JP2855685B2 - Method for producing urethane resin - Google Patents

Description

The present invention relates to a method for producing a urethane resin.

(Prior Art) Urethane resins, especially linear urethane resins having an isocyanate group at a molecular terminal, are mainly used as wet-curable adhesives, taking advantage of the fact that they can be cured by moisture.

For example, JP-A-62-81375 discloses a method for producing a urethane resin as described above, which comprises reacting a linear aliphatic saturated polyester diol with an aromatic diisocyanate or an alicyclic diisocyanate under diisocyanate excess conditions. Is described.

(Problems to be Solved by the Invention) However, a urethane resin having an isocyanate group at a molecular terminal produced by using an aromatic diisocyanate or an alicyclic diisocyanate has, for example, a cohesive force when used as a reactive hot melt adhesive. And poor initial adhesion.

(Means for Solving the Problems) The present inventors have conducted intensive studies in view of the above situation,
Using polymethylene diisocyanate instead of aromatic diisocyanate or alicyclic diisocyanate, in reacting polymethylene diisocyanate with linear aliphatic saturated polyester diol, polymethylene diisocyanate under conditions of linear aliphatic saturated polyester diol excess To obtain a urethane prepolymer having a hydroxyl group at the molecular terminal, and then reacting the urethane prepolymer with a diisocyanate and a diisocyanate in an excess of diisocyanate to form a linear aliphatic saturated polyester skeleton and a polymethylene skeleton. It is found that a linear urethane resin having an isocyanate group at the molecular terminal, which is substantially a repeating unit having only a structure directly bonded through a bond, has excellent initial adhesiveness and is suitable as a hot melt adhesive, Book Which resulted in the completion of the Akira.

That is, in the present invention, a linear aliphatic saturated polyester diol (A) and a polymethylene diisocyanate (B) are reacted under an excess of the linear aliphatic saturated polyester diol (A) to have a hydroxyl group at a molecular terminal. A method for producing a urethane resin having an isocyanate group at a molecular end, characterized in that a urethane prepolymer is obtained and then reacted with a diisocyanate (C) under an excess of diisocyanate (C), preferably a linear fatty acid. The aliphatic saturated polyester diol (A) is a polyester diol obtained by reacting a polymethylene diol (a1) with a polymethylene dicarboxylic acid (a2), and preferably the linear aliphatic saturated polyester diol (A) is an even number Having a hydroxyl group bonded directly to both ends of a polymethylene skeleton having a number of carbon atoms And a dicarboxylic acid in which carboxyl groups are directly bonded to both ends of a polymethylene skeleton having an even number of carbon atoms. Preferably, the polymethylene diisocyanate (B) has an even number of carbon atoms. It is intended to provide a method for producing a urethane resin having an isocyanate group at a molecular terminal, which is a diisocyanate in which isocyanate groups are directly bonded to both ends of a polymethylene skeleton having

Examples of the linear aliphatic saturated polyester diol (A) according to the present invention include: a linear aliphatic saturated diol;
Examples thereof include those obtained by reacting at least one compound selected from the group consisting of a linear aliphatic saturated dicarboxylic acid, a linear aliphatic saturated dicarboxylic anhydride, and a linear aliphatic saturated dicarboxylic acid dialkyl ester. More specifically, polymethylene diol (a ₁ )
Examples thereof include those obtained by reacting at least one compound (a ₂ ) selected from the group consisting of polymethylene dicarboxylic acid, polymethylene dicarboxylic anhydride and polymethylene dicarboxylic acid dialkyl ester.

In the present invention, polymethylene diol (a ₁ ) refers to a diol in which hydroxyl groups are directly bonded to both ends of a polymethylene skeleton, and compound (a ₂ ) is a dicarboxylic acid in which a carboxy group is directly bonded to both ends of a polymethylene skeleton , Its anhydrides and dialkyl esters.

The linear aliphatic saturated polyester diol (A) includes polymethylene diol having an even number of carbon atoms, polymethylene dicarboxylic acid having an even number of carbon atoms, an anhydride thereof, and a dialkyl ester thereof. A polyester diol comprising at least one compound selected is preferred.

The molecular weight of the linear aliphatic saturated polyester diol (A) is preferably from 300 to 5,000, and more preferably from 500 to 3,500. As the straight-chain aliphatic saturated polyester diol (A) has a higher molecular weight, the resulting urethane resin or its cured product becomes more rigid, and conversely, a lower molecular weight becomes more flexible. do it.

