Patent ID: 12258469

EXAMPLE 1

Batches of the polybutylene adipate terephthalate (PBAT) dispersion were manufactured using a high-pressure reactor. These were all stabilised using polyvinyl alcohol (PVOH). In each example the PBAT and PVOH were heated to 140° C. and stirred for an hour at 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 crosslinking agents were post-added to the cooled dispersions (<40° C.) and stirred until homogenous. The formulations were as shown in Table 1 below:

TABLE 1Index of formulations, PBAT and crosslinkerExample 1Example 2Example 3Example 4% of% of% of% ofRaw MaterialformulationformulationformulationformulationPBAT40404040PVOH2.672.672.672.67adipic acid0100glyoxal000.080citric acid0000.5water57.3356.3357.2556.83
Carnauba wax was added to the dispersions to further improve the water resistance of the dried films. The formulations were as shown in Table 2 below.

TABLE 2Index of formulations, PBAT, wax and crosslinkerExample 5Example 6Example 7Example 8% of% of% of% ofRaw MaterialformulationformulationformulationformulationPBAT36363636carnauba wax4444PVOH2.672.672.672.67adipic acid0100glyoxal000.080citric acid0000.5water57.3356.3357.2556.83
The dispersions were coated on kraft paper at a dry coat weight of 10 g/m2and dried in an oven at 130° C. for 1 minute. A Cobb test was conducted on each film for 2, 5 and 10 minutes and the blanching of the coating was observed at 2 and 10 minutes. The results are set out in Table 3 below:

TABLE 3PBAT resultsCobb value (g/m2)BlanchingExample2510210No.CrosslinkedCrosslinkerminsminsminsminsmins1N—3.419.2616.47NY2Yadipic acid2.355.429.35NN3Yglyoxal2.637.019.89NN4Ycitric acid3.629.8116.5NY5N—2.24.8414.42NY6Yadipic acid2.004.608.13NN7Yglyoxal1.955.208.03NN8Ycitric acid2.496.6312.62NYY = YesN = No

The results showed that crosslinking did not have a significant effect after a 2-minute Cobb test had been conducted. Some improvement was seen in the Cobb value when the crosslinker was adipic acid or glyoxal after a 2-minute Cobb test. This was observed in both wax and non-wax containing formulations. There was not a significant difference in the Cobb values between un-crosslinked and citric acid crosslinked PVOH dispersions. Crosslinking with citric acid may occur more slowly in the stated drying conditions than for adipic acid and glyoxal, so that the coating may require stoving for a longer period of time for an improvement to be seen. None of the films blanched after the 2-minute Cobb test. This may be due to the short exposure time of the film to water.

After conducting longer Cobb tests for 5 and 10 minutes also on kraft paper at 10 g/m2, the effects of crosslinking were more noticeable. A suitable crosslinker reduced the uptake of water and hence had a lower Cobb value than an un-crosslinked sample. The appearance of the film was unaffected by water and did not blanch. The un-crosslinked film blanched after longer Cobb tests but the degree of blanching appeared to be dependent on particle size. Un-crosslinked films may also have significantly larger Cobb values indicating that the film absorbs more water than films which have been crosslinked with adipic acid or glyoxal. The Cobb results with formulations crosslinked with citric acid were comparable to those which had not been crosslinked, further indicating that citric acid is not a sufficient crosslinker and is not effective under the drying conditions. It should be noted however that although the Cobb values are similar the blanching was not as severe.

Incorporating wax into the formulation increased the hydrophobicity of the film. This may be due to the increased water repellence. Less water may be absorbed by the film leading to a reduction in the observed Cobb value. The reduced surface tension of the film due to the addition of wax caused the water to bead on the surface. Water appeared to spread across films that do not contain wax, giving a smaller contact angle and a larger amount of water is absorbed by the film.

EXAMPLE 2

Example 1 was repeated using a range of alternative polyacids to crosslink the PVOH. These included boric acid and maleic acid. The coatings were found to blanch after a 2-minute Cobb test. These polyacids were deemed to be unsuitable. Longer Cobb tests were not conducted.

