GB2030154A

GB2030154A - Resin-rubber polymeric blends

Info

Publication number: GB2030154A
Application number: GB7926433A
Authority: GB
Original assignee: American Cyanamid Co
Current assignee: Wyeth Holdings LLC
Priority date: 1978-09-18
Filing date: 1979-07-30
Publication date: 1980-04-02
Also published as: GB2106120B; JPH02138323A; GB2107329A; FR2491931A1; GB2107329B; FR2455066A1; DE2937718A1; GB2106914B; GB2106914A; FR2455066B1; FR2491930A1; GB2030154B; GB2106120A

Abstract

Polymeric blends having improved optical properties comprise (A) a major proportion of a resinous polymeric phase and (B) a minor proportion of a rubbery phase comprising at least one monomer compatible with the resinous phase grafted on to rubber in a ratio of 1:1 to 1:6 and containing no particles of diameter greater than 1 micron. The grafted elastomer may be prepared (a) by a sequential and controlled addition of monomers during grafting or (b) using a mixture of elastomer grafts having different rubber to monomer ratios or (c) by a multiple grafting technique.

Description

SPECIFICATION Polymeric blends It has been known to prepare thermoplastic molding compositions from various polymers and rubber latices by blending the polymers with the grafted rubber or by polymerizing the monomers used to produce the polymer in the presence of the rubber. For example, U.S. Patent No. 3,354,238 discloses such a molding composition wherein the resinous phase is composed of methylmethacrylate, styrene and acrylonitrile, and the rubber phase is composed of polybutadiene grafted with methylmethacrylate, styrene and acrylonitrile.

Similarly, U.S. Patent No. 3,261,887 discloses a molding composition substantially identical to that of the above-discussed patent except that the acrylonitrile is omitted therefrom. Also, similarly, U.S. Patent No.

4,085,116 discloses molding compositions wherein the acrylonitrile has been replaced by ethylacrylate.

These products exhibit acceptable properties when utilized as colored molding compositions, but have deficiencies when used in the absence of a coloring agent. In their uncolored states the products are not sufficiently transparent and, as a result, their use in such as packaging applications has been restricted.

Research has indicated that the optical properties of the molding compositions improve when the rubbery reinforcing elastomer, i.e. the polybutadiene phase in the above patents, is more uniformly distributed in the resinous polymer phase and the agglomerations of the elastomer, if any, are smaller than the wavelength of visible light. The smaller the agglomerations, the better are the optical properties.

While the wavelength of visible light is about 4000 to 7000 Angstroms and the polybutadiene previously used has generally had a diemeter on the order of less than 2000 Angstroms, the resultant products have still not been entirely satisfactory due to relatively poor haze and gloss characteristics.

It has now been discovered that by modifying the procedure by which the grafted elastomer is produced, an improved molding composition results since the rubbery phase is more uniformly distributed in the resin phase.

The grafted elastomeric phase is prepared by one of the following procedures: (a) a sequential and controlled addition of monomers (SCAM) during the grafting polymerization; (b) a mixture of two separately prepared grafts wherein the two grafts have different rubber to monomer ratios (MEG): or (c) a multiple grafting procedure wherein a second graft is performed in the presence of the first grafted product (DGMAC).

The present invention provides improved molding compositions for two phase plastic systems. Examples of the rubbery reinforcing portion of such systems include such as polybutadienes, poly(styrene/ butadienes), poly(methylmethacrylate/butadienes), polyisoprenes, polyisobutylenes, poly(isobutyleneisoprene) copolymers, poly(acrylonitrile/butadienes), polyacrylates, polyurethanes, neoprene, silicone robbers, chlorosulfonated polyethylene, ethylene-propylene rubbers and other such rubbery materials.

Grafted onto the above rubbers may be the monomers detailed belowforthe resin phase. The monomers to be grafted must be compatible with the particular monomers used in the resin phase for a particular composition. Preferably, the same monomers are used in both. By "compatible" is meant polymers which show a strong affinity for each other such that they may be dispersed into one another in small domain sizes.

The smaller the domain sizes, the more compatible are the polymers. Further details of compatibility are disclosed in Advances in Chemistry Series, No. 99, "Multi-Component Polymer Systems", edited by R.F.

Gould, 1971, incorporated herein by reference.

The resin phase is any polymer or copolymer which is compatible with the grafted rubber phase.

Examples of suitable monomers include: acrylates, melthacrylates, nitriles, styrenes, vinyl ethers, vinyl halides, and other similar mono-vinyl compounds. Particularly suitable monomers include methylacrylate, ethylacrylate, propylacrylate, methylmethacrylate, ethylmethacrylate, polymethacrylate, acrylonitrile, methacrylonitrile, styrene, a-methylstyrene, butyl vinyl ether, and vinyl chloride.

Preferably, for this invention, the rubber phase is polybutadiene grafted with methylmethacrylate, styrene and optionally a third monomer selected from methylacrylate, ethylacrylate or acrylonitrile. Preferably, the resin phase is a polymer of methylmethacrylate, styrene, and optionally a third monomer selected from methylacrylate, ethylacrylate and acrylonitrile.

Most preferably, the molding compositions are preferred from a graft polybutadiene phase and a polymeric resin phase where polybutadienefraction of the graft polybutadiene phase is 5 to 25% by weight of the total molding composition. The polymeric resin phase contains from about 60 to 80 parts of methylmethacrylate, 15 to 30 parts of styrene and 0 to 15 parts of either methylacrylate, ethylacrylate or acrylonitrile. The graft polybutadiene phase is polybutadiene latex grafted with methylmethacrylate, styrene and optionally either methylacrylate, ethylacrylate or acrylonitrile where the overall ratio of polybutadiene to graft monomers ranges from about 1:1 to about 6:1.The graft monomers are used in a ratio of from about 60 to 85 parts of methylmethacrylate, 15 to 30 parts of styrene and 0 to 15 parts of either methylacrylate, ethylacrylate or acrylonitrile.

In the SCAM procedure, which is essentially a standard free radical initiation polymerization at least the monomer having the best compatibility as a polymer to that of the resin phase is added to the rubber latex, and any other monomers which are also being grafted onto the rubber, in a sequential and controlled manner. Conventional initiators and other polymerization components are used. While not being bound by any theory, it is believed that SCAM results in non-agglomeration by putting an essentially uniform shell of resin around the rubber particles wherein the outer layer of the shell is composed primarily of the controllably added monomer.

