NEW PLASTICIZED COMPOSITIONS COMPRISING CELLULOSE ACETATE

Abstract

New plasticized compositions comprising cellulose acetate The present invention concerns a composition comprising: cellulose acetate, starch acetate, and at least one plasticizer, wherein cellulose acetate is present in an amount of at least 50% by weight with respect to the total weight of cellulose acetate, starch acetate and plasticizer(s), and wherein said at least one plasticizer is present in an amount of at most 18% by weight with respect to the total weight of cellulose acetate, starch acetate and plasticizer(s). The present invention also relates to a process for the manufacture of a plasticized article, to the use of said composition for producing a plasticized article, and to the use of starch acetate to prevent or diminish the exudation of one or more plasticizers from plastic materials containing cellulose acetate and such plasticizer(s), and/or to increase the maximal use temperature in application for a material comprising cellulose acetate.

Claims

1. A composition comprising: cellulose acetate, starch acetate, and at least one plasticizer, wherein the cellulose acetate is present in an amount of at least 50% by weight with respect to the total weight of the cellulose acetate, the starch acetate and the at least one plasticizer, and wherein the at least one plasticizer is present in an amount from 5 to 18% by weight with respect to the total weight of the cellulose acetate, the starch acetate and the at least one plasticizer.

2. The composition according to claim 1, wherein the at least one plasticizer is different from an alkenyl succinic anhydride.

3. The composition according to claim 1, wherein the cellulose acetate is present in an amount of 50% to 92% by weight with respect to the total weight of the cellulose acetate, the starch acetate and the at least one plasticizer.

4. The composition according to claim 1, wherein a DS of the cellulose is between 2 and 3.

5. The composition according to claim 1, wherein a molecular weight if of the cellulose acetate ranges between 30000 g/mol to 200000 g/mol.

6. The composition according to claim 1, wherein the starch acetate is present in an amount from 5% to 45% by weight with respect to the total weight of the cellulose acetate, the starch acetate and the at least one plasticizer.

7. The composition according to claim 1, wherein a degree of substitution of the starch acetate ranges between 0.5 and 3.0.

8. The composition according to claim 1, wherein a molecular weight of the starch acetate ranges between 20000 g/mol and 200000 g/mol.

9. The composition according to claim 1, wherein the amylose content present in the starch acetate is in an amount from 20% to 90% with respect to the total weight of the starch acetate.

10. The composition according to claim 1, wherein the cellulose acetate/starch acetate/plasticizer(s) weight ratio is at least one of 90/5/5, 85/5/10, 85/10/5, 80/5/15, 80/10/10, 80/15/5, 75/10/15, 75/15/10, 75/20/5, 70/15/15, 70/20/10, 70/25/5, 65/20/15, 65/25/10, 65/30/5, 60/25/15, 60/30/10, 60/35/5, 50/45/5, 50/40/10, or 50/35/15.

11. The composition according to claim 10, wherein the cellulose acetate/starch acetate/plasticizer(s) weight ratio is 70/15/15.

12. The composition according to claim 1, further comprising at least one of anti-UV compounds, UV absorbers, thermal stabilizers, light stabilizers, acid scavengers, lubricants, pigments, dyes, odor maskers, brighteners or mixtures thereof.

13. A process for the manufacture of a plasticized article comprising the steps of: (a) providing the composition according to claim 1, and (b) shaping by extruding or injection molding, the composition to produce the article.

14. (canceled)

15. (canceled)

16. The composition according to claim 3, wherein the cellulose acetate is present in an amount of 55% to 90% by weight with respect to the total weight of the cellulose acetate, the starch acetate and the at least one plasticizer.

17. The composition according to claim 4, wherein the DS of the cellulose is between 2.0 and 2.6.

18. The composition according to claim 5, wherein the molecular weight of the cellulose acetate ranges between 50000 g/mol and 150000 g/mol.

19. The composition according to claim 6, wherein the starch acetate is present in an amount from 10% to 40% by weight with respect to the total weight of the cellulose acetate, the starch acetate and the at least one plasticizer.

20. The composition according to claim 7, wherein the degree of substitution of the starch acetate ranges between 1.5 and 3.

