JPS61143470A - Polyurethane resin coating composition having excellent pigment dispersibility - Google Patents

Abstract

PURPOSE:To obtain the titled composition having excellent gloss, color tone and opacifying powder of the coating film, and suitable as a plastic coating material, etc., by using a polyurethane resin containing a specific amount of ether bond as a vehicle, and curing the vehicle with a polyisocyanate having a specific molecular weight. CONSTITUTION:The objective composition can be produced by curing (A) a polyurethane resin having a molecular weight of 5,000-100,000, having terminal hydroxyl group and containing 1-25wt% ether bond and produced by polymerizing (i) a long-chain polyol containing ether bond and having a molecular weight of >=500, (ii) a diisocyanate and (iii) a chain extender [the molar ratio of (the OH+active hydrogen of the polyol (the long-chain polyol+the chain extender)/ NCOis 0.8-12.0/1.0] with (B) a polyisocyanate containing >=2 isocyanate groups in a molecule and having a molecular weight of 500-5,000. Used for electrically conductive paint, adhesive, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a urethane resin composition with excellent pigment dispersibility.

In recent years, in place of conventional metals, wood, inorganic materials, etc., various plastic films and sheets, plastic molded products, and the combination of the features of each plastic are being used in all fields to achieve higher quality or suit special uses. Designed laminated films (laminates), laminates, matrix materials, etc. have been developed.

Inevitably, there are paints for the purpose of protecting and coloring the surfaces of these plastic materials, ink for printing on the surface, and in the case of laminated films, adhesives and binders sandwiched between these plastic materials and printing inks. It is hoped that the development of

Printing inks for plastic surfaces or plastics differ from those for metals because the base material has poor heat resistance and is a plastic that is more flexible than metals, so consideration must be given to coating film characteristics, curing conditions, etc. There is.

In other words, the baking process must be able to harden below the softening point of the base plastic, and since plastics are more flexible than metals and are more susceptible to thermal expansion (thermal deformation), the surface coating film must also have a flexible composition. In addition, a hard coating film cannot keep up with changes in the substrate and cannot absorb internal strain, resulting in decreased adhesion.Polyurethane, which can be cured and baked at room to medium temperatures and has excellent flexibility, Resin-based resins are attracting attention as binders for plastic coatings and printing inks.

Conventional urethane paints are mainly combinations of polyfunctional polyols and polyisocyanates with molecular weights of several hundred to several thousand, hydroxyl-containing acrylic polyols and polyfunctional polyisocyanates with molecular weights of several thousand to several hundred, etc. is the gloss of the urethane paint film applied to the plastic surface,
As a result of evaluating and studying the pigment dispersion ability of the vehicle and the pigment dispersion properties such as color tone, hiding power, etc., we found that there is a close relationship between the pigment dispersion ability of the vehicle and the coating/removal gloss, color tone, hiding power, and dispersion time. There is a relationship between pigment dispersibility and the pigment dispersibility is greatly influenced by the vehicle structure. In urethane vehicles, a certain amount of ether bonds (R-0-R' but R
, R' is a hydrocarbon residue), it was discovered that the pigment dispersibility (dispersibility) was significantly increased, leading to the present invention.

That is, a predetermined amount of ether bonds (R-0-R'
However, paints or printing inks using polyurethane resin vehicles containing R and R' (hydrocarbon residues) require less time for pigment dispersion, have excellent gloss, color tone, and hiding power, and have excellent adhesion to plastics. The present invention was based on the discovery that this material also has excellent properties.

