JPS63120722A - Urethane prepolymer - Google Patents

Abstract

PURPOSE:To obtain the title prepolymer excellent in compatibility with a hydrophobic material and moisture curability and suitable for, e.g., reactive hot-melt adhesives, water-stopping agents, coatings and sealing materials excellent in heat resistance, by mixing a specified mixed polyol with a polyisocyanate. CONSTITUTION:A mixed polyol (A) comprising 10-90pts.wt. hydroxyl-terminated hydrocarbon polyol (a) such as hydroxyl-terminated polybutadiene and 90-10pts. wt. (modified)polyoxybutylene glycol of an MW of 400-6,000 represented by, e.g., formula III (wherein n and m are integers) and obtained by addition- polymerizing a reaction initiator (b) of formula I (wherein m is 2-8) with butylene oxide of formula II and optionally ethylene oxide, etc., is mixed with a polyisocyanate (B) such as tolylene diisocyanate or phenylmethane diisocyanate in an NCO to OH equivalent ratio of 1.8-3.0, and the mixture is reacted in a nitrogen atmosphere.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to urethane prepolymers used in adhesives, etc., and in particular to moisture-curable urethane prepolymers that are compatible with hydrophobic substances and have moisture-curing properties. Regarding.

<Prior art and its problems> Recently, one-component waterproof materials, coating materials, adhesives, and
Adhesives, sealants, binders, injection materials, rust preventives,
Rooftop waterproofing materials are attracting attention.

Generally, the polyol used in moisture-curable urethane prepolymers is polyoxypropylene glycol (P
There are many PG) types.

However, urethane prepolymers using polyoxypropylene glycol polyols lack compatibility with hydrophobic (oleophilic) materials such as thermoplastic rubbers.

A urethane prepolymer consisting of a terminal hydroxyl hydrocarbon polyol having a hydrocarbon in its skeleton structure and a polyisocyanate is compatible with a hydrophobic substance under heating conditions or under specified or unspecified conditions when used in combination with a plasticizer or the like. The reason for their compatibility is thought to be the hydrocarbons in their skeletal structure.

As such moisture-curable urethane prepolymers, moisture-curable urethane prepolymers made of polybutadiene and diphenylmethane diisocyanate having terminal hydroxyl groups are commercially available, but they have poor moisture-curing properties and are not practical.

That is, among the conventionally known moisture-curing urethane prepolymers, there has been no one that satisfies both excellent compatibility with hydrophobic materials and excellent moisture-curing properties.

<Object of the Invention> The object of the present invention is to improve upon the prior art and provide a moisture-curing urethane prepolymer that exhibits good compatibility with hydrophobic substances and has excellent moisture-curing properties.

<Structure of the Invention> The present invention contains a mixed polyol having 10 to 90 parts by weight of a hydrocarbon-based polyol with a terminal hydroxyl group and 90 to 10 parts by weight of polyoxybutylene glycol having a molecular weight of 400 to 6,000, and a polyisocyanate. The present invention provides a urethane prepolymer which is characterized by being compatible with chemical substances and having excellent moisture curing properties.

Here, the polyoxybutylene glycol is preferably a urethane prepolymer modified with ethylene oxide.

Further, it is preferable that the urethane prepolymer has an equivalent ratio of hydroxyl groups to isocyanate groups (NCO/OH) of 1.8 to 3.0.

The present inventor conducted the following research in order to develop a urethane prepolymer that exhibits good compatibility with hydrophobic substances and has moisture curability.

In general, the compatibility of urethane prepolymers made of polyols such as ethylene glycol and pure MDI (diphenylmethane diisocyanate) with hydrophobic substances such as thermoplastic rubber, which constitute urethane prepolymers, has an effect on the skeletal structure of the polyol. It's easy to accept. Therefore, when the skeleton structure of the polyol is hydrocarbon, the compatibility is the best, followed by polyether and then polyester. However, sufficient compatibility cannot be obtained at the above polyether levels.

On the other hand, urethane prepolymers of hydrocarbon polyols have good compatibility with hydrophobic substances, but have a very slow moisture curing rate and, in some cases, do not cure.

