JP2003336030A - Reactive hot-melt adhesive composition for coating decorative sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactive hot-melt adhesive which can be applied at a relatively low temperature to a decorative sheet regardless of its kind, is excellent in adhesive properties, causes a crosslinking reaction in a short time after the decorative sheet is contact-bonded to a substrate material, does not suffer from adhesion peeling caused by shrinking force of the sheet, and permits quality inspection of the decorative material and a processing step for cutting and the like in a relatively short time after the end of the gluing step thereby ensuring early shipment of the product. <P>SOLUTION: The reactive hot-melt adhesive composition comprises, as a reactive component, a prepolymer terminated with an isocyanate group obtained by reacting a non-crystalline polyol with a polyisocyanate compound, and at least one of 2,2'-dimorpholinoethyl ether and bis(2,6-dimethylmorpholinoethyl) ether as a catalyst component in an amount of 0.05-6 wt.% in the composition. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hot melt adhesive composition used for adhering a decorative sheet or film having a pattern printed, grained, etc. to another member and coating the same, and Specifically, the present invention relates to a polyurethane-based reactive hot-melt adhesive composition for producing a decorative material by coating the above decorative sheet or film on wood, particle board, medium density fiberboard (MDF) or the like. .

[0002]

2. Description of the Related Art Adhesion used for manufacturing a cosmetic material by adhering a decorative sheet or film, which has been subjected to pattern printing, grain processing, etc., to another member, particularly wood, particle board, MDF, etc. As the agent, a reaction curing type solvent-based adhesive, especially a two-component type in consideration of the ease of reaction control, good adhesion to various substrates, and the toughness of the resin forming the adhesive layer. Most of the organic solvent-based polyurethane adhesives have been used. However, in recent years, the influence of organic solvents on the natural environment, the influence on the human body in the working environment of the bonding process, and the problem of fire have become more important, and adhesives that do not use organic solvents have been required. Hot melt adhesives have been investigated as such solventless adhesives.

[0003]

When adhering a decorative sheet to a particle board or the like, an adhesive, particularly a polyurethane-based adhesive, is generally attached to the adhesive surface of the decorative sheet using polyvinyl chloride or polyolefin as a resin material. Is applied, and this is pressure-bonded to the material to be bonded. That is, immediately after the bonding, the bonded state is maintained by the adhesive force. In the above-mentioned pressure bonding, tension is applied to the sheet so as not to cause wrinkles after the bonding, and the sheet is slightly stretched to perform the bonding. Therefore, a force of contracting the sheet is generated with the lapse of time after the adhesion, and therefore the adhesive force alone causes a problem that the decorative sheet 1 is peeled off from the base material 2 in the concave portion 3 shown in FIG. 1, for example.

In order to prevent the peeling of the above-mentioned adhesive, a urethane-based adhesive using a solvent-type isocyanate-based curing agent described in the section of the prior art is generally used, and crosslinking causes the adhesive resin to flow. Therefore, a means for preventing the peeling of the adhesive is adopted. The two-component curing solvent-type adhesive can be applied at room temperature, and therefore, it is possible to easily control the reaction rate by using a general curing catalyst.

However, the hot melt adhesive is applied by heating and melting, and cannot be applied at room temperature like a solvent type adhesive. Therefore, a general urethane-forming catalyst, that is, an organotin-based catalyst that accelerates the reaction of an isocyanate group and active hydrogen, is used so that the reaction-curable hot melt adhesive reacts and crosslinks rapidly so that the above-mentioned adhesion peeling does not occur. If you add a catalyst, use a special applicator,
Even if the moisture was shut off, the reaction proceeded by the heat during the heating and melting of the adhesive, and the stability could not be secured.

In order to solve this, a reaction catalyst is not used, and therefore it takes a long time to cure, but the following two methods are used as a means for preventing the peeling of the adhesive between the sheet and the substrate after pressure bonding until the curing. Is proposed. (I) Use a reactive hot melt based on a crystalline polyol compound. According to this adhesive, crystallization occurs quickly when the decorative sheet and the base material are pressure-bonded and then cooled,
Crystallization hinders the flow of the adhesive resin layer and prevents peeling of the adhesive. (Ii) Use a reactive hot melt adhesive that does not crystallize but has high adhesive strength. This method simply seeks to prevent debonding with a strong adhesive force.

