JP2545544B2 - Sulfur-containing urethane adhesive - Google Patents

Description

The present invention relates to a urethane-based adhesive having a long pot life and excellent water resistance.

[Conventional technology]

Urethane-based adhesives are applied and used in a wide range of materials as reactive adhesives. That is, the urethane adhesive contains a compound having an isocyanate group in its system system, and since the isocyanate group has a very strong activity, it reacts with the hydroxyl group contained in or adsorbed to most substances to be a strong agent. It can exhibit adhesive strength. Further, since urethane adhesives generally have excellent chemical resistance, cold resistance, and impact resistance, they have recently been used as structural adhesives that require semi-permanent bonding strength and high strength holding power. Is becoming.

Urethane-based adhesives are so-called two-component adhesives, in which the molecules are enlarged and cured by a three-dimensional cross-linking urethane reaction of polyisocyanate with polyester polyols and polyether polyols to obtain a strong adhesive force. It has been widely used. Conventionally, in order to improve the water resistance of the adhesive layer, a method of devising the selection of the type mainly according to the structure of the polyol and a combination with an epoxy resin having relatively good water resistance (Japanese Patent Publication No. No. gazette) has been tried.

[Problems to be solved by the invention]

Since the urethane-based adhesive has high reactivity, there is a problem that potability as an adhesive liquid before being applied to the adhesive surface is short and workability is not good. Further, the urethane resin has a higher water absorption rate than other resins, and since the urethane bond is essentially susceptible to hydrolysis, there is a problem that the urethane bond in the adhesive layer is cleaved. are doing.

Even by the conventional method for improving water resistance, even the urethane resin that is the adhesive layer having the lowest water absorption rate, 1.
It contains 0 to 2.0% by weight of water, leaving a problem that it causes a decrease in adhesive strength when the dry and wet periods are repeated or rainwater or the like hits the adhesive part directly. It was

In view of such a situation, an object of the present invention is to provide a urethane-based adhesive capable of maintaining a long pot life as an adhesive liquid and having excellent water resistance as an adhesive layer.

[Means for solving problems]

The present inventors have conducted extensive studies in order to solve the above problems, and by adopting polythiol as a compound that reacts with polyisocyanate, the polymerization rate at around room temperature is slower than in the case of polyol, and the pot It was found that the life can be maintained for a long time, and by further increasing the number of thiol groups in the isocyanate groups and polythiol compounds in the polyisocyanate in the molecule, it is possible to improve the state of imparting three-dimensional cross-linking as a resin for the adhesive layer. The present invention has been completed by finding that the water absorption rate is remarkably reduced and the water resistance is remarkably improved.

That is, the present invention provides a polyisocyanate compound having m (m is an integer of 2 or more) isocyanate groups in a molecule and a polythiol compound having n (n is an integer of 2 or more) thiol groups in a molecule. Is a sulfur-containing urethane adhesive obtained by selecting and mixing compounds such that the value of m + n is 5 or more.

M in one molecule used in the present invention (m is an integer of 2 or more)
Examples of the polyisocyanate compound having an isocyanate group include hexamethylene diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, diisocyanate cyclohexane, bis (isocyanatomethyl) cyclohexane, diisocyanate methylcyclohexane, bicycloheptane triisocyanate and lysine isocyanate-β- Aliphatic or alicyclic polyisocyanates such as isocyanate ethyl ester, tolylene diisocyanate, 4,4 '
-Aromatic aromatic compounds such as polyisocyanates in which isocyanate groups are directly bonded to aromatic compounds such as diphenylmethane diisocyanate, tolidine diisocyanate, and triphenylmethane triisocyanate, xylylene diisocyanate, mesitylene triisocyanate, and bis (α, α-dimethylisocyanate methyl) benzene And polyisocyanates bound to each other in the form of isocyanatomethylene groups, adduct reaction products of these polyisocyanates with trimethylolpropane, and isocyanurate compounds.

When it is necessary to avoid weathering, especially yellowing over time, such as in adhesives for automobile safety glass, aliphatic or cycloaliphatic polyisocyanates and aromatic isocyanates with less methylene tendency are used. Polyisocyanates bound in the radical state are preferred.

