GB2350117A - Polysiloxanes for deaeration of liquids - Google Patents

Abstract

A method for deaeration of a liquid comprises adding to said liquid a polysiloxane having an Si-C bonded substituent with at least one ether or alcohol oxygen having the general formula:<BR> ```QR<SP>1</SP><SB>2</SB>SiO (R<SP>1</SP>GSiO)<SB>j</SB> (R<SP>1</SP> <SB>2</SB>SiO)<SB>k</SB>SiR<SP>1</SP><SB>2</SB>Q<BR> wherein R<SP>1</SP> is a monovalent C<SB>1-30</SB> hydrocarbon, Q is R<SP>1</SP> or G, and G has the structure -D(OR')<SB>p</SB> Z or -D' ((OR')<SB>p</SB> Z)<SB>z-1</SB><BR> ```wherein D is a divalent C<SB>1-30</SB> hydrocarbon, D' is a tri or multi(Z)valent C<SB>1-30</SB> hydrocarbon radical, R' is alkylene, Z is a certain capping group. The polysiloxane is a polysiloxane-oxyalkylene copolymer or polysiloxane-polyoxyalkylene copolymer.

Description

2350117 A Method for Deaeration of Liquids This invention relates to a

method for removing air (deaeration) from liquids, e.g. solutions and slurries, for example in textile dyeing, fuel (diesel) usage and pulping processes. In particular the present invention relates to the process deaeration in the paper pulping process, the textile dyeing process, the paper coating process, paper deinking process, latex production process, waste water treatment process and diesel fuel transport process.

In many situations and processes, air may be entrapped in water or other liquids, for example, during mining processes, paper and pulp manufacturing stages, polymer synthesis processes, textile dyeing, detergent solutions usage, fuel transportation (including the transfer of fuel from one container to another).

Aeration happens normally where some agitation of a liquid takes place in the presence of air. As a result of this aeration, some of the air will be entrapped and remain entrapped in the liquid. The air which is present at the agitation action may be present in solution, but preferably is present as a gaseous phase.

Air may be entrapped in a liquid in several ways, and this entrapment cannot always be avoided. It is important to control the amount of air which is entrapped and more importantly the amount of air which remains entrapped. Air entrapment as a result of aeration is usually aided and increased by the presence of quantities of materials such as surfactants, fatty soaps, cellulose derivatives, fines e.g.

small fibers, small solid particles, inks, impurities or process chemicals in the liquid. This may result in the formation of foam of the liquid when it is agitated, or when it is decompressed. This foaming is not beneficial to processing steps or efficiency of the processes such as transferring of liquids by pouring, jetting, pumping etc., application of the liquid on substrates for purposes of dyeing or settling solids from slurries, resulting in uneven finishes, air bubbles, increased volume needed for storage and the like. There is thus a need to find ways of removing air from such liquids.

For example in the making of coated paper e.g. light weigh coated (or magazine) paper an appropriate deaerator is required in the 'paper coating' mixture. This is because entrapped air in a paper coating significantly increases the viscosity of a wet coating system and also causes surface imperfections in the coated paper when the bubbles rupture as the paper dries. Entrained air in the form of isolated bubbles dispersed throughout the fluid, as well as concentration of bubbles at the surface are troublesome.

Entrained air in the body of the coating is more difficult to detect or to isolate and remove than that which has accumulated on the surface as a conventional foam. Complex paper coatings, contain a wide variety of functional products. Pigments, impurities in natural adhesives, emulsifiers and dispersants in synthetic latices provide the surface active materials that induce severe deaeration problems in the paper coating application.

For the- making of surface sized paper fine paper e.g. multi purpose office paper an appropriate deaerator is required in the surface size mixture, as similarly to the paper coating application described above, entrapped air causes surface imperfections in the final paper when the bubbles rupture as the paper dries. Surface size mixtures, contain a variety of functional products: e. g. starch, optical brightener, surface size polymer (latex or solution polymer). Impurities in synthetic latices, combined with the water soluble polymers and the starch induce severe deaeration problem in the surface size application.