In the MEG procedure, a mixture of two rubbery grafts having different rubber monomer ratios are blended together. One of the rubbery phases used has a relatively high rubber monomer ratio, i.e. above about 2.5/1, preferably above about 3/1, and most preferably abour 3/1 to 511. This latex has considerable agglomeration of the rubber which causes the good physical, but poor optical, properties characteristic of such materials. The other latex has a relatively low rubber to monomer ratio, i.e. below about 2/1, peferably below about 1.5/1, and most preferably about 1/1. This latex has essentially no agglomerates which results in superior optical properties but also extremely poor physical properties.Upon using a mixture of the two rubbery phases, it would be expected to provide a product having, at best, physical and optical properties of the two rubbery phases. However, it has been found that by using a minor portion of the low rubber to monomer rubbery phase and a major portion of the other, a molding composition may be made having only a slight reduction in physical properties but greatly improved optical properties.

In the DGMAC procedure, at least two graft stages are run in succession by the addition of the rubber and grafting monomers, followed by more rubber, and more grafting monomers. The grafting procedure used in each stage is either a rubber with equilibrated monomer as in U.S. Patent 4,085,166 or a sequential and controlled addition of monomers (SCAM as described above). To the first stage graft product is added about 0.5-1.0% (based on second stage rubber latex weight) of a stabilizer such as potassium lauryl aryl sulfonate to ensure latex stability during the second stage polymerization. For further stages, further stabilizers may be added. The ratios of monomers, preferably methylmethacrylate, styrene and either methylacrylate, ethyl acrylate or acrylonitrile used in the individual grafting stages are the same as given above in the overall graft composition.The ratio of rubber to monomer in the individual grafting stages is bounded by the overall graft compositions biven above, i.e., from about 1:1 to about 6:1. The prime restriction on stage compositions is that each stage graft product by weight be at least as large as the earlier produced grafted rubbers. In a two stage system, the second stage preferably is at least 60% of the product and most preferably, about 65 to 95%. When calculating the subsequent stage graft rubber product wieght, the subsequent stage monomers are assumed to be equally distributed among the previous and new stage rubbers and the previous stage resin (graft monomer).

The compositions, however the grafted rubber is prepared, may be produced by blending the resinous phase, which may be prepared by a free radical initiated reaction in the presence of a solvent and in a two-stage system whereby the monomer blend is charged to a first reactor and polymerized to about 20 to 40% solids and then in a second reactor where complete conversion is carried out, with the rubbery phase in the appropriate amounts.

Any known procedure may be utilized to produce the resin phase. It is preferred, however, that the resin phase be produced by blending the appropriate concentration of monomers in a solvent such as toluene at about 60 to 80% monomers concentration. A suitable initiator such as benzoyl peroxide, di-t-butyl peroxide and the like may be added in the presence of a molecular weight control additive such as an alsyl mercaptan e.g., n-dodecyl mercaptan, n-octyl mercaptan, t-dodecyl mercaptan, benzyl mercaptan and the like. As mentioned above, this polymerization is preferably conducted in a two-stage system whereby the monomer solution is charged to the first stage reactor and polymerized at from about 80 to 11 OOC. for from about 12 to 24 hours. The rate of conversion is preferably adjusted to from about 1 to 3% solids per hour.The first stage polymer is then preferably transferred to a second stage such as a plug flow reactor where complete conversion of the monomer to polymer is carried out. The final solids content generally ranges from about 60 to 70%. Initiators may be used in amounts ranging from about 0.01 to 5.0 percent by weight, based on the weight of the monomers. The molecular weight control additive can be used in like amounts, by weight, again based on the weight of the monomers.

There may be added to the resin phase, after or during formation, such additives as heat and light stabilizers, antioxidants, lubricants, plasticizers, pigments, fillers, dyes and the like.

In the DGMAC procedure each stage may be either a conventional grafting process or a sequential and controlled addition of monomer (SCAM) process. Preferably, at least one of the stages is a SCAM process, and most preferably two stages are used with each being a SCAM process. While graftings may be done in a series of reactors, it has been found convenient to us a single reactor with the graftings done in succession.

These procedures result in a large number of individual grafted rubber particles with essentially no agglomeration and/or aggregation of the rubber particules. This results in improved optical properties as well as a composition having reduced taste and odor transfer characteristics.

In the SCAM procedure, (or as part of the DGMAC procedure), the monomer being sequentially added should be added over a period of at least 15 minutes, preferably at least 1 hour, and most preferably about 1 to 3 hours, with the grafting reaction occurring during the addition and preferably allowed to continue thereafter for about one hour. The initiator which is preferably a redox type may be included in the reactor initially, it may be added simultaneously as the monomer being added either in the same stream or in a separate stream; or ultraviolet light may be used. Generally, the initiator is used in an amount up to about four times the standard amounts as used in U.S. Patent 4,085,166. When a redox initiator is to be controllably added, (as opposed to being in the reactor initially) either the oxidant or reductant portion may be placed in the reactor initially and only the other portion need be controllably added. The reaction is conducted at a pH range of about 6.0 to 8.5 and in the temperature range of about 20 to 650C., though neither has been found to be critical to the present invention.

Examples of suitable redox initiator systems include: t-butyl hydroperoxide, cumene hydroperoxide, hydrogen peroxide or potassium persulfate-sodium formaldehyde sulfoxylate-iron; hydroperoxidestetraethylene pentamine or dihydroxyacetone; hydroperoxides-bisulfate systems; and other such well known redox initiators.

The rubber-to-monomer ratios of the graft polymerizations, be they conventional or SCAM, may be varied as desired to control the rubber-to-monomer ratios so as to produce the desired balance of properties in the final product. Hence, it is the desired final product which determines the actual ratios to be used in making the graft polymerizations. Generally, the rubber-to-monomer ratios should be in the range of about 1:1 to as high as 6:1, with the lower ratio materials providing the better optical properties and the higher ratio materials the better physical properties. Preferably in the MEG and DGMAC procedures one portion of the graft products has a rubber-to-monomer ratio of at least 2.5:1, and the other less than 2:1. Most preferably, one has a ratio of about 2.5:1 to 4:1, and the other from abour 1:1 to 2:1.