However, according to the method (i), the urethane hot melt adhesive using the polyol compound which is likely to be crystallized is adhered depending on the material of the decorative sheet to be adhered, particularly the type of polyvinyl chloride sheet. There is a problem that some do not, and the application range is limited.
In addition, the crystallinity alone does not cause the problem of peeling of the adhesive in a stationary state, but when the cosmetic material is cut or the like before curing, frictional heat causes the peeling of the sheet due to peeling of the adhesive at the cut end. Therefore, a long curing time is still required before processing, which is not preferable in the process.

On the other hand, according to the method (ii), since the adhesive resin has a high cohesive force, it is necessary to apply the adhesive resin at a high temperature, and depending on the type of the polyvinyl chloride sheet, the heat resistance is insufficient. The problem arises that the sheet melts.

Therefore, the object of the present invention is that regardless of the type of the decorative sheet, it can be applied at a relatively low temperature and has excellent adhesiveness, and the crosslinking reaction can be carried out in a short time after the decorative sheet and the base material are pressure-bonded. It is possible to perform processing steps such as quality inspection and cutting of the cosmetic material in a relatively short time after completion of the adhesion process without causing peeling of the adhesive due to the contracting force of the sheet, and the product is shipped early and preferably. Is to provide a reactive hot melt adhesive that can be done within one day.

[0010]

The present invention relates to a reactive hot melt adhesive composition for coating a decorative sheet, which comprises an isocyanate group-terminated prepolymer as a reactive component and 2,2'-dimorpholino as a catalyst component. It is characterized in that at least one of ethyl ether and bis (2,6-dimethylmorpholinoethyl) ether is contained in the composition in an amount of 0.05 to 6% by weight.

The isocyanate group-terminated prepolymer has reactivity, adheres to various substrates without selectivity, and is uncured, so that it has sufficient tackiness for laminating desired sheets. However, after curing, it exhibits a strong adhesive force to form a tough resin. Further, 2,2'-dimorpholinoethyl ether and bis (2,6-dimethylmorpholinoethyl) ether, which are the most characteristic features of the present invention, do not change the viscosity of the hot melt adhesive in the molten state, and after bonding, isocyanate is used. It has a function of promoting a reaction between the group and a hydroxyl group-containing compound such as water in the air and water contained in the substrate, and effectively preventing peeling of the adhesive due to shrinkage of the sheet due to cooling.

When the amount of the catalyst component is less than 0.05% by weight, the curing rate is out of the desired range, and when it is more than 6% by weight, the stability upon melting is lowered. The chemical structure of the catalyst is 2,2'-dimorpholinoethyl ether (DMDEE).
For (Chemical Formula 1) (a), and for bis (2,6-dimethylmorpholinoethyl) ether, (Chemical Formula 1) (b).
Respectively shown.

[0013]

[Chemical 1]

These catalysts promote the reaction of NCO groups with water contained in the air or in wood without impairing the melt stability of the hot melt adhesive composition, and as a result, the reaction rate of the polyurethane prepolymer. And has the effect of improving the adhesive strength. Other catalysts such as dibutyltin dilaurate promote the reaction of NCO groups with water,
Although the adhesive property is improved, at the same time, formation of allophanate bond and buret bond is promoted, and it becomes difficult to secure stability of melt viscosity and suppress variation in the manufacturing process and the processing process using the adhesive.

The reactive hot melt adhesive composition of the present invention preferably further contains a low molecular weight polymer of an ethylenically unsaturated monomer.

When only the polyurethane prepolymer is used as the resin component, the NCO group reacts and cures to increase the molecular weight, and sufficient adhesive strength is exhibited. However, in the prepolymer state, the initial adhesive strength is insufficient depending on the application. There is also.
When the degree of polymerization of the polyurethane prepolymer is increased, the melt viscosity is increased and it becomes difficult to use it as a hot melt adhesive. The low molecular weight polymer of ethylenically unsaturated monomer improves the initial adhesive strength in such applications, and the adhesive strength with PET resin, polyvinyl chloride resin, aluminum base material etc. It has the effect of improving.

The addition amount of the low molecular weight polymer of the ethylenically unsaturated monomer is such that the weight ratio of polyurethane prepolymer / low molecular weight polymer of the ethylenically unsaturated monomer is 5/95 to.
It is preferably in the range of 90/10. When the addition amount of the low molecular weight polymer of ethylenically unsaturated monomer (hereinafter simply referred to as “oligomer”) is 95 or more, the ratio of the polyurethane prepolymer having an NCO group becomes small, and the adhesive force is improved by the curing reaction. Is insufficient. If the addition ratio of the oligomer is 10 or less, the above effect cannot be sufficiently exhibited.

