JP4758630B2 - Moisture curable hot melt adhesive - Google Patents

Description

  The present invention is a moisture curable hot melt excellent in weather resistance, having a high moisture curing reaction rate and excellent in thermal stability, which is preferably used for producing various components by laminating transparent or translucent members. It relates to adhesives.

Moisture curable hot melt adhesives having an isocyanate group in the molecule are already known and are used in various fields. In this type of adhesive, the isocyanate group in the molecule reacts with moisture in the air or in the adherend (referred to as “moisture curing reaction”). Finally, the adhesive has a high elasticity having a crosslinked structure, Forms a high-strength film. The moisture-curable hot-melt adhesive has been developed and improved in various ways, and in particular, moisture-curing containing a urethane prepolymer obtained by reacting a polyol compound having a hydroxyl group with a polyisocyanate compound having an isocyanate group. Many type hot melt adhesives are used. Various polyisocyanate compounds have been researched and used, and among them, in view of safety and cost, 4,4′-diphenylmethane diisocyanate (p-MDI) is often used. (Patent Document 1)

However, when a moisture-curable hot melt adhesive using 4,4′-diphenylmethane diisocyanate (p-MDI) is used and a translucent or transparent adherend is bonded, it is exposed to ultraviolet rays. There has been a problem that a phenomenon (yellowing) in which the formed adhesive layer turns yellow is observed, or that the strength of the formed adhesive layer is reduced due to molecular cleavage. In order to prevent yellowing and molecular cleavage, a polyisocyanate compound subjected to various hydrogenation treatments may be used, or a polyisocyanate compound in which an aromatic ring and an isocyanate group are not directly connected may be used.
JP 2002-322453 A

  The above method has problems such as a decrease in safety of the polyisocyanate compound itself and an increase in cost. Further, in the market, in order to improve productivity, a moisture curable hot melt adhesive having a higher moisture curing reaction rate is demanded, and development and improvement of a moisture curing rate control technique are being performed. The method is mainly based on the addition of a catalyst. Specifically, for example, a morpholine amine compound is often used. However, if the molecular design is performed so that the moisture curing reaction rate is high, the thermal stability is improved. There was a problem that it decreased. The present invention has been made in view of the above problems, and in the case of manufacturing various components by bonding a transparent or translucent member using a moisture-curable hot melt adhesive, even under ultraviolet irradiation. An object of the present invention is to provide a moisture-curing hot melt adhesive that has little yellowing, has a fast moisture curing reaction rate, and has good thermal stability.

（構造式１中、Ｒは炭素数１〜２０のアルキル基である。） The present inventors have advanced the development to solve the above-mentioned problems of the prior art and have come to make the present invention.
That is, in the present invention, moisture curing containing a urethane prepolymer obtained by reacting a polyol compound having two or more hydroxyl groups in one molecule with a polyisocyanate compound having two or more isocyanate groups in one molecule. In the type hot melt adhesive , polyester polyol and polyoxypropylene glycol are used as the polyol compound, and the polyisocyanate compound has an isocyanate group directly bonded to an aromatic ring, and is represented by the following structural formula (1). Moisture-curable hot melt comprising 0.001 to 5% by weight of a hindered amine light stabilizer (referred to as “HALS”) and 0.001 to 30% by weight of an organic phosphorus compound that is solid at room temperature Adhesive.

(In Structural Formula 1, R is an alkyl group having 1 to 20 carbon atoms.)

  The moisture curable hot melt adhesive of the present invention has a terminal obtained by reacting a polyol compound having two or more hydroxyl groups in one molecule with a polyisocyanate compound having two or more isocyanate groups in one molecule. Contains a urethane prepolymer having an isocyanate group.

This reaction is usually carried out in a range of [NCO] / [OH] = 1.5 to 2.5 in terms of the molar ratio of the hydroxyl group (OH) in the polyol compound to the isocyanate group (NCO) in the polyisocyanate compound. . As said polyol compound, the well-known polyol compound normally used for manufacture of a polyurethane can be used. Is in such a polyol compound, a polyester polyol and polyether polyol is used.

