Description of PAC Polyanionic cellulose manufacturing process

PAC Polyanionic cellulose manufacturing process in details is below. Preparation method of water-based drilling high viscosity PAC polyanionic cellulose FIELD
  • 1 The present invention relates to a technical field of production of cellulose polyanionic, and particularly to a method for preparing water-based drilling polyanionic cellulose with a high viscosity.
  • Background technique
  • 2 The drilling mud is an oil-based and water-based drilling fluids. As the world increasingly stringent environmental regulations, water-based drilling fluids due to less pollution into the mainstream. And cellulose-based fluid loss, rheology modifiers, having a rich source, a biodegradable, low pollution characteristics, the main product is sodium carboxymethylcellulose (CMC-Na) and PAC polyanionic cellulose. They are by far the largest amount, the most versatile, environmentally friendly drilling fluid loss, rheology modifiers.
  • 3 With the development of oil exploration in marine formations, drilling increasingly harsh formation conditions, an increase in drilling depth. Generally speaking, drilling depth of 1,000 meters per extending downwardly, downhole temperature rises 30 ° C, when the depth of 4,000 meters, the temperature rises 120 ° C. So for high temperature drilling fluid components, tolerant increasingly high demand for an anti-fluid loss, viscosity and viscosity requirements degradation increases. Common PAC and CMC-Na not meet the requirements. CMC-Na and domestic manufacturers since PAC kneading process are simple, low-fold amount of ethanol as a solvent. We can manufacture  PAC Polyanionic Cellulose products. Most of these products can only meet the needs of drilling on land and shallow wells. The reason is because the domestic response equipment and technology, the heat transfer is not fast, small cooling area. When chloroacetic acid is added and basified, inevitably materials in strongly alkaline and high temperature; partially etherified material overheating temperature inevitably increases. The consequence is to reduce the cleavage of cellulose viscosity, as well as uneven etherification reaction problems. So do not reach the performance of domestic PAC polyanionic cellulose developed countries with isopropyl alcohol as a solvent of the slurry produced by the PAC. In order to meet the increasing offshore drilling and other drilling of complex formation conditions, subject to existing domestic equipment and technology to improve and necessary complement is imperative.
  • 4 Publication No. CN101838333A the invention discloses a method for preparing a high viscosity polyanionic cellulose. The step of preparing refined cotton cellulose as a raw material, there was basified comprising cellulose mixed etherified cellulose plus agents, cellulose ethers, post treatment and washing, the product; prepared according to the method further comprising the step of cross-linking reaction, the cross-linking reaction step is carried out between the etherified cellulose and the neutralization washing step, the cross-linking reaction step of crosslinking agent is N, N’- ethylene Methylene bis acrylamide was added to polyanionic cellulose crosslinking reaction. Wherein there are shortcomings: 1 starting material, before basifying, alkali, alcohol or the like without any treatment before entering the kneader, for a short time only 10_30min be mixed in a kneader, the (longer unlikely because the reaction was in this equipment in the long-term stay, it will seriously affect the yield of the entire production line), so that, because of the high initial temperature, since the alkaline lysis cellulose is exothermic reaction, the temperature will result in a higher starting basified, basified starting temperature is one of the key factors affecting the viscosity of the product, this will lead to decrease viscosity of the final product; 2, the temperature during the whole was basified higher, at 15-40 ° C, to a large extent the impact of high viscosity products the obtained product viscosity is not high, resulting in higher fluid loss when used in water-based drilling fluids, poor salt tolerance. 3, the etherifying agent is still using a single acid, which entails a large amount of alkali, basified etherification reaction exotherm large, the viscosity of the product is greatly lowered. Although the products when they reach the degree of substitution of 0. 99-1. 03, Brookfield viscosity of 1% aqueous solution of PAC 6300-7000mpa.s (i.e. uniform substituted CMC) product, but still far from the high level of foreign.

  • 6 The object of the present invention is to overcome the above drawbacks of the prior technology, there is provided a method for preparing foreign high-performance equivalent to the performance of water-based drilling PAC Polyanionic Cellulose products with a high viscosity, manufactured polyanionic cellulose having ultra high viscosity, water-based drilling fluids, good salt tolerance, high apparent viscosity and low fluid loss.
  • 7 aspect of the present invention to solve the technical problem are:
  • 8  species of water-based drilling poly anionic cellulose with the preparation of high viscosity, prepared according to the following steps:
  • 9  low temperature cooling water, to a concentration of 45-50% by mass aqueous sodium hydroxide and aqueous ethanol concentration of 85-95% by 1: 14-25 weight ratio of homogeneous mixing, to give 8-13 ° C in an alcohol – a mixture of a base.
  • 10 The present step is the key point of the present invention, the present invention breaks the conventional, first basified using alcohol – low temperature process in a base material outside the kneader, and then the reaction was basified with into the kneader refined cotton, this can significantly reduce the temperature of the reaction was basified (particularly the temperature at the start), there will be no local overheating occurs, the uniformity of the refined cotton basified good, i.e., reducing the refined cotton cellulose cleavage, thereby increasing the viscosity of the product .
  • 11  a high degree of polymerization refined cotton shredded, and alcohol – alkaline mixture into a kneader, and refined cotton alcohol – molar ratio of the base mixture of the base is 1: 19-25 of refined cotton low temperature basified basified temperature of 8-13 ° C, basified time 30_60min.
