Method for preparing a polyolefin coating for a paper substrate
A method using poly-C2-C3-olefin particles and C5-C8-alkyl primary aliphatic amides on paper substrates addresses the challenge of achieving low coating weights with improved MVTR and CoF, facilitating recyclable packaging solutions.
Patent Information
- Application Number
- JP2024571309
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-06-09
- Filing Date
- 2023-06-02
- Publication Date
- 2025-07-08
AI Technical Summary
Existing methods struggle to achieve ultra-low coating weights of less than 10 g/m² on paper substrates with polyolefin coatings while meeting water vapor transmission rate (MVTR) and coefficient of friction (CoF) targets, especially for flexible packaging applications requiring high recyclability and low basis weight.
A method involving the application of a composition comprising poly-C2-C3-olefin particles, a dispersant, and a C5-C8-alkyl primary aliphatic amide on a paper substrate, followed by drying to form a coating weight ranging from 1 g/m² to 20 g/m², utilizing specific particle sizes and concentrations to enhance MVTR and CoF characteristics.
The method achieves desirable water vapor transmission rates and coefficient of friction properties, enabling the production of recyclable packaging with ultra-low coating weights, thereby addressing the challenges of existing technologies.
Smart Images
Figure 2025521185000001 
Figure 2025521185000002 
Figure 2025521185000003
Abstract
Description
Technical Field
[0001] The present invention relates to a method for preparing a thin polyolefin coating for a paper substrate. The coated paper has been found to have useful water vapor transmission rate properties.
[0002] Consumer demands for sustainable paper used in packaging are focused on improving the barrier properties and recyclability of coated paper. The barrier performance of paper is known to be enhanced with polyolefin coatings, which also provide heat seal properties. Further, it has been difficult to achieve a coating surface density (coating weight) of less than 10 g / m² by applying an extruded polyolefin layer onto a paper substrate. Achieving these ultra-low coating weights is particularly important in flexible packaging applications where the paper substrate has a basis weight (grammage) of less than 60 g / m² and the market requires a fiber recycling of more than 85% by weight based on the mass of the article. 2 As disclosed in U.S. Patent No. 10,612,193 (B2) (column 2, Table 2), ultrathin coatings can be prepared by applying an aqueous polyolefin emulsion onto a paper substrate and subsequently curing it. Nevertheless, it remains difficult to meet the targets for water vapor transmission rate (MVTR) and coefficient of friction (CoF). Therefore, preparing a thin coating that meets the application requirements for MVTR and provides recyclable packaging would be an advancement in the field of coated paper substrates. 2 As disclosed in U.S. Patent No. 10,612,193 (B2) (column 2, Table 2), ultrathin coatings can be prepared by applying an aqueous polyolefin emulsion onto a paper substrate and subsequently curing it. Nevertheless, it remains difficult to meet the targets for water vapor transmission rate (MVTR) and coefficient of friction (CoF). Therefore, preparing a thin coating that meets the application requirements for MVTR and provides recyclable packaging would be an advancement in the field of coated paper substrates.
[0003] As disclosed in U.S. Patent No. 10,612,193 (B2) (column 2, Table 2), ultrathin coatings can be prepared by applying an aqueous polyolefin emulsion onto a paper substrate and subsequently curing it. Nevertheless, it remains difficult to meet the targets for water vapor transmission rate (MVTR) and coefficient of friction (CoF). Therefore, preparing a thin coating that meets the application requirements for MVTR and provides recyclable packaging would be an advancement in the field of coated paper substrates.
Summary of the Invention
[0004] The present invention provides a method for preparing a thin polyolefin coating for a paper substrate, the method comprising: a) applying onto the paper a composition comprising poly-C2-C3-olefin particles, a dispersant, and an aqueous dispersion of a C5-C8-alkyl primary aliphatic amide; and b) drying the composition to form a coating having a coating weight of from 1 g / m² to 20 g / m². 26 -alkyl primary aliphatic amide of an aqueous dispersion of the composition on the paper coating step, b) the composition was dried to 1g / m 2 ~20g / m 2Forming a coating having a coating weight in the range of, to address the needs in the art. The method of the present invention can be used to provide an ultrathin coating on a paper substrate having advantageous water vapor transmission rate and coefficient of friction characteristics.
DETAILED DESCRIPTION OF THE INVENTION
[0005] The present invention relates to a method comprising a) applying to paper a composition comprising an aqueous dispersion of poly-C2-C3-olefin particles, a dispersant, and a C5-C 26 -alkyl primary aliphatic amide, and b) drying the composition to form a coating having a coating weight in the range of 1 g / m 2 to 20 g / m 2 .
