Acrylate latex pressure-sensitive adhesive for BOPP film labels and preparation method thereof

Abstract

The invention discloses an acrylic latex pressure-sensitive adhesive for BOPP film labels and a preparation method thereof, comprising the following raw materials in parts by weight: 40.0-55.0 parts of soft monomers; 3.0-10.0 parts of hard monomers; 1.0-5.0 parts of functional monomers; 0.02-0.1 parts of molecular weight regulators; 0.5-3.0 parts of emulsifiers; 0.02-0.1 parts of buffers; 0.2-0.6 parts of thermal initiators; 0.03-0.2 parts of oxidants; 0.03-0.2 parts of reducing agents; 0.3-1.0 parts of pH regulators; 0.3-1.0 parts of wetting agents; and 40.0-50.0 parts of deionized water. The acrylic latex pressure-sensitive adhesive for BOPP film labels of the invention has the following beneficial effects: simple preparation process, stable storage, good comprehensive mechanical properties, good anti-overflow performance, short-term re-sticking without residual glue, and excellent water vapor resistance.

Description

Technical Field

[0001] The invention relates to the technical field of pressure-sensitive adhesives, and in particular to an acrylic latex pressure-sensitive adhesive for a BOPP film label and a preparation method thereof. Background Art

[0002] Since BOPP (biaxially oriented polypropylene) film has the advantages of light weight, high strength, excellent printing performance, dimensional stability, water resistance, outstanding chemical resistance and not easy to age, self-adhesive label products using BOPP film as a printing carrier are widely used in the fields of food and beverage, daily chemicals, medicine, etc., occupying a large proportion in the self-adhesive label market, and the share is still expanding. Faced with the emergence of new terminal application fields, the increasing demand of printing manufacturers to improve the efficiency of die-cutting waste discharge, and the increasing demand of labeling manufacturers to improve the efficiency of reworking defective products, the performance requirements for acrylic latex pressure-sensitive adhesives for BOPP film labels are also constantly increasing.

[0003] At present, the quality of acrylic latex pressure-sensitive adhesive for BOPP film labels on the market is generally between ordinary and mid-range levels, and there are common problems such as high-temperature overflow (reducing the efficiency of die-cutting waste discharge), poor short-term re-stickability (reducing the efficiency of reworking defective labeling products), foggy shadows, and poor water vapor resistance (easy to debond in a humid environment). As a result, high-end products are mainly based on solvent-based acrylic pressure-sensitive adhesives, but considering production costs and environmental protection, water-based acrylic latex pressure-sensitive adhesives are the future development trend.

[0004] In the prior art:

[0005] CN 105504148 A discloses a water-based pressure-sensitive adhesive and a preparation method thereof. By adding a polymethylol compound and making it cross-linked with the methylol or carboxyl group on the polymer side chain during film formation, the cross-linking effect of the water-based pressure-sensitive adhesive is increased, the cohesive strength is high, the anti-overflow performance is good, and the anti-residual adhesive performance is excellent. However, due to the activation period problem of the added cross-linking agent, the use period of the prepared pressure-sensitive adhesive is short, the coating production operation is complicated, and the scope of use is limited.

[0006] In summary, there is an urgent need for an acrylic latex pressure-sensitive adhesive for BOPP film labels, which not only requires a simple preparation process and stable storage, but also requires the performance of strong adhesion, good anti-overflow performance, excellent short-time re-positioning ability, and water resistance without debonding. Summary of the invention

[0007] The purpose of the present invention is to provide an acrylic latex pressure-sensitive adhesive for BOPP film labels and a preparation method thereof.

[0008] The pressure-sensitive adhesive prepared by the above method can meet most application scenarios of BOPP film labels and is suitable for use with anilox roller coating equipment. The pressure-sensitive adhesive also has the characteristics of simple preparation process, stable storage, good comprehensive mechanical properties, good anti-overflow performance, short-term re-sticking without residual adhesive, and excellent water vapor resistance.

[0009] An acrylic latex pressure-sensitive adhesive for BOPP film labels.

[0010] The invention comprises the following raw materials in parts by weight:

[0011] 40.0-55.0 parts of soft monomer;

[0012] 3.0 to 10.0 parts of hard monomer;

[0013] 1.0 to 5.0 parts of functional monomer;

[0014] 0.02-0.1 parts of molecular weight regulator;

[0015] 0.5-3.0 parts of emulsifier;

[0016] 0.02-0.1 parts buffer;

[0017] 0.2-0.6 parts of thermal initiator;

[0018] 0.03-0.2 parts of oxidant;

[0019] 0.03-0.2 parts of reducing agent;

[0020] 0.3-1.0 parts of pH regulator;

[0021] 0.3-1.0 parts of wetting agent;

[0022] 40.0-50.0 parts of deionized water.

