JPH09302307A - Coating agent for plastic sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating agent for a plastic sheet, excellent in adhesion to the plastic sheet and heat resistance without yellowing and coloring a coating film even when used as the coating agent for the plastic sheet and heat-treating the resultant sheet. SOLUTION: This coating agent for a plastic sheet consists essentially of a polyurethane resin prepared by reacting a polymeric polyol with a diisocyanate compound, a chain extender and, as necessary, a chain length terminator. A polymeric diol containing 5-50wt.% cyclohexane ring content in the total polymeric polyol component without having an aromatic ring is used as the polymeric polyol.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating agent for plastic sheets. Specifically, the coating agent for a plastic sheet of the present invention is a paint for a porcelain tape used as an audio / video material, laminated plastic sheets as a food packaging material, or stuck a plastic sheet and a metal foil or a metal can. It can be used for printing inks and the like that are used together.

[0002]

2. Description of the Related Art In recent years, a wide variety of plastic products have been used in various industrial fields such as the construction industry, the automobile industry, the packaging industry, the audio / video industry. Among these plastic products, as a coating agent for a plastic sheet, a polyurethane resin having excellent adhesiveness and flexibility has been favored. Generally, a polyurethane resin obtained by reacting a polymer polyol composed of an aliphatic polyester polyol or an aliphatic polyether polyol, a diisocyanate compound and a chain extender is used.

[0003]

Such a polyurethane resin has good adhesiveness to a plastic sheet, but generally has a drawback that it has a low glass transition temperature and poor heat resistance. Therefore, when the plastic sheet is coated with the coating agent and then subjected to heat treatment such as boil / retort sterilization, the coating agent is peeled off from the plastic sheet. In particular, when the plastics are coated with the coating agent and then the metals are pasted together using an adhesive, the coating agent tends to peel off from the plastic sheet because the thermal expansion coefficients of the metals and the plastics are significantly different. Is.

In order to solve these problems, it has been proposed to use an aromatic dicarboxylic acid as a polybasic acid component of a polyester polyol as a polymer polyol component (JP-A-6-80921). However, when an aromatic polybasic acid type polyester polyol is used as the high molecular weight polyol component, although the heat resistance of the polyurethane resin is improved, there is a problem that the coating film turns yellow when heat-treated. Was there.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the present inventors have made extensive studies on a polymer polyol component constituting a polyurethane resin used as a main component of a coating agent for a plastic sheet. As a result, as the polymer polyol component, the content of the cyclohexane ring in the total polymer polyol component was 5 to 50% by weight.
In addition, a polyurethane resin prepared by using one that does not have an aromatic ring has excellent heat resistance to a plastic sheet, and the coating film does not turn yellow even when it is subjected to a heat treatment by being applied to a coating agent for a plastic sheet. This has led to the completion of the present invention.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a cyclohexane ring is used as a polymer polyol component of a polyurethane resin in an amount of 5 to 5
The one containing 50% by weight is used. The cyclohexane ring in the polymer polyol component is generally derived from a low molecular diol compound having a cyclohexane ring or a dibasic acid compound having a cyclohexane ring,
All of these compounds preferably have a molecular weight of 300 or less. Examples of such a low molecular weight diol compound having a cyclohexane ring include cyclohexanediol, cyclohexanedimethanol and hydrogenated bisphenol A, and examples of the dibasic acid compound having a cyclohexane ring include cyclohexanedicarboxylic acid.

Specific examples of the high molecular weight polyol component having a cyclohexane ring include, for example, ring-opening addition of ethylene oxide, propylene oxide, tetrahydrofuran or the like to the aforementioned low molecular weight diol compound having a cyclohexane ring or a dibasic acid compound having a cyclohexane ring. High molecular weight polyether polyol; High molecular weight polyester polyol obtained by ring-opening addition of a lactone compound such as ε-caprolactone or β-methyl-δ-valerolactone to a low molecular weight diol compound having a cyclohexane ring; A low-molecular diol compound and / or a dibasic acid compound having a cyclohexane ring is used, if necessary, with a low-molecular diol compound having no cyclohexane ring and / or a dibasic acid compound having no cyclohexane ring, which will be described later. Phosgene low molecular diol compound having a cyclohexane ring, no cyclohexane ring to be described later as required with low-molecular diol compound; a polymeric polyester polyols obtained by polycondensation
Examples thereof include polymer polycarbonate polyols obtained by reacting with ethylene carbonate, dimethyl carbonate, diphenyl carbonate and the like.