The reason for this is thought to be that the entire system is made of hydrophobic materials and the rate of moisture permeation is extremely low.

In order to improve moisture curing properties, ethylene oxide (
An attempt was made to perform addition polymerization of co2-CI+2), but although the addition polymerization step was completed, a large amount of polymerization catalyst remained in the industrial purification step, and a polyol of urethane prepolymer grade could not be obtained.

In order to improve moisture curability without impairing compatibility with hydrophobic materials, it is necessary to replace a portion of the urethane prepolymer of the hydrocarbon polyol with a moisture curable urethane prepolymer. When a urethane prepolymer using a polymer polyol is replaced, relatively compatibility is shown, but the urethane prepolymer still separates at around room temperature and is insufficient.

Inspired by polymer polyols, the present inventor conducted extensive research into polyols that have a skeleton structure that is more hydrophobic than polymer polyols, and whose urethane prepolymers have excellent moisture curing properties. Polyoxybutylene glycol (hereinafter abbreviated as PBG) was obtained.

That is, the present invention provides a moisture-curable urethane prepolymer having good compatibility with hydrophobic substances by using a mixed polyol of a hydrocarbon-based polyol with a terminal hydroxyl group and polyoxybutylene glycol.

The hydrophobic substances mentioned here include hydrophobic and relatively hydrophobic plasticizers, softeners, stabilizers, flame retardants, fillers, lubricants,
Antiaging agents, catalysts, solvents, bituminous substances (petroleum-based, coal-based),
Additives for plastics and rubber such as tackifiers, EV
A. Thermoplastic resins such as PVC, urethane, nylon, rubber, and ionomers, and various rubbers.

The structure of the urethane prepolymer of the present invention will be explained in detail below.

(a) Hydrocarbon-terminated polyol A hydroxyl-terminated hydrocarbon-based polyol is a hydrocarbon-based polyol that has a hydrocarbon skeleton and a hydroxyl group at the end, and is a polymer of butadiene, including hydroxyl-terminated polybutadiene (abbreviated as POD) and isoprene. Polymer of hydroxyl-terminated polyisoprene (PIF
) etc. are representative examples. Hydrocarbon moieties other than those mentioned above include polystyrene, polynitrile, butadiene, polychloroprene, etc., and some are hydrogenated to eliminate double bonds in the hydrocarbon moiety.

(b) Polyoxybutylene glycol The polyoxybutylene glycol (PBG) of the present invention is:
Butylene oxide (C113-C)lz -CIlC to the reaction initiator (initiator) II +0H)l
H2) is added and polymerized and is represented by the following general formula. Usually m=2 to 8, preferably m=2 to 4.

) In is, for example, when m = 2, ethylene glycol, diethylene glycol, when m = 3, glycerin, trimethylolpropane, when m = 4, pentaerythritol, when m = 6, sorbitol, m = In the case of 8, the shoe close is well known.

The average molecular weight of PBG is determined by n, and the average number of functional groups is determined by m.

In addition, if the average molecular weight of PBG is low, the compatibility will decrease, so the average molecular weight is preferably 400 or more, and the average molecular weight is preferably 6.
If it exceeds 000, moisture curing properties will deteriorate, so it is preferably 6000 or less. Preferably it is 1000-5000.

PBG is characterized by containing a large amount of ethyl groups (-CIl2-CH3), which are hydrophobic substances, and also contains ether bonds, which are parent wood groups. Due to its hydrophobicity, it exhibits compatibility with hydrophobic substances and moisture curing properties.

Furthermore, in order to improve moisture curing properties, it is effective to use modified PBG in which ethylene oxide (CIl2-CH2) or propylene oxide (CH3-GH-CH2) is block-polymerized at the end of PBG or randomly polymerized with butylene oxide. It is. However, as the amount of modification increases, the hydrophilicity becomes stronger, so the compatibility with the aqueous substance decreases.

Therefore, the amount of modification is preferably 18% or less.

