JP3813199B2 - Hydroxyisobutyric acid ester with improved storage stability and metal corrosivity - Google Patents

Description

（前記式中、Ｒは炭素数１〜４のアルキル基を表す。）
当該ヒドロキシイソ酪酸エステル中の水分の含有量を０．５重量％以下に調整することを特徴とする貯蔵安定性および金属腐食性の改善されたヒドロキシイソ酪酸エステルに関する。
【００１０】
以下、本発明を詳細に説明する。
本発明におけるヒドロキシイソ酪酸エステルとしては、α−ヒドロキシイソ酪酸メチル、α−ヒドロキシイソ酪酸エチル、α−ヒドロキシイソ酪酸プロピル、α−ヒドロキシイソ酪酸ブチルなどのα−ヒドロキシイソ酪酸アルキルエステル（一般式［１］に相当）、β−ヒドロキシイソ酪酸メチル、β−ヒドロキシイソ酪酸エチル、β−ヒドロキシイソ酪酸プロピル、β−ヒドロキシイソ酪酸ブチルなどのβ−ヒドロキシイソ酪酸アルキルエステル（一般式［２］に相当）が挙げられる。
【００１１】
ヒドロキシイソ酪酸エステルの製造法は従来から種々知られているが、硫酸、塩酸、強酸性イオン交換樹脂等の触媒存在下でのヒドロキシイソ酪酸のエステル化反応、シアンヒドリンのアルコリシス反応、ヒドロキシイソ酪酸アミドとギ酸エステルとの交換反応などによる製造法が一般的である。なお、本発明のヒドロキシイソ酪酸エステルは上記方法によって製造されたものに限定されるものではなく、いずれの方法によって得られたヒドロキシイソ酪酸エステルも本発明の対象となりうるものである。
【００１２】
ヒドロキシイソ酪酸エステル中に水分が混入する原因としては種々考えられるが、代表的な原因として以下のことが挙げられる。すなわち、ヒドロキシイソ酪酸エステルを製造するに際し、原料として用いた水や原料中に含まれる水分、あるいはエステル化時に副生する水分、更には、製造中に外気から吸湿する水分などがある。このようにして吸湿した水分は、蒸留精製工程においてもヒドロキシイソ酪酸エステルと完全に分離することは難しく、一部は製品ヒドロキシイソ酪酸エステル中に混入してしまうのである。また、ヒドロキシイソ酪酸エステル自体も吸湿性が高いため、貯蔵中に水分を吸収してしまうこともある。
【００１３】
ヒドロキシイソ酪酸エステルの貯蔵中における分解、変色や金属材料への腐食などを防止するためには、ヒドロキシイソ酪酸エステルに含まれる水分を０．５重量％以下にすることが必要である。好ましくは０．３重量％以下、特に好ましくは０．１重量％以下にするのがよい。
【００１４】
ヒドロキシイソ酪酸エステル中への水分の混入を抑制する方法としては、いろいろな方法により行うことができる。例えば、ヒドロキシイソ酪酸エステルを製造するに際し、製造装置の内部を乾燥不活性ガスでシールすることにより外気との接触を遮断し吸湿を防ぐ方法がある。あるいは、製造工程中に吸湿してしまった場合には、蒸留精製工程時に分離効率の良い精留塔を使用することにより、混入した水分を除去することが可能である。また、水分を含んだヒドロキシイソ酪酸エステルはモレキュラーシーブなどの脱水剤で処理することによっても水分を除去することができる。いかなる方法にせよヒドロキシイソ酪酸エステル中の水分含有量を０．５重量％以下に調整することが重要である。
【００１５】
ヒドロキシイソ酪酸エステルの水分含有量はできるだけ少ないほうが好ましいが、実質的に０重量％とするには極めて過酷な操作条件を必要とし、必然的に大幅なコストアップとなり経済的ではない。そのため、ヒドロキシイソ酪酸エステル中の水分含有量の下限値としては０．００１重量％程度でよい。
【００１６】
さらに、本発明者らの研究によれば、ヒドロキシイソ酪酸エステル中にヒドロキシイソ酪酸エステル製造時に使用される酸成分が不純物として混入している場合、ヒドロキシイソ酪酸エステルの加水分解が促進されることが判明した。このため、ヒドロキシイソ酪酸エステルの加水分解を助長する酸成分はなるべく混入しないようにするのが好ましい。ヒドロキシイソ酪酸エステル中に混入する可能性のある酸成分としては、ヒドロキシイソ酪酸エステル製造時において使用される硫酸、塩酸、硝酸、リン酸、酢酸、プロピオン酸、ベンゼンスルホン酸、トルエンスルホン酸、安息香酸などの無機酸あるいは有機酸類、あるいはヒドロキシイソ酪酸エステル製造時の酸性副生物であるメタクリル酸、ヒドロキシイソ酪酸、アルコキシイソ酪酸などが挙げられる。
【００１７】
【実施例】
以下、実施例を示して本発明をさらに具体的に説明するが、本発明は以下の実施例に何ら限定されるものではない。
【００１８】
実施例１〜２および比較例１〜２
表１に示す水分含有量のα−ヒドロキシイソ酪酸メチル５０kgを直径５０cm、高さ８０cmの炭素鋼製(SS-41) ドラム内に密封して、貯蔵温度を２０〜３０℃に保ち、直射日光に当たらないようにして１年間保存した。この間、３ヶ月ごとに内容物を取り出して、内容物の外観観察、純度分析、およびドラム材質の外観観察を行った。結果を表１に示す。
【００１９】
【表１】

