JPH04328187A - Aqueous adhesive and method of bonding - Google Patents

Abstract

PURPOSE:To obtain an aqueous adhesive suitable for non-rigid polyvinyl chloride or decorative paper, etc., having excellent adhesiveness especially at low temperature, comprising a crystalline polyurethane as an essential component. CONSTITUTION:The objective adhesive comprising a crystalline polyurethane obtained by reacting (A) a crystalline polyester polyol preferably having 1,000-3,500 number-average molecular weight, composed of a polyester diol preferably prepared by reacting polymethylenediol with a polymethylene dicarboxylic acid with (B) a polyisocyanate such as 2,4-tolylene diisocyanate as an essential component. The endothermic peak of the resin by differential thermal analysis exists at 30-100 deg.C (preferably 30-80 deg.C) and strength thereof is 5-30cal/g (preferably 7-15cal/g).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous adhesive, and more particularly to an aqueous adhesive containing a crystalline aqueous polyurethane resin as an essential component.

0002

[Prior Art] Conventionally, as a water-based adhesive containing a water-based polyurethane resin as an essential component, Japanese Patent Application Laid-Open No. 55-110173
The publication describes ``a heat-setting adhesive for heat-setting interlining made of polyurethaneurea, in which the polyurethaneurea produces a prepolymer from a polymeric diol and diisocyanate;
A prepolymer obtained by chain extension using (a) a low molecular diol containing a side chain or an ether group and (b) a low molecular diol without a side chain as a chain extender is emulsified in two steps using a nonionic emulsifier. "Heat-setting adhesive for interlining, which is characterized by being a finely dispersed polyurethaneurea obtained by reacting it with water and a diamine."

0003

However, the polyurethane polyurea described in JP-A-55-110173 cannot adhere well to base materials unless it is heated to 100 to 150°C.

[0004] Therefore, it has the disadvantage that it cannot be applied to substrates that soften or discolor when heated at the above-mentioned high temperatures, such as low-melting synthetic resins such as soft PVC, and decorative paper.

[0005]

[Means for Solving the Problems] The present inventors have conducted intensive studies to obtain a polyurethane resin water-based adhesive that can bond base materials together at lower temperatures than conventional ones, and have found that using a polyurethane resin having crystallinity can be used even at low temperatures. We discovered the fundamental fact that sufficient adhesion can be achieved, and completed the present invention.

That is, the present invention provides a water-based adhesive containing a crystalline polyurethane resin as an essential component and an adhesion method in which the adhesive is applied onto a paper base material, dried, and then pressure-bonded to a plastic base material.

It is extremely important that the aqueous adhesive of the present invention contains a crystalline polyurethane resin as an essential component. In addition, the crystalline polyurethane resin according to the present invention is
It may have only urethane bonds, or it may have both urethane bonds and urea bonds.

[0008] The crystalline polyurethane resin in the present invention has an endothermic peak at 30 to 100°C in differential thermal analysis, and has an endothermic peak intensity of 5 to 30 cal/g.
It refers to something. Among them, 7 in the range of 30 to 80℃
-15 cal/g is more preferable.

The method and conditions for differential thermal measurement are not particularly limited, but for example, a polyurethane resin film is formed on the sample, and the sample is heated at a rate of 5 to 30°C per minute over a temperature range of -50 to 120°C to absorb heat. All you have to do is confirm the presence of the peak. Examples of the differential heat measuring device include the Rigaku Thermal Analyzer DSC8230 manufactured by Rigaku Denki Co., Ltd., and the like.

[0010] The aqueous adhesive used in the present invention refers to one in which the polyurethane resin is dissolved or dispersed in an aqueous medium, and a dispersion system is preferable in that the solid content can be increased more than a dispersion system.

[0011] The aqueous medium refers to a medium containing water as an essential component and optionally containing an organic solvent. As the aqueous medium, it is preferable to use one that does not contain organic solvents, since there is less risk of fire or pollution.

