Moisture-curing hot melt adhesive, book using said adhesive, and method for manufacturing book

Abstract

To provide a moisture-curable hot-melt adhesive that is excellent in coatability, cutting suitability, spreadability, bookbinding strength as well as deformation resistance.SOLUTION: A moisture-curable hot-melt adhesive contains a urethane polymer having an isocyanate group obtained by the reaction of a polyol compound (A) and a polyisocyanate (B). The polyol compound (A) has crystalline polyester polyol (a1) obtained by condensation polymerization of a C8-16 linear polycarboxylic acid and a linear polyol, polypropyleneglycol (a2), and polyethylene glycol (a3).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a moisture-curable hot melt adhesive, a book using the same, and a method for producing a book. [Background technology]

[0002] Hot melt adhesives, which undergo repeated reversible changes of melting and solidifying due to heat, are used to bond the internal stack of paper to the back of the cover of books such as textbooks, comics, and magazines. EVA (ethylene-vinyl acetate copolymer)-based hot melt adhesives are the mainstream resin used because of their excellent initial adhesive strength immediately after solidification.

[0003] However, previously known EVA-based hot melt adhesives required a thick coating to achieve sufficient adhesive strength, but this resulted in a lack of bookbinding ability, making it difficult to strike a balance between the two.

[0004] The adhesive developed for this purpose is the reactive hot melt adhesive, which combines the advantages of hot melt adhesives, such as excellent initial adhesive strength immediately after solidification, with the advantages of liquid reactive adhesives, such as strong adhesion and high durability. Most liquid reactive adhesives contain a base agent that utilizes a heat-induced curing reaction and a curing agent, and may or may not contain an organic solvent. If it contains an organic solvent, it is applied to one of the objects to be bonded, the organic solvent is allowed to volatilize, and then the other object is placed on top of it to allow the curing reaction to proceed. If it does not contain an organic solvent, the adhesive is heated to reduce its viscosity and applied to one of the objects to be bonded, and then the other object is placed on top of it to allow the curing reaction to proceed. While liquid reactive adhesives have excellent strong adhesion and high durability, the curing reaction has not progressed sufficiently immediately after the objects to be bonded are placed on top of each other, so the initial adhesive strength is low. On the other hand, reactive hot melt adhesives achieve initial adhesive strength by solidification, and strong adhesion and high durability by curing. There are several methods for imparting reactivity to reactive hot melt adhesives, but the adhesive that has been most widely used is a moisture-curing urethane-based reactive hot melt adhesive (hereinafter referred to as moisture-curing hot melt adhesive), which uses the reaction between the isocyanate group at the end of the molecule and moisture in the environment (in the air or the object to be bonded) to harden the adhesive.

[0005] Here, the bookbinding process using a moisture-curing hot melt adhesive will be described. In bookbinding using a bookbinding machine, several cuts and holes are made in the edge of a stack of papers aligned by a collating machine (the spine where it is to be glued together), then moisture-curing hot melt adhesive is applied with a roll coater, the stack of papers is wrapped in a cover, and the spine of the stack of papers is pressed against the inside (backside) of the spine of the cover, and the stack of papers and cover are combined together; alternatively, several cuts and holes are made in the edge of the stack of papers aligned by a collating machine (the spine where it is to be glued together) to prepare a stack of papers for gluing, a separate moisture-curing hot melt adhesive is applied to the inside of the spine of the cover, the spine of the stack of papers is pressed against the inside of the spine of the cover, the stack of papers and cover are combined together, and then the stack is quickly cut by a paper cutter to produce the book.

[0006] Moisture-curing hot melt adhesives for bookbinding are required to have basic book-related properties, such as ease of opening and adhesive strength (also known as bookbinding strength), as well as properties required for bookbinding, such as suitability for coating and cutting. For example, Patent Document 1 describes a moisture-curable polyurethane hot melt adhesive for bookbinding that is excellent in high-speed application suitability, cutting suitability, double-page spreadability, initial strength, and bookbinding strength. A moisture-curable polyurethane hot melt adhesive is disclosed that contains a urethane prepolymer having an isocyanate group, which is a reaction product of a polyol containing polyol, polyoxyethylene polyoxypropylene glycol, other polyether polyol, acrylic polyol, and polycaprolactone polyol, and a polyisocyanate. The use of polypropylene glycol as another polyether polyol is also disclosed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2017-222758 A Summary of the Invention [Problem to be solved by the invention]

[0008] By the way, in the case of books with relatively thin covers, such as magazines, they are cut by a paper cutter, and after the books are produced, they are bound together in groups of several dozen with polypropylene (PP) bands, which are convenient and economical for transportation. When binding, strong pressure is applied to the area fastened by the PP bands made of moisture-curing hot melt adhesive, that is, the area between the front and back of the cover (corners). The adhesive described in Patent Document 1 has a long open time (time during which the adhesive can be bonded), but because it takes time for the adhesive to harden, the adhesive itself before hardening does not have sufficient deformation resistance. Therefore, if multiple books are bound together with PP bands in a short time after binding, there is a problem that the corners between the front and spine parts of the covers of each book are deformed. In particular, deformation of the corners of the two outermost books is a big problem. In addition, strong pressure is applied to the bottom books in a stack, which causes deformation of the adhesive parts (spine parts) of the bottom books.

