The invention relates to a carboxymethyl cellulose slurry and a process for the preparation thereof.

Carboxymethyl cellulose (CMC) is often used in the form of its sodium salt for modifying the rheologic properties of aqueous liquids. The applications to be considered are the clarification of water, the treatment of minerals, the thickening of foodstuffs and medication, the thickening of farm products, the use in oil drilling liquids, the use in building materials, such as concrete, the modification of ceramic materials, the modification of latex colours, the use in paper coating and the use as a protective colloid in emulsion and suspension polymerization.

CMC has conventionally been delivered in dry, particulate form. The drawbacks are hereby the formation of dust, the poor dispersing in aqueous liquids and too long dissolution times when dissolved in water.

The same problems are encountered with the treatment of CMC type powders as generally with dry particulate materials. Since CMC type powders are hygroscopic and absorb moisture from the air their particles can therefore become agglomerated. It is very difficult to disperse agglomerated particles in aqueous liquids. The dissolution of CMC powder is difficult in other respects, too, since the powder tends during the dissolution to form an agglomerate, the gel on the surface of which prevents water from penetrating into the dry powder inside the agglomerate and from dissolving it.

For the above-mentioned reasons users of CMC products can require them in a form in which it can easily be dissolved in the aqueous system of their process.

The FI-application 885969 presents the delivery of CMC products e.g. in the form of such aqueous dispersions that contain particulate CMC product, polyethylene glycol having a low molecular mass (LWPEG) , water and polyethylene glycol having a high molecular mass (HWPEG) . LWPEG was defined in the publication as a substituted or non-substituted polyethylene glycol being liquid at room temperature and having a molar mass of about 200 to 700g/mol. HWPEG was defined as a substituted or non-substituted polyethylene glycol being solid at room temperature and having a molar mass of over 3000g/mol.

According to the examples of the publication the part of the CMC(Na-salt) -product in the whole mixture counts for 20 to 23% by weight. The part of LWPEG counts for 41 to 48% by weight, the part of water counts for 29 to 33% by weight and the part of HWPEG counts for 3 to 4.5% by weight. The molar masses of the LWPEG-samples used were 200, 300, and 400g/mol. The molar mass of the HWPEG-samples used was 20,000g/mol.

The drawback of the product presented in the Fl-publication mentioned was that its maximum CMC content giving a sufficiently flowing but stable dispersion, is only about 20% by weight. Despite this the product according to the publication has a very low dispersion stability. Of the CMC dispersions prepared in the examples only two were stable after 24 hours from the time of preparation. It is clear that such a product cannot be used after storage and transport without cumbersome redispersion.

The aim of the invention is to remove these drawbacks, i.e. to provide a stable, concentrated, easily pumpable dispersion or slurry which allowes the dissolution of the CMC product more quickly into water. Such a product is easily storable, transportable, pumpable and dissolvable in aqueous mixtures without the formation of precipitations or

aggolomerates typical of the handling and treatment of dry powders.

The aims of the invention have now been achieved by a new carboxymethyl cellulose slurry or dispersion, which is mainly characterized by what has been stated in the characterizing clause of claim 1. It has thus been realized that the above-mentioned usability can be provided by adding to the carboxymethyl cellulose LW polyethylene glycol having a molar mass of below about lOOOg/mol, and an inert powder or dispersion. With this inert powder or dispersion extremely high carboxylmethyl cellulose concentrations can be achieved, which we characterize as slurry. Despite the high concentration the slurry is very stable and simultaneously easily pumpable. When mixing the slurry in water the sodium carboxymethyl cellulose content of the slurry is quickly and evenly dissolved in water without agglomeration or precipitation.

Practically all CMC qualities, derivatives and particle sizes are suitable for the slurry according to the invention. CMC is usually in the form of its sodium salt. The preparation of the slurry can be done with both technical and purified CMC qualities. Other CMC derivatives, such as carboxymethyl hydroxyethyl cellulose (CMHEC) and crosslinked carboxymethyl cellulose (RSCMC) are also suitable for the preparation of the slurry according to the invention.

According to one embodiment of the invention the part of carboxymethyl cellulose counts for about 10 to 60% and preferably about 25 to 45% of the total weight of the CMC slurry.

In the carboxymethyl ceilulose slurry according to the invention the polyethylene glycol used has an average molar mass, which is below about lOOOg/mol, preferably between about 200 to 700g/mol, most pregerably between 400 to

600g/mol, where the polyethylene glycol usually is liquid. The polyethylene glycol used is preferably of one kind with respect to its molar mass. The molar mass distribution is preferably mono odal, whereby by the monomodal polyethylene glycol is essentially meant a polyethylene glycol, of the macromolecules of which preferably at least 40% by weight is within the molar mass range M ± 20%, where M is said average molar mass. With this kind of monotype LW polyethylene glycol a synergetic effect is achieved together with said inert powder or dispersion.

