U.S. patent application number 11/013402 was filed with the patent office on 2005-07-07 for anti-fouling agent and method for producing the same.
This patent application is currently assigned to Kuraray Co., Ltd.. Invention is credited to Fujiwara, Naoki, Kato, Masaki, Kusudou, Takeshi, Somemiya, Kazuyuki.
Application Number | 20050148736 11/013402 |
Document ID | / |
Family ID | 34587694 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050148736 |
Kind Code |
A1 |
Kato, Masaki ; et
al. |
July 7, 2005 |
Anti-fouling agent and method for producing the same
Abstract
Disclosed is an anti-fouling agent which is superior in
viscosity stability, water resistance of its film and ability of
preventing a scale from depositing on the inner wall of a
polymerization reactor and which can prevent the contamination of
foreign substances into a polymeric product caused by exfoliation
of a scale depositing on the inner wall of a polymerization reactor
and exfoliation of the anti-fouling agent itself, the anti-fouling
agent comprising an aqueous solution containing a polyvinyl alcohol
that is obtained through saponification of a polyvinyl ester that
contains monomer units having a specific silyl group and that
satisfies the following formulae (I) and (II):
370<P.times.S<9000 (I) wherein P indicates the
viscosity-average degree of polymerization of the polyvinyl
alcohol, and S indicates the content (mole %) of the monomer units
having a silyl group of formula (1) in the polyvinyl alcohol;
0.2/100.ltoreq.(A-B)/(B).ltoreq.75/100 (II) wherein A indicates the
content (ppm) of silicon atoms in the polyvinyl alcohol, and B
indicates the content (ppm) of silicon atoms in the polyvinyl
alcohol that was washed with sodium hydroxide-containing methanol
and then washed with methanol by Soxhlet extraction.
Inventors: |
Kato, Masaki;
(Kurashiki-shi, JP) ; Somemiya, Kazuyuki;
(Kurashiki-shi, JP) ; Kusudou, Takeshi;
(Kurashiki-shi, JP) ; Fujiwara, Naoki;
(Chiyoda-ku, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Kuraray Co., Ltd.
Kurashiki-shi
JP
|
Family ID: |
34587694 |
Appl. No.: |
11/013402 |
Filed: |
December 17, 2004 |
Current U.S.
Class: |
525/330.3 |
Current CPC
Class: |
C08F 8/12 20130101; C08F
218/08 20130101; C08F 8/12 20130101; C08F 230/08 20130101; C08F
218/08 20130101 |
Class at
Publication: |
525/330.3 |
International
Class: |
C08F 002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 7, 2004 |
JP |
2004-002464 |
Claims
What is claimed is:
1. An anti-fouling agent comprising an aqueous solution containing
a polyvinyl alcohol obtained through saponification of a polyvinyl
ester that contains monomer units having a silyl group of formula
(1): 7wherein R.sup.1 represents an alkyl group having from 1 to 5
carbon atoms; R.sup.2 represents an alkoxyl or acyloxyl group
optionally having an oxygen-containing substituent; and m indicates
an integer of from 0 to 2, wherein the polyvinyl alcohol satisfies
the following formulae (I) and (II): 370<P.times.S<9000 (I)
wherein P indicates the viscosity-average degree of polymerization
of the polyvinyl alcohol, and S indicates the content (mole %) of
the monomer units having a silyl group of formula (1) in the
polyvinyl alcohol; 0.2/100.ltoreq.(A-B)/(B).l- toreq.75/100 (II)
wherein A indicates the content (ppm) of silicon atoms in the
polyvinyl alcohol, and B indicates the content (ppm) of silicon
atoms in the polyvinyl alcohol that was washed with sodium
hydroxide-containing methanol and then washed with methanol by
Soxhlet extraction, wherein A and B are measured by ICP emission
spectrometry after ashing of a sample.
2. The anti-fouling agent according to claim 1 wherein the aqueous
solution has a pH of from 10 to 14.
3. The anti-fouling agent according to claim 1 wherein the content
of the polyvinyl alcohol is from 0.1 to 10% by weight.
4. A method for producing an anti-fouling agent wherein the method
comprises obtaining a polyvinyl alcohol satisfying formulae (I) and
(II) defined below by saponifying a polyvinyl ester that contains
monomer units having a silyl group of formula (1): 8wherein R.sup.1
represents an alkyl group having from 1 to 5 carbon atoms; R.sup.2
represents an alkoxyl or acyloxyl group optionally having an
oxygen-containing substituent; and m indicates an integer of from 0
to 2, and then preparing an aqueous solution by dissolving the
polyvinyl alcohol in water: 370<P.times.S<9000 (I) wherein P
indicates the viscosity-average degree of polymerization of the
polyvinyl alcohol, and S indicates the content (mole %) of the
monomer units having a silyl group of formula (1) in the polyvinyl
alcohol; 0.2/100.ltoreq.(A-B)/(B).l- toreq.75/100 (II) wherein A
indicates the content (ppm) of silicon atoms in the polyvinyl
alcohol, and B indicates the content (ppm) of silicon atoms in the
polyvinyl alcohol that was washed with sodium hydroxide-containing
methanol and then washed with methanol by Soxhlet extraction,
wherein A and B are measured by ICP emission spectrometry after
ashing of a sample.
5. The method for producing an anti-fouling agent according to
claim 4, wherein said polyvinyl alcohol is obtained by saponifying
said polyvinyl ester, subsequently neutralizing a remaining
saponification catalyst, and then subjecting to a heat treatment in
an organic solvent.
6. The method for producing an anti-fouling agent according to
claim 5 wherein said organic solvent is used in an amount of from 1
to 20 times the weight of polyvinyl alcohol during the heat
treatment.
7. The method for producing an anti-fouling agent according to
claim 5 wherein said organic solvent is a mixed solvent of a lower
alcohol and a lower fatty acid ester.
8. The method for producing an anti-fouling agent according to
claim 5 wherein the treatment temperature is from 40.degree. C. to
100.degree. C. and the treatment time is from 30 minutes to 10
hours in said heat treatment.
9. The method for producing an anti-fouling agent according to
claim 4 wherein said polyvinyl alcohol and a base are dissolved in
water.
10. A method for producing a polymer wherein polymerization is
conducted using a polymerization reactor having an inner wall
covered with the anti-fouling agent according to claim 1.
11. The method for producing a polymer according to claim 10
wherein the polymerization is suspension polymerization or emulsion
polymerization.
12. The method for producing a polymer according to claim 10
wherein the polymer is polyvinyl chloride.
13. A polyvinyl alcohol for anti-fouling agents wherein said
polyvinyl alcohol is obtained through saponification of a polyvinyl
ester having monomer units that contains monomer units having a
silyl group of formula (1): 9wherein R.sup.1 represents an alkyl
group having from 1 to 5 carbon atoms; R.sup.2 represents an
alkoxyl or acyloxyl group optionally having an oxygen-containing
substituent; and m indicates an integer of from 0 to 2, and wherein
the polyvinyl alcohol satisfies the following formulae (I) and
(II): 370<P.times.S<9000 (I) wherein P indicates the
viscosity-average degree of polymerization of the polyvinyl
alcohol, and S indicates the content (mole %) of the monomer units
having a silyl group of formula (1) in the polyvinyl alcohol;
0.2/100.ltoreq.(A-B)/(B).l- toreq.75/100 (II), wherein A indicates
the content (ppm) of silicon atoms in the polyvinyl alcohol, and B
indicates the content (ppm) of silicon atoms in the polyvinyl
alcohol that was washed with sodium hydroxide-containing methanol
and then washed with methanol by Soxhlet extraction, wherein A and
B are measured by ICP emission spectrometry after ashing of a
sample.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an anti-fouling agent,
especially, an anti-fouling agent comprising an aqueous solution
containing a polyvinyl alcohol.
[0003] Moreover, the present invention relates also to a method for
producing the anti-fouling agent and to a method for producing a
polymer using the anti-fouling agent.
