FIELD OF THE INVENTION
[0001] The present invention relates to a composition for processing paper. More particularly,
the present invention relates to a paper-processing composition capable of imparting
superior barrier property, superior coating property and sufficient strength to paper,
particularly a composition capable of imparting excellent barrier property such that
a paper coated therewith can prevent permeation of air and oils.
[0002] Also, the present invention relates to a laminate such as a heat-sensitive recording
material and a release paper, to which the above-mentioned composition has been applied,
and more particularly, the invention relates to a heat-sensitive recording material
wherein a heat-sensitive coloring agent layer comprising the composition as mentioned
above, a coloring substance and a color developer is formed on a substrate such as
paper and plastic film, and to a release paper comprising a glassine paper as a base
paper, which has superior releasing property, recycling property and resistance to
solvent in the releasing agent to be coated.
BACKGROUND OF THE INVENTION
[0003] Conventionally, vinyl ester resins, particularly polyvinyl alcohol resins, have been
widely used as coating agents (processing agents) for paper surfaces to achieve improved
paper surface properties inclusive of strength, smoothness, gloss and tackiness.
[0004] The present applicant has also proposed a paper coating composition comprising, as
the main component, a modified polyvinyl alcohol having lactone ring in a molecule
(Japanese Examined Patent Publication No. 39442/1977).
[0005] On the other hand, there have been proposed a composition for preventing tackiness
(Japanese Unexamined Patent Publication No. 40579/1982) comprising a copolymer of
a polymerizable compound containing perfluoroalkyl having 3 to 12 carbon atoms and
a compound capable of copolymerization thereof, and a shellac (secreted from Taccardia
Lacca), and a composition for preventing tackiness (Japanese Unexamined Patent Publication
No. 57688/1994) comprising an organic fluoro compound as an active ingredient, which
is to be used for printing newspaper by offset printing, both aiming at improving
tackiness of the paper surfaces.
[0006] According to the technique disclosed in Japanese Examined Patent Publication No.
39442/1977, however, while barrier property of paper as requested those days was ensured,
its level is far from satisfactory when recent requirements are to be fulfilled. The
technique disclosed in Japanese Unexamined Patent Publication No. 40579/1982) and
Japanese Unexamined Patent Publication No. 57688/1994 has succeeded in improving tackiness,
but an improved barrier property of paper to air and ink is unlikely to be attained
by this technique. Thus, a need exists for a paper processing agent noticeably superior
in imparting barrier property, paper strength, coating property required by high speed
processing of paper painting, particularly, a composition capable of imparting markedly
superior barrier property which prevents permeation of air or oil through paper after
coating.
[0007] In the meantime, a heat-sensitive recording method utilizing heat has been spreading,
since it does not, unlike conventional printing methods, require steps of development
and fixing or supply of materials, but permits easy recording.
[0008] In particular, a method comprising heating a color developing substance such as Crystal
violet lactone and a color developer such as phenol compounds to allow reaction for
color development, stands high in evaluation and has been put to practical use.
[0009] This method involves use of a water soluble compound such as polyvinyl alcohol (PVA)
as a binder of both the aforementioned color developing substance and color developer.
However, an extended heating and recording is associated with problems in that leaf
of PVA attaches to a thermal head due to the abrasion, the thermal head and heat-sensitive
recording paper stick to each other during high temperature treatment (sticking),
the printed matter disappears upon contact of the recorded paper with water or plasticizer,
and the recording paper becomes sticky.
[0010] To solve these problems, the use of an itaconic acid modified PVA as a binder (Japanese
Patent Unexamined Publication No. 189889/1982), the use of an ethylene-carboxyl group
modified PVA as an overcoating agent (Japanese Patent Unexamined Publication No. 156424/1996),
the use of a carboxyl group modified PVA as a dispersing agent of heat-sensitive dye
(Japanese Patent Unexamined Publication No. 48076/1996) and the use of a protecting
layer (overcoating layer) comprising a modified PVA and zinc stearate (Japanese Patent
Unexamined Publication No. 164763/1997) have been proposed. The present applicant
has also proposed a heat-sensitive recording paper using an ethylenic unsaturated
dicarboxylic monoamide modified PVA (Japanese Patent Unexamined Publication No. 252977/1996).
[0011] When the technique disclosed in the above-mentioned Japanese Patent Unexamined Publication
No. 189889/1982 is used, color sensitivity becomes poor on recent high speed recording
machines (e.g., recorder and printer); when the techniques disclosed in Japanese Patent
Unexamined Publication Nos. 156424/1996 and 48076/1996 are used, bubbling and cissing
occur during high speed printing; when the technique disclosed in Japanese Patent
Unexamined Publication No. 164763/1997 is used, water resistance becomes insufficient;
and when the technique disclosed in Japanese Patent Unexamined Publication No. 252977/1996
by the present applicant is used, the production thereof becomes very difficult due
to the technique required for the use of a specific modified PVA. Thus, there is left
a room for an improvement, and a heat-sensitive recording paper superior in printing
performance, oil resistance, solvent resistance and water resistance is awaited.
[0012] In the meantime, a release paper has been used in wide applications as a base material
of pressure sensitive adhesive label, pressure sensitive adhesive tape, pressure sensitive
adhesive sheet and the like.
[0013] Such release paper generally comprises a base paper and a layer of a release agent
formed thereon. For the purpose of forming the layer of a release agent on the surface
of the base paper without allowing permeation thereof into paper, a polyolefin resin
layer of polyethylene or a barrier layer of polyvinyl alcohol resin, carboxymethyl
cellulose, casein, polyvinyl acetate emulsion and the like is formed in the interface
thereof.
[0014] When a polyolefin resin layer is formed, a barrier effect may be sufficient. However,
its resin waste poses a big problem when the paper is recycled. In the case of a conventional
layer of polyvinyl alcohol, the recycling problem can be overcome, whereas barrier
property is not sufficient. Thus, a release paper having a barrier layer simultaneously
satisfying recyclability and barrier property, which has superior releasability, is
desired.
