JPH0450277A - Prepolymer for polyurethane paint having extensibility and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject prepolymer having excellent storing stability for a long period of time without toxicity nor irritating property by reacting specific two species of diisocyanate and polycaprolactone polyol having a constant molecular weight under a specific condition. CONSTITUTION:(A) Hexamethylene diisocyanate is reacted with (B) isophorone diisocyanate and (C) polycaprolactone diol and/or triol having 500-1500 number- averaged molecular weight under the condition of said components A/B=99/1-1/99, 5-40 NCO/OH equivalent ratio and at 20-200 deg.C temperature. Next, after finish of the reaction, unreacted component A and unreacted component B in the reacted mixture are removed and recovered using a thin film evaporating device, etc., to make total weight of the component A and the component B to <=1wt.% to afford the aimed prepolymer for paint suitable for resin article in an automobile such as bumper or exterior, etc., of a building.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a prepolymer for use in polyurethane paints having expandability and a method for producing the same.

More specifically, the present invention relates to a prepolymer for two-component polyurethane paints that has expandability and has an improved drying rate and is used for automobile resin products such as bumpers, architectural exterior materials, and the like.

[Conventional technology]

In recent years, various resin products have been adopted as automobile parts instead of steel materials, as exemplified by automobile bumpers, for the purpose of improving safety, reducing weight, and absorbing shock. However, resin products generally suffer from aging due to outdoor exposure, that is, discoloration and deterioration in performance over time. Therefore, coating is required from the viewpoint of anti-aging and cosmetic properties. In this case, the performance required of the paint is that it must withstand all the environments in which the automobile is used. In other words, it maintains the flexibility, impact resilience, and rigidity of the plastic to be coated, while maintaining good physical properties such as flexibility, impact resistance, and adhesion at temperatures as low as -30°C. Weather resistance is required. Similar physical properties are also required for building exterior material applications as they are exposed to severe weather conditions.

As a method to easily obtain these required physical properties in a two-component polyurethane paint, a polyisocyanate obtained from a polycaprolactone diol and/or triol of a specific molecular weight and an aliphatic or alicyclic diisocyanate is used as a curing agent for a polyurethane paint. It has been proposed to do so (Japanese Unexamined Patent Publication No. 61-28518).

[Problem to be solved by the invention]

However, in the polyisocyanate described above, when a polyisocyanate obtained by using an aliphatic diisocyanate such as hexamethylene diisocyanate as the raw material diisocyanate is used, the progressability and low-temperature physical properties are Although an excellent coating film can be obtained, the drying rate of the coating film is significantly slower than when a normal curing agent is used, and the work efficiency is poor. Further, polyisocyanates obtained by using alicyclic diisocyanates as raw material diisocyanates have good drying properties, but do not have sufficient spreadability and low-temperature physical properties, which are the original objectives.

Under these circumstances, it has progressability and excellent low-temperature physical properties,
There was also a strong demand for polyisocyanate prepolymers as curing agents for polyurethane paints with good drying properties.

[Means to solve the problem]

As a result of repeated research in order to solve the above problems, the present inventors have discovered that a polyisocyanate in which two specific types of diisocyanates and a polycaprolactone polyol of a specific molecular weight are bonded via a urethane bond solves the above problems. The present invention has been completed based on the discovery that this problem can be overcome.

That is, the present invention provides the following formula: ■'l;'+0CONH-R-NCO), I (wherein
is an integer of 2 or 3, R is a mixture of a hexamethylene group and a residue obtained by removing two isocyanate groups from isophorone diisocyanate, and the mixing ratio is 1/99 to 99/
1, and Z represents the residue represented by or the residue represented by or a mixture thereof.

Here, A is a residue obtained by removing the OH group from a C3-C1o diol or triol, 1+ J+ k+ L
m is an integer, and the number average molecular weight of the residues of ■ and ■ is 55
It is 0 to 1.500. ) and its production method.

The prepolymer of the present invention requires the presence of both hexamethylene diisocyanate, which is an aliphatic diisocyanate, and isophorone diisocyanate, which is an alicyclic diisocyanate, as its constituent diisocyanates. be.

