CA1156789A - Coating ingredient and method of making same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The volatile alkali salt of the reaction product of a waxy starch product having a high amylopectin content and styrene-maleic anhydride copolymer and the method of making such product comprising hydrolyzing the copolymer in the presence of the high amylopectin starch product at an elevated temperature and in the presence of water for a time sufficient to hydrolyze the copolymer, disperse the starch to react, adding a volatile alkali to the heated mixture, and continuing the heating for a time sufficient to form the volatile alkali salt of said reaction product. The invention also comprises coatings comprising the volatile alkali salt of said reaction product

Description

1 1~6789 The present ~nvention relates to coating ingredients suitable for use in coating compositions and to methods of making the coating ingredients. Because the coating ingredients of the invention have wide application in that they may be used in varîous coating compositions, the appendent claims are directed to the coating ingredients per se rather than to the coating composition containing it At t~e present time proteinaceous polymers such as casein and soy protein are used in various coating compositions;
paper coatings and paints and the like, These proteinaceous materials, and particularly casein,-have probably been the most generally used colloidal materials in the coating industry, i espec;ally for high grade paper coatings. Dispersions of - casein are readîly prepared and are good as pigment dispersion media. ~oreover, they are compatible with many resin and elastomeric latices and the casein is easily insolubilized.
Pigmented coatings are generally applied to various substrates for several reasons, i.e,, for protection of the substrate, fQr decorative purposes, and for making the substrate

2~ more suitable for other operations such as printing or lamina-ting.
. While clearly suitable, casein and soy protein are susceptible to bacterial degradation and more particularly, these proteinaceous materials are subject to very extensive variations in terms of cost and avàilability since they are ~ - ...

7~9 used as food proteins and hence often become too expensive or unavailable for usage in coating as discussed above.
The problem with which the application is concerned is to find suitable substitutes for these proteinaceous polymers. Past efforts have not been successful either because the substitute materials used did not give the desired coating or dispersing properties of the proteinaceous materials, or because the substitute materials did not have stable viscosities at high and medium solids concentrations, or failed to give the proper adhesive strength and pigment binding power. In short, they did not give the desired rheological properties obtained when casein is used, With the foregoing in mi,nd, we provide in accordance with the in~ention a coating ingredient, characterized in that it comprises a volatile alkali salt of a reaction product of a hydrolyzed styrene-maleicanhydride copolymer and a dispersed high amylopectin starch product.
The invention also involves a method of making a - coating ingredient which is suitable as a substitute for proteinaceous polymers heretofore used in coatings and is characterized by admixing a high amylopectin starch product and a styrene-maleic anhydride copolymer in water, heating at a temperature and for a time sufficient to (a) hydrolyze the copolymer, (b) disperse the starch, and (c) form the coating ingredient, and thereafter adding volatile alkali for neutralizing the product thus formed, The coating ingredients may be incorporated in, for example, paper coating and paint compositions, 1 15~78~

As will be seen from the disclosure to follow, the coating ingredients of the invention are suitable and economic replacements for proteinaceous polymers, such as casein and soy protein, and exhibit properties in coating compositions that are equivalent to or superior to these proteinaceous polymers.
The reaction coating ingredient of the present invention is formed by reacting a high amylopectin containing waxy starch product with a styrene-maleic anhydride copolymer in water in the presence of a volatile alkali salt.
As to the waxy starch product, it is preferred to use the high amylopectin conversion products, It is known that all starches contain two types of molecular structures;
an amylose fraction which is essentially linear and an amylopectin fraction which is highly branched Products from which starc~ is obtained, such as corn, have been developed which contain a high percentage of the amylopectin fraction;
such as waxy maize, and waxy sorghum. Such waxy products, and like products having a high amylopectin content and their conversion products are well-known to those skilled in this art and are herein referred to as 'Ihigh amylopectin starches".
High amylopectin starches are readily available, commercial examples being CPC International's product, Texofilm 6448, Anheuser Busch product, AB 7348, and National Starch & Chemical product, Amioca 50.
!,..
The high amylopectin starches are preferred becàuse they form more stable aqueous dispersions than normal starches (less setback or gelling) and this results in reaction products .. . . ... .. . . . . .. .. ~