SUMMARY OF THE INVENTION
[0015] According to the present invention, a composition for processing paper is provided,
which comprises a carboxyl group containing polyvinyl alcohol resin, and a hydrophilic
group and fluorine containing compound. This composition affords superior barrier
property, paper strength, coating property, particularly superior barrier property
to prohibit permeation of air or oil through paper after coating. A composition comprising,
as the hydrophilic group and fluorine containing compound, a compound of the following
formula (1) noticeably shows the above-mentioned action and effect:
C
nF
2n+1-(X)
k-(CH
2-CH
2-O)
m-H (1)
wherein X is -SO
2NR- in which R is a hydrogen, an alkyl or a carbonyl, n is an integer of 1 to 40,
m is an integer of 1 to 100 and k is 0 or 1.
[0016] In another aspect of the present invention, a laminate comprising a layer made from
the above-mentioned composition, which is laminated on a base material, particularly,
a heat-sensitive recording material and a release paper, are provided.
DETAILED DESCRIPTION OF THE INVENTION
[0017] In the present invention, any carboxyl group containing polyvinyl alcohol resin may
be used and the production method thereof is not particularly limited. For example,
the production method may be one comprising producing a copolymer of an unsaturated
monomer having a carboxyl group and a vinyl ester compound and hydrolyzing the copolymer,
or one comprising reacting a polyvinyl alcohol resin and a polyfunctional carboxylic
acid having two or more carboxyl groups or a compound having, in a molecule, a functional
group reactive with OH group in polyvinyl alcohol and carboxyl group. The former method
is practical in terms of production steps and property of the resin.
[0018] This method is explained in detail in the following.
[0019] Examples of the unsaturated monomer having carboxyl group include ethylenically unsaturated
monocarboxylic acid (e.g., acrylic acid, methacrylic acid and crotonic acid), ethylenically
unsaturated dicarboxylic acid (e.g., maleic acid, fumaric acid and itaconic acid),
ethylenically unsaturated dicarboxylic monoester (e.g., monoalkyl maleate, monoalkyl
fumarate and monoalkyl itaconate), ethylenically unsaturated dicarboxylic diester
(e.g., dialkyl maleate, dialkyl fumarate and dialkyl itaconate, note that a part of
the ester moiety of the diester must be converted to carboxyl by hydrolysis upon preparation
of polyvinyl alcohol), ethylenically unsaturated carboxylic anhydride (e.g., maleic
anhydride and fumaric anhydride) and salts thereof, with preference given to ethylenically
unsaturated dicarboxylic monoester and salt thereof.
[0020] Examples of vinyl ester compounds include vinyl formate, vinyl acetate, vinyl propionate,
vinyl butyrate, vinyl caprylate, vinyl laurate, vinyl versate, vinyl palmitate, vinyl
stearate and the like, which may be used alone or in combination. Preferred from the
practical viewpoint is vinyl acetate.
[0021] In the present invention, polymerization may be carried out in the presence of, in
addition to the above-mentioned monomer having carboxyl group and vinyl ester compound,
a monomer copolymerizable with vinyl ester, such as allyl ester of saturated carboxylic
acid (e.g., allyl stearate, allyl laurate, allyl ester of coconut oil fatty acid,
allyl octylate and allyl butyrate), α-olefin (e.g., ethylene, propylene, α-hexene,
α-octene, α-decene, α-dodecene, α-hexadecene and α-octadecene), alkyl vinyl ether
(e.g., propyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, octyl vinyl ether,
decyl vinyl ether, dodecyl vinyl ether, tetradecyl vinyl ether, hexadecyl vinyl ether
and octadecyl vinyl ether), alkyl allyl ether (e.g., propyl allyl ether, butyl allyl
ether, hexyl allyl ether, octyl allyl ether, decyl allyl ether, dodecyl allyl ether,
tetradecyl allyl ether, hexadecyl allyl ether and octadecyl allyl ether), (meth)acrylamide,
(meth)acrylonitrile, (meth)allylsulfonate, ethylenically unsaturated sufonate, styrene,
vinyl chloride and the like, in a proportion of not more than 50 mol%.
[0022] The copolymerization is subject to no particular limitation, and a known polymerization
method is used. It is typically a solution polymerization using alcohol (e.g., methanol
or ethanol) as a solvent.
[0023] According to this method, monomers are charged as in the following. First, the entire
amount of vinyl ester compound and a part of the above-mentioned carboxyl group containing
unsaturated monomer are charged to initiate polymerization, and the remaining unsaturated
monomer is successively or portionwise added during the polymerization period, or
the total amount of the two monomers is charged at once to initiate polymerization.
The copolymerization reaction is carried out using a known radical polymerization
catalyst such as azobisisobutyloni trile, acetyl peroxide, benzoyl peroxide, lauroyl
peroxide and the like. The reaction temperature is selected from the range of from
50°C to boiling point.
[0024] The copolymer thus obtained is then hydrolyzed to give a carboxyl group containing
unsaturated monomer.
[0025] For hydrolysis, the copolymer is dissolved in alcohol, acetic acid ester or a mixed
solvent thereof and the reaction is carried out in the presence of an alkaline catalyst.
As the alcohol, used is methanol, ethanol, butanol and the like, and the acetic acid
ester is exemplified by methyl acetate, ethyl acetate and the like.
[0026] The concentration of the copolymer in alcohol is 20-50 wt%. As the hydrolysis catalyst,
it is required to use a hydroxide of alkali metal, such as sodium hydroxide, potassium
hydroxide, sodium methylate, sodium ethylate and potassium methylate, and an alkali
catalyst such as alcolate. The catalyst is added in an amount of 1-100 mmol equivalent
of the vinyl ester compound.
[0027] The hydrolysis temperature is not particularly limited. It is generally 10-70°C and
particularly 30-40°C. The reaction generally proceeds for 2-3 hours. The preferable
degree of hydrolysis is 10-100 mol%, more preferably 50-100 mol%, most preferably
70-100 mol%.
[0028] When a vinyl alcohol component is added, the method is not limited to the one mentioned
above. For example, alkylene oxide is reacted with polyvinyl alcohol (e.g., partially
hydrolyzed compound and completely hydrolyzed compound).
