METHOD UPON A TEMPERATURE INCREASE OF COUNTERACTING A VISCOSITY DECREASE OR PROVIDING A VISCOSITY INCREASE IN A WATER-BASE SYSTEM CONTAINING A POLYMER AS VISCOSITY AGENT

Abstract: The invention relates to a method in a water-base system for at least partially avoiding an expected viscosity decrease or providing a viscosity increase upon a temperature increase, by using a system containing as viscosity-adjusting agents a nonionic cellulose ether in such an amount that the aqueous solution thereof has a viscosity of 10-10,000 cP, measured according to Brookfield LV, 12 rpm at 20 DEG C, and an ionic surface-active compound in an amount of 1-30 mmol per litre of water.

Description: METHOD UPON A TEMPERATURE INCREASE OF COUNTERACTING A VISCOSITY DECREASE OR PROVIDING A VISCOSITY INCREASE IN A WATER-BASE SYSTEM CONTAINING A POLYMER AS VISCOSITY AGENT The present invention relates to a method, in a water-base system, of at least partially avoiding an expected viscosity decrease or of providing a visco¬ sity increase upon a temperature increase, by using a system containing as viscosity-adjusting agent a nonionic water-soluble cellulose ether and a water- soluble ionic surface-active compound. Water-soluble polymers in most cases give rise to a substantial viscosity increase when dissolved in water. A large number of water-base systems there¬ fore contain polymers and viscosity-adjusting agents. Also small additions, e.g. below 1% by weight, may cause considerable changes in the viscosity of the aqueous solution and even give rise to gelation. The viscosity of an aqueous solution of a polymer general¬ ly is dependent on concentration and temperature. Nor¬ mally, the viscosity increases upon an increase of the polymer concentration or upon a temperature drop. Examples of polymers exhibiting such a temperature dependence are sodium alginate, polyvinyl alcohol and tragacanth. There are many types of gel-forming water-soluble polymers. In most of these polymers, gelation occurs upon a temperature drop. Some polymers exhibit in aqueous solution a so-called turbidity point or floc- culation temperature, which means that the polymer precipitates when the temperature is raised above a critical temperature. Known examples of such polymers are nonionic cellulose ethers. The normal behaviour of nonionic cellulose ethers is that the viscosity is reduced when the temperature is increased above room temperature. The reduction continues until flocculation temperature is attained. At this temperature, the solu¬ tion starts becoming turbid and if the concentration of the polymer is sufficiently high, a viscosity increase can be observed. The process is reversible. Protein solutions are somewhat exceptional in respect of temperature dependence. They often exhibit irreversible processes depending on so-called denatu- ration of the proteins when the temperature is raised. This in turn may give rise to irreversible gelation upon a temperature increase. Thus, it can be concluded that the viscosity of a polymer solution is reduced upon a temperature in¬ crease, although certain polymers exhibit a substan- tial viscosity increase at their flocculation tempe¬ ratures_ In many applications it is desirable to have access to water-base polymer solutions which exhibit a smaller viscosity decrease upon a temperature in- crease than current polymers or even a maintained or increased viscosity before gelation (viscosity in¬ crease associated with phase separation) possibly occurs. Such properties are valuable in ceramic processes when aqueous mixtures should be extruded and the pro¬ duct thereafter heated with unaltered geometry. To this end, a constant or an increasing viscosity with increasing temperature is needed in order that the structure of the extruded product should not collapse. This is also the case in several applications within the food industry where extrusion is often carried • out with subsequent heating. In deep-frying, it may sometimes be desirable to increase the viscosity when the temperature is raised so as to reduce the penetra- tion of frying-oil into the food product. Other fields of use are liquid compositions for therapeutic or cosmetic treatment of man and animal where it is de- sirable in many cases that the viscosity of the compo¬ sitions be raised, possibly followed by gelation upon heating to body temperature. Further examples are found in suspension polymerisation when it is desirable