Heat sealing coating
By using a water-based coating containing two polyacrylate emulsions, the performance deficiencies of existing heat-sealing coatings in the preparation of blister cover foils are resolved, high heat-sealing strength and anti-blocking properties are achieved, and the sealing effect of the blister cover foil is improved.
Patent Information
- Application Number
- CN202380092831.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-02-02
- Publication Date
- 2025-10-03
AI Technical Summary
Existing solvent-based and water-based ethylene vinyl acetate heat seal coatings have poor performance in the preparation of blister lidding foils, especially in terms of heat seal strength and blocking resistance.
A water-based coating comprising two polyacrylate emulsions, namely a first polyacrylate emulsion and a second polyacrylate emulsion, is used to form a coating with high heat sealing strength and anti-blocking properties by controlling their glass transition temperature and composition ratio, combined with an appropriate tackifier, a wax emulsion and a water-based ethylene vinyl acetate resin.
A heat seal strength of greater than 7.5N/15mm at 150°C and good anti-blocking properties at 50°C were achieved, improving the sealing performance of the blister cover foil.
Smart Images
Figure SMS_1 
Figure SMS_2 
Figure SMS_3
Abstract
Description
Technical Field
[0001] The present disclosure relates to heat seal coatings. More particularly, the present disclosure relates to water-based heat seal coatings. Even more particularly, the present disclosure relates to water-based heat seal coatings used in the preparation of blister lidding foils. Background Art
[0002] Heat seal coatings are currently primarily based on solvent-based or water-based ethylene vinyl acetate and ethylene acrylic acid chemistries. Summary of the Invention
[0003] A water-based coating comprising two polyacrylate emulsions is disclosed. The water-based coating may comprise 35 wt.% to 60 wt.% of a first polyacrylate emulsion, based on the weight of the water-based coating. The water-based coating may comprise 30 wt.% to 45 wt.% of a second polyacrylate emulsion, based on the weight of the water-based coating. The first polyacrylate emulsion may comprise butyl acrylate and styrene. The first polyacrylate emulsion may comprise butyl acrylate to styrene in a ratio of 1.4 to 5.6. The second polyacrylate emulsion may comprise butyl acrylate and styrene. The second polyacrylate emulsion may comprise butyl acrylate to styrene in a ratio of 0.4 to 1.3. The first polyacrylate emulsion may have a glass transition temperature of -25°C to 10°C, and the second polyacrylate emulsion may have a glass transition temperature of 15°C to 45°C. DETAILED DESCRIPTION
[0004] The terms "comprising," "including," "having," and their derivatives are not intended to exclude the presence of any additional components, steps, or procedures, whether or not they are specifically disclosed. For the avoidance of any doubt, all compositions claimed through use of the term "comprising" may include any additional additives, adjuvants, or compounds, whether polymeric or otherwise, unless indicated to the contrary. In contrast, the term "consisting essentially of excludes from the scope of any subsequent statement any other components, steps, or procedures, except those that are not essential for operability. The term "consisting of excludes any component, step, or procedure not specifically described or listed.
[0005] The numerical ranges disclosed herein include all values from and including the lower and upper limits. For ranges containing specific values (e.g., a range from 1, or 2, or 3 to 5, or 6, or 7), any subrange between any two specific values is included (e.g., the above range 1 to 7 includes subranges 1 to 2; 2 to 6; 5 to 7; 3 to 7; 5 to 6, etc.).
[0006] The term "composition" refers to a mixture of materials comprising the composition, as well as reaction products and decomposition products formed from the materials of the composition.
[0007] As used herein, the term "polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. Thus, the generic term polymer encompasses the term homopolymer (used to refer to a polymer prepared from only one type of monomer) and the term "copolymer or interpolymer." Trace amounts of impurities (e.g., catalyst residues) may be incorporated into and / or within the polymer. A polymer may be a single polymer, a blend of polymers, or a mixture of polymers, including mixtures of polymers formed in situ during polymerization.
[0008] As used herein, the term "polyolefin" refers to polymers that comprise, in polymerized form (based on the weight of the polymer), a majority amount of an olefin monomer (eg, ethylene or propylene) and, optionally, may contain one or more comonomers.
[0009] As used herein, the term "copolymer" refers to any polymer having two or more monomers.
[0010] Water-based coating
[0011] The disclosed water-based coating can include a first polyacrylate emulsion and a second polyacrylate emulsion. Based on the weight of the water-based coating, the water-based coating can include 35 wt.% to 60 wt.% of the first polyacrylate emulsion. All internal values and ranges are disclosed. For example, based on the weight of the water-based coating, the water-based coating can include 35 wt.% to 45 wt.% or 40 wt.% to 55 wt.% of the first polyacrylate emulsion.
