JP6233514B2 - Hot melt adhesive - Google Patents

Description

  The present invention relates to a hot melt adhesive.

  The hot-melt adhesive is heated and melted using a special coating machine, applied to the adherend, bonded to the adherend, and then the adhesive is cooled and solidified to obtain initial adhesion in a short time. Since the hot melt adhesive does not contain an organic solvent or the like and is applied by heating and melting, it does not require solvent drying and is excellent in initial adhesiveness compared to an adhesive applied by diluting with an organic solvent or the like. Since application and bonding using a large applicator are also easy to automate, hot melt adhesives are mainly used in assembly lines such as packaging, woodwork, plywood, bookbinding and canning.

  Hot melt adhesives are widely used in fields such as packaging, bookbinding, plywood and woodworking. The amount of hot melt adhesive used is increasing year by year due to its short solidification time after application and the absence of solvent. The hot melt adhesive has a product form that is cut into small pieces such as a pellet, a square plate, and a bead, but most of them are pellet-shaped hot melt adhesives.

  However, the hot melt adhesive may cause strong blocking between pellets due to the manufacturing process, subsequent storage, transportation, and the like. Further, since the fluidity is extremely poor, there has been a problem that much labor is required in the operation of pulverizing the blocked hot melt adhesive during production and packaging. Therefore, storage, transportation, etc. for a long time are difficult. As methods for solving these problems, various methods for preventing blocking have been proposed.

  As a method for preventing blocking, for example, an inorganic substance such as talc and silica, a polyolefin fine powder, a polyethylene wax and a dispersion thereof are coated on the pellet surface, a higher fatty acid or a salt thereof, N, N′-ethylenebisoleate. There is a method of mixing amide, N, N′-ethylenebiserucamide, N, N′-dioleyl dipimide, N, N′-dielsyl adipimide.

Japanese Patent No. 4730698 US Pat. No. 3,528,841 JP 56-67209 A JP 48-32939 A JP 2006-117829 A

However, there are many problems with the various methods described above.
For example, as in the method described in Patent Document 1, when talc, silica, or the like, which is an inorganic powder, is attached to the surface of a hot melt block, a large amount of addition is required to obtain pellet fluidity. In addition, since the inorganic powder has poor compatibility with the hot melt adhesive, the function of the end product may be significantly impaired.

  In the method of coating a polymer pellet with an aqueous slurry of polyolefin fine powder described in Patent Document 2, the dispersibility of the fine powdered polyolefin in an aqueous system is extremely poor, and adhesion to a hot melt adhesive composition However, since it is weak, it is impossible to reach an area that actually prevents stickiness and ensures good fluidity.

  Patent Document 3 discloses a hot melt composition obtained by coating a polyethylene wax or a dispersion containing polyethylene wax as a main component on ethylene copolymer pellets. When such a hot melt composition is melted, it exhibits an emulsion, which is restricted from the application.

  Patent Document 4 proposes a technique using an ethylene interpolymer of a grade that is relatively hard and has low adhesion, with respect to polymer pellets coated with an anti-blocking agent. Even in this case, the anti-blocking effect is insufficient and the desired adhesiveness may not be obtained.

  The present applicant has also proposed a method for preventing blocking of hot melt adhesives by coating the surface of the hot melt adhesive with a specific surfactant as disclosed in Patent Document 5. Although this measure is good to some extent in terms of the blocking suppression effect under high temperature and high humidity, it still needs to be improved with respect to blocking suppression under a load. In particular, further improvement is desired with respect to blocking properties after being left in a hot and humid environment in the Asian region, such as summer in Japan.

  Therefore, one aspect of the present invention has been made in view of the above-described problems of the prior art, and the hot melt adhesive is intended to further improve the blocking resistance when left in a high temperature and high humidity environment. It is in.

  As a result of extensive research to solve these problems, the present invention provides a hot melt adhesive having a molded article of an adhesive composition and a coating material adhering to the surface of the molded article. . The adhesive composition includes an ethylene-vinyl acetate copolymer, a tackifying resin, and a wax. The coating material includes an anionic surfactant and polyethylene wax.