Of polyethylene glycol also the names polyoxyethylene and polyethylene oxide are used and it is known as a polymer having the formula H(OCH ₂ CH ₂ ) _n OH. The abbreviation PEG is usually used of it, after which abbreviation is generally given the molar mass of the product expressed as g/mol. Thus e.g. PEG 300 means polyethylene glycol having the molar mass 300g/mol.

In the slurry according to the invention, most preferably a polyethylene glycol having a molar mass of about 400 to 600g/mol is used. The preferable portion of polyethylene glycol in the slurry is about 40 to 60% and the most pre¬ ferable about 50 to 60% of the total weight of the slurry.

The inert powder, which is a main characteristic of the carboxymethyl cellulose slurry according to the invention, can be any pigment, such as a mineral based, finely-powdered pigment, e.g. a calcium carbonate, clay, talc, titanium dioxide or gypsum based pigment. Calcium carbonate based pigments are known, among others, by the trade names Hydrocarb, Setacarb, Faxe Chalk, DX-40, OPACARB. Clay based pigments are known, among others, by the trade names SPS, Alphafine, Amazon, Superclay, Nuclay. Talc based pigments, among others, are known by the trade name Finntalc. Titanium dioxide based pigments are known, among others, by the trade names Finntitan, and Bayertitan. Gypsum based pigments are known, among others, by the trade name Cocoat.

The inert powder can also be a polymer, resin, or wax based pigment, such as those having the registered trade names Rhodopas, Lytron and Pergopak.

The most advantageous pigments are the calcium carbonate- and clay based pigments and their mixtures. The portion of pigments in the slurry according to the invention is usually about 1 to 50%, preferably about 2 to 15% of the total weight of the slurry.

The inert dispersion component of the CMC slurry according to the invention, is preferably a latex emulsion, a paraffin wax dispersion or a calcium stearate dispersion. Typical latex emulsions are Acronal ^R , Primal ^R , Raisional ^R . Typical paraffin wax dispersions are Mobilwax ^R , Kenosize ^R and Aquamol ^R . Calcium stearate dispersions are Raisacoat ^R , Nopcote ^R and Valke ^R . Preferable portions of the dispersion is about l to about 50%, most preferably about 2 to about 15%, calculated as dry weight, based on the total weight of the slurry.

According to one preferred embodiment of the invention the carboxymethyl cellulose slurry can also contain water. The portion of water usually is about 1 to 40% and preferably about 2 to 10% of the total weight of the slurry. The water can be added to the composition with the carboxymethyl cellulose and/or the stabilizing inert powder and/or dispersion.

According to the most preferred embodiment of the invention the carboxymethyl cellulose slurry comprises (a) about 30 to 40%, based on the total weight of the slurry, of carboxymethyl cellulose, (b) about 40 to 60%, based on the total weight of the slurry, of polyethylene glycol, the molar mass distribution of which is preferably of one type or

monomodal, and the average molar mass of which is between about 200 and 600 g/1, and (c) about 10%, based on the total weight of the slurry, of a pigment.

The order of addition has no essential significance on the properties of the slurry. Preferably the pigment is added as an aqueous slurry, the water content of which usually is 20 to 50% and preferably about 30% calculated on the total weight of the aqueous pigment slurry. If the dispersion added is an emulsion, e.g. a latex, the dry content is preferably about 20 to 50%, most preferably about 30%, calculated on the weight of the added dispersion.

As far as the method is concerned it is also advantageous if the CMC slurry of the invention is stabilized by adding water or an aqueous solution of another water-soluble substance to it. The components are thereby the same as the ones presented above in the description of the slurry according to the invention. The viscosity of the slurry can further be lowered by adding still more polyethylene glycol to it.

In the following the invention is illustrated by means of some examples. The meaning of the used trade names are explained after the examples.

Example 1

200g of PEG 400 was weighed to a vessel of 600ml, after which 200g of Finnfix 10 was added to it and the mixture was agitated for about 3 minutes. Finally, lOOg of Hydrocarb 90- dispersion was added under constant agitation. The concentration of the slurry with respect to CMC is in this example 36%, the viscosity of the slurry was 3600mPas and it was stable at room temperature for over 6 months.

Example 2

200g of PEG 400 was weighed to a vessel of 600ml, after which 200g of Finnfix 10 was added to it and the mixture was agitated for about 5 minutes. Finally, 60g of Cocoat gypsum dispersion was added under constant agitation. The viscosity of the slurry was 3700mPas and it was stable at room tem¬ perature for over 8 months. The concentration of the slurry with respect to CMC is in this example 39%.

