IL32342A - Acrylic modifiers for polymers - Google Patents

Description

Acrylic modifiers for polymers ROHM AND H AS GOMPAIY Ci 30639 The invention is concerned with multi-stage polymers which, when admixed with other polymers, modify the properties of the other polymers in a beneficial manner, processes for their preparation and compositions containing them. In parti-cular the multi-stage heteropolymers of the invention, when admixed with thermoplastic polymers such as vi nyl chloride polymers, yield thermoplastic polymers possessing improved physical properties such as one or more of the following: toughness, hardness, rigidity, impact-resistance , durability and good resistance to deformation at elevated temperatures under load (DTUL). The multi-stage polymers with which the invention is particularly concerned are three-stage heteropolymers wherein the first stage comprises the mers of cross-linked acrylates, the second stage comprises the mers of sty-rene or substituted styrene or mixtures of them, sometimes preferably crosslinked, and the third stage comprises non-crosslinked mers or oo-mers chosen as to composition and as to quantity upon consideration of the following factors: compatibility of modifier with the polymer or polymers to be modi-fied, the effect of the modifier on the DTUL of the polymer, the impact strength desired, and durability upon exposure to the elements including the weather.

Accordingly this invention provides a sequentially polymerised thermoplastic particulate polymer comprising having an average particle diameter of at least 1500 A0 I. a first stage/comprising units of one or more alkyl, alkylthioalkyl or alkoxyalkyl acrylates having from 2 to 14 carbon atoms in the alkyl, alkylthioalkyl or alkoxyalkyl group, the balance (if any) comprising croeslinking units, preferably from one or more copolymerisable polyethylenically unsaturated monomers, II. a second stage comprising units of one or more monovinyl aromatic monomers the balance (if any) comprising units from one or more copolymerisable polyethylenically unsaturated monomers, and III. a third stage comprising units of one or more alkyl, aryl alkaryl or aralkyl methacrylates or acrylates, bicyclic acrylates or methacrylates, halogenated versions of these acrylates and methacrylates, monovinyl aromatic monomers, acrylonitrile and methacrylonitrile . The bicyclic methacrylates or acrylates have the formula: where A is -CHg-, -CH(CH5)-, or -θζθΗ^-, Z is -H or -CH_, M is -H or -CH-j, and n is 0 or an integer from 1 to 5 or, where a mixture of bicyclic compounds is used, has an average value from 0 to 3.

Suitable bicyclic methacrylate or acrylate esters for use in the compounds of the invention are isobornyl methacrylate and acrylate, bornyl methacrylate and acrylate, fenchyl methacrylate and acrylate, isofenchyl methacrylate and acrylate, norbornyl methacrylate and acrylate, and mixtures of those bicyclic methacrylates and acrylates. These esters are known compounds and may be prepared in known fashion, For ex-example , bornyl methacr late may be prepared from -pinene and methacrylic acid, and the isobornyl ester may be prepared from camphene and methacrylic acid in known manner.

The stage II polymer preferably has a second order transition temperature not above -20°C.

The of this invention are effective as impact strength improvers in rigid plastics. or example, the polymers gompeoitiono of this invention are particularly preferred as modi iers¾ for vinyl chloride polymers. For the purposes of ication this specif »_a and claims "vinyl chloride polymers" means homo-polymers of vinyl chloride and copolymers of vinyl chloride with up to 20$ by weight of the total copolymer of one or more other ethylenically unsaturated compounds, and further includes chlorinated vinyl chloride polymers. Preferably, the vinyl chloride polymer employed is a ho opolymer of vinyl chloride, i.e. poly(vinyl chloride). The one or more other ethylenically unsaturated compounds referred to include, for example, vinyl alkanoates, such as vinyl acetate, and vinyl propionate; vinyl halides, such as vinylidene bromide, vinylidene chloride and vinylidene fluorochloride; unsaturated hydrocarbons, such as ethylene, propylene, isobutylene; halogenated (i.e., chlorinated) hydrocarbons such as chlorinated ethylene; allyl compounds such as allyl acetate, allyl chloride and allyl ethyl ether. These unsaturated compounds may be copolymerized O--pol «&y.rae4-i situ with the vinyl chloride or may be polymerized separately and added as a modifier to the polyvinyl chloride to make up the vinyl chloride polymers as defined. ¾e modifiers of this invention may he used in polymers having molecular weights in an extremely wide range, For example, an indication of the preferred molecular weight of those vinyl chloride polymers, preferred and particularly useful, may he obtained by reference to the Fikentscher K-value of the vinyl chloride polymer and those resins having a Fikentscher K-value of about 45 or higher, and preferably between 45 and 0 are suitable for use in the blends of the invention.