[0012] The water-based coating can include 30 wt.% to 45 wt.% of the second polyacrylate emulsion, based on the weight of the water-based coating. All internal values and ranges are disclosed. For example, the water-based coating can include 35 wt.% to 40 wt.% of the second polyacrylate emulsion, based on the weight of the water-based coating.
[0013] The water-based coating can include a water-based tackifier. Based on the weight of the water-based coating, the water-based coating can include 0 wt.% to 10 wt.% of the water-based tackifier. All internal values and ranges are disclosed. For example, based on the weight of the water-based coating, the water-based coating can include 0 wt.% to 5 wt.% or 5 wt.% to 10 wt.% of the water-based tackifier.
[0014] The water-based coating can include a wax emulsion. Based on the weight of the water-based coating, the water-based coating can include 0 wt.% to 10 wt.% of the wax emulsion. All internal values and ranges are disclosed. For example, based on the weight of the water-based coating, the water-based coating can include 1 wt.% to 9 wt.% of a water-based wax.
[0015] The water-based coating can include a water-based ethylene vinyl acetate resin. Based on the weight of the water-based coating, the water-based coating can include 0 wt.% to 30 wt.% of the ethylene vinyl acetate resin. All internal values and ranges are disclosed. For example, based on the weight of the water-based coating, the water-based coating can include 5 wt.% to 15 wt.% or 15 wt.% to 30 wt.% of the ethylene vinyl acetate resin.
[0016] The water-based coating may contain a filler. The water-based coating may contain 0 wt.% to 5 wt.% of the filler based on the weight of the water-based coating. The filler has a particle size of less than 6 µm.
[0017] The water-based coating may be free of polyurethane dispersion (PUD). The water-based coating may be free of natural rubber. The water-based coating may optionally contain polyurethane dispersion (PUD). The water-based coating may optionally contain natural rubber.
[0018] The heat seal strength of a laminate produced using a water-based coating can be greater than or equal to 7.5 N / 15 mm. The heat seal strength of a laminate produced using a water-based coating can range from 7.5 N / 15 mm to 11.0 N / 15 mm at 150°C. All internal values and subranges are disclosed. For example, the heat seal strength of a laminate produced using a water-based coating can range from 7.5 N / 15 mm to 8.5 N / 15 mm, or from 10 N / 15 mm to 11.0 N / 15 mm at 150°C.
[0019] First polyacrylate emulsion
[0020] The first polyacrylate emulsion can comprise butyl acrylate to styrene in a ratio of 1.4 to 5.6. All individual values and subranges are disclosed. For example, the first polyacrylate emulsion can comprise butyl acrylate to styrene in a ratio with a lower limit of 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, or 5.0 and an upper limit of 5.6, 5.4, 5.2, 5.0, 4.8, 4.6, 4.4, 4.2, 4.0, 3.8, 3.6, 3.4, 3.2, 3.0, 2.8, 2.6, 2.4, 2.2, or 2.0.
[0021] The first polyacrylate emulsion may have a T of -25°C to 10°C. g All individual values and subranges are disclosed. For example, the first polyacrylate emulsion may have a T of -20°C to 5°C or -25°C to -15°C. g .
[0022] The first polyacrylate emulsion can be produced by introducing an initiator into a kettle of water into which an emulsified monomer mixture is fed. The initiator can be configured to react with at least one monomer to form an emulsion polymer comprising monomer subunits. The initiator can react with the monomers dispersed throughout the aqueous medium until all or substantially all of the monomers are polymerized. The end result can be a dispersion of polymer particles in the aqueous medium, the polymer particles comprising monomer subunits. Such a dispersion is generally referred to as an emulsion polymer. An additional redox initiator can be introduced into the emulsion polymer after all monomers have been fed into the emulsion polymer to reduce residual monomer levels.
[0023] Reduction-oxidation (redox) initiator systems consisting of at least one (typically inorganic) reducing agent and an inorganic or organic oxidizing agent are particularly suitable. For example, the oxidizing component may include ammonium and alkali metal salts of peroxodisulfuric acid (e.g., sodium peroxodisulfate), hydrogen peroxide, or organic peroxides (e.g., tert-butyl peroxide, tert-amyl peroxide). For example, the reducing component may include: alkali metal salts of sulfurous acid, such as sodium sulfite and sodium bisulfite; alkali metal salts of disulfurous acid, such as sodium metabisulfite; addition compounds of bisulfites with fatty aldehydes and ketones, such as acetone bisulfite; or reducing agents, such as hydroxymethanesulfinic acid and its salts, Bruggolite® FF6, or isoascorbic acid. Redox initiator systems can be used with soluble metal compounds having a metal component capable of existing in multiple valence states.
