Antimicrobial acrylic latex composition

Abstract

The present invention relates to a composition comprising: a) an aqueous dispersion of polymer particles having a z-average particle size in the range of 50 nm or 80 nm to 500 nm or to 300 nm or to 200 nm as measured using dynamic light scattering; and b) a C4-C10-alkyl hydrogen peroxide in a concentration in the range of 250 ppm to 5000 ppm, based on the weight of the composition. The composition of the present invention provides a latex that is resistant to microbial growth even in the absence of a biocide.

Description

Background Art

[0001] The present invention relates to an acrylic latex composition that is resistant to microbial growth even in the absence of a biocide.

[0002] Aqueous dispersions of polymer particles (i.e., latex) used in the coating industry are stored with antimicrobial agents to inhibit the formation and growth of biological organisms (such as bacteria, yeast, and mold) during storage. The inhibition of these organisms prevents product degradation and spoilage, as well as the outgassing of volatile products and the subsequent pressure buildup in closed containers. Therefore, preservation is necessary for health, safety, and performance reasons.

[0003] Can preservatives such as isothiazolinones are facing intense regulatory scrutiny due to their real or perceived adverse effects on health, safety, and the environment; in fact, a complete ban on these biocides appears imminent in many parts of the world. To the extent that the development of new biocides is not possible due to cost reasons and the widespread perception (whether justified or not) of the inherent dangers of these biocides, there is a need to replace biocides with alternative, safer and more sustainable non-biocidal preservatives.

[0004] Can be found in EP 3 456 787 B1 for the recent example of the non-biocidal method that is used to preserve coating to prevent microbial contamination, this document discloses pH is adjusted to the aqueous coating formulation in the range of 10 to 12.5.Although effective on the surface, the formulations of these very high pH have produced other safety and sanitation problems, making this method impractical.As adding other non-traditional methods such as silver or zinc ions, may adversely affect the characteristic of coating, and also face regulatory review.For these reasons, need for other safer and more sustainable methods of the material used in preservation coating and coating. Summary of the Invention

[0005] In one aspect, the present invention addresses the need in the art by providing a composition comprising: a) an aqueous dispersion of acrylic-based polymer particles having a z-average particle size in the range of 50 nm to 500 nm; and b) a C4-C50 polymer in a concentration in the range of 125 ppm to 2500 ppm, based on the weight of the composition. 10 -alkyl hydroperoxides.

[0006] The composition of the present invention provides a latex that is resistant to microbial growth even in the absence of a biocide. DETAILED DESCRIPTION

[0007] In a first aspect, the present invention is a composition comprising: a) an aqueous dispersion of acrylic-based polymer particles having a z-average particle size in the range of 50 nm to 500 nm; and b) a C4-C50 polymer in a concentration in the range of 125 ppm to 2500 ppm, based on the weight of the composition. 10 -alkyl hydroperoxides.

[0008] The aqueous dispersion of acrylate-based polymer particles is advantageously prepared by contacting acrylate monomers, methacrylate monomers, and acid monomers under emulsion polymerization conditions. The resulting dispersion containing structural units of acrylate monomers, methacrylate monomers, and acid monomers, as well as residual unreacted monomers, is then reacted with a reducing agent such as isoascorbic acid or disodium 2-hydroxy-2-sulfinatoacetic acid and t-C4 ... 10 -alkyl hydroperoxide contact to track residual monomers to an acceptable level. Preferably, t-C4-C 10 The -alkyl hydroperoxide is tert-butyl hydroperoxide (t-BHP) or tert-amyl hydroperoxide (t-AHP) or a combination thereof.

[0009] As used herein, the terms "acrylate monomer," "methacrylate monomer," and "acid monomer" refer to one or more of acrylate, methacrylate, or acid monomers. As used herein, "acrylic-based" means that at least 70% by weight, preferably at least 80% by weight, and more preferably at least 90% by weight of the monomers used to prepare the aqueous dispersion of acrylic-based polymer particles are acrylate, methacrylate, and acid monomers.

[0010] As used herein, a "structural unit" of a given monomer refers to the residue of the monomer after polymerization. For example, the structural unit of methyl methacrylate (MMA) is illustrated as follows:

[0011]

[0012] The dotted lines represent the connection points between the structural units and the polymer backbone.