The DGMAC procedure of the present invention provides a more intimate blending of different rubber-to-monomer ratio rubbery phases than was heretofore possible. Different rubber-to-monomer ratios are readily obtained even when the same ratio of rubber to monomer is added in each stage, due to the first grafted rubber being in the reactor when the next graft is performed.

For example, an intimate blend of a 3:1 and a 1:1 rubber:monomer may be prepared from two 2:1 graftings as follows: Graft 1 uses a total of three parts by weight reactants - 2 parts rubber and 1 part monomers - to produce a 2:1 product. Thereafter, a second graft is performed using nine parts reactants - 6 parts rubber and 3 parts monomers - together with the first graft product. In the second graft, the new monomers will be attracted to the first product and the newly added rubber essentially in the ratio in which these are present in the reactor.

Hence, in this example, 6/9 of the 3 parts newly added monomers will graft onto the new rubber, i.e., 6 parts rubber to 2 parts monomer - a 3:1 ratio, and 3/9 will graft onto the previous graft, i.e., 2 parts rubber to 1 part first monomers plus 1 part new monomer - a 1:1 ratio. Thus, the resultant mixed graft will contain 4 parts of a 1:1 graft and 8 parts of a 3:1 graft which are intimately admixed.

In the MEG procedure the two graft parts are preferably each polybutadiene grafted with methylmethacrylate, styrene and optionally either methylacrylate, ethylacrylate or acrylonitrile. One part is 95 to 60% by weight of the graft polybutadiene phase and has a ratio of polybutadiene to graft monomers which ranges from about 2.5:1 to about 6:1, the other part is correspondingly 5 to 40% by weight of the graft polybutadiene phase wherein the ratio of polybutadiene to graft monomers ranges from about 1:1 to about 2:1. The graft monomers for both parts are in the same ratio of from about 60 to 85 parts of methylmethacrylate, 15 to 30 parts styrene and 0 to 15 parts of either methylacrylate, ethylacrylate or acrylonitrile.

The resinous phase and the rubbery phase, however prepared, may be blended together in any known manner such as by utilizing a ball mill, hot rolls, emulsion blending or the like.

It is preferred that the blending operation be carried out in a devolatilizer-extruder in a manner described at column 3, lines 3 to 72 of the above-mentioned U.S. Patent 3,354,238, which section thereof is hereby incorporated herein by reference.

As mentioned above, the compositions of the instant invention have utility where toughness, rigidity and transparency are necessary and may be utilized in the injection molding of highly engineered parts, blow molding and thermoforming of containers or other desired articles.

The following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by weight unless otherwise indicated. Examples 1-40 exhibit the SCAM procedure; Examples 41-50 exhibit the MEG procedure; and Examples 51-63 exhibit the DGMAC procedure.

Example 1 A 71.5/23.5/5/0 methylacrylate/styrene/ethylacrylate terpolymer composition is prepared by polymerizing the following monomer-solvent blend: 51.6 parts methylmethacrylate 17.0 parts styrene 3.6 parts ethylacrylate 27.5 parts toluene 0.022 parts n-dodecylmercaptan 0.30 parts di-t-butylperoxide The polymerization is carried out in a two-stage system, i.e., the monomer-solvent blend is charged to a first stage reactor and polymerized to about 28 to 30% solids at 90-95 C. for about 15 hours. The rate of conversion is about 2% solids per hour. The first stage reaction product is then transferred to a plug flow reactor where complete conversion of monomer to polymer is carried out. The final solids content is near 72%.

A graft rubber composition is prepared by charging 79.19 parts of polybutadiene latex (43.3% solids, 34.29 parts of polybutadiene) and 7.48 parts of deionized water to a reactor, and adjusting the pH to about 8.3 with 1.5% aqueous ammonia. To this is charged 2.29 parts of styrene with stirring and the equilibrating mixture is purged with nitrogen to provide a near oxygen-free atmosphere. Then 1.51 parts of sodium formaldehyde sulfoxylate chelate solution of the following composition is added.

96.26% deionized water 3.51% sodium formaldehyde sulfoxylate 0.19% ethylenediamine tetraacetic acid tetra sodium salt 0.04% ferric chloride hexahydrate 100% After five minutes and continuing the stirring 9.14 parts of methyl methacrylate and 0.39 parts of tert-butyl hydroperoxide solution (5.85% t-butyl hydroperoxide and 94.15% deionized water) are pumped into the reactor. The methylmethacrylate rate is 0.0508 part per minute for 3 hours. The t-butylhydroperoxide solution rate is 0.0195 part per minute for 10 minutes, then 0.00108 part per minute for 180 minutes. One hour after the monomer addition is completed the conversion to polymer is 98-99%.

Twenty parts of the above grafted rubber are then blended with 80 parts of the above terpolymer so as to provide a final polybutadiene content of 15%. The blending is conducted on a devolalitizer-extruder at a temperature on the inlet end of about 250"F. and at the die end of abour 560OF. under a vacum of 25-27 in Hg.

The resultant transparent composition is then formed into various specimens and tested. The results are given in Table I below along with the results for the conventionally prepared product.

As can be seen from Table I, the sequential and controlled addition of monomers produced a product of equivalent impact strength and greatly superior optical properties (high gloss, lower haze, and increased transmission) as compared to conventionally prepared material.

Table 1 Notched Izoda Gloss % b Total Haze % c y % ft.lbs.lin 20 60 Y Z Transmission Example 1 1.6 64 86 13.0 7.8 90.5 comparison 1.6 47 81 17.0 10.0 89.8 a) ASTM D 256, method A; molded specimens 1/4 x x 5 inches.

b) ASTM D 2457-70, 1/8 inch molded disks.

c) ASTM D 1003-61, 1/8 inch molded disks.

Examples 2 - 6 The procedure of Example 1 is repeated except varying the rubber to monomer ratio of the graft polymer and the pumping time is 1 hour instead of 3 hours. Comparison products are made by the conventional procedures. Molding compositions are prepared wherein the ratio of the resin phase to the rubber phase is varied such as to produce products having a constant 14.5% polybutadiene.

The results for injection moldings are summarized in Table II below, and for thermoformed moldings 0.012 in. thick in Table Ill below.

