MXPA01000815A - Waterborne coatings with cationically modified associative ethers - Google Patents

Abstract

A coating composition is composed of a water soluble polysaccharide composition comprising at least one hydrophobic group selected from aryl,alkyl, alkenyl, aralkyl and mixtures thereof and at least one quaternary ammonium salt group, both connected to a polysaccharide backbone by covalent bonds. This coating is used for improving the leveling of waterborne paints.

Description

"COATINGS TRANSPORTED BY WATER WITH ASSOCIATIVE ETHERS CATIÓNICALLY MODIFIED" This invention relates to the use of cationically modified associative cellulose ethers as rheology modifiers for water-borne coatings, and more particularly, the use of these cellulose ethers having a cationic residue containing quaternary nitrogen and a hydrophobic residue attached to it. foundation of cellulose ether to improve leveling in waterborne paints.

BACKGROUND OF THE INVENTION Cellulose ethers have been widely used in the paint industry as thickeners for emulsion paints. Although these products as well as hydroxyethyl cellulose, methylcellulose derivatives, ethylhydroxyethyl cellulose and carboxymethyl cellulose provide paints with a number of good paint properties, these materials demonstrate effects in the area of rheology. The quality of the paints has been constantly improved over the last decade with the demand to improve the flow, film construction, and splash resistance increasing as well.

The associative cellulose ethers were developed to fill this increase in demand for paints with better performance properties. Associative thickeners such as hydrophobically modified ethoxylated urethanes (HEURS) were not able to be used as a single thickener in medium to high pigmented latex paints because the amount of binder present in these paints is relatively low. Associative thickeners such as hydrophobically modified hydroxyethylcellulose (HMHEC) were developed by Aqualon Company, a division of Hercules Incorporated, for use primarily in the paint industry. These HMHEC products are sold commercially under the Natrosol Plus® factory name and function extremely well compared to those prepared with other well-known cellulosic polymers to improve flow, film construction, and splash resistance in paints. These Natrosol Plus products, on the other hand, thicken the paint by means of double mechanism, that is, the thickening of water phase and network formation through hydrophobic interactions, and can, therefore, be used as a single thickener. These Natrosol Plus® products are hydrophobically modified modified cellulose ether derivatives with long-chain alkyl groups described by Landoll in US Patent Nos. 4,228,277 and 4,352,916. Other patents describing hydrophobically modified modified cellulose ethers useful in the paints are U.S. Patent No. 4,902,733 (Angerer) and U.S. Patent Nos. 5,124,445 and 5,120,838 (Just et al.). However, this main use of the product is in medium to high pigmented paints (ie paints with a pigment volume concentration (PVC) of more than 40 percent). The market is still requiring a new generation of products with increased thickening efficiency and film construction properties. The present invention addresses this need by introducing an additional thickening mechanism to the thickening efficiency of Natrosol Plus products; it has been found that hydrophobically modified ionically modified hydroxyethyl cellulose ethers using a cationic residue containing quaternary nitrogen can improve the efficiency of all waterborne paints. Cellulose ethers containing water-soluble quaternary nitrogen have been described in US Patent Number 3,472,840 (Stone et al.) Which are useful in a variety of applications. U.S. Patent Number 4,663,159 also describes a i. - water-soluble cationic polysaccharide, including quaternary nitrogen-containing cellulose ethers, which contain a hydrophobic substitution which provides aqueous solutions having improved viscosity, foaming and preferably improved surface properties; These cationic polysaccharides are useful in personal care, emulsion and cleanser products.

SUMMARY OF THE INVENTION The present invention is directed to a coating composition comprising as a thickener a water-soluble cellulose ether and comprising at least one hydrophobic group selected from the group consisting of aryl, alkyl, alkenyl and aralkyl. and at least one quaternary ammonium salt, both connected to a cellulosic base by covalent bonds.

