KR100738126B1 - Preparation methods of high heat resistant uv-cured polyurethane dispersion - Google Patents

Abstract

A method for preparing a highly heat resistant UV curable aqueous polyurethane resin is provided to obtain an aqueous polyurethane having improved heat resistance, fast reaction completion behavior and improved surface properties. The method for preparing a highly heat resistant UV curable aqueous polyurethane resin comprises the steps of: reacting a carboxy group-containing diol with a linear diisocyanate in a weight ratio of 1:2 to provide an isocyanate-terminated oligomer; forming a soft segment and a hard segment; mixing the soft segment with the hard segment in a weight ratio of 7:3-9:1 to provide a prepolymer; reacting the prepolymer with a monovalent hydroxy acrylate in a weight ratio of 43:1 to allow the isocyanate terminal to be end-capped with acrylate; dispersing the end-capped product in water to provide an aqueous polyurethane; and curing the aqueous polyurethane resin with UV rays under a dose of 800-1150 mJ/cm^2 for 10-120 seconds.

Description

Preparation method of high heat-resistant UV-curable water-based polyurethane resin {Preparation Methods of High Heat Resistant UV-Cured Polyurethane Dispersion}

The present invention relates to a method for producing a high heat-resistant UV-curable aqueous polyurethane resin, and more particularly, using an anhydride as a chain extender, introducing an imide group into a hard segment, and introducing a hydroxy acrylate at the end of the main chain to enable ultraviolet curing. The present invention relates to a method for producing a high heat-resistant UV-curable aqueous polyurethane resin in which synergistic effects such as heat resistance improvement, rapid reaction completion, and surface property improvement of an aqueous polyurethane occur.

Polyurethane has a lack of heat resistance for structural reasons and has been studied in various aspects to solve this problem. Among them, an imide group is introduced into a hard segment by using an anhydride as a chain extender in a solvent-type polyurethane or by blending a polyurethane-polyimide copolymer or two polymers. The heat resistance of resin is improved by various methods, such as introduction.

Introduction of an imide group in a chain using an anhydride as a chain extender increases heat resistance compared to a conventional urethane-bonded or urea-bonded polyurethane, but this study is limited to solvent-type polyurethane. Conventional solvent-based polyurethanes are limited in use in many countries due to their stability and environmental regulations in conventional applications. Therefore, in many fields, the conventional solvent type polyurethane is gradually replaced by an aqueous polyurethane due to the environmental advantages and the steady increase of the solvent price.

Accordingly, the present inventors use anhydride as a chain extender to introduce an imide group into the hard segment, and to introduce ultraviolet cure by introducing a hydroxy acrylate at the end of the main chain to improve the heat resistance of the aqueous polyurethane, and to complete the reaction quickly. The present invention has a synergistic effect such as surface property improvement.

Accordingly, an object of the present invention is to provide a method for producing a high heat-resistant UV-curable aqueous polyurethane resin having improved heat resistance, fast reaction completion, and improved surface properties.

The present invention comprises a step of synthesizing an oligomer at the end of an isocyanate group by reacting a diol having a carboxyl group with a linear diisocyanate in a 1: 2 weight ratio;

Two steps of generating soft segments and hard segments;

Mixing the soft segment with the hard segment in a weight ratio of 9: 1 to 7: 3 to generate a prepolymer;

 Reacting the prepolymer with monovalent hydroxy acrylate at a weight ratio of 43: 1 to cap the isocyanate group end with acrylate;

5 steps to produce an aqueous polyurethane by dispersing after the capping step; And

Characterized in the method for producing a high heat-resistant UV-curable water-based polyurethane resin comprising six steps of UV-curing the prepared water-based polyurethane resin in the range of 800 ~ 1150 mJ / ㎠ for 10 to 120 seconds.

The present invention will be described in more detail as follows.

The present invention uses an anhydride as a chain extender to introduce an imide group into the hard segment, and to introduce a hydroxy acrylate at the end of the main chain to enable ultraviolet curing, thereby improving the heat resistance of the aqueous polyurethane, completing the reaction quickly, and surface properties. It is a manufacturing method of the high heat-resistant ultraviolet-curable aqueous polyurethane resin which has synergistic effects, such as improvement.

