JP2009091312A - Method for producing epoxy group-terminated (meth)acrylate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an epoxy group-terminated (meth)acrylate, in which the polymerization of the epoxy group-terminated (meth)acrylate during distillation purification can be prevented, which results in the production of an epoxy group-terminated (meth)acrylate in high yield and in high purity. <P>SOLUTION: Provided is a method for producing the epoxy group-terminated (meth)acrylate, comprising performing a transesterification of a lower alkyl (meth)acrylate with an alkanediol monoglycidyl ether represented by general formula (1) in the presence of a metal alkoxide and then distilling and purifying the resultant epoxy group-terminated (meth)acrylate represented by general formula (2) in the presence of a polymerization-preventing agent, when the content of the metal originated from the metal alkoxide is controlled to ≤2.5 times moles that of the polymerization-preventing agent existing during the distillation purification. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an epoxy group-terminated (meth) acrylate.

  4-glycidyloxybutyl acrylate (hereinafter abbreviated as “4HBAGE”) and epoxy group-terminated (meth) acrylates typified by glycidyl methacrylate are useful compounds as raw materials for improving paints and resins ( Patent Documents 1 and 2). Among them, 4HBAGE is a very useful compound because it does not lose its flexibility even after crosslinking and exhibits excellent properties as a coating film.

  By the way, as a general manufacturing method of the epoxy group terminal (meth) acrylate represented by the following general formula (2), (meth) acrylic acid lower alkyl ester and the following general formula ( There is a method of transesterifying the alkanediol monoglycidyl ether represented by 1) (Patent Document 3).

（上記一般式（１）及び（２）中、Ｙは炭素数２〜８の飽和炭化水素基を表す。上記一般式（２）中、Rは水素原子またはメチル基を表す。）

(In the general formulas (1) and (2), Y represents a saturated hydrocarbon group having 2 to 8 carbon atoms. In the general formula (2), R represents a hydrogen atom or a methyl group.)

  Examples of the transesterification catalyst include metal alcoholates typically represented by titanium alcoholates and the like, and organic tin, alkali metal or alkaline earth metal weak acid salts (for example, carbonates, acetates, and phosphates). Are known.

  After completion of the transesterification reaction, the used catalyst is generally removed, and a highly purified epoxy group-terminated (meth) acrylate is obtained as a distillate by distillation purification. As a method for removing a metal alcoholate of a transesterification reaction catalyst, for example, a method is known in which water is added and stirred at room temperature to hydrolyze the catalyst, and then removed by liquid separation or filtration (Patent Document 4). .

  By the way, epoxy group terminal (meth) acrylate is easily polymerized by heating during distillation, etc., and when the hydrolysis and / or removal of the metal alcoholate of the transesterification reaction catalyst is insufficient, the metal alcoholate or the metal component derived therefrom Remains in the system and accelerates the polymerization of the terminal (meth) acrylate of the epoxy group.

Japanese Patent Publication No. 48-22169 Japanese Patent No. 3645037 JP-A-8-99968 JP 2005-247810 A

  The present invention has been made in view of the above circumstances, and its purpose is to prevent the polymerization of an epoxy group-terminated (meth) acrylate during distillation purification, and as a result, an epoxy group that can be obtained in high yield and high purity. It is providing the manufacturing method of terminal (meth) acrylate.

  That is, the gist of the present invention is obtained after an ester exchange reaction between a lower alkyl ester of (meth) acrylic acid and an alkanediol monoglycidyl ether represented by the following general formula (1) in the presence of a metal alcoholate. The polymerization inhibitor present in the distillation purification of the metal content derived from the metal alcoholate when the obtained epoxy group-terminated (meth) acrylate represented by the following general formula (2) is purified by distillation in the presence of the polymerization inhibitor. The present invention resides in a method for producing an epoxy group-terminated (meth) acrylate, characterized in that the molar amount is 2.5 times or less of the amount.

（上記一般式（１）及び（２）中、Ｙは炭素数２〜８の飽和炭化水素基を表す。上記一般式（２）中、Rは水素原子またはメチル基を表す。）

(In the general formulas (1) and (2), Y represents a saturated hydrocarbon group having 2 to 8 carbon atoms. In the general formula (2), R represents a hydrogen atom or a methyl group.)