Table II Rubber to Monomer Notched Izod Gloss % Total Heze % % Y Ratio fppi 20 60 Y Z Transmission Ex.2 1/1 0.41 69 89 6.4 7.3 86.4 Comp. 1/1 0.47 58 83 11.8 13.6 78.4 Ex.3 2/1 0.54 62 86 8.7 10.7 84.3 Comp. 2/1 0.81 59 84 9.0 10.3 84.1 Ex.4 3/1 2.1 60 86 9.5 11.1 83.8 Comp. 3/1 1.9 58 85 12.9 13.8 83.1 Ex.5 4/1 2.0 54 83 10.2 11.0 86.0 Comp. 4/1 1.6 57 83 15.9 17.3 77.0 Ex.6 5/1 1.7 52 81 11.3 12.0 84.7 Table III Gloss % Total Haze % % Y 20 60 Y Z Transmission Ex.4 61 89 3.0 4.2 92.5 Comparison 51 87 3.1 4.2 92.7 Examples 7-24 The procedure of Example 1 is repeated while varying (1 ) the rubber to monomer ratio of the grafted rubber, (2) the pumping times, (3) putting the t-butylhydroperoxide in the reactor initially, and (4) the amount of each part of the initiator system (the amounts of Ex. 1 being the standard - STD).

The variations together with the properties of resultant molding compositions which are made to each have 14.5% polybutadiene are summarized in Table IV below. In the table:MMA is methylmethacrylate; TBHP is t-butylhydroperoxide; and SFS-Chelate is sodium formaldehyde sulfoxylate-chelate solution. Table IV Rubber to Pump times lnitiator conc. Notched Gloss Total Y Monomer (hr.) SFS- Izod % Haze % Trans Ex.Ratio MMA TBHP TBHP chelate fppi 20 60 Y Z mission % 7 3/1 0.25 0 STD STD 1.8 53 83 15.8 17.3 74.5 8 " 0.25 0.25 STD STD 1.6 62 84 19.7 20.3 72.7 9 " 0.25 0 4 STD 4 STD 1.9 51 80 17.3 16.7 81.6 10 " 0.25 0.25 4 STD 4 STD 1.9 55 82 18.2 18.1 79.7 11 " 1 1 STD 5 STD 1.9 63 86 10.1 11.4 84.0 12 " 1 1 STD STD 2.1 60 86 9.5 11.1 83.8 13 " 1 1 2.5 STD 1.2 STD 1.9 54 82 8.5 10.6 87.1 14 " 1 1 4 STD 2 STD 1.8 57 83 10.2 12.8 79.2 15 " 1 1 2 STD 4 STD 1.8 54 82 9.9 11.9 80.7 16 " 2 0 STD STD 1.5 60 85 14.4 15.8 78.9 17 " 3 0 STD STD 2.0 34 74 17.9 19.3 84.3 18 " 3 3 STD STD 2.0 - - - 19 " 3 3 4 STD 2 STD 1.3 - - 7.8 11.0 87.0 20 " 5 0 STD STD 1.6 60 85 11.5 11.9 83.4 21 1/1 1.25 1.25 2.5 STD 1.2 STD 0.37 66 86 9.6 11.3 83.2 22 " 1 1 4 STD 2 STD 0.35 65 85 6.4 7.5 67.6 23 " 3 3 4 STD 2 STD 0.32 68 87 6.3 8.0 84.7 24 " 5 5 4 STD 2 STD 0.29 67 84 5.8 7.2 66.4 Examples 25 - 29 The procedure of Example 1 is repeated except varying the initiator and pumping times. The STD level for each initiator is the equivalent mole basis based on the t-butyl-hydroperoxide of Example 1.

The results are as in Table V below.

Table V Pump Times Notched Total Y (hr.) Initiator Conc. Izod Gloss % Haze % Trans Ex. Initiator MMA Init. Init. SFS-Chelate fppi 20 60 Y Z mission, % 25 CHP (1) 1 1 STD STD 1.5 56 81 9.6 10.4 85.6 26 H2O2 1 1 STD STD 1.8 55 82 12.6 12.8 84.6 27 H2O2 3 3 STD STD 1.8 49 80 - - 28 (NH4)2S2O3 1 1 STD .5 STD 1.7 57 84 10.2 12.1 82.6 29 K2S2O8 1 1 STD .5STD 1.5 59 83 9.5 10.0 83.3 (1)Cumene hydroperoxide Example 30 The procedure of Example 1 is repeated except the t-butylhydroperoxide is placed in the reactor and the sodium formaldehyde sulfoxylate-chelate solution is metered in. The time of pumping for both the methylmethacrylate and the solution is one hour. Standard amounts of the initiator are used.

The resultant product (14.5% polybutadiene) shows the following properties; Notched Izod, fppi 2.1 Gloss, % 20 47 60 81 Total Haze,%Y 13.4 Z 15.5 YTransmission, % 83.8 Example 31 The process of Example 1 is repeated except that a mixture of methylmethacrylate and styrene monomer is metered into the reactor. The pumping time is one hour for both the monomers and the initiator. The resultant composition with 14.5% polybutadiene has the following properties: Notched Izod, fppi 2.2 Gloss, % 20" 58 60 84 Total Haze,%Y 8.5 Z 9.4 Y Transmission, % 86.4 Example 32 The procedure of Example 1 is repeated except that a portion of the methylmethacrylate which is metered in is replaced by ethylacrylate and the pumping time is one hour.The resultant composition, having 14.5% polybutadiene, has the following properties: Notched Izod, fppi 2.0 Gloss, % 20" 51 60 81 Total Haze, % Y 11.1 Z 15.3 YTransmission, % 84.8 Examples 33 - 35 The procedure of Example 1 is repeated except that molding compositions are prepared with varying amounts of polybutadiene in the final product. The results are as shown in Table VI.

