JP4217329B2 - Polyester resin and composition for powder coating, and powder coating using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester resin and composition for a powder coating material that can obtain a coating film having excellent slipperiness, and a powder coating material using the same.
[0002]
[Prior art]
Steel bookshelves, display shelves, and the like repeatedly put items in and out, so that the coating film is easily damaged by contact with the items, and the paint used for this is required to have scratch resistance. In addition, outdoor installations such as home appliances such as refrigerators and microwave ovens or vending machines are often contaminated with food, dust, and the like, and are required to have contamination resistance. In order to give scratch resistance and stain resistance to these coated objects, the frictional resistance of the coating surface is lowered to slide the contact object, making it difficult to get scratches and suppressing the adhesion of things that cause contamination. This method is effective.
[0003]
Conventionally, in order to obtain such a slippery coating film, a method of simply adding a lubricant such as wax or silicone oil to the paint has been performed. However, such a method has a problem that silicone and wax bleed out to the surface of the coating film when applied to a polyester resin-based paint having poor compatibility with these lubricants.
[0004]
As a method for solving the above-described drawbacks, a method in which a siloxane compound such as siloxane diol is copolymerized in a resin has been proposed (Japanese Patent Laid-Open Nos. 8-151537 and 8-143790). However, the siloxane compound has poor compatibility with the polyester resin, and the hydroxyl group directly bonded to the silicon atom has a low reactivity, so that it is difficult to copolymerize, and the unreacted siloxane compound bleeds out.
[0005]
[Problems to be solved by the invention]
The present invention solves such a problem, and a polyester resin and composition for powder coatings capable of obtaining a coating film excellent in slipperiness without bleeding out of a siloxane compound, and a powder using the same A paint is provided.
[0006]
[Means for Solving the Problems]
As a result of repeated studies to solve the above problems, the present inventors have found that this object can be achieved by using a polyester resin copolymerized with a specific siloxane compound, and have reached the present invention. That is, the gist of the present invention is as follows.
(1) A block copolymer of a polyorganosiloxane and an aliphatic polyester is 0.5 to 20 with respect to a polyester composed of an acid component mainly composed of an aromatic dicarboxylic acid and an alcohol component mainly composed of an aliphatic diol. A polyester resin for powder coatings, which is copolymerized so as to have a weight%, has an intrinsic viscosity of 0.10 to 0.40 dl / g, and a hydroxyl value of 15 to 75 mgKOH / g.
(2) above (1) and the powder coating polyester resin according, for powder coating polyester resin composition comprising a curing agent having a functional group reactive with a hydroxyl group of the Poriesu ether resin.
(3) A powder coating using the polyester resin composition for powder coating described in (2) above.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0008]
The polyester resin of the present invention contains an acid component mainly composed of aromatic dicarboxylic acid and an alcohol component mainly composed of aliphatic diol as essential components.
[0009]
As the aromatic dicarboxylic acid, terephthalic acid and isophthalic acid are mainly used because of the required resin properties and cost performance. As required, 5-sodium sulfoisophthalic acid, phthalic anhydride, naphthalenedicarboxylic acid Adipic acid such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid, alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid, and the like may be used in combination. In addition, trifunctional or higher functional carboxylic acids such as trimellitic acid, pyromellitic acid and trimesic acid can be used in combination as long as the polyester resin is not gelled.
[0010]
As the aliphatic diol, neopentyl glycol and ethylene glycol are mainly used for reasons such as required resin characteristics and cost performance, but diethylene glycol, propylene glycol, 1,4-butanediol, 1, Aromatics such as aliphatic glycols such as 6-hexanediol, alicyclic glycols such as 1,4-cyclohexanedimethanol and 1,4-cyclohexanediol, bisphenol A ethylene oxide adducts, bisphenol S ethylene oxide adducts, etc. A small amount of glycol may be used in combination. In addition, trifunctional or higher functional polyols such as trimethylolpropane, glycerin and pentaerythritol can be used in combination as long as the polyester resin is not gelled.
