Abstract:
This invention pertains to multilayer compositions, articles and processes for preparing and thermoforming said compositions and articles. Multilayer compositions exemplified comprise: 
     (A) a first layer of a polyvinyl chloride composition comprising the specified compounding ingredients and represented herein by preferred embodiments; and 
     at least one other layer (B) comprising: a polyvinyl chloride composition together with specified and preferred compounding ingredients and including a heat distortion temperature improving additive, wherein the heat distortion temperature of the dominant phase, preferably a single phase, is at least three degrees celsius higher than said heat distortion temperature of said first layer. 
     Thermoformed articles of the invention are useful for example as inner-liners or door liner panels for referigerators where contact with HCFC chemicals, present in foam insulation, is necessary. Impact resistance is maximized, while chemical resistance and heat deflection temperature are maintained at performance levels acceptable in these applications.

Description:
FIELD OF THE INVENTION 
     This invention pertains to thermoplastic compositions which are chemically resistant to chlorofluoro carbon (CFC) compounds such as the recently developed hydrochlorofluorocarbons (CFC). Vinyl based articles coming in contact with HCFC compounds used as blowing agents are exemplified and exhibit good chemical resistance, barrier properties, heat deflection performance and thermoformability compared with conventional styrenic compositions used as components for example in thermoformed refrigerator inner liners. 
     BACKGROUND OF THE INVENTION 
     With the phase-out of certain environmentally damaging CFC compounds, new HCFC compounds have been offered. CFC numbers R11 (CC1 3  F) and R12 (CC1 2  F 2 ) are currently targeted for replacement. HCFC types designated R123 (CHC1 2  --CF 3 ) and R141b (CC1 2  F--CH 3 ) are currently being utilized as chemical blowing agents and have been shown to exhibit severe attack on certain conventional thermoplastic polymeric compositions rendering these useless in direct contact with R123 and R141b. 
     Polyvinyl chloride (PVC) would have chemical resistance to R123 and 141b, however many formulated PVC compounds show some detrimental effects, and lack several properties for successful commercial applications for instance in housings and components in direct contact with blown-in foams containing HCFC compounds. Typically, conventional PVC compositions have insufficient heat deflection temperature for some of these applications, and typically have unacceptable thermoforming properties such as a limited draw-ratio of original thickness to drawn thickness. More over, formulated PVC compounds having a heat distortion additive were observed to be deficient in chemical resistance due in part to higher required impact modifier levels which interfered with HCFC resistance. Because PVC has some inherent favorable properties, it would be desirable to provide PVC based compositions and thermoformed articles derived therefrom which exhibit a combination of properties rendering these useful in applications where direct contact with HCFC chemicals may be necessary. 
     SUMMARY OF THE INVENTION 
     It is one aspect of the present invention to provide improved polyvinyl chloride compounds having resistance to the effects of direct contact with HCFC compounds. 
     It is another aspect of the present invention to provide PVC compositions and shaped articles derived therefrom which exhibit good chemical resistance in contact with HCFC compounds. 
     It is yet another aspect of the present invention to provide novel multilayer compositions and articles comprising PVC in each layer, wherein the composite possesses improved thermoformability and heat deflection performance for use in componentry which may come in direct contact with HCFC compounds. 
     It is a further aspect of the present invention to provide multilayer extruded articles wherein each layer comprises a polyvinyl chloride compound and said layers possess similar melt viscosities for multi-layer extrusion; said layers also exhibit high inter-layer adhesion; and wherein the multilayer article exhibits high impact strength. 
     In yet another aspect of the present invention, a multilayer article comprising polyvinyl chloride is provided which can be preprocessed as regrind and incorporated into one of the compositions used to form the (A) or preferably the (B) layer. When reprocessed, the PVC compound may be mixed with virgin compound. The major phase of a reprocessed (B) layer will have a heat deflection temperature which is at least 3° C. higher than the major phase heat deflect temperature of the (A) layer. 
     In yet another aspect, this invention pertains to processes for preparing a multilayer sheet, and for thermoformed articles derived from said sheet. 
     It is a still further aspect of the present invention to provide improved multilayer articles each layer comprising polyvinyl chloride which exhibit good dimensional stability and flexural modulus under extended exposure to HCFC compounds, and wherein said multilayer articles comprise one layer which is preferably not objectionable for direct food contact. These and other aspects of the present invention are achieved by forming a multilayer article comprising: 
     (A) a first layer of a polyvinyl chloride composition comprising the specified compounding ingredients and represented herein by preferred embodiments wherein the heat distortion temperature of the dominant phase of the first layer is defined; and at least one other layer 
     (B) comprising: 
     a polyvinyl chloride composition together with specified and preferred compounding ingredients including a heat deflection temperature improving additive, wherein the heat distortion temperature of the dominant phase, preferably a single phase, is at least three degrees celsius higher than said heat distortion temperature of said (A) layer. 
     There may be combined with said multilayer article a third layer (C) which comprises a polyvinyl chloride compound, contacting layer (A) or preferably layer (B). The arrangement of layers in one embodiment containing three layers is such that preferably layer (B) is between the other layers. In the embodiment comprising a two layer structure, layer (A) preferably provides an appearance layer when the article is contacted with an HCFC compound from the side opposite the appearance layer. For example, in a thermoformed refrigerator inner liner, the multilayer article is thermoformed into an open box shape, conforming to the dimensional requirements of the refrigerator. Blown foam insulation is introduced between the liner and the outer shell. HCFC will contact the inner liner. It has been found that certain formulated PVC multilayer compositions disclosed herein possess enough chemical resistance to withstand this contact without suffering unacceptable deterioration and/or distortion due to the heat buildup during the foaming process. 
     The general object of the present invention for the multilayer articles disclosed herein invention is to provide improvements in the following desired properties: 
     
         ______________________________________(A) Layer   1.    high impact strength.   2.    high initial gloss and retention of gloss after         thermoforming, in the appearance layer.   3.    acceptable direct food contact, for the         appearance layer.   4.    excellent resistance to HCFC.   5.    good stability and processability.   6.    good thermoforming properties including deep         draw capability.(B) Layer   1.    melt viscosity for extrusion adjusted to that         similar to (A).   2.    increased HDT above (A).   3.    good processability and stability.   4.    good HCFC resistance.   5.    colorability to match (A).   6.    excellent adhesion to (A).   7.    good thermoformability in combination         with (A).   8.    adequate impact strength.______________________________________ 
    
    
    
