KR100417087B1 - Method for preparing self curable silicon-modified polyester resin and heat resistant coating comprising the same - Google Patents

Abstract

PURPOSE: Provided are a method for preparing a self curable silicon-modified polyester resin which can be used at relatively high temperature(250-400 deg.C), and a heat resistant coating comprising the same. CONSTITUTION: The method comprises the steps of (i) copolymerizing a polyether polyol having number average molecular weight of 100-1000, reactive hydroxyl number of 100 mgKOH/g or more, with silicon intermediate to form a silicon modified polyester resin, and (ii) polymerizing a hydroxyl group of the silicon modified polyester resin with a silane having at least two alkoxy groups in equivalent ratio of 1:0.5-2. The polyester polyol of the step(i) is obtained by copolymerizing a mixture of at least one glycol having at least two hydroxyl groups, at least two carboxylic acids or derivatives thereof.

Description

Manufacturing method of self-curing silicone-modified polyester resin and heat resistant paint containing same

The present invention relates to a silicone-modified resin that can be used at a relatively high temperature (250 ~ 400 ℃), more specifically, a polyester polyol containing two or more reactive hydroxyl groups and a silicone intermediate having two or more reactive groups prepared by copolymerization The present invention relates to a method for producing a self-curing silicone-modified polyester resin prepared by polymerizing with a silicone-modified resin and an alkoxy silane and a heat resistant paint containing the same.

Generally, silicone is widely used for adhesives and coating resins requiring heat resistance. This is because silicone has a very high reactivity with organics and also has excellent heat, cold and weather resistance. In addition, since silicone is very excellent in water repellency, mold release property and slipperiness, its use has been diversified.

However, although silicone has such an advantage, there is a disadvantage in that the mechanical strength that the organic resin composition can exhibit is low.

Therefore, a method of preparing an organic-modified silicone resin that can make the best use of the characteristics of the silicone and also utilize the advantages of the organic resin has been disclosed through Japanese Patent No. 81-131673, the contents of which are reactive to the polyester resin. By introducing a cyrylcone compound (polysiloxane), weather resistance, chemical resistance, and solvent resistance can be improved.

On the other hand, a method for producing a silicone-modified polyester resin is disclosed in US Patent No. 4,289,677, German Patent No. 2,949,725, Japanese Patent Publication No. 81-81372, Japanese Patent Publication No. 56-157462, and 56-157461 The present invention relates to a method of preparing a low molecular weight polyester and then reacting a reactive silicone compound using a hydroxyl group at the end, or simultaneously reacting a reactive silicone compound and a raw material used for preparing a polyester, but a reaction of a reactive silicone compound It is difficult to precisely control the degree, and in some cases, because the reaction with the organic acid, the silicon compound reacts with each other to form a silicon bead. In addition, even if the silicone beads are not formed, the stability is poor and the viscosity increases at room temperature. As a result, a gel or a high temperature reaction of 250 ° C. or higher does not occur even if a crosslink is not formed or a crosslinking reaction occurs during heating. When necessary, yellowing occurs during the crosslinking reaction or the physical properties are significantly lowered. In addition, when a curing agent such as amino formaldehyde or blocked isocyanate is added to lower the temperature of the crosslinking reaction, the crosslinking reaction temperature can be lowered, but heat resistance and yellowing resistance become poor.

The present invention relates to a self-curable silicone-modified polyester resin through the reaction of a silicone-modified polyester resin prepared by reacting a low molecular weight polyester polyol and a silicone intermediate and an alkoxy silane having at least two reactive alkoxy groups to solve these disadvantages. It is possible to cure by crosslinking reaction of the resin itself when heated to 150 ° C. or higher, and the cured cured product can provide a method for producing a self-curing silicone-modified polyester resin that can withstand a long time at a temperature of 250 ° C. or higher. Leave.

In addition, another object of the present invention is to provide a paint containing a thermosetting silicone-modified polyester resin prepared by the above method.

