Coated paper articles

Abstract

The present invention relates to a coated paper article comprising a coating superimposed on a first surface of a paper substrate, wherein the coating comprises polyacrylate and starch, and the polyacrylate comprises structural units of 1) n-butyl acrylate or ethyl acrylate or a combination thereof, 2) acrylonitrile, and 3) itaconic acid. The coated article of the present invention exhibits excellent oxygen barrier properties and resistance to oils, greases, and blocks.

Description

[Technical Field]

[0001] The present invention relates to a coated paper article, and more particularly to paper covered with a coating comprising polyacrylate and starch. [Background technology]

[0002] Paper is favored by the packaging industry and consumers because it is bio-derived, recyclable, and does not remain in the environment. Advantageously, when coated, paper exhibits improved barrier properties against moisture, oils and greases, as well as oxygen. Such coatings are well known in the art. For example, U.S. Patent No. 9,950,502(B2) (Seyffer) discloses a coating composition derived from the emulsion polymerization of acrylate monomers in the presence of decomposed starch for producing a coating composition that is reported to exhibit shear stability, low hexane permeability, and little to no pore formation.

[0003] Double-sided coated paper using standard in-line coating process conditions presents a particular challenge. After applying a barrier coating layer to each side of the paper, the coating is dried and immediately wound back onto a roll. Depending on the size of the paper roll, this process causes contact between the coatings at high temperatures and considerable pressure. Even low levels of blocking can cause damage to the barrier coating or paper fibers, and in extreme cases, the entire roll will stick together. Therefore, finding a composition that exhibits excellent blocking resistance without sacrificing important barrier properties would represent progress in the field of coated paper. [Overview of the Initiative]

[0004] The present invention addresses the needs of the art by providing a coated paper article comprising a coating superimposed on a first surface of a paper substrate, wherein the coating comprises polyacrylate and starch, the polyacrylate comprising 1) n-butyl acrylate or ethyl acrylate or a combination thereof, 2) acrylonitrile, and 3) structural units of itaconic acid, the starch concentration being in the range of 20 to 50 weight percent based on the weight of starch and polyacrylate, and the calculated glass transition temperature of the polyacrylate being in the range of -10°C to 35°C.

[0005] The coated articles of the present invention exhibit excellent oxygen barrier properties, as well as resistance to oils, greases, and blocks. [Modes for carrying out the invention]

[0006] The present invention relates to a coated paper article comprising a coating superimposed on a first surface of a paper substrate, wherein the coating comprises polyacrylate and starch, the polyacrylate comprising 1) n-butyl acrylate or ethyl acrylate or a combination thereof, 2) acrylonitrile, and 3) structural units of itaconic acid, the starch concentration being in the range of 20 to 50 weight percent based on the weight of starch and polyacrylate, and the calculated glass transition temperature of the polyacrylate being in the range of -10°C to 35°C.

[0007] As used herein, "polyacrylate" refers to the residue of an aqueous dispersion of polymer particles (latex) after applying a composition containing latex and starch to paper and allowing it to dry.

[0008] As used herein, the “structural units” of the listed monomers refer to the monomer residues after polymerization. For example, the structural units of ethyl acrylate are shown as follows:

[0009] [ka] In the formula, the dotted lines represent the bonding points of structural units to the polymer backbone.

[0010] Where used herein, "calculated glass transition temperature" refers to the homopolymer T reported in Polymer Handbook (4th Edition), John Wiley & Sons (2005). g The glass transition temperature (T) calculated by the Fox equation using the Fox formula g ) refers to the calculation of polyacrylate T g This range is from -10°C, or from -5°C, or from 0°C to 35°C, or up to 25°C, or up to 20°C, or up to 15°C.

[0011] The polyacrylate preferably comprises structural units of ethyl acrylate, acrylonitrile, and itaconic acid, or structural units of n-butyl acrylate, acrylonitrile, and itaconic acid. When the polyacrylate comprises structural units of ethyl acrylate, the concentration of structural units of ethyl acrylate is preferably in the range of 65 or 67 weight percent to 75 or 73 or 71 weight percent, the concentration of structural units of acrylonitrile is preferably in the range of 23 or 25 or 27 weight percent to 33 or 31 weight percent, and the concentration of structural units of itaconic acid is preferably in the range of 1.5 or 1.9 weight percent to 6 or 5 or 4.5 weight percent, all weight percentages being based on the weight of the polyacrylate.