Next, four methods for producing the aqueous dispersion of crystalline polyurethane according to the present invention will be explained. ■A urethane prepolymer made from a crystalline polyester polyol and a polyisocyanate, which has a hydrophilic atomic group or an atomic group that can become hydrophilic through neutralization, and also has an isocyanate group at the end (hereinafter referred to as a prepolymer). This organic solvent solution or organic solvent dispersion is reacted with an aqueous solution or dispersion of a chain extender when a prepolymer having a hydrophilic atomic group is used to neutralize it as a prepolymer. When a chain extender having an atomic group that can become hydrophilic is used, a manufacturing method in which a chain extender and a neutralizing agent are reacted with an aqueous solution or dispersion. ■Using crystalline polyester polyol and polyisocyanate,
A production method in which a prepolymer is produced and an aqueous dispersion obtained by emulsifying and dispersing the prepolymer in an aqueous medium using an emulsifier is reacted with an aqueous solution or dispersion of a chain extender. ■Using a crystalline polyester polyol and polyisocyanate, it has a hydrophilic atomic group or an atomic group that can become hydrophilic by neutralization,
A urethane prepolymer that also has an isocyanate group at the end is produced, and when a prepolymer having a hydrophilic atomic group is used, this is reacted with a chain extender, and the prepolymer is made hydrophilic by neutralization. When using a substance that has an atomic group that can be used as a chain extender, the process involves reacting the chain extender with a neutralizing agent, and then forcibly emulsifying it in an aqueous medium using an emulsifier if necessary. ■A production method in which a prepolymer is produced using a crystalline polyester polyol and a polyisocyanate, the prepolymer is reacted with a chain extender, and then the prepolymer is forcibly emulsified in an aqueous medium using an emulsifier.

[0013] As an aqueous dispersion of crystalline polyurethane resin, one that does not contain an emulsifier has excellent water resistance and strength of the resin film finally obtained. preferable. Among the methods (1) and (2), it is particularly preferable to use a crystalline polyurethane resin having an atomic group that can become hydrophilic by neutralization and in which the neutralizing agent evaporates by drying.

There are various methods for obtaining the crystalline polyurethane resin used in the present invention, but for example, it is preferable to react the crystalline polyester polyol as an essential component with a polyisocyanate. Such a crystalline polyester polyol refers to a polyester polyol that is white solid at room temperature, melts when heated, and becomes a transparent liquid.

Examples of such crystalline polyester polyols include the group consisting of linear aliphatic saturated diols, linear aliphatic saturated dicarboxylic acids, linear aliphatic saturated dicarboxylic acid anhydrides, and linear aliphatic saturated dicarboxylic acid dialkyl esters. Examples include those obtained by reacting with at least one type of compound selected from the following. More specifically, examples include those obtained by reacting polymethylene diol with at least one compound selected from the group consisting of polymethylene dicarboxylic acid, polymethylene dicarboxylic anhydride, and polymethylene dicarboxylic acid dialkyl ester.

In the present invention, polymethylene diol refers to a diol in which hydroxyl groups are directly bonded to both ends of a polymethylene skeleton, and polymethylene dicarboxylic acid refers to a dicarboxylic acid in which carboxyl groups are directly bonded to both ends of a polymethylene skeleton. , as well as its anhydrides and dialkyl esters.

[0017] As the crystalline polyester polyol,
a polymethylene diol having an even number of carbon atoms;
A polyester diol comprising at least one compound selected from the group consisting of polymethylene dicarboxylic acid having an even number of carbon atoms, its anhydride and its dialkyl ester is preferred.

The number average molecular weight of the crystalline polyester polyol is 300 to 5000, especially 1000 to 3500.
This is preferable because the resulting crystalline polyurethane resin has sufficient cohesive strength and therefore has good adhesive strength, and also has good non-stick properties and heat sealability at low temperatures.

Further, in the present invention, it is particularly preferable to use two or more types of crystalline polyester polyols having different number average molecular weights, and it is preferable that the difference in molecular weight is at least 500 or more.

The polymethylene diol used in producing the crystalline polyester polyol of the present invention includes:
For example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12- Dodecanediol, 1,20-eicosandiol, etc.
Examples of polymethylene dicarboxylic acids include succinic acid,
Glutanic acid, adipic acid, suberic acid, azelaic acid,
Sebacic acid, 1,10-decanedicarboxylic acid, 1,12
-todecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,20-eicosanedicarboxylic acid, and anhydrides or ester-forming derivatives of these dicarboxylic acids.

[0021] As the crystalline polyester polyol,
Particularly preferred are those obtained from a polymethylene diol having an even number of carbon atoms and a polymethylene dicarboxylic acid having an even number of carbon atoms.

