U.S. patent application number 11/907358 was filed with the patent office on 2008-07-24 for coating emulsion composition, and water/oil-repellent paper and making method.
This patent application is currently assigned to Shin-Etsu Chemical Co., Ltd.. Invention is credited to Yoshihito Osawa, Yasunori Watanabe, Kenji Yamamoto.
Application Number | 20080176991 11/907358 |
Document ID | / |
Family ID | 38992576 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080176991 |
Kind Code |
A1 |
Osawa; Yoshihito ; et
al. |
July 24, 2008 |
Coating emulsion composition, and water/oil-repellent paper and
making method
Abstract
An organopolysiloxane containing at least two silicon-bonded
hydroxyl groups, the reaction product of an amino-containing
organoalkoxysilane with a dicarboxylic anhydride, and an
organopolysiloxane containing long-chain alkyl and alkoxy groups,
but free of hydroxyl groups are emulsified and dispersed in water
in the presence of a surfactant to form a coating emulsion
composition.
Inventors: |
Osawa; Yoshihito;
(Annaka-shi, JP) ; Yamamoto; Kenji; (Annaka-shi,
JP) ; Watanabe; Yasunori; (Tokyo, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Shin-Etsu Chemical Co.,
Ltd.
|
Family ID: |
38992576 |
Appl. No.: |
11/907358 |
Filed: |
October 11, 2007 |
Current U.S.
Class: |
524/539 ;
428/219; 428/447 |
Current CPC
Class: |
D21H 19/46 20130101;
D21H 19/16 20130101; D21H 19/62 20130101; Y10T 428/31663 20150401;
C09D 183/04 20130101; D21H 19/32 20130101; C09D 183/04 20130101;
C08J 2383/04 20130101; D21H 21/16 20130101; C08L 83/06 20130101;
D21H 19/64 20130101; C08J 3/03 20130101; C08L 83/00 20130101; C08K
5/544 20130101 |
Class at
Publication: |
524/539 ;
428/447; 428/219 |
International
Class: |
C08L 51/00 20060101
C08L051/00; B32B 9/00 20060101 B32B009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 13, 2006 |
JP |
2006-279800 |
Oct 13, 2006 |
JP |
2006-279815 |
Claims
1. A coating emulsion composition comprising (A) 100 parts by
weight of an organopolysiloxane containing at least two
silicon-bonded hydroxyl groups in a molecule, (B) 0.5 to 20 parts
by weight of the reaction product of an amino-containing
organoalkoxysilane with a dicarboxylic anhydride, (C) 0 to 20 parts
by weight of an epoxy-containing organoalkoxysilane and/or a
partial hydrolyzate thereof, (D) 0 to 50 parts by weight of
colloidal silica and/or polysilsesquioxane, (E) 0 to 10 parts by
weight of a curing catalyst, and (F) 0.5 to 20 parts by weight of
an organopolysiloxane containing long-chain alkyl and alkoxy
groups, but free of hydroxyl groups, components (A) to (F) being
emulsified and dispersed in water in the presence of a
surfactant.
2. The emulsion composition of claim 1, wherein component (F) has
the average compositional formula (2): ##STR00007## wherein R.sup.1
is each independently C.sub.1-C.sub.3 alkyl or phenyl, Q is each
independently C.sub.4-C.sub.20 alkyl, Z is each independently a
group of --OR.sup.2, --C.sub.2H.sub.4--Si(OR.sup.2).sub.3 or
--C.sub.3H.sub.6--Si(OR.sup.2).sub.3 wherein R.sup.2 is
C.sub.1-C.sub.6 alkyl, the subscript d is a positive number of 1 to
100, e is a positive number of 1 to 100, f is a positive number of
0.1 to 30, and q is 0, 1, 2 or 3.
3. The emulsion composition of claim 1, wherein component (F) has
the average compositional formula (3): ##STR00008## wherein Q is
each independently selected from hexyl, octyl, decyl, and dodecyl,
Z is each independently selected from methoxy, ethoxy and
--C.sub.2H.sub.4--Si(OCH.sub.3).sub.3, the subscript d is a
positive number of 1 to 100, e is a positive number of 1 to 100,
and f is a positive number of 0.1 to 30.
4. A water- and oil-repellent paper sheet having improved fold
resistance, said paper sheet comprising a paper substrate and a
water- and oil-repellent, releasable silicone resin layer on at
least one surface of the paper substrate, said paper sheet
including a planar portion normally and a folded portion when
folded, the planar portion exhibiting an oil resistance which is at
least 9 in Kit value and the folded portion exhibiting an oil
resistance which is at least 8 in Kit value, both as measured at
20.degree. C and a humidity 50% by J. TAPPI paper/pulp test No.
41-83, and the planar portion exhibiting a water repellency which
is at least R8 and the folded portion exhibiting a water repellency
which is at least R7, both as measured by J. TAPPI paper/pulp test
No. 68:2000.
5. The water- and oil-repellent paper sheet of claim 4, wherein
said silicone resin layer is formed by coating a water- and
oil-repellent composition on the surface of the paper substrate,
said composition primarily comprising an aqueous silicone resin
emulsion comprising (a) 100 parts by weight of an
organopolysiloxane containing at least two silicon-bonded hydroxyl
groups in a molecule, (b) 0.5 to 20 parts' by weight of a
dicarboxylic acid base curing agent, (c) 1 to 50 parts by weight of
silica, (d) 2 to 4 parts by weight of an organopolysiloxane
containing long-chain alkyl and alkoxy groups, but free of hydroxyl
groups, and (e) an effective amount to form an emulsion of a
surfactant.
6. A method for preparing a water- and oil-repellent paper sheet,
comprising coating a water- and oil-repellent composition primarily
comprising an aqueous silicone resin emulsion on at least one
surface of a paper substrate so as to give a dry coating weight of
at least 1.0 g/m.sup.2, for thereby forming a water- and
oil-repellent, releasable silicone resin layer, the paper substrate
being selected from the group consisting of kraft paper, wood-free
paper, paper board, liner, glassine paper and parchment paper.
7. The method of claim 6, wherein the water- and oil-repellent
composition primarily comprises an aqueous silicone resin emulsion
comprising (a) 100 parts by weight of an organopolysiloxane
containing at least two silicon-bonded hydroxyl groups in a
molecule, (b) 0.5 to 20 parts by weight of a dicarboxylic acid base
curing agent, (c) 1 to 50 parts by weight of silica, (d) 2 to 4
parts by weight of an organopolysiloxane containing long-chain
alkyl and alkoxy groups, but free of hydroxyl groups, and (e) an
effective amount to form an emulsion of a surfactant.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This non-provisional application claims priority under 35
U.S.C. .sctn.119(a) on Patent Application Nos. 2006-279800 and
2006-279815 filed in Japan on Oct. 13, 2006 and Oct. 13, 2006,
respectively, the entire contents of which are hereby incorporated
by reference.