21. The composition according to claim 8, wherein the molecular weight of the starch acetate ranges between 40000 g/mol and 120000 g/mol.

22. The composition according to claim 9, wherein the amylose content present in the starch acetate is in an amount from 35% to 80% by weight with respect to the total weight of the starch acetate.

Description

EXAMPLES

Example 1: Preparation, Through Melt Extrusion of Ternary Blends According to the Invention and of Comparative Binary Blends, at Screening Scale (10 Grams of Material)

[0147] Three compositions according to the invention comprising CA/SA/TA ternary blends (CI, C2 and C3) and two comparative binary blends CA/TA (C4 and C5) are prepared through melt extrusion by using a microcompounder.

[0148] As shown in Table 1 below, concerning the compositions according to the invention, three kinds of SA (SA 1, SA 2 and SA 3) comprising a specific amylose content, a specific DS and a specific viscosity in solution and one kind of CA (CA 1) comprising a specific DS are used. More particularly, CA 1 is a cellulose acetate sold under the name Rhodia Acetol by Solvay Company and TA is a triacetin sold under the name Eastman Triacetin by Eastman Chemical Company.

[0149] Concerning the comparative binary blends CA/TA, the same CA (that is to say CA 1) and the same TA as the ones used for ternary blends according to the invention are used.

[0150] All the components: powder of CA and optionally SA, triacetin liquid plasticizer are first dry blended in the correct ratio; and then introduced in the microcompounder for the melt blending to obtain the ternary compound.

[0151] The respective weight ratios of the ternary blends according to the invention and of the comparative binary blends are indicated in Table 1.

[0152] For example, when 10 grams of material are prepared, 5 g of CA, 3.5 g of SA and 1.5 g of TA are used in order to obtain a ternary blend according to the invention with a weight ratio 50/35/15.

[0153] By analogy, when 10 grams of material are prepared, 7 g of CA, and 3 g of TA are used in order to obtain a comparative binary blend with a weight ratio 70/30.

[0154] The microcompounder used (DSM Midi 2000 commercialized by DSM) is a batch mini-extruder (15 mL leading to 10 grams of product per run) with 2 co-rotating conic screws. It operates under inert atmosphere (N2) but it is not completely tight. This tool allows controlling the residence time, independently of screw speed, using a recirculating system. The following process conditions are used:

[0155] Barrel temperature: 180 C.

[0156] Screw speed: 100 rpm

[0157] Residence time: 5 min

[0158] During the processing, the axial force (that is to say force at the plateau) applied is recorded by a force sensing cell. This force is an indication of the material viscosity, and of the processability of the given composition. The corresponding values of the force at the plateau are summarized in Table 1.

TABLE-US-00002 TABLE 1 Starch acetate Composition Viscosity in Cellulose acetate CA/(SA)/ Force at Starch Amylose solution Cellulose triacetin the plateau Composition acetate content DS (cP) acetate DS (% wt/wt/wt) (N) C1 according to SA 1 20% 2.62 60 CA 1 2.45 50/35/15 4800 the invention C2 according to SA2 35% 2.57 75 CA 1 2.45 50/35/15 4800 the invention C3 according to SA3 60% 2.58 63 CA 1 2.45 50/35/15 4800 the invention Comparative C4 CA 1 2.45 70/30 3000 (50 rpm for screw speed) Comparative C5 CA 1 2.45 80/20 6400 (50 rpm for screw speed)

[0159] Conclusion

[0160] At 180 C., according to axial force measured, whatever the amylose content in the SA, the ternary blend (50/35/15) exhibits typically a viscosity between the binary 80/20 and the binary 70/30.

[0161] Thus, the processability in melt processes of this ternary blend composition is expected to stand between CA/TA blends 80/20 and 70/30 ones.

Example 2: Preparation, Through Melt Extrusion of Ternary Blends According to the Invention and of Comparative Binary Blends, at Lab Scale (Few Tens of Kg of Material)

[0162] Three compositions according to the invention comprising CA/SA/TA ternary blends (C6, C7 and C8) and two comparative binary blends CA/TA (C9 and CIO) are prepared in twin screw extrusion.