Each step of the method for producing a high heat-resistant ultraviolet-curable aqueous polyurethane resin of the present invention will be described in more detail as follows.

Referring to the first step of synthesizing the oligomer in detail as follows.

First, a diol having a carboxyl group is reacted with a linear diisocyanate in a 1: 2 weight ratio to synthesize an oligomer at the end of an isocyanate group, and when the ratio is less than 1: 2, no isocyanate terminal ends are obtained. There is a problem that is not obtained.

The diol having the carboxyl group uses dimethylol propionic acid, dimethylol butanoic acid, and mixtures thereof, and the diisocyanate is 1,6-hexamethylene diisocyanate, 4,4-dicyclohexylmethane diisocyanate, and their It is more effective to use mixtures and to use 1,6-hexamethylene diisocyanate which increases the flexibility of the ion center.

The second step of generating the soft segment and the hard segment will be described in detail.

First, the second step is to add 11 to 23 parts by weight of diisocyanate and 0.14 to 0.2 parts by weight of dibutyltin dilaurate as a catalyst, based on 100 parts by weight of polyol, to produce a soft segment at the hydroxyl end. When the amount of the diisocyanate is less than 11 parts by weight based on 100 parts by weight of the polyol, hydroxyl group ends cannot be obtained, and when the amount of the diisocyanate exceeds 23 parts by weight, a soft segment having an appropriate molecular weight may not be obtained. The polyol uses an ether or ester type polyol, and there is no restriction on molecular weight, and the dithiocyanate uses 1,6-hexamethylene diisocyanate, 4,4-dicyclohexylmethane diisocyanate and mixtures thereof. When the use amount of the dibutyl tin dilaurate catalyst is less than 0.14 parts by weight, the reaction rate is too slow, and when the content exceeds 0.2 parts by weight, the reaction rate is too fast, it is difficult to control the viscosity during polymerization.

Secondly, 8 to 27 parts by weight of the diisocyanate and 2 to 17 parts by weight of a chain extender are added to 100 parts by weight of the soft segment, which is the hydroxyl group terminal produced above, to prepare a hard segment at the end of the isocyanate group having an imide group. When the diisocyanate content is less than 8 parts by weight, no isocyanate ends are obtained, and when the diisocyanate content is more than 27 parts by weight, hard segments of appropriate molecular weight are not obtained. In addition, when the content of the chain extender is less than 2 parts by weight, the content of the hard segment is small, so that it is difficult to improve heat resistance. The chain extender uses divalent anhydride, pyromellitic dihydride, 4,4-carbonyldiphthalic anhydride, 4,4-nonphthalic anhydride, 4,4-oxydiphthalic anhydride 1 type, or 2 or more types of mixtures selected from a hydride, a 2, 2-bis (3, 4- dicarboxyphenyl) hexafluoro propane dianhydride, etc., and the said diisocyanate is 1, 6- hexamethylene diisocyanate. , 4,4-dicyclohexylmethane diisocyanate and mixtures thereof are used.

The three steps of generating the prepolymer will be described in detail.

End of the hydroxyl group A prepolymer is prepared by mixing a soft segment with a hard segment in a weight ratio of 7: 3 to 9: 1. When the weight ratio is less than 7: 3, a change over time due to crystallization of the hard segment occurs, and when the weight ratio exceeds 9: 1, It is difficult to improve the heat resistance because the content of the hard segment made of an imide group is small.

The four steps of capping the end of the isocyanate group with acrylate will be described in detail.

The prepolymer is reacted with hydroxy acrylate at a weight ratio of 43: 1 to cap an isocyanate group end with acrylate. When the 43: 1 weight ratio is not obtained, the acrylate end is not obtained. Roxy acrylate causes a problem that causes the generation of volatile organic compounds (Volatile Organic Compounds) during drying or ultraviolet curing. In the capping step, the main chain terminal has an acrylic double bond by capping with hydroxy acrylate.

Hereinafter, the five steps of preparing the aqueous polyurethane will be described in detail.

