COMPRISING THEREOF

FIELD OF THE INVENTION

The present invention relates to a poly(vinyl acetate) dispersion. Especially, the present invention relates to a high pigment volume concentration (PVC) paint formulation comprising the poly(vinyl acetate) dispersion.

INTRODUCTION

Poly(vinyl acetate) dispersions are used in the paint industry because they are cost- efficient and environmental friendly compared to other polymer dispersions commonly used in the industry, and therefore provide better hiding efficiency to the paint formulation. However, they are not good at providing competitive washability and early chalking resistance, especially in paints with PVC higher than 60%.

Research has been conducted and it is discovered that phosphorus-containing monomers such as phosphoethyl methacrylate (PEM) can dramatically improve paint washability, but, unfortunately, brings stability issues to the paints.

It is therefore desired in the paint industry polymer dispersions providing satisfactory paint stability, washability, and early chalking resistance to the paint formulation.

SUMMARY OF THE INVENTION

The present invention provides a polymer dispersion comprising by dry weight based on total dry weight of the polymer dispersion, a) from 60% to 95% a vinyl acetate monomer, b) from 0.2% to 2.5% a phosphorus-containing allylic monomer; and c) from 0.2% to 2.5% an itaconic acid monomer; wherein the total amount of monomers b) and c) is from 0.5% to 2.5% by dry weight based on total dry weight of the polymer dispersion, and the dry weight ratio of monomer b) to monomers b) and c) is from 0.2 to 0.6.

The present invention further provides a paint formulation of PVC higher than 60% comprising the polymer dispersion.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a polymer dispersion of polymer particles comprising, by dry weight based on total dry weight of the polymer particles, a) from 60% to 95%, preferably from 65% to 90%, and more preferably from 70% to 85%, a vinyl acetate; b) from 0.2% to 2.5%, preferably from 0.4% to 2.0%, and more preferably from 0.8% to 1.5%, a phosphorous-containing allylic monomer; and c) from 0.2% to 2.5%, preferably from 0.4% to 2.0%, and more preferably from 0.8% to 1.5%, an itaconic acid.

The total amount of monomers b) and c) is from 0.5% to 2.5%, preferably from 0.7% to 2.0%, and more preferably from 1.0% to 1.5% by dry weight based on total dry weight of the polymer dispersion.

The dry weight ratio of monomer b) to monomers b) and c) is from 0.2 to 0.6, preferably from 0.25 to 0.55, and more preferable from 0.3 to 0.5.

The phosphorus-containing allylic monomer has a chemical structure of formula (I):

[CH ₂ =CH— CH ₂ — R ² — O— ] _x P(=0)(OM) _3-x (I),

wherein:

R ² is a linking divalent group, preferably a (poly)oxyalkylene group,

x is an average number of from 1 to 2, and

M, identical or different, is a hydrogen atom or a cationic counter-ion.

If M is a hydrogen atom, the phosphorus-containing allylic monomer is considered as being in an acid form. If M is a counter-ion, the allylic monomer is considered as being in a salt form or in a neutralized form. M is NH ₄ ⁺ , Na ⁺ or K ⁺ . The phosphorus-containing allylic monomer can be partially acidic and partially neutralized. Neutralization can occur upon addition of the monomer in the polymerization medium.

The phosphorus-containing allylic monomer can be a mixture of a phosphate mono- ester with x=l, and a phosphate di-ester with x=2. The respective amounts of mono-ester and di-ester are such that x is equal to or higher than 1, for example, equal to or higher than 1.01, and equal to or lower than 2, for example, equal to or lower than 1.99. Number x is preferably from 1 to 1.5, more preferably from 1 to 1.2, and most preferably from 1.01 to 1.2. It is mentioned that x=1.2 corresponds to a molar ratio mono-ester/di-ester of 80/20.

Group R ² is a linking divalent group, preferably comprising carbon atoms, and optionally hetero atoms. Examples of group R ² include divalent alkylene groups with from 2 to 20 carbon atoms and (poly)oxyalkylene groups. Preferably group R ² is a (poly)oxyalkylene group of formula — [O— A— ] _n — , wherein:

A, identical or different, is a group of formula — CH ₂ — CH ₂ — or — CH ₂ — CH(C¾)— , or— CH(C¾)— CH ₂ — , and

n is an average number of at least 1.

