IL26379A - Thermoplastic polymeric modifiers for vinyl halide polymers,process for making same,and blends thereof with vinyl halide polymers - Google Patents

Description

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This invention relates to solid, thermoplastic polymeric products resulting from a sequential polymerization procedure and it also relates to high impact-resistant and transparent materials which result from blending such products with other polymeric materials, particularly homopolymers and copolymers of vinyl chloride. The copolymers which are of at least one other monoethylenically unsaturated compound copolymerizable therewith, particularly a mono- vinylidene compound (i.e. a compound containing a single CH?=C f group) such as vinyl acetate, methyl methacrylate or styrene.

Rigid and semi-rigid or lightly plasticized vinyl products and compositions have had an impressive grov/th in the plastics industry during the last few years. In part at least, this growth has been facilitated by the advent and commercialization of modifiers for vinyl chloride resins which have the ability to improve processing characteristics, increase impact strength and develop other useful properties in the basic vinyl chloride resin system. Typically, these modifiers are based on an elastomeric copolymer with unsaturation, such as a butadiene-styrene copolymer. Such modifiers, while helpful and useful in nony respects, do not stand up well to outdoor exposure and also cause an appreciable drop in transparency as compared with the unmodified vinyl reerin system.

This invention provides new acrylic modifiers capable of imparting improved impact resistance to homopolymers and copolymers of vinyl chloride.

•V - The modifiers of the invention are sequentially emulsion polymerized polymers as hereinafter defined comprising (A) a crossed-linked rubbery polymer which has a glass transition temperature not exceeding -30° C. and which contains at least 80% by weight of mers of one or more alkyl acrylates having 3 to 8 carbon atoms in the alkyl group and/or one or more alkoxyethyl acrylates having 1 to 8 carbon atoms in the alkoxy group, (B) a cross-linked polymer which is attached to said rubbery polymer (A) and which contains at least 80% by weight of mers of at least one monovinyl aromatic compound and (C) a hard polymer of monoethylenically unsaturated monomers, which contains at least 80% by weight of mers of one or more alkyl methacrylates containing 1 to 4 carbon atoms in the alkyl group and which is attached to (A) and (B).

The term "sequentially emulsion polymerized polymers" refers to polymers (homopolymers or copolymers) which are prepared by the aqueous emulsion technique and in which successive monomers charges are polymerized in the presence of a preformed latex prepared from a prior monomer charge in the preceding stage substantially no new additional and distinct particles being formed after the first stage of polymerisation. ¾ _ In a sequential type of polymerization, the polymer formed in each succeeding stage is attached to and intimately f associated with the polymer formed 'in the preceding stage.

The exact nature of this attachment is not know, and it may be chemical or physical or both.

- - Preferably the modifiers are made in the manner described below. In the first stage, a rubbery cross-linked copolymer is formed by emulsion copolymerizing a monomer charge containing at least 8θ?ά by weight of one or more of the above defined alkyl or alkoxyethyl acrylates and a small amount of a cross-linking monomer.

The emulsion polymerization can be effected with the aid of -afecujj one to three per cent by weight (based on monomer weight) of a suitable eraulsifier and an initiating system, preferably redox in nature. The copolymerization is conducted under such reaction conditions as to form a small particle size latex. Then, as a second stage, and in the presence of the preformed latex, there is polymerized one or more monovinyl aromatic compounds such as styrene, containing a small amount of a cross-linking monomer, preferably divinylbettzene, under conditions such that the cross-linked chains of the aromatic polymer become intimately attached to, e.g. by entanglement with, the cross-linked chains of the acrylate polymer prepared in the first stage. During the second stage, additional initiator may be added, but no additional emulsifier is used, so that essentially no new, additional and distinct particles are produced. Preferably, the monovinyl aromatic compound, used in the second stage, is added gradually. After completion of the second-stage polymerization, a C^-C^ alkyl methacrylate is added and polymerized in the presence of the two-stage latex. Again, no additional emulsifier is used, so that essentially no new additional and distinct particles are formed. More initiator may be used, however, if desired.

The resultant solid, thermoplastic, polymeric product may be isolated from the emulsion by evaporation, by suitable coagulation and washing, such as by salt coagulation, freezing, etc, or it may be isolated as by spray drying.

The physical make-up of the polymeric particles produced by the three-stage emulsion polymerization technique described above most probably consists of (1) cross-linked rubbery acrylate polymers for example poly(butyl acrylate) or poly(methoxyethyl acrylate) and, contained within or intertwined with this rubbery mass, (2) the cross-linked aromatic polymer and (3) surrounding the rubbery mass composed of (l) and (2) and in intimate contact therewith a hard, substantially continuous, layer or cover of the raethacrylate polymer. The nature and proportion of the reactants, the physical make-up or morphology of the polymeric particles and the polymerization techniques used all combine to produce a product which has the desired properties, particularly the impact resistance and light transmission properties, as will be demonstrated more fully hereinafter.

