Hot melt adhesive for sealing envelopes and laminate using said hot melt adhesive

Abstract

To provide a hot-melt adhesive which has appropriate seal performance and adhesive strength for sealing an envelope sealing a content, and has such adhesive strength and impact resistance as to prevent scattering of the content at the time of conveyance at low temperature atmosphere of -20°C or lower and falling.SOLUTION: A hot-melt adhesive for sealing an envelop contains 10-30 mass% of a wax (A) having a melting point of 60-90°C, 1-9 mass% of a styrenic elastomer (B), 35-55 mass% of an olefinic polymer (C), and 20-40 mass% of a tackifier resin (D) having a softening point of 90-130°C, wherein a melt flow rate measured under conditions of a load of 21.18 N and 230°C of the styrenic elastomer (B) is 5-10 g / 10 min, and a melt flow rate measured under conditions of a load of 21.18 N and 190°C of the olefinic polymer (C) is 600-1,400 g / 10 min.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a hot melt adhesive for sealing envelopes, and more specifically to a hot melt adhesive for sealing envelopes that has excellent adhesive strength in a low-temperature atmosphere and cold impact resistance. [Background technology]

[0002] When sealing bags for use as postal envelopes or document holders, a flap is generally attached to the opening edge of the bag body and folded over to the back side of the bag body to close the opening. In this case, the back side of the flap that covers the opening of the bag is coated with water-based glue or hot melt adhesive and attached, or adhesive tape is used to seal the bag.

[0003] In view of this, hot melt adhesives that can be used for envelopes and the like have been proposed in the past, as shown in Patent Document 1 below.

[0004] Patent Document 1 discloses a hot melt adhesive that is composed of an olefin polymer, a styrene elastomer, a tackifier resin, and a wax having a number average molecular weight of 200 to 3000, and has excellent high-temperature and low-temperature adhesive properties.

[0005] However, the hot melt adhesive of Patent Document 1 has a problem in that it is poor in cold impact resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP2015-120825A Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, conventional hot melt adhesives had the problem that in cold regions with low-temperature atmospheres of -20°C or below, the adhesive strength and cold impact resistance of the hot melt adhesive decreased, causing the envelope to open due to impact when transported or dropped, causing the contents to scatter.

[0008] The present invention aims to provide a hot melt adhesive that has appropriate sealing performance and adhesive strength for sealing an envelope containing contents, and has adhesive strength and impact resistance that prevents the contents from scattering even when the envelope is dropped or transported in a low-temperature atmosphere of -20°C or below. [Means for solving the problem]

[0009] The present invention relates to a composition for producing a tackifier resin composition comprising: a wax (A) having a melting point of 60°C to 90°C; a styrene-based elastomer (B); an olefin-based polymer (C); and a tackifier resin (D) having a softening point of 90 to 130°C, The melt flow rate of the styrene-based elastomer (B) measured under a load of 21.18 N and at 230°C is 5 to 10 g / 10 min., and The melt flow rate of the olefin polymer (C) measured under a load of 21.18 N and at 190°C is 600 to 1,400 g / 10 min. With respect to the total mass of the wax (A), the styrene-based elastomer (B), the olefin-based polymer (C), and the tackifier resin (D), Wax (A) 10 to 30 mass %, 1 to 9 mass% of a styrene-based elastomer (B), 35 to 55% by mass of an olefin-based polymer (C), and Tackifier resin (D) 20~40% by mass, The present invention relates to a hot melt adhesive for sealing envelopes, comprising:

[0010] The present invention also relates to the above hot melt adhesive for sealing envelopes, wherein the tackifier resin (D) contains a petroleum-based tackifier resin (D1) having a softening point of 90°C or higher and lower than 110°C and a petroleum-based tackifier resin (D2) having a softening point of 110°C or higher and 130°C or lower.

