U.S. patent application number 09/740365 was filed with the patent office on 2001-08-16 for process for production of chlorinated polyvinyl chloride resin.
This patent application is currently assigned to Kaneka Corporation. Invention is credited to Isshiki, Minoru, Suzuki, Takeyuki, Tadokoro, Tadashi.
Application Number | 20010014721 09/740365 |
Document ID | / |
Family ID | 16464872 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014721 |
Kind Code |
A1 |
Tadokoro, Tadashi ; et
al. |
August 16, 2001 |
Process for production of chlorinated polyvinyl chloride resin
Abstract
A polyvinyl chloride resin having an average particle diameter
of not less than 150 .mu.m and porosity at 31-1,011 psi of not less
than 0.15 cc/g is suspended in an aqueous medium and chlorinated by
blowing gaseous chlorine into the aqueous suspension. In this way,
the floating resin formation during chlorination can be prevented
and a chlorinated polyvinyl chloride resin excellent in free flow
property and showing good resistance to initial discoloration and
good thermal stability in heating and molding processes can be
produced.
Inventors: |
Tadokoro, Tadashi; (Hyogo,
JP) ; Suzuki, Takeyuki; (Hyogo, JP) ; Isshiki,
Minoru; (Shiga, JP) |
Correspondence
Address: |
JORDAN AND HAMBURG LLP
122 East 42nd Street
New York
NY
10168
US
|
Assignee: |
Kaneka Corporation
|
Family ID: |
16464872 |
Appl. No.: |
09/740365 |
Filed: |
December 19, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09740365 |
Dec 19, 2000 |
|
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09119386 |
Jul 20, 1998 |
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6242539 |
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Current U.S.
Class: |
525/356 ;
522/113 |
Current CPC
Class: |
C08F 14/06 20130101;
C08F 8/22 20130101; C08F 8/22 20130101 |
Class at
Publication: |
525/356 ;
522/113 |
International
Class: |
C08F 008/22 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 1997 |
JP |
9-202888 |
Claims
What is claimed is:
1. A process for the production of chlorinated polyvinyl chloride
resins which comprises chlorinating a polyvinyl chloride resin
having an average particle size of not less than 150 .mu.m and
porosity at 31-1,011 psi of not less than 0.15 cc/g as suspended in
an aqueous medium in a reaction vessel.
2. The process of claim 1, wherein said porosity is not less than
0.19 cc/g, and the bulk density of said polyvinyl chloride resin is
not less than 0.54 g/cc.
3. The process of claim 1 or 2, wherein the average particle
diameter of the polyvinyl chloride resin is not less than 200
.mu.m.
4. The process of any of claims 1 to 3, wherein the chlorination
reaction is carried out by blowing chlorine gas into the
above-mentioned aqueous suspension under UV irradiation with a
mercury lamp.
5. The process of any of claims 1 to 4, wherein the chlorination
reaction temperature is in the range from 40 to 90.degree. C.
6. The process of any of claims 1 to 5, wherein the reaction vessel
inside pressure during the chlorination reaction is in the range
from 0 to 1.5 kg/cm.sup.2.
7. The process of any of claims 1 to 6, wherein a polyvinyl
chloride resin prepared by a suspension polymerization process
using at least one polyvinylalcohol species as the suspending agent
together with a chain transfer agent is chlorinated.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a process for the
production of chlorinated polyvinyl chloride resin. More
particularly, it relates to a process for producing chlorinated
polyvinyl chlorides which process can prevent the formation of
floating resin in the step of chlorination and can give a
chlorinated polyvinyl resin excellent in free flow property and in
further, which is superior in initial coloring as well as heat
stability at a time of heated molding processing, can be
obtainable.
[0003] 2. Prior Art
[0004] A chlorinated polyvinyl chloride resin (here in after
referred to as "CPVC") can be obtained by chlorination of polyvinyl
chloride resin (here in after referred to as "PVC"). Processes for
chlorinating PVC suspended in an aqueous medium are known in the
prior art and described, for example, in Japanese Laid Open Patent
specifications Kokai Sho 58-103507 (1983) and Sho 64-6002
(1989).
[0005] When CPVC is chlorinated in aqueous suspension, the resins
tend to float up, and because of this tendency, in the step of
discharging the resins from the reaction vessel after completion of
the reaction, the resins may partly remain in the vessel
undischarged, or in the step of transportation of resin slurries,
these may cause pump cavitation troubles. For these and other
reasons, there arises a low productivity problem.
