WO2010098210A1

WO2010098210A1 - Primer composition

Info

Publication number: WO2010098210A1
Application number: PCT/JP2010/051941
Authority: WO
Inventors: 裕章西村
Original assignee: 日本ポリウレタン工業株式会社
Priority date: 2009-02-25
Filing date: 2010-02-10
Publication date: 2010-09-02
Also published as: JPWO2010098210A1; CN102317389B; JP5585849B2; CN102317389A

Abstract

Disclosed is a primer composition comprising (A) a polyfunctional urethane-urea resin that is obtained by reacting (A1) an organic polyisocyanate, (A2) a polymer polyol, and (A3) a chain extender made of a hydroxyl group-containing diamine, and that has hydroxyl groups derived from the aforementioned chain extender on molecule side chains, 5-20 functional groups and a number average molecular weight of 10,000-50,000, and (B) an organic solvent. The primer composition exhibits sufficient adhesion to an adherend made of a plastic, such as nylon, and a coating film with excellent solvent resistance can be formed even when the curing time is short.

Description

Primer composition

The present invention relates to a primer composition containing a urethane / urea resin.

For example, as a primer for a molded product made of plastic or the like, a primer made of a polyurethane-urea resin solution obtained by reacting an organic diisocyanate, a polymer diol, and an amine chain extender is known (for example, Patent Document 1).

The primer described in Patent Document 1 has good water resistance and heat resistance as compared with a polyurethane resin solution, and is a molded article (adhesion) made of nylon by a urea bond similar to an amide bond. Body).

Japanese Patent Laid-Open No. 62-129361

For example, a primer-based coating film applied to automobile-related parts may come into contact with a solvent, gasoline, or the like, and therefore the coating film is required to have solvent resistance.
However, the coating film by the primer described in Patent Document 1 does not have sufficient solvent resistance (for example, corrosion resistance to a mixture of gasoline and alcohol) or is long before sufficient solvent resistance is developed. Time (for example, a curing time of about 120 hours) is required.
In addition, good moisture and heat resistance is also required for a coating film using a primer applied to automobile-related parts and the like.

The present invention has been made based on the above situation.
An object of the present invention is to provide a primer capable of exhibiting sufficient adhesion to an adherend made of plastic such as nylon and capable of forming a coating film excellent in solvent resistance even when the curing time is short. It is to provide a composition.
Another object of the present invention is to provide a primer composition capable of forming a coating film excellent also in heat and moisture resistance.

The primer composition of the present invention comprises (A1) an organic polyisocyanate, (A2) a polymer polyol having a number average molecular weight of 500 to 5,000, and (A3) a chain extender comprising a hydroxyl group-containing diamine. Polyurethane / urea resin obtained, having a hydroxyl group derived from the chain extender in a molecular side chain, a functional group number of 5 to 20, and a number average molecular weight of 10,000 to 50,000 It contains a urethane / urea resin (A) and an organic solvent (B).

In the primer composition of the present invention, the following forms are preferable.
(1) The number of functional groups of the polyfunctional urethane / urea resin (A) is 8.5 to 18.5, particularly 8.5 to 17.
(2) The polymer polyol is an amorphous polyol.
(3) The polymer polyol is an amorphous polyol obtained by reacting two or more kinds of low-molecular polyols having no side chain with a linear aliphatic polycarboxylic acid.
(4) The molecular end of the polyfunctional urethane / urea resin (A) is blocked with an end-capping agent comprising a hydroxyl group-containing monoamine.
(5) The polyfunctional urethane / urea resin (A) reacts the organic polyisocyanate with the polymer polyol to produce an isocyanate group-terminated urethane prepolymer, and the obtained isocyanate group-terminated urethane prepolymer; It is obtained by reacting the hydroxyl group-containing diamine and the hydroxyl group-containing monoamine.
(6) The concentration of the polyfunctional urethane / urea resin (A) is 5 to 15% by mass, and the organic solvent (B) has a boiling point of 130 to 180 with the organic solvent (B1) having a boiling point of less than 130 ° C. It is composed of an aliphatic solvent (B2) at 0 ° C., does not contain an organic solvent having a boiling point exceeding 180 ° C., and is (B1) :( B2) = 95-50: 5-50 (mass ratio).
(7) A one-component curable primer composition for forming a primer layer on which a resin composition containing polyisocyanate as a curing agent is coated.
(8) A two-component curable primer composition containing polyisocyanate as a curing agent component.
(9) The primer composition is applied to the adherend by spraying.

According to the primer composition of the present invention, it is possible to form a coating film (primer layer) exhibiting sufficient adhesion to an adherend made of plastic such as nylon, and even with a short curing time. A coating film excellent in solvent resistance can be formed.
Moreover, according to the primer composition of this invention which concerns on the form of said (6), the coating film (primer layer) excellent also in heat-and-moisture resistance can be formed.

The urethane / urea resin that is the resin component of the primer composition of the present invention is obtained by reacting (A1) an organic polyisocyanate, (A2) a polymer polyol, and (A3) a chain extender comprising a hydroxyl group-containing diamine. can get.

<(A1) Organic polyisocyanate>
The organic polyisocyanate used for obtaining the urethane-urea resin is not particularly limited, but an aliphatic diisocyanate and an alicyclic diisocyanate are preferable because a coating film having good weather resistance can be formed. Considering the adhesiveness of the coating film, alicyclic diisocyanate is preferable.
Specific examples include hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, cyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and norbornane diisocyanate. These may be used alone or in combination of two or more. it can. Of these, isophorone diisocyanate is particularly preferred.

Examples of organic diisocyanates that can be used in combination with the above aliphatic diisocyanates and / or alicyclic diisocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4 Aromatic diisocyanates such as' -diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, paraphenylene diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, orthoxylylene diisocyanate, metaxylylene diisocyanate And non-yellowing organic diisocyanates such as paraxylylene diisocyanate, which may be used alone or in combination of two or more. Kill.

<(A2) Polymer polyol>
The high molecular polyol used to obtain the urethane / urea resin is a polyester having a number average molecular weight of 500 to 5,000, preferably 1,000 to 3,000, and an average functional group number of 1.9 to 3. Examples thereof include polyols, polyether polyols, polycarbonate polyols, and polyolefin polyols.

Here, “polyester polyol” includes phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, kurtaconic acid, azelain. Acid, sebacic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, 1,4-cyclohexyldicarboxylic acid, α-hydromuconic acid, β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α, β -One or more kinds of dicarboxylic acids such as diethylsuccinic acid, maleic acid, fumaric acid or their anhydrides, and ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1 6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, diethylene glycol, Dipropylene glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer acid diol, bisphenol A ethylene oxide and propylene oxide adducts, bis (β-hydroxyethyl) benzene, xylylene glycol, glycerin , Trimethylolpropane, pentaerythritol, and other low molecular polyols such as those obtained from a polycondensation reaction with one or more kinds. Further, lactone-based polyester polyols obtained by ring-opening polymerization of cyclic ester (so-called lactone) monomers such as ε-caprolactone, alkyl-substituted ε-caprolactone, δ-valerolactone, and alkyl-substituted δ-valerolactone. Furthermore, a polyester-amide polyol obtained by replacing a part of the low molecular polyol with a low molecular polyamine such as hexamethylene diamine, isophorone diamine or monoethanolamine or a low molecular amino alcohol can also be used.

