JPH0241379A - Resin composition for primer - Google Patents

Abstract

PURPOSE:To obtain the title composition applicable to various kinds of plastic materials, having excellent freeze resistance, heat resistance and hydrolysis resistance consisting essentially of a polyurethane resin prepared by reacting a specific polymer diol with a specific or organic diisocyanate and a chain extender. CONSTITUTION:The aimed composition consisting essentially of a polyurethane resin soluble in organic solvents, having 10,000-50,000 number-average molecular weight prepared by reacting (A) a polymer diol comprising a polyester diol having 1,500-4,000 molecular weight, containing monomers shown by formula I and formula II in the molar ratio of (100/0)-(10/90) and/or a polycarbonate diol as a main component with (B) an aliphatic and/or alicyclic diisocyanate and (C) a chain extender comprising an aliphatic and/or alicyclic diamine (with the proviso that one of the components B and C is alicyclic compound) in the molar ratio of the component A/B of 1.5-3.0.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a resin composition for a primer that can be applied to electrocoated steel plates for automobile bodies and various plastic materials.

(Prior Art) Conventionally, steel sheets for automobile bodies have been subjected to chemical conversion treatment, electrodeposition coating, partial chipping primer or stone guard coating, intermediate coating, and top coating. On the other hand, various plastic parts are coated with a special primer for each plastic material, and then coated with a top coat of amino alkyd resin, amino acrylic resin, or polyurethane resin paint. In addition, in the case of integral painting with the car body, a special primer is applied to the plastic, and then an intermediate paint whose main ingredients are fatty acid-modified polyester resin, oil-free polyester resin, etc. suitable for the steel plates that make up the car body is applied.
Baking is carried out at ~150°C for 10-60 minutes, and then a top coat containing aminoalkyd resin or aminoacrylic resin as the main component is applied and baked at 130°-150°C for 10-60 minutes.
Baking is being performed for 0 minutes.

(Problems to be Solved by the Invention) According to such conventional painting methods, the coating film compositions are different on the steel plate material and the plastic material, and the appearance such as color tone and gloss of the steel plate material part and the plastic material part are different. This causes a difference in the durability of the paint film and impairs the beauty of the car. In addition, if you apply a special primer to the plastic material and then attach it to the steel plate material and then apply the coating at the same time, the above problem will disappear, but when selecting the intermediate and top coats, it is better to use a soft coating film that is suitable for plastic materials, making it resistant to weathering. On the other hand, if a hard coating is used for steel sheet materials, impact resistance at low temperatures on plastic materials will decrease, etc. There are also problems with restrictions on intermediate and top coat paints.

Due to this background, we currently have products that have excellent adhesion to all plastic materials, are heat resistant, cold resistant, weather resistant, hot water resistant,
There is a demand for a high-performance primer or a diisomer specifically for plastic materials that can be applied simultaneously to plastic materials and steel sheet materials, and can provide a coating film with excellent impact resistance and solvent resistance.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors found that by using a specific polyurethane resin as a primer, it can be used for car body outer panels and parts. Good adhesion to various plastic materials and cold resistance.
The present invention was achieved by discovering that it has excellent heat resistance and hydrolysis resistance.

That is, the present invention provides a resin composition for a primer comprising as a main component an organic solvent-soluble polyurethane resin obtained by reacting a polymeric diol, a diisocyanate, and a chain extender, wherein the polyurethane resin is The following conditions (A
), (B), (C) (A) The structural units (1) and (■) represented by the formula % as units based on diol in the molecule are combined into structural units (1) and (■).
)/structural unit (II) molar ratio of 100/(1 to 10/
Molecular weight 1500 to 90 (including O)
(B) The organic diisocyanate is an aliphatic and/or alicyclic diisocyanate, and the chain extender is an aliphatic and/or alicyclic diisocyanate. A diamine containing an alicyclic compound as at least one of the diisocyanate and the chain extender.
(C) The molar ratio of organic diisocyanate to polymeric diol is in the range of 1.5 to 3.0, and the polyurethane has a number average molecular weight of 10,000 to 5,000 G. shall be.

Furthermore, in order to make the effects of the present invention more remarkable,
The polyurethane resin in the present invention is a polymeric diol (1
) and organic diisocyanate (II) and chain extender ([[
When synthesized from [), first (1) and (II) are synthesized from (
1): (II) is reacted at a molar ratio of 1:1.2 to 2.0 to synthesize a prepolymer of terminal isocyanate, and then to this prepolymer, 0 to 1 mole of (I) is added.
．． This is achieved by using a polyurethane obtained by additionally reacting 3 to 1.0 moles of (II) and (II[).