[0012] If the polyacrylate contains n-butyl acrylate structural units, the weight percentage of n-butyl acrylate structural units is preferably in the range of 50, 52, or 54 weight percent to 60 or 58 weight percent, the weight percentage of acrylonitrile structural units is preferably in the range of 35, 38, or 40 weight percent to 46 or 44 weight percent, and the weight percentage of itaconic acid structural units is preferably in the range of 1.5 or 1.9 weight percent to 6, 5, or 4.5 weight percent, all weight percentages are based on the weight of the polyacrylate.

[0013] The type of starch is not limited and may include starches derived from corn, wheat, oats, barley, rice, millet, potatoes, peas, tapioca, sorghum, and sago. The starch concentration ranges from 20, 25, or 28 weight percent to 50, 40, 35, or 32 weight percent based on the weight of starch and polyacrylate. Similarly, the polyacrylate concentration ranges from 50, 60, 65, or 68 weight percent to 80, 75, or 72 weight percent based on the weight of starch and polyacrylate.

[0014] Compositions used to coat paper substrates can be prepared by first preparing an aqueous dispersion (latex) of polymer particles by emulsion polymerization, followed by the addition of starch in the form of an aqueous slurry or as a dry powder. Alternatively, the composition can be prepared by polymerizing monomers under emulsion polymerization conditions in the presence of starch.

[0015] The composition may be applied to a paper substrate using means known in the art to form coated paper, which is then preferably dried at a high temperature to a desired coating weight, which is approximately 5 g / m². 2 Alternatively, 8g / m 2The thickness ranges from (gsm) to 20gsm, 15gsm, or 10gsm. The paper may be coated on a first surface and optionally on a second surface. When the paper is coated on both sides, the total coating weight is generally in the range of 5gsm, or 8gsm to 25gsm, or 20gsm, or 15gsm, or 10gsm. Starch and polyacrylate preferably constitute 70, 80, 90, or 95 weight percent or 98 weight percent of the coating, or up to 100 weight percent of the coating. The coating may further contain one or more additional components, including organic or inorganic opaque pigments, fillers, colorants, dispersants, rheology modifiers, and defoamers.

[0016] A coating with excellent oxygen barrier properties and resistance to oils, greases, and blocks was prepared using the composition of the present invention. [Examples]

[0017] In the following examples, particle size refers to the z-average particle size diameter due to dynamic light scattering.

[0018] Preparation of intermediate Example 1-70EA / 28AN / 2IA latex composition DI water (681.54 g), sodium lauryl sulfate (SLS, 28% active, 39.30 g), and 4-hydroxy-TEMPO (5%, 0.65 g) were added to a 5 L four-necked round-bottom flask (kettle) equipped with a paddle stirrer, thermometer, N2 inlet, and reflux condenser. The kettle was heated to 86 °C under N2. A monomer emulsion (ME) was prepared by mixing DI water (638.19 g), SLS (28%, 13.10 g), ethyl acrylate (EA, 1033.62 g), acrylonitrile (AN, 413.43 g), and itaconic acid (IA, 29.55 g). A portion of the ME (42.56 g) was added to the kettle, and the container for the ME was rinsed with DI water (10 g). Next, a solution of sodium persulfate (NaPS, 7.31 g in 35 g of DI water) was added to the kettle, and the container for NaPS was rinsed with DI water (5 g). Exothermic reaction was observed, and the mixture was held at the peak temperature for 5 minutes. The remainder of ME was supplied to the kettle over 90 minutes, with the temperature set to 81°C, at a rate of 13.0 g / min for the first 20 minutes, and then at a rate of 26.1 g / min for the last 70 minutes. Simultaneously, a solution of NaPS (2.81 g in 100 g of DI water) was supplied to the kettle over 90 minutes, at a rate of 0.65 g / min for the first 20 minutes, and then at a rate of 1.29 g / min for the last 70 minutes. Upon completion of supply, the addition container was rinsed with DI water (110 g), the reaction was held at 80°C for 10 minutes, and then cooled to 75°C. While cooling, a solution of ferrous sulfate heptahydrate (0.15% solution, 12.00 g) was added to the kettle. At 75°C, the first chase solution of t-butyl hydroperoxide (t-BHP, 70% solution, 7.41 g in 40 g of DI water) was added to the kettle simultaneously with a solution of isoascorbic acid (IAA, 3.59 g in 50 g of DI water) over 30 minutes. After the addition of the first chase solution was complete, the reaction was held at 75°C for 10 minutes, and then cooled to 70°C. At 70°C, the second chase solution of t-BHP (70% solution, 5.60 g in 26 g of DI water) was added to the kettle simultaneously with a solution of IAA (2.79 g in 35 g of DI water) over 30 minutes. After the addition of the second chase solution was complete, the reaction mixture was neutralized by the addition of ammonium hydroxide (30%, 16.61 g). Next, the contents of the kettle were cooled to room temperature and filtered to remove any lumps.The resulting dispersion had a solids content of 45.0%, a pH of 6.5, a particle size of 118 nm, and a calculated T of 3.6 °C. g It had.