[0029] In this way, a carboxyl group containing polyvinyl alcohol resin is obtained. The
carboxyl content is preferably 0.1-10 mol%, more preferably 0.5-5 mol%, of resin.
When the carboxyl content is less than 0.1 mol%, the use thereof for a heat-sensitive
recording material results in degraded oil resistance and solvent resistance, and
the use thereof for a release paper results in degraded solvent resistance of the
release paper. When the content exceeds 10 mol%, the solubility of the processing
agent (e.g., coating liquid) becomes undesirably low.
[0030] In the present invention, an average degree of polymerization of the carboxyl group
containing polyvinyl alcohol resin is preferably 100-10000, more preferably 300-3000.
When the average degree of polymerization is less than 100, the strength of paper
reduces to the point that printing property becomes defective. When it is used for
a heat-sensitive recording material, the color development of the recorded matter
becomes poor. In addition, the thermal head is more stained, and when it is applied
to a release paper, the barrier property of the paper reduces, thus increasing the
amount of releasing agent permeated into paper. When the average degree of polymerisation
exceeds 10000, the coating property thereof when prepared into a processing agent
undesirably becomes poor.
[0031] Examples of the hydrophilic group and fluorine containing compound to be added with
the above-mentioned carboxyl group containing polyvinyl alcohol resin include a compound
containing perfluoroalkyl group (C
nF
2n+1- in which n is an integer of 1-40) and a hydrophilic group such as alkylene oxide
and sulfonic acid group, inclusive of alkyl oligomer and urethane oligomer. A compound
of the following formula (1) containing perfluoroalkyl group (C
nF
2n+1- in which n is an integer of 1-40) and alkylene oxide is preferable:
C
nF
2n+1-(X)
k-(CH
2-CH
2-O)
m-H (1)
wherein X is -SO
2NR- in which R is a hydrogen, an alkyl preferably having 1 to 20 carbon atoms or a
carbonyl, n is an integer of 1 to 40, m is an integer of 1 to 100 and k is 0 or 1.
[0032] In this formula (1), n is preferably 3-20, more preferably 5-10, and m is preferably
3-30, more preferably 5-20.
[0033] This compound is commercially available as "MEGAFAC F-142D" and "MEGAFAC F-144D"
manufactured by DAINIPPON INK AND CHEMICALS, INC.
[0034] The inventive composition for paper processing comprises a carboxyl group containing
polyvinyl alcohol resin and a hydrophilic group and fluorine containing compound.
The proportion of the hydrophilic group and fluorine containing compound is preferably
0.01-5.0 parts by weight per 100 parts by weight of the carboxyl group containing
polyvinyl alcohol resin. When the content is less than 0.01 part by weight, the addition
produces no effect, whereas when it exceeds 5.0 parts by weight, the paper strength
decreases to ultimately produce cissing during painting, thus failing to accomplish
the object of the present invention. When this composition is used for a heat-sensitive
recording material, ink is repelled to show poor printing property, whereas when it
is used for release paper, the barrier property of paper reduces to allow an increased
amount of releasing agent to be permeated through paper and poor adhesion to the releasing
agent to be coated thereon. The more preferable content is 0.05-3.0 parts by weight,
and particularly preferably 0.1-2.0 parts by weight.
[0035] The thus-obtained composition for paper processing of the present invention is generally
used upon dissolution in water. An organic solvent may be also used. The kind of solvent
may be appropriately determined according to the property of the carboxyl group containing
polyvinyl alcohol resin, and the contents of the carboxyl group containing polyvinyl
alcohol resin and the hydrophilic group and fluorine containing compound. For example,
a composition having a relatively low hydrolysis degree is obtained in a paste. Thus,
the solvent used for polymerization or hydrolysis may be used as it is, or the solvent
may be changed. Specific examples of the solvent are methyl alcohol, ethyl alcohol,
propyl alcohol, isopropyl alcohol, methyl acetate, ethyl acetate, ethylene glycol,
propylene glycol, butanediol and the like.
[0036] The composition for paper processing of the present invention is used as a coating
liquid. The coating liquid may be prepared by any method as long as the above-mentioned
carboxyl group containing polyvinyl alcohol resin and hydrophilic group and fluorine
containing compound are mixed with water or a solvent. The concentration thereof is
appropriately adjusted according to the object. A particularly preferable concentration
of the mixture of carboxyl group containing polyvinyl alcohol resin and hydrophilic
group and fluorine containing compound is generally 0.1-40% by weight, more preferably
1-20% by weight, in view of the workability. When a release paper is to be produced,
the concentration is generally about 0.1-20% by weight, more preferably 0.1-10% by
weight.
[0037] The composition for paper processing of the present invention contains, as mentioned
above, a carboxyl group containing polyvinyl alcohol resin and a hydrophilic group
and fluorine containing compound. Where necessary, known additives such as water resistance
imparting agents (e.g., glyoxal, poly(amide amine), polyethyleneimine, isocyanate,
glutaraldehyde methylolled melamine, zirconium salt such as ammonium zirconium carbonate,
titanate such as tetra-n-butyl titanate, epichlorohydrin and urea resins), defoaming
agents, releasing agents, surfactants (exclusive of hydrophilic group and fluorine
containing compounds mentioned above), preservatives, insecticides, rust preventing
agents, tackifiers and the like. As long as the characteristic features of the present
invention are not impaired, polyvinyl alcohol, starch, carboxymethyl cellulose, poly(vinylpyrrolidone),
acrylic latex, SBR latex, pigment such as kaolin, calcium carbonate, clay, titanium
oxide and the like may be also added.
[0038] The paper on which the paper processing composition (coating liquid) of the present
invention is to be applied is not subject to any particular limitation, and is exemplified
by heat-sensitive recording paper, release paper, ink-jet paper, carbonic paper, noncarbonic
paper, stencil for paper cup, oil proofing paper, cardboard such as manila board,
white board and liner, paper of generally fine quality, paper of middle quality, printing
paper such as paper for gravure printing, high, middle or lower class paper, paper
for newspaper and the like.
[0039] For coating a paper processing composition, a known method such as size press coating
method, roll coater method, air doctor method, blade coater method, gate roll coater
method, spray coater method and the like may be used.
