Reactive melt extrusion grafting of thermoplastic polyvinyl alcohol/polyolefin blends

TECHNICAL FIELD
The present invention relates to melt extrudable blends of polyolefins and thermoplastic polyvinyl alcohol (PVOH) and, more particularly, relates to reactive extrusion grafted blends of polyolefins and thermoplastic PVOH.
BACKGROUND OF THE INVENTION
One of the more useful methods to modify polymers involves blending them with other polymers of different structures and properties. In fact, the subject of polymer blends has been one of the key research and development areas in the field of polymers in the past decade. In a few cases, polymer blend combinations are miscible, i.e., they exhibit thermodynamic miscibility and are mixed at the scale of molecular dimensions. These blends are mechanically compatible.
However, most blends are phase separated and generally exhibit poor mechanical compatibility. Phase separated systems in several cases can exhibit mechanical compatibility where the polymer compositions are similar, e.g., polyolefin blended with other polyolefins, or where interfacial agents are added to improve the compatibility at the interface between the constituents of the polymer blend.
For blends of polyolefins and PVOH, the extremes in polymer compatibility are expectedly observed. Polyolefins are very water insensitive whereas PVOH dissolves in water. Polyolefins are sensitive to hydrophobic compounds, e.g. oils and grease, whereas PVOH is very resistant.
Polymer blends of polyolefins and thermoplastic PVOH are melt processible, however, they exhibit very poor mechanical compatibility. This poor mechanical compatibility is manifested in the mechanical property profile of the blends relative to the properties of the unblended constituents where the blends suffer significantly in elongation at break, tensile strength and toughness. In addition, the blends exhibit non-homogeneity as noted in the injection molded surface and topology of the fractured samples for mechanical testing.
The utility of polyolefin/thermoplastic PVOH blends, if mechanical compatibility could be achieved, can be envisioned for many applications including barrier films, foam, injected molded articles and extrusion applications. The potential utility of polyolefin/thermoplastic PVOH blends has been noted in the patent literature. These patents note the poor mechanical compatibility of polyolefins and thermoplastic PVOH and many note various approaches towards solving this deficiency. Thus, modifications of polyolefin/thermoplastic PVOH blends are necessary in order to obtain useful properties.
U.S. Pat. No. 4,600,746 discloses the compatabilization of PVOH with a functional polymer, i.e., polyolefin or an ethylene-ester copolymer with groups capable of reacting with the hydroxyl of PVOH, e.g. carboxylic acid, anhydride, for barrier polymer blends. Ethylene-acrylic acid, ethylene-methacrylic acid, ionomers, and maleic anhydride grafted polyolefins are disclosed in blends with PVOH as melt processible alloys.
U.S. Pat. No. 4,950,513 discloses a laminate of a polyolefin, a melt blend of a polyamide and a PVOH, and an alkyl carboxyl-substituted polyolefin. The laminate is used as a barrier film composition.
U.S. Pat. No. 4,806,597 discloses a blend of an aromatic polycarbonate, polyolefin, ethylene-vinyl alcohol copolymer and a hydrogenated styrene/butadiene block copolymer modified with unsaturated dicarboxylic acid or anhydride.
U.S. Pat. No. 4,362,844 discloses a biaxially stretched mixture of polypropylene and an ethylene-vinyl alcohol copolymer. Coupling agents proposed to improve the compatibility include maleic anhydride or acrylic acid grafted polypropylene or ethylene-acrylic acid copolymers.
The above references disclose various methods involving modification of olefins to improve compatibility with PVOH. These methods comprise including polar groups in the polyolefin structure or potentially reactive groups, for example, carboxylic acid or anhydride functionality.
Borggreve, R. J. M., et al, "Brittle-Tough Transition In Nylon-Rubber Blends: Effect Of Rubber Concentration And Particle Size", POLYMER, 1987, Vol 28, August, (1489-1496) discloses a one-pass extrusion operation for polyolefin compatibilization with polyamides where the maleic anhydride is grafted to polyolefins utilizing peroxide.
SUMMARY OF THE INVENTION
The present invention provides a single pass, melt reactive extrusion compatibilization of polyolefin and a PVOH. The melt reactive grafting of unsaturated acids or anhydrides to polyolefins followed by reaction with thermoplastic PVOH provides mechanical compatibility which affords significant advantages over the prior art where a pregrafted polyolefin is mixed in a melt blending operation with the PVOH.
Specifically, the method for preparing a compatible blend of polyolefin and thermoplastic PVOH by single pass, melt reactive extruding comprises:
(1) melting polyolefin in a melt extruder;
(2) melt blending an unsaturated carboxylic acid or anhydride into the melted polyolefin;
(3) adding a free radical source to the melt blend and grafting the unsaturated carboxylic acid or anhydride onto the polyolefin;
(4) melt blending thermoplastic PVOH into the grafted polyolefin/unsaturated carboxylic acid or anhydride melt mixture, and optionally;
(5) extruding through a die; and
(6) cooling and pelletizing.
Advantages of the single pass reactive melt extrusion compatibilization procedure include the following:
(a) uniformity of the blend leading to improved water resistance;
(b) the residual unsaturated carboxylic acid or anhydride can react with PVOH or plasticizer containing hydroxyl groups and thus not yield problems associated with residual material that will result if the constituents were prepared separately; and
(c) an economic advantage in conducting the single reactive extrusion process instead of preparing, pelletizing and reextruding the grafted polyolefin with thermoplasic PVOH;

DETAILED DESCRIPTION OF THE INVENTION
The mechanical and visual compatability of blends of thermoplastic PVOH and various polyolefins is very poor. The present invention provides for the melt reactive extrusion grafting of an unsaturated carboxylic acid or anhydride onto the polyolefin followed by melt mixing with a thermoplastic PVOH in a single pass, thus eliminating the need to prepare a grafted polyolefin and recovering the product only to reextrude it with the thermoplastic PVOH in a second operation.
"Reactive extrusion" is the use of chemical reactions during polymer extrusion to form desired products. Free radical initiators, crosslinking agents, and other reactive additives can be injected into the extruder to cause these reactions.
