JPH0470331B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a thermosetting resin useful for paints, especially for powder paints, and more particularly, it relates to a method for producing a thermosetting resin useful for paints, especially for powder paints, and more particularly, it relates to a method for producing a thermosetting resin useful for paints, especially for powder paints, and more particularly, it relates to a method for producing a thermosetting resin useful for paints, especially for powder paints, and more particularly, it relates to a method for producing a thermosetting resin useful for paints, especially powder paints, and more particularly, it relates to a method for producing a thermosetting resin useful for paints, especially powder paints, and more particularly, it relates to a method for producing a thermosetting resin useful for paints, especially powder paints. The present invention relates to a method for producing a specific thermosetting resin for powder coatings modified with a specific compound. A composition containing a so-called thermosetting resin as an essential resin component, such as polyester, acrylic, or epoxy resin, on the surface of a material such as metal by powder coating (hereinafter, these are referred to as thermosetting resin compositions). It is known to coat objects (referred to as objects).
In recent years, it has been widely used for decorative coatings, especially as a pollution control measure or because it is suitable for automation. By the way, thick film coating has been the characteristic of conventional powder coating, but in recent years, thinner films have been developed from the perspective of resource conservation or for the development of applications for automobile top coats. It is becoming more and more required. When trying to apply conventional powder coatings to thin films in order to meet the demands of the times, conventional paints generally do not have sufficient smoothness in thin films.
The reality is that there is currently no satisfactory powder coating that meets the demand for thinner coatings. However, as a result of intensive studies in view of the current situation, the present inventors discovered that a thermosetting resin into which a specific silicon-containing compound was introduced is very effective in improving the smoothness of a thin film, and the present invention has been developed based on this finding. I have reached the point where I have completed it. That is, the present invention provides thermosetting resins selected from the group consisting of polyesters, epoxy resins, and vinyl polymers or their resin-forming components, with 0.01 to 30% based on the weight of these resins or resin-forming components. A silicon-containing compound (hereinafter also referred to as a silyl group-containing compound) having no vinyl polymerizable unsaturated bond is reacted within the range of
The object of the present invention is to provide a method for producing a thermosetting resin for powder coatings modified with the silicon-containing compound (silyl group-containing compound). In the present invention, the above-mentioned resin-forming component is not limited to only intermediates, but is used in a broad sense, including monomers, as in the case of vinyl polymers. Therefore, when referring to the resin-forming component, both the intermediate in the case of polyester and the respective monomers in the case of vinyl polymer are used without distinction. Here, typical silicon-containing compounds include organosilane carboxylic acids such as trimethylsilylacetic acid; organosilicon isocyanates such as trimethylsilicon isocyanate; organosilicon isothiocyanates such as trimethylsilicon isothiocyanate; organosilthians such as silthian; organomercaptosilanes such as trimethoxypropylmercaptosilane; organoalkoxysilanes such as methoxytrimethylsilane; organosilanols such as trimethylcyanol; or aminosilanes such as N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane. The amount of the silicon-containing compound used is 0.01 to 30% by weight, preferably 0.01 to 30% by weight in the thermosetting resin.
In proportions ranging from 0.1 to 20% by weight. If the amount of the silicon-containing compound in the thermosetting resin is less than 0.01% by weight, the modification effect is insufficient, and if it exceeds 30% by weight, gelation may occur. Both are unfavorable because they make it easier to do so. On the other hand, as the above-mentioned thermosetting resin, conventionally known thermosetting resins can be used as they are, and among them, representative ones include polyester type, vinyl polymer type, and epoxy resin type. First of all, polyester-based thermosetting resins include both those that are made by adding a curing agent to polyester obtained from polyhydric alcohol and polyhydric carboxylic acid, and those that are already self-crosslinking and hardening. Typical vinyl polymer thermosetting resins include resins or compounds that have functional groups such as hydroxyl groups, glycidyl groups, carboxyl groups, or oxazolinyl groups. Vinyl copolymers obtained from vinyl monomers and other vinyl monomers mixed with a curing agent, and vinyl copolymers with self-crosslinking functional groups such as butoxymethylamide groups. It may be a combination of vinyl copolymers, or it may be a combination of both types of vinyl copolymers mentioned above modified with epoxy resin, polyester resin, or the like. Here, the curing agent to be used is determined depending on the functional group of each polyester-based or vinyl polymer-based polymer as described above. For example, if this functional group is a hydroxyl group,
