WO2018039172A1

WO2018039172A1 - Heat stabilizer for halogen-containing polymers

Info

Publication number: WO2018039172A1
Application number: PCT/US2017/047917
Authority: WO
Inventors: Peter Frenkel; Andrew Joseph CLOCK
Original assignee: Galata Chemicals Llc
Priority date: 2016-08-26
Filing date: 2017-08-22
Publication date: 2018-03-01

Abstract

The present invention relates to solid free-flowing catalysts or heat stabilizer compositions of high efficiency for halogen-containing polymers; the stabilizers comprise liquid stabilizers selected from liquid alkyltin compounds, liquid phosphite ester compounds or mixtures thereof on metal silicates.

Description

HEAT STABILIZER FOR HALOGEN-CONTAINING POLYMERS

FIELD OF THE INVENTION

[0001] The present invention relates to heat stabilizer compositions. More particularly, the present invention relates to solid, free-flowing heat stabilizer compositions for halogen-containing polymers having liquid stabilizer components concentrated on metal silicates.

BACKGROUND AND PRIOR ART

[0002] Halogen-containing polymers, such as polyvinylchloride (PVC), are some of the most widely used plastics in the world. PVC in particular is widely used in such applications as pipes and pipe fittings, film and sheet, flooring, cables and construction profiles. However, PVC can decompose during processing, upon heating or on prolonged exposure to sunlight due to loss of HCl from the polymer, resulting in discoloration and embrittlement. A variety of liquid and solid stabilizers are known to be effective in preventing discoloration of halogen-containing polymers at elevated temperatures, for example, "PVC Degradation and Stabilization," Wypich, George, ChemTec, Toronto 2008; "Handbook of Vinyl Formulating", 2^nd edition, Grossman, Richard F., Wiley & Sons, 2008; and "PVC Handbook", Wilkes, Charles E., et al, Hanser, Cincinnati 2005.

[0003] Typical liquid heat stabilizers/co-stabilizers include alkyltin compounds (alkyltin mercaptides, alkyltin carboxylates, alkyltin sulfides and their mixtures) and phosphite esters. A number of these are very effective in stabilizing the chlorine-containing polymers. However, their use may have several undesirable consequences. First, they can result in accidental splashing or spills during transportation and use. They can also require collection and processing of their returnable packaging containers. Precipitation can occur in the liquid stabilizers, resulting in a shorter product shelf-life and negative effects on the physical properties of stabilized polymeric compounds, such as Heat Deflection Temperature (HDT) and melt strength, or reduced compatibility with the polymer and increases potential for plate-out.

[0004] Advantages of solid stabilizers include safer and easier handling, since they eliminate any potential for splash or spills during transportation and use. There is also no need to return specially designed packaging containers. Further, solid stabilizers eliminate concern regarding product precipitation over time, as discussed above. This improves compatibility with the polymers, reducing the potential for plate-out, and may enable a reduction in the lubricant level typically used in combinations with liquid heat stabilizers.

[0005] The most conventional approach for the preparation of solid heat stabilizers for chlorine- containing polymers includes precipitation and/or crystallization of compounds that have a melting point greater than 25°C. However, work has been ongoing to develop improved stabilizers.

[0006] U.S. Patent 4,358,555 discloses a stabilizer composition comprising three components: a) at least one alkyltin mercaptide, b) at least one zinc mercaptoester, and c) at least one alkali or alkaline-earth metal compound; sodium silicate was specifically mentioned as an example. All the components of these stabilizers were added directly to PVC dry blends, as opposed to being pre-blended together prior to addition to the compound. Optional components included fillers, pigments, plasticizers, dyes, lubricants, antioxidants, and UV-absorbers.

[0007] PCT Patent Application WO 2010/131782 discloses a method for heat-stabilizing chlorine- containing resin compositions by adding: (a) 0.004 to 10 parts by weight of a perchlorate solution containing 1 to 60 % by weight of perchlorate, 5 to 50 % by weight of water-soluble organic solvent and 20 to 94 % by weight of water, and (b) 0.001 to 10 parts by weight of at least one silicate compound represented by the general formula (I) to 100 parts by weight of a chlorine- containing resin: M(0)a nSi02mH₂0 (I) in which M is at least one metal selected from alkaline earth metals and aluminum, a is 1 when M is an alkaline earth metal and 3/2 where M is aluminum, n is from 1 to 5, and m is any positive integer.

[0008] U.S. Patent 5,225,108 discloses a stabilizer composition comprising sodium perchlorate and calcium silicate, where aqueous solutions of sodium perchlorate were combined with calcium silicate.

[0009] Nevertheless, a need exists for improved solid heat stabilizers. In particular, there is an ongoing need for highly effective free-flowing solid stabilizers that avoid the challenges presented by liquid stabilizers.

