U.S. patent application number 10/098241 was filed with the patent office on 2003-09-18 for rigid pvc compounding compositions exhibiting weather resistance and pvc degradation resistance in hot sunny climates.
This patent application is currently assigned to PolyOne Corporation. Invention is credited to Hawrylko, Roman Bohdan, Krause, Peter Wolfgang, Levesque, Michel.
Application Number | 20030176544 10/098241 |
Document ID | / |
Family ID | 28039342 |
Filed Date | 2003-09-18 |
United States Patent
Application |
20030176544 |
Kind Code |
A1 |
Hawrylko, Roman Bohdan ; et
al. |
September 18, 2003 |
Rigid PVC compounding compositions exhibiting weather resistance
and PVC degradation resistance in hot sunny climates
Abstract
Rigid PVC resins are compounded with a chalk-like Caribbean
micritic calcium carbonate to provide improved weathering
resistance of rigid PVC articles subjected to external exposures of
heat and sunlight. The effective resistance to heat and sunlight is
substantially increased by rigid PVC resins compounded with
European chalk and Caribbean micritic calcium carbonate, zinc
dialkyl ester scavenger and organotin stabilizer to provide
considerably increased PVC degradation resistance.
Inventors: |
Hawrylko, Roman Bohdan;
(Avon Lake, OH) ; Krause, Peter Wolfgang; (Grand
Valley, CA) ; Levesque, Michel; (Beauharnois,
CA) |
Correspondence
Address: |
HUDAK, SHUNK & FARINE, CO., L.P.A.
2020 FRONT STREET
SUITE 307
CUYAHOGA FALLS
OH
44221
US
|
Assignee: |
PolyOne Corporation
|
Family ID: |
28039342 |
Appl. No.: |
10/098241 |
Filed: |
March 15, 2002 |
Current U.S.
Class: |
524/180 ;
524/269; 524/425 |
Current CPC
Class: |
C08K 3/26 20130101 |
Class at
Publication: |
524/180 ;
524/269; 524/425 |
International
Class: |
C08K 005/00 |
Claims
What is claimed is:
1. A weather resistant polyvinyl chloride (PVC) resin compounding
composition, comprising: a rigid PVC resin; and at least about 2
weight parts of non-precipitated, sedimentary Caribbean calcium
carbonate per 100 weight parts of PVC resin, the calcium carbonate
having a particle size less than about 10 microns and is about 98%
or more by weight pure calcium carbonate essentially free of
iron.
2. The rigid PVC compounding composition of claim 1, wherein the
Caribbean calcium carbonate particle size is less than about 6
microns.
3. The rigid PVC compounding composition of claim 1, wherein the
particle size of the Caribbean calcium carbonate is less than about
3 microns.
4. The rigid PVC compounding composition of claim 1 , wherein the
particle size of the Caribbean calcium carbonate comprises from
about 1 to about 3 microns or lower.
5. The rigid PVC compounding composition of claim 1, wherein the
Caribbean calcium carbonate contains impurities by weight are less
than about 1% magnesium carbonate, less than about 0.3% acid
insolubles, and less than about 0.1% silica.
6. The rigid PVC compounding composition of claim 1, wherein the
calcium carbonate is Jamaican calcium carbonate.
7. The rigid PVC compounding composition of claim 1, containing
from about 2 to about 50 weight parts of Caribbean calcium
carbonate.
8. The rigid PVC compounding composition of claim 2, containing
from about 5 to about 15 weight parts of Jamaican calcium
carbonate.
9. The rigid PVC compounding composition of claim 1, wherein the
Caribbean calcium carbonate is wet ground calcium carbonate.
10. The rigid PVC compounding composition of claim 1, wherein the
Caribbean calcium carbonate is dry ground calcium carbonate.
11. The rigid PVC compounding composition of claim 1, wherein the
micritic calcium carbonate particles are surface treated with a
stearate.
12. The rigid PVC compounding composition of claim 1, containing at
least about 0.5 weight part s of organotin stabilizer based on 100
weight parts of PVC.
13. The rigid PVC compounding composition of claim 2, containing
from about 0.5 to about 3 weight parts of organotin stabilizer.
14. The rigid PVC compounding composition of claim 6, containing
from about 1 to about 2 weight parts of organotin stabilizer.
15. The rigid PVC compounding composition of claim 12, wherein the
organotin stabilizer comprises substituted mono-alkyl or dialkyl or
trialkyl esters of tin with mono-, di-, or tri-substituted active
mercapto groups or carboxylate groups.
16. The rigid PVC compounding composition of claim 15, wherein the
organotin stabilizer comprises mercapto groups.
17. The rigid PVC compounding composition of claim 12, wherein the
organotin stabilizer comprises a dialkyl mercapto compound.
18. The PVC compounding composition of claim 13, wherein the
organotin stabilizer comprises dialkyl ester mercaptide.
19. The PVC compounding composition of claim 13, wherein the
organotin stabilizer comprises dibutyl tin mercaptide.
