USE OF COATINGS MADE FROM AQUEOUS POLYMER DISPERSIONS HAVING A CORE/SHELL STRUCTURE FOR CAPTURING VOLATILE ORGANIC COMPOUNDS SUCH AS ALDEHYDES

Abstract

The invention concerns a method comprising the steps of irreversibly capturing and trapping at least one organic volatile compound bearing a function among aldehyde, ketone, or amine, using an aqueous polymer dispersion of core/shell structure particles having an MFFT of 0 to 50° C., with the polymer phase P1 being a hard core with a Tg1 of 60 to 120° C. and the polymer phase P2 being a soft shell with a Tg2 of −20 to 40° C. and with P1, comprising a monomer M1 with two polymerisable ethylenic unsaturations and an ethylenically unsaturated monomer M2 bearing a carboxylic acid/anhydride function and P2, representing 40% to 85% by weight of P1+P2 and comprising in its structure units from at least one monomer M3 bearing a polymerisable ethylenic unsaturation and, in addition, a ureido functional group or a functional group having a mobile hydrogen alpha to a ketonic carbonyl.

Claims

1. A method for capturing organic volatile compounds, said method comprising the steps of irreversibly capturing and trapping at least one organic volatile compound bearing a function among aldehyde, ketone or amine, using an aqueous polymer dispersion having a minimum film-forming temperature (MFFT) of 0 to 50° C., measured according to the standard ISO 2115 and comprising polymer particles of hard core P1/soft shell P2 structure, with P1 being the hard polymer phase in the core of said particle, with a glass transition temperature Tg1 of 60 to 120° C., and said phase P1 comprising in its structure units from at least one monomer M1 having at least two copolymerisable ethylenic unsaturations and having a role of cross-linker and units from at least one ethylenically unsaturated monomer M2 bearing at least one carboxylic acid and/or carboxylic anhydride function P2 being the soft polymer phase in the shell having a glass transition temperature Tg2 of −20 to 40° C., with P2 representing 40% to 85% by weight, of the total weight of P1+P2 and comprising in its structure units from at least one monomer M3 bearing a polymerisable ethylenic unsaturation and, in addition, an ureido functional group or a functional group having a mobile hydrogen in alpha position to a ketonic carbonyl.

2. The method of claim 1, wherein said functional group of said monomer M3 is selected from the group consisting of ureido, acetoacetoxy and diacetone.

3. The method of claim 1 wherein said monomer M3 is selected from the group consisting of diacetone acrylamide (DAAM), acetoacetoxyethyl (meth)acrylate (AAEM), acetoacetoxypropyl (meth)acrylate (AAPM), N-(2-(meth)acryloyloxyethyl) ethylene urea (or ureidoethyl (meth)acrylate: UMA).

4. The method of claim 1 wherein that the level of said monomer M3 bearing said functional group varies from 50 to 1000 mmol per kg of said polymer (P1+P2).

5. The method of claim 1 wherein said monomer M3 is present in said phase P2 at a level of 1% to 25% by weight relative to the total weight of P1+P2.

6. The method of claim 1 wherein said phase P2 further comprises at least one transfer agent selected from hydrophilic mercaptans bearing an ionic group.

7. The method of claim 1 wherein said phase P2 comprises at least a second transfer agent selected from hydrophobic mercaptans having a weight ratio of hydrophilic agent to hydrophobic agent greater than 1.

8. The method of claim 1 wherein the overall level of said first and second transfer agents represents 0.02% to 2% by weight relative to the total weight of the phases P1+P2.

9. The method of claim 1 wherein the difference between said Tg1 and Tg2 varies from 20 to 140° C. and preferably from 30 to 115° C.

10. (canceled)

11. (canceled)

12. (canceled)

13. (canceled)

14. The method of claim 1 wherein said dispersion comprises in dispersion with the polymer particles at least one compound comprising at least one hydrazine or hydrazide function.

