AQUEOUS BIOPOLYMER DISPERSIONS

Abstract

An aqueous biopolymer dispersion composition comprises: a blend of two or more biopolymers, consisting of polycaprolactone (PLC) and one or more selected from the group consisting of: polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polylactic acid (PLA), poly(3-hydroxybutyrate) (PHB) and mixtures thereof, a stabilising agent selected from the group consisting of: polyvinyl alcohol, fatty alcohol ethoxylates, ethylene oxide/propylene oxide (EO/PO) block copolymers, salts of fatty acids and mixtures thereof, a cross linking agent; an optional rheology modifier; optional further ingredients; and water.

Claims

1. An aqueous biopolymer dispersion composition comprising: a blend of two or more biopolymers, consisting of polycaprolactone (PCL) and one or more further biopolymers selected from the group consisting of: polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polylactic acid (PLA), poly(3-hydroxybutyrate) (PHB) and mixtures thereof, a stabilizing agent selected from the group consisting of: polyvinyl alcohol, fatty alcohol ethoxylates, ethylene oxide/propylene oxide (EO/PO) block copolymers, salts of fatty acids and mixtures thereof, a cross-linking agent; optionally, a rheology modifier; optional further ingredients; and water.

2. The composition of claim 1, wherein the blend of two or more biopolymers are polycaprolactone (PCL) and one or more further biopolymers selected from the group consisting of: polybutylene succinate (PBS), polybutylene succinate adipate (PBSA) and mixtures thereof.

3. The composition of claim 2, wherein the ratio by weight of the polycaprolactone (PCL) to further biopolymer or biopolymers is in the range of PCL to further biopolymer or biopolymers of from about 60:40 to about 1:20.

4. The composition of claim 1, wherein the blend of two or more biopolymers is present in the aqueous biopolymer dispersion composition in the amount of from 10 wt % to 80 wt % based on the total weight of the aqueous biopolymer dispersion composition.

5. The composition of claim 1 further comprising a wax or a tackifier selected from the group consisting of: a carnauba wax, a beeswax, a polyethylene, a copolymer of polyethylene, an oxidized polyethylene, a copolymer of oxidized polyethylene, a polyether, a lanolin, a shellac, a paraffin, a candelilla, a microcystalline wax, a soy wax, a montan wax, a rosin ester, a terpene resin, a terpene-phenol resin, a terpene phenol, a pentaerythritol rosin ester, a modified terpene resin, a polyterpene, a phenol modified copolymer of styrene, an alpha methyl styrene, a hydrocarbon resin, and mixtures thereof.

6. The composition of claim 1, wherein the stabilizing agent is polyvinyl alcohol.

7. The composition of claim 1, wherein the stabilizing agent is present in the aqueous biopolymer dispersion composition in an amount of from 1 wt % to 6 wt %.

8. The composition of claim 1, wherein the rheology modifier is selected from the group consisting of: xanthan gum, cellulose ether, carboxymethylcellulose, guar, a polysaccharide, a fully hydrolyzed polyacrylic acid, a polyurethane thickener, and mixtures thereof.

9. The composition of claim 8, wherein the cross-linking agent is a bifunctional carboxylic acid or bifunctional aldehyde.

10. The composition of claim 9, wherein the cross-linking agent is selected from the group consisting of: oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undercanedioic acid, dodecanedioic acid, brassylic acid, thapsic acid, japanic acid, phellogenic acid, equisetolic acid, maleic acid, fumaric acid, acetylenedicarboxylic acid, glutaconic acid, traumatic acid, muconic acid, glutinic acid, citraconic acid, mesaconic acid, itaconic acid, tartronic acid, mesoxalic acid, malic acid, tartaric acid, oxaloacetic acid, aspartic acid, ?-hydroxyglutaric acid, arabinaric acid, acetonedicarboxylic acid, ?-ketoglutaric acid, glutamic acid, diaminopimelic acid, saccharic acid, malondialdehyde, succinaldehyde, glutaraldehyde, isocitric acid, aconitric acid, propane-1,2,3-tricarboxylic acid, trimesic acid and mixtures thereof.

11. The composition of claim 10, wherein the cross-linking agent is selected from the group consisting of: adipic acid, maleic acid, glyoxal, citric acid and mixtures thereof.