Rigid polymers such as vinyl chloride polymers commonly offer limited resistance to sharp impact. It is well known in the art that styrene and substituted styrene polymers, acrylo-nitrile and methacrylonitrile polymers, acrylic polymers, vinyl chloride polymers and copolymers of all these polymers may be toughened by the addition of rubbery materials. SUch common modifiers include butadiene or butadiene-styrene rubbers, acrylo-nitrile-butadiene-styrene modifiers and crosslinked alkyl acryl-ates. These and other common modifiers improve the impact strength of rigid polymers, including vinyl chloride polymers; however, most of the other physical or chemical properties are substantially or even seriously affected. Some of the quiities and characteristics of the polymer most adversely affected includes the DTTJL, mechanical properties such as modulus and strength, weathering resistance as characterized by either appearance and/or reduction of the physical properties, processing characteristics, consistency from batch to batch and within the part calendered, extruded, or moulded therefrom as to the physical characteristics, including impact resistance, impact resistance with pigment or filler loading, clarity and flame resistance.

A particularly critical problem with rigid vinyl chloride polymer compositions is that the articles fabricated therefrom have a relatively low service temperature. In practice, the practical service temperature of thermoplastic bodies is dictated by the softening temperature of the thermoplastic material, or by its heat distortion temperature, or by its deformation temperature under load, said terms denoting the lowest temperature at which the material being tested, of specific dimensions, yields a specified distance under a specified loading (DTUL). Fo example, the service temperatures of reasonably processable vinyl chloride polymers are about 140-l60°F, a temperature range which prevents the material from finding use in many applications; for example, in hot-fill food packaging applications, or in applications involving cleaning temperatures of hot water or even in outdoor applications in the sun, parti-cularly when used in dark colours, -^or example, it is most difficult to retain the service temperature of chlorinated polyvinyl chloride when adding modifiers heretofore suggested for improved processing and/or impact strength. ¾e modifiers of this invention may be used to improve the processing character-istics, in particular thermoformability, and increase the impact strength of chlorinated polyvinyl chloride. Modifiers which improve the DTUL characteristics of rigid vinyl chloride polymers have recently "been introduced in the art. &uc modifiers include polymers containing the bicyclic methacrylates described above, polymers containing ot-methylstyrene, polymers containing acrylonitrile and polymers containing mixtures of these monomers. ¾ese polymers, while they effectively increase the DTUL, may detract from the polymers' resistance to impact or reduce the effectiveness of common impact modifiers, ^-s noted above, common impact modifiers generally reduce the heat distortion temperature or other properties; thus, only a com-promise balance of properties is available in the field, making commercial acceptance limited. ¾e modifier of this invention may be used to obtain a polymer that offers a balance of improvements in all or most of the following characteristics: good impact strength at low levels of incorporation of the modifier, good resistance to DTUL at elevated temperatures, good process-ability, good outdoor weather resistance and good chemical resistance. For example, when the modifiers are included in vinyl chloride polymers, excellent flame resistance may be retained. Also, for example, the inclusion of the modifiers of this in-vention may actually improve the processability of vinyl chloride polymers, i.e., thermoformability. Thus, the polymers of this invention offer substantial advantages over prior art modifiers in most individual characteristics and, further, the balance of properties now offered may be substantially better. ¾e polymers of this invention may be prepared using aqueous emulsion or suspension techniques in three or more stages. Polymerization of each stage should generally and preferably be essentially complete before starting polymerization of a subsequent stage.

Stage I comprises an alkyl, alkoxyalkyl or alkylthioalkyl acrylate crosslinked preferably by di- and/or polyfunctional monomers commonly used in the art. Alternative methods of cross-linking inclu¾ the use of functional monomers which, when post-reacted, give rise to covalent crosslinks. ¾e composition of stage I determines satisfactory retention of appearance and/or physical properties upon exposure to the elements, particularly outdoors. T e alkyl or alkoxyalkyl acrylate chosen depends on the polymer to be modified as well as the amount and type of crosslinker chosen. In general, it is preferred that the alkyl or alkoxyalkyl portion of the acrylate should contain no more than 14 carbon atoms, and is preferably not branched. polymer with a glass temperature less than -20°C is preferred. Acrylate mers preferred include ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, myristyl acrylate, butoxyethyl acrylate, etc. Δ particular preference is n-butyl acrylate, which is particularly effective in modifying vinyl chloride resins, and offers excellent outdoor durability among other advantages. The choice of the crossiinking monomer is not critical and the compounds found effective include 1,3-butylene dimethacrylate, eUylene diacrylate or methacrylate , trimethylolethane di- or triacrylate or methacrylate, trimethylol ropane di- or "tri-acrylate or methacrylate, glyceryl di- or triacrylate or methacrylate., the polyacrylate or methacrylate of pentaerythritol, divinyl or trivinylbenzene , etc. s the amount of 1,3-butylene diacrylate in the first stage of the modifier is increased, the modified compound during extrusion yields reduced swelling of the polymer melt as it emerges from the die-lips, as compared to the size of the die aperture. Δ preferred crosslinking monomer is 1,3-butylene diacrylate. Other difunctional polymerizahle monomers will immediately occur to one skilled in the art as possible substitutions, and these will include diallyl carbonate, diallyl phthalate, diallyl ether, divinyl ether, etc. The ratio of the polyfunctional monomer to the alkyl or alkoxyalkyl acrylate is critical. As the amount of crosslinking monomer is reduced, the modifier may begin to behave erratically and the impact strength of the extruded or moulded part may be much less than desired or the physical properties will be quite sensitive to the processing conditions. s the amount of the crosslinking monomer is in-creased, the impact strength obtained is decreased. The amount of crosslinking monomer can range from about 0.05 to 2.0 per cent and above by weight based en the weight of the alkyl, alkoxyalkyl or alkylthioalkyl acrylate. A preferred range is 0.2 to 1.0 per cent. When stage I is polymerized in emulsion, the particle size at the end of said polymerization may be important. As the particle size is reduced to 1,5008. diameter, the impact strength and other properties may begin to suffer. Particle sizes greater than about 1,600 are preferred. As the particle size is increased o above 2,000 A, the impact strength of the modified polymer con-tinues to improve and there is no known upper limit to the particle size as to the effectiveness of the polymer as a modifier. These particle size measurements may be made by standard light scatter- ing methods (blue light) or by electron microscopy. It is important that as few as possible new particles are generated during the preparation of the second and third stages. It is preferred that essentially no new particles are generated during these latter stages. This may be achieved by maintaining the emulsifier level below the critical micelle concentration except at the beginning of stage I. Also, this condition may be attained by polymerization of a portion of the stage I monomer mix under conditions such that essentially all of the emulsifier is adsorbed on the particles formed. Measurement of the surface tension will indicate if this state has been attained. Surface tension has been found to exceed 60-65 dynes/centimetre. T e remaining monomer mixture may then be charged gradually at an appropriate temperature, or be added incrementally. The batch size, temperature, the cooling capacity of the reactor, etc., all control the time required for addition of the stage I monomer mix. The portion polymerized initially (the seed) may be prepared in situ, or the proper quantity of preformed seed may be used, whichever is convenient.