[0019] Preparation of Intermediate Example 2 - 56BA / 42AN / 2IA Latex Composition The composition was prepared by the procedure described in Intermediate Example 1, except that ME contained DI water (638.19 g), SLS (28%, 13.10 g), n - butyl acrylate (826.90 g), AN (620.15 g), and IA (29.55 g). After the seed step, the remainder of ME was fed to the kettle over 120 minutes at a rate of 9.5 g / min for the first 20 minutes and then at a rate of 19.1 g / min for the last 100 minutes. The resulting dispersion had a solids content of 45.2%, a pH of 6.6, a particle size of 108 nm, and a calculated T of -5.6 °C g It had.

[0020] Preparation of Intermediate Example 3 - 68EA / 28AN / 4IA Latex Composition The composition was prepared by the procedure described in Intermediate Example 1, except that ME contained DI water (638.19 g), SLS (28%, 13.10 g), EA (1004.09 g), AN (620.15 g), and IA (59.10 g). The amount of ammonium hydroxide used in the neutralization step was 33.22 g. The resulting dispersion had a solids content of 44.0%, a pH of 6.8, a particle size of 142 nm, and a calculated Tg of 6.2 °C.

[0021] Preparation of Comparative Intermediate Example 1 - 54EA / 44MMA / 2IA Latex Composition The composition was prepared by the procedure described in Intermediate Example 1, except that ME contained DI water (638.19 g), SLS (28%, 13.10 g), EA (797.36 g), methyl methacrylate (MMA, 649.70 g), and IA (29.55 g). The resulting dispersion had a solids content of 45.1%, a pH of 6.8, a particle size of 102 nm, and a calculated T of 22.9 °C g It had.

[0022] Preparation of Comparative Intermediate Example 2 - 70EA / 28AN / 2AA Latex Composition The composition was prepared by the procedure described in Intermediate Example 1, except that ME contained DI water (638.19 g), SLS (28%, 13.10 g), EA (1004.09 g), AN (620.15 g), and acrylic acid (AA, 29.55 g). The resulting dispersion had a solids content of 44.8%, a pH of 7.9, a particle size of 124 nm, and a calculated T of 3.2 °C g and had.

[0023] Table 1 summarizes the amounts of monomers and neutralizing agents used to prepare the latex intermediates.

[0024] [Table 1]

[0025] Intermediate Example 4 to Intermediate Example 6 and Comparative Example 3 and Comparative Example 4 were prepared by the following procedure by combining each of the latex intermediate and the comparative intermediate with starch: A starch solution (45% solids content) was prepared by dissolving ICB 3000 corn starch (100 g, 95% solids content) in DI water (111.11 g) with stirring at 50 °C. Then, a portion (125 g) of the latex intermediate was placed in a 250 mL plastic container, followed by the addition of a portion (53.58 g) of the starch solution. The mixture was mixed at 1800 rpm for 2 minutes using a speed mixer. The starch loading was 30% based on the weight of the total solids in the composition.

[0026] Paper Coating Procedure Coated paper articles (Examples 1-3 and Comparative Examples 1 and 2) were prepared by applying the composition to the uncoated glossy surface of a paper substrate (obtained from UPM) having a coating weight of 62 gsm. Dry coating weights in the range of 8-9 gsm were achieved using a wound drawdown bar. The samples were dried in an oven (Fisher Scientific Isotemp 180L Oven Fa) at 100°C for 2 minutes.

[0027] Court weight measurement 7.2 inches of coated and uncoated paper 2 (46.3cm 2 Sections of the sample were cut out, and the coating weight was measured by placing the section in a 100°C oven for 2 minutes. Then, all samples were weighed, and the difference between the coated and uncoated samples was measured and divided by the area of ​​the sample to determine the coating weight.

