Cleaning composition for plastic recycling

Abstract

The cleaning composition comprises a surfactant having a cloud point of 60° C. or greater and a glycol ether having a hydrophilic-lipophilic balance (HLB) of 6 to 10. If the surfactant has a cloud point greater than 90° C., the glycol ether has an HLB of less than 7.5, or if the surfactant has a cloud point between 60° C. and 75° C., the glycol ether has an HLB of greater than 8.5, or if the surfactant has a cloud point between 75° C. and 90° C., the glycol ether has an HLB of 7 to 9.

Description

[Technical Field]

[0001] The present disclosure relates to cleaning compositions, and more particularly to cleaning compositions for recycled plastics. [Background technology]

[0002] Introduction The production and use of recycled plastics is a growing market. Commercial production of recycled plastics is achieved through mechanical recycling, which involves crushing, washing, and drying post-consumer plastics to produce clean plastic flakes that can be converted into new products. The cleaning process requires high-temperature processes at approximately 80°C, cleaning solutions consisting of additives such as surfactants and / or detergents, and caustic soda to remove contaminants. Of particular concern for removal is the adhesive used to label bottles. Removal of adhesives and other contaminants is important because these contaminants can adversely affect the properties of recycled plastics (i.e., haze, mechanical properties, etc.). At a minimum, cleaning compositions should remove more than 50% of residual adhesive to make recycled plastic usable.

[0003] In cleaning compositions utilizing surfactants, the surfactant's cloud point should be within ±5°C of the target cleaning temperature to maximize cleaning power. If the surfactant's cloud point is much higher or lower than the temperature used for cleaning, the surfactant will lose its cleaning ability. Complicating the issue of cloud point and cleaning power is the fact that the inclusion of caustic soda in a cleaning solution containing a surfactant tends to lower the surfactant's cloud point. Unfortunately, the cloud point reduction with caustic soda is dependent on the amount of caustic soda and the type of surfactant present, but it does not occur in a linear or predictable manner. Typical caustic soda concentrations in cleaning mixtures range from 1% to 2% by weight. Therefore, surfactant-containing cleaning compositions cannot be easily interchanged between mechanical recycling operations using different amounts of caustic soda without costly and time-consuming reformulation or trial-and-error testing. Furthermore, simply substituting a higher cloud point surfactant to compensate for the lowered cloud point is undesirable, as it may mean using a solid surfactant that adds additional handling problems and provides worse cleaning performance. It is desirable that adhesive removal not vary by more than 20% over the 1% to 2% by weight caustic soda range.

[0004] In view of the above, it would be surprising to find a cleaning composition that achieves greater than 50% removal of adhesives and also exhibits adhesive removal that does not vary more than 20% over the 1 wt% to 2 wt% caustic soda range. Summary of the Invention

[0005] The present inventors have surprisingly discovered cleaning compositions that achieve greater than 50% adhesive removal and exhibit adhesive removal that does not vary more than 20% across a range of caustic soda concentrations from 1% to 2% by weight. The present inventors have discovered that the use of glycol ethers as cosolvents with surfactants improves the performance of surfactants used with alkali salts. Specifically, the selection of a surfactant-glycol ether combination depends on the hydrophilic-lipophilic balance ("HLB") of the glycol ether and the cloud point of the surfactant. For example, if the surfactant has a cloud point greater than 90°C to 105°C, the glycol ether has an HLB of less than 7; if the surfactant has a cloud point between 60°C and less than 75°C, the glycol ether has an HLB of 7 to 9; or if the surfactant has a cloud point between 75°C and 90°C, the glycol ether has an HLB of greater than 9. Advantageously, by utilizing the specific combination of surfactant cloud point values and glycol ether HLB values outlined above, the cleaning composition can be substituted into different cleaning mixtures for recycled plastics without concern that different alkali salt concentrations will affect the cleaning power of the cleaning composition. Furthermore, the use of specific surfactant cloud point and glycol ether HLB combinations avoids the use of solid surfactants and their associated handling issues in high temperature cleaning environments, since the cloud point depression of alkali salts is eliminated.

[0006] The present application is particularly useful for providing cleaning compositions for use in cleaning polymeric materials.