[0006] As used herein, "poly-C2-C3-olefin particles" refers to polyethylene particles, polypropylene particles, and poly(ethylene-propylene) copolymer particles. Polyethylene may be an ethylene-C4-C 10 -α-olefin copolymer (i.e., linear low density polyethylene), such as ethylene-1-butene copolymer, ethylene-1-hexene copolymer, and ethylene-1-octene copolymer.
[0007] Commercially available linear low-density polyethylene is AFFINITY PL1280 LLDPE ethylene-octene copolymer (a registered trademark of The Dow Chemical Company or its affiliates). The polyethylene may also be, for example, high-density polyethylene commercially available as DOW (trademark) DMDA-8940 NT 7 HDPE resin, or low-density polyethylene. An example of a commercially available ethylene-propylene copolymer is VERSIFY (trademark) 4200 propylene-ethylene copolymer (a trademark of The Dow Chemical Company or its affiliates), and a commercially available polypropylene is Braskem 6D43 random copolymer. Particles containing C2-C3 polyolefins and some amount of dispersant and a primary aliphatic amide associated therewith preferably have a volume average particle size in the range of 200 nm or 300 nm to 5 μm or 3 μm or 1.5 μm when measured by dynamic light scattering.
[0008] The dispersant is a copolymer of ethylene and a carboxylic acid monomer or its salt. Examples of suitable dispersants include ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and ethylene-itaconic acid copolymers, and their lithium, sodium, and potassium salts.
[0009] The weight-to-weight ratio of ethylene structural units to carboxylic acid monomer or its salt is preferably in the range from 95:5, more preferably from 90:10, most preferably from 85:15, to 70:30, more preferably to 75:25. As used herein, the term "structural unit" of a specified monomer refers to the residue of the monomer after polymerization. For example, the structural unit of methacrylic acid is as follows.
[0010]
Chemical formula
[0011] Examples of commercially available dispersants include PRIMACOR™ 5980i ethylene-acrylic acid copolymer and NUCREL 960™ ethylene-methacrylic acid copolymer (trademarks of The Dow Chemical Company or its affiliates).
[0012] C5-C 26 -alkyl primary aliphatic amides may be linear or branched and may be saturated or partially unsaturated with one or two or three double bonds. The aliphatic amide may also be a C 10- -C 24 -alkyl primary aliphatic amide or a C 16 -C 22 -alkyl primary aliphatic amide. Examples of suitable aliphatic amides include linear and branched C 18- -alkyl monounsaturated aliphatic amides, linear and branched C 18 -alkyl saturated aliphatic amides, linear and branched C 22 -alkyl monounsaturated aliphatic amides, and linear and branched C 22 -alkyl saturated aliphatic amides. The C5-C 26 -alkyl primary aliphatic amide preferably has a melting point in the range of 50 °C or 65 °C to 115 °C or 100 °C or 90 °C.
[0013] The concentration of poly-C2-C3-olefin particles minus any associated dispersant or primary aliphatic amide is preferably in the range of 40 or 60 or 70 weight percent to 95 or 90 weight percent based on the weight of the polyolefin, dispersant, and C5-C 26 -alkyl primary aliphatic amide. The concentration of the dispersant is preferably in the range of 4 or 9 or 15 weight percent to 50 or 40 or 30 weight percent based on the weight of the polyolefin particles, dispersant, and C5-C 26 -alkyl aliphatic amide. The concentration of the C5-C 26 -alkyl primary aliphatic amide is preferably in the range of 40 or 60 or 70 weight percent to 95 or 90 weight percent based on the weight of the polyolefin particles, dispersant, and C5-C 26- Based on the weight of the alkyl aliphatic amide, preferably in the range of 0.5 or 1 to 5 or 4 or 3 weight percent. The pH of the composition is preferably within the range of 8 to 11. To adjust the pH to the desired level, a neutralizing agent such as KOH is advantageously used.
[0014] The composition advantageously comprises C 10 -C 24 a stabilizing amount of an anionic surfactant such as a linear or branched alkyl or aralkyl carboxylate, sulfate, or phosphate, or a nonionic surfactant such as a secondary alcohol ethoxylate or an ethylene oxide propylene oxide block copolymer surfactant. The composition is advantageously applied to a paper substrate using a drawdown bar, followed by removal of water at an elevated temperature, preferably as described in the next section.