The most distinctive feature of the polyurethane resin, which is the main component of the resin composition for primers of the present invention, is that it contains 2-methyl-1,8-octanediol as an essential component and further contains 1,9-nonanediol as a diol component. The objects of the present invention are achieved by the use of polyester diols and/or polycarbonate diols, and the use of aliphatic or ring-based diisocyanates and diamines, and by the polyurethane with the specific composition and molecular weight obtained in this way. be done.

Polymer diols conventionally used in polyurethane resins include polyester diols, polycaprolactone diols, polypropylene glycols, and polytetramethylene glycols, which are composed of dibasic acids such as adipic acid and diols such as ethylene glycol, butanediol, and hexanediol. Polyether glycols are commonly used, but polyurethanes made of these polymeric diols have major problems in hydrolysis resistance, oil resistance, heat resistance, light resistance, low-temperature properties, etc. Among these, polycaprolactone diol is the most preferable in terms of overall performance, but it still has a drawback in hydrolysis resistance, and when a more flexible polyurethane is attempted, its crystallinity causes problems in impact resistance at low temperatures.

On the other hand, tolylene diisocyanate and 4.4°-diphenylmethane diisocyanate are generally used as diisocyanates for polyurethane, but polyurethanes made from aromatic ring diisocyanates have poor light resistance and are used at low temperatures. The disadvantage is that it has poor impact resistance. However, the light resistance and impact resistance at low temperatures of polyurethanes made from q-group or alicyclic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and 4,4° dicyclohexylmethane diisocyanate are in good condition,
Among them, polyurethanes made of hexamethylene diisocyanate and isophorone diisocyanate have excellent impact resistance at low temperatures.

However, these diisocyanates have the disadvantage of inferior heat resistance compared to aromatic diisocyanates. As described above, it is difficult to achieve both heat resistance and low-temperature properties as paint properties, but by achieving a specific composition range with a specific combination of the polymer diol of the present invention, diisocyanate, and chain extender, it is possible to achieve low-temperature properties. It was discovered that both characteristics and heat resistance can be achieved.

One of the reasons why the polyurethane resin, which is the main component of the resin composition for primers of the present invention, has excellent heat resistance and low-temperature properties is as follows.
-Methyl-1,8-octanediol (MOD) as an essential component, and further 1,9-nonanediol (ND)
By using polyester diol and/or polycarbonate diol containing as a diol component. This combination of long-chain diols suppresses the crystallinity of the polyester diol or polycarbonate diol, imparts flexibility, and improves cold resistance. MOD/
The molar ratio of ND needs to be in the range of too10 to to/90, more preferably 10010 to 20/10. When the ND ratio is greater than 10/90, the crystallinity increases and the low temperature characteristics become poor.

The dicarboxylic acid for molding the polyester diol used in the present invention is preferably an aliphatic or aromatic dicarboxylic acid having 5 to 12 carbon atoms. Among them, aliphatic dicarboxylic acids are preferred. Examples of aliphatic dicarboxylic acids include glutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid, sepacic acid, etc., and examples of aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, etc. It will be done. From the viewpoint of hydrolysis resistance and flexibility under low temperature atmosphere, it is preferable to use adipic acid, azelaic acid or sepacic acid, especially azelaic acid. These dicarboxylic acids may be used alone or in combination of two or more.

In addition, as a method for producing the polycarbonate diol used in the present invention, only a mixed diol mainly consisting of 2-methyl-1,8-octanediol and 1,9-nonanediol and diphenyl carbonate, dialkyl carbonate, or ethylene carbonate, etc. are used. It can be produced by a polycondensation reaction with a bonate compound.

What is more important is the molecular weight of the polymeric diol, which preferably ranges from 1,500 to 4,000. If a polymeric diol having a molecular weight of less than 1500 is used, the low temperature properties will be poor.

Moreover, when the molecular weight exceeds 4000, mechanical performance becomes poor.

The second reason for the excellent heat resistance and cold resistance is due to the use of ring group or aliphatic diisocyanates and diamines and their appropriate proportions. Heat resistance and cold resistance can be improved by using a ring group compound for at least one of organic diisoneanate and diamine, and by setting the molar ratio of organic diisocyanate to polymer diol in the range of 1.5 to 3.0. It becomes possible to achieve both.