Stage II is a rigid polymer. Stage II comprises a polymer ^ containing a single CH2=C roup of a mo»«*¾-Hy¾r aromatic compound/such as styrene, a-methyl-styrene, vinyl toluene, tert-butylstyrene , halogen-substituted styrene such as chlorostyre e, dichlorostyrene , mixtures of these monomers, etc. It has been found that, although not necessary, crosslinking of stage II is beneficial in obtaining a preferred balance of properties, consistency of these properties, etc.

The crosslinking monomers listed in conjunction with stage I may all be used for stage II. The monomers preferred for stage II are styrene, divinylbenzene and trivinylbenzene .

The monomer charge for stage II may be added in a single shot or may be added gradually, and an incremental addition is not precluded. The monomers may be emulsified before addition to the batch.

Upon essential completion of the polymerization of stage II, the monomer charge of stage III may be charged. The composition of this third stage depends greatly upon the qualities desired in the modified polymer and on the compatibility of stage III in the polymer to be modified. In the case of vinyl chloride polymers, a mixture of a bicyclic methacrylate described earlier and an alkyl methacrylate, particularly methyl methacrylate, with or without other minor amounts of other monomers has been found to be particularly effective. The type of polymer chosen for the stage III particularly depends upon the level of service temperature desired, the outdoor durability desired and the balance of properties desired. For example, if the polymer to be modified is the vinyl chloride polymer described earlier, and a high resistance to deformation under load at elevated tem-peratures and outdoor weather resistance is desired, the monomers chosen may be .a bicyclic methacrylate and alkyl methacrylate with or without minor amounts of other monomers. Should the interest be primarily in raising the DTUL, the monomers of stage III may a be chosen from the group including ^-methylstyrene, acrylonitrile, and styrene. Should the interest be in modifying the vinyl chloride polymers to provide good impact strength with excellent outdoor durability, the monomers chosen for stage III may be chosen from the group consisting of isobutyl methacrylate, methyl methacrylate and ethyl acrylate. Thus, the monomers satisfactory for inclusion in stage III monomer charge include: the bicyclic methacrylates or acrylates described earlier, alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate; cyclohexyl methacrylate, aryl, alkaryl or aralkyl methacrylates such as phenyl methacrylate, benzyl methacrylate, xylyl meth-acrylate; alkyl acrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate; styrenes such as styrene, ^methylstyrene , ring-substituted styrene such as vinyl-toluene, tert-butylstyrene , halogen-substituted styrene such as chlorostyrene and dichlorostyrene, acrylenitrile and methacrylo-nitrile. The choice depends on the physical properties required and the polymer to be modified and, of couse, mixtures may be used. In all cases, compatibility with the polymer to be modified is a major factor to be considered in the choice of the monomers of stage III. For example, methyl methacrylate or mixtures of the bicyclic methacrylate and alkyl methacrylate with or without other monomers in minor proportions are particularly effective in vinyl chloride polymers. More particularly, mixtures of iso-bornyl methacrylate and methyl methacrylate are preferred. ¾e ratio of isobornyl methacrylate to methyl methacrylate may vary from 5/5 to 5/ 5· ^ all amounts of other monomers may be included in this system. Preferred monomer systems for stage III are those based on major amounts, that is, greater than 5 , of those chosen from the group consisting of alkyl, bicyclic, aryl, cyclohexyl, alkaryl and aralkyl methacrylates and acrylates.

More preferred are those systems for stage III containing greater than JOfo of these acrylic monomers.

The monomer charge of stage III is preferably added as a mixture rather than by adding each monomer separately. Again, the monomer charge may be emulsified before addition to the reaction vessel.