“Polyether polyol” includes two active hydrogen groups such as the above-mentioned low molecular polyols or low molecular polyamines such as ethylenediamine, propylenediamine, toluenediamine, metaphenylenediamine, diphenylmethanediamine, and xylylenediamine. As described above, preferably having 2 to 3 compounds as initiators, alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, alkyl glycidyl ethers such as methyl glycidyl ether, and aryl glycidyl ethers such as phenyl glycidyl ether And those obtained by addition polymerization of cyclic ether monomers such as tetrahydrofuran.

Examples of the “polycarbonate polyol” include those obtained from a dealcoholization reaction or a dephenol reaction between one or more of the above-mentioned low molecular polyols and ethylene carbonate, diethyl carbonate, or diphenyl carbonate. In addition, the transesterification product of the above-mentioned polycarbonate polyol and polyester polyol can also be used.

Examples of the “polyolefin polyol” include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, hydrogenated polyisoprene, and the like.

The polymer polyol used for obtaining the urethane / urea resin is preferably an amorphous polyol. Here, "non-crystalline polyol" refers to a polyol that is amorphous at room temperature.

By using an amorphous polyol, tackiness is imparted to the resulting urethane / urea resin, and the adhesion of the coating film formed by the primer composition of the present invention to the adherend can be further improved.
Moreover, since the non-crystalline polyol has a low cohesive force, the low-temperature storage stability of the primer composition of the present invention can be improved.
Furthermore, the amorphous polyol has good solubility in a diluting solvent.

The non-crystalline polyol suitable as the polymer polyol is a polyester polyol obtained from a low-molecular polyol having a side chain and a linear aliphatic polycarboxylic acid, two or more kinds of low-molecular polyols (with or without a side chain). ) And a linear aliphatic polycarboxylic acid, a polyester polyol obtained from a low molecular weight polyol, an aromatic polycarboxylic acid and a linear aliphatic polycarboxylic acid, and a low molecular weight polyol as an initiator. Polyol obtained by ring-opening addition of a cyclic ester monomer having a ring, polyether polyol obtained by ring-opening addition of a cyclic ether monomer having a side chain using a low molecular polyol as an initiator, and a low molecular polyol having a side chain And a low molecular weight carbonate compound Mention may be made of a turbo sulfonate polyol.

Of these, polyester polyols obtained from two or more kinds of low molecular polyols having no side chain and linear aliphatic polycarboxylic acids are preferred. In particular, the carbon number of each of two or more kinds of low molecular polyols having no side chain is preferably 6 or less.
The side chain of the low-molecular polyol constituting the non-crystalline polyol tends to inhibit the adhesion of the coating film to nylon by the resulting primer composition, so use a low-molecular polyol that does not have a side chain. Thereby, the adhesiveness of the coating film when nylon is used as the adherend can be further improved.

<(A3) Chain extender comprising hydroxyl group-containing diamine>
The hydroxyl group-containing diamine (chain extender) used to obtain the urethane / urea resin is composed of two amino groups (limited to primary amino groups or secondary amino groups) and one or more hydroxyl groups. It is a compound possessed in the molecule.

Specifically, 2-hydroxyethylethylenediamine (β-aminoethylethanolamine), 2-hydroxyethylpropylenediamine (β-aminopropylethanolamine), N, N′-di-2-hydroxyethylethylenediamine, N, N Examples thereof include '-di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine (β-aminoethylpropanolamine), N, N'-di-2-hydroxypropylethylenediamine, and 2-hydroxypropanediamine.

By using a hydroxyl group-containing diamine as a chain extender, a hydroxyl group can be introduced into the molecular side chain of the urethane / urea resin obtained.
Moreover, the polyfunctional urethane / urea resin obtained by the diamine containing a primary hydroxyl group is excellent in reactivity with isocyanate (curing agent).
The chain extender used for obtaining the urethane / urea resin is preferably composed only of a hydroxyl group-containing diamine, but a diamine that does not contain a hydroxyl group may be used in combination with the hydroxyl group-containing diamine.

<(A4) End-Capping Agent Containing Hydroxyl-Containing Monoamine>
The molecular ends of the urethane / urea resin constituting the primer composition of the present invention are preferably blocked with an end-capping agent comprising a hydroxyl group-containing monoamine.
Here, the hydroxyl group-containing monoamine that can be used to obtain a urethane / urea resin is composed of one amino group (limited to a primary amino group or a secondary amino group) and one or more hydroxyl groups. It is a compound possessed in one molecule.

Specifically, monoethanolamine, diethanolamine, N-methylethanolamine, N-ethylethanolamine, Nn-butylethanolamine, Nt-butylethanolamine, hydroxyethylpiperazine, N- (3-aminopropyl ) Diethanolamine, N-cyclohexylethanolamine and the like.

By using a hydroxyl group-containing monoamine as a terminal blocking agent, the molecular ends of the obtained urethane / urea resin can be blocked with a hydroxyl group-containing group.

<Polyfunctional urethane / urea resin (A)>
The polyfunctional urethane / urea resin constituting the primer composition of the present invention has a hydroxyl group derived from a hydroxyl group-containing diamine (chain extender) in the molecular side chain.
Moreover, it preferably has a hydroxyl group derived from a hydroxyl group-containing monoamine (end-capping agent) at the molecular end.

The hydroxyl group introduced into the polyfunctional urethane / urea resin reacts with the isocyanate group, whereby a cross-linked structure is formed in the coating film (primer layer) of the primer composition of the present invention. As a result, the coating film has excellent solvent resistance.

Here, the isocyanate group that reacts with the hydroxyl group in the polyfunctional urethane / urea resin is a resin composition (for example, two-component curing for forming a base layer or a top coat layer) on the coating film by the primer composition of the present invention. In the curing agent of the primer composition, or when the primer composition of the present invention is two-component curable, it is contained in the curing agent of the primer composition.
That is, in order to form a crosslinked structure in the coating film (primer layer) of the primer composition of the present invention, an isocyanate group (a curing agent containing an isocyanate compound) is present in at least one of the primer composition and the resin composition to be overcoated. It is necessary to be included.