[0028] Block Test A coating block test was performed using a metal spring load compression device. A dried and conditioned substrate was cut into a rectangle (3.8 cm × 7.0 cm), and the coated surfaces were placed facing each other between the metal plates of the device to measure the coating-coating block (block c / c). The spring was compressed to apply a pressure of 2600 Torre to the substrate, and the entire device was placed in a 60°C oven for 1 hour. After that, the items were removed from the oven and allowed to cool at room temperature for 30 minutes. The cooled sheets were carefully removed and separated, and the block c / c was evaluated according to the following scale. 1 = The sheet was pulled away without resistance. 2 = Minimum force required to separate the sheets; audible noise detected during separation. 3 = Similar to Post-it notes, the force required to separate the sheets was constant. 4 = Minimum amount of fiber tearing observed. 5 = Significant fiber tearing was observed where the sheets were completely bonded.

[0029] Heat seal test The heat seal of coated paper samples was tested using an HST-H3 seal tester. The samples were cut into 2.5 × 5 cm strips and loaded with the coated sides in contact with each other between the jaws. Pressure was applied at 190°C for 0.5 seconds (3600–4150 Torque). The samples were removed from the tester and allowed to cool at room temperature for 1 minute. The paper samples were then separated, and the coating-to-coating heat seal (heat seal c / c) was evaluated using P, M, or F as follows: P: Passed, the paper peels off when pulled. M: Insufficient, the paper peels off like a sticky note. F: Failed, the paper separates without resistance.

[0030] Kit testing for oil and grease resistance Coated paper was tested for oil and grease resistance (OGR) according to the TAPPI test method T559cm-12. A kit solution consisting of a mixture of castor oil, toluene, and heptane was applied to the coated substrate in droplet form. After 15 seconds, leakage of the solvent into the coating was observed, and the solution was wiped off the substrate. Discoloration or changes in appearance of the substrate were also considered failures for that particular kit solution. A score evaluation from 1 to 12 was assigned to the kit solution with the highest number that passed the test, with 12 indicating the best performance. All samples showed a kit evaluation of 12.

[0031] OTR Test The oxygen transmission rate (OTR) of the film was measured at 23°C, 50% relative humidity, and 760 Torr using a MOCON OXTRAN 2 / 22 H module according to ASTM D-3985. Approximately 30 cm 2 A coated paper test piece was cut out, then masked, and loaded directly into the module for measurement. The masking material was a 0.08 mm thick aluminum sheet with an acrylic adhesive layer for creating a seal. The effective test area was 20.3 cm².2 The test gas used contained 100% oxygen to ensure that the permeation did not exceed the detection range of the module. The OTR was cc / m³. 2 • Measured at d. All samples were considered acceptable at 20 cc / m³. 2 • Showed an OTR of less than d.

[0032] Table 2 shows the block c / c, heat seal c / c, and the average of two OTR measurements (OTR 平均 ) indicates.

[0033] [Table 2]

[0034] The data shows that samples prepared from EA / AN / IA and BA / AN / IA latex exhibited an excellent balance of block c / c, heat-sealed c / c, OTR, and OGR.

Claims

1. A coated paper article comprising a coating superimposed on a first surface of a paper substrate, wherein the coating comprises polyacrylate and starch, the polyacrylate comprising 1) n-butyl acrylate or ethyl acrylate or a combination thereof, 2) acrylonitrile, and 3) structural units of itaconic acid, the concentration of the starch being in the range of 20 to 50 weight percent based on the weight of the starch and the polyacrylate, and the calculated glass transition temperature of the polyacrylate being in the range of -10°C to 35°C.

2. The calculated glass transition temperature of the polyacrylate is in the range of -5°C to 25°C, the polyacrylate contains structural units of ethyl acrylate, acrylonitrile, and itaconic acid, and based on the weight of the polyacrylate, the concentration of structural units of ethyl acrylate is in the range of 65 to 73 weight percent, the concentration of structural units of acrylonitrile is in the range of 23 to 33 weight percent, the concentration of structural units of itaconic acid is in the range of 1.5 to 6 weight percent, and the coating is 5 g / m² ２ ~20g / m ２ A coated paper article according to claim 1, having a coating weight in the range of [value].

3. The concentration of the starch is in the range of 25 to 40 weight percent based on the weight of the starch and the polyacrylate, the concentration of the structural units of the ethyl acrylate is in the range of 67 to 71 weight percent based on the weight of the polyacrylate, the concentration of the structural units of the acrylonitrile is in the range of 25 to 31 weight percent, the concentration of the structural units of the itaconic acid is in the range of 1.9 to 4.5 weight percent, the calculated glass transition temperature is in the range of 0°C to 15°C, and the coating is 5 g / m² ２ ~15g / m ２ A coated paper article according to claim 2, having a coating weight in the range of [value].

