Adhesive composition for cold sealing

Abstract

Provided is an adhesive composition for cold sealing which can be used for bonding even in a wet environment and is excellent in terms of adhesiveness and safety.　The adhesive composition for cold sealing comprises (A) 20-65 mass% of an α-olefin copolymer, (B) 0-25 mass% of a thermoplastic block copolymer, (C) 20-65 mass% of a tackifier resin, and (D) 0-20 mass% of a wax and / or a plasticizer (the sum of the amounts of the components (A), (B), (C), and (D) is 100 mass%). The adhesive composition for cold sealing has a probe tack less than 700 gf. The pressure-sensitive adhesive strength between an adherend and the adhesive composition or between the adhesive composition and itself is 3 N / 15 mm or greater.

Description

Cold seal adhesive composition

[0001] The present invention relates to a cold seal adhesive composition.

[0002] Cold seal adhesives are pressure-sensitive adhesives that do not develop tack at room temperature. Generally, they exhibit weak adhesive strength when bonded to different materials, but when bonded to other cold seal adhesives of the same type, they exhibit strong adhesive strength with only slight pressure. They are typically provided coated on substrates such as paper or film, but their lack of tack means they do not require a release liner, offering environmental benefits such as resource efficiency and waste reduction. Furthermore, because they bond at room temperature without the need for heat or solvents, they are widely used in applications such as binding tape, adhesive envelopes, and packaging materials.

[0003] Known types of cold seal adhesives include solvent-based, emulsion-based, and hot-melt-based adhesives. For example, Patent Document 1 discloses a cold seal adhesive made of a solution in which a solid material containing synthetic rubber is dissolved in an organic solvent. However, such solvent-based cold seal adhesives require a process of drying the solvent after application, making it difficult to improve production efficiency. Furthermore, when used as food packaging material or binding tape for vegetables, the migration of residual solvent in the adhesive into the food can be a problem.

[0004] Furthermore, as an emulsion type, Patent Document 2, for example, discloses a cold seal adhesive containing 20 to 70% by weight of modified natural rubber latex obtained by graft polymerization of an acrylic acid ester compound onto natural rubber latex. However, emulsion type cold seal adhesives have problems such as a long drying process and poor water resistance, which means that they do not exhibit sufficient adhesiveness in humid environments.

[0005] Meanwhile, Patent Document 3 discloses a hot-melt cold seal adhesive containing an olefin resin and a wax with a softening point of 80°C to 170°C. Such hot-melt cold seal adhesives are highly productive because they do not require a drying process after application to a substrate, and they exhibit adhesive properties even in humid environments. However, their weak adhesive strength can make them difficult to apply to applications requiring strong adhesive strength. As described above, it has traditionally been difficult for cold seal adhesives to achieve excellent adhesive strength in humid environments while maintaining the safety required for applications such as food packaging.

[0006] Japanese Patent Laid-Open No. 5-148463 Japanese Patent Laid-Open No. 2002-138266 Japanese Patent Laid-Open No. 2002-241723

[0007] An object of the present invention is to provide an adhesive composition for cold sealing which can bond even in a humid environment and has excellent adhesive properties and safety.

