 below.

(10) TABLE-US-00003 TABLE 3 P865 polyester (DSM)   .sup. 68.4% Primid XL-552 HAA curing agent (EMS-Griltech)   .sup. 3.6% Resiflow PL-200 flow control additive (Estron)   .sup.  1% Degassing Agent  .sup.  0.5-1% Titanium Dioxide filler (Chemours, Kronos) 26-25.5-%

(11) FIG. 1 illustrates Threshold Film Thickness (“TFT”) of various degassing agents, including a preferred embodiment of the present invention identified by the trade name Oxymelt A-8, previous to pinhole detection in sample powder coating formulations.

(12) Individual degassing agents Powdermate 542 DG, Oxymelt A-4, Benzoin, and Oxymelt A-8, were added to individual samples of like powder coating formulations at 0.5 weight percent. As best shown in FIG. 4, samples were then sprayed to 4″×12″ panels 20 along a thickness gradient, from a minimum thickness 50 to a maximum thickness 100 to form a wedge 10.

(13) Each panel 20 was subsequently oven-cured at 180° C. for 10 minutes. The precise location upon the wedge 10 where pinholes 500 first appeared was noted for each sample and measured with a digital caliper. The thickness of the wedge 10 immediately preceding the location where pinholes 500 first formed is known as the Threshold Film Thickness (“TFT”) corresponding to 100% degassing efficacy at a corresponding thickness of the wedge 10, denoted by reference character 502 in FIG. 4. The greater the TFT for a particular sample, the greater the efficacy of the particular degassing agent. As a reference thickness, paint is typically applied to a surface at a nominal thickness of 60-80 μm. The tolerance of the experiment performed is taken to be within +/−5 μm.

(14) As shown in FIG. 1, Powdermate 542 DG exhibited a TFT of 90 μm; at thicknesses greater than 90 μm pin-holing occurred and the efficacy of Powdermate 542 DG as a degassing agent thereafter failed. Oxymelt A-4, another proprietary formulation of the instant assignee of the present inventive disclosure, remained effective as a degassing agent up to 100 μm. Benzoin, used as a degassing agent by itself in many formulations known in the art, presented a TFT of 105 μm. Oxymelt A-8, the preferred embodiment set forth herein, attained a TFT of 115 μm, exhibiting degassing efficacy at least as effective as pure benzoin (comparable TFT within the error rate 11% of the time), but likely exceeding benzoin (comparable TFT above benzoin outside the error rate 89% of the time). The advantages of the preferred embodiment over pure benzoin include less yellow color change exhibited in the samples (see FIG. 3, discussed below). Thus, even where Oxymelt A-8 performs as efficaciously as a degassing agent comparable to pure benzoin, it nonetheless presents a useful improvement thereover—by minimizing the amount of benzoin used, less color change (yellowing or other discoloration) results. Nonetheless, the increased probability of Oxymelt A-8's TFT outperforming benzoin beyond the error rate over the average should not be discounted.

(15) FIG. 2 illustrates the results of TFT measurements for the preferred embodiment Oxymelt A-8 at different weight percentage additions to like powder coating formulations. At 0.3 weight percent loading, Oxymelt A-8 yielded a TFT of 110 μm. At 0.5 weight percent, Oxymelt A-8 yielded a TFT of 115 μm. At 1 and 1.5 weight percentages, Oxymelt A-8 yielded TFTs of 120 μm. The recommended loading of Oxymelt A-8 to powder coating formulations is 0.5 weight percent.

(16) FIG. 3 illustrates data for b* (blue to yellow) values generated as part of the International Commission on Illumination's CIELab color scale as measured with a spectrophotometer. The lower the number, the less yellowing recorded.

(17) Powder formulations containing 1 weight percent degassing agents were spread onto 4″×6″×0.032″ cold-rolled steel panels and cured at 180° C. for 10 minutes. Color of each sample was then measured with a spectrophotometer and the b* value recorded for each sample shown. A degree of yellowing off-white from the original sample was therefore determinable.

(18) The spectrophotometric results show that benzoin yielded a b* vale of 2.14. Oxymelt A-4 yielded a b* value of 1.53. Powdermate 542 DG yielded a b* value of 0.86. Oxymelt A-8, the preferred embodiment set forth herein, yielded a b* value of only 0.63, more than three times less than benzoin.