1 15~783 that have the suitable rheological properties required for acceptable coatings and other applications.
Wîth respect to the styrene-maleic anhydride copolymer, while any of such commercially available copolymers can be used, we have ~ound that superior compositions result if SMA 3000 by A~CO Chemical Company is used. SMA 3000 is a resin prepared from a 3:1 ratio of styrene to maleic anhydride having a molecular weight of 1900 and an acid number of 275.
Other copolymers that can be used include LYTRON~ 1~ by Monsanto Company made from a 1:1 ratio of styrene to maleic anhydride having a molecular weight of 50,000 and an acid number of 320.
As to proportions, the ratio of copolymer to starch may be varied over a wide range depending upon the desired effect and/or economic considerations, Suitable products are obtained with ratios of 5% to 45% by weight copolymer to correspondingly 95% to 55% by weight of the high amylopectin starch. The preferred range is 10% to 30% by weight copolymer and correspondingly 90% to 70% by weight starch, Referring to the volatile alkali, it can be any of those known and conventionally used to neutralize acidic reaction products. Ammonium hydroxide, preferably 28%
ammonium hydroxide, is particularly useful for the neutraliza-tion because it is less expensive than other volatile alkali materials. The volatile alkali leaves the a~ueous composition on drying and thereby adds more water resistance to the resultant dried film. The amount used is that sufficient to neutralize the reaction product acid groups as discussed fra~ r~

)78 9 below. Preferably, for coating applications sufficient alkali is added to neutralize and give the reaction product salt a pH over about 8.5.
While not essential, in some instances it may be beneficial to add small quantities of a metal oxide, such as zinc oxide, to the reaction mixture. These are added in very limited amounts; preferably from about 0.5% to 5% by weight based on the weight of the styrene-maleic anhydride copolymer.
The method of making the coating ingredient is critical. It is essential that the high amylopectin starch and styrene-maleic anhydride copolymer aqueous mixture be heated at an elevated temperature for a time sufficient to ensure that the starch is dispersed, the copolymer is hydrolyzed, and the reaction between the two is substantially completed.
A temperature range from ambient temperature to about 200F can be used with the preferred range being about 16Q to 175F, At room temperature the copolymer will hydrolize very.slowly and, of course, if ambient temperature is too cold the starch will not be dispersed. For practîcal commercial operations elevated temperatures should be used. At elevated temperatures the reactio~ will be complete in about 25 to 45 minutes~ At this point, the ammonium hydroxide is added with mixing and the heating at the same temperatures as initially is continued preferably for 10 to 15 minutes until such time as a homogeneous mixture is formed, Neutralization is essentially instantaneous.

~ 156789 The temperature-time relationships are not critical, but important, again, in an economic sense. Again, the important aspect of the initial heating is to insure that all the styrene-maleic anhydride copolymer is hydrolyzed, the starch fully dispersed, and the reaction between them substantially completed. The reaction is essentially complete when the copolymer is completely hydrolyzed. As noted above, heating after addition of the volatile alkali is simply to ensure that a homogeneous mixture is formed.
-While the precise structure of the coating ingredient reaction product is not presently known, a reaction product does result from the reaction between the copolymer and the starch. It is presently believed that the reaction occurs between the acid groups formed as the copolymer hydrolyzes and the hydroxyl groups of the starch. The remaining acid groups are converted by the ammonium hydroxide to the ammonium salt. This product, gives good film integrity and is a good pigment dispersion media. Also, the resultant dried film is continuous and quite water resistant and, of course, as noted, the aqueous dispersions of the reaction products are excellent pigment dispersion media.
The conclusion that a reaction has occurred is supported by film characteristics of cast films. It has been found that if an ammoniacal solution is made of the styrene-maleic anhydride copolymer only and cast as a film anddried, the resulting film is readily shattered. If the starch is heated at the temperatures discussed above, with or without ammonium hydroxide, cast as a film on glass and then dried, while it has better integrity than the styrene-maleic anhydride film discussed above, it is also quite friable, Likely, if there is simply an admixture of the copolymer solutîon and the starch solution and such solution is cas~ -as a film on glass and dried, it also is quite friable and readily shattered. It is only when one follows the conditions noted above in ma~ing the reaction product that one is able to obtain a resulting dried film showing a high degree of integrity, good water resistance, and one which is not readily shattered.
The reaction product solution of the present invention when added in place of casein solutions in various standard coating formulas shows equal or better properties.
The concentration, of course, of the cook and the amounts added to a coating composition may be widely varied and adapted to suit each specific need.
In the examples that follow with respect to coating formulations of various types, the compositions utilizing the instant invention have been evaluated against similar coating compositions made with casein. In every instance, with respect to the following properties, it has been shown that the compositions of this invention are equivalent or superior to their casein counterparts.
.1) Stable viscosities at medium and high solids 25concentrations, 2) Adhesive strength and pigment bonding power,