[0008] The present invention comprises the following claims 1 to 16. <Claim 1> A cold seal adhesive composition containing 20 to 65 mass% of (A) an α-olefin copolymer, 0 to 25 mass% of (B) a thermoplastic block copolymer, 20 to 65 mass% of (C) a tackifying resin, and 0 to 20 mass% of (D) a wax and / or plasticizer (wherein the total of components (A), (B), (C), and (D) is 100 mass%), wherein the cold seal adhesive composition has a probe tack of less than 700 gf and a pressure-sensitive adhesive strength of 3 N / 15 mm or greater between an adherend and the adhesive composition, or between the adhesive compositions themselves. <Claim 2> The cold seal adhesive composition according to claim 1, which has a melt viscosity at 180°C of 3,000 to 50,000 mPa s. <Claim 3> The cold seal adhesive composition according to claim 1 or 2, wherein component (A) has a melt viscosity at 180°C of 30,000 mPa s or less and a melting point of 110°C or less. <Claim 4> The density of component (A) is 0.88 g / cm ３The cold seal adhesive composition of claim 1 or 2, wherein the α-olefin monomer constituting component (A) is one or more selected from propylene, 1-butene, 1-hexene, and 1-octene. <Claim 6> The cold seal adhesive composition of claim 1 or 2, wherein component (A) is one or more selected from ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, propylene-1-butene copolymer, propylene-1-hexene copolymer, and propylene-1-octene copolymer. <Claim 7> The cold seal adhesive composition of claim 1 or 2, wherein component (A) is polymerized using a metallocene catalyst. <Claim 8> The cold seal adhesive composition of claim 1 or 2, wherein component (B) is a block copolymer comprising at least one hard segment and at least one soft segment, the main constituent monomer of which is at least one selected from styrene, olefins, and acrylic acids. <Claim 9> The cold seal adhesive composition of claim 1 or 2, wherein component (C) is at least one selected from terpene resins and hydrogenated petroleum resins. <Claim 10> The cold seal adhesive composition of claim 1 or 2, wherein the proportion of plasticizer in component (D) is less than 50 mass% of the total mass of component (D). <Claim 11> The cold seal adhesive composition of claim 1 or 2, wherein the wax is at least one selected from Fischer-Tropsch wax, polyethylene wax, polypropylene wax, vegetable wax, and hydrogenated fats and oils. <Claim 12> The cold seal adhesive composition of claim 1 or 2, wherein the wax has a melting point of 60°C to 160°C. <Claim 13> A method for using the cold seal adhesive composition according to claim 1 or 2, comprising the steps of applying the cold seal adhesive composition to a substrate and contacting the adhesive layer of the substrate to which the cold seal adhesive composition has been applied with an adherend, or contacting the adhesive layers with each other. <Claim 14> A packaging bag using the cold seal adhesive composition according to claim 1 or 2.<Claim 15> An envelope using the cold seal adhesive composition according to claim 1 or 2. <Claim 16> A label using the cold seal adhesive composition according to claim 1 or 2.

[0009] According to the present invention, it is possible to provide an adhesive composition for cold sealing which can bond even in a humid environment and has excellent adhesive properties and safety.

[0010] The present invention will be described below by constituent element. <(A) α-olefin copolymer> The (A) α-olefin copolymer is a copolymer obtained by randomly polymerizing at least one α-olefin monomer and, if necessary, ethylene. The α-olefin monomer is a chain alkene having a carbon-carbon double bond at the molecular chain terminal and having 3 to 20 carbon atoms. Specific examples of the α-olefin monomer include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, and 1-dodecene. Of these, propylene, 1-butene, 1-hexene, and 1-octene are preferred.

[0011] The α-olefin copolymer (A) is a copolymer obtained by polymerizing at least one α-olefin monomer and, if necessary, ethylene in the presence of a metallocene catalyst, and its density is usually 0.88 g / cm ３ The copolymerization ratio of these monomers to be used is not particularly limited. Specific examples of the (A) α-olefin copolymer include an ethylene-propylene copolymer, an ethylene-1-butene copolymer, an ethylene-1-hexene copolymer, an ethylene-1-octene copolymer, a propylene-1-butene copolymer, a propylene-1-hexene copolymer, and a propylene-1-octene copolymer. The (A) α-olefin copolymer is available as Vistamaxx manufactured by ExxonMobil, AFFINITY manufactured by Dow Chemical, or the like. These may be used alone or in combination of two or more.

[0012] The melt viscosity of the α-olefin copolymer (A) at 180°C is preferably 30,000 mPa·s or less, and more preferably 20,000 mPa·s, from the viewpoint of adhesiveness in a low-temperature atmosphere. The melting point of the α-olefin copolymer (A) is preferably 110°C or less, and more preferably 100°C or less, from the viewpoint of adhesiveness in a low-temperature atmosphere. Furthermore, the glass transition temperature of the α-olefin copolymer (A) is preferably -20°C or less, and more preferably -30°C or less, from the viewpoint of adhesiveness in a low-temperature atmosphere.

[0013] The proportion of the α-olefin copolymer (A) in the composition of the present invention is 20 to 65% by mass, preferably 25 to 50% by mass. If it is less than 20% by mass, it may be difficult to obtain sufficient adhesive strength, while if it exceeds 65% by mass, the melt viscosity of the composition may increase, resulting in poor coatability.