SUMMARY OF THE INVENTION

[0010] The subject matter of the present disclosure relates to heat stabilizer compositions for halogen-containing polymers, such as PVC and CPVC. In one embodiment, the present disclosure provides a heat stabilizer composition comprising a metal silicate containing a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester or mixtures thereof, the heat stabilizer composition being a free-flowing solid.

[0011] In an alternate embodiment, the present disclosure provides a process comprising applying a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester or mixtures thereof to the surface of a solid metal silicate, thereby forming a heat stabilizer composition, wherein the heat stabilizer composition is a free-flowing solid.

[0012] In another alternate embodiment, the present disclosure provides a stabilized polymer composition comprising a halogen-containing polymer and a heat stabilizer composition comprising a metal silicate containing a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester or mixtures thereof, the heat stabilizer composition being a free-flowing solid.

[0013] In still another embodiment, the present disclosure provides a process for preparing a stabilized polymer composition comprising blending and compounding a halogen-containing polymer and a heat stabilizer composition comprising a metal silicate containing a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester or mixtures thereof, the heat stabilizer composition being a free-flowing solid.

[0014] In another embodiment, the present disclosure provides a heat stabilizer composition produced by a process comprising applying a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester or mixtures thereof to the surface of a metal silicate, wherein the heat stabilizer composition is a free-flowing solid.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The inventive heat stabilizer composition for halogen-containing polymers of the current subject matter is a highly effective, free-flowing solid powder, where liquid alkyltin stabilizer compounds and/or liquid phosphite ester co- stabilizers are absorbed onto solid metal silicates prior to contact of the stabilizer composition with the polymers. Therefore, in one embodiment, the present disclosure provides a heat stabilizer composition comprising a metal silicate containing a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester, or mixtures thereof, the heat stabilizer composition being a free-flowing solid. For the purposes of this specification, the term "heat stabilizer composition" refers to a metal silicate that contains a liquid stabilizer that has been absorbed into the solid metal silicate. In this way, when the heat stabilizer composition is added to a halogen-containing polymer, the metal silicate and liquid stabilizer are added simultaneously as one solid material.

Liquid Alkyltin Compounds

[0016] When the heat stabilizer composition of the current subject matter contains a liquid alkyltin compound, the liquid alkyltin compound is selected from alkyltin mercaptides, alkyltin carboxylates, alkyltin sulfides or mixtures thereof. Alkyltin mercaptides may include alkyltin mercaptocarboxylic acid esters and alkyltin 2-mercaptoethylcarboxylates.

[0017] Preferred examples of liquid alkyltin mercaptocarboxylic acid ester components include: mono-alkyltin tris(2-ethylhexyl mercaptoacetate), di-alkyltin bis(2-ethylhexyl mercaptoacetate), dialkyltin bis(ethylene glycol di-mercaptoacetate) and mixtures thereof, where the alkyl group is selected from C1-C12 linear, branched or cyclic hydrocarbons. Preferably, the alkyl groups are selected from methyl, n-butyl or n-octyl. The weight ratio of the mono- to dialkyltin mercaptides ranges from 1/99 to 99/1, preferably from 5/95 to 95/5 and more preferably from 20/80 to 50/50.

[0018] The alkyl groups in the liquid alkyltin 2-mercaptoethylcarboxylates are selected from Ci- C12 linear, branched or cyclic hydrocarbons. Preferably, the alkyl groups are methyl, n-butyl or n- octyl. Preferred examples of liquid alkyltin 2-mercaptoethylcarboxylate components include dimethyltin bis(2-mercaptoethyltallate) and mono-methyltin tris(2-mercaptoethyltallate).

[0019] Preferably, the liquid alkyltin carboxylates are dialkyltin bis(carboxylate) components that are selected from dialkyltin bis (ethylmaleate), dialkyltin bis (laurate), dialkyltin bis (neodecanoate), dialkyltin bis(2-ethylhexanoate), dialkyltin bis (oleate), dialkyltin bis (2- ethylhexanoate) or mixtures thereof, where the alkyl group is selected from C1-C12 linear, branched or cyclic hydrocarbons. Preferably the alkyl groups are methyl, n-butyl or n-octyl. The dialkyltin bis(carboxylates) may contain mono-alkyltin tris(carboxylates).

[0020] When alkyltin sulfides are the liquid alkyltin stabilizers, the alkyl groups are selected from C1-C12 linear, branched or cyclic hydrocarbons. Preferably, the alkyl groups are methyl, n-butyl or n-octyl. Preferably, the alkyltin sulfide is dibutytin sulfide.

[0021] Suitable alkyltin mercaptides and alkyltin sulfides are also disclosed in U.S. Patent 4,255,320.