Groups— O— A— wherein A is— CH ₂ — CH ₂ — correspond to ethoxy groups that can be obtained from ethylene oxide. Groups— O— A— wherein A is— CH ₂ — CH(C¾)— or— CH(C¾)— CH ₂ — correspond to propoxy groups that can be obtained from propylene oxide. (Poly)oxyalkylene groups of formula— [O— A— ] _n — can comprise both ethoxy groups and propoxy groups, arranged randomly or by blocks.

Preferably R is a polyoxyethylene group of formula— [O— CH ₂ — CH ₂ ] _n — , wherein n is an average number of from 2 to 10, preferably of from 2.5 to 7.

Suitable examples of the phosphorus-containing allylic monomers with formula (I) include SIPOMER™ COPS-3 and SIPOMER PAM-5000 both commercially available from Solvay Company.

The polymer dispersion of the present invention may further comprise by dry weight based on total dry weight of the polymer particles, from 1% to 40%, preferably from 5% to 35%, and more preferably from 10% to 30%, an ethylenically unsaturated nonionic monomer.

As used herein, the term "nonionic monomer" refers to the monomer that does not bear an ionic charge between pH=l-14. Examples of suitable ethylenically unsaturated nonionic monomers include alkyl esters of (methyl) acrylic acids such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, methyl methacrylate, butyl methacrylate, isodecyl methacrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and any combination thereof; (meth)acrylonitrile; (meth)acrylamide; amino-functional and ureido-functional monomers such as hydroxyethyl ethylene urea methacrylate; monomers bearing acetoacetate-functional groups such as acetoacetoxyethyl methacrylate (AAEM); monomers bearing carbonyl-containing groups such as diacetone acrylamide (DAAM); butadiene; a-olefins such as ethylene, propylene, and 1-decene; vinyl butyrates, vinyl versatates and other vinyl esters such as versatic vinyl ester; vinyl monomers such as vinyl chloride and vinylidene chloride; glycidyl (meth)acrylate; and any combination thereof. Commercially available versatic vinyl esters include Veova 8, Veova™ 9, Veova™ 10 and Veova™ 11 from Momentive Specialty Chemicals.

Preferably, the ethylenically unsaturated nonionic monomer is selected from versatic vinyl esters, butadiene, a-olefins, C ₂ -C ₁₂ alkyl esters of (methyl) acrylic acids, any derivative thereof, and any combination thereof.

The polymer dispersion of the present invention may further comprise, by dry weight based on total dry weight of the polymer particles, from 0.01% to 5%, preferably from 0.1% to 3%, and more preferably from 0.3% to 2%, a stabilizer monomer.

Suitable examples of the stabilizer monomers include sodium styrene sulfonate (SSS), sodium vinyl sulfonate (SVS), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide (AM), and any combination thereof. Preferably, the stabilizer monomer is selected from SVS, AMPS, and the combination thereof.

The polymer dispersion may further comprise by dry weight based on total dry weight of the polymer particles, up to 3%, preferably from 0.05% to 1.5%, more preferably from 0.1% to 1%, an alkoxysilane functionalized monomer. Suitable examples of the alkoxysilane functionalized monomers include vinyltrialkoxysilane such as vinyltrimethoxysilane and alkylvinyldialkoxysilane, (meth)acryloxyalkyltrialkoxysilane such as (meth)acryloxyethyltrimethoxysilane and (meth)acryloxypropyltrimethoxysilane, any derivatives thereof, and any combination thereof.

The polymerization of the polymer particles can be any method known in the art, including emulsion polymerization, mini-emulsion polymerization, and mechanical dispersing technology. Suitable examples of the polymerization process include those disclosed in US 7,579,081 B2, US 7,357,949 B2 and WO 2010074865 Al .

The polymer dispersion of the present invention can be made into a paint formulation by addition of pigments, extenders, and paint additives.

