Method for improving Anti-blocking properties in a coating composition using a phosphate ester surfactant additive

Abstract

The invention relates to a method for imparting or improving block resistance, preferably early high-temperature blocking resistance, of a waterborne coating composition comprising adding to said coating composition an effective amount of at least one anti-blocking additive comprising a phosphate ester surfactant, wherein the phosphate ester surfactant comprises an acid or a salt of an ethoxylated alkyl phosphate ester comprising a C4-C20 carbon chain and a number of ethylene oxide units strictly greater than 0 and lower or equal to 3.

Description

METHOD FOR IMPROVING ANTI BLOCKING PROPERTIES IN A COATING COMPOSITION USING A PHOSPHATE ESTER SURFACTANT ADDITIVE

[0001] This application claims priority filed on 2024-04-26 in UNITED STATES with Nr 63 / 639291, the whole content of this application being incorporated herein by reference for all purposes.FIELD OF THE INVENTION

[0002] This invention relates to a method and a use of phosphate ester surfactants for improving block resistance, specifically early high-temperature blocking resistance, of a coating composition, such as a paint or an adhesive for example. The invention also relates to such a coating composition showing improved block resistance compared to coating compositions of the prior art.PRIOR ART

[0003] In the field of composition coatings, such as paints for example, improved block resistance is attributed to increased bulk modulus or surface hardness of coating film, in particular paint film.

[0004] One of the challenges for low-VOC coatings is simultaneously attaining smooth film formation and acceptable block resistance and film hardness. Smooth film formation is obtained at the minimum film forming temperature (acronym MFFT), which is the minimum temperature at which a waterborne emulsion (latex) coalesces when laid on a substrate as a thin film.

[0005] Several approaches exist to address this challenge. First is a latex with core-shell morphology, which is a common approach. Another approach is the blending of a high MFFT latex with a low MFFT latex. Crosslinking of the paint film or latex particle to increase the film hardness has also been proposed, as well as anti-block additives that can quickly move to the air / paint film interface and lower the surface tension of the paint film. Alternatively, combinations of the above techniques may be employed to improve anti-blocking property of paints.

[0006] For example, document WO2022 / 150168 shows that neutralized Cs-Ci2 nonethoxylated phosphate esters are used as paint additives, that is, as an additive added directly into the final paint, in order to deliver early hot block performances in the paint. As a clarification, non-ethoxylated phosphate esters are phosphate esters that do not have ethylene oxide (i.e. ethylene glycol, “EO”) units, having the formula -O-CH2-CH2- and making the link between the alkyl group and the phosphate group in the formula.

[0007] Moreover, fluorocarbon surfactants (acronym FCS), such as Capstone FS-63, are currently being used in latex synthesis to improve early (1 day dry) oven / hot block resistance (also called high temperature block resistance) of architectural water based coatings, which is a desirable property for semigloss and gloss coatings.

[0008] While the manufacturing of fluorocarbon surfactants do not directly involve the use of perfluorooctanoic acid (acronym PFOA), PFOA is an unintended by-product that may be found in trace amounts in some products. As there is a much scrutiny regarding elimination of PFOA’s, especially due to do potential negative impact on the environment and human health, it is desirable to replace FCS in the coating formulations while delivering similarly good early hot block performance without the health issues associated with FCS.SUMMARY OF THE INVENTION

[0009] The present invention aims to overcome the aforementioned drawback. The invention especially aims to improve block resistance, also called “anti-blocking”, in various coating compositions, such as paints, adhesives, inks or varnishes for example, without using fluorocarbon surfactants.

[0010] To this end, the invention proposes to use a phosphate ester surfactant and to add it directly into the coating composition.

[0011] In other words, the phosphate ester surfactant is used as an additive, incorporated into the coating composition, to impart or improve the block resistance of said coating composition, preferably early blocking resistance at high temperature (generally called “early high-temperature blocking resistance” or “early hot blocking resistance” or “early oven block resistance”). The coating composition may be, for example, a paint, a varnish, an ink, or an adhesive.

[0012] The early high-temperature blocking resistance is defined and measured according to the standard ASTM D4946-89 at 50°C.

[0013] For clarification, a coating composition such as a paint is prepared from a latex polymer, or just “latex” by adding pigments, liquid agents such as water, solvents, glycols, or coalescing agents, and additives such as defoamers, surfactants, dispersants, or additives having very specific properties such as those which improve open time, freeze thaw or resistance to corrosion. The latex itself is prepared from the polymerization of a corresponding monomer emulsion.