[0011] The present invention also relates to a laminate in which a hot melt adhesive layer formed from the above hot melt adhesive is laminated on one or both sides of a paper substrate. Effect of the Invention

[0012] The present invention has made it possible to provide a hot melt adhesive that has the appropriate sealing performance and adhesive strength for sealing an envelope containing enclosed contents, and has adhesive strength and impact resistance that prevents the contents from scattering even when the envelope is dropped or transported in a low-temperature atmosphere of -20°C or below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention is a hot melt adhesive containing a specific wax, an olefin-based polymer, a styrene-based elastomer, and a tackifier resin, and has strong adhesive strength and impact resistance in low-temperature environments of -20°C or below, thereby achieving the effect of achieving suitability for use as a hot melt adhesive for sealing envelopes even in cold regions. The present invention will be described in detail below.

[0014] In this specification, unless otherwise specified, a numerical range specified using "~" is intended to include the numerical values ​​before and after "~" as the lower and upper limit values ​​of the range.

[0015] <Wax (A)> Examples of the wax (A) constituting the hot melt adhesive of the present invention include synthetic waxes such as Fischer-Tropsch wax, paraffin wax, microcrystalline wax, montan wax, polyethylene wax, polypropylene wax, polyethylene-polypropylene wax, carnauba wax, low molecular weight polyethylene, low molecular weight polypropylene, low molecular weight ethylene-propylene copolymer, oxide of low molecular weight ethylene-propylene copolymer, low molecular weight ethylene-butene copolymer, low molecular weight propylene-butene-ethylene copolymer, styrene graft of low molecular weight ethylene-propylene copolymer, maleic anhydride oxide of ethylene-propylene copolymer, maleic anhydride oxide of propylene-butene-ethylene copolymer, and the like. Among them, Fischer-Tropsch wax, which has excellent thermal stability and low viscosity, is preferred. These waxes may be used alone or in combination.

[0016] The melting point of the wax (A) is 60 to 90°C, and more preferably 65 to 85°C. When the wax has a melting point of 60 to 90°C, the adhesive strength can be maintained in a low-temperature atmosphere. In the present invention, the melting point is the peak temperature when the temperature rises at a rate of 10°C / min in a differential scanning calorimeter (DSC) measurement. Details will be described in the Examples section.

[0017] <Styrene-based elastomer (B)> The styrene-based elastomer (B) has a melt flow rate (hereinafter, MFR) measured under conditions of a load of 21.18 N and 230° C. in the range of 5 to 10 (g / 10 min), and more preferably 6 to 9 (g / 10 min). By having an MFR of 5 to 10 (g / 10 min), it is possible to impart heat resistance to the hot melt adhesive. The styrene-based elastomer (B) preferably contains at least one selected from the group consisting of styrene-butadiene-styrene block copolymer (hereinafter also abbreviated as "SBS"), hydrogenated styrene-butadiene-styrene block copolymer (hereinafter also abbreviated as "SEBS"), styrene-isoprene-styrene block copolymer (hereinafter also abbreviated as "SIS"), hydrogenated styrene-isoprene-styrene block copolymer (hereinafter also abbreviated as "SEPS"), styrene-butadiene-isoprene-styrene block copolymer (hereinafter also abbreviated as "SBIS"), and hydrogenated styrene-butadiene-isoprene-styrene block copolymer (hereinafter also abbreviated as "SEEPS"). The copolymers may be carboxyl-modified, and the styrene block in the copolymer may contain a copolymer of styrene and other aromatic vinyl compounds such as α-methylstyrene.The styrene elastomer (B) preferably contains styrene in an amount of 3 to 30% by weight because of its excellent flexibility. The styrene-based elastomer (B) can be used alone or in combination of two or more. SEPS is preferred because of its excellent thermal stability, adhesive strength in low-temperature atmospheres, and impact resistance. The styrene-based elastomer (B) is not limited to those having only triblock structural parts, and may also have a diblock structural part in part. The content of the diblock structural part is preferably 50% by weight or less from the viewpoint of excellent adhesive strength.

[0018] <Olefin Polymer (C)> The olefin polymer (C) has an MFR in the range of 600 to 1,400 g / 10 min under conditions of 190° C. and 21.18 N. When the MFR is in the range of 600 to 1,400 g / 10 min, excellent processability during coating is achieved. The copolymer may be an olefin homopolymer or an olefin copolymer, and specific examples thereof include homopolymers such as polyethylene, polypropylene, polybutene, polyisobutylene, polypentene, polyhexene, polyheptene, polyoctene, and polydetene; copolymers of ethylene and an olefin other than ethylene and propylene; copolymers of propylene and an olefin other than ethylene and propylene; and copolymers of olefins other than ethylene and propylene and olefins other than ethylene and propylene.