15. The method of claim 1 wherein said volatile organic compound to be captured or trapped has a boiling point at atmospheric pressure below 250° C.

16. The method of claim 1 wherein said volatile organic compound to be captured or trapped is a C.sub.1 to C.sub.8 aldehyde selected from the group consisting of formaldehyde, acetaldehyde, propanal, acrolein (acrylaldehyde), butanal, pentanal, hexanal, heptanal and octanal.

17. The method of claim 1 comprising polymer derived from said dispersion, wherein said polymer is in film or coating form.

18. The method of claim 1 comprising polymer derived from said dispersion, wherein said polymer is used in the form of a thin layer or a coating applied on a porous or fibrous substrate.

19. The method of claim 1 comprising polymer derived from said dispersion, wherein said polymer is used in the form of a qualitative or quantitative probe for detecting said volatile compound.

20. (canceled)

21. (canceled)

22. The method of claim 1 comprising capturing in the atmosphere in direct contact with the surface of polymer derived from said dispersion which is in the form of a thin layer of polymer or coating.

23. The method of claim 1 comprising capturing formaldehyde emitted by coatings applied as a sublayer or first layer relative to the capture coating, with said capture coating being used as a surface coating.

24. The method of claim 1 comprising capturing formaldehyde emitted by a substrate which is coated or impregnated with a capture coating derived from said polymer dispersion.

25. The method of claim 24 wherein said formaldehyde-emitting substrate is selected from the group consisting of: pressed wood, sandwich-structured wood and plywood glued together using urea-formaldehyde adhesives, sandwich-structured wood and plywood glued together using melamine-formaldehyde adhesives, treated textile and fibres treated with a formaldehyde-generating treatment composition.

26. The method of claim 1 comprising capturing formaldehyde emitted by a first “generator” substrate on which is applied in contact, a second “capture” substrate Impregnated or coated with said aqueous polymer dispersion or with the polymer derived from said dispersion.

27. The method of claim 26 wherein said second “capture” substrate in contact with said first “generator” substrate is selected from: non-woven fabrics, organic fibre fabrics, and inorganic fibre fabrics, for insulating or renovating interior walls.

28. The method of claim 1 further comprising the step of impregnating air filters or smoke filters with said aqueous polymer dispersion.

Description

EXPERIMENTAL SECTION

1) Tests Performed: See Table 1 Below

[0061] Two dispersions were prepared, one according to the invention (test 1) and one comparative outside the invention (test 2). The dispersion according to the invention of test 1 is comparable to that of test 2 outside the invention, with the difference being the fact that the dispersion according to test 1 has polymer particles of core/shell structure as indicated in table 1 and the dispersion of test 2 is an ordinary dispersion without structured particles, with the composition of the two tests adjusted so as to have the same film-forming temperature with an MFFT of 5° C. The phase P1 in the case of test 1 comprises HDDA as the monomer M1 (2.5% by weight vs P1) and MAA as the monomer M2 (1.6% by weight vs P1).

[0062] The core/shell structure is shown by atomic force microscopy (AFM) on the film obtained by coalescence of the dispersion of test 1, with the image in FIG. 1 showing the hard phase of the core, appearing as a light area, and the continuous phase coalesced around said cores, corresponding to the shell, appearing as a dark area.

[0063] Tack tests (touching with a finger) on the films obtained show that the film obtained with the structured-particle dispersion of test 1 is not tacky and that the film obtained with the dispersion of test 2 is tacky to the touch (after at least 24 hours of drying).