With further reference to the first-stage reactants, the alkyl or alkoxy group in the monomers can be a straight or branched chain. Preferred alkyl acrylates are butyl acrylate and 2-ethylhexyl acrylate. Polymers formed in the first stage must have a glass transition temperature of -30° C. or below (e.g., -35° C, - θβ C. , etc.). Part of the alkyl or alkoxyethyl acrylate, up to a maximum of afcowfc 20$ by weight, can be replaced with a non-cross-linking (with respect to the alkyl acrylate or alkoxyethyl acrylate) monoethylenically misaturated, particularly monovinylidene, monomer copolymerizable or interpolymerizable therewith.

Examples of vinylidene monomers copolymerizable with the acrylate monomer are vinylidene chloride, vinyl chloride, acrylonitrile, vinyl esters, alkyl methacrylic esters and methacrylic and acrylic acids. The cross-linking monomer used is polyfunctional monomer containing two or more functional groups and in general, the amount thereof used is 0,1 to by weight based on the essential acrylate monomer component, with 0.3 to 1.5# by weight being preferred. Suitable cross-linking monomers include divinylbenzone, divinyl esters of di- or tri-basic acids (such as divinyl adipate) , diallyl esters of polyfunctional acids (such as diallyl phthalate) , divinyl ethers of polyhydric alcohols (divinyl ether of ethylene glycol) , and di- and tri-methacrylic and acrylic estersjof polyhydric alcohols. Particularly preferred are the commercially available di- and tri«-methacrylic and acrylic esters of polyhydric alcohols, since they are effective cross-linkers for acrylic esters, and impart better heat stability to the final blend.

Suitable examples are ethylene glycol dimethacrylate , propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1 j butylene glycol dimethacrylate, and the corresponding diacrylates.

With further reference to the second-stage reactants the vinyl aromatic compound is preferably one which is very readily polymerizable in emulsion by free radical techniques. Styrene is preferred, but ring-substituted styrenes such as vinyl toluene, p-isopropylstyrene, 3t^-dimethylstyrcne, etc., as well as halogen-substituted derivatives such as p-bromostyrene or also can^/be used. Part of the styrone (or ring-substituted styrene) up to a maximum of efemtt 20?o by weight, can be replaced with a non-cross-linking (with respect to the styrene) monoethylenically unsaturated monomer copolymorizable ox interpolymerizable therewith, particularly a copolymerizable monovinylideno monomer.

Examples of monomers copolymerizable with styrene are vinylidene chloride, vinyl chloride, acr lonitrile, vinyl esters, alkyl acrylates and methacrylates, and methacrylic and acrylic acids. The cross^Linking agent is a polyfunctional monomer which, in general is used in amount of 0»1 to 5»C$ by weight based on the aromatic monomer, with 0,¾o to 1.0^ by weight being preferred. For optimum clarity, divinylbenzene is the cross-linker of choice; other cross-linkers that can be used include divinyl esters of di- or tribasic acids (such, as divinyl adipate) , dialkyl esters of polyfunctional acids (such as dialkyl phthalate), divinyl ethers of polyhydric alcohols such as the divinyl ether of ethylene glycol, and di- and tri-methacrylic and acrylic esters of polyhydric alcohols; for example, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, ,^-butylene glycol dimethacrylate, etc. In polymerizing the monovinyl aromatic compound in the presence of preformed latex from the first-stage polymerization, it is essential that new additional and distinct particles be avoided, such as would occur if the vinyl aromatic compound polymerized by itself. This can be accomplished by keeping an insufficient supply of cmulsifier present during the second-stage polymerization. Thus, the simplest practice is to rely upon the eraulsifier present from the first-stage polymerization and not add any new emulsifier during the second stage. However, if any emulsifier is added, the amount must not exceed that required to reach the critical micelle concentration. At such low levels of emulsifier, which will vary somewhat with, but can be readily determined for, the particular emulsifier used, the entire amount of emulsifier is concentrated on the preformed particles.

The product resulting upon completion of the second-stage polymerization may be conveniently termed "a two-stage latex." In the third stage* a lower alkyl methacrylate is polymerized in the presence of the two-stage latex. Again, no additional emulsifier is used, so that no new additional and distinct particles are formed. Additional initiator may be used if desired. The lower alkyl methacrylate of choice is methyl methacrylate, but, generally, any lower alkyl ester of methacrylic acid in which the lower alkyl group has a value of to may be used. Preferably, the lower alkyl methacrylate monomer(s) used is or are such as to result in a polymer which has a glass transition temperature of 60° C, or higher. Suitable methacrylates apart from methyl methacrylate, are ethyl methacrylate, isopropyl methacrylate, sec. -butyl methacrylate, tert. -butyl methacrylate, and the like. The hardphase polymeric methacrylate comprises a cover or layer for the softer or rubbery inner mass and imparts compatibility to the product with vinyl halide polymers such as polyvinyl chloride. Part of the lower alkyl methacrylate, up to a maximum of -efeettt by weight, can be replaced with a non-cross-linking monoethylenically unsaturated monomer copolymerizable or intorpolynerizable thcrowithf particularly a motovinylidene monomer. Examples of vinylidene monomers copolymerizable with the lower alkyl methacrylate( s) are vinylidene chloride, vinyl chloride, acrylonitrile, vinyl esters, alkyl acrylic esters, rnethacrylic and acrylic acids, styrene and the like.

