Coatings Technology Handbook 2010 Part 11 ppsx

72-4 Coatings Technology Handbook, Third Edition72.4.1.2 Acetal The most effective mold release agents in acetal are fatty amides in general and fatty bisamides amides in particular.. Th

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70 Silane Adhesion

Promoters

References 70-3

Silane adhesion promoters are organofunctional silicon compounds that promote adhesion of coatings

to substrates, especially improving their resistance to debonding under humid conditions It must be emphasized that these silanes are not related to polydimethylsiloxane fluids, which cause cratering and poor repaintability in coatings Silane adhesion promoters may help overcome such problems of poor wetting and intercoat adhesion in coatings

Silane adhesion promoters are generally formulated into primers or added at relatively low levels to coatings, in contrast to silicone resins, which are typically used at about 30% level in silicone-alkyd or silicone-acrylic formulations These silanes are ambifunctional compounds of the general structure (CH3O)3 Si–R–X, where X is an organofunctional group chosen for compatibility with the organic coating and the alkoxysilane portion provides bonding to mineral substrates.1

The alkoxysilane may be prehydrolyzed to silanols that are reactive with hydrate metal oxide surfaces and contribute siloxane cross-links Methoxysilanes also react directly with metal hydroxides and then cross-link in the presence of atmospheric moisture

Silane adhesion promoters are often effective in improving the adhesion of coatings to plastic surfaces

or to oily metal surfaces As additives in paints, they may be useful in improving intercoat adhesion

A recent trend is to formulate adhesion promoters by mixing silane monomers, partially prehydrolyzing the silanes, or by mixing silanes with polymer precursors such as epoxies and melamines Silane adhesion promoters are offered by silane manufacturers Dow Corning Corporation, Union Carbide Corporation, Petrarch Chemicals Division of Dynamit Nobel, and Peninsular Chemical Research, as well as by pro-prietary formulators such as Hughson Chemical Division of Lord Corporation Adhesion promoters Walker2 reviewed a study of silane primers and additives for adhesion of a two-part epoxy paint with polyamide cure, and a two-part aliphatic isocyanate adduct cured polyester paint on mild steel, aluminum, cadmium, copper, and zinc surfaces Silanes were tested as primers (essentially monolayer coverage on aluminum, indicate that the diamine-functional silane gave uniformly improved retention of adhesion under wet conditions and gave greater recovery of adhesion when the panels were dried Methacrylate-, epoxy-, and mercaptofunctional silanes were also useful as adhesion promoters Results were similar on cadmium, copper, and zinc Paints with some silane additives showed little deterioration in performance during 9 months of storage

Some general recommendations on use of silane adhesion promoters of Table 70.1 for coating on glass,

3

Edwin P Plueddemann

Dow Corning Corporation

DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM

supplied by Dow Corning and recommended for coatings are described in Table 70.1

metal), and as 0.1 to 0.4% additive based on total paint Results, summarized in Table 70.2 for iron and

aluminum, and steel are summarized in Table 70.3

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71 Chromium Complexes

71.1 Introduction 71-1 71.2 Manufacture 71-1 71.3 Methacrylic Acid Types 71-1 71.4 End Uses 71-2 71.5 Application Methods 71-3 71.6 Governmental and Other Regulations 71-4

71.1 Introduction

Chromium complexes are widely used for changing the characteristics of paper, glass, and other hydroxylic surfaces, and the surfaces of materials such as polyethylene, which can be made functional by corona discharge and similar methods These binuclear compounds have the approximate formula shown in

in effect converted to –R groups The radical R is of two general types: long chain saturated hydrocarbon, incorporated by the use of a fatty acid, and unsaturated hydrocarbon, incorporated as methacrylic acid The fatty acids are used to change the physical properties of the surface, whereas the function of the methacrylic acid is to change its chemical properties

The chromium in these complexes is exclusively trivalent As is discussed below, the health hazard associated with hexavalent chromium compound is not present in these products, which have the approval

of the U.S Food and Drug Administration (FDA)

71.2 Manufacture

The starting point for these materials is a solution of a basic chromium chloride, which is converted to the complex by reaction with the appropriate acid The products are green solutions, with such depth

of color that they appear black In addition to being classed as flammable liquids, they are corrosive, since some of the chlorine (see Figure 71.1) is hydrolyzed and therefore exists in the form of HCl In use, both hazards are removed by dilution and neutralization

71.3 Methacrylic Acid Types

The du Pont Company makes methacrylatochromium complexes under the name Volan bonding agent Although the methacrylic acid types are used to coat substrates, the coating is always reacted further before the end use is reached They are therefore not normally considered to be coatings per se, and are discussed only briefly

A methacrylate group can polymerize with any other molecule undergoing vinyl polymerization If Volan-treated glass fiber, for instance, is impregnated with an unsaturated polyester, then when the latter