[0009] An object of the present invention is to provide a moisture-curable hot melt adhesive that is excellent in coating property, cuttability, book-spreading property, bookbinding strength, as well as deformation resistance. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. That is, an embodiment of the present invention is a moisture-curable hot melt adhesive containing a urethane polymer having an isocyanate group obtained by reacting a polyol compound (A) with a polyisocyanate (B), in which the polyol compound (A) is a moisture-curable hot melt adhesive containing a crystalline polyester polyol (a1) obtained by condensation polymerization of a linear polycarboxylic acid having 8 to 16 carbon atoms and a linear polyol, a polypropylene glycol (a2), and a polyethylene glycol (a3).

[0011] Another embodiment of the present invention is the moisture-curable hot melt adhesive, comprising 60 to 100 mass% in total of the crystalline polyester polyol (a1), polypropylene glycol (a2), and polyethylene glycol (a3) ​​in 100 mass% of the polyol compound (A).

[0012] Another embodiment of the present invention is the moisture-curable hot melt adhesive, comprising 20 to 50 mass% of the crystalline polyester polyol (a1), 30 to 50 mass% of polypropylene glycol (a2), and 5 to 30 mass% of polyethylene glycol (a3) ​​relative to 100 mass% of the polyol compound (A).

[0013] In addition, the embodiment of the present invention is a composition having a viscosity of 1000 to 25000 mPa·s at 120°C. The moisture-curable hot melt adhesive is as described above.

[0014] In another embodiment of the present invention, the number average molecular weight of the polyethylene glycol (a3) ​​is 200 The moisture-curable hot melt adhesive has a viscosity of 0 to 10,000.

[0015] Another embodiment of the present invention is the moisture-curable hot melt adhesive described above, which contains a tackifier resin.

[0016] Another embodiment of the present invention is the moisture-curable hot melt adhesive described above, which contains 2 to 50 parts by mass of a tackifier resin based on 100 parts by mass of the urethane polymer.

[0017] Another embodiment of the present invention is the moisture-curable hot melt adhesive, wherein the tackifier resin has a softening point of 80° C. or higher.

[0018] Another embodiment of the present invention is the moisture-curable hot melt adhesive described above, wherein the tackifier resin is a petroleum resin.

[0019] Another embodiment of the present invention is the moisture-curable hot melt adhesive described above, wherein the petroleum resin is aromatic.

[0020] Another embodiment of the present invention is the above moisture-curable hot melt adhesive for bookbinding.

[0021] Another embodiment of the present invention is a book having a stack of multiple overlapping sheets of paper and a cover for covering three sides of the stack of paper, wherein an end of the stack of paper and a portion of the cover are bonded together with a hardened product of the moisture-curing hot melt adhesive described above.

[0022] Another embodiment of the present invention is a method for manufacturing a book having a stack of multiple sheets and a cover for covering three sides of the stack, comprising: The moisture-curing hot melt adhesive is applied in a molten state to the spine of the paper bundle, The moisture-curing hot melt adhesive applied to the spine of the paper bundle is brought into contact with the back side of the spine of the cover sheet, and the moisture-curing hot melt adhesive is allowed to solidify. The isocyanate groups in the moisture-curing hot melt adhesive react with the moisture in the environment, The paper stack and the cover are bonded together with a hardened moisture-curing hot melt adhesive. This is a method of manufacturing books. Effect of the Invention

[0023] The moisture-curing hot melt adhesive of the present invention is superior in deformation resistance compared to conventional moisture-curing hot melt adhesives. The present invention can provide a moisture-curing hot melt adhesive that does not deform even when a strong pressure is applied. In addition, the moisture-curing hot melt adhesive of the present invention is suitable as a bookbinding adhesive for bonding a paper bundle and a cover because it has excellent coating properties, cuttability, book-opening properties, bookbinding strength, and deformation resistance. Furthermore, the moisture-curing hot melt adhesive of the present invention has a relatively low viscosity and moderate permeability into the substrate, so it can be suitably used for clothing applications and bonding nonwoven fabrics, cloth, and leather. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The moisture-curable hot melt adhesive of the present invention will be described. In this specification, "parts" and "%" respectively mean "parts by mass" and "% by mass" unless otherwise specified. Furthermore, "molecular weight" means number average molecular weight (Mn) unless otherwise specified. Incidentally, "Mn" is the number average molecular weight in terms of polystyrene obtained by gel permeation chromatography (GPC) measurement.