20. The rigid PVC compounding composition of claim 8, wherein the
organotin stabilizer comprises dibutyl tin ethyl hexyl
mercaptoacetate.
21. The PVC compounding composition of claim 15, wherein the
organotin stabilizer comprises active carboxylate groups.
22. The PVC compounding composition of claim 21, wherein the
carboxylate group comprises carboxylic acid.
23. The rigid PVC compounding composition of claim 21, wherein the
carboxylate group comprises an ester of carboxylic acid.
24. The rigid PVC compounding composition of claim 12, containing
at least about 0.1 weight parts of zinc dialkyl ester scavenger per
100 weight parts of PVC resin.
25. The rigid PVC compounding composition of claim 15, containing
at least about 0.1 weight parts of zinc dialkyl ester scavenger per
100 weight parts of PVC resin, provided the equivalents of active
mercapto groups or carboxylate groups in the organotin are equal to
or exceed the equivalents of dialkyl ester groups in the zinc
dialkyl ester.
26. The rigid PVC compounding composition of claim 20, containing
from about 0.1 to about 2 weight parts of zinc dialkyl ester.
27. The rigid PVC compounding composition of claim 1, wherein the
PVC resin is essentially a homopolymer.
28. The rigid PVC compounding composition of claim 1, wherein the
PVC comprises a copolymer of copolymerized vinyl chloride monomer
with less than 5% by weight copolymerized other unsaturated
co-monomer.
29. The rigid PVC compounding composition of claim 28, wherein the
other unsaturated co-monomer is a vinyl monomer.
30. The rigid PVC compounding composition of claim 28, wherein the
other unsaturated co-monomer is a mono-ethylenically unsaturated
monomer.
31. A weather resistant polyvinyl chloride (PVC) compounding
composition, comprising: a rigid PVC resin; at least about 2 weight
parts of a non-precipitated, finely divided, chalk calcium
carbonate having a particle size less than about 10 microns and at
least about 98% pure calcium carbonate essentially free of iron; at
least about 0.5 weight parts of an alkyl substituted organotin
having one, two, or three non-alkyl substituted active mercapto or
carboxylate groups; at least about 0.1 weight parts of zinc dialkyl
ester scavenger, where the equivalents of zinc alkyl groups is less
than the equivalents of non-alkyl active mercapto or carboxyl
groups of the organotin; and where all weight parts are based on
100 weight parts of PVC resin.
32. The rigid PVC resin compounding composition of claim 31,
containing from about 2 to about 50 weight parts of said calcium
carbonate.
33. The rigid PVC resin compounding composition of claim 32,
containing from about 0.5 to about 3 weight parts of said
organotin.
34. The rigid PVC compounding composition of claim 33, wherein the
organotin comprises a mercapto compound.
35. The rigid compounding composition of claim 33, wherein the
organotin comprises a carboxylate compound.
36. The rigid PVC compounding composition of claim 33, containing
from about 0.1 to about 2 weight parts of said zinc dialkyl
ester.
37. A process for producing a rigid polyvinyl chloride (PVC) resin
compounding composition, the process comprising: providing a
non-precipitated, sedimentary Caribbean micritic calcium carbonate
having a particle size less than about 10 microns, at least about
98% pure calcium carbonate, and essentially free of iron; and
mixing the calcium carbonate with PVC resin to form a PVC
compounding composition containing at least about 2 weight parts
calcium carbonate per 100 weight parts of PVC resin.
38. The process of claim 37, wherein the compounded PVC resin and
micritic calcium carbonate are mixed with at least about 0.5 weight
parts of organotin stabilizer based on 100 weight parts of PVC
resin.
39. The process of claim 38, wherein the Caribbean calcium
carbonate is wet or dry ground to provide a particle size less than
about 6 microns.
40. The process of claim 39, wherein the Caribbean calcium
carbonate is wet ground to provide the particle size.
41. The process of claim 39, wherein the Caribbean calcium
carbonate is dry ground to provide the particle size.
42. The process of claim 37, wherein the PVC compounding
composition is formed into a rigid PVC article.
43. The process of claim 37, wherein the PVC compounding
composition is extruded into a rigid PVC article.
44. The process of claim 37, wherein the PVC compounding
composition is molded into a rigid PVC article.
45. A rigid PVC article comprising the composition of claim 1.
46. A rigid PVC article comprising the composition of claim 8.
47. A rigid PVC article comprising the composition of claim 12.
48. A rigid PVC article comprising the composition of claim 20.
Description
[0001] This invention pertains to polyvinyl chloride (PVC) and more
particularly to weather and heat resistant rigid PVCs used
externally and exposed to harsh environmental conditions of
excessive heat and sun common in southern exposures.
BACKGROUND OF THE INVENTION
[0002] Rigid PVCs contain little or no plasticizer and are commonly
used in a wide variety of internal uses sheltered from direct
outside environmental exposure. Rigid PVCs are known to degrade
upon exposure to sunlight, heat and UV, which degrades the
polymeric structure of PVCs and generates trapped HCl acid. To have
any practical commercial use in outdoor environments, products made
from rigid PVCs, such as house siding, door and window profiles,
shutters, roof vents and sashes, outdoor fencing and decking, and
similar exterior applications, the PVC polymeric structures must be
stable and resistant to heat and sunlight. Colors for rigid or
semi-rigid PVCs, if used externally, are typically limited to white
and light pastel colors due to color fade and deterioration.
