JPH04239517A - Polyisocyanate excellent in extensibility and drying property - Google Patents

Abstract

PURPOSE:To obtain a new polyisocyanate, excellent in especially extensibility and drying properties by reacting a specific polyol with a diisocyanate. CONSTITUTION:A polyisocyanate, having an isocyanurate structure and is obtained by reacting 100 pts. diisocyanate composed of hexamethylene diisocyanate alone or a mixture of the hexamethylene diisocyanate with isophorone diisocyanate with 20-60 pts. polytetramethylene glycol having 700-1600 number-average molecular weight in the presence of an isocyanuration catalyst. The aforementioned polyisocyanate is excellent in both extensibility and drying properties. Since drying can be carried out in a shorter time than that in a conventional method, operating efficiency is remarkably improved. Coated materials having beautiful coated surfaces can be obtained.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention is in the field of paints for automobiles, buildings, electrical appliances, etc., and is particularly suitable for applications such as resin urethane bumpers and architectural exterior materials.
This invention relates to a polyisocyanate for two-component polyurethane paints that has excellent drying properties and weather resistance.

0002

[Prior Art] In recent years, various resin products have been adopted as automobile parts in place of steel materials in the automobile field from the viewpoint of weight reduction and shock absorption ability.The paints used for these resin products have excellent properties. In addition to weather resistance and adhesion, properties such as good extensibility and impact resistance are also required.

[0003] As described above, in fields such as automobiles and buildings where weather resistance is particularly required, non-yellowing polyisocyanates derived from saturated hydrocarbon diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate are used as curing agents for polyurethane resins. However, in addition to this, various urethane prepolymers obtained by reacting diisocyanates and polyols have been proposed as having improved extensibility at low temperatures, impact resistance, etc.

For example, in JP-A-58-59213 and JP-A-62-53525, a polyurethane elastomer obtained from a polyol and diisocyanate obtained by copolymerizing polytetramethylene glycol and caprolactone is also disclosed in JP-A-61 JP-A-12753 proposes a prepolymer consisting of polycaprolactone polyol and diisocyanate having a specific number average molecular weight, and JP-A-54-60395 proposes a prepolymer of polytetramethylene glycol and diisocyanate.

[0005]

[Problems to be Solved by the Invention] However, these proposed prepolymers have poor drying properties, and it takes several days for them to leave no marks on painted objects when touched. As a result, not only the workability deteriorates significantly, but also problems such as dust adhering to the painted surface and making it dirty occur. Therefore,
In order to improve workability and obtain a clean painted product, there is a need for a coating that maintains a certain degree of extensibility while drying quickly enough to leave no marks when touched after painting. .

[0006]

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have discovered that a polyisocyanate obtained by reacting a specific polyether polyol with a diisocyanate can achieve the above-mentioned purpose. The present invention was completed based on the discovery that the invention satisfies the requirements of the invention. That is, in the present invention, 20 to 60 parts of polytetramethylene glycol having a number average molecular weight of 700 to 1,600 is added to 100 parts of a diisocyanate consisting of hexamethylene diisocyanate alone or a mixture of hexamethylene diisocyanate and isophorone diisocyanate as an isocyanurate catalyst. It is a polyisocyanate having an isocyanurate structure obtained by reacting in the presence of polyisocyanate.

The polytetramethylene glycol used in the present invention has a number average molecular weight within a specific molecular weight range of 700 to 1,600. If the polyisocyanate is synthesized from polytetramethylene glycol having a number average molecular weight of less than 700, the elongation of the coating film will be insufficient. Also,
Polyisocyanate synthesized from polytetramethylene glycol having a number average molecular weight of more than 1,600 has insufficient drying properties of the coating film.

Further, the amount of polytetramethylene glycol must be within the range of 20 to 60 parts per 100 parts of diisocyanate. If the amount of polytetramethylene glycol is less than 20 parts, the elongation of the coating film will be insufficient. In addition, the amount of polytetramethylene glycol is 6
If it exceeds 0 parts, the drying properties of the coating film will be insufficient. The polyisocyanate that is the object of the present invention is produced, for example, by the following method.

[0009] To 100 parts of diisocyanate, 20 to 60 parts of polytetramethylene glycol having a number average molecular weight within the range of 700 to 1,600 is charged to perform a urethanization reaction, and then an isocyanurate conversion catalyst is added to perform an isocyanurate conversion reaction. After the reaction is completed, excess diisocyanate is removed. The reaction may be carried out with or without a solvent. When using a solvent, it is natural to select a solvent that does not have reactive activity toward isocyanate groups. Specific examples of the solvent include aromatic hydrocarbons such as toluene and xylene, and esters such as ethyl acetate and butyl acetate.