[0004] 2. Description of the Related Art
[0005] Heretofore, when vinyl chloride is polymerized alone or
copolymerized with a monomer copolymerizable therewith in an
aqueous medium by suspension polymerization, polymer scale deposits
on the inner wall of a polymerization reactor, the surface of a
stirring blade, the surface of a baffle, the inner wall of a pipe
mounted in the polymerization reactor, the inner wall of a
condenser and so on. The deposition of scale has resulted, for
example, in decrease in cooling capacity of the polymerization
reactor and deterioration of the quality of products caused by
exfoliation and contamination of the depositions. Thus, the inner
wall of a polymerization reactor must be cleaned every time
polymerization has finished and this has caused the decrease in the
operating rate of polymerization reactors and the increase in
production cost. To solve these problems, the method of applying
various kinds of anti-fouling agents onto the inner walls of
polymerization reactors in advance has been proposed. JP-A
59-184208 discloses a method using a silanol-modified polyvinyl
alcohol as an anti-fouling agent, but its effect of preventing the
adhesion of scale is still insufficient.
SUMMARY OF THE INVENTION
[0006] The present invention was made for solving the
above-mentioned problems. The object of the present invention is to
provide an anti-fouling agent which is superior in viscosity
stability, water resistance of its film and ability of preventing a
scale from depositing on the inner wall of a polymerization reactor
and which can prevent the contamination of foreign substances into
a polymeric product caused by exfoliation of a scale deposited on
the inner wall of a polymerization reactor and exfoliation of the
anti-fouling agent itself. Another object of the present invention
is to provide a method for producing such an anti-fouling agent and
a method for producing a polymer using the agent.
[0007] The above problems can be solved by providing an
anti-fouling agent comprising an aqueous solution containing a
polyvinyl alcohol obtained through saponification of a polyvinyl
ester that contains monomer units having a silyl group of formula
(1): 1
[0008] wherein R.sup.1 represents an alkyl group having from 1 to 5
carbon atoms; R.sup.2 represents an alkoxyl or acyloxyl group
optionally having an oxygen-containing substituent; and m indicates
an integer of from 0 to 2,
[0009] wherein the polyvinyl alcohol satisfies the following
formulae (I) and (II):
370<P.times.S<9000 (I)
[0010] wherein
[0011] P indicates the viscosity-average degree of polymerization
of the polyvinyl alcohol,
[0012] and S indicates the content (mole %) of the monomer units
having a silyl group of formula (1) in the polyvinyl alcohol;
b 0.2/100.ltoreq.(A-B)/(B).ltoreq.75/100 (II)
[0013] wherein
[0014] A indicates the content (ppm) of silicon atoms in the
polyvinyl alcohol,
[0015] and B indicates the content (ppm) of silicon atoms in the
polyvinyl alcohol that was washed with sodium hydroxide-containing
methanol and then washed with methanol by Soxhlet extraction,
wherein A and B are measured by ICP emission spectrometry after
ashing of a sample.
[0016] The aqueous solution preferably has a pH of from 10 to 14.
The content of the polyvinyl alcohol is preferably from 0.1 to 10%
by weight.
[0017] The above-mentioned problems can be solved also by providing
a method for producing an anti-fouling agent wherein the method
comprises obtaining a polyvinyl alcohol satisfying formulae (I) and
(II) defined below by saponifying a polyvinyl ester that contains
monomer units having a silyl group of formula (1) above and then
preparing an aqueous solution by dissolving the polyvinyl alcohol
in water. In one preferred embodiment, the polyvinyl alcohol is
obtained by saponifying said polyvinyl ester, subsequently
neutralizing a remaining saponification catalyst, and then
subjecting to a heat treatment in an organic solvent. It is
desirable that the organic solvent is used in an amount of from 1
to 20 times the weight of the polyvinyl alcohol during the heat
treatment. It is also desirable that the organic solvent is a mixed
solvent of a lower alcohol and a lower fatty acid ester. It is also
desirable that the treatment temperature is from 40.degree. C. to
100.degree. C. and the treatment time is from 30 minutes to 10
hours in said heat treatment. It is also desirable that the
polyvinyl alcohol and a base are dissolved in water.
[0018] The above-mentioned problems can be solved also by providing
a method for producing a polymer where in polymerization is
conducted using a polymerization reactor having an inner wall
covered with the anti-fouling agent described above. It is
desirable that the polymerization is suspension polymerization or
emulsion polymerization. It is also desirable that the polymer is
polyvinyl chloride.
[0019] In addition, the above-mentioned problems can be solved also
by providing a polyvinyl alcohol for anti-fouling agents wherein
the polyvinyl alcohol is obtained through saponification of a
polyvinyl ester having monomer units that contains monomer units
having a silyl group of formula (1) above and wherein the polyvinyl
alcohol satisfies the aforementioned formulae (I) and (II).
[0020] The anti-fouling agent of the present invention is superior
in viscosity stability, water resistance of its film and ability of
preventing a scale from depositing on the inner wall of a
polymerization reactor and can prevent the contamination of foreign
substances into a polymeric product caused by exfoliation of a
scale depositing on the inner wall of a polymerization reactor and
exfoliation of the anti-fouling agent itself.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] The polyvinyl alcohol used in the anti-fouling agent of the
present invention is a polyvinyl alcohol obtained through
saponification of a polyvinyl ester that contains monomer units
having a silyl group of formula (1): 2
[0022] wherein R.sup.1 represents an alkyl group having from 1 to 5
carbon atoms; R.sup.2 represents an alkoxyl or acyloxyl group
optionally having an oxygen-containing substituent; and m indicates
an integer of from 0 to 2. The polyvinyl alcohol must satisfy the
following formulae (I) and (II):
370<P.times.S<9000 (I)
[0023] wherein
[0024] P indicates the viscosity-average degree of polymerization
of the polyvinyl alcohol,
[0025] and S indicates the content (mole %) of the monomer units
having a silyl group of formula (1) in the polyvinyl alcohol;
0.2/100.ltoreq.(A-B)/(B).ltoreq.75/100 (II)
[0026] wherein
[0027] A indicates the content (ppm) of silicon atoms in the
polyvinyl alcohol,
[0028] and B indicates the content (ppm) of silicon atoms in the
polyvinyl alcohol that was washed with sodium hydroxide-containing
methanol and then washed with methanol by Soxhlet extraction,
wherein A and B are measured by ICP emission spectrometry after
ashing of a sample.
[0029] In formula (1), which represents a silyl group contained in
the polyvinyl alcohol, R.sup.1 represents an alkyl group having
from 1 to 5 carbon atoms; R represents an alkoxyl or acyloxyl group
optionally having an oxygen-containing substituent; and m indicates
an integer of from 0 to 2.
[0030] Examples of the alkyl group having from 1 to 5 carbon atoms
represented by R.sup.1 include a methyl, ethyl, n-propyl,
isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, n-pentyl,
tert-pentyl and isopentyl groups. Examples of the alkoxyl group
represented by R.sup.2 include a methoxy, ethoxy, propoxy,
isopropoxy, butoxy, tert-butoxy, pentoxy, hexyloxy, octyloxy,
lauryloxy and oleyloxy groups. The acyloxyl group includes, for
example, an acetoxy and propionyloxy groups. The alkoxyl or acyloxy
group may have an oxygen-containing substituent, the examples of
which include alkoxyl groups such as methoxy and ethoxy.
[0031] The polyvinyl alcohol may be produced by copolymerizing a
vinyl ester monomer with a monomer having a silyl group of formula
(1) and then saponifying the resulting polyvinyl ester.
[0032] Alternatively, the polyvinyl alcohol can also be produced by
copolymerizing a vinyl ester monomer with a monomer having a silyl
group of formula (1) in the presence of a thiol compound such as
2-mercaptoethanol, n-dodecylmercaptan, mercaptoacetic acid and
3-mercaptopropionic acid and then saponifying the resulting
polyvinyl ester. These methods give a polyvinyl alcohol having a
functional group derived from a thiol compound as a terminal
group.
[0033] Examples of the vinyl ester monomer used in the production
of the polyvinyl alcohol include vinyl formate, vinyl acetate,
vinyl propionate, vinyl valerate, vinyl caprylate, vinyl laurate,
vinyl stearate, vinyl benzoate, vinyl pivalate and vinyl versatate.
Vinyl acetate is particularly preferred.