[0006] On the other hand, CPVC is characterized by their higher
heat resistance as compared with PVC, and therefore that is used in
manufacturing pipes, joints, industrial plates, sheets or the like
where heat resistance is required.
[0007] However, CPVC is inferior in heat stability to PVC, and
therefore, it easily undergoes scorching during molding processes,
hence are not suited for long time processing for molding.
Discoloration troubles thus may be encountered in transparent
moldings production, for instance.
[0008] Further, CPVC easily becomes electrified and therefore its
free flow property is not good. For this reason, they tend to cause
blocking of the hopper of an extruder, disturbing the intended
constant extrusion, among others.
[0009] For these reasons, as a measure for resin floating, a
technology was proposed in Japanese Laid Open Patent specification
Kokai Hei 9-95513 (1997). The proposed method comprises
chlorinating a PVC obtained by suspension polymerization in the
presence of a specific amount of a specific polyvinyl alcohol as a
suspending agent. This method indeed improves productivity since
the floating resin problem can be avoided.
[0010] However, this proposed method is not yet free from the
problems of heat stability in molding processes and/or
discoloration of moldings, for transparent applications. In
addition, the free flow property problem is still to be solved and,
therefore, a constant extrusion operation is often difficult to
achieve because of blocking of the hopper of the extruder, among
others.
OBJECTS
[0011] Purpose of the Invention
[0012] It is an object of the present invention to provide a
(novel) process for the production of chlorinated polyvinyl
chloride resin (CPVC), which prevents resin floating in the
chlorination process and gives CPVC having excellent free flow
property and further showing good resistance to initial
discoloration as well as good heat stability at the time of heating
and molding processing.
SUMMARY OF THE INVENTION
[0013] As a result of an intensive study made by the inventors of
the present invention to solve the above-mentioned problems, the
inventors found that by chlorinating PVC having a specific average
particle diameter as well as specific porosity in aqueous
suspension, the resin floating problem at the time of chlorination
can be prevented, and the CPVC obtained by this process have
excellent free flow property and that, in addition, the CPVC shows
good resistance to initial discoloration and good heat stability in
the heating and molding process, and they have now completed this
invention.
[0014] More precisely, the process for the production of CPVC
according to the present invention is characterized in that a PVC
having an average particle diameter not less than 150 .mu.m and
porosity not less than 0.15 cc/g at 31-1,011 psi is suspended in an
aqueous medium in a reaction vessel and the above-mentioned
chlorination reaction of PVC is carried out in said aqueous
suspension.
[0015] By this invention, a process for the production of CPVC can
be provided, which the process for the production of CPVC prevents
resin floating in the chlorination process and gives CPVC having
excellent free flow property and further showing good resistance to
initial discoloration as well as good heat stability in the heating
and molding process.
DETAILED DESCRIPTION OF THE INVENTION
[0016] THE PVC in the present invention includes homo-and
copolymers of vinyl chloride.
[0017] Monomers copolymerizable with vinyl chloride monomer are for
example ethylene, propylene, vinyl acetate, allyl chloride, allyl
glycidyl ether, acrylic acid esters, methacrylic acid esters, vinyl
ethers and the like. These monomers may be used alone or in
combination. The amount of these comonomers, when used, is about
0-20 parts by weight per 100 parts by weight of vinyl chloride
monomer.
[0018] The average polymerization degree of PVC is not particularly
limited.
[0019] Since the obtained CPVC is mainly used in the production of
pipes, joints, industrial plates, sheets or the like, the average
polymerization degree of PVC is preferably in the range of
400-2,000. When the average polymerization degree is lower than
400, the impact strength of molded CPVC products becomes not
enough, and when it is over 2,000, the melt viscosity of CPVC
becomes high rendering processing thereof very difficult.
[0020] The term "average particle diameter" as used herein means
the value which is calculated from a cumulative distribution by
using standard sieves of 42 mesh, 60 mesh, 80 mesh, 100 mesh, 120
mesh, 150 mesh and 200 mesh, according to the test method of JIS Z
8801.
[0021] The average particle diameter of PVC in this invention is
limited to not less than 150 .mu.m. When the average particle
diameter is less than 150 .mu.m, resin floating tends to occur at
the time of chlorination, and the obtained CPVC may have low free
flow property.
[0022] The use of a PVC having an average particle diameter of not
less than 200 .mu.m is more preferable since resin floating at the
time of chlorination and the free flow property of the obtained
CPVC can be further improved.