[0010] The reaction temperature is usually 60~
160°C, and the isocyanurate reaction temperature is selected from the range of 40 to 120°C. The progress of the reaction can be tracked by measuring the NCO% or refractive index of the reaction solution. Also,
It is generally said that the isocyanurate reaction occurs via a uretdione structure, which is a cyclic dimer with low thermal stability, or that a uretdione structure occurs as a side reaction. Therefore, if the reaction is stopped at a low conversion rate, the uretdione concentration in the product tends to increase. therefore,
In order to suppress the uretdione content in the product, it is necessary to select a catalyst that leaves little uretdione residue. Catalysts suitable for such conditions include (1) hydroxides and organic weak acid salts of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium; (2) such as trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, and triethylhydroxypropyl; hydroxyalkyl ammonium hydroxides and organic weak acid salts such as ammonium and triethylhydroxyethylammonium; ■ alkali metal salts of alkyl carboxylic acids such as acetic acid, caproic acid, octylic acid, and myristic acid; and ■ tin of the above alkyl carboxylic acids; Examples include metal salts such as zinc and lead, and compounds containing aminosilyl groups such as hexamethyldisilazane.

[0011] The catalyst concentration varies depending on the catalyst used and the reaction concentration, but is usually 10% to diisocyanate.
-1000 ppm. Furthermore, if the isocyanurate formation reaction progresses too much, the isocyanurate polymer content increases, resulting in adverse effects such as an increase in the viscosity of the product, making it impossible to obtain a product with desired physical properties. Therefore, it is preferable to keep the conversion rate of the reaction at about 25% or less. However, since the initial reaction rate of the isocyanurate reaction is very fast, it is difficult to stop the progress of the reaction at an early stage, and the reaction conditions, especially the amount and method of addition of the catalyst, must be carefully selected. There is. For example, a method of adding the catalyst in portions at regular intervals is recommended as a suitable method.

When the reaction reaches the desired conversion rate, a catalyst deactivator such as sulfuric acid or phosphoric acid is added to stop the reaction. After stopping the reaction and removing the deactivated catalyst if necessary, excess diisocyanate and solvent are removed to obtain a product. The diisocyanate and solvent are removed by, for example, a thin film evaporation can or a solvent extraction method. Furthermore, the polyisocyanate of the present invention can be used in two-component polyurethane paints, adhesives, etc. in combination with known polyols such as acrylic polyols, polyester polyols, and fluorine-containing polyols. In addition to the above components, organic solvents such as ethyl acetate, butyl acetate, toluene, xylene, methyl ethyl ketone, and cellosolve acetate, colored pigments, extender pigments, dispersants, antifoaming agents, leveling agents, etc. may be added as necessary. Moreover, in order to accelerate the curing reaction, a catalyst such as an organic tin compound or a tertiary amine compound may be added. Furthermore, stabilizers such as hindered phenol, benzotriazole, and hindered amine stabilizers may be added to prevent photodeterioration and oxidative deterioration.

It is also possible to block the polyisocyanate of the present invention with a known blocking agent such as alcohol, phenol, oxime, caprolactam, or active methylene, and use it in a one-component polyurethane paint.

[0014]

[Examples] The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to these Examples. In addition, the physical property values of the product were determined by the following method. The viscosity is
Measurement was performed at 25°C using a B-type viscometer.

The NCO content is determined by adding excess di-n-butylamine to the product and reacting it with isocyanate.
The amount of unreacted amine was determined by back titration with hydrochloric acid. The amount of residual hexamethylene diisocyanate (hereinafter abbreviated as HDI) or residual isophorone diisocyanate (hereinafter abbreviated as IPDI) was measured using a gas chromatograph (manufactured by Hitachi, Ltd., F
ID detector) using an internal standard method.

The IR measurement was carried out using a Fourier transform infrared spectrophotometer (manufactured by Shimadzu Corporation) by a rock salt plate coating method. The curing time is determined by leaving the painted sample in an atmosphere of 20℃ and placing a weight with a diameter of 25 mm (weight 100 g) on top of 5 sheets of Japanese Pharmacopoeia gauze on the painted surface for 1 minute. The standing time until no gauze marks remained was measured.

[0017] Measurement of tensile strength and elongation is based on JIS K 630.
It was carried out according to 1. (Test temperature = 20℃)

[0018]

[Example 1] In a four-neck flask equipped with a stirrer, a cooling tube, and a thermometer, 400 g of HDI and PTG1000 (polytetramethylene glycol manufactured by Hodogaya Chemical Industry Co., Ltd.),
Product name, physical properties listed in catalog: Average molecular weight = 1000
, hydroxyl value=112, acid value 0.05 or less) was charged, and a urethane-forming reaction was carried out at 100° C. for 1 hour with stirring. Then, after lowering the temperature to 60°C, 0.2 g of tetramethylammonium caprate was divided into 3 portions as a catalyst.
Added every 0 minutes.

