U.S. patent application number 09/775776 was filed with the patent office on 2001-06-28 for aqueous dispersion of a peelable coating composition.
This patent application is currently assigned to Rinrei Wax Co., Ltd.. Invention is credited to Akasaka, Kensaku, Asai, Hirotaka, Kurota, Hisashi, Matsuki, Masayuki, Matsuyama, Noritsumi, Obara, Hideki, Tojo, Hideaki, Yamashita, Kenji.
Application Number | 20010005733 09/775776 |
Document ID | / |
Family ID | 27542699 |
Filed Date | 2001-06-28 |
United States Patent
Application |
20010005733 |
Kind Code |
A1 |
Yamashita, Kenji ; et
al. |
June 28, 2001 |
Aqueous dispersion of a peelable coating composition
Abstract
The aqueous dispersion of a peelable coating composition of the
present invention is (a) a mixture containing 5-40% by weight of an
emulsion of an acrylic copolymer having a glass transition
temperature (hereinafter referred to as "Tg") of not lower than
40.degree. C., and 95-60% by weight of an emulsion of another
acrylic copolymer having a Tg ranging from -20.degree. C. through
5.degree. C. The acrylic copolymer emulsion mixture (b) contains
ethylenically unsaturated vinyl monomers having acid value in a
total amount of 0.5-1.0% by weight, and (c) at least one of the
acrylic copolymer emulsions is an acrylic copolymer which has been
polymerized by use of a reactive surfactant, and (d) the particle
size of the acrylic copolymer emulsions is not more than 200
nm.
Inventors: |
Yamashita, Kenji;
(Hadano-shi, JP) ; Matsuki, Masayuki; (Hadano-shi,
JP) ; Asai, Hirotaka; (Hadano-shi, JP) ;
Matsuyama, Noritsumi; (Hadano-shi, JP) ; Tojo,
Hideaki; (Tokyo, JP) ; Kurota, Hisashi;
(Tokyo, JP) ; Akasaka, Kensaku; (Tokyo, JP)
; Obara, Hideki; (Tokyo, JP) |
Correspondence
Address: |
Charles A. Muserlian
c/o Bierman, Muserlian and Lucas
600 Third Avenue
New York
NY
10016
US
|
Assignee: |
Rinrei Wax Co., Ltd.
|
Family ID: |
27542699 |
Appl. No.: |
09/775776 |
Filed: |
February 2, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09775776 |
Feb 2, 2001 |
|
|
|
08953090 |
Oct 17, 1997 |
|
|
|
6211282 |
|
|
|
|
Current U.S.
Class: |
524/501 ;
524/522; 524/523; 524/533; 525/228 |
Current CPC
Class: |
C08L 2666/04 20130101;
C08L 33/06 20130101; C09D 133/06 20130101; Y10T 428/31928 20150401;
Y10T 428/31699 20150401; C09D 133/06 20130101; Y10T 428/31649
20150401; Y10T 428/31935 20150401; C09D 5/20 20130101 |
Class at
Publication: |
524/501 ;
524/522; 524/523; 524/533; 525/228 |
International
Class: |
C08L 033/02; C08L
033/08; C08L 033/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 23, 1996 |
JP |
8-100986 |
Claims
What is claimed is:
1. An aqueous dispersion of a peelable coating composition
comprising: (a) a mixture containing 5-40% by weight of an emulsion
of an acrylic copolymer having a glass transition temperature
(hereinafter referred to as "Tg") of not lower than 40.degree. C.,
and 95-60% by weight of an emulsion of another acrylic copolymer
having a Tg ranging from -20.degree. C. through 5.degree. C.;
wherein (b) the acrylic copolymer emulsion mixture (a) contains
ethylenically unsaturated vinyl monomers having acid value in a
total amount of less than 2.0% by weight; and (c) the acrylic
copolymer emulsion mixture (a) contains no nitrogen-containing
vinyl monomers in the form of a monomer.
2. An aqueous dispersion of a peelable coating composition of the
present invention according to claim 1, wherein at least one of the
acrylic copolymer emulsions described in (a) is an acrylic
copolymer which has been polymerized by use of a reactive
surfactant, and the particle size of the acrylic copolymer
emulsions is not more than 200 nm.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an aqueous dispersion of a
peelable coating composition which is intended to be used for
temporary protection of articles and is effective in temporary
storage of articles during distribution, where articles may be
temporarily stored in the open air or exposed to the open air
during distribution.
