JP2000230031A - Curing agent for polymer containing thiol group and curing composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a curing compsn. showing little increase in tensile strength even exposed to heat after curing and suitable as a sealing material, and a curing agent for manufacturing a polymer contg. a thiol group. SOLUTION: This curing agent for a polymer contg. a thiol group is a compd. contg. not less than 2 isocyanate groups in a molecule and obtd. by reacting an aliphatic polyisocyanate, an alicyclic polyisocyanate, at least an arom. polyisocyanate shown by the formula wherein R1 and R2 are each a 1-3C alkyl group, and a compd. having not less than 2 active hydrogens in a molecule, and the concn. of unreacted polyisocyanate is not more than 1 wt.%. This curing compsn. comprises the curing agent and a polymer having not less than 2 thiol groups in a molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a curing agent for a thiol group-containing polymer and a curable composition, and more particularly to a cured product having a small increase in tensile stress even when exposed to heat after curing. The present invention relates to a curing composition suitable for use as a material and a curing agent for obtaining the same.

[0002]

2. Description of the Related Art A polymer containing two or more thiol groups in a molecule is easily cured when mixed with an oxidizing agent, and the thiol group is easily reacted with an epoxy group, an isocyanate group and the like to increase the molecular weight. Therefore, it is widely used for sealing materials, paints and adhesives.

Examples of such a thiol group-containing polymer include a polysulfide polymer described in US Pat. No. 2,466,963 and Japanese Patent Application Laid-Open No. 4-36.
The polysulfide polyether polymer described in Japanese Patent No. 3325 is exemplified.

Further, Japanese Patent Laid-Open Publication No. 52-125563,
JP-A-4-366121 discloses a sealing material in which the above-mentioned polysulfide polymer and the above-mentioned polysulfide polyether polymer are cured with an isocyanate compound, the foaming is small, the weather resistance is good, and a white cured product can be easily obtained. A curable composition suitable for the above has been proposed.

[0005]

However, when these compositions are exposed to heat after being cured, there is a problem that the tensile stress increases and the durability as a sealing material decreases.

Accordingly, an object of the present invention is to provide a cured composition which is capable of obtaining a cured product having a small increase in tensile stress even when exposed to heat after curing and which is suitable for use as a sealing material. It is to provide a curing agent for manufacturing.

[0007]

In order to solve the above problems, the present invention has the following constitution.

That is, an aliphatic polyisocyanate, an alicyclic polyisocyanate, and the following general formula

[0009]

Embedded image (Where R ₁ and R ₂ are alkyl groups having 1 to 3 carbon atoms) obtained by reacting at least one aromatic polyisocyanate represented by the formula (I) with a compound containing two or more active hydrogens in the molecule. A compound having two or more isocyanate groups in the molecule, wherein the concentration of unreacted polyisocyanate is 1% by weight or less, and a curing agent for a thiol group-containing polymer; And a polymer having a thiol group.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

In the present invention, the thiol group-containing polymer refers to a polymer having two or more thiol groups in a molecule. Specifically, the polymer skeleton has a polyether, polythioether, polyester, or acrylic copolymer. Preferred are those having a structure of a coalescence, urethane copolymer, polyacetal, polybutadiene, polyisoprene, polyolefin, polychloroprene, polysulfide, and a copolymer of these. Particularly, a polysulfide polymer having a polysulfide structure and a polysulfide polyether polymer are preferable. The position of the thiol group is not particularly limited, but is preferably located at the end of the molecular skeleton.

The above-mentioned polysulfide polymer and polysulfide polyether polymer will be described more specifically. (1) Polysulfide polymer The polysulfide polymer has (a)-(C ₂ H) in the main chain.
₄ OCH ₂ OC ₂ H ₄ -S _X )-(where x is an integer of 1 to 5), and at the terminal,
(B) It has a thiol group represented by -C ₂ H ₄ OCH ₂ OC ₂ H ₄ -SH. This polysulfide polymer has fluidity at room temperature and has a number average molecular weight of usually 100 to 200,
000, more preferably 400 to 50,000.

[0013] Such polysulfide polymers are preferred.
A good example is described in U.S. Pat. No. 2,466,963.
Have been. (2) Polysulfide polyether polymer The polysulfide polyether polymer has, in its main chain,
(C)-(R₁O) n-(however, R₁Is an alk having 2 to 4 carbon atoms
A len group and n represent an integer of 6 to 200. )
Reether part and (d)-(C_TwoH_FourOCH_TwoOC_TwoH_Four-S_X-)-Oh
And-(CH_TwoCH (OH) CH_Two-S_X)-(Where x is an integer of 1 to 5)
Is a number. ) And a terminal
2, (e) -C_TwoH_FourOCH_TwoOC_TwoH_Four-SH and / or -CH_TwoCH
(OH) CH _TwoHaving a thiol group represented by -SH
You.