Curing agents such as amino resins such as hexamethoxymethylmelamine or tetrabutoxybenzoquanamine; or blocked polyisocyanates can be used, and if the functional group is a carboxyl group, curing agents such as epoxy resins or polyoxazolines can be used. However, when the functional group is a glycidyl group, it is preferable to use compounds such as polyhydric carboxylic acids or polyhydric phenols as the curing agent. Furthermore, typical examples of the above-mentioned epoxy resin-based thermosetting resins include a combination of a bisphenol type or ester type polyvalent epoxy compound and a curing agent such as amines or acids. be. To describe the method of the present invention in more detail, when modifying the various thermosetting resins shown above with the silicon-containing compounds mentioned above, the silicon-containing compounds include amino groups, as mentioned above, There are those that have functional groups such as glycidyl groups, hydroxyl groups, or mercapto groups, and those that do not have such special functional groups, and any of them can be used for the modification, but this is one of the objects of the present invention. In order to improve the smoothness of the thin film, the former type of so-called functional group-containing silicon-containing compounds are preferred. Therefore, in carrying out the method of the present invention, if a silicon-containing compound containing an amino group is used, it is necessary to react with the amino group in the thermosetting resin component to be modified. If a thermosetting resin contains a glycidyl group or an acid group, the silicon-containing compound can be introduced into the thermosetting resin through each functional group in both components. Next, regarding the silicon-containing compound containing a glycidyl group, the thermosetting resin component to be modified contains an amino group, an amide group, an acid group, or a hydroxyl group that reacts with the glycidyl group. If the silicon-containing compound contains an alkoxy group, it is possible to introduce the silicon-containing compound into the thermosetting resin through each functional group in both components. If some of the resin components contain hydroxyl groups that are reactive with this alkoxy group, the silicon-containing compound of the thermosetting resin can be removed through an exchange reaction between these alkoxy groups and hydroxyl groups. Furthermore, for silicon-containing compounds containing mercapto groups or hydroxyl groups, the thermosetting resin component to be modified may contain
If there is a product that contains acid groups or glycidyl groups that are reactive with these mercapto groups or hydroxyl groups, it can be added to the thermosetting resin through arbitrary reactions between the functional groups in each of these components. The silicon-containing compound can be introduced into. As described above, in the method of the present invention, various silicon-containing compounds are introduced into the thermosetting resin through modification with the silicon-containing compound. ,
In other words, for example, as in the case of the above-mentioned vinyl polymer-based resin, a method may be used in which various silicon-containing compounds are simultaneously blended and polymerized at the time of charging each vinyl monomer as a resin-forming component. First, a thermosetting resin is prepared in advance, and then a silicon-containing compound containing a functional group that is reactive with the functional group in the obtained resin is combined with the resin to form a thermosetting resin. It goes without saying that the reaction may be carried out by a method such as a reaction between functional groups, and any known and commonly used polymerization method or reaction method can be used in any of these methods. The thus obtained thermosetting resin modified with a silicon-containing compound can be directly applied as a paint, especially as a powder coating, in applications where conventional (powder) coatings are used, but This modified resin has the advantage of excellent coating surface smoothness in a thin film state, and is therefore particularly useful for applications that require thin films, such as automobile top coats. Next, the present invention will be explained in detail with reference to Examples and Comparative Examples, but all parts and percentages hereinafter are based on weight. Example 1 In a reactor equipped with a thermometer, a stirrer and a reflux condenser, 100 parts of xylene was added and heated to 125°C, and 40 parts of styrene, 28 parts of glycidyl methacrylate, and 2 parts of β-hydroxypropyl methacrylate were added thereto. A mixture of 29 parts of isobutyl methacrylate, 1 part of γ-glycidoxypropyltrimethoxysilane, 4 parts of azobisisobutyronitrile and 1 part of t-butyl perbenzoate was added dropwise over 2 hours, and the mixture was heated to the same temperature. After holding for 10 hours,
A solvent mixture of xylene and methanol produced through a modification reaction is removed to obtain a material with a softening point (ring and ball method; hereinafter the same) of 109°C and a number average molecular weight of 5000.
A vinyl polymer thermosetting resin modified with a silicon-containing compound was obtained. At this time, the removed solvent mixture was subjected to gas chromatography, and the point at which a predetermined amount of methanol was confirmed was defined as the end point of the modification reaction. Next, 85 parts of the modified resin obtained here, 1,
15 parts of 10-decanedicarboxylic acid, "Modaflow"
(Fluidity adjuster made by Monsanto, USA) and 25 parts of titanium oxide were heated to 100°C using three rolls.