4. The calculated glass transition temperature of the polyacrylate is in the range of -10°C to 10°C, the polyacrylate contains structural units of n-butyl acrylate, acrylonitrile, and itaconic acid, and based on the weight of the polyacrylate, the concentration of the n-butyl acrylate structural units is in the range of 50 to 60 weight percent, the concentration of the acrylonitrile structural units is in the range of 35 to 46 weight percent, the concentration of the itaconic acid structural units is in the range of 1.5 to 6 weight percent, and the coating is 5 g / m² ２ ~20g / m ２ A coated paper article according to claim 1, having a coating weight in the range of [value].

5. The starch concentration is in the range of 25 to 40 weight percent based on the weight of the starch and the polyacrylate; the concentration of the n-butyl acrylate structural units is in the range of 52 to 58 weight percent based on the weight of the polyacrylate; the concentration of the acrylonitrile structural units is in the range of 38 to 44 weight percent; the concentration of the itaconic acid structural units is in the range of 1.9 to 4.5 weight percent; the calculated glass transition temperature is in the range of -10°C to 5°C; and the coating is 5 g / m². ２ ~15g / m ２ A coated paper article according to claim 4, having a coating weight in the range of [value].

6. The coated paper article according to any one of claims 1 to 5, wherein the starch is derived from corn, wheat, oats, barley, rice, millet, potato, pea, tapioca, sorghum, or sago, and the concentration of the starch is in the range of 28 to 32 weight percent based on the weight of the starch and the polyacrylate.

7. The coated paper article according to claim 6, wherein the starch is corn starch.

8. Further includes a coating on the second surface of the paper substrate, and the total coating weight of the coating is 5 g / m ２ ~15 g / m ２ The coated paper article according to claim 1, which is in the range of.

9. A coated paper article comprising a coating superimposed on a first surface of a paper substrate, wherein the coating is a) A polyacrylate comprising 1) n-butyl acrylate or ethyl acrylate or a combination thereof, 2) acrylonitrile, and 3) structural units of itaconic acid, b) Starch having a concentration in the range of 20 to 50 weight percent based on the weight of the starch and the polyacrylate, comprising: When the polyacrylate contains structural units of ethyl acrylate, acrylonitrile, and itaconic acid, based on the weight of the polyacrylate, the concentration of structural units of ethyl acrylate is in the range of 65 to 73 weight percent, the concentration of structural units of acrylonitrile is in the range of 23 to 33 weight percent, and the concentration of structural units of itaconic acid is in the range of 1.5 to 6 weight percent. A coated paper article in which, when the polyacrylate contains structural units of n-butyl acrylate, acrylonitrile, and itaconic acid, the concentration of the structural units of n-butyl acrylate is in the range of 50 to 60 weight percent, the concentration of the structural units of acrylonitrile is in the range of 35 to 46 weight percent, and the concentration of the structural units of itaconic acid is in the range of 1.5 to 6 weight percent, based on the weight of the polyacrylate.

10. The concentration of the starch is in the range of 25 to 40 weight percent based on the weight of the starch and the polyacrylate, and when the polyacrylate contains structural units of ethyl acrylate, acrylonitrile, and itaconic acid, the concentration of the structural units of ethyl acrylate is in the range of 67 to 71 weight percent, the concentration of the structural units of acrylonitrile is in the range of 25 to 31 weight percent, and the concentration of the structural units of itaconic acid is in the range of 1.9 to 4.5 weight percent, and when the polyacrylate contains structural units of n-butyl acrylate, acrylonitrile, and itaconic acid, the concentration of the structural units of n-butyl acrylate is in the range of 52 to 58 weight percent, the concentration of the structural units of acrylonitrile is in the range of 38 to 44 weight percent, and the concentration of the structural units of itaconic acid is in the range of 1.9 to 4.5 weight percent, and the coating is 5 g / m ２ ~20g / m ２ A coated paper article according to claim 9, having a coating weight in the range of [value].

11. The starch is derived from corn, wheat, oats, barley, rice, millet, potatoes, peas, tapioca, sorghum, or sago, and the starch constitutes 25 to 35 percent by weight of the coating, and the coating is 5 g / m². ２ ~15g / m ２ A coated paper article according to any one of claims 8 to 10, having a coating weight in the range of [specify range].

12. The coated paper article according to claim 11, wherein the starch is corn starch.

13. The second surface of the paper substrate further includes a coating, the total coating weight of which is 5 g / m². ２ ~25g / m ２ A coated paper article according to claim 9, which is within the range of the specified range.

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