WO2019000339A1

WO2019000339A1 - Aqueous emulsion and use thereof

Info

Publication number: WO2019000339A1
Application number: PCT/CN2017/090916
Authority: WO
Inventors: Leif Robertsen; Feng Chen; Fengyang LI; Elsi TURUNEN
Original assignee: Kemira Oyj; Kemira (Asia) Co., Ltd.
Priority date: 2017-06-29
Filing date: 2017-06-29
Publication date: 2019-01-03

Abstract

Disclosed are an aqueous emulsion of discrete droplets of polymer dispersed in a continuous water phase and the use of the emulsion．The emulsion comprises at least 3 weight-％ of at least one hydrophobic (meth)acrylate polymer, at least 0.01 weight-％ of hydrophobic microparticles, preferably silica based particles, at least 1 weight-％ of at least one surfactant, and at least 40 weight-％ of water, which forms the continuous phase of the emulsion．

Description

[Title established by the ISA under Rule 37.2] AQUEOUS EMULSION AND USE THEREOF

THECINICAL FIELD

The present invention relates to an aqueous emulsion of discrete droplets of polymer dispersed in a continuous water phase and to the use of the emulsion according to the preambles of the enclosed independent claims.

BACKGROUND ART

Various defoaming compositions or defoamers are used in different industries to control foaming, also in pulp and paper industry. The purpose of defoaming compositions is to reduce the foam formation or prevent it completely.

Many effective defoamers are extremely hydrophobic compositions and/or contain organic diluents. These can be used for example in petroleum and mining industry. Such defoamers may comprise an organic carrier fluid anda defoaming agent or they may be mineral oil based compositions, which optionally may contain silica.

Use of defoamers that are hydrophobic and/or contain large amounts of organic diluents is problematic in aqueous processes as they are not easily dispersed in process water. This has limited the use of these defoamersfor example in pulp, paper and board industry. Consequently, there is a need for effective defoamers for water-intensive processes.

DESCRIPTION OF INVENTION

An object of this invention is to minimise or possibly even eliminate the disadvantages existing in the prior art.

Another object of the present invention is to provide an effective defoamer for pulp, paper and board making processes.

A further object of the invention is to provide a defoamer that is also able to increase the drainage during paper or board manufacture.

These objects are attained with the invention having the characteristics presented below in the characterising parts of the independent claims. Some preferred embodiments of the invention are presented in the dependent claims.

The embodiments mentioned in this text relate, whenever applicable, to all aspects of the invention, even if this is not always separately mentioned.

Typical aqueous emulsion of discrete droplets of polymer, dispersed in a continuous water phase, according to the present invention comprises

-at least 3 weight-％of at least one hydrophobic (meth) acrylate polymer,

-at least 0.01 weight-％of hydrophobic microparticles, preferably silica based particles,

-at least 1 weight-％of at least one surfactant, and

-at least 40 weight-％of water, which forms the continuous phase of the emulsion.

Typicaluse of an aqueous emulsion according to the present invention is as a defoameragent or drainage agent in making of pulp, paper, board or the like.

Now it has been surprisingly found that an aqueous emulsion comprising (meth) acrylate polymer, surfactant and hydrophobic microparticles is effective for reducing or inhibiting foam formation in pulp, paper and board making. Furthermore it was unexpectedly observed that the emulsion provided significantly improved drainage properties during web formation. The aqueous emulsion is also advantageous as it is easier and safer to use thandefoamers based on organic diluents.

In the present context all weight-％relating to the aqueous emulsion are calculate from the total weight of the emulsion, including the water phase.

Typical aqueous emulsion according to the invention comprisesdiscrete polymer droplets, which are dispersed in a continuous water phase. The droplets of polymer are small, and preferably the droplets of polymer dispersed in a continuous water phase have a droplet size D50 ≤15 μm, preferably ≤10 μm and/or droplet size D90 ≤ 35 μm, preferably ≤ 30 μm. Small droplets of polymer improve the stability of the emulsion, while providing an effective defoamingperformance. The polymer droplets may further have mode <10 μm. The mode represents the droplet size most commonly found in the distribution.