[0034] Examples of the monomer having a silyl group of formula (1)
used for the radical copolymerization with the vinyl ester monomer
include compounds represented by the following formula (2) or (3):
3
[0035] wherein R.sup.1 represents an alkyl group having from 1 to 5
carbon atoms; R.sup.2 represents an alkoxyl or acyloxyl group
optionally having an oxygen-containing substituent; m indicates an
integer of from 0 to 2; and n indicates an integer of from 0 to 4,
4
[0036] wherein R.sup.1 represents an alkyl group having from 1 to 5
carbon atoms; R.sup.2 represents an alkoxyl or acyloxyl group
optionally having an oxygen-containing substituent; R.sup.3
represents a hydrogen atom or a methyl group; R.sup.4 represents a
hydrogen atom or an alkyl group having from 1 to 5 carbon atoms;
R.sup.5 represents an alkylene group having from 1 to 5 carbon
atoms or a divalent hydrocarbon group containing an oxygen or
nitrogen atom; and m indicates an integer of from 0 to 2.
[0037] In formulae (2) and (3), examples of the alkyl group having
from 1 to 5 carbon atoms represented by R.sup.1 include a methyl,
ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,
isobutyl, n-pentyl, tert-pentyl and isopentyl groups. Examples of
the alkoxyl group represented by R.sup.2 include a methoxy, ethoxy,
propoxy, isopropoxy, butoxy, tert-butoxy, pentoxy, hexyloxy,
octyloxy, lauryloxy and oleyloxy groups. The acyloxyl group
includes, for example, an acetoxy and propionyloxy groups. The
alkoxyl or acyloxy group may have an oxygen-containing substituent,
the examples of which include alkoxyl groups such as methoxy and
ethoxy. Examples of the alkyl group having from 1 to 5 carbon atoms
represented by R.sup.4 include a methyl, ethyl, n-propyl,
isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, n-pentyl,
tert-pentyl and isopentyl groups. Examples of the alkylene group
having from 1 to 5 carbon atoms represented by R.sup.5 include a
methylene, ethylene, dimethylethylene, trimethylene, tetramethylene
and pentamethylene groups. Examples of the divalent hydrocarbon
group containing an oxygen or nitrogen atom include
--CH.sub.2CH.sub.2NHCH.sub.- 2CH.sub.2CH.sub.2--,
--CH.sub.2CH.sub.2NHCH.sub.2CH.sub.2--,
CH.sub.2CH.sub.2NHCH.sub.2--,
--CH.sub.2CH.sub.2N(CH.sub.3)CH.sub.2CH.sub- .2--,
--CH.sub.2CH.sub.2N(CH.sub.3)CH.sub.2--,
--CH.sub.2CH.sub.2OCH.sub.2- CH.sub.2CH.sub.2--,
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2--, and
--CH.sub.2CH.sub.2OCH.sub.2--.
[0038] Examples of the monomer represented by formula (2) include
vinyltrimethoxysilane, vinylmethyldimethoxysilane,
vinyldimethylmethoxysilane, vinyltriethoxysilane,
vinylmethyldiethoxysila- ne, vinyldimethylethoxysilane,
allyltrimethoxysilane, allylmethyldimethoxysilane,
allyldimethylmethoxysilane, allyltriethoxysilane,
allylmethyldiethoxysilane, allyldimethylethoxysilan- e,
vinyltris(.beta.-methoxyethoxy)silane,
vinylisobutyldimethoxysilane, vinylethyldimethoxysilane,
vinylmethoxydibutoxysilane, vinyldimethoxybutoxysilane,
vinyltributoxysilane, vinylmethoxydihexyloxys- ilane,
vinyldimethoxyhexyloxysilane, vinyltrihexyloxysilane,
vinylmethoxydioctyloxysilane, vinyldimethoxyoctyloxysilane,
vinyltrioctyloxysilane, vinylmethoxydilauryloxysilane,
vinyldimethoxylauryloxysilane, vinylmethoxydioleyloxysilane, and
vinyldimethoxyoleyloxysilane.
[0039] When a silyl group-having monomer of formula (2) where n is
1 or more is copolymerized with a vinyl ester monomer, the degree
of polymerization of the resulting polyvinyl ester may lower. On
the other hand, vinyltrimethoxysilane can be favorably employed
because when it is copolymerized with a vinyl ester monomer, the
lowering of the degree of polymerization of the resulting polyvinyl
ester is suppressed. And industrial production of
vinyltrimethoxysilane is easy, therefore, vinyltrimethoxysilane is
obtainable at low cost.
[0040] Examples of the monomer of formula (3) include
3-(meth)acrylamido-propyltrimethoxysilane,
3-(meth)acrylamido-propyltriet- hoxysilane,
3-(meth)acrylamido-propyltri(.beta.-methoxyethoxy)silane,
2-(meth)acrylamido-ethyltrimethoxysilane,
1-(meth)acrylamido-methyltrimet- hoxysilane,
2-(meth)acrylamido-2-methylpropyltrimethoxysilane,
2-(meth)acrylamido-isopropyltrimethoxysilane,
N-(2-(meth)acrylamido-ethyl- )-aminopropyltrimethoxysilane,
(3-(meth)acrylamido-propyl)-oxypropyltrimet- hoxysilane,
3-(meth)acrylamido-propyltriacetoxysilane,
2-(meth)acrylamido-ethyltriacetoxysilane,
4-(meth)acrylamido-butyltriacet- oxysilane,
3-(meth)acrylamido-propyltripropionyloxysilane,
2-(meth)acrylamido-2-methylpropyltriacetoxysilane,
N-(2-(meth)acrylamido-ethyl)-aminopropyltriacetoxysilane,
3-(meth)acrylamido-propylisobutyldimethoxysilane,
2-(meth)acrylamido-ethy- ldimethylmethoxysilane,
3-(meth)acrylamido-propylmethyldiacetoxysilane,
2-(meth)acrylamido-2-methylpropylhydrogendimethoxysilane,
3-(N-methyl-(meth)acrylamido)-propyltrimethoxysilane, and
2-(N-ethyl-(meth)acrylamido)-ethyltriacetoxysilane.
[0041] Among these monomers,
3-(meth)acrylamido-propyltrimethoxysilane and
3-(meth)acrylamido-propyltriacetoxysilane can be favorably employed
because their industrial production is relatively easy and it is
obtainable at low cost. Moreover,
2-(meth)acrylamido-2-methylpropyltrimet- hoxysilane and
2-(meth)acrylamido-2-methylpropyltriacetoxysilane can be favorably
employed because their amide bond is extremely stable to acid or
alkali.
[0042] By copolymerizing a monomer of formula (2) with a vinyl
ester monomer, a polyvinyl ester having monomer units of formula
(4) shown below is obtained. The polyvinyl ester is converted to a
polyvinyl alcohol according to the method described below. The
polyvinyl alcohol used in the present invention desirably is a
polyvinyl alcohol having monomer units represented by the following
formula (4): 5
[0043] wherein R.sup.1 represents an alkyl group having from 1 to 5
carbon atoms; R.sup.2 represents an alkoxyl or acyloxyl group
optionally having an oxygen-containing substituent; m indicates an
integer of from 0 to 2; and n indicates an integer of from 0 to
4.
[0044] By coplymerizing a monomer represented by formula (3) shown
above with a vinyl ester monomer, a polyvinyl ester containing
monomer units represented by formula (5) shown below is obtained.
The polyvinyl ester is converted to a polyvinyl alcohol according
to the method described below. The polyvinyl alcohol used in the
present invention desirably is a polyvinyl alcohol having monomer
units represented by the following formula (5): 6
[0045] wherein R.sup.1 represents an alkyl group having from 1 to 5
carbon atoms; R.sup.2 represents an alkoxyl or acyloxyl group
optionally having an oxygen-containing substituent; R.sup.3
represents a hydrogen atom or a methyl group; R.sup.4 represents a
hydrogen atom or an alkyl group having from 1 to 5 carbon atoms;
R.sup.5 represents an alkylene group having from 1 to 5 carbon
atoms or a divalent hydrocarbon group containing an oxygen or
nitrogen atom; and m indicates an integer of from 0 to 2.