[0022] In producing the above-mentioned crystalline polyester polyol, other raw materials may be used in combination as necessary, provided that the amount used does not impair the crystallinity of the polyester polyol. Other raw materials include propylene glycol, 1,3-butanediol, 3-methyl-
1,5-pentanediol, neopentyl glycol,
Diethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,
4-Cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A, bishydroxyethoxybenzene, bisphenol A, 4,4'-
Glycols such as dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, and hydroquinone, and diols such as their alkylene oxide adducts; maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid ,
1,4-cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 1, 2-bis(phenoxy)ethane-p,p'-
In addition to difunctional raw materials such as dicarboxylic acids such as dicarboxylic acids; hydroxycarboxylic acids such as p-hydroxybenzoic acid and p-(2-hydroxyethoxy)benzoic acid; cyclic ester compounds such as ε-caprolactone and γ-butyrolactone,
Examples include polyhydroxy compounds such as glycerin, trimethylolethane, trimethylolpropane, sorbitol, and pentaerythritol; polycarboxylic acids such as trimellitic acid and pyromellitic acid.

[0023] In addition, polyester polyols using the above-mentioned raw materials other than these, or polypropylene glycol, polyethylene glycol, polytetramethylene glycol, and copolymers thereof, in amounts that do not impair the crystallinity of the polyurethane resin finally obtained. Polyether polyols such as the following may be used in combination with the crystalline polyester polyol.

In the present invention, chain extenders used in addition to the above polyol components include, for example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol,
1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, dipropylene glycol, bishydroxyethoxybenzene, 1,4-cyclohexanediol ,1
, 4-cyclohexanedimethanol, bisphenol A
, hydrogenated bisphenol A, hydroquinone and other glycols; ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2
, 5-dimethylpiperazine, isophoronediamine, 4,
4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine,
Diamines such as 1,4-cyclohexanediamine; polyamines such as diethylenetriamine, dipropylenetriamine, and triethylenetetramine; hydrazines; acid hydrazides, and water; these may be used alone or in combination as necessary. Ru.

Examples of the polyisocyanate used in the method of the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, and 4,4'-diphenylmethane diisocyanate. ,2
, 4'-diphenylmethane diisocyanate, 2,2'
-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,
3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1 , 6-hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1
, 3-cyclohexylylene diisocyanate, 1,4-cyclohexylylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate,
Hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate, and the like.

As a compound having a hydrophilic atomic group or an atomic group that can become hydrophilic by neutralization (hereinafter referred to as a hydrophilic group-containing compound) used for dispersing the prepolymer or polyurethane resin in water, teeth,
Groups having at least one active hydrogen atom in the molecule and consisting of repeating units of ethylene oxide, groups consisting of repeating units of ethylene oxide and other repeating units of alkylene oxide, salts of carboxylic acids, salts of sulfonic acids , a quaternary amino group, a carboxylic acid group, a sulfonic acid group, and a tertiary amino group.

Examples of such hydrophilic group-containing compounds include 2-oxyethanesulfonic acid, phenolsulfonic acid,
Sulfobenzoic acid, sulfosuccinic acid, 5-sulfoisophthalic acid, sulfanilic acid, 1,3-phenylenediamine-
4,6-disulfonic acid, 2,4-diaminotoluene-5
- Sulfonic acid-containing compounds such as sulfonic acid and derivatives thereof or polyester polyols obtained by copolymerizing these; 2,2-dimethylolpropionic acid, 2,2-
Dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dioxymaleic acid, 2,6-dioxybenzoic acid, 3,4-
A polyester polyol obtained by copolymerizing carboxylic acid-containing compounds such as diaminobenzoic acid, derivatives thereof, or these; containing at least 30% by weight of repeating units of ethylene oxide;
Molecular weight 300 to 20,00 containing active hydrogen
0 polyoxyethylene glycol or polyoxyethylene-polyoxypropylene copolymer glycol, polyoxyethylene-polyoxybutylene copolymer glycol, polyoxyethylene-polyoxyalkylene copolymer glycol or its monoalkyl ether, etc. Group-containing compounds or polyester polyether polyols obtained by copolymerizing these may be mentioned, and these may be used alone or in combination.

Emulsifiers that can be used in the method of the invention include, for example, polyoxyethylene nonylphenyl ether,
Polyoxyethylene lauryl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene sorbitol tetraoleate, polyoxyethylene
Nonionic emulsifiers such as polyoxypropylene copolymers;
Fatty acid salts such as sodium oleate, alkyl sulfate salts, alkylbenzene sulfonate salts, alkyl sulfosuccinates, naphthalene sulfonate salts, polyoxyethylene alkyl sulfate salts, alkanesulfonate sodium salts, alkyldiphenyl ether sulfonate sodium salts, etc. Examples include anionic emulsifiers.