to provide stabilisation of monomer-containing droplets at increased temperatures. Canadian Patent Specification 1,072,413 discloses a method for preparing water-base polymer compositions which are liquid at room temperature, but lose their fluidity and form a gel upon a temperature increase. This is achieved by using a gel-forming component in the form of a special type of block polymer of ethylene oxide and propylene oxide, optionally in combination with a modifying polymer component. It has now surprisingly been found that the expect¬ ed viscosity decrease upon a temperature increase in a water-base polymer system containing a liquid phase of which at least 85% by weight is water, is consider¬ ably reduced and in many cases even changed into a viscosity increase by using a water-base polymer system the liquid phase of which contains as viscosity-adjusting agent: a) a nonionic cellulose ether in such an amount that the aqueous solution thereof has a viscosity of 10-10,000 cP, preferably 30-5,000 cP, measured accord¬ ing to Brookfield LV, 12 rp at 20°C, and b) a water-soluble ionic surface-active compound in an amount of 1-30 mmol, preferably 2-20 mmol per litre of water. The system thus obtained exhibits a surprisingly advantageous viscosity behaviour upon a temperature in¬ crease. By adjusting the flocculation temperature of the cellulose ether and the amount of ionic surface- active compound, gels and gel-like structures can also be obtained. Especially advantageous are the properties of the system at low shear rates, such as shear rates of about 5 s , preferably below 1 s . The content of the ionic surface-active compound is preferably se¬ lected so as to be of the same order of magnitude as the critical micelle-forming concentration, although evident viscosity-improving effects can be observed at a lower concentration. A suitable added amount of the ionic surface-active compound is about 0.2-5 times the critical micelle-forming concentration. The ionic surface-active compounds may be both cationic and anionic micelle-forming compounds. Exam- pies of suitable cationic compounds are quaternary ammonium compounds with at least one hydrocarbon group having 8-24 carbon atoms. Examples of suitable anionic surface-active compounds primarily are sulphates, such as ether sulphates and alkyl sulphates, with a hydro- carbon group having 8-24 carbon atoms, but also car- boxylates, sulphonates, ether phosphates, phosphates and phosphonates with one or more hydrocarbon groups having 8-24 carbon atoms are advantageously used. The - hydrocarbon groups may be both aliphatic and aromatic. The cellulose ethers according to the invention should be water-soluble at the temperature at which the aqueous solution is prepared. They suitably have such a degree of polymerisation that a 1% aqueous so¬ lution thereof has a viscosity of 10-10,000 cP, pre- ferably 30-5,000 cP, measured according to Brookfield LV, 12 rpm at 20°C. They may exhibit hydrophobic hydro¬ carbon groups, such as methyl, ethyl, propyl, butyl., benzyl and higher hydrocarbon groups having 8-24 carbon atoms or polar hydroxyl groups, such as hydroxyethyl, hydroxypropyl and hydroxybutyl, or mixtures of hydro¬ carbon groups and polar groups. The flocculation tem¬ perature of the cellulose ethers suitably is above room temperature and is adjusted to the field of use of the system. Examples of suitable cellulose ethers are methylcellulose, ethylcellulose, hydroxyethylcellu¬ lose, hydroxypropylcellulose, methylhydroxyethylcellu- lose, ethylhydroxypropylcellulose, ethylhydroxyethylcel- lulose and benzylethylhydroxyethylcellulose. The present invention can be used at different pH values, although strongly basic and acid pH values should be avoided as well as high electrolyte contents. The po¬ lymer system may advantageously be used as a coating to establish a barrier, e.g. for preventing dehydration. Components having therapeutic and cosmetic effects can also be incorporated in the system. It is also possible in the liquid phase to disperse solid and liquid mate¬ rials, such as fillers and binders, e.g. in the produc¬ tion of ceramic materials and foodstuffs. Example Nonionic cellulose derivatives and ionic surface- active compounds are added to water in the amounts stated in the following Tables. The viscosity of the compositions was measured at different temperatures and different shear rates. The results appear from the Tables. Table 