The reactive hot melt adhesive composition of the present invention preferably further contains a thermoplastic block copolymer having two or more polystyrene blocks and an elastic polymer block.

The thermoplastic block copolymer having two or more polystyrene blocks and an elastic polymer block has a function of immediately exhibiting an initial adhesive force when the adhesive is cooled and solidified, and various adherends. It has an effect of improving wettability to the (base material) and improving adhesiveness.

The addition amount of the thermoplastic block copolymer is 1 to 2 with respect to 100 parts by weight of the polyurethane prepolymer.
It is preferably in the range of 00 parts by weight. If it is 1 part by weight or less, the properties are not different from the case where only the prepolymer is used.
If it is added in an amount of 200 parts by weight or more, the abundance ratio of the polyurethane prepolymer becomes small and the improvement of the adhesive force due to the curing reaction becomes insufficient.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The polyurethane prepolymer used as a component of the reactive hot melt adhesive of the present invention is a compound having an NCO group which is a functional group having reactivity, and a polyol which is an oligomer having a hydroxyl group. Polyisocyanate compound in equivalent ratio NCO / OH> 1
It can be obtained by reacting under the conditions. Preferably N
The CO / OH equivalent ratio is in the range of 1.2 to 2.5. 1.
When it is 2 or less, the concentration of NCO group becomes too low.
When it is 5 or more, a large amount of the raw material polyisocyanate compound monomer remains, which is not preferable.

The polyol component used as a raw material of the above-mentioned polyurethane prepolymer has an average number of functional groups (average value of the number of hydroxyl groups in one molecule) of 1.9 to 2.2,
It is preferable to use a polyol having a hydroxyl value of 15 to 150 (KOHmg / g). If the average number of functional groups is less than 1.9, chain extension does not occur sufficiently even by reaction with water, and physical properties peculiar to polyurethane cannot be obtained.
The properties of hot melt adhesives are not satisfactory. When a polyol having a functional group number of 2.2 or more is used, a gel component is likely to be generated in the adhesive composition.

If the hydroxyl value of the polyol is 15 or less, the relative concentration of the reactive NCO groups in the polyurethane prepolymer decreases, resulting in insufficient effect of crosslinking. On the other hand, when a polyol having a hydroxyl value of 150 or more is used, the concentration of NCO groups in the polyurethane prepolymer becomes too high.

By setting the hydroxyl value of the polyol and the NCO / OH equivalent ratio during the synthesis of the prepolymer in the above range, the concentration of NCO groups in the polyurethane prepolymer is 0.25 to 25% by weight, preferably 0.5. -10% by weight, most preferably 1.5-5% by weight, and the free polyisocyanate component in the final composition is 4%.
It can be suppressed to less than or equal to wt%.

As the polyol used in the present invention, a compound having at least two active hydrogen atoms in the molecule and usually used in the synthesis of polyurethane is used. Specifically, polyols classified into ether-based, ester-based, polycarbonate-based, polydiene-based, castor oil-based, acrylic-based, etc. can be used and are appropriately selected depending on the application, and two or more types are used in combination as necessary. . As the ether-based polyol, polyoxytetramethylene polyol (PTMG), polyoxypropylene polyol (PPG), etc., and as the ester-based polyol, polyethylene adipate (PEA), polybutylene adipate (PBA), polycaprolactone polyol (PC)
L), polyethylene adipate or a copolymer oligomer thereof, polyalkylene terephthalate, polyalkylene isophthalate, polyalkylene phthalate and the like. In addition, these copolymers, for example, block copolymers of PTMG and caprolactone, copolymers of polyester polyol and polyether polyol, and the like can also be used.
These copolymers can be synthesized by, for example, a method of ring-opening copolymerization of PTMG with ε-caprolactone, a method of ring-opening copolymerization of tetrahydrofuran, ethylene oxide, or propylene oxide with polyester polyol. The aforementioned polyols are mainly difunctional,
That is, it is preferable that one molecule has two hydroxyl groups, but it is also possible to use a polyfunctional polyol having three or more hydroxyl groups in one molecule in combination, if necessary.

The reactive hot melt adhesive of the present invention is one which reacts and crosslinks in a relatively short time after bonding the decorative sheet and the substrate, and it is not necessary to use a crystalline polyol compound. It is preferable to use a non-crystalline polyol compound that adheres regardless of the type of sheet, but it is also possible to use a crystalline polyol,
The feature is that it enables early quality inspection and cutting.

