Europaisches Patentamt (19) J European Patent Office Office europeen des brevets (11) EP 0 931 795 A1 (12) EUROPEAN PATENT APPLICATION published in accordance with Art. 158(3) EPC (43) Date of publication: (51) Intel6: C08F2/22, C08F 12/00, 28.07.1999 Bulletin 1999/30 C08F 20/00, C08F2/38, (21) Application number: 96933610.6 C08L 101/00, C08L 25/00, C08L 33/00 (22) Date of filing: 11.10.1996 (86) International application number: PCT/JP96/02941 (87) International publication number: WO 98/16561 (23.04.1998 Gazette 1 998/1 6) (84) Designated Contracting States: • MASUDA, Hiroshi DE FR GB IT Nippon Carbide Kogyo K.K. Sano-ryo Tochigi 327-0818 (JP) (71) Applicant: . SERIZAWA, Hiroshi NIPPON CARBIDE KOGYO KABUSHIKI KAISHA Saitama 347-0032 (JP) Tokyo 100-0005 (JP) (74) Representative: (72) Inventors: Albrecht, Thomas, Dr. • YOSHIDA, Eiichi Kraus, Weisert & Partner Nippon Carbide Inogashira-ryo, Patent- und Rechtsanwalte Tokyo 181-0001 (JP) Thomas-Wimmer-Ring 15 • OGAWA, Manabu, 80539 Munchen (DE) Nice Urban Hiratsuka Sogokoen 202, Kanagawa 254-0017 (JP) (54) POLYMER OBTAINED BY EMULSION POLYMERIZATION METHOD (57) A polymer of a low molecular weight having a very little odor is produced by emulsion-polymerizing a radical-polymerizable unsaturated monomer at a tem- perature of 1 15°C or higher in the presence or absence of a chain transfer agent. LO co O Q_ LU Printed by Xerox (UK) Business Services 2.16.7/3.6 EP 0 931 795 A1 Description Technical Field 5 [0001 ] The present invention relates to a polymer of a low molecular weight obtained by an emulsion polymerization method, more specifically to a polymer of a low odor and a low molecular weight obtained by an emulsion polymeriza- tion method and a production process for the same. Background Art 10 [0002] A size of a molecular weight of a polymer exerts a strong influence on the chemical properties and the physical properties of the polymer. [0003] In general, as the molecular weight of a polymer grows larger, shown are tendencies such as an increase in the strength of the polymer, a reduction in blocking and an improvement in the weatherability. On the other hand, as the 15 molecular weight of a polymer decreases, shown are tendencies such as an improvement in a heat-melting property, a heat fluidity, an adhesive property to various materials and a penetrability of the polymer and a gloss of the paint film formed. [0004] Making use of these characteristics of polymers having a low molecular weight, the polymers having a low molecular weight are used in large quantities for molding resins having a good fluidity, electrophotographic toners, base 20 materials for hot melt type coating agents, coating resin-modifying agents having good penetrability and wetting prop- erty against substrates, and tackifiers. Further, since the polymers having a low molecular weight have a good mixing property or dispersibility in various materials, they are useful for specific uses such as pigment dispersants, mineral dis- persants, water-treating agents in boilers, cooling tower, reverse osmosis treatment, sugar refining, paper making, geo- thermal treatment, oil wells and the like, and detergent additives acting as builders, film-forming preventives, 25 sequestering agents and adhesion-inhibiting agents. [0005] Such polymers having a low molecular weight are obtained by polymerizing various monomers by methods such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization and the like, and they are produced preferably by emulsion polymerization because of the reasons that polymerization can easily be control led and the resulting polymers are easy to handle. 30 [0006] Usually, when polymers having a low molecular weight are obtained by emulsion polymerization, the polymer- ization has so far been carried out in the coexistence of a chain transfer agent in order to reduce the molecular weight. In general, in this case, aliphatic mercaptan base and halogenated hydrocarbon base chain transfer agents are mainly used as chain transfer agents for industrial purposes. [0007] However, a polymer dispersion obtained in the presence of mercaptans has undesired specific odor even if the 35 remaining mercaptan content is small. When halogenated organic compounds (for example, carbon tetrachloride, bro- moform, bromotrichloromethane and the like) are used as a chain transfer agent, the content of the chain transfer agent remaining in the polymer dispersion is relatively much remained, so that problems on air pollution and toxicity are brought about. [0008] A principal object of the present invention is to produce a polymer of a low molecular weight having no or little 40 odor by an emulsion polymerization method. [0009] Intensive researches continued by the present inventors have resulted in finding that a polymer of a low molec- ular weight having no or little odor can readily be produced by emulsion-polymerizing a radical-polymerizable unsatu- rated monomer on a higher polymerization temperature condition than a polymerization temperature usually used for emulsion polymerization, and thus have come to complete the present invention. 