J Rufford Harrison

E I du Pont de Nemours &

Company

Release • Water Resistance • Grease Resistance

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72 Nonmetallic Fatty Chemicals as Internal Mold Release Agents

in Polymers

72.1 Introduction 72-1 72.2 Test Procedure 72-2 72.3 Experimental 72-2 72.4 Results 72-3 72.5 Conclusions 72-7 Acknowledgment 72-7

A major problem in injection molding is removal of the part from the mold If the part has a large surface area or a certain type of surface, it may be almost impossible to remove the piece without damage The force of the ejector can be increased to some extent, but this increases the possibility of damage to the piece The use of some type of mold treatment is well known in the industry The most common treatment

is spraying a silicon- or fluorocarbon-type mold release agent directly on the mold This procedure makes

it considerably easier to remove the piece from the mold, but unfortunately it causes other problems The spray-on mold release is typically good for eight to 10 moldings and then must be resprayed Continued respraying eventually causes a buildup on the mold, which must be removed Both the respraying and the cleaning cause an increase in cycle time

The use of an internal mold release agent can eliminate or lessen the problems of spray-on mold release It would not be necessary to continually spray the mold, and there would not be as much buildup

on the mold when internal mold release agents are used

One theory about how mold release additives work is that the additive exudes to the surface in the time between injection and ejection and serves to lubricate the boundary area during ejection The mold release agent may also serve to reduce electrostatic attraction during ejection in some cases If these assumptions are true, then a number of things can affect the usefulness of an additive: solubility in the resin, rate of migration in the resin, lubricity of the additive, melting point of the additive, and ability

of the additive to reduce electrostatic attraction, to name some Since most of these interrelationships are not well known, it follows that a large part of mold release is done on a trial-and-error basis Eventually what will and will not work can be predicted for a given resin, but these predictions are made only on the basis of how similar compounds behave

Kim S Percell

Witco Corporation

Harry H Tomlinson

Witco Corporation

Leonard E Walp

Witco Corporation

Results • Polyolefins

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72-4 Coatings Technology Handbook, Third Edition

72.4.1.2 Acetal

The most effective mold release agents in acetal are fatty amides in general and fatty bisamides amides

in particular Ethylene bisoleamide shows 25.1% reduction of mold release force at 5000 ppm but causes

a visible darkening of the resin during processing Ethylene bisstearamide, a saturated amide, is nearly

as good, showing 23.3% reduction at a level of 5000 ppm; it does not cause any color problems Other secondary amides, such as stearyl stearamide and stearyl erucamide, give mold release improvement nearly as good as the bisamides (see Table 72.3) Primary amides such as erucamide, oleamide, and stearamide also show good mold release enhancement in acetal

None of the nonamide materials examined has the mold release effectiveness of the amides The best ester mold release agent is cetyl palmitate, which exhibited a 16.5% reduction in mold release force at a

5000 ppm treatment level

The optimum amount of ethylene bisstearamide is 5000 ppm When used above that level, there is little increase in effectiveness; below that amount, the maximum effectiveness is not reached

The use of fatty amides as mold release agents has negligible effect on mechanical properties (see Table 72.4)

72.4.1.3 Polybutylene Terephthalate

Fatty bisamides are the best mold release agents in polybutylene terephthalate (PBT) Both saturated and unsaturated bisamides show about 10% reduction of ejection force when used at a level of 5000 ppm The bisoleamide, however, causes some darkening of the resin during processing (see Table 72.5)

TABLE 72.3 Effectiveness of Mold Release Agents in Acetal Release Agent Level (ppm) Reduction of Ejection Force (%)

N,N′ -Ethylene bisstearamide 7500 26.0

N,N′ -Ethylene bisoleamide a 5000 25.1

a Causes resin to darken during processing.

TABLE 72.4 Mechanical Properties of Acetal with N,N′ -Ethylene Bisstearamide Present

Property

N,N′ -Ethylene Bisstearamide (ppm)

Tensile strength at yield, psi 9965 9883 9818

Izod impact, ft-lb/in 1.30 1.32 1.35

TABLE 72.5 Effectiveness of Mold Release Agents in PBT Release Agent Level (ppm) Reduction of Ejection Force (%)

N,N′ -Ethylene bisoleamide 5000 9.8

N,N′ -Ethylene bisstearamide 5000 9.4

a May cause resin to darken during processing.