[0025] <Urethane polymer having isocyanate groups> The urethane polymer having an isocyanate group is a reaction product obtained by a urethane reaction between one or more polyol compounds (A) and one or more polyisocyanates (B) described below. During the reaction, the polyisocyanate is used in a molar ratio (NCO / OH ratio) such that the isocyanate groups (isocyanato groups) of the polyisocyanate are greater than the hydroxyl groups of the polyol compound. This results in a urethane polymer with isocyanate groups at the molecular ends. These isocyanate groups can react with moisture in the air or in the object to be bonded to form a crosslinked structure. The urethane polymer having an isocyanate group can be used alone or in combination of two or more kinds.

[0026] The weight average molecular weight (Mw) of the urethane polymer having an isocyanate group is preferably from 10,000 to 50,000, and more preferably from 10,000 to 30,000. By adjusting the Mw within the above range, the coatability and the initial adhesive strength can be improved.

[0027] <Polyol compound (A)> The polyol compound (A) is a polyol having two or more hydroxyl groups in one molecule. The polyol compound (A) includes a crystalline polyester polyol (a1) obtained by condensation polymerization of a linear polycarboxylic acid having 8 to 16 carbon atoms and a linear polyol, a polypropylene glycol (a2), and a polyethylene glycol (a3).

[0028] <Crystalline polyester polyol (a1)> The crystalline polyester polyol (a1) contains a reaction product of at least one or more specific linear polycarboxylic acids and at least one or more linear polyols. In the present invention, the crystallinity is such that an exothermic peak accompanying a change in state from liquid to solid upon cooling can be confirmed using a differential scanning calorimetry (DSC) device.

[0029] Among the polycarboxylic acids used to form the polyester, examples of aliphatic polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutamic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, dodecanedioic acid, tetradecanedioic acid, and hexadecanedioic acid. Among these, the present invention uses a linear polycarboxylic acid having 8 to 16 carbon atoms to increase the crystallization temperature and further improve the cuttability. That is, the present invention uses suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, dodecanedioic acid, tetradecanedioic acid, and hexadecanedioic acid, and preferably uses sebacic acid, dodecanedioic acid, tetradecanedioic acid, and hexadecanedioic acid.

[0030] Among the polyols used to form the polyester, examples of aliphatic polyols include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, trimethylolpropane, trimethylolethane, glycerin, etc. Among these, in the present invention, by using a linear polyol, the crystallization temperature can be increased and the cuttability can be further improved. That is, in the present invention, it is preferable to use ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, or 1,10-decanediol, and it is more preferable to use 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, or 1,10-decanediol.

[0031] When the number average molecular weight of the crystalline polyester polyol (a1) is 500 or more, it is possible to impart cohesive strength to the moisture-curable hot melt adhesive and improve the bookbinding strength. On the other hand, when the number average molecular weight of the crystalline polyester polyol (a1) is 10,000 or less, it is possible to reduce the melt viscosity and improve the coatability. The number average molecular weight of the crystalline polyester polyol is preferably 500 to 10,000, more preferably 1,000 to 5,000.

[0032] When the crystallization temperature of the crystalline polyester polyol (a1) is 30°C or higher, the cuttability and deformation resistance of the moisture-curable hot melt adhesive can be improved. On the other hand, when the crystallization temperature of the crystalline polyester polyol (a1) is 100°C or lower, an appropriate open time can be designed, and coatability can be improved. The crystallization temperature of the crystalline polyester polyol (a1) is preferably 30 to 100°C, more preferably 40 to 70°C. The crystalline polyester polyol (a1) can be used alone or in combination of two or more kinds.

[0033] The crystalline polyester polyol (a1) is used mainly to accelerate the solidification of the moisture-curable hot melt adhesive, although the effect is not limited thereto. By making the crystalline polyester polyol (a1) 20% by mass or more in 100% by mass of the polyol compound (A), the solidification can be accelerated and the cuttability can be improved, and by making the crystalline polyester polyol (a1) 50% by mass or less, the opening property becomes better. In 100% by mass of the polyol compound (A), the content of the crystalline polyester polyol (a1) is preferably 25 to 50% by mass, more preferably 35 to 50% by mass.

[0034] <Polypropylene glycol (a2)> Polypropylene glycol (a2) is a compound having oxypropylene repeating units and hydroxyl groups at both ends. It is not particularly limited as long as it is made from propylene oxide as a starting material and is generally used as a raw material for urethane resins, etc., but examples thereof include Sannix series from Sanyo Chemical Industries and Uniol series from NOF Corporation.

[0035] When the number average molecular weight of the polypropylene glycol (a2) is 200 or more, the flexibility of the moisture-curable hot melt adhesive can be improved, and the openability and open time can be improved. On the other hand, when the number average molecular weight of the polypropylene glycol is 10,000 or less, the curing speed can be designed to be appropriate, and the cuttability becomes better. The number average molecular weight of the polypropylene glycol is preferably 200 to 10,000, and more preferably 500 to 5,000. The polypropylene glycol (a2) can be used alone or in combination of two or more kinds.