Several methods of restricting air entrapment in liquids have been proposed in the art. For instance, it has been proposed to use mechanical means to restrict the amount of air present at agitation stages or to allow air to escape after it has been entrapped. Similarly, it has been proposed to use chemical foam control agents such as C,-C,, alcohols, polyalkylene glycols, fatty acids, fatty acid esters, amides, and organic phosphates to decrease the formation of foam when such liquids are agitated. These approaches, however, are still in need of improvements.

The present invention is not merely addressing the problem of avoiding the formation of foam. The main approach is to actually remove air from liquid solutions or slurries. A clear result of this would be the reduction of foam formation when agitation takes place, but there are other benefits to the removal of air, such as increased stability of products, especially if they are susceptible to oxidation and improved purity of products, as no air-borne impurities would be present.

Many foam control agents are known, including polysiloxane based foam control agents which are generally known for use in aqueous systems. The use of these materials may be limited, however, because many of them may cause spotting in processes where deposition on substrates or colouring is required. Moreover, polysiloxanes may interfere with the physical properties of some substrates and they may interfere with subsequent processes applied to substrates, e. g. printing and coating. As many of these foam control agents comprise solid fillers, they are not often suitable for use in processes where reasonable purity is required, or where solid particles are to be avoided, e.g. in fuels such as diesel.

For example US 3,528,929 describes a foam control composition which comprises finely divided silica dispersed into a mixture of mineral oil, a hydrophobic agent and an alkoxysilicon chloride. This composition is taught to assist in de-aeration and drainage during paper making.

We have surprisingly found that certain siloxane based materials are especially useful as deaeration agents for liquid solutions and slurries.

The present invention provides in one of its aspects a process of deaeration of liquid materials, characterised in that the method comprises adding to said liquid a polysiloxane having an Si-C bonded substituent with at least one ether or alcohol oxygen or a Si-OC bonded polyoxyalkylene group.

The polysiloxanes useful in the process of the present invention comprise a polysiloxane backbone, which may be cyclic or linear polysiloxane and at least one Si-C bonded substituent with at least one ether or alcohol oxygen or a Si-OC bonded polyoxyalkylene group. Ether oxygens link two carbon atoms together, while alcohol oxygens, where used herein, link a hydrogen atom and a carbon atom, thus forming a C-OH alcohol group.

It is generally preferred to use a polysiloxane having either of the following formulae: 5 QR12S'O(R1GSiO) j (R12S'O) kSiRl2Q (1) F (R' G Si % - (R12 S'O)k -1 In this structure, R' is a monovalent hydrocarbon group having 1 to 30 carbon atoms. Preferably R' is a non- halogenated hydrocarbon group. Examples of groups suitable as R' include alkyl radicals such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, octyl and decyl; alkenyl groups, e.g. vinyl, allyl and hexenyl; cycloaliphatic groups such as cyclohexyl; aryl groups such as phenyl, tolyl and xylyl; arylalkyl groups such as benzyl and phenylethyl. Preferred R' groups include methyl and phenyl. Most preferably substantially all R' groups are methyl radicals.

In the above formula (1), Q is R' or G. G has the average structure:

-Dq (OR')pZ (2) or -D' q ( (OR') p Z) -, (3) In formula (2) D is a divalent hydrocarbon radical having from 1 to 30 carbons atoms. Examples of suitable groups D include alkylene radicals including methylene, ethylene, propylene, iso-propylene, butylene, iso-butylene, phenylene, trimethylene, 2-methyltrimethylene, pentamethylene, hexamethylene, 3 -ethyl -hexamethylene, octamethylene and - (CH,),,-, cycloalkylene -containing radicals such as cyclohexylene, alkenylene radicals, e.g. propenylene, vinylene, hexenylene, arylene radicals such as phenylene, combinations of divalent hydrocarbon radicals such as benzylene (-CACH,-). Preferably D is a divalent hydrocarbon radical having from 2 to 20 carbon atoms. Most preferably D is a trimethylene group.

In formula (3), D' is a trivalent or multivalent hydrocarbon group having 1 to 30 carbon atoms, R' and Z are as defined for formula (2) and z denotes the valency of the hydrocarbon group W. Examples of suitable groups D' include -C-CH=, -C=C=, -CC=- Groups G of structure (2) are however, preferred.