[0022] The alkyltin compounds can be present in compositions containing the heat stabilizer composition and halogen-containing polymers in an amount of from 0.01 to 10, preferably from 0.05 to 5, and more preferably from 0.1 to 3 parts by weight per 100 parts by weight of halogen- containing polymers.

Liquid Phosphite Ester Stabilizers

[0023] When liquid phosphite ester stabilizers are present in the heat stabilizer composition, they are selected from thiophosphites and thiophosphates, triaryl phosphites such as triphenyl phosphite, tris(amylphenyl) phosphite and tris(nonylphenyl) phosphite, diphenyl alkyl phosphites, such as diphenyl isodecyl phosphite, diphenyl tridecyl phosphite and 2-ethylhexyl diphenyl phosphite, diphenyl phosphite, phenyl dialkyl phosphites, such as phenyl diisodecyl phosphite, and tris(alkyl) phosphites, such as trilauryl phosphite, tri-isodecyl phosphite, tri-isotridecyl phosphite and tris(2-ethylhexyl) phosphite, poly (dipropylene glycol) phenyl phosphite, tetraphenyl dipropyleneglycol diphosphite, phenyl neopentylene glycol phosphite, tris (dipropyleneglycol) phosphite, poly 4,4' isopropylidenediphenol-Cio alcohol phosphite and poly 4,4' isopropylidenediphenol-C 12-15 alcohol phosphite.

[0024] The phosphites can be present in the compositions containing the heat stabilizer compositions and the halogen-containing polymers in an amount of from 0.01 to 10, preferably from 0.05 to 5, and more preferably from 0.1 to 3 parts by weight per 100 parts by weight of halogen-containing polymers.

Metal Silicates

[0025] The heat stabilizer composition of the present subject matter also includes metal silicates. Metals in the metal silicates are alkaline-earth metals (such as Mg, Ca, or Ba) or aluminum. Preferably, the metal silicate is calcium silicate. A suitable calcium silicate material may contain up to 15% moisture, surface area of >100 m²/g, bulk density of 6-10 lb/ft³ and an average particle size of 4-8 microns (measured via Horiba LA 300 laser diffraction method).

Production of free-flowing stabilizers

[0026] In an alternate embodiment, the present disclosure provides a process comprising applying a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester or mixtures thereof to the surface of a solid metal silicate, thereby forming a heat stabilizer composition, wherein the heat stabilizer composition is a free-flowing solid.

[0027] For the preparation of the free-flowing solid stabilizer compositions, liquid stabilizers are either sprayed-on or mixed with a metal silicate, so that the liquid stabilizer is absorbed by the metal silicate. When liquid stabilizers are mixed with the metal silicate, conventional mixing equipment can be used. When they are sprayed onto the metal silicate, conventional spray equipment can be used. The weight ratio of the total amount of the liquid stabilizer components to the amount of the silicate (liquid/silicate, wt/wt) ranges from 1/99 to 80/20, more preferably from 20/80 to 75/25 and more preferably from to 50/50 to 70/30. After the liquid stabilizers are absorbed into the pores of the metal silicate, the resultant impregnated material is a free-flowing solid, with no free liquid present. For the purposes of this specification, the term "free-flowing" means that a bulk solid flows easily, i.e., it does not agglomerate significantly and flows out of a container due to the force of gravity alone in a continuous, steady stream, and no flow promoting devices are required.

[0028] Preferably, the amount of liquid stabilizer applied to the metal silicate is less than the silicate point of incipient wetness, where for purpose of this specification, the term "incipient wetness point" or "point of incipient wetness" means the point at which liquid has just completely occupied the available pore volume of the silicate. If desired, the silicates can be either partially or completely dehydrated at about 150°C prior to absorbing the liquid stabilizers. Preferably, the dehydration is carried out at a temperature of from 110 to 170 °C. Dehydration of the metal silicate may enhance the effectiveness of the heat stabilizer by about 10%. The free-flowing heat stabilizer compositions that are formed enable the delivery of stabilizer compositions comprising a liquid alkyltin stabilizer and/or a liquid phosphite ester stabilizer and a metal silicate, all together simultaneously in the same solid particle.

Additives

[0029] The stabilizer compositions described above can also contain co- stabilizers such as metal soaps, metal perchlorates, beta-diketones and other additives, provided that the additives do not materially degrade the thermal stability imparted by the stabilizer compositions described herein. Such additives include, without limitation, light stabilizers, antioxidants, lubricants, fillers, fusion promoters, plasticizers, pigments, flame retardants, smoke suppressants, UV absorbers, chemical foaming agents, impact modifiers, antistatic agents, reinforcing agents, metal release agents, dispersants, whitening agents, gelling assistants and processing aids. These additives may be added to the resin using techniques and equipment well known to those of ordinary skill in the art.