     DETAILED DESCRIPTION 
     Polyvinyl chloride polymers are well known and commercially available worldwide. Polyvinyl chloride polymers contemplated for use in the present invention include those prepared in a variety of ways. The particular method of preparation is beyond the scope of the present invention. Preferred methods are outlined below. 
     The PVC polymers can be prepared by polymerization methods including: mass, suspension, dispersion, and emulsion processes. A mass process is described in U.S. Pat. No. 3,522,227. A phase inversion process may also be used and is disclosed in U.S. Pat. No. 3,706,722. In the phase inversion process, the monomer is the continuous phase during the early part of the polymerization and after about 10% conversion additional water is added followed by phase inversion wherein water becomes the continuous phase and the monomer the discontinuous phase. 
     A skinless, suspension PVC (PVC5) resin is taught in U.S. Pat. No. 4,711,908. Reference is made to example 4 of U.S. Pat. No. 4,471,908 wherein low hydrolysis polyvinyl alcohol (PVA) and polyacrylic acid are used as vinyl chloride dispersants and wherein after commencement of polymerization, a base is introduced into the suspension thereby stripping off the polyacrylic acid dispersant layer from the particle surface. What remains is a porous particle achieved by the use of the porosifiying effects of the low hydrolysis PVA, and substantially or completely devoid of a pericellular membrane. 
     The preparation of porous, skinless, crosslinked PVC (PVC6) resin is taught in U.S. Pat. No. 4,755,699. Reference is also made to example 1 of U.S. Pat. No. 4,775,699 where a skinless crosslinked PVC is shown which is similar to the skinless resin above in U.S. Pat. No. 4,471,908 except for the use of a copolymerizable crosslinking monomer e.g. diallyl phthalate. 
     Preferably, preparation of said PVC polymer is carried out in mass or by the aqueous suspension process. For the sake of brevity, an exemplary description for preparing the vinyl chloride polymers useful herein will pertain to the preparation of this component by the suspension method. It is understood that this description is not a limitation as to the specific polymer compositions nor the particular polymerizing technique for PVC which can be employed in preparing PVC used in this invention. 
     The suspension polymerization technique to prepare vinyl chloride polymers is well-known in the art and generally set forth in The Encyclopedia of PVC, pp. 76-85, Marcel Decker, Inc. (1976). Vinyl chloride polymer prepared by suspension polymerization employs an aqueous medium containing: (1) primary suspending agent(s) consisting of one or more polyvinyl alcohol polymers having a chosen degree of hydrolysis of generally 60-95%, cellulose ether, hydroxypropyl methylcellulose, partially hydrolyzed polyvinyl acetate, vinyl acetate-maleic anhydride, partially saponified polyalkyl acrylate or gelatin, and combinations of any of these; (2) optional secondary dispersing agents such as polyvinyl alcohol having a lower degree of hydrolysis of from about 20-60% (3) a monomer soluble polymerization initiator and (4) optional solvents such as THF. 
     Suitable polymerization initiators are selected from the conventional free radical initiators such as organic peroxides and azo compounds. The particular free radical initiator will depend upon the monomeric materials being copolymerized, the molecular weight and color requirements of the copolymer and the desired temperature of the polymerization reaction. A satisfactory amount of initiator is in the range of about 0.005 part by weight to about 1.00 part by weight, based on 100 parts by weight of monomer(s) being polymerized. Optional copolymerizable comonomers can be included for example, the esters of acrylic acid, for example, methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, cyanoethyl acrylate, and the like; vinyl esters such as vinyl acetate and vinyl propionate; esters of methacrylic acid, such as methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate, butyl methacrylate, and the like; nitriles, such as acrylonitrile and methacrylonitrile; acrylamides, such as methyl acrylamide, N-methylol acrylamide, N-butoxy methacrylamide, and the like; halogen containing vinyl monomers such as vinylidene chloride vinylidene fluoride, and vinyl bromide; vinyl ethers such as ethylvinyl ether, chloroethyl vinyl ether and the like; the vinyl ketones, styrene derivatives including α-methyl styrene, vinyl toluene, chlorostyrene; vinyl naphthalene; olefins such as ethylene, butene, isobutylene, propylene and hexene; and other copolymerizable monomers or mixtures of monomers having suitable reactivity ratios with vinyl chloride and known to those skilled in the art. Some embodiments of the present invention may employ PVC blends with crosslinked PVC or crosslinked PVC alone. Crosslinked PVC polymers can be made by polymerizing vinyl chloride in the presence of cross-linking monomers such as the aforementioned diallyl phthalate, trimethylol propane triacrylate, allyl methacrylate, and the like as taught in U.S. Pat. No. 4,755,699. Preferred comonomers are olefins. Particularly preferred are PVC copolymers with about 0.5 to about 5 phr isobutylene (PVC 3B). 
     After conversion of monomers, which said percent conversion is generally 50% or higher, the resin suspension is stripped of residual monomer, and dried to a free flowing powder. Suspension resins have generally average particle sizes ranging from about 50 to 250 microns. The preferred PVC polymer is a homopolymer or a copolymer with the preferred comonomer(s) in a minor amount of up to about 10 parts by weight. Particularly preferred are polyvinyl chloride resins substantially free of gel particles. 
     The inherent viscosity (I.V.) of polyvinyl chloride can be controlled by a variety of well understood methods such as control of polymerization temperature. The I.V. of polyvinyl chloride used in this invention can range from about 0.3 to about 4.0, with a preferred I.V. range of from about 0.5 to about 1.6. High I.V. PVC can also be incorporated as a minor component. Present at from about 1 to about 99 phr, preferably from 3 to about 50 phr. When used in this manner, it is preferred that the I.V. of the minor PVC component will be at least 0.2 I.V. units higher, more preferably at least about 0.35 units higher than the I.V. of the polyvinyl chloride used in a major amount. 
     The PVC compounds used herein typically contain other components including compounds selected from the group consisting of: lubricants, impact modifiers, tinting colorants, blueing agents, pigments, blowing agents, coupling agents, antioxidants, heat stabilizing ingredients, co-stabilizers, processing aids, and plasticizers. 
     Exemplary antioxidants include hindered alkylated phenolics as antioxidants include 2,6-di-t-butyl-4-methyl phenol also referred to as butylated hydroxy toluene, bis-phenols such as 2,2&#39;-methylenebis(4-methyl-7-t-butylphenol), thio-phenols such as 4,4&#39;-dihydroxydiphenyl sulfide, otherwise referred to as thiodiphenol, and di-phenyl ethers such as 4,4&#39;-dihydroxydiphenyl ether, and mixtures thereof. These types of antioxidants when used are generally present in an amount from about 0.05 to 5 parts per hundred weight parts PVC in one layer (phr). Preferred antioxidants and heat stabilizers are those having acceptability under applicable FDA regulations. 
     Heat stabilizing ingredients employable in any layer herewith include alkyltin compounds such as dimethyl tin-bis isooctylthioglycolate (methyltin), di-butyltin-bis-isooctylthioglycolate (butyltin), octyltin, mixed metal alkyltins, dialkyl tin di-carboxylates, methyltin mercaptides, butyltin mercaptides, dialkyl tin bis(alkyl mercaptocarboxylate) including di-n-octyltin-S,S&#39;-bis(isooctyl mercaptoacetate), and butylthiostannoic acid, and mixtures thereof. Any alkylated tin having features such as low toxicity e.g. higher alkyl types, FDA approval, USP class 6 approval, good color, clarity and compatibility, low plateout on equipment, and non-staining properties are desirable and preferred for use in this invention. Other useful stabilizers include metal or mixed metal soaps such as calcium/zinc soap stabilizers. Examples of suitable calcium soaps are calcium stearate, calcium laurate, calcium oleate, calcium palmitate, calcium octanoate, and calcium benzoate. Calcium stearate or combinations with stearic acid are preferred calcium soap stabilizer compositions. Examples of suitable zinc soaps are zinc stearate, zinc laurate, zinc palmitate, zinc 2-ethyl hexoate, zinc octanoate, zinc oleate, and zinc benzoate, and mixtures thereof. Zinc stearate is a preferred zinc soap. Lead or cadmium containing heat stabilizers are preferably absent in a layer having direct food contact. Metal soaps can be used at levels ranging from about 0.5 to 10  phr, preferably from about 1 to about 5 phr. 
     Co-stabilizers can be included with PVC in any layer, for example, phosphite stabilizers, polymeric phosphites, thioesters such as dilauryl thiodipropionate and beta-diketones. Plasticizing co-stabilizers known in the art can be optionally included for improved heat stability. Exemplary co-stabilizing plasticizers include epoxy derivatives such as epoxidized soybean oil and epoxidized linseed oil. Liquid stabilizing plasticizers are preferably absent or are present, at from 0.5 to about 10 phr, preferably from 1 to 5 phr. 