  According to the present invention, polymerization at the time of distillation purification can be avoided, and an epoxy group-terminated (meth) acrylate, which is a useful compound as a raw material for improving paints, resins, etc., can be obtained in high yield and high quality. I can do it.

  Hereinafter, the present invention will be described in detail.

  The method for producing an epoxy group-terminated (meth) acrylate according to the present invention comprises the step of removing (lower) (meth) acrylic acid in the presence of a metal alcoholate while removing the produced lower alcohol out of the reaction system using azeotropy with a solvent. The transesterification reaction is carried out between an alkyl ester and an alkanediol monoglycidyl ether.

  From the viewpoint of appropriately proceeding the transesterification reaction, the molar ratio of the total amount of water in the reaction system is usually 5 times or less, preferably 3 times or less, more preferably 1.5 times or less as a ratio to the metal alcoholate. .

  As a method for reducing the moisture in the reaction system, for example, before using the metal alcoholate to add excessively the solvent used for azeotropy with the raw material (meth) acrylic acid lower alkyl ester and the lower alcohol to be produced. A method of previously removing water in the reaction system out of the system by distillation can be mentioned. Moreover, the method etc. which reduce the total amount of water | moisture content by a process with a dehydrating agent are also mentioned. Usually, a Karl Fischer moisture meter is used to measure moisture.

  In the (meth) acrylic acid lower alkyl ester used as a raw material, the lower alkyl usually means a linear or branched alkyl group having 1 to 6 carbon atoms. Specific examples of the (meth) acrylic acid lower alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid-n-propyl, (meth) acrylic acid-n-butyl, and the like. Of these, methyl (meth) acrylate is preferred. Depending on the type of (meth) acrylic acid lower alkyl ester to be used, a lower alcohol having a corresponding structure is produced by transesterification.

  The use ratio of the (meth) acrylic acid lower alkyl ester is usually 1 to 10 times mol, preferably 1.1 to 5 times mol for the alkanediol monoglycidyl ether used. Since the transesterification reaction is an equimolar reaction of (meth) acrylic acid lower alkyl ester and alkanediol monoglycidyl ether, if the proportion of (meth) acrylic acid lower alkyl ester used is less than the above range, transesterification The reaction may not be completed and the yield may decrease. Moreover, when the usage-amount of (meth) acrylic-acid lower alkyl ester exceeds said range, there is no effect by it and it is not practical.

  The alkanediol monoglycidyl ether represented by the general formula (1) used as a raw material can be obtained by a known production method, for example, the production method described in Patent Document 3. Generally, it is obtained by directly dehalogenating addition reaction of alkanediol and epihalohydrin using an alkali compound.

  In the general formula (1), Y of the intermediate group may be a saturated hydrocarbon group having 2 to 8 carbon atoms, and part or all of the intermediate group has an alicyclic structure represented by, for example, a cyclohexane ring. You may have. Specific examples of alkanediol monoglycidyl ether include ethylene glycol monoglycidyl ether, 1,3-propanediol monoglycidyl ether, 1,4-butanediol monoglycidyl ether, 1,6-hexanediol monoglycidyl ether, 1,8 -Octanediol monoglycidyl ether, 1,4-cyclohexanedimethanol monoglycidyl ether, 1,4-cyclohexanediol monoglycidyl ether and the like.

  Examples of the metal alcoholate of the stealter exchange reaction catalyst include titanium alcoholate, zirconium alcoholate, aluminum alcoholate, and antimony alcoholate. As the alcohol constituting the alcoholate, lower alcohols are usually used, and examples thereof include methanol, ethanol, n-propanol, n-butanol and the like. Among these, titanium alcoholates such as titanium tetramethoxide, titanium tetraethoxide, titanium tetra-n-propoxide, titanium tetra-n-butoxide (hereinafter abbreviated as “TBT”) are preferable, and TBT is particularly preferable.

  The ratio of the metal alcoholate used is usually 0.001 to 0.1 times mol, preferably 0.005 to 0.05 times mol for the alkanediol monoglycidyl ether. When the proportion of metal alcoholate used is less than the above range, the transesterification reaction progresses slowly or the reaction is not completed, and when it exceeds the above range, no improvement effect on the amount of use can be expected. Operation such as removal may be difficult.