In the present invention, it is essential to use the above-mentioned polymer polyol having a cyclohexane ring as the polymer polyol component, but the polymer polyol having the cyclohexane ring may be used alone or in the cyclohexane ring. You may use together with the high molecular polyol which does not have. However, it is necessary that the content of the cyclohexane ring in all the polymer polyol components used is 5 to 50% by weight. When the cyclohexane ring content is less than 5% by weight, the resulting polyurethane resin does not have sufficient heat resistance and the coating film tends to peel off from the plastic sheet after heat treatment, while when it exceeds 50% by weight. The obtained polyurethane resin film tends to be too hard, and the post-processing suitability tends to deteriorate, which is not preferable in any case.

The polymeric polyol components having no cyclohexane ring which can be used in the present invention are as follows. Ethylene glycol, 1,2-propanediol,
1,3-propanediol, 1,3-butanediol,
Molecular weight of 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, diethylene glycol, triethylene glycol, dipropylene glycol, etc. Various known low molecular weight diol compounds having no cyclohexane ring of 300 or less, or adipic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, etc. Polyether polyols obtained by ring-opening addition of ethylene oxide, propylene oxide, tetrahydrofuran, etc. to a dibasic acid compound having a molecular weight of 300 or less and having no cyclohexane ring; − Caprolactone, β- methyl -δ-
Polymer polyester polyols obtained by ring-opening addition of a lactone compound such as valerolactone; Polymer polyester obtained by dehydration condensation of the low-molecular diol compound having no cyclohexane ring and the dibasic acid compound having no cyclohexane ring Polyols; Polymeric polycarbonate polyols obtained by reacting low-molecular diol compounds having no cyclohexane ring with phosgene, ethylene carbonate, dimethyl carbonate, diphenyl carbonate; Polymeric polybutadiene glycols, etc., generally used for producing polyurethane Various known polymer polyols are exemplified. The polymer polyol component of the present invention does not contain an aromatic ring because of the problem of yellowing. Therefore, the low molecular weight diol compound having no cyclohexane ring and the dibasic acid compound having no cyclohexane ring are limited to those having no aromatic ring.

The number average molecular weight of the high molecular weight polyol is appropriately determined in consideration of the heat resistance, yellowing and the like of the resulting polyurethane resin, and usually the number average molecular weight of all the high molecular weight polyols used is within the range of 500 to 2,500. Good to do.
When the number average molecular weight of the polymer polyol is less than 500, yellowing tends to be poor with an increase in the diisocyanate content, while when it exceeds 2500, the heat resistance tends to be low and the coating film tends to peel off from the plastic sheet after heat treatment. is there.

Examples of the diisocyanate compound constituting the polyurethane resin include aromatic, aliphatic or alicyclic diisocyanate compounds. For example, 1,5
-Naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1, 4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, cyclohexane-1, 4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexane diisocyanate, dimer diisocyanate, and the like as typical examples. These isocyanate compounds may be used alone or in combination of two or more. Among these diisocyanate compounds, alicyclic diisocyanate compounds are preferable in consideration of heat resistance and yellowing.

As the chain extender constituting the polyurethane resin, diamines such as ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine and dimerdiamine, 2-hydroxyethylethylenediamine, 2-hydroxyethyl propylene diamine, di-
Diamines having a hydroxyl group in the molecule such as 2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, diethylenetriamine, triethylenetetramine,
Tetraethylenepentamine, dipropylenetriamine,
Examples thereof include polyamines such as bishexamethylenetriamine and tris (3-aminopropyl) amine, and polyamines having a hydroxyl group in the molecule such as N′-hydroxypropyltriethylenetetramine. These chain extenders are also preferably alicyclic compounds in consideration of heat resistance and yellowing.
Furthermore, in the present invention, a chain length terminating agent can be used if necessary. As the chain length terminator, for example, di-n
-Dialkylamines such as butylamine, and hydroxyalkylamines such as monoethanolamine and diethanolamine.

As a method for producing the polyurethane resin of the present invention, first, a polymer polyol component and a diisocyanate compound are reacted under the condition of excess isocyanate groups,
A two-step method in which a prepolymer having an isocyanate group at both ends of a high molecular weight polyol is prepared, and then this is reacted with a chain extender and optionally a chain length terminating agent in a suitable solvent, and a high molecular weight polyol component, Although any one-step method in which a diisocyanate compound, a chain extender and, if necessary, a polymerization terminator are reacted at once in a suitable solvent can be adopted, the former method is preferable for the purpose of obtaining a uniform polymer solution. .

In these production methods, the solvent used is usually an aromatic solvent such as benzene, toluene and xylene, which is well known as a solvent for coating agents for plastic sheets; esters such as ethyl acetate and butyl acetate. Solvents; alcohol solvents such as methanol, ethanol, isopropanol and n-butanol; ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone. These solvents can be used alone or as a mixture of two or more kinds.

