GB2254329A - Polyvinyl chloride blends - Google Patents

Abstract

A polymer blend useful in applications requiring heat distortion resistance under low load, comprises polyvinyl chloride and a copolymer of vinyl aromatic, e.g. methylstyrene, and alkyl (meth)acrylate.

Description

HEAT DISTORTION IMPROVERS This invention relates to poly(vinyl chloride) blends with improved resistance to distortion under low load. Specifically, it relates to poly(vinyl chloride) blends with an immiscible or partially immiscible crpolvTner rom-priced of a-methylstyrene units and methyl methacrylate units.

BACKGROUND OF THE INVENTION Poly(vinyl chloride) has been widely used in rigid compositions since the discovery of suitable stabilizers against thermal decomposition and processing aids to aid in the processing of such materials. Its combination of relatively reasonable toughness, and good flame resistance, plus its ability readily to be toughened by a variety of impact-strength modifiers, has made it useful in food packaging, bottling, extruded and injection molded containers and packaging applications, for housing of many components, for extnided profile, including foamed profile, and for exterior siding applications.

A deficiency of poly(vinyl chloride) (PVC) in several of these applications has been its relatively poor resistance to distortion at elevated temperatures, either under its own weight, or when further stress is applied. Thus in the packaging of foods, such as ketchup, jellies, and the like, where hot-fill processes are used, the package has distorted under the weight of the hot filling material. In housings for electronic components, where heat is generated, the endosures formed from PVC distort at unacceptably low temperatures compared to other engineering resins. Vinyl siding in dark colors tcrds to distort or ripple (known as "oil-canning") under summer exposure conditions.

Different polymers when blended together are said to be compatible with each other when the resulting blend is either one phase (polymers are misdble) or two phases (polymers are immiscible or partially miscible) provided that the blend results in a polymer blend having good mechanical and physical properties. Different polymers when blended together are said to be incompatible and are generally immiscible with each other when the resulting blend has poor mechanical or physical properties.

The terms "miscibility" and "miscible" as used hereinafter shall mean the ability or tendency of one polymer to mix or blend uniformly with another polymer in the way that methanol is miscible with water, or in the sense that one polymer is soluble in another polymer. The term "immiscible" as used herein is descriptive of polymers of the same phase or state of matter that cannot be uniformly mixed or blended, i.e. oil and water are "immiscible". There are certain materials that are partially miscible or partially immiscible with one another in certain circumstances.

Blends of two or more polymers have often been made, for example in attempts to combine desirable properties of the individual polymers into the blend, to seek unique properties in the blend, or to produce less costly polymer products by inducing ..g less e^ens.-çe or scrap polymers in the blend. Polymers tend to form blends that contain domains of the individual polymers; in the case of "miscible" polymers these occur at the molecular scale, resulting in properties usually considered characteristic of a single polymer. These may include occurrence of a single glass transition temperature and optical clarity.

Such blends are frequently termed "alloys". Such properties as tensile strength, which rely upon adhesion of the domains to one another, tend not to be degraded when miscible or partially miscible polymers are blended.

Unfortunately many polymers are poorly compatible with one another. Poor compatibility cannot necessarily be predicted accurately for a given polymer combination, but in general it may be expected when non-polar polymers are blended with more polar polymers.

Poor compatibility in a blend is apparent to those skilled in the art, and often evidences itself in poor tensile strength or other physical properties, especially when compared to the tensile strength or physical properties of individual component polymers of the blend.

Microscopic evidence of poor compatibility may also be present, in the form of large, poorly adhered domains of one or more polymer components in a matrix of another polymer component of the blend.

As noted above, compatibility is not easily predicted. As a general rule non-polar polymers are poorly compatible with more polar polymers, but poorly compatible blends may also be found experimentally among polar-polar or non-polar-non-polar blends.

Much research has been directed toward finding ways to increase the compatibility of poorly compatible polymers when blended.

Approaches that have been used include adding to the blend polymers which show compatibility with the other, mutually incompatible polymers; such added polymers act as a bridge or interface between the incompatible components, and often decrease domain size.

Chlorinated polyethylene has been used as such an additive polymer, especially in blends of polyolefins with other, poorly compatible polymers.