[0036] The polypropylene glycol (a2) is used mainly to impart flexibility to the moisture-curable hot melt adhesive, although the effects are not limited thereto. By making the polypropylene glycol (a2) 30% by mass or more in 100% by mass of the polyol compound (A), the openability can be improved, and by making the polypropylene glycol (a2) 50% by mass or less, the deformation resistance is improved. In 100% by mass of the polyol compound (A), the content of the polypropylene glycol (a2) is preferably 35 to 45% by mass, more preferably 40 to 45% by mass.

[0037] <Polyethylene glycol (a3)> Polyethylene glycol (a3) ​​is a compound having oxyethylene repeating units and hydroxyl groups at both ends. It is not particularly limited as long as it is made from ethylene oxide as a starting material and is generally used as a raw material for urethane resins, etc., but examples thereof include the PEG series from Sanyo Chemical Industries and the PEG series from NOF Corporation.

[0038] When the number average molecular weight of the polyethylene glycol (a3) ​​is 1000 or more, the hardness of the moisture-curable hot melt adhesive when solidified increases, and cuttability and deformation resistance can be improved. On the other hand, when the number average molecular weight of the polyethylene glycol is 20000 or less, the melt viscosity can be reduced, and coatability can be improved. The number average molecular weight of the polypropylene glycol (a3) ​​is preferably 1000 to 20000, and more preferably 2000 to 10000. The polypropylene glycol (a3) ​​can be used alone or in combination of two or more kinds.

[0039] Polyethylene glycol (a3) ​​is used mainly to impart deformation resistance to moisture-curable hot melt adhesives, although the effects are not limited thereto. It also plays a role in lowering the melt viscosity, and can further improve the coatability. By making the polyethylene glycol (a3) ​​5% by mass or more in 100% by mass of the polyol compound (A), the deformation resistance is excellent, and by making the polyethylene glycol (a3) ​​30% by mass or less, the opening property is good. In 100% by mass of the polyol compound (A), the content of polyethylene glycol (a3) ​​is preferably 10 to 30% by mass, more preferably 10 to 25% by mass.

[0040] The polyol compound (A) contains the crystalline polyester polyol (a1), polypropylene glycol (a2), and polyethylene glycol (a3) ​​and may contain other polyols as necessary.

[0041] Examples of the other polyols that can be used include polyoxyethylene polyoxypropylene glycol, polybutylene glycol, polytetramethylene glycol, polybutadiene diol, glycerin, trimethylolpropane, and trimethylolethane. The other polyols can be used alone or in combination of two or more kinds.

[0042] The moisture-curable hot melt adhesive of the present invention preferably contains 60 to 100 mass%, preferably 70 to 100 mass%, of (a1) to (a3) ​​in total, relative to 100 mass% of the polyol compound (A). By reducing the amount of polyol compounds other than (a1) to (a3) ​​and making the total of (a1) to (a3) ​​60 mass% or more, the coating property, cuttability, book-spreading property, bookbinding strength, and deformation resistance are improved.

[0043] <Polyisocyanate (B)> The polyisocyanate (B) is a polyisocyanate having two or more isocyanate groups in one molecule. The polyisocyanate (B) is preferably a bifunctional isocyanate (also called a diisocyanate) having two isocyanate groups in one molecule. Examples of the polyisocyanate (B) include 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), p-phenylene diisocyanate, toluene diisocyanate (TDI), 1,5-naphthalene diisocyanate (NDI), xylylene diisocyanate (XDI), 1,5-octylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), hydrogenated MDI (hydrogenated MDI), hydrogenated XDI (hydrogenated XDI), polymeric MDI, etc. Among these, it is preferable to use an aromatic polyisocyanate from the viewpoint of reactivity. MDI, p-phenylene diisocyanate, TDI, NDI, XDI and polymeric MDI are preferred, MDI and polymeric MDI are more preferred, and as MDI, 4,4'-MDI is preferred. The polyisocyanate (B) can be used alone or in combination of two or more kinds.

[0044] The method for producing the urethane prepolymer will be described. However, the present invention is not limited to the following method. For example, (a1) to (a3) ​​are placed in a reaction vessel. Other additives may be added at this time, if necessary. (a1) to (a3) ​​are heated and melted, stirred while being heated to 100 to 140°C using a heater that can be controlled with a uniform temperature distribution, and dehydrated thoroughly under reduced pressure. Next, a predetermined amount of polyisocyanate (B) is added, dry nitrogen is blown into the reaction vessel, and the reaction is carried out at 90 to 140°C while preventing moisture from entering, thereby producing the product. This reaction does not require a solvent, but a solvent may be used. In this case, the reaction temperature needs to be below the boiling point of the solvent.

[0045] When producing the urethane prepolymer, the equivalent ratio of the isocyanate groups in the polyisocyanate (B) to the hydroxyl groups in the polyol compound (A) (isocyanate groups / hydroxyl groups) is preferably 1.1 to 2.0, and more preferably 1.2 to 1.6, from the viewpoints of coatability and safety.