[0040] Thus, the composition for paper processing is coated in an amount of carboxyl group
containing polyvinyl alcohol resin of 0.1-20 g/m
2 (converted to solid), preferably 0.1-10 g/m
2 (converted to solid), more preferably 0.5-10 g/m
2 (converted to solid), and most preferably 0.5-5 g/m
2 (converted to solid). The coating method is not limited to the above-mentioned method,
but may be an internal sizing method wherein the inventive composition for paper processing
is dissolved in a pulp dispersion and paper is made therefrom, or a method including
mixing the inventive composition for paper processing in the form of powder or fiber
in paper or other method, whereby the inventive composition for paper processing can
be applied to paper.
[0041] The inventive composition for paper processing is generally used as a clear coating
agent as mentioned above. It can be also used as a binder for a pigment, wherein the
pigment may be a conventional one (e.g., clay, calcium carbonate, kaoline, diatom
earth, titanium oxide, iron oxide, satin white and the like). When it is used as a
binder, a clay shock, which has been the problem in conventional pigment coating (a
phenomenon of pigment agglutination upon addition of binder to pigment dispersion),
does not occur, thus exhibiting very superior effect in terms of dispersibility of
pigment.
[0042] The inventive heat-sensitive recording material comprises a base material and a layer
formed from the paper processing composition as mentioned above, hereinafter composition
(a), comprising the carboxyl group containing polyvinyl alcohol resin and the hydrophilic
group and fluorine containing compound which are laminated directly or via a different
layer on said base material. The composition (a) can be added to (i) heat-sensitive
color developing layer, (ii) protecting layer or (iii) undercoat layer. It is also
possible to concurrently use composition (a) in two of the layers (i) to (iii) or
three of the layers (i) to (iii). These layers are explained in detail in the following.
(i) heat-sensitive color developing layer
[0043] Using the composition (a) as a binder, a mixture comprising the binder, a color developing
substance and a color developer is applied to a base material. A homogeneous coating
dispersion for forming said heat-sensitive color developing layer is obtained by preparing
an aqueous dispersion containing the color developing substance and an aqueous dispersion
containing the color developer separately, thoroughly stirring same, finely dividing
same and mixing the both dispersions by stirring. The composition (a) as a binder
is added to the aqueous dispersion containing the color developing substance and/or
the aqueous dispersion containing the color developer in a proportion of 10-200 wt%
of the total amount of the color developing substance and the color developer. The
solid content of said coating dispersion is 10-40 wt% in view of the workability.
[0044] Examples of the color developing substance include leuco compound of triphenylmethane
dye such as 3,3-bis(p-dimethylaminophenyl)-phthalide, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide
[Crystal violet lactone], 3,3-bis(p-dimethylaminophenyl)-6-diethylamino-phthalide,
3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3-dimethyl-amino-6-methoxyfluorane,
7-acetamido-3-diethylaminofluorane, 3-diethylamino-5,7-dimethylfluorane, 3-diethylamino-5,7-dimethylfluorane,
3,6-bis-β-methoxyethoxyfluorane, 3,6-bis-β-cyanoethoxyfluorane and the like.
[0045] The color developer may be any as long as it develops color upon reaction during
heating with the above-mentioned color developing substance, and liquidized or gasified
at not less than normal temperature, preferably at not less than 70°C. Examples thereof
include phenol, p-methylphenol, p-tert-butylphenol, p-phenylphenol, α-naphthol, β-naphthol,
4,4'-isopropyridenediphenol (bisphenol A), 4,4'-sec-butylidenediphenol, 4,4'-cyclohexylidenediphenol,
4,4'-isopropylidenebis(2-tert-butylphenol), 4,4'-(1-methyl-n-hexylidene)diphenol,
4,4'-isopropylidenedicatechol, 4,4'-pendilidenediphenol, 4,4-isopropylidenebis(2-chlorophenol),
phenyl-4-hydroxybenzoate, salicylic acid, 3-phenylsalicylic acid, 5-methylsalicylic
acid, 3,5-di-tert-butylsalicylic acid, 1-oxy-2-naphthoenoic acid, m-oxybenzoic acid,
4-oxyphthalic acid, gallic acid and the like. The color developing substance and color
developer are not limited to those exemplified.
[0046] The base material to be coated with said coating dispersion is not particularly limited,
and may be paper (e.g., cardboard such as manila board, white board and liner, general
fine quality paper, paper of middle quality, printing paper such as paper for gravure
printing, high, middle or lower class paper, paper for newspaper, release paper, carbonic
paper, noncarbonic paper, glassine paper and the like), plastic film (e.g., polyester
film, nylon film, polyolefin film, polyvinyl chloride film and laminates thereof)
and the like. For coating, a known method may be used, such as roll coater method,
air doctor method, blade coater method, bar coater method and the like. The amount
to be coated is 1-20 g/m
2, particularly 3-10 g/m
2, by dry weight.
(ii) protecting layer
[0047] The protecting layer is applied to a heat-sensitive color developing layer comprising
a color developing substance, a color developer and a binder which may be composition
(a) or a composition comprising undenatured PVA, modified PVA (e.g., carboxyl group
containing PVA), methylcellulose, carboxymethylcellulose, starch, latex, etc. The
composition (a) is contained in the protecting layer. The coating liquid for the protecting
layer is suitably an aqueous solution containing the composition (a) in a proportion
of 1-10 wt%. The amount to be coated is about 0.5-5 g/m
2 by the dry weight of the composition (a). After coating, the layer is air dried or
lightly heated to give an objective protecting layer.
[0048] For the coating, roll coater method, air doctor method, blade coater method, bar
coater method, rod coater method and the like may be used.
[0049] The protecting layer may contain various known auxiliaries or such auxiliaries may
be applied before or after application of the coating liquid or otherwise. Examples
of auxiliaries include glyoxal, methylolled melamine, epihalohydrinic resins such
as polyamide epichlorohydrin, epibromohydrin and the like, potassium persulfate, ammonium
persulfate, persulfuric carbonate, metal salts such as ferric chloride, magnesium
chloride and the like, polyfunctional isocyanates such as diisocyanate, and compounds
known as water resistance imparting agent such as ammonium chloride, formalin, glycine,
glycydyl ester, glycydyl ether, dimethylol urea, ketene dimer, boric acid and sodium
tetraborate, and the like.
