JP4060781B2 - Method for modifying silicate compounds - Google Patents

Description

  The present invention relates to a method for modifying a silicate compound and a modified silicate obtained thereby.

It is known that a silicate compound, which is a condensate of tetraalkoxysilane, is added to a coating material to make the coating film surface hydrophilic by moving to the surface and hydrolyzing it when forming the coating film. It is known that the molecular weight affects the transferability of the silicate compound to the surface, and when the molecular weight is increased, the compatibility with the binder component of the coating is lowered, and the transferability to the surface is increased. If the molecular weight of the silicate compound can be adjusted, it is expected that excellent transferability to the surface can be secured for a paint containing a special binder such as a highly hydrophobic fluororesin.
However, it is difficult to control the degree of hydrolysis condensation using water to adjust the molecular weight of the silicate compound, it is difficult to reproducibly, or there is a problem with the stability of the resulting condensate. Yes. Therefore, there are only a few types of silicate compounds that are actually commercially available.

On the other hand, a modified condensate of alkoxysilane having at least one polyoxyalkylene group and an alkoxy group and a method for producing the same are disclosed as silicate compounds having excellent compatibility with water-based paints (see, for example, Patent Document 1). . However, this production method cannot adjust the molecular weight of the silicate compound.
WO99 / 05228 pamphlet (pages 4-7)

  An object of the present invention is to provide a method for adjusting the molecular weight of a silicate compound that is reproducible and has no problem with the stability of the resulting condensate.

The method for modifying a silicate compound according to the present invention is a method for modifying a silicate compound in which a silicate compound having an alkoxy group bonded to an average of 6 or more Si atoms is reacted with a diol to obtain a reaction mixture. The molecular weight of the diol is 160 or less. The SiO ₂ concentration of the reaction mixture is 70% or more of the SiO ₂ concentration of the silicate compound. Here, the alkoxy group bonded to the Si atom may be a methoxy group and / or an ethoxy group, and a part thereof is a propyloxy group, a butoxy group, a benzyloxy group, a 2-butoxyethyloxy group, 3 It may be substituted with a -methoxy-1-propyloxy group. The calculated molecular weight of the silicate compound may be 258-3500. Furthermore, in the reaction with the diol, a monovalent alcohol having an alkoxy group different from the alkoxy group bonded to the Si atom can coexist, and the monovalent alcohol includes methanol, ethanol, propanol, It can be selected from butanol, benzyl alcohol, butyl cellosolve, 3-methoxy-1-propanol. Further, the amount of the diol may be 0.6 mol times or less of the silicate compound, and the weight average molecular weight of the reaction mixture may be 1000 to 20000.

  Further, in the method for modifying a silicate compound of the present invention, the reaction with the diol is performed in multiple stages, and the amount of the diol used in the first stage reaction is not more than 0.6 mol times the amount of the silicate compound. The amount of diol used in the reaction in each stage after the second stage may be 0.6 mol times or less of the diol used in the reaction in the immediately preceding stage. Furthermore, the total amount of diols used in the multistage reaction may be 1 mol or less of the silicate compound, and the weight average molecular weight of the reaction mixture may be 2400-50000.

  The modified silicate of the present invention is obtained by the above-described method for modifying a silicate compound. In the modified silicate of the present invention, one alkoxy group is removed from the condensate of tetraalkoxysilane to the oxygen atoms at both ends of the diol unit obtained by removing hydrogen atoms from two hydroxyl groups of a diol having a molecular weight of 160 or less. It consists of a compound having a structure in which silicate units are bonded to each other. Here, at least one of the silicate units may be bonded to another silicate unit via another diol unit, and may have a weight average molecular weight of 1,000 to 50,000.

  The coating composition of the present invention contains the aforementioned modified silicate and contains a fluororesin as a binder component. Here, it is preferable that the fluorine content of the fluororesin is 15% or more.

The method for modifying a silicate compound of the present invention is reproducible and the resulting condensate is stable. Moreover, since the SiO ₂ concentration of the resulting modified silicate is not greatly reduced, the molecular weight of the silicate compound can be substantially increased.