R' in the above formulae (2) and (3) is an alkylene is radical having up to 10 carbon atoms, preferably from 2 to 10 carbon atoms. R' is exemplified by methylene, ethylene, propylene, isopropylene, butylene, iso-butylene, hexylene, octylene or a decylene radical. Most preferably R' contains from 2 to 4 carbon atoms. It is noted that if multiple (OR') groups are present in the molecule the groups can be a combination of alkylene oxide radicals such as, for example, a combination of ethylene oxide and propylene oxide units, which may be present at random or in blocks.

p in the above formulae (2) and (3) has a value f rom 0 to 50 inclusive, provide that if p is zero, the capping group Z in formula (2) contains the requisite ether or alcohol oxygen.

q has a value of 0 or 1, but will only be 0 if it links a polyoxyalkylene group. Preferably q has a value of 1.

Z is a capping group selected from the group consisting 2 2 3 of -OR, R 3 and - OC (0) R3. R is hydrogen or a group R, which is a monovalent hydrocarbon group having 1 to 18, preferably 1 to 6 carbon atoms such as methyl, ethyl, propyl, butyl or phenyl, optionally substituted with one or more hydroxyl groups and/or alkoxy groups having up to 6 carbon atoms. Examples of suitable groups Z include -OH; -O(CH2) OH; 0 (CH2 (CA,) CHPI-I; -OCI-I3; -CH3; -CH (OH)- CH2OH; -C(CH20H) 2 - CH2CH,; -C,>H,,m-OCH3.p-OH; and CH(OW-CH2) 4-CH3; where r denotes an integer.

In the above formula (1), j has a value from 0 to 150 inclusive, provided that if j is 0, at least one of the groups Q is G. Preferably j is from 1 to 30.

In the above formula, k has a value of from 0 to 1,500 or more. Preferably k is from 1 to 200.

Examples of suitable groups G, which must include at least one ether or alcohol oxygen atom, include oxyalkylene containing substituents, monoand multiple alcoholfunctional substituents and phenol -containing substituents.

sugars and lactones.

Examples of suitable G groups where q is 0, include polyoxyalkylene groups, preferably having oxyethylene and/or oxypropylene units and a hydroxyl, methyl or acyl end capping group.

In a first preferred method according to the invention, the polysiloxane having an Si-C bonded substituent with at least one ether or alcohol oxygen is a polysiloxane oxyalkylene copolymer or polysiloxane polyoxyalkylene copolymer. Many of these materials are known and commercially available. They are characterised by the presence of alkylene oxide units in the G radical, resulting for the most preferred materials in the following structure f or G:

-D(OCH2-CH,)m(OCH, - CH), Z (4) 1 CH3 in which D and Z are as defined above. Preferably, Z is an -OH or an -OC(O)R 3 group. The most preferred Z is -OC(O)CH3 The symbol m which defines the number of - (OCH2-CH, units can have a value as low as 0 and can range up to 50 or more. Preferably in will have an average value of from 0 to 20. The symbol n which defines the number of - (OCH2 - CH (CH,)) units can have a value as low as 0 and can range up to 50 or more. Preferably n will have an average value of 0 to 20. Where oxyalkylene groups are present in G according to formula (4), m + n must have a value of at least 2.

Particularly preferred groups G have the average structure:

- CH2CH2-CH2-(OCH2 - CH) 12 (OCH2CH2)12 OH or CH3 -CH2-CH2-CH2-(0 CH2-CH2)12 OCOCH3 In another preferred method according to the invention, the polysiloxane having an Si-C bonded substituent with at least one ether or alcohol oxygen is a polysiloxane oxyalcohol polymer or polysiloxane polyoxyalcohol copolymer. These materials are characterised by the presence of an oxyalcohol group on the polysiloxane and G has the structure 5 (2) or (3), wherein D and D' are as defined above, p is 1, R' is -CH2 and Z is a substituent having one or more hydroxyl groups linked to carbon atoms. Z may have the f ormula - (CH OH) q (C (CH20H) 2) t (CH2) v - R4 (5) wherein q, t and v independently have a value from 0 to 10 inclusive and R 4 is a hydrogen, hydroxyl or a hydrocarbon radical having from 1 to 6 carbon atoms. It is preferred that either q or t has a value of 0, and that when q and t are 0, R 4 is a carbon-bonded hydroxyl group. The groups (CH OH), (C (CH20H) 2) and (CH2) may be present in any order. it is however clear to the person skilled in the art that other substituents are also possible. 20 The preferred structure of G, when it represents an oxyalcohol group is - CH2 - CH2 - CH2 0 CH2 CH - CH2 OH 1 OH Some oxyalcohol containing materials are known in the art and are described, for example, in US pat No 5262155.

The group G of f ormula (1) may also be a alcohol group, which has the same structure as the oxyalcohol, with the exception of the ether oxygen group. Aromatic alcohols and substituted alcohols may also be used. Examples of the latter include eugenol substituted siloxanes, sugars.

Polysiloxanes which are useful in a method according to the present invention may be made by known processes. A suitable process for making the polysiloxanes is a hydrosilylation reaction between a polysiloxane material having some silicon-bonded hydrogen atoms and alkenyl endblocked alcohols, oxyalcohols, polyoxyalkylenes and other compounds having an ether or alcohol oxygen present as defined above.

The polysiloxanes having an Si-C bonded substituent with at least one ether or alcohol oxygen as described above can be diluted in a suitable solvent, if desired, or may be supplied in the form of a blend or an emulsion. Suitable solvents include e.g. 1,2 propanediol, 2 -butoxyethanol and butylglycol. Suitable surfactants for making emulsions of the relevant silicone materials have a hydrophilic/lipophilic balance (HLB) of from 10 to 15.

Generally, it is preferred that they are used undiluted for most applications. In the most preferred method for paper related processes, e. g. the paper coating the polysiloxanes are used in emulsion form or in solvent. In most applications it is particularly preferred that the polysiloxanes are used in the absence of any inorganic fillers, such as silica, as fillers of that kind are likely to interfere with the efficiency of certain processes, e.g. by being deposited on cellulosic fibres of paper or on textile fibres, thus causing deficiencies in the paper or textile goods which are produced. It is however possible,.

and in some cases preferred to use polysiloxanes having Si-C bonded substituents with an ether or alcohol oxygen, in a method according to the invention in conjunction with one or more known foam control agents, e - 9 - C7-22 alcohols, polyalkylene glycols, fatty acids, fatty acid esters, amides and organic phosphates, polysiloxane based foam control agents, even if they contain inorganic fillers such as silica. The polysiloxanes, whether used alone or in conjunction with other foam control agents may also be provided in emulsion form. It is even possible, though not preferred, to provide emulsions which comprise the polysiloxanes and other foam control agents.

In a method according to the invention, the polysiloxane having an Si-C bonded substituent with at least one ether or alcohol oxygen is added to the liquid, e.g. pulp liquor, dyeing solution, paper coating, synthesis of coating binder, production of internal sizing, diesel fuel, deinking bath. The addition may take place immediately prior to use of the liquid, or may be pre-added e.g. with one or more of the ingredients which are used in the liquid. In the case of diesel transportation, it is preferred to do the addition as soon as possible after the separation of the fuel from the cracking process. In the case of a deinking bath, pulp liquor, or textile dyeing bath, it would be more appropriate to do the addition at regular intervals during the process, especially if a continuous process is envisaged.

The polysiloxanes having an Si-C bonded substituent with at least one ether or alcohol oxygen can be added by any convenient means and at a concentration sufficient to effect deaeration. Generally, a sufficient concentration is in the range of from about 0.001 wt O-o to about 1wt. 9s, preferably from about 0.01 to about 0.1 wt. 2,; based on the weight of the liquid.

The process according to the invention is applicable to a large number of applications, including in particular the use in paper pulping process, paper making process, paper coating process, textile dyeing process, fuel transportation, diesel dewatering process, radiator coolant filling process and polymerisation process. Most preferably the process is used with aqueous systems for solutions and slurries, especially in the pulp and paper industry.