Graft polymers, as of incompatible polymers A onto B, are known to aid in blending polymers A and B. Such graft polymers may also serve to aid in blending other incompatible polymers C and D, where A and C are compatible and B and D are compatible.

What has also been difficult to predict in polymer science is the extent to which such a graft polymer will be effective in enhancing desirable properties of the blend over those of the incompatible blend alone. Consequently, those skilled in the art have had to treat each combination of graft polymer and other component polymers of a given blend as a special case, and determine experimentally whether an improvement in such properties as ;.e,.lc strength could be obtained by adding a specific graft polymer to a specific blend.

A variety of polymers believed to be compatible with PVC have been studied for this use. It has been felt that miscibility was required for clarity purposes in packaging, for achieving effectiveness in raising the heat distortion resistance, and for uniformity in blending. Such polymers have included homopolymers of methyl methacrylate, copolymers of methyl methacrylate with bicyclic methacrylates, such as isobornyl methacrylate, ter-polymers of a-methylstyrene, acrylonitrile, and methyl methacrylate, imidized polymers of methyl methacrylate, and the like.

Modifiers for glassy amorphous PVC can be categorized into six groups. These groups are: 1) High-efficiency impact modifiers, used in opaque compounds where impact resistance is the major consideration.

2) Clear impact modifiers, used when optical and impact properties are called for.

3) Heat distortion modifiers, used to increase the service temperature of PVC.

4) General purpose modifiers, used to provide some basic improvements to impact resistance, hot strength, and low-temperature flexibility.

5) Weatherable modifiers, used in out-dcor application nd to provide some resistance to UV degradation.

6) Processing aids, used to improve the melt properties of PVC by decreasing fusion time.

Heat distortion modifiers increase the effective thermal use temperature of PVC. Adding heat distortion modifiers to PVC increases rigidity, has minimal effect on tensile strength, and often lowers impact resistance strength. These modifiers are usually composed of poly alpha-methyl styrene/acrylonitrile (AMS/AN) or glutarimides. The AMS polymers increase the PVC heat distortion by the steric hindrance of the methyl groups attached to styrene. The glutarimide polymers increase heat distortion of the PVC matrix via the heterocyclic ring structure which increases polymer chain rigidity.

SUMMARY OF THE INVENTION We have discovered a polyvinyl halide blend comprising from about 50 to about 92 parts of PVC and from about 8 to about 50 parts of a PVC partially miscible additive copolymer. The partially miscible additive copolymer is comprised of from about 20 to about 40 parts by weight of units derived from vinyl aromatics such as ume & hylstyTene (AMS), or substituted vinyl aromatics such as 2,5dimethylstyrene and 2,4,6-trimethylstyrene with from about 80 to 60 parts by weight of units derived from one or more alkyl acrylates or methacrylates such as methyl methacrylate or ethyl acrylate and the like.

The examples show, at about 8% by weight of total formulation that the additive copolymer, the vinyl aromatic/alkyl acrylate copolymer begins to exhibit partial miscibility in the blend with the polyvinyl chloride. The glass transition temperature (Tg) of the PVC additive copolymer blend with about 8% by weight of the copolymer or greater will be about 800C as determined by ASTM D 3418 test method.

Such PVC blends with the copolymer additive are useful in applications requiring heat distortion resistance-under low load, such as extruded exterior siding, hot-fill packaging applications, and electronic housings. The blend is further useful in filled and foamed applications.

To meet the heat distortion resistance requirements under low stress loads for most applications the preferred PVC-additive copolymer blend will contain between about 8% to as much as about 50% by weight of the additive copolymer and have a glass transition temperature of not less than about 800C.

DETAILED DSCRiPON OF m THE Th4VENON PVC useful in this invention comprises homo- and copolymers of vinyl chloride. Such copolymers will contain at least about 80 weight percent of units derived from vinyl chloride, the remaining units being derived from ethylene, propylene, vinyl acetate, vinyl esters of aliphatic or aromatic acids such as vinyl propionate or vinyl benzoate, styrene, substituted styrenes, such as I2-methylstyrene, alkyl acrylates, such as ethyl acrylate, alkyl methacrylate, such as methyl methacrylate, vinylidene chloride, acrylonitrile, and the like.Other useful vinyl chloride copolymers also include graft copolymers of vinyl chloride onto rubbery substrates such as polybutyl acrylate; vinyl chloride copolymers with polyolefins such as polyethylene, polypropylene, polybutenes, polyisoprene and their copolymers; vinyl chloride copolymers with ethylene-vinyl ester copolymers, ethylene-alkyl acrylate copolymers and the like. For cost and availability reasons, the copolymers of vinyl chloride with ethylene, propylene, and vinyl acetate are preferred. For achieving the highest values of heat distortion resistance, the homopolymer of vinyl chloride is preferred.