The method for dispersing the crystalline polyurethane resin of the present invention in an aqueous medium is to produce a prepolymer in an organic solvent as described above, then disperse it in an aqueous medium, and then react with a chain extender. There are two methods: one is to obtain an aqueous dispersion of crystalline polyurethane resin, and the other is to prepare crystalline polyurethane resin in advance in an organic solvent and then disperse it in an aqueous medium. -Alternatively, phase inversion emulsification may be achieved by dropping water into an organic solvent solution of a polyurethane resin while stirring, or by dropping a prepolymer or an organic solvent solution of a polyurethane resin into well-stirred water. Good too. Further, these methods may be of a batch type or a continuous type using a tubular mixer having no moving parts and having a plurality of mixing elements fixed therein.

The amount of the crystalline polyester polyol used in producing the crystalline polyurethane resin in the present invention is not particularly limited, but the amount necessary to impart crystallinity to the polyurethane resin, for example, the amount necessary to impart crystallinity to the polyurethane resin. It is preferably contained in an amount of 65 to 95 parts, particularly 70 to 90 parts, based on 100 parts of solid content. When the content of the crystalline polyester polyol in the solid content of the polyurethane resin is within the above range, the polyurethane resin will not only have good crystallinity, but will also have significantly excellent non-stick properties at room temperature and heat sealability at low temperatures. Moreover, the cohesive force after heat-sealing is also extremely excellent, so that sufficient adhesive strength can be obtained, which is particularly preferable.

The method for producing the prepolymer or polyurethane resin in the present invention is not particularly limited, and can be produced by conventionally known methods. For example, in the case of a prepolymerization reaction of a polyol component containing the crystalline polyester polyol as a main component, a polyisocyanate, and a chain extender, the equivalent ratio of isocyanate groups to active hydrogen groups is 1.1:1 to 3:1. 1, preferably 1.2:1-2:
In the case of urethanization reaction, the ratio is 0.9:1 to 1.
．． 20-120°C, preferably 30-120°C in a 1:1 ratio
A method of reacting at 100° C. can be mentioned.

These reactions can be carried out without a solvent, but an organic solvent can also be used for the purpose of controlling the reaction system or reducing the viscosity. Examples of such organic solvents include aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane; acetate esters such as ethyl acetate and butyl acetate; nitriles such as acetonitrile; Amides such as dimethylformamide and N-methylpyrrolidone are mentioned. Particularly preferred organic solvents in the present invention include solvents having a boiling point of 100° C. or lower, inert to isocyanate groups, and hydrophilic, such as acetone and methyl ethyl ketone.

When the crystalline polyurethane resin is dispersed in an aqueous medium, the content of hydrophilic atomic groups or atomic groups that can become hydrophilic in the polyurethane resin is, for example, carboxylic acid groups, sulfonic acid groups, tertiary amine groups. hydrophilic groups such as
In the case of functional groups that can become hydrophilic, such as carboxylic acid groups, sulfonic acid groups, and tertiary amino groups, the amount is at least 0.01 equivalent per 100 parts by weight of the solid content of the final polyurethane resin, preferably 0.01 to An amount equivalent to 0.2 equivalent is required, and in the case of a group consisting of an alkylene oxide repeating unit that essentially contains a repeating unit of ethylene oxide, which is a hydrophilic atomic group, for example, the weight of the repeating unit of ethylene oxide is At least 3 parts per 100 parts by weight of final polyurethane resin solids
An amount corresponding to at least 5% by weight, preferably from 5 to 30% by weight is required. When manufacturing crystalline polyurethane resin,
When a compound with a functional group that can become hydrophilic is used as a hydrophilic group-containing compound, the neutralizing agent necessary to convert the functional group that can be hydrophilic into a hydrophilic group is added to the functional group that can become hydrophilic. to 0.5:1 to 1.5:1 in equivalent ratio
, preferably in a ratio of 1:1 to 1.3:1.

[0034] Examples of the above-mentioned neutralizing agent include bases and acids. Examples of the base include ammonia; inorganic bases such as sodium hydroxide and potassium hydroxide; organic tertiary amines such as trimethylamine and triethylamine; among them, ammonia and organic tertiary amines with relatively low boiling points are preferred. .