  • 12 basified temperature, and basified alcohol feedstock – alkaline mixture uniform temperature control, to ensure the uniformity of the refined cotton basified basified good, good quality products. Basified raw material alcohol – Effect of base temperature of the mixture was basified temperature control and control of the viscosity of the product key exception, the inventors have found that after a long exploration practice, a temperature of 13 ° C was basified with a threshold value, which is conventional in the art for the Introduction nonobvious features, basified temperature exceeds 13 ° C, as the temperature increases, the viscosity of the product will be significantly decreased, thus the present invention controls the temperature of 13 ° C and basified less, reducing the low temperature i.e. refined cotton cellulose cleavage, help to improve the viscosity of the product, but in the course of industrial production, the lower the temperature, the required equipment is expensive, and severe conditions, high production costs, and therefore, in order to meet the needs of industrial production (low production costs) and performance (more excellent performance) balance consideratio
  • ns, basified controlled temperature and basified starting alcohol – are in the base temperature of the mixture 8-13 ° C.
  • 13 After basified etherifying agent is added, and refined cotton etherifying agent molar ratio of 1. 4-20: 1, etherifying agent addition was completed, added the second sodium hydroxide, the molar ratio of sodium hydroxide and refined cotton 0. 1-02: 1, then warmed to 75-80 ° C etherification reaction 35_90min.
  • 14 In the prior art, i.e., alkali hydroxide is typically added in one portion at basified basified heat capacity this will inevitably cause a reaction, and the alkali concentration kneader larger, etherifying agent is added (conventionally of chloroacetic acid) corresponding to the demand increases, resulting in large amounts of acid and base in an etherifying agent is added and the reaction exotherm, generating a lot of heat, seriously reduce the viscosity of the product. Accordingly, the present invention takes basified end, the etherifying agent after completion of the addition of sodium hydroxide was added to separate into the original primary alkali alkali present twice, which can effectively control the exothermic reaction is too large to ensure that the product has high viscosity.
  • After 15 etherification reaction, the product was neutralized to pH 7-7. 5, washed, dried, pulverized to obtain a water-based drilling fluid with high viscosity polyanionic cellulose.
  • 16 Advantageously, step (3) of the etherifying agent is chloroacetic acid and sodium chloroacetate molar ratio is 0. 5-3: 1 mixture of etherifying agent is added in the form of a solution in ethanol, the etherifying agent is ethanol solution accounting for 50-75% by mass percentage. Sodium chloroacetate is added to a fine powder.
  • 17 The compositions etherifying agent is another key point of the present invention, the inventors have added a single conventional break mode acid etherifying agent, development of a novel combination of an etherifying agent, by the addition of sodium chloroacetate, both the amount of the base can be reduced when the basified, but also reduce the acid (TCA) an amount such that, regardless basified etherification or etherification, the reaction system is reduced by exothermic maximum control, which can effectively reduce the refined cotton viscosity loss, greatly improve product viscosity.
  • 18 The purpose is to obtain alkalized sodium carboxymethylcellulose, also the remaining portion of the base, the next etherification, the etherifying agent (acid) to neutralize the remaining alkali and basified to give sodium chloroacetate, and sodium carboxymethylcellulose and obtained by reacting sodium chloroacetate polyanionic cellulose. The use of combination of the invention etherifying agent, there is a considerable share of sodium chloroacetate directly, without a large amount of alkali (base basified remaining portion) obtained by reacting chloroacetic acid, which can effectively reduce the required amount of base was basified, can reducing the amount of acid required etherification, basified whether or etherification, the reaction system is reduced by exothermic maximum control, so that the loss can effectively reduce the viscosity of the refined cotton, greatly enhance product viscosity wide supplier.
  • 19 Advantageously, step (3) the time etherifying agent added is controlled 20-50min, the temperature during the addition of etherifying agent in controlled below 25 ° C. Help improve product viscosity.
  • 20 Preferably, the etherifying agent is added during the addition of the crosslinking agent, the crosslinking agent is used in an amount of 0. 2-1. 0% by weight of refined cotton. Preferably, the crosslinking agent is selected from dichloroacetic acid, diluted with epichlorohydrin An chloro-propanol, with ethanol and a crosslinking agent concentration of 3% -5% then added.
  • 21 The crosslinking agent can greatly increase the viscosity of the product, by practice of the invention, the inventors to explore the crosslinking agent is selected from dichloroacetic acid, epichlorohydrin, one of chlorine-propanol, using best, the product The viscosity increase effective.
  • 22 Advantageously, step (2) the high degree of polymerization degree of polymerization of 2600 or more refined cotton. Such refined cotton original viscosity 1¾, the viscosity of the resulting product is also guaranteed widely.
  • 23 Advantageously, step (2) a high degree of polymerization refined cotton shredded, and an alcohol – a base mixture into the kneader, the kneader kneader purged with nitrogen to exclude oxygen. Exclusion of oxygen can be reduced i.e. cleavage refined cotton cellulose, commercially beneficial to provide a wide product viscosity.
  • 24 Advantageously, step (3) was added sodium hydroxide or sodium hydroxide in the form of a sheet-like solid was added aqueous sodium hydroxide concentration in the aqueous solution is 45-50%.
  • 25 Advantageous effects of the present invention is that: the prepared polyanionic cellulose having ultra high viscosity, low production cost, when used in water-based drilling fluids, good salt tolerance, high apparent viscosity, low fluid loss.