Such PVC polymers may be prepared by any of a variety of processes. The molecular weight of the poly(vinyl chloride) homo- or copolymer to be used (for which the abbreviation PVC will be used) may vary depending on the end use. Generally weight a-v-e-age molecular weight values of about 60,000 to about 350,000 grams per mole will be utilized. The higher molecular weight is desirable for extrusion applications, the lower molecular weight for injection molding applications.

The K values for the PVC materials relate directly to solution viscosities of the materials, and indirectly to their molecular weights.

Such K values were determined according to ASTM Standard Test Method D-1243-66, using 0.5 gram of PVC polymer dissolved in 100 ml cyclohexanone, and a viscosity measurement temperature of 250C. The K value for extruded exterior siding is preferably about 67. The K value for injection molding application is about 48 and the K value for bottles and containers is about 58.

The copolymer additives which are copolymers of one or more alkyl acrylates or methacrylates such as methyl methacrylate (MMA) with the vinyl aromatics such as a-methylstyrene (AMS) which contain up to maximum of about 40 weight percent a-methylstyrene.

The copolymer should contain a minimum of about 20 weight percent a-methylstyrene, as otherwise they will not exhibit a sufficiently high heat distortion temperature to improve significantly the heat resistance of the blend. For a balance of good thermal stability, reasonahie I?!jnzerizztion kinetics, sufficiently high molecular weight, and a high enough heat distortion temperature, from about 23 to about 26 weight percent a-methylstyrene is preferred for certain applications.

Preferably the copolymer will contain between from about 20 to about 40 weight percent a-methylstyrene (AMS) from about 80 to about 60 weight percent methyl methacrylate (MMA) and up to about 5 weight percent ethyl acrylate (EA). The weight average molecular weight of the copolymer can vary from about 50,000 to about 150,000 grams per mole. For PVC bottle formulation applications it is preferred to have copolymer containing about 35 weight percent AMS with a copolymer weight average molecular weight of about 90,000 grams per mole.

The preferred copolymer is obtained by reacting AMS and MMA in the presence of a small amount of ethyl acrylate (EA); an AMS/MMA/EA copolymer.

The copolymers may be prepared in bulk, suspension, solution, non-aqueous dispersion, or aqueous emulsion. The temperatures and ratios of monomers are important in obtaining high conversions and thermally stable polymers. Chain transfer agents, such as mercaptans, cycloalkenes, and the like may be useful in controlling the molecular weight and obtaining more stable polymer.

Sulfur containing chain transfer agents which can be used to advantage in the polymerization, not only for control of the molecular weight and hence of the viscosity and the processing of the copolymer, but also to increase its thermal stability, are primarily the alkyl mercaptans, for example n-butyl mercaptan or tert-dodecyl mercaptan or thioglycolic acid esters such as thioglycolic acid 2-ethylhexyl ester, and also thiophenol or polyfunctional mercaptans having from 2 to 6 mercaptan groups.

Preferred for preparing and isolating the partially miscible copolymer is an emulsion polymerization technique, as follows: The monomeric compounds are polymerized as a monomer blend in an aqueous medium at temperatures ranging from about 30 C. to 1500 C., the weight ratio of the amount of water to the amount of a-methylstyrene and methyl methacrylate monomers ranging from 70:30 to 30:70, and preferably 62:38.

The polymerization initiators used may be water soluble peroxygen compounds such as alkali metal persulfate or hydrogen peroxide, for example, but also organic peroxides or redox systems such as sodium pyrosulfite/potassium persulfate or preferably t-butyl hydroperoxide/sulphoxylate of sodium formaldehyde. The amount of initiator may vary greatly from a low of less than about 0.01% up to about 1.0% and preferably from about 0.06% to about 0.5% based on the weight of monomers to be polymerized.