[0014] Latexes are products well known to those skilled in the art. They consist of aqueous dispersions of water-insoluble polymers. These fluid systems contain, as dispersed phase, particles of polymers consisting of several entangled polymer chains in an aqueous dispersion medium. The diameter of the polymer particles within thedispersion can range between 10 nm and 500 nm. In the present text, the terms “waterbased polymer emulsion”, water-based polymer dispersion” and “latex” refer to the same chemical object and are used indifferently.

[0015] On this basis, an object of the invention is a method for imparting or improving block resistance, preferably early high-temperature blocking resistance, of a waterborne coating composition comprising adding to said coating composition an effective amount of at least one anti-blocking additive comprising a phosphate ester surfactant, wherein the phosphate ester surfactant comprises an acid or a salt of an ethoxylated alkyl phosphate ester comprising a C4-C20 carbon chain and a number of ethylene oxide units strictly greater than 0 and lower or equal to 3.

[0016] In other terms, the invention proposes the use an effective amount of at least one phosphate ester surfactant as an anti-blocking additive added in a waterborne coating composition to impart or improve early high-temperature blocking resistance of said coating composition, wherein the phosphate ester surfactant comprises an acid or a salt of an ethoxylated alkyl phosphate ester comprising a C4-C20 carbon chain and a number of ethylene oxide units strictly greater than 0 and lower or equal to 3.

[0017] The term “strictly greater (or lower) than” means than the corresponding value in excluded from the range. The term lower (or higher) or equal to” means that the corresponding value in included in the range. In the term “strictly greater than 0 and lower or equal to 3”, the value 0 is excluded from the range, the value 3 is included in the range, and the range encompasses any integer or decimal within said range.

[0018] The term “1-3” means between 1 and 3 ethylene oxide units, and may be any number, integer or decimal, between 1 and 3, including the lower and upper limits 1 and 3 themselves.

[0019] The number of EO is determined by Mass Spectrometry, and the weighted average of the molecules with different EO units in the product is calculated and used as the final EO unit number for the product. The number of EO thus may be decimal.

[0020] The term “EO” means ethylene oxide or oxyethylene, and refers to the number of ethoxylation (derived from ethylene glycol) of the surfactant, having the formula -O- CH2-CH2- and making the link between the alkyl group and the phosphate group of the surfactant.

[0021] In the following of the text, the terms “ethylene oxide”, “ethylene oxide unit(s)”,“ethylene glycol”, “ethylene glycol unit(s)”, “ethoxylation(s)”, and “EO” are used indifferently and all refer to the ethylene oxide groups having the formula -O-CH2-CH2-.

[0022] In the following of the text, the phosphate ester surfactant may be referred to as “surfactant” or “phosphate ester surfactant” to simplify the text.

[0023] According to other optional features of the method of the invention: the phosphate ester surfactant comprises between 1 and 2 ethylene oxide units; the alkyl group of the phosphate ester surfactant is a C4-C15 carbon chain, preferably a Cs-Cn carbon chain, optionally branched and / or substituted; the phosphate ester surfactant has a Cs-Cn carbon chain and 1 EO, preferably a C12 carbon chain and 1 EO; the phosphate ester surfactant is a potassium salt, a sodium salt, an ammonium salt, or an organic amine salt; the phosphate ester surfactant comprises a C10-C12 carbon chain, between 1 and 2 ethylene oxide units, preferably between 1 and 1.5 ethylene oxide units, and a potassium salt;the effective amount of anti-blocking additive is greater or equal to 0.010% by weight, preferably greater or equal to 0.05% by weight, based on the total amount of the coating composition; the effective amount of anti-blocking additive is lower or equal to 1.0% by weight, preferably lower or equal to 0.5% by weight, based on the total amount of the coating composition; the method further comprises the addition of at least one sulfate, sulfonate, and / or phosphate alkyl surfactant, ethoxylated or non ethoxylated; the anti -blocking additive comprises:• at least one phosphate ester surfactant comprising a C4-C20 carbon chain, preferably a Cs-Ci2 carbon chain, a number of ethylene oxide units strictly greater than 0 and lower or equal to 3, preferably strictly greater than 0 and lower or equal to 2, and a potassium salt, a sodium salt, an ammonium salt, or an organic amine salt; and• at least one olefin sulfate, sulfonate, and / or phosphate alkyl surfactant, preferably a C10-C20 olefin sulfate, sulfonate, and / or phosphate alkyl surfactant. the anti -blocking additive comprises:• at least one phosphate ester surfactant comprising a C10-C12 carbon chain, between 0 and 2 ethylene oxide units, and a potassium salt; and• at least one Cie-Cis olefin sulfonate, the anti -blocking compound comprises:• at least one phosphate ester surfactant comprising a Cs-Cio carbon chain, a number of ethylene oxide units strictly greater than 0 and lower or equal to 1, and a potassium salt; and at least one Ci6-Cis olefin sulfonate; the phosphate ester surfactant of the anti-blocking additive may be for example Dermalcare® MAP L-213 / K, which is a solution of the potassium salt of laureth phosphate ester, commercialized by Syensqo.