[0046] The isocyanate group content (hereinafter abbreviated as "NCO%) of the obtained urethane prepolymer is preferably 0.5 to 3.5, and more preferably 1.0 to 2.0, from the viewpoint of suppressing an increase in viscosity during heating storage or coating. The NCO% of the urethane prepolymer is measured by potentiometric titration in accordance with JIS K1603-1 and calculated based on the following formula. NCO% = 4.202 × (V1-V2) × c / m V1: Amount of hydrochloric acid used in the blank test (mL) V2: The amount of hydrochloric acid used to titrate the sample (mL) c: Concentration of hydrochloric acid (mol / L) m: mass of the sample (g) 4.202: Equivalent weight of NCO groups (42.02 mg / mEq).

[0047] The urethane prepolymer itself can be used as the moisture-curing hot melt adhesive of the present invention, or a tackifier resin can be added to the urethane prepolymer to form the moisture-curing hot melt adhesive of the present invention. When the moisture-curable hot melt adhesive contains a tackifier resin, the NCO% of the moisture-curable hot melt adhesive is the total amount of the urethane prepolymer and the tackifier resin in the above formula, "m: mass of sample (g)." From the viewpoint of suppressing an increase in viscosity during heated storage or coating, the NCO% of the moisture-curable hot melt adhesive is preferably 0.5 to 3.5, and more preferably 1.0 to 2.0.

[0048] <Tackifier resin> Examples of the tackifier resin include phenolic resin, modified phenolic resin, terpene phenolic resin, xylene phenolic resin, xylene resin, cyclopentadiene-phenolic resin, aliphatic, alicyclic, and aromatic petroleum resin, hydrogenated aliphatic, alicyclic, and aromatic petroleum resin, phenol-modified petroleum resin, rosin ester resin, modified rosin ester resin, low molecular weight polystyrene resin, terpene resin, and hydrogenated terpene resin. These can be used alone or in combination of two or more. Among these, terpene phenolic resin, rosin ester resin, maleic acid modified rosin ester resin, and aromatic petroleum resin are preferably used, and rosin ester resin and aromatic petroleum resin are more preferably used. The rosin ester resin is not particularly limited as long as it is a commonly used one, and examples thereof include the Super Ester series from Arakawa Chemical Industry Co., Ltd. and the Haritac series from Harima Chemical Industry Co., Ltd. In addition, the aromatic petroleum resin is not particularly limited as long as it is a commonly used one, and examples thereof include the Crystallex series from Eastman Chemical Company and the FTR series from Mitsui Chemical Industry Co., Ltd.

[0049] When the softening point of the tackifier resin is 80° C. or higher, the deformation resistance and heat resistance of the moisture-curable hot melt adhesive can be improved. On the other hand, when the softening point of the tackifier resin is 130° C. or lower, the compatibility with the urethane prepolymer is good and the adhesive can be used preferably. In the present invention, the softening point is measured by the ring and ball method in accordance with JIS K5601-2-2.

[0050] Although the effect of the tackifier resin is not limited, the bookbinding strength and deformation resistance can be further improved by using it in combination with the urethane prepolymer. By using 2 to 50 parts by mass of the tackifier resin per 100 parts by mass of the urethane prepolymer, the bookbinding strength and deformation resistance can be further improved without significantly decreasing the coating property and the opening property. The content of the tackifier resin per 100 parts by mass of the urethane prepolymer is preferably 5 to 40 parts by mass, more preferably 10 to 30 parts by mass.

[0051] The moisture-curable polyurethane hot melt adhesive of the present invention contains the urethane prepolymer, and may further contain other additives as necessary.

[0052] Examples of the other additives that can be used include chain extenders, curing catalysts, moisture removers, antioxidants, plasticizers, stabilizers, fillers, dyes, pigments, fluorescent brighteners, silane coupling agents, waxes, thermoplastic resins, etc. These additives may be used alone or in combination of two or more.

[0053] From the viewpoint of coatability, the melt viscosity of the moisture-curable hot melt adhesive of the present invention at 120° C. is preferably 1000 to 25000 mPa s, and more preferably 3000 to 10000 mPa s. The method for measuring the melt viscosity will be described in detail in the examples described later.

[0054] The moisture-curable hot melt adhesive of the present invention can be used as a bookbinding adhesive for bonding a bundle of paper sheets formed by stacking a number of sheets together and a cover for covering three sides of the bundle of paper sheets.

[0055] Examples of the paper used for the paper bundle include book paper, high-quality paper, recycled high-quality paper, waste paper, etc., and may be paper that has been appropriately printed, etc. The printing may be performed by any of the conventionally known printing methods, such as letterpress printing, gravure printing, offset printing, etc.

[0056] A book can be manufactured, for example, by applying the moisture-curing hot melt adhesive of the present invention, melted at a temperature of 100 to 140°C, preferably 110 to 130°C, to the inside of the spine of a stack of papers or the spine of a cover; while the stack of papers and the cover are in contact with each other, the moisture-curing hot melt adhesive is allowed to solidify; and then the isocyanate groups in the moisture-curing hot melt adhesive are reacted with the moisture in the environment (air or paper), and the stack of papers and the cover are bonded together with the hardened moisture-curing hot melt adhesive.