Pigments of the present invention are typically inorganic pigment particles, and preferably particulate inorganic materials which are capable of materially contributing to the opacity or hiding capability of a paint. Such materials typically have a refractive index of equal to or greater than 1.8 and include titanium dioxide (Ti0 ₂ ), zinc oxide, zinc sulfide, barium sulfate, and barium carbonate. Titanium dioxide (T1O ₂ ) is preferred. Extenders are typically a particulate inorganic materials having a refractive index of less than or equal to 1.8 and greater than 1.3 and include calcium carbonate, clay, calcium sulfate, aluminosilicate, silicate, zeolite, mica, diatomaceous earth, solid or hollow glass, and ceramic bead.

The paint formulation of the present invention may further contain at least one conventional paint additives such as coalescing agents, cosolvents, surfactants, buffers, neutralizers, thickeners, non-thickening rheology modifiers, dispersants, humectants, wetting agents, mildewcides, biocides, plasticizers, antifoaming agents, defoaming agents, anti- skinning agents, colorants, flowing agents, crosslinkers, and anti-oxidants.

In a preferred embodiment, the paint PVC is higher than 60%, preferably higher than

65%, and more preferably higher than 70%.

PVC (pigment volume concentration) of a paint is calculated as follows,

PVC (%) = [volume of pigment(s) + volume of extender(s)] / total dry volume of paint.

The preparation of the paint formulation involves the process of selecting and admixing appropriate paint ingredients in the correct proportions to provide a paint with specific processing and handling properties, as well as a final dry paint film with the desired properties.

The paint formulation may be applied by conventional application methods such as brushing, roller application, and spraying methods such as air-atomized spray, air-assisted spray, airless spray, high volume low pressure spray, and air-assisted airless spray.

Suitable substrates for paint application include concrete, cement board, medium- density fiberboard (MDF) and particle board, gypsum board, wood, stone, metal, plastics, wall paper and textile, etc. Preferably, all the substrates are pre-primed by waterborne or solvent-borne primers.

EXAMPLES

I. Raw Materials svs sodium vinyl sulfonate

AMPS 2-acrylamido-2-methyl-l-propanesulfonic acid sodium

SPS sodium persulfate

t-BHP tert-butyl hydroperoxide

IAA isoascorbic acid

EDTA ethylene diamina tetra-acetic acid

II. Test procedures

1. Washability

Paint drawdown was performed on a panel by using a 175um film caster, starting from the secured end of the panel. Paint drawdown was then air-dried horizontally for 7 days in a Constant Temperature Room (CTR). A brush was soaked in soap water overnight before use, and was then mounted in a holder with the brush's bristle-side down to start the test. The scrub media was a 0.5% soap solution. More soap solution may be added onto paint drawdown if needed. The number of cycles for removing completely the paint drawdown was recorded. The number of cycles for comparative example 1 was recorded as 100%, and the numbers of cycles for other examples were relative percentage values compared to that of comparative example 1.

2. Paint stability

A Stormer viscometer was used to test the viscosity of a paint formulation according to the ASTM (American Society for Testing and Materials) D562 method. After the paint formulation was formed and stored at room temperature overnight, an initial medium shear viscosity, Initial KU, of the paint formulation was tested at room temperature. The paint formulation was then placed in an oven at 50°C for 10 days. The viscosity of the paint formulation after storage was tested and recorded as Final KU. The absolute value difference between Initial KU and Final KU was defined as the viscosity change, AKU. The smaller the total AKU value was, the better the viscosity stability was.

3. Early chalking resistance

Early chalking resistance was detected according to ASTM D4214-07 Method. The test included the evaluation of the degree of chalking on white paint films, that is, the chalk transferred to a fabric compared to photographic reference standards. The chalk rating for each paint sample was recorded. The higher the rating was, the better the early chalking resistance was.