That is, the present invention provides a coating composition in which a pigment is dispersed, wherein the vehicle composition is (A) a long-chain polyol containing an ether bond and having a molecular weight of 500 or more, 0 diisocyanate,
and the molecular weight obtained by polymerizing the 0 chain extender, s, o o o
At least 100,000 and having a terminal hydroxyl group, weight%
Polyushituff 1M resin containing 1 to 25% of ether bonds in the resin has a molecular weight of 500 to 5.5% and contains isocyanate groups of 2 m or more in the molecule. This relates to a coating composition characterized by being cured with a polyisocyanate of It is obtained by addition polymerization using a polyester polyol made from Glyfur and a dibasic acid, or an active hydrogen compound such as ethylene oxide (hereinafter abbreviated as EO), propylene oxide (hereinafter abbreviated as PO), or tetramethylene oxide as an initiator. General polyethylene glycol (hereinafter PEG, !: abbreviated t)
, polypropylene ether glycol (hereinafter abbreviated as PPG), polytetramethylene ether glycol (hereinafter referred to as P
This refers to ether polyols (abbreviated as TMG) and copolymers or modified products of the above. More specifically, modified polyethers such as diethylene glycol, triethylene glycol, and EO or PO adducts of spiroglycol A (or hydrogenated bisphenol A) are used as glycols containing ether bonds to introduce ether bonds into polyester polyols. Polyionyl is mentioned.

Dicarboxylic acids that participate in esterification with glycol include:
Examples include aliphatic dicarboxylic acids such as succinic acid, adipic acid, heptanosic acid, and azelaic acid, and aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid.

Polyether polyols are included in this invention because they contain ether bonds (-0-) in repeating units, but
In particular, it is preferable to use a polyester polyol obtained from a dicarboxylic acid and a glycol as the long-chain polyol in terms of the balance between durability and dispersibility. These long-chain polyols may be used alone or mixed with other polyols in various ratios depending on the desired properties.

The diisocyanate referred to in the present invention includes tetra'thi'
Aliphatic diisocyanates such as cyyyyate, 1"1,000" diisocyanate, m-fuynylene diisocyanate 7
p-phenylene diisocyanate, 2.4
-) lylene diisocyanate, 216-lylene diisocyanate, diphenylmethane diisocyanate), 3
．． 3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 4,4'-diisocyanate diphenyl ether 1,5-naphthalene diisocyanate,
Aromatic diisocyanates such as 2.4-naphthalene diisocyanate, alicyclic diisocyanates such as 1.3-diisocyanatemethylcyclohexane, 1.4-diisocyanatemethylcyclohexane, 4.4'-diisocyanate dicyclysilmethane, inphone diisocyanate, etc. can be mentioned.

The chain extender referred to in the present invention refers to an active hydrogen group that reacts with an isocyanate group (for example, -O
H, -NH! , /NH). Examples of glycols include ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexane glycol, and neopentyl. Glycol (hereinafter abbreviated as NPG), 1,4-bis(β-hydrosheddopal)benzene, xylene glycol, diethylene glycol (hereinafter abbreviated as DEC),
Examples include triethylene glycol, spiroglycol, EO or PO adducts of bisphenol A, and examples of diamines include aliphatic diamines such as tetramethylene diamine and hexamethylene diamine, ln-phenylene diamine, p-phenylene diamine, 2 .4-) Lylene diamine, 2,6-dolylene diamine, m-xylylene diamine, p-xylylene diamine, diphenylmethane diamine, 3,3'-dimethoxy-4,4'-biphenylene diamine, 3,31-dimethyl- 4,4'-biphenylene diamine, 4,4-di7minodiphenyl ether,
1,5-naphthalenecyamine, 2,4-su7talendi7
Aromatic diamines such as 1,3-diaminomethylcyclohexane, 1,4-diaminomethylcyclohexane,
Examples of the amino alcohols include monoethanolamine, monoisobutanolamine, N-
Examples include methyljetanolamine.

When producing polyurethane resin, it is necessary to adjust the molar ratio of the long-chain polyols, diisocyanates, and chain extenders listed above so that they are substantially hydroxyl-terminated, and to achieve the desired physical properties. The OH/active hydrogen/NCO molar ratio of the polyol (long-chain polyol + chain extender) and diisocyanate is set to 0.0%, taking into account impurities in the raw materials. 8-1. 2 0 / 1. 0 0, preferably 0. 9 0 ~ 1. 0 0 /1,00 is desirable. If the content is outside these ranges, the excellent properties aimed at by the present invention cannot be exhibited, which is not preferable. Furthermore, in producing polyurethane resin, conventionally known methods can be used, such as mixing in a molten state in the presence of a catalyst if desired, pouring it onto a flat plate, heating it, cooling it and then crushing it, or reacting it. The mixture is injected into an extruder and reacted in a single or mixed organic solvent such as dimethylacetamide, toluene, xylene, dioxane, cyclohexanone, methyl ethyl ketone, ethyl acetate, butyl acetate, methyl imbutyl ketone, cellosolve acetate, etc. Conventional manufacturing methods such as solution reaction can be used, and catalysts, various additives, and stabilizers that are usually added to polyurethane resins can be used.