[0013] Examples of suitable acrylate monomers include C1-C 10Acrylates, such as ethyl acrylate, n-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, and 2-propylheptyl acrylate. Examples of suitable methacrylate monomers include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, and ureido methacrylate. Methyl methacrylate is a preferred methacrylate monomer; ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate are preferred acrylate monomers. The polymer particles preferably contain structural units of acrylate and methacrylate monomers in an amount of 70%, 80%, or 90% to 99% by weight, based on the weight of the polymer particles.

[0014] Examples of suitable acid monomers include carboxylic acid monomers and salts thereof, such as acrylic acid, methacrylic acid, and itaconic acid, and salts thereof; phosphoric acid monomers and salts thereof, such as phosphoethyl methacrylate and salts thereof; and sulfonic acid monomers and salts thereof, such as 2-acrylamido-2-methyl-1-propanesulfonic acid and salts thereof; vinylsulfonic acid and salts thereof; sodium 4-vinylbenzenesulfonate; and 2-propylene-1-sulfonic acid and salts thereof. Sodium 4-vinylbenzenesulfonate (also known as sodium styrenesulfonate or SSS) is a preferred sulfonate. The polymer particles preferably contain from 0.1% to 10% by weight of structural units of one or more acid monomers, based on the weight of the polymer particles.

[0015] Other monomers such as acrylonitrile, acrylamide or C1-C6-alkylacrylamide, and polyethylenically unsaturated monomers including divinylbenzene and allyl methacrylate may also be used to prepare the polymer particles. The z-average particle size of the polymer particles as measured using dynamic light scattering is in the range of 50 nm or 80 nm to 500 nm or to 300 nm or to 200 nm.

[0016] In the tracking step, t-C4-C 10 - the molar ratio of alkyl hydroperoxide to reducing agent is in the range of 1: 1 or 3: 1 or 3.5: 1 or 4.5: 1 or 5.5: 1 or 6.5: 1 or 7.0: 1 to 50: 1 or to 30: 1 or to 20: 1 or to 15: 1 or to 10: 1. The efficiency of this redox system can be controlled by a number of factors, including the optional addition of a) a catalytic amount of a redox reaction catalytic metal salt, such as a salt of iron (II) such as FeSO4, copper, manganese, vanadium, silver, platinum, nickel, chromium, palladium or cobalt, or a combination thereof; b) the addition of a chelating agent for the metal salt; c) adjusting the temperature; and d) adjusting the pH.

[0017] Therefore, t-C4-C 10-alkyl hydroperoxide and reducing agent, optionally in the presence of catalytic metal salt and chelating agent, can be contacted with the aqueous dispersion of polymer particles in a single stage or in multiple stages, using the same or different molar ratios in each stage, provided that the added t-C4-C 10 - The molar ratio of the total amount of alkyl hydroperoxide to the total amount of reducing agent added in the multiple steps is within the specified range.

[0018] The resulting aqueous dispersion of polymer particles is preferably neutralized to a pH in the range of 7.5 or 8.0 or 8.5 or 8.8 to 10.0 or to 9.5 or to 9.2.

[0019] The resulting composition comprises from 125 ppm or 150 ppm or 175 ppm or 225 ppm or 275 ppm or 350 ppm to 2500 ppm or to 1250 ppm or to 1500 ppm of t-C4-C 10 -alkyl hydroperoxide and preferably less than 1000 ppm, more preferably less than 500 ppm of residual monomers. 10 The concentration of -alkyl hydroperoxides was determined using NMR spectroscopy as detailed in the experimental section.

[0020] In another aspect, the present invention is a method comprising the steps of:

[0021] a) contacting monomers comprising acrylate monomers, methacrylate monomers, and acid monomers under emulsion polymerization conditions to form an aqueous dispersion of acrylic-based polymer particles and residual monomers;

[0022] b) mixing the dispersion of the acrylic acid-based polymer particles with a reducing agent and t-C4-C 10 -alkyl hydroperoxide to reduce the concentration of residual monomers in the aqueous dispersion to less than 1000 ppm of residual monomers; wherein the t-C4-C 10 The molar ratio of the alkyl hydroperoxide to the reducing agent is in the range of 1:1 to 50:1.

[0023] The compositions of the present invention have been found to be resistant to the growth of mold, bacteria and yeast under heat aging conditions.