  In the transesterification reaction, it is preferable to use a polymerization inhibitor for the purpose of preventing polymerization of the (meth) acryloyl group. As the polymerization inhibitor, aromatic amines such as phenothiazine and p-phenylenediamine; 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and 4-hydroxy-2,2,6,6 -N-oxylamines such as tetramethyl-1-piperidinyloxy (HTEMPO); phenol derivatives such as hydroquinone and p-methoxyphenol; nitroso compounds; aromatic nitroso compounds; copper dibutyldithiocarbamate (hereinafter abbreviated as "CBC") And copper-based compounds such as copper acetate; lead-based compounds such as lead stearate. Two or more of these polymerization inhibitors may be used in combination. Depending on the type of the polymerization inhibitor, there are some which can obtain a higher polymerization prevention effect by introducing oxygen into the reaction system. In this case, it is preferable to introduce oxygen gas diluted with an inert gas into the reaction system so that the reaction system does not enter the explosion range, and it is preferable to introduce the oxygen gas by blowing it into the reaction solution. More preferred.

  The usage-amount of a polymerization inhibitor is 0.01-1 weight part normally with respect to 100 weight part of alkanediol monoglycidyl ether, Preferably it is 0.1-0.3 weight part.

  Since the transesterification reaction is an equilibrium reaction, in order to perform the transesterification reaction in a high yield, the lower alcohol produced by the reaction is removed outside the system using azeotropy with a solvent or the like. The solvent used is azeotropic with the lower alcohol produced, and preferably has an azeotropic temperature lower than the azeotropic temperature of the lower alkyl (meth) acrylate and the lower alcohol. It is selected from those which do not react with lower alkyl esters of acrylic acid and alkanediol monoglycidyl ether. Examples of such a solvent include aliphatic hydrocarbon solvents such as n-hexane, n-heptane, and cyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; ether solvents such as tetrahydrofuran and dibutyl ether; Examples thereof include ketone solvents such as methyl isobutyl ketone. In addition, the raw material (meth) acrylic acid lower alkyl ester can be used in excess and used as a solvent. The reaction can also be carried out under conditions where the solvent and the lower alcohol do not azeotrope, but in this case, the lower alcohol removal efficiency is lower than in the case of azeotropic distillation. Therefore, it is preferable to carry out the reaction under azeotropic conditions. In these, the combination of methyl (meth) acrylate and n-hexane is preferable.

  Moreover, said solvent can also be used as a reaction solvent. By using the reaction solvent, the temperature and concentration of the reaction solution can be controlled, and polymerization and side reactions in the liquid phase can be suppressed. In particular, in the case of a water-insoluble reaction solvent, it is possible to expect effects such as promoting separation and acting as an extraction solvent when the organic layer and the aqueous layer are separated by post-treatment. When using a reaction solvent, if a large amount of an azeotropic solvent with a low boiling point is used, the temperature of the reaction system tends to decrease. It is preferable to use in combination. For example, for a combination of methyl (meth) acrylate and n-hexane (azeotropic system of methanol and n-hexane), a method of further using toluene as a reaction solvent can be mentioned.

  Since the ratio of the solvent used varies depending on the type of lower alcohol produced and the ratio of the azeotropic composition when azeotroped with the solvent, it cannot be said unconditionally. An amount of the solvent that can be removed by azeotropic removal of the total amount of the lower alcohol to be generated (based on the theoretical calculation amount when the reaction rate is 100%) is required, and the weight ratio to the theoretical calculation amount is usually 1 to 10 times. Preferably they are 1.1 times-5 times. When the proportion of the solvent used is less than the above range, the removal of the lower alcohol may be insufficient and the reaction may not be completed. When it exceeds the above range, there is no effect and it is not practical.

