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
2001-05-15
2003-12-02
Reddick, Judy M. (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...
C525S056000, C525S059000, C525S060000
Reexamination Certificate
active
06657004
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a film for packaging chemical agents, which film comprising an oxyalkylene-containing polyvinyl alcohol resin (hereinafter sometimes to be abbreviated as EO-PVA) and a carboxyl-containing polyvinyl alcohol resin (hereinafter sometimes to be abbreviated as C-PVA).
BACKGROUND OF THE INVENTION
It has been conventionally proposed to divide (unit package) chemical agents, such as agricultural chemicals, detergents and the like, by placing them in bags made of a polyvinyl alcohol (hereinafter sometimes to be abbreviated as PVA) resin film, because PVA has water-soluble property.
However, a long-term storage of a chemical agent and the like in a bag made of a PVA film sometimes results in a failure to retain the water-soluble property inherent to PVA, thus leading to decreased solubility of the PVA film.
To prevent this, for example, the use of a sulfo-containing modified PVA film (JP-A-9-272774) and addition of a reducing agent and the like to a PVA film (JP-A-9-316270) have been proposed.
The inventor of this application has also proposed a film for packaging an alkaline substance, which film is made from PVA containing at least one of oxyalkylene, sulfo and cation (JP-A-63-168437).
However, there is a possibility of degraded film strength of the modified PVA film described in the above-mentioned JP-A-9-272774 when it is used to package an acidic substance having a low pH. Furthermore, because the modified PVA film described in JP-A-9-316270 contains a reducing agent and other additives, as mentioned above, these additives may exert an adverse influence on the chemical agent to be packaged, and the reducing agent may elute out when the film is dissolved, often causing disadvantages. Moreover, a film for packaging an alkaline substance, which is described in JP-A-63-168437, does not have a sufficient mechanical strength. Thus, there is a demand for the development of a film for packaging chemical agents, which is free of these problems.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a film for packaging chemical agents, which is superior in water-soluble property and impact strength, and which is free of degradation of the water-soluble property even after a long-term storage of the chemical agent.
Such object can be achieved by the present invention described in the following.
Accordingly, the present invention provides the following.
(1) A film for packaging chemical agents, which comprises EO-PVA (A) and C-PVA (B).
(2) The film for packaging chemical agents of (1) above, wherein the EO-PVA (A) comprises an oxyalkylene unit in a proportion of 1-10 mol %, and the C-PVA (B) comprises carboxyl in a proportion of 1-10 mol %.
(3) The film for packaging chemical agents of (1) or (2) above, wherein the EO-PVA (A) and the C-PVA (B) are comprised in a weight ratio (A/B) of 50/50-80/20.
(4) The film for packaging chemical agents of (1) or (2) above, wherein the EO-PVA (A) and the C-PVA (B) are comprised in a weight ratio (A/B) of 60/40-80/20.
(5) The film for packaging chemical agents of (1) above, which further comprises S-PVA (C).
(6) The film for packaging chemical agents of (5) above, wherein the S-PVA (C) comprises sulfo in a proportion of 1-10 mol %.
(7) The film for packaging chemical agents of (5) or (6) above, wherein the S-PVA (C) is comprised in a proportion of 10-30 parts by weight per 100 parts by weight of the EO-PVA (A) and the C-PVA (B) in total.
(8) The film for packaging chemical agents of any of (1), (2), (5) and (6) above, which is used for packaging a chemical agent that shows a pH of not more than 5 or not less than 9, when dissolved or dispersed in water.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is hereinafter explained by referring to the structural formulas and the like. In the numerous structural formulas recited in this specification, the numbers of moles n and m of repeating units in each structural formula do not mean the same in a different structural formula.
The EO-PVA (A) to be used in the present invention contains an oxyalkylene unit, which is specifically a PVA containing a group of the following formula (1):
In the above formula, R
1
and R
2
are each hydrogen or alkyl. The alkyl preferably has 1 to 6, particularly preferably 1 to 3, carbon atoms. Examples thereof include methyl, ethyl, isopropyl and the like.
X is an organic residue such as hydrogen, alkyl, acyl, alkylcarbonylamino, sulfonate (—SO
3
Na etc.) and the like.
The “n” (number of moles of oxyalkylene) is a positive integer. The “n” in the above formula (1) is not particularly limited, but is preferably 3-20, more preferably 4-19, particularly 5-18. When n is less than 3, the solubility (water-soluble property) tends to decrease, whereas when it exceeds 20, the film tends to show lower mechanical strength.
As the above-mentioned oxyalkylene, polyoxyethylene, polyoxypropylene, polyoxybutylene and the like are preferable.
EO-PVA can be produced by an optional method. For example, 1) vinyl ester compound is polymerized in the presence of polyoxyalkylene, which is followed by saponification, 2) unsaturated monomer having an oxyalkylene unit and vinyl ester compound are copolymerized, which is followed by saponification, and the like. The method 2) is practical from the aspects of production and properties of the resin.
The method 2) is explained in detail in the following.
Examples of unsaturated monomer having an oxyalkylene unit are as follows, to which the present invention is not limited.
[(meth)acrylic Acid Ester Type]
wherein R
1
and R
2
are as defined with regard to the formula (1), R
3
is hydrogen or methyl, A is alkylene, substituted alkylene, phenylene or substituted phenylene, m is an integer of not less than 0 and n is a positive integer, which is preferably 3 to 20. Specific examples include polyoxyethylene (meth)acrylate, polyoxypropylene (meth)acrylate and the like.
[(meth)acrylamide Type]
wherein R
1
, R
2
, R
3
, A, n and m are as defined with regard to the formula (2), and R
4
is hydrogen, alkyl or a group of the following formula (4):
wherein R
1
, R
2
and n are as defined with regard to the formula (2). Examples of such (meth)acrylamide type compound include polyoxyethylene (meth)acrylamide, polyoxypropylene (meth)acrylamide, polyoxyethylene (1-(meth)acrylamide-1,1-dimethylpropyl) ester and the like.
[(meth)allyl Alcohol Type]
wherein R
1
, R
2
, R
3
and n are as defined with regard to the formula (2). Examples of such (meth)allyl alcohol type compound include polyoxyethylene (meth)allyl ether, polyoxypropylene (meth)allyl ether and the like.
[Vinyl Ether Type]
wherein R
1
, R
2
, A, n and m are as defined with regard to the formula (2). Examples of such compound include polyoxypropylene vinyl ether and the like.
Of the above-mentioned unsaturated monomers having an oxyalkylene unit, preferred is a (meth)allyl alcohol type compound.
EO-PVA can be also obtained by copolymerizing polyoxyalkylene allylamine (e.g., polyoxyethylene allylamine, polyoxypropylene allylamine etc.), polyoxyalkylene vinylamine (e.g., polyoxyethylene vinylamine, polyoxypropylene vinylamine etc.), and the like with a vinyl ester compound, which is followed by saponification.
Examples of vinyl ester compound include vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versate, vinyl palmitate, vinyl stearate and the like, which can be used alone or in combination. From the practical viewpoint, vinyl acetate is preferably used.
In the context of the present invention, typical monomers other than the aforementioned unsaturated monomer having an oxyalkylene unit and vinyl ester compound may be added during polymerization to the extent that the water-soluble property is not impaired. Examples of such monomers are as follows.
[Ethylenically Unsaturated Carboxylic Acid, its Alkyl Ester and the Like]
methyl crotonate, ethyl crotonate, methyl itaconate, ethyl itaco
Leydig, Voit & Meyer Ltd.
Reddick Judy M.
The Nippon Synthetic Chemical Industry Co., Ltd.
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