Any of a variety of common emulsifiers well known in the art for emulsion polymerization of styrene, acrylates, and methacrylates can be used. A low level of emulsifier is desirable, preferably below one per cent by weight based on the total weight of polymerizable monomers charged.

Useful emulsifying agents include common soaps, alkyl-benzenesulfonates, such as sodium dodecyl benzene sulfonate, alkylphenoxypolyethylene sulfonates, sodium lauryl sulfate, salts of long-chain amines, salts of long-chain carboxylic and sulfonic acids, etc. In general, the emulsifier should be compounds containing hydrocarbon groups of 8-22 carbon atoms coupled to highly polar solubilizing groups such as alkali metal and ammonium carboxylate groups, sulfate half ester groups, sulfonate groups and phosphate partial ester groups.

The polymerization medium in each stage will preferably contain a suitable oil-soluble, water-i soluble, free radical generating polymerization initiator, which is activated either thermally or by an oxidation-reduction (or redox) reaction. The preferred initiators are those which are the result of redox reactions, since they allow rapid polymerization at low reaction temperatures. Examples of suitable initiators are combinations such as cumene hydroperoxide-sodium metabisulfite, diisopropylbenzene hydroperoxide-sodium formaldehyde sulfoxylate, tertiary butyl peracetate-sodium hydrosulfite and cumene hydroperoxide-sodiuin formaldehyde sulfoxylate, etc* Water-soluble initiators may also be used, although less desirable; examples of such initiators or initiator combinations are sodium persulfate, potassium persulf te-sodium formaldehyde sulfoxylate, etc.

The sequential emulsion polymerizations can be Λ/' carried out at temperatures ranging from -efeewt 0° C, to 90° C. , with 30° C* to 70° C. being preferred. The polymerization medium may contain, in accordance with known practice, a chain transfer agent such as tertiary dodecyl mercaptan, secondary butyl mercaptan, normal dodecyl mercaptan, and the like, particularly for limiting, where desired, the molecular weight of the alkyl raethacrylate phase. The free radical initiator will be used in an effective amount, which will vary depending on the monomers, the temperature and the method of addition, but, generally, the quantity of __> /i initiator will vary from -abau-t 0.001 to 2% by weight " in each polymerization stage based on the weight of the monomer charge, with up to a maximum of -abouti- by weight based on the total weight of the monomers charged.

In order to achieve such objects as enhancement of impact resistance and transparency or matching of refractive index when the acrylic modifier is used with vinyl halide resins, the relative proportions of the major constituents of the acrylic modifier should, in general, be within the range of kO to 60 parts of the first-stage alkyl and/or alkoxycthyl aerylate monomer(s), 60 to ho parts of the second-stage monovinyl aromatic monomer(s), and to 100 parts of the third-stage lower alkyl raethacrylate monomer(s), all parts being by weight. A preferred range is ^5 to 55 parts alkyl and/or alkoxyothyl acrylate monomer(s), 55 to k parts aromatic monomer(s) , and to 60 parts methacrylate monomers, all parts by weight.

Blends of the acrylic modifiers of the present invention with other polymeric materials may be prepared by techniques known in the art. Frequently, a dry blend of the modifier and other polymeric material such as polyvinyl chloride is first prepared. Intimate fusion or fluxed lands of the acrylic modifier and other polymeric material such as polyvinyl chloride can be prepared by admixing on or in conventional equipment, for example, on a heated two-roll mill, a Banbury mixer, an extruder, etc.

The product can then be pelletizod, if desired, for use in further moulding or forming operations. On a weight basis* the most useful range of blends is about one part to 50 parts of acrylic modifier per 100 parts of vinyl halide resin, with five parts to 30 parts of acrylic modifier per 100 parts of vinyl halide resin being preferred.

Convenient and customary operating conditions for preparing blends of the acrylic modifier with polyvinyl chloride and the like are 00° F. and from 5 to 15 minutes' time on a two-roll mill. Milled blonds can bo compression moulded, for example, at a temperature of about 3 0° F. and a pressure of 1800 p.s.i. Injection moulding can take place under a variety of conditions, depending mostly on the molecular weight of the polyvinyl chloride used and the equipment employed for such purpose.

Certain processing aids, such as stabilizers and U.V, absorbers, are often incorporated in the blends.