TECHNICAL FIELD
[0002] This invention relates to a coating emulsion composition
featuring uniformity of coating. It also relates to a water- and
oil-repellent paper and a method for preparing the same, the paper
finding use in food packages and wrappers including base paper and
wrappers for chocolate and snacks, paper boxes and bags for fried
potato, fried chicken, doughnuts, crackers and cakes, and wrappers
for hamburgers and fried items.
BACKGROUND ART
[0003] A number of cross-linking silicone emulsion compositions
which cure into rubber coatings are known in the art, as disclosed
in JP-A 5-98579 corresponding to U.S. Pat. No. 5,254,621, JP-A
8-85760, JP-A 9-208826 corresponding to U.S. Pat. No. 5,827,921,
JP-A 2000-34410 corresponding to U.S. Pat. No. 6,140,414, and JP-A
2001-55510. Effective coating treatment is possible when these
compositions are applied to fabrics, building members, and other
substrates having an irregular surface. Problems arise, however,
when they are applied to films, paper sheets, and other substrates
having a relatively smooth surface to form a thin coating thereon.
The coating weight will vary during the coating step, failing to
form a coating having a uniform thickness.
[0004] Water- and oil-repellent paper sheets having a function of
restraining oil penetration are commonly utilized as food packages
and wrappers for packaging or wrapping oily food items such as
fried items and oil and fat-containing foods. These water- and
oil-repellent paper sheets are not only desired to be fully water-
and oil-repellent, but must also be safe. A number of proposals are
known in the art. Recently, those water- and oil-repellent paper
sheets having organic fluororesins incorporated therein drew a
concern about safety. As a substitute, those paper sheets having a
water- and oil-repellent layer formed on a paper substrate were
proposed as disclosed in JP-A 8-209590 and JP-A 9-87994.
[0005] As compared with the prior art water- and oil-repellent
paper sheets having organic fluororesins incorporated therein,
those paper sheets having a water- and oil-repellent layer formed
on a paper substrate for insuring safety are difficult to provide a
sufficient level of water and oil repellency. It is pointed out
that particularly when the paper sheets are folded for use as boxes
or base sheets, the folded portions suffer from noticeable losses
of water and oil repellency.
DISCLOSURE OF THE INVENTION
[0006] A first object of the invention is to provide a coating
emulsion composition featuring uniformity of coating. A second
object is to provide a water- and oil-repellent paper having
improved water and oil repellency, experiencing little losses of
water and oil repellency at folds when folded, and having release
and safety features, and a method for preparing the same.
[0007] The first object is attained by a coating emulsion
composition which is obtained by emulsifying and dispersing
components (A) to (F), defined below, in water in the presence of a
surfactant because the resulting coating emulsion composition is
improved in the uniformity of coating.
[0008] In the first aspect, the invention provides a coating
emulsion composition comprising
[0009] (A) 100 parts by weight of an organopolysiloxane containing
at least two silicon-bonded hydroxyl groups in a molecule,
[0010] (B) 0.5 to 20 parts by weight of the reaction product of an
amino-containing organoalkoxysilane with a dicarboxylic
anhydride,
[0011] (C) 0 to 20 parts by weight of an epoxy-containing
organoalkoxysilane and/or a partial hydrolyzate thereof,
[0012] (D) 0 to 50 parts by weight of colloidal silica and/or
polysilsesquioxane,
[0013] (E) 0 to 10 parts by weight of a curing catalyst, and
[0014] (F) 0.5 to 20 parts by weight of an organopolysiloxane
containing long-chain alkyl and alkoxy groups, but free of hydroxyl
groups,
[0015] components (A) to (F) being emulsified and dispersed in
water in the presence of a surfactant.
[0016] A coating resulting from the coating emulsion composition is
uniform and fully adherent to any underlying substrate. When
fibers, paper, film, leather and building materials are treated
with the composition, the resultant coating imparts water
repellency, water-proof and parting properties. Best results are
obtained when substrates with a less irregular surface are coated.
The composition can also be used as a binder for functional
inorganic fillers such as photocatalysts.
[0017] Coating treatment with the inventive composition provides a
uniform coating without variations.
[0018] An embodiment of the invention that attains the second
object is a water- and oil-repellent paper sheet having improved
fold resistance, the paper sheet comprising a paper substrate and a
water- and oil-repellent, releasable silicone resin layer on at
least one surface of the paper substrate. Provided that the paper
sheet includes a planar portion normally and a folded portion when
folded, the planar portion exhibits an oil resistance which is at
least 9 in Kit value and the folded portion exhibiting an oil
resistance which is at least 8 in Kit value, both as measured at
20.degree. C. and a humidity 50% by J. TAPPI paper/pulp test No.
41-83, and the planar portion exhibiting a water repellency which
is at least R8 and the folded portion exhibiting a water repellency
which is at least R7, both as measured by J. TAPPI paper/pulp test
No. 68:2000.
[0019] Since the paper sheet of the invention has a silicone resin
layer having water and oil repellency and release property, it
exhibits improved water and oil repellency normally. Even when it
is folded, the folded portion experiences little losses of water
and oil repellency. The paper sheet thus finds use in food packages
and wrappers including base paper and wrappers for chocolate and
snacks, paper boxes and bags for fried potato, fried chicken,
doughnuts, crackers and cakes, and wrappers for hamburgers and
fried items.
[0020] The invention also provides a method for preparing a water-
and oil-repellent paper sheet, comprising coating a water- and
oil-repellent composition primarily comprising an aqueous silicone
resin emulsion on at least one surface of a paper substrate so as
to give a dry coating weight of at least 1.0 g/m.sup.2, for thereby
forming a water- and oil-repellent, releasable silicone resin
layer. The paper substrate is selected from among kraft paper,
wood-free paper, paper board, liner, glassine paper and parchment
paper.
[0021] By coating a surface of a paper substrate with a water- and
oil-repellent composition primarily comprising an aqueous silicone
resin emulsion, a paper sheet with improved water and oil
repellency is easily prepared.
[0022] The paper sheet of the invention has improved water and oil
repellency due to the silicone resin layer having water and oil
repellency and release property, and even when folded, maintains
the repellency with little losses or at the practically acceptable
level in the folded portion. Thus the water- and oil-repellent
paper sheet is useful in commercial food packages and wrappers for
packaging or wrapping a variety of oily food items such as fried
items and oil and fat-containing foods.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] In the disclosure, the notation (Cn-Cm) means a group
containing from n to m carbon atoms per group. All parts are by
weight unless otherwise stated.
First Embodiment
[0024] Described below are components in the coating emulsion
composition according to the first embodiment of the invention.
[0025] Component (A) is an organopolysiloxane containing at least
two silicon-bonded hydroxyl groups in a molecule, and typically an
organopolysiloxane having the average compositional formula
(1):
##STR00001##
Herein R is each independently a C.sub.1-C.sub.20 alkyl group or a
C.sub.6-C.sub.20 aryl group. X is each independently a
C.sub.1-C.sub.20 alkoxy group or a hydroxyl group, with the proviso
that at least two X's are hydroxyl groups. The subscript "a" is 0
or a positive number of 0<a.ltoreq.1,000, "b" is a positive
number of 100.ltoreq.b.ltoreq.10,000, "c" is 0 or a positive number
of 0<c.ltoreq.1,000, 100.ltoreq.axc+b.ltoreq.100,000, and r is
1, 2 or 3.