Examples of the polymethylene diol (a ₁ ) used for producing the linear aliphatic saturated polyester diol (A) include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,
6-hexanediol, 1,8-octanediol, 1,10-
Decane diol, 1,12-dodecane diol, 1,16-hexadecane diol, 1,20-eicosane diol and the like include, as the compound (a ₂ ), for example, succinic acid, glutanic acid,
Adipic acid, suberic acid, azelaic acid, sebacic acid,
1,10-decanedicarboxylic acid, 1,12-dotecandicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,20-eicosandicarboxylic acid, succinic anhydride, adipic anhydride,
Azelaic anhydride, 1,10-decanedicarboxylic anhydride, dimethyl glutanate, diethyl suberate, dipropyl sebacate, diethyl 1,12-dodecanedicarboxylate, dimethyl 1,20-eicosandicarboxylate Esters and the like.

The polymethylene diisocyanate (B) according to the present invention is a diisocyanate in which isocyanate groups are directly bonded to both ends of a polymethylene skeleton, and examples thereof include tetramethylene diisocyanate, hexamethylene diisocyanate, and octamethylene diisocyanate. preferable.

Examples of the diisocyanate (C) according to the present invention include tolylene diisocyanate, diphenylmethane diisocyanate, liquid diphenylmethane diisocyanate,
Aromatic diisocyanates such as naphthylene diisocyanate and crude diphenylmethane diisocyanate; aliphatic diisocyanates such as hexamethylene diisocyanate, lysine diisocyanate and octamethylene diisocyanate; and alicyclic diisocyanates such as isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate and xylene diisocyanate.

As a method for producing a urethane resin having an isocyanate group at a molecular terminal according to the present invention, a linear aliphatic saturated polyester diol (A) and a polymethylene diisocyanate (B) are reacted under an excess of (A) to obtain a molecular terminal. To obtain a urethane prepolymer having a hydroxyl group, and then reacting this with a diisocyanate (C) under an excess of (C).

In the production method of the present invention, reaction conditions other than those described above are not particularly limited, but usually, a polymethylene diisocyanate (B) is added to a polyester diol (A) in a hydroxyl group / isocyanate group (equivalent ratio) in the presence of an inert gas. ) = 1.2 to 2.0, and reacted until the isocyanate group abundance becomes zero to obtain a urethane prepolymer, and then diisocyanate (C) is added with isocyanate group / hydroxyl group (equivalent ratio) = 1.3 to 2.0. It suffices that the reaction is carried out until the hydroxyl group abundance becomes zero.

However, since the production method of the present invention is an isocyanate excess reaction, it is preferable to carry out the reaction under mild reaction conditions, for example, at a relatively low temperature (50 to 80 ° C.) for 1 to 10 hours. When using a catalyst, it is better to keep it to the minimum necessary.

Examples of the catalyst that can be used in this case include nitrogen-containing compounds such as triethylamine, triethylenediamine, and morpholine, and organic metal compounds such as potassium acetate, zinc stearate, tin octylate, and dibutyltin dilaurate.

In the production method of the present invention, the method (A),
It is particularly preferable to use only the components (B) and (C).

In addition, other raw materials may be used as long as the initial adhesiveness of the urethane resin finally obtained is not impaired.

The present invention is excellent in that the molecular weight distribution of the finally obtained urethane resin having an isocyanate group at the molecular terminal is sharp.

The diisocyanate (C) used in the second-stage reaction includes polymethylene diisocyanate (B)
Aromatic diisocyanates are preferred in that they are less toxic in the free state, and it is preferred to use only diphenylmethane diisocyanate in that they do not easily inhibit the crystallinity of the obtained polyurethane resin.

However, a polyisocyanate having more than two functions may be used as long as the toxicity in the free state is not significantly increased as compared with the case where only the aromatic diisocyanate is used, or the crystallinity of the obtained polyurethane resin is not significantly impaired. .

When the urethane resin having an isocyanate group at the molecular terminal obtained by the method of the present invention is used as a moisture-curable urethane-based adhesive, its melt viscosity at 100 to 130 ° C. is 5000 to 100,000 CPS, and the obtained urethane resin weight is of
The reaction is preferably performed so that 0.5 to 4% by weight is the isocyanate content.

The urethane resin obtained by the production method of the present invention can be used as it is as a moisture-curable adhesive, but if it is dissolved in an organic solvent as needed, it can be used as a solvent-type adhesive.

The urethane resin obtained by the production method of the present invention may be used in combination with a resin such as an ethylene-vinyl acetate copolymer which has been conventionally used as a hot melt adhesive.

Further, secondary materials and additives used in ordinary adhesives in a range that does not inhibit the crystallinity of the obtained urethane resin, for example, a plasticizer, a thermoplastic polymer, a tackifier, a filler, a pigment,
It is also possible to use curing catalysts, moisture removers, storage stabilizers, anti-aging agents and the like.