[0003] 2. Description of the Related Art
[0004] In more and more cases, articles such as automobiles and
other vehicles, machine parts, metallic household articles and
other ferrous and non-ferrous articles, wooden articles, glass
articles, rubber articles, and coated rubber articles (hereinafter
collectively referred to as "articles") reach the hands of
consumers after being transported from the manufacturer and stored
temporarily in the open air. In such cases, during the period
before these articles are in hands of consumers (generally this
period is 2-12 months in duration), the surfaces of these goods are
prone to becoming scratched, stained, discolored, or contaminated
due to, for example, deposits such as sandy dust, iron powder,
salts, alkalis, acids, soot and smoke, dead bodies or body fluids
of insects, and excrement of birds and insects; sunlight; and wind
and rain. Moreover, the material may come to have marks due to
physical forces.
[0005] These deposits, etc. must be removed as soon as possible, as
they may reduce the value of goods. However, removal of deposits
requires elaborate work, which is accompanied by additional
costs.
[0006] Thus, in order to temporarily protect surfaces of an article
from being damaged by the aforementioned deposits, sunlight,
elements, or scratches, and to eliminate the elaborate work and
accompanying costs, there have been proposed a number of strippable
coating compositions which areapplied to surfaces of an article
when the article is shipped, and which, after a predetermined
period of custody is over, can be easily stripped off.
[0007] For example, two types of strippable coating compositions
are used for outer panels of automobiles: one is a so-calledoily
wax type in which paraffin wax is dispersed in a petroleum-based
solvent, and the other is a type in which a mixture of calcium
carbonate powder in paraffin wax is dispersed in a petroleum-based
solvent.
[0008] These strippable coating compositions call for use of a
petroleum-based solvent for removal, and in addition, they may
raise the fear of environmental problems such as air pollution.
Compositions of a type in which an alkali-soluble resin is the
primary component are also used, and these require an alkali
detergent for removal, and therefore involve the problem of
environmental pollution such as water contamination.
[0009] Accordingly, in order to eliminate the aforementioned
problems, there have been proposed emulsion-type coating
compositions which form a coating film capable of being peeled off
by hand after they have carried out their function of protection
(see, for example, Japanese Patent Publication (kokoku) Nos.
50-39685 and 44-29583).
[0010] However, the above-described conventional coating
compositions of the emulsion type have the following drawbacks.
[0011] 1) The coating compositions disclosed in Japanese Patent
Publication (kokoku) No. 50-39685 are made from a single starting
material. Therefore, their peeling property is not satisfactory
under environmental conditions in which they are usually used. For
example, they cannot be satisfactorily peeled off in a wide
temperature range from low temperatures around 5.degree. C. to high
temperatures around 40.degree. C.: at low temperatures the formed
film breaks during the peeling operation, whereas at high
temperatures it stretches and thus is not quickly peeled off.
[0012] 2) Japanese Patent Publication No. 44-29593 discloses a
coating composition obtained through emulsion polymerization in
water of acrylonitrile and an acrylic acid ester of an lower
alkyl.
[0013] Aqueous dispersions of an acrylic resin which contains
acrylonitrile as an essential component raise a problem that
harmful nitrogen oxides are produced during incineration of waste
films that have been peeled and cause environmental pollution.
[0014] In the meantime, regarding peelable coating compositions for
use with automobile outer panels, there exists need for
compositions capable of forming a protective film that exerts
contrasting functions simultaneously in terms of adhesion; i.e.,
proper adhesiveness and holding power that does not permit release
of the film with ease during water-resistance tests or that never
permits release during transportation of vehicles under protection
by the film, and ease in peeling of the film with fingers after the
period of protection by the film is over.
SUMMARY OF THE INVENTION
[0015] To solve the above-described problems and meet the
above-stated need, the present inventors have carried out careful
studies on dispersion compositions that do not contain a
nitrogen-containing vinyl monomer, and have found that an aqueous
dispersion of a peelable coating composition having excellent
peelability can be obtained by forming an e mulsion having the
following characteristics: 1) the emulsion is an acrylic copolymer
emulsion which is a mixture of two acrylic copolymer emulsions,
wherein the acrylic copolymers have different predetermined glass
transition temperatures, 2) the amount of ethylenically unsaturated
monomers having acid value contained in the mixture is not higher
than a predetermined level, and 3) the emulsion does not make use
of a nitrogen-containing monomer. The present invention has been
accomplished based on this finding.
