Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-05-06
2001-02-13
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C127S030000, C127S046100, C127S053000, C127S061000, C536S120000, C536S124000, C516S077000, C516S099000, C516S902000, C424S484000
Reexamination Certificate
active
06187842
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a novel useful sugar compound, a process for preparing the sugar compound, an organic gelling agent containing the sugar compound, a heat-reversible gel prepared using the organic gelling agent, a process for preparing the gel and its use.
The present invention also concerns with a novel useful gelling agent composition which can be used for an aqueous medium, a process for preparing the gelling agent composition, and a gel composition prepared using the gelling agent composition.
The term “gel” used herein refers, from the viewpoint of industrial meaning, to a state of a substance wherein the substance is non-flowable and has a yield value of at least 60 g/cm
2
although it contains a large amount of a medium, or to a substance in such state. Further, the term “gelling agent composition” is used herein to mean a composition capable of gelling a medium when dissolved or dispersed in the medium. The term “gel composition” used herein means a gel comprising at least a gelling agent composition and a medium as constituent elements.
BACKGROUND ART
Dibenzylidene sorbitol derivatives or dibenzylidene xylitol derivatives even used in a small amount can gel a wide range of organic solvents or polymers (Kobayashi et al Journal of Japan Rheology Society, vol. 17, p.104 (1989) and Kobayashi et al, Journal of Japan Rheology Society, vol. 17, p.112 (1989)). These derivatives are used in a wide variety of applications, chiefly as solid marking agents, solid adhesives, effluent oil gelling agents, sol-gel transition type clarifying nucleating agents for polyolefins and so on. However, said derivatives are sparingly dissolved in water and can not be used as a gelling agent alone for water.
Various high molecular weight gelling agents useful in forming a heat-reversible water-containing gel are known and include non-electrolytic polymers such as natural high molecular weight starch or cellulose derivatives, electrolytic polymers such as alginic acid, agar and carrageenan, and protein-containing polymers such as gelatin, collagen and casein. Synthetic polymers such as copolymers of poval and sodium polyacrylate, semi-synthetic polymers such as starch-acrylic acid graft polymers, and the like are widely used as a water-absorbing polymer in the manufacture of paper diapers. However, natural materials have a drawback of decomposing. The gel-forming ability of electrolytic polymers is seriously affected by a salt and is markedly impaired in the presence of a salt. These polymers pose a problem of operational efficiency because they are dissolved in water usually at a low rate and a sol system is given an elevated viscosity.
Sericin, which is expensive and a specific species of amino acid, has an ability to gel water, but its gelling ability is markedly affected by the acidity of a system. Further, sericin involves a problem in terms of preservation. For these reasons, sericin has not been put to practical use.
When an aqueous medium is gelled using a conventional low molecular weight gelling agent, typically a dibenzylidene sorbitol derivative, an organic solvent is essentially used in combination.
In the above situation, there is an earnest desire for neutral low molecular weight organic gelling agents free from said defects, namely, those which can be stored without decomposition, do not adversely affect the environment, show high efficiency in a gel-forming process from a stage of sol formed on dissolution and are not affected by the presence of an inorganic salt.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a novel useful low molecular weight organic gelling agent which is usable for gelling an aqueous medium.
Another object of the invention is to provide a gelling agent composition capable of easily gelling an aqueous medium even in the environment wherein a heat source can not be used.
In view of the foregoing situation, the inventors conducted extensive research on the aqueous medium-gelling properties of various low molecular weight organic compounds, and found that a sugar compound having a specific structure which is undisclosed in literature has a remarkable ability to specifically gel an aqueous medium. A further finding was that the organic gelling agent containing the sugar compound is a neutral low molecular weight organic gelling agent which not only has a gelling ability insusceptible to influence from the presence of an inorganic salt in a system but also can be stored without decomposition, and is unlikely to adversely affect the environment and capable of achieving a gel-forming process with high efficiency without elevation of viscosity in a sol stage. The present invention was completed based on these novel findings.
The sugar compound of the present invention is characterized by being represented by the formula (1) or the formula (2)
wherein R
1
and R
2
are the same or different and each represents an alkyl group having 1 to 3 carbon atoms, an alkoxyl group having 1 to 3 carbon atoms or a halogen atom, and p is 0 or 1.
The present inventors conducted extensive research on the aqueous medium-gelling properties of various low molecular weight organic compounds, and found that a composition of specific formula comprising a sugar compound of specific structure and a dispersant can form a gel when dissolved in an aqueous medium with heating and cooled, and also can easily form a gel approximately at room temperature without heating. Based on this novel finding, the present invention was accomplished.
The gelling agent composition of the invention comprises 100 parts by weight of at least one sugar compound selected from the group consisting of sugar compounds represented by the formula (1) and sugar compounds represented by the formula (2), and 1 to 1000 parts by weight of at least one dispersant selected from the group consisting of nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants and hydrophilic organic solvents
wherein R
1
and R
2
are the same or different and each represents an alkyl group having 1 to 3 carbon atoms, an alkoxyl group having 1 to 3 carbon atoms or a halogen atom, and p is 0 or 1.
Examples of the sugar compounds of the formula (1) or the formula (2) are mono(3-chloro-4-methylbenzylidene)-D-sorbitol, mono(3,4-dimethoxybenzylidene)-D-sorbitol, mono(3-ethyl-4-methylbenzylidene)-D-sorbitol, mono(3-methyl-4-ethylbenzylidene)-D-sorbitol, mono(3-propyl-4-methylbenzylidene)-D-sorbitol, mono(3,4-diethylbenzylidene)-D-sorbitol, mono(3,4-dichlorobenzylidene)-D-sorbitol, mono(3,4-dimethylbenzylidene)-D-sorbitol, mono(3,4-dipropylbenzylidene)-D-sorbitol, mono(3,4-diethoxybenzylidene)-D-sorbitol, mono(3,4-diisopropoxybenzylidene)-D-sorbitol and like sorbitol derivatives; and mono(3-ethyl-4-methylbenzylidene)-xylitol, mono(3-methyl-4-ethylbenzylidene)-xylitol, mono(3-propyl-4-methylbenzylidene)-xylitol, mono(3,4-diethylbenzylidene)-xylitol, mono(3,4-dichlorobenzylidene)-xylitol, mono(3,4-dimethylbenzylidene)-xylitol, mono(3,4-dipropylbenzylidene)-xylitol, mono(3-chloro-4-methylbenzylidene)-xylitol, mono(3,4-dimethoxybenzylidene)-D-xylitol and like xylitol derivatives.
The sugar compounds of the present invention can be prepared by the following process.
A process for preparing the contemplated sugar compound comprises the step of subjecting a sugar alcohol (A) and a benzaldehyde derivative (B) to dehydration condensation in water or in an organic solvent, said sugar alcohol (A) being at least one member selected from the group consisting of sorbitols and xylitols, and said benzaldehyde derivative (B) being at least one member selected from the group consisting of 3,4-disubstituted benzaldehyde represented by the formula (3) and dialkyl ether of 3,4-disubstituted benzaldehyde represented by the formula (4), the molar ratio (A/B) of the sugar alcohol (A) to the benzaldehyde derivative (B) being 2/1 to 1/2, thereby producing the contemplated sugar compound at a high reactivity and a high selectivity:
wherein R
1
and R
2
are the same or different
Ando Kenshi
Kobayashi Toshi-aki
Nomoto Harutomo
Larson & Taylor PLC
New Japan Chemical Co. Ltd.
Nutter Nathan M.
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