[0030] Suitable lubricants include calcium stearate, montan wax, fatty acid esters, polyethylene waxes, chlorinated hydrocarbons, glycerol esters and combinations thereof. The lubricants are added in the amounts from 0.1 to 3 phr based on the weight of the halogen-containing polymer. Suitable fillers include titanium dioxide, calcium carbonate, kaolin, glass beads, glass fibers, talc, wood floor and mixtures thereof.

[0031] When present, the fillers are present in an amount from 0.1 to 50 parts by weight per 100 parts of the halogen-containing polymers.

Stabilized Polymer Compositions

[0032] In another alternate embodiment, the present disclosure provides a stabilized polymer composition comprising a halogen-containing polymer and a heat stabilizer composition comprising a metal silicate containing a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester or mixtures thereof, the heat stabilizer composition being a free-flowing solid. In still another embodiment, the present disclosure provides a process for preparing a stabilized polymer composition comprising blending a halogen-containing polymer and a heat stabilizer composition comprising a metal silicate containing a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester, or mixtures thereof, the heat stabilizer composition being a free-flowing solid.

[0033] The halogen-containing polymer, heat stabilizer, and other additives present can be blended via compounding by well-known processes such as extrusion, calendaring, molding and combinations thereof. Compounding of the halogen-containing polymer and the stabilizer composition can also include first blending the components followed by compounding.

Halogen-Containing Polymers

[0034] The halogen-containing polymers include homopolymers and copolymers of vinyl halogens, post-halogenated polymers and co-polymers of vinyl halogens, and halogenated polymers of olefins, such as ethylene, propylene, and 1-butene. The halogen of such polymers can be fluorine, chlorine, bromine, iodine, or mixtures thereof.

[0035] Preferably, the halogen-containing polymer is selected from polyvinyl chloride, polyvinylidene chloride, chlorinated polyvinyl chloride ("CPVC") or mixtures thereof. More preferably, the halogen-containing polymer is polyvinyl chloride. The PVC can be obtained via polymerization in bulk or in suspension, in emulsion, in micro suspension, or in suspended emulsion.

[0036] As employed herein, the term PVC is intended to include both homopolymers and copolymers of vinyl chloride, i.e., vinyl resins containing vinyl chloride units in their structure, e.g., copolymers of vinyl chloride and vinyl esters of aliphatic acids, in particular vinyl acetate; copolymers of vinyl chloride with esters of acrylic and methacrylic acid and with acrylonitrile; copolymers of vinyl chloride with diene compounds and unsaturated dicarboxylic acids or anhydrides thereof, such as copolymers of vinyl chloride with diethyl maleate, diethyl fumarate or maleic anhydride; post-chlorinated polymers and copolymers of vinyl chloride; copolymers of vinyl chloride and vinylidene chloride with unsaturated aldehydes, ketones and others, such as acrolein, crotonaldehyde, vinyl methyl ketone, vinyl methyl ether, vinyl isobutyl ether, and the like.

[0037] The term PVC as employed herein is also intended to include graft polymers of PVC with ethyl-vinyl acetate ("EVA"), acrylonitrile/butadiene-styrene ("ABS"), and meth-acrylate- butadiene ("MBS"). Preferred substrates are also mixtures of the above-mentioned homopolymers and copolymers, preferably vinyl chloride homopolymers, with other thermoplastic and/or elastomeric polymers, more preferably blends with ABS, MBS, acrylonitrile butadiene ("NBR"), styrene-acrylonitrile ("SAN"), EVA, chlorinated polyethylene ("CPE"), poly(methyl methylacrylate), ethylene propylene diene monomer ("EPDM"), and polylactones. Preferably, vinyl acetate, vinylidene dichloride, acrylonitrile, chlorofluoroethylene and/or the esters of acrylic, fumaric, maleic and/or itaconic acids are monomers that are copolymerizable with vinyl chloride.

[0038] The content of the subject heat stabilizer composition within the stabilized polymer composition is typically between 0.01 parts and 10 parts by weight, preferably between about 0.1 and 7.0, and more preferably between 0.25 and 5.0 parts by weight for 100 parts by weight of the halogen-containing polymer.

[0039] EXAMPLES

The following examples further detail and explain preparation of the inventive heat stabilizers, and demonstrate their efficacy for preventing discoloration (caused by high shear and exposure to heat) of halogen-containing polymers, such as PVC and CPVC, and for reducing odor during handling and processing due to lower volatility of the stabilizers. Those skilled in the art will recognize many variations that are within the spirit of the invention and scope of the claims.

Liquid Alkyltin compounds tested

[0040] High purity mono-n-octyltin tris(2-ethylhexylmercaptoacetate) available from Galata Chemicals as Mark 21 MOK-A. [0041] High purity di-n-butyltin bis(2-ethylhexylmercaptoacetate) available from Galata Chemicals as Mark 292.