[0026] Specifically, R is each independently selected from
C.sub.1-C.sub.20 alkyl groups and C.sub.6-C.sub.20 aryl groups, for
example, chain-like alkyl groups such as methyl, ethyl, propyl,
butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl,
tetradecyl, hexadecyl, and octadecyl, cycloalkyl groups such as
cyclopentyl, cyclohexyl and cycloheptyl, and aryl groups such as
phenyl, tolyl and naphthyl, with methyl being preferred. X is each
independently selected from C.sub.1-C.sub.20, preferably
C.sub.1-C.sub.6 alkoxy groups and hydroxyl groups, and examples of
suitable alkoxy groups include methoxy, ethoxy, propoxy, butoxy and
pentoxy groups.
[0027] If "a" is in excess of 1,000, the resulting coating has an
insufficient strength. Thus "a" is 0 or a positive number from more
than 0 to 1,000, and preferably a positive number from more than 0
to 200. If "b" is less than 100, the resulting coating becomes less
flexible. If "b" is in excess of 10,000., the resulting coating
lowers in tear strength. Thus "b" is a positive number from 100 to
10,000, and preferably a positive number from 1,000 to 5,000.
Preferably "c" is a positive number from 1 to 1,000. It is noted
that in view of crosslinking, the organopolysiloxane (A) should
contain at least two silicon-bonded hydroxyl groups in a
molecule.
[0028] Examples of the organopolysiloxane (A) include those of the
following formulae (i) to (vi).
##STR00002##
Herein Me stands for methyl, and Ph stands for phenyl. The
subscript "m" is 0 or a positive number of 0<m.ltoreq.1,000, and
preferably 0<m.ltoreq.200; n is a positive number of
100.ltoreq.n.ltoreq.10,000, and preferably
1,000.ltoreq.n.ltoreq.5,000; and p is 0 or a positive number of
0<p.ltoreq.1,000, and preferably 1.ltoreq.p.ltoreq.1,000.
[0029] The organopolysiloxane can be prepared by well-known
techniques. For example, it may be prepared through equilibration
reaction between a cyclic siloxane such as
octamethylcyclotetrasiloxane and an
.alpha.,.omega.-dihydroxysiloxane oligomer in the presence of a
catalyst such as metal hydroxides. Since component (A) is
preferably used in emulsion form, it may be obtained as an emulsion
by a well-known emulsion polymerization technique. Specifically, it
may be readily prepared by previously emulsifying and dispersing a
cyclic siloxane and a .alpha.,.omega.-dihydroxysiloxane oligomer,
.alpha.,.omega.-dialkoxysiloxane oligomer or alkoxysilane in water
with the aid of an anionic or cationic surfactant, optionally
adding a catalyst such as an acidic or alkaline material, and
effecting polymerization reaction.
[0030] The emulsion is preferably prepared by emulsifying and
dispersing the organopolysiloxane as mentioned above in an aqueous
medium in the presence of at least one anionic surfactant selected
from organic sulfonic acids, organic sulfates and organic
sulfonates to form an initial emulsion, causing the initial
emulsion to polymerize, and neutralizing. The emulsion is
preferably formed to an average particle size of up to 500 nm, and
more preferably up to 400 nm. With a particle size in excess of 500
nm, the emulsion becomes unstable and slow in polymerization
reaction, requiring a longer process time.
[0031] For polymerization of the emulsion, the polymerization
temperature is preferably between 0.degree. C. and 90.degree. C.,
and more preferably between 5.degree. C. and 80.degree. C. A
temperature below 0.degree. C. may retard the polymerization
reaction whereas above 90.degree. C., the emulsion may lose
stability during the polymerization reaction. The time for
polymerization reaction is preferably 1 to 200 hours, and more
preferably 5 to 100 hours. Preferably the polymerization reaction
proceeds under static holding or with moderate stirring.
[0032] After the completion of polymerization reaction, the system
is neutralized, preferably at pH 4 to 9 by adding an alkaline
material. If the pH is below 4 or above 9, the resulting
organopolysiloxane emulsion may become low in long-term stability.
The more preferred pH range is pH 5 to 8. Examples of the alkaline
material to be added include inorganic alkaline compounds such as
alkali metal hydroxides, alkaline earth metal hydroxides, alkali
metal carbonates and alkaline earth metal carbonates, and organic
alkaline compounds such as ammonia and organic amines.
[0033] To enhance the stability of the organopolysiloxane emulsion
obtained by emulsion polymerization as component (A), any of other
anionic surfactants, nonionic surfactants and ampholytic
surfactants may be added prior to or subsequent to the emulsion
polymerization, or subsequent to neutralization as long as the
object of the invention is not impaired. Suitable anionic
surfactants include salts of higher alkyl sulfates, salts of alkyl
phenyl ether sulfates, salts of alkylbenzenesulfonic acids, salts
of higher alkyl phosphates, salts of ethoxylated higher alkyl
sulfates, salts of ethoxylated alkyl phenyl ether sulfates, and
salts of ethoxylated higher alkyl phosphates. Suitable nonionic
surfactants include ethoxylated higher alcohols, ethoxylated alkyl
phenols, polyhydric alcohol fatty acid esters, ethoxylated
polyhydric alcohol fatty acid esters, ethoxylated fatty acids,
ethoxylated fatty acid amides, sorbitol, sorbitan fatty acid
esters, ethoxylated sorbitan fatty acid esters, and sucrose fatty
acid esters. Suitable ampholytic surfactants include amino acid and
betaine surfactants.
[0034] Component (B) is the reaction product of an amino-containing
organoalkoxysilane with a dicarboxylic anhydride. It is effective
for enhancing the adhesion of a silicone coating to a substrate. It
is obtained by reacting an amino-containing organoalkoxysilane with
a dicarboxylic anhydride. One reactant, amino-containing
organoalkoxysilane is an organoalkoxysilane having the general
formula:
A(R).sub.gSi(OR).sub.3-g
wherein R is as defined above, A is an amino-containing group of
--R.sup.3(NHR.sup.3).sub.hNHR.sup.4 (wherein R.sup.3 is each
independently a C.sub.1-C.sub.6 divalent hydrocarbon group, R.sup.4
is R or hydrogen, h is an integer of 0 to 6), and g is 0, 1 or 2,
that is, an organoalkoxysilane containing an unsubstituted amino
group (i.e., --NH.sub.2) or substituted amino group (i.e.,
--NHR.sup.4) . Illustrative examples of the organoalkoxysilane are
given below.