[0003] Heat and sunlight degrade the polymeric structure of PVC by
generating HCl acid trapped in the rigid polymeric structures where
formation of HCl is catalytic and in turn accelerates further
degradation and further generation of HCl acid along with
additional degradation. The tendency to decompose is accelerated at
elevated temperatures and direct sun exposure or by catalytic
materials such as traces of iron or zinc compounds. Zinc compounds
such as zinc acetate are known to react with PVCs to cause
dechlorination and similarly can react with tin compounds to form
detrimental zinc chloride. In harsh environments, particularly hot
and dry sunny climates, the sun and heat cause a considerably
increased rate of degradation of the PVC polymeric structure. Dark
colors are more prone to absorb heat and further increases
instability and degradation of PVCs. Consequently, the exposed
plastic materials made of rigid PVCs rapidly discolor, frequently
become brittle, and otherwise crack and deteriorate.
[0004] According to J. of Vinyl Technology, September, 1983, vol.
5, No. 3, pages 91-95, degradation of PVC by exposure to heat and
sunlight is known to cause degradation of the PVC polymeric
structure wherein UV light imparts sufficient energy to break PVC
chemical bonds, while visible light causes color discoloration, and
near infrared light contributes to heat degradation and poor
weatherability. PVC degradation generates HCl while causing double
bond formation in the PVC polymeric structure. PVC physical
deterioration absorbs light causing poor weathering resistance
including yellowing and oxidation bleaching. Oxidized PVC becomes
water sensitive causing surface erosion, brittleness and cracking,
according to the journal article. Such PVC polymeric degradation is
especially critical in rigid PVCs substantially free of
plasticizers.
[0005] In contrast, semi-rigid or flexible PVCs containing
appreciable amounts of plasticizer do not tend to degrade and thus
are used for exterior moldings and extrusions for trim and siding
of buildings exposed to outside environments. The degradation is
particularly sever in rigid PVCs with no plasticizer, while
semi-rigid or flexible PVCs containing appreciable levels of
plasticizer provide a porosity in the plastic structure and
facilitate expulsion of HCl acid formation, which in turn minimizes
the sunlight and heat degradation. Similarly, foamed PVC plastic
materials are inherently porous and provide a means for expulsion
of HCl acid that may be generated and otherwise retained.
Semi-rigid PVCs ordinarily contain above about 10 weight parts
external plasticizer, while flexible PVCs ordinarily contain more
than about 25 weight parts, both based on 100 weight parts of PVC
resin. Since plasticized PVCs are more resistant to heat and
sunlight, rigid PVCs ordinarily are not used in external exposures,
especially in harsh hot and sunny climates, due to the inherent
degradation of rigid PVCs and inherent characteristic of retaining
acid generated on exposure to heat and sun.
[0006] Stabilizers are known to reduce the adverse weathering
effects of exposure to heat and sun and are frequently added to
PVCs used externally. Alkaline materials such as barium oxide or
sodium silicate or certain organometalic materials of tin or lead
can stabilize PVCs by removing traces of HCl chemically as the HCl
forms and thereby eliminate HCl degeneration as well as the
catalytic effect of HCL acid generation. The stabilizers are known
as heat stabilizers and can include alkaline oxides, hydroxide
carbonates, amines, lead salts, sodium silicate, barium-cadmium
soaps, and dibutyl tin dilaurates. To obtain maximum effectiveness,
a mixture of stabilizers frequently is utilized, where one
stabilizer may be effective against heat, while another may be
effective against sunlight. Such stabilizer combinations are
helpful in semi-rigid or flexible PVCs, but are only marginally
helpful in compounding rigid PVCs. However, rigid structures are
preferred for most structural applications due to structural
integrity and durability such as impact resistance.
[0007] Calcium carbonates are commonly used as filler materials in
PVCs, but are not known to provide weather resistance or resistance
to polymeric degradation upon exposure to heat and sunlight. In the
United States, calcium carbonates are based on limestone or marble
deposits. Commercial grades ordinarily are processed precipitated
calcium carbonates and typically contain perceptible levels of iron
of trace amounts above about 200 ppm iron which can activate HCl
generation in PVCs. In England and Europe, calcium carbonates are
primarily chalky ore deposits. Caribbean calcium carbonates
described as micritic chalk-like, marine based and sedimentary in
origin are disclosed in U.S. Pat. No. 5,102,465 for use as filler
material in polyester molding compounds.