[0019] As the olefin other than ethylene and propylene in the copolymer of ethylene and olefin other than ethylene and propylene, an olefin having 4 to 10 carbon atoms is preferred. Specifically, ethylene-1-butene copolymer, ethylene-1-pentene copolymer, ethylene-1-hexene copolymer, ethylene-1-heptene copolymer, ethylene-1-octene copolymer, ethylene-1-nonene copolymer, ethylene-1-decene copolymer, ethylene-cis-2-butene copolymer, ethylene-trans-2-butene copolymer, ethylene-isobutylene copolymer, ethylene-cis-2-pentene copolymer, ethylene-trans-2-pentene copolymer, ethylene-3-methyl-1-butene copolymer, ethylene-2-methyl-2-butene copolymer, and ethylene-2,3-dimethyl-2-butene copolymer are mentioned. Among these, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, and ethylene-1-octene copolymer are preferred in terms of excellent flexibility and adhesive strength in a low-temperature atmosphere, and ethylene-1-octene copolymer is particularly preferred.

[0020] In the copolymer of propylene with ethylene and an olefin other than propylene, the olefin other than ethylene and propylene is preferably an olefin having a carbon number of 4 to 10. Specific examples thereof include a propylene-1-butene copolymer, a propylene-1-pentene copolymer, a propylene-1-hexene copolymer, a propylene-1-heptene copolymer, a propylene-1-octene copolymer, a propylene-1-nonene copolymer, a propylene-1-decene copolymer, a propylene-cis-2-butene copolymer, a propylene-trans-2-butene copolymer, a propylene-isobutylene copolymer, a propylene-cis-2-pentene copolymer, a propylene-trans-2-pentene copolymer, a propylene-3-methyl-1-butene copolymer, a propylene-2-methyl-2-butene copolymer, and a propylene-2,3-dimethyl-2-butene copolymer. Among these, propylene-1-octene copolymer is preferred because it has excellent flexibility and adhesive strength in a low-temperature atmosphere.

[0021] Examples of copolymers of olefins other than ethylene and propylene with olefins other than ethylene and propylene include butene-1-hexene copolymers, butene-1-octene copolymers, butene-1-decene copolymers, hexene-1-octene copolymers, hexene-1-decene copolymers, and octene-1-decene copolymers. Among these, butene-1-octene copolymer is preferred because it has excellent flexibility and adhesive strength in a low-temperature atmosphere.

[0022] The olefin-based polymer (C) may be used alone or in combination of two or more kinds, but it is preferable that the polymer contains an ethylene-1-octene copolymer, because it is excellent in flexibility and adhesive strength in a low-temperature atmosphere.

[0023] <Tackifying resin (D)> Examples of the tackifier resin (D) include terpene resins, hydrogenated terpene resins, rosin resins, hydrogenated rosin resins, hydrocarbon resins, hydrogenated hydrocarbon resins, epoxy resins, hydrogenated epoxy resins, polyamide resins, hydrogenated polyamide resins, elastomer resins, hydrogenated elastomer resins, phenol resins, hydrogenated phenol resins, ketone resins, hydrogenated ketone resins, petroleum resins, hydrogenated petroleum resins, styrene resins, and hydrogenated styrene resins. Among these, hydrogenated petroleum resins are preferred because they are colorless, transparent, and have excellent heat resistance. These tackifier resins can be used alone or in combination of two or more.

[0024] The softening point of the tackifier resin (D) is 90 to 130° C., more preferably 92 to 128° C. Furthermore, it is particularly preferable to use a tackifier resin (D1) having a softening point of 90° C. or more and less than 110° C. in combination with a tackifier resin (D2) having a softening point of 110° C. to 130° C. The softening point of the tackifier resin (D1) is more preferably 92° C. to 108° C., and even more preferably 95° C. to 105° C. The softening point of the tackifier resin (D2) is more preferably 112° C. to 128° C., and even more preferably 114° C. to 127° C. By using the tackifier resin (D1) and the tackifier resin (D2) in combination, a hot melt adhesive having excellent adhesive strength in low temperature and high temperature atmospheres can be obtained. The softening point in the present invention is a temperature determined by the method specified in JIS K 6863. Details will be described in the Examples section.