After the capping step, to neutralize and add 2 to 4 parts by weight of tertiary amine with respect to 100 parts by weight of the prepolymer, and then dispersing by adding 1 to 3 parts by weight of photoinitiator and 200 to 900 parts by weight of water. When less than 2 parts by weight of the carboxyl group is not effectively neutralized, the hydrophilicity of the prepolymer is reduced and the particle stability after water dispersion is reduced, when the excess of 4 parts by weight of the problem of increase in soaking occurs, the reaction rate when the photoinitiator is less than 1 part by weight It is slow, the reaction rate is too fast when more than 3 parts by weight, when the water is less than 200 parts by weight does not obtain a stable particle after water dispersion, when the weight is greater than 900 parts by weight due to a small decrease in film thickness after drying There is a problem that the drying time is long. The photoinitiator is 1-hydroxy-cyclohexyl-phenyl ketone, α, α-dimethoxy-α-hydroxy acetophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl-propane-1 -One, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-propan-1-one and mixtures thereof are used.

The ultraviolet curing step is described in detail as follows.

The aqueous polyurethane resin prepared above is cured with ultraviolet light in the range of 800 to 1150 mJ / cm 2 for 10 to 120 seconds. When the ultraviolet light is less than 800 mJ / cm 2, the UV curing is too slow, and when it exceeds 1150 mJ / cm 2. Too fast a problem occurs, when the curing time is less than 10 seconds, the reaction is not completed, when more than 120 seconds a large energy loss occurs. The double bond of the acryl group causes a radical reaction by ultraviolet irradiation to form a three-dimensional crosslinked structure.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited to the examples.

Preparation Example 1 to 3, Comparative Production Example 1

Nitrogen was injected into a 500 ml round four-necked flask equipped with a thermometer and a stirrer as shown in Tables 1 to 3, and hexamethylene diisocyanate and dimethylol butanoic acid at 80 ° C in a weight ratio of 1: 1.96 as shown in Table 1 below. Reaction is carried out for about 1 hour to synthesize an isocyanate group terminal oligomer. 16 parts by weight of 4,4-dicyclohexylmethane diisocyanate and 0.17 parts by weight of the catalyst dibutyltindilaurate were injected with respect to 100 parts by weight of polytetramethylenediol and reacted at 80 ° C. for about 3 hours to synthesize a soft segment at the hydroxyl end. (Table 2). Next, 4,4-dicyclohexylmethane diisocyanate and pyromellitic dianhydride were added to 100 parts by weight of the soft segment, followed by reaction at 80 ° C. for 5 hours to form a hard phase (Table 3). The terminal prepolymer is synthesized (Table 4).

Example  1 to 3 and Comparative example  One

As shown in Tables 5 to 7, Preparation Examples 1 to 4 and Comparative Production Example 1 were cooled to a temperature of 70 ° C., and then the prepolymer and the hydroxyethyl acrylate were mixed at a weight ratio of 43.05: 1, and then capped all of the isocyanate groups of the prepolymer. (Table 5). After the capping step, the mixture was stirred at a speed of 500 rpm for 3 hours while cooling to 30 ° C, and neutralized by adding 4 parts by weight of triethylamine (tertiary amine) and 4 parts by weight of photoinitiator to 100 parts by weight of the capped prepolymer, Water is dispersed by adding 240 parts by weight of water (solid content concentration of 30% by weight) based on 100 parts by weight of the capped prepolymer (Table 6).

Classification (weight ratio) usage Dimethylol Butanoic Acid One Diisocyanate 1.96

Classification (part by weight) usage Polytetramethylenediol 100 4,4-dicyclohexylmethane diisocyanate 16 Dibutyl tin dilaurate 0.17

Classification (part by weight) Preparation Example 1 Preparation Example 2 Preparation Example 3 Comparative Production Example 1 Soft segment 100 100 100 100 4,4-dicyclohexylmethane diisocyanate 8.75 16.66 26.80 - Pyromeric Dion Hydride 2.43 8.38 16.05 -

Classification (part by weight)  Preparation Example 1  Preparation Example 2 Preparation Example 2  Comparative Production Example 1 Soft segment 90 80 70 100 Hard segment 10 20 30 -

Classification (weight ratio) Example 1 Example 2 Example 3 Comparative Example 1 Prepolymer 43.05 43.05 43.05 43.05 Hydroxyethyl acrylate One One One One