  According to the hot melt adhesive of the present invention, the hot melt adhesives are sufficiently suppressed from blocking even in a high temperature and high humidity environment. Moreover, the effect of blocking suppression in the state which received the loading load is also acquired. Since the hot melt adhesive of the present invention exhibits excellent blocking resistance even when stored for a long period of time, it also has excellent storage stability. In addition, the present invention can provide a hot-melt adhesive having excellent adhesion to an adherend having poor adhesion such as carton paper.

It is sectional drawing which shows one Embodiment of a hot-melt-adhesive.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  The hot melt adhesive of this embodiment has a coating material that adheres to the surface of the molded article of the adhesive composition and contains an anionic surfactant whose main hydrophilic group is an anionic type. The molded article of the adhesive composition is a main component of the hot melt adhesive, and includes an ethylene-vinyl acetate copolymer, a tackifying resin, and a wax. The dressing further includes polyethylene wax.

  FIG. 1 is a cross-sectional view showing an embodiment of a hot melt adhesive. A hot melt adhesive 1 shown in FIG. 1 includes a molded product 10 of an adhesive composition that is a main component of the hot melt adhesive, and a covering material 20 attached to the surface of the molded product 10. The covering material 20 is not necessarily required to cover the entire surface of the molded article 10, and a part of the surface of the molded article 10 may be exposed. Although FIG. 1 shows one molded product of the hot melt adhesive, the hot melt adhesive actually used may be an assembly of a plurality of molded products.

  The molded product 10 shown in FIG. 1 is a spherical granular material. However, the molded article may be an adhesive composition having a certain shape, and may be a regular or irregular shaped granular material (pellet), or may have any shape such as a square plate shape or a rod shape. Good. When the molded product 10 is a granular body, the major axis diameter (in the case of a spherical body) may be 3 to 30 mm. If the long axis diameter of the molded product is smaller than 3 mm, it becomes difficult to obtain a spherical molded product, and it tends to take time to produce a hot melt adhesive. If the long axis diameter of the molded product 10 is larger than 30 mm, it tends to be difficult to uniformly coat the molded product with an anionic surfactant and polyethylene wax. Further, it may be difficult to transport the hot melt adhesive with a hot melt applicator using a hose. From the viewpoint of blocking inhibition and the like, the molded product may be spherical. However, the “spherical shape” is not limited to a true spherical shape, but includes a substantially spherical shape having an aspect ratio (major axis diameter / minor axis diameter) of 1 to 3. Fine irregularities may be formed on the surface of the spherical molded product.

  50-99 may be sufficient as the Shore hardness A in 23 degreeC prescribed | regulated to JISK6253 of the hot-melt-adhesive 1 (or adhesive composition). The Shore hardness A may be 60 to 95, or 70 to 90. If the Shore hardness A is less than 50, the hardness is too low and the hot melt adhesive becomes soft, so that the effect of blocking suppression tends to be small. If the Shore hardness A is greater than 99, the hardness is too high and the adhesiveness tends to be relatively lowered.

  60-150 degreeC may be sufficient as the softening point by the ring-and-ball method of the hot-melt-adhesive 1 (or adhesive composition). When the softening point is lower than 60 ° C., in an environment close to 40 ° C. as in summer, partial melting starts and tack occurs, so that the effect of blocking suppression may be reduced. When the softening point is higher than 150 ° C., it takes time to melt the hot melt adhesive, and power saving tends to be difficult.

  The vinyl acetate (VA) content of the ethylene-vinyl acetate copolymer used in the adhesive composition may be 10 to 50% by mass based on the mass of the ethylene-vinyl acetate copolymer. The melt flow rate (MFR) of the ethylene-vinyl acetate copolymer may be 200 to 3000 g / 10 minutes. The ring-and-ball method softening temperature of the ethylene-vinyl acetate copolymer may be 60 to 120 ° C.

  The VA (vinyl acetate) content of the ethylene-vinyl acetate copolymer may be 15 to 35% by mass, and the ring and ball softening temperature may be 75 to 95 ° C. One kind of ethylene-vinyl acetate (EVA) copolymer may be used alone, or two or more kinds may be used in combination.

  Usually, the melt flow rate (MFR) refers to a value measured under conditions of 190 ° C. and a load of 21.18 N in accordance with JIS K7210. The ring-and-ball method softening temperature refers to a value measured according to JIS K6863 (or JIS K2207).