     At least one optional plasticizer may be included in any layer. Specific examples of plasticizers include derivatives of carboxylic acid esters including the various derivatives of adipic acid, azelaic acid, phthalic acid, benzoic acid, and citric acid, isobutyric acid, isophthalic acid derivatives, sebacic acid derivatives, isosebacic acid derivatives, stearic acid, tartaric acid, oleic acid, succinic acid; phosphoric acid derivatives; derivatives of terephthalates, pentaerythritol, trimellitic acid, and mixtures. Plasticizers, if present, are desiredly used at from 1 to 20 phr and preferably from 1 to about 10 phr. The articles of the present invention are preferably rigid therefore plasticizer levels are limited in any one layer. Other plasticizers can be included for example, partial esters of the above carboxylic acids, ethers, glycol derivatives, glycolates, glycerol derivatives. These are set forth in The Technology of Plasticizers, by Sears and Darby, pages 893-1085, John Wiley &amp; Sons, New York, 1982. Preferred plasticizers are C 10  and higher alkyl diesters of phthalic acid, bisphthalates, C 8  and higher alkyl triesters of trimellitic acid, for example di-isodecyl phthalate (DiDP) and tri-octytrimellitate (TOTM). 
     In addition to the foregoing plasticizers, which are monomeric, various polymers can also be utilized such as the polyesters, halogenated polyolefins, oxidized polyolefins, polyepichlorohydrins, polyacrylates, ethylene copolymers, copolymers prepared from diolefins and, overpolymers of polar monomers overpolymerized onto flexible materials. 
     Polyester plasticizers are generally made from a dicarboxylic acid having from about 3 to about 12 carbon atoms and from a diol having from about 2 to about 1000 carbon atoms with propylene glycol being preferred. Examples of suitable polyesters include various esters made from adipic acid such as a polyester having a molecular weight of 6,000, e.g., Paraplex® G-40, a polyester made from adipic acid having a molecular weight of about 2,200, Paraplex® G-50, a polyester made from adipic acid having a molecular weight of about 3,300, Paraplex® G-54, a polyester made from azelaic acid having a molecular weight of about 2,200, Plastolein® 975, a polyester made from sebacic acid such a Paraplex® G-25, a polyester made from glutaric acid, a polycaprolactone polyester, and the like. Paraplex is a trademark of C.P. Hall Co. and Plastolein is a trademark of Emery Industries, Inc. 
     Other components in said PVC containing layers may include fillers, pigments, antistatic agents, anti-fogging agents, colorants and processing aids all of which are commercially available and listed in Modern Plastics Encyclopedia 1988 published by McGraw Hill Co. 
     At least one impact modifier is necessary in at least one layer. Optionally at least one impact modifier is present in more than one layer. In the preferred embodiment minimum amounts of impact modifier are used. Preferred levels are less than 20 phr in the layer having the highest HCFC resistance. More preferred levels of impact modifier are from 0 to 15 phr, still more preferred are levels from 0 to 10 and most preferred are levels ranging from 0 to 5 phr in the layer having the higher HCFC resistance. These include acrylonitrile butadiene styrene terpolymers (ABS) and methacrylate butadiene styrene (MBS). Other impact modifiers are disclosed in Plastics compounding, November/December, 1983: &#34;Update: Impact Modifiers for Rigid PVC,&#34; by Mary C. McMurrer. Impact modifiers generally contain a rubbery core component. Various embodiments are commercially available and include polybutadienes jointly graft-copolymerized with styrene and methyl methacrylate (MBS). Paraloid® KM-653 (M24), BTA-733 (M25) from Rohm and Haas, or Kanegafuchi B-56 and B-22KO MBS types; polybutadienes jointly graft-copolymerized with acrylonitrile and styrene (ABS), low rubber types are preferred; nitrile rubber blended with SAN; polybutadienes jointly graft-copolymerized with acrylonitrile and alpha-methyl styrene; ethylene-propylene-diene rubber, referred herein as EPDM graft-copolymerized with vinyl chloride, EPDMs jointly graft-copolymerized with styrene and acrylonitrile, polybutadienes graft-copolymerized with styrene, methyl methacrylate and acrylonitrile (MABS); polyacrylates such as those believed to be polybutyl acrylate graft-copolymerized with methyl methacrylate, (KM®-323B, KM®-330 Trademark of Rohm and Haas); polybutyl acrylate jointly graft-copolymerized with methyl methacrylate and styrene, polybutyl acrylate graft polymerized with acrylonitrile and styrene (Blendex® 975,977, or 979-Trademark of General Electric); butyl rubbers graft-copolymerized with vinyl chloride, block copolymers of styrene-butadiene-styrene, radial block copolymers of styrene and butadiene, styrene-butadiene rubbers, vulcanizable acrylate rubbers, EPDMs and the like. Various preferred impact modifiers are commercially available and specified hereinbelow. Chlorinated polyethylene (CPE) is an exemplary impact modifier. Percent chlorine content preferably ranges from about 25% to 40%. CPE containing 25% (CPE25) and 36% (CPE36) are commercially available from Dow Chemical Inc. 
     Exemplary antistats are commercially available under the Glycolube® trademark of Lonza Corp. An exemplary antifogging agent includes the alkyl phenol ethoxylates as for example those commercially available under the Surfonic trademark of Texaco, Inc. 
     Exemplary lubricants are the various hydrocarbons, such as paraffins, paraffin oils, low molecular weight polyethylene, oxidized polyethylene, fatty acids such as stearic acid, fatty alcohols such as cetyl, stearyl, or octadecyl alcohol; the aforementioned metal soaps such as calcium or zinc salts of stearic acid; amides of organic acids such as stearamide, ethylene-bis-stearamide; esters and partial esters such as butyl stearate, glycerol monostearate, hexaglycerol distearate; and ester waxes such as stearyl esters. Combinations of mineral oil, stearic acid derivatives and waxes at from 2 to 5 phr total are a suggested example of lubricant combinations. In one preferred example of a lubricant package, mineral oil, stearic acid, metal salt of stearic acid, paraffin wax are combined and used at from 3 to 5 phr total. A combination of hydroxy stearic acid, oxidized polyethylene, ester wax and acrylic processing aid is a desirable lube package (L1). A lubricant combination of mineral oil and calcium stearate (L2), of hydroxy stearic acid, oxidized polyethylene and LOXIOL® G-705 Trademark of Ionza (L3), or a combination of mineral oil and stearic acid (L4) may be advantageously used; a combination of ester wax, oxidized polyethylene and stearic acid (L5) is suggested; and a combination of stearic acid, calcium stearate, and mineral oil (L6) is suggested. The externally acting lubricants listed among those above are less polar, and typically have longer alkyl chains such as paraffins, stearates, and bis-stearamides. However, combinations of internal and external lubricants may also be used. Lubrication of the PVC compound of the present invention is a complex art. Since many lubricants can be combined in countless variations, the total amount of lubricant may vary generally from about 2 to 10 phr, preferably from 3 to about 6 phr total in any layer. A variety of combinations were found to give good results with different I.V. PVC. Generally, a lesser total amount of lubricants was required when lubricating a PVC having an I.V. less than about 0.6. Whereas, when lubricating a PVC of I.V. 0.8 or higher, relatively more lubricating ingredients were needed. Several combinations are suggested herein within practical ranges. Optimization of particular individual formulations is beyond the scope of the present invention, and can be achieved by one skilled in the art with routine trial and error. 
     Exemplary processing aids are acrylic polymers such as poly methyl acrylate based materials. Adjustment of melt viscosity can be achieved as well as increasing melt strength by employing commercial acrylic process aids such as those from Rohm and Haas under the Paraloid® Trademark. Paraloid® K-120ND, K-120N, K-175, and other processing aids are disclosed in The Plastics and Rubber Institute; International Conference on PVC Processing, Apr. 26-28 (1983), Paper No. 17. One useful processing aid is a copolymer of styrene and acrylonitrile, such as 75:25 styrene: acrylonitrile copolymer (M13) made by batch emulsion polymerization. 
     Exemplary fillers are optional and include clay, barytes, calcium carbonate and talc. Preferred opacifying pigments when used are the various titanium dioxides (TiO 2 ) which are commercially available. Useful TiO 2  types are uncoated, rutile titanium dioxide powder exhibiting high chalking, such as Ti-Pure® R-100 from E.I. DuPont De Nemours and Co. Inc. (DuPont). 
     Exemplary heat distortion improving agents include styrene-acrylonitrile copolymer, alpha methyl styrene-styrene-acrylonitrile terpolymer, a polymer of alpha methyl styrene-styrene-N-cyclohexyl maleimide, N-phenylmaleimide, imidized polymethyl methacrylate, post-chlorinated polyvinyl chloride, styrenemaleic anhydride polymer, imidized styrene-maleic anhydride polymer, acrylicimide copolymer, acrylonitrile-acrylate copolymer, acrylonitrile-acrylatepolybutadiene graft copolymer, alpha methyl styrene-methylmethacrylateacrylonitrile terpolymer, polycarbonate, and brominated polycarbonate (M26). 
     