[0042] A mixture of mono-n-octyltin tris(2-ethylhexylmercaptoacetate) and di-n-octyltin bis(2- ethylhexylmercaptoacetate) available from Galata Chemicals as Mark 17MOK.

[0043] A mixture of mono-methyltin tris(2-ethylhexylmercaptoacetate) and di-methyltin bis(2- ethylhexylmercaptoacetate) available from Galata Chemicals as Mark 1984E.

[0044] A mixture of mono-methyltin tris(2-mercaptoethyltallate) and dimethyltin bis(2- mercaptoethyltallate) available from Galata Chemicals as Mark 2909.

[0045] Dibutyltin bis-laurate available from Galata Chemicals as Fomrez SUL-4.

Liquid Phosphite Esters tested

[0046] 2-Ethylhexyl diphenyl phosphite available from Galata Chemicals as Markphos EHDP.

[0047] Diphenyl iso-decyl phosphite available from Galata Chemicals as Markphos DPDP.

[0048] Tri-iso-tridecyl phosphite available from Galata Chemicals as Markphos TTDP.

[0049] Tris(2-ethylhexyl) phosphate available from Galata Chemicals as D 16-051

Silicate tested

[0050] Calcium silicate marketed by J.M. Huber Corporation as Hubersorb^® 600 was used to prepare solid form concentrates of liquid stabilizers.

Preparation of alkyltin compounds in a solid form in accordance with present invention

[0051] Liquid alkyltin compound controls and free-flowing solid concentrates prepared in according with the invention from the controls and calcium silicate are shown in Table 1.

Table 1. Liquid Alkyltin Compound Controls and their Prepared Solid Concentrates

(as opposed to be pre -blended into the solid stabilizer) to the dry-blend prior to compounding it.

[0052] It is remarkable that in certain cases calcium silicate absorbed more than double the amount of alkyltin compounds in terms of weight/weight. For example, a free-flowing solid Sample A3 was prepared by mixing 30 g of calcium silicate and 70 g of Mark 1984E. So that lg of calcium silicate absorbed about 2.3 g of Mark 1984E. [0053] Free-flowing solid samples of Fomrez SUL-4 catalysts were also prepared.

Preparation of phosphite esters in a solid form in accordance with the present invention

[0054] Liquid phosphite ester controls and free-flowing solid concentrates prepared in accordance with the invention from the controls and calcium silicate are shown in Table 2.

Table 2. Liquid Phosphite ester Controls and their Prepared Solid Concentrates

*In the comparative Example F3, the Markphos EHDP and calcium silicate components were added separately (as opposed to be pre-blended into the solid stabilizer) to the dry-blend prior to compounding it.

PVC Compounding

[0055] The alkyltin stabilizers of the current subject matter were compounded with other components into rigid PVC or CPVC compounds (using the Brabender torque rheometer) that were tested for the dynamic heat stability.

[0056] The phosphite ester stabilizers of the current invention were compounded with other components into a flexible (plasticized) PVC compound (using a two-roll mill) that was tested for the static heat stability. Dynamic Heat Stability Test Method

[0057] Rigid PVC dry blend formulations were prepared using the stabilizer formulations of Table 1. The stabilizers were loaded at the same weight level of 1.5 parts of the alkyltin compound parts per hundred ("phr") of PVC. Each PVC compound test sample (prepared according to the formulation described in Table 3) was placed into a Brabender mixer operated at 190°C and 65 RPM. Sample chips were taken every three minutes. Fusion time was approximately the same for each test series.

Table 3. Tested rigid PVC compounds

Brabender Test Conditions: Temperature 190°C, 60 rpm, sample weight 65g, chips were taken every 3 minutes.

[0058] CPVC dry blend formulations were prepared using stabilizers B l and B2 of Table 1. The stabilizers were loaded at the same weight level of 1.5 parts of the alkyltin compound parts per hundred ("phr") of CPVC. Each CPVC compound test sample (prepared according to the formulation described in Table 4) was placed into a Brabender mixer operated at 190°C and 40 rpm. Sample chips were taken every 3 minutes.

Table 4. Tested CPVC Compounds

Brabender Test Conditions: Temperature 190°C, 40 rpm, sample weight 65g, chips are taken every 3 minutes. Static Heat Stability Test Method

[0059] Static heat stability of plasticized PVC compositions containing various stabilizers was determined by milling the compositions into sheets. The sheets were prepared under standardized conditions using a two-roll mill (Dr. Collin GmbH, Ebersberg, Germany). The gap between the rolls was about 0.5 mm, and the temperature of the rolls was 165°C. The time for preparation and homogenization was 5 minutes. Sheet thickness was 0.5 mm. The PVC sheet was continuously moved from the two sides to the center, and the enlargement thus obtained was distributed over the gap with a wooden spatula over the roll with intensive homogenization of all components.