In the polysulfide polyether polymer, the polyether portion of (c) and (d)
May be linked in an arbitrary sequence. Also the ratio, the above (c) - (R ₁ O) n-component 2 to 95% by weight, _{(C 2 H 4 OCH 2 OC} 2 H 4 -S X) component of (D) 3 to 70 it preferably has a weight% and _{(CH 2 CH (OH) CH} 2 -S X) component is 1 to 50 wt%. The number average molecular weight of this polysulfide polyether polymer is usually 6
00 to 200,000, preferably 800 to 5
It is 0000.

Such a polysulfide polyether polymer can be produced, for example, by the method described in JP-A-4-363325.

In the present invention, the compound containing two or more isocyanate groups in the molecule (hereinafter, simply referred to as an isocyanate group-containing compound) means an aliphatic polyisocyanate, an alicyclic polyisocyanate and a compound represented by the following general formula:

[0017]

Embedded image (Wherein R ₁ and R ₂ are alkyl groups having 1 to 3 carbon atoms) containing at least one polyisocyanate (hereinafter referred to as an organic polyisocyanate compound) and two or more active hydrogens in the molecule (Hereinafter, referred to as an active hydrogen-containing compound) containing an active isocyanate group.

Specific examples of the aliphatic polyisocyanate include hexamethylene diisocyanate and lysine diisocyanate. Specific examples of the alicyclic polyisocyanate include isophorone diisocyanate, norbornane diisocyanate and 1,3-bis (isocyanate). Art methyl) -cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, and the like. Specific examples of the aromatic polyisocyanate represented by the above general formula include xylylene diisocyanate and tetramethyl xylylene diisocyanate. In the invention,
One type or a combination of two or more types can be used.

Examples of the active hydrogen-containing compounds include hydroxyl-terminated polyesters, polyvalent polyalkylene ethers, hydroxyl-terminated polyurethane polymers, acrylic polyols having hydroxyl groups introduced into acrylic copolymers, hydroxyl-terminated polybutadienes, polyvalent polythioethers, polyacetals, and the like. Aliphatic polyols, and alkanes including alkylene thiols having two or more SH groups, alkenes and aliphatic thiols, polysulfide polymers having terminal SH groups,
Diamines, including aromatic, aliphatic and heterocyclic diamines, and the like, and mixtures thereof.

As such a compound having two or more isocyanate groups in a molecule, a compound obtained by adding hexamethylene diisocyanate to polyoxypropylene glycol is industrially versatile and is preferred.

In the present invention, the concentration of the unreacted polyisocyanate, that is, the unreacted organic polyisocyanate compound must be 1% by weight or less. When the concentration of the organic polyisocyanate compound exceeds 1% by weight, the effect of suppressing an increase in tensile stress after heating becomes insufficient.

In addition, the curable composition comprising the thiol group-containing polymer curing agent of the present invention and a polymer containing two or more thiol groups in the molecule is economical, operable at the time of applying the composition, and has a low cost. For the purpose of improving the physical properties after curing, fillers such as calcium carbonate, talc, clay, titanium oxide and silica, and plasticizers can be added.

In addition, the curable composition comprising the thiol group-containing polymer curing agent of the present invention and a polymer having two or more thiol groups in the molecule is used in order to make curing after application quick and reliable. It is possible to add a catalyst for the reaction between a thiol group and an isocyanate group and an acidic substance as a curing retarder.

As the above reaction catalyst, a tertiary amine, an organometallic compound and the like are used.

Examples of the tertiary amine include monoamines, diamines, triamines, polyamines, cyclic amines,
There are alcohol amines, ether amines and the like, and specific examples are triethylamine, N, N-dimethylcyclohexylamine, N, N, N ′, N′-tetramethylethylenediamine, N, N, N ′, N′-. Tetramethylpropane-1,3-diamine, N, N, N ′, N′-tetramethylhexane-1,6-diamine, N, N,
N ', N ", N" -pentamethyldiethylenetriamine, N, N, N', N ", N" -pentamethyldipropylenetriamine, tetramethylguanidine, N, N-dipolyoxyethylenestearylamine, N, N -Dipolyoxyethylene tallow alkylamine, triethylenediamine, N, N'-dimethylpiperazine, N-methyl-N '
-(2 dimethylamino) -ethylpiperazine, N-methylmorpholine, N-ethylmorpholine, N- (N ',
N'-dimethylaminoethyl) -morpholine, 1,2-
Dimethylimidazole, dimethylaminoethanol, dimethylaminoethoxyethanol, N, N, N'-trimethylaminoethylethanolamine, N-methyl-
N '-(2hydroxyethyl) -piperazine, N- (2
(Hydroxyethyl) -morpholine, bis- (2-dimethylaminoethyl) ether, ethylene glycol bis-
(3 dimethyl) -aminopropyl ether and the like. Two or more of these tertiary amines may be used.

Examples of the organometallic compound include an organic tin compound, an organic mercury compound, and an organic lead compound. Specific examples include tin octylate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin mercaptide, and dibutyltinthiothioate. Examples include carboxylate, dibutyltin maleate, dioctyltin mercaptide, dioctyltin thiocarboxylate, phenylmercuric propionate, and lead octenoate. Two or more of these organometallic compounds may be used.