  This is considered to be because two molecules of the silicate compound can be efficiently reacted with one molecule of the diol by regulating the molecular weight and the amount of the diol in the reaction between the silicate compound and the diol. It is done. In the method for modifying a silicate compound of the present invention, the reaction control can be easily performed as compared with the conventional hydrolytic condensation reaction of tetraalkoxysilane using water.

  When using the method for modifying a silicate compound of the present invention, it has a molecular weight and an alkoxy group concentration adapted to the properties of various paints, particularly by selecting the amount of silicate compound used as a raw material and the amount of diol used and the addition method. Silicate compounds can be designed freely.

  In the method for modifying a silicate compound of the present invention, a reaction mixture is obtained by reacting a silicate compound with a diol.

  The silicate compound used as a raw material in the present invention has an average of 6 or more alkoxy groups bonded to Si atoms. The number of carbon atoms in the alkyl part of the alkoxy group is preferably 6 or less from the viewpoint of hydrolysis reactivity, and the alkoxy group is more preferably a methoxy group and / or an ethoxy group. Further, the silicate compound may be a mixture of two or more.

  The raw silicate compound is preferably a tetraalkoxysilane condensate. Specific examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and tetrahexyloxysilane. As described above for the preferred alkoxy groups, tetramethoxysilane and tetraethoxysilane are particularly preferred. Tetramethoxysilane and tetraethoxysilane condensates are commercially available from Mitsubishi Chemical as the MKC silicate series and from Colcoat as the ethylsilicate series, respectively. The raw material silicate compound having a methoxysilyl group and an ethoxysilyl group is condensed using tetramethoxysilane and tetraethoxysilane at the same time, or the methoxy group of the condensate of tetramethoxysilane is partially substituted with ethanol. Can be obtained.

  Moreover, a part of the alkoxy group of the raw material silicate compound may be substituted with a benzyloxy group, a 2-butoxyethyloxy group, or a 3-methoxy-1-propyloxy group. In this case, the substitution rate is preferably 50% or less of the alkoxy group of the silicate compound.

Since the silicate compound as a tetraalkoxysilane condensate is a mixture of various structures such as the degree of condensation, branching and presence / absence of crosslinking, it is difficult to clearly identify the structure as the silicate compound. For this reason, the information obtained about commercially available silicate compounds is usually limited to the type of alkoxy group and the SiO ₂ concentration. On the other hand, those skilled in the art can determine the weight average molecular weight of this silicate compound by using gel permeation chromatography (GPC). Here, a plurality of peaks exist in the chart obtained by GPC measurement. The plurality of peaks gradually increase in height as the holding time increases, but at some point shows a maximum value, and thereafter decreases. Peaks exist at almost equal intervals, and the rate of increase and decrease in height is almost the same before and after the maximum peak, so the difference in peak retention time seems to be due to the difference in the degree of condensation. . A person skilled in the art can estimate the degree of condensation corresponding to each peak by comparing with a chart of known compounds as necessary.

  Therefore, in this specification, the structure of the raw silicate compound is treated as having a structure represented by the following formula (I), which is a linear condensate having no branching or crosslinking. Furthermore, the value of n in this formula (I) is the degree of condensation of what is attributed to the maximum peak in the chart obtained by GPC measurement. Note that the value of n may be an integer or may have a decimal part.

(R is the same or different alkyl group having 1 to 6 carbon atoms, and a part thereof may be replaced by a benzyl group, a 2-butoxyethyl group, or a 3-methoxy-1-propyl group. .)

The difference between the SiO ₂ concentration calculated from the structural formula thus defined and the known SiO ₂ concentration obtained by firing at a high temperature of 500 ° C. or more is preferably 10% or less. If it exceeds 10%, it is difficult for the compound represented by the formula (I) to represent the raw material silicate compound. Incidentally, the SiO ₂ concentration, and Si atoms and oxygen atoms attached thereto in the silicate compound means a weight percentage of silicate compound. Further, when there are a plurality of types of alkoxy groups bonded to Si atoms, the abundance ratio of the alkoxy groups in formula (I) is determined by measuring a nuclear magnetic resonance (NMR) spectrum.