Here, as a typical lamination mode performed using the primer composition of the present invention,
(1) A primer layer is formed by the primer composition of the present invention not containing an isocyanate group, a base layer is formed on the primer layer by a resin composition not containing an isocyanate group, and an isocyanate group is formed on the base layer. An embodiment of forming a topcoat layer with a two-component curable resin composition comprising
(2) A primer layer is formed from the primer composition of the present invention containing an isocyanate group (two-component curable resin composition), and a base layer is formed on the primer layer from a resin composition not containing an isocyanate group. A mode in which a top coat layer is formed on the base layer by a resin composition not containing an isocyanate group,
(3) A primer layer is formed from the primer composition of the present invention containing an isocyanate group (two-component curable resin composition), and a base layer is formed on the primer layer from a resin composition not containing an isocyanate group. An example in which a top coat layer is formed on the base layer with a two-component curable resin composition containing an isocyanate group can be mentioned.

The number of functional groups (f) of the polyfunctional urethane / urea resin is 5 to 20, preferably 8.5 to 18.5, and more preferably 8.5 to 17.
In the present invention, the “number of functional groups” refers to the number of hydroxyl groups in one molecule of a polyfunctional urethane / urea resin, and those introduced into the side chain of a molecule by a hydroxyl group-containing diamine (chain extender) and hydroxyl group-containing monoamines (terminals). The total number of molecules introduced at the molecular ends by the sealing agent).

The number of functional groups (f) of the polyfunctional urethane / urea resin is calculated from the measurement value (Mn) of the number average molecular weight of the resin and the measurement value (c) (unit: mmol / g) of the hydroxyl group content of the resin. The following formula is calculated: f = Mn · c / 1000.

When the number of functional groups is 0 (no hydroxyl group is introduced into the urethane / urea resin), sufficient solvent resistance cannot be exhibited even when the curing time of the formed coating film is 100 hours or more ( Comparative Example 1).
Further, when the number of functional groups is less than 5, it takes a long time (for example, 48 hours or more) until the formed coating film exhibits solvent resistance (see Comparative Example 2 and Comparative Example 3).
On the other hand, when the number of functional groups exceeds 20, the adhesion of the formed coating film to the adherend is inferior, and the solvent resistance (necessary curing time) of the formed coating film varies. This occurs (see Comparative Example 4).

The number average molecular weight (Mn) of the polyfunctional urethane / urea resin is 10,000 to 50,000, preferably 15,000 to 41,000.
When the number average molecular weight is less than 10,000, the coating film formed from the resulting primer composition does not have sufficient mechanical properties.
On the other hand, when the number average molecular weight exceeds 50,000, the applicability of the resulting primer composition is impaired, resulting in uneven coating and the like, which may cause variations in solvent resistance (necessary curing time).

The functional group equivalent (Mn / f) of the polyfunctional urethane / urea resin is preferably 5,000 or less, more preferably 2,500 or less, and particularly preferably 1,500 to 2,500. When the functional group equivalent exceeds 5,000, the distance between the cross-linking points becomes long, so that the coating strength and solvent resistance are lowered.

As a method of synthesizing a polyfunctional urethane / urea resin, an organic polyisocyanate and a polymer polyol are reacted to obtain an isocyanate group-terminated urethane prepolymer, and a hydroxyl group-containing diamine (chain extender) and a hydroxyl group-containing monoamine ( A so-called prepolymer method is employed in which the end-capping agent is reacted.
According to the so-called one-shot method, urea aggregates are formed by the reaction of organic polyisocyanate and an amine compound (hydroxyl group-containing diamine / hydroxyl group-containing monoamine), which is not preferable.

An example of a method for preparing a solution of a polyfunctional urethane / urea resin is as follows. First, an organic diisocyanate is added to a solution of a polymer polyol using a solvent having no active hydrogen (eg, ketone, ester, aromatic hydrocarbon, etc.). The isocyanate group-terminated urethane prepolymer is synthesized by reacting at 30 to 100 ° C. for several hours in the presence of a urethanization catalyst.
At this time, the use ratio of the organic diisocyanate and the polymer polyol is preferably such that the NCO group / OH group molar ratio is 1.1 to 2.5, particularly 1.5 to 2.0. If the NCO group / OH group molar ratio is less than 1.1, the resulting primer composition coating film may not have sufficient solvent resistance. On the other hand, when the molar ratio of NCO group / OH group exceeds 2.5, the solubility of the resulting resin may be reduced, or the coating film obtained from the resulting primer composition may not have sufficient adhesiveness. .
Next, a hydroxyl group-containing diamine (chain extender) and a hydroxyl group-containing monoamine (end-capping agent) are added to the isocyanate group-terminated urethane prepolymer solution and reacted at 30 to 50 ° C. until the isocyanate group disappears.

Here, as a solvent used in the synthesis of the polyfunctional urethane / urea resin (final solvent constituting the solution of the polyfunctional urethane / urea resin), aromatic solvents such as toluene and xylene, ethyl acetate , Ester solvents such as butyl acetate, ketone solvents such as acetone and methyl ethyl ketone, alcohol solvents such as methanol, ethanol, and isopropanol. These may be used alone or in combination of two or more. it can.
In particular, it is preferable to use three kinds of mixed solvents of toluene and methyl ethyl ketone having good solubility in a polyol skeleton or urethane skeleton, and isopropanol having good solubility in a urea group.

The resin concentration (solid content) in the solution of the polyfunctional urethane / urea resin obtained as described above is preferably 10 to 60% by mass, more preferably 15 to 55% by mass.
The primer composition of the present invention can be prepared by further diluting the polyfunctional urethane / urea resin solution with a solvent as necessary.

Here, the concentration of the polyfunctional urethane / urea resin in the primer composition of the present invention is preferably 5 to 15% by mass.
When the concentration of the polyfunctional urethane / urea resin is too low, it is necessary to increase the coating amount, paint sagging occurs, and a uniform coating film (primer layer) cannot be formed. On the other hand, when this concentration is too high, the spray coating property is impaired, the smoothness of the primer layer to be formed is lowered, and the solvent resistance may vary.

<Organic solvent (B)>
The organic solvent (B) constituting the primer composition of the present invention is usually a solvent used when synthesizing a polyfunctional urethane / urea resin (a solvent constituting a solution of the polyfunctional urethane / urea resin), and It consists of the solvent used to dilute the solution of the polyfunctional urethane / urea resin.

A preferable organic solvent (B) constituting the primer composition of the present invention comprises an organic solvent (B1) having a boiling point of less than 130 ° C. and an aliphatic solvent (B2) having a boiling point of 130 to 180 ° C. In which (B1) :( B2) = 95 to 50: 5 to 50 (mass ratio) is not included.

Examples of the organic solvent (B1) having a boiling point of less than 130 ° C. include aromatic solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, ketone solvents such as acetone and methyl ethyl ketone, methanol, ethanol, and isopropanol. The alcohol solvent can be mentioned.
As a suitable organic solvent (B1), a mixed solvent of toluene, methyl ethyl ketone and isopropanol can be exemplified.

