Process For Manufacture of Plasticized Homopolymeric Polyvinyl Alcohol and Plasticized Polyvinyl Alcohol Polymer Obtained Therefrom

Abstract

A method for manufacture of plasticized homopolymeric polyvinyl alcohol, the method comprising the steps of: introducing into a mixing reactor a polyvinyl alcohol polymer comprising polyvinyl alcohol or a blend thereof having a degree of hydrolysis in the range of 93 wt % to 98 wt %; wherein the mixing reactor comprises a blending chamber having a primary inlet, a primary outlet and at least two inter-engaging components extending between the primary inlet and primary outlet, the components being arranged to apply a shearing force to the polymer while the polymer is conveyed by the components from the inlet through a reaction zone to the outlet; one or more secondary inlets located downstream from the primary inlet for introducing reactants comprising a processing aid, a plasticizer and a reactive stabiliser stabilizer to the chamber to form a reaction mixture; wherein the plasticizer is selected from the group consisting of: sugar alcohols, diols, triols, polyols and mixtures thereof; wherein the reactive stabilizer is selected from the group consisting of: sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethyl propionic acid, and mixtures thereof; wherein the blending chamber comprises a plurality of heated regions arranged so that the mixture is subjected to a temperature profile whereby the temperature increases from the inlet to the outlet; a secondary outlet located between the reaction zone and primary outlet arranged to allow removal of processing aid from the chamber; reacting the processing agent, plasticizer and polymer in the reaction zone to form plasticized polymer; and allowing the plasticized polymer to pass from the primary outlet.

Claims

1. A method for manufacture of plasticised plasticized homopolymeric polyvinyl alcohol, the method comprising the steps of: introducing into a mixing reactor a polyvinyl alcohol polymer comprising polyvinyl alcohol or a blend thereof having a degree of hydrolysis in the range of 93 wt % to 98 wt %; wherein the mixing reactor comprises a blending chamber having a primary inlet, a primary outlet and at least two inter-engaging components extending between the primary inlet and primary outlet, the components being arranged to apply a shearing force to the polymer while the polymer is conveyed by the components from the inlet through a reaction zone to the outlet; one or more secondary inlets located downstream from the primary inlet for introducing reactants comprising a processing aid, a plasticizer and a reactive stabilizer to the chamber to form a reaction mixture; wherein the plasticizer is selected from the group consisting of: sugar alcohols, diols, triols, polyols and mixtures thereof; wherein the reactive stabilizer is selected from the group consisting of: sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethyl propionic acid, and mixtures thereof; wherein the blending chamber comprises a plurality of heated regions arranged so that the mixture is subjected to a temperature profile whereby the temperature increases from the inlet to the outlet; a secondary outlet located between the reaction zone and primary outlet arranged to allow removal of processing aid from the chamber; reacting the processing agent, plasticizer and polymer in the reaction zone to form plasticizer polymer; and allowing the plasticized polymer to pass from the primary outlet.

2. A method as claimed in claim 1, wherein the reactive stabilizer is sodium benzoate.

3. A method as claimed in claim 1, wherein the amount of the reactive stabilizer is from 0.2 wt % to 5 wt %.

4. A method as claimed in claim 3, wherein the amount of the reactive stabilizer is from 0.5 wt % to 3 wt %.

5. A method as claimed in claim 4, wherein the amount of the reactive stabilizer is from 0.5 wt % to 2 wt %.

6. A method as claimed in claim 5, wherein the amount of reactive stabilizer is from 0.5 wt % to 1.5 wt %, preferably 1 wt %.

7. A method as claimed in claim 1, wherein the polyvinyl alcohol polymer comprises polyvinyl alcohol or a blend thereof wherein the polyvinyl alcohol has a degree of hydrolysis of 93 wt % to less than 98 wt %.

8. A method as claimed in claim 7, wherein the degree of hydrolysis is 93 wt % to 97 wt %.

9. A method as claimed in claim 8, wherein the degree of hydrolysis is 93 wt % to 95 wt %.

10. A method as claimed in claim 1, wherein the polyvinyl alcohol polymer is a blend of two or more polyvinyl alcohol polymers with a relatively high molecular weight and a relatively low molecular weight respectively.

11. A method as claimed in claim 10, wherein the blend comprises a low viscosity grade having a molecular weight in the range 13,000 to 27,000 and a degree of polymerization polymerization of 300-600 and a medium/high viscosity grade having a molecular weight in the range 107,000 to 120,000 and a degree of polymerization of 2,400 to 2,600.

12. A method as claimed in claim 1, wherein the plasticizer is selected from the group consisting of: (a) sugar alcohols selected from the group consisting of: diglycerol, triglycerol, fructose, ribose, xylose, D-mannitol, triacetin, and mixtures thereof; polyols selected from the group consisting of: pentaerythritol, dipentaerythritol, and mixtures thereof; (b) diols selected from the group consisting of: methyl pentanediol, 1,2-propanediol, 1,4-butanediol, 2-hydroxy-1,3-propanediol, 3-methyl-1,3-butanediol, 3,3-dimethyl-1,2-butanediol, and mixtures thereof; (c) glycols selected from the group consisting of: polyethylene glycol 300, polyethylene glycol 400, alkoxylated polyethylene glycol, and mixtures thereof; (d) caprolactam, tricyclic trimethylolpropane formal, rosin esters, euricamide, and mixtures thereof.