[0025] <Blend amount> The content of the wax (A) constituting the hot melt adhesive of the present invention is 10 to 30% by mass, preferably 12 to 28% by mass. The content of the styrene-based elastomer (B) is 1 to 9% by mass, preferably 2 to 8% by mass. The content of the olefin-based polymer (C) is 35 to 55% by mass, preferably 37 to 53% by mass. The content of the tackifier resin (D) is 20 to 40% by mass, preferably 22 to 38% by mass. However, the above contents are values ​​when the total of the wax (A), the styrene-based elastomer (B), the olefin-based polymer (C), and the tackifier resin (D) is taken as 100% by mass.

[0026] When the content of the tackifier resin (D) is 20 to 40 mass% relative to 100 mass% of the total of the wax (A), the styrene-based elastomer (B), the olefin-based polymer (C), and the tackifier resin (D), the content of the tackifier resin (D1) is preferably 15 to 25 mass%, and the content of the tackifier resin (D2) is preferably 5 to 15 mass%. Furthermore, when the content of the tackifier resin (D) is 22 to 38 mass% relative to 100 mass% of the total of the wax (A), the styrene-based elastomer (B), the olefin-based polymer (C), and the tackifier resin (D), the content of the tackifier resin (D1) is preferably 16 to 24 mass%, and the content of the tackifier resin (D2) is preferably 6 to 14 mass%.

[0027] <Other ingredients> Additives such as antioxidants, silane coupling agents, silicone oils, and antiblocking agents may be added to the hot melt adhesive of the present invention as long as the object of the invention is not impaired.

[0028] Examples of the antioxidant include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, diethyl [[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate, 4,6-bis(octylthiomethyl)-o-cresol, ethylene bis(oxyethylene) bis[3-(5-t-butyl-4-hydroxy-m-tolyl]propionate, tris(2,4-di-t-butylphenyl)phosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, etc. These antioxidants may be used alone or in combination of two or more.

[0029] The silane coupling agent is not particularly limited, and examples thereof include vinyl trimethoxysilane, vinyl triethoxysilane, methacryloxypropyl trimethoxysilane, γ-methacryloxypropyl methyl dimethoxysilane, γ-glycidoxypropyl trimethoxysilane, γ-glycidoxypropyl methyl dimethoxysilane, γ-glycidoxypropyl methyl diethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, γ-aminopropyl trimethoxysilane, γ-aminopropyl triethoxysilane, γ-aminopropyl methyl methoxysilane, N-(2-aminoethyl) 3-aminopropyl trimethoxysilane, N-(2-aminoethyl) 3-aminopropyl methyl dimethoxysilane, γ-mercaptopropyl trimethoxysilane, γ-mercaptopropyl triethoxysilane, mercaptobutyl trimethoxysilane, and γ-mercaptopropyl methyl dimethoxysilane. These silane coupling agents may be used alone or in combination of two or more.

[0030] Examples of silicone oils include dimethyl silicone oil, methyl phenyl silicone oil, methyl hydrogen silicone oil, modified silicone oils such as reactive silicone oil and non-reactive silicone oil, etc. These can be used alone or in combination of two or more kinds.

[0031] As the blocking inhibitor, for example, inorganic fine powder and organic fine powder can be used. As inorganic fine powder, heavy calcium carbonate, light calcium carbonate, silica, talc, clay, silicic acid fine powder, synthetic silicate, precipitated barium sulfate, calcium silicate, aluminum hydroxide, etc. can be used, and as organic fine powder, fillers made of heat-resistant polyethylene, polypropylene, urethane, acrylic, nylon, urea-based resin, etc., styrene crosslinked filler, benzoguanamine crosslinked filler, citric acid fatty acid monoglyceride, glycerin monostearate, glycerin monobehenate, glycerin monooleate, etc. can be used alone or in combination of two or more.

