Process of incorporating solid inorganic additives into solid polymers using a liquid dispersion

Abstract

Disclosed is a process to produce an improved formulated vinylidene chloride polymer comprising a solid inorganic additive and producing improved vinylidene chloride polymer film products. The process includes adding the inorganic solid additive (such as magnesium hydroxide and/or other inorganic acid scavenger) in a dispersion of a liquid, such as a liquid plasticizer or stabilizer to improve distribution through the polymer and reduction of relatively large sized particles or agglomerates in the polymer and film.

Claims

1. A process for adding a inorganic solid additive to solid polymer particles, the process comprising the steps of: A. preparing a liquid dispersion comprising (1) the inorganic solid additive and (2) optionally one more other dispersible solid additives with (3) a liquid dispersing medium; B. combining the liquid dispersion with solid polymer; C. mixing the components (1), (3), and if present, (2); wherein the inorganic solid additive is present in the dispersion in a range of from 25 to 55 weight percent solid, based on total weight solid additives and dispersing medium, wherein the inorganic solid additive is magnesium hydroxide, wherein the liquid dispersing medium is epoxidized vegetable oil, and wherein the solid polymer is vinylidene chloride polymer or polyvinyl chloride.

2. The process according to claim 1 wherein the liquid dispersion comprises from 40 to 50 weight percent solid inorganic solid additive.

3. The process according to claim 1 wherein the liquid dispersion viscosity is from 50 to 500 centipoise (cP) when initially being combined with the solid polymer.

4. The process according to claim 1 wherein the epoxidized vegetable oil is epoxidized soybean oil.

5. The process according to claim 1 wherein the solid polymer is a vinylidene chloride polymer.

6. The process according to claim 5 wherein the solid polymer is a vinylidene chloride copolymer also comprising from 3.5 to 10 weight percent methyl acrylate.

7. A process for adding an inorganic solid additive to solid vinylidene chloride polymer particles according to claim 1, the process comprising the steps of: A. preparing a liquid dispersion comprising (1) from 40 to 50 weight percent inorganic solid acid scavenger additive and (2) optionally one more other dispersible solid additives with (3) from 60 to 50 weight percent of a liquid epoxidized vegetable oil dispersing medium which weight percent are based on (1) and (2); B. combining the liquid dispersion with solid vinylidene chloride polymer particles; C. mixing the components (1), (3), and if present, (2).

8. A process for adding an inorganic solid additive to solid polymer particles, the process comprising the steps of: A. preparing a liquid dispersion comprising (1) the inorganic solid additive and (2) optionally one more other dispersible solid additives with (3) a liquid dispersing medium; B. combining the liquid dispersion with solid polymer; C. mixing the components (1), (3), and if present, (2); wherein the inorganic solid additive is present in the dispersion in a range of from 40 to 50 weight percent solid, based on total weight solid additives and dispersing medium, wherein the inorganic solid additive is selected from: magnesium hydroxide, calcium hydroxide, calcium oxide, calcium carbonate, magnesium oxide, hydrotalcite, talc, clay, ignition resistance additives or combinations of two or more of these, wherein the liquid dispersing medium is selected from: epoxidized vegetable oil, epoxidized linseed oil, acetyl tributyl citrate, dibutyl sebecate, mineral oil, and combinations of two or more of these, and wherein the solid polymer is a vinylidene chloride copolymer also comprising from 3.5 to 10 weight percent methyl acrylate.

9. The process according to claim 8 wherein the liquid dispersion viscosity is from 50 to 500 centipoise (cP) when initially being combined with the solid polymer.

10. The process according to claim 8 wherein the inorganic solid additive is magnesium hydroxide.

11. The process according to claim 8 wherein the liquid dispersing medium is an epoxidized vegetable oil.

12. The process according to claim 11 wherein the epoxidized vegetable oil is epoxidized soybean oil.

13. A process for adding an inorganic solid additive to solid vinylidene chloride polymer particles according to claim 8, the process comprising the steps of: A. preparing a liquid dispersion comprising (1) from 40 to 50 weight percent inorganic solid acid scavenger additive and (2) optionally one more other dispersible solid additives with (3) from 60 to 50 weight percent of a liquid epoxidized vegetable oil dispersing medium which weight percent are based on (1) and (2); B. combining the liquid dispersion with the solid vinylidene chloride polymer particles; C. mixing the components (1), (3), and if present, (2).

Description

(1) This invention is further illustrated by the following examples. Unless stated otherwise all percentages, parts and ratios are by weight.

EXPERIMENTS

(2) The materials employed in the Experiments are described in Table 1 below.

(3) TABLE-US-00003 TABLE 1 Experimental Film Raw Material Components Material Brand Name Source Comments Magnesium hydroxide MAGSHIELD UF Martin Marietta 1 m avg particle size (Mg(OH).sub.2) 10 m max particle size Epoxidized soybean oil (ESO) Plas-Chek 775 Ferro oxirane content 6.8-8.0 Vinylidene chloride/methyl The Dow Chemical 91,000 Mw acrylate copolymer (1% ESO) Company MP - 151 C. 1 wt % ESO Ex. Films 1-3 Vinylidene chloride/methyl The Dow Chemical 91,000 Mw acrylate copolymer (2% ESO) Company MP - 151 C. 2 wt % ESO Ex. Films A-I Low density polyethylene 501i The Dow Chemical (LDPE) Company

(4) Experimental Film 1A liquid dispersion of 45 weight percent Mg(OH).sub.2 in 55 weight percent epoxidized soybean oil is prepared by ball milling. The dispersion is heated to 140 F. (60 C.), filtered through a 100-micron bag filter, and spray added to the vinylidene chloride copolymer (containing 1% ESO from production) at a temperature of about 80 F. (27 C.). The resulting resin is determined to contain approximately 1% Mg(OH).sub.2 uniformly dispersed and having little or no agglomerates. A cast monolayer film is prepared from this resin using a 1.75 inch (44 millimeter) Welex extruder. Resulting film samples are visually inspected for white specks (agglomerate particles having a volume median particle size in the range from 200 to 600) and none were observed.