The stabilizers, which serve to prevent breakdown of the polyvinyl chloride, are of several different types commonly available and well known in the art. Some help to stabilize against heat-caused degradation and some against ultra-violet light. Representative ultra-violet absorbers include, for example} 2(2l-hydroxy-5,"Eiethylphenyl)-benzotriazole, available under the trademark "Tinuvin P"; S-hydroxy-f-methoxybonzophenone; representative heat and light stabilizers include, for example, dibutyltin bis(isooctyl acetomercaptide) , available under the trademark "Advastab TM-180"; dibutyltin bis(dodecyl raercaptide) , available under the trademark "Advastab TM-918 ; dibutyltin maleatej dibutyltin laurate-maleate; barium, cadmium phosphite* epoxide combinations, and many others. Typically, such stabilizers are based upon tin, barium or cadmium compounds, as noted above and as will be seen from the examples below. In those situations where clarity is not necessary, common pigments, colouring matter and dyes may be incorporated in the acrylic-vinyl halide systems.

The acrylic modified polyvinyl halide compositions of this invention are tough, rigid, thermoplastic, chemically resistant materials having high impact strength over a wide range of temperatures, excellent resistance to light and oxidative degradation, and excellent optical properties, such as transparency and freedom from haze (when unpigmented) » They are useful in forming sheet for vacuum forming operation, moulding compositions, particularly for blow-moulded bottles, injection moulding, extrusion moulding, etc. The compositions may be formed into plastic pipe and extruded products of similar nature, into films useful as free films and for laminates or for protective layers such as in building and construction panels. Other applications include moulded signs, light covers, and general lighting and architectural applications.

The invention described above is illustrated more fully by the following examples and tables. Unless otherwise noted, all parts and percentates are by weight.

Example I Preparation of Acrylic Modifiers and Blends Thereof with Polyvinyl Chloride To a suitable reaction vessel equipped with stirrer j degassing tube, thermometer, and addition funnel are charged 5500 parts deionized water, 1^7 parts of a 10 aqueous solution of sodium lauryl sulfate and 732.5 parts n-butyl acrylate, 7·3 parts 1 ,3-butylene glycol dimethacrylate, 0.7 part glacial acetic acid, and 1.83 parts diisopropylbenzene hydroperoxide (DIBHPj · The temperature is adjusted to 306 C, and the pH determined to be 2- , The solution is sparged with nitrogen entering under the surface for 60 minutes. Δ previously degassed solution of 1.46 parts sodium formaldehyde sulfoxylate in 50 parts of water is then added. An immediate exotherm occurs. Fifteen minutes after the peak temperature occurs, which may range from 4-5 to 55° C., depending upon the equipment chosen, a degassed mixture of 1.98 parts sodium formaldehyde sulfoxylate in 20 parts water is added, followed immediately by the gradual addition over an 80-85 minute period of a degassed mixture of 793·5 parts styronc, 3.97 parts of DIBHP, and 3.97 parts of divinylbenzono. After addition of this mixture, the temperature is adjusted to 50° C. and the reaction stirred for one hour. There is then added a solution of O.076 part sodium formaldehyde sulfoxylate in 5 parts water, followed by the gradual addition over a period of about one hour of a previously degassed mixture of 0.38 part DIBHP and 763 parts methyl methacrylato. The reaction is stirred for one-half hourafter the peak temperature is reached, allowed to cool, and the polymer emulsion filtered. The acrylic modifier polymer is then isolated from its emulsion by spray drying.

It can also be isolated or separated by evaporation or by coagulation.

The acrylic modifier polymer is blended with polyvinyl chloride (Diamond ½50, a medium molecular weight material), stabilizers, etc., by mixing in a Waring Blendor, then milling the mixture for four minutes at ½00° F. on a differential speedjeompounding roll, folding the mill stock and compression moulding into test specimens at a two-minute pre-heat at 36Ο0 F. , one minute at ^Ο-βΟ tons' pressure. Testing is done by standard methods; total light transmission and haze are determined ori 0.065" thick sheet.

The blends are prepared from polyvinyl chloride, 100-X parts, modifier X parts (where X is 10, 15 or 20) , 2 parts "Advawax 1^0" (trademark for a fatty acid ester processing lubricant), 0.5 part "Hostawax OP" (trademark for a stearic acid processing lubricant) , and two parts "Advastab TM-180" (trademark for a liquid organotin mercaptide stabilizer) . The results are shown in Table I belowe TABLE I Izod impact determined according to ASTM D 256-56 Light transmission determinations made in accordance with ASTM D 1003 (Haze and luminous transmission of transparent plastics) .