  Examples of the polyester polyol include terephthalic acid, isophthalic acid, 1,5-naphthalic acid 2,6-naphthalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and decamethylene. Polycarboxylic acids such as dicarboxylic acids and dicarboxylic acids such as dodecamethylene dicarboxylic acid and, for example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentane Examples thereof include polyester polyols obtained by reaction with polyols such as diol, 1,6-hexanediol, diethylene glycol, and cyclohexanediol, and poly-ε-caprolactone polyols obtained by ring-opening polymerization of ε-caprolactone.

An example of the polyether polyol is polyoxypropylene glycol .

  The polyisocyanate compound used in the present invention is characterized in that an isocyanate group is directly bonded to an aromatic ring. For example, diphenylmethane diisocyanate, a liquid modified product of diphenylmethane diisocyanate, polymeric MDI (methane diisocyanate), tolylene diisocyanate, And naphthalene-1,5-diisocyanate. Of these, diphenylmethane diisocyanate and its modified products are preferred from the viewpoints of low vapor pressure, low toxicity, and ease of handling. The said polyisocyanate compound is used individually or in mixture of 2 or more types.

The moisture-curable hot melt adhesive of the present invention contains a hindered amine light stabilizer (HALS) represented by the following structural formula 1 . This ensures that the moisture-curable hot-melt adhesive of the present invention, varying less yellowing due to ultraviolet exposure, shows a very good weatherability. In the present specification, the hindered amine light stabilizer means one having a structure in which the 2 and 6 positions of the piperidine ring structure are substituted with a substituent such as a methyl group.

The Ruhi Ndadoamin based light stabilizer used in the present invention, HALS is used represented by the structural formula 1, which contains at least one more. The content, Ru 0.001-5 wt% der as moisture vapor-curable hot-melt adhesive.

  R in Structural Formula 1 is an alkyl group having 1 to 20 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, and an octyl group.

  The HALS represented by the structural formula 1 is characterized in that a tertiary amine is modified with an amino ether group, and when added to a moisture-curable hot melt adhesive, it has the characteristic of improving thermal stability. . As HALS in which the tertiary amine is modified with an amino ether group, for example, TINUVIN 123 (trade name, manufactured by Ciba Geigy Co., Ltd.) with R being an octyl group, bis (N-octoxy-2,2,6,6-tetra) Methyl-4-piperidyl) sebacate etc. are mentioned and used suitably.

Examples of the organic phosphorus compound that is solid at room temperature include triphenyl phosphate, triphenyl phosphine, triphenyl phosphine oxide, and aromatic phosphoric acid condensed ester. By adding a solid organophosphorus compound at room temperature, it is possible to improve thermal stability without reducing the moisture curing reaction rate under room temperature curing. The addition amount, Ru is added in an amount of each 0.001 wt% moisture-curable hot-melt adhesive.

  Other moisture stabilizers can be added to the moisture curable hot melt adhesive of the present invention, and further, weather resistance can be further improved by adding a combination of an antioxidant, an ultraviolet absorber and the like. Can do.

  Examples of the antioxidant include hindered phenol antioxidants, such as pentaerythritol tetrakis [3- (3.5-di-tert-butyl-4-hydroxyphenyl) propionate], thiodiethylene bis [ 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, benzenepropanoic acid, 3,5 -Bis (1,1-dimethylethyl) -4-hydroxy, C7-C9 side chain alkyl ester, 2,4-dimethyl-6- (1-methylpentadecyl) phenol, diethyl [[3,5-bis (1 , 1-dimethylethyl) -4-hydroxyphenyl] methyl] phosphonate, 3,3 ′, 5,5 ′, 5 ″ -hex Tert-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl) tri-p-cresol, 4,6-bis (octylthiomethyl) -o-cresol, ethylenebis ( Oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate], hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1 , 3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 1,3 5-tris [(4-tert-butyl-3-hydroxy-2,6-xylyl) methyl] -1,3,5-triazine-2,4,6- (1H, 3H, 5H) -trione, etc. It is done.