The melt extruder used in the present extrusion operation is designed to conduct several operations during the preparation of the blends. The polyolefin is fed into the initial elements of the extruder. After melting the polyolefin in the initial elements, the unsaturated carboxylic acid or anhydride is fed into the extruder and, further down the extruder barrel, a free radical source such as a peroxide is fed to the extruder to yield improved grafting efficiency. After a length of extrusion sufficient to accomplish polyolefin grafting of the acid or anhydride, i.e., sufficient time, the thermoplastic PVOH is fed to the molten, grafted polyolefin stream either as pellets or powder through an open throat to the extruder or as a molten stream fed through a side stream extruder. After melt consolidation of the grafted polyolefin/thermoplastic PVOH blend, a vacuum port can optionally be used to removed ungrafted or unreacted maleic anhydride. Optionally, additional PVOH plasticizer can be pumped into the extruder after the vacuum port as makeup for any devolatilized PVOH plasticizer, if a low boiling plasticizer has been used.
The resulting reactive melt extrusion, compatibilized blend is extruded through die(s) at the end of the extruder and cooled on a chilled belt and pelletized, all procedures well known in the art. Water cooling can be used where higher levels of polyolefin are present in the blend, e.g., greater than 50% volume fraction.
While the above procedure is the preferred embodiment, other single pass extrusion conditions can be employed. Such processes would involve the addition of the acid or anhydride and peroxide at the same location along the extruder.
The polyolefins suitable for use in the present invention include polypropylene, polyethylene (including high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene and linear very low density polyethylene), poly(butene-1) and ethylene-propylene rubber. Such polyolefins would have average molecular weights ranging from 20,000 to 2,000,000, preferably 50,000 to 700,000. Such polyolefins would have melt index values [44 psi (3.1 kg/cm.sup.2), 190.degree. C.] of 0.01 to 200 dg/min, preferably 0.5 to 40 dg/min.
The polyethylenes contemplated can be copolymerized with propylene, butene, hexene, octene and the like to achieve the various densities available for these materials. Ethylene copolymers such as ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers and ionomers, and ethylene-methacrylic acid copolymers and ionomers are additional polyolefins suitable for this invention. Also considered as a polyolefin for purposes of this invention are styrene-ethylene/butylene-styrene ABA block copolymers of greater than 50 wt % of the ethylene/butylene block.
The polyolefin content of the polyolefin/thermoplastic PVOH blend is 10-80 wt %, preferably 25-75 wt %.
A thermoplastic PVOH is required in the present process. As noted in a recent review of PVOH given by F. L. Marten in the Encyclopedia Of Polymer Science And Engineering, Second Ed., Vol 17, p 167, John Wiley & Sons, New York, 1989, several patents claim the preparation of extrudable PVOH using high boiling, water-soluble organic compounds containing hydroxyl groups. These compounds, for example glycerol, low molecular weight polyethylene glycols, are plasticizers which lower the melting point of PVOH into a processible range. Other suitable plasticizers such as sulfonamides are suitable if they are high boiling and miscible with PVOH.
The preferred thermoplastic PVOH for use in the present process, however, is that disclosed in U.S. Pat. No. 5,051,222 which is incorporated by reference. U.S. Pat. No. `222 discloses a thermoplastic PVOH prepared by a melt extrusion process which comprises adding sufficient energy to the PVOH (preferably with a plasticizer) to both melt the PVOH and essentially eliminate the crystallinity in the melt while simultaneously removing energy from the melt at a rate sufficient to avoid decomposition of the PVOH. Such thermoplastic PVOH's are commercially available from Air Products and Chemicals, Inc. under the VINEX trademark.
Suitable PVOH's have a 70-99+ mole % hydrolysis, preferably 78-94 mole %, and a degree of polymerization of 200 to 4000, preferably 300 to 1500.
In addition to plasticizers, the thermoplastic PVOH can contain other water soluble polymers such as poly(vinylpyrrolidone), poly(ethyloxazoline) and poly(ethylene oxide).
Also suitable as the thermoplastic PVOH are the hydrolysis product of a vinyl acetate copolymer which is at least 70 wt % vinyl acetate, especially ethylene-vinyl alcohol copolymers since they also exhibit poor mechanical compatibility with polyolefins. Ethylene content of up to 30 wt % can be used. These copolymers are produced by the hydrolysis of ethylene-vinyl acetate copolymers using methods similar to that for PVOH and are readily available commercially. Hydrolysis levels (based on vinyl acetate) of greater than 70 mole % are desired.
The amount of thermoplastic PVOH in the blend is 20-90 wt %, preferably 25-75 wt %.
Of the unsaturated carboxylic acids and anhydrides that are used for compatibilization of the polyolefin/thermoplastic PVOH blends, maleic anhydride is the preferred material. However, vinyl-containing carboxylic acids, such as acrylic acid or methacrylic acid can also be used, as can be mixtures of maleic anhydride and such carboxylic acids. The amount of the carboxylic acid or anhydride used will vary with the polyolefin selected, however, a range of 0.1 to 4 wt % based on polyolefin is desirable.
The free radical source suitable for use in the process are those materials typically used for polyolefin compounding and exhibiting free radical generation in the melt processing range typically used for polyolefins. Specific examples include 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane; t-butylperoctoate; t-butylperoxypivalate; dicumylperoxide; 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane; bis(t-butylperoxy-isopropyl)benzene and the like.
Blends of the reactive extruded polyolefin-PVOH compositions produced according to the present invention with PVOH, polyolefins or other polymers is also contemplated. Other polymers would include polystyrene, poly(.epsilon.-caprolactone), ABS, PVC, poly(methyl methacrylate), poly(vinylidene chloride), poly(vinylidene fluoride), styrene-maleic anhydride copolymers, poly(phenylene oxide)/polystyrene blends and the like.
Applications for the reactive extruded polyolefin-PVOH compositions produced according to the present invention include films, antistatic additives, injection molded articles, extruded profiles, fiber additives, foam and barrier containers. The reactive extruded compositions can be used as an adhesive interliner between films of polyolefins and PVOH. These compositions can be added to polyolefin or to PVOH, or to both, to improve the adhesion between layers of polyolefin and PVOH films.
REACTIVE MELT EXTRUSION PROCESS USED IN THE EXAMPLES
A twin screw extruder (Werner & Pfleiderer ZSK-40 extruder) was set-up to conduct the Runs as discussed in the following Examples. The screw design was held constant and the feed ports for the constituents of the blends were kept constant. The polyolefin was fed to the extruder using conventional equipment designed to deliver constant flow rates. Maleic anhydride was melted and fed to the extruder as a liquid at a position where the polyolefin stream was fluxed. At a position further down the barrel of the extruder the peroxide was fed (as a liquid) optionally diluted with xylene. A mixing zone was utilized to assure mixing of the maleic anhydride and peroxide with the polyolefin and to allow for sufficient grafting to occur. After this reactive extrusion stage, the thermoplastic PVOH pellets were fed to an open throat of the extruder. A mixing zone was utilized to blend the grafted polyolefin with the thermoplastic PVOH followed by a vacuum port to remove unreacted maleic anhydride. The product was extruded through six dies onto a chilled belt and pelletized.