The silicone-modified polyester resin according to the present invention comprises a step of preparing a silicone-modified polyester resin by copolymerizing a polyether polyol having a number average molecular weight of 100 to 1000, a reactive hydroxyl value of 100 mgKOH / g or more, and a silicone intermediate; And a silane having two or more alkoxy groups with respect to the hydroxyl equivalent of the silicone-modified polyester resin in two stages of polymerization at a ratio of 0.5 to 2 equivalents.

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

The self-curing silicone-modified polyester resin prepared in the present invention is excellent in storage stability at room temperature and at the same time to be cured by the silicone crosslinking reaction of the resin itself when heated to 150 ~ 200 ℃ to have a high heat resistance even at 250 ~ 400 ℃ It has its features.

In detail, a polyester polyol having a number average molecular weight of 1000 or less and a reactive hydroxyl value of 100 mgKOH / g or more is prepared, and a silicone polymer having a silicon content of 20 to 80% is polymerized by polymerizing a silicone polymer having a reactive hydroxyl group, a hydroxyl group or an alkoxy group of the polyol. A polyester resin is prepared. In this case, when the polyester polyol having a number average molecular weight of 1000 or more is used, mechanical properties such as adhesion and flexibility are improved, but heat resistance is significantly reduced, which is not preferable. The silicone content affecting the heat resistance is less than 20% of the silicone-modified polyester resin, poor heat yellowing resistance, and more than 80% is excellent in heat resistance, so it can withstand a long time at 400 ° C or higher, but it has high bending resistance, tensile strength, friction resistance, Since solvent resistance is poor, its content is very important. A silane having two or more alkoxy groups is added to a silicone-modified polyester resin having a silicon content of 20 to 80% by weight in an equivalence ratio of 0.5 to 2 to the hydroxyl equivalent value of the silicone-modified resin and reacted with a hydroxyl group of the silicone-modified resin. A self-curing silicone-modified polyester resin is produced by reaching a constant viscosity in the range of 20 ~ 70% of the phosphorus methanol outflow. At this time, the alkoxy silane used must have 2 or more reactive groups, and if it is used at 0.5 or less with respect to the hydroxyl equivalent value, the storage stability will be poor, and the crosslink density will be low during heat curing, and if it is 2 or more, it will be sensitive to moisture. Gel particles are generated as well as a high temperature is required for heat curing. At this time, in order to improve the sclerosis | hardenability at low temperature, it is preferable that the alkoxy group of a silane is a methoxy or an ethoxy group.

The structural formula of the silane which has two or more alkoxy groups used for this invention is as follows.

Dialkoxy silane trialkoxy silane tetraalkoxy silane

In the present invention, the polyester polyol has a molecular weight of 1000 or less and a hydroxyl value of 100 mgKOH / g or more, which is a mechanical strength is improved when the molecular weight of the polyol is 1000 or more, but the heat resistance is significantly weak, when the hydroxyl value is 100 mgKOH / g or less This is because the crosslinking density is lowered at the time of heat curing, and the physical properties of the cured product are significantly reduced.

The polyester polyol in the present invention was prepared and used through the reaction of a divalent or higher glycol with a divalent or higher carboxylic acid and its derivatives.

As glycols having a divalent or higher reactive hydroxyl group, ethylene glycol, propylene glycol, 1,4-butylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanediol, 2-butyl2-ethylpentane Dihydric glycols such as diol; Trivalent glycols such as trimethylolpropane, trimethylolethane, trihydroxyisocyanurate, glycerin; Tetrahydric glycols such as pentaerythritol can be used, and in the case of using linear glycols having a high molecular weight, the final resin can be used when the crosslink density of the final resin is small and when the glycol having a small molecular weight and a high reactive group is used. The bonding density of is high and it is easy to gelate during storage.