  As a commercial item of an ethylene-vinyl acetate copolymer, for example, Ultrasen 684 (VA content 20% by mass, melt flow rate (MFR) = 2000, ring and ball method softening temperature 80 ° C., trade name of Tosoh Corporation, "Ultrasen" is a registered trademark), Ultrasen 722 (VA content 28% by mass, melt flow rate (MFR) = 400, ring and ball method softening temperature 82 ° C, trade name manufactured by Tosoh Corporation, "Ultrasen" is registered Trademark), Ultrasen 735 (VA content 28 mass%, melt flow rate (MFR) = 1000, ring and ball method softening temperature 85 ° C., trade name of Tosoh Corporation, “Ultrasen” is a registered trademark).

  The content of the ethylene-vinyl acetate copolymer in the adhesive composition is 30 to 60% by mass, 30 to 45% by mass, or 33 to 40% by mass based on the mass of the adhesive composition (molded product 10). It may be. When the content of the ethylene-vinyl acetate copolymer is less than 30% by mass, the adhesiveness at a low temperature may be lowered. When the content of the ethylene-vinyl acetate copolymer exceeds 60% by mass, an increase in viscosity and a relative decrease in creep resistance may occur.

  The tackifying resin used in the adhesive composition is not particularly limited, but examples thereof include aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic hydrocarbon resins, styrene resins, polyterpene resins, and rosins. Petroleum resins such as resin, and modified products thereof. These can be used alone or in combination of two or more. Although it does not specifically limit as a modified product of petroleum resin, For example, what gave modification | denaturation means, such as hydrogenation, disproportionation, dimerization, esterification, is mentioned. Hydrogenated (hydrogenated) petroleum resins are particularly preferred.

  The aliphatic hydrocarbon resin is not particularly limited. For example, the aliphatic hydrocarbon resin is a heavy polymer containing a C4 to C5 mono- or diolefin such as 1-butene, isobutylene, butadiene, pentene, isoprene, piperidine, 1,3-pentadiene as a main component. Coalescence is mentioned.

  The alicyclic hydrocarbon resin is not particularly limited. For example, a resin produced by cyclizing and dimerizing an acyclic diene component in a C4 to C5 fraction and polymerizing the dimer monomer, Examples thereof include a resin produced by polymerizing a cyclized monomer such as cyclopentadiene, and a resin produced by hydrogenating an aromatic hydrocarbon resin.

  The aromatic hydrocarbon resin is not particularly limited, and examples thereof include resins containing as a main component a C9 to C10 vinyl aromatic hydrocarbon such as vinyltoluene, indene, α-methylstyrene, and cyclopentadiene.

  The styrene resin is not particularly limited, and examples thereof include polymers of styrene, vinyl toluene, α-methyl styrene, and isopropenyl toluene.

  The polyterpene-based resin is not particularly limited, and examples thereof include an α-pinene polymer, a β-pinene polymer, a dipentene polymer, a terpene-phenol polymer, and an α-pinene-phenol polymer.

  The rosin resin is not particularly limited, and examples thereof include rosins such as gum rosin, wood rosin and tall oil.

  As described above, hydrogenated petroleum resin is preferable as the tackifying resin, and dicyclopentadiene (DCPD) / aromatic copolymer hydrogenated petroleum resin, hydrogenated C9 petroleum resin, and hydrogenated C5 petroleum resin are more preferable. preferable. The hydrogenated petroleum resin of dicyclopentadiene (DCPD) / aromatic copolymer is generally obtained by copolymerizing a cyclopentadiene compound or a derivative thereof with an aromatic compound, and hydrogenating the resulting copolymer. This is a hydrogenated petroleum resin obtained.

  For example, East tack C115W (hydrogenated C5 petroleum resin, trade name manufactured by Eastman Chemical Co., Ltd.), Alcon M100, Alcon P115, Alcon SM-10 (hydrogenated C9 petroleum resin, trade names manufactured by Arakawa Chemical Industries, Ltd., “ Alcon is a registered trademark), Imabu P100, Imabu P125, Imabu P140, Imabu S100, Imabu S100 (dicyclopentadiene (DCPD) / aromatic copolymer hydrogenated petroleum resin, trade name of Idemitsu Kosan Co., Ltd.) A commercially available resin such as “I-MABE” can be used as a tackifying resin.