Experiment 1 was repeated using borax and ammonium zirconium carbonate (AZC) to crosslink the PVOH. The AZC crosslinked PBAT dispersion also blanched after a 2-minute Cobb test and was deemed unsuitable. Borax destabilised the dispersion and therefore films were unable to be prepared for testing.

Improved Cobb values were seen in PBAT dispersion films that are crosslinked with adipic acid and glyoxal. This became more apparent with longer Cobb tests. This showed that the improvement in water resistance of the films was due to crosslinking. The crosslinking of PVOH with adipic acid and glyoxal unexpectedly appeared to make the film resistant to blanching. This was more evident after longer exposure to water. Although the degree of blanching and the Cobb value were reduced when crosslinking the PVOH in non-wax formulations, further wax was required to improve the water resistance. Incorporating a wax into the formulation was found to increase hydrophobicity of the film and reduce the amount of water which is absorbed and therefore reducing the Cobb value.

EXAMPLE 3—EFFECT OF GLYOXAL IN DIFFERENT BIOPOLYMERS DISPERSIONS

Experiments were carried out to investigate the effect of adipic acid and glyoxal in crosslinking various PVOH stabilised biopolymer dispersions.

EXPERIMENTAL

Batches of the polybutylene succinate (PBS) and polybutylene succinate adipate (PBSA) dispersion were manufactured using a high-pressure reactor. The batches were stabilised using polyvinyl alcohol (PVOH). In each example the biopolymer and PVOH were heated to −130° C. and stirred for an hour at 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 crosslinkers were post-added to the cooled dispersions (<40° C.) and the resultant mixtures were stirred until homogenous. The formulations were as set out in Table 4 below:

TABLE 4Index of formulations, PBS, wax and crosslinkerExample 9Example 10Example 11Example 12% of% of% of% ofRaw MaterialformulationformulationformulationformulationPBS40403636PVOH2.672.672.672.67wax0044glyoxal00.2500.25water57.3357.0857.3357.08

TABLE 5Index of formulations, PBSA, wax and crosslinkerExample 13Example 14Example 15Example 16% of% of% of% ofRaw MaterialformulationformulationformulationformulationPBSA40403636PVOH2.672.672.672.67wax0044glyoxal00.1200.12water57.3357.2157.3357.21
The dispersions were then coated on kraft paper at a dry coat weight of 10 g/m2and dried in an oven at 130° C. for 1 minute. A Cobb test was conducted on each film for 2, 5 and 10 minutes and the blanching observed at 2 and 5 minutes. The results are set out in Table

TABLE 6Results PBS, PBSACobb value (g/m2)BlanchingExample2510210No.CrosslinkedWaxminsminsminsminsmins9NN3.116.207.33NY10YN2.464.718.47NN11NY2.095.347.01NY12YY2.144.086.51NN13NN2.8214.0815.60YY14YN2.9510.5614.19NN15NY3.4312.8514.82YY16YY2.959.2912.98NNY = YesN = No

No significant differences between the Cobb values of crosslinked and un-crosslinked films after a 2-minute Cobb test were observed. No blanching was observed. This may be due to the short exposure time of the film to the water. The effect of crosslinking with glyoxal was more apparent after longer Cobb tests. Crosslinking PVOH in PBS dispersions with glyoxal improved the Cobb value after longer Cobb tests had been conducted. There was no sign of blanching of films which had been crosslinked. This result was consistent on films both with and without wax.

PBSA naturally has poorer water resistance than PBS and PBAT and this may have resulted in the larger Cobb values observed as more water is absorbed by the film. This was more noticeable after longer Cobb tests have been conducted. Crosslinking the PVOH with glyoxal in PBSA dispersions prevented blanching and improved the water resistance of the film and so improved the Cobb value. As seen previously, incorporating a wax into the formulation reduces the surface tension of the film creating a more hydrophobic coating causing water to bead on the film. Films of PBSA dispersions not containing wax have a higher surface tension in comparison and the water therefore spreads across the film after a Cobb test.

Crosslinking the PVOH in PBS and PBSA dispersions with glyoxal improved the Cobb results and prevents blanching. The benefits of crosslinking were more noticeable after longer Cobb tests had been conducted. Blanching was also prevented, and the films remained intact.