In order to improve the compatibility with hydrophobic substances, when synthesizing the urethane prepolymer, it is necessary to increase the ratio of terminal hydroxyl group hydrocarbon polyol/PBG, and to improve moisture curability, it is necessary to increase the ratio of terminal hydroxyl group hydrocarbon type polyol/PBG. Hydrogen polyol/PBG
It is important to reduce the ratio of The ratio of terminal hydroxyl group hydrocarbon type polyol/PBG that satisfies both compatibility and curability of the composition of the present invention is 10/90 to 90/10,
Preferably it is in the range of 20/80 to 80/20 (parts by weight).

The reason why moisture curing progresses even if the ratio of the terminal hydroxyl group hydrocarbon polyol, which has poor moisture curing properties, is relatively high is that when the PBG urethane prepolymer reacts with atmospheric moisture, the amino groups (
-NO3) and carbon dioxide gas are generated, and the generated amino groups react with the isocyanate of the urethane prepolymer of the hydrocarbon polyol, and it is presumed that polymerization progresses. or,
It is known that the generated amino group has a catalytic effect and acts as an internal neutralization catalyst for carbamic acid.

The reaction mechanism is believed to be based on the following formula.

-NCO+l(20→-Ni+(:0011(carbamic acid)) 18112◆-NCO→-NIICON)l-(polymerization)(urea bond) The present invention is a mixture of polyoxybutylene glycol and a hydrocarbon-based polyol with a terminal hydroxyl group. Although it is characterized by a urethane polymer consisting of polyol and polyisocyanate, the present invention also includes the use of short chain diols, polyether polyols, and polyester polyols as part of the mixed polyol in order to obtain specific performance depending on the application. Needless to say, it is also possible in the present invention to separately synthesize a polyoxybutylene glycol-based urethane prepolymer and a urethane prepolymer of a terminal hydroxyl group hydrocarbon-based polyol, and then mix them together before use, instead of using a mixed polyol. Included in

To improve the compatibility between hydrophobic substances and urethane prepolymers,
It is also good to add a surfactant.

(c) Polyisocyanate The polyisocyanate component that constitutes the urethane prepolymer together with the above mixed polyol includes tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and bitolylene diisocyanate (TDI).
ODI), isophorone diisocyanate (IPDI)
, xylylene diisocyanate (XDI), etc., which are normally used for urethane resins, can be used, but considering moisture curing speed, industrial cost, safety and health, etc., MDI
Preferred are polyisocyanates.

MDI-based polyisocyanates include pure MDI, decarboxylated modified MDI (also known as liquid MDI), and crude MDI, but pure MDI and liquid MDI are preferred in order to obtain the thermal stability of the urethane prepolymer. Of course, it is not a problem to use various types of polyisocyanates together.

When synthesizing a urethane prepolymer, (-Nil:
0)/(-OH) equivalent ratio is important. (-N(:0
)/(-014) When the equivalent ratio is less than 1.8, as the equivalent ratio decreases, the amount of urethane prepolymer increases, resulting in an increase in viscosity and a lack of thermal stability. Furthermore, as the equivalent ratio increases to 1.8 or more, the thermal stability of the urethane prepolymer is improved, but the amount of free polyisocyanate (single substance) increases, and (-NGO)/(-01+) equivalent ratio = 3. If it exceeds this amount, compatibility with hydrophobic substances is unfavorable.

In addition, when the amount of free polyisocyanate increases, it rapidly reacts with moisture, resulting in rapid generation of carbon dioxide gas.
During moisture curing, carbon dioxide gas cannot dissipate in time, causing air bubbles to be mixed in. Furthermore, as the equivalent ratio increases, the storage stability of the urethane prepolymer is improved. Therefore,
(-N(:O)/(-on) equivalent ratio is 1.8 to 3.
0 is preferred.

<Example> The present invention will be specifically described below with reference to Examples.

Example = 1 Butyl rubber (Exxon Chemical, Exxon Butyl-268)
100 parts, polybutene (Nisseki Chemical: Nisseki Polybutene HV
-300) and 150 parts of carbon (Sanmugi Kasei: Dia Black G) were kneaded with a rubber kneading roll, and the mixture (A
) was obtained.

