Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-04-06
2001-03-06
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S307200, C526S318300, C526S320000, C526S321000, C526S328000, C526S346000
Reexamination Certificate
active
06197907
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is the national phase of International PCT application PCT/JP96/02941, filed Oct. 11, 1996.
TECHNICAL FIELD
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 polymerization method and a production process for the same.
BACKGROUND ART
The size of a molecular weight of a polymer exerts a strong influence on the chemical properties and the physical properties of the polymer.
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 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.
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 materials for hot melt type coating agents, coating resin-modifying agents having good penetrability and wetting property 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 dispersants, water-treating agents in boilers, cooling tower, reverse osmosis treatment, sugar refining, paper making, geothermal treatment, oil wells and the like, and detergent additives acting as builders, film-forming preventives, sequestering agents and adhesion-inhibiting agents.
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 controlled and the resulting polymers are easy to handle.
Usually, when polymers having a low molecular weight are obtained by emulsion polymerization, the polymerization 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.
However, a polymer dispersion obtained in the presence of mercaptans has undesired specific odor even if the remaining mercaptan content is small. When halogenated organic compounds (for example, carbon tetrachloride, bromoform, 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.
A principal object of the present invention is to produce a polymer of a low molecular weight having no or little odor by an emulsion polymerization method.
Intensive researches continued by the present inventors have resulted in finding that a polymer of a low molecular weight having no or little odor can readily be produced by emulsion-polymerizing a radical-polymerizable unsaturated 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.
DISCLOSURE OF INVENTION
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 average molecular weight falling in a range shown by the following equation (1):
3≦log Mw<1.50−1.18×log (S+0.001) (1)
wherein
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.
Further, the present invention provides a production process for a polymer, characterized by emulsion-polymerizing a radical-polymerizable unsaturated monomer at a temperature of 115° 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):
3≦log Mw<4.11−0.93×log (T+0.1) (2)
wherein
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.
The polymer and the production process according to the present invention shall be explained below in detail.
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.
That is, the polymer of the present invention has a weight average molecular weight and a content of a polyatomic 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 100 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:
3≦log Mw<1.50−1.18×log (S+0.001) (1)
preferably
3.18≦log Mw<1.24−1.18×log (S+0.001) (1-1)
and more preferably
3.3≦log Mw<1.06−1.18×log (S+0.001) (1-2)
The chain transfer agent is split 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 radicals, 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 inequality described above is an equivalent number per 100 g of the polymer, of ┌a 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.
For example, trichloromethane (CHCl
3
) is cleaved at a part of C—H in emulsion polymerization into a monoatomic radical (H.) and a polyatomic radical (CCl
3
.). When emulsion polymerization is carried out using as a chain transfer agent, mercaptans (RCH
2
SH) or dimercaptans (RCH
2
S—SCH
2
R′), bromotrichloromethane (CCl
3
Br) or carbon tetrachloride (CCl
4
), or dichlorodibromomethane (CCl
2
Br
2
), polyatomic radical parts (chain transfer agent fragments) introduced into the chain terminals of the resulting polymer are ┌RCH
2
S.┘, ┌CCl
3
.┘ and ┌CCl
2
Br.┘ respectively.
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.
First, a polymer dispersion is allowed to stand overnight −20° C. to be frozen and then molten at a room temperature. Furthe
Masuda Hiroshi
Ogawa Manabu
Serizawa Hiroshi
Yoshida Eiichi
Nippon Carbide Kogyo Kabushiki Kaisha
Pezzuto Helen L.
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