If the compression is less than 1.5, mechanical properties, heat resistance, and heat and humidity resistance will be poor, and if it exceeds 3.0, solvent solubility and low-temperature impact resistance will be poor.

In the present invention, in order to further improve heat resistance and cold resistance, the polyurethane 11 fingers of the present invention are polymeric diol (1
), organic diisocyanate (II) and chain extender (II)
When synthesized from [), first ([) and (II) are synthesized by (
Synthesize a prepolymer of terminal isocyanate by reacting at a molar ratio of [):(II) of 1:12 to 2.0,
Then, to this prepolymer, 0,
This is achieved by using a polyurethane obtained by additionally reacting 3 to 1.0 moles of (II) and (III).

In addition, particularly preferable organic diisocyanates from the viewpoint of low temperature properties (cold resistance) are hexamethylene diisocyanate or isophorone diisocyanate, and a combination of both is good.

If heat resistance is important, isophorone diisocyanate is preferred.

As the chain extender, ring group diamine is preferable from the viewpoint of heat resistance, solvent solubility and solution stability, and the particularly preferable ring group diamine is isophorone diamine.

Polyurethane produced in this way can be used as a solution dissolved in a solvent such as toluene, xylene, hexane, ethyl acetate, methyl ethyl ketone, isopropyl alcohol, etc., but the molecular weight of polyurethane is determined based on mechanical properties, solution viscosity, spray workability, etc. Polyurethanes with a molecular weight of 10,000 to 50,000 are preferred.

In the present invention, the polymeric diol containing 2-methyl-1,8-octanediol and 1,9-nonanediol alone provides excellent impact resistance and cold resistance at low temperatures, but the Molecular weight 1000 within the range of mol%
When polytetramethylene glycol of ~3000 is used in combination, even better low-temperature properties are exhibited. If it exceeds 40 mol%, heat resistance and weather resistance decrease, which is not preferable.

When the polyurethane solution of the present invention is applied to plastics and metals, it may be applied as is, but it may be added to 1 mol of trifunctional or higher functional polyisocyanate, such as trimethylolpropane, which is commonly used in the field of polyurethane coatings. It is also possible to use a material to which approximately 3 moles of isophorone diisocyanate or hexamethylene diisocyanate is added, or a trimer integrated with hexamethylene diisonanate (Coronate EH: manufactured by Nippon Polyurethane).

As other components, a conductive material can be added to enable intermediate and/or top coating on the plastic material. Conductive carbon is often used as the conductive material. The ratio of conductive carbon to polyurethane fat is 5 to 35% by weight, preferably 8 to 20%.
It is 14%.

The composition of the present invention may contain additives such as pigments, porcelain, ultraviolet absorbers, antioxidants, antistatic agents, and the like.

In the present invention, the primer film thickness may be about 3 to 40 microns.

Next, the present invention will be explained in detail using Examples, Comparative Examples, and Reference Examples. In the examples, parts are parts by weight and % are weight %. The compounds used are shown using abbreviations, and the relationship between the abbreviations and compounds is shown in Table 1.

Esterification was carried out while distilling off. When the acid value of the polyester became about 1 or less, the degree of vacuum was gradually increased using a vacuum pump to complete the reaction. Thus, the hydroxyl value is 56,
A polyester diol (hereinafter referred to as polyester A) having an acid value of 0.23 was obtained.

Reference Examples 2 to 8 In the same manner as Reference Example I except that the acid component and diol component shown in Table 2 were used, the hydroxyl value was 5.
In Example 6, a polyester diol having an acid value and a molecular weight shown in Table 2 was obtained.