Those emulsifiers generally used in common emulsion polymerization techniques may be employed to prepare the polymers of this invention. Thus, anionic, cationic, or nonionic emulsifiers may be used. Mixtures of these may also be used.

Anionic emulsifiers are preferred and more preferred are sodium or potassium lauryl sulfate and sodium dodecylbenzene sulfonate.

Initiators employed in common aqueous and emulsion polymerization techniques are satisfactory for the preparation of the polymers of this invention. These include sodium, potassium, or ammonium persulfate, with or without reducing agents such as sodium sulfite, sodium metabisulfite, sodium formaldehyde sulfoxylate, sodium hydrosulfite and sodium thiosulfate. ¾e temperature of the polymerization will depend on the nature of the initiator, and the recommended temperatures for each initiating system are well known to one skilled in the art. For example, with sodium persulfate in the absence of a reducing agent, a convenient temperature range is 60-90°C, with 70-80°C preferred.

As noted earlier, each successive stage is polymerized in the aqueous emulsion or suspension of the earlier stages.

Thus, stage II polymerizes primarily on the surface of the particles of stage I. Further, stage III is polymerized primarily on the particles comprised of stages I and II, and so on. It is not known exactly how the subsequent stages attach to the part-icles prepared in the earlier stage or stages. It is possible that the later stages polymerize in such close contact to these particles that covalent forces closely associate the various stages. It is equally feasible that the later stages significantly penetrate into the particles before and during polymeri-zation, thus changing the composition of the earlier stages to some degree. It is also possible that there is essentially little penetration of the particles during the polymerization of the later stages. In this last possibility, the structure of the particles might be described as a core of stage I followed by subsequent sheaths of stages II, III, etc. Unfortun ely, the physical and/or chemical structure of the particle construction is not known exactly and must be described in terms of the components used and the -Applicants do not wish to be bound by any theoretical considerations as to the physical relationship be-tween the stages in the final modifier. ¾e solids content at the end of each stage will depend on the total amount of water and other materials charged during the preparation of the modifi or. It is convenient, but not necessary, to adjust these amounts so that the final solids will be in the range of 30-50 , with 40-45$ preferred.

The ratio of the amounts or proportions between the three stages may be varied widely, depending upon: the polymer to be modified, the "balance of physical properties desired, whether the polymer has already "been modified for improved processing or for increased DTUL, the effectiveness of the modifier with particular polymers, etc. With 100 parts stage I, the amount of stage II may preferably vary from about 10 to about 80 parts and in some cases even up to 100 parts. The amount of stage II is particularly preferably in the range of 10 to 60 parts per 100 parts of stage I. The amount of stage II most preferred is 20 to - parts per 100 parts of stage I. T e preferred amount of stage III per 100 parts of stage I may vary widely from about 20 parts to about 300 parts. In the lower range of about 10 parts to about 100 parts of stage III, the modifier is particularly useful in vinyl chloride resins in which a processing and/or DTUL improver has already been added. In these instances, a range of 20 to 60 parts stage III per 100 parts of stage I is more preferred. In the upper range of proportions of stage III, the modifier is particularly useful in modifying vinyl chloride polymers to provide not only improved impact strength but better processing and substantially increased DTUL. The range of 100 to 300 parts stage III per 100 stage I is preferred. In these instances the more preferred range is 200 to 300 parts stage III per 100 parts stage I. As the amounts of stages II and III are decreased, the physical properties of the modified polymer suffer, in particular compatibility and impact strength. Further, at lower levels of stages II and III, isolation of the modifier, using spray drying technique, becomes increasingly difficult. As the amount of stages II and III is increased, the amount of modifier necessary to impart the desired impact strength must he considered. In the cases where processing modifiers and DTUL modifiers have already been added, lower quantities of stages II and III are preferred. However, when the modifier is designed to impart impact strength and to increase the DTUL, the proportion of stage III is increased substantially. Thus; the larger amount of modifier of this invention necessary to impart the desired impact strength is satisfactory under these conditions. As the amount of stage II is reduced, the impact strength improving effectiveness is reduced, the properties are more sensitive to processing conditions, etc. As the amount of stage II is increased* the amount of modifier necessary to impart the desired impact strength is increased* the outdoor durability is adversely affected, etc.

For example , when the modi iers of this invention are added to chlorinated polyvinyl chloride or chlorinated resins containing more chlorine than the homopolymer of vinyl chloride, the amount of stage III is kept to a minimum in that no DTUL improvement is generally necessary.

As the proportion of stage III is increased, it becomes more desirable to control the molecular weight of this stage.

In other words, when the proportion of stage III is increased in order to improve the DTUL characteristics to a major degree or to act as a processing improver for the polymer to be modified (i.e. about 100 to 3OO parts stage III per 100 parts stage i), the molecular weight of this stage begins to dominate or substantially affect the flow characteristics of the entire modifier and the modified polymer. This is particularly important when the modifiers of this invention are to he used with other polymers to prepare injection molding compounds. Under these circumstances chain transfer agents, such as mercaptans, may be used to control the molecular weight of stage III. Other than this optional addi-tion to stage III, the addition of chain transfer agents is not necessary in any of the stages.