SUMMARY OF THE INVENTION
[0008] It now has been found that certain chalk-like marine calcium
carbonates known as Caribbean micritic calcium carbonates derived
from soft friable marine fossil sedimentary deposits are especially
useful in rigid PVCs and surprisingly function as a scavenger for
free HCl acid generated in PVCs to provide considerable weathering
resistance, in addition to contributing an inexpensive source of
filler material to the compounding of the rigid PVCs. It has been
further found that a combination of limited amounts of a lower
dialkyl acid ester of zinc scavenger, especially zinc octoate, and
an organotin acid stabilizer together provide especially improved
degradation resistance in combination with the Caribbean calcium
carbonate, which collectively provide considerably improved
degradation resistance when subjected to hot and sunny exposures.
The Caribbean calcium carbonate surprisingly exhibits HCl scavenger
properties and contributes to neutralization or absorption of HCl
to eliminate HCl acid evolving upon heat and sunlight exposure
degradation. The Caribbean calcium carbonate is an effective
scavenger by itself, but is especially effective in conjunction
with low levels of zinc dialkyl ester scavenger and organotin
stabilizer, where the HCl scavenger effectiveness is increased
considerably with increased levels of Caribbean calcium carbonate.
Low levels of zinc dialkyl ester likewise function as an HCl
scavenger without degrading the polymeric structure of PVCs to
provide weathering resistance, eliminates any sulfur generated by
tin mercaptide stabilizers, and surprisingly does not adversely
interact with the organotin stabilizer.
[0009] In accordance with this invention, extruded or molded rigid
PVCs can be particularly utilized for exterior exposures in hot and
sunny environments utilizing rigid PVCs to form plastic components
for external use. The rigid PVCs exhibit substantially improved
resistance to acid generation, acid degradation, discoloration,
cracking and other weathering physical deterioration of PVCs due to
excessive heat and sun exposure. Enhanced color retention and
stability can be achieved with white pigmented PVCs, along with
pastels and medium depth pigmented colors, as well as with darker
colors. These and other advantages of the invention will become
more apparent by reference to the detailed description and the
illustrative examples hereinafter.
[0010] Briefly, the invention comprises rigid PVCs utilized for
extrusion, molding or other formation of rigid plastic components
utilized particularly for external exposures to heat and sunlight.
The rigid PVC compounded compositions contain at least about 2
weight parts of Caribbean micritic calcium carbonate based on 100
weight parts PVC resin to scavenger and prevent the generation and
autocatalytic acceleration of HCl acid. The scavenger
characteristics of the Caribbean calcium carbonate are enhanced
considerably by compounding PVC with the combination of at least
about 0.1 weight parts of a lower dialkyl ester of zinc scavenger,
preferably a zinc octoate, and at least about 0.5 weight parts of
an organotin heat stabilizer, preferably a dibutyl tin mercaptide,
both weight parts based on 100 weight parts of PVC.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The invention is based on rigid PVCs for exterior exposure
containing Caribbean micritic calcium carbonate as an HCl acid
scavenger and optionally enhanced with a zinc organic dialky ester
scavenger in conjunction with an organotin stabilizer
[0012] Referring first to the micritic calcium carbonate, Caribbean
calcium carbonates are distinguished from calcium carbonates mined
from limestone or marble ore deposits in the United States or chalk
deposits in England or Europe in that the Caribbean calcium
carbonates are mined from soft and friable, finely divided,
chalk-lines marine sedimentary deposits frequently occurring as
surface deposits in the Caribbean area. Caribbean calcium
carbonates are high purity, finely divided, fine particle size
friable deposits described as Caribbean micritic limestone in U.S.
Pat. No. 5,102,465, hereby fully incorporated by reference, and
sedimentary in origin comprising a combination of reef limestone
deposits of reef fossil fragments, betrital deposits of fibrous
skeletal and non-skeletal grains, micrite deposits of naturally
formed precipitated calcium carbonate in beds or matrix with
betrital, and chalk deposits of disarticulated caccolith fragments.
Caribbean micritic calcium carbonates are soft and friable,
chalk-like consistency, sedimentary deposits comprising reefs,
betritals, micrite and chalky deposits. Caribbean calcium carbonate
deposits tend to agglomerate in the natural sedimentary state but
can be readily broken down or commutated to produce rounded porous
particles comparable to naturally occurring particles less than
about 6 microns. Useful Caribbean calcium carbonates have a
particle size less than about 10 microns, desirably about 6 microns
or less, preferably having a typical particle size distribution of
about 70% less than about 3 microns, where particles from about 1
to about 3 microns or lower are most preferred. Smaller particles
increase the surface area and in turn increases the scavenger
effectiveness against PVC degradation. Caribbean micritic calcium
carbonates are found throughout the Caribbean basin with
significant deposits found in Haiti and Jamaica. Caribbean micritic
calcium carbonates, especially Jamaican origin, are very high in
purity typically exhibiting above 98% and typically more than about
99% pure calcium carbonate, with minimal amounts of impurities.
Both wet ground and dry ground Caribbean calcium carbonates are
effective for eliminating free HCl acid generation in PVCs,
although water ground is preferred and has been found to be more
effective. In contrast, chemically processed precipitated Caribbean
micritic calcium carbonates are not effective HCl scavengers nor
prevent PVC degradation in accordance with this invention.