Examples of ultraviolet absorbers include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and benzoate glaze stabilizers, such as 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4-6-bis (1-methyl-1-phenylethyl) phenol, 2- [5-chloro (2H)-
Benzotriazol-2-yl] -4-methyl-6- (tert-butyl) phenol, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2- (2H -Benzotriazol-2-yl) -4,6-di-tert-pentylphenol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, Reaction product of methyl 3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate and polyethylene glycol (Mw 300), 2- (2H-benzotriazole-2 -Yl) -6-dodecyl-4-methylphenol, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5 [(Hexyl) oxy] - phenol, Okutabenzon, 2,4-di -tert- butyl-3,5-di -tert- butyl-4-hydroxybenzoate, and the like.

  One or more of each of the antioxidant and the ultraviolet absorber may be added, or a combination of a plurality of types may be added. Although it does not specifically limit as addition amount, It is preferable to add in the range of 0.001 to 10 weight% as a moisture hardening type hot-melt-adhesive, respectively.

  To the moisture curable hot melt adhesive of the present invention, a tackifying resin, oil, and thermoplastic elastomer can be further added to enhance the adhesiveness.

  Examples of tackifying resins include rosin resins, terpene resins, aliphatic petroleum resins or aromatic petroleum resins. Preferably, those having a ring and ball softening point of 90 to 150 ° C are used. These tackifying resins may be used alone or in combination of two or more depending on the compatibility with other components and the type of adherend. Examples of the oil include process oil, extender oil, softener, naphthenic oil of non-aromatic oil, and paraffinic oil, which are generally used as a rubber softener.

  Examples of the thermoplastic elastomer include a styrene-conjugated diene block copolymer, an ethylene-vinyl acetate copolymer, an ethylene-acrylic ester copolymer, a polyolefin elastomer, a polyester elastomer, and a polyurethane elastomer.

  Other additives can be added to the moisture curable hot melt adhesive of the present invention. Other additives include fillers, softeners and stabilizers. In addition, an amine-based or tin-based catalyst for increasing moisture reactivity can also be added. Furthermore, anti-aging agents, wetting agents, thickening agents, antifoaming agents, coloring agents, and the like can be added.

  The amine catalyst is preferably a morpholine compound, for example, 2,2′-dimorpholinodiethyl ether, di (2,6-dimethylmorpholinoethyl) ether, bis (2- (2,6-dimethyl-4 -Morpholino) ethyl- (2- (4-morpholino) ethyl) amine, bis (2- (2,6-dimethyl-4-morpholino) ethyl)-(2- (2,6-diethyl-4-morpholino) ethyl ) Amine, tris (2- (4-morpholino) ethyl) amine, tris (2- (4-morpholino) propyl) amine, tris (2- (4-morpholino) butyl) amine, tris (2- (2,6) -Dimethyl-4-morpholino) ethyl) amine, tris (2- (2,6-diethyl-4-morpholino) ethyl) amine, tris (2- (2-ethyl-4-morpholino) ) Ethyl) amine, tris (2- (2-ethyl-4-morpholino) ethylamine and the like.

  As the stabilizer, various compounds can be added, and among them, organic phosphorus compounds are preferable. For example, tricresyl phosphate, triethyl phosphate, tributyl phosphate, tris (2-ethylhexyl) phosphate, trisbutoxyethyl phosphate Fate, triphenyl phosphate, octyl diphenyl phosphate, tris (isopropylphenyl) phosphate, cresyl diphenyl phosphate, triphenyl phosphite, triphenyl phosphine, triphenyl phosphine oxide, aromatic phosphate condensed ester However, an organic phosphorus compound that is solid at room temperature is more preferable.

(Function)
The moisture-curable hot melt adhesive of the present invention contains a urethane prepolymer using polyester polyol and polyoxypropylene glycol and a hindered amine light stabilizer represented by the above structural formula (1), so that it is irradiated with ultraviolet rays. In addition, since there is little molecular cleavage and the like, yellowing due to exposure to ultraviolet rays is small, and deterioration due to molecular cleavage is also small, it has very good weather resistance. Further, by using the HALS represented by the structural formula (1), it is possible to provide a moisture curable hot melt adhesive having more excellent thermal stability.