[0014] <(B) Thermoplastic Block Copolymer> The (B) thermoplastic block copolymer is a block copolymer comprising at least one hard segment and at least one soft segment, the main constituent monomer of which is one or more selected from styrene, olefins, and acrylic acids. Specific examples include styrene-based thermoplastic block copolymers, olefin-based thermoplastic block copolymers, and acrylic thermoplastic block copolymers. Examples of the styrene-based thermoplastic block copolymer include styrene-isoprene-styrene block copolymers, styrene-butadiene-styrene block copolymers, styrene-ethylene-butylene-styrene block copolymers, styrene-ethylene-propylene-styrene block copolymers, and styrene-farnesene-styrene block copolymers. Examples of the olefin-based thermoplastic block copolymers include block copolymers containing a polyethylene block as a hard segment and an ethylene / α-olefin copolymer block as a soft segment within the molecule, polyethylene-ethylene-propylene rubber (EPR) block copolymers, polypropylene-EPR block copolymers, polyethylene-ethylene-propylene-diene rubber (EPDM) block copolymers, polypropylene-EPDM block copolymers, and polybutylene-EPR block copolymers. Examples of acrylic thermoplastic block copolymers include methyl methacrylate-butyl acrylate-methyl methacrylate block copolymers and methyl methacrylate-butyl acrylate-2-ethylhexyl acrylate-methyl methacrylate block copolymers. The mass ratio of the hard segments to the entire (B) thermoplastic block copolymer is preferably 50% or less. These thermoplastic block copolymers may be used alone or in combination of two or more. Furthermore, the glass transition temperature of the (B) thermoplastic block copolymer is preferably 0°C or less, more preferably -10°C or less. The glass transition temperature of the (B) thermoplastic block copolymer is a value measured according to JIS K6240, Raw Rubber - Determination of Glass Transition Temperature by Differential Scanning Calorimetry (DSC).

[0015] The proportion of the thermoplastic block copolymer (B) in the composition of the present invention is 0 to 25% by mass, preferably 3 to 20% by mass. If it exceeds 25% by mass, the melt viscosity of the composition increases, which may deteriorate the coatability, and this is not preferred.

[0016] <(C) Tackifying Resin> Examples of the (C) tackifying resin include terpene resins and hydrogenated petroleum resins. These may be used alone or in combination of two or more.

[0017] Among the (C) tackifying resins, examples of the terpene resins include terpene resins obtained by (co)polymerizing one or more terpene monomers such as α-pinene, β-pinene, and dipentene, aromatic-modified terpene resins obtained by copolymerizing a terpene monomer with an aromatic monomer, terpene phenol resins obtained by copolymerizing a terpene monomer with a phenol, and hydrogenated products thereof. Commercially available terpene resins include YS Resin PX, YS Resin TO, YS Polystar, and Clearon, both manufactured by Yasuhara Chemical Co., Ltd., and Silverez, both manufactured by Kraton.

[0018] Hydrogenated petroleum resins are resins obtained by at least partially hydrogenating resins obtained by polymerizing or copolymerizing C5 fractions containing pentene, isoprene, piperine, 1,3-pentadiene, etc., mainly obtained by cracking naphtha, and C9 fractions containing indene, vinyltoluene, α- or β-methylstyrene, etc. Examples include hydrogenated dicyclopentadiene resins obtained by hydrogenating C5 petroleum resins obtained by copolymerizing C5 fractions, partially hydrogenated aromatic-modified dicyclopentadiene resins, resins obtained by hydrogenating C9 petroleum resins obtained by copolymerizing C9 fractions, and resins obtained by hydrogenating copolymerized petroleum resins of the above-mentioned C5 and C9 fractions. Commercially available hydrogenated petroleum resins include Easttack and Ligalets, both manufactured by Eastman Chemical; Alcon, manufactured by Arakawa Chemical Industries; T-REZ, manufactured by ENEOS; and Imave, manufactured by Idemitsu Kosan.