[0024] Examples of common redox initiator systems are tert-butyl hydroperoxide / sodium bisulfite, tert-butyl hydroperoxide / isoascorbic acid, and tert-butyl hydroperoxide / sodium hydroxymethanesulfinate. The individual components (e.g., the reducing component) can also be mixtures, such as a mixture of the sodium salt of hydroxymethanesulfinic acid and sodium metabisulfite.
[0025] Second polyacrylate emulsion
[0026] The second polyacrylate emulsion can comprise butyl acrylate to styrene in a ratio of 0.4 to 1.3. All individual values and subranges are disclosed. For example, the second polyacrylate emulsion can comprise butyl acrylate to styrene in a ratio with a lower limit of 0.4, 0.5, 0.6, 0.8, or 1.0 and an upper limit of 1.3, 1.2, 1.0, 0.8, or 0.9.
[0027] The second polyacrylate emulsion may have a T of 15°C to 45°C. g All internal values and subranges are disclosed. For example, the second polyacrylate emulsion can have a T of 20°C to 40°C or 15°C to 25°C. g.
[0028] The second polyacrylate emulsion can be produced by introducing an initiator into a water kettle into which the emulsified monomer mixture is fed. The initiator can be configured to react with at least one monomer to form an emulsion polymer comprising monomer subunits. The initiator can react with the monomers dispersed throughout the aqueous medium until all or substantially all of the monomers are polymerized. The end result can be a dispersion of polymer particles in the aqueous medium comprising monomer subunits. Such dispersions are commonly referred to as emulsion polymers. An additional redox initiator can be introduced into the emulsion polymer after all monomers have been fed into the emulsion polymer to reduce residual monomer levels.
[0029] Reduction-oxidation (redox) initiator systems consisting of at least one (typically inorganic) reducing agent and an inorganic or organic oxidizing agent are particularly suitable. For example, the oxidizing component may include ammonium and alkali metal salts of peroxodisulfuric acid (e.g., sodium peroxodisulfate), hydrogen peroxide, or organic peroxides (e.g., tert-butyl peroxide, tert-amyl peroxide). For example, the reducing component may include: alkali metal salts of sulfites, such as sodium sulfite and sodium bisulfite; alkali metal salts of metabisulfites, such as sodium metabisulfite; addition compounds of bisulfites with fatty aldehydes and ketones, such as acetone bisulfite; or reducing agents, such as hydroxymethanesulfinic acid and its salts, Bruggolite® FF6, or isoascorbic acid. Redox initiator systems can be used with soluble metal compounds having a metal component capable of existing in multiple valence states.
[0030] Examples of common redox initiator systems are tert-butyl hydroperoxide / sodium bisulfite, tert-butyl hydroperoxide / isoascorbic acid, and tert-butyl hydroperoxide / sodium hydroxymethanesulfinate. The individual components (e.g., the reducing component) can also be mixtures, such as a mixture of the sodium salt of hydroxymethanesulfinic acid and sodium metabisulfite.
[0031] Tackifier
[0032] The water-based coating can include 0 wt.% to 10 wt.% of the water-based adhesion promoter, based on the weight of the water-based coating. All internal values and ranges are disclosed. For example, the water-based coating can include 3 wt.% to 9 wt.% of the water-based adhesion promoter, based on the weight of the water-based coating.
[0033] The tackifier may have a melting temperature of 60°C to 150°C. All values and subranges therein are disclosed. For example, the tackifier may have a melting temperature of 70°C to 120°C. Examples of suitable tackifiers include, but are not limited to, rosin resin.
[0034] wax
[0035] The water-based coating may include 0 wt.% to 10 wt.% of a wax emulsion based on the weight of the water-based coating. The wax emulsion may include carnauba wax or paraffin wax. The wax emulsion may have a melting temperature of 50°C to 150°C.
[0036] Water-based ethylene vinyl acetate resin
[0037] The water-based ethylene vinyl acetate resin may include 4 wt.% to 40 wt.% vinyl acetate. All individual values and subranges are disclosed. For example, the vinyl acetate resin may include 18 wt.% to 33 wt.% ethylene vinyl acetate.
[0038] Test Procedure
[0039] Glass transition temperature (T g )
[0040] Drops of latex were placed in an aluminum crucible and kept in a fume hood for 3 days to dry at room temperature. The samples were then tested using a TA Instruments DSC Q2000 using the following procedure: 1. Increase the temperature from -80°C to 170°C; 2. Cool to -80°C; 3. Increase the temperature to 170°C. The transition was defined as the glass transition temperature (T g ).
[0041] Heat seal strength
[0042] The coated Al / HSC was sealed to a PVC substrate at 150°C with a pressure of 300 N and a dwell time of 1 second, then cooled to room temperature. Three strips were tested for each sample, and the average value was calculated in N / 15 mm.