The size of the particles in the dispersion is of- particular importance. Very finely divided polymer dispersions are preferred. As a rule, the particle diameter should range from 40 to 1000 nanometers (nm), preferably from 40 to 300 nm, and most preferably from 50 to 300 nm. The preferred copolymer of methyl methacrylate and alphamethylstyrene will have a particle size of from about 70 to about 120 nanometers. The partides size can be determined by means of an electron microscope or an ultracentrifuge.

The emulsifiers employed should be used in amounts of less than 2.0 percent, preferably 1.8% or less by weight of the water phase.

The emulsion polymerization is preferably carried out under an inert gas (nitrogen, argon, etc.). It can be run either as a single kettle process, a gradual addition process, or a continuous process. In the batch process all monomers, chain transfer agents, auxiliary agents, etc., are charged together in a stirred tank reactor. Quite generally, processes are particularly preferred in which over 45 percent, and preferably over 90 percent, by weight of the total monomers is added to the polymerization mixture before about 20 percent and more preferably about 10 percent by weight of the monomers are polymerized. For a continuous process, a tubular reactor or cascaded stirred tank reactors are particularly suitable. It is preferable to use a batch gradual addition process.Care should be taken to add as little inhibitor, for example atmosDheric oxygen, as possible with the monomers. Rather, care should be taken to carry out the polymerization with the smallest possible amount of initiator, and hence with the lowest possible initiator/chain transfer agent ratio.

Moreover, the isolation of the copolymer, and hence the separation of water and with it the separation of substances interfering with the further processing of the polymer, are effected by methods for separating solids such as spray drying or coagulation.

If the additive copolymer is prepared by emulsion polymerization, the polymer may be spray-dried to form a fine powder, or it may be coagulated, preferably at high temperatures, and washed, or it may be added as the emulsion to a devolatilizing extruder containing coagulant, the water removed as liquid, and the polymer isolated as pellets. Prior to or during isolation, stabilizers, antioxidants, and the like may be blended with the additive copolymer.

For ease in processing with PVC, it is preferred that the copolymer (hereinafter called the "additive copolymer") be comminuted in particle size. If the additive copolymer is prepared in bulk, the polymer may be crushed, processed by solvent extraction, devolatilization or the like, to remove unreacted monomers, and then ground to small chunks or extruded into pellets. If the additive copolymer is prepared in suspension the particle size is acceptable, but it may be desirable to remove redua1 monomers. The additive copolymer and other ingredients are preferably blended with the PVC particles prior to the processing operations.

As is well known in processing of poly(vinyl chloride), usually more than one additive will be present in the PVC/ additive copolymer blend. Other additives such as toners, lubricants, antioxidants, colorants, ultraviolet stabilizers, hindered amine light stabilizers, impact modifiers, pigments, fillers, fibers, flame retardants and the like, may be added to the polymer blend, prior to extrusion into pellets, strands, sheet, or film. An effective amount of an additive is that amount which people skilled in the art would add, and which functions to give the polymer blend composition the desired characteristics of the additive. Materials known as "plasticizers" are usually not utilized in more than very small amounts in such formulations for rigid PVC, as they will decrease the service temperature of the resulting product. Known plasticizers include organic esters, and phthalates.

Very low amounts of toners, colorants (e.g. pigments and dyes), and color agents or concentrates can be used to correct undesirable color found in polymers. The following coloring agents expressed by a name or number described in the Color Index [in the Society of Dyers and Colourists, U.S.A.] can be chosen for use in polymer compositions described herein: Pigment Black 7, Pigment Whitc 6, P.b...e,.. l^t"e 21, Pigment Green 7, Pigment Blue 15, Solvent Orange 60, Solvent Red 179, Solvent Green 28, Solvent Blue 45, Solvent Blue 101, Solvent Violet 14, and Disperse Yellow 54. An example of a useful toner is Irisol NTM (1-p-Toluidino, 4 hydroxy anthraquinone). Further, the use of blue colorants are preferred for correcting yellowness problems.