3) Film forming properties which enhance ink, varnish and grease resistance,

4) Easy dispersion in water and more resistant to bacterial degradation,

5) Better finish after calendering,

6) Lighter film color which decreases the amount of titanium dioxide needed for desired whiteness,

7) Better flow and leveling properties, and

8) Adhesion and control of penetration into paper stocks.
As used herein, the term "paint resin" is used to refer to the usual resins or elastomers, such as polyacrylate dispersions, that are presently used in paint formulations and where presently materials such as casein solutions are used as pigment dispersion media.
The invention will be further described in connection with the examples that follow in which proportions are in pounds unless expressly stated to the contrary.

The general method of forming the reaction products is carried out by first a~mixing the following materials until a smooth, substantially uniform mixture is attained:
~ Percent by Weight -``` Starch (TEXOFILM 6448) 20.0 Copolymer (SMA 3000) 5.0 Defoamer (Tributyl Phosphate) 0,2 Water 70,8 The mixture is heated to 165F and held at that temperature until the starch is fully cooked and the resin hydrolyzed. The disappearance of the majority of resin particles indicates substantial completion of hydrolysis which occurs, at the specified heating temperature, in about 20 to ~ tr~o~

1 1~6789 45 minutes. Ammonium Hydroxide (28%), in an amount that is 80% by weight of the copolymer weight, is then thoroughly admixed therewith to achieve a homogeneous product having a pH over 8.5; about 10 to 15 minutes.

A high solids coating color for application on a Champion Coater was prepared by first admixing the following materials until a substantially uniform mixture is formed:
Water 3800 lbs.
Tetrasodium Pyrophosphate 8 lbs.
Tributyl Phosphate 8 lbs.
Clay (ASP - 100~ 3450 lbs.
~ Titaniu~JDioxide '400 lbs.

i ~ (Tipure~R 901) To this is added: -Styrene-Maleic Anhydride75 lbs.
Copolymer (SMA 3000) High Amylopectin Starch300 lbs.
Conversion (Texofilm #6448) Pine Oil 7 lbs, . Mixing was continued until a smooth mixture was formed and the mixture was then heated to 165F., held a~ this temperature for 30 minutes, and there was then added 60 lbs.
of ammonium hydroxide (28%). The entire mixture was then cooked at 165 to 170F for 15 to 20 minutes and there was then added:
Water 1300 lbs.

Polyacrylat Latex 810 lbs.
(Rhophlex~ C-34) This product is an excellent high solids coating color.
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l 156789 A low solids coating color for reverse roll coaters was prepared by first stirring with a high speed mixer until a substantially uniform mixture was obtained:
Water .5080 lbs.
Tributyl Phosphate 8 lbs.
Clay (Ultra Cote) 3700 lbs.
To this mîxture was added:
Styrene-Maleic Anhydride 100 lbs.
10Copolymer (SMA 3000) High Amylopectin~ tarch 400 lbs.
Conversion (A #7348) Mixing was continued until the entire mixture was smooth. It was then heated to 165T, held at that temperature for 30 minutes, 80 lbs. of ammonium hydroxide (28%) were then added, the entire mixture was cooked at 165 to 175F for 15 to 20 minutes, cooled, and there was then added 480 lbs. of an SBR latex (Polyco 2440), .
This low solids coating color performs as well as similar coatlng colors utilizing casein.

A high solids coating color for on-machine coating of paper or paperboard using separate reaction product solution and clay dispersion was prepared by first mixing until a sub-stantially uniform mixture was formed:
The reaction product solution consisted of a mixture of the following:
ffw~e~e~k~

1 ~5~739 Water 2300 lbs.
Tributyl Citrate 6 lbs.
Styrene-Maleic Anhydride207 lbs.
(Copolymer (SMA 3000) High Amylopectin Starch483 lbs.
Conversion (Texofilm ~6448) The mixture was heated to 165F, held for 15 minutes at this temperature, 35 lbs. of ammonium hydroxide (28%) were' ' 10 added and admixed, and the entire mixture held at 165 to 170F for 5 minutes. This was followed by adding!an ~:
additional 105 lbs. of ammonium hydroxide and mixing and holding at the same temperature for 30 minutes.
S'eparately, the following materials were admixed in a high speed mixer until a substantially uniform clay dispersion was formed:
Water 1720 lbs.
Defoamer (Nopco JMY)25 lbs.
- Sodium Hexametaphosphate10 lbs.
Clay (BG~90)~ 4250 lbs.
Titanium Dioxide 470 lbs.
(Tioxide RHL) ' To the clay dispersion was added'2875 lbs. o the reaction product solution prepared as described above. The two were admixed until a uniform mixture was formed and then 650 1bs. of an SBR Latex (DOW~ 20) was uniformly admixed therewith.