Classification (part by weight) Example 1 Example 2 Example 3 Comparative Example 1 Prepolymer After Capping 100 100 100 100 Triethylamine 4 4 4 4 Photo Start Limited 4 4 4 4 water 240 240 240 240

Experimental Example  One

The heat resistance of the UV curable aqueous polyurethane synthesized by the method of Examples 1 to 3 and Comparative Example 1 was measured by thermogravimetric method, and the results are shown in Table 7 below. The weight of the specimen used was 7 ~ 10 mg, the measuring equipment was used TGA Q50 V6.2 (TA), the temperature range was 40 ~ 500 ℃, the temperature increase rate was measured under nitrogen filled at 5 ℃ / min.

division Example 1 Example 2 Example 3 Comparative Example 1 UV (mJ / cm ² ) 950 950 950 950 Time in seconds 60 60 60 60 Heat resistance (℃) 303.63 317.79 341.02 298.37

In summary, as shown in Table 7, the decomposition method of the aqueous polyurethane production method of Examples 1 to 3 according to the present invention increases as the content of the hard segment increases compared to Comparative Example 1. That is, when the urethane main chain is made of only the soft segment, it may be confirmed that the case includes the hard segment made of the imide group, and the heat resistance is improved as the content of the hard segment is increased.

As described above, the method for producing a polyurethane high heat-resistant UV-curable aqueous polyurethane resin of the present invention has a large intermolecular interaction force, which is not a conventional urethane group or a urea group, which has a hard segment, and excellent thermal stability even at high temperature. It can be applied to various industrial purposes as well as paints.

Claims (8)

Reacting a diol having a carboxyl group with a linear diisocyanate in a 1: 2 weight ratio to synthesize an oligomer at an isocyanate group terminal; Two steps of generating soft segments and hard segments; Mixing the soft segment with the hard segment in a weight ratio of 7: 3 to 9: 1 to generate a prepolymer;  Reacting the prepolymer with monovalent hydroxy acrylate in a 43: 1 weight ratio to cap the isocyanate group terminal with acrylate; 5 steps to produce an aqueous polyurethane by dispersing after the capping step; And Method for producing a high heat-resistant UV-curable water-based polyurethane resin, characterized in that it comprises six steps of ultraviolet-curing the prepared water-based polyurethane resin in the range of 800 ~ 1150 mJ / ㎠ for 10 to 120 seconds. The method of claim 1, In the second step, 11 to 23 parts by weight of diisocyanate and 0.14 to 0.2 parts by weight of dibutyltin dilaurate as a catalyst are added to 100 parts by weight of the polyol to produce a soft segment at the hydroxyl end, and 100 parts by weight of the soft segment 8 to 27 parts by weight of isocyanate and 2 to 17 parts by weight of a chain extender to produce a hard segment at the end of the isocyanate group having an imide group. The method of claim 1 The step 5 is a step of adding and neutralizing 2 to 4 parts by weight of the tertiary amine with respect to 100 parts by weight of the prepolymer, and then neutralizing and then dispersing it by adding 2 to 4 parts by weight of the photoinitiator and 200 to 900 parts by weight of water. Method for producing an aqueous polyurethane resin. The method of claim 1, The diol is a dimethylol propionic acid, dimethylol butanoic acid, and a mixture thereof, a method for producing a high heat resistant ultraviolet curable aqueous polyurethane resin. The method of claim 2, The polyol is a method of producing a high heat-resistant UV-curable aqueous polyurethane resin, characterized in that the ether or ester polyol. The method of claim 2, The diisocyanate is 1,6-hexamethylene diisocyanate, 4,4-dicyclohexylmethane diisocyanate, and a mixture thereof, a method for producing a high heat resistant ultraviolet curable aqueous polyurethane resin. The method of claim 2, The chain extender is a method for producing a high heat resistant ultraviolet curable aqueous polyurethane resin, characterized in that it is a divalent anhydride. The method of claim 3, wherein The photoinitiator is 1-hydroxy-cyclohexyl-phenyl ketone, α, α-dimethoxy- α-hydroxy acetophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl-propane-1 High-temperature, ultraviolet-curable aqueous polyurethane resin, characterized in that -one, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-propan-1-one and mixtures thereof Method of preparation.