The prepolymer of the present invention may be used in combination with a third diisocyanate as long as the properties of the polyisocyanate are not lost. Examples of diisocyanates that can be used in combination include 2,2,4-1-limethylhexane diisocyanate, 1,4-diisocyanatocyclohexane,
Bis(isocyanatomethyl)cyclohexane, bis(
Examples include 4-isocyanatomethylcyclohexyl)methane.

Further, it is essential that the prepolymer of the present invention contains a polycaprolactone polyol having a specific number average molecular weight as a constituent component.

For the sole purpose of obtaining a prepolymer having propagation properties, various other hydroxyl group-terminated polyols having flexible molecular chains, such as condensation polyester polyols from glycol and adipic acid, polyether polyols such as polypropylenoxide, etc. It is possible to use a polybutadiene polyol or the like as a constituent unit. However, all of these polyols have poor weather resistance, which is an essential requirement for raw materials for paints used outdoors, and have little practical value.

On the other hand, a coating film obtained from a prepolymer containing polycaprolactone polyol as a constituent has excellent not only weather resistance but also heat resistance and water resistance, and is extremely excellent as a raw material for outdoor paints.

The prepolymer of the present invention cannot be obtained unless a polycaprolactone polyol having a specific molecular weight range of 500 to 1.500 in number average molecular weight is used as a constituent unit. That is, a coating film using a prepolymer made of polycaprolactone polyol having a number average molecular weight of 500 or less as a curing agent does not have sufficient spreadability. In addition, the number average molecular weight is 1
．． The prepolymer consisting of polycaprolactone polyol of 500 or more is solid or waxy, and NGO
Its content is low, and its solubility in paint solvents is poor, making it less practical.

The number average molecular weight in the present invention is a value determined by measuring the hydroxyl value of polycaprolactone polyol and using the following formula.

Number average molecular weight = (56, IIX N x 1000)
/Hydroxyl valueHydroxyl value/JIS K-1557 6.4
Value measured according to N: Valency of polyhydric alcohol as an initiator The polycaprolactone polyol used in the present invention is obtained by ring-opening polymerization of ε-caprolactone using a dihydric or trihydric alcohol as an initiator. .

Specific examples of the initiator include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, trimethylolpropane, and glycerin. The amount of these initiators added is determined based on the desired molecular weight of the polycaprolactone polyol. From the viewpoint of obtaining a prepolymer with low viscosity, it is preferable to use a trihydric alcohol. Titanium-based compounds or tin-based compounds are often used as ring-opening polymerization catalysts. Typical polymerization conditions are a catalyst addition amount of 0.1 to 1100 pp and a reaction temperature of 150 to 2
00°C, reaction time 4 to 10 hours.

Commercially available polycaprolactone polyols include Plaxel 305, Plaxel 308, Plaxel 312AL, Plaxel 205, and Plaxel 21.
2AL (both manufactured by Daicel Chemical Industries (Kiyomi, trade name)), etc.

The reaction between polycaprolactone polyol, hexamethylene diisocyanate and isophorone diisocyanate is carried out as follows.

Reaction temperature is 20-200°C, preferably 80-140°C
is within the range of The reaction may be carried out without a solvent, or any solvent inert to isocyanate groups and hydroxyl groups may be used. Further, if necessary, a catalyst that promotes the reaction between isocyanate groups and hydroxyl groups may be used.

The equivalent ratio of diisocyanate and polycaprolactone polyol is important during the reaction, and the NGO10H equivalent ratio needs to be in the range of 5 to 40. If this equivalent ratio is less than 5, the proportion of polymers produced by the sequential addition reaction between diisocyanate and polycaprolactone polyol will increase, which is undesirable and increases the viscosity of the prepolymer. Not only do they tend to have poor compatibility, but they also have an unfavorable effect on the spreadability of the coating film. Furthermore, if the NGO10H equivalent ratio is greater than 40, productivity will be poor (this is not preferable).

When the reaction is completed, unreacted diisocyanate in the reaction mixture is removed and recovered using, for example, a thin film evaporator or a solvent extraction method. It is necessary to remove this unreacted diisocyanate as completely as possible so that the total amount of unreacted diisocyanate contained in the prepolymer is 1% or less.

This is because if more diisocyanate monomers are contained, problems such as toxicity and irritation caused by the vapor will arise.