【００２０】
実施例３〜４および比較例３〜４
表２に示す水分含有量のα−ヒドロキシイソ酪酸エチルをガラス容器に入れ、その中に金属テストピース（60×20× 2mm）を浸漬させ、液温を６０℃に保ち１週間放置した。浸漬後、液および金属テストピースの目視観察を行った。結果を表２に示す。
【００２１】
【表２】

【００２２】
実施例５〜６および比較例５〜６
はんだ（Sn-37Pb ）付けを施したプリント配線基板（銅張積層板）を、表３に示す水分含有量のβ−ヒドロキシイソ酪酸メチル１００g 中に６０℃で１週間浸漬した。浸漬後、２−プロパノールによる１分間のリンス洗浄、熱風乾燥を行った後、金属部分（はんだ、銅）を目視により観察した。結果を表３に示す。
【００２３】
【表３】

【００２４】
【発明の効果】
従来用いられているヒドロキシイソ酪酸エステルは貯蔵中に分解、変色を生じたり、金属材料の腐食を引き起こすという問題を有していた。しかし、本発明のヒドロキシイソ酪酸エステルはヒドロキシイソ酪酸エステル中の水分含有量を０．５重量％以下に調整しているため貯蔵中の分解、変色および金属材料への腐食を著しく抑制することが可能となった。このようなヒドロキシイソ酪酸エステルの発明により金属部品、電子部品などの洗浄用途や溶剤用途などへの使用が可能となった。[0001]
[Industrial application fields]
The present invention relates to a hydroxyisobutyric acid ester having improved storage stability and corrosiveness to a metal material, and the hydroxyisobutyric acid ester is used for metal parts, electronic parts cleaners and paints, and adhesives which are reluctant to corrode metals. It is useful for a wide range of applications such as solvents such as agents.
[0002]
[Prior art and its problems]
Hydroxyisobutyric acid ester is a useful compound as a cleaning agent, solvent, and synthetic raw material. However, the conventionally used hydroxyisobutyric acid ester has a problem that the hydroxyisobutyric acid ester is decomposed and discolored during long-term storage, resulting in loss of commercial value.
[0003]
In addition, the partially decomposed hydroxyisobutyric acid ester has strong corrosiveness to metal materials, so it cannot be used safely for cleaning applications such as metal parts and electronic parts and solvent applications. Alternatively, when the hydroxyisobutyric acid ester is stored, it is difficult to store it in a container made of carbon steel, tinplate or the like generally used for industrial use. In order to prevent such corrosion of the metal material, measures such as addition of a corrosion inhibitor are taken, but it is still difficult to completely prevent corrosion.
[0004]
For these reasons, there is a strong industrial demand for the appearance of a hydroxyisobutyric acid ester that has excellent storage stability that does not decompose or discolor during storage and that does not corrode metal materials.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a hydroxyisobutyric acid ester that solves the above-described problems, has excellent storage stability without being decomposed or discolored, and does not corrode metal materials.
[0006]
[Means for Solving the Problems]
As a result of intensive studies on the stability of hydroxyisobutyric acid ester and the corrosiveness of hydroxyisobutyric acid ester to metal materials, the inventors have found that the cause of decomposition, discoloration of hydroxyisobutyric acid ester and corrosion on metal materials is More specifically, it was found that the water caused the hydrolysis of hydroxyisobutyric acid ester, and the resulting acid component decomposed and discolored during storage. And found that it is a cause of corrosion of metal materials.
[0007]
Furthermore, when the acid component used in the production of hydroxyisobutyrate is mixed as an impurity in the product hydroxyisobutyrate, the decomposition of hydroxyisobutyrate is less than when no acid component is mixed. It has been found that discoloration, and metal corrosion are significantly accelerated.
[0008]
That is, the poor storage stability such as decomposition and discoloration of hydroxyisobutyric acid ester, and the corrosiveness to metal materials are due to moisture contained as impurities in hydroxyisobutyric acid ester, and the water content falls within a specific range. The inventors have found that the above-described object can be achieved by adjusting, and have completed the present invention.
[0009]
In the hydroxyisobutyric acid ester represented by the general formula [1] or the general formula [2],