Exaaple II Comparison of Non-Cross-Linkod and Cross-Linked Modifiers Example I is repeated except for the following: twenty parts of the acrylic modifier are blended with each 80 parts of polyvinyl chloride; the amount of cross-linking agent employed in the second-stage (styrene) polymerization is varied from 0 to $J in one instance, (II-A), no cross-linking agent is used in the first-stage (butyl acrylate) polymerization. In all other instances, II-B to II-C, the cross-linker for the first stage is the same as in Example I and the cross-linker for the second stage is varied according to the tabulation shown in Table II.

TABLE II Acrylic Divinyl- Li.ght Transmission Izod Impact Modifier benzene, % Total % Scatter ft.-lb,/in. Code % (Haze) 73°F. 50°F. oa 57 27 17.9 3.7 0 56 27 20.2 12 0.2 81 7 25.1 10.0 0.5 85 7 23.6 13.1 II-E 190 83 6 22.8 Example III Particle-Size Variation of First Stage Acrylate Latex The particle size of the first-stage latex can be varied over a fairly wide range, depending upon such factors as the nature of the acrylic ester used, the cross-linker, etc., but, in general and for best results, the particle size radius should be in the range of ateowfe 200-800 A0.

Decreasing particle size tends to increase light transmission properties without substantial change in impact properties.

In obtaining the results tabulated in Table III below, Example I is repeated except that the particle size of the first-stage acrylate latex is varied by adjusting the concentration of the initiator-redox system from 0.2% by weight of sodium formaldehyde sulfoxylate (based on the weight of the butyl acrylate as in Example I) to 0.02% by weight on the butyl acrylate. The particle size radiue in Angstrom (A°) is determined by a soap titration method; see, for example, the method described in Brodnyan and Brown, "J. Colloid Sci.", 15» 76Ο96Ο) .

As in Example IIs 20 parts of the acrylic modifier are blended with each 80 parts of polyvinyl chloride.

TABLE III *SFS is abbreviation for sodium formaldehyde sulfox late.

Example IV Effect of Varying Ratio of Second-Stage Vinyl Aromatic Compound to First-Stage Acrylate In Example I the ratio of butyl acrylate to styrene is 48 parts of butyl acrylate to 52 parts of styrene. A series of modifiers is prepared according to the teachings of Example I, except that (a) the ratio of butyl acrylate to styrene is varied and (b) the amounts of divinylbonzone and diisopropyl hydroperoxide are also varied but the relative amount of each to the styrene is maintained at the same ratio or level as in Example I. The results are tabulated in Table IV. (Twenty parts of the acrylic modifier are blended with each 80 parts of polyvinyl chloride, as in Example II.).

TABLE IV Acrylic Light Transmission Modifier Parts Parts % Total % Scatter Izod Impact Code BA Styrene (Haze) 73°F. 50°F.

IV-A 30 70 67 13 20,3 1.0 IV-B ho 60 83 23*7 7.8 IV-C k 56 86 if 22,0 1.2 IV-D S <* 85 5 23.2 IV-E k3 32. 85 7 23.6 13.1 IV-F 50 50 83 6 2^.2 IV-G 52 i 8 82 8 2kA 11,0 IV-H 55 ^5 75 13 25.5 13.9 IV-I 65 35 61 25 25.1 21.3 Examination of Table IV illustrates that a desirable ratio of the first-stage alkyl aer late, e.g. , butyl acrylate, to the second-stage vinyl aromatic compound (e.g., styrene) is from «.feewt to 55 parts of alkyl acrylate with, correspondingly, efeeut 60 to 5 parts' of vinyl aromatic.

Within these ranges, the refractive index of the acrylic modifier and the vinyl halide polymer (e.g., polyvinyl chloride) are essentially matched. However, and quite surprisingly, in order to achieve the desired objectives, such as good light transmission properties and good impact properties, merely using the polymerizable reactants in proper proportions will not yield the significant and improved results of the present invention. The manner in which the correctly proportioned, polymerizable reactants are, so to speak, put together, the factors of sequential polymerization, avoidance of new particles, cross-linkers, etc., all combine to give the improved results, as is apparent from the following: A series of acrylic modified polyvinyl chloride compositions is prepared.

TABLE V A. Formulation Parts by Weight Polyvinyl Chloride 160 Acrylic Modifier hO Processing Lubricant k Stearic, cid Lubricant 1 Organo-tin Stabilizer h B. Processing All stocks are dry blended (premixed) in a Waring Blendor, then milled for four minutes on a two-roll mill at 00° F. roll temperature, compression moulded at F. and cooled in a separate press, Izod impact tests are run on 1/8" thick nox-ched specimens at 75° F. , 60° F. , 50° F, * and ^0° F. Total light transmission and per cent scatter are measured on 0*065" sheet. Results of testing compositions prepared in accordance with the formulation of Table V are recorded in Table VI below.

TABLE VI * All modifiers are emulsion polymerized and contain 48 parts of n-butyl acrylate and 52 parts of styrene with V/o by weight of 1 , 3-butylene glycol dimethacrylate cross-linking agent based on the butyl acrylate and 0,5$ by weight of divinylbenzene cross-linking agent based on the styrene. Modifiers VI-C and VI-E contain 50 parts of methyl methacrylate in addition to the aforementioned amounts of butyl acrylate and styrene.