[0057] After the moisture-curing hot melt adhesive has solidified with the paper stack and cover in contact with each other, it is preferable to allow them to cure at 25°C and 50% RH for at least one day.

[0058] Methods for applying the moisture-curing hot melt adhesive to the spine of the paper bundle or the inside of the spine of the cover include a roll coater method, a slot die method, a nozzle method, a spray method, and the like. EXAMPLES

[0059] The present invention will be described in more detail below with reference to Production Examples and Examples. The present invention is not limited to the examples.

[0060] [Molecular weight measurement] The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) under the following conditions. Both Mw and Mn are polystyrene equivalent values.

[0061] Measurement equipment: Shoko Science Co., Ltd. GPC equipment "SHODEX GPC-101" Column: KF-G 4A / KF-805 / KF-803 / KF-802 Temperature: 40℃ Eluent: tetrahydrofuran (THF) Flow rate: 1.0mL / min Detector: RI (differential refractometer)

[0062] Manufacturing Example 1 (Synthesis of crystalline polyester polyol a1-1) 280g (1.0mol) of hexadecanedioic acid was reacted with 130g (1.1mol) of 1,6-hexanediol to obtain a crystalline polyester polyol a1-1 having a hydroxyl value of 38.7, a number average molecular weight of 2900, a melting point of 82.1°C and a crystallization temperature of 64.5°C.

[0063] (Method of evaluating hydroxyl value and number average molecular weight) The hydroxyl value of the resulting polyester polyol was measured in accordance with JIS K 1557-1, and the number average molecular weight is a value measured by the above-mentioned GPC method.

[0064] (Method of evaluating melting point and crystallization temperature) The melting point and crystallization temperature of the obtained polyester polyol were determined from the maximum endothermic and exothermic peak temperatures using a differential scanning calorimetry (DSC) device "DSC220C" manufactured by SII Nano Technology Co., Ltd. The DSC measurement was performed at a heating rate of 10°C / min and a cooling rate of -10°C / min.

[0065] (Production Examples 2 to 6) Crystalline polyester polyols a1-2 to a1-5 and a1'1 were obtained by carrying out the same reaction as in Production Example 1 using the compositions shown in Table 1. The results of the hydroxyl value, number average molecular weight, melting point and crystallization temperature are shown in Table 1.

[0066] [Table 1]

[0067] Example 1 (Moisture-curing hot melt adhesive) A reaction vessel equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a pressure reducing device was charged with 35 parts of the a1-1 as crystalline polyester polyol (a1), 40 parts of Sannix PP-1000 (Sanyo Chemical Industries, number average molecular weight 1000) as polypropylene glycol (a2), and 25 parts of PEG4000 (Sanyo Chemical Industries, number average molecular weight 3400) as polyethylene glycol (a3), which were heated and melted, and heated under reduced pressure at 120 ° C. for 2 hours. After cooling the inside of the reaction vessel to 110 ° C., 21 parts of 4,4'-diphenylmethane diisocyanate (hereinafter referred to as 4,4'-MDI) heated and melted at 70 ° C. under a nitrogen atmosphere was added, and the mixture was reacted at 110 ° C. for 4 hours to obtain a urethane polymer having an isocyanate group, and the urethane polymer was used as a moisture-curing hot melt adhesive. The obtained moisture-curing hot melt adhesive was used as a bookbinding adhesive, and according to the methods described below, the coatability was evaluated based on the viscosity at 120°C, the cutting suitability based on the solidification property, the deformation resistance after solidification and before hardening, the opening property based on the breaking elongation after hardening, and the strength as a book (bookbinding strength) based on the breaking strength after hardening.

[0068] (Examples 2 to 5) Moisture-curable hot melt adhesives were prepared in the same manner as in Example 1, except that a1-2 to a1-5 obtained in Production Examples 2 to 5 were used instead of the crystalline polyester polyol a1-1, and were similarly evaluated.

[0069] (Examples 6 to 7) A moisture-curing hot melt adhesive was prepared in the same manner as in Example 1, except that a1-3 was used as the crystalline polyester polyol, Sannix PP-1000 was used as the polypropylene glycol (a2), and PEG2000 having a number average molecular weight of 2000 and PEG1000 having a number average molecular weight of 1000, manufactured by Sanyo Chemical Industries, were used instead of PEG4000 as the polyethylene glycol (a3), and the adhesive was evaluated in the same manner. However, Examples 6 and 7 are reference examples.

[0070] (Examples 8 to 18) A moisture-curing hot melt adhesive was prepared in the same manner as in Example 3, except that the amounts of the crystalline polyester polyol a1-3, the polypropylene glycol (a2) Sannix PP-1000, and the polyethylene glycol (a3) ​​PEG4000 were changed as shown in Table 2, and evaluated in the same manner.