[0024] Another object of the invention is a coating composition presenting block resistance, preferably early high-temperature blocking resistance properties, comprising:- at least one latex polymer,- optionally, at least one pigment,- water,- an anti-blocking additive comprising a phosphate ester surfactant, wherein the phosphate ester surfactant comprises an acid or a salt of an ethoxylated alkyl phosphate ester comprising a C4-C20 carbon chain and a number of ethylene oxide units strictly greater than 0 and lower or equal to 3.

[0025] According to other optional features of the coating composition of the invention: the coating composition further comprises one or more additional components selected from defoamers, rheology modifiers, solvents, biocides, neutralizing agents, and preservatives; the coating composition presents a block resistance, preferably an early high- temperature blocking resistance improved by at least 2 units compared to the same coating composition lacking the anti-blocking additive; the coating composition presents a block resistance, preferably an early high- temperature blocking resistance between 5 and 10, preferably between 6 and 9; the coating composition is prepared from an (meth)acrylic or a styrene- (meth)acrylic latex polymer; the coating composition is a paint intended to be applied to a substrate, an adhesive optionally pressure-sensitive, a varnish, or an ink. The substrate may be for example wood, concrete, paper, metal, another paint, tiles, cement, etc.

[0026] In the present text, it should be noted that in specifying any range of concentration, weight ratio or amount, any particular upper concentration, weight ratio or amount can be associated with any particular lower concentration, weight ratio or amount, respectively.

[0027] As used herein, the term “alkyl” or “alkyl group” means a saturated hydrocarbon radical, which may be straight, branched or cyclic, such as, for example, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, t-butyl, pentyl, n-hexyl, cyclohexyl.DETAILED DESCRIPTION OF THE INVENTION

[0028] The invention generally relates to the use of a 1-3 EO phosphate ester surfactant as an additive, added directly into a coating composition to impart or improve block resistance, preferably early high-temperature anti-blocking of said coating composition.

[0029] A decisive advantage of the method of the invention is that the corresponding coating compositions show good early hot block resistance properties without using fluorocarbon surfactants.

[0030] Of course, one or more of such phosphate ester surfactants may be added in the coating composition.

[0031] Preferably, the ethoxylated phosphate ester surfactant contains between 1 and 2 ethoxylations, i.e. EO units.

[0032] The number of ethoxylations, or EO, is the number of ethylene oxide units in the phosphate ester surfactant. This number may be an integer or a decimal.

[0033] The phosphate ester surfactant may be a mono-ester phosphate, a di-ester phosphate, a tri-ester phosphate, or mixture thereof. Preferably, the phosphate ester surfactant is a mixture of the mono-ester phosphate and the di -ester phosphate.

[0034] Preferably, the phosphate ester surfactant has the following formula (I): R’-O-CCIL-CIL-C n-X1(I) whereinR1is a C4-C20 substituted or an unsubstituted alkyl group, preferably a C4-C15 alkyl group, and more preferably a Cs-Cn alkyl group;-O-CH2-CH2- is a divalent oxyethylene (EO) group, n being an integer or a decimal between 1 and 3;X1is a phosphate group.

[0035] The salt is preferably a sodium, potassium, ammonium, or organic amine salt.

[0036] When the phosphate ester surfactant contains a di-ester, the latter preferably has the following formula (II):R2-O-(CH2-CH2-O)„-X2-(O-CH2-CH2)n-O-R2(II) whereinR2is a C4-C20 substituted or an unsubstituted alkyl group, preferably a C4-C15 alkyl group, and more preferably a Cs-Ci2 alkyl group;-O-CH2-CH2- is a divalent oxyethylene (EO) group, n being an integer or a decimal between 1 and 3;X2is a phosphate group.