TABLE-US-00001 TABLE 1 features of the tests performed Test number 1 2 Test type Invention Outside the invention (comparative) % AAEM by weight (monomer M3  10* 10 vs the total weight of the polymer) % weight P1 40 — % weight P2 60 — Total 100  100 Fox Tg1 vs P1 (° C.) 70 — Fox Tg2 vs P2 (° C.) −10  — Overall Fox Tg (° C.)  17** −6 MFFT measured by ISO 2115 (° C.)  5 5 *16.6% relative to P2 **Overall Tg calculated assuming an unstructured particle with miscible phases P1 and P2

TABLE-US-00002 TABLE 2 Raw materials used in the synthesis of the test dispersions 1 and 2 Technical Component function Chemical nature Supplier Aerosol ® Surfactant Ethoxylated fatty alcohol Cytec A102 sulphosuccinate, sodium salt (C.sub.10-C.sub.12) 30% solution in water Disponil ® Surfactant Polyglycol ether fatty Cognis FES 32 alcohol sulphate, sodium salt 31% solution in water Tergitol ® Surfactant Secondary ethoxylated Dow 15S9 fatty alcohol with 9 EO, 100% Emulan ® TO Surfactant Ethoxylated fatty alcohol BASF 4070 with 40 EO, 70% HDDA Cross-linker Hexanediol diacrylate Sartomer (HDDA) BuA Monomer Butyl acrylate Arkema MMA Monomer Methyl methacrylate Arkema AA Monomer Acrylic acid Arkema MAA Monomer Methacrylic acid Arkema AAEM Cross-linker Acetoacetoxyethyl Eastman methacrylate nDDM Mercaptan n-Dodecyl mercaptan Acros MPP Mercaptan Mercaptopropionic acid, Acros 80% Na.sub.2S.sub.2O.sub.8 Peroxide Sodium persulphate Aldrich Na.sub.2S.sub.2O.sub.5 Reducer Sodium metabisulphite Prolabo TBHP Peroxide tert-Butyl hydroperoxide, Aldrich 70% SFS Reducer Sodium formaldehyde Bruggeman sulphoxylate NaOH Neutralisation Sodium hydroxide Prolabo Acticide MBS Biocide Aqueous solution of Thor methylisothiazolinone (MIT) and benzisothiazolinone (BIT) (2.5% MIT/ 2.5% BIT)

[0064] All of the calculated Tg values are calculated according to Fox's law, as already indicated in the description.

[0065] The Tg values of the homopolymers corresponding to the monomers used, for purposes of calculating Tgs according to Fox's law, are given in ° C. in table 2a) below.

TABLE-US-00003 TABLE 2a) Tgs of the homopolymers of the monomers used, for Fox's relationship Monomer I Abbreviation Tg (° C.) Acrylic acid AA 106 Methacrylic acid MAA 228 Butyl acrylate BuA −54 Acetoacetoxyethyl methacrylate AAEM 18 Methyl methacrylate MMA 105

[0066] The minimum film-forming temperature (MFFT) is measured according to the standard ISO 2115.

[0067] The viscosity cited is a Brookfield viscosity at 10 rpm according to the standard ISO 2555.

[0068] The dry extract of the aqueous dispersion is measured according to the standard ISO 3251.

[0069] Particle size is measured by photon correlation spectroscopy (PSC), using a Beckman Coulter N4+ analyser. The sample is diluted (3 to 5 drops of emulsion in 50 ml of water) in a polystyrene tank using deionised water on a 0.22 μm acetate filter. Particle size is measured at a temperature of 25° C., a measurement angle of 90° and a laser wavelength of 633 nm.

[0070] The AFM image is formed on an instrument: AFM Nanoscope IIIa (Veeco Digital Instruments) in tapping mode on film obtained after deposition of a drop of aqueous dispersion according to test 1, diluted 1:100 on a mica flake, and drying for at least 24 hours under at room temperature.

2) Protocol for Test 1

Materials Used

[0071] A jacketed 3-litre (internal capacity) glass reactor, equipped with efficient agitation (vortex), triple-flux refrigerant, a control unit and regulation of the temperature of the material, is used. The reactor comprises the number of inlets necessary for the separate introduction of the various components and also an inlet dedicated to rendering the unit inert with nitrogen (placed under inert nitrogen atmosphere). Leak-tightness is confirmed before each synthesis. The apparatus is equipped with a system for controlling the flow rates at which the components are Introduced.