         ______________________________________Polyvinyl Chloride Resin TypesType  I.V.    Type          Notes______________________________________1     0.54    Suspension    Geon ® 110 × 3772     0.68    Mass          Geon ® 86 × 13A    0.65    Suspension3B    0.65    Suspension    Isobutylene Copolymer4     0.92    Suspension    Geon ® 103EP-F765     1.6     Suspension    Skinless6     NA      Crosslinked PVC                       Skinless7     0.46*   CPVC (63.5% Cl)                       *of PVC precursor8     0.46*   CPVC (68.5% Cl)                       *of PVC precursor______________________________________ 
    
     The above listed polymers are exemplary of polyvinyl chloride and/or post-chlorinated polyvinyl chloride polymers preferably contained in each layer of the present invention. These polymers were formulated with stabilizer, impact modifier(s), processing aid(s), filler, pigment, lubricants and in some instances colorants. Below are listed some compounding additives used in the samples. 
     
         ______________________________________MODIFIERMod.   Believed        CommercialType No.  Composition Type                  Designation______________________________________M1     ABS             Blendex ® 310.sup.1M2     ABS             Blendex ® 338M3     ABS             Blendex ® 467M4     ASA             Blendex ® 975M5     ASA             Blendex ® 977M6     ASA             Blendex ® 979M7     α-MS/SAN/ABS                  Blendex ® 703M8     MMA/S/AN        Blendex ® 590M9     MBS             Kane-Ace ® B-56.sup.2M10    MBS             Kane-Ace ® B-22KOM11    Acrylic         Paraloid ® KM 330.sup.3M12    Acrylic         Durastrength ® 200.sup.4M13    SAN             Processing AidM14    SMA             Dylark 378 ®.sup.5M15    α-MS/SAN  Blendex ® 586M16    DOP             Di-2-ethylhexyl phthalateM17    ESO             Epoxidized soy oilM18    glycerol monostearate                  Glycolube 825.sup.6M19    EVA/CO          Elvaloy 741 ®.sup.7M20    Acrylic Imide   Paraloid ® HT-510.sup.3M21    Acrylic         Paraloid ® K-120N.sup.3M22    SAN             SAN ® 125.sup.8M23    Nitrile         Chemigum ® P-83.sup.9M24    MBS             Paraloid ® KM-653.sup.3______________________________________ .sup.1 Trademark of G.E. Spec. Chemicals; .sup.2 Trademark of Kanegafuchi; .sup.3 Trademark of Rohm &amp; Haas; .sup.4 Trademark of Atochem; .sup.5 Trademark of Arco .sup.6 Trademark of Glyco .sup.7 Trademark of DuPont .sup.8 Trademark of Dow Chemical .sup.9 Trademark of Goodyear 
    
     Compounding Additives 
     The samples each comprise PVC resin or blends of PVC resins along with any of the packages listed below: 
     
         ______________________________________     (Wt.)     Amount PHR             (PHR)______________________________________Standard Package A     Standard Package B______________________________________Alkyl tin stab.       2          Methyltin     3M13         3          M21           1.5CaCO.sub.3  5          M16           2TiO.sub.2   2          M17           4.5L2          4.2        M18           1M2          12         CaCO.sub.3    12                  L1            2.6______________________________________Standard Package C     Standard Package D______________________________________Methyltin   2          Methyltin     3CaCO.sub.3  5          CaCO.sub.3    12M13         3          M21           1.5TiO.sub.2   10         M16           2L2          4          M17           4.5M1          15         TiO.sub.2     3.5                  M18           1                  L1            2.6                  Paraloid ® K175                                1.0______________________________________Standard Package E     Standard Package F______________________________________M21         2          M21           2methyltin   2          methyltin     2M17         3          M17           1TiO.sub.2   4.5        TiO.sub.2     4.5Calcium Stearate       1.5        Calcium Stearate                                1.5M18         1.0        M18           1.0______________________________________Standard Package G______________________________________M12         2M11         6L4          2.3______________________________________ **Trademark of Witco Inc. 
    
