JPH0797558A - Polyurethane adhesive - Google Patents

Abstract

PURPOSE:To obtain a polyurethane adhesive having excellent adhesiveness and spray-coatability to a polyolefin substrate and suitable for the production of a composite panel such as interior trim for automobile by mixing a specific polyurethane resin with a urethane prepolymer and a polyisocyanate. CONSTITUTION:This polyurethane adhesive can be produced by mixing (A) a crystalline thermoplastic polyurethane resin such as a polyurethane resin having a weight-average molecular weight of about 150,000-250,000 and produced by reacting a C2n straightchain alkylene glycol (n>=2) with a C2n straight-chain alkylene dicarboxylic acid and reacting the resultant crystalline polyester glycol with an aromatic polyisocyanate, (B) a urethane prepolymer having active isocyanate group and obtained by reacting a hydrogenated polybutadiene polyol with a polyisocyanate and (C) a polyisocyanate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyurethane adhesive, and more particularly to a polyurethane adhesive for a vehicle ceiling material having a polyolefin base material as a core material.

[0002]

2. Description of the Related Art Adhesives used for vehicle ceiling materials, which are obtained by adhering a core material made of a polyolefin base material and a decorative sheet, are not only adhesive to the polyolefin base material, but also have irregularities. A better initial adhesion is needed than with certain shapes.

In JP-A-3-247468 and JP-A-3-247685, a main component composed of a thermoplastic polyurethane resin obtained by reacting polyester glycol with an aliphatic and alicyclic diisocyanate is disclosed. An adhesive for a polyolefin base material obtained by mixing a urethane prepolymer having an active isocyanate group obtained by reacting hydrogenated polybutadiene glycol with polyisocyanate and a curing agent composed of polyisocyanate. Has been described.

[0004]

However, when the adhesive described in the above publication is used for a vehicle ceiling material composed of a polyolefin base material, hydrogenated polybutadienediol-modified polyisocyanate is used as a curing agent. However, the adhesive strength, especially the initial adhesive strength, is insufficient.

[0005]

Means for Solving the Problems The inventors of the present invention have made diligent studies in view of the above situation. As a result, if a thermoplastic polyurethane resin having crystallinity is used as the thermoplastic polyurethane resin, the adhesive force to a polyolefin substrate, especially The inventors have found that an adhesive having an extremely high initial adhesive strength can be obtained, and completed the present invention.

That is, the present invention relates to a urethane prepolymer having an active isocyanate group obtained by reacting a thermoplastic polyurethane resin (A) having crystallinity with hydrogenated polybutadiene polyol and polyisocyanate.
The present invention provides an adhesive obtained by mixing (B) and polyisocyanate (C) as an essential component.

The thermoplastic thermoplastic polyurethane resin (A) having crystallinity, which is used as the main ingredient of the adhesive of the present invention, has a urethane bond in the molecule obtained by reacting a polyester resin having a hydroxyl group at the terminal with polyisocyanate. It means a resin having, and a resin having a crystal part derived from an alkylene chain in the resin. The degree of crystallinity of the resin having crystallinity can be expressed by the heat of crystallization by differential thermal analysis and the weight average molecular weight. To achieve the object of the present invention, the heat of crystallization by differential thermal analysis is 5 cal / g Above, it is necessary that the resin has a weight average molecular weight of 50,000 to 300,000.

The heat of crystallization of the thermoplastic thermoplastic polyurethane resin (A) of the present invention by differential thermal analysis is, for example, in the case of polyester polyol, polyester polyol
A control is possible by a combination of diol, a dicarboxylic acid, and polyisocyanate, which are the raw materials of the polyol, but differential thermal analysis is required to develop the excellent adhesiveness, particularly the initial adhesiveness, which is the object of the present invention. Heat of crystallization by 10c
It is preferably at least al / g. The weight average molecular weight is preferably 150,000 to 250,000 in consideration of the crystallinity, the initial adhesive strength and the viscosity.