[0019] The softening point of the (C) tackifier resin is preferably 70 to 150°C. If it is less than 70°C, heat resistance may be reduced. On the other hand, if it exceeds 150°C, adhesiveness may be reduced, which is undesirable. The softening point of the (C) tackifier resin is defined as a value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. A (C) tackifier resin having a softening point within the above range may be selected from various tackifier resins by measuring their softening points based on the above. Furthermore, the weight average molecular weight of the (C) tackifier resin in terms of polystyrene is preferably 400 to 5,000.

[0020] In addition to the tackifier resin (C) within the preferred ranges described above, or a mixture thereof, a tackifier resin outside the preferred ranges may be mixed with the tackifier resin (C) of the present invention in order to adjust physical properties such as cohesive strength and viscosity.

[0021] The blending amount of (C) tackifier resin is 20 to 65% by mass, preferably 25 to 45% by mass. If it is less than 20% by mass, it is difficult to obtain heat-resistant adhesion, while if it is more than 65% by mass, the adhesion may decrease.

[0022] <(D) Wax and / or Plasticizer> Next, the wax (D) used in the present invention is not particularly limited as long as it is one that is usually incorporated into hot melt adhesives, and examples thereof include vegetable waxes such as candelilla wax, carnauba wax, rice bran wax, Japan wax, and jojoba oil; animal waxes such as beeswax, lanolin, and spermaceti; mineral waxes such as montan wax, ozokerite, and ceresin; petroleum waxes such as paraffin wax, microcrystalline wax, and petrolatum; synthetic hydrocarbons such as Fischer-Tropsch wax, polyethylene wax, and polypropylene wax; and hydrogenated oils and fats in which some or all of the unsaturated bonds of oils and fats such as castor oil, rapeseed oil, rice bran oil, corn oil, palm oil, and olive oil are hydrogenated. Among these, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, vegetable wax, and hydrogenated oils and fats are preferred. These may be used alone or in combination of two or more. The melting point of the wax (D) is preferably 60°C to 160°C, more preferably 75°C to 150°C, and even more preferably 90°C to 140°C. If the melting point of the wax is less than 60°C, heat resistance may decrease, and if it exceeds 160°C, sufficient adhesive strength may not be exhibited. Here, the melting point is measured by differential scanning calorimetry (DSC) in accordance with JIS K7121.

[0023] The plasticizer (D) is a component that has the function of reducing the melt viscosity of the adhesive composition, and any conventionally known substance that can be used as the plasticizer of the present invention may be used, such as liquid paraffin, paraffinic, naphthenic, or aromatic process oils, liquid rubbers such as liquid polyisoprene, ester-based plasticizers, vegetable oils, liquid polybutene, acid anhydride-modified polybutene, or acid anhydride-modified liquid polyisoprene, which may be used alone or in combination of two or more. Preferably, at least one selected from the group consisting of liquid paraffin, process oil, and liquid polybutene, which have a significant effect of improving fluidity, is used.

[0024] The blending amount of (D) wax and / or plasticizer in the present invention is 0 to 20% by mass, preferably 3 to 15% by mass. If the blending amount is more than 20% by mass, sufficient adhesive strength may not be obtained. As component (D), the wax and plasticizer may be used alone or in combination. The proportion of plasticizer in component (D) is preferably less than 50% by mass of the total component (D). If it is 50% by mass or more, the probe adhesive strength may become too high, which is not preferable.

[0025] The melt viscosity of the adhesive composition of the present invention at 180°C is not particularly limited, but is preferably in the range of 3,000 to 50,000 mPa·s, and more preferably 3,000 to 30,000 mPa·s. If the viscosity is less than 3,000 mPa·s, the cohesive strength of the adhesive may decrease, while if it exceeds 50,000 mPa·s, the application performance may decrease and the adhesive may become more susceptible to stringiness. Here, the melt viscosity of the adhesive composition of the present invention at 180°C is a value measured in accordance with the Japan Adhesive Industry Association standard JAI-7-1999. The melt viscosity of the adhesive composition of the present invention can be adjusted, for example, by appropriately selecting the ratios of the above-mentioned components (A) to (D).