A low solids coating color for paper or paperboard was prepare'd by admixing in a Cowles dissolver:
~ tr~

1 15678~

Water 3525 lbs.
Defoamer (Colloid 680)10 lbs, Clay (Astraglaze~3450 lbs, Titanium Dioxide380 lbs.
(Tipure ~931) To this was added 2120 lbs, of the reaction product solution prepared as in Example 4, which was admixed there-with until a substantially uniform mixture was obtained.
Lastly, 480 lbs. of SBR Latex (DOW 620) were added and the entire mixture mixed until a smooth, uniform mixture was obtained.

.
A polyvinyl acetate homopolymer emulsion based coating color for a trailing blade coater was formed by 15 admixing in a Kady mill until a substantially uniorm mixture was obtained:
Water 7750 lbs.
Tributyl Citrate1.5 lbs.
Tetrasodium Pyro~ osphate 1.5 lbs.
Clay (HydraGlQss #9)1350 lbs.
Titanium Dioxide150 lbs, To this was added:
Styrene-~aleic Anhydride 60 lbs.
Copolymer (S~ 30Q0) High Amylopectin Starch 180 lbs.
Conversion (Amioca #50~
It was mixed smooth, heated to 165F, held ~or 30 minutes at this temperature, and then 10 lbs, of ammonium hydroxide ~28%) were added and the entire mixture mixed at , , , , ~ , ,, . .... , . .. , . .... ,. __.

I l~g789 165F for 5 minutes. An additional 30 lbs. of ammonium hydroxide (28%) were then added and admixed therewith at the same temperature for 30 minutes.
Lastly, 15 lbs. pine oil and 500 lbs. of a polyvinyl acetate homopolymer (Vinac 880) were added and thoroughly admixed with the heated mixture, An ethylene-vinyl acetate copolymer based coating color for an Air Knife Coater was prepared by admixing until 10 smooth (a substantially,uniform mixture in a high speed dispenser:
Water 5550 lbs.
Tributyl Phosphate3.5 lbs.
Tetrasodium Pyrophosphate 3.5 lbs.
Clay (Hydrotex SD)3260 lbs.
- To this smooth mixture was added:
Styrene-Maleic Anhydride40 lbs.
Copolymer (SMA 3000) High Amylopectin Starch160 lbs.
Conversion (AB #7348) The entire mixture was mixed until smooth, heated to 165F, held at this temperature for 15 to 20 minutes, and then 32 lbs. of ammonium hydroxide (28%~were added and admixed therewith.
The mixture was then held at 165 to 175F for 30 minutes and then mixed therewith until smooth were:
Pine oil 10 lbs, Ethylene-vinyl Acetat,,e950 lbs, Copolymer (Airfle~100 HS) l 1567~9 A flat wall paint using a polyacrylate dispersion was prepared by forming the reaction product from the follow-ing constituents which were mixed until smooth:
Water 985 lbs, Tributyl Citrate2,5 l~st High Amylopectin Starch250 lbs.
Conversion CAmioca #50) ~ Styrene-Maleic Anhydride100 lbs~
Copolymer (SMA 3000) The smooth mixture was then heated to 165~F, held for 15 to 20 minutes, 17 lbs, of ammonium hydroxide (28%) were then admixed therewith and the entire mixture held at 165~F for 5 minutes. An additional 51 lbs, of ammonium hydroxide (28%~ were then admixed and the entire mixture held at the same temperature for 30 minutes~
The flat wall paint was prepared by admixîng until smooth:
~ Water 100Q lbs~
Defoamer CColloid ~7112lQ lbs t Surfactant CTriton GS-10~ 20 lbs~
. ,~ .
Reaction product139Q lbs, (prepared a~ove2 Then 250 lbs, of hexylene glycol and lQQ lbs, of ethylene glycol were mixed therewith until smooth.~
- ` There was then mixed therewith with a Cowles dissolver:
Titanium Dioxide 750. lbs~
(.Tipure R9.al~
Calcium. Carbonate ~TOMITE2 223Q lbs~ -Silicon dioxide 500 lbs (.Insi~ ica 1~312 1 1567~