According to one preferable embodiment of the invention the emulsion has a viscosity in the range of 50–2000 cP, preferably 100–1000 cP, 150–600 cP, measured with Brookfield, spindle #63, 100 rpm, at 25 ℃. The viscosity of the emulsion is adjusted to suit the water-intensive process where it is used, such as pulp, paper and board making. With the defined viscosities the defoamer is easily mixed with the aqueous liquid phase present in the said processes and it is easy to pump and transport inside the mills.

One important property for a defoamer is its stability during storage. The present emulsion shows excellent stability and shelf-life, even under long storage periods. The emulsion is preferably free from phase separation. The emulsion preferably has a Turbiscan Stability Index TSI < 5 for 4 weeks and < 10 for 3 months.

The aqueous emulsion comprises at least 3 weight-％of at least one hydrophobic (meth) acrylate polymer. It is possible that the emulsion comprises more than one hydrophobic (meth) acrylate polymer, i.e. plurality of (meth) acrylate polymers, dispersed as discrete particles in the continuous water phase. By using a plurality of polymers it is possible to accurately tailor the defoaming ability and process compliance of the emulsion.

The (meth) acrylate polymersthat are suitable for usein the present invention may be obtained by polymerisation of alkyl (meth) acrylate monomers and/or hydroxyalkyl (meth) acrylate monomers and optionally acrylic acid monomers. The alkyl groups may be branched or linear, and they may contain 1 to 18 carbon atoms and/or at least one hydroxy group on the alkyl chain, at any location. Suitable alkyl groups are, for example, 2-ethylhexyl, 1-hydroxyethyl, 2-hydroxyethyl, 1-hydroxypropyl, 2-hydroxypropyl, 3-hydroxypropyl, 1-hydroxyisopropyl, 2-hydroxyisopropyl, 3-hydroxyisopropyl, 1-hydroxybutyl, 2- hydroxybutyl, 3-hydroxybutyl and4-hydroxybutyl. Preferably the (meth) acrylate monomers are selected from 1-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate and/or (meth) acrylic acid. According to one embodiment the (meth) acrylate polymer may be obtained by polymerisation of (meth) acrylate monomers and 1-20 mol-％, preferably 5–12 mol-％, of (meth) acrylic acid.

The polymerisationof the suitable (meth) acrylate polymers may be performed by any suitable manner known in the art, preferably in an organic diluent in the presence of a free radical generating catalyst.

According to one preferable embodimentthe emulsion comprises 3–60weight-％, preferably 10–50 weight-％, more preferably 12–40 weight-％, of at least one (meth) acrylate polymer. It was unexpected that the emulsion shows good defoaming ability even if the amount (meth) acrylate polymer is relatively low.

The emulsion further comprises at least 0.01 weight-％of hydrophobic microparticles, preferably silica based particles. According to one preferable embodiment the emulsion comprises 0.01–12weight-％, preferably 0.1–8 weight-％, more preferably 0.2–3 weight-％, of hydrophobic microparticles, preferably silica based particles. The hydrophobic particles effectively break air bubbles of the foam and thus improve the defoaming effect that is obtained with the emulsion.

According to one preferable embodiment of the invention the hydrophobic microparticles are silica based particles, preferably fumed silica particles, colloidalsilica particles or precipitated silica particles, even more preferably fumed silica particles. The silica based particles may have BET specific surface area in the range of 75–300 m²/g, carbon content in the range 0.5–4.5 weight-％and/or tamped density in the range 35–65 g/l. These properties assist the optimal defoaming and drainage results which are achieved in pulp, paper and board manufacture.

The emulsion according to the invention comprises at least 1 weight-％of at least one surfactant. According to one embodiment the emulsion comprises 1–40weight-％, preferably 2–30 weight-％, more preferably 5–15 weight-％, of at least one surfactant. The surfactant improves the dispersion of the polymer droplets in the continuous water phase and the storage stability of the obtained emulsion.