EXAMPLE 1
The first series of Runs 1-7 involved blends of a thermoplastic PVOH (Vinex 2025: Air Products and Chemicals, Inc.) with polypropylene (Profax 6723: Himont). The feed rates of the thermoplastic PVOH, polypropylene, L-101 peroxide [2,5-dimethyl-2,5-bis(t-butylperoxy)hexane], and maleic anhydride are noted in Table 1. The extrusion temperature settings were 200.degree. C. across the extruder. The melt flow data in Table 1 were obtained at 200.degree. C. using a procedure similar to ASTM-D1238. Samples of the Runs were injection molded at 200.degree. C. into test specimens with properties obtained dry and after 25 days at 50% R. H. conditioning. The mechanical properties (tensile modulus, tensile strength, ultimate elongation) were determined using procedures similar to ASTM-D638. Note that 1P, 5P, and 10P refer to 44 psi (3.1 kg/cm.sup.2), 220 psi (15.5 kg/cm.sup.2), and 440 psi (31 kg/cm.sup.2) loading applied to the melt index apparatus. The notched impact strength was determined using the procedure described by ASTM D-256. The mechanical properties are noted in Table 1. The major difference noted was the improved homogeneity of the injection molded surface with addition of both maleic anhydride and peroxide. Additionally, the ultimate elongation showed a distinct improvement with reactive modification using maleic anhydride and peroxide.
TABLE 1__________________________________________________________________________RUN 1 2 3 4 5 6 7__________________________________________________________________________Vinex 2025 40 40 40 40 40 40 40Feed Rate(lb/hr)Polypropy- 40 40 40 40 40 40 40leneFeed Rate(lb/hr)Maleic -- -- 1.5% 1.5% 3.0% -- 0.75Anhydride*L-101 -- -- 2300 4600 4600 4600 4600(peroxide)*Conc. (ppm)Vacuum No Yes Yes Yes Yes Yes YesMelt Flow 8.5(1P) 7.6(1P) 5.8(5P) 62.5(5P) 37.7(5P) 20.4(1P) 14.8dg/min200.degree. C.(1P)Mechanical rough rough uniform uniform uniform rough uniformProperties(Dry)MoldedSurfaceTensile 197,000 198,000 189,000 189,000 162,000 193,000 204,000Modulus (psi)Tensile 4,800 4,500 4,600 4,900 4,000 4,400 4,500Strength(psi)Elongation @ 6 6 16 17 16 5 10Break (%)Notched Izod 1.0 1.1 0.84 1.1 1.0 0.9 0.82ImpactStrengthft. lbs./in.of notchMechanical Properties (50% RH: Conditioned for 25 days)Tensile 197,000 194,000 174,000 185,000 176,000 168,000 175,000Modulus(psi)Tensile 4,230 4,140 4,210 4,680 4,590 3,960 4,190Strength(psi)Elongation @ 6.0 5.0 14.0 21.3 17.6 6.3 8.8Break (%)Notched Izod 1.3 1.2 0.8 1.6 0.8 1.0 0.7ImpactStrengthft. lbs./in.of notch__________________________________________________________________________
EXAMPLE 2
Runs 8-20 involved blends of Vinex 2025 thermoplastic PVOH and linear low density polyethylene (LLDPE) (Tuflin HS-7027: Union Carbide). The same extruder and extrusion conditions were employed as in Example 1 except for specific concentrations of the peroxide (L-101) and maleic anhydride. The specific Runs, and the property data of the resultant blends (controls and reactive extruded blends) are listed in Table 2. One blend (Run 20) utilized a 50/50 blend of LLDPE and polypropylene (Profax 6723) with Vinex 2025 PVOH. The property data were determined according to the procedures noted in Example 1. The addition of peroxide and/or maleic anhydride to the blends resulted in lower melt flow (higher melt viscosity). At higher levels of maleic anhydride and peroxide (Runs 11 and 12), the samples were too crosslinked to test. At the lower levels of maleic anhydride and peroxide, improved homogeneity of the blends was observed along with increased tensile strength and elongation at break compared to the control blend (Runs 8 and 9) as well as the blends with either peroxide or maleic anhydride addition (Runs 10 and 19).