12. The composition of claim 11, wherein the cross-linking agent is present in an amount of from 0.05 wt % to 3 wt %.

13. The composition of claim 5, wherein the amount of the wax or the tackifier is from 1 wt % to 12 wt %.

14. A method of manufacture of a biopolymer coated cellulosic article comprising the steps of: applying an aqueous biopolymer composition of claim 1 to a surface of a cellulosic substrate to form a coated substrate; allowing water to vaporize from the coated substrate to form a dry coated substrate; and heating the dry coated substrate to cure the composition to from a biopolymer film coated article.

15. A coated article comprising a cellulosic substrate coated with a film formed from a coating composition of claim 1.

16. The composition of claim 5, wherein the wax or the tackifier is present in an amount of from 1 wt % to 12 wt %.

17. An aqueous biopolymer dispersion composition comprising: a blend of two or more biopolymers, consisting of a first biopolymer that is polycaprolactone (PCL) and a second biopolymer selected from the group consisting of: polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polylactic acid (PLA), poly(3-hydroxybutyrate) (PHB) and mixtures thereof, a stabilizing agent selected from the group consisting of: polyvinyl alcohol, fatty alcohol ethoxylates, ethylene oxide/propylene oxide (EO/PO) block copolymers, salts of fatty acids and mixtures thereof, a cross-linking agent; a rheology modifier; and water.

18. The aqueous biopolymer dispersion composition of claim 17, wherein the cross-linking agent is selected from the group consisting of: oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undercanedioic acid, dodecanedioic acid, brassylic acid, thapsic acid, japanic acid, phellogenic acid, equisetolic acid, maleic acid, fumaric acid, acetylenedicarboxylic acid, glutaconic acid, traumatic acid, muconic acid, glutinic acid, citraconic acid, mesaconic acid, itaconic acid, tartronic acid, mesoxalic acid, malic acid, tartaric acid, oxaloacetic acid, aspartic acid, ?-hydroxyglutaric acid, arabinaric acid, acetonedicarboxylic acid, ?-ketoglutaric acid, glutamic acid, diaminopimelic acid, saccharic acid, malondialdehyde, succinaldehyde, glutaraldehyde, isocitric acid, aconitric acid, propane-1,2,3-tricarboxylic acid, trimesic acid and mixtures thereof.

19. The composition of claim 18 further comprising a wax or a tackifier selected from the group consisting of: a carnauba wax, a beeswax, a polyethylene, a copolymer of polyethylene, an oxidized polyethylene, a copolymer of oxidized polyethylene, a polyether, a lanolin, a shellac, a paraffin, a candelilla, a microcystalline wax, a soy wax, a montan wax, a rosin ester, a terpene resin, a terpene-phenol resin, a terpene phenol, a pentaerythritol rosin ester, a modified terpene resin, a polyterpene, a phenol modified copolymer of styrene, an alpha methyl styrene, a hydrocarbon resin, and mixtures thereof.

20. The aqueous biopolymer dispersion composition of claim 19, wherein the blend of two or more biopolymers is present in the amount of from 10 wt % to 80 wt %; the stabilizing agent is present in an amount of from 1 wt % to 6 wt %; the ratio by weight of the first biopolymer to the second biopolymer is in the ratio range of from about 60:40 to about 1:20; the cross-linking agent is present in an amount of from 0.05 wt % to 3 wt %; and the amount of the wax or the tackifier is present in an amount of from 1 wt % to 12 wt %.

Description

EXAMPLE 1

[0058] Polycaprolactone Polybutylene Succinate Adipate Blends.

Polycaprolactone (PCL) and polybutylene succinate adipate (PBSA) blends were manufactured using a high-pressure reactor (HPR). These were all stabilised using polyvinyl alcohol (PVOH). The PCL, PBSA and PVOH were all heated to 110? C. and stirred for one hour maintaining this temperature. Water was then slowly added to the vessel over a period of 30 to 45 minutes before the batch was cooled and the pressure was released. The dispersion was tested with and without crosslinker. The crosslinker was post-added to the dispersion and stirred until homogeneous. The formulations were as follows:

TABLE-US-00001 TABLE 1 Index of PBSA formulations Example 1 Example 2 Example 3 Raw Material % of formulation % of formulation % of formulation PBSA (FD92PM) 36 18 18 PCL (CAPA 6250) 0 18 18 Antioxidant 0.5 0.5 0.5 Wax 4 4 4 Crosslinker 1 0 1 PVOH 2.67 2.67 2.67 Water 55.83 56.83 55.83