When the polyurethane resin used in the present invention is produced by the two-step method, the conditions for reacting the high molecular weight polyol component and the diisocyanate compound are not limited, except that they are in excess of isocyanate. It is preferable to react so that the groups are in an equivalent ratio range of 1 / 1.2 to 1/3. Further, the conditions for reacting the obtained prepolymer with a chain extender and a chain length terminating agent used as necessary are not limited, but with respect to a free isocyanate group at the end of the prepolymer, a chain extender and The chain length terminating agent is reacted so that the amino groups capable of reacting with the isocyanate groups are excessive, and the amine value is 0.5 to 20 per 1 g of the solid content of the polyurethane resin.
It is preferable that When the amine value is less than 0.5, the adhesiveness to plastic tends to decrease, and when the amine value exceeds 20, the coating film tends to yellow. As a method for obtaining such an amine-valued polyurethane resin, generally, when the free isocyanate group at the terminal of the prepolymer is 1 equivalent, the isocyanate group in the chain extender and the chain length terminator is The total equivalent of reactive amino groups is 1.01 to 1.30.
The reaction may be carried out within the equivalent range.

The number average molecular weight of the polyurethane resin thus obtained is preferably in the range of 5,000 to 100,000. If the number average molecular weight is less than 5,000, the adhesiveness of the plastic sheet coating agent using polyurethane resin as a binder is not sufficient, while if it exceeds 100,000, the viscosity of the polyurethane resin solution increases and coating Aptitude tends to be poor.

The resin solid content concentration of the polyurethane resin solution obtained as described above is not particularly limited and is appropriately determined in consideration of workability at the time of coating, and usually 15
６０60% by weight. The viscosity is 50 to 10000c
P / 25 ° C is practically suitable.

Further, in the coating agent for a plastic sheet, which contains the polyurethane resin of the present invention as a main component, the following resins may be used together as an auxiliary component, if necessary. For example, polyurethane resin other than the present invention, polyester resin, alkyd resin, polyvinyl butyral resin, polyamide resin, nitrocellulose resin, acetyl cellulose resin, acrylic resin, vinyl chloride / vinyl acetate copolymer resin, chlorinated polypropylene resin, phenolic resin , Rosin resins and the like.

Further, the coating agent for a plastic sheet of the present invention may optionally contain a colorant, a solvent, a surfactant, a wax, and other additives. The solid content of the polyurethane resin of the present invention in the coating agent for plastic sheets is preferably 3 to 30% by weight.

[0020]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Production Examples, Examples and Comparative Examples, but the present invention is not limited to these Examples. In each example, all parts and percentages are by weight unless otherwise specified.

Production Example 1 A round-bottomed flask equipped with a stirrer, a thermometer and a nitrogen inlet tube was used, which was composed of cyclohexanedimethanol, 1,6-hexanediol and adipic acid and had a number average molecular weight of 2000 and a cyclohexane ring content of 10%. 1000 parts of polyester diol and 222 parts of isophorone diisocyanate were charged and reacted at 100 ° C. for 6 hours under a nitrogen stream to obtain a prepolymer having a free isocyanate value of 3.36%.
To this was added 815 parts of methyl ethyl ketone to obtain a uniform urethane prepolymer solution. Then, 86.7 parts of isophorone diamine, 3.0 parts of dibutyl amine, 1224 parts of methyl ethyl ketone and 10 parts of isopropyl alcohol.
In the presence of a mixture of 19 parts, 2037 parts of the urethane prepolymer solution was added and reacted at 50 ° C. for 3 hours. The polyurethane resin solution thus obtained had a resin solid content concentration of 30%, a viscosity of 1000 cP / 25 ° C., an amine value of 2.8 per 1 g of resin solid content, and a polyurethane resin number average molecular weight of 29,600. .

Production Example 2 The same reactor as in Production Example 1 was charged with a cyclohexane ring content of cyclohexanedimethanol, cyclohexanedicarboxylic acid and adipic acid having a number average molecular weight of 1,000 and a cyclohexane ring content of 4
1000 parts of 0% polyester diol and 333 parts of isophorone diisocyanate were charged, and 1 part was prepared under a nitrogen stream.
The reaction was carried out at 00 ° C. for 10 hours to give a free isocyanate value of 3.
A 10% prepolymer was prepared, and 889 parts of methyl ethyl ketone was added thereto to prepare a uniform solution of urethane prepolymer. Then, 2222 parts of the above urethane prepolymer solution was added in the presence of a mixture consisting of 93.8 parts of isophorone diamine, 3.0 parts of dibutylamine, 1334 parts of methyl ethyl ketone and 1111 parts of isopropyl alcohol, and reacted at 50 ° C. for 3 hours. It was The polyurethane resin solution thus obtained had a resin solid content concentration of 30%, a viscosity of 1300 cP / 25 ° C., an amine value of 5.6 per 1 g of the resin solid content, and a number average molecular weight of the polyurethane resin of 17,200. .

