MXPA96004895A - Aqueous suspension of an ether of cellulose, metodopes the production of the same and composite - Google Patents

Abstract

The present invention relates to an aqueous suspension of water soluble nonionic cellulose ether, in which the aqueous phase contains an electrolytic salt, characterized in that the nonionic cellulose ether, which is entangled with glyoxal, totals 6.36% in weight of the suspension and has before the entanglement a turbidity point of 25-100 ° C as measured in a 1% aqueous solution and that the electrolytic salt sum of 3-§2% by weight of the suspension and consists of a salt or a mixture of salts which, in water and at a concentration involved, gives a pH value below 8.0, preferably below 7.

Description

AQUEOUS SUSPENSION OF A CELLULOSE ETHER. METHOD FOR THE PRODUCTION OF THE SAME AND COMPOSITION DESCRIPTION OF THE INVENTION This invention relates to a suspension of a water-soluble interlaced cellulose ether having a moderately low salt content. The suspension is advantageously produced by adding water to a composition in the form of a dry mixture containing crosslinkable, water-soluble cellulose ether and a salt. Water-soluble nonionic cellulose ethers are used in many industrial processes, as well as in many consumer products. Therefore, such ethers are used in mining, papermaking, water purification and textile treatment, as well as in paint compositions, cleaning agents and cosmetics. However, it is difficult to dissolve the nonionic and water soluble cellulose ethers in powdery water, due to their tendency to gelation and agglomeration. One way to solve this problem is to suspend the ethers of water-soluble cellulose containing a considerable amount of electrolyte and, optionally, a dispersing agent and / or a stabilizer. When mixed in water, the electrolyte content is reduced and the cellulose ethers dissolve without any gelling or lumping. The cellulose ethers thus suspended in water have proven to be suitable for use as an intermediate product in industrial processes and in the manufacture of consumer products. European Patent Application 413 274 discloses an aqueous suspension of hydroxyethylcellulose. This suspension contains 8-28% by weight of water soluble hydroxyethylcellulose; 20-35% by weight of potassium carbonate, based on the weight of potassium carbonate and water; 0.2-8% by weight of a wetting agent having an HLB value of 6-9; and 0.08-0.6% by weight of a thickener soluble in water or swelling in water, both contents being based on the total weight of the suspension. Also, European Patent Application 482 533 teaches the suspension of a nonionic cellulose ether, such as hydrophobe modified hydroxyethylcellulose, methylcellulose and hydroxyethylcellulose, in an aqueous solution of sodium formate. It is evident from the Examples that a gel and not a liquid suspension is obtained when the sodium format content is 20% by weight or 25% by weight of the total composition. According to this European patent application the sodium format has to be present in an amount of at least 30% by weight if a suspension is to be obtained. However, although stable and useful suspensions can be produced in accordance with those two European patent applications, those suspensions will contain unacceptably high electrolyte contents. European Patent Application 3 582 teaches a method for reducing the electrolyte content of suspensions of water-soluble nonionic cellulose ethers. According to this patent application, this is obtained by adding not only an electrolytic salt but also an aluminum oxide compound. Due to the addition of aluminum oxide, the electrolyte content can, according to the patent application, be reduced from about 25% to 10%. The presence of aluminum oxide, either in the solid or colloidal state, may, however, have subsequent adverse effects when the suspension is used. It is an object of the present invention to provide a suspension of a low salt cellulose ether without the use of any water-insoluble metal oxides. Another object of the invention is to allow the production of suspensions having a low content as well as a high content of cellulose ether. Even another object of the invention is to allow the simple and advantageous production of the suspension in the place when it is used, avoiding the unnecessary transports of water.

In accordance with the present invention, it has been found that these objects are achieved by an aqueous suspension of a water-soluble nonionic cellulose ether., which is entangled with glyoxal and has a cloud point of 25-100 ° C, preferably 30-80 ° C, as measured in a 1% aqueous solution, and an electrolytic salt having a pH value below of 8.0, preferably below 7.5, in water and at a concentration used in the suspension. Conveniently, the cellulose ether is present in an amount of 6-36%, based on the weight of the suspension, while the electrolytic salt is present in an amount of 4-12%, preferably 5-8%, based on the weight of the suspension. Apart from the cellulose ether and the electrolytic salt, the suspension suitably contains a stabilizer consisting of a viscosity-increasing polymer that is soluble in the electrolytic solution and is present in an amount of 0.01-3%, based on the weight of the suspension. Conveniently, the suspension further contains a dispersing agent, such as a surfactant in an amount of 0.5-4% by weight. Usually, the dispersing agent has a stabilization and viscosity reduction effect. When the suspension of the invention occurs, all the dry substances, except the nonionic cellulose ether, can be mixed, after which the water and any liquid or paste-like additive can be added. The cellulose ether is then added to the resulting aqueous fluid. In a preferred method for the production of cellulose ether suspension, the water included is combined with a dry mixture containing the cellulose ether, the electrolytic salt and preferably the other components of the suspension as well. In the event that one or more of the components are in a liquid state, this component or those components are conveniently applied to a vehicle and then incorporated into the dry mixture. If so desired, one or more of the components, except the cellulose ether and the electrolytic salt, may also be added to the water after and / or before mixing to the water of the dry mixture containing the cellulose ether-and the electrolytic salt. Through the test it has been shown that this mixing method can only be used if the cellulose ether is interlaced, since the lower amounts of the cellulose ether would dissolve in another way to form a gel. The first stage dry combination of all the components involved, except water, has important advantages, allowing the preparation of a suspension of the cellulose ether by the addition of water to an individual dry composition.