[0016] Moreover, the present inventors have found that, in addition
to the above-mentioned features 1) through 3), when 4)
polymerization is performed under conditions in which at least one
of the emulsions contains a reactive surfactant and 5) the particle
size of the emulsions is controlled to fall within a predetermined
range, there can be obtained an aqueous dispersion of a peelable
coating composition having further improved water resistance and
excellent adhesiveness, leading to completion of the present
invention.
[0017] Accordingly, a first aqueous dispersion of a peelable
coating composition of the present invention is characterized by
comprising
[0018] (a) a mixture containing 5-40% by weight of an emulsion of
an acrylic copolymer having a glass transition temperature
(hereinafter referred to as "Tg") of not lower than 40.degree. C.,
and 95-60% by weight of an emulsion of another acrylic copolymer
having a Tg ranging from -20.degree. C. through 5.degree. C.;
wherein
[0019] (b) the acrylic copolymer emulsion mixture (a) contains
ethylenically unsaturated vinyl monomers having acid value in a
total amount of less than 2.0% by weight; and
[0020] (c) the acrylic copolymer emulsion mixture (a) contains no
nitrogen-containing vinyl monomers in the form of a monomer.
[0021] A second aqueous dispersion of a peelable coating
composition of the present invention is characterized by, in
addition to the aforementioned requirements (a), (b), and (c),
[0022] (d) at least one of the acrylic copolymer emulsions to be
incorporated into the mixture is an acrylic copolymer which has
been polymerized by use of a reactive surfactant, and
[0023] (e) the particle size of the acrylic copolymer emulsions is
not more than 200 nm.
MODES FOR CARRYING OUT THE INVENTION
[0024] Next will be described modes for carrying out the present
invention.
[0025] A first mode of the present invention is drawn to the first
aqueous dispersion of a peelable coating composition characterized
by an acrylic copolymer emulsion having the below-described
features (a) through (c). Synergism of these features afford, as
demonstrated in Examples hereinbelow, not only excellent
physicochemical properties including water resistance, adhesive
strength, protective power, and weatherability during the period of
protection, but also excellent peelability in a wide temperature
range from low temperatures (about 5.degree. C.) to high
temperatures (about 40.degree. C.) after the protection period is
over, and in addition, when the after-use waste film is
incinerated, the film does not generate nitrogen oxides and thus
eliminates adverse effects of environmental pollution, etc.
[0026] (a) The acrylic copolymer emulsion mixture of the present
invention contains 5-40% by weight of an emulsion of an acrylic
copolymer having a glass transition temperature o f not lower than
40.degree. C. and 95-60% by weight of an emulsion of another
acrylic copolymer having a Tg ranging from -20.degree. C. through
5.degree. C.
[0027] (b) The acrylic copolymer emulsion mixture (a) contains
ethylenically unsaturated vinyl monomers having acid value in a
total amount of less than 2.0% by weight.
[0028] (c) The acrylic copolymer emulsion mixture (a) contains no
nitrogen source such as acrylonitrile in the form of a monomer.
[0029] A second mode of the present invention is drawn to the
second aqueous dispersion of a peelable coating composition of the
present invention characterized by, in addition to the
aforementioned requirements (a), (b), and (c), the following
features (d) and (e). Synergism of all these features afford, as
demonstrated in Examples hereinbelow, excellent physicochemical
properties including water resistance, adhesive strength, and so
on.
[0030] (d) At least one of the acrylic copolymer emulsions to be
incorporated into the mixture is an acrylic copolymer which has
been polymerized by use of a reactive surfactant.
[0031] (e) The particle size of the acrylic copolymer emulsions is
not more than 200 nm.