[0007] According to a first aspect of the present disclosure, a cleaning composition comprises a surfactant having a cloud point of 60°C or greater and a glycol ether having a hydrophilic-lipophilic balance (HLB) of 6 to 10, wherein when the surfactant has a cloud point greater than 90°C, the glycol ether has an HLB of less than 7.5; when the surfactant has a cloud point between 60°C and less than 75°C, the glycol ether has an HLB of greater than 8.5; and when the surfactant has a cloud point between 75°C and 90°C, the glycol ether has an HLB of 7 to 9.

[0008] According to a second feature of the present disclosure, the surfactant is non-ionic.

[0009] According to a third feature of the present disclosure, the glycol ether is 25% by weight to 75% by weight of the total weight of the cleaning composition, and the surfactant is 25% by weight to 75% by weight of the total weight of the cleaning composition.

[0010] According to a fourth feature of the present disclosure, the surfactant has a cloud point of 60°C to less than 75°C, and the glycol ether has an HLB of 7 to 9.

[0011] According to a fifth feature of the present disclosure, the surfactant has a cloud point of 75°C to 90°C, and the glycol ether has an HLB of greater than 9.

[0012] According to a sixth feature of the present disclosure, the surfactant has a cloud point of more than 90°C to 105°C, and the glycol ether has an HLB of less than 7.

[0013] According to a seventh feature of the present disclosure, the glycol ether is selected from the group consisting of diethylene glycol monohexyl ether and tripropylene glycol mono n-butyl ether.

[0014] According to an eighth aspect of the present disclosure, the surfactant is a C 1000 stearate copolymer having an average of 15 moles of ethylene oxide. 12 ~C 15 It is a secondary alcohol.

[0015] According to a ninth aspect of the present disclosure, the cleaning mixture includes 0.01 wt % to 2.00 wt % of a cleaning composition based on the total weight of the cleaning mixture, 0.01 wt % to 3.00 wt % of an alkali salt based on the total weight of the cleaning mixture, and water.

[0016] According to a tenth aspect of the present disclosure, a cleaning method includes the steps of adding a polymeric material to a cleaning mixture and washing the polymeric material in the cleaning mixture at a temperature of 60°C to 90°C. DETAILED DESCRIPTION OF THE INVENTION

[0017] As used herein, the term "and / or," when used in a list of two or more items, means that any one of the listed items can be used by itself, or any combination of two or more of the listed items can be used. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone, B alone, C alone, A and B in combination, A and C in combination, B and C in combination, or A, B, and C in combination.

[0018] Unless otherwise stated, all ranges are inclusive of the endpoints.

[0019] Test methods refer to the most current test method as of the priority date of this document unless the test method number indicates a date with a two-digit number with a hyphen. References to test methods include both a reference to the testing organization and the test method number. Test method organizations are referred to by one of the following abbreviations: ASTM refers to ASTM International (formerly the American Society for Testing and Materials), IEC refers to the International Electrotechnical Commission, EN refers to European Norm, DIN refers to the Deutsches Institut fur Normung, and ISO refers to the International Organization for Standards.

[0020] As used herein, the term weight percent ("wt. %") refers to the weight percentage that a component represents of the total weight of the polymer composition, unless otherwise specified.

[0021] As used herein, Chemical Abstract Services Registry Number ("CAS#") refers to the unique numeric identifier last assigned to a chemical compound by the Chemical Abstract Service as of the priority date of this document.

[0022] Cleaning Composition The present disclosure relates to a cleaning composition. The cleaning composition comprises a surfactant and a glycol ether. As described in more detail below, the surfactant has a cloud point of 60°C or higher, and the glycol ether has a hydrophilic-lipophilic balance (HLB) of 6 to 10. The combination of surfactant and glycol ether used in the cleaning composition is selected based on their respective cloud points and HLBs. Specifically, when the surfactant has a cloud point greater than 90°C, the glycol ether has an HLB of less than 7.5; when the surfactant has a cloud point between 60°C and less than 75°C, the glycol ether has an HLB of greater than 8.5; and when the surfactant has a cloud point between 75°C and 90°C, the glycol ether has an HLB of 7 to 9. In some examples, the surfactant has a cloud point between 60°C and less than 75°C, and the glycol ether has an HLB of 7 to 9. In some examples, the surfactant has a cloud point between 75°C and 90°C, and the glycol ether has an HLB of greater than 9. In some examples, the surfactant has a cloud point greater than 90°C to 105°C and the glycol ether has an HLB greater than 7.