The modifiers of this invention are effective in vinyl chloride polymers which include the chlorinated polyvinyl chloride^ These modifiers are also effective to increase toughness and ether physical properties in rigid thermoplastic polymers. ¾ese polymers include but are not limited to the polymers of styrene, substituted styrene, acrylonitrile , methacrylonitrile , c-methyl-styrene, and copolymers of these; acrylic polymers such as alkyl methacrylate polymers and copolymers, in particular methyl meth-acrylate polymers and copolymers with minor quantities of alkyl ' acrylates; engineering plastics such as polycarbonates, polyacetals, polysulfones and the like; and other thermoplastic polymers.

The quantity of the modifiers of this invention incorporated in the polymers to be modified varies greatly, depending upon the exact composition of the modifier, the polymer to be modified, the physical properties desired, etc. One factor to be considered is the quantity of the modifiers of this invention necessary to obtain the desired impact strength. he modifiers of this invention are very effective at low levels of incorporation to yield good impact strength. For example, in vinyl chloride polymers, in particular the homopolymer of vinyl chloride, the addition of based sufficient modifier to provide less than Yfo stage i/on the total polymer mix hardly affects the impact strength, Ag the stage I content is increased to 2$ on the weight of modified polymer, the impact strength is only slightly affected. At 3 levels of stage I on the total modified polymer weight, the improvement on impact strength is significant but still at a lew level. At levels of stage I on the total modified polymer weight of less than 5$> the impact strength is marginal. In vinyl chloride polymers wherein the DTUL modifier has already been added, the preferred stage I level is 7·5 to 10$ based on the total weight of the modified polymer. As the stage I level is increased further, the improvement in impact strength obtained per amount of stage I included is continuously reduced, and it is preferred to be less than 20$ on the total modified polymer weight in vinyl chloride polymers.

These modifier levels vary, depending upon the polymer to be modified. For example, with chlorinated polyvinyl chloride, less than 5$ stage I content on the total modified polymer gives only slight improvement in impact resistance. Further, the incorporation of 7«5$ stage I gives only moderate improvement in impact strength of the total polymer. A range of 6$ to 9$ stage I is preferred on the total modified polymer weight based upon chlorinated polyvinyl chloride. In poly(methyl methacrylate) polymers, 15$ of stage I gives moderate impact resistance and greater than 25$ of stage I is preferred, the percentages being based on the total weight of the modified polymer.

T e modifiers of this invention may be added in the range of about 1$ to 0$» based on the total weight of the modified polymer. Stated otherwise, the modifiers of this invention are par icularly /effective when incorporated in the weight range of 1 to 100 parts per 100 parts of polymer to be modified. At levels higher than 50 , the modifiers of this invention are effective, but must be considered as being modified by the polymer or polymers to which they are added.

For example, in vinyl chloride polymers in which a DTUL improver has been added, the preferred range of incorporation of the modifier is 6 to 4-0$· Δ more preferred range is 9 to 27$.

T e most preferred range is 10 to 20$. In vinyl chloride polymers in which the modifier is designed to act as an impact improver, DTUL improver and processing aid, higher levels of incorporation are acceptable. In these instances, a preferred level of incorporation of this multifunctional modifier is 10 to 50$ and above; a more preferred range is 16$ to 0 and above. ¾e most pre- ferred range is from 25 to 0$ and above. polymers Throughout this application the «* pmm&er/of this invention have been referred to as "modifiers". However, the polymers of this invention may be used alone to take advantage of superior properties, in particular high impact strength and resistance to heat deformation at elevated temperatures or outdoor weather resistance. Thus the invention also provides shaped articles such as granules, pellets, moulding powder or sheet formed from the poly- as mers of the invention. The polymers/prepared by this invention may be used by incorporating additives such as plasticizers, processing agents, stabilizers, etc., for example, as a molding compound.

The invention will now be more particularly described in and by the following E amples which are given for the purposes of illustration only and in which all parts and percentages are by weight unless otherwise specified.

Example .1 To a reactor kettle fitted with a stirrer, condenser, holding tank* and means for bubbling inert gas through the reaction mixture, there are charged 534 parts deionized water, 0.14 part sodium lauryl sulfate and 0.28 part sodium persulfate. After solid materials have dissolved, 56.3 parts n-butyl acrylate and glycol 0.28 part 1,3-butylene/diacrylate are charged. Nitrogen is bubbled through the stirred mixture and the batch is heated to 60°C. When polymerization begins, the nitrogen sparge is stopped and a very slow nitrogen sweep is maintained over the liquid. After 45 minutes from the incidence of polymerization at 60-65°C., a solution of I.25 parts sodium lauryl sulfate is added as a 15$ solution in deionized water. ¾e batch is stirred for five minutes and a mixture of 248 parts n-butyl acrylate and 1.23 parts 1,5-butylene diacrylate is added. In small batches this charge may be added in one shot, but under production conditions the addition may take one to two hours. During this addition the temperature is maintained in the range of 70-80°C. (end of stage I). ¾e stirring is continued for 15 minutes after the monomer charge addition has been completed. ¾e mixture is then cooled to 50°C A sample of the emulsion at the end of stage I (15 minutes glycol after the addition of n-butyl acrylate and 1,3-butylene/diacrylate has been completed) is found by standard light scattering techniques to have a. particle diameter of 2,095 as measured with blue light. There are charged 195 parts deionized water and Ο.42 part diisopropylbenzene hydroperoxide (supplied as $ in benzene), ^i e minutes after this charge has been added, 0.42 part (supplied as a 10$ aqueous solution) of sodium formaldehyde sulfoxylate is added. Fi e minutes later a mixture of 82.6 parts styrene monomer and I.69 parts divinylbenzene (40-60$ active) is added. The temperature of the batch is maintained in the range of 0- °C for one hour and then raised to 7 °^. and hdd for minutes (end of stage II).