[0023] The term "porosity at 31-1,011 psi" as used herein means the
value obtained by dividing, by the resin weight, the total volume,
measured with a mercury penetration method porosimeter at 31-1,011
psi, of porosity occurring in the vinyl chloride resin and having
an average diameter of 5.9-0.17 .mu.m.
[0024] In the present invention, the porosity of PVC at 31-1,011
psi is limited to not less than 0.15 cc/g. When the said porosity
value is below 0.15 cc/g, the gelation property of CPVC is
deteriorated and/or the resistance to initial discoloration and the
heat stability become poor.
[0025] When the above-mentioned porosity value is not less than
0.19 cc/g and the bulk density is not less than 0.54 g/cc, the
resin floating-preventing effect resulting from said average
particle diameter, free flow property improving effect resulting
from said bulk density and the initial discoloration resistance and
heat stability improving effect in the heating and molding process
as resulting from said porosity can preferably be increased.
[0026] The Chlorination process for obtaining CPVC by chlorination
of PVC is carried out in a conventional manner in aqueous
suspension. There is no particular limitation posed on this
process. The process comprising blowing gaseous chlorine into PVC
under irradiation with a mercury lamp, which is most simplified one
from the equipment viewpoint, is preferred, however.
[0027] The temperature at the time of chlorination is preferably
40-90.degree. C. from the plant's corrosion resistance viewpoint
and also for improving the resistance to initial discoloration as
well as the heat stability of the obtained CPVC.
[0028] Further, the chlorination is preferably conducted in a
pressure range of 0-1.5 kg/cm.sup.2 G from the viewpoint of plant's
resistance to corrosion and pressure.
[0029] The preventive effect on the resin floating during the
chlorination reaction, and the improving effect on the free flow
property of the obtained CPVC and on the resistance to initial
discoloration and the heat stability, in the heating and molding
step become optimal when the PVC used is one produced by suspension
polymerization in the presence of at least one polyvinyl alcohol
species as a suspending agent and in the presence of a chain
transfer agent (added to the polymerization system).
[0030] On that occasion, the polyvinyl alcohol to be used is
preferably one having a degree of hydrolysis of 65-93 mole %.
[0031] The above -mentioned chain transfer agent is not
particularly limited, but can be selected from among 2-
mercaptoethanol, 3-mercaptopropanol, thiopropylene glycol,
thioglycerrol, thioglycolic acid, thiohydroacrylic acid, thiolactic
acid, thiomalic acid, thioacetic acid, iso-octyl thioglycolate,
n-butyl 3- mercaptopropionate, n-butyl thioglycolate, glycol
dimercaptoacetate, trimethylolpropane trithioglycolate,
alkylmercaptanes and the like.
[0032] The chlorination degree of the CPVC obtainable by this
invention is not particularly limited, but it is preferably 60-73%
by weight. More preferably, it is 62-70% by weight from the
viewpoint of excellent process ability in the heating and molding
process.
EXAMPLES
[0033] Hereinafter, the present invention will be described in more
detail by way of the following Examples and Comparative Examples,
but the invention is not limited to the following Examples.
[0034] In the following description, "part(s)" and "%" means
"part(s) by weight" and "% by weight" respectively unless otherwise
specified.
[0035] The characteristic properties of the respective polyvinyl
chloride resins were measured by the following test methods.
[0036] (Average Particle Diameter)
[0037] The standard sieves prescribed in JIS Z 8801 (42 mesh, 60
mesh, 80 mesh, 100 mesh, 120 mesh, 150 mesh and 200 mesh) were
used, and, from the cumulative weight distribution curve, the
particle diameter correspoinding to 50% by weight was determined as
the average particle diameter.
[0038] (Porosity)
[0039] A "porosimeter" made by AMINCO CO., LTD. was used.
Approximately 0.2 g of the polyvinyl chloride resin was accurately
weighed and poured into a penetrometer. And then, this penetrometer
was set in a pressure reduction unit, and after reducing the
pressure to not more than 0.1 Torr, the pressure was allowed to
resume atmospheric pressure while simultaneously filling the
penetrometer with mercury in order to cause mercury to penetrate
into porosity of the polyvinyl chloride resin. Then, the
penetrometer was set in a pressurizing unit filled with
isopropanol, and then, by increasing the pressure gradually, the
relationship between the volume of penetrated mercury and the
pressure was determined and the porosity between 31 psi and 1,011
psi, was determined. The porosity was expressed in terms of cc/g,
ie. cc per gram of the polyvinyl chloride resin.