The emulsion may comprise one surfactant or a plurality of different surfactants. The surfactant (s) maybe selected from a group consisting of polyethylene glycol, polypropylene glycol, polypropylene triol, butoxy polypropylene polyethylene glycol, alkoxylated dimethylpolysiloxane, alkyl modified siloxanes, fluorine modified siloxanes, mercapto modified siloxanes, hydroxy modified siloxanes, siloxane wax, ethylene oxide/propylene oxide block copolymer, the esters of polyethylene glycol, the esters of polypropylene glycol, the esters of polypropylene triol, the esters of butoxy polypropylene polyethylene glycol, ethylene oxide/propylene oxide block copolymer, alkylpolyoxyethylene ethers, alkylpolyoxyethylenes, polyoxypropylene ethers, fatty acid polyoxyethylene esters, fatty acid polyoxyethylenesorbitan esters, fatty acid polyoxypropylene sorbitol esters, polyoxyethylene castor oils, alkylpolyoxyethylene amines and amides, fatty acid sorbitan esters, fatty acid polyglycerin esters, and fatty acid sucrose esters, preferably from sorbitan or sorbitol esters. According to one preferable embodiment the surfactant (s) are selected from a group consisting ofsorbitantrioleate, sorbitol ethoxylate esters, fatty acid ethoxylates and any of their mixtures. These surfactants show good compatibility with the environment of pulp, paper and board manufacturing processes and other chemicals and additives used therein.

The emulsion comprises at least 40 weight-％of water. Water forms the continuous phase of the emulsion into which the polymer droplets are dispersed evenly through the whole emulsion volume. This means that the emulsion is free from layers, which contain different concentrations of the polymer droplets. Typically the emulsion comprises 40–90weight-％, preferably 45–85 weight-％, more preferably 50–80 weight-％, of water, which form the continuous phase of the emulsion. The relatively high amount of water is advantageous, as it enables the use of the emulsion in pulp, paper and board manufacture, which are water based processes.

According to one embodiment of the invention the emulsion may comprise one or more biocidal agent for improving the storage properties of the emulsion and inhibiting undesired growthof microorganisms. The biocidal agent (s) may be selected from non-oxidizing biocides including glutaraldehyde, 2, 2-dibromo-3-nitrilopropionamide (DBNPA) , 2-bromo-2-nitropropane-1, 3-diol (Bronopol) , carbamates, 5-chloro-2-methyl-4-isothiazoIin-3-one (CMIT) , 2-methyl-4-isothiazoIin-3-one (MIT) , 1, 2-dibromo-2, 4-dicyano butane, bis (trichloromethyl)-sulfone, 2-bromo-2-nitrostyrene, 4, 5-dichloro-1, 2-dithiol-3-one, 2-n-octyl-4-isothiazolin-3-one, 1, 2-benzisothiazolin-3-one, ortho-phthaldehyde, quaternary ammonium compounds (＝ "quats" ) , such as n-alkyl dimethyl benzyl ammonium chloride, didecyl dimethyl ammonium chloride (DDAC) or alkenyl dimethylethyl ammonium chloride, other guanidines than dodecylguanidine salts, biguanidines, pyrithiones, 3-iodopropynyl-N-butylcarbamate, phosphonium salts, such as tetrakishydroxymethylphosphoniumsulfate (THPS) , dazomet, 2-(thiocyanomethylthio) benzothiazole, methylene bisthiocyanate (MBT) , and any combinations thereof. Preferably non-oxidizing biocidal agents are selected from glutaraldehyde, 2, 2-dibromo-3-nitrilopropionamide (DBNPA) , 2-bromo-2-nitropropane-1, 3-diol (Bronopol) , carbamates, 5-chloro-2-methyl-4-isothiazoIin-3-one (CMIT) , 2-methyl-4-isothiazoIin-3-one (MIT) , and any combinations thereof. The emulsion may comprise biocidal agent in amount of 0.01–1weight-％, preferably 0.02–0.5 weight-％, more preferably 0.05–0.2 weight-％.