  If removal of lower alcohol by azeotropy becomes insufficient due to lack of solvent, it is possible to add solvent later, but consider the total amount of water contained in the additional solvent. Be careful as it is necessary. Alternatively, a method in which an amount of a solvent capable of maintaining an azeotropic state until the reaction is completed during the transesterification reaction is sequentially charged into the reaction system. Care must be taken because it is necessary to consider all the water contained in the amount. When a solvent is used also as a reaction solvent, a solvent as a reaction solvent component is required separately from the component used for azeotropy, but the amount is a volume ratio to the alkanediol monoglycidyl ether used. As a rule, it is usually 0.5 to 20 times, preferably 1 to 5 times. When the proportion of the reaction solvent used is less than the above range, the effect as a reaction solvent cannot be expected so much, and when it is more than the above range, there is not only the effect but also the reaction rate decreases due to dilution. And there is a risk that control of moisture will be difficult due to the decrease in concentration relative to the total amount of moisture.

  The reaction temperature of the transesterification reaction depends on the (meth) acrylic acid lower alkyl ester used and the type of solvent, but is usually 50 to 130 ° C., preferably 60 to 120 ° C., and the reaction time is usually 1 to 24. Time, preferably 3-12 hours. When the reaction temperature is low, the progress of the transesterification reaction is slow. Conversely, when the reaction temperature is too high, the risk of polymerization of the (meth) acryloyl group may be increased. In the transesterification reaction, the reaction time can be shortened by removing the lower alcohol from the reaction system as quickly as possible while maintaining the azeotropic temperature (azeotropic composition).

  After completion of the transesterification reaction, water is added to the reaction solution to deactivate the catalyst, and the insolubilized catalyst is removed by a method such as filtration. If the deactivation of the metal alcoholate is insufficient, the metal component derived from the catalyst that has not been filtered may remain or may cause problems such as clogging during filtration and a decrease in filterability. . When the metal component derived from the catalyst remains, there is a high risk of causing a polymerization or disproportionation reaction of the (meth) acryloyl group during heating in the subsequent steps.

  The amount of water added is usually 10 to 200 parts by weight, preferably 20 to 50 parts by weight, based on 1 part by weight of the catalyst, although it depends on the molecular weight and the amount of catalyst used. When the proportion of water used is less than the above range, the catalyst may be insufficiently hydrolyzed, or the separability when separating the organic layer and the aqueous layer may be deteriorated. Moreover, when there is more usage-amount of water than said range, there is no effect by it, and when the organic layer and an aqueous layer are isolate | separated on the contrary, the loss to the aqueous layer of an epoxy-group terminal (meth) acrylate increases. In addition, when removing the catalyst insolubilized by filtration, it is preferable to use filter aids, such as diatomaceous earth, for the purpose of improving filterability or preventing the mixture of the catalyst insolubilized due to leakage or the like.

  Since metal alcoholates easily react with water, usually adding a large excess of water causes hydrolysis, but it is preferable to deactivate the catalyst sufficiently for the above reasons, and water was added for this purpose. It is preferable to hydrolyze the reaction liquid later by heating. Although the hydrolysis conditions depend on the amount of the catalyst, the hydrolysis temperature is usually 30 ° C. or higher, preferably 40 to 100 ° C., more preferably 50 to 80 ° C., and the hydrolysis time is usually 5 minutes to 24 hours, preferably 10 minutes to 12 hours, more preferably 15 minutes to 6 hours. When the hydrolysis temperature is low or when the hydrolysis time is too short, there is a risk that the deactivation of the catalyst may be insufficient, and it takes a long time to sufficiently deactivate the catalyst at a low temperature. Conversely, when the hydrolysis temperature is too high, the epoxy group terminal (meth) acrylate itself may be hydrolyzed to reduce the yield, but the time required for hydrolysis of the catalyst is shortened.

  After completion of hydrolysis, an organic layer containing an epoxy group-terminated (meth) acrylate and an aqueous layer are separated. In practice, it is often difficult to separate the organic layer and the aqueous layer in a state where the catalyst is insolubilized and dispersed. Therefore, it is preferable to separate the organic layer and the aqueous layer after removing the insolubilized catalyst by filtration or the like. At this time, a water-insoluble solvent may be used to promote separation of the organic layer and the aqueous layer. The solvent used may be the same as or different from the azeotropic solvent used in the transesterification reaction, but in general, an aromatic hydrocarbon solvent such as toluene or xylene is preferred. These solvents can also be used in advance as a reaction solvent from the transesterification stage.

