Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-07-30
2003-07-22
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S445000, C524S446000, C524S503000, C525S062000, C418S087000, C418S087000, C418S087000, C418S087000
Reexamination Certificate
active
06596807
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing vinyl alcohol polymer compositions having excellent gas-barrier properties, in particular excellent gas-barrier properties under high-humidity conditions.
2. Discussion of the Background
Materials for packaging foods and other various items are often required to have good gas-barrier properties, in particular good oxygen gas-barrier property, in order to prevent the contents from being degraded by, for example, oxidation with oxygen or similar oxidants. Presence of oxygen causes microorganisms to proliferate and rot the contents, especially in packaged foods. Conventional packaging materials for foods are therefore provided with a gas-barrier layer to protect the contents against penetration of oxygen or the like.
Examples of a gas-barrier layer are metal foils and layers on which a metal or metal compound has been deposited. In general, aluminum foils and layers on which aluminum has been deposited are used for this purpose. However, use of these metals causes the contents to become invisible and the packaging materials to become difficult to dispose after use.
Vinyl alcohol polymers having good gas-barrier properties, such as polyvinyl alcohol and ethylene-vinyl alcohol copolymer are sometimes used as the gas-barrier layer. These vinyl alcohol polymers have the advantages of being transparent and causing fewer problems on disposal after use, so that they have been applied to wider range of uses.
These vinyl alcohol polymers show good gas-barrier properties because they crystallize due to hydrogen bonding of hydroxyl groups present in their molecules. They exhibit therefore good gas-barrier properties when they are dry. However, it is known that, when they have absorbed moisture such as water vapor present in the surrounding atmosphere, the hydrogen bonds are loosened. As a result, the vinyl alcohol polymers tend to exhibit poor gas-barrier properties. Thus, it is difficult to provide conventional vinyl alcohol polymers, such as polyvinyl alcohol, with satisfactory gas-barrier properties even under high-humidity conditions.
A method for decreasing the moisture-absorbing property of vinyl alcohol polymers comprises copolymerizing an olefin such as ethylene, yielding ethylene-vinyl alcohol copolymer. However, this kind of copolymerization, which decreases the content of vinyl alcohol units, tends to impair the inherent gas-barrier properties. Consequently, this method cannot produce vinyl alcohol polymers having good gas-barrier properties under both dry and high-humidity conditions.
In recent years, a process for preparing organic/ inorganic complexes comprising an organic polymer and a metal oxide dispersed relatively finely in the polymer has been proposed. This process comprises, making use of what is known as sol gel process, polycondensing a metal alkoxide such as a silicon alkoxide in the presence of an organic polymer. For example, in order to produce vinyl alcohol polymer-based materials possessing improved water resistance, Japanese Patent Nos. 2446940 and 2880654 disclose a composition obtained by a process which comprises hydrolyzing and polycondensing a tetraethoxysilane in the presence of polyvinyl alcohol and/or ethylene-vinyl alcohol copolymer and a silane-coupling agent. Japanese Patent Application Laid-open No. 278968/1997 discloses a composition obtained by hydrolyzing and polycondensing tetraethoxysilane in the presence of a silyl-modified vinyl alcohol polymer modified with a reactable silane compound such as triethoxychlorosilane. Japanese Patent Application Laid-open No. 1515/1998 discloses a silyl-modified vinyl alcohol polymer composition obtained by hydrolyzing with hydrochloric acid a copolymerized product of a polymerizable silane compound (e.g. vinyl trimethoxysilane) and a vinyl carboxylate (e.g. vinyl acetate).
According to the study performed by the present inventors, it has been found that with the compositions described in the above Japanese Patent Nos. 2446940 and 2880654, there occurs poor phase separation condition (i.e. increase in the size of phase separation), which is considered to be due to high crystallinity of the starting material vinyl alcohol polymer.
The compositions described in the above Japanese Patent Application Laid-open Nos. 278968/1997 and 1515/1998 have been found to be still insufficient in water resistance, although they have improved the condition of phase separation to some extent. This is attributable to non-uniformity in the positions of introduction of the modifying groups as caused by different reactivity of the hydroxyl groups present in the vinyl alcohol polymer and by poor copolymerizability of the polymerizable silane compound and vinyl carboxylate compound.
It has also been found as the results of the study performed by the present inventors, that the compositions described in Japanese Patent Nos. 2446940 and 2880654 and Japanese Patent Application Laid-open Nos. 278968/1997 and 1515/1998 give, when used as coating agents, solutions having poor stability and being unstorable for a long period of time. Such solutions tend to cause poor applicability, uneven coating and uneven and poor gas-barrier properties.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a process for producing vinyl alcohol polymer compositions having excellent gas-barrier properties, in particular excellent gas-barrier properties under high-humidity conditions.
Another object of the present invention is to provide a coating agent comprising an intermediate product in the above process, said intermediate product having excellent storage stability and being able to yield, according to the above process, vinyl alcohol compositions having excellent gas-barrier properties, in particular excellent gas-barrier properties at high humidities.
Still another object of the present invention is to provide a laminate obtained by applying the above coating agent, said laminate having minimal application unevenness.
Yet another object of the present invention is to provide a gas-barrier material comprising the above laminate as a component, said material having excellent gas-barrier properties, in particular excellent gas-barrier properties under high-humidity conditions.
As a result of an intensive study to solve the above problems, the present inventors found that above and other objects of the present invention can be achieved by providing a process which comprises saponifying a vinyl carboxylate polymer in the presence of a metal alkoxide and/or an oligomer derived from the metal alkoxide, to obtain a vinyl alcohol polymer composition, and then further adding to a solution containing the composition the same or other metal alkoxide and/or oligomer derived therefrom or solutions containing these and removing the solvent, to obtain the desired vinyl alcohol polymer composition. The present invention was completed based on this finding.
The present invention thus provides a process for producing a vinyl alcohol polymer composition, comprising:
providing a reaction liquid comprising a solution containing a vinyl carboxylate polymer and, a first metal alkoxide (I) having at least one functional group and/or an oligomer (I) having at least one functional group obtained from said metal alkoxide (I);
a step of simultaneously effecting (a) saponification of said vinyl carboxylate polymer and (b) reaction in which at least part of the functional groups of said metal alkoxide (I) and/or said oligomer (I) participates, thereby obtaining a vinyl alcohol polymer composition (I); and
a step of preparing a solution (A) containing said vinyl alcohol polymer composition (I), followed by adding to the solution (A) a second metal alkoxide (II) and/or an oligomer (II) obtained from the metal alkoxide (II) or another solution (B) containing the metal alkoxide (II) and/or the oligomer (II) derived from the metal alkoxide (II), to prepare an intermediate product solution (C), and then removing the solvent from said solution (C)
Ito Kanenori
Kanao Syuichi
Kawakami Naoki
Komiya Yukiatsu
Oshita Tatsuya
Kuraray Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pezzuto Helen L.
LandOfFree
Process for producing vinyl alcohol polymer compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing vinyl alcohol polymer compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing vinyl alcohol polymer compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3108183