[0046] Examples of the method for copolymerizing a silyl
group-having monomer with a vinyl ester monomer include known
methods such as bulk polymerization, solution polymerization,
suspension polymerization and emulsion polymerization. Among these
methods, generally employed is bulk polymerization conducted in the
absence of solvent or solution polymerization conducted in a
solvent such as alcohol. When the copolymerization is conducted
using solution polymerization, examples of the alcohol used as a
solvent include lower alcohols such as methyl alcohol, ethyl
alcohol and propyl alcohol. Examples of the initiator used for the
copolymerization include known initiators such as azo-type
initiators e.g. 2,2'-azobisisobutyronitrile,
2,2'-azobis(2,4-dimethylvale- ronitrile),
1,1'-azobis(cyclohexane-1-carbonitrile) and
2,2'-azobis(N-butyl-2-methylpropionamide); and peroxide initiators
e.g. benzoyl peroxide and n-propyl peroxycarbonate. The
polymerization temperature at which the copolymerization is
conducted is not specifically restricted, but appropriately is set
within the range from 5.degree. C. to 180.degree. C.
[0047] When a silyl group-having monomer is radical-copolymerized
with a vinyl ester monomer, other copolymerizable monomers may, if
desired, also be copolymerized unless the effect of the present
invention is affected. Examples of such monomers include
.alpha.-olefins such as ethylene, propylene, 1-butene, isobutene
and 1-hexene; carboxylic acids and their derivatives such as
fumaric acid, maleic acid, itaconic acid, maleic anhydride and
itaconic anhydride; acrylic acid and its salts; acrylates such as
methyl acrylate, ethyl acrylate, n-propyl acrylate and isopropyl
acrylate; methacrylic acid and its salts; methacrylates such as
methyl methacrylate, ethyl methacrylate, n-propyl methacrylate and
isopropyl methacrylate; acrylamide and acrylamide derivatives such
as N-methylacrylamide and N-ethylacrylamide; methacrylamide and
methacrylamide derivatives such as N-methylmethacrylamide and
N-ethylmethacrylamide; vinyl ethers such as methyl vinyl ether,
ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether and
n-butyl vinyl ether;
[0048] hydroxy group-having vinyl ethers such as ethylene glycol
vinyl ether, 1,3-propanediol vinyl ether and 1,4-butanediol vinyl
ether; allyl acetate and isopropenyl acetate; allyl ethers such as
propyl allyl ether, butyl allyl ether and hexyl allyl ether;
monomers having an oxyalkylene group; .alpha.-olefins having a
hydroxy group such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol,
7-octen-1-ol, 9-decen-1-ol and 3-methyl-3-buten-1-ol; monomers
having a sulfonic acid group such as ethylenesulfonic acid,
allylsulfonic acid, methallylsulfonic acid and
2-acrylamido-2-methylpropane sulfonic acid; and monomers having a
cationic group such as vinyloxyethyltrimethyl ammonium chloride,
vinyloxybutyltrimethylammonium chloride,
vinyloxyethyldimethylamine, vinyloxymethyldiethylamine,
N-acrylamidomethyltrimethylammonium chloride,
N-acrylamidoethyltrimethylammonium chloride,
N-acrylamidodimethylamine, allyltrimethylammonium chloride,
methallyltrimethylammonium chloride, dimethylallylamine and
allylethylamine. The amount of such a monomer to be used for the
copolymerization which is copolymerizable with both of a silyl
group-having monomer and a vinyl ester monomer varies depending on
the object of its use and the application of the resulting
copolymer, but it generally is up to 20 mole %, preferably up to 10
mole % of the total amount of all the monomers to be used for the
copolymerization.
[0049] The polyvinyl ester obtained through the copolymerization of
a silyl group-having monomer and a vinyl ester monomer is then
saponified in a solvent according to a known method, thereby
forming a polyvinyl alcohol.
[0050] As a catalyst for the saponification of the polyvinyl ester,
an alkaline substance is generally used. Examples thereof include
alkali metal hydroxide such as potassium hydroxide and sodium
hydroxide; and alkali metal alkoxides such as sodium methoxide. The
amount of the alkaline substance used is preferably within the
range of from 0.004 to 0.5, more preferably within the range of
from 0.005 to 0.05 in terms of the molar ratio thereof to the vinyl
ester monomer units in the polyvinyl ester. The saponification
catalyst may be added to the reaction system all at a time in the
initial stage of the saponification, or may be added thereto in
such a manner that a part thereof is added in the initial stage of
the saponification and the remaining part thereof is added during
the saponification.
[0051] Examples of a solvent usable for the saponification include
methanol, methyl acetate, dimethylsulfoxide, diethylsulfoxide and
dimethylformamide. Among these solvents, methanol is preferably
employed. In its use, the water content thereof is preferably
adjusted to 0.001-1% by weight, more preferably 0.003-0.9% by
weight, even more preferably 0.005-0.8% by weight.
[0052] The saponification is conducted preferably at a temperature
of from 5 to 80.degree. C., more preferably from 20 to 70.degree.
C. The time required for the saponification is preferably from 5
minutes to 10 hours, more preferably from 10 minutes to 5 hours.
The saponification may be conducted either batchwise or
continuously. After the completion of the saponification, the
remaining catalyst may, if desired, be neutralized. Examples of
usable neutralizing agents include organic acids such as acetic
acid and lactic acid; and ester compounds such as methyl
acetate.
[0053] There is no particular limitation on the degree of
saponification of the polyvinyl alcohol used in the present
invention. It, however, is preferably at least 80 mole %, more
preferably at least 85 mole %, and even more preferably at least 90
mole %. From the viewpoint of forming a film of good water
resistance containing a polyvinyl alcohol and an inorganic
substance, the optimum degree of saponification of the polyvinyl
alcohol is at least 95 mole %.
[0054] The viscosity-average degree of polymerization (P) of the
polyvinyl alcohol used in the present invention is determined
according to JIS K6726. Specifically, a polyvinyl alcohol having a
silyl group is resaponified so as to have a degree of
saponification of at least 99.5 mole % and subsequently refined.
The product is measured for its intrinsic viscosity [.alpha.]in
water at 30.degree. C. The viscosity-average degree of
polymerization (P) can be determined based on the intrinsic
viscosity [.eta.](dL/g) according to the following formula:
P=([.eta.].times.1000/8.29).sup.(1/0.62)
[0055] In the polyvinyl alcohol used in the present invention, the
content (S:mole %) of silyl group-having monomers is determined
based on the .sup.1H-NMR spectrum of the corresponding polyvinyl
ester before saponification. Prior to the .sup.1H-NMR analysis, the
polyvinyl ester before saponification is purified by
reprecipitation from hexane-acetone to completely remove the
unreacted silyl group-having monomer from the polymer, and then the
resulting polymer is dried at 90.degree. C. under reduced pressure
for 2 days, dissolved in CDCl.sub.3 and thereafter subjected to the
analysis.
[0056] The polyvinyl alcohol used in the present invention must
satisfy the relationship 370<P.times.S<9000, wherein
(P.times.S) is the product of the viscosity-average degree of
polymerization (P) of the polyvinyl alcohol and the content (S) of
the silyl group-having monomer. Preferably, the product P.times.S
satisfies the relationship 390<P.times.S<8950, more
preferably 390<P.times.S<8900. It is undesirable that
P.times.S is 370 or less because it may result in a poor water
resistance of a film formed of the silyl group-containing PVA and a
reduced effect of preventing the adhesion of scale. It is also
undesirable that P.times.S is 9000 or more because it may lead to
an extremely high viscosity of an aqueous solution, resulting in a
reduced handleability thereof.
[0057] The polyvinyl alcohol used in the invention must satisfy the
following formula:
0.2/100.ltoreq.(A-B)/(B).ltoreq.75/100 (II)
[0058] wherein A indicates the silicon atom content (ppm) of the
polyvinyl alcohol, B indicates the silicon atom content (ppm) of
the polyvinyl alcohol that was washed with sodium
hydroxide-containing methanol and then washed with methanol by
Soxhlet extraction.