(C.sub.2H.sub.5O).sub.3SiC.sub.3H.sub.6NH.sub.2
(C.sub.2H.sub.5O).sub.2(CH.sub.3)SiC.sub.3H.sub.6NH.sub.2
(CH.sub.3O).sub.3SiC.sub.3H.sub.6NH.sub.2
(CH.sub.3O).sub.2( CH.sub.3)SiC.sub.3H.sub.6NH.sub.2
(CH.sub.3O).sub.3SiC.sub.3H.sub.6NHC.sub.2H.sub.4NH.sub.2
(CH.sub.3O).sub.2(CH.sub.3)SiC.sub.3H.sub.6NHC.sub.2H.sub.4NH.sub.2
[0035] Examples of the dicarboxylic anhydride to be reacted with
the amino-containing organoalkoxysilane include maleic anhydride,
phthalic anhydride, succinic anhydride, methylsuccinic anhydride,
glutaric anhydride, and itaconic anhydride. Of these, maleic
anhydride is preferred. The reaction may be readily carried out by
combining the amino-containing organoalkoxysilane and the
dicarboxylic anhydride in such a ratio that the molar ratio of
amino group to acid anhydride may range from 0.5:1 to 2:1, and
mixing them at room temperature or elevated temperature, optionally
in a hydrophilic organic solvent. Suitable hydrophilic organic
solvents include alcohols such as methanol, ethanol, isopropanol
and butanol, ketones such as acetone and methyl ethyl ketone,
acetonitrile, tetrahydrofuran, and the like.
[0036] Component (B) is compounded in an amount of 0.5 to 20 parts
by weight per 100 parts by weight of component (A). Less than 0.5
part of component (B) is less effective in enhancing substrate
adhesion whereas more than 20 parts of component (B) gives a
coating which is hard and brittle. The preferred amount is 1 to 10
parts.
[0037] Component (C) is an epoxy-containing organoalkoxysilane
and/or a partial hydrolyzate thereof. It is effective for enhancing
the adhesion of a silicone coating to a substrate. Examples include
[0038] .gamma.-glycidoxypropyltrimethoxysilane, [0039]
.gamma.-glycidoxypropyldimethoxymethylsilane, [0040]
.beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and [0041]
.beta.-(3,4-epoxycyclohexyl)ethyldimethoxymethylsilane. Component
(C) is compounded in an amount of 0 to 20 parts by weight per 100
parts by weight of component (A). More than 20 parts of component
(C) gives a coating which is hard and brittle. The preferred amount
is 1 to 10 parts.
[0042] Component (D) is colloidal silica and/or polysilsesquioxane
and is added as a film reinforcement. Examples include colloidal
silica and polymethylsilsesquioxane which is a hydrolytic
condensate of trimethoxymethylsilane. The type of colloidal silica
is not limited. Typical are those having a particle size of 5 to 50
nm and stabilized with sodium, ammonia or aluminum. The colloidal
silica which can be used herein is commercially available under the
trade name of Snowtex from Nissan Chemical Industries Ltd., Ludox
from W. R. Grace & Co., Silicadol from Nippon Chemical
Industrial Co., Ltd., Adelite AT from Asahi Denka Kogyo K.K., and
Cataloid S from Catalysts & Chemicals Industries Co., Ltd.
[0043] The polymethylsilsesquioxane is obtained by adding a
condensation catalyst selected from acids such as sulfuric acid and
alkaline compounds such as potassium hydroxide to an aqueous
solution of a surfactant, adding dropwise trimethoxymethylsilane
thereto, and agitating the solution for emulsification, thereby
yielding an emulsion containing polymethylsilsesquioxane. It is
acceptable to add an alkoxytrialkylsilane, dialkoxydialkylsilane or
tetraalkoxysilane during the process for adjusting the degree of
crosslink of polysilsesquioxane. It is also acceptable to add a
vinylsilane, epoxysilane, acrylic silane or methacrylic silane for
increasing the reactivity of polysilsesquioxane. Component (D) is
compounded in an amount of 0 to 50 parts by weight per 100 parts by
weight of component (A). More than 50 parts of component (D) gives
a silicone coating which is hard and brittle. The preferred amount
is 1 to 30 parts and more preferably 2 to 25 parts. Component (D)
preferably has a particle size of 2 to 200 nm.
[0044] Component (E) is a curing catalyst which promotes
condensation reaction of components in the composition to effect
crosslinking and curing. Suitable catalysts include metal salts of
organic acids such as dibutyltin dilaurate, dibutyltin dioctate,
dioctyltin dilaurate, dioctyltin diversatate, dioctyltin diacetate,
dibutyltin bisoleylmalate, tin octylate, zinc stearate, zinc
octylate, zinc acetate, and iron octylate; and amine compounds such
as n-hexylamine and guanidine. Except for those catalysts which are
water soluble, desirably the curing catalysts are previously
converted to emulsion form by emulsifying and dispersing them in
water with the aid of a surfactant. Component (E) is compounded in
an amount of 0 to 10 parts and preferably 0 to 5 parts by weight
per 100 parts by weight of component (A). If the amount of
component (E) is more than 10 parts, the catalyst component which
is left in the coating as nonvolatile matter can adversely affect
the characteristics of a coating. Even when the amount of component
(E) is zero, crosslinking reaction will proceed because the
reaction product of an amino-containing organoalkoxysilane with a
dicarboxylic anhydride as component (B) can serve as a co-catalyst.
Addition of component (E) in an amount of up to 10 parts, and
preferably up to 5 parts allows the curing rate and the
characteristics of a coating to be regulated.
[0045] Component (F) is an organopolysiloxane containing long-chain
(preferably C.sub.4-C.sub.20) alkyl and alkoxy groups, but free of
hydroxyl groups, and is compounded for improving coating uniformity
during coating operation. Preferably, component (F) is an
organopolysiloxane having the average compositional formula
(2).
##STR00003##
[0046] Herein R.sup.1 is each independently C.sub.1-C.sub.3 alkyl
or phenyl, Q is each independently C.sub.4-C.sub.20 alkyl, Z is
each independently a group of --OR.sup.2,
--C.sub.2H.sub.4--Si(OR.sup.2).sub.3 or
--C.sub.3H.sub.6-Si(OR.sup.2).sub.3 wherein R.sup.2 is
C.sub.1-C.sub.6 alkyl, the subscript d is a positive number of 1 to
100, e is a positive number of 1 to 100, f is a positive number of
0.1 to 30, and q is 0, 1, 2 or 3.
[0047] Specifically, R.sup.1 is each independently phenyl or a
C.sub.1-C.sub.3 alkyl group, examples of which include methyl,
ethyl and propyl, with methyl being preferred. Q is each
independently a C.sub.4-C.sub.20 alkyl group, for example, butyl,
pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl,
hexadecyl and octadecyl. Of these, hexyl, octyl, decyl and dodecyl
are preferred. Z is each independently a group of --OR.sup.2,
--C.sub.2H.sub.4--Si(OR.sup.2).sub.3 or
--C.sub.3H.sub.6--Si(OR.sup.2).sub.3 wherein R.sup.2 is a
C.sub.1-C.sub.6 alkyl group. Examples of Z include methoxy, ethoxy,
propoxy, butoxy, pentyloxy, hexyloxy,
--C.sub.2H.sub.4--Si(OCH.sub.3).sub.3,
--C.sub.2H.sub.4--Si(OC.sub.2H.sub.5).sub.3,
--C.sub.3H.sub.6--Si(OCH.sub.3).sub.3,
--C.sub.3H.sub.6--Si(OC.sub.2H.sub.5).sub.3, etc. Of these,
methoxy, ethoxy and --C.sub.2H.sub.4--Si(OCH.sub.3).sub.3 are
preferred.