and let down with:
Water 2000 lbs, Defoamer (COLLOID 680)20 lbs.
Polyacrylate Dispersion2300 lbs.
(~hoplex AC-34) This paint performs in every respect as well as those utilizing casein or any other protein colloidal material used for this purpose.
The listing below identifies the manufacturers of the various materials identified by their trade marks or trade names herein:
SMA resins are made by Arco Chemical Co.
Lytron Resins are made by Monsanto Chemical Co.
High amylopectin starch conversions are made by CPC
International CTexofilm 6448), Anheuser Busch (AB 7438~, Natîonal Starch & Chemical (Amioca 50) - Also American Maize Amaizo 835, Clays ASP-100, Ultra Cote, and BG-90 are made by Engelhard.
29 Clays HydraGloss ~9 and Hydratex SD are made by J,M. Huber, Astraglaze clay is made by Georgia Kaolin.
Atomite is calcium carbonate sold by Thompson-Weiman, Insil Silica #31 is made by Illinois Mineral, Tipure R901 and Tipure R931 are titanium dioxide made by DuPo,nt, Tioxide RHL is titanium dioxide made by Tioxide of Canada.
.; .~ -- ~
; ~ Zopaqué R-77 is titanium oxide made by Glidden, Rhoplex AC-34 is a polyacrylate dispersion made by Rohm & Haas.
Airflex 100 HS is an ethylene-vinylacetate polymer dispersion and Vinac 880 is a polyvinyl acetate homopolymer dispersion; both made by Air Products.
Dow 620 is an SBR latex made by Dow Chemical.

, ..... . . . , . _ .

37~

Polyco 2440 is an SBR latex made by Borden, Nopco JMY is a defoamer made by Diamond Shamrock.
Colloid 680 and 711 are defoamers made by Colloids Inc.
Triton GF-10 is a surfactant made by Rohm & Haas.
Tributyl Phosphate and Tributyl Citrate are defoamers.
While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of ~he invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modificatîons, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A coating ingredient, characterized in that it comprises a volatile alkali salt of a reaction product in an aqueous medium of a hydrolized styrene-maleic anhydride copolymer and a dispersed high amylopectin starch product.
2. The coating ingredient of claim 1, characterized in that the copolymer comprises a 3:1 ratio of styrene to maleic anhydride and a has a molecular weight of 1900 and an acid number of 275 and that the high amylopectin starch comprises a waxy maize and/or waxy sorghum.
3. The coating ingredient of claim 1, characterized in that it has a pH of at least 8.5 and that the volatile alkali is ammonium hydroxide, .
4. The coating ingredient of any one of the preceding claims, characterized in that it forms part of a film-forming composition which includes (a) at least one paper coating pigment and an elastomeric or resin latex or (b) a paint resin.
5. The coating ingredient according to any one of claims 1 to 3, characterized in that it is included in a coating applied to paper sheet.
6. The method of making a coating ingredient suitable for use in film-forming coating compositions, characterized by admixing a high amylopectin starch product and a styrene-maleic anhydride copolymer in water, heating at a temperature and for a time sufficient to (a) hydrolyze the copolymer, (b) disperse the starch, and (c) form the coating ingredient, and thereafter adding volatile alkali for neutralizing the product thus formed.

7. The method of claim 6, characterized in that the high amylopectin starch comprises a waxy maize and/or waxy sorghum and that the copolymer in the admixture is prepared from a 3:1 ratio of styrene to maleic anhydride, the copolymer having a molecular weight of 1900 and an acid number of 275.
8. The method of claim 6, characterized in that the heating is at a temperature of from about 160° to 175°F
for a period of from about 25 to 45 minutes.
9. The method according to claim 6, 7 or 8, characterized in that ammonium hydroxide is added in an amount sufficient to give a pH of at least 8.5.
10. A film-forming coating composition, characterized in that it includes the coating ingredient of claim 3.

11. A film-forming coating composition, characterized in that it includes the coating ingredient of claim 2.
12. A film-forming coating composition, characterized in that it includes the coating ingredient of claim 3.
14. A coated paper comprising a paper sheet coated with the film-forming composition of claim 10, 11 or 12.
15. A paint comprising at least one paint pigment, a paint resin and the film-forming composition of claim 10, 11 or 12.