Where the process relates to pulp manufacture, it is preferred that the silicones of formula (i) are used in conjunction with known foam control agents, of the organic type or of a silicone based type, even if including fillers. Such foam control agents are well known, and have been described in the art.

Where the process is related to textile dyeing processes, it is preferred that the material according to formula (i) is used in emulsion or solution form.

Where the process is related to the paper making process, only materials of formula (i) above, preferably in formulations, are to be considered which have G groups of formula (2), therein p is a positive integer of at least 2, and Z is selected from hydroxyl groups and acyloxy groups.

Where the process relates to the paper coating process, it is preferred that the materials used in the process have been fully deaerated prior to use in the process. This is to ensure good coverage-with a minimal amount of defaults.

Where the process relates to paper deinking process, it is preferred that the silicones of formula (i) are used in conjunction with known foam control agents, of the organic type or of a silicone based type, even if including fillers.

Such foam control agents are well known, and have been described in the art.

Where the process relates to the manufacturing process of polymers, in particular of latex, it is preferred that deaeration takes place in the purification step, e.g. the stripping of unreacted monomers, which may cause foaming. Silicone products as described in formula (1) with groups Z which have substituted hydroxyl or alkoxy group are particularly helpful in this process, as these are very effective and can be used at low concentrations. Polymers could be water-soluble, water- dispersible or water-insoluble Where the process relates to waste water treatment process it is preferred that the silicones of formula (i) are used in conjunction with known foam control agents, of the organic type or of a silicone based type, even if including fillers. Such foam control agents are well known, and have been described in the art.

Where the process relates to diesel fuel transport process, it is preferred that the siloxane materials used are of formula (i) above, where G denotes a formula (2) or (3), wherein Z is a monovalent hydrocarbon group which comprises at least two hydroxyl group substituents.

In order that the invention may be more fully understood, there now follows a number non-limiting examples which illustrate the invention. All parts and percentages are given by weight and all viscosities are measured at 251C unless otherwise indicated.

ExamT)le 1 Styrene butadiene latex (SBL) is a polymer which is widely used for paper and other coating applications. SEL is polymerized in general in emulsion form, containing the monomers (styrene and butadiene), water, emulsifier and a catalyst system. Because of the nature of this system it tends to generate and stabilize foam while normal agitation is applied during the chemical reaction. After the polymerization, the unreacted monomers have to be removed from the latex emulsion, which is done by water steam distillation which generates a huge amount of foam because of the injected steam and the stabilisation of the foam by rest monomers. This process step requires an efficient antifoam in order to use the full capacity of the reactor and to keep the stripping period as short as possible.. A foam control agent must however not cause surface defects in the downstream application of the final latex.

The deaeration and antifoam performance was evaluated with a sparge test using a fish tank aerator stone as injection medium for the air. 100ml of SBR latex emulsion were set in a calibrated 500ml cylinder and put in a thermostatic bath at 750C. When the SER latex was at 750C, the fish tank aerator with an adjusted volume of 4 1 air/min was put into the latex. The foam height (total volume in the calibrated cylinder) was recorded after 30 s, 60s, 120s, 180s, 300s and 600 s. The used SBR latex emulsion was supplied by Synthomer Limited with the trade name SYNTHOMERO 72H10. The polymer in this emulsion is a carboxylated styrene butadiene acrylonitrile polymer with an active content of 500-. in water. This latex type is used for paper coating applications. Foam control agents and deaerators were added to the latex at concentrations indicated in Table 2, and the test repeated as indicated above.

Surface defects were tested by taking 100ml latex from the antifoam performance test and mix them with 40OAl of a l'-. aqueous solution of Aniline Blue, water-soluble 256 + NaCl. When the latex had been cooled down to room temperature, about 3 ml of the latex were coated on copy paper (standard Xerox copy paper) and on polyetheylene (PE) (LDPE with a surface tension of 28 dyne/cm). on the dry film the number of fish eyes were determined by counting.

If no closed film could be obtained it was only classified with many or very many defects.