TABLE 2__________________________________________________________________________RUN 8 9 10 11 12 13 14__________________________________________________________________________Vinex 2025 40 40 40 40 40 40 40Feed Rate(lb/hr)LLDPE 40 40 40 40 40 40 40Feed Rate(lb/hr)Maleic -- -- -- 3.0 3.0 1.0 1.25Anhydride*Conc. (%)L-101 2000 2000 1000 1000 1000(peroxide)*Conc. (ppm)Vacuum No Yes Yes Yes Yes Yes YesMelt Flow 12.6(1P) 12.0(1P) 6.1(1P) No flowdg/min (10P)14.4(10P)MechanicalProperties(Dry)Tensile 188,000 167,000 185,000 Too Cross- Too Cross- 145,001 169,000Modulus (psi) linked to linked toTensile 3,600 3,700 3,820 test test 4,400 4,500Strength(psi)Elongation @ 6 5 5 7 28Break (%)Notched Izod 1.2 1.3 1.3 1.2 1.3ImpactStrengthft. lbs./in.of notchMechanical Properties (50% RH: Conditioned for 25 days)Tensile 139,000 163,000 145,000 126,000 122,000Modulus(psi)Tensile 2,950 3,094 3,239 3,390 3,550Strength(psi)Elongation @ 6.3 6.8 5.7 7.3 38.8Break (%)Notched Izod 1.5 1.5 1.5 1.5 2.2ImpactStrengthft. lbs./in.of notch__________________________________________________________________________ RUN 15 16 17 18 19 20__________________________________________________________________________ Vinex 2025 40 40 50 -- 40 40 Feed Rate (lb/hr) LLDPE 40 40 50 40 40 40 Feed Rate (lb/hr) Maleic 0.5 0.5 0.5 0.5 0.5 1.0 Anhydride* Conc. (%) L-101 1000 500 500 500 -- 1000 (peroxide)* Conc. (ppm) Vacuum Yes Yes Yes Yes Yes Yes Melt Flow 23.9(10P) 14.4(10P) 21.4(10P) 7.2(5P) 3.34(1P) dg/min 1.88(10P) Mechanical Properties (Dry) Tensile 173,000 158,000 180,000 56,000 164,000 157,000 Modulus (psi) Tensile 4,900 4,400 4,600 2,500 2,800 4,700 Strength (psi) Elongation @ 9 7 6 939 4 6 Break (%) Notched Izod 1.0 1.0 1.1 No 1.4 1.0 Impact break Strength ft. lbs./in. of notchMechanical Properties (50% RH: Conditioned for 25 days)Tensile 139,000 134,000 127,000 58,000 143,000 139,000Modulus(psi)Tensile 3,980 3,645 3,660 2,610 2,350 4,015Strength(psi)Elongation @ 18.5 11.1 10.0 978 6.0 6.3Break (%)Notched Izod 1.4 1.3 1.2 No 1.4 1.2Impact BreakStrengthft. lbs./in.of notch__________________________________________________________________________ *Based on LLDPE weight 50/50 blend of LLDPE/Profax 6723 PP
EXAMPLE 3
Runs 21-27 involved blends of Vinex 2025 thermoplastic PVOH and ethylene-propylene rubber (Vistalon 719 EPR: Exxon). Except for the specific concentrations of the peroxide (L-101) and maleic anhydride, the same extruder and extrusion conditions were employed as in Example 1. The specific experiments and the property data of the resultant blends (controls and reactive extruded blends) are listed in Table 3. The reactive extruded blends (Runs 23-25 and 27) yielded higher tensile strength, higher elongation at break, and much higher notched izod impact strength than the control blend (Run 21) or the control blend with peroxide addition (Run 22). Maleic anhydride addition alone (Run 26) gave higher tensile strength and elongation relative to the control blend and the control blend with peroxide but not as good overall as the blends with both maleic anhydride and peroxide addition.
TABLE 3__________________________________________________________________________RUN 21 22 23 24 25 26 27__________________________________________________________________________Vinex 2025 48 48 48 48 48 48 48Feed Rate(lb/hr)EPR 32 32 32 32 32 32 32Feed Rate(lb/hr)Maleic -- -- 1.25 0.9 0.9 0.9 0.6Anhydride*Conc. (ppm)L-101 -- 1000 1000 1000 600 -- 600(peroxide)*Conc. (ppm)Vacuum Yes Yes Yes Yes Yes Yes YesMelt Flow 61.1(5P) 50.5(5P) No flow 0.95(10P) 1.27(10P) 1.18(10P)dg/min (10P)4.91(10P)MechanicalProperties(Dry)Tensile 117,000 124,000 153,000 143,000 164,000 151,000 139,000Modulus (psi)Tensile 3,500 3,200 5,200 5,300 5,400 5,500 5,100Strength(psi)Elongation @ 9 7 81 78 73 16 88Break (%)Notched Izod 1.2 1.2 21.9 18.9 20.3 1.6 11.5ImpactStrengthft. lbs./in.of notchMechanical Properties (50% RH: Conditioned for 25 days)Tensile 82,000 88,000 72,000 73,000 82,000 86,000 68,000Modulus(psi)Tensile 2,015 1,925 2,995 2,900 3,015 3,500 2,860Strength(psi)Elongation @ 15.7 13.6 179 184 156 79 222Break (%)Notched Izod 1.5 1.6 20.8 19.6 22.8 10.8 19.3ImpactStrengthft. lbs./in.of notch__________________________________________________________________________ *Based on EPR weight
EXAMPLE 4
Runs 28-31 involved blends of Vinex 2025 thermoplastic PVOH and a 75/25 blend of polypropylene (Profax 6723)/ethylene-propylene rubber (Vistalon 719). A thermoplastic PVOH/polyolefin blend ratio of 50/50 (by weight) was employed. Except for specific concentrations of the peroxide (L-101) and maleic anhydride, the same extruder and extrusion conditions were employed as noted in Example 1. The specific Runs and property data of the resultant blends (control and reactive extruded blends) are noted in Table 4. The data were obtained using the procedures noted in Example 1. The reactive extruded blends (Runs 28-30) exhibited significantly improved homogeneity over the blend control alone (Run 31) with increased tensile strength and ultimate elongation.
TABLE 4__________________________________________________________________________ Vinex ProfaxRUN 28 29 30 31 2025 6723__________________________________________________________________________Vinex 2025 40 40 40 40 Control ControlFeed Rate(lb/hr)Polyolefin 40 40 40 40Feed Rate(lb/hr)Maleic 0.5 1.0 1.0 --Anhydride*Conc. (ppm)L-101 500 1000 2000 --(peroxide)*Conc. (ppm)Vacuum Yes Yes Yes YesMelt Flow 12.0(10P) 1.44(10P) 17.1(10P) 6.3(1P) 55.2(5P) 83.2(10P)dg/minMechanicalProperties(Dry)Tensile 164,000 180,000 146,000 162,000 283,000 127,000Modulus (psi)Tensile 4,800 5,200 4,800 4,400 10,570 5,100Strength(psi)Elongation @ 6 25 33 5 55 58Break (%)Notched Izod 0.83 1.23 1.50 1.1 0.69 2.2ImpactStrengthft. lbs./in.of notchMechanical Properties (50% RH: Conditioned for 25 days)Tensile 157,000 169,000 135,000 156,000 120,000 137,000Modulus(psi)Tensile 4,400 4,580 4,275 3,640 4,170 5,105Strength(psi)Elongation @ 7.1 38.9 79.6 6.3 226 65.3Break (%)Notched Izod 1.1 1.9 2.8 1.6 38.1 2.2ImpactStrengthft. lbs./in.of notch__________________________________________________________________________ *Based on Polyolefin weight 75/25 Polypropylene/EPR
EXAMPLE 5
This Example compares a pregrafted polyolefin melt extruded with a thermoplastic PVOH (Run A) as taught in U.S. Pat. No. 4,600,746 (essentially a two pass operation) with the single pass, reactive extrusion process according to the present invention.
