JPH0684416B2 - Moisture curable urethane prepolymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a moisture-curable urethane prepolymer having excellent long-term storage stability, which is used as a paint, an adhesive, and the like.

More specifically, the present invention relates to a method for producing a moisture-curable urethane prepolymer capable of maintaining yellowing resistance against an external factor such as oxygen for a long period of time.

(Prior Art) Polyurethane is a polymer substance excellent in impact resistance, chemical resistance, abrasion resistance, cold resistance, etc., so it has been conventionally used in various fields and applications. Is. However, on the other hand, polyurethane has a property that it is easily affected by external factors such as light, heat, moisture, oxygen, etc., and these external factors cause the deterioration of the surface condition of the polyurethane molded article to occur. An unfavorable phenomenon occurs for the quality of the product.

Moisture-curable urethane prepolymer
The phenomenon of yellowing from the surface is observed during storage, and in products using the yellowed urethane prepolymer, partial yellowing is often seen in spots. This is considered to be the coloring caused by the condensation of the peroxide produced by oxygen in the air, which was decomposed by the alkali catalyst. In the manufacturing industry, on the other hand
It was managed by doing work so that it would not come into contact with oxygen at each stage of storage.

(Problems to be Solved by the Invention) However, it is not easy to completely stop contact with oxygen in all steps, and it is not preferable for human handling.

In view of such a situation, in order to establish a method for producing a moisture-curable urethane prepolymer capable of maintaining yellowing resistance for a long period of time regardless of contact with oxygen, the present inventors have earnestly studied, as a result, This led to the present invention.

(Structure of the Invention) That is, in the present invention, the urethane prepolymer is composed of 4.4'-diphenylmethane diisocyanate and a polyol,
The terminal is 4.4'-diphenylmethane diisocyanate, and the terminal isocyanate group is contained in an amount of 7 to 15% by weight. 0.1 to 2.0 parts by weight of a curing catalyst and 0.1 to 2.0 parts by weight of a storage stabilizer with respect to the urethane prepolymer. Parts and 0.01 to 3.0 parts by weight of an antioxidant are added, and the present invention relates to a moisture-curable urethane prepolymer having excellent long-term stability.

Here, the polyol is composed of polyether polyol and polyester polyol. Examples of the polyether polyol include polyethylene polyether glycol, polypropylene ether glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, polyoctamethylene ether glycol, polydecamethylene ether glycol, and mixtures thereof.

Examples of the polyester polyol include those obtained by first reacting a dibasic acid with glycol. Examples of the dibasic acid used at this time include adipic acid, succinic acid, sepacic acid, terephthalic acid, alkyl derivatives and halogen derivatives of these acids, and glycols such as ethylene glycol, diethylene glycol and propylene glycol. Further, polycaprolactone polyol obtained by ring-opening polymerization of lactone can also be used.

Here, the polyol has two hydroxyl groups in one molecule,
And those having a number average molecular weight in the range of 400 to 2500, or those having three hydroxyl groups in one molecule and having a number average molecular weight in the range of 400 to 2500 are mixed to obtain an average hydroxyl group per molecule. It is a mixture of 2 or more and 2.5 or less. Therefore, it has two hydroxyl groups in one molecule,
Moreover, it is also possible to use alone those having a number average molecular weight in the range of 400 to 2500.

If the average number of hydroxyl groups per molecule of the polyol is less than 2, the urethane prepolymer does not always have an isocyanate group at the end, and therefore the molecular extension due to the reaction with water is limited. Therefore, it becomes impossible to take a long-chain molecular structure. Therefore, the polymer after curing by the reaction with water cannot exhibit sufficient strength when applied as a paint or an adhesive and cannot be used.

On the other hand, when the average number of hydroxyl groups per molecule of the polyol exceeds 2.0, a part forming a network structure is generated by the reaction between the urethane prepolymer and water, and the hardness gradually increases as the network structure increases. . In this way, when the average number of hydroxyl groups per molecule of the polyol exceeds 2.5, on the contrary, since the number of network structures in the constituent molecules becomes large, the length of the segment becomes too messy,
As the hardness increases, the expression of brittleness begins to stand out,
It is not suitable when used as an adhesive.