[0023] As a further improvement of the present solution, the soft monomer includes but is not limited to one or more of n-butyl acrylate, n-butyl methacrylate, isooctyl acrylate, lauryl methacrylate and dodecyl acrylate.

[0024] As a further improvement of the present solution, the hard monomer includes but is not limited to one or more of methyl methacrylate, methyl acrylate, vinyl acetate, styrene and ethyl acrylate.

[0025] As a further improvement of the present scheme, the functional monomers include but are not limited to one or more of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, N-hydroxymethyl acrylamide, ethyl acetoacetate methacrylate, diacetone acrylamide, adipic acid dihydrazide, oxalic acid dihydrazide, vinyl trimethoxysilane and γ-methacryloxypropyl trimethoxysilane.

[0026] As a further improvement of the present solution, the functional monomer is one or more of acrylic acid, hydroxyethyl acrylate, diacetone acrylamide, adipic acid dihydrazide and vinyl trimethoxy silane.

[0027] As a further improvement of this solution, the molecular weight regulator includes but is not limited to one or more of n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoethanol and thioglycolic acid.

[0028] As a further improvement of this solution, the emulsifier includes but is not limited to one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate, vinyl sulfonate and sodium diethyl sulfosuccinate.

[0029] As a further improvement of this scheme,

[0030] The emulsifier is a mixture of sodium lauryl sulfate and allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate, and the mass ratio of the two is between 4:1 and 1:4;

[0031] The buffering agent includes but is not limited to one or more of sodium bicarbonate, ammonium bicarbonate, sodium carbonate, ammonium carbonate, potassium bicarbonate and potassium carbonate;

[0032] The thermal initiator includes but is not limited to one or more of potassium persulfate, ammonium persulfate and sodium persulfate;

[0033] The oxidant includes but is not limited to one or more of tert-butyl hydroperoxide, hydrogen peroxide, potassium persulfate, ammonium persulfate and sodium persulfate;

[0034] The reducing agent includes but is not limited to one or more of ferrous sulfate, sodium bisulfite, sodium formaldehyde sulfoxylate and sodium isoascorbate;

[0035] The pH adjuster includes but is not limited to one or more of ammonia water, sodium hydroxide, triethanolamine and sodium acetate;

[0036] The wetting agent includes, but is not limited to, one or more of dioctyl sodium sulfosuccinate, diisooctyl sodium sulfosuccinate, sodium octylphosphonate and sodium laurylphosphonate.

[0037] A method for preparing an acrylic latex pressure-sensitive adhesive for a BOPP film label comprises the following preparation steps:

[0038] Step A: Pre-emulsification stage

[0039] All emulsifiers, 30-40% of deionized water, acrylate soft monomers, acrylate hard monomers, 80-100% of functional monomers and molecular weight regulators are sequentially added into an emulsifying kettle and stirred and dispersed to prepare a pre-emulsion;

[0040] Step B: Primer

[0041] Add 45-55% deionized water and buffer into a reaction kettle, heat to 50-70°C, add 1-10% pre-emulsified liquid to prepare a kettle bottom liquid;

[0042] Step C: Seed priming stage

[0043] The bottom liquid of the kettle is further heated to 78-85°C, and 10-40% of a thermal initiator dissolved in 1-5% deionized water is added to the bottom liquid of the kettle under stirring, and the reaction time is 20-60 minutes to obtain a seed emulsion;

[0044] Step D: Polymerization stage

[0045] Under stirring conditions, the remaining thermal initiator and the remaining pre-emulsion dissolved in 1-5% deionized water are uniformly added to the seed emulsion, and the adding time is controlled within 3-5 hours. After the adding, the temperature is kept for 1-2 hours; the temperature is lowered to 60-75°C, and the oxidant and the reductant are respectively dissolved in 1-5% deionized water, and the two are added simultaneously, and the adding time is controlled within 30-60 minutes;

[0046] Add stage after step E

[0047] The product in step D is cooled to below 40° C., and a pH adjuster is added to a pH value of 7.0 to 8.0; the remaining functional monomers are added, and the temperature is cooled to room temperature after being evenly dispersed, and a wetting agent is added, and the temperature is filtered after being completely dispersed to obtain an acrylic latex pressure-sensitive adhesive;

[0048] The prepared acrylic ester latex pressure-sensitive adhesive has a solid content of 54-56% and a viscosity of 80-250 mPa.s.