The maleic anhydride grafted polyethylene produced in Run 18 was recovered as pellets. The Run 18 pellets were blended with 50% by weight of thermoplastic PVOH (Vinex 2025) in a 1" Killion extruder 30/1 L/D at 200.degree. C. The resultant product (Run A) was injection molded into test specimens. The tensile properties of the Run A sample were significantly improved over the control samples (Runs 8 and 9). The Run A blend, however, was deeper in color (yellow) than either Runs 8 and 9 (control) or the reactive extrusion Runs.
Additionally, the Run A blend exhibited poor water resistance. Samples of Run A were placed in water at 23.degree. C. along with samples of Run 9 (control) and Runs 13 and 16 (reactive extrusion). The sample of Run A became sticky on the surface when exposed to water, and water immersion (24 hours) resulted in sample disintegration. Samples of Runs 9, 13 and 16 did not exhibit the same degree of surface stickiness when exposed to water and did not disintegrate after 24 hour water immersion although they exhibited some swelling and surface softness. The improved water resistance is of significant benefit for certain barrier film applications.
EXAMPLE 6
A blend of 50% Vinex 2025 PVOH and 50% of the reactive extrusion blend of Run 23 (Vinex 2025/EPR: 60/40) was prepared in a 1" Killion extruder at 200.degree. C. The resultant pelletized blend was injection molded at 200.degree. C. and mechanical properties were obtained on dry samples as noted in Table 5.
EXAMPLE 7
A blend of 50% Vinex 2025 PVOH and 50% of the reactive extrusion blend of Run 25 (Vinex 2025/EPR: 60/40) was prepared in a 1" Killion extruder at 200.degree. C. The resultant pelletized blend was injection molded at 200.degree. C. and mechanical properties were obtained on dry samples as noted in Table 5.
EXAMPLE 8
A blend of 75% Vinex PVOH 2025 and 25% of the reactive extrusion blend of Run 25 (Vinex 2025/EPR: 60/40) was prepared in a 1" Killion extruder at 200.degree. C. The resultant pelletized blend was injection molded at 200.degree. C. and mechanical properties were obtained on dry samples as noted in Table 5.
TABLE 5__________________________________________________________________________ Tensile ImpactStrength Modulus Tensile % ft. lbs/Example Composition (psi) Strength Elongation in of notch__________________________________________________________________________6 50% Vinex 2025 282,000 8,986 40 4.1 50% Run 237 50% Vinex 2025 288,000 9,178 26 5.8 50% Run 258 75% Vinex 2025 315,000 11,375 27 1.4 25% Run 25__________________________________________________________________________
EXAMPLE 9
Blends of polypropylene (Profax 6723) and Vinex 2034 PVOH were extruded with variations in maleic anhydride and peroxide (L-101) addition. The data for Runs 41-49 are shown in Table 6. Runs 47-49 were at different Vinex/PP ratios.
TABLE 6__________________________________________________________________________RUN 41 42 43 44 45 46__________________________________________________________________________Vinex .TM. Type 2034 2034 2034 2034 2034 2034Vinex Feed Rate (lbs/hr) 40 40 40 40 40 40Polyolefin Type PP PP PP PP PP PP Profax Profax Profax Profax Profax Profax 6723 6723 6723 6723 6723 6723Polyolefin Feed Rate (lbs/hr) 40 40 40 40 40 40Maleic Anhydride Conc. (%)* -- -- 2.2% 2.2% 3.2% 3.2%L-101 (peroxide) Conc. (ppm)* -- -- 3000 4000 4000 3000Melt Flow dg/min (200.degree. C.) 10.2(1P) 8.3(1P) 62.6(10P) 110(10P) 86.8(10P)Mechanical Properties (Dry)Tensile Modulus (psi) 110,000 110,000 124,000 124,000 137,000 140,000Tensile Strength (psi) 3,100 3,100 4,900 4,900 5,000 5,100Elongation @ Break (%) 16 17 105 126 91 101Notched Izod Impact Strength 1.1 1.5 0.78 0.77 0.82 0.78ft-lbs/in of notchMechanical Properties (50% RH: Conditioned for 25 days)Tensile Modulus (psi) 96,000 86,000 107,000 104,000 99,000 108,000Tensile Strength (psi) 3,000 2,800 4,200 4,200 4,200 4,200Elongation @ Break (%) 21 24 262 133 201 358Notched Izod Impact Strength 2.0 2.0 1.0 0.90 1.0 1.0ft-lbs/in of notch__________________________________________________________________________ RUN 47 48 49__________________________________________________________________________ Vinex .TM. Type 2034 2034 2034 Vinex Feed Rate (lbs/hr) 74 50 50 Polyolefin Type PP PP PP Profax Profax Profax 6723 6723 6723 Polyolefin Feed Rate (lbs/hr) 40 27 16 Maleic Anhydride Conc. (%)* 2.2% 2.1% 3.5% L-101 (peroxide) Conc. (ppm)* 4000 4000 4000 Melt Flow dg/min (200.degree. C.) 44.9(10P) 10.0(10P) 15.8(10P) Mechanical Properties (Dry) Tensile Modulus (psi) 110,000 126,000 124,000 Tensile Strength (psi) 4,600 4,800 3,400 Elongation @ Break (%) 75 11 9 Notched Izod Impact Strength 0.81 0.68 0.89 ft-lbs/in of notch Mechanical Properties (50% RH: Conditioned for 25 days) Tensile Modulus (psi) 83,000 75,000 59,000 Tensile Strength (psi) 3,800 3,700 2,400 Elongation @ Break (%) 148 33 37 Notched Izod Impact Strength 1.1 0.95 1.6 ft-lbs/in of notch__________________________________________________________________________ *Based on polyolefin weight
EXAMPLE 10
Blends of polypropylene (Profax 8623}and Vinex 2034 were prepared via reactive extrusion. Profax 8623 PP is an impact grade polypropylene. The data for Runs 50-54 are shown in Table 7.