As a raw material of the polyurethane prepolymer used in the present invention, in addition to the above-mentioned polyol, an active hydrogen-containing compound such as a low molecular weight polyfunctional alcohol, that is, a chain extender may be used. Such a chain extender can improve the physical properties of polyurethane and exert the action of increasing the adhesive strength.

Specific examples of the chain extender include polyhydric alcohols such as ethylene glycol, 1,4-butanediol, neopentyl glycol, xylylene glycol and trimethylolpropane, 4,4'-diaminodiphenylmethane, Amines such as isophoronediamine, N-
Examples thereof include amino alcohols such as methyldiethanolamine, and one or more of these are used.

The isocyanate component of the polyurethane prepolymer of the present invention is not particularly limited as long as the reactivity, physical properties after curing and the like meet the purpose, but in terms of price, diphenylmethane diisocyanate (MDI) and tolylene diisocyanate ( The use of aromatic polyisocyanate compounds (including various isomers) such as TDI) is preferable. However, if necessary, other polyisocyanates may be used for the purpose of improving the properties as long as the object of the present invention is not impaired. Examples of such polyisocyanates include aromatic polyisocyanates such as naphthylene diisocyanate (NDI) and phenylene diisocyanate (PDI), and isophorone diisocyanate (IP).
DI), hexamethylene diisocyanate (HDI),
Cyclohexane diisocyanate, hydrogenated MDI (H
Examples thereof include aliphatic polyisocyanates such as MDI).

The low molecular weight polymer (oligomer) of an ethylenically unsaturated monomer preferably used in the hot melt adhesive composition of the present invention has a weight average molecular weight of 10,000.
-30000 polymers are preferred. It is also preferable that such an oligomer contains a reactive silyl group, particularly an alkoxysilyl group or an isocyanate group. The reactive silyl group contributes to the crosslinking of molecules by reacting with moisture in the air, and also contributes to the improvement of adhesion when the adherend is glass or metal oxide.

As the ethylenically unsaturated monomer constituting the oligomer, acrylic acid and methacrylic acid have 1 carbon atoms.
To 12 alkyl esters, vinyl acetate and other vinyl esters, vinyl ethers, styrene and other aromatic monomers, vinyl chloride, acrylonitrile, maleic acid esters, fumaric acid esters, etc. The above is selected and used.

As a compound used for introducing a reactive silyl group into an oligomer, an ethylenically unsaturated monomer having a reactive silyl group can be used, such as vinyltrichlorosilane, vinyltriethoxysilane and vinyltrimethoxy. Silane, vinyltris (2-methoxyethoxy) silane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltris (2-methoxyethoxy) silane, vinyltriacetoxysilane, 4
-(3-trimethoxysilylpropyl-benzyl) styrene sulfonate, 3-acryloxypropyltrimethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, vinylmethyldiacetoxysilane, Examples thereof include 3-methylacryloxypropylmethyl-diethoxysilane and 3-acryloxypropyldimethylmethoxysilane.

A monomer having a hydroxyl group and a monomer having an isocyanate group may be copolymerized as a component of the above-mentioned oligomer. As the monomer having such a functional group, specifically, a hydroxyl group is used. Examples of the monomer having are hydroxyethyl acrylate, hydroxyethyl methacrylate and the like, and examples of the monomer having an isocyanate group are isocyanate ethyl methacrylate, m-isopropenyl-γ, γ-dimethylbenzyl isocyanate and the like.

As a method for adding the above-mentioned oligomer to the reactive hot melt adhesive composition of the present invention, for example, the following method is possible. A method in which an oligomer is independently produced and added at the time of producing a reactive hot melt adhesive composition. Oligomer is manufactured independently and added to polyurethane prepolymer. An ethylenically unsaturated monomer is dissolved in a polyol which is a raw material for a polyurethane prepolymer, and an oligomer is formed by radical polymerization using a chain transfer agent such as n-dodecyl mercaptan in the polyol, if necessary. An ethylenically unsaturated monomer is dissolved in a polyurethane prepolymer, and a chain transfer agent such as n-dodecyl mercaptan is optionally used in a polyol to form an oligomer by radical polymerization. (In the case of a monomer having no hydroxyl group, such a method is also possible.)

As an elastic polymer block of a thermoplastic block copolymer having two or more polystyrene blocks according to claim 3 of the present application and an elastic polymer block,
Polymer blocks using at least one diene monomer such as butadiene and polyisoprene, or hydrogenated polymer blocks of these are suitable. When the polystyrene block is A and the elastic polymer block is B, the thermoplastic block copolymer is A-B-A or A- (B-
A) _n and A- (BA) _n- B. In addition, n is an integer of 2 to 50.
Further, not only linear molecules but also those having a structure such as star polymer may be used. Specific examples of such a thermoplastic resin include SBS, SIS, SEBS and the like.