[0048] Of the organopolysiloxanes having the average compositional
formula (2), those having the average compositional formula (3) are
more preferred.
##STR00004##
[0049] Herein Q is each independently selected from hexyl, octyl,
decyl, and dodecyl, Z is each independently selected from methoxy,
ethoxy and --C.sub.2H.sub.4--Si(OCH.sub.3).sub.3, the subscript d
is a positive number of 1 to 100, e is a positive number of 1 to
100, and f is a positive number of 0.1 to 30.
[0050] From the standpoint of coating uniformity, d is a positive
number of 1 to 100, e is a positive number of 1 to 100, and f is a
positive number of 0.1 to 30; and preferably d is a positive number
of 2 to 90, e is a positive number of 2 to 90, and f is a positive
number of 0.1 to 20.
[0051] Component (F) is compounded in an amount of 0.5 to 20 parts
by weight per 100 parts by weight of component (A). Less than 0.5
part of component (F) is ineffective for imparting coating
uniformity whereas more than 20 parts interferes with curing of a
coating and adversely affects coating properties. The preferred
amount of component (F) is 1 to 15 parts, and more preferably 1 to
10 parts by weight per 100 parts by weight of component (A).
[0052] A surfactant (G) is used to keep the foregoing components in
emulsion form. It is not particularly limited. Suitable surfactants
include anionic surfactants, for example, alkyl sulfates,
alkylbenzenesulfonates, and alkyl phosphates (i.e., salts);
nonionic surfactants, for example, polyoxyethylene alkyl ethers,
polyoxyethylene alkyl phenyl ethers, and polyoxyethylene fatty acid
esters; cationic surfactants, for example, quaternary ammonium
salts and alkylamine acetates; and ampholytic surfactants, for
example, alkyl betaine and alkylimidazoline compounds. Also useful
are water-soluble polymers such as polyvinyl alcohol.
[0053] The coating emulsion composition of the invention may be
prepared by emulsifying and dispersing the foregoing components (A)
to (F) in water in the presence of surfactant (G). The emulsifying
and dispersing step to produce an emulsion composition is desirably
conducted under a high shear pressure of at least 10 MPa using a
high-pressure emulsifying machine, typically homogenizer. If the
pressure is below 10 MPa, it may be difficult to produce an
emulsion having an average particle size of up to 500 nm. A shear
pressure in excess of 200 MPa is inefficient because the effect of
further reducing the average particle size is not expected. The
preferred shear pressure is 15 to 150 MPa and more preferably 20 to
100 MPa. Prior to this high-pressure emulsification, preliminary
emulsification may be conducted, if desired, using a homomixer,
Agi-Homo-Mixer (Primix Corp.), Combi-Mix (Primix Corp.), Supraton
(trade name), Clear-Mix (M Technique), colloid mill or the like.
Similar emulsifying and dispersing techniques are applicable in an
embodiment wherein components (A) to (F) are individually prepared
as separate emulsions before they are combined together.
[0054] The method of coating a substrate with the coating emulsion
composition of the invention is not particularly limited. The
composition is applied to a substrate by any of well-known coating
techniques including brush coating, roll coating, gravure coating,
bar coating, spraying, knife coating, and dipping, and thereafter,
water is evaporated off, yielding a silicone coating. For improving
the efficiency of coating operation, a thickener or the like may be
added to the composition to adjust the viscosity thereof. Suitable
thickeners include carboxymethyl cellulose, sodium polyacrylate,
starch, casein, cellulose acetate, hydroxyethyl cellulose, and
polyvinyl alcohol.
[0055] The coating emulsion composition of the invention may be
used as a water repellent, anti-water-absorbing agent, release
agent, or anti-fouling agent to be applied to films, paper sheets
and the like, but its use is not limited thereto.
Second Embodiment
[0056] Next, the water- and oil-repellent paper sheet according to
the second embodiment of the invention is described.
[0057] The water- and oil-repellent paper sheet includes a water-
and oil-repellent, releasable silicone resin layer on at least one
surface of a paper substrate.
[0058] The paper substrate used herein is not particularly limited.
A choice of paper may be made depending on a particular application
as long as a silicone resin layer can be formed on at least one
surface thereof. Suitable paper substrates include kraft paper,
wood-free paper, paper board, liner, glassine paper, and parchment
paper. The fibrous material of which the paper substrate is made is
not limited to cellulose and cellulose derivatives. Also, instead
of paper substrates, woven fabrics and non-woven fabrics comprising
fibers derived from raw materials other than cellulose and
cellulose derivatives may be used as the substrate.
[0059] The silicone resin layer or coating has not only good water
repellency and release characteristic of silicone, but also good
film strength and oil repellency due to a three-dimensional
crosslinked structure characteristic of resin. Because of this
nature, it can impart oil repellency, water repellency and release
at the same time. Since the silicone resin is more flexible than
other organic resins, it forms a coating having good fold
resistance. Then the paper sheet maintains good oil and water
repellency even when folded.
[0060] For convenience of description, the paper sheet includes a
planar portion normally and a folded portion when folded. Since the
water- and oil-repellent paper sheet of the invention has a
silicone resin layer featuring flexibility, oil repellency, water
repellency and releasability, it exhibits improved oil resistance
and water repellency as demonstrated below. The planar portion
exhibits an oil resistance which is at least 9 in Kit value and the
folded portion exhibits an oil resistance which is at least 8 in
Kit value, both as measured at a temperature 20.degree. C. and a
humidity 50% by J. TAPPI paper/pulp test No. 41-83. This indicates
that oil resistance is little reduced by folding. Also, the planar
portion exhibits a water repellency which is at least R8 and the
folded portion exhibits a water repellency which is at least R7,
both as measured by J. TAPPI paper/pulp test No. 68:2000. This
indicates that water repellency is little reduced by folding.
[0061] The water- and oil-repellent paper sheet may be prepared by
coating a water- and oil-repellent composition primarily comprising
an aqueous silicone resin emulsion on at least one surface of a
paper substrate so as to give a dry coating weight of at least 1.0
g/m.sup.2, and preferably a dry coating weight of 1.0 to 4.0
g/m.sup.2 sufficient to ensure water and oil repellency and to
maintain paper flexibility, with a dry coating weight of 1.0 to 2.0
g/m.sup.2 being more preferred from a commercial standpoint. It is
noted that an appropriate coating weight may vary with the type of
paper substrate and a particular application.