[0026] In addition to the above components (A) to (D), the cold seal adhesive composition of the present invention may contain additives such as antioxidants, other thermoplastic resins, elastomers, rubbers, lubricants, antiblocking agents, color inhibitors, fillers, plasticizers, and extenders.

[0027] The cold seal adhesive composition of the present invention can be prepared by known methods. For example, it can be prepared by conventional procedures using equipment equipped with heating, stirring, and kneading functions, such as a single- or twin-screw extruder, mixer, kneader, or Banbury mixer. The kneading of the components varies depending on the composition and the equipment used, but is usually carried out at 120 to 180°C, preferably 130 to 160°C, for 30 to 120 minutes, preferably 40 to 90 minutes.

[0028] The cold seal adhesive composition of the present invention obtained in this manner contains the above-mentioned components (A) to (D) as main components, has a probe tack strength of less than 700 gf, and a pressure-sensitive adhesive strength of 3 N / 15 mm or more between the adhesive composition and an adherend, or between the adhesive compositions themselves. Here, a probe tack strength of 700 gf or more is undesirable because it may unintentionally adhere to a paper substrate or the like at room temperature. The probe tack strength is preferably less than 500 gf, more preferably less than 300 gf. In this specification, room temperature refers to a temperature range of 5°C to 35°C inclusive, based on JIS Z8703-1983. The probe tack strength is measured using a SUS probe in an atmosphere of 23°C, after preparing a test piece by coating the cold seal adhesive composition on a PET film. The test piece is prepared by coating a 25 μm-thick PET film with the adhesive composition to a thickness of 30 μm. The measurement was carried out by contacting a 5 mm diameter SUS probe with the adhesive surface of the test piece with a pressure of 100 g for 5 seconds, and then pulling it away in the direction perpendicular to the adhesive surface at a rate of 5 mm / sec, and the peak tackiness at the time of pulling it away was taken as the probe tackiness. In the cold seal adhesive composition of the present invention, the probe tackiness can be adjusted by changing the amount of wax and tackifying resin added.

[0029] Furthermore, if the pressure-sensitive adhesive strength is less than 3 N / 15 mm, the adhesive will easily peel off with a weak force after adhesion, which is not preferable for applications that do not require re-peeling, such as adhesive envelopes and packaging materials. The pressure-sensitive adhesive strength is preferably 5 N / 15 mm or more, more preferably 10 N / 15 mm or more. This pressure-sensitive adhesive strength includes the following two types of pressure-sensitive adhesive strength.

[0030] The pressure-sensitive adhesive strength (face-to-face) is the peel strength measured when a test sheet prepared by laminating the adhesive surfaces of two PET films coated with the cold seal adhesive composition is peeled in a T-shape. The test sheet is prepared by coating a 25 μm-thick PET film with the cold seal adhesive composition to a thickness of 30 μm to produce an adhesive-coated film, and then laminating the adhesive surfaces of the adhesive-coated films together using a 2 kg roller in a 23°C atmosphere. After 30 minutes, the resulting sheet is cut into 15 mm-wide strips. The value is measured by T-shape peeling the test sheet at a 23°C atmosphere at a pulling rate of 300 mm / min. In the cold seal adhesive composition of the present invention, the pressure-sensitive adhesive strength can be improved by increasing the amount of thermoplastic block copolymer and / or tackifier resin.

[0031] The pressure-sensitive adhesive strength (to PET) is the peel strength measured when a test sheet prepared by laminating the adhesive surface of a PET film coated with a cold seal adhesive composition to a PET film not coated with the adhesive composition is peeled in a T-shape. The test sheet is prepared by coating a 25 μm-thick PET film with a 30 μm-thick cold seal adhesive composition to produce an adhesive-coated film, and then laminating the adhesive surface of the adhesive-coated film to the PET film not coated with the adhesive composition by rolling a 2 kg roller back and forth once in an atmosphere of 23°C. After 30 minutes, the resulting sheet is cut into 15 mm-wide strips. The value is measured by peeling the test sheet in a T-shape at a pulling rate of 300 mm / min in an atmosphere of 23°C.