[0015] 1 g / m 2 or 2 g / m 2 or 5 g / m 2 to 20 g / m 2 or 12 g / m 2 or 10 g / m 2 It has been found that coating weights in the range up to can be achieved with desirable water vapor transmission rate (MVTR) and coefficient of friction (CoF) characteristics.
[0016] Method for preparing a coated substrate and method for measuring coating weight UPM Brilliant 62 Glassine Paper (basis weight 62 g / m 2 ) was coated with a polyolefin dispersion using a drawdown bar and dried in a forced air oven at 100 °C for 2 minutes to obtain a coating weight of 8 g / m 2The final coating surface density (coating weight) was set to (~8 - 9 μm coating thickness). The coating weight was measured by punching holes in the coated UPM paper and the uncoated UPM paper with a circular die to form disks having a specific diameter (D cm). The coated disk (W1) was weighed against the uncoated disk (W2), and the coating weight was calculated by the following formula.
[0017]
Number
[0018] Measurement of water vapor transmission rate The water vapor transmission rate (MVTR) was determined according to ASTM E96 / E96M. The coated paper sample was sealed to the open end of a permeation cup, and subsequently the sample was exposed to a controlled temperature and humidity environment (typically a humidity chamber). The MVTR was determined based on measuring the mass uptake of the cup as a function of time.
[0019] Measurement of coefficient of dynamic friction The coefficient of dynamic friction (CoF) was measured using a Texture Analyzer equipped with a sliding friction rig according to TAPPI T549. One piece of the coated paper was fixed at the bottom of a 200 g weight thread with the coated side facing down. Another piece of the coated paper was fixed flat with the coated side facing up. A thread was attached to the thread, and the thread was pulled so that it crossed at least a 100 mm plane at a speed of 2.5 mm / s. The force Fd (unit: gram weight) reaching the plateau when the thread was moved steadily was recorded. The dynamic CoF was calculated as Fd / 200.
[0020] Calculation of degree of neutralization The degree of neutralization of the polyolefin dispersion was determined by the following formula.
[0021]
Number
Examples
[0022] Table 1 shows the components and feed rates used to prepare Examples 1 to 4 and Comparative Examples 1 to 5. The feed rates are shown in parentheses. The general procedure is shown in Table 1 below. PO refers to polyolefin. Amide refers to aliphatic amide. H2O o refers to the initial water ratio. H2O d refers to the dilution water ratio. Solids refer to the solids weight % of polyolefin, dispersant, aliphatic amide, and anionic surfactant in the dispersion, and PS refers to the particle size in micrometer units determined by dynamic light scattering.
[0023] PL1280 refers to AFFINITY (trademark) PL 1280 LLDPE ethylene-octene copolymer. V4200 refers to VERSIFY (trademark) ethylene-propylene copolymer. N960 refers to NUCREL (trademark) N960 ethylene-methacrylic acid copolymer. OA (oleamide, melting point 70 °C) is C 18 -alkyl mono-unsaturated primary aliphatic amide. EA (erucamide, melting point 80 °C) is C 22 -alkyl mono-unsaturated primary aliphatic amide. BA (behenamide, melting point 112 °C) is C 22 -alkyl saturated primary aliphatic amide. EBS (ethylene bis-stearamide, melting point 145 °C) is C 38 -alkyl secondary aliphatic amide. OPA (oleyl palmitamide, melting point 60 - 66 °C) is C 34 -alkyl secondary aliphatic amide. SEA (stearyl erucamide, melting point 70 - 75 °C) is C 40 -alkyl secondary aliphatic amide.
[0024] The neutralization degrees of Comparative Examples 1 to 4 and Examples 1 to 6 were 75%, and those of Comparative Example 5 and Example 7 were 80%.
[0025]
Table 1
[0026] General procedure for preparing a polyolefin dispersion which is an aqueous dispersion The aqueous dispersion was prepared by the following general procedure. PO, N960, and amide (except for Comparative Examples 1 and 5) were fed into a 25-mm diameter twin-screw extruder using separately controlled speed feeders. An anionic surfactant (oleic acid) was pumped as a liquid into the melt zone of the extruder at a feed rate of 3.4 mL / min using an Isco syringe pump. PO, N960, and amide were passed through the extruder and melted to form a liquid melt material which is an intermediate.
