JP7611692B2 - Moisture-curing reactive hot melt adhesive - Google Patents

Description

The present invention relates to a moisture-curing reactive hot melt adhesive.

In general, hot melt compositions are solvent-free, environmentally friendly, can be cured in a short time, and are very easy to handle, making it possible to improve the working environment at manufacturing sites. For this reason, hot melt compositions are widely used in precision fields such as automobiles and electrical machinery, as well as in the construction field.

In the past, the applicant invented a moisture-curing reactive hot melt adhesive containing an isocyanate-terminated urethane prepolymer obtained by reacting a polyol composition (A) containing an amorphous polyester polyol (a1) having an aromatic dicarboxylic acid as a constituent unit and a liquid polyester polyol (a2) having an aromatic dicarboxylic acid as a constituent unit, the total of (a1) and (a2) being 50% by weight or more relative to the total polyol, with a polyfunctional isocyanate compound (B) (Patent Document 1). This hot melt adhesive has good adhesion to aromatic group-containing substrates, such as polyester sheets, even at low temperatures, and is useful for laminating decorative polyester sheets, etc.

JP 2008-255187 A

Conventionally, moisture-curing reactive hot melt adhesives have been used in the manufacturing process of building materials. Specifically, they are used when bonding a plastic surface material to a wood-based substrate. The moisture-curing reactive hot melt adhesive shown in Patent Document 1 has a relatively high moisture permeability, so there is a possibility that the wood-based substrate will gradually deform due to absorption of moisture that passes through the adhesive surface, and there is room for improvement. In addition, when a polyvinyl chloride resin-based surface material is bonded, the phthalate ester added to the resin as a plasticizer gradually seeps out and is absorbed by the adhesive surface, which can cause a phenomenon in which the adhesive strength decreases, and further improvement is required.

The problem that the present invention aims to solve is to provide a moisture-curing reactive hot melt adhesive that maintains good adhesion and melt viscosity while having a short tack-free time for high curing properties, a high elastic modulus for excellent elasticity and impact resistance, low moisture permeability for less deterioration of the substrate, and suppressed absorption of phthalate esters.

The present invention is a moisture-curable reactive hot melt adhesive that contains an isocyanate-terminated urethane prepolymer obtained by reacting a polyol compound (A) containing a polycarbonate polyol (a1-1) derived from a sugar alcohol with a polyisocyanate compound (B).

The moisture-curing reactive hot melt adhesive of the present invention has the following advantages: while maintaining good adhesive properties and melt viscosity, it has a short tack-free time, which allows for high curing, a high elastic modulus, which provides excellent elasticity and impact resistance, low moisture permeability, which makes the substrate less susceptible to deterioration, and suppresses absorption of phthalate esters.

<Polyol Compound>
In the present invention, a polyol compound (A) is used. Examples of the polyol compound include polycarbonate polyol (a1), polyester polyol (a2), polyether polyol (a3), and polybutadiene polyol (a4).

Polycarbonate polyol (a1) is a polyol compound having a carbonate structure as the skeleton, and can generally be obtained by reacting an alcohol having two or more hydroxyl groups with a carbonate ester having two or more carbonate groups.

In particular, the present invention uses polycarbonate polyol (a1-1) derived from a sugar alcohol. The (a1-1) component uses a sugar alcohol or an anhydride thereof as an alcohol having two or more hydroxyl groups. The sugar alcohol can be obtained by reducing the carbonyl group in the sugar structure, and the anhydride can be obtained by dehydrating and condensing the sugar alcohol. Examples of sugar alcohols include lactitol, maltitol, mannitol, and sorbitol, and examples of anhydrides include isosorbide, which is obtained by dehydrating and condensing sorbitol.

In particular, it is preferable that the component (a1-1) has a structure represented by formula (1) as a structural unit.

The inventors of the present invention discovered that by using the (a1-1) component as a polyol compound, good adhesion and melt viscosity are maintained while the tack-free time is short, resulting in high curing properties, the elastic modulus is high, resulting in excellent elasticity and impact resistance, the moisture permeability is low, resulting in less deterioration of the substrate, and the absorption of phthalate esters is suppressed, leading to the completion of the present invention.

Examples of carbonate esters having two or more carbonate groups include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, diphenyl carbonate, and dicaprylyl carbonate.

The number average molecular weight of the (a1-1) component is preferably 300 to 10,000, more preferably 400 to 8,000, and particularly preferably 500 to 6,000.

Specific examples of the (a1-1) component include HS0830B (product name, manufactured by Mitsubishi Chemical Corporation, isosorbide-based, number average molecular weight: 800) and HS0840H (product name, manufactured by Mitsubishi Chemical Corporation, isosorbide-based, number average molecular weight: 800).

In addition, polycarbonate polyols (a1-2) other than the (a1-1) component can be used as long as the effects of the present invention are not impaired.

The (a1-2) component can be obtained by reacting an alcohol having two or more hydroxyl groups (excluding sugar alcohols and their anhydrides) with a carbonate ester having two or more carbonate groups.