Examples of the above-mentioned acids include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and sulfonic acid, and organic acids such as formic acid, acetic acid, and propionic acid. Among them, organic acids with relatively low boiling points are used. preferable.

[0036] Also, as described above, a method for producing an aqueous crystalline polyurethane dispersion using a mixture of two or more types of crystalline polyester polyols having different number average molecular weights as the crystalline polyester polyol and containing the same and polyisocyanate as essential components has been described. However, there is also a similar method in which two or more types of crystalline polyester polyols with different number average molecular weights are individually reacted with a polyisocyanate to individually produce a crystalline polyurethane resin aqueous dispersion, and these are then mixed together. Can be mentioned.

The aqueous dispersion of crystalline polyurethane resin thus obtained is then distilled under reduced pressure to remove the organic solvent, if necessary, if an organic solvent is also used in the production method. At this time, either a batch type or a continuous type using a thin film evaporator or the like may be used.

The water-based adhesive of the present invention must contain the crystalline polyurethane resin obtained as described above as an essential component, but even if these crystalline polyurethane resins are used alone, they may contain other water-based resins. May be used together. Other aqueous resins include emulsions such as vinyl acetate, ethylene vinyl acetate, acrylic, and acrylic styrene; latex such as styrene-butadiene, acrylonitrile-butadiene, and acrylic-butadiene; polyethylene and polyolefin. ionomers such as polyurethane, polyester, polyamide, epoxy, chlorinated polyethylene, chlorinated polypropylene, etc., in any ratio.

The water-based adhesive of the present invention may contain various crosslinking agents for the purpose of improving various durability such as water resistance, heat resistance, and solvent resistance after adhesion, such as epoxy resin, melamine resin, etc. , free isocyanate compounds, blocked isocyanate compounds, aziridine compounds, and polycarbodiimide compounds. Among these, epoxy resins, free isocyanate compounds, aziridine compounds, and carbodiimide compounds whose crosslinking is completed by heat treatment at room temperature or relatively low temperature are particularly preferred. The amount of these crosslinking agents can be set at any ratio depending on the composition of the water-based adhesive.
．． A range of 5 to 30 parts is used.

The aqueous adhesive of the present invention may further contain fillers such as carbon black, clay, talc, and aluminum hydroxide; additives such as silica sol, alumina sol, plasticizers, and pigments; and film-forming aids such as alkylene glycol derivatives. Agents; various thickeners of alkali thickening type or additive type; leveling agents; emulsifiers; blowing agents, etc. can also be used in combination.

The water-based adhesive obtained by the method of the present invention can be used to bond a wide variety of base materials together, such as various plastics including polyvinyl chloride, metals, inorganic materials, textiles, paper, leather, and wood. .

Examples of combinations of base materials include those shown in Table 1 below. Assuming that the two base materials are base material 1 and base material 2, the combination of base material 1 and base material 2 is shown by the intersection of the vertical axis and the horizontal axis in Table 1. The adhesive of the present invention has good adhesive properties in all combinations shown in Table 1.

[0043]

[Table 1]

[0044] As a method of bonding two base materials, the water-based adhesive of the present invention may be applied to one or both of the two base materials to be bonded, dried, and then the base materials are overlapped and pressure bonded.

The adhesive can be applied to the base material by various methods such as spray coating, roll coating, gravure coating, knife coating, and dot coating.

The above-mentioned drying may be performed by air drying at room temperature, or by using a hot air dryer, an infrared dryer, or the like. The pressure bonding may be performed using a tool capable of applying pressure, for example, a cold press, applying a pressure of 0.1 to 10 kg/cm<2>. In addition, the press machine was heated to a lower temperature than before, such as 30 to 100°C, and the
A method of heat sealing by applying pressure for 30 seconds may also be used. Of course, crimping by cold press and crimping by hot press may be used together.

[0047] According to the above-described bonding method, two base materials can be firmly bonded together at a lower temperature than conventionally,
For example, adhesive processing of polyvinyl chloride and plywood, adhesive processing of paper and plywood, lamination of polyvinyl chloride film and printing coated paper, lamination of crystalline polypropylene film and printing coated paper, polyethylene terephthalate (P
ET) Lamination of film and printing coated paper, lamination processing of various films and aluminum foils, adhesion processing of printing coated paper and various plastic base materials and metals, adhesion processing of nonwoven fabrics and various textiles and polyvinyl chloride sheets, etc. Useful for a wide range of applications.