[0032] A method for using the cold seal adhesive composition according to the present invention includes at least the steps of applying the cold seal adhesive composition to a substrate and contacting the adhesive layer of the substrate to which the cold seal adhesive composition has been applied with an adherend or contacting the adhesive layers with each other. Between the two steps, the method may further include the steps of cooling the cold seal adhesive composition applied to the substrate, winding the substrate to which the cold seal adhesive composition has been applied into a roll, and transporting the wound roll to a place of use, and preferably includes the step of cooling the cold seal adhesive composition applied to the substrate.

[0033] The process of applying the cold seal adhesive composition to a substrate will now be described. The cold seal adhesive composition obtained by kneading the components is pumped from a melting tank using various pumps and applied. The device used to apply the composition to the substrate is not particularly limited, and conventionally known devices can be used, such as a roll coater, slot orifice coater, head coater, extrusion coater, hand gun, and applicator. Examples of substrates to which the cold seal adhesive composition of the present invention can be applied include paper, wood, plastic moldings, plastic films, metals, glass, and ceramics. The shape of the applied adhesive is not particularly limited, and may be linear, thread-like, bead-like, dot-like, spiral, spider web-like, fibrous, or full-surface application, and any appropriate application device can be used. The application temperature for the cold seal adhesive composition of the present invention varies depending on the adhesive composition and application device, but is typically 100°C to 200°C, preferably 120°C to 180°C.

[0034] Next, the substrate coated with the adhesive composition is cooled to room temperature as needed, and the adhesive layer on the substrate is brought into contact with the adherend or the adhesive layers themselves, and adhesion is easily completed by applying a load, such as by finger pressure, as appropriate. The cold seal adhesive composition of the present invention does not adhere to adherends such as paper and wood at room temperature, but can adhere to adherends with smooth surfaces such as polyethylene terephthalate (PET) film, polypropylene (PP) film, glass, and metal. The cold seal adhesive composition of the present invention can be used to bond a variety of articles, and is particularly suitable for bonding packaging materials, envelopes, labels, and the like.

[0035] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples as long as they do not depart from the gist of the invention. In the examples, parts and percentages are by mass unless otherwise specified.

[0036] The physical properties measured in the examples and comparative examples are as follows. <Evaluation of melt viscosity> In accordance with the Japan Adhesives Industry Association standard JAI-7-1999, the melt viscosity was measured at a temperature of 180°C using a Brookfield B-type viscometer digital rheometer DV-11 (rotor No. 27) and evaluated according to the following criteria: ○ 3,000 mPa·s or more and 30,000 mPa·s or less △ More than 30,000 mPa·s and 50,000 mPa·s or less × More than 50,000 mPa·s

[0037] <Evaluation of Probe Adhesion Strength> A test specimen was prepared by applying the cold seal adhesive composition to a PET film (25 μm thick) to a thickness of 30 μm. This test specimen was fixed on a stage in an atmosphere of 23°C, and a 5 mm diameter SUS probe was brought into contact with the test specimen from above the adhesive surface at a pressure of 100 g for 5 seconds, and the probe was immediately pulled upward at a rate of 5 mm / second. The load value at the time of pulling was taken as the probe adhesion strength and evaluated according to the following criteria: ◎ Less than 300 gf ○ 300 gf or more but less than 500 gf Δ 500 gf or more but less than 700 gf × 700 gf or more

[0038] <Evaluation of Pressure-Sensitive Adhesive Strength> An adhesive-coated film was prepared by coating a PET film (25 μm thick) with a cold seal adhesive composition to a thickness of 30 μm. In an atmosphere of 23°C, the adhesive surfaces of the adhesive-coated films were placed face to face (face to face) or the adhesive surface was placed against a PET film not coated with adhesive (against PET), and the films were laminated by rolling a 2 kg roller back and forth once. After 30 minutes, the laminated film was cut into 15 mm wide strips to prepare test sheets. In an atmosphere of 23°C, the test sheets were peeled in a T-shape at a pulling rate of 300 mm / min. The peel strength was evaluated as pressure-sensitive adhesive strength according to the following criteria: ◎ 10 N / 15 mm or more; ◯ 5 N / 15 mm or more, less than 10 N / 15 mm; Δ 3 N / 15 mm or more, less than 5 N / 15 mm; × Less than 3 N / 15 mm

