Comb-type polymer, preparation method and application thereof

The invention discloses a comb-type polymer or a salt thereof. The comb type polymer has a structural formula as follows; R1-R6 and R9-R10 are the same or different, and can be independently selected from hydrogen and C1-C22 alkyl; R7 is selected from hydrogen and alkyl sulfonic acid containing 1-22 carbon atoms; R8 is selected from hydrogen, C1-C22 alkyl, carboxylic acid groups and groups with the general formula COO[(CH2)xO]mCH3; and R11 is selected from (CH2)nCH3(CH2) and [(CH2)xO]mCH3, wherein a:b:c is 20-50:9-49:1-60, x is an integer from 2 to 4, n is an integer from 14 to 22, and m is an integer from 5 to120. The comb-type polymer provided by the invention can be used as a filtrate reducer in water base drilling fluid, makes up the failure of a conventional filtrate reducer under high temperature and high salinity conditions, and has good high temperature resistance and salt resistance; and the production process is simple and at low cost. The comb-type polymer provided by the invention as the filtrate reducer has very good effect of reducing the filter loss even the addition amount in drilling fluid is low.