TABLE 7__________________________________________________________________________RUN 50 51 52 53 54__________________________________________________________________________Vinex .TM. Type 2034 2034 2034 2034 2034Vinex Feed Rate (lbs/hr) 40 40 40 40 40Polyolefin Type PP PP PP PP PP Profax Profax Profax Profax Profax 8623 8623 8623 8623 8623Polyolefin Feed Rate (lbs/hr) 40 40 40 40 40Maleic Anhydride Conc. (%)* -- 2.0% 3.5% 2.1% 3.1%L-101 (peroxide) Conc. (ppm)* -- 4000 3000 3000 4000Melt Flow dg/min (200.degree. C.) 7.9(1P) 102.2(10P) 27.5(10P) 59.0(10P) 28.1(10P)Mechanical Properties (Dry)Tensile Modulus (psi) 111,000 111,000 109,000 114,000 113,000Tensile Strength (psi) 3,400 3,900 4,000 4,000 3,900Elongation @ Break (%) 16 153 104 87 124Notched Izod Impact Strength 1.9 1.1 1.1 1.2 1.1ft-lbs/in of notchMechanical Properties (50% RH: Conditioned for 25 days)Tensile Modulus (psi) 72,000 85,000 77,000 64,000 75,000Tensile Strength (psi) 2,800 3,800 3,200 3,200 3,300Elongation @ Break (%) 37 494 325 280 349Notched Izod Impact Strength 2.7 1.7 2.1 2.0 2.0ft-lbs/in of notch__________________________________________________________________________ *Based on polyolefin weight
EXAMPLE 11
Blends of polypropylene (Profax 8623) and Vinex 2025 PVOH were prepared for comparison with similar blends employing Vinex 2034 PVOH. The data for Runs 55-57 are shown in Table 8. Vinex 2034 PVOH yielded much higher ultimate elongation with Profax 8623 PP than similar blends with Vinex 2025 PVOH. Reactive extrusion yielded significant improvements for both blends.
TABLE 8__________________________________________________________________________Run 55 56 57 58__________________________________________________________________________Vinex .TM. Type 2025 2025 2025 2025Vinex Feed Rate (lbs/hr) 40 40 40 40Polyolefin Type PP PP PP PP Profax Profax Profax Profax 8623 8623 8623 6723Polyolefin Feed Rate (lbs/hr) 40 40 40 40Maleic Anhydride Conc. (%)* 3.1% 2.0% -- 2.1%L-101 (peroxide) Conc. (ppm)* 4000 3000 -- 3000Melt flow dg/min (200.degree. C.) 28.4(10P) 2.5(1P) 11.7(1P) 3.2(1P)Mechanical Properties (Dry)Tensile Modulus (psi) 158,000 168,000 179,000 179,000Tensile Strength (psi) 4,100 4,100 4,500 5,100Elongation @ Break (%) 34 18 5 19Notched Izod Impact Strength 1.3 1.1 1.3 0.84ft-lbs/in of notchMechanical Properties(50% R.H. Conditioning for 25 days)Tensile Modulus (psi) 112,000 116,000 135,000 151,000Tensile Strength (psi) 3,600 3,600 4,000 4,700Elongation @ Break (%) 45 29 11 34Notched Izod Impact Strength 1.6 1.1 1.5 0.70ft-lbs/in of notch__________________________________________________________________________ *Based on polyolefin weight
EXAMPLE 12
A 50/50 blend of Vinex 2025 PVOH/Profax 6723 PP (Run 58 of Table 8) was made for comparison with Vinex 2034 PVOH/Profax 6723 PP reactive extruded blends. Vinex 2034 PVOH offered significantly higher ultimate elongation.
EXAMPLE 13
50/50 blends of Vinex 2025/LLDPE (LL-1002; Exxon Chemical) were prepared and subjected to reactive extrusion conditions. The data for Runs 59-62 are shown in Table 9. Polyethylene led to crosslinking with peroxide addition unlike polypropylene for which chain scission dominated resulting in high melt viscosity. Consequently, much lower levels of maleic anhydride and peroxide were employed. The addition of maleic anhydride and peroxide led to significant improvements in ultimate elongation, tensile strength and notched toughness except for Run 62 which appeared anomalous.
TABLE 9__________________________________________________________________________Run 59 60 61 62__________________________________________________________________________Vinex .TM. Type 2025 2025 2025 2025Vinex Feed Rate (lbs/hr) 40 40 40 40Polyolefin Type LLDPE LLDPE LLDPE LLDPE LL-1002 LL-1002 LL-1002 LL-1002Polyolefin Feed Rate (lbs/hr) 40 40 40 40Maleic Anhydride Conc. (%)* 0.5% 0.5% -- 0.62%L-101 (peroxide) Conc. (ppm)* 600 400 -- .about.400Melt flow dg/min (200.degree. C.) 0.9(10P) 2.3(10P) 11.5(1P) 1.4(10P)Mechanical Properties (Dry)Tensile Modulus (psi) 135,000 132,000 124,000 120,000Tensile Strength (psi) 4,300 4,600 3,200 3,700Elongation @ Break (%) 85 52 7 7Notched Izod Impact Strength 3.4 1.9 1.3 1.2ft-lbs/in of notchMechanical Properties(50% R.H. Conditioning for 25 days)Tensile Modulus (psi) 52,000 62,000 75,000 74,000Tensile Strength (psi) 3,200 3,100 2,300 2,600Elongation @ Break (%) 171 120 30 12Notched Izod Impact Strength N.B.** 11.8 2.1 1.4ft-lbs/in of notch__________________________________________________________________________ *Based on polyolefin weight **N.B. = No Break
EXAMPLE 14
Runs 63-66 were 50/50 blends of Vinex 2034 PVOH and LLDPE (HS-7027) which offered significant improvements in ultimate elongation and tensile strength with maleic anhydride and peroxide addition as shown in Table 10.
TABLE 10__________________________________________________________________________Run 63 64 65 66 67 68__________________________________________________________________________Vinex .TM. Type 2034 2034 2034 2034 2034 2034Vinex Feed Rate (lbs/hr) 40 40 40 40 60 60Polyolefin Type LLDPE LLDPE LLDPE LLDPE PP 6723/ PP6723/ HS-7027 HS-7027 HS-7027 HS-7027 EPR-719 EPR-719Polyolefin Feed Rate (lbs/hr) 40 40 40 40 30/10 30/10Maleic Anhydride Conc. (%)* 0.75% 0.75% 0.5% -- 2.2% 2.4%L-101 (peroxide) Conc. (ppm)* 400 600 600 -- 1900 1900Melt flow dg/min (200.degree. C.) 2.3(10P) 2.3(10P) 10.6(10P) 9.2(10P) 10.6(10P)2.9(10P)Mechanical Properties (Dry)Tensile Modulus (psi) 87,000 87,000 87,000 77,000 108,000 109,000Tensile Strength (psi) 3,600 3,800 3,500 2,700 4,200 4,300Elongation @ Break (%) 25 147 100 23 73 55Notched Izod Impact Strength 1.2 2.6 1.4 1.5 1.4 1.3ft-lbs/in of notchMechanical Properties(50% R.H. Conditioning for 25 days)Tensile Modulus (psi) 52,000 40,000 47,000 48,000 61,000 75,000Tensile Strength (psi) 2,900 3,100 2,800 2,300 3,400 3,500Elongation @ Break (%) 53 235 135 41 99 79Notched Izod Impact Strength 2.2 N.B.** 6.6 2.0 3.5 2.6ft-lbs/in of notch__________________________________________________________________________ *Based on polyolefin weight **No break
EXAMPLE 15
Runs 67 and 68 involved a 60/30/10 blend of Vinex 2034/Profax 6723/EPR-719. See Table 10 for data.