[0039] The raw materials used in the examples and comparative examples are as follows: Affinity GA1900 (manufactured by Dow, ethylene-1-octene random copolymer, density 0.87 g / cm ３, melt viscosity 8,200 mPa s (177 ° C), melting point 68 ° C) Vistamaxx 8780 (manufactured by ExxonMobil, propylene-ethylene random copolymer, density 0.864 g / cm ３ , melt viscosity 3,980 mPa s (190 ° C), melting point 96 ° C) REXtac 2330 (manufactured by REXtac, amorphous poly-α-olefin, density 0.89 g / cm ３ , melt viscosity 3,000 mPa·s (190°C), melting point 141°C) Ultrathene 735 (manufactured by Tosoh, ethylene-vinyl acetate copolymer)

[0040] (B) Thermoplastic block copolymers Infuse 9507 (manufactured by Dow, ethylene-1-octene block copolymer) Dynaron 6200P (manufactured by JSR, crystalline olefin-ethylene-butylene-crystalline olefin block polymer (CEBC)) Kraton G1657 (manufactured by Kraton, styrene-ethylene-butylene-styrene block copolymer (SEBS)) Septon 2063 (manufactured by Kuraray, styrene-ethylene-propylene-styrene block copolymer (SEPS)) Asaprene N515 (manufactured by Asahi Kasei, styrene-butadiene-butylene-styrene block copolymer (SBBS)) Septon BIO-series SF904 (manufactured by Kuraray, styrene-farnesene-styrene block copolymer) Kurariti LA2250 (manufactured by Kuraray, methyl methacrylate-butyl acrylate-methyl methacrylate block copolymer)

[0041] (C) Tackifying resins YS Resin PX1000 (Yasuhara Chemical, terpene resin, softening point 100°C) YS Resin TO105 (Yasuhara Chemical, aromatic modified terpene resin, softening point 105°C) T-REZ HA105 (ENEOS, hydrogenated dicyclopentadiene resin, softening point 105°C) T-REZ HA125 (ENEOS, hydrogenated dicyclopentadiene resin, softening point 125°C) T-REZ HB103 (ENEOS, hydrogenated dicyclopentadiene / C9 resin, softening point 103°C) Alcon P100 (Arakawa Chemical Industries, hydrogenated C9 resin, softening point 100°C) Alcon M100 (manufactured by Arakawa Chemical Industries, hydrogenated C9 resin, softening point 100°C) Neopolymer L90 (manufactured by ENEOS, C9 resin, softening point 90°C) Super Ester A100 (manufactured by Arakawa Chemical Industries, rosin ester, softening point 100°C)

[0042] (D) Wax or plasticizer Sasol H1 (manufactured by Sasol, Fischer-Tropsch wax, melting point 112°C) Hiwax 110P (manufactured by Mitsui Chemicals, polyethylene wax, melting point 109°C) Viscol 660P (manufactured by Sanyo Chemical Industries, polypropylene wax, melting point 145°C) Ricothene 1302 (manufactured by Clariant, polypropylene / polyethylene wax, melting point 82°C) SS-2 (manufactured by Boso Oil & Fats, rice bran wax, melting point 79°C) Process oil PW90 (manufactured by Idemitsu Kosan, paraffin oil)

[0043] Other ingredients (antioxidants): Sonnox 1010FF (manufactured by Songwon Industrial, hindered phenol antioxidant)

[0044] Examples 1 to 28 and Comparative Examples 1 to 11 Adhesive compositions were prepared by heating the components according to the formulations shown in Tables 1 to 3 at 160°C for 1 hour to uniformly mix and dissolve them. The melt viscosity, probe tack and adhesive strength of each resulting composition were measured and evaluated using the methods described above. The results are shown in Tables 1 to 3.