[0060] To measure heat stability, 15 mm wide strips were cut from each milled sheet such that eight rectangular samples (15 mm x 10 mm) from each sheet were produced. The samples were placed in an oven (Blue M Company, New Columbia, PA, USA) operating at 177°C for thermal aging. The samples were removed from the oven at the rate of one sample every 15 minutes. Assessment of the thermal stability of the flexible PVC formulations was carried out by determining the discoloration due to the polymer degradation expressed in Yellowness Index (ASTM D 1925-70 Yellowness Index of plastics).

[0061] Milled sheets were prepared in accordance with formulations of Table 5, using stabilizers Example Fl, Example F2 and Example F3 as well as the Mark 6727 control, a solid calcium- zinc- containing stabilizer available from Galata Chemicals, LLC, (shown in Table 2) and its combination with Hubersorb 600.

Table 5. Tested plasticized PVC compounds

Measurement of Yellowness Index

[0062] Heat stability of PVC and CPVC compounds was determined using the microprocessor- controlled Hunterlab Labscan Spectra Colorimeter, Type 5100 measuring Yellowness Index (YI) of the sample chips (in accordance with (ASTM D 1925-70 Yellowness Index of plastics). Lower YI signifies lower discoloration as a result of thermal decomposition, and therefore, superior thermal stabilization more effective the stabilizer. The decomposition time measured in the dynamic heat stability test indicates time to the complete PVC degradation. The longer the decomposition time, the more thermally stable compound is.

[0063] Results of the dynamic heat stability for alkyltin-containing stabilizers are shown in Table 6-8, 10-12. Results of the static heat stability for phosphite ester-containing stabilizers are shown in Table 13.

Table 6. Dynamic heat stability (in Yellowness Index) of the Mark 1984E-stabilized PVC compounds

[0064] Example A2 solid of the current subject matter imparted dynamic heat stability that was comparable to that of the Example Al liquid control. Unexpectedly, the Example A3 solid imparted long-term heat stability (>21 min in the dynamic heat stability test) that was superior (lower YI) to that of the Example Al liquid control. Surprisingly, both Example A2 and Example A3 of the current subject matter were superior to that of the Example A4 control, where the liquid and the solid components were added separately into the dry blend.

[0065] Table 6 demonstrates that Yellowness Index data for Example A4 were inferior (higher) to both Example A2 and Example A3 throughout of the test. Unexpectedly, it has been found that calcium silicate when pre-mixed with Mark 1984E functions not just as a carrier but also as an effective co-stabilizer for the alkyltin stabilizer. The decomposition time results were consistent with the Yellowness Index data: longer for Example A3 than that for the Example Al liquid control and Example A4.

Table 7. Dynamic heat stability (in Yellowness Index) of the Mark 292- stabilized PVC compounds

[0066] A solid Example B2 of this invention imparted dynamic heat stability that was superior to that of the Example B l liquid control throughout the test. Unexpectedly, a solid Example B3 imparted long-term heat stability (>21 min in the dynamic heat stability test) that was superior (lower YI) to that of the Example B l liquid control. Both Example B2 and Example B3 demonstrated that calcium silicate pre-mixed with Mark 292 functions not just as a carrier but also as an effective co- stabilizer for the alkyltin stabilizer in PVC. The decomposition time results were consistent with the Yellowness Index data, showing longer times to the degradation for Example B2 and Example B3 compared with the Example B l liquid control. Table 8. Dynamic heat stability (in Yellowness Index) of the Mark 2909- stabilized PVC compounds

Odor scale: 1-faint, 2-slight, 3-mild, 4-strong, 5-very strong.

[0067] A solid Example C2 of the present subject matter imparted dynamic heat stability that was superior to that of the Example CI liquid control throughout most of the dynamic heat stability test. For Example C2, Yellowness Index results were considerably lower at 9-21 min. than that for Example C2. Additionally, Example C2 extended long-term heat stability beyond 21 min. of the Example CI liquid control up to 36 min. The decomposition time was also increased from 20:32 to 33:48, greater than a 50% extension. It was also noted that the solid Example C2 imparted lower odor intensity during the compounding step compared with that of the Example C 1 liquid control, where the same amount of the same alkyltin stabilizer was applied for stabilizing PVC. Example C2 demonstrated that calcium silicate pre-mixed with Mark 2909 functions not just as a carrier but also as an effective co- stabilizer for the alkyltin stabilizer. Table 9. Volatility* of Mark 2909-based Stabilizers

Volatility was measured as a per cent weight loss at 160°C over 10 min.

[0068] It was surprisingly found that volatility of the solid stabilizers Example C2 and C3 (2.1 and 2.5%, respectively) of this invention prepared by pre-blending of liquid alkyltin compounds, such as Mark 2909, with calcium silicate was lower than that of the individual components (12.3 and 2.6% for calcium silicate and Example CI liquid control, respectively) as it can be seen in Table 9.