1 to 25% ether bond by weight in polyurethane resin
The inclusion of the ether bond is an essential condition of the present invention, and the ether bond has hydrophilicity, as can be seen from the properties of polyethylene glyfur, which has a structure of HO+CH, CH, and 0% H. Silica, talc, red iron oxide, iron oxide (magnetic iron oxide)
These pigments have adsorbed water, bound water, etc. on their surfaces and are hydrophilic, so resins containing hydrophilic groups in these pigments can be adsorbed through their parent wood groups (ether bonds in the case of the present invention). It is thought that the pigment is wrapped in a resin layer with the ether bond of the tree IJk on the pigment side and the lipophilic chain on the outside, and the pigment particles are dispersed into individual primary particles.

If the ether bond concentration is too low, the adsorption effect will be small and dispersibility will not improve.On the other hand, if there are too many ether bonds, the resin itself will become too hydrophilic and the ether bond concentration will be higher than necessary for adsorption to the pigment, resulting in poor affinity between resins. It exhibits a strong titanium a) fluidity and is not suitable as a paint, and is highly hydrophilic, so it easily attracts moisture into the system, resulting in poor water resistance and moist heat resistance of the coating film.

Urethane 1 due to its balance of pigment dispersibility and paint/coating film properties
8 Tanaka may contain 1% to 25% by weight, preferably 5% to 20% of ether bonds.

In addition, if the molecular weight of the polyurethane resin is less than 5,000, the mechanical properties will be weak and it will not have sufficient durability.
, ooo or more, the durability is excellent, but the viscosity of the paint increases and there are operational problems, and the molecular weight is too large and the pigment dispersibility decreases even if an ether bond is introduced.
The molecular weight must be limited to s,ooo or more and less than ioo,ooo.

In the method of the present invention, the above-mentioned polyurethane resin is finally cured with a suitable curing agent.
Molecular weight 500-5 containing isocyanate groups or more
．． 000 polyisocyanates, such as Corneto L
1 flone) - HL, coronet) - EH% prone) -
N, Desmodule R1 (both manufactured by Nippon Polyurethane Industries), and Desmodule RF (manufactured by Bayer). Although the ratio of polyurethane resin to polyisocyanate is not particularly limited, it is preferable to add 3 to 30 parts of polyisocyanate to 100 parts of polyurethane resin and cure the urethane resin after curing under normal curing conditions. It can greatly improve the mechanical strength, heat resistance, hot water resistance, and solvent resistance of.

In addition, if necessary in the present invention, thermoplastic polyurethane resin, vinyl chloride, etc., which are normally used as a paint vehicle,
By using vinyl acetate copolymers, cellulose resins, polyvinyl butyral resins, polyester resins, xylene resins, acrylic polyols, etc., the curing speed can be increased.
There is no problem in adjusting the hardness, etc.

Since the polyurethane resin of the present invention has excellent properties such as excellent pigment dispersibility, adhesion to plastics, and flexibility, it can be used for various purposes other than vehicles for plastic paints. Examples of its uses include conductive paints such as paints for electromagnetic shielding, ink binders, binders for magnetic recording media, adhesives, anchor coating agents, and the like.

A paint or ink composition containing the pigment of the present invention dispersed therein is produced by dispersing the pigment in the urethane resin by a method known in the art. The variance is usually
It is carried out to the desired extent using a ball mill, sand mill, continuous disperser, etc. At this time, a wetting agent, surfactant or antifoaming agent may be added if necessary in the present invention.