TABLE-US-00002 TABLE 2 Index of formulations with and without coalescing agent Example 3 Example 4 Raw Material % of formulation % of formulation PBSA (FD92PM) 18 18 PCL (CAPA 6250) 18 18 Antioxidant 0.5 0.5 Wax 4 4 Adipic acid 1 1 Coalescent 0 1 PVOH 2.67 2.67 Water 56.83 55.83

TABLE-US-00003 TABLE 3 Summary of PBSA/PCL film properties Film properties MVTR MFFT Cobb value (g/m.sup.2) Heat seal value Example (? C.) 2 mins 5 mins 10 mins temp (? C.) Kit value (g/m.sup.2 .Math. day) 1 85-90 3.43 9.29 14.98 110 4 293.88 2 82-85 3.38 7.78 13.63 110 12 221.26 3 82-85 3.37 5.92 12.17 110 12 178.24 4 72-75 2.81 5.36 11.57 110 12 163.93
FIG. 1: All films were single coated at 10 gsm on Sappi paper and film formed in an oven at 110? C. for 1 minute. MVTR was tested on double coated films.

[0059] Incorporating polycaprolactone (CAPA 6250) into the PBSA formulation may result in a considerable improvement in the Cobb values. Comparison of the reduced Cobb value of an un-crosslinked PBSA/PCL film to a crosslinked PBSA film demonstrated that incorporating PCL into the formulation significantly improves the water resistance of the film. It should be noted however, that this improvement may be greatest after longer Cobb tests have been completed. Furthermore, the un-crosslinked and crosslinked PBSA/PCL films perform comparably after a 2-minute Cobb test has been conducted. The effect of crosslinking on the film may not be detected until longer Cobb tests have been conducted. For example, after a 10-minute Cobb test had been conducted the Cobb value decreased from 13.63 g/m.sup.2 to 12.17 g/m.sup.2 in the un-crosslinked and crosslinked film, respectively. In addition to improving the water resistance of the film, crosslinking of the PBSA/PCL film may also prevent blanching after the film has come into contact with water.

[0060] Additionally, the results showed that there was also a considerable improvement of the grease resistance of the film. A PBSA film has very poor grease resistance and may have a kit value of only 4. The addition of PCL into the formulation may greatly improve the grease resistance of the film. A kit value of 12 may be achieved. Crosslinking may not improve the grease resistance.

[0061] All films which underwent MVTR testing were double coated. As the formulations all contained wax the hydrophobicity of the film was increased and the film could not be overcoated by the same film once it has been film-formed as the top film pooled considerably. Therefore, to overcoat for MVTR testing the first film was air-dried which resulted in formation of a white chalky looking film before over coating and stoving in the oven at 110? C. for 1-minute and resulted in formation of a glossy film. The films were double coated for MVTR testing to prevent the result being influenced by any potential pinholes formed. The addition of PCL alone improved the MVTR value from 293.88 to 221.26 g/m.sup.2.Math.day. Crosslinking of the PVOH in the PBSA/PCL formulation improved the water resistance of the film. This was shown in the further reduction of the MVTR value to 178.24 g/m.sup.2.Math.day.

[0062] The minimum film formation temperature was observed to decrease from 85-90? C. to 82-85? C. by incorporation of PCL (CAPA 6250) into the formulation. There is no benefit of crosslinking the PVOH with adipic acid in reduction of MFFT.

[0063] The addition of a citrate ester coalescent improves the appearance of the film. The film was observed to be much glossier. The use of a coalescent gave enhanced water resistance of the film. This is demonstrated in the Cobb and MVTR values being much improved. The Cobb value after a 10-minute Cobb test had been done was reduced from 12.17 g/m.sup.2 to 11.57 g/m.sup.2 with the use of a coalescent. The enhanced water resistance was shown in the reduction in MVTR. The use of the citrate ester reduced the MVTR from 178.24 to 163.93 g/m.sup.2.Math.day. Other film properties such as grease resistance are not affected as the kit value of the blend is already at a maximum value of 12 and therefore could not be improved further. Finally, the addition of 1% citrate ester reduces the MFFT from 82-85? C. to 72-75? C.

EXAMPLE 2

[0064] Polycaprolactone and Polybutylene Succinate Blends.