Table VI % Polybuta- Notchedlzod Gloss % Total Haze % Trans Ex. diene fppi 20 60 Y Z mission, % 33 14.5 2.2 59 86 10.0 12.1 84.9 34 12.5 2.0 58 86 9.3 11.3 84.1 35 10.5 1.7 64 87 8.0 9.6 86.2 Examples 36 - 37 The procedure of Example 4 is repeated to produce thermoformed moldings having a thickness of 0.004 0.0065 inches. The moldings are evaluated for optical properties in comparison with conventially prepared material.The results are shown in Table VII Table VII Gloss, % Total Haze, % Example %Polybutadiene 20 60 Y Z Y Transmission % 36 14.5 20 67 20.0 26.7 91.5 37 12.5 32 76 15.5 17.2 91.7 COMPARISON 14.5 9 59 23.1 30,9 91.3 Examples 38-39 The procedure of Example 4 is repeated to produce 16 oz. margarine tubs by thermoforming a 0.035 in.

thick extruded sheet at 350-365"F. The rubber phase has a rubber-to-monomer ratio of 3/1, and the overall compositions contain 14.5% polybutadiene. The results are shown in Table VIII.

Table VIII 0.02in. Thick Gloss, % Pump Times Dart Impact Side-0.011in. Thick Bottom-0.017in. Thick Example MMA In it. Strength (fppi) 20 60 20 60 38 3 0 25.2 19 65 42 82 Comp. - - 30.3 2 36 19 61 39 3 3 29.6 10 55 45 81 Comp. - - 30.0 , 2 30 17 63 Example 40 The procedure of Example 38 is repeated except varying the forming temperature of the margarine tubs.

The results shown in Table XI demonstrate that the cisual clarity of thermoformed compositions of the present invention is essentially insensitive to variations in forming temperature whereas conventionally prepared materials deteriorate in visual clarity as the temperature increases.

Table IX Forming Temperature, "F Example 300 335 345 355 360 380 390 40 Good Good Good Good-Fair COMPARISON Fair Fair-Poor Poor Poor Examples 41-48 A. A monomer composition containing 51.6 parts methylmethacrylate, 17.0 parts styrene, and 3.6 parts ethylacrylate is polymerized in the presence of 0.30 parts di-t-butyl peroxide, 27.5 parts toluene, and 0.022 parts n-dodecyl mercaptan in a two-stage system, i.e. the monomers are individually charged to a first stage reactor and polymerized to 28 to 30% solids at 90-95"C for 16-20 hours. The rate of conversion is about 2.0% solids per hour. When the appropriate solids content is reached, the first stage reaction material is then transferred to a plug flow reactor where complete conversion of monomer to polymer is carried out.The final solids content is 68 to 70%.

B. A rubber composition is prepared by blending 75.0 parts of polybutadiene in latex from with 19.6 parts of methylmethacrylate and 5.4 parts of styrene. The rubber to monomer ratio is 3:1. The monomers are then grafted onto the polybutadiene by a redox initiated polymerization using, based on monomer, 0.05 part of t-butylhydroperoxide, 0.06 part sodium formaldehyde sulfoxylate, 27 ppm. ferric chloride.6H2O and 127 ppm. ethylenediamine tetraacetic acid.4Na salt at room temperature for 2-5 hours.

C. A second rubber composition is prepared by blending 50.0 parts polybutadiene in latex form, 10.8 parts styrene, 0.12 parts sodium formaldehyde sulfoxylate, 54 ppm. ferric chloride.6H20 and 254 ppm.

ethylenediamine tetraacetic acid.4Na salt. A graft polymerization is then conducted by independently monitoring into the above mixture 39.2 parts methylmethacrylate and 0.05 parts t-butylhydroperoxide during a three-hour period. The rubber to monomer ratio is 1:1. The reaction is continued for one hour and the grafted rubber results.

Six compositions are then prepared by blending the polymer Awith the rubbers B and C such that each of the compositions has a final polybutadiene content of abour 14.5%. Table X gives the ratios of B and C grafted rubbers. The blending is conducted in a devolitilizer-extruder at a temperature on the inlet end of about 250"F. and at the die end of about 560"F. under a vacum of 25-27 in. Hg.

The resultant compositions are then formed into a series of samples and tested to determine the physical properties thereof. In addition, the gloss is determined by ASTM D2457-70 and the haze by ASTM D1003-61.

The results are detailed in Table X below.

The results show that when the rubber to monomer graft ratio is 3/1, the composition has good impact properties but high haze and low gloss. When the percentage of the 1/1 graft material in a mixture of rubbery phases is increased up to about 35%, a decided improvement in the haze and gloss characteristics is recorded with only a slight reduction in the still good impact strength.

Examples 47 and 48 demonstrate the vast improvement in optical propertes of compositions which have been thermoform molded at 350-3650F.

Table X Ratio of mixed Grafted Rubbersl Total Total Gloss Values 3:1 1:1 Notchedlzod Gardnerlmpacts Haze Haze Front Back Ex. Rubber Rubber Ft. Ibs.lin. in. Ibs.lpermil Y Z 20 60 20 60 41 100 0 1.8 0.52 14.9 19.2 36 76 44 77 42 90 10 1.8 0.51 11.0 13.7 42 79 41 76 43 80 20 1.8 0.49 10.4 13.2 45 81 44 80 44 65 35 1.6 0.48 10.9 14.8 47 81 52 81 45 50 50 0.57 0.38 14.9 19.3 58 83 64 86 46 0 100 0.51 0.31 8.7 11.9 59 85 57 83 47* 100 0 15 71 48* 65 35 28 87 * Thermoformed moldings (1) Total polybutadiene content in all blends is 14.5% by weight Example 49 The procedure of Examples 41-48 is again followed except that the 1::1 rubber to monomer material is prepared in the conventional way as is disclosed for the 3:1 material. Similar results are observed.

Example 50 The procedure of Examples 41-48 is again followed except that the ethylacrylate is directly replaced with acrylonitrile. Again similar results are observed.

Example 51 A 71.5/23.5/5.0 methylmethacrylate/styrene/ethylacrylate terpolymer composition is prepared by polymerizing the following monomer-solvent blend: 51.6 parts methylmethacrylate 17.0 parts styrene 3.6 parts ethylacrylate 27.5 parts toluene 0.022 part n-dodecylmercaptan 0.30 part di-t-butylperoxide The polymerization is carried out in a two-stage system, i.e., the monomer-solvent blend is charged to a first stage reactor and polymerized to about 28 to 30% solids at 90-95"C. for about 15 hours. The rate of conversion is about 2% solids per hour. The first stage reaction product is then transferred to a plug flow reactor where complete conversion of monomer to polymer is carried out. The final solids content is near 72%.

