UV-CROSSLINKED HOT-MELT PRESSURE-SENSITIVE ADHESIVE USED FOR POLYVINYL CHLORIDE INSULATION ADHESIVE TAPE

Abstract

The present invention provides a UV-crosslinked hot-melt pressure-sensitive adhesive used for a polyvinyl chloride (PVC) insulation adhesive tape, made by mixing a polymer of vinyl monomers, functional monomers, special soft monomers, and photoinitiators with a tackifying resin and an antioxidant in certain proportions; the composition of the photoinitiator polymer contains a copolymer of one or more polymerizable photosensitive initiators and acrylate monomers, or a mixture of oligomers of one or more polymerizable photosensitive initiators and acrylate high polymers. The PVC adhesive tape made using such a pressure-sensitive adhesive has the advantages of excellent mechanical properties, bonding performance, and resistance to high temperatures, and is energy-saving and environmentally friendly; the present invention overcomes the defect of the prior art that a relatively long thermal oven is needed to volatilize a solvent in the glue when coating a PVC adhesive tape, which is applicable for wrapping and strapping cable bundles in different positions of the body of an automobile, can satisfy the requirement for uses on high temperature-resistant positions of an engine inside the automobile, and reaches a long-term temperature resistance level of 125° C.

Claims

1. A composition for a UV-crosslinked hot-melt pressure-sensitive adhesive used for a PVC insulation adhesive tape, comprising the following major components: polymers containing vinyl monomers, functional monomers, soft monomers, and photoinitiators, a polymerization initiator, and an antioxidant; wherein the vinyl monomer is selected from a group consisting of one or more n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isobornyl acrylate, n-dodecyl acrylate, methyl n-butyl acrylate, methyl 2-ethylhexyl acrylate, and methyl n-octyl acrylate, and the amount of the vinyl monomer is 40-65% of the total amount; wherein the functional monomer is N-vinylpyrrolidone, and the amount thereof is 2-10% of the total amount; wherein the soft monomer is C17 acrylate or C17 methacrylate, and the amount thereof is 5-15% of the total amount; wherein the photoinitiator is methacryloyloxy or acryloyloxy containing acetophenone or benzophenone derivative, and the amount thereof is 2-10% of the total amount; and wherein the polymerization initiator comprises azo compounds, acyl peroxides, and alkyl peroxides, the azo compound being 2,2-azobisisobutyronitrile, and the acyl peroxides being benzoyl peroxide, didecanoyl peroxide or isononanoyl peroxide, or the polymerization initiator is benzotriazole-1-yl-oxy-tris(dimethylamino) phosphonium hexafluorophosphate, and the amount of the polymerization initiator is 1-10% of the total amount.

2. The composition for a UV-crosslinked hot-melt pressure-sensitive adhesive used for a PVC insulation adhesive tape according to claim 1, further comprising a copolymer of one or more polymerizable photosensitive initiators and acrylate monomers, or comprising a mixture of oligomers of one or more polymerizable photosensitive initiators and acrylate high polymers.

3. The composition for a UV-crosslinked hot-melt pressure-sensitive adhesive used for a PVC insulation adhesive tape according to claim 1, further comprising a tackifying resin, the tackifying resin comprising one or more selected from the group consisting of rosin resins, terpene resins, petroleum resins, and corresponding hydrogenated or esterified modified resins, and the amount of the tackifying resin being 2-20% of the total amount.

4. The composition for a UV-crosslinked hot-melt pressure-sensitive adhesive used for a PVC insulation adhesive tape according to claim 1, wherein the antioxidant is an aromatic antioxidant, a hindered phenol antioxidant, or a secondary antioxidant, and the amount thereof is 0.5-1.5% of the total amount.

5. The composition for a UV-crosslinked hot-melt pressure-sensitive adhesive used for a PVC insulation adhesive tape according to claim 4, wherein the antioxidant is dianiline, p-dianiline, or pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0022] Exemplary embodiments of the present solution will be described in detail below, and the effects of the UV-crosslinked hot-melt pressure-sensitive adhesive used for a PVC insulation adhesive tape according to the present invention will be described through the following embodiments, comparative embodiments, and performance data in Table 1. The purpose of providing these exemplary embodiments is to enable those skilled in the art to clearly understand the present invention and to implement the present invention according to the description herein. The specific embodiments are not intended to limit the present invention, and the scope of the present invention is defined by the appended claims.

Embodiment 1

[0023] Add 30% (wt) ethyl acetate into a reactor, heat to boil and maintain for 30 min, mix 53.9% (wt) n-butyl acrylate (BA), 3.5% (wt) acrylic acid (AA), 3.5% (wt) acryloyloxy acetophenone, 1.4% (wt) N-vinylpyrrolidone (NVP), 3.5% (wt) C17 acrylate (from BASF), and 3.5% (wt) benzotriazole-1-yl-oxy-tris(dimethylamino) phosphonium hexafluorophosphate (BOP) as an initiator and add dropwise the mixture into the reactor, fill the reactor with nitrogen for protection, and complete the dropwise addition within 1 h. After the titration is completed, continue to heat for 4 h; at 4 h, add 0.7% (wt) antioxidant Irganox 1010, maintain the heating state, vacuumize the reactor until the solvent (i.e., ethyl acetate) is completely separated, and remove the solvent to obtain a hot-melt pressure-sensitive adhesive with no solvent.

