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
2002-07-17
2003-12-16
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...
C524S503000, C525S056000, C525S059000
Reexamination Certificate
active
06664332
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a resin composition for recording papers or sheets to be printed by ink jet method, offset printing method, flexographic printing method, heat-sensitive recording method and the like. More particularly, the present invention relates to a resin composition suitable for forming an ink receptive layer of recording papers or sheets, which has excellent printability such as ink receptivity, feathering prevention, gloss and weatherability.
Heretofore, for the purpose of improving the printability of recording sheets for ink jet printing, offset printing, flexographic printing, heat-sensitive recording or the like, it has been tried to provide a particular coating layer (ink receptive layer) on the surface of the sheet substrates.
For example, (1) JP-A-61-10483 discloses using a cation-modified polyvinyl alcohol in the coating layer for the purpose of improving ink receptivity and sharpness of recorded images; (2) JP-A-10-309780 discloses using an alkyleneoxide-modified polyvinyl alcohol resin in the coating layer for the purpose of improving ink absorption, water resistance, resolution of images and blocking resistance; and (3) JP-A-2001-121814 discloses using a composition comprising an acrylic copolymer having a crosslinkable group and a polyvinyl alcohol resin for forming the coating layer for the purpose of improving uniformity and sharpness of images, and water resistance.
However, as a result of detail review of these publications, it has been found that further improvement in gloss and weatherability is desired in proposal (1), that feathering may occur in the coating layer to deteriorate the image stability in proposal (2), and that further improvement in gloss and weatherability is desired in proposal (3). Accordingly, there is a demand for a coating resin composition excellent in all of ink receptivity, feathering prevention property, gloss and weatherability.
An object of the present invention is to provide a resin composition for recording sheets, which has excellent printability in respect of ink receptivity, feathering prevention property, gloss, weatherability and the like.
A further object of the present invention is to provide a resin composition suitable for production of recording sheets for ink jet printing, offset printing, flexographic printing, heat-sensitive recording or the like, and applicable to not only paper substrate but also plastic substrates to form the ink receptive layer thereon.
Another object of the present invention is to provide a recording sheet having excellent ink receptivity, feathering prevention property, gloss, weatherability or the like.
These and other objects of the present invention will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
It has now been found that recording sheets having excellent properties such as ink receptivity, feathering prevention property, gloss and weatherability can be obtained when an ink receptive layer is formed on recording sheet substrates from a coating composition prepared by using an oxyalkylene group-containing polyvinyl alcohol resin (A) and a cationic group-containing polyvinyl alcohol resin (B) in combination so that a solution of a mixture of the resins (A) and (B) dissolved in water in a concentration of 15% by weight has a transparency of at least 50% measured according to JIS K 6726.
Thus, in accordance with the present invention, there is provided a resin composition for recording sheets, comprising (A) a polyvinyl alcohol resin containing oxyalkylene groups and (B) a polyvinyl alcohol resin containing cationic groups, wherein a 15% by weight aqueous solution of the mixture of said resin (A) and said resin (B) has a transparency of not less than 50% measured according to JIS K 6726.
DETAILED DESCRIPTION
The oxyalkylene group-containing polyvinyl alcohol resin (A) used in the present invention includes polyvinyl alcohol resins containing an oxyalkylene group of the formula (1):
wherein R
1
and R
2
are a hydrogen atom or an alkyl group (particularly methyl group or ethyl group), R
3
is a hydrogen atom, an alkyl group or an alkylamide group, and n is a positive integer.
The oxyalkylene group-containing polyvinyl alcohol resin (A) can be obtained, for instance, by copolymerizing a vinyl ester compound with an unsaturated monomer having oxyalkylene group (1) and hydrolyzing the resulting copolymer.
The unsaturated monomers having oxyalkylene group (1) include, for instance, the following compounds, but are not limited thereto in the present invention.
(Meth)acrylic Acid Esters
There are mentioned monomers of the following formula (2), examples of which are polyoxyethylene (meth)acrylate, polyoxypropylene (meth)acrylate and the like:
wherein R is a hydrogen atom or a methyl group, R
1
and R
2
are independently a hydrogen atom or an alkyl group, R
3
is a hydrogen atom, an alkyl group or an alkylamide group, A is an alkylene group, a substituted alkylene group, a phenylene group or a substituted phenylene group, m is 0 or an integer of not less than 1, n is an integer of 1 to 100.
(Meth)acrylamides
There are mentioned monomers of the following formula (3), examples of which are polyoxyethylene(meth)acrylamide, polyoxy-propylene(meth)acrylamide, polyoxyethylene(1-(meth)acrylamide-1,1-dimethylpropyl) ester and the like:
wherein A, R, R
1
, R
2
, R
3
, m and n are as defined above, and R
4
is a hydrogen atom, an alkyl group or a group of the following formula (4):
wherein R
1
, R
2
and R
3
are as defined above, and n is an integer of 1 to 300.
(Meth)allyl Alcohols
There are mentioned monomers of the following formula (5), examples of which are polyoxyethylene (meth)allyl ether, polyoxypropylene (meth)allyl ether and the like.
wherein R, R
1
, R
2
, R
3
and n are as defined above.
Vinyl Ethers
There are mentioned monomers of the following formula (6), examples of which are polyoxyethylene vinyl ether, polyoxypropylene vinyl ether and the like:
wherein A, R
1
, R
2
, R
3
, m and n are as defined above.
Of these unsaturated monomers containing oxyalkylene group, (meth)allyl alcohol compounds (5) are preferably used.
Polyoxyalkylene allylamines such as polyoxyethylene allylamine and polyoxypropylene allylamine, and polyoxyalkylene vinylamines such as polyoxyethylene vinylamine and polyoxypropylene vinylamine, can also be used.
The oxyalkylene group-containing unsaturated monomers may be used alone or in admixture thereof.
Examples of the vinyl ester compounds to be copolymerized with the oxyalkylene group-containing unsaturated monomers are, for instance, vinyl formate, vinyl acetate, vinyl trifluroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl pivalate, and the like. These may be used alone or in admixture thereof. Vinyl acetate is preferred in practical use.
Upon the copolymerization of vinyl esters and oxyalkylene group-containing monomers, the polymerization method is not particularly limited, and known polymerization methods can be suitably used. A solution polymerization using an alcohol such as methanol, ethanol or isopropanol as a solvent is usually practiced. Emulsion polymerization and suspension polymerization are also of course adoptable. As to a manner of charging monomers in such a solution polymerization, any manners can be used, e.g., a manner wherein first the whole amount of a vinyl ester and a part of an oxyalkylene group-containing unsaturated monomers are charged in a reactor and the polymerization is started, and the remaining monomer is then continuously, intermittently or stepwise added during the polymerization period, and a manner wherein monomers are added at one time in the initial stage of the polymerization. The copolymerization reaction is carried out by using known polymerization catalysts such as radical polymerization catalysts and low-temperature active catalysts, e.g., azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide and lauroyl peroxide. The reaction temperature is selected from
Reddick Judy M.
The Nippon Synthetic Chemical Industry Co., Ltd.
Ware Fressola Van Der Sluys & Adolphson LLP
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