Examples of the aliphatic solvent (B2) having a boiling point of 130 to 180 ° C. include propylene glycol monomethyl ether acetate (boiling point: 146 ° C.), cyclohexanone (boiling point: 156 ° C.) and diacetone alcohol (boiling point: 168 ° C.). Can do.

According to the primer composition composed of the organic solvent (B) containing the aliphatic solvent (B2) at a ratio of 5% by mass or more, when this is spray coated, the organic solvent in the coating film is rapidly evaporated. As a result, the coating film is smoothed in the presence of the organic solvent, and a coating film (primer layer) having excellent leveling properties can be formed. And, since the coating film excellent in leveling property formed by such a primer composition has no or very few voids due to air entrained during spray coating, It is possible to avoid such a problem that the solvent or moisture penetrates into the gap from the outside and the adhesiveness to the adherend is lowered. In addition, the coating film having high leveling properties does not have large unevenness that causes floating or peeling due to stress concentration when the constituent resin such as the primer layer swells. As a result, the primer layer formed of such a primer composition has further improved solvent resistance and excellent moisture and heat resistance compared to a primer layer made of a primer composition not containing an aliphatic solvent (B2). It will be.

Moreover, according to the primer composition containing the organic solvent (B) which does not contain the organic solvent in which the ratio of the aliphatic solvent (B2) is 50% by mass or less and the boiling point exceeds 180 ° C., the coating film is dried ( Removal of the organic solvent) can be performed efficiently.

When an aromatic solvent having a boiling point of 130 to 180 ° C. is used in place of the aliphatic solvent (B2), the polyfunctional urethane / urea resin may be aggregated depending on the solvent used in combination. .

The primer composition of the present invention may contain various optional components as long as the effects of the present invention are not impaired.
Such optional components include resins other than polyfunctional urethane / urea resins, curing agent components such as blocked isocyanates, pigments (organic pigments, inorganic pigments), antioxidants, ultraviolet absorbers, fillers, plasticizers, antistatic agents. And usual additives for paints such as dispersants and catalysts.

The primer composition of the present invention can be used as a one-component curable composition containing no curing agent component (isocyanate group-containing compound).
In this case, at least one of the resin compositions to be overcoated on the coating film by the primer composition of the present invention needs to contain a curing agent component (isocyanate group-containing compound). In the coating film by the one-component curable primer composition, the hydroxyl group of the polyfunctional urethane / urea resin constituting this reacts with the isocyanate group of the curing agent component of the resin composition coated on the coating film. By doing so, a crosslinked structure (urethane bond) is introduced into the coating film.

The primer composition of the present invention can also be used as a two-component curable composition containing a curing agent component (isocyanate group-containing compound).

The primer composition of the present invention can be suitably used for plastic molded articles typified by (exterior) parts of automobiles, and is sufficient for adherends made of nylon that are difficult to adhere. Adhesive strength can be expressed.

The primer composition of the present invention is applied to an adherend by a method such as spraying, brushing or dipping.
The coating film of the primer composition of the present invention is dried to remove the solvent. The coating film is dried at 10 to 50 ° C. for 1 to 30 minutes, for example.
The coating film by the primer composition of this invention is normally heat-processed, and is hardened | cured by this. The heating condition is, for example, 60 to 100 ° C. and 10 to 60 minutes. The heat treatment may be performed after the coating film is dried, or may be performed after the resin composition is overcoated on the coating film to form an upper layer (for example, a base layer and a top layer). However, when the primer composition does not contain a curing agent component (isocyanate group-containing compound), it is carried out after the upper layer is formed by laminating with the resin composition containing the curing agent component.

The resin composition overcoated on the coating film by the primer composition of the present invention is not particularly limited, and may be a thermoplastic resin or a thermosetting resin (one-component curable type or two-component curable type). Specifically, common paints such as acrylic acid, alkyd, urethane, epoxy, melamine alkyd, and acrylic urethane can be exemplified.

Forming a coating film (primer layer) and an upper layer (for example, a base layer and a top layer) by the primer composition of the present invention (after heat-treating the primer layer) to ensure necessary adhesive strength and sufficient solvent resistance In addition, curing for a certain time is performed. Here, a preferable curing environment is a temperature of 10 to 30 ° C. and a relative humidity of 50 to 70%.

When a conventionally known primer composition (for example, the primer composition described in Patent Document 1) is used, a curing time exceeding 120 hours is required.
On the other hand, by using the primer composition of the present invention, a coating film (primer layer) excellent in solvent resistance can be formed even if the curing time is within 12 hours.
This is presumably because the curing reaction by the hydroxyl groups and isocyanate groups in the primer layer is completed in a short time, and a high-density crosslinked structure is introduced in the primer layer.

Examples of the present invention will be described below, but the present invention is not limited to these examples.

<Example 1>
(1) Preparation of isocyanate group-terminated urethane prepolymer solution:
A polyester diol having a number average molecular weight of 2047 obtained by reacting ethylene glycol, 1,4-butanediol and adipic acid in a reaction apparatus having a capacity of 2000 mL equipped with a stirrer, a thermometer, an Allen cooling pipe and a nitrogen gas introduction pipe [ Hereinafter, 419 g of “polyester (1)”] and 217 g of toluene were charged and stirred uniformly at 45 ° C. to prepare a polymer polyol solution.
This polymer polyol solution was charged with 91 g of isophorone diisocyanate (IPDI) and 0.05 g of dioctyltin dilaurate (DOTDL) and reacted at 75 ° C. for 3 hours under a nitrogen stream, whereby an isocyanate group-terminated urethane prepolymer solution was obtained. Obtained. The prepolymer had an NCO content of 2.30%.

(2) Preparation of polyfunctional urethane / urea resin solution:
To this prepolymer solution, 152 g of toluene and 491 g of methyl ethyl ketone (MEK) were added and stirred uniformly, then the liquid temperature was cooled to 30 ° C., 369 g of isopropanol (IPA), and 16.9 g of isophoronediamine (IPDA). Then, an amine solution prepared by previously mixing 6.8 g of β-aminoethylethanolamine (A-EA), which is a hydroxyl group-containing diamine, and 7.0 g of diethanolamine (DEA), which is a hydroxyl group-containing monoamine, is added at 40 ° C. A polyfunctional urethane / urea resin was synthesized by a chain extension reaction for 4 hours to prepare a resin solution. The resin concentration (solid content) of this resin solution was 30%, and the viscosity (25 ° C.) was 90 mPa · s.
The number average molecular weight (Mn) of the obtained polyfunctional urethane / urea resin was measured by GPC (gel permeation chromatography) to be 15,000. Here, the measurement conditions are as follows.