Therefore, in the present invention, a polyol was prepared by appropriately mixing divalent glycol and trivalent glycol.

Organic acids and derivatives thereof having a divalent or higher reactive carboxylic acid group, such as terephthalic acid and derivatives thereof, isophthalic acid and derivatives thereof, phthalic anhydride and derivatives thereof, divalent acids such as succinic acid, adipic acid and azelacic acid and trimellitic anhydride Trivalent acid can be used.

In the present invention, in order to prevent gelation during storage and to have an appropriate crosslinking density during heat curing, a number average molecular weight of 1000 or less and a reactive hydroxyl value of 100 mgKOH / g or more are used using divalent and trivalent glycols and divalent organic acids or derivatives thereof. It was made.

The production of silicone-modified polyester resin is carried out by gradually heating a silicone polymer having a polyester polyol having a number average molecular weight of 1000 or less and a hydroxyl value of 100 mgKOH / g or more and a reactive methoxy or silanol group to 100 to 200 ° C in the presence of a titanium catalyst. By-product methanol or effluent is removed to cool the resin and dilute as an organic solvent. If the viscosity becomes too high during the polymerization reaction, organic solvents such as esters, ethers and ketones can be added to lower the viscosity. At this time, it is not preferable to use aromatic hydrocarbons such as xylene and toluene as a solvent. In the dilution of the modified silicone-modified resin, an organic solvent having a relatively polar group such as ketones, ethers, and esters is used. This is because silicone-modified polyesters cannot be dissolved in solvents of aromatic or aliphatic hydrocarbons, and typical solvents that can be used are low boiling point methyl ethyl ketone, isopropyl acetate, acetone, isopropyl acetate, methyl acetate, methyl isobutyl Ketones, and the like, and cellosolbuacetate, cyclohexanone, methyl amyl ketone, diisobutyl ketone and isobutyl isobutylate for high boiling point. These may be used by mixing in an appropriate ratio, or as a diluent of the resin liquid dissolved therein, hydrocarbons such as xylene, toluene and the like may be mixed and used at a constant ratio.

Silicone-modified resins are prepared using low molecular weight polyols and reactive silicone intermediates, in which case silicone intermediates are important to exhibit heat resistance properties. Generally, silicon intermediates are roughly classified into those having a reactive methoxy group and those having a reactive silanol, and the intermediates having a methoxy group are highly reactive. This is because the boiling point of methanol, a reaction by-product generated during the reaction of the methoxy intermediate, is lower than the effluent generated by the reaction of the silanol intermediate.

Si-O-CH ₃ + HO-R → Si-OR + HOCH ₃ ↑ (reaction of methoxy intermediate)

Si-OH + HO-R ₁ → Si-O-R1 + H ₂ O ↑ (reaction of silanol intermediates)

After preparing the silicon intermediate, the difference in structure and physical properties is as follows. That is, the intermediate having a methoxy reactor is present in the liquid phase at room temperature and the content of methoxy groups capable of reacting with organic hydroxyl groups is 10 to 25% by weight, the weather resistance and workability in the production of silicone-modified polyester resin is good for coil coating It is suitable for use. Intermediates having silanol groups have a solid form at room temperature and have a hydroxyl content of about 2 to 10% by weight, and generally have high hardness when producing silicone-modified polyester resins.

Table 1 below shows representative methoxy and silanol intermediates that are commercially available.

Structural formula (1) is a silicon intermediate having a silanol reactor, and structural formula (2) is a silicon intermediate having an alkoxy reactor.

Wherein R is phenyl or methyl.

Wherein R is phenyl or methyl.

The silicon intermediate has a certain amount of organic substituents attached to the silicon, and the organic substituents may be generally divided into phenyl groups and methyl groups, and in some cases, may be substituted with methyl or propyl groups in consideration of compatibility with organic resins. Depending on the content of organic substituents, silicon intermediates have different compatibility with organic resins, temperature characteristics, and mechanical properties.In general, when the phenyl group content is high, the heat resistance, water resistance, and scratch resistance are high. The back is excellent.