EXAMPLE 4—OPTIMISING THE LEVEL OF CROSSLINKER

An experiment was carried out to determine an optimal amount of adipic acid crosslinker in PVOH stabilised polybutylene adipate terephthalate (PBAT) dispersions. Batches of the polybutylene adipate terephthalate (PBAT) dispersion were manufactured using a high-pressure reactor. These were stabilised using polyvinyl alcohol (PVOH). In each example the PBAT and PVOH were heated to 140° C. and stirred for an hour at 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 crosslinking agents were post-added at varying levels to the cooled dispersions (<40° C.) and stirred until homogenous. The formulations are as set out in Table 7 below:

TABLE 7Index of formulations, PRAT, wax and varying crosslinker levelExampleExampleExampleExampleExampleExample171819202122% of% of% of% of% of% ofRawformu-formu-formu-formu-formu-formu-MateriallationlationlationlationlationlationPBAT363636363636PVOH2.672.672.672.672.672.67carnauba444444waxadipic acid00.10.50.7511.5water57.3357.2356.8356.5856.3355.83

The dispersions were then coated on kraft paper at a dry coat weight of 10 g/m2and dried in an oven at 130° C. for 1 minute. A Cobb test was conducted on each film for 2, 5 and 10 minutes and the degree of blanching was observed after 2 and 5 minutes. The results are shown in Table 8 below.

TABLE 8Results using PBAT at varying crosslinker levelsCobb value (g/m2)BlanchingExample251025No.CrosslinkedWaxminsminsminsminsmins17YY3.419.2616.47Ny18YY3.46.0614.82YY19YY2.957.9012.98YY20YY2.367.0510.59NN21YY2.004.608.13NN22YY2.396.8011.78NN

Having too much or too little crosslinker may also affect the film properties. For example, too little crosslinker may reduce the amount of blanching which occurs but may not totally prevent it from occurring. For example, crosslinking the PBAT dispersion with 0.1% adipic acid results in a similar Cobb value to un-crosslinked PBAT after a 2-minute Cobb test. However, there appeared to be a reduction in Cobb value after longer Cobb tests had taken place. It was noted however that the films had blanched. This amount of cross-linker had appeared to improve the Cobb value however as the film had been affected. It is possible some of the film had been removed producing a lower Cobb value. An amount of 0.1% adipic acid may be unsuitable to maintain film properties after contact with water. Increasing the amount of adipic acid to 0.5% prevented blanching from occurring after two- and five-minute Cobb tests but was seen after a 10-minute Cobb test.

Increasing the amount of adipic acid to 1% reduced the Cobb value by the greatest amount and therefore appeared to be an optimum amount of this crosslinker.

Using 1.5% adipic acid to crosslink the PVOH may not be suitable because as shown in the Table, although blanching was prevented the Cobb value was not further reduced. It is possible that there was free unreacted adipic acid in the film as insufficient PVOH was available to be crosslinked. Therefore, an excess of adipic acid may have been present.

EXAMPLE 5—CROSSLINKING AN AQUEOUS PBAT DISPERSION

A PBAT dispersion which is stabilised with PVOH was manufactured in a high pressure reactor. The raw materials and initial water were placed in the vessel which was then sealed and heated to 140° C. At this temperature pressure built up in the vessel and reached approx. 2.6 bar. When the mix has reached the process temperature (140° C.) it was stirred for 1 hour at 300 rpm. Water was added in parts at different flow rates to create the particle size. Hot water 1 was added over 18 mins. Hot water 2 was added over 10 mins. The stirrer speed was then reduced, and the mixture was allowed to cool in a water bath. When the temperature was below 40° C. the dispersion was taken out of the vessel and filtered through a 150 μm sock. The dispersion was thickened using a 2% xanthan gum solution. The formulation is shown in Table 9 below:

TABLE 9Raw Material%PBAT36PVOH2.67antioxidant0.5adipic acid1carnauba wax4initial water7.5hot water 112hot water 236.093xanthan gum0.087acticide FTW20.1acticide mv0.05
Once the dispersion has been thickened and the solids were within specification the dispersion was then re-filtered through a 50 μm sock and was quality control (QC) tested. The parameters for the QC testing are shown in Table 10 below:

TABLE 10ParameterSpecificationActualtotal solids (%)42-4443.5viscosity (cP)200-600410pH3-53.24particle size (μm)d501.366d954.102specific gravity (g/cm3)1.0-1.11.065

The dispersion was coated on kraft paper at 10 g/m2and dried in an oven for 1 min at 130° C. A smooth, glossy film was formed. The films were Cobb tested for 2, 5 and 10 minutes and then inspected for any film defects and/or blanching. As expected, the Cobb value increased as the length of time exposed to water was increased. As this PBAT dispersion contained wax the water beads on the surface after the Cobb test attributed to the hydrophobic effects of the film. The film remained intact and there was no sign of blanching even after a 10-minute Cobb test had taken place.

The film also heat sealed at 120° C. A-A and A-B at 2 bar pressure for a seal time of 1 second. When sealed at these parameters, and subsequently pulled apart using a tensiometer, substrate failure was observed. A seal was not formed at lower seal temperatures at the same pressure. Using the Tappi T559 grease resistance test the film had a kit test rating of 5. This demonstrated that the film had relatively good grease resistance.

EXAMPLE 6—CROSSLINKING AN AQUEOUS PBS DISPERSION

A PBS dispersion which was stabilised with PVOH was manufactured in the high pressure reactor. All of the raw materials and initial water were placed in the vessel which was then sealed and heated to 130° C. At this temperature pressure built up in the vessel and was approximately 1.8 bar. When the mix had reached the process temperature (130° C.) it was stirred for 1 hour at 300 RPM. Water was added in parts at different flow rates to create the desired particle size. Hot water batch 1 was added over 15 mins and hot water batch 2 was added over 10 mins. The stirrer speed was then reduced, and the mixture was allowed to cool in a water bath. When below 40° C. the dispersion was taken out of the vessel and filtered through a 150 μm sock. The formulation is shown in Table 11 below:

TABLE 11Raw Material%PBS36PVOH2.67antioxidant0.5maleic acid1carnauba wax4initial water9.0hot water 110hot water 236.83acticide FTW20.1acticide mv0.05

The PBS dispersion did not require thickening with xanthan gum as it was viscous. Once solids are within specification the dispersion was filtered through a 50 μm sock and QC tested. The QC test parameters are shown in Table 12 below:

TABLE 12ParameterSpecificationActualtotal solids (%)42-4443.35viscosity (cP)200-600580pH5-75.20particle size (μm)d501.882d956.837specific gravity (g/cm3)1.0-1.11.097

The dispersion was coated on kraft paper at 10 g/m2and was dried in an oven for 1 min at 130° C. A smooth, glossy film was formed. The films were Cobb tested for 2, 5 and 10 minutes and then inspected for any film defects and/or blanching. As this film also contained wax the water formed beads on the film surface after the Cobb test. As expected, the Cobb value increased as the length of time exposed to water was increased. The film remained intact and there was no sign of blanching after each Cobb test has taken place.

The PBS film was heat sealed at 120° C. A-A and A-B at 2 bar pressure for a seal time of 1 second. When sealed at these parameters and subsequently pulled apart using a tensiometer substrate failure was observed. A seal was not formed at lower seal temperatures at the same pressure. Using the Tappi T559 grease resistance test the film has a kit test rating of 12 indicating that the PBS film has extremely good grease resistance properties. The results are further demonstrated in the table on page 19.

EXAMPLE 7—CROSSLINKING AN AQUEOUS PBSA DISPERSION

A PBSA dispersion which was stabilised with PVOH was manufactured in a high pressure reactor. All of the raw materials and initial water were placed in the vessel which was then sealed and heated to 115° C. At this temperature pressure built up in the vessel and was approx. 0.6 bar. When the mixture had reached the process temperature (115° C.) it was stirred for 1 hour at 300 RPM. Water was added in parts at different flow rates to create the particle size. Hot water batch 1 was added over 15 mins and hot water batch 2 is added over 10 mins.