It is possible that the emulsion further comprises organic carrier (s) and/or organic diluent (s) . Typically the amount of organic carrier and/or organic diluent is relatively small. The amount of organic carrier may be in the range of 2-15 weight-％, preferably 4–10 weight-％, and the amount of organic diluent may be in the range of 0.01–1.6 weight-％. The organic carrier may be selected from polybutenes, dialkyl phthalates, fatty acid esters, polyethylene and polypropylene glycol and their esters, as well as any mixtures of these. The organic diluent may be selected from diisodecyl phthalate, diisooctyladipate, diisooctyl phthalate, bis-2- ethylhexyl adipate, dioctyladipate, 2-ethyl-1-hexanol, isooctyl alcohol, dihexyl phthalate and their mixtures.

The dosage of the emulsion according to the invention in a paper or board making process may be 20–1000 g/ton, preferably 40–500 g/ton, more preferably 50–200 g/ton. The amounts are given per ton produced paper or board. The emulsion may be dosed in a papermaking process in the thick stock tank, before the screens or before the headbox. In a pulp making process the emulsion may be dosed before the pulp washers. In general, the emulsion may be dosed in one dosing location or at several dosing locations.

The emulsion can be prepared, for example, by first mixing the hydrophobic (meth) acrylate polymer and the hydrophobic microparticles to form a homogenous mixture. The obtained polymer-microparticle mixture can be then mixed with the continuous water phase, which contains the surfactant. The mixing is continued an appropriate time after which the mixture may be filtrated and the emulsion is obtained.

EXAMPLES

Some embodiments of the invention are described in the following non-limiting examples.

Experimental

Example 1

Preparation of an aqueous emulsion of a polymer

194g of hydrophobic acrylate polymer is loaded in a beaker and mixing is started, mixing speed 1000 rpm. 6g of hydrophobic fumed silica (AEROSIL R 974) is loaded slowly under mixing. The mixing is continued at 2000 rpm for 1 h. Obtained mixture is homogenized with high-shear lab mixer (Silverson L5M-A) , 9K rpm, 3 min.

169g deionized water is loaded in a beaker and mixing is started at speed 2000 rpm. 25g of surfactant (Atlas G 1096) is loaded while mixing. The mixing is continuedfor 10 min at 2000 rpm. 83.3g of mixture comprising hydrophobic acrylate polymer and silica (prepared as described above) is added under mixing, which is continued for 20 min at 2000 rpm. Then the obtained pre-emulsion is homogenizedwith high-shear lab mixer (Silverson L5M-A) , 10K rpm, 45s. The obtained emulsion is filtrated by using 120 meshfilter. 0.23g of biocide (Fennocide IT21, KemiraOyj) is added under mixing, which is continued for 5min, at 800 rpm.

Test results for the polymer emulsion of Example 1

Turbiscan Stability Index TSI for the emulsion was 1.2 for 4 weeks.

Particle size distribution (bimodal) for the emulsion is shown in Figure 1, where X-axis gives the size classes in μm, and Y-axis gives the volume density in ％. The particle size was measured by using laser particle size analyzer (Malvern 3000) . The D50 value for the emulsion was 3.2 μm, D90 value was 15.8 μm and mode 8.45μm.

Example 2

Preparation of an aqueous emulsion of a polymer

388 g of hydrophobic acrylate polymer is loaded in a beaker and mixing is started, mixing speed 1000 rpm. 12 g of hydrophobic fumed silica (AEROSIL R 974) is loaded slowly under mixing. The mixing is continued at 2000 rpm for 1 h. Obtained mixture is homogenized with high-shear lab mixer (Silverson L5M-A) , 9K rpm, 3 min.

609g deionized water is loaded in a beaker and mixing is started at speed 2000 rpm. 90 g of surfactant (Tween 85) is loaded while mixing. The mixing is continuedfor 10 min at 3000 rpm. 300 g of mixture comprising hydrophobic acrylate polymer and silica (prepared as described above) is added under mixing, which is continued for 30 min at 3000 rpm. Then the obtained pre-emulsion is homogenizedwith high-shear lab mixer (Silverson L5M-A) , 10K rpm, 45s. The obtained emulsion is filtrated by using 120 meshfilter.