A graft rubber composition is prepared by a two-stage grafting polymerization as follows: A first grafted rubber composition is prepared by blending 100 parts of polybutadiene in latex form with 40 parts of methylmethacrylate.and 10 parts styrene. The rubber to monomer ratio is 2 to 1. The monomers are then grafted onto the polybutadiene by a redox initiated polymerization using, based on monomer, 0.1 part of t-butylhydroperoxide, 0.23 part sodium formaldehyde sulfoxylate, 27 ppm ferric chloride.6H2O and 127 ppm ethylene diamine tetraacetic acid - 4 Na salt at room temperature for 1 to 5 hours.

The second graft is prepared by placing the first graft of above in a reactor, adding 6.7 g of potassium lauryl aryl sulfonate, and then blending in 300 parts of polybutadiene in latex form, 120 parts of methylmethacrylate, 30 parts of styrene, and the like amounts of the initiator system of above. The second rubber to second monomer ratio in this stage is 2:1. The grafting reaction is run at room temperature for 1-5 hours with constant agitation.

In this example, the mixed grafted polybutadiene phase contains, by calculation, 1 part of a 1:1 graft for every 2 parts of a 3:1 graft wherein the grafts are intimately mixed. The overall rubber to monomer ratio is 2:1.

21.75 Parts of the above grafted rubber are then blended with 78.25 parts of the above terpolymer so as to prodvide a final polybutadiene content of 14.5%. The blending is conducted on a devolatilizer-extruder at a temperature on the inlet end of about 250"F. and at the die end of about 560"F. under a vacuum of 25-27 in Hg.

The resultant composition may then be formed into various specimens and tested for physical and optical properties. Superior optical properties are noted as compared to a conventionally prepared product wherein the grafted rubber is prepared from a 3:1 rubber-to-monomer single stage reaction as disclosed in U.S.

Patent 4,085,166.

Example 52 The procedure of Example 51 is repeated until the grafting polymerizations which are preformed as follows: A first grafted rubber composition is prepared by blending 325 parts of polybutadiene in latex form with 133 parts of methylmethacrylate and 33 parts of styrene. The rubber to monomer ratio is 1.963:1. The monomers are then grafted onto the polybutadiene by a redox initiated polymerization using, based on monomer, 0.33 part of t-butylhydroperoxide, 0.66 part of sodium formaldehyde sulfoxylate, 88 ppm ferric chloride.6H2O, and 408 ppm of ethylenediamine tetraacetic acid - 4Na salt at room temperature overnight.

The maximum exotherm was reached in 36 minutes. The solids content of the first stage is 45.1 %.

The first grafted product is placed in a reactor along with 17.48 parts of sodium lauryl aryl sulfonate and then 1646 parts of polybutadiene in latex form (44.8% solids, 737 parts polybutadiene) and deionized water.

The pH is adjusted to about 8.3 with 1.5% aqueous ammpnia. To this is charged 56 parts of styrene with stirring and the equilibrating mixture is purged with nitrogen to provide a near oxygen-free atmosphere.

Then 37 parts of sodium formaldehyde sulfoxylate chelate solution of the following is added: 96.25% deionized water 3.51% sodium formaldehyde sulfoxylate 0.19% ethylenediaminetetraacetic acid tetra sodium salt 0.04% ferric chloride hexahydrate 100% After five minutes and continuing the stirring, 222 parts of methyl methacrylate and 32.8 parisoTIerv-Dutys hydroperoxide solution 1.7% t-butyl hydroperoxide and 98.3% deionized water are pumped into the reactor.

The methylmethacrylate rate is 1.85 part per minute for 2 hours. The t-butylhydroperoxide solution rate is 1.64 part per minute for 10 Minutes, then 0.1367 part per minute for 120 minutes. The second rubber to second monomer ratio in this second stage is 2.666:1. One hour after the monomer addition is completed the conversion to polymer is 98-99%. The final solids are about 47%.

In this example, the mixed grafted polybutadiene phase contains by calculation 1 part of a 1.13:1 graft for every 2 parts of a 4:1 graft which are intimately mixed. The overall rubber to monomer ratio is 2.45:1.

20.4 Parts of the above grafted rubber are then blended with 79.6 parts of the above terpolymer so as to provide a final polybutadiene content of 14.5%. The blending is conducted on a devolalitizer-extruder at a temperature on the inlet end of about 250"F. and at the die end of about 560"F. under a vacuum of 25-27 in Hg.

The resultant transparent composition is then formed into various specimens and tested. The physical and optical properties were as follows: Notched Izod, fppi 2.14 Gloss %,20 56 Floss %, 60' 81 Examples 53 - 56 The procedure of Example 51 is repeated except that in the second grafting polymerization 0.4 part of sodium formaldehyde sulfoxylate, 89 ppm ferric chloride.6H20 and 407 ppm ethylene diamine tetraacetic acid - 4Na are used and the first grafting polymerization is performed by a SCAM procedure as follows: A graft rubber composition is prepared by charging 225 Parts of polybutadiene latex (44.5% solids, 100 parts of polybutadiene) and 25 parts of deionized water to a reactor, and adjusting the pH to about 8.3 with 1.5% aqueous ammonia. To this is charged 10 parts of styrene with stirring and the equilibrating mixture is purged with nitrogen to provide a near oxygen-free atmosphere. Then 6.6 parts of sodium formaldehyde sulfoxylate chelate solution of Example 2 is added. After five minutes and continuing the stirring, 40 parts of methyl methacrylate and 4.69 parts of tert-butyl hydroperoxide solution (2.13% t-butyl hydroperoxide and 97.87% deionized water) are pumped into the reactor. The methylmethacrylate rate is 0.6667 part per minute for 1 hour. The t-butylhydroperoxide solution rate is 0.235 part per minute for 10 minutes, then 0.0391 part per minute for 60 minutes.

The above procedure is repeated except that the styrene is pumped in together with the methylmethacrylate.

21.75 and 24.75 parts of each of the above grafted rubbers are then blended with 78.25 and 75.25 parts, respectively, of the above terpolymer so as to provide final polybutadiene contents of 14.5% and 16.5%. The blending is conducted on a decolalitizer-extruder at a temperature on the inlet end of about 250"F. and at the die end of about 560"F. under a vacuum of 25-27 in Hg.