[0011]
Furthermore, the polyester resin may be copolymerized with a small amount of an oxycarboxylic acid component such as 4-hydroxybenzoic acid or ε-caprolactone as long as the characteristics of the present invention are not impaired.
[0012]
The intrinsic viscosity of the polyester resin needs to be in the range of 0.10 to 0.40 dl / g, and preferably in the range of 0.15 to 0.35 dl / g. When the intrinsic viscosity is less than 0.15 dl / g, the molecular weight of the resin is low, so that the mechanical strength of the coating film is reduced or the blocking resistance when a powder coating is used is reduced. On the other hand, when the intrinsic viscosity exceeds 0.40 dl / g, the resin has a high molecular weight, so that the pulverization property of the coating is deteriorated or the fluidity of the coating is lowered and the smoothness of the coating film is deteriorated.
[0013]
The hydroxyl value of the polyester resin needs to be in the range of 15 to 75 mgKOH / g, and preferably in the range of 20 to 70 mgKOH / g. When the hydroxyl value is less than 15 mgKOH / g, the molecular weight of the resin becomes too high and the fluidity is lowered, resulting in large irregularities on the surface of the coating film, and the smoothness is lowered. On the other hand, when the hydroxyl value exceeds 75 mgKOH / g, the molecular weight of the resin becomes too low and the mechanical strength of the coating film decreases.
[0014]
The polyester resin of the present invention contains a block copolymer of polyorganosiloxane and aliphatic polyester (hereinafter referred to as “block copolymer”) in addition to the above-mentioned aromatic dicarboxylic acid component and aliphatic diol component. It is necessary to make it. “Contained” here means that the block copolymer is copolymerized or blended with the polyester resin. And, by containing this block copolymer, the affinity with the polyester resin is improved, and when it is used as a powder coating, a siloxane compound does not bleed out and a coating film with excellent slipperiness is obtained. Can do.
[0015]
The proportion of the block copolymer needs to be in the range of 0.5 to 20% by weight in the polyester resin, and is preferably in the range of 1 to 10% by weight. When this ratio is less than 0.5% by weight, the frictional resistance of the coating film is large and the slipperiness is insufficient. On the other hand, when this ratio exceeds 20% by weight, not only the frictional resistance and slipperiness effect of the coating film are saturated, but also the glass transition temperature of the polyester resin is lowered, and the blocking resistance when a powder coating is obtained. Decreases.
[0016]
Examples of the polyorganosiloxane block constituting the block copolymer include a modified polyorganosiloxane having a Si—H bond and a polyorganosiloxane having a functional group bonded to a silicon atom via an alkylene group. More specifically, alcohol-modified polyorganosiloxane having hydroxymethyl group, hydroxyethyl group, hydroxypropyl group, etc., amino-modified polyorganosiloxane having aminoethyl group, aminopropyl, etc., carboxylic acid modification having carboxyethyl group, etc. Examples thereof include polyorganosiloxane, and polyether-modified polyorganosiloxane having a polyether bond in which an alkylene oxide such as ethylene oxide or propylene oxide is added to these functional groups. Of these, polyether-modified polyorganosiloxane and carboxylic acid-modified polyorganosiloxane are preferred because they are easy to produce and have excellent heat resistance.
[0017]
On the other hand, aliphatic polyester blocks constituting the block copolymer include aliphatic polyesters obtained by ring-opening polymerization of cyclic lactones such as β-propiolactone, δ-valerolactone, and ε-caprolactone, adipic acid, and sebacin. Examples include aliphatic polyesters composed of aliphatic dicarboxylic acids such as acids and dodecanedioic acid and aliphatic glycols such as ethylene glycol, neopentyl glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and 1,6-hexanediol. Of these, aliphatic polyesters obtained by ring-opening polymerization of cyclic lactones are preferred, and polycaprolactone obtained by ring-opening polymerization of ε-caprolactone is particularly preferred.