  The molecular weight obtained by calculating from the structural formula of the raw material silicate compound thus determined is defined as the calculated molecular weight of the silicate compound. The calculated molecular weight is preferably 258-3500. Those modified with less than 258 have insufficient hydrophilicity on the surface of the coating film, and if it exceeds 3,500, there is a problem in the stability of those obtained by modification. A more preferable calculated molecular weight is 500 to 3000.

  In the method for modifying a silicate compound of the present invention, a diol having a molecular weight of 160 or less is reacted with a raw material silicate compound. When the molecular weight of the diol exceeds 160, the concentration of alkoxy groups bonded to Si atoms in the resulting modified silicate may be reduced. Examples of the diol having a molecular weight of 160 or less include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, and nonanediol. Among these, those having a molecular weight of 120 or less are more preferred, and ethylene glycol, which is a diol having the smallest molecular weight, is particularly preferred.

In the method for modifying a silicate compound of the present invention, the SiO ₂ concentration of the obtained reaction mixture is 70% or more of the SiO ₂ concentration of the silicate compound. If it is less than 70%, the concentration of the alkoxy group is remarkably lowered, and therefore there is a possibility that sufficient hydrophilicity cannot be imparted to the coating film even if it is hydrolyzed after moving to the surface in the coating film. The SiO ₂ concentration of the raw material silicate compound is obtained by calculating from the blending in the same manner as the SiO ₂ concentration of the reaction mixture is calculated from the structural formula determined previously. Specifically, the reaction rate between the hydroxyl group of the diol used in the reaction and the alkoxy group bonded to the Si atom of the raw material silicate compound is 95%, and the calculation is performed based on the amount of the raw material silicate compound and the diol as the reaction reagent.

In the method for modifying a silicate compound of the present invention, the reaction mixture obtained basically is used as a modified silicate as it is. Therefore, the amount of diol used in the reaction will effectively determine the SiO ₂ concentration of the reaction mixture. Therefore, the amount of the diol used in the reaction must be set so that the SiO ₂ concentration does not fall below the above specified value.

  In the method for modifying a silicate compound of the present invention, the reaction can be performed in multiple stages by adding the diol in several portions. At this time, the amount of the diol used in the first-stage reaction is preferably 0.6 mol times or less of the raw material silicate compound. If the amount exceeds 0.6 mole times, the reaction mixture may gel. This also applies when the reaction is only carried out in one stage. Similarly, the amount of the diol used in the reaction of each stage after the second stage is set to 0.6 mol times or less of the diol used in the reaction of the immediately preceding stage. In addition, since the raw material silicate compound used as a reference here is treated as a linear condensate structure as described above and its molecular weight is used, it depends on the difference between the determined structure and the actual structure. It includes the possibility of errors. However, the error is not to the extent that a large change is required in the formulation design, and in order to obtain the desired reaction mixture without causing gelation, the amount of blending is slightly reduced based on the above 0.6 mole multiple as one criterion. It is easy for those skilled in the art to make adjustments.

The reaction in the method for modifying a silicate compound of the present invention can be carried out according to a conventional transesterification method well known to those skilled in the art. In this reaction, a solvent is not particularly required, but when used, it is preferably 10 times or less based on the total weight of the reaction product. Specific examples of the solvent include aromatic hydrocarbons such as toluene, benzene and xylene, halogenated hydrocarbons such as dichloroethane, ethers such as tetrahydrofuran and dioxane, ketones such as methyl ethyl ketone and methyl isobutyl ketone, ethyl acetate and Examples include esters such as butyl acetate, dimethyl carbonate, and acetonitrile. It is also possible to use an alcohol corresponding to the alkoxy group possessed by the silicate used for modification, such as methanol or ethanol, as a solvent. The acids or bases that are used can be used. Examples of the acid include Bronsted acids such as hydrochloric acid, sulfuric acid, phosphoric acid and sulfonic acid, and Lewis acids such as organotin compounds. As the base, tertiary amines such as triethylamine, dimethylbenzylamine, diazabicyclo [2.2.2] octane, 1,8-diazabicyclo [5.4.0] undecene-7, and the like can be used.