(5) Experimental Films 2 and 3 and A-IThe multilayer experimental films below were prepared by the following film extrusion procedure. A multilayer cast coextruded film was made from layers of the indicated vinylidene chloride/methyl acrylate copolymer (PVDC) resins and layers of low density polyethylene (LDPE). The films had a total thickness of 2.0 mil and were 24 inches wide. The layer distribution was A/B/C/B/D from four extruders A through D as shown in Table 2. The PVDC layer (C) had a thickness of 0.2 mil. Layers A+B and B+D were 0.9 mil each. Extrusion conditions are shown in Table 2.

(6) TABLE-US-00004 TABLE 2 VDC Polymer Film Extrusion Conditions Extruder A Extruder B Extruder C Extruder D Extruder size 2.5 2 1.25 2 Resin 501i LDPE 501i LDPE PVDC 501i LDPE Extruder rpm 27 29 18 17 Barrel zone 1 370 F. 320 F. 300 F. 375 F. Barrel zone 2 380 340 315 375 Barrel zone 3 390 350 320 380 Barrel zone 4 390 350 320 380 Adapter/ 390 350 320 380 Transfer Die 390 Cast roll 70 Chill roll 70

(7) Experimental Films 2 and 3The following mixtures are made in a high shear Welex 35M blender. The Mg(OH).sub.2 is predispersed in the indicated amounts of dispersion ESO in the indicated wt %. (As noted, the PVDC resin initially contains ESO incorporated during its production.) The liquid dispersion is spray added to the agitated resin in the blender. Mixing is continued for 1 minute. The mixture is then held for 10 minutes. Then, 0.18 lb (0.082 kg, 0.6 wt parts) lubricant/processing aid package is then added and the mixture is mixed for an additional 1 minute. The blended resin product is then coextruded as a film using the standard procedure described above in Table 2 and the number of visible white specks per five minutes was counted. The white spec counts were 1 and 3 white specks per five minutes of film production, this representing about 420 square feet (38.5 square meters) of film and providing very acceptable and suitable films.

(8) TABLE-US-00005 Experimental Film No. 2 3 PVDC (1 wt % ESO) lbs 29.15 29.22 kg 13.22 13.25 (parts) (97.18) (97.4) Dispersion 0.67 lb (2.22 wt pts) 0.60 (2.00 wt pts) Mg(OH).sub.2 45 50 ESO 55 50 ESO in resin (from Dispersion) lbs 0.37 0.3 kg 0.17 0.14 (parts) (1.22) (1.0) MgOH in resin (from Dispersion) lbs 0.3 0.3 kg 0.14 0.14 (parts) (1.0) (1.0) White spec count 1 3 (#/5 min)

(9) The following comparison mixtures for Experimental Films A and B are made in a high shear Welex 35M blender. The vinylidene chloride/methyl acrylate copolymer (containing 2% epoxidized soybean oil) was combined with the magnesium hydroxide and 0.3 lb (0.6 parts) of lubricant/processing aides by physical dry mixing in the blender and mixed for 1 minute. The blended resin product is then coextruded as a film using the standard procedure as shown in Table 2 above and the numbers of visible white specks per five minutes (420 ft..sup.2, 38.5 m.sup.2 film) were counted. The white spec counts are 32 and 15 specks/5 minute, which are poor quality and unacceptable films.

(10) TABLE-US-00006 Experimental Film No. A B PVDC (2 wt % ESO) lbs 49.2 49.2 kg 22.3 22.3 (parts) (98.4) (98.4) Mg(OH).sub.2 lbs 0.5 0.5 kg 0.23 0.23 (parts) (1.0) (1.0) White spec count 32 15 (#/5 min)

(11) The following further comparison Experimental Films C-I are made using different lots of Mg(OH).sub.2 and demonstrate the difficulty in avoiding the solid additive agglomerates in dry blending the solid additive. Separate blends were made in a Lodige 4200 blender. The vinylidene chloride/methyl acrylate copolymer (containing 2% epoxidized soybean oil) was combined with the magnesium hydroxide and blended for 2 minutes. Then 30.5 lb (0.6 parts) of lubricant/processing aides are added to the blender and mixed for 8 minutes. The blended resin product is then coextruded as a film using the film extrusion procedure described in Table 2 above and the numbers of visible white specks per five minutes (420 ft..sup.2, 38.5 m.sup.2 film) were counted.

(12) TABLE-US-00007 Experimental Film Nos. C though I PVDC (2 wt % ESO) lbs 5000 kg 2268 (parts) (98.4) Mg(OH).sub.2 lbs 50.8 kg 23.0 (parts) 1.0

(13) TABLE-US-00008 Test Sample White Speck Count C 24 D 22 E >100 F >100 G 55 H 49 I 72