  Even if content of tackifying resin in an adhesive composition (molded article 10) is 25-70 mass%, 30-60 mass%, or 40-50 mass% on the basis of the mass of an adhesive composition. Good. When content of tackifying resin is less than 25 mass%, there exists a tendency for the heat resistance or the adhesive fall to generate | occur | produce. When the content of the tackifying resin exceeds 70% by mass, there is a tendency that workability is lowered due to viscosity reduction, adhesiveness is lowered at low temperature, and the like.

  The wax used in the adhesive composition (molded product 10) is not particularly limited as long as it is generally used in hot melt adhesives. For example, purified paraffin wax, paraffin wax, and micro wax are used. Examples include petroleum waxes such as crystallin wax, and synthetic waxes such as polyethylene wax, Fischer tropic wax, crystalline polyethylene wax, crystalline polypropylene wax, atactic polypropylene wax, and ethylene-carbon monoxide copolymer wax. . Among these, polyethylene wax and Fischer tropic wax are particularly suitable. These wax components may be used alone or in combination of two or more.

  The content of the wax in the adhesive composition (molded product 10) may be 5 to 30% by mass or 10 to 20% by mass based on the mass of the adhesive composition. When the content of the wax is less than 5% by mass, there is a tendency that an increase in viscosity or a decrease in solidification performance occurs. When the content of the wax exceeds 30% by mass, there is a tendency that relative adhesiveness decreases.

  Examples of preferable waxes include commercially available products such as Sasol H1 (manufactured by Sasol, Fischer Trophy wax, “SaSOL” is a registered trademark), CPW90F (manufactured by Chiba Fine Chemical Co., Ltd., polyethylene wax).

  The adhesive composition (molded product 10) may contain an olefin resin. The olefin resin used in the adhesive composition is generally a copolymer (olefin-based copolymer) of ethylene (ethylene-based resin) and an α-olefin (α-olefin-based resin) having 3 to 20 carbon atoms. Or α-olefin copolymer resin). The adhesive composition may contain at least one olefin copolymer. Examples of the α-olefin having 3 to 20 carbon atoms include propylene, isobutylene, butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Among the olefin copolymers, a copolymer of ethylene and an α-olefin having 4 to 8 carbon atoms is preferable. As the olefin resin, a copolymer of ethylene and butene or a copolymer of ethylene and propylene is more preferable. These α-olefin copolymers may be used alone or in combination of two or more.

  Preferable olefin resins include, for example, RT2115 (REXTAC, LLC, α-olefin copolymer resin), RT2304 (REXTAC, LLC, trade name, α-olefin copolymer resin), Affinity GA1900 (Dow Chemical Co., Ltd.) “Affinity” is a registered trademark, polyolefin resin), Tuffmer P0480 (manufactured by Mitsui Chemicals, ethylene / propylene copolymer, “Toughmer” is a registered trademark), Toughmer A4070S (ethylene / butene copolymer, Mitsui) Commercially available products such as those manufactured by Chemical Co., Ltd., α-olefin copolymer resin, “Toughmer” is a registered trademark), and the like.

  The content of the olefin resin in the adhesive composition (molded product 10) is 0.3 to 10% by mass, 0.5 to 4% by mass, or 1 to 3% by mass based on the mass of the adhesive composition. There may be. When the content of the olefin resin is less than 0.3% by mass, the effect of improving adhesion or suppressing stringing tends to decrease. When the content of the olefin resin exceeds 10% by mass, there is a possibility that compatibility or thermal stability may be reduced.

  The melting point determined by differential scanning calorimetry (DSC) of the polyethylene wax used for the coating material 20 may be 80 to 135 ° C. When the melting point by DSC of the polyethylene wax used as the coating material 20 (release agent) is less than 80 ° C., there is a possibility that the effect of blocking inhibition is reduced in a high temperature environment in Asia including Japan, and an adhesive. There is a possibility that the heat resistance of the will be reduced. On the other hand, polyethylene wax having a melting point exceeding 135 ° C. is difficult to obtain. The melting point is measured by DSC in a nitrogen atmosphere at a heating rate of 2 ° C./min. As a measuring device, for example, DSC 6220 (manufactured by SII) can be used.