-Measuring instrument: "HLC-8120" (manufactured by Tosoh Corporation)
Column: “Styragel HR2 DMF” (manufactured by Nippon Waters Co., Ltd.)
Particle size = 5 μm, size = 7.8 mm ID × 30 cm × 4, carrier: N, N-dimethylformamide (DMF) containing 0.1% LiBr
-Detector: Parallax refraction-Sample: 0.1% LiBr / DMF solution-Calibration curve: Polyethylene glycol

The hydroxyl group content (c) of this polyfunctional urethane / urea resin was measured by a method according to JIS K1557 and found to be 0.375 mmol / g.
Thereby, the functional group number (f) of this polyfunctional urethane-urea resin is 5.6.

(3) Preparation of primer composition:
100 parts by mass of the polyfunctional urethane / urea resin solution obtained in (2) above, 30 parts by mass of propylene glycol monomethyl ether acetate (PMA), 128 parts by mass of toluene, and 128 parts by mass of isobutanol were mixed with stirring. By mixing uniformly, the primer composition of the present invention having a resin concentration of 7.8% by mass was prepared.

<Example 2>
To the isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 1 (1), 147 g of toluene and 485 g of MEK were added and stirred uniformly, and 364 g of IPA and 16.9 g of β-aminoethylethanolamine were added. A polyfunctional urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution prepared by mixing 7.0 g of diethanolamine in advance was added to prepare a resin solution. did. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 90 mPa · s.
The resulting polyfunctional urethane / urea resin has a number average molecular weight (Mn) of 15,000 and a hydroxyl group content (c) of 0.567 mmol / g. Thus, the number of functional groups of the polyfunctional urethane / urea resin ( f) was 8.5.
Next, a primer composition of the present invention having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained polyfunctional urethane / urea resin solution was used.

<Example 3>
To the isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 1 (1), 146 g of toluene and 484 g of MEK were added and stirred uniformly, and 363 g of IPA, 17.8 g of β-aminoethylethanolamine and A polyfunctional urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution prepared by mixing 5.2 g of diethanolamine in advance was added to prepare a resin solution. did. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 350 mPa · s.
The resulting polyfunctional urethane / urea resin has a number average molecular weight (Mn) of 20,000 and a hydroxyl group content (c) of 0.519 mmol / g. f) is 10.4.
Next, a primer composition of the present invention having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained polyfunctional urethane / urea resin solution was used.

<Example 4>
To an isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 1 (1), 146 g of toluene and 484 g of MEK were added and stirred uniformly, and 363 g of IPA, 18.3 g of β-aminoethylethanolamine and A polyfunctional urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution prepared by premixing 4.2 g of diethanolamine was added to prepare a resin solution. did. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 350 mPa · s.
The obtained polyfunctional urethane / urea resin has a number average molecular weight (Mn) of 25,000 and a hydroxyl group content (c) of 0.490 mmol / g. f) is 12.3.
Next, a primer composition of the present invention having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained polyfunctional urethane / urea resin solution was used.

<Example 5>
To the isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 1 (1), 146 g of toluene and 483 g of MEK were added and stirred uniformly, and 363 g of IPA, 18.6 g of β-aminoethylethanolamine and A polyfunctional urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution obtained by mixing 3.5 g of diethanolamine in advance was added to prepare a resin solution. did. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 400 mPa · s.
The resulting polyfunctional urethane / urea resin has a number average molecular weight (Mn) of 30,000 and a hydroxyl group content (c) of 0.471 mmol / g. Thus, the number of functional groups of the polyfunctional urethane / urea resin ( f) is 14.1.
Next, a primer composition of the present invention having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained polyfunctional urethane / urea resin solution was used.

<Example 6>
To the isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 1 (1), 145 g of toluene and 483 g of MEK were added and stirred uniformly, and 362 g of IPA and 18.9 g of β-aminoethylethanolamine were obtained. A polyfunctional urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution prepared by mixing 3.0 g of diethanolamine in advance was added to prepare a resin solution. did. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 800 mPa · s.
The obtained polyfunctional urethane / urea resin has a number average molecular weight (Mn) of 37,000 and a hydroxyl group content (c) of 0.458 mmol / g. f) is 16.9.
Next, a primer composition of the present invention having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained polyfunctional urethane / urea resin solution was used.

<Example 7>
To an isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 1 (1), 145 g of toluene and 483 g of MEK were added and stirred uniformly, and 362 g of IPA and 19.0 g of β-aminoethylethanolamine were obtained. A polyfunctional urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution obtained by mixing 2.6 g of diethanolamine in advance was added to prepare a resin solution. did. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 1,200 mPa · s.
The obtained polyfunctional urethane / urea resin has a number average molecular weight (Mn) of 41,000 and a hydroxyl group content (c) of 0.447 mmol / g. f) is 18.3.
Next, a primer composition of the present invention having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained polyfunctional urethane / urea resin solution was used.

<Example 8>
Instead of the polyester diol (1), a polyester diol having a number average molecular weight of 2045 obtained by reacting 3-methyl-1,5-pentanediol (low molecular polyol having a side chain) with adipic acid [hereinafter referred to as “polyester” (Referred to as “(2)”) An isocyanate group-terminated urethane prepolymer solution was obtained in the same manner as in Example 1 (1) except that 419 g was used. The prepolymer had an NCO content of 2.30%.
To the isocyanate group-terminated urethane prepolymer solution thus obtained, 146 g of toluene and 484 g of MEK were added and stirred uniformly, and 363 g of IPA, 17.8 g of β-aminoethylethanolamine, 5.2 g of diethanolamine, A polyfunctional urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution prepared by mixing the above was added to prepare a resin solution. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 350 mPa · s.
The resulting polyfunctional urethane / urea resin has a number average molecular weight (Mn) of 20,000 and a hydroxyl group content (c) of 0.519 mol / g. f) is 10.4.
Next, a primer composition of the present invention having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained polyfunctional urethane / urea resin solution was used.

<Comparative Example 1>
To the isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 1 (1), 153 g of toluene and 494 g of MEK were added and stirred uniformly to obtain 373 g of IPA, 28.2 g of IPDA, 4.8 g of diethylamine, A urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution prepared by previously mixing was added to prepare a resin solution. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 90 mPa · s.
The number average molecular weight (Mn) of the obtained urethane / urea resin is 15,000, and the hydroxyl group content (c) is 0 mmol / g, whereby the number of functional groups (f) of this urethane / urea resin is 0. .
Next, a comparative primer composition having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained urethane / urea resin solution was used.

<Comparative example 2>
To an isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 1 (1), 153 g of toluene and 493 g of MEK were added and stirred uniformly to obtain 370 g of IPA, 28.2 g of IPDA, and monoethanolamine. A urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution mixed with 0 g in advance was added to prepare a resin solution. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 90 mPa · s.
The resulting urethane / urea resin has a number average molecular weight (Mn) of 15,000 and a hydroxyl group content (c) of 0.122 mmol / g, whereby the number of functional groups (f) of this urethane / urea resin is 1 .8.
Next, a comparative primer composition having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained urethane / urea resin solution was used.