[0032] Examples of the acrylic copolymer emulsion of the present
invention include, but are not limited to, copolymer emulsions of
one or more acrylic acid alkyl esters and/or methacrylic acid alkyl
esters and one or more vinyl monomers which are capable of being
polymerized with the acrylic alkyl esters and/or methacrylic alkyl
esters, wherein the vinyl monomers include vinyl acetate,
hydroxyl-group-containing vinyl monomers such as hydroxyethyl
acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate,
hydroxypropyl methacrylate, and allyl alcohol,
epoxy-group-containing vinyl monomers such as glycidyl acrylate and
glycidyl methacrylate, and aromatic vinyl monomers such as styrene,
methylstyrene, dimethylstyrene, ethylstyrene, butylstyrene, and
benzylstyrene; and copolymer emulsions of a
carboxyl-group-containing vinyl monomer such as acrylic acid,
methacrylic acid, itaconic acid, citraconic acid, and crotonic acid
and the aforementioned one or more vinyl monomers which are capable
of being polymerized with the acrylic alkyl esters and/or
methacrylic alkyl esters.
[0033] It should, however, be noted that nitrogen-containing
monomers including acrylonitrile, aminoalkyl acrylates such as
diethylaminoethyl acrylate and aminodimethyl acrylate, cyanoethyl
acrylate, and isocyanate adducts are excluded from constituent
monomers of the aforementioned acrylic copolymer emulsions.
[0034] With this exclusion, the waste coating film does not
generate nitrogen oxides when incinerated, thus eliminating the
fear of environmental pollution.
[0035] According to the present invention, two acrylic copolymer
emulsions having different Tg ranges are mixed. Specifically, the
Tg range of a first acrylic copolymer is equal to or greater than
40.degree. C., and that of a second acrylic copolymer is from
-20.degree. C. to 5.degree. C.
[0036] The proportions of these two emulsions are preferably such
that the acrylic copolymer emulsion having a Tg of not lower than
40.degree. C. is between 5% by weight and 40% by weight inclusive
and the acrylic copolymer emulsion having a Tg from -20.degree. C.
to 5.degree. C. is between 95% by weight and 60% by weight
inclusive.
[0037] More preferably, the proportions of these two emulsions are
such that the acrylic copolymer emulsion having a Tg of not lower
than 40.degree. C. is between 10% by weight and 35% by weight
inclusive and the acrylic copolymer emulsion having a Tg from
-20.degree. C. to 5.degree. C. is between 90% by weight and 65% by
weight inclusive.
[0038] Also, the proportion of the ethylenically unsaturated vinyl
monomers having acid value in the acrylic copolymer emulsion
mixture system is not more than 2.0% by weight, more preferably
0.2-0.8% by weight, with respect to the weight of the entirety of
the mixture.
[0039] If ethylenically unsaturated vinyl monomers having acid
value are contained in amounts in excess of 2.0% by weight, water
resistance of the resultant coating film becomes poor, and in
addition, adhesive strength increases to render the film
excessively heat- and weather- resistant and therefore the film may
not be easily peeled off, which is not preferred.
[0040] The ethylenically unsaturated vinyl monomers having acid
value may be--among those which constitute the aforementioned
acrylic copolymer emulsion--carboxy-containing vinyl monomers such
as acrylic acid, methacrylic acid, itaconic acid, citraconicacid,
and crotonic acid. How ever, the ethylenically unsaturated vinyl
monomers having acid value are not limited only to these
compounds.
[0041] In the present invention, examples of the reactive
surfactants include "Aqualon RN" series (tradename, Dai-ichi Kogyo
Seiyaku K.K.) which are surfactants of the polyoxyethylene
alkylphenyl ether type in which a radical-polymerizable propenyl
group has been introduced into the hydrophobic group; anionic
surfactants, "Aqualon HS" series (tradename, Dai-ichi Kogyo Seiyaku
K.K.) which are based on the sulfuric ester salts of "Aqualon RN";
acrylic anion surfactants, "Eleminol RS30" and "Eleminol JS-2"
(tradenames, both by Sanyo Chemical Industries, Ltd.) and "Adeka
Reasoap" series (trade name, Asahi Denka Kogyo K.K.). When reactive
surfactants are added upon synthesis of acrylic copolymer
emulsions, water resistance of the coating film is improved, film
strength is enhanced, and peelability of the film is promoted.
[0042] The particle size of the acrylic copolymer emulsions is
preferably not more than 200 nm, more preferably not more than 100
nm. When the particle size is in excess of 200 nm, a sufficient
contact area cannot be obtained between the composition and the
surface of the object to be coated, which leads to poor water
resistance.