The prepolymer of the present invention can be blended with various polyols such as acrylic polyols, fluorine-containing polyols, polyester polyols, etc. to provide polyurethane paints with excellent spreadability and drying properties. The mixing ratio of polyol and prepolymer is preferably NCO/OH ratio of 0.5 to 2.0. If the NGO10H ratio is less than 0.5, it will give unfavorable results in terms of weather resistance and solvent resistance;
If it exceeds this amount, satisfactory results may not be obtained in terms of drying properties.

Further, if necessary, a curing reaction catalyst such as triethylamine, tetra(2-ethylhexyl) titanate, di-n-butyltin dilaurate, etc. can be added.

〔Effect of the invention〕

The prepolymer of the present invention is a non-toxic, non-irritating, difunctional and/or trifunctional terminal NGO that is stable on long-term storage.
It is of the type that has This prepolymer can be applied to a wide range of fields, including polyurethane paints for plastics that require elasticity, and extensible polyurethane paints for building exterior materials that can follow cracks in concrete.

Further, when the prepolymer of the present invention is used, it is convenient to use a common base agent when repairing an automobile exterior panel (steel material) and a plastic part (plastic bumper) at the same time. In addition, if the prepolymer of the present invention is used as a curing agent, the mixing ratio of main resin/curing agent must be changed in order to maintain an appropriate NGOlo)1 ratio, and a two-component system can be created without problems caused by mixing errors. It has great advantages.

In addition, the coating film made from the coating composition of the present invention has good transparency resistance, flexibility at a low temperature of ~30°C, impact resistance,
It has excellent water resistance, weather resistance, and heat resistance, making it suitable for painting resin parts such as automobile bumpers.

Furthermore, since it has high drying properties, it has a great advantage in terms of work efficiency.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these Examples.

Example 1 In a 2-liter flask equipped with a thermometer, condenser, and stirrer, 403 g (4.8 equivalents) of hexamethylene diisocyanate, 533 g (4,8 equivalents) of isophorone diisocyanate, and polycaprolactone polyol [Daicel Chemical Co., Ltd. Made by Kiki, product name "Plaxel 305", number average molecular weight 5
50, hydroxyl value 305mg KOH/g) 115.3
g (0.63 equivalents) and stirred at 100°C.
Allowed time to react.

The obtained reaction solution was heated to 160°C and heated to 0.8 mm for the first time.
Hg, 0 for the second time. Thin film distillation was performed at lmmHg to remove unreacted diisocyanate. The obtained pale yellow viscous liquid prepolymer was mixed with ethyl acetate to give a solid content of 75% by weight.
A solution of This solution had an NGO concentration of 8.1% and 25°
The viscosity at C was 230 cp, and the content of unreacted hexamethylene diisocyanate and isophorone diisocyanate determined by gas chromatography was 0.1% and 0.4%, respectively, as a pale yellow, transparent liquid. Ta.

The weight ratio of hexamethylene diisocyanate and isophorone diisocyanate in the recovered diisocyanate was 40/60 (molar ratio 47153), indicating that the content of isophorone diisocyanate was increased compared to the charged mixture. Ta.

Note that the theoretical value when it is assumed that the sequential addition reaction of 0% NC of this prepolymer solution is not occurring is 8.3%, and the difference from the actual value is small. Therefore, it is suggested that the content of sequential addition polymers in this prepolymer is small.

Example 2 The amounts of hexamethylene diisocyanate and inphorone diisocyanate were each 605 g (7.2 equivalents).
, 266 g (2.4 equivalents), the same reaction, purification and mixing operations as in Example 1 were carried out, and the NGO concentration was 8.4%, the viscosity at 25 °C was 200 cp, and unreacted hexamethylene. A pale yellow transparent liquid was obtained, containing 04% and 062% of diisocyanate and inphorone diisocyanate, respectively.

Example 3 The amounts of hexamethylene diisocyanate and isophorone diisocyanate were each 202 g (2.4 equivalents).
, 799 g (7.2 equivalents), the same reaction, purification, and mixing operations as in Example 1 were carried out, and the NGO concentration was 7.8%, the viscosity at 25°C was 260 cp, and unreacted hexamethylene diethylene chloride. A pale yellow transparent liquid was obtained, containing 0.1 g and 0.4% of isocyanate and isophorone diisocyanate, respectively.