[0071] (Examples 19 to 21) As shown in Table 3, the crystalline polyester polyol a1-3, the polypropylene glycol (a2) Sannix PP-1000, the polyethylene glycol (a3) ​​PEG4000, and another polyol, polytetramethylene glycol "PTMG2000" having a number average molecular weight of 2000 manufactured by Mitsubishi Chemical Corporation, were reacted with 4,4'-MDI in the same manner as in Example 3 to obtain moisture-curable hot melt adhesives containing a urethane polymer having an isocyanate group, which were then evaluated in the same manner as described below.

[0072] (Examples 22 to 29) A tackifier resin shown in Table 3 was added to 125 parts of the urethane polymer obtained in Example 8 and melted at 110° C. to prepare a moisture-curable hot melt adhesive, which was then evaluated in the same manner as described below.

[0073] Comparative Example 1 A moisture-curing hot melt adhesive was prepared in the same manner as in Example 3, except that, instead of the crystalline polyester polyol a1-3 obtained in Production Example 3 using a linear polycarboxylic acid having 12 carbon atoms as the raw material, the crystalline polyester polyol a' obtained in Production Example 6 using a linear polycarboxylic acid having 6 carbon atoms as the raw material was used to obtain a urethane polymer having an isocyanate group, and the adhesive was evaluated in the same manner as in Example 3.

[0074] Comparative Example 2 Except for using other polyol components instead of polyethylene glycol (a3) ​​as shown in Table 3 to obtain a urethane polymer having an isocyanate group, moisture-curable hot melt adhesives were prepared in the same manner as in each example, and were evaluated in the same manner.

[0075] Comparative Example 3 As shown in Table 3, polypropylene glycol (a2) was not used, and crystalline polyester polyol a1-3 and polyethylene glycol (a3) ​​having an isocyanate group were used. Except for obtaining a urethane polymer, moisture-curable hot melt adhesives were prepared in the same manner as in each of the Examples, and were evaluated in the same manner as described below.

[0076] The abbreviations in Tables 2 and 3 are as follows. Polypropylene glycol (a2) Sannix PP-1000 (Sanyo Chemical Industries, number average molecular weight 1000)

[0077] Polyethylene glycol (a3) ·PEG4000 (Sanyo Kasei, number average molecular weight 3400) ·PEG2000 (Sanyo Kasei Co., Ltd., number average molecular weight 2000) ·PEG1000 (Sanyo Kasei, number average molecular weight 1000)

[0078] Polyisocyanate (B) 4,4'-Diphenylmethane Diisocyanate ("4,4'-MDI")

[0079] Tackifying Resin Crystallex F-100 (Eastman Chemical Company, aromatic petroleum resin, softening point 100°C) Super Ester A-100 (Arakawa Chemical, rosin ester, acid value 3.1 mgKOH / g, softening point: 100°C) Ester gum H (Arakawa Chemical, hydrogenated rosin ester, softening point 68°C)

[0080] Other polyol components Newpol 80-4000 (Sanyo Chemical Industries, polyoxyethylene polyoxypropylene glycol, number average molecular weight 4000) PTMG2000 (Mitsubishi Chemical Corporation, polytetramethylene glycol, number average molecular weight 2000) · Acrylic polyol AcPOH (polymerization of methyl methacrylate, n-butyl methacrylate, and 2-hydroxyethyl methacrylate, number average molecular weight 20,000) · Capa6400 (Perstorp, caprolactone polyol, number average molecular weight 37,000)

[0081] (Viscosity at 120℃: Coatability) The melt viscosity of the obtained moisture-curable hot melt adhesive at 120° C. was measured using a B-type viscometer (rotor #3, rotation speed 12 rpm or 3 rpm), and the coatability was evaluated as follows. 〇(Excellent): 1000mPa·s or more, 10000mPa·s or less. 〇△(Good): 10000mPa·s or more, 25000mPa·s or less. △(Acceptable): 25000mPa·s or more, 50000mPa·s or less. × (Not acceptable): Less than 1000 mPa·s or more than 50000 mPa·s.

[0082] (Solidification: Cutting suitability) The obtained moisture-curing hot melt adhesive was weighed into several shallow metal containers in 10g portions and melted in a 120°C oven, and all of the containers were removed from the oven and placed in a constant temperature room at 25°C and 50%RH. After removal, a 1kg weight was placed on the molten adhesive surface in turn every minute, with the tip of the weight touching the surface, and a load of 0.6MPa was applied for 5 seconds. The time elapsed after removal when no traces of the protrusion holes remained on the adhesive surface was defined as the solidification speed. If the solidification speed is fast, the cutting process can be started quickly after application, which is excellent from the viewpoint of productivity. 〇(Excellent): Less than 8 minutes. 〇△(Good): More than 8 minutes, less than 10 minutes. △(Acceptable): More than 10 minutes, but less than 12 minutes. ×(Not allowed): 12 minutes or more.

[0083] (Resistance to deformation after solidification and before hardening) 10 g of the obtained moisture-curing hot melt adhesive was weighed into a shallow metal container and melted in an oven at 120°C. The container was then removed from the oven into a constant temperature room at 25°C and 50% RH. After 10 minutes, the JISA hardness of the moisture-curing hot melt adhesive surface was measured in accordance with JIS K7312. When the "solidification property: cuttability" was rated as "△" or "×", the "resistance to deformation after solidification but before hardening" could not be evaluated. 〇(Excellent): Over 40°. 〇△(Good): Over 35°, under 40°. △(Acceptable): Over 25° and under 35°. ×(Not acceptable): Less than 25°.