After kneading with a 150-mesh wire mesh, a powder coating with a mesh size of 150 mesh or less was obtained. Example 2 In the same manner as used in Example 1, 100 parts of xylene was placed in a reactor and heated to 125°C, followed by 40 parts of styrene, 30 parts of glycidyl methacrylate,
A mixture of 29 parts of isobutyl methacrylate, 1 part of γ-aminopropyltrimethoxysilane, 4 parts of azobisisobutyronitrile and 1 part of t-butyl perbenzoate was added over a period of 2 hours, and 10 parts of A modification reaction was carried out by holding the resin for an additional period of time to obtain a solution of a vinyl polymer thermosetting resin into which a silicon-containing compound had been introduced. The amount of hydroxyl groups was determined by measuring the hydroxyl value, and it was confirmed that the hydroxyl group had a predetermined value. Next, the solvent is removed from this resin solution, and the softening point is 108°C and the number average molecular weight is 5000.
A modified thermosetting resin containing hydroxyl groups was obtained. Thereafter, a powder coating material was obtained in the same manner as in Example 1 except that this modified resin was used. Comparative Example 1 An unmodified resin for comparison was obtained by repeating the same procedure as in Example 2, except that the amount of glycidyl methacrylate used was increased to 31 parts, but no silicon-containing compound was used, and then A powder coating containing the resin was obtained. Example 3 A mixture consisting of 43 parts of 1,6-hexanediol, 466 parts of neopentyl glycol, 440 parts of dimethyl terephthalate, and 0.5 parts of zinc acetate was charged into a reaction vessel, and the methanol produced was removed from the system. While gradually increasing the temperature to 210℃,
Thereafter, the same temperature was maintained for 2 hours to continue the alcohol conversion reaction. Then 394 parts of isophthalic acid, and di-n
- Add 0.5 part of butyltin oxide, raise the temperature to 240°C over 8 hours, and then perform dehydration condensation at the same temperature to obtain an intermediate polyester with a hydroxyl value of 38 and an acid value of 6. Ta. Then, 10 parts of γ-glycidoxypropyltrimethoxysilane was reacted with 1000 parts of this intermediate polyester at 200°C to obtain a product with a softening point of 110°C, a hydroxyl value of 40, and A modified thermosetting resin containing hydroxyl groups and having an acid value of 3 was obtained. Next, for 85 parts of this modified resin, 15 parts of "B-1530" (isophorone diisocyanate adduct manufactured by Huels, West Germany; isocyanate group content = 15%) was used as a curing agent. A powder coating was obtained in the same manner as in Example 1 except for this. Example 4 2 equipped with thermometer, stirring device and heating device
In a four-necked flask, 800 parts of "Epicote 1004" (bisphenol A type epoxy resin manufactured by Schier, Netherlands) and N-β-(aminoethyl)-
15 parts of γ-aminopropyltrimethoxysilane were dissolved in 400 parts of xylene and reacted at 140°C for 3 hours, and the reaction mixture was heated to 160°C under reduced pressure.
Solvent removal at ℃ to remove xylene,
A modified thermosetting resin was obtained. Next, for 75 parts of this modified resin, 25 parts of "Findik M-8540" [acid type polyester manufactured by Dainippon Ink and Chemicals Co., Ltd.] as a curing agent was used. A powder coating material was obtained in the same manner as in Example 1. Comparative Example 2 A control unmodified resin was obtained in the same manner as in Example 3, except that no silicone compound was used, and then a control powder coating was obtained. Comparative Example 3 A control unmodified resin was obtained in the same manner as in Example 4, except that no silicone compound was used at all, and then a control powder coating was obtained. Each powder coating obtained in each example and comparative example was applied separately to a zinc phosphate-treated steel plate by electrostatic spraying, and then baked at 170°C for 20 minutes to form a coating film with a dry film thickness of 30 μm. I got it. A coating surface smoothness test was attempted for each of these coating films, and the results shown in Table 1 were obtained. 【table】

Claims (1)

[Claims] 1. A thermosetting resin selected from the group consisting of polyester, epoxy resin, and vinyl polymer or its resin-forming component is added with vinyl in an amount of 0.01 to 30% based on the weight of these resins or resin-forming components. A method for producing a thermosetting resin for powder coatings modified with the above-mentioned silicon-containing compound, the method comprising reacting a silicon compound having no polymerizable unsaturated bonds.