  When no catalyst is used, the reaction temperature is 70 to 160 ° C., preferably 70 to 150 ° C., and the reaction time can be about 1 hour or more.

  The reaction is usually carried out until the distillation of alcohol by the transesterification reaction is stopped. In addition, GPC and viscosity can be continuously measured, and the process can be terminated when they no longer change. These are applied for each stage when the reaction is carried out in multiple stages.

  In the method for modifying a silicate compound of the present invention, the reaction can be carried out in the presence of a monohydric alcohol together with a diol. This monovalent alcohol has an alkoxy group different from the alkoxy group bonded to the Si atom in the raw silicate compound. By making such alcohol coexist with the diol, simultaneously with the reaction with the diol, the alkoxy group bonded to the Si atom in the raw material silicate compound can be substituted with a different alkoxy group.

In view of the preferable alkoxy group of the silicate compound described above, the monovalent alcohol may be selected from methanol, ethanol, propanol, butanol, benzyl alcohol, butyl cellosolve, and 3-methoxy-1-propanol. preferable. When the reaction is carried out in the presence of such a monohydric alcohol, it is necessary to handle the monohydric alcohol as a reaction reagent similar to the diol in the calculation of the SiO ₂ concentration of the reaction mixture.

  In this way, the reaction mixture obtained by the method for modifying a silicate compound of the present invention is a modified silicate. This modified silicate is a colorless and transparent liquid, which is mainly composed of a reaction product of the raw material silicate compound and the diol, and may contain a small amount of the raw material components such as the silicate compound and the diol. The reaction product of the raw silicate compound and the diol is considered to have a structure in which the raw silicate compound is basically bonded to both ends of the diol, but is not expected to have a single structure. Originally, since the raw material silicate compound itself is a mixture containing a plurality of condensates having different degrees of condensation, the modified silicate can be regarded as a composition comprising compounds having various structures.

  The weight average molecular weight of the modified silicate varies depending on the molecular weight of the raw material silicate, the amount of diol used, and the number of reaction stages, but is preferably 1000 to 50000. When the reaction is one stage, it is preferably 1000 to 10,000, and when it is multistage, it is preferably 2400 to 50,000. A more preferable upper limit in the case of multiple stages is 20000. These values can be obtained by GPC.

  The modified silicate has a silicate unit in which one alkoxy group is removed from the condensate of tetraalkoxysilane to the oxygen atom at both ends of the diol unit obtained by removing a hydrogen atom from two hydroxyl groups of a diol having a molecular weight of 160 or less. It consists of a compound having a bonded structure. Here, at least one of the silicate units may be bonded to another silicate unit via another diol unit.

  The above structure is estimated as follows. That is, when the silicate compound having an alkoxy group bonded to 6 or more Si atoms on average is a tetraalkoxysilane condensate, each of the two hydroxyl groups of the diol has one alkoxy group of the two tetraalkoxysilane condensates and As a result of the transesterification reaction, a reaction product in which a tetraalkoxysilane condensate is bonded to both ends of the diol is obtained. In particular, when the amount of tetraalkoxysilane condensate present in the system relative to 1 mol of diol is 2 mol, it is considered that a reactant having this structure is preferentially produced. However, it is difficult to completely control that the reactant having this structure further reacts with the diol.

  Further, when the reaction is performed in multiple stages, the diol is reacted with the reactant having the above structure. In this case, the reaction between the alkoxy group of the tetraalkoxysilane condensate in which the diol has already been bonded by transesterification and one hydroxyl group of another diol proceeds. Under the above reaction conditions, since there is little possibility that a hydroxyl group remains as it is, another hydroxyl group reacts with another alkoxy group of a tetraalkoxysilane condensate in which a diol has already been bonded by transesterification. It seems to be. As a result, a compound having a structure in which several tetraalkoxysilane condensates are connected by a diol is obtained. However, how many tetraalkoxysilane condensates, that is, how many silicate units are contained in the molecule can be determined only as an average value determined from the average molecular weight. However, all of the main components constituting the modified silicate have a structure in which tetraalkoxysilane condensates are connected by a diol. A part of the alkoxy group of the tetraalkoxysilane condensate may be substituted with an alkoxy group different from the alkoxy group of tetraalkoxysilane. These specific examples are the same as those described above.