DETAILED DESCRIPTION OF THE INVENTION It has been found that modified hydrophobic modified cellulose ethers further to contain cationic groups separated from the hydrophobic groups in the cellulose ether base will provide an additional thickener mechanism that improves the high shear viscosity of the coatings. transported by water. The modified cationic ether, the hydrophobically modified cellulose ether of the present invention can be produced from easily obtainable materials. These cellulose ethers are first alkylated with a long-chain alkyl compound which is then quaternized with a nitrogen-containing compound. The compounds containing hydrophobe and nitrogen are separately fixed to the cellulose ether of the base. The starting materials of the present invention include water soluble polysaccharides such as cellulose ethers for example hydroxyethyl cellulose (EHEC), ethyl hydroxyethyl cellulose (HEC), hydroxypropylmethyl cellulose (HPMC), methyl cellulose (MC), hydroxypropylmethyl cellulose ( HPMC), and methylhydroxyethyl cellulose (MHEC), hydroxyethylmethyl cellulose (HEMC), hydroxyethylcarboxymethyl cellulose (HECMC), and guar and guar derivatives and the like. A preferred cellulose ether starting material with particularity is hydroxyethylcellulose. The polysaccharide or polygalactomannan starting material of this invention must possess a degree of polymerization (DP) generally of at least about 500, preferably greater than 750, and especially preferably greater than 1000. The DP of the materials of Starting can be controlled through controlled degradation procedures known in the art. The hydrophobically modified cationic alkyl modified polysaccharide (such as a cellulose ether) of the present invention is usually prepared through a sequence of reactions that are known in the prior art. A cellulose ether such as hydroxyethylcellulose is first reacted with a hydrophobic residue such as cetiglycidyl ether to form the hydrophobically modified cellulose ether. This reaction must be carried out so that the content of the hydrophobe is elevated in such a way as to have a content of greater than about 0.6 weight percent, preferably at least 0.8 weight percent, and especially preferably so less than 1.0 percent by weight. It should be noted that the amount of modification of the hydrophobe alone does not provide improved release of the paints (see table 3 on page 7, infra). However, it is essential to provide a modified precursor with appropriate hydrophobe. This hydrophobically modified high-cellulose ether is then reacted in a separate reaction with a quaternary ammonium salt such as glycidyltrimethyl ammonium chloride, in order to add the cationic residue to the base of the hydrophobically modified cellulose ether. In this step, a sufficient amount of cationic residue is added to the cellulose ether in the foundation to improve the leveling amount of the water-borne paints above the amount of the non-moistened cellulose ethers. Typically, the amount of the cationic degree of substitution (DS) should have a lower limit of 0.005, preferably a lower limit of 0.05, and especially a lower limit of 0.07. The upper limit of the cationic DS must be 0.5, preferably 0.25, and especially preferably 0.22. The hydrophobic residues of the present invention are hydrocarbons of the alkyl, aplo, alkenyl or aralkyl groups of at least 10 carbon atoms, preferably at least about 13 carbon atoms, and especially preferably at least of 16 carbon atoms in the alkyl chain. The upper limit of the carbon atoms of the hydrocarbon residue is 24 carbon atoms, preferably 20 carbon atoms, and especially preferably 18 carbon atoms. The hydrophobe containing hydrocarbon may be unsubstituted, i.e., simply a long chain alkyl group, or substituted with non-reactive groups such as aromatic materials, i.e., aralkyl groups. Typical alkylating agents reactive with the hydroxyl groups of cellulose ether include halides, epoxides, isocyanates, carboxylic acids, or acid halides. The cellulose ethers are provided with quaternary nitrogen-containing substituents through quaternization reactions which can be achieved by reacting the polysaccharides with quaternization agents which are quaternary ammonium salts, including mixtures thereof, to effect the substitution of the polysaccharide with groups that contain quaternary nitrogen in the foundation. Typical quaternary ammonium salts that may be used include halides, halohydrins and epoxides containing quaternary nitrogen. Examples of the quaternary ammonium salts include one or more of the following: 3-chloro-2-hydroxypropyl dimethyldodecyl ammonium chloride; 3-chloro-2-hydroxypropyl dimethyloctadecyl ammonium chloride; 3-chloro-2-hydroxypropyl dimethyloctyl ammonium chloride; 3-chloro-2-hydroxypropyl trimethyl ammonium chloride; 2-chloroethyl trimethyl ammonium chloride; 2,3-epoxypropyl trimethyl ammonium chloride; and similar. Preferred quaternizing agents include 3-chloro-2-hydroxypropyl trimethyl ammonium chloride; 3-chloro-2-hydroxypropyl dimethyloctadecyl ammonium chloride; ammonium chloride of 3-chloro-2-hydroxypropyl dimethyltetradecyl; ammonium chloride of 3-chloro-2-hydroxypropyl dimethylhexadecyl; 3-chloro-2-hydroxypropyl dimethyldodecyl ammonium chloride; and 3-chloro-2-hydroxypropyl dimethyloctadecyl ammonium chloride. Quaternization can also be achieved by using a two-step synthesis of (1) aminating the polysaccharide by reaction with an amination agent, such as amine halide, halohydrin or epoxide, followed by (2) quaternization of the product of step (1) by reaction with the quaternizing agent, or mixtures thereof, containing an operating group that forms a salt with the amine. Preferred quaternizing agents include a hydrophobe containing long-chain alkyl halides, including halides of the alkylating agent such as dodecyl bromide or octadecyl chloride. The coating composition of the present invention is a latex-based paint having a lower limit of the pigment volume (PVC) concentration of 10 percent. The upper limit of PVC is 90 percent. In accordance with the present invention, a wide range of paint systems (ie, gloss, semi-gloss and flat) can be thickened with the ether al ^ cationically modified, hydrophobically modified cellulose of the present invention. The broad scope of the invention will be illustrated in the following examples with a hydrophobically modified cationically modified hydroxyethylcellulose (CATHMHEC). The process of manufacturing these cationically modified associative thickeners was as follows: the associative thickener such as HMHEC was formed in slurry thickened in acetone in the presence of water and caustic. The cationic reagent, glycidyltrimethylammonium chloride (GTMAC) was added to the slurry and the reaction mass was heated to a temperature of about 45 ° C for about 4 hours under a blanket of nitrogen. After completion of the reaction, the reaction mass was cooled to room temperature and neutralized. The salts were then washed to leave the product in a mixture of acetone and water. Then, the product dried and was ready to be used.