Manufacturing method of self-curing silicone modified polyester resin

Since the silicone modified resin manufactured to have excellent storage properties by the conventional method cannot be self-cured, it has excellent thermal curing properties and mechanical properties of the cured product by using a generally widely used curing agent such as methoxy melamine or block isocyanate. However, when exposed to high temperature at 250 ~ 400 ℃ for a long time, yellowing occurs, gloss decreases, and mechanical properties deteriorate rapidly.

In the present invention, in order to overcome the disadvantages of the conventional resin, the alkoxy silane is copolymerized to form silicone crosslinks during heat curing to improve heat resistance.

The manufacturing method will be described in detail.

To the silicone-modified polyester resin solution diluted with an organic solvent, a silane containing a divalent or more reactive alkoxy group is added at a ratio of 0.5 to 2 equivalents of the hydroxyl equivalent value of the resin solution, and stirred sufficiently for about 30 minutes so that it can be uniformly mixed at 60 ° C. or lower. 0.01 to 1% by weight of alkoxy titanate is added, and then slowly heated to a temperature of 100 to 150 ° C. to remove the reaction effluent. When the amount of such effluent reaches 20 to 70%, it is rapidly cooled to 100 ° C. or lower and stored. In order to suppress a thickening phenomenon, alcoholic solvents, such as normal butanol, isopropyl alcohol, and isobutyl alcohol, are added, and are prepared by adding 2 to 6 weight% of a resin solution.

The paint composition using the thermosetting silicone modified resin prepared as described above is 30 to 60% by weight of the thermosetting silicone modified resin, 15 to 30% by weight of titanium dioxide, 5 to 10% by weight of zinc oxide, 0.1 to 5% by weight of magnesium silicate, zinc octo It can be prepared by mixing and stirring 0.01 to 1% by weight of the solvent, a solvent and other additives. The titanium dioxide, zinc oxide, magnesium silicate, zinc octoate serves to enhance the role and heat resistance of the pigment. Considering the general physical properties and heat resistance of the coating film it is appropriate to constitute a paint composition in the above content range.

Hereinafter, the present invention will be described in detail through examples. These examples are provided for effectively explaining the present invention, and do not limit the scope of the present invention.

Glycols having a divalent or higher reactive hydroxyl group and an organic carboxylic acid having a divalent or higher reactive carboxylic acid group were added to a four-necked flask, and 0.01 to 0.5% by weight of dibutyltin oxide, an ester reaction catalyst, was gradually heated to 140 to 250 ° C. After the reaction by-products were removed by the theoretical amount, when the resin became transparent and the carboxylic acid value became 10 mgKOH / g or less, it was cooled and diluted with the prepared solvent to terminate the reaction.

Table 2 shows a preparation example of the polyester polyol used in the present invention.

Preparation of Silicone Modified Polyester Resin

Preparation Example 1 (A)

770g of polyester polyol (P-1) resin solution and 500g of Dow Corning's Z-6018 with 5.5 wt% silanol content as a silicon intermediate were added to a four-necked flask with stirring, and 1 part by weight of tetrabutyl titanate was dissolved. In addition, the catalyst was completely dispersed by high-speed stirring, and heating was continued to gradually remove the reaction effluent while increasing the temperature to 100-200 ° C. When the reaction effluent reaches the theoretical amount (22.5 g), the reactant sample is poured into a glass plate, cooled to room temperature, and reaches a transparent state. When the reaction solution reaches a transparent state, the reactant is cooled, and 380 g of xylene solvent is added to give 60% of the resin solid content. A silicone modified resin having a Y-, a molecular weight of 8000, and a reactive hydroxyl value of 190 was prepared.