[0032] The amount of additives such as antioxidants, silane coupling agents, silicone oils, and antiblocking agents that can be added within a range that does not impair the object of the present invention is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, based on 100% by mass of the total of (A) to (D). By making the amount of additives 0 to 10% by mass, bleeding out of optional components is less likely to occur.

[0033] <Manufacturing method> The method for producing the hot melt adhesive of the present invention is not particularly limited, and any method can be used, such as the hot melt method in which the adhesive is heated and mixed using a mixing roll, roll, Banbury mixer, single-screw or twin-screw extruder, kneader, extruder, melt extruder, or melting kettle equipped with a stirrer, or the solvent method in which the adhesive is dissolved in a suitable solvent, but the hot melt method is preferred because it has a smaller impact on the environment.

[0034] <Coating method> The hot melt adhesive of the present invention is preferably applied at 150 to 190°C to prevent deterioration caused by application of excessive heat, and is also compatible with rolls that require application at low viscosity and melting kettles equipped with stirrers for melting. From this perspective, the hot melt adhesive of the present invention preferably has a viscosity at 180°C of 500 to 5,000 mPa·s, more preferably 550 to 4,950 mPa·s, and even more preferably 600 to 4,900 mPa·s. With a viscosity in the range of 500 to 5,000 mPa·s at 180°C, the hot melt adhesive does not drip even when a large amount is applied, ensuring ease of use during application. The viscosity of the hot melt adhesive was measured using a Brookfield viscometer, and details are given in the Examples section.

[0035] The hot melt adhesive of the present invention can be applied in various patterns such as bead, mirror, foamed, spiral, and foamed by using a coating machine or hot melt coating machine that is normally used on a sheet-like substrate such as paper or resin, and then heated and cooled as necessary to form a hot melt adhesive layer, thereby obtaining various laminates in which hot melt adhesive layers are laminated. The hot melt adhesive layers can be coated in layers, or two types of hot melt adhesive layers can be coated in parallel on the same sheet-like substrate.

[0036] The substrate is preferably a paper substrate composed of at least one selected from a resin sheet and paper. For example, the resin sheet may be a resin sheet formed from an olefin resin such as polyethylene or polypropylene, a polyethylene terephthalate resin, or a polystyrene resin. For paper, Yupo paper, coated paper, fine paper, cardboard, or the like may be used. The resin sheet or paper may be used alone or in combination. The paper may be coated with varnish, rewettable paste, or ink.

[0037] The layer structure of the laminate is not particularly limited, but preferred examples include "coated paper / hot melt adhesive / coated paper" and "high-quality paper / hot melt adhesive / high-quality paper." EXAMPLES

[0038] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, "parts" and "%" respectively mean "parts by mass" and "% by mass" unless otherwise specified.

[0039] The melting point, MFR and softening point were measured by the following methods.

[0040] [Melting point] Using a differential scanning calorimeter (DSC, device name: DSC-60A Plus), about 2.5 mg of the sample was weighed onto a crimp cell, the temperature was raised at 10°C / min, and the endothermic peak temperature of the obtained chart was read. The value at the peak top was taken as the melting point. [MFR] It was determined by the method specified in JIS K 7210. Specifically, a certain amount of resin was placed in a cylindrical container heated by a heater at a temperature of 190°C (olefin-based polymer) or 230°C (styrene-based elastomer) and pressurized with a load of 21.18N, and the amount of resin extruded per 10 minutes from an opening (nozzle) at the bottom of the container was measured and expressed in "g / 10 min." [Softening point] It was determined by the method specified in JIS K 6863. Specifically, a specified ring filled with a resin composition was left to stand for 12 hours or more, and then placed in a heating medium of glycerin, and a specified ball was placed on the specified ring filled with the resin composition, and the temperature of the heating medium was increased at a constant rate. The softening point was determined as the temperature at which the ball sank due to softening of the resin composition and touched the bottom plate of the ring stand. [viscosity] Measurements were performed using a Brookfield viscometer (Toki Sangyo Co., Ltd., model number: RB-85L) under the following conditions. Temperature: 180℃ Sample size: 300g Rotor No.:3 Rotor speed: 30 rpm Rotation time: 30 seconds

[0041] <Manufacturing of hot melt adhesives> [Example 1] The wax (A), styrene-based elastomer (B), olefin-based polymer (C), and tackifier resin (D) were added to a kettle equipped with a stirrer in the amounts and materials shown in Table 1, and stirred at 150°C for 3 hours to obtain the hot melt adhesive of Example 1. [Examples 2 to 18, Comparative Examples 1 to 9] According to the compositions in Tables 1 to 3, the hot melt adhesives of Examples 2 to 18 and Comparative Examples 1 to 9 were obtained in the same manner as in Example 1.