     
         ______________________________________Series ASample Composition______________________________________A1    Control 1A2    Control 2A3    Control 3A4    Control 4A5    Control 5A6    100 parts PVC 3A/std. pkg. A/12 phr M2A7    100 parts PVC 1/std. pkg. A/12 phr M2A8    100 parts PVC 2/std. pkg. A/12 phr M2A9    100 parts PVC 4/std. pkg. A/12 phr M2A11   100 parts PVC 3B/std. pkg. A/12 phr M2A15   100 parts PVC 4/std. pkg. AA16   100 parts PVC 2/10 phr CPE/std. Pkg. AA17   100 parts PVC 2/1 phr ester wax/0.5 phr oxidized polyethylene(PE)/2 phr TiO.sub.2 /1 phr Paraloid ® K175/ 2 phr methyltin/2 phr calcium stearate/0.1 phr stearic acid/0.1 phr paraffin waxA18   100 parts PVC 2/50 phr CPE/std. pkg. AA19   100 parts PVC 2/30 phr DiDP/std. pkg. AA20   100 parts PVC 4/30 phr CPE/std. pkg. AA21   100 parts PVC 4/30 phr DiDP/std. pkg. AA22   100 parts PVC 4/70 phr TOTM/std. pkg. AA23   100 parts PVC 4/70 phr DiDP/std. pkg. AA24   100 parts PVC 4/30 phr polyurethane**/std. pkg. AA25   100 parts PVC 4/10 phr DiDP/std. pkg. A/L4/ 2 phr stearic acidA26   100 parts PVC 4/30 phr ToTM/2 phr methyltin/3 phr M13/2 phr TiO.sub.2 /5 phr CaCO.sub.3 /L2/0.1 phr stearic acid/0.1 phr paraffin wax.A27   100 parts PVC 1/2 phr methyltin/5 phr CaCO.sub.3 /3 phr M13/10 phr TiO.sub.2 /L2/15 phr M1A28   100 parts PVC 2/std. pkg. BA29   100 phr CPVC/std. pkg. B/No CaCO.sub.3A30   100 phr CPVC 7/std. pkg. B/5 phr CaCO.sub.3A31   100 phr CPVC 8/std. pkg. B/No CaCO.sub.3A32   100 phr CPVC 8/std. pkg. B/2 phr DOP/1 phr M18/0.3 phr oxidized polyethylene/0.5 phr ester wax/ 1.0 phr K175A33   100 parts PVC 2/std. pkg. B/5 phr MgO/50 phr M19A34   100 parts PVC 2/std. pkg. B/5 phr MgO/50 phr M19A35   50 parts PVC 2/std. pkg. B/50 phr M23A36   100 parts PVC 2/std. pkg. B/50 phr M13A37   50 parts PVC 2/std. pkg. B/50 phr M13A38   90 parts PVC 1/10 parts PVC 4/std. pkg. CA39   70 parts PVC 1/30 parts PVC 4/std. pkg. CA40   50 parts PVC 1/50 parts PVC 4/std. pkg. CA41   100 parts PVC 2/std. pkg. D/50 phr M11A42   50 parts PVC 2/std. pkg. D/50 phr M11A43   50 parts PVC 2/std. pkg. D/50 phr M12A44   100 parts PVC 2/std. pkg. D/50 phr M12A45   100 parts PVC 2/std. pkg. D/12 phr M2/45 phr CaCO.sub.3A46   50 parts PVC 2/std. pkg. D/50 phr CaCO.sub.3A47   100 parts PVC 2/3 phr butyltin/std. pkg. D/12 phr M2A48   100 parts PVC 1/2 phr methyltin/5 phr CaCO.sub.3 /3 phr M13/10 phr TiO.sub.2 /2 phr mineral oil/2 phr calcium stearate/15 phr M1A49   100 parts PVC 2/std. pkg. B/L1/12 phr CaCO.sub.3 /12 phr M2/3.5 phr TiO.sub.2A50   100 parts PVC 2/std. pkg. B without M16/L1/12 phr M2/12 phr CaCO.sub.3 /3.5 phr TiO.sub.2A51   100 parts PVC 2/std. pkg. B without M16 and M17/ 12 phr M2 12 phr CaCO.sub.3 /3.5 phr TiO.sub.2 /L1A52   100 parts PVC 2/std. pkg. B without M16/L1/12 phr CaCo.sub.3 /3.5 phr TiO.sub.2A53   100 parts PVC 2/std. pkg. B without M16 and M17/ 3.5 phr TiO.sub.2 /L1A54   100 parts PVC 2/std. pkg. B without M16 and M17A55   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M1/L1A56   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M4/L1A57   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M6/L1A58   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M5/L1A59   100 parts PVC 2/std. pkg. B/12 phr M2/5 phr CaCO.sub.3 /12 phr M8/L1A60   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M3/L1A61   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M7/L1A62   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr CPE 36/L1A63   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M11/L1A64   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /5 phr CaCO.sub.3 / 12 phr M9/L1A65   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M2/L1A66   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M10/L1A67   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M12/L1A68   80 parts PVC 2/20 parts PVC 6/std. pkg. B/12 phr M2/L1A69   70 parts PVC 2/30 parts PVC 6/std. pkg. B/12 phr M2/ 10 phr M18/5 phr CaCO.sub.3 /L1A70   80 parts PVC 2/20 parts PVC 5/std. pkg. B/12 phr M2/ 5 phr CaCO.sub.3 /L1A71   70 parts PVC 2/30 parts PVC 5/std. pkg. B/12 phr M2/ 5 phr CaCO.sub.3 /L1A72   70 parts PVC 2/30 parts PVC 4/std. pkg. B/12 phr M2/ 5 phr CaCO.sub.3 /L1A73   70 parts PVC 2/std. pkg. B/30 phr M2/5 phr CaCO.sub.3 /L1A74   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M4/L1A75   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M6/L1A76   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M5/L1A77   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M8/L1A78   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M3/L1A79   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M7/L1A80   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr CPE 36/L1A81   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M11/L1A82   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M9/L1A83   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M12/L1A84   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M10/L1A85   70 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /30 phr M1/L1A86   100 parts PVC 2/std. pkg. B/5 phr CaCO.sub.3 /12 phr M2/ 3.5 phr TiO.sub.2 /L1A87   80 parts PVC 2/std. pkg. B/3.5 phr M21/3.5 phr TiO.sub.2 12 phr M2/12 phr CaCO.sub.3 /20 phr M26/L1A88   70 parts PVC 2/std. pkg. B/3.5 phr M21/3.5 phr TiO.sub.2 12 phr M2/12 phr CaCO.sub.3 /30 phr M26/L1A89   50 parts PVC 2/std. pkg. B/62 phr M2/12 phr CaCO.sub.3 /L1A90   100 parts PVC 2/std. pkg. B/12 phr M2/12 phr CaCO.sub.3 /L1A91   100 parts PVC 4/1.5 phr methyltin/2 phr calcium stearate/7.5 phr TiO.sub.2 /2 phr amide wax/3 phr M13/5 phr Blendex ® 336/10 phr CaCO.sub.3A92   100 parts PVC 4/std. pkg. F/std. pkg. GA93   100 parts PVC 2/1.5 parts methyltin/2 phr calcium stearate/7.5 phr TiO.sub.2 /2 phr ethylene bis stearamide/3 phr M13/5 phr Blendex ® 336/10 phr CaCO.sub.3A94   100 parts PVC 2/std. pkg. F/std. pkg. GA95   100 parts PVC 2/std. pkg. F/std. pkg. G/8 phr M1A96   100 parts PVC 2/std. pkg. F/std. pkg. G/8 phr M2A97   100 parts PVC 2/std. pkg. F/std. pkg. G/8 phr M6A98   100 parts PVC 2/std. pkg. F/std. pkg. G/8 phr M3A99   100 parts PVC 2/std. pkg. F/std. pkg. G/8 phr M25A100  100 parts PVC 2/std. pkg. F/std. pkg. G/8 phr M10A101  100 parts PVC 2/std. pkg. F/std. pkg. G/8 phr M25A102  100 parts PVC 2/std. pkg. F/1.5 phr mineral oil/0.8 phr stearic acid/16 phr M24A103  100 parts PVC 2/std. pkg. F/L4/16 phr M1A104  100 parts PVC 2/std. pkg. F/L4/16 phr M6A105  100 parts PVC 2/std. pkg. F/16 phr M11______________________________________ **ex BFGoodrich Co. 
    
     PERFORMANCE RATING TESTS 
     The desired properties for using the PVC containing multilayer articles are: 
     1. HCFC Barrier properties 
     2. gloss 
     3. thermoforming performance 
     4. low incidence of gels 
     5. HCFC chemical resistance 
     HCFC BARRIER TEST 
     PVC compounds were mixed in a Henschel-type mixer, milled on a heated 2-roll mill with a roll temperature of approx. 368° F. (186° C.) and stock temperature of approx. 385° F. (196° C.). The fluxed compounds were extruded and cubed. The cubes were introduced into a 3/4 inch Brabender® extruder having an L/D of 20:1, and extruded through a 4 inch sheet die (10 cm). Extruder barrel zone temperatures were: 155° C., 170° C., and 185° C. with the temperature of the die at 190° C. The extruded strips were compression molded to 20 mills (0.05 cm.) thickness. Circular discs were punched out from these strips. A PVC disc was placed together with a 40-50 mil (0.2 cm) disc prepared from a conventional ABS compound used for refrigerator inner liners. A polyethylene o-ring type gasket was used. 
     The discs were sealed by a closure on top of 8 oz. jars containing the particular HCFC evaluated. The samples thus had the PVC layer directly exposed to HCFC vapors for 7 days exposure at ambient temperature. 
     Catastrophic failure is noted when the molded ABS compositions crack severely, or the surfaces exhibit small cracks or crazing throughout. These ABS compositions if contacted with HCFC are normally destroyed or severely damaged. To the extent that exposure of the ABS discs, separated from HCFC by the PVC disc, did not undergo degradation, this served as an indication of the barrier performance of the layer. For testing purposes single-layer compositions comprising PVC were shown. to exhibit a range of chemical resistance to HCFC. Chemical resistance ratings were made by observing the appearance of the ABS discs following exposure to HCFC: 
     
         ______________________________________Criteria (ABS)       Rating______________________________________Pits and blisters (large)                1Bonding of PVC to ABS                1-2Partial bonding to ABS                3-4Some surface damage to ABSSmall Pits           7-8Small crazes         9Stains/few small blisters                9ABS unaffected       10______________________________________ 
    
     Those samples rating high are more preferred, in terms of chemical resistance. One may select those compositions for use in preparing the (A) layer of this invention on the basis of the barrier performance listed in Tables 2A, 2B and 2C. 
     