Preferred examples of the acidic substance include organic acids such as citric acid, stearic acid and 2-ethylhexanoic acid.

The curable composition of the present invention comprises the aforementioned thiol group-containing polymer curing agent and a polymer having two or more thiol groups in the molecule.

The curing agent for a thiol group-containing polymer of the present invention is, for example, a thin film distillation product obtained by reacting the above-mentioned active hydrogen-containing compound with an organic polyisocyanate compound under an excess of the organic polyisocyanate compound. It can be produced by removing unreacted organic polyisocyanate compound by a method such as a vessel or extraction.

The curable composition can be obtained, for example, by mixing the curing agent obtained by the above method and a polymer having two or more thiol groups in the molecule.

In the curable composition of the present invention, the molar ratio (isocyanate group / thiol group) of the isocyanate group of the isocyanate group-containing compound to the thiol group in the thiol group-containing polymer is 0.3. ~
It is preferably 4.0.

[0032]

EXAMPLES The present invention will be described in more detail with reference to Examples.

In the present invention, the tensile adhesion test and the measurement of the unreacted polyisocyanate concentration in the isocyanate group-containing compound are performed by the following methods. (1) Tensile adhesion test A 50% tensile stress was determined according to JIS A-5758. (2) Unreacted polyisocyanate concentration in isocyanate group-containing compound Gel permeation chromatography (column TSKgel
Unreacted polyisocyanate was quantified using a G3000HXL + G2000HXL + G1000HXL detector differential refractometer.

Example 1 1,000 g of a bifunctional polypropylene glycol (OH value: 56.4 mg KOH / g) obtained by adding propylene oxide to propylene glycol, 107 g of epichlorohydrin, and 1.25 g of chlorohydrin Ditin pentahydrate was charged into a reaction vessel and stirred at 80 to 90 ° C. for 3 hours. In addition, 1,110 g of a polysulfide polymer (trade name “Thiokol LP55” manufactured by Toray Thiokol Co., Ltd.)
Was added and mixed, and 89.9 g of sodium bisulfide (purity: 7) was added.
2.3%) and stirred at 80 ° C. for 2 hours. afterwards,
The salt was removed, the mercaptan content was 2.0% by weight, and the viscosity was 80.
A pale yellow transparent polymer A of poise (25 ° C.) was obtained.

Next, a main agent was prepared by blending the polymer A with a plasticizer, a filler and the like in the proportions shown in Table 1. Unreacted hexamethylene diisocyanate of a prepolymer obtained by adding hexamethylene diisocyanate to polypropylene glycol was added to 390 parts by weight of the main agent in a thin-film evaporator.
94 parts by weight of a polyurethane prepolymer (isocyanate content: 2.8%) obtained by removing up to 7% by weight was mixed to obtain a curable composition. The obtained curable composition was subjected to a tensile adhesion test in a room (23 ° C.) using alumite sulfate as an adherend. Curing condition is 20 ℃ x
3 days + 50 ° C x 3 days (a), or further at 90 ° C for 1 day
Heat curing (b) was performed for 4 days. Table 2 shows the results.
It was shown to.

Comparative Example 1 A urethane prepolymer (isocyanate content 4.0%, unreacted hexamethylene diisocyanate 2.22%) obtained by adding hexamethylene diisocyanate to polypropylene glycol and 67 parts by weight 390 parts by weight of the main agent were mixed together and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0037]

[Table 1]

[0038]

[Table 2] As is clear from Table 2, the curable composition of the present invention was excellent with little increase in tensile stress even when exposed to heat after curing.

[0039]

As described above, the curable composition obtained by mixing the thiol group-containing polymer curing agent of the present invention with the thiol group-containing polymer is particularly effective when exposed to heat after curing. Also has a small rise in tensile stress,
It is suitable for use as a sealing material.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J034 BA03 BA10 DA01 DA07 DB04 DB05 DD01 DG02 DG27 DN03 DR01 GA72 HA07 HA11 HA13 HA14 HC03 HC12 HC16 HC22 HC46 HC52 HC61 HC73 JA41 KA01 RA08

Claims (2)

[Claims] 1. An aliphatic polyisocyanate, an alicyclic polyisocyanate, and a compound represented by the following general formula: (Where R ₁ and R ₂ are alkyl groups having 1 to 3 carbon atoms) obtained by reacting at least one aromatic polyisocyanate represented by the formula (I) with a compound containing two or more active hydrogens in the molecule. A compound having two or more isocyanate groups in the molecule, wherein the unreacted polyisocyanate concentration is 1% by weight or less. 2. An aliphatic polyisocyanate, an alicyclic polyisocyanate and a compound represented by the following general formula: (Wherein R ₁ and R ₂ are alkyl groups having 1 to 3 carbon atoms) by reaction of at least one aromatic polyisocyanate represented by the formula (I) with a compound containing two or more active hydrogens in the molecule. It comprises a curing agent having a polyisocyanate concentration of 1% by weight or less and a polymer having two or more isocyanate groups in the molecule and having two or more isocyanate groups in the molecule and having an unreacted thiol group. Curable composition.