  The polyethylene wax may be blended in the coating material as an emulsion wax. The polyethylene wax in an emulsion state is particularly easy to adhere to the surface of the molded article 10 of the adhesive composition.

  The surfactant used in the coating material is used to increase the affinity of the polyethylene wax. Polyethylene wax alone needs to be applied at a high concentration in order to obtain blocking resistance in a high-temperature and high-humidity environment, and it takes a lot of time to dry after application. In addition, the surfactant alone often does not provide sufficient blocking resistance in a hot and humid environment.

  The anionic surfactant of the covering material 20 may have a sulfonic acid group as a main hydrophilic group. Anionic surfactants are generally widely used as bases such as detergents, shampoos, hand creams, toothpastes, emulsifiers, dispersants, foaming agents and the like. For example, as the surfactant whose main hydrophilic group is an anionic type, sodium carboxymethyl cellulose, alkyl sulfate, polyoxyethylene alkyl ether sulfate, sulfosuccinic acid monoester salt, sulfosuccinic acid dialkyl salt, acyl sarcosine salt, potassium soap, Examples include lauryl ether carboxylate, alkylbenzene sulfonate, phosphoric acid monoester, and phosphoric acid diester. An anionic surfactant having a sulfonic acid group is desirable from the viewpoint of easily covering the surface of the adhesive composition (molded product 10), and alkylbenzene sulfonate is particularly preferable. These anionic surfactants can be used alone or in combination of two or more.

The adhesion amount of the anionic surfactant is 0.001 to 0.5 g / m ² or 0.01 to 0.00 with respect to the surface area of the fragmented adhesive composition (adhesive composition molding 10). It may be 06 g / m ² . If this adhesion amount (coating amount) is less than 0.001 g / m ² , the effect of inhibiting blocking tends to decrease, and if the adhesion amount exceeds 0.5 g / m ² , the adhesive strength of the hot melt adhesive is increased. There is a tendency to decrease relatively.

  As a method of adhering a coating material containing an anionic surfactant to a molded article of an adhesive composition, a method in which the coating thickness can be made uniform so that the hot melt adhesive that has been cut into pieces is free from coating leakage is preferable. If there is, it will not be specifically limited. For example, an aqueous solution containing 5 to 30% by mass of polyethylene wax and 0.3 to 3% by mass of an anionic surfactant is placed in a water tank used when cooling the molten adhesive composition, The coating material may be attached to the surface of the molded article by a method of immersing the hot melt adhesive. Alternatively, the surface of the molded article may be coated with a coating material by a method of cutting the molten adhesive composition into small pieces and then spraying the aqueous solution onto the cut hot melt adhesive. Alternatively, the aqueous solution may be sprayed onto a bead-shaped molded product of the adhesive composition, and the surface of the molded product of the adhesive composition may be coated with a coating material.

  The adhesive composition may further contain an antioxidant. Although it does not specifically limit as antioxidant used, A phenol type, an organic sulfur type, a hindered phenol type, a hindered amine type, an organic phosphorus type hindered phenol type, an amine type etc. are mentioned. For example, pentaerythriyltetrakis-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (trade name of SONGNOX1010, manufactured by SONGWON IND.) And n-octadecyl-3 as phenolic antioxidants -(3,5-di-tertiarybutyl-4-hydroxyphenyl) propionate (SONGNOX1076, a product name made by SONGWON IND.) And tris (2,4-di-tertiarybutylphenyl) phos as a phosphorus antioxidant Fight (SONGNOX1680, a product name made by SONGWON IND.) And the like. Moreover, these can be used 1 type or in combination of 2 or more types.

  The content of the antioxidant in the adhesive composition (molded product 10) may be 0.1 to 2% by mass, or 0.2 to 1% by mass based on the mass of the adhesive composition. When the content of the antioxidant is in the range of 0.1 to 2% by mass, the thermal stability and the like are further improved.