The polyester resin having a hydroxyl group at the terminal is generally a polyester polyol composed of a diol and a dicarboxylic acid, and the diol component used in this case is ethylene glycol or 1,3-propanediol.
1,4-butanediol, 1,5-pentanedio
, Neopentyl glycol, 3-methylpentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1, Examples thereof include aliphatic diols such as 20-eicosandiol, aromatic diols such as ethylene oxide adducts of bisphenol A and propylene oxide adducts of bisphenol A, and isophthalic acid as a dicarboxylic acid component. -Acid, terephthalic acid, dimethyl isophthalate, terephthalic acid diethyl succinic acid, adipic acid, azelaic acid, sebacic acid, 1,6-hexanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1, 20-eicosane dicarboxylic acid, succinic acid anhydride, adipic acid anhydride, azelaic acid anhydride, 1,10-decanedicarboxylic acid anhydride, sebacic acid Examples thereof include ethyl ester, 1,12-dodecanedicarboxylic acid diethyl ester, and 1,20-eicosanedicarboxylic acid dimethyl ester. Particularly, as the diol, a straight-chain alkylene glycol having an even number of carbon atoms of 4 or more is included. It is desirable to use one or more kinds of dicarboxylic acids and one kind of linear alkylenedicarboxylic acid having an even number of carbon atoms of 4 or more as the dicarboxylic acid. Further, it is also possible to use a lactone polyester polyol represented by ring-opening polymerization of ε-caprolactam, or a polycarbonate diol using a cyclic diol.

The polyisocyanate to be reacted with the above-mentioned polyester resin having a hydroxyl group is 2,4
-Tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, xylylene diisocyanate, polymeric Aromatic polyisocyanates such as diphenylmethane diisocyanate, carbodiimidated diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, ethylene diisocyanate, ethylidene diisocyanate, propylene Aliphatic polyisocyanates such as diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, hydrogenated diphenylmethane diisocyanate −
Alicyclic polyisocyanates such as hydrogen peroxide, isophorone diisocyanate, hydrogenated tolylene diisocyanate, etc., but the isocyanate used in the present invention is from the viewpoint of initial adhesive strength expression. Aromatic polyisocyanate
It is desirable to use a diphenylmethane diisocyanate, especially.

The hydrogenated polybutadiene polyol used in the urethane prepolymer (B) having an active isocyanate group used in the present invention means a polybutadiene glycol having hydroxyl groups at both ends of the polymer. It was obtained by doing. The skeleton of polybutadiene is 1,
Structure consisting of 2 bonds or 1,4 trans bonds alone 1,2
A mixed structure of bonds and 1,4 trans bonds, a mixed structure of 1,2 bonds and 1,4 trans bonds and 1,4 cis bonds,
It has a mixed structure of 1,4 trans bonds and 1,4 cis bonds. There is no limitation on the proportion of each bond in each mixed structure,
It is desirable that the content of 1,4 bonds is 50% or more.

The polyisocyanate to be reacted with the hydrogenated polybutadiene polyol is 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate. ,
Aromatic polyisocyanates such as 2,4-diphenylmethane diisocyanate, xylylene diisocyanate, polymeric diphenylmethane diisocyanate, carbodiimidated diphenylmethane diisocyanate, and 1,5-naphthylene diisocyanate , Ethylene diisocyanate, ethylidene diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene di Aliphatic polyisocyanates such as isocyanate, hydrogenated diphenylmethane diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate
And alicyclic polyisocyanates such as G.
These polyisocyanates are used alone or in admixture of two or more.

The polyisocyanate (C) used in the present invention is 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, xylylene diisocyanate, polymeric diphenylmethane diisocyanate, carbodiimide Diphenylmethane diisocyanate, 1,5-
Aromatic polyisocyanates such as naphthylene diisocyanate, ethylene diisocyanate, ethylidene diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate ,
Aliphatic polyisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate, hydrogenated diphenylmethane diisocyanate, isophorone diisocyanate
And alicyclic polyisocyanates such as hydrogenated tolylene diisocyanate. These polyisocyanates are used alone or in admixture of two or more.