Lubricants are well-known components of acrylic-based molding materials, serving to prevent stickage to hot metal surfaces and release from the mold or die lips. Such lubricants include high molecular weight alcohols, such as those of twelve to twenty-four carbons, esters, especially long-chain alkyl esters of high molecular weight aids, such as butyl or stearyl stearate, monoesters of glycols, such as ethylene glycol monostearate, and the like. Preferred is stearyl alcohol. Levelsof lubricants, when used, may range from about 0.05 to about 0.50 weight percent on polymer; preferred is about 0.30%.

Antioxidants (thermal stabilizers) for the processing and molding may be present without detracting from the ultraviolet stability of the stabilized composition. A preferred class of thermal stabilizers are organophosphites, such as tris(aryl)-or tris(alkylaryl)-or tris(alkyl)-phosphites. Another preferred class is that of organophosphonites, such as trisaryl, trisalkaryl-or aryldialkaryl phosphonites, such as aryl-di(alkylphenyl)phosphonites. Preferred are neirl-stable tris(2-alkylaryl) phosphites, such as tris(2-tertiary alkylaryl) phosphite, or aryl di(2-alkylaryl) phosphonite. Especially preferred thermal stabilizers are tris-(nonylphenyl) phosphite, tris(2,di-tert- butylphenyl) phosphite, distearyl pentaerythritol diphosphite [Weston 618TM] and tetrakis (2, 4-tert butylphenyl) 4,4'-biphenylene diphosphonite. Another preferred class of anti-oxidants are thioesters, such as dilauryl thiodipropionate, ditridecyl thiopropionate, and distearyl thiodipropionate.

The polymer blend may also contain ultraviolet stabilizers.

Ultraviolet stabilizers are well-known additives for thermoplastics, and indude hydroxy benzophenones, salicylate esters and benzofriazoles.

The amount of ultraviolet stabilizer needed is from about 0.10 to about 0.50 weight percent of the polymer composition. For ultraviolet light stability (ultraviolet light stabilizers), hindered amines are useful.

Examples of hindered amines which can be employed include: bis (2,2,6,StetramethylOpiperidinyl) sebacate; 2,2,6,6- tetramethyl-4- piperidinyl) benzoate; 1,2,3,4-tetrakis- (2,2,6A-tetramethyl- piperidinyl)butane tetracarboxylate; 1,2-bis (2-oxo-3,3,5,5 tetramethyl-1- piperidinyl) ethane; 1 -(3,5-di-tert-butyl-4-hydroxyphenyl)-2,2-bis (2,2,6,6tetramethyl-4- piperidinyloxycarbonyl)-hexane; poly(1-oxyethylene (2,2,6,6-tetramethyl-1,4-piperidinyl) oxysuccinyl;N,N'bis (2,2,6,6 tetramethyl-4-piperidinyl) -1 ,6-hexanediamine; (4-hydroxy-2,2,6,6 tetrrnthyl- 1-psreridme ethyl; p^!y(2-(',',3,3- tetraethylbutylimino)-4,6-triazinediyl- (2,2,6,6-tetramethyl-4piperidinyliminohexamethylene-(2,2,6,6-tetramethyl-4- piperidinyliminohexamethylene- (2,2,6,6-tetramethyl-4piperidinyl)imino) or their N-methyl derivatives.

Examples of benzotriazole stabilizers functioning as absorbers of the harmful portion of the UV spectrum, are 2-(2'-hydroxy-5'methylphenyl)benzotriazole; 2-(2'-hydroxy-3'-5'-di-tert-butyl)5chlorobenzotriazole; 2-(2'-hydroxy-3'-tert-butyl-5-5'-methylphenyl)5chlorobenzotriazole; 2-(2'-hydroxy-3 '-5'-di-tert-butyl-phenyl) benzotriazole; 2-(2'-hydroxy-5'-tert-butylphenyl benzotriazole; 2-(2'hydroxy-5'-octylphenyl) benzotriazole, of which 2-(2'-di-hydroxy-5'methylphenyl) benzotriazole and 2-(2'-hydroxy5'-tert-o ctylphenyl) benzotriazole are preferred.

The PVC blend should include a PVC stabilizer. Suitable antioxidants for poly(vinyl chloride) include a wide variety of stabilizer systems that are comprised primarily of acid acceptors such as metallic salts or soaps. Common to all PVC stabilizing agents or coagents is their ability to react with hydrogen chloride that has evolved from PVC resin degradation. Preferably an organotin mercapto-type stabilizers, or alkytin maleate derivatives are used. Specific PVC stabilizer include dibutyl tin bis(lauryl mercaptide), dibutyltin disorbate, dibutyltin furoate, dibutyltin dicinnamate, dibutyltin malet etc.