[0042] The abbreviations in Tables 1 to 3 are shown below. <Wax (A)> Wax 1: Fischer-Tropsch wax (manufactured by Sasol Chemical Industrial, product name: Sasol C80, melting point 82°C) Wax 2: Fischer-Tropsch wax (manufactured by Qingdao Bouni Chemical Co., Ltd., product name: FT WAX T70, melting point 74°C) Wax 3: Paraffin wax (King Honor International, product name: KH Paraffin 80M, melting point 79°C) Wax 4: Paraffin wax (manufactured by Nippon Seiro Co., Ltd., product name: Paraffin wax 150, melting point 66°C) Wax 5: Polyethylene wax (manufactured by Mitsui Chemicals, product name: Hiwax 200P, melting point 124°C) <Styrene-based elastomer (B)> Styrene-based elastomer 1: SEPS (manufactured by Kuraray, product name: Septon 2063, MFR: 7g / 10min) Styrene-based elastomer 2: SEBS (Kraton Polymer Japan, product name: Kraton G1652, MFR: 1g / 10min) Styrene-based elastomer 3: SEBS (Kraton Polymer Japan, product name: Kraton G1657, MFR: 9g / 10min) <Olefin Polymer (C)> Olefin polymer 1: Ethylene-1-octene copolymer (SK Global Chemical, product name: Solutack 6810, MFR: 1000 g / 10 min) Olefin polymer 2: Ethylene-1-octene copolymer (Dow Chemical Company, product name: Affinity GA 1875, MFR: 1250 g / 10 min) Olefin polymer 3: Ethylene-1-octene copolymer (manufacturer: SK Global Chemical, product name: Solutack7405, MFR: 500g / 10min) Olefin polymer 4: Ethylene-1-octene copolymer (manufacturer: Dow Chemical Company, product name: Affinity GA 1000R, MFR: 660g / 10min) <Tackifying resin (D)> Tackifying resin 1: Hydrogenated C5 petroleum resin (Idemitsu Kosan Co., Ltd., product name: Imave P-100, softening point 100°C) Tackifying resin 2: Hydrogenated C9 petroleum resin (manufactured by Arakawa Chemical Industries, product name: Alcon M-90, softening point 90°C) Tackifier resin 3: Rosin ester resin (manufactured by Arizona Chemical Company, product name: SYLVALITE RE105L, softening point 104°C) Tackifying resin 4: Hydrogenated C9 petroleum resin (manufactured by Arakawa Chemical Industries, product name: Alcon P-115, softening point 115°C) Tackifying resin 5: Hydrogenated C9 petroleum resin (manufactured by Arakawa Chemical Industries, product name: Alcon P-125, softening point 125°C) Tackifier resin 6: C9 petroleum resin (manufactured by Tosoh Corporation, product name: Petcole 120, softening point 120°C) Tackifying resin 7: Hydrogenated C9 petroleum resin (manufactured by Arakawa Chemical Industries, product name: Alcon P-140, softening point 140°C) <Other ingredients> Antioxidant 1: Antioxidant (manufactured by Songwon Industrial, product name: Sonnox 21B)

[0043] <Preparation of test pieces for adhesive strength test> [Examples 1 to 18, Comparative Examples 1 to 9] The obtained hot melt adhesive was heated to 180°C and applied in the form of a bead onto a 25 mm x 60 mm coated paper at a coating weight of 1 g / m. This was then bonded to another 25 mm x 60 mm coated paper with an open time of 2 seconds to produce a laminate with a structure of "coated paper / hot melt adhesive / coated paper", which was designated as test piece 1.