Deaerators were prepared as follows: Di is a polysiloxane oxyalcohol polymers with structure (6), where the parameters j and k are as set forth in Table 1.

Comparative materials were prepared, (CHO 3S'O (CH3GSiO) j ( (CHO 2S'O) k Si (CHO 3 (6) wherein G (CHO 30CH2 CHCH20H 1 OH Table 1:

Polysiloxane D1 Oxyalcohol k D1A 20 180 D1B 15 85 D1C 6 54 D1D 10 40 DlE 15 35 D1F 4 16 D1G 8 12 A comparative deaerator (CD1) was tested, which was a standard polydimethyl siloxane foam control agent with hydrophobic silica in a 10-. oil-in-water emulsion.

Deaerators from D1A to D1G were also formulated into oil-inwater emulsions at 10% with a similar formulation to CD1 (referred to as DlAe etc.). Another delivery system for D1A to D1G was prepared by mixing with a solvent to form a 100-. solution. Solvents were selected from butoxyethanol (DlAb) and VammerO 10 (DiAv), which is a didecylether. Table 2 shows the concentration of deaerator used (in ppm based on the weight of the total mixture), foamheight obtained after 1 and after 10 minutes aeration (in ml), knock down time, which is a measure of destruction efficiency of the foam build up.

Table 2

Deaerator conc (ppm) foamheight knock down CD1 100 390/460 SLOW CD1 300 290/350 MEDIUM D1A 100 400/240 MEDIUM D1B 100 290/235 MEDIUM D1C 100 350/155 D1D 100 330/210 MEDIUM D1E 100 210/120 FAST D1F 100 220/130 MEDIUM D1G 100 360/125 MEDIUM DlEe 300 335/300 D1Fe 300 320/260 D1Ab 300 235/225 DlEb 300 160/230 D1Fb 300 165/195 D1Av 300 180/260 D1Ev 300 160/135 D1Fv 300 180/260 When coated on paper, some fish eye effects were seen in some cases. When coated onto polyethylene, the comparative example was not able to form a film, whereas the illustrative examples showed a film, which in some cases had some fish eye effect.

Example 2 The deaeration of the paper furnish is crucial to the paper making process. Paper slurries can contain up to 3% air.

High air contents will interfere with the process and the paper quality. Due to the higher machine speeds and the closure of the water loops, the temperatures of the systems are constantly increasing. Traditional defoamers based on fatty alcohol emulsions are loosing performance at high 5 temperatures.

Siloxanes have been tested in two different versions of a pump test. Both methods involved the preparation of a 2% consistency paper slurry, adding a foaming rosin soap, circulating the slurry in a cylinder to incorporate air, adding antifoam, measuring the decrease of the total volume after 1 minute and repeating this procedure up to 5 minutes, or in the case of silicone polyoxyalkylenes, every 15 seconds f or up to 3 minutes. In the f irst method a mixture of newspaper and magazine recycling paper was used and the cylinder was not heated. The second method uses a paper slurry prepared with newspaper only, a double jacket heatable cylinder and a reduced rosin soap dosage to reduce surface foam.

The following products were evaluated: siloxane polymers for use in a process according to the invention prepared by hydrosilylation of SiH containing polysiloxanes of various degrees of polymerisation (DP) and mole percent (MPC) Si-H groups (respectively for polymer D2A, D2B, D2C, D2D and D2E, DP was 26, 46, 19, 20 and 20, and MPC was 7.1, 16.9, 44, 40 and 60) with 3-allyloxy-1,2-propanediol (H2C=CH-CH2-0-CH2- CH(OH)-CH2OH). Siloxane polymers prepared by hydrosilylation of SiH containing polysiloxanes of various degrees of polymerisation (DP) and mole percent (MPC) Si-I-I groups (respectively for polymer D2F, D2G, D2H and D2K.. DP was 26.7, 138, 19 and 20, and MPC was 7.1, 11.5, 44 and 60) with allylalcohol (CH,=CHCH,OH) and for polymers D2L, D2M and D2N (DP was 26.7, 138 and 19 and MPC was 7.1, 11.5 and 44) with undecenylalcohol (CH2=CH(CH2)90H) and siloxane polyoxyalkylene copolymers having the structure 5 CH, - (0 CH2 CH2) r - (OS i (CH,) 2) 70 - 0 (CH2 CH2 0) r CH3 wherein r has a value of 6 for G2 and 11 for G3.