Table 10. Dynamic heat stability (in Yellowness Index) of the Mark 17MOK- stabilized PVC compounds

[0069] The Example D2 solid of the present subject matter extended long-term heat stability of the Example Dl liquid control from 18 to 21 minutes, and increased the decomposition time imparted by the control from 17:52 to 22: 16. Example D2 demonstrated that calcium silicate pre- mixed with Mark 17MOK functions not just as a carrier but also as an effective co-stabilizer for the alkyltin stabilizer. Table 11. Dynamic heat stability (in Yellowness Index) of the Mark 21MOK-A-stabilized PVC compounds

[0070] Compared with the Example El liquid control, a solid Example E2 of the present subject matter imparted superior heat stability (lower YI) at > 6 min., extended long-term heat stability beyond 18 min of the liquid control to 21 min. and increased the decomposition time imparted by the control from 17:28 to 19:20. Therefore, it has been demonstrated that Example D2, a solid stabilizer of the present subject matter, where calcium silicate was pre-mixed with liquid Mark 21MOK-A, functions not just as a carrier but also as an effective co-stabilizer for the alkyltin stabilizer.

Table 12. Dynamic heat stability (in Yellowness Index) of the Mark 292-stabilized CPVC compounds

[0071] Compared with the Example B l-CPVC liquid control, the Example B2 solid prepared according to the present subject matter imparted superior heat stability (lower YI) on CPVC at > 9 min., extended long-term heat stability from 12 to 15 min. and increased the decomposition time imparted by the liquid control from 11:44 to 14:56. Solid Example B2, where calcium silicate was pre-mixed with Mark 292 prior to being added to the dry blend, functioned not just as a carrier but also as an effective co-stabilizer for the alkyltin stabilizer in CPVC.

Table 13. Static heat stability (in Yellowness Index) of the Markphos EHDP-stabilized plasticized PVC compounds

[0072] Mark 6727 is a solid Ca/Zn stabilizer that was used for stabilizing a plasticized compound shown in Table 5. Use of Markphos EHDP added to a dry blend in its liquid form at 0.5 phr as a phosphorous-containing co-stabilizer (Example Fl) for Mark 6727 added even at a reduced loading of 1.5 phr resulted in a slight improvement in the imparted heat stability (most of the YI was reduced slightly throughout the test up to 75 min.).

[0073] Use of Hubersorb 600 (calcium silicate solid) at 0.33 phr as a calcium-containing co- stabilizer for Mark 6727 added to a dry blend at 1.5 phr resulted in a more significant improvement in the imparted heat stability, extending the low YI values especially from 60 to 90 min. Addition of both Hubersorb 600 as a calcium-containing solid co-stabilizer at 0.33 phr and Markphos EHDP as a phosphorous-containing liquid co-stabilizer, at 0.5 phr separately (Example F3) to the dry blend resulted in a further improvement in the imparted heat stability, reducing YI values further throughout the test and maintaining the low YI values for up to 90 min. Unexpectedly, addition of a free-flowing solid Markphos EHDP, a phosphorous -containing co-stabilizer, pre-blended with Hubersorb 600 in accordance with this invention (Example F2) resulted in even further improvement in the imparted heat stability, extending the low YI values for up to 105 min. [0074] Other features, advantages and embodiments of the invention disclosed herein will be readily apparent to those exercising ordinary skill after reading the foregoing disclosure. In this regard, while specific embodiments of the invention have been described in considerable detail, variations and modifications of these embodiments can be effected without departing from the spirit and scope of the invention as described and claimed.

Claims

A heat stabilizer composition comprising a metal silicate containing a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester or mixtures thereof, the heat stabilizer composition being a free-flowing solid.

The heat stabilizer composition of claim 1 wherein the liquid stabilizer is a liquid alkyltin compound.

The heat stabilizer composition of claim 1 wherein the liquid stabilizer is a liquid phosphite ester.

The heat stabilizer composition of claim 1 wherein the free-flowing solid has no free liquid. The heat stabilizer composition of claim 4 wherein the free-flowing solid is below its point of incipient wetness.

The heat stabilizer composition of claim 1 wherein the metal in the metal silicate is selected from magnesium, calcium, barium, aluminum or mixtures thereof.

The solid heat stabilizer composition of claim 6 wherein the metal silicate is calcium silicate.

The heat stabilizer composition of claim 1 comprising 20.0 to 99.0 wt% of the metal silicate and 1.0 to 80.0 wt% of the liquid stabilizer, based on the total weight of the heat stabilizer composition.

The heat stabilizer composition of claim 8 comprising 25.0 to 80.0 wt% of the metal silicate and 20.0 to 75.0 wt% of the liquid stabilizer, based on the total weight of the heat stabilizer composition.

