Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-04-12
2002-08-06
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S327400, C525S329100, C525S329400, C525S329500, C525S329700, C525S330300, C525S366000, C525S367000, C526S317100
Reexamination Certificate
active
06429265
ABSTRACT:
1. BACKGROUND FIELD OF THE INVENTION
The present invention relates to a moisture-absorbing and desorbing polymer having high moisture-absorbing and desorbing properties and particularly having high moisture-absorbing and desorbing rates and also relates to compositions containing the same.
2. DESCRIPTION OF THE RELATED ART
With regard to a means for removing moisture in air, moisture absorbents such as lithium chloride, calcium chloride, magnesium chloride and phosphorus pentaoxide have been used. However, although such moisture absorbents have much moisture absorbing capacity and quick moisture absorbing rate, they are deliquescent and, therefore, there are disadvantages that they are liquefied after absorption of moisture and soil other substance, apt to be dissolved and difficult for their regeneration. Although other moisture absorbents such as silica gel, zeolite, sodium sulfate, active alumina and active carbon do not have such a problem, they have disadvantages that their moisture absorbing capacity is low, their moisture absorbing rate is slow, their regeneration require a high temperature and their repeated absorption and desorption of moisture result in pulverization which are causes that their practical use is disturbed.
On the other hand, with regard to moisture absorbents of an organic type, ultra water-absorbing resins represented by that of a polyacrylate type may be utilized as a moisture absorbent. However, in the case of such ultra water-absorbing resins, their water-absorbing property is very good but their moisture-absorbing property is not satisfactory. The specific problems are that their retention of water is so high that desorption of moisture hardly occurs, an equilibrium moisture absorption capacity at low humidity is low, they become tacky with absorption of moisture and their moisture absorbing rate is slow. With regard to the poor moisture desorption and problems at low temperature and of tackiness, solutions thereof have been attempted in the Japanese Laid-Open Patent Hei-05/132,858 by the proposal of highly moisture-absorbing and desorbing fiber consisting of organic polymer and in the Japanese Laid-Open Patent Hei-08/225,610 by the proposal of organic moisture-absorbing and desorbing fine particles. However, slow moisture-absorbing and desorbing rates have been still pointed out as a problem.
With regard to the moisture-absorbing rate, there is a proposal, for example, in the Japanese Laid-Open Patent Hei-05/105,704for a method where polyacrylate and deliquescent inorganic salt are jointly used. It is mentioned there that, according to the said method, moisture-absorbing and desorbing properties at low humidity are improved whereby a product having a high moisture-absorbing property without dropping of water can be obtained. However, the time necessary for moisture absorption is in a level of hours (in the Examples, a significant increase in moisture absorption is noted during ten hours) and such a method is not satisfactory for the use requiring the moisture absorbing rate in the level of minutes or even seconds such as a rotary dehumidifier.
Such a moisture-absorbing rate is described in
Kogyo Zairyo,
volume 29, no. 8, page 18 where it is pointed out that highly hydrophilic polymers such as a high water-absorbing resin usually have slow moisture-absorbing rate. The reason therefor is mentioned that, because of an interaction among polar groups in the polymer, molecular movement of the polymer itself is suppressed whereby diffusion of water hardly takes place. It is also described that, with regard to a highly equilibrium moisture-absorbing amount at high humidity, the said interaction is gradually lost as the absorption of moisture proceeds whereby plasticization progresses and diffusion of water is apt to occur and, as a result, a relatively highly equilibrium moisture-absorbing amount is resulted at last.
PROBLEMS TO BE SOLVED BY THE INVENTION
An object of the present invention is to offer a polymer having high moisture-absorbing and desorbing properties and being able to express such moisture-absorbing and desorbing properties within a short period or, in other words, a polymer having moisture-absorbing and desorbing rates and also to offer compositions containing the said polymer. The present inventor has carried out an intensive study concentrating to moisture-absorbing and desorbing properties or, especially, moisture-absorbing and desorbing rates of moisture-absorbing and desorbing materials. As a result, he has found that the type of the salt of a carboxyl group greatly affects the moisture-absorbing and desorbing rates and has been able to prepare an organic polymer having high moisture-absorbing and desorbing properties and exhibiting excellent moisture-absorbing and desorbing rates which have not been available up to now whereupon the present invention has been accomplished.
SUMMARY OF THE INVENTION
The above-mentioned object of the present invention can be achieved by a moisture-absorbing and desorbing polymer which is characterized in that the said polymer is an organic high-molecular substance containing 1.0-8.0 meq/g of carboxyl group of a potassium salt type and having a cross-linking structure. Such a moisture-absorbing and desorbing polymer may be in any of the forms of fiber, particles and sheets and compositions containing the said polymer is useful where the rate of absorption and desorption of moisture is requested. As hereinafter, the present invention will be illustrated in detail.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First, it is necessary that the moisture-absorbing and desorbing polymer of the present invention contains 1.0-8.0 meq/g of carboxyl group of a potassium salt type and having a cross-linking structure. The highlight of the present invention and the key for achieving the excellent moisture-absorbing rate are that the carboxyl group is in a potassium salt type. Probably due to the fact that potassium is a commonly used alkaline metal, carboxyl group of a potassium type has been described by means of exemplification in the patents up to now including the known patents intended to give a high moisture-absorbing amount. However, that which has been described is merely exemplification and there has been no patent in which the relation between moisture-absorbing rate and the salt type of carboxyl group is specifically reported.
The present inventor has studied the relation between the moisture-absorbing and desorbing rates and the salt type of carboxyl group. In the literatures up to now, moisture-absorbing and desorbing properties at the equilibrium stage have been mostly discussed. Even in a few cases where moisture-absorbing and desorbing rates are discussed, the discussion is in a level of around ten minutes at the shortest and there has been no discussion in the level of one or two minutes or of seconds. The reason is due to the difficulty in a quantitative determination of the moisture-absorbing and desorbing rates of moisture-absorbing and desorbing materials. Thus, in the measurement of moisture-absorbing and desorbing rates of moisture-absorbing and desorbing material per se within a short period of time, the moisture-absorbing and desorbing rates are greatly affected by various factors such as form and shape of the moisture-absorbing and desorbing materials, measuring method, measuring conditions and measuring apparatus whereby a correct measurement is not possible. Against such a problem, the present inventor has succeeded in making a moisture-absorbing and desorbing material into a sheet on which the material is thinly and uniformly applied whereby it is subjected to a corrugate process to evaluate under a predetermined condition to overcome the problem whereupon a quantitative measurement of moisture-absorbing and desorbing rates within a short period of time has been made possible.
When the exchanging capacity of carboxyl group is same, the order of equilibrium moisture-absorbing amount per unit weight is sodium salt>potassium salt=lithium salt>rubidium salt>cesium salt but it
Japan Exlan Company Limited
Wenderoth , Lind & Ponack, L.L.P.
Zitomer Fred
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