<Comparative Example 3>
To the isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 1 (1), 155 g of toluene and 496 g of MEK were added and stirred uniformly, and IPA 372 g, IPDA 28.2 g, diethanolamine 7.0 g, A urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution prepared by previously mixing was added to prepare a resin solution. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 90 mPa · s.
The resulting urethane / urea resin has a number average molecular weight (Mn) of 15,000 and a hydroxyl group content (c) of 0.251 mmol / g, whereby the number of functional groups (f) of this urethane / urea resin is 3 .8.
Next, a comparative primer composition having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained urethane / urea resin solution was used.

<Comparative example 4>
To an isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 1 (1), 145 g of toluene and 483 g of MEK were added and stirred uniformly, and 362 g of IPA, 19.3 g of β-aminoethylethanolamine and A polyfunctional urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 1 (2) except that an amine solution prepared by mixing 2.1 g of diethanolamine in advance was added to prepare a resin solution. did. This resin solution had a solid content of 30% and a viscosity (25 ° C.) of 2,500 mPa · s.
The obtained polyfunctional urethane / urea resin has a number average molecular weight (Mn) of 53,000 and a hydroxyl group content (c) of 0.433 mmol / g. f) is 22.9.
Next, a comparative primer composition having a resin concentration of 7.8% by mass was prepared in the same manner as in Example 1 (3) except that the obtained polyfunctional urethane / urea resin solution was used.

Formulations for Examples 1 to 8 and Comparative Examples 1 to 4 (unit is “g”), solid content of resin solution (resin concentration), viscosity of resin solution, number average molecular weight of urethane / urea resin, The hydroxyl group content, the number of functional groups, and the resin concentration in the primer composition are summarized in Table 1 below.

(1) Adhesiveness (normal adhesion):
Each of the primer compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 4 was used, and the adhesion (normal adhesion) was evaluated as follows.
Here, the resin composition for forming a base layer to be overcoated on the coating film of the primer composition is composed of 100 parts by mass of acrylic resin “Acridic A-801-P” (manufactured by DIC Corporation), 20 parts by mass of titanium oxide, It was prepared by adding 230 parts by mass of toluene and kneading in a disperser for 10 minutes.
The resin composition for forming the top layer was prepared by adding 100 parts by mass of an acrylic resin “Acridic A-801-P” (manufactured by DIC Corporation) to a polyisocyanate curing agent “Coronate HX” (manufactured by Nippon Polyurethane Industry Co., Ltd.). ) 18 parts by mass (NCO / OH = 1) and 110 parts by mass of toluene were added, and the mixture was uniformly stirred at room temperature.

The surface of the adherend composed of 6-nylon “nylon 1022B” (manufactured by Ube Industries) was thoroughly degreased with methanol and dried at room temperature.
The primer composition was applied to the surface of the adherend by air spraying and dried at room temperature (25 ° C.) for 10 minutes to form a dry coating film having a thickness of 8 μm.
Next, the base layer-forming resin composition was applied by air spray on the dried coating film (primer layer) of the primer composition, and dried at room temperature for 10 minutes to form a dry coating film having a thickness of 10 μm.
Next, a top layer-forming resin composition is applied by air spray onto a dry coating film (base layer) made of a base layer-forming resin composition, and dried at room temperature for 10 minutes to dry a coating film (30 μm thick) ( The top layer was laminated.
Next, heat treatment was performed in a dryer at 80 ° C. for 30 minutes, followed by curing for 48 hours in an environment at a temperature of 20 ° C. and a relative humidity of 65%.
With respect to each of the test pieces thus obtained (adhered body in which the primer layer, the base layer, and the top layer are laminated), a 1 mm square grid (10 × 10) cut is formed on the coating surface. After forming, a peel test with a tape was performed to measure the number of remaining sheets.
Three test pieces were prepared for each of Examples 1 to 8 and Comparative Examples 1 to 4, and the average value of the remaining number of the three test pieces was obtained. The results are shown in Table 2 below.

(2) Required curing time:
Using each of the primer compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 4, the curing time until the solvent resistance was developed was measured as follows.
Here, the structure of the adherend, the resin composition for forming the base layer and the resin composition for forming the top layer, the primer composition, the resin composition for forming the base layer and the coating method for the resin composition for forming the top layer, and the drying conditions The heat treatment conditions and the curing environment are the same as in (1) Evaluation of adhesiveness.

In the same manner as in the above (1) adhesive evaluation, the primer composition is applied and dried, the base layer forming resin composition is applied and dried, and the top layer forming resin composition is applied and dried. After the test, test pieces having different curing times (adhered bodies in which a primer layer, a base layer, and a top layer were laminated) were produced.
In addition, three test pieces for each of Examples 1 to 8 and Comparative Examples 1 to 4 for each curing time (3 hours, 6 hours, 12 hours, 24 hours, 48 hours, 72 hours, 120 hours). (Example: 8 × 7 × 3 = 168, Comparative example: 4 × 7 × 3 = 84).

First, for each of Examples 1 to 8 and Comparative Examples 1 to 4, each of test pieces (12 × 3 = 36 pieces) obtained by curing for 3 hours was mixed with a mixed solvent of gasoline: ethanol = 9: 1 ( 20 ° C.), the time (immersion time) until the coating float (peeling) from the edge of the test piece reaches 2 mm or more inside from the edge is measured, and the solvent resistance is based on the following evaluation criteria. Sex was evaluated.

(Evaluation criteria)
・ 30 minutes or more: Pass (Evaluation: ◎)
・ 20 minutes to less than 30 minutes: Pass (Evaluation: ○)
-Less than 20 minutes: Fail (Evaluation: x)

Next, for each of Examples 1 to 8 and Comparative Examples 1 to 4, the solvent resistance of each of the test pieces (12 × 3 = 36) obtained by curing for 6 hours was evaluated in the same manner as described above. . As a result, in Examples 2 to 8, all three test pieces passed (evaluation: ：) (sufficient solvent resistance was exhibited after a curing time of 6 hours), so Examples 2 to 8 The test about was finished.

Next, for each of Example 1 and Comparative Examples 1 to 4, the solvent resistance of each of the test pieces (5 × 3 = 15 pieces) obtained by curing for 12 hours was evaluated in the same manner as described above. As a result, in Example 1, since all the three test pieces passed (evaluation:）), the test for Example 1 was completed.

Next, for each of Comparative Examples 1 to 4, the solvent resistance of each test piece obtained by curing for 24 hours or longer was evaluated in the same manner as described above.
The above results are shown in Table 2 below.