[0024] Preparation of a high temperature resistant PVC adhesive tape: complete the preparation with a slot die coating or a rolling or laminating coating process on a hot-melt coating machine, install a high temperature resistant PVC substrate on an unwinding shaft, and drag it to a winding shaft. Set the temperature of a melt tank at 130-140° C. and the temperature of a coating head at 135° C., and adjust the ratio of the rotational speed of an adhesive pump to the speed of a main machine according to the weight of loaded adhesive. Set the winding tension and unwinding tension, and turn on a cooling device. Adjust the speed of the main machine, slowly move the coating head to the PVC film surface, turn on the adhesive pump switch for coating, adjust the space between the coating head and the substrate, and adjust the speed of the coating machine for coating. The coating amount of the hot-melt pressure-sensitive adhesive is 18 g/m.sup.2, and the adhesive layer is crosslinked and cured by UV irradiation with a group of UV lamps. The UV lamps that are used include high-pressure mercury lamps, medium to low-pressure mercury lamps, or LED lamps, and the minimum UV irradiation energy thereof needs to reach 10 mJ/cm.sup.2. The crosslinked and cured adhesive tape is wound and divided to obtain the high temperature resistant PVC adhesive tape product.

Embodiment 2

[0025] Preparation of a high polymer (A): add 30% (wt) ethyl acetate into a reactor, heat to boil and maintain for 30 min, mix 63% (wt) n-butyl acrylate (BA), 3.5% (wt) acrylic acid (AA), and 3.5% (wt) benzotriazole-1-yl-oxy-tris(dimethylamino) phosphonium hexafluorophosphate (BOP) and add dropwise the mixture into the reactor, fill the reactor with nitrogen for protection, and complete the dropwise addition within 1 h. After the titration is completed, continue to heat for 4 h; at 4 h, maintain the heating state, vacuumize the reactor, and discharge the high polymer (A) for later use;

[0026] Preparation of an oligomer (B): add 50% (wt) toluene into a reactor, heat to boil and maintain for 30 min, mix 33% (wt) n-butyl acrylate (BA), 1.5% (wt) acrylic acid (AA), 5% (wt) acryloyloxy acetophenone as a photo-initiator, 2.5% (wt) benzotriazole-1-yl-oxy-tris(dimethylamino) phosphonium hexafluorophosphate (BOP), 5% (wt) C17 acrylate (from BASF), and 2% (wt) N-vinylpyrrolidone (NVP), and add dropwise the mixture into the reactor, and complete the dropwise addition within 2 h. After the dropwise addition is completed, add 1% (wt) antioxidant 1010, maintain the heating state, vacuumize the reactor, and discharge the oligomer (B) for later use; mix the high polymer A and the oligomer B (50% of A and B respectively), heat to 130° C., stir thoroughly and mix homogeneously, and then cool for later use; use the same method as the one in Embodiment 1 to obtain the high temperature resistant PVC adhesive tape.

[0027] Embodiment 3: heat 95% (wt) Embodiment 1 and 5% (wt) hydrogenated petroleum resin Regalite® 1090 (Eastman, USA) to 130° C., stir thoroughly, and mix homogeneously to prepare the product; use the same method as the one in Embodiment 1 to obtain the high temperature resistant PVC adhesive tape.

Comparative Embodiment 1

[0028] Synthesis of an Acrylate Copolymer Emulsion:

[0029] (1) Divide an overall monomer formula [20 g isooctyl acrylate (2-EHA), 50 g butyl acrylate (BA), 60 g dibutyl maleate (DBM), 50 g methyl methacrylate (MMA), 7.5 g hydroxyethyl acrylate (HEA), 4.5 g acrylic acid (AA), and 8.0 g N-hydroxymethyl acrylamide (N-MAM)] into two components, Component A and Component B, for respective mixing and preparation of pre-emulsions, wherein Component A comprises the following ingredients: 50 g BA, 50 g MMA, 4.5 g HEA, 2.8 g AA, and 8.0 g N-MAM; and Component B comprises the following ingredients: 20 g 2-HEA, 60 g DBM, 3.0 g HEA, and 1.7 g AA;

[0030] (2) Add 160 g deionized water, 2.6 g sodium bicarbonate as a buffer, and 0.78 g emulsifier Co-436 (a product from Rhodia Inc.) into a 1000 ml three-neck round bottom flask, mix homogeneously, heat to raise the temperature to 78° C., add an aqueous solution of 0.40 g ammonium persulfate as an initiator, and maintain the temperature at 82-84° C. while adding the pre-emulsion of monomers in Component A at an even rate for a first phase of copolymerization of the emulsion. Complete the addition within 1.5 h, and after the addition is completed, maintain the temperature in the temperature range while adding the pre-emulsion of monomers in Component B at an even rate for a second phase of copolymerization of the emulsion. Complete the addition within 2.5 h;