[0059] In the determination of the silicon atom content (B), one
standard method of washing the polyvinyl alcohol comprises
repeating five times an operation of washing the polymer with
sodium hydroxide-containing methanol (specifically, an operation
comprising adding 10 parts by weight of a sodium
hydroxide-containing methanol solution to one part by weight of the
polyvinyl alcohol so that the molar ratio of sodium hydroxide to
the vinyl alcohol monomer units of the polyvinyl alcohol be 0.01,
then boiling the resulting mixture for one hour and separating the
polymer by filtration), and then subjecting the thus-washed polymer
to Soxhlet extraction with methanol for one week. In the washing
method, the washing operation with sodium hydroxide-containing
methanol and the Soxhlet extraction with methanol are repeated or
continued until almost no change is found in the silicon atom
content of the thus-processed polyvinyl alcohol. Therefore, as far
as this condition is satisfied, the repetition number of the
washing operation with sodium hydroxide-containing methanol and the
duration of the Soxhlet extraction with methanol may be suitably
changed.
[0060] The silicon atom content (A) of the polyvinyl alcohol is
assumed to indicate the content of all the silicon atoms contained
in the polyvinyl alcohol. On the other hand, the silicon atom
content (B) of the polyvinyl alcohol that was washed with sodium
hydroxide-containing methanol and then washed with methanol by
Soxhlet extraction is assumed to indicate the content of the
silicon atoms derived from the silyl group-containing monomers
incorporated directly in the main chain of the polyvinyl
alcohol.
[0061] Before the determination of the silicon atom content (B),
the polyvinyl alcohol is washed with sodium hydroxide-containing
methanol. Siloxane bonds (--Si--O--Si--) are broken during the
washing treatment. During this treatment, the silyl group-having
monomers that are not incorporated directly in the main chain of
the polyvinyl alcohol but are bonded to the main chain via a
siloxane bond are cut away from the polyvinyl alcohol and removed
from the polymer. Therefore, the silicon atom content (B) of the
polyvinyl alcohol is assumed to indicate the silicon atom content
of a polyvinyl alcohol after the silyl group-having monomers not
incorporated directly in the main chain of the polymer has been
removed. Accordingly, the (A-B) in the above-mentioned formula (II)
is assumed to indicate the content of the silyl groups derived from
the silyl group-having monomers not incorporated directly in the
main chain of the polyvinyl alcohol.
[0062] The fact that the value (A-B)/(B) of the polyvinyl alcohol
is large means that the polyvinyl alcohol contains a large amount
of monomer units having excess silyl groups. On the other hand, the
fact that the value (A-B)/(B) of the polyvinyl alcohol is small
means that the amount of the monomer units having excess silyl
groups, the units not being incorporated directly in the main chain
of the polyvinyl alcohol, is small.
[0063] If the value (A-B)/(B) is too large, it is expected that a
large number of siloxane bonds (--Si--O--Si--) will be formed
between monomer units having excess silyl groups and silyl
group-containing monomer units incorporated in the main chain of
the polymer. Therefore, in such a case, it is also expected that
the molecular mobility of the polyvinyl alcohol may be restricted
and, therefore, the viscosity stability of an aqueous solution of
the polyvinyl alcohol may be lowered.
[0064] If the value (A-B)/(B) is too small, it is expected that the
proportion of the siloxane bonds (--Si--O--Si--) to be formed
between monomer units having excess silyl groups and silyl
group-containing monomer units incorporated in the main chain of
the polymer will be small and, as a result, the water resistance of
a film will be poor.
[0065] The (A-B)/(B) preferably ranges from 1/100 to 70/100, more
preferably from 5/100 to 60/100, and even more preferably from
7/100 to 50/100. If the (A-B)/(B) is larger than 75/100, the
viscosity stability of the aqueous anti-fouling agent of the
present invention will be poor. Moreover, the film formability
achieved when a film is formed by applying and then drying the
anti-fouling agent to the wall of a polymerization reactor will be
poor and the effect of suppressing the adhesion of scale on the
wall of a polymerization reactor will be reduced. On the other
hand, if the (A-B)/(B) is smaller than 0.2/100, the water
resistance of a film will be reduced when the film is formed
through application of an anti-fouling agent to the wall of a
polymerization reactor.
[0066] The method for adjusting the value (A-B)/(B) of the
polyvinyl alcohol used in the present invention is not particularly
restricted. One of the methods which the inventors recommend is a
method comprising dissolving a polyvinyl alcohol in water, the
polyvinyl alcohol being obtained by saponifying said polyvinyl
ester, subsequently neutralizing a remaining saponification
catalyst, and then subjecting to a heat treatment in an organic
solvent.
[0067] Examples of a solvent to be used suitably for the heat
treatment include lower alcohol and lower fatty acid ester.
Particularly, it is preferable to use a lower alcohol in view of
the rate of the reaction and the ease of controlling the reaction.
Among lower alcohols, alcohols having 3 or less carbon atoms are
preferred. Specifically, methanol, ethanol, 1-propanol and
2-propanol are preferable. Methanol and ethanol are more
preferable. Methanol is even more preferable. Among lower fatty
acid esters, preferred are fatty acid esters resulting from
dehydration between alcohol having 3 or less carbon atoms and
carboxylic acid having 3 or less carbon atoms. Specifically, methyl
acetate, ethyl acetate, methyl propionate and ethyl propionate are
preferable. Methyl acetate and ethyl acetate are more preferable.
Methyl acetate is even more preferable.
[0068] Moreover, it is desirable to use a mixed solvent of a lower
alcohol and a lower fatty acid ester as the solvent for the heat
treatment. When the mixed solvent is used, there is no particular
limitation on the mixing ratio of the lower alcohol and the lower
fatty acid ester. The lower alcohol/lower fatty acid ester weight
ratio is preferably from 25/75 to 99.99/0.01, more preferably from
50/50 to 99.95/0.05, and even more preferably from 75/25 to
99.9/0.1. In comparison to use of methanol as a solvent, use of the
mixed solvent is advantageous in that the rate of reaction can be
controlled easier through control of the mixing ratio of the mixed
solvent and therefore it is easy to adjust the (A-B)/(B) value. In
particular, this advantage will contribute greatly to the
production in industrial scale. These solvents may contain a small
amount of water, alkali or acid.
[0069] Moreover, when conducting the heat treatment, one may apply
the heat treatment to a wet polyvinyl alcohol immediately after the
neutralization following the saponification, or alternatively may
apply the heat treatment to a polyvinyl alcohol dried after the
neutralization following the saponification. From the viewpoint of
the rate of reaction and the ease of controlling the reaction, it
is preferable to apply heat treatment to a wet polyvinyl alcohol
immediately after the neutralization following the
saponification.
[0070] Treatment conditions for the heat treatment may be selected
arbitrarily depending, for example, on the conversion achieved when
vinyl ester monomers and silyl group-having monomers are
copolymerized, the degree of polymerization of a polyvinyl ester
obtained by the copolymerization, and the degree of saponification
of a polyvinyl alcohol obtained by saponifying the polyvinyl
ester.
[0071] As regards the mixing ratio of the polyvinyl alcohol and the
solvent in the heat treatment, it is desirable to use the solvent
in an amount of from 1 to 20 times the weight of solid polyvinyl
alcohol. The amount of the solvent used is preferably from 3 to 15
times, more preferably from 5 to 12 times the weight of the
polyvinyl alcohol.
[0072] The temperature when conducting the heat treatment is
desirably from 40 to 100.degree. C. For increasing the rate of
reaction and the productivity, the reaction temperature is
preferably 40.degree. C. or higher, more preferably 50.degree. C.
or higher, and even more preferably 60.degree. C. or higher. On the
other hand, from the viewpoint of preventing an excessive
advancement of the reaction, it is desirable for the temperature
during the heat treatment not to become higher than 100.degree. C.
Moreover, from the viewpoint of the quality stability in industrial
production, it is particularly desirable to heat under the
condition where the solvent used in the heat treatment is
refluxed.
[0073] The heat treatment time is preferably from 30 minutes to 10
hours. The heat treatment time is preferably 45 minutes or more,
and more preferably one hour or more. On the other hand, the heat
treatment time is preferably 8 hours or less, more preferably 6
hours or less, and even more preferably 4 hours or less.