Preparation of the Initial Load of the Starting Medium

[0072] The starting medium consists of 14.1 g of Disponil® FES 32 solubilised in 327 g of demineralised water. The temperature of said medium is brought to 85° C.

Preparation of the Seed P0

[0073] Mix 6.9 g of MMA and 6.9 g of BuA.

Preparation of the Pre-Emulsion P′1

[0074] 4.2 g of Aerosol® A102 and 7.1 g of Disponil® FES 32 are dispersed in 44.1 g of demineralised water with good agitation.

[0075] The following are added in turn with good agitation: [0076] 130.9 g of MMA [0077] 18.5 g of BuA [0078] 4.2 g of HDDA [0079] 2.8 g of MAA

[0080] The pre-emulsion thus formed is white and stable and it will be maintained with gentle agitation. It will be used for the synthesis of the particle core P1, consisting of P0 and P′1 (P1=P0+P′1).

Preparation of the Pre-Emulsion P2

[0081] 4.2 g of Aerosol® A102 and 9.1 g of Tergitol® 15S9 are dispersed in 74.4 g of water with good agitation. The following are added in turn with agitation: [0082] 70 g of MMA [0083] 135.7 g of BuA

[0084] A stable, white pre-emulsion is obtained. 10% of this pre-emulsion, or 29.3 g, will be withdrawn and used to carry out a seeding prior to the introduction of P2. The following are then added to the pre-emulsion, still with good agitation: [0085] 42.4 g of AAEM [0086] 8.5 g of AA [0087] 1.06 g of MPP [0088] 0.08 g of nDDM

[0089] This stable, white pre-emulsion, P2, will be used for the synthesis of the particle shell (P2).

Preparation of the Catalyst Solutions

[0090] 1.48 g of sodium persulphate is solubilised in 28.2 g of water. [0091] 0.42 g of sodium metabisulphite is solubilised in 3.8 g of water. [0092] 0.6 g of TBHP (70%) is solubilised in 2.65 g of water. [0093] 0.34 g of SFS is solubilised in 8.1 g of water.

Polymerization Method

i) Seeding of P0

[0094] With the reaction mixture comprising the initial load stable at 85° C., the mixture of MMA and BuA specified above is introduced to seed P0. Once the temperature stabilises, 70% of the sodium persulphate solution is added. The maximum release of energy marks the conclusion of this step, the particle size is about 30 nm and the conversion is above 70%.

ii) Synthesis of the Core P1

[0095] The introduction of the pre-emulsion P′1 lasts 120 minutes, at a polymerisation temperature of 85° C.

iii) Step of Heat Curing and Cooling

[0096] The temperature is maintained at 85° C. for 60 minutes. At the conclusion of the heat curing, the reaction medium is cooled to 65° C. The conversion is then near 100%.

iv) Synthesis of the Shell P2

[0097] At 65° C., the seed made up of 29.3 g of a fraction of P2 (without functional monomers or transfer agents) is introduced into the reactor. Mixing is carried out for at least minutes before beginning the separate introductions of: [0098] The remaining 100% of the second pre-emulsion P2 [0099] The remaining 30% of the initiator solution (sodium persulphate) [0100] 100% of the activator solution (sodium metabisulphite)

[0101] During the introductions, which last 150 minutes, the temperature of the medium is maintained at 65° C. This step is followed by a post-curing for 30 minutes at 65° C.

v) Redox treatment

[0102] The TBHP and SFS solutions are added at 65° C. over 30 minutes. This redox treatment is followed by a curing at 65° C. for 30 minutes before cooling to room temperature.

vi) Final Additions

[0103] At 30-35° C., the latex is neutralised to pH 8 by adding sodium hydroxide and is post-supplemented with a biocide. It is then filtered through 100 μm fabric. The dry extract is 44.5%.