EXAMPLE A This Example demonstrates the case where the hydrophobic content of HMHEC is too low (at 0.6 weight percent) in a CATHMHEC so that the cationic modification does not yield a product with good performance in the paints. A modified GTMAC hydroxyethylcellulose (modified C16) was evaluated in a gloss emulsion paint based on the product Primal® HG74D, a modified acrylic emulsion, sold by Rohm and Haas. The formulation of the gloss emulsion paint is given below in Table 1 and the results of the evaluation are shown in Table 2. TABLE 1 Parts by weight Water 49.7 Sodium hexametaphosphate 2.0 Polymer dispersant - BYKC154 1.0 Preservative - Mergal® K6Na 1.0 Defoamer - Agitan® 280 ^ 2.0 Thickener On demand Titanium dioxide 210.9 Primal HG74D 650.0 Propylene glycol 10.0 Texanol® coalescence agent ^ -. solvent 15.0 Water 58.5 1000.0 a) Sold by Riedel de Haen, Germany b) Sold by Munching Chemie, Germany c) Sold by BYK d) Sold by Eastman Co.

TABLE 2 Example GTMAC- Thickener * Viscosity Viscosity Leveling '' DS (% by weight) Storm ICI- (KU) (mPas) HMHEC *** - 0.29 101 90 4 HMHEC 0.036 0.38 103 90 5-6 HMHEC 0.07 0.38 102 100 6 HMHEC 0.20 0.40 100 90 5-6 HMHEC 0.29 0.46 104 100 6 * Amount of thickener required for a stormer viscosity of approximately 100 KU. ** Leneta descent method; classification 1-10; 10 = better *** Hydroxyethyl cellulose modified with cetylglycidyl ether; 0 6 percent by weight average molecular weight: -300,000 Dalton. It seems that the modification of the hydrophobe was too low for good flow properties with CATHMHEC®.

EXAMPLE 1 The substitution of the hydrophobe of Example A was increased to 1.3 to 2.0 weight percent C16. To this high substitution of the hydrophobe the HMHEC was modified with different CTMAC levels, that is, CTMA-DS between 0.078 and 0.320. The following Table 3 shows the composition of the CATHMHECs and the results of the evaluation of these materials in a flat emulsion paint (65 percent PVC) based on the product Mowilith® DM21, an emulsion of vinyl acetate-copolymer of versatate, sold by Hoechst Chemical Co.

TABLE 3 Results of the evaluation of paint with CATHMHECs with high substitution of hydrophobe in a flat paint based on Mowilith DM21.

Sample% of GTMA-DS Thickener ViscosiNivelaSalpi¬ C16 (% in Weight) ICI cation (mPas) HMHEC1 0.6 - 0.53 100 2 7 HMHEC2 1.3 - 0.46 60 2 5 CATHMHEC0 0.6 0.200 0.58 100 2 7 CATHMHEC1 1.3 0.078 0.36 70 8 7 CATHMHEC2 1.3 0.163 0.37 70 9 5-6 CATHMHEC3 1.3 0.22 0.42 70 7 5 CATHMHEC4 1.5 0.231 0.48 70 4 5 CATHMHEC5 2.0 0.32 0.45 70 4 4 These results demonstrate that a critical hydrophobic substitution scale and cationic modification level provide flat paint with excellent leveling ratings. Excellent leveling for a flat paint means a rating of 7 and higher.