In the present invention, when the moisture-curable urethane prepolymer is used as a paint or an adhesive, the polyol and 4,4 ′ are used.
-React with diphenylmethane diisocyanate, and those with terminal -NCO groups in the range of 7 to 15% have suitable strength,
It was found to be tenacious.

On the other hand, when a polyol having a number average molecular weight of 400 or less is used when synthesizing a urethane prepolymer having an NCO group in the range of 7 to 15% by weight, the viscosity of the urethane prepolymer increases excessively. The drawback is that it becomes difficult to apply. Even if this is applied,
A cured product obtained by a reaction with water is hard and too brittle, and thus is not suitable for use in paints, adhesives and the like.

On the contrary, a urethane prepolymer having a number average molecular weight of 2500 or more and having a -NCO group in the range of 7 to 15% by weight cannot be obtained because the viscosity becomes too high and the coating amount cannot be secured. It is not possible to expect an excellent binder effect.

As the compounding effect by adjusting the number of hydroxyl groups of the present invention, by adjusting the number of functional groups, even if the prepolymers have the same -NCO group content (7 to 15% by weight in the present invention), (1) the viscosity Can be adjusted to obtain a desired viscosity. (2) It is possible to adjust the hardness and strength of the cured coating film.

The tertiary amine which is the curing catalyst of the present invention is specifically triethylenediamine, N, N, N ′, N ′, N ″ -pentamethyldipropylenetriamine, N, N, N ′, N ′, N ″. -Pentamethyldiethylenetriamine, N, N, N ', N'-tetramethylhexamethylenediamine, bis (dimethylaminoethyl) ether, 2- (N, N'-dimethylamino) ethyl-3- (N, Ndimethylamino ) Propyl ether, N, N '
-Dimethylcyclohexylamine, N, N-dicyclohexylmethylamine, methylenebis (dimethylcyclohexyl) amine, triethylamine, N, N-dimethylcetylamine, N, N-dimethyldodecylamine, N, N-dimethylhexadecylamine, N, N , N ', N', N "-tetramethyl-1,3-butanediamine, N, N-dimethylbesidylamin, morpholine, N-methylmorpholine, N-ethylmorpholine, N- (2-dimethylaminoethyl) Morpholine, 4,4'-oxydiethylenedimorpholine, N, N'-diethylpiperazine, N, N'-dimethylpiperazine, N-
Methyl-N'-dimethylaminoethylpiperazine, 2,4,
6-tri (dimethylaminomethyl) phenol, tetramethylguanidine, 3-dimethylamino-N, N-dimethylbropionamide, N, N, N ', N'-tetra (3-dimethylaminopropyl) methanediamine, N, N-dimethylaminoethanol, ethoxylated hydroxylamine, N,
N, N ', N'-tetramethyl-1,3-diamino-2-propanol, N, N, N'-trimethylaminoethylethanolamine, 1,4-bis (2-hydroxypropyl) 2-methylpiperazine, 1- (2-hydroxypropyl) imidazole, 3,3-diamino-N-methyldipropylamine, 1,8-diazobicyclo (5,4,0) -undecene-7,
There are N-methyl-N'-hydroxyethylpiperazine and the like, but preferably bis (dimethylaminoethyl) ether, 2- (N, N-dimethylamino) ethyl-3- (N, N
-Dimethylamino) propyl ether, triethylamine, N- (2-dimethylaminoethyl) morpholine, 3
-Dimethylamino-N, N-dimethylpropionamide,
It is composed of one kind or a combination of two or more kinds of N, N-dimethylaminoethanol and is preferably added in an amount of 0.1 to 2 parts by weight with respect to the urethane prepolymer.

As the storage stabilizer used in the present invention, the storage stability of the urethane prepolymer can be increased by adding an acid chloride compound. The following compounds may be used as specific compounds of acid chloride. For example, isophthaloyl chloride, 2-ethylhexanoyl chloride, octanoyl chloride, -chlorobenzoyl chloride, benzoyl chloride, stearoyl chloride, sacoyl chloride, decanoyl chloride, dodecanoyl chloride, nonanoyl chloride, palmitoyl chloride,
3-phenylpropenoyl chloride, n-butanoyl chloride,
Hexanoyl chloride, 2-methylpropanoyl chloride, 2,4
-Dichlorobenzoyl chloride, 2,6-dichlorobenzoyl chloride, lauroyl chloride, methyl benzoyl chloride and the like.
It is possible to use one of the above acid chlorides or a combination of two or more thereof.