Since the moisture-curable hot melt adhesive of the present invention contains a urethane prepolymer using polyester polyol and polyoxypropylene glycol and a hindered amine light stabilizer represented by the above structural formula (1), it is translucent. Alternatively, even when bonding is performed using a transparent member, yellowing due to exposure to ultraviolet rays is small, and the weather resistance is very good. In addition, the curing rate is faster than that of conventional moisture curable hot melt adhesives, which greatly contributes to improvement of user productivity. Furthermore, by adding an organic phosphorus compound that is solid at room temperature, excellent thermal stability can be exhibited.

Hereinafter, the present invention will be specifically described by describing examples and comparative examples.
In addition, this invention is not limited only to the following Example.

( Comparative Example 1 )
Dynacol 7381 (manufactured by Huls) as a polyol compound and tinuvin 765 (manufactured by Ciba Specialty Chemicals) as a hindered amine light stabilizer having a tertiary amine are melt-kneaded under heating at 120 ° C., and the pressure is reduced to 133 Pa or less. And dehydrated. Thereafter, the temperature of the system was adjusted to 100 ° C., and then Isonate 125M (manufactured by Mitsubishi Chemical Corporation) was added as an isocyanate compound under a nitrogen atmosphere. After reacting for 3 hours, a moisture-curing hot melt adhesive solid at room temperature was obtained.

( Comparative Examples 2-7 , Example 1 )
A moisture-curable hot melt adhesive was prepared in the same manner as in Comparative Example 1 with the composition shown in Table 1.

数字は重量部を示している。

The numbers indicate parts by weight.

Evaluation method <Weather resistance evaluation>
Comparative Examples 1-7 About the moisture hardening type hot melt adhesive of Example 1 , a sheet having a thickness of 0.5 mm was prepared, punched into a No. 2 dumbbell shape, then subjected to a tensile test, and the dumbbell strength was measured. . Furthermore, after wrapping a new test piece with a polyethylene (PE) film and sealing it with a heat seal, it was exposed to ultraviolet rays for 60 days with a sunshine weatherometer tester, and then subjected to a tensile test to calculate a dumbbell strength reduction rate. . (Test temperature: 20 ° C., pulling speed: 100 mm / min) Further, the degree of yellowing was visually confirmed.

<Evaluation of curing speed>
For each moisture curable hot melt adhesive, MDF (medium) was coated with a moisture curable hot melt adhesive (40 μm) with a knife coater on a polyester (PET) sheet (thickness 100 μm) and heated to 50 ° C. in advance. And laminated with a rubber roll. The bonded body thus obtained was subjected to a 90-degree peel-resistant heat-resistant creep test after curing for 1, 3, and 5 days in an atmosphere of 23 ° C. and 55% RH, and the deviation width was measured. (Test temperature: 60 ° C., load: 4.9 N / inch, time: 1 hour)

<Thermal stability evaluation>
About each moisture hardening type hot-melt-adhesive, after measuring the viscosity in 120 degreeC with a BM type | mold viscosity meter, it enclosed with a sealed container and left still for 24 hours at 110 degreeC atmosphere, and again, BM type viscosity The viscosity at 120 ° C. was measured with a meter, and the thickening rate (unit%) was calculated.

  Table 2 shows the evaluation results of the weather resistance evaluation, the curing rate evaluation, and the thermal stability evaluation.

  It is used as a moisture-curing hot melt adhesive used for laminate production.

Claims (1)

A urethane prepolymer obtained by reacting a polyol compound containing polyester polyol and polyoxypropylene glycol with a polyisocyanate compound having an isocyanate group directly bonded to two or more aromatic rings in one molecule , the following structural formula (1 hindered amine light stabilizer 0.001 to 5% by weight represented by), and moisture-curable hot-melt adhesives characterized by containing an organophosphorus compound 0.001% by weight of solid at room temperature .

(In Structural Formula 1, R is an alkyl group having 1 to 20 carbon atoms.)