[0050] In addition, known additives such as a thermoplastic material (e.g., higher fatty
amide), a filler (e.g., calcium carbonate and titanium dioxide), a dispersing agent
and the like may be added.
(iii) undercoat layer
[0051] An undercoat layer is disposed as necessary between a base material and a heat-sensitive
color developing layer, and comprises the composition (a). The base material on which
the undercoat layer is to be formed is not particularly limited and may be paper,
plastic film and the like. The coating method may be a known one such as roll coater
method, air doctor method, blade coater, bar coater method, size press method, gate
roll method and the like. The coating liquid used for this end is suitably an aqueous
solution having a concentration of the composition (a) of 0.5-20 wt%. The amount to
be coated is about 0.5-5 g/m
2 by the dry weight of the composition (a). After coating, the layer is air dried or
lightly heated to give an objective undercoat layer.
[0052] The undercoat layer may contain various known additives as does the protecting layer.
[0053] The inventive heat-sensitive recording material can be obtained by forming a heat-sensitive
color developing layer, or heat-sensitive color developing layer and a protecting
layer on the undercoat layer thus formed.
[0054] In the heat-sensitive recording material of the present invention having a layer
structure of base material/undercoat layer/heat-sensitive color developing layer/protecting
layer, base material/ undercoat layer/heat-sensitive color developing layer, base
material/heat-sensitive color developing layer/protecting layer, or base material/heat-sensitive
color developing layer need only comprise any of the above-mentioned layers (i) to
(iii) using the composition (a) and is subject to no other limitation. Other layers
may be formed by a method conventionally known. It is possible to combine two or more
kinds of layers from the above-mentioned layers (i) to (iii).
[0055] When the composition (a) is applied to a release paper to be formed, the base paper
is not particularly limited. Examples thereof include glassine paper, semiglassine
paper, graft paper, Japanese paper, woodfree paper, nonwoven fabric and the like,
with preference given to glassine paper and semiglassine paper.
[0056] A release paper can be obtained by forming a layer of a releasing agent on the layer
of the composition (a) formed on a base paper. The releasing agent is not particularly
limited and is exemplified by silicone resin, fluororesin and the like.
[0057] The present invention is explained in detail by way of Examples, wherein "part" and
"%" mean "part by weight" and "wt%" unless otherwise specified.
Example 1
Preparation of carboxyl group containing polyvinyl alcohol resin
[0058] Vinyl acetate (500 parts), maleic acid (3.4 parts) and methanol (85 parts) were charged
in a polymerization vessel. The system was heated in a nitrogen stream while stirring
and refluxed at 60°C for 30 min. Azobisisobutylonitrile was added in a proportion
of 0.08 mol% of the vinyl acetate. The polymerization was carried out for 6 hr, during
which time a solution of maleic acid in methanol was dropwise added to make the degeneration
degree 1.0 mol%. After the completion of the reaction, methanol vapor was blown in
to remove unreacted monomers to give a solution of copolymer in methanol.
[0059] The thus-obtained methanol solution was diluted to 40% with methanol. Sodium hydroxide
was added in a proportion of 40 mmol% of the vinyl acetate in the copolymer for hydrolysis.
The hydrolyzed product thus obtained was filtrated and dried at 70°C to give a carboxyl
group containing polyvinyl alcohol resin (degree of hydrolysis 94.0 mol%, average
degree of polymerization 1700).
preparation of coating material
[0060] The above-mentioned carboxyl group containing polyvinyl alcohol resin (6 parts) was
dissolved in water (94 parts), and a hydrophilic group and fluorine containing compound
of the formula : C
8F
17-(CH
2-CH
2-O)
10-H (0.048 part, 0.8 part per 100 parts of polyvinyl alcohol resin) was added to give
a coating composition, which was applied in a proportion of 2.0 g/m
2 to an acid paper (basic weight 60 g/m
2) by size press coating (rate; 90 m/min, linear load; 11 kg/cm), which was followed
by drying with a cylindrical rotary dryer at 105°C for 2 min and finishing of both
sides by super calendar (temperature; 80°C, linear load; 40 kg/cm) to give a coating
material.
[0061] The barrier properties (air permeation and oil absorption), paper surface strength
and coating property of the obtained paper were evaluated by the following methods.
barrier properties
• air permeation
[0062] According to JIS P 8117, a test strip was fixed on an Okenshiki gas permeation tester
(manufactured by ASAHI SEIKO CO., LTD.) and the time (sec) necessary for 100 ml of
air to pass the paper was measured.
• oil absorption
[0063] According to JIS P 8130, the time (sec) necessary for oil to be absorbed by paper
from the surface thereof to the inside thereof was measured by an oil absorption tester
(manufactured by KUMAGAI RIKI KOGYO CO., LTD.).
paper surface strength
[0064] Using IGT print tester (manufactured by KUMAGAI RIKI KOGYO CO., LTD.) and FINE INK
TV-20 (manufactured by DAINIPPON INK AND CHEMICALS, INC.), IGT pick strength (cm/sec)
was measured.
coating property
[0065] The gloss and cissing of the coating layer were visually observed and evaluated as
follows.
- ○ :
- fine gloss, no cissing
- △ :
- fine gloss, occurrence of cissing
- X :
- less gloss, occurrence of cissing
Examples 2-17, Comparative Examples 1-3
[0066] In the same manner as in Example 1, carboxyl group containing polyvinyl alcohol resins
and hydrophilic group and fluorine containing compound as shown in Table 1 were used
to give heat-sensitive recording materials which were subjected to evaluation.
[0067] In Examples 5 and 6, itaconic acid was used instead of maleic acid. The evaluation
results are shown in Table 2.