[0084] (Breaking elongation after curing: openability) The moisture-curing hot melt adhesive was heated to 120°C to melt it, and then coated to a thickness of 250 μm on a release-treated polyethylene terephthalate film (hereinafter referred to as release PET film) using an applicator. It was left for 24 hours at 25°C and 50% RH, and the disappearance of the isocyanate group was confirmed by IR, and the moisture-curing hot melt adhesive was cured. A 250 μm thick cured coating was isolated from the release PET film, and a measurement sample of a specified shape was cut out. The sample was pulled at a pulling speed of 100 mm / min in accordance with JIS K7311, with a measurement sample width of 10 mm, a chuck distance (measurement sample length) of 24 mm, and the breaking elongation was determined. When a book is opened and left still, it needs to remain open, and it is undesirable for the book to close immediately. A high elongation rate is suitable for bookbinding because it allows the book to remain open. The stretch rate is defined as 100% when a 24 mm long sample is stretched to 48 mm. The measurement limit of the device used is 900%. 〇(Excellent): Over 500%. 〇△(Good):300 % More than 500%. △(possible) :150 % More than 300%. × (unacceptable): Less than 150%.

[0085] (Breaking strength after hardening: bookbinding strength) The breaking strength was calculated together with the breaking elongation after curing. The cross-sectional area of ​​the cured coating was 2.5 mm 2 The tensile strength was measured at 100° C. and the tensile strength was expressed as a value per unit area. 〇(Excellent): 4.0MPa or more. 〇△(Good):3.0 MPa or more, but less than 4.0MPa. △(Acceptable):1.5 MPa or more, but less than 3.0MPa. ×(Not possible): Less than 1.5MPa.

[0086] [Table 2]

[0087] [Table 3]

[0088] The moisture-curable hot melt adhesives of the present invention shown in Examples 1 to 29 in Tables 2 and 3 were excellent in coating properties, cuttability, openability, bookbinding strength, as well as deformation resistance.

[0089] On the other hand, the moisture-curable hot melt adhesive shown in Comparative Example 1 in Table 3 does not contain the crystalline polyester polyol (a1), and the cuttability was unacceptable.

[0090] Moreover, the moisture-curable hot melt adhesive shown in Comparative Example 2 in Table 3 does not contain the polyethylene glycol (a3), and has poor deformation resistance.

[0091] Moreover, the moisture-curable hot melt adhesive shown in Comparative Example 3 in Table 3 does not contain the polypropylene glycol (a2), and the double-spreadability was not possible. [Industrial Applicability]

[0092] The moisture-curable hot melt adhesive of the present invention has a relatively low viscosity and suitable permeability into substrates, and therefore can be suitably used not only for bookbinding, but also for clothing applications and for bonding nonwoven fabrics, cloth, and leather.

Claims

1. A moisture-curable hot melt adhesive containing a urethane polymer having an isocyanate group obtained by reacting a polyol compound (A) with a polyisocyanate (B), wherein the polyol compound (A) contains a crystalline polyester polyol (a1) obtained by condensation polymerization of a linear polycarboxylic acid having 8 to 16 carbon atoms and a linear polyol, a polypropylene glycol (a2), and a polyethylene glycol (a3) ​​having a number average molecular weight of 3,400 to 10,000; Moisture curing hot melt adhesive.

2. The crystalline polyester polyol (a1), the polypropylene glycol (a2), and the polyethylene glycol (a3) ​​are contained in a total amount of 60 to 100 mass% based on 100 mass% of the polyol compound (A). The moisture-curable hot melt adhesive according to claim 1.

3. The polyol compound (A) contains 20 to 50 mass% of the crystalline polyester polyol (a1), 30 to 50 mass% of polypropylene glycol (a2), and 5 to 30 mass% of polyethylene glycol (a3), relative to 100 mass% of the polyol compound (A). The moisture-curable hot melt adhesive according to claim 2.

4. The moisture-curable hot melt adhesive according to any one of claims 1 to 3, having a viscosity at 120 ° C. of 1000 to 25000 mPa · s.

5. The moisture-curable hot melt adhesive according to any one of claims 1 to 4, further comprising a tackifier resin.

6. The moisture-curable hot melt adhesive according to claim 5, containing 2 to 50 parts by mass of a tackifier resin per 100 parts by mass of the urethane polymer.

7. 7. The moisture-curable hot melt adhesive according to claim 5 or 6, wherein the tackifier resin has a softening point of 80° C. or higher.

8. The moisture-curable hot melt adhesive according to any one of claims 5 to 7, wherein the tackifier resin is a petroleum resin.

9. 9. The moisture-curable hot melt adhesive according to claim 8, wherein the petroleum resin is aromatic.

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