The stirrer speed was then reduced, and the mixture was allowed to cool in a water bath. When below 40° C. the dispersion is taken out of the vessel and filtered through a 150 μm sock. The dispersion s thickened using a 2% solution of xanthan gum. The formulation is shown in Table 13 below:

TABLE 13Raw Material%PBSA36PVOH2.67antioxidant0.5adipic acid1carnauba wax4initial water7.5hot water 110hot water 238.24xanthan gum0.087acticide FTW20.1acticide mv0.05
Once the dispersion has been thickened and the solids are within specification the dispersion was re-filtered through a 50 μm sock and was QC tested. The parameters for the QC testing are shown in Table 14 below:

TABLE 14ParameterSpecificationActualtotal solids (%)42-4442.95viscosity (cP)200-600390pH5-74.95particle size (μm)d501.604d955.190specific gravity (g/cm3)1.0-1.11.071
The dispersion was coated on kraft paper at 10 g/m2and dried in an oven for 1 min at 110° C. A smooth, glossy film was formed. The films were Cobb tested for 2, 5 and 10 minutes and then inspected for any film defects and/or blanching. As this film also contained wax the water formed beads on the film surface after the Cobb test. As expected, the Cobb value increased as the length of time exposed to water is increased. The film remained intact and there was no sign of blanching after each Cobb test has taken place. The results are shown in Table 15 below:

TABLE 15Heat sealGreaseCobb value (g/m2)MVTRtemp (° C.)resist-Ex.2510Blan-(g/m2·mode ofanceNo.minminminchingday)A-AA-Bfailurekit test52.004.608.13N119.20120120substrate562.144.716.51N221.31120120substrate1272.959.2912.98N272.88105105substrate4

The PBSA film heat sealed at 105° C. A-A and A-B. The mode of failure was substrate failure as the substrate tears when pulled apart on the tensiometer. Temperatures sealed below this do not form a seal at this pressure. Additionally, using the Tappi T559 grease resistance test the film had a kit test rating of 4. PBSA was the least effective film for grease resistance out of all the biopolymers tested.

EXAMPLE 8—CROSSLINKING POLYCAPROLACTONE AND POLYBUTYLENE SUCCINATE BLENDS

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 set out in Table 16 below:

TABLE 16Index of PCL/PBS formulations with and without crosslinkerExample 1Example 2Raw Material% of formulation% of formulationPBS (FZ71PM)1818PCL (CAPA 6250)1818Antioxidant0.50.5Wax44Maleic anhydride01(Crosslinker)PVOH2.672.67Water56.8355.83

TABLE 17Summary of PBS/PCL film propertiesFilm propertiesCobb value (g/m2)MVTRMFFT2510Heat sealKitvalueExample(° C.)minsminsminstemp (° C.)value(g/m2· day)699-1041.804.178.6212012120.50799-1041.373.736.761201263.53

All films were single coated at 10 g/m2on Sappi paper and film formed in an oven at 130° C. for 1 minute. MVTR was tested on double coated films.

Crosslinking the PVOH in the PBS/PCL blend improved the water resistance of the film. This was shown in the reduced Cobb values seen at two, five and ten minutes. There were also no signs of blanching on the crosslinked film. Blanching had been seen on un-crosslinked films particularly when longer Cobb tests had been conducted. In addition to the reduction of the Cobb values, the use of crosslinker in the PBS/PCL film almost halved the MVTR value from 120.5 to 63.53 g/m2·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.

EXAMPLE 9—CROSSLINKING POLYCAPROLACTONE AND POLYBUTYLENE SUCCINATE BLENDS

A PBS and PCL blend dispersion which is stabilised with PVOH was manufactured in the HPR. All of the raw materials and initial water were placed in the vessel which was then sealed and heated to 130° C. At this temperature pressure built up in the vessel and was approx. 0.6 bar. When the mix reached the process temperature (130° C.) it was stirred for 1 hour at 300 RPM. Water was added in parts at different flow rates to create the particle size. Hot water 1 was added over 15 mins and hot water 2 was added over 10 mins. The stirrer speed was then reduced, and the mixture was allowed to cool in a water bath. When below 40° C. the dispersion was taken out of the vessel and filtered through a 150 μm filter. The dispersion was thickened using a 2% solution of xanthan gum. The formulation is shown in Table 18 below:

TABLE 18Index of PCL/PBS formulations with and without crosslinkerExample 1Example 2Raw Material% of formulation% of formulationPBS1818PCL1818PVOH2.672.67Antioxidant0.50.5Adipic acid10Wax44Initial water99Hot water 11010Hot water 22525Hot water 313.2412.59Xanthan gum0.0870.087Acticide FTW20.10.1Acticide mv0.050.05
Once the dispersion had been thickened and the solids were within specification the dispersion was then re-filtered through a 50 μm sock and was QC tested. The parameters for the QC testing are shown in Table 19 below:

TABLE 19ParameterSpecificationTotal solids (%)42-44Viscosity (cP)200-600pH5-7particle size (μm)d50d95specific gravity (g/cm3)1.0-1.1

TABLE 20Summary of PBS/PCL film propertiesFilm propertiesCobb value (g/m2)MFFT2510Heat sealKitMVTR valueExample(° C.)minsminsminstemp (° C.)value(g/m2· day)199-1041.804.178.6212012120.50299-1041.373.736.761201263.53
Table 20: 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.

Crosslinking the PVOH in the PBS/PCL blend improved the water resistance of the film. This was shown in the reduced Cobb values seen at two, five and ten minutes. There were also no signs of blanching on the crosslinked film. Blanching had been seen on un-crosslinked films particularly when longer Cobb tests had been conducted. In addition to the reduction of the Cobb values, the use of crosslinker in the PBS/PCL film almost halved the MVTR value from 120.5 to 63.53 g/m2·day. Other film properties such as grease resistance were not affected as the kit value of the blend was already at a maximum value of 12 and therefore could not be improved further.

EXAMPLE 10—CROSSLINKING A POLYBUTYLENE SUCCINATE ADIPATE AND POLYBUTYLENE SUCCINATE BIOPOLYMER BLENDS

A PBSA and PBS blend dispersion which is stabilised with PVOH was manufactured in the HPR. All of the raw materials and initial water were placed in the vessel which was then sealed and heated to 130° C. At this temperature pressure built up in the vessel and was approx. 0.6 bar. When the mixture had reached the process temperature (130° C.) it was stirred for 1 hour at 300 RPM. Water was added in parts at different flow rates to create the particle size. Hot water 1 was added over 15 mins and hot water 2 was added over 10 mins. The stirrer speed was then reduced, and the mixture was allowed to cool in a water bath. When below 40° C. the dispersion was taken out of the vessel and filtered through a 150 μm filter. The dispersion was thickened using a 2% solution of xanthan gum. The formulation is shown in Table 21 below:

TABLE 21Index of PBSA/PBS formulations with and without crosslinkerExample 3Example 4Raw Material% of formulation% of formulationPBSA2727PBS99PVOH2.672.67Antioxidant0.50.5Adipic acid10Wax44Initial water99Hot water 11010Hot water 22525Hot water 313.2412.59Xanthan gum0.0870.087Acticide FTW20.10.1Acticide mv0.050.05
Once the dispersion had been thickened and the solids were within specification the dispersion was then re-filtered through a 50 μm sock and was QC tested. The parameters for the QC testing are shown in Table 22 below:

TABLE 22ParameterSpecificationTotal solids (%)42-44Viscosity (cP)200-600pH5-7particle size (μm)d50d95specific gravity (g/cm3)1.0-1.1
The dispersion was single coated on kraft paper at 10 g/m2and dried in an oven for 1 min at 130° C. A smooth, glossy film was formed. Cobb tests were performed on the film to determine the water barrier properties of the film. The film was also inspected for any film defects and/or blanching after water exposure. As with the other examples, this formulation also contained wax therefore it was expected that water formed beads upon the surface. The barrier properties of the film are shown in Table 23 below:

TABLE 23Film propertiesCobb value (g/m2)MFFT2510Heat sealKitMVTR valueExample(° C.)minsminsminstemp (° C.)value(g/m2· day)380-851.704.428.6212012220480-852.216.5110.1912012248
Test Methods

Cobb Value—The 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/m2. 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 cm3of 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.

Blanching—This defines a whitened area of the film after exposure to water. An internal test which is determined by eye.

Grease resistance kit test—The test is in accordance with Tappi T559. The kit number is assigned when the coating has been visually affected by the mixture.