A mixture of 79 ·1 parts isobornyl methacrylate and 79 ·1 parts methyl methacrylate is charged and the batch is held for one hour at 7O-80°C. (end of stage III). The batch is then cooled to 50 c«> filtered through cheesecloth, and the modifier is isolated by spray drying.

Example 2 Example 1 is repeated except that ten times as much 1,3- glycol butylene/diacrylate is used. The diameter of the emulsion particles at the end of stage I is 18685. The apparent intrinsic viscosity of the multipolymer is 1.08 dl/gm in tetrahydrofuran at 30°C.

Example 3 Example 1 is repeated except that one-tenth as much 1,3- ygiycoi butylene/diacrylate is used. The diameter of the emulsion particles is 2,084 at the end of stage I. The apparent intrinsic viscosity for the final product is 1.0 dl/gm in tetrahydrofuran at 30°C.

Example ά Example 1 is repeated except that the divinylbenzene of stage II is omitted. The particle size at the end of stage I is 2Ο9Ο .

Example 5 Example 1 is repeated except that six times as much sodium lauryl sulfate is used to prepare the seed latex. The second charge of emulsifier is unchanged. This change results in a particle size of 1520 S at the end of stage I.

Example 6 Example 1 is repeated except that 158,2 parts of methyl methacrylate is used in stage III instead of the mixture of iso-"bornyl methacrylate and methyl methacrylate. The methyl methacrylate is added gradually. At the end of stage I, the particle size is larger than 2,300 The apparent intrinsic viscosity of the final polymer is 0,44 dl/gm in tetrahydrofuran at ^>0°C , Example 7 Dry hiends are prepared "by thoroughly mixing the following ingredients in a Waring Blender for 2 to 3 minutes: Vinyl chloride homopolymer (medium molecular weight) 6l parts DTUL modifier * 22 parts Modifier (as prepared in xampies 1 to 6) 17 parts Titanium dioxide (RA.NC), when used 3 parts The DTUL modifier used was prepared as described in our Israeli Patent Application No. 30 , 142 filed 7th June 1968 and was a copolymer of 50% isobornyl meth-acrylate and 50% methyl methacrylate.

Heat stabilizers are oommonly added to compounds based on vinyl chloride polymers such as organotin oompounds , etc . Lubricants may al so be used as. well as oxidation inhibitors.

The mixes are blended on a 2-roll mill at 365°F for five minutes after fluxing. The mixes are then compression molded by conventional methods , cooled under pressure , and test specimens cut for determinations of impact strength and DTUL, at 26 psi. The Izod impact strength (IZOD) , reported in foot pounds per inch of notch, is determined according to ASTM D-256-56. The DTUL, reported in degrees centigrade, is deter-mined in accordance with ASTM D-648-56 ( l96l) .

The following properties are obtained with the modifiers noted: MODIFIER RANC PRESENT? IZOD IMPACT DTUL Example 1 HO I5.3 17.7 75 II II Fes I3.I - 1 .1 76 Exampl e 2 No 0.8 1.5 73-74 II II Yes 1.0 - 1.1 75 Example 3 No 6.6 _ 11.0 74 Yes 2.4 - 7.7 76 Example 4 No 7.3 - 14.6 75 II II Yes 2.2 - 6.3 77 Example 5 No 7.5 II - 1Θ.1 71 Yes 2.3 - 12.7 73 Example 6 Yes 10.4 - 12.1 73 Comparative Test No 0.5 0.7 70 (no modifier) Example 8 Example 1 is repeated, except that stage III is added as a mixture of 6Θ5 parts isobornyl methacrylate and 685 parts methyl methacrylate. Incorporating 39 parts of the resulting modifier in medium molecular weight vinyl chloride homopolymer, polymer is obtained. The IZOD is 12 to 13 ft. lbs ./inch of notch, and the Vicat temperature is 95°C Grood results are also obtained when ten times the charge of stage III is used in Example 1.