[0104] The final particle size is about 90 nm; the viscosity is below 100 mPa.Math.s; the measured MFFT is 5 SC.

3) Protocol for Test 2

Materials Used

[0105] A jacketed 3-litre (internal capacity) glass reactor, equipped with efficient agitation (vortex), triple-flux refrigerant, a control unit and regulation of the temperature of the material, is used. The reactor comprises the number of inlets necessary for the separate introduction of the various components and also an inlet dedicated to rendering the unit inert with nitrogen. Leak-tightness is confirmed before each synthesis. The apparatus is equipped with a system for controlling the flow rates at which the components are introduced.

Preparation of the Initial Load of the Starting Medium

[0106] The starting medium consists of 33 g of Disponil® FES 32 solubilised in 802 g of demineralised water. The temperature of said medium is brought at 85° C.

Preparation of the Seed P0

[0107] Mix 17.9 g of MMA and 17.9 g of BuA.

Preparation of the Complementary Pre-Emulsion P′

[0108] 11 g of Aerosol® A102, 29.3 g of Disponil® FES 32 and 23.6 g of Emulan® TO 4070 are dispersed in 316.7 g of demineralised water with good agitation.

[0109] The following are added in turn with good agitation: [0110] 356 g of MMA [0111] 565 g of BuA [0112] 110 g of AAEM [0113] 11 g of HDDA [0114] 5.5 g of MAA [0115] 16.5 g of AA

[0116] The pre-emulsion P′ thus formed is white and stable and it will be maintained with gentle agitation. It will be used for the synthesis of the polymer particle P, composed of P0 and P′ as defined for this test 2 (P=P0+P).

Preparation of the Catalyst Solutions

[0117] 3.9 g of sodium persulphate is solubilised in 73.2 g of water. [0118] 1.6 g of TBHP (70%) is solubilised in 6.9 g of water. [0119] 0.9 g of SFS is solubilised in 21.1 g of water.

Polymerisation Method

i) Seeding of P0

[0120] With the reaction mixture comprising the initial load stable at 85° C., the mixture of MMA and BuA specified above is introduced to seed P0. Once the temperature stabilises, 20% of the sodium persulphate solution is added. The maximum release of energy marks the conclusion of this step. The particle size is about 40 nm and the conversion is above 70%.

ii) Synthesis of the Polymer Particle P (Unstructured)

[0121] The introduction of the pre-emulsion P′ lasts 240 minutes, at a polymerisation temperature of 85° C. Jointly, 71.1% of the sodium persulphate solution is introduced at the same time.

iii) Step of Consuming Residual Monomers, Heat Curing and Cooling

[0122] After the conclusion of the introduction of the pre-emulsion P′, the remaining 8.9% of the sodium persulphate solution is introduced, still at 85° C. The temperature is maintained at 85° C. for 20 minutes. At the conclusion of the heat curing, the reaction medium is cooled to 65° C. The conversion is then near 100%.

iv) Redox Treatment

[0123] The TBHP and SFS solutions are added at 65° C. over 30 minutes. This redox treatment is followed by a curing at 65° C. for 30 minutes before cooling to room temperature.

v) Final Additions

[0124] At 30-35° C., the latex is neutralised to pH 8 by adding sodium hydroxide and is post-supplemented with a biocide. It is then filtered through 100 μm fabric. The dry extract is 45.5%.

[0125] The final particle size is about 90 nm, the viscosity is below 200 mPa.Math.s, the measured MFFT is 5° C.

4) Evaluation of Formaldehyde Capture Performance

4.1) Test Method

[0126] The performance of the product tested to reduce, by capture, the concentration of formaldehyde in indoor air is evaluated using the standard ISO 16000-23. ISO 16000-23 specifies a general laboratory test method for evaluating the reduction of concentration of formaldehyde by sorptive building materials. It is based on the test chamber method as specified in the standard ISO 16000-9, where the test chamber must simulate the parameters of the reference piece.