The resultant transparent compositions are then formed into various specimens and tested. The results are as detailed below in Table Xl.

Table Xl Notched % Polybutadiene Styrene Izod ''' Gloss % t2) Example in Blend Pumped fppi 20 60 53 14.5 No 1.5 51 81 54 16.5 No 2.0 48 80 55 14.5 Yes 2.1 47 79 56 16.5 Yes 2.4 46 70 (1) ASTM 256, Method A (2) ASTM 2457 Example 57 The procedure of Example 51 is repeated to prepare the resinous polymer. The grafted Rubber is prepared as follows: A first grafted rubber composition is prepared by charging 151 parts of polybutadiene latex (44.8% solids, 67. 65 parts of polybutadiene) and 19.5 parts of deionized water to a reactor and adjusting the pH to about 8.3 with 1.%5 aqueous ammonia.To this is charged 6.8 parts of styrene with stirring and the equilibrating mixture is purged with nitrogen to provide a near oxygen-free atmosphere. Then 4.48 parts of the sodium formaldehyde sulfoxylate chelate solution of Example 2 is added. After five minutes and continuing the stirring, 27.1 parts of methylmethacrylate and 10 parts of tert-butyl hydroperoxide solution (0.678% t-butylhydroperoxide and 99.322% deionized water) are pumped into the reactor. The methylmethacrylate rate is 0.3985 part per minute for 66 minutes. The t-butyl hydroperoxide solution rate is 0.5 part per minute for 10 minutes and then 0.0833 part per minute for 60 minutes. The rubber to first monomer ratio is 2:1. This product is about 46% solids.

To the first grafted product are added 18.5 parts of a 23% aqueous solution of potassium lauryl aryl sulfonate and 36 parts of deionized water with stirring, then 453 parts of polybutadiene latex (44.8% solids, 203 parts of polybutadiene). The pH is adjusted to about 8.3 with 1.5% aqueous ammonia. To this is charged 20.3 parts of styrene with stirring and the equilibrating mixture is purged with nitrogen to provide a near oxygen-free atmosphere. Then 13.4 parts of sodium formaldehyde sulfoxylate chelate solution of Example 2 is added. After five minutes and continuing the stirring, 81.2 parts of methylmethacrylate and 10 parts of t-butyl hydroperoxide solution (2.03% t-butyl hydroperoxide and 97.97% deionized water) are pumped into the reactor. The methyl methacrylate rate is 1.3533 part per minute for 1 hour.The t-butyl hydroperoxide rate is 0.5 part per minute for 10 minutes, then 0.033 part per minute for 1 hour. The second rubber to second monomer ratio in the second state is 2:1. The final solids are 47.5%.

In this Example the mixed grafted polybutadiene phase contains by calculation 1 part of a 1:1 graft for every 2 parts of a 3:1 graft which are intimately mixed. The overall rubber to monomer ratio is 2:1.

21.75 parts of the above grafted rubber are then blended with 78.25 parts of the above terpolymer so as to provide a calculated final polybutadiene content of 14.5%. The blending is conducted on a decolalitizerextruder at a temperature on the inlet end of about 250 F. and at the die end of about 56"F. under a vacuum of 25-27 in. Hg.

The resultant transparent composition is then formed into various specimens and tested. The results are given below in Table XII along with results for products produced by the conventional procedure with a rubber to monomer ratio of 3:1 and the MEG procedure of above by mixing a 3:1 graft rubber with a 1:1 rubber. The percent polybutadiene analyzed represents 80-85% of the polybutadiene present in the composition and the numbers are intended solely for a comparison of relative amounts of polybutadiene actually present.

As can be readily seen from the results, the DGMAC process results in improved optical properties over both the conventionally prepared sample and that of the MEG process (mixed elastomer grafts). The DGMAC process also provides a product with impact strengths almost identical to the conventionally prepared material. The superior optical properties are best seen in the thermoformed samples.

Example 58 The procedure of Example 57 is repeated except that the first rubber to first monomer ratio is 1.963:1 and the second rubber to second monomer ratio is 2.666:1. Therefore, the mixed polybutadiene phase contains, by calculation, 1 part of 1.13:1 graft for every 2 parts of a 4:1 graft which are intimately mixed. The overall rubber to monomer ratio is 2.45:1.

The resultant transparent composition is then form Table Xll MEG Conventionally (Mixing of Prepared Elastomer Product grafts) Example 57 %PolybutadieneAnalyzed 14.3 12.8 11.7 Molded Samples Notched Izod, fppi 1.8 1.1 1.4 Dart Impact, fppi(l) 41.5 34.8 39.3 TotalZ Haze, % (2' 8.1 10.8 8.1 Gloss, % 20 55 61 65 60 82 85 86 Thermoformed Samples Glass, % 20 2 13 15 60 32 59 65 (1) ASTM 3029m, modified TUP (2) ASTM 1003 (3)Samples thermoformed at 350-365"F. in the shape of margarine tubes with outside walls 0.011 in. thick.

ed into various specimens and tested. The results are as follows: Notched lzod,fppi 2.1 Gloss %, 20' 57 60 82 Example 59 The procedures of Examples 51-57 were repeated, except that the ethylacrylate in the resin portion is replaced by methylacrylate. Similar results are observed.

Example 60 The procedures of Examples 51-57 are repeated except that the ethylacrylate in the resin portion is omitted and the ratios of the monomers is varied to compensate for the resultant change in refractive index. Similar results are noted.

Example 61 The procedures of Examples 51-57 are repeated except that the polybutadiene latex is replaced by a polyisoprene latex, and the monomer ratios in both the graft and the resin phases are varied to compensate for the difference in the rubber refractive index. Comparable results are achieved.

Example 62 The procedures of Examples 51-57 are repeated except that 3 parts of methylmethacrylate on the graft polymerizations are replaced by 3 parts of ethylacrylate. Similar results are observed.

Example 63 To determine the taste-transfer and odor characteristics of compositions of the present invention as opposed to prior compositions and glass, bottles were made from each material being tested.

For the taste-transfer test water was put in each bottle and allowed to sit at room temperature for one week. At which time, a sample of the water from each bottle was poured into separate glass beakers, drunk by a panel of six participants, and rated by each participant from best (least taste-transfer) to worst (most taste-transfer). The procedure was run in duplicate and the resluts are summarized in Table Xlil below.