From about 0.1 to about 25 percent by weight flame retardant can be employed, preferably compounds of bromine, chlorine, antimony, phosphorus aluminum trihydrate, certain organic compounds containing two or more hydroxyl groups, or mixtures thereof. More specific examples of flame retardants are triphenyl phosphate, phosphonium bromide, phosphonium oxide, tris(di-bromo propyl) phosphate, cycloaliphatic chlorides, chlorinated polyethylene, antimony oxide, ammonium polyphosphate, decabromo-diphenyl ether and chlorinated polyphosphonate.

A wide variety of fillers can be employed. Surprisingly large amounts of filler such as hydrated alumina can be blended with the polymer blend, up to about 60 to 70 percent, while maintaining thermoformability. On the other hand, most thermoplastic systems cannot accept more than about 40 percent inert filler with retention of thermoformability. The novel polymer blend can be blended with glass reinforcement to enhance strength, stiffness, creep resistance and deformation resistance at high temperatures and to reduce the thermal expansion co-efficient. The compatibility of the glass reinforcement with the novel polymer blend is usually high and frequently permits the use of glass reinforcement which has standard coupling agents rather than specially prepared reinforcements.Examples of reinforcing or filler materials which may be used separately, or in combination glass fibers, polymeric fibers, glass beads, titanium dioxide, talc, mica, clay, and the like. They may also be used in combination with other polymers with which they are compatible.

While only a few of such materials have been specifically recited, it is not intended to exclude others; the recitation is exemplary only, and each category of additive is common and well known in the art, induding extremely large numbers of materials which are equally well suited for indusion in the materials of the present invention.

Such inclusions in the materials of the present invention can be made at the dry-blend stage of preparation, in accordance with techniques well known to those of ordinary skill in the art, in proportions which are commonly employed.

To assist those skilled in the art in the practice of the present invention, the following examples are set forth. Parts and percentages being by weight unless otherwise specifically noted.

EXAMPLE - PREPARATION OF ADDITIVE COPOLYMER A latex emulsion containing a copolymer of 74 parts methyl methacrylate, 24 parts alpha-methylstyrene, and 2 parts ethyl acrylate using 0.6 parts of sodium dodecylbenzene sulfonate, 0.2 parts n-dodecyl mercaptan in 150 parts water is prepared by feeding the emulsified monomers and 0.2 parts of sodium persulfate to the aqueous phase over 4 hours at RR , The resulting polym'r contains 40% solids by weight.

The additive copolymer is isolated by feeding the latex, along with a 4% aqueous solution of calcium hypophosphite (0.8% on solids:solids basis) into a coagulating extruder. The resulting coagulum is fed directly into a non-intermeshing twin screw extruder where water and water soluble salts are removed through a dewatering vent.

The copolymer passes through a devolatilizing zone to remove residual water and other volatiles, and is then expelled as a strand, cooled and cut into pellets. The pellets, either as extruded or after comminution to reduce the particle size, are dried at 600C for 12 hours.

The material is then ready for blending with the PVC.

Alternately, the copolymer may also be isolated by spray drying or other coagulation methods, in which case the dried powder produced is ready for blending and milling with the PVC.

The additive copolymer used in the examples shown in Table 1, 2 and 3 was prepared using 24 parts AMS, 74 parts MMA and 2 parts EA and is partially miscible in PVC.

X varies in the following examples from 5 to 50 parts per hundred parts resin.

FORMULATION Ingredient Parts per hundred parts resin Polyvinyl chloride 10bX Additive Copolymer X Tin containing Thermal Stabilizer Lubricants Glycerol and paraffin wax 0.8 Processing Aids Acrylic copolymer and a 2.0 multiphase acrylic composite polymer Impact Modifier Methacrylate-butadiene- 15.0 styrene copolymer PVC/Additive Copolvmer Weight%Additive Copolymer in Total Formulation 100/0 o 95/5 4.2 90/10 8.3 80/20 16.6 70/30 24.9 60/40 33.3 50/50 41.6 Each blend was milled for five minutes on a Getty Two Roll Mill. The front roll was at a temperature of 365" F. and turned at 26 revolutions per minute (RPM). The back roll, at 3620 F. turned at 20 RPM.