Example 9 Example 1 is repeated, except that the stage III monomer charge is composed of 3^8.5 parts methyl methacrylate, 158.2 parts ethyl acrylate and Ο.527 part tert-butyl mercaptan. The modifier is then tested as in Example 7 except that the formulation is as follows: 21 Vinyl chloride homopolymer (low molecular weight) 73 parts 62.5 parts DTUL modifier - copolymer of 0$ methyl methacrylate and 0$ iso- bornyl methacrylate — 10.5 parts Modifier of Example 9 27 parts 27 parts Titanium dioxide (EAMC) 3 parts 3 parts Typical physical properties obtained from the compression moldings of formulations Δ and 9^ are shown in Table I: TABLE I Effect of Modifier on Melt Flow and Impact Strenh Value Compound 9A Compound 9B IZOD 22-23 I3.5-I5 Vicat Softening Temperature (°C) 79 83 DTTJL — 76 Melt viscosity at 400°F./l000 3300 323Ο Excellent results are obtained when compounds Δ and S are injection molded.

Example 10 Example 1 is repeated except that the stage III monomer charge is composed of 474·5 parts methyl methacrylate and 52.6 parts ethyl acrylate without any molecular weight or chain regulators. Δ dry mix is prepared by blending the following ingredients: 80 parts high molecular weight vinyl chloride homo-polymer, 20 parts of the modifier of this example 10, and 3 parts titanium dioxide along with appropriate stabilizers and the like. The compound is extruded into a sheet through a single screw machine with barrel and die temperatures in the range of 3 Ο0 to 400°P. Impact strength tests on this sheet indicate that the sheet is isotropics IZOD at 70°P Parallel to extrusion 24.9 Perpendicular to extrusion 24·2 IZOD at 50°F.

Parallel to extrusion 22.9 Perpendicular to extrusion 21.9 IZOD at 32°F Parallel to extrusion 18.4 Perpendicular to extrusion 18.

Example 11 Example 1 is repeated, except that the stage III monomer charge is composed of 23.6 parts of isobornyl methacrylate, 134* 6 parts methyl methacrylate, and 0.79 part tert-butyl mercaptan. When this modifier is substituted into the formulation of Example 7 > the IZOD obtained is 3 to 6 ft. -lbs/inch of notch and the ^icat temperature is . The melt flow rate at 400°F./ 1000 seconds"""'" is about 3200. An identical procedure, eliminating the mercaptan, yields a melt flow rate of about 4000.

Example 12 Example 1 is repeated, except that stage III is composed of 23.6 parts isobornyl methacrylate and 134*6 parts methyl methacrylate. This modifier is added to the level of 12$ in chlorinated polyvinyl chloride which has a total chlorine content of 66-68$. Before modification, the chlorinated polyvinyl chloride has an IZOD of about 0.7 ft. -lbs ./inch of notch and a DTUL of about 105°C. At the 12$ level of modifier, the IZOD is 8 to 10 and DTUL is about IO3.

Example 13 Example 1 is repeated, except that the stage III charge is composed of 94* 8 parts ot-methylstyrene , 47 · 4 parts acrylo-nitrile, and 15.8 parts styrene. The intrinsic viscosity of the modifier is O.3O dl/gm in ethylene dichloride. This modifier was substituted for the one used in Example 7 above and gave good results.

Example 14 Example 1 is repeated, using, in turn 2-ethylhexyl acrylate, decyl/octyl acrylates (mixture) and butoxyethyl acrylate instead of the total charge of n-butyl acrylate. ¾en the modifier containing 2-ethylhexyl acrylate is tested by Example 7 , a polymer with an IZOD of 2 is obtained.

When the mixture of decyl and octyl acrylates is used, the particle diameter at the end of stage I is about 2136 S.

When the modifier obtained is tested as in Example 7 » an IZOD of about 11 is obtained.

When butoxyethyl acrylate is used, the particle diameter at the end of stage 1 is about 2259 and the refractive index at the end of the modifier preparation is about I.466 , and the intrinsic viscosity is Ο.43 dl gm. ¾e this modifier is tested as in Example 7 » the IZOD is about 5 · ^ood results are also obtained when octoxyethyl acrylate and ethoxyethyl acrylate are used as above.

E ample Example 1 is repeated except that the same weight monomer charges comprise for stage I 55$ ethylthioethyl acrylate, 45$ ethyl acrylate and 0.5$ divinylbenzene; for stage II, 86$ tert-butylstyrene, 10$ styrene, and 2$ div nylbenzene 5 and, for stage III, 100$ methyl methacrylate. The particle diameter at the end of stage I is 2240 When 20 parts by weight of this modifier is added to 80 parts by weight of polyvinyl chloride, using the methods of Example » an IZOD of greater than 15 is obtained.

Example 16 Example 1 is repeated, except that in turn 82.6 parts chlorostyrene , 82.6 parts tert-butylstyrene . and 82.6 parts vinyltoluene (mixture of o_ and j>) are used as stage II. 'When the modifiers obtained are tested as in Example 7 » satisfactory results are obtained.

Example 1 is repeated, except that the amount of poly-functional monomer in stage II is varied from 0 to 25$ of the weight of the stage II monomer charge. Good results are obtained in this range.

