# Patent

## Title
Ambient self-crosslinkable latex

## Abstract

The present invention relates to storage stable film forming latex particles substantially free of adipic acid dihydrazide (ADH) that crosslink under ambient conditions during or after drying. Monomers for the formation of the crosslinkable moieties in the latex particles include diacetone acrylamide (DAAM) or the likes and methacrylamide (MAM) or the likes with or without styrene. A paint composition comprising the storage stable latex particles was described.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of U.S. Non-provisional patent application Ser. No. 14/343,292 submitted on Mar. 6, 2014, entitled “Hydroxyethyl Cellulose Grafted Acrylic Latex” which claims priority to International Patent Application No. PCT/US2012/055,883, filed Sep. 18, 2012, entitled “Hydroxyethyl Cellulose Grafted Acrylic Latex” which claims priority to the U.S. Provisional Application No. 61/536,264, filed Sep. 19, 2011, entitled “Hydroxyethyl Cellulose Grafted Acrylic Latex.” The contents of all parent applications are incorporated herein by reference in their entireties.


FIELD OF THE INVENTION
This invention generally relates to aqueous latex compositions comprising self-crosslinkable polymer emulsions and methods for preparing same, as well as products formed with said composition. Specifically, the invention involves a novel crosslinking mechanism involving diacetone acrylamide and methacrylamide but that does not require the presence of adipic dihydrazide (ADH).
BACKGROUND OF THE INVENTION
There is increasing societal sensitivity to environmental issues, including restrained use of organic solvents, volatile organic compounds (VOCs) and other additives such as coalescent agents due to health concerns. One area in which the foregoing has become important is architectural coatings, especially aqueous latex paints and water borne coating compositions. As a result, aqueous latex paints and water borne coating compositions are gaining popularity.
In practice, however, it is a challenge to minimize the use of organic solvents, VOCs and additives without diminution of the performance of the coatings. Coalescence is a process whereby polymer particles in an aqueous latex or dispersion come into contact with one another during film-forming process and polymer chains diffuse across boundaries of latex/dispersion particles to yield continuous films with good bonding of the polymer particles. There is a balance between achieving the desired hardness of a resulting dried film from an aqueous paint composition and having the proper coalescence.
A method of improving the properties of films formed by water-borne compositions is to include polymer latex particles that are capable of being crosslinked. In one example, diacetone acrylamide (DAAM) is included in the latex particles as moieties. Crosslinking agents within the aqueous composition but not part of the latex particles can be used to crosslink the polymer latex particles when the aqueous composition is applied to a substrate under ambient conditions. Adipic dihydrazide (ADH) is one of these crosslinking agents that have been used for aqueous latex polymers. However, the conventional approach of using diacetone acrylamide (DAAM) as part of the latex and adipic dihydrazide (ADH) as free floating agents in the aqueous composition sometimes allows crosslinking reactions between the DAAM and ADH to take place during storage, i.e., while the latex particles are in the aqueous phase. This may diminish shelf stability and reduce intra particle crosslinking under ambient drying conditions. Other conventional two-component crosslinking approaches have similar stability issues as well as VOC and odor concerns.
U.S. Pat. No. 3,838,104 to Hayashi et al. discloses an oil and water-repellent copolymer by copolymerizing diacetone acrylamide (DAAM), diacetonemethacrylamide (DAMAM) or a lower alkylol derivative thereof and a fluoroalkyl monomer. Hayashi does not disclose an aqueous latex composition that may crosslink when applied to a substrate under ambient conditions. CN 101348541 to Li discloses a crosslinking acrylate composite emulsion. The functional monomers include diacetone acrylamide (DAAM) and adipic dihydrazide (ADH). U.S. Pat. No. 3,451,480 to Zeh discloses a copolymer of acrylamide and diacetone acrylamide (DAAM) as a friction reducer in brines used in oil well fracturing. Up to 0.006% of N,N′-methylene bisacrylamide may be included as a cross-linking agent. WO 03/068880 A1 describes a latent cross-linking thickener composition including diacetone acrylamide (DAAM) and adipic dihydrazide (ADH).
Lu et al. (Zhongguo Jiaonianji, 15 (1), 2006, pp. 17-20) describes a blend of self-crosslinking acrylate latexes. Each of the latexes is copolymerized from diacetone acrylamide (DAAM), acrylamide (AM) or N-methylacrylamide, among other monomers. However, a blend of DAAM containing copolymer with an AM containing copolymer shows a lack of water resistance. U.S. Pat. No. 3,497,467 to Coleman discloses an aqueous polymer latexes having diacetone acrylamide (DAAM) monomer as the main component. The DAAM dominant polymer can be a copolymer with a vinyl or another acrylic monomer. WO 02/087734 A1 discloses hydrophobic membranes modified with a surface coating that includes a cross-linked ter-polymer. The monomers include diacetone acrylamide (DAAM), N,N′-methylenebisacrylamide and N,N-dimethylacrylamide.
All patents and publications discussed herein are incorporated by reference herein in their entirety.
There remains an unmet need for an aqueous latex composition that is stable during storage while still being capable of crosslinking when applied on a substrate without additional water borne crosslinking agents such as ADH during or after drying under ambient conditions. Crosslinking after film formation would improve film strength, block and water resistances and bring other benefits to the water borne coatings all while achieving proper film formation.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a latex composition that remains substantially free of crosslinking reactions during storage, thus having improved shelf life, but that allows self-crosslinking to occur under ambient conditions after application to a substrate. In one embodiment, the object is achieved by an inventive aqueous composition comprising latex particles polymerized from principally acrylic and/or vinyl acrylic monomers with moieties of diacetone acrylamide (DAAM) monomers or the likes and methacrylamide (MAM) monomers or the likes, wherein the latex particles crosslink when the water content is reduced or substantially depleted under ambient conditions by drying or evaporation. Preferably, the inventive self-crosslinkable latex particles can crosslink substantially without a crosslinking agent such as adipic dihydrazide that would reside in the water component.
It is another object of the present invention to provide an aqueous core/shell latex composition which crosslinks during or after the evaporation of water.
It is still yet another object of the present invention to provide an aqueous composition comprising latex particles having a C4-C18 ethylenically unsaturated monomer moiety containing a ketone and a C3-C18 ethylenically unsaturated monomer moiety containing a primary amide, wherein the ketone is substantially unreactive to the primary amide when the latex is in storage in an aqueous solution and wherein the ketone reacts with the primary amide and latex particles crosslink when water is at least partially removed from the latex under ambient conditions substantially without a water borne cross-linking agent.
One embodiment of the present invention is directed to an aqueous composition comprising latex particles, which comprise a film forming monomer, a C4-C18 ethylenically unsaturated monomer moiety containing a ketone and a C3-C18 ethylenically unsaturated monomer moiety containing a primary amide. The ketone is substantially unreactive to the primary amide when the latex particles are in storage in water and wherein the ketone reacts with the primary amide and latex particles crosslink when water is at least partially removed from the latex particles under ambient conditions. The monomer containing a ketone can be diacetone acrylamide, diacetone methacrylamide, or acetoacetoxyethyl methacrylate, or combinations thereof. The monomer containing a primary amide can be methacrylamide and/or acrylamide.
Another embodiment of the present invention is directed to an aqueous composition comprising film forming latex particles having crosslinking moieties. The crosslinking moieties comprise a diacetone acrylamide moiety and a methacrylamide moiety. The latex particles cross-link when applied to a substrate at ambient conditions. In one aspect of the present invention, the composition is substantially free of adipic acid dihydrazide or the like.
The film forming latex particles preferably comprise acrylic latex particles. Alternatively, the film forming latex particles may also comprise at least about 75% acrylic or vinyl monomers. The ratio by weight of diacetone acrylamide to methacrylamide ranges from about 20:1 to about 1:20 by weight, preferably from about 6:1 to about 1:3, more preferably from about 4:1 to about 1:2.
A ratio by weight of diacetone acrylamide and methacrylamide to film forming monomers ranges from about 0.1:100 to 10:100, preferably from about 0.5:100 to 5:100, more preferably from about 1:100 to 3:100. The latex particles may have a molecular weight from about 20K to about 500K Daltons based on GPC measurement, preferably from about 80K to about 300K Daltons based on GPC measurement.
The latex particles should have a MFFT from about −10° C. to about 50° C., more preferably from about −5° C. to about 25° C.
The present invention is also directed to an aqueous composition comprising core shell latex particles having a shell polymer comprising diacetone acrylamide and methacrylamide moieties, wherein the latex particles crosslink when applied to a substrate at ambient conditions. Preferably, the core polymer has a diacrylate crosslinker.


DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment of the invention, self-crosslinking latex polymers and resins can advantageously comprise at least a pair of crosslinkable functional groups or moieties that are reactive with one another under ambient conditions in the absence of water or reduced water content to form a covalent bond, but which are substantially not reactive with each other during storage in water, and the ambient self-crosslinking occurs preferably without a crosslinking agent(s) that resides in the water. These crosslinking agents such as ADH are reactive and can cause crosslinking of the latexes while suspended in water. Other compounds may be needed in the composition to control the reactivity of the crosslinking agents, which may also have unpleasant odors.
As discussed in the parent application PCT/US2012/055,883, the present inventors have discovered that when methacrylamide (MAM) and a ketone functionalized acrylamide, such as diacetone acrylamide (DAAM), are used in predetermined amounts as monomers for the latex polymer suspended in water they act as self-crosslinking moieties under ambient conditions. After the latex compositions are applied on a substrate or surface without using heat or dryers, a crosslinking reaction takes place.
However, substantially no crosslinking reaction in the aqueous phase occurs during storage. Without being bound to any particular theory, the present inventors believe that the self-crosslinking reaction occurs through particle-to-particle or inter-polymer chain interactions of the functional groups, e.g., methacrylamide and diacetone acrylamide moeities, incorporated onto the polymer chains. Molecular inter-diffusion between neighboring latex particles, which is important for the generation of latex film strength takes place prior to the crosslinking reaction. However, strongly crosslinked particles are unable to inter-diffuse. It is also believed that the primary amide nitrogen on the methacrylamide unit may react with the carbonyl group of the diacetone acrylamide unit or other active carbonyl groups to form an imine linkage Inter-chain hydrogen bonding and chain entanglements are also likely to be present, which further enhances the mechanical strength of the film. The hydroxyl group in hydroxyethyl cellulose (HEC) grafting may also play certain functions for the ambient crosslinking in our system.
In one embodiment, diacetone acrylamide (DAAM) or diacetone methacrylamide (DAMAM) monomer is copolymerized as part of the latex particles and functions as a self-crosslinking moiety. Instead of or in addition to DAAM, diacetone methacrylamide (DAMAM) and/or acetoacetoxyethyl methacrylate (AAEM) can be used singly or with each other.
In another embodiment, methacrylamide (MAM) and/or acrylamide (AM) monomer is copolymerized as part of the latex particles and functions as another self-crosslinking moiety.
In one preferable embodiment, latex particles are polymerized from film forming monomers, including diacetone acrylamide (DAAM) and methacrylamide (MAM) in a predetermined ratio relative to each other (DAAM/MAM) and in an amount together (DAAM+MAM) relative to the total amount of the film forming monomers by weight. Film forming monomers are the monomers that form the dried polymeric film or dried paint layer (polymeric film, pigments and colorants, etc.). Suitable film forming monomers include but are not limited to vinyl monomers, acrylic monomers and styrene monomers, discussed in detail below. These monomers are polymerized to form latex particles suspended in an aqueous solution, which cross-link to each other to form a film or paint layer. In one embodiment, the film forming monomers do not include the crosslinkable monomers/moieties discussed above, such as DAAM, DAMAN, AAEM, MAM or AM.
Preferably the ratio by weight of diacetone acrylamide or the likes (e.g., DAMAM or AAEM) to methacrylamide or the likes (e.g., acrylamide) in the latex particles ranges from about 20:1 to about 1:20 by weight. More preferably the ratio by weight of diacetone acrylamide to methacrylamide in the latex particles ranges from about 6:1 to about 1:3. Most preferably the ratio by weight of diacetone acrylamide to methacrylamide in the latex particles ranges from about 4:1 to about 1:2. Said ratio can also be from about 10:1 to 1:10, or 4:1 to 1:2 or 2:1 to 1:1 by weight.
Preferably the weight ratio of diacetone acrylamide and methacrylamide to the film forming monomers ranges from about 0.1:100 to 10:100. More preferably, the ratio of the weight of diacetone acrylamide and methacrylamide to the film forming monomers ranges from about 0.5:100 to 5:100. Most preferably the ratio of the weight of diacetone acrylamide and methacrylamide to the film forming monomers ranges from about 1:100 to 3:100.
The present invention also relates to the impact of the crosslinking on the properties of the coating or film formed from the composition, particularly on the mechanical, chemical, physical, and physico-chemical properties of the coating. These properties can include, but are not limited to, the minimum film forming temperature (“MFFT”), block resistance, scrub resistance, molecular weight, pencil hardness, viscosity, water resistance, water stain resistance, scratch resistance, shelf/incubation stability, and the like, and combinations thereof.
Preferably acrylic monomers principally form the latex particles that the MAM and DAAM form moieties thereon. Any acrylic monomers can be used in the present invention. Suitable acrylic monomers include, but are not limited to methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate, butyl acrylate and butyl methacrylate, iso-octyl methacrylate and acrylate, lauryl acrylate and lauryl methacrylate, 2-ethyl hexyl acrylate, stearyl acrylate and methacrylate, isobornyl acrylate and methacrylate, methoxy ethyl acrylate and methacrylate, 2-ethyoxy ethyl acrylate and methacrylate, 2-hydroxyethyl acrylate, 2-hydroxybutyl, dimethylamino ethyl acrylate and methacrylate, acrylates, alkyl(meth)acrylic acids such as methyl acrylic acids, wet adhesion monomers, such as N-(2-methacryloyloxyethyl)ethylene urea, and multifunctional monomers such as divinyl benzene, diacrylates, for crosslinking functions etc., acrylic acids, ionic acrylate salts, alkacrylic acids, ionic alkacrylate salts, haloacrylic acids, ionic haloacrylate salts, acrylamides, alkacrylamides, monoalkyl acrylamides, monoalkyl alkacrylamides, alkyl acrylates, alkyl alkacrylates, acrylonitrile, alkacrylonitriles, dialkyl acrylamides, dialkyl alkacrylamides, hydroxyalkyl acrylates, hydroxyalkyl alkacrylates, only partially esterified acrylate esters of alkylene glycols, only partially esterified acrylate esters of non-polymeric polyhydroxy compounds like glycerol, only partially esterified acrylate esters of polymeric polyhydroxy compounds, and combinations thereof. The alkyl methacrylate monomer is preferably methyl methacrylate.
Preferred monomers containing aromatic groups are styrene and α-methylstyrene. Other suitable monomers containing aromatic groups include, but are not limited to, 2,4-diphenyl-4-methyl-1-pentene, 2,4-dimethylstyrene, 2,4,6-trimethylstyrene, 2,3,4,5,6-pentafluorostyrene, (vinylbenzyl)trimethylammonium chloride, 2,6-dichlorostyrene, 2-fluorostyrene, 2-isopropenylaniline, 3(trifluoromethyl)styrene, 3-fluorostyrene, α-methylstyrene, 3-vinylbenzoic acid, 4-vinylbenzyl chloride, α-bromostyrene, 9-vinylanthracene, and combinations thereof.
Preferred monomers containing primary amide groups are methacrylamide, and acrylamide. Other suitable monomers containing amide groups include, but are not limited to, N-vinylformamide, or any vinyl amide, N,N-dimethylacrylamide, N-(1,1-dimethyl-3-oxobutyl)(meth)acrylamide, N-(hydroxymethyl)(meth)acrylamide, N-(3-methoxypropyl)acrylamide, N-(butoxymethyl)acrylamide, N-(isobutoxymethyl)acryl(methacryl)amide, N-[tris(hydroxymethyl)methyl]acryl(methacryl)amide, 7-[4-(trifluoromethyl)coumarin](meth)acrylamide, 3-(3-fluorophenyl)-2-propenamide, 3-(4-methylphenyl)acrylamide, N-(tert-butyl)(meth)acrylamide, and combinations thereof. These monomers can be polymerized with acrylic monomers, listed above. General formula for vinyl(form)amides:




and (meth)acrylamides:





where R1 is H, CH3, CH2CH3, or other substituted functional groups, and R2 can be —H, —CH3, —CH2CH3, and other substituted organic functional groups.