Conveniently, such dry composition contains 50-90% by weight of a cellulose ether, preferably 60-85% by weight and 10-50% by weight of the electrolytic salt, preferably 15-40% by weight. In addition, the dry composition may contain 0.02-6% by weight of a stabilizer and 0.1-8% by weight of a dispersing agent. As mentioned in the above, the electrolytic salt consists of a salt or salt mixture which gives a pH value below 8.0, preferably below 7.5, in the contemplated electrolytic content of the aqueous suspension. The reason for this is that the crosslinked cellulose ether is partially hydrolyzed at high pH values to form a gel. Examples of suitable salts are NaCl, Na 2 SO 4, K 2 SO 4, NaN 3 and MgSO 4. Especially preferred salts are alkali salts with divalent anions, such as Na 2 SO 4 and K 2 SO 4. By selecting an electrolytic salt which at least partially, preferably by at least 50% by weight, consists of salts with divalent anions, it has been proved that it is possible to maintain the salt content of the suspension at a level below 8% in weight. In addition, the amount of salt required depends on the degree of entanglement of the cellulose ether, the turbidity point of the cellulose ether and the temperature of the suspension. Therefore, the need for salt decreases as the temperature increases, the degree of entanglement increases and the turbidity time decreases. The nonionic cellulose ethers employed are conventional cellulose ethers which are entangled with glyoxal. Examples of suitable crosslinkable cellulose ethers are the water soluble alkyl cellulose ethers, such as methyl cellulose and ethyl cellulose; hydroxyalkyl cellulose ethers, such as hydroxypropyl cellulose, hydroxypropylhydroxybutyl cellulose, hydroxyethylhydroxypropyl cellulose, hydroxyethylhydroxybutyl cellulose and hydroxyethylhydroxypropylhydroxybutyl cellulose; alkylhydroxyalkyl cellulose ethers, such as methylhydroxyethyl cellulose, methylhydroxypropyl cellulose, ethylhydroxyethyl cellulose, ethylhydroxypropyl cellulose, methylethylhydroxyethyl cellulose and methylethylhydroxypropyl cellulose; and water soluble cellulose ethers modified with hydrophobic groups according to US-A-4, 228, 277 and US-A-5, 140, 099. The nonionic cellulose ethers are entangled with glyoxal in a manner known per se same An interlaced cellulose ether has an adequate degree of entanglement when a 1% water paste thereof at 20 ° C and a pH value of 7.0 is the result, after 5 minutes of stirring, at a viscosity increase of less of 5%, preferably less than 1%, of the viscosity obtained when the entangled cellulose ether is completely dissolved. The cellulose ethers having an adequate degree of entanglement are obtained by reacting 0.05-2 parts by weight of glyoxal with 100 parts by weight of dry cellulose ether. In order to improve the stability of the suspension, it has been found convenient to add polymeric stabilizers which are soluble in an electrolytic solution, such as xanthan gum and CMC. Examples of suitable dispersing agents are ionic low molecular weight polymers having a molecular weight of 1,000-15,000, such as low molecular weight polyacrylic acids; nonionic surfactants, such as ethylene oxide adducts of alcohols having 10-18 carbon atoms, alkylphenols having a total of 14-18 carbon atoms, and block polymers of ethylene oxide and propylene oxide; anionic surfactants, such as linear alkylbenzene sulfonate, lauryl ether sulfate and fatty alcohol ethoxylate phosphate esters; cationic surfactants, such as tertiary or quaternary g-^ g mono- or alkylamines; and amphoteric surfactants, such as betaines. Apart from the components indicated in the above, the composition may contain biocides, foam inhibitors, corrosion inhibitors and so on.

The invention will now be illustrated with the help of a few examples.