[0027] The temperature profile of the extruder was raised to a maximum of 150 °C. Water and 30% KOH aqueous solution were mixed, and after a uniform polymer melt was formed, it was fed into the extruder at the first water introduction location, and then dilution water was fed into the extruder. The extruder speed was 450 rpm for all samples except for Comparative Example 5 where the extruder speed was 400 rpm. At the extruder outlet, a back pressure regulator was used to adjust the pressure inside the extruder barrel to a pressure adapted to reduce steam formation, generally in the range of 2 MPa to 4 MPa.
[0028] Each aqueous dispersion was taken out from the extruder and first filtered through a 200-μm filter. The solid content of the dispersion was measured using an infrared solid analyzer, and the volume average particle size of the polymer particles was measured using a COULTER (trademark) LS-230 particle size analyzer (Beckman Coulter Corporation, Fullerton, CA).
[0029] Table 2 shows the MVTR and CoF of the examples and comparative examples. The coating thickness of each sample was 8 gsm. PO:N960:amide refers to the w / w / w ratio of polyolefin, dispersant, and aliphatic amide.
[0030]
Table 2
[0031] The data show the improvement in MVTR of coatings containing primary aliphatic amides when compared to either coatings without amide additives or coatings containing secondary aliphatic amides. For certain applications, a dynamic CoF of 0.3 or less is acceptable, and for other applications, a CoF of less than 0.2 is required.
Claims
Claim 1 a) Poly-C ２ ~C ３ -olefin particles, a dispersant, and an aqueous dispersion of a C ５ ~C ２６ -alkyl primary aliphatic amide on paper, and b) drying the composition to form a coating having a coating weight in the range of 1 g / m ２ ~20 g / m ２ of the method, including the step of forming a coating having a coating weight in the range of 1 g / m to 20 g / m. Claim 2 The poly-C in the composition ２ to C ３ -olefin particles, the dispersant, and the C ５ to C ２６ -alkyl primary aliphatic amide, the concentration of the polyolefin particles is in the range of 40 to 95% by weight, the concentration of the dispersant is in the range of 4 to 50% by weight, and the C ５ to C ２６ -alkyl primary aliphatic amide is in the range of 0.5 to 5% by weight, the method according to claim 1. Claim 3 The dispersant is an ethylene-acrylic acid copolymer or a salt thereof, or an ethylene-methacrylic acid copolymer or a salt thereof, and the C ５ to C ２６ -alkyl primary aliphatic amide is a C １０ to C ２４ -alkyl primary aliphatic amide, and the composition is dried to form a coating having a coating weight in the range of 5 g / m ２ to 10 g / m ２ The method according to claim 2, wherein the method is carried out. Claim 4 Said C １０ to C ２４ -alkyl primary aliphatic amide has a melting point in the range of 50°C to 115°C, and the C １６ to C ２２ -alkyl primary aliphatic amide, and the poly-C ２ to C ３ -olefin particles are ethylene-C ４ to C １０ -α-olefin copolymer particles. The method according to claim 3 Claim 5 The ethylene-C ４ -C １０ -α-olefin copolymer particles are ethylene-1-octene copolymer particles, the method according to claim 4. Claim 6 Said C １０ to C ２４ -alkyl primary aliphatic amide has a melting point in the range of 50°C to 115°C, and the C １６ to C ２２ -alkyl primary aliphatic amide, and the poly-C ２ to C ３ -olefin particles are polypropylene particles. The method according to claim 3. Claim 7 Said C １０ to C ２４ -alkyl primary aliphatic amide has a melting point in the range of 50 °C to 115 °C, and is a C １６ to C ２２ -alkyl primary aliphatic amide, and the poly-C ２ to C ３ -olefin particles are poly(ethylene-propylene) copolymer particles. The method according to claim 3 Claim 8 said poly-C ２ -C ３ -olefin particles, said dispersant, and said C ５ -C ２６ -alkyl primary aliphatic amide, based on the weight of said poly-C ２ -C ３ -olefin concentration is in the range of 60 to 90% by weight, said dispersant concentration is in the range of 9 to 40% by weight, and said C ５ -C ２６ -alkyl primary aliphatic amide concentration is in the range of 1 to 4% by weight, the method according to claim 2. Claim 9 Said poly-C ２ -C ３ -olefin particles, said dispersant, and said C １６ -C ２２ -alkyl primary aliphatic amide, based on the weight of said poly-C ２ -C ３ -olefin concentration is in the range of 60 to 90% by weight, said dispersant concentration is in the range of 9 to 40% by weight, and said C １６ -C ２２ -alkyl primary aliphatic amide concentration is in the range of 1 to 4% by weight, the method according to any one of claims 4 to 7.