Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2003-01-03
2004-09-28
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S065000
Reexamination Certificate
active
06797735
ABSTRACT:
TECHNICAL FIELD
This invention, in the production of a porous polymer having open cells form open pores extending from the surface through the interior thereof by polymerizing a water-in-oil type high internal phase emulsion (hereinafter occasionally abbreviated as “HIPE”), relates to a method for producing the porous polymer by curing the HIPE in a very short period of time. More particularly, this invention relates to a method for the production of a porous polymer having open cells and proving to be useful in a wide range of applications including (1) liquid absorbing materials such as, for example, (a) absorbing materials for such humoral fluids as urine and blood, typified by cores in disposable diapers and (b) absorbing materials for water, oil, and organic solvents, typified by agents for disposing of waste water, waste oil, and waste solvent, (2) energy absorbing materials such as, for example, absorbing materials for sound and heat, typified by sound insulators and heat insulators, and (3) bases for impregnation with pharmaceutical preparations such as, for example, household articles impregnated with aromatic agents, cleaning agents, lustering agents, surface protecting agents, and flame retardants.
BACKGROUND ART
The term HIPE refers to an emulsion having a water phase which is a disperse phase (inner phase) and an oil phase which is an outer phase at a ratio (W/O ratio) of not less than about 3/1. It has been known to produce a porous polymer by polymerizing this HIPE. While a porous polymer which is produced by using a foaming agent without involving conversion into an HIPE (hereinafter occasionally referred to briefly as “foam”) is liable to afford a foam made up of discrete cells of a relatively large pore diameter, the method for producing a porous polymer from the HIPE (hereinafter occasionally referred to briefly as “HIPE method”) is an excellent process for the production of a foam of low density made up of open cells of a minute pore diameter.
Methods proposed with the object of producing porous polymers from an HIPE have been disclosed in JP-A-57-98713, JP-A-62-50002, U.S. Pat. No. 5,252,619, and U.S. Pat. No. 5,189,070, for example.
JP-A-57-98713 and JP-62-50002 disclose a method which comprises preparing an HIPE containing a water-soluble and/or an oil-soluble polymerization initiator and thermally polymerizing this HIPE at 50° C. or 60° C. for a period of from 8 hours through 72 hours. U.S. Pat. No. 5,210,104 discloses a method which comprises preparing an HIPE and subsequently adding a polymerization initiator thereto, U.S. Pat. No. 5,252,619 discloses a method which comprises preparing an HIPE containing a polymerization initiator and then polymerizing the HIPE at a temperature of not lower than 90° C., and U.S. Pat. No. 5,189,070 discloses a method which comprises forming a gel possessing a prescribed dynamic shear modulus from an emulsion at a temperature of 20° —less than 65° C. and then polymerizing this gel at a temperature of not lower than 70° C.
The methods which are disclosed in JP-A-57-98713 and JP-62-50002, however, require unduly long times for polymerization and suffer from unsatisfactory efficiency of production. While the methods of U.S. Pat. No. 5,252,619 and U.S. Pat. No. 5,189,070 are capable of completing polymerization in comparatively short periods of time when the temperatures used are high, they still require unduly long times approximating several hours for polymerization and, depending on conditions, impair the stability of a relevant HIPE, tend to entail liberation of a large quantity of water, and eventually fail to obtain a porous polymer of a prescribed pore diameter. The method of U.S. Pat. No. 5,210,104 is described to require several hours as the time for polymerization, though it is capable of improving the stability of the emulsification of an HIPE owing to the addition of a polymerization initiator subsequently to the preparation of the HIPE.
We have taken notice of the time required for the polymerization of an HIPE, pursued a study in search of a method for producing a porous polymer by polymerizing (curing) an HIPE in a very short period of time, perfected a procedure for fulfilling this method, and filed the invention covering this method for patent (Japanese Patent Application No. 290141/1999). Though this procedure has been confirmed to improve markedly the factor of the time for polymerization and enhance the productivity, it has betrayed the possibility of varying the particle diameter of an emulsion and the distribution thereof depending on the kind of emulsion and the conditions of polymerization during the change of the temperature of the emulsion particularly at a specific rate of temperature increase and consequently inducing fine variation in the particle diameter of the produced foam and preventing the form from manifesting expected foam properties.
The object of this invention, therefore, comprises solving such a technical problem as implied above and providing a method for the production of a porous polymer which can produce the porous polymer with further exalted foam properties such as, for example, the absorption properties of foam in a very short period of time such as, for example, not more than 30 minutes and preferably not more than 20 minutes.
DISCLOSURE OF THE INVENTION
We, as a result of performing a diligent study with a view to developing a method for producing a porous polymer from an HIPE in a very short period of time, have discovered that a porous polymer excelling in foam properties can be produced preferably continuously in a very short period of time such as, for example, not more than 30 minutes and preferably not more than 10 minutes in the method for the production of a porous polymer which comprises (a) an emulsifying step for producing an HIPE, (b) a shaping step for imparting a prescribed shape to the HIPE, and (c) a polymerizing step for polymerizing the formed HIPE, by heeding changes of temperature of the HIPE during the component steps (a)-(c) of the process mentioned above and controlling the temperature of the emulsion so as not to produce a change exceeding 10° C. in the intervals between the component steps of the process or in the method for the production of a porous polymer which comprises (a) an emulsifying step for preparing an HIPE, (b) a shaping step for imparting a shape to the HIPE, and (c) a polymerizing step for polymerizing this HIPE, by controlling the temperatures in the component steps of the process mentioned above so as to remain in respectively specified ranges. This invention has been consequently perfected.
The object mentioned above is accomplished by the following items (1)-(7).
(1) A method for the production of a porous polymer by the polymerization of a water-in-oil type high internal phase emulsion obtained from an oil phase containing a polymerizing monomer component and a surfactant and a water phase containing water, which method is characterized by comprising (a) an emulsifying step for forming a water-in-oil type high internal phase emulsion, (b) a shaping step for shaping the emulsion in the form of a sheet or a film, and (c) a polymerizing step for polymerizing the emulsion and having the temperatures during the component steps mentioned above so controlled as to produce no change exceeding 10° C.
(2) A method for the production of a porous polymer by the polymerization of a water-in-oil type high internal phase emulsion obtained from an oil phase containing a polymerizing monomer component and a surfactant and a water phase containing water, which method is characterized by comprising (a) a continuous emulsifying step for continuously forming a water-in-oil type high internal phase emulsion, (b) a continuous shaping step for continuously shaping the emulsion in the form of a sheet or a film, and (c) a continuous polymerizing step for continuously polymerizing the emulsion and having the temperatures during the component steps mentioned above so controlled as to produce no change exceeding 10° C.
(3) A method for the production of a p
Fujimaru Hirotama
Kadonaga Kenji
Minami Kenji
Nagasuna Kinya
Nogi Kozo
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