[0045] As can be seen from Tables 1 and 2 (Examples), the cold seal adhesive composition of the present invention has a melt viscosity of less than 50,000 mPa·s, and therefore exhibits good applicability to substrates. Furthermore, while the adhesive surfaces exhibit excellent pressure-sensitive adhesive strength of 3 N / 15 mm or more, as can be seen from the probe tack of less than 700 gf, the surface tack at room temperature is low, resulting in weak adhesion to paper substrates and other substrates, demonstrating favorable performance as a cold seal adhesive. In contrast, Table 3 (Comparative Examples) reveals the following: When the raw materials corresponding to component (A) and component (C) are not those specified in the present invention (Comparative Examples 1, 2, 8, and 9), or when the blending ratios of the raw materials corresponding to component (C) and component (D) are higher than the ranges specified in the present invention (Comparative Examples 4, 7, and 10), sufficient pressure-sensitive adhesive strength is not exhibited. Furthermore, when the blending ratio of the raw materials corresponding to component (C) is lower than the range specified in the present invention (Comparative Examples 5 and 6), the melt viscosity becomes too high and adhesive strength is not exhibited. When the blending ratio of the raw material corresponding to component (B) is higher than the range specified in the present invention (Comparative Example 3), the melt viscosity becomes too high, resulting in poor application properties. Also, when the proportion of wax in component (D) is less than 50 mass% (Comparative Example 11), the probe adhesion becomes too high.

[0046]

[0047]

[0048]

[0049] According to the present invention, it is possible to provide a cold seal adhesive composition that can adhere even in a humid environment and has excellent adhesion and safety. Suitable applications of the cold seal adhesive composition of the present invention include packaging bags, envelopes, labels, etc.

Claims

1. A cold seal adhesive composition containing 20 to 65 mass% of (A) an α-olefin copolymer, 0 to 25 mass% of (B) a thermoplastic block copolymer, 20 to 65 mass% of (C) a tackifying resin, and 0 to 20 mass% of (D) a wax and / or plasticizer (wherein the total of components (A), (B), (C), and (D) is 100 mass%), wherein the cold seal adhesive composition has a probe tack of less than 700 gf and a pressure-sensitive adhesive strength of 3 N / 15 mm or greater between the adhesive composition and an adherend or between the adhesive compositions themselves.

2. The adhesive composition for cold sealing according to claim 1, which has a melt viscosity at 180°C of 3,000 to 50,000 mPa·s.

3. The cold seal adhesive composition according to claim 1 or 2, wherein component (A) has a melt viscosity at 180°C of 30,000 mPa·s or less and a melting point of 110°C or less.

4. The density of component (A) is 0.88 g / cm ３ 3. The cold seal adhesive composition according to claim 1, wherein the viscosity is less than 1000 MPa.

5. The cold seal adhesive composition according to claim 1 or 2, wherein the α-olefin monomer constituting component (A) is at least one selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene.

6. The cold seal adhesive composition according to claim 1 or 2, wherein component (A) is at least one selected from the group consisting of ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, propylene-1-butene copolymer, propylene-1-hexene copolymer, and propylene-1-octene copolymer.

7. The cold seal adhesive composition according to claim 1 or 2, wherein component (A) is polymerized using a metallocene catalyst.

8. A cold seal adhesive composition according to claim 1 or 2, wherein component (B) is a block copolymer consisting of at least one hard segment and at least one soft segment, the main constituent monomer of which is one or more selected from styrene, olefins, and acrylic acids.

9. The adhesive composition for cold seal applications according to claim 1 or 2, wherein component (C) is at least one selected from the group consisting of terpene resins and hydrogenated petroleum resins.

10. An adhesive composition for cold sealing according to claim 1 or 2, wherein the proportion of the plasticizer in component (D) is less than 50% by mass of the entire component (D).

11. The cold seal adhesive composition according to claim 1 or 2, wherein the wax is at least one selected from the group consisting of Fischer-Tropsch wax, polyethylene wax, polypropylene wax, vegetable wax and hydrogenated fats and oils.

12. The cold seal adhesive composition according to claim 1 or 2, wherein the wax has a melting point of 60°C to 160°C.

13. A method for using a cold seal adhesive composition, comprising the steps of applying the cold seal adhesive composition according to claim 1 or 2 to a substrate, and contacting the adhesive layer of the substrate to which the cold seal adhesive composition has been applied with an adherend, or contacting the adhesive layers with each other.

14. A packaging bag using the cold seal adhesive composition according to claim 1 or 2.

15. An envelope using the cold seal adhesive composition according to claim 1 or 2.

16. A label using the cold seal adhesive composition according to claim 1 or 2.

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