Examples of alcohols with two or more hydroxyl groups (excluding sugar alcohols and their anhydrides) include chemical substances with 2 to 24 carbon atoms, such as ethylene glycol, diethylene glycol, 1,2-propylene glycol, dipropylene glycol, 1,2-, 1,3-, or 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,3-, 1,4-, 1,6-, or 2,5-hexanediol, 1,2- or 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,18-octadecanediol, and 1,20-eicosanediol.

Examples of carbonate esters having two or more carbonate groups include the compounds mentioned above.

Furthermore, in the present invention, polyol compounds other than polycarbonate polyol (a1) can be used for the purpose of improving tensile strength.

In the present invention, polyester polyol (a2) can be used. The (a2) component is a polyol compound having an ester structure as the skeleton, and can be divided into crystalline and non-crystalline ones. The (a2) component can be obtained by condensation polymerization of alcohols having two or more hydroxyl groups and carboxylic acids having two or more carboxyl groups.

Examples of alcohols having two or more hydroxyl groups include the compounds mentioned above.

Examples of carboxylic acids having two or more carboxyl groups include chemical substances having about 2 to 24 carbon atoms, such as oxalic acid, malonic acid, succinic acid, glutaric acid, methylsuccinic acid, dimethylmalonic acid, β-methylglutaric acid, ethylsuccinic acid, isopropylmalonic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, tridecanedicarboxylic acid, tetradecanedicarboxylic acid, hexadecanedicarboxylic acid, octadecanedicarboxylic acid, eicosanedicarboxylic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, and terephthalic acid.

The number average molecular weight of the (a2) component is preferably 500 to 15,000, more preferably 800 to 12,000, and particularly preferably 1,000 to 10,000.

The blending ratio of the (a2) component is preferably 30 to 800 parts by weight, more preferably 50 to 700 parts by weight, and particularly preferably 100 to 600 parts by weight, per 100 parts by weight of the (a1-1) component.

Specific examples of the (a2) component include HS2H-201AP (product name, Toyokuni Oil Mills, 1,6-hexanediol-based, number average molecular weight: 2,000), HS2H-451A (product name, Toyokuni Oil Mills, 1,6-hexanediol-based, number average molecular weight: 4,500), HS2E-581A (product name, Toyokuni Oil Mills, glycol-based, number average molecular weight: 5,500), HS Polyol 1000 (product name, Toyokuni Oil Mills, aromatic, number average molecular weight: 3,000), and P-7730 (product name, Evermore, glycol-based, number average molecular weight: 3,000).

In the present invention, polyether polyol (a3) can be used. The (a3) component is a polyol compound having an ether structure as the skeleton. The (a3) component can be obtained by addition polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, or the like to the above-mentioned alcohols having two or more hydroxyl groups. Specific examples of chemical substances include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

The number average molecular weight of the (a3) component is preferably 300 to 10,000, more preferably 400 to 8,000, and particularly preferably 500 to 5,000.

The blending ratio of the (a3) component is preferably 10 to 300 parts by weight, more preferably 30 to 250 parts by weight, and particularly preferably 50 to 200 parts by weight, per 100 parts by weight of the (a1-1) component.

Specific examples of the (a3) component include PTMEG2000 (product name, manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, number average molecular weight: 2,000), Hiflex D-1000 (product name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., polypropylene glycol, number average molecular weight: 1,000), and Hiflex D-2000 (product name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., polypropylene glycol, number average molecular weight: 2,000).

In the present invention, polybutadiene polyol (a4) can be used. The (a4) component is a polyol having a butadiene structure as the skeleton.

The number average molecular weight of the (a4) component is preferably 1,000 to 20,000, more preferably 1,200 to 15,000, and particularly preferably 1,500 to 10,000.

The blending ratio of the (a4) component is preferably 10 to 200 parts by weight, more preferably 30 to 150 parts by weight, and particularly preferably 50 to 120 parts by weight, per 100 parts by weight of the (a1-1) component.

Specific examples of the (a4) component include G-3000 (product name, manufactured by Nippon Soda Co., Ltd., number average molecular weight: 3,000).

<Polyisocyanate Compound>
In the present invention, a polyisocyanate compound (B) is used. The component (B) preferably has two or more isocyanate groups at its terminals. Examples of the type of component (B) include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

Specific examples of the compound (B) include methylene diphenyl diisocyanate (MDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), and hydrogenated products thereof.

When reacting the polyol compound (A) containing the component (a1-1) with the polyisocyanate compound (B), the molar ratio of the hydroxyl groups of the polyol compound to the isocyanate groups of the polyisocyanate compound is preferably 1:1-5, more preferably 1:1.1-4, and particularly preferably 1:1.2-3.

When using multiple polyol compounds to produce an isocyanate-terminated urethane prepolymer, it is preferable to add a catalyst as necessary, thoroughly mix them, and then add polyisocyanate compound (B) and allow the reaction to proceed.