  The modified silicate of the present invention can be used as an additive for imparting low contamination to a paint. Although the coating material to be applied is not particularly limited, a coating material in which a fluororesin that is a highly hydrophobic resin is used as a binder component is preferable. The binder component can include a curing agent.

  When the modified silicate of the present invention is added to the paint, the blending ratio is 0.1 to 50 parts by weight, preferably 1 to 40 parts by weight, and more preferably 3 to 20 parts by weight with respect to 100 parts by weight of the solid content of the paint. is there. If the blending ratio of the modified silicate is too small, the resulting coating film has insufficient stain resistance. Conversely, if the blending ratio is too large, the gloss of the coating film and the coating adhesion may decrease.

  The modified silicate of the present invention contains, in addition to the binder component, pigment components such as coloring pigments and extender pigments, an anti-settling agent, a curing catalyst, an ultraviolet absorber, an antioxidant, a leveling agent, a surface conditioner, A paint can be obtained by mixing various additive components such as a stopper, a thickener, and an antifoaming agent by a method known to those skilled in the art. The obtained paint is applied to various substrates by a normal method such as a brush, spray, roller, coater, etc., and then cured under a predetermined heating condition to give a coating having a thickness of about 5 to 200 μm. A membrane can be obtained. The coating film obtained in this manner has excellent contamination resistance because the water contact angle of the surface is lower than usual, and is used by being formed on a base material such as an aluminum building material used outdoors. It is preferable.

In the examples, “parts” and “%” are based on mass unless otherwise specified.
Structure determination of silicate compound A chart was obtained by GPC using polystyrene as a standard substance and chloroform as an eluent for MKC silicate 51 (manufactured by Mitsubishi Chemical Corporation, SiO ₂ concentration 51%), which is a condensate of tetramethoxysilane. The weight average molecular weight was 661. The degree of condensation due to the maximum peak in this chart was analyzed and determined to be 5. When the MKC silicate 51 is represented by the following structural formula (II), the calculated SiO ₂ concentration is 52.1%. The difference between the value described in the catalog and the SiO ₂ concentration of 51% was 1.1%, and it was judged that there was no problem using this structural formula.

On the other hand, MKC silicate 56 (manufactured by Mitsubishi Chemical Corporation, SiO ₂ concentration 56%), which is a condensate of tetramethoxysilane, was examined in the same manner as described above. As a result, the degree of condensation due to the maximum peak was determined to be 10. When the MKC silicate 56 is represented by the following structural formula (III), the calculated SiO ₂ concentration is 54.2%. The difference between the value described in the catalog and the SiO ₂ concentration of 56% was 1.8%, and it was judged that there was no problem using this structural formula. In addition, the weight average molecular weight by GPC was 1212.

Example 1
The inside of a reactor equipped with a heating apparatus, reflux condenser, dehydration apparatus and stirrer was purged with nitrogen, and then 864 parts of the above-mentioned MKC silicate 51 was added. Further, 46.6 parts of ethylene glycol as a diol was stirred while stirring the silicate compound. Added in minutes. Since the structure of MKC silicate 51 has been previously determined by the following formula (II), the amount of this ethylene glycol corresponds to 0.5 mole times the amount of the raw silicate compound.

The temperature of the system was raised to 120 ° C., and the reaction was carried out for 3 hours while removing methanol produced by the transesterification reaction. After confirming that distillation of methanol had stopped, the reaction was terminated, and 820.8 parts of modified silicate was obtained as a reaction mixture. The SiO ₂ concentration of the modified silicate calculated from the formulation was 52.2%, and the ratio of the raw material silicate to the calculated SiO ₂ concentration of 52.1% was 100%. The resulting modified silicate had a weight average molecular weight of 1076.