Below is a margin reference example 1 2-Methi/I/-L, S-:tkta:/')t-ru 1
600 g and adipic acid 1460 g (2-methyl-t
, g-octanediol/adipic acid molar ratio: IJ
Reference Example 11: 2-Methyl-1,8-octanediol 8 under a nitrogen stream under a normal pressure of 2-methyl-1,8-octanediol.
? A mixture of Og, 870 g of 1,9-nonanediol, and 2,140 g of diphenyl carbonate was heated to 190° C. to distill off phenol from the reaction system. The temperature was gradually raised to 210°C to 220°C, and after most of the phenol had been distilled off, vacuum was applied, and the remaining phenol was completely distilled off at 210°C to 220°C under a vacuum of 6 to 1oII+nHg. As a result, a paste-like substance with a hydroxyl value of 56 was obtained. The number average molecular weight was about 2,000 (Polycarbonate A) Reference Examples 12-13 Polycarbonate diols shown in Table 3 were synthesized using the same recipe (Polycarbonate B-C) Example 1 Polyester diols shown in Table 2 ( A) 2000 parts (1 mol) and 333 parts (1 mol) of isophorone diisocyanate
, 5 mol) were charged into a round bottom flask equipped with a stirrer and a thermometer, mixed uniformly, and reacted at 90°C for 8 hours to obtain a prepolymer having isocyanate groups at the terminals. To this, 3760 g of toluene was charged, and after dissolving, 155.4 parts (0.7 mol) of isophorone diisocyanate was added, and then a mixture of 204 parts (1.2 mol) of isophorone diamine and 2500 g of isopropanol was gradually added. Addition was stopped when the viscosity reached 30 poise.

The number average molecular weight of this polyurethane was 25,200. This polyurethane solution is cast and dried to a thickness of O,1
A uniform transparent film of 5 mm was obtained. Table 4 shows the cold resistance, heat resistance, and hydrolysis resistance of this film.

Evaluation method (1) Number average molecular weight A polyurethane film was dissolved in dimethylformamide and measured by gel permeation chromatography.

(2) Coatable polyurethane solution to toluene-isopropanol mixed solution (toluene/isopropanol = 6/4 (weight ratio)
) to reduce the spray viscosity to about 1 in a Ford cup #4.
The spraying time was adjusted to 3 seconds (20° C.), and the spray coating properties were evaluated.

(3) Cold resistance A test piece was prepared from a polyurethane film with a thickness of 0.2 mm, and measured using a dynamic viscoelasticity measuring device Rheospectra-D V E -V 4' (11) 1z) manufactured by Shioroji Co., Ltd. The main dispersion temperature [T, (atE“), see Figure 1]
It was shown in

(3) Hydrolysis resistance (%) The film was immersed in hot water at 100° C. for 10 days, and the retention rate (%) of the number average molecular weight was shown.

(4) Heat resistance Similarly to cold resistance, the flow initiation temperature obtained by dynamic viscoelasticity measurement (see T-1 Figure 1) is shown.

(Effects of the Invention) The resin composition for primers of the present invention can be applied to various plastic materials used for automobile body W4 boards and parts, and has excellent cold resistance, heat resistance, and hydrolysis resistance. . Therefore, by applying the resin composition for primer of the present invention, it is possible to simultaneously coat steel plates for automobile bodies and plastic materials, simplifying the coating process and reducing coating costs, and improving the chipping resistance of the M plate part.
There are effects such as improved scap resistance and thread rust resistance, and a coating film with excellent finished appearance.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining how to obtain the main dispersion temperature used to evaluate cold resistance.

Claims (1)

[Scope of Claims] 1. A resin composition for a primer comprising as a main component a polyurethane resin soluble in an organic solvent obtained by reacting a polymeric diol, an organic diisocyanate, and a chain extender, the polyurethane resin is the following conditions (A), (B),
(C) (A) Polymer diol is a unit based on diol in the molecule, and there are formulas ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (I) -O-(CH_2)_8-O-(II) Structural unit represented by (I) and (II) are the structural units (
I)/structural unit (II) molar ratio of 100/0 to 10/
Molecular weight contained in a ratio of 90 (including 0) 1500 to 4
(B) The organic diisocyanate is an aliphatic and/or alicyclic diisocyanate, and the chain extender is an aliphatic and/or alicyclic diamine. At least one of the diisocyanate and the chain extender contains an alicyclic compound, and (C) the molar ratio of the organic diisocyanate to the polymeric diol is 1.5 to 3.0. A resin composition for a primer, which is a polyurethane having a number average molecular weight of 10,000 to 50,000, which satisfies the following. 2. When polyurethane resin is synthesized from polymeric diol (I), organic diisocyanate (II), and chain extender (III), first, (I) and (II) are synthesized in the molar ratio of (I):(II). are reacted at a ratio of 1:1.2 to 2.0 to synthesize a prepolymer having terminal isocyanate groups, and then to this prepolymer, 0.3 to 1% of (I) is added to 1 mole of (I).
Claim (1) whose main component is a polyurethane resin obtained by additionally reacting 1.0 mol of (II) and (III).
) The resin composition for primers described in (1).