If the amount of acid chloride added is less than 0.1 parts by weight relative to 100 parts by weight of urethane prepolymer, it will react with a small amount of moisture in the air during the process of coating, packaging, etc., and storage stability Since the effect as an agent is lost, the storage stability effect is not exhibited. Further, no effect was observed even when the treatment was carried out while paying sufficient attention to the moisture content in the air.

On the contrary, when the amount of the acid chloride added is more than 2.0 parts by weight, the storage stability brings about an excellent effect, but since the effect speed due to the reaction with water during use is too slow, the paint,
Poor workability when used as an adhesive. Furthermore, a pungent odor peculiar to acid chloride is generated, which adversely affects the work.

In addition, since moisture-curable urethane prepolymers generate carbon dioxide gas as they react with water and become high molecular weight, when used in paints, adhesives, etc., the resin fires, causing a decrease in strength. Or it may cause a stain on the appearance. As a method of suppressing the foaming caused by the generation of carbon dioxide gas, 0.01 to 1.
It is satisfied by adding 0 part by weight. This silicone-based defoaming agent is not always used, but may be used depending on the occasion.

As the antioxidant which can be used in the present invention, any one may be used as long as it is a fingered phenol compound having at least one branched lower aliphatic hydrocarbon group bonded at the ortho position. Those having 1 to 4 molecules in one molecule are preferable. 1 phenolic nucleus
When two or more molecules are present in the molecule, there is no particular limitation on the binding state. As the above branched lower aliphatic hydrocarbon group, those having 3 to 7 carbon atoms are generally preferable, and examples thereof include an isopropyl group, an isobutyl group, a t-butyl group, an isopenzyl group, a t-pentyl group and an isohexyl group. However, a particularly preferable one is a t-butyl group. Various other displacement devices may be combined with the above-mentioned findered phenol compound. Specific examples of the above-mentioned findered phenol compound, for example,
The following compounds can be mentioned.

The above antioxidants can be used in the present invention either individually or as a mixture of two or more kinds.

The amount of the antioxidant used in the present invention is 0.
01 to 3.0 parts by weight is preferable. When it is less than this range, the whiteness of the produced polyurethane is prevented from being maintained for a long period of time, and when it is more than this range, the solubility may be exceeded, resulting in the strength and elongation of the product. It is not preferable because the physical properties such as degree are lowered.

Regarding the addition method of the antioxidant used in the present invention,
It is desirable to disperse or heat-dissolve the antioxidant in a part of the raw material for polyurethane production in advance,
The effect can also be obtained by adding and mixing after the production of polyurethane.

(Examples) Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. All "parts" in the examples are parts by weight.

(Example-1) 474 parts of 4,4 'diphenylmethane diisocyanate was weighed in a three-neck separable flask and heated to 50 ° C.
Next, 526 with polypropylene glycol having an average molecular weight of 700
Weigh in the dropping funnel, set in a separable flask,
The total amount of polypropylene glycol was added dropwise over 1 hour while stirring the flask. At this time the internal temperature of the flask is
The temperature was controlled to be in the range of 50-80 ° C. After the completion of dropping all the amount of polypropylene glycol, the temperature inside the flask was kept at 75 ° C. and stirring was continued for 3 hours to synthesize a urethane prepolymer. The content of terminal -NCO groups in this product was measured by titration to be 5.0% by weight.

Next, with respect to 100 parts by weight of the urethane prepolymer, 0.8 part of dimethylaminoethanol as a curing catalyst, 0.5 part of benzoyl chloride as a storage stability, and 0.1 part of a silicon-based defoaming agent were added, and an antioxidant represented by the following formula 0.1 part was added and stirred thoroughly. This completes the synthesis of the moisture-curable urethane prepolymer.

(Example-2) Using the same apparatus as in (Example-1), 474 parts of 4,4'diphenylmethane diisocyanate was weighed, and (Example-
A urethane prepolymer was synthesized by the same operation as in 1). Next, 0.8 part of dimethylaminoethanol and 0.5 part of benzoyl chloride are used with respect to 100 parts of the urethane prepolymer.
Part, 0.1 part of a silicon-based defoaming agent, and further (Example-
0.2 part of the same antioxidant as in 1) was added and sufficiently stirred to synthesize a moisture-curable urethane prepolymer.