Example 1 The dry compositions containing the nonionic cellulose ethers were produced by mixing the following components. 1) Turbidity point 68 ° C, viscosity increase after 5 minutes = 0 2) Turbidity point > 100 ° C, increase in viscosity after 5 minutes = 0 3) Turbidity point 56 ° C, increase in viscosity after 5 minutes = 0 4) Turbidity point 58 ° C, increase in viscosity after 5 minutes = 0 5 ) Turbidity point 68 ° C, there was no entanglement. Aqueous formulations in accordance with the The following table was prepared based on those dry compositions. The viscosity and stability of the aqueous formulations was determined, and the following results were obtained. 1) viscosity ++ = < 5000 mPas, + = = 5000 mPas (without gelation), 0 = gel 2) Stability: + = separation observed within 6 hours, ++ = stable after 6 hours but not after 10 days, +++ = stable after of 10 days. The aqueous formulations that gelled are not suitable for use, while liquid or highly liquid formulations are acceptable. All suspensions that were separated after storage for some time could be returned to the state of a homogeneous suspension after slight agitation.

Example 2 The following aqueous formulations were produced by mixing the involved components, except water and then suspending the dry mixture obtained. 1) According to Example 1. The following results were obtained.

Composition Appearance Viscosity Stability 5 ++ +++ 6 + ++ 7 + ++ 8 + ++ 9 + +++ 10 + +++ 11 ++ +++ It is evident from these results that all pastes were acceptable, although those formulations 6, 7 and 8 have limited stability. The suspensions 5 and 11 have a cellulose ether content of 22% by weight which exhibited both excellent stability and low viscosity. Formulations 6, 7 and 8 which were separated after storage for some time, formed homogeneous suspensions after agitation.

Example 3 The aqueous formulations of Example 2 were prepared by dissolving all the components, except the cellulose ether, in water. It was not until after the cellulose ether was added. The resulting pastes exhibited the same properties as the corresponding pastes of Example 2.

Claims (14)

1. l. An aqueous suspension of a nonionic cellulose ether soluble in water, in which the aqueous phase contains an electrolytic salt, characterized in that the nonionic cellulose ether, which is entangled with glyoxal, adds up to 6-36% by weight of the suspension and has before the entanglement a turbidity point of 25-100 ° C as measured in a 1% aqueous solution, and that the electrolytic salt adds up to 3-12% by weight of the suspension and consists of a salt or a mixture of salts which, in water and at a concentration involved, gives a pH value below 8.0, preferably below 7.5.
2. 2. An aqueous suspension according to claim 1, characterized in that the interlaced cellulose ether, in a 1% water paste having a temperature of 20 ° C and a pH value of 7.0, results in a lower viscosity increase of 5%, preferably less than 1% of the viscosity obtained with the cellulose ether, is completely dissolved.
3. 3. An aqueous suspension according to claim 1 or 2, characterized in that it contains 5-8%, based on the weight of the suspension, of the electrolytic salt.
4. 4. An aqueous suspension according to claims 1-3, characterized in that at least 50% by weight of the electrolytic salt consists of a salt with bivalent anions.
5. 5. An aqueous suspension according to any of claims 1-4, characterized in that it contains, as a stabilizer, 0.01-3% by weight, based on the weight of the suspension, of a viscosity-increasing polymer that is soluble in the electrolytic solution. .
6. 6. An aqueous suspension according to claim 5, characterized in that the stabilizing polymer is xanthan gum.
7. 7. An aqueous suspension according to any of claims 1-6, characterized in that it contains 0.05-4% by weight of a dispersing agent.
8. 8. An aqueous suspension according to claim 7, characterized in that the dispersing agent is a nonionic, anionic or cationic surfactant.
9. 9. An aqueous suspension according to claim 7, characterized in that the dispersing agent is a low molecular weight ion polymer having a molecular weight of 1,000-15,000.
10. 10. A method for the production of a suspension according to claims 1-9, characterized in that the included water is mixed with a dry mixture containing the cellulose ether and the electrolytic salt.
11. 11. A method according to claim 10, characterized in that the dry mixture contains all the components of the aqueous phase.
12. 12. A dry mixture, characterized in that it contains a cellulose ether entangled with glyoxal according to any of claims 1-4, as well as an electrolytic salt as claimed in any of claims 1-4, the content of the cellulose ether being of 50-90% by weight and the content of the electrolytic salt being 10-50% by weight.
13. 13. A dry mixture according to claim 12, characterized in that it contains 0.02-6% by weight of a stabilizer as claimed in claim 5 or 6.
14. 14. A dry mixture according to claim 13, characterized in that it contains 0.1-8% by weight of a dispersing agent as claimed in claim 7, 8 or 9.