Examples of the polythiol compound having n thiol groups (n is an integer of 2 or more) in one molecule include bis (2-methicaptoethyl) ether, 1,2-ethanedithiol, 1,4-
Butanedithiol, bis (2-mercaptoethyl) sulfide, ethylene glycol bis (2-mercaptoacetate), ethylene glycol bis (3-mercaptopropionate), 2,2-dimethylpropanediol bis (2-mercaptoacetate), 2 , 2-dimethylpropanediol, bis (3-mercaptopropionate),
Trimethylolpropane tris (2-mercaptoacetate), trimethylolpropane tris (3-mercaptopropionate), trimethylolethanetris (2
-Mercaptoacetate), trimethylolethane tris (3-mercaptopropionate), pentaerythritol tetrakis (2-mercaptoacetate), pentaerythritol tetrakis (3-mercaptopropionate), dipentaerythritol hexakis (2-mercaptoacetate) ), Dipentaerythritol hexakis (3-mercaptopropionate), 1,2-dimercaptobenzene, 4-methyl-1,2-dimercaptobenzene, 3,6-dichloro-1,2-dimercaptobenzene, 3,
Examples include 4,5,6-tetrachloro-1,2-dimercaptobenzene, xylylenedithiol, 1,3,5-tris (3-mercaptopropyl) isocyanurate, and the like.

The combination of these polyisocyanate compound and polythiol compound is a polyisocyanate compound having m (m is an integer of 2 or more) isocyanate groups in one molecule, and n (n is 2 or more) in one molecule. In the polythiol compound having an (integer) thiol group, the compound is selected so that the value of m + n is 5 or more.

The polyisocyanate compound and the polythiol compound are preferably used in a molar ratio of NCO / SH functional groups of 0.5 to 3.0, particularly 0.5 to 1.5.

In the present invention, the urethane polymerization reaction of polyisocyanate and polythiol is much slower than that of polyol, and the viscosity increase after mixing the two liquids is also small. This tendency is the same when amines, organometals, quaternary ammonium fluoride, etc., which are polymerization catalysts, are added. However, in order to accelerate the heat-curing reaction after adhesion, an organotin compound, which has a weak polymerization catalyst action at around room temperature and exerts a strong polymerization catalyst action at the time of heat curing, such as dibutyltin dilaurate or dibutyltin bis (octylthio). It is desirable to add 0.01 to 1.0% by weight of a polymerization catalyst such as glycol ester) or dibutyltin bis (isooctyl mercaptoacetate).

Further, if necessary, for example, in order to prevent the coloring of the adhesive layer formed by the adhesive in the safety glass of automobiles or the like over time, a UV absorber, an antioxidant, an anti-coloring agent, etc. may be colored on the adhesive layer. Alternatively, a dye or an infrared absorber may be added as appropriate in order to provide a heat blocking effect.

In the adhesive of the present invention, an organic solvent may be used in order to appropriately maintain the viscosity of the adhesive liquid at the time of adhesion, but in this case, a solvent having no reactivity with polyisocyanate or polythiol, that is, an ester. It is preferable to use a class, halogenated hydrocarbon or aromatic hydrocarbon.

Thus, in order to obtain a urethane adhesive having a low water absorption rate and good water resistance according to the present invention, an organic solvent, an ultraviolet absorber, an antioxidant, an anti-coloring agent or a dye is added to either or both of polyisocyanate and polythiol. It is possible to obtain an adhesive liquid by adding a near-infrared absorbing agent and the like to dissolve or disperse it well and, before use, appropriately add a liquid containing a polyisocyanate, a liquid containing a polythiol and a polymerization catalyst and mix them well.

Since the sulfur-containing urethane adhesive thus obtained may react with moisture in the air, it is preferable to use it quickly or place the adhesive liquid in a nitrogen gas atmosphere.

The heating temperature and heating time required for curing the adhesive solution are usually 30 to 180 ° C. and several minutes to several days, although they vary depending on the types of polyisocyanate, polythiol and catalyst used.