For the Sag test specimen results presented in Table 3 the milled stock is compression molded. The stock sheet is folded over and over to mold a 6 1/2" x 10" x 1/8" sheet. Compression molding is done at 365"F with a 70 ton hydraulic press using 10 tons pressure for 3 minutes followed by an increase to 70 tons pressure for 2 minutes followed by cool down to 1500F in the press under pressure (5 minutes).

The number of centimeters of vertical Sag from the original horizontal status is measured on a 4" x 1/2" x 1/8" single cantiliver test beam after 30 minutes in an air oven at the temperatures specified in the table. The test specimen is 6" x 1/2" x 1/8" where 2" of test specimen length is held in damps.

TABLE 1: GLASS TRANSITION TEMPERATURE (Tg) SHIFT WITH WEIGHT % ADDITIVE COPOLYMER IN PVC-RICH PE ^,Sw Weight % Additive Copolymer Actual Tg C Actual Calculated* 78 0 0 79 8.3 2.8 81.3 16.6 9.1 82.3 24.9 11.8 83.8 33.3 15.6 83.9 41.6 15.8 *NOTE: The weight percentages shown in the column labeled calculated above were calculated using an adaption of the Flory-Fox equation. This equation is not very accurate, but sufficies to show comparisons between samples. This is evident by the increase in Tg upon each addition of additive copolymer. Tg determined by ASTM D 3418 standard test method.

Table I shows, to achieve a given glass transition temperature (Tg), that the amount of additive copolymer required is significantly greater for a copolymer partially miscible in PVC than the calculated amount for a PVC miscible copolymer.

TABLE 2: HEAT RESISTANCE PROPERTIES High Stress Tests Low Stress Tests DTUFL DTUFL VICAT VICAT TYPE & ommat;264 psi & ommat;66 psi 5kg 1kg C C C C PVC Control 69.2 73.0 73.0 80.0 % Additive Copolymer 4.2 70.9 74.6 74.2 80.0 8.3 69.0 72.5 71.5 82.3 16.6 74.0 77.8 77.9 89.4 24.9 76.3 78.9 80.6 100.3 33.3 78.9 80.4 83.2 108.8 41.6 78.2 88.3 85.2 110.8 DTUFL - ASTM D648 VICAT - ASTM D1525 TABLE 3:CANTILEVER SAG RESULTS (In Centimeters from horizontal) Oven Temperature C 70 75 80 85 900 950 1000 1050 110 PVC Control 1.1 4.6 6.3 6.6 7.5 - - - - % Additive Copolymer 8.3 - 4.0 5.2 6.0 6.3 - - - - 16.6 - - 2.9 3.3 4.4 4.8 - - 24.9 - - " - 1.3 1.7 2.1 6.4 - 33.3 - - - - 0.8 0.7 1.2 4.1 - 41.6 - - - - 0.2 0.8 1.1 1.4 2.7 These examples show that the partially miscible methyl methacrylate-alpha-methylstyrene additive copolymer has high efficiency as a low stress heat distortion modifier ideal for use in PVC resins for injection molding applications where sag resistance is required and superior stiffness at temperatures above 1000 C. is required. (See Table 3).

Example This example illustrates a blend of poly(vinyl chloride) PVC with additive copolymer of AMS/MMA/EA for use in hot-fill bottle applications. The AMS level of the additive copolymer was about 35% by weight, the MMA was about 63% by weight, and the EA was about 2% weight.

The hot-fill bottle formulation based on parts per hundred by weight of PVC resin is shown below. The ingredients were blended and pelletized on an American Leistritz Extruder and the bottles were blow molded on a Bekum Plastics Machinery unit. The bottles were evaluated as shown in the following tables.