It is apparent from Table VI that a blend of poly(n-butyl acrylate) and polystyrene latices when employed as a modifier (VI-A) is defective in both light transmission properties and impact properties; that (VI-B) interpolymers of n-butyl acrylate and styrene are defective in lower temperature impact. Modifier VI-C, which is prepared by polymerizing methyl methacrylate in the presence of a mixture of latices of VI-A, is defective in light transmission properties, while VI-E, prepared by polymerizing methyl methacrylate on a copolymer of butyl acrylate and styrene, is deficient in impact strength even at higher temperatures.

Example V (a) To a suitable reaction vessel equipped with stirrer, degassing tube, thcraoao iir, and addition funnel are charged 5500 parts deiohized water, 1^7 parts of a 10$ solution of sodium lauryl sulfate and 732.5 parts n-butyl acrylate, 7.5 parts 1 , 3-—butylene glycol diacr late, 0.7 part glacial acetic acid, and 1.83 parts diisopropylbenzene hydroperoxide (DIBHP). The temperature is adjusted to 30° C. and the pH determined to be 2-k, The solution is sparged with nitrogen entering under the surface for 60 minutes. A previously degassed solution of 0.1½ part sodium formaldehyde sulfoxylate in parts of water is then added. At£:.. immediate exotherm occurs. Fifteen minutes after the peak temperature occurs, which may range from k$ to 55° C., depending upon the equipment chosen, a degassed mixture of 1.98 parts of sodium formaldehyde sulfoxylate in 20 parts water is added, followed immediately by the gradual addition over an δθ-85 minute period of a degassed mixture of 793·$ parts styrenej 3.97 parts DIBHP and 3.97 parts of divinylbenzene. After addition of this mixture, the temperature is adjusted to 50° C. and the reaction stirred for one hour. There is then added a solution of 0,0?6 part of sodium formaldehyde sulfoxylate in 5 parts of water, followed by the gradual addition over a period of about one hour of a previously degassed mixture of 0,38 part DIBHP and 7^3 parts methyl nethacrylate. The reaction la stirred for one half hour after the pea!k temperature is reached, allowed to cool, and the polymer emulsion filtered. The polymer is then isolated from its emulsion by spray-drying. It can also be isolated by evaporation or by coagulation, (b) Example V(a) is repeated except that allyl methacrylato is substituted for the 1,3-butylene glycol diacrylate as the polyfunctional cross-linking monomer' in the first-stage polymerization, (c) Example V(a) is repeated except that divinylbenzene is substituted for the 1,3-butylene glycol diacrylate as the polyfunctional cross-linking monomer in the first-stage polymerization, (d) Example V(a) is repeated except that diallyl phthalate is substituted for the 1,3-butylene glycol diacrylate as the polyfunctional cross-linking monomer in the first-stage polymerization, (e) Example V(a) is repeated, except that 1,3-butylene glycol dimethacrylate is substituted for the 1,3-butylene glycol diacrylate in the first-stage polymerization and 1,3-butylene glycol dimethacrylate is substituted for the divinylbenzene in the second-stage polymerization, (f) Example V(e) is repatod, except that 1,3-butylene glycol diacrylate is substituted for the 1 ,3-butylene glycol dimothacrylate in the second-stage polymerization.

Stabilized polyvinyl chloride compositions containing the modifiers of Examples V(a)-V(e) at the level of 25 parts of modifier per 100 parts of polyvinyl chloride display the following light transmission and impact performance properties: TABLE VII Light Transmission Izod Notched Impact ft.-lb./in.

Modifier % Total % Scatter (R.T.) (Haze) 73° F. 60° F. 50° F.

V(a) 71 17 21.0 12.* .3 V(b) 70 15 2i ,3 1.6 1.0 V(c) 82 7 22.7 17.9 8.9 V(d) 82 8 2^.2 1^.3 6.5 V(e) 66 19 Z . 17.1 1^.7 V(f) 73 15 25.0 19.9 17.6 Example VI (a) To a suitable reaction vessel equipped with stirrer, degassing tube, thermometer, and addition funnel are charged 5500 parts deionized water, 1½7 parts of a 10# solution of sodium lauryl sulfate and 732· 5 parts 2-methoxyethyl acrylate, 7·3 parts 1 ,3-butylene glycol dimethacr late, 0,7 part glacial acetic acid, and 1.83 parts diisopropylbenzene hydroperoxide (DIBHP). The temperature is adjusted to ° C. and the pH determined to be Z- » The solution is sparged with nitrogen entering under the surface for 60 minutes. Δ previously degassed solution of 0.1½ part sodium formaldehyde sulfoxylate in 5 parts of water is then added.