In the urethane resin obtained by the production method of the present invention,
By adding and mixing the inorganic filler, the initial adhesion to the adherend and the rapid solidification can be further improved. The method of addition is not particularly limited.For example, a method of adding and mixing an inorganic filler sufficiently removed from water to the obtained urethane resin, adding and mixing in an optional step of urethane resin production, and reacting in the presence of the inorganic filler. Is performed.

Examples of the inorganic filler that can be used at this time include calcium carbon, magnesium oxide, talc, aerosil, barium sulfate, silica sand, aluminum hydroxide, kaolin clay, and the like.

Among these inorganic fillers, inorganic fillers having a pH of 7 or less, particularly kaolin clay, are particularly preferred in that they have excellent thermal stability during heating when the adhesive is actually used.

The amount of the inorganic filler to be added is preferably 3 parts by weight or more based on 100 parts by weight of the solid content of the obtained urethane resin, and 3 to 50 parts by weight from the viewpoint of obtaining a viscosity suitable for practical use.

Next, the present invention will be described with reference to examples. Hereinafter, unless otherwise specified, “part” indicates “part by weight” and “%” indicates “% by weight”.

Reference Examples 1 to 4 (Preparation of Linear Aliphatic Saturated Polyester Diol (A)) In a flask equipped with a dehydration circuit, the linear aliphatic saturated diol and the linear aliphatic saturated dicarboxylic acid in a predetermined amount described in Table 1 were prepared. Add 0.05 g of isopropyl titanate,
Condensation at a temperature of 220 ° C. until the acid value becomes 1.0% or less and the water content becomes 0.06% or less.
1 to A-4 were obtained.

Example 1 A reflux circuit was set, and a polyester diol A-1 was placed in a two-necked four-necked flask in which air was previously replaced with nitrogen gas.
After 900 g and 0.05 g of dibutyltin dilaurate were added and stirred and uniformly melted, 25 g of hexamethylene diisocyanate was added dropwise at 80 ° C., and the reaction was carried out at the same temperature until the isocyanate content became 0%.

Then, 75 g of diphenylmethane diisocyanate was added thereto all at once and reacted at 80 ° C. until the isocyanate content became constant. Thereafter, degassing was performed under reduced pressure, the urethane resin was taken out at 100 ° C., and allowed to cool at room temperature.

The properties and adhesive properties of the urethane resin were measured. The results are shown in Table 2.

 In addition, each characteristic was based on the following measuring method.

1) Melt viscosity The urethane resin was heated to 100 ° C. and measured using a BH type viscometer No. 6 rotor.

2) Softening point The urethane resin was heated and melted at 100 ° C. and measured by a ball and ring method (using silicone oil).

3) the setting time 100 ° C. to heat molten urethane resin is applied to birch controlled at 20 ° C. at a rate of 200 g / mm ^2, a cover member having a 2 cm × 2 cm of the bottom surface (the bonding surface) on the The time until the plane tensile strength became 2.5 kg / cm ² or more was set as the setting time. The measurement was performed at 20 ° C. × 65% RH.

4) Initial adhesive strength 3mm according to the measuring method of setting time of (3)
An 8 mm thick birch material having a 2 cm × 2 cm bottom surface (adhered surface) was bonded to a thick ABS plate, and when the urethane resin was solidified, a plane tensile test was performed at the same time to evaluate the strength and the adhesion state.

Judgment criteria ◎ = Cohesive failure of adhesive with strength of 5 kg / cm ² or more.

＝= Cohesive failure of the adhesive with a strength of 2.5 kg / cm ² or more and less than 5 kg / cm ² .

Δ = 0 kg / cm ² or more and less than 2.5 kg / cm ² with cohesive failure of the adhesive.

× = Interfacial fracture with birch material or ABS.

5) Adhesive strength (180 ° peel strength)
After applying urethane resin melted at 80 ° C to 80 g / m ² , laminating and then 0.1 kg / cm ^{2 by} hot pressing at 100 ° C.
For 30 seconds to adhere. After allowing this to cool at room temperature, it was left in an atmosphere of 20 ° C. × 65% RH for 7 days to obtain a test sample. The combination of the two specimens is iron plate × canvas cloth, ABS resin plate × canvas cloth and vinyl chloride resin plate × canvas cloth.

At 20 ° C, pulling speed 200mm / min so that the angle between the test sample canvas cloth and the other specimen becomes 180 °
And the maximum value of the strength was taken as the adhesive strength.