Suitable styrene monomers include, but are not limited to, styrene, methylstyrene, chlorostyrene, methoxystyrene and the like. In this embodiment, styrene monomers are preferably co-polymerized with methacrylamide and acrylamide monomers.
In one embodiment, the aqueous latex polymer may also comprise vinyl monomers. Monomers of this type suitable for use in accordance with the present invention include any compounds having vinyl functionality, i.e., —CH═CH2 group. Preferably, the vinyl monomers are selected from the group consisting of vinyl esters, vinyl aromatic hydrocarbons, vinyl aliphatic hydrocarbons, vinyl alkyl ethers and mixtures thereof.
Suitable vinyl monomers include vinyl esters, such as, for example, vinyl propionate, vinyl laurate, vinyl pivalate, vinyl nonanoate, vinyl decanoate, vinyl neodecanoate, vinyl butyrates, vinyl caproate, vinyl benzoates, vinyl isopropyl acetates and similar vinyl esters; nitrile monomers, such acrylonitrile, methacrylonitrile and the like; vinyl aromatic hydrocarbons, such as, for example, styrene, methyl styrenes and similar lower alkyl styrenes, chlorostyrene, vinyl toluene, vinyl naphthalene and divinyl benzene; vinyl aliphatic hydrocarbon monomers, such as, for example, vinyl chloride and vinylidene chloride as well as alpha olefins such as, for example, ethylene, propylene, isobutylene, as well as conjugated dienes such as 1,3-butadiene, methyl-2-butadiene, 1,3-piperylene, 2,3-dimethyl butadiene, isoprene, cyclohexene, cyclopentadiene, and dicyclopentadiene; and vinyl alkyl ethers, such as, for example, methyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, and isobutyl vinyl ether.
Preferably, the film forming monomers are the principal monomers in the latex and the two crosslinkable moieties make up small portions of the latex, as discussed in the ratios above. The film forming monomers preferably make up more than about 75% by weight of the latex particles, more preferably more than about 85% and more preferably more than about 90%.
The present inventors have conducted a number of experiments to show the efficacy of the self-crosslinkable polymer latex with at least two types of crosslinkable moieties. Each moiety may exist at multiple locations in the latex particles. These moieties may crosslink a single latex particle to itself (intra particle cross-linking); however as shown in the Examples below, they could crosslink to other latex particles (inter particle cross-linking) to form a strong paint film. It is noted that Examples 1-6 discussed below were reported in the parent PCT international application as Examples 4, 5A, 5B, 6, 8 and 9, respectively. As discussed below, these examples and others illustrate the inventive use of the MAM and DAAM moieties to crosslink latex polymers.
The crosslinking is demonstrated by measuring water sensitivity of dried latex films. The procedure for the water sensitivity test is described in the Material and Methods section, as shown below. Films were dried under ambient conditions before the water sensitivity test was performed. The results for the water sensitivity tests for latexes from Examples 1-3 are shown below. In Example 1 the latex contains both diacetone acrylamide (DAAM) and methacrylamide (MAM) moieties in the composition; Example 2 contains MAM but not DAAM moiety; and Example 3 contains DAAM but not MAM. As shown below, the dried film of Example 1 has significantly better water resistance, suggesting significantly more crosslinking when DAAM is used with MAM even when no heat or dryer is used. In contrast, when either one of these two components, DAAM and MAM, is omitted as in the cases of Examples 2 and 3, the resulting dried latex is very sensitive to water, which means that the crosslinking is unsatisfactory. No crosslinking agent, such as ADH, is added to the aqueous composition in Examples 1-3. Comparative Experiment A shows the results of water sensitivity tests performed on latex films of Examples 1-3 made with the inventive latex.
Examples 4, 5 and 6 all have MAM/DAAM crosslinking moieties in addition to hydroxyl cellulose (HEC) in the composition. Example 5 and 6 further contains methylol methacrylamide monomer to improve latex stability and the dried film's water permeability.
The self-crosslinking under ambient conditions when the latex is coated on a substrate using the DAAM/MAM does not require any dryer, or a crosslinking agent in water phase, e.g. ADH, to initiate the crosslinking. This novel combination also minimizes the volatile organic compounds (VOC) or odor issues associated with conventional two-component approaches, such as DAAM in the latex and adipic dihydrazide (ADH) in the water phase discussed above. Meanwhile it improves the film's mechanical strength, and extends the storage life of the latex in the aqueous phase. Preferably, the latex composition is substantially free of water borne crosslinking agents, such as adipic dihydrazide or the like. Water molecules appeared to play a significant role in latex stability. The premature crosslinking reactions are significantly restricted in the presence of water, probably because particle-particle inter-diffusions or inter-chain interactions are hindered. The latex sample disclosed in Example 1 remains stable even after one year Of storage and the dry film formed from this aged latex still exhibits excellent water sensitivity and crosslinking ability.
The performances in terms of the scrub resistance, block resistance, water sensitivity, and water stain are related to crosslinking. A paint from a commercial latex which does not contain any DAAM or MAM functional monomers in its composition was used as a control for comparison with paints made from inventive latex samples of Examples 7-10 as shown in Comparative Experiment B. The control sample did not form a cross-linked dry film and has relatively poor scrub resistance and water sensitivity compared with the paints made with inventive latexes of Examples 7-10 which are incorporated with self-crosslinking functional monomers DAAM and MAM, but which are substantially free of ADH. The results clearly demonstrate that the addition of DAAM and MAM as a functional moiety pair to the polymer chains constitutes a novel approach to achieve ambient cross-linking without a crosslinking agent in the water phase such as adipic dihydrazide (ADH).
Example 11 shows an inventive core/shell latex with the DAAM and MAM moieties in the shell and Examples 12 to 14 show core/shell latexes with only one DAAM or MAM moiety. These latexes are prepared in a two-stage process, allowing additional control over the composition and structure of the polymer films. The first stage process produces a core of the latex and the second stage provides a shell for the latex. The core is provided with a non-ambient crosslinker (also called crosslinking monomers), e.g. 1,4-butanediol diacrylate (i.e. SR-213) in the pre-emulsion composition and no MAM or DAAM is present in the first stage pre-emulsion composition. The crosslinking of the core polymers imparts improved hardness and weathering property to the resulting latex.
In Example 11, the shell contains both DAAM and MAM moieties and the latex is capable of crosslinking when the aqueous environment is at least partially depleted of water. The shell composition of Example 12 is different from Example 11 only in that the former contains no MAM monomer in the pre-emulsion composition. On the other hand, shell compositions of Examples 13 and 14 lack DAAM in contrast to Example 11. Example 14 is further different from Example 11 in that the BA monomer is replaced with 2-EHA.
Comparative Experiment C shows the physical and mechanical properties of paint samples made from the core-shell latexes in Examples 11-14. This comparative experiment shows the efficacy of having the DAAM and MAM moieties on the shell or second phase of the core-shell latex. It demonstrates the effectiveness of ambient curing/crosslinking using block resistance as an indicator. A paint film was drawn down on a Leneta card for each latex sample. It was dried for 7 days at room temperature before being placed into a 120° F. oven for 24 hours. The block resistance was rated on a numerical scale of 1 to 5 with 5 being the best. The block resistance test was conducted according to ASTM_D4946-89. The results for the above examples demonstrated that the MAM/DAAM moiety pair formed a cross-linked networks effectively at ambient temperature, which improved the block resistance of the paint sample made with inventive Example 11.
The paint sample with the MAM and DAAM crosslinking pair shows superior physical and mechanical properties in comparison with a control paint sample without any crosslinkers. Comparative Experiment D compares the performance of paints made from inventive examples 15 and 16, both of which have MAM/DAAM crosslinkers with control paint Example I, which does not use a crosslinking latex. While both paints using inventive latex have the same block resistance as the control paint Example I which does not have any crosslinker, they show other superior mechanical and physical properties.
The effectiveness of the inventive crosslinking between MAM and DAAM moieties was further compared in Comparative Experiment E with a paint sample that uses a single conventional crosslinking moiety, such as DAAM, and a crosslinking agent, such as ADH, in the water phase. The performance of these two paints is comparable. The inventive paint is made of Example 16 latex and contains the MAM and DAAM crosslinking moiety pair. The paint control Example II is made of a latex containing the DAAM moiety and the ADH crosslinking agent in the water phase. This result shows that the scrub resistance of the paints using the inventive latex containing MAM and DAAM is somewhat better than the paint using latex containing DAAM and ADH in the water phase and the water resistances of the two paint samples are identical.
More direct evidence for the self-crosslinking of the latex under ambient conditions is provided by Examples 17 and 18. The molecular weights of the samples were measured on a GPC instrument from WATERS Corp. The molecular weight analysis was first performed on the latex samples before curing. Then, the latex samples were drawn into a three mil thickness film and dried. It is observed that there were insoluble gels for both samples in the solvent used for the Mw analysis and the gels would not dissolve even by solvent heating. Molecular weight analysis fig the soluble portion of the 7-day cured film was made. The presence of the insoluble gel even at an elevated temperature (in Tetrahydrofuran-THF solvent and about 70° C.) is consistent with the crosslinking of the latex and make it difficult to dissolve, i.e., thus improving solvent resistance. The polymer converts to thermoset matrix after it is cross-linked and loses its chain mobility. One of the polymer thermoset features is the superior solvent/chemical resistance, which renders it non-soluble or difficult to dissolve in strong organic solvent. It is also common practice to measure the degree of crosslinking through solvent solubility test and swell ratio measurement.
The soluble portions of the two cured samples also show increased molecular weights. For the cured sample from Example 17, the molecular weight of the soluble portion increases from 161K to 178K. The sample from Example 18 shows a similar degree of increase, from 159.2K to 180.3K. This result is consistent with the crosslinking of the polymers, resulting in an increase of the measured molecular weight.
Without being bound to any particular theory, the present inventors believe that in a conventional two-component cross-linking system, such as in the case of DAAM and ADH, component ADH is water soluble and can move freely in the aqueous latex compositions or paints. ADH or hydrazide containing particles can then react with the DAAM resulting in premature crosslinking while the aqueous latex compositions or paints are still in storage. In contrast, in the inventive DAAM and MAM crosslinking system, both the DAAM and MAM units are moieties or parts of the latex particles and water acts to separate the latex particles away from each other thereby inhibiting cross-linking while being dispersed in water. On the other hand, when the latex is drying or dried, the DAAM and MAM moieties can react more readily resulting in better mechanical strength of the dry film as demonstrated in Example 1.
It is to be understood that the present approach is not limited to the DAAM and MAM combination but can be tailored to different functional group combinations for many other applications. Although there may be some limited intra-particle/intra-chain crosslinking, the present inventors believe that the majority of the crosslinking reactions occur when the latex particles inter-diffused in contact with neighboring particles during the drying and coalescence process. This conclusion is supported by the observations that a latex sample of Example 1 which has stored for one year still maintained its crosslinking ability, when it was coated on a substrate under ambient conditions as described above.
As used herein, the term “substantially free” or “substantially without”, referring to a component in a composition, mean that the composition comprises not more than about 1 wt %, preferably not more than about 0.5 wt %, more preferably not more than about 0.1 wt %, most preferably not more than about 0.02 wt %, or in some cases completely none (about 0%), of the component.
The present invention may be understood more readily by reference to the following description of the invention, and to the Examples included therein.
Before the present compositions of matter and methods are disclosed and described, it is to be understood that this invention is not limited to specific synthetic methods or to particular formulations, unless otherwise indicated, and, as such, may vary from the disclosure. It is also to be understood that the terminology used is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the invention.
EXAMPLES
Material and Methods
Particle size distribution is determined by Microtrac 250 particle size analyzer using light scattering technology. Particle size means an average particle size based on the diameter of the particles.
Rheological curves are measured by a Bohlin CVO Rotational Viscometer (0.5° cone and 40 mm diameter plate).
The water sensitivity test (1 minutes and 5 minutes water spot test) is illustrated by the following procedures. Emulsion latex samples were drawn down on a sealed Leneta card (made by BYK for example) to form a dry film using a BYK-GARDNER 3 MIL WET FILM draw down bar. The latex film was air-dried on a flat horizontal surface for one week before testing. To the dried film surface, 3-5 drops of water were placed and the water sensitivity of the latex film was rated using the finger nail scratching method for rating the dry film strength after 1 minute and 5 minute soaking periods. The wet films are rated for resistance to finger nail scratching from 1 to 5, with 5 being the best.
The water stain resistance is tested by a visual rating of water stain on the dried paint film. A 3 mil film of paint is dried for 7 days at room temperature, and 3 ml of DI water is placed on the horizontal dried paint film for 3 minutes, and then the Leneta card is raised to a vertical position to allow water to flow down across the surface of the film. The film is placed in a vertical position while the water evaporates. The water stain mark on the film surface is visually inspected and assigned a number from 1 to 5, 5 being the best and 1 being the worst.
Water vapor permeability for grafted and control acrylic latex samples was measured by an internal method which followed the procedures given by the ASTM D1653-93 method (standard test methods for water vapor transmission of organic coating films). The test specimen was sealed to the open mouth of a cup or dish containing water, and the assembly was placed in a controlled atmosphere environment at constant humidity and temperature. The permeability cups used for the testing were BYK-Gardner PO-2301 (25 cm2) and the parchment paper for vapor permeability test were from All-State International, Inc. The drawdown films were made on a parchment paper using the latex samples with a 3-mil drawdown′bar and then the films were dried for one week before the water vapor permeability measurement. The dried film was cut into a proper size for the cup, the thickness of the film and paper was measured, and the weight of each coating sample was recorded. The permeability cup was filled with deionized water and the opening was sealed with the dry film. The samples were weighed to the 0.0001 g accuracy before and after 24 hours evaporation. The permeability was calculated using the formulae defined in section 13 of ASTM method D1653-93.
The molecular weights were measured on a GPC instrument from WATERS Corp. The molecular weight analysis was performed on the latex samples (before curing). The latex samples were then drawn into three mil thickness films and dried for 7 days. The molecular weights of cured samples were measured on the soluble portion in THF solvent. The molecular weights reported are all weight average molecular weights using polystyrene calibration standards.
As used herein, MFFT is the minimum temperature at which the latex will form a continuous film. MFFT was determined on a MFFT Bar-90 from Rhopoint Instruments according to ASTM D2354-98 and ISO 2115:1996) (American Standard Test Method for Minimum Film Formation Temperature). The emulsions were applied using a 75 micron cube applicator to form tracks. Emulsions were allowed to dry for 3 hours. The MFFT were determined as points on tracks where the film has coalesced over 90% of the track width (no cracking).
The MFFT of the inventive latexes range from about −10° C. to about 50° C., preferably about −5° C. to about 28° C., more preferably about 2° C. to about 25° C. and most preferably about 4° C. to about 18° C.
Block resistance, or the propensity of a coating to adhere to itself instead of to its substrate, was measured according to a modified version of ASTM D4946-89. On a sealed white LenetaTM WK card, a 3 mil thick coating was prepared. After one week of drying at room temperature, the coating was cut into four one inch squares. Two of the squares were oriented face to face (i.e., coated sides touching) and are placed under a 100-gram weight in a 120° F. oven for about 24 hours. The other two of the squares were oriented face to face and placed under a 100-gram weight at room temperature for about 24 hours. Both sets of face to face squares were then allowed to equilibrate to ambient temperature for about 1⁄2 hour. Each set of squares was then pulled apart using a slow and steady force, forming a T pattern. Block resistance was rated based on the percentage of area of the paint on one surface that was transferred to the other surface. 0% transfer indicates a perfect blocking resistance while 100% transfer indicated paints on both sides are completely stuck together.
The residual monomers were measured by a gas chromatography (GC) instrument equipped with a FID or a Mass detector. This method is the industry accepted standard procedure for testing residual monomers, and is known to those of ordinary skill in the art.
Scrub Test. The scrub resistance is determined by ASTM Method D2846. In this test, a 7 mil drawdown of paint(s) is prepared on a scrub panel and allowed to air dry at room temperature for one week. A medium bristle brush is soaked overnight in deionized water for conditioning prior to running the test. Two glass plates are placed in the tray of the Abrasion tester, and three brass shims are placed on the plates in such a way that each paint being tested would have a shim under it. The test panel with the dried paint is secured to the two glass plates on the Gardner Abrasion Tester. Ten grams of abrasive scrub medium are applied to the bristles of the brush and the brush is then placed in a brush holder which is secured to the cables of the Abrasion Tester. Five cc of deionized water is applied to the test panel, and the scrub cycles are started. Every 400 cycles another 10 g of abrasive medium is applied to the brush and another 5 cc of deionized water is applied to the panel. The test is continued until paint is removed in one continuous line across its own shim and the number of cycles required to reach this point is recorded.