Accordingly, non-precipitated Caribbean calcium carbonates excludes
those Caribbean deposits chemically processed to form precipitated
calcium carbonates.
[0013] Jamaican micritic calcium carbonate is preferred and
characteristically contains high purity calcium carbonate,
typically more than about 99% by weight pure calcium carbonate, and
commonly mined from surface sedimentary chalky marine deposits of
friable fragile agglomerated particles. The deposits can be
subsequently wet or dry ground by grinding for instance by a hammer
mill followed by ball mill grinding to obtain the small particle
size. Useful Jamaican micritic calcium carbonates are obtained
directly by grinding without using a chemical precipitation
processing commonly used in the U.S. with U.S. limestone and marble
deposits. U.S. deposits also typically contain perceptible levels
of iron which can promote discoloration and degradation of PVCs. In
contrast, Caribbean and Jamaican micritic calcium carbonates are
free of measureable amounts of iron. Preferred Jamaican calcium
carbonate particles are approximately six microns or less in
particle size. At about six microns or below, the ground calcium
carbonate particles are hydrophobic and become more effective with
decreasing particle sizes. Most preferred particles sizes are about
predominately about 3 microns or below for protecting rigid PVCs in
accordance with this invention, while particles less than about 1.5
microns are best. Purity of the ground particles on a weight basis
ordinarily is above about 99%, typically above about 99.3% pure
calcium carbonate, essentially free of iron (that is less than
about 0.5% or less than about 0.2%, or nil), and with minimal
impurities of less than about 1.0% or about 0.4% magnesium
carbonate, less than about 0.1% crystalline silicates, and less
than about 0.3%, acid insolubles, if any. Preferred useful
commercial Jamaican calcium carbonates are Optifil and Optifil T
calcium carbonates supplied by J. B. Huber Co. and described as 99%
pure, virtually free of crystalline silica and other impurities
such as magnesium carbonate and silicates, and free of other metals
such as iron. Optfil T is preferred and is surface treated with
stearate. Published physical properties of Optifil and Optifil T
calcium carbonates from Jamaica are as follows.
1 Grind (Hegman) 6 microns Oil absorption 1.7 lbs/100 lbs (Optifil)
1.6 lbs/100 lbs (Optifil T) Moisture 0.2% Specific surface area
3.45 m.sup.2/gm Calcium carbonate 99% Magnesium carbonate 0.4%
Crystalline silica 0.1% maximum Silicates 0.2% maximum
[0014] In accordance with this invention, at least about 2 weights
parts of Caribbean calcium carbonate, advantageously between about
2 and about 50 weight parts, and preferably between about 5 and
about 15 weight parts are compounded with 100 weight parts of rigid
PVC resin to obtain desired effective results of using Caribbean
calcium carbonate in this invention. Higher levels and smaller
particles of Caribbean calcium carbonate provide increased
effectiveness as an HCl scavenger.
[0015] In a preferred aspect of this invention, Caribbean calcium
carbonate is utilized in conjunction with an organotin heat
stabilizer to further enhance the effective resistance to HCl acid
generation in PVCs. Useful organotin stabilizers are mono-, di-, or
tri-substituted alkyl or alkyl esters of tin known as alkyltins,
where the remaining valences of the alkyltins are activated mono-,
di-, or tri-substituted active mercapto groups (mercaptoacids and
their esters, or mercaptides), or active carboxylic acids and their
esters known as carboxylates (e.g. maleic or lauric acids, or
maleic esters or half esters) such as dibutyl tin carboxylates.
Active mercapto tin compounds ordinarily are referred to as
thiotins, while active carboxylic acid or esters of tin are known
as carboxylates. Organotins are excellent heat stabilizers and
considerably enhance the short and long term stability of PVCs
containing Caribbean calcium carbonate in accordance with this
invention. The effectiveness of the organotins is primarily
influenced by the non-alkyl activated mono-, di-, or
tri-substituted mercapto groups or carboxylate groups, where
thiotins and especially dialkythiotins are preferred. Preferred
alkyltin stabilizers contain reactive mercapto ligands
substitutions in thioglycolates (mercaptide) and/or reverse
mercaptide esters. Preferred stabilizers are metallic tin salts of
organic acid comprising tin dialkyl ester mercaptides. Useful
organotin mercaptide ester stabilizers comprise alkyl tins
including methyl tins, butyl tins, reverse ester tins, octyl tins,
and tin corboxylates, where dibutyl tin mercaptides are preferred,
and the most preferred is dibutyl tin ethyl hexyl mercaptoacetate.
A commercially preferred organotin stabilizer is Thermolite T-31
sold by Atochem and described as dibutyl tin ethyl hexyl
mercaptoacetate. The organotin stabilizers effectively prevent or
counteract HCl generated in PVCs by heat and sunlight exposure and
avoid degradation of PVC polymers. Organotin stabilizers are
believed to deactivate labile chlorine atoms in the PVC chain by
replacement by the ligand groups of the stabilizer, and/or bind HCl
evolved in incipient degradation, and/or reaction with double bonds
of polyene sequences, and/or scavenging of free radicals, and/or
decomposition of peroxide groups forming due to PVC decomposition.