Test results for the polymer emulsion of Example 2

Turbiscan Stability Index TSI for the emulsion was 3.0 for 4 weeks.

Particle size distribution (bimodal) for the emulsion is shown in Figure 2, where X-axis gives the size classes in μm, and Y-axis gives the volume density in ％. The particle size was measured by using laser particle size analyzer (Malvern 3000) . The D50 value for the emulsion was 5.62 μm, D90 value was 29.8.8 μm and mode 8.49μm.

Example 3

Polymer Emulsion to be tested

The aqueous emulsion of hydrophobic polymer is prepared as in Example 1. The viscosity of the obtained emulsion was 195 cP, measured with Brookfield , spindle #63, 100 rpm, at 25 ℃, and the Turbiscan Stability Index TSI was 1.9 for 4 weeks.

Particle size distribution for the emulsion is shown in Figure 3, where X-axis gives the size classes in μm, and Y-axis gives the volume density in ％. . The particle size was measured by using laser particle size analyzer (Malvern 3000) . The D50 value for the emulsion was 3.47 μm, D90 value was 12.8 μm and mode 5.12μm.

Drainage Performance

Drainage performance of the prepared aqueous polymer emulsion was tested against an existing commercial water-based defoamer. Added individual amounts of emulsion and commercial defoamer were 15 μl. As reference were used samples without deoamer addition, taken at the beginning and end of the drainage experiment. The drainage experiments were carried out by using well known Dynamic Drainage Analyzer (DDA) .

The results of Figure 4 and 5 show that the new polymer emulsion according to invention provides quicker drop than the commercial defoamer, andthe drainage time of is shorter. Therefore the polymer emulsion according to the invention gives better drainage than the commercial defoamer, which is known for its good performance.

Samples in Figures 4 and 5 use following abbreviations:

1, 4 ＝ reference samples, so-called 0-sample, no defoamer added

2 ＝ commercial defoamer

3 ＝ polymer emulsion to be tested

FEAT DefoamingPerformance

Defoaming performance of of prepared aqueous polymer emulsion was tested against an existing commercial defoamer. The test was conducted by using a FEAT system with synthesized white water. Synthesized white water was prepared by mixing 20 lof deionized water, 100g of sugar, 4g of calcium sulphate and 1 ml of dispersant (FennoDispo 5700, KemiraOyj) . The test temperature was 45℃ and defoamer dosage was 100 μlof defoamer in 900 mlof synthesized white water. The defoamerwas injected once the density of defoaming liquor decreased to about 900 g/l.

The Foam and Entrained Air Tester (FEAT) is a testing apparatus used to determine the efficacy of defoaming agents in a laboratory setting. The apparatus measures the change in the density as a function of time of the filtrate as the defoaming agent is introduced. The measure of the change in density of a filtrate is a direct measurement of the change in entrained air. The experimental set up contains a water bath, temperature control, a foam column, a pump, a density meter, a computer, and acquisition software. Testing of the samples utilizes a recirculatory foam cell attached to a pump. The hose leading from the pump is connected to a density meter, which is connected back to the top of the foam cell.

The results of defoaming performance test are shown in Figure 6. The new polymer emulsion A (same as sample 3 in Figs. 4 and 5) according to invention showed better defoaming performance and better persistence than the conventional water based defoamer B (same as sample 2 in Figs. 4 and 5) .

Even if the invention was described with reference to what at present seems to be the most practical and preferred embodiments, it is appreciated that the invention shall not be limited to the embodiments described above, but the invention is intended to cover also different modifications and equivalent technical solutions within the scope of the enclosed claims.