For the odor test, a new bottle of each material is allowed to sit uncapped overnight, then it is capped and allowed to sit at room temperature for one week. Each bottle is uncapped and each of six participants rates the bottles from best (low odor) to worst (high odor). The results are summarized in Table XIII below.

The following materials were tested: A. Product of Example 58 except the methyl methacrylate is pumped in for one hour.

B. Same as A but made on a different day.

C. Conventionally prepared material as in U.S. Patent 4,085,116.

D. Conventionally prepared material as in U.S. Patent 3,354,238 wherein the ethylacrylate is replaced by acrylonitrile.

E. Product of Example 57.

F. Glass G. Same as C, but a different sample.

The results clearly demonstrate greatly reduced taste-transfer and-odor for compositions of the present invention (A, B and E) as compared to conventionally prepared materials of the same composition (C and G) as well as to compositions containing acrylonitrile (D).

Table Xlil Results of Example 13 Taste-Transfer Odor

Best E B F E B A # A D D G G Worst C C 1) Samples grouped together were indistinguishable in either taste-transfer or odor.

2) Participants said that the tastes of Samples C and G were especially poor.

Claims

1. A molding composition char. icterized by exhibiting superior optical properties comprising: (A) a major portion of a resinous polymeric phase, and (B) a minor portion of a rubbery phase, said rubbery phase being prepared from rubber and one or more monomers which are grafted thereon and are compatible with said resinous phase, wherein the rubbery phase is essentially uniformly dispersed and essentially non-agglomerated and contains essentially no particles greater in diameter than about 1 micron, the ratio of rubber to monomer being from about 1:1 to 6:1.

2. The composition of Claim 1 wherein the rubbery phase grafted polymer is prepared by a sequential and controlled addition wherein at least the monomer having the best compatibility as polymer with the resinous phase is added over at least 15 minutes and the grafting reaction occurs during said addition.

3. The composition of Claim 2 wherein a redox initiator is used and either the reductant or the oxidant portion of the initiator is added simultaneously with the monomer which is controllably added.

4. The composition of Claim 2 wherein the ratio of rubber to monomer in the rubbery phase is from about 2.5:1 to 4:1.

5. The composition of Claim 2 wherein the addition is for at least one hour.

6. The composition of Claim 1 wherein the rubbery phase is a mixture of two discrete rubbery phases, said rubbery phases each being prepared from a rubber and one or more monomers which are grafted thereon and are compatible with said resinous phase, one of said rubbery phases having a rubber to monomer ratio of at least 2.5:1 while the other of said rubbery phases has a rubber to monomer ratio of less than about 2:1, wherein the rubbery phase having the higher rubber to monomer ratio is present in excess of the one having the lower rubber to monomer ratio.

7. The composition of Claim 6 wherein the higher the rubber to monomer ratio is about 3:1 to 5:1,the lower rubber to monomer ratio is below about 1.5:1, and the lower rubber to monomer ratio rubbery phase is about 5 to 40% by weight of the total rubbery phase.

8. The composition of Claim 1 wherein the rubbery phase is a mixture of two rubbery phases each being prepared from a rubber and one of more monomers which are grafted thereon and are compatible with said resinous phase, one of said rubbery phases having a rubber-to-monomer ratio of at least 2.6:1 while the other of said rubbery phases has a rubber-to-monomer ratio of less than about 2.0:1, wherein the rubbery phase having the higher rubber-to-monomer ratio is present in excess of the one having the lower rubber-to-monomer ratio, and is prepared in the presence of the one having the lower rubber-to-monomer ratio.

9. The composition of Claim 8 wherein at least one of said rubbery phases is prepared by a sequential and controlled addition during the grafting reaction of at least the monomer having the best compatibility to that of the resinous phase and wherein the addition is for at least 15 minutes.

10. The composition of claim 8 wherein two stages of grafting are used and the rubbery phase contains two different rubber-to-monomer ratio portions.

11. The composition of Claims 8-10 wherein each stage of grafting is performed by a sequential and controlled addition during the grafting reaction of at least the monomer having the best compatibility to that of the resinous phase and wherein each addition is for at least 15 minutes.

12. The composition of Claims 1-11 wherein the resinous phase is a polymer of about 60 to 80 parts methylmethacrylate, about 15 to 30 parts styrene, and about 0 to 15 parts of a monomer selected from the group consisting essentially of methylacrylate, ethylacrylate, or acrylonitrile.

13. The composition of Claims 1-12 wherein the rubber is polybutadiene in latex form and it is present as about 5 to 25% by weight of the molding composition.

14. The composition of Claims 1-13 wherein the rubbery phase is polybutadiene grafted with methylmethacrylate, styrene, and optionally a monomer selected from methylacrylate, ethylacrylate and acrylonitrile.

15. A method of preparing a non-agglomerating, readily dispersible grafted rubber comprising: (1 ) placing a rubber latex in a reaction vessel; (2) adding thereto one or more monomers to be grafted thereon; (3) equilibrating said rubber latex; (4) controllably adding to said equilibrated rubber latex at least one monomer to be grafted thereon, wherein the addition of said monomer takes at least 15 minutes; during which time a grafting reaction occurs.

16. A method of preparing an improved non-agglomerating, readily-dispersible mixture of grafted rubbers comprising performing a series of grafted polymerization reactions, each later reaction being performed in the presence of the products of the earlier of said reactions.

17. The method of Claim 15 wherein at least one of the grafted polymerizations is a sequential and controlled addition of monomer polymerization and the controlled addition is for at least 15 minutes during which timethe graft polymerization occurs.

18. The method of Claims 15-17 wherein the rubber latex is polybutadiene, the monomer controllably added is methylmethacrylate, a pH of from about 6 to 8.5 is used, and a temperature of about 20 to 65"C is used.

19. The method of claims 15-18 wherein a redox initiator is used and either the reductant or the oxidant portion of the initiator is controllably added at the same time as the monomer which is controllably added.

20. The method of Claims 15-19 wherein one or more other graftable monomers are placed in the reaction vessel along with the rubber latex and said other graftable monomers are styrene and optionally a monomer selected from the group consisting essentially of methylacrylate, ethylacrylate, and acrylonitrile.