Example 4 "In place of Plaxel 305 J 115.3 g, [Plaxel 308. + [Daicel Chemical Industries (manufactured by Kiki, trade name, number average molecular weight 850, hydroxyl value 195 KOH/g)
The same reaction, purification, and mixing operations as in Example 1 were performed except that 180 g (0.63 equivalents) was used, and the NGO concentration was 6.
．． A pale yellow transparent liquid was obtained with a viscosity of 220 cp at 25° C. and a content of unreacted hexamethylene diisocyanate and isophorone diisocyanate of 0.1% and 0.5%, respectively.

Example 5 Instead of Plaxel 305J 115.3 g, Plaxel 312ALJ C manufactured by Daicel Chemical Industries ■, trade name, number average molecular weight 1250, hydroxyl value 195 ■KOH/
g) The same reaction, purification, and mixing operations as in Example 1 were carried out except for using 260 g (0.63 equivalents), and the NGO concentration was 5.3%, the viscosity at 25 °C was 260 cp, and unreacted hexamethylene. The content of diisocyanate and isophorone diisocyanate is 0.2% and 0.6%, respectively.
A pale yellow transparent liquid was obtained.

Comparative Example 1 Using only 806 g (9,6 equivalents) of hexamethylene diisocyanate as the diisocyanate, Example 1
The same reaction, purification, and mixing operations as above were performed until the NGO concentration was 8.
A pale yellow transparent liquid was obtained with a viscosity of 160 cp at 25° C. and a content of unreacted hexamethylene diisocyanate of 0.2%.

Comparative Example 2 Isophorone diisocyanate 1 as diisocyanate
Using only 066 g (9.6 equivalents), the same reaction, purification, and mixing operations as in Example 1 were performed, and the NGO concentration was 7.3.
%, viscosity at 25 DEG C. 280 C1) 1 A pale yellow transparent liquid was obtained containing 0.2% of unreacted inphorone diisocyanate.

Examples 6 to 10 and Comparative Examples 3 to 4 (Coating film test) Example 1
-5 and Comparative Examples 1 and 2 were sprayed with acrylic polyol as the main ingredient to evaluate the coating films.

Acrylic polyol manufactured by Futari Nippon Ink Kagaku Kogyo ■, product name: Acrylic DIC A-801 NGO10H = 1.0 Solvent composition: ethyl acetate/toluene/butyl acetate/xylene/cellosolve acetate (20/30/30/1515) Paint viscosity :Ford Cup #4.13 seconds Drying conditions: 20
Table 1 shows the evaluation results at 165% RH.

(Margins below) Table 1): ○:〉50%, △: 10-50%, X:
<10%2): ○: Good, △: Good, ×: Crack occurrence 3): Koenig hardness after 1 day (Glass plate =
180)○:〉10, △:5~10, ×:<5

[Brief explanation of the drawing]

FIG. 1 is an infrared absorption spectrum of the prepo+)mer obtained in Example 4. Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] 1. The following general formula I ▲ Numerical formulas, chemical formulas, tables, etc. are included ▼ I It is a mixture of residues excluding the nato group, and the mixing ratio is 1/9.
It is in the range of 9 to 99/1, and Z is ▲ Residues represented by ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ II or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Residues represented by III or these Represents a mixture. Here, A is the residue obtained by removing the OH group from the diol or triol of C_3-C_1_0, i, j, k, l, m are integers, and the number average molecular weight of the residues II and III is 550.
~1,500. ) Prepolymer 2 for polyurethane paints represented by (a) hexamethylene diisocyanate, (b) isophorone diisocyanate and (c) number average molecular weight 50
0 to 1,500 polycaprolactone diol and/or triol (a)/(b) = 99/1 to 1/99
, for polyurethane paints, characterized in that the reaction is carried out under conditions of an NCO/OH equivalent ratio of 5 to 40, and then the total amount of unreacted hexamethylene diisocyanate and isophorone diisocyanate is removed until the total amount is 1% by weight or less. Prepolymer manufacturing method. 3. A composition comprising the prepolymer for polyurethane paint according to claim 1 and a polyhydric hydroxyl compound, the composition having an NCO/OH ratio of 0.5 to 2.0.