[0043] Anti-blocking
[0044] The hydrothermal sealant-coated sample was cut into 100 mm x 100 mm pieces. Four samples were then stacked face-to-face on a glass plate. A 1.0 kg weight was then placed on top. This assembly was then placed in a 50°C oven for two hours. The assembly was then removed and inspected to see if the coating adhered to the back surface.
[0045] Example
[0046] The materials used are listed in Table 1 below. All DOW TM Commercial samples are available from Dow Chemical.TM Chemical).
[0047] Table 1: Raw materials list
[0048]
[0049] Preparation of Polyacrylate Composition (PAC)
[0050] A monomer emulsion was prepared by adding 0.1% surfactant, based on the total monomer weight, to deionized water. While the mixture was stirred, styrene and butyl acrylate were slowly added until a monomer emulsion with a solids content of 74% and the BA / styrene ratios listed in Table 2 was obtained. 1% surfactant, based on the total monomer weight, and deionized water were charged to a 5-neck, 5-liter round-bottom flask equipped with a thermocouple, a cooling condenser, and a stirrer. The flask was then heated to 70°C under nitrogen. A small amount of 2% acrylic acid in 60°C deionized water was added to the kettle. 4.5% of the previously prepared monomer emulsion was then added to the kettle, followed by a 0.3% (based on the total monomer weight) deionized water solution of ammonium persulfate (APS) and a 0.15% (based on the total monomer weight) deionized water solution of sodium bisulfite (SBS) added to the kettle under stirring. When the exotherm peaked and the temperature rose to 70°C, the remaining monomers, 0.18% (based on the total monomer amount) of ammonium persulfate (APS) in deionized water, and 0.09% (based on the total monomer amount) of sodium bisulfate in deionized water were added to the kettle over 120 minutes, while the polymerization temperature was maintained at 69°C-71°C. After the additions were complete, the container containing the monomer emulsion and the feed line to the flask were rinsed with deionized water, which was then added back to the flask and fed into the kettle. The kettle was then held at 70°C for 15 minutes while tert-butyl hydroperoxide solution (0.08% based on the total monomer amount in deionized water) and FF6 solution (0.06% based on the total monomer content in deionized water) were added, and then held for an additional 15 minutes after the additions were complete. A solution of tert-butyl hydroperoxide (0.29% based on total monomer weight in deionized water) and FF6 (0.25% based on total monomer weight in deionized water) was then gradually added over 60 minutes, after which the reaction was cooled to room temperature. Ammonium solution was then added to adjust the pH to between 6.5 and 7.5. The finished polyacrylate sample should have a solids content of 45%.
[0051] Table 2: Polyacrylate compositions
[0052]
[0053] Coating process
[0054] The formulations from Table 3 were coated onto Al substrates. The dry coating weight was 2.0 gsm - 2.5 gsm. After the Al was coated, it was placed in an 80°C oven for 1 minute to remove water, after which the Al was removed from the oven and tested.
[0055] Table 3: Inventive Examples and Comparative Examples
[0056]
[0057] Table 4: Performance results
[0058]
Claims
1. A water-based coating comprising: a based on the weight of the water-based coating, 35 wt.% to 60 wt.% of a first polyacrylate emulsion, wherein, The first polyacrylate emulsion comprises: i. Butyl acrylate and styrene ii. Butyl acrylate to styrene ratio of 1.4 to 5.6 b. Based on the weight of the water-based coating, 30 wt.% to 45 wt.% of a second polyacrylate emulsion, the second polyacrylate emulsion comprising: i. Butyl acrylate and styrene ii. Butyl acrylate to styrene ratio of 0.4 to 1.3 Wherein, the first polyacrylate emulsion has a T of -25°C to 10°C g , and the second polyacrylate emulsion has a T of 15°C to 45°C g .
2. The first polyacrylate emulsion according to any preceding claim, comprising butyl acrylate to styrene in a ratio of 1.5 to 5.
3. The second polyacrylate emulsion according to any preceding claim, comprising butyl acrylate to styrene in a ratio of 0.5 to 1.
2.
4. A water-based coating according to any preceding claim, further comprising a water-based adhesion promoter.
5. A water-based coating according to any preceding claim, further comprising a wax emulsion.
6. A water-based coating according to any preceding claim, further comprising a water-based ethylene vinyl acetate resin.
7. A laminate comprising a coating according to any preceding claim.
8. The water-based coating according to claim 4, wherein The water-based tackifier has a melting temperature of 60°C to 150°C.
9. The water-based coating according to claim 6 or 9, wherein The water-based coating comprises 0 wt.% to 30 wt.% of ethylene vinyl acetate resin, based on the weight of the water-based coating.
10. The water-based coating of claim 1 applied to an aluminum substrate used to form an enclosure with a PVC blister.