Examples

















Monomers (grams)
1
2
3
4
5
6
7
8
9
10




















MMA
270.5
290.0
300.6
259.3
265.3
278.7
254.0
270
251.0
265.3


BA
310.9
309.0
374.4
322.5
306.6
252.7
311.0
310
308.0
307.4


2-EHA


23.2

25.6
84.3



19.2


MAA
4.7
4.4
6.2
5.2
5.4
5.3
4.7
4.8
5.4
5.5


AA












Vinyl neodecanoate












(VeoVa TM 10)












Styrene
29.5
12.9
40.0
29.8


38.6
29.5
51.5
12.8


N-(2-methacryloyloxyethyl)
25.7
26.3
17.5
25.9
25.6
11.7
26.5
25.7
25.8
25.6


ethylene urea












N-Methylol methacrylamide




7.4
7.8






DAAM
2.9

3.4
2.9
2.9
2.6
4.5
2.9
0.7
2.9


MAM
2.5
2.6

2.5
2.6
5.2
1.8
2.5
3.2
2.5


1,4-butanediol diacrylate (i.e.












SR-213)












DAAM & MAM to total latex
0.84
0.40
0.44
0.83
0.86
1.20
0.98
0.84
0.60
0.84


monomers












DAAM/MAM ratio
1.16


1.16
1.12
0.50
2.50
1.16
0.22
1.16


Test of paints
†
†
†



‡
‡
‡
‡





† See Comparative Experiment A


‡ See Comparative Experiment B


















Examples
















11
12
13
14























Monomers (grams)
Stage1
Stage2
Stage1
Stage2
Stage1
Stage2
Stage1
Stage2 
15
16
17
18






















MMA
284.0
330.0
284.0
330.0
284.0
330.0
284.0
330.0
430.0
430.0
675.5
676.5


BA
118.4 
281.0
118.4
281.0
118.4
281.0


435.0
424.0
606.0
603.0


2-EHA






118.4 
281.0






MAA

10.2

10.2

10.2

10.2
9.0
8.2
14.0



AA
4.0

4.0

4.0

4.0







Vinyl neodecanoate

460.1

460.1

460.1

460.1






(VeoVa TM 10)














Styrene









27.1




N-(2-

21.3

21.3

21.3

21.3
19.2
18.2
30.6
30.6


methacryloyloxyethyl)














ethylene urea














N-Methylol














methacrylamide














DAAM

1.6

1.6




8.3
12.2 
18.2
22.5


MAM

1.2



1.2

1.2
5.5
2.8
4.2
5.1


1,4-Butanediol
1.6

1.6

1.6

1.6







diacrylate (i.e. SR-213)














DAAM & MAM to total 

0.25

0.15

0.11

0.11 
1.52
1.63
1.66
2.06


latex monomers














DAAM/MAM ratio

1.33






1.51
4.36
4.33
4.41















Test of paints
§
§
§
§
§§
§§







§ See Comparative Experiment C


§§ See Comparative Experiments D and E






Example 1
To a 5-liter 4-necked round bottom glass reactor equipped with a mechanical stirrer, a thermocouple, a condenser, and nitrogen purge, 445.0 g of deionized (DI) water and 2.0 g of emulsifier which is a branched sodium dodecylbenzene sulfonate (i.e., Rhodacal® DS-4 std), were added and heated to 79° C.
To an Erlenmeyer flask, the following ingredients were added and stirred to form a stable monomer pre-emulsion. Monomer pre-emulsion composition:













Methyl methacrylate (MMA) monomer
270.5 g


Butyl acrylate (BA) monomer
310.9 g


Methacrylic acid (MAA) monomer
 4.7 g


Methacrylamide (MAM) monomer
 2.5 g


Diacetone acrylamide monomer (DAAM)
 2.9 g


Styrene monomer
 29.5 g


N-(2-methacryloyloxyethyl) ethylene urea
 25.7 g


DI water
210.0 g


Sodium dioctyl sulfosuccinate surfactant (75% active) 
 2.2 g


Tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl
 3.8 g


sulfosuccinamate surfactant (35% active)



Ammonium salt of phosphate ester surfactant (100%)
 1.0 g









Suitable surfactants include AEROSOL® 22 and AEROSOL® OT-75 made by Cytec Industries and POLYSTEP TSP-16PE. About 1.9 g of ammonium hydroxide (28%) was also added to the monomer mix for pH adjustment.
About 10 ml of 12.8% aqueous potassium persulfate (KPS) initiator solution and 35.0 g of the monomer pre-emulsion were charged to the reactor at 79° C. to form seed particles. After about 20 minutes at 79° C. with agitation, the delay feed of the monomer pre-emulsion together with 30 ml of 4.2% aqueous KPS initiator solution was started. The delay feed rate for the reaction was as follows:
about 4.6 ml/min for the first hour; and
about 5.5 ml/min for the remaining monomers.
In a separate container, 3.2 g of hydroxyethyl cellulose (HEC) and 88.0 g of DI water were mixed together. This HEC solution was mixed with the last 15% of the monomer pre-emulsion. The following additional surfactants were also added into HEC solution at this stage:














(i)
branched alcohol ethoxy phosphate surfactant or 
6.0 g



polyoxyethylene tridecyl ether phosphate (25% active)



(ii)
ammonium salt of phosphate ester surfactant (100% active)
3.0 g









Suitable phosphate ester surfactants include but are not limited to tristyrylphenol ethoxylate phosphate ester. The tristyrylphenol ethoxylate phosphate ester (100% solids) was diluted with DI water in 20% and neutralized with ammonium hydroxide to the pH value of 9.5-10.0 before use. 17 g of 20% tristyrylphenol ethoxylate phosphate ester (neutralized) was used in the above example. The addition of extra surfactants together with HEC solution was surprisingly effective in preventing the gel formation from the grafting.
About 15-30 minutes after the feed, the batch became viscous and then returned to a workable viscosity again after holding the temperature at 82° C. for an additional 30-60 minutes. The batch was cooled down to 65-68° C., and chasers (t-butyl hydroperoxide and sodium formaldehyde sulfoxylate) and ammonium hydroxide were added with agitation. The properties of the produced latex were shown in the following table.

















MFFT
Particle 
Particle size
Mechanic


Solids
pH
(° C.)
size(mV)
(mV)
Stability





















After
pH 
Rhopoint 
Before HEC
After HEC
10,000 
rpm












filtration
meter
WP
addition
addition














43.0%
8.0
12.8
145 nm
543 nm
>30 
min.









As discussed above, this HEC grafted acrylic latex sample showed excellent water resistance and was water permeable. Water permeability results are shown in the following table. This property allows applications in areas outside the paint industry, e.g., the HEC grafted acrylic latex may be suitable as a material for contact lenses.














Specific Permeability(3)



Sample ID
mg/cm2 · mm · 24 hr








Control latex without HEC(1)
0.38



HEC grafted Latex(2)
1.01





(1)Control acrylic latex sample without any HEC during the reaction.


(2)HEC grafted acrylic latex sample from example 1. HEC is about 0.5% vs. total weight of monomers.


(3)See Material and Methods Section






Example 2
To the same reactor setup as described in Example 1, 460 g of DI water and 0.65 g of sodium bicarbonate were added. The reactor was heated to 78° C. and agitated at 160 RPM. The following ingredients were mixed to form monomer pre-emulsion.
Monomer Pre-Emulsion Composition
















Methyl methacrylate (MMA) monomer
290.0 g



Butyl acrylate (BA) monomer
309.0 g



Methacrylic acid (MAA) monomer
 4.4 g



Methacrylamide (MAM) monomer
 2.6



Styrene monomer
 12.9 g



N-(2-methacryloyloxyethyl)ethylene urea
 26.3 g



DI water
226.0 g



Sodium dioctyl sulfosuccinate surfactant
 6.0 g



Blend of anionic and nonionic surfactants
 3.0 g










A suitable example of a blend of anionic and nonionic surfactants can be Cytec XSM 1110 (50% active). After the monomer pre-emulsion formed, 2.9 g of ammonium hydroxide (28%) was added to the monomer emulsion for a pH of 6.2.
About 41.0 g of this monomer emulsion and about 10 ml of 12.6% aqueous potassium persulfate (KPS) initiator solution were charged into the reactor for seed. After 20 minutes of heating at 79° C., seed particles formed, and the monomer pre-emulsion was fed into the reactor at the following rate:
about 4.6 ml/min. for the first hour; and
about 5.5 ml/min. for the rest of the monomer emulsion.
About 25 ml of 4% KPS initiator in DI water was also co-fed with the monomer emulsion.
When about 8-10% of total monomer pre-emulsion was remaining, 83 g of 3.9% HEC solution in DI water together with 5.2 g of RHODAFAC® RS610/A25 and 5.5 g of AEROSOL® 22 surfactants were added to the 8-10% remaining monomer emulsion to complete the delay feed in 40-60 minutes. The totals were fed completely in about 3 hours and the latex was held at about 82° C. for additional 50-60 minutes and then cooled down to 65° C. Chasers and ammonium hydroxide were added. The properties of the produced latex are shown in the table below.

















Particles size (mV) 
Particle size (mV)


Solids
MFFT (° C.)
pH
before HEC grafting 
after HEC grafting







43%
13
8.0
191 nm
239 nm









The paint sample made with this latex showed water sensitivity due to the absence of the monomer combination methacrylamide/DAAM/styrene. The grafting was not as effective as in Examples 1 and 4 due to insufficient monomer emulsion (about 8%) when HEC was added. The final average particle size (mV) after the HEC grafting reaction was smaller than that of the typical HEC grafted samples which ranges from about 300 nm to about 900 nm.
Example 3
To the same reactor setup as described in Example 1, 534 g of DI water was added. The reactor was heated to 79° C. and agitated at 180 RPM. To a 2 liter Erlenmeyer flask, the following ingredients were mixed together and agitated for at least 20 minutes to form a stable monomer pre-emulsion.
Monomer Pre-Emulsion Composition















Methyl methacrylate (MMA) monomer 
300.6 g



Butyl acrylate (BA) monomer
374.4 g



Methacrylic acid (MAA) monomer
 6.2 g



Diacetone acrylamide (DAAM)
 3.4 g



Styrene monomer
 40.0 g



N-(2-methacryloyloxyethyl) ethylene urea
 17.5 g



Wet adhesion monomer (50%)




2-Ethylhexyl acrylate (2-EHA)
 23.2 g



DI water
264.0 g



Sodium dioctyl sulfosuccinate surfactant
 2.6 g



Tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl
 4.6 g



Sulfosuccinamate surfactant (35% active)




Ammonium salt of phosphate ester surfactant
 8.4 g









After the monomer pre-emulsion formed, 1.7 g of ammonium hydroxide (28%) was added to the monomer emulsion for a pH of 6.5.
About 50.4 g of this monomer emulsion and about 15 ml of 10.6% aqueous potassium persulfate (KPS) initiator solution were charged into the reactor for seeding. After 20 minutes of heating at 79° C., seed particles were formed, and the monomer pre-emulsion was delay fed into the reactor at the following rates:
about 6.5 ml/min. for the first hour; and
about 7.4 ml/min. for the rest of the monomer emulsion.
About 68 ml of 2.4% KPS initiator in DI water was also co-fed with the monomer emulsion.
When about 10-14% of total monomer pre-emulsion was remaining, 99 g of 3.9% HEC solution in DI water together with 7.8 g of polyoxyethylene tridecyl ether phosphate, ammonium salt and 20.4 g of ammonium salt of phosphate ester surfactant (neutralized at 20%) were added into the remaining monomer pre-emulsion and delay fed into the reactor together with KPS solution. The latex became very viscous near the end of the HEC feed but the viscosity would eventually drop after one hour holding. The agitation RPM was raised to ensure proper mixing. The total feed time for the monomers was about 3 hours and the batch was then held at about 82° C. for additional 60 minutes. After the hold, the batch was cooled down to 65° C. and the chasers and ammonium hydroxide were added for reducing residual monomer and pH control. The properties of the produced latex are in following table.


