III. Experimental examples

1. Preparation for the Polymer Dispersions

A monomer emulsion was prepared by mixing 249g BA, 1387.4g VA, 14.17g SVS, 4.96g SILQUEST A-171 monomer, 8.27g IA, 20.48g (40% active) SIPOMER COPS-3 monomer, 13.61g TERGITOL 15-S-40 surfactant (70% active), 66.16g RHODAFAC RS- 610/A25 surfactant (25% active) and 310.35g de-ionized (DI) water and emulsifying with stirring. 590g DI water and 90g of the monomer emulsion were charged to a five-liter multi- neck flask fitted with mechanical stirring. The contents of the flask were heated to 84°C under a nitrogen atmosphere. 0.02g FeS0 ₄ .7H ₂ 0 and 0.02g EDTA in 5g DI water, 3.5 lg SPS and 0.3 lg sodium acetate in 31g DI water were added to the stirred flask. The remainder of the monomer emulsion, 3.51g SPS in 66g DI water, and 0.75g IAA in 66g DI water were added to the flask gradually over 180 minutes. Reaction temperature was maintained at 75°C. Then, 30g DI water was used to rinse the feed line of the flask, and 4.2g t-BHP in 60g DI water and 3.23g SBS in 60g water were fed into the flask over 30min with agitation. The content of flask was cooled to room temperature. 1.5g NaOH in 28.5g DI water was added as neutralizer over 1 Omin to get the Polymer Dispersion 1.

Polymer Dispersions (PD) 2 to 7 and Comparative Polymer Dispersions (Comp. PD) 1 to 6 were prepared according to the preparation for the Polymer Dispersion 1 with different amounts of COPS-3 and IA as listed in Table 1.

Polymer Dispersion 7 used 249g VEOVA 10 monomer replacing B A.

The particle sizes of each Polymer Dispersion were tested by a BI-90 Particle Size Analyzer commercially available from Brookhaven Instruments Corporation.

The Solids of each Polymer Dispersion were tested in a 150°C oven for 40min.

TABLE 1

Comp. PDs 4 and 5 used respectively 1% AA, and 1% MAA replacing IA.

2. Preparation for Paint formulations

Paints containing different Polymer Dispersions were prepared using the following procedure as shown in Table 2. The grind ingredients were mixed using a high speed Cowles disperser, and the let-down ingredients were added using a conventional lab mixer. TABLE 2

Material Weight(g)

"Grind"

Water 300

CELLOSIZE QP-30000 thickener 3

AMP-95 neutralizer 2

Dispelair CF-246 defoamer 2

OROTAN 1288 dispersant 7

TRITON BD-405 wetting agent 2

SR-237 titanium dioxide 30

DB-80 calcined clay 80

ASP 170 extender 60

CC-700 calcium carbonate 310

ROCIMA 363 biocide

"Let-down"

Water 31

TEXANOL coalescent 9

Propylene glycol 9

KATHON LXE biocide 2

DISPELAIR CF-246 defoamer 1

Polymer Dispersion 120

ACRYSOL TT-935 thickener 4

Water 26

Total 1000

PVC 78%

IV. Results

TABLE 3

The results were shown in Table 3. Comparative Paint 8 (Comp. 8) was a paint formulation comprising a poly(vinyl acetate) dispersion, and had a poor early chalking resistance (chalk rating being 2). With the same vinyl acetate concentrations, Comparative Paints 9 (Comp. 9) and 10 (Comp. 10) further and respectively comprised the phosphorus- containing allylic monomer (COPS-3), and the itaconic acid (IA) of the present invention, compared to Comp. 8, both Comp. 9 and Comp. 10 improved in paint washability performance, while either of them still had very serious paint stability issue (Comp. 9 had a AKU of 18) or early chalking issue (Comp. 10 had a chalk rating of 3). This indicated the important role of either the phosphorus-containing allylic monomer or the itaconic acid played to paint early chalking resistance or the paint stability. Still under the same vinyl acetate concentrations, Comparative Paints 11 (Comp. 11) and 12 (Comp. 12) respectively used AA and MAA replacing IA, compared to Paint 4 using IA, had worse paint washability performances. This indicated the critical role of IA to the paint washability. Comparative Paint 13 (Comp. 13) comprised both COPS-3 and IA, while the dry weight ratio of COPS- 3/(IA+COPS-3) exceeded the required range, and was 0.77. Comp. 13 had a poor paint stability (AKU being 14.4). Under the same vinyl acetate concentrations, Paints 1-7 were good at paint washability, stability and early chalking resistance performances.