Claims

An aqueous emulsion of discrete droplets of polymer dispersed in a continuous water phase, the emulsion comprising

- at least 3 weight-％of at least one hydrophobic (meth) acrylate polymer,

- at least 0.01 weight-％of hydrophobic microparticles, preferably silica based particles,

- at least 1 weight-％of at least one surfactant, and

- at least 40 weight-％of water, which forms the continuous phase of the emulsion.
Emulsion according to claim 1, characterised in that the emulsion comprises 3 –60weight-％, preferably 10 –50 weight-％, more preferably 12 –40 weight-％, of at least one (meth) acrylate polymer.
Emulsion according to claim 1 or 2, characterised in that the at least one (meth) acrylate polymer is obtained by polymerisation ofalkyl (meth) acrylate monomers and/orhydroxyalkyl (meth) acrylate monomers and optionally acrylic acid monomers.
Emulsion according to claim 1, 2 or 3, characterised in that the emulsion comprises 0.01 –12weight-％, preferably 0.1 –8 weight-％, more preferably 0.2 –3 weight-％, of hydrophobic microparticles, preferably silica based particles.
Emulsion according to any of preceding claims1 –4, characterised in thatthe hydrophobic microparticles are silica based particles, preferably fumed silica particles or precipitated silica particles.
Emulsion according to claim 5, characterised in thatthe hydrophobic microparticles are silica based particles, which have BET specific surface area in the range of 75 –300 m2/g, carbon content in the range 0.5 –4.5 weight-％and/or tamped density in the range 35 –65 g/l.
Emulsion according to any of preceding claims 1 –6, characterised in that the emulsion comprises 1 –40weight-％, preferably 2 –30 weight-％, more preferably 5 –15 weight-％, of at least one surfactant.
Emulsion according to any of preceding claims 1 –7, characterised in that the at least one surfactant is selected from a group consisting of polyethylene glycol, polypropylene glycol, polypropylene triol, butoxy polypropylene polyethylene glycol, alkoxylated dimethylpolysiloxane, alkyl modified siloxanes, fluorine modified siloxanes, mercapto modified siloxanes, hydroxy modified siloxanes, siloxane wax, ethylene oxide/propylene oxide block copolymer, the esters of polyethylene glycol, the esters of polypropylene glycol, the esters of polypropylene triol, the esters of butoxy polypropylene polyethylene glycol, ethylene oxide/propylene oxide block copolymer, alkylpolyoxyethylene ethers, alkylpolyoxyethylenes, polyoxypropylene ethers, fatty acid polyoxyethylene esters, fatty acid polyoxyethylenesorbitan esters, fatty acid polyoxypropylene sorbitol esters, polyoxyethylene castor oils, alkylpolyoxyethylene amines and amides, fatty acid sorbitan esters, fatty acid polyglycerin esters, and fatty acid sucrose esters, preferably from sorbitan or sorbitol esters.
Emulsion according to claim 8, characterised in that the at least one surfactant is selected from a group consisting ofsorbitantrioleate, sorbitol ethoxylate esters, fatty acid ethoxylates and any of their mixtures.
Emulsion according to any of preceding claims 1 –9, characterised in that the emulsion comprises 40 –90weight-％, preferably 45 –85 weight-％, more preferably 50 –80 weight-％, of water, forming the continuous phase of the emulsion.
Emulsion according to any of preceding claims 1 –10, characterised in that the emulsion comprises 0.01 –1weight-％, preferably 0.02 –0.5 weight-％, more preferably 0.05 –0.2 weight-％, of at least one biocide.
Emulsion according to any of preceding claims 1 –11, characterised in that the emulsion further comprises carriers and/or diluents.
Emulsion according to any of preceding claims 1 –12, characterised in that the droplets of polymer dispersed in a continuous water phase has a D50 size <10 μm and/or D90 size < 30 μm and/or mode <10 μm.
Emulsion according to any of preceding claims 1 –13, characterised in that the emulsion has a viscosity in the range of 50 –2000 cP, preferably 100 –1000 cP, 150 –600 cP, measured with Brookfield, spindle #63, 100 rpm, at 25 ℃.
Polymer emulsion according to any of preceding claims 1 –12, characterised in that the emulsion has a TSI value < 5 in 4 weeks and < 10 in 3 months.
Use of an aqueous emulsion according to claims 1 –15 as a defoameragent or drainage agent in making of pulp, paper, board or the like.
Use according to claim 16, characterised in that the emulsion dosage is 20 –1000 g/ton, preferably 40 –500 g/ton, more preferably 50 –200 g/ton.