Particles size

Particle size 





(mV)

(mV)





before HEC 

after HEC


Solids
MFFT (° C.)
pH
grafting
η (cP)
grafting







41.2%
6.0
8.8
177 nm
410
639 nm









Comparative Experiment A
The water sensitivity tests were performed on the latexes of the paint samples for Examples 1-3 following the procedure in the Material and Methods section. The results are summarized in the following table.















Film Drying time
4 hrs.
5 hrs.
6.5 hrs.
24 hrs.
7 days


Water wetting time
5 min.
5/10 min.
5/10/25 min.
10 min.
25 min.







Water sensitivity
4+
5/4−
5+/5/4
Not
Not


(1-5) 



scratchable
scratchable


Example 1



5+
5+


DAAM/MAM







combo







Water sensitivity
0
Not available
Not available
Poor film
Poor water


(1-5 )



strength
sensitivity


Example 2



1+
2


without DAAM







Water sensitivity
1−
1/1−
1+/1/0-1
Poor film
Scratchable


(1-5)



strength
3


Example 3



2



without MAM









Example 4
HEC Added with 31% Monomer Pre-Emulsion
To the same reactor setup as described in Example 1, 425.0 g of deionized (DI) water was added and heated to 79° C.
To an Erlenmeyer flask, the following ingredients were added and stirred to form a stable monomer pre-emulsion.
Monomer Pre-Emulsion Composition















Methyl methacrylate (MMA) monomer
259.3 g



Butyl acrylate (BA) monomer
322.5 g



Methacrylic acid (MAA) monomer
 5.2 g



Methacrylamide (MAM) monomer
 2.5 g



Diacetone acrylamide (DAAM) monomer
 2.9 g



Styrene monomer
 29.8 g



N-(2-methacryloyloxyethyl)ethylene urea
 25.9 g



Wet adhesion monomer




DI water
210.0 g



Sodium dioctyl sulfosuccinate surfactant
 2.1 g



(AEROSOL ® OT-75) (75% active)




Tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl
 5.2 g



Sulfosuccinamate surfactant (AEROSOL ® 22) (35%)




Ammonium salt of phosphate ester surfactant (100%)
 0.6 g









About 1.8 g of ammonium hydroxide (28%) was also added for pH adjustment.

About 15 ml of 8.6% potassium persulfate (KPS) aqueous initiator solution and about 40.0 g of the monomer pre-emulsion were charged to the reactor at 79° C. to form seed particles. After about 20 minute at 79° C. with agitation, the delay feed of monomer pre-emulsion, together with 30 ml of 4.1% aqueous KPS initiator solution was started. The delay feed rate for the reaction was as follows:
about 4.6 ml/min for the first hour; and
about 5.5 ml/min for the remaining monomers.
In a separate container, 3.2 g of hydroxyethyl cellulose (HEC) and 91.0 g of DI water were mixed together. This HEC solution (3.5%) and additional surfactants were mixed with the last 31% of monomer pre-emulsion and feeding was continued. When the monomer pre-emulsion was 80-85% fed, the remaining pre-emulsion (20%-15%) was mixed with the following ingredients and the feed was continued.













Branched alcohol ethoxy phosphate surfactant (25% active)
6.0 g


Ammonium salt of phosphate ester surfactant (100% active)
3.4 g









About 20 minutes after all the ingredients were fed, the latex became viscous, and then reduced to normal viscosity after 45-60 minutes holding the temperature at 82° C. The batch was cooled down to 66° C., and chasers (t-BHP and SFS (sodium formaldehyde sulfoxylate)) and ammonium hydroxide were added. The properties of the produced latex were shown in the table below.

















MFFT 
Particle size 
Particle size
Mechanic


Solids

(° C.)
(mV)
(mV)
Stability


After
pH
Rhopoint 
Before HEC
After HEC
10,000 


filtration
pH meter
WP
addition
addition
rpm







43.6%
8.0
10.1
162 nm
548 nm
>30 min.









The particle size of this batch showed a bimodal distribution for the sample taken at 45 minutes hold, and uni-modal distribution after 100 minutes hold.
Example 5
To the same reactor setup as described in Example 1, 420 g of DI water was added with nitrogen sweep and agitation at 170 RPM. The following ingredients were mixed to form a monomer pre-emulsion.
Monomer Pre-Emulsion Composition













Methyl methacrylate (MMA) monomer
265.3 g


Butyl acrylate (BA) monomer
306.6 g


Methacrylic acid (MAA) monomer
 5.4 g


Methacrylamide (MAM) monomer
 2.6 g


Diacetone acrylamide (DAAM) monomer
 2.9 g


2-Ethylhexylacrylate (2-EHA) monomer
 25.6 g


N-(2-methacryloyloxyethyl)ethylene urea wet adhesion monomer
 25.6 g


N-methylol methacrylamide monomer
 7.4 g


DI water
220.0 g


Sodium dioctyl sulfosuccinate surfactant
 2.3 g


Tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl
 5.4 g


Sulfosuccinamate surfactant (50%)









After the monomer pre-emulsion is formed, about 1.5 g of ammonium hydroxide (28%) was added to the monomer emulsion for pH adjustment.

About 41.0 g of this monomer pre-emulsion and about 10 ml of 12.6% potassium persulfate (KPS) initiator solution were charged into the reactor forming seed particles. After 20 minutes heating at 79° C., the monomer pre-emulsion was delay fed into the reactor at the following rate:
about 4.6 ml/min for the first hour; and
about 5.5 ml/min. for the rest of the monomer emulsion.
About 30 ml of 4.1% potassium persulfate (KPS) initiator in DI water was also co-fed with the monomer pre-emulsion.
When about 3% of total monomer pre-emulsion was remaining, 94.0 g of 3.9% pre-dissolved HEC water solution, together with 6.0 g of polyoxyethylene tridecyl ether phosphate, ammonium salt and 3.3 g of ammonium salt of phosphate ester (100%) surfactants were added to the 3% remaining monomer emulsion to complete the delay feed in about 50 minutes. The batch was held at 82° C. for additional 50-60 minutes and then cooled down to 65° C. Chasers and ammonium hydroxide were added. The properties of the produced latex were shown in the table below.

















Particles size (mV) 
Particle size (mV)


Solids
MFFT (° C.)
pH
before HEC grafting
after HEC grafting







43.2%
6.8
8.0
198 nm
235 nm









Example 6
To the same reactor setup as described in Example 1, 435 g of DI water was added with nitrogen sweep and agitation at 170 RPM. The following ingredients were mixed to form a monomer pre-emulsion.
Monomer Pre-Emulsion Composition













Methyl methacrylate (MMA) monomer
278.7 g


Butyl acrylate (BA) monomer
252.7 g


Methacrylic acid (MAA) monomer
 5.3 g


Methacrylamide (MAM) monomer
 5.2 g


Diacetone acrylamide (DAAM) monomer
 2.6 g


2-ethylhexylacrylate (2-EHA) monomer
 84.3 g


N-(2-methacryloyloxyethyl)ethylene urea
 11.7 g


wet adhesion monomer (50% solution in water)



N-Methylol methacrylamide monomer (N-MMAA)
 7.8 g


DI water
220.0 g


Sodium dioctyl sulfosuccinate surfactant
 2.0 g


Tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl
 5.2 g


Sulfosuccinamate surfactant (50%)



Ammonium salt of phosphate ester surfactant
 0.4 g









Suitable phosphate ester surfactants include but are not limited to tristyrylphenol ethoxylate phosphate ester, which may be diluted with DI water. After the monomer pre-emulsion is formed, about 1.8 g of ammonium hydroxide (28%) was added to the monomers for pH adjustment.
About 40.0 g of above monomer pre-emulsion and 10 ml of 13.0% potassium persulfate (KPS) initiator solution were charged into the reactor for seed particles. After 20 minutes heating at 79° C., and the monomer pre-emulsion was delay fed into the reactor at the following rate:
about 4.6 ml/min. for the first hour; and
about 5.5 ml/min. for the rest of the monomer emulsion.
About 30 ml of 4.1% potassium persulfate (KPS) in DI water was also co-fed with the monomer pre-emulsion.
When about 36% of total monomer pre-emulsion remained, 94.0 g of 3.9% pre-dissolved HEC water solution, together with 6.0 g of polyoxyethylene tridecyl ether phosphate, ammonium salt and 3.3 g of ammonium salt of phosphate ester (100%) surfactants were added to the 36% remaining monomer emulsion to complete the delay feed in about 40 minutes. The batch was held at 82° C. for additional 60 minutes and then cooled down to 65° C. Chasers and ammonium hydroxide were added. The properties of the produced latex were shown in the table below.

