1 List of substances used Code Compound Flocculation Viscosity 1% solu¬ temperature tion 20°C Brook¬ °C field LV, 12 rpm A Ethylhydroxyethyl- cellulose 45 4800 B If 38 34 C Hydroxypropyl- cellulose 45 2500 D Hydroxyethylcellulose modified with Ch¬ alky! groups >100 175 E Ethylhydroxyethyl- cellulose 73 4500 F Me hylcellulose 44 55 CTAB 'Cetyltrimethyl ammonium bromide SDS Sodium dodecylsulphate Table 2 Results Test Addi¬ Cone. Viscosity 0.0147 s tive Ether % by weight Surfac¬ tant mmol 20°C 30°C 40°C 50°C 60°C 70°C 1 A 1 9000 6700 4400 1900 - - 2 A 1 21000 24000 26000 34000 49000 - CTAB 10 3 B 1 300 400 700 500 100 - 4 B 1 400 600 1600 6100 , - 9100 CTAB 12 Table 3 Results -1 Test Addi¬ Cone. Viscosity 0.0147 s tive Ether % by weight Surfac¬ tant mmol 20°C 30°C 40°C 50°C 60°C 70°C 5 A 1 1-10 4 2-10 4 2-10 4 2-10 4 4-10 4 1-10 4 6 A 1 1 -10 4 20-10 4 25-20 4 40-10 4 50-10 4 50-10 4 SDS 5 7 A 1 20-10 4 30-10 4 40-10 4 50-10 4 50-10 4 - SDS 10 8 A 0.5 5000 10000 15000 20000 30000 30000 SDS 5 9 A 0.5 3000 15000 9000 10000 20000 30000 SDS 10 10 A 0.25 300 2500 4000 6000 8000 10000 SDS 10 11 D 1 3000 4000 3000 300 - - 12 D 1 3-10 5 2-10 5 2-10 5 2-10 5 - - SDS 5 13 C 1 3000 1500 500 8000 7000 8000 14 C 1 2-10 5 3-10 5 4-10 5 4-10 5 3-10 5 2-10 5 SDS 5 15 E 0.5 3500 4000 4000 4000 3000 1500 16 E 0.5 1200 3000 5000 7000 4000 11000 SDS 5 Table 4 Results -1 Test Addi¬ Cone. Viscosity 0.0147 s tive Ether % by weight Surfac¬ tant mmol 20°C 30°C 40°C 50°C 60°C 70°C 17 A 1 2200 1900 1400 900 600 - 18 A 1 12000 14000 15000 21000 24000 - CTAB 10 19 B 1 60 60 90 30 20 - 20 B 1 350 450 1500 5800 5800 - CTAB 12 21 A 1 2.5-10 4 2.5-10 4 3-10 4 2.5-10 4 2-10 4 1.5-10 4 SDS 5 22 A 1 4-10 4 6-10 4 4-10 4 3.5-10 4 3-10 4 2-10 4 SDS 10 23 A 0.5 400 200 150 70 30 - 24 A 0.5 1500 2100 3000 6000 ' 5000 1600 SDS 5 25 A 0.5 1000 100 1300 160 300 500 SDS 10 26 A 0.25 20 300 600 900 1200 1500 SDS 10 27 D 1 250 150 100 60 30 40 28 D 1 3-10 5 2-10 5 2-10 5 2-10 5 2-10 5 2-10 5 SDS 5 29 C 1 1500 1200 800 30 70 100 30 C 1 2-10 4 2-10 4 1.5-10 4 1.5-10 5 1.5-10 4 3-10 3 SDS 5 31 E 0.5 500 300 2500 170 120 60 32 E 0.5 20 25 50 90 110 200 SDS 5 2 33 F 2 1.5-10 3 7-ιcr 4-10 2 2-10 2 - - 34 F 2 8-10 3 5-10 3 4-10 3 5-10 3 - - SDS 10 From the above results appears that water-base polymer systems containing as viscosity-adjusting agents both a nonionic cellulose ether and an ionic surface-active compound have a considerably improved viscosity evolution at raised temperatures than such systems as contain a nonionic cellulose ether alone.

Claims: CLAIMS 1. Method upon a temperature increase of a water- base system containing a liquid phase of which at least 85% is water and which contains a polymer as viscosity agent, of reducing an expected viscosity decrease or changing the viscosity decrease into a viscosity in¬ crease, c h a r a c t e r i s e d by using a system the liquid phase of which contains as viscosity-adjust¬ ing agent: a. a nonionic cellulose ether in such an amount that the aqueous solution thereof has a viscosity of 10-10,000 cP, measured according to Brookfield LV, 12 rpm at 20°C, and b. an ionic surface-active compound in an amount of 1-30 mmol per litre of water. 2. Method as claimed in claim 1, c h a r a c ¬ t e r i s e d in that the cellulose ether is an al¬ kylhydroxyalkylcellulose. 3. Method as claimed in claim 1 or 2, c h a ¬ r a c t e r i s e d in that the cellulose ether is added in such an amount that it has a viscosity of 30-5,000 cP, measured according to Brookfield LV, 12 rpm at 20°C. 4. Method as claimed in any one of claims 1-3, ' c h a r a c t e r i s e d in that the ionic compound is a sulphate with a hydrocarbon group having 8-24 car¬ bon atoms. 5. Method as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that the compound is a quaternary ammonium compound with a hydrocarbon group having 8-24 carbon atoms. 6. Method as claimed in any one of claims 1-5, c h a r a c t e r i s e d in that the ionic compound is added in an amount of 2-20 mmol per litre of water. 7. Method as claimed in claims 1-6, c h a r a c ¬ t e r i s e d in that the ionic surface-active com¬ pound is added in a content of 0.2-5 times its critical micelle-forming concentration.

Inventors: CARLSSON ANDERS, LINDMAN BJOERN, STENBERG OLLE, CARLSSON, ANDERS, LINDMAN, BJOERN, STENBERG, OLLE
Applicants: BEROL NOBEL STENUNGSUND AB
Application year: 1989
Main classification: C08L1
IPC codes: A23L1, A61K8, A61K47, C08L1, C09K3