[0074] The anti-fouling agent of the present invention comprises an
aqueous solution obtained by dissolving the above-described
specific polyvinyl alcohol in water. There is no particular
limitation on the concentration of the aqueous solution, but it is
preferably from 0.1 to 10% by weight from the viewpoint of
workability when applying the aqueous solution to the inner wall of
a polymerization reactor. From the viewpoint of shortening the
drying time required after the application of the aqueous solution
and forming a uniform film on the inner wall of a polymerization
reactor, the concentration of the aqueous solution is preferably
0.5% by weight or higher, more preferably 1% by weight or higher,
even more preferably 2% by weight or higher, and still more
preferably 3% by weight or higher. Unless the effect of the present
invention is affected, the aqueous solution may contain a small
amount of organic solvent. However, from the viewpoint of working
environment, it is desirable for the aqueous solution to contain
substantially no organic solvent.
[0075] When preparing the aqueous solution, it is desirable to
prepare it under alkaline conditions using a base such as sodium
hydroxide, potassium hydroxide, ammonia and ammonium hydroxide.
Sodium hydroxide and potassium hydroxide are preferred as the base
from the viewpoint of reduction in environmental load during the
drying step following the application of the aqueous solution. In
addition, the aqueous solution preferably has a pH of 9 or higher
from the viewpoint of viscosity stability of the aqueous
solution.
[0076] The method for applying the anti-fouling agent to the inner
wall of a polymerization reactor is not particularly restricted.
For example, conventional methods are available such as brush
coating, dip coating and spray coating. In the case of coating a
large polymerization reactor, spray coating is preferably used from
the viewpoint of workability. In spray coating, the solvent is
required to have a higher fluidity in comparison to brush coating
or dip coating. As is clear from the following Examples, the
anti-fouling agent of the present invention exhibits an extremely
high fluidity when the aqueous solution has a pH of 10 or higher,
preferably 11 or higher, and more preferably 12 or higher. As a
result, the inner wall of a polymerization reactor coated with the
anti-fouling agent of the present invention can inhibit the
adhesion of scales very effectively.
[0077] For securing a long-term storage stability of the aqueous
solution and a fluidity thereof at the time of spray coating, the
aqueous solution preferably has a pH of 14 or lower, more
preferably 13.5 or lower.
[0078] The method for preparing the aqueous solution is not
particularly restricted. For example, available are a method in
which a predetermined amount of the polyvinyl alcohol and the base
are mixed in a lump with water and a method in which the base is
dissolved in water and then the polyvinyl alcohol is added in a
lump or in installments. For shortening the dissolving time and
obtaining a homogeneous solution, it is desirable to dissolve the
substances by heating under stirring when preparing the aqueous
solution.
[0079] The amount of the anti-fouling agent of the present
invention to be applied to the inner wall of a polymerization
reactor is not particularly limited, but it is desirably from 0.001
to 5 g/m.sup.3 in terms of the weight the polyvinyl alcohol. The
polymerization reactor having an inner wall to which the
anti-fouling agent of the present invention has been applied is
desirably subjected to drying treatment before its use for
polymerization. The method of drying is not particularly restricted
and may be, for example, a method in which hot air is circulated
and a method in which the polymerization reactor is heated using a
jacket or the like. For obtaining a homogeneous film, the method in
which a polymerization reactor is heated by a jacket or the like is
suitable. The drying temperature is also not particularly limited.
However, it is preferably not lower than 40.degree. C., more
preferably not lower than 50.degree. C. from the viewpoint of
forming a film having a high strength. From the viewpoint of
inhibiting coloring of the anti-fouling agent and reducing the
adverse effect on the hue of the polymer formed in the
polymerization reactor, the drying temperature is preferably not
higher than 100.degree. C., and more preferably not higher than
90.degree. C. The anti-fouling agent of the present invention has a
good film formability and, therefore, it can form a film at a lower
temperature in comparison to conventional products. From such a
viewpoint, the present invention is of great significance.
[0080] The drying time is also not particularly limited and may be
appropriately determined depending, for example, on the size of the
polymerization reactor, the amount of the anti-fouling agent to be
applied, the concentration of the anti-fouling agent and the drying
temperature. It is preferably from 1 minute to one hour, more
preferably from 1 minute to 30 minutes. When shortening the drying
time, it is possible to improve the working efficiency and to
reduce the adverse effect on the hue of the polymer formed in the
polymerization reactor through inhibition of coloring of the
anti-fouling agent.
[0081] The method for producing a polymer using the anti-fouling
agent of the present invention may be, for example, suspension
polymerization, emulsion polymerization, solution polymerization,
bulk polymerization and vapor phase polymerization. Examples of
monomers to be used include vinyl halide such as vinyl chloride;
vinyl ester such as vinyl acetate and vinyl propionate; acrylic
acid, methacrylic acid and their esters and salts; maleic acid,
fumaric acid and their esters and anhydrides; styrene,
acrylonitrile, vinylidene chloride and vinyl ether. Especially, the
anti-fouling agent of the present invention is suitable for a
polymer production in which only vinyl chloride or vinyl chloride
and a monomer copolymerizable therewith are subjected to suspension
polymerization or emulsion polymerization in an aqueous medium.
[0082] Examples of the comonomer to be copolymerized with vinyl
chloride include vinyl ester such as vinyl acetate and vinyl
propionate; (meth)acrylic ester such as methyl (meth)acrylate and
ethyl (meth)acrylate; .alpha.-olefin such as ethylene and
propylene; unsaturated dicarboxylic acid such as maleic anhydride
and itaconic acid; acrylonitrile, styrene, vinylidene chloride,
vinyl ether, and other monomers copolymerizable with vinyl
chloride.
[0083] Examples of the polymerization initiator to be used for the
polymerization include organic peroxides such as benzoyl peroxide,
lauroyl peroxide, octyl peroxydicarbonate, acetylcyclohexylsulfonyl
peroxide and azo compounds such as 2,2'-azobisisobutyronitrile and
2,2'-azobis(2,4-dimethylvaloronitrile). A redox system comprising a
combination of peroxide and a reducing agent is also available.
[0084] In suspension polymerization, various additives may be added
to a polymerization system. Examples of the additives include
polymerization regulators such as aldehydes, halogenated
hydrocarbons and mercaptans; and polymerization inhibitors such as
phenol compounds, sulfur compounds, and N-oxide compounds.
Moreover, pH regulators, crosslinking agents and the like may also
be added, if needed. Two or more of the above-mentioned additives
may be used in combination.
[0085] In suspension polymerization, dispersion stabilizers may be
used. Examples of the dispersion stabilizers include those usually
employed when a vinyl compound is suspension polymerized in an
aqueous medium such as water-soluble polymers including
water-soluble cellulose ethers e.g. methylcellulose,
hydroxyethylcellulose, hydroxypropylcellulose and
hydroxypropylmethylcellulose; water-soluble polymers e.g. polyvinyl
alcohol and gelatin; oil-soluble emulsifiers such as sorbitan
monolaurate, sorbitan trioleate, glycerol tristearate, and ethylene
oxide-propylene oxide block copolymer; water-soluble emulsifiers
such as polyoxyethylene sorbitan monolaurate, polyoxyethylene
glycerol oleate, and sodium laurate.
[0086] In suspension polymerization, the temperature of the aqueous
medium is not particularly limited. Not only cool water of about
20.degree. C. but also hot water of 90.degree. C. or higher is
suitably employed. The aqueous medium may be not only pure water
but also may comprise an aqueous solution containing various kinds
of additional ingredients or an aqueous medium containing organic
solvents. When feeding the aqueous medium to a polymerization
system, the amount thereof is required only to be an amount such
that the polymerization system can be fully heated. Moreover, a
polymerization reactor fitted with a reflux condenser is also
preferably used in order to enhance the heat removal
efficiency.
EXAMPLES
[0087] The invention is described in more detail with reference to
the following Examples and Comparative Examples. Unless otherwise
specifically indicated, "part" and "%" in the following Examples
and Comparative Examples are all by weight.
[0088] I. Silyl Group-Containing Polyvinyl Alcohol PVA was produced
according to the method mentioned below, and the degree of
saponification, the content of silyl group-having monomer units,
and the silicon atom content were determined.
[0089] [Degree of Saponification of PVA]
[0090] The degree of saponification of PVA was determined according
to the method described in JIS K6726.