[0037] The salt is preferably a sodium, potassium, ammonium, or organic amine salt.

[0038] When the phosphate ester surfactant contains a tri-ester, the latter preferably has the following formula (III):R3-O-(CH2-CH2-O)n-X3-(O-CH2-CH2)„-O-R3p Q6HC p(III) whereinR3is a C4-C20 substituted or an unsubstituted alkyl group, preferably a C4-C15 alkyl group, and more preferably a Cs-Ci2 alkyl group;-O-CH2-CH2- is a divalent oxyethylene (EO) group, n being an integer or a decimal between 1 and 3;X3is a phosphate group.

[0039] The salt is preferably a sodium, potassium, ammonium, or organic amine salt.

[0040] With respect to the effective amount of anti-blocking additive to be added in the coating composition, it is preferably greater or equal to 0.010% by weight based on the total amount of the coating composition.

[0041] Moreover, said effective amount of anti-blocking additive is preferably lower or equal to 1.0% by weight based on the total amount of the coating composition.

[0042] Preferably, said coating composition is prepared from an (meth)acrylic or a styrene-(meth)acrylic latex polymer.

[0043] The method of the invention significantly increases the early high-temperature blocking resistance. After the addition of the anti -blocking additive, the coating composition presents an early high-temperature blocking resistance: improved by at least 2 units compared to the same coating composition lacking the anti-blocking additive. These units are those of the scale ranging from 1 to 10 as defined in the standard ASTM D4946-89; comprised between 5 and 10, preferably between 6 and 9.

[0044] The method of the invention also leads to great performance of early hot antiblocking after heat aging of the coating. In other words, the anti-blocking effect remains high even after the coating is heat-aged.

[0045] The coating composition of the invention presents great early high- temperature blocking resistance properties, and comprises:- at least one latex polymer,- optionally, at least one pigment,- water,- an anti-blocking additive comprising a phosphate ester surfactant, wherein the phosphate ester surfactant comprises an acid or a salt of an ethoxylated alkyl phosphate ester comprising a C4-C20 carbon chain and between 1 and 3 ethylene oxide units.

[0046] The coating composition may be prepared from an (meth)acrylic or a styrene- (meth)acrylic latex polymer.

[0047] The coating composition may comprise further components selected from defoamers, rheology modifiers, solvents, biocides, neutralizing agents, and preservatives.

[0048] The coating composition may be a paint, an adhesive optionally pressuresensitive, a varnish, or an ink.

[0049] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.EXAMPLES OF EMBODIMENTS OF THE INVENTION

[0050] General procedure for the preparation of phosphate ester surfactants

[0051] Phosphate ester surfactants are prepared by the reaction of an alcohol with polyphosphoric acid and / or phosphoric anhydride to give a phosphate ester composition having varying levels of phosphoric acid, monoalkyl phosphate, dialkyl phosphate, trialkyl phosphate, and residual starting alcohol. The ratio of the two phosphorylating reagents (polyphosphoric acid and phosphoric anhydride) to the alcohol, and to each other when used together, are varied to target a desirable phosphate ester composition.

[0052] The phosphate esters products are then neutralized to a salt using KOH.

[0053] Preparation of paint compositions

[0054] Several phosphate ester additives are added to paint formulations, namely Capstone FS-63 (fluorocarbon surfactant), Rhodafac® RS610 and Dermalcare® (Cs- C12 / IEO).

[0055] The Semigloss Formulations used to Prepare Water-based Paints for Testing are shown in Table 1 below.Table 1 : Semigloss formulations for water-based paints

[0056] Block resistance test (D 4946-89 (2017)) is performed on dry paint films. The results are shown in Table 2 below.

[0057] With respect to these results, paints 2 and 4 show to good early 1-day oven (hot) block resistance (around 9), and the results are even better after 7 days (around 10).

[0058] Paint 1 is the control and paint 3 containing Rhodafac® (counter-example) shows a much lower hot blocking resistance of 4 (1 day dry) and 6 (7 day dry).Table 2: Block resistance results

[0059] The test procedure for Early (1 day dry) “hot” block Resistance is detailed in the following section. This procedure is carried out as per ASTM Standard Test Method for Blocking Resistance of Architectural Paints, Designation D 4946-89 (2017); Resistance Test Method # 502: Peel Block Resistance.