                       TABLE 2A______________________________________HCFC BARRIER RATING - A SERIES          Pass - FailSample #         123    141b______________________________________A1               10     10A2               10     7A3               2      2A4               10     6A5               10     6A6               8      10A7               10     10A8               10     10A9               9.5    10--               --     --A11              10     7--               --     ----               --     ----               --     --A16              8      10A17              8      10A18              4      2A19              2      2A20              5      5A21              2      2A22              1      2A23              1      2A24              3      8A25              5      8A26              9      10A27              10     10A28              9      8.5A29              9.5    8.5A30              13     6A31              10     9.8A32              10     5A33              1      4A34              1      3A35              1      4A36              1      6A37              5      4A38              1      10A39              10     10A40              10     10A41              1      7A42              1      1A43              1      4A44              1      6A45              3      8.5A46              1      3A47              8.5    8.5--                --    --______________________________________ 
    
     
                       TABLE 2B______________________________________HCFC BARRIER RATING - A SERIES          Pass - FailSample #         123    141b______________________________________A48              9.8    10A49              1      9.2A50              9.8    9.3A51              10     10A52              9.7    10A53              10     9.8A54              10     10A55              9.7    8.8A56              8.9    8.7A57              9      9.2A58              9.5    9.7A59              8.7    9A60              8.7    9A61              9.4    10A62              9.2    9A63              8.8    9.8A64              9.3    8.7A65              10     8.6A66              9.7    8.8A67              9.2    8.3A68              9.6    8.5A69              8.5    8.5A70              9.5    9.2A71              9.3    8.7A72              9.8    9.2A73              1      7A74              1      6A75              1      5A76              1      6A77              1      1A78              1      5A79              1      8.7A80              3      6A81              7      7A82              1      1A83              1      1A84              F      7A85              1      7.5A86              8.5    8.5A87              8.8    9.3A88              7.5    8.5A89              1      2A90              9.2    9______________________________________ 
    
     
                       TABLE 2C______________________________________HCFC BARRIER RATING - A SERIES          Pass - FailSample #         123    141b______________________________________A91              P      PA92              F      PA93              P      PA94              P      PA95              P      PA96              P      PA97              P      PA98              P      FA99              F      FA100             P      PA101             P      PA102             F      PA103             F      FA104             P      PA105             P      P______________________________________ 
    
     From the HCFC barrier data of tables 2A, B and C it can be seen that PVC having an I.V. of 0.54 (A7, A38, A39, A40); as well as PVC having I.V. of 0.68 (A8, A50-54 etc.); CPVC (A31); and PVC blends of different I.V. (A38-A40, A70, A72) can be formulated to give good HCFC barriers as tested. It has been found that various compounding ingredients, when present, interfere with HCFC barrier performance. Therefore these are preferably absent or present at minimal levels in the compounds used to derive articles having contact with HCFC. Liquid plasticizers such as epoxidized soy oil and di-2-ethylhexyl phthalate are detrimental (A38-40, A50-54 versus A28A30). 
     Higher molecular weight plasticizers DIDP, and TOTM for example, did not interfere significantly, therefore when optional plasticizers are used, those having a molecular weight equal or greater than di-2-ethylhexyl phthalate (390) are preferred. Such exemplary phthalates and bisphthalates are n-octyl n-decyl phalate, di-isodecyl phthalate, heptyl nonyl undecyl, di-undecyl phthalate, di-tridecyl phthalate, ethylene glycol bis(n-butyl phthalate) and 7-(2,6,6,8 tetramethyl-4-oxa-3oxo-nonyl) phthalate. Trimellitates can be used, such as alkyl-aryl trimellitate, tri-2-ethylhexyltrimellitate (TOTM) and heptyl nonyl trimellitate. 
     The preferred PVC compounds in the A-layer are those exhibiting adequate barrier properties in at least one HCFC, and most preferably more than one HCFC. Polyvinyl chloride compounds preferably contain: PVC having an I.V. of between about 0.3 and 2.0, preferably from about 0.5 to 1.6 and most preferably from about 0.6 to 1.0. Preferred components include methacrylate-butadiene-styrene polymers; optional chlorinated polyethylene; preferred are acrylic impact modifiers; stabilizer for PVC; lubricants preferably external types; optional plasticizers of preferred molecular weight; optional acrylonitrile-styrene-acrylic (ASA) polymeric modifiers; optional styreneacrylonitrile copolymers (SAN); optional polymeric plasticizers such as: polyesters and polyethers; other plasticizers such as sulfonamides, glycol esters, glycerol esters, chlorinated paraffins; citrates, sebacates, benzoates, phosphates, and adipates. 
     Thermoformability 
     The compositions used to form multilayer layer articles were evaluated for thermoforming performance. A detailed review of sheet thermoforming of PVC compounds is provided in PVC Technology by W. V. Titow, 4th.ed., Elsevier Applied Science, at chapter 16, pp. 743-763. Thermoformable composite sheets of ABS in one layer and PVC in the other layer are known and discussed in Plastics Rubber Weekly, Nov. 23, 1979, pp. 17-26. Any thermoforming method may be used among various methods known in the art of sheet thermoforming, or the thermoforming of cast, or extruded melts. For the sake of brevity thermoforming of prepared sheets will be described by the straight thermoforming method also known as the negative forming method. 
     In the negative forming method a sheet is clamped over a cavity mold and heated until the desired temperature is reached, vacuum is applied from underneath as the sheet is drawn into the mold. Typically, where drawing into a deep mold a heated plug, roughly conforming to the mold shape is used to force the sheet down into the mold while vacuum is applied to complete the process. Sheets may be preheated with infra-red radiant heaters or convection ovens. The temperature most desired for the sheet is that temperature which gives the maximum elongation at break. This temperature depends on the composition of the sheet and can be empirically derived through trial and error. In production thermoforming, acceptable rigid thermoplastic PVC compounds for this process must exhibit a range of performance characteristics including high elongation over a broad temperature range. Conventional PVC compounds used to form single-layer sheets are noted for limited draw-ratio. This is the ratio of original sheet thickness to the maximum thickness at a point which has been drawn to narrower thickness. Rigid PVC compounds typically break at a point where the draw ratio exceeds about 10. Unexpectedly, it was observed that the multilayer PVC articles could be successfully drawn to a ratio of greater than 15:1 and as high as 20:1. At a draw ratio of 20:1, a 140 mil sheet (0.35 cm) sheet was successfully drawn to 7 mils (0.018 cm). 
     In a laboratory method used to evaluate extruded sheets, the sheets were preheated and drawn into a cone-shaped mold. A qualitative rating was used to compare each sample. Higher scores indicate better thermoformability. 
     
         ______________________________________Criteria           Rating______________________________________Large blow out at tip              1good form to cone  9Small blowout at tip              5thin at tip        10thick at tip       8poor tip and cone shape              6-7necking            0______________________________________ 
    
     Rigid PVC compounds of the present invention exhibited a thermoforming rating of 8, more desirably, a thermoform rating of 9 and most desirably a thermoform rating 10. 
     From the Tables below it can be observed that, on the basis of thermoformability, Samples A7, A28, A58 and A76 are most desirable. Polyvinyl chloride having an I.V. of 0.54 (A7) and 0.68 (A28) can be utilized in compounds exhibiting good thermoformability. Noting from the Table above, those samples rating 9 or higher are numerous-A2, A3, A17, A18, A27, A29-33, A37-42, A44, A60, A66, A73, A79, A80, A94, A98 and A103, etc.. The compositions of the samples exhibiting desirable thermoforming ratings of 8 or above show that CPVC can also be compounded with or without plasticizer (A31 vs A32). Samples A38-A41 illustrate that a blend of two different PVC polymers each having a different I.V. of at least 0.2 I.V. units will exhibit desirable thermoforming characteristics. Samples A68 and A69 illustrate that PVC blended with crosslinked PVC will, in compounded form give good thermoforming performance. Blends of PVC, impact modifier and chlorinated polyethylene (A80) show good thermoforming. Blends of PVC and ASA (modifier M6) shown in A76 and A98 are desirable. Blends of PVC and ABS (low rubber) in A103, and with high rubber ABS (A7) are good thermoforming compounds. 
     Good thermoforming characteristics are necessary but not sufficient to define the preferred embodiments of the present invention because other desired properties outlined above should be exhibited. 
     