[0018]
The ratio of the polyorganosiloxane block to the aliphatic polyester block in the block copolymer is preferably in the range of 90/10 to 30/70 by weight, and preferably in the range of 70/30 to 40/60. Particularly preferred. When the proportion of the polyorganosiloxane block is less than 30% by weight, the glass transition temperature of the polyester resin is lowered, the blocking resistance when used as a paint is deteriorated, and the slipperiness of the coating film is insufficient. . On the other hand, when the ratio of the polyorganosiloxane block exceeds 90% by weight, the compatibility with the polyester resin is deteriorated, and the block copolymer bleeds out on the surface of the coating film or the block copolymer is uniformly contained. I can't do that.
[0019]
The block copolymer is a polyorganosiloxane block having a number average molecular weight of 500 to 35000, an aliphatic polyester block having a number average molecular weight of 100 to 39000, and a block copolymer having a number average molecular weight of 600 to 40,000. preferable. When the number average molecular weight of the polyorganosiloxane block is less than 500, the slipperiness of the coating film is poor. On the other hand, if the number average molecular weight of the polyorganosiloxane block exceeds 35000, the compatibility with the polyester resin will be poor, and the block copolymer will bleed out on the surface of the coating, or the block copolymer will be contained uniformly. There are times when you can't.
[0020]
The polyester resin satisfying the above characteristics is made from an acid component such as aromatic digalbonic acid, an alcohol component such as aliphatic diol (including ester-forming derivatives thereof) and a block copolymer as raw materials, After esterification or transesterification at a temperature of 200 to 280 ° C, a polycondensation reaction is performed at a temperature of 200 to 300 ° C, preferably 230 to 290 ° C under a reduced pressure of 5 hPa or less to obtain a polyester having a high degree of polymerization. Furthermore, it can be prepared by a method in which an alcohol component such as trimethylolpropane, neopentyl glycol, glycerin or the like is added to perform a depolymerization reaction.
[0021]
Alternatively, an acid component such as an aromatic dicarboxylic acid, an alcohol component such as an aliphatic diol (including ester-forming derivatives thereof) and a block copolymer are used as raw materials, and the ester is formed at a temperature of 200 to 280 ° C. by a conventional method. By a polycondensation reaction under normal pressure or reduced pressure of about 50 to 100 hPa at a temperature of 200 to 300 ° C., preferably 220 to 280 ° C., until a predetermined intrinsic viscosity is obtained. Can also be prepared.
[0022]
In the esterification, transesterification reaction and polycondensation reaction, a conventionally known reaction catalyst or the like can be used.
[0023]
Furthermore, a polyester resin satisfying the above characteristics is obtained by using an acid component such as aromatic digalbonic acid and an alcohol component such as an aliphatic diol (including ester-forming derivatives thereof), It can also be prepared by melt-kneading the block copolymer described above.
[0024]
The polyester resin composition of this invention needs to mix | blend the hardening | curing agent which has a functional group which reacts with the hydroxyl group of a polyester resin in the said polyester resin. As the curing agent, an isocyanate curing agent is preferable. Moreover, you may add hardening accelerators, such as a tin compound, as needed.
[0025]
Examples of the isocyanate curing agent include ε-caprolactam blocked isophorone diisocyanate blocked with a blocking agent such as ε-caprolactam, and uretdione-bonded isocyanate which is a self-blocking type. Examples of such ε-caprolactam-blocked isophorone diisocyanate include “Vestagon B 1530” manufactured by Huls, and “Clelan U-1” manufactured by Bayer. In addition, examples of uretdione-linked isocyanate include those manufactured by Huls. “Vestagon BF 1540” can be mentioned, but “Vestagon B 1530” is preferable from the viewpoint of coating film performance.
[0026]
As the tin-based curing accelerator, a dioctyl tin maleate-based curing catalyst is preferable, and “Stann OMF” manufactured by Sansha Co., Ltd. may be mentioned.