Particles size (mV)
Particle size (mV)


Solids
MFFT (° C.)
pH
before HEC grafting
after HEC grafting







42.4%
4.3
8.0
170 nm
255 nm









The final average particle was smaller when using 2-ethylhexylacrylate (2-EHA) monomer and N-methylol methacrylamide monomer (VISIOMER® N-MMAA) in the acrylic composition, even when HEC was mixed with higher concentration of monomer pre-emulsion. However, when 2-EHA was used in the acrylic monomer compositions, the particle size distribution of the grafting reaction did not go through a bimodal distribution stage, indicating more resistance to coagulation/gelling. The samples taken at different holding time after the HEC addition all showed unimodal particle distributions.
Example 7
To a three-neck 5 L reactor equipped with a digital agitator and temperature controller was added 445 grams of DI water. The reactor was heated to 82.0° C. with N2 sweep and agitated at a speed of 170-185 RPM. Then a monomer emulsion (41.0 g) of the following composition and KPS (1.35 g) were both charged to the reactor to form latex seeds. After the seed particles were formed in about 20 minutes, the remaining monomer emulsion was fed into the reactor at 5.0 ml/minute. An amount of KPS initiator aqueous solution (30 ml, at 4.1% concentration by weight) was co-fed with the remaining monomer emulsion during the 3 hours feed time.
Monomer Pre-Emulsion Composition















Methyl methacrylate (MMA) monomer
254.0 g



Butyl acrylate (BA) monomer
311.0 g



Methacrylic acid (MAA) monomer
 4.7 g



Methacrylamide (MAM) monomer
 1.8 g



Diacetone acrylamide (DAAM) monomer
 4.5 g



Styrene
 38.6 g



N-(2-Methacryloyloxyethyl)Ethylene Urea
 26.5 g



25% Solution in Methylmethacrylate




DI water
215.0 g



Sodium dioctyl sulfosuccinate surfactant (75%)
 2.2 g



Tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl
 5.2 g



Sulfosuccinamate surfactant




Ammonium hydroxide (28%)
 1.8 g









Into a separate container equipped with a magnetic stirring bar, hydroxyethyl cellulose (HEC) (3.2 grams) was dissolved in DI water (88 g) for a subsequent use.
After 80%-90% of the monomer emulsion was fed, the above solution of HEC in DI water (88.0 g), phosphate ester surfactant (20%, 16.0 g), and polyoxyethylene tridecyl ether phosphate, ammonium salt (6.0 g) from Rhodia were properly mixed into the remaining monomer emulsion. The resulting monomer emulsion with HEC was fed into the reactor which was held at 82° C. for about another hour to complete the polymerization. The HEC grafting reaction initially increased the viscosity of the batch which would become normal again after 1⁄2 hour of agitation during the hold period.
The redox chasers t-BHP and SFS were added into the reactor after the batch was cooled down to about 65° C. for residual monomer reduction. The latex in the reactor was neutralized with ammonium hydroxide aqueous solution until its pH was about 8.3.










Properties of the latex of Example 7
















Mechanical 
Film gloss 


pH
Solids %
Particle size
MFFT
Stability
(60°)





8.3
41.6%
430 nm
13.5° C. 
Pass
83









Mechanical stability test was conducted by a high speed mixer with a rotational speed range of 10,000-18,000 RPM, e.g., bench top mixer model No. 936 made by Hamilton Beach. A mass of about 250 g-300 g of emulsion latex is placed into a stainless cup and agitated at about 12,000 RPM for 30 minutes. Defoamer agent can be added if the latex becomes foamy due to mixing. If the latex survives the 30 minutes mixing without gelation, the latex emulsion passes the mechanical stability test.

Example 8
Similar to the setup as described in Example 7, DI water (445.0 g) and sodium dodecylbenzene sulfonate (2.0 g) were charged into a reactor which was then heated to 82.0° C. In a separate container, HEC (3.2 g) was dissolved in DI water (88.0 g) in 20-30 minutes with agitation until the solution turned clear.
A monomer emulsion was prepared with the following components. An amount of this monomer emulsion (about 40.0 g) and KPS (1.3 g) were charged into the reactor to form the latex seed particles. The remaining monomer emulsion was then co-fed into the reactor with a KPS solution (30 ml, 3.4% concentration by weight) in about 2.5 hours. The HEC solution prepared above was added to the monomer emulsion remained and feeding was continued. The batch was then held at 82° C. for another 60 minutes to complete the polymerization.
Monomer Pre-Emulsion Composition















Methyl methacrylate (MMA) monomer
 270 g



Butyl acrylate (BA) monomer
 310 g



Methacrylic acid (MAA) monomer
 4.8 g



Methacrylamide (MAM) monomer
 2.5 g



Diacetone acrylamide (DAAM) monomer
 2.9 g



Styrene
29.5 g



N-(2-Methacryloyloxyethyl)Ethylene Urea
25.7 g



25% Solution in Methylmethacrylate 




Ammonium hydroxide (28%)
 1.9 g



DI water
 220 g



Sodium dioctyl sulfosuccinate (75%)
 2.2 g



Tetrasodium N-((1,2-dicarboxyethyl)-N-octadecyl
 3.8 g



sulfosuccinamate (35%)




Phosphate ester surfactant (20%)
 5.0 g









The solids at different time intervals were taken from the reactor and latex particle sizes analyzed. The results are summarized in the following table.
















20 min
Sample before
Sample at the 



ID
seeds
HEC addition
end of reaction




















Solids %
5%
39.6%
43.0%



Particle size (nm)
36 nm
122 nm
542 nm









The test results for latex sample are shown the table below.










Properties of the latex of Example 8











pH
Solids
Particle size
MFFT(° C.)
Mechanical Stability (30 min.)





8.2
43.0%
542 nm
14.0
Pass









Example 9
Similar to the setup as described in Example 7, DI water (445 g) was added and the reactor heated to about 82.0° C. The following components were mixed to form a stable monomer emulsion by agitation.
Monomer Pre-Emulsion Composition














Methyl methacrylate (MMA) monomer
251.0 
g


Butyl acrylate (BA) monomer
308.0 
g


Methacrylic acid (MAA) monomer
5.4 
g


Methacrylamide (MAM) monomer
3.2 
g


Diacetone acrylamide (DAAM) monomer
0.7 
g


Styrene
51.5 
g


N-(2-Methacryloyloxyethyl)Ethylene Urea
25.8 
g


25% Solution in Methylmethacrylate




Ammonium hydroxide (28%)
1.9
g


Sodium dioctyl sulfosuccinate surfactant (75%)
2.2 
g


Tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl
5.3 
g


sulfosuccinamate surfactant




Phosphate ester surfactant
16.0
g


Polyoxyethylene tridecyl ether phosphate, ammonium 
6.0 
g


salt (25%)









To the reactor, ammonium hydroxide (28%, 2.8 g) was added to bring the pH from about 6.0 to 8.3. Other additives such as biocides and stabilizers can also be added to the final emulsion polymer latex. The following table contains the results from the latex sample:










Properties of the latex of Example 9














Stability 

MFFT 
Film Gloss 


pH
Solids
(30 min.)
Particle size
(° C.)
(60°)





8.3
43.0%
Pass
660 nm
14.0
81





MFFT is the minimum film forming temperature. Film gloss was measured by a BYK-Gardner gloss meter.






Example 10
To a similar reactor setup described as in the Example 7, DI water (420 g) and sodium dodecylbenzene sulfonate (1.5 g) were added. 42 g of the following monomer emulsion and KPS (1.3 g) were added to the reactor at 82° C. to form the seed particles. The remaining monomer emulsion was fed into the same reactor at a rate of 5.0 ml/minute. In a separate container, HEC (3.30 g) was dissolved in DI water (91 g) for subsequent use.
The following ingredients were mixed together by agitation until a stable monomer emulsion was formed.
Monomer Pre-Emulsion Composition

















Methyl methacrylate (MMA) monomer
265.3 
g



Butyl acrylate (BA) monomer
307.4 
g



Methacrylic acid (MAA) monomer
5.5 
g



Methacrylamide (MAM) monomer
2.5
g



Diacetone acrylamide (DAAM) monomer 
2.9 
g



Styrene
12.8 
g



N-(2-Methacryloyloxyethyl)Ethylene Urea
25.6 
g



25% Solution in Methylmethacrylate





2-Ethylhexylacrylate (2-EHA) monomer
19.2 
g



DI water
220
g



Sodium dioctyl sulfosuccinate surfactant (75%)
2.1 
g



Tetrasodium N-(1,2-dicarboxyethyl)-N-oetadecyl
5.1 
g



sulfosuccinamate





Tristyrylphenol ethoxylate phosphate ester (20% active)
1.0 
g



Ammonium hydroxide (28%)
1.6 
g










After about 85% of the monomer emulsion had been fed into the reactor, a HEC solution (94.3 g, at a concentration of 3.4% by weight) was added into the remaining monomer emulsion together with tristyrylphenol ethoxylate phosphate ester (18.5 g) and Polyoxyethylene tridecyl ether phosphate (5.8 g) to complete the feed as described in Example 7.
After a one hour hold at 82° C., the batch was cooled down to about 60° C. Redox chasers (t-BHP/SFS) and ammonium hydroxide were added for residual monomer reduction. The table below shows the properties of the obtained latex.










Properties of the latex of Example 10















Mechanical


% Solids
MFFT (° C.)
Particle size
pH
Stability (30 min.)





43.7%
8.5 ° C.
178 nm
8.1
>30 min. Pass









Comparative Experiment B
Paint samples substantially free of ADH were made from the latexes from Examples 7-10 and commercial latex free of MAM and DAAM using the following procedure. A grind was made from following components in section A in a stainless container. The components were mixed by agitation at a very high RPM for at least 15 minutes before being switched to a lower RPM. The letdown was made from the ingredients in section B.










SECTION A (Grind)


















Water
35.0



Preservative
2.0



Mildewcide
2.5



Acrylic Polymer Dispersant 1
9.0



Ethoxylated Nonionic Surfactant 1 (80% in water)
3.0



TiO2 Pigment
200.0



Defoamer 1
0.75



Additional DI Water
76.2



2-Amino-2-methyl-1-propanol (95% in water) 
1.5



co-dispersant




Non-ionic surfactant 2 (80% in water)
5.0



Water
20.0




















SECTION B (Letdown)
















HEUR Rheology Modifier
12.0


Latex binders
470.0


Acrylic Polymer Open Time Extender (25% in water)
10.0


Polyurethane Resin (35% in water)
30.0


Coalescent
15.0


Suppressor HEA
4.5


Hydrophobically modified polyether rheology modifier
17.0


(18% in water)



Modified paraffin wax emulsion (38% in water)
12.0


Fluorosurfactant
2.0


Propylene Glycol
12.0


DI Water
54.2









The data on scrub resistance, block resistance, and other related properties were generated from the paint samples made from latex samples 7-10 for comparison purpose. The evaluation methods used are standard ASTM D4946-89, ASTM 2486-06, and ASTM D7190-10 (American Standard Test Method) procedures described in the material and methods section. The reference methods can be found in the ASTM website (http://www.astm.org/). The table below shows the scrub resistance, block resistance, water sensitivity and water stain resistance results for the paint samples made from latexes of Examples 7-10. A control sample which contains no crosslinking monomer is included for comparison.
















MAM:

Block
Water 
Water 



DAAM
Scrub
resis-
sensitivity
stain


ID
(weight ratio)
resistance
tance
(2 min.)
resistance




















Example 7
1:2.5
1430
5 Pass
4.5
5


Example 8
1:1.16
1300
5 Pass
4.5
5


Example 9
1:0.22
1043
5 Pass
4.5
5


Example 10
1:1.16
1296
5 Pass
4.8
5


Control Sample
N/A
516
5 Pass
1.5
2









Example 11
To a similar reactor setup as described in Example 7, DI water (681.0 g) and sodium dodecylbenzene sulfonate (8.5 g) were added and the mixture was heated to a temperature of 81° C. with N2 sweep. The following components were added into an Erlenmeyer flask with agitation until a stable monomer emulsion was formed. To the reactor, an amount of stage I monomer emulsion (70.0 g) together with KPS (2.1 g) was charged. The agitation was maintained at a speed of 190 RPM for about 20 minutes. After the emulsion seed was formed, the rest of the stage I monomer emulsion was fed into the reactor with a KPS solution (27 ml, 0.4% by weight) in about 1 hour and 5 minutes.
Stage I monomer pre-emulsion. (Tg is estimated at about 41.0° C.)