[0023] surfactants The cleaning composition contains a surfactant. As used herein, a surfactant is a compound that reduces the surface tension (or interfacial tension) between two materials. Specifically, a surfactant contains a hydrophobic portion and a hydrophilic portion. The cleaning composition may contain 25% to 75% by weight of surfactant, based on the total weight of the cleaning composition. For example, the cleaning composition may contain 25% by weight or more, or 30% by weight or more, or 35% by weight or more, or 40% by weight or more, or 45% by weight or more, or 50% by weight or more, or 55% by weight or more, or 60% by weight or more, or 65% by weight or more, or 70% by weight or more, while simultaneously containing 75% by weight or less, or 70% by weight or less, or 65% by weight or less, or 60% by weight or less, or 55% by weight or less, or 50% by weight or less, or 45% by weight or less, or 40% by weight or less, or 35% by weight or less, or 30% by weight or less of surfactant, based on the total weight of the cleaning composition.

[0024] The surfactant has a cloud point of 60°C or greater, as measured according to ASTM D2024-09. Because cloud point measurements are unreliable above 100°C, the cloud point of the surfactant is sometimes reported as >100°C, indicating that the surfactant did not produce cloudiness at temperatures below 100°C. The surfactant may have a cloud point of 60°C or greater, or 62°C or greater, or 64°C or greater, or 66°C or greater, or 68°C or greater, or 70°C or greater, or 72°C or greater, or 74°C or greater, or 76°C or greater, or 78°C or greater, or 80°C or greater, or 82°C or greater, or 84°C or greater, or 86°C or greater, or 88°C or greater, or 90°C or greater, or 92°C or greater, or 94°C or greater, or 96°C or greater, or 98°C or greater, or >100°C, as measured according to ASTM D2024-09.

[0025] A variety of surfactant types can be utilized in the cleaning composition. For example, surfactants include C2 to C 20The surfactant may be a linear or branched alkoxylated alcohol. The surfactant may contain an average of 5 to 20 units of ethylene oxide and / or propylene oxide. The surfactant may contain an aromatic or phenyl moiety. The surfactant may be ionic. The surfactant may be nonionic. In a specific example, the surfactant is a C alkoxylated alcohol having an average of 15 moles of ethylene oxide. 12 ~C 15 It is a secondary alcohol. Examples of commercially available surfactants include TERGITOL™ 15-S-9, TERGITOL™ 15-S-12, TERGITOL™ 15-S-15, TRITON™ X-100, TERGITOL™ 23-6.5, TRITON™ DF-16, and TRITON™ DF-20, all available from The Dow Chemical Company (Midland, Michigan).

[0026] Glycol Ether The cleaning composition includes a glycol ether. As used herein, glycol ether is an alkyl ether of ethylene glycol or propylene glycol. The cleaning composition may include 25% to 75% by weight of glycol ether, based on the total weight of the cleaning composition. For example, the cleaning composition may include 25% by weight or more, or 30% by weight or more, or 35% by weight or more, or 40% by weight or more, or 45% by weight or more, or 50% by weight or more, or 55% by weight or more, or 60% by weight or more, or 65% by weight or more, or 70% by weight or more, while simultaneously including 75% by weight or less, or 70% by weight or less, or 65% by weight or less, or 60% by weight or less, or 55% by weight or less, or 50% by weight or less, or 45% by weight or less, or 40% by weight or less, or 35% by weight or less, or 30% by weight or less of glycol ether, based on the total weight of the cleaning composition.