As shown in Table 2 above, according to the primer compositions according to Examples 1 to 8, in particular, according to the primer compositions according to Examples 1 to 6, the adherend made of nylon considered to be hardly adhesive is used. A primer layer that exhibits sufficient adhesiveness can be formed.
In addition, according to the primer compositions according to Examples 1 to 8, particularly the primer compositions according to Examples 2 to 8, solvent resistance (corrosion resistance to a mixed solvent of gasoline and alcohol) even with a short curing time. It is possible to form a primer layer excellent in property.
On the other hand, the primer composition according to Comparative Example 1 in which the number of functional groups of the resin component is 0 cannot form a solvent-resistant primer layer even after 120 hours of curing.
Further, in the primer compositions according to Comparative Examples 2 to 3 in which the number of functional groups of the resin component is less than 5, a long curing time is required to form a solvent-resistant primer layer.
Moreover, in the primer composition which concerns on the comparative example 4 in which the functional group of a resin component exceeds 20, the adhesiveness with respect to a to-be-adhered body is inferior, and also the curing time required in order to express solvent resistance is recognized. .

<Example 9>
(1) Preparation of isocyanate group-terminated urethane prepolymer solution:
In accordance with the formulation shown in Table 3 below, a reactor with a capacity of 2000 mL equipped with a stirrer, a thermometer, an Allen cooling pipe, and a nitrogen gas introduction pipe was charged with 708.0 g of polyester (1) and 216.0 g of MEK which is an organic solvent (B1). And uniformly stirred at 45 ° C. to prepare a polymer polyol solution.
This polymer polyol solution was charged with 153.8 g of IPDI and 0.08 g of DOTDL, and reacted at 75 ° C. for 3 hours under a nitrogen stream to obtain an isocyanate group-terminated urethane prepolymer solution. The NCO content of this prepolymer was 2.70%.

(2) Preparation of polyfunctional urethane / urea resin solution:
In accordance with the prescription shown in Table 3 below, 356.0 g of MEK was added to this prepolymer solution and stirred uniformly, then the liquid temperature was cooled to 30 ° C., and 28.5 g of IPDA and A-EA (hydroxyl group-containing diamine) 11 0.5 g, DEA (hydroxyl group-containing monoamine) 11.9 g and MEK 342.0 g in advance are added to an amine solution, and a polyfunctional urethane / urea resin is obtained by chain extension reaction at 40 ° C. for 4 hours. A resin solution was prepared by synthesis. This resin solution had a solid content of 50% and a viscosity (25 ° C.) of 3,800 mPa · s.
When the number average molecular weight (Mn) of the obtained polyfunctional urethane / urea resin was measured by GPC, it was 15,000.

(3) Preparation of primer composition:
In accordance with the formulation shown in Table 3 below, 100.0 parts by mass of the polyfunctional urethane / urea resin solution obtained in (2) above, 30.0 parts by mass of PMA as the aliphatic solvent (B2), and an organic solvent (B1 ) And toluene / MEK / IPA = 3/4/3 (mass ratio) mixed solvent (513.0 parts by mass) is mixed by stirring and mixed uniformly, whereby the resin concentration is 7.8% by mass. Inventive primer compositions were prepared. The proportion of the aliphatic solvent (B2) in the organic solvent (B) constituting the primer composition is 5.1% by mass.

<Examples 10 to 18>
According to the formulation shown in Table 3 below, 356.0 g of MEK was added to the isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 9 (1) and stirred uniformly to obtain A-EA, DEA, and MEK. A polyfunctional urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 9 (2) except that each amine solution mixed in advance was added, and a resin solution having a solid content of 50% was prepared. did. For each of the obtained resin solutions, the viscosity (25 ° C.), the number average molecular weight (Mn) of the polyfunctional urethane / urea resin, the hydroxyl group content (c) and the number of functional groups (f) are shown in Table 3 below.
Next, according to the formulation shown in Table 3 below, 100.0 parts by mass of each of the obtained resin solutions, PMA or diacetone alcohol (DAA) as the aliphatic solvent (B2), and toluene / MEK / IPA The primer composition of the present invention having a resin concentration of 7.8% by mass was prepared by stirring and mixing the mixed solvent and mixing uniformly.
The ratio of the aliphatic solvent (B2) in the organic solvent (B) constituting each of the obtained primer compositions is also shown in Table 3 below.

<Example 19>
According to the formulation shown in Table 3 below, 356.0 g of MEK was added to the isocyanate group-terminated urethane prepolymer solution obtained in the same manner as in Example 9 (1) and stirred uniformly to obtain 32.1 g of A-EA and DEA4. A polyfunctional urethane / urea resin was synthesized by a chain extension reaction in the same manner as in Example 9 (2) except that an amine solution prepared by previously mixing 4 g and MEK 327.0 g was added, and a solid content of 50 % Resin solution was prepared. The viscosity (25 ° C.) of this resin solution was 23,000 mPa · s.
The obtained polyfunctional urethane / urea resin has a number average molecular weight (Mn) of 41,000 and a hydroxyl group content (c) of 0.447 mmol / g. f) is 18.3.
Next, according to the prescription shown in Table 3 below, 100.0 parts by mass of the obtained resin solution, 59.3 parts by mass of the aromatic hydrocarbon solvent “Solvesso 100” (manufactured by Exxon Chemical Co., Ltd.), toluene / MEK The primer composition of the present invention having a resin concentration of 7.8% by mass was prepared by stirring and mixing uniformly with 483.7 parts by mass of / IPA mixed solvent.

<Example 20>
According to the formulation shown in Table 3 below, an isocyanate group-terminated urethane prepolymer solution was obtained and obtained in the same manner as in Example 9 (1) except that 708.0 g of polyester (2) was used instead of polyester (1). Except that MEK 356.0 g was added to the isocyanate group-terminated urethane prepolymer solution and stirred uniformly, and an amine solution prepared by previously mixing 30.1 g of A-EA, 8.8 g of DEA, and 329.0 g of MEK was added. In the same manner as in Example 9 (2), a chain extension reaction was performed to synthesize a polyfunctional urethane / urea resin to prepare a resin solution having a solid content of 50%. The viscosity (25 ° C.) of this resin solution was 3,900 mPa · s.
The resulting polyfunctional urethane / urea resin has a number average molecular weight (Mn) of 20,000 and a hydroxyl group content (c) of 0.519 mmol / g. f) is 10.4.
Next, according to the formulation shown in Table 3 below, 100.0 parts by mass of the obtained resin solution, 59.3 parts by mass of N-methylpyrrolidone, and 483.7 parts by mass of a mixed solvent of toluene / MEK / IPA were stirred. By mixing and mixing uniformly, a primer composition of the present invention having a resin concentration of 7.8% by mass was prepared.