Production Example 3 A reactor similar to that of Production Example 1 was charged with 1000 parts of poly-ε-caprolactone glycol having a number average molecular weight of 2000 and 222 parts of isophorone diisocyanate, and the mixture was reacted at 100 ° C. for 6 hours under a nitrogen stream to release the compound. A prepolymer having an isocyanate value of 3.40% was prepared, and 815 parts of methyl ethyl ketone was added thereto to prepare a uniform solution of urethane prepolymer. Then, 87.7 parts of isophorone diamine,
Dibutylamine 3.0 parts, methyl ethyl ketone 1225
Part of the urethane prepolymer solution 203 in the presence of a mixture of 10 parts of isopropyl alcohol and 1020 parts of isopropyl alcohol.
7 parts was added and reacted at 50 ° C. for 3 hours. The polyurethane resin solution thus obtained has a resin solid content concentration of 30.
%, The viscosity was 3000 cP / 25 ° C., the amine value per 1 g of the resin solid content was 2.8, and the number average molecular weight of the polyurethane resin was 29600.

Production Example 4 A reactor similar to that of Production Example 1 was charged with 1000 parts of a polyester diol having a number average molecular weight of 2000 and composed of 1,6-hexanediol and isophthalic acid, and 222 parts of isophorone diisocyanate, and heated at 100 ° C. under a nitrogen stream. In 6
The reaction was carried out for a time to form a prepolymer having a free isocyanate value of 3.40%, and 815 parts of methyl ethyl ketone was added to the prepolymer to prepare a uniform solution of the urethane prepolymer. Then, in the presence of a mixture of 87.7 parts of isophorone diamine, 3.0 parts of dibutylamine, 1225 parts of methyl ethyl ketone and 1020 parts of isopropyl alcohol, 2037 parts of the urethane prepolymer solution is added, and reacted at 50 ° C. for 3 hours. It was The polyurethane resin solution thus obtained had a resin solid content concentration of 30% and a viscosity of 2
It was 200 cP / 25 ° C., the amine value per 1 g of the resin solid content was 2.8, and the number average molecular weight of the polyurethane resin was 29600.

Examples 1 and 2 and Comparative Examples 1 and 2 (Composition of white coating agent) Titanium white (rutile type) 30 parts Polyurethane resin solution shown in Table 1 50 parts Toluene 10 parts Isopropyl alcohol 10 parts Mixture of the above composition Each was kneaded in a ball mill to prepare a white coating agent. To 100 parts of each of the obtained coating agents, 35 parts of toluene and 15 parts of isopropyl alcohol were further added to adjust the viscosity. The coating agent thus obtained was used as a bar coater No. Apply to polyester sheet at 14, 40-5
It was dried at 0 ° C to obtain a coated sheet. Further, a polyurethane adhesive having a solid content of 25% was applied to the coated surface of the obtained coated sheet with a bar coater No. After coating and drying in 6, an aluminum sheet was laminated to obtain a laminated sheet. The adhesiveness, heat resistance and yellowing of the thus obtained laminate sheet were measured. Table 1 shows the measurement results.

(Adhesiveness) The laminated sheet was cut into a width of 15 mm, and a T-type peel strength (g / 15) was measured by a peel tester.
mm).

(Heat resistance) The laminated sheet was steam-treated at 140 ° C. for 2 hours, cut into a width of 15 mm, and the T-type peel strength (g / 15 mm) was measured by a peel tester.

(Yellowness) The yellowing of the coating film of the laminate sheet after the laminate sheet was steam-treated at 140 ° C. for 2 hours was visually evaluated according to the following criteria. ◯: No yellowing. X: Yellowed.

[0029]

[Table 1]

Claims (4)

[Claims] 1. A coating agent for a plastic sheet, which comprises as a main component a polyurethane resin obtained by reacting a high molecular weight polyol, a diisocyanate compound, a chain extender and, if necessary, a chain length terminating agent. A coating agent for a plastic sheet, which contains 5 to 50% by weight of a cyclohexane ring in a molecular polyol component and has no aromatic ring. 2. The number average molecular weight of the polymer polyol is 50.
The coating agent for a plastic sheet according to claim 1, which is 0 to 2500. 3. The coating agent for a plastic sheet according to claim 1, wherein the free amine value per 1 g of the solid content of the polyurethane resin is 0.5 to 20. 4. The number average molecular weight of the polyurethane resin is 50.
The coating agent for a plastic sheet according to claim 1, 2 or 3, which is from 00 to 100,000.