An immediate exotherm occurs. Fifteen minutes after the peak temperature occurs, which may range from h$ to 55° C. , depending upon the equipment chosen, a degassed mixture of .98 parts of sodium formaldehyde sulfoxylate in parts water is added, followed immediately by the gradual addition over an 80-85 minute period of a degassed mixture of 793·5 parts styrene, 3.97 parts DIBHP and 3.97 parts of divinylbenzene. After addition of this mixture, the temperature is adjusted to 50° C. and the reaction stirred for one hour. There is then added a solution of Ο.Ο76 part of sodium formaldehyde sulfoxylate in 5 parts of watert followed by the gradual addition over a period of about one hour of a previously degassed mixture of 0,38 part DIBHP and 763 parts methyl methacrylate. The reaction is stirred for one half hour after the peak temperature is reached, allowed to cool, and the polymer emulsion filtered.

The polymer is then isolated from its emulsion by spray-drying. (b) The above polymer is evaluated as a modifier for polyvinyl chloride as follows: 1βθ parts of polyvinyl chloride, O parts of the modifier (in this case, the modifier based on the first-stage methoxyothyl acrylate), k parts of an ester-type wax (Advawax 1^0) , and one part stearic acid lubricants and * parts of a liquid organo-tin mercaptide (Advastab TM-180) are blended by premixing in a Waring Blendor, milling for four minutes on a two-roll mill at kOO" F, , and then oonpression-moulding at 400° F.

Izod notched impact tests are run on samples cut from 1/8" thick sheet, prepared as above, at 75° F. , 60e F. , and 10* F. These test results are tabulated below* Light Transmission ( % total,...8k ( % scatter ( (haze) 6.5 Izod Notched Impact ( 75° F 9A ( 60° F 1,7 ( k0° F 1.0 These results may be compared with unmodified polyvinyl chloride which has an Izod notched impact value of about 0.7 at 75° F. (c) Analogous modifier polymers can be made by replacing the methoxyethyl acrylate in (a) above with one of the following: ethoxyethyl acrylate propoxyethyl acrylate isopropox ethyl acrylate butoxyethyl acrylate hexoxyethyl acrylate 2-ethylhexoxyethyl acrylate octoxyethyl acrylate.

Such polymers may be incorporated in vinyl chloride homopolymers or copolymers and exhibit similar improvement in light transmission and impact properties.

Example VII This example illustrates that part of the first-stage alkyl acrylate can be replaced with a monovinylidene monomer copolymerizable therewith and that part of the second-stage vinyl aromatic compound can be replaced with a monovinylidene monomer copolymerizable therewith.

The teachings of Bample I are followed with exception that the following charge ratios are used.

First-stage charge; Butyl acrylate/styrene/ ,3- butylene glycol dimethacrylate = 660 parts/73 parts/7,3 parts Second-stage charge; Styrene/butyl acrylate divinylbenzene = 71^ parts/79 parts/7*9 parts Third-stage charge; Methyl methacrylate = 763 parts.

After isolation of the polymer from the emulsion by spray-drying, the acrylic modifier polymer is blended with polyvinyl chloride as in Example I in the ratio of 20 parts of the modifier for each 80 parts of polyvinyl chloride.

Test results show thatimpact resistance of this composition at 73° F. is greater than 22 ft.-lbs. and light transmission is 83^ total with 5%> scatter. Impact resistance at 60° F. is 17.3 ft.-lbs. , and at 0° F. it is 2.1 ft.-lbs.

Accelerated ultraviolet light exposure tests in a 6OOO watt Xenon light Weatherometer have shown that polyvinyl halide, and particularly polyvinyl chloride, blends or eoapocitians containing the acrylic modifiers of the present invention have excellent impact retention and colour/ gloss durability. A stabilized polyvinyl chloride composition is modified with 20 parts by weight of the acrylic modifier of Example I for each 80 parts of polyvinyl chloride. Initial room temperature Izod notched impact strength is 22.5 ft#-lb./in. After 2^7 hours in the Weatherometer, the impact value is 21.2; after ^ hours the impact value is 19.2; after 1000 hours the value is 19.8; after 1500 hours the value is 19.^5 at the expiration of 2000 hours the impact value is 19·9· Only a very slight change in appearance is noted in colour and gloss after the expiration of the 2000-hour Weatherometer exposure. A comparison is made by substituting as the modifier, in the same stabilized polyvinyl chloride composition as above, parts of a commercially available copolymer having unsaturation (i.e., a butadiene-styrene copolymer) for each 80 parts of polyvinyl chloride. Initial Izod notched impact is 21.1 ft.-lbs./in. ; after 2 ? hours, the impact value is 22.5j after ½99 hours the value is 19.2; after 1000 hours the value has dropped to 10.8; after 1500 h6urs the value is 10.3; at the expiration of 2000 hours the impact value is only >,k* A very noticeable darkening of this composition is noted after the expiration of the 2000-hour Weatherometer test.