[0062] The coating operation may be conducted in an ordinary way
using any desired applicator such as a calender roll, size press
roll, roll coater, blade coater, air knife coater, bar coater, and
gravure coater. The number of coating steps may be determined
appropriate in accordance with a coating weight of one pass and the
final coating weight. The buildup of the water- and oil-repellent
composition on the paper substrate is then dried, for example, at a
temperature of 80 to 160.degree. C. for 20 seconds to 2 minutes
whereby the composition is cured simultaneously, forming a silicone
resin layer. The silicone resin layer generally has a thickness of
about 1 .mu.m to about 4 .parallel.m.
[0063] Described below is the water- and oil-repellent composition
used to form the silicone resin layer on the paper substrate. From
the safety aspect, the composition is preferably a silicone-based
water- and oil-repellent composition primarily comprising an
aqueous silicone resin emulsion, and specifically an aqueous
silicone resin emulsion comprising components (a) to (e):
[0064] (a) 100 parts by weight of an organopolysiloxane containing
at least two silicon-bonded hydroxyl groups in a molecule,
[0065] (b) 0.5 to 20 parts by weight of a dicarboxylic acid base
curing agent,
[0066] (c) 1 to 50 parts by weight of silica,
[0067] (d) 2 to 4 parts by weight of an organopolysiloxane
containing long-chain alkyl and alkoxy groups, but free of hydroxyl
groups, and
[0068] (e) an effective amount to form an emulsion of a
surfactant,
because the resulting coating has improved oil repellency, water
repellency, release and flexibility.
[0069] Component (a) is an organopolysiloxane containing at least
two, preferably 2 to 200, silicon-bonded hydroxyl groups in a
molecule. The organopolysiloxane has a main skeleton of
polysiloxane which is a generally linear structure having a degree
of polymerization of 100 to 10,000, and may be branched to such an
extent that the flexibility of a resultant coating is not
compromised. If the degree of polymerization is less than 100, the
coating becomes poor in oil repellency when folded. If the degree
of polymerization is more than 10,000, the coating becomes less oil
repellent. The preferred degree of polymerization is 1,000 to
5,000.
[0070] The organopolysiloxane also contains organic groups attached
to silicon atoms at ends and side chains, which include
C.sub.1-C.sub.20 alkyl groups and C.sub.6-C.sub.20 aryl groups, and
if partially, C.sub.1-C.sub.20 alkoxy groups. From the crosslinking
standpoint, at least two silicon-bonded hydroxyl groups must be
included per molecule. Illustrative examples of suitable organic
groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,
octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl,
cyclopentyl, cyclohexyl, cycloheptyl, phenyl, tolyl, and naphthyl,
with methyl being preferred. Suitable alkoxy groups include
methoxy, ethoxy, propoxy, butoxy, hexyloxy, heptyloxy, octyloxy,
decyloxy, and tetradecyloxy.
[0071] Examples of organopolysiloxane (a) may be the same as
component (A) and include those of formulae (i) to (vi).
[0072] Component (b) is a dicarboxylic acid curing agent which
serves as a crosslinker for forming a cured silicone coating and
also serves to improve adhesion to the substrate. The dicarboxylic
acid curing agent is typically selected from dicarboxylic
anhydrides and reaction products thereof.
[0073] Examples of the dicarboxylic anhydride include oxalic
anhydride, maleic anhydride, phthalic anhydride, succinic
anhydride, and methylsuccinic anhydride.
[0074] The dicarboxylic anhydride may be used as its reaction
product with an alkaline compound for further improving solubility
or with a silane coupling agent for improving adhesion to the
substrate. Examples of the silane coupling agent used herein
include alkyl silicates such as tetraethyl silicate, and
organoalkoxysilanes, for example, alkylalkoxysilanes such as
methyltriethoxysilane, alkenyl-containing alkoxysilanes such as
vinyltriethoxysilane, amino-containing alkoxysilanes such as
3-aminopropyltriethoxysilane, methacryloxy-containing alkoxysilanes
such as methacryloxypropyltriethoxysilane, and condensates of the
foregoing.
[0075] As component (b), examples of component (B) described
earlier may be used.
[0076] Component (b) is compounded in an amount of 0.5 to 20 parts
by weight per 100 parts by weight of component (a). Less than 0.5
part of component (b) is less effective in enhancing substrate
adhesion whereas more than 20 parts of component (b) gives a
coating which is hard and brittle and becomes less oil and water
repellent when folded. The preferred amount is 1 to 10 parts.
[0077] Component (c) is silica and is added as a film
reinforcement. Use may be made of silicas prepared by wet and dry
processes and silicas commercially available as water dispersions.
Although the type of silica is not limited, hydrophilic silicas are
preferred. Preferred are silicas having a specific surface area of
10 to 1,000 m.sup.2/g as measured by the BET method and an average
particle size for primary particles of 2 to 200 nm. Examples of
silica used include AEROSIL (Nippon Aerosil Co., Ltd.), TOKUSIL
(Tokuyama Co., Ltd.), NIPSIL (Tosoh Silica Co., Ltd.), and SYLYSIA
(Fuji Sylysia Co., Ltd.). Colloidal silica of component (D) may
also be used as component (c), examples of which include Snowtex
(Nissan Chemical Industries Ltd.), Ludox (W. R. Grace & Co.),
Silicadol (Nippon Chemical Industrial Co., Ltd.), Adelite AT (Asahi
Denka Kogyo K.K.), and Cataloid S (Catalysts & Chemicals
Industries Co., Ltd.).
[0078] Component (c) is compounded in an amount of 1 to 50 parts by
weight per 100 parts by weight of component (a). If the amount of
component (c) is less than 1 part, the coating has a low strength
and poor oil repellency. More than 50 parts of component (c) gives
a coating which is hard and brittle and becomes less oil repellent
when folded. The preferred amount is 5 to 30 parts.
[0079] Component (d) is an organopolysiloxane containing long-chain
alkyl and alkoxy groups, but free of hydroxyl groups, and serves to
facilitate coating of the silicone base oil repellent composition.
It improves leveling properties during coating, ensures to form a
coating having improved flatness and uniformity, and eventually
improves the performance of the resulting paper sheet.
[0080] This organopolysiloxane has a generally linear structure
having a degree of polymerization of 5 to 260 and contain organic
groups attached to. silicon atoms at ends and side chains. The
organic groups are mainly C.sub.1-C.sub.3 alkyl groups. For the
effect of improving coating ability, the organopolysiloxane should
contain per molecule 1 to 100, more preferably 1 to 80 long-chain
alkyl groups of 4 to 20 carbon atoms, and 0.1 to 30, more
preferably 1 to 30 C.sub.1-C.sub.6 alkoxy groups or C.sub.2-C.sub.3
alkyl groups having substituted thereon alkoxysilyl groups
containing C.sub.1-C.sub.6 alkoxy groups.