[0043] The aforementioned mixture may incorporate, as desired,
small amounts of additives which may be useful in the manufacture
of peelable-coating compositions. Such additives include
plasticizers (e.g., phthalate esters and fatty acid esters), wax
emulsions (including polyethylene-based emulsions and
polypropylene-based emulsions), defoaming agents (e.g., mineral
oils and silicone oils), Rheology modifier (including inorganic
type and organic type), UV absorbents (e.g., benzotriazoles and
benzophenones), pH modifiers (e.g., organic alkalis and
ethanolamines), preservatives (e.g., benzoisothiazolines and
triazines), coalescing agents (e.g., alkyl ethers of mono- or
di-ethylene glycol and alkyl ethers of mono- or di-propylene
glycol), anti-freezing agents (e.g., polyhydric alcohols),
peelability-improving agents (e.g., silicone emulsions and
alkylphosphoric esters), drying accelerators (e.g., lower alcohols
such as ethyl alcohol).
[0044] The peelable coating composition of the present invention is
intended to be applied onto surfaces of articles such as
automobiles and other vehicles, machine parts, metallic household
articles and other ferrous and non-ferrous articles, wooden
articles, glass articles, rubber articles, and coated rubber
articles, to thereby protect the surfaces of the articles in the
open air or indoors. Needless to say, the composition of the
present invention may be used for protecting surfaces of objects
other than the above articles.
[0045] Specifically, the aqueous dispersion of peelable coating
composition of the present invention is advantageously used, for
example, for the following purposes.
[0046] 1) Prevention of stains and scratches, or degradation due to
UV rays, etc. of panel coatings and resin portions of
automobiles.
[0047] 2) Prevention of rust stains of machine parts.
[0048] 3) Prevention of stains of edible oil and dirt from hands,
when applied to ventilation fans and kitchen devices and
utensils,
[0049] 4) Prevention of stains and scratches of aluminum
fences.
[0050] 5) Prevention of stains and scratches of indoor floors.
[0051] 6) Protection of the wall or floor materials in a paint
booth against splashing of paints.
[0052] 7) Prevention of scratches, or maintenance of good
appearance when applied to skis made of an FRP resin.
EXAMPLES
[0053] The present invention will next be described by way of
Examples which demonstrate the effects of the invention as
contrasted to Comparative Examples. However, the present invention
should not be construed as being limited by the examples.
[0054] The emulsions having Tgs and particle sizes as shown in
Tables 1 through 3 below were prepared, and subjected to the tests
described hereinbelow.
[0055] The glass transition temperature (Tg) of each composition
was measured in accordance with JIS K7121 "Testing Methods for
Transition Temperatures of Plastics"
1TABLE 1 1) Acrylic copolymer emulsion having a Tg of 40.degree. C.
or more Tg Particle Ethylenically unsaturated (.degree. C.) size
(nm) Surfactant monomer having acid value (wt %) A1 58 80 Reactive
0.6 A2 58 80 Non-reactive 0 B1 46 75 Reactive 0.8 B2 46 75 Reactive
5.0 C 46 250 Reactive 0.5 D 46 100 Non-reactive 0.1
[0056]
2TABLE 2 2) Acrylic copolymer emulsion having a Tg from -20.degree.
C. to 5.degree. C. Tg Particle Ethylenically unsaturated (.degree.
C.) size (nm) Surfactant monomer having acid value (wt %) F1 2 85
Reactive 0.4 F2 2 85 Reactive 0 G 2 300 Reactive 0.5 H 2 250
Non-reactive 0.7 I -15 80 Reactive 0.7
[0057]
3TABLE 3 3) Acrylic copolymer emulsion having a Tg from 5.degree.
C. to 40.degree. C. Tg Particle Ethylenically unsaturated (.degree.
C.) size (nm) Surfactant monomer having acid value (wt %) E 15 80
Reactive 0.5
[0058] 4) Method for emulsion polymerization
[0059] <Emulsion A1>
[0060] In a glass reactor equipped with a reflux condenser, a
stirrer, a thermometer, a dropping funnel, and a gas-introduction
tube were charged ammonium persulfate (1.25 parts), water (250
parts), a reactive surfactant "Aqualon RN-20" (trade name, Dai-ichi
Kogyo Seiyaku K.K.) (1.8 parts), methyl methacrylate (MMA) (25
parts), butyl acrylate (BA) (23 parts), acrylic acid (AA) (2.3
parts), and t-dodecylmercaptane (0.9 parts). While the contents of
the reactor were stirred, the air in the reactor was purged with
nitrogen gas, and subsequently, the reactor was heated in a water
bath (maintained at 60.degree. C.).