Preparation Example 2 (B)

770g of polyester polyol (P-2) resin solution and 500g of Shinnets KR216 with 5.5 wt% silanol content as a real medium were added to a four-necked flask with stirring, and 1g of tetraisopropyl titanate was added when the contents melted. In addition, the catalyst was completely dispersed by high-speed stirring, continued heating, and the reaction was heated up to 100-200 ° C. so that the reaction effluent came out. Then, when the reaction effluent (22.5 g) reached the theoretical amount, the reactant sample was flowed onto the glass plate. When cooled to room temperature, the reaction product was cooled, the reaction product was cooled, and 380 g of toluene solvent was added to dilute the resin solid content to 60%, thereby preparing a silicone-modified resin having a Gardner viscosity X + of 25 ° C, a molecular weight of 7000, and a reactive hydroxyl value of 160.

Preparation Example 3 (C)

770 g of polyester polyol (P-3) resin solution and 220 g of Wacker SY231 with 15 wt% of methoxy as a silicon intermediate were added to a four-necked flask with stirring, and 0.7 g of tetraisobutyl titanate was added to the mixture to stir at high speed. After completely dispersing and heating, it is heated up to 100 ~ 180 ℃ and the methanol is removed when the theoretical amount (33.6g) is removed. 200 g of solbu acetate solvent was added and diluted to 60% resin solid content to obtain a Gardner viscosity of W + at 25 ° C to prepare a silicone-modified resin having a molecular weight of 3000 and a hydroxyl value of 130.

Preparation of Self Curing Silicone Modified Polyester Resin

A silane containing a divalent or more reactive alkoxy group is added to the silicone-modified polyester resin solution diluted with an organic solvent at a ratio of 0.5 to 2 equivalents of the hydroxyl equivalent value of the resin solution, so that the mixture is uniformly mixed at 60 ° C. or less for about 30 minutes. After stirring and adding 0.01-0.2wt% of tetraisopropyl titanate, the reaction mixture is gradually heated to 100-150 ° C to remove the reaction effluent. When the viscosity of the resin solution reaches a certain level, it is rapidly cooled and stored below 100 ° C. In order to suppress the midpoint phenomenon in the solvent, solvents such as normal butanol, isopropyl alcohol, and isobutyl alcohol are added to 2 to 6 wt% of the resin solution.

The following Table 3 is a production example of a thermosetting silicone modified resin.

Silicone Modified Resin Comparative Example 1 (K-1)

Into a stirred four-necked flask, 770 g of polyester polyol (P-4), 550 g of SY231 from Wacker company with 15% methoxy content as a silicon intermediate, and 200 g of cellosolve acetate solvent were added, and 1 g of tetraisobutyl titanate was added while stirring. After the catalyst was completely dispersed, the mixture was heated, heated to a temperature of 100 to 180 ° C., and 25 g of methanol was removed. Then, the catalyst was rapidly cooled to 50 ° C. and 30 g of normal butanol was added thereto. In this way, a silicone modified resin having a number average molecular weight of 8500, a reactive hydroxyl value of 140, a nonvolatile resin solid content of 61%, and a viscosity of Y (Gardner, 25 ° C) was prepared.

Silicone Modified Resin Comparative Example 2 (K-2)

A silicone-modified resin was prepared in the same manner as in Comparative Example 1 except that polyol (P-5) was used. Number average molecular weight 9000, reactive hydroxyl value 150, non-volatile resin solid content 59%, viscosity Y + (Gardner, 25 degreeC).

Paint Production Example

The paint was prepared as follows using the thermosetting silicone-modified resin prepared above.

①Resin solution: 18 g

② xylene: 9g

③ Cellosol Part Acetate: 4.4g

④ Titanium Dioxide: 18g

⑤ Zinc oxide: 7 g

⑥Magnesium silicate: 1.5g

⑦ silicone wax: 1 g

⑧Acrylic Resin: 1g

⑨ Zinc octoate: 0.1 g

용 Resin solution: 40g

After mixing and stirring the materials from ① to ⑧, and when fluidity occurs, it is dispersed for 1 hour with a Red Devil Disperser, and when the particle size is 5μ or less, ⑨ and ⑩ are added and the mixture is stirred at a high speed so that the viscosity of the paint becomes 40 seconds with Pod Cup No. 4. It was.