(* 1) IPDI: Isophorone diisocyanate (* 2) DOTDL: Dioctyltin dilaurate (* 3) IPDA: Isophorone diamine (* 4) A-EA: β-aminoethylethanolamine (hydroxyl group-containing diamine)
(* 5) DEA: Diethanolamine (hydroxyl group-containing monoamine)
(* 6) PMA: Propylene glycol monomethyl ether acetate (boiling point = 146 ° C)
(* 7) DAA: diacetone alcohol (boiling point = 168 ° C)
(* 8) Solvesso 100: Aromatic hydrocarbon solvent “Solvesso 100” (boiling point = 154 to 181 ° C., manufactured by Exxon Chemical Co., Ltd.)
(* 9) N-methylpyrrolidone: Boiling point = 202 ° C
(* 10) Mixed solvent: Mixed solvent of toluene / MEK / IPA = 3/4/3 (mass ratio)

The following items were evaluated for each of the primer compositions obtained in Examples 9 to 20. The evaluation results are shown in Table 4 below.

(1) Room temperature drying property of primer coating film:
The surface of the adherend composed of 6-nylon “nylon 1022B” (manufactured by Ube Industries) was thoroughly degreased with methanol and dried at room temperature.
The primer composition is applied to the surface of the adherend by air spray to form a coating film having a thickness of 7 μm. The coating film is dried at room temperature (25 ° C.), and the coating film surface is found to be tacky. The time until disappearance (tack free time) was measured.

(2) Glossiness of primer coating film:
The glossiness at 85 ° of the 7 μm-thick coating film formed on the surface of the adherend according to the above (1) was measured using a haze-gloss reflectometer according to JIS Z8741. The higher the glossiness, the better the leveling property of the coating film.

(3) Adhesion (normal adhesion):
The surface of the adherend composed of 6-nylon “nylon 1022B” (manufactured by Ube Industries) was thoroughly degreased with methanol and dried at room temperature.
On the surface of this adherend, the primer composition was applied by air spray and dried at room temperature (25 ° C.) for 10 minutes to form a coating film having a thickness of 7 μm.
Next, the base layer forming resin composition was applied by air spray on the coating film (primer layer) of the primer composition, and dried at room temperature for 10 minutes to form a dry coating film having a thickness of 10 μm.
Next, a top layer-forming resin composition is applied by air spray onto a dry coating film (base layer) made of a base layer-forming resin composition, and dried at room temperature for 10 minutes to dry a coating film (30 μm thick) ( The top layer was laminated.
Next, heat treatment was performed in a dryer at 80 ° C. for 30 minutes, followed by curing for 48 hours in an environment at a temperature of 20 ° C. and a relative humidity of 65%.
A test piece (adhered body in which a primer layer, a base layer, and a top layer are laminated) is formed on a coating film forming surface with a 1 mm square grid (10 × 10) cut. The remaining number of sheets was measured by performing a peel test using a tape.
Three test pieces were prepared for each of Examples 9 to 20, and the average value of the remaining number of the three test pieces was obtained.

(4) Solvent resistance:
A test piece (adhered body in which a primer layer, a base layer, and a top layer are laminated) prepared in the same manner as (3) above is immersed in a mixed solvent (20 ° C.) of gasoline: ethanol = 9: 1. The time (immersion time) until the float (peeling) of the coating film generated from the edge of the test piece reached 2 mm or more inside from the edge was measured.
In Examples (1), Examples 16, 18, and 20 where the tack-free time was 20 minutes or longer were evaluated using test pieces prepared by changing the drying time of the primer coating to 30 minutes. did.

(5) Moist heat resistance:
A test piece obtained in the same manner as in (3) above (an adherend on which a primer layer, a base layer, and a top layer were laminated) was left in an environment of a temperature of 50 ° C. and a relative humidity of 90% for 240 hours. Thereafter, a 1 mm square grid (10 × 10) cut was formed on the coating surface, and a tape peel test was performed to measure the number of remaining sheets.
In Examples (1), Examples 16, 18, and 20 where the tack-free time was 20 minutes or longer were evaluated using test pieces prepared by changing the drying time of the primer coating to 30 minutes. did.
Three test pieces were prepared for each of Examples 9 to 20, and the average value of the remaining number of the three test pieces was determined.

As shown in Table 4 above, according to the primer compositions according to Examples 9 to 20, it is possible to form a primer layer that exhibits sufficient adhesion to an adherend made of nylon.
Further, according to the primer compositions according to Examples 9 to 20, it is possible to form a primer layer having excellent solvent resistance.
According to the primer compositions according to Examples 9 to 14, 16, 18, and 20, a primer layer that can form a coating film with excellent leveling properties, is particularly excellent in solvent resistance, and is excellent in moisture and heat resistance. Can be formed.
Moreover, according to the primer compositions according to Examples 9 to 14, 15, 17, and 19, it is possible to form a primer coating film having excellent drying properties.

Claims

(A1) an organic polyisocyanate;
(A2) a polymer polyol having a number average molecular weight of 500 to 5,000,
(A3) a urethane-urea resin obtained by reacting with a chain extender comprising a hydroxyl group-containing diamine,
Having a hydroxyl group derived from the chain extender in the molecular side chain;
The number of functional groups is 5-20,
A primer composition comprising a polyfunctional urethane / urea resin (A) having a number average molecular weight of 10,000 to 50,000, and an organic solvent (B).
2. The primer composition according to claim 1, wherein the number of functional groups of the polyfunctional urethane / urea resin (A) is 8.5 to 18.5.
The primer composition according to claim 1 or 2, wherein the polymer polyol is an amorphous polyol.
The primer composition according to claim 3, wherein the amorphous polyol is obtained by reacting two or more kinds of low-molecular polyols having no side chain with a linear aliphatic polycarboxylic acid.
(A4) The primer composition according to claim 1, wherein a molecular terminal of the polyfunctional urethane / urea resin (A) is blocked with an end-capping agent comprising a hydroxyl group-containing monoamine.
The polyfunctional urethane / urea resin (A) reacts the organic polyisocyanate with the polymer polyol to produce an isocyanate group-terminated urethane prepolymer, and the obtained isocyanate group-terminated urethane prepolymer and the hydroxyl group-containing product The primer composition according to claim 5, wherein the primer composition is obtained by reacting diamine and the hydroxyl group-containing monoamine.
The concentration of the polyfunctional urethane / urea resin (A) is 5 to 15% by mass,
The organic solvent (B) is composed of an organic solvent (B1) having a boiling point of less than 130 ° C. and an aliphatic solvent (B2) having a boiling point of 130 to 180 ° C., and (B1) :( B2) = 95 to 50 The primer composition according to claim 1, wherein the primer composition is 5 to 50 (mass ratio).
The primer composition according to claim 1,
A one-component curable primer composition for forming a primer layer on which a resin composition having a polyisocyanate as a curing agent is overcoated.
The primer composition according to claim 1,
A two-component curable primer composition comprising polyisocyanate as a curing agent component.
The primer composition according to claim 1, which is applied to an adherend by spraying.