[0027] The glycol ether has an HLB of 6.0 to 10.0 when measured according to the Davies HLB test method described in more detail below. For example, the glycol ether may have an HLB of 6.0 or greater, or 6.2 or greater, or 6.4 or greater, or 6.6 or greater, or 6.8 or greater, or 7.0 or greater, or 7.2 or greater, or 7.4 or greater, or 7.6 or greater, or 7.8 or greater, or 8.0 or greater, or 8.2 or greater, or 8.4 or greater, or 8.6 or greater, or 8.8 or greater, or 9.0 or greater, or 9.2 or greater, or 9.4 or greater, or 9.6 or greater, or 9.8 or greater when measured according to the Davies HLB test method described in more detail below. , while simultaneously having an HLB of 10.0 or less, or 9.8 or less, or 9.6 or less, or 9.4 or less, or 9.2 or less, or 9.0 or less, or 8.8 or less, or 8.6 or less, or 8.4 or less, or 8.2 or less, or 8.0 or less, or 7.8 or less, or 7.6 or less, or 7.4 or less, or 7.2 or less, or 7.0 or less, or 6.8 or less, or 6.6 or less, or 6.4 or less, or 6.2 or less.

[0028] Various glycol ethers can be used in the cleaning composition.For example, the glycol ether can include ethylene glycol monohexyl ether, tripropylene glycol mono-n-butyl ether, diethylene glycol monohexyl ether, dipropylene glycol mono-n-butyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol dimethyl ether, propylene glycol phenyl ether, dipropylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monopropyl ether, ethylene glycol phenyl ether, diethylene glycol monobutyl ether, ethylene glycol monopropyl ether, diethylene glycol monophenyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monomethyl ether, and / or other glycol ethers. Examples of commercially available glycol ethers that may be used in the cleaning compositions include hexyl CELLOSOLVE™, DOWANOL™ TPnB, hexyl CARBITOL™, DOWANOL™ DPnB, DOWANOL™ PnB, PROGLYDE™ DMM glycol, DOWANOL™ PPh, DOWANOL™ DPnP, butyl CELLOSOLVE™, DOWANOL™ PnP, DOWANOL™ Eph, butyl CARBITOL™, propyl CELLOSOLVE™ solvent, DOWANOL™ DiEPh, butoxytriglyceride, DOWANOL™ TPM, DOWANOL™ DPM, all available from The Dow Chemical Company (Midland, Michigan).

[0029] additives The cleaning composition may contain one or more additives. The cleaning composition may contain 0% to 20% by weight of each additive, based on the total weight of the cleaning composition. For example, the cleaning composition may contain 0% or more by weight, or 1% or more by weight, or 2% or more by weight, or 3% or more by weight, or 4% or more by weight, or 5% or more by weight, or 6% or more by weight, or 7% or more by weight, or 8% or more by weight, or 9% or more by weight, or 10% or more by weight, or 11% or more by weight, or 12% or more by weight, or 13% or more by weight, or 14% or more by weight, or 15% or more by weight, or 16% or more by weight, or 17% or more by weight, or 18% or more by weight, based on the total weight of the cleaning composition. The additive may comprise 19% by weight or more, while simultaneously comprising 20% by weight or less, or 19% by weight or less, or 18% by weight or less, or 17% by weight or less, or 16% by weight or less, or 15% by weight or less, or 14% by weight or less, or 13% by weight or less, or 12% by weight or less, or 11% by weight or less, or 10% by weight or less, or 9% by weight or less, or 8% by weight or less, or 7% by weight or less, or 6% by weight or less, or 5% by weight or less, or 4% by weight or less, or 3% by weight or less, or 2% by weight or less, or 1% by weight or less of an additive. The additive may comprise one or more diluents such as water, propylene glycol, and / or other diluents. The additive may comprise one or more hydrotropes such as octenyl succinic acid. The additive may comprise one or more defoamers and / or wetting agents such as surfactants or high molecular weight polyglycols. The additive may comprise one or more water-soluble acrylic copolymers.The additive may comprise one or more chelating agents such as ethylenediaminetetraacetic acid ("EDTA"), citric acid, potassium citrate, sodium citrate, tetrasodium ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetic acid, diammonium ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetic acid tetrahydrate, disodium ethylenediaminetetraacetic acid tetrahydrate, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid dihydrate, calcium disodium ethylenediaminetetraacetic acid dihydrate, pentasodium diethylenetriaminepentaacetic acid, pentasodium diethylenetriaminepentaacetic acid, trisodium n-(hydroxyethyl)-ethylenediaminetriacetic acid, iron disodium n-(hydroxyethyl)-ethylenediaminetriacetate, ethylenediaminetetraacetic acid, and combinations thereof.