[0044] <Evaluation of test specimens> The adhesive strength (at −20° C., 23° C. and 40° C.) of the obtained test piece 1 was evaluated according to the method described below. The results are shown in Table 1.

[0045] Test piece 1 was folded into a T shape and placed in a tensile tester and conditioned at each temperature (-20°C, 23°C, 40°C) for 15 minutes. After that, a T-shaped peel was performed at a speed of 200 mm / min, and the maximum strength at the time of peeling was taken as the adhesive strength (N / 25 mm). Measurements were performed at n=3 points for each test piece, and the average value was calculated and judged according to the following criteria. ◯ was judged to be practical. [Adhesive strength at -20℃] 〇: 2.0N or more ×: Less than 2.0N [Adhesive strength at 23℃] 〇: 3.0N or more ×: Less than 3.0N [Adhesive strength at 40℃] 〇: 2.0N or more ×: Less than 2.0N

[0046] <Preparation of test specimens for cold shock resistance test> [Examples 1 to 18, Comparative Examples 1 to 9] The obtained hot melt adhesive was heated to 180°C and applied in a bead shape to a 25 mm width of 25 mm x 100 mm corrugated cardboard (K-liner, B flute) at a coating weight of 2 g / m, and with an open time of 2 seconds, it was attached to another 25 mm x 100 mm corrugated cardboard with an overlap of 40 mm to produce a laminate with a configuration of "corrugated cardboard / hot melt adhesive / corrugated cardboard". The laminate was sandwiched between two 25 mm x 100 mm SUS plates to produce test piece 2. The SUS plates and the laminate were fixed with double-sided tape.

[0047] <Evaluation of Test Piece 2> The cold impact resistance of the obtained test piece 2 was evaluated according to the method described below. The results are shown in Tables 1 to 3.

[0048] <Cold resistance shock test> Test piece 2 was conditioned at -20°C for 1 hour, and immediately after removal, a 50g iron ball was dropped from a height of 50cm from the test piece to determine the substrate destruction rate (%). The substrate destruction rate was determined by visually checking the proportion of the hot melt adhesive surface occupied by the cardboard pieces that had peeled off due to the impact. n=3 points were measured, and the average value was calculated and judged according to the following criteria. ◎ and ◯ were judged to be practical. ◎: Substrate destruction rate is 85% or more, 100% or less ○: Substrate destruction rate is 70% or more and less than 85% △: Substrate destruction rate is 50% or more but less than 70% ×: Substrate destruction rate is less than 50%

[0049] [Table 1]

[0050] [Table 2]

[0051] [Table 3]

[0052] The results in Tables 1 to 3 show that the hot melt adhesive for sealing envelopes of the present invention maintains excellent adhesive strength and cold impact resistance in a low-temperature atmosphere.

Claims

1. The composition comprises a wax (A) having a melting point of 60° C. to 90° C., a styrene-based elastomer (B), an olefin-based polymer (C), and a tackifier resin (D) having a softening point of 90 to 130° C., The melt flow rate of the styrene-based elastomer (B) measured under conditions of a load of 21.18 N and 230° C. is 5 to 10 g / 10 min, and The melt flow rate of the olefin polymer (C) measured under a load of 21.18 N and at 190° C. is 600 to 1,400 g / 10 min. relative to the total mass of the wax (A), the styrene-based elastomer (B), the olefin-based polymer (C), and the tackifier resin (D), Wax (A) 10 to 30% by mass, 1 to 9% by mass of a styrene-based elastomer (B), 35 to 55% by mass of an olefin-based polymer (C), and Tackifying resin (D) 20 to 40% by mass, A hot melt adhesive for sealing envelopes, comprising:

2. 2. The hot melt adhesive for sealing envelopes according to claim 1, wherein the tackifier resin (D) contains a tackifier resin (D1) having a softening point of 90° C. or more and less than 110° C. and a tackifier resin (D2) having a softening point of 110° C. or more and 130° C. or less.

3. 3. A laminate comprising a hot melt adhesive layer formed from the hot melt adhesive according to claim 1 or 2 laminated on at least one side of a paper substrate.

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