[0040] (Bulk Density)
[0041] The bulk density was measured according to JIS K 6721, and
by using a bulk density measuring instrument made by TOYO SEIKI CO.
The measurement results are shown in terms of cc/g.
[0042] (Viscosity Average Polymerization Degree)
[0043] The measurements were conducted according to JIS K 6721.
[0044] On the other hand, the free flow property test, the heat
stability test and the initial color measurement were carried out
as follows.
[0045] (Free Flow Property Test)
[0046] 100 g of CPVC or its compound was placed in a small-size
funnel, and the pass through time until all of the resin or
compound falling down from the funnel was measured. The funnel was
tightly connected with a conical beaker for receiving the falling
resin or compound from the funnel so that the system was
airtight.
[0047] The formulation of the compound used for this free flow
property test is as in the following Table 1, and each of the
compounds was prepared by hot-blending using a Henshel mixer.
1TABLE 1 CPVC 100 parts MBS (KaneAce B-561 made by Kanegafuchi
Chem., Co.) 6 parts Chlorinated polyethylene 3 parts Tin stabilizer
(octyltin-mercaptide) 2 parts Polyethylene wax 2 parts Titanium
oxide 5 parts
[0048] (Heat Stability Test)
[0049] 50.times.40 mm sheet specimens cut from each of the roll
milled sheets were put in a gear oven which was heated up to
200.degree. C. and kept constantly at that temperature, and the
specimens were taken out one by one from the gear oven every 15
minutes, and evaluated by the eye for the extent of blackening. The
time required until changing to black color (blackening time:
minutes) was determined.
[0050] (Initial Color)
[0051] By using a color difference meter (.SIGMA.80 COLOR MEASURING
SYSTEM made by NIPPON DENSHOKU KOGYO CO.), the "a value" (redness)
of the pressed plate was measured.
[0052] For evaluating each CPVC for physical properties, the
following formulated compound was roll-milled and pressed to make
specimens, which were submitted to the following tests.
[0053] (Physical Property Tests of CPVC)
[0054] Using the CPVC obtained in Examples and Comparative
Examples, compounds which were formulated as in the following Table
2 were prepared.
2TABLE 2 CPVC 100 parts MBS (KaneAce B31 made by Kanegafuchi Chem.
Co.) 10 parts Tin stabilizer (octyltin-mercaptide) 2 parts Stearic
acid 1 parts Paraffin wax 0.7 parts
[0055] Each of these compounds was roll-milled at 190.degree. C.
for 3 minutes with a 0.2 mm clearance. Specimens, 50
mm(vertical).times.40 mm (width) in size, were cut out from each
roll-milled sheet, and subjected to heat stability testing. On the
other hand, the obtained sheets of each formulation were piled up
and pressed together at 200.degree. C. for preparing a pressed
plate with a thickness of 3 mm. The "a value"(redness) of the plate
was measured by using the color difference meter.
Example 1
[0056] A stainless autoclave equipped with a stirrer was charged
with 120 parts of deionized water, 0.08 part of polyvinylalcohol
(degree of hydrolysis: 79.5 mole %, viscosity of 4% aqueous
solution at 20.degree. C.: 41.0 cps), 0.004 part of
2-mercaptoethanol and 0.04 part of t-butyl peroxyneodecanoate as an
oil-soluble polymerization initiator. Then, after evacuation of the
autoclave, 100 parts by weight of vinyl chloride was injected
thereinto under pressure. The polymerization reaction was then
carried out at 58.degree. C. for 5 hours with stirring, to give a
PVC.
[0057] Next, 15 kg of the above-mentioned PVC powder and 35 kg of
ion-exchanged water were charged into a chlorination reaction
vessel, and stirred thoroughly. Then, the inside air was suctioned
out by vacuum pumping to thereby keep the inside air pressure at
-0.6 kg/cm.sup.2 G for 10 minutes.
[0058] Therafter, the remaining oxygen gas was further purged by
passing nitrogen gas through the reactor, and again suctioned by
vacuum pumping while keeping the above-mentioned pressure for 10
minutes, for further removal of oxygen.
[0059] Next, chlorine gas was fed into the vessel, and after 10
minutes of substitution of the vessel inside with chlorine gas, the
chlorination reaction was carried out while keeping the pressure at
0.2 kg/cm.sup.2 G and irradiating the vessel contents with UV using
a high-pressure mercury lamp, 100 W in the initial stage and 200 W
after the lapse of 2 hours. The chlorination reaction temperature
was initially 40.degree. C., then raised to 75.degree. C. in 1.5
hours and thereafter kept at 75.degree. C. constantly.