EXAMPLE 2 The thickening efficiency of CATHMHEC is also superior in relation to commercial grade HMHEC1. The lower ICI viscosity of paints containing CATHMHECs can be corrected to the desired viscosity by combining CATHMECs with synthetic thickeners of a hydrophobic terminal block polyethylene oxide (HMPEO), an associative acrylic thickener like the Primal RM5 product or a urethane hydrophobically modified ethoxylate (HEUR) such as the product Primal RM8 or Primal RM1020 (all Primal products are sold by Rohm and Haas.) The 65 percent flat emulsion paint formulation with PVC will be given below in Table 4 and the ICI and leveling results are shown in Table 5.

TABLE 4 Flat emulsion paint (65 percent PVC) based on Mowilith® DM21.

Parts in Weight Water 197 Hexametaphosphate, sodium 1 Polyacrylic acid, ammonium salt 2 Condom Mergal® K6Na 2 Defoamer Shake 280 ° 1 Ti02 159 Calcium carbonate 273 Talcum 23 Mowilith DM2 lc 167 Propylene glycol 15 Texanol ^ 4 Defoamer6 1 Water + thickener 155 1000 a) Sold by Riedel de Haen, Germany b) Sold by Munching Chemie, Germany c) VeoVA Vinyl Acetate Latex, sold by Hoechst Co. d) Coalescence Agent, solvent sold by Eastman Co. e) Agitan 280, sold by Munching Chemie, Germany TABLE 5 Sample Thickener Viscosity ICI Leveling. { % in weigh; (mPas) CATHMHEC1 0.36 70 CATHMHEC1 0.18 Primal® RM8a 0.36 160 CATHMHEC1 0.27 HMPEO 0685-5 0.27 150 10 CATHMHEC2 0.19 Primal®a RM1020 1.2 200 Urethane associative thickener, sold by Rohm and Haas Co.

EXAMPLE 3 The good leveling classifications obtained with CATHMHEC 1, 2 and 3 indicated in Table 3 are not restricted to specific paint formulations. This will be demonstrated using the following two additional paint systems: (a) Enamel paint (15 percent PVC) based on the Primal® HG74D product; (b) Semi-enamel paint based on the Uramul® CC280 product.

The formulation of the enamel paint (a) is the same as that shown in Table 1 and the formulation of the semi-enamel paint (b) is given below in Table 6.

TABLE 6 Semi-enamel paint based on Uramul CC280 Parts in Weight Water 180 Sodium hexametaphosphate 2.5 Polymeric Dispersant 2.5 Condom - Mergal K6N 3 Defoamer - Agitan 280 2.5 Ti02 240 Calcium carbonate 40 Uramul® CC280a 500 Propylene glycol 10 Texanol® 15 Water + thickener 64.5 1060 Acrylic latex, sold by DSM resins The results of the evaluation of the paint are summarized in Table 7: TABLE 7 Paint Type Thickener Viscosity Leveling Thickener (% by weight) Stormer (KU) Enamel CATHMHEC1 0.17 89 10 CATHMHEC2 0.18 97 9-10 I- CATHMHEC1 0.07 93 9-10 Enamel CATHMHEC2 0.08 95 10 Example 4 Other water-soluble, cationically modified polymers, hydrophobically modified, were evaluated in a flat paint with PVC of 65 as indicated in Table 4. The results of the evaluation of the paint are summarized in Table 8, infra.

TABLE 8 Sample% GTMA- Thickener Viscosi- Nivela- Salpí- C16 DS (% by weight) ICI cation ICI (mPas) HMEHEC1 * 0.9 - 0.49 70 2 5 CATHMEHEC1 * A 0.9 0.152 0.41 70 7 6 HMHEGuar ** 1.2 - 0.57 60 1 3 CATHMHEGuar ** a 1.2 0.146 0.49 65 6 5 HMMHEC *** 1.1 - 0.67 80 3 6 CATHMMHEC *** A 1.1 0.161 0.41 60 7 6 HMHPC **** 1.1 - 0.71 85 2 4 CATHMHPC **** A 1.1 0.154 0.45 70 6 6 * Bermocol EHM 100, a commercial product sold by AKZO Nobel, which was hydrophobically modified with 0.9 percent by weight of C16 and then cationically modified with GTMAC (see CATHMEHEC, a) ** Base HEGuar with Mw - 270,000 Dalton was modified with 1.2 percent by weight of C16 and then cationically modified with GTMAC (a) *** MHEC Base with Mw -240,000 Dalton with OCH3-DS of 1.43 and with HE-MS of 1.1 was modified with 1.1 weight percent of C16; then it was modified cationically with GTMAC (a) **** Base: HPC with Mw -250,000 Dalton and HP-MS 2.7 was then modified with 1.1 weight percent of C16 and then modified cationically (a)

Claims (31)

REVINDICATIONS:

1. A coating composition comprising a water soluble polysaccharide composition comprising at least one hydrophobic group selected from the group consisting of aryl, alkyl, alkenyl, aralkyl and mixtures thereof and at least one salt group quaternary ammonium, both connected to a polysaccharide base by covalent bonds.