At least about 0.5 weight part, desirably from about 0.5 to about 3
weight parts, and preferably from about 1 to about 1.5 or about 2
weight parts of organotin stabilizer are used with 100 weight parts
PVC resin.
[0016] In a preferred aspect of this invention, Caribbean micritic
calcium carbonate is utilized in conjunction with an organotin
stabilizer and optionally in combination with limited amounts of a
dialkyl ester scavenger. Useful organic scavengers comprise dialkyl
organic esters of zinc comprising zinc metal reacted with a lower
aliphatic alkyl mono-caroxylic acid having from about 4 to about 12
carbon atoms, preferably a lower fatty acid having from about 6 to
about 10 carbon atoms, where about 7 to about 9 carbon atoms are
most preferred. Useful preferred alkyl ester groups include hexyl,
septyl, octyl, nonyl, and decyl esters, where the dialkyl ester
groups can be the same or different alkyl chains. The most
preferred alkyl is octyl and zinc octoate is the most preferred
commercial zinc octoate is L 230 sold by Baerlocher U.S.A. located
in Dover, Ohio. Zinc alkyl esters interact with the organotin
compound to prevent PVC degradation but surprisingly do not form
zinc chloride, a known PVC destabilizer, provided the equivalents
of zinc do not exceed the active equivalents of non-alkyl mercapto
or carboxylate components in the organotin stabilizer. The limited
levels of zinc dialkyl ester combined with excess organotin
considerably increase the effectiveness of the Caribbean micritic
calcium carbonate and provides considerable weather and degradation
resistance in accordance with this invention. The zinc dialkyl
ester scavenger is limited relative to the amount of organotin in
that the non-alkyl active ligand comprising mercapto or carboxylate
groups exceed the equivalent alkyl content in the zinc dialkyl
ester. A deficiency of mercapto or carboxylate equivalent relative
to excess zinc has been found to generate free zinc and will cause
detrimental zinc deterioration of PVC and formation of undesirable
zinc chloride. Conversely, excess equivalents of mercapto or
carboxylate groups available to complex with lesser equivalents of
zinc avoids free zinc and avoids zinc deterioration of PVC. With
higher substituted organotins, such as tri-functional mecapto
groups, the ratio of tin to zinc can be as low as 0.75 to about 1,
while di-functional substituted active groups, such as di-mercapto
groups, the equivalent tin to zinc ratio is from about 10 to about
5.0, where the preferred ratio is from about 1.5 to 3. Similarly,
mono-substituted mercapto organotins will be higher to provide
sufficient mercapto groups to complex with less zinc dialkyl ester.
Excess organotin equivalents relative to deficient zinc ester
equivalents have been found to increase the overall efficiency for
precluding and avoiding PVC degradation. On a weight basis, PVC
resin is compounded with zinc dialkyl ester at a level above about
0.1 weight part, usefully from about 0.1 to about 3 weight parts or
more depending on the active non-alkyl active ligand group in the
organotin, preferably from about 0.1 to about 2 weight parts, where
the most preferred levels are from about 0.5 to about 1 weight
parts, based on 100 weight parts of PVC resin.
[0017] Other supplementary additional stabilizers can be added if
desired. Lead salt stabilizers are useful and further enhance
weather resistance where lead reacts with and neutralizes nascent
HCl generated to form an inert lead chloride which remains stable
and non-autocatalytic. Lead chloride does not promote degradation
of rigid PVC polymers, although performance of lead stabilizers may
be diminished in the presence of other co-stabilizers other than
cadmium/barium stabilizers. Other useful stabilizers include
alkaline materials such as barium oxide or sodium silicate for
providing weather resistance. Useful heat stabilizers include
alkaline hydroxides, hydroxide carbonates, amines, sodium silicate,
and barium cadmium soaps. To obtain maximum effectiveness, a
mixture of stabilizers can be used where one stabilizer may be
effective against heat while another may be effective against
sunlight. The foregoing stabilizers can be used in conjunction with
the organotin stabilizer, if desired. Another useful stabilizer is
a calcium zinc compound where calcium forms harmless calcium
chloride and avoid formation of detrimental zinc chloride.