[0065] The PCL and PBS blends were manufactured using a high-pressure reactor (HPR). These were all stabilised using PVOH. The PCL, PBS and PVOH were all heated to 130? C. and stirred for one hour maintaining this temperature. Water was then slowly added to the vessel over a period of 30 to 45 minutes before the batch was cooled and the pressure was released. The dispersion was tested with and without crosslinker. The crosslinker was post-added to the dispersion and stirred until homogenous. The formulations are as follows:

TABLE-US-00004 TABLE 1 Index of formulations with and without crosslinker Example 5 Example 6 Example 7 Raw Material % of formulation % of formulation % of formulation PBS (FZ71PM) 36 18 18 PCL (CAPA 6250) 0 18 18 Antioxidant 0.5 0.5 0.5 Wax 4 4 4 Adipic acid 1 0 1 PVOH 2.67 2.67 2.67 Water 56.83 56.83 55.83

TABLE-US-00005 TABLE 2 Summary of PBS/PCL film properties Film properties MFFT Cobb value (g/m.sup.2) Heat seal MVTR value Example (? C.) 2 mins 5 mins 10 mins temp (? C.) Kit value (g/m.sup.2 .Math. day) 5 115-120 1.97 4.77 9.95 120 12 222.48 6 99-104 1.80 4.17 8.62 120 12 120.50 7 99-104 1.37 3.73 6.76 120 12 63.53
FIG. 1: All films were single coated at 10 gsm on Sappi paper and film formed in an oven at 130? C. for 1 minute. MVTR was tested on double coated films.

[0066] Blending PCL with PBS provided a film with improved water resistance. Similarly, to the PBSA/PCL blend, a significant improvement was not seen on the 2-minute Cobb value. When longer Cobb tests were conducted, the improved water resistance of the film became more apparent. For example, a 10-minute Cobb test on a PBS film gave a Cobb value of 9.95 g/m.sup.2. This was reduced to 8.62 g/m.sup.2 on the PBS/PCL blend. It should be noted that the PVOH in the PBS film had been crosslinked with adipic acid and the PBS/PCL film was un-crosslinked. Crosslinking the PVOH in the PBS/PCL blend further improved the water resistance of the film. This was shown in the reduced Cobb value even after two minutes. There were also no signs of blanching on the crosslinked film. Blanching had been seen on un-crosslinked films when longer Cobb tests had been conducted.

[0067] The PBS film already had a kit value of 12. Blending with PCL did not appear to have a benefit on the grease resistance as the kit value was already at the maximum. There was no change to the heat seal temperature by blending in the PCL or by crosslinking.

[0068] All films which were subjected to MVTR tested were double coated to prevent any possible pin hole formation influencing the value. The PBS/PCL blend was found to significantly improve the MVTR value from 222.45 g/m.sup.2.Math.day to 120.50 g/m.sup.2.Math.day. This further demonstrated that the incorporation of PCL greatly improved the water resistance of the film. Additionally, the use of crosslinked PBS/PCL film almost halved the MVTR value to 63.53 g/m.sup.2.Math.day. Crosslinking the PVOH greatly improved the water resistance of the film. This was demonstrated by the substantial reduction in the MVTR rate.

[0069] The minimum film formation temperature was found to decrease from 115-120? C. to 99-104? C. by incorporation of PCL into the formulation. There is no benefit of crosslinking the PVOH with adipic acid in reducing the MFFT value.

Test Methods

[0070] Cobb ValueThe Cobb value is defined as the amount of water absorbed in a specific time by 1 square meter of paper under 1 cm of water measured in g/m.sup.2. The test is in accordance with Tappi T 441. The specimen is weighed to the nearest 0.01 g and placed into the specimen holder. 100 cm 3 of demineralised water is poured into the specimen holder and the timer is started. Approximately ten seconds before the end of the test, the water is poured out and the substrate is dried by placing blotting paper on top of the specimen and rolling with a hand roller. The specimen is then reweighed, and the Cobb value calculated. The specified times used in this investigation are 2, 5 and 10 minutes.

[0071] BlanchingThis defines a whitened area of the film after exposure to water. It is an internal test which is determined by eye.

[0072] Grease resistance kit testThe test is in accordance with Tappi T 559. The kit number is assigned when the coating has been visually affected by the mixture.

[0073] Water vapor tranmission rateWVTR is defined as the steady state rate at which water vapor permeates through a film at specified conditions of temperature and relative humidity. The films tested in this report were subjected to tropical conditions of 37.8? C. and 90% RH (relative humidity).