[0061] When the temperature of the mixture in the reactor reached
60.degree. C., a monomer mixture consisting of "Aqualon RN-20" (8.2
parts), methyl methacrylate (MMA) (112.5 parts), butyl acrylate
(BA) (102 parts), acrylic acid (AA) (10.2 parts), and
t-dodecylmercaptane (3.9 parts) and 2 wt. % aqueous sodium
hydrogensulfite solution (32 parts) were added dropwise
respectively for two hours.
[0062] After completion of addition, the system was stirred for 2
hours at 60.degree. C.
[0063] After completion of reaction, the mixture was cooled to
obtain a thermoplastic resin emulsion containing 48% solids and
having a pH of 3.2.
[0064] This system was neutralized with ammonia water to thereby
obtain a stable emulsion A1. The Tg of this emulsion as measured in
accordance with JIS K7121 was 58.degree. C., and the average
particle size was 80 nm.
[0065] <Emulsions B1, B2, C, E, F1, F2, G, I>
[0066] In a manner similar to that employed for emulsion A1,
Emulsions B1, B2, C, E, F1, F2, G, and I were prepared by changing
the proportions of the monomers and changing the amounts of
surfactants, to thereby obtain emulsions B1, B2, C, E, F1, F2, G,
and I, having different particle sizes.
[0067] <Emulsions A2, D, and H>
[0068] In the case of emulsions A2, D, and H in which a nonreactive
surfactant was used, a surfactant (trade name "Triton X-301," Rohm
& Haas), an initiator, and water were charged from the first,
and when the temperature of the mixture reached 60.degree. C., a
monomer mixture and a terminator were added to thereby obtain an
emulsion A2, D, or H.
[0069] Through use of emulsions A1 through I, the following
compositions, i.e., representatives of the present invention and
the comparative examples, were obtained.
Example 1
[0070]
4 (unit: part(s) Composition by weight) Emulsion D 35 Emulsion H 63
Defoaming agent 0.4 Rheology modifier 0.1 pH modifier 1.5 MFT
(minimum film-forming temperature) = 12.degree. C. 0.49% by weight
Ethylenically unsaturated monomer having acid value
Example 2
[0071]
5 Composition (unit: part(s) by weight) Emulsion C 37 Emulsion G 59
Defoaming agent 0.5 Rheology modifier 0.1 Peelability-improving
agent 1.0 pH modifier 1.4 Coalescing agent 1.0 MFT = 5.degree. C.
0.50% by weight Ethylenically unsaturated monomer having acid
value
Example 3
[0072]
6 Composition (unit: part(s) by weight) Emulsion D 35 Emulsion F 63
Defoaming agent 0.4 Rheology modifier 0.1 pH modifier 1.5 MFT =
12.degree. C. 0.16% by weight Ethylenically unsaturated monomer
having acid value
Example 4
[0073]
7 Composition (unit: part(s) by weight) Emulsion A2 30 Emulsion F2
67 Defoaming agent 0.5 Rheology modifier 0.1 Peelability-improving
agent 1.0 pH modifier 1.4 MFT = 12.degree. C. 0% by weight
Ethylenically unsaturated monomer having acid value
Example 5
[0074]
8 Composition (unit: part(s) by weight) Emulsion B2 37 Emulsion F2
60 Defoaming agent 0.4 Rheology modifier 0.1 pH modifier 1.5
Coalescing agent 1.0 MFt = 10.degree. C. 1.94% by weight
Ethylenically unsaturated monomer having acid value
Example 6
[0075]
9 Composition (unit: part(s) by weight) Emulsion A 30 Emulstion I
68 Defoaming agent 0.4 Rheology modifier 0.1 pH modifier 1.5 MFT
< 0.degree. C. 0.67% by weight Ethylenically unsaturated monomer
having acid value
Example 7
[0076]
10 Composition (unit: part(s) by weight) Emulsion B 37 Emulsion I
60 Defoaming agent 0.5 Rheology modifier 0.1 Peelability-improving
agent 1.0 pH modifier 1.4 MFT < 0.degree. C. 0.74% by weight
Ethylenically unsaturated monomer having acid value
Example 8
[0077]
11 Composition (unit: part(s) by weight) Emulsion B 25 Emulsion F
73 Defoaming agent 0.4 Rheology modifier 0.1 pH modifier 1.0