[0027]
The blending amount of the curing agent is suitably 0.8 to 1.2 times equivalent, preferably 1.0 times equivalent to the hydroxyl value of the polyester resin. Further, the blending amount of the curing accelerator is preferably 0.4 to 1.0 part by weight with respect to 100 parts by weight of the total of the polyester resin and the curing agent, from the viewpoint that both the smoothness of the coating film and the curability of the paint can be achieved.
[0028]
The powder coating material of the present invention comprises the above-described polyester resin, curing agent, and curing accelerator, if necessary, a conventionally known leveling agent and other additives such as pigments such as titanium dioxide and carbon black. The mixture can be prepared by melt-kneading at 70 to 150 ° C. using a kneader or a roll.
[0029]
The obtained powder coating material is applied to an object to be coated, and is usually baked at a temperature of 170 to 200 ° C. for 15 to 25 minutes to give a coating film having excellent slipperiness.
[0030]
[Action]
When the resin composition for powder coatings of the present invention is used, the reason why a coating film excellent in slipperiness can be formed without bleeding out of the block copolymer is that the block copolymer is constituted. This is presumably because the aliphatic polyester block present improves the affinity with the polyester resin.
[0031]
【Example】
Next, the present invention will be specifically described with reference to Examples and Comparative Examples.
In Examples and Comparative Examples, the characteristic values of the polyester resin and the performance evaluation of the powder paint and the coating film were measured by the following methods.
(a) The measurement was carried out at 20 ° C. using an equal weight mixture of intrinsic viscosity phenol and ethane tetrachloride as a solvent.
(b) After acetylation with hydroxyl group acetic anhydride, titration was performed with 0.5 N potassium hydroxide methanol solution.
(c) Using a glass transition temperature differential scanning calorimeter (DSC-220, manufactured by Seiko Denshi Kogyo Co., Ltd.), the temperature was determined at a heating rate of 10 ° C / min.
(d) Anti-blocking diameter 3cm, 7cm high bottomed glass tube with powder coating up to 4cm in height, left in a constant temperature bath at 40 ° C for 1 week, then the glass tube is inverted and powdered The paint was taken out and evaluated in the following two stages depending on the state of the paint.
○: There is no lump in the paint, or the lump is small and cannot be lifted by hand.
X: There is a large lump in which the paint is agglomerated and solidified, and the lump can be lifted by hand.
(e) Smoothness The smoothness of the coating film was visually evaluated in the following two stages.
◯: The coating film has few irregularities and good smoothness.
X: The coating film has large unevenness and the smoothness is not good.
(f) 60 degree specular gloss
Determined according to JIS K 5400.
(g) Impact resistance
In accordance with JIS K 5400, a coated steel plate is sandwiched between a shooting type with a spherical surface with a diameter of 1.27 cm and a cradle with a hollow corresponding to it, and a weight of 1 kg is placed vertically from above the coated steel plate. The height at which the coating film was destroyed was determined. (If this value is 30cm or more, it is acceptable.)
(h) Eriksen
Determined according to JIS Z 2247.
○: No cracking occurs in the coating film even if it is extruded 9 mm or more.
X: A crack occurs in the coating film when extruded 9 mm or more.
(i) Dynamic friction coefficient
In accordance with JIS K 7125, the frictional resistance between the chrome-plated slider and the coating surface was measured to determine the dynamic friction coefficient. (If this value is 0.2 or less, it is acceptable.)
[0032]
Examples 1-9 and Comparative Examples 1-4
Dicarboxylic acids, diols and block copolymers shown in Tables 1 to 3 were used in the amounts shown in Tables 1 to 3 (however, in mol parts for dicarboxylic acids and diols, in weight percent in the polyester resin for block copolymers). In the esterification reaction vessel, the esterification reaction was carried out at a pressure of 0.3 MPaG and a temperature of 260 ° C. for 4 hours.