E ample 17 Example 1 is repeated by adding the same weight amount of the stage III monomer charge, except that the following weight ratios of monomers are used, yielding the IZOD noted when tested as in xample 7 s Stage III monomer Charge IZOD isobutyl methacrylate/ 70 methyl methacrylate 14-15 trichloroethyl methacrylate/ 70 methyl methacrylate I4-I6 benzyl methacrylate/ 70 methyl methacrylate 15 styrene/ 70 methyl methacrylate 12-13 0 chlorostyrene/ 0 methyl methacrylate 12-14 0 tert-butylstyrene/ 0 methyl methacrylate 12-14 The modifier as prepared in x mple 1 is effective in concentrations of to on the total weight of modified polymer for improving impact strength in polymers of methyl methacrylate and styrene and copolymers of these monomers with other common monomers such as alkyl acrylate, acrylonitrile and a-methylstyrene . ¾e polymer as prepared in ¾ample 8 is us eful as a thermoplastic polymer to prepare moldings with good physical properties when ueed alone. - 30 - 32342/3

Claims (19)

1. A sequentially polymerised thermoplastic partioulato polymer comprising I a first stage having an average particle diameter size of at least 1500 X comprising units of one or more alkyl, alkylthloalkyl or alkoxyalkyl acrylates having frooj 2 to 14 carbon atoms in the alkyl, alkylthloalkyl or alkoxyalkyl group, and from one or more copolymerisable polyethyl-enically unsaturated cross-linking monomers; II a second s a^$ comprising units of one or more mono-aromatic compounds containing a single CH2=C< group the balance (if any) comprising units from one or more copolymerisable polyethylenically unsaturated monomers; and III a third stage comprising units of one or more alkyl, aryl, alkaryl or aralkyl methacrylates or t acrylates, bicyclic acrylates or methacrylates, halogen-substituted versions of these acrylates and methaorylates, aromatic compounds containing a single CH^-O

2. A polymer as claimed in Claim 1 wherein the average relative weight proportions of each atage in each particle arc 100 parts stage I : 10 to 100 parts stage II : 20 to 300 par r; stage III.

3. · A polymer as claimed in Claim 2, wherein the average relative weight proportions of each stage in each particle are 100 parts stage I : 10 to 60 parts stage II to 20 to 300 parte stage III.

4. A polymer as claimed in any preceding claim.'., wherein the amount of cross-linking monomer in stage I is about O.O5 to 2.05&, preferably 0.2 to 1.0?S by weight of the alkyl, Alkoxyalkyl or alkylthloalkyl aer late. '

5. A polymer as claimed in any preceding claim in which the balance of units in stage II comprises 0.05 to 257° of the weight of the units in stage II.

6. Λ polymer as claimed in any preceding claim wherein the stage I polymer alone would have a second order transition temperature below -20°C.

7. A polymer as claimed in any preceding claim wherein the stage I polymer comprises units of butyl acrylate cross-linked by units from 1,3-butylene diacrylate.

8. Δ polymer as claimed in any preceding claim wherein the stage II polymer is polystyrene.

9. A polymer as claimed in any of Claims 1 to where-in the stage II polymer comprises units of styrene crosslinked with units from di- and/or tri-vinylbenzene.

10. A polymer as claimed in any preceding claim in which the stage II polymer comprises units from one or more of the following monomers: methyl methacrylate and bicyclic acryl-ates or methacrylates of the formula: wherein A is -CH :,2-, -CH(CH3)-, or -C(CH3)2-5 M is -Ξ or -CH.,; n is 0 or an integer from 1 to 3 or, when a mixture - 32 - 32342/2 of bicyclic compounds is used the average value of n is from 0 to 3.

11. A polymer as claimed in Claim 10 wherein the bicyclic methacrylate is isobornyl methacr late.

12. A polymer as claimed in any preceding claim wherein the average relative weight proportion of stage II in each particle is 10 to 80 parts per 100 parts of stage I.

13. A polymer as claimed in any preceding claim wherein the average relative weight proportion of stage II in each particle is 10 to 40 parts per 100 parts of stage I.

14. A A polymer as claimed in any preceding claim wherein the average relative weight proportion of stage III in each particle is 10 to 100 parts per 100 parts of stage I.

15. A polymer as claimed in any one of Claims 1 to 13 , wherein the average relative weight proportion of stage III in each particle is 100 to 300 parts per 100 parts of stage I.

16. A polymer as claimed in Claim 15 in which stage III includes units from one or more of a-methylstyrene, acrylonitrile and styrene.

17. A polymer as claimed in Claim 1 substantially as hereinbefore described in any of the foregoing Examples 1 to 6 , 8 and 11 to 17.

18. A polymer as claimed in Claim 1 as hereinbefore described in Examples 9 or 10.

19. A process for the preparation of a thermoplastic sequentially polymerized particulate polymer which comprises - 33 - 32342/2 (A) taking a polymeric system formed by subjecting to aqueous emulsion or suspension polymerisation a monomeric system comprising one or more alky1, alkylthioalkyl or alkoxyalkyl acrylates having from 2 to 14 carbon atoms in the alk 1, alkylthioalkyl or alkoxyalkyl group, and from one or more poly- monomers, ethylenically unsaturated cross-blinking/copolymerisable therewith, the emulsion or suspension polymerisation being carried out under such conditions that the resulting polymer is in the form of particles having an average diameter of at least 1500 &, (B) adding thereto a monomer system comprising one or more aromatic compounds containing a single CH2=C