It was found that for silicone alcohols the lower the DP and the higher the MPC the better were the results. The higher chain length of the undecanol. resulted in a better performance. Oil-in-water emulsions (30% by weight of oil) of the silicones were also prepared using a C16-2. fatty alcohol, PVA or vinyl pyrrolidone/acrylic acid as emulsifier, giving stable emulsions, dispersible in water. Especially preferred were emulsions using PVA as emulsifier, as they were liquid, very stable and perfectly dispersible in water, with no fatty touch. Emulsions turned out to be a very good delivery system. Beside that, solvents were also used as a delivery system, using for example butyldiglycol Examples G2 and G3 were used, diluted in isopropanol to 50%, and showed a very efficient knock down, but with improved persistence of foam control over time, compared to other tested materials.

On the whole it was shown that the deaeration behaviour can be significantly improved by a hydrophobic termination of silicone oxyalkylene copolymers or by increasing the mole percentage of diol functional groups whilst maintaining a low degree of polymerisation. Silicone propanediols seem to have no limitation at high temperatures (600C), which makes them superior to organic deaerators.

Example 3

A deaerator was tested in the liquid of the foam tank of a deinking plant. This was tested with emulsions of silicone based foam control agents (SiFCA) in absence or presence of a silicone as described in Example 2 above as D2D. It was found that adding small amounts (1 or 2 -. based on the weight of the emulsion of silicone based foam control agent) of D2D the knockdown performance was significantly improved, and the amount of silicone based foam control agent required was significantly reduced.

The test carried out consisted of putting 300 g of a deinking slurry in a beaker and heating this to 500C. The deinking slurry is then poured into a cylinder, and circulation (9 1/min) for 2 minutes by pumping is carried out. The level of foam is immediately read, and again after 2 minutes(t=O) After the pump has been stopped, the antifoam (12.5mg) is added drop by drop, the pump is started up again and the level of foam is read An organic material was tested as benchmark (AfranilO HTO (30%)). Results are shown in Table 3 Table 3

Deaerator foam height (in cm) 2 min 4 min 8 min 12 min Afranil HTO 9.5 5 5.5 7.5 SiFCA 9.5 6.5 7.5 8 SiFCA + 1% D2D 9 5 6 6.5 SiFCA + 2% D2D 8.5. 5.5 6 6 Example 4

Deaeration of pulp (Kraft process) was tested by filling a beaker with 1 liter of black liquor and heating it to 890C, and using a centrifugal pump to circulate the 5 liquor till 0.8 liters of foam is formed on the surface. With the pump continuing to run, 1 ml of a deaerator is added and the amount of foam left is read and the time is measured necessary for the foam level to return to 0.8 liter. It was found that the presence of a small amount of D2D from example 2 in a mixture of silicone based foam control agent and siloxane oxyalkylene copolymers produced a very effective knock down of the foam, and kept the foam down substantially longer with an increased amount of D2D.

Example 5

The addition of products described in Example 2 as D2D were tested as deaerators in diesel, by shaking 100 ml of the diesel in a glass bottle of 120 ml size for 1 minute with an agitation speed of 350 movements per minute with an arms length of 325mm. D2D was diluted in isopropanol to 0.5-.. The diesel contained 1500 ppm. of water. The samples were then stored for 4 weeks at room temperature. The time for the foam to collapse was measured, as well as the foam height generated. The foam height generated was a factor of 5 to 100 better (lower) than that using traditional oxyalkylene siloxane copolymers at the same concentration. The time required to effect full collapse of the foam was also improved by a factor of 2 to 10 on average.

The tests were repeated with siloxanes of a similar structure, except that the DP ranged from 20 to 200 and the MPC from 10 to 40. Best results were obtained with a DP or from 50 to 200, ideally around 100 and a MPC of from 10 to 20 on average.