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mold release agents, although not as good as erucamide (see Table 72.9) Secondary amides and bisamides are not as good mold release agents as the primary amides

In addition to primary fatty amides, ethoxylated fatty amines are useful mold release agents in HDPE

At a level of 5000 ppm, ethoxylated oleyl amine and ethoxylated tallow amine show nearly a 20% decrease

in mold release force (see Table 72.9) The use level is higher than the primary amide usage level, but the ethoxylated amines are also known as antistatic agents and therefore could solve two problems with one additive

Fatty esters have also been tested for mold release, but with the exception of glyceryl monostearate, they do not have much usefulness as mold release agents GMS, used at a level of 5000 ppm, shows a 14.8% reduction of ejection force, but this is not as good as the primary amides or the ethoxylated amines The use of primary amides or ethoxylated amines as mold release agents in HDPE has negligible effect

on mechanical properties when tested at room temperature (see Table 72.10)

72.4.2.3 Linear Low-Density Polyethylene

The results of testing for mold release in linear low-density polyethylenes (LLDPEs) are quite similar to The primary amides can be used at lower concentrations, because they are more efficient in LLDPE Erucamide shows 30.3% reduction of mold release force when used at a level of 1000 ppm, while in HDPE it must be used at a level of 5000 ppm to achieve the same effect

The ethoxylated amines are also useful mold release agents and exhibit the same increased efficiency reported for the primary amides (see Table 72.11) As in HDPE, the ethoxylated amines are also useful

as antistatic agents

TABLE 72.8 Mechanical Properties of Polypropylene with and without Glyceryl Monostearate

Property

Glyceryl Monostearate, 45% α -ester (ppm)

Tensile strength at yield, psi 4848 505 Elongation at break, % 295 60 Izod impact, ft-lb/in 0.65 0.72

TABLE 72.9 Effectiveness of Mold Release Agents in HDPE Release Agent Level (ppm) Reduction of Ejection Force (%)

Ethoxylated oleyl amine 5000 18.9 Ethxylated tallow amine 5000 19.8

TABLE 72.10 Mechanical Properties of HDPE with Various Additives

Property Level (ppm) Tensile Strength at Yield (psi) Elongation at Break (%)

those in HDPE Erucamide is the most effective mold release agent (see Table 72.11)

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73 Organic Peroxides

73.1 Introduction 73-1 73.2 Types and Properties 73-1 73.3 Application in Coatings 73-4 73.4 Safety Factors and Producers 73-5 73.5 Future Trends 73-5 References 73-5

Organic peroxides are derivatives of hydrogen peroxide, HOOH, wherein one or both hydrogens are replaced by an organic group (i.e., ROOH or ROOR).1–5 They are thermally sensitive and decompose by homolytic cleavage of the labile oxygen–oxygen bond to produce two free radicals:

(73.1) The temperature activity of organic peroxides varies from below room temperature to above 100°C, depending on the nature of the R groups In addition to thermal decomposition, certain organic peroxides can be decomposed by activators or promoters at temperatures well below the normal decomposition temperature

A major application of these compounds is as free radical initiators in the polymerization of vinyl and diene monomers in the plastics and coatings industries They are also used as cross-linking and modifying agents for polyolefins, as vulcanizing agents for elastomers, and as curing agents for polyester resins

73.2 Types and Properties

Peroxide manufacturers now offer over 50 different organic peroxides in more than 100 formulations including dilutions in solvents, pastes, and filler-extended grades In most cases, these formulations are designed for specific applications and to allow shipping and handing with a reasonable degree of safety peroxides are commonly reported in terms of half-life (t1/2) temperature, that is, the time at which 50%

of the peroxide has decomposed at a specified temperature Table 73.1 lists the 10-hour t1/2 temperature ranges for the major organic peroxide types Peroxides of certain types, such as hydroperoxides and ketone peroxides, are primarily used in combination with promoters and are employed at temperatures much lower then their measured 10-hour t1/2 temperature

ROOR′ →∆RO⋅+ ⋅OR′

Peter A Callais

Pennwalt Corporation

Peroxide Selection • Radical Types

The major classes of commercial organic peroxides are shown in Table 73.1 Decomposition rates of

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16 M Takahashi, Polym Plast Technol Eng., 15, 1 (1980)

17 L W Hill and Z W Wicks, Jr., Prog Org Coat., 10, 55 (1982)

18 R H Kuhn, N Roman, and J D Whitman, Mod Paint Coat., 71(5), 50 (1981)

19 R F Storey, in Surface Coatings, A L Wilson, J W Nicholson, and H J Prosser, Eds London:

Elsevier Applied Science, 1987, p 69

20 C J Bouboulis, U.S Patent 4,739,006 (1988)

21 D Rhum and P F Aluotto, U.S Patent 4,075,242 (1978)

22 Y Eguchi and A Yamada, U.S Patent 4,687,882 (1987)

23 W R Berghoff, U.S Patent 4,716,200 (1987)

24 R A Gray, J Technol., 57(728), 83 (1985)

25 R Buter, J Technol., 59(749), 37 (1987)

26 D Rhum and P F Aluotto, J Technol., 55(703), 75 (1983)

27 V R Kamath and J D Sargent, Jr., J Coat Technol., 59(746), 51 (1987)

28 V R Kamath, U.S Patent pending

29 F M Merrett, Trans Faraday Soc., 50, 759 (1954)

30 D H Solomon, J Oil Colour Chem Assoc., 45, 88 (1962)

31 J Sanchez, U.S Patent 4,525,308 (1985)

32 A J D’Angelo and O L Mageli, U.S Patents 4,304,882 (1981), 3,952,041 (1976), 3,991,109 (1976),

3,706,818 (1972), and 3,839,390 (1974)