  Adhesive composition is made of a release agent such as higher fatty acid and higher fatty acid metal salt, coupling agent, stress relaxation agent such as silicone oil and silicone rubber powder, pigment or dye such as carbon black, UV absorption An appropriate amount of an agent, a surfactant other than the anionic surfactant that coats the surface of the main component, a non-halogen, non-antimony flame retardant, and the like may be included.

  The adhesive composition may contain a flame retardant containing phosphorus and nitrogen for the purpose of further improving the flame retardancy.

  The adhesive composition can be prepared by any method as long as various raw materials can be uniformly dispersed and mixed. As a general method, a raw material of a predetermined blending amount is sufficiently mixed with a mixer, etc., and then mixed or melt-kneaded with a mixing roll, an extruder, a raking machine, a planetary mixer, etc., and defoamed as necessary. Can be mentioned.

  In the coating material 20 that covers the surface of the molded article 10 of the adhesive composition as the main component of the hot melt adhesive, the mixing ratio of the polyethylene wax and the surfactant is not particularly limited and is arbitrary. The content ratio of the surfactant may be smaller than the content of the polyethylene wax. The content of the polyethylene wax may be 1 to 99% by mass or 70 to 99% by mass based on the mass of the covering material 20. The content of the surfactant may be 1 to 99% by mass or 1 to 30% by mass based on the mass of the coating material 20.

  The method for obtaining a molded article of the adhesive composition is not particularly limited. For example, a method of cutting the solidified adhesive composition with a cutter after melting can be employed. In this case, a cutter that can be continuously cut, such as a rotary blade, can be used. In order to prevent the adhesive composition from adhering to the cutter, an anionic surfactant aqueous solution may be sprayed in the vicinity of the cutter, or the adhesive composition may be cut in the aqueous solution.

  Next, the present invention will be specifically described using examples and comparative examples. However, the present invention is not limited to these examples.

Examples 1-6, Comparative Examples 1-4
A hot melt adhesive was prepared according to the formulation shown in Table 1. The blending unit in Table 1 is mass%.
The ethylene-vinyl acetate copolymer (EVA) used for the study was Ultrasen 722 (trade name, manufactured by Tosoh Corporation, vinyl acetate (VA) content 28 mass%, melt flow rate (MFR) = 400, ring and ball method Softening point 82 ° C.) and Ultrasen 735 (trade name, manufactured by Tosoh Corporation, VA content 28 mass%, melt flow rate (MFR) = 1000, ring and ball method softening point 85 ° C.).
As the olefin resin, Tuffmer P0480 (trade name, manufactured by Mitsui Chemicals, ethylene / propylene-based α-olefin copolymer resin) was used.
As the tackifying resin, petroleum resin Alcon P100 (trade name, manufactured by Arakawa Chemical Industries, hydrogenated C9 petroleum resin, softening point 100 ° C) and Alcon P125 (trade name, manufactured by Arakawa Chemical Industries, hydrogenated C9 petroleum) Two types of resin (softening point 125 ° C.) were used.
As the wax, Sasol H1 (trade name, Fistrotropics Wax, manufactured by Sasol) was used.
As polyethylene wax, AQACER 1547 (trade name, manufactured by Big Chemie Japan Co., Ltd., oxidized high-density polyethylene wax emulsion, melting point 125 ° C., non-volatile content 35%) and HORDMERPE 03 (trade name, manufactured by Big Chemie Japan Co., Ltd., polyethylene wax emulsion, Three types of AQUAMAT208 (trade name, oxidized high-density polyethylene wax emulsion, melting point 135 ° C., non-volatile content 35%, manufactured by Big Chemie Japan 3 type company) were used. CERAFLOUR 970 (trade name, polypropylene wax, melting point 160 ° C. manufactured by Big Chemie Japan Co., Ltd.) was used as the polypropylene rubber. The melting points of polyethylene wax and polypropylene wax were measured using DSC 6220 manufactured by SII under a nitrogen atmosphere under a temperature rising rate of 2 ° C./min.
As surfactants, Monogen Y100 (trade name of Daiichi Kogyo Seiyaku Co., Ltd., higher alcohol sodium sulfate ester (sodium lauryl sulfate), anionic surfactant) and Coatamine 24P (trade name of Kao Corporation, lauryl trimethyl ammonium) Chloride, a cationic surfactant).