TABLE 1 Ingredients Control With Additive Copolymer PVC (K=58) 100.0 100.0 Tin stabilizer 2.0 2.0 Glycerol lubricant 0.6 0.6 Paraffin lubricant 0.2 0.2 Acrylic copolymer 1.0 1.0 processing aid Multiphase acrylic 0.5 0.5 composite polymer processing aid Blue toner (1%) 0.06 0.06 Methacrylate-butadiene 12.0 16.0 styrene copolymer impact modifier Additive Copolymer " 20.0 TABLE 2 HOT-FILL STUDY % CHANGE IN BOTILE WIDTH Without With Hot Fill Additive Additive Temperature OC. Copolymer Copolymer 70 0.23 0.00 75 0.25 0.02 80 0.00 0.00 85 0.46 0.00 90 0.62 0.08 95 1.97 0.00 100 2.47 0.23 TABLE 3 % CHANGE IN BOTTLE HEIGHT Without With Hot Fill Additive Additive Temperature OC Copolymer Copolymer 70 0.09 0.02 75 0.15 0.17 80 0.16 0.17 85 1.00 0.37 90 1.40 0.93 95 2.44 1.32 100 2.22 1.60

Claims (22)

WE CLAIM:

1. A polyvinyl halide polymer blend comprising A) from about 50 to 92 parts by weight of poly(vinyl chloride), and B) from about 8 to about 50 parts by weight of a copolymer of a vinyl aromatic and one or more alkyl methacrylates or acrylates.

2. The blend of Claim I wherein the copolymer comprises from about 20 up to about 40 parts by weight of a vinyl aromatic with from about 60 up to about 80 parts by weight of one or more alkyl acrylates or methacrylates.

3. The blend of Claim 2 wherein the vinyl aromatic is a-methylstyrene and the alkyl methacrylate is methyl methacrylate.

4. The blend of Claim 3 wherein the copolymer further contains up to about 5 parts by weight of another alkyl acrylate where the alkyl group has from one to eight carbon atoms.

5. The blend of claim 4 wherein another alkyl acrylate is ethyl acrylate.

6. The blend of claim 5 wherein the glass transition temperature of the poly(vinyl chloride) rich phase is not less than about 80" C.

7. The blend of claim 6 wherein the copolymer comprises at least about 15 weight % of the polymer blend.

8. The blend of claim 1 which further contains up to about 40 parts by weight of a particulate filler.

9. The blend of claim 7 wherein the weatherable particulate filler is titanium dioxide.

10. The blend of daim 1 further containing reinforcing fibers.

11. An article prepared from the blend of daim 7.

12. The article of claim 11 in the form of extruded siding or profile.

13. The blend of Claim 11 in foamed form.

14. The article of claim 11 in the form of a molded object, sheet or film.

15. A blend of a v mt! halide polymer and not less than about 8.3% by weight based on weight of total blend formulation of a copolymer based on weight of the vinyl halide polymer, said copolymer being partially miscible in the vinyl halide polymer and wherein said copolymer comprises from about 20 to 40 parts by weight of units derived from a-methylstyrene with from about 80 to about 60 parts by weight of units derived from methyl methacrylate.

16. An article prepared from the blend of claim 15.

17. A blend of a vinyl halide polymer and not less than about 15% of a polymer by weight, based on the weight of the total blend formulation of another polymer wherein said another polymer is partially miscible in the vinyl halide polymer phase and said another polymer comprises from about 20 to about 40 parts by weight of units derived from a-methylstyrene, from about 60 to about 80 parts by weight of units derived from methyl methacrylate, and up to about 5 parts by weight of units derived from another alkyl acrylate having one to eight carbon atoms and wherein the vinyl halide polymer rich phase has a glass transition temperature of at least 800C.

18. An article prepared from the blend of claim 17.

19. The article of daim 18 wherein the article is a container and the copolymer contains about 35 parts by weight a-methylstyrene, about 63 parts by weight methyl methacrylate and about 2 parts by weight ethyl acrylate.

20. The blend of daim 1 wherein the copolymer also contains up to about 5 parts by weight of units derived from ethyl acrylate.

21. A process for preparing a polymeric blend of partially miscible polymers for injection molding applications comprising (a) admixing by application of heat and shear sufficient to form an intimate mixture of: (1) a copolymer of alpha-methylstyrene and methyl methacrylate, and (2) poly(vinyl chloride) wherein said polymeric blend has a glass transition temperature of the poly(vinyl chloride) rich phase of not less than about 80"C, and the copolymer is partially miscible in the .poly.(vinyl chloride).

22. The process of claim 21 wherein the copolymer also contains ethyl acrylate.