Claims (17)

1. Claims

   A method for deaerating a liquid by adding to said liquid a polysiloxane having either an Si-C bonded substituent with at least one ether or alcohol oxygen or a SiOC bonded polyoxyalkylene and having the average general formula:

   QR12S'0 (R1GSiO) j (RI 2S'O) kSiRl,Q or [- (R' G Si % - (R12 S'O)k -1 - 1 wherein R' is a monovalent hydrocarbon group having 1 to 30 carbon atoms, Q is R' or G, and G is a radical having the average structure -Dq(ORI), Z or -D'q ((OR1)p Z)-, wherein D is a divalent hydrocarbon radical having from 1 to 30 carbons atoms, D' is a tri or multi(z)valent hydrocarbon radical having from 1 to 30 carbon atoms, R' is an alkylene radical having up to 10 carbon atoms, Z is a capping group selected from the group consisting of -OR 2, R 3 and -OC (0) R 3, wherein R 2 is hydrogen or a group R 3, and R 3 is a monovalent hydrocarbon group having 1 to 18 carbon atoms, optionally substituted with one or more hydroxyl groups and/or alkoxy groups, having up to 6 carbon atoms, p has a value f rom 0 to 50 inclusive, provided that if p is zero, q has a value of 0 or 1, provided q is only 0 if (OR')PZ or ((OR1)p Z).-, is polyoxyalkylene; Z contains the requisite ether or alcohol oxygen, j has a value from 0 to 150 inclusive, provided that if j is 0, at least one of the groups Q is G, k has a value of from 0 to 1,500 or more and z denotes the valency of hydrocarbon W.
2. 2. A method according to Claim 1, further characterised in that in the polysiloxane k is from 1 to 200, j is from 1 to 30, Q is R1, D or D' have from 2 to 20 carbon atoms and R' has from 2 to 10 carbon atoms.
3. 3. A method according to Claim 2, further characterised in that G is an oxyalkylene -containing group having the average structure:

   -D(OCH2-CH2) m (OCH2-CH), Z 1 CH3 in which m and n independently have a value from 0 to 20, provided that m + n equals at least 2.
4. 4. A method according to Claim 2 or 3, further characterised in that Z is a substituent having one or more hydroxyl groups linked to carbon atoms, having the formula - (CH OH) q (C (CH20H) 2) t (CH2) v - R 4 wherein q, t: and v independently have a value from 0 to 10 inclusive and R 4 is a hydrogen, hydroxyl or a hydrocarbon radical having from 1 to 6 carbon atoms.
5. 5. A method according to Claim 4, further characterised in that G is an oxyalcohol group of the formula CH2 - CH2 - CH2 0 CH2 CH - CH2 OH 1 OH
6. 6. A method according to any one of the preceding Claims, further characterised in that the polysiloxane having an Si-C bonded substituent with at least one ether or alcohol oxygen is diluted in a suitable solvent or provided in an emulsion form.
7. 7. A method according to any one of the preceding Claims, further characterised in that the polysiloxane is used in conjunction with one or more known foam control agents selected from C7-22 alcohols, polyalkylene glycols, fatty acids, fatty acid esters, amides and organic phosphates.
8. 8. A method according to any one of the preceding Claims, further characterised in that the polysiloxane is used in a concentration in the range of from about 0.001 wt % to about 1wtA based on the weight of the liquid.
9. 9. A method according to any one of the preceding Claims in which the liquid is an aqueous solution or slurry.
10. 10. A method according to any one of the preceding Claims used in a paper pulping process.
11. 11. A method according to any one of the preceding Claims used in a paper making process.
12. 12. A method according to any one of the preceding Claims used in a paper coating process.
13. 13. A method according to any one of the preceding Claims used in a textile dyeing process.
14. 14. A method according to any one of the preceding Claims used in fuel transportation.
15. 15. A method according to any one of the preceding Claims used in a diesel dewatering process.
16. 16. A method according to any one of the preceding Claims used in a radiator coolant filling process.
17. 17. A method according to any one of the preceding Claims used in a polymerisation process.