[0091] [Content of the Silyl Group-Having Monomer Units of PVA]
[0092] A polyvinyl ester before saponification was purified through
reprecipitation from hexane-acetone so that unreacted monomers
having a siliy group were completely removed from the polymer.
Then, the resulting polymer was dried under reduced pressure at
90.degree. C. for 2 days, and then dissolved in CDCl.sub.3 to yield
a sample for analysis. The sample was analyzed using a 500 MHz
.sup.1H-NMR spectrometer (JEOL GX-500), to determine the content of
silyl group-having monomer units of PVA.
[0093] [Method for Determining Silicon Atom Content of PVA]
[0094] The silicon atom content of PVA is determined by the use an
ICP spectrophotometer IRIS AP manufactured by Jarrell-Ash Co.,
Ltd., according to the method described above.
[0095] PVA-1
[0096] Into a 100-liter reactor equipped with a stirrer and a
temperature sensor, 2450 parts of vinylacetate (VAc), 1050 parts of
methanol (MeOH) and 18.4 parts of vinyltrimethoxysilane (VMS) were
fed. The atmosphere in the reactor was replaced with nitrogen under
stirring and then the temperature of the reaction system was
increased to 60.degree. C. 0.8 parts of 2,2'-azobisisobutyronitrile
(AlBN) was added to the reaction system to initiate polymerization.
The polymerization was continued along with a continuous addition
of 125 parts of methanol containing 1% of vinyltrimethoxysilane.
Then, the polymerization was stopped when four hours had elapsed
since the start thereof. When the polymerization was stopped, the
solid concentration in the system was 30.8%. Next, methanol vapor
was introduced into the system to expel the unreacted vinyl acetate
monomer. This gave a methanol solution containing polyvinyl ester
at a concentration of 40%.
[0097] To the methanol solution containing polyvinyl ester at a
concentration of 40%, methanol and a methanol solution containing
sodium hydroxide at a concentration of 10% were added in this order
under stirring so that the molar ratio of sodium hydroxide to the
vinyl acetate units in the polyvinyl ester would become 0.025 and
the concentration of solid polyvinyl ester would become 25%. Then,
saponification of the polyvinyl acetate was started at 40.degree.
C.
[0098] When six minutes had elapsed since the addition of methanol
solution containing the sodium hydroxide, a gel was generated.
Immediately after the generation of the gel, it was separated from
the reaction system by filtration and then was ground in a mixer.
The resulting ground product was left stand in the air at
25.degree. C. to allow the saponification to proceed. When one hour
had elapsed since the start of the saponification, the ground
product was moved to another reactor and then methyl acetate of a
weight twice the ground product was added thereto to neutralize the
saponification catalyst. After the addition of methyl acetate,
stirring was continued for one hour and then the ground product was
separated by filtration. Thus, silyl group-containing polyvinyl
alcohol (solid content: 92%) swollen with methanol was
obtained.
[0099] The silyl group-containing polyvinyl alcohol resulting from
the saponification was subjected to heat treatment according to the
method below. 100 parts of the resulting silyl group-containing
polyvinyl alcohol swollen with methanol (solid content: 92 parts)
was moved into a reactor fitted with a reflux condenser. And then
600 parts, which corresponds to 6.5 times the weight of the solid
of the silyl group-containing polyvinyl alcohol, of a mixed solvent
consisting of methanol and methyl acetate in a weight ratio of
90/10 were added thereto.
[0100] Then, the reactor was heated and the heat treatment was
conducted at 65.degree. C. for one hour. During the treatment, the
solvent was refluxed by heating. After the heat treatment, the
solvent was removed by filtration and the residue was dried at
65.degree. C. for 16 hours, resulting in a silyl group-containing
polyvinylalcohol (PVA-1).
[0101] The sily group-containing polyvinyl alcohol (PVA-1) had a
vinyltrimethoxysilane unit content of 0.50 mole %, a degree of
saponification of 98.5 mole % and a degree of polymerization of
1700. The value (A-B)/(B) was 12/100, which was determined by the
previously mentioned method for analyzing the content of silicon
atoms in PVA.
[0102] PVA-2 to PVA-15
[0103] PVA-2 to PVA-15 were obtained by methods the same as that
for the preparation of PVA-1 except varying the kind of silyl
group-having monomer, the amounts of vinyl acetate, methanol and
silyl group-having monomer to be fed, the amount of polymerization
initiator to be used, the condition for consecutive addition of
silyl group-having monomers, and the heat treatment condition as
shown in Table 1. Note that as regards PVA-13, the heat treatment
was not conducted and only filtration was conducted after stirring
at 30.degree. C. for 30 minutes.
Example 1
[0104] Into a 1-liter separable flask equipped with a stirrer and a
reflux condenser, 93 parts of water and 2 parts of sodium hydroxide
were fed. Under stirring, 5 parts of the silyl group-containing
polyvinyl alcohol (PVA-1) prepared by the method described above
was added and the inner temperature was increased up to 90.degree.
C. Two hours later, the inner temperature was reduced to 30.degree.
C. to yield a 5% aqueous PVA solution. The aqueous PVA solution had
a pH of 13. The resulting aqueous solution was evaluated for the
viscosity stability, the water resistance of its film, the amount
of scale depositing to a polymerization reactor and the amount of
foreign substance contaminating a polyvinyl chloride when being
used as an anti-fouling agent according to the methods shown below.
Note that the viscosity stability of an aqueous PVA solution was
evaluated using a 8% aqueous PVA solution prepared in a similar
manner. The results are shown in Table 2.
Examples 2 to 16
[0105] Using PVA-1 to PVA-10, aqueous solutions were prepared in a
manner the same as Example 1 except varying the composition of
aqueous solution as shown in Table 2. Each of the resulting aqueous
solutions was evaluated for the viscosity stability, the water
resistance of its film, the amount of scale depositing to a
polymerization reactor and the amount of foreign substance
contaminating a polyvinyl chloride when being used as an
anti-fouling agent in a manner the same as Example 1. The results
are summarized in Table 2.
Comparative Examples 1 to 5
[0106] Aqueous solutions were prepared in a manner the same as
Example 1 except using PVA-11 to PVA-15. Each of the resulting
aqueous solutions was evaluated for the viscosity stability, the
water resistance of its film, the amount of scale depositing to a
polymerization reactor and the amount of foreign substance
contaminating a polyvinyl chloride when being used as an
anti-fouling agent in a manner the same as Example 1. The results
are summarized in Table 2.
[0107] [Viscosity Stability of Aqueous PVA Solution]
[0108] An 8% aqueous PVA solution was prepared and was left stand
in a thermostatic bath at 10.degree. C. The viscosity of the
aqueous PVA solution was measured just after the temperature of the
solution reached 10.degree. C. and seven days later. The quotient
of the viscosity measured seven days later divided by the viscosity
measured just after the temperature of the aqueous PVA solution
reached 10.degree. C. (7 days later/just after) was determined and
judgment was made according to the following criteria:
[0109] A: less than 1.5,
[0110] B: not less than 1.5, but less than 2.5,
[0111] C: not less than 2.5, but less than 4.0,
[0112] D: not less than 4.0, but PVA has not been gelated, and
[0113] E: PVA has lost its fluidity to gelate.
[0114] [Water Resistance of Film]
[0115] A 5% aqueous PVA solution was cast at 20.degree. C. to form
a film having a thickness of 40 .mu.m. The film was heat treated at
120.degree. C. for 10 minutes and then cut into a size of 10 cm in
length and 10 cm in width to yield a specimen. The specimen was
immersed in distilled water at 20.degree. C. for 24 hours and then
was taken out. The moisture adhering on the surface thereof was
wiped off and the weight of the specimen in the water-swollen state
was measured. The specimen whose weight in the water-swollen state
was measured was dried at 105.degree. C. for 16 hours and then the
weight in the dry state was measured. The quotient of the weight in
the water-swollen state divided by the weight in the dry state was
calculated and was used as a degree of swelling. Judgment was made
according to the following criteria:
[0116] A: less than 5.0,
[0117] B: not less than 5.0, but less than 8.0,
[0118] C: not less than 8.0, but less than 12.0,
[0119] D: not less than 12.0, but a specimen after immersion in
distilled water was able to be taken out, and
[0120] E: a specimen after immersion in distilled water was not
able to be taken out.