[0030] Cleaning mixture The present disclosure also relates to a cleaning mixture. The cleaning mixture is a mixture of a cleaning composition and an alkali salt. The alkali salt is selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, and / or combinations thereof. The cleaning mixture may contain 0.01 wt. % to 2.00 wt. % of the cleaning composition based on the total weight of the cleaning mixture. For example, the cleaning mixture may contain 0.01 wt. % or more, or 0.25 wt. % or more, or 0.50 wt. % or more, or 0.75 wt. % or more, or 1.00 wt. % or more, or 1.25 wt. % or more, or 1.50 wt. % or more, or 1.75 wt. % or more, while simultaneously containing 2.00 wt. % or less, or 1.75 wt. % or less, or 1.50 wt. % or less, or 1.25 wt. % or less, or 1.00 wt. % or less, or 0.75 wt. % or less, or 0.50 wt. % or less, or 0.25 wt. % or less of the cleaning composition based on the total weight of the cleaning mixture.

[0031] The cleaning mixture may include 0.01% to 3.00% by weight of the alkali salt, based on the total weight of the cleaning mixture. For example, the cleaning mixture may comprise 0.01 wt. % or more, or 0.25 wt. % or more, or 0.50 wt. % or more, or 0.75 wt. % or more, or 1.00 wt. % or more, or 1.25 wt. % or more, or 1.50 wt. % or more, or 1.75 wt. % or more, or 2.00 wt. % or more, or 2.25 wt. % or more, or 2.50 wt. % or more, or 2.75 wt. % or more, while simultaneously comprising 3.00 wt. % or less, or 2.75 wt. % or less, or 2.50 wt. % or less, or 2.25 wt. % or less, or 2.00 wt. % or less, or 1.75 wt. % or less, or 1.50 wt. % or less, or 1.25 wt. % or less, or 1.00 wt. % or less, or 0.75 wt. % or less, or 0.50 wt. % or less, or 0.25 wt. % or less of an alkali salt, based on the total weight of the cleaning mixture.

[0032] The balance of the cleaning composition may be water or other diluent.

[0033] Cleaning Method The present disclosure also relates to a cleaning method utilizing the cleaning mixture. The cleaning method of the present disclosure includes adding a polymeric material to the cleaning mixture. The polymeric material can be a post-consumer recycled thermoplastic, such as polyethylene terephthalate, high-density polyethylene, or biaxially oriented polypropylene. The polymeric material can be processed into flakes, chips, and / or pellets. The polymeric material can be contaminated with adhesives, food waste, dust, and other contaminants.

[0034] The cleaning method also includes washing the polymeric material in a cleaning mixture at a temperature of 60° C. to 90° C. The cleaning mixture can be at a temperature of 60° C. or higher, or 65° C. or higher, or 70° C. or higher, or 75° C. or higher, or 80° C. or higher, or 85° C. or higher, while simultaneously being at a temperature of 90° C. or lower, or 85° C. or lower, or 80° C. or lower, or 75° C. or lower, or 70° C. or lower, or 65° C. or lower. Washing the polymeric material can include stirring, mixing, agitating, and / or ultrasonically shaking the cleaning mixture. Mechanical scrubbing of the polymeric material may be utilized in washing the polymeric material.

[0035] The cleaning method removes adhesive present on the polymeric material. The cleaning method removes a percentage of the adhesive present on the polymeric material. For example, the adhesive removal from the polymeric material achieved by the cleaning method can be 50% or more, or 55% or more, or 60% or more, or 65% or more, or 70% or more, or 75% or more, or 80% or more, or 85% or more, or 90% or more, or 95% or more, or 100%.

[0036] The cleaning method may use cleaning mixtures having a range of alkali salt concentrations, and over a cleaning mixture alkali salt concentration of 1 wt. % to 2 wt. %, the adhesive removal ability of the cleaning mixtures and methods varies by no more than 20% when measured between the highest and lowest adhesive removal values obtained within that range. [Example]

[0037] material The materials used in the examples are listed in Table 1. All materials were supplied by The Dow Chemical Company (Midland, Michigan).