EXAMPLE 16
Surlyn 9020/Vinex PVOH blends without reactive extrusion exhibit reasonable mechanical compatibility. Runs 69-76 were conducted with reactive extrusion processing. As shown in Table 11, modest improvements in tensile strength were observed with reactive processing. However, lower ultimate elongation was observed. In this case, reactive extrusion is not necessary and not desired except where improved water resistance may be required as exemplified in Example 5.
EXAMPLE 17
Vinex 2025/Surlyn 8660 blends (Runs 77 and 78) were prepared via reactive extrusion and no advantage of reactive processing versus the control (Run 79) is clear from Table 11 other than where improved water resistance is required as exemplified in Example 5.
TABLE 11__________________________________________________________________________Run 69 70 71 72 73 74__________________________________________________________________________Vinex .TM. Type 2025 2025 2025 2025 2025 2025Vinex Feed Rate (lbs/hr) 40 40 40 40 40 40Polyolefin Type Surlyn Surlyn Surlyn Surlyn Surlyn Surlyn 9020 9020 9020 9020 9020 9020Polyolefin Feed Rate (lbs/hr) 40 40 40 40 40 40Maleic Anhydride Conc. (%)* -- -- 0.4% 0.4% 0.6% 0.6%L-101 (peroxide) Conc. (ppm)* -- 400 400 600 600 --Melt flow dg/min (200.degree. C.) 80.0(5P) 58.8(5P) 30.2(5P) 11.2(5P) 10.8(5P) 9.8(5P)Mechanical Properties (Dry)Tensile Modulus (psi) 63,000 138,000 134,000 130,000 145,000 123,000Tensile Strength (psi) 3,500 4,800 4,800 4,800 5,100 5,000Elongation @ Break (%) 291 114 174 147 78 24Notched Izod Impact Strength 3.4 1.7 2.5 1.9 2.3 1.9ft-lbs/in of notchMechanical Properties(50% R.H. Conditioning for 25 days)Tensile Modulus (psi) 28,000 84,000 83,000 83,000 92,000 39,000Tensile Strength (psi) 3,350 3,900 3,700 3,700 3,700 3,300Elongation @ Break (%) 403 281 246 202 131 257Notched Izod Impact Strength 8.2 4.1 3.4 4.1 3.7 3.2ft-lbs/in of notch__________________________________________________________________________Run 75 76 77 78 79__________________________________________________________________________Vinex .TM. Type 2025 2034 2025 2025 2025Vinex Feed Rate (lbs/hr) 40 40 40 40 40Polyolefin Type Surlyn Surlyn Surlyn Surlyn Surlyn 9020 9020 8660 8660 8660Polyolefin Feed Rate (lbs/hr) 40 40 40 40 40Maleic Anhydride Conc. (%)* 0.5% 0.5% 0.75% 1.0% --L-101 (peroxide) Conc. (ppm)* 500 500 500 1000 --Melt flow dg/min (200.degree. C.) 16.3(5P) 10.4(5P) 26.8(1P) 22.0(1P) 32.2(1P)Mechanical Properties (Dry)Tensile Modulus (psi) 140,000 80,000 141,000 83,000 160,000Tensile Strength (psi) 5,100 3,900 5,200 2,950 5,400Elongation @ Break (%) 89 171 54 16 87Notched Izod Impact Strength 2.9 3.4 0.92 0.64 0.76ft-lbs/in of notchMechanical Properties(50% R.H. Conditioning for 25 days)Tensile Modulus (psi) 83,000 73,000 92,000 59,000 126,000Tensile Strength (psi) 4,100 3,500 3,800 2,300 4,400Elongation @ Break (%) 202 94 343 23 248Notched Izod Impact Strength 6.3 8.9 1.1 0.85 1.1ft-lbs/in of notch__________________________________________________________________________ *Based on polyolefin weight
EXAMPLE 18
Blends of 50/50 Vinex 2025/Primacor 5981 (high melt flow EAA - 20 wt % AA) were prepared as Runs 80 and 81. Reactive extrusion (Run 81) improved the strength, elongation and toughness. A different ratio Vinex 2025/Primacor 5981 (54/36) in control Run 82 was prepared to determine if a high melt flow product would be obtained.
A control Run 83 and a reactive extruded blend of Primacor 1430/Vinex 2025 (50/50) (Run 84) were prepared. Primacor 1430 EAA is a high molecular ethylene-acrylic acid copolymer (.about.8 wt % AA; Dow Chemical Co.) that offers fair mechanical compatibility with Vinex PVOH. The data for Runs 80-84 are shown in Table 12. Reactive extrusion only shows an improvement in notched toughness with decreases in elongation and tensile strength.
TABLE 12__________________________________________________________________________Run 80 81 82 83 84__________________________________________________________________________Vinex .TM. Type 2025 2025 2025 2025 2025Vinex Feed Rate (lbs/hr) 40 40 54 40 40Polyolefin Type Primacor Primacor Primacor Primacor Primacor 5981 5981 5981 1430 1430Polyolefin Feed Rate (lbs/hr) 40 40 36 40 40Maleic Anhydride Conc. (%)* -- 0.5% -- -- 0.5%L-101 (peroxide) Conc. (ppm)* -- 500 -- -- 500Melt flow dg/min (200.degree. C.) 17.0(1P) 7.3(1P) 3.4(1P) 5.4(1P) 3.0(5P)Mechanical Properties (Dry)Tensile Modulus (psi) 37,000 36,000 45,000 141,000 109,000Tensile Strength (psi) 1,700 2,000 2,400 4,700 4,000Elongation @ Break (%) 20 71 39 100 61Notched Izod Impact Strength 0.53 0.89 0.80 0.80 1.5ft-lbs/in of notchMechanical Properties(50% R.H. Conditioning for 25 days)Tensile Modulus (psi) 33,000 36,000 43,000 102,000 87,000Tensile Strength (psi) 1,500 2,200 2,600 3,800 3,600Elongation @ Break (%) 20 64 47 306 134Notched Izod Impact Strength 0.59 0.77 0.68 1.3 2.2ft-lbs/in of notch__________________________________________________________________________ *Based on polyolefin weight
EXAMPLE 19
Runs 85-88 were performed to determine if the reactive extrusion procedure was applicable to ethylene/vinyl alcohol copolymers (e.g. EVAL EP-F). The results in Table 13 show only a modest increase in elongation and thus indicates that reactive extrusion is of more benefit to PVOH.