[0121] [Application to the Inside of Polymerization Reactor]A 5%
aqueous PVA solution was applied by spraying onto the inner wall of
a 100-liter glass-lined autoclave. Thereafter, it was dried at a
jacket temperature of 60.degree. C. for five minutes and then
washed fully with water. The application quantity was 0.3 g/m.sup.2
in terms of solid content.
[0122] [Suspension Polymerization of Vinyl Chloride]
[0123] 40 parts of an aqueous solution containing 0.075% by weight
of dispersion stabilizer dissolved in deionized water and 0.04
parts of a 70% diisopropylperoxydicarbonate solution in toluene
were fed into the glass-lined autoclave coated with the
anti-fouling agent. The dispersion stabilizer was an unmodified PVA
having a polymerization degree of 2000 and a degree of
saponification of 80 mole %. The oxygen in the system was
subsequently removed by degassing the autoclave to 0.0067 MPa.
Then, 30 parts of vinyl chloride monomer was fed and the system was
heated to 57.degree. C. under stirring to conduct polymerization.
At the start of the polymerization, the pressure in the autoclave
was 0.83 MPa. When seven hours had elapsed since the start of the
polymerization and the pressure had reached 0.44 MPa, the
polymerization was stopped. The unreacted vinyl chloride monomer
was purged and the content was taken out. Then, the inner wall of
the autoclave was washed lightly with water.
[0124] [Amount of Scale Deposition]
[0125] After a polymer slurry was taken out from a polymerization
reactor, the condition of scale deposition inside the
polymerization reactor was visually observed and judged according
to the following criteria:
[0126] A: no deposition of polymer scale was found,
[0127] B: almost no deposition of polymer scale was found,
[0128] C: polymer scale was found on the inner wall of the
polymerization reactor,
[0129] D: much polymer scale was found on the inner wall of the
polymerization reactor, and
[0130] E: a great amount of polymer scale was found on the inner
wall of the polymerization reactor.
[0131] [Amount of Foreign Substance into Polyvinyl Chloride]
[0132] A polymer slurry was dried at 65.degree. C. Then, 100 g of
polyvinyl chloride was spread on a sheet of Kent paper and the
number of foreign substances was visually counted.
[0133] A: Less than one.
[0134] B: Not less than one but less than 3.
[0135] C: Not less than 3 but less than 5.
[0136] D: Not less than 5.
1 TABLE 1 Consecutive Addition Heat Treatment Initial Feeding VMS
Solvent- Heating VAc MeOH VMS AIBN Concentration Amount Polymer
Temperature Time (part) (part) (part) (part) (wt %) (part) Ratio
*1) (.degree. C.) (hour) Examples 1, 9-14 PVA-1 2450 1050 18.4 0.8
1 125 6.5 65 1 2 PVA-2 1200 1800 36.7 1.5 2 193 6.5 60 3 3 PVA-3
2450 1050 11 0.8 0.5 150 10 65 5 4 PVA-4 1200 1800 36.7 1.5 2 193
15 65 8 5 PVA-5 1200 1800 114.79 2 5 240 5 60 1 6 PVA-6 2400 800
92.1 0.5 3 161 4 55 0.5 7 PVA-7 2400 800 92.1 0.5 3 161 4 45 0.5 8
PVA-8 2400 800 92.1 0.5 3 161 4 105 0.5 15 PVA-9 2700 300 AMS *2) 2
0 0 6.5 65 1 25.5 16 PVA-10 2450 1050 AMPS *3) 0.8 AMPS *3) 10 AMPS
*3) 6.5 65 1 1.8 150 Comparative Examples 1 PVA-11 2450 1050 3.7
0.7 0.3 83 6.5 65 1 2 PVA-12 2450 1050 234.4 1.3 6 262 6.5 60 3 3
PVA-13 2450 1050 18.4 0.8 1 125 -- -- -- 4 PVA-14 2400 600 29 0.5 1
109 15 65 12 5 PVA-15 2450 1050 -- 0.7 -- -- 6.5 65 1 *1) Weight
ratio of the solvent to the PVA (solid) swollen with methanol *2)
Allyltrimethoxysilane (AMS) *3)
2-Acrylamido-2-methylpropyltrimethoxysilane (AMPS)
[0137]
2 TABLE 2 Specification of PVA Degree Evaluation of Composition of
Aqueous Solution Contam- Saponi- pH of Vis- Water ination S *1)
Degree fication PVA Aque- cosity Resis- Amount of Hard PVA (mole of
Polym- (mole (A - B)/ *2) Water *2) NaOH ous Sta- tance of Spots
into used %) erization P P .times. S %) (B) (part) (part) (part)
Solution bility of Film Scale Polymer Ex- amples 1 PVA-1 0.5 1700
850 98.5 12/100 5(8) 93(90) 2 13 A A A A 2 PVA-2 2 500 1000 98
20/100 5(8) 93(90) 2 13 A A A A 3 PVA-3 0.3 1700 510 98.5 5/100
5(8) 93(90) 2 13 A B B A 4 PVA-4 2 500 1000 98 0.8/100 5(8) 93(90)
2 13 A B C B 5 PVA-5 6 500 3000 98 60/100 5(8) 93(90) 2 13 B A B A
6 PVA-6 2.5 2000 5000 98.5 70/100 5(8) 93(90) 2 13 B A C B 7 PVA-7
2.5 2000 5000 98.5 75/100 5(8) 93(90) 2 13 C A C B 8 PVA-8 2.5 2000
5000 98.5 10/100 5(8) 93(90) 2 13 A B C B 9 PVA-1 0.5 1700 850 98.5
12/100 5(8) 95(92) 0.02 11 B A B B 10 PVA-1 0.5 1700 850 98.5
12/100 5(8) 95(92) 0.002 10 B B B B 11 PVA-1 0.5 1700 850 98.5
12/100 5(8) 95(92) 0.0002 9 C B C C 12 PVA-1 0.5 1700 850 98.5
12/100 0.5(8) 97.5(90) 2 13 A B B B 13 PVA-1 0.5 1700 850 98.5
12/100 1.5(8) 96.5(90) 2 13 A A B B 14 PVA-1 0.5 1700 850 98.5
12/100 12(8) 86(90) 2 13 A A B B 15 PVA-9 0.5 1700 850 98.5 11/100
5(8) 93(90) 2 13 A A A A 16 PVA-10 0.5 1700 850 98.5 10/100 5(8)
93(90) 2 13 A A A A Com- parative Ex- amples 1 PVA-11 0.1 1700 170
98.5 12/100 5(8) 93(90) 2 13 A D D C 2 PVA-12 6 1700 10200 98
20/100 5(8) 93(90) 2 13 D B D C 3 PVA-13 0.5 1700 850 98.5 85/100
5(8) 93(90) 2 13 D B D C 4 PVA-14 0.8 2500 2000 98 0.05/ 5(8)
93(90) 2 13 B D D C 100 5 PVA-15 0 1700 0 98.5 -- 5(8) 93(90) 2 13
B E E D *1) Content of silyl group-having monomer units *2) Numbers
in parentheses indicate mixing ratios used in evaluation of
viscosity stability.
[0138] Tables 1 and 2 show that in Examples 1 to 16, in which the
PVAs have a silyl group and satisfy formulae (I) and (II), the
aqueous solutions are superior in viscosity stability and water
resistance of films formed therefrom and can inhibit the deposition
of scale and the contamination of hard spots into a polymer formed.
On the other hand, in Comparative Example 1, in which P.times.S is
too small, the water resistance of the film is insufficient. In
Comparative Example 2, in which P.times.S is too large, the
viscosity stability of the aqueous solution is insufficient. In
Comparative Example 3, in which (A-B)/(B) is too large, the
viscosity stability of the aqueous solution is insufficient. In
Comparative Example 4, in which (A-B)/(B) is too small, the water
resistance of the film is insufficient. In Comparative Example 5,
in which PVA having no silyl group was used, the water resistance
of the film is quite insufficient. Thus, in Comparative Examples 1
to 5, the inhibition of the adhesion of scale and the contamination
of hard spots into a polymer formed was achieved
insufficiently.
* * * * *