The adhesive of the present invention comprises, as a main component, a crystalline thermoplastic polyurethane resin (A) having a hydroxyl group at the terminal, which is obtained by reacting the above-mentioned polyester resin having a hydroxyl group at the terminal with an isocyanate. A main agent is mixed with a curing agent containing a urethane prepolymer (B) having an active isocyanate group obtained by reacting hydrogenated polybutadiene polyol and polyisocyanate and a polyisocyanate (C). Obtained.

A thermoplastic polyurethane resin (A) having crystallinity as a main component, a urethane prepolymer (B) and a polyisocyanate (C) having an active isocyanate group.
The curing agent obtained by mixing is adjusted as follows, for example.

The thermoplastic polyurethane resin (A) having crystallinity is dissolved in a suitable solvent, that is, a method of adding and reacting with the polyester polyol in the solvent, the polyester polyol and the polyisocyanate in the absence of the solvent. It is used as the main agent by the method of reacting with and dissolving it in a solvent.
In that case, it is possible to use an appropriate chain extender in any method.

As the solvent, acetone, methyl ethyl ketone, toluene, xylene, ethyl acetate and the like can be used, and these solvents can be used alone or in a mixture. Further, the urethane prepolymer (B) and polyisocyanate (C) having an active isocyanate group used as a curing agent can be obtained by reacting hydrogenated polybutadiene polyol with an excess amount of polyisocyanate. That is, the polyisocyanate is used in an amount such that the polyisocyanate is in an excess amount with respect to the hydroxyl groups of the hydrogenated polybutadiene polyol, preferably 30 to 150 equivalents of the isocyanate groups. As a result, the urethane prepolymer (B) and the polyisocyanate (C) are present in the present form. Further, after adjusting the prepolymer (B), the polyisocyanate (C) is used.
It is also possible to dilute with. This curing agent is dissolved in an appropriate solvent and used as a curing agent.

As the solvent, acetone, methyl ethyl ketone, toluene, xylene, ethyl acetate and the like can be used, and these solvents can be used alone or in a mixture. The amount of the curing agent used is preferably 0.1 to 30 parts by weight, and more preferably 1 to 20 parts by weight, based on 100 parts by weight of the main agent, in terms of solid content.
Parts by weight are suitable. If the amount of the curing agent is 0.1 parts by weight or less, the final adhesive force may be impaired, and if it is 30 parts by weight or more, the initial adhesive force may be decreased.

The adhesive of the present invention is usually a two-component mixed type adhesive consisting of the above-mentioned main component and curing agent, and the two liquids are mixed just before use. In addition to the above components, a solvent, an inorganic filler, a colorant, a stabilizer and other additives may be mixed if necessary. The two liquids of the mixed liquid in which the main agent and the curing agent are mixed do not separate during the pot life. Since this mixed solution is a dispersion having a low viscosity, it has good sprayability and can be uniformly applied in the form of fine particles.

The adhesive of the present invention has a good adhesion of the thermoplastic polyolefin resin to the molded plate and has an excellent initial adhesion. Further, even after the adhesive layer is aged under the conditions of heat and high temperature and high humidity, the adhesive strength thereof does not significantly decrease.

[0021]

EXAMPLES Next, examples and comparative examples of the present invention will be shown. Hereinafter, unless otherwise specified, parts indicate weight ratios, and% indicates% by weight.

<Synthesis of Main Agent> 400 parts of polyester diol (1,4-butanediol-adipic acid system) having a molecular weight of 3000 was charged in a 2 L four-necked flask and dehydrated, and then a reflux circuit was set. 2 parts of 1,4 butanediol
Parts, 500 parts of methyl ethyl ketone, 150 parts of toluene
Add parts to dissolve evenly. Dibutyltin dilaurate 50
ppm was added, and 38 parts of diphenylmethane diisocyanate was added all at once at 75 ° C., and the reaction was carried out at the same temperature until the NCO% became 0%. Thereafter, 377 parts of toluene was added to obtain Resin 1 containing 30% of the active ingredient at the OH end. Resin 1
The weight average molecular weight of the active ingredient was 185,000 and the heat of crystallization was 11.9 cal / g.