[0038] [Table 1]

[0039] Table 2 provides a description of the adhesives used in the examples.

[0040] [Table 2]

[0041] Test Method Davies HLB: The hydrophilic-lipophilic balance (HLB) value was calculated using the group contribution method of Davies (JT Davies, EK Rideal, Interfacial Phenomena, Academic Press, New York, 1961, p. 371), which assumes that the HLB value is given by the following formula:

[0042]

number

[0043] [Table 3]

[0044] Cloud Point: Cloud point was measured according to ASTM D2024-09.

[0045] Sample preparation Polyethylene terephthalate ("PET") (obtained from ePlastics, San Diego, California, USA) and biaxially oriented polypropylene (obtained from Multi Plastics Inc., Lewis Center, Ohio, USA) substrates were coated with thin films of either an acrylic-based pressure-sensitive adhesive or a styrene-based pressure-sensitive adhesive. The styrene-based adhesive was applied to the substrate using a Cheminstruments HLCL-1000 hot melt coater laminator, and the acrylic adhesive was applied to the substrate using a drawdown coater. Some samples were then laminated with a silicone-coated release liner to protect the adhesive film, while others were laminated with BOPP film. After coating, each sample was allowed to cure for at least 48 hours before use. After curing, the samples were hand-cut into 7.62 cm x 3.81 cm pieces, each with a nominal adhesive loading of approximately 15-20 grams per square meter or GSM (approximately 40-50 mg / sample). The silicone coated release liner was removed immediately prior to the cleaning experiment to prevent dust accumulation on the coated surface.

[0046] For the BOPP-laminated samples, the PET was laminated with a 1.9 mm thick BOPP film rather than a silicone-coated release liner. These samples were cut into approximately 1 cm x 1 cm squares before being added to the cleaning mixture.

[0047] After sample preparation and curing, 800 g of each inventive or comparative cleaning mixture was preheated to approximately 70°C in a 1 L Pyrex bottle. The solution typically contained 0.5 wt% to 2 wt% of 40 wt% NaOH in the indicated water, 0.05 wt% to 1 wt% of the cleaning composition, and water. After preheating, the solution was poured into a 1 L beaker and then further heated to 80°C with stirring. Once at the desired temperature, the substrate samples were washed for 8 minutes at a stirring speed of 500 rpm. For each example, samples were washed in triplicate along with a blank (no adhesive) for a total of four samples per beaker.

[0048] After the washing step, the samples were rinsed in a beaker containing 500 mL of deionized water for 3 min at 21° C. using a stirring speed of 400 rpm.

[0049] After rinsing, the samples were placed flat on a metal tray and dried under high convection at a temperature of 40-45°C for approximately 16 hours. The next day, the samples were allowed to come to a temperature of approximately 23°C before being weighed.

[0050] The BOPP laminated sample was washed in a similar manner, however, in this case 40 grams of flakes were washed with only 400 grams of solution. All subsequent steps were carried out in the same manner.

[0051] Quantification of adhesive removal was determined using Equation 1.

[0052]

number

[0053] result Table 4 provides the results for inventive examples (IE) and comparative examples (CE). Specifically, the results in Table 3 were obtained under the following test conditions: the substrate was PET, the NaOH dosage was 1 wt%, the temperature was 80°C, the cleaning additive was 50 wt% of the indicated surfactant and 50 wt% of the indicated glycol ether, the adhesive type was Type 1, and the balance of the cleaning mixture used was water.

[0054] [Table 4]

[0055] As can be seen from Table 4, the examples of the present invention can provide greater than 50% adhesive removal when the NaOH concentration is held constant. IE1 is technically below the 50% cutoff range, but the 10.25% measurement error suggests that the true value may exceed 50%. Notably, IE1 represents an approximately 13% improvement over CE2. While CE5-CE15 can achieve greater than 50% adhesive removal, the absence of glycol ethers or a relationship between the specified surfactant cloud point and glycol ether HLB likely means that changing the NaOH concentration will have a negative and unpredictable effect on adhesive removal.

[0056] Table 5 shows the ability of examples of the present invention to maintain cleaning performance over a range of NaOH concentrations. The experiments in Table 5 were conducted under the following conditions: the substrate was PET, the temperature was 80°C, the cleaning additive was 50% by weight of the indicated surfactant and 50% by weight of the indicated glycol ether, the adhesive type was Type 1, and the balance of the cleaning mixture used was water.