The heat stabilizer composition of claim 9 comprising 30.0 to 50.0 wt% of the metal silicate and 50.0 to 70.0 wt% of the liquid stabilizer, based on the total weight of the heat stabilizer composition.

The heat stabilizer composition of claim 1 wherein the liquid alkyltin compound is selected from alkyltin mercaptides, alkyltin carboxylates, alkyltin sulfides or mixtures thereof. The heat stabilizer composition of claim 11 wherein the alkyltin mercaptides are selected from alkyltin mercaptocarboxylic acid esters and alkyltin 2-mercaptoethylcarboxylates. The heat stabilizer composition of claim 12 wherein the alkyltin mercaptocarboxylic acid esters are selected from mono-alkyltin tris(2-ethylhexyl mercaptoacetate), di-alkyltin bis(2-ethylhexyl mercaptoacetate), dialkyltin (ethylene glycol di-mercaptoacetate) or mixtures thereof, where the alkyl group is a C1-C12 linear, branched or cyclic hydrocarbon.

14. The heat stabilizer composition of claim 13 wherein the alkyl groups are methyl, n-butyl or n-octyl.

15. The heat stabilizer composition of claim 13 wherein a weight ratio of the mono- to dialkyltin mercaptides ranges from 1/99 to 99/1.

16. The heat stabilizer composition of claim 15 wherein the weight ratio of the mono-to dialkyltin mercaptides ranges from 5/95 to 95/5.

17. The heat stabilizer composition of claim 16 wherein the weight ratio of the mono- to dialkyltin mercaptides ranges from 20/80 to 50/50.

18. The heat stabilizer composition of claim 11 wherein the liquid alkyltin carboxylates are mono-alkyltin tris(carboxylates) or dialkyltin bis(carboxylates) selected from dialkyltin bis (laurate), dialkyltin bis (neodecanoate), dialkyltin bis (oleate), dialkyltin bis (2- ethylhexanoate), dialkyltin bis (ethylmaleate), or mixtures thereof, and where the alkyl group is C1-C12 linear, branched or cyclic hydrocarbon.

19. The heat stabilizer composition of claim 18 wherein the alkyl groups are methyl, n-butyl or n-octyl.

20. The heat stabilizer composition of claim 1 wherein the liquid phosphite esters are selected from thiophosphites, thiophosphates, triaryl phosphites, diphenyl alkyl phosphites, diphenyl phosphite, phenyl dialkyl phosphites, and tris(alkyl) phosphites, poly (dipropylene glycol) phenyl phosphite, tetraphenyl dipropyleneglycol diphosphite, phenyl neopentylene glycol phosphite, tris (dipropyleneglycol) phosphite, poly 4,4' isopropylidenediphenol-Cio Alcohol Phosphite and poly 4,4' isopropylidenediphenol-Cn- 15 Alcohol Phosphite, or mixtures thereof.

20. The heat stabilizer composition of claim 1 wherein the liquid phosphite ester is selected from 2-ethylhexyl diphenyl phosphite, diphenyl iso-decyl phosphite, Tri-iso-tridecyl phosphite, tris(2-ethylhexyl) phosphate or mixtures thereof.

21. A process comprising:

applying a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester or mixtures thereof to the surface of a solid metal silicate, thereby forming a heat stabilizer composition, wherein the heat stabilizer is a free-flowing solid.

22. The process of claim 21 wherein the metal silicate is treated to remove water prior to applying the liquid stabilizer.

23. The process of claim 22 wherein the metal silicate is treated by heating at a temperature from 110 to 170°C.

24. The process of claim 23 wherein the heating is conducted under vacuum.

25. The process of claim 21 wherein the heat stabilizer composition has no free liquid.

26. The process of claim 21 wherein the heat stabilizer is below its point of incipient wetness.

27. The process of claim 21 wherein the liquid stabilizer is applied by spraying the liquid onto the surface of the metal silicate.

28. The process of claim 21 wherein the liquid stabilizer is applied by mixing the liquid with the metal silicate.

29. A stabilized polymer composition comprising:

a halogen-containing polymer; and

a heat stabilizer composition comprising a metal silicate containing a liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester, or mixtures thereof, the heat stabilizer composition being a free-flowing solid.

30. A process for preparing a stabilized polymer composition comprising blending and compounding:

a halogen-containing polymer; and

a heat stabilizer composition comprising a metal silicate containing at least one liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester, or mixtures thereof, the heat stabilizer being a free-flowing solid.

31. A heat stabilizer composition produced by a process comprising:

applying liquid stabilizer selected from a liquid alkyltin compound, a liquid phosphite ester or mixtures thereof to the surface of a metal silicate, wherein the heat stabilizer composition is a free-flowing solid.