(In the above formula, R represents an alkyl group having 1 to 4 carbon atoms.)
The present invention relates to a hydroxyisobutyric acid ester having improved storage stability and metal corrosiveness, wherein the water content in the hydroxyisobutyric acid ester is adjusted to 0.5% by weight or less.
[0010]
Hereinafter, the present invention will be described in detail.
Examples of the hydroxyisobutyric acid ester in the present invention include α-hydroxyisobutyric acid alkyl esters such as methyl α-hydroxyisobutyrate, ethyl α-hydroxyisobutyrate, propyl α-hydroxyisobutyrate, and butyl α-hydroxyisobutyrate (general formula [ 1]), β-hydroxyisobutyric acid alkyl esters such as methyl β-hydroxyisobutyrate, ethyl β-hydroxyisobutyrate, propyl β-hydroxyisobutyrate, butyl β-hydroxyisobutyrate (corresponding to general formula [2] ).
[0011]
Various methods for producing hydroxyisobutyric acid esters have been known, but esterification reaction of hydroxyisobutyric acid in the presence of a catalyst such as sulfuric acid, hydrochloric acid, strong acid ion exchange resin, alcoholysis reaction of cyanohydrin, hydroxyisobutyric acid amide A production method by an exchange reaction between benzene and formate is common. The hydroxyisobutyric acid ester of the present invention is not limited to those produced by the above method, and the hydroxyisobutyric acid ester obtained by any method can be the subject of the present invention.
[0012]
There are various possible causes of water mixing in the hydroxyisobutyric acid ester. Typical examples include the following. That is, when producing a hydroxyisobutyric acid ester, there are water used as a raw material, moisture contained in the raw material, moisture generated as a by-product during esterification, and moisture absorbed from outside air during production. It is difficult to completely separate the moisture absorbed in this way from the hydroxyisobutyric acid ester even in the distillation purification process, and a part of it is mixed in the product hydroxyisobutyric acid ester. Further, since hydroxyisobutyric acid ester itself is highly hygroscopic, it may absorb moisture during storage.
[0013]
In order to prevent decomposition, discoloration, corrosion of metal materials, and the like during storage of the hydroxyisobutyric acid ester, it is necessary to reduce the water content in the hydroxyisobutyric acid ester to 0.5% by weight or less. The amount is preferably 0.3% by weight or less, particularly preferably 0.1% by weight or less.
[0014]
As a method for suppressing the mixing of moisture into the hydroxyisobutyric acid ester, various methods can be used. For example, when producing a hydroxyisobutyric acid ester, there is a method of preventing moisture absorption by blocking the contact with the outside air by sealing the inside of the production apparatus with a dry inert gas. Alternatively, when moisture has been absorbed during the production process, it is possible to remove the mixed water by using a rectification column with good separation efficiency during the distillation purification process. In addition, moisture can be removed by treating the hydroxyisobutyric acid ester containing moisture with a dehydrating agent such as molecular sieve. In any method, it is important to adjust the water content in the hydroxyisobutyric acid ester to 0.5% by weight or less.
[0015]
The moisture content of the hydroxyisobutyric acid ester is preferably as low as possible, but in order to make it substantially 0% by weight, extremely severe operating conditions are required, which inevitably results in a significant cost increase and is not economical. Therefore, the lower limit of the water content in the hydroxyisobutyric acid ester may be about 0.001% by weight.
[0016]
Furthermore, according to the study by the present inventors, when the acid component used in the production of hydroxyisobutyric acid ester is mixed as an impurity in the hydroxyisobutyric acid ester, hydrolysis of the hydroxyisobutyric acid ester is promoted. There was found. For this reason, it is preferable that an acid component that promotes hydrolysis of the hydroxyisobutyric acid ester is not mixed as much as possible. Acid components that may be mixed in the hydroxyisobutyric acid ester include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid, propionic acid, benzenesulfonic acid, toluenesulfonic acid, benzoic acid used in the production of hydroxyisobutyric acid ester. Examples thereof include inorganic acids or organic acids such as acids, or methacrylic acid, hydroxyisobutyric acid, and alkoxyisobutyric acid, which are acidic by-products when producing hydroxyisobutyric acid ester.
[0017]
【Example】
EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited to a following example at all.
[0018]
Examples 1-2 and Comparative Examples 1-2
50 kg of water-containing methyl α-hydroxyisobutyrate shown in Table 1 made of carbon steel with a diameter of 50 cm and a height of 80 cm (SS-41). Sealed in a drum, keeping the storage temperature at 20-30 ° C, direct sunlight It was stored for one year without hitting it. During this time, the contents were taken out every three months, and the appearance of the contents were observed, the purity was analyzed, and the appearance of the drum material was observed. The results are shown in Table 1.
[0019]
[Table 1]