[0163] As shown in Table 2 below, concerning the compositions according to the invention, one kind of SA (SA 1) comprising a specific amylose content, a specific DS and a specific viscosity in solution and one kind of CA (CA 2) comprising a specific DS are used. More particularly, CA 2 is a cellulose acetate sold under the name Rhodia Acetol by Solvay Company and TA is a triacetin sold under the name Eastman Triacetin by Eastman Chemical Company.

[0164] Concerning the comparative binary blends CA/TA, the same CA (that is to say CA 2) and the same TA as the ones used for ternary blends according to the invention are used.

[0165] The respective weight ratios of the ternary blends according to the invention and of the comparative binary blends are indicated in Table 2.

[0166] A twin screw extruder Clextral, with a diameter 32 mm and a length over diameter ratio L/D of 44 is used. All the components are introduced in the 2 first zones of the barrel. The following conditions are used:

[0167] Rate: 10 kg/h

[0168] Screw speed: 200 rpm

[0169] Temperatures profile from the feeding zone to the die: from 20 C. to 225 C.

[0170] At the exit of the die, the stand is granulated. 25 kg of each composition are prepared to be then molded in injection.

[0171] The pellets prepared are then molded through injection molding process to form disks of 3 mm thick, diameter 85 mm and tensile bars 1 A IS0527. An injection molding machine BILLION H260/100 commercialized by BILLION is used, with the following conditions:

[0172] Barrel temperatures along the single screw from the feeding zone to the nozzle: from 210 C. to 240 C.

[0173] Mold temperature: 30 C.

[0174] Injection cycle time: from 48 to 57 s

[0175] The following table 2 summarizes the compositions realized.

TABLE-US-00003 TABLE 2 Cellulose acetate Starch acetate Specific Composition Viscosity in viscosity CA/(SA)/ Starch Amylose solution Cellulose Acetyl (ASTM triacetin Composition acetate content OS (cP) acetate title D871-72) (% wt/wt/wt) C6 according to SA4 60% 2.43 74 CA2 55.2% 0.332 50/35/15 the invention C7 according to SA4 60% 2.43 74 CA2 55.2% 0.332 60/25/15 the invention C8 according to SA4 60% 2.43 74 CA2 55.2% 0.332 70/15/15 the invention Comparative C9 CA2 55.2% 0.332 70/30 Comparative C1O CA2 55.2% 0.332 85/15

Example 3: Properties of Ternary Blends According to the Invention (CI) Versus Comparative Binary Blends (C4 and C5) at Screening ScaleMaximum Use Temperature in Application

[0176] DMTA thermograms of the ternary blend composition according to the invention named CI and of two comparative binary blends named C4 and C5 which are prepared at screening scale in example 1 are performed. A DMTA RSA II Rheometrics Scientific is used, in the linear response domain. The temperature until which the elastic modulus E is kept larger than 1 GPa is determined to evaluate the maximal use temperature in applications.

[0177] The results are summarized in Table 3 below.

TABLE-US-00004 TABLE 3 Starch acetate Cellulose Composition Viscosity in acetate CA/(SA)/ Temperature Starch Amylose solution Cellulose triacetin until which Composition acetate content DS (cP) acetate DS (% wt/wt/wt) E > lGPa C1 according to SA 1 20% 2.62 60 CA 1 2.45 50/35/15 110 C. the invention Comparative C4 CA 1 2.45 70/30 60 C. Comparative C5 CA 1 2.45 80/20 80 C.

[0178] Conclusion

[0179] So, ternary blends according to the invention can be used at larger temperatures, keeping a good level of mechanical properties, than comparative binary CA/TA blends.

Example 4: Properties of Ternary Blends According to the Invention (C6, C7 and C8) Versus Comparative Binary Blends (C9 and CIO) at Lab ScaleResistance to ExudationMechanical Properties

[0180] Quantitative Evaluation of Resistance to Exudation of the Different Ternary Blend Compositions According to the Invention (C6, C7 and C8)

[0181] Isothermal ThermoGravimetric Analysis (I-TGA) performed at a given temperature (generally higher than ambient temperature) during a given time (generally several hours) permits to measure the amount of plasticizer that can migrate outside the polymer matrix over time. This is a common way for observing the accelerated exudation of the plasticizer from the polymer matrix and identify the difference between the behavior a different typologies of plasticizers.