[Work]

It is considered that the sulfur-containing urethane adhesive solution of the present invention has a long pot life because the polythiol used as a compound that reacts with the polyisocyanate compound has a smaller polymerization rate at around room temperature than a polyol. Further, the reason why the sulfur-containing urethane adhesive of the present invention has a low water absorption is not always clear, but a normal urethane bond Compared with, thiocarbamate bond Has a low affinity for water and maintains the three-dimensional cross-linking by regulating the number of isocyanate groups and thiol groups in the molecule, and both effects are combined to prevent water molecules from entering the adhesive layer resin. It is presumed to be because.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples.
The present invention is in no way limited by this embodiment.

 Parts in Examples are parts by weight.

The test method used in the examples will be described below.

(Pot life test) Polyisocyanate and polythiol were left in a 50 ml Erlenmeyer flask with a ground stopper at 25 ° C for 1 week without using a polymerization catalyst at a ratio shown in the examples. Those that did not exist were marked with x.

(Adhesive force) The adhesive force obtained by adhering two aluminum test pieces was measured for shear force at a speed of 50 mm / min in a temperature control chamber of 25 ° C by an autograph manufactured by Shimadzu Corporation.

(Adhesive force after hot water treatment) The adhesive to which two aluminum test pieces were adhered was immersed in warm water at 60 ° C for 1 week, pulled up, left at room temperature for 24 hours, and then the adhesive force was measured by the above method.

(Water absorption rate) After measuring the amount of the cured product which was applied and cured on one side of the pre-weighed aluminum plate shown in the example, it was immersed in water (25 ° C)
After soaking for a period of time, it was taken out, the adhering water was wiped off, and the increased weight was quickly measured to measure the increase ratio with respect to the amount of the cured product.

(Example-1) 22.3 parts of isophorone diisocyanate, pentaerythritol tetrakis (3-mercaptopropionate) 2
4.4 parts and 0.08 part of dibutyltin dilaurate were added and mixed well to be uniform.

The mixing was fast and there was almost no thickening at room temperature even after 6 hours. This adhesive solution was applied to an aluminum test piece with a bar coater, sandwiched between other aluminum test pieces, and heat-cured at 150 ° C. for 30 minutes under a contact pressure of 1 kg / cm ² .

Further, in order to prepare a test piece for measuring the water absorption rate of the adhesive layer, the adhesive liquid is applied to the aluminum test piece with a thickness of 50 μm.
The test piece coated so as to have the above composition was heated and cured at a temperature of 130 ° C. for 1 hour.

When the two kinds of test pieces thus obtained were tested by using the test method described above, the results shown in Table 1 were obtained.

(Example-2) 1,3-xylylene diisocyanate 18.8 parts, pentaerythritol tetrakis (3-mercaptopropionate) 24.4 parts, ultraviolet absorber (Kyodo Chemical Co., Ltd., trade name Bio soap 583) 0.04 parts, and dibutyltin. 0.05 part of (octyl thioglycol ester) was mixed well so as to be uniform. Mixing is fast and thickening at room temperature is 6
Almost no time later.

Using this adhesive liquid, two types of test pieces were prepared in the same manner as in Example 1.

The performance of the adhesive thus obtained is shown in Table 1.

(Example-3) 1,3-bis (isocyanatomethyl) cyclohexane 1
5.5 parts, tolylene diisocyanate 3.5 parts, butyl acetate 20
Parts, dipentaerythritol hexakis (3-mercaptopropionate) 26.1 parts and dibutyltin dilaurate 0.04 parts were well mixed to be uniform. The mixing was fast and there was almost no thickening at room temperature even after 6 hours.

Using this adhesive liquid, two types of test pieces were prepared in the same manner as in Example 1.

The performance of the adhesive thus obtained is shown in Table 1.

(Example-4) 1,3-bis (α, α-dimethylisocyanatomethyl) benzene 24.4 parts, xylene 20 parts, 1,3,5-tris (3-mercaptopropyl) isocyanurate 23.4 parts and dibutyltin dilaurate 0.2 parts Were mixed well to be uniform.

The mixing was fast and there was almost no thickening at room temperature even after 6 hours.

Two kinds of test pieces were prepared in the same manner as in Example 1 using this adhesive solution.

The performance of the adhesive thus obtained is shown in Table 1.