The sequentially emulsion polymerized acrylic modifiers of this invention may be Used to advantage in modifying a wide range of vinyl chloride polymers or resins. Thus, Vinyl chloride polymers in the low, medium and high molecular weight ranges can be used, although the improvements become more demonstrable where they are needed most, viz., in the medium and higher molecular weight vinyl chloride resins.

Examples of vinyl chloride copolymers which may be modified are those containing rners from vinyl esters often as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl chloroacetatc, vinyl chloropropionate, vinyl benzoate and vinyl chlorobenzoate; acrylic and alpha-acrylic acids, their alkyl esters and their amides, such as acrylic acid and methacrylic acid, methyl aerylate, ethyl acrylate, butyl acrylate, methyl raothacr late, ethyl methacrylatc, acrylamide, N-methyl acrylaraide, methacrylamide, and various other readily polymerizable compounds containing a single olefinic double bond, especially those containing the CH^C ^ group. The proportions of the various monomers in the monoraeric mixtures polymerized to give ninyl chloride polymers and copolymers may be varied considerably as long as the vinyl halide constitutes at least 60 weight per cent of the total, and, more preferably, at least 8o weight per cent of the total.

Polyvinyl chloride sheet stock incorporating the acrylic modifiers of the present invention can be formed into a multiplicity of useful articles by conventional techniques such as by vacuum forming, thermoforming, etc.

Examples of such articles are, for instance, luggage and luggage covers, electric motor covers, vehicle protective covers, processing trays, bins and containers of all kinds, bottles, etc*

Claims (1)

1. ascertained the nature of our invention is to be 29 declare that we claim A sequentially emulsion polymerized as hereinbefore defined a rubbery polymer which has a glass transition temperature not exceeding which contains at least by weight of of or more alkyl acrylates having to 8 carbon atoms in the alkyl a aromatic polymer which is attached to said rubbery polymer and which contains at least by weight of mers at least one monovinyl aromatic and a hard polymer of monoethylenically unsaturated monomers which contains at mers of least by of one or more alkyl containing 1 to carbon atoms in the alkyl group and which is attached to and A polymer according to Claim wherein the hard polymer has a glass transition temperature of at least A polymer according to Claim 1 or wherein each of the rubbery polymer and the aromatic polymer is with to weight per cent of functional A polymer according to any one of the preceding comprising parts by weight of said rubbery polymer parts by weight of said aromatic polymer and parts by weight of said hard polymer A polymer according to any one of the preceding claims in which the aromatic polymer contains at least by weight of styrene A polymer according to any one of Claims wherein the hard polymer contains at least by weight of methyl methacrylate of by of one or more to Cg alkyl acrylates and by weight of at least one different monovinylidene monomer copolymerizable while in contact with to weight per cent of polyfunctional monomer based on the weight of the first monomer such polymerization being carried out to result in a rubbery polymer having a glass transition temperature not exceeding adding to aaid stage latex a second monomer charge of by weight of at least one aromatic compound and by weight of at least one different monovinylidene monomer copolymerizable and emulsion polymerizing in a second stage said second monomer charge in the presence of a free radical initiator while in contact with to weight per cent of polyfunctional monomer based on the weight of the second monomer charge to form thereby a latexj and adding to said latex a third monomer charge of by weight of at least one to alkyl methacrylate and of at least one different monovinylidene monomer copolymerizable therewith and emulsion polymerizing said third monomer charge in a third stage in the presence of a free radical wherein the total amount of emulsifying agent employed in the process is sufficient to carry out the polymerizations in emulsion but insufficient to allow appreciably the formation of additional new and distinct particles in the second and third A process according to Claim 13 in which there are used parts of the first monomer parts of the second monomer and parts of the third monomer all parts being on a weight A process according to Claim or as applied to the preparation of a polymer according to any one of Claims A process according to modified in that the to Cg acrylate component in the first monomer charge is wholly or partially replaced by one or acrylates having 1 to 8 carbon atoms in the A polymer whenever prepared by a process according to any one of Claims A polymer whenever prepared by a process according to Claim A thermoplastic composition comprising a blend of a vinyl chloride polymer containing at least by weight of vinyl chloride and by based on the vinyl chloride of an acrylic polymer according to Claim A composition according to Claim 19 in which the vinyl chloride polymer contains at least by weight of vinyl chloride A composition according to Claim wherein the vinyl chloride polymer is a A composition according to any one of Claims wherein the acrylic polymer is present in an amount from by weight based on the vinyl chloride A composition according to any one of Claims which is substantially clear and A composition according to any one of Claims in sheet A composition according to Claim 2k containing an acrylic polymer according to any one of Claims A composition according to any one of Claims modified in that the acrylic polymer therein is a polymer as claimed in any one of Claims t 1966 the insufficientOCRQuality