[0018] In a less preferred aspect of this invention, some European
(including England) calcium carbonates comprise naturally occurring
chalk ore deposits useful in this invention in conjunction with an
organotin stabilizer and limited amounts of zinc alkyl ester
scavenger to provide enhanced resistance to heat, sunlight and
weathering degradation of rigid PVCs. Chalk is a soft amorphous
calcium carbonate formed by fossil shells known as coccolith
shells. Chalk calcium carbonates differ in origin from limestone
and marble found in North America in that chalk origin comprises
shells of coccolith organisms. In this aspect of the invention,
European naturally occurring chalk calcium carbonates can be milled
to micron size particles less than about 10 microns, preferably
less than about 5 microns, and most preferably from about 1 to 3
about microns, or less, which exhibit improved heat and weather
resistance to PVC degradation in conjunction with the combination
of organotin stabilizer and limited amounts of zinc alkyl ester
scavenger. Useful European chalk calcium carbonates are
non-precipitated friable chalk deposits inasmuch as chemically
processed precipitated European calcium carbonates are ineffective
and do not impart any reduction in heat or weathering degradation
in rigid PVCs. Unlike Caribbean micritic calcium carbonate,
European non-precipitated chalk calcium carbonate alone does not
provide significant resistance to PVC degradation. Accordingly, in
this aspect of the invention, non-precipitated chalky European
calcium carbonate particles in conjunction with the combination of
organotin stabilizer and limited levels of zinc alkyl ester
scavenger considerably improves resistance to HCl generation and
further enhances HCl scavenger characteristics. The levels of
European calcium carbonate useful in PVC resin compounding are
comparable to Caribbean micritic calcium carbonate as well as
useful levels of organotins and zinc alkyl esters previously
described, provided the reactive equivalents of zinc are less than
the non-alkyl activated ligand equivalents on the organotin to
assure a deficiency of zinc relative to excess equivalents of
active ligands to complex with deficient zinc.
[0019] Rigid PVCs utilized in this invention comprise PVC being
essentially a homopolymer with minimal amounts of less than about
5% by weight copolymerized other vinyl comonomer, but preferably
little or no copolymerized other vinyl monomer. Commercial PVC
ordinarily comprises about 56% by weight chlorine. Poly (vinyl
chloride) comprises polymerized vinyl chloride monomer where
preferred PVC polymers are essentially homopolymerized vinyl
chloride with little or no copolymerized other vinyl co-monomers.
Preferred PVCs are essentially homopolymers of polymerized vinyl
chloride. Useful vinyl co-monomers if desired include vinyl
acetate, vinyl alcohol, vinyl acetals, vinyl ethers, and vinylidene
chloride. Other useful co-monomers comprise mono-ethylenically
unsaturated monomers and include acrylics such as lower alkyl
acrylates or methacrylates, acrylic and methacrylic acids, lower
alkyl olefins, vinyl aromatics such as styrene and styrene
derivatives, and vinyl esters. Useful commercial co-monomers
include acrylonitrile, 2-hexyl acrylate, and vinylidene chloride.
Although co-monomers are not preferred, useful PVC copolymers can
contain about 0.1% to about 5% by weight copolymerized co-monomer,
if desired.
[0020] Preferred PVCs are suspension polymerized vinyl chloride
monomer, although mass (bulk) polymerized polymers can be useful,
but are less preferred. Rigid PVCs contain little or no
plasticizer, and, if present, ordinarily no more than about 5
weight parts placticizer per 100 weight parts of PVCs. The PVCs of
this invention have an inherent viscosity from about 0.45 to about
1.5, preferably from about 0.5 to about 1.2, as measured by ASTM D
1243 using 0.2 grams of resin in a 100 ml of cyclohexanone at 30
degrees C.
[0021] In compounding the rigid PVCs, other compounding components
are desirably incorporated into the PVC resins to form compounded
PVCs useful for forming extrusion or molded components used in
exterior environments. In addition to heat stabilizers, other
compounding ingredients can include fillers, pigments and
colorants, processing lubricants, impact modifiers, other
processing aids, as well as other additives if desired, such as
biocides and flame retardants. Fillers ordinarily are used to
reduce cost and gloss and can include conventional calcium
carbonates derived from limestone or marble but ordinarily will not
be used in this invention with the Caribbean micritic calcium
carbonate. Other fillers include clay, talc, mica, and diatomaceous
earth fillers. Useful pigments and colorants can be organic, but
preferably inorganic mineral, such as titanium dioxide for opacity
and UV absorption. Processing lubricants can be external lubricants
to reduce sticking to hot processing metal surfaces and can include
low molecular weight polyethylene, paraffin oils, and paraffin
waxes. Internal lubricants increase flow of resin particles within
the resin melt and can include metal stearates such as stearic
acid. Impact modifiers are useful in rigid PVCs to increase
toughness and can include chlorinated polyethylenes, ABS
polybutadiene, acrylic or methacylic polymers or copolymers, or
butadiene-styrene (MBS). Other processing aids for extruding rigid
PVCs in complex profiles include acrylic or styrene-acrylonitrile
copolymers to prevent edge tear in the extrusion of complex
profiles.
[0022] In compounding the rigid PVCs, the PVC resin is mixed with
the various other compounding ingredients in low shear mixers such
as a paddle or ribbon blender, although high shear mixers
ordinarily are preferred. Useful mixers include a Ross Planetary
mixer, a Henshel mixer, Hobart mixers, Banbury mixer, and a Henshel
mixer and ribbon blender. In high speed mixing, heat is typically
generated while mixing. The compounded PVCs are then cooled to
avoid thermal degradation and thereafter can be stored for later
use. Compounded rigid PVCs typically are extruded to form pellets
or other solid particles useful in molding or extruding operations
to produce rigid plastic components, such as sheets for roofing and
wall panels, cladding, house siding, window frames, linear trim and
similar exterior uses. Similarly, rigid PVC can be extruded or
molded as cap stock fused or otherwise adhered to substrate
plastics other than rigid PVC. Co-extruded or laminated cap stock
can be prepared as shown in U.S. Pat. No. 4,100,325 to form a
composite layer or laminated plastic article. Co-extrusion
comprises extrusion of two or more polymeric layers simultaneously
brought together into contact at a point prior to extrusion through
a shape forming co-extrusion die such as shown in U.S. Pat. No.