[0060] Test Method Highlights:1) Cast the test paint on an all white sealed Leneta chart with a 3mil Bird applicator in the controlled temperature room. Allow test samples to dry.2) Cut out 1-1 / 2” by 1-1 / 2” sections (to run duplicates) from white area of each conditioned panel.3) Place the cut sections with the paint surfaces face-to-face.4) Place the face-to-face specimens in a 50°C ( 120°F) oven on a flat metal plate. Top each individual specimen with a heated, solid #8 rubber stopper and place a heated 1000 gram weight on each stopper.5) After exactly 30 minutes, remove the stoppers and weights and remove the test specimens from the oven. All to cool for 30 minutes at room temperature.6) After cooling, separate the sections with slow and steady force. Pull apart at an angle of approximately 180° and listen for tack. Rate the samples for block resistance on a scale of 0-10.SCALE (from ASTM):10: no tack perfect9: trace tack excellent8: slight tack very good7: good6: moderate tack good5: fair4: severe tack, no seal fair3: 5-25% seal poor2: 25-50% seal poor1: 50-75% seal very poor0: complete seal very poor

Claims

CLAIMS1. Method for imparting or improving block resistance, preferably early high-temperature blocking resistance, of a waterborne coating composition comprising adding to said coating composition an effective amount of at least one anti-blocking additive comprising a phosphate ester surfactant, wherein the phosphate ester surfactant comprises an acid or a salt of an ethoxylated alkyl phosphate ester comprising a C4-C20 carbon chain and a number of ethylene oxide units strictly greater than 0 and lower or equal to 3.

2. Method according to claim 1, wherein the phosphate ester surfactant comprises between 1 and 2 ethylene oxide units.

3. Method according to claim 1 or claim 2, wherein the alkyl group of the phosphate ester surfactant is a C4-C15 carbon chain, preferably a Cs-Cn carbon chain, optionally branched and / or substituted.

4. Method according to any of the preceding claims, wherein the phosphate ester surfactant is a potassium salt, a sodium salt, an ammonium salt, or an organic amine salt.

5. Method according to any of the preceding claims, wherein the effective amount of antiblocking additive is greater or equal to 0.010% by weight, preferably greater or equal to 0.05% by weight, based on the total amount of the coating composition.

6. Method according to any of the preceding claims, wherein the effective amount of antiblocking additive is lower or equal to 1.0% by weight, preferably lower or equal to 0.5% by weight, based on the total amount of the coating composition.

7. Method according to any of the preceding claims, wherein the anti-blocking additive comprises:• at least one phosphate ester surfactant comprising a C4-C20 carbon chain, preferably a Cs-Ci2 carbon chain, a number of ethylene oxide units strictly greater than 0 and lower or equal to 3, preferably strictly greater than 0 and lower or equal to 2, and a potassium salt, a sodium salt, an ammonium salt, or an organic amine salt; andat least one olefin sulfate, sulfonate, and / or phosphate alkyl surfactant, preferably a C10-C20 olefin sulfate, sulfonate, and / or phosphate alkyl surfactant.

8. Coating composition presenting block resistance, preferably early high-temperature blocking resistance properties, comprising:- at least one latex polymer,- optionally, at least one pigment,- water,- an anti-blocking additive comprising a phosphate ester surfactant, wherein the phosphate ester surfactant comprises an acid or a salt of an ethoxylated alkyl phosphate ester comprising a C4-C20 carbon chain and a number of ethylene oxide units strictly greater than 0 and lower or equal to 3.

9. Coating composition according to claim 8, said coating composition presenting a block resistance, preferably an early high-temperature blocking resistance improved by at least 2 units compared to the same coating composition lacking the anti-blocking additive.

10. Coating composition according to claim 8 or claim 9, said coating composition presenting a block resistance, preferably an early high-temperature blocking resistance between 5 and 10, preferably between 6 and 9.

11. Coating composition according to any of claims 8 to 10, further comprising one or more additional components selected from defoamers, rheology modifiers, solvents, biocides, neutralizing agents, and preservatives.

12. Coating composition according to any of claims 8 to 11, said coating composition being a paint intended to be applied to a substrate, the substrate being preferably wood, concrete, paper, metal, another paint, tiles, or cement, or said coating composition being an adhesive optionally pressure-sensitive, a varnish, or an ink.

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