If desired, other additives may be added to the reactive hot melt adhesive of the present invention. Examples of such additives include plasticizers, viscosity modifiers (viscosity improvers), and oxidation agents. Examples include inhibitors, pigments, stabilizers and the like.

[0037]

EXAMPLES Examples of the present invention will be described below based on experimental examples. The formulations are summarized in the upper part of Table 1. As the polyether polyol, PPG (bifunctional, molecular weight 2
000) was used. The production of the reactive hot melt adhesive composition is performed by a method well known to those skilled in the art, and one example thereof is as follows.

(Experimental Example) A polyol was charged into a four-necked flask equipped with a thermometer, a stirrer, and a nitrogen gas inlet tube,
Heat to 0 ° C. and reduce the pressure to remove water. Then, a predetermined MDI is charged and heated to 100 to 120 ° C. to carry out a reaction for 1 hour to synthesize a prepolymer having an NCO group terminal. Further, a viscosity improver and a catalyst were added to obtain a hot melt adhesive composition. The catalyst may be added before the prepolymer synthesis.

[0039]

[Table 1]

(Evaluation) (1) Measurement of melt viscosity The hot melt adhesive was heated and melted, and the viscosity at 120 ° C. was measured by a Brookfield Thermocel viscometer.

(2) Evaluation of adhesiveness (a) Preparation of evaluation sample Polyvinyl chloride (PVC) having a thickness of 200 μm as a base material
Using a decorative sheet for making, a hot melt adhesive composition heated and melted at 120 ° C. was applied so as to have a thickness of 50 μm, and the MDF was pressure-bonded and coated so that the situation as shown in FIG. 1 was obtained. A sample was prepared. About 2 on the decorative sheet
% Elongation was given. The cross-sectional shape of the MDF was 80 mm in width, 15 mm in height, and the recess 3 was formed in a semicircular shape with a radius of 3 mm, and a base material having a length of 200 cm was used.

The evaluation sample obtained by the method described in (b) Evaluation method / sheet coverage evaluation sample preparation was visually observed immediately after adhesion. The evaluation results are displayed as follows.

Pre-reaction Creep resistance The adhesion state of the evaluation sample after 2 hours from the pressure bonding, especially the concave portion 3
The floating and peeling based on the sheet shrinkage in Table 1 was visually evaluated.

The PVC adhesion evaluation sample is left standing at 20 ° C. and 60% RH for 48 hours for curing, and then left at 20 ° C. for 30 minutes and then PVC.
The sheet was peeled by hand, and the condition was visually evaluated.
The evaluation results are displayed as follows.

Curing speed: An adhesive film having a thickness of 50 μm was formed on a release paper using an applicator, and immediately thereafter, this adhesive film was transferred to a wood board and cured at 20 ° C. and 60% RH. Infrared absorption spectrum was measured after 4 hours and 2
The absorption intensity based on the NCO group found near 270 cm ⁻¹ was measured, and the reaction rate of the NCO group was determined from the change,
Those having a reaction rate of 80% or more are indicated by ◯.

(Evaluation Results) Table 2 shows the results of measurement and evaluation by the above methods.

[0047]

[Table 2]

From the above table, the following findings were obtained, and the hot melt adhesive of the present invention has good adhesiveness to polyvinyl chloride regardless of whether it is a sticky type or a sticky type. It is clear that the adhesiveness of the substrate after the pressure bonding, that is, the creep does not occur, and that the substrate exhibits excellent coverage.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a decorative sheet is bonded to a particle board having recesses.

Claims (3)

[Claims] 1. A reactive hot melt adhesive composition for coating a decorative sheet, comprising an isocyanate group-terminated prepolymer as a reactive component, comprising an amorphous polyol and a polyisocyanate compound. Of at least one of 2,2'-dimorpholinoethyl ether and bis (2,6-dimethylmorpholinoethyl) ether as a catalyst component and 0.05 to 6 relative to the composition.
Reactive hot melt adhesive composition containing wt%. 2. A low molecular weight polymer of an ethylenically unsaturated monomer having a weight average molecular weight of 10,000 to 3
The reactive hot melt adhesive composition according to claim 1, which comprises a low molecular weight polymer of 0000. 3. The reactive hot melt adhesive composition according to claim 1, further comprising a thermoplastic block copolymer having two or more polystyrene blocks and one or more elastic polymer blocks.