33 A J D’Angelo, U.S Patent 3,671,651 (1972)

34 R A Bafford, U.S Patent 3,800,007 (1974)

35 R A Bafford, E R Kamens, and O L Mageli, U.S Patent 3,763,112 (1973)

36 O L Mageli, R E Light, Jr., and R B Gallagher, U.S Patent 3,536,676 (1970)

37 H Ohmura and M Nakayama, U.S Patent 4,659,769 (1987)

38 C S Sheppard and R E MacLeay, U.S Patents 4,042,773 (1977) and 4,045,427 (1977)

39 T N Myers, European Patent Appl., 223,476 (1987)

40 P A Callais, V R Kamath, and J D Sargent, Proc Water-Borne Higher Solids Coatings Symp., 15,

104 (1988)

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74 Surfactants for Waterborne Coatings

Applications

74.1 Introduction 74-1 74.2 Chemistry 74-1 74.3 Theory 74-2 74.4 Foam Control 74-3 74.5 Wetting 74-4 74.6 Conclusion 74-5

As governmental regulations become increasingly restrictive, waterborne coatings appear to be the logical choice for many paint manufacturers However, the technological switch from solvent to waterborne systems requires an understanding of the challenges that lay ahead with respect to wetting, foam control, and coverage over difficult-to-wet substrates

This chapter will help explain the important contribution of wetting agents and defoamers to the emerging technology of waterborne coatings Topics will include the chemistry of several surfactants along with a thorough analysis and understanding of surface tension Surface tension reduction and mechanisms relating to foam stabilization will be reviewed

74.2 Chemistry

All surfactants fall into two classifications, nonionic and ionic Within the ionic category, surfactants can

be further subdivided into anionic, cationic, or amphoteric types For coatings, most surfactants utilized are either nonionic or anionic For wetting agents, the products we will compare include alkylphenol ethoxylates, sodium dioctyl sulfosuccinates, sodium laurel sulfates, block copolymers of ethylene and propylene oxides, alkyl benzene sulfonates, and, finally, a specialty class called acetylenic glycols We start with this

Acetylenic glycols are a chemically unique group of nonionic surface active agents that have been especially designed to provide multifunctional benefits to a wide array of waterborne coating products Two key benefits include an unusual combination of wetting and foam control properties

Characterized as an acetylenic diol, we have a 10-carbon backbone molecule with a triple bond, two adjacent hydroxyl groups, and four symmetrical methyl groups Based on acetylene chemistry, this product is unlike any other surfactant molecule The combination of the triple bond and the two hydroxyl groups creates a domain of high electron density, making this portion of the molecule polar and thus

Samuel P Morell

S P Morell and Company

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75 Surfactants, Dispersants, and Defoamers for the Coatings, Inks, and Adhesives Industries

75.1 Introduction 75-1 75.2 Wetting and Dispersing Process 75-2

75.3 Silicones and Surface Flow Control Agents 75-6

75.4 Defoaming Additives 75-9

75.5 Conclusion 75-12 References 75-12

Over the history of coatings, inks, and adhesives, many evolutionary changes have occurred; not only have the ingredients used to make the formulations been changed, but also the physical characteristics

of the formulations along with their application, cure, and performance parameters have changed

Of course, each trend poses challenges to both raw material suppliers and formulators alike Because additives are used to enable and enhance system performance, the evolution of resins, pigments, solvents, and application technologies pose special challenges for additive suppliers

Resin and solvent combinations used in the good old days were typically quite low in surface tensions

in comparison to modern formulations Today’s more environmentally friendly formulations with little

or no solvents, or in the case of aqueous formulations, with little or no cosolvents, require increased use

of interfacially active materials in order to provide adequate substrate wetting, surface flow, and the prevention of foaming and air entrapment

John W Du

BYK-Chemie USA

The Wetting and Dispersing Process • Waterborne Systems •

Background • Chemical Structure of “Silicones” • Surface Solvent-Based Systems • Classification • Summary

Phenomena and the Elimination of Defects • Summary

Selection Criteria and Test Methods • Summary

The Nature of Foam • Defoamers versus Air Release Agents • for Aqueous Systems • Defoamers for Solvent-Based Systems • The Mechanisms of Defoaming and Air Release • Defoamers

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