[0127] The sample to be tested is applied with a specific loading factor and placed in a test chamber (the sampling, transport and storage of the samples to be tested and the preparation of the samples to be tested being specified in the standard ISO 16000-11).

[0128] Formaldehyde is mixed into the air supply in order to measure the sorption flux and the mass of saturation per unit area. The first is a direct indication of the performance of the samples relative to the reduction of the concentration of formaldehyde at a given moment.

[0129] The second (mass of saturation per unit area) relates to the ability of a tested sample to maintain this performance.

[0130] In practical terms, at selected time intervals, a known volume of air is withdrawn from the test chamber. The formaldehyde is thus trapped and transformed into a hydrazone derivative by means of a cartridge filled with silica gel impregnated with 2,4-DNPH (2,4-dinitrophenyl hydrazine). The stable hydrazone derivative formed is desorbed with acetonitrile and analysed by HPLC with an ultraviolet detector (the sampling of air and the analysis methods for determining formaldehyde are specified in the standard ISO 16000-3).

[0131] The results obtained are then expressed as concentration of formaldehyde inside the chamber in μg/m.sup.3 and/or as sorption flux in μg/m.sup.2 per hour.

[0132] The performance of the sample to be tested in its ability to reduce the concentration of formaldehyde is evaluated by comparing the amount of formaldehyde found inside the chamber containing the sample to be tested with that of the empty chamber (with no sample). The formaldehyde consumption FC by said tested sample (in %) can then be calculated (see §5.3 below for definitions of the magnitudes measured).

5.2) Operating Conditions

[0133] Test parameters in the emission chamber [0134] Chamber volume: 119 litres [0135] Temperature: 23 t 1° C. [0136] Relative humidity: 50±5% [0137] Air change rate: 0.5 h.sup.−1 [0138] Loading factor. 1 m.sup.2/m.sup.3

Sample Preparation

[0139] One layer of coating in the wet state (aqueous dispersion) at 100 g/m.sup.2.

[0140] Formaldehyde injection: constant concentration inside the chamber throughout the duration of the test with a mean concentration inside the chamber of 78 μg/m.sup.3.

Method of Analysis:

[0141] Method: ISO 16000-23, EN ISO 16000-3 [0142] Principle: HPLC-UV [0143] Formaldehyde detection limit: 3 μg/m.sup.3 [0144] Uncertainty of detection/analysis of formaldehyde by HPLC-UV detector: ±22%.

5.3) Results

[0145] The results of formaldehyde consumption (FC) are presented in table 3 below. The formaldehyde consumption FC (in %) is calculated using the following formula:

FC=(C.sub.inlet−C.sub.chamber)/C.sub.inlet

with the definitions of C.sub.inlet and C.sub.chamber being the same as those below for calculating sorption flux F.

TABLE-US-00004 TABLE 3 Formaldehyde consumption FC (%) Duration Ref sample 4 hours 8 hours 1 day 7 days Test 1 76 56 42 26 Test 2 36 15 18 2

[0146] The sorption flux F of formaldehyde results are presented in table 4 below:

[0147] The sorption flux F is calculated according to the following formula:

F=(C.sub.inlet−C.sub.chamber)*Qc/A

With:

[0148] F: sorption flux in μg/m.sup.2 per hour FC: formaldehyde consumption in %, as defined above
C.sub.inlet: concentration at the chamber inlet, in μg/m.sup.3
C.sub.chamber: concentration inside the chamber, in μg/m.sup.3
Qc: flow of formaldehyde-mixed air inside the chamber=0.06 m.sup.3/h
A=0.119 m.sup.2, representing the surface area of the sample (coating)

TABLE-US-00005 TABLE 4 Sorption flux F of formaldehyde (in μg/m.sup.2 per hour) Duration Ref sample 4 hours 8 hours 1 day 7 days Test 1 31 23 18 8 Test 2 15 6 8 1