[0048]

[Examples] The present invention will be explained in detail by examples below, but the present invention is not limited to these examples in any way unless it deviates from the technical idea of the present invention. In addition, parts and %
are all based on weight. Example 1 Into a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser, an OH value of 5 was first added.
Add 380.8 parts of 1,4-butanediol/adipic acid polyester of No. 6 and 253.9 parts of 1,4-butanediol/adipic acid polyester with an OH value of 37, and dehydrate at 120-130°C under reduced pressure. and then cooled to 50°C and added 30.2 parts of dimethylolpropionic acid and 5 parts of dimethylolpropionic acid.
After adding 18.7 parts of methyl ethyl ketone and thoroughly stirring and mixing, 113.1 parts of tolylene diisocyanate was added, heated to 70°C, and reacted at this temperature until NCO% reached 1.0%. A prepolymer solution having isocyanate groups was obtained. Then, while stirring at high speed with a homomixer, 1570 parts of water containing 22.8 parts of triethylamine was added.
120 parts of an aqueous solution containing 12.3 parts of anhydrous piperazine was added to prepare an aqueous dispersion of prepolymer.
It takes a few minutes to drip. The milky white aqueous dispersion thus obtained was desolventized under reduced pressure to remove methyl ethyl ketone, and an aqueous dispersion of polyurethane resin with a solid content of 40% (
Contains no methyl ethyl ketone. ) was obtained. The content of crystalline polyester polyol in the solid content of this polyurethane resin was 80%.

[0049] This polyurethane resin aqueous dispersion was poured onto a glass plate to form a dry film, and differential thermal analysis by DSC was performed, and the resin had a strength of 11 cal/g and a dry film of 51.
It had a peak due to crystallinity at the temperature position of °C.

Solid content of this polyurethane resin aqueous dispersion: 1
A mixture of 00 parts and 3 parts of trimethylolpropane triglycidyl ether was applied onto a polyvinyl chloride film using a bar coater to a dry film thickness of 7 g/m2, and dried at room temperature for 30 minutes. did. Even when the coated surfaces of this coated film were stacked together, there was no adhesion at all. Next, the polyvinyl chloride coated with adhesive and dried was stacked on the coated paper, and heated at 50°C x 0.5 kg/c.
Heat pressed under the conditions of m2, 1 hour after lamination and 1
Table 2 shows the results of evaluating the peel strength and heat creep resistance after several days. Example 2 In the same manner as in Example 1, 437.1 parts of a 1,4-butanediol/adipic acid polyester with an OH value of 56 and 109.3 parts of a 1,6-hexanediol/adipic acid polyester with an OH value of 37 were prepared. , 32.8 parts of dimethylolpropionic acid and 155.4 parts of isophorone diisocyanate were reacted to obtain a prepolymer solution having terminal isocyanate groups. Next, triethylamine 24. was added while stirring at high speed with a homomixer.
7 parts of water were added to prepare an aqueous dispersion of the prepolymer, and 169 parts of an aqueous solution containing 16.9 parts of anhydrous piperazine was added dropwise over about 1 minute. The milky white aqueous polyurethane resin dispersion thus obtained was desolventized under reduced pressure to remove methyl ethyl ketone, thereby obtaining an aqueous polyurethane resin dispersion (not containing methyl ethyl ketone) with a solid content of 40%. The content of crystalline polyester polyol in the solid content of this aqueous polyurethane resin dispersion was 73%.

[0051] This polyurethane resin aqueous dispersion was poured onto a glass plate to form a dry film, and differential thermal analysis by DSC was performed. As a result, this resin had a strength of 9 cal/g and a strength of 52
It had a sharp endothermic peak due to crystallinity at the temperature position of ℃.

When this aqueous polyurethane resin dispersion was coated and dried in the same manner as in Example 1, there was no adhesion at all even when the coated surfaces of the coated films were overlapped. Then laminated with coated paper at 50℃ x 0.5Kg/cm
Table 2 shows the results of hot pressing under the conditions of 2 and evaluating the peel strength and heat creep resistance 1 hour and 1 day after lamination. Comparative Example 1 The OH value was determined in the same manner as in Example 1.
331.5 parts of 1,4-butanediol/adipic acid polyester No. 56, 25 parts of dimethylolpropionic acid.
8 parts, 12.8 parts of 1,4-butanediol, and 139.2 parts of tolylene diisocyanate were reacted to obtain a prepolymer solution having terminal isocyanate groups. Next, add triethylamine 19. while stirring at high speed with a homomixer.
4 parts of water were added to prepare an aqueous dispersion of the prepolymer, and 245 parts of an aqueous solution containing 24.5 parts of anhydrous piperazine was added dropwise over about 1 minute. The milky white aqueous dispersion thus obtained was desolventized under reduced pressure to remove methyl ethyl ketone, thereby obtaining an aqueous polyurethane resin with a solid content of 40%. The content of crystalline polyester in the solid content of this aqueous polyurethane resin was 62%.