13. A method as claimed in claim 1, wherein two or more of the following plasticiser plasticizer are used in combination: dipentaerythritol, methyl pentanediol, triacetin, 2-hydroxy-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, tricyclic trimethylolpropane formal, D-mannitol, triglycerol, and xylose.

14. A method as claimed in claim 1, wherein the following plasticizer are used alone or in combination with each other: caprolactam, alkoxylated polyethylene glycol.

15. A plasticized polyvinyl alcohol polymer manufactured by the method of claim 1.

Description

EXAMPLE 1: USE OF SODIUM BENZOATE

[0096] Sodium benzoate was used as a reactive stabiliser with various plasticisers and combinations of plasticisers as listed below: [0097] trimethylolethane (TME) and trimethylolpropane (TMP) 1:2 ratio [0098] trimethylolethane (TME) and trimethylolpropane (TMP) 1:1 ratio [0099] trimethylolethane (TME) and trimethylolpropane (TMP) 2:1 ratio [0100] neopentyl glycol (NPG) and trimethylolpropane (TMP) 1:1 ratio [0101] neopentyl glycol (NPG) and trimethylolpropane (TMP) 2:1 ratio [0102] neopentyl glycol (NPG) and trimethylolpropane (TMP) 3:1 ratio [0103] tripentaerytheritol (TPE) and trimethylolpropane (TMP) 1:4 ratio [0104] diethylpentanediol dineopentanoate (DEPD) and trimethylolpropane (TMP) 1:3 ratio [0105] diethylpentanediol dineopentanoate (DEPD) and trimethylolpropane (TMP) 1:2 ratio [0106] diethylpentanediol dineopentanoate (DEPD) and trimethylolpropane (TMP) 1:1 ratio

[0107] Sodium benzoate was used as the reactive stabiliser and the plasticiser combinations and ratios were changed.

[0108] The results show that when using sodium benzoate as a reactive stabiliser and changing the plasticiser combinations and plasticiser ratios the degradation of the polymer can be controlled. For example, with the NPG:TMP plasticiser combination increasing the ratio of NPG to the TMP results in a larger increase in the degradation of the polymer. When using the same plasticiser ratio of 3:1 but with different plasticisers specifically, pentaerythritol, TME and NPG, it was found that the TME:TMP combination was superior and had the least degradation. From the degradation data the preferred plasticiser combinations are TME:TMP and DEPD:TMP.

[0109] Crystallinity of the polymer is important as it can affect the secondary and tertiary processes needed to create a final product. For example, if the film is too crystalline then the ability to process the film into product is hindered as it is too brittle. Crystallinity of the polymer in the form of a pellet, film or conditioned film (that is film that has been exposed to humidity) has been compared. The results are shown below.

[0110] The addition of a reactive stabiliser in accordance with this invention may reduce the crystallinity of the film. In general, the crystallinity values of the pellets were slightly higher or similar to that of the films. However, there was no significant change in the crystallinity before and after humidity treatment.

[0111] When an alternative plasticiser was used in the formulation, the Tg value could be observed by DSC analysis. The Tg values obtained were in the region of 44-65° C. The melting peak (Tm) for all of the reactive stabiliser and plasticiser combinations were within the region of 200-215° C. Therefore, from a thermal perspective the combinations of plasticisers and reactive stabilisers are shown to be suitable for processing. However, a preferred combination is sodium stearate with the plasticiser combination TMP and pentaerythritol.

[0112] The results are shown in the following Table:

TABLE-US-00004 Plasticiser Reactive Stabiliser Tg ° C. Tm ° C. (peak) Polyol 3990/Penta bis-MPA 57 208 TMP/Penta sodium benzoate 47 211 TMP/Penta potassium oleate 47 210 TMP/Penta sodium stearate 44 209 D-Mannitol sodium stearate 49 211 MPD/Di penta sodium benzoate 59 213

[0113] The phase separation of a film which does not contain a reactive stabiliser was observed after 24 hours. The film became milky. Using sodium benzoate as the stabiliser in combination with various plasticisers and combinations of plasticisers resulted in a clear film after conditioning.

[0114] Torque analysis of the polyvinyl alcohol homopolymers stabilised with various reactive stabilisers was carried out in a batch mixer. Processing was performed with total batches of 40 g at 190° C. and 60 rpm for 8 min. All stabilisers reduced the torque. A combination of calcium stearate with stearic acid gave the biggest reduction. The results are shown below and in the accompanying FIGURE.

TABLE-US-00005 Max Torque Torque Levelled Reactive stabiliser Temp (Nm) Value (Nm) No stabiliser 190° C. 17.7 9.6 calcium stearate 190° C. 13.7 8.2 stearic acid 190° C. 11.4 8.2 calcium stearate and stearic 190° C. 9.3 7.7 acid Sodium stearate 190° C. 10.7 7.7 Sodium benzoate 190° C. 14.9 9.2 potassium oleate 190° C. 12.7 8.0

DSC Data

[0115]

TABLE-US-00006 Reactive stabiliser Tm ° C. Crystallization % No stabiliser 206 45 calcium stearate 202 59 stearic acid 205 58 calcium stearate and stearic acid 203 59 sodium stearate 206 52 sodium benzoate 206 49 potassium oleate 204 51