Table 2
|
barrier property |
paper surface strength (cm/sec) |
coating property |
|
air permeation (sec) |
oil absorption (sec) |
|
|
Ex. 1 |
30 |
25 |
200 |
○ |
Ex. 2 |
35 |
30 |
195 |
○ |
Ex. 3 |
25 |
25 |
175 |
○ |
Ex. 4 |
35 |
35 |
190 |
○ |
Ex. 5 |
30 |
30 |
180 |
○ |
Ex. 6 |
35 |
30 |
190 |
○ |
Ex. 7 |
40 |
35 |
200 |
○ |
Com.Ex.1 |
15 |
10 |
175 |
△ |
Com.Ex.2 |
18 |
12 |
180 |
△ |
Com.Ex.3 |
10 |
8 |
150 |
X |
[0068] The composition for paper processing of the present invention is capable of imparting
superior barrier property, paper strength and coating property, particularly superior
barrier property prohibiting permeation of air or oil after coating, as a result of
the addition of a carboxyl group containing polyvinyl alcohol resin and a hydrophilic
group and fluorine containing compound. The composition can be appropriately used
for heat-sensitive recording paper, separating paper, release paper, ink jet paper,
carbonic paper, noncarbonic paper, base paper for paper cup, oil resistant paper,
paper board such as manila board, white board and liner, general fine quality paper,
paper of middle quality, (light weight) coat paper, wrapping paper, printing paper
such as paper for gravure printing, high, middle or lower class paper, paper for newspaper
and the like.
Example 8
Preparation of carboxyl group containing polyvinyl alcohol resin
[0069] In the same manner as in Example 1, a carboxyl group containing polyvinyl alcohol
resin (degree of hydrolysis 94.0 mol%, average degree of polymerization 1700) was
obtained.
[0070] The above-mentioned carboxyl group containing polyvinyl alcohol resin (6 parts) and
a hydrophilic group and fluorine containing compound of the formula : C
8F
17-(CH
2-CH
2-O)
10-H (0.048 part, 0.8 part per 100 parts of polyvinyl alcohol resin) were dissolved
in water (94 parts) to give a coating composition (A).
[0071] Using the coating composition (A), a heat-sensitive recording material was prepared
as in the following.
A liquid |
Crystal violet lactone |
10 parts |
coating composition (A) |
10 parts |
water |
15 parts |
B liquid |
bisphenol A |
50 parts |
5% aqueous solution containing same carboxyl group containing polyvinyl alcohol resin
as in A liquid |
50 parts |
water |
75 parts |
[0072] The above-mentioned A liquid and B liquid were separately divided to an average particle
size of about 2 µm in a sand grinder, and A liquid, B liquid, calcium carbonate (50
parts) and a 15% aqueous solution of the same carboxyl group containing polyvinyl
alcohol resin as in A liquid were mixed to give a coating liquid.
[0073] The obtained coating liquid was applied to a fine quality paper (base material, basic
weight 50 g/m
2), so that the coated amount after drying became 5.0 g/m
2, dried and a heat-sensitive color developing layer of (i) was formed, whereby a heat-sensitive
recording material was prepared.
[0074] The color density of the printed letters, resistance to plasticizer, oil resistance,
organic solvent resistance, water resistance and staining of thermal head were evaluated
by the following methods.
[0075] The evaluation results are shown in Table 4.
color density of the printed letters
[0076] The printed letters were allowed to develop color under the conditions of 120°C,
2 kg/cm
2, 5 sec using a Heat Gradient tester (manufactured by TOYOSEIKI SEISAKUSHO CO., LTD.)
and the color density was determined by Macbeth densitometer (RD-100R type, manufactured
by Macbeth, using an Umber filter).
resistance to plasticizer
[0077] A recording paper after color development was sandwiched between soft vinyl chloride
sheets. A load of 20 g/cm
2 was applied and left standing at 40°C for 168 hr. The color density (x) of the letters
was determined by Macbeth densitometer and the difference from the color density (y)
of the letters before standing was calculated from the following formula and taken
as color remaining percentage (%).
oil resistance
[0078] Several drops of edible soybean oil were dropped on the color developed letters,
and allowed to stand at room temperature for 24 hr. The soybean oil was wiped off
and color remaining percentage (%) from the color density thereof before dropping
oil was calculated in the same manner as in resistance to plasticizer.
organic solvent resistance
[0079] Several drops of ethyl acetate were dropped on the heat-sensitive recording material
and left standing at room temperature for one hour. Ethyl acetate was wiped off and
color density was calculated by Macbeth densitometer, wherein smaller values mean
better resistance to organic solvent.
water resistance
[0080] Several drops of water were dropped on the part where color had been developed, and
left standing at room temperature for one hour. Water was wiped off and color remaining
percentage (%) from the color density thereof before dropping was calculated in the
same manner as in resistance to plasticizer.
staining of thermal head
[0081] A lattice pattern was printed by facsimile for consecutive 100 m, and occurrence
of sticking and leaf remaining on the thermal head was visually observed. Evaluation
was done in four levels of Ⓞ-X.
- Ⓞ :
- Excellent
- ○ :
- Good
- △ :
- Normal
- X :
- Bad
Examples 9-16, Comparative Examples 4-6
[0082] In the same manner as in Example 8, carboxyl group containing polyvinyl alcohol resins
and hydrophilic group and fluorine containing compound as shown in Table 3 were used
to give heat-sensitive recording materials which were subjected to evaluation as heat-sensitive
color developing layer (binder).
[0083] The evaluation results are shown in Table 4.