Similarly, the resin 1 has a molecular weight of 300.
0 polyester diol (1,4-butanediol
Resin 2 was obtained by using 400 parts of polyester diol (ethylene glycol / adipic acid type) having the same molecular weight instead of (adipic acid type). The weight average molecular weight of the active ingredient of Resin 2 was 180,000, and the heat of crystallization was 4.3 cal / g.

A 2 L 4-necked flask was charged with 400 parts of polyester diol (1,4-butanediol-adipic acid system) having a molecular weight of 3000 and dehydrated, and then a reflux circuit was set to set 1,4 butanedio-. 2 parts, methyl ethyl ketone 500 parts, and toluene 150 parts were added and uniformly dissolved. 50 ppm of dibutyltin dilaurate was added, and diphenylmethane diisocyanate 30 was added at 75 ° C.
Parts were added all at once and the reaction was carried out at the same temperature until the NCO% became 0%. Thereafter, 358 parts of toluene was added to obtain Resin 3 containing 30% of the active ingredient at the OH end. The weight average molecular weight of the active ingredient of Resin 3 is 43,000 and the heat of crystallization is 16.3 ca.
1 / g.

A 2 L 4-necked flask was charged with 400 parts of polyester diol (1,6-hexanediol, neopentyl glycol / adipic acid system) having a molecular weight of 2000, and after dehydration, a reflux circuit was set. , 9 parts of neopentyl glycol and 0.3 parts of trimethylolpropane
Parts, 500 parts of methyl ethyl ketone, 150 parts of toluene
Part of the mixture was added and uniformly dissolved. Dibutyltin dilaurate 50
ppm was added, and 48 parts of hexamethylene diisocyanate was added all at once at 75 ° C., and the reaction was carried out at the same temperature until the NCO% became 0%. Thereafter, 417 parts of toluene was added to obtain Resin 4 containing 30% of the active ingredient at the OH end. Resin 4
The weight average molecular weight of the active ingredient was 131,000 and the heat of crystallization was 4.2 cal / g.

The base compounds blended as shown in Tables 1 and 2 were used as Examples and Comparative Examples. At this time, the viscosity was adjusted with toluene, methyl ethyl ketone, acetone or the like, if necessary.

<Synthesis of Curing Agent> 42 parts of hydrogenated polybutadiene polyol having a molecular weight of 1200 was charged into a 2 L four-necked flask, a reflux circuit was set for dehydration, and 240 parts of toluene was added and uniformly dissolved. At 75 ° C., 336 parts of polymeric diphenylmethane diisocyanate was added all at once, and the reaction was carried out until the NCO% became constant. After that, 350 parts of toluene was added to obtain a curing agent.

Examples 1 to 4 and Comparative Examples 1 to 5 These base materials and curing agents were mixed. Example 1 Resin 1 alone as a main component was mixed with a curing agent at a compounding ratio shown in Table 1 and used as an adhesive. Example 2 Resins 1 and 2 were mixed as a main component with a curing agent at a compounding ratio shown in Table 1 and used as an adhesive. Example 3 Resins 1 and 3 were mixed as a main component with a curing agent in a compounding ratio shown in Table 1 and used as an adhesive. Example 4 Resins 1 and 4 were mixed as a main component with a curing agent in a compounding ratio shown in Table 1 and used as an adhesive. Comparative Example 1 Resin 2 alone as a main component was mixed with a curing agent at a compounding ratio shown in Table 2 and used as an adhesive. Comparative Example 2 Resin 3 alone was mixed with a curing agent at a compounding ratio shown in Table 2 as a main component and used as an adhesive. Comparative Example 3 Resin 4 alone was mixed with a curing agent at a compounding ratio shown in Table 2 as a main component and used as an adhesive. Comparative Example 4 Resins 2 and 3 were mixed as a main component with a curing agent at a compounding ratio shown in Table 2 and used as an adhesive. Comparative Example 5 Resins 2 and 4 were mixed as a main component with a curing agent in a compounding ratio shown in Table 2 and used as an adhesive.