                       TABLE 3A______________________________________Thermoforming Ratings   Sample         Rating______________________________________   A1    8   A2    9   A3    9   A4    8   A5    8   A6    8   A7    10   A8    --   A9    --   A10   A11   8   A12   --   A13   A14   A15   --   A16   --   A17   9   A18   9   A19   A20   8   A21   9   A22   9   A23   --   A24   8   A25   A26   9   A27   9.8   A28   10   A29   9.5   A30   9.8   A31   9.8   A32   9   A33   9   A34   1   A35   7.2   A36   8   A37   9   A38   9.7   A39   9.8   A40   9.8   A41   9.3   A42   9.5   A43   9   A44   9.8   A45   8.5   A46   9   A47   1______________________________________ 
    
     
                       TABLE 3B______________________________________Thermoforming Ratings   Sample         Rating______________________________________   A48   --   A49   --   A50   8   A51   A52   8   A53   --   A54   8   A55   5   A56   5   A57   8   A58   10   A59   8   A60   9   A61   A62   A63   A64   5   A65   8   A66   9   A67   8   A68   8   A69   8   A70   8   A71   8   A72   8   A73   9   A74   8.5   A75   5   A76   10   A77   8   A78   3   A79   9   A80   9   A81   8   A82   5   A83   8   A84   8   A85   5   A86   8   A87   8   A88   5   A89   8   A90   8   A91   1   A92   2   A93   8   A94   9   A95   7.5   A96   5   A97   10   A98   9.5   A99   8    A100 8    A101 5    A102 8    A103 9    A104 8.5    A105 8______________________________________ 
    
     Chemical Resistance 
     Compounds were mixed in a Henschel mixer, milled on a heated 2-roll mill and cut into 4&#34;×8.5&#34; (10×21.6 cm.) strips of 0.07-0.075 mills. The 4&#34; strips were compression molded and died into 1/2 inch wide (1.3 cm.) strips. 
     Chemical resistance to HCFC compounds was evaluated by a &#34;bent-bar&#34; test. Samples of 1/8 inch nominal (0.31 cm.) thickness were used for chemical resistance testing. These strips were placed on a bend over a round object and retained in this strained position during exposure above HCFC liquid in a closed vessel. Exposure was maintained at ambient temperature for 7 days, after which the samples were observed and rated. The visual test focused on the appearance of crazing at the point of greatest stress where crazing was most likely to occur. Where large cracks were observed anywhere on the sample, a low rating was given. 
     
         ______________________________________Criteria             Rating (PTS)______________________________________1.    Perfect, no cracks,                    10 no distortion or curling.2.    Small cracks on each side                    9 but not completely through.3.    Cracks at ends of strips.                    7.5-8.54.    Curling or distortion                    subtract 1 pt.5.    Exudation minor              subtract 0.5 major (proportional to #)                    subtract 1-2 large blisters (proportional to                    subtract 2-4 size and #)______________________________________ 
    
     As noted from the Tables below, widely varying results were observed after exposure to HCFC. Higher ratings are preferred and can be seen in A6, A16, A18, A20, A21, A24, A26, A32, A35, A49, A50, A52, A53, A64, A68, A69, A71, A81, A85 and so forth. Polivinyl chloride polymers, blends of two polyvinyl chloride polymers and PVC, and chlorinated polyvinyl chloride polymers formulated as in the above listed compounds exhibited good bent bar ratings. Combinations of PVC and CPE; PVC and polyurethane (A24), PVC and nitrile rubber (A35), PVC absent DOP, PVC (I.V. 0.68) blended with PVC (I.V. 1.6) (A71); PVC (I.V. 0.68), crosslinked PVC (A68, A69); PVC in combination with high acrylonitrile ABS, ASA polymers, or acrylate-styrene-acrylonitrile polymer; PVC with MBS and/or acrylic impact modifier are preferred. 
     
                       TABLE 4a______________________________________BENT BAR RATINGS          RatingSample #         123    141b______________________________________A1               9      7A2               6      5A3               8      10A4               10     10A5               7      8.5A6               10     10A7               8.5    6A8               6      5A9               9      7A11              9      7--               --     ----               --     ----               --     --A15              10     9A16              10     10A17              9.5    10A18              9      9A19              9.5    9A20              10     9A21              9.5    10A22              1      1A23              1      1A24              9      10A25              8      7A26              9.5    10A27              8.2    9.1A28              8.3    8.5A29              7      8.8A30              8      8.5A31              8      6A32              8.7    8.7A33              7      6A34              5      8.3A35              9.1    9.3A36              7.8    8.9A37              8      8.7A38              8      9.8A39              7.5    8A40              5.5    7.5A41              8.9    9.5A42              8.3    8.9A43              8.4    9A44              8.5    8.5A45              9      8.7A46              9      8.3A47              8.7    8.8______________________________________ 
    
     
                       TABLE 4b______________________________________BENT BAR RATINGS          Pass - FailSample #         123    141b______________________________________A48              8      9.6A49              9.1    9.2A50              9.2    9A51              9      8.5A52              10     10A53              9.6    9.6A54              9      9A55              8      6.5A56              8.3    6.8A57              8.5    9A58              8      6A59              7.5    6.5A60              8      6.5A61              7      7.5A62              8.3    7A63              8.5    8A64              9      9A65              8      8A66              8.8    9A67              7.5    7A68              9      9.2A69              9.1    9.1A70              5      9.2A71              9.6    9A72              8.3    9.2A73              6.5    8.7A74              6      8.8A75              5      8.7A76              8.5    8.8A77              7.5    7.3A78              9.5    8.5A79              6.5    7A80              9.6    8.3A81              9.5    9.4A82              9.3    8.6A83              8.5    7A84              9.5    8.5A85              9.4    9.1A86              9      9.3A87              8.5    8.3A88              8.0    9.2A89              9.2    8A90              8.5    9______________________________________ 
    
     General Appearance Rating Gels-Gloss 
     The samples evaluated above were also relatively rated in appearance. Sample clarity was given a relative rating and the incidence of gel particle imperfections and surface gloss were numerically rated from 1-10, higher numbers indicating better properties. Gloss was measured by a Gardner® Gloss meter at 60°. 
     Table V illustrates a wide range of performance of the samples in terms of appearance qualities i.e., incidence of gel imperfections and surface gloss. By inspection of the illustrated performance, and the sample compositions, one can identify those compositions such as A3, A5, A8, A42 and A45, etc. which are good in terms of appearance properties such as gels and gloss. 
     
                       TABLE V______________________________________Sample         Gels    Gloss______________________________________A1             --      --A2             --      --A3             9       9A4             --      --A5             9.1     9.2A6             --      --A7             8.6     6A8             8.9     6.0A9             8.6     8.9A10            8.8     8.5A11            8.8     8.8A12            9       8A13            9       9A14            8       8A15            8.8     8.5A16            8.8     8.8A17            6       8A18            8       8A19            9       8.8A20            9       9A21            8.3     9A22            8.5     8.5A23            9.5     9.3A24            9       3.5A25            9       3A26            8.7     4A27            8.5     4.5A28            8.7     8.9A29            8.5     8.5A30            8.6     8.9A31            8.9     9A32            9.2     9.2A33            9       3A34            7       9A35            2       8A36            9.2     9A37            8.3     9A38            8.5     3A39            9.3     9.3A40            8.8     9.3A41            9.5     8.7A42            9       8A43            8.6     8A44            1       8A45            10      9A46            8.5A47            8.6     8.9A48            9.3     8A49            8.5     9______________________________________ 
    
     B Series 
     Various polyvinyl chloride containing compounds as well as chlorinated polyvinyl chloride compounds were evaluated for use as the B-layer of the present invention. The B-layer composition, comprising PVC, blends of two PVC&#39;s, CPVC or a blend of PVC and CPVC will exhibit a higher heat distortion temperature than the composition comprising the A-layer. Sample B-layer compositions evaluated are listed below: 
     