[0031] (3) Maintain the temperature at 83-85° C., continue stirring to react for 1 h, then cool and filter to discharge the material, and obtain an acrylate copolymer emulsion that can be used to further prepare an emulsion pressure-sensitive adhesive;

[0032] (4) Preparation of a pressure-sensitive adhesive: add 45 g of a commercially available polyvinyl acetate emulsion into 300 g of the acrylate copolymer emulsion synthesized above, mix homogeneously, and then use ammonia to adjust the pH to 7-8 to obtain a desired emulsion pressure-sensitive adhesive, which has a solid content of 53%;

[0033] (5) Performance testing: coat the obtained emulsion pressure-sensitive adhesive on a 0.15 mm-thick soft PVC (SPVC) film substrate to prepare small rolls of an electric pressure-sensitive adhesive tape with a dry adhesive layer thickness of 20 μm; cure for 8 h in a 70° C. environment, then test various properties of the adhesive tape, and test the adhesive tape's 180° peel strength according to the Chinese national standard GB/T2792-1998.

Comparative Embodiment 2

[0034] Add 30% (wt) ethyl acetate into a reactor, heat to boil and maintain for 30 min, mix 58.9% (wt) n-butyl acrylate (BA), 3.5% (wt) acrylic acid (AA), 3.5% (wt) acryloyloxy acetophenone, and 3.5% (wt) benzotriazole-1-yl-oxy-tris(dimethylamino) phosphonium hexafluorophosphate (BOP) as an initiator and add dropwise the mixture into the reactor, fill the reactor with nitrogen for protection, and complete the dropwise addition within 1 h. After the titration is completed, continue to heat for 4 h; at 4 h, add 0.7% (wt) antioxidant Irganox 1010, maintain the heating state, and vacuumize the reactor until the solvent is completely separated.

[0035] The tack, 180° peel strength, and low-speed unwinding strength of the pressure-sensitive adhesive tapes in Table 1 are determined using methods according to Chinese national standards GB/T 4852-1984, GB/T 8451-1998, GB/T2792-1998, and GB/T4850-1984, respectively; the method for determining temperature stability is as follows: use a pressure-sensitive adhesive tape to wind around cables, age for 24 h at 150° C., observe whether the aged cables have curled tapes at the edge or have loose tapes, or whether there is overflown adhesive liquid, and determine that the pressure-sensitive adhesive tape is qualified when the tape is not curled, the tape does not become loose, or there is no overflown adhesive liquid; the method for determining flexibility is: treat an adhesive tape (having a width of 19-25 mm) with a length of at least 10 m wound around a paper core (having an outer diameter of 36 mm and a paper core wall thickness of 3-4 mm) at 20±1° C. and a relative humidity of 50±5% for 24 h, unwind the adhesive tape at a speed of 15-20 cm/s to evenly open up the adhesive tape, and determine that the flexibility is good if there is no noise and no sticky-sliding/skidding phenomenon; if the unwinding is skidding or has noise, determine that the flexibility is poor.

TABLE-US-00001 TABLE 1 Performance testing results for soft PVC adhesive tapes Low-speed Tack 180° peel unwinding (number strength strength Flexibility and Temperature of balls) (N/cm) (N/cm) adhesion tests stability Embodiment 1 17 1.5 2.4 Good flexibility, no noise No edge curling, no during rapid unwinding, loose adhesive, and and no adhesive falling no overflown off during rapid adhesive unwinding Embodiment 2 18 1.4 2.2 Good flexibility, no noise No edge curling, no during rapid unwinding, loose adhesive, and and no adhesive falling no overflown off during rapid adhesive unwinding Embodiment 3 16 1.7 3.0 Good flexibility, no noise No edge curling, no during rapid unwinding, loose adhesive, and and no adhesive falling no overflown off during rapid adhesive unwinding Comparative 8 1.1 2.1 Slightly poorer flexibility, Loose adhesive Embodiment 1 and noise during rapid tape, and overflown unwinding adhesive liquid Comparative 16 1.4 2.4 Slightly poorer flexibility, Loose adhesive Embodiment 2 and noise during rapid tape, and overflown unwinding adhesive liquid

[0036] It can be seen by comparing Embodiments 1-3 and Comparative Embodiments 1-2 that the soft PVC adhesive tapes made with the UV-crosslinked hot-melt pressure-sensitive adhesive used for soft PVC insulation adhesive tapes have significantly higher temperature resistance than that of the adhesive tapes made with the emulsion-type pressure-sensitive adhesive. The use of the functional monomers improves the adhesive's adhesion to the PVC substrate and resistance to plasticizers. The addition and use of the special soft monomers improves the flexibility of the PVC adhesive tapes.