The moisture-curing reactive hot melt adhesive of the present invention may contain other components such as fillers such as calcium carbonate, talc, and clay, as well as various additives such as antioxidants and preservatives.

<Examples and Comparative Examples>
The raw materials other than the polyisocyanate compound were charged into a separable flask equipped with a stirrer, temperature controller, and vacuum pump in the formulation shown in Table 1, and after stirring and dehydrating at 120°C under reduced pressure for 1 hour, the polyisocyanate compound was added and stirred and reacted at 100°C under a nitrogen atmosphere for 1 hour and at 100°C under reduced pressure for 1 hour to obtain a moisture-curable reactive hot melt adhesive according to the present invention. Here, the numerical values in Table 1 represent parts by weight. The compounds used are shown below.
HS0830B (product name): Mitsubishi Chemical Corporation, polycarbonate polyol (isosorbide type), number average molecular weight: 800
NL1010DB (product name): polycarbonate polyol (1,10-decanediol type) manufactured by Mitsubishi Chemical Corporation, number average molecular weight: 1,000
NL1030B (product name): Mitsubishi Chemical Corporation, polycarbonate polyol (neopentyl glycol type), number average molecular weight: 1,000
HS2H-451A (product name): Toyokuni Oil Mills, polyester polyol (1,6-hexanediol type), number average molecular weight: 4,500
HS Polyol 1000 (product name): Toyokuni Oil Mills, polyester polyol (aromatic), number average molecular weight: 3,000
P-7730 (product name): Evermore Corporation, polyester polyol (glycol type), number average molecular weight: 3,000
PTMEG2000 (product name): Mitsubishi Chemical Corporation, polyether polyol (polytetramethylene ether glycol), number average molecular weight: 2,000
Filler: Talc (average particle size: 5 μm)
Polyisocyanate compound: a mixture of 4,4'-methylenediphenyl diisocyanate and 2,4'-methylenediphenyl diisocyanate (weight ratio 1:1)

The following physical properties were evaluated for the moisture-curing reactive hot melt adhesives obtained in the above examples. The results are shown in Table 2.

<Melt Viscosity>
The moisture-curable reactive hot melt adhesive was melted at 120°C using a Brookfield viscometer, and the measurement temperature was 120°C, spindle No. 29 was used, and rotation was started at 10 rpm. The melt viscosity (mPa·s) was measured after 15 minutes. Measurement values of 30,000 mPa·s or less were evaluated as ◯, and values of more than 30,000 mPa·s were evaluated as ×.

<Tuck free time>
The moisture-curing reactive hot melt adhesive was melted at 120°C, and a coating film was prepared using an applicator to a thickness of 100 µm. The coating film was then left to stand at room temperature (23°C), and the time until the tack disappeared when touched with a finger was measured.

<Adhesiveness>
The moisture-curing reactive hot melt adhesive was melted at 120°C and applied to an olefin sheet at 80 g/ ^m2 with an applicator, and then immediately laminated to a wood-based substrate (MDF) and left to harden at room temperature (23°C) for one week. The olefin sheet was then pulled at 180° peel to check the state of failure.

<Tensile test>
The moisture-curing reactive hot melt adhesive was melted at 120°C to prepare a sheet with a thickness of 500 µm, which was then left to harden at room temperature (23°C) for one week. The sheet was then processed into a dumbbell size No. 8, and the stress at break (N/ ^mm2 ) and modulus of elasticity (N/ ^mm2 ) were measured using a tensile tester.

<Moisture permeability>
The moisture-curable reactive hot melt adhesive was melted at 120° C. to prepare a coating film having a thickness of 175 μm, which was then left to stand at room temperature (23° C.) for one week to cure. Thereafter, the moisture permeability was measured at 40° C. and 90% RH in accordance with JIS Z 0208.

<Plasticizer resistance>
The moisture-curing reactive hot melt adhesive was melted at 120°C, and a coating film with a thickness of 125 μm was prepared using an applicator, and the coating film was left to harden at room temperature (23°C) for one week. Then, a test piece of 30 mm x 40 mm was prepared, placed in a glass bottle (100 ml) with a lid, and diisononyl phthalate was poured into the bottle until the test piece was completely immersed. After the bottle was closed, the test piece was left to stand in a thermostatic bath (40°C) for one week. The test piece was then removed, and the diisononyl phthalate adhering to the surface was wiped off with a rag, and the weight increase rate was calculated using the following formula.
Weight increase rate (%)=(weight after test−weight before test)/weight before test×100

Claims (2)

The composition contains an isocyanate-terminated urethane prepolymer obtained by reacting a polyol compound (A) containing 30 to 800 parts by weight of a polyester polyol (a2) per 100 parts by weight of an isosorbide- based polycarbonate polyol (a1-1) with a polyisocyanate compound (B);
A moisture-curable reactive hot melt adhesive, characterized in that the isosorbide-based polycarbonate polyol (a1-1) has two functional groups. The moisture-curing reactive hot melt adhesive according to claim 1, characterized in that it is used for bonding polyvinyl chloride resin surface materials.