[0049] As a further improvement of this solution, in steps A to E, the stirring speed is 150 to 500 rpm.

[0050] Compared with the prior art, the acrylic latex pressure-sensitive adhesive for BOPP film labels prepared by the present invention has the following beneficial effects:

[0051] (1) The present invention uses a non-reactive emulsifier, sodium dodecyl sulfate, and a reactive emulsifier, allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate, as anionic emulsifiers for use together. First, the non-reactive emulsifier provides good polymerization stability; second, the reactive emulsifier participates in the free radical polymerization reaction through double bonds, which reduces the migration ability of the emulsifier molecules to the film interface, improves the water vapor resistance of the acrylic latex, and solves the shedding phenomenon caused by insufficient water vapor resistance during the protective process.

[0052] (2) The functional monomers used in the present invention, firstly, provide polar groups containing carboxyl and hydroxyl groups, thereby enhancing the bonding force with the BOPP film and reducing the residual adhesive phenomenon peeled off from the adhered substrate; secondly, the crosslinking density of the polymer chain segment is increased through the hydrazide self-crosslinking reaction, thereby improving the cohesive strength, further enhancing the bonding force with the BOPP film and improving the short-term re-adhesiveness; thirdly, organic silicon molecules are introduced into the polymer molecular chain segment, and the bond energy of the Si-O bond is greater than the bond energy of the CC bond, thereby improving the high temperature resistance of the adhesive film and avoiding the overflow of adhesive during high temperature die cutting.

[0053] (3) The preparation process of the present invention is simple, uses water instead of organic solvent as the medium, is low-carbon and environmentally friendly, and saves costs.

[0054] (4) The acrylic latex pressure-sensitive adhesive of the present invention has stable storage, high solid content, low viscosity, fast coating speed, and is suitable for use with anilox roller coating equipment. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described below in conjunction with Examples 1 to 7:

[0056] Example 1

[0057] An acrylic latex pressure-sensitive adhesive for BOPP film labels, the composition of which is calculated by weight: 18.7 parts of butyl acrylate [soft monomer], 25.0 parts of isooctyl acrylate [soft monomer], 5.1 parts of methyl methacrylate [hard monomer], 0.5 parts of acrylic acid [functional monomer], 1.0 parts of hydroxyethyl acrylate [functional monomer], 0.6 parts of diacetone acrylamide [functional monomer], 0.3 parts of adipic acid dihydrazide [functional monomer], 0.3 parts of vinyltrimethoxysilane [functional monomer], 0.05 parts of n-dodecyl mercaptan, 0.8 parts of sodium dodecyl sulfate [emulsifier], 1.2 parts of allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate [emulsifier], 0.05 parts of sodium bicarbonate, 0.3 parts of ammonium persulfate, 0.1 parts of tert-butyl hydroperoxide, 0.1 parts of sodium formaldehyde sulfoxylate, 0.4 parts of ammonia water, 0.5 parts of dioctyl sodium sulfosuccinate and 45.0 parts of deionized water.

[0058] A method for preparing an acrylic latex pressure-sensitive adhesive for a BOPP film label comprises the following preparation steps:

[0059] Step A: Pre-emulsification stage

[0060] 0.8 parts of sodium lauryl sulfate, 1.2 parts of allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate, 15.0 parts of deionized water, 18.7 parts of butyl acrylate, 25.0 parts of isooctyl acrylate, 5.1 parts of methyl methacrylate, 0.5 parts of acrylic acid, 1.0 parts of hydroxyethyl acrylate, 0.6 parts of diacetone acrylamide, 0.3 parts of vinyl trimethoxy silane and 0.05 parts of n-dodecyl mercaptan are sequentially added into an emulsifying kettle and stirred and dispersed to prepare a pre-emulsion;

[0061] Step B: Primer

[0062] Add 25.0 parts of deionized water and 0.05 parts of sodium bicarbonate into a reaction kettle, raise the temperature to 50-70°C, add 3% of pre-emulsified liquid to prepare a kettle bottom liquid;

[0063] Step C: Seed priming stage

[0064] The bottom liquid of the kettle is further heated to 78-85°C, and 0.05 parts of ammonium persulfate dissolved in 1.0 parts of deionized water is added to the bottom liquid of the kettle under stirring, and the reaction time is 20-60 minutes to obtain a seed emulsion;