[0053] This water-based polyurethane resin was poured onto a glass plate to form a dry film, and differential thermal analysis by DSC was performed. This resin had a strength of 1 cal/g and a temperature position of 42°C due to crystallinity. A weak endothermic peak was observed.

When this aqueous polyurethane resin was coated in the same manner as in Example 1, there was no adhesion at all even when the coated surfaces of the coated films were overlapped. Then, it was laminated with coated paper and hot pressed at 50° C. x 0.5 kg/cm 2 . The peel strength and heat creep resistance were evaluated one hour and one day after lamination. The results are shown in Table 2.

[0055]

[Table 2]

*1 180 degree peeling data for a 25mm wide test piece *2 Creep length was measured for the same test piece 2 days after lamination Temperature: 60°C
Load: 200g
Time: 2 hours later

[0057]

[Effects of the Invention] Since the water-based adhesive of the present invention uses a polyurethane resin having crystallinity, it has a film that is non-tacky at room temperature, compared to conventional polyurethane resin water-based adhesives, but can be used at temperatures of 30 to 100°C. It is possible to easily press-bond two base materials together at such a low temperature, and it has excellent adhesive properties.

Although the adhesive of the present invention is non-tacky at room temperature, it can be used only by applying pressure or at a relatively low temperature (for example, 3
It can be sufficiently heat-activated and bonded by heat-pressing (0 to 100℃), and has excellent adhesion to various base materials, so it can be used for soft polyvinyl chloride and decorative paper, which were previously unsatisfactory. Adhesion processing for base materials whose quality is relatively susceptible to quality effects such as softening and discoloration due to heat, or adhesion processing for which sufficient heat treatment cannot be applied to water-based adhesives due to processing conditions such as processing speed. Processing is now possible.

Claims (10)

[Claims] 1. A water-based adhesive containing a crystalline polyurethane resin as an essential component. 2. The adhesive according to claim 1, wherein the crystalline polyurethane resin has an endothermic peak at 30 to 100° C. as determined by differential thermal analysis, and has an intensity of 5 to 30 cal/g. 3. The adhesive according to claim 1, wherein the crystalline polyurethane resin is a product obtained by reacting a crystalline polyester polyol and a polyisocyanate as essential components. 4. The adhesive according to claim 3, wherein the content of the crystalline polyester polyol constituting the crystalline polyurethane resin is 65 to 95 parts based on 100 parts of the solid content of the polyurethane resin. 5. The adhesive according to claim 4, wherein the crystalline polyester polyol is a polyester diol obtained by reacting polymethylene diol and polymethylene dicarboxylic acid. 6. A claim in which the crystalline polyester polyol is a polyester diol obtained by reacting a diol in which hydroxyl groups are directly bonded to both ends of a polymethylene skeleton with a dicarboxylic acid in which carboxyl groups are directly bonded to both ends of the polymethylene skeleton. 4. Adhesive according to 4. 7. The crystalline polyester polyol includes a diol having a hydroxyl group directly bonded to both ends of a polymethylene skeleton having an even number of carbon atoms, and a diol having a carboxyl group directly bonding to both ends of a polymethylene skeleton having an even number of carbon atoms. The adhesive according to claim 4, which is a polyester diol reacted with a dicarboxylic acid. 8. The adhesive according to claim 3, wherein the crystalline polyester polyol has a number average molecular weight of 1,000 to 3,500. 9. The crystalline polyester polyol is a mixture of at least two types of polyesters, and the difference in number average molecular weight between the polyester polyol having the highest number average molecular weight and the polyester polyol having the lowest number average molecular weight among them is at least 500. The adhesive according to claims 3 to 8, which is a polyester polyol obtained by mixing them so that the adhesive has the following properties. 10. An adhesion method comprising applying the adhesive according to claim 1 onto a paper base material, drying it, and press-bonding it to a plastic base material.