Methyl methacrylate (MMA) monomer
284.0 
g


Butyl acrylate (BA) monomer
118.4 
g


Acrylic acid (AA)
4.0 
g


1,4-Butanediol diacrylate (SR-213)
1.6 
g


DI water
255.6 
g


Sodium dodecylbenzene sulfonate (RHODACAL ® DS-4) std
19.9 
g


(23% active)




Sodium lauryl sulfate (30% active)
10.5 
g


Ammonium hydroxide (28%)
0.6 
g









The Stage II monomer emulsion has the following composition. It was prepared in a similar procedure as disclosed for the stage I monomer emulsion. It was then fed into the reactor after the stage I monomer emulsion feed was finished. The total feed of stage II monomer emulsion and a KPS solution (83 ml, 0.4% by weight) was completed in about 2 hours and 10 minutes. The batch was then held at 82° C. for another 50-60 minutes and cooled down to about 65° C. The redox chasers t-BHP (0.04%) and FF6 (0.03%) were added to the batch for the residual monomer control. The pH value of the latex batch was adjusted with appropriate amounts of ammonium hydroxide. Other preservatives and stabilizers can also be added to the latex batch for improving the shelf life and performances.
Stage II monomer pre-emulsion. The estimated Tg is about 13.9° C.














Methyl methacrylate (MMA) monomer
330.0 
g


Butyl acrylate (BA) monomer
281.0 
g


Methacrylic acid (MAA) monomer
10.2 
g


Methacrylamide (MAM) monomer
1.2 
g


Diacetone acrylamide (DAAM) monomer
1.6 
g


N-(2-Methacryloyloxyethyl)Ethylene Urea 50% Solution In 
21.3 
g


Water (VISIOMER ® 6852-O)




Vinyl neodecanoate (VEOVA TM 10)
460.1 
g


DI water
582.2 
g


Sodium lauryl sulfate (30%)
37.0 
g


Sodium vinyl sulfonate (SVS)
3.1 
g


Sulfosuccinate surfactant (50%)
10.0 
g


Ammonium salt of phosphate ester surfactant (20%)
30.5 
g


Ammonium hydroxide
1.2 
g









The latex batch has the following parameters in following table and was made into paint using the similar procedures disclosed in above example.






















Total residual


Solids
Particle 

Mechanic


monomers by


%
size
MFFT
Stability
pH
Mw
GC method







45.9%
123 nm
8.0 ° C.
>30 min. pass
8.2
110,000
0.2%









Example 12
This experiment was run with the same procedures and composition described in example 11 as a control. However, it contains only DAAM (1.6 g) and no MAM (0.0%) in its second stage monomer emulsion. The block resistance test of the paint sample made from this latex generated poor block resistance result. It failed the block resistance test at 120° F. for 24 hours.
The data in the following table was measured on the latex sample. The smaller particle size is due to the higher surfactant level, sodium dodecylbenzene sulfonate, in the initial water phase.















Solids %
Particle size
MFFT
Stability
pH
Mw







44.9%
72 nm
8.0° C.
>30 min. pass
8.3
78,000









Example 13
This experiment was run with the same procedures and composition as described in Example 11. However, it contains only 1.2 g of MAM and without any DAAM (0.0%) in its second stage monomer emulsion. The block resistance test of the paint sample made from this latex generated poor block resistance result under the ASTM method conditions of 120° F. for 24 hours. The smaller particle size is due to the higher surfactant level in its water phase. Table 17 shows the test results of the latex sample.















Solids %
Particle size
MFFT
Mechanic stability
pH
Mw







44.3%
77 nm
7.0° C.
>30 min. pass
8.3
88,400









Example 14
This example was run with the same procedure as described in example 11 except that the there is no DAAM in its composition and that BA monomer was replaced by 2-EHA monomer. The sodium dodecylbenzene sulfonate surfactant is also higher in the initial water phase. Therefore the average particle size (mV) of this batch is also smaller. A person skilled in the arts can easily adjust the surfactant levels and combinations to achieve the desired particle size distributions.
Stage I monomer emulsion. The estimated Tg for stage I polymer is about 41.0° C.

















Methyl methacrylate (MMA) monomer
284.0 
g



Butyl acrylate (BA) monomer
118.4 
g



Acrylic acid (AA)
4.0 
g



1,4-Butanediol diacrylate
1.6 
g



DI water
255.6 
g



Sodium dodecylbenzene sulfonate (23% active)
19.9 
g



Sodium lauryl sulfate (30% active)
10.5 
g



Ammonium hydroxide (28%)
0.6 
g










Stage II monomer emulsion. The estimated Tg for stage II is about −1.5° C.














Methyl methacrylate (MMA) monomer
330.0 
g


Methacrylic acid (MAA) monomer
10.2 
g


Methacrylamide (MAM) monomer
1.2 
g


N-(2-Methacryloyloxyethyl)Ethylene Urea (50% in water)
21.3 
g


2-Ethylhexyl acrylate (2-EHA)
281.0 
g


Vinyl neodecanoate
460.1 
g


DI water
582.2 
g


Sodium lauryl sulfate (30%)
37.0 
g


Sodium vinyl sulfonate (SVS)
3.1 
g


Sulfosuccinate surfactant (50%)
10.0 
g


Ammonium salt of phosphate ester surfactant (20%)
30.5 
g


Ammonium hydroxide (28%)
1.2 
g









The latex has the following characteristic results as shown in the table below.
















Solids
Particle size
MFFT
Mechanic stability
pH
Mw







44.8%
75 nm
5.6° C.
>30 min.
8.2
103,000









Comparative Experiment C
The following table shows the results of block resistance for paint samples made from the latex of Examples 11-14 for comparison.














ID
Example 11
Example 12
Example 13
Example 14







MAM:DAAM
1:1.33
N/A
N/A
N/A


(weight ratio)






Block
4 (pass)
2 (fail)
3 (fail)
3 (fail)


Resistance






Tinted color
Hamilton blue
Hamilton blue
Hamilton blue
Hamilton blue









Example 15
To a similar reactor set up to Example 7 DI water (450.0 g), sodium C14-C16 olefin sulfonate (40% active, 1.5 g), and 1.0 g of NaHCO3 were added and heated to 82.0° C. with N2 sweep and agitation. The monomer emulsion was formed in a separate Erlenmeyer flask using the ingredients listed below.
Monomer Pre-Emulsion Composition













Methyl methacrylate (MMA) monomer
430.0 g


Butyl acrylate (BA) monomer
435.0 g


Methacrylic acid (MAA) monomer
 9.0 g


Methacrylamide (MAM) monomer
 5.5 g


Diacetone acrylamide (DAAM) monomer
 8.3 g


N-(2-methacryloyloxyethyl)ethylene urea
 19.2 g


wet adhesion monomer (50%)



Ammonium hydroxide (28%)
 1.0 g


Sodium C14-C16 olefin sulfonate (40%)
 5.8 g


Polyoxyethylene tridecyl ether phosphate, ammonium salt (25%)
 16.0 g


tristyrylphenol ethoxylate phosphate ester (20%)
 18.5 g


DI water
360.0 g









Into a separate container, HEC (0.9 g) was dissolved in DI water (40.0 g) which will be added later with the remaining 25% monomer emulsion during the feed.
Following surfactants were mixed with HEC solution before addition to the feed, which would prevent the coagulation/gelling.
Polyoxyethylene Tridecyl Ether Phosphate, Ammonium Salt
















(RHODAFAC ® RS 610/A25) (25%)
10.6 g



POLYSTEP ® TSP-16 PE30
16.7 g










An amount of monomer emulsion (60.0 g) and KPS (1.75 g) were charged to the reactor to form latex seed particles. The remaining monomer emulsion and KPS solution (90 ml, 1.1% by weight) were co-fed during a 3 hours period and then held for another hour. The t-BHP/FF6 pair (1.0 g t-BHP/0.85 g FF6) was used at the end of the reaction for residual monomer control, as well as the ammonium hydroxide to adjust the pH value to 8.2 and also other necessary preservatives such as Polycide 428 by example. The latex was filtered through a 140 mesh size screen filter and tested, and has the following parameters for reference:
















MAM:DAAM






Solid
(weight ratio)
Particle size
MFFT
Film Gloss
pH







46.6%
1:1.51
141 nm
10.6° C.
72 (60°)
8.2









Example 16
Using the same procedure and setup as disclosed in Example 15, 450.0 g of DI water, 1.5 g of sodium C14-C16 olefin sulfonate (40% active) and 1.0 g of NaHCO3 were charged into the reactor and the mixture heated to 82.0° C.
The following monomer emulsion was delay fed into the reactor with KPS solution. When there was about 20% monomer emulsion remaining, 40.0 g of pre dissolved HEC solution was added to the monomer emulsion and the feed was continued until finished. After a one-hour hold, the batch was cool down to 65° C., redox pair, ammonium hydroxide, and other preservatives were added. Extra surfactant can also be added at this stage to improve the mechanical stability.
Monomer Pre-Emulsion Composition













Methyl methacrylate (MMA) monomer
430.0 g


Butyl acrylate (BA) monomer
424.0 g


Methacrylic acid (MAA) monomer
 8.2 g


Methacrylamide (MAM) monomer
 2.8 g


Diacetone acrylamide (DAAM) monomer
 12.2 g


Styrene
 27.1 g


N-(2-methacryloyloxyethyl)ethylene urea
 18.2 g


Wet adhesion monomer (50% in water)



Ammonium hydroxide (28%)
 2.0 g


Sodium C14-C16 olefin sulfonate (40%)
 5.8 g


Polyoxyethylene tridecyl ether phosphate, ammonium salt (25%)
 16.0 g


Ammonium salt of phosphate ester surfactant (20%)
 18.5 g


DI water
360.0 g









The following HEC solution was added with 20% remaining monomer emulsion and delay fed into the reactor.













Hydroxyethyl cellulose (HEC)
 0.9 g


DI water
39.1 g


Polyoxyethylene tridecyl ether phosphate, ammonium salt (25%)
10.6 g


Ammonium salt of phosphate ester surfactant (20%)
16.7 g









Latex Parameters:

















MAM:DAAM
Particle 

Mechanical



Solid
(weight ratio)
size
MFFT
stability
pH







47.6%
1:4.36
126 nm
13° C.
Pass
8.2









The mechanical stability is described in the earlier section and pass is rated when there is no gel formation after 30 minutes stirring at 12,000 RPM.

Paint examples A, B and C were made according to the following procedure and the paint samples are tested for their mechanical and physical properties.
Comparative Experiment D
Control Paint Example I
A standard paint was prepared as follows. Formulation of a control paint example I uses an all acrylic latex composition without crosslinking functionality. All weights are in grams.