  When a solvent is used to promote separation of the organic layer and the aqueous layer, the use ratio is usually 0.1 to 10 times, preferably 0, as a volume ratio with respect to the organic layer containing an epoxy group-terminated (meth) acrylate. .2-5 times. Moreover, you may add water as needed and may perform a water-washing process. By adding this water washing step, the hydrophilic compound represented by the general formula (1) can be removed almost completely.

  By concentrating the organic layer containing the above epoxy group-terminated (meth) acrylate and removing low-boiling components such as solvents by distillation, an epoxy group-terminated (meth) acrylate crude product can be obtained as a distillation residue. . The concentration conditions depend on the type of solvent, but from the viewpoint of preventing polymerization of the (meth) acryloyl group, concentration under reduced pressure is performed at a temperature lower than the temperature during the transesterification reaction in the presence of a polymerization inhibitor. Is preferred.

  An epoxy group-terminated (meth) acrylate (such as 4HBAGE), which is the object of the present invention, can be obtained by purifying the product solution by distillation. In the present invention, however, distillation purification is performed in the presence of a polymerization inhibitor. To do. At this time, the metal content derived from the metal alcoholate is set to 2.5 mol or less with respect to the polymerization inhibitor present in the distillation purification. By satisfying such conditions, polymerization at the time of distillation purification can be avoided, and the target epoxy group-terminated (meth) acrylate can be obtained with high quality and high yield.

  As distillation purification conditions, the liquid temperature is usually 180 ° C. or lower, preferably 160 ° C. or lower, and the distillation time is usually 20 hours or shorter, preferably 12 hours or shorter.

  The polymerization inhibitor used during the distillation purification can be selected from a group of polymerization inhibitors that can be used during the transesterification reaction, but a copper-based polymerization inhibitor is preferred, and CBC is particularly preferred. Moreover, you may use together with another polymerization inhibitor. In particular, the use of p-methoxyphenol or the like in combination can be expected to prevent polymerization in the column. Depending on the type of the polymerization inhibitor, there may be obtained a higher polymerization prevention effect by introducing oxygen into the concentrated distillation system. In this case, it is preferable to introduce oxygen gas diluted with an inert gas into the reaction system so that the concentrated distillation system does not enter the explosion range, and it is introduced by blowing it into the concentrated liquid. Is more preferable. The polymerization inhibitor may be added at the time of distillation purification or may be allowed to coexist from the step before the distillation step.

  The metal content derived from the metal alcoholate is 2.5 times mol or less, preferably 1.2 times mol or less, more preferably 0.6 times mol or less with respect to the polymerization inhibitor present during distillation purification. . The metal derived from the metal alcoholate is a metal species constituting the metal alcoholate used as the transesterification catalyst, and can be quantified by atomic absorption measurement or the like. When the metal alcoholate is sufficiently deactivated and removed after the transesterification reaction, the metal species derived from the metal alcoholate can usually be reduced to 2 ppm or less.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded.

Example 1:
In a 500 ml four-necked flask equipped with a distillation apparatus, thermometer and stirring apparatus, 100.0 g of 1,4-butanediol monoglycidyl ether (purity: 98.3%, 0.67 mol in terms of purity), methyl acrylate 87.6 g, toluene 70.3 g, n-hexane 128.4 g, and MEHQ 0.03 g were added to prepare a raw material mixture (total 386.3 g). It was 840 ppm when the water | moisture content of this raw material liquid mixture was measured with the Karl Fischer moisture meter. Therefore, the total amount of moisture contained in this raw material mixture is 0.32 g (0.018 mol).

  When TBT 4.6g (0.014mol) was added to said raw material liquid mixture and it heated and heated under normal pressure and stirring, the azeotropic reflux of methanol / n-hexane began immediately from the reaction liquid temperature vicinity of 72 degreeC. . The gas temperature was 50-52 ° C. While maintaining this azeotropic temperature (azeotropic composition), an azeotropic liquid of methanol / n-hexane was extracted. In addition, since the amount of methanol produced decreases from the time when the reaction is almost finished, and it becomes difficult to maintain the azeotropic temperature (azeotropic composition), the gas temperature rose to 64 ° C., but the extraction was continued as it was. . Finally, 88.8 g of a methanol / n-hexane mixed fraction was withdrawn in 8 hours, the reaction was terminated at a reaction liquid temperature of 92 ° C., and the reaction liquid was cooled to 258.5 g of a reaction liquid containing 4HBAGE (49.4 wt%). Obtained. The quantitative yield of 4HBAGE is 94.8%. The molar ratio of the total amount of water in this reaction system is 1.3 times the TBT used.