(Comparative Example-1) When 18.8 parts of 1,3-xylylene diisocyanate was added to a mixture of 12.6 parts of polypropylene glycol (molecular weight 420) and 18.2 parts of polypropylene triol (molecular weight 410), a slight amount of heat was generated to increase the viscosity, and finally, rapidly. The polymerization reaction proceeded and the adhesion operation was impossible. Therefore, it is not listed in Table 1.

(Comparative Example-2) 30 parts of "Coronate L" (trade name, manufactured by Takeda Chemical Industries, Ltd.), which is a tolylene diisocyanate adduct of trimethylolpropane, and "Nipporan 3002", which is a saturated polyester modified with unend hydroxyl group isocyanate (Japan 9 parts by trade name of Polyurethane Industry Co., Ltd. were mixed so as to be uniform.

Mixing was fast, but thickening was observed after 6 hours at room temperature. Two kinds of test pieces were prepared in the same manner as in Example 1 using the adhesive solution before thickening. The performance of the adhesive thus obtained is shown in Table 1.

(Comparative Example-3) 1,3-Xylylene diisocyanate 18.8 parts, ethylene glycol bis (2-mercaptopropionate) 23.8
And 0.05 part of dibutyltin bis (octylthioglycol ester) were evenly mixed. The mixing was fast and there was almost no thickening at room temperature even after 6 hours. Two kinds of test pieces were prepared from this adhesive solution in the same manner as in Example 1.

The performance of the adhesive thus obtained is shown in Table 1.

In the case of Examples 1 to 4 in which a polythiol compound is used as a compound to be reacted with the polyisocyanate compound and the value of m + n is 5 or more, the pot life is long and the adhesive strength is
While the adhesive strength and water absorption after hot water treatment are both good,
In Comparative Example-2 using the polyol compound, although the test piece was prepared before thickening, the pot life was short, the adhesive strength after the hot water treatment was low, and the water absorption rate was large.

Also in Comparative Example-3 using the polythiol compound, m +
Since n was 4 and less than 5, the pot life was long, but the adhesive strength and the adhesive strength after hot water treatment were low, and the water absorption rate was also high.

〔The invention's effect〕

The sulfur-containing urethane adhesive obtained by the present invention has a pot life which is extremely long as compared with a urethane-based adhesive using an ordinary polyol, when compared without adding a polymerization catalyst. By selecting it, it becomes possible to freely select the pot life of the adhesive liquid.

Further, the moisture absorption rate of the adhesive layer obtained by applying the sulfur-containing urethane adhesive of the present invention to only one surface of a steel sheet and curing it (ISO R62B
Method, that is, the test piece is immersed in distilled water at 23 ° C for 24 hours, and then weighed immediately to see the increase.)
Is 0.02 to 0.30% by weight, which is dramatically lower than the moisture absorption rate obtained by a similar method using a conventional urethane adhesive, and the adhesive strength after immersion in hot water is maintained at a high level.

Therefore, the sulfur-containing urethane adhesive of the present invention is extremely good as a structural adhesive for a portion which is always exposed to rainwater or the like, an adhesive for wood, or an adhesive for cloth which requires washing resistance.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-60-199016 (JP, A) JP-A-63-245421 (JP, A) JP-A-59-22976 (JP, A) JP-A-58- 187477 (JP, A) JP 61-26633 (JP, A) JP 55-160071 (JP, A)

Claims (3)

(57) [Claims] 1. A polyisocyanate compound having m (m is an integer of 2 or more) isocyanate groups in one molecule and 1
A sulfur-containing urethane adhesive obtained by selecting and mixing a polythiol compound having n thiol groups (n is an integer of 2 or more) in the molecule so that the value of m + n is 5 or more. 2. A polyisocyanate compound and a polythiol compound are used at a molar ratio of NCO / SH functional groups of 0.5 to 0.5.
The sulfur-containing urethane adhesive according to claim 1, which is in the range of 3.0. 3. An organotin compound catalyst in an amount of 0.01 to 1.0% by weight in a mixture of a polyisocyanate compound and a polythiol compound.
The sulfur-containing urethane adhesive according to claim 1, which is added.