[0057] [Table 5]

[0058] Table 5 demonstrates that including an appropriate glycol ether with a surfactant having a cloud point higher than that required for a 1-2 wt% NaOH concentration (i.e., a cloud point above the cleaning temperature) can impart good adhesive removal performance across the range of NaOH concentrations used in the material without requiring formulation changes. Specifically, IE16 shows only about a 10% change across the 1 wt% to 2 wt% NaOH concentration range. As shown, CE16 exhibits greater than 20% adhesive removal when NaOH is varied from 1 wt% to 2 wt%, which is undesirable. Other cleaning compositions would likely exhibit less than a 20% change in adhesive removal across the specified NaOH range if they contained glycol ethers with an HLB of less than 7.5 when the surfactant had a cloud point above 90°C, or glycol ethers with an HLB of greater than 8.5 when the surfactant had a cloud point below 60°C to 75°C, or glycol ethers with an HLB of 7-9 when the surfactant had a cloud point between 75°C and 90°C.

[0059] Table 6 shows the ability of examples of the present invention to maintain cleaning performance over a range of glycol ether to surfactant weight ratios. The experiments in Table 6 were conducted under the following conditions: the substrate was PET, the cleaning composition dosage was 0.2 wt%, the NaOH concentration was 1 wt%, the temperature was 80°C, the adhesive type was Type 1, and the balance of the cleaning mixture used was water.

[0060] [Table 6]

[0061] Table 7 shows the ability of examples of the present invention to maintain adhesive removal across a range of cleaning composition concentrations in the cleaning mixture. The experiments in Table 7 were conducted under the following conditions: the substrate was PET, the NaOH concentration was 1 wt%, the glycol ether to surfactant weight ratio was 1:1, the temperature was 80°C, the adhesive type was Type 1, and the balance of the cleaning mixture used was water.

[0062]

Table 7

Claims

1. 1. A cleaning composition comprising: a surfactant having a cloud point of 60°C or higher; a glycol ether having a hydrophilic-lipophilic balance (HLB) of 6 to 10; 1. A cleaning composition comprising: when the surfactant has a cloud point above 90°C, the glycol ether has an HLB of less than 7.5; when the surfactant has a cloud point between 60°C and less than 75°C, the glycol ether has an HLB of greater than 8.5; and when the surfactant has a cloud point between 75°C and 90°C, the glycol ether has an HLB of 7-9.

2. The cleaning composition of claim 1 wherein the surfactant is nonionic.

3. 3. The cleaning composition of claim 1, wherein the glycol ether is from 25% to 75% by weight of the total weight of the cleaning composition, and the surfactant is from 25% to 75% by weight of the total weight of the cleaning composition.

4. A cleaning composition according to any one of claims 1 to 3, wherein the surfactant has a cloud point of from 60°C to less than 75°C and the glycol ether has an HLB of from 7 to 9.

5. A cleaning composition according to any preceding claim, wherein the surfactant has a cloud point of from 75°C to 90°C and the glycol ether has an HLB greater than 9.

6. 4. The cleaning composition of claim 1, wherein the surfactant has a cloud point of greater than 90°C to 105°C and the glycol ether has an HLB of less than 7.

7. 7. The cleaning composition of claim 6, wherein the glycol ether is selected from the group consisting of diethylene glycol monohexyl ether and tripropylene glycol mono n-butyl ether.

8. The surfactant is a C having an average of 15 moles of ethylene oxide. １２ ~C １５ 8. The cleaning composition of claim 7, which is a secondary alcohol.

9. 1. A cleaning mixture comprising:

9. The cleaning composition of claim 1, wherein the cleaning composition is from 0.01% to 2.00% by weight, based on the total weight of the cleaning mixture; 0.01% to 3.00% by weight of an alkali salt, based on the total weight of the cleaning mixture; A cleaning mixture comprising: water;

10. 1. A cleaning method comprising: adding a polymeric material to the cleaning mixture of claim 9; cleaning said polymeric material in said cleaning mixture at a temperature of from 60°C to 90°C.

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