After the obtained esterified product was transferred to a polycondensation reaction tank, antimony trioxide 3.2 × 10 ⁻⁴ mol / acid component 1 mol was added, the pressure was reduced to 0.5 hPa, and a polycondensation reaction was performed at 280 ° C. for 4 hours. A polyester having an intrinsic viscosity of 0.45 dl / g was obtained.
Next, the depolymerizing agent shown in Tables 1 to 3 was added to this polyester in the amounts (mole parts) shown in Tables 1 to 3, and a depolymerization reaction was performed at 270 ° C. for 1 hour under normal pressure. A polyester resin having a characteristic value of ˜3 was obtained.
Ε-Caprolactam block type isophorone diisocyanate curing agent ("Vestagon B 1530" manufactured by Huls), dioctyltin maleate-based curing catalyst ("Stann OMF" manufactured by Sansha Co., Ltd.), butyl polyacrylate Leveling agent (BASF "Acronal 4F"), benzoin and rutile type titanium dioxide pigment (Ishihara Sangyo "Taipeku CR-90") are added in the amounts (parts by weight) shown in Tables 1 to 3, and Henschel mixer (Mitsui Miike Seisakusho, FM 10B) After dry blending, using Kneader (Buss, PR-46), melt kneaded at 125 ° C, cooled, crushed, 140 mesh (106μm) The powder coating was obtained by classifying with a wire mesh.
The obtained powder coating material was electrostatically coated on a zinc phosphate-treated steel sheet so as to have a film thickness of 50 to 60 μm, and baked at 180 ° C. for 20 minutes.
[0034]
Comparative Example 5
A polyester resin was obtained in the same manner as in Example 1 except that polydimethylsiloxane diol (with a molecular weight of 1000, added by 10% by weight) was used instead of the block copolymer.
In this polyester resin, since a bleedout of polydimethylsiloxane diol was observed on the resin surface, no powder coating was prepared.
[0035]
Tables 1 to 3 show the production conditions and characteristic values of polyester resins in Examples 1 to 9 and Comparative Examples 1 to 5, coating composition and performance, and evaluation results of coating film performance.
[0036]
[Table 1]
[0037]
[Table 2]
[0038]
[Table 3]
[0039]
All of the coating films obtained in Examples 1 to 9 had no bleed-out of the silicone compound, good mechanical properties, a small coefficient of dynamic friction on the coating film surface, and excellent slipperiness. Moreover, the blocking resistance of the powder coating was also good.
[0040]
In contrast, the comparative example has the following problems.
In Comparative Example 1, since the block copolymer was not copolymerized with the polyester resin, the dynamic friction coefficient on the coating film surface was high, and the slipperiness was poor.
In Comparative Example 2, since the copolymerization amount of the block copolymer was large, the glass transition temperature of the polyester resin was lowered, and the blocking resistance of the powder coating was inferior.
In Comparative Example 3, it was difficult to obtain a powder coating because the intrinsic viscosity of the polyester resin was large.
In Comparative Example 4, since the intrinsic viscosity of the polyester resin was small, the impact resistance of the coating film and the mechanical strength such as elixir were low, and the blocking resistance of the paint was also inferior.
[0041]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the polyester resin for powder coating materials and composition which can form the coating film excellent in slipperiness without bleeding out a siloxane compound, and a powder coating material using the same are obtained. .

Claims (3)

An acid component and an aliphatic diol mainly composed of aromatic dicarboxylic acids the polyester composed of an alcohol component mainly, a block copolymer of polyorganosiloxane and aliphatic polyester and 0.5 to 20 wt% A polyester resin for powder coatings, characterized by being copolymerized to have an intrinsic viscosity of 0.10 to 0.40 dl / g and a hydroxyl value of 15 to 75 mgKOH / g. A powder coating polyester resin of claim 1 wherein, for powder coating polyester resin composition comprising a curing agent having a functional group reactive with a hydroxyl group of the Poriesu ether resin.   The powder coating material using the polyester resin composition for powder coating materials of Claim 2.