Example 2
In Example 1, the reaction was conducted in the same manner except that 774.2 parts of MKC silicate 56 was used instead of 864 parts of MKC silicate 51, and the amount of ethylene glycol was changed from 46.6 parts to 21.7 parts. went. Since the structure of MKC silicate 56 has been previously determined by the following formula (III), the amount of this ethylene glycol corresponds to 0.5 mole times the amount of the raw silicate compound. The amount of the modified silicate obtained as a reaction mixture was 734.8 parts, and its weight average molecular weight was 2880. Further, the SiO ₂ concentration of the modified silicate calculated from the blending was 54.3%, and the ratio of the raw silicate compound to the calculated SiO ₂ concentration of 54.3% was 100%.

Example 3
In Example 2, 90.4 parts of industrial alcohol having a mass ratio of ethanol to methanol of 89/11 was added along with the addition of ethylene glycol. After heating at 80 ° C. for 2 hours, the temperature of the system was raised to 120 ° C., and the reaction was carried out for 3 hours while removing methanol produced by the transesterification reaction. After confirming that distillation of methanol had stopped, the reaction was completed, and 758.1 parts of a denatured silicate was obtained as a reaction mixture. Moreover, when NMR of the modified silicate was measured, the ratio of methoxysilyl group / ethoxysilyl group was 90/10. The SiO ₂ concentration of the modified silicate calculated from the formulation and the ratio of methoxysilyl group / ethoxysilyl group was 52.9%, and the ratio of the raw silicate compound to the calculated SiO ₂ concentration of 54.3% was 98%. Moreover, in the molecular weight measurement by GPC, the weight average molecular weight of the obtained modified silicate was 2517.

Example 4
After reacting in the same procedure as in Example 3, 108.6 parts of a 10% mass solution of ethylene glycol in methyl ethyl ketone was added and heated at 120 ° C. for 1 hour. Thereafter, 54.3 parts of a 10% mass solution of ethylene glycol in methyl ethyl ketone was added and heated at 120 ° C. for 1 hour to obtain 744.4 parts of a modified silicate. When NMR of the modified silicate was measured, the ratio of methoxysilyl group / ethoxysilyl group was 90/10. The SiO ₂ concentration of the modified silicate calculated from the composition and the ratio of methoxysilyl group / ethoxysilyl group was 53%, and the ratio of the raw silicate compound to the calculated SiO ₂ concentration of 54.3% was 98%. Moreover, in the molecular weight measurement by GPC, the weight average molecular weight of the obtained modified silicate was 11654.

Example 5
In Example 3, a modified silicate was obtained in the same manner except that 36.5 parts of pentanediol was used instead of ethylene glycol.

Example 6
A modified silicate was obtained in the same manner as in Example 3, except that a mixture of 206.5 parts of MKC silicate 51 and 367.5 parts of MKC silicate 56 was used as the raw silicate compound.

Example 7
In Example 3, a modified silicate was obtained in the same manner except that the amount of ethylene glycol was increased to 26.0 parts. These results are summarized in Table 1.

Comparative Example 1
After the inside of the reactor equipped with a heating device, reflux condenser, dehydration device and stirrer was purged with nitrogen, 774.2 parts of MKC silicate 56 was added, and 4.2 parts of distilled water and 4.2 parts of 35% hydrochloric acid were further added. Added in 10 minutes with stirring. The temperature of the system was raised to 150 ° C., and the reaction was carried out for 3 hours while removing methanol produced by the dehydration condensation reaction. The resulting modified silicate had a weight average molecular weight of 3851.

<Storage stability evaluation>
The obtained modified silicate was kept in an environment at 60 ° C., and the result after 7 days had passed was visually observed according to the following criteria.
○: No change ×: Gelation or obvious increase in viscosity is confirmed

<Reproducibility evaluation>
About each Example and Comparative Example 1, it reacted again and it was examined whether the same thing as the modified | denatured silicate obtained previously could be obtained.
○: The same thing was obtained ×: The same thing was not obtained The above results are summarized in Table 1 below.