2. The coating composition of claim 1, wherein the hydrophobic group has at least 10 carbon atoms.

3. The coating composition of claim 1, wherein the hydrophobic group has a lower limit of 13 carbon atoms.

4. The coating composition of claim 1, wherein the hydrophobic groups have a lower limit of 16 carbon atoms.

5. The coating composition of claim 1, wherein the upper limit of the hydrophobic group is 24 carbon atoms.

6. The coating composition of claim 1, wherein the upper limit of the hydrophobic group is 20 carbon atoms.

7. The coating composition of claim 1, wherein the upper group of the hydrophobic group is 18 carbon atoms.

The coating composition of claim 1, wherein at least one quaternary ammonium salt is selected from the group consisting of 3-chloro-2-hydroxypropyl dimethyldodecyl ammonium chloride, 3-dimethyloctadecyl ammonium chloride chloro-2-hydroxypropyl, 3-chloro-2-hydroxypropyl dimethyloctyl ammonium chloride, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, 2-chloroethyl trimethyl ammonium chloride, and trimethyl ammonium chloride of 2,3-epoxypropyl.

9. The coating composition of claim 8, wherein at least one quaternary ammonium salt is glycidyltrimethyl ammonium chloride.

The coating composition of claim 1, wherein the polysaccharide foundation is selected from the group consisting of hydroxyethyl cellulose (EHEC), ethyl hydroxyethyl cellulose (HEC), hydroxypropylmethyl cellulose (HPC), methyl cellulose (MC), hydroxypropylmethyl cellulose (HPMC), methyl hydroxyethylcellulose (MHEC), hydroxyethylmethyl cellulose (HEMC), hydroxyethylcarboxymethyl cellulose (HECMC), guar and guar derivatives.

11. The coating composition of claim 1, wherein the polysaccharide base is hydroxyethylcellulose.

12. The coating of claim 1, wherein the content of the hydrophobic group is greater than 0.6 percent by weight.

The coating of claim 1, wherein the content of the hydrophobic groups is greater than 0.8 percent by weight.

14. The coating of claim 1, wherein the content of the hydrophobic groups is greater than 1.0 percent by weight.

15. The coating of claim 1, wherein the content of the hydrophobic groups has an upper limit of 2.5 weight percent.

16. The coating of claim 1, wherein the quaternary ammonium salt has a degree of substitution or greater than 0.005.

17. The coating of claim 1, wherein the quaternary ammonium salt has a degree of substitution with a lower limit of 0.05.

18. The coating of claim 1, wherein the quaternary ammonium salt has a degree of substitution at a lower limit of 0.07. ^ aajsftjg * • ** & *.

19. The coating of claim 1, wherein the quaternary ammonium salt has a degree of substitution with an upper limit of 0.5.

The coating of claim 1, wherein the quaternary ammonium salt has a degree of substitution with an upper limit of 0.25.

The coating of claim 1, wherein the quaternary ammonium salt has a degree of substitution with an upper limit of 0.

22. The coating of claim 1, wherein the starting material of the polysaccharide foundation has a degree of polymerization of at least about 500.

23. The coating of claim 1, wherein the polysaccharide backing material has a degree of polymerization greater than 750.

The coating of claim 1, wherein the polysaccharide backing material has a degree of polymerization greater than 1000.

25. The coating composition of claim 1, wherein the synthetic thickener is also present.

26. The coating composition of claim 25, wherein the synthetic thickness is a hydrophobically modified ethylene oxide. k?

27. The coating composition of claim 25, wherein the synthetic thickener is an associative acrylic polymer.

28. The coating composition of claim 25, wherein the synthetic thickener is a hydrophobically modified ethoxylated urethane.

29. The coating composition of claim 1, wherein the coating composition is a latex-based paint.

30. The coating composition of claim 29, wherein the latex-based paint has a pigment volume concentration greater than 10 percent.

31. The coating composition of claim 30, wherein the upper limit of the pigment volume concentration is 90 percent.