[0081] Examples of the C.sub.1-C.sub.3 alkyl groups include methyl,
ethyl, and propyl, with methyl being preferred. Examples of the
long-chain alkyl groups of 4 to 20 carbon atoms include butyl,
pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl,
hexadecyl, and octadecyl, with hexyl, octyl, decyl and dodecyl
being preferred. Examples of the C.sub.1-C.sub.6 alkoxy groups
include methoxy, ethoxy, propoxy, butoxy, pentyloxy, and hexyloxy.
Examples of the C.sub.2-C.sub.3 alkyl groups having substituted
thereon alkoxysilyl groups containing C.sub.1-C.sub.6 alkoxy groups
include --C.sub.2H.sub.4--Si(OCH.sub.3).sub.3,
--C.sub.2H.sub.4--Si(OC.sub.2H.sub.5).sub.3,
--C.sub.3H.sub.6--Si(OCH.sub.3).sub.3,
--C.sub.3H.sub.6--Si(OC.sub.2H.sub.5).sub.3, etc. Of these,
methoxy, ethoxy and --C.sub.2H.sub.4--Si(OCH.sub.3).sub.3 are
preferred.
[0082] As component (d), examples of component (F) described
earlier may be used.
[0083] Component (d) is compounded in an amount of 2 to 4 parts by
weight per 100 parts by weight of component (a). Less than 2 parts
is little effective for facilitating coating operation whereas more
than 4 parts may adversely affect the oil repellency of a
coating.
[0084] Component (e) is a surfactant which is used to keep the
foregoing components in emulsion form. Its type is not particularly
limited. Suitable surfactants include anionic surfactants, for
example, alkyl sulfates, alkylbenzenesulfonates, and alkyl
phosphates (i.e., salts); nonionic surfactants, for example,
polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers,
and polyoxyethylene fatty acid esters; and cationic surfactants,
for example, quaternary ammonium salts and alkylamine acetates.
Those as exemplified for component (G) are useful.
[0085] The amount of component (e) used is not particularly limited
as long as it is effective to form an emulsion. Usually component
(e) is used in an amount of 1 to 20 parts by weight per 100 parts
by weight of component (a).
[0086] In the water- and oil-repellent composition, a catalyst for
promoting condensation reaction of the foregoing components for
curing may be added, if desired, in an amount of up to 10 parts,
and more specifically up to 5 parts by weight per 100 parts by
weight of component (a). The catalyst need not always be added
because component (b) has such catalysis.
[0087] In the water- and oil-repellent composition, any of
commercial silicone resin emulsions to be applied to paper
substrates and clearing the food safety standards may be admixed
insofar as the objects of the invention are not compromised. Also,
defoamers or the like may be compounded in the silicone base water-
and oil-repellent composition for improving the smoothness of a
silicone resin layer or the like.
EXAMPLE
[0088] Examples and Comparative Examples are given below for
further illustrating the invention, but the invention is not
limited thereto. In Examples, all parts and percents are by
weight.
Synthesis Example 1
[0089] A 2-L polyethylene beaker was charged with 498 g of
octamethylcyclotetrasiloxane, 2 g of triethoxyphenylsilane, 50 g of
10% sodium laurylsulfate aqueous solution, and 50 g of 10%
dodecylbenzenesulfonic acid aqueous solution. Using a homomixer,
the components were emulsified uniformly, after which 400 g of
water was slowly added for dilution. This was passed two times
through a high-pressure homogenizer under a pressure of 30 MPa,
obtaining a uniform white emulsion. The emulsion was transferred to
a 2-L glass flask equipped with an agitator, thermometer, and
reflux condenser where polymerization reaction was effected at
50.degree. C. for 24 hours. It was allowed to mature at 10.degree.
C. for 24 hours before it was neutralized to pH 6.2 with 12 g of
10% sodium carbonate aqueous solution. This emulsion had a
nonvolatile content of 45.4% after drying at 105.degree. C. for 3
hours and contained an organopolysiloxane in a non-flowing soft gel
form which had the average compositional formula shown below and
was end-capped with hydroxyl groups. In this way, an emulsion (A-1)
containing 44.4% of component (A) was obtained.
##STR00005##
Herein Me stands for methyl, Ph stands for phenyl, m=1, and
n+p=1,000.
Synthesis Example 2
[0090] A 2-L polyethylene beaker was charged with 500 g of
octamethylcyclotetrasiloxane, 50 g of 10% sodium laurylsulfate
aqueous solution, and 50 g of 10% dodecylbenzenesulfonic acid
aqueous solution. Using a homomixer, the components were emulsified
uniformly, after which 400 g of water was slowly added for
dilution. This was passed two times through a high-pressure
homogenizer under a pressure of 30 MPa, obtaining a uniform white
emulsion. The emulsion was transferred to a 2-L glass flask
equipped with an agitator, thermometer, and reflux condenser where
polymerization reaction was effected at 50.degree. C. for 24 hours.
It was allowed to mature at 10.degree. C. for 24 hours before it
was neutralized to pH 6.2 with 12 g of 10% sodium carbonate aqueous
solution. This emulsion had a nonvolatile content of 45.5% after
drying at 105.degree. C. for 3 hours and contained an
organopolysiloxane in a gum form which had the formula:
HO--[(CH.sub.3).sub.2SiO].sub.n--H and a viscosity of more than
1,000 Pa-s. In this way, an emulsion (A-2) containing 44.5% of
component (A) was obtained.
Synthesis Example 3
[0091] In 500 g of ethanol was dissolved 154 g of maleic anhydride.
To the solution, 346 g of 3-aminopropyltriethoxy-silane was added
dropwise at room temperature over one hour, followed by reaction
for 24 hours under ethanol reflux at 80.degree. C. This yielded a
pale yellow clear solution (B-1) containing 50% of component (B).
This solution had a nonvolatile content of 45.1% after drying at
105.degree. C. for 3 hours. On analysis by IR, GC, NMR and GCMS,
the reaction product in the solution consisted of about 60% of a
mixture of compounds of the formulae:
(C.sub.2H.sub.5O).sub.3SiC.sub.3H.sub.6--NHCO--CH.dbd.CHCOOH
and
(C.sub.2H.sub.5O).sub.3SiC.sub.3H.sub.6--NH.sub.3.sup.+C.sub.2H.sub.5OCO-
CH.dbd.CHCOO--
and the balance (about 40%) of oligomers derived therefrom.
Synthesis Example 4
[0092] A 2-L polyethylene beaker was charged with 300 g of
dioctyltin dilaurate and 50 g of polyoxyethylene nonyl phenyl ether
(EO 10 mole addition product), which were uniformly mixed by a
homomixer. Water, 650 g, was slowly added to the mixture whereby
the components were emulsified and dispersed in water. This was
passed two times through a high-pressure homogenizer under a
pressure of 30 MPa, yielding an emulsion (E-1) containing 30% of
component (E).