Next, 40 parts of polybutadiene with a terminal hydroxyl group having an average molecular Jfi of 2800 (Idemitsu Petrochemical: R-45HT) and 60 parts of bifunctional polyoxybutylene glycol (modified product with a hydroxyl value of 37.4 and a terminal ethylene oxide of 7%) were added to a reaction pot. The mixture was then dehydrated under vacuum at 110° C. for 4 hours. Next, dry nitrogen gas was filled in and the temperature was controlled at 80°C. Furthermore, pure-MD
I (MD Kasei: is□nate 125M) is 18.6
(-NCO/-OH equivalent ratio 2.0) was added from the inlet and reacted for 5 hours in a nitrogen gas atmosphere to reduce NGO%.
-2,4! A urethane prepolymer having a viscosity of 230 PS (80°C) was obtained.

Next, 50 parts of the mixture (8) and 50 parts of the urethane prepolymer were placed in a horizontal kneader and kneaded at room temperature for 15 minutes under vacuum to obtain a kneaded product (B).

Next, the weight ratio of R-45HT/polyoxybutylene glycol was adjusted to 10010.90/10.80/20.60/
Urethane prepolymers having different concentrations of 40.20/80.10/90.0/100 were synthesized and kneaded with the above mixture in the same manner to obtain a kneaded product (B).

The kneaded material (B) was evaluated as follows, and the results were summarized in 7S1.
Shown in the table.

(1) Compatibility: Evaluated visually after mixing in a kneader.

The above mixture (^) remains in the form of granules in the kneaded material (B) (×) Slightly remains in the form of granules (△), no granules (0) (2) Curable, iron mold with top open to the atmosphere (150
The kneaded material was placed in a x150x2 (thickness) (mll)), a release paper was placed on top of the kneaded material, and a 21 IM thick sheet was formed using a hand press. After molding, the layered paper pattern was removed and left to stand for 6 days under the conditions of 20° C. and 65R11, and the hardening state and bubble generation state were checked.

The evaluation is as follows.

Deep uncured (×), deep semi-hardened (△), deep hardened (O)
, Lots of bubbles (×), Some bubbles (△), No bubbles (0) Table 1 Note (*l) indicates gelation during urethane polymer synthesis.

Example-2 Ethylene oxide content 7%, average molecular weight approximately 3000
using modified PBG with a weight ratio of PBD/modified PBG of 40.
760 (average hydroxyl value 40.8), -Nl;0/
-011 equivalent ratio 1.8, 2.0, 2.2.2.5.
Pure MDI urethane prepolymers 2.7, 3.0, and 4.0 were synthesized. N00% of urethane prepolymer,
The viscosity was measured and shown in Table 2 as an initial value. The thermal stability of these urethane prepolymers was determined at 580°C, 100°C, and 1
After being left at each temperature of 20° C. for 3 days, the NCO% viscosity was measured and evaluated. The results are shown in Table-2. The viscosity was measured using an E-type rotational viscometer (manufactured by Tokyo Keiki).

<Effects of the Invention> Since the urethane prepolymer of the present invention uses a mixed polyol containing a terminal hydroxyl group hydrocarbon polyol and a predetermined amount of polyoxybutylene glycol, it is highly compatible with hydrophobic materials and has good moisture curing properties. has.

Therefore, it can be effectively used industrially as follows.

(+) A urethane prepolymer that is compatible with thermoplastic rubber and has moisture curability is produced, resulting in a reactive hot melt adhesive that improves the heat resistance of currently available hot melt adhesives.

(2) It can be used for one-component moisture-curing lumber, coating materials, adhesives, adhesives, sealants, binders, injection materials, rust prevention materials, rooftop waterproofing materials, road paving materials, etc.

Claims (3)

[Claims] (1) Contains a mixed polyol having 10 to 90 parts by weight of a hydrocarbon-based polyol with a terminal hydroxyl group and 90 to 10 parts by weight of polyoxybutylene glycol having a molecular weight of 400 to 6,000, and a polyisocyanate, and is compatible with hydrophobic substances. A urethane prepolymer characterized by having excellent moisture curing properties. (2) The urethane prepolymer according to claim 1, wherein the polyoxybutylene glycol is modified with ethylene oxide. (3) The urethane prepolymer according to claim 1 or 2, wherein the urethane prepolymer has an equivalent ratio of hydroxyl groups to isocyanate groups (NCO/OH) of 1.8 to 3.0.