  135.7 g of water was added to the above reaction solution, heated to 60 ° C. under normal pressure and stirring, and then subjected to heat hydrolysis at 60 ° C. for 30 minutes. The reaction solution was cooled and suction filtered using a filter covered with celite to remove insoluble catalyst. The filtrate was separated into an organic layer and an aqueous layer to obtain 255.5 g of an organic layer containing 4HBAGE (47.6% by weight). The quantitative yield of 4HBAGE is 90.4%.

  The organic layer containing 4HBAGE was concentrated under reduced pressure using a rotary evaporator to obtain 123.6 g of a 4HBAGE crude product (purity 97.7%). The quantitative conversion yield of 4HBAGE in terms of purity is 90.1%. This 4HBAGE crude product was a transparent liquid with almost no coloration, and the TBT-derived titanium content used as a catalyst was below the detection limit (2 ppm) of the atomic absorption measuring device.

  Distillation purification was performed by adding 0.6 g of CBC to the 4HBAGE crude liquid. 4HBAGE was purified by distillation under distillation conditions of 100 to 135 ° C / 2.7 to 5.3 hPa, an oil bath temperature of 120 to 160 ° C, and 8 hours. 111.1 g of 4HBAGE (purity 98.6%) was recovered. No polymer was observed in the distillation residue and in the system.

Example 2:
The reaction was carried out under the same reaction conditions as in Example 1. Except that the catalyst was hydrolyzed at 25 ° C., the post-treatment was carried out in the same manner as in Example 1. As a result, 121.0 g of crude 4HBAGE (97.2%) was recovered. The amount of titanium in the collected liquid was quantified with an atomic absorption measuring device and found to be 28 ppm. This amount of titanium corresponds to 0.071 mmol. CBC 27.9 mg (corresponding to Ti / CBC = 1.2 mol / mol) was added to this crude 4HBAGE solution, and distillation was performed under the same distillation conditions as in Example 1. 110.7 g (purity 98.6%) of 4HBAGE was recovered. No polymer was observed in the distillation residue and in the system.

Test Examples 1-7:
TBT was added to product 4HBAGE, CBC was further added as a polymerization inhibitor, and a 4HBAGE thermal stability test at 160 ° C. was conducted to compare the polymerizability. The conditions were 4HBAGE: 100 g, CBC 0.2 g, under nitrogen, and the method for confirming the polymerization was visually performed. The results are shown in Table 1. “O” means no polymerization and “x” means polymerization. Test Examples 1 to 3 are test examples for comparison, and Test Examples 4 to 7 are test examples for explaining the present invention.

Claims (5)

In the presence of a metal alcoholate, a transesterification reaction between a lower alkyl ester of (meth) acrylic acid and an alkanediol monoglycidyl ether represented by the following general formula (1) was performed, and the resulting general formula (2) When the epoxy group-terminated (meth) acrylate represented by the formula is distilled and purified in the presence of a polymerization inhibitor, the metal content derived from the metal alcoholate is 2.5 times the mole of the polymerization inhibitor present during the distillation purification. The manufacturing method of the epoxy-group terminal (meth) acrylate characterized by the following.

(In the general formulas (1) and (2), Y represents a saturated hydrocarbon group having 2 to 8 carbon atoms. In the general formula (2), R represents a hydrogen atom or a methyl group.)   The process according to claim 1, wherein the metal alcoholate is a titanium alcoholate.   The production method according to claim 1 or 2, wherein the polymerization inhibitor is a copper-based compound.   The production method according to claim 3, wherein the polymerization inhibitor which is a copper compound is copper dibutyldithiocarbamate.   The epoxy group-terminated (meth) acrylate is 4-glycidyloxybutyl acrylate in which Y in the general formula (2) is a linear methylene group having 4 carbon atoms and R is a hydrogen atom. The manufacturing method in any one of.