[0065] Step D: Polymerization stage

[0066] Under stirring conditions, 0.25 parts of ammonium persulfate dissolved in 2.0 parts of deionized water and the remaining pre-emulsion are uniformly added to the seed emulsion, and the adding time is controlled within 3 to 5 hours. After the adding, the temperature is kept for 1 to 2 hours; the temperature is lowered to 60 to 75°C, 0.1 parts of tert-butyl hydroperoxide and 0.1 parts of sodium formaldehyde sulfoxylate are respectively dissolved in 1.0 parts of deionized water, and the two are added simultaneously, and the adding time is controlled within 30 to 60 minutes;

[0067] Add stage after step E

[0068] The product in step D is cooled to below 40°C, and 0.4 parts of ammonia water are added to a pH value of 7.0-8.0; 0.3 parts of adipic acid dihydrazide are added, and the mixture is uniformly dispersed and then cooled to room temperature, and 0.5 parts of dioctyl sodium sulfosuccinate are added, and the mixture is completely dispersed and then filtered to obtain an acrylic latex pressure-sensitive adhesive.

[0069] As a further preferred embodiment, in the steps A to E, the stirring speed is 150 to 500 rpm.

[0070] Example 2

[0071] The steps of Example 1 were adopted, but in step A, the amount of sodium lauryl sulfate was changed to 0.4 parts, and the amount of allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate was changed to 1.6 parts.

[0072] Example 3

[0073] The procedure of Example 1 was followed, except that in step A, the amount of acrylic acid was changed to 1.0 part.

[0074] Example 4

[0075] The steps of Example 1 were adopted, but in step A, the amount of hydroxyethyl acrylate was changed to 1.5 parts.

[0076] Example 5

[0077] The steps of Example 1 were adopted, but in step A, the amount of vinyltrimethoxysilane was changed to 0.5 parts.

[0078] Example 6

[0079] The steps of Example 1 were adopted, but in step A, the amount of acrylic acid was changed to 0.9 parts, and the amount of hydroxyethyl acrylate was changed to 0.6 parts.

[0080] Example 7

[0081] The steps of Example 1 were adopted, except that in step A, the amount of diacetone acrylamide was changed to 1.0 part; and in step E, the amount of adipic acid dihydrazide was changed to 0.5 part.

[0082] Comparative Example 1

[0083] The steps of Example 1 were adopted, but in step A, the amount of sodium lauryl sulfate was changed to 2.0 parts, and the emulsifier allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate was not contained.

[0084] Comparative Example 2

[0085] The steps of Example 1 were adopted, but in step A, the amount of acrylic acid was changed to 0.2 parts, and the functional monomer hydroxyethyl acrylate was not contained.

[0086] Comparative Example 3

[0087] The steps of Example 1 are adopted, but diacetone acrylamide is not contained in step A; and adipic acid dihydrazide, a functional monomer, is not contained in step E.

[0088] Comparative Example 4

[0089] The steps of Example 1 are adopted, but the functional monomer vinyltrimethoxysilane is not contained in step A.

[0090] Performance Test:

[0091] The samples of Examples 1 to 7 and Comparative Examples 1 to 4 were coated on 61 g / m2 White release paper with silicone coating, the coating amount is 19.0±1g / m 2 After coating, put it in an oven at 80-90℃ for 5 minutes and take it out. Then transfer the film to the corona surface of 75um matte white BOPP film surface material. Finally, stick the adhesive surface of the surface material to 61g / m 2 The silicon-coated surface of the white release paper was equilibrated for 72 hours in a standard environment (temperature 23±2°C, humidity 50±5%) before testing.

[0092] 1. Initial adhesion: Tested according to the "Ring Initial Adhesion Test" FTM9.

[0093] 2. Peel force: Tested according to "90° Peel Force Test" FTM2.

[0094] 3. Adhesion: Tested according to the "Adhesion Test on Standard Panels" FTM8.

[0095] 4. Water vapor resistance: Soak the corona surface of the BOPP substrate evenly coated with pressure-sensitive adhesive in 25°C tap water for 14 days and observe the debonding.

[0096] 5. Short-term re-adhesion: Stick the corona surface of the BOPP substrate evenly coated with pressure-sensitive adhesive to the PET bottle for 48 hours, then remove it and observe the residual adhesive.

[0097] 6. High temperature glue overflow resistance: Roll a BOPP self-adhesive sample roll coated with pressure-sensitive adhesive (MD direction length: 200m;

[0098] CD direction length: 190mm) put it in 60℃ high temperature conditions for 7 days, then take it out for die cutting, label die cutting size: 2mm (MD direction) * 3mm (CD direction), waste discharge edge width: 1mm.

[0099] After die-cutting, observe the glue overflow on the edge of the label.