(Example-3) Using the same apparatus as in (Example-1), 474 parts of 4,4'diphenylmethane diisocyanate was weighed, and (Example-
A urethane prepolymer was synthesized by the same operation as in 1). Next, 0.8 part of dimethylaminoethanol and 0.5 part of benzoyl chloride are used with respect to 100 parts of the urethane prepolymer.
Part, 0.1 part of a silicon-based defoaming agent, and 0.1 part of the following antioxidant were further added and sufficiently stirred to synthesize a moisture-curable urethane prepolymer.

(Example-4) Using the same apparatus as in (Example-1), 474 parts of 4,4'diphenylmethane diisocyanate was weighed, and (Example-
A urethane prepolymer was synthesized by the same operation as in 1). Next, 0.8 part of dimethylaminoethanol and 0.5 part of benzoyl chloride are used with respect to 100 parts of the urethane prepolymer.
Part, 0.1 part of a silicon-based defoaming agent, and further (Example-
0.2 part of the same antioxidant as in 3) was added and sufficiently stirred to synthesize a moisture-curable urethane prepolymer.

(Example-5) Using the same apparatus as in (Example-1), 474 parts of 4,4'diphenylmethane diisocyanate was weighed, and (Example-
A urethane prepolymer was synthesized by the same operation as in 1). Next, 0.8 part of dimethylaminoethanol and 0.5 part of benzoyl chloride are used with respect to 100 parts of the urethane prepolymer.
Part, 0.1 part of a silicon-based defoaming agent, and further (Example-
0.5 part of the same antioxidant as 3) was added and sufficiently stirred to synthesize a moisture-curable urethane prepolymer.

<Comparative Example-1> Using the same apparatus as in (Example-1), 474 parts of 4,4'diphenylmethane diisocyanate was weighed, and (Example-
A urethane prepolymer was synthesized by the same operation as in 1). Next, 0.8 part of dimethylaminoethanol and 0.5 part of benzoyl chloride are used with respect to 100 parts of the urethane prepolymer.
Part, 0.1 part of a silicon-based defoaming agent, and thoroughly stirred,
A moisture-curable urethane prepolymer was synthesized.

The moisture-curable urethane prepolymers obtained in (Examples 1 to 5) and <Comparative example-1> were placed in a heat-resistant glass bottle, and Ai
In an r atmosphere, an evaluation test was conducted in which heating was accelerated at 80 degrees to change with time. This shows that the moisture-curable urethane prepolymers synthesized in the examples can maintain yellowing resistance for a long time. The results are shown in Table-1.

Claims (5)

[Claims] 1. A urethane prepolymer comprising 4.4'-diphenylmethane diisocyanate and a polyol, wherein the terminal is 4.4'-diphenylmethane diisocyanate, and the terminal isocyanate group is contained in an amount of 7 to 15% by weight. A moisture-curable urethane prepolymer excellent in long-term stability, characterized by adding 0.1 to 2.0 parts by weight of a curing catalyst, 0.1 to 2.0 parts by weight of a storage stabilizer, and 0.01 to 3.0 parts by weight of an antioxidant to a polymer. . 2. The polyol comprises a polyether polyol or a polyester polyol and has 2 or 3 hydroxyl groups in one molecule, and the average number of hydroxyl groups per molecule is 2 or more and 2.5 or less, and the number average molecular weight is 400 to. The moisture-curable urethane prepolymer according to claim 1, which is in the range of 2500. 3. A moisture-curable urethane prepolymer according to claim 1, wherein the curing catalyst is a tertiary amine and is composed of one or a combination of two or more tertiary amines. 4. The moisture-curable urethane prepolymer according to claim 1, wherein the storage stabilizer is an acid chloride and is composed of one kind or a combination of two or more kinds of acid chlorides. 5. The moisture-curable urethane according to claim 1, wherein the antioxidant is a hindered phenol compound having at least one branched lower aliphatic hydrocarbon group bonded at the ortho position. Prepolymer.