Example 8
The amount of the modified silicate obtained in Example 4 corresponding to 13.3% of the resin solid content was added to Duflon K300 matte black (thermosetting fluororesin paint manufactured by Nippon Paint Co., Ltd.). The coating material thus obtained was applied on an aluminum plate so as to have a dry film thickness of 30 μm, and dried by heating at 170 ° C. for 20 minutes to obtain a cured film. When this cured film was immersed in distilled water for 24 hours and dried, the water contact angle was measured and found to be 51 degrees. In addition, the water contact angle when MKC silicate 56 was used instead of the modified silicate was 78 degrees.

  In the method for modifying a silicate compound of the present invention, the molecular weight of the modified silicate obtained as a reaction mixture was larger than that of the raw material silicate, so that it was confirmed that the reaction with the diol had proceeded. Moreover, the modified silicate of the present invention was stable, and reproducibility of the modification method was also confirmed. On the other hand, in the conventional hydrolysis condensation using water, the reaction could not be reproduced, and the obtained product lacked storage stability. Moreover, when the modified silicate obtained in Example 4 was added to the fluorine paint, it was found that the surface of the coating film can be sufficiently hydrophilized as compared with the conventional alkyl silicate.

  The modified silicate obtained by the modification method of the present invention can impart stain resistance to a paint by adding it to a paint containing a highly hydrophobic fluororesin.

Claims (14)

In the method for modifying a silicate compound, a silicate compound having an alkoxy group bonded to an average of 6 or more Si atoms is reacted with a diol to obtain a reaction mixture.
The diol is at least one diol selected from the group consisting of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, and nonanediol ;
The method for modifying a silicate compound, wherein the SiO ₂ concentration of the reaction mixture is 70% or more of the SiO ₂ concentration of the silicate compound. At least one alcohol selected from the group consisting of methanol, ethanol, propanol, butanol, benzyl alcohol, butyl cellosolve, and 3-methoxy-1-propanol, wherein the alkoxy group is different from the alkoxy group bonded to the Si atom. The method for modifying a silicate compound according to claim 1, wherein the silicate compound is reacted with the diol in the presence of an alcohol having the alcohol. The method for modifying a silicate compound according to claim 1 or 2, wherein the diol is ethylene glycol. The method for modifying a silicate compound according to any one of claims 1 to 3, wherein the alkoxy group bonded to the Si atom is a methoxy group and / or an ethoxy group. Some alkoxy groups attached to the Si atom, a propyloxy group, a butoxy group, benzyloxy group, 2-butoxyethyl group, 3-methoxy-1-claims have been replaced by propyl group 1-4 The modification | denaturation method of the silicate compound as described in any one of these . The method for modifying a silicate compound according to any one of claims 1 to 5, wherein the amount of the diol is not more than 0.6 mol times the amount of the silicate compound. The reaction of the diol is carried out in multiple stages, the amount of diol used in the reaction of the first stage is, according to any one of claims 1 to 6 is 0.6 times the molar amount following the silicate compound A method for modifying a silicate compound. The method for modifying a silicate compound according to claim 7 , wherein the amount of the diol used in the reaction of each stage after the second stage is 0.6 mol times or less of the diol used in the reaction of the immediately preceding stage. The method for modifying a silicate compound according to claim 7 or 8, wherein the total amount of diols used in the multistage reaction is 1 mol or less of the silicate compound. Modified silicate obtained by the method for modifying the silicate compound as claimed in any one of claims 1-9. The oxygen atoms at both ends of the diol units excluding each a hydrogen atom from two hydroxyl groups di ol having, removing one silicate unit alkoxy groups from the condensation product of tetraalkoxysilane a compound having a structure bonded respectively A modified silicate ,
A modified silicate, wherein the diol is at least one diol selected from the group consisting of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, and nonanediol .
The modified silicate according to claim 11 , wherein at least one of the silicate units is bound to another silicate unit via another diol unit. A coating composition comprising the modified silicate according to any one of claims 10 to 12 . The coating composition of Claim 13 which contains a fluororesin as a binder component.