  The ethylene-vinyl acetate copolymer, olefin resin, tackifying resin and wax were put into a heating kneader set at 180 ° C. and sufficiently melted. The melted mixture was kneaded until uniform, and then molded to obtain a molded product of a bead-like (hot melt) adhesive composition. An aqueous solution containing polyethylene wax or polypropylene wax at a concentration of 12% by mass and a surfactant at a concentration of 3% by mass was applied to the molded article of the adhesive composition using a spray. Next, the applied aqueous solution was dried by applying hot air of 40 ° C. to obtain a hot melt adhesive to which the coating material was adhered.

  The resulting hot melt adhesive was evaluated for viscosity, softening point, blocking resistance, peel adhesion strength, creep resistance, and thermal stability by the following methods. The results are shown in Table 2.

Viscosity Based on JIS K6862, the viscosity of each hot melt adhesive at 180 ° C. was measured with a BH type rotational viscometer using a No. 2 rotor at a rotation speed of 10 rpm.

Softening point The softening point of each hot melt adhesive was measured by the ring and ball method in accordance with JIS K6863.

Blocking resistance Instead of the method by spraying, the coating material was adhered to the molded product by a method of immersing the molded product of the adhesive composition in an aqueous solution containing the coating material. Thereafter, the molded product of the adhesive composition was filtered through a mesh (80 mesh: opening 180 μm) and then dried at 40 ° C. for 30 minutes. Put the molded product of the adhesive composition (hot melt adhesive) to which the coating material is attached into a cup and apply a load of 58.8 N (6 kgf) for 12 hours or more in a high temperature and high humidity environment of 40 ° C. and 90% RH. I left it alone.
Thereafter, the cup was turned upside down, and the mass of the hot melt adhesive dropped was measured. From the following formula, blocking resistance was evaluated. It shows that blocking resistance is so high that a number is large.
Blocking resistance [%] = {mass of hot melt adhesive dropped / total mass of hot melt adhesive} × 100

Peeling adhesive strength A hot melt adhesive heated to 180 ° C. and melted is applied to the surface of the carton paper in a bead shape of about 0.07 g / 25 mm, and the back surface of the carton paper is pasted with an open time of about 2 seconds. A test piece in which the carton paper was bonded by a hot melt adhesive was produced by pressing for about 2 seconds. Using this test piece, a 180 ° peeling test was measured by an autograph (tensile speed: 100 mm / min, sample temperature: 23 ° C.). The adhesive of the test piece after the measurement was visually observed to confirm the breaking condition. Symbol A indicates destruction at the interface between the adherend (carton paper) and the adhesive, and symbol B indicates destruction of the carton paper (material destruction).

Creep resistance A hot melt adhesive melted by heating to 180 ° C. was applied to carton paper (2 × 25 × 100 mm) in a bead shape having a diameter of 4 mm over a length of 25 mm in the width direction of the carton paper. After leaving for 2 seconds, the other corrugated cardboard was overlaid on the applied adhesive and pressed at 9.8 × 10 ⁴ Pa for 5 seconds. After bonding, leave at room temperature (25 ° C) for 1 day, then apply a load of 0.5N (50gf) / 25mm in an atmosphere of 50 ° C and set the time (hr) until the cardboard falls to creep resistance It was measured as an index.

Thermal stability 150 g of the hot melt adhesive was taken in a 250 ml sample bottle and allowed to stand at 180 ° C. for 336 hours while heating. The change of the state after being left was observed, and the thermal stability of the hot melt adhesive was evaluated according to the following criteria.
“A”: No change in state “B”: Slight separation, but in a practically acceptable range “C”: Generation of gelled products, carbides, etc.