Peelability-improving agent 0.5 MFT = 7.degree. C. Ethylenically
unsaturated monomer 0.35% by weight having acid value:
Example 9
[0078]
12 Composition (unit: part(s) by weight) Emulsion D 20 Emulsion I
77 Defoaming agent 0.5 Rheology modifier 0.1 Peelability-improving
agent 1.0 pH modifier 1.4 MFT < 0.degree. C. Ethylenically
unsaturated monomer 0.53% by weight having acid value:
Comparative Example 1
[0079]
13 Composition (unit: part(s) by weight) Emulsion A 48 Emulsion F
48 Defoaming agent 0.4 Rheology modifier 0.1 pH modifier 1.5
Coalescing agent 2.0 MFT (minimum film-forming temperature) =
10.degree. C. Ethylenically unsaturated monomer 0.50% by weight
having acid value:
Comparative Example 2
[0080]
14 Composition (unit: part(s) by weight) Emulsion B2 36 Emulsion F
59 Defoaming agent 0.4 Rheology modifier 0.1 pH modifier 1.5
Coalescing agent 2.0 MFT (minimum film-forming temperature) <
0.degree. C. Ethylenically unsaturated monomer 2.34% by weight
having acid value:
Comparative Example 3
[0081]
15 Composition (unit: part(s) by weight) Emulsion E 98 (Tg:
15.degree. C.) Defoaming agent 0.4 Rheology modifier 0.1 pH
modifier 1.5 MFT (minimum film-forming temperature) = 12.degree. C.
Ethylenically unsaturated monomer 0.5% by weight having acid
value:
[0082] (Test Items and Methods)
[0083] <Preparation of Test Specimens>
[0084] The specimens used in the tests were coated plates prepared
as follows. Electrodeposited mild steel plates were spray-coated
with an aminoalkyd resin-base paint. When the surface drys to
Touch, an acrylic resin-base clear paint was sprayed, and the
plates were subsequently baked at 140.degree. C. for 20 minutes. To
the resultant painted plates were applied each of the compositions
prepared in the above-described Examples and Comparative Examples
so as to have a film thickness of 70 .mu.m (dry). A diversified
tests were performed in terms of the below-described properties by
use of the thus-prepared coated plates as test specimens.
[0085] Peelability
[0086] Peelability of test specimens placed at 5.degree. C.,
25.degree. C., or 40.degree. C. was checked.
[0087] Acid Resistance
[0088] A droplet of 40% sulfuric acid aq.soln was placed on each
test specimen, and the specimen was allowed to stand for 15 minutes
in a 60.degree. C. thermostatic chamber.
[0089] After the specimen was cooled to room temperature, the film
was peeled off, and changes of the paint were checked.
[0090] Alkali Resistance
[0091] A droplet of 0.1N sodium hydroxide aq.soln was placed on
each test specimen, and the specimen was allowed to stand for 3
hours at 70.degree. C. After the specimen was cooled to room
temperature, the film was peeled off, andchanges of the paint were
checked.
[0092] Water Resistance
[0093] The film-coated test specimens were soaked in 25.degree. C.
water for 24 hours, and the whitening degree was observed.
[0094] Adhesive Strength
[0095] The film-coated test specimens were soaked in 25.degree. C.
water for 24 hours, and presence or absence of natural peeling-off
was observed.
[0096] Peelability After Heated
[0097] The test specimens were left in a 80.degree. C. thermostatic
chamber for 500 hours and subsequently peelability was checked at
room temperature.
[0098] Accelerated Weather Resistance
[0099] The test specimens were placed in an SWOM tester for 500
hours so as to accelerate degradation of the film and subsequently
peelability was checked.
[0100] Cycle Test
[0101] Each test specimen was subjected to a cycle test, in which
each cycle consisted of heating at 80.degree. C. for 24 hours and
subsequent cooling at 0.degree. C. for 24 hours. After the test
specimen had undergone 10 cycles, peelability of the specimen was
checked.