[0020]
Examples 3-4 and Comparative Examples 3-4
Ethyl α-hydroxyisobutyrate having a water content shown in Table 2 was placed in a glass container, and a metal test piece (60 × 20 × 2 mm) was immersed therein, and the liquid temperature was kept at 60 ° C. and left for 1 week. After immersion, the liquid and metal test pieces were visually observed. The results are shown in Table 2.
[0021]
[Table 2]

[0022]
Examples 5-6 and Comparative Examples 5-6
A printed wiring board (copper-clad laminate) to which solder (Sn-37Pb) was applied was immersed in 100 g of methyl β-hydroxyisobutyrate having a moisture content shown in Table 3 at 60 ° C. for 1 week. After immersing, after rinsing with 2-propanol for 1 minute and hot air drying, the metal part (solder, copper) was visually observed. The results are shown in Table 3.
[0023]
[Table 3]

[0024]
【The invention's effect】
Conventionally used hydroxyisobutyric acid ester has problems that it decomposes or discolors during storage and causes corrosion of metal materials. However, the hydroxyisobutyric acid ester of the present invention adjusts the water content in the hydroxyisobutyric acid ester to 0.5% by weight or less, so that it can remarkably suppress decomposition, discoloration and corrosion of metal materials during storage. It has become possible. The invention of such hydroxyisobutyric acid ester has made it possible to use it for cleaning applications such as metal parts and electronic parts, and for solvent applications.

Claims (2)

In the hydroxyisobutyric acid ester represented by the general formula [1] or the general formula [2],

(In the above formula, R represents an alkyl group having 1 to 4 carbon atoms.)
A hydroxyisobutyric acid ester having improved storage stability and metal corrosiveness, wherein the content of water in the hydroxyisobutyric acid ester is adjusted to 0.5% by weight or less. Hydroxyisobutyric acid ester is methyl α-hydroxyisobutyrate, ethyl α-hydroxyisobutyrate, propyl α-hydroxyisobutyrate, butyl α-hydroxyisobutyrate, methyl β-hydroxyisobutyrate, ethyl β-hydroxyisobutyrate, β- The hydroxyisobutyric acid ester having improved storage stability according to claim 1, which is selected from propyl hydroxyisobutyrate and butyl β-hydroxyisobutyrate.