Fluid loss additive products can be divided into granular materials, water-soluble polymers and organic materials. Among the granular materials, latex has become a research hotspot because of its good filtration reduction, gas channeling prevention and toughening. Most of the fluid loss additive products are water-soluble polymers and organic materials, which can be divided into modified natural products and synthetic polymers. In addition, many researches have been done on environmental protection fluid loss additive abroad.

Classification

1. Modified natural product fluid loss additive

Modified cellulose is a kind of fluid loss additive widely used in water-soluble natural products. The modified cellulose which can be used as fluid loss reducer are CMC (carboxymethyl cellulose), HEC (hydroxyethyl cellulose), cmhec (carboxymethyl hydroxyethyl cellulose), etc. CMC makes cement slurry flocculate and has strong retarding property, so it is not used now. The comprehensive performance of HEC is acceptable, and there are a few applications.

CMHEC is widely used in foreign countries, but rarely produced in China. The common disadvantages of modified cellulose are poor water solubility, high viscosity, poor temperature resistance and delay of cement strength development. It is a good method to improve the properties of cellulose by chemical graft copolymerization and introducing other functional monomers.

2. Polymer fluid loss additive

The synthetic polymer fluid loss additive has many kinds and excellent performance, which has some incomparable characteristics of natural products, so it has become the focus of researchers in various countries.

1) Nonionic polymer

PVA (polyvinyl alcohol) system is a kind of non-ionic fluid loss additive which is widely used in China. It has unique advantages, such as ZOD-86S produced by Qingdao Zoranoc company. The operating temperature of the system is up to 95 ℃. When the temperature is higher than 95 ℃, the crosslinking bond is destroyed and the filtration performance is poor. In addition, the salt resistance of the system is poor, and the salt resistance is usually less than 5%. In order to improve the poor temperature and salt resistance of PVA system, chemical crosslinking method can be used to modify PVA. For example, aldehyde or acid condensation agent is used to condense the alcohol group of PVA to obtain partially crosslinked PVA. Chemical crosslinked PVA can be used alone without borax and other crosslinking agents. The temperature resistance can reach 120 ℃, the salt resistance can reach 8%, and the filtration rate can be controlled below 50ml.

2) Anionic polymer

Anionic polymer is a kind of fluid loss additive with the most extensive research and products at home and abroad. Its comonomers include nonionic and anionic monomers. Nonionic monomers mainly include am (acrylamide), NVP (N-vinylpyrrolidone), NNDMA (n, N-dimethylacrylamide), St (styrene), VI (vinyl imidazole), VFA (vinyl formamide), VP (vinylpyridine), vmaa (n-methyl-n-vinyl acetamide), etc. Among these monomers, am is easy to hydrolyze, so the content of am in the copolymer should not be too much; NNDMA introduces the non hydrolyzable group, which can obviously improve the high temperature resistance, but this monomer is expensive and is still in the pilot stage in China. Anionic monomers mainly include two types: one is sulfonate monomer, such as amps (2-acrylamido-2-methylpropanesulfonic acid), SS (styrene sulfonate), vs (ethylene sulfonate), PS (propylene sulfonate); the other is carboxylate monomer, such as AA (acrylic acid), MAA (methacrylic acid), hea (hydroxyethyl acrylic acid), IA (itaconic acid), etc. Amps has strong temperature and salt resistance, high polymerization activity, and is widely used. Large scale production has been formed in China.

3.Environmentally friendly fluid loss additive

With the increasing attention to environmental protection, foreign researchers have increased the research and development of environmental protection fluid loss additive in recent years. The so-called environmental protection type fluid loss additive refers to the product with better biodegradation performance. The main ways to develop environmental friendly fluid loss additive are as follows: (1) developing natural products with fluid loss reducing function; (2) modifying the existing natural product fluid loss additive to broaden its application range; (3) developing fluid loss additive which is stable in strong alkaline environment but degraded in neutral water medium; (4) crosslinking low molecular weight polymer with degradable crosslinking agent to obtain high molecular weight reduction (5) to modify the degradable synthetic polymer to make it have the function of fluid loss reduction; (6) to develop the synthetic polymer fluid loss agent which is similar to the natural product in structure and can be degraded by microorganism.