Table 3
|
polyvinyl alcohol resin |
hydrophilic group and fluorine containing compound |
|
carboxyl content (mol%) |
amount (parts) |
kind |
amount (parts) |
Exs. 8, 17, 26 |
1.0** |
100 |
F-1 |
0.8 |
Exs. 9, 18, 27 |
2.0** |
100 |
F-1 |
0.8 |
Exs. 10, 19, 28 |
1.0** |
100 |
F-2 |
1.8 |
Exs. 11, 20, 29 |
3.0*** |
100 |
F-1 |
0.8 |
Exs. 12, 21, 30 |
1.5** |
100 |
F-3 |
0.5 |
Exs. 13, 22, 31 |
1.0** |
100 |
F-4 |
1.5 |
Exs. 14, 23, 32 |
1.0*** |
100 |
F-1 |
1.0 |
Exs. 15, 24, 33 |
1.5*** |
100 |
F-2 |
1.2 |
Exs. 16, 25, 34 |
3.0** |
100 |
F-5 |
3.0 |
Com.Exs. 4, 7, 10 |
1.0** |
100 |
not added |
Com.Exs. 5, 8, 11 |
1.0** |
100 |
F-0 |
0.8 |
Com.Exs. 6, 9, 12 |
0**** |
100 |
F-1 |
0.8 |
Note
∗∗ modified with maleic acid |
∗∗∗ modified with itaconic acid |
∗∗∗∗ not modified |
[0084]
Table 4
|
color density of print |
resistance to plasticizer (%) |
resistance to oil (%) |
resistance to organic solvent |
water resistance(%) |
staining of thermal head |
Ex. 8 |
1.51 |
96 |
90 |
0.25 |
85 |
Ⓞ |
Ex. 9 |
1.46 |
93 |
85 |
0.25 |
83 |
○ |
Ex. 10 |
1.48 |
95 |
88 |
0.20 |
90 |
Ⓞ |
Ex. 11 |
1.52 |
95 |
89 |
0.19 |
92 |
○ |
Ex. 12 |
1.40 |
96 |
93 |
0.18 |
90 |
Ⓞ |
Ex. 13 |
1.42 |
93 |
90 |
0.18 |
89 |
○ |
Ex. 14 |
1.50 |
94 |
91 |
0.20 |
90 |
Ⓞ |
Ex. 15 |
1.50 |
92 |
92 |
0.20 |
88 |
Ⓞ |
Ex. 16 |
1.53 |
95 |
88 |
0.23 |
90 |
Ⓞ |
Com.Ex.4 |
1.32 |
88 |
75 |
0.43 |
89 |
○ |
Com.Ex.5 |
1.30 |
86 |
73 |
0.45 |
88 |
△ |
Com.Ex.6 |
1.03 |
48 |
60 |
0.75 |
46 |
X |
Example 17
[0085] A heat-sensitive recording material was prepared in the following manner.
A liquid |
Crystal violet lactone |
10 parts |
unmodified PVA 5% aqueous solution (degree of hydrolysis 99.0 mol%, 4% aqueous solution
viscosity 14 cps/20°C) |
10 parts |
water |
15 parts |
B liquid |
bisphenol A |
50 parts |
5% aqueous solution containing same unmodified PVA as in A liquid |
50 parts |
water |
75 parts |
[0086] The above-mentioned A liquid and B liquid were separately divided to an average particle
size of about 2 µm in a sand grinder, and 15% aqueous solution of the same unmodified
PVA (500 parts) used in A and B solutions was added to give a coating liquid.
[0087] The obtained coating liquid was applied to a fine quality paper (base material, basic
weight 50 g/m
2), so that the coated amount after drying became 5.0 g/m
2 and dried.
[0088] Thereto was applied a coating liquid comprising a 10% aqueous solution of the coating
composition (A) used in Example 8 and calcium carbonate (5 parts) by a Dickson coater
at 1.5 g/m
2 (net), air dried and a protecting layer was formed, whereby a heat-sensitive recording
material was prepared.
[0089] The obtained heat-sensitive recording material was evaluated in the same manner as
in Example 8.
[0090] The evaluation results are shown in Table 5.
Examples 18-25, Comparative Examples 7-9
[0091] In the same manner as in Example 17, the composition (see Table 3) used in the above-mentioned
Examples 9-16, Comparative Examples 4-6 to give heat-sensitive recording materials
which were subjected to evaluation for (ii) protecting layer.
[0092] The evaluation results are shown in Table 5.
Table 5
|
color density of print |
resistance to plasticizer (%) |
resistance to oil (%) |
resistance to organic solvent |
water resistance(%) |
staining of thermal head |
Ex. 17 |
1.48 |
90 |
92 |
0.10 |
89 |
Ⓞ |
Ex. 18 |
1.43 |
83 |
90 |
0.13 |
88 |
Ⓞ |
Ex. 19 |
1.47 |
85 |
90 |
0.13 |
89 |
Ⓞ |
Ex. 20 |
1.53 |
92 |
98 |
0.05 |
94 |
Ⓞ |
Ex. 21 |
1.44 |
90 |
96 |
0.09 |
92 |
Ⓞ |
Ex. 22 |
1.42 |
88 |
90 |
0.17 |
87 |
Ⓞ |
Ex. 23 |
1.47 |
91 |
91 |
0.11 |
91 |
Ⓞ |
Ex. 24 |
1.51 |
93 |
94 |
0.10 |
93 |
Ⓞ |
Ex. 25 |
1.47 |
85 |
93 |
0.10 |
90 |
Ⓞ |
Com.Ex.7 |
1.38 |
72 |
78 |
0.33 |
85 |
○ |
Com.Ex.8 |
1.00 |
74 |
80 |
0.31 |
80 |
○ |
Com.Ex.9 |
1.03 |
50 |
59 |
0.80 |
57 |
△ |
Example 26
[0093] A heat-sensitive recording material was prepared in the following manner.
[0094] A 5% aqueous solution of coating composition (A) used in Example 8 was applied to
a fine quality paper (base material, basic weight 50 g/m
2) using a size pressing device for testing (manufactured by KUMAGAI RIKI KOGYO CO.,
LTD.) at 1.5 g/m
2 (net) and dried at 110°C for one min to give a coated paper having an undercoat layer.
A liquid |
Crystal violet lactone |
10 parts |
unmodified PVA 5% aqueous solution (degree of hydrolysis 99.0 mol%, 4% aqueous solution
viscosity 14 cps/20°C) |
10 parts |
water |
15 parts |
B liquid |
bisphenol A |
50 parts |
5% aqueous solution containing same unmodified PVA |
50 parts |
water |
75 parts |
[0095] The above-mentioned A liquid and B liquid were separately divided to an average particle
size of about 2 µm in a sand grinder, and 15% aqueous solution of the same unmodified
PVA (500 parts) used in A and B liquids was added to give a coating liquid.