Grind:


















Propylene Glycol
10.8



Water
104.5



Biocide 1
1.5



Antimicrobial 1
1.9



Acrylic polymer dispersant 2 
7.7



Potassium carbonate
1.7



Titanium dioxide pigment
232.1



Extender Pigment 1
37.1



Extender Pigment 2
25.5



Extender Pigment 3
34.8



Extender Pigment 4
8.5



Extender Pigment 5
8.5



Defoamer 2
0.7




















Letdown:
















Phosphate Ester Surfactant, Ammonium Salt (25%)
1.5


Nonionic Surfactant 3
3.5


Nonionic surfactant 4
0.8


Anionic Surfactant 1 (60%)
1.5


Coalescent
13.2


All Acrylic Latex without Crosslinking Functionality
321.1


Polyurethane resin
19.3


Hydrophobically modified polyether rheology modifier
18.6


Hydrophobically modified polyethylene oxide urethane
7.0


Defoamer 2
2.3


Defoamer 3
2.3


Water
33.1









The paint has a viscosity of 99 KU and 1.862 ICI.

Paint Example with Inventive Latex from Example 15
A paint composition using latex of Example 15 is prepared in the same manner as described for Control Paint Example I except that 351.4 g of Example 15 latex is used instead of 321.1 g of the control acrylic latex and 2.8 g of water is used in the letdown instead of 33.1 g of water. Also, 20 g of hydrophobically modified polyether rheology modifier is used instead of 18.6, and the amount of hydrophobically modified polyethylene oxide urethane is decreased by 0.5 g (to 6.5 g) to yield a paint composition with a viscosity of 95 KU and 1.717 ICI.
Paint Example (a) with Inventive Latex from Example 16
A paint composition using the latex of Example 16 was prepared in the same manner as described for control paint Example I except that 351.4 g Example 16 latex was used instead of 321.1 g control acrylic latex and 2.8 g water was used in the letdown instead of 33.1 g water. Also, 15 g of hydrophobically modified polyether rheology modifier was used instead of 18.6 g, and the hydrophobically modified polyethylene oxide urethane amount was decreased by 3.5 g (to 3.5 g) to yield a paint with a viscosity of 104 KU and 1.679 ICI.
The paint samples as described above were tested for their physical and mechanical properties and the results were entered into the table below. Effect of crosslinking on the physical and mechanical properties




















Block







resistance



MAM:DAAM
Scrub
Water stain
Water sensitivity 
(24 hrs at


ID
(weight ratio)
(Cycles)
resistance
(5 min.)
120° F.)







Control Paint Example I
N/A
1050
2
3
4


Paint/Example 15
1:1.51
2100
2
3
4


Paint/Example 16
1:4.36
2050
4
5
4









Comparative Experiment E
Control Paint Example II
A control eggshell paint was prepared with an all acrylic latex having DAAM composition with cross-linking functionality. A crosslinking agent, ADH is included in the formulation. All weights are in grams.










Grind:


















DI Water
153.1



Biocide 1
2.3



Biocide 2
2.8



Acrylic Copolymer Dispersant 3 
9.4



Potassium Carbonate
2.6



Titanium dioxide pigment
323.2



Extender Pigment 6
22.7



Extender Pigment 1
39.7



Extender Pigment 2
56.7



Extender Pigment 3
17.0



Extender Pigment 4
13.6



Extender Pigment 5
13.6



Defoamer 2
1.1




















Letdown:
















Phosphate Ester Surfactant, Ammonium Salt (25%)
2.3


Nonionic Surfactant 3
2.3


Nonionic Surfactant 4
1.1


Anionic Surfactant 1 (60%)
2.3


Coalescent
27.2


ADH
4.4


All Acrylic Control Latex with DAAM
453.6


Styrene/acrylic copolymer
28.3


Hydrophobically modified polyether rheology modifier
25


Polysiloxane modified resin
5.7


hydrophobically modified polyethylene oxide urethane 2
3.5


Defoamer 2
3.4


Defoamer 3
3.4


DI Water
67









The paint has a viscosity of 95 KU and an ICI of 1.746.

Paint Example (b) with Inventive Latex from Example 16
A paint composition using the latex of Example 16 was prepared by following the paint formulation procedure of Control Paint Example II, except that (1) the Example 16 latex (486 g) was used instead of the all acrylic control latex with DAAM (453.6 g), (2) the ADH was left out of the formulation, (3) the amount of water used in the letdown was 34.6 g instead of 67 g, (4) the amount of hydrophobically modified polyether rheology modifier used was 10 g instead of 25 g, and (5) the amount of hydrophobically modified polyethylene oxide urethane used was 1 g instead of 3.5 g. The resulting paint composition had a viscosity of 102 KU and 1.017 ICI.
Comparative Examples of Two-Part Crosslinking Vs. Invention Example



















Water





Scrub
resistance (5



ID
Crosslinkers
(cycles)
min.)









Control Paint
ADH/DAAM
2200
3



Example II






Paint (b)/Example 16
MAM/DAAM
2350
3




(1:4.36)










Example 17
To a 5-liter 4-necked round bottom glass reactor equipped with a mechanical stirrer, a thermocouple, a condenser, and nitrogen purge, 600 g of DI water, 2.1 g of sodium (C14-C16) olefin sulfonate, and 1.5 g of sodium bicarbonate were added and then heated to 82° C. The following surfactants and monomers were made into a pre-emulsion through agitation, 91.0 g of pre-emulsion and 2.6 g of KPS were charged to the reactor and heated for 20 minutes, and the rest of the pre-emulsion together with 91 ml of 1.0% KPS solution were delay fed in about three hours. After a one-hour hold at 84.0° C., the batch was cooled down to 65° C. and t-BHP/FF6 (Bruggolite® FF6, Disodium salts of 2-Hydroxy-2-sufinatoacetic acid and 2-Hydroxy-2-sufonatoacetic acid) chasers were added, and the pH of the latex was adjusted to about 8.0-8.5 using aqueous ammonia concentrate (28%). The latex sample was then ready for paint evaluations.
Monomer Pre-Emulsion Composition
















Methyl methacrylate (MMA) monomer
675.5 g



Butyl acrylate (BA) monomer
606.0 g



Methacrylic acid (MAA) monomer
 14.0 g



Methacrylamide (MAM) monomer
 4.2 g



Diacetone acrylamide (DAAM) monomer
 18.2 g



N-(2-methacryloyloxyethyl)ethylene urea




Wet adhesion monomer (50%)
 30.6 g



Ammonia (28%)
 1.7 g



DI water
540.0 g



Branched alcohol Ethoxy phosphate (25%)
 53.6 g



Sodium olefin sulfonate (40%) 
 16.4 g










Example 18
The latex was made by following a similar procedure as Example 17 using the following pre-emulsion compositions:
Monomer Pre-Emulsion Composition
















Methyl methacrylate (MMA) monomer
676.5 g



Butyl acrylate (BA) monomer
603.0 g



Methacrylic acid (MAA) monomer
 14.1 g



Methacrylamide (MAM) monomer
 5.1 g



Diacetone acrylamide (DAAM) monomer
 22.5 g



N-(2-methacryloyloxyethyl)ethylene urea




Wet adhesion monomer (50%)
 30.6 g



Ammonia (28%)
 1.8 g



DI water
540.0 g



Branched alcohol Ethoxy phosphate (25%)
 53.6 g



Sodium olefin sulfonate (40%)
 16.4 g










Molecular weight increases for the same latex samples after the 7 day cure



















Mw 
Mw after 






MAM:DAAM
before 
7 days

Particle



ID
(weight ratio)
cure
cure*
pH
size
Solids







Example 17
1:4.33
161,000
178,000
8.5
130 nm
49.2%


Example 18
1:4.41
159,200
180,300
8.3
132 nm
49.2%





*Mw for the after 7-day cure came from the souble portion only.






While it is apparent that the illustrative embodiments of the invention disclosed herein fulfill the objectives stated above, it is appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments, which would come within the spirit and scope of the present invention.

## Claims

1. An aqueous composition comprising latex particles comprising a film forming monomer, a C4-C18 ethylenically unsaturated monomer moiety containing a ketone and a C3-C18 ethylenically unsaturated monomer moiety containing a primary amide, wherein the ketone is substantially unreactive to the primary amide when the latex particles are in water and wherein the ketone reacts with the primary amide and latex particles crosslink when water is at least partially removed from the latex under ambient conditions.

2. The aqueous composition of claim 1, wherein the monomer containing a ketone is diacetone acrylamide, diacetone methacrylamide, or acetoacetoxyethyl methacrylate.

3. The aqueous composition of claim 1, wherein the monomer containing a primary amide is methacrylamide or acrylamide.

4. An aqueous composition comprising film forming latex particles having crosslinking moieties, wherein the crosslinking moieties comprise a diacetone acrylamide moiety and a methacrylamide moiety, wherein the latex particles cross-link when applied to a substrate at ambient conditions.

5. The aqueous composition of claim 4 further comprising styrene.

6. The aqueous composition of claim 4, wherein the composition is substantially free of adipic acid dihydrazide or the like.

7. The aqueous composition of claim 4, wherein the film forming latex particles comprise acrylic latex particles.

8. The aqueous composition of claim 7, wherein the film forming latex particles comprises at least about 75% acrylic or vinyl monomers.

9. The aqueous composition of claim 4, wherein the ratio by weight of diacetone acrylamide to methacrylamide ranges from about 20:1 to about 1:20 by weight.

10. The aqueous composition of claim 4, wherein the ratio by weight of diacetone acrylamide to methacrylamide ranges from about 6:1 to about 1:3.

11. The aqueous latex composition of claim 4, wherein the ratio by weight of diacetone acrylamide to methacrylamide ranges from about 4:1 to about 1:2.

12. The aqueous latex composition of claim 4, wherein the latex particles are polymerized from film forming monomers, wherein a ratio by weight of diacetone acrylamide and methacrylamide to the film forming monomers ranges from about 0.1:100 to 10:100.

13. The aqueous latex composition of claim 12, wherein the ratio ranges from about 0.5:100 to 5:100.

14. The aqueous latex composition of claim 12, wherein the ratio ranges from about 1:100 to 3:100.

15. The aqueous latex composition of claim 4, wherein the latex particles have a molecular weight from about 20K to about 500K Daltons based on GPC measurement.

16. The aqueous latex composition of claim 4, wherein the latex particles have a molecular weight from about 80K to about 300K Daltons based on GPC measurement.

17. The aqueous composition of claim 4, wherein the latex particles have a MFFT from about −10° C. to about 50° C.

18. The aqueous composition of claim 4, wherein the latex particles have a MFFT from about −5° C. to about 25° C.

19. An aqueous composition comprising core shell latex particles having a shell polymer comprising diacetone acrylamide and methacrylamide moieties, wherein the latex particles crosslink when applied to a substrate at ambient conditions.

20. The aqueous composition of claim 19, further comprising a core polymer having a diacrylate crosslinker.