[0024] Example

[0025] NMR spectroscopy determination of t-AHP or t-BHP in serum phase

[0026] Into 10-mL polycarbonate tube, load 3.0mL latex sample, 3.0mL Milli-Q water, and centrifuge 15 minutes with 100,000rpm.Gained clear supernatant is decanted and transferred in 5-mm NMR tube.The flame sealed capillary that is filled with external standard (D containing 5.00wt% d4-trimethylsilyl propionate sodium O) is added to NMR tube.Carefully note the correct alignment of external standard in NMR tube.Use the Bruker AVANCEIII 600 spectrometer that is equipped with 5-mm BroadBand CryoProbe to obtain NMR spectrum.Each sample is tuned and shimmed individually, but pulse width and receiver gain remain constant for sample series. The concentration of free tert-amyl hydroperoxide was measured by using a zg pulse sequence with the following parameters: acquisition time (aq) = 2.5 seconds, recycle delay (d1) = 30 seconds, number of transients (ns) = 1024, receiver gain (rg) = 32, and pulse width (p1) = 11 milliseconds. All other parameters (time domain size, sweep width, dwell time, prescan delay, and carrier frequency) were kept at default values. The concentration of free hydrogen peroxide was calculated by comparing the integral of the peak resonating around 1.2 ppm with the peak of an external standard at 0.0 ppm. The spectra were referenced to an external standard at 0.0 ppm on the trimethylsilyl chemical shift scale. The hmbcgplpndqf pulse sequence was used. 1 H- 13 The purity of the hydrogen peroxide resonances was clearly confirmed by C heteronuclear multiple bond coherence (HMBC) experiments. The SSS oligomer content was calculated by comparing the normalized integral of the peak resonating around 7 ppm with the peak of an external standard at 0.0 ppm. The normalized integral was estimated by determining the weight-average mass of the SSS oligomers using a diffusion-ordered spectroscopy (DOSY) experiment using an LEDBPGP2S pulse sequence.

[0027] Preparation of samples for antimicrobial resistance

[0028] The antimicrobial properties of the samples were tested "as is" (not heat aged) and after being subjected to 50°C for four weeks (heat aged). A 10-g aliquot was taken from each sample and heated to 10 6 -10 7The samples were inoculated three times with a pool of standard bacteria, yeasts and molds (obtained from the American Type Culture Collection (ATCC) at 30 colony forming units per milliliter of sample (CFU / mL) for common contaminants in coatings) at 7-day intervals. After inoculation, the samples were stored in a 25°C incubator. The microbial contamination of the test samples was monitored by agar plate inoculation using a standard streak plate method. Samples were inoculated onto tryptic soy agar (TSA) and potato dextrose agar (PDA) plates on the 1st and 7th days after each microbial attack. All agar plates were checked daily until the 7th day after inoculation to determine the number of microorganisms that survived in the test samples. Between inspections, the agar plates were stored in an incubator at 30°C for TSA plates and at 25°C for PDA plates. The degree of microbial contamination was determined by counting colonies, with the rating score determined based on the number of microbial colonies observed on the agar plates. The reported results were from the 7th day readings and summarized for both "as is" and heat-aged samples. The results are described by a score for each type of microorganism: B = bacteria, Y = yeast, and M = mold. For example, 3B describes a plate with a score of 3 for bacteria, or Tr Y(1) describes a plate with trace yeast (1 colony on the plate). Table 1 illustrates the rating system used to estimate the level of microbial contamination on the planned plate. Colony refers to the number of colonies on the plate.

[0029] Table 1 - Rating system for evaluating microbial contamination

[0030] Colony Rating score pollute result none 0 none qualified 1-9 Tr trace amount qualified 10 to 99 1 Very mild Unqualified 100 to approximately 1000 2 slight Unqualified About 1000 to 10,000 3 Moderate Unqualified >10,000 4 severe Unqualified

[0031] In Table 1, "pass" means that fewer than ten colonies were detected on the plate on a particular day after inoculation (day 1 (D1) or day 7 (D7)). "Fail" means that ten or more different colonies were detected on the plate on a particular day after inoculation.

[0032] Comparative Example 1 - Method for preparing acrylic latex

[0033] A monomer emulsion was prepared by mixing deionized water (800 g), sodium lauryl sulfate (16.59 g, 28% active), n-butyl acrylate (1016.58 g), methyl methacrylate (889.53 g), ureido methacrylate (39.1 g, 50% active), methacrylic acid (19.55 g), and sodium 4-vinylbenzenesulfonate (10.87 g, 90% active).

[0034] To a 5-L four-necked round-bottom flask equipped with a paddle stirrer, a thermometer, an N2 inlet, and a reflux condenser were added deionized water (730 g), sodium lauryl sulfate (19.73 g, 28% active), and an aqueous solution of sodium carbonate (6.84 g) dissolved in deionized water (70 g). The contents of the flask were heated to 87° C. under N2 and stirring was initiated.