Synthesis Example 5
[0093] A 2-L polyethylene beaker was charged with 500 g of an
organopolysiloxane containing long-chain alkyl and alkoxy groups
represented by the average compositional formula shown below, and
having a dynamic viscosity of 37 mm.sup.2/s, 20 g of
polyoxyethylene decyl ether (EO 4 mole addition product), and 5 g
of sodium sulfosuccinate, which were uniformly mixed by a
homomixer. Water, 475 g, was slowly added to the mixture whereby
the components were emulsified and dispersed in water. This was
passed two times through a high-pressure homogenizer under a
pressure of 30 MPa, yielding an emulsion (F-1) containing 50% of
component (F).
##STR00006##
Examples 1-4 & Comparative Examples 1-3
[0094] Component (C) used was y-glycidoxypropyltrimethoxy-silane
(C-1). Component (D) used was colloidal silica (Snowtex C, Nissan
Chemical Industries Ltd., effective component 20%). A series of
silicone emulsion compositions were prepared by mixing components
(A) to (F) in accordance with the recipe (in amounts of neat
components) of Table 1. Using a wire bar, the silicone emulsion
compositions were coated onto white paper board to a net coating
weight of 2 g/m.sup.2, and the coating surface state (coated state)
was visually observed. The coating was dried at 80.degree. C. for
one minute, after which the coating was examined for surface tack
and adhesion to the substrate. The coating was also examined for
release by attaching a pressure-sensitive adhesive tape to the
coating surface and peeling the tape. The results are shown in
Table 1.
TABLE-US-00001 TABLE 1 Comparative Example Example 1 2 3 4 1 2 3
Composition Component (A) A-1 100 100 100 -- 100 100 100 based on
neat A-2 -- -- -- 100 -- -- -- component Component (B) B-1 1 1 1.5
2 1 1 1 (pbw) Component (C) C-1 1 1 -- 2 1 1 1 Component (D) D-1 14
14 14 20 14 14 14 Component (E) E-1 -- 0.3 -- -- -- 0.3 --
Component (F) F-1 3 3 3 3 -- -- 25 Coated state *1 .largecircle.
.largecircle. .largecircle. .largecircle. X X .largecircle. Coating
Tack *2 .largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. X Adhesion *3 .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. X Release *4 .largecircle. .largecircle.
.largecircle. .largecircle. X X .largecircle. *1 .largecircle.:
even, X: uneven *2 .largecircle.: tack-free, X: tack *3
.largecircle.: coating does not peel off on finger rubbing, X:
coating peels off on finger rubbing *4 .largecircle.: light
release, X: resistant to release due to local adhesion to
substrate
Example 5
[0095] The following components: [0096] component (a): linear
methylpolysiloxane (degree of polymerization 1,000, hydroxyl
content 0.004 mole/100 g), 100 g [0097] component (b): reaction
product of maleic anhydride and 3-aminopropyltriethoxysilane (molar
ratio=1/1), 1 g component (c): untreated dry silica (BET surface
area 200 m.sup.2/g, primary average particle size 10 nm), 15 g
[0098] component (d): linear polysiloxane (degree of polymerization
30, organic groups attached to silicon atoms consisted of 10% octyl
groups, 2% propoxy groups and the balance of methyl groups), 3 g
sodium laurylsulfate, 10 g water, 129 g were mixed together and
uniformly emulsified on a homomixer to form a uniform white aqueous
silicone resin emulsion. It was a silicone base water- and
oil-repellent composition with 50% of effective components.
[0099] The paper substrate used was a white paper board (base
paper) having a basis weight of 350 g/m.sup.2 which had not been
coated with a functional agent. Using a wire bar #5, the silicone
base water- and oil-repellent composition was coated onto one
surface of the base paper so as to give a dry coating weight of 1.5
to 2.0 g/m.sup.2. The coating was dried and cured at 120.degree. C.
for 30 seconds to form a silicone resin layer. A water- and
oil-repellent paper sheet was prepared in this way.
[0100] The water- and oil-repellent paper sheet was determined for
oil resistance, water repellency and release by the following
tests. The results are shown in Table 2.
Oil resistance of planar portion:
[0101] The coated surface was measured according to J. TAPPI
paper/pulp test No. 41-83 (Kit method). The measurement was by
visual observation.
Oil resistance of folded portion:
[0102] A paper sample was folded in two sections so that the coated
surface faced outside. The folded portion was compressed from above
under conditions: width 1.0 mm, depth 0.7 mm, and pressure 2.5
kgf/cm.sup.2-sec, to define a complete fold. Then the paper sample
was opened again, and the folded portion was measured for oil
resistance according to J. TAPPI paper/pulp test No. 41-83 (Kit
method). The measurement was by visual observation.
Water repellency of planar portion:
[0103] The coated surface was measured according to J. TAPPI
paper/pulp test No. 68:2000. The measurement was by visual
observation.
Water repellency of folded portion:
[0104] A paper sample was folded in two sections so that the coated
surface faced outside. The folded portion was compressed from above
under conditions: width 1.0 mm, depth 0.7 mm, and pressure 2.5
kgf/cm.sup.2-sec, to define a complete fold. Then the paper sample
was opened again, and the folded portion was measured for water
repellency according to J. TAPPI paper/pulp test No. 68:2000. The
measurement was by visual observation.
Release:
[0105] A 18 mm.times.35 mm piece of pressure-sensitive adhesive
tape (Cellotape.RTM. by Nichiban Co., Ltd.) was attached to the
coating surface and pressed thereto by rolling a tape roller of 2
kg one stroke. The assembly was held at 25.degree. C. for one hour,
after which the adhesive tape was manually peeled. The release
property of the coated paper was rated ".largecircle."](smooth
release) when the adhesive tape was readily peeled manually without
noise and ".times." (poor release) when the adhesive tape was
peeled with noise or manually peeled with a heavy feel.
Comparative Example 4
[0106] This is a reference. A white paper board (base paper) having
a basis weight of 350 g/m.sup.2 without coating of the silicone
base water- and oil-repellent composition was examined as in
Example 5.
Comparative Example 5
[0107] A coated paper sample was prepared as in Example 5 except
that an aqueous silicone resin emulsion without component (d) was
prepared and used as a silicone base water- and oil-repellent
composition with 50% of effective components. It was similarly
tested.
TABLE-US-00002 TABLE 2 Comparative Example Example Test 5 4 5 Oil
resistance of planar portion 10 0 8 Oil resistance of folded
portion 9 0 6 Water repellency of planar portion R9 R0 R7 Water
repellency of folded portion R8 R0 R6 Release .largecircle. X
.largecircle.
[0108] It is seen from Table 2 that the water- and oil-repellent
paper sheet of the invention exhibits excellent oil resistance,
water repellency and release property. The values of a folded
portion are comparable to those of a planar portion. Only minimal
losses of oil resistance and water repellency occur when
folded.
[0109] Japanese Patent Application Nos. 2006-279800 and 2006-279815
are incorporated herein by reference.
[0110] Although some preferred embodiments have been described,
many modifications and variations may be made thereto in light of
the above teachings. It is therefore to be understood that the
invention may be practiced otherwise than as specifically described
without departing from the scope of the appended claims.
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