Pigments used in the practice of this invention include, for general purposes, pigments well known in the art such as titanium dioxide, zinc oxide, basic lead carbonate, barium carbonate, calcium carbonate, magnesium silica, cadmium yellow,
Cadmium red, toluidine red, iron oxide, etc. are used, but when the purpose is for conductive paint compositions, silver powder, aluminum powder, copper powder is used, and when the purpose is for magnetic recording media, iron oxide, etc.
Magnetic powder such as CO-containing iron oxide or Fe-C0-Ni alloy is used.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited only by these Examples. "%" in Examples and Comparative Examples indicates weight %.

Preparation Examples of ether bond-containing polyurethane resins, 1-
8. Comparative Example, 1.2. 5I equipped with a thermometer, stirrer, and cooling tower! A polyol solution was prepared by adding diethylene adipate (diethylene adipate) 1000 (hereinafter abbreviated as DEA-1000) 1000r, ethylene glycol (hereinafter abbreviated as E and G) 312, and ethyl acetate 1300F as a solvent.
DI258F and 0.2 f of dibutyltin dilaurate were added as a reaction catalyst to proceed with the urethanization reaction at 75°C. When the viscosity reached approximately 500.000 CP/25°C, toluene/ethyl acetate = □ (weight ratio) 1100 F was added to obtain a polyurethane resin (Example 1) with a solid content of 35%. The viscosity of this product was 8500. It showed cP/25°C.

This resin contains 6.4% ether groups and has a molecular weight MN=3.
．． It is an OH-terminated polyurethane resin with a Mw of 50,000" and a Mw of 65,000". Furthermore, the resins of Example 2 and following were prepared in the same manner as in Example 1 by changing the type of polyol, and the raw material formulations and physical property data of the resulting resins are shown in Table 1.

However, Examples 6 to 8 and Comparative Example 2 used a prepolymer method in which a polyol and a diisocyanate were first reacted to form a prepolymer, and then a diamine was extended at room temperature.

Ether bound gold content: 8.2% by gel permeation chromatography.

Notes to Table 1 1) Polyester polyol with molecule jilo00 obtained from diethylene glycol = 1,4-butylene glycol = 5:5 (mole ratio) glycol component and adipic acid 2) Polypropylene ether glycol molecular weight 3) DE
Polyester polyol with a molecular weight of 1000 obtained using a glycol component of G:BG = 5:5 (mole ratio) and an acid component of a 7-dipic acid: isophthalic acid = 5:5 molar ratio 4) Polybutylene 7-dipate molecular weight ioo.

5) Abbreviation of tolylene diisocyanate 6) Abbreviation of diphenylmethane diisocyanate 7) Abbreviation of infron diisocyanate Coating The resins prepared in each example and comparative example were mixed in a mixed solvent of toluene:cyclohexanone = 1:1 (weight ratio). A solution with a solid content of 20% was obtained. To 100 parts of this solution, 10 parts of red iron oxide was added as a pigment, and 100 parts of glass beads each having a diameter of IIIllφ were processed and each was shaken for a certain period of time in a paint shaker to form a paint. Paint obtained in this way 1
After adding and mixing 2 parts of Conate L to 0.00 parts and homogenizing the mixture, the mixture was coated on a 0.5 M thick polished mild steel plate to a dry film thickness of 30 μm, and aired at a temperature of 120 to 130° C. for 10 minutes. The glossiness of each coating film was measured from 60° to 60' reflective gloss. The paint film characteristics are visually checked for brightness ◎, 01
It was judged as ×. The results are shown in Table 2.

Table 2

Claims (1)

[Claims] In a coating composition in which pigments are dispersed, the vehicle composition is (A) a long-chain polyol containing an ether bond and having a molecular weight of 500 or more, (B) a diisocyanate, and (C)
Molecular weight 5,000 or more 100, obtained by polymerizing a chain extender,
A polyurethane resin with a molecular weight of less than 000 and having a hydroxyl group at the end and containing 1 to 25% by weight of ether bonds in the resin, with a molecular weight of 50 or more containing two or more isocyanate groups in the molecule.
A coating composition characterized by being cured with a polyisocyanate having a molecular weight of 0 to 5,000.