Example 3

200g of PEG 400 was weighed to a vessel of 600ml, after which 160g of Finnfix 10 was added to it and the mixture was agitated for about 3 minutes. Finally, 36g of SPS pigment dispersion and 3.5g of titanium dioxide powder were added under constant agitation. The concentration of the slurry with respect to CMC is in this example 38%, the slurry was very fluid and stable at room temperature for over 5 months.

Example 4 200g of PEG 400 was weighed to a vessel of 600ml, after which 123g of Finnfix BX was added to it and the mixture was agitated for about 3 minutes. Finally, 90g of Hydrocarb 90- dispersion was added under constant agitation. The concen¬ tration of the slurry with respect to CMC is in this example 28%, the slurry was very fluid and stable at room tempe¬ rature for over 6 months.

Example 5

200g of PEG 400 was weighed to a vessel of 600ml, after which 200g of Finnfix 10 was added to it and the mixture was agitated for about 4 minutes. Finally, 85g of Zetacarb powder was added under constant agitation. The concentration of the slurry with respect to CMC is in this example 37%, the slurry was very fluid and stable at room temperature for over 8 months.

Example 6

200g of PEG 400 was weighed to a vessel of 600ml, after which 69g of Hydrocarb 90 dispersion was added to it and the mixture was agitated for about 2 minutes. Finally, 128g of Finnfix 3500 was added. The concentration of the slurry with respect to CMC is in this example 29%, the slurry was very fluid and stable at room temperature for over 3 months.

Example 7 200g of PEG 400 was weighed to a vessel of 600ml, after which 200g of Finnfix 10 was added to it and the mixture was agitated for about 5 minutes. Thereafter 53g of Hydrocarb 90 was added and, finally, 56g of Finnfix 10 was added under constant agitation. The concentration of the slurry is in this example 45%. The slurry was very fluid and stable at room temperature for over 5 months.

Example 8

200g of PEG 400 was weighed to a vessel of 600ml, after which 15Og of Finnfix 10 was added to it and the mixture was agitated for about 3 minutes. Finally, 36g of Finntalk- pigment dispersion was added under constant agitation. The concentration of the slurry with respect to CMC is in this example 26%, the slurry was very fluid and stable at room temperature for over 3 months.

Example 9

200g of PEG 400 was weighed to a vessel of 600ml, after which 200g of Finnfix 10 was added to it and the mixture was agitated for about 4 minutes. Thereafter, 125g of PCC-powder was added, after which 20g of water was added under constant agitation. The concentration of the slurry with respect to CMC in this example was 33% by weight, the slurry was very fluid and stable at room temperature for over 3 months.

Example 10

200g of PEG 400 was weighed to a vessel of 600ml, after which 200g of Finnfix 10 was added to it and the mixture was

agitated for about 4 minutes. Finally 100 g of the plastic pigment dispersion Rhodopas S0501 was added. In this example, the concentration of the slurry with respect to CMC is 36% by weight. The slurry was very fluid and stable at room temperature for over 6 months.

Example 11

200g of PEG 400 was weighed into a vessel of 600ml, after which 200g of Finnfix 10 was added thereto and the mixture was agitated for about 4 minutes. Thereafter, 120 g of Raisional 1116 latex dispersion was added under constant agitation. The concentration of the slurry with respect to CMC in this example was 35% by weight, the slurry was very fluid and stable at room temperature for over 3 months.

Example 12

200g of PEG 400 was weighed into a vessel of 600ml, after which 200g of Finnfix 10 was added thereto and the mixture was agitated for about 4 minutes. Thereafter, 25% of Nopcote 104 Ca stearate dispersion was added, and finally 30 g of PEG 400 was added under constant agitation. The concentration of the slurry with respect to CMC in this example was 40% by weight, the slurry was very fluid and stable at room temperature for over 5 months.

Example 13

200g of PEG 400 was weighed into a vessel of 600ml, after which 200g of Finnfix 10 was added thereto and the mixture was agitated for about 3 minutes. Thereafter, 50 g of Aquamol 1200 paraffin wax dispersion was added under constant agitation. The concentration of the slurry with respect to CMC in this example was 40% by weight, the slurry was very fluid and stable at room temperature for over 6 months.

Finnfix 10 = NaCMC powder

Hydrocarb 90 = calcium carbonate pigment

Cocoat = gypsum based pigment

SPS clay based pigment

Finnfix BX NaCMC powder Setacarb calcium carbonate pigment Finnfix 3500 NaCMC powder Finntalc talc pigment PCC powder precipitated calcium carbonate Rhodopas S0501 styrene based polymer pigment Raisional 1116 polyvinyl acetate based latex Nopcote 104 calcium stearate water dispersion Aquamol 1200 paraffin wax water dispersion