[0182] Isothermal ThermoGravimetric Analysis (I-TGA) is carried out with TG209 Fl Thermogravimetric Analyser commercialized by the NETZSCH Company and is performed at 60 C. during 20 hours for each ternary blend according to the invention on plates obtained from injection molding techniques in example 2, that is to say for C6, C7 and C8 according to the invention. These measurements are compared to results obtained with two comparative CA/TA binary blends (70/30 and 85/15, that is to say respectively comparative C9 and CIO) following obviously the same time-temperature conditions.

[0183] Comparative 70/30 (comparative C9) binary blend corresponds to a classical amount of plasticizer (30% by weight with respect to the total weight of CA and plasticizer(s)) permitting the melt processing of Cellulose. The minimum amount of plasticizer required for plasticizing Cellulose Acetate is around 5% by weight. However, even if it is associated to a higher amount of plasticizer, the comparative 85/15 (comparative CIO) binary blend corresponds to a situation much more critical than the classical 70/30 composition in terms of Cellulose Acetate plasticization process.

[0184] Measurements of the Mechanical Properties of the Ternary Blends According to the Invention (C6, C7 and C8)

[0185] Different mechanical properties are measured on plates of ternary blends obtained from injection molding techniques, in example 2. These properties concern the following specific measurements: [0186] Tensile Testing at room temperature according to ISO standard 527-1 and 527-2. Tensile testing permits to reach mechanical parameters such as Young Modulus, Yield Stress and deformation at Break; [0187] Notched Charpy Impact Testing at room temperature according to ISO standard 179/leA. Charpy impact test permit to access to parameters such as Impact Resistance

[0188] These measurements are also compared to results obtained with two comparative CA/TA binary blends (70/30 and 85/15, that is to say respectively comparative C9 and CIO) obviously realized under the same experimental conditions in example 2.

[0189] The results of mechanical properties and of resistance to exudation are summarized in the following Tables 4 and 5:

TABLE-US-00005 TABLE 4 Composition Exudation CA/(SA)/triacetin amount Young Modulus Composition (% wt/wt/wt) (% w) (MPa) C6 according to the 50/35/15 0.3 (0.1) 2809 (215) invention C7 according to the 60/25/15 0.6 (0.1) 2897 (142) invention C8 according to the 70/15/15 0.6 (0.1) 2880 (108) invention Comparative C9 70/30 3.9 (0.3) 1663 (102) Comparative C10 85/15 1.6 (0.3) 3677 (111)

TABLE-US-00006 TABLE 5 Composition Yield Deformation Impact CA/(SA)/triacetin Stress at break resistance Composition (% wt/wt/wt) (MPa) (%) (kJ/m2) C8 according to the 70/15/15 55.6 (0.7) 9.2 (1.1) 3.5 (0.4) invention Comparative C9 70/30 25.4 (1.4) 14.6 (2.1) 15.4 (2.6) Comparative C10 85/15 71.6 (0.9) 7.0 (0.6) 3.7 (0.7)

[0190] Conclusion

[0191] It is deduced from these specific data that blends of CA/SA according to the invention retain much more the plasticizer(s) than CA itself (considered alone, comparative binary blends). These observations are particularly effective if the exudation of triacetin (TA) from the 70/15/15 ternary blend is compared with the exudation of the same plasticizer from the comparative binary blend containing the same amount (85/15) where a factor 2.7 in terms of decreasing of exudation is measured.

[0192] In terms of mechanical properties, the results obtained clearly show that: The mechanical properties of the 70/15/15 ternary blend according to the invention stand in the range of properties defined by the two comparative binary blends for both tensile testing and notched impact testing.

[0193] After a strict comparison between the results coming from the different examples (examples 3 and 4), it appears that the 70/15/15 ternary blend composition assumes the best compromise of properties, considering the resistance to exudation, the maximum use temperature in applications and the level of the mechanical performances of the corresponding material.