[0096] The obtained coating liquid was applied to the paper having the above-mentioned undercoat
layer, so that the coated amount after drying became 5.0 g/m
2 and dried to give a heat-sensitive recording material.
[0097] The obtained heat-sensitive recording material was evaluated for color density of
the printed letter and staining of thermal head as in Example 8.
[0098] The evaluation results are shown in Table 6.
Examples 27-34, Comparative Examples 10-12
[0099] In the same manner as in Example 26, the composition (see Table 3) used in the above-mentioned
Examples 9-16, Comparative Examples 4-6 to give heat-sensitive recording materials
which were subjected to evaluation for protecting layer.
[0100] The evaluation results are shown in Table 6.
Table 6
|
color density of print |
staining of thermal head |
Ex. 26 |
1.50 |
Ⓞ |
Ex. 27 |
1.45 |
○ |
Ex. 28 |
1.46 |
○ |
Ex. 29 |
1.51 |
Ⓞ |
Ex. 30 |
1.40 |
○ |
Ex. 31 |
1.41 |
○ |
Ex. 32 |
1.48 |
○ |
Ex. 33 |
1.49 |
Ⓞ |
Ex. 34 |
1.47 |
Ⓞ |
Com.Ex.10 |
1.31 |
○ |
Com.Ex.11 |
1.25 |
○ |
Com.Ex.12 |
1.11 |
△ |
[0101] The heat-sensitive recording material of the present invention comprises the specific
composition in at least one layer of a heat-sensitive color developing layer, a protecting
layer and an undercoat layer. As a consequence, it affords superior printing property,
and particularly when it is used for a heat-sensitive color developing layer or a
protecting layer, it imparts superior resistance to plasticizer, oil resistance, solvent
resistance and water resistance, while causing less staining of a thermal head.
Example 35
[0102] In the same manner as in Example 1, a carboxyl group containing polyvinyl alcohol
resin (degree of hydrolysis 94.0 mol%, average polymerization degree 1700) was obtained.
[0103] The above-mentioned carboxyl group containing polyvinyl alcohol resin (6 parts) was
dissolved in water (94 parts), and a hydrophilic group and fluorine containing compound
of the formula : C
8F
17-(CH
2-CH
2-O)
10-H (0.048 part, 0.8 part per 100 parts of polyvinyl alcohol resin) was added to give
a coating liquid, which was applied in a proportion of 0.7 g/m
2 in resin solid component to one surface of a glassine paper (basic weight 65 g/m
2, gas permeation 100 sec). The paper was dried using a cylindrical rotary dryer at
105°C for 2 min, passed through super calendar (temperature; 80°C, linear load; 40
kg/cm), and a solution of a releasing agent [electron beam cure type non-solvent silicone,
100 parts, X-52-131 manufactured by Shin-Etsu Chemical Co., Ltd. and platinum catalyst
30 parts) was applied to the coated/dried surface in a solid content of 1.0 g/m
2, which was followed by electron beam irradiation to form a releasing layer, whereby
a release paper was obtained.
[0104] The obtained release paper was evaluated for barrier property (gas permeation) and
releasing property in the following manner.
releasing property
[0105] An acrylic emulsion adhesive (Nicazol L-145, manufactured by Nippon Carbide Industries
Co., Inc.) was applied to the surface of the releasing agent layer of a release paper
so that the applied amount was 25 g/m
2 by reverse roll coater. After hot air drying at 130°C, a fine quality paper (basic
weight 65 g/m
2) was adhered. The peel strength (g/50 mm) when peeled at 0.3 m/min at normal condition
was measured and evaluated as follows.
- ○ :
- less than 100 g/50 mm
- △:
- less than 100 - 200 g/50 mm
- X:
- 200 g/50 mm or above
[0106] The obtained release paper was easily dissolved in water by regular recycling steps,
and could be recovered as waste paper.
Examples 36-41, Comparative Examples 13-15
[0107] Using carboxyl group containing polyvinyl alcohol resins and hydrophilic group and
fluorine containing compounds as shown in Table 7 were used, evaluation was performed.
[0108] In Examples 39 and 40, itaconic acid was used instead of maleic acid.
[0109] The evaluation results are shown in Table 8.
Table 7
|
polyvinyl alcohol resin |
hydrophilic group and fluorine containing compound |
|
carboxyl content (mol%) |
amount (parts) |
kind |
amount (parts) |
Ex. 35 |
1.0** |
100 |
F-1 |
0.8 |
Ex. 36 |
2.0** |
100 |
F-2 |
0.8 |
Ex. 37 |
1.5** |
100 |
F-3 |
0.5 |
Ex. 38 |
1.0** |
100 |
F-4 |
1.5 |
Ex. 39 |
1.0*** |
100 |
F-1 |
1.0 |
Ex. 40 |
1.5*** |
100 |
F-2 |
1.2 |
Ex. 41 |
3.0** |
100 |
F-5 |
3.0 |
Com.Ex.13 |
1.0** |
100 |
F-1 |
not added |
Com.Ex.14 |
1.0** |
100 |
F-0 |
0.8 |
Com.Ex.15 |
0**** |
100 |
F-1 |
0.8 |
Note
∗∗ modified with maleic acid |
∗∗∗ modified with itaconic acid |
∗∗∗∗ not modified |
[0110]
Table 8
|
barrier property gas permeation (sec) |
releasing property |
Ex. 35 |
5100 |
○ |
Ex. 36 |
6800 |
○ |
Ex. 37 |
5000 |
○ |
Ex. 38 |
5200 |
○ |
Ex. 39 |
7800 |
○ |
Ex. 40 |
8000 |
○ |
Ex. 41 |
7500 |
○ |
Com.Ex.13 |
3200 |
△ |
Com.Ex.14 |
2500 |
△ |
Com.Ex.15 |
2000 |
X |
[0111] The release paper of the present invention comprising the specific composition in
the base paper shows superior barrier property. As a consequence, it can prevent permeation
of a releasing agent and is superior in releasing property. In addition, the release
paper can be easily dissolved in water through regular recycling steps, and can be
recovered as waste paper. Thus, the inventive release paper is useful as a base material
of adhesive label, heat-sensitive label, adhesive tape, adhesive sheet and the like.