[0035] A portion of the monomer emulsion (58.8 g) was then added to the flask, followed by the rapid addition of an aqueous solution of ammonium persulfate (6.8 g) dissolved in deionized water (20 g), followed by a rinse with deionized water (5 g). After stirring for 5 minutes, the remaining monomer emulsion and a solution containing ammonium persulfate (1.04 g) dissolved in deionized water (92 g) were each added to the flask over a total period of 65 minutes. The contents of the flask were maintained at 87° C. during the addition of the monomer emulsion. When all additions were complete, the container containing the residual monomer emulsion was rinsed with deionized water (25 g), which was then added to the flask. The contents of the flask were cooled to 75° C., and an aqueous solution of FeSO₄ (20.1 g, 0.1% solids) and an aqueous solution of tetrasodium EDTA (2 g, 1% solids) were added to the kettle. A catalyst / activator pair of a) tert-amyl hydroperoxide (t-AHP, 1.27 g, 85% active) dispersed in 40 g of deionized water and b) isoascorbic acid (IAA, 0.75 g) dissolved in 40 g of deionized water were then added linearly and separately to the flask over 20 minutes. The contents of the flask were maintained at 75° C. during the addition of the catalyst / activator pair.

[0036] The polymer was then neutralized to pH 9.0 using aqueous ammonium hydroxide solution and deionized water. The z-average particle size was measured to be 116 nm using a Brookhaven BI-90 Plus particle size analyzer; the solids were measured to be 50.3%.

[0037] Example 1-4 - Method for preparing acrylic latex with excess t-AHP

[0038] The method of Comparative Example 1 was repeated, except that the amount by weight of t-AHP added after the flask was cooled to 75° C. was increased by 2 times (Example 1), 3 times (Example 2), 4 times (Example 2), and 5 times (Example 4).

[0039] Table 2 shows the relative concentrations of t-AHP added relative to Comparative Example 1, as well as the concentrations of t-AHP and t-amyl hydroperoxide (t-AmOH) measured in the final neutralized dispersion.

[0040] Table 2 - Relative concentration of t-AHP

[0041]

[0042]

[0043] Table 3 shows the thermal aging challenge test results of the samples.

[0044] Table 3 - Thermal aging stimulation test results

[0045] C1 C2 Comparative Example 1 Unqualified Unqualified Example 1 qualified qualified Example 2 qualified qualified Example 3 qualified qualified Example 4 qualified qualified

[0046] The data demonstrate that increasing t-AHP levels is effective in preserving acrylic acid-based latexes against microbial growth.

Claims

1. A composition comprising: a) an aqueous dispersion of acrylic-based polymer particles having a z-average particle size in the range of 50 nm to 500 nm as measured using dynamic light scattering; and b) a C4-C50-containing organic solvent in a concentration in the range of 125 ppm to 2500 ppm based on the weight of the composition. 10 -Alkyl hydroperoxides.

2. The composition according to claim 1, wherein the C4-C 10 -alkyl hydroperoxide is in the range of 150 ppm to 1250 ppm, and the C4-C 10 - the alkyl hydroperoxide is tert-butyl hydroperoxide or tert-amyl hydroperoxide or a combination thereof; wherein the composition has a pH in the range of 7.5 to 10.

0.

3. The composition according to claim 1, wherein the C4-C 10 -alkyl hydroperoxide is in the range of 225 ppm to 1250 ppm, and the C4-C 10 - the alkyl hydroperoxide is tert-amyl hydroperoxide; wherein the composition has a pH in the range of 8.0 to 9.

5.

4. The composition according to claim 3, wherein the C4-C 10 - said concentration of alkyl hydroperoxide is in the range of 275 ppm to 750 ppm.

5. The composition according to claim 4, wherein the C4-C 10 The -alkyl hydroperoxide is tert-butyl hydroperoxide or tert-amyl hydroperoxide or a combination thereof.

6. The composition according to claim 5, wherein the C4-C 10 -Alkyl hydroperoxide is tert-amyl hydroperoxide.

7. The composition according to any one of claims 1 to 6, wherein the acrylic-based polymer particles comprise structural units of methacrylate, acrylate, and acid monomers, wherein the methacrylate is methyl methacrylate; the acrylate comprises butyl acrylate or 2-ethylhexyl acrylate or a combination thereof; and the acid comprises acrylic acid or methacrylic acid.

8. The composition of claim 7, wherein the acid further comprises sodium 4-vinylbenzene sulfonate.

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