These adhesives are made of glass fiber (length 50 m).
m) and polyethylene powder were mixed at a weight ratio of 5: 1 and air spray-applied at a rate of 250 g / m ² on a molding plate having a sandwich structure using a polyethylene film, and an adhesive was applied. The surface was dried at 100 ° C. for 3 minutes. The molded plate coated with this adhesive has 100
Nonwoven fabrics with a PP film (adhesive surface) heated at 10 ° C. for 10 seconds are overlaid and pressed at room temperature for 15 seconds. The pressure at this time is 0.2 kg / m ² .

The obtained processed product was tested as follows to evaluate the adhesive. <Test method and evaluation criteria> Heat-resistant creep resistance; 1 inch for processed products after lamination
A test piece is cut into a size of (width) × 10 cm (length (initial adhesiveness)). This test piece is lamination 1
After 0 minutes, in a 50 ° C. atmosphere, after 4 hours and 24 hours, 1
A 90-degree creep test with a load of 300 g / inch was carried out in an atmosphere of 00 ° C., and the peeling length after standing for 24 hours was measured. Peel strength; 24 minutes after lamination of the test piece, 24
180 degree peel strength (adhesive strength) after 23 hours × 65%
Peel strength was measured using Tensilon under RH atmosphere. Also, the peel strength of the test piece after 24 hours in hot (80 ° C), 23 ° C after heat aging (80 ° C x 400 hours) and after wet heat aging (50 ° C x 65% RH x 400 hours) x
The peel strength in a 65% RH atmosphere was measured.

[0031]

[Table 1] In the table, the unit of thermal creep resistance is mm, and the unit of adhesive strength is Kg / inch.

[0032]

[Table 2] In the table, the unit of thermal creep resistance is mm, and the unit of adhesive strength is Kg / inch.

[0033]

When the polyurethane adhesive of the present invention is used as an adhesive between a polyolefin thermoplastic resin molded plate and a decorative sheet, it has extremely excellent adhesiveness, particularly initial adhesiveness. Moreover, the adhesive strength at the time of heat is excellent, and the decrease in the adhesive strength due to heat or wet heat is small. In addition, spray to the base material
Since atomization is easy in the coating process, coating can be performed without coating defects.

Therefore, if this polyurethane adhesive is used for a composite panel used as an automobile interior material composed of the above-mentioned base material, it is possible to easily manufacture a composite panel having high performance at low cost.

Claims (6)

[Claims] 1. An active isocyanate obtained by reacting a thermoplastic polyurethane resin (A) having crystallinity with a hydrogenated polybutadiene polyol and polyisocyanate.
An adhesive obtained by mixing a urethane prepolymer (B) having a vinyl group with a polyisocyanate (C) as an essential component. 2. The adhesive according to claim 1, wherein the polyurethane resin (A) is obtained by reacting a crystalline polyester glycol with an aromatic polyisocyanate. 3. A crystalline polyester glycol is prepared by reacting one or more linear alkylene glycols having an even number of carbon atoms of 4 or more with a linear alkylene dicarboxylic acid having an even number of carbon atoms of 4 or more. The adhesive according to claim 2, wherein the adhesive is obtained. 4. The adhesive according to claim 1, wherein the weight average molecular weight of the polyurethane resin (A) is 150,000 to 250,000. 5. The polyurethane resin (A) is 50% or more based on the weight of the total solid content.
The adhesive according to any one of to 4. 6. The adhesive according to claim 1, wherein the polyurethane resin (A) is a thermoplastic polyurethane resin having a heat of crystallization of 10 cal / g or more in a differential thermal analysis.