EXAMPLE 20
Blends of Vinex 2025 PVOH and an ethylene-vinyl acetate copolymer (LD-706; Exxon Chemical) were prepared as Runs 89-92 of Table 13. Definite improvements in tensile strength, ultimate elongation and notched toughness were observed with reactive extrusion.
EXAMPLE 21
Blends of Vinex 2025 PVOH and Vistalon ethylene-propylene rubber (EPR 3708; Exxon Chemical) were prepared (Runs 93-96). Significant improvements were observed in ultimate elongation, tensile strength and notched toughness at the higher maleic anhydride/peroxide levels as shown in Table 13.
EXAMPLE 22
Run 97 involved the normal addition of Vinex 2034 PVOH after addition of maleic anhydride and peroxide to the polypropylene. Run 98 involved addition of both Vinex 2034 PVOH and polypropylene to the front of the extruder followed by maleic anhydride and peroxide addition. The results in Table 13 clearly show that this procedure is not desired for the conditions of this experiment. The maleic anhydride probably crosslinks the PVOH, the peroxide degrades the polypropylene and minimal grafting occurs. However, low maleic anhydride levels with ethylene-based polyolefins may be of interest using this approach.
TABLE 13__________________________________________________________________________Run 85 86 87 88 89 90__________________________________________________________________________Vinex .TM. Type EVAL EP-F EVAL EP-F EVAL EP-F EVAL EP-F 2025 2025Vinex Feed Rate (lbs/hr) 40 40 40 40 40 40Polyolefin Type PP PP PP PP 6723/ LD-706 LD-706 Profax Profax Profax EPR-719 EVA EVA 6723 6723 6723Polyolefin Feed Rate (lbs/hr) 40 40 40 30/10 40 40Maleic Anhydride Conc. (%)* -- -- 1.0% 1.0% -- 0.5%L-101 (peroxide) Conc. (ppm)* -- 1500 1500 1500 -- 500Melt flow dg/min (200.degree. C.) 4.5(1P) 17.6(1P) 9.7(1P) 3.9(5P) 18.2(1P)Mechanical Properties (Dry)Tensile Modulus (psi) 190,000 185,000 168,000 129,000 96,000 67,000Tensile Strength (psi) 5,600 4,800 4,700 3,300 2,300 2,700Elongation @ Break (%) 6 7 10 12 8 51Notched Izod Impact Strength 1.2 0.85 0.73 1.0 1.3 3.5ft-lbs/in of notchMechanical Properties(50% R.H. Conditioningfor 25 days)Tensile Modulus (psi) 183,000 190,000 182,000 144,000 38,000 37,000Tensile Strength (psi) 5,600 5,000 5,200 3,500 1,900 2,300Elongation @ Break (%) 6 6 12 13 31 198Notched Izod Impact Strength 1.1 0.66 0.59 0.92 1.9 7.7ft-lbs/in of notch__________________________________________________________________________Run 91 92 93 94 95 96 97 98__________________________________________________________________________Vinex .TM. Type 2025 2025 2025 2025 2025 2025 2034 2034.sup.#Vinex Feed Rate (lbs/hr) 40 40 54 54 54 54 60 60Polyolefin Type EVA EVA EPR EPR EPR EPR PP PP LD-706 LD-706 3708 3708 3708 3708 Profax Profax 6723 6723Polyolefin Feed Rate (lbs/hr) 40 40 36 36 36 36 40 40Maleic Anhydride Conc. (%)* 0.8% 1.0% -- 0.4% 0.9% 1.0% 2.2% 1.0%L-101 (peroxide) Conc. (ppm)* 800 1200 -- 400 900 1200 3000 2000Melt flow dg/min (200.degree. C.) 5.2(10P) 3.9(10P) 2.1(1P) 1.9(1P) 2.4(10P) 36.0(5P) 4.7(1P)2.5(10P)Mechanical Properties (Dry)Tensile Modulus (psi) 88,000 124,000 138,0000 137,000 112,000 137,000 109,000 124,000Tensile Strength (psi) 3,100 3,700 3,300 3,400 3,800 4,400 4,800 2,400Elongation @ Break (%) 60 61 5 6 129 129 48 7Notched Izod Impact Strength 3.1 7.9 1.2 0.94 20.1 21.1 0.86 0.77ft-lbs/in of notchMechanical Properties(50% R.H. Conditioningfor 25 days)Tensile Modulus (psi) 37,000 43,000 70,000 70,000 36,000 63,000 78,000 86,000Tensile Strength (psi) 2,500 2,600 2,100 2,100 2,700 3,000 3,900 2,100Elongation @ Break (%) 216 170 13 21 388 373 333 12Notched Izod Impact Strength N.B.** N.B.** 1.7 1.8 N.B.** N.B.** 1.4 0.96ft-lbs/in of notch__________________________________________________________________________ *Based on polyolefin weight **N.B. = No Break .sup.# Vinex 2025 fed to barrel 1
STATEMENT OF INDUSTRIAL APPLICATION
The present invention provides a process for the reactive melt extrusion grafting of polyolefin/thermoplastic PVOH blends which are suitably used in barrier films, foam, injection molded articles and extrusion applications.

Number	Name	Date
4001172	Steinkamp et al.	Jan 1977
4362844	Lemstra	Dec 1982
4600746	Schmuckler	Jul 1986
4612155	Wang et al.	Jul 1986
4806597	Gallucci et al.	Feb 1989
4857600	Gross et al.	Aug 1989
4937284	Bergstrom	Jun 1990
4943399	Taubitz et al.	Jul 1990
4950513	Mehra	Aug 1990
5230935	Delimoy et al.	Jul 1993
5260371	Chen	Nov 1993
5296552	Ohmae et al.	Mar 1994

Reactive melt extrusion grafting of thermoplastic polyvinyl alcohol/polyolefin blends

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