[0102] External Exposure
[0103] The test specimens were exposed to the open air in Okinawa
prefecture. When six months (including 3 months in summer) had
passed, peelability of the specimen was checked.
[0104] Combustion Test
[0105] A small amount of film that had peeled off was collected and
burned. Nitrogen oxides contained in the combustion gas were
analyzed in accordance with JIS K0104.
[0106] The test results are shown in Table 4.
[0107] The evaluation standards were as follows:
[0108] A: very good, B: Good, C: Poor, and D: Very poor.
16TABLE 4 Test Results Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 A
Peelability A B A A A A B Acid resistance B A A A A A C Alkali
resistance B A A A A A D Water resistance B B B B A A E Adhesive
strength B A B B A A F Peelability after heated A B A B A A G
Accelerated weather resistance A B B B A A H Cycle test B A B B A A
I External exposure B A B B A A J Combustion test A A A A A A MFT
(.degree. C.) 12 5 12 12 10 <0 Ethylenically unsaturated 0.49
0.5 0.16 0 1.94 0.67 monomers having acid value Emulsion particle
size 100/250 250/300 100/85 80/85 75/85 80/80 Surfactant N/N R/R
N/R N/R R/R R/R Comp. Ex. Comp. Ex. Comp. Ex. Ex. 7 Ex. 8 Ex. 9 1 2
3 A Peelability A A A D D D B Acid resistance A A A A B A C Alkali
resistance A A A A D A D Water resistance A A A A B A E Adhesive
strength A A A A B A F Peelability after heated A A A C D C G
Accelerated weather resistance A A A C D D H Cycle test A A A D D C
I External exposure A A A D D B J Combustion test A A A A A A MFT
(.degree. C.) <0 7 <0 10 <0 12 Ethylenically unsaturated
0.74 0.35 0.58 0.5 2.34 0.5 monomers having acid value Emulsion
particle size 75/85 75/85 100/80 80/85 75/85 80 Surfactant R/R R/R
N/R R/R R/R R/R A: Very good B: Good C: Poor D: Very poor N:
Non-reactive surfactant R: Reactive surfactant
[0109] As shown in Table 4, whereas specimens falling within the
scope of the present invention were excellent with respect to all
the test items, those of comparative examples were inferior to the
specimens of the invention, proving the synergism achieved by the
present invention.
[0110] As described hereinabove by way of examples, the aqueous
dispersion of peelable coating composition of the present invention
which is an acrylic copolymer emulsion exhibits excellent
peelability due to the synergism of the following features: 1) The
composition comprises a mixture of two acrylic copolymer emulsions,
wherein the acrylic copolymers have different predetermined glass
transition temperatures, 2) the amount of ethylenically unsaturated
monomers having acid value in the mixture is not higher than a
predetermined level, and 3) the emulsion does not make use of a
nitrogen-containing monomer.
[0111] Moreover, in addition to the above-mentioned features 1)
through 3), when 4) polymerization is performed under conditions in
which at least one of the emulsions contains a reactive surfactant
and 5) the particle size of the emulsions is controlled to fall
within a predetermined range, there can be obtained, as a result of
further synergism, an aqueous dispersion of a peelable coating
composition having further improved water resistance, adhesiveness,
and peelability.
[0112] Furthermore, since no nitrogen-containing monomers such as
acrylonitrile are contained in the acrylic emulsions, when the film
is peeled off after the protection period is over and the waste
film is burned and disposed of, gases containing nitrogen oxides
are not generated and thus there is no fear of environmental
pollution.
[0113] Accordingly, the aqueous dispersion of peelable coating
composition of the present invention enables to achieve protective
effects superior to those obtained from previous products when
used, for example, for the following purposes.
[0114] 1) Prevention of stains and scratches, or degradation due to
UV rays, etc. of panel coatings and resin portions of
automobiles.
[0115] 2) Prevention of rust stains of machine parts.
[0116] 3) Prevention of stains of edible oil and dirt from hands,
through application to ventilation fans and kitchen devices and
utensils,
[0117] 4) Prevention of stains and scratches of aluminum
fences.
[0118] 5) Prevention of stains and scratches of indoor floors.
[0119] 6) Protection of the wall or floor materials in a paint
booth against splashing of paints.
[0120] 7) Prevention of scratches, or maintenance of good
appearance when applied to skis made of an FRP resin.
* * * * *