3,476,627.
[0023] An important accelerated test for measuring resistance to
heat, sunlight, and UV radiation, and particularly measuring color
changes due to the accelerated exposures, is the QUV weather tester
manufactured by Q-Panel Company, which uses UV-B lamps with an
energy peak at 313 mm. The QUV accelerated weathering cycle is
about 20 hours of light exposure at 50 degrees C., followed by
about 4 hours darkness with condensation at 40 degrees C. Color
changes are measured by delta E calculated by the
Friele-McAdams-Chickering equations as found in Journal of the
Optical Society of America, 58, 290 (1960) authored by G.
Wyszeck.
[0024] The merits of the invention are further illustrated and
exemplified by the following examples.
EXAMPLES 1 TO 14
[0025] The following raw materials were compounded into rigid PVC
resin to form experimental compositions Examples 1-14 at a constant
weight parts level indicated as follows.
2 WEIGHT COMPONENT MATERIAL DESCRIPTION PARTS a. SE 950 EG PVC of
0.9 inherent viscosity 100 b. T-31 (S008) Dibutyl tin ethyl hexyl
mercaptoacetate 1 c. Baerostab L230 Zinc octoate 0.5 d. Calcium
stearate Calcium stearate 1.25 e. Loxiol G33 Mixture ester fatty
acids/alcohols 0.25 f. Paraffin 165F Paraffin wax 0.65 g. EBS wax
powder Ethylene bis-steramide 0.5 h. Paraloid K120N Methacrylate
processing aid 1 i. Kronos 2160 TiO.sub.2 durable grade 10 j.
Paraloid K175 Acrylic lubricant processing aid 1 k. Filler
CaCO.sub.3 indicated in Table Variable
[0026] Using the above components as a basic mixture for all
experimental samples compounded, variable filler additives
indicated in the table below were added to form individual
compositions for Examples 1 to 14 inclusive below.
[0027] Filler Information
3 C. E. B. Optifil Camel F. Brand A. Optifil JS D. Cal Polar Name
Optifil T 100T (W1T) Omyalite ST 8101C Ore Type Chalk Chalk Chalk
Chalk Lime- Chalk stone Country Jamaica Jamaica Jamaica France USA
Jamaica Origin Mfg. Dry Dry Wet Wet Wet Precipit. Process Dry Y 93
93.9 96 brightness Mean 1.5 1.3 1.2 0.7 particle size (microns) %
less 50% than 2 microns % less 19% than 1 micron Coating 1% 1% 1%
1% Level Coating Stearic Stearic Stearic Stearic Type % CaCO.sub.3
99% 99.2% 99.3% 90% % MgCO.sub.3 0.4% 0.3% 0.3% % SiO.sub.2 0.1%
0.02% 0.02% 0.15%
[0028] Compounding compositions 1 to 14
4 EX1 EX2 EX3 EX4 EX5 EX6 EX7 EX8 EX9 EX10 EX11 EX12 EX13 EX14 A 12
6 B 12 6 C 12 6 D 12 6 E 12 6 5 F (8102c) 12 F (8103C) 12 F (8101C)
12 6
[0029] Test panels of about 0.070 inch thickness by 3.5 inch wide
were extruded for QUV accelerated testing purposes and exposed to
QUV testing as follows.
[0030] QUV Weathering
[0031] QUV accelerated testing was under UVA 340 lamp, 50 degrees
C., with 4 hours condensation. Measurements are in Hunter Delta
B.
5 EX1 EX2 EX3 EX4 EX5 EX6 EX7 EX8 EX9 EX10 EX11 EX12 EX13 EX14 350
HRS -0.32 0.08 0.02 -0.06 -0.43 -0.42 -0.61 -0.34 -0.17 -0.13 -0.15
-0.12 0.53 0.33 700 HRS -0.19 0.32 0.47 0.23 -0.34 -0.19 -0.56
-0.03 0.37 0.6 0.96 1.35 1,050 HRS 0.5 1.18 1.29 1.82 0.74 1 -0.38
0.24 1.09 1.17 2.16 2.6 1,500 HRS 2.05 2.72 3.98 3.37 0.83 2.01
0.07 0.66 1.63 2.18 1.65 2.24 2000 HRS 2.57 3.18 2.04 3.02 2.29
2.65 1.26 2.57 1.01 1.75
[0032] While in accordance with the Patent Statutes the best mode
and preferred embodiments have been set forth, the scope of the
invention is not intended to be limited thereto, but rather only by
the scope of the attached claims
* * * * *