After carrying out the isocyanurate reaction at 60° C. for 4 hours, 0.15 g of 89% phosphoric acid was added as a terminator to terminate the reaction. Further, the temperature was raised to 90° C. and heating was continued for 1 hour, and then cooled to room temperature to precipitate tetramethylammonium phosphate as a deactivated catalyst. After removing this precipitate by filtration, using a falling thin film evaporation can,
1st time 0.5mmHg/150℃, 2nd time 0.1mmH
Unreacted HDI was removed and collected under conditions of g/160°C.

The product obtained was a pale yellow, transparent liquid with a viscosity of 2700 cP, an NCO content of 11.6%, and a free HDI content of 0.1%. When this product was subjected to IR measurement, absorption of isocyanurate rings was observed around 1680 cm-1. This polyisocyanate was used as an acrylic polyol (manufactured by Dainippon Ink Chemical Co., Ltd., product name: Acridic A-801, property values listed in the catalog: nonvolatile content = 50%, viscosity = P to T, oxidation 3 or less, color number 1 or less, hydroxyl value = 50, solvent composition: toluol/butyl acetate), prepare an equivalent blend so that NCO/OH = 1, and dibutyltin dilaurate as a catalyst at 300%
After adding ppm, add 15 ppm with toluene in a Ford cup.
Diluted to Sec. There is no cloudiness in this paint liquid,
The compatibility with polyol was good. After spray painting this coating liquid, the coating film was left at a temperature of 20° C. and the curing time was measured. The results are shown in Table 1.

[0021] In addition, the above-mentioned spray-painted coating film was
After drying at 00°C for 1 hour, tensile strength and elongation were measured. The results are shown in Table 1.

[0022]

Examples 2 to 5 The same procedure as in Example 1 was carried out except that the molecular weight of polytetramethylene glycol, the charging ratio, and the type of diisocyanate were changed. The results are shown in Table 1. From the results shown in Table 1, all of the polyisocyanates of the present invention have a short curing time and are excellent in the extensibility of the coating film.

[0023]

[Comparative Example 1] Polycaprolactone polyol (manufactured by Daicel Chemical Industries, Ltd., trade name: Plaxel 312) was used instead of polytetramethylene glycol in Example 1. Physical properties listed in the catalog: average molecular weight = 1250, hydroxyl value = 1
Example 1 except that 130 g of 35, acid value 1 or less) was used.
I did it in the same way. The results are shown in Table 2. Although this polyisocyanate has a significantly short curing time, the elongation of the coating film is extremely low, making it unsuitable for practical use.

[0024]

[Comparative Example 2] A four-necked flask equipped with a stirrer, a cooling tube, and a thermometer was charged with 400 g of HDI and 160 g of Plaxel 312, and a urethane reaction was carried out at 100° C. for 1 hour with stirring. After that, using a falling thin film evaporation can, the first time was 0.5 mmHg/150℃, the second time was 0.1 mmHg/
Unreacted HDI was removed and collected under conditions of 160°C.

The product obtained was a pale yellow, transparent liquid with a viscosity of 5200 cP, an NCO content of 9.5%, and a free HDI content of 0.1%. The urethane prepolymer thus obtained was evaluated in the same manner as in Example 1. The results are shown in Table 2. Since this urethane prepolymer does not have an isocyanurate structure, the curing time is extremely long and it is not suitable for practical use.

[0026]

[Comparative Examples 3 to 6] Comparisons were carried out in the same manner as in Example 1, except that the molecular weight of polytetramethylene glycol in Example 1 and the charging ratio were changed outside the claimed range. The results are shown in Table 2. Those with a low charging ratio and those with a small molecular weight have a short curing time, but the elongation of the coating film is very small, so they are not suitable for practical use. Moreover, those with a high charging ratio and those with a large molecular weight have extremely long curing times and are not suitable for practical use.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Effects of the Invention] The polyisocyanate of the present invention has the contradictory properties of sufficient extensibility and good drying properties. Therefore, the drying time after painting can be shortened, so that the amount of dust and the like that adheres to the paint film during drying can be reduced, and workability can also be greatly improved.

Furthermore, since the polyisocyanate of the present invention has an isocyanurate structure, it has extremely superior weather resistance compared to the urethane prepolymers commonly used at present. Therefore, it is extremely useful particularly in applications where weather resistance is important, such as exterior applications for automobiles and buildings.

Claims (1)

[Claims] Claim 1: Diisocyanate 100 consisting of hexamethylene diisocyanate alone or a mixture of hexamethylene diisocyanate and isophorone diisocyanate.
A polyisocyanate having an isocyanurate structure obtained by reacting 20 to 60 parts of polytetramethylene glycol having a number average molecular weight of 700 to 1,600 per part of the polytetramethylene glycol in the presence of an isocyanurate catalyst.