As shown in Table 2, the hot melt adhesives of Comparative Example 1 that does not contain a surfactant in the coating material and Comparative Example 2 that does not contain polyethylene wax in the coating material are inferior in terms of blocking resistance. It was.
The polypropylene wax having a melting point of 160 ° C. used in Comparative Example 3 could not be mixed with the anionic surfactant. Therefore, the coating material could not be attached to the molded article of the adhesive composition containing the ethylene-vinyl acetate copolymer as the main material, and evaluation as a hot melt adhesive could not be performed. In addition, in the case of Comparative Example 4 using a cationic surfactant as a surfactant for the coating material, the coating material could be attached to the molded article of the adhesive composition, but the blocking resistance was 5%. Inferior, the peel adhesion strength was as low as 4.0 N / 25 mm.
On the other hand, in Examples 1 to 6, the blocking resistance was 90% or more, and the material breakage occurred in the measurement of the peel adhesion strength. The peel adhesion strength, which is an index of adhesion, was 4.0 N or more, and the creep resistance was 10 hr. Thermal stability was also good.
From the above experimental results, according to the present invention, it was confirmed that blocking was sufficiently suppressed even in a high-temperature and high-humidity environment, and a hot-melt adhesive excellent in adhesion to carton paper could be provided.

Examples 7-10, Comparative Examples 5-8
According to the formulation shown in Table 3, a spherical hot melt adhesive was produced in the same manner as in Example 1 and the like. The blending unit in Table 3 is mass%.
As the olefin resin, RT2585A (trade name, manufactured by REXTAC, LLC, ethylene / propylene-based α-olefin copolymer resin) was used. As other components, the same materials as in Example 1 were used.

  The obtained hot melt adhesive was evaluated for softening point, blocking resistance, and Shore hardness. Shore hardness was evaluated by the following method. Other evaluations were performed in the same manner as in Example 1 and the like. The results are shown in Table 4.

Shore hardness Based on JIS A Shore hardness, the 23 degreeC Shore hardness of each hot-melt-adhesive was measured.

As shown in Table 4, in the case of the hot melt adhesive of Comparative Example 5 that did not contain an ethylene-vinyl acetate copolymer, the Shore hardness A was less than 30, and the blocking resistance was poor. Moreover, the hot-melt adhesive of Comparative Example 6 in which the coating material did not contain polyethylene wax was also inferior in blocking resistance.
The polypropylene wax having a melting point of 160 ° C. used in Comparative Example 7 could not be mixed with the anionic surfactant. Therefore, the coating material could not be attached to the molded article of the adhesive composition containing the ethylene-vinyl acetate copolymer as the main material, and evaluation as a hot melt adhesive could not be performed. In addition, in the case of Comparative Example 8 using a cationic surfactant as a surfactant for the coating material, the coating material could be attached to the molded article of the adhesive composition, but the blocking resistance was 5%. It was inferior.
On the other hand, Examples 7 to 10 had a good blocking resistance of 90% or more. According to the present invention, it has been confirmed that a hot melt adhesive that sufficiently suppresses blocking even in a hot and humid environment can be obtained.

  The hot melt adhesive according to the present invention can be used for bonding various adherends, and particularly for difficult-to-adhere adherends such as carton paper and water-repellent processed paper. Can exhibit excellent adhesion.

  DESCRIPTION OF SYMBOLS 1 ... Hot melt adhesive, 10 ... Molded product of adhesive composition, 20 ... Coating material.

Claims (7)

A molded article of the adhesive composition;
A covering material adhering to the surface of the molded article;
Have
The adhesive composition comprises an ethylene-vinyl acetate copolymer, a tackifying resin and a wax;
The coating material comprises an anionic surfactant and polyethylene wax;
Hot melt adhesive. The adhesive composition is 30 to 60% by mass of the ethylene-vinyl acetate copolymer, 25 to 60 % by mass of the tackifying resin, and 5 to 5% of the wax, based on the mass of the adhesive composition. The hot melt adhesive according to claim 1, comprising 30% by mass.   The hot melt adhesive according to claim 1 or 2, wherein the adhesive composition further comprises an olefin resin.   The hot melt adhesive according to claim 3, wherein the adhesive composition contains 0.3 to 10% by mass of the olefin resin.   The hot melt adhesive according to any one of claims 1 to 4, wherein the polyethylene wax has a melting point of 80 to 135 ° C as measured by differential scanning calorimetry.   The hot melt adhesive according to any one of claims 1 to 5, wherein the molded product is a granular material having a major axis diameter of 3 to 30 mm.   The softening point of the hot melt adhesive is 60 to 150 ° C, and the Shore hardness A defined in JIS K6253 of the hot melt adhesive is 50 to 99 at 23 ° C. The hot melt adhesive according to one item.

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