[0060] The chlorination degree was calculated from the hydrogen
chloride concentration of the reaction solution, and the mercury
lamp beaming was terminated at the point of 67% chlorine content
along with stopping of the chlorine gas supply. Simultaneously the
reaction vessel was cooled down and the remaining chlorine gas was
purged with nitrogen gas, and the chlorination reaction was then
completed.
[0061] After purging of the remaining chlorine gas, the slurry was
discharged from the bottom of the reaction vessel with keeping
stirring. The slurry discharged was resinous and uniform. Almost no
resin was found remaining in the vessel.
[0062] After dehydration of the slurry discharged and washing with
deionized water, followed by draining and drying a white CPVC
powder was obtained. The obtained CPVC was subjected to physical
properties testing.
Comparative Example 1
[0063] A PVC was obtained by the same PVC process as in Example 1
without using 0.004 part by weight of 2-mercaptoethanol.
[0064] Using this PVC, a white CPVC powder was obtained by the same
chlorination reaction as in Example 1. On the occasion of slurry
discharge, the slurry discharged was resinous and uniform. Almost
no resin was remaining in the reaction vessel. The obtained CPVC
was subjected to physical properties testing.
Comparative Example 2
[0065] A PVC was obtained by the same PVC polymerization process as
in Example 1 except that the use of 0.004 part by weight of
2-mercaptoethanol was omitted and instead of 0.08 part by weight of
polyvinylalcohol as the suspending agent, 0.05 part by weight of
hydroxypropylmethylcellulose (methoxyl group content 21.5%,
hydroxypropoxyl group content 8.0%).
[0066] Using this PVC, a white CPVC powder was obtained by the same
chlorination reaction as in Example 1. On the occasion of slurry
discharge, a nonviscous slurry of lower resin concentration was
discharged at the early stage of discharge and a muddy slurry of
higher resin concentration was discharged at the last stage of
discharge. A fairly large amount of the resin remained in the
reaction vessel. The obtained resin was subjected to physical
properties testing.
Comparative Example 3
[0067] A PVC was obtained by the same PVC polymerization process as
in Example 1 except that the use of 0.004 part by weight of
2-mercaptoethanol was omitted and 0.05 part by weight of
vinylpyrrolidone was used instead of 0.08 part by weight of
polyvinylalcohol as the dispersion agent.
[0068] Using this PVC, a white CPVC powder was obtained by the same
chlorination reaction as in Example 1. On the occasion of slurry
discharge, a resinous and uniform slurry was discharged. Almost no
resin remained in the reaction vessel. The obtained CPVC was
subjected to physical properties testing.
[0069] The results of physical properties testing of the CPVC
obtained in Example 1 and Comparative Examples 1 to 3, and the
powder characteristics of the PVCs are shown in Table 3.
3 TABLE 3 Example Example Example Comparative Comparative
Comparative 1 2 3 Example 1 Example 2 Example 3 A 224 180 155 126
107 190 B 0.196 0.180 0.172 0.177 0.196 0.100 C 0.563 0.570 0.518
0.558 0.505 0.596 D 1000 1000 1000 1000 1000 1000 E good good good
good bad good F 192 194 251 387 no falling 184 G 222 226 239 299 no
falling 212 H 105 105 105 90 105 90 I 1.5 1.6 1.1 2.9 1.2 3.4
[0070] In the above Table, the alphabetical letters denote the
following:
[0071] A: Average particle diameter (.mu.m) of the PVC.
[0072] B: Porosity (cc/g) of the PVC.
[0073] C: Bulk density (g/cc) of the PVC.
[0074] D: Viscosity average polymerization degree of the PVC.
[0075] E: Sedimentation tendency in the chlorination reaction
process
[0076] F: Free flow property of the CPVC resin (seconds)
[0077] G: Free flow property of the CPVC compound (seconds)
[0078] H: Heat stability of the CPVC (blackening time: minutes)
[0079] I: Initial color of the CPVC (pressed plate: "a" value)
[0080] As clearly seen from the above Table 3, the process of the
present invention prevents resin floating during the chlorination
reaction for making CPVC and the CPVC obtained by the process of
this invention have excellent free flow property, and further show
good resistance to initial discoloration as well as good heat
stability at the time of heating and molding processing.
* * * * *