         ______________________________________Sample Composition______________________________________B1    100 parts PVC 4/std. pkg. A/50 phr M15B2    70 parts PVC 2/std. pkg. B/30 phr M14B3    60 parts PVC 2/std. pkg. B/40 phr M14B4    50 parts PVC 2/std. pkg. B/50 phr M14B5    60 parts PVC 2/std. pkg. B/40 phr M15B6    50 parts PVC 2/std. pkg. B/50 phr M15B7    60 parts PVC 2/std. pkg. B/40 phr M22B8    50 parts PVC 2/std. pkg. B/50 phr M22B9    60 parts PVC 2/std. pkg. B/40 phr M20B10   50 parts PVC 2/std. pkg. B/50 phr M20B11   50 parts PVC 2/std. pkg. F/50 phr M20B12   30 parts PVC 2/std. pkg. F/70 phr M15B13   50 parts PVC 2/std. pkg. F/50 phr M14B14   30 parts PVC 2/2.5 phr M21/3 phr methyltin/ 2 phr M17/3.5 phr TiO.sub.2 /2 phr M18/0.8 phr stearic acid/10 phr M12/10 phr M24/70 phr M15/1 phr ester wax/0.5 phr oxidized polyethylene (PE)B15   30 parts PVC 2/2.5 phr M21/3 phr methyltin/ 3 phr M17/5 phr TiO.sub.2 /2 phr M18/6 phr M12/ 1 phr stearic acid/5 phr M24/70 phr M15/ 0.5 phr oxidized PE/1.5 phr ester waxB16   30 parts PVC 2/2.5 phr M21/3 phr methyltin/ 3 phr M17/5 phr TiO.sub.2 /1.5 phr M18/6 phr M12/ 1 phr stearic acid/1 phr mineral oil/1 phr stearic acid/ 5 phr M24/70 phr M15/1 phr oxidized PE/1.5 phr ester waxB17   40 parts PVC 2/2.5 phr M21/3 phr methyltin/2 phr M17 5 phr TiO.sub.2 /1.5 phr M18/6 phr M12/L4/5 phr M24/ 35 phr M15/25 M20/1 phr oxidized PE/1.5 phr ester wax______________________________________ *Sold by BFGoodrich Co., Cleveland, Ohio **Estane ® 58206 polyester urethane sold by BFGoodrich Co.CO 
    
     From the Table below it is noted that the (B) layer compounds exhibit a wide variation in performance under the tests conducted. Sample B1 illustrates the preferred combination of chemical resistance, thermoforming and barrier properties. Where (B) layers come in contact with HCFC 141b, Samples B2, B3, B4 and B8 will give good performance and are preferred (B) layer components in the multilayer articles. Where contact of the B layer is with HCFC 123, the sample B2, B3, B9, and B10 exhibit good resistance to this HCFC. 
     It has been observed that a PVC compound formulated with from up to 70% by weight of the B layer of acrylic imide or alpha methyl styrene-styrene-acrylonitrile polymers exhibit improved HDT, and thermoforming in a multilayer compositions of the present invention. Formulations suggested above in terms of impact modification, polymer modifiers, stabilizers, and lubrication in combination with PVC and the specified heat distortion improving agents are useful for shaped articles, in particular, thermoformed articles in applications such as inner liners of insulated refrigerator housings and door panels. 
     
         ______________________________________BENT BAR        THERMOFORM   BARRIERSAMPLE  123     141B    --         123   141b______________________________________B1      7.5     10      8          8     10B2      9       9.1     9.5        3     7B3      8.7     9       9          1     6B4      7.8     8.7     --         1     3B5      7       8.5     6          1     6B6      6       7       8          1     5B7      8.5     8       8.5        1     7B8      2       8.7     10         1     5B9      8.7     8       9          1     8B10     8.7     8       9          1     8B11     --      --      9          --    --B12     --      --      8.5        --    --B13     --      --      --         --    --B14     --      --      8.5        --    --B15     --      --      7          --    --B16     --      --      6          --    --B17     --      --      7          --    --______________________________________ 
    
     EXTRUSION OF MULTILAYER SHEETS 
     Samples of PVC compounds were formulated for co-extrusion of multilayer sheets useful for thermoforming into articles having contact with HCFC&#39;s. Two compounds were formulated in such a manner to exhibit melt viscosity as measured by the widely recognized Brabender Plasticorder equipped with a torque measuring device. Each compound, one representing layer (A) and the other (B) were evaluated separately and the torque characteristics noted. Sixty-five grams of polyvinyl chloride compound cubed samples evaluated for Brabender torque were placed into the Brabender bowl heated to 400° F. (204° C.). The cubes were allowed to preheat in the bowl for 3 minutes before starting the mixing. The torque at which fusion began when the mass underwent melt transition was noted as &#34;fusion torque&#34;. Beyond that point, the melt viscosity decreased characteristically to what is referred to as &#34;Min. Torque&#34;. This torque at the minimum is characteristic of equilibrium torque exhibited during continuous melt processing as in production extrusion processes. The sample temperature is monitored with a thermal probe attached on the Brabender bowl and which protrudes into the sample as it passes. Torque is measured in meter-grams. Brabender torque measurements are considered accurate to ±100 meter grams. A more precise measurement can be obtained by the use of a capillary rheometer, but for the purpose of demonstrating the invention herein, Brabender torque measurements were obtained. 
     Torque matching two or more compounds for optimum multilayer coextrusion can be achieved by a process of trial and error in the use of the various polymeric modifiers such as processing aids, lubricants, plasticizers, and by selecting molecular weights of various components in order to match the minimum torque exhibited. Much art is involved and the practitioner may use various approaches in arriving at desired torque-matched compounds. By trial and error two examples of two-layer compounds were made and given below. 
     
         ______________________________________ITEM      Wt. PARTS  ITEM        Wt. PARTS______________________________________(A) Layer No. 1  (B) Layer No. 1______________________________________PVC 2     100        PVC 2       50M21       2          M20         50Stabilizer     2          M21         2M17       3          Stabilizer  3TiO.sub.2 4.5        M17         1M18       1          TiO.sub.2   3.5M12       2          M18         1Acrylic Impact     6          M12         6Modifier             Acrylic Impact                            5MBS Impact     8          ModifierModifier             Oxidized PE 0.4L6        3.8        L5          2.2______________________________________A) Layer No. 2   (B) Layer No. 2______________________________________PVC 2     100        PVC 2       50M21       2          M20         50Stabilizer     3          Stabilizer  3TiO.sub.2 3.5        M17         0.5Acrylic Impact     6.0        M21         2Modifier             TiO.sub.2   3.5L6        3.8        M18         1.0M12       2          M12         6M25       6          L5          2.5M18       1          M24         5MBS Impact     6          Modifier    8Colorants 0.024      Colorants   0.024______________________________________ 
    
     Each of the above compounds were prepared for co-extrusion by first combining the particulate ingredients on a Henschel® mixer, followed by melt mixing on a Banbury® mixer and treated roll mill. Coextrusion was carried out on a Brabender® extruder having a screw of length/diameter (L/D) of 20:1 and equipped with a 4 inch (10 cm) sheet die/ The following conditions were noted. length/diameter (L/D) of 32:1 and equipped with a 44 inch (112 cm.) sheet die to produce a 3-layer sheet as an A-B-A configuration. The following conditions were noted. 
     
         ______________________________________      Temperature °F./°C.      A1     A2       B1       B2______________________________________Henschel ® drop        250/121  250/121  250/121                                 250/121temp.Banbury ® drop temp.        356/180  356/180  358/181                                 358/181Banbury stock temp.        388/197  388/197  354/195                                 384/195Brabender torque min.        1300     1100     --     --meter-grams______________________________________ 
    
     Preferably the difference in Brabender torque between the layers will not exceed 400 meter-grams. Most preferredly, the Brabender torque values of each layer will not vary by more than about 200 meter-grams. 
     The 3-layer composite sheets were evaluated for heat distortion temperature (HDT) under a 264 psi load per ASTM D-648. Below are heat distortion temperatures of A, B layer sheets and the multilayer sheet. The preferred multi-layer articles derived from the above described compositions thus will have one layer which exhibits a heat distortion temperature (HDT), measured as a single layer, of at least 3° C. (5° F.) higher than the HDT of the other layer. 
     
         ______________________________________      HDT °F./°C.______________________________________A Layer      Approx. 158°/68°B Layer      Approx. 181°/83°Multilayer   Approx. 174°/79°______________________________________