6) Heat-resistant creep temperature 0.13mm thick, 1 inch wide, epoxy back coated aluminum foil and 3mm thick plywood are bonded to the back coat surface and plywood, and the test sample is prepared in the same manner as (4). I got With the aluminum foil of the test sample facing down, a static load of 1 kg was applied to the aluminum foil at 90 ° to the test sample, and the aluminum foil was left at a constant temperature for 1 hour. Measurement temperature is 20 from 80 ℃ every 10 ℃
Performed to 0 ° C. The maximum temperature at which the aluminum foil was completely removed was defined as the heat-resistant creep temperature.

Examples 2 to 4 and Comparative Examples 1 and 2 Various urethane resins were synthesized in the same manner as in Example 1. The raw materials of the urethane resin and the reaction ratio are shown in Table 2.

The properties and adhesive properties of the resin were also measured in the same manner.
The results are shown in Table 2 together.

Example 5 A water content of 0.02 was added to 95 parts of the urethane resin obtained in Example 2.
% Of kaolin clay ASP-100 [surface-treated kaolin clay, manufactured by Tsuchiya Kaolin Co., Ltd.] was added thereto and mixed well to obtain a urethane resin containing an inorganic filler.

The urethane resin containing the inorganic filler was a pale gray solid with an isocyanate content of 1.24%. The adhesive properties were measured in the same manner as in Example 1. The results are shown in Table 3.

Example 6 A polyester diol A-2 was placed in a two-necked four-necked flask in which a reflux circuit was set and air was previously replaced with nitrogen gas.
Kaolin clay ASP-170 dried to 683 and water content 0.02%
[Surface treated kaolin clay, Tsuchiya Kaolin Co., Ltd.
111 g and dibutyltin dilaurate 0.05 g were added, stirred and uniformly melted, and hexamethylene diisocyanate 127 g was added dropwise at 80 ° C., and the reaction was continued at the same temperature until the isocyanate content became 0%. went.

Next, 190 g of diphenylmethane diisocyanate was added all at once and reacted at 80 ° C. until the isocyanate content became constant. Thereafter, defoaming was performed under reduced pressure, the urethane resin containing the inorganic filler was taken out at 100 ° C., and allowed to cool at room temperature. The urethane resin containing the inorganic filler was a light gray solid with an isodianate content of 2.95%. The adhesive properties were measured in the same manner as in Example 1. The results are shown in Table 3.

(Effect of the Invention) When the urethane resin obtained by the production method of the present invention is used as a hot-melt type adhesive, the setting time is shorter, the initial adhesiveness is excellent, and the crosslinking reaction type adhesive is used as compared with the conventional urethane resin. It has the heat resistance close to that of the agent and the high adhesive strength, and particularly has the advantage of high adhesiveness to plastics such as vinyl chloride.

For this reason, the reactive hot-melt adhesive using the urethane resin obtained by the production method of the present invention is most suitable for various uses related to automobiles, electric machines, architecture, and woodwork, particularly for assembly use, and for example, an automobile head Lights, beacon lamps, door members, side moldings; electric motor-related polarizing yoke, refrigerator inner and outer casing seals, various chip parts for copper-clad laminates; construction, woodworking-related honeycomb panels, cabinets Various bonding applications such as edge bonding of various boards and surface processing of aluminum sashes are conceivable.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-50-35301 (JP, A) JP-A-61-42525 (JP, A) JP-A-3-37218 (JP, A) JP-A 61-35218 174219 (JP, A) JP-A-62-132913 (JP, A) JP-B-30-92 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08G 18/00-18 / 87 C09J 175/00-175/16

Claims (4)

(57) [Claims] 1. A urethane having a hydroxyl group at a molecular terminal by reacting a linear aliphatic saturated polyester diol (A) with a polymethylene diisocyanate (B) under an excess of the linear aliphatic saturated polyester diol (A). A prepolymer, which is then combined with a diisocyanate (C)
Is reacted under conditions of an excess of diisocyanate (C) to produce a urethane resin having an isocyanate group at the molecular end. 2. The method according to claim 1, wherein the linear aliphatic saturated polyester diol (A) is a polyester diol obtained by reacting polymethylene diol (a1) with polymethylene dicarboxylic acid (a2). 3. A straight-chain aliphatic saturated polyester diol (A) comprising a diol in which hydroxyl groups are directly bonded to both ends of a polymethylene skeleton having an even number of carbon atoms, and both ends of a polymethylene skeleton having an even number of carbon atoms. The production method according to claim 1, wherein the polyester diol is obtained by reacting a dicarboxylic acid having a carboxyl group directly bonded to a polyester diol. 4. The polymethylene diisocyanate (B)
2. The method according to claim 1, wherein the isocyanate group is a diisocyanate in which isocyanate groups are directly bonded to both ends of a polymethylene skeleton having an even number of carbon atoms.