45 Disclosure of Invention [0010] Thus, the present invention provides a polymer obtained by emulsion-polymerizing a radical-polymerizable unsaturated monomer in the presence or absence of a chain transfer agent, wherein the above polymer has a weight so average molecular weight falling in a range shown by the following equation (1): 3s|0g Mw<1. 50 - 1.18 x log (S + 0.001) (1) wherein 55 Mw represents the weight average molecular weight of the polymer, and S represents an equivalent number of a polyatomic radical part of the chain transfer agent bonded to the end of the polymer chain per 100 g of the polymer. 2 EP 0 931 795 A1 [001 1 ] Further, the present invention provides a production process for a polymer, characterized by emulsion-polym- erizing a radical-polymerizable unsaturated monomer at a temperature of 1 15°C or higher in the presence or absence of a chain transfer agent, wherein the polymer has a weight average molecular weight falling in a range shown by the following equation (2): 5 3§logMw<4.11 -0.93 x log (T + 0.1) (2) wherein 10 Mw represents the weight average molecular weight of the resulting polymer, and T represents parts by weight of the chain transfer agent used for the polymerization per 100 parts by weight of the unsaturated monomer. [001 2] The polymer and the production process according to the present invention shall be explained below in detail. 15 [001 3] The polymer of the present invention is produced by emulsion polymerization in the absence of a chain transfer agent or the presence of a small amount, though used, of the chain transfer agent, and it is characterized by having a low molecular weight and a small content of chain transfer agent fragments introduced into the polymer as compared with those of polymers produced by conventional emulsion polymerization methods. [0014] That is, the polymer of the present invention has a weight average molecular weight and a content of a polya- 20 tomic radical part of the chain transfer agent falling in a range in which a relation shown by the following inequality is set up between the weight average molecular weight (Mw) and an equivalent number (S; S = 0 when the chain transfer agent is not used in emulsion polymerization) per 1 00 g of the polymer, of a polyatomic radical part (hereinafter referred to as a chain transfer agent fragment) of the remaining chain transfer agent bonded to the end of the polymer chain as a result of emulsion polymerization: 25 3s|0g Mw<1. 50 - 1.18 x log (S + 0.001) (1) preferably 30 3.18s|0g Mw<1. 24- 1.18 x log (S + 0.001) (1-1) and more preferably 3.3§|0g Mw<1 .06 - 1 .18 x log (S + 0.001) (1 -2) 35 [0015] The chain transfer agent is splitted at a part where it is most easily cleaved in a chain transfer reaction and is turned into a monoatomic radical and a polyatomic radical which is composed of plural atoms, or two polyatomic radi- cals, wherein one of them is bonded to a polymer radical to terminate a chain propagation reaction, and the other becomes a starting point for a new chain propagation reaction to be bonded to a newly formed polymer. "S" used in the 40 inequality described above is an equivalent number per 100 g of the polymer, of ra polyatomic radical] bonded to the polymer as a result of such reaction. In general, it falls preferably in a range of 0 to 0.05, particularly 0 to 0.015 and above all, 0 to 0.005. [0016] For example, trichloromethane (CHCI3) is cleaved at a part of C-H in emulsion polymerization into a mono- atomic radical (H •) and a polyatomic radical (CCI3 •)■ When emulsion polymerization is carried out using as a chain 45 transfer agent, mercaptans (RCH2SH) or dimercaptans (RCH2S-SCH2R'), bromotrichloromethane (CCI3Br) or carbon tetrachloride (CCI4), or dichlorodibromomethane (CCI2Br2), polyatomic radical parts (chain transfer agent fragments) r introduced into the chain terminals of the resulting polymer are RCH2S • J , rCCI3 • J and rCCL2Br • j respectively. [001 7] An amount of the chain transfer agent fragments bonded to the chain terminals of the polymer of the present invention can be determined in the following manner. so [0018] First, a polymer dispersion is left for standing at -20°C through one night to be frozen and then molten at a room temperature. Further, the polymer is separated by means of a ultracentrifuge. The separated polymer is dissolved or swollen in a good solvent such as toluene and then precipitated again in a poor solvent such as methanol or water and washed.