[0100] Table 1. Performance test results

[0101]

[0102] It can be seen from the data in Table 1 that the acrylic latex pressure-sensitive adhesive for BOPP film labels prepared by the present invention has a ring initial adhesion greater than 9N / 25mm, a peeling force greater than 7N / 25mm, and a lasting adhesion greater than 300h through the coordination of the overall formula components, combined with the use of functional monomers acrylic acid, hydroxyethyl acrylate, diacetone acrylamide, adipic acid dihydrazide, vinyl trimethoxysilane, and emulsifier allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate. It has good mechanical properties and high cohesive strength, can ensure that high-temperature die-cutting in summer does not overflow the glue, and the die-cutting waste discharge efficiency is high; no glue residue is left on the PET material with high surface energy within 48 hours, and the short-term re-pasteability is excellent; there is no degumming after soaking in water for 14 days, and the water vapor resistance is excellent, which can meet most application scenarios of BOPP film labels.

[0103] It can be seen from the data in Table 1 that when only any one of acrylic acid, hydroxyethyl acrylate, diacetone acrylamide, adipic acid dihydrazide, and vinyl trimethoxysilane is added as the functional monomer, the adhesion is affected, the water vapor resistance and short-time re-lamination properties are affected, debonding and residual glue will occur, and glue overflow will occur during high-temperature die-cutting in summer.

[0104] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent changes made using the present invention are within the patent protection scope of the present invention.

Claims

1. An acrylic latex pressure-sensitive adhesive for BOPP film labels, the constituent raw materials of which are, by weight: 18.7 parts of butyl acrylate, 25.0 parts of isooctyl acrylate, 5.1 parts of methyl methacrylate, 0.5 parts of acrylic acid, 1.0 parts of hydroxyethyl acrylate, 0.6 parts of diacetone acrylamide, 0.3 parts of adipic acid dihydrazide, 0.3 parts of vinyl trimethoxy silane, 0.05 parts of n-dodecyl mercaptan, 0.8 parts of sodium lauryl sulfate, 1.2 parts of allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate, 0.05 parts of sodium bicarbonate, 0.3 parts of ammonium persulfate, 0.1 parts of tert-butyl hydroperoxide, 0.1 parts of sodium formaldehyde sulfoxylate, 0.4 parts of ammonia water, 0.5 parts of dioctyl sodium sulfosuccinate and 45.0 parts of deionized water; The method for preparing the acrylic latex pressure-sensitive adhesive for BOPP film labels comprises the following preparation steps: Step A: Pre-emulsification stage 0.8 parts of sodium lauryl sulfate, 1.2 parts of allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate, 15.0 parts of deionized water, 18.7 parts of butyl acrylate, 25.0 parts of isooctyl acrylate, 5.1 parts of methyl methacrylate, 0.5 parts of acrylic acid, 1.0 parts of hydroxyethyl acrylate, 0.6 parts of diacetone acrylamide, 0.3 parts of vinyl trimethoxy silane and 0.05 parts of n-dodecyl mercaptan are sequentially added into an emulsifying kettle and stirred and dispersed to prepare a pre-emulsion; Step B: Primer Add 25.0 parts of deionized water and 0.05 parts of sodium bicarbonate into a reaction kettle, raise the temperature to 50-70°C, add 3% of pre-emulsified liquid to prepare a kettle bottom liquid; Step C: Seed priming stage The bottom liquid of the kettle is further heated to 78-85°C, and 0.05 parts of ammonium persulfate dissolved in 1.0 parts of deionized water is added to the bottom liquid of the kettle under stirring, and the reaction time is 20-60 minutes to obtain a seed emulsion; Step D: Polymerization stage Under stirring conditions, 0.25 parts of ammonium persulfate dissolved in 2.0 parts of deionized water and the remaining pre-emulsion are uniformly added to the seed emulsion, and the adding time is controlled within 3 to 5 hours. After the adding, the temperature is kept for 1 to 2 hours; the temperature is lowered to 60 to 75°C, 0.1 parts of tert-butyl hydroperoxide and 0.1 parts of sodium formaldehyde sulfoxylate are respectively dissolved in 1.0 parts of deionized water, and the two are added simultaneously, and the adding time is controlled within 30 to 60 minutes; Add stage after step E The product in step D is cooled to below 40°C, 0.4 parts of ammonia water are added until the pH value is 7.0-8.0; 0.3 parts of adipic acid dihydrazide are added, the mixture is uniformly dispersed, and the mixture is cooled to room temperature; 0.5 parts of dioctyl sodium sulfosuccinate are added, the mixture is completely dispersed, and the mixture is filtered to obtain an acrylate latex pressure-sensitive adhesive; In the steps A to E, the stirring speed is 150 to 500 rpm.

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