Physical property test results of the paints prepared in the above examples are shown in Table 4 below.

*Test Methods

Heat resistance test: It carries out after hold | maintaining an initial stage cured coating film at 300 degreeC for 8 hours.

Storage: Measure the initial viscosity of the paint with Pod Cup No. 4, place it in a closed container for 7 days in an oven at 60 ° C, and measure the viscosity in the same manner.

Application: The dry coating is coated with an applicator to 30 탆 and then cured in a 200 ° C. hot air oven.

Curability: The number of times after the cotton glove was soaked with methyl ethyl ketone solvent until the coating was rubbed off.

Pencil hardness: MIT-UMI pencil test.

Flexibility: Determination of peeling of the coating film when the coated specimen is placed in a vise and bent at 180 °.

Adhesion: A thin film is cut on the coating film with an X-shape at intervals of 1 mm and the adhesion test is performed with a tape.

Impact property: Drop the weight of 500g on the coating film at 50cm height and check the peeling condition of the coating film.

Boiling resistance: Put the coated specimen in boiling water at 100 ℃ and leave for 4 hours to check the condition of the coating film.

As can be seen from Table 4, the paint of the present invention is not only excellent in curing conditions and storage properties, but also particularly excellent in heat resistance compared to the conventional one.

Claims (8)

1 step of preparing a silicone-modified polyester resin by copolymerizing a polyether polyol having a number average molecular weight of 100 to 1000 and a reactive hydroxyl value of 100 mgKOH / g or more with a silicone intermediate; And A method for producing a self-curing silicone-modified polyester resin comprising two steps of polymerizing a silane having two or more alkoxy groups to a hydroxyl equivalent of the silicone-modified polyester resin in a 0.5 to 2 equivalent ratio. The method of claim 1, The polyester polyol in the first step is a method of producing a self-curing silicone-modified polyester resin, characterized in that the copolymer of two or more kinds of glycols having two or more hydroxyl groups, and copolymerized two or more carboxylic acids or derivatives thereof. The method of claim 1, In one step, the silicone-modified polyester resin is a method of producing a self-curable silicone-modified polyester resin, characterized in that the copolymerization to produce a silicon content of 20 ~ 80wt%. The method of claim 1, When copolymerizing silicone-modified polyester resin in step 1, ketones composed of 25 to 100 parts by weight of methyl isobutyl ketone, methyl isoamyl ketone and cyclohexanone with respect to 100 parts by weight of copolymer, and normal butyl acetate, methyl amyl acetate and cellol A method of producing a self-curing silicone-modified polyester resin, characterized in that the copolymer further by adding at least one selected from the group consisting of solbu acetate, 2-ethylhexyl acetate and ethylene glycol diacetate as a solvent. The method of claim 1, Method for producing a self-curing silicone-modified polyester resin, characterized in that the silicon intermediate in the first step is 2 to 10wt% hydroxyl content or 10 to 25wt% alkoxy content. The method of claim 1, The silane having two or more alkoxy groups in two steps is selected from the compound of the following structural formula. Wherein R 'is methyl, ethyl, propyl or phenyl, R '' is methyl or ethyl. The method of claim 1, A method for producing a thermosetting silicone-modified polyester resin, characterized by further adding 0.01 to 1% by weight of alkoxy titanate in each of the first and second steps. 30 to 60% by weight of the self-curing silicone-modified ester resin prepared in claim 1; 15-30% by weight of titanium dioxide; 5-10 weight% of zinc oxide; 0.1-5% by weight of magnesium silicate; And 0.01-1% by weight of zinc octoate.